Published online May 26, 2020. doi: 10.4330/wjc.v12.i5.192
Peer-review started: January 3, 2020
First decision: February 19, 2020
Revised: March 27, 2020
Accepted: May 12, 2020
Article in press: May 12, 2020
Published online: May 26, 2020
Processing time: 143 Days and 9.7 Hours
Nicotine, the main addictive compound in tobacco, is associated with major cardiovascular adverse events, such as heart failure and hypertension. One of the molecular mechanisms underlying nicotine-induced cardiotoxicity is elevation of renin-angiotensin-aldosterone system (RAAS) activity. Nicotine, and its major metabolite in humans cotinine, have been reported to induce RAAS activation, resulting in hyperaldosteronism. Aldosterone has myriad adverse cardiac effects and is produced by the adrenal cortex in response to angiotensin II (AngII) acting through its type 1 receptors (AT1Rs). AT1Rs induce aldosterone production via both Gq/11 proteins and βarrestin1 (Arrestin-2).
It was hypothesized that nicotine activates adrenal ßarrestin1, thereby contributing to RAAS activation and heart disease development.
We tested our hypothesis by investigating the effects of nicotine on aldosterone production in vitro and on aldosterone levels and cardiac function of experimental animals in vivo.
We used the human adrenocortical zona glomerulosa (AZG) cell line H295R, in which we performed real-time polymerase chain reaction (PCR) and western blotting to measure βarrestin1 mRNA and protein levels, respectively, as well as ELISA to measure aldosterone secretion. We also manipulated βarrestin1 expression via siRNA-mediated knockdown in H295R cells. For the in vivo studies, we used adult male Sprague-Dawley rats, which we exposed to chronic nicotine administration after adrenal-specific, βarrestin1 siRNA-mediated knockdown or control scrambled siRNA delivery in vivo.
Nicotine and cotinine upregulate βarrestin1 mRNA and protein levels in AZG cells, which augments aldosterone synthesis and secretion. In contrast, siRNA-mediated βarrestin1 knockdown mitigates the effects of nicotine on AngII-induced aldosterone production. In vivo, 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.
Adrenal βarrestin1 upregulation is one of the mechanisms by which tobacco, i.e. nicotine, promotes cardio-toxic hyperaldosteronism that accelerates cardiac functional decline, both in vitro and in vivo.
Adrenal βarrestin1 pharmacological blockade or genetic deletion (or knockdown) represents a novel therapeutic strategy to ameliorate tobacco-related heart disease morbidity and mortality.