Docosahexaenoic acid protects against alcohol-induced constriction of cerebral arteries and inhibition of vascular smooth muscle BK channels.

Abstract

Background: Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid used as a dietary supplement with health benefits. Alcohol in moderate-to-high concentrations constricts cerebral arteries and triggers brain ischemia. Here, we probed the ability of DHA to protect against alcohol action on cerebral artery diameter and on the activity of calcium-/voltage-gated potassium channels of large conductance (BKs) in vasculature.

Methodology: Adult Sprague-Dawley rats received daily oral DHA supplementation for up to 18-23 weeks. Constriction of middle cerebral artery (MCA) pial branches was probed using a cranial window upon infusion of 50 mM alcohol into the cerebral circulation. DHA and alcohol were also probed ex vivo in MCAs upon vessel pressurization at 60 mmHg. DHA's effect on alcohol-induced inhibition of BK channels in MCA myocytes was probed using patch-clamp recording of BK currents at physiological membrane voltage and intracellular calcium.

Results: DHA protected males but not females against alcohol-induced vasoconstriction in vivo. Oral DHA increased DHA levels in the MCA of male but not female rats. Arteries from male rats on control chow that were pressurized ex vivo and perfused with 3 μM DHA lost their constriction by alcohol. Incubation of freshly isolated myocytes of male MCAs in DHA prevented alcohol-induced inhibition of BK channels. However, DHA protection was absent when DHA was perfused to excised patches. DHA did not alter the amount of BK channel subunits within the myocyte plasmalemma of male MCAs. DHA protection against alcohol-induced constriction persisted in arteries expressing BK channel with a mutation on a previously identified fatty acid-sensing site.

Conclusions: DHA protects against alcohol-induced cerebral artery constriction and BK channel inhibition in a sexually dimorphic manner via cellular mechanisms in vascular myocytes. This action of DHA is independent of changes in BK subunit membrane levels and of a previously identified fatty acid-sensing site in the BK channel.