Down-regulation of M6A demethylase ALKBH5 facilitates morphine tolerance via SGK1 in mice

  • Br J Pharmacol. 2026 Jun;183(11):2739-2760. doi: 10.1111/bph.70365.
Yufei Shi  1  2 ,  Wei Cao  1 ,  Manyu Xing  1 ,  Zhengyiqi Li  1 ,  Jingyi Peng  1 ,  Li Tian  2 ,  Wangyuan Zou  1  3
Affiliations
  • 1. Department of Anesthesiology, Xiangya Hospital, Hunan Province Clinical Research Center for Anesthesia and Perioperative Medicine, Central South University, Changsha, China.
  • 2. Shanghai Key Laboratory of Anesthesiology and Brain Functional Modulation, Translational Research Institute of Brain and Brain-Like Intelligence, Clinical Research Center for Anesthesiology and Perioperative Medicine, Department of Anesthesiology and Perioperative Medicine, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China.
  • 3. National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, China.
PMID: 41666459 DOI: 10.1111/bph.70365
Abstract

Background and purpose: The development of drug tolerance following prolonged use of opioids, such as morphine, limits their analgesic efficacy and clinical utility. Epigenetic modifications, particularly N6-methyladenosine (m6A), have garnered increasing research interest. AlkB homologue 5 (ALKBH5), a key m6A demethylase, has been implicated in cancers and neurological disorders. However, its role in morphine tolerance remains unclear.

Experimental approach: A mouse model of morphine tolerance was established via repeated subcutaneous morphine administration. The m6A methylation levels and related Enzymes expression in the spinal cord were assessed. Functional validation was conducted via adeno-associated virus (AAV)-mediated ALKBH5 overexpression in the spinal dorsal horn. Next-generation Sequencing and GO/KEGG pathway analysis were performed to identify potential downstream target genes, followed by validation via pharmacological inhibition of SGK1.

Key results: Morphine-tolerant mice exhibited significantly elevated spinal m6A methylation, mainly because of reduced ALKBH5 expression in superficial dorsal horn neurons. ALKBH5 overexpression attenuated the development of morphine tolerance and partly restored opioid analgesic efficacy, reducing spinal m6A methylation levels and SGK1 expression. Transcriptomic analysis and subsequent validation identified SGK1-associated immune signalling pathways as a pivotal mediator of morphine tolerance.

Conclusions and implications: Decreased expression of ALKBH5 contributes to elevated spinal m6A methylation and SGK1 expression, promoting morphine tolerance. Targeted overexpression of ALKBH5 mitigates morphine tolerance, most likely through modulation of SGK1-associated immune signalling pathways. These findings suggest that the ALKBH5-m6A-SGK1 axis may participate in the epigenetic modulation of morphine tolerance and provides a promising molecular target for mitigating morphine tolerance.

Keywords
ALKBH5; SGK1; m6A methylation; morphine tolerance; spinal cord.
Products