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Immunoperoxidase (A-G) and immunofluorescence (inset in D) micrographs showing anti-AQP8 (AQP81-A) labeling in myoepithelial cells in rat parotid (A and B), submandibular (C), and sublingual (D) salivary glands. A-D: AQP8 is present in the myoepithelial cells (arrowheads) around the acini (indicated by A) and the intercalated duct cells (indicated by ID). No labeling was observed in the secretory cells or in the excretory duct system, including the granular duct (indicated by GD). E-G: immunolabeling controls of parotid (E), submandibular (F), and sublingual (G) glands, using antiAQP8 preabsorbed with immunizing peptide, show absence of labeling. Magnification: 200 (A), 530 (B-D), 180 (E-G).
Source publication
The purpose of this study was to determine the cellular and subcellular localization of aquaporin-8 (AQP8) in rat kidney and other organs by RT-PCR analyses and by immunoblotting and immunohistochemistry using peptide-derived rabbit antibodies to rat AQP8. RT-PCR and Southern blotting revealed the presence of AQP8 mRNA in all kidney zones. LLC-PK(1...
Contexts in source publication
Context 1
... in the di- gestive tract. In the digestive tract, AQP8 immunola- beling was examined in the salivary glands and in the different segments of the small and large intestine as well as the liver. In the parotid, submandibular, and sublingual salivary glands, immunolabeling was ob- served in myoepithelial cells surrounding acinar and ductal cells (Fig. 9, A-D), outlining the classic organi- zation of the myoepithelial cells as basket cells (Fig. 9C). No labeling of ductal cells or acinar cells was observed ( Fig. 9). Immunolabeled controls were nega- tive ( Fig. 9, ...
Context 2
... salivary glands and in the different segments of the small and large intestine as well as the liver. In the parotid, submandibular, and sublingual salivary glands, immunolabeling was ob- served in myoepithelial cells surrounding acinar and ductal cells (Fig. 9, A-D), outlining the classic organi- zation of the myoepithelial cells as basket cells (Fig. 9C). No labeling of ductal cells or acinar cells was observed ( Fig. 9). Immunolabeled controls were nega- tive ( Fig. 9, ...
Context 3
... intestine as well as the liver. In the parotid, submandibular, and sublingual salivary glands, immunolabeling was ob- served in myoepithelial cells surrounding acinar and ductal cells (Fig. 9, A-D), outlining the classic organi- zation of the myoepithelial cells as basket cells (Fig. 9C). No labeling of ductal cells or acinar cells was observed ( Fig. 9). Immunolabeled controls were nega- tive ( Fig. 9, ...
Context 4
... and sublingual salivary glands, immunolabeling was ob- served in myoepithelial cells surrounding acinar and ductal cells (Fig. 9, A-D), outlining the classic organi- zation of the myoepithelial cells as basket cells (Fig. 9C). No labeling of ductal cells or acinar cells was observed ( Fig. 9). Immunolabeled controls were nega- tive ( Fig. 9, ...
Citations
... It is poorly permeable to water [66]. In the kidney, it is predominantly and selectively expressed in the endoplasmic reticulum of proximal tubular epithelial cells [67] and is an intracellular protein similar to AQP8 [68]. The endoplasmic reticulum is an organelle involved in the processing of protein translation, translocation, protein folding, and n-glycosylation of many intact membrane proteins and is an important site for protein synthesis, transport, etc. Morishita et al. [67] found that vacuoles produced by the endoplasmic reticulum in AQP11 − / − mice without an electron density led to the swelling of a number of proximal tubules, which subsequently developed into small cysts, which gradually developed into large cysts and finally caused the death of the mice due to renal failure. ...
Autosomal dominant polycystic kidney disease is a genetic kidney disease caused by mutations in the genes PKD1 or PKD2. Its course is characterized by the formation of progressively enlarged cysts in the renal tubules bilaterally. The basic genetic explanation for autosomal dominant polycystic kidney disease is the double-hit theory, and many of its mechanistic issues can be explained by the cilia doctrine. However, the precise molecular mechanisms underpinning this condition’s occurrence are still not completely understood. Experimental evidence suggests that aquaporins, a class of transmembrane channel proteins, including aquaporin-1, aquaporin-2, aquaporin-3, and aquaporin-11, are involved in the mechanism of autosomal dominant polycystic kidney disease. Aquaporins are either a potential new target for the treatment of autosomal dominant polycystic kidney disease, and further study into the physiopathological role of aquaporins in autosomal dominant polycystic kidney disease will assist to clarify the disease’s pathophysiology and increase the pool of potential treatment options. We primarily cover pertinent findings on aquaporins in autosomal dominant polycystic kidney disease in this review.
... T-ammonia formed during the metabolism of glutamine leaves the mitochondria for the cell cytoplasm. A member of aquaporin family, AQP8, has been first localized in the mitochondrial membrane of rat kidney and suggested as NH 3 channel involved in ammonia diffusion from the mitochondria to the cytoplasm of proximal tubular cells [33,83]. Indeed, in addition to its ability to transport H 2 O, mouse, rat, or human AQP8 when heterologously expressed in cell lines has been shown to allow NH 3 diffusion [58,77,96]. ...
The disposal of ammonia, the main proton buffer in the urine, is important for acid–base homeostasis. Renal ammonia excretion is the predominant contributor to renal net acid excretion, both under basal condition and in response to acidosis. New insights into the mechanisms of renal ammonia production and transport have been gained in the past decades. Ammonia is the only urinary solute known to be produced in the kidney and selectively transported through the different parts of the nephron. Both molecular forms of total ammonia, NH3 and NH4⁺, are transported by specific proteins. Proximal tubular ammoniagenesis and the activity of these transport processes determine the eventual fate of total ammonia produced and excreted by the kidney. In this review, we summarized the state of the art of ammonia handling by the kidney and highlighted the newest processes described in the last decade.
... In mouse salivary glands, AQP7 was detected in the endothelial cells [27]. AQP8 is expressed in salivary gland myoepithelial cells [45][46][47]. In mouse salivary glands, AQP9 distribution remains to be fully assessed [26,27,33] and AQP11 was detected in ductal cells [26,27]. ...
Aquaporins (AQPs), transmembrane proteins permeable to water, are involved in gastrointestinal secretion. The secretory products of the glands are delivered either to some organ cavities for exocrine glands or to the bloodstream for endocrine glands. The main secretory glands being part of the gastrointestinal system are salivary glands, gastric glands, duodenal Brunner’s gland, liver, bile ducts, gallbladder, intestinal goblet cells, exocrine and endocrine pancreas. Due to their expression in gastrointestinal exocrine and endocrine glands, AQPs fulfill important roles in the secretion of various fluids involved in food handling. This review summarizes the contribution of AQPs in physiological and pathophysiological stages related to gastrointestinal secretion.
... 7,14,15 Knockdown of AQP8 has been found to impair basal canalicular water movement, leading to approximately 70% decline in canalicular volume. AQP8 has also been shown to be localized in intracellular vesicles 16,17 and exists as a non-glycosylated protein in the mitochondria. 18 Glucagon can regulate AQP8 by transporting vesicles to the hepatocellular membrane via cAMP-protein kinase A (PKA), and this process is involved in phosphatidylinositol 3-kinase (PI3K) signaling pathways and microtubule-associated proteins, together with an upregulation of AQP8 expression, which in turn contribute to a significant increase in hepatocellular water permeability. ...
Aquaporin-8(AQP8), is a transmembrane channel protein that abounds in liver, which mainly promotes water transport, modulating bile acid formation. However, its role in hepatic lipid metabolism remains unclear. In this study, we found the expression of AQP8 was reduced in liver specimens of patients with NAFLD, high-fat diet (HFD)-induced mice and genetically obese db/db mice. Knockdown of AQP8 in hepatocytes exacerbated the intracellular lipid accumulation induced by free fatty acid (FFA) mixtures. In contrast, hepatic AQP8 overexpression activated farnesoid X receptor (FXR), inhibiting gene expression associated with lipogenesis, which further reduced intrahepatic triglyceride overload in obese mice. FXR knockout abrogated the ameliorating effect of AQP8 overexpression on NAFLD in mice. These findings indicate that AQP8 overexpression protects against fatty liver through activating the FXR pathway.
... Four water channels (AQP1, AQP3, AQP4, and AQP5) have been identified in the respiratory system. Furthermore, AQP 1 and AQP 3-8 have been identified in the small intestine of rats (Koyama et al., 1999;Ramirez-Lorca et al., 1999;Elkjaer et al., 2001;Matsuzaki et al., 2003;Laforenza et al., 2009;Chang et al., 2014). AQP5 is present in the apical membrane of alveolar type I cells and nasopharyngeal secretory glands, trachea, and upper bronchus (Gomes et al., 2009). ...
Various direct and indirect environmental constraints have an impact on livestock performance. The physiological parameters, such as rectal temperature, heart rate, and respiratory rate, are the primary indicators of thermal stress. Under a stressed environment temperature humidity index (THI) had established as a vital measurement to identify the thermal stress in livestock. THI in association with climatic variations can define the environmental effect as stressful or comfortable for livestock. Goats are small ruminants that adapt to a wide range of ecological variations due to their anatomical and physiological characteristics. However, the productivity of animals declines at the individual level during thermal stress. Stress tolerance can be determined through genetic studies associated with at the cellular level using physiological as well as molecular approaches. Information on genetic association with thermal stress in goats is scanty, this severely affects their survival and hence productivity of livestock. The ever-increasing demand for food across the globe needs deciphering novel molecular markers as well as stress indicators that play a vital role in livestock improvement. This review represents an analysis of current knowledge of phenotypic differences during thermal stress and signifies the importance of physiological responses and their association at the cellular level in goats. The regulation of vital genes associated with thermal stress such as Aquaporins (AQP 0, 1, 2, 4, 5, 6, 8), aquaglyceroporins (AQP3, 7, 9, and 10) and super-aquaporins (AQP 11, 12); BAX inhibitors such as PERK (PKR like ER kinase), IRE 1(inositol-requiring-1); Redox regulating genes such as NOX; Transport of Na+ and K+ such as ATPase (ATP1A1) and several heat shock proteins have been implicated in heat-stress related adaptations have been elucidated. As these changes have a significant impact on production performance as well as on livestock productivity. Such efforts may help in the development of molecular markers and will assist the breeders to develop heat-tolerant goats with improved productivity.
... In the kidney, aquaporin 8 (APQ8) is present in the proximal tubule (Fig 1), cortical collecting duct, and outer medullary collecting duct. 53 Many but not all aquaporin family proteins can also transport ammonia, and APQ8 has been shown to transport ammonia. 54,55 Utilizing cell cultures, APQ8 is present in the inner mitochondrial membrane and, when knocked down, altered ammonia secretion. ...
Acid-base homeostasis is critical to the maintenance of normal health. The kidneys have a central role in bicarbonate generation , which occurs through the process of net acid excretion. Renal ammonia excretion is the predominant component of renal net acid excretion under basal conditions and in response to acid-base disturbances. Ammonia produced in the kidney is selectively transported into the urine or the renal vein. The amount of ammonia produced by the kidney that is excreted in the urine varies dramatically in response to physiological stimuli. Recent studies have advanced our understanding of ammonia metab-olism's molecular mechanisms and regulation. Ammonia transport has been advanced by recognizing that the specific transport of NH3 and NH 4 1 by specific membrane proteins is critical to ammonia transport. Other studies show that proximal tubule protein, NBCe1, specifically the A variant, significantly regulates renal ammonia metabolism. This review discusses these critical aspects of the emerging features of ammonia metabolism and transport.
... AQP6 is another classic aquaporin although it has low water permeability. AQP8 is expressed in many organs such as liver, pancreas, salivary gland, kidney, heart, and testis (Elkjaer et al. 2001). Immunohistochemical examination has revealed that AQP8 is localized intracellularly in these tissues (Elkjaer et al. 2001). ...
... AQP8 is expressed in many organs such as liver, pancreas, salivary gland, kidney, heart, and testis (Elkjaer et al. 2001). Immunohistochemical examination has revealed that AQP8 is localized intracellularly in these tissues (Elkjaer et al. 2001). Expression of AQP6 and AQP8 have been reported in epithelial cells of ovarian tumor (Ma et al. 2016). ...
Aquaporins constitute a family of transmembrane proteins that function to transport water and other small solutes across the cell membrane. Aquaporins family members are found in diverse life forms. Aquaporins share the common structural fold consisting of six transmembrane alpha helices with a central water-transporting channel. Four such monomers assemble together to form tetramers as their biological unit. Initially, aquaporins were discovered as water-transporting channels, but several studies supported their involvement in mediating the facilitated diffusion of different solutes. The so-called water channel is able to transport a variety of substrates ranging from a neutral molecule to a charged molecule or a small molecule to a bulky molecule or even a gas molecule. This article gives an overview of a diverse range of substrates conducted by aquaporin family members. Prime focus is on human aquaporins where aquaporins show a wide tissue distribution and substrate specificity leading to various physiological functions. This review also highlights the structural mechanisms leading to the transport of water and glycerol. More research is needed to understand how one common fold enables the aquaporins to transport an array of solutes.
Graphical abstract
... Regarding AQP8, its expression was observed only in spermatogonium and Leydig cells. Surprisingly, several contradicted results have been published regarding the expression and localization of AQP8 in the rat testes and testicular sperm (Calamita et al., 2001a(Calamita et al., , 2001bElkjaer et al., 2001;Tani et al., 2001;Badran & Hermo 2002;Yeung et al., 2009). However, to the best of our knowledge, this is the first report about the expression of AQP8 in Ledyig cells in mouse testes. ...
Many efforts have been made to study the expression of aquaporins (AQP) in the mammalian reproductive system, but there are not enough data available regarding their localized expression to fully understand their specific roles in male reproduction. The present study investigated the expression and localization patterns of different AQP subtypes in the adult mouse testes and testicular spermatozoa using an immunofluorescence assay. All the studied AQPs were expressed in the testes and revealed subtype-specific patterns in the intensity and localization depending on the cell types of the testes. AQP7 was the most abundant and intensive AQP subtype in the seminiferous tubules, expressing in Leydig cells and Sertoli cells as well as all stages of germ cells, especially the spermatids and testicular spermatozoa. The expression pattern of AQP3 was similar to that of AQP7, but with higher expression in the basal and lower adluminal compartments rather than the upper adluminalcompartment. AQP8 expression was limited to the spermatogonia and Leydig cells whereas AQP9 expression was exclusive to tails of the testicular spermatozoa and elongated spermatids. Taken together, the abundance and distribution of the AQPs across the different cell types in the testes indicating to their relavance in spermatogenesis, as well as in sperm maturation, transition, and function.
... It has been demonstrated that AQP8 is highly expressed in the columnar epithelial cells of mammalian colonic mucosa facing lu-men, indicating that AQP8 plays potential roles in the physiology and pathophysiology of gastrointestinal tract [16][17][18][19]. In contrast to mammals, three kinds of aqp8s (aqp8aa, aqp8ab, and aqp8b) are have been reported in zebrafish [20,21]. ...
The aquaporin 8 (AQP8) is a small integral membrane protein that selectively transports water and other small uncharged solutes across cell plasma membranes. It has been demonstrated that AQP8 is ubiquitously present in various tissues and organs of mammals, and participates in many physiological and pathological processes. Recent studies showed that AQP8 is highly expressed in the columnar epithelial cells of mammalian colonic mucosa facing lumen, indicating that AQP8 plays potential roles in the physiology and pathophysiology of gastrointestinal tract. However, the role of AQP8 during gastrointestinal tract development is unclear. In the present study, RT-PCR results reveal that the zebrafish genome encodes three kinds of aqp8s ( aqp8aa, aqp8ab, and aqp8b). We use whole mount in situ hybridization to describe aqp8 genes spatiotemporal expression pattern, and the results show that aqp8ab mRNA is detectable mainly in the zebrafish embryonic intestine. To reveal the details of aqp8ab distribution, histological sections are employed. Transverse sections indicate that aqp8ab mRNA expression is more intense in the layer lining the intestinal cavity. Knockout of aqp8ab using the CRISPR/Cas9 system induces intestine development defects and abnormal formation of intestinal lumen. In addition, aqp8ab mRNA significantly rescues the intestine defects in the aqp8ab mutant. These results indicate that aqp8ab is required in the intestine development of zebrafish.
... In humans, AQP8 protein is found as a water selective channel [51] and is located in the absorptive columnar epithelia in duodenum, jejunum, and colon. Many functions of AQPs in the stomach and intestine physiology is confirmed, including water transfer, gastric juice secretion, barrier function [52]. ...
Objective
Investigate the effect and mechanism of berberine on the small intestinal mucosa of non-steroidal anti-inflammatory drugs (NSAIDs) related small intestinal injury.
Materials and methods
Twenty-four SD rats were randomly divided into control group, model group and intervention group. The model group and intervention group were treated with diclofenac (7.5 mg/kg·d, 2/d), a total of 4 days tube feeding, and the intervention group was treated with 50 mg/kg·d intragastric administration of berberine after 2 days. The control group was treated with 7.5 mg/kg·d, 2/d 0.9% saline tube feeding. Then we screened differential expression of colonic mucosal gene by the liquid chip technology.
Results
Compared with the control group, macroscopic and histology score of the model group increased significantly ( P < 0.05), HTR4, HTR1a, F2RL3, CALCA, NPY, CRHR2, IL1b, P2RX3, TPH1, HMOX1, TRPV1, VIP, F2RL1, SLC6A4, TFF2, AQP8 content were significantly increased ( P < 0.05), NOS1 content decreased significantly ( P < 0.05); Compared with the model group, macroscopic and histology score of the intervention group improved significantly ( P < 0.05), and HTR4, F2RL3, NPY, CRHR2, IL1b, VIP, AQP8 content were significantly lower ( P < 0.05), NOS1 content increased significantly ( P < 0.05).
Conclusion
Berberine has a protective effect on NSAID-associated small intestinal injury, the mechanism may be that berberine decreases the expression of intestinal mucosa HTR4, F2RL3, NPY, CRHR2, IL1b, VIP, AQP8, and increases the expression of NOS1, that to reduce intestinal permeability and protect intestinal mucosal barrier.
