[Regulatory effect of Ac-SDKP on phosphorylated heat shock protein 27/SNAI1 pathway in silicotic rats]

Objective: To study the effect of anti-fibrotic tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) on phosphorylated heat shock protein 27 (P-HSP27) and zinc finger family transcriptional repressor 1 (SNAI1) expression to explore the anti-silicosis fibrosis effect of Ac-SDKP. Methods: In December 2014, the rat silicosis animal model was prepared by one-time bronchial infusion of silicon dioxide (SiO(2)) dust. 80 SPF healthy adult Wistar rats were selected, and the rats were divided into 8 groups according to the random number table method, 10 in each group. Model control group for 4 weeks (feeding for 4 weeks) , model control group for 8 weeks (feeding for 8 weeks) : bronchial perfusion with normal saline 1.0 ml per animal. Silicosis model group for 4 weeks (feeding for 4 weeks) and silicosis model group for 8 weeks (feeding for 8 weeks) : bronchial perfusion of 50 mg/ml SiO(2) suspension 1.0 ml per animal. Ac-SDKP administration group for 4 weeks (feeding for 4 weeks) , Ac-SDKP administration group for 8 weeks (feeding for 8 weeks) : Ac-SDKP 800 μg·kg(-1)·d(-1) was administered by intraperitoneal pump. Ac-SDKP preventive treatment group: 48 h after Ac-SDKP 800 μg·kg(-1)·d(-1) administration, bronchial perfusion of SiO(2) suspension 1.0 ml per animal, raised for 8 weeks. Ac-SDKP anti-fibrosis treatment group: after bronchial perfusion of 1.0 ml of SiO(2) suspension for 4 weeks, Ac-SDKP 800 μg·kg(-1)·d(-1) was administered for 4 weeks. Western blotting was used to detect the expression of P-HSP27, SNAI1, α-smooth muscle actin (α-SMA) , and collage typeⅠ and Ⅲ in each group. The expression of P-HSP27 and SNAI1 was detected by immunohistochemistry, and the co-localized expression of P-HSP27 and α-SMA was detected by laser confocal microscopy. Results: Compared with the model control group, the expressions of P-HSP27, SNAI1, α-SMA, and collage typeⅠ and Ⅲ in the silicosis fibrosis area of the rats in the silicosis model group were enhanced, and the differences were statistically significant (P<0.05) . After Ac-SDKP intervention, compared with silicosis model group for 8 weeks, the expressions of P-HSP27, SNAI1 α-SMA, and collage typeⅠ and Ⅲ in the Ac-SDKP preventive and anti-fibrosis treatment groups were significantly decreased, and the differences were statistically significant (P<0.05) . However, the expressions of P-HSP27 SNAI1, and collage typeⅠ and Ⅲ between the Ac-SDKP administration group and the model control group did not change significantly, and the differences were not statistically significant (P>0.05) . Laser confocal results showed that the positive cells expressing P-HSP27 and α-SMA in the lung tissue of the silicosis model group were more than those in the model control group. Compared with the silicosis model group, the Ac-SDKP prevention and anti-fibrosis treatment groups expressing the positive cells of P-HSP27 and α-SMA decreased. Compared with the model control group for 8 weeks, there were some double-positive cells expressing P-HSP27 and α-SMA in the nodules of the silicosis model group for 8 weeks. Conclusion: Ac-SDKP may play an anti-silicic fibrosis effect by regulating the P-HSP27/SNAI1 pathway.