Rozas Pablo, Lazcano Pablo, Piña Ricardo, Cho Andrew, Terse Anita, Pertusa Maria, Madrid Rodolfo, Gonzalez-Billault Christian, Kulkarni Ashok B, Utreras Elias
Laboratory of Molecular and Cellular Mechanisms of Pain, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile Department of Biology, Faculty of Chemistry and Biology, University of Santiago de Chile, Santiago, Chile Functional Genomics Section, Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
Pain. 2016 Jun;157(6):1346-1362. doi: 10.1097/j.pain.0000000000000527.
We reported earlier that TNF-α, a proinflammatory cytokine implicated in many inflammatory disorders causing orofacial pain, increases the activity of Cdk5, a key kinase involved in brain development and function and recently found to be involved in pain signaling. To investigate a potential mechanism underlying inflammatory pain in trigeminal ganglia (TGs), we engineered a transgenic mouse model (TNF) that can conditionally overexpresses TNF-α upon genomic recombination by Cre recombinase. TNF mice were bred with Nav1.8-Cre mouse line that expresses the Cre recombinase in sensory neurons to obtain TNF-α:Nav1.8-Cre (TNF-α cTg) mice. Although TNF-α cTg mice appeared normal without any gross phenotype, they displayed a significant increase in TNF-α levels after activation of NFκB signaling in the TG. IL-6 and MCP-1 levels were also increased along with intense immunostaining for Iba1 and GFAP in TG, indicating the presence of infiltrating macrophages and the activation of satellite glial cells. TNF-α cTg mice displayed increased trigeminal Cdk5 activity, and this increase was associated with elevated levels of phospho-T407-TRPV1 and capsaicin-evocated Ca influx in cultured trigeminal neurons. Remarkably, this effect was prevented by roscovitine, an inhibitor of Cdk5, which suggests that TNF-α overexpression induced sensitization of the TRPV1 channel. Furthermore, TNF-α cTg mice displayed more aversive behavior to noxious thermal stimulation (45°C) of the face in an operant pain assessment device as compared with control mice. In summary, TNF-α overexpression in the sensory neurons of TNF-α cTg mice results in inflammatory sensitization and increased Cdk5 activity; therefore, this mouse model would be valuable for investigating the mechanism of TNF-α involved in orofacial pain.
我们之前报道过,肿瘤坏死因子-α(TNF-α)是一种涉及多种导致口面部疼痛的炎症性疾病的促炎细胞因子,它可增加细胞周期蛋白依赖性激酶5(Cdk5)的活性,Cdk5是一种参与脑发育和功能的关键激酶,最近发现其也参与疼痛信号传导。为了研究三叉神经节(TGs)炎性疼痛的潜在机制,我们构建了一种转基因小鼠模型(TNF),该模型可通过Cre重组酶进行基因组重组来条件性过表达TNF-α。将TNF小鼠与在感觉神经元中表达Cre重组酶的Nav1.8-Cre小鼠品系杂交,以获得TNF-α:Nav1.8-Cre(TNF-α cTg)小鼠。尽管TNF-α cTg小鼠外观正常,没有任何明显的表型,但在TG中激活NFκB信号后,它们的TNF-α水平显著升高。IL-6和MCP-1水平也升高,同时TG中Iba1和GFAP的免疫染色增强,表明存在浸润的巨噬细胞和卫星神经胶质细胞的激活。TNF-α cTg小鼠的三叉神经Cdk5活性增加,这种增加与培养的三叉神经神经元中磷酸化T407-TRPV1水平升高和辣椒素诱发的Ca内流有关。值得注意的是,Cdk5抑制剂roscovitine可阻止这种效应,这表明TNF-α过表达诱导了TRPV1通道的敏化。此外,与对照小鼠相比,在操作性疼痛评估装置中,TNF-α cTg小鼠对面部有害热刺激(45°C)表现出更多的厌恶行为。总之,TNF-α cTg小鼠感觉神经元中TNF-α的过表达导致炎症敏化和Cdk5活性增加;因此,该小鼠模型对于研究TNF-α参与口面部疼痛的机制具有重要价值。