Kuy-Sook Lee

PPARδ agonist L-165041 inhibits rat vascular smooth muscle cell proliferation and migration via inhibition of cell cycle

The peroxisome proliferator-activated receptor (PPAR) family of nuclear hormone receptors consists of three subtypes (alpha, beta/delta, and gamma). PPAR delta is ubiquitously expressed and involved in lipid and glucose metabolism. However, the effect of PPAR delta on vascular smooth muscle cell (VSMC) proliferation and migration has not been fully elucidated yet. Here, we investigated the effect of L-165041, a selective ligand for PPAR delta, on PDGF-induced rat VSMC proliferation. Our data show that L-165041 inhibited rat VSMC proliferation in a dose dependent manner by blocking G(1) to S phase progression and repressing the phosphorylation of retinoblastoma protein (Rb). Furthermore, L-165041 inhibited PDGF-induced expression of cyclin D1 and CDK4. These effects less likely involve PPAR gamma pathway because PPAR gamma antagonist GW9662 pretreatment failed to reverse the inhibitory effect of L-165041 on rVSMC proliferation and migration. For in vivo studies, L-165041 was administered to Sprague-Dawley rats using osmotic pumps before and after the carotid balloon injury, and L-165041 decreased neointima formation after the carotid injury. In conclusion, our results suggest that PPAR delta ligand L-165041 can be a therapeutic agent to control pathologic cardiovascular conditions such as restenosis and atherosclerosis.

Hip osteoarthritis and risk factors in elderly Korean population.

OBJECTIVE To investigate the prevalence of hip osteoarthritis (OA) in a community-based elderly Korean population and to identify its risk factors. DESIGN Radiographs of hip and knee were evaluated in 288 men and 386 women (age>or=65 years) that participated in the Korean Longitudinal Study on Health and Aging (KLoSHA). Minimum joint space widths (JSW), center-edge angles (CEA), and neck-shaft angles were measured on hip radiographs, and tibio-femoral angles on knee radiographs. Hip OA was defined as minimum JSW of <or=2mm or <or=2.5mm. The following potential risk factors of OA were examined; demographic data, acetabular dysplasia, large CEA (>or=40 degrees) and deformities of femoral neck and knee joint. Multivariate analysis with generalized estimating equation (GEE) model was performed to exclude confounding factors. RESULTS When hip OA was defined as JSW<or=2mm, the overall prevalence of the disease was 2.1% (95% confidence interval [CI], 1.0-3.2%), and only older age (>or=70 years) was identified as a significant risk factors with an odds ratio (OR) of 10.0. However, when hip OA was defined as a JSW of <or=2.5mm, the overall prevalence of the disease was 13.1% (95% CI, 10.5-15.6%), and older age (>or=70 years), female, large CEA (>or=40 degrees), and acetabular dysplasia (CEA<20 degrees) were identified as significant risk factors with ORs of 2.1, 2.1, 2.3, and 10.2, respectively. CONCLUSIONS The prevalence of hip OA in elderly Korean was 2.1% (JSW<or=2mm) in community-based population. Older age (>or=70 years), female, large CEA (>or=40 degrees), and acetabular dysplasia (CEA<20 degrees) appeared to be significant risk factors of hip OA.

PPARδ activation inhibits angiotensin II induced cardiomyocyte hypertrophy by suppressing intracellular Ca2+ signaling pathway

Peroxisome proliferator‐activated receptors δ (PPARδ) is known to be expressed ubiquitously, and the predominant PPAR subtype of cardiac cells. However, relatively less is known regarding the role of PPARδ in cardiac cells except that PPARδ ligand treatment protects cardiac hypertrophy by inhibiting NF‐κB activation. Thus, in the present study, we examined the effect of selective PPARδ ligand L‐165041 on angiotensin II (AngII) induced cardiac hypertrophy and its underlying mechanism using cardiomyocyte. According to our data, L‐165041 (10 µM) inhibited AngII‐induced [3H] leucine incorporation, induction of the fetal gene atrial natriuretic factor (ANF) and increase of cardiomyocyte size. Previous studies have implicated the activation of focal adhesion kinase (FAK) in the progress of cardiomyocyte hypertrophy. L‐165041 pretreatment significantly inhibited AngII‐induced intracellular Ca2+ increase and subsequent phosphorylation of FAK. Further experiment using Ca2+ ionophore A23187 confirmed that Ca2+ induced FAK phosphorylation, and this was also blocked by L‐165041 pretreatment. In addition, overexpression of PPARδ using adenovirus significantly inhibited AngII‐induced intracellular Ca2+ increase and FAK expression, while PPARδ siRNA treatment abolished the effect of L‐165041. These data indicate that PPARδ ligand L‐165041 inhibits AngII induced cardiac hypertrophy by suppressing intracellular Ca2+/FAK/ERK signaling pathway in a PPARδ dependent mechanism. J. Cell. Biochem. 106: 823–834, 2009.

Anti-diabetic efficacy of KICG1338, a novel glycogen synthase kinase-3β inhibitor, and its molecular characterization in animal models of type 2 diabetes and insulin resistance

Selective inhibition of glycogen synthase kinase-3 (GSK3) has been targeted as a novel therapeutic strategy for diabetes mellitus. We investigated the anti-diabetic efficacy and molecular mechanisms of KICG1338 (2-(4-fluoro-phenyl)-3H-imidazo[4,5-b]pyridine-7-carboxylic acid(4-methyl-pyridin-3-yl)-amide), a GSK3β inhibitor, in three animal models: Otsuka Long-Evans Tokushima Fatty (OLETF) rats, leptin receptors-deficient db/db mice, and diet-induced obese (DIO) mice. Biochemical parameters including glucose tolerance tests and gene expressions associated with glucose metabolism were investigated. Glucose excursion decreased significantly by KICG1338-treated OLETF rats, accompanied by increase in insulin receptor substrate-1 and glucose transporter (GLUT)-4 expressions in muscle and decreased GLUT-2 expression in liver. Glucose-lowering effects were similarly observed in KICG1338-treated db/db and DIO mice. KICG1338 treatment increased adiponectin levels and decreased TNF-α levels. KICG1338 therapy also led to greater β-cell preservation and less hepatic fat infiltration with decreased expressions of genes involved in inflammation and endoplasmic reticulum stress. These data demonstrate anti-diabetic efficacy of KICG1338, a novel GSK3β inhibitor.

Effect of a new PPAR-gamma agonist, lobeglitazone, on neointimal formation after balloon injury in rats and the development of atherosclerosis

OBJECTIVE The ligand-activated transcription factor peroxisome proliferator-activated receptor gamma (PPARγ) is a key factor in adipogenesis, insulin sensitivity, and cell cycle regulation. Activated PPARγ might also have anti-inflammatory and antiatherogenic properties. We tested whether lobeglitazone, a new PPARγ agonist, might protect against atherosclerosis. METHODS A rat model of balloon injury to the carotid artery, and high-fat, high-cholesterol diet-fed apolipoprotein E gene knockout (ApoE(-/-)) mice were studied. RESULTS After the balloon injury, lobeglitazone treatment (0.3 and 0.9 mg/kg) caused a significant decrease in the intima-media ratio compared with control rats (2.2 ± 0.9, 1.8 ± 0.8, vs. 3.3 ± 1.2, P < 0.01). Consistent with this, in ApoE(-/-) mice fed a high-fat diet, lobeglitazone treatment (1, 3, and 10 mg/kg) for 8 weeks reduced atherosclerotic lesion sizes in the aorta compared with the control mice in a dose-dependent manner. Treatment of vascular smooth muscle cells with lobeglitazone inhibited proliferation and migration and blocked the cell cycle G0/G1 to S phase progression dose-dependently. In response to lobeglitazone, tumor necrosis factor alpha (TNFα)-induced monocyte-endothelial cell adhesion was decreased by downregulating the levels of adhesion molecules. TNFα-induced nuclear factor kappa-B (NF-κB) p65 translocation into the nucleus was also blocked in endothelial cells. Insulin resistance was decreased by lobeglitazone treatment. Circulating levels of high sensitivity C-reactive protein and monocyte chemoattractant protein-1 were decreased while adiponectin levels were increased by lobeglitazone in the high-fat diet-fed ApoE(-/-) mice. CONCLUSION Lobeglitazone has antiatherosclerotic properties and has potential for treating patients with diabetes and cardiovascular risk.

HB-EGF induces cardiomyocyte hypertrophy via an ERK5-MEF2A-COX2 signaling pathway.

Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family that binds to and activates the EGF receptor. Transactivated by angiotensin II, ET-1, and various growth factors in cardiomyocytes, HB-EGF is known to induce cardiac hypertrophy via the PI3K-Akt, MAP kinase, and JAK-STAT pathways. However, little is known about the potential involvement of the ERK5 pathway in HB-EGF-induced cardiac hypertrophy. In the present report, we identify and characterize a novel MEK5-ERK5 pathway that is involved in HB-EGF-induced cardiomyocyte hypertrophy. HB-EGF (10ng/ml) significantly increased [(3)H]-leucine incorporation and atrial natriuretic factor (ANF) mRNA expression in H9c2 cells. In addition, HB-EGF activated a MEK5-ERK5 pathway. Pretreatment with the EGFR inhibitor AG1478 attenuated the activation of ERK5. Blockade of MEK5-ERK5 signaling using MEK5 siRNA reduced the ability of HB-EGF to increase cell size and the expression of ANF mRNA, suggesting the involvement of an EGFR-ERK5 pathway in HB-EGF-induced cardiomyocyte hypertrophy. We further analyzed cyclooxygenase-2 (COX-2). HB-EGF enhanced the expression of COX-2, a response mediated by MEK5-ERK5 signaling, while the COX-2 inhibitor rofecoxib attenuated HB-EGF-induced ANF mRNA expression, suggesting that COX-2 is also associated with HB-EGF-induced cardiomyocyte hypertrophy. It has been known that ERK5 activates the myocyte enhancer factor (MEF) 2 family of transcription factor, we next tested whether activation of MEF2A contributes to HB-EGF-induced COX-2 expression. Inhibition of MEF2A using siRNA attenuated HB-EGF-induced COX-2, ANF expression and cell size. In conclusion, HB-EGF induces cardiomyocyte hypertrophy through an EGFR-ERK5-MEF2A-COX-2 pathway. Our findings will help us to better understand the molecular mechanisms behind HB-EGF-induced cardiomyocyte hypertrophy.

PPARδ ligand L-165041 ameliorates Western diet-induced hepatic lipid accumulation and inflammation in LDLR−/− mice

Although peroxisome proliferator-activated receptor delta (PPARdelta) has been implicated in energy metabolism and lipid oxidation process, detailed roles of PPARdelta in lipid homeostasis under pathologic conditions still remain controversial. Thus, we investigated the effect of PPARdelta ligand L-165041 on Western diet-induced fatty liver using low-density lipoprotein receptor-deficient (LDLR(-/-)) mice. LDLR(-/-) mice received either L-165041 (5mg/kg/day) or vehicle (0.1N NaOH) with Western diet for 16 weeks. According to our data, L-165041 drastically reduced lipid accumulation in the liver, decreasing total hepatic cholesterol and triglyceride content compared to the vehicle group. Gene expression analysis demonstrated that L-165041 lowered hepatic expression of PPARgamma, apolipoprotein B, interleukin 1 beta (IL-1beta), and interleukin-6. In contrast, L-165041 increased hepatic expressions of PPARdelta, lipoprotein lipase (LPL), and ATP-binding cassette transporter G1 (ABCG1). Our data suggest that L-165041 might be effective in preventing Western diet-induced hepatic steatosis by regulating genes involved in lipid metabolism and the inflammatory response.

The PPARδ ligand L‐165041 inhibits vegf‐induced angiogenesis, but the antiangiogenic effect is not related to PPARδ

Peroxisome proliferator‐activated receptor (PPAR)δ is known to be expressed ubiquitously and involved in lipid and glucose metabolism. Recent studies have demonstrated that PPARδ is expressed in endothelial cells (ECs) and plays a potential role in endothelial survival and proliferation. Although PPARα and PPARγ are well recognized to play anti‐inflammatory, antiproliferative, and antiangiogenic roles in ECs, the general effect of PPARδ on angiogenesis in ECs remains unclear. Thus, we investigated the effect of the PPARδ ligand L‐165041 on vascular EC proliferation and angiogenesis in vitro as well as in vivo. Our data show that L‐165041 inhibited VEGF‐induced cell proliferation and migration in human umbilical vein ECs (HUVECs). L‐165041 also inhibited angiogenesis in the Matrigel plug assay and aortic ring assay. Flow cytometric analysis indicated that L‐165041 reduced the number of ECs in the S phase and the expression levels of cell cycle regulatory proteins such as cyclin A, cyclin E, CDK2, and CDK4; phosphorylation of the retinoblastoma protein was suppressed by pretreatment with L‐165041. We confirmed whether these antiangiogenic effects of L‐165041 were PPARδ‐dependent using GW501516 and PPARδ siRNA. GW501516 treatment did not inhibit VEGF‐induced angiogenesis, and transfection of PPARδ siRNA did not reverse this antiangiogenic effect of L‐165041, suggesting that the antiangiogenic effect of L‐165041 on ECs is PPARδ‐independent. Together, these data indicate that the PPARδ ligand L‐165041 inhibits VEGF‐stimulated angiogenesis by suppressing the cell cycle progression independently of PPARδ. This study highlights the therapeutic potential of L‐165041 in the treatment of many disorders related to pathological angiogenesis. J. Cell. Biochem. 113: 1947–1954, 2012.