Here we show that periostin is involved in myocardial fibrosis in STZ-induced type 1 diabetic mice. Furthermore, resveratrol suppresses HG-induced differentiation of mCFs via ROS/ERK/TGF-?/periostin pathway and suppresses HG-induced proliferation of mCFs via ROS/ERK pathway. Our results suggest that ROS/ERK/TGF-?/periostin pathway may contribute to myocardial fibrosis in DCM and resveratrol has a therapeutic potential in ameliorating these processes.
Resveratrol is a naturally existing phytoalexin found largely in grapes. It exerts potent antioxidant effects and cardioprotective effects, including myocardial ischemia-reperfusion injury [13], cardiomyocyte hypertrophy [10], myocardial inflammation [14] and atherosclerosis [9]. Here, our in vitro experiments demonstrated that resveratrol treated group manifested less fibrosis level than no resveratrol treated group, evidenced by a significant decrease in CVF using Masson’s trichrome staining. This was accompanied by decreased oxidative stress evidenced by downregulation of p47phox, p66shc, gp91phox and ROS level. Supporting these statements, Qin et al. demonstrated that reduction of oxidative stress was a potential mechanism contributed to the beneficial effects of resveratrol in diet-induced metabolic heart disease in mice [10]. However, the exact mechanisms remain poorly understood, which was heavily studied in this present study.
Periostin, a secreted extracellular matrix (ECM) protein, is upregulated dramatically under transverse aortic constriction (TAC) stress [2, 15, 16], myocardial infarction [3, 17] or heart failure [1]. An accumulating body of evidence suggests that periostin plays an important role in fibrosis by regulating ECM molecules such as collagen and fibronectin [18]. The importance of periostin in fibrogenesis was also documented in studies utilizing periostin knock-out animal, where deletion of periostin dramatically suppressed muscular fibrosis [19]. However, to our knowledge, there was little information about its profibrotic effect in DCM to date. In our diabetic mice, periostin expression was significantly increased in diabetic hearts compared with nondiabetic hearts. In cultured mCFs, HG induced the protein level of periostin, which was accordance to previous studies of rat cardiac fibroblasts [20]. Interestingly, administration of resveratrol partly blunted these changes, suggesting that resveratrol may suppress interstitial fibrosis via inhibition of periostin.
CFs, the predominant cells in ventricular, mediates cardiac fibrosis via their proliferation and differentiation into myofibroblasts. Proliferation and differentiation of mCFs to myofibroblast phenotype can contribute to excessive secretion of ECM proteins and then promote cardiac fibrosis [21]. So the precise mechanisms how resveratrol suppresses the proliferation and differentiation of mCFs induced by HG were also investigated in this study.
Evidence has accumulated that ERK signaling activation was involved in fibroblast proliferation under various stimulation [22–24]. Here, we found a significantly increased proliferation and activity of ERK under high glucose condition, while U0126, an inhibitor of MEK, ameliorated mCFs proliferation induced by HG. These results suggested that HG promoted mCFs proliferation via ERK related signaling pathway, which supported previous observations that ERK was an important mediator in fibroblast proliferation induced by HG, angiotensin II (AngII), TGF-? or basic fibroblast growth factor (bFGF) [22–24]. However, the role of ERK in the amelioration of HG-induced mCFs proliferation by resveratrol is poorly understood. As mentioned above, oxidative stress plays a central role in fibrosis of DCM. Therefore, we postulated that ROS production was an important contributing factor for active ERK in DCM. In this investigation, we reported that administration of resveratrol significantly decreased ERK phosphorylation both in vitro and in vivo. Furthermore, NAC, an antioxidant, mimicked the effect of resveratrol. Collectively, these data demonstrated that resveratrol mitigated HG-induced mCFs proliferation via inhibition of ROS/ERK pathway. In favor of these results, Li et al. recently found that ?-lipoic acid (ALA), another antioxidant, favorably shifted redox homeostasis and suppressed ERK activation in diabetic hearts [8].
Differentiation of myofibroblast, as evidenced by ?-SMA and collagens expression, is largely mediated by TGF-? [21]. TGF-? has been proposed a profibrotic factor to promote the synthesis of ECM and contribute to cardiac fibrosis [21, 25, 26]. In addition, it is generally accepted that AngII induced increased expression of TGF-? in CFs [27, 28], and several studies have shed light on the effect of ERK signaling on AngII-induced TGF-? expression [28–30]. Likewise, in this study, addition of MEK inhibitor U0126 normalized the elevated TGF-? induced by HG, suggesting that HG increased expression of TGF-? via ERK signaling pathway. Furthermore, in vitro and in vivo experiments demonstrated that resveratrol treatment significant abolished the upregulation of pERK and TGF-? in diabetic heart or HG condition, which was in line with two novel studies showing that resveratrol inhibited high glucose-induced TGF-? in cardiac fibroblasts [25, 26]. These results suggested that resveratrol could ameliorate TGF-? expression via ROS/ERK pathway.
In addition to Smad2/3 activation, increasing evidence supported the involvement of periostin in TGF-? induced fibrosis [6, 28, 31–33]. Most studies agreed that periostin was a downstream signal molecule of TGF-? and participated in TGF-?-induced cardiac fibrosis [5, 34]. In this present study, anti-TGF-? antibody attenuated HG-induced periostin expression, which showed the involvement of TGF-? in upregulated periostin expression induced by HG. To our knowledge, this study is the first attempt to block the upregulated expression of periostin as well as myocardial fibrosis in vivo by daily treatment with resveratrol. Thus it provides a novel mechanism by which resveratrol inhibited diabetes-induced fibrosis in myocardium.