| Hemoglobin-based oxygen carriers (HBOCs) as blood substitute, is prepared by modification, intermolecular or intramolecular crosslinking of hemoglobin to form high molecular weight polymers. HBOCs have several advantages, including oxygen carrying ability, rapid expansion of the blood volume after hemorrhage, no need to type and cross-match,, lack of infectious risk and have long-term storage. HBOCs as a promising blood substitute can replace part of the kinetic energy of blood or red blood cells. pPolyHb with glutaraldehyde as crosslinking agent and porcine hemoglobin as source to synthesize the polymerization of hemoglobin, belongs to the family of HBOCs.Organs will be severely damaged after ischemia. The main treatment is to restore blood supply. However, restoration of blood supply would lead to ischemia/reperfusion injury. This is not because of ischemia itself, but due to excess free radicals attacks inducing by blood supply, so-called ischemia-reperfusion injury(I/RI). I/RI is a complex process, in which several signaling pathways and a variety of cytokines participate. The study found that SIRT1 in cardiovascular disease has played an important role in regulating. FOXO1 is an important SIRT1 substrate. SIRT1 can adjust the acetylation level of FOXO1 to induce myocardial apoptosis.The object of current study is to investigate the effect of pPolyHb on myocardial I/RI.In vitro study,H9C2 cells were cultivated. Two groups of pPolyHb (10μM and 20μM) were chosen according to their MTT assay. After pretreatment with different agents, I/R model was established.LDH and CK activity in supernatant fluid were detected. Cell apoptosis rate after ischemia reperfusion was determined by TUNEL method. Western Blot was used to detect the expression of related proteins. The results indicated that LDH and CK activities as well as cell apoptosis dropped significantly in HES and pPolyHb groups comparing to I/R group. Western bolt results showed pPolyHb could up regulate the expression of Bcl2 and down regulate the expression of Caspase3 and Bax, which suggested that pPolyHb may exert protective effect upon myocardial I/R injury via reducing cell apoptosis.In vivo, Rats were divided into four groups, Sham, I/R, I/R+HES, I/R+pPolyHb. Cardiac function of rats were recorded via a small animal ultrasonic equipment. LDH and CK activity in serum was analyzed after myocardial I/R. Evans blue and TTC double staining were performed to detect myocardial infarction area in rats. Myocardial cell apoptosis rate was measured via TUNEL detection. Meanwhile, Western Blot was used to analyze the expression of related proteins. The results demonstrated that LDH and CK activities in I/R+HES and I/R+pPolyHb groups decreased significantly comparing to I/R group, so as to the infarct size and cell apoptosis rate. Western blot results verified that pretreatment with pPolyHb could up regulate the expression of Bcl2 and down regulate the expression of Caspase3 and Bax. Moreover, the expression of SIRT1 and Ac-Foxol in SIRT1 signal pathway was detected. The results showed pretreatment with pPolyHb lowered Ac-Foxol expression, meanwhile, increased the expression of SIRT1, which suggested pPolyHb protect myocardial against I/R injury via activating SIRTlpathway.
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