TGF-β/Smad signaling pathway plays a crucial role in patulin-induced pro-fibrotic changes in rat kidney via modulation of slug and snail expression

Patulin (PAT) is a mycotoxin that contaminates a variety of food and foodstuffs. Earlier in vitro and in vivo findings have indicated that kidney is one of the target organs for PAT-induced toxicity. However, no study has evaluated the chronic effects of PAT exposure at environmentally relevant doses or elucidated the detailed mechanism(s) involved. Here, using in vitro and in vivo experimental approaches, we delineated the mechanism/s involved in pro-fibrotic changes in the kidney after low-dose chronic exposure to PAT. We found that non-toxic concentrations (50 nM and 100 nM) of PAT to normal rat kidney cells (NRK52E) caused a higher generation of reactive oxygen species (ROS) (mainly hydroxyl (center dot OH), peroxynitrite (ONOO-), and hypochlorite radical (ClO-). PAT exposure caused the activation of mitogen-activated protein kinases (MAPKs) and its downstream cJun/Fos signaling pathways. Moreover, our chromatin immunoprecipitation (ChIP) analysis suggested that cJun/Fos binds to the promoter region of Transforming growth factor beta (TGF-beta(1)) and possibly induces its expression. Results showed that PAT-induced TGF-beta(1) further activates the TGF-beta(1)/smad signaling pathways. Higher activation of slug and snail transcription factors further modulates the regulation of pro-fibrotic molecules. Similarly, in vivo results showed that PAT exposure to rats through gavage at 25 and 100 mu g/kg b. wt had higher levels of kidney injury/toxicity markers namely vascular endothelial growth factor (VEGF), kidney Injury Molecule-1 (Kim-1), tissue inhibitor of metalloproteinase-1 (Timp-1), and clusterin (CLU). Additionally, histopathological analysis indicated significant alterations in renal tubules and glomeruli along with collagen deposition in PAT-treated rat kidneys. Overall, our data provide evidence of the involvement of ROS mediated MAPKs and TGF-beta(1)/smad pathways in PAT-induced pro-fibrotic changes in the kidney via modulation of slug and snail expression.

Automated summary

In this study, the mechanism involved in pro-fibrotic changes in the kidney after low-dose chronic exposure to PAT was investigated using in vitro and in vivo approaches. The results demonstrated that PAT exposure caused the generation of reactive oxygen species (ROS), activation of MAPKs and cJun/Fos signaling pathways, and induction of TGF-β(1) expression. Additionally, it was found that PAT-induced TGF-β(1) further activated the TGF-β(1)/smad signaling pathways and modulated the expression of slug and snail, leading to the regulation of pro-fibrotic molecules. The in vivo results also confirmed the kidney injury/toxicity effects of PAT exposure in rats.