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Hypercholesterolaemia is well known to be associated with mitochondrial dysfunction, subsequently leading to multiple organ failure. Similar to other natural products, sericin is a candidate for adjunctive therapy in hyperlipidaemic conditions. However, the cholesterol-lowering mechanisms of sericin are multifactorial and controversial. Here, a high-cholesterol-fed rat model with or without sericin treatment was established using a dosage of 1000 mg/kg/day for 30 days. Blood lipid profiles, oxidative stress markers (superoxide dismutase, SOD; malondialdehyde, MDA; nuclear factor erythroid 2-related factor, Nrf-2), dysmorphic mitochondria in relation to fission (dynamin-related protein-1; Drp-1) and fusion (guanosine triphosphatase mutated in dominant optic atrophy; OPA-1) markers and biosynthetic markers (aquaporin, AQP-1; tubulin-4β, Tb4B) in the pancreas and adrenal gland were evaluated. The results showed that sericin reduced blood cholesterol and increased high-density lipoprotein (HDL) by acting against oxidative stress. Hypocholesterolaemic and antioxidant conditions further preserved heart and liver mitochondrial architecture; however, this protection was not exhibited in the kidney, where a high level of renal mitophagy, indicating by LC-3 up-regulation, was presented. The steps of ultrastructural alteration of mitochondria from degenerative changes to necrosis were also demonstrated. Sericin also conserved AQP-1 and Tb4B levels in the exocrine pancreatic acinar cells and zona glomerulosa cells, which were positively correlated with serum lipase, HDL, antioxidative markers and mitochondrial integrity. The present study revealed that sericin not only has antioxidant capacity but also balances pancreatic and adrenal cell biosynthesis, especially lipase activity, which may have played an important role in improving lipid dysregulation in the hypercholesterolaemic rat model, leading to the reduction of dysmorphic mitochondria, particularly in the heart and liver. [ABSTRACT FROM AUTHOR]

Abstract: Aquaporin-1 (AQP1) is expressed in human and mouse hearts, but little is known about its cellular and subcellular localization and regulation. The aim of this study was to investigate the localization of AQP1 in the mouse heart and to determine the effects of ischemia and hypoxia on its expression. Mouse myocardial cells were freshly isolated and split into cardiomyocyte and non-cardiomyocyte fractions. Isolated, Langendorff-perfused C57Bl6 mouse hearts (n=46) were harvested with no intervention, subjected to 35min of ischemia or ischemia followed by 60min of reperfusion. Eleven mouse hearts were perfusion-fixed for electron microscopy. Forty C57Bl6 mice were exposed to normobaric hypoxia for one or two weeks (n=12). Needle biopsies of human left ventricular myocardium were sampled (n=30) during coronary artery bypass surgery before cardioplegia and after 30min of reperfusion. Human umbilical vein endothelial cells (HUVECs) were subjected to 4h of hypoxia with reoxygenation for either 4 or 24h. AQP1 expression was studied by electron microscopy with immunogold labeling, Western blot, and qPCR. Expression of miR-214 and miR-320 in HUVECs with hypoxia was studied with qPCR. HUVECs were then transfected with precursors and inhibitors of miR-214. AQP1 expression was confined to cardiac endothelial cells, with no signal in cardiomyocytes or cardiac fibroblasts. Immunogold electron microscopy showed AQP1 expression in endothelial caveolae with equal distribution along the basal and apical membranes. Ischemia and reperfusion tended to decrease AQP1 mRNA expression in mouse hearts by 37±9% (p=0.06), while glycosylated AQP1 protein was reduced by 16±9% (p=0.03). No difference in expression was found between ischemia alone and ischemia-reperfusion. In human left ventricles AQP1 mRNA expression was reduced following cardioplegia and reperfusion (p=0.008). Hypoxia in mice reduced AQP1 mRNA expression by 20±7% (p<0.0001), as well as both glycosylated (−47±10%, p=0.03) and glycan-free protein (−34±16%, p=0.05). Hypoxia and reoxygenation in HUVECs downregulated glycan-free AQP1 protein (−34±24%, p=0.04) and upregulated miR-214 (+287±52%, p<0.05). HUVECs transfected with anti-miR-214 had increased glycosylated (1.5 fold) and glycan-free (2 fold) AQP1. AQP1 in mouse hearts is localized to endothelial cell membranes and caveolae. Cardioplegia, ischemia and hypoxia decrease AQP1 mRNA as well as total protein expression and glycosylation, possibly regulated by miR-214. [Copyright &y& Elsevier]

Abstract: The aquaporins (AQPs) are a family of transmembrane water channel proteins widely distributed and play a major role in transcellular and transepithelial water movement. Moreover, recent evidence indicates that AQPs may be involved in cell migration, angiogenesis, and tumor growth. This review article summarizes literature data concerning the involvement of AQP-1 and -4 in human brain tumor growth and edema formation and suggests a potential therapeutic approach by antagonizing their biological activity. [Copyright &y& Elsevier]

Abstract: We examined the expression of aquaporin (AQP)-1 in monolayers of the rat gastric epithelial cell line RGM1 and investigated the roles AQP1 plays in the epithelial restitution during wound healing. A round wound of constant size was produced in the center of a confluent cell monolayer using a rotating silicon tip. The RGM1 cells expressed AQP1 mRNA. Hg2+ (HgCl2), an inhibitor of AQPs, suppressed cell migration during wound repair in a concentration-dependent manner. Likewise, cell migration was also impaired in cells in which AQP1 was knocked down by RNA interference, resulting in a marked delay of wound healing. The AQP1 knockdown RGM1 cells showed a decrease in the formation of membrane protrusions (lamellipodia) at the leading edge of the wound as compared with control RGM1 cells. These results suggest for the first time that AQP1 plays a crucial role in gastric epithelial cell migration during wound healing. [Copyright &y& Elsevier]

Abstract: Aquaporin-4 (AQP4) has been implicated in cytotoxic brain edema resulting from water intoxication, brain ischemia or meningitis. AQP4 inhibitors suitable for clinical use would thus be expected to help protect against brain edema. Here, we report the effect of inhibitors on water conduction by AQP4 and AQP1 reconstituted into liposomes. Acetazolamide (AZA), an inhibitor of sulfonamide carbonic anhydrase (CA), reversibly inhibits water permeation through AQP4, but not through AQP1. Methazolamide (MZA), another sulfonamide CA inhibitor similar in chemical structure to AZA, shows no significant effect on water conduction by AQP4 or AQP1. Our results thus demonstrate that AZA acts as a reversible inhibitor for AQP4-mediated water conduction and indicate that AZA is specific, at least to some degree, for AQP4. AZA may thus serve as a lead compound for the development of AQP4-specific inhibitors for clinical applications. [Copyright &y& Elsevier]

Abstract: Water channel proteins, known as aquaporins, are transmembrane proteins that mediate osmotic water permeability. In a previous study, we found that acetazolamide could inhibit osmotic water transportation across Xenopus oocytes by blocking the function of aquaporin-1 (AQP1). The purpose of the current study was to confirm the effect of acetazolamide on water osmotic permeability using the human embryonic kidney 293 (HEK293) cells transfected with pEGFP/AQP1 and to investigate the interaction between acetazolamide and AQP1. The fluorescence intensity of HEK293 cells transfected with pEGFP/AQP1, which corresponds to the cell volume when the cells swell in a hyposmotic solution, was recorded under confocal laser fluorescence microscopy. The osmotic water permeability was assessed by the change in the ratio of cell fluorescence to certain cell area. Acetazolamide, at concentrations of 1 and 10μM, inhibited the osmotic water permeability in HEK293 cells transfected with pEGFP/AQP1. The direct binding between acetazolamide and AQP1 was detected by surface plasmon resonance. AQP1 was prepared from rat red blood cells and immobilized on a CM5 chip. The binding assay showed that acetazolamide could directly interact with AQP1. This study demonstrated that acetazolamide inhibited osmotic water permeability through interaction with AQP1. [Copyright &y& Elsevier]

Aquaporin-1 (AQP1) water channel plays a critical role for water reabsorption in the urinary concentrating mechanism. AQP1 expression in renal cells is upregulated by hypertonicity, but not urea, suggesting the requirement of an osmotic gradient. To investigate whether AQP1 expression is regulated by apical and/or basolateral hypertonicity, murine renal medullary mIMCD-K2 cells grown on permeable support were exposed to hypertonic medium. When the medium on the apical or basolateral membrane side was switched to hypertonic, the transcellular osmotic gradient was dissipated within 8h. Basolateral hypertonicity increased AQP1 expression more than apical hypertonicity. Comparable apical and basolateral hypertonicity without a transcellular hypertonic gradient, however, increased AQP1 expression. Cell surface biotinylation experiments revealed that hypertonicity promoted AQP1 trafficking to both plasma cell membranes. These results indicate that AQP1 expression is predominantly mediated by basolateral hypertonicity but a transcellular osmotic gradient is not necessary for its induction. [Copyright &y& Elsevier]

Retinoids have been implicated in the control of cell proliferation, differentiation, and developmental processes. We report here that aquaporin-1 (AQP1) is specifically induced by retinoic acid (RA) in human erythroleukemia HEL cells. Both all-trans-RA (ATRA) and 9-cis-RA (9CRA) strongly induced the AQP1 mRNA and protein in a dose-dependent manner. AQP1 protein was mainly expressed in plasma membrane in cells induced by RAs. To identify the RA response element (RARE) in the human AQP1 promoter, the 5′-flanking region of AQP1 promoter was isolated and transient transfection experiment in HEL cells was performed. Deletion analysis of the AQP1 promoter revealed that one putative DR5-like RARE with five spaces was located in the region from −2218 to −2202; AGGGCAgggacAGGTGA. Electrophoretic mobility shift assay (EMSA) experiment demonstrated that two slowly migrated complexes (C1 and C2) capable of binding the RARE sequence were present in nuclear extracts prepared from cells and the complex C1 was strongly increased in nuclear extracts by RA stimulation. The complexes C1 and C2 were significantly abolished by an excess unlabeled probe. These results indicate that RAs strongly stimulate the human AQP1 gene expression through the RARE and define a novel role in the regulation of erythropoiesis. [Copyright &y& Elsevier]

The AQP1 gene is transcriptionally upregulated in response to hypertonicity. However, the molecular mechanism in hypertonicity-induced transcription in the AQP1 gene has been poorly understood. Here we report a novel hypertonicity response element (HRE) in the AQP1 gene. A critical cis-acting element to hypertonicity in the AQP1 promoter is located at −54 to −46 and the change from GCTCCCCCC to GCTTTCCCC completely abolished the hypertonic induction and osmotic response, thus implicating the importance of the first CC sequence in the region. Two prominent DNA–protein complexes were observed electrophoretic mobility shift assay (EMSA), and the band intensities in nuclear extracts from osmotically stressed cells were much higher than that of isotonic nuclear extracts. The EMSA supershift assay with anti-Sp1 antibody showed that two retarded bands did not bind to anti-Sp1 antibody, suggesting that the DNA binding proteins bound to the HRE are not Sp1 family proteins. These data suggest that the transcription of the AQP1 by hypertonicity in renal cells is upregulated by the interaction with putative DNA binding proteins to a novel HRE located at −54 to −46 in the AQP1 gene. [Copyright &y& Elsevier]

Aquaporin 1 (AQP1), a transmembrane protein that forms water channels, has previously been shown to facilitate growth and progression of many types of tumors by modulating tumor cell migration, proliferation and angiogenesis. Here, we determined the impact of AQP1 expression in the tumor environment on the progression of brain tumors. Primary microglia from wild type(WT) and AQP1 knockout(KO) mice were used to test AQP1 effect on microglia function by using Western blot, quantative PCR, in an experimental in vivo mouse glioma model and organotypic brain slice culture. Deletion of AQP1 in the host tissue significantly reduced the survival of the mice implanted with GL261 glioma cells. The density of glioma-associated microglia/macrophages was almost doubled in AQP1KO mice. We found that factors secreted from GL261 cells decrease microglial AQP1 expression via the MEK/ERK pathway, and that inhibition of this pathway with Trametinib reduced tumor growth and prolonged the survival of tumor bearing mice, an effect which required the presence of microglia. Deletion of AQP1 in cultured microglia resulted in an increase in migratory activity and a decrease in TLR4-dependent innate immune responses. Our study demonstrates a functional relevance of AQP1 expression in microglia and hints to AQP1 as a potential novel target for glioma therapy. • Microglial cells participate in glioma progression through multiple interaction pathways. • Aquaporin 1 knock-out on microglial cells affect microglial function including migration and phenotype change. • Aquaporin 1 deletion on microglia promote glioma growth in the tumor micro-environment. • MEK/ERK signaling cascades regulate aquaporin 1 expression in microglia. • Inhibition of MEK/ERK signaling pathway by trametinib suppress microglia induced glioma growth. [ABSTRACT FROM AUTHOR]

• Blood pressure drives water & oncotically-acive solutes like albumin into artery walls that can affect early cholesterol buildup/atherogenesis. • Blood pressure compresses the arterial subendothelial intima to inhibit this flow; endothelial cell aquaporin-1 controls this compression. • Surprisingly, oncotic are comparable to hydrostatic forces at low pressures until intima compression; increased aquaporins delays compression. • One expects oncotic forces due to aquaporin to stop flow into the wall, but media filtration raises intima albumin to reverse their direction. • Theory predicts raising endothelial aquaporin levels would decompress the intima at physiologic pressures, increase flow & slow atherogenesis. Atherosclerosis starts with transmural (transwall) pressure-driven advective transport of blood-borne low-density lipoprotein (LDL) cholesterol across rare endothelial cell (EC) monolayer leaks into the arterial subendothelial intima (SI) wall layer where they can spread, bind to extracellular matrix and seed lesions. The local SI LDL concentration, which governs LDL's binding kinetics, depends on the overall diluting transmural liquid flow. Transmural pressures typically compress the SI at physiological pressures, which keeps this flow low. Nguyen et al. (2015) showed that aortic ECs express the water channel protein aquaporin-1 (AQP1) and the transEC (δP) portion of the transmural (Δ P) pressure difference drives, in parallel, water across AQP1s and plasma across interEC junctions. Since the lumen is isotonic, selective AQP1-mediated water flow should quickly render the ECs' lumen side hypertonic and the SI hypotonic; resulting transEC oncotic pressure differences, δπ , should oppose δP and quickly halt transEC flow. Yet Nguyen et al.'s (2015) transAQP1 flows persist for hours. To resolve this paradox, we extend our fluid filtration theory Joshi et al. (2015) to include mass transfer for oncotically active solutes like albumin. This addition nonlinearly couples mass transfer, fluid flow and wall mechanics. We simultaneously solve these problems at steady state. Surprisingly it finds that media layer filtration causes steady SI to exceed EC glycocalyx albumin concentration. Thus δπ reinforces rather than opposes δP , i.e., it sucks water from, rather than pushing water into the lumen from the SI. Endothelial AQP1s raise the overall driving force for flow across the EC above δP , most significantly at pressures too low to compress the SI, and they increase the Δ P needed for SI compression. This suggests the intriguing possibility that increasing EC AQP1 expression can raise this requisite compression pressure to physiological values. That is, increasing EC AQP1 may decompress the SI at physiological pressures, which would significantly increase SI thickness, flow and subsequently SI LDL dilution. This could retard LDL binding and delay preatherosclerotic lesion onset. The model also predicts that glycocalyx-degrading enzymes decrease overall transEC driving forces and thus lower, not raise, transmural water flux. [ABSTRACT FROM AUTHOR]