A20 is critical for protection of the intestinal epithelium from LPS or TNF induced apoptosis

Abstract

Backgromtd/Aims: A20 is an important regulator of TNF induced NF-kB activity, and programmed cell death. Mice deficient for A20 develop colitis The aim of this stud}, was to determine whether A20 plays a role in the regulation of TNF induced NF*kB acti~ W and apoptosis in the intestinal epithelnim Methods: Young adult mouse colonocytes (YAMC), from a conditionally immortalized murine colonic epithelial cell line, were treated with TNF. A20 mRNA and protein expression induced TNF in YAMC cells were assessed by' Northern and Western analysis, respectivdy. TNF-induced NF-kB in YAMC cells was assessed dectrophoretic mobility shiR assay. Wildwpe (wt) and A20-/mice (generated gene targeting) were m/ected with lipopolysaccharide (LPS) or TNF intraperitoneally. The developmere of enteritis and intestinal epithelial cell apoptos~s in these mice were evaluated histology and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphae rock end-labeling (2LINED method. Resuhs: A20 mRNA and protein expression in YAMC ceils were induced by TNF. YAMC ceils responded to TNF by' activating and terminating NF-kB activity. These results suggest that A20 is expressed in mouse intestinal epithelkal cells (IEC) and regulates TNF niduced NF-kB activity in YAMC cells. A20G mice died within 2 hours of injection of either EPS or TNF, where as wt mice survived. A204mice that were treated with LPS or TNF developed severe enteritis with marked intestinal epithehal cell exfoliations. There was a tremendous increase in the number of apoptotic IEC demonstrated in both histology and TUNEr. staining, lntraepithehal lymphocytes may' have an ~mplication on the 1EC apoptosis. However, double mutant A20-/recombinase-activating gene-1 deficient (RAG-i-/-) mice lacking all matm'e lymphocytes also developed severe emerins with marked 1EC apoptosts and died within 2 hours after LPS injection. Conclusions: A20 is expressed in IEC and is cntical for protecting the intestinal epithelium trom LPS or TNF induced enteritis. The protection of the intestinal epithelium A20 may be importam for the prevention of IBD