Ethanol increases superoxide anion production stimulated with 4beta-phorbol 12-myristate 13-acetate in human polymorphonuclear leukocytes. Involvement of protein kinase C.

Abstract

Stimulation of human polymorphonuclear leukocytes (PMNs) with PMA initiates a cascade of events leading to the production and release of superoxide anion (O-2), a major component in anti-bacterial defense. Generation of O-2 by PMA-stimulated PMNs occurs through the translocation and activation of protein kinase C (PKC). In this study, using freshly isolated PMNs, we examined the effect of ethanol on this response to PMA. Our results show that the basal production of O-2 was not affected by ethanol. In contrast, the response induced by PMA was potentiated by ethanol. This potentiation was observed even at high doses of PMA (200 nM) which alone had stimulated the O-2 response maximally. This enhanced response was not due to an increase of PMA uptake by PMNs. The maximal effect was obtained when the cells were preincubated with 80 mM of ethanol before PMA stimulation. Measurement of PKC activity in the cytosolic and membrane fractions showed that pretreatment of PMNs with ethanol increased twofold the PMA-stimulated PKC activity in the membrane fraction. Furthermore, Western blot analysis verified that this increase in PKC activity in the membrane fraction was linked to an increase in the translocation of PKC-alpha and -beta isoforms to the membrane. These results suggest that ethanol potentiates PMA-induced O-2 production through increasing PKC translocation and activity in PMNs.