The enhanced susceptibility of ADAM-17 hypomorphic mice to DSS-induced colitis is not ameliorated by loss of RIPK3, revealing an unexpected function of ADAM-17 in necroptosis

// Johaiber Fuchslocher Chico 1, * , Maren Falk-Paulsen 2, * , Anne Luzius 2 , Carina Saggau 1 , Barbara Ruder 3 , Julia Bolik 4 , Dirk Schmidt-Arras 4 , Andreas Linkermann 5 , Christoph Becker 3 , Philip Rosenstiel 2 , Stefan Rose-John 4 and Dieter Adam 1 1 Institut für Immunologie, Christian-Albrechts-Universität zu Kiel, 24105 Kiel, Germany 2 Institut für Klinische Molekularbiologie, Christian-Albrechts-Universität zu Kiel, 24105 Kiel, Germany 3 Medizinische Klinik 1, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91052 Erlangen, Germany 4 Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany 5 Medizinische Klinik und Poliklinik III, Universitätsklinikum Carl Gustav Carus, 01307 Dresden, Germany * These authors have contributed equally to this work Correspondence to: Dieter Adam, email: dadam@email.uni-kiel.de Keywords: ADAM17; DSS; colitis; RIPK3; necroptosis Received: November 11, 2017 Accepted: January 25, 2018 Published: February 05, 2018 ABSTRACT The disintegrin metalloprotease ADAM17 has a critical role in intestinal inflammation and regeneration in mice, as illustrated by the dramatically increased susceptibility of ADAM17 hypomorphic (ADAM17 ex/ex ) mice to dextran sulfate sodium (DSS)-induced colitis. Similarly, necroptosis has been implicated in inflammatory responses in the intestine. In this study, we have investigated the contribution of necroptosis to ADAM17-regulated intestinal inflammation in vivo by crossing ADAM17 ex/ex mice with mice that lack the necroptotic core protein RIPK3. Despite the loss of RIPK3, ADAM17 ex/ex /RIPK3 -/- mice showed the same increased susceptibility as ADAM17 ex/ex mice in both acute and chronic models of DSS-induced colitis. Mice of both genotypes revealed comparable results with regard to weight loss, disease activity index and colitis-associated changes of inner organs. Histopathological analyses confirmed similar tissue destruction, loss of barrier integrity, immune cell infiltration, and cell death; serum analyses revealed similar levels of the pro-inflammatory cytokine KC. Resolving these unexpected findings, ADAM17 ex/ex mice did not show phosphorylation of RIPK3 and its necroptotic interaction partner MLKL during DSS-induced colitis, although both proteins were clearly expressed. Consistent with these findings, murine embryonic fibroblasts derived from ADAM17 ex/ex mice were protected from tumor necrosis factor (TNF)-induced necroptosis and failed to show phosphorylation of MLKL and RIPK3 after induction of necroptosis by TNF, revealing a novel, undescribed role of the protease ADAM17 in necroptosis.