The Effect Of Dexmedetomidine On Lipopolysaccharide-Induced Macrophage Inflammation And Intracellular Lactate Level

Objective: To investigate the effect of dexmedetomidine on macrophage inflammation and lactate level under lipopolysaccharide(LPS)stimulation,further to find its underlying mechanism.Methods: Part 1: We performed three groups as follows:Control group: neither LPS nor dexmedetomidine(DEX)administrated;LPS+DEX group: DEX10μmmol/L,30 min before LPS,500ng/m L administrated;LPS group: LPS,500ng/m L.After 0.5h,1h,1.5h,2h,3h,6h,12 h respectively,RT-PCR and Western Blot were used to determine the levels of Nur77 m RNA and protein.Moreover,the concentrations of interleukin-1β(IL-1β)and interleukin-10(IL-10)were detected by enzyme linked immunosorbent assay(ELISA)kits;Meanwhile,the lactic acid concentration was detected by lactate assay kit.Part 2: We set seven groups as follows: Control group: neither LPS nor DEX administrated;LPS group: 500ng/m L LPS;LPS+si NC:after transfected si NC for 72 h,500ng/m L LPS;LPS+si Nur77: after transfected si Nur77 for 72 h,500ng/m L LPS;LPS+DEX: DEX 10μmmol/L,30 min before LPS administrated;LPS+DEX+si NC group:aftertransfected si NC for 72 h,DEX 10μmmol/L,30 min before LPS administrated;LPS+DEX+si Nur77group: after transfected si Nur77 for 72 h,DEX 10μmmol/L,30 min before LPS administrated.At 3h,the expression of Nur77 protein in above groups was detected and the concentration levels of IL-1β and IL-10 in culture supernate were determined by the ELISA kits.Results:Part 1: Under LPS stimulation,the relative expression level of Nur77 m RNA and protein from macrophage increased from 0.5h and reached a peak at 1 h.With DEX pretreatment,Nur77 relative expression level increased over time points.Furthermore,at 2h,the relative level of Nur77 m RNA and protein were significantly higher than those induced by simple LPS stimulation(P<0.05),which was a peak in the group of LPS+DEX;however,when observation time point was more than 2h,DEX decreased LPS-induced Nur77 m RNA and protein;but at 12 h,DEX up-regulated the level of Nur77 protein.Moreover,DEX significantly decreased LPS-induced IL-1βexpression level before 3 h(P<0.05)and significantly increased IL-10 level;but whenindicated time points was more than 3h,DEX represented opposite results.What’s more,DEX obviously decreased LPS-induced intracellular lactate concentration before 2 h,but dexmedetomidine significantly increased lactate level at 3h and 6h(P<0.05);however,at12 h,lactate level was lower in LPS+DEX group than that in LPS group(P<0.05).Part 2:The level of Nur77 protein in si Nur77 transfected groups was lower than that of the pre-transfection cells in corresponding groups.Meanwhile,we found IL-10 concentration in the LPS +DEX+si Nur77 group’s culture supernate was significantly lower than that in LPS+DEX group(347.91±5.46 vs.394.55±3.23 pg/m L,P<0.05),but the IL-1β concentration was significantly higher(100.15±2.29 vs.81.04±1.22 pg/m L,P<0.05).Conclusion: The mechanism of DEX on LPS-induced inflammation at the early time points(less than or equal to 3h)was through up-regulating the level of Nur77.DEX decreased the intracellular lactate level induced by LPS in the early observation time points(less than or equal to 2h),but showed the opposite results during the longer time points of co-action.This mechanism needs to be further explored.