Objective:To investigate the role and mechanism of PM(2.5)exposure on airway inflammation in juvenile rats based on macrophage recruitment induced by JNK/CCl2 signaling pathway.Methods:A total of 50 juvenile SD rats were randomly divided into 5 groups(n=10).The control group received no treatment,the PM(2.5)group received PM(2.5)particulate matter expo-sure,and the PM(2.5)+Anisomycin group received PM(2.5)exposure and Anisomycin,an activator of JNK,intravenously.Rats in the PM(2.5)+SP600125 group received PM(2.5)exposure and intravenous administration of the JNK inhibitor SP600125,and rats in the PM(2.5)+Pirfenidone group received PM(2.5)exposure and intravenous administration of Pirfenidone,a CCl2 inhibitor.The rats were euthanized and lung tissue was harvested.JNK,phosphorylated JNK(p-JNK)and CCl2 protein expressions were detected by Western blot.Hematoxylin-eosin(HE)staining was used to detect the pathological changes of lung airway tissue and score the pulmo-nary bronchial inflammation.The number of macrophages in alveolar lavage fluid was analyzed by flow cytometry.The levels of IL-6,IL-1β,and TNF-α in alveolar lavage fluid were determined by ELISA.Results:The expression levels of JNK,p-JNK,and CCl2 among all groups(F=205.296,950.408,260.019;all P<0.001)and macrophage content(F=48.414;P<0.001),pulmonary bronchial inflammation score(F=101.703;P<0.001)and IL-6(H=44.890;P<0.001),IL-1β(H=42.071;P<0.001),TNF-α(F=297.154;P<0.001)were statistically significant.Compared with the control group,the expressions of JNK/CCl2 pathway proteins JNK,p-JNK,and CCl2 in PM(2.5)group were significantly up-regulated(all P<0.05),while the content of macrophages was increased(P<0.05),and the pulmonary and bronchial inflammation score was significantly increased(P<0.05).The levels of IL-6,IL-1β,and TNF-α were up-regulated(all P<0.05).Compared with PM(2.5)group,the content of macrophages in PM(2.5)+Anisomycin group was sig-nificantly increased(P<0.05),the pulmonary bronchial inflammation score was significantly increased(P<0.05),and the levels of IL-6,IL-1β,and TNF-α were increased(all P<0.05).The expression levels of JNK,p-JNK,and CCl2 were increased(all P<0.05).Compared with PM(2.5)group,the content of macrophages in PM(2.5)+SP600125 group and PM(2.5)+Pirfenidone group were signifi-cantly decreased(P<0.05),and the pulmonary bronchial inflammation score was significantly decreased(P<0.05).In addition,the levels of IL-6,IL-1β,and TNF-α were significantly decreased(all P<0.05).Compared with PM(2.5)group,the expression levels of JNK,p-JNK,and CCl2 in PM(2.5)+SP600125 group were down-regulated(all P<0.05),and the expression level of CCl2 in PM(2.5)+Pirfenidone group was down-regulated(all P<0.05).Conclusion:JNK/CCl2 pathway induces macrophage recruitment and pro-motes allergic airway inflammation induced by PM(2.5)particulate matter exposure in juvenile rats.