Tranilast prevents renal interstitial fibrosis by blocking mast cell infiltration in a rat model of diabetic kidney disease

Renal interstitial fibrosis is a final pathway that is observed in various types of kidney diseases, including diabetic kidney disease (DKD). The present study investigated the effect of tranilast on renal interstitial fibrosis and the association between its role and mast cell infiltration in a rat model of DKD. A total of 30 healthy 6-week-old male Sprague-Dawley rats were randomly divided into the following four groups: Normal control group; DKD model group; low-dose tranilast group (200 mg/kg/day); and high-dose tranilast group (400 mg/kg/day). The morphological alterations of tubulointerstitial fibrosis were evaluated by Masson's trichrome staining, while mast cell infiltration into the renal tubular interstitium was measured by toluidine blue staining and complement C3a receptor 1 (C3aR) immunohistochemical staining (IHC). The expression of fibronectin (FN), collagen I (Col-I), stem cell factor (SCF) and proto-oncogene c-kit (c-kit) was detected by IHC, western blotting and reverse transcription-quantitative-polymerase chain reaction. The results demonstrated that tubulointerstitial fibrosis and mast cell infiltration were observed in DKD model rats, and this was improved dose-dependently in the tranilast treatment groups. The expression of FN, Col-I, SCF and c-kit mRNA and protein was upregulated in the tubulointerstitium of DKD model rats compared with the normal control rats, and tranilast inhibited the upregulated expression of these markers. Furthermore, the degree of SCF and c-kit expression demonstrated a significant positive correlation with C3aR-positive mast cells and the markers of renal interstitial fibrosis. The results of the present study indicate that mast cell infiltration may promote renal interstitial fibrosis via the SCF/c-kit signaling pathway. Tranilast may prevent renal interstitial fibrosis through inhibition of mast cell infiltration mediated through the SCF/c-kit signaling pathway.