Oxidative stress impairs heme detoxification in the midgut of the cattle tick, Rhipicephalus (Boophilus) microplus
Oxidative stress impairs heme detoxification in the midgut of the cattle tick, Rhipicephalus (Boophilus) microplus
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DOI：
10.1016/j.molbiopara.2006.10.008
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发表时间：
2007-01-01
影响因子：
1.5
通讯作者：
Oliveira, Pedro L.
中科院分区：
文献类型：
--
作者：
Citelli, Marta;Lara, Flavio A.;Oliveira, Pedro L.
在牛蜱中，微蜱（Boophilus）对血液的消化是在细胞内进行的，由充满中肠腔的所谓消化细胞完成。这些细胞的消化囊泡中血红蛋白的水解导致大量促氧化化合物血红素的释放，其铁原子与H2O2一起参与芬顿反应，导致羟基自由基的产生。在这里，我们研究了过氧化氢酶的作用，过氧化氢酶是一种负责H2O2解毒的酶。充分充血的雌蜱注射了过氧化氢酶抑制剂3-氨基-1,2,4-三唑（AT）后，肠道中H2O2含量增加，同时寿命缩短，产卵率降低。AT治疗2天后，进一步注射外源性过氧化氢酶，逆转了AT注射后死亡率的增加，证实了死亡的增加是由于AT对该酶的抑制。在消化细胞原代培养中，细胞内H2O2仅限于特定的细胞器，而体外AT处理导致H2O2在整个细胞中扩散，证实了过氧化氢酶在调节H2O2水平中的作用。喂食注射了AT的小牛的蜱虫表现出肠道过氧化氢酶活性的明显抑制，寿命缩短，产卵和充血。这些蜱虫的消化细胞形态发生了改变，显示血红素遍布细胞质，而不是局限于血凝体。在at处理的牛中，分离的血红体中发现的聚集血红素的数量也大大减少。综上所述，我们的研究结果表明，过氧化氢酶在控制血红蛋白的氧化还原平衡中起着重要作用，这极大地影响了血红体的形成和稳定性。这种酶可能是开发蜱虫控制新方法的一个目标。(c) 2006 Elsevier B.V.版权所有
In the cattle tick Rhipicephalus (Boophilus) microplus digestion of blood is intracellular, accomplished by the so-called digest cells that fill the midgut lumen. Hydrolysis of hemoglobin in the digestive vesicles of these cells results in the release of large amounts of heme, a pro-oxidant compound, whose iron atom, together with H2O2, may participate in the Fenton reaction and lead to the production of hydroxyl radicals. Here, we investigated the role of catalase, an enzyme responsible for H2O2 detoxification. Fully engorged female ticks injected with 3-amino-1,2,4-triazole (AT), a catalase inhibitor, showed increased H2O2 in the gut, together with diminished life span and lower egg-laying rates. Increased mortality observed upon AT injection was reversed by further injection of exogenous catalase, 2 days after AT treatment, confirming that increased death was due to inhibition of this enzyme by AT. In primary cultures of digest cells, intracellular H2O2 is limited to specific organelles, while treatment with AT in vitro resulted in increased H2O2 spreading all over the cell, confirming the role of catalase in regulating H2O2 levels. Ticks fed on a calf that had been injected with AT showed marked inhibition of catalase activity in the gut and diminished life span, oviposition and engorgement. Digest cells of these ticks had an altered morphology, showing heme spread all over the cytosol, instead of being limited to the hemosomes. The amount of aggregated heme found in isolated hemosome was also strongly decreased in AT-treated cattle. All together, our results indicate that catalase performs an important role in the control of redox balance in R. microplus, which dramatically affects hemosome formation and stability. This enzyme may be a target in the development of new methods for tick control. (c) 2006 Elsevier B.V. All rights reserved.