Anti-fibrotic role of AcSDKP through inhibition of P38MAPK pathway activity mediated transforming growth beta receptors in rat with silicosis

Abstract

To investigate the distribution and expression of transforming growth factor beta (TGF-β) receptors I and II, p38 mitogen-activated protein kinase (p38 MAPK), and type I and type III collagen in the lungs of rats with silicosis and cultured pulmonary fibroblasts, and to investigate the relationship of the anti-fibrosis effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) with its inhibition of TGF-β receptor-mediated p38 MAPK pathway activity. Rats were randomly divided into control group, silicosis model group, and AcSDKP treatment group (n = 10 for each group). For the model group and AcSDKP treatment group, rats were intratracheally instilled with silica to establish a silicosis model. Cultured pulmonary fibroblasts from neonatal rats were divided into control group, TGF-β1 stimulation group, TGF-β receptor inhibition group, p38 MAPK pathway inhibition group, and AcSDKP treatment group. The protein expression of TGF-β receptors I and II, p38 MAPK, and type I and type III collagen were determined by immunohistochemistry and Western blot. The mRNA expression of TGF-β receptors I and II were determined by real-time PCR. The distribution and nuclear translocation of phospho-p38 MAPK in cultured fibroblasts were determined by laser scanner confocal microscopy. In the AcSDKP treatment group, AcSDKP reduced the expression of TGF-β receptors I and II, phospho-p38 MAPK, and type I and type III collagen to 86.12%, 41.01%, 42.63%, 89.05%, and 52.71%, respectively, of those of the silicosis model group (P < 0.05). In cultured fibroblasts, AcSDKP reduced the mRNA expression of TGF-β receptors I and II to 42.26% and 54.33%, respectively, of those of the TGF-β1 stimulation group; the protein expression of TGF-β receptors I and II, phospho-p38 MAPK, and type 1 and type III collagen was reduced to 58.14%, 51.40%, 45.6%, 58.04%, and 44.74%, respectively, of those of the TGF-β1 stimulation group. The phospho-p38 MAPK translocation from plasma to the nucleus was also inhibited; the nucleus/plasma ratio of p38 MAPK and the protein expression of type I and type III collagen were reduced to 68.60%, 58.04%, and 44.74%, respectively, of those of the TGF-β stimulation group (P < 0.05). AcSDKP can inhibit the expression of collagen through inhibition of TGF-β receptor-mediated p38 MAPK pathway activity, and is thus able to exert anti-fibrosis effect in rats with silicosis.