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Dayuan Li

Publications and source records attributed to Dayuan Li.

At least 19 recordsLinked to original sources
PubMed2006

Suppression of atherogenesis by delivery of TGFbeta1ACT using adeno-associated virus type 2 in LDLR knockout mice.

TGFbeta(1) deficiency has been attributed to the development of atherosclerosis. There is, however, little direct evidence for this concept. To examine this hypothesis, low-density lipoprotein receptor knockout (LDLR(-/-)) mice were injected via tail vein with recombinant adeno-associated virus type 2 (rAAV) carrying a bioactive TGFbeta(1) mutant (AAV/TGFbeta1ACT, n=10) or granulocyte-macrophage-colony stimulating factor (AAV/GM-CSF, n=10, a negative control) or saline (n=9, control), and then put on a high cholesterol diet. At 18 weeks, blood lipids were found to be similarly elevated in all LDLR(-/-) mice. TGFbeta1ACT and GM-CSF (DNA, mRNA, and protein) were highly expressed in the tissues of mice given TGFbeta1ACT or AAV/GM-CSF, respectively, showing sustained transfection following gene delivery by the systemic route. Saline-treated and AAV/GM-CSF-treated LDLR(-/-) mice showed extensive areas of atherosclerotic lesion formation. There was evidence of intense oxidative stress (nitrotyrosine staining), inflammation (CD68 staining), and expression of adhesion molecules and the ox-LDL receptor LOX-1 (gene array analysis) in the atherosclerotic tissues. Importantly, atherosclerotic lesion formation was markedly inhibited in the LDLR(-/-) mice given AAV/TGFbeta1ACT. Expression of adhesion molecules and LOX-1, oxidative stress, and inflammatory response all were inhibited in the mice given AAV/TGFbeta1ACT (P<0.05 vs. saline-treated or GM-CSF-treated LDLR(-/-) mice). These data for the first time demonstrate that systemic delivery of TGFbeta1ACT gene via AAV can inhibit formation of atherosclerotic lesions, possibly via anti-inflammatory and anti-oxidant mechanisms. These findings suggest a novel view of TGFbeta(1) in atherogenesis and a potential new gene therapy for treatment of atherosclerosis.

Adenoviridae↗
PubMed2005

Proliferation and anti-apoptotic effects of human urotensin II on human endothelial cells.

BACKGROUND: Human urotensin II (hU-II) is a potent vasoconstrictor, highly expressed in cardiac tissues and blood vessels. Recent studies indicate that hU-II participates in vascular and myocardial remodeling after injury. This study was designed to study the role of hU-II in cell DNA synthesis and apoptosis in human umbilical vein endothelial cells (HUVECs) and underlying intracellular signaling mechanisms. METHODS AND RESULTS: Cultured HUVECs were incubated with hU-II (10(-10)-10(-8)M) for 24h. Cell DNA synthesis was examined by 3H thymidine incorporation. Apoptosis was detected by flow cytometry and TUNEL. hU-II increased the 3H thymidine incorporation into DNA in a concentration-dependent manner. hU-II inhibited endothelial apoptosis induced by serum withdrawal (5.74+/-0.64% versus 13.20+/-1.96%, P<0.01) and TNFalpha (6.76+/-0.70% versus 13.80+/-1.02%, P<0.01). The data from flow cytometry and TUNEL are consistent. Further studies showed that hU-II caused the phosphorylation of mitogen-activated protein kinasep42/44 (MAPKp42/44) in a concentration-dependent manner and this effect of hU-II was inhibited by pretreatment of cells with the MEK inhibitor (PD98059, 10muM). In addition, the use of PD98059 also attenuated 3H thymidine incorporation and anti-apoptotic effect elicited by hU-II (both P<0.01 versus hU-II alone). CONCLUSIONS: Our observations provide evidence that hU-II promotes cell proliferation and inhibits apoptosis in HUVECs, and MAPKp42/44 activation may play a signal transduction role in this process.

Apoptosis↗
PubMed2005

Inhibition of atherogenesis in LDLR knockout mice by systemic delivery of adeno-associated virus type 2-hIL-10.

Atherosclerosis is an inflammatory disease of the arteries. Interleukin-10 (IL-10) is known to be an anti-inflammatory cytokine which might be useful for counteracting the development of atherosclerosis. As long-term systemic cytokine delivery is prohibitively expensive, gene therapy might be a suitable approach. To test this idea, low-density lipoprotein receptor (LDLR) knockout mice were injected with recombinant adeno-associated virus type 2 (AAV)/interleukin-10 virus or AAV/granulocyte macrophage-colony stimulating factor (GM-CSF) virus and then put on a high-cholesterol diet. Upon harvesting the animals at 18 weeks, elevated blood lipids could be documented and AAV/IL-10 and AAV/GM-CSF DNA and mRNA could be found in various mouse organs. The mice receiving the AAV/IL-10 virus had significantly lower levels of atherogenesis (Sudan IV-staining and histology) than the untreated or the AAV/GM-CSF-treated animals, dropping from 53% to 17% (p < 0.05). The aortas of the AAV/IL-10-treated animals displayed higher IL-10 expression and lower CD68 and nitrotyrosine expression. These data are similar to those of Yoshioka et al. [Yoshioka, T, Okada, T, Maeda, Y, et al. Adeno-associatedvirus vector-mediated interleukin-10 gene transfer inhibits atherosclerosis in apolipoprotein E-deficient mice. Gene Ther 2004;11:1772-9] in which AAV/IL-10 was delivered into the tibial muscle of ApoE-deficient mice, instead of tail vein injection used here. These data indicate that systemic AAV/IL-10 gene delivery, with resulting inhibition of inflammation and oxidative stress, was able to limit atherogenesis, and suggest that this approach is worthy of further study.

Animals↗
PubMed2005

Adhesion molecule expression in fibroblasts: alteration in fibroblast biology after transfection with LOX-1 plasmids.

The endothelial lectinlike, oxidatively (ox-) modified LDL receptor LOX-1 is a critical player in the pathogenesis of atherosclerosis and myocardial ischemia. Ox-LDL binding of LOX-1 results in the expression of various adhesion molecules, which attract monocytes to endothelial cells, an initial step in atherogenesis. We wished to examine the role of the ox-LDL/LOX-1 signaling pathway in fibroblasts, which naturally express low levels of LOX-1. Rat cardiac fibroblasts were transfected with either cytomegalovirus (CMV)-LOX-1wt (amino acids [aa] 1 to 273) or CMV-LOX-1(1-261) (an ox-LDL-binding negative mutant, aa 1 to 261) plasmid. Western blots showed that LOX-1 protein expression was increased significantly in cells transfected with CMV-LOX-1wt or CMV-LOX-1(1-261) plasmid (P<0.01 vs control). Fibroblasts transfected with CMV-LOX-1wt showed ox-LDL binding, whereas fibroblasts without transfection and those transfected with CMV-LOX-1(1-261) did not bind ox-LDL. Compared with untransfected cells, ox-LDL treatment (50 microg/mL, 24 hours) markedly induced the expression of the leukocyte adhesion molecules intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM)-1 as well as matrix metalloproteinase (MMP)-1 in cells transfected with CMV-LOX-1wt (P<0.05) but not in cells transfected with CMV-LOX-1(1-261). Concurrently, ox-LDL treatment enhanced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) (P<0.05 vs control) in CMV-LOX-1wt-transfected cells. These data suggest that in cardiac fibroblasts, ox-LDL binds to LOX-1 and activates p38 MAPK, followed by the expression of ICAM-1, VCAM-1, and MMP-1. Thus, fibroblasts transform into an endothelial phenotype on transfection with CMV-LOX-1wt and subsequent exposure to ox-LDL. This study provides a useful model system (plasmid-transfected fibroblasts) to study the molecular biology of LOX-1.

Animals↗
PubMed2005

Cross-talk between dyslipidemia and renin-angiotensin system and the role of LOX-1 and MAPK in atherogenesis studies with the combined use of rosuvastatin and candesartan.

There is increasing evidence of cross-talk between dyslipidemia and renin-angiotensin system (RAS) in atherogenesis. Both dyslipidemia and RAS activation enhance the expression of a newly described receptor for oxidized-low density lipoprotein (ox-LDL), lectin-like ox-LDL receptor-1 (LOX-1). We postulated that the blockade of dyslipidemia with rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor and RAS with candesartan, an angiotensin II type 1 receptor blocker, would have a synergistic inhibitory effect on LOX-1 expression and atherogenesis. Apo-E knockout mice were fed a high-cholesterol diet (1% cholesterol, HC-diet) alone, or HC-diet with rosuvastatin (1mg/(kgd)), candesartan (1mg/(kgd)) or with both. Twelve weeks later the extent of atherosclerosis was determined by Sudan IV staining. Apo-E knockout mice on HC-diet had extensive atherosclerosis. Both rosuvastatin and candesartan decreased the extent of atherosclerosis (by 23 and 26%, respectively), despite the HC-diet; however, the combination of rosuvastatin and candesartan reduced atherosclerosis further (by 67%). Rosuvastatin decreased plasma levels of total cholesterol by over 50%, whereas candesartan had no effect. LOX-1 protein expression was found to be markedly up-regulated in HC-diet-fed apo-E knockout mice. While rosuvastatin and candesartan each had a small inhibitory effect on the expression of LOX-1 in the atherosclerotic tissues, the combination totally blocked the up-regulation of LOX-1. P38 mitogen-activated protein kinase (MAPK) expression and phosphorylation were increased in apo-E knockout mice, attenuated by rosuvastatin or candesartan alone, and completely blocked by the combination of the two agents. P44/42 MAPK expression and phosphorylation were not affected by the HC-diet, rosuvastatin, candesartan, or their combination. This study demonstrates the potent effect of rosuvastatin and candesartan on atherogenesis, as well as on the expression of LOX-1 and on the activation of p38 MAPK, but not p44/42 MAPK.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

The effects of PPAR-gamma ligand pioglitazone on platelet aggregation and arterial thrombus formation.

BACKGROUND: It has been suggested that peroxisome proliferator-activated receptor (PPAR)-gamma ligands reduce the development of atherosclerosis and myocardial ischemia-reperfusion injury; both of these phenomena are associated with platelet activation. We postulated that PPAR-gamma activation would inhibit platelet activation and intra-arterial thrombus formation. METHODS AND RESULTS: Sprague-Dawley rats were fed chow mixed with pioglitazone (1 or 10 mg/kg/day) for 7 to 10 days. A filter soaked in 30% FeCl(3) was applied around the abdominal aorta to study the patterns of arterial thrombogenesis. The aortic blood flow was continuously monitored using an ultrasonic Doppler flow probe. ADP and arachidonic acid-induced platelet aggregation and the expression of constitutive nitric oxide synthase (cNOS) and thrombomodulin in aorta were measured. Pioglitazone feeding delayed the time to occlusive thrombus formation by 40% (P<0.01 vs. control, n=9) without affecting the weight of the thrombus. ADP- as well as arachidonic acid-induced platelet aggregation was also inhibited by pioglitazone feeding (P<0.01 vs. control, n=9). Pioglitazone feeding also upregulated the aortic expression of cNOS and thrombomodulin; both are considered important factors in platelet aggregation and thrombus formation in vivo. The effect of a high dose (10 mg/kg/day) of pioglitazone was not more potent than that of a low dose (1 mg/kg/day). CONCLUSION: These results indicate that pioglitazone administration decreases platelet aggregation and delays intra-arterial thrombus formation in rats, at least partially, by an increase in the expression of cNOS and thrombomodulin.

Animals↗
PubMed2004

Transforming growth factor beta receptor endoglin is expressed in cardiac fibroblasts and modulates profibrogenic actions of angiotensin II.

Angiotensin II (Ang II) is a powerful mediator of adverse cardiac remodeling and fibrosis. However, the mechanisms of Ang II-induced myocardial fibrosis remain to be clarified. We postulated that Ang II alters transforming growth factor beta (TGF-beta) receptor expression, specifically that of endoglin, and thereby modulates cardiac fibroblast (CF) collagen metabolism. Experiments were conducted using CF from adult Sprague Dawley rats to determine the expression of TGF-beta1 receptors including endoglin, and the role of Ang II type 1 (AT1) and type 2 (AT2) receptors, and MAPK p42/44 in this process. The functional role of endoglin in modulating Ang II effects on matrix metalloproteinase-1 (MMP-1) and type I collagen expression was also analyzed. Endoglin gene and protein expression were consistently identified in quiescent CFs. Ang II increased the expression of endoglin mRNA and protein in a concentration and time-dependent manner, with no effect on TGF-beta receptors I and II expression. This effect was AT1 receptor mediated, because AT1 receptor antagonists valsartan, candesartan, and losartan inhibited Ang II-induced endoglin expression, whereas the AT2 receptor antagonist PD123319 had no effect. MAPKp42/44 inhibition attenuated Ang II-induced endoglin expression. Ang II-induced decrease in MMP-1 protein expression and increase in type I collagen protein expression were both blocked by a specific endoglin antibody. Hence, our results indicate that endoglin is upregulated in CFs by Ang II via the AT1 receptor and modulates profibrotic effects of Ang II. These findings provide novel insights into Ang II-induced cardiac remodeling.

Angiotensin II↗
PubMed2004

Angiotensin II regulation of collagen type I expression in cardiac fibroblasts: modulation by PPAR-gamma ligand pioglitazone.

Angiotensin II (Ang II)-mediated stimulation of fibroblast growth and collagen type I synthesis is believed to be an important component of the cardiac remodeling process in hypertension and chronic ischemia. Ang II-mediated oxidative stress could be important in enhanced fibroblast growth and collagen formation. Accordingly, we postulated that the PPAR-gamma ligand, pioglitazone, which is known to modulate oxidative stress, would alter Ang II-induced formation of collagen type I in cardiac fibroblasts. Cardiac fibroblasts were treated with different concentrations (10(-8) to 10(-6) M) of Ang II for different times (6 hours, 12 hours, and 24 hours). Ang II increased the expression of collagen type I in a concentration- and time-dependent fashion (P<0.01 versus control). Ang II also decreased the expression and activity of matrix metalloproteinase (MMP)-1 (MMP-1, P<0.05 versus control). These effects of Ang II were attenuated by pretreatment of cells with pioglitazone (10 micromol/L). Ang II stimulated the intracellular generation of reactive oxygen species (ROS), and this effect was also attenuated by pioglitazone. Ang II treatment activated the redox-sensitive transcription factor NF-kappaB, and pioglitazone pretreatment blocked this effect of Ang II. Ang II also activated another transcription factor, AP-1, but this effect of Ang II was not modulated by pioglitazone. In other experiments, we observed that trolox, the water soluble analog of vitamin E, attenuated the effects of Ang II on the expression of collagen type I and MMP-1, in a manner similar to pioglitazone. Thus, pioglitazone attenuates Ang II-mediated collagen type I synthesis in cardiac fibroblasts. The effects of pioglitazone are mediated by the modulation of ROS release and redox-sensitive transcription factor NF-kappaB.

Angiotensin II↗
PubMed2004

Regulatory role of endothelium in the expression of genes affecting arterial calcification.

Vascular calcification is a highly regulated process sharing features of bone mineralization. Since endothelium regulates many of the processes during atherogenesis, we monitored the expression of genes involved in calcification upon exposure of human coronary artery endothelial cells (HCAECs) to atherogenic stimuli. Genes studied were: core binding factor alpha-1 (Cbfa1/Runx2), a pivotal transcriptional regulator of osteogenesis; bone morphogenetic protein-2 (BMP2), an inducer of cartilage and bone; and matrix gla-protein (MGP), a potent inhibitor of calcification, which exerts its action by blocking BMP2. HCAECs were treated with oxidized-low density lipoprotein (ox-LDL, 80 microg/mL) or tumor necrosis factor-alpha (TNFalpha, 10 ng/mL), and the expression of Cbfa1, BMP2, and MGP was quantified by real-time PCR. Cbfa1 was expressed at low levels in untreated HCAECs, and its expression did not change with ox-LDL or TNFalpha treatment. The expression of BMP2 and MGP increased early after exposure to ox-LDL or TNFalpha (at 2-8 h), and the increase was not evident at 24 h. Ox-LDL exerted a stronger effect on MGP than on BMP2 expression. The effects of ox-LDL, but not TNFalpha, on MGP and BMP2 expression were inhibited by pretreatment of cells with an antibody directed at LOX-1, a lectin-like receptor for ox-LDL (10 microg/mL). Thus, the endothelium, when exposed to atherogenic stimuli, ox-LDL in particular, regulates the process of calcification by enhancing the expression of the bone inhibitory MGP, while the expression of Cbfa1 remains unchanged. Upregulation of BMP2 may represent a feedback upregulation in response to increase in MGP. The effect of ox-LDL appears to be mediated by LOX-1 activation.

Antibodies↗
PubMed2004

Human urotensin II modulates collagen synthesis and the expression of MMP-1 in human endothelial cells.

OBJECTIVES: Human urotensin II (hU-II) is a cyclic peptide highly expressed in cardiac tissues and blood vessels. hU-II is a potent vasoconstrictor. Recent studies indicate that urotensin II participates in myocardial remodeling after injury. This study was designed to study the role of hU-II in the expression of matrix metalloproteinase-1 (MMP-1) and collagen-1 in human umbilical vein endothelial cells (HUVECs) and underlying intracellular signaling mechanisms. METHODS AND RESULTS: Cultured HUVECs were incubated with hU-II (10 to 80 nM) for 3 to 24 hours. hU-II increased the expression (mRNA and protein) of collagen-1 in a concentration- and time-dependent manner. In contrast, hU-II decreased the expression and activity of MMP-1. Further, hU-II caused the phosphorylation of mitogen-activated protein kinase p42/44 (MAPKp42/44). This effect of hU-II was inhibited by pretreatment of cells with the MEK inhibitor (PD98059, 10 microM). In addition, treatment of cells with PD98059 attenuated protein expression of collagen-1 and MMP-1 elicited by hU-II (P < 0.01 versus hU-II alone). CONCLUSIONS: Our observations provide evidence that hU-II modulates the expression of MMP-1 and collagen-1 in HUVECs, and MAPKp42/44 activation may play a signal transduction role in this process.

Cells, Cultured↗
PubMed2004

Anoxia-reoxygenation stimulates collagen type-I and MMP-1 expression in cardiac fibroblasts: modulation by the PPAR-gamma ligand pioglitazone.

BACKGROUND: Cardiac remodeling after ischemic injury is a major cause of heart failure. In this process, fibroblast growth and collagen synthesis and degradation play a critical role. Recent studies indicate that ligands of the peroxisome proliferator-activated receptors-gamma (PPAR-gamma) alter cardiac remodeling during chronic ischemia. This study was designed to investigate if the PPAR-gamma ligand pioglitazone would modulate fibroblast growth and collagen type-I synthesis (and expression) in cardiac fibroblasts exposed to anoxia-reoxygenation (A-R). METHODS AND RESULTS: Cardiac fibroblasts were exposed to anoxia (95% N2/5% CO2) and then reoxygenation (95% air/5% CO2). A-R increased fibroblast growth (MTT assay) as well as collagen type-I synthesis (H-proline incorporation) and protein expression (Western analysis). Concurrently, there was a parallel increase in the expression of matrix metalloproteinase-1 (MMP-1) in fibroblasts. Pretreatment of cardiac fibroblasts with pioglitazone (10 M) reduced all these effects of A-R. Further, A-R stimulated intracellular reactive oxygen species (ROS) generation and activated the redox-sensitive transcription factor NF-kappaB (both P < 0.05). Both these phenomena were inhibited by pretreatment of cells with pioglitazone. CONCLUSION: Thus, it appears that A-R stimulates fibroblast cell growth, collagen type-I synthesis, and MMP-1 expression in cardiac fibroblasts, most likely a result of ROS generation. Inhibition of ROS generation and induction of NF-kappaB in cardiac fibroblasts during A-R may be a mechanism of action of pioglitazone.

Animals↗
PubMed2004

Inhibitory effect of candesartan and rosuvastatin on CD40 and MMPs expression in apo-E knockout mice: novel insights into the role of RAS and dyslipidemia in atherogenesis.

BACKGROUND: There is increasing evidence of cross-talk between renin-angiotensin system (RAS) and dyslipidemia in atherogenesis mediated via activation of inflammatory cascade, involving CD40 and matrix metalloproteinases (MMPs). We postulated that inhibition of RAS with candesartan and dyslipidemia with rosuvastatin would have additive inhibitory effect on CD40 and MMPs expression and atherogenesis. METHODS AND RESULTS: Apo-E knockout mice were fed high-cholesterol diet alone, or with candesartan or rosuvastatin or both. C57BL/6J mice on regular mice chow served as control. Twelve weeks later, apo-E knockout mice with high-cholesterol diet had extensive atherosclerosis, whereas C57BL/6J mice had no atherosclerosis. Candesartan and rosuvastatin alone decreased the extent of atherosclerosis. However, the combined feeding of candesartan and rosuvastatin reduced atherosclerosis in an additive fashion. The expression of CD40 and MMPs was found to be up-regulated in apo-E knockout mice. While candesartan and rosuvastatin each had a small inhibitory effect on the expression of CD40 and MMPs, the combination completely blocked the up-regulation of these inflammatory mediators. CONCLUSION: This study, for the first time, demonstrates that the combination of candesartan and rosuvastatin markedly affects the expression of CD40 and MMPs, resulting in a greater anti-atherosclerotic effect.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2004

Role of AIF in human coronary artery endothelial cell apoptosis.

Apoptosis-inducing factor (AIF), which exerts its effect via a caspase-independent pathway, has been suggested to be a mediator of cell injury. We have recently identified the expression of AIF in human coronary artery endothelial cells (HCAECs). The present study was designed to determine the pathophysiological role of AIF in oxidized low-density lipoprotein (ox-LDL)-induced apoptosis of HCAECs. The cells were cultured and treated with ox-LDL (40 microg/ml) for 24 h. Ox-LDL increased AIF expression, caused apoptosis of HCAECs (determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and large-scale DNA fragmentation), and induced translocation of AIF from the cytoplasm to the nucleus (fluorescence immunocytochemistry). Pretreatment of HCAECs with a caspase inhibitor (ZVAD-fmk) did not influence AIF-mediated apoptosis in response to ox-LDL. We developed a specific antisense oligonucleotide targeted to the 5'-TCG CCG AAA TGT TCC GGT GTG GA-3' portion of the human AIF mRNA sequence (AIF-AS) to bind a complementary sequence overlapping the translational start site. Pretreatment of cells with the AIF-AS for 24 h resulted in suppression of ox-LDL-upregulated AIF protein, as measured by immunoblot analysis. AIF-AS also reduced apoptosis and AIF translocation (P < 0.01 vs. ox-LDL alone). Next, we constructed a recombinant AIF plasmid by inserting whole-length AIF cDNA into the expression vector pcDNA3.1 with a cytomegalovirus promoter. HCAECs transfected with plasmid showed a two- to fourfold increase in AIF expression, extensive apoptosis, and translocation of AIF from the cytoplasm to the nucleus. These results from two approaches indicate that AIF plays an important role in ox-LDL-induced endothelial injury.

Apoptosis↗
PubMed2004

Tumor necrosis factor-alpha-induced apoptosis of human coronary artery endothelial cells: modulation by the peroxisome proliferator-activated receptor-gamma ligand pioglitazone.

The cytokine tumor necrosis factor-alpha (TNF-alpha) plays an important role in endothelial injury, which is associated with the release of reactive oxygen species and the induction of apoptosis. We report on our study of TNF-alpha-induced apoptosis in human coronary artery endothelial cells and its modulation by the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand pioglitazone. Treatment of cells with TNF-alpha (40 ng/mL) resulted in apoptosis as measured by DNA laddering and caspase-3 activation. TNF-alpha treatment decreased the expression of antiapoptotic protein Bcl-2 (P <.05 vs control), but not the expression of Fas or FLIP, in human coronary artery endothelial cells. Treatment of cells with TNF-alpha also enhanced lipid peroxidation (P <.01 vs control). Pretreatment of cells with the PPAR-gamma ligand pioglitazone blocked TNF-alpha-mediated apoptosis, caspase-3 activation, expression of Bcl-2, and lipid peroxidation (P <.01 vs TNF-alpha alone). These results indicate that TNF-alpha induces oxidative stress in human coronary artery endothelial cells, resulting in apoptosis through a reduction in Bcl-2 expression and the subsequent activation of caspase-3. The PPAR-gamma ligand pioglitazone modulates lipid peroxidation, alters Bcl-2 expression and caspase-3 activation, and finally reduces apoptosis. The antioxidant and antiapoptotic effects of pioglitazone may be the mechanism by which this agent reduces endothelial injury.

Apoptosis↗
PubMed2003

Role of caspases in Ox-LDL-induced apoptotic cascade in human coronary artery endothelial cells.

Oxidized low-density lipoprotein (ox-LDL) induces apoptosis in endothelial cells. However, steps leading to ox-LDL-induced apoptosis remain unclear. We examined the role of ox-LDL and its newly described receptor LOX-1 in the expression of intracellular pro- and antiapoptotic proteins and caspase pathways in human coronary artery endothelial cells (HCAECs). Cells were cultured and treated with different concentrations (10 to 80 microg/mL) of ox-LDL for different times (2 to 24 hours). Ox-LDL induced apoptosis in HCAECs in a concentration- and time-dependent manner. Ox-LDL also activated caspase-9 and caspase-3, but not caspase-8. After ox-LDL treatment, there was a significant release of activators of caspase-9, including cytochrome c and Smac from mitochondria to cytoplasmic compartment, and their release was not affected by treatment of cells with inhibitors of either caspase-8 or caspase-9. Ox-LDL also decreased expression of antiapoptotic proteins Bcl-2 and c-IAP (inhibitory apoptotic protein)-1, which are involved in the release of cytochrome c and Smac and activation of caspase-9, in a concentration- and time-dependent manner. On the other hand, ox-LDL did not change the expression of Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (FLIP) and proapoptotic protein Fas, which are required for the activation of caspase-8. Further, ox-LDL did not cause the truncation of Bid, which implies the activation of caspase-8. In other experiments, pretreatment of HCAECs with the caspase-9 inhibitor z-LEHD-fmk, but not the caspase-8 inhibitor z-IETD-fmk, blocked ox-LDL-induced activation of caspase-3 and apoptosis. As expected, pretreatment with the caspase-3 inhibitor DEVD-CHO inhibited ox-LDL-induced activation of caspase-3 and resultant apoptosis. The proapoptotic effects of ox-LDL were mediated by its receptor LOX-1, because pretreatment of HCAECs with antisense-LOX-1, but not sense-LOX-1, blocked these effects of ox-LDL. These findings suggest that ox-LDL through its receptor LOX-1 decreases the expression of antiapoptotic proteins Bcl-2 and c-IAP-1. This is followed by activation of apoptotic signaling pathway, involving release of cytochrome c and Smac and activation of caspase-9 and then caspase-3.

Apoptosis↗
PubMed2003

Pioglitazone inhibits LOX-1 expression in human coronary artery endothelial cells by reducing intracellular superoxide radical generation.

OBJECTIVE: LOX-1, a novel lectin-like receptor for oxidized LDL (ox-LDL), is expressed in response to ox-LDL, angiotensin II (Ang II), tumor necrosis factor (TNF)-alpha, and other stress stimuli. It is highly expressed in atherosclerotic tissues. Peroxisome proliferator-activated receptor (PPAR)-gamma ligands, such as pioglitazone, exert antiatherosclerotic effects. This study examined the regulation of LOX-1 expression in human coronary artery endothelial cells (HCAECs) by pioglitazone. METHODS AND RESULTS: Fourth generation HCAECs were treated with ox-LDL, Ang II, or TNF-alpha with or without pioglitazone pretreatment. All 3 stimuli upregulated LOX-1 expression (mRNA and protein). Pioglitazone, in a concentration-dependent manner, reduced LOX-1 expression (P<0.01 versus ox-LDL, Ang II, or TNF-alpha alone). Ox-LDL, Ang II, and TNF-alpha each enhanced intracellular superoxide radical generation, and pioglitazone pretreatment reduced superoxide generation (P<0.01 versus ox-LDL, Ang II, or TNF-alpha). Furthermore, all 3 stimuli upregulated the expression of the transcription factors nuclear factor-kappaB and activator protein-1 (determined by electrophoretic mobility shift assay), and pioglitazone pretreatment reduced this expression (P<0.01 versus ox-LDL, Ang II, or TNF-alpha). To determine the biological significance of pioglitazone-mediated downregulation of LOX-1, we studied monocyte adhesion to ox-LDL-treated HCAECs. Pioglitazone reduced the adhesion of monocytes to activated HCAECs in a fashion similar to that produced by antisense to LOX-1 mRNA. CONCLUSIONS: These observations suggest that the PPAR-gamma ligand pioglitazone reduces intracellular superoxide radical generation and subsequently reduces the expression of transcription factors, expression of the LOX-1 gene, and monocyte adhesion to activated endothelium. The salutary effect of PPAR-gamma ligands in atherogenesis may involve the inhibition of LOX-1 and the adhesion of monocytes to endothelium.

Angiotensin II↗
PubMed2003

Oxidized LDL through LOX-1 modulates LDL-receptor expression in human coronary artery endothelial cells.

Experimental studies have shown that oxidized low-density lipoprotein (ox-LDL) up-regulates its receptor LOX-1. Both ox-LDL and LOX-1 are expressed in atherosclerotic plaques. Native LDL concentrations are elevated in atherosclerosis, suggesting a reduction in LDL-receptors. We hypothesized that ox-LDL via LOX-1 could influence the expression of LDL-receptors. This study was designed to examine the interaction between ox-LDL, LOX-1, and LDL-receptors in human coronary artery endothelial cells (HCAECs). HCAECs were incubated with ox-LDL (10-80 microg/ml) for 3-24h. Ox-LDL decreased the expression of LDL-receptor in a concentration- and time-dependent fashion. The effects of ox-LDL were mediated by its endothelial receptor LOX-1, since pretreatment of HCAECs with a blocking antibody to LOX-1 (JTX92, 10 microg/ml) prevented the effect of ox-LDL on LDL-receptor expression. The role of LOX-1 was further confirmed by the use of an antisense to LOX-1 mRNA, which also blocked the effect of ox-LDL in LDL-receptor expression. In other experiments, ox-LDL as expected induced superoxide anion generation; and pretreatment of HCAECs with the anti-oxidants trolox and alpha-tocopherol (each 10 microM) inhibited the formation of superoxide anions as well as the down-regulation of LDL-receptor in response to ox-LDL. These studies provide the first evidence that ox-LDL via LOX-1 modulates LDL-receptor expression in HCAECs. The generation of free radicals elicited by ox-LDL may be a key step in this process.

Antioxidants↗