Jorge Plutzky

Upregulation of Endothelial Nitric Oxide Synthase by HMG CoA Reductase Inhibitors

BACKGROUND Oxidized low-density lipoprotein (ox-LDL) causes endothelial dysfunction in part by decreasing the availability of endothelial nitric oxide (NO). Although HMG CoA reductase inhibitors restore endothelial function by reducing serum cholesterol levels, it is not known whether they can also directly upregulate endothelial NO synthase (ecNOS) activity. METHODS AND RESULTS Human saphenous vein endothelial cells were treated with ox-LDL (50 microg/mL thiobarbituric acid reactive substances 12 to 16 nmol/mg) in the presence of HMG CoA reductase inhibitors simvastatin and lovastatin. In a time-dependent manner, ox-LDL decreased ecNOS mRNA and protein levels (91+/-4% and 67+/-8% reduction after 72 hours, respectively). Both simvastatin (1 micromol/L) and lovastatin (10 micromol/L) upregulated ecNOS expression by 3.8-fold and 3.6-fold, respectively, and completely prevented its downregulation by ox-LDL. These effects of simvastatin on ecNOS expression correlated with changes in ecNOS activity. Although L-mevalonate alone did not affect ecNOS expression, cotreatment with L-mevalonate completely reversed ecNOS upregulation by simvastatin. Actinomycin D studies revealed that simvastatin stabilized ecNOS mRNA (tau1/2, 43 versus 35 hours). Nuclear run-on assays and transient transfection studies with a -1.6 kb ecNOS promoter construct showed that simvastatin did not affect ecNOS gene transcription. CONCLUSIONS Inhibition of endothelial HMG CoA reductase upregulates ecNOS expression predominantly by posttranscriptional mechanisms. These findings suggest that HMG CoA reductase inhibitors may have beneficial effects in atherosclerosis beyond that attributed to the lowering of serum cholesterol by increasing ecNOS activity.

Primary Prevention of Cardiovascular Diseases in People With Diabetes Mellitus A Scientific Statement From the American Heart Association and the American Diabetes Association

The American Heart Association (AHA) and the American Diabetes Association (ADA) have each published guidelines for cardiovascular disease prevention: The ADA has issued separate recommendations for each of the cardiovascular risk factors in patients with diabetes, and the AHA has shaped primary and secondary guidelines that extend to patients with diabetes. This statement will attempt to harmonize the recommendations of both organizations where possible but will recognize areas in which AHA and ADA recommendations differ.

International union of pharmacology. LXI. Peroxisome proliferator-activated receptors

The three peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors of the nuclear hormone receptor superfamily. They share a high degree of structural homology with all members of the superfamily, particularly in the DNA-binding domain and ligand- and cofactor-binding domain. Many cellular and systemic roles have been attributed to these receptors, reaching far beyond the stimulation of peroxisome proliferation in rodents after which they were initially named. PPARs exhibit broad, isotype-specific tissue expression patterns. PPARα is expressed at high levels in organs with significant catabolism of fatty acids. PPARβ/δ has the broadest expression pattern, and the levels of expression in certain tissues depend on the extent of cell proliferation and differentiation. PPARγ is expressed as two isoforms, of which PPARγ2 is found at high levels in the adipose tissues, whereas PPARγ1 has a broader expression pattern. Transcriptional regulation by PPARs requires heterodimerization with the retinoid X receptor (RXR). When activated by a ligand, the dimer modulates transcription via binding to a specific DNA sequence element called a peroxisome proliferator response element (PPRE) in the promoter region of target genes. A wide variety of natural or synthetic compounds was identified as PPAR ligands. Among the synthetic ligands, the lipid-lowering drugs, fibrates, and the insulin sensitizers, thiazolidinediones, are PPARα and PPARγ agonists, respectively, which underscores the important role of PPARs as therapeutic targets. Transcriptional control by PPAR/RXR heterodimers also requires interaction with coregulator complexes. Thus, selective action of PPARs in vivo results from the interplay at a given time point between expression levels of each of the three PPAR and RXR isotypes, affinity for a specific promoter PPRE, and ligand and cofactor availabilities.

Peroxisome proliferator-activated receptor gamma activators inhibit gene expression and migration in human vascular smooth muscle cells

Migration of vascular smooth muscle cells (VSMCs) plays an important role in atherogenesis and restenosis after arterial interventions. The expression of matrix metalloproteinases (MMPs), particularly MMP-9, contributes to VSMC migration. This process requires degradation of basal laminae and other components of the arterial extracellular matrix. Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor family, regulate gene expression after activation by various ligands. Recent studies have suggested opposing effects of PPAR gamma (PPARgamma) activation on atherogenesis. The present study tested the hypotheses that human VSMCs express PPAR alpha (PPARalpha) and PPARgamma and that PPAR agonists in VSMCs modulate MMP-9 expression and activity, as well as VSMC migration. Human VSMCs expressed PPARalpha and PPARgamma mRNA and protein. Treatment of VSMCs with the PPARgamma ligands troglitazone and the naturally occurring 15-deoxy-Delta12, 14-prostaglandin J2 (15d-PGJ2) decreased phorbol 12-myristate 13-acetate-induced MMP-9 mRNA and protein levels, as well as MMP-9 gelatinolytic activity in the supernatants in a concentration-dependent manner. Six different PPARalpha activators lacked such effects. Addition of prostaglandin F2alpha, known to limit PPARgamma activity, diminished the MMP-9 inhibition seen with either troglitazone or 15d-PGJ2, further implicating PPARgamma in these effects. Finally, troglitazone and 15d-PGJ2 inhibited the platelet-derived growth factor-BB-induced migration of VSMCs in vitro in a concentration-dependent manner. PPARgamma activation may regulate VSMC migration and expression and activity of MMP-9. Thus, PPARgamma activation in VSMCs, via the antidiabetic agent troglitazone or naturally occurring ligands, may act to counterbalance other potentially proatherosclerotic PPARgamma effects.

PPARα Activators Inhibit Cytokine-Induced Vascular Cell Adhesion Molecule-1 Expression in Human Endothelial Cells

Background—Adhesion molecule expression on the endothelial cell (EC) surface is critical for leukocyte recruitment to atherosclerotic lesions. Better understanding of transcriptional regulation of adhesion molecules in ECs may provide important insight into plaque formation. Peroxisome proliferator–activated receptor-α (PPARα), a member of the nuclear receptor family, regulates gene expression in response to certain fatty acids and fibric acid derivatives. The present study investigated PPARα expression in human ECs and their regulation of vascular cell adhesion molecule-1 (VCAM-1). Methods and Results—Immunohistochemistry revealed that human carotid artery ECs express PPARα. Pretreatment of cultured human ECs with the PPARα activators fenofibrate or WY14643 inhibited TNF-α–induced VCAM-1 in a time- and concentration-dependent manner, an effect not seen with PPARγ activators. Both PPARα activators decreased cytokine-induced VCAM-1 mRNA expression without altering its mRNA half-life. Transient transfection...

Macrophages in Human Atheroma Contain PPARγ: Differentiation-Dependent Peroxisomal Proliferator-Activated Receptor γ (PPARγ) Expression and Reduction of MMP-9 Activity through PPARγ Activation in Mononuclear Phagocytes in Vitro

Mononuclear phagocytes play an important role in atherosclerosis and its sequela plaque rupture in part by their secretion of matrix metalloproteinases (MMPs), including MMP-9. Peroxisomal proliferator-activated receptor γ (PPARγ), a transcription factor in the nuclear receptor superfamily, regulates gene expression in response to various activators, including 15-deoxy-Δ 12,14 -prostaglandin J 2 and the antidiabetic agent troglitazone. The role of PPARγ in human atherosclerosis is unexplored. We report here that monocytes/macrophages in human atherosclerotic lesions ( n = 12) express immunostainable PPARγ. Normal artery specimens ( n = 6) reveal minimal immunoreactive PPARγ. Human monocytes and monocyte-derived macrophages cultured for 6 days in 5% human serum expressed PPARγ mRNA and protein by reverse transcription-polymerase chain reaction and Western blotting, respectively. In addition, PPARγ mRNA expression in U937 cells increased during phorbol 12-myristate 13 acetate-induced differentiation. Stimulation of PPARγ with troglitazone or 15-deoxy-Δ 12,14 -prostaglandin J 2 in human monocyte-derived macrophages inhibited MMP-9 gelatinolytic activity in a concentration-dependent fashion as revealed by zymography. This inhibition correlates with decreased MMP-9 secretion as determined by Western blotting. Thus, PPARγ is present in macrophages in human atherosclerotic lesions and may regulate expression and activity of MMP-9, an enzyme implicated in plaque rupture. PPARγ is likely to be an important regulator of monocyte/macrophage function with relevance for human atherosclerotic disease.

Cardiovascular disease risk in type 2 diabetes mellitus: insights from mechanistic studies

Subjects with diabetes have increased cardiovascular disease risk compared to those without diabetes. Addressing residual cardiovascular disease risk in this disease, beyond blood pressure and LDL cholesterol control, remains important as the prevalence of diabetes increases worldwide. The accelerated atherosclerosis and cardiovascular disease in diabetes is likely multifactorial and there are numerous therapeutic approaches that can be considered. Results of mechanistic studies conducted in isolated cells, animals, or humans can provide important insights with potential to influence clinical management decisions and improve outcomes. In this review, we focus on three areas in which pathophysiologic considerations could be particularly informative in this regard; the roles of hyperglycemia, diabetic dyslipidemia (beyond LDL cholesterol level), and inflammation (including that in adipose tissue) for accelerating vascular injury and the rates of cardiovascular disease in Type 2 diabetes are outlined and evaluated.Individuals with type 2 diabetes mellitus have increased cardiovascular disease risk compared with those without diabetes. Treatment of the residual risk, other than blood pressure and LDL-cholesterol control, remains important as the rate of diabetes increases worldwide. The accelerated atherosclerosis and cardiovascular disease in diabetes is likely to be multifactorial and therefore several therapeutic approaches can be considered. Results of mechanistic studies done in vitro and in vivo--animals and people--can provide important insights with the potential to improve clinical management decisions and outcomes. In this Review, we focus on three areas in which pathophysiological considerations could be particularly informative--ie, the roles of hyperglycaemia, diabetic dyslipidaemia (other than the control of LDL-cholesterol concentrations), and inflammation (including that in adipose tissue) in the acceleration of vascular injury.

PPARγ Activation in Human Endothelial Cells Increases Plasminogen Activator Inhibitor Type-1 Expression PPARγ as a Potential Mediator in Vascular Disease

Abstract—Plasminogen activator inhibitor type-1 (PAI-1) is a major physiological inhibitor of fibrinolysis, with its plasma levels correlating with the risk for myocardial infarction and venous thrombosis. The regulation of PAI-1 transcription by endothelial cells (ECs), a major source of PAI-1, remains incompletely understood. Adipocytes also produce PAI-1, suggesting possible common regulatory pathways between adipocytes and ECs. Peroxisomal proliferator-activated receptor-γ (PPAR)γ is a ligand-activated transcription factor that regulates gene expression in response to various mediators such as 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and oxidized linoleic acid (9- and 13-HODE). The present study tested the hypotheses that human ECs express PPARγ and that this transcriptional activator regulates PAI-1 expression in this cell type. We found that human ECs contain both PPARγ mRNA and protein. Immunohistochemistry of human carotid arteries also revealed the presence of PPARγ in ECs. Bovine ECs transfec...

Primary prevention of cardiovascular diseases in people with diabetes mellitus: A scientific statement from the American Heart Association and the American Diabetes Association

The American Heart Association (AHA) and the American Diabetes Association (ADA) have each published guidelines for cardiovascular disease prevention: the ADA has issued separate recommendations for each of the cardiovascular risk factors in patients with diabetes, and the AHA has shaped primary and secondary guidelines that extend to patients with diabetes. This statement will attempt to harmonize the recommendations of both organizations where possible but will recognize areas in which AHA and ADA recommendations differ.

PPAR Activators as Antiinflammatory Mediators in Human T Lymphocytes Implications for Atherosclerosis and Transplantation-Associated Arteriosclerosis

Abstract— Activation of T lymphocytes and their ensuing elaboration of proinflammatory cytokines, such as interferon (IFN)-&ggr;, represent a critical step in atherogenesis and arteriosclerosis. IFN&ggr; pathways also appear integral to the development of transplantation-associated arteriosclerosis (Tx-AA), limiting long-term cardiac allograft survival. Although disruption of these IFN&ggr; signaling pathways limits atherosclerosis and Tx-AA in animals, little is known about inhibitory regulation of proinflammatory cytokine production in humans. The present study investigated whether activators of peroxisome proliferator-activated receptor (PPAR)&agr; and PPAR&ggr;, with their known antiinflammatory effects, might regulate the expression of proinflammatory cytokines in human CD4-positive T cells. Isolated human CD4-positive T cells express PPAR&agr; and PPAR&ggr; mRNA and protein. Activation of CD4-positive T cells by anti-CD3 monoclonal antibodies significantly increased IFN&ggr; protein secretion from 0 to 504±168 pg/mL, as determined by ELISA. Pretreatment of cells with well-established PPAR&agr; (WY14643 or fenofibrate) or PPAR&ggr; (BRL49653/rosiglitazone or pioglitazone) activators reduced anti-CD3-induced IFN&ggr; secretion in a concentration-dependent manner. PPAR activators also inhibited TNF&agr; and interleukin-2 protein expression. In addition, PPAR activators markedly reduced cytokine mRNA expression in these cells. Such antiinflammatory actions were also evident in cell-cell interactions with medium conditioned by PPAR activator-treated T cells attenuating human monocyte CD64 expression and human endothelial cell major histocompatibility complex class II induction. Thus, activation of PPAR&agr; and PPAR&ggr; in human CD4-positive T cells limits the expression of proinflammatory cytokines, such as IFN&ggr;, yielding potential therapeutic benefits in pathological processes, such as atherosclerosis and Tx-AA.