TLR4 Signaling Selectively and Directly Promotes CGRP Release from Vagal Afferents in the Mouse
TLR4 Signaling Selectively and Directly Promotes CGRP Release from Vagal Afferents in the Mouse
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DOI：
10.1523/eneuro.0254-20.2020
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发表时间：
2021-01-01
期刊：
影响因子：
3.4
通讯作者：
Gautron, Laurent
中科院分区：
文献类型：
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作者：
Jia, Lin;Lee, Syann;Gautron, Laurent
关于外周传入神经在介导外周炎性损伤引起的快速发作性厌食症等反应中的作用，一直存在长期的争论。因此，目前的研究评估了外周传入表达Toll样受体4（TLR 4）的启动由外周细菌脂多糖（LPS）引起的厌食症的充分性。我们产生了Tlr 4无效（Tlr 4（LoxTB））小鼠，其中Tlr 4表达被loxP侧翼的转录阻断（TB）盒全面破坏。这种新的小鼠模型使我们能够恢复特定细胞类型中的内源性TLR 4表达。使用Zp 3-Cre和Na（v）1.8-Cre小鼠，我们产生了分别在所有细胞（Tlr 4（LoxTB）X Zp 3-Cre）和外周传入（Tlr 4（LoxTB）X Na（v）1.8-Cre）中表达TLR 4的小鼠。我们验证了TLR 4（LoxTB）小鼠，其表型与先前报道的整体TLR 4敲除小鼠相同。与我们的预期相反，LPS的给药没有引起Na（v）1.8限制性TLR 4小鼠的快速发作厌食症。后来的结果促使我们确定Tlr 4表达迷走神经传入使用原位杂交（ISH）。在体内，我们发现，Tlr 4 mRNA主要富集在位于颈静脉神经节的迷走神经Na（v）1.8传入共表达降钙素基因相关肽（CGRP）。在体外，应用LPS培养的Na（v）1.8限制性TLR 4传入足以刺激CGRP的释放。总之，我们使用一种新的小鼠模型证明了迷走神经表达的TLR 4选择性地参与刺激CGRP的释放，但不引起厌食症。
There has been a long-standing debate regarding the role of peripheral afferents in mediating rapid-onset anorexia among other responses elicited by peripheral inflammatory insults. Thus, the current study assessed the sufficiency of peripheral afferents expressing toll-like receptor 4 (TLR4) to the initiation of the anorexia caused by peripheral bacterial lipopolysaccharide (LPS). We generated a Tlr4 null (Tlr4(LoxTB)) mouse in which Tlr4 expression is globally disrupted by a loxP-flanked transcription blocking (TB) cassette. This novel mouse model allowed us to restore the endogenous TLR4 expression in specific cell types. Using Zp3-Cre and Na(v)1.8-Cre mice, we produced mice that express TLR4 in all cells (Tlr4(LoxTB) X Zp3-Cre) and in peripheral afferents (Tlr4(LoxTB) X Na(v)1.8-Cre), respectively. We validated the Tlr4(LoxTB) mice, which were phenotypically identical to previously reported global TLR4 knock-out mice. Contrary to our expectations, the administration of LPS did not cause rapid-onset anorexia in mice with Na(v)1.8-restricted TLR4. The later result prompted us to identify Tlr4-expressing vagal afferents using in situ hybridization (ISH). In vivo, we found that Tlr4 mRNA was primarily enriched in vagal Na(v)1.8 afferents located in the jugular ganglion that co-expressed calcitonin gene-related peptide (CGRP). In vitro, the application of LPS to cultured Na(v)1.8-restricted TLR4 afferents was sufficient to stimulate the release of CGRP. In summary, we demonstrated using a new mouse model that vagally-expressed TLR4 is selectively involved in stimulating the release of CGRP but not in causing anorexia.