Krasnov Aleksei, Wesmajervi Breiland Mette S, Hatlen Bjarne, Afanasyev Sergey, Skugor Stanko
Nofima AS, PO Box 6122, NO-9291 Tromsø, Norway.
Nofima AS, PO Box 6122, NO-9291 Tromsø, Norway; Sechenov Institute of Evolutionary Physiology and Biochemistry, M. Toreza av. 44, Peterburg 194223, Russia.
Gen Comp Endocrinol. 2015 Feb 1;212:34-43. doi: 10.1016/j.ygcen.2015.01.002. Epub 2015 Jan 16.
The crustacean ectoparasitic salmon louse (Lepeophtheirus salmonis) is a major problem of Atlantic salmon aquaculture in the Northern hemisphere. Host-pathogen interactions in this system are highly complex. Resistance to the parasite involves variations in genetic background, nutrition, properties of skin, and status of the endocrine and immune systems. This study addressed the relationship between sex hormones and lice infection. Field observation revealed a sharp reduction of lice prevalence during sexual maturation with no difference between male and female fish. To determine if higher resistance against lice was related to sex hormones, post-smolt salmon were administered control feed and feeds containing 17β-estradiol (20 mg/kg) and testosterone (25 mg/kg) during a 3-week pre-challenge period. After challenge with lice, counts were reduced 2-fold and 1.5-fold in fish that received 17β-estradiol and testosterone, respectively. Gene expression analyses were performed from skin of salmon collected in the field trial and from the controlled lab experiment at three time points (end of feeding-before challenge, 3 days post challenge (dpc) and 16 dpc) using oligonucleotide microarray and qPCR. Differential expression was observed in genes associated with diverse biological processes. Both studies revealed similar changes of several antibacterial acute phase proteins; of note was induction of cathelicidin and down-regulation of a defensin gene. Treatment with hormones revealed their ability to modulate T helper cell (Th)-mediated immunity in skin. Enhanced protection achieved by 17β-estradiol administration might in part be due to the skewing of Th responses away from the prototypic anti-parasitic Th2 immunity and towards the more effective Th1 responses. Multiple genes involved in wound healing, differentiation and remodelling of skin tissue were stimulated during maturation but suppressed with sex hormones. Such opposite regulation suggested that these processes were not associated with resistance to the parasite under the studied conditions. Both studies revealed regulation of a suite of genes encoding putative large mucosal proteins found exclusively in fish. Marked decrease of erythrocyte markers indicated reduced circulation while down-regulation of multiple zymogen granule membrane proteins and transporters of cholesterol and other compounds suggested limited availability of nutrients for the parasites.
甲壳类外寄生性鲑鱼虱（鲑鱼虱）是北半球大西洋鲑鱼养殖中的一个主要问题。该系统中的宿主 - 病原体相互作用高度复杂。对这种寄生虫的抗性涉及遗传背景、营养、皮肤特性以及内分泌和免疫系统状态的差异。本研究探讨了性激素与虱子感染之间的关系。实地观察发现，在性成熟期间虱子感染率急剧下降，雄鱼和雌鱼之间没有差异。为了确定对虱子的更高抗性是否与性激素有关，在为期3周的预激发期内，对后洄游鲑鱼投喂对照饲料以及含有17β - 雌二醇（20毫克/千克）和睾酮（25毫克/千克）的饲料。在用虱子激发后，接受17β - 雌二醇和睾酮的鱼体内虱子数量分别减少了2倍和1.5倍。使用寡核苷酸微阵列和定量聚合酶链反应（qPCR），在三个时间点（投喂结束 - 激发前、激发后3天（dpc）和16 dpc）对实地试验收集的鲑鱼皮肤以及对照实验室实验中的鲑鱼皮肤进行基因表达分析。在与多种生物学过程相关的基因中观察到差异表达。两项研究均揭示了几种抗菌急性期蛋白的类似变化；值得注意的是，cathelicidin的诱导和一种防御素基因的下调。激素处理显示它们能够调节皮肤中辅助性T细胞（Th）介导的免疫。给予17β - 雌二醇所实现的增强保护可能部分归因于Th反应从典型的抗寄生虫Th2免疫向更有效的Th1反应的倾斜。在成熟过程中，多个参与皮肤组织伤口愈合、分化和重塑的基因受到刺激，但被性激素抑制。这种相反的调节表明，在研究条件下，这些过程与对寄生虫的抗性无关。两项研究均揭示了一组仅在鱼类中发现的推定大型粘膜蛋白编码基因的调节。红细胞标志物的显著下降表明循环减少，而多种酶原颗粒膜蛋白以及胆固醇和其他化合物转运蛋白的下调表明寄生虫可利用的营养物质有限。
