Mechanisms underlying the exquisite sensitivity of Candida albicans to combinatorial cationic and oxidative stress that enhances the potent fungicidal activity of phagocytes.
Mechanisms underlying the exquisite sensitivity of Candida albicans to combinatorial cationic and oxidative stress that enhances the potent fungicidal activity of phagocytes.
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DOI：
10.1128/mbio.01334-14
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发表时间：
2014-07-15
期刊：
影响因子：
6.4
通讯作者：
Brown AJ
中科院分区：
文献类型：
--
作者：
Kaloriti D;Jacobsen M;Yin Z;Patterson M;Tillmann A;Smith DA;Cook E;You T;Grimm MJ;Bohovych I;Grebogi C;Segal BH;Gow NA;Haynes K;Quinn J;Brown AJ
免疫细胞利用活性氧（ROS）和阳离子通量来杀死微生物病原体，如真菌白色念珠菌。然而，白色念珠菌在体外对这些压力有抵抗力。因此，是什么解释了中性粒细胞有效的抗真菌活性？我们表明，同时暴露于氧化和阳离子应激比单独应激本身更有效，并且这种组合应激在体外协同杀死白色念珠菌。我们还表明，人类中性粒细胞的高杀真菌活性依赖于氧化爆发和阳离子通量的组合作用，因为它们的药理衰减与罗布麻碱或格列本脲在相似程度上降低了吞噬能力。组合阳离子+氧化应激（我们称之为应激途径干扰的现象）的极端效力的机制基础在于阳离子对过氧化氢解毒的抑制。在白色念珠菌中，这导致细胞内ROS的积累，Cap1（一种转录激活因子，通常驱动氧化应激的转录反应）的抑制，以及应激激活蛋白激酶Hog1的读数改变。这导致氧化和阳离子应激转录输出的损失，应激适应的急剧崩溃和细胞死亡。这种胁迫途径的干扰可以通过异位过氧化氢酶（Cat1）的表达来抑制，Cat1可以抑制细胞内ROS的积累，并通过组合阳离子+氧化应激协同杀死白色念珠菌细胞。应激途径干扰是宿主采用的一种强大的杀真菌机制，为增强抗真菌治疗提供了新的途径。免疫系统通过吞噬细胞识别并杀死致病微生物来对抗感染。人类中性粒细胞通过一种包括活性氧（ROS）和阳离子在内的强效化学混合物杀死念珠菌感染。然而，白色念珠菌在体外相对抵抗这些压力。我们发现，正是氧化和阳离子胁迫的结合有效地杀死了酵母，我们确定了这种效力背后的分子机制。阳离子抑制过氧化氢酶。这导致细胞内ROS的积累，并抑制转录因子Cap1，这对白色念珠菌的氧化应激反应至关重要。这引发了真菌压力适应和细胞死亡的急剧崩溃。阻断人类中性粒细胞的氧化爆发或阳离子通量显著降低了它们杀死这种真菌病原体的能力，表明组合应激对免疫监视至关重要。
Immune cells exploit reactive oxygen species (ROS) and cationic fluxes to kill microbial pathogens, such as the fungus Candida albicans. Yet, C. albicans is resistant to these stresses in vitro. Therefore, what accounts for the potent antifungal activity of neutrophils? We show that simultaneous exposure to oxidative and cationic stresses is much more potent than the individual stresses themselves and that this combinatorial stress kills C. albicans synergistically in vitro. We also show that the high fungicidal activity of human neutrophils is dependent on the combinatorial effects of the oxidative burst and cationic fluxes, as their pharmacological attenuation with apocynin or glibenclamide reduced phagocytic potency to a similar extent. The mechanistic basis for the extreme potency of combinatorial cationic plus oxidative stress—a phenomenon we term stress pathway interference—lies with the inhibition of hydrogen peroxide detoxification by the cations. In C. albicans this causes the intracellular accumulation of ROS, the inhibition of Cap1 (a transcriptional activator that normally drives the transcriptional response to oxidative stress), and altered readouts of the stress-activated protein kinase Hog1. This leads to a loss of oxidative and cationic stress transcriptional outputs, a precipitous collapse in stress adaptation, and cell death. This stress pathway interference can be suppressed by ectopic catalase (Cat1) expression, which inhibits the intracellular accumulation of ROS and the synergistic killing of C. albicans cells by combinatorial cationic plus oxidative stress. Stress pathway interference represents a powerful fungicidal mechanism employed by the host that suggests novel approaches to potentiate antifungal therapy. The immune system combats infection via phagocytic cells that recognize and kill pathogenic microbes. Human neutrophils combat Candida infections by killing this fungus with a potent mix of chemicals that includes reactive oxygen species (ROS) and cations. Yet, Candida albicans is relatively resistant to these stresses in vitro. We show that it is the combination of oxidative plus cationic stresses that kills yeasts so effectively, and we define the molecular mechanisms that underlie this potency. Cations inhibit catalase. This leads to the accumulation of intracellular ROS and inhibits the transcription factor Cap1, which is critical for the oxidative stress response in C. albicans. This triggers a dramatic collapse in fungal stress adaptation and cell death. Blocking either the oxidative burst or cationic fluxes in human neutrophils significantly reduces their ability to kill this fungal pathogen, indicating that combinatorial stress is pivotal to immune surveillance.