N-Acetylcysteine Inhibits Aortic Stenosis Progression in a Murine Model by Blocking Shear-Induced Activation of Platelet Latent Transforming Growth Factor Beta 1

Objective Aortic stenosis (AS) is characterized by narrowing of aortic valve opening, resulting in peak blood flow velocity that induces high wall shear stress (WSS) across the valve. Severe AS leads to heart failure and death. There is no treatment available for AS other than valve replacement. Platelet-derived TGF-β1 partially contributes to AS progression in mice, and WSS is a potent activator of latent TGF-β1. N-acetylcysteine (NAC) inhibits WSS-induced TGF-β1 activation in vitro. We hypothesize that NAC will inhibit AS progression by inhibiting WSS-induced TGF-β1 activation. Approach We treated a cohort of Ldlr(-/-)Apob(100/100) (LDLR) mice fed a high fat diet with N-acetylcysteine (NAC, 2% in drinking water) at different stages of disease progression and measured its effect on AS progression and TGF-β1 activation. Results Short-term NAC treatment inhibited AS progression in mice with moderate and severe AS relative to controls, but not in LDLR mice lacking platelet-derived TGF-β1 (TGF-β1platlet-KO-LDLR). NAC treatment reduced TGF-β signaling, p-Smad2 and collagen levels, and mesenchymal transition from Isolectin-B4 and CD45-positive cells in LDLR mice. Mechanistically, NAC treatment resulted in plasma NAC concentrations ranging from 75.5 to 449.2 ng/ml, which was sufficient to block free thiol labeling of plasma proteins and reduce active TGF-β1 levels without substantially affecting reactive oxygen species-modified products in valvular cells. Conclusions Short-term treatment with NAC inhibits AS progression, by inhibiting WSS-induced TGF-β1 activation in the LDLR mouse model of AS, motivating a clinical trial of NAC and/or other thiol-reactive agent(s) as a potential therapy for AS.