Septic plasma suppresses superoxide anion synthesis by normal homologous polymorphonuclear leukocytes.

In vitro exposure of normal O,Rh- PMN to plasma obtained from patients with septic shock results in inhibition of formyl-methionyl-leucyl-phenylalanine stimulated superoxide anion (O2.-) production by 40%. Although all reaction velocities and extent of reaction at 5 min were suppressed, neither lag time preceding O2.- production nor duration of initial velocity linearity was affected. No such inhibition was noted when plasma from healthy controls or nonseptic critically ill patients was utilized in the reaction. These results demonstrate that neutrophils are not only a cause, but also a target of the septic shock host inflammatory response.

In vitro modulation of human neutrophil superoxide anion generation by various calcium channel antagonists used in ischemia-reperfusion resuscitation.

Generation of toxic oxygen species by activated polymorphonuclear leukocytes (PMNs) may represent an important mechanism of ischemia-reperfusion injury. Concentration-response data concerning inhibition of superoxide anion (O2-) generation by NADPH oxidoreductase (NADPH OR) from isolated human PMN were generated for five calcium channel antagonists commonly utilized in ischemia-reperfusion investigational therapeutics. Regression analysis derived IC50 values for verapamil, nimodipine, nicardipine and lidoflazine were 45, 20, 12 and 7 microM respectively. Inhibition of the extent of reaction at 5 min paralleled inhibition of initial velocity. No inhibition by flunarizine was noted at concentrations less than or equal to 25 microM (where it did not alter reaction mixture composition). Only nicardipine demonstrated a significant concentration-response effect relative to prolonging lag time preceding O2- synthesis. Inhibition appeared at least partially reversible for all five agents. Neither PMN activation/desensitization, free-radical scavenging, nor PMN cytotoxicity appeared to be involved in the inhibition of PMN O2- synthesis by these agents. Ca2+ antagonist inhibition of PMN NADPH OR appears to involve more than simple inhibition of Ca2+ flux across the PMN plasma membrane. Direct inhibition of the intracellular events involved in the activation and/or activity of NADPH OR may be operative.