Oxygen consumption of human blood platelets. I. Effect of thrombin

Modulatory effects of dietary saturated fatty acids on platelet mitochondrial function following short-term exposure to ambient Particulate Matter (PM2.5)

Exposure to ambient fine particulate matter (PM2.5) was found to produce vascular injury, possibly by activating platelets within days after exposure. The aim of this study was to investigate the modulatory effects of dietary saturated fatty acids on platelet mitochondrial respiratory parameters following short-term inhalational exposure to PM2.5. A total of 22 healthy male volunteers were recruited from the Research Triangle area of North Carolina. Platelets were isolated from fresh whole blood samples and mitochondrial respiratory parameters were measured using an extracellular flux analyzer. Intake of saturated fat was averaged from multiple 24-hr dietary recalls. Daily ambient PM2.5 concentrations were obtained from ambient air quality monitoring stations. Correlation and ANOVA were used in data analyses, along with the pick-a-point method and the Johnson-Neyman technique for probing moderation. After controlling for age and omega-3 index, the intake of dietary saturated fatty acids after reaching 9.3% or higher of the total caloric intake significantly moderated the associations between PM2.5 exposure and several platelet mitochondrial respiratory parameters. In conclusion, dietary saturated fatty acids above 9.3% of total caloric intake influenced the relationship between short-term PM2.5 exposure and platelet mitochondrial respiration. Further research is needed to understand these associations and their implications for cardiovascular health.

Rapid kinetics of changes in oxygen consumption rate in thrombin-stimulated platelets measured by high-resolution respirometry

Platelet activation plays a key role in normal haemostasis and pathological thrombosis. Platelet activation is rapid; within minutes of stimulation, platelets generate bioactive phospholipids, secrete their granule contents, activate integrins and aggregate together to form a haemostatic plug. These events are dependent on ATP synthesis. Mitochondrial function in platelets from healthy volunteers and patients with a range of diseases indicate an important role for oxygen consumption in oxidative phosphorylation in normal and pathological function. Platelets also consume oxygen during oxidation reactions, such as cyclooxygenase-dependent thromboxane A₂ synthesis. In this study, we used high-resolution respirometry to investigate rapid changes in oxygen consumption during platelet activation. We demonstrated a rapid, transient increase in oxygen consumption rate within minutes of platelet stimulation by the physiological activator, thrombin. This was partly inhibited by aspirin and by oligomycin. This shows that high resolution respirometry can provide information regarding rapid and dynamic changes in oxygen consumption during platelet activation.

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High resolution respirometry can be used to investigate the rapid kinetics of changes in platelet oxygen consumption rate.

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Thrombin triggers a rapid, transient increase in platelet oxygen consumption rate.

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Aspirin and oligomycin partially inhibit the increased oxygen consumption rate.

An explanation of how migraine headaches can trigger relapse in systemic lupus erythematosus

Except for a few diseases of molecular mimicry such as rheumatic fever, post-streptococcal glomerulonephritis in children, and gluten-sensitive enteropathy, the cause of autoimmune diseases is unknown. Most autoimmune diseases are remitting-relapsing and the pathophysiology of either the initial attack or subsequent relapses is a mystery. Migraine headaches in systemic lupus erythematosus patients are statistically associated with disease activity, i.e. the patients with bad lupus are the ones who get migraine. T lymphocytes reactive against self are normally suppressed by immunoregulatory T cells (Tregs), but suppression can be broken by CD28 ligation of Tregs. This raises intracellular levels of H2O2, which is a second messenger in the CD28 signaling cascade. Migraine headaches are often accompanied by systemic platelet activation and a brief but intense platelet oxidative burst which raises extracellular H2O2 levels to the point where H2O2 diffusing passively across lymphocyte cell membranes can raise intracellular H2O2 sufficiently to turn off regulatory T cell function via the CD28 signaling cascade. Passive diffusion of H2O2 mimics the effect of H2O2 formation triggered by CD28 ligation. This eliminates the immunosuppressive hold of Tregs on self-reactive T cells and the development or worsening of autoimmune disease ensues spontaneously.

Effect of vitamin E on platelet enzymatic anti-oxidants in the patients of myocardial infarction

Effect of administration of 600 mg. vitamin E each day, for six days, was observed on activity of some of the anti-oxidant enzymes and levels of malondialdehyde (as an index of free radical mediated damage) in the platelets of patients reperfused after myocardial infarction. It has been found that vitamin E administration significantly lowers the level of malondialdehyde in the patients. Vitamin E administration increases the activities of anti oxidant enzymes (viz. superoxide dismutase, glutathione reductase and catalase) tested both in the patients and healthy controls. Vitamin E administration causes general stimulation of anti-oxidant enzyme activities both in healthy persons and the patients, however, lowering of lipid per-oxidation upon administration of vitamin E is specific for patients. These findings exhibit beneficial role of vitamin E administration in the management of the patients reperfused after myocardial infarction.

Cell integrity and mitochondrial function after Mirasol-PRT treatment for pathogen reduction of apheresis-derived platelets: Results of a three-arm in vitro study

BACKGROUND

Mirasol pathogen reduction technology (PRT) treatment uses riboflavin (vitamin B(2)) in combination with ultraviolet light (UV) to inactivate pathogens in platelet concentrates (PCs). This treatment has been reported to increase glycolytic flux, which could result from damage to mitochondria and/or increased ATP demand.

DESIGN

Triple-dose PCs were collected by the Trima Accel device. Immediately after splitting, single units were designated to Mirasol-PRT treatment (M), gamma irradiation (X) or remained untreated (C). Platelet (PLT) mitochondrial transmembrane potential (Deltapsi) was evaluated (JC-1 assay) as well as mitochondrial enzymatic activity (MTS assay). LDH release, p selectin expression, glucose/oxygen consumption and lactate production rates were quantified and compared among study groups during 7days of storage.

RESULTS

Immediately after PRT treatment, no significant changes were found in JC-1 signal, MTS activity, and LDH release indicating that PRT treatment did not alter functional/structural cell or mitochondrial integrity as evidenced by LDH release comparable to untreated study groups. In parallel to significantly higher p selectin expression, treated PLTs exhibited significantly accelerated oxygen and glucose consumption rates associated with increased acidity due to higher lactate production rates throughout storage. Despite larger cell populations with depolarized Deltapsi particularly at days 5 and 7, mitochondrial reduction activity of M units as measured by the MTS assay was maintained and appeared to be up-regulated relative to untreated and irradiated controls.

CONCLUSION

Mirasol-PRT treated PLTs increased both glycolytic flux as well as respiratory/enzymatic mitochondrial activity. An increased demand for ATP due to increased alpha granule degranulation may be the driving force for these observations.

Effect of vitamin E on the platelet xanthine oxidase and lipid peroxidation in the patients of myocardial infarction

Platelets play important role in precipitating ischaemic myocardial syndromes in many ways. One of the consequences of ischaemic diseases is excessive generation of oxygen derived free radicals that have numerous pathophysiological consequences. Platelet pro-oxidant enzyme, xanthine oxidase is one of the sources of generation of free radicals. In the present paper, we report the effect of administration of vitamin E along with aspirin on the levels of platelet xanthine oxidase and extent of free radical mediated damage in the patients reperfused after myocardial infarction.Our findings show that administration of 400 mg. vitamin E for six days along with 80 mg. aspirin has an excellent anti-oxidant effect as evidenced by reduced platelet xanthine oxidase activity and lowering of malondialdehdye (MDA) levels which is an index of the extent of free radical mediated damage.

Opsonized-zymosan induces a respiratory burst in human blood platelets

Opsonized-zymosan-stimulated polymorphonuclear cells show a cyanide-insensitive oxygen consumption. We have investigated whether opsonized-zymosan could induce similar metabolic change in human blood platelets. Preparation of intact human blood platelets, obtained by separation through a Ficoll layer (23% w/v) were challenged with opsonized-zymosan. The polymorphonuclear cell contamination was less than 1/10(8) platelets. The opsonized-zymosan-stimulated platelets showed an increase of oxygen consumption. The mean of oxygen burst measured by a polarographic method with a Clark electrode was 11 nmole/10(9) platelets/min (S.E.M. 4; n = 15). The duration of the burst was 2 min. Unstimulated platelets did not show the oxygen burst. The inhibitors of respiratory chain and prostaglandin synthesis completely abolished the oxygen consumption by opsonized-zymosan-stimulated platelets. The simultaneous addition of NADH (1 mM) and opsonized-zymosan induced a burst of oxygen consumption, which occurred after a variable lag phase (10-12 min) from the stimulation, also in the presence of inhibitors. This burst, which lasted about 1 min, amounted to 10 nmole/10(9) platelets/min (S.E.M. 2; n = 15) and it was higher in the presence of NAN3, a catalase inhibitor. Zymosan treated with hydrazine or heated plasma (56 degrees C) did not cause increased oxygen consumption. Inulin or inulin-treated serum did not stimulate platelets. In these experimental conditions some NADH disappeared, as shown by isotachophoresis. The results demonstrated that an immunological stimulus may activate a membrane-linked cyanide-insensitive oxygen metabolizing system.

Oxygen consumption of human blood platelets. II. Effect of inhibitors on thrombin-induced oxygen burst

The effect of selected inhibitors on the thrombin-stimulated burst and the basal oxygen consumption of washed human platelets were investigated and compared with inhibition of the release reaction. Cyanide (0.2 mM) caused complete inhibition of the basal respiration, but only 15% inhibition of the thrombin-stimulated burst of oxygen consumption. Similar differential inhibitory effects were observed with oligomycin, antimycin, rotenone and N-ethylmaleimide. Prostaglandin E1 (0.03 mM) and acetylsalicylic acid (0.8 mM) had little effect on basal respiration, but inhibited the thrombin-stimulated burst of oxygen consumption. N-Ethylmaleimide (0.4 mM) inhibited the release of calcium from platelets by 90%, while prostaglandin E1, acetylsalicylic acid and the above mitochondrial inhibitors caused no more than 30% inhibition of the release reaction. Our results provide evidence that basal respiration and a portion of the thrombin-stimulated burst of oxygen consumption are involved in respiratory chain phosphorylation, and that this component of the thrombin-stimulated burst may be coupled to the maintenance of the release reaction.