title: The effect of oxidative stress on Ca2+ release and capacitative Ca2+ entry in vascular endothelial cells.
abstract: Oxidative stress imposed by the accumulation of oxygen free radicals (reactive oxygen species, ROS) has profound effects on Ca2+ homeostasis in the vascular endothelium, leading to endothelial dysfunctions and the development of cardiovascular pathologies. We tested the effect of the oxidant and ROS generator tert-butyl-hydroperoxide (tBuOOH) on Ca2+ signaling in single cultured calf pulmonary artery endothelial (CPAE) cells loaded with the fluorescent Ca2+ indicator indo-1. Acute brief (5 min) exposures to tBuOOH had no effect on basal cytosolic free Ca2+ ([Ca2+](i)), agonist (ATP)-induced Ca2+ release from the endoplasmic reticulum (ER) and on Ca(2+) store depletion-dependent capacitative Ca2+ entry (CCE). Prolonged (60 min) exposure to tBuOOH did not affect intracellular Ca2+ release, but caused a profound inhibition of CCE. After 120 min of treatment with tBuOOH not only was CCE further reduced, but also ATP-induced Ca2+ release due to a slow depletion of the stores that resulted from CCE inhibition. The antioxidant Trolox (synthetic vitamin E analog) prevented the inhibition of CCE by tBuOOH and attenuated the increase of [ROS](i), indicating that inhibition of CCE was due to the oxidant effects of tBuOOH. The data suggest that in vascular endothelial cells oxidative stress primarily affects Ca2+ influx in response to Ca2+ loss from internal stores. [Ca2+](i) is an important signal for the production and release of endothelium-derived factors such as nitric oxide (NO). Since CCE is the preferential Ca2+ source for NO synthase activation, the finding that oxidative stress inhibits CCE may explain how oxidative stress contributes to endothelial dysfunction-related cardiovascular pathologies.
authors.affiliation: Department of Physiology, Loyola University Chicago, 2160 S. First Avenue, Maywood, IL 60153, USA.
authors.forename: Stela M
authors.initials: SM
authors.lastname: Florea
authors.forename: Lothar A
authors.initials: LA
authors.lastname: Blatter
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006706:Homeostasis; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*; D019284:Thapsigargin / Q000378:metabolism; D020122:tert-Butylhydroperoxide / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D020122:tert-Butylhydroperoxide; D002118:Calcium