Emodin alleviates renal fibrosis by targeting the ALKBH1/m5C axis to sustain TRPV4 expression and inhibit TGF-β1/Smad2/3 signaling.

Renal fibrosis is the hallmark pathological outcome of chronic kidney disease (CKD), and effective anti-fibrotic therapies remain scarce. This study investigates the renoprotective effects and underlying mechanisms of emodin. A rat model of renal fibrosis was established using doxorubicin hydrochloride (DXR, 4 mg/kg), and NRK-52E cells were treated with angiotensin II (Ang II, 1 μM) to induce renal fibrosis in vitro. The regulatory effects of emodin (oral gavage of 40 mg/kg/day for 4 weeks in vivo and 100 μmol/L in vitro) on renal dysfunction, fibrosis, oxidative stress, and pyroptosis were evaluated. Additionally, the role of emodin in mediating the 5-methylcytosine (m5C) modification of transient receptor potential vanilloid 4 (TRPV4) was investigated in vitro. The interaction between emodin and the m5C regulatory protein AlkB homolog 1 (ALKBH1), as well as the association between ALKBH1 and TRPV4 mRNA, were detected. Emodin significantly ameliorated renal dysfunction and attenuated fibrosis in DXR-induced rats. Emodin also restored TRPV4 expression, which was downregulated in the fibrotic models. Conversely, TRPV4 knockdown partially reversed the protective effects of emodin, leading to exacerbated activation of the transforming growth factor-β1 (TGF-β1)/Smad2/3 pathway, along with enhanced fibrosis and pyroptosis. Mechanistically, Ang II elevated global m5C RNA modification and upregulated the demethylase ALKBH1; these effects were reversed by emodin. Furthermore, ALKBH1 overexpression promoted the destabilization of TRPV4 mRNA via site-specific m5C demethylation. Emodin alleviates renal fibrosis by preserving TRPV4 expression through targeting the ALKBH1-dependent m5C demethylation axis. Targeting the ALKBH1-m5C-TRPV4 axis may represent a promising therapeutic strategy for renal fibrosis.