In our study, we observed that treatment with Sch B in mice after MI could increase survival rate, improve heart function and decrease infarct size compared to the control group. And administration of Sch B after MI could attenuate myocardial fibrosis, inflammatory and apoptosis. These effects sequentially retard the progression of myocardial remodeling after MI. Furthermore, in our in vitro study, pre-treatment with Sch B in H9c2 cells could alleviate hypoxia induced inflammation and apoptosis. The potential mechanisms might be associated with down-regulated expression of TGF-β1, TNF-α, IL-1β, ASK1, NF-κB Bax, up-regulated expression of Bcl-2 and Gata4, activation of eNOS pathway to ameliorate myocardial ischemia, and enhanced cardiac repair. These findings indicate that Sch B could be an effective, preventive and therapeutic drug against progression of heart remodeling after MI.
After myocardial ischemia induced by coronary artery ligation, global expression of inflammatory markers increased in mice. The pro-inflammatory cytokines, including TGF-β1, TNF-α, and IL-1β, play crucial roles in myocardial fibrosis and the pathological progression of LV remodeling by inducing inflammatory action via the NF-κB pathway 
. Moreover, Oxidative stress in acute MI trigger this process in chain with the pro-inflammatory cytokines. And oxidative stress stimulates expression of ASK1 and secondary activates NF-κB, leading to produce TNF-α 
. The overexpression of these inflammatory cytokines activates myocardial hypertrophic response, then myocardial remodeling and HF 
. In our study, we found that the expression of inflammatory mediators were increased in MI mice and then caused myocardial remodeling, which was in line with the previous studies. It has also been demonstrated that Sch B had anti-inflammatory and anti-fibrotic activity in several studies in vitro
. Consistent with these findings, our data showed that administration of Sch B could decrease the expression of TGF-β1, TNF-α, NF-κB and ASK1 in a concentration-dependent manner. Our results indicate that Sch B therapy may reduce cardiac remodeling via anti-inflammatory, anti-fibrotic as well as anti-oxidative stress.
The present study demonstrates that treatment with Sch B can enhance the anti-apoptotic effect 
. Apoptosis plays an important role in cardiovascular diseases. Recent studies have demonstrated that ischemic-induced apoptosis and necrosis contribute to autophagic cardiomyocyte death and cardiomyocyte loss in myocardial ischemic injury 
. In acute MI, the inflammatory cytokines in injured myocardium, e.g. TNF-α and IL-1β also stimulate apoptosis contributing to the process of myocardial remodeling 
. Consistently, we found that apoptotic cells were prominent in MI mice. And the apoptotic index in border regions of infarcted myocardium after MI correlates well with previous studies 
. Our data also indicate that Sch B treatment may have the capability of reducing apoptosis in a mice model of MI as well as a hypoxia model in H2c9 cells. The mechanism underlying this phenomenon might include up-regulated expression of Bcl-2 and suppressed expression of Bax, leading to an increased Bcl-2/Bax ratio which has been proved to play an important role in the regulation of cell apoptosis 
. Our finding correlates well with previous studies, and provides further evidence that Sch B exerts anti-apoptotic functions in infarct expansion during LV remodeling after myocardial ischemic injury.
GATA4 is the early cardiac transcription factor which is able to reprogram cardiac fibroblasts. This factor can further enhance the degree of cardiac repair and improve cardiac function after MI 
. It has been shown that up-regulating of GATA4 by reprogramming mesenchymal stem cells can induce extensive survival through attenuation of infarct size in mice model with acute MI 
. In line with these studies, our data showed that Sch B treatment stimulated the expression of GATA4 and reduced the mortality as well as infarct size after MI. Moreover, Qian et al 
demonstrated that GATA4 plays a role of cardiac repair by reprogramming resident nonmyocytes in the heart into newly born cardiomyocyte-like cells. Interestingly, our data showed the proliferation marker BrdU dyed cells appeared to be replicating at the border of the infarct area and migrating inward. Based on cardiac function improving in our MI mice, we hypothesize that these proliferating cells could regenerate muscle fibers or improve angiogenesis. Cells viability detected by MTT assay revealed that cell proliferation might be produced by the anti-apoptotic effect of Sch B. These results indicate that Sch B treatment has an ability of cardiac repair and enhancing cells proliferation after MI. Future studies are needed to identify the specific composition of these proliferated cells.
Several studies have shown that eNOS Ser1177 phosphorylation is associated with cardioprotective effects after myocardial ischemia 
. In our study, we observed that administration of Sch B stimulated eNOS phosphorylation and significantly increased the level of p-eNOS in mice after MI. It has been proved that activation of eNOS pathway can induce eNOS to be phosphorylated and then synthesizes NO 
. Both eNOS and NO can protect cardiac function via regulation of vascular remodeling and angiogenesis 
. These data indicate that the activation of eNOS pathway when treated with Sch B may contribute to the protective effects on the infarcted myocardium.
To the best of our knowledge, our study is the first to report that Sch B treatment can reduce the mortality of mice with MI. Moreover, Sch B therapy may contribute to long-term improvement of LV function after MI by inhibiting myocardial fibrosis, inflammatory, apoptosis and enhancing cardiac repair. However, our study still has several limitations. First, although treatment with Sch B has a significant improvement in LV function, only parts of the potential underlying mechanisms were examined in the present studies. The therapeutic effects of Sch B may involve multiple pathways and further studies are needed to demonstrate additional pathways. Second, whether a combination of Sch B and other medications could achieve better therapeutic effects needs to be further investigated.
In conclusion, we have shown that administration with Sch B has notable benefits on cardiac function to reduce mortality and attenuates the progression of heart remodeling after MI. Given our evolving understanding of Sch B and cardiovascular diseases, Sch B therapy could be effective in ischemic heart diseases as a window of opportunity.