Huangqi-Danshen decoction alleviates renal fibrosis through targeting SCD1 to modulate cGAS/STING signaling

The Huangqi-Danshen decoction (HDD) is composed of Huangqi (Astragali Radix) and Danshen (Salviae Miltiorrhizae Radix et Rhizoma) and has been shown to alleviate renal fibrosis. However, the potential therapeutic mechanisms and effective components of HDD remain unclear.

Both lipid metabolism and cGAS/STING signaling play vital roles in the development and progression of renal fibrosis. However, their relationship in renal fibrosis is largely unknown. The present study aimed to investigate the antifibrotic mechanisms of HDD from the perspective of lipid remodeling and cGAS/STING signaling.

In vivo, renal fibrosis was induced by feeding male C57BL/6 mice with 0.2% adenine-diet for 28 consecutive days. The treatment groups were orally administered HDD at low, medium, and high doses of 3.4 g/kg/d, 6.8 g/kg/d, and 13.6 g/kg/d simultaneously with modeling. Renal function was evaluated by the serum levels of urea nitrogen and creatinine, pathological changes of renal tissue were evaluated by Periodic acid-Schiff and Masson's trichrome staining, and renal lipid metabolites were analyzed by lipidomics. Western blotting, immunohistochemistry, and immunofluorescence were used to detect the expressions of fibrosis-related proteins, SCD1, and cGAS/STING signaling-related proteins in renal tissue. In vitro, mouse primary proximal tubular epithelial cells (PTECs) were treated with transforming growth factor-β1 (TGF-β1) or stearoyl-CoA desaturase 1 (SCD1) inhibitor A939572. Additionally, UHPLC-QE-MS analysis and TCMSP database were used to screen the effective components of HDD, and the action mechanisms of these components were verified in mouse primary PTECs.

HDD dose-dependently improved renal function, pathological injury, and fibrosis in adenine-induced chronic kidney disease (CKD) mice model. Moreover, cGAS/STING signaling was significantly activated in fibrotic kidney and was suppressed by HDD treatment. In renal lipidomics analysis, 521 and 138 differential lipids were identified in control vs. CKD and CKD vs. CKD + HDD, respectively. Of note, lipids increased in fibrotic kidneys were more saturated (fewer double bonds), whereas lipids increased by HDD were less saturated (more double bonds). Further, SCD1 expression was significantly down-regulated in fibrotic kidney and could be restored by HDD treatment. The expression of SCD1 was also down-regulated in Ju CKD patients' dataset and TGF-β1-induced fibrogenic responses in mouse primary PTECs. Mechanistically, specific inhibition of SCD1 expression could activate cGAS/STING signaling in primary PTECs. In addition, three components of HDD (isoimperatorin, baicalin, and miltirone) were screened out. Furthermore, administration of these three components, especially isoimperatorin and miltirone, counteracted the activation of cGAS/STING signaling induced by SCD1 pharmacological inhibition.

HDD could alleviate renal fibrosis, which may be related to the regulation of cGAS/STING signaling through targeting SCD1.