DNMT3a methylation in neuropathic pain

Abstract

Background

Mu opioid receptor (MOR) plays a crucial role in mediating analgesic effects of opioids and is closely associated with the pathologies of neuropathic pain. Previous studies have reported that peripheral nerve injury downregulates MOR expression, but the epigenetic mechanisms remain unknown.

Objective

Therefore, we investigated DNA methyltransferase3a (DNMT3a) expression or methylation changes within MOR promoter in the spinal cord in a neuropathic pain induced by a chronic constriction injury (CCI) mouse model and further determined whether these injury-associated changes are reversible by pharmacological interventions.

Methods

A CCI mouse model was established and tissue specimens of lumbar spinal cords were collected. The nociception threshold was evaluated by a Model Heated 400 Base. DNMT3a and MOR mRNA and protein level were detected by real-time-polymerase chain reaction and Western blot, respectively. Methylation of DNMT3a gene was measured by methylation-specific PCR.

Results

Our data showed that chronic nerve injury led to a significant upregulation of DNMT3a expression that was associated with increased methylation of MOR gene promoter and decreased MOR protein expression in the spinal cord. Inhibition of DNMT3a catalytic activity with DNMT inhibitor RG108 significantly blocked the increase in methylation of the MOR promoter, and then upregulated MOR expression and attenuated thermal hyperalgesia in neuropathic pain mice.

Conclusion

This study demonstrates that an increase of DNMT3a expression and MOR methylation epigenetically play an important role in neuropathic pain. Targeting DNMT3a to the promoter of MOR gene by DNMT inhibitor may be a promising approach to the development of new neuropathic pain therapy.

Keywords:

• DNMT3A
• pain
• MOR
• RG108
• neuropathic pain

Acknowledgments

This work was supported by the Youth Fund of National Natural Science Foundation of China (grant no. 81100813 to Cuijie Shao), Natural Science Foundation for Colleges and Universities of Jiangsu Education Department (grant no. 11KJB320018 to Cuijie Shao), China Postdoctoral Science Foundation (grant no. 2012M510189 to Cuijie Shao), a Fund of the Qing Lan Project of Jiangsu, Science and Technology Planning Project of Shandong Educational Commission (grant no. J14LL02 to Cuijie Shao), Natural Science Foundation of Shandong Province. (No. ZR2017MH125 to Cuijie Shao), Youth Fund of Affiliated Hospital of Binzhou Medical College (grant no. 2013QNKYJJ09), and the Doctor Startup Fund Program funded by the Affiliated Hospital of Binzhou Medical College. The authors are thankful for the grants, and to Xiao Song for raising the animals, and to Junli Cao, Licai Zhang, and Dan Wang for guiding the experiments.

Author contributions

Cuijie Shao conceived, designed, and performed the experiments. Deqiang Wang guided the experiments. All authors contributed toward data analysis, drafting and critically revising the paper, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.