The generation of superoxide anion in blood platelets in response to different forms of Proteus mirabilis lipopolysaccharide: Effects of staurosporin, wortmannin, and indomethacin

Lipopolysaccharide (LPS), the major component of the outer membrane of Gram -negative bacteria may activate blood platelets. The aim of our study was t o evaluate the effects of different forms of Proteus mirabilis LPS and isol ated lipid A and polysaccharide part on the production of superoxide radica ls in blood platelets and to estimate the role staurosporin, wortmannin and indomethacin on this process. We compared the generation of superoxide rad icals in platelets treated with LPS after preincubation with inhibitors of the signal transduction pathways, namely staurosporin (inhibitor of protein kinase C), wortmannin (inhibitor of phosphoinositide 3-kinase), and indome thacin (inhibitor of cycloxygenase). Our results demonstrate that all LPS m olecules and their fragments caused a stimulation Of O-2(-) generation in p latelets (P < 0.5). LPS S1959 had the strongest stimulatory effect. Stauros porin and wortmannin, but not indomethacin inhibited O-2(-) production in L PS-stimulated platelets. Staurosporin (8 nM) and wortmannin (50 nM) caused about 50% inhibition of thrombin-induced O-2(-) generation in platelets, wh ile indomethacin (10 muM) had only a slight inhibitory effect on this proce ss. Our results provide support that in LPS- and thrombin-activated platele ts, at least part of O-2(-) is generated due to the activation of the enzym es (protein kinase C and phosphoinositide 3-kinase) involved in signal tran sduction pathway. Cycloxygenase seems to be not involved in this process. ( C) 2001 Elsevier Science Ltd. All rights reserved.