Attila Mohácsi

NEUTROPHILS OBTAINED FROM OBLITERATIVE ATHEROSCLEROTIC PATIENTS EXHIBIT ENHANCED RESTING RESPIRATORY BURST AND INCREASED DEGRANULATION IN RESPONSE TO VARIOUS STIMULI

Tissue destruction in atherosclerosis is partly due to uncontrolled protease and oxygen radical release. In this study we investigated the release of elastase and myeloperoxidase, as well as the production of reactive oxygen species by polymorphonuclear leukocytes (PMNLs) obtained from patients with obliterative atherosclerotic of the lower legs. In addition we measured the plasma concentration of xanthine oxidase. PMNLs of atherosclerotic patients have a greater ability to increase elastase and myeloperoxidase release after their stimulation with formyl-methionin-leucyl-phenylalanin (fMLP) and calcium ionophore, A23187, independently of their age, than PMNLs of healthy middle-aged subjects. Similarly to healthy elderly subjects there was an increased superoxide anion (O2-) production under basal condition in both atherosclerotic patient age-groups. The activation of PMNLs with fMLP and A23187 enhanced O2- formation both in healthy subjects and in patients with atherosclerotic disease of the lower legs, however the increase was significantly less in the latter group. No biochemical parameters showed significant correlation with patients risk factors, however myeloperoxidase production was significantly higher in less severe stage of the disease (P < 0.05). We found that patients with atherosclerotic disease of the lower legs have higher plasma xanthine oxidase level than control subjects. This study indicates an other piece of evidence suggesting the activation and involvement of neutrophils in the pathogenesis of atherosclerosis of the lower legs. The similar tendencies in the reactivity of neutrophils during aging and in atherosclerosis suggest that atherosclerosis may be an early aging process.

Age-dependent alterations of human recombinant GM-CSF effects on human granulocytes

The granulocyte-macrophage colony stimulating factor (GM-CSF) is an important in vivo regulator of granulopoiesis and neutrophil functions. It is well-known that the immune response and the transmembrane signalling in immune cells change with aging. We wished to elucidate the effects of GM-CSF in itself and in priming the activities of other inflammatory agents on neutrophils of elderly persons. Neutrophils of 20 healthy elderly (aged 60-90 years) and 20 healthy young (aged 20-25 years) subjects were studied for superoxide anion production, intracellular free calcium mobilization, antibody dependent cellular cytotoxicity (ADCC) and intracellular killing activities. It was found that GM-CSF is unable to prime neutrophils of elderly subjects to the action of FMLP, metenkephalin or opsonized zymosan. By the use of Pertussis toxin and H7 it was demonstrated that a different signal transduction pathway in neutrophils of elderly subjects is activated by GM-CSF or FMLP if compared to that of young subjects. These results suggest that the lack of priming could contribute to the greater susceptibility of the elderly to infections and that the change of the signal transduction mechanism in neutrophils of elderly subjects might partly explain this phenomenon.

C4B*Q0 allotype as risk factor for myocardial infarction

The prevalence of the deficient, silent allotype of the C4B gene (C4B*Q0) is lower in elderly than in young healthy people, particularly in men.1 This may reflect increased mortality from some disease in middle aged carriers of the C4B*Q0 gene. We determined the presence of the gene in patients with acute myocardial infarction because myocardial infarction is the leading cause of death among middle aged Hungarians. We studied 181 consecutive patients with confirmed Q wave myocardial infarction admitted to four hospital departments between June 1992 and January 1993 (125 men, 56 women, aged 42-78), 93 consecutive patients with symptoms of angina pectoris (65 men, 28 women; aged 43-62) who were examined by coronary angiography (coronarography), and 737 previously tested healthy controls (252 young people aged 22-45 and 485 elderly people aged 60-99).1 Myocardial infarction was diagnosed as typical chest pain lasting …

Effects of Endothelins on Cardiac and Vascular Cells: New Therapeutic Target for the Future?

The predominant isoform of the endothelin peptide family. endothelin-1 (ET-1) exerts various biological effects. These include effects on arterial smooth muscle cells causing intense vasoconstriction and stimulation of cardiac cells. ET-1 promotes changes in cardiomyocytes that are consistent with electrical remodelling such as changes in ionic current density and inhomogeneous prolongation of action potential duration resulting in increased dispersion. As for the underlying mechanisms, ET-1 was shown to suppress several cAMP-dependent ionic currents, such as ICa, IK and ICl in various mammalian cardiac preparations including human myocytes; however, the degree of suppression of these currents is different and highly dependent on experimental conditions. The proposed arrhythmogenic effects of ET-1 may also involve enhancement of Ca2+ release from intracellular stores, generation of IP3, and acidosis due to stimulation of the Na+/H+ exchange. Furthermore, ET-1 acts as the natural counterpart to endothelium-derived nitric oxide, which exerts vasodilator, antithrombotic and antiproliferative effects, and inhibits leukocyte adhesion to the vascular wall. Effects of ET-1 are mediated through interaction with two major types of cell surface receptors. ETA receptors have been associated with electrical remodelling, vasoconstriction and cell growth, while ETB receptors are involved in the clearance of ET-1, inhibition of endothelial apoptosis, release of NO and prostacyclins, and inhibition of the expression of ET-1 converting enzyme. The derangement of endothelial function in various cardiovascular diseases, such as cardiomyopathies, hypertension or arteriosclerosis, is a crucial element of the pathomechanism, thus ET receptors are considered as important therapeutic targets. Indeed, ET receptor antagonists may be able to preserve or restore endothelial integrity and may have antiarrhythmic properties; therefore, they are promising tools in cardiovascular medicine.

Superoxide anion production and intracellular free calcium levels in resting and stimulated polymorphonuclear leukocytes obtained from healthy and arteriosclerotic subjects of various ages

It has been established that phagocytic cells are integral components of advanced arteriosclerotic plaques but their role in plaque formation remains unclear. Therefore, toxic agents, such as superoxide anion produced by polymorphonuclear leukocytes (PMNLs) were studied in a clinically defined group of arteriosclerotic patients suffering from obliterative arteriosclerosis of the lower legs. Owing to a close correlation between O2- generation and calcium, the intracellular free calcium concentrations of PMNLs were measured in a resting state and after stimulation with various agents, for example, opsonized zymosan (OZ), the chemotactic peptide f-met-leu-phe (FMLP), and the calcium ionophore A23187. Healthy aged-matched controls were employed. The patients were divided into two age groups: 30-59 years and 60-80 years. We found that in the younger group of arteriosclerotic patients, superoxide anion production and intracellular free calcium concentrations were increased even in the resting state, and only a slight increase was observed after stimulation compared with healthy controls. Granulocyte responses seemed to be similar, independent of the patients age, to those found in healthy elderly subjects. Arteriosclerosis appears to be associated with an early aging process expressing marked alterations that are greater than those associated with normal aging.

Enhanced Repolarization Capacity: New Potential Antiarrhythmic Strategy Based on hERG Channel Activation

The delayed rectifier potassium current (I(K)) is the major outward current responsible for ventricular repolarization in cardiac tissues. Based on kinetic properties and drug sensitivity it is composed of a slow (I(Ks)) and a rapid (I(Kr)) component, the latter is mediated by hERG channels. Suppression of IKr is the common mechanism of action of all class III antiarrhythmics, causing prolongation of the refractory period. However, lengthening of repolarization - either by a pathological factor or due to a pharmacological intervention - threatens with an increased risk of EAD generation and the concomitant sudden cardiac death. Therefore, a new potential anti-arrhythmic strategy, based on augmentation of the repolarization reserve, has been emerged. Recently a new class of compounds has been introduced as activators of the hERG channel. In this article we systematically review the chemical structures found to enhance IKr. Since the majority of previous experiments were performed in expression systems or in rodent cardiac preparations (neither is relevant to the human heart), in the second part of this article we present some results obtained with NS1643, the best examined hERG activator, in canine ventricular cardiomyocytes. This preparation is believed to have electrophysiological parameters most resembling those of human. NS1643 shortened the duration of canine ventricular action potential and was shown to interact with several transmembrane ion currents, including I(Ca), I(Kr), I(Ks), and I(to). However, the action potential shortening effect of NS1643 is likely related to inhibition of ICa, in addition to the enhancement of IKr. Although the multiple ion channel activity of NS1643 may carry proarrhythmic risk, the rationale of antiarrhythmic strategy based on I(Kr) activation is not questioned.

Mistyping of angiotensinogen M235T alleles

Conflicting results are to be found in the literature on the relationship between the M235T polymorphism of the angiotensinogen (AGT) gene and hypertension. The controversy may be due to insufficient numbers of subjects, the variability of the inclusion criteria and the different genotype analysis methods used. We have experienced that the most frequently used, original polymerase chain reaction (PCR)−restriction fragment length polymorphism (RFLP) method involves significant uncertainties when the TT genotype is determined, independently of the restriction digestion. To make the determination more accurate, we improved the PCR by designing a new antisense primer containing only one mismatch instead of the two in the original protocol and also by adding DMSO to the PCR reaction mixture. The original and our improved methods were compared by using DNA from 123 patients: parallel determinations resulted in values of 33 MM, 90 MT and 0 TT with the original method and of 33 MM, 56 MT and 34 TT with the improved RFLP protocol. In summary, a plausible explanation for some of the conflicting data published on AGT M235T polymorphism may be that inaccuracies arose during the determination of the genotype.