Lai Floriana, Royan Muhammad R, Gomes Ana S, Espe Marit, Aksnes Anders, Norberg Birgitta, Gelebart Virginie, Rønnestad Ivar
Department of Biological Sciences, University of Bergen, Bergen, Norway.
Institute of Marine Research, Bergen, Norway.
Gen Comp Endocrinol. 2021 Nov 1;313:113894. doi: 10.1016/j.ygcen.2021.113894. Epub 2021 Aug 31.
Corticotropin-Releasing Factor (CRF) is one of the main mediators of the Hypothalamic-Pituitary-Interrenal (HPI) axis to stress response. In Atlantic salmon, a comparative understanding of the crf1 paralogs role in the stress response is still incomplete. Our database searches have identified four crf1 genes in Atlantic salmon, named crf1a1, crf1a2, crf1b1 and crf1b2. Brain distribution analysis revealed that the four crf1 paralogs were widely distributed, and particularly abundant in the telencephalon, midbrain, and hypothalamus of Atlantic salmon post-smolts. To increase the knowledge on crf1-mediated response to stress, Atlantic salmon post-smolts were exposed to either repeated chasing, hypoxia or a combination of chasing and hypoxia for eight days, followed by a novel-acute stressor, confinement. Cortisol, glucose, lactate, and creatinine levels were used as markers for the stress response. The crf1 paralogs mRNA abundance showed to be dependent on the stress exposure regime. Both crf1 mRNA levels in the telencephalon and crf1a1 mRNA levels in the hypothalamus showed similar response profiles to the serum cortisol levels, i.e., increasing levels during the first 24 h after stress exposure followed by a decline during the eight-day exposure. The similar trend between crf1 and cortisol disappeared once exposed to the novel-acute stressor. There was a minor response to stress for both crf1b1 and crf1b2 in the hypothalamus, while no changes at mRNA level were observed in the hypothalamic crf1a2 under the different stress conditions. No or weak relationship was found between the crf1 paralogs mRNA expression and the other serum stress-indicators analysed. In summary, our data provide novel insights on the dynamic of the HPI axis activation in Atlantic salmon, and thus underline the involvement of the crf1 paralogs as additional factors in the regulation of the stress response in this species. Likewise, the data highlight the importance of analysing all crf1 paralogues response to a stress-condition, in particular in this premature knowledge stage of their functionality. Further analysis and a more detailed time-point series will help to elucidate the response of the HPI axis and the link of crf1 paralogs in the stress response mechanism.
促肾上腺皮质激素释放因子（CRF）是下丘脑 - 垂体 - 肾间（HPI）轴对应激反应的主要介质之一。在大西洋鲑鱼中，对crf1旁系同源基因在应激反应中作用的比较性理解仍不完整。我们通过数据库搜索在大西洋鲑鱼中鉴定出四个crf1基因，分别命名为crf1a1、crf1a2、crf1b1和crf1b2。脑部分布分析表明，这四个crf1旁系同源基因广泛分布，在大西洋鲑鱼洄游后幼鱼的端脑、中脑和下丘脑尤为丰富。为了增加对crf1介导的应激反应的了解，将大西洋鲑鱼洄游后幼鱼暴露于重复追逐、低氧或追逐与低氧组合的环境中八天，随后施加新的急性应激源——限制。皮质醇、葡萄糖、乳酸和肌酐水平用作应激反应的标志物。crf1旁系同源基因的mRNA丰度显示取决于应激暴露方式。端脑中的crf1 mRNA水平和下丘脑中的crf1a1 mRNA水平对血清皮质醇水平表现出相似的反应模式，即在应激暴露后的最初24小时内升高，随后在八天暴露期间下降。一旦暴露于新的急性应激源，crf1和皮质醇之间的相似趋势就消失了。下丘脑中的crf1b1和crf1b2对应激的反应较小，而在不同应激条件下，下丘脑crf1a2的mRNA水平未观察到变化。在分析的crf1旁系同源基因mRNA表达与其他血清应激指标之间未发现或仅发现微弱的关系。总之，我们的数据为大西洋鲑鱼HPI轴激活的动态提供了新的见解，从而强调了crf1旁系同源基因作为该物种应激反应调节中的额外因素的参与。同样，这些数据突出了分析所有crf1旁系同源基因对应激条件反应的重要性，特别是在它们功能的这个早期认知阶段。进一步的分析和更详细的时间点序列将有助于阐明HPI轴的反应以及crf1旁系同源基因在应激反应机制中的联系。
