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ChemInform Abstract: Chemical Biology of Histone Acetyltransferase Natural Compounds Modulators
Abstract
Histone acetyltransferases (HATs) are a class of epigenetic enzymes crucial for chromatin restructuring and transcriptional regulation in eukaryotic cells, thus being a promising target for therapeutic development. Nonetheless, differently from histone deacetylases (HDACs) inhibitors, there is still paucity of small-molecule modulators of HAT activity. After a decline during past decade, natural products and their derivatives could be once again a valuable tool in the lead discovery process and meet such need of Novel Chemical Entities (NCEs). In this review, we will provide a comprehensive summary on the discovery of small-molecule HAT modulators from naturally occurring molecular scaffolds.
... Histone acetylation is involved in chromatin remodelling leading to transcription of genes. However, acetylation and deacetylation are not restricted to histones, various non-histone proteins such as p53, tubulin, Hsp90, c-Myc, FOXO, and the androgen receptor can likewise be substrates of HDACs and HATs with consequences on function and stability of these non-histone substrates (Roth et al. 2001; Sterner and Berger 2000; Dal Piaz et al. 2011). Meanwhile, several PPAP-type HAT inhibitors have been identified including garcinol and its derivatives (Dal Piaz et al. 2011). ...
... However, acetylation and deacetylation are not restricted to histones, various non-histone proteins such as p53, tubulin, Hsp90, c-Myc, FOXO, and the androgen receptor can likewise be substrates of HDACs and HATs with consequences on function and stability of these non-histone substrates (Roth et al. 2001; Sterner and Berger 2000; Dal Piaz et al. 2011). Meanwhile, several PPAP-type HAT inhibitors have been identified including garcinol and its derivatives (Dal Piaz et al. 2011). Garcinol (1) and isogarcinol (15) inhibit various HATs such as p300-HAT (IC 50 ca. ...
Kokum (Garcinia indica) has been applied for dishes of the Konkan region of Western India for centuries. There is growing evidence that its major ingredients like hydroxycitric acid (HCA) and garcinol have beneficial health effects. While HCA is considered to be a suitable tool to manage obesity, the polyisoprenylated benzophenone garcinol has revealed potent anticancer, antibacterial, anti-inflammatory, and anti-ulcer effects. This chapter provides an overview of the latest developments of garcinol and its derivatives concerning the prevention and treatment of various cancer diseases. After a short introduction, important chemical aspects of garcinol are discussed followed by an overview of inflammation-related targets of garcinol such as NF-κB, 5-LOX, and STAT proteins playing also a big role in cancer progression. Interference of chromatin regulation and HAT substrate stability by the HAT inhibitor garcinol and a final comment on the anti-ulcer activity of garcinol complete this chapter. Pertinent literature is covered up to 2014.
... The curcumin, anacardic acid, plumbagin, catechin, and their derivatives, garcinol and its derivatives are plant-derived molecules [18][19][20][21][22] ; whereas, isothiazolinone, C646, cinnamoyl, quinolines, thiazoles, and C107 are synthetic molecules [23][24][25][26][27][28] ; both groups of molecules are reported as the p300 HAT inhibitors. The virtual screening analysis is a prominent tool to identify the suitable p300 HAT inhibitors. ...
The chromatin modification is regulated by the histone acetyltransferase (HAT) and histone deacetyltransferase (HDAC) enzymes; abnormal function of these enzymes leads to several malignant diseases. The inhibition of these enzymes using natural ligand molecules is an emerging technique to cure these diseases. The in vitro analysis of natural molecules, venenatine, spinosine, palmatine and taxodione are giving the best inhibition rate against p300 HAT enzyme. However, the detailed understanding of binding and the stability of these molecules with p300 HAT is not yet known. The aim of the present study is focused to determine the binding strength of the molecules from molecular dynamics simulation analysis. The docking analysis confirms that, the venenatine (-6.97 kcal/mol - conformer 8), spinosine (-6.52 kcal/mol conformer -10), palmatine (-5.72 kcal/mol conformer-3) and taxodione (-4.99 kcal/mol conformer-4) molecules form strong hydrogen bonding interactions with the key amino acid residues (Arg1410, Thr1411 and Trp1466) present in the active site of p300. In the molecular dynamics (MD) simulation, the spinosine retain these key interactions with the active site amino acid residues (Arg1410, Thr1411, and Trp1466) than venenatine and are stable throughout the simulation. The RMSD value of spinosine (0.5 to 1.3 Å) and venenatine (0.3 to 1.3 Å) are almost equal during the MD simulation. However, during the MD simulation, the intermolecular interaction between venenatine and the active site amino acid residues (Arg1410, Thr1411, and Trp1466) decreased on comparing with the spinosine-p300 interaction. The binding free energy of the spinosine (-15.30 kcal/mol) is relatively higher than the venenatine (-11.8 kcal/mol); this increment is attributed to the strong hydrogen bonding interactions of spinosine molecule with the active site amino acid residues of p300.
... The activation of histone acetylation and the inhibition of histone deacetylation make the same impact and maintain the histone acetylation level. To stop the abnormal function of these enzymes, there are natural and synthetic molecules such as Garcinol (Dal Piaz et al., 2011), Curcumin (Devipriya & Kumaradhas, 2013b;Renuga Parameswari, Rajalakshmi, & Kumaradhas, 2015), Cinnamoyl (Costi et al., 2007), C646 (Van Den Bosch et al., 2016), Nemorosone (Dal Piaz et al., 2010), N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide (CTPB) (Devipriya & Kumaradhas, 2013a), N-(4chloro-3-trifluoromethyl-phenyl)-2-ethoxybenzamide (CTB) (Devipriya & Kumaradhas, 2010), and Anacardic acid (Devipriya & Kumaradhas, 2012) that are reported as the potential p300 HAT modulators. Among these modulators, the benzamide derivatives of CTPB and CTB are synthetic HAT activators that promote the transcription by increasing the H3 and H4 acetylation in nucleosome. ...
The CBP (CREB-binding protein) and p300 are related to transcriptional coactivator family and are involved in several post-translational modifications, in which the acetylation is an important factor because it commences the transcription process. Experimental studies report that CTPB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide) and CTB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxybenzamide) are good activators of p300 HAT enzyme, but yet, the molecular mechanism of their activation is not explored. The present study pertains to determine the intermolecular interactions, stability and binding free energy of CTB and CTPB from the molecular docking, molecular dynamics (MD) simulation and binding free energy calculation. The docking studies of the molecules reveal that the docking score of CTPB (-15.64 kcal/mol) is higher than that of CTB (-12.30 kcal/mol); on the contrary, CTB forms a strong interaction with the key residues of catalytic site (Tyr1467 and Trp1436) compared with CTPB. The MD simulation shows the stability of both molecules in the active site of p300 and their interactions. Furthermore, both docking and MD simulation studies of CTB confirm that it forms expected key interactions and retain the interactions with the active site amino acid residues of p300 when compared with CTPB. For this reason, the CTB recruits more acetyl-CoA in the active site of p300 compared with CTPB; it leads to activate the acetylation process; hence, CTB may be a best activator than CTPB. The binding free energy value of CTPB (-24.79
±
2.38 kcal/mol) is higher when compared with that of CTB (-12.14
±
1.30 kcal/mol) molecule; perhaps, the interaction of pentadecyl chain of CTPB with p300, whereas in CTB, such a group is absent. Communicated by Ramaswamy H. Sarma.
... In fact, several HDAC inhibitors are used in cancer treatment or are currently in clinical trials [26]. HAT inhibitors, on the other hand, are still in the preclinical phase, although various effective inhibitors have been described [22,27,28]. These include acetyl-CoA-derived bisubstrates, natural products, and synthetic compounds such as isothialozones. ...
Xylosides are a group of compounds that can induce glycosaminoglycan (GAG) chain synthesis independently of a proteoglycan core protein. We have previously shown that the xyloside 2-(6-hydroxynaphthyl)β-D-xylopyranoside has a tumor-selective growth inhibitory effect both in vitro and in vivo, and that the effect in vitro was correlated to a reduction in histone H3 acetylation. In addition, GAG chains have previously been reported to inhibit histone acetyltransferases (HAT). To investigate if xylosides, or the corresponding xyloside-primed GAG chains, can be used as HAT inhibitors, we have synthesized a series of naphthoxylosides carrying structural motifs similar to the aromatic moieties of the known HAT inhibitors garcinol and curcumin, and studied their biological activities. Here, we show that the disubstituted naphthoxylosides induced GAG chain synthesis, and that the ones with at least one free phenolic group exhibited moderate HAT inhibition in vitro, without affecting histone H3 acetylation in cell culture. The xyloside-primed GAG chains, on the other hand, had no effect on HAT activity, possibly explaining why the effect of the xylosides on histone H3 acetylation was absent in cell culture as the xylosides were recruited for GAG chain synthesis. Further investigations are required to find xylosides that are effective HAT inhibitors or xylosides producing GAG chains with HAT inhibitory effects.
... To further address the importance of HAT inhibition in LCSC survival, we analyzed the effect of both p300/ CBP HAT inhibitors Curcumin [37] and C646 [38] on cell viability of LCSC136 line grown as undifferentiated multicellular spheroids (Stem) or as differentiated in adherent conditions (Diff). Interestingly, both Curcumin ( Figure 4E) and C646 (Supplementary Figure S4B) reduced cell viability of LCSC136 cells grown as tumor spheroids, whilst differentiated progeny were more resistant to either Curcumin or C646 induced cell death ( Figure 4E, Supplementary Figure S4B). ...
Cancer stem cells (CSCs) play an important role in tumor initiation, progression, therapeutic failure and tumor relapse. In this study, we evaluated the efficacy of the thiazole derivative 3-methylcyclopentylidene-[4-(4'-chlorophenyl)thiazol-2-yl]hydrazone (CPTH6), a novel pCAF and Gcn5 histone acetyltransferase inhibitor, as a small molecule that preferentially targets lung cancer stem-like cells (LCSCs) derived from non-small cell lung cancer (NSCLC) patients. Notably, although CPTH6 inhibits the growth of both LCSC and NSCLC cell lines, LCSCs exhibit greater growth inhibition than established NSCLC cells. Growth inhibitory effect of CPTH6 in LCSC lines is primarily due to apoptosis induction. Of note, differentiated progeny of LCSC lines is more resistant to CPTH6 in terms of loss of cell viability and reduction of protein acetylation, when compared to their undifferentiated counterparts. Interestingly, in LCSC lines CPTH6 treatment is also associated with a reduction of stemness markers. By using different HAT inhibitors we provide clear evidence that inhibition of HAT confers a strong preferential inhibitory effect on cell viability of undifferentiated LCSC lines when compared to their differentiated progeny. In vivo, CPTH6 is able to inhibit the growth of LCSC-derived xenografts and to reduce cancer stem cell content in treated tumors, as evidenced by marked reduction of tumor-initiating capacity in limiting dilution assays. Strikingly, the ability of CPTH6 to inhibit tubulin acetylation is also confirmed in vivo. Overall, our studies propose histone acetyltransferase inhibition as an attractive target for cancer therapy of NSCLC.
... After exposure to pro-inflammatory stimuli, I-κB will be degraded by I-κB kinase and induce the translocation of NF-κB to the nucleus [20,30]. 6SA-induced activation of NF-κB subunit p65 may occur due to the degradation of I-κB because it has been reported that anacardic acid and its derivatives can induce the degradation of I-κB [31]. ...
Amphipterygium adstringens is a plant traditionally used to treat gingivitis, gastric ulcer and even gastric cancer but the mechanism involved in the regulation of the immune response is not elucidated yet. The 6-pentadecylsalicylic acid (6SA) is the main anacardic acid found in A. adstringens. In order to evaluate the immune-modulatory abilities of 6SA, we used mouse splenocytes and determined the phosphorylation of the transcription factor NF-κB and MAP kinases ERK1/2, JNK and p38 in helper and cytotoxic T cells, natural killer (NK) cells and F4/80(+) macrophages. Treatment with 6SA was not cytotoxic as measured by both trypan blue exclusion and tetrazolium salts (MTT) tests. Additionally, 6SA did not alter the proportion of helper and cytotoxic T lymphocytes, NK cells or macrophages. Moreover, 6SA treatment significantly increased the phosphorylation of ERK1/2, JNK, P38 and NF-κB mainly in macrophages. In this cells (peritoneal macrophages), treatment with 6SA increased the secretion of nitric oxide (NO), interleukin (IL)-6 and tumour necrosis factor (TNF)-α and decreased the secretion of IL-4 and IL-10 depending on MAPK and NF-κB phosphorylation. In addition, 6SA increased the migration and phagocytic activity of macrophages also depending on the phosphorylation of different kinases. These data suggest that 6SA induces the classical activation pathway in macrophages via the phosphorylation of MAP kinases and NF-κB thus activating the adaptive immune system.
... Für weitaus mehr Naturstoffe als an dieser Stelle zusammengefasst wurden bereits modulatorische Effekte auf die HAT-Aktivität in der Literatur berichtet, darunter auch Alkaloide wie Sanguinarin 14 und Solanaceae-Peptide wie Lunasin. 101 Aspekte der Zugänglichkeit, Reinheit und Selektivität erweisen sich häufig als limitierend für potenzielle therapeutische Einsätze. Dennoch dienen diese Substanzen fortwährend als Leitstrukturen für weitere Optimierung. ...
Die Enzymklasse der Histon-Acetyltransferasen (HATs) spielt in zellbiologischen Vorgängen und in der Ätiologie zahlreicher Erkrankungen eine fundamentale Rolle. Der Entwicklung von HAT-Inhibitoren als epigenetische Werkzeuge kommt eine wesentliche Bedeutung hinsichtlich neuer Erkenntnisse über zukünftige therapeutische Ansätze und die zugrunde liegenden Mechanismen zu.
Im Rahmen der vorliegenden Arbeit wurden, ausgehend von Ergebnissen der Leitstruktursuche und -optimierung mittels computergestützter Methoden, zwei Substanzklassen als HAT-Hemmstoffe identifiziert. Anschließend wurden Strukturderivate synthetisiert und bezüglich ihrer HAT-Hemmung in vitro charakterisiert. Die abgeleiteten Struktur-Wirkungs-Beziehungen zeigten wiederum Ansatzpunkte für weitere Strukturoptimierung innerhalb der Enzymklasse auf. Hierzu wurde das in der Arbeitsgruppe für PCAF verfügbare antikörperbasierte heterogene Testsystem auf weitere Vertreter der HAT-Familie (Gcn5, CBP, p300) zwecks der Durchführung von Selektivitätsstudien übertragen. Darüber hinaus erfolgte erstmals in unserer Gruppe die Etablierung eines bakteriellen Überexpressionssystems zur heterologen PCAF-Gewinnung.
Zum einen wurden Pyridoisothiazolone mit variierenden aromatischen Substituenten am Isothiazolon-Stickstoffatom als potente HAT-Hemmstoffe identifiziert. Diese Verbindungsklasse bildet nach Spaltung der S—N-Bindung kovalente Disulfid-Addukte mit Cysteinresten in Zielproteinen. Es konnte gezeigt werden, dass Substitutionsmuster am Isothiazolon-Stickstoffatom entscheidend für das Selektivitätsprofil der Inhibitoren ist. N-Phenyl-Derivate hemmten alle getesteten HATs im niedrigen mikromolaren Bereich, wohingegen N-Benzyl-Analoga selektive CBP-Hemmstoffe sind. Die Untersuchungen zur Aufklärung des zugrunde liegenden irreversiblen Hemmmechanismus belegen, dass die PCAF-Hemmung sehr schnell und vom Cofaktor unabhängig erfolgt und mit der Bildung stabiler Enzym-Inhibitor-Addukte einhergeht, welche sich durch nachträgliche Thioleinwirkung nicht spalten lassen. Die Ergebnisse der vorgenommenen Verdünnungsexperimente stützen zudem die Hypothese einer irreversiblen Hemmung. Die Reaktivität der S—N-Bindung im Isothiazolongrundgerüst wurde durch eine zweistufige Schwefeloxidation deutlich herabgesetzt, was in Inkubationsstudien mit Modellnukleophilen simuliert werden konnte und einen Verlust der HAT-Hemmung in vitro herbeiführte. Vergleichbare Effekte wurden für die Bindungsaffinität oxidierter Derivate an das Humane Serumalbumin (HSA) gefunden. In Kooperationsprojekten wurden für Vertreter dieser Substanzklasse wachstumshemmende Eigenschaften in mehreren Krebszelllinien aufgezeigt.
Im Rahmen dieser Arbeit wurden weiterhin Rhodanin-Indolinon-Carbonsäuren als eine neue Klasse von HAT-Hemmstoffen charakterisiert, welche Vertreter der GNAT- und der p300/CBP-Familie ohne deutliche Selektivitätstendenzen hemmen. Die vorgenommenen chemischen Modifikationen ließen den Indolinonsubstituenten zum einen und den Rhodanin-Carbonsäure-Linker zum anderen als die Strukturbausteine mit einem entscheidenden Einfluss auf die Hemmeigenschaften und somit als Ansatzpunkte für eine weitere Optimierung erkennen. Im Einklang mit den Vorhersagen und Bindungsinteraktionen aus dem Molecular Modelling wurde zudem gezeigt, dass das Vorhandensein einer freien Carboxylfunktion essenziell für die In-vitro-Hemmung ist.
... Hence, the development and the evaluation of small-molecule HAT inhibitors may provide novel therapeutic approaches. 25,26 Several structurally different HAT inhibitors have been reported, including bisubstrate inhibitors, [27][28][29][30] natural products 31 and synthetic compounds like isothiazolones containing derivatives 25,[32][33][34] and carboxylic acids. 35,36 However, the lack of cell permeability and metabolic stability represent major drawbacks of peptidic inhibitors. ...
We have previously described novel histone acetyltransferase (HAT) inhibitors that block neuroblastoma cell growth in vitro. Here we show that two selected pyridoisothiazolone HAT inhibitors, PU139 and PU141, induce cellular histone hypoacetylation and inhibit growth of several neoplastic cell lines originating from different tissues. Broader in vitro selectivity profiling shows that PU139 blocks the HATs Gcn5, p300/CBP-associated factor (PCAF), CREB (cAMP response element-binding) protein (CBP) and p300, whereas PU141 is selective toward CBP and p300. The pan-inhibitor PU139 triggers caspase-independent cell death in cell culture. Both inhibitors block growth of SK-N-SH neuroblastoma xenografts in mice and the PU139 was shown to synergize with doxorubicin in vivo. The latter also reduces histone lysine acetylation in vivo at concentrations that block neoplastic xenograft growth. This is one of the very few reports on hypoacetylating agents with in vivo anticancer activity.
... The peptide substrate binding site in the only solved structure is shallow and solvent accessible, reducing its capacity to be targeted by drugs (Arrowsmith et al., 2012). Among the inhibitors so far described are natural substances that promiscuously bind a variety of targets (Piaz et al., 2011), or isothiazolone covalent modifiers (Ghizzoni et al., 2009). These latter include the more recently developed pyridoisothiazolones that effectively inhibit cancer cell proliferation (Furdas et al., 2011). ...
... The peptide substrate binding site in the only solved structure is shallow and solvent accessible, reducing its capacity to be targeted by drugs (Arrowsmith et al., 2012). Among the inhibitors so far described are natural substances that promiscuously bind a variety of targets (Piaz et al., 2011), or isothiazolone covalent modifiers (Ghizzoni et al., 2009). These latter include the more recently developed pyridoisothiazolones that effectively inhibit cancer cell proliferation (Furdas et al., 2011). ...
The discovery of the epigenetic regulation of gene expression has revolutionized both our understanding of how genomes function and approaches to the therapy of numerous pathologies. Schistosomes are metazoan parasites and as such utilize most, if not all the epigenetic mechanisms in play in their vertebrate hosts: histone variants, histone tail modifications, non-coding RNA and, perhaps, DNA methylation. Moreover, we are acquiring an increasing understanding of the ways in which these mechanisms come into play during the complex schistosome developmental program. In turn, interest in the actors involved in epigenetic mechanisms, particularly the enzymes that carry out epigenetic modifications of histones or nucleic acid, as therapeutic targets has been stimulated by the finding that their inhibitors exert profound effects, not only on survival, but also on the reproductive function of Schistosoma mansoni. Here, we review our current knowledge, and what we can infer, about the role of epigenetic mechanisms in schistosome development, differentiation and survival. We will consider which epigenetic actors can be targeted for drug discovery and what strategies can be employed to develop potent, selective inhibitors as drugs to cure schistosomiasis.
... Among these KATis, we find two naturally occurring compounds: anacardic acid and curcumin that may have beneficial effects in pathological conditions like PD [155,199,200] and AD [201,202]. The former compound inhibits CBP/p300, PCAF and Tip60, whereas the latter is more specific for CBP/p300 [203]. However, neither compound is very specific; in fact, curcumin also interferes with HDAC and DNA methyltransferase activities [204], which reduces its potential as an effective therapeutic drug. ...
Neuropsychiatric pathologies, including neurodegenerative diseases and neurodevelopmental syndromes, are frequently associated with dysregulation of various essential cellular mechanisms, such as transcription, mitochondrial respiration and protein degradation. In these complex scenarios, it is difficult to pinpoint the specific molecular dysfunction that initiated the pathology or that led to the fatal cascade of events that ends with the death of the neuron. Among the possible original factors, epigenetic dysregulation has attracted special attention. This review focuses on two highly related epigenetic factors that are directly involved in a number of neurological disorders, the lysine acetyltransferases CREB-binding protein (CBP) and E1A-associated protein p300 (p300). We first comment on the role of chromatin acetylation and the enzymes that control it, particularly CBP and p300, in neuronal plasticity and cognition. Next, we describe the involvement of these proteins in intellectual disability and in different neurodegenerative diseases. Finally, we discuss the potential of ameliorative strategies targeting CBP/p300 for the treatment of these disorders.
... In the present study, we explore the potential efficacy of a relatively novel and naturally-occurring HAT inhibitor known as garcinol [54,55], derived from the rind of the fruit of the Kokum tree (Garcinia indica), in the treatment of newly formed and reactivated fear memories. We show that garcinol impairs histone acetylation in the lateral nucleus of the amygdala (LA) associated with fear conditioning and retrieval of a fear memory. ...
The study of the cellular and molecular mechanisms underlying the consolidation and reconsolidation of traumatic fear memories has progressed rapidly in recent years, yet few compounds have emerged that are readily useful in a clinical setting for the treatment of anxiety disorders such as post-traumatic stress disorder (PTSD). Here, we use a combination of biochemical, behavioral, and neurophysiological methods to systematically investigate the ability of garcinol, a naturally-occurring histone acetyltransferase (HAT) inhibitor derived from the rind of the fruit of the Kokum tree (Garcina indica), to disrupt the consolidation and reconsolidation of Pavlovian fear conditioning, a widely studied rodent model of PTSD. We show that local infusion of garcinol into the rat lateral amygdala (LA) impairs the training and retrieval-related acetylation of histone H3 in the LA. Further, we show that either intra-LA or systemic administration of garcinol within a narrow window after either fear conditioning or fear memory retrieval significantly impairs the consolidation and reconsolidation of a Pavlovian fear memory and associated neural plasticity in the LA. Our findings suggest that a naturally-occurring compound derived from the diet that regulates chromatin function may be useful in the treatment of newly acquired or recently reactivated traumatic memories.
... Such modifications are tightly regulated, and are cell type specific 4 . Each of the principal enzyme classes responsible for acetylation, the histone acetyl transferases (HATs) and histone deacetylases (HDACs), have several family members, and the balance of HAT versus HDAC activity governs the overall levels of histone acetylation 7,35 . It is notable in this regard that we observed a relative decrease in overall HDAC activity after morphine treatment with unchanged overall HAT activity consistent with greater DNA acetylation in response to this drug. ...
Unlabelled:
Repeated administration of opioids such as morphine induces persistent behavioral changes including opioid-induced hyperalgesia (OIH), tolerance, and physical dependence. In the current work we explored how the balance of histone acetyltransferase (HAT) versus histone deacetylase (HDAC) might regulate these morphine-induced changes. Nociceptive thresholds, analgesia, and physical dependence were assessed during and for a period of several weeks after morphine exposure. To probe the roles of histone acetylation, the HAT inhibitor curcumin or a selective HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) was administered daily to groups of animals. Histone acetylation in spinal cord was assessed by Western blot and immunohistochemistry. Concurrent administration of curcumin with morphine for 4 days significantly reduced development of opioid-induced mechanical allodynia, thermal hyperalgesia, tolerance, and physical dependence. Conversely, the HDAC inhibitor SAHA enhanced these responses. Interestingly, SAHA treatment after the termination of opioid administration sustained these behavioral changes for at least 4 weeks. Histone H3 acetylation in the dorsal horn of the spinal cord was increased after chronic morphine treatment, but H4 acetylation was unchanged. Moreover, we observed a decrease in HDAC activity in the spinal cords of morphine-treated mice while overall HAT activity was unchanged, suggesting a shift toward a state of enhanced histone acetylation.
Perspective:
The current study indicates that epigenetic mechanisms play a crucial role in opioid-induced long-lasting neuroplasticity. These results provide new sight into understanding the mechanisms of opioid-induced neuroplasticity and suggest new strategies to limit opioid abuse potential and increase the value of these drugs as analgesics.
... Classes of HAT enzymes Four classes of HAT enzymes have yet been identified based on their primary sequence homology, namely MYST (MOZ, Ybf2/Sas3, Sas2, and Tip60), Gcn5/PCAF (general control non-repressed protein 5 and p300-associated and CBP-associated factor), p300/ CBP (protein of 300 kDa and CREB-binding protein) and Rtt109 (regulator of Ty1 Transposition gene product 109). Moreover, several other proteins, such as the transcriptional coactivators, for example, activating transcription factor (ATF) 2 or TBP-associated factor 250 (TAFII250), and nuclear steroid receptor coactivators posses intrinsic HAT activity (Piaz et al. 2011). ...
Continuously increasing understanding of the molecular triggers responsible for the onset of diseases, paralleled by an equally dynamic evolution of chemical synthesis and screening methods, offers an abundance of pharmacological agents with a potential to become new successful drugs. However, before patients can benefit of newly developed pharmaceuticals, stringent safety filters need to be applied to weed out unfavourable drug candidates. Cost effectiveness and the need to identify compound liabilities, without exposing humans to unnecessary risks, has stimulated the shift of the safety studies to the earliest stages of drug discovery and development. In this regard, in vivo relevant organotypic in vitro models have high potential to revolutionize the preclinical safety testing. They can enable automation of the process, to match the requirements of high-throughput screening approaches, while satisfying ethical considerations. Cultures of primary hepatocytes became already an inherent part of the preclinical pharmaco-toxicological testing battery, yet their routine use, particularly for long-term assays, is limited by the progressive deterioration of liver-specific features. The availability of suitable hepatic and other organ-specific in vitro models is, however, of paramount importance in the light of changing European legal regulations in the field of chemical compounds of different origin, which gradually restrict the use of animal studies for safety assessment, as currently witnessed in cosmetic industry. Fortunately, research groups worldwide spare no effort to establish hepatic in vitro systems. In the present review, both classical and innovative methodologies to stabilize the in vivo-like hepatocyte phenotype in culture of primary hepatocytes are presented and discussed.
... Moreover, nonhistone protein substrates of PCAF have been described, such as p53 protein, which is one of the main regulators of crucial cellular functions [5]. Thus, the PCAF acetyltransferase has been proposed to constitute a promising target for therapeutic development and small-molecule inhibitors of PCAF are investigated intensively [19]. ...
Acetylation of histones and nonhistone proteins is a posttranslational modification which plays a major role in the regulation of intracellular processes involved in tumorigenesis. It was shown that different acetylation of proteins correlates with development of leukemia. It is proposed that histone acetyltransferases (HATs) are important novel drug targets for leukemia treatment, however data are still not consistent. Our previous data showed that a derivative of anacardic acid - small molecule MG153, which has been designed and synthesized to optimize the HAT inhibitory potency of anacardic acid, is a potent inhibitor of p300/CBP associated factor (PCAF) acetyltransferase. Here we ask whether inhibition of PCAF acetyltransferase with MG153 will show proapoptotic effects in cells expressing BCR-ABL, which show increased PCAF expression and are resistant to apoptosis. We found that inhibition of PCAF decreases proliferation and induces apoptosis, which correlates with loss of the mitochondrial membrane potential and DNA fragmentation. Importantly, cells expressing BCR-ABL are more sensitive to PCAF inhibition compared to parental cells without BCR-ABL. Moreover, inhibition of PCAF in BCR-ABL-expressing cells breaks their resistance to DNA damage-induced cell death. These findings provide direct evidence that targeting the PCAF alone or in combination with DNA-damaging drugs shows cytotoxic effects and should be considered as a prospective therapeutic strategy in chronic myeloid leukemia cells. Moreover, we propose that anacardic acid derivative MG153 is a valuable agent and further studies validating its therapeutic relevance should be performed.
... An array of HAT inhibitors have been identified and reviewed 129,130 . However, most of these compounds are either promiscuous natural substances that bind multiple classes of proteins 129 or they are covalently modifying isothiazolones 131 . ...
Epigenetic regulation of gene expression is a dynamic and reversible process that establishes normal cellular phenotypes but also contributes to human diseases. At the molecular level, epigenetic regulation involves hierarchical covalent modification of DNA and the proteins that package DNA, such as histones. Here, we review the key protein families that mediate epigenetic signalling through the acetylation and methylation of histones, including histone deacetylases, protein methyltransferases, lysine demethylases, bromodomain-containing proteins and proteins that bind to methylated histones. These protein families are emerging as druggable classes of enzymes and druggable classes of protein-protein interaction domains. In this article, we discuss the known links with disease, basic molecular mechanisms of action and recent progress in the pharmacological modulation of each class of proteins.
... An important discovery that has led to the understanding of the estrogenic activity of genistein in which prenatal exposure to genistein permanently affects the erythropoiesis in fetus and alters the gene expression and DNA methylation in hematopoietic cells (75). Also, ligands for isoflavones in the ERamediated HAT activity have been identified, and genistein has been observed to cause modulation of the HAT activity and extent of histone acetylation (64). These studies underscore the estrogenic nature of the phytoestrogen and genistein and their effects on ERa, which may be seriously considered for use as an anticancer agent. ...
Unlabelled:
In living systems, the mechanisms of inheritance involving gene expression are operated by (i) the traditional model of genetics where the deoxyribonucleic acid (DNA) transcription and messenger ribonucleic acid stability are influenced by the DNA sequences and any aberrations in the primary DNA sequences and (ii) the epigenetic (above genetics) model in which the gene expression is regulated by mechanisms other than the changes in DNA sequences. The widely studied epigenetic alterations include DNA methylation, covalent modification of chromatin structure, state of histone acetylation, and involvement of microribonucleic acids.
Significance:
Currently, the role of cellular epigenome in health and disease is rapidly emerging. Several factors are known to modulate the epigenome-regulated gene expression that is crucial in several pathophysiological states and diseases in animals and humans. Phytochemicals have occupied prominent roles in human diet and nutrition as protective antioxidants in prevention/protection against several disorders and diseases in humans.
Recent advances:
However, it is beginning to surface that the phytochemical phenolic antioxidants such as polyphenols, flavonoids, and nonflavonoid phenols function as potent modulators of the mammalian epigenome-regulated gene expression through regulation of DNA methylation, histone acetylation, and histone deacetylation in experimental models.
Critical issues and future directions:
The antioxidant or pro-oxidant actions and their involvement in the epigenome regulation by the phytochemical phenolic antioxidants should be at least established in the cellular models under normal and pathophysiological states. The current review discusses the mechanisms of modulation of the mammalian cellular epigenome by the phytochemical phenolic antioxidants with implications in human diseases.
The p300 histone acetyltransferase (HAT) enzyme acetylates the lysine residue of histone promotes the transcription reaction. The abnormal function of p300 HAT enzyme causes various diseases such as Cancer, Asthma, Alzheimer, Diabetics, and AIDS. In the recent years, several studies have been conducted to design potential drug to inhibit this enzyme. Recently, an in vitro study has been performed on the synthetic molecules PU139 and PU141 to inhibit the p300 HAT enzyme. The present study aims to understand the binding affinity, intermolecular interactions, conformational stability and binding energy of PU139 and PU141 molecules in the active site of p300 HAT enzyme from the in silico studies. The molecular docking and molecular dynamics (MD) simulations were carried out for both ligands with the p300 HAT enzyme. The molecular docking and MD simulations reveals that both molecules forms expected interactions with the catalytic site key residues of p300 enzyme. The MD simulation shows the maximum RMSD value for the PU141 is 2.3 Å, whereas for PU139 is 3.3 Å; these low RMSD values indicate that both molecules are highly stable in the active site of p300. The calculated binding free energy of PU141 (−20.62 kcal/mol) is higher than the molecule PU139 (−17.67 kcal/mol). Among the results, PU141 shows the high binding affinity with p300 while comparing with PU139. The results of this in-silico study coupled with the findings reported in the in vitro study confirm that PU141 may be suitable for clinical study.
Communicated by Ramaswamy H. Sarma
Acetylation, a key component in post-translational modification regulated by HATs and HDACs, is relevant to many crucial cellular contexts in organisms. Based on crucial pharmacophore patterns and the structure of targeted proteins, HAT inhibitors are designed and modified for higher affinity and better bioactivity. However, there are still some challenges, such as cell permeability, selectivity, toxicity and synthetic availability, which limit the improvement of HAT inhibitors. So far, only few HAT inhibitors have been approved for commercialization, indicating the urgent need for more successful and effective structure-based drug design and synthetic strategies. Here, we summarized three classes of HAT inhibitors based on their sources and structural scaffolds, emphasizing on their synthetic methods and structure–activity relationships and molecular mechanisms, hoping to facilitate the development and further application of HAT inhibitors.
Among the other posttranslational modifications, protein acetylation has been identified as one of the key mechanisms in the regulation of biological functions. Acetylation is a dynamic process that involves the transfer or removal of acetyl groups to ϵ‐amino group of lysine residues and is mediated by acetyltransferase and deacetylase enzymes, respectively. Lysine acetyltransferase (KAT) enzymes could be classified using different classifications on the basis of their subcellular localization or on the basis of their structural homology and/or catalytic mechanism. The general control non‐repressible 5‐related N‐acetyltransferase (GNAT) family is evolutionarily conserved from bacteria to mammals. KAT2A is an example for substrate discrimination by the structural motifs that are a typical feature of GNAT family. More commonly referred to as Hat1, KAT1 is a cytoplasmic KAT enzyme that acetylates newly synthesized free histones during chromatin assembly. One of the hypotheses to explain the mechanism underlying the acetylation of mitochondrial proteins is the existence of mitochondrial acetyltransferases.
This thesis focuses on the metabolism of the parasite Schistosoma mansoni. During its life cycle, S. mansoni experiences drastic environmental changes that include: free-living stages in water and endoparasitism in invertebrate (i.e. snails) and vertebrate (i.e. mammals) hosts. In consequence, this parasite shows an amazing metabolic plasticity characterized by drastic metabolic switches from one stage to another. One of the more interesting is the switch from oxidative phosphorylation to aerobic glycolysis that occurs when the free-living stage, cercariae, infects the mammalian host. This switch is dependent on host glucose and is totally reversible when glucose concentration is low. Here, we study in details the evolution of the glucose transporters of S. mansoni as well as the potential role of histone modifying enzymes (i.e. sirtuins) in the regulation of the metabolic switch. The thesis is organized of three chapters. Chapter I is a general introduction to genus schistosoma, its taxonomy and more prominent members, their epidemiology and current control strategies. We further introduce our current knowledge on the epigenetic machinery of these parasites as well as the sirtuin protein family. In Chapter II we present the results of the thesis and this chapter is separated in two parts: (i) the evolution and molecular properties of glucose transporters in S. mansoni, (ii) and the role of Sirtuin 1 in the regulation of the mitochondrial metabolism of schistosomula, the mammalian stage of S. mansoni. We found that the glucose transporters from S. mansoni, SGTP1, SGTP2, SGTP3 and SGTP4 followed different evolutionary paths. Our results suggested that S. mansoni class I glucose transporters (SGTP2 and SGTP3) lost their capacity to transport glucose and that this function evolved independently in the Platyhelminthes-specific glucose transporters (SGTP1 and SGTP4). Regarding the role of sirtuins in the regulation of glucose metabolism in S. mansoni, we found that at high concentrations of glucose, S. mansoni sirtuin 1 (SmSirt1) stimulate mitochondrial activity. Sirtuin 1 Inhibitors as well as SmSirt1 gene knockdown, by RNA interference, reduce the mitochondrial activity of schistosomula. In addition, SmSirt1 is a repressor of pyruvate dehydrogenase kinase 1 (PDK1), a major regulator of mitochondrial activity. However, SmSirt1 did not appear to repress the S. mansoni glucose transporters. This is in agreement with our analysis of glucose transporter evolution because in mammals, Sirt1 regulates the expression of class I glucose transporters and our results showed that class I glucose transporters in S. mansoni do not transport glucose. Finally, in Chapter III we make a general discussion of the main findings of the thesis.
Epigenetic modifications, including DNA methylation, covalent histone modifications, and small noncoding RNAs, play a key role in regulating the gene expression. This regulatory mechanism is important in cellular differentiation and development. Recent advances in the field of epigenetics extended the role of epigenetic mechanisms in controlling key biological processes such as genome imprinting and X-chromosome inactivation. Aberrant epigenetic modifications are associated with the development of many diseases. The role of epigenetic modifications in various neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease, Huntington disease, epilepsy, and multiple sclerosis is rapidly emerging. The use of epigenetic modifying drugs to treat these diseases has been the interest in recent years. A number of natural products having diverse mechanism of action are used for drug discovery. For many years, natural compounds have been used to treat various neurodegenerative diseases, but the use of such compounds as epigenetic modulators to reverse or treat neurological diseases are not well studied. In this chapter, we mainly focus on how various epigenetic modifications play a key role in neurodegenerative diseases, their mechanism of action, and how it acts as a potential therapeutic target for epigenetic drugs to treat these diseases will be discussed.
Chemical constituents isolated from food and other natural sources can interfere with many biological targets in human beings. Compounds like curcumin, genistein, plant and food polyphenols, resveratrol, and sulforaphane are able to modulate the biological activity of cell pathways and its functions in relation to metabolism and epigenetics. While the mechanisms by which these compounds exert their roles are still far to be fully elucidated, their usage has emerged in the past years for conceiving new cancer prevention strategies and novel therapeutic interventions. A deeper understanding on how metabolism and epigenetics are influenced by food and natural components can be achieved at molecular level by using a variety of chemoinformatic and computer-aided techniques that include data mining, molecular databasing, and molecular design techniques like pharmacophore-based methods or molecular docking. In this chapter, we will describe these in silico techniques as valuable tools to explore molecular determinants, and pharmacological role of food and other natural constituents in cancer epigenetics and metabolism. © 2014 Springer International Publishing Switzerland. All rights are reserved.
As a class, epigenetic enzymes have been identified as clear targets for cancer therapeutics based on their broad hyperactivity in solid and hematological malignancies. The search for effective inhibitors of histone writers and of histone erasers has been a focus of drug discovery efforts both in academic and pharmaceutical laboratories and has led to the identification of some promising leads. This review focuses on the discovery strategies and preclinical evaluation studies of a subset of the more advanced compounds that target histone writers or histone erasers. The specificity and anticancer potential of these small molecules is discussed within the context of their development pipeline.
The explosion in the generation of information parallels the explosion of computational resources. The use of computers to collect, store and manipulate chemical information is at the heart of chemoinformatics. These methodologies, whose main target thus far has been the pharmaceutical field, are general and can be applied to other types of chemical data sets, such as those containing food chemicals. While the use of chemical information methodologies to address food-related challenges is still in its infancy, interest is growing and will continue to do so as the methods prove useful, particularly for providing practical solutions to food industry challenges. Foodinformatics gives an overview of basic concepts, applications, tools and perspectives of the emerging field of foodinformatics. The book is an important addition to the literature and will be of interest of food chemists, nutritionists, informaticians and scientists of related fields. © 2014 Springer International Publishing Switzerland. All rights are reserved.
A series of Δ(2)-isoxazoline constrained analogues of procaine/procainamide (7a-k and 8a-k) were prepared and their inhibitory activity against DNA methyltransferase 1 (DNMT1) was tested. Among them, derivative 7b is far more potent in vitro (IC(50) = 150 μM) than other non-nucleoside inhibitors and also exhibits a strong and dose-dependent antiproliferative effect against HCT116 human colon carcinoma cells. The binding mode of 7b with the enzyme was also investigated by means of a simple competition assay as well as of docking simulations conducted using the recently published crystallographic structure of human DNMT1. On the basis of the findings, we assessed that the mode of inhibition of 7b is consistent with a competition with the cofactor and propose it as a novel lead compound for the development of non-nucleoside DNMT inhibitors.
A charge density analysis has been performed on gas phase and docked forms of anacardic acid molecule to understand its charge density distribution, electrostatic moments and the conformation in the active site of p300 enzyme. Here, we report the binding affinity of anacardic acid with the p300 enzyme calculated from docking analysis. The charge density distribution of anacardic acid molecule in the gas phase as well as the docked form has been determined from the high level quantum chemical calculations using HF and DFT methods coupled with AIM theory. The charge density study on both forms of anacardic acid differentiates its structural and the electrostatic properties in different environments. When the molecule enters into the active site of p300 its conformation, charge density distribution, dipole moment and electrostatic potential are significantly altered in comparison to its gas phase structure. In the active site, the molecule adopts different conformations, its pentadecyl chain is found to be highly twisted; the charges are redistributed and the dipole moment increases from 2.37 to 3.17D. Due to the charge redistribution, the electronegative region of carboxyl group increased as it is found small in the gas phase. The comparisons between both forms reveal the flexibility of anacardic acid in the active site.
Alteration of the acetylation state of histone proteins contributes to transcriptional regulation and epigenetic inheritance. Dysregulation of these processes may lead to human diseases, especially cancer. One of the major chromatin modifications is histone acetylation and this review gives an overview of the role of histone acetyltransferases, their structural aspects, as well as of chemical modulators targeting their enzymatical activities. Inhibitors and activators of histone acetyltransferases are presented and their capability to influence histone and non-histone protein acetylation levels is discussed. Development of small molecules as epigenetic tools that alter histone acetyltransferase activity will be helpful to better understand the consequences of histone and generally protein acetylation and potentially offer novel therapeutic approaches for the treatment of cancer and other diseases.
The transcription initiation factor TFIID is a multimeric protein complex composed of TATA box–binding protein (TBP) and many TBP-associated factors (TAFIIs). TAFIIs are important cofactors that mediate activated transcription by providing interaction sites for distinct activators. Here, we present evidence that human TAFII250 and its homologs in Drosophila and yeast have histone acetyltransferase (HAT) activity in vitro. HAT activity maps to the central, most conserved portion of dTAFII230 and yTAFII130. The HAT activity of dTAFII230 resembles that of yeast and human GCN5 in that it is specific for histones H3 and H4 in vitro. Our findings suggest that targeted histone acetylation at specific promoters by TAFII250 may be involved in mechanisms by which TFIID gains access to transcriptionally repressed chromatin.
Garcinol, harvested from Garcinia indica, has traditionally been used in tropical regions and appreciated for centuries; however its biological properties are only beginning to be elucidated. There is ample data to suggest potent antioxidant properties of this compound which have been used to explain most of its observed biological activities. However, emerging evidence suggests that garcinol could be useful as an anti-cancer agent, and it is increasingly being realized that garcinol is a pleiotropic agent capable of modulating key regulatory cell signaling pathways. Here we have summarized the progress of our current research knowledge on garcinol and its observed biological activities. We have also provided an explanation of observed properties based on its chemical structure and provided an insight into the structure and properties of chalcones, the precursors of garcinol. The available data is promising but more detailed investigations into the various properties of this compound, particularly its anti-cancer activity are urgently needed, and it is our hope that this review will stimulate further research for elucidating and appreciating the value of this nature's wonder agent.
Whether garcinol, the active component of Garcinia indica, can modulate the sensitivity of cancer cells to TRAIL, a cytokine currently in phase II clinical trial, was investigated. We found that garcinol potentiated TRAIL-induced apoptosis of cancer cells as indicated by intracellular esterase activity, DNA strand breaks, accumulation of the membrane phospholipid phosphatidylserine, mitochondrial activity, and activation of caspase-8, -9, and -3. We found that garcinol, independent of the cell type, induced both of the TRAIL receptors, death receptor 4 (DR4) and DR5. Garcinol neither induced the receptors on normal cells nor sensitized them to TRAIL. Deletion of DR5 or DR4 by small interfering RNA significantly reduced the apoptosis induced by TRAIL and garcinol. In addition, garcinol downregulated various cell survival proteins including survivin, bcl-2, XIAP, and cFLIP, and induced bid cleavage, bax, and cytochrome c release. Induction of death receptors by garcinol was found to be independent of modulation of CCAAT/enhancer-binding protein-homologous protein, p53, bax, extracellular signal-regulated kinase, or c-Jun-NH(2)-kinase. The effect of garcinol was mediated through the generation of reactive oxygen species, in as much as induction of both death receptors, modulation of antiapoptotic and proapoptotic proteins, and potentiation of TRAIL-induced apoptosis were abolished by N-acetyl cysteine and glutathione. Interestingly, garcinol also converted TRAIL-resistant cells into TRAIL-sensitive cells. Overall, our results indicate that garcinol can potentiate TRAIL-induced apoptosis through upregulation of death receptors and downregulation of antiapoptotic proteins. Mol Cancer Ther; 9(4); 856-68. (c)2010 AACR.
Many new polyisoprenylated benzophenones with a bicyclo[3.3.1]-nonane-2,4,9-trione core structure have been isolated from plants in the Clusiaceae family, and their potent biological properties have been the subject of several studies. This review summarizes the biological activities reported for these secondary metabolites including cytotoxic, antimicrobial, antioxidant, and anti-inflammatory activities. Our efforts during the past years have foremost been directed towards isolating new polyisoprenylated benzophenones, as well as understanding the possible target and mechanism of action through which these compounds arrest cancer cells and inhibit the progression of the cell-cycle. The transcription of genes is affected in cancer cells treated with polyisoprenylated benzophenones; the oncogene c-Myb is down-regulated and endoplasmatic stress genes XBP1, ATF4, and DDIT3/CHOP are turned on. Consequently, the expression of iNOS and cell cycle regulators such as cyclin D and E are reduced. Evidence presented by independent investigators suggests that polyisoprenylated benzophenones affect the mediators in the Akt/mTOR stress pathway, although the specific target remains to be discovered. In addition, benzophenones isolated from plants display high antioxidant capacity and protect cells from oxidative stress and the formation of ROS involved during the inflammatory process. Since antiviral activity was initially reported for guttiferone A, potent synthetic analogues have been developed as effective new non-nucleoside reverse transcriptase inhibitors (NNRTI) to treat drug resistant HIV-1. In addition, benzophenones exert antimicrobial effects particularly against MRSA. The structure-activity relationships of polyisoprenylated benzophenones from natural sources and those of synthetic analogues are included in this review. Absorption, metabolism, and elimination of benzophenones are also discussed.
Lysine acetyltransferases (KATs), p300 (KAT3B), and its close homologue CREB-binding protein (KAT3A) are probably the most widely studied KATs with well documented roles in various cellular processes. Hence, the dysfunction of p300 may result in the dysregulation of gene expression leading to the manifestation of many disorders. The acetyltransferase activity of p300/CREB-binding protein is therefore considered as a target for new generation therapeutics. We describe here a natural compound, plumbagin (RTK1), isolated from Plumbago rosea root extract, that inhibits histone acetyltransferase activity potently in vivo. Interestingly, RTK1 specifically inhibits the p300-mediated acetylation of p53 but not the acetylation by another acetyltransferase, p300/CREB-binding protein -associated factor, PCAF, in vivo. RTK1 inhibits p300 histone acetyltransferase activity in a noncompetitive manner. Docking studies and site-directed mutagenesis of the p300 histone acetyltransferase domain suggest that a single hydroxyl group of RTK1 makes a hydrogen bond with the lysine 1358 residue of this domain. In agreement with this, we found that indeed the hydroxyl group-substituted plumbagin derivatives lost the acetyltransferase inhibitory activity. This study describes for the first time the chemical entity (hydroxyl group) required for the inhibition of acetyltransferase activity.
Because the p300/CBP-mediated hyperacetylation of RelA (p65) is critical for nuclear factor-kappaB (NF-kappaB) activation, the attenuation of p65 acetylation is a potential molecular target for the prevention of chronic inflammation. During our ongoing screening study to identify natural compounds with histone acetyltransferase inhibitor (HATi) activity, we identified epigallocatechin-3-gallate (EGCG) as a novel HATi with global specificity for the majority of HAT enzymes but with no activity toward epigenetic enzymes including HDAC, SIRT1, and HMTase. At a dose of 100 micromol/L, EGCG abrogates p300-induced p65 acetylation in vitro and in vivo, increases the level of cytosolic IkappaBalpha, and suppresses tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB activation. We also showed that EGCG prevents TNFalpha-induced p65 translocation to the nucleus, confirming that hyperacetylation is critical for NF-kappaB translocation as well as activity. Furthermore, EGCG treatment inhibited the acetylation of p65 and the expression of NF-kappaB target genes in response to diverse stimuli. Finally, EGCG reduced the binding of p300 to the promoter region of interleukin-6 gene with an increased recruitment of HDAC3, which highlights the importance of the balance between HATs and histone deacetylases in the NF-kappaB-mediated inflammatory signaling pathway. Importantly, EGCG at 50 micromol/L dose completely blocks EBV infection-induced cytokine expression and subsequently the EBV-induced B lymphocyte transformation. These results show the crucial role of acetylation in the development of inflammatory-related diseases.
Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.
The possibility that the heightened cardiovascular risk associated with the menopause can be reduced by increasing dietary isoflavone intake was tested in 17 women by measuring arterial compliance, an index of the elasticity of large arteries such as the thoracic aorta. Compliance diminishes with age and menopause. An initial 3- to 4-week run-in period and a 5-week placebo period were followed by two 5-week periods of active treatment with 40 mg and then 80 mg isoflavones derived from red clover containing genistein, daidzein, biochanin, and formononetin in 14 and 13 women, respectively, with 3 others serving as placebo controls throughout. Arterial compliance, measured by ultrasound as a pressure (carotid artery) and volume (outflow into aorta) relationship, was determined after each period; plasma lipids were measured twice during each period. Urinary output of isoflavones was also determined. Arterial compliance rose by 23% relative to that during the placebo period with the 80-mg isoflavone dose and slightly less with the 40-mg dose (mean6SEM: placebo, 19.761.5; 40 mg, 23.760.7; 80 mg, 24.46 1.4). In the three women receiving continuous placebo, compliance was 16 6 2.2, similar to that during the run-in period for the remaining subjects (17 6 2.1). ANOVA showed a significant (P 5 , 0.001) difference between treatments; by Bonferroni multiple comparisons and by paired t test, differences were significant between placebo and 40- and 80-mg isoflavone doses (by paired t test: P50.039 for placebo vs. 40 mg; P 5 0.018 for placebo vs. 80 mg). Plasma lipids were not significantly affected. An important cardiovascular risk factor, arterial compliance, which diminishes with menopause, was significantly improved with red clover isoflavones. As diminished compliance leads to systolic hypertension and may increase left ventricular work, the findings indicate a potential new therapeutic approach for improved cardiovascular function after menopause.<br /
CREB-binding protein (CBP) is a transcriptional coactivator that has intrinsic histone acetyltransferase (HAT) activity. CBP is the causative gene of Rubinstein-Taybi syndrome (RTS). To investigate the relationships between CBP HAT activity and RTS, we analyzed 16 RTS patients. A microdeletion was identified in one patient by fluorescent in situ hybridization analysis. Heteroallelic mutations were identified in five patients by reverse transcriptase-polymerase chain reaction-single-strand conformation polymorphism analysis and sequencing. These included a 2 bp deletion between nucleotides 4319 and 4320, an 11 bp deletion between nucleotides 4898 and 4908, a 14 bp insertion (CCTCGGTCCTGCAC) between nucleotides 5212 and 5213, a 2 bp deletion between nucleotides 5222 and 5223, and a missense mutation from guanine (G) to cytosine (C) at nucleotide 4951 that changed codon 1378 from CGG (arginine) to CCG (proline). The identical missense mutation was introduced into the recombinant mouse CBP. It abolished the HAT activity of CBP and the ability of CBP to transactivate cyclic AMP-response element binding protein (CREB), in HAT assays and in microinjection experiments, respectively. These results suggest that the loss of the HAT activity of CBP may cause RTS, as the first example of a defect of HAT activity in a human disease. Our findings raise the possibility that treatment of RTS patients with histone deacetylase inhibitors might have beneficial effects.
Cancer is one of the leading causes of death in the world. American Cancer Society reported 12 million new cases of malignancy diagnosed worldwide in 2007, with 7.6 million people dying from the disease. Plant-derived molecules have played an important role in cancer chemotherapy. Many cytotoxic plant-derived molecules such as vinblastine, vincristine, navelbine, etoposide, teniposide, taxol, taxotere, topotecan and irinotecan have been approved as anticancer drugs. Flavonoids, a plant-derived molecule has shown to regulate proliferation and cell death pathways leading to cancer. Some Flavonoids have already entered in clinical trials, among them Quercetin is emerging as prospective anticancer drug candidates and its prodrug QC12 has entered in phase-I clinical studies. In this review authors have tried to cover in brief but comprehensive way, the chemistry related to synthesis and uses of "Quercetin & its derivatives" with special emphasis on the anticancer properties.
Polycyclic polyprenylated acylphloroglucinols (PPAPs) are a class of compounds that reveal intriguing biological activities and interesting and challenging chemical structures. These products are claimed to possess antioxidant, antiviral, and antimitotic properties. Increasing interest is related to their function in the CNS as modulators of neurotransmitters associated to neuronal damaging and depression. All these features make PPAPs targets for synthesis. We decided to focus our own initial efforts in this area on the type A PPAP, nemorosone because we thought that its fairly simple structure relative to other PPAPs would present fewer hurdles as we developed our methodology.In the past decade many approaches to the synthesis of the bicyclo[3.3.1]nonane-2,4,9-trione structure of type A PPAPs have been reported, but only two total syntheses of any PPAP, garsubellin A by Shibasaki and Danishefsky, have been published recently, near the end of 2005. All approaches have relied on the ??,????-annulation of a three-carbon bridge onto a cyclohexanone, although the methods used to execute this annulation differ dramatically. The methods most often used to form the two new C–C bonds have involved classical carbonyl chemistry.We have developed a short and efficient synthetic approach to the bicyclo[3.3.1]nonane skeleton of the PPAPs that involves a novel three-carbon ??,????-annulation of a sterically hindered cyclic ??-keto ester with 3,3-diethoxypropyne. The alkynylation reaction permits the construction of the two contiguous quaternary centers of the PPAPs in reasonable yield and without complications from side reactions. We have also successfully applied a recently developed syn hydrosilylation to the very hindered product of this alkynylation reaction. Our methodology received positive feedback already, and we see this total synthesis of nemorone as an ideal platform for the implementation of new synthetic methodologies.
Ten phenolic compounds were isolated from the CHCl3 extract of Ginkgo biloba sarcotestas (Ginkgoaceae) as a new class of phosphatidylinositol-specific phospholipase Cgamma1 (PI-PLCgamma1) inhibitors. The substances without the long chain were ineffective. On the other hand, the activities of these compounds were dramatically decreased by acetylation of aromatic hydroxyl groups of cardanol, phenolic acid, and bilobol and by methylation of the aromatic carboxyl group of phenolic acid. The unsaturated long chain as well as the aromatic hydroxyl and carboxyl groups might play a key role for the PI-PLCgamma1 inhibitory activity. These compounds also inhibited the growth of a number of human cancer cell lines, but were less cytotoxic against a human normal colon cell line.
Considerable progress has been made during the past year on structure determinations of eukaryotic transcription factors that function as DNA-binding proteins in concert with RNA polymerase II. New structures include two TATA box-binding proteins bound to distinct TATA elements, two b/HLH/Z factors, Max and USF, recognizing CACGTG, and four helix-turn-helix variants, the third repeat of c-Myb, the POU-specific domain of Oct-1, an atypical homeodomain from LFB1/HNF1, and the fork head domain of HNF-3γ complexed with DNA. Other novel structures include the DNA-binding domain of GATA-1 complexed with DNA, the nucleic acid-binding domain of transcription factor IIS and the five zinc-finger GLI-DNA complex.
The quaternary benzo[c]phenanthridine alkaloids (QBA) produce a plethora of species- and tissue-specific effects but the molecular basis of their biological activities remain mysterious. The objective of the present study was to investigate the cytotoxicity of QBA alkaloids, sanguinarine (SA), chelerythrine (CHE), fagaronine (FA), and the extract from Macleaya cordata in primary cultures of human and porcine hepatocytes. The cellular damage was assessed by the MTT assay, lactate dehydrogenase (LDH) leakage and the determination of intracellular glutathione (GSH) levels. The results are summarised as follows: (i) The alkaloids tested in doses 0.1 and 10 μM did not display statistically significant cytotoxicity for 0–3 h incubation; (ii) SA and CHE showed the dose- and time-dependent toxicity within the range 25–100 μM whereas FA was not toxic; (iii) the LDH leakage into the medium was higher for SA than for CHE, thus revealing a potent potential of SA to disturb cell-membrane integrity; (iv) after 3 h incubation with 100 μM SA/CHE, mitochondrial dehydrogenase activity (MTT assay) and the cellular GSH levels decreased to residual values of about 40% suggesting that mitochondria are unlikely to be a primary target for SA/CHE in the cell; (v) no differences were found in the response to QBA application in human vs porcine hepatocyte.
We have cloned a novel member of the nuclear receptor superfamily. The cDNA of clone 29 was isolated from a rat prostate cDNA library and it encodes a protein of 485 amino acid residues with a calculated molecular weight of 54.2 kDa. Clone 29 protein is unique in that it is highly homologous to the rat estrogen receptor (ER) protein, particularly in the DNA-binding domain (95%) and in the C-terminal ligand-binding domain (55%). Expression of clone 29 in rat tissues was investigated by in situ hybridization and prominent expression was found in prostate and ovary. In the prostate clone 29 is expressed in the epithelial cells of the secretory alveoli, whereas in the ovary the granulosa cells in primary, secondary, and mature follicles showed expression of clone 29. Saturation ligand-binding analysis of in vitro synthesized clone 29 protein revealed a single binding component for 17beta -estradiol (E2) with high affinity (Kd = 0.6 nM). In ligand-competition experiments the binding affinity decreased in the order E2 > diethylstilbestrol > estriol > estrone > 5alpha -androstane-3beta ,17beta -diol >> testosterone = progesterone = corticosterone = 5alpha -androstane-3alpha ,17beta -diol. In cotransfection experiments of Chinese hamster ovary cells with a clone 29 expression vector and an estrogen-regulated reporter gene, maximal stimulation (about 3-fold) of reporter gene activity was found during incubation with 10 nM of E2. Neither progesterone, testosterone, dexamethasone, thyroid hormone, all-trans-retinoic acid, nor 5alpha -androstane-3alpha ,17beta -diol could stimulate reporter gene activity, whereas estrone and 5alpha -androstane-3beta ,17beta -diol did. We conclude that clone 29 cDNA encodes a novel rat ER, which we suggest be named rat ERbeta to distinguish it from the previously cloned ER (ERalpha ) from rat uterus.
ANACARDIC acid, the major component of the liquid extracted by solvent from cashew-nut shells1, was regarded as a homogeneous chemical entity containing in its aliphatic side-chain of fifteen carbon atoms two double bonds until recently, when it was shown by Izzo and Dawson2 to be in fact a mixture of olefinic components of which they identified the mono-olefin in the form of a crystalline glycol of the methylated anacardic acid. The present communication reports the complete separation of the mixture into its several components and the determination of their olefinic structure.
Two prostaglandin synthetase inhibitory anacardic acids were isolated from O. mucronata. The structures of these inhibitors were established by spectroscopic means. Efficient syntheses of these two via directive metallation were reported.
The rat estrogen receptor (ER) exists as two subtypes, ERα and ERβ, which differ in the C-terminal ligand binding domain and in the N-terminal transactivation domain. In this study we investigated the messenger RNA expression of both ER subtypes in rat tissues by RT-PCR and compared the ligand binding specificity of the ER subtypes.
Saturation ligand binding analysis of in vitro synthesized human ERα and rat ERβ protein revealed a single binding component for 16α-iodo-17β-estradiol with high affinity[ dissociation constant (Kd) = 0.1 nm for ERα protein and 0.4 nm for ERβ protein]. Most estrogenic substances or estrogenic antagonists compete with 16α-[125I]iodo-17β-estradiol for binding to both ER subtypes in a very similar preference and degree; that is, diethylstilbestrol > hexestrol > dienestrol > 4-OH-tamoxifen > 17β-estradiol > coumestrol, ICI-164384 > estrone, 17α-estradiol > nafoxidine, moxestrol > clomifene > estriol, 4-OH-estradiol > tamoxifen, 2-OH-estradiol, 5-androstene-3β,17β-diol, genistein for the ERα protein and dienestrol > 4-OH-tamoxifen > diethylstilbestrol > hexestrol > coumestrol, ICI-164384 > 17β-estradiol > estrone, genistein > estriol > nafoxidine, 5-androstene-3β,17β-diol > 17α-estradiol, clomifene, 2-OH-estradiol > 4-OH-estradiol, tamoxifen, moxestrol for the ERβ protein. The rat tissue distribution and/or the relative level of ERα and ERβ expression seems to be quite different, i.e. moderate to high expression in uterus, testis, pituitary, ovary, kidney, epididymis, and adrenal for ERα and prostate, ovary, lung, bladder, brain, uterus, and testis for ERβ. The described differences between the ER subtypes in relative ligand binding affinity and tissue distribution could contribute to the selective action of ER agonists and antagonists in different tissues.
Histone acetylation is important in chromatin remodelling and gene activation. Nearly all known histone-acetyltransferase (HAT)-associated transcriptional co-activators contain bromodomains, which are ~110-amino- acid modules found in many chromatin-associated proteins. Despite the wide occurrence of these bromodomains, their three-dimensional structure and binding partners remain unknown. Here we report the solution structure of the bromodomain of the HAT co-activator P/CAF (p300/CBP-associated factor). The structure reveals an unusual left-handed up-and-down four-helix bundle. In addition, we show by a combination of structural and site-directed mutagenesis studies that bromodomains can interact specifically with acetylated lysine, making them the first known protein modules to do so. The nature of the recognition of acetyl-lysine by the P/CAF bromodomain is similar to that of acetyl-CoA by histone acetyltransferase. Thus, the bromodomain is functionally linked to the HAT activity of co-activators in the regulation of gene transcription.
The nuclear factor NF-κB is a pleiotropic transcription factor whose activation results in inflammation, viral replication,
and growth modulation. Due to its role in pathogenesis, NF-κB is considered a key target for drug development. In the present
report we show that sanguinarine (a benzophenanthridine alkaloid), a known anti-inflammatory agent, is a potent inhibitor
of NF-κB activation. Treatment of human myeloid ML-1a cells with tumor necrosis factor rapidly activated NF-κB, this activation
was completely suppressed by sanguinarine in a dose- and time-dependent manner. Sanguinarine did not inhibit the binding of
NF-κB protein to the DNA but rather inhibited the pathway leading to NF-κB activation. The reversal of inhibitory effects
of sanguinarine by reducing agents suggests a critical sulfhydryl group is involved in NF-κB activation. Sanguinarine blocked
the tumor necrosis factor-induced phosphorylation and degradation of IκBα, an inhibitory subunit of NF-κB, and inhibited translocation
of p65 subunit to the nucleus. As sanguinarine also inhibited NF-κB activation induced by interleukin-1, phorbol ester, and
okadaic acid but not that activated by hydrogen peroxide or ceramide, the pathway leading to NF-κB activation is likely different
for different inducers. Overall, our results demonstrate that sanguinarine is a potent suppressor of NF-κB activation and
it acts at a step prior to IκBα phosphorylation.
Tea and tea constituents have been shown by different investigators to inhibit lung tumorigenesis in different animal model systems. This includes lung tumorigenesis in A/J mice induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosodiethylamine, benzo[a]pyrene, N-nitrosomethylurea, or cisplatin. Inhibition of lung tumorigenesis has also been demonstrated in C3H mice treated with N-nitrosodiethylamine. In most of these experiments, reduction in tumor number and tumor size has been observed in the tea-treated group, and in some experiments, decreased tumor incidence has also been observed. The green tea constituent, epigallocatechin-3-gallate (EGCG), and the black tea constituent, theaflavins, have also been shown to be effective. Black tea preparations have been shown to reduce the incidence and number of spontaneously generated lung adenocarcinomas and rhabdomyosarcoma in A/J mice, as well as inhibit the progression of lung adenoma to adenocarcinoma. The mechanisms for the inhibitory action have not been well elucidated. It may be related to the antiproliferative, proapoptotic, and antiangiogenic activities of tea constituents that have been demonstrated in some experiments. These activities may be a result of the inhibition of key protein kinases involved in signal transduction and cell cycle regulation. Tea catechins, such as EGCG, have been suggested to be the effective components. However, a study suggests that caffeine is the key effective constituent for the inhibitory activity of lung tumorigenesis in Fisher 344 rats by black tea. In many of the experiments, tea consumption resulted in the reduction of body fat and body weight; these factors may also contribute to the inhibition of tumorigenesis.
A large-scale isolation of the constituents of the cashew shell oil (Anacardium occidentale) was performed by medium-pressure liquid chromatography. A series of 12 components was isolated, including derivatives of anacardic acid, cardol, 2-methylcardol, and cardanol that differ in their side chain. These were tested against Biomphalaria glabratus, one of the snail vectors of schistosomiasis, and their structure-activity relationship is discussed. The principal components in the shell oil, nuts, and fruit juice were also quantitatively determined by high-performance liquid chromatography.
Sixteen phenolic compounds have been isolated from the cashew Anacardium occidentale (Anacardiaceae) nut shell oil. Their antimicrobial activity has been tested against four typical microorganisms, Bacillus subtilis, a Gram-positive bacterium; Escherichia coli, a Gram-negative bacterium; Saccharomyces cereuisiae, a yeast; and Penicillium chrysogenum, a mold. Most of them exhibited potent antibacterial activity against only Gram-positive bacteria, among which Streptococcus mutans, one of several bacteria responsible for tooth decay, and Propionibacterium acnes, one of the bacteria responsible for acne, were the most sensitive bacteria. Anacardic acids also showed weak activity against molds. Their structure-activity relationships are also described.
Screening for microbial metabolites that induce transcriptional activation of the SV40 promoter resulted in the identification of two known compounds, FR901228 and trichostatin A (TSA). FR901228 is a potent antitumor drug that is currently under clinical investigation. TSA is a specific inhibitor of histone deacetylase. Despite structural unrelatedness, both FR901228 and TSA greatly enhanced the transcriptional activity of the SV40 promoter in an enhancer-dependent manner. The effects of FR901228 on the cell cycle, chromatin structure, and histone acetylation were examined and compared with those of TSA. Both compounds caused arrest of the cell cycle at both G1and G2/M phases and induction of internucleosomal breakdown of chromatin. FR901228, like TSA, inhibited intracellular histone deacetylase activity, as a result of which marked amounts of acetylated histone species accumulated. FR901228 is therefore a new type of histone deacetylase inhibitor, whose chemical structure is unrelated to known inhibitors such as trichostatins and trapoxins.
Many chemopreventive agents have been shown to modulate gene expression including induction of phase II detoxifying enzymes, such as glutathione S-transferases (GST) and quinone reductases (QR). Induction of phase II enzymes in general leads to protection of cells/tissues against exogenous and/or endogenous carcinogenic intermediates. The antioxidant or electrophile response element (ARE/EpRE) found at the 5′-flanking region of these phase II genes may play important role in mediating their induction by xenobiotics including chemopreventive agents. Members of the basic leucine zipper (bZIP) transcription factor, Nrf2 which heterodimerizes with Maf G/K, are found to bind to the ARE, and transcriptionally-activated ARE. Recently, we showed that the mitogen-activated protein kinases (MAPK) were activated by phase II gene inducers such as phenolic antioxidant butylated hydroxyanisol (BHA) and isothiocyanate sulforaphane (SUL), and involved in the transcription activation of ARE-mediated reporter gene. Transfection studies with wild-type and dominant negative mutants of Nrf2 and MAPK showed synergistic response during co-transfection as well as to phase II gene inducers. However, increasing the concentrations of these compounds such as BHA, the activities of cell death signaling molecules, caspases, were stimulated and resulted in apoptotic cell death. At these concentrations, BHA stimulated loss of mitochondrial membrane potential, cytochrome c release, and activation of caspase 3, 8 and 9 preceding apoptosis. Further increase in concentrations led to rapid cell necrosis. A model is proposed for BHA and SUL, in that at low concentrations, these potential chemopreventive agents may modulate MAPK pathway leading to transcription activation of Nrf2 and ARE with subsequent induction of cellular defensive enzymes including phase II detoxifying enzymes as well as other defensive genes, which may protect the cells against cellular injury, which is a homeostatic response. At higher concentrations, these agents may activate the caspase pathways, leading to apoptosis, a potential beneficial effect if occurs at preneoplastic/neoplastic tissues, but a potential cytotoxic response if occurs in normal tissues. On the other hand, some phenolic compounds such as resveratrol inhibits TPA- or UV-induced AP-1-mediated activity through the inhibition of c-Src non-receptor tyrosine kinase and MAPK pathways. It is possible that in proliferating or stimulated cells, these chemopreventive compounds may block proliferation by inhibiting these signaling kinases, whereas in non-proliferating or quiescent cells, some of these compounds may activate these signaling kinases leading to gene expression of cellular defensive enzymes such as phase II detoxifying enzymes. The studies of these and other signaling pathways may yield insights into the development of potential chemopreventive compounds.
Histone acetyltransferases (HATs) play important roles in the regulation of gene expression. In this report, we describe the design, synthesis, and application of peptide CoA conjugates as selective HAT inhibitors for the transcriptional coactivators p300 and PCAF. Two inhibitors (Lys-CoA for p300 and H3-CoA-20 for PCAF) were found to be potent (IC50 ≅ 0.5 μM) and selective (∼200-fold) in blocking p300 and PCAF HAT activities. These inhibitors were used to probe enzymatic and transcriptional features of HAT function in several assay systems. These compounds should be broadly useful as biological tools for evaluating the roles of HATs in transcriptional studies and may serve as lead agents for the development of novel antineoplastic therapeutics.
Hybrid polar compounds (HPCs) have been synthesized that induce terminal differentiation and/or apoptosis in various transformed cells. We have previously reported on the development of the second-generation HPCs suberoylanilide hydroxamic acid (SAHA) and m-carboxycinnamic acid bishydroxamide (CBHA) that are 2,000-fold more potent inducers on a molar basis than the prototype HPC hexamethylene bisacetamide (HMBA). Herein we report that CBHA and SAHA inhibit histone deacetylase 1 (HDAC1) and histone deacetylase 3 (HDAC3) activity in vitro. Treatment of cells in culture with SAHA results in a marked hyperacetylation of histone H4, but culture with HMBA does not. Murine erythroleukemia cells developed for resistance to SAHA are cross-resistant to trichostatin A, a known deacetylase inhibitor and differentiation inducer, but are not cross-resistant to HMBA. These studies show that the second-generation HPCs, unlike HMBA, are potent inhibitors of HDAC activity. In this sense, HMBA and the second-generation HPCs appear to induce differentiation by different pathways.
Insulin and its receptor are broadly expressed throughout the brain and have been postulated to play a crucial role in synaptic plasticity. Although structural remodeling of dendritic spines is associated with stable expression of synaptic plasticity, the role of insulin receptor (IR) signaling in the establishment and dynamic changes of dendritic spines remains unclear. Here we report that insulin promotes dendritic spine formation in primary cultures of rat hippocampal neurons. Conversely, downregulation of IR signaling using a blocking antibody or short hairpin RNAs (shRNAs) resulted in a decrease in number of dendritic spines and caused a significant reduction in the frequency of miniature excitatory postsynaptic currents (mEPSCs) without affecting the distribution of their amplitudes. Pharmacological blockade of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway and the small GTPase Rac1 specifically prevented the insulin-induced increase in dendritic spine density. In parallel, genetic ablation of Rac1 expression by lentiviral infection with shRNA abrogated the increase in dendritic spines induced by insulin. More importantly, the increase in dendritic spine density by insulin was accompanied by increasing in presynaptic marker staining density and displayed an increase in mEPSC frequency. Taken together, these results reveal a novel role for IR signaling in the regulation of dendritic spine formation and excitatory synapse development in hippocampal neurons through activation of the PI3K/Akt/mTOR and Rac1 signaling pathways.
Many severe human pathologies are related to alterations of the fine balance between histone acetylation and deacetylation; because not all such diseases involve hypoacetylation, but also hyperacetylation, compounds able to enhance or repress the activities of histone acetyltransferases (HATs) could be promising therapeutic agents. We evaluated in vitro and in cell the ability of eleven natural polyisoprenylated benzophenone derivatives to modulate the HAT activity of p300/CBP, an enzyme that plays a pivotal role in a variety of cellular processes. Some of the tested compounds bound efficiently to the p300/CBP protein: in particular, guttiferone A, guttiferone E and clusianone inhibit its HAT activity, whereas nemorosone showed a surprising ability to activate the enzyme. The ability of nemorosone to penetrate cell membranes and modulate histone acetylation into the cell together with its high affinity for the p300/CBP enzyme made this compound a suitable lead for the design of optimized anticancer drugs. Besides, the studies performed at a cellular and molecular level on both the inhibitors and the activator provided new insights into the modulation mechanism of p300/CBP by small molecules.
Post-translational modifications, such as acetylation or phosphorylation, play a crucial role in the regulation of gene transcription in eukaryotes. Different subtypes of histone acetyl transferases (HATs) catalyze the acetylation of histones on specific lysine residues. A potential role of HATs in the pathology of cancer, asthma, COPD and viral infection has been described. This indicates that specific HAT inhibitors are potential tools for pharmacological research and might find therapeutic applications. This review focuses on the role of the HATs p300, CBP, PCAF and GCN5 in different diseases and the development of small-molecule inhibitors of these enzymes as potential drugs.
DNA-binding anticancer agents cause alteration in chromatin structure and dynamics. We report the dynamic interaction of the DNA intercalator and potential anticancer plant alkaloid, sanguinarine (SGR), with chromatin. Association of SGR with different levels of chromatin structure was enthalpy driven with micromolar dissociation constant. Apart from DNA, it binds with comparable affinity with core histones and induces chromatin aggregation. The dual binding property of SGR leads to inhibition of core histone modifications. Although it potently inhibits H3K9 methylation by G9a in vitro, H3K4 and H3R17 methylation are more profoundly inhibited in cells. SGR inhibits histone acetylation both in vitro and in vivo. It does not affect the in vitro transcription from DNA template but significantly represses acetylation-dependent chromatin transcription. SGR-mediated repression of epigenetic marks and the alteration of chromatin geography (nucleography) also result in the modulation of global gene expression. These data, conclusively, show an anticancer DNA binding intercalator as a modulator of chromatin modifications and transcription in the chromatin context.
Dysfunction of histone acetyltransferases (HATs) leads to several diseases including cancer, diabetes, and asthma. Therefore, small molecule inhibitors and activators of HATs are being considered as new generation therapeutics. Here, we report the molecular mechanisms of p300 HAT inhibition by specific and nonspecific HAT inhibitors: garcinol, isogarcinol, and 1 (LTK14). The p300 specific HAT inhibitor 1 behaves as a noncompetitive inhibitor for both acetyl-CoA and histone, unlike nonspecific HAT inhibitors garcinol and isogarcinol. The isothermal calorimetric data suggest that there is a high affinity enthalpy driven single binding site for 1 on p300HAT domain in contrast to two binding sites for garcinol and isogarcinol. Furthermore, the precise nature of molecular interactions was determined by using fluorescence, docking, and mutational studies. On the basis of these observations, we have proposed the mechanisms of specific versus nonspecific HAT inhibition by these small molecule compounds, which may be useful to design therapeutically favorable HAT inhibitors.
During the eukaryotic cell cycle, chromosomes undergo large structural transitions and spatial rearrangements that are associated with the major cell functions of genome replication, transcription and chromosome condensation to metaphase chromosomes. Eukaryotic cells have evolved cell cycle dependent processes that modulate histone:DNA interactions in chromosomes. These are; i) acetylations of lysines; ii) phosphorylations of serines and threonines and iii) ubiquitinations of lysines. All of these reversible modifications are contained in the well-defined very basic N- and C-terminal domains of histones. Acetylations and phosphorylations markedly affect the charge densities of these domains whereas ubiquitination adds a bulky globular protein, ubiquitin, to lysines in the C-terminal tails of H2A and H2B. Histone acetylations are strictly associated with genome replication and transcription; histone H1 and H3 phosphorylations correlate with the process of chromosome condensation. The subunits of histone H1 kinase have now been shown to be cyclins and the p34CDC2 kinase product of the cell cycle control gene CDC2. It is probable that all of the processes that control chromosome structure:function relationships are also involved in the control of the cell cycle.
C22:1 omega 5-anacardic acid was found to be a good inhibitor of both potato lipoxygenase and ovine prostaglandin endoperoxide synthase with approximate IC50's of 6 and 27 microM, respectively. Very similar inhibition was seen with the crude exudate, rich in omega 5-anacardic acids, from glandular trichomes of an arthropod-resistant strain of geranium, Pelargonium xhortorum. The saturated anacardic acid (C22:0 sat), abundant in the trichome exudate of susceptible strains, was nearly as inhibitory toward both prostaglandin endoperoxide synthase and lipoxygenase as the omega 5-unsaturated compound. However, the dimethyl derivative of C22:1 omega 5-anacardic acid was a poor inhibitor of prostaglandin endoperoxide synthase and caused only moderate (32%) inhibition of lipoxygenase even at 135 microM. The possible role of prostaglandin endoperoxide synthase and lipoxygenase inhibition in the enhanced pest resistance of geraniums which produce the omega 5-AnAs is discussed.
To search for histone domains that may regulate transcription in vivo, we made deletions and amino acid substitutions in the histone N-termini of S. cerevisiae. Histone H4 N-terminal residues 4-23, which include the extremely conserved, reversibly acetylated lysines (at positions 5, 8, 12, and 16), were found to encompass a region required for the activation of the GAL1 promoter. Deletions in the H4 N-terminus reduce GAL1 activation 20-fold. This effect is specific to histone H4 in that large deletions in the N-termini of H2A, H2B, and H3 do not similarly decrease induction. Activation of the PHO5 promoter is reduced approximately 4- to 5-fold by these H4 deletions. Mutations in histone H4 acetylation sites and surrounding residues can cause comparable and, in some cases, even greater effects on induction of these two promoters. We postulate that the H4 N-terminus may interact with a component of the transcription initiation complex, allowing nucleosome unfolding and subsequent initiation.
The data reviewed indicate that extracts of Curcuma longa exhibit anti-inflammatory activity after parenteral application in standard animal models used for testing anti-inflammatory activity. It turned out that curcumin and the volatile oil are at least in part responsible for this action. It appears that when given orally, curcumin is far less active than after i.p. administration. This may be due to poor absorption, as discussed. Data on histamine-induced ulcers are controversial, and studies on the secretory activity (HCl, pepsinogen) are still lacking. In vitro, curcumin exhibited antispasmodic activity. Since there was a protective effect of extracts of Curcuma longa on the liver and a stimulation of bile secretion in animals, Curcuma longa has been advocated for use in liver disorders. Evidence for an effect on liver disease in humans is not yet available.
From the facts that after oral application only traces of curcumin were found in the blood and that, on the other hand, most of the curcumin is excreted via the faeces it may be concluded that curcumin is absorbed poorly by the gastrointestinal tract and/or underlies pre-systemic transformation. Systemic effects therefore seem to be questionable after oral application except that they occur at very low concentrations of curcumin. This does not exclude a local action in the gastrointestinal tract.
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