Recent studies have shown that endogenous metabolites act via
aryl hydrocarbon receptor (AhR) signalling pathway in tubulointerstitial
fibrosis (TIF) pathogenesis. However, the mechanisms underlying endogenous metabolite-mediated AhR activation are poorly characterised. In this study, we conducted untargeted metabolomics analysis to identify the significantly altered intrarenal metabolites in a mouse model of unilateral
ureteral obstruction (UUO). We found that the levels of the metabolite
1-methoxypyrene (MP) and the
mRNA expression of AhR and its target genes
CYP1A1,
CYP1A2, CYP1B1 and COX-2 were progressively increased in the obstructed kidney at Weeks 1, 2 and 3. Furthermore, these changes were positively correlated with progressive TIF in UUO mice. In NRK-52E, RAW 264.7 and NRK-49F cells, MP dose-dependently upregulated the
mRNA expression of AhR and its four target genes and the
protein expression of nuclear AhR, accompanied by the upregulated
protein expression of
collagen I, α-SMA and
fibronectin, as well as downregulated
E-cadherin expression. Consistently,
oral administration of MP in mice progressively enhanced AhR activity and upregulated profibrotic
protein expression in the kidneys; these effects were partially inhibited by AhR knockdown in MP-treated mice and cell lines. In addition, we screened and identified erythro-guaiacylglycerol-β-
ferulic acid ether (GFA), which was isolated from
Semen plantaginis, as a new AhR antagonist. GFA significantly attenuated TIF in MP-treated NRK-52E cells and mice by partially antagonising AhR activity. Our results suggest that MP activates AhR signalling, thus mediating TIF through epithelial-mesenchymal transition and macrophage-myofibroblast transition. MP is a crucial metabolite that contributes to TIF via AhR signalling pathway.