Activation of phosphoinositide‐specific phospholipase C of rat neutrophils by the chemotactic aldehydes 4‐hydroxy‐2,3‐trans‐nonenal and 4‐hydroxy‐2,3‐trans‐octenal

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Abstract
A comparison has been made between the effects of 4‐hydroxy‐2,3‐trans‐nonenal (HNE) and 4‐hydroxy‐2,3‐trans‐octenal (HOE), two lipid peroxidation products, on the basal and GTPgammaS‐stimulated activities of phosphoinositide‐specific phospholipase C (PL‐C) of rat polymorphonuclear leukocytes. PL‐C activity was determined in vitro by measuring the hydrolysis of [3H] phosphatidylinositol‐4,5‐bis‐phosphate (PtdIns‐P2) added as exogenous substrate to neutrophil plasma membranes. PL‐C was activated by concentrations of HNE ranging from 10−8 to 10−6M both in the presence and in the absence of 2 × 10−5M GTPgammaS; HOE stimulated the enzymatic activity between 10−11 and 10−8M; maximal stimulation was given by 10−11M HOE plus GTPgammaS. The aldehyde concentrations able to accelerate PtdIns‐P2 breakdown displayed a good correspondence with those which have been reported to stimulate the oriented migration of rat neutrophils. Pretreatment of neutrophils with pertussis toxin prevented the stimulation of PL‐C by 10−11M HOE and by HOE plus GTPgammaS. Our results suggest that the chemotactic action of HNE and HOE might depend on the activation of PL‐C; furthermore a regulatory G protein appears to be involved in the acceleration of PtdIns‐P2 turnover by HOE.

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