EGFR-dependent ERK activation triggers hydrogen peroxide-induced apoptosis in OK renal epithelial cells.
ABSTRACT Oxidative stress induces activation of extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase families. However, it is unclear in renal epithelial cells whether the ERK activation is involved in cell survival or cell death in H2O2-treated cells. The present study was undertaken to determine the role of the ERK activation in H2O2-induced apoptosis of renal epithelial cells using opossum kidney (OK) cells, an established proximal tubular epithelial cell line. H2O2 resulted in a time- and dose-dependent apoptosis of OK cells. H2O2 treatment caused marked sustained activation of ERK. The ERK activation was prevented by PD98059 and U0126, inhibitors of ERK1/2 upstream kinase MEK1/2. Apoptosis caused by H2O2 was prevented by U0126. Transient transfection with constitutive active MEK1 increased the H2O2-induced apoptosis, whereas transfection with dominant-negative mutants of MEK1 decreased the apoptosis. H2O2 produced hyperpolarization of mitochondrial membrane potential and activation of caspases-3. H2O2-induced ERK activation was inhibited by the Src family selective inhibitor PP2 and the epidermal growth factor receptor inhibitor AG1478. The presence of AG1478, but not PP2, prevented H2O2-induced cell death. Taken together, our findings suggest that the ERK activation mediated by epidermal growth factor receptor plays an active role in inducing H2O2-induced apoptosis of OK cells and functions upstream of mitochondria-dependent pathway to initiate the apoptotic signal.
Article: Salvianolic acid B inhibits hydrogen peroxide-induced endothelial cell apoptosis through regulating PI3K/Akt signaling.[show abstract] [hide abstract]
ABSTRACT: Salvianolic acid B (Sal B) is one of the most bioactive components of Salvia miltiorrhiza, a traditional Chinese herbal medicine that has been commonly used for prevention and treatment of cerebrovascular disorders. However, the mechanism responsible for such protective effects remains largely unknown. It has been considered that cerebral endothelium apoptosis caused by reactive oxygen species including hydrogen peroxide (H(2)O(2)) is implicated in the pathogenesis of cerebrovascular disorders. By examining the effect of Sal B on H(2)O(2)-induced apoptosis in rat cerebral microvascular endothelial cells (rCMECs), we found that Sal B pretreatment significantly attenuated H(2)O(2)-induced apoptosis in rCMECs. We next examined the signaling cascade(s) involved in Sal B-mediated anti-apoptotic effects. We showed that H(2)O(2) induces rCMECs apoptosis mainly through the PI3K/ERK pathway, since a PI3K inhibitor (LY294002) blocked ERK activation caused by H(2)O(2 )and a specific inhibitor of MEK (U0126) protected cells from apoptosis. On the other hand, blockage of the PI3K/Akt pathway abrogated the protective effect conferred by Sal B and potentated H(2)O(2)-induced apoptosis, suggesting that Sal B prevents H(2)O(2)-induced apoptosis predominantly through the PI3K/Akt (upstream of ERK) pathway. Our findings provide the first evidence that H(2)O(2) induces rCMECs apoptosis via the PI3K/MEK/ERK pathway and that Sal B protects rCMECs against H(2)O(2)-induced apoptosis through the PI3K/Akt/Raf/MEK/ERK pathway.PLoS ONE 02/2007; 2(12):e1321. · 4.09 Impact Factor