Pioglitazone enhances cytokine-induced apoptosis in vascular smooth muscle cells and reduces intimal hyperplasia

Long-term effects of the PPAR gamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

We investigated the long-term effects of the thiazolidinedione PPARgamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of malignant of hypertension. Six-week-old SHRSP were treated with pioglitazone (10 mg/kg per day p.o.) for 20 weeks. The rise in systolic blood pressure (SBP) in SHRSP was only transiently and slightly attenuated by pioglitazone (P < 0.05). On one hand, cardiac hypertrophy was little affected by the pioglitazone treatment, and there was only a reduction of subepicardial interstitial fibrosis. On the other hand, left ventricular NFkappaB and AP-1 binding activities, the expression of TNFalpha, and the adhesion of molecule PECAM were significantly decreased by pioglitazone treatment. Expression of the pro-apoptotic proteins p53 and bax was significantly increased by pioglitazone. Thus, pioglitazone-attenuated cardiac inflammation in SHRSP had little effect on BP or cardiac hypertrophy. PPARgamma activation may play a preventive cardiovascular role by offsetting the cardiac inflammatory response as demonstrated in this genetic model of malignant hypertension.

Pioglitazone induces vascular smooth muscle cell apoptosis through a peroxisome proliferator-activated receptor-gamma, transforming growth factor-beta1, and a Smad2-dependent mechanism

Thiazolidinediones, such as pioglitazone, seem to exert direct antiatherosclerotic and antirestenotic effects on type 2 diabetes, in part due to an induction of vascular smooth muscle cell (VSMC) apoptosis. We aimed to study the role of transforming growth factor (TGF)-beta in rat aortic VSMC. Pioglitazone at 100 micromol/l increased apoptosis without affecting DNA synthesis, and this effect was reversed by an anti-TGF-beta1 antibody. Extracellular TGF-beta1 levels were rapidly increased after treatment with pioglitazone in a peroxisome proliferator-activated receptor (PPAR)-gamma-dependent mechanism because this secretion was blocked by the PPAR-gamma inhibitor GW9662. Pioglitazone subsequently increased the nuclear recruitment of phospho-Smad2, without any effect on protein expression. According to our results, we propose that the apoptotic effect of pioglitazone on VSMC depends on the following sequence: PPAR-gamma activation, TGF-beta1 release, and selective phospho-Smad2 nuclear recruitment. Management of Smad signaling on VSMC might provide future clinical benefits in vascular diseases.

New targets for PPARgamma in the vessel wall: implications for restenosis

Peroxisome proliferator-activated receptor {gamma} (PPARgamma), the nuclear receptor that binds the insulin-sensitizing thiazolidinediones (TZDs), is prominently upregulated in intimal vascular smooth muscle cells (VSMC) after mechanical injury to the vessel wall. Several TZD PPARgamma ligands have been shown to inhibit neointima formation in both normal and insulin-resistant vasculature. The suppression of intimal hyperplasia by TZD PPARgamma ligands probably results from their activity to inhibit VSMC growth and promote apoptosis. TZDs prevent VSMC proliferation by blocking the activity of regulatory proteins, such as phosphorylation of the retinoblastoma protein (Rb). Rb functions as a G(1) gatekeeper by controlling S phase gene expression mediated by the E2F transcription factor. Consistent with their effect on Rb phosphorylation, PPARgamma ligands inhibit the mitogenic induction of minichromosome maintenance (MCM) proteins 6 and 7, two E2F-regulated S phase genes essential for DNA replication. PPARgamma ligands also induced apoptosis in VSMC, which correlated with a potent induction of GADD45, a gene implicated in controlling cell growth and survival. A constitutively active form of PPARgamma targeted the same cell cycle regulators as did PPARgamma ligands, consistent with a nuclear-receptor-dependent mechanism of action. This review will summarize mechanisms through which PPARgamma modulates VSMC proliferation and apoptosis suggesting that PPARgamma itself is a novel important regulator of cell cycle and apoptosis and may provide a new therapeutic approach to prevent restenosis.

Translocation of caveolin regulates stretch-induced ERK activity in vascular smooth muscle cells

Mechanical stress contributes to vascular disease related to hypertension. Activation of ERK is key to mediating cellular proliferation and vascular remodeling in response to stretch stress. However, the mechanism by which stretch mediates ERK activation in the vascular tissue is still unclear. Caveolin, a major component of a flasklike invaginated caveolae, acts as an adaptor protein for an integrin-mediated signaling pathway. We found that cyclic stretch transiently induced translocation of caveolin from caveolae to noncaveolar membrane sites in vascular smooth muscle cells (VSMCs). This translocation of caveolin was determined by detergent solubility, sucrose gradient fractionation, and immunocytochemistry. Cyclic stretch induced ERK activation; the activity peaked at 5 min (the early phase), decreased gradually, but persisted up to 120 min (the late phase). Disruption of caveolae by methyl-beta-cyclodextrin, decreasing the caveolar caveolin and accumulating the noncaveolar caveolin, enhanced ERK activation in both the early and late phases. When endogenous caveolins were downregulated, however, the late-phase ERK activation was subsided completely. Caveolin, which was translocated to noncaveolar sites in response to stretch, is associated with beta1-integrins as well as with Fyn and Shc, components required for ERK activation. Taken together, caveolin in caveolae may keep ERK inactive, but when caveolin is translocated to noncaveolar sites in response to stretch stress, caveolin mediates stretch-induced ERK activation through an association with beta1-integrins/Fyn/Shc. We suggest that stretch-induced translocation of caveolin to noncaveolar sites plays an important role in mediating stretch-induced ERK activation in VSMCs.

The effect of nitric oxide synthase inhibitor on improved insulin action by pioglitazone in high-fructose-fed rats

The present study was performed to investigate whether nitric oxide synthase (NOS) inhibition influences the increased whole-body insulin action by pioglitazone in high-fructose-fed rats. Male Wistar rats aged 6 weeks were randomly divided into 3 groups and each group was fed one of the following diets for 3 weeks: standard chow diet (control group), high-fructose diet (fructose-fed group), and high-fructose diet plus pioglitazone (pioglitazone-treated group). The control and pioglitazone-treated groups were further divided into 2 subgroups respectively, and some rats of each subgroup were infused the NOS inhibitor, N(G)-monomethyl-l-arginine (L-NMMA), during the euglycemic clamp studies. In vivo insulin action was determined by the 2-step (3 and 30 mU/kg body weight [BW]/min low- and high-dose, respectively) hyperinsulinemic euglycemic clamp procedure in the awake condition. Glucose infusion rate (GIR) was considered as the index of insulin action. Endothelium-type NOS (eNOS) and inducible NOS (iNOS) in skeletal muscle were also measured. At the low-dose clamp, high-fructose feeding produced a marked decrease in GIR compared with the control group. Pioglitazone-treated animals showed a significant increase in GIR, reaching a similar level as the control group. However, the improved GIR was decreased to the level of the fructose-fed group by L-NMMA infusion. The GIR of the control group was not affected by L-NMMA infusion. The same tendency as the low-dose clamp was found at the high-dose clamp. In skeletal muscle, eNOS and iNOS protein content were not affected by high-fructose feeding and/or pioglitazone treatment. These results suggest that NOS inhibition can decrease the improved insulin resistance by pioglitazone in high-fructose-fed rats. Therefore, although NOS protein content is not changed by high-fructose feeding and/or pioglitazone treatment, it could be concluded that nitric oxide (NO) plays an important role in the improvement of insulin action by pioglitazone.

Thiazolidinedione regulation of smooth muscle cell proliferation

Vascular smooth muscle cells (VSMCs) in the media of adult arteries are normally quiescent, proliferate at low frequency, and are arrested in the G(0)/G(1) phase of the cell cycle. Proliferation of VSMCs occurs in response to arterial injury and plays a crucial role in the atherosclerotic process and in the pathogenesis of restenosis. Patients with type 2 diabetes mellitus are at increased risk for postangioplasty restenosis, which results from excessive intimal hyperplasia. Insulin sensitizers of the thiazolidinedione (TZD) class inhibit growth of VSMCs by attenuating the activity of important cell-cycle regulators. The TZDs inhibit progression from G(1) to S phase in the cell cycle by blocking growth factor-induced phosphorylation of retinoblastoma tumor suppressor protein (Rb). In animal models of restenosis, TZDs inhibit intimal hyperplasia after mechanical injury in both insulin-sensitive and insulin-resistant vessels. Preliminary clinical studies using troglitazone demonstrate less intimal hyperplasia with this TZD after implantation of coronary stents in individuals with type 2 diabetes. Further large trials are needed to confirm that treatment with a TZD can protect against postangioplasty restenosis.

Antiangiogenetic therapy with pioglitazone, rofecoxib, and metronomic trofosfamide in patients with advanced malignant vascular tumors

BACKGROUND

Systemic therapy options for patients with advanced angiosarcomas are limited, and their prognosis is poor. The idea of angiostatic therapy following the paradigm of metronomic dosed chemotherapeutics combined with proapoptotic biomodulators had not been considered previously in these patients. Therefore, in a pilot study, the efficacy of metronomically scheduled, low-dose trofosfamide in combination with the peroxisome proliferator-activated receptor gamma agonist, pioglitazone, and the selective cyclooxygenase-2 inhibitor, rofecoxib, was evaluated in patients with advanced vascular malignancies.

METHODS

Six patients with advanced and pretreated but progressive, malignant vascular tumors (5 angiosarcomas and 1 hemangioendothelioma) received a combination of pioglitazone (45 mg per day orally) plus rofecoxib (25 mg per day orally) and, after 14 days, trofosfamide (3 x 50 mg per day orally). The therapy was administered continuously until progression was observed. If necessary, doses were modified according to side effects.

RESULTS

Two patients responded with complete remission of disease, one patient responded with partial remission, and three patients achieved stabilization of disease (no change). The median progression-free survival was 7.7 months (range, 2-15 months). Side effects generally were mild (World Health Organization Grade 1-2). Hospitalization was not necessary.

CONCLUSIONS

This new triple combination of low-dose metronomic trofosfamide, pioglitazone, and rofecoxib may represent a feasible new alternative in the palliative treatment of patients with advanced malignant vascular tumors.

Pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus: an intravascular ultrasound scanning study

BACKGROUND

It has been reported that pioglitazone reduces neointimal hyperplasia after balloon-induced vascular injury in an experimental model.

METHODS

To determine whether pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus, we studied 44 stented lesions in 44 patients with diabetes mellitus who underwent successful coronary stent implantation. Study patients were randomized into 2 groups: the pioglitazone group (23 patients with 23 lesions) and the control group (21 patients with 21 lesions). All patients underwent serial quantitative coronary angiography and serial intravascular ultrasound scanning studies. With a motorized pullback system, multiple image slices within the stent were obtained at every 1 mm. The stent area and lumen area were measured, and the neointimal area was calculated. Measurements were averaged over the number of selected image slices. The neointimal index was calculated as the averaged neointimal area divided by the averaged stent area multiplied by 100 (%).

RESULTS

After 6 months of treatment, angiographic in-stent restenosis (17% vs 43%, respectively, P =.0994) and target lesion revascularization (13% vs 38%, respectively, P =.0835) were less frequent in the pioglitazone group than the control group; however, these differences did not reach significance. The intravascular ultrasound scanning study demonstrated that the neointimal index in the pioglitazone group was significantly smaller than that in the control group (28% +/- 9% vs 48% +/- 15%, respectively, P <.0001).

CONCLUSION

A serial intravascular ultrasound scanning assessment demonstrated that pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus.

Cardioprotection with pioglitazone is abolished by nitric oxide synthase inhibitor in ischemic rabbit hearts--comparison of the effects of pioglitazone and metformin

BACKGROUND

The effects of two drugs representing different classes of antidiabetic pharmacology (pioglitazone, a thiazolidinedione; and metformin, a biguanide) on the myocardial metabolism in the ischemia are poorly understood.

METHODS

To test the hypothesis that cardioprotection of pioglitazone and metformin is associated with nitric oxide (NO), we studied the high energy phosphate metabolism by 31P-nuclear magnetic resonance (NMR) in isolated rabbit hearts. Forty-five minutes of continuous normothermic global ischemia was carried out. Pioglitazone or metformin was administered at the beginning, 60 min prior to the global ischemia, with or without the nitric oxide synthase inhibitor, L-NAME, administered 5 min or 60 min prior to the ischemia. In the first experiment, whether NO was produced or not by administration of pioglitazone, for the prevention of myocardial ischemic injury, was investigated. Hearts of male Japanese white rabbits were divided into 4 experimental groups: the control (C) group, the P group consisting of pioglitazone treatment, the P + L5 group consisting of pioglitazone treatment with L-NAME (5 min before ischemia), and the P + L60 group consisting of pioglitazone treatment with L-NAME (60 min before ischemia). In the next experiment, a comparison between the effects of pioglitazone and metformin in preventing ischemic injury were studied. The hearts were divided into 4 experimental groups: the control (C) group, the P group consisting of pioglitazone treatment, the P + L5 group consisting of pioglitazone treatment with L-NAME (5 min before ischemia), the M group consisting of metformin treatment, and the M + L5 group consisting of metformin treatment with L-NAME (5 min before ischemia).

RESULTS

In the first experiment, the decrease in adenosine triphosphate (ATP) during ischemia was significantly inhibited in the P group in comparison with the C group (P < 0.01). However, the decrease in ATP was not inhibited in the P + L5 group during ischemia. In contrast, in the P + L60 group, the decrease in ATP was not inhibited during a part of ischemia. In the next experiment, a comparison between the effects of pioglitazone and metformin in preventing ischemic injury was studied. As a result of administration of either pioglitazone or metformin, there was no difference between groups with and without L-NAME.

CONCLUSION

These results suggest that pioglitazone has a significant beneficial effect on improving the myocardial energy metabolism during ischemia. This cardioprotection may be dependent on nitric oxide (NO) synthase during ischemia more than preischemia. Furthermore, the present findings suggest that both pioglitazone and metformin have equal cardioprotective effects mediated by NO on myocardial ischemic injury in rabbits.

Peroxisome proliferator-activated receptor gamma inhibits expression of minichromosome maintenance proteins in vascular smooth muscle cells

Using a cDNA array consisting only of cell cycle genes, we found that a novel nonthiazolidinedione partial peroxisome proliferator-activated receptor gamma (PPARgamma) agonist (nTZDpa) inhibited expression of minichromosome maintenance (MCM) proteins 6 and 7 in vascular smooth muscle cells. MCM proteins are required for the initiation and elongation stages of DNA replication and are regulated by the transcription factor E2F. Mitogen-induced MCM6 and MCM7 mRNA expression was potently inhibited by nTZDpa and to a lesser degree by the full PPARgamma agonist, rosiglitazone. Inhibition of MCM6 and MCM7 expression by nTZDpa and rosiglitazone paralleled their effect to inhibit phosphorylation of the retinoblastoma protein and cell proliferation. Transient transfection experiments revealed that the nTZDpa inhibited mitogen-induced MCM6 and MCM7 promoter activity, implicating a transcriptional mechanism. Adenoviral-mediated E2F overexpression reversed the suppressive effect of nTZDpa on MCM6 and MCM7 expression. Furthermore, activity of a luciferase reporter plasmid driven by multiple E2F elements was inhibited by nTZDpa, indicating that their down-regulation by nTZDpa involves an E2F-dependent mechanism. Overexpression of dominant-negative PPARgamma or addition of a PPARgamma antagonist, GW 9662, blocked nTZDpa inhibition of MCM7 transcription. Adenovirus-mediated overexpression of constitutively active PPARgamma inhibited MCM7 expression in a similar manner as the nTZDpa. These findings provide strong evidence that activation of PPARgamma attenuates MCM7 transcription and support the important role of this nuclear receptor in regulating vascular smooth muscle cell proliferation.

Oral treatments for type II diabetes in patients with cardiovascular disease

The incidence of type II diabetes mellitus is rising rapidly, both in the United States and worldwide. Often, the disease is first diagnosed by cardiologists during an evaluation for coronary or peripheral vascular disease. It is therefore important to understand the basic pathophysiology of insulin resistance, its role in the development of type II diabetes, and its association with accelerated atherosclerosis. An appreciation of when to begin testing for diabetes, how to make the diagnosis, and what treatment strategy to choose is imperative. While there are as yet little randomized data to guide hypoglycemic therapy as it pertains to reducing cardiovascular risk, evidence is accumulating that treatment of diabetes will have an impact on cardiovascular outcomes.

The role of PPARs in atherosclerosis

Peroxisome proliferator-activated receptors (PPARs) are lipid-activated transcription factors that regulate lipid and lipoprotein metabolism, glucose homeostasis and inflammation. The PPAR family consists of three proteins, alpha, beta/delta and gamma. Recent data suggest that PPAR alpha and gamma activation decreases atherosclerosis progression not only by correcting metabolic disorders, but also through direct effects on the vascular wall. PPARs modulate the recruitment of leukocytes to endothelial cells, control the inflammatory response and lipid homeostasis of monocytes/macrophages and regulate inflammatory cytokine production by smooth muscle cells. Experiments using animal models of atherosclerosis and clinical studies in humans strongly support an anti-atherosclerotic role for PPAR alpha and gamma in vivo. Thus, PPARs remain attractive therapeutic targets for the development of drugs used in the treatment of chronic inflammatory diseases such as atherosclerosis. Future research will aim for the development of more potent drugs with co-agonist activity on PPAR alpha, PPAR beta/delta and/or PPAR gamma as well as tissue and target gene-selective PPAR receptor modulators (SPPARMs).

Optimizing the diabetic formulary: beyond aspirin and insulin

Type 2 diabetes mellitus (DM) afflicts nearly 16 million persons in the U.S. Forty million people have impaired glucose tolerance and thus have a 10% annualized risk of developing type 2 DM. These prevalence rates are estimated to double within the next two decades. At-risk groups appear to be the elderly and minorities including African, Hispanic and Native Americans. While the epidemiologic underpinnings for this increase are not fully realized, there has been a parallel increase in societal obesity, sedentary lifestyle and a marked increase in type 2 DM among children. Although there have recently been noteworthy advances in the field of cardiovascular medicine, cardiovascular case fatalities remain the leading cause of death among diabetic patients. According to national health statistics, there continues to be a downward trend in cardiovascular mortality and morbidity. This observation has not been consistently noted among patients with DM and has led many to re-evaluate current treatment goals and pharmacologic regimens for the at-risk patients with type 2 DM. This shifting treatment paradigm for diabetic patients has led to a ratcheting down of targeted risk factor goals including low-density lipoprotein cholesterol, systolic and diastolic blood pressure, and serum glucose levels with a requisite increase in the number of pharmacologic agents being administered. This review focuses on the current adjunctive pharmacologic treatment regimen that is well suited for patients with type 2 DM.

Considerations for treating dyslipidemia in special diabetic populations

This is a review of the problem of dyslipidemia and cardiovascular disease (CVD) in special diabetic populations. Clearly all patients with diabetes are at increased risk for CVD compared to non-diabetic populations. But within the subset that is patients with diabetes there are individuals who are particularly vulnerable. These groups include women, who are often overlooked and undertreated for their cardiovascular risk. Additionally, it includes those with fewer resources, many from minority populations, who are at very high risk for poor preventive care and serious cardiovascular morbidity. This review details the risk for CVD in a variety of different diabetic high-risk groups. It then discusses treatment options and approaches that should be employed in these populations.