THE EFFECT OF DEXMEDETOMIDINE ON THE H/R INJURY OF RAT CARDIOMYOCYTES AND ITS MECHANISM

Jia Chen^1#, Lifeng Meng^2#*

¹Department of Anesthesiolog,Traditional Chinese Medical Hospital of Zhuji, Zhuji 311800, PR China - ²Department of Anesthesiolog, Zhuji People’s Hospital of Zhejiang Province, Zhuji 311800, PR China

Objective: To analyse the effect and mechanism of dexmedetomidine (Dex) on hypoxia/reoxygenation (H/R) injury of rat cardiomyocytes. 

Methods: Rat cardiomyocytes (H9C2 rat cardiomyocytes and primary neonatal rat cardiomyocytes) were cultured in vitro. The cells were randomly divided into four groups: control, H / R, dexmedetomidine (DEX) and toll-like receptor 4 (TLR4), in which the normal cells were normal cells. The cells in the H / R group were treated with sodium bisulfite for 1 hour and the normal medium for 12 hours. The cells in the DEX pre-treatment group were treated with DEX of different concentrations (0.1 μ m, 1 μ m, 10 μ m) for 1 hour before hypoxia and the rest were treated with the same method as those in the H / R group. The cells in the TLR4 group were transfected with liposomes for 24 hours before hypoxia DNA was transferred into the cells; the rest of the treatment was the same as that for the DEX group. The MTT method was used to detect the survival rate of cardiomyocytes, 2,4-dinitrophenylhydrazine was used to detect the activity of lactate dehydrogenase (LDH) in the supernatant of culture medium, the qRT-PCR method was used to detect the expression levels of tumour necrosis factor-α (TNF-α), interleukin-1 β (IL-1 β) and interleukin-6 (IL-6) mRNA in cells, and the Western method was used. The expression levels of TLR4 and NF-κB in the nucleus were detected through blotting and the effects and mechanisms of DEX on H / R injury in the myocardium of rats were analysed. 

Results: The survival rate of cardiomyocytes in the H / R group was significantly lower than that in the control group, that in the DEX group was significantly higher than that in the H / R group and that in the TLR4 group was significantly lower than that in the DEX group (p<0.05). LDH activity in the H/R group was significantly higher than that in the control group and LDH activity in the DEX group was significantly lower than that in the H / R group. LDH activity in the TLR4 group was significantly higher than that in the DEX group (p<0.05). The expression levels of TNF-α, IL-6, IL-1 β mRNA in the H/R group were significantly higher than those in the control group. The expression levels of TNF-α, IL-6, IL-1 β mRNA in the DEX group were significantly lower than those in the H/R group. The expression levels of TNF-α, IL-6, IL-1 β mRNA in the TLR4 group were significantly higher than those in the DEX group (p<0.05). The expression levels of TLR4 and NF-κB in the H/R group were significantly higher than those in the control group, those in the DEX group were significantly lower than those in the H/R group and those in the TLR4 group were significantly higher than those in the DEX group (p<0.05). 

Conclusion: DEX pre-treatment can reduce the release of TNF-α, IL-6, IL-1 β and other inflammatory mediators in mouse cardiomyocytes, thus reducing the H/R injury of rat cardiomyocytes. The mechanism may be related to the down-regulation of the TLR4 / NF-кB inflammatory pathway by DEX.