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Toll-like receptor 4 signaling in T cells promotes autoimmune inflammation.

ABSTRACT: Toll-like receptors (TLRs) are critical components of innate immunity and function as rapid pathogen sensors. TLR4 is expressed on CD4(+) T cells as well, the functional significance of which is unclear. In this study, we analyzed the function of TLR4 in T cells but did not find a role in promoting T helper (Th) cell polarization. Instead, TLR4 ligation enhanced both CD4(+) T-cell proliferation and survival in vitro. Using the experimental autoimmune encephalomyelitis (EAE) model, we found that the loss of TLR4 solely in CD4(+) T cells almost completely abrogated disease symptoms, mainly through blunted Th17 and, to a lesser degree, Th1 responses. Moreover, Tlr4(-/-) ?? T cells were defective in IL-17 and IFN-? production following EAE induction. This study supports an important role of this innate receptor in the direct regulation of T-cell activation and survival during autoimmune inflammation.

SUBMITTER: Reynolds JM

PROVIDER: S-EPMC3420161 | biostudies-other | 2012 Aug

REPOSITORIES: biostudies-other

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Toll-like receptor 4 signaling in T cells promotes autoimmune inflammation.

Reynolds Joseph M JM Martinez Gustavo J GJ Chung Yeonseok Y Dong Chen C

Proceedings of the National Academy of Sciences of the United States of America 20120723 32

Toll-like receptors (TLRs) are critical components of innate immunity and function as rapid pathogen sensors. TLR4 is expressed on CD4(+) T cells as well, the functional significance of which is unclear. In this study, we analyzed the function of TLR4 in T cells but did not find a role in promoting T helper (Th) cell polarization. Instead, TLR4 ligation enhanced both CD4(+) T-cell proliferation and survival in vitro. Using the experimental autoimmune encephalomyelitis (EAE) model, we found that ...[more]

PMID: 22826216

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Project description:Bruton's tyrosine kinase (Btk) is a signaling molecule involved in development and activation of B cells through B-cell receptor (BCR) and Toll-like receptor (TLR) signaling. We have previously shown that transgenic mice that overexpress human Btk under the control of the CD19 promoter (CD19-hBtk) display spontaneous germinal center formation, increased cytokine production, anti-nuclear autoantibodies (ANAs), and systemic autoimsmune disease upon aging. As TLR and BCR signaling are both implicated in autoimmunity, we studied their impact on splenic B cells. Using phosphoflow cytometry, we observed that phosphorylation of ribosomal protein S6, a downstream Akt target, was increased in CD19-hBtk B cells following BCR stimulation or combined BCR/TLR stimulation, when compared with wild-type (WT) B cells. The CD19-hBtk transgene enhanced BCR-induced B cell survival and proliferation, but had an opposite effect following TLR9 or combined BCR/TLR9 stimulation. Although the expression of TLR9 was reduced in CD19-hBtk B cells compared to WT B cells, a synergistic effect of TLR9 and BCR stimulation on the induction of CD25 and CD80 was observed in CD19-hBtk B cells. In splenic follicular (Fol) and marginal zone (MZ) B cells from aging CD19-hBtk mice BCR signaling stimulated in vitro IL-10 production in synergy with TLR4 and particularly TLR9 stimulation, but not with TLR3 and TLR7. The enhanced capacity of CD19-hBtk Fol B cells to produce the pro-inflammatory cytokines IFNγ and IL-6 compared with WT B cells was however not further increased following in vitro BCR or TLR9 stimulation. Finally, we used crosses with mice deficient for the TLR-associated molecule myeloid differentiation primary response 88 (MyD88) to show that TLR signaling was crucial for spontaneous formation of germinal centers, increased IFNγ, and IL-6 production by B cells and anti-nuclear autoantibody induction in CD19-hBtk mice. Taken together, we conclude that high Btk expression does not only increase B cell survival following BCR stimulation, but also renders B cells more sensitive to TLR stimulation, resulting in increased expression of CD80, and IL-10 in activated B cells. Although BCR-TLR interplay is complex, our findings show that both signaling pathways are crucial for the development of pathology in a Btk-dependent model for systemic autoimmune disease.

Project description:Extracellular adenosine triphosphate (ATP) and its receptor, P2X7 receptor (P2X7R), are playing an important role in the pathological process of renal ischemia-reperfusion injury, but their underlying mechanism remains unclear. Also, the effects of tubular epithelium-expressed P2X7 receptor on ischemia acute kidney injury is still unknown. The aim of this study is to clarify if this mechanism involves the activation of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in the renal tubular epithelial cells. In our research, we used male C57BL/6 wild type and P2X7R (-/-) mice, cultured human proximal tubular epithelial cells, and kidneys from acute kidney injury patients. Mice underwent for unilateral nephrectomy combined with the lateral renal pedicle clamping. Cultured cells were subjected to hypoxia/reoxygenation or ATP. Apyrase and A438079 were used to block the extracellular ATP/P2X7 receptor pathway. We also constructed radiation-induced bone marrow (BM) chimeras by using P2X7R (-/-) mice and P2X7R (+/+) wild-type mice. P2X7 receptor deficiency protected from renal ischemia-reperfusion injury and attenuated the formation of NLRP3 inflammasome. By using BM chimeras, we found a partial reduction of serum creatinine and less histological impairment in group wild-type BM to P2X7R (-/-) recipient, compared with group wild-type BM to wild-type recipient. In renal tubular epithelial cells, hypoxia/reoxygenation induced ATP release and extracellular ATP depletion reduced the expression of active IL-1β. ATP activated the NLRP3 inflammasome in renal tubular epithelial cells, which were blunted by transient silence of P2X7 receptor, as well as by P2X7 receptor blocking with A438079. In human samples, we found that patients with Stage 3 AKI had higher levels of P2X7 receptor expression than patients with Stage 1 or Stage 2. Extracellular ATP/P2X7 receptor axis blocking may protect renal tubular epithelial cells from ischemia-reperfusion injury through the regulation of NLRP3 inflammasome.

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Toll-like receptor 4 signaling in T cells promotes autoimmune inflammation.

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Toll-like receptor 4 signaling in T cells promotes autoimmune inflammation.

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