TLR4-KO Mice Research Articles

Toll-like receptor 2 represses nonpilus adhesin-induced signaling in acute infections with the Pseudomonas aeruginosa pilA mutant.

Expression of pili and associated proteins is an important means of host invasion by bacterial pathogens. Recent evidence has suggested that the binding of Pseudomonas aeruginosa through nonpilus adhesins may also be important in respiratory diseases, since adhesins bind mucins. Using wild-type C57BL/6 and TLR2KO mice, we compared the induction levels of the host response to P. aeruginosa that either expressed pili or lacked pilus expression due to a mutation in the structural gene pilA. In C57BL/6 mice, deletion of pili led to a decreased immune response, evidenced by a lower secretion of cytokines and a lack of neutrophil chemotaxis. By contrast, the P. aeruginosa pilA mutant induced a hyperresponsive phenotype in TLR2KO mice. TLR2KO mice showed an increased number of neutrophils in lavage fluid compared to the levels seen when either mouse strain was exposed to wild-type P. aeruginosa. Further analysis indicated that the increased neutrophil influx was associated with an increased expression of calgranulins, possibly through an induction of Toll-like receptor 4 (TLR4) expression. The hyperresponsive phenotype of TLR2KO mice exposed to the P. aeruginosa pilA mutant was associated with TLR4 induction and indicated that nonpilus adhesin-induced signaling was repressed by TLR2 function and, if not blocked by the host, could induce airway hyperresponsiveness.

エンドトキシン不応答性ノックアウトマウスの作製と解析

Toll in Drosophila is a receptor that is required for dorsoventral polarity during development, and also involved in host defence against fungal infection. Recently, mammalian homologues of Toll, designated as Toll-like receptors (TLRs) have been identified. The TLR family harbors an extracellular leucine-rich repeat (LRR) domain and a cytoplasmic domain that is homologous to that of the IL-1R family. Analogous to the IL-1R, TLR recruits IRAK via adaptor MyD88, and then induces activation of TRAF6, NIK and finally NF-κB.In order to examine the role of TLR family, we have generated mice lacking TLR2, TLR4, and MyD88. TLR4 KO mice are hyporesponsive to LPS. On the other hand, TLR2 KO mice are hyporesponsive to peptidoglycan from gram-positive bacteria, but not to LPS. MyD88 KO mice are unresponsive to LPS. Taken together, these results demonstrate that responses to bacterial cell wall components are differentially mediated by TLR2 and TLR4, and that LPS signaling is mediated by TLR4 via MyD88.

Iliac crest periosteum responds to the level of physical activity in human adults

The aim of this study was to characterize the formation and progression of experimentally induced periapical lesions in TLR2 knockout (TLR2 KO) mice.Periapical lesions were induced in molars of 28 wild type (WT) and 27 TLR2 KO mice. After 7, 21, and 42 days, the animals were euthanized, and the mandibles were subjected to histotechnical processing. Hematoxylin-eosin–stained sections were examined under conventional light microscopy for the description of pulpal, apical, and periapical features and under fluorescence microscopy for the determination of the periapical lesion size. The subsequent sections were evaluated by tartrate resistant acid phosphatase histoenzymology (osteoclasts), Brown and Brenn staining (bacteria), and immunohistochemistry (RANK, RANKL, and OPG). Data were analyzed by the Mann-Whitney U and Kruskal-Wallis tests (α = 0.05).The WT group showed significant differences (P < .05) in the periapical lesion size and the osteoclast number between 7 and 42 days and between 21 and 42 days. In the TLR2 KO group, significant differences (P < .05) in the periapical lesion size and the osteoclast number were found between 7 days and the other periods. There was a significant difference (P < .05) between the 2 types of animal regarding the periapical lesion size, which was larger in the TLR2 KO animals. No significant differences (P > .05) were found between WT and TLR2 KO mice related to the pulpal, apical, and periapical features; bacteria localization; and immunohistochemical results (except for RANK expression).TLR2 KO animals developed larger periapical lesions with a greater number of osteoclasts, indicating the important role of this receptor in the host's immune and inflammatory response to root canal and periradicular infection.