Mechanisms involved in the contraction of endothelial cells by hydrogen peroxide

The importance of endothelial contraction in the genesis of inflammatory ed ema has been reported. ROS are metabolites synthesized in pathological cond itions in that a significant intravascular fluid leak occurs, such as ische mia-reperfusion. Present experiments were designed to test the hypothesis t hat ROS, particularly H2O2, may elicit the contraction of endothelial cells , and to explore the mechanisms involved. Bovine aortic endothelial cells i ncubated with H2O2 showed a significant reduction in planar cell surface ar ea (PCSA), and a significant increase in myosin light chain phosphorylation (MLCP), with a time- and dose-dependent pattern, without any significant t oxicity. This effect of H2O2 was not blocked by sulotroban (TxA(2) antagoni st) or BN 52021 (PAF antagonist). Lanthanum chloride (calcium channel block er) and EGTA partially inhibited the increase in MLCP induced by H2O2. H7 a nd staurosporine, PKC inhibitors, and PKC down-regulation (phorbol myristat e acetate treatment, 24 h) also blocked H2O2-dependent endothelial contract ion, measured as PCSA or MLCP. H2O2 increased the intracellular calcium con centration, an effect blunted by EGTA and lanthanum chloride. H2O2 also inc reased the phosphorylation of an 80 kD polypeptide, probably MARCKS, a PKC substrate. In summary, the present results demonstrate the ROS-dependent co ntraction of endothelial cells, an effect that could explain the intravascu lar fluid leak observed in some pathophysiological situations. Calcium and PKC may be involved in the development of this contraction. (C) 1999 Elsevi er Science Inc.