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The PTEN tumor suppressor gene modulates several cellular functions, including cell migration, survival, and proliferation [1] by antagonizing phosphatidylinositol 3-kinase (PI 3-kinase)-mediated signaling cascades. Mechanisms by which the expression of PTEN is regulated are, however, unclear. The ligand-activated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) [2] has been shown to regulate differentiation and/or cell growth in a number of cell types [3, 4, 5], which has led to the suggestion that PPARgamma, like PTEN [1, 6], could act as a tumor suppressor. PPARgamma has also been implicated in anti-inflammatory responses [7, 8], although downstream mediators of these effects are not well defined. Here, we show that the activation of PPARgamma by its selective ligand, rosiglitazone, upregulates PTEN expression in human macrophages, Caco2 colorectal cancer cells, and MCF7 breast cancer cells. This upregulation correlated with decreased PI 3-kinase activity as measured by reduced phosphorylation of protein kinase B. One consequence of this was that rosiglitazone treatment reduced the proliferation rate of Caco2 and MCF7 cells. Antisense-mediated disruption of PPARgamma expression prevented the upregulation of PTEN that normally accompanies monocyte differentiation and reduced the proportion of macrophages undergoing apoptosis, while electrophoretic mobility shift assays showed that PPARgamma is able to bind two response elements in the genomic sequence upstream of PTEN. Our results demonstrate a role for PPARgamma in regulating PI 3-kinase signaling by modulating PTEN expression in inflammatory and tumor-derived cells.

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The peroxisome proliferator-activated receptors (PPARs) are a family of fatty acid-activated transcription factors which control lipid homeostasis and cellular differentiation. PPAR␣ (NR1C1) controls lipid oxidation and clearance in hepatocytes and PPAR␥ (NR1C3) promotes preadipocyte differentiation and lipogenesis. Drugs that activate PPAR␣ are effective in lowering plasma levels of lipids and have been used in the management of hyperlipidemia. PPAR␥ agonists increase insulin sensitivity and are used in the management of type 2 diabetes. In contrast, there are no marketed drugs that selectively target PPAR␦ (NR1C2) and the physiological roles of PPAR␦ are unclear. In this report we demonstrate that the expression of PPAR␦ is increased during the differentiation of human macrophages in vitro. In addition, a highly selective agonist of PPAR␦ (compound F) promotes lipid accumulation in primary human macrophages and in macrophages derived from the human monocytic cell line, THP-1. Compound F increases the expression of genes involved in lipid uptake and storage such as the class A and B scavenger receptors (SRA, CD36) and adipophilin. PPAR␦ activation also represses key genes involved in lipid metabolism and efflux, i.e. cholesterol 27-hydroxylase and apolipoprotein E. We have generated THP-1 sublines that overexpress PPAR␦ and have confirmed that PPAR␦ is a powerful promoter of macrophage lipid accumulation. These data suggest that PPAR␦ may play a role in the pathology of diseases associated with lipidfilled macrophages, such as atherosclerosis, arthritis, and neurodegeneration.

Abstract-We studied the expression of lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ), an enzyme capable of hydrolyzing platelet-activating factor (PAF), PAF-like phospholipids, and polar-modified phosphatidylcholines, in human and rabbit atherosclerotic lesions. Oxidative modification of low-density lipoprotein, which plays an important role in atherogenesis, generates biologically active PAF-like modified phospholipid derivatives with polar fatty acid chains. PAF is known to have a potent proinflammatory activity and is inactivated by its hydrolysis. On the other hand, lysophosphatidylcholine and oxidized fatty acids released from oxidized low-density lipoprotein as a result of Lp-PLA 2 activity are thought to be involved in the progression of atherosclerosis. Using combined in situ hybridization and immunocytochemistry, we detected Lp-PLA 2 mRNA and protein in macrophages in both human and rabbit atherosclerotic lesions. Reverse transcriptase-polymerase chain reaction analysis indicated an increased expression of Lp-PLA 2 mRNA in human atherosclerotic lesions. In addition, Ϸ6-fold higher Lp-PLA 2 activity was detected in atherosclerotic aortas of Watanabe heritable hyperlipidemic rabbits compared with normal aortas from control rabbits. It is concluded that (1) macrophages in both human and rabbit atherosclerotic lesions express Lp-PLA 2 , which could cleave any oxidatively modified phosphatidylcholine present in the lesion area, and (2) modulation of Lp-PLA 2 activity could lead to antiatherogenic effects in the vessel wall.

Objective-Comparison of gene expression in stable versus unstable atherosclerotic plaque may be confounded by interpatient variability. The aim of this study was to identify differences in gene expression between stable and unstable segments of plaque obtained from the same patient. Methods and Results-Human carotid endarterectomy specimens were segmented and macroscopically classified using a morphological classification system. Two analytical methods, an intraplaque and an interplaque analysis, revealed 170 and 1916 differentially expressed genes, respectively using Affymetrix gene chip analysis. A total of 115 genes were identified from both analyses. The differential expression of 27 genes was also confirmed using quantitative-polymerase chain reaction on a larger panel of samples. Eighteen of these genes have not been associated previously with plaque instability, including the metalloproteinase, ADAMDEC1 (Ϸ37-fold), retinoic acid receptor responder-1 (Ϸ5-fold), and cysteine protease legumain (Ϸ3-fold). Matrix metalloproteinase-9 (MMP-9), cathepsin B, and a novel gene, legumain, a potential activator of MMPs and cathepsins, were also confirmed at the protein level. Key Words: atherosclerosis Ⅲ gene expression Ⅲ stroke Ⅲ affymetrix Ⅲ MMP-9 Ⅲ legumain Ⅲ plaque instability A therosclerosis is a chronic inflammatory disease that remains a major cause of morbidity in the Western world. The composition and vulnerability of the atherosclerotic plaque are considered to be important factors in the development of arterial thrombus and embolic complications. 1 However, the precise mechanisms by which plaque ruptures remain to be determined 2,3 Gene expression techniques such as microarrays and representational difference analysis are powerful tools that can be used to probe the complexities underlying atherosclerotic plaque initiation and progression. 4 -6 These techniques have already been used to show altered gene expression between normal and diseased arteries, 6,7 between different stages in disease progression 8,9 and differential expression in samples of atherosclerotic plaque classified according to patient symptomatology. 10 However, there are drawbacks to these types of comparisons. The differences in the cellular composition and morphology between plaque and normal arterial wall may lead to differences in gene expression that simply reflect this variation. In addition, the high degree of variability in plaque composition and gene expression in different patients may confound comparative analysis in studies that use pooled samples. [11][12][13] Features of unstable plaque such as surface ulceration and rupture occur in both symptomless and symptomatic patients, 14 and this can also confound studies that classify samples according to patient symptomatology. Conclusions-TheThe aim of this study was to use a whole transcriptome analysis to characterize the gene expression signature of unstable regions of carotid endarterectomy (CEA) specimens using a stable region of the same specimen as an internal control. ...

Chlamydia psittaci is an obligate intracellular bacterium. Interest in Chlamydia stems from its high degree of virulence as an intestinal and pulmonary pathogen across a broad range of animals, including humans. C. psittaci human pulmonary infections, referred to as psittacosis, can be life-threatening, which is why the organism was developed as a bioweapon in the 20th century and is listed as a CDC biothreat agent. One remarkable recent result from comparative genomics is the finding of frequent homologous recombination across the genome of the sexually transmitted and trachoma pathogen Chlamydia trachomatis. We sought to determine if similar evolutionary dynamics occurred in C. psittaci. We analyzed 20 C. psittaci genomes from diverse strains representing the nine known serotypes of the organism as well as infections in a range of birds and mammals, including humans. Genome annotation revealed a core genome in all strains of 911 genes. Our analyses showed that C. psittaci has a history of frequently switching hosts and undergoing recombination more often than C. trachomatis. Evolutionary history reconstructions showed genome-wide homologous recombination and evidence of whole-plasmid exchange. Tracking the origins of recombinant segments revealed that some strains have imported DNA from as-yet-unsampled or -unsequenced C. psittaci lineages or other Chlamydiaceae species. Three ancestral populations of C. psittaci were predicted, explaining the current population structure. Molecular clock analysis found that certain strains are part of a clonal epidemic expansion likely introduced into North America by South American bird traders, suggesting that psittacosis is a recently emerged disease originating in New World parrots.

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