Cholesterol homeostasis and cell proliferation by mitogenic homologs: insulin, benzo-α-pyrene and UV radiation.

Low-Density Lipoprotein (LDL) is known to promote the unregulated proliferation of cells that is progression of cancer. We aimed to investigate the effect of mitogens on the expression of cell cycle proteins, nuclear cholesterol and cell proliferation. We observed that insulin and benzo-α-pyrene (BaP) induced the expression of Low-Density Lipoprotein receptor (LDLR) on HepG2 cells, thereby enhancing the uptake of LDL. The internalized LDL increased the concentration of cholesterol in the cytoplasm and nucleus of the cell. At the same time, insulin and BaP also stimulated the expression of cell cycle proteins viz., Cyclin E and Cdk2, and thus induced more incorporation of Bromodeoxyuridine (BrdU) in cultured cells indicating increased DNA synthesis. Increased expression of cell cycle proteins and DNA synthesis are the indications of DNA replication and new cell synthesis. This suggests a link between the enhanced nuclear cholesterol concentration and new cell formation. On the other hand, UV irradiation with selectively given dose of cell death eventually decreases nuclear cholesterol concentration and LDLR expression. Reduced LDLR shows low functional activity. This, again, repeated the plausibility of the same link between intracellular cholesterol concentration and cell population. The biasness of adverse effect observed by UV irradiation has been compromised by inactivating LDLR with anti-LDLR antibody, resulting in similar effects on Cyclin E expression in the cultured cells. Hence, we concluded that in all the conditions, LDLR expression was found to be a translational event of its transcription factor, SREBP-2, by the induction of insulin, BaP and UV irradiation.

Differential Expressions of p53, p53R2, hRRM2 and PBR in Chronic Lymphocytic Leukemia: A Correlation with Intracellular Cholesterol.

Regulation of intracellular cholesterol homeostasis exists under balance between intracellular biosynthesis and uptake from extracellular origin by cell surface transport proteins. Expected role of cholesterol on either tumor suppressor gene and/or DNA synthesis has been aimed in the present study to explore intracellular cholesterol homeostasis in CLL subjects. Higher expressions of p53R2 (p53 dependent subunit of ribonucleotide reductase) and p53 were found in lymphocytes of chronic human lymphocytic leukemia as comparison to their normal counterparts. Inverse relation was found with p53 independent R2 subunit (in human hRRM2) of ribonucleotide reductase, which was found to be decreased from its control group. More expression of peripheral type benzodiazepine receptor, a cholesterol transporter, was noticed in isolated nuclear fraction with simultaneous increase of cholesterol concentration in cytoplasmic and nuclear compartments. A parallel increase of cholesterol in cell nucleus with increased p53R2 expression shows priority of the involvement of cholesterol in the process of cell replication.

Estradiol regulates insulin dependent stimulation of LDL-receptor expression in HepG(2) cells.

The low density lipoprotein, one of the major vehicle for extraneous cholesterol, internalizes into the cells through the process of LDL-receptor mediated endocytosis. The expression of LDL-receptor on the cell surface is a function of various hormone regulated transcription of the receptor gene. The present study elucidates the differential expression pattern of LDL-receptor protein in human hepatoma HepG(2) cells by the influence of two hormones, insulin and estrogen (ß-estradiol), as compared to the basal level expression of the receptor protein. The combined effect of insulin and ß-estradiol reveals that ß-estradiol is the ultimate regulator between these two hormones and supershades the message of insulin on LDL-receptor expression. The receptor protein level immunobloted by anti LDL-receptor antibody after treating cells with insulin, ß-estradiol and mixture of both also reflects the same phenomena. This comparative study makes it consistent that cell saturation with sterol (ß-estradiol) is the prime regulator of LDL-receptor expression between the two hormones, insulin and estrogen.

Reperfusion therapy in patients with acute myocardial infarction and prior coronary artery bypass graft surgery (National Registry of Myocardial Infarction-2).

We reviewed data from the National Registry of Myocardial Infarction-2 to determine the differences in characteristics and outcomes in patients with acute myocardial infarction (AMI) who have undergone previous coronary artery bypass grafting (CABG), and those who have not, and between post-CABG patients who were treated with alteplase (recombinant tissue-type plasminogen activator [rt-PA]) and those who were treated with primary percutaneous transluminal coronary angioplasty (PTCA). Demographic, therapeutic, and outcome data from patients with AMI were collected at > 1,000 hospitals in the United States in collaboration with National Registry of Myocardial Infarction-2. Of the 45,925 patients receiving reperfusion therapy, 2,544 of the 39,574 treated with rt-PA (6.4%) had a history of CABG, and 375 of the 6,351 treated with primary PTCA (5.9%) had a history of CABG. Patients with a history of CABG were older, more likely to be men, and had more comorbidities, but prior CABG was still an independent predictor of mortality after multivariate regression analysis (odds ratio 1.23; 95% confidence interval 1.05 to 1.44). Among the post-CABG patients who received rT-PA or underwent PTCA, there was no significant difference in in-hospital mortality rate or the combined end point of death and nonfatal stroke. Thus, (1) prior CABG is an independent predictor of mortality, and (2) for post-CABG patients with AMI who are not in shock and who are lytic-eligible, reperfusion therapy with rt-PA and PTCA result in similar outcomes with regard to in-hospital mortality and the combined end point of death and nonfatal stroke.

Observations of the treatment of women in the United States with myocardial infarction: a report from the National Registry of Myocardial Infarction-I.

BACKGROUND: To determine whether there are sex differences in the demographics, treatment, and outcome of patients with acute myocardial infarction in the United States, data from the National Registry of Myocardial Infarction-I from September 1990 to September 1994 were examined. METHODS: The National Registry of Myocardial Infarction-I is a national observational database consisting of 1234 US hospitals in which each hospital submits data from each patient with acute myocardial infarction to a central data collection center. For these analyses, the following variables were examined in 354 435 patients with acute myocardial infarction: demographics; use of medical therapy including thrombolytic agents; use of procedures including cardiac catheterization, percutaneous transluminal coronary angioplasty, and coronary artery bypass surgery; length of hospital stay; adverse events (stroke, major bleeding, or recurrent myocardial infarction); and causes of death. RESULTS: In comparison with men, women experiencing acute myocardial infarction in the United States are older, with 55.7% older than 70 years. Women have a higher mortality rate than men even when controlled for age and die less often from arrhythmia but more often from cardiac rupture whether or not thrombolytic therapy is used. Treatment with aspirin, heparin, or beta-blockers is less frequent in women. When thrombolytic therapy is used, women are treated an average of almost 14 minutes later than men and experience a greater incidence of major bleeding. Cardiac catheterization, percutaneous transluminal coronary angioplasty, and coronary artery bypass surgery are used less often in women. CONCLUSIONS: Observations from the National Registry of Myocardial Infarction-I document important sex differences in demographics, treatment, and outcome of patients with acute myocardial infarction in the United States.

Refining the treatment of women with unstable angina--a randomized, double-blind, comparative safety and efficacy evaluation of Integrelin versus aspirin in the management of unstable angina.

BACKGROUND: Although women typically develop coronary artery disease several years after men, once they have symptomatic disease their thromboembolic complications are worse than in men. The mechanism mediating this gender difference in outcome after thromboembolic events is unknown. We previously studied platelet functions in siblings from patients with premature coronary artery disease. We observed that platelets from women are responsive than their male counterparts. In particular, platelets from women stimulated ex vivo with various agonists bind more fibrinogen molecules than platelets from men. HYPOTHESIS: We hypothesized that in patients with acute coronary events, the control of platelet activity might require stronger antagonists in women than in men. METHODS: To test this hypothesis, we investigated retrospectively the results of a trial on Integrelin in unstable angina. RESULTS: We report that platelet aggregation and Holter-detected ischemic episodes are significantly reduced in women with unstable angina treated with the specific GPIIb-IIIa inhibitor, Integrelin, compared with the standard platelet inhibitor aspirin. In contrast, both platelet aggregation and Holter-detected ischemic events are well controlled in men with unstable angina treated with standard therapy including aspirin. CONCLUSION: Integrelin does provide protection in men, but, in contrast with women, not beyond what can be achieved with aspirin. Our data are consistent with the concept that the platelets from women require stronger and more specific inhibitors to limit their activity, and that platelets may play a more important role in women with acute coronary syndromes than in men. Most important, specific GPIIb-IIIa inhibitors may represent a therapeutic option which provides as much suppression of ischemic events in women as they do in men with coronary artery disease.

Effects of integrelin, a platelet glycoprotein IIb/IIIa receptor antagonist, in unstable angina. A randomized multicenter trial.

BACKGROUND: Although aspirin is beneficial in patients with unstable angina, it is a relatively weak inhibitor of platelet aggregation. The effect of Integrelin, which inhibits the platelet fibrinogen receptor glycoprotein (GP) IIb/IIIa, on the frequency and duration of Holter ischemia was evaluated in 227 patients with unstable angina. METHODS AND RESULTS: Patients received intravenous heparin and standard ischemic therapy and were randomized to receive oral aspirin and placebo Integrelin; placebo aspirin and low-dose Integrelin. 45 micrograms/kg bolus followed by a 0.5 microgram.kg-1. min-1 continuous infusion; or placebo aspirin and high-dose Integrelin, 90 micrograms/kg bolus followed by a 1.0-microgram.kg-1, min-1 constant infusion. Study drug was continued for 24 to 72 hours, and Holter monitoring was performed. Patients randomized to high-dose Integrelin experienced 0.24 +/- 0.11 ischemic episodes (mean +/- SEM) on Holter lasting 8.41 +/- 5.29 minutes over 24 hours of study drug infusion. Patients randomized to aspirin experienced a greater number (1.0 +/- 0.33, P < .05) and longer duration (26.2 +/- 9.8 minutes, P = .01) of ischemic episodes than the high-dose Integrelin group. There was no evidence of rebound ischemia after withdrawal of study drug. In 46 patients, platelet aggregation was rapidly inhibited by Integrelin in a dose-dependent fashion. The number of clinical events was small, and there were no bleeding differences in the three treatment arms. CONCLUSIONS: Intravenous Integrelin is well tolerated, is a potent reversible inhibitor of platelet aggregation, and added to full-dose heparin reduces the number and duration of Holter ischemic events in patients with unstable angina compared with aspirin.

Treatment of myocardial infarction in the United States (1990 to 1993). Observations from the National Registry of Myocardial Infarction.

BACKGROUND: Multiple clinical trials have provided guidelines for the treatment of myocardial infarction, but there is little documentation as to how consistently their recommendations are being implemented in clinical practice. METHODS AND RESULTS: Demographic, procedural, and outcome data from patients with acute myocardial infarction were collected at 1073 US hospitals collaborating in the National Registry of Myocardial Infarction during 1990 through 1993. Registry hospitals composed 14.4% of all US hospitals and were more likely to have a coronary care unit and invasive cardiac facilities than nonregistry US hospitals. Among 240,989 patients with myocardial infarction enrolled, 84,477 (35.1%) received thrombolytic therapy. Thrombolytic recipients were younger, more likely to be male, presented sooner after onset of symptoms, and were more likely to have localizing ECG changes. Among the 60,430 patients treated with recombinant tissue-type plasminogen activator (rTPA), 23.2% received it in the coronary care unit rather than in the emergency department. Elapsed time from hospital presentation to starting rTPA averaged 99 minutes (median, 57 minutes). Among patients receiving thrombolytic therapy, concomitant pharmacotherapy included intravenous heparin (96.9%), aspirin (84.0%), intravenous nitroglycerin (76.0%), oral beta-blockers (36.3%), calcium channel blockers (29.5%), and intravenous beta-blockers (17.4%). Invasive procedures in thrombolytic recipients included coronary arteriography (70.7%), angioplasty (30.3%), and bypass surgery (13.3%). Trend analyses from 1990 to 1993 suggest that the time from hospital evaluation to initiating thrombolytic therapy is shortening, usage of aspirin and beta-blockers is increasing, and usage of calcium channel blockers is decreasing. CONCLUSIONS: This large registry experience suggests that management of myocardial infarction in the United States does not yet conform to many of the recent clinical trial recommendations. Thrombolytic therapy is underused, particularly in the elderly and late presenters. Although emerging trends toward more appropriate treatment are evident, hospital delay time in initiating thrombolytic therapy remains long, aspirin and beta-blockers appear to be underused, and calcium channel blockers and invasive procedures appear to be overused.

Prophylactic antiarrhythmic therapy of high-risk survivors of myocardial infarction: lower mortality at 1 month but not at 1 year.

To determine whether prophylactic antiarrhythmic therapy influences mortality in high-risk patients after acute myocardial infarction, 143 such patients were randomized in a double-blind individually dose-adjusted, placebo-controlled trial an average of 14 +/- 7 days after myocardial infarction and followed for 1 year. Patients were judged to be at high risk on the basis of (1) ejection fraction less than 40% (n = 60), (2) arrhythmias of Lown class 3 or higher (n = 26), or (3) both (n = 57). Aprindine was chosen because of its long half-life, few side effects, and antiarrhythmic efficacy. Baseline characteristics in the treatment arms did not differ. Holter-detected arrhythmias were reduced in aprindine-treated patients at 3 months (p less than .001) and at 1 year (p less than .001). One patient was lost to follow-up; in the remaining patients 1 year mortality was 20% (28/142; 12 aprindine and 16 placebo). There was no significant difference between the two study arms in overall mortality and sudden death. However, among those who died, median duration of survival was longer in aprindine-treated patients (86 vs 21.5 days) (p = .04). Although antiarrhythmic treatment with aprindine of high-risk patients after myocardial infarction does not affect 1 year survival, mortality appears to be delayed; thus there may be a role for short-term treatment before more definitive therapy such as surgery.

Effect of the addition of propranolol to therapy with nifedipine for unstable angina pectoris: a randomized, double-blind, placebo-controlled trial.

The value of the addition of beta-blockers to coronary vasodilator therapy in the treatment of patients with unstable angina at rest is controversial. We conducted a double-blind, randomized, placebo-controlled 4 week trial of propranolol in 81 patients with unstable angina, 39 of whom were assigned to placebo and 42 of whom received propranolol in a dose of at least 160 mg daily. All patients were also treated with coronary vasodilators, including 80 mg nifedipine daily and long-acting nitrates. The incidences of cardiac death, myocardial infarction, and requirement for bypass surgery or coronary angioplasty did not differ between the two groups (propranolol = 16; placebo = 18). The propranolol group had a lower cumulative probability of experiencing recurrent resting angina than the placebo group (p = .013), and over the first 4 days of the trial the mean number of clinical episodes of angina (propranolol 0.9 +/- 0.2, placebo 1.8 +/- 0.3, p = .036), duration of angina (propranolol 15.1 +/- 4.3 min, placebo 38.1 +/- 8.4, p = .014), and nitroglycerin requirement (propranolol 1.1 +/- 0.3 tablets, placebo 3.5 +/- 0.8, p = .003) were also fewer. Continuous electrocardiographic recording for ischemic ST segment changes revealed fewer daily ischemic episodes in the propranolol group (2.0 +/- 0.5) than in the placebo group (3.8 +/- 0.7, p = .03), and a shorter duration of ischemia (propranolol 43 +/- 10 min, placebo 104 +/- 28 min, p = .039). Thus propranolol, in patients with unstable angina, in the presence of nitrates and nifedipine is not detrimental and reduces the frequency and duration of symptomatic and silent ischemic episodes.