Activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) by atorvastatin is mediated by 15-deoxy-delta-12,14-PGJ2

Co-Administration of Vitamin E and Atorvastatin Improves Insulin Sensitivity and Peroxisome Proliferator-Activated Receptor-γ Expression in Type 2 Diabetic Patients: A Randomized Double-Blind Clinical Trial

Background

Negative effects of statins on glucose metabolism have been reported. The present study aimed to investigate the effects of co-administration of vitamin E and atorvastatin on glycemic control in hyperlipidemic patients with type 2 diabetes mellitus (T2DM).

Methods

A randomized double-blind clinical trial was conducted at Vali-e-Asr Teaching Hospital (Zanjan, Iran) from July 2017 to March 2018. A total of 30 T2DM female patients were allocated to two groups, namely atorvastatin with placebo (n=15) and atorvastatin with vitamin E (n=15). The patients received daily 20 mg atorvastatin and 400 IU vitamin E or placebo for 12 weeks. Anthropometric and biochemical measures were recorded pre- and post-intervention. Peroxisome proliferator-activated receptor-γ (PPAR-γ) expression was measured in peripheral blood mononuclear cells (PBMCs). Independent sample t test and paired t test were used to analyze between- and within-group variables, respectively. The analysis of covariance (ANCOVA) was used to adjust the effect of baseline variables on the outcomes. P<0.05 was considered statistically significant.

Results

After baseline adjustment, there was a significant improvement in homeostatic model assessment for insulin resistance (HOMA-IR) (P=0.04) and serum insulin (P<0.001) in the atorvastatin with vitamin E group compared to the atorvastatin with the placebo group. In addition, co-administration of vitamin E with atorvastatin significantly upregulated PPAR-γ expression (OR=5.4, P=0.04) in the PBMCs of T2DM patients.

Conclusion

Co-administration of vitamin E and atorvastatin reduced insulin resistance and improved PPAR-γ mRNA expression. Further studies are required to substantiate our findings.

Trial registration number

IRCT 20170918036256N.

Oxylipin patterns in human colon adenomas

OBJECTIVE

Cyclooxygenase (COX)-derived prostaglandin E₂ (PGE₂) is an important lipid mediator in colorectal carcinoma (CRC) pathogenesis. Other lipid mediators derived from lipoxygenases (LOX) have also been implicated in neoplastic processes in the colon. In this study we aimed to characterize lipid mediators, so called oxylipins, in human colon adenomatous polyps.

DESIGN

We quantified oxylipins in healthy colon tissue and colorectal adenoma tissue procured during routine colonoscopy examinations. Lipid metabolite profiles were analyzed by liquid chromatography-tandem mass spectrometry.

RESULTS

Adenoma tissue showed a distinct prostaglandin profile as compared to normal colon mucosa. Interestingly, PGE₂ was not higher in adenoma tissue as compared to normal mucosa. In contrast, we found significantly lower levels of prostaglandin D₂, prostaglandin J₂, and prostaglandin D₁ in adenoma tissue. Furthermore, levels of 5-LOX and 12-LOX pathway products were clearly increased in adenoma biopsy samples. We also investigated the effect of aspirin treatment on prostaglandin profiles in adenoma tissue in a subset of patients and found a trend towards decreased prostaglandin levels in response to aspirin.

CONCLUSION

The human data presented here show specific changes of oxylipin profiles in colon adenoma tissue with decreased prostaglandin D₂ levels as well as increased 5- and 12-LOX metabolites.

Cardioprotective Effects of Atorvastatin Are Mediated Through PPARγ in Paraquat-Exposed Rats

BACKGROUND

Paraquat poisoning is one of leading intoxication worldwide without an effective antidote and treatment protocol. Among the other organs, cardiotoxicity of paraquat has been frequently reported.

AIM

The protective effects of atorvastatin (STN) on paraquat-induced cardiotoxicity and the role of peroxisome proliferator-activated receptors γ in the mediation of STN effects were investigated.

METHODS

Forty-two male Wistar rats were aliquoted into control or test groups. The animals in test groups in addition of paraquat received saline normal (PQ), pioglitazone (PGT), atorvastatin (STN), PGT + STN, PGT + GW9662, and/or STN + GW9662 for 14 days.

RESULTS

PGT and STN lowered lipid peroxidation rate, nitric oxide concentration, and activity of myeloperoxidase and CK/MB in the heart. PGT and STN protected from thiol molecules reduction and PQ-induced histopathological injuries. STN regulated the PQ-induced upregulation of COX-II expression in the heart. All STN-related protective effects were reversed by GW9662 as PPARγ antagonist.

CONCLUSIONS

These data suggest a cardioprotective effect for STN against the PQ-induced inflammation and oxidative stress. The pharmacologic approach of these findings indicates that STN through PPARγ pathway lowered the PQ-induced cardiotoxicity.

Exogenous natural EPA-enriched phosphatidylcholine and phosphatidylethanolamine ameliorate lipid accumulation and insulin resistance via activation of PPARα/γ in mice

Dietary eicosapentaenoic acid in the form of phosphatidylcholine and phosphatidylethanolamine improves lipid accumulation and insulin resistance via activation of PPARα/γ.

Effects of statins on the chemoresistance-The antagonistic drug-drug interactions versus the anti-cancer effects

There has been growing interest in the potential anti-cancer activity of statins based on evidence of their anti-proliferative, pro-apoptotic, and radiosensitizing properties, but no studies have focused on the effects of statins on the chemoresistance. In spite of their direct cytostatic/cytotoxic effects on the cancer cells, statins via drug interactions may affect therapeutic effects of the chemotherapy agents and so cause chemoresistance in cancer cells. Here, we aim to present the molecular mechanisms underlying cytotoxic effects of statins on the cancer cells against those mechanisms by which statins may lead to chemoresistance, in order to clarify whether the positive effects of the co-treatment of statins on the efficiency of chemotherapeutic agents is due to the natural anti-cancer effects of statins or it is due to increasing the cellular concentrations of chemotherapy drugs in cancer cells.

Aspirin alone and combined with a statin suppresses eicosanoid formation in human colon tissue

Eicosanoids, including prostaglandins (PGs) and thromboxanes, are broadly bioactive lipid mediators and increase colon tumorigenesis possibly through chronic inflammatory mechanisms. Epidemiological and experimental data suggest that acetylsalicylic acid (ASA) helps prevent colorectal cancer (CRC), possibly through cyclooxygenase (COX)-mediated suppression of eicosanoid, particularly PGE2, formation. Recent studies suggest that statins prevent CRC and improve survival after diagnosis. We identified patients on ASA and/or statin treatment undergoing routine colonoscopy and measured eicosanoid levels in colonic mucosa with targeted metabolomics technology (LC-MS/MS). ASA-treated individuals (n = 27) had significantly lower tissue eicosanoid levels of most COX-derived metabolites than untreated individuals (n = 31). In contrast, COX-derived lipid metabolites tended to be higher in patients with statin treatment (n = 7) as compared with those not receiving statins (n = 24). This effect was not discernible in subjects treated with ASA and statins (n = 11): Individuals treated with both drugs showed a pronounced suppression of COX-derived eicosanoids in colon tissue, even compared with subjects treated with ASA alone. Our data from a routine clinical setting support the hypothesis that ASA and statins could inhibit CRC development via lipid mediator modification. Further studies should directly investigate the effect of dual ASA and statin treatment on colon tumorigenesis in humans.

PPARgamma-2 and ADRB3 polymorphisms in connective tissue diseases and lipid disorders

Background

The aim of the research genetic study was to investigate the association between variants (C1431T and Pro12Ala) of the peroxisome proliferator-activated receptor (PPARgamma-2) gene, Trp64Arg polymorphism of the beta-3-adrenergic receptor gene and lipid profile in Polish population including group of 103 patients with connective tissue disease (CTD) and 103 sex-and age-matched controls in context of statin use.

Methods

Anthropometric and biochemical parameters were measured by routine methods, followed by genotyping (TagMan^® Genotyping Assays, PCR-restriction fragment length polymorphism analysis). Nearly 30% of CTD patients used statins and 10% of the control group.

Results

Although there were no differences between alleles and genotypes prevalence between CTD vs control groups, interesting lipid-gene associations were noted in this study. A higher level of triglycerides (TAG) and TAG/high-density lipoprotein (HDL) ratios was observed in CTD patients compared to controls. Similar differences were noted in CTD and control groups without statin treatment. Atherogenic markers: the atherogenic index of plasma, TAG/HDL and low-density lipoprotein/HDL ratio were low in the analyzed groups. Of the six analyzed polymorphisms, the Pro12Pro or C14131C or Trp64Trp genotypes were related to higher TAG and TAG/HDL ratios in patients with CTD; however, the highest TAG values were observed in the presence of the Trp64Trp genotype.

Conclusion

Lipid disorders were present in both groups independent of statin treatment (mixed dyslipidemia and hypercholesterolemia were observed in the CTD and control groups, respectively). The risk of dyslipidemia increases with age. The presence of Pro12Pro, C14131C and Trp64Trp genotypes is related to higher TAG level in CTDs, and of these the Trp64Trp variant most reliably predicts hypertriglyceridemia.

Atorvastatin prevents advanced glycation end products (AGEs)-induced cardiac fibrosis via activating peroxisome proliferator-activated receptor gamma (PPAR-γ)

BACKGROUND

Previous studies have shown that the activation of advanced glycation end products (AGEs) contributed to the cardiac fibrosis in diabetic patients. Although it had been reported that statins have beneficial effects on cardiac fibrosis in hypertension and myocardial ischemia models, their effects on AGEs models have not been studied. We aimed to investigate the effects of atorvastatin (Ator) on the AGEs-induced cardiac fibrosis both in vitro and vivo.

METHODS

Male Sprague-Dawley rats were randomly divided into four groups: Control, AGEs, Ator or AGEs+Ator. The cardiac function was evaluated with the echocardiography at the second and the third month. Fibrosis area, α-SMA and RAGE expression in cardiac tissue were measured. For in vitro study, rat cardiac fibroblasts were treated with PD98059 (ERK inhibitor), Ator or Ator+GW9662 (PPAR-γ antagonist), and then were stimulated with AGEs. Fibroblasts proliferation, ERK1/2, phosphorylated ERK1/2, α-SMA, and RAGE expression were studied.

RESULTS

Compared with the control group, in vivo treatment with Ator significantly retarded the AGEs-induced diastolic function and attenuated cardiac fibrosis, α-SMA, and RAGE over expression induced by AGEs. Consistently, Ator prominently downregulated RAGE and α-SMA, while inhibited phosphorylation of ERK1/2 and fibroblast proliferation induced by AGEs in vitro. The GW9662 neutralized these effects of Ator on cardiac fibroblasts stimulated by AGEs.

CONCLUSION

In this study, we demonstrated that AGEs-induced fibroblast proliferation and differentiation were dependent on AGEs-RAGE-ERK1/2 pathway and that atorvastatin could block this pathway via activating PPAR-γ.

Elucidation of novel 13-series resolvins that increase with atorvastatin and clear infections

Endogenous mechanisms leading to host protection and resolution of infections without immunosuppression are of wide interest^1,2. Here we elucidated the structures of four new host-protective molecules produced in neutrophil-endothelial co-cultures, and present in human and mouse tissues after sterile inflammation or infection. These bioactive molecules contained conjugated triene and diene double bonds with each carrying a 13-carbon position alcohol and were derived from n-3 docosapentaenoic acid (DPA, C22:5). These compounds, termed 13-series resolvins (RvT), demonstrated potent protective actions increasing mice survival during Escherichia coli infections. RvT also regulated human and mouse phagocyte responses stimulating bacterial phagocytosis and regulating inflammasome components. Their biosynthesis during neutrophil-endothelial cell interactions was initiated by endothelial cyclooxygenase-2 (COX-2) and increased by atorvastatin via S-nitrosylation of COX-2. The actions of atorvastatin and RvT were additive in E. coli infections in mice where they accelerated resolution of inflammation and increased survival >60%. These results document novel host protective molecules in bacterial infections, namely 13-series resolvins, derived from n-3 DPA via transcellular biosynthesis and increased by atorvastatin. These novel molecules regulate key innate protective responses in the resolution of infectious-inflammation.

PTEN upregulation may explain the development of insulin resistance and type 2 diabetes with high dose statins

PURPOSE

Statins increase the incidence of new onset diabetes. Prolonged statin therapy upregulates PTEN expression. PTEN levels are also elevated in diabetic animals. Activation of protein kinase A by cAMP decreases PTEN expression. We assessed whether prolonged treatment with rosuvastatin (ROS) induces glucose intolerance by upregulating Phosphatase and Tensin Homologue on Chromosome 10 (PTEN) in mice receiving normal (ND) or Western Diet (WD) and whether concomitant treatment with cilostazol (CIL, a phosphodiesterase-3 inhibitor) attenuates the effects.

METHODS

PTEN(loxp/cre) or PTEN(+/-) mice received ND or WD without or with ROS (10 mg/kg/day). Wild-type mice received ND or WD without or with ROS, CIL (10 mg/kg/day), or ROS+CIL for 30 days. Fasting insulin and glucose tolerance test were measured as well as PTEN and P-AKT levels in skeletal muscle.

RESULTS

Serum glucose after intraperitoneal injection of glucose was higher in PTEN(loxp/cre) mice receiving WD or ROS and especially WD+ROS. Levels were lower in PTEN(+/-) mice compared to PTEN(loxp/cre) in each treatment group. CIL decreased glucose levels in mice receiving WD, ROS and their combination. Insulin levels were higher in the WD+ROS group. CIL decreased insulin in mice receiving WD+ROS. WD, ROS and especially their combination increased PTEN and decreased P-AKT levels. CIL attenuated the effect of WD, ROS and their combination.

CONCLUSIONS

Long-term ROS can induce diabetes by upregulating PTEN. CIL attenuates these changes. Partial knockdown of PTEN also ameliorates ROS-induced insulin resistance. Further studies are needed to assess the effects of increasing cAMP levels to prevent the induction of diabetes by statins.

Atorvastatin attenuates the paraquat-induced pulmonary inflammation via PPARγ receptors: a new indication for atorvastatin

This study was carried out to highlight the role of PPARγ receptors and atorvastatin's protective effect on paraquat (PQ)-induced inflammation in the lungs. Forty-two male Wistar rats were exposed either against saline as control or PQ (3.5 mg/kg, IP) as test groups for 14 days. The test groups were nominated as: PQ, pioglitazone (PGT, 10 mg/kg, orally), atorvastatin (STN, 10 mg/kg, orally), PGT+STN, PGT+GW9662 (1 mg/kg) and STN+GW9662 (1 mg/kg). PGT and STN significantly (P<0.05) reduced the PQ-elevated myeloperoxidase activity, nitric oxide and malondialdehyde contents of the lungs and IL-6 and TNF-α concentrations in serum. Histopathological studies revealed alveolar edema and hemorrhages along with hyaline exudates in alveoli confirming that PGT and STN reduced the damages. Immunohistochemistry studies showed that the PQ-induced inflammation resulted in a severe recruitment of CD68(+) macrophages, which PGT and STN remarkably diminished them. STN regulated the PQ-up-regulated COX-2 expression. The antagonistic effect of GW9662 as an absolute antagonist of PPARγ receptors on anti-inflammatory effect of STN in the regulation of COX-2 expression was observed. These data provide a molecular proof(s) of the STN-produced protective effects on the PQ-induced pulmonary inflammation, which is antagonized by PPARγ antagonist indicating its anti-inflammatory effects via PPARγ receptors. Moreover, a new indication for atorvastatin is suggested.

Antifibrotic effect of atorvastatin on paraquat-induced pulmonary fibrosis: role of PPARγ receptors

This study was carried out to highlight the role of PPARγ in the paraquat (PQ)-induced pulmonary fibrosis. Forty-two male Wistar rats were exposed either against saline as a control group or PQ (3.5mg/kg, i.p.) as test groups. The test groups were nominated as PQ (PQ-exposed non-treated animals), pioglitazone (PGT, 10mg/kg, orally), atorvastatin (STN, 10mg/kg, orally), PGT+STN, PGT+GW9662 (1mg/kg, i.p.) and STN+GW9662 (1mg/kg). Atorvastatin but not PGT was able to reverse significantly (P<0.05) the PQ-increased ratio of lung to body weight. STN was successfully able to recover the PQ-reduced antioxidant potency and the GW9662 administration resulted in antagonizing the protective effect of both PGT and STN. Although both PGT and STN were able to reduce the hydrxoproline content of the lungs, GW9662, however, could reverse only STN-related effect. Histochemical studies revealed that PQ exposure resulted in a remarkable increase of fibroblasts and collagen fibers in the interstitial tissue and around vessels and bronchioles, which was improved by the STN administration. Only STN-received animals showed the down-regulation of the TGF-β1 expression and GW9662 was able to antagonize this down-regulation. Co-administration of PGT and STN could not exert any synergistic protective effect. These data suggest that the PQ-induced pulmonary fibrosis could be more effectively reversed by STN rather than PGT. Moreover, STN-induced protective effects might attribute to the regulation of TGF-β1 expression, which is antagonized by PPARγ antagonist, suggesting that STN may improve the PQ-induced damages via PPARγ.

Determinants of bone marrow adiposity: the modulation of peroxisome proliferator-activated receptor-γ2 activity as a central mechanism

Although the presence of adipocytes in the bone marrow is a normal physiological phenomenon, the role of these cells in bone homeostasis and during pathological states has not yet been fully delineated. As osteoblasts and adipocytes originate from a common progenitor, with an inverse relationship existing between osteoblastogenesis and adipogenesis, bone marrow adiposity often negatively correlates with osteoblast number and bone mineral density. Bone adiposity can be affected by several physiological and pathophysiological factors, with abnormal, elevated marrow fat resulting in a pathological state. This review focuses on the regulation of bone adiposity by physiological factors, including aging, mechanical loading and growth factor expression, as well as the pathophysiological factors, including diseases such as anorexia nervosa and dyslipidemia, and pharmacological agents such as thiazolidinediones and statins. Although these factors regulate bone marrow adiposity via a plethora of different intracellular signaling pathways, these diverse pathways often converge on the modulation of the expression and/or activity of the pro-adipogenic transcription factor peroxisome proliferator-activated receptor (PPAR)-γ2, suggesting that any factor that affects PPAR-γ2 may have an impact on the fat content of bone.

Myeloid Elf-1-like factor stimulates adipogenic differentiation through the induction of peroxisome proliferator-activated receptor γ expression in bone marrow

Myeloid Elf-1 like factor (MEF) is one of the Ets transcription factors known to regulate cell proliferation and differentiation. A previous report has shown that osteoblast-specific MEF transgenic mice (Col1a1-MEF TG mice) have low bone mass but high bone marrow adiposity. In the present study, we explored a previously unappreciated mechanism whereby MEF promotes adipogenesis in bone marrow. An adipogenic colony-forming unit assay showed that bone marrow cells derived from Col1a1-MEF TG mice had a higher adipogenic differentiation potential compared to those from wild-type. The levels of adipogenic marker genes expression in 3T3L1 cells were higher when co-cultured with Col1a1-MEF TG bone marrow cells than with wild-type cells. MC3T3-E1 preosteoblasts transfected with MEF secreted higher levels of 15-deoxy-delta (12, 14)-prostaglandin J(2), a potent endogenous ligand of peroxisome proliferator-activated receptor γ (PPARγ), under adipogenic conditions. MEF overexpression increased the adipogenic marker genes expression including PPARγ and lipid droplet accumulation in MC3T3-E1 preosteoblasts and 3T3L1 preadipocytes. Endogenous MEF expression levels increased as adipocyte differentiation proceeded. Knockdown of MEF by siRNA suppressed expression levels of adipogenic marker genes including PPARγ. MEF directly bound to the MEF binding element on the mouse PPARγ promoter, transactivating promoter activity. Immunohistochemical staining of tibia sections demonstrated that bone lining cells and bone marrow cells express higher levels of PPARγ protein in Col1a1-MEF TG mice than in wild-type mice. These results suggest that MEF transactivates PPARγ expression, which, in turn, enhances adipogenic differentiation. Furthermore, MEF overexpressing osteoblasts secrete higher levels of adipogenic factors, creating a marrow microenvironment that favors adipogenesis.

The potential effects of anti-diabetic medications on myocardial ischemia-reperfusion injury

Heart disease and stroke account for 65% of the deaths in people with diabetes mellitus (DM). DM and hyperglycemia cause systemic inflammation, endothelial dysfunction, a hypercoagulable state with impaired fibrinolysis and increased platelet degranulation, and reduced coronary collateral blood flow. DM also interferes with myocardial protection afforded by preconditioning and postconditioning. Newer anti-diabetic agents should not only reduce serum glucose and HbA1c levels, but also improve cardiovascular outcomes. The older sulfonylurea agent, glyburide, abolishes the benefits of ischemic and pharmacologic preconditioning, but newer sulfonylurea agents, such as glimepiride, may not interfere with preconditioning. GLP-1 analogs and sitagliptin, an oral dipeptidyl peptidase IV inhibitor, limit myocardial infarct size in animal models by increasing intracellular cAMP levels and activating protein kinase A, whereas metformin protects the heart by activating AMP-activated protein kinase. Both thiazolidinediones (rosiglitazone and pioglitazone) limit infarct size in animal models. The protective effect of pioglitazone is dependent on downstream activation of cytosolic phospholipase A(2) and cyclooxygenase-2 with subsequent increased production of 15-epi-lipoxin A(4), prostacyclin and 15-d-PGJ(2). We conclude that agents used to treat DM have additional actions that have been shown to affect the ability of the heart to protect itself against ischemia-reperfusion injury in preclinical models. However, the effects of these agents in doses used in the clinical setting to minimize ischemia-reperfusion injury and to affect clinical outcomes in patients with DM have yet to be shown. The clinical implications as well as the mechanisms of protection should be further studied.

Peroxisome proliferator-activated receptors in the modulation of the immune/inflammatory response in atherosclerosis

Inflammation has been recognized as an important hallmark of atherosclerosis. The pharmacological activation of PPAR-γ by the thiazolidinediones in diabetes, and of PPAR-α by the fibrates in hyperlipidemia has been shown to help to reduce inflammatory markers in preclinical and clinical studies. PPARs are known to modulate immune pathways through at least three different mechanisms: by direct binding to PPRE of anti-inflammatory cytokines genes; by transrepression of transcription factors like NF-κB and AP-1; or by corepression. The regulation of the inflammatory pathways by PPARs can be achieved on each one of the cells involved in the atherosclerotic process, that is, monocytes, macrophages, T cells, endothelial cells, and smooth muscle cells. Moreover, as each of these cellular components is interconnected with each other, PPAR activation in one cell type could affect the other ones. As activation of PPARs has clear ant-inflammatory benefits, PPARs ligands should be considered as a new therapeutical approach to ameliorate the exacerbated immune response in atherosclerotic diseases.

Peroxisome Proliferator-Activated Receptor-gamma Ligands: Potential Pharmacological Agents for Targeting the Angiogenesis Signaling Cascade in Cancer

Peroxisome proliferator-activated receptor-γ (PPAR-γ) has currently been considered as molecular target for the treatment of human metabolic disorders. Experimental data from in vitro cultures, animal models, and clinical trials have shown that PPAR-γ ligand activation regulates differentiation and induces cell growth arrest and apoptosis in a variety of cancer types. Tumor angiogenesis constitutes a multifaceted process implicated in complex downstream signaling pathways that triggers tumor growth, invasion, and metastasis. In this aspect, accumulating in vitro and in vivo studies have provided extensive evidence that PPAR-γ ligands can function as modulators of the angiogenic signaling cascade. In the current review, the crucial role of PPAR-γ ligands and the underlying mechanisms participating in tumor angiogenesis are summarized. Targeting PPAR-γ may prove to be a potential therapeutic strategy in combined treatments with conventional chemotherapy; however, special attention should be taken as there is also substantial evidence to support that PPAR-γ ligands can enhance angiogenic phenotype in tumoral cells.

PPARγ in coronary atherosclerosis: in vivo expression pattern and correlations with hyperlipidemic status and statin treatment

OBJECTIVE

Peroxisome proliferator-activated receptor-γ (PPARγ) is involved in regulation of macrophage inflammation and in atherosclerosis. Herein we investigate the influence of statin treatment on PPARγ expression in coronary artery disease.

METHOD

PPARγ expression was investigated in coronary atherosclerotic atherectomies (N=48) and arteries (N=12) from patients with stable or unstable coronary syndromes or undergoing cardiac transplantation for end-stage ischemic cardiomyopathy, respectively, by immunohistochemistry. Plaque components and tissue factor immunoreactivity were also investigated. Atherectomies were obtained from de novo culprit lesions of hypercholesterolemic (16 statin-treated and 16 untreated) and normolipidemic (N=16) patients. Furthermore, PPARγ expression was evaluated in patients peripheral blood monocytes and in monocytic U937 cells after atorvastatin incubation, by Western blot analysis.

RESULT

PPARγ expression was higher in coronary plaques and peripheral blood monocytes of statin-treated patients, and it significantly increased in monocytes after 24h atorvastatin incubation (p<0.05). Intra-plaque macrophage content, atheroma, neoangiogenesis and hemorrhage, and circulating CRP levels were lower in statin-treated than untreated hypercholesterolemic patients and comparable with normolipidemic subjects. PPARγ immunoreactivity was localized to neointima and media, its distribution pattern being different from that of tissue factor.

CONCLUSION

PPARγ expression was enhanced in statin-treated patients with different distribution and behavior as compared to atheroma, macrophage content, tissue factor immunoreactivity and serum CRP. In vitro studies showed increased PPARγ expression in monocytes after atorvastatin incubation. These findings provide further evidence as to the protective role of statins in coronary artery disease and their influence on PPARγ expression in coronary plaques and on the inflammatory status of patients.

Simvastatin attenuates cardiopulmonary bypass-induced myocardial inflammatory injury in rats by activating peroxisome proliferator-activated receptor γ

Statins have been shown to downregulate the systemic inflammatory response after cardiopulmonary bypass. However, the role of statins as anti-inflammatory agents in heart tissue remains unknown. The aim of this study was to test whether statin pretreatment attenuates local inflammatory cytokines production in heart and to explore whether the underlying mechanism involves peroxisome proliferator-activated receptor (PPAR) γ. A rat model of cardiopulmonary bypass was established. The animals were pretreated with simvastatin 5 mg/kg/day or 10 mg/kg/day for 7 days before operation. The serum concentration and myocardial level of tumor necrosis factor (TNF)-α, interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1 was evaluated by enzyme linked immunosorbent assay. The polymorphonuclear neutrophils accumulation in heart tissue was determined by myeloperoxidase activity assay. The activity of nuclear factor (NF)-κB and PPARγ in the heart was determined by electrophoretic mobility shift assay. The myocardial PPARγ expression was also examined by immunohistochemistry. The systemic and local TNF-α, IL-6 and MCP-1 were all significantly elevated after cardiopulmonary bypass. In contrast, simvastatin pretreatment significantly decreases the serum and myocardial expression level of above cytokines, myocardial myeloperoxidase activity and myocardial NF-κB activity. However, there was an evident increase in the activity and expression of PPARγ. In conclusion, simvastatin pretreatment not only attenuates acute systemic and local inflammatory response induced by cardiopulmonary bypass. The anti-inflammatory effect of simvastatin in myocardium may be partly related to the activation of PPARγ and inhibition of NF-κB.

Phenylbutyrate induces apoptosis and lipid accumulations via a peroxisome proliferator-activated receptor gamma-dependent pathway

The effects of the selective peroxisome proliferator activated receptor-gamma (PPAR-gamma) inhibitor GW9662 on phenylbutyrate (PB)-induced NMR-detectable lipid metabolites was investigated on DU145 prostate cancer cells. DU145 cells were perfused with 10 mM PB in the presence or absence of 1 microM of GW9662 and the results monitored by (31)P and diffusion-weighted (1)H NMR spectroscopy. GW9662 completely reversed PB-induced NMR-visible lipid and total choline accumulation in (1)H spectra and glycerophosphocholine and beta-NTP in (31)P spectra. In addition, pre-incubation with GW9662 significantly reduced PB-induced caspase-3 activation, reversed the G(1) block as measured by flow cytometry, and otherwise had little effect on cell survival as measured by MTT assay. These results suggest that the NMR visible lipid accumulation and apoptosis induced by PB treatment occurs through a mechanism that is mediated by PPAR-gamma.

The myocardial infarct size-limiting effect of sitagliptin is PKA-dependent, whereas the protective effect of pioglitazone is partially dependent on PKA

Pioglitazone (PIO) and glucagon-like peptide-1 (GLP-1) analogs limit infarct size (IS) in experimental models. The effects of the dipeptidyl-peptidase-IV inhibitors, which increase the endogenous levels of GLP-1, on myocardial protection, are unknown. We studied whether sitagliptin (SIT) and PIO have additive effects on IS limitation in the mouse. Mice received 3-day or 14-day oral SIT (300 mg.kg(-1).day(-1)), PIO (5 mg.kg(-1).day(-1)), SIT + PIO, or vehicle. In addition, mice received intravenous H-89 [20 mg/kg, a protein kinase A (PKA) inhibitor] or vehicle 1 h before ischemia. Rats underwent 30 min myocardial ischemia and 4 h reperfusion. SIT, PIO, and SIT + PIO for 3 days significantly reduced IS (24.3 +/- 2.7, 23.0 +/- 0.8, and 14.7 +/- 0.9%) compared with controls (46.2 +/- 2.8%). H-89 completely blocked the effect of SIT and partially blocked the PIO effect. SIT, but not PIO, increased cAMP levels. PKA activity was increased by PIO and to a greater extent by SIT. PIO, but not SIT, increased cytosolic phospholipase A(2) and cyclooxygenase-2 activity. Accordingly, 6-keto-PGF(1alpha) and 15-deoxy-PGJ(2) increased by PIO but not SIT. In contrast, SIT, and to a lesser extent PIO, increased 15-epi-lipoxin A(4) levels. H-89 completely blocked the effect of SIT and PIO on 15-epi-lipoxin A(4) levels. PIO, and to a greater extent SIT, increased endothelial nitric oxide synthase and cAMP response element-binding protein phosphorylation, an effect that was blocked by H-89. With a 14-day pretreatment experiment, IS was 46.4 +/- 1.0% in the control group, 16.9 +/- 0.6% in SIT (P < 0.001), 19.1 +/- 1.1% in PIO (P = 0.014), and 12.9 +/- 0.7% in SIT + PIO (P < 0.001). We found that SIT and PIO limit IS using different pathways. The protective effect of SIT is via cAMP-dependent PKA activation, whereas PIO mediates its effects via both PKA-dependent and -independent pathways.

HMG-CoA reductase inhibitors (statins) activate expression of PPARalpha/PPARgamma and ABCA1 in cultured gallbladder epithelial cells

In gallbladder epithelial cells (GBEC), PPARalpha and PPARgamma ligands modulate inflammation by suppression of TNFalpha production and prevent excessive accumulation of cholesterol by ABCA1 activation. Recently, HMG-CoA reductase inhibitors (statins) were shown to activate PPARalpha and PPARgamma in various cells but no studies of their effects in GBEC have been conducted. The objective of this study was, therefore, to determine the effects of statins on PPAR and ABCA1 expression and the anti-inflammatory effect of statins in GBEC. Canine GBEC were cultured on Petri dishes. Expression of the proteins PPARalpha, PPARgamma, and ABCA1 was measured by western blotting analysis after treatment with simvastatin, pravastatin, NO-pravastatin, PPARalpha ligand, or PPARgamma ligand in the culture media. Expression of ABCA1 and LXRalpha mRNAs was estimated by RT-PCR. Expression of TNFalpha mRNA was measured by RT-PCR after 24 h pre-treatment with the statins, preceding 1 h of lipopolysaccharide (LPS) loading. Simvastatin, pravastatin, and NO-pravastatin increased expression of the proteins PPARalpha, PPARgamma, and ABCA1, and expression of the mRNA of ABCA1 and LXRalpha in GBEC. Pre-treatment with simvastatin, pravastatin, and NO-pravastatin suppressed the production of TNFalpha mRNA induced by LPS. In conclusion, statins probably contribute to the preservation of GBEC function by activation of PPARalpha and PPARgamma, which have anti-inflammatory effects by suppression of pro-inflammatory cytokines, and ABCA1 activation mediated by LXRalpha, which prevents the accumulation of cholesterol in GBEC.

Pioglitazone protects the myocardium against ischemia-reperfusion injury in eNOS and iNOS knockout mice

Endothelial nitric oxide synthase (eNOS) activation with subsequent inducible NOS (iNOS), cytosolic phospholipase A2 (cPLA2), and cyclooxygenase-2 (COX2) activation is essential to statin inhibition of myocardial infarct size (IS). In the rat, the peroxisome proliferator-activated receptor-gamma agonist pioglitazone (Pio) limits IS, upregulates and activates cPLA2 and COX2, and increases myocardial 6-keto-PGF1alpha levels without activating eNOS and iNOS. We asked whether Pio also limits IS in eNOS-/- and iNOS-/- mice. Male C57BL/6 wild-type (WT), eNOS-/-, and iNOS-/- mice received 10 mg.kg(-1).day(-1) Pio (Pio+) or water alone (Pio-) for 3 days. Mice underwent 30 min coronary artery occlusion and 4 h reperfusion, or hearts were harvested and subjected to ELISA and immunoblotting. As a result, Pio reduced IS in the WT (15.4+/-1.4% vs. 39.0+/-1.1%; P<0.001), as well as in the eNOS-/- (32.0+/-1.6% vs. 44.2+/-1.9%; P<0.001) and iNOS-/- (18.0+/-1.2% vs. 45.5+/-2.3%; P<0.001) mice. The protective effect of Pio in eNOS-/- mice was smaller than in the WT (P<0.001) and iNOS-/- (P<0.001) mice. Pio increased myocardial Ser633 and Ser1177 phosphorylated eNOS levels in the WT and iNOS-/- mice. iNOS was undetectable in all six groups. Pio increased cPLA2, COX2, and PGI2 synthase levels in the WT, as well as in the eNOS-/- and iNOS-/-, mice. Pio increased the myocardial 6-keto-PGF1alpha levels and cPLA2 and COX2 activity in the WT, eNOS-/-, and iNOS-/- mice. In conclusion, the myocardial protective effect of Pio is iNOS independent and may be only partially dependent on eNOS. Because eNOS activity decreases with age, diabetes, and advanced atherosclerosis, this effect may be relevant in a clinical setting and should be further characterized.

The role of eNOS, iNOS, and NF-kappaB in upregulation and activation of cyclooxygenase-2 and infarct size reduction by atorvastatin

Pretreatment with atorvastatin (ATV) reduces infarct size (IS) and increases myocardial expression of phosphorylated endothelial nitric oxide synthase (p-eNOS), inducible NOS (iNOS), and cyclooxygenase-2 (COX2) in the rat. Inhibiting COX2 abolished the ATV-induced IS limitation without affecting p-eNOS and iNOS expression. We investigated 1) whether 3-day ATV pretreatment limits IS in eNOS(-/-) and iNOS(-/-) mice and 2) whether COX2 expression and/or activation by ATV is eNOS, iNOS, and/or NF-kappaB dependent. Male C57BL/6 wild-type (WT), University of North Carolina eNOS(-/-) and iNOS(-/-) mice received ATV (10 mg.kg(-1).day(-1); ATV(+)) or water alone (ATV(-)) for 3 days. Mice underwent 30 min of coronary artery occlusion and 4 h of reperfusion, or hearts were harvested and subjected to ELISA, immunoblotting, biotin switch, and electrophoretic mobility shift assay. As a result, ATV reduced IS only in the WT mice. ATV increased eNOS, p-eNOS, iNOS, and COX2 levels and activated NF-kappaB in WT mice. It also increased myocardial COX2 activity. In eNOS(-/-) mice, ATV increased COX2 expression but not COX2 activity or iNOS expression. NF-kappaB was not activated by ATV in the eNOS(-/-) mice. In the iNOS(-/-) mice, eNOS and p-eNOS levels were increased but not iNOS and COX2 levels; however, NF-kappaB was activated. In conclusion, both eNOS and iNOS are essential for the IS-limiting effect of ATV. The expression of COX2 by ATV is iNOS, but not eNOS or NF-kappaB, dependent. Activation of COX2 is dependent on iNOS.