Low‐intensity Pulsed Ultrasound Ameliorates Angiotension Ii-induced Cardiac Fibrosisbyalleviating Inflammation via a Caveolin-1-dependent Pathway

Abstract Background: Cardiac hypertrophy and fibrosis are major pathological manifestations observed in left ventricular remodeling induced by Angiotensin II (AngII). Concerning the fact that low‐intensity pulsed ultrasound (LIPUS) has been reported to improve cardiac dysfunction and myocardial fibrosis in myocardial infarction (MI) through mechanotransductionanditsdownstream pathways, we aimed to investigate whether LIPUS could also exert a protective effect on ameliorating AngII-induced cardiac hypertrophy and fibrosis andand if so, to further elucidate the underlying molecular mechanisms.Methods: In our study, we used AngII to mimic the animal and cell culture models of cardiac hypertrophy and fibrosis, where LIPUS irradiation (0.5MHz, 77.20mW/cm2) was applied for 20 minutes every 2 days from 1 week before surgery to 4 weeks after surgery in vivo, and every 6 hours for a total of 2 times in vitro. Following that, the levels of cardiac hypertrophy and fibrosis were evaluated by echocardiographic, histopathological, and molecular biological methods. Results: Our results showed that LIPUS irradiation could ameliorate left ventricular remodeling in vivo and cardiac fibrosis in vitro by reducing AngII-inducedrelease of inflammatory cytokines, while the protective effects were limited on cardiac hypertrophy in vitro. Given that LIPUS irradiation increased the expression of caveolin-1 related to mechanical stimulation, we inhibited caveolin-1 activity with pyrazolopyrimidine 2 (pp2) in vitro, by which LIPUS-induced downregulation of inflammation was reversed and the anti-fibrosis effects of LIPUS irradiation were absent. Conclusions: Taken together, these results indicate that LIPUS irradiation could ameliorate AngII-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway, providing new insights for the development of novel therapeuticapparatus in clinical practice.