Roundtable discussion. Achieving more aggressive low-density lipoprotein cholesterol lowering.
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Anticholesteremic Agents↗
Biomedical subjects
J L Mehta
Publications and source records attributed to J L Mehta.
Inflammation in ischemic heart disease: response to tissue injury or a pathogenetic villain?
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Animals↗
gamma-tocopherol decreases ox-LDL-mediated activation of nuclear factor-kappaB and apoptosis in human coronary artery endothelial cells.
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 P < 0.01 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 P < 0.01 vs ox-LDL alone). The presence of gamma-tocopherol also reduced ox-LDL-induced apoptosis (P < 0.01 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.
Apoptosis↗
Upregulation of endothelial receptor for oxidized low-density lipoprotein (LOX-1) in cultured human coronary artery endothelial cells by angiotensin II type 1 receptor activation.
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 125I-labeled ox-LDL binding assay (Bmax, 29.7 ng/mg protein). The HCAECs also exhibited Ang II receptors (AT1>AT2), as determined by RT-PCR and 125I-labeled Ang II binding assay (Bmax, 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 125I-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 AT1 blocker, but not by PD123319, a specific AT2 blocker. These observations indicate the following: (1) HCAECs possess abundant LOX-1 as well as Ang II (AT1>AT2) receptors, (2) Ang II upregulates LOX-1 receptor and ox-LDL uptake, (3) the effects of Ang II are mediated by AT1 activation, and (4) Ang II enhances ox-LDL-mediated injury to HCAECs.
Angiotensin II↗
Angiotensin-converting enzyme inhibitor-induced pancreatitis.
Approximately 2% of pancreatitis in adults is drug induced. Although some angiotensin-converting enzyme (ACE) inhibitors have been associated with pancreatitis, to the knowledge of the authors this is the first reported case involving benazepril. This case report presents laboratory- and image-proven pancreatitis in a noninsulin dependent 70-year-old man. The patient took benazepril at three different times and experienced the same epigastric symptoms 30 min after each dose. Possible mechanisms are reviewed. Clinicians should strongly consider discontinuing ACE inhibitors, including benazepril, in patients with pancreatitis of no identifiable source.
Acute Disease↗
Kinetics of tumor necrosis factor alpha in plasma and the cardioprotective effect of a monoclonal antibody to tumor necrosis factor alpha in acute myocardial infarction.
BACKGROUND: Inflammation plays a critical role in acute myocardial infarction (AMI) and tumor necrosis factor alpha (TNF-alpha) is a potent inflammatory trigger. This study was designed to examine the kinetics of TNF-alpha in plasma in patients with AMI and the potential benefit of inhibition of TNF-alpha monoclonal antibody in AMI. METHODS AND RESULTS: TNF-alpha levels in plasma were measured in 42 patients with AMI. TNF-alpha levels were elevated at 4 hours after onset of chest pain and declined to control values at 48 hours. TNF-alpha levels were higher in patients with Killip III and IV than in those with Killip I and II (P <.01). To examine the pathogenic role of TNF-alpha, New Zealand White rabbits were treated with buffer or a TNF-alpha monoclonal antibody before left anterior descending artery (LAD) ligation. Treatment with the TNF-alpha monoclonal antibody decreased area of necrosis, number of circulating endothelial cells, and lipid peroxidation product malonaldehyde bis(dimethyl acetal). There was a significant correlation of TNF-alpha levels with peak CK-MB in AMI patients, and area of necrosis, MDA, and circulating endothelial cells in rabbits (all P <.05). CONCLUSIONS: TNF-alpha release early in the course of AMI contributes to myocardial injury and dysfunction. Treatment with the monoclonal antibody against TNF-alpha can be cardioprotective, particularly in the setting of heart failure in patients with AMI.
Adult↗
Modulation of constitutive nitric oxide synthase, bcl-2 and Fas expression in cultured human coronary endothelial cells exposed to anoxia-reoxygenation and angiotensin II: role of AT1 receptor activation.
BACKGROUND: Angiotensin II (Ang II) plays a critical role in the pathophysiology of myocardial ischemia-reperfusion injury. We have recently shown that reoxygenation following a period of anoxia causes apoptosis of cultured human coronary artery endothelial cells (HCAECs). Ang II further enhances apoptosis of HCAECs via Ang II type 1 receptor (AT1R) activation. Recent studies suggest an important role of constitutive nitric oxide synthase (cNOS), Fas and bcl-2 proteins in apoptosis. This study was designed to examine the modulation of cNOS, and Fas and bcl-2 expression in HCAECs during exposure to anoxia-reoxygenation and Ang II. METHODS AND RESULTS: HCAECs were exposed to anoxia-reoxygenation and Ang II. Anoxia-reoxygenation significantly decreased cNOS mRNA, protein and activity in cultured HCAECs (P < 0.05 vs. control). Anoxia-reoxygenation also caused an increase in Fas and a decrease in bcl-2 protein expression in cultured HCAECs (both P < 0.05 vs. control). The presence of Ang II (0.3 microM) further enhanced these effects of anoxia-reoxygenation on cNOS, Fas and bcl-2 expression. The effects of Ang II were significantly attenuated by the AT1R inhibitor losartan (10 microM). CONCLUSION: During exposure of HCAECs to anoxia-reoxygenation and Ang II, AT1R activation induces important changes in cNOS mRNA, protein expression and activity, as well as bcl-2 and Fas protein expression which may have a bearing on the development of apoptosis.
Analysis of Variance↗
Tumor necrosis factor-alpha enhances hypoxia-reoxygenation-mediated apoptosis in cultured human coronary artery endothelial cells: critical role of protein kinase C.
BACKGROUND: Ischemia and tumor necrosis factor-alpha (TNF alpha) released during ischemia both cause apoptosis and necrosis of myocardial tissues. Since endothelium may be critically important in determination of cardiac function, we examined the interaction between TNF alpha and hypoxia-reoxygenation with regard to induction of apoptosis and underlying signaling pathway in cultured human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: HCAECs were cultured and exposed to hypoxia alone, hypoxia-reoxygenation, TNF alpha alone, TNF alpha plus hypoxia-reoxygenation, or TNF alpha only during the period of reoxygenation. Apoptosis was evaluated by transmission electron microscopy, DNA nick-end labeling and DNA laddering. Hypoxia alone caused modest time-dependent apoptosis of cultured HCAECs, and reoxygenation increased the number of apoptotic cells (P < 0.01 vs. hypoxia alone). TNF alpha induced concentration-dependent apoptosis, and enhanced reoxygenation-mediated apoptosis in cultured HCAECs (P < 0.01 vs. hypoxia-reoxygenation alone). As expected, monoclonal antibody to TNF alpha significantly blocked the pro-apoptotic effect of TNF alpha-induced apoptosis (P < 0.01). TNF alpha-induced apoptosis was found to be associated with marked activation of protein kinase C (PKC), and pretreatment of cells with a specific PKC inhibitor markedly reduced TNF alpha-mediated PKC activity and apoptosis. CONCLUSION: These observations indicate that hypoxia alone causes modest apoptosis, reoxygenation increases apoptosis beyond that caused by hypoxia in cultured HCAECs. TNF alpha alone causes apoptosis, and further enhances apoptosis caused by hypoxia-reoxygenation. The activation of PKC plays a critical role in TNF alpha-induced apoptosis of cultured HCAECs.
Antibodies, Monoclonal↗
Differential effects of alpha- and gamma-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis.
OBJECTIVES: This study was designed to examine the differential effects of alpha- and gamma-tocopherol on parameters of oxidation-antioxidation and thrombogenesis. BACKGROUND: Experimental studies have shown that antioxidants, such as vitamin E (alpha-tocopherol), improve atherosclerotic plaque stability and vasomotor function, and decrease platelet aggregation and tendency to thrombus formation. METHODS: Sprague Dawley rats were fed chow mixed with alpha- or gamma-tocopherol (100 mg/kg/day) for 10 days. A filter soaked in 29% FeCl3 was 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. RESULTS: Both alpha- and gamma-tocopherol decreased platelet aggregation and delayed time to occlusive thrombus (all p < 0.05 vs. control). Both alpha- and gamma-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 gamma-tocopherol were more potent than those of alpha-tocopherol (p < 0.05). CONCLUSIONS: This study indicates that both alpha- and gamma-tocopherol decrease platelet aggregation and delay intraarterial thrombus formation, perhaps by an increase in endogenous antioxidant activity. Gamma-tocopherol is significantly more potent than alpha-tocopherol in these effects.
Animals↗
Vitamins C and E prolong time to arterial thrombosis in rats.
To examine the modulation of arterial thrombosis by vitamins C and E, Sprague-Dawley rats were fed nonpurified diet, or diet mixed with vitamin C [100 mg/(kg body weight.d)], vitamin E [100 mg/(kg.d)] or both vitamins C and E [each 100 mg/(kg.d)], for a period of 9-19 d (mean 15 d). An occlusive aortic thrombus was created by application of a Whatman filter soaked in 1 mol/L FeCl3. Both vitamins C and E and their combination decreased platelet aggregation and delayed time to occlusive thrombus formation (P < 0.05 vs. control). Vitamins C and E decreased arterial superoxide generation (P < 0.05 vs. control). Interestingly, vitamin E also increased endogenous superoxide dismutase activity (SOD) and protein expression in aortic tissues (P < 0.05 vs. control). The combination of vitamins C and E was not superior to each vitamin alone with regard to effect on time to thrombus formation, but it was more potent with regard to platelet inhibition. The increase in endogenous antioxidant activity by vitamin E is an intriguing observation. This study shows that the antioxidant vitamins C and E have important effects on platelet aggregation, SOD activity, superoxide generation and thrombus formation.
Animals↗
Proapoptotic effects of ANG II in human coronary artery endothelial cells: role of AT1 receptor and PKC activation.
Anoxia-reoxygenation, tumor necrosis factor-alpha (TNF-alpha), and angiotensin II (ANG II) have been shown to induce apoptosis in myocytes. However, the role of these mediators in causing apoptosis of human coronary artery endothelial cells (HCAEC) is not known. This study was designed to examine the interaction of these mediators in induction of apoptosis in HCAEC. Cultured HCAEC were exposed to anoxia-reoxygenation, TNF-alpha, and ANG II. TNF-alpha enhanced apoptosis of HCAEC (determined by DNA nick-end labeling in situ and DNA laddering) caused by anoxia-reoxygenation. ANG II increased apoptosis beyond that caused by anoxia-reoxygenation and TNF-alpha. Apoptosis caused by ANG II was reduced by losartan, a specific ANG II type 1 receptor (AT1R) blocker, whereas PD-123,177, a specific ANG II type 2 receptor blocker, under identical conditions had minimal effect. The proapoptotic effects of ANG II were associated with the activation of protein kinase C (PKC). The importance of PKC activation as a signal transduction mechanism became evident in experiments wherein treatment of HCAEC with a specific inhibitor of PKC activation decreased ANG II-mediated apoptosis. Thus AT1R activation appears to be responsible for apoptosis caused by ANG II in HCAEC, and AT1R activation-mediated apoptosis involves activation of PKC.
Angiotensin II↗
Inhibition of arterial thrombus formation by ApoA1 Milano.
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% FeCl3 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<0. 01), inhibited platelet aggregation (25+/-7% versus 50+/-11%, P<0. 01), and reduced weight of the thrombus (18.5+/-1.8 versus 23.7+/-2. 3 mg/cm, P<0.01). Total cholesterol and HDL levels remained similar in both groups of rats, but plasma apoA1 Milano levels were elevated in apoA1 Milano-treated rats. In in vitro studies, incubation of platelets with apoA1 Milano reduced ADP-induced platelet aggregation by about 50%, but apoA1 Milano had no direct effect on vasoreactivity. This study provides further evidence for critical role of platelets in thrombosis. Use of apoA1 Milano offers a novel approach to inhibit arterial thrombosis.
Animals↗
Role of TGF-beta1 in platelet-mediated cardioprotection during ischemia-reperfusion in isolated rat hearts.
Platelets protect myocardium against ischemia-reperfusion injury. This study examined the role of platelet-derived TGF-beta1 in cardioprotection during ischemia-reperfusion. Isolated Sprague Dawley rat hearts were perfused with K-H buffer and subjected to 25 min of global ischemia followed by 30 min of reperfusion. Ischemia-reperfusion resulted in myocardial dysfunction indicated by increase in CPP and LVEDP, and decrease in dLVP. Perfusion of hearts with washed platelets or supernatant of aggregated platelets attenuated (P < 0.01) of myocardial dysfunction following ischemia-reperfusion. Ischemia-reperfusion resulted in a decrease in myocardial TGF-beta1 determined by immunohistochemistry. ELISA showed an increase in latent TGF-beta1, but a decrease in active TGF-beta1. Perfusion of hearts with platelets or aggregated platelet supernatant preserved myocardial TGF-beta1 content upon ischemia-reperfusion. Perfusion of hearts with recombinant TGF-beta1 also resulted in cardioprotection following ischemia-reperfusion qualitatively similar to that observed with platelets or aggregated platelet supernatants. RT-PCR analysis showed an increase in myocardial TGF-beta1 mRNA following ischemia-reperfusion. These observations indicate that platelets protect the myocardium against ischemia-reperfusion-mediated dysfunction at least in part by releasing TGF-beta1. Increase in both TGF-beta1 mRNA and latent TGF-beta1 does not indicate a defect in the translation of mRNA. Reduction in myocardial TGF-beta1 following ischemia-reperfusion suggests a defect in the conversion of latent TGF-beta1 to active TGF-beta1.
Animals↗
Should fibrinogen be measured routinely in patients with unstable coronary heart disease?
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Angina, Unstable↗
Hypoxia-reoxygenation-induced apoptosis in cultured adult rat myocytes and the protective effect of platelets and transforming growth factor-beta(1).
The outcome of myocardial ischemia-reperfusion has been partially attributed to the degree of apoptosis in cardiomyocytes. Aggregating platelets by release of transforming growth factor-beta(1) (TGF-beta(1)) protect the isolated heart against ischemia-reperfusion injury and preserve myocardial TGF-beta(1) content. To gain more insight into the modulation of hypoxia-reoxygenation-induced injury (apoptosis and necrosis) to myocytes by TGF-beta(1) and aggregating platelets, cultured adult rat myocytes were exposed for 48 or 72 h to hypoxia alone, or to hypoxia followed by 3 h of reoxygenation. Apoptosis in the cells was determined by in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining and DNA fragmentation on gel electrophoresis. Hypoxia alone caused a time-dependent increase in myocyte apoptosis (number of apoptotic cells: 19+/-3% at 48 h and 39+/-5% at 72 h compared with 5+/-1% in control cells, based on a 500-cell count). Three hours of reoxygenation after 48 h of hypoxia further increased the number of apoptotic cells (34+/-8 versus 19+/-3% in hypoxia for 48 h), but reoxygenation after 72 h of hypoxia did not additionally increase the number of apoptotic cells, perhaps because of extensive cell necrosis on prolonged hypoxia. Forty-eight hours of hypoxia followed by 3 h of reoxygenation also resulted in a decrease in Bcl-2 and an increase in Fas protein level. Incubation of myocytes with either recombinant TGF-beta(1) (0.5-5 ng/ml) or aggregated platelet supernatant (from 2-3 x10(7) platelets/ml, containing approximately 0.5 ng/ml of TGF-beta(1)) markedly (P<.01) decreased the number of apoptotic cells after hypoxia-reoxygenation. Incubation with TGF-beta(1) also reduced myocyte necrosis as evident from lactate dehydrogenase release and trypan blue dye exclusion. These data demonstrate that hypoxia-reoxygenation results in apoptosis and necrosis in cultured adult rat myocytes; this can be attenuated by TGF-beta(1). Similarity of data with TGF-beta(1) and aggregated platelet supernatant suggests that platelet-mediated cardioprotection during hypoxia-reoxygenation may relate in part to the release of TGF-beta(1).
Animals↗
Modulation of arterial thrombosis by angiotensin-converting enzyme inhibition and angiotensin II type 1-receptor blockade.
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Angiotensin II↗
Critical role of AT1 receptor expression after ischemia/reperfusion in isolated rat hearts: beneficial effect of antisense oligodeoxynucleotides directed at AT1 receptor mRNA.
To examine the relevance of angiotensin II type 1 receptor (AT1R) expression in the determination of myocardial function after ischemia/reperfusion, Sprague-Dawley rats were treated intravenously with antisense oligodeoxynucleotides (AS-ODNs) directed at AT1R mRNA (100 microg/rat, n=9) or scrambled antisense oligodeoxynucleotides (Scr-ODNs, 100 microg/rat, n=6). Both AS-ODNs and Scr-ODNs were given along with 300 microg/rat of liposome DOTAP/DOPE, a positive electron carrier (wt:wt= 1:1). The hearts from AS-ODN- or Scr-ODN-treated rats were excised 24 hours later, perfused in vitro, and subjected to 25 minutes of global ischemia followed by 30 minutes of reperfusion. Parallel groups of rats were given the specific AT1R antagonist losartan (10 mg/kg IV, n=6) or saline (n=7) 4 to 6 hours before excising the hearts. Ischemia/reperfusion resulted in a significant increase in myocardial AT1R expression (autoradiography and binding assay) and myocardial dysfunction, indicated by increases in coronary perfusion pressure and left ventricular end-diastolic pressure and a decrease in developed left ventricular pressure (all P<0.01 versus baseline) in the saline-treated group. AT1R protein and mRNA levels also increased in ischemic/ reperfused myocardial tissues. Administration of AS-ODNs or losartan, but not Scr-ODNs, preserved myocardial function and blocked the increased AT1R binding after ischemia/reperfusion (both P<0.01). Myocardial AT1R mRNA levels were not affected by either AS-ODNs or losartan, and the AT1R protein levels were significantly reduced by AS-ODN, but not losartan, treatment. Plasma angiotensin II levels increased after administration of losartan but not after administration of AS-ODNs. These observations imply a critical role of AT1R upregulation in determining myocardial function immediately after ischemia/reperfusion. AS-ODNs to AT1R mRNA may be more beneficial than losartan, because losartan does not affect the plasma angiotensin II level. The sustained increase in AT1R mRNA, but diminished protein expression, in rat hearts treated with AS-ODNs suggests that AS-ODNs block AT1R at the translational level.
Analysis of Variance↗
Identification and autoregulation of receptor for OX-LDL in cultured human coronary artery endothelial cells.
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.
Cells, Cultured↗