Ethanol inhibits astroglial cell proliferation by disruption of phospholipase D-mediated signaling

The activation of phospholipase D (PLD) is a common response to mitogenic s timuli in various cell types. As PLD-mediated signaling is known to be disr upted in the presence of ethanol, we tested whether PLD is involved in the ethanol-induced inhibition of cell proliferation in rat cortical primary as trocytes. Readdition of fetal calf serum (FCS) to serum-deprived astroglial cultures caused a rapid, threefold increase of PLD activity and a strong m itogenic response; both effects were dependent on tyrosine kinases but not on protein kinase C. Ethanol (0.1-2%) suppressed the FCS-induced, PLD-media ted formation of phosphatidic acid (PA) as well as astroglial cell prolifer ation in a concentration-dependent manner. Moreover, exogenous bacterial PL D increased astroglial proliferation in an ethanol-sensitive manner, wherea s exogenous PA or lysophosphatidic acid was less effective. Formation of PA and astroglial proliferation were strongly inhibited by I-butanol (0.1-1%) , a substrate of PLD, but were unaffected by 1-butanol, a non-substrate; 2- butanol had intermediate effects. Platelet-derived growth factor and endoth elin-l mimicked the mitogenic effect of FCS; their effects were also inhibi ted by the butanols in the potency order l-butanol > 2-butanol > tert-butan ol. Our results, in particular, the differential effects of 1-, 2-, and ter t-butanol with respect to PA formation and astroglial proliferation, strong ly suggest that the antiproliferative effects of ethanol in glial cells are due to the disruption of the PLD signaling pathway. This mechanism may als o contribute to the inhibition of astroglial growth and brain development o bserved in alcoholic embryopathy.