Knockout of the tumor necrosis factor α receptor 1 gene can up-regulate erythropoietin receptor during myocardial ischemia-reperfusion injury in mice

Background Tumor necrosis factor a receptor 1 （TNFaR1） plays an important role in the signal pathway of apoptosis. The objective of this study was to investigate the effects of TNFaR1 knockout on the up-regulation of erythropoietin receptor （Epo-R） and the coordinated anti-apoptosis functions during myocardial ischemia-reperfusion injury in mice. Methods The ischemia-reperfusion injury model for cardiomyocytes was performed by ligating the left circumflex branch artery of TNFaR1 knockout （P55/） C17 B6 mice, as well as wild-type （P55^＋/^＋） C17 B6 mice. Triphenyltetrazolium chloride （TTC） staining was performed to observe the damaged area of the heart. TUNEL staining and DNA fragmentation were used to identify apoptosis. Mitochondrial Bcl-2 and Bax as well as expression of Epo-R and its downstream genes （Jak-2, stat-5, Akt, lkB-a, HIF-1a） were measured by Western blotting. The gene knockout mice were assigned into those undergoing the apoptosis surgical model group （KO group）, and those subjected to sham operation （KOs group）. Similarly, wild-type mice were either exposed to the surgical model （WT group） or subject to a sham operation （WTs group）. Results The myocardial damage ratio of the wild-type group after the operation was significantly higher than that of the knockout group, （50.5±6.4）% vs （36.9±6.9）%, P 〈0.01. Similarly, TUNEL positive ratio of the wild-type group was significantly higher than that of the knockout group, （63.1±5.6）% vs （42.1±4.7）%, P〈0.01. The gray value ratios of Epo-R, Jak-2, stat-5, Akt, IkB-a, HIF-1 and mitochondrial Bcl-2 in the KO group were significantly higher than those of the WT group, P 〈0.05; however, mitochondrial Bax was significantly lower than that of the WT group significantly （P 〈0.05）. Conclusions Using the ischemia-reperfusion injury model in mice, cardiomyocytes of TNFaR1 knockouts exhibited anti-apoptotic characteristics. This information could be used to coordinate the prevention of myocardial apoptosis by up-regulating and activating the Epo-R pathway.