[HTML][HTML] RIPK1 regulates RIPK3-MLKL-driven systemic inflammation and emergency hematopoiesis

JA Rickard, JA O'Donnell, JM Evans, N Lalaoui… - Cell, 2014 - cell.com
JA Rickard, JA O'Donnell, JM Evans, N Lalaoui, AR Poh, TW Rogers, JE Vince, KE Lawlor
Cell, 2014cell.com
Upon ligand binding, RIPK1 is recruited to tumor necrosis factor receptor superfamily
(TNFRSF) and Toll-like receptor (TLR) complexes promoting prosurvival and inflammatory
signaling. RIPK1 also directly regulates caspase-8-mediated apoptosis or, if caspase-8
activity is blocked, RIPK3-MLKL-dependent necroptosis. We show that C57BL/6 Ripk1−/−
mice die at birth of systemic inflammation that was not transferable by the hematopoietic
compartment. However, Ripk1−/− progenitors failed to engraft lethally irradiated hosts …
Summary
Upon ligand binding, RIPK1 is recruited to tumor necrosis factor receptor superfamily (TNFRSF) and Toll-like receptor (TLR) complexes promoting prosurvival and inflammatory signaling. RIPK1 also directly regulates caspase-8-mediated apoptosis or, if caspase-8 activity is blocked, RIPK3-MLKL-dependent necroptosis. We show that C57BL/6 Ripk1−/− mice die at birth of systemic inflammation that was not transferable by the hematopoietic compartment. However, Ripk1−/− progenitors failed to engraft lethally irradiated hosts properly. Blocking TNF reversed this defect in emergency hematopoiesis but, surprisingly, Tnfr1 deficiency did not prevent inflammation in Ripk1−/− neonates. Deletion of Ripk3 or Mlkl, but not Casp8, prevented extracellular release of the necroptotic DAMP, IL-33, and reduced Myd88-dependent inflammation. Reduced inflammation in the Ripk1−/−Ripk3−/−, Ripk1−/−Mlkl−/−, and Ripk1−/−Myd88−/− mice prevented neonatal lethality, but only Ripk1−/−Ripk3−/−Casp8−/− mice survived past weaning. These results reveal a key function for RIPK1 in inhibiting necroptosis and, thereby, a role in limiting, not only promoting, inflammation.
cell.com