Hydrogen Peroxide Mobilizes Ca2+ Through Two Distinct Mechanisms In Rat Hepatocytes
Aim:Hydrogen peroxide (H\"2O\"2) is produced during liver transplantation. Ischemia/reperfusion induces oxidation and causes intracellular Ca2+ overload, which harms liver cells. Our goal was to determine the precise mechanisms of these processes.Methods:Hepatocytes were extracted from rats. Intracellular Ca2+ concentrations ([Ca2+](i)), inner mitochondrial membrane potentials and NAD(P)H levels were measured using fluorescence imaging. Phospholipase C (PLC) activity was detected using exogenous PIP\"2. ATP concentrations were measured using the luciferin-luciferase method. Patch-clamp recordings were performed to evaluate membrane currents.Results:H\"2O\"2 increased intracellular Ca 2+ concentrations ([Ca2+](i)) across two kinetic phases. A low concentration (400 Î¼mol/L) of H\"2O\"2 induced a sustained elevation of [Ca2+](i) that was reversed by removing extracellular Ca2+. H\"2O\"2 increased membrane currents consistent with intracellular ATP concentrations. The non-selective ATP-sensitive cation channel blocker amiloride inhibited H\"2O\"2-induced membrane current increases and [Ca2+](i) elevation. A high concentration (1 mmol/L) of H\"2O\"2 induced an additional transient elevation of [Ca 2+](i), which was abolished by the specific PLC blocker U73122 but was not eliminated by removal of extracellular Ca2+. PLC activity was increased by 1 mmol/L H\"2O\"2 but not by 400 Î¼mol/L H\"2O\"2.Conclusion:H\"2O\"2 mobilizes Ca2+ through two distinct mechanisms. In one, 400 Î¼mol/L H\"2O\"2-induced sustained [Ca2+](i) elevation is mediated via a Ca2+ influx mechanism, under which H\"2O\"2 impairs mitochondrial function via oxidative stress, reduces intracellular ATP production, and in turn opens ATP-sensitive, non-specific cation channels, leading to Ca2+ influx. In contrast, 1 mmol/L H\"2O\"2-induced transient elevation of [Ca 2+](i) is mediated via activation of the PLC signaling pathway and subsequently, by mobilization of Ca2+ from intracellular Ca 2+ stores. Â© 2009 CPS and SIMM.
Acta Pharmacologica Sinica
Digital Object Identifier (DOI)
Sato, Hirohiko; Takeo, Teruko; Liu, Qiang; Nakano, Kyoko; Osanai, Tomohiro; Suga, Sechiko; Wakui, Makoto; and Wu, Jie, "Hydrogen Peroxide Mobilizes Ca2+ Through Two Distinct Mechanisms In Rat Hepatocytes" (2009). Neurobiology. 431.