Multiple signaling pathways regulate NF-κB–dependent transcription of the monocyte chemoattractant protein-1 gene in primary endothelial cells

Abstract

IntroductionEndothelial cells, strategically located between blood and tissue compartments, play an important role for initiation and regulation of inflammatory events. Targeted by cytokines, such as tumor necrosis factor (TNF)-␣ or interleukin (IL)-1, or by bacterial lipopolysaccharides, they sequentially express adhesion molecules that mediate rolling, adhesion, and transmigration of blood leukocytes from the vessel lumen to the underlying tissue. Moreover, endothelial cells represent a cytokine source that allows them to communicate with other cells and organs. One important cytokine produced by endothelial cells is monocyte chemoattractant protein-1 (MCP-1), a member of the C-C subfamily of chemokines. It exhibits chemoattractive activity on monocytes and T lymphocytes (see Mantovani et al 1 and Baggiolini et al 2 for a review). MCP-1 expression by endothelial cells contributes to the establishment of a chemokine gradient that facilitates subset-specific recruitment of leukocytes to sites of inflammatory challenge. 3 Under flow conditions, MCP-1 triggers firm adhesion of rolling monocytes to E-selectin-expressing vascular endothelium, 4 thus contributing to recruitment of monocytes from the vascular compartment. Experimental models with mice lacking MCP-1 or its receptor, CCR2, or employing neutralizing antibodies against MCP-1 have established the prominent role of this chemokine in the pathogenesis of inflammatory disorders. [5][6][7][8] Induced expression of MCP-1 is strongly dependent on activation of the transcription factor NF-B, whereas basal transcription is regulated by SP-1. 9,10 Exposure of cells to TNF␣ results in the sequential activation of NF-B-inducing kinases (NIKs) and IB kinases ␣ and ␤ (IKK␣/␤). IKKs promote the critical step in which IB␣ phosphorylation finally leads to IB␣ degradation and p50/p65 translocation to the nucleus. Data from IKK knock-out mice suggest that the ␤ isoform of IKKs is the main mediator of pro-inflammatory signaling (see Karin 11 for a review). The transcriptional activity of nuclear NF-B factors is further modulated by protein modification and/or cofactor recruitment. 12,13 Thus, additional signaling events are required. Indeed several pathways have been shown to interfere with NF-B activation: Phosphatidylcholine-specific phospholipase C (PC-PLC), a component of the acidic sphingomyelin pathway, may promote the generation of ceramide upon TNF␣ stimulation and has been implicated in activation of NF-B. 14 Furthermore, members of the mitogen-activated protein (MAP) kinase family such as p38 were shown to be involved in TNF␣-mediated gene expression during inflammatory activation of 21 Recent studies demonstrate that activation of p38 even inhibits TNF␣-induced NF-B activation under certain conditions. 22 Thus, the cross-talk between the p38 MAP kinase cascade and the NF-B-activating pathway may occur at different levels, depending on the extracellular stimuli, the individual gene, and the cell type. We have recently demonstrated that p38 significantly contributes...

Candida albicans Triggers Activation of Distinct Signaling Pathways to Establish a Proinflammatory Gene Expression Program in Primary Human Endothelial Cells

“…In this study, we demonstrate for the first time that Candida activates IKK2 resulting in phosphorylation and subsequent degradation of I B␣ as well as NF-B-dependent transcription. However, in sharp contrast to the prototypical activator of endothelial chemokine expression TNF-␣, the kinetics of IKK2 activation by Candida is markedly delayed, which is in line with reports on other stress-like endothelial stimuli such as PMA, LPS, or nickel chloride (21,36,37). Delayed and persistent activation imply a different mode of activation.…”

“…Albeit the mechanism of p38-dependent gene regulation is not completely understood, increasing evidence suggests an involvement of this pathway in specific posttranscriptional events that result in stabilization or destabilization of mRNA (22,40). Furthermore, p38 may modulate gene expression at the level of transactivation by interacting with components of the enhanceosome, such as the transcriptional coactivator CBP/p300 (21). Highlighting the regulatory complexity, mitogen-and stress-activated protein kinase-1 (MSK1), which acts downstream of p38, has been identified to phosphorylate the NF-B/Rel family member p65 as well as components of the chromatin environment, thereby interfering with NF-B-dependent gene transcription (41,42).…”

Platelet-activating Factor-induced Chemokine Gene Expression Requires NF-κB Activation and Ca2+/Calcineurin Signaling Pathways

“…The role of NF-B activation on chemokine CCL2 production is well established (19,50,51). However, Satonaka et al (48), recently demonstrated that CCL2 gene expression in vascular myocytes requires Ca 2ϩ /calmodulin-mediated calcineurin activation.…”

Stephania delavayi Diels. inhibits breast carcinoma proliferation through the p38 MAPK/NF-κB/COX-2 pathway

“…the NF-κB signaling pathway promotes tumorigenesis and progression (3) by inhibiting apoptosis (4) and inducing G1/s phase transition (5). It is controversial because the effect (i.e., activation or inactivation) of activated p38 MApK on its downstream target NF-κB depends on cell type, environmental conditions, and the substance activating p38 MApK (23)(24)(25)29). However S. delavayi Diels.…”