Targeting STING and protecting mitochondrial function with Nephropathy Ⅱ decoction to alleviate renal fibrosis

Background

Nephrology II Decoction (NED), a compound from traditional Chinese medicine, has been used in the clinical treatment of chronic kidney disease (CKD) for a long time. However, the specific active ingredients and the mechanisms by which they operate are not yet fully understood.

Objective

The study aims to explore how NED eases CKD, with an emphasis on its influence on stimulator of interferon genes (STING)-mediated mitochondrial balance within kidney cells.

Methods

Various CKD mouse models, including folic acid nephropathy (FAN), unilateral ureteral obstruction (UUO), and bilateral renal ischemia-reperfusion injury (bIRI), were administered with NED via oral gavage for three weeks. This study evaluated kidney function, pathological alterations, and fibrosis markers (fibronectin, collagen I, TGF-β, α-SMA) were assessed. Bulk RNA-sequencing of kidney tissues identified key targets, with molecular docking, dynamics simulations, and microscale thermophoresis were used to predict active components and pathways. These components and pathways were confirmed in renal tissues from CKD mice and renal tubular cells induced by folic acid. Additionally, oxidative stress induced by Tert‑butyl hydroperoxide (t-BHP) in HK2 cells was used to replicate CKD-induced renal fibrosis in vitro.

Results

NED significantly improved renal function, reduced pathological damage, and decreased fibrosis in mice with CKD. Bulk RNA-seq identified STING as a pivotal target, and molecular docking demonstrated a strong binding affinity between NED's active components and murine STING. NED inhibited the cGAS/STING/TBK1/IRF3/IFN-β pathway, thereby alleviating renal fibrosis. It also corrected defects in mitochondrial oxidative phosphorylation, diminished inflammatory responses, and reduced apoptosis in fibrotic kidneys. In vitro, NED prevented mitochondrial DNA leakage induced by t-BHP, preserved mitochondrial function, and suppressed STING activation. STING inhibitor C176 effectively reduced fibrosis in both FAN mice and folic acid -induced cells, whereas the STING agonist DMXAA intensified fibrosis. There were potential interactions observed when DMXAA was combined with NED.

Conclusions

This study clarified the anti-fibrotic mechanisms of NED through the cGAS/STING pathway, highlighting STING as a primary target and the involvement of mitochondrial phosphorylation. NED appears to be a promising candidate for the treatment of CKD and reductions of renal fibrosis.