The Combined Administration of Vitamin C and Copper Induces a Systemic Oxidative Stress and Kidney Injury.

Vitamin C (ascorbic acid; AA) and copper (Cu2+) are well used supplements with many health-promoting actions. However, when they are used in combination, the Fenton reaction occurs, leading to the formation of highly reactive hydroxyl radicals. Given that kidney is vulnerable to many toxicants including free radicals, we speculated that the in vivo administration of AA plus Cu2+ may cause oxidative kidney injury. The purpose of this study was to address this possibility. Mice were administered with AA and Cu2+, alone or in combination, via oral gavage once a day for various periods. Changes in the systemic oxidative status, as well renal structure and functions, were examined. The administration of AA plus Cu2+ elevated protein oxidation in serum, intestine, bladder, and kidney, as evidenced by the increased sulfenic acid formation and decreased level of free sulfhydryl groups (-SH). The systemic oxidative stress induced by AA plus Cu2+ was associated with a significant loss of renal function and structure, as indicated by the increased blood urea nitrogen (BUN), creatinine and urinary proteins, as well as glomerular and tubular cell injury. These effects of AA and Cu2+ were only observed when used in combination, and could be entirely prevented by thiol antioxidant NAC. Further analysis using cultured renal tubular epithelial cells revealed that AA plus Cu2+ caused cellular protein oxidation and cell death, which could be abolished by NAC and catalase. Moreover, coincubation of AA and Cu2+ led to H2O2 production. Collectively, our study revealed that a combined administration of AA and Cu2+ resulted in systemic oxidative stress and renal cell injury. As health-promoting supplements, AA and Cu2+ should not be used together.

Connexin43 hemichannel-mediated regulation of connexin43.

BACKGROUND: Many 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 (Cd(2+)), we tested this hypothesis. PRINCIPAL FINDINGS: Incubation of Cx43-transfected LLC-PK1 cells with Cd(2+) led to an increased expression of Cx43. This effect of Cd(2+) 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 Cd(2+) on JNK activation and Cx43 expression. Indeed, Cd(2+) 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 Cd(2+). CONCLUSIONS: Collectively, our results thus indicate that Cd(2+)-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.

Multi-glycoside of Tripterygium wilfordii Hook. f. reduces proteinuria through improving podocyte slit diaphragm dysfunction in anti-Thy1.1 glomerulonephritis.

ETHNOPHARMACOLOGICAL RELEVANCE: Multi-glycoside of Tripterygium wilfordii Hook. f. (GTW) has been proved clinically effective in reducing proteinuria in chronic kidney disease in China. However, the mechanisms involved are still unclear. In this study we examined the effects of GTW at the different dosages on proteinuria and podocyte slit diaphragm (SD) dysfunction in anti-Thy1.1 glomerulonephritis (GN). MATERIALS AND METHODS: Rats with anti-Thy1.1 GN were divided into 2 groups, a GTW group and a vehicle group, and sacrificed at 30 min, on day 7, and on day 14 in Experiments 1, 2 and 3, respectively. The administration of GTW at the moderate and high doses was started 3 days before or at the same time of antibody injection till sacrifice. Proteinuria was determined in Experiments 1, 2, and 3. After sacrifice, the staining intensity of SD-associated key functional molecules including nephrin and podocin, podocyte structure, mesangial change, macrophage infiltration, and blood biochemical parameters were examined, respectively. Protein and mRNA expressions of nephrin and podocin in glomeruli were also investigated. Besides, liver histological characteristics were analyzed. RESULTS: In Experiment 1, GTW pretreatment at the medium dose (75 mg/kg body weight) caused no influence on the induction of anti-Thy1.1 GN and the basal nephrin expression. In Experiment 2, the high dosage (100mg/kg body weight) of GTW ameliorated proteinuria, the distribution of nephrin and podocin, mesangial proliferation, and the activated macrophage accumulation, as compared with vehicle group (P<0.05). Additionally, it increased mRNA and protein expressions of nephrin and podocin in glomeruli on day 7, but had no influence on podocyte structure. In Experiment 3, the medium dosage (75 mg/kg body weight) of GTW improved proteinuria, the partial matrix expansion, and the distribution of nephrin and podocin on day 14, as compared with anti-Thy1.1 GN rats (P<0.05). GTW at the high or moderate dose did not affect hepatic function on day 7 and on day 14. CONCLUSIONS: Podocyte SD dysfunction, such as the disordered distribution and down-regulation of nephrin and podocin expression, is critically involved in the pathogenesis of anti-Thy1.1 GN induced by mAb 1-22-3. The restoration of the distribution and expression of nephrin and podocin by GTW could be an important mechanism by which GTW ameliorates proteinuria and podocyte SD dysfunction.

[Regulative mechanism of Chinese herbal medicine on cell signaling pathway in kidney].

In kidney, the role of cell proliferation, differentiation, apoptosis, inflammatory mediators and cytokines expression is closely related with cell signaling pathways, including tyrosine kinase pathway, transforming growth factor-beta/Smad pathway, Rho/Rho-associated coiled-coil forming protein kinase pathway, phosphoinositol pathway, cyclic nucleotide pathway, nuclear factor kappaB pathway and so on. Some Chinese herbs and their extracts, such as rhubarb and triptolide, as well as some Chinese herbal prescriptions, such as astragalus-angelica mixture and Chailing decoction, not only could ameliorate proliferation, differentiation and apoptosis of renal cell by regulating cell signaling pathways, but also could control target gene transcription, expression and its biological effects through inhibiting the phosphorylation of key signaling molecules.

Multi-glycoside of Tripterygium wilfordii Hook f. ameliorates prolonged mesangial lesions in experimental progressive glomerulonephritis.

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-beta, IL-2, and IFN-gamma) 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-beta, IL-2, and IFN-gamma. CONCLUSION: GTW ameliorates prolonged glomerular lesions presumably through suppression of cytokine production (TGF-beta, IL-2, and IFN-gamma). GTW could be an effective therapeutic agent for treatment of chronic renal diseases.