We investigated the potential involvement of connexin hemichannels in cadmium ions (Cd 2+ )-elicited cell injury. Transfection of LLC-PK1 cells with a wild-type connexin43 (Cx43) sensitized them to Cd 2+ -elicited cell injury. The cell susceptibility to Cd 2+ was increased by depletion of glutathione (GSH) with DL-buthionine-[S,R]-sulfoximine, and decreased by N-acetyl-cysteine or glutathione reduced ethyl ester. Fibroblasts derived from Cx43 wild-type (Cx43+/+) and knockout (Cx43-/-) fetal littermates displayed different susceptibility to Cd 2+

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Albumin (Alb) is the most abundant plasma protein with multiple biological functions, including antioxidative property through its thiol activity. Given that inflammatory bowel disease is associated with a decreased level of Alb and an increased level of Alb oxidation, we asked whether Alb could have a therapeutic effect on colitis. Here we tested this possibility. Bovine serum albumin (BSA) was reductively modified with dithiothreitol (DTT) and administrated via gavage or intraperitoneal injection. Dextran sulfate sodium (DSS)-induced mice colitis was associated with massive oxidative stress, as indicated by the elevated sulfenic acid formation in blood, colon tissues, and feces. Treatment of mice with the reductively modified albumin (r-Alb) attenuated the oxidative stress and reduced local inflammation and tissue injury. These effects of r-Alb were only partially achieved by unmodified Alb and wholly lost after blocking the –SH groups with maleimide. In cultured colon epithelial cells, r-Alb prevented DSS- and H 2 O 2 -induced ROS elevation and barrier dysfunction, preceded by inhibition of sulfenic acid formation and P38 activation. Further analysis revealed that Alb was susceptible to H 2 O 2 -induced oxidation, and it detoxified H 2 O 2 in a –SH group-dependent way. Moreover, Alb reacted with GSH/GSSG via thiol-disulfide exchange and reciprocally regulated the availability of –SH groups. Collectively, our study shows that r-Alb effectively attenuates DSS colitis via –SH group-mediated antioxidative action. Given that the oxidative stress underlies many life-threatening diseases, r-Alb, functioning as a potent antioxidant, could have a wide range of applications.

Flufenamic acid (FFA) is a nonsteroidal anti-inflammatory drug (NSAID). It has anti-inflammatory and antipyretic properties. In addition, it modulates multiple channel activities. The mechanisms underlying the pharmacological actions of FFA are presently unclear. Given that AMP-activated protein kinase (AMPK) has both anti-inflammatory and channel-regulating functions, we examined whether FFA induces AMPK activation. 1) Exposure of several different types of cells to FFA resulted in an elevation of AMPK␣ phosphorylation at Thr172. This effect of FFA was reproduced by functionally and structurally similar mefenamic acid, tolfenamic acid, niflumic acid, and meclofenamic acid. 2) FFA-induced activation of AMPK was largely abolished by the treatment of cells with 1,2-bis(2-aminophenoxy)ethane-N,N,NЈ,NЈ-tetraacetic acid tetrakis(acetoxymethyl ester) (an intracellular Ca 2ϩ chelator) or depletion of extracellular Ca 2ϩ , whereas it was mimicked by stimulation of cells with the Ca

BackgroundMany signaling molecules and pathways that regulate gap junctions (GJs) protein expression and function are, in fact, also controlled by GJs. We, therefore, speculated an existence of the GJ channel-mediated self-regulation of GJs. Using a cell culture model in which nonjunctional connexin43 (Cx43) hemichannels were activated by cadmium (Cd2+), we tested this hypothesis.Principal FindingsIncubation of Cx43-transfected LLC-PK1 cells with Cd2+ led to an increased expression of Cx43. This effect of Cd2+ was tightly associated with JNK activation. Inhibition of JNK abolished the elevation of Cx43. Further analysis revealed that the changes of JNK and Cx43 were controlled by GSH. Supplement of a membrane-permeable GSH analogue GSH ethyl ester or GSH precursor N-acetyl-cystein abrogated the effects of Cd2+ on JNK activation and Cx43 expression. Indeed, Cd2+ induced extracellular release of GSH. Blockade of Cx43 hemichannels with heptanol or Cx43 mimetic peptide Gap26 to prevent the efflux of GSH significantly attenuated the Cx43-elevating effects of Cd2+.ConclusionsCollectively, our results thus indicate that Cd2+-induced upregulation of Cx43 is through activation of nonjunctional Cx43 hemichannels. Our findings thus support the existence of a hemichannel-mediated self-regulation of Cx43 and provide novel insights into the molecular mechanisms of Cx43 expression and function.

Background/Aims: Multi-glycoside from Tripterygium wilfordii Hook f. (GTW) is used for treatment of progressive glomerulonephritis (GN) in China. We have previously reported the beneficial effects of GTW on acute GN induced by an anti-Thy-1.1 monoclonal antibody (mAb). In the present study, the effect and potential mechanisms of GTW on the chronic irreversible model of GN were investigated. Methods: Progressive GN was induced in rats by two intravenous injections of anti-Thy-1.1 mAb 1-22-3. Daily oral administration of GTW was started before the second injection of mAb until the day of sacrifice. Ten rats were randomly divided into a control (vehicle-treated) and a GTW-treated group, and sacrificed on day 45 after the first injection of mAb 1-22-3. Proteinuria was determined on days 0, 1, 3, 5, 7, 10, 14, 20, 25, 30, 35, 40, and 45. Blood biochemical parameters, morphological changes of mesangium, glomerular infiltration of macrophage and T lymphocyte, and glomerular mRNA expression of cytokines (TGF-β, IL-2, and IFN-γ) were examined from the samples taken at terminal sacrifice. Results: GTW treatment significantly ameliorated proteinuria, renal function, prolonged mesangial lesions and inflammatory cell accumulation in glomerulus. In addition, it significantly reduced the glomerular mRNA expression for TGF-β, IL-2, and IFN-γ. Conclusion: GTW ameliorates prolonged glomerular lesions presumably through suppression of cytokine production (TGF-β, IL-2, and IFN-γ). GTW could be an effective therapeutic agent for treatment of chronic renal diseases.

Thiol antioxidants play important roles in cell and body defense against oxidative stress. In body fluid, albumin is the richest source of thiol antioxidants. One recent study showed that the reductive modification of thiol residues in albumin potentiated its antioxidative activity. Given that whey protein (WP) contains albumin and other thiol-active proteins, this property of WP could be exploited to develop novel thiol antioxidants. The aim of this study was to address this possibility. WP was reductively modified with dithiothreitol (DTT). The modified protein exhibited significantly elevated free sulfhydryl groups (-SH) and thiol antioxidative activity. It detoxified H2O2 and prevented H2O2-initiated protein oxidation and cell death in a -SH group-dependent way in vitro. In addition, it reacted with GSH/GSSG and altered the GSH/GSSG ratio via thiol–disulfide exchange. In vivo, oral administration of the reductively modified WP prevented oxidative stress and renal damage in a mouse model of renal injury caused by ischemia reperfusion. It significantly improved renal function, oxidation, inflammation, and cell injury. These protective effects were not observed in the WP control and were lost after blocking the -SH groups with maleimide. Furthermore, albumin, one of the ingredients of WP, also exhibited similar protective effects when reductively modified. In conclusion, the reductive modification of thiol residues in WP transformed it into a potent thiol antioxidant that protected kidneys from ischemia reperfusion injury. Given that oxidative stress underlies many life-threatening diseases, the reductively modified dietary protein could be used for the prevention and treatment of many oxidative-stress-related conditions, such as cardiovascular diseases, cancer, and aging.