Epithelial Cell-Derived a Disintegrin and Metalloproteinase-17 Confers Resistance to Colonic Inflammation Through EGFR Activation

Epithelial regeneration is a key process for the recovery from ulcerative colitis (UC). Here we demonstrate that a disintegrin and metalloproteinase-17 (ADAM17), a main sheddase for tumor necrosis factor (TNF)-α, is essential for defensive epithelial properties against UC by promoting epithelial cell growth and goblet cell differentiation in mouse and human. Mice with systemic deletion of Adam17 developed severe dextran sulfate sodium-induced colitis when compared to mice with myeloid cell Adam17 deletion or control littermates. ADAM17 was predominantly expressed by regenerating epithelia in control mice, and its loss or inhibition attenuated epidermal growth factor receptor (EGFR) activation, epithelial proliferation, mucus production and barrier functions. Conversely, ectopic EGFR stimulation promoted epithelial regeneration thereby partially rescuing the severe colitis caused by ADAM17 deficiency. In UC patients, epithelial ADAM17 expression positively correlated with both cell proliferation and goblet cell number. These findings suggest that maintaining ADAM17–EGFR epithelial signaling is necessary for the recovery from UC and would be beneficial to therapeutic strategies targeting ADAM17-mediated TNF-α shedding.

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Mice with systemic deletion of ADAM17, but not with its myeloid cell-specific deficiency, are more sensitive to colitis.

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ADAM17-EGFR axis promotes repair processes through epithelial cell proliferation and goblet cell differentiation.

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Epithelial ADAM17 expression correlates with cell growth and mucus production in ulcerative colitis patients.

Epithelial regeneration is a key process for the recovery from ulcerative colitis (UC). We now demonstrate that a disintegrin and metalloproteinase-17 (ADAM17) is essential for defensive epithelial properties against UC by driving repair processes in mouse and human. During colonic inflammation, ADAM17 is up-regulated in regenerating epithelia, and its loss or inhibition attenuated epidermal growth factor receptor (EGFR) activation, epithelial proliferation, mucus production and barrier functions. These findings suggest that maintaining ADAM17–EGFR epithelial signaling is necessary for the recovery from UC and would be beneficial to therapeutic strategies targeting ADAM17-mediated tumor necrosis factor-α shedding.

Long-term Branched Chain Amino Acid Supplementation Ameliorates Diethylnitrosamine-induced Liver Glutathione S-transferase-p Positivity in Zucker Fatty Rats

BACKGROUND

Obesity increases the risk of fatty liver disease and liver cancer. There are several models of obesity-associated hepatocellular carcinoma, but tumor development in these models is slow.

MATERIALS AND METHODS

We investigated Zucker fatty rats, a model of obesity and insulin resistance, to discover if diethylnitrosamine (DEN), a potent liver carcinogen, might enhance liver carcinogenesis. We also investigated the effect of branched chain amino acids (BCAA) against the development of liver cancer.

RESULTS

Incidence and number of hepatocellular carcinomas and adenomas were significantly greater in DEN-treated Zucker fatty rats than in DEN-treated lean rats. All treated Zucker fatty rats developed hepatocellular carcinoma within 16 weeks. Long-term BCAA supplementation significantly reduced expression of CyclinD1, PCNA, thymidine kinase, Bcl-2, and GST-p and increased expression of p21 in the liver. Furthermore, BCAA treatment significantly reduced the area of GST-p positive foci.

CONCLUSION

Long-term BCAA treatment may induces cell cycle arrest and apoptotic induction, thus suppressing pre-neoplastic lesions.