The Effect Of All-trans Retinoic Acid On Bleomycin Induced Pulmonary Fibrosis In Rats

Objective:To observe the outcome of the all-trans retinoic acid on bleomycin-induced pulmonanry fibrosis in rats and to investigated the effects of the IL-17 on Pulmonary fibrosis.Methods:Sixty weight 18-22g male C57/BL6 mice (6-8 weeks old) were randomly divided into control group (group A, n=20), a bleomycin-induced pulmonary fibrosis model group (group B, n=20), dexamethasone-treated group (group C), different doses of all-trans retinoic acid-treated groups (group D, E, F, n=5). The mice of group A to receive intratracheal instillation of normal saline in zero day as a control; The mice of groups B,C,D,E,F to receive intratracheal instillation of bleomycin in zero day to establish fibrosis mode; The mice of group C were injected into abdominal cavity with dexamethasone (1mg/kg) every day after they received intratracheal instillation of bleomycin in zero day; The mice of groups D,E,F were injected into abdominal cavity with different doses of all-trans retinoic acid (0.25mg, 0.5mg,0.75mg) after they received intratracheal instillation of bleomycin in zero day.Five rats in both group A and group B were randomly killed on the 3rd,7th,14th and 28th day; All rats in group C,D,E,F were killed on the 28th day. And lung tissue samples were harvested for study. To observed the gross change of the lung tissue and lung indexes; HE and Masson staining were used to determine the extent of alveolus inflammation and pulmonary fibrosis,respectively; Immunohistochemistry was used to determine the levels of IL-17 A protein in lung tissue at different time points in each group. Results:1 During different time points in the control group (group A), inflammatory cell infiltrate was rarely to be found, without finding proliferation of fibroblast and alterations of PF from the investigation of histopathology of the lung tissues. In the bleomycin-induced pulmonary fibrosis model group (group B), there were a good deal of inflammatory cells infiltration in the alveolar wall in the lung tissues at the 7th day; At the 14th day, inflammatory cells can be seen gradually reduced and a lot of proliferating fibroblasts could be seen; There were a number of fibroblasts and pulmonary fibrosis was formed at the 28th day. The scores of the alveolitis and lung fibrosis of model group (group B) was higher than that of control group (group A). There were statistically significant in groups(P<0.05).2 Compared to the pulmonary fibrosis model group (B group), the alveolitis, pulmonary fibrosis, lung index and hydroxyproline (HYP) content decreased significantly in the drug treatment groups (C,D,E,F groups) (P<0.05). All treatment groups (C,D,E,F groups) for multiple comparisons with LSD test:the effect of treatment in E group was better than other treatment groups (C,D,F groups) (P<0.05); No significant difference was detected among other treatment groups (C,D,F groups) (P>0.05).3 Immunohistochemistry revealed:despite IL-17A protein gray value was decreased in B group than that of A group on the 3rd day, but there was no significant difference (P> 0.05). IL-17A protein gray value decreased significantly on the 7th,14th day, increased on the 28th day, but there was a significant difference on the 7th,14th,28th day(P<0.05). IL-17A protein gray value increased significantly (P<0.05) in treatment groups (C,D,E,F groups) than in model group(B group).Conclusion:1 IL-17 presents of high expression of pulmonary fibrosis, it may be play an important role in the process of pulmonary fibrosis.2 All-trans-retinoic acid can reduce bleomycin-induced alveolar inflammation and pulmonary fibrosis, possibly through lower IL-17 expression reduce the formation of pulmonary fibrosis.3 The effect of all-trans retinoic acid on bleomycin-induced alveolitis and pulmonary fibrosis in mice was associated with concentration.4 Dexamethasone, different doses of all-trans-retinoic acid intervention group were able to reduce different extent of bleomycin-induced in mice pulmonary fibrosis. With dexamethasone,all-trans-retinoic acid (D, F) of pulmonary fibrosis of no obvious difference improve. But all-trans-retinoic acid (E) groups of mice pulmonary fibrosis treatment effect is the most significant.