curcumin and diphenyleneiodonium

Cytosolic phospholipase A(2) (cPLA(2)) plays a pivotal role in mediating agonist-induced arachidonic acid (AA) release for prostaglandin (PG) synthesis during inflammation triggered by tumor necrosis factor-α (TNF-α). However, the mechanisms underlying TNF-α-induced cPLA(2) expression and PGE(2) synthesis in human tracheal smooth muscle cells (HTSMCs) remain unknown. Here, we report that TNF-α-induced cPLA(2) protein and mRNA expression, PGE(2) production, and phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK1/2, which were attenuated by pretreatment with a ROS scavenger [N-acetyl-L-cysteine, (NAC)] and the inhibitors of NADPH oxidase [apocynin (APO) and diphenyleneiodonium chloride (DPI)], MEK1/2 (U0126), p38 MAPK (SB202190), and JNK1/2 (SP600125) or transfection with siRNA of Nox2, p47(phox) , MEK1, p42, p38, or JNK2. TNF-α-induced cPLA(2) expression was also inhibited by pretreatment with a selective NF-κB inhibitor [helenalin (HLN)] or transfection with dominant negative mutants of NF-κB inducing kinase (NIK) or IκB kinase (IKK)α/β. TNF-α-induced NF-κB translocation was blocked by pretreatment with NAC, DPI, APO, or HLN, but not by U0126, SB202190, or SP600125. In addition, pretreatment with curcumin (a p300 inhibitor) or transfection with p300 siRNA blocked cPLA(2) expression and PGE(2) synthesis induced by TNF-α. We further confirmed that p300 was associated with the cPLA(2) promoter which was dynamically linked to histone H4 acetylation stimulated by TNF-α, determined by chromatin immunoprecipitation assay. Association of p300 and histone H4 to cPLA(2) promoter was inhibited by U0126, SB202190, and SP600125. These results suggested that in HTSMCs, activation of p47(phox) , MAPKs, NF-κB, and p300 is essential for TNF-α-induced cPLA(2) expression and PGE(2) release.

Topics: Acetophenones; Acetylation; Acetylcysteine; Cell Line; Curcumin; Dinoprostone; E1A-Associated p300 Protein; Enzyme Inhibitors; Free Radical Scavengers; Histones; Humans; Membrane Glycoproteins; Metabolic Networks and Pathways; Mitogen-Activated Protein Kinases; Myocytes, Smooth Muscle; NADPH Oxidase 2; NADPH Oxidases; NF-kappa B; Onium Compounds; Phospholipases A2; Phosphorylation; Sesquiterpenes; Sesquiterpenes, Guaiane; Trachea; Tumor Necrosis Factor-alpha

Glycated serum albumin (GSA) promotes vascular complications in diabetes. The aim of this study was to determine if GSA induces chemokine, particularly CXCL8 (IL-8), and to determine intracellular signaling pathways activated by GSA in vascular smooth muscle cells (VSMCs). GSA increased IL-8 transcription via promoter activation and enhanced CXCL8 release from VSMCs. GSA-induced promoter activation of the IL-8 gene was suppressed by dominant-negative mutants of TLR-4, MyD88, and TRIF, but not by a dominant-negative form of TLR-2. In addition, IL-8 up-regulation in response to GSA was inhibited by resveratrol, curcumin, diphenyleneiodium, U0126, and SB202190. Mutation at the NF-kappaB- or C/EBP-binding site, but not at the AP-1-binding site, in the IL-8 promoter region suppressed GSA-induced promoter activation. Moreover, gene delivery of IkappaB suppressed CXCL8 release. This study suggests that GSA induces expression of IL-8 in VSMCs and that TLR-4, mitogen-activated protein kinases, NF-kappaB, and NADPH oxidase are involved in that process.

Topics: Butadienes; Cells, Cultured; Curcumin; Glycated Serum Albumin; Glycation End Products, Advanced; Humans; Interleukin-8; Mitogen-Activated Protein Kinase Kinases; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; NADPH Oxidases; NF-kappa B; Nitriles; Onium Compounds; Promoter Regions, Genetic; Resveratrol; Serum Albumin; Stilbenes; Toll-Like Receptor 4; Transcriptional Activation; Up-Regulation

Up-regulation of cytosolic phospholipase A2 (cPLA2) by cigarette smoke extract (CSE) may play a critical role in airway inflammatory diseases. However, the mechanisms underlying CSE-induced cPLA2 expression in human tracheal smooth muscle cells (HTSMCs) remain unknown. CSE induced cPLA2 protein and mRNA expression, and ROS generation was attenuated by pretreatment with a reactive oxygen species (ROS) scavenger (N-acetylcysteine), or inhibitors of NADPH oxidase (diphenyleneiodonium chloride, apocynin) and transfection with p47phox siRNA, suggesting that CSE-induced cPLA2 expression was mediated through NADPH oxidase activation and ROS production in HTSMCs. Furthermore, CSE-induced cPLA2 expression was attenuated by pretreatment with the inhibitors of MEK1/2 (U0126), p38 MAPK (SB202190), and JNK (SP600125), which were further confirmed by transfection with siRNAs of JNK1, p42, and p38 to down-regulate the expression of respective proteins and reduce cPLA2 expression. Induction of cPLA2 by CSE was attenuated by selective inhibitors of NF-kappaB (helenalin) and AP-1 (curcumin). Moreover, promoter assays revealed that increases of cPLA2, NF-kappaB, and AP-1 luciferase activities stimulated by CSE were attenuated by these inhibitors. These results suggest that in HTSMCs, CSE induced NADPH oxidase activation leading to phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK. These reactions induced nuclear transcription NF-kappaB and AP-1 activities which were essential for CSE-induced cPLA2 gene expression.

Topics: Acetophenones; Acetylcysteine; Butadienes; Cells, Cultured; Curcumin; Cytoplasm; Gene Expression Regulation, Enzymologic; Humans; MAP Kinase Kinase Kinases; Myocytes, Smooth Muscle; NADPH Oxidases; NF-kappa B; Nitriles; Onium Compounds; Oxidative Stress; p38 Mitogen-Activated Protein Kinases; Phospholipases A2; RNA, Small Interfering; Sesquiterpenes; Sesquiterpenes, Guaiane; Smoking; Trachea; Transcription Factor AP-1; Transcriptional Activation