Multi-level intervention of Tangluoning on mitochondrial thioredoxin deficiency in Schwann cells ameliorates diabetic peripheral neuropathy.

BACKGROUND: Diabetic peripheral neuropathy (DPN), the most prevalent complication of diabetes, currently lacks disease-modifying therapies. While Tangluoning recipe (TLN)-a traditional Chinese herbal medicine derived from Huangqi Guizhi Wuwu decoction-demonstrates therapeutic efficacy against DPN symptoms, its mechanism remained elusive. This study pioneers two transformative advances: Uncovering a previously unrecognized pathogenic axis linking mitochondrial thioredoxin (Trx2) deficiency to DPN demyelination; Establishing a novel dual-target therapeutic strategy that concurrently rescues mitochondrial dysfunction and lipid metabolic homeostasis.

METHODS: UHPLC-MS/MS was used to qualitative analysis the chemical profile of TLN. Three dosage gradients of TLN were administered to streptozotocin (STZ)-induced diabetic rats, with corresponding medicated serum concentrations applied to high glucose-exposed Schwann cells (SCs).Western blot (WB) and immunofluorescence assays were systematically performed to (1) elucidate TLN's regulatory effects on Pmpca SUMOylation-mediated Trx2 processing in both sciatic nerve tissues and SC mitochondria and decipher TLN's modulatory impact on the SUMOylation pathway. Mitochondrial ultrastructure was quantitatively analyzed using transmission electron microscopy (TEM), mitochondrial membrane potential and reactive oxygen species (ROS) production were monitored via confocal laser scanning microscopy. SCs was transfected with Trx2 siRNA to determine the specificity of TLN's action on the Trx2-dependent pathway. Comprehensive proteomic and lipidomic profiling was conducted to identify differential protein/lipid signatures in Trx2-deficient SCs and caracterize TLN-mediated regulatory effects on metabolic network homeostasis.

RESULTS: The 209 compounds were identified based on high-accuracy mass to-charge ratios and fragmentation patterns. TLN enhances Trx2 processing through a unique SUMOylation-dependent activation of mitochondrial-processing peptidase subunit α (Pmpca)-a mechanism previously unreported in DPN therapeutics. Furthermore, Trx2 deficiency disrupts inter-organelle communication (involving 56 dysregulated proteins) and lipid metabolism (17 key regulators), thereby establishing the first evidence of a mitochondria-lipid metabolic axis in DPN pathogenesis. Significantly, TLN coordinately rescues 370 dysregulated lipid species, predominantly glycerophospholipids (GP, 50.27%) and sphingolipids (SP, 11.08%), demonstrating a mechanistically distinct dual-target efficacy: mitochondrial repair coupled with lipid homeostasis restoration.

CONCLUSION: Mitochondrial morphological abnormalities and dysfunction in SCs, driven by impaired Trx2 protein processing, constitute a novel pathogenic mechanism underlying demyelination in DPN. Specifically, Trx2 deficiency disrupts inter-organelle communication, triggering mitochondria-mediated lipid metabolism dysregulation. TLN ameliorates DPN demyelination through two mechanistically distinct pathways: (1) Restoring Trx2 processing via enhanced Pmpca SUMOylation, thereby rescuing mitochondrial structure and function; (2) Reestablishing lipid metabolic homeostasis-particularly glycerophospholipid and sphingomyelin balance-by correcting inter-organelle communication defects in Trx2-deficient SCs.