Induction Of Circulating Phospholipase-A2 Activity By Intravenous-Infusion Of Endotoxin In Patients With Neoplasia

The purpose of this study was to evaluate the impact of repeated intravenous infusions of endotoxin (EN) in patients with cancer on the systemic release of extracellular proinflammatory phospholipase A2 (PLA2) and its relationship to the release of tumor necrosis factor (TNF) and interleukin-6 (IL-6). Six patients received 15 infusions of EN isolated from Salmonella abortus equi at a dose of 4 ng/kg. Marked increase in the activity of circulating PLA2 was noted within 3 h after the first EN infusion and reached a maximal level of 20.4-fold greater than baseline 24 h after infusion. In five patients challenged with EN 2 weeks later, PLA2 reached peak levels 15.5-fold greater than baseline. In two patients who received three sequential daily infusions, the incremental increase in PLA2 activity after the second and third challenge reached maximum levels 6 h after EN infusion. PLA2 response followed those of TNF and IL-6 but was quantitatively different. Whereas maximal levels of TNF and IL-6 declined substantially after repeat EN challenges, no such decline occurred in PLA2 activity. Since, in the clinical setting of gram-negative sepsis, there is recurrent increase in circulating EN, our study approximates this clinical situation and shows that extracellular release of PLA2 folloWS temporally that of proximal cytokines such as TNF and IL-6. These cytokines may be related to PLA2 release and sustained high activity in the systemic circulation. Since, in gram-negative sepsis, the activity of circulating PLA2 correlates to circulatory collapse, adult respiratory distress syndrome, and outcome, analysis of the regulatory mechanisms of PLA2 may contribute to the understanding of gram-negative septic shock.