Hydrogen peroxide attenuates refilling of intracellular calcium store in mouse pancreatic acinar cells

摘要

Intracellular calcium (Ca2+) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide (H₂O₂) on intracellular Ca2+ accumulation in mouse pancreatic acinar cells. Perfusion of H₂O₂ at 300 μM resulted in additional elevation of intracellular Ca2+ levels and termination of oscillatory Ca2+ signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca2+. Antioxidants, catalase or DTT, completely prevented H₂O₂-induced additional Ca2+ increase and termination of Ca2+ oscillation. In Ca2+-free medium, H₂O₂ still enhanced CCh-induced intracellular Ca2+ levels and thapsigargin (TG) mimicked H₂O₂-induced cytosolic Ca2+ increase. Furthermore, H₂O₂-induced elevation of intracellular Ca2+ levels was abolished under sarco/endoplasmic reticulum Ca2+ ATPase-inactivated condition by TG pretreatment with CCh. H₂O₂ at 300 μM failed to affect store-operated Ca2+ entry or Ca2+ extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca2+ uniporter blocker, failed to attenuate H₂O₂-induced intracellular Ca2+ elevation. These results provide evidence that excessive generation of H₂O₂ in pathological conditions could accumulate intracellular Ca2+ by attenuating refilling of internal Ca2+ stores rather than by inhibiting Ca2+ extrusion to extracellular fluid or enhancing Ca2+ mobilization from extracellular medium in mouse pancreatic acinar cells.