Calvani Nichola Eliza Davies, De Marco Verissimo Carolina, Jewhurst Heather Louise, Cwiklinski Krystyna, Flaus Andrew, Dalton John Pius
Molecular Parasitology Laboratory (MPL), Centre for One Health and Ryan Institute, School of Natural Sciences, University of Galway, H91 DK59 Galway, Ireland.
Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool L69 3BX, UK.
Antioxidants (Basel). 2022 Sep 30;11(10):1968. doi: 10.3390/antiox11101968.
The antioxidant superoxide dismutase (SOD) catalyses the dismutation of superoxide, a dangerous oxygen free radical, into hydrogen peroxide and molecular oxygen. Superoxide generation during the oxidative burst of the innate immune system is considered a key component of the host defence against invading pathogens. We demonstrate the presence and differential expression of two SODs in , a leaderless cytosolic (FhSOD1) and an extracellular (FhSOD3) form containing a secretory signal peptide, suggesting that the parasites exploit these enzymes in distinct ways to counteract reactive oxygen species (ROS) produced by cellular metabolism and immune defences. Both enzymes are highly expressed by the infective newly excysted juvenile (NEJ) stages and are found in abundance in their excretory-secretory products (ES), but only FhSOD1 is present in adult ES, suggesting that the antioxidants have different functions and pathways of secretion, and are under separate temporal expression control during the migration, growth, and development of the parasite. Functionally, the recombinant FhSOD1 and FhSOD3 exhibit similar activity against superoxide to their mammalian counterparts. Confocal immuno-localisation studies demonstrated the presence of FhSOD1 and FhSOD3 on the NEJ tegument and parenchyma, supporting our suggestion that these enzymes are secreted during host invasion to protect the parasites from the harmful oxidative bursts produced by the activated innate immune response. By producing superoxide enzymatically in vitro, we were able to demonstrate robust killing of NEJ within 24 h post-excystment, and that the lethal effect of ROS was nullified with the addition of SOD and catalase (the antioxidant enzyme responsible for the dismutation of hydrogen peroxide, a by-product of the SOD reaction). This study further elucidates the mechanism by which protects against ROS derived from cellular metabolism and how the parasite could mitigate damage caused by the host's immune response to benefit its survival.
抗氧化超氧化物歧化酶（SOD）催化超氧化物（一种危险的氧自由基）歧化为过氧化氢和分子氧。先天免疫系统氧化爆发过程中产生的超氧化物被认为是宿主抵御入侵病原体的关键组成部分。我们证明了两种SOD在[具体寄生虫名称未给出]中的存在及差异表达，一种是无信号肽的胞质形式（FhSOD1），另一种是含有分泌信号肽的细胞外形式（FhSOD3），这表明寄生虫以不同方式利用这些酶来对抗细胞代谢和免疫防御产生的活性氧（ROS）。这两种酶在感染性新脱囊幼虫（NEJ）阶段均高表达，且在其排泄-分泌产物（ES）中大量存在，但只有FhSOD1存在于成虫的ES中，这表明抗氧化剂具有不同的功能和分泌途径，并且在寄生虫的迁移、生长和发育过程中受不同的时间表达控制。在功能上，重组FhSOD1和FhSOD3对超氧化物的活性与其哺乳动物对应物相似。共聚焦免疫定位研究证明了FhSOD1和FhSOD3存在于NEJ的体表和实质组织中，支持了我们的观点，即这些酶在宿主入侵期间分泌，以保护寄生虫免受活化的先天免疫反应产生的有害氧化爆发的影响。通过体外酶促产生超氧化物，我们能够证明在脱囊后24小时内对NEJ有强大的杀伤作用，并且添加SOD和过氧化氢酶（负责将SOD反应的副产物过氧化氢歧化的抗氧化酶）可消除ROS的致死作用。这项研究进一步阐明了[具体寄生虫名称未给出]抵御细胞代谢产生的ROS的机制，以及寄生虫如何减轻宿主免疫反应造成的损害以利于其生存。
