Abstract
Atrial hypertrophy and fibrosis are essential pathological features of atrial fibrillation. Recently, adiponectin has become a protein of interest due to its beneficial effects on cardiovascular diseases. However, the molecular mechanism of atrial structural remodeling and signaling pathways evoked by adiponectin remain unclear. In the present study, we investigated the cardioprotective effect of globular adiponectin (gAcrp) on angiotensin II-induced atrial hypertrophy and fibrosis in neonatal Sprague-Dawley rat. To further investigate the molecular mechanisms underlying the preventive effect of gAcrp, transfection of cells with siRNA was used to suppress the mRNA expression of adiponectin receptor 1 (AdipoR1) and its downstream adaptor protein APPL1. Non-silencing-Cy-3 labelled siRNA was used to determine transfection efficiency using fluorescence microscopy. The expression of atrial natriuretic peptide and procollagen type1 α-1, hypertrophy marker and fibrosis one, respectively, was detected by real-time PCR. Furthermore, the expression of adenosine monophosphate-activated protein kinase (AMPK), phosphatidylinositol 3-kinase (PI3K) and Akt was detected by western blotting. In addition, nuclear p65 translocation activity was analyzed by EMSA supershift assay. Our results showed that AdipoR1 and the adaptor protein APPL1 mediated the protective effects of gAcrp. In addition, the function of adiponectin and phosphorylation of AMPK were prominently diminished by inhibition of PI3K. Furthermore, nuclear factor-κB (NF-κB) transcription was diminished by the specific inhibition of AMPK. Taken together, AMPK pivotally interacts with NF-κB and PI3K, mediating the cardioprotective effect of adiponectin, and may serve as a therapeutic target for preventing atrial hypertrophy and fibrosis. Our present study suggests that gAcrp could ameliorate AngII-induced cardiac hypertrophy and fibrosis in rat atrial cells, which is mediated by the activation of AMPK signaling pathways. APPL1 and AdipoR1 are the key factors involved in the downstream of gAcrp approach.
Highlights
Atrial fibrillation (AF) is a common sustainable arrhythmia in clinical practice [1]
Globular adiponectin attenuates cardiac hypertrophy and fibrosis induced by angiotensin II (AngII) in myocytes and fibroblasts isolated from the atria of neonatal rats
We constructed a model of atrial hypertrophy and fibrosis with myocytes and fibroblasts isolated from neonatal SD rats
Summary
Atrial fibrillation (AF) is a common sustainable arrhythmia in clinical practice [1]. AF is one of the leading causes of stroke among the elderly and accounts for one-third of strokes among patients over the age of 65 [2]. Atrial structural remodeling is one of the most pivotal substrates in AF and leads to progressive architectural aggravation of atria after continuous episodes of AF. The primary changes of structural remodeling involve myocytic hypertrophy, myolysis, and interstitial fibrosis [3]. It has been demonstrated that the activation of the renin-angiotensin system (RAS) plays a pivotal role in atrial structural remodeling of AF [4,5]. Angiotensin II (AngII) has been shown to be a key trigger of atrial hypertrophy and fibrosis. The molecular mechanism of atrial structural remodeling still remains unclear
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