Ethanol-Induced Contractions in Cerebral Arteries

Abstract

Background and Purpose —The relationship between alcohol consumption and stroke appears complex; moderate ingestion is associated with reduced stroke risk, while heavy intake is associated with increased stroke risk. Ethanol has been shown both experimentally and epidemiologically to induce hemorrhagic and ischemic strokes, which are associated with cerebral vasoconstriction. Ethanol is known to induce contraction in isolated cerebral arteries and intact microvessels from diverse mammalian animals. The relationships between ethanol-induced contractions in cerebral arteries, intracellular free Ca ²⁺ ([Ca ²⁺ ] _i ), tyrosine kinases (including the src family), and mitogen-activated protein kinases (MAPK) were investigated in the present study. Methods —Cerebral arterial muscle tension and [Ca ²⁺ ] _i were quantified by an isometric contraction technique and direct visualization of Ca ²⁺ in single cells. Results —Ethanol induces concentration-dependent contractions in intact canine basilar arteries, which are attenuated significantly by pretreatment of the arteries with low concentrations of an antagonist of protein tyrosine kinases (genistein); an src homology 2 (SH2) domain inhibitor peptide; a highly specific antagonist of p38 MAPK (SB-203580); a potent, selective antagonist of MEK1/MEK2 (U0126); and a selective antagonist of mitogen-activated protein kinase kinase (MAPKK) (PD-98059). IC ₅₀ levels obtained for these 5 antagonists are consistent with reported K _i values for these tyrosine kinase, MAPK, and MAPKK antagonists. Ethanol induces transient and sustained increases in [Ca ²⁺ ] _i in primary single smooth muscle cells from canine basilar arteries, which are markedly attenuated in the presence of genistein, an SH2 domain inhibitor peptide, SB-203580, U0126, and PD-98059. Several specific antagonists of known endogenously formed vasoconstrictors do not inhibit or attenuate either the ethanol-induced contractions or the elevation of [Ca ²⁺ ] _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 [Ca ²⁺ ] _i in smooth muscle cells from canine basilar arteries. The results could be used to suggest that selective antagonists of protein tyrosine kinases and MAPK may be useful both prophylactically and therapeutically in alcohol-induced strokes.