[Effects of carbon monoxide release molecule-2 on sepsis-induced myocardial dysfunction in rats]

To investigate the protective effect of carbon monoxide release molecule-2 (CORM-2) on sepsis-induced myocardial dysfunction in rats.

140 healthy male Sprague-Dawley (SD) rats were divided into sham operation (Sham) group, model group, CORM-2 pretreatment group, inactivated carbon monoxide release molecule-2 (iCORM) pretreatment group, and dimethyl sulfoxide (DMSO) control group by random number table, with 28 rats in each group. The rat sepsis model was reproduced by intraperitoneal injection of 10 mg/kg lipopolysaccharide (LPS). The rats in the Sham group were injected intraperitoneally with the same dose of normal saline (NS). The rats in the CORM-2 and iCORM-2 pretreatment groups were injected intraperitoneally with 8 mg/kg CORM-2 or iCORM-2 at 1 hour before LPS injection, respectively, and those in the DMSO group were injected intraperitoneally with the same dose of DMSO, but the rats in the Sham group and the model group were not treated after injection of NS or LPS. Twenty rats were randomly selected from each group to observe 10-day survival rate. Transthoracic echocardiography was performed on the remaining 8 rats at 12 hours after modeling, and the left ventricular ejection fraction (LVEF) and left ventricular fraction shortening (LVFS) were calculated to evaluate heart function. The blood of the inferior vena cava was harvested, then serum myocardial troponin I (cTnI) and brain natriuretic peptide (BNP) levels were measured by enzyme-linked immunosorbent assay (ELISA). Then the rats were sacrificed, and the myocardial tissues were harvested, the pathological morphology and ultrastructure of myocardium were observed.

(1) Survival rates: all rats in the Sham group survived; compared with the Sham group, the survival rates of the model group, CORM-2 pretreatment group, iCORM-2 pretreatment group and DMSO control group were significantly decreased at 10 days [10% (2/20), 70% (14/20), 25% (5/20), 15% (3/20) vs. 100% (20/20), all P < 0.01]. However, the 10-day survival rate in the CORM-2 pretreatment group was significantly higher than those in the model group, iCORM-2 pretreatment group and DMSO control group (all P < 0.01). (2) Cardiac function: compared with the Sham group, LVEF and LVFS in the model group, CORM-2 pretreatment group, iCORM-2 pretreatment group and DMSO control group were significantly decreased, and left ventricular dilatation was obvious, indicating myocardial dysfunction in rats. However, LVEF and LVFS in the CORM-2 pretreatment group were significantly higher than those in the model group, iCORM-2 pretreatment group, and DMSO control group [LVEF: 0.760±0.029 vs. 0.634±0.021, 0.629±0.066, 0.673±0.023; LVFS: (39.32±2.38)% vs. (29.75±1.52)%, (29.61±4.15)%, (32.43±1.66)%, all P < 0.05], and the left ventricular dilatation in the septic rats was attenuated. (3) Myocardial injury markers: compared with the Sham group, serum cTnI and BNP levels were significantly higher in the model group, CORM-2 pretreatment group, iCORM-2 pretreatment group and DMSO control group. However, the levels of cTnI and BNP in the CORM-2 pretreatment group were significantly lower than those in the model group, iCORM-2 pretreatment group and DMSO control group [cTnI (ng/L): 3 283.54±803.50 vs. 6 449.18±1 105.10, 5 919.21±1 068.27, 6 349.80±1 153.08; BNP (ng/L): 3 456.62±905.85 vs. 6 070.18±1 287.62, 5 581.13±1 161.17, 5 974.89±988.89, all P < 0.05]. (4) Myocardial histopathological observation: optical microscope showed that the pathological changes in myocardial tissue of the model group, iCORM-2 pretreatment group and DMSO control group were severe. Transmission electron microscopy showed mitochondrial swelling, and some vacuoles changed. But the myocardial pathological morphology and mitochondrial ultrastructural integrity of the CORM-2 pretreatment group were significantly better than other groups of sepsis.

CORM-2 can attenuate myocardial dysfunction and improve survival rate of septic rats, especially to protect myocardial mitochondrial integrity in sepsis.