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Role of Nitric Oxide in Inflammatory Conditions
Abstract
Nitric oxide (NO) plays an important regulatory/modulatory role in a variety of inflammatory conditions. NO is a small, short-lived molecule that is released from a variety of cells in response to homeostatic and pathologic stimuli. It may act as a vasodilator and a platelet inhibitor and may interfere with adhesion molecules to prevent neutrophil adhesion. NO release may also lead to the formation of highly reactive species such as peroxynitrite and stable nitrosothiols and may cause mitochondrial damage and nitration of protein tyrosine residues. In addition, NO inhibits cell proliferation via inhibition of polyamine synthesis and cell uptake and may well act as a 'brake' on the proliferative response following cytokine exposure. All three isoforms of nitric oxide synthases are found in the kidney during inflammation. The site of NO release impacts significantly on its net function and structural impact. NO plays a protective role in many forms of immune injury, such as nephrotoxic serum-induced glomerulonephritis, autoimmune tubular interstitital nephritis, and experimental allergic encephalomyelitis. NO overproduction in sepsis, after cytokine exposure, inducible NO synthase transcription, and local inflammation can autoinhibit endothelial NO synthase, leading to selective renal and mesenteric vasoconstriction.
... In a chronic phase of inflammation, the inflammatory signal can be magnified by the production of molecules such as nuclear transcription factor kappa β (NF-kβ), TNF-α, and interferon-gamma (IFN-γ) which promote transcription of iNOS, generating large amounts of NO, greater vasodilation, edema, and plasma exudation that can even damage the DNA double helix [37][38][39][40]. High production of NO can be associated with the development of diseases such as Alzheimer's, cardiovascular, rheumatoid arthritis, pulmonary fibrosis, diabetes, and cancer, among others [41][42][43][44][45][46]. This is why the iNOS enzyme is essential in the inflammatory process and allows us to understand the mechanism of action of active ingredients from medicinal plants [47][48][49]. ...
This work reports the isolation, purification, and anti-inflammatory evaluation of compounds from the plant species Ageratina pichinchesis. Using open-column chromatography, 11 known compounds were purified, whose chemical structures were elucidated by nuclear magnetic resonance techniques (1D and 2D). All compounds were evaluated in the in vitro model of RAW 264.7 mouse macrophage cells measuring nitric oxide inhibition as a determination of the anti-inflammatory effect. Outstandingly, the compound betuletol 3-O-β-glucoside (11) exhibited inhibition of nitric oxide with an IC50 of 75.08 ± 3.07% at 75 µM, additionally, it inhibited the secretion of interleukin 6 (IL-6) and activation of nuclear factor (NF-kβ). These results show that compound 11 could be considered as a potential anti-inflammatory agent in suppressing the expression of NF-kβ target genes such as the proinflammatory pathway and inducible nitric oxide synthase (iNOS). Consequently, the medicinal use attributed in traditional medicine to the A. pichinchensis species is due to the diversity of compounds that the plant biosynthesizes, demonstrating that its effect relates to anti-inflammatory effects associated with compound 11.
... We found that rats post CUMS showed increased nNOS and iNOS but decreased eNOS in LHb, which may be accounted by the neurotoxic effect of nNOS and iNOS on NO [71] and the neuroprotective effect of eNOS on NO [26,83]. As reported, inhibitors of NOS reduced the severity of inflammation in animal models of inflammatory diseases [7]. LNAME was no exception by ameliorating the inflammation in the study. ...
Background:
Depression is a severe emotional condition that significantly affects the quality of life. Acupuncture exerts preventive effects on depression in rats with post-chronic unpredictable mild stress (CUMS). Methods The study involved chronic unpredictable mild stress (CUMS) depression model mice to administer acupuncture as a preventative measure to investigate the mechanism of acupuncture's antidepressant and observe the effect of acupuncture on impact via the Lateral Habenula (LHb) and Gut-Liver-Brain Axis. The researcher investigated molecules correlating with a nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway and assessed inflammation in the LHb and liver. In addition, 16S rDNA bioinformatics study revealed the quantity and variety of gut microbiota. Rats were randomly divided into five groups: control (CON), CUMS, CUMS + acupuncture (AP), CUMS + fluoxetine (FX) and CUMS + N(G) -nitro -L- arginine methyl ester (LNAME) group. Except for the CON group, other rats were exposed to CUMS condition for 28 days. Simultaneously, manual acupuncture (at Fengfu and Shangxing acupoints, once every other day) and fluoxetine gavage (2.1mg/kg, 0.21mg/mL, daily) were conducted to the groups of AP and FX, respectively, after stressors. Rats in LNAME group were treated with LNAME normal saline (10mg/kg, 1mg/mL, i.p.) solution. Behavioural tests and biological detection methods were conducted sequentially to evaluate depressionlike phenotype in rats.
Results:
The results showed CUMS induced depression-like behaviours, hyper-activation of NO/cGMP signaling pathway, inflammation in serum, LHb and liver, and dysbiosis of the gut microbiota. These changes could be prevented and ameliorated by acupuncture to varying extents.
Conclusion:
Acupuncture prevented and attenuated depression-like phenotype induced by CUMS, possibly via regulating the NO/cGMP signaling pathway and thus improving inflammation in serum, LHb and liver, and gut microbiota dysbiosis. In addition, these can be evidence of the existence of the gut-liver-brain axis.
... The iNOS expression can be induced in cells and tissues by pro-inflammatory cytokine and other triggers such as bacteria and lipopolysaccharides (LPS) (Kleinert, Schwarz, and Förstermann 2003). •NO plays a crucial role in the inflammatory process since it can inhibit cell proliferation via polyamine synthesis and the proliferative response following cytokine exposure (Blantz and Munger 2002). Additionally, macrophages are a primary defense line against toxic stimuli, and thus, LPS induced anti-inflammatory of RAW 264.7 cells are used as models to determine the anti-inflammatory capacity of several molecules and natural products extracts. ...
The increasing demand for nutraceuticals in the circular economy era has driven the research toward studying bioactive compounds from renewable underexploited resources. in this regard, the exploration of brown algae has shown significant growth and maintains a great promise for the future. One possible explanation could be that brown algae are rich sources of nutritional compounds (polyunsaturated fatty acids, fiber, proteins, minerals, and vitamins) and unique metabolic compounds (phlorotannins, fucoxanthin, fucoidan) with promising biological activities that make them good candidates for nutraceutical applications with increased value-added. in this review, a deep description of bioactive compounds from brown algae is presented. in addition, recent advances in biological activities ascribed to these compounds through in vitro and in vivo assays are pointed out. Delivery strategies to overcome some drawbacks related to the direct application of algae-derived compounds (low solubility, thermal instability, bioavailability, unpleasant organoleptic properties) are also reviewed. Finally, current commercial and legal statuses of ingredients from brown algae are presented, considering future therapeutical and market perspectives as nutraceuticals.
... Post-translational modifications (PTMs) introduce a series of crucial protein modifications after the translation phase (Saraswathy and Ramalingam, 2011). PTMs alter and derivate intra-molecular bonds of amino acids with drastic impacts on proteomic analysis and biological processes, such as cellular signal transduction, metabolism, subcellular localization, protein folding, and protein degradation (McDowell and Philpott, 2016;Weissman et al., 2003;Ghauri et al., 2018;Blantz and Munger, 2002). Hence, efficient identification and appropriate understanding of PTM sites are essential for basic research in the fields of disease detection and prevention, and drug development (Chou, 2015;Qiu et al., 2016). ...
Post-translational modification (PTM) is defined as the enzymatic changes of proteins after the translation process in protein biosynthesis. Nitrotyrosine, which is one of the most important modifications of proteins, is interceded by the active nitrogen molecule. It is known to be associated with different diseases including autoimmune diseases characterized by chronic inflammation and cell damage. Currently, nitrotyrosine sites are identified using experimental approaches which are laborious and costly. In this study, we propose a new machine learning method called PredNitro to accurately predict nitrotyrosine sites. To build PredNitro, we use sequence coupling information from the neighboring amino acids of tyrosine residues along with a support vector machine as our classification technique.Our results demonstrates that PredNitro achieves 98.0% accuracy with more than 0.96 MCC and 0.99 AUC in both 5-fold cross-validation and jackknife cross-validation tests which are significantly better than those reported in previous studies. PredNitro is publicly available as an online predictor at: http://103.99.176.239/PredNitro.
... Post-translational modifications (PTMs) introduce a series of crucial protein modifications after the translation phase [1]. PTMs alter and derivate intra-molecular bonds of amino acids with drastic impacts on proteomic analysis and biological processes, such as cellular signal transduction, metabolism, subcellular localization, protein folding, and protein degradation [2,3,4,5]. Hence, efficient identification and appropriate understanding of PTM sites are essential for basic research in the fields of disease detection and prevention, and drug development [6,7]. Among 20 fundamental amino acid residues that build proteins, modifications at tyrosine residue (Y) are usually referred to as tyrosine PTM or Y-PTM. ...
Post-translational modification (PTM) is defined as the enzymatic changes of proteins after the translation process in protein biosynthesis. Nitrotyrosine, which is one of the most important modifications of proteins, is interceded by the active nitrogen molecule. It is known to be associated with different diseases including autoimmune diseases characterized by chronic inflammation and cell damage. Currently, nitrotyrosine sites are identified using experimental approaches which are laborious and costly. In this study, we propose a new machine learning method called PredNitro to accurately predict nitrotyrosine sites. To build PredNitro, we use sequence coupling information from the neighboring amino acids of tyrosine residues along with a support vector machine as our classification technique.Our results demonstrates that PredNitro achieves 98.0% accuracy with more than 0.96 MCC and 0.99 AUC in both 5-fold cross-validation and jackknife cross-validation tests which are significantly better than those reported in previous studies. PredNitro is publicly available as an online predictor at: http://103.99.176.239/PredNitro.
... Synthesized from L-arginine and molecular oxygen, the signaling molecule nitric oxide is actively involved in innate immunity and inflammation [13,57] and is produced by cells including macrophages actively involved in immune regulation [58]. Regulating nitric oxide production during inflammation is necessary to avoid the progression of acute inflammation to chronic. ...
Natural α-bisabolol has been widely used in cosmetics and is sourced mainly from the stems of Candeia trees that have become endangered due to over exploitation. The in vitro anti-inflammatory activity of cotton gin trash (CGT) essential oil and the major terpenoid (β-bisabolol) purified from the oil were investigated against lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages as well as the 3t3 and HS27 fibroblast cell lines. Nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and interleukin 8 (IL-8) were measured using Greiss reagent, enzyme-linked immunosorbent assay (ELISA), and cytokine bead array (CBA)-flow cytometry. Non-toxic concentrations of CGT oil and β-bisabolol (1.6–50.0 µg/mL) significantly inhibited the production of the inflammatory mediators in a dose-dependent manner. Maximal inhibition by β-bisabolol was 55.5% for NO, 62.3% for PGE2, and 45.3% for TNF-α production in RAW cells. β-Bisabolol induced a level of inhibition similar to an equal concentration of α-bisabolol (50.0 µg/mL), a known anti-inflammatory agent. These results suggest β-bisabolol exerts similar in vitro effects to known topical anti-inflammatory agents and could therefore be exploited for cosmetic and therapeutic uses. This is the first study to report the in vitro anti-inflammatory activity of β-bisabolol in CGT essential oil.
... Nitric oxide synthase (NOS) has three isoforms: neuronal NOS (nNOS; NOS1), iNOS (NOS2), and endothelial eNOS (NOS3) [32]. iNOS is an inducible form that is upregulated in response to various stimuli, including LPS, cytokines, chemokines, and stress, while nNOS and eNOS are constitutive forms that catalyze continuous NO secretion at basal concentrations [33]. ...
We previously investigated the methanolic extract of Morus alba bark and characterized 11 compounds from the extract: kuwanon G (1), kuwanon E (2), kuwanon T (3), sanggenon A (4), sanggenon M (5), sanggenol A (6), mulberofuran B (7), mulberofuran G (8), moracin M (9), moracin O (10), and norartocarpanone (11). Herein, we investigated the anti-inflammatory effects of these compounds on microglial cells (BV2) and macrophages (RAW264.7). Among them, 3 and 4 markedly inhibited the lipopolysaccharide (LPS)-induced production of nitric oxide in these cells, suggesting the anti-inflammatory properties of these two compounds. These compounds inhibited the production of prostaglandin E2, interleukin-6, and tumor necrosis factor-α, and the expression of inducible nitric oxide synthase and cyclooxygenase-2 following LPS stimulation. Pretreatment with 3 and 4 inhibited the activation of the nuclear factor kappa B signaling pathway in both cell types. The compounds also induced the expression of heme oxygenase (HO)-1 through the activation of nuclear factor erythroid 2-related factor 2. Suppressing the activity of HO-1 reversed the anti-inflammatory effects caused by pretreatment with 3 and 4, suggesting that the anti-inflammatory effects were regulated by HO-1. Taken together, 3 and 4 are potential candidates for developing therapeutic and preventive agents for inflammatory diseases.
... NO causes inflammation by iNOS and acts as a regulatory and proinflammatory mediator [28]. The release of NO may also lead to the formation of highly reactive species such as peroxynitrite and stable nitrosothiols and may result in mitochondrial damage [29]. The expression of iNOS is one of the direct consequences of inflammation development [30]. ...
Aim
Nephrotoxicity is the major limiting factor for the clinical use of vancomycin (VCM) for treatment against multi-resistant Gram-positive bacteria. The present research aimed to investigate the ability of selenium nanoparticles (SeNPs) to protect against VCM-induced nephrotoxicity in rats.
Main methods
Experimental rats were divided into five groups; the first was the normal control, the second was treated with VCM (200 mg/kg twice/day, i.p.) for 7 days. The third, fourth, and fifth groups were treated orally with SeNPs (0.5, 1, and 2 mg/kg/day); respectively. SeNPs were administered for 12 days before VCM, 1 week simultaneously with VCM, and for another 1 week after its administration.
Key findings
Levels of malondialdehyde (MDA), inducible nitric oxide synthase (iNOS), nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), and kidney injury molecule-1 (KIM-1) were significantly increased in kidney tissue after VCM administration. Expression of adenosine 5′-monophosphate-activated protein kinase (AMPK), Bcl-2 associated X protein (Bax), caspase 3 and caspase 9 in kidney tissue was significantly increased, while the antioxidant enzymes, mitochondrial complexes, the ATP levels and B-cell lymphoma protein 2 (Bcl-2) were decreased in kidney in the VCM-treated rats compared to the normal control group. Treatment with SeNPs significantly decreased levels of MDA, iNOS, NO, TNF-α, and KIM-1 in the kidney tissue. Administration of SeNPs also downregulated the expression of the proapoptotic agents and enhanced the activities of the antioxidant enzymes and the mitochondrial enzyme complexes in the kidney.
Significance
SeNPs alleviated VCM-induced nephrotoxicity through their anti-oxidant, anti-inflammatory, anti-apoptotic and mitochondrial protective effects.
... Therefore, LPS-stimulated macrophages and microglia cell models have been widely used to investigate the antiinflammatory effects of candidate materials. In the present study, we used the LPS-induced RAW264.7 macrophages and BV2 microglial cells to examine the anti-inflammatory effects of cudraflavanone B. NO is one of the critical inflammatory mediators that is synthesized from L-arginine by three different isoforms of the enzyme NO synthase (NOS), including neuronal nNOS (NOS1), inducible iNOS (NOS2), and endothelial eNOS (NOS3) [34,35]. The enzymes nNOS and eNOS are expressed via a calcium-dependent process. ...
A prenylated flavonoid, cudraflavanone B, is isolated from Cudrania tricuspidata. In this study, we investigated its anti-inflammatory and anti-neuroinflammatory effects in lipopolysaccharide (LPS)-induced RAW264.7 and BV2 cells. In our initial study of the anti-inflammatory effects of cudraflavanone B the production of nitric oxide and prostaglandin E2 was attenuated in LPS-stimulated RAW264.7 and BV2 cells. These inhibitory effects were related to the downregulation of inducible nitric oxide synthase and cyclooxygenase-2. In addition, cudraflavanone B suppressed the production of pro-inflammatory cytokines such as interleukin-6 and tumor necrosis factor-α in LPS-induced RAW264.7 and BV2 cells. Moreover, the evaluation of the molecular mechanisms underlying the anti-inflammatory effects of cudraflavanone B revealed that the compound attenuated the nuclear factor-kappa B signaling pathway in LPS-induced RAW264.7 and BV2 cells. In addition, cudraflavanone B inhibited the phosphorylation of extracellular signal-regulated kinase mitogen-activated protein kinase signaling pathways in these LPS-stimulated cells. Thus, cudraflavanone B suppressed nuclear factor-κB, and extracellular signal-regulated kinase mitogen-activated protein kinase mediated inflammatory pathways, demonstrating its potential in the treatment of neuroinflammatory conditions.
... NO plays a crucial role in the signal transduction pathway involved in cell proliferation, survival, and cell death in almost all types of cells 51,52 . Additionally, NO is a well-known critical factor involved in inflammatory responses in many types of cells, including macrophages 53,54 . The abnormal generation of NO induces an inflammatory response that is potentially toxic to adjacent cells and host tissues. ...
Lactobacillus paracasei is a major probiotic and is well known for its anti-inflammatory properties. Thus, we investigated the effects of L. paracasei-derived extracellular vesicles (LpEVs) on LPS-induced inflammation in HT29 human colorectal cancer cells and dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice. ER stress inhibitors (salubrinal or 4-PBA) or CHOP siRNA were utilized to investigate the relationship between LpEV-induced endoplasmic reticulum (ER) stress and the inhibitory effect of LpEVs against LPS-induced inflammation. DSS (2%) was administered to male C57BL/6 mice to induce inflammatory bowel disease, and disease activity was measured by determining colon length, disease activity index, and survival ratio. In in vitro experiments, LpEVs reduced the expression of the LPS-induced pro-inflammatory cytokines IL-1α, IL-1β, IL-2, and TNFα and increased the expression of the anti-inflammatory cytokines IL-10 and TGFβ. LpEVs reduced LPS-induced inflammation in HT29 cells and decreased the activation of inflammation-associated proteins, such as COX-2, iNOS and NFκB, as well as nitric oxide. In in vivo mouse experiments, the oral administration of LpEVs also protected against DSS-induced colitis by reducing weight loss, maintaining colon length, and decreasing the disease activity index (DAI). In addition, LpEVs induced the expression of endoplasmic reticulum (ER) stress-associated proteins, while the inhibition of these proteins blocked the anti-inflammatory effects of LpEVs in LPS-treated HT29 cells, restoring the pro-inflammatory effects of LPS. This study found that LpEVs attenuate LPS-induced inflammation in the intestine through ER stress activation. Our results suggest that LpEVs have a significant effect in maintaining colorectal homeostasis in inflammation-mediated pathogenesis.
... The multifaceted role of NO, in both inflammation and the regulation of adaptive immune responses, is not fully understood [2]. The administration of NOS inhibitors in rodent models of inflammatory diseases curtails the severity of inflammation [3][4][5][6]. In addition, there is a correlation between the activity of the disease and iNOS expression in inflamed tissues or circulating monocytes [7]. ...
Activated macrophages upregulate inducible nitric oxide synthase (iNOS) leading to the profuse production of nitric oxide (NO) and, eventually, tissue damage. Using macrophage NO production as a biochemical marker of inflammation, we tested different parts (flower, leaf, and stem) of the medicinal plant, Spilanthes acmella. We found that extracts prepared from all three parts, especially the flowers, suppressed NO production in RAW macrophages in response to interferon-γ and lipopolysaccharide. Follow up experiments with selected bioactive molecules from the plant (α-amyrin, β-caryophylline, scopoletin, vanillic acid, trans-ferulic acid, and spilanthol) indicated that the N-alkamide, spilanthol, is responsible for the NO-suppressive effects and provides protection from NO-dependent cell death. Spilanthol reduced the expression of iNOS mRNA and protein and, as a possible underlying mechanism, inhibited the activation of several transcription factors (NFκB, ATF4, FOXO1, IRF1, ETS, and AP1) and sensitized cells to downregulation of Smad (TF array experiments). The iNOS inhibitory effect translated into an anti-inflammatory effect, as demonstrated in a phorbol 12-myristate 13-acetate-induced dermatitis and, to a smaller extent, in cerulein-induced pancreatitis. In summary, we demonstrate that spilanthol inhibits iNOS expression, NO production and suppresses inflammatory TFs. These events likely contribute to the observed anti-inflammatory actions of spilanthol in dermatitis and pancreatitis.
... It can modulate the release of various inflammatory mediators from a wide range of cells participating in inflammatory responses (e.g., leukocytes, macrophages, mast cells, endothelial cells, and platelets). However, high levels of NO cause inflammatory diseases, such as atherosclerosis, bowel disease, rheumatoid arthritis, hypertension, diabetes, neurodegenerative disorders, and septic shock (Blantz and Munger 2002). Thus, inhibitors of NO might be of therapeutic importance in preventing pathological conditions catalyzed by inflammation. ...
Basil (Ocimum basilicum L.) has been used not only as culinary herb for flavor, but traditional medicines such as antiseptic, antispasmodic, digestive regulatory, anti-oxidant and antimicrobial properties. However, the anti-inflammatory activity of plant tissue cultures developed from Ocimum basilicum L. remains unknown. This study aimed to investigate the effect of callus induction and the ethanol extract of in vivo leaf and in vitro (leaf, callus light and dark condition) of Ocimum basilicum L. to examine its anti-inflammatory activity on LPS-stimulated RAW 264.7 macrophage cells in vitro. Callus induction from leaf explants of Ocimum basilicum L. was conducted by incubating leaf explants on MS medium supplemented with various concentrations of KIN in combination with 2,4-D. The constituents of leaf and leaf callus ethanol extracts of Ocimum basilicum L. were quantified using GC–MS analysis. Additionally, cell viability was determined using an MTT assay and anti-inflammatory effects were investigated by measuring NO production. The results showed that the leaf callus was induced on MS medium supplemented with various combination of KIN and 2,4-D over a short time period. Analyses confirmed that in vivo leaf contained many of the constituents than in vitro leaf and callus. Moreover, the ethanol extracts of leaf and leaf callus of Ocimum basilicum L. exhibited non-cytotoxicity and reduced NO production in LPS-stimulated RAW 264.7 macrophage cells. Thus, these results suggest that Ocimum basilicum L. may have potential benefits in preventing pathological inflammation.
... When exposed to the stimulators of inflammation, immune cells produce high amounts of nitric oxide (NO) by the upregulation of the iNOS gene via different signaling pathways including the nuclear factor kappa B (NF-kB) and activator protein 1 (AP-1), making NO a key mediator for tissue damage in inflammatory diseases [10,11]. NO release leads to the formation of highly reactive species such as peroxynitrite and stable nitrosothiols which causes mitochondrial damage and nitration of protein tyrosine residues resulting in protein modification and the shutting-down of cellular activities [12]. Therefore, NO production induced by cytokines and bacterial toxins have been widely used to reflect the degree of inflammation and provide a measure to assess the effect of drugs on the inflammatory process [13]. ...
The bioassay-guided isolation of new anti-inflammatory metabolites from the Australian Indigenous plant Angophora costata led to the discovery of three new 4-phenylcoumarins, costatamins A – C (1–3). The structures were determined by detailed spectroscopic analysis. Costatamins A – C were evaluated for their inhibitory effects on (a) NO production and (b) TNF-α release in RAW 264.7 macrophages, displaying an IC(50) value of 20–30 μg/mL for both the inflammatory markers.
... Low concentrations are, in most cases, sufficient to exert these beneficial effects. However, overproduction of this free radical may induce several undesired deleterious effects, including inflammatory and autoimmune diseases [4,5]. The search for substances capable of preventing overproduction of NO has, therefore, received increasing attention, and numerous extracts of edible and/or medicinal plants have been shown to exert potent NO scavenging activities [6,7]. ...
The present study aimed at developing an original pre-column HPLC assay allowing rapid characterization of nitric oxide (NO) scavengers from complex plant extracts. Sodium nitroprusside (SNP) was employed as a NO donor and spiked with an aqueous extract from Aloysia triphylla leaves prior to HPLC analysis. Relying on the ability of radical scavenging constituents to be oxidized upon reaction with radicals, this assay successfully allowed direct identification of three potential NO scavengers, including verbascoside, isoverbascoside, and luteolin-7-O-diglucuronide. These three phenolics were also individually assessed for their NO scavenging activities by using a Griess colorimetric assay. With respective IC50 values of 56 ± 4, 51 ± 3, and 69 ± 5 µg/mL, verbascoside, isoverbascoside, and luteolin-7-O-diglucuronide were all reported as potent NO scavenging compounds, confirming the efficiency of the SNP spiking HPLC assay. The present method can, thus, be considered as a valuable and effective approach for speeding up the discovery of NO scavenging constituents.
... iNOS is expressed in macrophages after stimulation by pro-inflammatory cytokines and produces NO in far greater amounts than eNOS. iNOS derived NO, in higher amounts, serves important immune function (39), but also damages normal tissues (9). Therefore, high levels of nitrite in MetS may be attributed to iNOS overexpression. ...
Objectives
Plasma nitrite is a metabolite of nitric oxide (NO) and reflects endogenous nitric oxide synthase (NOS) activity. Although plasma nitrites were previously linked with obesity and metabolic syndrome (MetS), but the direction of association remains inconsistent, possibly due to sample heterogeneity. In a relatively homogeneous population, we hypothesized that nitrite levels will be positively associated with overweight/obesity and MetS.
Methods
Fasting nitrite levels were measured in 116 Old Order Amish (78% women). We performed age‐and‐sex‐adjusted ANCOVA analyses to compare nitrite levels between three groups: a) overweight/obese(‐)MetS(‐), b) overweight/obese(+)MetS(‐) and c) overweight/obese(+)MetS)(+). Multivariate linear regressions were conducted on nitrite associations with continuous metabolic variables, with successive adjustments for demographics, BMI, C‐reactive protein and neopterin.
Results
Nitrite levels were higher in the obese/overweight(+)MetS(+) group than in the other two groups (p<0.001). Nitrites were positively associated with levels of triglycerides (p < 0.0001), total cholesterol (p = 0.048), HDL/cholesterol ratio (p < 0.0001), and fasting glucose (p < 0.0001), and negatively correlated with HDL‐cholesterol (p < 0.0001). These associations were robust to adjustments for BMI and inflammatory markers.
Conclusion
Further investigation of the connection between obesity/metabolic syndrome and plasma nitrite levels may lead to novel dietary and pharmacological approaches that ultimately may contribute to reducing the increasing burden of obesity, metabolic syndrome and cardiovascular morbidity and mortality.
... Expression of the inducible NOS (iNOS) is stimulated by inflammatory cytokines or bacterial products such as lipopolysaccharide (LPS) [3]. Prolonged exposure to NO can cause inflammatory diseases like inflammatory bowel disease, atherosclerosis, rheumatoid arthritis, glomerulonephritis, and septic shock [4][5][6][7]. Therefore, NO production, through iNOS induction by LPS, may reflect the degree of inflammation in LPS stimulated RAW 264.7 cells and may provide possible ways to screen various anti-inflammatory compounds. ...
This study identifies the efficacy of an ethyl acetate extract of Garcinia mangostana as a potent inhibitor of nitric oxide (NO) production. Crude extract in the range from 0.906µg/ml to 15.625µg/ml significantly decreased nitrite production in LPS-stimulated RAW 264.7 cells in vitro in a concentration dependent manner (11 μmol to 2.5 μmol) (p<0.01). The findings also demonstrated that extract was not cytotoxic to cells by MTT assay at these concentrations (0.906µg/ml to 15.625µg/ml).
... NO is synthesized from the amino acid L-arginine by NO synthase (NOS). It is released by neurons, endothelial cells, platelets, and neutrophils in response to homeostatic and pathological stimuli [65]. Large amounts of NO are produced in inflammatory processes, which are primarily generated by the inducible isoform (iNOS) and can be toxic. ...
Inflammation is a protective reaction of the microcirculation. However, sustained inflammation can lead to undesired effects. Thuja occidentalis Linn has many pharmacological properties but has no anti-inflammatory activity described. Thus, this study aims evaluating the anti-inflammatory activity of the aqueous extract (AE) and the polysaccharide fraction (PLS) of T. occidentalis L. in mice. The results of our evaluations in various experimental models indicated that AE and PLS (3, 10, and 30 mg/kg, i.p.) reduced (p ˂ 0.05) paw edema induced by carrageenan, dextran sulfate (DEX), compound 48/80, serotonin (5-HT), bradykinin (BK), histamine (HIST), and prostaglandin E2 (PGE2). Furthermore, it inhibited neutrophils recruitment; decreased MPO activity, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels, vascular permeability, nitrite concentration, and MDA concentration; and maintained the GSH levels in the peritoneal exudate. The AE and PLS reduced neutrophil infiltration and cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) immunostaining in paw tissue.
... Furthermore, NO is reported to be involved in central perception of pain to thermal stimulus determined by hot plate or tail flick tests [22,30,[56][57][58]. There are also contradictory reports in the literature concerning role of NO as an anti-inflammatory or proinflammatory mediator [9,[59][60][61][62][63]. We have previously shown that systemic administration of LPS (10 mg/ kg, i.p.) increases nitrite, PGF 1α , and/or thromboxane B 2 levels in the serum, kidney, and lung of mice as well as increased mortality [54,[64][65][66]. ...
The nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3), an intracellular signaling molecule that senses many environmental- and pathogen/host-derived factors, has been implicated in the pathogenesis of several diseases associated with inflammation. It has been suggested that NLRP3 inflammasome inhibitors may have a therapeutic potential in the treatment of NLRP3-related inflammatory diseases. The aim of this study was to determine whether inhibition of NLRP3 inflammasome prevents inflammatory hyperalgesia induced by lipopolysaccharide (LPS) in mice as well as changes in expression/activity of nuclear factor κB (NF-κB), caspase-1/11, nicotinamide adenine dinucleotide phosphate oxidase (NOX), and endothelial/neuronal/inducible nitric oxide synthase (eNOS/nNOS/iNOS) that may regulate NLRP3/apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)/pro-caspase-1 inflammasome formation and activity by using a selective NLRP3 inflammasome inhibitor, MCC950. Male mice received saline (10 ml/kg; i.p.), LPS (10 mg/kg; i.p.), and/or MCC950 (3 mg/kg; i.p.). Reaction time to thermal stimuli within 1 min was evaluated after 6 h. The mice were killed and the brains, hearts, and lungs were collected for measurement of NF-κB, caspase-1, caspase-11, NLRP3, ASC, NOX subunits (gp91phox; NOX2), and p47phox; NOXO2), nitrotyrosine, eNOS, nNOS, iNOS, and β-actin protein expression, NOS activity, and interleukin (IL)-1β levels. LPS-induced hyperalgesia was associated with a decrease in eNOS, nNOS, and iNOS protein expression and activity as well as an increase in expression of NF-κB p65, caspase-1 p20, caspase-11 p20, NLRP3, ASC, gp91phox, p47phox, and nitrotyrosine proteins in addition to elevated IL-1β levels. The LPS-induced changes were prevented by MCC950. The results suggest that inhibition of NLRP3/ASC/pro-caspase-1 inflammasome formation and activity prevents inflammatory hyperalgesia induced by LPS in mice as well as changes in NF-κB, caspase-11, NOX2, NOXO2, and eNOS/nNOS/iNOS expression/activity.
... NO is a highly reactive, short-lived molecule produced from a group of enzymes known as NOS [16]. NO is produced from enzymes NOS which exists in three isoforms, from the amino acid L-arginine in the presence of many cofactors NADPH using flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), heme, thiol and tetrahydrobiopterin, and oxygen [17]. ...
Nitric oxide (NO) is an endogenous molecule which functions as a neurotransmitter, hormone, free radical, etc. NO has been found to regulate the release of neurotransmitters, synaptic transmission, cell death, etc. NO is involved in the pathogenesis of various neuropsychiatric and neurodegenerative disorders. NO plays a key role in cellular apoptosis and neuronal degeneration. Parkinson' disease (PD) is a neurodegenerative disorder characterized by motor dysfunction that can be seen in the patients suffering from PD. The motor dysfunction is due to the progressive degeneration of dopaminergic neurons in mid brain. Dopamine (DA) is highly reactive molecule and is prone to the oxidation very much. The oxidation of DA is accompanied by the production of the reactive oxygen species that activates microglia cells. Upon activation, microglia cells cause the upregulation of inducible NO synthase, the enzyme involved in the production of NO. NO thus plays a key role in the neurodegeneration process implicated in PD. Thus, the aim of the present manuscript is to describe the possible role of NO in PD.
... NO is a highly reactive, short-lived molecule produced from a group of enzymes known as NOS [16]. NO is produced from enzymes NOS which exists in three isoforms, from the amino acid L-arginine in the presence of many cofactors NADPH using flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), heme, thiol and tetrahydrobiopterin, and oxygen [17]. ...
Nitric oxide (NO) is an endogenous molecule which function as a neurotransmitter, hormone, free radical, etc. NO has been found to regulate the release of neurotransmitters, synaptic transmission, cell death, etc. NO is involved in the pathogenesis of various neuropsychiatric and neurodegenerative disorders. NO plays a key role in cellular apoptosis and neuronal degeneration. Parkinson’ disease (PD) is a neurodegenerative disorder characterized by motor dysfunction that can be seen in the patients suffering from PD. The motor dysfunction is due to the progressive degeneration of dopaminergic neurons in mid brain. Dopamine (DA) is highly reactive molecule and is prone to the oxidation very much. The oxidation of DA is accompanied by the production of the reactive oxygen species (ROS) that activates microglia cells. Upon activation microglia cells cause the upergulation of iNOS, the enzyme involved in the production of NO. NO thus plays a key role in the neurodegeneration process implicated in PD. Thus the aim of the present manuscript is to describe the possible role of NO in PD
... However, excess production of NO, which is synthesized by the inducible NOS (iNOS), can be harmful and can trigger rheumatoid arthritis, gastritis, bowel inflammation, neuronal cell death, and bronchitis [50,51]. Macrophages produce large quantities of NO after stimulation with bacterial lipopolysaccharide (LPS), and concomitantly produced inflammatory cytokines participate in the pathogenesis of inflammatory diseases [52]. Overproduction of NO by iNOS appears to be involved in the pathogenesis of various inflammatory diseases [53]. ...
Importance of herbal medicines have recently increased owing to rising interest in their health benefits. However, medicinal plant extracts are complex mixtures of phytochemicals that act synergistically or additively on specific and/or multiple molecular and cellular targets. Thus, it is difficult to examine the actual pharmacological roles of active compounds in plant extracts. This review describes a new strategy for isolating target compounds from plant extracts using immunoaffinity columns coupled with monoclonal antibodies (mAbs) against natural compounds. Through one-step purification using mAb-coupled immunoaffinity columns, we succeeded in preparing a knockout (KO) extract, which contains all components except the target compound. Furthermore, we investigated the pharmacological effects of the KO extract to reveal the actual effects of a bioactive compound in the crude extract. This approach may help determine the potential function of target compounds in herbal medicines.
... NO, a bioactive free radical which is one of the critical reactive nitrogen intermediates produced by inducible NO synthase (iNOS) in inflammatory macrophages when stimulated by bacterial membrane components, LPS, and cytokines (Knowles & Moncada, 1994), is an important component of the innate immune system. High-output NO by iNOS has been reported to provoke inflammatory response (Blantz & Munger, 2002). In this study, TCE is reported to inhibit the nitrite production. ...
Terminalia chebula, traditionally regarded as universal panacea, is known for its pleiotropic effects, including the effects on oxidative stress, malignant tumor growth, wound healing, and insulin sensitivity in Type 2 diabetes. This study reports the effect of dry fruit extract of T. chebula (TCE) on Th1/Th2-mediated immune responses in mice. TCE was administered orally for 10 consecutive days, after which mice were immunized with goat RBC (gRBC) or ovalbumin. TCE enhanced the expression of Th1 cytokine, interferon γ, decreased interleukin 4, and increased the number of plaque-forming cells in gRBC-immunized mice. The percentage of CD4+ cells and delayed-type hypersensitivity response also increased in these mice. Treatment is reported to increase lymphocyte proliferation and macrophage phagocyte response, but decrease nitrite production. The bone marrow cellularity and WBC count also increased in the treated mice. None of the group showed any sign of toxicity. The data indicate that TCE elicits a significant dose-dependent Th1 response.
... A NO a vesében fiziológiás körülmények között részt vesz a tubuláris Na +transzport, a tubulo-glomeruláris feedback szabályozásában és szerephez jut számos patofiziológiai folyamatban is (38). A NO szintézis gátlása a vesében a pre-és posztglomeruláris ellenállás, valamint a glomeruláris kapilláris nyomás emelkedéséhez vezet, miközben a glomeruláris filtrációs ráta (GFR) nem változik számottevően (39). ...
... For example, tyrosine nitration has been detected under physiological conditions in most organ systems and in a number of cellular models. Furthermore, accumulating data support a strong link between protein tyrosine nitration and the activation of signaling pathways in a variety of cellular responses and pathological conditions, including the cellular response to irradiation, acute and chronic inflammation, graft rejection, chronic hypoxia, tumor vascularization and the microenvironment, atherosclerosis, myocardial infarction, chronic obstructive pulmonary disease, diabetes, Parkinson disease, and Alzheimer disease (MacMillan-Crow et al. 1996;Giasson et al. 2000;Blantz and Munger 2002;Reynolds et al. 2005;Pacher et al. 2007;Reynolds et al. 2007;Donnini et al. 2008;Naito et al. 2008;Reyes et al. 2008;Upmacis 2008;Jones et al. 2009;Koeck et al. 2009;Pieper et al. 2009;Smith 2009;Brindicci et al. 2010;Kang et al. 2010;Pavlides et al. 2010;Zhang et al. 2010). ...
Molecular and epidemiological evidence has established important roles for reactive oxygen/reactive nitrogen species (ROS/RNS) in tumor cells, supporting stromal cells and infiltrating leukocytes in tumor initiation and progression. RNS-dependent posttranslational protein modifications (tyrosine nitration and S-nitrosylation) are well-accepted markers of the tissue inflammation, but also modulate the functions of proteins critical in carcinogenesis and tumor growth. Normal tissues utilize predominantly the stable free radical NO• in their signaling pathways, whereas tumor tissues appear to thrive under conditions of elevated RNS other than NO•. As a consequence, different downstream pathways can be modulated upon stimulation of nitric oxide synthase (NOS) activity. This switching mechanism may account for the different responses of normal and tumor tissues to an inflammatory environment and explain why NOS activity is cytoprotective for tumor cells.
The hallmarks of cancer comprise biological capabilities acquired during tumor progression and that facilitate tumor evolution and ultimately survival. A recent review by Hanahan and Weinberg updates the list of hallmarks to include sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, activating invasion and metastasis, genome instability, inflammation, reprogramming of energy metabolism, and evading immune destruction (Hanahan and Weinberg, 2011). An important question is whether these hallmarks are relatively independent or can influence the activities of each over. This chapter describes how inflammation modulates the other hallmarks by RNS-dependent posttranslational protein modifications.
... Inducible nitric oxide synthase (iNOS), which is induced in stimulated macrophages, neutrophils, endothelial and smooth muscle cells, catalyzes large amounts of NO production. It is believed that long-term exposure to such a high concentration of nitric oxide is associated with inflammatory diseases such as rheumatoid arthritis, atherosclerosis, inflammatory bowel disease, septic shock and glomerulonephritis (Bingham, 2002;Blantz & Munger, 2002;Dusting, 1996;Knowles & Moncada, 1994;Perner & Rask-Madsen, 1999;Wong & Billiar, 1995). In addition to iNOS, cyclooxygenase 2 (COX-2) can also be induced by cytokines, bacterial endotoxins, growth factors, and phorbol esters (Smith, DeWitt, & Garavito, 2000) and it subsequently catalyzes a large amount of prostaglandin E 2 (PGE 2 ) production. ...
Corchorus olitorius L. is grown in Taiwan during summer. Tender leaves are crushed and washed by running water before eating. Five fractions including crude phenolic extracts (using 80 per cent aqueous acetone) of whole plant, leaf, stem, washed leaf (WL) and dried water washing material (WW) were used in this study. Linoleic acid autoxidation inhibitions on all fractions were higher than that on α-tocopherol. Except for WL and WW, other fractions also showed DPPH radical scavenging efficiency. The effect of all fractions on the regulation of inflammatory responses in lipopolysaccharide (LPS)-stimulated J774A.1 macrophage cells was investigated. All fractions diminished LPS-induced protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2). Nitric oxide (NO) and prostaglandin E2 (PGE(2)), downstream products, were also suppressed in dose-dependent manners, except for WL and WW. Oxidative modification and loss of leaf phenolics after kneading and washing greatly affected DPPH radical scavenging and inflammatory responses.
... Kidney International (2007) 71, 1215-1222 serum-induced glomerulonephritis or autoimmune tubular interstitial nephritis. 39 Statins also protect against the oxidation of LDL and thereby reduce oxidative stress. 35,36 The antioxidant effects of statins enhance endothelial function and support normal vascular reactivity. ...
During the last two decades, numerous studies have demonstrated that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) diminish the risk of cardiovascular morbidity and mortality. Although these studies have focused primarily on the ability of statins to lower circulating levels of low-density lipoprotein cholesterol, more recent research has shown that statins may protect the vasculature via pleiotropic effects not directly related to lipid lowering. These include adjustments in cell-signaling pathways that play a role in atherogenesis and that affect the expression of inflammatory elements, curtail oxidative stress, and enhance endothelial function. More recently, researchers have begun to explore whether these agents exert similar beneficial effects in renal parenchymal and renovascular disease. This review examines the available evidence that dyslipidemia may augment the inflammatory reaction of cytokines in patients with renal disease and that statins may improve renal dysfunction by altering the response of the kidney to dyslipidemia, even in persons with end-stage renal disease on dialysis or with renal transplantation. In this context, some data suggest that statin-mediated alterations in inflammatory responses and endothelial function may reduce proteinuria and the rate of progression of kidney disease.Keywords: dyslipidemia, kidney disease, proteinuria, statins
The phytochemical investigation on the methanol extract of the rhizomes of Atractylodes macrocephala resulted in the discovery of one new compound 9α-hydroxyatractylenolide ( 1 ) and 21 known compounds including atractylone ( 2 ), 3β-acetoxyatractylon ( 3 ), atractylenolide I ( 4 ), atractylenolide II ( 5 ), 8-epiasterolid ( 6 ), atractylenolide III ( 7 ), atractylenolide VII ( 8 ), 8-epiatractylenolide III ( 9 ), eudesm-4(15)-ene-7α,11-diol ( 10 ), linoleic acid ( 11 ), myristic acid ( 12 ), 3- O -caffeoyl-1-methyquinic acid ( 13 ), (2E,8E,10E)-tetradecatriene-4,6-diyne-1,14-diol ( 14 ), 14-aceroxy-12-senecioyloxytetradeca-2E,8Z,10E-trien-4,6-diyn-1-ol ( 15 ), isoscopoletin ( 16 ), caffeic acid ( 17 ), protocatechic acid ( 18 ), 3- O -caffeoylquinic acid ( 19 ), 4- O -caffeoylquinic acid ( 20 ), 1,5-di- O -caffeoylquinic acid ( 21 ), and nicotinic acid ( 22 ). Their structures were identified using nuclear magnetic resonance (NMR) and mass spectroscopy, and by comparison with previously published data. Compounds 4 , 5 , 6 , 8 , and 10 – 22 significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages, and compounds 4 , 5 , 6 , 16 , and 17 showed those responses in BV2 microglial cells. Especially, compound 6 showed the second-best effect, and inhibited the LPS-induced production of prostaglandin E2 (PGE 2 ), the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and the production of cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in both cells. These inhibitory effects were mediated by the inactivation of nuclear factor kappa B (NF-κB) signaling pathway.
Ribonucleotide reductase (RNR) is a multi-subunit enzyme responsible for catalyzing the rate-limiting step in the production of deoxyribonucleotides essential for DNA synthesis and repair. The active RNR complex is composed of multimeric R1 and R2 subunits. The RNR catalysis involves the formation of tyrosyl radicals in R2 subunits and thiyl radicals in R1 subunits. Despite the quarternary structure and cofactor diversity, all the three classes of RNR have a conserved cysteine residue at the active site which is converted into a thiyl radical that initiates the substrate turnover, suggesting that the catalytic mechanism is somewhat similar for all three classes of the RNR enzyme. Increased RNR activity has been associated with malignant transformation, cancer cell growth, and tumorigenesis. Efforts concerning the understanding of RNR inhibition in designing potent RNR inhibitors/drugs as well as developing novel approaches for antibacterial, antiviral treatments, and cancer therapeutics with improved radiosensitization have been made in clinical research. This review highlights the precise and potent roles of NO in RNR inhibition by targeting both the subunits. Under nitrosative stress, the thiols of the R1 subunits have been found to be modified by S-nitrosylation and the tyrosyl radicals of the R2 subunits have been modified by nitration. In view of the recent advances and progresses in the field of nitrosative modifications and its fundamental role in signaling with implications in health and diseases, the present article focuses on the regulations of RNR activity by S-nitrosylation of thiols (R1 subunits) and nitration of tyrosyl residues (R2 subunits) which will further help in developing design new drugs and therapies.
Diabetic nephropathy is a microvascular complication of diabetes. Its etiology involves metabolic disorder-induced endothelial dysfunction. Endothelium-derived nitric oxide (NO) plays an important role in a number of physiological processes, including glomerular filtration and endothelial protection. NO dysregulation is an important pathogenic basis of diabetic nephropathy. Hyperglycemia and dyslipidemia can lead to oxidative stress, chronic inflammation and insulin resistance, thus affecting NO homeostasis regulated by endothelial nitric oxide synthase (eNOS) and a conglomerate of related proteins and factors. The reaction of NO and superoxide (O2.-) to form peroxynitrite (ONOO-) is the most important pathological NO pathway in diabetic nephropathy. ONOO- is a hyper-reactive oxidant and nitrating agent in vivo which can cause the uncoupling of eNOS. The uncoupled eNOS does not produce NO but produces superoxide. Thus, eNOS uncoupling is a critical contributor of NO dysregulation. Understanding the regulatory mechanism of NO and the effects of various pathological conditions on it could reveal the pathophysiology of diabetic nephropathy, potential drug targets and mechanisms of action. We believe that increasing the stability and activity of eNOS dimers, promoting NO synthesis and increasing NO/ONOO- ratio could guide the development of drugs to treat diabetic nephropathy. We will illustrate these actions with some clinically used drugs as examples in the present review.
The phytochemical investigation on the methanol extract of the rhizomes of Atractylodes macrocephala resulted in the discovery of one new compound 9α-hydroxyatractylenolide ( 1 ) and 21 known compounds including atractylone ( 2 ), 3β-acetoxyatractylon ( 3 ), atractylenolide I ( 4 ), atractylenolide II ( 5 ), 8-epiasterolid (6), atractylenolide III ( 7 ), atractylenolide VII ( 8 ), 8-epiatractylenolide III ( 9 ), eudesm-4(15)-ene-7α,11-diol ( 10 ), linoleic acid ( 11 ), myristic acid ( 12 ), 3- O -caffeoyl-1-methyquinic acid ( 13 ), (2 E ,8 E ,10 E )-tetradecatriene-4,6-diyne-1,14-diol ( 14 ), 14-aceroxy-12-senecioyloxytetradeca-2 E ,8 Z ,10 E -trien-4,6-diyn-1-ol ( 15 ), isoscopoletin ( 16 ), caffeic acid ( 17 ), protocatechic acid ( 18 ), 3- O -caffeoylquinic acid ( 19 ), 4- O -caffeoylquinic acid ( 20 ), 1,5-di- O -caffeoylquinic acid ( 21 ), and nicotinic acid ( 22 ). Their structures were identified using nuclear magnetic resonance (NMR) and mass spectroscopy, and by comparison with previously published data. Compounds 4 , 5 , 6 , 8 , and 10 – 22 significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages, and compounds 4 , 5 , 6 , 16 , and 17 showed those responses in BV2 microglial cells. Especially, compound 6 showed the second-best effect, and inhibited the LPS-induced production of prostaglandin E2 (PGE 2 ), the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and the production of cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in both cells. These inhibitory effects were mediated by the inactivation of nuclear factor kappa B (NF-κB) signaling pathway.
The immune system is an evolutionary hallmark of higher organisms that defends the host against invading pathogens and exogenous infections. This defense includes the recruitment of immune cells to the site of infection and the initiation of an inflammatory response to contain and eliminate pathogens. However, an inflammatory response may also be triggered by noninfectious stimuli such as major surgery, and, in case of an overshooting, still not comprehensively understood reaction, lead to tissue destruction and organ dysfunction. Unfortunately, in some cases, the immune system may not effectively distinguish between stimuli elicited by major surgery, which ideally should only require a modest inflammatory response, and those elicited by trauma or pathogenic infection. Surgical procedures thus represent a potential trigger for systemic inflammation that causes the secretion of proinflammatory cytokines, endothelial dysfunction, glycocalyx damage, activation of neutrophils, and ultimately tissue and multisystem organ destruction. In this review, we discuss and summarize currently available mechanistic knowledge on surgery-associated systemic inflammation, demarcation toward other inflammatory complications, and possible therapeutic options. These options depend on uncovering the underlying mechanisms and could include pharmacologic agents, remote ischemic preconditioning protocols, cytokine blockade or clearance, and optimization of surgical procedures, anesthetic regimens, and perioperative inflammatory diagnostic assessment. Currently, a large gap between basic science and clinically confirmed data exists due to a limited evidence base of translational studies. We thus summarize important steps toward the understanding of the precise time- and space-regulated processes in systemic perioperative inflammation.
Context Litsea cubeba (Lour.) Pers. (Lauraceae) has long been used as a folk remedy in Traditional Chinese Medicine (TCM) for the treatment of rheumatic diseases. Previous studies from our laboratory indicated that L. cubeba extract showed anti-arthritic activity in rats.
Objective To study L. cubeba chemically and biologically and to find the potential constituents responsible for its anti-arthritic effect.
Materials and methods The compounds were isolated from the root of L. cubeba by column chromatography which eluted with PE:EtOAc gradient system, and the structures were elucidated by detailed spectroscopic data analysis; the anti-inflammatory activity of the isolated compounds was evaluated by lipopolysaccharide (LPS)-induced RAW 264.7 cells and the TNF-α and NO level were measured by ELISA (commercial kit); The iNOS and COX-2 mRNA expression were measured by RT-PCR and the phosphorylation of IκBα, IKKβ, P38 and Akt were determined by western blots.
Results A novel 9-fluorenone, 1-ethoxy-3,7-dihydroxy-4,6-dimethoxy-9-fluorenone (1), together with 4 known compounds, namely pinoresinol (2), syringaresinol (3), 9,9′-O-di-(E)-feruloyl-meso-5,5′-dimethoxysecoisolariciresinol (4) and lyoniresinol (5) were isolated from the root of L. cubeba for the first time. The IC50 for NO inhibition on compounds 1 and 4 were 56.1 ± 1.2 and 32.8 ± 2.3 μM, respectively. The IC50 for TNF-α inhibition were 28.2 ± 0.9 and 15.0 ± 1.0 μM, respectively. Both 1 and 4 suppress mRNA expression of iNOS, COX-2 and protein phosphorylation of IκBα, IKKβ in LPS-induced RAW 264.7 cells.
Discussion and conclusion Compounds 1 and 4 isolated from L. cubeba exhibited potent anti-inflammatory activity through the NF-κB signal pathway.
3-hydroxy-3-methylglutaryl (HMG)-CoA reductase is a rate-limiting enzyme of the mevalonate pathway for cholesterol synthesis. Statins inhibit this enzyme, thus having functions for lowering cholesterol. There is also a growing body of evidence that statins have pleiotropic effects, independent of lowering cholesterol. These pleiotropic effects are partly exerted by inhibiting synthesis of isoprenoids, which are downstream molecules of the mevalonate pathway, involved in the activation of small GTPases that eventually modulate an intracellular signal cascade. These effects include: (i) anti-atherosclerosis and plaque stabilizating effects by inhibiting various steps of athelogenic and plaque formation cascades; (ii) inhibiting inflammation, which plays a pivotal role in the pathogenesis of atherosclerosis; (iii) neovascularizing or increasing blood flow in ischemic tissue, leading to cardio- and neuroprotective effects and subsequent improvements of vascular dementia; (iv) favorable effects on such neurodegenerative diseases as Alzheimer disease and Parkinson disease; (v) improving bone health through stimulation of bone formation and osteoclast inhibition ; (vi) improving renal dysfunction and preventing the progression of chronic kidney diseases; and finally (vii) negative or at least neutral effects on the development of some kinds of cancers. This chapter highlights current knowledge on the potential mechanisms for statin-mediated pleiotropic effects. Since these pleiotropic effects are significant on the aging-related or lifestyle-related diseases which have increasingly attracted global health concern, e.g. metabolic, neurological, and neoplastic diseases, this chapter will help researchers to develop new treatment strategies that incorporate statins as comprehensively effective agents, ultimately leading to prevent or regress such diseases.
This chapter provides an overview of the scope and diversity of approximately 60 genes that contribute to the ovulatory process. Most of the genes have been directly or indirectly associated with acute inflammatory reactions and the references are specifically selected in an effort to characterize the role of each gene in inflammation. The various genes are discussed in terms of their contributions to (1) an immediate early gene response that initiates an inflammatory reaction, (2) pro-inflammatory events that lead to proteolytic degradation of ovulatory follicles, (3) endogenous anti-inflammatory activity that promotes healing and repair of the traumatized ovary, and (4) protection of the tissue from oxidative stress that is generated locally during the ovulatory process. In addition, this chapter considers ovarian steroidogenesis and angiogenesis that occur during the transition of an ovulatory follicle into a metabolically active corpus luteum. Collectively, this overview of ovarian gene expression makes it clear that the molecular and biochemical events of ovulation are far more complicated than was imagined only a decade ago. It also appears that only a fraction of the entire complement of ovulation-related genes has been discovered thus far.
In humans, the free radical nitric oxide (NO·) is a concentration-dependent multifunctional signaling or toxic molecule that modulates various physiological and pathological processes, and innate immunity against bacterial infections. Because the expression of bacterial genes encoding nitrite reductase (AniA) and NO· reductase (NorB) is highly upregulated in biofilms in vitro, it is important to investigate whether bacterial NO·-metabolism might subvert host NO· signaling and play pathogenic roles during infection. The Moraxella catarrhalis AniA and NorB directly function in production and reduction of NO∙. Using M. catarrhalis-human bronchial epithelial cell (HBEC) co-cultures, we recently reported AniA/nitrite-dependent cytotoxic effects on HBECs, including altered protein profiles of HBECs and induced HBEC apoptosis, suggesting bacterial nitrite reduction likely dysregulates host cell gene expression. To further clarify whether nitrite reduction-derived NO∙ or nitrite-dependent stimulation of bacterial growth was responsible for adverse effects on HBECs, we monitored bacterial nitrite reduction, levels of NO· in co-cultures and resulted dynamic effects on HBEC proliferation and bacterial viability. This study demonstrated that M. catarrhalis nitrite reduction-derived NO· was responsible for observed adverse effects on HBECs at mid-to-late stages of infection. More importantly, our data showed that while nitrite promoted bacterial growth and biofilm formation at early hours of infection, nitrite reduction-derived NO∙ was toxic towards M. catarrhalis in maturing biofilms, suggesting nitrite reduction-derived NO∙ might be a possible dualistic mechanism by which M. catarrhalis promotes diseases and spontaneous resolutions.
This chapter provides an overview of ovulation-a complicated path of molecular events initiated when luteinizing hormone (LH) couples with LH/human chorionic gonadotropin (hCG) receptors located in the membranes of granulosa cells as well as theca cells of mature ovarian follicles. These G-protein-coupled receptors operate through cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling pathways to induce the expression of a repertoire of genes in granulosa cells that are associated with the up-regulation of inflammatory cytokines such as IL-1β, IL-6, and TNF-α. Within this inflammatory blitz of up-regulated gene expression is the inducible form of cyclooxygenase, namely COX-2, which catalyzes the conversion of arachidonic acid into several prostanoids including the vasodilatory prostaglandin E2. One known, critical site of prostaglandin E2 (PGE2) action occurs during cell-enclosed oocyte complex (COC) expansion where this prostaglandin induces TSG-6, a factor that is obligatory for stabilizing the extracellular hyaluronan-rich COC matrix. A possible additional consequence of the biological action of prostaglandins is the hyperemic response that occurs during the first hours of the ovulatory process.
Two new rare 8-methylbenzo[h]coumarins, muralatins A and B (1, 2), nine new C-8-substituted coumarins, muralatins C-K (3-11), and 22 known analogues (12-33) were isolated from the leaves of Murraya alata. The absolute configurations of compounds 5, 11, 23, 24, 27, 30, and 33 were assigned via comparison of their specific rotations, by Mosher's method, and by single-crystal X-ray diffraction and electronic circular dichroism (ECD) data of the in situ formed transition metal complexes. A putative biosynthesis pathway to 1 and 2 is proposed, and the chemical synthesis of 1 was accomplished through electrocyclization of 5,7-dimethoxy-8-[(Z)-3-methylbut-1,3-dienyl)]coumarin (12). Compounds 1, 2, 8, 12, and 31 showed inhibition of nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophages with IC50 values of 6.0-14.5 μM.
In the continuous search for new antiinflammatory agents from natural products, dichloromethane (DCM), ethyl acetate (EtOAc) and methanol (MeOH) extracts of Ipomea fistulosa leaves were evaluated for inhibition of production of nitric oxide (NO), interleukin 1beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in lipopolysaccharide (LPS) stimulated J774A.1 cells. Among the tested extracts, the ethyl acetate (EtOAc) extract was found to be most active and activity based fractionation of this extract by column chromatography led to the identification of seven compounds for the first time from this plant. Furthermore, 3,4-dimethoxy cinnamic acid (1) exhibited two folds more potent inhibition of LPS-induced NO production (IC50 = 10.7 μg/mL) as compared with the standard, L-NAME (IC50 = 19.8 μg/mL). The present study supports the use of Ipomea fistulosa leaves for the treatment of inflammation.
Inflammatory bowel disease (IBD) is debilitating chronic inflammatory disorder of the intestine. The interactions between enteric bacteria and genetic susceptibilities are major contributors of IBD etiology. Though genetic variants with loss or gain of NOD2 functions have been linked to IBD susceptibility, the mechanisms coordinating NOD2 downstream signaling, especially in macrophages, during IBD pathogenesis is not precisely identified. Here, studies utilizing murine DSS model of colitis revealed the crucial roles for iNOS in regulating pathophysiology of IBDs. Importantly, stimulation of NOD2 failed to activate sonic hedgehog (SHH) signaling in iNOS null macrophages implicating NO mediated cross-talk between NOD2 and SHH signaling. NOD2 signaling upregulated the expression of a NO responsive microRNA, miR-146a, that targeted NUMB gene and alleviated the suppression of SHH signaling. In-vivo and ex-vivo studies confirmed the important roles for miR-146a in amplifying inflammatory responses. Collectively, we have identified new roles for miR-146a that established novel cross-talk between NOD2-SHH signaling during gut inflammation. Potential implications of these observations in therapeutics could increase the possibility of defining and developing better regime to treat IBD pathophysiology.
Nasal and oral corticosteroid therapy is the ultimate treatment for sinonasal polyposis. Although there are numerous clinical studies regarding the factors associated with the formation of nasal polyposis, there is not enough literature on how these factors are influenced by steroid treatment. Twenty-one patients that had no prior medical therapy for nasal polyposis or had received medical therapy at least 6 months earlier were included in the study. Patients were treated with oral and nasal corticosteroid therapy. Nasal polyp biopsies were taken before and after medical treatment and immunohistochemical staining for cyclooxygenase 2 (COX-2), vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS) were applied to the specimens. In this study, we tried to demonstrate the effects of corticosteroid therapy on nasal polyposis tissue immunohistochemically. There was no change at immunohistochemical expression level of COX-2; however, the decline of immunohistochemical expression levels of VEGF and iNOS was statistically significant. Short-term steroid therapy does not affect COX-2 level of the nasal polyposis tissue, but has an influence on iNOS and VEGF levels. Our findings were harmonious with those of the previous studies of the literature. Further studies are needed to demonstrate the long-term effects with a larger patient group.
We have been studying the occurrence of low velocity detonations (LVI) in several liquid explosives. A hypothesis based on shock wave interactions and Mach reflections was proposed to explain the initiation and propagation of LVD. Using the card gap test we found general experimental agreement with this hypothesis. However, certain anomalous effects were noted. In addition, we developed a method to study the internal wave structure of a shocked liquid. This technique was applied to a liquid that sustains LVD and to one that does not. A comparison of these liquids shows that the reaction zone in a liquid explosive undergoing LVD is consistent with the Mach zone hypothesis.
The anomalous effects noted during gap testing were subjected to a photographic study using a high speed framing camera. The results of this study showed that mechanisms other than that explainable by the Mach zone hypothesis were also responsible for LVD initiation. These were wave reflections from witness plates for high sound speed-high strength confinement and donor air shock initiation for lead (low sound speed-low strength) confinement. We conclude that there appears to be no unique mechanism for LVD and that each mechanism proposed so far explains some of the observations.
Statins reduce serum cholesterol and cardiovascular morbidity and mortality. The mechanisms for these beneficial effects are reviewed. Altered inflammatory responses and improved endothelial function mediated by statins are thought to be partly responsible for the reduction of morbidity and mortality as a result of cardiovascular events. In analogy, whether statins confer similar benefits on the kidney has not been established. This review critically considers the available data whereby dyslipidemia mediates renal dysfunction by modulating the inflammatory response to diverse cytokines. Also reviewed is the emerging database indicating that statins may modulate renal function by altering the response of the kidney to dyslipidemia.
ABSTRACT Edible Mushroom is a profilic source of bioactive metabolites for the development of drugs and nutraceuticals. In this work, four new monoterpenoids (1-4) and one new sesquiterpenoid (6) were isolated from the mycelia of the edible mushroom Pleurotus cornucopiae fermented on rice. Their structures were established by NMR, MS, and CD data analysis. Compound 1 possesses an unusual spiro[benzofuran-3,2'-oxiran] skeleton. The absolute configuration of the 6,7-diol moieties in 1, 2, and 6 was assigned by using the in situ dimolybdenum CD method. Compounds 1-5, 7, and 8 showed moderate inhibitory activity against nitric oxide production in lipopolysaccaride-activated macrophages with IC50 value in the range of 60-90 µM. Compounds 6 and 7 also exhibited slight cytotoxicity against Hela and HepG2 cells.
An unusual dimeric guaianolide, artemilinin A (1) and a sesquiterpene-monoterpene lactone, isoartemisolide (2), were isolated from the leaves of Artemisia argyi. Their structures were elucidated on the basis of extensive spectroscopic analysis (IR, HR-ESIMS, 1D- and 2D- NMR), and the absolute configurations were determined by CD spectra and quantum chemical ECD calculation. Furthermore, in in vitro assay, compound 2 exhibited pronounced inhibition on the lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells with an IC(50) value of 4.00μM.
Endotoxemic shock is a systemic inflammatory response that is associated with increased nitric oxide (NO) production by inducible NO synthase (iNOS) which contributes to hypotension, vascular hyporeactivity, and multiple organ failure. Oxidative stress (OS) is a major contributing factor to high morbidity and mortality in endotoxemic shock. We have previously demonstrated that endotoxin-induced fall in blood pressure is associated with an increase in nitrite levels in serum, kidney, heart, thoracic aorta (TA), and superior mesenteric artery (SMA), a decrease in malondialdehyde (MDA) levels in the kidney, heart, TA, and SMA, and an increase in myeloperoxidase (MPO) activity in the heart and TA, but a decrease in the kidney and SMA of rats. In this study, we further investigated whether increased production of iNOS-derived NO contributes to endotoxin induced changes in the biomarkers of OS in the liver, lungs, brain, spleen, and femoral artery (FA) of rats. Endotoxin-induced increase in nitrite production was associated with a decrease in reduced glutathione levels in the liver, lungs, brain, spleen, and FA. MPO activity was increased by endotoxin in the lungs, spleen, and FA, but decreased in the liver and brain. MDA levels were increased by endotoxin in the lungs, brain, spleen, and FA, but were decreased in the liver. Activities of superoxide dismutase and catalase were decreased in the liver and spleen, but were increased in the lungs, brain, and FA. These effects of endotoxin were prevented by a selective iNOS inhibitor, phenylene-1,3-bis[ethane-2-isothiourea] dihydrobromide. These data suggest that iNOS-derived NO mediates selective organ-specific effects of endotoxin on OS.
Background:
Polygonum viviparum L. (PV) is a member of the family Polygonaceae and is widely distributed in high-elevation areas. It is used as a folk remedy to treat inflammation-related diseases. This study was focused on the anti-inflammatory response of PV against lipopolysaccharide (LPS)-induced inflammation in RAW264.7 macrophages.
Results:
Treatment with PV did not cause cytotoxicity at 0-50 µg mL(-1) in RAW264.7 macrophages, and the IC(50) value was 270 µg mL(-1). PV inhibited LPS-stimulated nitric oxide (NO), prostaglandin (PG)E(2) , interleukin (IL)-1β and tumour necrosis factor (TNF)-α release and inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 protein expression. In addition, PV suppressed the LPS-induced p65 expression of nuclear factor (NF)-κB, which is associated with the inhibition of IκB-α degradation. These results suggest that, among mechanisms of the anti-inflammatory response, PV inhibits the production of NO and these cytokines by down-regulating iNOS and COX-2 gene expression. Furthermore, PV can induce haem oxygenase (HO)-1 protein expression through nuclear factor E2-related factor 2 (Nrf2) activation. A specific inhibitor of HO-1, zinc(II) protoporphyrin IX, inhibited the suppression of iNOS and COX-2 expression by PV.
Conclusion:
These results suggest that PV possesses anti-inflammatory actions in macrophages and works through a novel mechanism involving Nrf2 actions and HO-1. Thus PV could be considered for application as a potential therapeutic approach for inflammation-associated disorders.
Sepsis is a systemic inflammatory response syndrome with a suspected or proven infection caused by any pathogen or a clinical syndrome associated with a high probability of infection. The definition of septic shock includes sepsis-induced hypotension despite adequate fluid resuscitation, along with the presence of organ perfusion abnormalities, and ultimately cell dysfunction. As the most common causes of morbidity and mortality in intensive care units worldwide, the societal and economic costs of sepsis and septic shock are staggering. The molecular pathophysiology of sepsis and septic shock and the complex roles played by cytokines, reactive oxygen and nitrogen species, and eicosanoids remain controversal despite decades of study. The lipid A part of lipopolysaccharide, also known as endotoxin, is the most potent microbial mediator of the pathogenesis of sepsis and septic shock. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a vasoconstrictor ω-hydroxylation product of arachidonic acid that is produced by cytochrome P450 (CYP) enzymes, mainly by CYP4A and CYP4F isoforms. Studies from our laboratory and others have provided substantial evidence that administration of a synthetic analog of 20-HETE, N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine, prevents endotox-ininduced vascular hyporeactivity, hypotension, and mortality associated with increased formation of inducible nitric oxide synthase-derived nitric oxide (NO) and cyclooxygenase-2-derived vasodilator prostanoids as well as decreased expression and activity of CYP4A1 and 20-HETE production in a rodent model of septic shock. CYP4A- and CYP4F-derived 20- HETE is also a proinflammatory mediator of endotoxin-induced acute systemic inflammation. In this review, we will present an overview of our current understanding of the interactions between prostanoids, NO, and 20-HETE in sepsis, and provide a rationale for the development of synthetic 20-HETE analogs for the treatment of sepsis and septic shock.
Violaxanthin is a major carotenoid of microalgae Chlorella ellipsoidea and is also found in dark-green leafy vegetables, such as spinach. In this study, the anti-inflammatory effect of violaxanthin isolated from C. ellipsoidea was examined using lipopolysaccharide (LPS)-stimulated RAW 264.7 mouse macrophage cells. In addition, the anti-inflammatory activity and mechanism of action of purified violaxanthin was assessed using various assays, such as quantitative real-time polymerase chain reaction (PCR), Western blotting, and electrophoretic-mobility shift assay (EMSA). The results of this combined analysis revealed that violaxanthin significantly inhibited nitric oxide (NO) and the prostaglandin E₂ (PGE₂). Interestingly, violaxanthin effectively inhibited LPS-mediated nuclear factor-κB (NF-κB) p65 subunit translocation into the nucleus, suggesting that the violaxanthin anti-inflammatory activity may be based on inhibition of the NF-κB pathways. In conclusion, violaxanthin of C. ellipsoidea holds promise for use as a potential anti-inflammatory agent for either therapeutic or functional adjuvant purposes.
In mammalian cells, nitric oxide (NO·) is an important signal molecule with concentration-dependent and often controversial functions of promoting cell survival and inducing cell death. An inducible nitric oxide synthase (iNOS) in various mammalian cells produces higher levels of NO· from l-arginine upon infections to eliminate pathogens. In this study, we reveal novel pathogenic roles of NO· generated by bacteria in bacterium-host cell cocultures using Moraxella catarrhalis, a respiratory tract disease-causing bacterium, as a biological producer of NO·. We recently demonstrated that M. catarrhalis cells that express the nitrite reductase (AniA protein) can produce NO· by reducing nitrite. Our study suggests that, in the presence of pathophysiological levels of nitrite, this opportunistic pathogen hijacks host cell signaling and modulates host gene expression through its ability to produce NO· from nitrite. Bacterium-generated NO· significantly increases the secretion of tumor necrosis factor alpha (TNF-α) and modulates the expression of apoptotic proteins, therefore triggering host cell programmed death partially through TNF-α signaling. Furthermore, our study reveals that bacterium-generated NO· stalls host cell division and directly results in the death of dividing cells by reducing the levels of an essential regulator of cell division. This study provides unique insight into why NO· may exert more severe cytotoxic effects on fast growing cells, providing an important molecular basis for NO·-mediated pathogenesis in infections and possible therapeutic applications of NO·-releasing molecules in tumorigenesis. This study strongly suggests that bacterium-generated NO· can play important pathogenic roles during infections.
Mice deficient in inducible nitric oxide synthase (iNOS) were generated to test the idea that !NOS defends the host against infectious agents and tumor cells at the risk of contributing to tissue damage and shock. iNOS-I- mice failed to restrain the replication of Listeria monocytogenes in vivo or lymphoma cells in vitro. Bacterial endotoxic lipopolysaccharide (LPS) caused shock and death in anesthetized wild-type mice, but in iNOS-I- mice, the fall in central arterial blood pressure was markedly attenuated and early death averted. However, unanesthetized iNOS-I- mice suffered as much LPS-induced liver damage as wild type, and when primed with Propionobacterium acnes and challenged with LPS, they succumbed at the same rate as wild type. Thus, there exist both iNOS-dependent and iNOS-independent routes to LPS-Induced hypotension and death.
This study was performed to determine the influence of neuronal nitric oxide synthase (nNOS) on renal arteriolar tone under conditions of normal, interrupted, and increased volume delivery to the macula densa segment and on the microvascular responses to angiotensin II (ANG II). Experiments were performed in vitro on afferent (21.2 +/- 0.2 microns) and efferent (18.5 +/- 0.2 microns) arterioles of kidneys harvested from male Sprague-Dawley rats, using the blood-perfused juxtamedullary nephron technique. Superfusion with the specific nNOS inhibitor, S-methyl-L-thiocitrulline (L-SMTC), decreased afferent and efferent arteriolar diameters, and these decreases in arteriolar diameters were prevented by interruption of distal volume delivery by papillectomy. When 10 mM acetazolamide was added to the blood perfusate to increase volume delivery to the macula densa segment, afferent arteriolar vasoconstrictor responses to L-SMTC were enhanced, but this effect was again completely prevented after papillectomy. In contrast, the arteriolar diameter responses to the nonselective NOS inhibitor, N omega-nitro-L-arginine (L-NNA) were only attenuated by papillectomy. L-SMTC (10 microM) enhanced the efferent arteriolar vasoconstrictor response to ANG II but did not alter the afferent arteriolar vasoconstrictor responsiveness to ANG II. In contrast, L-NNA (100 microM) enhanced both afferent and efferent arteriolar vasoconstrictor responses to ANG II. These results indicate that the modulating influence of nNOS on afferent arteriolar tone of juxtamedullary nephrons is dependent on distal tubular fluid flow. Furthermore, nNOS exerts a differential modulatory action on the juxtamedullary micro-vasculature by enhancing efferent, but not afferent, arteriolar responsiveness to ANG II.
Polydisperse [3h] dextran was infused into eight Munich-Wistar rats in the early autologous phase of nephrotoxic serum nephritis (NSN), thereby permitting direct measurements of pressures and flows in surface glomeruli and fractional clearances for dextrans [(U/P) dextran/(U/P) inulin] ranging in radius from 18 to 42 A. Despite glomerular injury, evidenced morphologically and by a marked reduction in the glomerular capillary ultrafiltration coefficient, the glomerular filtration rate remained normal because of a compensating increase in the mean net ultrafiltration pressure. In NSN rats, as in normal controls, inulin was found to permeate the glomerular capillary wall without measurable restriction, and dextrans were shown to be neither secreted nor reabsorbed. For dextran radii of 18, 22, 26, 30, 34, 38, and 42 A, (U/P) dextran/(U/P) inulin in NSN and control rats, respectively, averaged 0.90 vs. 0.99, 0.81 vs. 0.97, 0.63 vs. 0.83, 0.38 vs 0.55, 0.20 vs. 0.30, 0.08 vs. 0.11, and 0.02 vs. 0.03. Using a theory based on macromolecular transport through pores, the results indicate that in NSN rats, effective pore radius is the same as in controls, approximately 50 A. In NSN, however, the ratio of total pore surface area to pore length, a measure of the number of pores, is reduced to approximately 1/3 that of control, probably due to a reduction in capillary surface area. These results suggest that proteinuria in glomerular disease is not due simply to increases in effective pore radius or number of pores, as previously believed. Using a second theoretical approach, based on the Kedem-Katchalsky flux equations, dextran permeability across glomerular capillaries was found to be slightly lower, and reflection coefficient slightly higher in NSN than in control rats.
Clinical assessment of the activity of tumor necrosis factor (TNF) against human cancer has been limited by a dose-dependent cardiovascular toxicity, most frequently hypotension. TNF is also thought to mediate the vascular collapse resulting from bacterial endotoxin. The present studies address the mechanism by which TNF causes hypotension and provide evidence for elevated production of nitric oxide, a potent vasodilator initially characterized as endothelium-derived relaxing factor. Nitric oxide is synthesized by several cell types, including endothelial cells and macrophages, from the guanidino nitrogen of L-arginine; the enzymatic pathway is competitively inhibited by NG-methyl-L-arginine. We found that hypotension induced in pentobarbital-anesthetized dogs by TNF (10 micrograms/kg, i.v., resulting in a fall in mean systemic arterial pressure from 124.7 +/- 7 to 62.0 +/- 22.9 mmHg; 1 mmHg = 133 Pa) was completely reversed within 2 min following administration of NG-methyl-L-arginine (4.4 mg/kg, i.v.). In contrast, NG-methyl-L-arginine failed to reverse the hypotensive response to an equivalent depressor dose of nitroglycerin, a compound that acts by forming nitric oxide by a nonenzymatic, arginine-independent mechanism. The effect of NG-methyl-L-arginine on TNF-induced hypotension was antagonized, and the hypotension restored, by administration of excess L-arginine (100 mg/kg, i.v.). Our findings suggest that excessive nitric oxide production mediates the hypotensive effect of TNF.
In serum sickness, mechanisms by which circulating immune complexes become localized in the walls of vessels and glomeruli have been studied. In affected arteries, morphologic observations showed that circulating marker particles of carbon would rapidly deposit along the luminal surface of the internal elastic lamina. This, as in previous studies, suggested an increase in vascular permeability during which large molecules were capable of being trapped by a filtering membrane in the vessel wall.
In attempts to prevent the increase in vascular permeability, rabbits were treated with antagonists of histamine and serotonin. Such treatment markedly inhibited the localization of immune complexes in glomeruli, the development of proteinuria, and glomerular endothelial proliferation. Cardiovascular lesions also were largely prevented from developing. Depletion of platelets, the principal reservoir of vasoactive amines, had a similar though less pronounced effect. While the deposition of immune complexes was inhibited, allergic inflammation in general was not, since normal rabbits treated as above were found capable of developing full Arthus reactions and acute nephrotoxic nephritis.
Hydrodynamic factors were noted to be important in determining the location of arterial lesions. Studies of aortas from unmodified rabbits and from those with surgically induced coarctations of the abdominal aorta revealed intimal lesions concentrated at areas of high turbulence, such as at branches, bifurcations, outflows and zones of configurational change. Lesions in these areas were also largely inhibitable by depletion of platelets or by antagonists of histamine and serotonin.
Transsexuals have the strong feeling, often from childhood onwards, of having been born the wrong sex. The possible psychogenic or biological aetiology of transsexuality has been the subject of debate for many years. Here we show that the volume of the central subdivision of the bed nucleus of the stria terminals (BSTc), a brain area that is essential for sexual behaviour, is larger in men than in women. A female-sized BSTc was found in male-to-female transsexuals. The size of the BSTc was not influenced by sex hormones in adulthood and was independent of sexual orientation. Our study is the first to show a female brain structure in genetically male transsexuals and supports the hypothesis that gender identity develops as a result of an interaction between the developing brain and sex hormones.
Nitric oxide (NO) is a biological mediator which is synthesized from L-arginine by a family of nitric oxide synthases (NOS). Previously we have shown that NO is synthesized ex vivo by glomeruli obtained from animals with acute immune complex glomerulonephritis. We have now sought evidence for the in vivo induction of NOS in glomeruli by immunohistochemistry using specific antisera raised against a peptide sequence of inducible mouse macrophage NOS and by in situ hybridization. The expression of the enzyme was studied in kidneys of rats with acute unilateral immune complex glomerulonephritis, induced by cationized IgG, by immunohistochemistry. Inducible NOS (iNOS) was present in glomeruli in nephritic (left) kidneys at the time of maximum macrophage infiltration, both within intraglomerular mononuclear cells and cells emigrating into Bowman's space. iNOS expressing cells were also present in interstitial infiltrates. There was no expression in normal rat kidneys or in glomeruli in the non-nephritic (right) kidneys of experimental rats. In situ hybridization confirmed the immunohistochemical localization. These results provide the first direct evidence for the presence and localization of inducible NOS in glomeruli and support a significant role for NO in the pathogenesis of immune complex glomerulonephritis.
To assess the functional relevance of the enhanced glomerular nitric oxide (NO) synthesis during acute nephrotoxic serum (NTS) nephritis, a NO synthesis inhibitor (NOI) NG-monomethyl-L-arginine was administered to normal (N + NOI) and acutely nephritic (NTS + NOI) Munich-Wistar rats, and systemic and glomerular hemodynamic responses were contrasted with those observed in vehicle-treated normal and nephritic (NTS) controls. Urinary protein excretion rates were equal in normal and N + NOI rats but were markedly elevated in NTS animals and further increased in NTS+NOI. NO inhibition in normal animals (normal versus N + NOI) led to reductions in glomerular plasma flow rate and the glomerular capillary ultrafiltration coefficient (Kf) and elevations in afferent and efferent arteriolar resistances and net transcapillary hydraulic pressure difference (delta P), as well as an increase in systemic arterial pressure. The increase in delta P offset the falls in glomerular plasma flow rate and Kf, and GFR was preserved. Directionally similar responses in efferent resistance occurred in NTS + NOI compared with NTS, however, afferent resistance was not further affected by NOI. Additionally, although Kf was severely depressed in the NTS group (approximately 60% versus normal), it was not further depressed by NOI treatment. Polymorphonuclear cell (PMN) infiltration/glomerulus was mildly increased in N + NOI over normal. In contrast, PMN number in NTS + NOI rats was diminished as compared with NTS.(ABSTRACT TRUNCATED AT 250 WORDS)
Until recently, conversion of arginine to agmatine by arginine decarboxylase (ADC) was considered important only in plants and bacteria. In the following, we demonstrate ADC activity in the membrane-enriched fraction of brain, liver, and kidney cortex and medulla by radiochemical assay. Diamine oxidase, an enzyme shown here to metabolize agmatine, was localized by immunohistochemistry in kidney glomeruli and other nonrenal cells. Production of labeled agmatine, citrulline, and ornithine from [3H]arginine was demonstrated and endogenous agmatine levels (10(-6)M) in plasma ultrafiltrate and kidney were measured by HPLC. Microperfusion of agmatine into renal interstitium and into the urinary space of surface glomeruli of Wistar-Frömter rats produced reversible increases in nephron filtration rate (SNGFR) and absolute proximal reabsorption (APR). Renal denervation did not alter SNGFR effects but prevented APR changes. Yohimbine (an alpha 2 antagonist) microperfusion into the urinary space produced opposite effects to that of agmatine. Microperfusion of urinary space with BU-224 (microM), a synthetic imidazoline2 (I2) agonist, duplicated agmatine effects on SNGFR but not APR whereas an I1 agonist had no effect. Agmatine effects on SNGFR and APR are not only dissociable but appear to be mediated by different mechanisms. The production and degradation of this biologically active substance derived from arginine constitutes a novel endogenous regulatory system in the kidney.
Excess NO generation plays a major role in the hypotension and systemic vasodilatation characteristic of sepsis. Yet the kidney response to sepsis is characterized by vasoconstriction resulting in renal dysfunction. We have examined the roles of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) on the renal effects of lipopolysaccharide administration by comparing the effects of specific iNOS inhibition, -N6-(1-iminoethyl)lysine (L-NIL), and 2,4-diamino6-hydroxy-pyrimidine vs. nonspecific NOS inhibitors (nitro- -arginine-methylester). cGMP responses to carbamylcholine (CCh) (stimulated, basal) and sodium nitroprusside in isolated glomeruli were used as indices of eNOS and guanylate cyclase (GC) activity, respectively. LPS significantly decreased blood pressure and GFR (112+/-4 vs. 83+/-4 mmHg; 2.66+/-0.29 vs. 0. 96+/-0.22 ml/min, P < 0.05) and inhibited the cGMP response to CCh. GC activity was reciprocally increased. L-NIL and 2, 4-diamino-6-hydroxy-pyrimidine administration prevented the decrease in GFR (2.71+/-0.28 and 3.16+/-0.18 ml/min, respectively), restored the normal response to CCh, and GC activity was normalized. In vitro application of L-NIL also restored CCh responses in LPS glomeruli. Neuronal NOS inhibitors verified that CCh responses reflected eNOS activity. L-NAME, a nonspecific inhibitor, worsened GFR (0.41+/-0.15 ml/min), a reduction that was functional and not related to glomerular thrombosis, and eliminated the CCh response. No differences were observed in eNOS mRNA expression among the experimental groups. Selective iNOS inhibition prevents reductions in GFR, whereas nonselective inhibition of NOS further decreases GFR. These findings suggest that the decrease in GFR after LPS is due to local inhibition of eNOS by iNOS, possibly via NO autoinhibition.
Nitric oxide (NO), generated by inducible NO synthase (iNOS) in migrating macrophages, is increased in glomerulonephritis. This study investigates the effect of NO inhibition on rat nephrotoxic nephritis (NTN) to clarify the role of NO production in glomerular damage. NTN was induced in Sprague Dawley rats by an injection of an anti-glomerular basement membrane (GBM) antibody. Urinary nitrite excretion and nitrite release from kidney slices (5.47 +/- 1.19 versus 2.15 +/- 0.73 nmol/mg protein, NTN versus Control, P < 0.05) were increased in NTN on day 2. Glomerular macrophage infiltration and intercellular adhesion molecule (ICAM)-1 expression increased from day 2. iNOS expression was increased in interstitial macrophages. Glomerular endothelial cell NOS (ecNOS) expression evaluated by counting immunogold particles along GBM was suppressed (0.06 +/- 0.02 versus 0.35 +/- 0.04 gold/micron GBM, P < 0.0001). Glomerular damage developed progressively. NG-nitro-L-arginine methyl ester (L-NAME), which inhibits both iNOS and ecNOS and aminoguanidine (AG), a relatively selective inhibitor for iNOS, equally suppressed nitrite in urine and renal tissue. Glomerular ICAM-1 expression and macrophage infiltration were reduced by L-NAME, but not by AG. Expression of ecNOS was significantly increased by L-NAME (0.91 +/- 0.08, P < 0.0001 versus NTN), but slightly by AG (0.18 +/- 0.04). AG significantly and L-NAME slightly attenuated the glomerular damage at day 4. In conclusion, suppression of iNOS prevents glomerular damage in the early stage of NTN. Treatment by L-NAME reduces macrophage infiltration by suppression of ICAM-1 expression, which may be explained by an increase in ecNOS expression.
Polyamines are required for entry and progression of the cell cycle. As such, augmentation of polyamine levels is essential
for cellular transformation. Polyamines are autoregulated through induction of antizyme, which represses both the rate-limiting
polyamine biosynthetic enzyme ornithine decarboxylase and cellular polyamine transport. In the present study we demonstrate
that agmatine, a metabolite of arginine via arginine decarboxylase (an arginine pathway distinct from that of the classical
polyamines), also serves the dual regulatory functions of suppressing polyamine biosynthesis and cellular polyamine uptake
through induction of antizyme. The capacity of agmatine to induce antizyme is demonstrated by: (a) an agmatine-dependent translational frameshift of antizyme mRNA to produce a full-length protein and (b) suppression of agmatine-dependent inhibitory activity by either anti-antizyme IgG or antizyme inhibitor. Furthermore, agmatine
administration depletes intracellular polyamine levels to suppress cellular proliferation in a transformed cell line. This
suppression is reversible with polyamine supplementation. We propose a novel regulatory pathway in which agmatine acts as
an antiproliferative molecule and potential tumor suppressor by restricting the cellular polyamine supply required to support
growth.
Tubuloglomerular feedback (TGF) stabilizes nephron function by causing changes in single-nephron GFR (SNGFR) to compensate for changes in late proximal flow (VLP). TGF responds within seconds and reacts over a narrow range of VLP that surrounds normal VLP. To accommodate sustained increases in VLP, TGF must reset around the new flow. We studied TGF resetting by inhibiting proximal reabsorption with benzolamide (BNZ; administered repeatedly over a 24-hour period) in Wistar-Froemter rats. BNZ acutely activates TGF, thereby reducing SNGFR. Micropuncture was performed 6-10 hours after the fourth BNZ dose, when diuresis had subsided. BNZ caused glomerular hyperfiltration, which was prevented with inhibitors of macula densa nitric oxide synthase (NOS). Because of hyperfiltration, BNZ increased VLP and distal flow, but did not affect the basal TGF stimulus (early distal salt concentration). BNZ slightly blunted normalized maximum TGF response and the basal state of TGF activation. BNZ sensitized SNGFR to reduction by S-methyl-thiocitrulline (SMTC) and caused the maximum TGF response to be strengthened by SMTC. Sensitization to type I NOS (NOS-I) blockers correlated with increased macula densa NOS-I immunoreactivity. Tubular transport measurements confirmed that BNZ affected TGF within the juxtaglomerular apparatus. During reduced proximal reabsorption, TGF resets to accommodate increased flow and SNGFR through a mechanism involving macula densa NOS.
Expression of iNOS, eNOS and peroxynitrite-modified proteins in experimental anti-MPO associated necrotizing crescentic glomerulonephritis. Nitric oxide radicals are recognized as important mediators in various physiological and pathophysiological processes. During inflammation, increased amounts of nitric oxide (NO) are produced, but it is unclear whether NO radicals are either protective or harmful. To obtain more insight into the role of NO in glomerular inflammation, we studied the temporal expression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) in conjunction with platelet aggregation, inflammatory cell influx, superoxide anion production cells, and nitrotyrosine formation in an experimental model of anti-myeloperoxidase (MPO) associated necrotizing crescentic glomerulonephritis (NCGN). Brown Norway rats were immunized with MPO in complete Freund's adjuvant (CFA) or CFA alone. After two weeks, the left kidney was perfused with a neutrophil lysosomal extract and H2O2. Rats were sacrificed at 24 hours, four days, and 10 days after perfusion. Kidney sections were stained by immunohistochemistry for eNOS, iNOS, platelets, nitrotyrosines, polymorphonuclear cells (PMN), monocytes, and T-cells. Superoxide anion producing cells were identified by enzyme cytochemistry using diaminobenzidine. Strong staining for eNOS was found in glomerular capillaries and interstitial tubular capillaries and larger vessels from non-perfused kidneys. At 24 hours after perfusion, glomerular and interstitial eNOS staining was greatly reduced, which was associated with massive platelet aggregation. At later time points, eNOS expression was absent in severely damaged glomeruli. Inducible NOS expression was found at all time points in infiltrating inflammatory cells, which by double labeling studies were identified as PMNs and monocytes. The peak in iNOS expression was observed at four days after perfusion but declined thereafter. Superoxide anion and nitrotyrosine generating cells were also found at all time points, but were most abundantly present at four days after perfusion, coinciding with the peak in iNOS expression. Double labeling experiments revealed that most nitrotyrosine generating cells also produced superoxide anions and expressed iNOS. In conclusion, these studies suggest that during the course of anti-MPO associated NCGN, loss of NO production by eNOS in conjunction with NO radical production by iNOS contribute to tissue injury. This is compatible with a protective role for eNOS contrasting with the possibly harmful effects of iNOS in anti-MPO associated NCGN.Keywords: nitric oxide radicals, anti-myeloperoxidase and crescentic GN, glomerulonephritis, peroxynitrite-modified proteins
T lymphocytes are exquisitely sensitive to the antiproliferative effects of nitric oxide. We examined the effects of oral administration of two nitric oxide synthase inhibitors, Nw-nitro-L-arginine methyl ester (L-NAME) and L-N6-(1-iminoethyl)lysine (L-NIL), on the course of T cell-dependent autoimmune interstitial nephritis in Brown Norway rats. Kidneys from rats immunized to produce interstitial nephritis display a net generation of nitric oxide end products. By immunohistochemical staining, the cytokine-inducible nitric oxide synthase (iNOS) is expressed in cortical tubular epithelial cells. Treatment with either inhibitor results in markedly more severe disease following immunization. Animals receiving L-NAME were hypertensive, while those treated with L-NIL, a highly selective inhibitor of iNOS, were not. Evaluation of the expression of IFN-gamma, IL-2, and IL-4 in diseased kidneys by quantitative reverse transcriptase-PCR demonstrated that L-NAME-treated animals displayed significantly augmented levels of IFN-gamma and IL-2 with preserved ratios of IFN-gamma/IL-4 and IL-2/IL-4, while L-NIL-treated animals had augmented levels of IL-2 and IFN-gamma with augmented IFN-gamma/IL-4 and IL-2/IL-4 ratios. Animals treated with L-NAME or L-NIL both had augmented Ag-specific IgG responses. The L-NAME group demonstrated increases in both the IgG2a and IgG1 subtypes, with a constant IgG2a/IgG1 ratio, while the L-NIL group demonstrated an increase in the ratio of the IgG2a/IgG1 response. These Ab and cytokine data suggest that the L-NIL-treated animals had a skewing of their immune response toward a Th1-like response. We conclude that in autoimmune interstitial nephritis, generation of nitric oxide through the iNOS pathway has host-protective effects, and suggest that this may be broadly applicable to T cell-mediated pathologies.
In a rat model of glomerular immune injury induced by administration of anti-glomerular basement membrane antibody and resembling human rapidly progressive glomerulonephritis, we explored whether activation of inducible nitric oxide synthase (iNOS) regulates synthesis of eicosanoids originating from cyclooxygenation or lipoxygenation of arachidonic acid. At early stages (24 hr) of injury, inhibition of iNOS using the selective inhibitor L-N6-(1-iminoethyl) lysine (L-NIL) at doses sufficient to reduce urinary excretion of nitrate/nitrite, reduced glomerular synthesis of the prostaglandins PGE2 and PGI2, but had no effect on that of thromboxane A2 (TxA2). The syntheses of 5-hydroxyeicosatetraenoic acid (HETE), 15-HETE and leukotriene B4 (LTB4) were also reduced. That of 12-HETE remained unchanged. We also explored the effect of arachidonate cyclooxygenation and lipoxygenation eicosanoids on iNOS expression. Administration of the cyclooxygenase (COX) inhibitor, indomethacin, at doses sufficient to inhibit glomerular prostaglandin synthesis, increased iNOS mRNA levels in glomeruli. Administration of the 5-lipoxygenase (5-LO) inhibitor, MK-0591, at doses sufficient to inhibit glomerular LTB4 synthesis also increased iNOS mRNA. The effect of 5-LO inhibition on iNOS expression was more pronounced than that of COX inhibition. In nephritic animals given the iNOS inhibitor, L-NIL, or indomethacin proteinuria worsened. In those given the 5-lipoxygenase inhibitor there was no change in urine protein excretion. These observations point to regulatory interactions between the arachidonic acid and the L-arginine: NO pathways in glomerulonephritis. These interactions are of importance in considering antiinflammatory strategies based on inhibition of iNOS or of specific eicosanoids.
Escherichia coli endotoxin (LPS) can induce the clinical syndrome of septic shock and renal cortical necrosis and can stimulate nitric oxide (NO) production from macrophages, vascular smooth muscle, and glomerular mesangial cells in vitro. NO is an endogenous vasodilator, which also inhibits platelet aggregation and adhesion. We therefore sought to determine whether LPS would stimulate NO production in vivo and, if so, whether this NO would modulate endotoxin-induced glomerular thrombosis. The stable NO end-products, NO2 and NO3, were measured in serum and urine collections from rats during baseline and after injection of LPS, with or without substances that modulate NO synthesis. The urinary excretion of NO2/NO3 was 1,964 +/- 311 nm/8 h during the baseline and increased to 6,833 +/- 776 nm/8 h after a single intraperitoneal injection of 0.1 mg/kg LPS (P < 0.05). The serum concentration of NO2/NO3 also significantly increased after LPS injection. Both the urine and serum stimulation was significantly prevented by the NO synthesis inhibitor, Nw-nitro-L-arginine methyl ester (L-NAME). L-Arginine, given with LPS+L-NAME significantly restored the NO2/NO3 levels in the urine. Ex vivo incubation of tissues from rats treated with LPS demonstrated NO production by the aorta, whole kidney, and glomeruli, but not cortical tubules. Histological examination of kidneys from rats given either LPS or L-NAME alone revealed that 2 and 4.5% of the glomeruli contained capillary thrombosis, respectively. In contrast, rats given LPS+L-NAME developed thrombosis in 55% of glomeruli (P < 0.001), which was significantly prevented when L-arginine was given concomitantly. We conclude that LPS stimulates endogenous production of NO in vivo and that this NO is critical in preventing LPS-induced renal thrombosis.
Systemic sepsis is associated with acute deterioration in renal function despite normal or increased cardiac output. The kidney is often structurally normal, but severe renal vasoconstriction underlies a marked decrease in the glomerular filtration rate (GFR). The mechanisms underlying renal vasoconstriction in sepsis include locally and systemically released vasoconstrictors. Novel peptide and lipid-derived mediators that have been implicated in experimental models of sepsis include endothelin (ET)-1, thromboxane A2 (TXA2), leukotrienes (LTs), and, most recently, noncyclooxygenase-derived prostaglandin F2 (PGF2) analogues. Plasma ET-1 levels are elevated in septic patients and following endotoxin administration in experimental animals; antagonism of the endogenous actions of ET-1 is associated with improvement in renal perfusion and function during experimental endotoxemia. Antagonists of the TXA2 receptor and/or TXA2 synthesis in vivo have been associated with selective improvement in renal vascular tone and preservation of GFR during experimental endotoxemia in several mammalian species. Furthermore, antagonism of the TXA2 receptor inhibits the actions of endogenously released free radical-generated PGF compounds. The latter are the most potent renal vasoconstrictors among the family of arachidonic acid derivatives. Sulfidopeptide LTs, in particular LTC4 and LTD4, are also implicated in the renal vasoconstriction that attends sepsis in rats and other experimental animals. LT hepatobiliary elimination is suppressed during sepsis and endogenous LT production is enhanced. Antagonism of LTD4 receptors is associated with amelioration of renal vasoconstriction. Taken together, these novel potential mediators of renal vasoconstriction during sepsis constitute specific molecular targets for future therapeutic interventions.
The oxygen-derived free radical superoxide anion (.O2-) plays an important role in the pathogenesis of various diseases. Recent demonstrations that .O2- inactivates the potent vasodilator endothelium-derived relaxing factor (EDRF) and that EDRF is probably nitric oxide (NO) suggest that EDRF(NO) may act as an endogenous free radical scavenger. This hypothesis was tested in an in vitro system by analyzing the effect of authentic NO (dilutions of a saturated aqueous solution) on .O2- production (detected spectrophotometrically as reduction of cytochrome c) by fMet-Leu-Phe-activated human leukocytes (PMN). NO depressed the rate of reduction of cytochrome c by .O2- released from PMN's or generated from the oxidation of hypoxanthine by xanthine oxidase. This effect was concentration-dependent and occurred at dilutions of the saturated NO solution (1:250 to 1:10) which inhibited platelet aggregation. NO had no direct effect on cytochrome c or on xanthine oxidase. These observations indicate that NO(EDRF) can be regarded as a scavenger of superoxide anion and they suggest that EDRF(NO) may provide a chemical barrier to cytotoxic free radicals (.O2-).
Sepsis and its sequelae (sepsis syndrome and septic shock) are increasingly common and are still potentially lethal diagnoses. Many mediators of the pathogenesis of sepsis have recently been described. These include tumor necrosis factor alpha (TNF alpha), interleukins, platelet activating factor, leukotrienes, thromboxane A2, and activators of the complement cascade. Neutrophil and platelet activation may also play a role. Other agents that may participate in the sepsis cascade include adhesion molecules, kinins, thrombin, myocardial depressant substance, beta-endorphin, and heat shock proteins. Endothelium-derived relaxing factor and endothelin-1 are released from the endothelium and seem to exert a regulatory effect, counterbalancing each other. A central mediator of sepsis does not seem to exist, although TNF alpha has been commonly proposed for this role. Animal studies are difficult to extrapolate to the clinical setting because of cross-species differences and variations in experimental design. Rather than being caused by any single pathogenic mechanism, it is more likely that sepsis is related to the state of activation of the target cell, the nearby presence of other mediators, and the ability of the target cell to release other mediators. Also important is the downregulation or negative feedback of these mediators or the generation of natural inflammation inhibitors, such as interleukin-4 and interleukin-8. Endothelial damage in sepsis probably results from persistent and repetitive inflammatory insults. Eventually, these insults produce sufficient damage that downregulation can no longer occur; this leads to a state of metabolic anarchy in which the body can no longer control its own inflammatory response.
The amino acid L-arginine can be metabolized through a nitric oxide-synthesizing pathway (NOSP) to produce L-citrulline and reactive nitrogen intermediates. Among these nitrogen intermediates, NO has been implicated as the mediator of a variety of biological effects including vasodilatation, inhibition of platelet aggregation, tumor cytotoxicity and microbiostasis by activated macrophages and generalized suppression of macrophage functions. Work reported here demonstrated that the NOSP is expressed in Con A-stimulated rat splenic cell (SC) cultures and is associated with a profound suppression of lymphocyte proliferation. Inhibition of the NOSP by NG-monomethyl-L-arginine (N-MMA) or binding of its products by hemoglobin, either free in solution or contained in RBC, markedly promotes rat SC mitogenic response to Con A. Mouse SC do not express the NOSP under the conditions used in these experiments. Consequently, their mitogenic response to Con A is not affected by N-MMA or hemoglobin. These data confirm and expand the apparent role of NO as a regulator of immune responses while indicating potentially important species differences.
These studies were conducted in the conscious, chronically catheterized rat to determine whether the endothelial derived relaxing factor (EDRF) controls renal function in the normal state. Administration of the EDRF synthesis inhibitors N-monomethyl-L-arginine (NMA; 100 mg/kg body weight) or N-nitro-L-arginine methylester (NAME; 10 mg/kg body wt) led to a large, sustained rise in blood pressure, a large rise in renal vascular resistance, a fall in renal plasma flow, a relatively slight reduction in glomerular filtration rate, and a consequent rise in filtration fraction. In addition, a marked natriuresis occurred because of a reduction in the fractional reabsorption of sodium. In separate studies, a continuous infusion of excess L-arginine (300 mg/kg body wt bolus followed by 50 mg/kg body wt per min) attenuated the NMA- or NAME-induced rise in blood pressure and reversed the renal hemodynamic effects such that a significant rise in renal plasma flow was seen. L-Arginine alone produced a selective renal vasodilation and large increases in sodium excretion. These observations support earlier suggestions that tonic release of EDRF controls the basal blood pressure and also show that renal function in the normal unstressed rat is markedly influenced by EDRF. These studies suggest that, in addition to controlling renal plasma flow, EDRF may have other, complex actions at the glomerulus. The natriuresis seen after acute inhibition of EDRF with NMA or NAME was probably the result of a pressure natriuretic response to the abrupt rise in blood pressure and also, perhaps, reflects removal of an EDRF influence to directly enhance sodium reabsorption somewhere in the nephron.
Activated macrophages synthesize nitric oxide (NO) from L-arginine. In culture, the major stable end product is nitrite (NO2). Activated macrophages accumulate in glomeruli and are responsible for injury in experimental immune complex glomerulonephritis. We examined NO2- production by isolated glomeruli and urinary NO2- in accelerated nephrotoxic nephritis in the rat. Normal glomeruli did not produce NO2- spontaneously or when stimulated with lipopolysaccharide (LPS) (1 microgram/ml) or A23187 (2 microgram/ml). Cultured mesangial cells at first or seventh passage did not produce NO2- spontaneously or when stimulated. Nephritic glomeruli spontaneously produced NO2 at all times studied; this production was maximal at 24 hours after induction of glomerulonephritis (158.4 +/- 8.4 nmol/48 hr/ml, N = 3). The production of NO2- was inhibited 75 to 100% by NG-monomethyl-L-arginine (L-NMMA), and this inhibition was reversed by L-arginine, indicating NO2- production from L-arginine via NO. The production of NO2- was increased by LPS (1 microgram/ml) at 2, 7 and 21 days. NO2- was undetectable in normal rat urine; however, it was present in urine of rats with glomerulonephritis (Day 0 to 1:8161 +/- 2605 nmol/24 hr. N = 12). The production of NO in nephritic glomeruli may have implications for both the mechanism of glomerular injury and glomerular hemodynamics.
E. coli lipopolysaccharide (LPS; 15 mg kg-1 i.v.) produced a long-lasting reduction in mean arterial blood pressure (MAP) in the anaesthetized rat. Inhibition of nitric oxide endothelium-derived relaxing factor (EDRF) synthesis with NG-monomethyl-L-arginine (MeArg, 1 mg kg-1 min-1 i.v. for 30 min) produced an increase in MAP and largely attenuated the LPS-induced hypotension; both effects were significantly reversed with L-arginine (6 mg kg-1 min-1 i.v.). When compared to MeArg, phenylephrine (300 mg kg-1 h-1 i.v.) produced a similar pressor response, but much less attenuation of the hypotensive response to LPS. Thus, a stimulation of EDRF release contributes to the LPS-induced hypotension in the anaesthetized rat.
We utilized a model of experimental interstitial nephritis induced by renal tubular antigen in complete Freund's adjuvant to examine a mechanism of immunologic tolerance produced by priming immunization with tubular antigen in incomplete Freund's adjuvant. Brown Norway rats primed with tubular antigen in incomplete adjuvant do not develop significant nephritis after challenge with antigen in complete adjuvant, and this tolerance can be transferred to naive recipients with donor T cells. These T cells also specifically suppress a delayed-type hypersensitivity response to soluble tubular antigen in recipients immunized to produce disease. This suppression is MHC-restricted and is mediated by OX8+ T cells which bind antigen and bear idiotypes cross-reactive with those on antibodies eluted from the tubular basement membrane. Despite the suppression of histologic disease, tolerized animals were able to produce significant titers of antibodies to tubular basement membrane. Our findings demonstrate an additional strategy for altering the natural history of immune-mediated renal disease, and further refine the characterization of the suppressive effect produced by incomplete Freund's adjuvant.
The chapter reviews several forms of experimental nephritis, especially from the point of view of understanding the pathogenic mechanisms in terms of immunological events. The chapter is arranged in three sections. The first section deals with nephritide caused by antikidney antibodies—namely, the heterologous antikidney antibodies of nephrotoxic serum nephritis. The second section deals with circulating antigen–antibody complex induced nephritis. The third section deals with nephritis produced by immunization to kidney in which both of the above mechanisms appear to play a role. It is now possible to account qualitatively and sometimes even quantitatively for the glomerular changes in two forms of experimental nephritis—namely, those due to nephrotoxic serum and to circulating antigen-antibody complexes. A third form induced by immunization with renal antigens is cause of controversy and confusion. In some species such as the sheep true autoantibodies against glomerular capillaries are produced and are pathogenic, whereas in other species such as the rat the damage is due to complexes of antibody and nonglomerular antigen.
The characterization and cloning of constitutive and inducible nitric oxide (NO)-synthesizing enzymes and the development of specific inhibitors of the L-arginine NO pathway have provided powerful tools to define the role of NO in renal physiology and pathophysiology. There is increasing evidence that endothelium-derived NO is tonically synthesized within the kidney and that NO plays a crucial role in the regulation of renal hemodynamics and excretory function. Bradykinin and acetylcholine induce renal vasodilation by increasing NO synthesis, which in turn leads to enhancement of diuresis and natriuresis. The blockade of basal NO synthesis has been shown to result in decreases of renal blood flow and sodium excretion. These effects are partly mediated by an interaction between NO and the renin angiotensin system. Intrarenal inhibition of NO synthesis leads to reduction of sodium excretory responses to changes in renal arterial pressure without an effect on renal autoregulation, suggesting that NO exerts a permissive or a mediatory role in pressure natriuresis. Nitric oxide released from the macula densa may modulate tubuloglomerular feedback response by affecting afferent arteriolar constriction. Nitric oxide produced in the proximal tubule possibly mediates the effects of angiotensin on tubular reabsorption. In the collecting duct, an NO-dependent inhibition of solute transport is suggested. The L-arginine NO pathway is also active in the glomerulus. Under pathologic conditions such as glomerulonephritis, NO generation is markedly enhanced due to the induction of NO synthase, which is mainly derived from infiltrating macrophages. An implication of NO in the mechanism of proteinuria, thrombosis mesangial proliferation, and leukocyte infiltration is considered. In summary, the data presented on NO and renal function have an obvious clinical implication. A role for NO in glomerular pathology has been established. Nitric oxide is the only vasodilator that closely corresponds to the characteristics of essential hypertension. Using chronic NO blockade, models of systemic hypertension will provide new insights into mechanisms of the development of high blood pressure.
Arrest of cell division is a prerequisite for cells to enter a program of terminal differentiation. Mitogenesis and cytostasis of neuronal cell precursors can be induced by the same or by different growth or trophic factors. Response of PC12 cells to nerve growth factor (NGF) involves a proliferative phase that is followed by growth arrest and differentiation. Here we present evidence that the cytostatic effect of NGF is mediated by nitric oxide (NO), a second messenger molecule with both para- and autocrine properties that can diffuse freely and act within a restricted volume. We show that NGF induces different forms of nitric oxide synthase (NOS) in neuronal cells, that nitric oxide (NO) acts as a cytostatic agent in these cells, that inhibition of NOS leads to reversal of NGF-induced cytostasis and thereby prevents full differentiation, and that capacity of a mutant cell line to differentiate can be rescued by exogenous NO. We suggest that induction of NOS is an important step in the commitment of neuronal precursors and that NOS serves as a growth arrest gene, initiating the switch to cytostasis during differentiation.
Paradoxically, nitric oxide (NO) has been found to exhibit cytotoxic, antiproliferative, or cytoprotective activity under different conditions. We have utilized Salmonella mutants deficient in antioxidant defenses or peptide transport to gain insights into NO actions. Comparison of three NO donor compounds reveals distinct and independent cellular responses associated with specific redox forms of NO. The peroxynitrite (OONO-) generator 3-morpholinosydnonimine hydrochloride mediates oxygen-dependent Salmonella killing, whereas S-nitrosoglutathione (GSNO) causes oxygen-independent cytostasis, and the NO. donor diethylenetriamine-nitric oxide adduct has no antibacterial activity. GSNO has the greatest activity for stationary cells, a characteristic relevant to latent or intracellular pathogens. Moreover, the cytostatic activity of GSNO may best correlate with antiproliferative or antimicrobial effects of NO, which are unassociated with overt cell injury. dpp mutants defective in active dipeptide transport are resistant to GSNO, implicating heterolytic NO+ transfer rather than homolytic NO. release in the mechanism of cytostasis. This transport system may provide a specific pathway for GSNO-mediated signaling in biological systems. The redox state and associated carrier molecules are critical determinants of NO activity.
Nitric oxide (NO) is a recently discovered messenger for the activation of soluble guanylate cyclase in a wide variety of cell types. Although enzymes involved in NO synthesis have been discovered, the regulation of their action is not clear. The possibility of NO regulating the activity of a crude NO synthase (EC 1.14.23) preparation from bovine cerebellum was investigated. Authentic NO (50-400 microM) produced a marked attenuation of NO synthase activity, as measured by the stoichiometric conversion of L-[3H]arginine to L-[3H]citrulline. This inhibition was mimicked by the nitrovasodilators S-nitroso-N-acetylpenicillamine, sodium nitroprusside, and glyceryl trinitrate. NO was most potent in inhibiting the enzyme activity, followed by S-nitroso-N-acetylpenicillamine, sodium nitroprusside, and glyceryl trinitrate. The effects of NO and the nitrovasodilators were concentration dependent and reversible. Oxyhemoglobin (50 microM), a scavenger of NO, partially prevented the inhibition of NO synthase activity by NO. Inorganic nitrite (5 mM), the oxidation product of NO, did not produce any effect on the enzyme activity. The Km for L-arginine was not significantly changed by NO (200 microM) (from 6.4 +/- 0.8 microM to 10.6 +/- 1.6 microM), whereas the Vmax of the enzyme was markedly decreased (from 80 +/- 4 to 45 +/- 4 pmol/min/mg of protein). This study suggests that NO production may be regulated by a direct effect of NO on the activity of NO synthase.
Nitric oxide (NO), the molecule of the year 1992, is gaining recognition as an important biological mediator. Its multitude of physiologic and pathophysiologic functions result from both a wide distribution of synthesis and diverse mechanisms of action. Besides its functions as a potent vasodilator and neurotransmitter, NO is important in inflammation and immunity. Both beneficial and detrimental consequences of induced synthesis have been discovered. Information is now accumulating on the regulation and function of induced NO. The recent cloning of human inducible NO cDNA should assist in defining the role of inducible NO in human physiology and pathophysiology.
The effects of endotoxin on the activities of the major Na(+)-independent amino acid transporters in rat liver (Systems n, asc, L, bo,+, and y+) were studied using using hepatic plasma membrane vesicles (HPMVs). Rats were treated with a single dose of Escherichia coli endotoxin (E. coli lipopolysaccharide 0127:B8 (LPS), 7.5, 15, or 30 mg/kg BW) and HPMVs were prepared by Percoll density gradient centrifugation at various timepoints after LPS administration. Vesicle purity and integrity was established by assay of enzyme markers and identical equilibrium uptakes. The activities of the Na(+)-independent amino acid transport systems y+ and bo,+ (arginine), asc (alanine and cysteine), L (leucine), and n (glutamine) were evaluated by measuring the uptake of radiolabeled amino acids using a rapid mixing/filtration technique. Amino acid uptake by HPMVs consisted of saturable and nonsaturable components. Prior treatment with endotoxin did not alter the activities of Systems n, asc, or L but resulted in a time- and dose-dependent stimulation of saturable arginine transport. Arginine transport increased within 2 h of LPS administration and exhibited a return towards basal levels by 24 h. Nonsaturable uptake (diffusion) in HPMVs was unaltered by LPS treatment. Kinetic analysis of arginine transport demonstrated the presence of both a high affinity and a low affinity carrier. Treatment with LPS resulted in a 73% increase in the Vmax of the high affinity carrier (System y+) and a 25% increase in the Vmax of the low affinity transporter (System bo,+). The data indicate selective stimulation of Na(+)-independent arginine transport in the liver during endotoxemia which may serve to support important arginine-dependent pathways during sepsis.
Nitric oxide (NO) is an important mediator of the hemodynamic response to sepsis; however, its visceral microcirculatory effects are largely unknown. To determine the role of NO in renal microvascular responses to bacteremia, rat hydronephrotic kidneys with intact neurovascular supplies were exteriorized into a tissue bath. Videomicroscopy was used to measure vessel diameters (interlobular artery, ILA; afferent arteriole, AFF; efferent arteriole, EFF) and optical Doppler velocimetry was used to quantitate ILA flow. In controls, topical L-arginine (L-Arg; 10(-4) M), the NO synthase (NO-S) substrate, resulted in mild pre- and postglomerular dilation and increased flow. Inhibition of NO-S by N omega-nitro-L-arginine methyl ester (L-NAME: 10(-4) M) caused preglomerular constriction (ILA = -22%; AFF = -20% from baseline) and reduced ILA flow by 39%, while postglomerular diameters (EFF) were unchanged. Bacteremic rats had similar alterations (ILA = -22%; AFF = -20%; flow = -56%). Topical L-NAME in bacteremic rats resulted in further constriction (ILA = -38%; AFF = -37%), decreased ILA flow (-75%) and constricted EFF (-30%). L-Arg ameliorated constriction (ILA = -11%; AFF = -7%) and flow (-34%) during bacteremia. We conclude that: (1) NO is important in basal preglomerular tone; (2) Escherichia coli causes selective preglomerular constriction and hypoperfusion; (3) maintenance of EFF tone during bacteremia is NO dependent; and (4) different pre- and postglomerular NO mechanisms exist during basal and bacteremic states. These data indicate that NO is an important mediator of renal microvascular responses to sepsis.
Although glomerular disease remains the most common cause of end-stage renal disease worldwide, major advances have been made recently in understanding the cellular and molecular mechanisms which mediate these disorders. Nephrotic syndrome in non inflammatory lesions such as minimal-change/focal sclerosis and MN results from disorders of the GEC which can be simulated in animal models by antibodies to various GEC membrane epitopes. Clarification of how these antibodies effect the GEC to induce a loss of glomerular barrier function should substantially improve understanding of the pathogenesis of minimal change/focal sclerosis. In MN, proteinuria is mediated primarily by C5b-9 through similar mechanisms that also involve the GEC as a target. Inflammatory glomerular lesions are induced by circulating inflammatory cells or proliferating resident glomerular cells. Understanding of how these cells induce tissue injury has also evolved considerably over the past decade. Neutrophil-induced disease involves leukocyte adhesion molecules in regulating neutrophil localization; proteases, oxidants, and myeloperoxidase in mediating injury and platelets in augmenting these processes. The activated mesangial cell exhibits altered phenotype and proliferation with release of oxidants and proteases. Mesangial cell proliferation may be initiated by basic fibroblast growth factor and is maintained by an autocrine mechanism involving PDGF. TGF-beta is important in the subsequent development of sclerosis. As understanding of these areas evolves, numerous new therapeutic strategies can now be devised, including agents which block or inhibit complement effects, oxidants, proteases, growth factors, and other cytokines. Appreciation of the role of several natural inhibitors of these mechanisms may also allow therapeutic manipulations that upregulate regulatory proteins, with a consequent therapeutic benefit.(ABSTRACT TRUNCATED AT 250 WORDS)
Influence of arachidonate cyclooxygenase (COX) products on endothelin (ET)-evoked renal vasoconstriction was assessed. In microperfused rat afferent (AA) and efferent arterioles (EA), indomethacin had no effects on the maximal contraction of both AA and EA by ET, but reduced the duration of ET-induced constriction in both arterioles. ET infusion to rats in vivo resulted in a selective increase in efferent but not afferent arteriolar resistance, leading to a dramatic increase in transcapillary hydraulic pressure difference. Glomerular filtration rate (GFR), which fell progressively during infusion of ET alone, was markedly preserved by COX inhibition, but not during selective thromboxane A2 antagonism. In isolated glomeruli, release of prostaglandin (PG) F2 alpha in response to 10(-6) mol/l ET exceeded that the PGE2 by a ratio of 3.2. Collectively, these data provide strong evidence that locally released COX products, possibly PGF2 alpha, play a key role in sustaining ET-induced renal arteriolar constriction. COX inhibition leads to acute vasorelaxation of AA despite continued ET administration, without affecting EA constriction in vivo, thereby resulting in a dramatic reversal of the effects of ET on GFR.
Nitric oxide (NO) generated from arginine exerts a variety of renal and extrarenal physiological and pathophysiological effects. NO is generated by two types of nitric oxide synthases: acutely responsive, constitutive NOS and slower, more persistent inducible NOS (iNOS). The latter is transcriptionally dependent, often stimulated by cytokines. NO regulates glomerular ultrafiltration, tubular reabsorption, and intrarenal renin secretion; many of these renal effects are mediated by interactions with angiotensin II and adrenergic (alpha 2) activity. Decreased NO activity also enhances tubuloglomerular feedback activity, which could contribute to renal vasoconstriction, NaCl retention, and elevated blood pressure. Loss of renal function could influence NO activity via: (1) endothelial dysfunction; (2) decreased arginine synthesis by kidney; (3) responses to arginine analogs that act as NOS inhibitors; (4) increased cytokine activity; and (5) altered oxidation:reduction status of cells, etc. For example, platelet dysfunction in uremia may be caused by cytokine-induced iNOS activation. Moreover, acutely responsive, constitutive NOS activity may be depressed in progressive loss of renal function. Decreased NO activity might contribute to baroreceptor dysfunction observed in hypertension and progressive renal disease. Studies of the impact of uremia suggest that iNOS may be chronically stimulated by cytokines, whereas acutely responsive, constitutive NOS activity may be concurrently depressed.
Arginine decarboxylase is present in the kidney and metabolizes the amino acid, arginine, to agmatine. Agmatine increases filtration rate in single nephrons (J. J. Lortie, W. F. Novotny, O. W. Peterson, V. Vallon, K. Malvey, M. Mendonca, J. Satriano, P. Insel, S. C. Thomson, and R. C. Blantz. J. Clin. Invest. 97:413-420, 1996). Experiments were conducted to determine whether exogenously administered agmatine exerts these effects via interaction with nitric oxide synthase (NOS) and whether this interaction depends upon alpha 2-adrenergic receptors. Agmatine microperfused (1 microM) into the urinary space of surface glomeruli of the rat increased nephron filtration rate from 33 +/- 4 to 40 +/- 5 nl/min with complete recovery within 10 min. When NG-monomethyl-L-arginine (L-NMMA), a nonselective NOS inhibitor, was systemically infused, agmatine no longer increased single-nephron glomerular filtration rate (SNGFR). BHT-933, an alpha 2-adrenergic agonist, did not increase SNGFR and was unaffected by concurrent L-NMMA. In vitro incubation of freshly harvested glomeruli with agmatine resulted in significant increases in the generation of cGMP, effects similar to carbachol, and blocked by nitro-L-arginine methyl ester (L-NAME) but not yohimbine, an alpha 2-adrenergic antagonist. Agmatine exerts effects on glomerular ultrafiltration via a constitutive NOS-dependent mechanism, and this does not require the participation of alpha 2-adrenoreceptors.
The presence of nitric oxide (NO) in the kidney has been implicated in the pathogenesis of human glomerulonephritis. However, the exact type of glomerular cells that express NO synthase (NOS) and the NOS isoform involved in the local production of NO has not been identified in the human diseased kidney. We examined the expression of three isoforms of NOS, inducible NOS (iNOS), endothelial NOS (eNOS) and brain NOS (bNOS) in the renal tissue of patients with IgA nephropathy (IgAN, N = 10), lupus nephritis (LN, N = 5), membranous nephropathy (MN, N = 5) and minimal change nephrotic syndrome (MCNS, N = 5). Sections were immunostained and the correlation between the expression of each NOS and the degree of glomerular injury in that section was also examined. Normal portions of surgically resected kidneys served as controls. eNOS was present in glomerular endothelial cells and endothelium of cortical vessels in the control and diseased kidneys. iNOS was localized in mesangial cells, glomerular epithelial cells and infiltrating cells in the diseased glomeruli, whereas immunostaining for iNOS was hardly detected in control kidneys. In addition, the expression pattern of eNOS in each glomerulus was the reverse of that of iNOS. In IgAN and LN, the extent of staining for eNOS correlated negatively with the degree of glomerular injury, while the extent of staining for iNOS correlated positively with the degree of glomerular injury in the same tissues. bNOS was not detected in normal or nephritic glomeruli. Our results indicate the presence of a NO pathway in human diseased kidney, and suggest that NO derived from eNOS and iNOS may be involved in the progression of renal diseases and that NO derived from each NOS may play an important role in different way in human inflamed glomeruli.
Bacterial lipopolysaccharide (LPS) in the presence of interferon gamma (IFNgamma) stimulates the synthesis of the cationic amino acid transporter 2B (CAT-2B) and inducible nitric oxide synthetase (iNOS) in RAW264 macrophages, which are thought to underlie the increased rate of arginine uptake into these cells and its conversion to nitric oxide, respectively. Here I demonstrate that the LPS- and IFNgamma-induced increase in arginine uptake into RAW264 cells is partially suppressed in the presence of PD 98059, partially suppressed in the presence of SB 203580, and completely inhibited by both drugs. In contrast, the LPS- and IFNgamma-induced synthesis of CAT-2B mRNA and iNOS protein is unaffected by PD 98059 and SB 203580. The results indicate that the MAPK/ERK and SAPK2/p38 cascades are both rate-limiting for LPS- and IFNgamma-stimulated arginine uptake, but not for iNOS synthesis. They also suggest that PD 98059 and SB 203580 suppress CAT-2B synthesis at a post-transcriptional level.
Nitric oxide (NO) has been described to exert cytostatic effects on cellular proliferation; however the mechanisms responsible for these effects have yet to be fully resolved. Polyamines, conversely, are required components of cellular proliferation. In experimental models of inflammation, a relationship between these two pathways has been suggested by the temporal regulation of a common precursor, arginine. This study was undertaken to determine the effects NO and the NO synthase (NOS)-inducing cytokines, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), exert on polyamine regulation. The transformed kidney proximal tubule cell line, MCT, maintains high constitutive levels of the first polyamine biosynthetic enzyme, ornithine decarboxylase (ODC). NO donors markedly suppressed ODC activity in MCT and all other cell lines examined. TNF-alpha and IFN-gamma induction of NO generation resulted in suppressed ODC activity, an effect prevented by the inducible NOS inhibitor L-N6-(1-iminoethyl)lysine (L-NIL). Dithiothreitol reversal of NO-mediated ODC suppression supports nitrosylation as the mechanism of inactivation. We also evaluated polyamine uptake, inasmuch as inhibition of ODC can result in a compensatory induction of polyamine transporters. Administration of NO donors, or TNF-alpha and IFN-gamma, suppressed [3H]putrescine uptake, thereby preventing transport-mediated reestablishment of intracellular polyamine levels. This study demonstrates the capacity of NO and inflammatory cytokines to regulate both polyamine biosynthesis and transport.
Nitric oxide can be generated by macrophages, as well as many other cell types, through a cytokine inducible isoform of nitric oxide synthase. Historically the effector functions ascribed to iNOS-generated NO have been the control of intracellular organisms and tumor cell cytotoxicity. However, there is a growing appreciation that iNOS generated NO can additionally play an important role in immunoregulation. In this review, the authors outline the effects of iNOS inhibition or genetic deletion on the expression of several autoimmune diseases and discuss potential mechanisms underlying the immunosuppressive effects of NO.
Studies performed over the last 10 years have evaluated the role of nitric oxide (NO) in the control of renal hemodynamics. This article reviews the effects of administration of nitric oxide synthase (NOS) blockers on renal function in experimental animals and human volunteers. These studies show that NOS blockade increases renal vascular resistances and decreases the glomerular ultrafiltration coefficient. These experimental studies also support the presence of an important interaction between NO, angiotensin II, and renal nerves in the control of renal function. The use of acute and chronic administration of NOS blockers has generated a great deal of new and exciting information regarding the role of NO in the regulation of normal renal function.
Blockade or gene deletion of inducible nitric oxide synthase (iNOS) fails to fully abrogate all the sequelae leading to the high morbidity of septicemia. An increase in substrate uptake may be necessary for the increased production of nitric oxide (NO), but arginine is also a precursor for other bioactive products. Herein, we demonstrate an increase in alternate arginine products via arginine and ornithine decarboxylase in rats given lipopolysaccharide (LPS). The expression of iNOS mRNA in renal tissue was evident 60 but not 30 min post-LPS, yet a rapid decrease in blood pressure was obtained within 30 min that was completely inhibited by selective iNOS blockade. Plasma levels of arginine and ornithine decreased by at least 30% within 60 min of LPS administration, an effect not inhibited by the iNOS blocker L-N(6)(1-iminoethyl)lysine (L-NIL). Significant increases in plasma nitrates and citrulline occurred only 3-4 h post-LPS, an effect blocked by L-NIL pretreatment. The intracellular composition of organs harvested 6 h post-LPS reflected tissue-specific profiles of arginine and related metabolites. Tissue arginine concentration, normally an order of magnitude higher than in plasma, did not decrease after LPS. Pretreatment with L-NIL had a significant impact on the disposition of tissue arginine that was organ specific. These data demonstrate changes in arginine metabolism before and after de novo iNOS activity. Selective blockade of iNOS did not prevent uptake and can deregulate the production of other bioactive arginine metabolites.
Changes in the expression of alternate arginine metabolic pathways have been implicated in the pathogenesis of experimental glomerulonephritis. Agmatine, decarboxylated arginine, has been shown in vitro to suppress both inducible nitric oxide synthase and the rate-limiting enzyme of polyamine biosynthesis, ornithine decarboxylase (ODC). This study was undertaken to determine whether agmatine administration could reduce tissue injury by decreasing nitric oxide, and reduce cell proliferation, by diminishing ODC activity, in experimental mesangial proliferative glomerulonephritis (Thy-1 nephritis). Agmatine treatment (50 mg/kg per d intraperitoneally) in Thy-1 nephritis rats prevented a reduction in GFR at day 1. Agmatine treatment decreased nitric oxide production in Thy-1 nephritis rats by 23% and 41% at days 1 and 4, respectively. Agmatine treatment also reduced ODC activity and glomerular (3)H-thymidine incorporation on days 1, 4, and 7. Histologic evaluation revealed a decline in mesangial cell proliferation and extracellular matrix accumulation associated with agmatine treatment administered before or 24 h after Thy-1 antibody, and this was confirmed by a reduction in the number of cells expressing proliferating cell nuclear antigen on days 4 and 7. These studies provide the first in vivo evidence that agmatine administration can reduce cellular proliferation in Thy-1 nephritis and attenuate the initial reduction in renal function associated with this model.
The induction of inducible nitric oxide synthase (iNOS) serves an important immuno-protective function in inflammatory states, but ungoverned nitric oxide (NO) generation can contribute to a number of pathologic consequences. Delineation of the mechanisms that can downregulate iNOS-generated NO in inflammation could have therapeutic relevance. Here we show that agmatine, a metabolite of arginine, inhibits iNOS mediated nitric oxide generation in cytokine stimulated cell culture preparations. This effect was not cell type specific. Increased diamine oxidase (DAO) and decreased aldehyde dehydrogenase (AldDH) activities are also representative of inflammatory settings. Increasing the conversion of agmatine to an aldehyde form by addition of purified DAO or suppression of aldehyde breakdown by inhibition of AldDH activity increases the inhibitory effects of agmatine in an additive fashion. Inhibitors of DAO, but not monoamine oxidase (MAO), decreased the inhibitory effects of agmatine, as did the addition of AldDH or reacting aldehydes with phenylhydrazine. We examined rats given lipopolysaccharide (LPS) to evaluate the potential effects of agmatine in vivo. Endotoxic rats administered agmatine prevented the decreases in blood pressure and renal function normally associated with sepsis. Agmatine treatment also increased the survival of LPS treated mice. Our data demonstrate the capacity of agmatine aldehyde to suppress iNOS mediated NO generation, and indicate a protective function of agmatine in a model of endotoxic shock. How agmatine may aid in coordinating the early NO phase and the later repair phase responses in models of inflammation is discussed.