Angiotensin II (ANG II) via AT1 receptors induces apoptosis in cardiomyocytes in vitro. We tested the hypothesis that in vivo AT1 receptor stimulation is accompanied by cardiac apoptosis and attempted to elucidate the molecular mechanisms involved in the death signaling pathway. Male Sprague-Dawley rats received ANG II (120 ng · kg−1 · min−1 sc) for 7 days with or without the AT1 receptor antagonist losartan (10 mg · kg−1 · day−1orally). Cardiac function was assessed by echocardiography. Apoptosis in the heart was detected and quantified by in situ TdT-mediated dUTP nick-end labeling (TUNEL) and radiolabeled DNA laddering. Expression of bax, bcl-2, caspase 3, and AT1 and AT2receptors was examined by Western blot analysis. Activity of caspase 3 was also measured by a fluorometric immunosorbent enzyme assay. Tail cuff systolic blood pressure was elevated ( P < 0.01, n = 6) in ANG II-infused rats (173 ± 3 mmHg) versus controls (111 ± 2 mmHg) and reduced by losartan (134 ± 4 mmHg). Cardiac function was essentially unchanged in ANG II-infused rats. Increased internucleosomal DNA cleavage by TUNEL assay and radiolabeled DNA laddering showed results compatible with enhanced cardiomyocyte apoptosis in the hearts of ANG-II infused rats. The bax-to-bcl-2 ratio, expression of the active form of caspase 3 (17 kDa), and activity of caspase 3 in the hearts of the ANG II group increased more than twofold above controls. Protein expression of AT1 and AT2 receptors was significantly increased in ANG II-infused rats compared with control rats. Losartan-treated ANG II-infused rats exhibited normalized apoptosis, bax, caspase 3 activity, and AT1 receptors. ANG II stimulation of AT1 receptors in the heart in vivo is associated with an increased rate of apoptosis without major hemodynamic consequences. Bax and caspase 3 are involved in the apoptotic signaling pathway in this experimental paradigm.
Shengxian decoction decreases doxorubicin‑induced cardiac apoptosis by regulating the TREM1/NF‑κB signaling pathway
