Molecular Cell Biology Laboratory, Infectious Diseases and Immunology Division, Indian Institute of Chemical Biology, Kolkata 700 032, India.
J Immunol. 2011 Aug 1;187(3):1322-32. doi: 10.4049/jimmunol.1004237. Epub 2011 Jun 24.
To reside and multiply successfully within the host macrophages, Leishmania parasites impair the generation of reactive oxygen species (ROS), which are a major host defense mechanism against any invading pathogen. Mitochondrial uncoupling proteins are associated with mitochondrial ROS generation, which is the major contributor of total cellular ROS generation. In the present study we have demonstrated that Leishmania donovani infection is associated with strong upregulation of uncoupling protein 2 (UCP2), a negative regulator of mitochondrial ROS generation located at the inner membrane of mitochondria. Functional knockdown of macrophage UCP2 by small interfering RNA-mediated silencing was associated with increased mitochondrial ROS generation, lower parasite survival, and induction of marked proinflammatory cytokine response. Induction of proinflammatory cytokine response in UCP2 knocked-down cells was a direct consequence of p38 and ERK1/2 MAPK activation, which resulted from ROS-mediated inhibition of protein tyrosine phosphatases (PTPs). Administration of ROS quencher, N-acetyl-l-cysteine, abrogated PTP inhibition in UCP2 knocked-down infected cells, implying a role of ROS in inactivating PTP. Short hairpin RNA-mediated in vivo silencing of UCP2 resulted in decreased Src homology 2 domain-containing tyrosine phosphatase 1 and PTP-1B activity and host-protective proinflammatory cytokine response resulting in effective parasite clearance. To our knowledge, this study, for the first time, reveals the induction of host UCP2 expression during Leishmania infection to downregulate mitochondrial ROS generation, thereby possibly preventing ROS-mediated PTP inactivation to suppress macrophage defense mechanisms.
为了在宿主巨噬细胞中成功生存和繁殖，利什曼原虫寄生虫会削弱活性氧（ROS）的产生，ROS 是宿主抵御任何入侵病原体的主要防御机制。解偶联蛋白与线粒体 ROS 的产生有关，而线粒体 ROS 的产生是总细胞 ROS 产生的主要贡献者。在本研究中，我们已经证明，感染杜氏利什曼原虫与解偶联蛋白 2（UCP2）的强烈上调有关，UCP2 是位于线粒体内膜的线粒体 ROS 产生的负调节剂。通过小干扰 RNA 介导的沉默对巨噬细胞 UCP2 的功能敲低与线粒体 ROS 产生增加、寄生虫存活率降低以及诱导明显的促炎细胞因子反应有关。UCP2 敲低细胞中促炎细胞因子反应的诱导是 p38 和 ERK1/2 MAPK 激活的直接结果，这是由于 ROS 介导的蛋白酪氨酸磷酸酶（PTP）抑制所致。ROS 清除剂 N-乙酰-l-半胱氨酸的给药消除了 UCP2 敲低感染细胞中的 PTP 抑制，这意味着 ROS 在使 PTP 失活中起作用。短发夹 RNA 介导的体内 UCP2 沉默导致 Src 同源性 2 结构域含酪氨酸磷酸酶 1 和 PTP-1B 活性降低和宿主保护性促炎细胞因子反应，从而有效清除寄生虫。据我们所知，这项研究首次揭示了在利什曼原虫感染期间诱导宿主 UCP2 表达以下调线粒体 ROS 产生，从而可能防止 ROS 介导的 PTP 失活以抑制巨噬细胞防御机制。
