Antioxidant and cardioprotective effects of Danshensu (3-(3, 4-dihydroxyphenyl)-2-hydroxy-propanoic acid from Salvia miltiorrhiza) on isoproterenol-induced myocardial hypertrophy in rats

Abstract

Myocardial hypertrophy has been linked to the development of a variety of cardiovascular diseases, and is a risk factor for myocardial ischemia, arrhythmias, and sudden cardiac death. The objective of the present study was to evaluate the cardioprotective effects of Danshensu (DSS), a water-soluble active component of Danshen, on cardiac hypertrophy in rats. We are the first to report that DSS reversed Cx43 down-regulation in ventricular tissue. Cardiomyopathy in rats was produced using isoproterenol (Iso) treatment (2.5 mg/kg/d, s.c.) for seven days. DSS (3 and 10 mg/kg/d, i.p.) and Valsartan (Val) (10 mg/kg, i.g.) were administered on days 4–7 of Iso-treatment. Heart weight index, hemodynamic parameters, and ECG II parameters were monitored and recorded; protein expression of left ventricular connexin 43 (Cx43) and the activity of the redox system were assayed, and arrhythmias were produced using a coronary ligation/reperfusion procedure. The results demonstrated that DSS treatment significantly decreased heart weight/body weight (HW/BW) and left ventricular weight/body weight (LVW/BW) ratios. The protective role of DSS against Iso-induced myocardial hypertrophy was further confirmed using ECG. The incidences of ventricular tachycardia and ventricular fibrillation (VT, VF) and arrhythmic scores were higher in the model group and were suppressed by DSS. DSS decreased the serum and myocardium levels of creatine kinase, lactate dehydrogenase, and malondialdehyde (CK, LDH, and MDA) and increased serum activity of superoxide dismutase (SOD) in a dose-dependent manner. Cx43 expression in the left ventricle was down-regulated, and there was significant oxidative stress in this model of cardiomyopathy. DSS reversed the down-regulated Cx43 protein levels and showed potent anti-oxidative activities and cellular protection. These data demonstrate that DSS can prevent cardiac I/R injury and improve cardiac function in a rat model of hypertrophy, the effects partially resulting from antioxidants and the protection from Cx43 expression.

Introduction

Cardiovascular disease remains a major contributor to the high cause of death occurring among the population worldwide (Jay and Hassan 2006), with ∼25% of cardiovascular-related deaths due to arrhythmias. In clinical practice, most life-threatening arrhythmias occur in a diseased heart containing the structural and electrical remodeling processes that contribute to an increase in pro-arrhythmic phenotypes. The mechanisms underlying cardiac arrhythmias in a diseased heart are involved in several components, including altered ion channels in cell membranes, dissociated FKBP12.6 at the ryanodine macromolecule, and abnormal gap junction channels (Xia et al. 2006). Traditional antiarrhythmic drugs that block Na⁺, K⁺, and Ca²⁺ channels are unsuccessful in preventing lethal arrhythmias due to the complexity of the mechanisms underlying sudden cardiac death. Improving cardiac injury and attenuating cardiac remodeling are of utmost importance in protecting the heart. Alternative medicine is also a growing interest in the long-term prevention of heart attacks in high risk patients (Sun et al. 2005).

The preservation of cardiac electrical coupling is controlled primarily by cardiac myocyte gap junctions. Alterations in gap junction organization and connexin expression have gained wider acceptance in contributing to abnormal impulse propagation and arrhythmias in acquired adult heart disease (Imanaga, 2010, Song et al., 2009). The major cardiac gap junction subtype Cx43 is regarded as a promising target in the treatment of cardiovascular disease, and could lead to novel therapies in the future.

Danshensu (DSS), chemical name: 3-(3,4-dihydroxyphenyl)-2-hydroxy-propanoic acid, is an active water-soluble component of the Chinese medicine Labiate plant, Salvia (Fig. 1). Previous studies have shown that DSS posses potent antioxidant activities against peroxidative damage to biomembranes (Liu et al., 2001, Xing et al., 2006). It has been shown to be useful against heart ischemia and can protect endothelial progenitor cells from oxidized low-density lipoprotein-induced impairment (Wu et al., 2007, Ji et al., 2010). Our previous data suggest that DSS pretreatment can effectively inhibit I/R arrhythmias in hypertrophy-induced rats by l-thy, prevent hypertrophy progression in rats, and normalize serum NO content and eNOS activity (Le et al. 2008). To the best of our knowledge, there is no information reported on the relationship between the antiarrhythmic effects of Danshensu and cardiac gap junction regulation. Through our recent findings, we have evaluated the antiarrhythmic potential of DSS in treating isoproterenol (Iso)-induced myocardial hypertrophy in rats.

Recent reports indicate that angiotensin receptor blockers (ARB) have protective effects on various organs in addition to their blood pressure lowering abilities (Piechowski-Jóźwiak and Bogousslavsky, 2005, Okada et al., 2004). Experiments have demonstrated that ARB treatment resulted in improvement in myocardial function and suppressed cardiac and renal fibrosis through an antioxidative mechanism (Kobayashi et al., 2010, Arozal et al., 2009). In the present study, we used Valsartan (Val), an oral ARB, as a positive control.