Arsenite Activation of PI3K/AKT Cell Survival Pathway is Mediated by p38 in Cultured Human Keratinocytes

Abstract

analysis was performed for the determination of generation of reactive oxygen species. Results: Arsenite induced the activation of AKT at both Ser473 and Thr308, and its downstream effector eNOS in cultured human keratinocytes. Arsenite also induced phosphorylation of p38. PI-3-kinase inhibitors, Wortmannin and LY294002 inhibited arsenite-induced phosphorylation of AKT and eNOS but had no effect on phosphorylation of p38. Interestingly, however, SB203580, a known p38 inhibitor, completely inhibited arsenite-induced phosphorylation of AKT and eNOS. Arsenite induced generation of reactive oxygen species and inactivated phosphatase activity, but did not activate EGF receptor tyrosine phosphorylation. Conclusions: Collectively, our data indicate that arsenite induces activation of AKT and eNOS, via PI-3-kinase and p38 pathway, likely bypassing the activation of EGF receptor in cultured human keratinocytes. AbstractBackground: Arsenic has been considered as a carcinogen. Recently the issue of arsenic in drinking water raised an unprecedented social concern on human health, and yet the molecular mechanisms through which arsenic induces cancer remain unknown. Activation of cell survival pathway leading to the activation of eNOS has been associated with various types of cancer. The objective of this study was to investigate the pathway leading to the activation of eNOS in response to arsenite using human keratinocytes. Materials and Methods: Cultured keratinocytes (HaCat cells) were exposed to arsenite with or without pretreatment of various inhibitors. Western blot analysis was performed to determine the activation of p38, AKT, eNOS. EGFR tyrosine phosphorylation was detected by immunoprecipitation and Western blot analysis. pNPP assay was used to measure phosphatase activity in cell lysate. FACS

Heavy metals, islet function and diabetes development

“…53 Increased PI3K-mediated PKB/Akt phosphorylation has been reported in β-cells exposed to high dose of arsenic. 54 The phosphorylation of PKB/Akt signaling was also one of the key steps in the activation of glucose transporter 4 (GLUT4) by insulin. 55 Thus, it has been suggested that the exposure to high dose of arsenic might mimic the action of insulin by phosphorylation of PKB/Akt-mediated GLUT4 expression in vitro.…”

“…54 The phosphorylation of PKB/Akt signaling was also one of the key steps in the activation of glucose transporter 4 (GLUT4) by insulin. 55 Thus, it has been suggested that the exposure to high dose of arsenic might mimic the action of insulin by phosphorylation of PKB/Akt-mediated GLUT4 expression in vitro. However, exposure to low dose of arsenic has been shown to inhibit ISGU in 3T3-L1 adipocytes; the phosphorylation of PKB/Akt was suppressed in exposed cells, which was an important requirement for GLUT4 translocation to the cellular membrane in response to insulin.…”

Examination of the effects of arsenic on glucose homeostasis in cell culture and animal studies: Development of a mouse model for arsenic-induced diabetes

“…Increased PI-3K-mediated PKB/Akt phosphorylation has been reported in cells exposed to toxic concentrations (200-500 μM) of iAs III (McDowell et al, 1997;Souza et al, 2001). Stress-induced phosphorylation of PKB/Akt is associated with the activation of pro-survival mechanisms aimed at preventing apoptosis and promoting cell proliferation (Dudek et al, 1997;Ibuki and Goto, 2000;Zhou et al, 2000).…”

Phosphoproteomic profiling of arsenite-treated human small airway epithelial cells

“…Arsenite has been used as a chemotherapeutic drug to treat acute promyelocytic leukemia cases (44). Thus, sodium arsenite seems to trigger caspase activation by activation of AKT1 and downstream glycogen synthase 3ß (GSK3ß), which are crucial for caspase signaling network AKT1 activation they also can act as an alternate cell survival pathway that is mediated via PI-3 kinase and p38 and bypass the activation of EGF receptor in cultured human keratinocytes (45).…”