FABP4 inhibitor BMS309403 protects against hypoxia‐induced H9c2 cardiomyocyte apoptosis through attenuating endoplasmic reticulum stress

Acute myocardial infarction is characterized by ischaemia‐induced cardiomyocyte apoptosis, in which the endoplasmic reticulum (ER) stress plays an important role. The fatty acid‐binding protein‐4 (FABP4) has been implicated in regulating ER stress and apoptosis. Yet, whether FABP4 is involved in modulating cardiomyocyte apoptosis remains unclarified. By applying an in vitro model of hypoxia‐induced apoptosis of H9c2 cardiomyocytes, we found that FABP4 expression was elevated upon hypoxia stimulation, which was further demonstrated to be transcriptionally activated by the hypoxia‐inducible factor 1a (HIF‐1α). In addition, the pharmacological inhibition of FABP4 with BMS309403 protected against hypoxia‐induced apoptosis in cardiomyocytes, indicating that FABP4 induction is detrimental for cardiomyocyte survival under hypoxic condition. Moreover, BMS309403 attenuated ER stress in cardiomyocytes exposed to hypoxia, which, however, was reversed by tunicamycin, an ER stress activator. More importantly, the protective effect of BMS309403 on cardiomyocytes vanished in the presence of tunicamycin. Thus, these observations establish that FABP4 inhibitor BMS309403 reduces hypoxia‐induced cardiomyocyte apoptosis through attenuating excessive ER stress, implying that FABP4 inhibition may be of clinical benefit for MI treatment.