Characterization of phospholipase C from Pseudomonas aeruginosa as a potent inflammatory agent

Phospholipase C (PLC) from Pseudomonas aeruginosa induced a marked inflammatory response when injected intraperitoneally in C3H/HeJ mice. This inflammation was characterized by the accumulation of inflammatory cells and plasma protein and the release of arachidonic acid metabolites (6-trans-12-epi-leukotriene B4 [LTB4], 6-trans-LTB4, LTB4, 5-HETE (5-hydroxyeicosatetraenoic acid), LTC4, LTD4, LTE4, prostaglandin E2 [PGE2], PGF2-alpha, and thromboxane B2 [TxB2]) in the peritoneal cavity of the mice. Heat-inactivated PLC did not evoke any of these effects, suggesting that enzyme activity is necessary for PLC-induced inflammation. When human granulocytes were incubated with PLC in vitro, 6-trans-12-epi-LTB4, 6-trans-LTB4, LTB4, 5-HETE, and PGE2 were generated. Mouse peritoneal cells stimulated with PLC released 6-trans-LTB4, LTB4, PGE2, PGF2-alpha, and TxB2. Both human granulocytes and mouse peritoneal cells stimulated with PLC generated significantly increased levels of arachidonic acid metabolites as compared with cells incubated with heat-inactivated PLC. Leukotriene production by both populations of cells was inhibited when the cells were preincubated with nordihydroguaiaretic acid and subsequently stimulated with PLC. Similarly, both cell types released significantly lower amounts of cyclooxygenase pathway products when they were preincubated with indomethacin and subsequently stimulated with PLC.