title: TLR3, TRIF, and caspase 8 determine double-stranded RNA-induced epithelial cell death and survival in vivo.
abstract: TLR3 signaling is activated by dsRNA, a virus-associated molecular pattern. Injection of dsRNA into mice induced a rapid, dramatic, and reversible remodeling of the small intestinal mucosa with significant villus shortening. Villus shortening was preceded by increased caspase 3 and 8 activation and apoptosis of intestinal epithelial cells (IECs) located in the mid to upper villus with ensuing luminal fluid accumulation and diarrhea because of an increased secretory state. Mice lacking TLR3 or the adaptor molelcule TRIF mice were completely protected from dsRNA-induced IEC apoptosis, villus shortening, and diarrhea. dsRNA-induced apoptosis was independent of TNF signaling. Notably, NF-κB signaling through IκB kinase β protected crypt IECs but did not protect villus IECs from dsRNA-induced or TNF-induced apoptosis. dsRNA did not induce early caspase 3 activation with subsequent villus shortening in mice lacking caspase 8 in IECs but instead caused villus destruction with a loss of small intestinal surface epithelium and death. Consistent with direct activation of the TLR3-TRIF-caspase 8 signaling pathway by dsRNA in IECs, dsRNA-induced signaling of apoptosis was independent of non-TLR3 dsRNA signaling pathways, IL-15, TNF, IL-1, IL-6, IFN regulatory factor 3, type I IFN receptor, adaptive immunity, as well as dendritic cells, NK cells, and other hematopoietic cells. We conclude that dsRNA activation of the TLR3-TRIF-caspase 8 signaling pathway in IECs has a significant impact on the structure and function of the small intestinal mucosa and suggest signaling through this pathway has a host protective role during infection with viral pathogens.
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: McAllister
authors.forename: Omar
authors.initials: O
authors.lastname: Lakhdari
authors.forename: Guillaume
authors.initials: G
authors.lastname: Pineton de Chambrun
authors.forename: Mélanie G
authors.initials: MG
authors.lastname: Gareau
authors.forename: Alexis
authors.initials: A
authors.lastname: Broquet
authors.forename: Gin Hyug
authors.initials: GH
authors.lastname: Lee
authors.forename: Steven
authors.initials: S
authors.lastname: Shenouda
authors.forename: Lars
authors.initials: L
authors.lastname: Eckmann
authors.forename: Martin F
authors.initials: MF
authors.lastname: Kagnoff
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000172:deficiency / Q000502:physiology*; D000818:Animals; D053181:Caspase 8 / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000276:immunology* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011070:Poly I-C / Q000633:toxicity*; D012367:RNA, Viral / Q000633:toxicity; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D051196:Toll-Like Receptor 3 / Q000172:deficiency / Q000502:physiology*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D053181:Caspase 8; D011070:Poly I-C; D012367:RNA, Viral; D051196:Toll-Like Receptor 3; C476286:Ticam1 protein, mouse; C519703:TLR3 protein, mouse; C505526:Casp8 protein, mouse