The therapeutic mechanisms of Compound Kushen Injection in relieving cancer-induced bone pain by targeting Nav1.7 and microglial activation.

Abstract

Ethnopharmacological relevance: In traditional Chinese medicine (TCM) theory, Compound Kushen Injection (CKI) possesses multiple therapeutic effects, including heat-clearing, detoxification, blood-cooling, dampness-resolving, and pain relief. CKI has been used clinically for 30 years as an adjunctive drug alongside chemotherapy and radiotherapy for cancer treatment. However, the effects of CKI on cancer-induced bone pain (CIBP) and potential mechanisms remain poorly understood.

Aim of the study: To investigate the therapeutic effects of CKI on CIBP and elucidate its mechanisms based on Nav1.7 and microglial activation.

Methods: The therapeutic effect of CKI in CIBP was systematically evaluated using behavioral tests, X-ray, HE staining, Micro-CT and TRAP staining. The mechanisms of CKI were explored by examining Nav1.7 expression and microglial activation both in vivo and in vitro. We further examined the effects of CKI on the blood-spinal cord barrier (BSCB) damage in CIBP rats. Inspired by the mechanisms of CKI, we further investigated whether inhibition of Nav1.7 could inhibit microglial activation and attenuates BSCB damage, thereby alleviating CIBP.

Results: In CIBP rats, CKI significantly alleviated pain hypersensitivity. Furthermore, CKI enhanced trabecular bone quantity and continuity, reduced trabecular separation, and decreased the number of TRAP-positive cells, thereby preserving tibial structural integrity. Notably, CKI significantly reduced Nav1.7 expression in the spinal cord and DRG. Meanwhile, CKI and its primary active ingredients, matrine and oxymatrine, dose-dependently suppressed Nav1.7 expression in vitro. Additionally, CKI attenuated microglial hyperactivation, restored the expression of spinal barrier proteins (Claudin1 and Occludin) in the spinal cord, and disrupted the vicious cycle between microglial activation and BSCB damage. In LPS-activated BV-2 microglial cells, CKI, matrine and oxymatrine inhibited the release of NO, and restored the balance of anti-inflammatory and pro-inflammatory (IL-4/TNF-α), thereby inhibiting BV-2 cell activation. Moreover, PF05089771 relieved CIBP by significantly decreasing osteoclasts number, suppressing microglial activation in the spinal cord, and attenuating BSCB damage.

Conclusion: CKI significantly alleviated CIBP likely through downregulating Nav1.7, thereby suppressing microglial activation and attenuating BSCB damage. Overall, this study not only uncovered the novel mechanisms of CKI in combating CIBP, but also unveiled Nav1.7 as a promising pharmacological target for CIBP therapy.