Nicotine-induced adrenal beta-arrestin1 upregulation mediates tobacco-related hyperaldosteronism leading to cardiac dysfunction.

BACKGROUND

Tobacco-related products, containing the highly addictive nicotine together with numerous other harmful toxicants and carcinogens, have been clearly associated with coronary artery disease, heart failure, stroke, and other heart diseases. Among the mechanisms by which nicotine contributes to heart disease is elevation of the renin-angiotensin-aldosterone system (RAAS) activity. Nicotine, and its major metabolite in humans cotinine, have been reported to induce RAAS activation, resulting in aldosterone elevation in smokers. Aldosterone has various direct and indirect adverse cardiac effects. It is produced by the adrenal cortex in response to angiotensin II (AngII) activating AngII type 1 receptors. RAAS activity increases in chronic smokers, causing raised aldosterone levels (nicotine exposure causes the same in rats). AngII receptors exert their cellular effects either G proteins or the two βarrestins (βarrestin1 and-2).

AIM

Since adrenal ßarrestin1 is essential for adrenal aldosterone production and nicotine/cotinine elevate circulating aldosterone levels in humans, we hypothesized that nicotine activates adrenal ßarrestin1, which contributes to RAAS activation and heart disease development.

METHODS

We studied human adrenocortical zona glomerulosa H295R cells and found that nicotine and cotinine upregulate βarrestin1 mRNA and protein levels, thereby enhancing AngII-dependent aldosterone synthesis and secretion.

RESULTS

In contrast, siRNA-mediated βarrestin1 knockdown reversed the effects of nicotine on AngII-induced aldosterone production in H295R cells. Importantly, nicotine promotes hyperaldosteronism adrenal βarrestin1, thereby precipitating cardiac dysfunction, also , since nicotine-exposed experimental rats with adrenal-specific βarrestin1 knockdown display lower circulating aldosterone levels and better cardiac function than nicotine-exposed control animals with normal adrenal βarrestin1 expression.

CONCLUSION

Adrenal βarrestin1 upregulation is one of the mechanisms by which tobacco compounds, like nicotine, promote cardio-toxic hyperaldosteronism and . Thus, adrenal βarrestin1 represents a novel therapeutic target for tobacco-related heart disease prevention or mitigation.