Effect Of JNK Signaling Pathway On Fibroblast Transdifferentiation In Rats With Pulmonary Fibrosis

Background:Pulmonary fibrosis is a lethal form of diffuse lung disease for which no current treatment is effective and the etiology is unknown. The traditional treatment is to inhibit the inflammatory response, but these treatments are of unproven benefit. High expression of the α-smooth muscle actin (α-SMA) during the conversion of fibroblasts into myofibroblasts is an essential feature of pulmonary fibrosis, but its mechanism is unclear. In recent years, signaling pathways involved in the pathological process of pulmonary fibrosis transdifferentiation has been the research focus. C-jun N-terminal kinase (JNK) signaling pathway involved in the regulation of cell proliferation, differentiation and apoptosis, is a member of mitogen-activiated protein kinases. Studies have found that the INK signaling pathway in human lung fibroblasts to myofibroblasts play a role, but the effects of the INK signaling pathway in pulmonary fibrosis transdifferentiation in vivo experiment have not been reported. SP600125as a INK kinase inhibitor, can specifically inhibit INK signaling pathway. We use SP600125in this experiment to determine the expression of α-SMA and p-JNK protein in rats with pulmonary fibrosis, and to further explore the role that INK signaling pathway plays in the pathogenesis.Objective:Using the bleomycin-induced pulmonary fibrosis rats, among the three groups, we observe the pathological changes of the lung, measure the content of hydroxyproline in lung tissue, as well as survey the expression of α-SMA and p-JNK protein in rats, to further explore the role that INK signaling pathway plays in the pathogenesis.Methods:Fifty-four healthy male Wistar rats(weight:200g±20g)were randomly assigned to control group,model group and SP600125group. Each group contained eighteen rats. Model group was injected i.p with DMSO after a single intratracheal injection of bleomycin at a dose of5mg/kg; SP600125group was injected i.p with SP600125at a dose of15mg/kg(dissolved in DMSO)after instillation of bleomycin; Control group was injected i.p with DMSO after instillation of saline. Rats were randomly sacrificed on days7,14and28. Pathological changes under light microscope were examined after extracting the lung tissues followed by staining with H&E and Masson’s trachoma. The level of hydroxyproline(Hyp)in the lung tissue was detected applying alkaline hydrolysis technique, and expression levels of α-SMA and p-JNK protein were tested via immunohistochemical assay.Results:1、In model group, alveolitis was most serious on day7and marked pulmonary fibrosis was formed on day28. However, lung injury in SP600125group got better than that in model group.2、The content of hydroxyproline was increased gradually depending on time both in model group and SP600125group. On day7, the expression of hydroxyproline in model group was higher than that in control group (P<0.01), while no obvious difference existed between SP600125group and model control group. The expression of hydroxyproline in model group was significantly higher than that in control group on day14and28(P<0.01), and that in SP600125group was significantly lower compared with model group (P<0.01).3、The a-SMA and p-JNK protein in model group were higher on time and the peak expression on day14. Compared with those in model group, lower expression was shower on day14and28in control group and SP600125group(P<0.05).4、The a-SMA protein in lung of model group was positively correlated with p-JNK protein(r=0.927, P<0.05).Conclusion:The pathogenesis of pulmonary fibrosis may be associated with expression of p-JNK and activation of the a-SMA. SP600125is capable of inhibiting pulmonary fibrosis.