The American journal of pathology
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Apoptosis is implicated in the progressive cell loss and fibrosis both at glomerular and tubulointerstitial level. In this study, we examined the potential mechanisms by which persistent proteinuria (protein-overload model) could induce apoptosis. After uninephrectomy (UNX), Wistar rats received daily injections of 0.5 g of bovine serum albumin (BSA)/100 g body weight or saline. ⋯ The administration of BSA to UNX rats induced a diminution in the phosphorylation of ERK with respect to UNX-control at all times studied. The changes observed in ERK activities took place without alterations of ERK1/2 protein levels. In summary, our data suggest that persistent proteinuria causes apoptosis in tubular cells through the activation of AT2 receptor, which can, in turn, inhibit MAP kinase (ERK1/2) activation and Bcl-2 phosphorylation.
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Endotoxin (lipopolysaccharide, LPS)-induced tumor necrosis factor-alpha (TNF-alpha) release from Kupffer cells is critically involved in the pathogenesis of alcohol-induced liver injury. We recently reported that inhibition of alcohol-induced plasma endotoxin elevation contributes to the protective action of zinc against alcoholic hepatotoxicity. The present study was undertaken to determine whether zinc interferes with the endotoxin-TNF-alpha signaling pathway, and possible mechanism(s) by which zinc modulates the endotoxin-TNF-alpha signaling. ⋯ Fluorescent microscopy of superoxide by dihydroethidine and of zinc ions by Zinquin in the liver of MT-KO mice showed that zinc pretreatment increased the intracellular labile zinc ions and inhibited LPS-induced superoxide generation. These results demonstrate that zinc inhibits LPS-induced hepatic TNF-alpha production through abrogation of oxidative stress-sensitive NF-kappaB pathway, and the action of zinc is independent of MT. Thus, zinc may be beneficial in the treatment of LPS-induced liver injuries, such as sepsis and alcoholism.