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.
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ABSTRACT: The vascular endothelium is specifically sensitive to oxidative stress, and this is one of the mechanisms that causes widespread endothelial dysfunction in most cardiovascular diseases and disorders. Protection against reactive oxygen species (ROS)-mediated oxidative damage via antioxidant mechanisms is essential for tissue maintenance and shows therapeutic potential for patients suffering from cardiovascular and metabolic disorders. Salvianolic acid B (SalB), a natural bioactive component known from Traditional Chinese Medicine, has been reported to exert cellular protection in various types of cells. However, the underlying mechanisms involved are not fully understood. Here, we showed that SalB significantly promoted the migratory and tube formation abilities of human bone marrow derived-endothelial progenitor cells (BM-EPCs) in vitro, and substantially abrogated hydrogen peroxide (H2O2)-induced cell damage. SalB down-regulated Nox4 and eNOS, as well as nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase expression upon H2O2 induction that in turn prevents oxidative-induced endothelial dysfunction. Moreover, SalB suppressed the Bax/Bcl-xL ratio and caspase-3 activation after H2O2 induction. Furthermore, our results provide mechanistic evidence that activation of the mTOR/p70S6K/4EBP1 pathways is required for both SalB-mediated angiogenic and protective effects against oxidative stress-induced cell injury in BM-EPCs. Suppression of MKK3/6-p38 MAPK-ATF2 and ERK1/2 signaling pathways by SalB significantly protected BM-EPCs against cell injury caused by oxidative stress via reduction of intracellular ROS levels and apoptosis. Taken together, by providing a mechanistic insight into the modulation of redox states in BM-EPCs by SalB, we suggest that SalB has a strong potential of being a new proangiogenic and cytoprotective therapeutic agent with applications in the field of endothelial injury-mediated vascular diseases.Biochemical pharmacology 04/2014; · 4.25 Impact Factor
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ABSTRACT: The Sonic hedgehog (SHH) signaling pathway plays a pivotal role in neurogenesis and brain damage repair. Our previous work demonstrated that the SHH signaling pathway was involved in the neuroprotection of cortical neurons against oxidative stress. The present study was aimed to further examine the underlying mechanism. The cortical neurons were obtained from one-day old Sprague-Dawley neonate rats. Hydrogen peroxide (H(2)O(2), 100 μmol/L) was used to treat neurons for 24 h to induce oxidative stress. Exogenous SHH (3 μg/mL) was employed to activate the SHH pathway, and cyclopamine (20 μmol/L), a specific SHH signal inhibitor, to block SHH pathway. LY294002 (20 μmol/L) were used to pre-treat the neurons 30 min before H(2)O(2) treatment and selectively inhibit the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. The cell viability was measured by MTT and apoptosis rate by flow cytometry analysis. The expression of p38, p-p38, ERK, p-ERK, Akt, p-Akt, Bcl-2, and Bax in neurons was detected by immunoblotting. The results showed that as compared with H(2)O(2) treatment, exogenous SHH could increase the expression of p-Akt by 20% and decrease the expression of p-ERK by 33%. SHH exerted no significant effect on p38 mitogen-activated protein kinase (p38 MAPK) pathway. Blockade of PI3K/Akt pathway by LY294002 decreased the cell viability by 17% and increased the cell apoptosis rate by 2-fold. LY294002 treatment could up-regulate the expression of the pro-apoptotic gene Bax by 12% and down-regulate the expression of the anti-apoptotic gene Bcl-2 by 54%. In conclusion, SHH pathway may activate PI3K/Akt pathway and inhibit the activation of the ERK pathway in neurons under oxidative stress. The PI3K/Akt pathway plays a key role in the neuroprotection of SHH. SHH/PI3K/Bcl-2 pathway may be implicated in the protection of neurons against H(2)O(2)-induced apoptosis.Journal of Huazhong University of Science and Technology 12/2012; 32(6):856-60. · 0.58 Impact Factor
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ABSTRACT: In order to study the nature of aging-dependent apoptosis resistance, we compared the activation pattern of mitogen-activated protein kinases (MAPK) in response to three different stress modalities: hydrogen peroxide (H(2)O(2)), staurosporine, and thapsigargin. We observed the agonist-specific activation pattern of MAP kinases in human diploid fibroblasts (HDFs). When young HDFs were treated with PD98059, a specific inhibitor of extracellular signal-regulated kinase (ERK), H(2)O(2)-induced apoptosis was blocked, whereas staurosporine-induced apoptosis was inhibited by treatment with SB203580, a specific inhibitor of p38. In addition, the levels of anti-apoptotic protein Bcl-2 (B-cell lymphoma protein-2) were restored by PD98059 or SB239063 in cells treated with H(2)O(2) or staurosporine, respectively. We also found that inhibition of the nuclear import of p-Erk and p-p38 using wheat germ agglutinin induced apoptosis resistance in young HDF cells in response to H(2)O(2) or staurosporine. These data indicate a potential role of the nuclear translocation of apoptotic signals in the induction of apoptosis. Moreover, the nuclear translocation of activated ERK1/2 and p38 in response to H(2)O(2) or staurosporine was significantly compromised in senescent HDFs, compared with young cells. Taken together, we propose that the apoptosis resistance of senescent HDFs might be related to the defective nuclear translocation of stress-activated signals in an agonist-specific manner, which would imply the operation of an aging-dependent functional nucleo-cytoplasmic trafficking barrier.Apoptosis 06/2011; 16(8):795-807. · 4.07 Impact Factor