cFLIP Alleviates Myocardial Ischemia-Reperfusion Injury by Inhibiting Endoplasmic Reticulum Stress.

Purpose: Endoplasmic reticulum stress (ERS) plays a crucial role in myocardial ischemia-reperfusion injury (MIRI). Cellular FLICE-inhibitory protein (cFLIP) is an essential regulator of apoptosis and plays a major role in regulating ERS. The present study aimed to investigate the effects of long isoform cFLIP (cFLIP) on endogenous apoptosis and the mechanism of ERS in MIRI.

Methods: The cFLIP recombinant adenovirus vector was used to infect H9c2 cells and Sprague-Dawley (SD) rats. After infection for 72 h, ischemia was induced for 30 min, and reperfusion was then performed for 2 h to establish the MIRI model in SD rats. H9c2 cells were hypoxic for 4 h and then reoxygenated for 12 h to simulate ischemia/reperfusion (I/R) injury. Model parameters were evaluated by assessing cardiomyocyte viability, cell death (apoptosis), and ERS-related protein expression. In addition, tunicamycin (TM), an ERS agonist, was also added to the medium for pretreatment. Coimmunoprecipitation (Co-IP) of cFLIP and p38 MAPK protein was performed.

Results: cFLIP expression was decreased in I/R injury and hypoxia/reoxygenation (H/R) injury, and cFLIP overexpression reduced myocardial infarction in vivo and increased the viability of H9c2 cells in vitro. I/R and H/R upregulated the protein expression of GRP78, IRE-1, and PERK to induce ERS and apoptosis. Interestingly, overexpression of cFLIP significantly inhibited ERS and subsequent apoptosis, which was reversed by an agonist of ERS. Moreover, Co-IP showed that cFLIP attenuated ERS and was associated with inhibiting the activation of p38 protein.

Conclusion: The expression of cFLIP is significantly downregulated in MIRI, and it is accompanied by excessive ERS and apoptosis. Upregulated cFLIP suppresses ERS to reduce myocardial apoptosis, which is associated with inhibiting the activity of p38 MAPK. Therefore, cFLIP may be a potential intervention target for MIRI.