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Objective-Peroxisome proliferator-activated receptor ␥ (PPAR␥) ligands reduce lesion formation in animal models of atherosclerosis by mechanisms that have not been defined completely. We hypothesized that PPAR␥ ligands stimulate endothelial-derived nitric oxide release (·NO) to protect the vascular wall. Methods and Results-The PPAR␥ ligands, 15-deoxy-⌬ 12,14 -prostaglandin J 2 (15d-PGJ 2 ) or ciglitazone, stimulated a PPAR response element-luciferase reporter construct in transfected porcine pulmonary artery endothelial cells (PAECs), demonstrating that PPAR␥ was transcriptionally functional. Treatment with 15d-PGJ 2 or ciglitazone significantly increased release of ·NO from PAECs or human aortic endothelial cells and augmented calcium ionophore-induced ·NO release from human umbilical vein endothelial cells measured by chemiluminescence analysis of culture media. Increases in ·NO release caused by treatment with 15d-PGJ 2 occurred at 24 hours, but not after 1 to 16 hours, and were abrogated by treatment with the transcriptional inhibitor ␣-amanitin. Overexpression of PPAR␥ or treatment with 9-cis retinoic acid also enhanced PAEC ·NO release. Neither 15d-PGJ 2 nor ciglitazone altered eNOS mRNA, whereas 15d-PGJ 2 , but not ciglitazone, decreased eNOS protein. Key Words: peroxisome proliferator-activated receptor ␥ Ⅲ endothelium Ⅲ nitric oxide Ⅲ nitric oxide synthase Ⅲ thiazolidinedione T he production of nitric oxide (·NO) by vascular endothelial cells is critical for maintenance of normal vascular physiology. 1 In endothelial cells (ECs), the type III endothelial nitric oxide synthase (eNOS) produces ·NO from the amino acid L-arginine. Our preliminary observations, 2 as well as reports by others, [3][4][5] indicate that exogenous fatty acids alter EC ·NO production. The molecular mechanism contributing to fatty acid-induced alterations in EC ·NO production remain unexplored. One potential mechanism for fatty acidinduced alterations in gene expression is the activation of peroxisome proliferator-activated receptors (PPARs). Originally described in 1990, PPARs belong to the nuclear hormone receptor superfamily of ligand-activated transcription factors including steroid, thyroid, and retinoid hormone receptors. 6 Structurally diverse ligands including long-chain fatty acids, eicosanoids, thiazolidinediones, and fibrates activate PPARs, which form obligate heterodimers with the 9-cis retinoic acid receptor, RXR. 7 On ligand binding, PPARs become transcriptionally active at PPAR response elements (PPRE) and alter the expression of target genes. Conclusions-TakenPPAR␥ is expressed in vascular endothelial cells 8 -11 and smooth muscle cells. 12 The expression of PPARs in vascular wall cells suggests their potential role in vascular disease. 8 -10 Some in vitro studies suggest potential atherogenic effects of PPAR␥ activation, 8,[13][14][15] whereas other studies associate PPAR␥ with potential vascular protective effects. 16 -21 Importantly, two independent in vivo studies using the LDL receptor knockout mouse demo...

Trehalose-6,6'-dimycolate (TDM), or cord factor, is a mycobacterial cell wall component that induces granuloma formation and proinflammatory cytokine production in vivo and in vitro. The purpose of this work was to better understand the mechanisms by which TDM promotes lung granuloma formation. This was accomplished by characterizing cytokine mRNA expression during TDM-induced alveolitis culminating in cohesive granuloma development. A single intravenous injection of TDM given to C57BL/6 mice produced lung granulomas that peaked in number 5 days after challenge and were nearly resolved by 14 days. mRNA in whole lung preparations was quantitated by bioluminescent RT-PCR. Tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 were significantly elevated during granuloma development and decreased during granuloma resolution. There were no detectable changes in mRNA for interferon-y (IFN-y), IL-2, IL-4, IL-5, IL-10, and IL-12(p40). The level of TNF-alpha protein extracted from lung minces highly correlated with morphologic indices of granulomatous inflammation, indicating that it may be an important modulator of the inflammatory intensity induced by TDM. TDM may interact specifically with macrophages in vivo, as evidenced by induction of TNF-alpha, IL-1beta, and IL-6, but not IFN-gamma, protein in bone marrow-derived macrophages from C57BL/6 mice. TDM may therefore play an important role early in macrophage activation during the host granulomatous response to mycobacteria.

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Mycobacterium tuberculosis (Mtb) infection induces the expression of matrix metalloproteinase-9 (MMP-9) in mouse lungs. In cultured human monocytic cells, Mtb bacilli and the cell wall glycolipid lipoarabinomannan (LAM) stimulate high levels of MMP-9 activity. Here, we explore the cellular mechanisms involved in the induction of MMP-9 by Mtb. We show that infection of THP-1 cells with Mtb caused a fivefold increase in MMP-9 mRNA that was associated with increased MMP-9 activity. MMP-9 induction was dependent on microtubule polymerization and protein kinase activation and was associated with increased DNA binding by the transcription factor activator protein-1 (AP-1), which appeared to be important for MMP-9 expression. We then explored the surface molecules potentially involved in Mtb induction of MMP-9, focusing on ligands of the mannose and beta-glucan receptors. MMP-9 activity was induced by the mannose receptor ligands mannan, zymosan, and LAM, whereas the beta-glucan receptor ligand laminarin was not effective. The most active inducers of MMP-9 activity were the particulate ligand zymosan and LAM. Pretreatment of cells with an anti-mannose receptor monoclonal antibody, but not anti-complement receptor 3, decreased the induction of MMP-9 activity by Mtb bacilli. Together, these results suggest that MMP-9 induction by Mtb occurs by receptor-mediated signaling mechanisms involving the binding of mannosylated ligands to mannose receptors, the modulation by cytoskeletal elements such as microtubules, the activation of protein kinases, and transcriptional activation by AP-1.