Role of mitochondrial permeability transition pore in lipid emulsion-induced inversion of bupivacaine myocardiotoxicity in rats

Objective To evaluate the effect of mitochondrial permeability transition pore(mPTP)in lipid emulsion-induced inversion of bupivacaine myocardiotoxicity in rats. Methods H9c2 cells were inoculated in 6-well plates at a density of 105 cells/ml, and were randomly divided into 4 groups(6 wells in each group, 2 ml/well)using a random number table: control group(group C), bupivacaine group(group B), lipid emusion+ bupivacaine group(group LB), and lipid emusion+ bupivacaine+ atractyloside group(group LBA). Phosphate buffer solution 100 μl was added to the culture medium in group C. In group B, bupivacaine was added to the culture medium with the final concentration of 1 mmol/L.In group LB, lipid emusion and bupivacaine were added to the culture medium with the final concentrations of 1% and 1 mmol/L, respectively.In group LBA, lipid emusion, bupivacaine and atractyloside(an mPTP opener)were added to the culture medium with the final concentrations of 1%, 1 mmol/L and 30 μmol/L, respectively.All the cells were incubated for 24 h. After the end of incubation, the expression of Bcl-2, Bax, phosphorylated Bad(p-Bad), caspase-3, activated caspase-3, caspase-9, activated caspase-9 and cytochrome c(Cyt c)was detected using Western blot.The expression of Bcl-2 mRNA, Bax mRNA, Bad mRNA, caspase-9 mRNA and Cyt c mRNA was detected using real-time reverse transcriptase polymerase chain reaction.The ratios of Bax/Bcl-2, activated caspase-3/caspase-3, activated caspase-9/caspase-9, and Bax mRNA/Bcl-2 mRNA were calculated. Results Compared with group C, the ratios of Bax/Bcl-2, activated caspase-3/caspase-3, activated caspase-9/caspase-9, and Bax mRNA/Bcl-2 mRNA were significantly increased, the expression of p-Bad was down-regulated, and the expression of Cyt c, Bad mRNA, caspase-9 mRNA and Cyt c mRNA was up-regulated in group B(P 0.05). Compared with group B, the ratios of Bax/Bcl-2, activated caspase-3/caspase-3, activated caspase-9/caspase-9, and Bax mRNA/Bcl-2 mRNA were significantly decreased, the expression of p-Bad was up-regulated, and the expression of Cyt c, Bad mRNA, caspase-9 mRNA and Cyt c mRNA was down-regulated in LB and LBA groups(P<0.05). Compared with group LB, the ratios of Bax/Bcl-2, activated caspase-3/caspase-3, activated caspase-9/caspase-9, and Bax mRNA/Bcl-2 mRNA were significantly increased, the expression of p-Bad was down-regulated, and the expression of Cyt c, Bad mRNA, caspase-9 mRNA and Cyt c mRNA was up-regulated in group LBA(P<0.05). Conclusion The mechanism underlying lipid emulsion-induced inversion of bupivacaine myocardiotoxicity is related to inhibited mPTP opening in rats. Key words: Mitochondrial membrane transport proteins; Fat emulsions, intravenous; Bupivacaine; Drug toxicity; Myocardium