Contribution of DNMT1 to neuropathic pain genesis partially through epigenetically repressing Kcna2 in primary afferent neurons

Expressional changes of pain-associated genes in primary sensory neurons of dorsal root ganglion (DRG) are critical for neuropathic pain genesis. DNA methyltransferase (DNMT)-triggered DNA methylation silences gene expression. We show here that DNMT1, a canonical maintenance methyltransferase, acts as the de novo DNMT and is required for neuropathic pain genesis likely through repressing at least DRG Kcna2 gene expression in male mice. Peripheral nerve injury upregulated DNMT1 expression in the injured DRG through the transcription factor cAMP response element binding protein-triggered transcriptional activation of Dnmt1 gene. Blocking this upregulation prevented nerve injury-induced DNA methylation within the promoter and 5′-untranslated region of Kcna2 gene, rescued Kcna2 expression and total Kv current, attenuated hyperexcitability in the injured DRG neurons, and alleviated nerve injury-induced pain hypersensitivities. Given that Kcan2 is a key player in neuropathic pain, our findings suggest that DRG DNMT1 may be a potential target for neuropathic pain management. Significance Statement In the present study, we reported that DNMT1, a canonical DNA maintenance methyltransferase, is upregulated via the activation of the transcription factor CREB in the injured DRG after peripheral nerve injury. This upregulation was responsible for nerve injury-induced de novo DNA methylation within the promoter and 5′-untranslated region of the Kcna2 gene, reductions in Kcna2 expression and Kv current and increases in neuronal excitability in the injured DRG. Since pharmacological inhibition or genetic knockdown of DRG DNMT1 alleviated nerve injury-induced pain hypersensitivities, DRG DNMT1 contributes to neuropathic pain genesis partially through repression of DRG Kcna2 gene expression.