Alzheimer amyloid β-peptides exhibit ionophore-like properties in human erythrocytes

Abstract. There is growing evidence that the amyloid β-peptide (β₁_₄₀) is involved in the aetiology of Alzheimer's disease also implicating an altered calcium homeostasis of affected cells. Beta₁_₄₀ has been proposed to form calcium channels in synthetic bilayer membranes [1]. We wanted to investigate in the present study whether β₁-₄₀ (or fragments thereof) could act as ionophores in a biological membrane like the one in human erythrocytes. Incubation of the cells for 2h and 4h at 37°C together with 6μmolL^-1 of β₁-₄₀ or of fragments β₁_₂₈and β₂₅-₃₅, resulted in a significantly decreased energy charge qualitatively similar to the one obtained by a known calcium ionophore (A 23187, 0.05μmolL^-1). Moreover, β₁_₄₀ and its two fragments induced a significant alteration of ⁴⁵Ca permeability in human red blood cells of the same type as the one achieved by the calcium ionophore. The ionophoric action of β₁_₄₀ and its two fragments may lead to an increase of the intracellular calcium ion concentration, in turn resulting in enhanced Ca²⁺-ATPase activity and a decrease in energy charge. This may be valid also for neuronal plasma membranes and could, therefore, be a possible aetiological mechanism in Alzheimer's disease.     

Erythroblast- and erythrocyte-bound antibodies in α and β thalassaemia syndromes*

Summary. Thirty-five Thai patients with various α-thalassaemia (α-thal 1/α-thal 2, α-thal 1/HbCS, HbCS/ HbCS) and yβ-thalassaemia (β-thal/HbE, severe and mild form, HbE/HbE) syndromes were examined for the presence of immunoglobulins and C3d on o-tolidine positive erythroblasts in the bone marrow, and for the amounts of IgG of some specificities bound to circulating erythrocytes. In mild, but not in severe yβ-thal/HbE and in α-thalassaemia, the percentages of Ig-positive erythroblasts were significantly higher than in controls and correlated well with the percentages of IgG-positive erythroblasts. By contrast, the percentages of IgM and C3d positive erythroblasts were low and similar in thalassaemic and control marrows. A substantial proportion of thalassaemic patients showed more erythrocyte-bound IgG than controls, but statistically significant elevations were seen only in severe β-thal/HbE. Within a particular syndrome erythrocyte-bound IgG was more abundant in splenectomized than non-splenectomized subjects. It showed specificity for spectrin in some β-thalassaemic patients and for band 3 protein in several individuals with α- or β-thalassaemia. The results suggest that IgG antibodies play a role in the haemolysis of thalassaemia and that they are likely to be involved in the ineffective erythropoiesis in at least some of the syndromes studied.     

β-Adrenoceptor density in patients with left-sided valvular regurgitation

Summary— Aortic regurgitation differs from mitral regurgitation in that it is a result of combined volume and pressure overload, while the latter represents an almost pure volume overload. In this study, we tested the possibility that these two forms of left ventricular volume overload exert different effects on β-adrenoceptor density. Lymphocyte (n = 33) and myocardial (n = 22) β-adrenoceptor densities were evaluated by [¹²⁵I]-iodocyanopindolol binding in volume-overloaded patients with left heart valvular disease, compared with 31 healthy donor blood and 15 donor heart controls, made available as a result of failing to get matching recipient. The total lymphocyte (LC) β-adrenoceptor density decreased from 43.4 ± 5.5 fmol mg^?1 protein in controls to 9.2 ± 2.7 fmol (P < 0.001) in heart valvular patients. In the myocardial controls, the left ventricular (LV)-receptor density was 126.7 ± 19.5 fmol; right ventricular (RV), 123.1 ± 14.6 fmol; left atrial (LA), 81.6 ± 10.5 fmol; and right atrial (RA), 108.1 ± 14.5 fmol mg^?1 protein. Compared to this group, the total LV-receptor density of the patients decreased by 63%, RV by 54%, LA by 31% and RA by 34%. The decrease in receptor density exhibited a positive correlation with increasing ejection fractions in both the left (r = 0.38) and right (r = 0.44) ventricles, indicating that the former was dependent on the extent of the disease. These changes were accompanied by a 44% increase in plasma epinephrine, 13% in norepinephrine and a 27% decrease in dopamine levels. Based on the predominant left ventricular volume overload classified as aortic regurgitation (AVR), mitral regurgitation (MVR) and mixed aortic and mitral regurgitation (MOL), the attenuation in myocardial-receptor densities showed the following trend: MOL > MVR > AVR. The results show a global reduction in myocardial and LC β-adrenoceptor density, which depends on the origin and the gravity of the LV volume overload.     

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)     

A home blood transfusion programme for β-thalassaemia patients

Although home transfusion programmes are relatively common in the USA (Anon, 1990, Home Care in the 1990s. Council on Scientific Affairs. Journal of the American Medical Association, 263, 1241-1244), this type of treatment has only recently been considered in Britain and, where it is in operation, is generally supervised by trained nursing staff or via a hospice. North Middlesex Hospital now has 3 years experience of a home transfusion programme operating for beta-thalassaemia major patients, in which relatives are trained and responsible for supervision of the red-cell transfusions at home. For families who request this service, and who are willing and able to undertake it responsibly, the scheme offers the advantages of improved patient comfort, reduced absences from education or employment and reduced hospital bed usage. Patients and their carers express improved satisfaction with the treatment delivered in this way.     

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.     

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)     

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.     

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.     

Erythrocyte and reticulocyte parameters in iron deficiency and thalassemia

Introduction: Red blood cells (RBCs) extended parameters or erythrocyte subsets are now reported by the new Sysmex XE 5000 analyzer. This study was aimed at establishing a characteristic analytical feature, including the new erythrocyte and reticulocyte parameters, in case of thalassemia trait and iron deficiency (IDA). Methods: Ninety healthy individuals, 136 β‐thalassemia carriers, 121 mild IDA, and 126 severe IDA patients were analyzed. Results: The values obtained for the RBC extended parameters were significantly different (P<0.0001) in the groups; the only exception was %Hypo‐He in the case of mild IDA and thalassemia (P=0.6226). %Hypo‐He was considerably greater in severe IDA (23.4%) than in mild cases (12.4%), P<0.0001. %MicroR was more increased in thalassemia (38.6 %) than in the mild IDA (16.5%, P<0.001) and in severe IDA (21.6%, P<0.001). Immature reticulocyte fraction (IRF) mean values in the groups were statistically different; the thalassemia group had an intermediate value (8.7%) between healthy (4.4%) and IDA (16.7 and 12.9%). Conclusions: Erythrocytosis and severe microcytosis, together with a high percentage of microcytes and a moderate increase in IRF, is the profile of β‐thalassemia carriers, whereas anisocytosis and the hypochromic subset correlates with the severity of the anemia in iron‐deficient patients. J. Clin. Lab. Anal. 25:223–228, 2011. © 2011 Wiley‐Liss, Inc.     

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.     

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.     

Characterization of lymphocyte β-adrenoceptor activity and Gs-protein in patients with rheumatic heart valvular disease

Summary— In order to test whether the β-adrenoceptor activity in rheumatic heart valvular disease depends on the ventricular load conditions, we determined their density and binding affinity to [¹²⁵I]-iodocyanopindolol in lymphocytes, as well as plasma catecholamine and cAMP levels in 69 patients with regurgitant and stenotic lesions of the aortic and mitral valves. The patients were classified as having left ventricular pressure overload (LVP), left ventricular volume overload (LVV), mixed lesions (MOL) or right ventricular pressure overload (RVP). The β-adrenoceptor activity was determined by radioligand binding methods, catecholamines by high performance liquid chromatography using an electrochemical detector and cAMP by radioimmunoassay. The mean β-adrenoceptor density (B_max) of the control group was 60.1 ± 9.5 /mol ( n = 29) per 10⁶ lymphocytes. In the study population, the density was decreased by 83% in LVP, 78% in LVV, 87% in MOL and 86% in RVP. Plasma norepinephrine was elevated by 89% in LVP and 60% in MOL, epinephrine by 43% in LVP, 50% in VOL, 115% in MOL and 20% in RVP, while dopamine was not significantly changed, and cAMP was slightly elevated in all four groups. Screening for activating mutational changes in the G_sα-protein gave negative results, possibly dissociating the elevation in plasma cAMP from stimulatory effects of such abnormalities in the G_s-protein signaling. These results show a significant attenuation in lymphocyte β-adrenoceptor density of patients with rheumatic heart valvular disease, irrespective of the type of the prevailing ventricular load conditions. The reduction in receptor density is accompanied by a significant increase in plasma norepinephrine levels in patients with a left ventricular pressure overload and epinephrine in those with volume overload.     

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.     

Differences in β-adrenergic receptor density and adenylate cyclase activity between normal and leukaemic leukocytes

Abstract. An identical class of high-affinity binding sites for the ¹²⁵I-labelled β-adrenergic antagonist hydroxybenzylpindolol, was identified on intact human normal and leukaemic peripheral blood leukocytes. On normal unfractionated lymphocytes, polymorphonuclear leukocytes, and monocytes, receptor density did not differ significantly (1200–1400 receptors per cell; P > 0.3), but it was higher on B- than on T-lymphocytes ( P < 005). In leukaemia, monocytic blast cells expressed highest receptor numbers, whereas very low receptor density was seen on the pathologic B-cells from chronic lymphocytic leukaemia. Among normal leukocytes, adenylate cyclase activation by hormones (isoproterenol, prostaglandin E₁, histamine) and sodium fluoride was strongest in plasma membranes from monocytes, but very weak in polymorphonuclear leukocytes either due to uncoupling of hormone receptors from adenylate cyclase or to low catalytic activity. In T-cells, enzyme activity was significantly lower than in B-cells. Loss of adenylate cyclase sensitivity to hormones and fluoride occurred in leukaemic cells from chronic and acute lymphocytic leukaemia.     

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.     

Vascular responses to 17β-oestradiol in postmenopausal women

Abstract. The vascular responses to 17β-oestradiol were examined in 23 postmenopausal women (59 ± 7 years [mean ± SD]) using a placebo-controlled double-blind crossover design. All women received 1 mg 17β-oestradiol or placebo (P) sublingually on consecutive days in random order. Axial diameters and blood flow rates of the left common femoral arteries were determined before and 60–80 min after application of verum or placebo as well as 10–30 min after 10 mg isosorbide dinitrate (ISDN) with a quantitative duplex ultrasound technique. Oestradiol induced a vasodilation of femoral arteries (+6.4±4.1% of basal, P < 0.001 vs. basal and P), the vessel diameter was unchanged with placebo (+0.7 ± 2.1%). The blood flow rate increased significantly after oestradiol application (+30 ± 28%, P < 0.05 vs. basal and P), but not after placebo (+11 ±21%). Mean blood pressure and heart rate remained constant with both drugs. Despite its vasodilatory effect, ISDN significantly reduced the arterial blood flow after pretreatment with oestradiol and placebo, probably through cardiac preload reduction. In conclusion, 17β-oestradiol alters the vascular tone of systemic arteries resulting in a vasodilation and increase of blood flow. We suggest that these direct vascular actions may contribute to the preventive properties of oestrogens on cardiovascular diseases in postmenopausal women.