Experimental researches on the role of phosphoinositide-specific phospholipase C in 4-hydroxynonenal induced exocytosis.

The action of 4-hydroxynonenal (HNE), a chemotactic aldehyde produced by lipid peroxidation, was analysed on exocytosis in parallel with its effects on phosphoinositide-specific phospholipase C (PLC) both in undifferentiated HL-60 cells and in cells induced to differentiate toward the granulocytic cell line by 1.25% DMSO. Exocytosis was evaluated by the secretion of beta-glucuronidase from cells incubated at 37 degrees C for 10 min in the presence of various aldehyde concentrations. HNE action was more pronounced in DMSO-differentiated cells, where concentrations between 10(-8) and 10(-6) m were able both to trigger exocytosis and to strongly activate PLC; in both processes maximal stimulation was given by 10(-7) m. HNE-induced exocytosis was completely prevented by pertussis toxin and by the PLC inhibitor U73122. The comparison between HNE and formyl-methionyl-leucyl-phenylalanine (fMLP), used as a positive control, showed that the tripeptide produced an higher stimulation of exocytosis than the aldehyde; by contrast HNE induced a stronger increase of PLC activity. Wortmannin, an inhibitor of phosphatidylinositol-3-kinase (PI3K), strongly inhibited the exocytosis induced by fMLP, while it failed to induce a statistically significant inhibition of HNE action. We conclude that both compounds trigger exocytosis through a Ptx-sensitive G protein; the present data support the hypothesis that the lower ability of the aldehyde to trigger exocytosis as compared to fMLP might depend upon a low ability to activate PI3K, while PLC activation appears to play a key role in HNE-induced exocytosis.

Copyright 2003 John Wiley & Sons, Ltd.