Cortex Mori Radicis Attenuates Streptozotocin-induced Diabetic Renal Injury in Mice via Regulation of Transient Receptor Potential Canonical Channel 6

Objective: Cortex Mori Radicis (CMR) has been reported to possess antipyretic, anti-convulsant, anti-allergic, anti-inflammatory, and anti-diabetic effects. In this study, we aimed to investigate the effect of CMR on streptozotocin (STZ)-induced diabetic renal injury in mice and explore the underlying mechanism. Methods: Mice were gavaged with different doses of CMR for continuous 7 days. Then, STZ (50 mg/kg) was applied to induce renal injury associated with type 1 diabetes. Firstly, blood glucose levels and metabolic parameters were evaluated, including weight, food intake, and excrement. HE and PAS staining were performed to examine renal histological changes. Renal inflammation, fibrosis, and oxidative stress were assayed by real-time PCR and ELISA, separately. Additionally, podocyte-related markers, such as nephrin and wilms' tumor-1 (WT-1), were detected by immunohistochemical staining and Western blot separately. Lastly, expression of transient receptor potential canonical channel 6 (TRPC6) and activation of MAPK signaling pathways were assayed. Results: CMR pretreatment significantly lowered the blood glucose levels, suppressed renal inflammation, fibrosis, and oxidative stress, and relieved renal pathological injury, accompanying the inhibition of nephrin and WT-1 expression in STZ-induced diabetic mice. Moreover, CMR decreased the expression of TRPC6 and suppressed the phosphorylation of ERK, but not P38 MAPK and JNK. Notably, the application of hyperforin, a specific activator of TRPC6, significantly abrogated the hypoglycemic effect of CMR and reversed the suppression of CMR on TRPC6 expression and ERK activation in the diabetic mice. Conclusion: Our findings indicated that CMR attenuated early renal injury in STZ-induced diabetic mice by inhibiting ERK signaling via regulation of TRPC6, suggesting that CMR can be considered as a promising candidate for the management of diabetes-related renal complications.