Yang Chul-Su, Yuk Jae-Min, Shin Dong-Min, Kang Junghee, Lee Sung Joong, Jo Eun-Kyeong
Department of Microbiology, College of Medicine, Chungnam National University, Daejeon, South Korea.
Glia. 2009 Aug 1;57(10):1091-103. doi: 10.1002/glia.20832.
In previous studies, we have shown that reactive oxygen species (ROS)-mediated inflammatory signaling is essential for microglial proinflammatory responses to Mycobacterium tuberculosis (Mtb). To further investigate the molecular mechanisms governing these processes, we sought to describe the role of phospholipase A(2) (PLA(2)) in Mtb-induced ROS generation and inflammatory mediator release by microglia. Inhibition of secretory PLA(2) (sPLA(2)), but not cytosolic PLA(2) (cPLA(2)), profoundly abrogated Mtb-mediated ROS release, the generation of various inflammatory mediators (tumor necrosis factor, interleukin-6, cyclooxygenase-2, inducible nitric oxide synthase, and matrix metalloproteinase-2 and -9), and the activation of nuclear factor (NF)-kappaB and MAPKs (ERK1/2, p38, and JNK/SAPK) by murine microglial BV-2 cells or primary mixed glial cells. Interruption of the Ras/Raf-1/MEK1/ERK1/2 pathway abolished Mtb-induced sPLA(2) activity, whereas the blockage of JNK/SAPK or p38 activity had no effect. Specific inhibition of sPLA(2), but not cPLA(2), suppressed the upregulation of ERK1/2 phosphorylation by Mtb stimulation, suggesting the existence of a mutual dependency between the ERK1/2 and sPLA(2) pathways. Moreover, examination of the protein kinase C (PKC) family revealed that classical PKCs are involved in Mtb-induced sPLA(2) activation by microglia. Taken together, our results demonstrate for the first time that sPLA(2), either through pathways comprising Ras/Raf-1/MEK1/ERK1/2 or the classical PKC family, plays an essential role in Mtb-mediated ROS generation and inflammatory mediator release by microglial cells.
在先前的研究中，我们已经表明，活性氧（ROS）介导的炎症信号传导对于小胶质细胞对结核分枝杆菌（Mtb）的促炎反应至关重要。为了进一步研究调控这些过程的分子机制，我们试图描述磷脂酶A(2)（PLA(2)）在Mtb诱导的小胶质细胞ROS生成和炎症介质释放中的作用。抑制分泌型PLA(2)（sPLA(2)），而非胞质型PLA(2)（cPLA(2)），可显著消除Mtb介导的ROS释放、多种炎症介质（肿瘤坏死因子、白细胞介素-6、环氧化酶-2、诱导型一氧化氮合酶以及基质金属蛋白酶-2和-9）的生成，以及小鼠小胶质细胞BV-2或原代混合胶质细胞对核因子（NF）-κB和丝裂原活化蛋白激酶（MAPKs）（ERK1/2、p38和JNK/SAPK）的激活。Ras/Raf-1/MEK1/ERK1/2通路的中断消除了Mtb诱导的sPLA(2)活性，而JNK/SAPK或p38活性的阻断则没有影响。特异性抑制sPLA(2)而非cPLA(2)，可抑制Mtb刺激引起的ERK1/2磷酸化上调，表明ERK1/2和sPLA(2)通路之间存在相互依赖性。此外，对蛋白激酶C（PKC）家族的研究表明，经典PKC参与了Mtb诱导的小胶质细胞sPLA(2)激活。综上所述，我们的结果首次证明，sPLA(2)通过包含Ras/Raf-1/MEK1/ERK1/2的通路或经典PKC家族，在Mtb介导的小胶质细胞ROS生成和炎症介质释放中起重要作用。
