Chuang Yu-Fan, Chen Mei-Chieh, Huang Shiu-Wen, Hsu Ya-Fen, Ou George, Tsai Yu-Jou, Hsu Ming-Jen
Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
Department of Microbiology and Immunology, College of Medicine, Taipei Medical University, Taipei, Taiwan.
PLoS One. 2015 Aug 28;10(8):e0137177. doi: 10.1371/journal.pone.0137177. eCollection 2015.
The lymphatic endothelium plays an important role in the maintenance of tissue fluid homeostasis. It also participates in the pathogenesis of several inflammatory diseases. However, little is known about the underlying mechanisms by which lymphatic endothelial cell responds to inflammatory stimuli. In this study, we explored the mechanisms by which lipopolysaccharide (LPS) induces cyclooxygenase (COX)-2 expression in murine lymphatic endothelial cells (SV-LECs). LPS caused increases in cox-2 mRNA and protein levels, as well as in COX-2 promoter luciferase activity in SV-LECs. These actions were associated with protein phosphatase 2A (PP2A), apoptosis signal-regulating kinase 1 (ASK1), JNK1/2 and p38MAPK activation, and NF-κB subunit p65 and C/EBPβ phosphorylation. PP2A-ASK1 signaling blockade reduced LPS-induced JNK1/2, p38MAPK, p65 and C/EBPβ phosphorylation. Transfection with PP2A siRNA reduced LPS's effects on p65 and C/EBPβ binding to the COX-2 promoter region. Transfected with the NF-κB or C/EBPβ site deletion of COX-2 reporter construct also abrogated LPS's enhancing effect on COX-2 promoter luciferase activity in SV-LECs. Taken together, the induction of COX-2 in SV-LECs exposed to LPS may involve PP2A-ASK1-JNK and/or p38MAPK-NF-κB and/or C/EBPβ cascade.
淋巴管内皮细胞在维持组织液稳态中发挥着重要作用。它还参与多种炎症性疾病的发病机制。然而，关于淋巴管内皮细胞对炎症刺激作出反应的潜在机制，人们了解甚少。在本研究中，我们探究了脂多糖（LPS）诱导小鼠淋巴管内皮细胞（SV-LECs）中环氧合酶（COX）-2表达的机制。LPS导致SV-LECs中cox-2 mRNA和蛋白水平升高，以及COX-2启动子荧光素酶活性增加。这些作用与蛋白磷酸酶2A（PP2A）、凋亡信号调节激酶1（ASK1）、JNK1/2和p38MAPK的激活，以及NF-κB亚基p65和C/EBPβ的磷酸化有关。PP2A-ASK1信号阻断降低了LPS诱导的JNK1/2、p38MAPK、p65和C/EBPβ磷酸化。用PP2A siRNA转染降低了LPS对p65和C/EBPβ与COX-2启动子区域结合的影响。用COX-2报告基因构建体的NF-κB或C/EBPβ位点缺失转染也消除了LPS对SV-LECs中COX-2启动子荧光素酶活性的增强作用。综上所述，暴露于LPS的SV-LECs中COX-2的诱导可能涉及PP2A-ASK1-JNK和/或p38MAPK-NF-κB和/或C/EBPβ级联反应。
