A nonerythropoietic derivative of erythropoietin protects the myocardium from ischemia–reperfusion injury

Abstract

The cytokine erythropoietin (EPO) protects the heart from ischemic injury, in part by preventing apoptosis. However, EPO administration can also raise the hemoglobin concentration, which, by increasing oxygen delivery, confounds assignment of cause and effect. The availability of EPO analogs that do not bind to the dimeric EPO receptor and lack erythropoietic activity, e.g., carbamylated EPO (CEPO), provides an opportunity to determine whether EPO possesses direct cardioprotective activity. In vivo, cardiomyocyte loss after experimental myocardial infarction (MI) of rats (40 min of occlusion with reperfusion) was reduced from Ϸ57% in MI-control to Ϸ45% in animals that were administered CEPO daily for 1 week (50 g͞kg of body weight s.c.) with the first dose administered intravenously 5 min before reperfusion. CEPO did not increase the hematocrit, yet it prevented increases in left ventricular (LV) end-diastolic pressure, reduced LV wall stress in systole and diastole, and improved LV response to dobutamine infusion compared with vehicle-treated animals. In agreement with the cardioprotective effect observed in vivo, staurosporineinduced apoptosis of adult rat or mouse cardiomyocytes in vitro was also significantly attenuated (Ϸ35%) by CEPO, which is comparable with the effect of EPO. These data indicate that prevention of cardiomyocyte apoptosis, in the absence of an increase in hemoglobin concentration, explains EPO's cardioprotection. Nonerythropoietic derivatives such as CEPO, devoid of the undesirable effects of EPO, e.g., thrombogenesis, could represent safer and more effective alternatives for treatment of cardiovascular diseases, such as MI and heart failure. Furthermore, these findings expand the activity spectrum of CEPO to tissues outside the nervous system. apoptosis ͉ cardioprotection ͉ cytokine ͉ tissue injury E rythropoietin (EPO) protects the brain and the spinal cord from ischemic and traumatic injury (1, 2), the peripheral nerve from diabetic damage (3), the kidney from ischemic (4, 5) or toxic insults (6), and the heart from acute ischemia, either permanent (7-9) or with reperfusion (10). Current data suggest that the observed protective effects of EPO depend on an antiapoptotic effect of this cytokine (7, 10). In the brain, EPO also greatly reduces the inflammatory response after ischemiareperfusion (11). It is notable that in several acute models, e.g., brain ischemia, a single dose of EPO that does not increase the Hb concentration nevertheless confers neuroprotection. However, in other in vivo injury models, including cardiac ischemia with reperfusion and diabetic neuropathy, injury develops gradually, and multiple doses of EPO appear superior but also increase the Hb concentration. The possibility that part of the benefit obtained with EPO in these models may depend on the increased oxygen-carrying capacity of the blood cannot be excluded. However, cardiac protection has clearly been demonstrated after only a single dose (8, 10) when evaluated 1-3 days after infarction before any increase i...

Carbamylated Erythropoietin and Its Role of Tissue Protection

“…The finding was further confirmed since the discovery of EPO receptors expressed in cardiomyocytes of adult rat (31). Similar to those observed for EPO, CEPO could attenuate staurosporine-induced apoptosis of adult rat or mouse cardiomyocytes in vitro and reduce cardiomyocyte loss after myocardial infarction (MI) of rats in vivo (32). In another similar experiment of a rat model of permanent coronary artery ligation, even a single bolus injection of CEPO could reduce the apoptosis in the myocardial area at risk (33).…”

Systems approaches to preventing transplanted cell death in cardiac repair

“…We pretreated cells 30 minutes before preparation for injection and injected them anywhere from 1 hour later to 6 hours later into a mouse pre-dosed with CEPO. In our system, Akt phosphorylation occurs even before the cells are removed from the plate, initiating the pro-survival pathway, presumably through Bcl-XL upregulation [89,108]. Failure to give the transplanted cells a head start in survival signaling could be responsible for that study's negative finding.…”

“…Akt phosphorylation was assessed in response to treatments of CEPO, EPO and heat shock, alone and in combination, as detailed in supplemental information. CEPO and EPO treatment include a 30-minute incubation at 100 ng/ml of cells in culture [89] before preparation for injection followed by each recipient animal receiving doses of 10 ng of drug per gram of animal weight at days 0 and 1.…”

“…The effect measured from heat shock could be compared to previously established effects seen in other cardiac cell transplantation studies. Erythropoietin (EPO) and its chemically modified derivative, carbamylated erythropoietin (CEPO) [89], were evaluated as a wholly new cell survival intervention. Heat shock, EPO and CEPO were used independently and in combination in comparison to untreated control injections.…”

Low‐dose erythropoietin improves cardiac function in experimental heart failure without increasing haematocrit

“…The possibility of separating the erythropoietic and tissue protective effects of EPO could be explained through interaction with different receptors in the bone marrow and in "peripheral" tissues. Two independent studies have demonstrated that these non-erythropoietic EPO's retain their acute cardioprotective potential [31,32]. It is however uncertain whether these new EPO's will also improve cardiac function in CHF.…”