Ethanol-induced contractions in cerebral arteries - Role of tyrosine and mitogen-activated protein kinases

Background and Purpose-The relationship between alcohol consumption and str oke appears complex; moderate ingestion is associated with reduced stroke r isk, while heavy intake is associated with increased stroke risk. Ethanol h as been shown both experimentally and epidemiologically to induce hemorrhag ic and ischemic strokes, which are associated with cerebral vasoconstrictio n. Ethanol is known to induce contraction in isolated cerebral arteries and intact microvessels from diverse mammalian animals. The relationships betw een ethanol-induced contractions in cerebral arteries, intracellular free C a2+ ([Ca2+](i)), tyrosine kinases (including the src family), and mitogen-a ctivated protein kinases (MAPK) were investigated in the present study. Methods-Cerebral arterial muscle tension and [Ca2+](i) were quantified by a n isometric contraction technique and direct visualization of Ca2+ in singl e cells. Results-Ethanol induces concentration-dependent contractions in intact cani ne basilar arteries, which are attenuated significantly by pretreatment of the arteries with low concentrations of an antagonist of protein tyrosine k inases (genistein); an src homology 2 (SH2) domain inhibitor peptide; a hig hly specific antagonist of p38 MAPK (SB-203580); a potent, selective antago nist of MEK1/MEK2 (U0126); and a selective antagonist of mitogen-activated protein kinase kinase (MAPKK) (PD-98059). IC50 levels obtained for these 5 antagonists are consistent with reported K-i values for these tyrosine kina se, MAPK, and MAPKK antagonists. Ethanol induces transient and sustained in creases in [Ca2+](i) in primary single smooth muscle cells from canine basi lar arteries, which are markedly attenuated in the presence of genistein, a n SH2 domain inhibitor peptide, SB-203580, U0126, and PD-98059. Several spe cific antagonists of known endogenously formed vasoconstrictors do not inhi bit or attenuate either the ethanol-induced contractions or the elevation o f [Ca2+](i). Conclusions-The present study suggests that activation of protein tyrosine kinases (including the src family) and MAPK appear to play important roles in the ethanol-induced contractions and the elevation of [Ca2+](i) in smoot h muscle cells from canine basilar arteries. The results could be used to s uggest that selective antagonists of protein tyrosine kinases and MAPK may be useful both prophylactically and therapeutically in alcohol-induced stro kes.