Glutathione S-transferase theta 1 modulates intestinal inflammation via interleukin-22 mediated goblet cell differentiation

Abstract

The glutathione S-transferases (GSTs) are a multigene family of enzymes importantly involved in detoxification, including reactive oxygen species (ROS). Furthermore, several members of GST superfamily were found to be partially associated with tyrosine kinases. In this study, I investigated the genetic association of glutathione S-transferase theta 1 (GSTT1) gene with susceptibility of intestinal Behçet’s disease (intestinal BD) and elucidated its role in colitis development based on that not only oxidative stress but also cytokine receptor pathways might be key contributors to the pathogenesis of inflammatory bowel disease (IBD) and intestinal BD. First I found the ratio of a single nucleotide polymorphism (SNP) rs17856199 was observed to be significantly different in intestinal BD patients using genome-wide association study (GWAS). For phenotypic study on GSTT1 in colitis, I confirmed decreased expression of GSTT1 in tissues from IBD and intestinal BD patients than control patients, and verified the attenuation of acute colitis and goblet cell hyperplasia through gene transfer of Gstt1 to mouse colo-rectal or intra-peritoneal pathway to dextran sodium sulfate (DSS)-induced colitis model using wild-type mice with genes mixed in polyethyleneimine transfection solution-containing sterile PBS solution. In order to determine the function of GSTT1 in colitis, I performed in vitro experiments using human colorectal adenocarcinoma cell line HT-29 and short-interfering RNA (siRNA) and found that genes essential for innate defense response such as Mucin 2 (MUC2) or Cathelicidin antimicrobial peptide (CAMP), are interestingly related with the existence of GSTT1. Another investigation using a knock-out cell line constructed by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system 9 (Cas9) gene knock-out system which is similar to rs17856199 mutation, diminished dimerization followed by the change dramatically connected to the insufficient phosphorylation of signal transducer and activator of transcription 3 (STAT3) and p38/mitogen-activated protein kinase (p38/MAPK) when stimulated by their common activator, recombinant human interleukin-22 (rhIL–22). In conclusion, GSTT1 in intestinal epithelial cells contributes as a modulator of phosphorylation of STAT3 and p38/MAPK in goblet cells in response to IL–22 through their homo-dimerization and a specific SNP mutation rs17856199 is attributed to the chronic intestinal inflammation due to its insufficient dimerization and following decreased phosphorylation of STAT3 and p38/MAPK.