Bicyclol protects cardiomyocytes from apoptosis in ischemia/reperfusion injury via inhibition of TLR4/NF-κB pathway

Toll-like receptor 4 (TLR4)-mediated apoptosis plays a critical role in the etiology and pathogenesis of myocardial ischemia/reperfusion (I/R) injury (MIRI). Bicyclol has been shown to possess a variety of pharmacological effects, but its anti-apoptotic property has garnered particular interest. The aim of this study is to elucidate the cardioprotective effect of bicyclol in I/R injury, and to explore the potential mechanisms involving in TLR4-medaited apoptotic cascade. Bicyclol was intragastrically administered in rats for three days before myocardial ischemia was induced at three different dosages: 25 mg/kg, 50 mg/kg and 100 mg/kg. The rat MIRI model was established by 30 min of left anterior descending (LAD) artery occlusion and 4 h of reperfusion. We then evaluated cardiac function using a biotic signal collection and processing system. H&E and Evans blue plus TTC staining were used to observe morphological changes and the infarct size of myocardium, respectively. TUNEL-positive cells were calculated to assess myocardial apoptosis. Quantitative RT-PCR was used to detect TLR4, NF-κB and TNF-α mRNA expression. Western blotting was performed to measure TLR4, nuclear NF-κB/p65, TNF-α, Bax, Bcl-2 and caspase-3 proteins levels. We determined that pretreatment with bicyclol improved cardiac function, reduced myocardial infarct size and ameliorated morphological lesions of the myocardium in a dose-dependent manner. In addition, the expression levels of TLR4, NF-κB and TNF-α were significantly down-regulated following bicyclol pretreatment. This was concomitant with inhibition of cardiomyocyte apoptosis, as evidenced by a decrease in TUNEL-positive cells and the deactivation of the Bax/Bcl-2 dependent apoptotic cascade. Taken together, our findings demonstrate that administration of bicyclol has a cardioprotective effect against I/R injury, possibly through down-regulation of myocardial apoptosis mediated by the TLR4/NF-κB signaling pathway.