Concentration-dependent Dual Effects of Hydrogen Peroxide on Insulin Signal Transduction in H4IIEC Hepatocytes

Abstract

BackgroundOxidative stress induced by the accumulation of reactive oxygen species (ROS) has a causal role in the development of insulin resistance, whereas ROS themselves function as intracellular second messengers that promote insulin signal transduction. ROS can act both positively and negatively on insulin signaling, but the molecular mechanisms controlling these dual actions of ROS are not fully understood.Methodology/Principal FindingsHere, we directly treated H4IIEC hepatocytes with hydrogen peroxide (H2O2), a representative membrane-permeable oxidant and the most abundant ROS in cells, to identify the key factors determining whether ROS impair or enhance intracellular insulin signaling. Treatment with high concentrations of H2O2 (25–50 µM) for 3 h reduced insulin-stimulated Akt phosphorylation, and increased the phosphorylation of both JNK and its substrate c-Jun. In contrast, lower concentrations of H2O2 (5–10 µM) enhanced insulin-stimulated phosphorylation of Akt. Moreover, lower concentrations suppressed PTP1B activity, suggesting that JNK and phosphatases such as PTP1B may play roles in determining the thresholds for the diametrical effects of H2O2 on cellular insulin signaling. Pretreatment with antioxidant N-acetyl-L-cysteine (10 mM) canceled the signal-promoting action of low H2O2 (5 µM), and it canceled out further impairment of insulin of insulin signaling induced by high H2O2 (25 µM).Conclusions/SignificanceOur results demonstrate that depending on its concentration, H2O2 can have the positive or negative effect on insulin signal transduction in H4IIEC hepatocytes, suggesting that the concentration of intracellular ROS may be a major factor in determining whether ROS impair or enhance insulin signaling.

Glutathione Peroxidase Mimic Ebselen Improves Glucose-Stimulated Insulin Secretion in Murine Islets

“…This again underscores the complexity of the ROS regulation on GSIS, and may be explained by the concentration-dependent dual effect of H 2 O 2 (29 (18) in the SKO and dKO islets. However, selenite did not affect GSIS of the WT and GKO islets, which was different from that reported in rat islets and min6 cells (13).…”

“…Thus, the relatively low expression of antioxidant enzymes in islets (39) may not only render them susceptible to oxidative insults, but also provide a necessary metabolic condition for their sensitive responses to reactive oxygen species (ROS)-mediated signaling in GSIS (49). In fact, hydrogen peroxide (H 2 O 2 ) functions as an essential second messenger (19) in initiating and regulating GSIS (49,50), and it demonstrates concentration-dependent dual effects on insulin signaling and other metabolic processes (29,51).…”

Skeletal muscle insulin resistance: role of mitochondria and other ROS sources

“…A direct link between mitochondrial H 2 O 2 production and JNK1 activation has not yet been demonstrated, but an inverse relationship between protein tyrosine phosphatase PTP-1B activity and JNK1 activation has been shown by treating H4IIEC hepatocytes with increasing concentrations of H 2 O 2 (Iwakami et al 2011). With relatively low concentrations of H 2 O 2 (≤5.0 μM), PTP-1B activity was inhibited and insulin-stimulated phosphorylation IRS and Akt was enhanced.…”

The two faces of reactive oxygen species (ROS) in adipocyte function and dysfunction

“…ROS have been implicated in the regulation of several processes such as cytokine secretion, proliferation, differentiation, gene expression and as cytotoxic molecules in immune responses against invading pathogens (Hensley et al, 2000). A study with H4IIEC hepatoma cells showed that different H 2 O 2 concentrations could either enhance, if in a low concentration such as 5 μm, or repress, if in a high concentration such as 50 μm, the insulin signaling pathway (Iwakami et al, 2011). Remarkably, adipocytes seem to adapt to dynamic changes in ROS levels and to use them as second messengers.…”