Casticin promotes M2 macrophage polarisation and dorsal root ganglion neuronal autophagy to alleviate cold hyperalgesia in knee osteoarthritis by regulating histone-lysine N-methyltransferase (SETDB2)

  • Br J Pharmacol. 2026 Aug;183(16):5033-5061. doi: 10.1111/bph.70512.
Yibao Wei  1  2 ,  Songjiang Yin  1  2 ,  Chen Kuang  1  2  3 ,  Deren Liu  1  2 ,  Enrui Hu  1  2 ,  Peng Wu  1 ,  Jun Mao  1 ,  Taiyang Liao  2  4 ,  Peimin Wang  1  5
Affiliations
  • 1. Department of Orthopedics and Traumatology, Affiliated Hospital of Nanjing University of Chinese Medicine, Jiangsu Provincial Hospital of Traditional Chinese Medicine, Nanjing, China.
  • 2. Key Laboratory for Metabolic Diseases in Chinese Medicine, Nanjing University of Chinese Medicine, Nanjing, China.
  • 3. Department of Orthopedics and Traumatology, Kunshan Affiliated Hospital of Nanjing University of Chinese Medicine, Kunshan, China.
  • 4. Department of Orthopedics and Traumatology, The Second Affiliated Hospital of Nanjing University of Chinese Medicine, Jiangsu Second Chinese Medicine Hospital, Nanjing, China.
  • 5. Nanjing University of Chinese Medicine Clinical Research Institute for Knee Osteoarthritis, Nanjing, China.
PMID: 42157429 DOI: 10.1111/bph.70512
Abstract

Background and purpose: Knee osteoarthritis (KOA) is a degenerative joint disease characterised by chronic pain. This study investigated the effects of casticin on KOA-associated cold hyperalgesia and its underlying mechanisms.

Experimental approach: KOA was induced in C57BL/6J mice using the destabilisation of the medial meniscus (DMM) model. Cold hyperalgesia was assessed through cold plate and acetone tests. Interleukin-4 was used to induce M2 macrophage polarisation, whereas dupilumab was employed to inhibit M2 activation. Casticin treatment was administered to evaluate its effects on SET domain bifurcated histone-lysine methyltransferase 2 (SETDB2) expression, macrophage polarisation, dorsal root ganglion neuronal Autophagy, and mitochondrial function. shRNA-mediated SETDB2 knockdown was performed to confirm its role in KOA pain modulation. Western blotting, quantitative Real-Time PCR (qPCR), immunofluorescence and enzyme-linked immunosorbent assays (ELISA) were used to analyse macrophage polarisation and Autophagy markers, mitochondrial function and mitochondrial membrane potential [MMP], and pain mediators.

Key results: M2 macrophage polarisation enhanced neuronal Autophagy, by increasing LC3B, p62 and Beclin1 expression, and improved mitochondrial function by reducing ROS accumulation, restoring ATP production and increasing MMP levels. These changes correlated with reduced cold hyperalgesia and decreased expression of nociceptive markers (CGRP and TRPA1). Casticin treatment further promoted M2 macrophage polarisation, enhanced neuronal Autophagy, and restored mitochondrial function, leading to significant pain relief. SETDB2 knockdown partially reversed these effects, confirming its essential role in M2-driven Autophagy activation and pain modulation.

Conclusions and implications: Casticin alleviated KOA-induced cold hyperalgesia by up-regulating SETDB2, promoting M2 macrophage polarisation, enhancing neuronal Autophagy, and restoring mitochondrial function.

Keywords
M2 macrophage polarisation; SETDB2; casticin; cold hyperalgesia; knee osteoarthritis.
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