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 via either G proteins or the twoβarrestins(βarrestin1 and-2).AIM Since adrenal?arrestin1 is essential for adrenal aldosterone production and nicotine/cotinine elevate circulating aldosterone levels in humans,we hypothesized that nicotine activates adrenal?arrestin1,which contributes to RAAS activation and heart disease development.METHODS We studied human adrenocortical zona glomerulosa H295R cells and found that nicotine and cotinine upregulateβarrestin1 mRNA and protein levels,thereby enhancing AngII-dependent aldosterone synthesis and secretion.RESULTS In contrast,siRNA-mediatedβarrestin1 knockdown reversed the effects of nicotine on AngII-induced aldosterone production in H295 R cells.Importantly,nicotine promotes hyperaldosteronism via adrenalβarrestin1,thereby precipitating cardiac dysfunction,also in vivo,since nicotine-exposed experimental rats with adrenal-specificβarrestin1 knockdown display lower circulating aldosterone levels and better cardiac function than nicotine-exposed control animals with normal adrenalβarrestin1 expression.CONCLUSION Adrenalβarrestin1 upregulation is one of the mechanisms by which tobacco compounds,like nicotine,promote cardio-toxic hyperaldosteronism in vitro and in vivo.Thus,adrenalβarrestin1 represents a novel therapeutic target for tobaccorelated heart disease prevention or mitigation.

GRK5 is an essential co-repressor of the cardiac mineralocorticoid receptor and is selectively induced by finerenone

BACKGROUND In the heart,aldosterone(Aldo)binds the mineralocorticoid receptor(MR)to exert damaging,adverse remodeling-promoting effects.We recently showed that G protein-coupled receptor-kinase(GRK)-5 blocks the cardiac MR by directly phosphorylating it,thereby repressing its transcriptional activity.MR antagonist(MRA)drugs block the cardiac MR reducing morbidity and mortality of advanced human heart failure.Non-steroidal MRAs,such as finerenone,may provide better cardio-protection against Aldo than classic,steroidal MRAs,like spironolactone and eplerenone.AIM To investigate potential differences between finerenone and eplerenone at engaging GRK5-dependent cardiac MR phosphorylation and subsequent blockade.METHODS We used H9c2 cardiomyocytes,which endogenously express the MR and GRK5.RESULTS GRK5 phosphorylates the MR in H9c2 cardiomyocytes in response to finerenone but not to eplerenone.Unlike eplerenone,finerenone alone potently and efficiently suppresses cardiac MR transcriptional activity,thus displaying inverse agonism.GRK5 is necessary for finerenone’s inverse agonism,since GRK5 genetic deletion renders finerenone incapable of blocking cardiac MR transcriptional activity.Eplerenone alone does not fully suppress cardiac MR basal activity regardless of GRK5 expression levels.Finally,GRK5 is necessary for the antiapoptotic,anti-oxidative,and anti-fibrotic effects of both finerenone and eplerenone against Aldo,as well as for the higher efficacy and potency of finerenone at blocking Aldo-induced apoptosis,oxidative stress,and fibrosis.CONCLUSION Finerenone,but not eplerenone,induces GRK5-dependent cardiac MR inhibition,which underlies,at least in part,its higher potency and efficacy,compared to eplerenone,as an MRA in the heart.GRK5 acts as a co-repressor of the cardiac MR and is essential for efficient MR antagonism in the myocardium.