Involvement of Ca2+ in the H2O2-induced increase in endothelial permeability.
We studied the role of Ca2+ in mediating the hydrogen peroxide (H2O2)-induced increase in endothelial permeability to 125I-labeled albumin using bovine pulmonary microvessel endothelial cells (BMVEC). Changes in cytosolic-free Ca2+ ([Ca2+]i) were monitored in BMVEC monolayers loaded with the Ca(2+)-sensitive membrane permeant fluorescent dye fura 2-AM. H2O2 (100 microM) produced a rise in [Ca2+]i within 10 s that was reduced by the addition of EGTA to the medium. Uptake of 45Ca2+ from the extracellular medium increased in the presence of H2O2 (100 microM) compared with control monolayers, suggesting that the H2O2-induced rise in [Ca2+]i is partly the result of extracellular Ca2+ influx. The effects of [Ca2+]i on endothelial permeability were addressed by pretreatment of BMVEC monolayers with BAPTA-AM (3-5 microM), a membrane permeant Ca2+ chelator, before the H2O2 exposure. BAPTA-AM produced an approximately 50% decrease in the H2O2-induced increase in endothelial permeability compared with endothelial cell monolayers exposed to H2O2 alone. The increase in endothelial permeability was independent of Ca2+ influx, since LaCl3 (0-100 microM), which displaces Ca2+ from binding sites on the cell surface, did not modify the permeability response. These results indicate that the rise in [Ca2+]i produced by H2O2 is a critical determinant of the increase in endothelial permeability.
Siflinger-Birnboim
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Department of Physiology and Cell Biology, Albany Medical College, New York 12208, USA.
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Del Vecchio
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Malik
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D000818:Animals; D002118:Calcium / Q000502:physiology*; D002199:Capillary Permeability / Q000187:drug effects*; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D008833:Microcirculation / Q000187:drug effects; D009994:Osmolar Concentration; D011652:Pulmonary Circulation / Q000187:drug effects*; D012709:Serum Albumin / Q000378:metabolism
D012709:Serum Albumin; D006861:Hydrogen Peroxide; D002118:Calcium