Behavioural fever and its underlying molecular mechanisms. Danio rerio

Fever implies a significant increase in corporal temperature that aids toward the resolution of infective processes such as viral disease. The majority of vertebrate species are not homeothermic therefore must rely upon the environment for temperature regulation. Here we show that in the zebrafish an artificial viral infection, induced by poly (I:C), induces a fever response regulated by the behavioral choice of temperature. We recorded 12 h of the diurnal cycle in zebrafish previously treated (first 12 hours dark cycle) with the pyrogen, poly (I:C) [10 μg⋅kg-1]. Fish, n=10, were held in a thermal gradient (36-180C) separated into 7 interconnected chambers. Presence or absence of individuals in each chamber was recorded each 15 minutes throughout the 12 hour period. After the experimental period we dissected whole brains for microarray analysis. In monitored zebrafish intraperitoneal treatment with poly (I:C) induced a febrile behaviour with significantly elevated temperature preference (T of about 32ºC) in stark contrast with the observed frequency for saline-injected fish (28ºC). Microarray analyses uncovered significant shifts in transcriptional activity that were highly directed in the poly (I:C)-treated fish housed in the thermal gradient. When compared to gene expression profiles from poly (I:C)-treated fish deprived of a thermal gradient we observed a less intense specific to the poly (I:C) challenge and interestingly observed a scattered generalised stress response. Our results highlight the influence of temperature preference in the development of the immune response in zebrafish. Overall design: Fever induced gene expression in zebrafish brain was measured at 24 after intra peritoneal injection with 1mg*Kg-1 of Poly (I:C) in zebrafish. Four independent experiments were performed to explore the transcriptomic profile induced by animals injected by Poly (I:C) with/whithout thermal gradient, saline solution (PBS), or control using different animals for each experiment.

发热（Fever）指机体体温显著升高，该过程有助于清除病毒感染等炎性病变。绝大多数脊椎动物并非恒温（homeothermic）生物，因此需依赖环境进行体温调节。本研究证实，在斑马鱼（zebrafish）中，由聚肌胞苷酸[poly(I:C)]诱导的人工病毒感染，可通过体温选择行为调控发热应答。我们对预先经致热原聚肌胞苷酸[poly(I:C)，10 μg·kg⁻¹]处理的斑马鱼开展了12小时昼夜周期监测（实验前12小时为黑暗周期）。将10尾实验鱼置于分为7个连通腔室的温度梯度（thermal gradient，范围18~36℃）装置中，在12小时实验周期内，每15分钟记录一次各腔室内的斑马鱼分布情况。实验结束后，我们解剖获取全脑组织用于基因芯片（microarray）分析。监测结果显示，经腹腔（intraperitoneal）注射聚肌胞苷酸处理的斑马鱼表现出发热行为（febrile behaviour），其偏好水温显著升高（约32℃），与注射生理盐水的对照组斑马鱼的偏好水温（28℃）形成鲜明对比。基因芯片分析表明，处于温度梯度环境中的聚肌胞苷酸处理组斑马鱼，其脑组织转录活性（transcriptional activity）发生了显著且定向的改变。与未处于温度梯度环境的聚肌胞苷酸处理组斑马鱼的基因表达谱相比，前者针对聚肌胞苷酸刺激的特异性应答强度更高，而后者则呈现出分散的全身性应激应答。本研究结果凸显了体温偏好对斑马鱼免疫应答发育的影响。实验总体设计：本研究检测了斑马鱼腹腔注射1mg·kg⁻¹聚肌胞苷酸后24小时，其脑组织中发热相关基因的表达情况。共开展4组独立实验，分别探究经聚肌胞苷酸注射且处于/未处于温度梯度环境的斑马鱼、注射生理盐水（PBS）的斑马鱼，以及空白对照组斑马鱼的转录组（transcriptomic）表达谱，每组实验均使用不同的实验动物。