Hirsutine attenuates renal injury in diabetic kidney disease by regulating Th17 cell differentiation via the TGFβ/SMAD Pathway.

Hirsutine (HS), a bioactive indole alkaloid isolated from Uncaria rhynchophylla, a traditional Chinese herb, has long been used in the treatment of hypertension and inflammatory disorders. However, its nephroprotective potential in diabetic kidney disease (DKD),-a primary cause of end-stage renal failure, remains insufficiently studied, particularly regarding its immunomodulatory mechanisms. High-throughput RNA sequencing was performed on renal tissues to identify differentially expressed genes (DEGs). Network pharmacology was employed to uncover potential HS targets and associated pathways relevant to DKD, while molecular docking predicted protein interactions. In vivo validation was conducted using db/db mice treated with HS, with evaluations of renal function, histopathology, Th17 cell differentiation, and the TGFβ/SMAD signaling pathway. Transcriptome analysis identified 837 DEGs. Enrichment analysis of these DEGs and network pharmacology revealed that TGFβ signaling-mediated Th17 cell differentiation could be a critical mechanism underlying the therapeutic effects of HS in DKD. In vivo experiments demonstrated that HS treatment inhibited Th17 cell differentiation and downregulated the expression of TGFβ1, p-SMAD2, and p-SMAD3. Histological analysis via HE staining showed only mild edema in renal tubular epithelial cells following HS treatment. Furthermore, HS treatment improved metabolic abnormalities, such as hyperglycemia and dyslipidemia, as well as renal function markers, including 24-h urinary protein excretion, (Urine albumin-to-creatinine ratio)UACR, blood urea nitrogen (BUN) and serum creatinine (Scr) levels. Co-administration of SRI with HS reversed these effects, with metabolic and renal function parameters returning to levels comparable to untreated db/db mice. This suggests that HS mediates its renoprotective effects by inhibiting the TGFβ signaling pathway, a key target in diabetic nephropathy. In conclusion, HS alleviates the progression of DKD by suppressing Th17 cell differentiation through modulation of the TGFβ/SMAD pathway. This study provides the first evidence of HS as a novel immunomodulatory agent for DKD, highlighting its potential as a promising botanical-based therapeutic strategy for DKD.