| Endotoxemia often causes multiple organ failure,which has a high morbidity and mortality in veterinary clinic,leading to secondary acute lung injury(ALI).Inflammation has always been a hot and difficult issue in Endotoxin-induced lung injury.Dexmedetomidine(DEX),an alpha 2 receptor agonist,has a good anti-inflammatory effect in a model of ALI caused by endotoxin,but its anti-inflammatory mechanism is still unclear.Therefore,male SD rats were used to establish ALI model induced by endotoxin by intraperitoneal injection of LPS and to explore the anti-inflammatory mechanism of DEX.Firstly,the optimal time point of inflammation injury was screened out.Then,based on this time point,we explore the regulation of DEX on GSK-3?/STAT3-NF-?B pathway,and add STAT3 inhibitor(NSC74859)and GSK-3? inhibitor(SB216763)to further verify the pharmacological mechanism of DEX.This study provides guidance for the clinical application of DEX as an anti-inflammatory drug and provides a theoretical basis for the development of new anti-inflammatory drugs.This experiment is divided into two parts.Firstly,the time point of LPS treatment was selected: 48 male healthy SD rats were randomly divided into blank control group(CON,n = 8)and LPS group(n = 40).LPS group was divided into 4,6,8,12,24 h subgroups.LPS group was intraperitoneally injected with 10 mg/kg LPS(10 mg LPS dissolved in 1 m L normal saline to prepare 10 mg/m L solution),and CON group was intraperitoneally injected with normal saline(1 m L/kg saline was given according to body weight).The levels of inflammatory factors in serum and MPO activity in lung tissue were measured.The pathological sections of lung were observed.The wet-dry weight ratio(W/D)of lung tissue and the content of inflammatory factors in lung tissue were measured.Secondly,the anti-inflammatory mechanism of DEX was studied: 56 male healthy SD rats were randomly divided into CON group,LPS group(LPS 10 mg/kg,ip),DEX + LPS group(DEX 30 ?g/kg + LPS 10 mg/kg,ip),NSC74859 group(STAT3 inhibitor,NSC74859 5 mg/kg + DEX 30 ?g/kg + LPS 10 mg/kg,ip),SB216763 group(GSK-3? inhibitor,SB216763 5 mg/kg + LPS 10 mg/kg,ip),DEX group(DEX 30 ?g/kg,ip)and DMSO(inhibitor solvent,ip)groups of 8 rats per group.DEX and SB216763 were injected intraperitoneally 30 min bef ore LPS administration,and NSC74859 was injected intraperitoneally 30 min before DEX administration.After 12 hours of LPS administration,the lungs were taken for reserve.To explore the protective effect and mechanism of DEX on acute lung injury induced by endotoxin in rats,the pathological sections and immunohistochemistry of lungs were observed,and the W/D ratio,MPO activity,related protein and m RNA content in lung tissues were measured.The results showed that lung injury occurred in LPS group,an d the pathological changes were significantly different from those in CON group(P < 0.01),and the pathological changes were most significant in LPS group at 12 h and 24 h.The ratio of W/D ratio in lung tissue of LPS group was increased compared with CON group,and LPS 12 h(P < 0.01)and 24 h(P < 0.05)were significantly different from CON group.Compared with CON group,the expression of IL-1 ? and TNF-? protein in lung tissue of LPS group increased gradually,and the expression of IL-1? and TNF-? protein was the most significant at 12 h and 24 h(P < 0.01).The myeloperoxidase(MPO)activity of the LPS group at each time point was also significantly higher than that of the CON group.At the same time,the levels of IL-1? and TNF-? in serum of LPS group were significantly higher than those of CON group(P < 0.01).The degree of lung injury and W/D ratio in the DEX + LPS group were significantly lower than those in the LPS group(P <0.01).There was no significant difference between the DEX group and the DMSO group compared to the CON group.DEX significantly inhibited the increase of MPO activity induced by LPS(P < 0.01),and significantly reduced the m RNA and protein expression of inflammatory factors in lung tissue(P < 0.01).The levels of IL-1? and TNF-? in lung tissue showed no significant difference between DEX group and DMSO group compared with CON group,while LPS group,DEX + LPS group,NSC74859 group and SB216763 group were significantly different from CON group.(P < 0.01).The phosphorylation level of nuclear transcription factor ?B(NF-?B)in lung tissue was significantly increased after LPS administration(P < 0.01).Early intervention with DEX on LPS-induced ALI significantly decreased the phosphorylation of NF-?B and increased the phosphorylation levels of STAT3 and GSK-3?(P < 0.01),while NSC74859 significantly inhibited the phosphorylation of GSK-3? and and reversed the protective effect of DEX on LPS.Meanwhile,SB216763 significantly inhibited the phosphorylation of NF-?B and produced the same lung protective effect as DEX.Combined with the above experimental results,it can be concluded that:(1)The model of ALI was successfully established by intraperitoneal injection of 10 mg/kg LPS,and the duration of lung injury was 4 h to 24 h and the most serious time point was 12 h.(2)DEX can protect lung by inhibiting inflammatory response.(3)The protective effect of DEX on LPS-induced ALI is through the GSK-3?/STAT3-NF-?B pathway. |
PDF Full Text Request