Tangzu granule alleviate neuroinflammation in diabetic peripheral neuropathy by suppressing pyroptosis through P2X7R /NLRP3 signaling pathway

Ethnopharmacological relevance: Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus, mainly manifested as paresthesia. Tangzu granule (TZG) is derived from famous traditional Chinese medicine decoctions and optimized by long-term temporary practice. TZG has good efficacy in improving numbness, pain and pruritus of the lower extremities of DPN patients. However, the overall regulatory mechanisms underlying its effects on DPN remain unclear.

Aim of the study: This study aims to explore the potential mechanism of TZG for treating DPN.

Materials and methods: Sprague-Dawley (SD) rats were used to establish an in vivo model of DPN with streptozotocin (STZ) injection and high-fat diet (HFD) feeding. Additionally, sciatic glial RSC96 cells were induced with high glucose in vitro. SD rats in intervention group received TZG treatment for 12 weeks. After 12 weeks of treatment, sciatic nerve function was evaluated by intelligent hot plate meter and neuro electrophysiology detector. The morphological changes of sciatic nerve cells were observed by hematoxylin-eosin staining and transmission electron microscope. IL-1β, IL-18 inflammatory cytokines, Pyroptosis and P2X7R/NLRP3 signaling pathway were observed by Western blotting, immunofluorescence staining and ELISA.

Results: TZG improved nerve conduction velocity and sciatic neuropathy rational structural changes in DPN rats. It also inhibited RSC96 inflammatory response and cell death that induced by high glucose. This may be related to TZG inhibiting P2X7R, decreasing the activation of NLRP3 inflammasomes, down-regulating the levels of Pyroptosis proteins such as Caspase-1, cleaved Caspase-1, gasdermin D (GSDMD), and GSDMD-N, and inhibiting the release of interleuki (IL)-18 and IL-1β inflammatory cytokines.

Conclusions: TZG inhibited Pyroptosis through P2X7R/NLRP3 signaling pathway, alleviated neuroinflammation, and showed protective effect in the treatment of DPN.

Diabetic peripheral neuropathy; Neuroinflammation; P2X7R/NLRP3 signaling pathway; Pyroptosis; Schwann cells; Traditional Chinese medicine (6 key words).