11-keto-β-boswellic acid and Z-guggulsterone suppress HMGB1/TLR4 pathway activity and modulate microglial polarization to remodel perineuronal nets after nerve injury

INTRODUCTION: Remodeling of perineuronal nets is an emerging strategy for treating neuropathic pain (NP) and aligns with the traditional Chinese medicine concept of dispersing blood stasis dispersion and dredging collateral channels. Frankincense and myrrh are known for their ability to promote blood circulation, eliminate blood stasis, unblock collateral channels, and relieve pain. However, the precise pharmacological components and mechanisms underlying their analgesic effects remain unclear. OBJECTIVES: This study aimed to clarify the mechanisms of action of 11-keto-β-boswellic acid (KBA, a component of frankincense) and Z-Guggulsterone (Z-GS, a component of myrrh) in remodeling perineuronal nets. METHODS: An NP model was developed via sciatic nerve chronic constriction injury (CCI), and possible targets and pathways were identified through transcriptomic analysis. To assess the effects of blocking the HMGB1/TLR4 signaling pathway on NP, the HMGB1 inhibitor BoxA and the TLR4 antagonist LRU were administered intrathecally. Additionally, KBA and Z-GS were administered via intraperitoneal injection for 14 days. The influence of KBA and Z-GS on perineuronal net remodeling via microglia polarization through HMGB1/TLR4 signaling was then investigated. RESULTS: Transcriptomic analysis suggested that HMGB1/TLR4-induced neuroinflammation may play a role in NP. Intrathecal BoxA and LRU administration significantly decreased mechanical and thermal pain sensitivity levels in CCI mice, promoted microglia polarization by modulating neuroinflammation, and reversed perineuronal net degradation. Further analyses revealed that combining KBA and Z-GS resulted in a more pronounced reduction in mechanical and thermal pain sensitivities, downregulation of HMGB1, TLR4, MyD88, p-P65, and TRPV1 in microglia of the spinal dorsal horn, and enhanced microglia polarization, ultimately facilitating perineuronal net remodeling. CONCLUSION: KBA and Z-GS alleviate NP in a combined effects, likely through inhibition of the HMGB1/TLR4 signaling pathway, which regulates microglia polarization and promotes perineuronal net remodeling. This suggests that targeting HMGB1/TLR4 signaling may be a promising means of treating NP.