T. Fülöp

Effect of elastin peptides on human monocytes: Ca2+ mobilization, stimulation of respiratory burst and enzyme secretion.

The effect of elastin peptides (Kappa-elastin) was investigated on human monocytes. The data presented here indicate that elastin peptides increase the intracellular Ca2+ level measured by Quin 2 fluorescence and mediate the release of beta glucuronidase and elastase. The O2 consumption and H2O2 release were stimulated in a dose-dependent manner. The early rise of cAMP was followed by a return to the original level at 30 min and by a concomitant increase of cGMP level. The action of elastin peptides on intracellular calcium level and cGMP levels may well be related to its previously demonstrated chemotactic activity. These activities may well play a role in the modifications of the extracellular matrix following elastin degradation as observed in atherosclerosis, emphysema and aging.

Signal transduction changes in granulocytes and lymphocytes with ageing

It is well known that the immune response declines with ageing. However, the exact cause of this decline is still unknown. In recent years signal transduction events leading to the transmission of a signal from the cell surface to the nucleus have been extensively studied in various cell systems. These studies have indicated that an alteration in signal transduction occurs with ageing. It is not possible to identify a single age-sensitive step in this sequence, but rather a series of deficiencies contributing to the decline in competency of aged lymphocytes and granulocytes to undergo normal activation. Thus, signal transduction events such as calcium mobilization, phosphatidylinositol breakdown, accumulation of proto-oncogene transcripts, expression of activation markers, and synthesis of new proteins are deficient in the aged. Other events in signal transduction have been much less studied such as protein tyrosine kinase activity and G-protein functions. alterations in these various intracellular signalling events may fundamentally influence the functional activity of lymphocytes and granulocytes in the aged, as suggested by several investigations performed in recent years and reviewed in the subsequent sections. Future study on the signal transduction pathways using well-defined experimental models and healthy individuals should help to elucidate the molecular basis of immunosenescence and to develop effective approaches for reducing age-associated deficits and thereby reducing the incidence of age-associated diseases.

A marked drop in the incidence of the null allele of the B gene of the fourth component of complement (C4B*Q0) in elderly subjects: C4B*Q0 as a probable negative selection factor for survival

SummaryThe incidence of allotypes of the genes of the fourth component (C4) and factor B of the complement system was compared in 252 persons under 45 years of fage (“young” group) with 482 people between 61 and 90 years of age (“old” group). One hundred people older than 90 years of age (nonagenarians) were also investigated. A striking difference was found between the “young” and “old” groups in the incidence (16.1% and 5.4%, respectively) of a silent gene of the C4B allele (C4B✸Q0). This difference was even more marked among “young” and “old” men (17.6% vs 3.4%). The incidence of the C4B✸Q0 allele in women dropped to the level of the men only in the nonagenarian group. The most probable explanation for this finding is that people carrying the C4B✸QO allele die from as yet unidentified disease(s) in their middle-age. Therefore, male (and to a lesser extent female) carriers of this allele may have a considerably shorter life expectancy than individuals without a silent gene in the C4B locus.

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 …

Cell surface markers, inositol phosphate levels and membrane potential of lymphocytes from young and old human patients

It is well known that most physiological functions change with aging, including the immune response. Data concerning the aging of lymphocyte subpopulations are conflicting. The antigen density of peripheral blood lymphocytes has been determined by fluorescently tagged OKT-3, OKT-4, OKT-8, OKT-11 and OKM1 monoclonal antibodies in a carefully selected aged (over 87 years) population, and compared to that of young subjects. A substantial difference was found in the percentage distribution of OKT8 and OKM1 subsets. The volume of lymphocytes of the elderly population was significantly less than that of the young. The effect of various monoclonal antibodies on phosphatidylinositol breakdown has also been studied. It was found that only OKT3, acting through the CD3 antigen receptor, was able to induce inositol phosphate formation in both young and elderly, although in the latter population this occurred at a lower level. Because the plasma membrane plays a regulatory role in this process, an important and sensitive functional parameter, the membrane potential, was also monitored and influenced by changing the extracellular K+ concentration. The lymphocytes of the elderly population responded less sensitively to changes in extracellular potassium concentration.

Age-dependent changes in transmembrane signalling: Identification of G proteins in human lymphocytes and polymorphonuclear leukocytes

In human neutrophils (PMNLs) we found that in the elderly IP3 formation was significantly decreased compared to that of young subjects. For FMLP receptor binding affinity and number no measurable differences occurred upon ageing, studying both the low or the high affinity receptors. The amount of ADP-ribosylated G proteins, catalysed by pertussis toxin (PT) or cholera toxin (CT), was significantly increased in PMNLs of the elderly. In lymphocytes, the PT-catalysed ADP ribosylation of G proteins was also increased with ageing, while the CT-catalysed ribosylation was decreased. The autoradiogram of [32P]ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40,000 M(r). In contrast, in lymphocytes of the elderly, the major polypeptide was 45,000 M(r). In PMNLs, CT labelled quite strongly the 45,000 M(r) band, mainly in the elderly. When PT was used, no age-related pattern changes could be demonstrated, while differences could be observed between the two types of cells. The use of antiserum P680 (G alpha common) showed no age-related pattern changes, while the intensity of the labelled proteins varies with age and cell type. The antiserum U46 (Go alpha) could identify in lymphocytes of young subjects two polypeptides 68,000 and 41,000 M(r). The prominent polypeptide in lymphocytes of the elderly was the 70,000 M(r) and no other polypeptides could be recognized. In PMNLs of young subjects the U46 and serum identified a range of species. In PMNLs of the elderly all these bands were weakly labelled. The present data indicate changes in the pattern and the quantity of G proteins in lymphocytes and PMNLs of elderly subjects.

Technetium-99m sestamibi scintigraphy for the assessment of lower extremity ischaemia in peripheral arterial disease

Technetium-99m sestamibi was used for functional investigation of the muscle perfusion of lower extremities in 35 patients with peripheral vascular disease. The aim was to test what useful information could be obtained by additional imaging of the legs in patients referred for risk stratification with dipyridamole myocardial scanning. Posterior images were acquired over the thighs and calves after postocclusive reactive hyperaemia and at rest. Inter- and intraextremity ratios and differences between the stress and rest data were used for the assessment of abnormal circulation. Arteriography was performed in every case, and surgical procedures or transluminal angioplasty in 31 patients. To estimate diagnostic accuracy, the results of99mTc-sestamibi scintigraphy were compared with those of angiography and the functional consequences of revascularization procedures. The sensitivity and specificity of99mTc-sestamibi scintigraphy were 55% and 25%, respectively, with an overall accuracy of 50%. Apparently methodological error was not responsible for these poor results. Instead, a paradoxically high uptake of the radiopharmaceutical in muscles supplied by significantly stenosed vessels was identified as the main source of both false-negative and false-positive results. This phenomenon resembles the findings of a previous study involving delayed administration of thallium-201 after exercise. In conclusion,99mTc-sestamibi scintigraphy has not proved sufficiently reliable to help in the management strategy for patients with peripheral vascular disease.

Elastin peptide concentration in human serum : variation with antibodies and elastin peptides used for the enzyme-linked immunosorbent assay

Discrepancies exist between the reported values for the mean elastin peptide (EP) concentration in human sera. In order to understand these discrepancies, several EP preparations were obtained in vitro and monoclonal and polyclonal antibodies were produced against them. These different EP preparations and antibodies were used in an enzyme-linked immunosorbent assay (ELISA) to study cross-reactivity between EP preparations and to quantitate EP concentration in human sera. The method of purification of elastin, the method of hydrolysis of elastin and the molecular weight of EP influence their reactivity with antibodies and the results of EP measurements in human sera. However, there is a good correlation between EP measurements carried out in several human sera with the different EP preparations and different antibodies. Although absolute values of the EP concentrations varied with the EP preparation and antibodies used for the ELISA, the variations of this EP concentration measured from one human serum to another are significant.

Transmembrane Signaling Changes with Aginga

Altered immune response and transmembrane signaling with aging has previously been demonstrated. The aim of the present study was to characterize PMNLs and lymphocyte G proteins and to determine whether their relative amounts are altered with aging. First we studied the effects of FMLP on PMNLs IP3 formation. It was found that in any group of elderly the PMNLs IP3 formation was significantly decreased compared to that of young subjects. In FMLP receptor binding affinity no measurable difference exists in either low- or high-affinity FMLP receptors. The autoradiogram of 32P-ADP-ribosylated proteins by CT in lymphocytes of young individuals showed a major polypeptide of 40 kDa, and two much less prevalent components of 52 and 45 kDa. In contrast, in lymphocytes of elderly subjects the major polypeptide was 45 kDa, and the two others were very weakly labeled. In PMNLs, CT labeled the 45-kDa band quite strongly, mainly in the elderly, and the 52- and 40-kDa bands were very weakly labeled, mainly in young subjects. When PT was used, no age-related pattern changes could be demonstrated, while differences could be observed between the two types of cells.

Age-Dependent Variations of Intralysosomal Enzyme Release from Human PMN Leukocytes under Various Stimuli

The intralysosomal beta glucuronidase and elastase release from polymorphonuclear leukocytes (PMNL) of young and aged male subjects were determined after 60-min incubation with 10 micrograms/ml Cytochalasin B (CB), 10(-6) M of Ca ionophore A 23187 and various concentrations of human low density lipoprotein (LDL). The beta glucoronidase secretion was triggered by both A 23187 and LDL; however, no significant differences were found between the enzyme release from PMNLs of young and aged subjects. In contrast, a marked elastase release was triggered in the young group only by LDL, whereas in the aged group, all of the applied drugs induced a significant elastase release. LDL caused the most dramatic enzyme release from PMNLs of aged males. It was concluded that the release of PMNL-elastase after LDL incorporation as well as by CB and Ca ionophore stimulation may be an age-related process.