Role and mechanism of extracellular signal-regulated kinase signaling pathway in chemokine secre-tion and neutrophil recruitment in hemorrhagic shock-induced lung injury
Objective To investigate the change of extracellular signal-regulated kinase(ERK)pathway and the protective effect of hemorrhagic shock(HS)inhibitors in acute lung injury(ALI).Methods SD rats were divided into the Sham group,HS 4 h group,HS 8 h group,intervention group,and solvent control group with 6 rats in each group.The HS group and the intervention group were set up with quantita-tive blood loss by femoral vein intubation,while the Sham group was only operated.The intervention group and solvent control group were intraperitoneally injected with ERK protein phosphorylation inhibitor Selu-metinib or equal-volume solvent 20 min after blood loss.Cell experiments were divided into normal culture group,oxygen-glucose deprivation(OGD)group,Selumetinib intervention group,and solvent control group.Lung tissue injury was evaluated by hematoxylin-eosin(HE)staining,immunohistochemical stai-ning,pathological examination,and inflammatory cell count.Chemokine content was analyzed by enzyme-linked immunosorbent assay(ELISA),and ERK protein phosphorylation level was analyzed by Western blotting.The unpaired t test or Welch's t test was used for statistical comparison between the two groups,One-Way ANOVA or Kruskal-Wallis test was used for multi-group comparison,and the Bonferroni post-hoc test was used for pair-to-group comparison.Results Neutrophils in the HS 8 h group(105.58±14.73)were significantly more than those in the Sham group(25.12±5.48,t=12.536,P＜0.05).The lung in-jury score in the HS 8 h group[(0.682±0.089)points]was significantly higher than that of the Sham group[(0.175±0.083)points,t=10.199,P＜0.05].The concentration of CXCL1 and CXCL2 in lung tissue of HS 4 h and HS 8 h groups was significantly higher than that of Sham group(CXCL1:F=89.38,P＜0.01;CXCL2:x2=15.158,P＜0.01).Serum CXCL1 and CXCL2 concentrations in HS 4 h and HS 8 h groups were significantly higher than those in sham operation group(CXCL1:x2=14.000,P＜0.01;CXCL2:x2=15.158,P＜0.01).The contents of IL-8,CXCL1,and CXCL2 increased significantly after 2,4,and 6 h of OGD cultured lung epithelial cells(A549 cells)(IL-8:x2=21.60,P＜0.01;CXCL1:F=341.043,P＜0.01;CXCL2:x2=17.78,P＜0.01).At the same time,the phosphorylation level of ERK protein was significantly increased(t=6.867,P＜0.05).Selumetinib significantly inhibited the se-cretion of the chemokines IL-8(t=10.497,P＜0.01),CXCL1(t=10.631,P＜0.01),and CXCL2(t=5.504,P＜0.01)in A549 cells.In animal experiments,Selumetinib inhibited CXCL1/2 secretion(P＜0.01)and neutrophil infiltration(t=9.731,P＜0.01),and alleviated lung injury(t=4.088,P＜0.01).Conclusion After HS,rat lung epithelial cells secrete chemokines and recruit neutrophils through the ERK pathway to aggravate lung injury.Inhibition of ERK protein phosphorylation can significantly alle-viate lung injury.
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