Effects of resveratrol, a grape polyphenol, on catecholamine secretion and synthesis in cultured bovine adrenal medullary cells

Abstract

We report the effects of resveratrol, a polyphenol found in the skins of red grapes, on catecholamine secretion and synthesis in cultured bovine adrenal medullary cells. Resveratrol suppressed catecholamine secretion and ²²Na⁺ and ⁴⁵Ca²⁺ influx induced by acetylcholine, an agonist of nicotinic acetylcholine receptors, in a concentration-dependent manner (IC₅₀ = 20.4, 11.0, and 62.8 μM, respectively). Resveratrol also inhibited catecholamine secretion induced by veratridine, an activator of voltage-dependent Na⁺ channels, and 56 mM K⁺, an activator of voltage-dependent Ca²⁺ channels, at concentrations similar to those for ⁴⁵Ca²⁺ influx. Resveratrol directly inhibited the current evoked by acetylcholine in Xenopus oocytes expressing α3β4 neuronal nicotinic acetylcholine receptors (IC₅₀ = 25.9 μM). Furthermore, resveratrol (IC₅₀ = 5.32 μM) attenuated ¹⁴C-catecholamine synthesis induced by acetylcholine. The present findings suggest that resveratrol inhibits acetylcholine-induced catecholamine secretion and synthesis through suppressing ion influx in cultured bovine adrenal medullary cells.

Introduction

Resveratrol (trans-3,4′,5-trihydroxystilbene) is a natural phytoestrogen found in grapes, berries, and red wine [1], [2]. Resveratrol has been reported to be implicated in the beneficial action of red wine, i.e., the lower incidence of coronary artery disease in certain populations such as the French and the Greek, despite a diet rich in saturated fat and high smoking. This effect has been dubbed the ‘French Paradox’, and has been attributed to the regular consumption of red wine in moderate amounts by these populations [3], [4]. Indeed, resveratrol is thought to protect against atherosclerosis and coronary heart disease through various mechanisms, including vasorelaxation [5], [6] and anti-platelet effects [7], [8]. The precise mechanism of resveratrol for cardioprotective effects, however, remains to be determined.

Adrenal medullary cells are derived from the embryonic neural crest and share many properties with sympathetic postganglionic neurons. In cultured bovine adrenal medullary cells, there are at least three distinct types of ionic channels involved in catecholamine secretion [9]; these are (1) nicotinic acetylcholine receptor-ion channels, (2) voltage-dependent Na⁺ channels, and (3) voltage-dependent Ca²⁺ channels. In these cells, our previous studies have shown that either carbachol-induced ²²Na⁺ influx via nicotinic acetylcholine receptor-ion channels or veratridine-induced ²²Na⁺ influx via voltage-dependent Na⁺ channels increases ⁴⁵Ca²⁺ influx via voltage-dependent Ca²⁺ channels, a prerequisite for secretion [9] and synthesis [10] of catecholamines; in contrast, high K⁺ directly gates voltage-dependent Ca²⁺ channels to increase ⁴⁵Ca²⁺ influx without increasing ²²Na⁺ influx. Since catecholamine secretion mediated by stimulation of these ion channels and the mechanism of stimulation of catecholamine synthesis in adrenal medullary cells are thought to be similar to those of norepinephrine in the sympathetic neurons, adrenal medullary cells have provided a good model for detailed analysis of the actions of cardiovascular drugs, such as α₂-adrenergic agonists [10], natriuretic peptides [11], carvedilol [12] and pimobendan [13].

Several lines of evidence have shown that resveratrol has inhibitory effects on some ion channels such as L-type voltage-dependent Ca²⁺ channels in rat ventricular myocytes [14], human cardiac voltage-dependent Na⁺ channels [15], and voltage-activated potassium currents in rat hippocampal neurons [16]. Evidence has accumulated that aberrant acute or chronic activation of the sympathoadrenal system is involved causally in the development of various cardiovascular diseases such as heart failures [17]. Furthermore, a recent study reported that upregulation of adrenal medullary G protein-coupled receptor kinase 2 mediates sympathetic hyperactivity in heart failure through an increase in catecholamine secretion in two different models of heart diseases [18]. These evidences suggest that catecholamines play an important role in the pathological events of cardiovascular diseases. There is, however, little evidence regarding the effects of resveratrol on ion channel-mediated secretion and synthesis of catecholamines. In the present study, we examined the direct effects of resveratrol on acetylcholine-induced synthesis and secretion of catecholamines in cultured bovine adrenal medullary cells and acetylcholine-induced currents in the Xenopus oocytes expressing cloned α3β4 nicotinic acetylcholine receptors. We found that resveratrol inhibits acetylcholine-induced catecholamine synthesis and secretion via suppression of nicotinic acetylcholine receptor-ion channels.