β-adrenoceptor blockade and migraine

Except for propranolol, no other Beta-blocker has been studied thoroughly in the prophylaxis of migraine. Of those studied, propranolol, atenolol and timolol were shown to be useful in double-blind clinical trials. The mode, or even the site of action of these drugs in unknown. Possible mechanisms of action are peripheral vascular effects, a central action, 5-HT antagonism, an anxiolytic effect and a multifactorial action. The only common property of the successful drugs is lack of partial agonist activity and their profiles do not fully support any of the above hypotheses. Trials of drugs in the prophylaxis of migraine have in general been unsatisfactory due to the difficulty in controlling many variables. Beta-blockers with differing properties offer an opportunity to define the properties necessary for anti-migraine activity and perhaps shed light on the pathogenesis of migraine.     

Hypo-β-Lipoproteinaemia Associated with Auto-Antibodies Against β-Lipoproteins

Abstract In a 19 year old patient, presenting a severe hypo-β-lipoproteinaemia and a polyclonal IgG gammopathy, all known causes of hypo-β-lipoproteinaemia could be excluded. The patient's IgG reacted with homologous and autologous low density lipoproteins like an antibody, the binding activity being localized in the Fab fragment of the IgG molecule. The reactive part of LDL appeared to be the protein moiety (apoprotein LDL). Turnover studies with radioiodinated LDL showed that the reduction of the LDL concentration in the patient's serum was due to a decreased synthesis of LDL and also possibly to an immunelimination of LDL.     

Empiric Therapy with β-Blockers

The only class of drugs with significant effects on ventricular fibrillation and sudden death in humans is that of β-blockers. The exact mechanisms for these prophyiactic effects are not knotvn but may be related to both ontiischemic or anliarrhythmic infiuences. It seems reasonable to suggest that one should use a β-blocker with proven effect on total mortality and sudden cardiac death after myocardial infarction as prophylaxis. Therefore, propranolol, timolol. or metoprolol. should be instituted in order to improve prognosis when there are no conlraindications. In addition to possible effects on survival one would aiso expect to reduce the risk for new ischemic events with angina or reinfarction. In contrast, class I antiarrhythmic agents are useful for symptomatic ventricular arrhythmias but there is no proof for any effect on ventricular fibrillation and sudden cardiac death.     

Primary headaches: reduced circulating β-lipotropin and β-endorphin levels with impaired reactivity to acupuncture

Eleven patients affected by common migraine (CM), eleven affected by daily chronic headache (DCH), and eight healthy volunteers were studied. Plasma levels of beta-endorphin (beta EP), beta-lipotropin (beta LPH). ACTH and cortisol were measured in basal conditions and after traditional Chinese acupuncture (TCA). Basal beta LPH and beta EP plasma levels (pg/ml) in the DCH patients (57.6 +/- 9.5 and 16.8 +/- 2.5, respectively; M +/- SE) were lower than those found in the controls (83.6 +/- 13.7 and 26.0 +/- 6.1; p less than 0.001), while those found in the CM cases showed inter-mediate values (75.3 +/- 12.0 and 24.4 +/- 5.8). ACTH and cortisol concentrations in both the CM and DCH patients were in the same range as those of the control group. TCA caused an increase in beta LPH and beta EP plasma concentrations in the control group (beta LPH: 117 +/- 16.9; beta EP: 44.1 +/- 6.7). Opioid plasma levels, however, remained unmodified after TCA in both the CM and DCH groups. ACTH plasma levels remained stable after TCA in all three subject groups. Patients suffering from primary headache are characterized by low beta LPH and beta EP plasma levels and by a poor reactivity of circulating opioids to non-stressful stimuli.     

A Taql polymorphism in the human interleukin-1β (IL-1β) gene correlates with IL-1β secretion in vitro

In the present study we searched for restriction fragment length polymorphisms (RFLP) in the human interleukin-1 beta (IL-1 beta) gene and for correlations to monocyte (Mo) function in non-related healthy donors and insulin-dependent diabetic patients. We demonstrated a diallelic polymorphism with the restriction enzyme TaqI consisting of fragments of 9.4 kb and 13.4 kb. No differences in allele or genotype frequencies of this RFLP were observed between randomly selected controls and randomly selected patients with insulin-dependent diabetes mellitus (IDDM). However, when analysing IDDM patients negative for HLA-DR3 and -DR4, our data demonstrate that the 13.4 kb allele is more frequent in this group compared to a matched control group. The functional impact of this RFLP was studied by analysing in vitro stimulated Mo IL-1 beta response. An IL-1 beta allele dosage effect on secretory capacity was observed after LPS-stimulation: 13.4/13.4 kb homozygous individuals secreted significantly more IL-1 beta than 9.4/13.4 kb heterozygous individuals, who secreted significantly more than 9.4/9.4 kb homozygous individuals. Analyses of supernatants from LPS-stimulated Mo cultures from individuals with each TaqI IL-1 beta genotype revealed no differences in the mouse thymocyte co-stimulatory assay when compared on a molar basis, indicating that the TaqI polymorphism gave rise only to quantitative differences in expression levels and probably not to a mutant IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of cell-surface TFPIα and β

BACKGROUND: Tissue factor pathway inhibitor (TFPI) is mainly produced by endothelial cells and alternative mRNA splicing generates two forms, TFPIalpha and TFPIbeta. A portion of expressed TFPI remains associated with the cell surface through both direct (TFPIbeta) and indirect (TFPIalpha) glycosylphosphatidyl-inositol (GPT)-mediated anchorage. OBJECTIVE: Compare the structure and properties of TFPIalpha and TFPIbeta. METHODS: TFPIalpha and TFPIbeta, with protein molecular masses of 36 and 28 kDa, respectively, migrate similarly (46 kDa) on SDS-PAGE. Experiments using specific glycosidases were carried out to determine the different glycosylation pattern of the two forms. ECV304 cells, a cell line with some endothelial properties, were stimulated with IL-lbeta, LPS, and TNFalpha for up to 24 hrs and mRNA levels and protein synthesis were determined. Stable clones of ECV304 cells that express reduced levels of TFPIalpha, TFPIbeta or both were produced using a plasmid-based small-interfering RNA technique. Surface TFPI activity was determined by a two-stage chromogenic assay based on the ability of each form to inhibit FXa activation by FVIIa on cells with comparable amount of tissue factor (TF). RESULTS AND CONCLUSIONS: The deglycosylation studies show that the difference in molecular masses is due to a greater degree of sialylation in O-linked carbohydrate in TFPIbeta. The mRNA and protein levels of neither form of TFPI were affected by stimulation of cells with inflammatory stimuli. Although TFPIalpha comprises 80% of the surface-TFPI, TFPIbeta was responsible for the bulk of the cellular FVIIa/TF inhibitory activity, suggesting a potential alternative role for cell surface TFPIalpha.     

Cardiac β-adrenoceptor sensitivity and Parkinson''s disease

Certain clinical manifestations of Parkinson's disease (PD) (speech or/and balance disturbances) are not linked to brain dopamine deficiency. The purpose of the present study was to search for a possible relationship between those so-called "non-dopamine-dependent" extrapyramidal manifestations and the sensitivity of cardiac beta-adrenoceptors. Fourteen patients aged 51 to 69 were included in the study after having given their informed consent. Any factor or pathology susceptible to modify receptor sensitivity entailed exclusion. In the absence of a reference model for measuring the reactivity of central beta-adrenoceptors, a computation of the isoprenalin dose necessary to increase the resting heart rate by 20 bpm was used as an index for beta-adrenergic system reactivity. In addition to that test, other parameters were recorded: disease duration, motor status scale (Columbia), some cognitive functions (MMS and image differed recall). The cardiac beta-receptor decrease in reactivity to isoproterenol is correlated to PD duration (r = 0.8, P less than 0.001). Conversely, the sensitivity of these receptors appeared to be unrelated to the extrapyramidal severity of the disease, hence to the degree of the so-called "non dopamine-dependent" disturbances. Furthermore, such results raise the meaning of the impairment of peripheral aminergic receptors in the cognitive disturbances linked to ageing and/or PD.     

CSF β-EP in headache and depression

Cerebrospinal fluid (CSF) levels of beta-endorphin (beta-EP) were measured in 9 migraineurs with interparoxysmal headache (MIH), in 13 patients with major depression in an active phase (5 suffered from MIH), and in 16 age-matched controls. beta-EP was measured by specific RIA after gel-chromatography. While beta-EP levels of depressed patients (58.5 +/- 21.0 fmol/ml, M +/- SD) were similar to those of controls (65.8 +/- 26.6), those of migraineurs (15.0 +/- 11.1) were significantly reduced (p less than 0.01). In depressed patients also suffering from MIH, beta-EP concentrations (22.8 +/- 7.2, p less than 0.05) were half those reported in depressed patients without pain problems. The reduced CSF beta-EP levels in patients whose headache and depression coexist support the notion that this neuropeptide is concerned with chronic pain, independently of the affective state.     

β-Blocker Therapy in Atrial Fibrillation

Beta-blocking agents are a generally established therapy to achieve rate control in patients with AF. With the widely spread belief that rhythm control is the therapy of choice, their use is currently limited to patients that were considered not suitable for specific antiarrhythmic drug therapy. In contrast to that belief, recent studies show that β-blockers do have some benefit in maintaining sinus rhythm or reducing the frequency of paroxysmal AF and that this benefit might be comparable to conventionally used antiarrhythmic drugs, with the exception of amiodarone. In addition, four prospectively randomized studies recently presented concluded that rate control may be an appropriate aim as a first line approach in patients with AF. Hence, an increased use of β-blockers in the treatment of patients with AF is to be expected, given the proven prognostic benefit of these drugs in many cardiovascular disorders that are associated with AF. However, no prospective study has yet proven that β-blockers do exert the same benefit in patients in AF, and one retrospective analysis suggests that there may be differences with regard to the potential benefits of β-blocker therapy when patients are in AF compared to sinus rhythm. The article summarizes available clinical studies and reviews some experimental data examining the treatment effects of antiadrenergic therapy in AF. (PACE 2003; 26[Pt. II]:1607–1612)     

Erythrocyte uroporphyrinogen-I-synthase activity in β-thalassaemic patients

Abstract. The haem pathway enzyme uroporphyrino-gen-I-synthase (UPGS) was assayed in erythrocyte samples from twenty normal, twenty β-thalassaemia heterozygotic and twenty jS-thalassaemia homozygotic subjects, after partial separation of the erythrocytes according to their age. UPGS erythrocyte enzyme concentration activity was significantly higher in the young than in the old erythrocytes of normal (66·5 ± 11·8 v. 45 ± 9·5 nmol h^-1 I^-1, mean ± SD, P < 0·001) and β-thalassaemia heterozygotic subjects (70·1 ± 18·7 v. 49·8 ± 14·5 nmol h^-1 I^-1, P lt; 0·001), but not in patients with homozygous β-thalassaemia (46·0 ± 12·8 v. 44·1 ± 12·5 nmol h^-1 I^-1, P = 0·65). Furthermore, UPGS enzyme concentration of both young and old erythrocytes of homozygous β-thalassaemia was significantly lower than that of the young ( P < 0·001) but similar to that of the old ( P > 0·2) erythrocytes of either normal or β-thalassaemia heterozygotic subjects. Since severe chronic haemolysis due to haemoglobinopathies is associated with increased UPGS enzyme concentration, these results suggest that UPGS activity may be suppressed in homozygous β-thalassaemia.     

GPVI and integrin αIIbβ3 signaling in platelets

This review summarizes recent developments in our understanding of the molecular basis of platelet activation by two distinct types of surface receptor, the immunoglobulin GPVI, and the integrin alphaIIb beta3 (also known as GPIIbIIIa). These two classes of receptor signal through similar yet distinct tyrosine kinase-based signaling cascades leading to activation of phospholipase C gamma2. The significance of these signaling cascades in platelet adhesion and platelet aggregation at arterial rates of shear is discussed.     

Three novel β3 domain-deletion peptides for the sensitive and specific detection of HPA-4 and six low frequency β3-HPA antibodies

Summary.  Background:  Antibodies against human platelet antigens (HPA) are clinically important in fetal–maternal alloimmune thrombocytopenia, refractoriness to platelet transfusions and post-transfusion purpura. Of the 16 HPAs, nine are located on the β3 subunit of the αIIbβ3 integrin. Antibody detection is generally based on platelet-derived αIIbβ3 from HPA-genotyped donors. Recombinant allelic β3 peptides, expressed at high levels would improve consistency in antibody detection, but the expression of soluble and monomeric integrins expressing complex dependent epitopes has previously proved challenging. Objectives:  We aimed to generate three recombinant β3 peptides for the detection of antibodies against HPA-4, HPA-8bw and five of the six remaining low frequency β3 alloantigens. Methods:  The removal of the specificity-determining loop from the βA domain and fusion of truncated β3 to calmodulin was exploited to obtain expression of monomeric protein. Using site-directed mutagenesis, the mutations for HPA-4b and HPA-8bw were introduced in the ITGB3*001 haplotype. A third peptide for the detection of antibodies against HPA coded by non-synonymous single nucleotide polymorphisms of low frequency was generated by the introduction of five mutations forming the basis of HPA-6bw, -7bw, -10bw, -11bw, and -16bw antigens. Results:  Reactivity of the three peptides with β3-specific murine monoclonal antibodies and human HPA-1a phage antibodies confirmed the structural integrity of the recombinant fragments, and reactivity with a unique panel of polyclonal anti-HPA sera confirmed expression of the relevant HPA epitopes. Conclusions:  These data demonstrate that β3 integrin domain-deletion fragments are suitable molecular targets for HPA antibody detection.     

Differential activation of β1-, β2- and β3-adrenoceptors by catecholamines in white and brown adipocytes

Summary— This review summarizes the experiments performed by various groups to determine how the activation of the different β-adrenoceptors (β-ARs) is ordinated when they are present in the same fat cell and involved in the same biological event. When expressed after the transfection of their genes in Chinese hamster ovary cell (CHO cells), β₁- and β₂-ARs present a higher affinity for catecholamines than β₃-ARs. In vitro, the lipolytic effect induced by low concentrations of catecholamines in dog and rat white fat cells is due to the selective activation of β₁- and/or β₂-ARs. Higher concentrations only are able to activate β₃-ARs. Similar results have been obtained in rat brown adipocytes. On the other hand, the lipolytic effect of catecholamines in human and primate adipocytes does not involve a β₃-AR component whatever the concentration used. In vivo experiments in the dog have also shown that lipomobilization induced by low doses of isoprenaline only involved β₁- and β₂-AR activation, this effect being blocked by β₁-/ β₂-antagonist pretreatment. However, in the same blockade conditions, perfusion of a 10-fold higher dose of isoprenaline revealed a β₃-AR contribution in the lipomobilizing effect. These data showed that brown and white adipocyte β₃-ARs possess a lower affinity for catecholamines than β₁- and β₂-ARs and are only recruited by high concentrations of the amines. Thus, even if the β₃-AR plays an indisputable role in the white and brown adipose tissue of some species, its physiological status and its expression are still subject to debate in human white fat cells.     

Distribution of β-endorphin in normal and schizophrenic human brains

beta-Endorphin was measured by radioimmunoassay in post-mortem human brains. Samples of brain were taken from five discrete areas, both from control brains and brains of schizophrenic patients. No difference in beta-endorphin levels was found in these two groups of brains. beta-Endorphin was confirmed to be widely distributed in the brain, but there were considerable differences in the concentrations in different areas.     

Different β-adrenoceptor-effector coupling in human ventricular and atrial myocardium

To examine whether the downregulation of beta-adrenoceptors is accompanied by reduced beta-adrenoceptor-mediated effects in atrial as well as in ventricular myocardium, we investigated the beta-adrenoceptor-effector coupling in atrial and papillary muscle strips from patients with terminal heart failure (heart transplantation because of dilated cardiomyopathy; New York Heart Association Class IV, NYHA IV) and moderate heart failure (mitral valve replacement, NYHA II-III) and in tissue from non-failing hearts. The isometric force of contraction induced by isoprenaline (0.001-1 mumoll-1) or Ca2+ (1.8-15 mmoll-1) in atrial muscle strips and papillary muscle strips has been measured. We also examined the number of beta-adrenoceptors in both tissues by radioligand binding. The degree of heart failure affected neither the potency (EC50: control: 0.01 (0.001-0.082) mumoll-1; NYHA II-III: 0.01 (0.001-0.125) mumoll-1; NYHA IV: 0.01 (0.001-0.160) mumoll-1) nor the efficacy (NYHA IV: 7.8 +/- 1.0 mN; NYHA II-III: 6.1 +/- 0.7 mN; control: 7.7 +/- 0.9 mN) of the isoprenaline-mediated increase in force of contraction in atrial muscle strips. This is in spite of a reduced number of beta-adrenoceptors in moderately (NYHA II-III) and terminally (NYHA IV) failing atrial myocardium compared to non-failing atrial myocardium (P less than 0.05). In contrast, in papillary muscle strips increasing degrees of heart failure were accompanied by a progressive reduction of the isoprenaline-mediated increase in force of contraction (P less than 0.05) as well as by a progressive decrease of beta-adrenoceptors (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

β-adrenergic priming of rats in vivo modulates the effect of β-agonist in vitro on surfactant phospholipid metabolism of isolated lungs

Abstract. To evaluate the effects of multiple β -adrenergic stimulations on pulmonary surfactant phospholipids, perfused lungs from β -adrenergic primed and non-primed rats were challenged with the β -agonist terbutaline in vitro . Cell-free lung lavage, lavagable alveolar cells and lung tissue were analysed for phospholipid content and incorporation of precursors. In lung lavage, terbutaline in vitro doubled the incorporation of ¹⁴C-choline and ³H-palmitate into total phosphatidylcholine (PC) and of ³H-palmitate into phosphatidylglycerol (PG). β -adrenergic priming in vivo prior to terbutaline in vitro lowered the increase of precursor incorporation. For lavagable cells, terbutaline in vitro increased the incorporation of ³H-palmitate into PC. Priming in vivo reduced this effect and diminished the specific ³H-choline incorporation into lavagable cell PC below control level. For lung tissue, priming increased the amounts of PC and disaturated PC (DSPC) whereas terbutaline in vitro decreased DSPC in both primed and non-primed lungs. Terbutaline in vitro slightly increased the incorporation of ¹⁴C-choline and ³H-palmitate into PC and DSPC in non-primed but not in primed lungs. β -adrenergic blockade by ICI 118.551 prevented all effects but generally increased ³H-palmitate incorporation into the phospholipids and, in lavagable cells, the amount of PC. We conclude that long-term β -adrenergic treatment may alter the metabolism of pulmonary surfactant phospholipids by increasing tissue PC and DSPC and by decreasing the secretion of newly-synthesized PC.