ABSTRACT
OBJECTIVE: To observe the effects and mechanism of uranium dust on collagen synthesis in fibroblastic cells.METHODS: i) RAW264. 7 macrophages were divided into solvent-control group and dust-affected group,and then treated with 0 and 120 mg / L( final concentration) uranium dust suspension for 0,2,4,8,16,24 and 32 hours. The supernatants of cells from these two groups were collected,and transforming growth factor beta 1( TGF-β1) levels were measured by enzyme-linked immunosorbent assay( ELISA). The best time phase was defined,and the supernatant of RAW264. 7 macrophages culture were separated as the conditioned medium( CM) for subsequent experiments. ii) Normal mouse lung fibroblasts L929 cells were divided into control group and uranium dust group,and treated with the CM of solvent-control group and dust-affected group respectively. After cultivated for 0,6,12,18,24,30 and 36 hours,the expression of α-smooth muscle actin( α-SMA) in L929 cells was detected by immunocytochemistry. The levels of extrac ellular collagen type Ⅰ( Col Ⅰ),collagen type Ⅲ( Col Ⅲ) and hydroxyproline( HYP) were detected by ELISA.RESULTS: i) The level of TGF-β1 in RAW264. 7 macrophages supernatant of the dust-affected group was higher than that of the solvent-control group after treatment with uranium dust for 4 hours,and showed an increasing trend with increasing time during 4-24 hours( P < 0. 05). The peak value was in 24 hours. The best time phase was 24 hours and used for CM of the two groups in subsequent experiments. ii) Compared with the control group at the same time points, the α-SMA expressions of L929 cells in uranium dust group increased after treatment with CM for 18-36 hours( P < 0. 05),the levels of Col Ⅰ,Col Ⅲ and HYP in uranium dust group increased after treatment with CM for 12-36 hours( P < 0. 05); both the expression of α-SMA and levels of Col Ⅲ and HYP increased with increasing time,showing a time-effect relationship( P <0. 05). CONCLUSION: Uranium dust can induce macrophages to secret TGF-β1 and affect fibroblast,increase α-SMAexpression,and increase the Col Ⅰ,Col Ⅲ and HYP synthesis. These might be the important mechanisms of lung fibrosis.