TLR3 and TLR9 mRNA expression is impaired in macrophages from severely burned mice (44.31)

Abstract

Abstract Classically activated Mϕ (CAMϕ) are not generated in mice with severe burn injuries even when they are stimulated with a mixture of poly I:C and CpG DNA (well-known inducers for CAMϕ). To investigate why the Mϕ conversion from burn mouse-derived Mϕ to CAMϕ was not induced after stimulation with a mixture of poly I:C and CpG DNA, the expression of receptors for poly I:C (TLR3) and CpG DNA (TLR9) in burn mouse-derived Mϕ were examined. BALB/c mice exposed to a flame burn injury (3rd degree, 25% TBSA burns) were used for these studies. Mϕ were prepared from the peritoneal cavities of mice 6, 24, 48, 120 and 168 hrs after burn injury using magnetic beads coated with anti-F4/80 mAb. Peritoneal Mϕ from unstimulated normal mice were utilized as a control. Then, Mϕ preparations obtained were analyzed for TLR3 and TLR9 mRNA expression using RT-PCR. In the results, TLR3 and TLR9 mRNAs were shown to be expressed by Mϕ from normal mice. However, TLR3 mRNA expression was not demonstrated in Mϕ from mice 6 to 168 hrs after burn injury. TLR9 mRNA expression was strongly impaired in Mϕ from mice 6 hrs after burn injury, and then it gradually recovered until 120 hrs after burn injury. These results indicate that burn mouse-derived Mϕ are shown to not be a carrier of TLR3 and TLR9. The unresponsiveness of burn mouse-derived Mϕ to the CAMϕ inducers may be related to the impaired expression of TLR3 and TLR9 that are receptors for poly I:C and CpG DNA, respectively. This study was supported by SHC NA #8550.