GAS1 Tumor necrosis factor receptors type 1 and 2 differentially regulate intestinal monolayer restitution. (Gastroenterology).

GAS1 TUMOR NECROSIS FACTOR RECEPTORS TYPE 1 AND 2 DIFFERENTIALLY REGULATE INTESTINAL MONOLAYER RESTITUTION. Julissa Corredor, MD, Chistopher Shen, Wei Tong, MD, PhD, Sutha John, MS, and D. Brent Polk, MD. Vanderbilt University Department of Pediatrics/Division of Gastroenterology, Hepatology and Nutrition, Nashville, Tenn.

Disruption in the mucosal lining of the gastrointestinal tract reseals by restitution, a process that involves the migration of linked sheets of mucosal enterocytes across a mucosal defect. Previous studlies in our laboratory have demonstrated a concentration dependent effect of tumor necrosis factor (TNF) on intestinal cell migration. Lower TNF concentrations stimulate migration while higher concentrations inhibit growth factor-stimulated cellular movement. We have also shown that intestinal epithelial cells express both TNF receptors on the cell surface, the TNFR1 and TNFR2, which appear to mediate opposing effects on cellular proliferation. To investigate the hypothesis that TNF regulates intestinal epithelial cell migration by activation of specific receptors, artificial wounds were created in confluent monolayers of the conditionally immortalized mouse small intestinal epithelium (MSIE), young adult mouse colon (YAMC) and the murine TNFR1 -/- colon cell lines. Media containing low dose TNF (100 ng/mL), h igh dose TNF (100 ng/mL), EGF (10 ng/mL) or control was individually added in the presence or absence of: a) TNFR1 receptor agonist polyclonal antibody or b) antagonist polyclonal antibodies to TNFR1 or TNFR2. Wound closure was studied by time-lapse video microscopy. Migration was quantified as the loss of cell free area for each wound compared to the original size at 8 and 24 hours post-wounding. The activating anti-TNFR1 receptor antibody resulted in inhibiting cell migration. TNF-stimulated cell migration was enhanced by low dose TNF in the presence of antagonist anti-TNFR1. Blocking antibodies to TNFR2 inhibited TNF-induced migration, whereas antagonist antibodies to TNFR1 inhibited the anti-migratory effects of high dose TNF. Both low dose TNF and EGF stimulated wound closure in the TNFR1 -/- colon cell line in a similar manner. However, TNF at high doses failed to inhibit EGF-stimulated migration in the absence of TNFR1. In summary, TNFR1 activation inhibits intestinal epithelial cell migration. If only the TNFR2 is activated, the effect is enhanced wound closure. Therefore, TNF differentially regulates intestinal epithelial cell migration by receptor-dependent mechanisms. Enhanced migration at low, physiological concentrations requires only the presence of TNFR2. However, inhibition of growth factor-stimulated migration at higher, pathological concentrations is mediated via TNFR1. These findings suggest a mechanism for disruption of the epithelial restitution process in an environment of high TNF levels present in inflammatory bowel disease.