[Effects of HMGB1 inhibition on endoplasmic reticulum stress after myocardial ischemia/reperfusion injury in rats].

OBJECTIVE: To investigate the effect of high mobility group protein B1 (HMGB1) inhibition on endoplasmic reticulum stress (ERS) after myocardial ischemia/reperfusion (I/R) in rats. METHODS: Forty male Sprague-Dawley (SD) rats were randomly divided into four groups (n = 10): sham operation group, I/R model group, Gene silencing (HMGB1-siRNA) group, and empty vector (Scrambled-siRNA) group. Coronary blood flow of the rats were ligated for 30 minutes, relaxed the ligament line for 2 hours, to establish I/R injury model; not ligation with the sham operation group. Each group was injected 1 mL phosphate buffer (PBS), HMGB1-siRNA mixture or Scrambled-siRNA mixture preoperative by tail vein 0 hour, 12 hours, and 24 hours before surgery. After 2 hours reperfusion, the levels of tumor necrosis factor-α (TNF-α), interleukins (IL-6, IL-8) in the serum were detected by enzyme linked immunosorbent assay (ELISA); the expression of HMGB1 protein in myocardium was detected by immunohistochemistry; the protein and mRNA expressions of HMGB1, GRP78, CHOP and caspase-12 in myocardium were detected by Western Blot and real-time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Compared with sham operation group, the levels of serum inflammatory factor, HMGB1 positive cells, and the protein and mRNA expressions of GRP78, CHOP, caspase-12 were significantly increased in I/R model group. The levels of serum inflammatory factor in HMGB1-siRNA group were significantly lower than those in the I/R model group [TNF-α (ng/L): 783.4±203.4 vs. 963.9±214.1, IL-6 (ng/L): 358.8±94.8 vs. 452.3±103.7, IL-8 (ng/L): 180.5±73.6 vs. 347.3±90.3, all P < 0.05], HMGB1 positive cells, and the protein and mRNA expressions of GRP78, CHOP, caspase-12 in HMGB1-siRNA group were significantly lower than I/R model group (HMGB1 protein: 1.59±0.26 vs. 3.21±0.40, GRP78 protein: 2.59±0.28 vs. 4.21±0.42, CHOP protein: 2.01±0.23 vs. 3.21±0.43, caspase-12 protein: 1.48±0.22 vs. 3.01±0.48; HMGB1 mRNA: 2.35±0.26 vs. 4.67±0.45, GRP78 mRNA: 6.59±0.26 vs. 11.21±0.40, CHOP mRNA: 2.01±0.43 vs. 5.21±0.63, caspase-12 mRNA: 4.48±0.32 vs. 8.41±0.52, all P < 0.05). There was no significant difference between the Scrambled-siRNA group and the I/R model group. CONCLUSIONS: HMGB1 may be involved in the activation of ERS in myocardial I/R injury and increase the damage of myocardial cells.