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Biomedical subjects

P Bellavite

Publications and source records attributed to P Bellavite.

At least 37 records · Page 2Linked to original sources

Decrease of platelet intracellular pH and adhesion by ticlopidine in patients with vascular disease.

BACKGROUND: Ticlopidine inhibits platelet aggregation by preventing the binding of fibrinogen to its platelet receptor. We examined whether this inhibition involved platelet transduction system such as Na+/H+ pump and platelet intracellular calcium. METHODS: Platelet adhesion in 13 patients with peripheral vascular disease treated with ticlopidine, 250 mg b.i.d for 30 days, was measured in culture microplates before and after therapy. The microplate wells were coated with human plasma, fibrinogen or collagen, and platelet adhesion was studied in the resting condition and after stimulation with 1 and 10 microM ADP. At the same time, platelet intracellular calcium and ADP-induced calcium increases were measured with the fluorescent indicator Fura 2. In addition, intracellular pH and thrombin-induced pH variations were measured with the fluorescent probe BCECF. RESULTS: Platelet adhesion to plasma and fibrinogen was significantly reduced (about 50%) after treatment with ticlopidine, while adhesion to collagen was not modified. Basal calcium and ADP-induced calcium increase were not significantly different before and after ticlopidine. Platelet basal intracellular pH was reduced (from 7.44+/-0.009 to 7.41+/-0.017, p<0.05), but agonist-induced alkalinisation was not significantly different. Early acidification, not dependent on Na+/H+ exchange, was also reduced (p<0.05). CONCLUSIONS: These data do not seem to support the hypothesis that ticlopidine-induced reduction of platelet adhesion depends on alteration of the mechanisms determining signal transduction, at least as far as basal and post-stimulation intracellular calcium is concerned. On the contrary, the possibility that ticlopidine inhibits the Na+/H+ antiport remains open to consideration.

Aged↗

Specific and long-lasting suppression of rat adjuvant arthritis by low-dose Mycobacterium butyricum.

We have tested the therapeutic effect of intraperitoneal injections of Mycobacterium butyricum on the development of adjuvant arthritis in rats and we have explored the specificity and the duration of effectivity of this treatment. Rats with induced arthritis were injected intraperitoneally with the causative antigen, Mycobacterium butyricum, at concentrations 10 times lower than the inducing one, on the 3rd and 10th day after arthritis induction. The severity of the disease was assessed on the basis of physical (arthritis index, paw swelling) and biochemical (serum interleukin-6) parameters. The treatment with Mycobacterium butyricum led to a significant suppression of adjuvant-induced arthritis. This therapeutic effect was both antigen-specific, because intraperitoneal aspecific inflammation did not prevent the disease, and long-lasting. The results obtained in this model confirm the possibility of modulating the autoimmune process even when the immunological response is already triggered, suggesting new therapeutic strategies, more suitable than preventive vaccination, in human autoimmune diseases.

Animals↗

A scientific reappraisal of the 'principle of similarity'.

In the history of therapeutics, the 'principle of similarity'--the treatment of 'same by same' or of 'like by like'--may be traced back to a number of medical traditions, including the systems of Hippocrates, Paracelsus and Hahnemann. Although in recent years we have witnessed a renaissance of interest in traditional medicines and 'holistic' medical practices, the reliability of the principle of similarity has still to be demonstrated on experimental grounds, and very few studies have been conducted to understand the underlying mechanism(s). Acceptance of this phenomenon requires supporting evidence of possible mechanisms and high-quality studies exploring its effectiveness in clinical medicine. The aim of this work is to provide a rational approach to the analysis of the various aspects of this historical yet also modern medical principle, in order to construct a plausible framework of ideas capable of facilitating further basic and clinical research into this field.

Animals↗

Study on paradoxical effects of NSAIDs on platelet activation.

We recently described a stimulatory effect of high doses (> 100 mumol/L) diclofenac on platelet adhesion. In this study we extend our research to the possible biochemical mechanisms of the observed effects, to other non steroidal anti-inflammatory drugs (NSAIDs) (flurbiprofen, indomethacin, acetylsalicylic acid, ibuprofen, nitrofenac and nitroflurbiprofen) and to the effect of high doses diclofenac and flurbiprofen on platelet aggregation. We observed that high doses of diclofenac and of flurbiprofen, but not of the other tested NSAIDs, increased platelet adhesion at doses ranging from 100 to 500 mumol/L, an effect completely removed by the 12-lipoxygenase-inhibitor nordihydroguaiaretic acid. Moreover, they had no pro-aggregating effect, inhibiting platelet aggregation induced by 10 mumol/L arachidonic acid and dose-dependently increasing the [Ca2+]i. Finally, whereas no basal nitric oxide release by washed platelets was detected, when platelets were incubated by 500 mumol/L diclofenac or flurbiprofen, the production of nitric oxide, as measured by amounts of nitrite released, was 4.4 +/- 0.5 and 3.8 +/- 0.4 pmol/5 x 10(8) platelets/min, respectively. Our data indicate that high doses diclofenac and flurbiprofen are promoters of the early phases of platelet activation, probably through the 12-lipoxygenase pathway.

Anti-Inflammatory Agents, Non-Steroidal↗

Studies of skin-window exudate human neutrophils: increased resistance to pentoxifylline of the respiratory burst in primed cells.

Human neutrophils were isolated both from peripheral blood (PB) and from aseptic inflammatory exudates obtained by the Senn's skin window technique (SW). The respiratory burst (O2- production) induced by in response to n-formyl-methionyl-lencyl-phenylalanine (fMLP) and by serum-treated zymosan (STZ) was investigated using a microplate assay. SW neutrophils were primed to enhanced fMLP-dependent O2- production in response to fMLP but not to STZ. Pentoxifylline, a cAMP-elevating drug, dose-dependently inhibited the respiratory burst in any experimental condition, but the dose-effect curves were markedly different according the stimulant used and the source of the cells. With fMLP as stimulant, a significant inhibition of the O2- production by PB neutrophils was obtained using doses of 10 micrograms/ml, while SW neutrophils were inhibited only by doses equal or higher than 100 micrograms/ml. With STZ as stimulant, the inhibition of the respiratory burst of PB neutrophils and of SW neutrophils was obtained only with doses higher than 400 micrograms/ml and 1 mg/ml respectively. Pentoxifylline dose-dependently (10 micrograms/ml to 1 mg/ml) increased the intracellular adenosine 3'-5'-cyclic monophosphate (cAMP) to the same extent in SW and in PB neutrophils. These data indicate that the priming of neutrophil oxidative metabolism by in vivo inflammation is associated with an increase in the resistance to the regulating effect of cAMP on the fMLP-dependent activation pathway of NADPH oxidase. The fact that therapeutic doses of pentoxifylline do not inhibit the respiratory burst of primed neutrophils may have relevance in the interpretation of the clinical effects of this drug.

Cyclic AMP↗

Changes of neutrophil migration without modification of in vitro metabolism and adhesion in Behçet's disease.

OBJECTIVE: Increase of neutrophil chemotaxis in Behçet's disease (BD) has been described, but it is not clear whether there is a correlation with other variables of neutrophil function and whether these modifications correlate with disease activity. METHODS: We studied neutrophil functions in patients with BD in the acute phase in comparison with healthy control subjects and with the same patients during disease remission, with or without therapy. We investigated in vivo neutrophil migration by Senn's skin window technique and measured adhesion assay and superoxide production in circulating and migrating neutrophils after different stimuli. RESULTS: Neutrophil migration in vivo was 101.3 +/- 17.9 x 10(6) polymorphonuclear lymphocytes (PMN)/cm2/24 h in patients with BD in the acute phase and 66.1 +/- 7.8 x 10(6) PMN/cm2/24 h in controls (p < 0.001). No correlation was found between leukocyte counts and neutrophil migration. Neutrophil migration evaluated in the same patients in a phase of disease remission was 58.3 +/- 10.3 x 10(6) PMN/cm2/24 h (p < 0.001 vs acute phase, not significant vs controls). The neutrophils of the exudate were normally primed to response to the chemotactic peptide fMLP. No differences between the 2 groups were found in superoxide production, adhesion under basal conditions, or in response to different stimuli by circulating and migrating neutrophils. CONCLUSION: Abnormally high migration of neutrophils in the active phase of BD is the only consistent neutrophil dysfunction. Since this modification is reversed by therapy, the evaluation of in vivo neutrophil migration may be useful in diagnosing and monitoring disease activity. Blood neutrophils have normal responses to different stimuli, indicating they are not primed by the disease state.

Adult↗

Changes of fatty acid composition and oxidative metabolism of human neutrophils migrating into an inflammatory exudate.

The peripheral blood neutrophils and the neutrophils accumulated into a skin-window experimental exudate were compared for their ability to release superoxide anion (O2-) and for their fatty acid composition, determined by capillary gaschromatography. The basal O2- release and the phorbol myristate acetate (PMA)-induced O2- release were not significantly different in the two neutrophil populations, while in response to formyl-methionyl-leucyl-phenylalanine (fMLP) the exudate cells showed an activity that was two fold higher than that of blood cells. The most significant changes of fatty acid composition of exudate versus blood cells were the following: i) increase of C16:0 (palmitic acid) from 21.3 +/- 1.2% to 23.5 +/- 1.3% (+ 10.2%) of total fatty acids (p < 0.001),ii) increase of C18:2 (linoleic acid) from 9.3 +/- 1.7% to 11.0 +/- 2.1% (+ 18.3%) (p = 0.005), iii) decrease of C20:4 (arachidonic acid) from 12.8 +/- 1.6% to 10.6 +/- 1.2% (-17.3%) (p < 0.001), whereas C18:1 (oleic acid) did not change. The total content of saturated or unsaturated fatty acids did not change. In exudate cells, a strong negative correlation was found between palmitic acid content and O2- release in response to both fMLP and PMA (r = -0.52, p < 0.02 and r = -0.49, p < 0.05, respectively) whereas arachidonic acid correlated positively, but weakly, with O2- (r = 0.40, p = 0.07 and r = 0.47, p = 0.05, with fMLP and PMA as stimulants respectively). A positive correlation was also found between the arachidonic acid content of blood cells and the number of cells that migrated into the inflammatory exudate. These results indicate that the process of extravasation from blood into the exudate causes specific and consistent modifications of the fatty acid composition of neutrophils and suggest that these modifications have a role in the activation and the regulation of the O2- forming system.

Chemotaxis, Leukocyte↗

Neutrophil migration, oxidative metabolism, and adhesion in elderly and young subjects.

OBJECTIVE: To evaluate neutrophil functions in the elderly. METHODS: We investigated the PMN migration in vivo and PMN superoxide production and adhesion in response to a variety of compounds; PMN have been isolated both from blood and from a skin experimental exudate (obtained by Senn's skin window technique) of 25 normal elderly and of 25 normal young control subjects. RESULTS: No difference was found in PMN migration in vivo (62.9 +/- 21.3 x 10(6) and 65.5 +/- 9.1 x 10(6) PMN/cm2/24 hours in elderly and young subjects respectively), neither were different the adhesion under basal condition and after some stimuli and the superoxide production in basal condition and in response to STZ and PMA in two groups. In elderly subjects superoxide production, in response to fMLP, markedly resulted lower than in young controls both by circulating PMNs (3.6 +/- 2.7 and 9.3 +/- 3.3 nMOLES O2-/10(6) PMN respectively, p < 0.0001) and by exudate PMNs (13.6 +/- 4.3 and 19.4 +/- 6 nMOLES O2-/10(6) PMNs respectively, p < 0.005). CONCLUSION: Many PMN functions in the elderly do not differ from young people, suggesting that the overall defense function of these cells is not affected by aging. The only parameter that we have found to be different between the two groups is the poor superoxide production after fMLP stimulus of PMNs. The stimulus- and function-specificity of this defect in PMNs from elderly subjects indicates the existence of a dysregulation of the signal transduction pathway distal to fMLP receptor and proximal to NADPH oxidase activation.

Adult↗

Dual effects of diclofenac on human platelet adhesion in vitro.

The effect of two non-steroidal anti-inflammatory drugs on the adhesion function of human platelets was evaluated. Platelets isolated from healthy human subjects were treated for 10 min with the indicated drugs and then incubated in fibrinogen-coated microwell plates in the absence or in the presence of ADP (10 microM) and thrombin (0.05 U/ml). After 1 h of incubation, adherent platelets were measured using an enzymatic assay. ADP- and thrombin-stimulated adhesion was significantly inhibited by high doses ( > 500 microM) of diclofenac, while doses ranging from 50 to 300 microM stimulated adhesion in the absence of agonists (resting platelets). A similar stimulatory effect on platelet adhesion was observed also with 200-500 microM flurbiprofen. Moreover, immunocytofluorimetry demonstrated that diclofenac dose-dependently (100-500 microM) induced the expression of GMP-140 and increased the expression of GPIIb/IIIa on the membrane of unstimulated platelets. High doses ( > 500 microM) of this drug inhibited thrombin-stimulated expression of GPIIb/IIIa and GMP-140.

Adenosine Diphosphate↗

Study of platelet adhesion in patients with uncomplicated hypertension.

OBJECTIVE: To evaluate platelet function in patients with essential hypertension by sensitive methods investigating platelet adhesion and expression of some platelet glycoproteins (GP), namely GPIIb/IIIa (CD41/alpha 2 beta 3) and GMP-140 (CD62/P-selectin/PADGEM). Other markers of platelet (beta-thromboglobulin) and endothelium activation (von Willebrand factor) were also measured. METHODS: We studied 21 uncomplicated essential hypertensive patients and 20 healthy normotensive control subjects, non-smokers, matched for age and sex. Resting and stimulated platelet adhesion was performed with a colorimetric method using the activity of platelet acid phosphatase for the determination of the number of platelets adhering to human plasma- or fibrinogen-coated microwells. Platelet activation was characterized by flow cytometric measurement of GPIIb/IIIa and GMP-140 in whole blood and washed platelets suspensions, with antihuman fluorescent monoclonal antibodies. RESULTS: Thrombin-stimulated platelet adhesion to human plasma-coated microwells was significantly higher in hypertensive patients than in control subjects (0.05 U/ml thrombin: 13.4 +/- 1.0 versus 7.7 +/- 0.6% adhesion; 0.1 U/ml thrombin: 19.4 +/- 2.3 versus 12.6 +/- 1.8%; means +/- SEM), whereas platelet adhesion to fibrinogen-coated wells did not differ in the two groups. Flow-cytometry analysis of whole blood demonstrated a significantly increased expression of GMP-140 in hypertensive patients compared with normal subjects (percentage of CD62+ platelets: 7.3 +/- 1.2 versus 3.7 +/- 1; means +/- SEM), whereas the expression of GPIIb/IIIa did not differ in the two groups (percentage of CD41a+ platelets: 72.5 +/- 4.5 versus 70.4 +/- 3.9). Moreover, flow cytometry showed an increased size of platelets in hypertensive patients compared with that in control subjects (forwards scattering: 46.5 +/- 1.5 versus 38.9 +/- 1.1; means +/- SEM). Flow-cytometric evaluation of washed platelet suspensions showed no statistically significant differences between the expression of GMP-140 and GPIIb/IIIa in the two groups. beta-Thrombo-globulin plasma levels were higher in hypertensive patients than they were in normal subjects (36.3 +/- 2.0 versus 28.2 +/- 1.3 ng/ml; means +/- SEM). Von Willebrand factor plasma levels were not significantly different in the two groups (101.2 +/- 10.3 versus 86.3 +/- 5.6 U/dl). CONCLUSIONS: These findings provide further evidence that there is a significant, albeit weak, platelet activation in hypertensive patients compared with normal subjects.

Adult↗

The antiplatelet effects of a new nitroderivative of acetylsalicylic acid--an in vitro study of inhibition on the early phase of platelet activation and on TXA2 production.

We studied in vitro the antiplatelet activity of a new nitroderivative chemically related to acetylsalicylic acid: 2 acetoxybenzoate 2-[1-nitroxy-methyl]-phenyl ester (NCX 4016), in order to identify any effects due to the release of nitric oxide and the blockade of cyclo-oxygenase. The effects of scalar doses of NCX 4016 on the early phase of platelet activation, platelet aggregation and thromboxane A2 production were investigated. We observed inhibitory effects of NCX 4016 on platelet adhesion (IC50 = 7.3 x 10(-5) M), platelet cytosolic calcium concentration, assayed by fluorescent probe Fura 2, and the expression of glycoprotein IIb/IIIa (CD41/alpha IIb beta 3) (IC50 = 3.4 x 10(-5) M) and P-selectin (CD62/GMP-140) (IC50 = 4.9 x 10(-5) M) measured by flow cytometry. NCX 4016 also prevented thrombin-induced platelet aggregation (IC50 = 3.9 x 10(-5) M). None of these parameters were affected by acetylsalicylic acid. These inhibitory activities of NCX 4016 were abolished by oxyhaemoglobin and methylene blue. Intracellular cyclic GMP observed during thrombin-induced aggregation was increased by incubation with NCX 4016. These results appear to be attributable to the release of nitric oxide, which activates soluble platelet guanylylcyclase and promotes intracellular cyclic GMP increase. NCX 4016 almost completely inhibited platelet thromboxane A2 production and arachidonic acid-induced platelet aggregation. This also occurred in the presence of oxyhaemoglobin and methylene blue, indicating that its antiplatelet activity can be attributed not only to nitric oxide release but also to cyclo-oxygenase inhibition.

Adult↗

Effect of acute exercise on some haematological parameters and neutrophil functions in active and inactive subjects.

In this work we studied the possible effects of acute exercise on some haematological parameters and on some functions of neutrophils in seven active and six inactive subjects. Physical exercise (10 min on a cycle ergometer at a heart rate of 150 beats.min-1) induced a significant increase in total leucocyte, lymphocyte and neutrophil concentrations in active subjects; serum iron and ferritin concentrations were lower in active compared to inactive subjects. Cellular adhesion, bactericidal activity and superoxide anion production did not change after exercise, while we also observed some differences between active and inactive subjects before exercise. In particular, the neutrophils from active subjects showed a significantly higher percentage of adhesion, higher bactericidal activity and lower superoxide anion production. In conclusion, the training induced changes in some neutrophil functions, while acute exercise influenced, overall, leucocyte concentrations.

Adult↗

Changes in several neutrophil functions in basketball players before, during and after the sports season.

Neutrophils play an important role in the immune system, forming the "first line of defence" against invading microorganisms and there are few data available concerning neutrophil functions in relation to exercise. We investigated in 7 basketball professional players possible changes before, during and after the sports season, in some haematological parameters and in several aspects of the phagocytic process of neutrophils, such as adhesion, superoxide anion release and bactericidal activity. Training and competitions produced a significant rise in the number of total leukocytes and differential counts, but the values returned to the pre-start levels 3 weeks after the end of the championship. The bactericidal activity and the superoxide anion released were significantly greater during the sports season, while the percentage of cellular adhesion significantly decreased during the championship; after the sports season the values returned to the control levels. As in the literature data concerning neutrophil functions in relation to exercise are non-convergent, it is important in our opinion, to understand whether the alterations induced by exercise can persist after repeated stimuli.

Adult↗

Correlations between the intensity of fMLP-dependent respiratory burst and cellular fatty acid composition in human neutrophils.

The peripheral blood neutrophils were isolated from a group of normal subjects and their fatty acid composition determined by capillary gas-chromatography. The superoxide (O2-) release by the same cell preparation in response to formyl-methionyl-leucyl-phenylalanine was also determined following cytochrome c reduction in a microplate assay. A strong negative correlation was found between C18:2 (linoleic acid) (r = 0.703, P = 0.001) and C:16:0 (palmitic acid) (r = 0.569, P = 0.009) and fMLP-stimulated O2- release, whereas C20:4 (arachidonic acid) correlated positively (r = 0.448, P = 0.048). Other fatty acids, namely C12:0, C14:0, C16:1, C18:1, C18:3, C18:4, C20:0, C20:1, C20:2, C20:5, C22:0, C22:1, C22:6, C24:0 and C26:0, were not correlated with O2-. No correlations were found between fatty acid composition and O2- release from resting cells and from cells stimulated by phorbol-myristate acetate. These results suggest that the fatty acid composition of blood neutrophils may be a critical factor determining the capability of releasing free radicals in response to formylpeptides. Moreover, since a concomitant increase of arachidonic acid and decrease of its precursor linoleic acid has been found in high-responsive neutrophils, the rate of the enzymes of the arachidonic acid biosynthetic pathway (elongases and desaturases) appear to play an important role.

Arachidonic Acid↗

A colorimetric method for the measurement of platelet adhesion in microtiter plates.

A procedure for the determination of the adhesion of human platelets to protein-coated culture microwells was developed. The number of platelets was quantitated by measuring the activity of acid phosphatase, a platelet enzyme whose activity is stable independently of platelet stimulation and is not released. Isolated and washed platelets were incubated in 96-well microtiter plates with flat-bottom wells that had been precoated with various compounds, including collagen, fibrinogen, human plasma, and human albumin. At the end of incubation (optimal time: 40-60 min), nonadherent platelets were washed out, adherent platelets were solubilized with Triton X-100, and the acid phosphatase activity was measured by using the substrate p-nitrophenyl phosphate. The p-nitrophenol produced was measured with a microplate reader at 405 nm and the percentage of adhesion was calculated with reference to known platelet standards. ADP and thrombin stimulated platelet adhesion in a dose-dependent manner to fibrinogen and human plasma, but not to human albumin. Platelets adhered to collagen even in the absence of stimulants. Simultaneous evaluation of adhesion and aggregation demonstrated that with ADP as stimulus, but not with thrombin, the two platelet responses were dissociated. Microscopic examination of culture wells showed that most of platelets adhered as single cells and not as aggregates. The sensitivity of this method allowed the assay of platelet adhesion by using only 2.5 x 10(5) platelets/well.

Acid Phosphatase↗

Studies of skin-window exudate human neutrophils: complex patterns of adherence to serum-coated surfaces in dependence on FMLP doses.

Human neutrophils were isolated both from peripheral blood (PB) and from aseptic inflammatory exudates obtained by the Senn's skin-window (SW) technique. The respiratory burst (O2- release) and the adherence to serum-coated wells of culture microplates was investigated using a simultaneous assay. Unstimulated PB resting neutrophils did not produce a significant amount of O2- and were incapable of adhering to serum-coated plastic surfaces, while unstimulated SW neutrophils showed augmented adhesion to serum-coated culture wells. SW neutrophils were primed to enhanced FMLP-dependent O2- release in response to n-formyl-methionyl-leucylphenylalanine (FMLP). Adhesion of SW neutrophils was significantly decreased by addition of low doses (10(-10)-10(-8) M) of FMLP (from 17.1% to 8.4%, P < 0.01, N = 12), while fully activating doses (> 5 x 10(-8) M) of FMLP induced a marked increase of the cell adhesion, more pronounced in SW (39.2%) than in PB cells (27.2%). Low (5 x 10(-9) M) and high (5 x 10(-7) M) FMLP doses induced morphological changes (polarization) and actin polymerization in the neutrophils from both sources. Biphasic dose-response curves of SW neutrophil adherence were observed using FMLP, but not using concanavalin A or phorbol myristate acetate as stimulatory agents. Therefore, the adherence of SW cells appears to be regulated in a complex fashion, nonlinearly dependent on the chemotactic peptide doses and specifically regulated according to the receptors involved.

Cell Adhesion↗

A simple assessment of human neutrophil adhesiveness.

The adhesiveness of human polymorphonuclear leukocytes was assessed in serum-coated polystyrene spectrophotometric cuvettes. Capped cuvettes, containing no more than 2 x 10(6) resting or concanavalin A-treated (100 micrograms/ml) polymorphonuclear leukocytes, were laid horizontally and subjected to three 90 degrees rotations on their major axis at fixed times. After incubation at room temperature, non-adherent cells remaining in suspension were counted on the Coulter counter STKS hematological analyzer. After a 16-min incubation (4 min each side of the cuvette) the adhesion of concanavalin A-activated neutrophils ranged from 98% to 100% and the adhesion of resting neutrophils from 30% to 35% (mean 32.4 +/- 2.2%, n = 10). An 8-min incubation (2 min each side) led to approximately 50% adhesion of concanavalin A-activated neutrophils (mean 49.9 +/- 2.2%, range 46%-54%, n = 16), whereas the adhesion of resting cells was about 21% (mean 21.4 +/- 1.6%, range 19%-24%, n = 16). The variation in percentage adhesion in repeated assays did not exceed 4% using concanavalin A-activated cells and 7.5% with resting neutrophils. The procedure is very rapid, easy to perform and precise, and no special apparatus or glassware is necessary. The method also allows microscopic evaluation of shape changes of adherent neutrophils through the clear sides of the cuvettes.

Animals↗