Lertpiriyapong, K. | bioRxiv Science

bioRxiv2018

TDAG8 (GPR65) Inhibits Intestinal Inflammation in the DSS-Induced Experimental Colitis Mouse Model

T cell death-associated gene 8 (TDAG8, also known as GPR65) is a proton-sensing G protein-coupled receptor (GPCR) predominantly expressed in immune cells. Genome-wide association studies identify TDAG8 as a susceptibility candidate gene linked to several human inflammatory diseases including inflammatory bowel disease (IBD), asthma, spondyloarthritis, and multiple sclerosis. In this study, our results demonstrate that mice deficient of TDAG8 exhibited more severe inflammatory phenotypes than wild-type mice in a chronic dextran sulfate sodium (DSS)-induced colitis mouse model. Several disease parameters, such as diarrhea, colon shortening, fibrosis, histopathological score, and mesenteric lymph node enlargement were aggravated in TDAG8-null mice in comparison to wild-type mice treated with DSS. Increased leukocyte infiltration and myofibroblast expansion were observed in colonic tissues of DSS-treated TDAG8-null mice. These changes may represent a cellular basis of the observed exacerbation of intestinal inflammation and fibrosis in these mice. In line with high expression of TDAG8 in infiltrated leukocytes, real-time RT-PCR revealed that TDAG8 mRNA expression was increased in inflamed intestinal tissue samples of IBD patients when compared to normal intestinal tissues. Altogether, our data demonstrate that TDAG8 suppresses intestinal inflammation and fibrosis in the chronic DSS-induced colitis mouse model, suggesting potentiation of TDAG8 with agonists may have anti-inflammatory therapeutic effects in IBD.

pathology↗

bioRxiv2017

Contextual Tumor Suppressor Function Of T Cell Death-Associated Gene 8 (TDAG8) In Hematological Malignancies

Key points1. TDAG8 (GPR65) gene expression is down-regulated in hematological malignancies.\n\n2. Restoration of TDAG8 gene expression in blood cancer cells suppresses tumor growth and metastasis.\n\nAbstractExtracellular acidosis is a condition found within the tumor microenvironment due to inadequate blood perfusion, hypoxia, and altered tumor cell metabolism. Acidosis has pleiotropic effects on malignant progression; therefore it is essential to understand how acidosis exerts its diverse effects. In this study a bioinformatics analysis revealed the expression of the proton sensing G-protein-coupled receptor TDAG8 is significantly reduced in human blood cancers in comparison to normal blood cells. To understand how TDAG8 functions in hematological malignancies, TDAG8 expression was restored in U937 acute myeloid leukemia cells and other blood cancer cells. It was discovered that severe acidosis, pH 6.4, inhibited U937 cell proliferation while mild acidosis, pH 6.9, stimulated cell proliferation. However, restoring TDAG8 gene expression modulated the U937 cell response to mild extracellular acidosis and physiological pH by reducing cell proliferation. Tumor xenograft experiments further revealed that restoring TDAG8 expression in U937 and Ramos cancer cells reduced tumor growth. It was also shown U937 cells with restored TDAG8 expression attached less to Matrigel, migrated slower toward a chemoattractant, and metastasized less in severe combined immunodeficient mice. These effects correlated with a reduction in c-myc oncogene expression. The mechanistic investigation indicated that G13/RhoA signaling arbitrated the TDAG8-mediated c-myc oncogene repression in response to acidosis. Overall, this study provides compelling data to support the concept that TDAG8 functions as a contextual tumor suppressor in hematological malignancies and sensitizes blood cancer cells to acidotic stress.

cancer biology↗