title: A critical role of toll-like receptor 4 (TLR4) and its' in vivo ligands in basal radio-resistance.
abstract: Toll-like receptor-4 (TLR4) plays a critical role in innate and acquired immunity, but its role in radio-resistance is unknown. We used TLR4 knockout (KO,(-/-)) mice and gut commensal depletion methods, to test the influence of TLR4 and its' in vivo agonist on basal radio-resistance. We found that mice deficient in TLR4 were more susceptible to IR-induced mortality and morbidity. Mortality of TLR4-deficient mice after IR was associated with a severe and persistent bone marrow cell loss. Injection of lipopolysaccharide into normal mice, which is known to activate TLR4 in vivo, induced radio-resistance. Moreover, TLR4 in vivo ligands are required for basal radio-resistance. We found that exposure to radiation leads to significant endotoxemia that also confers endogenous protection from irradiation. The circulating endotoxins appear to originate from the gut, as sterilization of the gut with antibiotics lead to increased mortality from radiation. Further data indicated that Myd88, but not TRIF, may be the critical adaptor in TLR4-induced radio-resistance. Taken together, these data strongly suggest that TLR4 plays a critical role in basal radio-resistance. Our data suggest, it is important not to give antibiotics that may sterilize the gut before the whole body irradiation. Further, these data also suggest that management of gut flora through antibiotic or possibly probiotic therapy may alter the innate response to the total body irradiation.
authors.affiliation: Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, People's Republic of China.
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: R E J
authors.initials: RE
authors.lastname: Mitchel
authors.forename: J
authors.initials: J
authors.lastname: Cui
authors.forename: J
authors.initials: J
authors.lastname: Lin
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Cai
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001854:Bone Marrow Cells / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D011836:Radiation Tolerance; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D008024:Ligands; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D051197:Toll-Like Receptor 4; C507780:Myd88 protein, mouse; C476286:Ticam1 protein, mouse; C493487:Tlr4 protein, mouse