The Effect Of Rosiglitazone On The Changes Of TGF-β1/JNK Signal Pathway Expression In OLETF Rats Lung

Objective:Diabetes mellitus (DM) is a group of clinical syndrome that caused by multiple factors and featured by chronical hyperglycemia. It can lead to multi-system damage. With the further study of DM complication, increasingly more attention has been paid to the damage of DM to the lung. Study confirmed lung damage was also a part of DM systemic diseases and DM can significantly increase the risk of pulmonary fibrosis. As a profibrotic cytokine, TGF-β1 plays an important role in the process of a variety of organ fibrosis. JNK signal pathway is an important downstream of TGF-β1, JNK may effect TGF-B1 activity, thereby chang the fibrosis process. Recent studies have found that, the excessive activation of JNK is closely related with DM liver fibrosis and non-diabetes pulmonary fibrosis, however, research on the relationship between TGF-β1/JNK signal transduction pathway and DM pulmonary fibrosis is little. a-smooth muscle actin (a-SMA) and type I collagen (COL I) are important factors of pulmonary fibrosis. Rosiglitazone (RGT)'is a synthetic ligand of peroxisome proliferator-activated receptor-r(PPAR-y). RGT is not only capable of lowering glucose and improving insulin sensitivity, but also capable of protecting organs from fibrosis. The aim of this study is to observe the changes of TGF-β1 by using enzyme linked immunosorbent assay (ELISA) and the changes of phosphorylated JNK (p-JNK), a-SMA and COL I in OLETF rat lung by Western Blotting and then investigate whether TGF-β1/JNK signal pathways is important to the pathogenesis of DM pulmonary fibrosis. Then we observed the changes of the above indicators in RGT intervention group so as to investigate whether RGT has a protective effect on DM pulmonary fibrosis.Methods:30 OLETF rats and 8 LETO rats which were 4 weeks old were reared in single cage with standard feed in specific pathogen-free conditions. They were taken OGTT every 4 weeks. To the age of 30 weeks, there were 16 OLETF rats modelled successfully and divided into 2 groups randomly:DM group and the RGT intervention group.8 LETO rats were taken as normal (N) group. The RGT group was administered with RGT (3 mg/kg) by gavage daily. DM group and N group were intragastric administered with equal distilled water daily for 12 weeks. After 12 weeks, the rats were sacrificed. Some lung was obtained and fixated with 10% formalin and some lung was fixated with liquid nitrogen and obtained at-80°C:①observed the morphological changes of the lung by HE staining;②observed collagen deposition in lung tissue of each group by Masson staining;③detected the expression of TGF-B1 in rat lung by ELISA and the protein concentration by ELISA with 450nm wavelength;④observed the changes of p-JNK, a-SMA and COL I in OLETF rats lung by Western Blotting and calculated relative expression by gel image processing system with B-actin or GAPDH as internal control.Results:①HE staining:N group had normal alveolar structure. While the lung tissue structure of DM group was disordered, bronchial wall became thicker, alveolar septum became wider, part of alveolar atrophy and collapse, pulmonary interstitium increased, and there were inflammatory cell infiltration. Lung damages in RGT group were alleviated, but it didn't recover to normal level.②Masson staining:alveolar septum, peribronchial and perivascular of N group had little collagen fibers, but in DM group they increased and disordered. Collagen deposition in RGT group was less than DM group, but still more than N group.③Compared with N group, the expression of TGF-β1, p-JNK, a-SMA and COL I in DM group increased obviously (P<0.05). the difference was statistically significant；compared with DM group, the expression of TGF-β1, p-JNK, a-SMA and COL I in RGT group decreased obviously (P<0.05), the difference was statistically significant.Conclusions:①Pathological changes and collagen fibers deposition occured in lung of OLETF rats, indicating that lung is aslo target organ of DM.②Compared with LETO rats, the expression of TGF-B1, p-JNK, a-SMA and COL I in OLETF rats lung increased obviously suggesting that TGF-β1/JNK signal transduction pathway may play a role in the pathogenesis of DM pulmonary damage.③The pathological changes of pulmonary in RGT group were slighter than DM group. The deposition of collagen and the expression of TGF-β1, p-JNK, a-SMA and COL I in RGT group decreased obviously, suggesting that RGT can alleviate DM pulmonary fibrosis probably by regulating TGF-β1/JNK signal pathway.