Research on JAK and STAT1 pathway in bleomycin-induced pulmonary fibrosis rats

Objective To study the expressions of STAT1,PDGF and PAI-1 in lung tissue of rats pulmonary fibrosis model induced by bleomycin(BLM),and discuss the possible mechanism of JAK and STAT1 pathway.Methods Thirty Wistar rats were randomly divided into two groups(15 in each group): BLM group and 0.9% NaCl solution(NS) group.The BLM group was intratracheally instilled with belomycin(5 mg/kg).The NS group was intratracheally instilled with NS in the same volume.Five rats in each group were sacrificed at 7,14and 28 days after intratracheal instillation.The bronchoalveolar lavage fluid(BALF) of right lung was performed and the cell counting as well as differentiation were figured out.collagen contents of the left lung tissue were assessed by hydroxyproline concentration.Lung expressions of STAT1,PDGF and PAI-1 protein were assessed by immunohistochemistry.Results The collagen in BLM group significantly increased compared with NS group at day 7;At day 14 and 28 the collagen in BLM group continued to elevate,and there was significant difference compared with NS group(P0.01).The expressions of STAT1 and PDGF protein in BLM group after bleomycin administration were the highest at day 7 and still elevated over NS group at day 28,and they were correlated with the total number of cells in BALF,respectively(r=0.880,P all 0.01).At day 7 the expression of PAI-1 protein was significantly increasing in BLM group,and was the highest at day 28.The expression of PAI-1 protein was correlated with the collagen contents of lung(r=0.952,P0.01).Conclusions There existed increased expressions of STAT1,PDGF and PAI-1 protein in lung tissue in bleomycin-induced pulmonary fibrosis rats.JAK and STAT1 pathway might take part in pulmonary fibrosis through increasing expressions of STAT1,PDGF and PAI-1 protein.