PPARα Activator Fenofibrate Research Articles

The PPARα activator fenofibrate inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells

We examined the effects of the PPARα activator fenofibrate on voltage-dependent K+ (Kv) channels using a patch clamp technique in native rabbit coronary arterial smooth muscle cells. Kv current was inhibited by application of fenofibrate in a concentration-dependent manner, with an apparent IC50 value of 6.39 ± 0.53μM and a slope value (Hill coefficient) of 1.63 ± 0.10. Fenofibrate accelerated the decay rate of Kv channel inactivation. The rate constants of association and dissociation for fenofibrate were 0.81± 0.05μM−1s−1 and 4.70 ± 0.47s−1, respectively. Although fenofibrate did not affect the steady-state activation curves, fenofibrate shifted the inactivation curves toward a more negative potential. Application of train pulses (1 or 2Hz) progressively increased the fenofibrate-induced inhibition of the Kv channel, and the recovery time constant from inactivation was increased in the presence of fenofibrate, which suggested that the inhibitory effect of fenofibrate is use-dependent. Another PPARα activator, bezafibrate and PPARα inhibitor, GW 6471, did not affect the Kv current and also did not change the inhibitory effect of fenofibrate on the Kv current. From these results, we suggest that fenofibrate inhibited Kv current in a state-, time-, and use-dependent manner, completely independent of PPARα activation.

Fenofibrate protects against acute myocardial I/R injury in rat by suppressing mitochondrial apoptosis as decreasing cleaved caspase-9 activation.

Peroxisome proliferator-activated receptor-α (PPAR-α) activation has been reported to reduce myocardial ischemia-reperfusion (I/R) injury by inhibiting cell apoptosis. However, the antiapoptotic mechanism of PPAR-α is still unknown. Fenofibrate is a PPAR-α agonist In the present study, we investigate the effects and relevant mechanism of fenofibrate on experimental myocardial ischemia-reperfusion (I/R) injury in rats. Adult male Wistar rats were pretreated with fenofibrate (80 mg/kg) daily for a period of 7 days. After the treatment period, myocardial I/R injury model was made by left anterior descending coronary artery ligation for 45 min and reperfusion for 120 min. Myocardial infarct size, malondialdehyde (MDA) cleaved-caspase-9 protein expression, PPARα and uncoupling protein 2 (UCP2) mRNA levels in myocardial tissue were detected Cell apoptosis was detected by Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Serum lactate dehydrogenase and creatine kinase activities were measured in rats pretreated with fenofibrate The ultrastructure of myocardial tissues was observed. Significant increases in myocardial cell apoptosis, malondialdehyde (MDA) level and cleaved-caspase-9 protein expression level in myocardial tissue were observed, along with reductions of PPARα and uncoupling protein 2 (UCP2) mRNA levels in myocardial tissue of the experimental myocardial ischemia-reperfusion (I/R) injury in rats. Impaired mitochondria were also observed under electron microscopic. However, pretreatment of ischemia/reperfusion rats with fenofibrate brought the biochemical parameters and related genes expression levels to near normalcy, indicating the protective effect of fenofibrate against myocardial ischemia/reperfusion injury in rats. The PPAR-α activator fenofibrate conferred cytoprotective effect against myocardial ischemia-reperfusion (I/R) injury in rats. Associated mechanisms involved decreased cleaved-caspase-9 expression and decreased cell apoptosis.

The effects of herbal composition Gambigyeongsinhwan (4) on hepatic steatosis and inflammation in Otsuka Long‐Evans Tokushima fatty rats and HepG2 cells

Ethnopharmacological relevanceHepatic steatosis has risen rapidly in parallel with a dramatic increase in obesity. The aim of this study was to determine whether the herbal composition Gambigyeongsinhwan (4) (GGH(4)), composed of Curcuma longa L. (Zingiberaceae), Alnus japonica (Thunb.) Steud. (Betulaceae), and the fermented traditional Korean medicine Massa Medicata Fermentata, regulates hepatic steatosis and inflammation. Materials and methodsThe effects of GGH(4) on hepatic steatosis and inflammation in Otsuka Long-Evans Tokushima fatty (OLETF) rats and HepG2 cells were examined using Oil red O, hematoxylin and eosin, and toluidine blue staining, immunohistochemistry, quantitative real-time polymerase chain reaction, and peroxisome proliferator-activated receptor α (PPARα) transactivation assay. ResultsAdministration of GGH(4) to OLETF rats improved hepatic steatosis and lowered serum levels of alanine transaminase, total cholesterol, triglycerides, and free fatty acids. GGH(4) increased mRNA levels of fatty acid oxidation enzymes (ACOX, HD, CPT-1, and MCAD) and decreased mRNA levels of lipogenesis genes (FAS, ACC1, C/EBPα, and SREBP-1c) in the liver of OLETF rats. In addition, infiltration of inflammatory cells and expression of inflammatory cytokines (CD68, TNFα, and MCP-1) in liver tissue were reduced by GGH(4). Treatment of HepG2 cells with a mixture of oleic acid and palmitoleic acid induced significant lipid accumulation, but GGH(4) inhibited lipid accumulation by regulating the expression of hepatic fatty acid oxidation and lipogenic genes. GGH(4) also increased PPARα reporter gene expression. These effects of GGH(4) were similar to those of the PPARα activator fenofibrate, whereas the PPARα antagonist GW6471 reversed the inhibitory effects of GGH(4) on lipid accumulation in HepG2 cells. ConclusionsThese results suggest that GGH(4) inhibits obesity-induced hepatic steatosis and that this process may be mediated by regulation of the expression of PPARα target genes and lipogenic genes. GGH(4) also suppressed obesity-related hepatic inflammation. Thus, GGH(4) may be a promising drug for the treatment of obesity-related liver diseases.

Effects of short-chain acyl-CoA dehydrogenase on cardiomyocyte apoptosis.

Short‐chain acyl‐CoA dehydrogenase (SCAD), a key enzyme of fatty acid β‐oxidation, plays an important role in cardiac hypertrophy. However, its effect on the cardiomyocyte apoptosis remains unknown. We aimed to determine the role of SCAD in tert‐butyl hydroperoxide (tBHP)‐induced cardiomyocyte apoptosis. The mRNA and protein expression of SCAD were significantly down‐regulated in the cardiomyocyte apoptosis model. Inhibition of SCAD with siRNA‐1186 significantly decreased SCAD expression, enzyme activity and ATP content, but obviously increased the content of free fatty acids. Meanwhile, SCAD siRNA treatment triggered the same apoptosis as cardiomyocytes treated with tBHP, such as the increase in cell apoptotic rate, the activation of caspase3 and the decrease in the Bcl‐2/Bax ratio, which showed that SCAD may play an important role in primary cardiomyocyte apoptosis. The changes of phosphonate AMP‐activated protein kinase α (p‐AMPKα) and Peroxisome proliferator‐activated receptor α (PPARα) in cardiomyocyte apoptosis were consistent with that of SCAD. Furthermore, PPARα activator fenofibrate and AMPKα activator AICAR treatment significantly increased the expression of SCAD and inhibited cardiomyocyte apoptosis. In conclusion, for the first time our findings directly demonstrated that SCAD may be as a new target to prevent cardiomyocyte apoptosis through the AMPK/PPARα/SCAD signal pathways.

Effects of ERK1/2/PPARα/SCAD signal pathways on cardiomyocyte hypertrophy induced by insulin-like growth factor 1 and phenylephrine

AimsShort-chain acyl-CoA dehydrogenase (SCAD) is a key enzyme in fatty acid oxidation. In the present study we aim to investigate the changes in SCAD between pathological and physiological cardiomyocyte hypertrophy. We also explore the different signaling pathways of pathological and physiological cardiomyocyte hypertrophy. Main methodsAfter neonatal rat cardiomyocytes were treated as setups, cell surface area, expression of SCAD, PPARα, phospho-ERK1/2, activity of SCAD, free fatty acid content and ATP content in the cardiomyocytes were measured. Key findingsNeonatal rat cardiomyocytes treated by PE showed an increased cell surface area and free fatty acid content, increased ERK1/2 phosphorylation, decreased expression of PPARα, decreased expression and activity of SCAD and decreased levels of ATP. Neonatal rat cardiomyocytes treated by IGF-1 showed the reverse effects except for the cell surface area. PPARα inhibitor GW6471 and PPARα activator Fenofibrate treatments abrogated the effects induced by IGF-1 and PE in cardiomyocytes respectively, as well as ERK1/2 activator EGF and ERK1/2 inhibitor PD98059. SignificanceSCAD has different changes between pathological and physiological cardiomyocyte hypertrophy. The ERK1/2/PPARα/SCAD signaling pathways play different roles in pathological and physiological cardiomyocyte hypertrophy. SCAD may be used as a new target to prevent the development of pathological cardiac hypertrophy.

Abstract 4180: miRNA-mediated anticancer properties of the PPARα-activator fenofibrate on glioblastoma cell growth and migration.

Abstract Background: Glioblastoma is an aggressive tumor which originates from the glial cells and accounts for nearly 50% of adult brain tumors. These tumors are characterized by rapid proliferation, aggressive metastatic potential, and resistance to radio- and chemotherapy. MicroRNAs (miRNAs) are 22-nucleotides long RNAs that regulate gene expression post-transcriptionally. Fenofibrate is a potent agonist of peroxisome proliferator activated receptor alpha (PPARα) that is used for the treatment of cardiovascular disease and various metabolic disorders. In addition, treatment with Fenofibrate results in the proliferation of peroxisomes and a marked reduction in the growth of Glioblastoma cells. Methods: To evaluate the effects of treatment on miRNA expression, we used TaqMan quantitative real-time PCR assays from Life Technologies (Grand Island, NY). miRNAs were cloned into BLOCK-iT Pol II miR RNAi Expression Vectors (Life Technologies). Cell growth was evaluated using Guava ViaCount Reagent (Guava Technologies, Hayward, CA). Migration of miRNA-expressing cells was assessed 24h after plating on 8 μm membranes (BD Biosciences, San Jose, CA). Results: In this study, we utilized the LN229 Glioblastoma cell line and found that among the miRNAs up-regulated by Fenofibrate treatment, miR-634 and miR-136 targeted CYR61, a protein involved in migration and proliferation of cancer cells. We additionally found that miR-136 was up-regulated by Fenofibrate treatment while miR-155, another miRNA previously shown to target CYR61, was down-regulated by Fenofibrate. All three miRNAs were predicted and validated to directly target the 3’-UTR of Cyr61. Over-expression of miR-136 and miR-634 miRNAs negatively affected proliferation, but not migration, of LN229 cells. Forced expression of miR-155 reduced migration and addition of recombinant Cyr61 reversed this impairment in migration. Investigation of the signaling pathways regulated by miR-634, revealed an increased phosphorylation of p70 S6 kinase (Thr389), suggesting an induction of the mammalian target of rapamycin (mTOR) complex 1 pathway. Induction of the mTOR pathway was dependent on Akt and Erk activation. In miR-634 overexpressing cells, TSC2, a negative regulator of mTOR signaling, was found to be decreased. Further studies on the differential roles of miRs-136, -155, and -634 in controlling cell growth, cell size, and migration will provide important information on the molecular mechanisms involved in the anticancer properties of Fenofibrate. Citation Format: Duane Jeansonne, Marco Pacifici, Adam Lassak, Krzysztof Reiss, Francesca Peruzzi. miRNA-mediated anticancer properties of the PPARα-activator fenofibrate on glioblastoma cell growth and migration. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4180. doi:10.1158/1538-7445.AM2013-4180

PPARα activator fenofibrate modulates angiotensin II-induced inflammatory responses in vascular smooth muscle cells via the TLR4-dependent signaling pathway

Angiotensin II (Ang II) is a crucial contributor to inflammatory processes involved in development and progression of atherosclerotic lesion. Toll-like receptor 4 (TLR4) signaling responsible for the initiation of inflammation also participates in pathogenesis of atherosclerosis. The protective effect of peroxisome proliferator-activated receptor α (PPARα) activators on atherosclerosis may be due to their impact on vascular inflammation, plaque instability and thrombosis. However, mechanisms underlying the inhibitory effects of PPARα activators on Ang II-induced vascular inflammation and the TLR4-dependent signaling pathway involved in vascular smooth muscle cells (VSMCs) remain unclear. The present study demonstrated that PPARα activator fenofibrate decreased Ang II-induced generation of pro-inflammatory mediators such as TLR4, MMP-9 and TNF-α, but enhanced production of anti-inflammatory molecules like PPARα and 6-keto-PGF 1α both in vivo and in vitro. Meanwhile, treatment of VSMCs with the TLR4 inhibitor or TLR4 siRNA showed that the inhibitory effects of fenofibrate on Ang II-induced inflammatory responses in VSMCs were dependent on TLR4. Furthermore, fenofibrate depressed Ang II-induced inflammatory responses in VSMCs by intervening the downstream effector molecules of the TLR4-dependent signaling pathway, including interferon-gamma inducible protein 10 (IP-10), protein kinases C (PKC) and nuclear factor κB (NF-κB). Thus, these findings provide the evidence for beneficial effects of PPARα activator fenofibrate to counter-regulate vascular inflammation induced by Ang II. More importantly, anti-inflammatory action of fenofibrate via interfering with the TLR4-dependent signaling pathway (TLR4/IP-10/PKC/NF-κB) works in concert to protect against atherosclerosis.

Effects and mechanisms of PPARα activator fenofibrate on myocardial remodelling in hypertension

Although peroxisome proliferator-activated receptor α (PPARα) is highly expressed in the heart, the effects of PPARα on cardiac remodelling and the underlying mechanisms are unclear. The present study was undertaken to test the hypothesis that PPARα activator fenofibrate plays a key role in left ventricular hypertrophic remodelling via the formation of c-fos/c-jun heterodimers in spontaneous hypertensive rats (SHRs). Twenty-four male 8-week-old SHRs were randomly divided into two groups, one group treated with oral saline (n= 10) and another treated with oral fenofibrate (60 mg.kg−1.d−1, n= 14). Ten same-aged Wistar–Kyoto (WKY) rats were selected as a normal control group. Using echocardiography, immunohistochemistry, co-immunoprecipitation, Western blot analysis and real-time RT-PCR, we showed that the left ventricular wall thickness and significantly reduced and left ventricular diastolic function improved in SHRs treated with fenofibrate compared with SHRs treated with saline. Similarly, the excessive collagen deposition and the up-regulation of collagen I, collagen III, c-fos and c-jun seen in SHRs receiving saline were significantly attenuated in SHRs receiving fenofibrate. In addition, fenofibrate markedly decreased the expression of AP-1 and c-fos/c-jun heterodimers (P < 0.01). These results demonstrated that PPARα activator fenofibrate may exert a protective effect on cardiac remodelling in SHRs by decreasing the expression of c-fos and c-jun and suppressing the formation of c-fos/c-jun heterodimers, which may further inhibit transcription of the downstream genes involved in the pathogenesis of left ventricular hypertrophy induced by hypertension.

Attenuation of cardiac dysfunction by a PPAR-α agonist is associated with down-regulation of redox-regulated transcription factors

Peroxisome proliferator-activated receptor-α (PPAR-α) is a key regulator of lipid and glucose metabolism and is implicated in inflammation. We investigated the effects of the PPAR-α activator fenofibrate on, as well as the role of redox-regulated transcription factors, in the development of left ventricular (LV) hypertrophy and heart failure in Dahl salt-sensitive (DS) rats. DS rats were fed a high-salt diet and treated with either fenofibrate (30 or 50 mg/kg per day) or vehicle from 7 weeks of age. Fenofibrate inhibited the development of compensated hypertensive LV hypertrophy, attenuated the LV relaxation abnormality and systolic dysfunction, and improved the survival rate in DS rats. It also prevented a decrease in the ratio of reduced to oxidized glutathione and inhibited up-regulation of the DNA binding activities of the redox-regulated transcription factors NF-κB, AP-1, Egr-1, SP1, and Ets-1 induced in the left ventricle by the high-salt diet. Expression of target genes for these transcription factors, including those for adhesion molecules (VCAM-1, ICAM-1), cytokines (MCP-1), growth factors (TGF-β, PDGF-B), and osteopontin, was also increased by the high-salt diet in a manner sensitive to treatment with fenofibrate. Furthermore, the infiltration of macrophages and T lymphocytes into the left ventricle and the increase in the plasma concentration of C-reactive protein were inhibited by fenofibrate. The PPAR-α activator fenofibrate thus attenuated the progression of heart failure and improved the survival rate in this rat model. These effects were associated with inhibition of the inflammatory response and of activation of redox-regulated transcription factors in the left ventricle.

The PPAR-α activator fenofibrate fails to provide myocardial protection in ischemia and reperfusion in pigs

Rodent studies suggest that peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation reduces myocardial ischemia-reperfusion (I/R) injury and infarct size; however, effects of PPAR-alpha activation in large animal models of myocardial I/R are unknown. We determined whether chronic treatment with the PPAR-alpha activator fenofibrate affects myocardial I/R injury in pigs. Domestic farm pigs were assigned to treatment with fenofibrate 50 mg.kg(-1).day(-1) orally or no drug treatment, and either a low-fat (4% by weight) or a high-fat (20% by weight) diet. After 4 wk, 66 pigs underwent 90 min low-flow regional myocardial ischemia and 120 min reperfusion under anesthetized open-chest conditions, resulting in myocardial stunning. The high-fat group received an infusion of triglyceride emulsion and heparin during this terminal experiment to maintain elevated arterial free fatty acid (FFA) levels. An additional 21 pigs underwent 60 min no-flow ischemia and 180 min reperfusion, resulting in myocardial infarction. Plasma concentration of fenofibric acid was similar to the EC50 for activation of PPAR-alpha in vitro and to maximal concentrations achieved in clinical use. Myocardial expression of PPAR-alpha mRNA was prominent but unaffected by fenofibrate treatment. Fenofibrate increased expression of carnitine palmitoyltransferase (CPT)-I mRNA in liver and decreased arterial FFA and lactate concentrations (each P < 0.01). However, fenofibrate did not affect myocardial CPT-I expression, substrate uptake, lipid accumulation, or contractile function during low-flow I/R in either the low- or high-fat group, nor did it affect myocardial infarct size. Despite expression of PPAR-alpha in porcine myocardium and effects of fenofibrate on systemic metabolism, treatment with this PPAR-alpha activator does not alter myocardial metabolic or contractile responses to I/R in pigs.

A novel thiazolidinedione MCC-555 down-regulates tumor necrosis factor-α-induced expression of vascular cell adhesion molecule-1 in vascular endothelial cells

Thiazolidinediones (TZDs) are anti-diabetic agents that enhance insulin sensitivity through activating peroxisome proliferator-activated receptor (PPAR) γ. Besides their glucose-lowering effects, TZDs are shown to exhibit anti-inflammatory properties in vascular cells, although their precise molecular mechanisms are unknown. In the present study, we examined the effects of a novel TZD MCC-555, which has unique characteristics of ability to activate not only PPARγ but also PPARα and PPARδ on vascular cell adhesion molecule-1 (VCAM-1) expression in vascular endothelial cells (ECs). Human aortic ECs were treated with MCC-555, followed by stimulation with tumor necrosis factor (TNF)-α. Cell surface VCAM-1 protein expression and human monocytoid U937 cell adhesion to these cells were determined. MCC-555 efficiently inhibited TNF-α-stimulated VCAM-11expression and U937 cell adhesion. Transient transfection of bovine aortic ECs with a VCAM-1 promoter construct revealed that MCC-555 inhibited TNF-α-induced VCAM-1 promoter activity. Electrophoretic mobility-shift assay demonstrated that MCC-555 reduced the amount of nuclear factor-κB (NF-κB) bound to its recognition site on the VCAM-1 promoter. The considered PPARδ activator GW501516 and the considered PPARα activator fenofibrate also inhibited TNF-α-induced VCAM-1 expression, whereas pioglitazone and rosiglitazone did not. These results indicate that MCC-555 is a strong TZD agent to inhibit the cytokine-induced VCAM-1 expression in vascular ECs. This effect is exerted probably through activation of PPARα and/or PPARδ, rather than PPARγ, mediating down-regulation of NF-κB activity.

Peroxisome proliferator-activated receptor alpha agonists increase nitric oxide synthase expression in vascular endothelial cells.

There has been accumulating evidence demonstrating that activators for peroxisome proliferator-activated receptor alpha (PPARalpha) have antiinflammatory, antiatherogenic, and vasodilatory effects. We hypothesized that PPARalpha activators can modulate endothelial nitric oxide synthase (eNOS) expression and its activity in cultured vascular endothelial cells. Bovine aortic endothelial cells were treated with the PPARalpha activator fenofibrate. The amount of eNOS activity and the expression of eNOS protein and its mRNA were determined. Our data show that treatment with fenofibrate for 48 hours resulted in an increase in eNOS activity. Fenofibrate failed to increase eNOS activity within 1 hour. Fenofibrate also increased eNOS protein as well as its mRNA levels. RU486, which has been shown to antagonize PPARalpha action, inhibited the fenofibrate-induced upregulation of eNOS protein expression. WY14643 and bezafibrate also increased eNOS protein levels, whereas rosiglitazone did not. Transient transfection experiments using human eNOS promoter construct showed that fenofibrate failed to enhance eNOS promoter activity. Actinomycin D studies demonstrated that the half-life of eNOS mRNA increased with fenofibrate treatment. PPARalpha activators upregulate eNOS expression, mainly through mechanisms of stabilizing eNOS mRNA. This is a new observation to explain one of the mechanisms of PPARalpha-mediated cardiovascular protection.

PPARα activator fenofibrate inhibits myocardial inflammation and fibrosis in angiotensin II-infused rats

Background. – Peroxisome proliferator-activated receptor (PPAR)α is highly expressed in the heart. PPARα may play a role in cardiac hypertrophy, but effects on cardiac function, inflammation, and fibrosis are unknown. We tested the hypothesis that the PPARα activator fenofibrate prevents myocardial inflammation and fibrosis in angiotensin (Ang) II-infused rats. Methods and results. – Sprague Dawley rats received Ang II (120 ng/kg/min subcutaneously), fenofibrate (100 mg/kg/d p.o.), or Ang II + fenofibrate. After 7 d, systolic blood pressure (mmHg) was elevated ( P < 0.01) in Ang II-infused rats (173 ± 4) vs. controls (115 ± 2) and reduced by fenofibrate (137 ± 5). Electrophoretic mobility shift assay demonstrated that Ang II upregulated cardiac nuclear factor kappa B activity by 50%. Ang II significantly increased cardiac expression of vascular-cell adhesion molecule-1, platelet endothelial cell adhesion molecule, and intercellular adhesion molecule-1. Increases in expression of these inflammatory mediators were normalized by fenofibrate. Ang II-induced expression of transforming growth factor-β1, collagen deposition, and macrophage infiltration were partially prevented by fenofibrate. Conclusions. – The PPARα activator fenofibrate prevented development of hypertension, and improved myocardial inflammation and collagen deposition in Ang II-infused rats. The hypolipidemic drug fenofibrate may be useful in prevention and treatment of myocardial disease associated with hypertension and hyperlipidemia.

RU486 antagonizes the inhibitory effect of peroxisome proliferator-activated receptor α on interleukin-6 production in vascular endothelial cells

Peroxisome proliferator-acitivated receptor α (PPARα) is a member of nuclear receptor superfamily. Recent studies have shown that the activators for PPARα inhibit the expression of some inflammatory molecules in vascular endothelial cells (ECs) and vascular smooth muscle cells, indicating the anti-inflammatory roles of PPARα on vascular walls. In this investigation, we showed that RU486, already proved to be an active anti-glucocorticoid and anti-progesterone agent, blocked the inhibition of tumor necrosis factor (TNF)-α-stimulated interleukin-6 (IL-6) production by the PPARα activator fenofibrate in human umbilical vein ECs. Transient transfection of bovine aortic ECs with an IL-6 promoter construct demonstrated that RU486 blocked the inhibitory effect of fenofibrate on TNF-α-induced IL-6 promoter activity. By fluorescence microscopy, RU486 was found to prevent fenofibrate-induced nuclear translocation of PPARα. Thus, RU486 has an antagonizing effect on PPARα-mediated down-regulation of IL-6 in vascular ECs. This effect may be exerted by its interference with the nuclear translocation of PPARα.