The role of high-mobility group box protein 1 in the signaling pathways of myocardial ischemia-reperfusion injury in rats

Objective To investigate the role of high-mobility group box protein 1 (HMGB1) in the signaling pathways of myocardial ischemia-reperfusion injury (MIRI) in rats. Methods Forty male Sprague-Dawley rats, weighing 200-250 g, were randomly divided into 4 groups (n=10) using a random number table: sham operation group (group sham), MIRI group (group IR-C), anti-HMGB1 antibody group (group IR-H-Ig), contrast antibody control group (group IR-Ig). The rat model of MIRI was established by 30 min occlusion of left anterior descending branch (LAD) of coronary artery followed by 180 min reperfusion. In sham group, no blocking of LAD was adopted after thoracotomy. Anti-HMGB1 antibody and contrast antibody immunoglobulin G (IgG) (2 mg/kg) were injected respectively at 30 min of reperfusion in IR-H-Ig and IR-Ig groups. Blood samples were collected from the femoral vein for determination of interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), HMGB1, creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) concentrations at 180 min of reperfusion. The rats were then sacrificed after blood samples were taken and the pathological changes of myocardial tissue were observed. The mRNA and protein expressions of HMGB1, toll-like receptor 4(TLR4) and nuclear factor (NF)-κB in myocardial tissues were detected by Western blot and real-time quantitative PCR respectively. Results Compared with the Sham group, the plasma level of IL-6, TNF-α, HMGB1 increased significantly and HMGB1, TLR4 and NF-κB mRNA and protein levels of myocardial tissues up-regulated in IR-C and IR-Ig groups (all P<0.05). The plasma level of CK-MB and cTnI increased significantly in IR-C, IR-H-Ig, IR-Ig group (all P<0.05). Compared with the IR-C group, the levels of the plasma HMGB1, the cytokines mentioned above, CK-MB and cTnI were significantly decreased, and mRNA and protein expressions of HMGB1, TLR4 and NF-κB of myocardial tissues down-regulated in IR-H-Ig group (all P<0.05). Inflammatory cell infiltration in MIRI groups increased significantly, while it was significantly reduced in IR-H-Ig group. Conclusion Blocking the combination of HMGB1 and TLR4 can effectively alleviate the tissue damage caused by myocardial ischemia-reperfusion in rats. Key words: High mobility group proteins; Myocardial reperfusion injury; Inflammation; Rats