Taubert A, Silva L M R, Velásquez Z D, Larrazabal C, Lütjohann D, Hermosilla C
Institute of Parasitology, Biomedical Research Center Seltersberg, Justus Liebig University Giessen, Schubertstr. 81, 35392 Giessen, Germany.
Institute of Clinical Chemistry and Clinical Pharmacology, University Clinics of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany.
Mol Biochem Parasitol. 2018 Jul;223:1-12. doi: 10.1016/j.molbiopara.2018.06.002. Epub 2018 Jun 15.
Obligate intracellular apicomplexan parasites are considered as deficient in cholesterol biosynthesis and scavenge cholesterol from their host cell in a parasite-specific manner. Compared to fast proliferating apicomplexan species producing low numbers of merozoites per host cell, (e. g. Toxoplasma gondii), the macromeront-forming protozoa Eimeria bovis is in extraordinary need for cholesterol for offspring production (≥ 170,000 merozoites I/macromeront). Interestingly, optimized in vitro E. bovis merozoite I production occurs under low foetal calf serum (FCS, 1.2%) supplementation. To analyze the impact of extensive E. bovis proliferation on host cellular sterol metabolism we here compared the sterol profiles of E. bovis-infected primary endothelial host cells grown under optimized (1.2% FCS) and non-optimized (10% FCS) cell culture conditions. Therefore, several sterols indicating endogenous de novo cholesterol synthesis, cholesterol conversion and sterol uptake (phytosterols) were analyzed via GC-MS-based approaches. Overall, significantly enhanced levels of phytosterols were detected in both FCS conditions indicating infection-triggered sterol uptake from extracellular sources as a major pathway of sterol acquisition. Interestingly, a simultaneous induction of endogenous cholesterol synthesis based on increased levels of distinct cholesterol precursors was only observed in case of optimized parasite proliferation indicating a parasite proliferation-dependent effect. Considering side-chain oxysterols, 25 hydroxycholesterol levels were selectively found increased in E. bovis-infected host cells, while 24 hydroxycholesterol and 27 hydroxycholesterol contents were not significantly altered by infection. Exogenous treatments with 25 hydroxycholesterol, 27 hydroxycholesterol, and 7 ketocholesterol revealed significant adverse effects on E. bovis intracellular development. Thus, the number and size of developing macromeronts and merozoite I production was significantly reduced indicating that these oxysterols bear direct or indirect antiparasitic properties. Overall, the current data indicate parasite-driven changes in the host cellular sterol profile reflecting the huge demand of E. bovis for cholesterol during macromeront formation and its versatility in the acquisition of cholesterol sources.
专性细胞内顶复门寄生虫被认为胆固醇生物合成能力不足，它们以寄生虫特有的方式从宿主细胞中摄取胆固醇。与在每个宿主细胞中产生少量裂殖子的快速增殖顶复门物种（如弓形虫）相比，形成大配子体的原生动物牛艾美球虫在产生后代（每个大配子体≥170,000个裂殖子I）时对胆固醇有极高需求。有趣的是，在低胎牛血清（FCS，1.2%）补充条件下，体外培养的牛艾美球虫裂殖子I产量得到优化。为了分析牛艾美球虫大量增殖对宿主细胞甾醇代谢的影响，我们在此比较了在优化（1.2% FCS）和非优化（10% FCS）细胞培养条件下生长的牛艾美球虫感染的原代内皮宿主细胞的甾醇谱。因此，通过基于气相色谱 - 质谱的方法分析了几种指示内源性从头合成胆固醇、胆固醇转化和甾醇摄取（植物甾醇）的甾醇。总体而言，在两种FCS条件下均检测到植物甾醇水平显著升高，表明感染引发的从细胞外来源摄取甾醇是甾醇获取的主要途径。有趣的是，仅在寄生虫增殖优化的情况下观察到基于不同胆固醇前体水平增加的内源性胆固醇合成的同时诱导，这表明存在寄生虫增殖依赖性效应。考虑到侧链氧化甾醇，在牛艾美球虫感染的宿主细胞中选择性地发现25 - 羟基胆固醇水平升高，而感染并未显著改变24 - 羟基胆固醇和27 - 羟基胆固醇含量。用25 - 羟基胆固醇、27 - 羟基胆固醇和7 - 酮胆固醇进行的外源处理显示对牛艾美球虫细胞内发育有显著不利影响。因此，发育中的大配子体的数量和大小以及裂殖子I的产量显著降低，表明这些氧化甾醇具有直接或间接的抗寄生虫特性。总体而言，当前数据表明寄生虫驱动宿主细胞甾醇谱的变化，反映了牛艾美球虫在大配子体形成过程中对胆固醇的巨大需求及其在获取胆固醇来源方面的多样性。
