Cyclocarya paliurus triterpenoids alleviate hyperuricemic nephropathy by regulating urate transporters and inhibiting the STAT3 signaling pathway

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Hyperuricemic nephropathy (HN), characterized by renal inflammation and fibrosis, has an increased risk of progression to end-stage renal disease, with therapeutic drugs currently insufficient. This study aimed to investigate the effects and mechanisms of triterpenoids of Cyclocarya paliurus leaves (CPT) on HN in vivo and in vitro. The HN rat model was established through gavage of adenine (150 mg/kg) and ethambutol (250 mg/kg) over three weeks. Concurrently, CPT (150 mg/kg) was administrated orally. The levels of uric acid (UA), creatinine, and urea nitrogen in plasma and urine were measured. Hematoxylin-eosin and Masson’s trichrome staining were performed on kidney tissues. The chemical composition of CPT was identified via HPLC-Q-TOF-MS/MS, and its targets for HN were screened through network pharmacology and molecular docking, cellular thermal shift assay (CETSA), surface plasmon resonance (SPR), and dual-luciferase reporter assay. Plasma metabolomics and renal proteomics were conducted to elucidate the mechanisms of CPT in mitigating HN. The renal expression of protein related to inflammation, fibrosis, and UA excretion in HN rats or UA-treated HK-2 cells was detected. CPT significantly reduced plasma UA levels and attenuated renal inflammation, fibrosis, and pathological alterations in HN rats. CPT promoted UA excretion and improved purine metabolism by downregulating the expressions of urate transporter 1 and glucose transporter 9 and upregulating the expression of organic anion transporter 1. Furthermore, CPT suppressed the inter interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3)/suppressors of cytokine signaling 3 (SOCS3) signaling pathway, decreased epithelial-mesenchymal transition, and reduced the levels of presenilin-associated rhomboid-like protein and cysteine and glycine-rich protein 2 (CSRP2) in both HN rats and UA-stimulated HK-2 cells. CETSA and SPR showed that CPT and cypaliuruside B (a seco-triterpenoid isolated from CPT) directly bind to STAT3. Moreover, STAT3 directly binds to the CSRP2 promoter, enhancing its transcriptional activity. These results indicated that CPT alleviated HN by regulating renal UA transporters and inhibiting STAT3, which supports the potential application of CPT in treating hyperuricemia and related kidney diseases.

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