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A critical role of toll-like receptor 4 (TLR4) and its' in vivo ligands in basal radio-resistance.

Liu C, Zhang C, Mitchel RE, Cui J, Lin J, Yang Y, Liu X, Cai J - Cell Death Dis (2013)

Bottom Line: We found that exposure to radiation leads to significant endotoxemia that also confers endogenous protection from irradiation.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, People's Republic of China.

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.

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Increased mortality in TLR4−/− mice exposed to IR. (a) Survival to day 360 of TLR4+/− mice and TLR4−/− mice without IR in SPF conditions (N=6). (b) TLR4+/− control (N=30) and TLR4−/− (N=18) mice ((TLR4+/− control (N=10) and TLR4−/− (N=6) in each group)) were each randomly divided into three groups and exposed to 5, 7 or 9 Gy 60Co-γ radiation (dose rate: 1 Gy/min). Survival was monitored until day 30 after IR. (c) Linear regression analysis of the survival rate for TLR4−/− mice and TLR4+/− control mice after IR. The equation and the correlation coefficient for the line are given. The calculated DRF using these equations was 1.5 (TLR4+/− mice versus TLR4−/− mice). Blue circles: TLR4+/− mice and red squares: TLR4−/− mice; *P<0.05.
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fig1: Increased mortality in TLR4−/− mice exposed to IR. (a) Survival to day 360 of TLR4+/− mice and TLR4−/− mice without IR in SPF conditions (N=6). (b) TLR4+/− control (N=30) and TLR4−/− (N=18) mice ((TLR4+/− control (N=10) and TLR4−/− (N=6) in each group)) were each randomly divided into three groups and exposed to 5, 7 or 9 Gy 60Co-γ radiation (dose rate: 1 Gy/min). Survival was monitored until day 30 after IR. (c) Linear regression analysis of the survival rate for TLR4−/− mice and TLR4+/− control mice after IR. The equation and the correlation coefficient for the line are given. The calculated DRF using these equations was 1.5 (TLR4+/− mice versus TLR4−/− mice). Blue circles: TLR4+/− mice and red squares: TLR4−/− mice; *P<0.05.

Mentions: We next studied the radio-sensitivity difference between different mouse genotypes. We exposed age- and sex-matched TLR4−/− mice and TLR4+/− mice to 0, 5, 7 and 9 Gy of γ-radiation. However, as TLR4−/− mice showed normal survival ability without radiation and can survive over a year under specific pathogen-free (SPF) conditions (Figure 1a), these animals showed severe mortality and morbidity after γ-irradiation (Figure 1b). Although TLR4+/− mice had 100% survival rate at the dose of 5 Gy, but TLR4−/− mice only had a survival rate of 60% (P<0.05). Consistent with the observed differences after 5 Gy, TLR4−/− mice also showed more mortality than TLR4+/− mice after 7 or 9 Gy (Figure 1b). Regression analysis of the radiation survival data produced LD50/LD30 values of 7.5 Gy for the TLR4+/− mice, and 5.7 Gy for the TLR4−/− mice. The calculated dose-reduction factor (DRF) was 1.32 (TLR4+/− mice versus TLR4−/− mice) (Figure 1c). Consistent with the observed differences in survival, TLR4−/− mice showed much more severe morbidity and weight loss with the TLR4+/− controls (Supplementary Figures S2A and S2B). In addition, throughout the duration of the experiment, 5 Gy exposed TLR4−/− animals were observed to be moribund, with a paralyzed posture and defective drinking and eating desire as opposed to 5 Gy exposed TLR4+/− mice, which remained active, mobile and seemingly healthy (Supplementary Figure S2C). To further support a role for TLR4 in radio-protection in vivo, we also performed a TLR4 in vivo knockdown (KD) assay in C57BL/10 mice. We found that mice injected with the TLR4 specific in vivo KD reagents displayed severe motility after 7 Gy compared to mice injected with the non-specific control in vivo KD reagents (Supplementary Figures S3A and S3B). These data, taken together, indicated that mice deficient in TLR4 were more susceptible to radiation-induced mortality and morbidity.


A critical role of toll-like receptor 4 (TLR4) and its' in vivo ligands in basal radio-resistance.

Liu C, Zhang C, Mitchel RE, Cui J, Lin J, Yang Y, Liu X, Cai J - Cell Death Dis (2013)

Increased mortality in TLR4−/− mice exposed to IR. (a) Survival to day 360 of TLR4+/− mice and TLR4−/− mice without IR in SPF conditions (N=6). (b) TLR4+/− control (N=30) and TLR4−/− (N=18) mice ((TLR4+/− control (N=10) and TLR4−/− (N=6) in each group)) were each randomly divided into three groups and exposed to 5, 7 or 9 Gy 60Co-γ radiation (dose rate: 1 Gy/min). Survival was monitored until day 30 after IR. (c) Linear regression analysis of the survival rate for TLR4−/− mice and TLR4+/− control mice after IR. The equation and the correlation coefficient for the line are given. The calculated DRF using these equations was 1.5 (TLR4+/− mice versus TLR4−/− mice). Blue circles: TLR4+/− mice and red squares: TLR4−/− mice; *P<0.05.
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fig1: Increased mortality in TLR4−/− mice exposed to IR. (a) Survival to day 360 of TLR4+/− mice and TLR4−/− mice without IR in SPF conditions (N=6). (b) TLR4+/− control (N=30) and TLR4−/− (N=18) mice ((TLR4+/− control (N=10) and TLR4−/− (N=6) in each group)) were each randomly divided into three groups and exposed to 5, 7 or 9 Gy 60Co-γ radiation (dose rate: 1 Gy/min). Survival was monitored until day 30 after IR. (c) Linear regression analysis of the survival rate for TLR4−/− mice and TLR4+/− control mice after IR. The equation and the correlation coefficient for the line are given. The calculated DRF using these equations was 1.5 (TLR4+/− mice versus TLR4−/− mice). Blue circles: TLR4+/− mice and red squares: TLR4−/− mice; *P<0.05.
Mentions: We next studied the radio-sensitivity difference between different mouse genotypes. We exposed age- and sex-matched TLR4−/− mice and TLR4+/− mice to 0, 5, 7 and 9 Gy of γ-radiation. However, as TLR4−/− mice showed normal survival ability without radiation and can survive over a year under specific pathogen-free (SPF) conditions (Figure 1a), these animals showed severe mortality and morbidity after γ-irradiation (Figure 1b). Although TLR4+/− mice had 100% survival rate at the dose of 5 Gy, but TLR4−/− mice only had a survival rate of 60% (P<0.05). Consistent with the observed differences after 5 Gy, TLR4−/− mice also showed more mortality than TLR4+/− mice after 7 or 9 Gy (Figure 1b). Regression analysis of the radiation survival data produced LD50/LD30 values of 7.5 Gy for the TLR4+/− mice, and 5.7 Gy for the TLR4−/− mice. The calculated dose-reduction factor (DRF) was 1.32 (TLR4+/− mice versus TLR4−/− mice) (Figure 1c). Consistent with the observed differences in survival, TLR4−/− mice showed much more severe morbidity and weight loss with the TLR4+/− controls (Supplementary Figures S2A and S2B). In addition, throughout the duration of the experiment, 5 Gy exposed TLR4−/− animals were observed to be moribund, with a paralyzed posture and defective drinking and eating desire as opposed to 5 Gy exposed TLR4+/− mice, which remained active, mobile and seemingly healthy (Supplementary Figure S2C). To further support a role for TLR4 in radio-protection in vivo, we also performed a TLR4 in vivo knockdown (KD) assay in C57BL/10 mice. We found that mice injected with the TLR4 specific in vivo KD reagents displayed severe motility after 7 Gy compared to mice injected with the non-specific control in vivo KD reagents (Supplementary Figures S3A and S3B). These data, taken together, indicated that mice deficient in TLR4 were more susceptible to radiation-induced mortality and morbidity.

Bottom Line: We found that exposure to radiation leads to significant endotoxemia that also confers endogenous protection from irradiation.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, People's Republic of China.

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.

Show MeSH
Related in: MedlinePlus