Resistin, originally described as an adipocyte‐specific hormone, has been suggested to be an important link between obesity, insulin resistance and diabetes. Although its expression was initially defined in adipocytes, significant levels of resistin expression in humans are mainly found in mononuclear leukocytes, macrophages, spleen and bone marrow cells. Increasing evidence indicates that resistin plays important regulatory roles apart from its role in insulin resistance and diabetes in a variety of biological processes: atherosclerosis and cardiovascular disease (CVD), non‐alcoholic fatty liver disease, autoimmune disease, malignancy, asthma, inflammatory bowel disease and chronic kidney disease. As CVD accounts for a significant amount of morbidity and mortality in patients with diabetes and without diabetes, it is important to understand the role that adipokines such as resistin play in the cardiovascular system. Evidence suggests that resistin is involved in pathological processes leading to CVD including inflammation, endothelial dysfunction, thrombosis, angiogenesis and smooth muscle cell dysfunction. The modes of action and signalling pathways whereby resistin interacts with its target cells are beginning to be understood. In this review, the current knowledge about the functions and pathophysiological implications of resistin in CVD development is summarized; clinical translations, therapeutic considerations and future directions in the field of resistin research are discussed. LINKED ARTICLES This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3

We reported previously that homocysteine (Hcy) inhibits endothelial cell (EC) growth by transcriptional inhibition of the cyclin A gene via a hypomethylationrelated mechanism. In this study, we examined the effect of Hcy on epigenetic modification of the cyclin A gene and its biologic role in human ECs. Cyclin A mRNA levels were significantly suppressed by Hcy and a DNA methyltransferase inhibitor. The cyclin A promoter contains a CpG island spanning a 477-bp region (؊277/200). Bisulfite sequencing followed by polymerase chain reaction (PCR) amplification of the cyclin A promoter (؊267/37) showed that Hcy eliminated methylation at 2 CpG sites in the cyclin A promoter, one of which is located on the cycle-dependent element (CDE). Mutation of CG sequence on the CDE leads to a 6-fold increase in promoter activity. Hcy IntroductionHyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease (CVD), but the underlying mechanisms remain unclear. Although numerous studies have established that homocysteine (Hcy) has atherogenic effects on cultured vascular cells and in animal models of HHcy, the biochemical basis by which HHcy contributes to arteriosclerosis remains largely undefined.We initially proposed hypomethylation as a specific biochemical mechanism by which Hcy induces vascular injury. 1,2 Hcy can use adenosine, a normal constituent of all body fluids, to form S-adenosyl-homocysteine (SAH), a potent inhibitor of cellular methylation. We have demonstrated that Hcy, but not cysteine, arrested cell growth and increased cellular SAH concentration in endothelial cells (ECs), but not in vascular smooth muscle cells (VSMCs). 3 The hypomethylation hypothesis is supported by clinical studies showing that elevated Hcy levels in patients are linked to increased SAH and impaired erythrocyte membrane protein methylation, 4 and by animal studies showing that cystathionine ␤-synthase (CBS)-deficient mice have increased SAH levels and decreased DNA methylation. 5,6 Because damage to and impaired regeneration of ECs is a key feature of arteriosclerosis, growth inhibition of ECs may represent an important mechanism by which Hcy induces atherosclerosis.Our recent work suggested that the cyclin A gene is an important molecular target that mediates Hcy-induced EC growth inhibition. 7 Cyclin A (also named cyclin A2 as opposed to the male germ cell-specific cyclin A1) promotes both G1/S and G2/M transitions of the cell cycle in somatic cells. Cyclin A is expressed in late G1 and throughout S phase, and is controlled mainly at the transcriptional level. We have shown that the cyclin A gene is differentially regulated at a transcriptional level by Hcy in vascular cells. In ECs, clinically relevant concentrations of Hcy (10-50 M) arrested the cell cycle at G1/S transition via cyclinAtranscriptional inhibition. 7 In contrast, a supraphysiological concentration of Hcy (1 mM) activated cyclin A and promoted cell proliferation of VSMCs. 8 Because cyclin A transcriptional inhibition by Hcy is associated with SAH accum...

The purpose of this study was to determine the effects and mechanisms of sCD40L on endothelial dysfunction in both human coronary artery endothelial cells (HCAECs) and porcine coronary artery rings. HCAECs treated with sCD40L showed significant reductions of endothelial nitric oxide synthase (eNOS) mRNA and protein levels, eNOS mRNA stability, eNOS enzyme activity, and cellular NO levels, whereas superoxide anion (O(2)(-)) production was significantly increased. sCD40L enhanced eNOS mRNA 3'UTR binding to cytoplasmic molecules and induced a unique expression pattern of 95 microRNAs. sCD40L significantly decreased mitochondrial membrane potential, and catalase and SOD activities, whereas it increased NADPH oxidase (NOX) activity. sCD40L increased phosphorylation of MAPKs p38 and ERK1/2 as well as IkappaBalpha and enhanced NF-kappaB nuclear translocation. In porcine coronary arteries, sCD40L significantly decreased endothelium-dependent vasorelaxation and eNOS mRNA levels, whereas it increased O(2)(-) levels. Antioxidant seleno-l-methionine; chemical inhibitors of p38, ERK1/2, and mitochondrial complex II; as well as dominant negative mutant forms of IkappaBalpha and NOX4 effectively blocked sCD40L-induced eNOS down-regulation in HCAECs. Thus, sCD40L reduces eNOS levels, whereas it increases oxidative stress through the unique molecular mechanisms involving eNOS mRNA stability, 3'UTR-binding molecules, microRNAs, mitochondrial function, ROS-related enzymes, p38, ERK1/2, and NF-kappaB signal pathways in endothelial cells.

Hyperhomocysteinemia (HHcy) has been established as a potent independent risk factor for cardiovascular disease (CVD) and the underlying mechanism is largely unknown. We were the first to propose that hypomethylation is the key biochemical mechanism by which homocysteine (Hcy) inhibits endothelial cell (EC) growth. We reported that clinically relevant concentrations of Hcy (10-50 micromol/L) exerts highly selective inhibitory effects on cyclin A transcription and EC growth through a hypomethylation related mechanism, which blocks cell cycle progression and endothelium regeneration. Recently, we demonstrated that Hcy reduces DNA methyltransferase 1 (DNMT1) activity and demethylates cyclin A promoter leading to cyclin A chromatin remodeling. We found that adenovirus-transduced DNMT1 gene expression reverses the inhibitory effect of Hcy on cyclin A expression and EC growth inhibition. We hypothesize that DNA hypomethylation is a key biochemical mechanism responsible for Hcy-induced cyclin A suppression and growth inhibition in EC and contributes to CVD.

AbstractmiRNAs are small, endogenously expressed noncoding RNAs that regulate gene expression, mainly at the post-transcriptional level, via degradation or translational inhibition of their target mRNAs. Functionally, an individual miRNA can regulate the expression of multiple target genes. The study of miRNAs is rapidly growing and recent studies have revealed a significant role of miRNAs in vascular biology and disease. Many miRNAs are highly expressed in the vasculature, and their expression is dysregulated in diseased vessels. Several miRNAs have been found to be critical modulators of vascular pathologies, such as atherosclerosis, lipoprotein metabolism, inflammation, arterial remodeling, angiogenesis, smooth muscle cell regeneration, hypertension, apoptosis, neointimal hyperplasia and signal transduction pathways. Thus, miRNAs may serve as novel biomarkers and/or therapeutic targets for vascular disease. This article summarizes the current studies related to the disease correlations and functional roles of miRNAs in the vascular system and discusses the potential applications of miRNAs in vascular disease. Keywordsatherosclerosis; biomarker; lipoprotein metabolism; miRNA; therapeutic target; vascular disease; vascular smooth muscle cell The cardiovascular system is composed of the heart, blood vessels and blood. It is connected intimately with every other organ system, and dysfunction of the cardiovascular system can have devastating downstream effects. The lumen of blood vessels is lined by a monolayer of endothelial cells, which forms the main physical barrier between the blood and vessel wall, controlling the movement of solutes and fluid from the vascular space to the surrounding tissues [1]. Endothelial dysfunction owing to breakdown of the endothelial cell-cell barrier can promote atherogenesis through the increased adherence of leukocytes, monocytes and macrophages, and subendothelial accumulation of cholesterol-bearing lipoproteins [2,3]. Meanwhile, vascular smooth muscle cells (VSMCs) below the endothelium undergo phenotypic modulation from a contractile phenotype to a proliferative state under the influence of mechanical stress, growth factors, inflammatory mediators, such as low-density lipoprotein (LDL) deposition, and leukocyte or monocyte infiltration [4]. Aberrant