Troglitazone inhibits vascular smooth muscle cell growth and intimal hyperplasia

The Role of NF-κB, PPAR-α, and PPAR-γ in Older Adults with Metabolic Syndrome

The etiopathogenesis of metabolic syndrome (MetS) has not been fully understood yet, and chronic low-grade inflammation is thought to be associated with the development of complications related to MetS. We aimed to investigate the role of Nuclear factor Kappa B ( NF-κB ), Peroxisome Proliferator-Activated Receptor- α and γ (PPAR-α, and PPAR-γ) which are the main markers of inflammation in older adults with MetS. A total of 269 patients aged≥18, 188 patients with MetS who met the diagnostic criteria of the International Diabetes Federation, and 81 controls who applied to geriatrics and general internal medicine outpatient clinics for various reasons were included in the study. Patients were separated into four groups: young with MetS (< 60, n=76), elderly with MetS (≥60, n=96), young control (< 60, n=31), elderly controls (≥60, n=38). Carotid intima-media thickness (CIMT) and NF-κB , PPAR-α, and PPAR-γ plasma levels were measured in all of the participants. Age and sex distribution were similar between MetS and control groups. C-reactive protein (CRP), NF-κB levels (p=0.001) and CIMT (p<0,001) of MetS group were significantly higher than in the control groups. On the other hand, the PPAR-γ (p=0.008) and PPAR-α (p=0.003) levels were significantly lower in MetS. ROC analysis revealed that the NF-κB, PPAR-α, and PPAR-γ could be used to indicate MetS in younger adults (AUC: 0.735, p<0.000; AUC: 0.653, p=0.003), whereas it could not be an indicator in older adults (AUC: 0.617, p=0.079; AUC:0.530, p=0.613). It seems that these markers have important roles in MetS-related inflammation. In our results, suggest that the indicator feature of NF-κB , PPAR-α and PPAR-γ in recognizing MetS in young individuals is lost in older adults with Mets.

Diabetes and restenosis

Restenosis, defined as the re-narrowing of an arterial lumen after revascularization, represents an increasingly important issue in clinical practice. Indeed, as the number of stent placements has risen to an estimate that exceeds 3 million annually worldwide, revascularization procedures have become much more common. Several investigators have demonstrated that vessels in patients with diabetes mellitus have an increased risk restenosis. Here we present a systematic overview of the effects of diabetes on in-stent restenosis. Current classification and updated epidemiology of restenosis are discussed, alongside the main mechanisms underlying the pathophysiology of this event. Then, we summarize the clinical presentation of restenosis, emphasizing the importance of glycemic control in diabetic patients. Indeed, in diabetic patients who underwent revascularization procedures a proper glycemic control remains imperative.

The Role of PPAR-γ in Allergic Disease

PURPOSE OF REVIEW

The incidence of allergic diseases such as asthma, rhinitis and atopic dermatitis has risen at an alarming rate over the last century. Thus, there is a clear need to understand the critical factors that drive such pathologic immune responses. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear receptor that has emerged as an important regulator of multiple cell types involved in the inflammatory response to allergens; from airway epithelial cells to T Helper (TH) cells.

RECENT FINDINGS

Initial studies suggested that agonists of PPAR-γ could be employed to temper allergic inflammation, suppressing pro-inflammatory gene expression programs in epithelial cells. Several lines of work now suggest that PPAR-γ plays an essential in promoting 'type 2' immune responses that are typically associated with allergic disease. PPAR-γ has been found to promote the functions of TH2 cells, type 2 innate lymphoid cells, M2 macrophages and dendritic cells, regulating lipid metabolism and directly inducing effector gene expression. Moreover, preclinical models of allergy in gene-targeted mice have increasingly implicated PPAR-γ in driving allergic inflammation. Herein, we highlight the contrasting roles of PPAR-γ in allergic inflammation and hypothesize that the availability of environmental ligands for PPAR-γ may be at the heart of the rise in allergic diseases worldwide.

The Effects of Glucose Lowering Agents on the Secondary Prevention of Coronary Artery Disease in Patients with Type 2 Diabetes

BACKGROUND

Patients with diabetes have a higher risk of requiring repeated percutaneous coronary intervention (PCI) than non-diabetic patients. We aimed to evaluate and compare the effects of anti-diabetic drugs on the secondary prevention of myocardial infarction among type 2 diabetes mellitus patients.

METHODS

We analyzed the general health check-up dataset and claims data of the Korean National Health Insurance Service of 199,714 participants (age ≥30 years) who underwent PCIs between 2010 and 2013. Those who underwent additional PCI within 1 year of their first PCI (n=3,325) and those who died within 1 year (n=1,312) were excluded. Patients were classified according to their prescription records for glucose-lowering agents. The primary endpoint was the incidence rate of coronary revascularization.

RESULTS

A total of 35,348 patients were included in the study. Metformin significantly decreased the risk of requiring repeat PCI in all patients (adjusted hazard ratio [aHR], 0.77). In obese patients with body mass index (BMI) ≥25 kg/m2, patients treated with thiazolidinedione (TZD) exhibited a decreased risk of requiring repeat revascularization than those who were not treated with TZD (aHR, 0.77; 95% confidence interval, 0.63 to 0.95). Patients treated with metformin showed a decreased risk of requiring revascularization regardless of their BMI. Insulin, meglitinide, and alpha-glucosidase inhibitor were associated with increased risk of repeated PCI.

CONCLUSION

The risk of requiring repeat revascularization was lower in diabetic patients treated with metformin and in obese patients treated with TZD. These results suggest that physicians should choose appropriate glucose-lowering agents for the secondary prevention of coronary artery disease.

The protective effect of HOXA5 on carotid atherosclerosis occurs by modulating the vascular smooth muscle cell phenotype

The phenotypic change of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic form is a key player in atherogenic processes. Homeobox A5 (HOXA5), a transcription factor of the homeobox gene family, has been shown to regulate cell differentiation and morphogenesis. The present study was designed to clarify the involvement of HOXA5 in VSMC phenotypic transition in carotid atherosclerosis (CAS). Activated VSMCs in vitro and ApoE^-/- mice in vivo were employed to determine HOXA5's function. Results showed that both the mRNA and protein expression levels of HOXA5 were decreased in platelet-derived growth factor-BB (PDGF-BB)-induced VSMCs. Overexpression of HOXA5 suppressed VSMC conversion from a contractile to a synthetic type in the presence of PDGF-BB, as evidenced by increased contractile markers (calponin, α-SMA and SM22α) along with decreased synthetic markers (vimentin, PCNA and thrombospondin). PDGF-BB-induced proliferation and migration of VSMCs were recovered by HOXA5. Knockdown of HOXA5 had the opposite effect on VSMCs. In vivo, a CAS model was established using ApoE^-/- mice fed with a Western-type diet and placing a perivascular carotid collar. We observed a significant reduction in HOXA5 in the carotid arteries of CAS mice. Similar to the in vitro results, HOXA5 overexpression reduced neointimal hyperplasia and plaque formation and inhibited VSMC dedifferentiation and migration. Furthermore, PPARγ was also downregulated in vitro and in vivo, and its antagonist GW9662 reversed HOXA5-mediated inhibition of VSMC dedifferentiation and migration. In summary, we suggest that HOXA5 protects against CAS progression by inhibiting VSMC dedifferentiation through activation of PPARγ.

Cardiovascular Outcomes in Patients With Previous Myocardial Infarction and Mild Diabetes Mellitus Following Treatment With Pioglitazone: Reports of a Randomised Trial From The Japan Working Group for the Assessment Whether ioglitazone rotects DM Patients gainst e-Infarction (PPAR Study)

BACKGROUND

Secondary prevention in patients with myocardial infarction (MI) is critically important to prevent ischaemic heart failure and reduce social burden. Pioglitazone improves vascular dysfunction and prevents coronary atherosclerosis, mainly via anti-inflammatory and antiatherogenic effects by enhancing adiponectin production in addition to antihyperglycemic effects, thus suggesting that pioglitazone attenuates cardiovascular events in patients with mild (HbA1c levels < 6·5%) diabetes mellitus (DM). Therefore, we evaluated the effects of pioglitazone on cardiovascular events in patients with both previous MI and mild DM.

METHODS

In this multicentre, prospective, randomised, open, blinded-endpoint trial, we randomly assigned 630 patients with mild DM with a history of MI to undergo either DM therapy with (pioglitazone group) or without (control group) pioglitazone. DM was diagnosed using the 75-g oral glucose tolerance test, and mild DM was defined if HbA1c level was < 6·5%. The primary endpoint was the composite of cardiovascular death and hospitalisation caused by acute MI, unstable angina, coronary revascularisation (including percutaneous coronary intervention and cardiac bypass surgery), and stroke.

FINDINGS

HbA1C levels were 5·9 and 5·8% (p = 0·71) at baseline and 6·0 and 5·8% (p < 0·01) at 2 years for the control and pioglitazone groups, respectively.The primary endpoint was observed in 14·2% and 14·1% patients in the control and pioglitazone groups during two years (95% confidential interval (CI):0.662-1·526, p = 0·98), respectively; the incidence of MI and cerebral infarction was 0·3% and 2·2% (95%CI: 0·786-32·415, p = 0·09) and 1·0% and 0·3% (95%CI: 0·051-3·662, p = 0·44), respectively. Post-hoc analyses of the 7-year observation period showed that these trends were comparable (21·9% and 19·2% in the control and pioglitazone groups, 95%CI: 0.618-1·237, p = 0·45).

INTERPRETATION

Pioglitazone could not reduce the occurrence of cardiovascular events in patients with mild DM and previous MI.

Assessment of potential biomarkers of atherosclerosis in Indian patients with type 2 diabetes mellitus

Background & objectives:

Various biological markers of subclinical atherosclerosis have been proposed to predict cardiovascular events in patients with diabetes mellitus (DM). However, there are only a few clinical studies assessing the role of invasive biomarkers [CD-36, peroxisome proliferator-activated receptor gamma (PPAR-γ) and YKL-40] in Indian patients with type 2 DM (T2DM). Hence, the present study was conducted to assess protein levels and gene expression of CD-36, PPAR-γ and YKL-40 in patients with T2DM and compare that with hypertensive and healthy controls.

Methods:

All the participants were subjected to medical history, anthropometric measurements and biochemical and biomarker (ELISA and real-time polymerase chain reaction) estimations. The study groups consisted of patients with T2DM (>5 yr) with hypertension (n=55), patients with T2DM (<2 yr) without hypertension (n=28), hypertensive controls (n=31) and healthy controls (n=30).

Results:

Gene expressions of YKL-40 and CD36 were significantly higher in patients with T2DM (>5 yr) with hypertension compared to healthy controls (P=0.006). In addition, a significant increase in serum levels of sCD36, PPAR-γ and YKL-40 was observed in patients with T2DM (>5 yr) with hypertension compared to healthy controls (P< 0.05). Serum levels as well as gene expression of CD36 showed significant correlation with serum levels as well as gene expression of PPAR-γ (ρ=0.45 and ρ=0.51; P< 0.001), respectively.

Interpretation & conclusions:

CD36 and YKL-40 may be potential inflammatory biomarkers for early onset of atherosclerosis in patients with T2DM.

Enzyme-modified non-oxidized LDL (ELDL) induces human coronary artery smooth muscle cell transformation to a migratory and osteoblast-like phenotype

Enzyme modified non-oxidative LDL (ELDL) is effectively taken up by vascular smooth muscle cells (SMC) and mediates transition into foam cells and produces phenotypic changes in SMC function. Our data show that incubation of human coronary artery SMC (HCASMC) with low concentration of ELDL (10 μg/ml) results in significantly enhanced foam cell formation compared to oxidized LDL (200 μg/ml; p < 0.01) or native LDL (200 μg/ml; p < 0.01). Bioinformatic network analysis identified activation of p38 MAPK, NFkB, ERK as top canonical pathways relevant for biological processes linked to cell migration and osteoblastic differentiation in ELDL-treated cells. Functional studies confirmed increased migration of HCASMC upon stimulation with ELDL (10 μg/ml) or Angiopoietin like protein 4, (ANGPTL4, 5 μg/ml), and gain in osteoblastic gene profile with significant increase in mRNA levels for DMP-1, ALPL, RUNX2, OPN/SPP1, osterix/SP7, BMP and reduction in mRNA for MGP and ENPP1. Enhanced calcification of HCASMC by ELDL was demonstrated by Alizarin Red staining. In summary, ELDL is highly potent in inducing foam cells in HCASMC and mediates a phenotypic switch with enhanced migration and osteoblastic gene profile. These results point to the potential of ELDL to induce migratory and osteoblastic effects in human smooth muscle cells with potential implications for migration and calcification of SMCs in human atherosclerosis.

Atherosclerosis is a vascular stem cell disease caused by insulin

The present article proposes the hypothesis that when multipotent vascular stem cells are exposed to excessive insulin in a rhythmic pattern of sharply rising and falling concentrations, their differentiation is misdirected toward adipogenic and osteogenic cell lineages. This results in plaque-like accumulation of adipocytes with fat and cholesterol deposition from adipocyte debris, and osteogenic (progenitor) cells with a calcified matrix in advanced lesions. The ingrowth of capillaries and infiltration with macrophages, which upon uptake of lipids turn into foam cells, are unspecific pro-resolving reactions. Epidemiological, histopathological, pharmacological, and experimental evidence in favour of this hypothesis is summarised.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

Arterial smooth muscle dynamics in development and repair

Arterial vasculature distributes blood from early embryonic development and provides a nutrient highway to maintain tissue viability. Atherosclerosis, peripheral artery diseases, stroke and aortic aneurysm represent the most frequent causes of death and are all directly related to abnormalities in the function of arteries. Vascular intervention techniques have been established for the treatment of all of these pathologies, yet arterial surgery can itself lead to biological changes in which uncontrolled arterial wall cell proliferation leads to restricted blood flow. In this review we describe the intricate cellular composition of arteries, demonstrating how a variety of distinct cell types in the vascular walls regulate the function of arteries. We provide an overview of the developmental origin of arteries and perivascular cells and focus on cellular dynamics in arterial repair. We summarize the current knowledge of the molecular signaling pathways that regulate vascular smooth muscle differentiation in the embryo and in arterial injury response. Our review aims to highlight the similarities as well as differences between cellular and molecular mechanisms that control arterial development and repair.

Pioglitazone Attenuates Injury-Induced Neointima Formation in Mouse Femoral Artery Partially through the Activation of AMP-Activated Protein Kinase

BACKGROUND/AIMS

Pioglitazone (PIO), an antidiabetic drug, has been shown to attenuate vascular smooth muscle cell (VSMC) proliferation, which is a major event in atherosclerosis and restenosis after angioplasty. Till date, the likely contributory role of AMP-activated protein kinase (AMPK) toward PIO inhibition of VSMC proliferation has not been examined in vivo. This study is aimed at determining whether pharmacological inhibition of AMPK would prevent the inhibitory effect of PIO on neointima formation in a mouse model of arterial injury.

METHODS

Male CJ57BL/6J mice were subjected to femoral artery injury using guidewire. PIO (20 mg/kg/day) was administered orally 1 day before surgery and for 3 weeks until sacrifice in the absence or presence of compound C (an AMPK inhibitor). Injured femoral arteries were used for morphometric analysis of neointima formation. Aortic tissue lysates were used for immunoblot analysis of phosphorylated AMPK.

RESULTS

PIO treatment resulted in a significant decrease in intima-to-media ratio by ∼50.3% (p < 0.05, compared with vehicle control; n = 6), which was accompanied by enhanced phosphorylation of AMPK by ∼85% in the vessel wall. Compound C treatment led to a marked reduction in PIO-mediated inhibition of neointima formation.

CONCLUSION

PIO attenuates injury-induced neointima formation, in part, through the activation of AMPK.

Alliin, a garlic organosulfur compound, ameliorates gut inflammation through MAPK-NF-κB/AP-1/STAT-1 inactivation and PPAR-γ activation

SCOPE

In this study, the anti-inflammatory effects and the molecular mechanism of alliin were analyzed in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide-stimulated RAW264.7 cell model.

METHODS

The phenotype of mice was recorded in the DSS-induced and/or alliin (500 mg/kg) groups. Histopathological alterations were analyzed by H&E staining. MPO and MDA of colon tissues were measured. The mRNA expression levels of inflammatory factors were determined by qRT-PCR, and protein expressions of inflammatory factors or activation of kinases were determined by Western blotting.

RESULTS

Oral administration of alliin significantly inhibited the decrease of body weight, improved the DAI and decreased the infiltration of inflammatory cells in colonic tissues. The content of NO, MDA, and MPO, the expression of iNOS and inflammatory factors as well as MAPK and the phosphorylation of PPAR-γ were inhibited in alliin-treated group. Treatment with alliin significantly repressed the expression of inflammatory factors in LPS-stimulated RAW264.7 cells. Further research demonstrated that alliin repressed LPS-induced AP-1/NF-κB/STAT-1 activation by inhibiting the phosphorylations of p38, JNK, and ERK1/2-regulated PPAR-γ activation.

CONCLUSION

Our results show that alliin ameliorates DSS-induced ulcerative colitis and inhibits the inflammatory responses in LPS-stimulated RAW264.7 cells partly through inhibiting ERK1/2-, JNK-/PPAR-γ-stimulated NF-κB/AP-1/STAT-1 activations.

Vascular smooth muscle cells in Marfan syndrome aneurysm: the broken bricks in the aortic wall

Marfan syndrome (MFS) is a connective tissue disorder with multiple organ manifestations. The genetic cause of this syndrome is the mutation of the FBN1 gene, encoding the extracellular matrix (ECM) protein fibrillin-1. This genetic alteration leads to the degeneration of microfibril structures and ECM integrity in the tunica media of the aorta. Indeed, thoracic aortic aneurysm and dissection represent the leading cause of death in MFS patients. To date, the most effective treatment option for this pathology is the surgical substitution of the damaged aorta. To highlight novel therapeutic targets, we review the molecular mechanisms related to MFS etiology in vascular smooth muscle cells, the foremost cellular type involved in MFS pathogenesis.

Impaired glucose tolerance: do pharmacological therapies correct the underlying metabolic disturbance?

Lifestyle intervention prevents or delays the conversion from impaired glucose tolerance (IGT) to type 2 diabetes. However, many subjects fail to achieve and/or maintain long-term weight loss and to follow a regular exercise regimen may require pharmacologic therapy. Insulin resistance in liver, muscle and fat, along with impaired beta-cell function, plays a central role in the pathogenesis of type 2 diabetes. Insulin sensitising drugs, including metformin and the thiazolidinediones, have significantly reduced the conversion rate of IGT to type 2 diabetes in subjects in several large, well designed clinical trials. Insulin-sensitising drugs are likely to play an important role in future strategies for diabetes prevention.

Review: Vascular protective effects of peroxisome proliferator-activated receptor agonists

ardiovascular disease is significantly increased in patients with the metabolic syndrome and type 2 diabetes. A clustering of risk factors, including dyslipidaemia, insulin resistance, hypertension, inflammation and coagulation disorders are acting in concert to promote cardiovascular events in these patients. Peroxisome proliferator-activated receptors (PPARs) are transcription factors that influence vascular function by altering gene expression in vascular tissue and indirectly via effects on other tissues. Indeed, PPAR activation displays beneficial effects on glucose homeostasis and lipid metabolism, and also on endothelial function and vessel wall inflammation. Clinically used PPARα agonists, such as fibrates, and PPARγ agonists, such as insulin-sensitising thiazolidinediones, may consequently alter the process of atherosclerosis, especially in subjects with the metabolic syndrome and type 2 diabetes. The present review highlights emerging evidence for beneficial effects of PPAR α and PPARγ in the prevention and treatment of atherosclerosis in such high-risk patients.

Angiotensin II Type 2 Receptor Inhibits Vascular Intimal Proliferation With Activation of PPARγ

BACKGROUND

Angiotensin II type 2 (AT2) receptor stimulation could exert beneficial effects on vascular remodeling. Previously, we reported that AT2 receptor stimulation ameliorated insulin resistance in diabetic mice accompanied by PPARγ activation which also plays a variety of crucial roles in the vasculature. Therefore, this study aimed to investigate the vascular protective effect of the AT2 receptor with activation of PPARγ involving AT2 receptor-interacting protein (ATIP).

METHODS AND RESULTS

Vascular injury was induced by polyethylene-cuff placement around the femoral artery in C57BL/6J mice. Treatment with compound 21 (C21), an AT2 receptor agonist, decreased neointimal formation, cell proliferation, and the mRNA levels of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor (TNF)-α, and interleukin-1β, and phosphorylation of nuclear factor-kappa B, and increased PPARγ DNA-binding activity in the injured artery, whereas these inhibitory effects of C21 were attenuated by co-treatment with a PPARγ antagonist, GW9662. Treatment of vascular smooth muscle cells (VSMC) with C21 prepared from smAT2 transgenic mice, which highly express the AT2 receptor in VSMC, increased both PPARγ activity and its DNA-binding activity determined by dual-luciferase assay and electrophoresis mobility shift assay (EMSA), respectively. We observed that ATIP was involved in PPARγ complex formation, and that transfection of siRNA of ATIP1 attenuated the AT2 receptor-mediated increase in PPARγ activity in VSMC. In response to AT2 receptor stimulation, ATIP was translocated from the plasma membrane to the nucleus.

CONCLUSIONS

Our results suggest a new mechanism by which AT2 receptor stimulation activates PPARγ, thereby resulting in amelioration of vascular intimal proliferation, and that ATIP plays an important role in AT2 receptor-mediated PPARγ activation.

Pioglitazone, a PPARγ agonist, attenuates PDGF-induced vascular smooth muscle cell proliferation through AMPK-dependent and AMPK-independent inhibition of mTOR/p70S6K and ERK signaling

Pioglitazone (PIO), a PPARγ agonist that improves glycemic control in type 2 diabetes through its insulin-sensitizing action, has been shown to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. Although PPARγ-dependent and PPARγ-independent mechanisms have been attributed to its vasoprotective effects, the signaling events associated with PIO action in VSMCs are not fully understood. To date, the likely intermediary role of AMP-activated protein kinase (AMPK) toward PIO inhibition of VSMC proliferation has not been examined. Using human aortic VSMCs, the present study demonstrates that PIO activates AMPK in a sustained manner thereby contributing in part to inhibition of key proliferative signaling events. In particular, PIO at 30μM concentration activates AMPK to induce raptor phosphorylation, which diminishes PDGF-induced mTOR activity as evidenced by decreased phosphorylation of p70S6K, 4E-BP1, and S6 and increased accumulation of p27(kip1), a cell cycle inhibitor. In addition, PIO inhibits the basal phosphorylation of ERK in VSMCs. Downregulation of endogenous AMPK by target-specific siRNA reveals an AMPK-independent effect for PIO inhibition of ERK, which contributes in part to diminutions in cyclin D1 expression and Rb phosphorylation and the suppression of VSMC proliferation. Furthermore, AMPK-dependent inhibition of mTOR/p70S6K and AMPK-independent inhibition of ERK signaling occur regardless of PPARγ expression/activation in VSMCs as evidenced by gene silencing and pharmacological inhibition of PPARγ. Strategies that utilize nanoparticle-mediated PIO delivery at the lesion site may limit restenosis after angioplasty without inducing PPARγ-mediated systemic adverse effects.

The PPAR-γ antagonist GW9662 elicits differentiation of M2c-like cells and upregulation of the MerTK/Gas6 axis: a key role for PPAR-γ in human macrophage polarization

Background

The nuclear receptors PPAR-γ and LXRs regulate macrophage lipid metabolism and macrophage mediated inflammation. We examined the influence of these molecules on macrophage alternative activation, with particular focus on differentiation of “M2c” anti-inflammatory cells.

Methods

We cultured human monocytes in M0, M1, M2a or M2c macrophage differentiating conditions, in the presence or absence of PPAR-γ and LXR ligands. Flow cytometry was used to analyze membrane expression of phenotypic markers. Basal and LPS-stimulated production of soluble mediators was measured by ELISA. Efferocytosis assays were performed by coincubating monocytes/macrophages with apoptotic neutrophils.

Results

We found that PPAR-γ inhibition, using the PPAR-γ antagonist GW9662, elicits differentiation of M2c-like (CD206⁺ CD163⁺ CD16⁺) cells and upregulation of the MerTK/Gas6 axis. Exposure of differentiating macrophages to IFN-γ, GM-CSF or LPS (M1 conditions), however, hampers GW9662 induction of MerTK and Gas6. When macrophages are differentiated with IL-4 (M2a conditions), addition of GW9662 results into an M2a (CD206⁺ CD209⁺ CD163⁻ MerTK⁻) to M2c (CD206^high CD209⁻ CD163⁺ MerTK⁺) polarization shift. Conversely, in the presence of dexamethasone (M2c conditions), the PPAR-γ agonist rosiglitazone attenuates CD163 and MerTK upregulation. The LXR agonist T0901317 induces MerTK independently of M2c polarization; indeed, CD206, CD163 and CD16 are downregulated. GW9662-differentiated M2c-like cells secrete high levels of Gas6 and low amounts of TNF-α and IL-10, mimicking dexamethasone effects in vitro. However, unlike conventional M2c cells, GW9662-differentiated cells do not show enhanced efferocytic ability.

Conclusions

Our results provide new insights into the role of PPAR-γ and LXR receptors in human macrophage activation and reveal the existence of different patterns regulating MerTK expression. Unexpectedly, PPAR-γ appears to negatively control the expansion of a discrete subset of M2c-like anti-inflammatory macrophages.

Ramalin inhibits VCAM-1 expression and adhesion of monocyte to vascular smooth muscle cells through MAPK and PADI4-dependent NF-kB and AP-1 pathways

Cell adhesion molecules play a critical role in inflammatory processes and atherosclerosis. In this study, we investigated the effect of ramalin, a chemical compound from the Antarctic lichen Ramalina terebrata, on vascular cell adhesion molecule-1 (VCAM-1) expression induced by TNF-α in vascular smooth muscular cells (VSMCs). Pretreatment of VSMCs with ramalin (0.1-10 μg/mL) concentration-dependently inhibited TNF-α-induced VCAM-1 expression. Additionally, ramalin inhibited THP-1 (human acute monocytic leukemia cell line) cell adhesion to TNF-α-stimulated VSMCs. Ramalin suppressed TNF-α-induced production of reactive oxygen species (ROS), PADI4 expression, and phosphorylation of p38, ERK, and JNK. Moreover, ramalin inhibited TNF-α-induced translocation of NF-κB and AP-1. Inhibition of PADI4 expression by small interfering RNA or the PADI4-specific inhibitor markedly attenuated TNF-α-induced activation of NF-κB and AP-1 and VCAM-1 expression in VSMCs. Our study provides insight into the mechanisms underlying ramalin activity and suggests that ramalin may be a potential therapeutic agent to modulate inflammation within atherosclerosis.

New mechanisms of antiplatelet activity of nifedipine, an L-type calcium channel blocker

Platelet hyperactivity often occursd in hypertensive patients and is a key factor in the development of cardiovascular diseases including thrombosis and atherosclerosis. Nifedipine, an L-type calcium channel blocker, is widely used for hypertension and coronary heart disease therapy. In addition, nifedipine is known to exhibit an antiplatelet activity, but the underlying mechanisms involved remain unclear. Several transcription factors such as peroxisome proliferator-activated receptors (PPARs) and nuclear factor kappa B (NF-κB) exist in platelets and have an ability to regulate platelet aggregation through a non-genomic mechanism. The present article focuses on describing the mechanisms of the antiplatelet activity of nifedipine via PPAR activation. It has been demonstrated that nifedipine treatment increases the activity and intracellular amount of PPAR-β/-γ in activated platelets. Moreover, the antiplatelet activity of nifedipine is mediated by PPAR-β/-γ-dependent upon the up-regulation of the PI3K/AKT/NO/cyclic GMP/PKG pathway, and inhibition of protein kinase Cα (PKCα) activity via an interaction between PPAR-β/-γ and PKCα. Furthermore, suppressing NF-κB activation by nifedipine through enhanced association of PPAR-β/-γ with NF-κB has also been observed in collagen-stimulated platelets. Blocking PPAR-β/-γ activity or increasing NF-κB activation greatly reverses the antiplatelet activity and inhibition of intracellular Ca²⁺ mobilization, PKCα activity, and surface glycoprotein IIb/IIIa expression caused by nifedipine. Thus, PPAR-β/-γ- dependent suppression of NF-κB activation also contributes to the antiplatelet activity of nifedipine. Consistently, administration of nifedipine markedly reduces fluorescein sodium-induced vessel thrombus formation in mice, which is considerably inhibited when the PPAR-β/-γ antagonists are administrated simultaneously. Collectively, these results provide important information regarding the mechanism by which nifedipine inhibits platelet aggregation and thrombus formation through activation of PPAR-β/-γ- mediated signaling pathways. These findings highlight that PPARs are novel therapeutic targets for preventing and treating platelet-hyperactivity-related vascular diseases.

Thiazolidinedione-independent activation of peroxisome proliferator-activated receptor γ is a potential target for diabetic macrovascular complications

Macrovascular complications are responsible for the high morbidity and mortality in patients with diabetes. Peroxisome proliferator‐activated receptor γ (PPARγ) plays a central role in the process of adipocyte differentiation and insulin sensitization, and also possesses anti‐atherogenic effects. Recently, some statins, angiotensin II type 1 receptor blockers and calcium channel blockers have been reported to activate PPARγ. However, the impact of PPARγ activation on diabetic macrovascular complications is not fully understood. It has been reported that the activation of PPARγ by thiazolidinediones induces anti‐atherogenic effects in vascular cells, including monocytes/macrophages, endothelial cells and smooth muscle cells, in atherosclerotic animal models and in clinical studies. We have reported that hydroxymethylglutaryl coenzyme A reductase inhibitors (statins), which are used for treatment of hypercholesterolemia, activate PPARγ and mediate anti‐atherogenic effects through PPARγ activation in macrophages. Also, telmisartan, an angiotensin type I receptor blocker, has been reported to have anti‐atherogenic effects through PPARγ activation. Furthermore, we have reported that nifedipine, a dihydropyridine calcium channel blocker, can activate PPARγ, thereby mediating anti‐atherogenic effects in macrophages. Therefore, statin therapy and part of anti‐hypertensive therapy might produce beneficial effects through PPARγ activation in hypercholesterolemic and/or hypertensive patients with diabetes, and PPARγ might be a therapeutic target for diabetic macrovascular complications. In the present review, we focus on the anti‐atherogenic effects of PPARγ and suggest potential therapeutic approaches to prevent diabetic macrovascular complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00182.x, 2012)

Pulmonary Arterial Hypertension and Insulin Resistance

The clinical recognition of pulmonary arterial hypertension (PAH) is increasing, and with recent therapeutic advances, short-term survival has improved. In spite of these advances, however, PAH remains a disease with substantial morbidity and long-term mortality. The pathogenesis of PAH involves a complex interaction of local and distant cytokines, growth factors, co-factors, and transcription factors occurring in the right genetic and environmental setting. These factors ultimately lead to the detrimental changes in vascular anatomy and function seen in PAH patients. An important association between obesity/insulin resistance and PAH has recently been identified. Both conditions occur in the presence of a chronic low-grade inflammatory state, and although it is unlikely that a single pathway is solely responsible for the observed association, deficiencies in adiponectin, apolipoprotein E (ApoE) and peroxisome proliferator-activator receptor gamma (PPAR-γ) activity likely play a prominent role. Although incompletely understood, it is clear that further investigation is warranted and the role of weight loss and improved glycemic control in the treatment of at-risk patients with PAH and obesity should be determined.

Ibuprofen inhibits migration and proliferation of human coronary artery smooth muscle cells by inducing a differentiated phenotype: role of peroxisome proliferator-activated receptor γ

OBJECTIVES

The search for agents that are capable of preventing restenosis and reduce the risk of late thrombosis is of utmost importance. In this study we aim to evaluate the in vitro effects of ibuprofen on proliferation and migration of human coronary artery smooth muscle cells and on endothelial cells.

METHODS

Cell proliferation was evaluated by trypan blue exclusion. Cell migration was assessed by wound-healing 'scratch' assay and time-lapse video microscopy. Protein expression was assessed by immunoblotting, and morphology by immunocytochemistry. The involvement of the PPARγ pathway was studied with the agonist troglitazone, and the use of selective antagonists such as PGF2α and GW9662.

KEY FINDINGS

We demonstrate that ibuprofen inhibits proliferation and migration of HCASMCs and induces a switch in HCASMCs towards a differentiated and contractile phenotype, and that these effects are mediated through the PPARγ pathway. Importantly we also show that the effects of ibuprofen are cell type-specific as it does not affect migration and proliferation of endothelial cells.

CONCLUSIONS

Taken together, our results suggest that ibuprofen could be an effective drug for the development of novel drug-eluting stents that could lead to reduced rates of restenosis and potentially other complications of DES implantation.

Pioglitazone modulates the proliferation and apoptosis of vascular smooth muscle cells via peroxisome proliferators-activated receptor-gamma

BACKGROUND

PPARγ is a member of the nuclear hormone receptor superfamily. It has been considered as a mediator regulating metabolism, anti-inflammation, and pro-proliferation in the Vascular Smooth Muscle Cells (VSMCs). Thiazolidinediones (TZDs), synthetic ligands of PPARγ, have anti-proliferative and pro-apoptotic effects on VSMCs, which prevent the formation and progression of atherosclerosis and restenosis following percutaneous coronary intervention (PCI). However, the underlying mechanism remains elusive. This present study therefore aimed to investigate the signaling pathway by which pioglitazone, one of TZDs, inhibits proliferation and induces apoptosis of VSMCs.

METHODS

The effects of pioglitazone on VSMC proliferation and apoptosis were studied. Cell proliferation was determined using BrdU incorporation assay. Cell apoptosis was monitored with Hoechst and Annexin V staining. The expression of caspases and cyclins was determined using real-time PCR and Western blot.

RESULTS

Pioglitazone treatment and PPARγ overexpression inhibited proliferation and induced apoptosis of VSMCs, whereas blocking by antagonist or silencing by siRNA of PPARγ significantly attenuated pioglitazone's effect. Furthermore, pioglitazone treatment or PPARγ overexpression increased caspase 3 and caspase 9 expression, and decreased the expression of cyclin B1 and cyclin D1 in VSMCs.

CONCLUSIONS

Pioglitazone inhibits VSMCs proliferation and promotes apoptosis of VSMCs through a PPARγ signaling pathway. Up-regulation of caspase 3 and down-regulation of cyclins mediates pioglitazone's anti-proliferative and pro-apoptotic effects. Our results imply that pioglitazone prevents the VSMCs proliferation via modulation of caspase and cyclin signaling pathways in a PPARγ-dependent manner.

The peroxisome proliferator activated receptor-γ pioglitazone improves vascular function and decreases disease activity in patients with rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is associated with heightened mortality due to atherosclerotic cardiovascular disease (CVD). Inflammatory pathways in RA negatively affect vascular physiology and promote metabolic disturbances that contribute to CVD. We hypothesized that the peroxisome proliferator activated receptor‐γ (PPAR‐γ) pioglitazone could promote potent vasculoprotective and anti‐inflammatory effects in RA.

Methods and Results

One hundred forty‐three non‐diabetic adult RA patients (76.2% female, age 55.2±12.1 [mean±SD]) on stable RA standard of care treatment were enrolled in a randomized, double‐blind placebo controlled crossover trial of 45 mg daily pioglitazone versus placebo, with a 3‐month duration/arm and a 2‐month washout period. Pulse wave velocity of the aorta (PWV), brachial artery flow mediated dilatation (FMD), nitroglycerin mediated dilatation (NMD), microvascular endothelial function (reactive hyperemia index [RHI]), and circulating biomarkers of inflammation, insulin resistance, and atherosclerosis risk all were quantified. RA disease activity was assessed with the 28‐Joint Count Disease Activity Score (DAS‐28) C‐reactive protein (CRP) and the Short Form (36) Health Survey quality of life questionnaire. When added to standard of care RA treatment, pioglitazone significantly decreased pulse wave velocity (ie, aortic stiffness) (P=0.01), while FMD and RHI remained unchanged when compared to treatment with placebo. Further, pioglitazone significantly reduced RA disease activity (P=0.02) and CRP levels (P=0.001), while improving lipid profiles. The drug was well tolerated.

Conclusions

Addition of pioglitazone to RA standard of care significantly improves aortic elasticity and decreases inflammation and disease activity with minimal safety issues. The clinical implications of these findings remain to be established.

Clinical Trial Registration

URL: ClinicalTrials.gov Unique Identifier: NCT00554853.

Smooth muscle cell hypertrophy, proliferation, migration and apoptosis in pulmonary hypertension

Pulmonary hypertension is a multifactorial disease characterized by sustained elevation of pulmonary vascular resistance (PVR) and pulmonary arterial pressure (PAP). Central to the pathobiology of this disease is the process of vascular remodelling. This process involves structural and functional changes to the normal architecture of the walls of pulmonary arteries (PAs) that lead to increased muscularization of the muscular PAs, muscularization of the peripheral, previously nonmuscular, arteries of the respiratory acinus, formation of neointima, and formation of plexiform lesions. Underlying or contributing to the development of these lesions is hypertrophy, proliferation, migration, and resistance to apoptosis of medial cells and this article is concerned with the cellular and molecular mechanisms of these processes. In the first part of the article we focus on the concept of smooth muscle cell phenotype and the difficulties surrounding the identification and characterization of the cell/cells involved in the remodelling of the vessel media and we review the general mechanisms of cell hypertrophy, proliferation, migration and apoptosis. Then, in the larger part of the article, we review the factors identified thus far to be involved in PH intiation and/or progression and review and discuss their effects on pulmonary artery smooth muscle cells (PASMCs) the predominant cells in the tunica media of PAs.

Pleiotropic effects of peroxisome proliferator-activated receptor γ and δ in vascular diseases

Peroxisome proliferator-activated receptors gamma (PPARγ) and delta (PPARδ) are nuclear receptors that have significant physiological effects on glucose and lipid metabolism. Experimental studies in animal models of metabolic disease have demonstrated their effects on improving lipid profile, insulin sensitivity, and reducing inflammatory responses. PPARγ and -δ are also expressed in the vasculature and their beneficial effects have been examined in various cardiovascular disease models such as atherosclerosis, hypertension, diabetic vascular complications, etc. using pharmacological ligands or genetic tools including viral vectors and transgenic mice. These studies suggest that PPARγ and δ are antiinflammatory, antiatherogenic, antioxidant, and antifibrotic against vascular diseases. Several signaling pathways, effector molecules, as well as coactivators/repressors have been identified as responsible for the protective effects of PPARγ and -δ in the vasculature. We discuss the pleiotropic effect of PPARγ and δ in vascular dysfunction, including atherosclerosis, hypertension, vascular remodeling, vascular injury, and diabetic vasculopathy, in various animal models, and the major underlying mechanisms. We also compare the phenotypes of several endothelial cell/vascular smooth muscle-specific PPARγ and -δ knockout and overexpressing transgenic mice in various disease models, and the implications underlying the functional importance of vascular PPARγ and δ in regulating whole-body homeostasis.

Doinseunggitang ameliorates endothelial dysfunction in diabetic atherosclerosis

Atherosclerosis, a chronic and progressive disease characterized by vascular inflammation, is a leading cause of death in diabetes patients. Doinseunggitang (DYSGT), traditional prescription, has been used for promoting blood circulation to remove blood stasis. The aim of this study was to investigate the beneficial effects of DYSGT on endothelial dysfunction in diabetic atherosclerosis animal model. Apolipoprotein E knockout (ApoE KO) mice fed on a Western diet were treated with DYSGT (200 mg/kg/day). DYSGT significantly lowered blood glucose level and glucose tolerance as well as systolic blood pressure. Metabolic parameter showed that DYSGT markedly decreased triglyceride and LDL-cholesterol levels. In the thoracic aorta, the impairment of vasorelaxation response to acetylcholine and atherosclerotic lesion was attenuated by DYSGT. Furthermore, DYSGT restored the reduction of endothelial nitric oxide synthase (eNOS) expression, leading to the inhibition of intracellular adhesion molecule-1 (ICAM-1) and endothelin-1 (ET-1) expression. In conclusion, DYSGT improved the development of diabetic atherosclerosis via attenuation of the endothelial dysfunction, possibly by inhibiting ET-1, cell adhesion molecules, and lesion formation. Therefore, these results suggest that Korean traditional prescription Doinseunggitang may be useful in the treatment and prevention of diabetic vascular complications.

Peroxisome proliferator-activated receptor targets for the treatment of metabolic diseases

Metabolic syndrome is estimated to affect more than one in five adults, and its prevalence is growing in the adult and pediatric populations. The most widely recognized metabolic risk factors are atherogenic dyslipidemia, elevated blood pressure, and elevated plasma glucose. Individuals with these characteristics commonly manifest a prothrombotic state and a proinflammatory state as well. Peroxisome proliferator-activated receptors (PPARs) may serve as potential therapeutic targets for treating the metabolic syndrome and its related risk factors. The PPARs are transcriptional factors belonging to the ligand-activated nuclear receptor superfamily. So far, three isoforms of PPARs have been identified, namely, PPAR- α, PPAR-β/δ, and PPAR-γ. Various endogenous and exogenous ligands of PPARs have been identified. PPAR- α and PPAR- γ are mainly involved in regulating lipid metabolism, insulin sensitivity, and glucose homeostasis, and their agonists are used in the treatment of hyperlipidemia and T2DM. Whereas PPAR- β / δ function is to regulate lipid metabolism, glucose homeostasis, anti-inflammation, and fatty acid oxidation and its agonists are used in the treatment of metabolic syndrome and cardiovascular diseases. This review mainly focuses on the biological role of PPARs in gene regulation and metabolic diseases, with particular focus on the therapeutic potential of PPAR modulators in the treatment of thrombosis.

Insulin resistance and atherosclerosis

Insulin resistance is a complex metabolic defect that has several causes dependent on an individual's genetic substrate and the underlying pathophysiologic state. Atherogenic dyslipidemia, hyperinsulinemia, dysglycemia, inflammation associated with obesity, and ectopic steatosis in liver and skeletal muscle all collude to facilitate endothelial dysfunction and predispose to the initiation and propagation of atherosclerosis. As aggressive management of the various risk factors does not seem to abrogate the so-called residual risk, more research is needed to define ways by which intervention can fundamentally alter the metabolic and vascular milieu and slow the pace of atherosclerosis, thus favorably affecting outcomes.

Endothelial dysfunction and cardiac allograft vasculopathy

Cardiac allograft vasculopathy remains a major challenge to long-term survival after heart transplantation. Endothelial injury and dysfunction, as a result of multifactorial immunologic and nonimmunologic insults in the donor and the recipient, are prevalent early after transplant and may be precursors to overt cardiac allograft vasculopathy. Current strategies for managing cardiac allograft vasculopathy, however, rely on the identification and treatment of established disease. Improved understanding of mechanisms leading to endothelial dysfunction in heart transplant recipients may provide the foundation for the development of sensitive screening techniques and preventive therapies.

High-mobility group A1 protein: a new coregulator of peroxisome proliferator-activated receptor-γ-mediated transrepression in the vasculature

RATIONALE

The nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) is an important regulator of gene transcription in vascular cells and mediates the vascular protection observed with antidiabetic glitazones.

OBJECTIVE

To determine the molecular mechanism of ligand-dependent transrepression in vascular smooth muscle cells and their impact on the vascular protective actions of PPARγ.

METHODS AND RESULTS

Here, we report a molecular pathway in vascular smooth muscle cells by which ligand-activated PPARγ represses transcriptional activation of the matrix-degrading matrix metalloproteinase-9 (MMP-9) gene, a crucial mediator of vascular injury. PPARγ-mediated transrepression of the MMP-9 gene was dependent on the presence of the high-mobility group A1 (HMGA1) protein, a gene highly expressed in vascular smooth muscle cells, newly identified by oligonucleotide array expression analysis. Transrepression of MMP-9 by PPARγ and regulation by HMGA1 required PPARγ SUMOylation at K367. This process was associated with formation of a complex between PPARγ, HMGA1, and the SUMO E2 ligase Ubc9 (ubiquitin-like protein SUMO-1 conjugating enzyme). After PPARγ ligand stimulation, HMGA1 and PPARγ were recruited to the MMP-9 promoter, which facilitated binding of SMRT (silencing mediator of retinoic acid and thyroid hormone receptor), a nuclear corepressor involved in transrepression. The relevance of HMGA1 for vascular PPARγ signaling was underlined by the complete absence of vascular protection through a PPARγ ligand in HMGA1(-/-) mice after arterial wire injury.

CONCLUSIONS

The present data suggest that ligand-dependent formation of HMGA1-Ubc9-PPARγ complexes facilitates PPARγ SUMOylation, which results in the prevention of SMRT corepressor clearance and induction of MMP-9 transrepression. These data provide new information on PPARγ-dependent vascular transcriptional regulation and help us to understand the molecular consequences of therapeutic interventions with PPARγ ligands in the vasculature.

The role of peroxisome proliferator-activated receptors in pulmonary vascular disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily that regulate diverse physiological processes ranging from lipogenesis to inflammation. Recent evidence has established potential roles of PPARs in both systemic and pulmonary vascular disease and function. Existing treatment strategies for pulmonary hypertension, the most common manifestation of pulmonary vascular disease, are limited by an incomplete understanding of the underlying disease pathogenesis and lack of efficacy indicating an urgent need for new approaches to treat this disorder. Derangements in pulmonary endothelial-derived mediators and endothelial dysfunction have been shown to play a pivotal role in pulmonary hypertension pathogenesis. Therefore, the following review will focus on selected mediators implicated in pulmonary vascular dysfunction and evidence that PPARs, in particular PPARγ, participate in their regulation and may provide a potential novel therapeutic target for the treatment of pulmonary hypertension.

Transcriptional Control of Vascular Smooth Muscle Cell Proliferation by Peroxisome Proliferator-Activated Receptor-gamma: Therapeutic Implications for Cardiovascular Diseases

Proliferation of vascular smooth muscle cells (SMCs) is a critical process for the development of atherosclerosis and complications of procedures used to treat atherosclerotic diseases, including postangioplasty restenosis, vein graft failure, and transplant vasculopathy. Peroxisome proliferator-activated receptor (PPAR) gamma is a member of the nuclear hormone receptor superfamily and the molecular target for the thiazolidinediones (TZD), used clinically to treat insulin resistance in patients with type 2 diabetes. In addition to their efficacy to improve insulin sensitivity, TZD exert a broad spectrum of pleiotropic beneficial effects on vascular gene expression programs. In SMCs, PPARgamma is prominently upregulated during neointima formation and suppresses the proliferative response to injury of the arterial wall. Among the molecular target genes regulated by PPARgamma in SMCs are genes encoding proteins involved in the regulation of cell-cycle progression, cellular senescence, and apoptosis. This inhibition of SMC proliferation is likely to contribute to the prevention of atherosclerosis and postangioplasty restenosis observed in animal models and proof-of-concept clinical studies. This review will summarize the transcriptional target genes regulated by PPARgamma in SMCs and outline the therapeutic implications of PPARgamma activation for the treatment and prevention of atherosclerosis and its complications.

PDGF-induced proliferation of smooth muscular cells is related to the regulation of CREB phosphorylation and Nur77 expression

This study examined the relationship between PDGF-induced proliferation of vascular smooth muscle cells (VSMCs) and Nur77 expression and the effect of atorvastatin on VSMC proliferation and Nur77 in PDGF-treated VSMCs. Rat VSMCs were isolated and cultured. After incubation with atorvastatin or Nur77 siRNA, the cells were stimulated with PDGF and detected for BrdU incorporation to measure the proliferation of the VSMCs. Quantitative PCR and Western blotting were used to determine the Nur77 protein and the CREB phosphorylation level, to observe their relations with PDGF-induced VSMC proliferation. Our results showed that PDGF increased the BrdU incorporation in VSMCs, suggesting that it induced the proliferation of the cells. The VSMC proliferation was associated with increased Nur77 expression and elevated CREB phosphorylation. Atorvastatin inhibited the PDGF-induced VSMC proliferation, suppressed Nur77 expression. After silencing of Nur77 gene, the PDGF-induced VSMC proliferation was decreased. It was concluded that PDGF-induced VSMC proliferation was related to the Nur77 expression and CREB phosphorylation. Atorvastatin reduced the Nur77 expression and, at the same time, inhibited the VSMC proliferation.

PPARs as therapeutic targets in cardiovascular disease

IMPORTANCE OF THE FIELD

The role of peroxisome proliferator-activated receptors PPARα, PPARδ and PPARγ in cardiovascular disease is receiving widespread attention. As ligand-activated nuclear receptors, they play a role in regulation of lipid and glucose metabolism. This feature of the PPARs has been successfully exploited to treat systemic metabolic diseases, like hyperlipidemia and type-2 diabetes. Indirectly, their lipid lowering effect also leads to a reduction of the risk for cardiovascular diseases, primarily atherosclerosis.

AREAS COVERED IN THIS REVIEW

The pleiotropic effects of each of the PPAR isotypes on vascular and cardiac disease are discussed, with special emphasis on the molecular mechanism of action and on preclinical observations. The mechanism underlying the beneficial effect of PPARs is not confined to whole body metabolism, but also includes modulation of other vital processes, such as inflammation and cell fate (proliferation, differentiation, apoptosis).

WHAT THE READER WILL GAIN

A large body of preclinical studies indicates that, in addition to their effect on atherogenesis, PPAR ligands also impact on ischemic heart disease and the development of cardiac failure. It remains to be established to what extent these intriguing observations can be translated into clinical practice.

TAKE HOME MESSAGE

The versatile mechanism of action extends the potential therapeutic profile of the PPARs enormously. Conversely, this versatility makes it harder to attain a specific therapeutic effect, without increasing the risk of undesirable side effects. The future challenge will be to design PPAR-based therapeutic strategies that minimize the detrimental side effects.

Oxidized phosphatidylcholine induces migration of bone marrow-derived mesenchymal stem cells through Krüppel-like factor 4-dependent mechanism

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) and PAF-like oxidized phospholipids including 1-palmitoyl-2-oxovaleroyl-sn-glycero-3-phosphorylcholine (POVPC) are generated upon LDL oxidation. The aim of this study was to evaluate the question of whether POVPC can regulate migration of human bone marrow-derived stem cells (hBMSCs) and to characterize signaling mechanisms involved in the POVPC-induced cell migration. POVPC treatment resulted in dose- and time-dependent increase of hBMSCs migration. Treatment of cells with BN52021, a specific antagonist of PAF receptor, completely blocked cell migration induced by not only PAF but also POVPC. Silencing of endogenous PAF receptor expression using PAF receptor-specific small interfering RNA resulted in significant attenuation of cell migration induced by PAF or POVPC. Both PAF and POVPC induced expression of Krüppel-like factor 4 (KLF4) in hBMSCs. POVPC- or PAF-induced cell migration was abrogated by small interfering RNA-mediated depletion of endogenous KLF4. These results suggest that PAF receptor plays a pivotal role in POVPC-induced migration of human BMSCs through PAF receptor-mediated expression of KLF4.

Rosiglitazone attenuates hypoxia-induced pulmonary arterial hypertension in rats

BACKGROUND AND OBJECTIVE

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) is decreased in the lungs of patients with pulmonary hypertension, and PPARgamma ligands have been associated with the release of vasoactive substances from vascular endothelial cells and prevention of vascular remodelling. We hypothesized that PPARgamma may play a critical role in the development of pulmonary hypertension induced by chronic hypoxia.

METHODS

Male adult Sprague-Dawley rats were exposed to normoxia, normoxia and rosiglitazone (8 mg/kg orally, 5 days/week), hypoxia (12% inspired O(2) fraction), or hypoxia and rosiglitazone for 4 weeks. On the last day of the fourth week, pulmonary arterial pressure was measured and morphological changes in pulmonary vessels were assessed. The expression of PPARgamma, endothelin (ET)-1 and vascular endothelial growth factor (VEGF) was also analysed.

RESULTS

Rosiglitazone inhibited the development of pulmonary hypertension, and pulmonary vascular remodelling induced by chronic hypoxia. PPARgamma expression was decreased and expression of ET-1 and VEGF was increased in lung tissues of the hypoxia group. Rosiglitazone treatment prevented the hypoxia-induced reduction in PPARgamma expression, and restored ET-1 and VEGF expression almost to the levels of the normoxia group.

CONCLUSIONS

Rosiglitazone inhibited the development of pulmonary hypertension induced by chronic hypoxia, perhaps by reversing the changes in PPARgamma, ET-1 and VEGF expression induced by hypoxia. These findings indicate that rosiglitazone may be beneficial in the treatment of chronic hypoxic pulmonary hypertension.

Sera from patients with diabetes do not alter the effect of mammalian target of rapamycin inhibition on smooth muscle cell proliferation

Clinical studies of drug-eluting stents delivering the mammalian target of rapamycin (mTOR) inhibitor, rapamycin (Sirolimus), have demonstrated a reduced efficacy for these devices in patients with diabetes, which suggests that the mTOR pathway may cease to be dominant in mediating the vascular response to injury under diabetic conditions. We hypothesized that changes in serum composition accompanying diabetes may reduce the role of mTOR in mediating the vascular response to injury. We measured the ability of a median dose of rapamycin (10 nM) to inhibit the proliferation of human coronary artery smooth muscle cells (huCASMCs) stimulated with serum obtained from donors with diabetes (n = 14) and without diabetes (n = 16). In an additional analysis, we compared the effects of rapamycin on huCASMCs stimulated with the serum of donors with metabolic syndrome (n = 15) versus those without (n = 7). There was no difference in the effect of rapamycin on huCASMC proliferation after stimulation with serum from either donors with diabetes or donors with metabolic syndrome compared with the respective controls. We conclude that the changes in the serum composition common to diabetes and metabolic syndrome are insufficient to diminish the role of mTOR in the progression of cardiovascular disease.

Thiazolidinediones prevent PDGF-BB-induced CREB depletion in pulmonary artery smooth muscle cells by preventing upregulation of casein kinase 2 alpha' catalytic subunit

BACKGROUND

The transcription factor CREB is diminished in smooth muscle cells (SMCs) in remodeled, hypertensive pulmonary arteries (PAs) in animals exposed to chronic hypoxia. Forced depletion of cyclic adenosine monophosphate response element binding protein (CREB) in PA SMCs stimulates their proliferation and migration in vitro. Platelet-derived growth factor (PDGF) produced in the hypoxic PA wall promotes CREB proteasomal degradation in SMCs via phosphatidylinositol-3-kinase/Akt signaling, which promotes phosphorylation of CREB at 2 casein kinase 2 (CK2) sites. Here we tested whether thiazolidinediones, agents that inhibit hypoxia-induced PA remodeling, attenuate SMC CREB loss.

METHODS

Depletion of CREB and changes in casein kinase 2 catalytic subunit expression and activity were measured in PA SMC treated with PDGF. PA remodeling and changes in medial PA CREB and casein kinase 2 levels were evaluated in lung sections from rats exposed to hypoxia for 21 days.

RESULTS

We found that the thiazolidinedione rosiglitazone prevented PA remodeling and SMC CREB loss in rats exposed to chronic hypoxia. Likewise, the thiazolidinedione troglitazone blocked PA SMC proliferation and CREB depletion induced by PDGF in vitro. Thiazolidinediones did not repress Akt activation by hypoxia in vivo or by PDGF in vitro. However, PDGF-induced CK2 alpha' catalytic subunit expression and activity in PA SMCs, and depletion of CK2 alpha' subunit prevented PDGF-stimulated CREB loss. Troglitazone inhibited PDGF-induced CK2 alpha' subunit expression in vitro and rosiglitazone blocked induction of CK2 catalytic subunit expression by hypoxia in PA SMCs in vivo.

CONCLUSION

We conclude that thiazolidinediones prevent PA remodeling in part by suppressing upregulation of CK2 and loss of CREB in PA SMCs.

Therapeutic Implications of PPARgamma in Cardiovascular Diseases

Peroxisome proliferator-activated receptor-γ (PPARγ) is the members of the nuclear receptor superfamily as a master transcriptional factor that promotes differentiation of preadipocytes by activating adipose-specific gene expression. Although PPARγ is expressed predominantly in adipose tissue and associated with adipocyte differentiation and glucose homeostasis, PPARγ is also present in a variety of cell types including vascular cells and cardiomyocytes. Activation of PPARγ suppresses production of inflammatory cytokines, and there is accumulating data that PPARγ ligands exert antihypertrophy of cardiomyocytes and anti-inflammatory, antioxidative, and antiproliferative effects on vascular wall cells and cardiomyocytes. In addition, activation of PPARγ is implicated in the regulation of endothelial function, proliferation and migration of vascular smooth muscle cells, and activation of macrophages. Many studies suggest that PPARγ ligands not only ameliorate insulin sensitivity, but also have pleiotropic effects on the pathophysiology of atherosclerosis, cardiac hypertrophy, ischemic heart, and myocarditis.