Effect of Morphine Withdrawal on Gls1 Gene Regulation in IEC18 Cells

Introduction: Inflammatory bowel disease (IBD), referring to two specific diseases: Crohn’s disease and ulcerative colitis, is a condition characterized by chronic inflammation caused by the immune system attacking the GI tract, eventually resulting in damage. The prevalence of IBD within the United States is particularly alarming with about 3.1 million adults having been diagnosed. In addition, IBD is commonly treated with narcotics, an addictive group of drugs with the potential to subject the patient to dependency and neurological implications. A more desirable approach would be to utilize epigenetics, altering gene expression without manipulating the gene sequence, to treat IBD without such implications. One such epigenetic modification of interest is DNA methylation, in which a methyl group is transferred to the carbon 5 position of cytosine by an enzyme called DNA methyltransferase from a compound called S-adenosylmethionine (SAM) already residing in the cell. Usually, methylation observed in a gene leads to its suppression. However, a paradoxical effect is observed when administering trinitrobenzenesulfonic acid (TNBS) to the intraepithelial cells in the colon of the rat where hypermethylation of the glutaminase1 (Gls1) gene results in activation or upregulation. The Gls1 gene codes for GLS1 protein which is the enzyme responsible for converting glutamine to glutamate, a neurotransmitter. In this study, we utilized TNBS to induce inflammation in intestinal epithelial cells (IEC18) of a rat and observe hypermethylation in the Gls1 gene, specifically to replicate findings from previous studies using rats in cell culture. IEC18 cells are present in the outermost layer of the colon, the mucosa layer, and are the most exposed cells to TNBS.

Methods: Intraepithelial cells-18 and BV2 were used in this study. Cells were treated with morphine for three days followed by washing these cells with PBS to mimic withdrawal. Cells were then induced with LPS treatments. Azacytidine is used in this study as a demethylating agent. DNA and RNA were extracted from the treated cells and were analyzed for methylation status of the Gls1 gene.
Results: Morphine withdrawal was unable to modulate Gls1 expression. Morphine withdrawal decreased LPS mediated inflammatory response in IEC18 and BV2 cells.