Episodic drinking with blood alcohol levels reaching 35-80 mM is associated with an increased risk for cerebrovascular ischemia, stroke, and death from ischemic stroke. Cerebral ischemia may result from enhanced constriction of cerebral arteries. In a rat model widely used to mimic human cerebral artery function, our group previously demonstrated that alcohol-induced cerebrovascular constriction is mediated by vascular smooth muscle (VSM) Ca2+/voltage-gated K+ channels of large conductance (BK channels). BK channels are critical regulators of arterial diameter and myogenic tone. VSM BK channel activation results in outward potassium currents that hyperpolarize the membrane, leading to diminished smooth muscle cell (myocyte) contractility. Thus, BK current inhibition by alcohol results in cerebral artery constriction. Factors that tune BK channel sensitivity to alcohol remain largely unknown. Our group has established that high-cholesterol diet that leads to elevated blood cholesterol (CLR) levels and hypercholesterolemia protects against alcohol-induced constriction via accumulation of CLR in cerebral artery tissue. Clinical trial evidence supports the use of omega-3 fatty acids (FAs) such as docosahexaenoic acid (DHA) as a dietary supplement to reduce CLR buildup in arterial tissue. Moreover, DHA represents one of the most prevalent fatty acids in the brain. Whether increase in DHA can modify effect of alcohol and CLR-alcohol interactions in control of BK channel activity and cerebral artery diameter remains unknown. To cover existing gap in knowledge we will address two independently testable yet related Specific Aims: 1) we will determine the impact of DHA on alcohol-induced constriction of cerebral artery at nave versus elevated CLR in arteries with intact and removed endothelium; 2) we will determine the BK protein structural basis of DHA effect on alcohol sensitivity of BK current in cerebral artery smooth muscle. In the course of the study, we will capitalize on our strong expertise in lipid modulation of alcohol effect on cerebral artery smooth muscle. We will utilize rat model of dietary lipid delivery, cerebral artery diameter monitoring in vivo and in vitro, biochemical determination of DHA and CLR levels, site-directed mutagenesis, tissue loading with engineered DNA, and BK channel knock-out mouse. Our proposal will for the first time establish the role of DHA in the alcohol-driven effect at the organ level of cerebral artery. Also, for the first time we will unveil molecular mechanism that enables FA-alcohol interplay in control of cerebral artery diameter. Considering that DHA dietary supplementation in clinical practice is widely recommended during multiple pathological conditions (such as hypercholesterolemia, atherosclerosis, Alzheimer?s disease, inflammation, etc.) data obtained during our study will have high translational value.
Epidemiological studies have described the deleterious effect of alcohol on cerebrovascular health, while dietary cholesterol is a major regulator of susceptibility of brain arteries to alcohol. The current proposal stems from the clinical trial evidence that supports use of omega-3 fatty acids such as docosahexaenoic acid (DHA) as a dietary supplement to exert anti-cholesterol effect in the body: we will study consequences of DHA food intake and tissue enrichment on cholesterol-alcohol interactions at the level of brain artery and at the level of individual protein target. Our work will expand current understanding of mechanisms by which omega-3 fatty acid supplementation exerts its physiological effects and controls health outcomes.
