Angiotensin-II type 1 receptor mediates pulmonary hypertension and right ventricular remodeling induced by inhaled nicotine.

Abstract

Use of electronic cigarettes is rapidly increasing among youth and young adults, but little is known regarding the long-term cardiopulmonary health impacts of these nicotine-containing devices. Our group has previously demonstrated that chronic, inhaled nicotine induces pulmonary hypertension (PH) and right ventricular (RV) remodeling in mice. These changes were associated with upregulated RV angiotensin-converting enzyme (ACE). Angiotensin-II receptor blockers (ARBs) have been shown to reverse cigarette smoking-induced PH in rats. ACE inhibitor and ARB use in a large retrospective PH patient cohort is associated with improved survival. Here, we utilized losartan (an ARB specific for angiotensin-II type 1 receptor) to further explore nicotine-induced PH. Male C57BL/6 mice received nicotine vapor for 12 hours per day, and exposure was assessed using serum cotinine to achieve levels comparable to human smokers or electronic cigarette users. Mice were exposed to nicotine for 8 weeks and a subset was treated with losartan via osmotic minipump. Cardiac function was assessed using echocardiography and catheterization. Although nicotine exposure increased angiotensin-II in the RV and lung, this finding was non-significant. Chronic, inhaled nicotine significantly increased RV systolic pressure and RV free wall thickness versus air control. These parameters were significantly lower in mice receiving both nicotine and losartan. Nicotine significantly increased RV internal diameter, with no differences seen between the nicotine and nicotine-losartan group. Neither nicotine nor losartan effect left ventricular structure or function. These findings provide the first evidence that antagonism of the angiotensin-II type 1 receptor can ameliorate chronic, inhaled nicotine-induced PH and RV remodeling.