Expression of acetyl-histone H3 and acetyl-histone H4 in dorsal root ganglion and spinal dorsal horn in rat chronic pain models.

AIMS: Histone acetylation and deacetylation are two histone posttranslational modifications that are usually controlled by histone acetyltransferases (HATs) and histone deacetylases (HDACs). Although HATs or HDACs Inhibitors could relieve pain hypersensitivities in chronic pain animal models, it is not clear on the expression of global histone acetylation in the dorsal root ganglion (DRG) or spinal dorsal horn in chronic pain conditions.

MAIN METHODS: A spinal nerve ligation (SNL)-induced neuropathic pain model and a complete Freund's adjuvant (CFA)-induced inflammatory pain model in rats were used to examine the expression of total acetyl-histone H3 (AcH3) and total acetyl-histone H4 (AcH4) by immunofluorescence or western blot.

KEY FINDINGS: AcH3 and AcH4 not only localized in neuronal nuclei, but also in nuclei of glial cells in the DRG. Unilateral SNL induced the increase of AcH3 and AcH4 expression in the injured lumbar 5 (L5) DRG, but not in the uninjured L5 DRG or the spinal dorsal horn, while unilateral intraplantar injection of CFA increased AcH3 and AcH4 expression in the ipsilateral L4/5 spinal dorsal horn, but not in the L4/5 DRG.

SIGNIFICANCE: These results provide morphological evidence for global histone acetylation expression in the DRG and spinal cord and indicate the differential expression in the DRG and spinal dorsal horn in different chronic pain models. More precise epigenetic mechanisms of histone acetylation on the target genes need to be revealed.