Nitric oxide--biological mediator, modulator and factor of injury: its role in the pathogenesis of atherosclerosis

Nitric oxide (NO) is generated from L-arginine by the family of isoenzymes called NO synthases (NOS). Gene cloning has identified neuronal, endothelial and cytokine-inducible isoforms of NOS. The effects of NO depend on its microenvironment and result from interactions with oxygen, heme proteins and thiols. NO regulates vascular homeostasis by controlling vascular resistance, blood pressure, cell-cell contact and proliferation. Atherogenesis leads to decreased bioactivity of NO and this, in turn, can precipitate enhanced cell adhesion, proliferation, vasoconstriction and accelerate the generation of atherosclerotic lesions. It is possible that some of the detrimental effects of atherosclerosis on the NO pathway result from the generation of secondary oxidants such as peroxynitrite, a product of the reaction of NO with superoxide. The pharmacologic strategies including the stimulation of generation of endogenous NO, NO-replacement therapy and decreasing oxidative stress may be useful for ameliorating the clinical course of atherosclerosis.

Effect of isosorbide-5-mononitrate on plasma and urine levels of cyclic GMP in relation to exercise in coronary patients compared with control subjects

Nitric oxide (NO) and atrial natriuretic peptide (ANP) relax vascular smooth muscle increasing levels of cyclic guanosine 3':5' monophosphate (cGMP). Nitrovasodilators act as exogenous nitric oxide donors. The aim of this study was to ascertain the response of cGMP to exercise without medication and after the administration of 20 mg of isosorbide-5-mononitrate (IS-5-MN) in coronary patients (n = 8) and healthy control subjects (n = 9). A third group of 10 normal volunteers was studied to test plasma cGMP response to second exercise test without IS-5-MN administration. Plasma cGMP increased significantly in both patients (P < 0.02) and controls (P < 0.01) after the first ergometry. After IS-5-MN administration, plasma cGMP did not increase either before or after exercise. In normal volunteers without IS-5-MN plasma cGMP increased significantly after first (P < 0.004) and second (P < 0.0008) exercise test. In conclusion, plasma cGMP increases during exercise. Administration of IS-5-MN does not raise plasma cGMP and neither does performance of further exercise after its administration.

The measurement of team process

The construct validity of measures of team process was evaluated using predictive, known groups and multitrait-multimethod (MTMM) validation strategies. Military air crews (N = 51) flew two simulated missions. Independent judges provided evaluations of the same six team process variables in both scenarios. An MTMM analysis of judges' ratings treating judges as a method variable showed good convergent and discriminant validity. Judges' mean ratings of the six process variables were correlated with mission effectiveness. Some process measures discriminated between student and instructor teams, thus showing discrimination between known groups. Conversely, an MTMM analysis of ratings treating scenarios as a method showed poor convergent validity. We concluded that important team process behaviors have been identified and can be rated validly but that multiple observations are necessary to assess characteristics of individual teams with any accuracy. The discussion includes implications for practice and future research.

Blood levels of cytokines in brain-dead patients: relationship with circulating hormones and acute-phase reactants

We hypothesized that increased levels of blood cytokines occur in brain-dead patients, and that these cytokines are responsible for some of the endocrine and/or acute-phase reactant abnormalities found in these patients. We measured blood levels of cytokines, hormones, and acute-phase reactants in 18 brain-dead potential organ donors at the moment of establishing the legal diagnosis of brain death and compared them with levels found in a control group. Although interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) levels were within the normal range, interleukin-6 (IL-6) levels were clearly above the normal range in all patients (median, 1,444 pg/mL; range, 75 to 11,780). In the brain-dead group, total thyroxine (tT4), free T4 (fT4), triiodothyronine (T3), thyrotropin (TSH), dehydroepiandrosterone sulfate (DHEA-S), testosterone, albumin, Zn, and osteocalcin levels were decreased, T3 resin uptake index (T3 RUI), corticotropin (ACTH), cortisol, 11-deoxycortisol (11-DOC), 17-hydroxyprogesterone (17-OHPr), aldosterone, luteinizing hormone, and follicle-stimulating hormone levels were normal, and reverse T3 (rT3), renin, and C-reactive protein (CRP) levels were increased. Multiple regression analysis demonstrated significant interrelations between IL-6 and T4, T3, testosterone, and CRP. We also studied the evolution of some of these parameters in four patients with severe head injury who finally developed brain death. IL-6 levels on admission to the intensive care unit (ICU) were above the normal limits, as in other patients with cranial trauma, but when the patients developed brain death, there was a pronounced increase in IL-6 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression and functional role of nitric oxide synthase in osteoblast-like cells

Nitric oxide synthases (NOS) are enzymes that produce nitric oxide (NO) from L-arginine in a reaction yielding citrulline as a coproduct. Nitric oxide modulates the activity of a wide variety of cells, but little is known about its effects on bone cells. In the present study we report that the NOS inhibitor NG-monomethyl-L-arginine (NMMA) induced a dose-dependent inhibitory effect on the proliferation of the osteoblast-like cell lines MG63 and ROS 17/2.8. The inhibitory effect was prevented by increasing L-arginine concentrations in the medium and by the NO donor sodium nitroprusside. Likewise, NMMA inhibited interleukin-6 secretion, independently of its effect on cell number. NOS expression by MG63 cells was confirmed by measuring their ability to metabolize radiolabeled L-arginine to citrulline. NOS bioactivity was detected in unstimulated cells, but was markedly increased by stimulating the cells with cytokines, lipopolysaccharide, or 1,25-dihydroxyvitamin D3. NOS activity was partially dependent upon the presence of calcium in the medium. Furthermore, constitutive-type NOS (c-NOS) and inducible-type NOS (i-NOS) mRNA expression was detected in ROS 17/2.8 cells after reverse transcription and polymerase chain reaction amplification. In conclusion, osteoblast-like cells express c-NOS and i-NOS, and NOS activity seems to play an important role in the regulation of cell proliferation and function.

Peroxynitrite induces both vasodilatation and impaired vascular relaxation in the isolated perfused rat heart

The effects of the oxidant species peroxynitrite (ONOO-) on coronary perfusion pressure and vasodilatation elicited by acetylcholine, isoproterenol, and S-nitroso-N-acetyl-DL-penicillamine were investigated in the isolated perfused rat heart. ONOO- (0.3-1000 microM) caused a concentration-dependent vasodilatation of the coronary vasculature. This dilator response was inhibited by oxyhemoglobin, indicating that it was due to the generation of nitric oxide. Tachyphylaxis to ONOO- developed rapidly, so that the response disappeared after three or four applications of this compound. ONOO- not only induced tachyphylaxis but also inhibited the vasodilatation induced by the three vasodilators studied. This latter effect of ONOO- was critically dependent on its concentration, since it occurred at 3 microM, which was subthreshold as a dilator, and at 1000 microM, which was supramaximal, but not at 30 and 100 microM. These latter concentrations inhibited the responses to vasodilators only in the presence of oxyhemoglobin. Thus, a wide range of concentrations of ONOO- induce a vascular dysfunction, as evidenced by the tachyphylaxis to its own vasodilator actions and the long-lasting impairment of the responses to other vasodilators. However, at the same time ONOO- generates nitric oxide, which at certain concentrations of ONOO- is sufficient to counteract its deleterious action. Coinfusion of S-nitroso-N-acetyl-DL-penicillamine or prostacyclin at low concentrations that did not produce vasodilatation also protected against ONOO(-)-induced vascular dysfunction: these compounds may be protective through a common mechanism, as yet undefined.

Comparative pharmacology of analogues of S-nitroso-N-acetyl-DL-penicillamine on human platelets

1. The effects of two new analogues of S-nitroso-N-acetyl-DL-penicillamine (SNAP), S-nitroso-N-formyl-DL-penicillamine (SNFP) and S-nitroso-DL-penicillamine (SNPL), on platelet function were examined in vitro. 2. SNAP and its analogues were potent inhibitors of platelet aggregation and inducers of disaggregation. 3. All compounds inhibited fibrinogen binding to platelets. 4. They also decreased the release of P-selectin from platelets. 5. Both inhibition of fibrinogen binding and release of P-selectin correlated with an increase in intraplatelet cyclic GMP concentrations. 6. At concentrations sufficient to inhibit platelet function and induce cyclic GMP formation (0.01-3 microM), the release of NO could be detected from SNPL but not from SNAP and SNFP. 7. Release of NO from all compounds was detected at concentrations > or = 10 microM. 8. Thus, the spontaneous release of NO from SNPL explains the actions of this compound on platelet function; however, platelet-mediated mechanisms may be involved in the release of NO from SNAP and SNFP.

Endothelium-independent relaxation by 17-alpha-estradiol of pig coronary arteries

We have studied the effects of 17-alpha-estradiol, a non-estrogenic steroid, on pig coronary arteries contracted by K+, Ca2+ or serotonin. Experiments were performed on helicoidal strips and rings of left circumflex coronary arteries from freshly slaughtered white pigs and on helicoidal strips of rat thoracic aorta. The strips and rings were suspended inside a water-jacketed muscle chamber in an oxygenated Krebs solution at 37 degrees C. From the initial K(+)-evoked contraction, 17-alpha-estradiol caused a relaxation with an IC50 (15 microM) which was in the range of the IC50s obtained for nitroglycerin (1.3 microM) and nicorandil (50 microM). Contractions evoked by Ca2+ were inhibited by 17-alpha-estradiol, but full blockade could not be achieved. Serotonin-evoked contractions were also blocked by 17-alpha-estradiol with an IC50 of 2.1 microM; 17-beta-estradiol also inhibited the serotonin-evoked contractions. In the presence of 100 microM of the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester, the relaxing properties of 17-alpha-estradiol in pig coronary arteries and rat thoracic aorta were unaffected, suggesting that endothelial NO release was unrelated to these effects. 17-alpha-Estradiol also relaxed denuded pig coronary artery strips, suggesting that other endothelial-derived relaxing factors were not involved in its vascular effects. The results are compatible with the idea that 17-alpha-estradiol causes relaxation of coronary vessels by acting directly on the cell membrane of smooth muscle cells; these effects seem to be unrelated to the genomic physiological effects of estrogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Local transdermal glyceryl trinitrate has an antiinflammatory action on thrombophlebitis induced by sclerosis of leg varicose veins

To test the antiinflammatory and analgesic effects of transdermal glyceryl trinitrate (GTN) the authors carried out a double-blind, randomized, controlled clinical study in 21 patients with mild to moderate leg varicose veins who underwent vein sclerotherapy in both legs. GTN or placebo ointment was applied in a blinded protocol along the surface of the sclerosed vein every eight hours until disappearance of inflammation signs. The varicose vein in one leg was treated with GTN and compared with placebo for the vein of the other leg used as control of thrombophlebitis (TP) signs. Fifteen minutes after first application inflammation signs were observed in all cases. The intensity of inflammation signs was assessed as 26% (10.4 +/- 4.1) in GTN-treated veins and as 61.5% (24.6 +/- 6.3) (P < 0.001) in the placebo-treated veins. One hour later only 63% of cases in the GTN group and all cases in the placebo group showed signs of TP (P < 0.001). The reduction in the intensity of signs at this time was 7.7 +/- 3.9 in the GTN group and 19.7 +/- 6.3 in the placebo group (P < 0.001). All veins in the GTN group were free of signs of TP in less than forty-eight hours. In the placebo group, 45% of veins required more than forty-eight hours for complete disappearance of signs of TP (P < 0.001). The authors conclude that GTN has an antiinflammatory effect in TP induced by sclerotherapy. This action may be related to the nitric oxide released from GTN, through a direct action on the vein and the surrounding inflamed tissue.

Influence of calorie source on the physiological response to parenteral nutrition in malnourished rabbits

The present study was designed to investigate whether calorie source influences sodium and water metabolism and sympathetic activity during parenteral nutrition (PN). 20 New Zealand rabbits were starved until a mean weight loss of 18% was achieved and then re-fed for 6 days with 2 formulae of PN with different glucose-fat proportions. In the Glucose group (n = 9), 70% of non-protein calories were given as glucose while in the Lipid group (n = 11), 70% of non-protein calories were administered as lipids. Rabbits with a high glucose intake showed significantly higher weight gain (151 +/- 87 vs. 52 +/- 7 g, P = 0.01), water cumulative balance (542 +/- 132 vs. 411 +/- 87 ml; P = 0.02) and urinary metanephrine excretion (0.42 +/- 0.12 vs. 0.30 +/- 0.1 mumol/d, P = .03). Only in this group, urinary metanephrines correlated positively with water and sodium balances (r2 = 0.6; P = 0.02 and r2 = 0.7; P = 0.009 respectively). The Glucose group showed 2 different responses and in a second experiment 10 additional rabbits were added to this group to allow a statistical analysis of the response pattern: half of the animals increased their extracellular water (ECW) compartment while the remaining animals did not. The former group had higher sodium balance (13.9 +/- 8 vs. 4.3 +/- 5; P = 0.004) and wet lung weight (8.9 +/- 0.9 vs. 7.9 +/- 0.8; P < 0.05) after re-feeding and, at the beginning of PN, their serum aldosterone concentration were also higher (221 +/- 11 vs. 130 +/- 47 pmol/l; P < 0.05). In conclusion, glucose based PN appears to increase sympathetic activity and induce spurious weight gain due to markedly positive wate and sodium balances. Plasma aldosterone concentration at the end of starvation period influences sodium retention and ECW expansion during high glucose re-feeding.

Induction of nitric oxide synthase in human mammary arteries in vitro

This study investigated whether human mammary arteries express an inducible nitric oxide (NO) synthase and, if so, what its effects are on vascular tone. In human mammary artery pre-contracted with phenylephrine there was a gradual time-dependent loss of tone over an 8 h period. L-Arginine and lipopolysaccharide enhanced the rate but not the magnitude of this loss in tone, whereas NG-nitro-L-arginine, NG-monomethyl-L-arginine, dexamethasone, and polymyxin B inhibited these effects. These findings indicate that incubation of human mammary artery with lipopolysaccharide resulted in the expression of an inducible NO synthase. The induction of this enzyme in human vessels may be important in the pathogenesis of septic shock.

[Does captopril possess antianginal actions? An evaluation of its effects on myocardial ischemia by stress tests in patients with stable angina and normal ventricular function]

INTRODUCTION

We have studied the effects of captopril on myocardial ischaemia in normotensive and hypertensive patients with coronary artery disease and stable effort-induced angina.

STUDY DESIGN

A maximal treadmill effort test (Bruce modified) was obtained before and after 60 min administration of 25 mg. p.o. of captopril. In a first open pilot essay, 12 patients were studied. In a double-blind randomized, placebo-controlled, without crossover, 20 patients with the same characteristics and methodology were divided in two groups (10 in placebo and 10 in captopril group) and compared in a maximal treadmill effort test.

RESULTS

In the pilot essay, the second test don't showed increments in heart rate, systolic and diastolic blood pressure showed a significant reduction at rest (p < 0.01) and at 1 mV ST segment depression (p < 0.01). Captopril increased exercise duration at 1 mV ST segment depression, time to angina and total exercise time (p < 0.01). In double-blind essay, captopril group results were similar to the pilot essay. In comparing results between placebo and captopril groups the most relevant differences were: significant increment in the time to 0.1 mV ST segment depression (p < 0.01), to angor (p < 0.05) and total exercise duration (p < 0.01). Maximal work-load sustained increased significantly with captopril (7.43 +/- 2.1 to 10.34 +/- 1.8 METS) (p < 0.01).

CONCLUSIONS

We conclude that captopril used in monotherapy in patients with chronic stable angina, seems to reduce clinical and electric ischemia and to ameliorate maximal exercise duration and work-load.

[Regulation of the response of the hypothalamo-hypophyseal-adrenal axis during anesthesia with diazepam-fentanyl in heart surgery]

OBJECTIVES

To study the response of the hypothalamic-hypophysial-adrenal axis during heart surgery under anesthesia with diazepam-fentanyl (D-F) at high doses.

MATERIAL AND METHODS

We studied the intraoperative response of cortisol, ACTH, and 11-deoxycortisol and aldosterone (RIA) to heart surgery under anesthesia with 0.5 mg/kg diazepam and 0.1 mg/kg fentanyl in 12 patients (group D-F) and the effect on that response of blocking peripheral cortisol production with etomidate (0.15 mg/kg bolus) (group D-F-E, n = 12).

RESULTS

Sharp drops in cortisol, ACTH and 11-deoxycortisol levels were observed in group D-F before the start of extracorporeal circulation (ECC). Albumin and red blood cell counts fell less sharply than did hormone levels. ACTH levels increased after ECC. Throughout surgery, ACTH and cortisol never rose over preanesthetic levels. The response in group D-F-E was similar, with a clear early rise in 11-deoxycortisol and a later rise in ACTH.

CONCLUSIONS

Anesthesia with D-F lowers levels in the hypothalamic-hypophysial-adrenal axis below baseline in the phase before ECC, despite the stimulus of surgery and the effect of hemodilution. After ECC, ACTH levels rise. The response seen in group D-F-E suggests that levels in the hypothalamic-hypophysial-adrenal axis are below normal, but that the mechanism is functioning appropriately.

Patients' beliefs about their lack of pain control in primary fibromyalgia syndrome

This study had two aims, first, to determine the expectancies of control over pain experience ('pain locus of control') of patients with primary fibromyalgia syndrome (PFS) and to compare them with other chronic rheumatic diseases. Second, to analyse the relationships between health status and locus of control. We applied the Multidimensional Health Locus of Control-Pain and the Arthritis Impact Measurement Scales (AIMS), by interviewing 137 out patients (32 PFS, 32 RA, 20 SLE, 22 AS and 31 OA). Data were analysed by ANOVA and partial correlation tests. PFS patients believed that their symptoms depended on uncontrollable events and that they could not influence their disease by themselves. PFS patients were the most disabled on the 'Affect' (P < or = 0.001) and 'Symptom' factors (P < or = 0.01). In the PFS group, patients who showed a 'Fate' locus of control orientation reported more disability on 'Affect' and 'Social Interaction' AIMS factors.

Low levels of intraplatelet cGMP in IDDM

OBJECTIVE

To determine the levels of intraplatelet cGMP, an index of activity of the antiaggregatory nitric oxide pathway, in IDDM patients.

RESEARCH DESIGN AND METHODS

We measured intraplatelet and plasmatic cGMP levels in 22 IDDM patients and 22 age- and sex-matched control subjects.

RESULTS

Intraplatelet cGMP levels decreased in the IDDM patients (0.32 +/- 0.16 pmol/10(9) platelets) when compared with the control group (0.52 +/- 0.32 pmol/10(9) platelets), P = 0.032. Plasmatic cGMP levels were not significantly different between groups. Intraplatelet cGMP levels correlated negatively with the duration of the disease (r = -0.43, P < 0.05).

CONCLUSIONS

IDDM patients have lower levels of intraplatelet cGMP, which may be responsible in part for their platelet hyperactivity.

[The incidence of arrhythmias in young persons without demonstrable heart disease: a 24-hour Holter study in 100 medical students]

A Holter monitorization study was performed in 100 voluntary university students (64 men and 36 women). The mean age was 23.6 years and organic heart disease was ruled out in all cases. Data were analysed in different subgroups including the practice of physical activity and subjects smokers or alcohol consumers. The maximum heart rate (HR) achieved during the wake period was 138.3 +/- 20.43 beat/m. Minimum daytime heart rate was 61.42 +/- 10.32 beat/m and it was below 60 beat/m in 41 subjects. During the nighttime period, the maximum heart rate achieved by the group was 89.34 +/- 11.31 beat/m. Minimum nighttime heart rate was 45.82 +/- 6.35 beat/m. Maximum heart rate in men was 134.3 +/- 21.35 beat/m, while in women was 145.42 +/- 16.36 beat/m. Eighty students presented one or more arrhythmias, among them 28 women and 52 men (p = NS): 92% in sportsmen and women groups as compared with 79% in the non sports practicers, 90% of alcohol consumers and 82% between subjects who smoked and drank, compared with 63% in the non drinkers (p < 0.006). 48% of the subjects presented one or more supraventricular arrhythmias during the daytime or during the nighttime (p = NS). Ventricular rhythm disturbances were found in 20 subjects. There was only one case who had a non sustained ventricular tachycardia of 4 complexes. These disturbances were not increased by practising sport nor by toxic habits. In 15 cases we found sinoatrial block, with a male predominance. Five subjects presented some type of atrioventricular block, 4 of which were alcohol and tobacco consumers.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide synthase activities in human myocardium

Myocardial constitutive and inducible nitric oxide (NO) synthase activities were measured in right ventricular tissue from 17 patients with dilated cardiomyopathy (DCM). A significant activity of inducible enzyme was accompanied by a low activity of the constitutive NO synthase. Thus, the myocardium has the capacity to express both NO synthases. NO may have a physiological as well as a pathological role in the human myocardium.

[The peripheral analgesic action of the exogenous nitric oxide donor: nitroglycerin. A placebo-controlled study of the transdermal action of nitroglycerin on pain sensitivity in the forearm]

Nitric oxide is a biological mediator. In nervous system it acts like neurotransmitter and also modulate acute inflammation. In the peripheral nervous system it blocks the nociceptive stimulus through an increase in postsynaptic neurone GMPc level. Nitro-vasodilator drugs like nitroglycerin are metabolised in the cell given rise to short lived intermediates, which liberating nitric oxide that activate the guanylate cyclase enzyme, increasing the GMPc in smooth muscle cell. This study show that nitroglycerin produces an analgesic action. The pain sensitivity to pinprick test in forearm with nitroglycerin has shown a decrease in a significative manner against placebo. We speculate that nitroglycerin could have a similar action as endogenous nitric oxide in nervous system.

The anti-inflammatory and analgesic action of transdermal glyceryltrinitrate in the treatment of infusion-related thrombophlebitis

We have carried out a prospective double-blind randomized study in 40 patients with infusion-related thrombophlebitis. Twenty-two patients were included in the glyceryltrinitrate (GTN) ointment group and 18 patients in the control heparinoid group. Pain was assessed by an analogue scale. At 48 hours the analgesic index was 84.6 +/- 18 units with GTN and 49 +/- 45 units with heparinoid ointment (P < 0.01). Faster relief of oedema was also observed in the GTN-treated group. All signs of thrombophlebitis were relieved in less than 4 days in the GTN group compared with 9 days in the controls (P < 0.005). We conclude that transdermal GTN is useful therapy for infusion-related thrombophlebitis showing evidence of anti-inflammatory and analgesic effect.

[Chronotropic changes and cardiac arrhythmias during anesthetic induction and intubation in patients undergoing heart surgery. Study of 79 patients using Holter monitoring]

OBJECTIVES

To assess changes in heart rate and cardiac arrhythmias during anaesthetic induction and tracheal intubation in patients undergoing cardiac surgery.

MATERIAL AND METHODS

79 patients scheduled for cardiac surgery were divided into three groups: group I, 36 valvular diseases with a good ventricular function, group II, 22 valvular diseases with an ejection fraction less than 0.5, and group III, included 21 patients with coronary artery disease. All patients had a Holter monitoring. Anesthesia was performed with diazepam and morphine in patients with valvular disease and with diazepam and fentanyl in those with coronary artery disease.

RESULTS

During anesthesia induction there were no significant increases in heart rate in the two groups of patients with valvular diseases: in group I (n = 36, with good ventricular function) heart rate increased by about 5.4 +/- 23% and in group II (n = 22, with ejection fraction less than 0.5) by 7.5 +/- 33%. In patients with coronary artery disease (n = 21) we did not observe significant decreases in heart rate (-4.28 +/- 17%). During tracheal intubation the heart rate increased by 15.9 +/- 30% in group I (p < 0.002), by 13.6 +/- 30% in group II (p < 0.02), but decreased by 1.19 +/- 23% (p = NS) in patients with coronary artery disease. During anesthetic induction we observed frequent premature beats (single forms) in 13.8% of patients in group I, 13.6% in group II, and 9.5% in group III. The incidence of this arrhythmia during tracheal intubation was 16.6%, 9%, and 14%, respectively for the three groups. Sustained ventricular tachycardia was only observed in one patient.

CONCLUSIONS

Changes in heart rate and ventricular arrhythmias occurring during anesthetic induction and tracheal intubation in patients undergoing valvular and coronary surgery were infrequent and not severe.