Erythropoietin pretreatment suppresses inflammation by activating the PI3K/Akt signaling pathway in myocardial ischemia-reperfusion injury

Erythropoietin (EPO), a glycoprotein originally known for its important role in the stimulation of erythropoiesis, has recently been shown to have significant protective effects in animal models of kidney and intestinal ischemia-reperfusion injury (IRI). However, the mechanism underlying these protective effects remains unclear. The aim of the current study was to evaluate the effects of EPO on myocardial IRI and to investigate the mechanism underlying these effects. A total of 18 male Sprague Dawley rats were randomly divided into three groups, namely the sham, IRI-saline and IRI-EPO groups. Rats in the IRI-EPO group were administered 5,000 U/kg EPO intraperitoneally 24 h prior to the induction of IRI. IRI was induced by ligating the left descending coronary artery for 30 min, followed by reperfusion for 3 h. Pathological changes in the myocardial tissue were observed and scored. The levels of the proinflammatory cytokines, interleukin (IL) -6, IL-1 beta and tumor necrosis factor (TNF)-alpha, were evaluated in the serum and myocardial tissue. Furthermore, the effects of EPO on phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling and EPO receptor (EPOR) phosphorylation were measured. Pathological changes in the myocardial tissue, increased expression levels of TNF-alpha, IL-6 and IL-1 beta in the myocardium, and increased serum levels of these mediators, as a result of IRI, were significantly decreased by EPO pretreatment. The effects of EPO were found to be associated with the activation of PI3K/Akt signaling, which suppressed the inflammatory responses, following the initiation of EPOR activation by EPO. Therefore, EPO pretreatment was demonstrated to decrease myocardial IRI, which was associated with activation of EPOR, subsequently increasing PI3K/Akt signaling to inhibit the production and release of inflammatory mediators. Thus, the results of the present study indicated that EPO may be useful for preventing myocardial IRI.