AGONIST-STIMULATED AND BASAL PHOSPHATIDYLETHANOL FORMATION IN NEUTROPHILS FORM ALCOHOLICS

Phospholipase D has been shown to be a key enzyme in the signal transd uction systems involved in neutrophil activation. In the presence of e thanol, the enzyme catalyzes a transphosphatidylation reaction through which phosphatidylethanol is formed instead of the normal product pho sphatidic acid. The effects of ethanol on the formation of phosphatidy lethanol and phosphatidic acid was studied in neutrophils from human a lcoholics in vitro. Neutrophils were isolated and cellular lipids were labeled with [H-3]oleate, whereafter the cells were preincubated with cytochalasin B. Subsequently, cells were stimulated with the chemotac tic peptide formyl-Met-Leu-Phe in the presence of ethanol concentratio ns ranging from 0 to 200 mM. In the presence of ethanol, both neutroph ils from alcoholics and controls produced phosphatidylethanol, with a concomitant reduction of the production of phosphatidic acid. The amou nts of phosphatidylethanol and phosphatidic acid formed were dependent on the concentration of ethanol. In neutrophils from alcoholics, a hi gher apparent K-m for the phospholipase D-mediated transphosphatidylat ion reaction was noted (58 mM ethanol compared with 28 mM in controls) . The in vivo mass of phosphatidylethanol in recently drinking alcohol ics was also analyzed in neutrophils. Measurable phosphatidylethanol l evels (average 5.6 pmol/10(6) neutrophils) were found in alcoholics up to 23 hr after the last intake of ethanol. Thus, in addition to the e thanol-induced changes in the normal production of phosphatidic acid, phosphatidylethanol accumulated in vivo in alcoholics may be expected to influence neutrophil function.