[Protective effect of carbon monoxide releasing molecules 2 on post-resuscitation myocardial dysfunction in rats]

Objective: To investigate the protective effect of carbon monoxide releasing molecule 2 (CORM-2) on post-resuscitation myocardial dysfunction in rats. Methods: Forty male SD rats which were healthy were randomly divided into 5 groups: sham operated group(sham group), cardiopulmonary resuscitation(PCR) group, DMSO group, inactivated CORM-2(iCORM-2) group and CORM-2 group (n=8 each). Established the model of post-cardiac arrest myocardial dysfunction by intravenous potassium chloride (4 ℃) injection combined with asphyxiation for 4 minutes and then followed by artificial chest compression for 3 minutes. Sham group: rats were instrumented with catheter without inducing cardiac arrest and resuscitation, and intraperitoneal injection of 0.9% normal saline (4 ml/kg) was performed 12 hours before catheterization. CPR group: rats were instrumented with catheters and underwent CPR, and intraperitoneal injection of 0.9% normal saline (4 ml/kg) was performed 12 hours before surgery.CORM-2 group: rats were instrumented with catheters and underwent CPR, intraperitoneally injected the prepared CORM-2 solution (4 mg/kg) at 12 hours before surgery. DMSO group: rats were instrumented with catheters and underwent CPR, intraperitoneally injected the prepared DMSO solution (4 ml/kg) at 12 hours before surgery. iCORM-2 group: rats were instrumented with catheters and underwent CPR, iCORM-2 solution (4 mg/kg) was intraperitoneally injected at 12 hours before surgery. Hemodynamic data (MAP, +dp/dtmax, -dp/dt) were continuously monitored and recorded for 4 hours after resuscitation (or catheterization) in each group. Myocardial tissue specimen and blood samples were taken after resuscitation (or catheterization). The myocardial ultrastructure was observed by transmission electron microscope. Lactate dehydrogenase (LDH) activity was measured by lactate-pyruvate method. Serum creatine kinase isoenzyme (CK-MB) concentration was measured by ELISA. Western blot was used to detect the levels of Caspase-3, Caspase-9 and Cyt-C protein in myocardial tissue. Results: MAP, +dp/dtmax and -dp/dt at 0.5, 1, 2, 3 and 4 hours post resuscitation were significantly lower than those immediately after catheterization in CRP, DMSO, iCORM-2 groups (all P<0.05). MAP at 0.5, 1, 2, 3, and 4 hours post resuscitation were significantly lower in CRP, DMSO and iCORM-2 groups than those at respective time points in sham group (all P<0.05), while MAP was similar between CORM-2 group and Sham group at these time points (all P>0.05). +dp/dtmax and -dp/dt values at 0.5, 1, 2, 3, and 4 hours post resuscitation were lower than those at respective time points in sham group and significance was found at 0.5, 1 and 2 hours post resuscitation (both P<0.05), while +dp/dtmax and -dp/dt values were similar between CORM-2 group and sham group at various time points (all P>0.05). Myocardial ultrastructure, especially mitochondrial structural integrity was better preserved in the CORM-2 group than those in the other resuscitation groups at 4 hours after resuscitation. Serum LDH activity and CK-MB concentration were significantly elevated at 4 hours after resuscitation in the CPR group, DMSO group and iCORM-2 group than those in sham group (all P<0.01); CK-MB concentration was also higher in CORM-2 group than that in sham group,and LDH level was similar between CORM-2 group and sham group (P>0.05). Serum LDH activity and CK-MB concentrations were significantly lower in the CORM-2 group than those in the other resuscitation groups (all P<0.01). The myocardial expressions of Caspase-3, Caspase-9 and Cyt-C at 4 hours after resuscitation were significantly higher in the CPR group, DMSO group and iCORM-2 group than those in sham group; the myocardial expressions of Caspase-3 and Caspase-9 were significantly higher in CORM-2 group than those in sham group (both P<0.05), while Cyt-C expression was similar between CORM-2 group and sham group. The expressions of the above 3 proteins were significantly lower in the CORM-2 group than those in the other resuscitation groups (all P<0.05). Conclusions: CORM-2 can effectively alleviate post-resuscitation myocardial injury in rats with cardiopulmonary resuscitation and improve cardiac function. Protecting myocardial mitochondria and inhibiting mitochondrial apoptosis pathway may serve as the protective mechanisms in this model.