Traumatic stress-induced persistent changes in DNA methylation regulate neuropeptide Y expression in rat jejunum

Abstract

Background

Stress-induced chronic neuropsychiatric conditions such as anxiety are often co-morbid with gastrointestinal malfunctions. While we find enduring anxiety-like symptoms following minimal traumatic brain injury (MTBI) in rats, gastrointestinal consequences of MTBI remain elusive.

Methods

In this study, we examined the effects of MTBI on a major gut peptide, neuropeptide Y (NPY) and gut motility. DNA methylation was studied as a possible epigenetic mechanism operative in the regulation of NPY expression in the gut.

Key Results

Minimal traumatic brain injury reduced the gut motility 48 hours and 30 days after trauma. The expression of DNA methyltransferase isoforms (DNMT1, DNMT3a, and DNMT3b) was altered in the jejunum 48 hours and 30 days after MTBI. However, the mRNA levels of growth arrest and DNA damage 45 (GADD45) isoforms, GADD45a, and GADD45b, which are believed to be involved in active DNA demethylation, initially decreased at 48 hours but subsequently increased after 30 days of trauma. Similarly, DNA hypomethylation at the NPY promoter region in the jejunum was correlated with the increase in NPY mRNA and protein levels 30 days post-trauma. On the other hand, DNA hypomethylation at 48 hours was associated with a decline in NPY expression. Treatment with 5-azacytidine (5-AzaC), a DNMT inhibitor, retarded DNA methylation and restored the NPY mRNA levels in the jejunum of MTBI-induced rats.

Conclusions & Inferences

These results suggest that DNA demethylation could be operative as an epigenetic mechanism in the long-term regulation of NPY gene expression to alter the gut motility during traumatic stress.

This study investigates the role of DNA methylation in long-lasting changes in trauma-induced neuropeptide Y (NPY) expression in the jejunum and gut motility. The persistent alterations in DNA methylation at the NPY gene promoter due to minimal traumatic brain injury (MTBI) plausibly increased NPY levels resulting into weakened gut motility. Therefore, the novel results of this study implicate DNA methylation as an epigenetic mechanism involved in the regulation of NPY expression in the gut and further suggest it as a therapeutic target for the trauma-induced gut functions.

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