PHOSPHOLIPASE-C FROM CLOSTRIDIUM-PERFRINGENS STIMULATES ACETYLTRANSFERASE-DEPENDENT FORMATION OF PLATELET-ACTIVATING-FACTOR IN CULTURED INTESTINAL EPITHELIAL-CELLS (INT-407)

The mechanisms by which phospholipase C from Clostridium perfringens s timulates the formation of platelet-activating factor (PAF-acether) in cultured intestinal epithelial cells (INT 407) were investigated. Alt hough stimulation with phospholipase C caused a significant formation of PAF-acether, there was no significant increase in the cellular leve ls of lysoPAF-acether after stimulation. Moreover, when cells prelabel ed with H-3-1-O-alkyl-2-acyl-sn-glycerophosphocholine were stimulated with phospholipase C, the H-3-lysoPAF-acether content was not increase d in stimulated cells as compared with unstimulated cells. When cells were preincubated with the calmodulin inhibitor trifluoperazine (TFPA) , the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylp iperazine (H-7), or the combined phospholipase A(2)-inhibitor and lipo xygenase inhibitor nordihydroguaiaretic acid (NDGA) before stimulation with phospholipase C, the PAF-acether formation was significantly dec reased. The phospholipase AZ inhibitor 4-bromophenacyl bromide (BPB), on the other hand, had no significant effect on the PAF-acether format ion. Preincubation with NDGA also decreased the levels of lysoPAF-acet her, whereas BPB, H7, or TFPA had no such effect. These findings indic ate that stimulation of acetyltransferase activity with increased acet ylation of lysoPAF-acether may be one way by which phospholipase C fro m C. perfringens stimulates formation of PAF-acether in INT 407 cells.