The effect of the menstrual cycle and of decompression stress on arachidonic acid-induced platelet aggregation and on intrinsic platelet thromboxane production in women compared with men

Heterogeneity of platelets and their responses

There has been increasing recognition of heterogeneity in blood platelets and their responses, particularly in recent years, where next-generation technologies and advanced bioinformatic tools that interrogate "big data" have enabled large-scale studies of RNA and protein expression across a growing list of disease states. However, pioneering platelet biologists and clinicians were already hypothesizing upon and investigating heterogeneity in platelet (and megakaryocyte) activity and platelet metabolism and aggregation over half a century ago. Building on their foundational hypotheses, in particular Professor Marian A. Packham's pioneering work and a State of the Art lecture in her memoriam at the 2023 International Society on Thrombosis and Haemostasis Congress by Anandi Krishnan, this review outlines the key features that contribute to the heterogeneity of platelets between and within individuals. Starting with important epidemiologic factors, we move stepwise through successively smaller scales down to heterogeneity revealed by single-cell technologies in health and disease. We hope that this overview will urge future scientific and clinical studies to recognize and account for heterogeneity of platelets and aim to apply methods that capture that heterogeneity. Finally, we summarize other exciting new data presented on this topic at the 2023 International Society on Thrombosis and Haemostasis Congress.

Modulation of Platelet Functions Assessment during Menstruation and Ovulatory Phases

During menstruation, endometrial hemostasis is achieved by platelet aggregation, fibrin deposition, and thrombus formation that interact with local endocrine and immunological factors which cause termination of menstrual bleeding. Interactions between steroidal sex hormones and platelet functions are not well understood. The aim of this study was to evaluate the effect of platelet function during the menstrual cycle and luteal phase in women of reproductive age. The cross-sectional study on women of reproductive age included 44 healthy women. Platelet function was assessed by PFA-100TM analyzer with collagen/epinephrine and collagen/ADP cartridges during the menstrual cycle and luteal phase. There were no significant differences in platelet function between menstruation and ovulatory phase. Platelet activity in Arab collagen/epinephrine cartridge increased during menstruation compared to non-Arab ethnic subjects and no significant differences in platelet function were found when using collagen/ADP cartridge. This study suggested modulation in platelet functions during menstruation and luteal phase in women of reproductive age. Further studies, including a large number of subjects, platelet genetic and progesterone factors change in platelet clotting associated to menstrual cycle should be conducted.

Comparative analysis of obesity-related cardiometabolic and renal biomarkers in human plasma and serum

The search for biomarkers associated with obesity-related diseases is ongoing, but it is not clear whether plasma and serum can be used interchangeably in this process. Here we used high-throughput screening to analyze 358 proteins and 76 lipids, selected because of their relevance to obesity-associated diseases, in plasma and serum from age- and sex-matched lean and obese humans. Most of the proteins/lipids had similar concentrations in plasma and serum, but a subset showed significant differences. Notably, a key marker of cardiovascular disease PAI-1 showed a difference in concentration between the obese and lean groups only in plasma. Furthermore, some biomarkers showed poor correlations between plasma and serum, including PCSK9, an important regulator of cholesterol homeostasis. Collectively, our results show that the choice of biofluid may impact study outcome when screening for obesity-related biomarkers and we identify several markers where this will be the case.

The effect of menstrual cycle on platelet aggregation in reproductive-age women

Our aim was to assess the change in platelet activity along the menstrual cycle. We conducted a prospective observational study. The study group included 16 healthy women with regular menstrual cycles, which were compared to a control group of 14 healthy males. Exclusion criteria were age <18 years or >45 years, use of oral contraceptives or any other forms of hormonal therapy and medical disorders or medications that might affect platelet aggregation. Blood samples were taken from each of the women at four different phases of the menstrual cycle: day 1 +/- 1, day 7 +/- 1, day 14 +/- 1, and day 21 +/- 1. A single blood sample was taken from the males. Platelet aggregation was assessed in whole blood samples using the Multiplate analyzer with three different agonists (ADP, arachidonic acid (AA), and thrombin-receptor activating peptide (TRAP)). Platelet aggregation for each of the women at each of the phases of the menstrual cycle was expressed as the percentage change from the day 1 +/- 1 value. A total of 390 aggregation assays were performed. The mean aggregation activity was significantly higher in females compared with males, irrespective of the agonist used. For the TRAP and the ADP agonists, the relative platelet activity decreased along the menstrual cycle from day 1 towards day 21 and from day 7 towards day 21, respectively, although differences reached statistical significance only for day 21 (-12.4% +/- 3.2%, P < 0.05 for TRAP, and -9.5% +/- 3.9%, P < 0.05 for ADP). When using AA to induce platelet aggregation, the relative platelet activity was highest around the time of ovulation (11.0% +/- 4.7%) and was significantly lower on day 21 (-8.5% +/- 6.7%, P < 0.05). In conclusion, platelet aggregation activity is higher in females compared with males. The association between the phase of the menstrual cycle and platelet activity appears to vary with the type of agonist, but platelet aggregation is consistently lowest in the mid-luteal phase irrespective of the agonist used.

The formation of platelet–leukocyte aggregates varies during the menstrual cycle

Platelet-leukocyte aggregates are considered to play a significant role in blood coagulation and inflammatory processes. We hypothesized that hormonal changes during the menstrual cycle affect the formation of heterotypic aggregates and therefore may constitute cycle-dependent variations of the susceptibility for thromboembolic events and inflammatory disease. We therefore measured platelet-leukocyte interaction by the determination of platelet-leukocyte aggregates (PLA), platelet P-Selectin expression, and platelet fibrinogen receptor activation by PAC-1 binding in 20 healthy women during their menstrual cycle by flow cytometry. The number of platelet-granulocyte aggregates (PGA) and platelet-monocyte aggregates (PMA) was higher at ovulation compared to any other time-point of the menstrual cycle (p = 0.005, p = 0.022, respectively). Likewise, P-Selectin expression peaked on day 14 (p = 0.040). The course of PLA formation during the menstrual cycle followed the course of estrogen levels, strongly suggesting direct effects of estrogen on platelet-leukocyte interaction. The susceptibility to form platelet-leukocyte aggregates that are inducible in vitro by a suboptimal concentration of thrombin receptor activating peptide-6 decreased slightly during the transition from day 1 to 14 (p = 0.040). These data indicate that platelet function varies during particular phases of the normal menstrual cycle.

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.

Acute coronary syndromes: should women receive less antithrombotic medication than men?

A recent meta-analysis of all randomised trials assessing the efficacy and safety of glycoprotein IIb/IIIa agents with acute coronary syndromes showed that there was a significant interaction with sex. Explaining this difference requires an analysis of whether it has any pathophysiological basis, whether antithrombotic medications are indeed less efficacious in women in different clinical situations, and whether there are any specific reasons that may have led to the provocative results of the meta-analysis.

Relationship of arachidonic acid concentration to cyclooxygenase-dependent human platelet aggregation

Inhibition of ex vivo arachidonic acid (AA)-induced aggregation is a biomarker for the isotype selectivity of cyclooxygenase (COX) inhibitors since platelets express COX-1 but not COX-2. At low concentrations, there is broad inter- and intrasubject variability in AA-induced aggregation of platelets ex vivo. This study defined a concentration that reliably induces aggregation without overcoming inhibition by therapeutic aspirin therapy (ASA, 81-mg) treatment. Logistic regression analysis of ex vivo aggregation, induced with increasing concentrations of AA in platelet-rich plasma (PRP), estimated that platelets from > or = 90% of subjects would aggregate at > or = 1.5 mM AA (95% confidence interval [CI], 1.1, 2.1). A concentration of 1.6 mM AA failed to aggregate platelets from 26 healthy volunteers, who had previously aggregated at this concentration, following six daily oral doses of 81 mg of ASA. These data demonstrate that 1.6 mM AA reproducibly induces platelet aggregation in PRP from healthy volunteers without overcoming the antiplatelet effect of daily low-dose aspirin therapy.

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.

Alterations in platelet function during the ovarian cycle

Steroid hormones may profoundly influence hemostasis; for example, as discussed for hormone replacement therapy, pregnancy and, being less obvious, for the ovarian cycle. We investigated primary hemostasis parameters using a platelet function analyzer (PFA-100) during the follicular and luteal phases in 18 healthy young women without oral contraceptives. During the follicular phase, the mean closure time (CT) was 164.7 +/- 56.7 s, and it decreased to 130.2 +/- 30.6 s in collagen/epinephrine cartridges in the luteal phase (P = 0.0095). No significant difference could be found for CT values in collagen/adenosine diphosphate cartridges during the follicular phase as compared with the luteal phase (97.2 +/- 24.2 s versus 89.6 +/- 18.4 s, P = 0.174). Negative correlations between the CT values in collagen/epinephrine cartridges and von Willebrand factor from both phases of the cycle were found (follicular phase: r = -0.53; luteal phase: r = -0.54). Fibrinogen and fibrinogen degradation products were significantly increased in the luteal phase (2.49 +/- 0.62 g/l versus 2.05 +/- 0.59 g/l and 0.12 +/- 014 versus 0.04 +/- 0.04, P = 0.02 for both parameters) as compared with the follicular phase. No significant differences could be detected for plasminogen, plasmin-antiplasmin complex, prothrombin fragment 1 + 2 and D-dimer between the groups. This study indicates that platelet function is periodically altered during the ovarian cycle due to the influence of progesterone and estrogen on von Willebrand factor concentrations.

Clinical benefit of glycoprotein IIb/IIIa blockade with Abciximab is independent of gender: pooled analysis from EPIC, EPILOG and EPISTENT trials. Evaluation of 7E3 for the Prevention of Ischemic Complications. Evaluation in Percutaneous Transluminal Coronary Angioplasty to Improve Long-Term Outcome with Abciximab GP IIb/IIIa blockade. Evaluation of Platelet IIb/IIIa Inhibitor for Stent

OBJECTIVES

We sought to determine the efficacy and safety of platelet glycoprotein IIb/IIIa receptor (GP IIb/IIIa) blockade with abciximab in women undergoing percutaneous coronary intervention.

BACKGROUND

Although gender differences in response to platelet glycoprotein IIb/IIIa receptor blockade have been described, there have been no large clinical studies to assess these differences.

METHODS

Outcomes were determined using meta-analysis technique.

RESULTS

In the pooled analysis, the primary end point of death, myocardial infarction (MI) or urgent revascularization within 30 days was reduced from 11.3% to 5.8% (p<0.001) in men and from 12.7% to 6.5% (p<0.001) in women treated with abciximab. At six months, death, MI or urgent revascularization was reduced from 14.1% to 8.3% (p<0.001) in men and 16.0% to 9.9% (p<0.001) in women receiving abciximab. At one year, mortality was reduced from 2.7% to 1.9% (p = 0.06) in men and 4.0% to 2.5% (p = 0.03) in women treated with abciximab. Major bleeding events occurred in 2.9% versus 3.0% (p = 0.96) of women and 2.7% versus 1.3% (p = 0.003) of men treated with placebo versus abciximab, respectively. Minor bleeding events occurred in 4.7% versus 6.7% (p = 0.01) of women and 2.3% versus 2.2% (p = 0.94) of men treated with placebo versus abciximab, respectively.

CONCLUSIONS

This pooled analysis demonstrated no gender difference in protection from major adverse outcomes with GP IIb/IIIa inhibition with abciximab. Although women had higher rates of both major and minor bleeding events with abciximab compared with men, major bleeding in women was similar with and without abciximab. There was a small increased risk of minor bleeding with abciximab in women.

Effects of chronic exercise and deconditioning on platelet function in women

To investigate the effects of chronic exercise and deconditioning on platelet function in women, 16 healthy sedentary women were divided into control and exercise groups. The exercise group cycled on an ergometer at 50% maximal oxygen consumption for 30 min/day, 5 days/wk, for two consecutive menstrual cycles and then were deconditioned for three menstrual cycles. During this period, platelet adhesiveness on a fibrinogen-coated surface, ADP-induced platelet aggregation and intracellular calcium concentration elevation, guanosine 3',5'-cyclic monophosphate (cGMP) content in platelets, and plasma nitric oxide metabolite levels were measured before and immediately after a progressive exercise test in the midfollicular phase. Our results indicated that, after exercise training, 1) resting heart rates and blood pressures were reduced, and exercise performance was improved; 2) resting platelet function was decreased, whereas plasma nitrite and nitrate levels and platelet cGMP contents were enhanced; and 3) the potentiation of platelet function by acute strenuous exercise was decreased, whereas the increases in plasma nitrite and nitrate levels and platelet cGMP contents were enhanced by acute exercise. Furthermore, deconditioning reversed these training effects. This implies that training-induced platelet functional changes in women in the midfollicular phase may be mediated by nitric oxide.

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

Previous studies have shown that premenopausal women have a low incidence of cardiovascular diseases, and that acute exercise affects male platelet function in an intensity-dependent manner. To investigate whether acute exercise affects female platelet function differently from males, sixteen sedentary women in the midfollicular phase or midluteal phase received strenuous or moderate exercise on a bicycle ergometer. Before and immediately after exercise, platelet adhesiveness, adenosine diphosphate-induced platelet aggregation and intracellular calcium concentration elevation, platelet cAMP and cGMP contents, urinary 11-dehydro-TXB2 and 6-keto-prostaglandin F1 alpha levels, and plasma nitric oxide metabolite level were determined. Our results showed no differences in exercise performance and in resting platelet function between two menstrual phases, with little change in urinary eicosanoid metabolites and platelet cAMP levels under all experimental conditions. In addition, for women in the midfollicular phase, (1) strenuous exercise increased platelet adhesiveness, adenosine-diphosphate-induced platelet aggregation, and intracellular calcium concentration elevation, whereas moderate exercise suppressed them; (2) moderate exercise enhanced plasma nitric oxide metabolite and platelet cGMP levels. In contrast, none of these platelet functions was affected by acute exercise in the midluteal phase. Therefore, we conclude that acute exercise affects female platelet function in an intensity-dependent manner in the midfollicular phase but not in the midluteal phase. The irresponsiveness of platelets to acute exercise in the luteal phase may partially explain why premenopausal women have a lower incidence of cardiovascular diseases than men.