Hydrogen peroxide activates agonist-sensitive Ca(2+)-flux pathways in canine venous endothelial cells.
The effect of the biological oxidant H2O2 on purinergic-receptor-stimulated Ca2+ signalling was determined in canine venous endothelial cells. H2O2 increased cytosolic free [Ca2+] ([Ca2+]i), the rate of rise of which was dose-dependently related to H2O2 concentration. The response of [Ca2+]i to H2O2 resulted in part from release of Ca2+ from internal stores. The H2O2-sensitive intracellular Ca2+ pool was characterized in cells suspended in Ca(2+)-free/EGTA buffer and stimulated in sequence with H2O2 and ionomycin or ATP. Under this condition, the rank order of apparent compartment size sensitive to each compound was ionomycin > H2O2 > ATP. Stimulation of cells with H2O2 eliminated any response of [Ca2+]i to subsequent addition of ATP. To test more directly whether H2O2 accesses the inositol trisphosphate-sensitive Ca2+ store, cells were pretreated with thapsigargin, a selective inhibitor of that store's Ca2+ pump. Release of Ca2+ from internal Ca2+ stores by H2O2 declined as the interval after thapsigargin addition increased, a finding that supports the contention that H2O2 accesses the inositol trisphosphate-sensitive Ca2+ store. H2O2-stimulated Ca2+ influx across the cell membrane was sensitive to Ni2+, La3+, and 1-(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl)-1H-imidazole HCl (SKF-96365), a selective inhibitor of the agonist-stimulated Ca(2+)-influx pathway. Ca2+ entry triggered by H2O2 appears to occur via the agonist-sensitive Ca2+ influx pathway. Together, these results suggest that H2O2, which is normally secreted by activated neutrophils and monocytes, may act as an intercellular messenger and stimulate Ca2+ signalling in target endothelial cells.
Doan
T N
TN
Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030.
Gentry
D L
DL
Taylor
A A
AA
Elliott
S J
SJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D007293:Inosine Triphosphate / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007601:Jugular Veins; D007811:Lanthanum / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D007093:Imidazoles; D013729:Terpenes; D007293:Inosine Triphosphate; D015759:Ionomycin; D019284:Thapsigargin; D007811:Lanthanum; D009532:Nickel; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium