Effects of short-term exercise on female platelet function during different phases of the menstrual cycle

Exercise Training Improves Mitochondrial Bioenergetics of Natural Killer Cells

INTRODUCTION

Mitochondrial bioenergetics is critical for immune function in natural killer (NK) cell. Physical exercise modulates NK cell functionality, depending on the intensity and type of exercise. This study elucidates how interval and continuous exercise regimens affect the phenotypes and mitochondrial bioenergetics of NK cells.

METHODS

Sixty healthy sedentary males were randomly assigned to engage in either high-intensity interval training (HIIT, 3-min intervals at 80% and 40% maximal O2, n = 20; age, 22.2 yr; body mass index [BMI], 24.3 kg·m-2) or moderate-intensity continuous training (MICT, sustained 60% maximal O2, n = 20; age, 22.3 yr; BMI, 23.3 kg·m-2) for 30 min·d-1, 5 d·wk-1 for 6 wk or were assigned to a control group that did not receive exercise intervention (n = 20; age, 22.6 yr; BMI, 24.0 kg·m-2). Natural killer cell phenotypes, granule proteins, and mitochondrial oxidative stress/oxidative phosphorylation after graded exercise test (GXT) were measured before and after the various interventions.

RESULTS

Before the intervention, the GXT increased the mobilization of CD57+NK cells into the blood and elevated mitochondrial matrix oxidant burden (MOB) in NK cells, Following the 6 wk of interventions, both HIIT and MICT (i) diminished mobilization of CD57+NK cells into the blood and depressed mitochondrial MOB level in NK cells immediately after GXT, (ii) increased mitochondrial membrane potential and cellular perforin and granzyme B levels in NK cells, and (iii) enhanced the maximal and reserve O2 consumption rates and heightened bioenergetic health index in NK cells. In addition, HIIT increased maximal work rate than those of MICT.

CONCLUSIONS

Either HIIT or MICT increases the expressions of cytotoxic granule proteins and depresses mitochondrial MOB elevated by GXT, along with improving mitochondrial bioenergetic functionality in NK cells. Moreover, HIIT is superior to MICT in improving aerobic capacity.

Platelet Activation Favours NOX2-Mediated Muscle Damage in Elite Athletes: The Role of Cocoa-Derived Polyphenols

Mechanisms of exercise-induced muscle injury with etiopathogenesis and its consequences have been described; however, the impact of different intensities of exercise on the mechanisms of muscular injury development is not well understood. The aim of this study was to exploit the relationship between platelet activation, oxidative stress and muscular injuries induced by physical exercise in elite football players compared to amateur athletes. Oxidant/antioxidant status, platelet activation and markers of muscle damage were evaluated in 23 elite football players and 23 amateur athletes. Compared to amateurs, elite football players showed lower antioxidant capacity and higher oxidative stress paralleled by increased platelet activation and muscle damage markers. Simple linear regression analysis showed that sNOX2-dp and H₂O₂, sCD40L and PDGF-bb were associated with a significant increase in muscle damage biomarkers. In vitro studies also showed that plasma obtained from elite athletes increased oxidative stress and muscle damage in human skeletal muscle myoblasts cell line compared to amateurs’ plasma, an effect blunted by the NOX2 inhibitor or by the cell treatment with cocoa-derived polyphenols. These results indicate that platelet activation increased muscular injuries induced by oxidative stress. Moreover, NOX2 inhibition and polyphenol extracts treatment positively modulates redox status and reduce exercise-induced muscular injury.

Associations of long-term exposure to air pollutants, physical activity and platelet traits of cardiovascular risk in a rural Chinese population

BACKGROUND

Long-term exposure to air pollutants relate to increase risk of cardiovascular diseases that may be partially attributable to platelet dysfunction. Physical activity (PA) may attenuate inflammation to modulate platelet function. Thus, this study aimed to evaluate associations of air pollutants and PA with platelet traits of cardiovascular risk.

METHODS

A total of 31,282 participants were obtained from the Henan Rural Cohort (n = 39,259). The concentrations of particulate matter (PM) (PM with an aerodynamic diameter ≤1.0 μm (PM₁), ≤2.5 μm (PM_2.5), or ≤10 μm (PM₁₀)) and nitrogen dioxide (NO₂) were evaluated by using a spatiotemporal model incorporated into satellites data. Independent and combined effects of air pollutants and PA on platelet traits were analyzed by linear mixed models.

RESULTS

Positive associations of PM₁, PM_2.5, PM₁₀ and NO₂ with platelet indices (mean platelet volume (MPV), platelet distribution width (PDW) and platelet large cell ratio (P-LCR), the MPV to platelet counts (PLT) ratio (MPVP)) were observed, whereas negative associations of PM₁₀ and NO₂ with PLT or plateletcrit (PCT) were observed; negative interaction effects of PM_2.5 PM₁₀ and NO₂ and PA on MPV, PDW or P-LCR were found; negative interaction effects of PM₁, PM_2.5 and PM₁₀ and PA on PCT were observed.

CONCLUSIONS

Long-term exposure to air pollutants were related to increase platelet size and these associations were attenuated by increased PA, implying that PA is a costless and affordable method to decrease adverse effects on platelet traits in relation to air pollutants.

High-Intensity Interval Training Improves Erythrocyte Osmotic Deformability

INTRODUCTION

Physical exercise or hypoxic exposure influences erythrocyte susceptibility to osmotic stress, and the aquaporin 1 (AQP1) facilitates the transport of water in erythrocytes. This study investigated whether high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) affect erythrocyte osmotic deformability by modulating AQP1 function under hypoxic stress.

METHODS

Forty-five healthy sedentary males were randomized to engage in either HIIT (3-min intervals at 40% and 80% V˙O2 reserve, n = 15) or MICT (sustained 60% V˙O2 reserve, n = 15) on a bicycle ergometer for 30 min·d, 5 d·wk for 6 wk, or to a control group that did not perform any exercise (n = 15). All subjects were analyzed with osmotic gradient ektacytometry for assessing erythrocyte membrane stability and osmotic deformability after hypoxic exercise (HE) (100 W under 12%O2 for 30 min).

RESULTS

Before the intervention, HE increased the shear stress at 50% of maximal elongation (SS1/2) and the ratio of SS1/2 to maximal elongation index (SS1/2/EImax) on erythrocytes pretreated with 50 Pa of shear stress for 30 min and diminished HgCl2-depressed osmolality at 50%EImax (Ohyper). However, both HIIT and MICT for 6 wk diminished the elevations of erythrocyte SS1/2 and SS1/2/EImax caused by HE. Moreover, HIIT also increased contents of erythrocyte AQP1 proteins while enhancing HgCl2-depressed Ohyper and area under elongation index-osmolarity curve after HE. Additionally, changes in erythrocyte AQP1 contents were associated with changes in HgCl2-depressed erythrocyte Ohyper and area under elongation index-osmolarity curve.

CONCLUSIONS

Acute HE reduces erythrocyte membrane stability, whereas either HIIT or MICT attenuates the depression of erythrocyte membrane stability by HE. Moreover, HIIT increases the AQP1 content and facilitates the HgCl2-mediated osmotic deformability of erythrocytes after HE.

Effects of normoxic and hypoxic exercise training on the bactericidal capacity and subsequent apoptosis of neutrophils in sedentary men

Phagocytosis and oxidative burst are essential mechanisms of innate immunity by which neutrophils eliminate invading pathogens. Afterwards, phagocytic neutrophils are dissipated by facilitating apoptosis to control inflammation. This study investigates how exercise training with or without hypoxic exposure affects the bactericidal activity and subsequent apoptosis of neutrophils following strenuous exercise. A total of 60 healthy, sedentary men were randomly divided into four groups (n = 15 in each group), who were exposed to 21% O₂ [normoxic control (NC)] or 15% O₂ [hypoxic control (HC)] at rest or were trained at 50% of peak work rate at 21% O₂ [normoxic training (NT)] or 15% O₂ [hypoxic training (HT)] for 30 min/day, 5 days/week for 4 weeks. Before the intervention, acute strenuous exercise (SE) enhanced the phagocytosis of Escherichia coli (E. coli) by neutrophils and the release of neutrophil oxidant products in response to E. coli, accompanied by increases in the expression of adhesion molecules (CD62L, CD11b, and CD11a), an opsonic receptor (FcγIIIBR), and complement receptors (C1qRp and CD5aR) on neutrophils. Subsequently, the SE facilitated caspase-3 activation and phosphatidylserine exposure in E. coli-stimulated neutrophils. Furthermore, 4 weeks of HT promoted the expressions of adhesion molecules and opsonic/complement receptors on neutrophils, and it also augmented the bactericidal and apoptotic activities of neutrophils at rest or after SE. However, NT, HC, and NC did not influence these neutrophil-related immune responses to strenuous exercise. Therefore, we conclude that the HT regimen effectively promotes the bactericidal capacity of neutrophils, and facilitates their subsequent apoptosis both at rest and following SE.

Aerobic exercise training lowers platelet reactivity and improves platelet sensitivity to prostacyclin in pre- and postmenopausal women

Essentials It is unknown how regular exercise affects platelet function after menopause. We studied the effect of 3-months of high-intensity exercise in pre- and postmenopausal women. Platelet sensitivity to the inhibitory effect of arterially infused prostacyclin was increased. Reduced basal platelet reactivity was seen in the premenopausal women only.

SUMMARY

Background The risk of atherothrombotic events increases after the menopause. Regular physical activity has been shown to reduce platelet reactivity in younger women, but it is unknown how regular exercise affects platelet function after the menopause. Objectives To examine the effects of regular aerobic exercise in late premenopausal and recent postmenopausal women by testing basal platelet reactivity and platelet sensitivity to prostacyclin and nitric oxide. Methods Twenty-five sedentary, but healthy, late premenopausal and 24 matched recently postmenopausal women, mean (95% confidence interval) 49.1 (48.2-49.9) and 53.7 (52.5-55.0) years old, participated in an intervention study: 3-month high-intensity supervised aerobic spinning-cycle training (1 h, × 3/week). Basal platelet reactivity was analyzed in platelet-rich plasma from venous blood as agonist-induced % aggregation. In a subgroup of 13 premenopausal and 14 postmenopausal women, platelet reactivity was tested ex vivo after femoral arterial infusion of prostacyclin, acetylcholine, a cyclooxygenase inhibitor, and after acute one-leg knee extensor exercise. Results Basal platelet reactivity (%aggregation) to TRAP-6 (1 μm) was higher in the postmenopausal, 59% (50-68), than the premenopausal women, 45% (35-55). Exercise training reduced basal platelet reactivity to collagen (1 μg mL-1 ) in the premenopausal women only: from 63% (55-71%) to 51% (41-62%). After the training intervention, platelet aggregation was more inhibited by the arterial prostacyclin infusion and the acute exercise in both premenopausal and postmenopausal women. Conclusions These results highlight previously unknown cardioprotective aspects of regular aerobic exercise in premenopausal and postmenopausal women, improving their regulation of platelet reactivity through an increased platelet sensitivity to prostacyclin, which may counterbalance the increased atherothrombotic risk associated with the menopause.

High-intensity Interval Training Improves Mitochondrial Function and Suppresses Thrombin Generation in Platelets undergoing Hypoxic Stress

This study elucidates how high-intensity interval training (HIT) and moderate-intensity continuous training (MCT) affect mitochondrial functionality and thrombin generation (TG) in platelets following hypoxic exercise (HE, 100 W under 12% O₂ for 30 min). Forty-five healthy sedentary males were randomized to engage either HIT (3-minute intervals at 40% and 80%VO_2max, n = 15) or MCT (sustained 60%VO_2max, n = 15) for 30 minutes/day, 5 days/week for 6 weeks, or to a control group (CTL, n = 15) that did not received exercise intervention. Before the intervention, HE (i) reduced the ATP-linked O₂ consumption rate (OCR), the reserve capacity of OCR, and the activities of citrate synthase (CS) and succinate dehydrogenase (SDH), (ii) lowered mitochondrial membrane potential (MP) and elevated matrix oxidant burden (MOB) in platelets, and (iii) enhanced dynamic TG in platelet-rich plasma (PRP), which responses were attenuated by pretreating PRP with oligomycin or rotenone/antimycin A. However, 6-week HIT (i) increased mitochondrial OCR capacity with enhancing the CS and SDH activities and (ii) heightened mitochondrial MP with depressing MOB in platelets following HE, compared to those of MCT and CTL. Moreover, the HIT suppressed the HE-promoted dynamic TG in PRP. Hence, we conclude that the HIT simultaneously improves mitochondrial bioenergetics and suppresses dynamic TG in platelets undergoing hypoxia.

Effects of Physical (In)activity on Platelet Function

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

Exercise-induced changes in inflammatory processes: Implications for thrombogenesis in cardiovascular disease

Sedentary lifestyle is a risk factor and a strong predictor for chronic disease and premature death. Low-grade inflammation has been proved a key player in the pathogenesis of cardiovascular disease. Inflammatory processes have been also involved in maintaining the balance between coagulation and fibrinolysis. In addition, an inverse linear dose-response relation between physical activity and mortality risks has also been reported. However, the favorable effects of structured exercise programs and the independent contribution of physical activity to cardiovascular risk are still under investigation. In response to heavy exercise, interleukin-6 (IL-6) is secreted by contracting skeletal muscles, followed by an acute reactant release of C-reactive protein (CRP). Both CRP and IL-6 can stimulate monocyte tissue factor production, provoke platelet hyperreactivity, promote fibrinogen biosynthesis, and enhance microparticle formation and erythrocyte aggregability, thus triggering prothrombotic state. By contrast, regular exercise and physical activity are protective against all-cause mortality through suppressing pro-inflammatory cytokine production, enhancing anti-inflammatory mediators and antioxidant development, and promoting fibrinolytic activity. Low-load resistance exercise also plays an advantageous role in thrombogenesis by reducing inflammatory processes and potentiating fibrinolytic features. In the present review article, we provide an overview of the impact of different modes and intensities of physical activity on vascular inflammation and thrombogenesis.

Effects of selective cyclooxygenase isoform inhibition on systemic prostacyclin synthesis and on platelet function at rest and after exercise in healthy volunteers

To test the hypothesis that selective inhibition of cyclooxygenase (COX)-2 would result in exercise-induced platelet activation by causing a shift in the endogenous thromboxane (TX)/prostacyclin balance, a double blind, randomized study comparing aspirin (300 mg/d) with rofecoxib (25 mg/d) (cross-over design, 14 days washout between treatments) in n = 10 trained healthy volunteers was carried out. Physical exercise resulted only in a minor platelet activation, as reflected by the expression of basal or ADP-stimulated platelet activation markers or basal plasma concentrations of TXB(2). Aspirin significantly reduced TXB(2) in plasma while rofecoxib significantly increased TXB(2) in urine. Although no increase in systemic prostacyclin concentration was observed, there was a significant exercise-related increase in both platelet cAMP and cGMP without any drug-related effects. It is concluded that, in trained healthy volunteers, selective inhibition of COX-1 (aspirin) or COX-2 (rofecoxib) does not affect systemic prostacyclin synthesis after physical exercise. However, our data do not exclude the possibility that in subjects at risk for atherothrombotic complications (e.g. patients with advanced atherosclerotic disease) COX-2 inhibitors may result in platelet activation by inhibiting endothelial prostacyclin formation.

Exercise intensity: platelet function and platelet-leukocyte conjugate formation in untrained subjects

INTRODUCTION

Strenuous and exhaustive exercise intensifies platelet activity as shown in the literature but effects of moderate exercise are still in discussion. The present study investigated effects of two different standardised exercise intensities controlled by individual anaerobic threshold (IAT) on platelet function and conjugate formation.

METHODS

20 healthy male non-smokers underwent two exercises at 80% (moderate) of IAT which corresponded to about 57% of peak oxygen consumption (peak VO(2)) in our subjects and 100% (strenuous) of IAT, corresponding to about 69% peak VO(2). Blood samples were taken after 30 min rest and immediately after exercise. CD62P expression and differentiated platelet-leukocyte conjugates (CD45, CD14, CD41) as well as microparticles and platelet-platelet aggregates were detected flow cytometrically with and without TRAP-6-stimulation.

RESULTS

CD62P expression and the number of aggregates were increased (P< or =0.05) after exercise in the TRAP-stimulation experiment independent of exercise intensity. The number of platelet-granulocyte (rest 5.7+/-1.8 to post 8.1+/-1.7 (80%) vs. 6.2+/-1.9 to 10.3+/-2.0 (100%)), platelet-monocyte (5.3+/-3.6 to 8.5+/-3.7 (80%) vs. 7.4+/-3.5 to 11.7+/-4.8 (100%)), and platelet-lymphocyte conjugates (4.4+/-1.2 to 6.4+/-1.3 (80%) vs. 4.6+/-1.7 to 7.8+/-1.8% positive cells (100%)) were also higher after both exercises but increased significantly weaker (P< or =0.05) after moderate exercise. These results were confirmed by the TRAP-stimulation experiment.

CONCLUSION

Although moderate exercise led to an increase in platelet reactivity and platelet-leukocyte conjugate formation the changes in conjugate formation were significantly weaker compared to strenuous exercise. Therefore it is recommended that submaximal endurance performance should be individually developed in order for everyone to be able to carry out normal daily activities and also to exercise well below the IAT.

A systematic review of the effects of acute psychological stress and physical activity on haemorheology, coagulation, fibrinolysis and platelet reactivity: Implications for the pathogenesis of acute coronary syndromes

Physical activity and psychological stress are two potential triggers for the onset of acute coronary syndromes (ACS). To examine the mechanisms underlying this association, we systematically reviewed the literature to determine the effects of acute psychological stress and physical activity on haemorheology and haemostasis. Studies examining the haemorheological and haemostatic response to an acute bout of physical activity (i.e. <60 min) or laboratory psychological stress task were eligible for inclusion. The experimental evidence, although compromised by various methodological weaknesses, suggests that low and moderate intensity physical activity may be cardio-protective through beneficial effects on fibrinolytic system. High levels of physical activity, and psychological to a lesser extent, have been consistently associated with robust changes in haemorheology and haemostasis. Such findings imply that such activities may have the potential to trigger the onset of ACS, although in reality this may be limited sedentary individual and/or those with pre-existing vascular disease. In addition, the data also suggest that individuals may be at a greatest risk of stress-induced thrombogenesis in the period immediately following physical activity or psychological stress, rather than during the activity per se. In conclusion, psychological stress and physical activity may act as potential triggers for the onset of ACS via effects on haemostasis and haemorheology.

Exercise prescription and thrombogenesis

Lifestyle habits, such as exercise, may significantly influence risk of major vascular thrombotic events. The risk of primary cardiac arrest has been shown to transiently increase during vigorous exercise, whereas regular moderate-intensity exercise is associated with an overall reduced risk of cardiovascular diseases. What are the mechanisms underlying these paradoxical effects of vigorous exercise versus exercise training on thrombotic modification? This review analyzes research regarding effects and their underlying mechanisms of acute exercise, endurance training, and deconditioning on platelets, coagulation, and fibrinolysis. Evidence suggests that (i) light, acute exercise ( < or = 49% VO(2 max)) does not affect platelet reactivity and coagulation and increases fibrinolytic activity; (ii) moderate, acute exercise (50 to approximately 74% VO(2 max)) suppresses platelet reactivity and enhances fibrinolysis, which remains unchanged in the coagulation system; and, (iii) strenuous, acute exercise ( > or = 75% VO(2 max)) enhances both platelet reactivity and coagulation, simultaneously promoting fibrinolytic activity. Therefore, moderate exercise is likely a safe and effective exercise dosage for minimizing risk of cardiovascular diseases by inducing beneficial anti-thrombotic changes. Moreover, moderate-intensity exercise training reduces platelet reactivity and enhances fibrinolysis at rest, also attenuating enhanced platelet reactivity and augmenting hyper-fibrinolytic activity during strenuous exercise. However, these favorable effects of exercise training on thrombotic modification return to a pre-training state after a period of deconditioning. These findings can aid in determining appropriate exercise regimes to prevent early thrombotic events and further hinder the cardiovascular disease progression.

Aggregation and Activation of Blood Platelets in Exercise and Training

This article presents an overview of the progress that has been made in recent years in our understanding of the interaction between exercise and platelets in health and disease. Although platelets are important in normal haemostasis, recent evidence emphasises the pivotal role of abnormal platelet function in acute coronary artery diseases, myocardial infarction, unstable angina and stroke. In light of the positive health benefits of exercise, interest has been heightened on the association between exercise and platelet aggregation and function, not only in normal healthy subjects but also in patients. However, the study of exercise effects on blood platelets are highly contentious because of the fact that the analytical methods employed to study platelets are bedevilled by numerous methodological problems. While exercise effects on platelet aggregation and function in healthy individuals have been extensively examined, the evidence reported has been conflicting. Somewhat less contradictory are the results generated from studies in patients with coronary heart disease, as the preponderance of evidence available would strongly suggest that platelet aggregation and function are increased with exercise. Several drugs are known to influence platelet aggregation and function, the most examined among these medications is aspirin (acetylsalicylic acid). However, aspirin appears to be ineffective to attenuate exercise-induced increases in platelet aggregation and activation. Few studies are available on the effect of training on blood platelets and the exact effects of exercise training on platelet activation and function is not as yet known. This lack of information makes further studies particularly important, in order to clarify whether there are favourable effects of exercise training on platelet aggregation and function in health and disease.

Effects of exercise on platelet and aortic functions in aged rats

AIM AND METHODS

To assess age- and exercise-related changes in platelet aggregation, we measured the magnitude of platelet aggregation with a four-channel aggregometer, plasma and aortic polyunsaturated fatty acids by gas chromatography and related prostanoids with a reagent kit in young and aged non-exercised and in aged exercised rats.

RESULTS

Platelet aggregation in platelet-rich plasma induced by ADP (5 microm) in the primary wave increased with age. In the non-exercised groups, the basal levels of thromboxane B2 in platelet-rich plasma increased in aged rats compared with young rats. In aged exercised rats, the basal levels of 6-keto-prostaglandin F1alpha in platelet-rich plasma were stimulated and those of thromboxane B2 were depressed, compared with non-exercised aged rats. The plasma levels of eicosapentaenoic acid and docosahexaenoic acid increased with age. Only aortic eicosapentaenoic acid in the aged group increased by exercise. In the aged non-exercised and exercised groups, the aortic, but not the plasma, levels of eicosapentaenoic acid correlated inversely with the basal levels of thromboxane B2 in platelet-rich plasma (r = -0.53, P < 0.05) and associated negatively with the magnitudes of platelet aggregation induced by ADP (5 microm) (r = -0.47, P < 0.05).

CONCLUSION

These findings suggest that exercise in aged rats increases aortic eicosapentaenoic acid concentrations, which in turn depress the basal levels of thromboxane, B2 in platelet-rich plasma to modulate platelet aggregation.

Strenuous, acute exercise affects reciprocal modulation of platelet and polymorphonuclear leukocyte activities under shear flow in men

Vigorous exercise transiently increases the risk of primary cardiac arrest. The reciprocal modulation of platelet and polymorphonuclear leukocyte (PMN) activities is important in the pathogenesis of thrombosis. This study investigates how strenuous, acute exercise affects platelet-PMN reciprocal modulation by closely examining 18 sedentary men who exercised strenuously on a bicycle ergometer. Shear-induced platelet activation, PMN interaction with surface-adherent platelets under shear flow, and PMN-dependent inhibition of platelet activation were measured both before and immediately after exercise. Analytical results can be summarized as follows: (i) shear-induced platelet adhesion on fibronectin-coated surface as well as ADP-induced release of platelet soluble P-selectin release and elevation of [Ca2+]i significantly increases after strenuous exercise; (ii) strenuous exercise is associated with higher velocity and percentage of rolling PMNs and lower numbers of PMNs remaining bound to surface-adherent platelets under shear flow than at rest; (iii) PMN-dependent inhibition of platelet [Ca2+]i elevation and soluble P-selectin release after strenuous exercise is much greater than that at rest; and (iv) strenuous exercise increases PMN-derived nitric oxide metabolite level and reduces oxidized low-density lipoprotein-promoted interaction between platelets and PMNs. Therefore, we conclude that platelet activity may be sensitized by strenuous exercise. However, strenuous exercise can also simultaneously enhance the antiplatelet effect of PMNs. The finding provides a new insight into the negative feedback of PMNs against exercise-evoked platelet-related thrombotic risk.

The effect of submaximal exercise on platelet aggregation during late follicular and midluteal phases in women

INTRODUCTION

The key role of platelets in the pathogenesis of atherosclerosis prompted considerable interest on the effect of physical exercise on platelets. Due to probable menstrual cycle variations, only a limited number of investigations have studied the effect of exercise on platelets in women. The study was undertaken to determine the effect of acute submaximal exercise on platelet aggregation and thromboxane A(2) (TxA(2)) formation in females during their late follicular and midluteal phases.

MATERIALS AND METHODS

Twelve healthy, sedentary, female volunteers performed 15 min of cycling exercise at a workload that increased their heart rate to 75% of maximal in two phases of the menstrual cycle. The maximal rate of ADP and collagen-induced platelet aggregation was evaluated on citrated whole blood using the impedance technique. Thrombin-induced thromboxane A(2) formation was evaluated by the measurement of thromboxane B(2) (TxB(2)) level by enzyme-linked immunoassay.

RESULTS AND CONCLUSION

No significant difference was found between maximal rates of platelet aggregation measured in the different phases of menstrual cycle. Collagen-induced platelet aggregation and platelet count increased significantly after the exercise in both late follicular and midluteal phases (p<0.05). ADP-induced platelet aggregation did not change due to the exercise during the two phases of menstrual cycle. The thromboxane B(2) level measured in the midluteal phase was significantly higher than that measured in late follicular phase at rest. It was significantly increased after the exercise in late follicular phase while no significant difference was found between pre-exercise and postexercise levels in the midluteal phase. The differences in thromboxane A(2) formation were pointed out in the changes in platelet reactivity status. The inhibitory systems for platelets need further investigations. Our findings support the idea that menstrual variations do not have pronounced and acute effects on both platelet aggregation and response of platelets to acute exercise.

Physiological changes in platelet aggregation and nitric oxide levels during menstrual cycle in healthy women

Hormonal levels, mainly those of estrogens, protect women from the appearance of cardiovascular diseases by an increasing nitric oxide (NO) activity. NO is an endogenous vasodilator and antiaggregating substance. We decided to investigate platelet function and plasma levels of nitric oxide during preovulatory and midluteal phases in young and healthy women with normal menstrual cycles (MCs). Nine young, healthy female subjects had recorded three consecutive MCs before entering this program. Platelet-rich plasma (PRP) was used for the determination of platelet aggregation and NO measurements. Moreover, platelet sensitivity to the inhibitory effect of exogenous NO was tested. The EC(50) of collagen showed no differences between the preovulatory (1.36+/-0.16 microg/mL) and the midluteal (1.31+/-0.08 microg/mL; P, NS) phases. However, the EC(90) during the preovulatory phase was higher (2.05+/-0.2 microg/mL) than during the midluteal phase (1.8+/-0.6 microg/mL). Plasma levels of NO were lower during the preovulatory phase (19.1+/-2 microM) in comparison to the midluteal phase (20.9+/-2.3 microM). Interestingly, the exogenous amount of NO to produce at least half of the inhibition of an EC(90) collagen-induced aggregation was higher at the preovulatory phase (323.3+/-60.9 nM) than during the midluteal phase (240.0+/-37.5 nM; P, NS). We propose that during the follicular phase platelets rather use NO produced by the endothelium; therefore, it is necessary to add more agonist to activate those, but it results in higher consumption of circulating NO, whereas during luteal-phase platelets are not able to use NO, requiring lower amounts of agonist and thus resulting in higher plasma levels of NO. This is an interesting fact in research on cardiovascular diseases of women.

Strenuous but not moderate exercise increases the thrombotic tendency in healthy sedentary male volunteers

We have investigated the effect of moderate and strenuous exercise on experimental arterial thrombus formation in men. Thrombogenesis was measured in 15 sedentary healthy male volunteers at rest or immediately after two standardized exercise tests performed for 30 min on a bicycle ergometer. The exercises were performed at a constant load corresponding to either 50 or 70% maximal oxygen uptake. Thrombus formation was induced ex vivo by exposing a collagen-coated coverslip in a parallel plate perfusion chamber to native nonanticoagulated blood for 3 min. The shear rate at the collagen surface was 2,600 s(-1). Platelet and fibrin deposition was quantified by immunoenzymatic methods. The results show that moderate exercise did not affect arterial thrombus formation. In contrast, platelet thrombus formation on collagen was increased on the average by 20% after 30 min at 70% maximal oxygen uptake (P = 0.03). Fibrin deposition on collagen remained unchanged with exercise, regardless of its intensity. Thus, with the use of a clinically relevant human experimental model of thrombosis, the present study suggests that exercise of heavy intensity may increase the risk for arterial thrombogenesis in sedentary young healthy male volunteers.

Effects of Welsh onion extracts on human platelet function in vitro

Welsh onion has been consumed for prevention of cardiovascular disorders. However, its underlying mechanisms are still unclear. This study investigated whether Welsh onion extracts can alter human platelet function (ie, platelet adhesion, aggregation, and thromboxane release). To clarify the underlying mechanisms, we also measured the intracellular calcium ([Ca2+]i) and cyclic nucleotide levels in platelets. Our results showed that 1) boiled extracts directly induced platelet aggregation in a dose-dependent manner; 2) raw extracts inhibited platelet adhesion and ADP-evoked platelet aggregation, while boiled extracts enhanced them; 3) raw green extract suppressed ADP-stimulated platelet [Ca2+]i elevation and thromboxane production, whereas boiled green extract enhanced them; 4) raw green extract elevated platelet cAMP level, whereas boiled green extract had no effect on cAMP level. Furthermore, the boiled green extract, but not the raw extract, induced pronounced platelet morphological changes. In conclusion, raw extracts of Welsh onion inhibit platelet function in vitro while boiled extracts activate platelets.

Chronic consumption of raw but not boiled Welsh onion juice inhibits rat platelet function

Welsh onion has been consumed for prevention of cardiovascular disorders. To study if it has antithrombotic effects, 9-wk-old male Sprague-Dawley rats were studied. Some rats were fed raw or boiled Welsh onion juice (2 g. kg(-1). d(-1)) for 4 wk, and the remaining acted as the control. Before and after feeding, their systolic blood pressure was measured by a tail-cuff method. Two days after the treatment period, tail bleeding time, platelet function (including platelet aggregation and adhesion), plasma levels of prostaglandins, and platelet cyclic nucleotide levels were determined. In comparison to the control, raw Welsh onion juice consumption significantly (1) lowered resting systolic blood pressure; (2) prolonged the bleeding time; (3) diminished platelet adhesion on a fibrinogen-coated surface, ADP-evoked platelet aggregation and ADP-stimulated thromboxane release; (4) elevated the concentration of cyclic AMP, but not cyclic GMP, in platelets; (5) increased the plasma level of 6-keto-prostaglandin F(1alpha), the stable prostacyclin metabolite, but not the plasma nitrite level. On the contrary, boiled Welsh onion juice consumption was totally ineffective. In conclusion, consuming raw Welsh onion juice, but not boiled juice, has blood pressure lowering and antithrombotic effects in rats. These effects may be mediated by PGI(2)-cAMP pathway.