Search

Carbon emissions trading system is expected to be both efficient and flexible in carbon reduction through green innovation. As the world’s largest CO2 emitter, China has launched the emissions trad...

Moisture and thermal are the key factors for influencing methane desorption during CBM exploitation. Using high-pressure water injection technology into coalbed, new fractures and pathways are formed to transport methane. A phenomenon of water-inhibiting gas flow existed. This study is focused on various water pressures impacted on gas-adsorbed coal samples, and then the desorption capacity could be revealed under different conditions. And the results are shown that methane desorption capacity was decreased with the increase in water pressure at room temperature and the downtrend would be steady until water pressure was large enough. Heating could promote gas desorption capacity effectively, with the increasing of water injection pressures, and the promotion of thermal on desorption became more obvious. These results are expected to provide a clearer understanding of theoretical efficiency of heat water or steam injection into coalbed, and they can provide some theoretical and experimental guidance on CBM production and methane control.

Moisture and thermal are the key factors for influencing methane desorption during CBM exploitation. Using high pressure water injection technology into coalbed, new fractures and pathways are formed to methane transport. It is existed a phenomenon of water inhibiting gas flow. This study is focused on various water pressures impacted on gas adsorbed coal samples, then the desorption capacity could be revealed under different conditions. And the results are shown that methane desorption capacity was decreased with water pressure increased at room temperature and the downtrend would be steady until water pressure was large enough. Heating could promote gas desorption capacity effectively, with the increasing of water injection pressures, the promotion of thermal on desorption became more obvious. There are the others effects on methane desorption capacity influenced by water injection and thermal.

Transforming growth factor beta(1) (TGFbeta(1)) has been purported to protect tissues from ischemia-reperfusion (I-R) injury. This study was designed to examine if overexpression of TGFbeta(1) using adeno-associated virus type 2 (AAV) protects cardiomyocytes from reoxygenation injury. TGFbeta(1) was overexpressed in cultured HL-1 mouse cardiomyocytes by transfection with AAV/TGFbeta(1)(Latent) or with AAV/TGFbeta(1)(ACT) (active TGFbeta(1)). TGFbeta(1) upregulation reduced cardiomyocyte apoptosis and necrosis induced by 24 h of hypoxia followed by 3 h of reoxygenation concomitant with reduction in reactive oxygen species release, activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and NF-kappaB expression. Transfection with AAV/TGFbeta(1)(ACT) was superior to that with AAV/TGFbeta(1)(Latent). To determine if AAV/TGFbeta(1)(ACT) upregulation in vivo would induce cardioprotection from I-R injury, rat hearts were injected with AAV/TGFbeta(1)(ACT) or phosphate-buffered saline (PBS). Six weeks later, TGFbeta(1)(ACT) was upregulated throughout the myocardium. Following I-R, AAV/TGFbeta(1)(ACT)-overexpressing rats had much smaller infarct size (P

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

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 (1 mg/(kg d)), candesartan (1 mg/(kg d)) 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.

Background : Aspirin is thought to exert salutary effects in vascular disease states by inhibiting platelet aggregation. Endothelial activation, accumulation of oxidized low-density lipoprotein (ox-LDL) and intense inflammation also characterize atherosclerotic plaque in acute myocardial ischemia. Ox-LDL induces expression of lectin-like receptors (LOX-1) on endothelial cells and leads to the expression of matrix metalloproteinases (MMPs), which destabilize the atherosclerotic plaque. We hypothesized that aspirin may interfere with LOX-1 expression and subsequent MMP activation. Methods and results : Cultured human coronary artery endothelial cells (HCAECs) were incubated with aspirin (1–5 mM), sodium salicylate (5 mM) or the cyclo-oxygenase inhibitor indomethacin (0.25 mM) before treatment with ox-LDL. Aspirin, in a dose- and time-dependent fashion, reduced ox-LDL-mediated LOX-1 expression ( P

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-γ 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 P

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.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 (P0.01 versus hU-II alone).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.

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.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.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.

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.

Uptake of oxidized low-density lipoprotein (ox-LDL) by endothelial cells is a critical step for the initiation and development of atherosclerosis. Adhesion molecules are inflammatory makers, which are upregulated by ox-LDL and play a pivotal role in atherogenesis. A number of studies suggest that fish and its constituents can reduce inflammation and decrease atherosclerosis. We hypothesized that fish oil constituents namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may reduce expression of adhesion molecules induced by ox-LDL. Cultured human coronary artery endothelial cells (HCAECs) were incubated with ox-LDL for 24 h. Parallel groups of cells were pretreated with DHA or EPA (10 or 50 microM) overnight before incubation with ox-LDL. Ox-LDL markedly increased the expression of P-selectin and intracellular adhesion molecule-1 (ICAM-1) (both protein and mRNA) in HCAECs, and enhanced the adhesion of monocytes to the cultured HCAECs. Both EPA and DHA decreased ox-LDL-induced upregulation of expression of P-selectin and ICAM-1, and the enhanced adhesion of monocytes to HCAECs. To determine the role of protein kinase B (PKB) as an intracellular-signaling pathway, HCAECs were treated with the PKB upstream inhibitor wortmannin (100 nM) or transfected with plasmids encoding dominant-negative mutants of PKB (PKB-DN) before treatment with DHA. Ox-LDL alone downregulated the activity of PKB; DHA attenuated this effect of ox-LDL, and both wortmannin and PKB-DN blocked the effect of DHA. The present study in human coronary endothelial cells suggests that both EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules, and the adhesion of monocytes to HCAECs by modulation of PKB activation. These effects may be important mechanisms of anti-atherosclerotic effects of fish and fish oils.

Background: Myocardial hypoxia-reoxygenation (H-R) is associated with upregulation of metalloproteinases (MMPs). Upregulation of MMPs is associated with cell injury. Previous studies have shown that fish oil can protect myocardium from injury induced by H-R. This study was designed to examine the effect of eicosapentanoic acid (EPA), one of the major components in fish oil, on the modulation of MMP-1 expression in response to H-R in cultured adult rat myocytes. Methods and results: Myocytes isolated from adult Sprague–Dawley rat hearts were cultured with or without EPA or arachidonic acid (AA) (10 and 50 μM) and exposed to 24 h of hypoxia followed by 3 h of reoxygenation (H-R). H-R resulted in myocyte injury (measured on LDH release), increase in p38MAPK phosphorylation (Western analysis), augmentation of lipid peroxidation, and upregulation of MMP-1 activity (zymography) and expression (RT-PCR and Western analysis) (all P

LOX-1, a receptor for oxidized low-density lipoprotein (ox-LDL), plays a critical role in endothelial dysfunction and atherosclerosis. LOX-1 activation also plays an important role in monocyte adhesion to endothelial cells. A number of studies show that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) reduce total LDL cholesterol and exert a cardioprotective effect. We examined the modulation of LOX-1 expression and its function by two different statins, simvastatin and atorvastatin, in human coronary artery endothelial cells (HCAECs). We observed that ox-LDL (40 microg/ml) treatment up-regulated the expression of E- and P-selectins, VCAM-1 and ICAM-1 in HCAECs. Ox-LDL mediated these effects via LOX-1, since antisense to LOX-1 mRNA decreased LOX-1 expression and subsequent adhesion molecule expression. Pretreatment of HCAECs with simvastatin or atorvastatin (1 and 10 microM) reduced ox-LDL-induced expression of LOX-1 as well as adhesion molecules (all P < 0.05). A high concentration of statins (10 microM) was more potent than the low concentration (1 microM) (P < 0.05). Both statins reduced ox-LDL-mediated activation of the redox-sensitive nuclear factor-kappaB (NF-kappaB) but not AP-1. These observations indicate that LOX-1 activation plays an important role in ox-LDL-induced expression of adhesion molecules. Inhibition of expression of LOX-1 and adhesion molecules and activation of NF-kappaB may be another mechanism of beneficial effects of statins in vascular diseases.

Background — Reoxygenation injury is a result of several complex events, including release of reactive oxygen species, protein kinase C (PKC) activation, and altered expression of transforming growth factor-β 1 (TGF-β 1 ). Nitric oxide (NO) generally protects tissues from reperfusion injury. Methods and Results — We examined the modulation of TGF-β 1 expression and activity and PKC activation in cultured rat heart myocytes exposed to a brief period of hypoxia-reoxygenation (H-R) by NO donor 3-morpholino-sydnonimine (SIN-1). H-R resulted in an increased expression of total TGF-β 1 (mRNA and protein) but a decrease in the release of active TGF-β 1 . Myocyte PKC-α protein level was not altered by H-R, but its phosphorylation was augmented. Pretreatment of myocytes with SIN-1 diminished myocyte injury quantified as lactate dehydrogenase release. Simultaneously, release of active TGF-β 1 increased and total TGF-β 1 expression decreased (all P 1 release increased, and total TGF-β 1 expression decreased. Conclusions — These observations suggest modulation of TGF-β 1 expression as a novel mechanism of salutary effect of NO donors. PKC-α activation may play an important role in the protective effect of NO against H-R injury.

As a tool for market-oriented environmental regulation, carbon emissions trading system is expected to be both efficient and flexible in carbon reduction through green innovation. As the world's la...

LOX-1, a receptor for oxidized low-density lipoprotein (ox-LDL), plays a critical role in endothelial dysfunction and atherosclerosis; both of these conditions are associated with diminished expression of constitutive endothelial nitric oxide synthase (eNOS). Recent studies show that HMG CoA reductase inhibitors (statins) exert cardioprotective effect. We examined the role of LOX-1 in eNOS expression and modulation of this relationship by two different statins, simvastatin and atorvastatin in human coronary artery endothelial cells (HCAECs). Ox-LDL (40 microg/ml) upregulated the expression of LOX-1; simultaneously, there was a reduction in eNOS expression. Pretreatment of HCAECs with simvastatin or atorvastatin (1 and 10 microM) reduced ox-LDL-induced upregulation of LOX-1 and downregulation of eNOS (both P0.05). High concentration of statins (10 microM) was more potent than the low concentration (1 microM) (P0.05). Both statins also attenuated ox-LDL-mediated activation of MAP kinase. These observations indicate that statins attenuate the effect of ox-LDL on eNOS expression. Inhibitory effect on LOX-1 and subsequently MAP kinase activity provides a potential mechanism of beneficial effects of statins beyond lowering cholesterol.

Myocardial hypoxia-reoxygenation (H-R) is associated with upregulation of inducible nitric oxide synthase (iNOS), decrease in endothelial NOS (eNOS), and increase in protein kinase B (PKB). Previous work also shows that transforming growth factor-β1 (TGF-β1) can attenuate myocardial injury induced by H-R. We examined the modulation of NOS and PKB expression in response to H-R by TGF- β1. Myocytes from Sprague-Dawley rat hearts were cultured and exposed to hypoxia (95% N2-5% CO2, Po 2 ∼30 mmHg) for 24 h and reoxygenation (95% air-5% CO2) for 3 h. Myocytes were then examined for lactate dehydrogenase (LDH) release, iNOS activity (conversion ofl-[3H]arginine tol-[3H]citrulline), iNOS and eNOS expression, and PKB phosphorylation. H-R alone resulted in myocyte injury, upregulation of iNOS activity and expression, decrease in eNOS expression, and increase in PKB phosphorylation (all P< 0.05 vs. cells cultured in normoxic conditions). Treatment of myocytes with TGF-β1 (1 ng/ml) resulted in a reduction in LDH release, attenuation of the alterations in NOS expression (both iNOS and eNOS), and PKB phosphorylation in response to H-R (all P < 0.05 vs. H-R alone). These observations suggest that TGF-β1 decreases H-R injury and attenuates alterations in NOS and PKB phosphorylation in myocytes exposed to H-R.

Background: oc-Tocopherol has received much attention in the primary and secondary prevention of coronary artery disease. Absence of other isoforms, such as y- and &-tocopherol, in commercial preparations of vitamin E may account for the inconsistent results of clinical trials. Since platelet aggregation is intimately involved in thrombogenesis, the relative effects of ox-, y-, and 6-tocopherol and their combination were examined on human platelet aggregation, lipid peroxidation, and constitutive nitric oxide synthase (cNOS) activity. Methods and Results: Human platelets were incubated with the three different isoforms of tocopherol and their combination for 30 minutes, and then ADP-induced platelet aggregation measured. All three isoforms of tocopherol markedly and similarly decreased platelet aggregation in a concentration (120-480,uM)-dependent manner. All three tocopherols also decreased the level of the lipid peroxidation product, malondialdehyde (MDA), and increased NO release (P < 0.05 vs control). These isoforms of tocopherol did not affect cNOS protein expression, but enhanced cNOS phosphorylation in platelets. The combination of three tocopherols in a concentration found in nature was more potent than oc-, y-, or 6-tocopherol alone in this regard. Conclusion: These observations suggest that all three major isoforms of tocopherol have a similar effect on human platelet aggregation. The three isoforns appear to attenuate platelet aggregation at least in part via a decrease in free radical generation and an increase in platelet cNOS activity. The combination of tocopherols has a synergistic platelet inhibitory effect. Future clinical trials should concentrate on the combination of these three isoforms of tocopherols.

BACKGROUND: Increasing evidence suggests that vitamin E prevents the progression of atherosclerosis by inhibiting platelet aggregation, monocyte adhesion, and improving plaque stability and vasomotor function. Recently, controversy has arisen as to the relative effects of alpha- and gamma-tocopherol in modulating some mediators of atherosclerosis. METHODS AND RESULTS: We examined the effects of alpha- and gamma-tocopherol on constitutive nitric oxide synthase (cNOS) and superoxide dismutase (SOD) activity and protein expression in rats. Sprague-Dawley rats were fed regular chow or chow mixed with alpha- or gamma-tocopherol (100 mg/kg/day) for 7 to 10 days. Plasma alpha- and gamma-tocopherol levels, low-density lipoprotein (LDL) oxidation, and cNOS and SOD activity and protein expression were measured. Plasma alpha-tocopherol levels were significantly increased (eP

OBJECTIVESThis study was designed to examine the differential effects of α- and γ-tocopherol on parameters of oxidation-antioxidation and thrombogenesis.BACKGROUNDExperimental studies have shown that antioxidants, such as vitamin E (α-tocopherol), improve atherosclerotic plaque stability and vasomotor function, and decrease platelet aggregation and tendency to thrombus formation.METHODSSprague Dawley rats were fed chow mixed with α- or γ-tocopherol (100 mg/kg/day) for 10 days. A filter soaked in 29% FeCl3was applied around the abdominal aorta to study the patterns of arterial thrombosis. The aortic blood flow was observed and continuously recorded using an ultrasonic Doppler flow probe. ADP-induced platelet aggregation, low-density lipoprotein oxidation induced by phorbol 12-myristate 13-acetate (PMA)-stimulated leukocytes, superoxide anion generation and superoxide dismutase (SOD) activity were also measured.RESULTSBoth α- and γ-tocopherol decreased platelet aggregation and delayed time to occlusive thrombus (all p < 0.05 vs. control). Both α- and γ-tocopherol decreased arterial superoxide anion generation, lipid peroxidation and LDL oxidation (all p < 0.05 vs. control), and increased endogenous SOD activity (p < 0.05). The effects of γ-tocopherol were more potent than those of α-tocopherol (p < 0.05).CONCLUSIONSThis study indicates that both α- and γ-tocopherol decrease platelet aggregation and delay intraarterial thrombus formation, perhaps by an increase in endogenous antioxidant activity. γ-Tocopherol is significantly more potent than α-tocopherol in these effects.

Abstract —The mutant form of human apoA1, known as apoA1 Milano, is formed as a result of arginine 173 to cysteine substitution and inhibits experimental atherosclerosis in cholesterol-fed animals. This study was designed to determine if apoA1 Milano would modify arterial thrombogenesis. Sprague Dawley rats were intravenously administered the carrier alone (n=8) or apoA1 Milano (20 mg · kg −1 · d −1 for 4 to 10 days, n=17). The abdominal cavity was opened, and the abdominal aorta was isolated. Whatman paper impregnated with 35% FeCl 3 was wrapped around the surface of the aorta, and aortic flow was recorded continuously. In carrier-treated rats, an occlusive platelet-fibrin-rich thrombus was formed in 21.2±4.1 (mean±SD) minutes. Treatment of rats with apoA1 Milano markedly delayed time to thrombus formation (38.8±11.9 versus 21.2±4.1 minutes, P P P

Angiotensin II type 1 receptor (AT1R) exerts growth-promoting and anti-apoptotic effects, which contribute to atherogenesis. In contrast, type 2 receptor (AT2R) activation exerts anti-growth and pro-apoptotic effects. We tested the hypothesis that over-expression of AT2R will attenuate formation of atherosclerotic lesions. Low-density lipoprotein receptor knockout (LDLR KO) mice were injected via tail vein with recombinant AAV carrying AT2R (agtr2) cDNA (AAV/AT2R), AAV/Neo, or saline, and then put on a high cholesterol diet. At 18 weeks, all animals were sacrificed, and the aortas were harvested for AT2R expression and determination of atherosclerotic lesion formation. AT2R was highly expressed in mice given AAV/AT2R, but not in other groups. Atherosclerotic lesion formation and thickness of intima were significantly reduced in the LDRL KO mice with AT2R over-expression compared to other LDLR KO mice. Concurrently, there was suppression of oxidative stress (NADPH oxidase p67phox and the transcription factor NF-κB) and increase in the free radical scavenger superoxide dismutase activity. Importantly, there was a marked increase in apoptosis in the atheromatous tissues in the LDLR KO mice with over-expression of AT2R. Thus, upregulation of AT2R by gene delivery in the LDLR KO mice reduces oxidative stress and increases apoptosis resulting in a reduction in atherosclerotic lesion formation.

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.

Background : It has been suggested that peroxisome proliferator-activated receptor (PPAR)-γ ligands reduce the development of atherosclerosis and myocardial ischemia–reperfusion injury; both of these phenomena are associated with platelet activation. We postulated that PPAR-γ 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% FeCl3 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

Endothelial dysfunction is recognized as an early event in the pathogenesis of atherosclerosis. Many risk factors cause endothelial dysfunction, such as hypercholesterolemia, hypertension, cigarette smoking, and diabetes mellitus. The precise steps leading to endothelial dysfunction are still being elucidated. Increasing evidence indicates that oxidized low-density lipoprotein (LDL) cholesterol (ox-LDL) plays an important role in endothelial dysfunction. Ox-LDL induces endothelial injury; inhibits apoptosis, monocyte adhesion, and platelet aggregation; and inhibits endothelial nitric oxide synthase (eNOS) expression/activity, all of which contribute to atherosclerotic process. Several pharmacologic agents, such as 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins), have been shown to provide endothelial stabilization through mechanisms that go beyond their primary therapeutic effect. Alteration in the endothelial function might result from increase in eNOS activity, reduction in the production of free radicals, inhibition of ox-LDL action, or other undefined mechanisms. This review will focus on the protective role and some of the mechanisms of statins in ox-LDL-induced endothelial dysfunction.

Oxidatively modified low-density lipoprotein (ox-LDL) causes endothelial activa-tion, dysfunction and injury, which are considered primary steps in atherogenesis. Recently, a novel lectin-like receptor for ox-LDL (LOX-1) has been identified, primarily in endothe-lial cells. This receptor mediates uptake of ox-LDL into the endothelial cells and activates a variety of signal transduction mechanisms that lead to endothelial cell activation and expres-sion of adhesion molecules. LOX-1 receptor is transcriptionally upregulated by various stimuli accompanying pathogenic states, including TNF-OC, angiotensin II, shear stress and ox-LDL itself. LOX-1 receptor expression has been demonstrated in animal models and humans with hypertension, diabetes mellitus and atherosclerosis. Expression of this receptor may also be pathogenically involved in arterial thrombosis and myocardial ischemia-reperfusion injury. Understanding the regulation and signal transduction pathways of this receptor may lead to new therapies in prevention and treatment of atherosclerosis, and its complications.

Upregulation of angiotensin II receptor, may be involved in the initiation and progression of atherosclerosis. To examine the contribution of AT1 receptor in the expression of matrix metalloproteinase-1 (MMP-1) and its tissue inhibitor (TIMP-2) in lipid-deposited arterial tissues, New Zealand white rabbits were given high-cholesterol chow (with losartan 25 mg/d or vehicle) for 10 weeks. Losartan reduced the areas of sudanophilia in the aorta of rabbits fed high-cholesterol diet (p < 0.01 vs. control). Losartan also significantly decreased the enhanced mRNA expression of MMP-1 and TIMP-2 in aortas of rabbits with high-cholesterol diet. Losartan-treated rabbits revealed a reduction in immunohistochemical expression of MMP-1, whereas TIMP-2 expression became localized to the intima. In addition, losartan treatment reduced the activation of NF-kappa B by inhibiting the degradation of its inhibitor I kappa-B alpha. These observations demonstrate that AT1 receptor blockade with losartan reduces lipid deposition and exerts potent inhibitory effects on NF-kappa B activation and modulates the expression of MMP-1 and TIMP-2 in hypercholesterolemic rabbits.

Hypoxia-reoxygenation (H-R) is associated with alterations in oxidant-antioxidant balance and L-arginine-nitric oxide system. Tocopherols decrease the activity of reactive oxygen species (ROS) and yet are not beneficial in clinical trials. It has been proposed that mixed tocopherols as found in nature may be more tissue protective than alpha-tocopherol alone found in commercial preparations. We compared the effect of a mixed tocopherol preparation with that of alpha-tocopherol alone on superoxide dismutase (SOD) activity and iNOS expression in cultured myocytes exposed to H-R. Myocytes from Sprague-Dawley rat hearts were subjected to hypoxia for 24 h followed by reoxygenation for 3 h H-R. Parallel groups of myocytes were pretreated with alpha-tocopherol alone or a mixed-tocopherol preparation (containing alpha-, gamma-, and delta-tocopherols) (50 microM) for 30 min. H-R resulted in myocyte injury (determined by LDH release), a decrease in SOD activity and an upregulation of iNOS expression/activity. Both tocopherol preparations attenuated cell injury and markedly decreased the effects of H-R on SOD activity and iNOS expression/activity (all P0.05 vs H-R group, n = 5). However, mixed-tocopherol preparation was much superior to alpha-tocopherol in terms of myocyte protection from the adverse effect of H-R (P0.05). Lack of efficacy of commercial tocopherol preparations in clinical trials may reflect absence of gamma- and delta-tocopherols.

Regular exercise resulting in release of catecholamines is an oxidant stress, and yet it protects humans from acute cardiac events. We designed this study to examine the effect of epinephrine on free radical release and endogenous superoxide dismutase (SOD) gene and protein expression in human coronary artery endothelial cells (HCAECs). HCAECs were incubated with epinephrine (10(-9) to 10(-5) M) alone or with the water-soluble analog of vitamin E (trolox) (10(-5) M), the lipid-soluble vitamin E (5 x 10(-5) M), or the beta(1)-adrenergic blocker atenolol (10(-5) M). At 1 and 24 h of incubation with epinephrine, superoxide anion generation increased by 102 and 81% in the HCAECs. There was a marked increase in both MnSOD and Cu/ZnSOD mRNA and protein, as determined by RT-PCR and Western Analysis, respectively. Both MnSOD and Cu/ZnSOD activities were also increased. Pretreatment of HCAECs with trolox and vitamin E decreased superoxide anion generation (p

Angiotensin-II (Ang-II) enhances the modification of LDL and the expression of its lectin-like receptor (LOX-1) by activating type 1 (AT(1)) receptors. This study was designed to determine the effect of hypercholesterolemia on LOX-1 expression in aorta and its modulation by the AT(1) receptor blocker losartan. Male New Zealand White rabbits were fed regular chow (Control group), chow with 1% cholesterol and 4% peanut oil (HC-diet group), or 1% cholesterol and 4% peanut oil diet plus losartan (25 mg/kg/day) (Losartan + HC-diet group) for 10 weeks. Animal body weight, serum cholesterol levels, and arterial blood pressure were measured. Aortic intimal thickening was quantitated in H&E-stained segments. LOX-1 expression in aortas was examined by immunohistochemistry and semi-quantitative RT-PCR. High-cholesterol diet did not affect body weight, but induced hypercholesterolemia and extensive intimal thickening. Aortas of rabbits in the control group showed a modest LOX-1 expression in the endothelium. Aortic intimal proliferation in HC-diet group was associated with a marked increase in LOX-1 expression (protein and mRNA) in the endothelium and neointima. Treatment with losartan attenuated aortic intimal proliferation and markedly decreased the enhanced LOX-1 expression. Thus high-cholesterol diet induces the upregulation of LOX-1 expression in neointima of aortas of rabbits. Treatment with losartan, an AT(1) blocker, markedly decreases this enhanced LOX-1 expression.

Angiotensin-converting enzyme (ACE) activity in the myocardium and angiotensin-II (Ang-II) levels in plasma increase after myocardial ischemia, which lead to exacerbation of myocardial injury and cardiac dysfunction. We examined the protective role of novel antisense-oligodeoxynucleotide (AS-ODN) directed at ACE mRNA in myocardial ischemic injury. Sprague-Dawley rats were treated with ACE-AS-ODN (200 microg per rat, n = 8, i.v.) or inverted-ODN (IN-ODN, 200 microg per rat, n = 8, i.v.), given with 600 microg per rat of liposome DOTAP/DOPE. Hearts from AS-ODN- or IN-ODN-treated rats were excised, perfused in vitro, and subjected to 25 min of global ischemia followed by 30 min of reperfusion. Parallel groups of rats were given ACE inhibitor captopril (5 mg/kg, n = 8) or saline (n = 8) before excising the hearts. Ischemia/reperfusion resulted in myocardial dysfunction (increase in coronary perfusion pressure and LV end-diastolic pressure and a decrease in developed LV pressure) in the saline-treated rats. Myocardial dysfunction was associated with evidence of lipid peroxidation and enzyme leakage (MDA and LDH levels in the myocardium) and up-regulation of ACE protein expression. Administration of AS-ODN or captopril, but not IN-ODN, reduced Ang-II levels in the plasma, decreased ischemia/reperfusion-mediated cardiac functional deterioration and lipid peroxidation, and preserved LDH in the myocardium (all P < 0.05 versus the saline group). AS-ODN and captopril had equipotent effects on cardiac dynamics. ACE protein expression (western blot) was decreased in the hearts of the AS-ODN-treated group, but not in IN-ODN-treated rat hearts. In contrast, ACE protein expression was significantly increased in captopril-treated rat hearts. These observations suggest that AS-ODN directed at ACE mRNA can ameliorate myocardial dysfunction and injury after ischemia/reperfusion, and its use is associated with decreased expression of ACE protein in the ischemic myocardium.

gamma-Tocopherol, produced by many plants, is the major form of tocopherol in the United States diet. It is an effecient protector of lipids against peroxidative damage. Epidemiologic studies show that supplementation of diet with gamma-tocopherol is inversely related to the risk of death from cardiovascular disease. This study was conducted to examine the role of gamma-tocopherol in oxidized LDL (ox-LDL)-induced nuclear factor (NF)-kappaB activation and apoptosis in human coronary artery endothelial cells (HCAECs). Cultured HCAECs were treated with ox-LDL (10-40 microgram/ml). Incubation of HCAECs with ox-LDL resulted in apoptosis of HCAECs, as determined by TUNEL and DNA laddering. Ox-LDL degraded IkappaB protein and activated NF-kappaB in HCAECs (both P0.01 vs control), as determined by Western blot. Treatment of cells with gamma-tocopherol attenuated ox-LDL-mediated degradation of IkappaB and activation of NF-kappaB (both P0.01 vs ox-LDL alone). The presence of gamma-tocopherol also reduced ox-LDL-induced apoptosis (P0.01 vs ox-LDL alone). A high concentration of gamma-tocopherol (50 micromol/L) was more effective than the low concentration of gamma-tocopherol (10 micromol/L) in this process. These observations show that ox-LDL induces apoptosis of HCAECs at least partially by activation of NF-kappaB signal transduction pathway. gamma-Tocopherol significantly decreases ox-LDL-induced apoptosis of HCAECs by inhibiting the activation of NF-kappaB.

Abstract —Cross talk between oxidized LDL (ox-LDL) and angiotensin II (Ang II) may be relevant in atherosclerosis. In this study, we examined the presence of a specific endothelial receptor for ox-LDL (LOX-1) and Ang II receptors in human coronary artery endothelial cells (HCAECs). In addition, we studied the effect of Ang II on LOX-1 gene and protein expression. LOX-1 was consistently identified in HCAECs by reverse transcriptase–polymerase chain reaction (RT-PCR), cDNA sequence, Western blot, and 125 I-labeled ox-LDL binding assay (B max , 29.7 ng/mg protein). The HCAECs also exhibited Ang II receptors (AT 1 >AT 2 ), as determined by RT-PCR and 125 I-labeled Ang II binding assay (B max , 2.21 and 1.19 fmol/mg protein, respectively). Incubation of HCAECs with Ang II markedly increased LOX-1 mRNA (RT-PCR) and protein (Western blot) expression. The increase in LOX-1 expression was dependent on Ang II concentration (10 –12 to 10 –6 mol/L). Ang II caused a concentration-dependent increase in 125 I-labeled ox-LDL uptake by HCAECs and enhanced ox-LDL–mediated cell injury, as evident from an increase in LDH release and a decrease in cell viability. These effects of Ang II were completely blocked by pretreatment of HCAECs with losartan, a specific AT 1 blocker, but not by PD123319 , a specific AT 2 blocker. These observations indicate the following: (1) HCAECs possess abundant LOX-1 as well as Ang II (AT 1 >AT 2 ) receptors, (2) Ang II upregulates LOX-1 receptor and ox-LDL uptake, (3) the effects of Ang II are mediated by AT 1 activation, and (4) Ang II enhances ox-LDL–mediated injury to HCAECs.

Although macrophages scavenge oxidatively modified low density lipoprotein (ox-LDL) via specific receptors, the uptake of ox-LDL by endothelial cells is thought to be mediated by a different receptor (LOX-1). We examined the presence of LOX-1 on cultured human coronary artery endothelial cells (HCAECs) by RT-PCR, radioligand blot, and binding assays. LOX-1 mRNA and protein were consistently identified in HCAECs. [125I]-ox-LDL binding assay also identified high affinity binding sites for LOX-1 on HCAECs (KD: 1.71 x 10(-8) M: Bmax: 29.7 ng/mg protein). There was no change in LOX-1 expression in HCAECs treated with native-LDL. In contrast, incubation of HCAECs with ox-LDL (10-40 micrograms/ml) increased LOX-1 expression (mRNA and protein). The upregulation of LOX-1 expression appeared to be dependent on ox-LDL concentration. Higher concentration (100 micrograms/ml) however, decreased LOX-1 expression, perhaps related to its cytotoxic effect. These observations indicate that ox-LDL upregulates its own receptor on HCAECs. This phenomenon may explain enhanced uptake of ox-LDL by HCAECs in hyperlipidemia resulting in cellular dysfunction.

Potassium reduces blood pressure in populations at high risk of developing hypertension, which suggests that potassium depletion may increase vascular resistance. This study was designed to examine the effect of potassium depletion on thel-arginine-nitric oxide pathway in arterial tissues. New Zealand White rabbits were fed either a control diet, containing a normal amount of potassium, or a low-potassium diet for 1–3 wk. As expected, the low-potassium diet resulted in reduced serum and urinary potassium levels. Carotid arteries were excised, and their contractile and relaxant responses were determined in vitro. Carotid arterial ring contractile response to norepinephrine was enhanced, and relaxation in response to the endothelium-dependent vasodilators acetylcholine and calcium ionophore A-23187 was attenuated, in rabbits fed low-potassium diet (all P < 0.01 compared with responses in rabbits fed control diet). The vasomotor responses were similarly altered in rabbits fed low-potassium diet for 1 or 3 wk. Both the enhanced contraction and attenuated relaxation were abolished by treatment of arterial rings with superoxide dismutase but not by treatment with l-arginine or indomethacin. Carotid artery rings from rabbits fed the low-potassium diet showed ∼100% greater superoxide anion formation than those from rabbits fed control diet ( P < 0.01), whereas plasma and urinary nitrite levels were similar in both groups of rabbits. These observations indicate that low-potassium diet enhances the sensitivity of the carotid artery to vasoconstrictor stimuli and reduces the sensitivity to endothelium-dependent stimuli. Attenuation of endothelium-dependent relaxation appears to be secondary to increased free radical generation, which may degrade nitric oxide. Altered vasoreactivity may underlie the genesis of hypertension in populations consuming diets low in potassium.

See also article by Zhu et al. [3] (pages 425–432) in this issue. There is a great deal of experimental, epidemiological, and clinical evidence suggesting that disorders of lipid metabolism play an important role in the pathogenesis of atherosclerosis. To date, there have been many studies investigating the mechanisms by which high levels of LDL-cholesterol affect biology of vessels and cause atherosclerotic lesion formation [1,2]. It has become abundantly clear over the last decade that the oxidatively modified form of LDL (ox-LDL) is more important than native LDL in atherogenesis. The study in this issue of Cardiovascular Research by Zhu et al. [3] demonstrates that ox-LDL downregulates ATP-binding cassette transporter-1 (ABCA1) in endothelial cells in a dose-dependent manner by inhibiting liver X receptor (LXR) activation. Ox-LDL also attenuates LXR activation by blocking LXR ligand binding and interfering with the generation of 27-hydroxycholesterol, an LXR endogenous ligand. Further, ox-LDL inhibits exogenous cholesterol and oxysterol-induced endothelial ABCA1 induction. Such activity of ox-LDL may contribute to endothelial dysfunction since ABCA1 mediates the active efflux of cholesterol and phospholipids, playing an important role in cholesterol homeostasis and thereby atherogenesis. The endothelial activation and/or dysfunction … *Corresponding author. Department of Internal Medicine, University of Arkansas for Medical Sciences, 4301 W Markham, Slot 532, Little Rock, AR 72205, United States. Tel.: +1 501 686 6724. Email address: lidayuan{at}uams.edu

OBJECTIVES The goal of this study was to determine the role of lectin-like oxidized low-density lipoprotein receptors (LOX-1), a recently identified oxidized low-density lipoprotein (ox-LDL) receptor, in ischemia-reperfusion injury to the heart. BACKGROUND Reactive oxygen species (ROS) released during ischemia-reperfusion oxidize low-density lipoproteins; LOX-1 is upregulated by ox-LDL and ROS, and is involved in cell injury. METHODS Anesthetized rats were subjected to left coronary artery ligation for 60 min (n = 10, ischemia group), or ischemia followed by 60 min of reperfusion (n = 30, ischemia-reperfusion group). Rats in the latter group were treated with saline, the LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat immunoglobulin G (IgG) (10 mg/kg). Ten other rats underwent thoracotomy without coronary ligation (sham control). RESULTS Ischemia-reperfusion was associated with an increase in LOX-1 expression, lipid peroxidation and apoptosis, a large infarct area, and a decrease in left ventricular function (all, p < 0.01 vs. sham control and ischemia alone groups). Treatment of rats with LOX-1 antibody prevented ischemia-reperfusion-induced upregulation of LOX-1. Importantly, the LOX-1 antibody reduced apoptosis by 48%, lipid peroxidation by 39%, and myocardial infarct size by 45%, and improved left ventricular function (first derivative of pressure measured over time: -47% to -18%, p < 0.01). Nonspecific IgG had no effect. CONCLUSIONS Lectin-like oxidized low-density lipoprotein receptors are upregulated during myocardial ischemia-reperfusion, and appear to be associated with apoptosis, necrosis, and left ventricular functional deterioration.