Forlenza Maria, Magez Stefan, Scharsack Jörn P, Westphal Adrie, Savelkoul Huub F J, Wiegertjes Geert F
Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, Wageningen, The Netherlands.
J Immunol. 2009 Oct 15;183(8):5319-32. doi: 10.4049/jimmunol.0901780. Epub 2009 Sep 28.
Functional characterization of TNF-alpha in species other than mammalian vertebrates is limited, and TNF-alpha has been studied in a limited number of fish species, primarily in vitro using recombinant proteins. Studies on TNF-alpha from different fish species so far pointed to several inconsistencies, in particular with respect to some receptor-mediated activities of fish TNF-alpha, such as the ability to directly activate phagocytes. In the present study a comprehensive analysis of in vitro as well as in vivo biological activities of two isoforms of carp TNF-alpha was performed. Our results show that carp TNF-alpha directly primes carp phagocytes and indirectly promotes typical receptor-mediated activities such as phagocyte activation by acting via endothelial cells. Additionally, for the first time in nonmammalian vertebrate species, the lectin-like activity of fish TNF-alpha homologs was investigated. Our results show an evolutionary conservation of function of this receptor-independent activity of TNF-alpha not only in cyprinid fish, but also in perciform and salmonid fish. The role of TNF-alpha in vivo, during infections of carp with the blood parasite Trypanoplasma borreli, was examined using three fundamentally different but complementary approaches: (1) inhibition of TNF-alpha expression, (2) overexpression of TNF-alpha, and (3) inhibition of shedding of membrane-bound TNF-alpha. Our results show that, also in fish, a tight regulation of TNF-alpha expression is important, since depletion or excess of TNF-alpha can make an important difference to survival of infection. Finally, we demonstrate a crucial protective role for membrane-bound TNF-alpha, which has a yet unexploited function in fish.
除哺乳动物脊椎动物外，肿瘤坏死因子-α（TNF-α）在其他物种中的功能特性研究有限，且TNF-α仅在少数鱼类物种中进行过研究，主要是在体外使用重组蛋白进行研究。迄今为止，对不同鱼类物种的TNF-α研究存在一些不一致之处，特别是在鱼类TNF-α的某些受体介导活性方面，例如直接激活吞噬细胞的能力。在本研究中，对鲤鱼TNF-α的两种亚型的体外和体内生物学活性进行了全面分析。我们的结果表明，鲤鱼TNF-α直接启动鲤鱼吞噬细胞，并通过作用于内皮细胞间接促进典型的受体介导活性，如吞噬细胞激活。此外，首次在非哺乳动物脊椎动物物种中研究了鱼类TNF-α同源物的凝集素样活性。我们的结果表明，TNF-α这种不依赖受体的活性不仅在鲤科鱼类中，而且在鲈形目和鲑科鱼类中，其功能在进化上具有保守性。利用三种根本不同但互补的方法，研究了鲤鱼感染血液寄生虫博氏锥虫期间TNF-α在体内的作用：（1）抑制TNF-α表达；（2）TNF-α过表达；（3）抑制膜结合TNF-α的脱落。我们的结果表明，在鱼类中，TNF-α表达的严格调控也很重要，因为TNF-α的缺乏或过量对感染的存活可能产生重大影响。最后，我们证明了膜结合TNF-α具有关键的保护作用，其在鱼类中具有尚未被开发利用的功能。
