Platelets of female mice are intrinsically more sensitive to agonists than are platelets of males

Brolucizumab and Platelet Activation and Reactivity

PURPOSE

This study explores the potential interaction of brolucizumab with platelets and its effects on platelet activation and reactivity, crucial in retinal vasculitis and retinal vascular occlusion. Safety concerns remain of interest, although brolucizumab showed superior retinal efficacy and reduced injection frequency compared to other licensed anti-VEGF agents.

METHODS

Resting and activated platelets of healthy volunteers were pretreated with brolucizumab at the following concentrations 0.6 µg/mL, 3 µg/mL, 6 µg/mL, 300 µg/mL, and 3000 µ/mL or its solvent or PBS. The surface expression of platelet activation markers GPIIb/IIIa and P-selectin was determined by multispectral imaging flow cytometry, which combines flow cytometry and fluorescence microscopy. Two different methods were used to examine the interaction of brolucizumab with platelets: 1) A cross-pretreatment experiment was performed with FITC-labeled brolucizumab and bevacizumab; 2) Resting and activated platelets were pretreated with brolucizumab or its solvent or PBS, followed by anti-brolucizumab antibody generated by rabbit immunization.

RESULTS

Brolucizumab did not significantly affect platelet activation compared to solvent or PBS, across a range of concentrations. No significant upregulation of CD62P and no activation of the fibrinogen receptor (GPIIb/IIa) were observed in resting and TRAP-activated platelets. After pretreatment with PBS, the level of brolucizumab-FITC was significantly lower in comparison to bevacizumab-FITC (normalized MFI = 3.32, CI = 3.16-3.48 vs. normalized MFI = 7.19, CI = 7.04-7.35; p < 0.001). Both brolucizumab- and bevacizumab-FITC were downregulated after pretreatment with brolucizumab or bevacizumab compared to pretreatment with PBS. Antibodies against brolucizumab did not show any significant difference between pretreatment with brolucizumab and its solvent in resting and TRAP-activated platelets.

CONCLUSION

Brolucizumab does not appear to directly affect platelet activation or reactivity to thrombin receptor agonists. No platelet interaction was observed after increasing brolucizumab concentrations or anti-brolucizumab antibodies in resting and activated platelets. However, brolucizumab might be taken up in platelets.

Considerations in Antiplatelet Therapy in Women Undergoing Treatment of Acute Coronary Syndrome or Percutaneous Coronary Intervention

Antiplatelet therapy is integral to reduce the risk of future ischemic events following acute coronary syndrome (ACS) or percutaneous coronary intervention (PCI); this aim must be balanced by limiting the risk of bleeding. Women with ACS or undergoing PCI have distinct platelet physiology, vascular anatomy, and clinical profiles that can influence the selection of an appropriate regimen. There are procedural techniques that can enhance safety in women. The poor inclusion of women in ACS and PCI trials limits our understanding of the ideal antiplatelet regimen in women, and future studies must find ways to increase the participation of female patients.

Reduced platelet activation and thrombus formation in male transgenic model mice of Alzheimer's disease suggests early sex-specific differences in platelet pathophysiology

Alzheimer's disease (AD) is the most common form of dementia and characterized by extracellular amyloid-β (Aβ) plaques, intracellular neurofibrillary tau tangles and neurodegeneration. Over 80 % of AD patients also exhibit cerebral amyloid angiopathy (CAA). CAA is a cerebrovascular disease caused by deposition of Aβ in the walls of cerebral blood vessels leading to vessel damage and impairment of normal blood flow. To date, different studies suggest that platelet function, including activation, adhesion and aggregation, is altered in AD due to vascular Aβ deposition. For example, the transgenic AD model mice APP23 mice that exhibit CAA and parenchymal Aβ plaques, show pre-activated platelets in the blood circulation and increased platelet integrin activation leading to a pro-thrombotic phenotype in these mice late stages of AD. However, it is still an open question whether or not platelets exhibit changes in their activation profile before they are exposed to vascular Aβ deposits. Therefore, the present study examined platelets from middle-aged transgenic APP23 mice at the age of 8-10 months. At this age, APP23 mice show amyloid plaques in the brain parenchyma but not in the vasculature. Our analyses show that these APP23 mice have unaltered platelet numbers and size, and unaltered surface expression of glycoproteins. However, the number of dense granules in transgenic platelets was increased while the release was unaltered. Male, but not female APP23 mice, exhibited reduced platelet activation after stimulation of the thrombin receptor PAR4 and decreased thrombus stability on collagen under flow conditions ex vivo compared to control mice. In an arterial thrombosis model in vivo, male APP23 mice showed attenuated occlusion of the injured artery compared to controls. These findings provide clear evidence for early changes in platelet activation and thrombus formation in male mice before development of overt CAA. Furthermore, reduced platelet activation and thrombus formation suggest sex-specific differences in platelet physiology in AD that has to be considered in future studies of platelets and their role in AD.

Sex-Dependent Occlusive Cardiovascular Disease Effects of Short-Term Thirdhand Smoke Exposure

INTRODUCTION

Thirdhand smoke (THS) is associated with many public health and disease concerns, such as respiratory illness, cancer, lipidemia, and cardiovascular disease (CVD). We have previously shown that a moderate to long-term exposure to THS increases the risk of thrombosis. However, whether short-term exposure to THS would produce any effects remains to be discovered. Therefore, this study investigated the impact of 1-month THS exposure on platelet function, in vivo and in vitro, and on cytokine response, in a sex-dependent manner.

AIMS AND METHODS

Secondhand smoke or clean air (CA) exposed upholstery materials for 1 week were kept in cages housed with 5-6 mice, and the procedure was repeated for 4 weeks. These THS-exposed mice were evaluated for thrombogenesis and platelet function assays. In addition, cytokines expression was evaluated from pooled serum.

RESULTS

Compared to the CA group, THS exposure significantly shortened the tail bleeding time and carotid artery thrombus formation. Moreover, the female mice appeared more sensitive to THS exposure than males. Furthermore, platelet aggregation, dense granule secretion, and P-selectin activation markers were significantly elevated due to THS exposure. In addition, high-throughput screening showed at least 30 cytokines differentially modulated by THS in females relative to 26 in male mice.

CONCLUSIONS

Collectively, these results demonstrate that 1 month of THS exposure represents a high health risk, in part, by triggering a prothrombotic phenotype that appears to be more significant in females, who are at a much higher risk for occlusive CVD. Additionally, changes in cytokine levels mediate some of the THS-induced occlusive effects.

IMPLICATIONS

This study revealed that THS exposure for 1 month is detrimental to the cardiovascular health of both sexes; however, females could be more aggressively affected than males. In addition, interleukins and chemokines could be critical factors for initiating prothrombotic activity due to THS exposure.

Sex Differences in the Dual Antiplatelet Therapy Versus Alteplase for Patients with Minor Nondisabling Acute Ischemic Stroke: A Secondary Analysis of the ARAMIS Study

BACKGROUND AND PURPOSE

Sex is associated with clinical outcome in stroke. The present study aimed to determine the effect of sex on efficacy of dual antiplatelet (DAPT) versus alteplase in ischemic stroke based on Antiplatelet versus recombinant tissue plasminogen activator (R-tPA) for Acute Mild Ischemic Stroke (ARAMIS) trial.

METHODS

In this secondary analysis of the ARAMIS study, eligible patients aged 18 years or older with minor nondisabling stroke who received dual antiplatelet therapy or intravenous alteplase within 4.5 h of stroke onset were divided into two groups: men and women. The primary endpoint was an excellent functional outcome, defined as a modified Rankin Scale (mRS) 0-1 at 90 days. Binary logistic regression analyses and generalized linear models were used.

RESULTS

Of the 719 patients who completed the study, 31% (223) were women, and 69% (496) were men. There were no significant sex differences in excellent functional outcome (unadjusted p = 0.304 for men and p = 0.993 for women; adjusted p = 0.376 for men and p = 0.918 for women) and favorable functional outcome (mRS score of 0-2; unadjusted p = 0.968 for men and p = 0.881 for women; adjusted p = 0.824 for men and p = 0.881 for women). But for the secondary outcomes, compared with alteplase, DAPT was associated with a significantly decreased proportion of early neurological deterioration within 24 h in men {unadjusted odds ratio [OR] = 0.440 [95% confidence interval (CI), 0.221-0.878]; p = 0.020; adjusted OR = 0.436 [95% CI, 0.216-0.877]; p = 0.020}, but not in women [unadjusted OR = 0.636 (95% CI, 0.175-2.319), p = 0.490; adjusted OR = 0.687 (95% CI, 0.181-2.609), p = 0.581]. For the safety outcomes, compared with the DAPT group, alteplase was associated with a significantly increased proportion of any bleeding events in men [unadjusted OR = 3.110 (95% CI, 1.103-8.770); p = 0.032], but not in women [unadjusted OR = 5.333 (95% CI, 0.613-46.407), p = 0.129; adjusted OR = 5.394 (95% CI, 0.592-49.112), p = 0.135].

CONCLUSION

Sex did not influence the effect of dual antiplatelet therapy versus intravenous alteplase in minor nondisabling stroke, but more early neurological deterioration and bleeding events occurred in men who received alteplase.

Sex-Specific Acute Cerebrovascular Responses to Photothrombotic Stroke in Mice

Mechanisms underlying cerebrovascular stroke outcomes are poorly understood, and the effects of biological sex on cerebrovascular regulation post-stroke have yet to be fully comprehended. Here, we explore the overlapping roles of gonadal sex hormones and rho-kinase (ROCK), two important modulators of cerebrovascular tone, on the acute cerebrovascular response to photothrombotic (PT) focal ischemia in mice. Male mice were gonadectomized and female mice were ovariectomized to remove gonadal hormones, whereas control ("intact") animals received a sham surgery prior to stroke induction. Intact wild-type (WT) males showed a delayed drop in cerebral blood flow (CBF) compared with intact WT females, whereby maximal CBF drop was observed 48 h following stroke. Gonadectomy in males did not alter this response. However, ovariectomy in WT females produced a "male-like" phenotype. Intact Rock2+/- males also showed the same phenotypic response, which was not altered by gonadectomy. Alternatively, intact Rock2+/- females showed a significant difference in CBF values compared with intact WT females, displaying higher CBF values immediately post-stroke and showing a maximal CBF drop 48 h post-stroke. This pattern was not altered by ovariectomy. Altogether, these data illustrate sex differences in acute CBF responses to PT stroke, which seem to involve gonadal female sex hormones and ROCK2. Overall, this study provides a framework for exploring sex differences in acute CBF responses to focal ischemic stroke in mice.

Thromboembolic Events after COVID-19 Vaccination: An Italian Retrospective Real-World Safety Study

INTRODUCTION

Real-world safety studies can provide important evidence on the thromboembolic risk associated with COVID-19 vaccines, considering that millions of people have been already vaccinated against COVID-19. In this study, we aimed to estimate the incidence of thromboembolic events after COVID-19 vaccination and to compare the Oxford-AstraZeneca vaccine with other COVID-19 vaccines.

METHODS

We conducted a retrospective real-world safety study using data from two different data sources: the Italian Pharmacovigilance database (Rete Nazionale di Farmacovigilanza, RNF) and the Campania Region Health system (Sistema INFOrmativo saNità CampanIA, SINFONIA). From the start date of the COVID-19 vaccination campaign (27 December 2021) to 27 September 2022, information on COVID-19 vaccinations and thromboembolic events were extracted from the two databases. The reporting rate (RR) and its 95% confidence interval (95%CI) of thromboembolic events for 10,000 doses was calculated for each COVID-19 vaccine. Moreover, the odds of being vaccinated with the Oxford-AstraZeneca vaccine vs. the other COVID-19 vaccines in cases with thromboembolic events vs. controls without thromboembolic events were computed.

RESULTS

A total of 12,692,852 vaccine doses were administered in the Campania Region, of which 6,509,475 (51.28%) were in females and mostly related to the Pfizer-BioNtech vaccine (65.05%), followed by Moderna (24.31%), Oxford-AstraZeneca (9.71%), Janssen (0.91%), and Novavax (0.02%) vaccines. A total of 641 ICSRs with COVID-19 vaccines and vascular events were retrieved from the RNF for the Campania Region, of which 453 (70.67%) were in females. Most ICSRs reported the Pfizer-BioNtech vaccine (65.05%), followed by Oxford-AstraZeneca (9.71%), Moderna (24.31%), and Janssen (0.91%). A total of 2451 events were reported in the ICSRs (3.8 events for ICSRs), of which 292 were thromboembolic events. The higher RRs of thromboembolic events were found with the Oxford-AstraZeneca vaccine (RR: 4.62, 95%CI: 3.50-5.99) and Janssen vaccine (RR: 3.45, 95%CI: 0.94-8.82). Thromboembolic events were associated with a higher likelihood of exposure to the Oxford-AstraZeneca vaccine compared to Pfizer-BioNtech (OR: 6.06; 95%CI: 4.22-8.68) and Moderna vaccines (OR: 6.46; 95%CI: 4.00-10.80).

CONCLUSION

We observed a higher reporting of thromboembolic events with viral-vector-based vaccines (Oxford-AstraZeneca and Janssen) and an increased likelihood of being exposed to the Oxford-AstraZeneca vaccine compared to the mRNA vaccines (Pfizer-BioNtech and Moderna) among thromboembolic cases.

Lenalidomide Promotes Thrombosis Formation, but Does Not Affect Platelet Activation in Multiple Myeloma

Lenalidomide, a well-established drug for the treatment of multiple myeloma, significantly enhances patients' survival. Previous clinical studies have demonstrated that its main side effect is an increased risk of thrombotic events. However, the underlying mechanism remains unexplored. Therefore, this study aims to elucidate the mechanism and offer insights into the selection of clinical thrombotic prophylaxis drugs. Firstly, we conducted a retrospective analysis of clinical data from 169 newly diagnosed multiple myeloma patients who received lenalidomide. To confirm the impact of lenalidomide on thrombosis formation, FeCl3-induced thrombosis and deep venous thrombosis models in mice were established. To investigate the effects of lenalidomide on platelet function, both in vivo and in vitro experiments were designed. During the follow-up period, 8 patients developed thrombotic events, including 8 venous and 1 arterial. Further investigation using mice models demonstrated that lenalidomide significantly promoted the formation of venous thrombosis, consistent with clinical findings. To elucidate the underlying mechanism, assays were conducted to assess platelet function and coagulation. We observed that lenalidomide did not have any noticeable impact on platelet function, both in vitro and in vivo, while administration of lenalidomide resulted in significant decreases in prothrombin time, thrombin time, and prothrombin time ratio in patients, as well as a remarkable reduction in tail-bleeding time in mice. The administration of lenalidomide had no significant impact on platelet function, which may affect venous thrombus formation by affecting coagulation. Therefore, anticoagulant drugs may be superior to antiplatelet drugs in the selection of clinical thrombus prophylaxis.

Sex Differences in Therapies against Myocardial Ischemia-Reperfusion Injury: From Basic Science to Clinical Perspectives

Mortality from myocardial infarction (MI) has declined over recent decades, which could be attributed in large part to improved treatment methods. Early reperfusion is the cornerstone of current MI treatment. However, reoxygenation via restored blood flow induces further damage to the myocardium, leading to ischemia-reperfusion injury (IRI). While experimental studies overwhelmingly demonstrate that females experience greater functional recovery from MI and decreased severity in the underlying pathophysiological mechanisms, the outcomes of MI with subsequent reperfusion therapy, which is the clinical correlate of myocardial IRI, are generally poorer for women compared with men. Distressingly, women are also reported to benefit less from current guideline-based therapies compared with men. These seemingly contradicting outcomes between experimental and clinical studies show a need for further investigation of sex-based differences in disease pathophysiology, treatment response, and a sex-specific approach in the development of novel therapeutic methods against myocardial IRI. In this literature review, we summarize the current knowledge on sex differences in the underlying pathophysiological mechanisms of myocardial IRI, including the roles of sex hormones and sex chromosomes. Furthermore, we address sex differences in pharmacokinetics, pharmacodynamics, and pharmacogenetics of current drugs prescribed to limit myocardial IRI. Lastly, we highlight ongoing clinical trials assessing novel pharmacological treatments against myocardial IRI and sex differences that may underlie the efficacy of these new therapeutic approaches.

Gender differences in efficacy and safety of antiplatelet strategies for acute coronary syndromes

INTRODUCTION

Dual antiplatelet therapy (DAPT) represents the cornerstone of secondary prevention in patients presenting with acute coronary syndrome (ACS) and undergoing percutaneous coronary intervention. Despite its undisputed efficacy in reducing thrombotic events, DAPT increases the risk of bleeding, which is associated with higher morbidity and mortality. Novel antiplatelet strategies (i.e. in terms of timing, selection of drugs and their combinations, and modulation strategies) have been tested in randomized trials, suggesting the utility of tailored approaches in selected populations (i.e. patients at high bleeding or ischemic risk). It remains uncertain whether the effect of these strategies is influenced by sex.

AREAS COVERED

This narrative review provides an overview of available evidence surrounding sex differences in the efficacy and safety of antiplatelet strategies for ACS and analyzes the potential reasons behind these findings. Relevant content was searched for in PubMed.

EXPERT OPINION

Significant differences between women and men exist in terms of clinical presentation, pharmacotherapies, interventional management, and prognosis of ACS. However, these observations do not appear to be attributed to different pharmacodynamic effects of antiplatelet therapies between women and men. Unfortunately, a critical issue depends on women being often underrepresented in clinical trials, leading to a substantial lack of sex-specific evidence.

AGK Potentiates Arterial Thrombosis by Affecting Talin-1 and αIIbβ3-Mediated Bidirectional Signaling Pathway

BACKGROUND

AGK (acylglycerol kinase) was first identified as a mitochondrial transmembrane protein that exhibits a lipid kinase function. Recent studies have established that AGK promotes cancer growth and metastasis, enhances glycolytic metabolism and function fitness of CD8+ T cells, or regulates megakaryocyte differentiation. However, the role of AGK in platelet activation and arterial thrombosis remains to be elaborated.

METHODS

We performed hematologic analysis using automated hematology analyzer and investigated platelets morphology by transmission electron microscope. We explored the role of AGK in platelet activation and arterial thrombosis utilizing transgenic mice, platelet functional experiments in vitro, and thrombosis models in vivo. We revealed the regulation effect of AGK on Talin-1 by coimmunoprecipitation, mass spectrometry, immunofluorescence, and Western blot. We tested the role of AGK on lipid synthesis of phosphatidic acid/lysophosphatidic acid and thrombin generation by specific Elisa kits.

RESULTS

In this study, we found that AGK depletion or AGK mutation had no effect on the platelet average volumes, the platelet microstructures, or the expression levels of the major platelet membrane receptors. However, AGK deficiency or AGK mutation conspicuously decreased multiple aspects of platelet activation, including agonists-induced platelet aggregation, granules secretion, JON/A binding, spreading on Fg (fibrinogen), and clot retraction. AGK deficiency or AGK mutation also obviously delayed arterial thrombus formation but had no effect on tail bleeding time and platelet procoagulant function. Mechanistic investigation revealed that AGK may promote Talin-1Ser425 phosphorylation and affect the αIIbβ3-mediated bidirectional signaling pathway. However, AGK does not affect lipid synthesis of phosphatidic acid/lysophosphatidic acid in platelets.

CONCLUSIONS

AGK, through its kinase activity, potentiates platelet activation and arterial thrombosis by promoting Talin-1 Ser425 phosphorylation and affecting the αIIbβ3-mediated bidirectional signaling pathway.

Immune-mediated platelet depletion augments Alzheimer's disease neuropathological hallmarks in APP-PS1 mice

In Alzheimer's disease (AD), platelets become dysfunctional and might contribute to amyloid beta deposition. Here, we depleted platelets in one-year-old APP Swedish PS1 dE9 (APP-PS1) transgenic mice for five days, using intraperitoneal injections of an anti-CD42b antibody, and assessed changes in cerebral amyloidosis, plaque-associated neuritic dystrophy and gliosis. In APP-PS1 female mice, platelet depletion shifted amyloid plaque size distribution towards bigger plaques and increased neuritic dystrophy in the hippocampus. In platelet-depleted females, plaque-associated Iba1+ microglia had lower amounts of fibrillar amyloid beta cargo and GFAP+ astrocytic processes showed a higher overlap with thioflavin S+ amyloid plaques. In contrast to the popular hypothesis that platelets foster plaque pathology, our data suggest that platelets might limit plaque growth and attenuate plaque-related neuritic dystrophy at advanced stages of amyloid plaque pathology in APP-PS1 female mice. Whether the changes in amyloid plaque pathology are due to a direct effect on amyloid beta deposition or are a consequence of altered glial function needs to be further elucidated.

Sex-related differences in the response of anti-platelet drug therapies targeting purinergic signaling pathways in sepsis

Sepsis, a complex clinical syndrome resulting from a serious infection, is a major healthcare problem associated with high mortality. Sex-related differences in the immune response to sepsis have been proposed but the mechanism is still unknown. Purinergic signaling is a sex-specific regulatory mechanism in immune cell physiology. Our studies have shown that blocking the ADP-receptor P2Y12 but not P2Y1 receptor was protective in male mice during sepsis, but not female. We now hypothesize that there are sex-related differences in modulating P2Y12 or P2Y1 signaling pathways during sepsis. Male and female wild-type (WT), P2Y12 knock-out (KO), and P2Y1 KO mice underwent sham surgery or cecal ligation and puncture (CLP) to induce sepsis. The P2Y12 antagonist ticagrelor or the P2Y1 antagonist MRS2279 were administered intra-peritoneally after surgery to septic male and female mice. Blood, lungs and kidneys were collected 24 hours post-surgery. Sepsis-induced changes in platelet activation, secretion and platelet interaction with immune cells were measured by flow cytometry. Neutrophil infiltration in the lung and kidney was determined by a myeloperoxidase (MPO) colorimetric assay kit. Sepsis-induced platelet activation, secretion and aggregate formation were reduced in male CLP P2Y12 KO and in female CLP P2Y1 KO mice compared with their CLP WT counterpart. Sepsis-induced MPO activity was reduced in male CLP P2Y12 KO and CLP P2Y1 KO female mice. CLP males treated with ticagrelor or MRS2279 showed a decrease in sepsis-induced MPO levels in lung and kidneys, aggregate formation, and platelet activation as compared to untreated male CLP mice. There were no differences in platelet activation, aggregate formation, and neutrophil infiltration in lung and kidney between female CLP mice and female CLP mice treated with ticagrelor or MRS2279. In human T lymphocytes, blocking P2Y1 or P2Y12 alters cell growth and secretion in vitro in a sex-dependent manner, supporting the data obtained in mice. In conclusion, targeting purinergic signaling represents a promising therapy for sepsis but drug targeting purinergic signaling is sex-specific and needs to be investigated to determine sex-related targeted therapies in sepsis.

Reduction in SOCE and Associated Aggregation in Platelets from Mice with Platelet-Specific Deletion of Orai1

Calcium signalling in platelets through store operated Ca²⁺ entry (SOCE) or receptor-operated Ca²⁺ entry (ROCE) mechanisms is crucial for platelet activation and function. Orai1 proteins have been implicated in platelet’s SOCE. In this study we evaluated the contribution of Orai1 proteins to these processes using washed platelets from adult mice from both genders with platelet-specific deletion of the Orai1 gene (Orai1^flox/flox; Pf4-Cre termed as Orai1^Plt-KO) since mice with ubiquitous Orai1 deficiency show early lethality. Platelet aggregation as well as Ca²⁺ entry and release were measured in vitro following stimulation with collagen, collagen related peptide (CRP), thromboxane A2 analogue U46619, thrombin, ADP and the sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibitor thapsigargin, respectively. SOCE and aggregation induced by Thapsigargin up to a concentration of 0.3 µM was abrogated in Orai1-deficient platelets. Receptor-operated Ca²⁺-entry and/or platelet aggregation induced by CRP, U46619 or thrombin were partially affected by Orai1 deletion depending on the gender. In contrast, ADP-, collagen- and CRP-induced aggregation was comparable in Orai1^Plt-KO platelets and control cells over the entire concentration range. Our results reinforce the indispensability of Orai1 proteins for SOCE in murine platelets, contribute to understand its role in agonist-dependent signalling and emphasize the importance to analyse platelets from both genders.

Sex-Related Differences in Platelet Aggregation: A Literature Review Supplemented with Local Data from a Group of Generally Healthy Individuals

The process of platelet aggregation is often influenced by several factors including sex and age. A literature review confirmed the existence of sex-related differences in platelet aggregation. Although 68 out of 78 papers found such differences, there are still some controversies regarding these differences, which can be due to multiple factors (age, trigger, concomitant disease, sample handling, etc.). These outcomes are discussed in line with novel results obtained from a local study, in which blood samples from a total of 53 overall healthy women and men with ages ranging from 20 to 66 years were collected. Aggregation was induced with seven different triggers (ristocetin, thrombin receptor activating peptide 6 [TRAP-6], arachidonic acid [AA], platelet-activating factor 16 [PAF-16], ADP, collagen, or thromboxane A₂ analog U-46619) ex vivo. In addition, three FDA-approved antiplatelet drugs (vorapaxar, ticagrelor, or acetylsalicylic acid [ASA]) were also tested. In general, women had higher aggregation responses to some agonists (ADP, TRAP), as well as lower benefit from inhibitors (ASA, vorapaxar). The aggregatory responses to AA and TRAP decreased with age in both sexes, while responses to ADP, U-46619, and PAF were affected by age only in women. In conclusion, more studies are needed to decipher the biological importance of sex-related differences in platelet aggregation in part to enable personalized antiplatelet treatment.

Mean platelet volume as a predictive biomarker for in-hospital mortality in patients receiving invasive mechanical ventilation

Background

Although mean platelet volume (MPV) has been reported to be associated with poor prognosis of various critical illness, the relationship between MPV and in-hospital mortality among patients undergoing invasive mechanical ventilation (IMV) is unclear.

Methods

A retrospective observational study including patients receiving IMV was conducted from January, 2014 to January, 2019. The patients were divided into two groups by MPV cutoff value. The receiver operating characteristics curve was used to evaluate the predictive ability of MPV for in-hospital mortality. Univariate and multivariate Cox regression analysis were conducted to analyze the value of MPV for predicting in-hospital mortality. Kaplan–Meier cumulative incidence curve was employed to observe the incidence of in-hospital mortality.

Results

A total of 274 patients were enrolled in the study, and 42 patients (15.3%) died in hospital. MPV > 11.4 fl was a valuable predictor for in-hospital mortality (AUC0.848; 95%CI, 0.800–0.889) with sensitivity 66.7%, and specificity = 86.21%. MPV > 11.4 fl was an independent risk factor for in-hospital mortality (adjusted HR 2.640, 95%CI, 1.208–5.767, P = 0.015). Compared to the group of MPV ≤ 11.4 fl, patients with MPV > 11.4 fl had increased mortality (log-rank test = 40.35, HR = 8.723, P < 0.0001). The relationship between MPV and in-hospital mortality was stronger in female patients than in male patients.

Conclusion

MPV > 11.4 fl is a more useful marker for predicting in-hospital mortality among critically ill patients receiving IMV, especially in female patients. Attention to the MPV marker is simple and profitable with immediate applicability in daily clinical practice.

Sex differences at the platelet-vascular interface

Platelets are multifunctional cells that ensure the integrity of the vascular wall and modulate the immune response at the blood/vascular interface. Their pathological activation results in both thrombosis and inflammation and implicates them in the pathogenesis of vascular disease. Vascular diseases are sexually dimorphic in terms of incidence, clinical presentation, outcome, and efficacy of anti-platelet therapy. We here provide an overview of what is known about the role of platelets in the initiation and progression of vascular diseases and summarize what is known about the sex differences in platelet reactivity and in the thromboinflammatory mechanisms that drive these diseases, with a particular focus on atherosclerosis, obstructive and non-obstructive coronary artery disease, and ischemic stroke. Understanding the sex differences at the platelet-vascular interface is clinically relevant as it will enable: (1) to design new therapeutic strategies that prevent the detrimental effects of the immune-modulatory function of platelets taking sex into account, and (2) to evaluate if sex-specific anti-platelet drug regimens should be used to reduce the risk not only of thrombosis but also of vascular disease progression.

Effects of Interleukin-17A on the Early Stages of Arterial Thrombosis in Mice

PURPOSE

Interleukin (IL)-17A has been suggested to play a role in the growth and organization of thrombi. We examined whether IL-17A plays a role in the early stages of thrombosis and whether there are sex differences in the effects of IL-17A.

MATERIALS AND METHODS

We performed a blinded, randomized, placebo-controlled study to compare time to thrombotic occlusion and sex differences therein between mice treated with IL-17A and those treated with saline using a ferric chloride-induced model. We also assessed thrombus histology, blood coagulation, and plasma levels of coagulation factors.

RESULTS

Time to occlusion values did not differ between the IL-17A group and the control group (94.6±86.9 sec vs. 121.0±84.4 sec, p=0.238). However, it was significantly shorter in the IL-17A group of female mice (74.6±57.2 sec vs. 130.0±76.2 sec, p=0.032). In rotational thromboelastometry, the IL-17A group exhibited increased maximum clot firmness (71.3±4.5 mm vs. 66.7±4.7 mm, p=0.038) and greater amplitude at 30 min (69.7±5.2 mm vs. 64.5±5.3 mm, p=0.040) than the control group. In Western blotting, the IL-17A group showed higher levels of coagulation factor XIII (2.2±1.5 vs. 1.0±0.9, p=0.008), monocyte chemoattractant protein-1 (1.6±0.6 vs. 1.0±0.4, p=0.023), and tissue factor (1.5±0.6 vs. 1.0±0.5, p=0.003).

CONCLUSION

IL-17A plays a role in the initial st ages of arterial thrombosis in mice. Coagulation factors and monocyte chemoattractant protein-1 may be associated with IL-17A-mediated thrombosis.

Scientific premise for the involvement of neutrophil extracellular traps (NETs) in vaccine-induced thrombotic thrombocytopenia (VITT)

Following on from the devastating spread of COVID-19, a major global priority has been the production, procurement, and distribution of effective vaccines to ensure that the global pandemic reaches an end. However, concerns were raised about worrying side effects, particularly the occurrence of thrombosis and thrombocytopenia after administration of the Oxford/AstraZeneca and Johnson & Johnson's Janssen COVID-19 vaccine, in a phenomenon being termed vaccine-induced thrombotic thrombocytopenia (VITT). Similar to heparin-induced thrombocytopenia (HIT), this condition has been associated with the development of anti-platelet factor 4 antibodies, purportedly leading to neutrophil-platelet aggregate formation. Although thrombosis has also been a common association with COVID-19, the precise molecular mechanisms governing its occurrence are yet to be established. Recently, increasing evidence highlights the NLRP3 (NOD-like, leucine-rich repeat domains, and pyrin domain-containing protein) inflammasome complex along with IL-1β and effete neutrophils producing neutrophil extracellular traps (NETs) through NETosis. Herein, we propose and discuss that perhaps the incidence of VITT may be due to inflammatory reactions mediated via IL-1β/NLRP3 inflammasome activation and consequent overproduction of NETs, where similar autoimmune mechanisms are observed in HIT. We also discuss avenues by which such modalities could be treated to prevent the occurrence of adverse events and ensure vaccine rollouts remain safe and on target to end the current pandemic.

Sex-Dependent Effect of Platelet Nitric Oxide: Production and Platelet Reactivity in Healthy Individuals

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Platelet reactivity is greater in healthy women compared with men.

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Following an oral nitrate load, platelet nitric oxide production increased disproportionately more in healthy women than healthy men with attenuated platelet reactivity in women and enhanced platelet reactivity in men.

A nitrate-rich diet has many cardiovascular benefits, but the mechanism behind this is unclear. We hypothesized that the ingestion of nitrate augments nitrate to nitrite reduction, leading to nitric oxide (NO) production, which may suppress platelet reactivity. In a randomized, double-blinded, placebo-controlled study involving healthy individuals, ingestion of nitrate augmented saliva and plasma nitrite/nitrate concentration and enhanced platelet NO production disproportionately in women compared with men. The response of elevated platelet NO in men was increased platelet reactivity and the response of markedly elevated platelet NO in women slightly inhibited platelet reactivity.

Roxadustat Does Not Affect Platelet Production, Activation, and Thrombosis Formation

Objective: Roxadustat is a new medication for the treatment of renal anemia. EPO (erythropoietin)-the current treatment standard-has been reported to enhance platelet activation and production. However, to date, the effect of roxadustat on platelets is unclear. To address this deficiency, herein, we have evaluated the effect of roxadustat on platelet production and function. Approach and Results: We performed several mouse platelet functional assays in the presence/absence of in vitro and in vivo roxadustat treatment. Both healthy and 5/6 nephrectomized mice were utilized. The effect of roxadustat on platelet function of healthy volunteers and chronic kidney disease patients was also evaluated. For platelet production, megakaryocyte maturation and proplatelet formation were assayed in vitro. Peripheral platelet and bone marrow megakaryocyte counts were also determined. We found that roxadustat could not stimulate washed platelets directly, and platelet aggregation, spreading, clot retraction, and P-selectin/JON/A exposure were similar with or without in vitro or in vivo roxadustat treatment among both healthy and 5/6 nephrectomized mice. In vivo mouse thrombosis models were additionally performed, and no differences were detected between the vehicle and roxadustat treatment groups. EPO, which was considered a positive control in the present study, promoted platelet function and production as reported previously. Megakaryocyte maturation and proplatelet formation were also not significantly different between control mice and those treated with roxadustat. After receiving roxadustat for 14 days, no difference in the peripheral platelet count was observed in the mice. Conclusions: Administration of roxadustat has no significant impact on platelet production and function.

Effect of leukopenia induced by cyclophosphamide on the initial stage of arterial thrombosis in mice

INTRODUCTION

Leukocytes are found in organizing thrombi and are associated with thrombus growth. However, their role in the initial stage of thrombus formation is not well known. We investigated the role of leukocytes in the early stage of arterial thrombosis by inducing leukopenia.

METHODS

In this double-blind, randomized, placebo-controlled study, 72 Institute of Cancer Research mice were randomly treated with intraperitoneal 100 mg/kg cyclophosphamide or normal saline. The primary outcome was time to occlusion after FeCl3 treatment. We also compared thrombus size, histological composition, and association with peripheral blood cell counts between cyclophosphamide and control groups.

RESULTS

Cyclophosphamide treatment significantly decreased leukocyte counts by 82.8% compared to placebo (P < 0.001). The time to occlusion was significantly longer in the cyclophosphamide group (3.31 ± 1.59 min) than in the control group (2.30 ± 1.14 min; P = 0.003). The immunoreactivity for Ly6G-positive cells, intracellular histone H3, and released histone H3 in thrombi was significantly reduced in the cyclophosphamide group by 92.8%, 50.2%, and 34.3%, respectively. Time to occlusion had a moderate negative correlation with leukocyte count in peripheral blood (r = -0.326, P = 0.022) in the entire group.

CONCLUSIONS

Cyclophosphamide-induced leukopenia attenuated thrombus formation during the early stage of arterial thrombosis. Our findings suggest the potential role of leukocytes in the initial stage of arterial thrombosis.

Female gender is associated with increased late luminal narrowing within the stent graft after thoracic endovascular aortic repair

BACKGROUND

Luminal narrowing, suspected secondary to thrombus, occurs within stent grafts at an unclear incidence after thoracic endovascular aortic repair (TEVAR). The significance of this phenomenon has not been determined, nor have the risk factors for development of intragraft luminal narrowing. Small graft diameter is hypothesized to be a risk factor for the development of ingraft stenosis.

METHODS

A retrospective analysis was performed of a multicenter healthcare system including all patients who underwent TEVAR between July 2011 and July 2019 with at least 1 year of subsequently available surveillance contrast-enhanced computed tomography imaging. Standard demographic, preoperative, intraoperative, and postoperative variables were collected. Measurements were obtained via direct off-line images from computed tomography scans. Patent intragraft diameters were compared with baseline and interval change values were normalized to time to follow-up. The primary outcome measure was annual rate of intragraft luminal narrowing.

RESULTS

There were 208 patients who met the inclusion criteria (94 women, 114 men) with a median follow-up of 822 days. The mean annual rate of percent intragraft diameter reduction was 10.5 ± 7.7% for women and 7.6 ± 5.6% for men (P = .0026). Multivariate analysis demonstrated female gender (P = .0283), preoperative diagnosis of hypertension (P = .0449), and need for coverage of the left subclavian artery (P = .0328) were all significant predictors of intragraft luminal narrowing. Small aortic diameters were not found to be associated independently with ingraft luminal narrowing nor was the concomitant use of antiplatelet or anticoagulation medications. Significant amounts of ingraft luminal narrowing, defined as a greater than 20% intragraft diameter decrease, were associated with an increased need for any reintervention, including for malperfusion, endoleak, and symptomatic aneurysm (P = .0249). Kaplan-Meier estimates demonstrated a significant gender-associated difference in high rates of intragraft luminal narrowing (P = .00189).

CONCLUSIONS

In this analysis, female gender is shown to be a significant nonmodifiable risk factor for intragraft luminal narrowing after TEVAR. The development of this phenomenon is not benign; as such, these findings were associated with an increased need for reintervention. This finding may be attributable to differences in aortic compliance or gender-associated differences in coagulation pathways and merits further investigation. Surveillance after thoracic stent grafting must account for patient-specific variations in complication risk.

Fluorometric Quantification of Human Platelet Polyphosphate Using 4',6-Diamidine-2-phenylindole Dihydrochloride: Applications in the Japanese Population

Polyphosphate (polyP), a biopolymer of inorganic phosphate, is widely distributed in living organisms. In platelets, polyP is released upon activation and plays important roles in coagulation and tissue regeneration. However, the lack of a specific quantification method has delayed the in-depth study of polyP. The fluorescent dye 4′,6-diamidine-2-phenylindole dihydrochloride (DAPI) has recently received attention as a promising probe for the visualization and quantification of cellular polyP levels. In this study, we further optimized quantification conditions and applied this protocol in quantification of platelet polyP levels in a Japanese population. Blood samples were collected from non-smoking, healthy Japanese subjects (23 males, 23 females). Washed platelets were fixed and probed with DAPI for fluorometric determination. PolyP levels per platelet count were significantly higher in women than that in men. A moderate negative correlation between age and polyP levels was found in women. Responsiveness to CaCl₂ stimulation was also significantly higher in women than that in men. Overall, our optimized protocol requires neither purification nor degradation steps, reducing both the time and bias for reproducible quantification. Thus, we suggest that despite its low specificity, this DAPI-based protocol would be useful in routine laboratory testing to quantify platelet polyP levels efficiently and economically.

Female sex as an independent predictor of high bleeding risk among East Asian percutaneous coronary intervention patients: A sex difference analysis

BACKGROUND

Sex differences in the outcomes following percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) have been identified in Western countries. However, data on the long-term outcomes for bleeding events, particularly in East Asia where the aging population is growing rapidly and consists predominantly of women, remain scarce.

METHODS

We analyzed 2,494 ACS survivors from a multicenter PCI registry who underwent PCI between 2009 and 2012. The primary outcome was readmission for major bleeding at 2 years. Survival curves were generated with the cumulative incidence function. The adjusted hazard ratios were evaluated for the primary outcomes by sex using (1) Fine-Gray models and (2) Cox regression models.

RESULTS

There were 548 women (22.0%) in this cohort. The women were older (73.7 ± 10.8 years vs. 65.4 ± 11.8 years, p < 0.001), had a lower body mass index (23.0 ± 3.9 vs. 24.3 ± 3.6, p < 0.001), and had more comorbidities such as renal failure (49.4% vs. 36.3%, p < 0.001) and previous heart failure (8.4% vs. 4.5%, p < 0.001). Fewer women were discharged with statins (81.9% vs. 86.5%, p = 0.025) or beta blockers (70.6% vs. 77.1%, p = 0.007). During the 2-year follow-up, the unadjusted readmission rates for bleeding were higher among women (4.9% versus 2.4% at 2 years after discharge). Multivariable competing risk analysis with the Fine-Gray model and Cox regression model further demonstrated that female sex was associated with a higher risk of bleeding.

CONCLUSIONS

Among patients treated with PCI, women had a higher incidence of bleeding events requiring readmission. Sex disparities in the etiologies of readmission following PCI suggest the need for targeted treatment strategies. A strict follow-up after discharge could be beneficial for women to further reduce their risk.

Role of Kv1.3 Channels in Platelet Functions and Thrombus Formation

Objective:

Platelet activation by stimulatory factors leads to an increase in intracellular calcium concentration ([Ca 2+ ] i ), which is essential for almost all platelet functions. Modulation of Ca 2+ influx and [Ca 2+ ] i in platelets has been emerging as a possible strategy for preventing and treating platelet-dependent thrombosis. Voltage-gated potassium 1.3 channels (Kv1.3) are highly expressed in platelets and able to regulate agonist-evoked [Ca 2+ ] i increase. However, the role of Kv1.3 channels in regulating platelet functions and thrombosis has not yet been elucidated. In addition, it is difficult to obtain a specific blocker for this channel, since Kv1.3 shares identical drug-binding sites with other K + channels. Here, we investigate whether specific blockade of Kv1.3 channels by monoclonal antibodies affects platelet functions and thrombosis.

Approach and Results:

In this study, we produced the anti-Kv1.3 monoclonal antibody 6E12#15, which could specifically recognize both human and mouse Kv1.3 proteins and sufficiently block Kv1.3 channel currents. We found Kv1.3 blockade by 6E12#15 inhibited platelet aggregation, adhesion, and activation upon agonist stimulation. In vivo treatment with 6E12#15 alleviated thrombus formation in a mesenteric arteriole thrombosis mouse model and protected mice from collagen/epinephrine-induced pulmonary thromboembolism. Furthermore, we observed Kv1.3 regulated platelet functions by modulating Ca 2+ influx and [Ca 2+ ] i elevation, and that this is mediated in part by P2X 1 . Interestingly, Kv1.3 −/− mice showed impaired platelet aggregation while displayed no abnormalities in in vivo thrombus formation. This phenomenon was related to more megakaryocytes and platelets produced in Kv1.3 −/− mice compared with wild-type mice.

Conclusions:

We showed specific inhibition of Kv1.3 by the novel monoclonal antibody 6E12#15 suppressed platelet functions and platelet-dependent thrombosis through modulating platelet [Ca 2+ ] i elevation. These results indicate that Kv1.3 could act as a promising therapeutic target for antiplatelet therapies.

Sex differences in the coagulation process and microvascular perfusion induced by brain death in rats

Brain death (BD) leads to a systemic inflammation associated with the activation of coagulation, which could be related to decreased microcirculatory perfusion. Evidence shows that females exhibit higher platelet aggregability than males. Thus, we investigated sex differences in platelets, coagulation and microcirculatory compromise after BD. BD was induced in male and female (proestrus) Wistar rats. After 3 h, we evaluated: (i) intravital microscopy to evaluate mesenteric perfusion and leucocyte infiltration; (ii) platelet aggregation assay; (iii) rotational thromboelastometry; and (iv) Serum NO x - . Female rats maintained the mesenteric perfusion, whereas male reduced percentage of perfused vessels. Male BD presented higher platelet aggregation than the controls. In contrast, female BD had lower platelet aggregation than the control. Thromboelastometry indicated a reduction in clot firmness with increased clotting time in the female group compared with the male group. Serum NO x - level in female BD was higher than that in the male BD and female control. There is sex dimorphism in platelet function and clotting process, which are altered in different ways by BD. Thus, it is possible to connect the reduction in microcirculatory perfusion in males to intravascular microthrombi formation and the maintenance of perfusion in females to a higher inflammatory response and NO synthesis.

Dark chocolate modulates platelet function with a mechanism mediated by flavan-3-ol metabolites

Cocoa is a rich source bioactive compounds, i.e., flavan-3-ols, and its consumption has been associated with several beneficial effects, such as the positive modulation of the hemostasis targeted by the platelet function. However, these phenolic compounds have a very low bioavailability and extensively undergo phase I and II metabolism, with the appearing into the bloodstream of (epi)catechin conjugates and phenyl-γ-valerolactones and their conjugates, at different times.The aims of this study were to explore the effect of dark chocolate on platelet function and to investigate the relationship between this interplay and flavan-3-ol derived metabolites.Eighteen healthy male volunteers ingested 50 g of 90% cocoa chocolate within 5 minutes. Blood samples were collected immediately before chocolate ingestion (T0) and 4 hours afterwards (T1). Platelet function analyzer (PFA)-100 closure time was assessed using collagen/adenosine-5'-diphosphate (COL/ADP) and collagen/epinephrine (COL/EPI) cartridges. Plasma flavan-3-ol metabolites were identified and quantified by means of liquid chromatography coupled to a triple quadrupole mass spectrometer (UHPLC-ESI-MS/MS).Results evidenced a significant increase of COL/ADP-induced PFA-100 closure time, but not COL/EPI, 4 hours after ingestion of dark chocolate. Total plasma structurally-related (epi)catechin metabolite (SREM) concentration significantly increased at T1, together with 4 out of the 6 detected metabolites. Total phenyl-γ-valerolactone concentrations remained unchanged. Spearman correlations evidenced a strong correlation between COL/ADP closure time and SREMs, mainly led by (epi)catechin-sulfate isomers.These data confirm that the potential beneficial effect of dark chocolate on primary hemostasis may be mediated by flavan-3-ol circulating metabolites.

Reprint of: Proteomics in cardiovascular diseases: Unveiling sex and gender differences in the era of precision medicine

Cardiovascular diseases (CVDs) represent the most important cause of mortality in women and in men. Contrary to the long-standing notion that the effects of the major risk factors on CVD outcomes are the same in both sexes, recent evidence recognizes new, potentially independent, sex/gender-related risk factors for CVDs, and sex/gender-differences in the clinical presentation of CVDs have been demonstrated. Furthermore, some therapeutic options may not be equally effective and safe in men and women. In this context, proteomics offers an extremely useful and versatile analytical platform for biomedical researches that expand from the screening of early diagnostic and prognostic biomarkers to the investigation of the molecular mechanisms underlying CDVs. In this review, we summarized the current applications of proteomics in the cardiovascular field, with emphasis on sex and gender-related differences in CVDs.

SIGNIFICANCE

Increasing evidence supports the profound effect of sex and gender on cardiovascular physio-pathology and the response to drugs. A clear understanding of the mechanisms underlying sexual dimorphisms in CVDs would not only improve our knowledge of the etiology of these diseases, but could also inform health policy makers and guideline committees in tailoring specific interventions for the prevention, treatment and management of CVDs in both men and women.

Proteomics in cardiovascular diseases: Unveiling sex and gender differences in the era of precision medicine

Cardiovascular diseases (CVDs) represent the most important cause of mortality in women and in men. Contrary to the long-standing notion that the effects of the major risk factors on CVD outcomes are the same in both sexes, recent evidence recognizes new, potentially independent, sex/gender-related risk factors for CVDs, and sex/gender-differences in the clinical presentation of CVDs have been demonstrated. Furthermore, some therapeutic options may not be equally effective and safe in men and women. In this context, proteomics offers an extremely useful and versatile analytical platform for biomedical researches that expand from the screening of early diagnostic and prognostic biomarkers to the investigation of the molecular mechanisms underlying CDVs. In this review, we summarized the current applications of proteomics in the cardiovascular field, with emphasis on sex and gender-related differences in CVDs.

SIGNIFICANCE

Increasing evidence supports the profound effect of sex and gender on cardiovascular physio-pathology and the response to drugs. A clear understanding of the mechanisms underlying sexual dimorphisms in CVDs would not only improve our knowledge of the etiology of these diseases, but could also inform health policy makers and guideline committees in tailoring specific interventions for the prevention, treatment and management of CVDs in both men and women.

Hemocompatibility of inhaled environmental nanoparticles: Potential use of in vitro testing

Hemocompatibility testing is an important part in the evaluation of nano-based medicines. However, it is not systematically used for the assessment of environmental particles since they do not come in contact with blood immediately. Studies on human exposure to air-borne particles and pulmonary exposure of rodents have reported alterations in blood physiology. It is not clear, whether these effects are majorly caused by tissue inflammation or translocated particles in blood. This review addresses the question, if in vitro hemocompatibility testing could help in the risk evaluation of inhaled particles. Particle blood concentrations were estimated based on exposure levels, ventilation volume, deposition rate, lung surface area, and permeability of the alveolar epithelium to particles. The categories of hemocompatibility, thrombosis, coagulation, platelets, hematology, and immunology, were introduced. Also, concentrations of ultrafine particles, silver nanoparticles, carbon nanotubes that caused adverse effects in human blood samples were compared to the estimated concentrations of translocated particles. The comparison suggested that, it is unlikely for translocated nanoparticles to be the sole cause of adverse blood effects. Nevertheless, the testing of specific hemocompatibility parameters (hemolysis and clotting) in healthy blood might help to compare biological effect of inhaled particles containing different amounts of contamination. Testing of samples from healthy and diseased persons might help to identify pathological dispositions that increase the possibility of adverse reaction of nanoparticles in blood.

RhoA/ROCK signaling contributes to sex differences in the activation of human platelets

Studies of sex-dependent differences in platelet aggregation and glycoprotein (GP)IIb/IIIa activation have demonstrated that platelets from females are more sensitive to agonists than those from males. To date, there is little understanding of these differences at a molecular level. Here, sex differences in reactivity of platelets from 86 women and 86 men were investigated. Platelet degranulation (CD62P expression) and activation of GPIIb/IIIa (PAC-1 binding), with and without ADP, were assessed. Extent of shape change (ESC) in response to ADP was measured. Basal CD62P and PAC-1 expression did not differ between the sexes. In response to ADP activation, mean PAC-1 binding in platelets from female donors was 17.9±3.5% vs. 14.0±4.1% in platelets from male donors, and ESC was significantly greater in platelets from females (p<0.05). Evaluation of basal expression of signaling molecules along the ADP receptor pathway leading to GPIIb/IIIa activation and subsequent RhoA/ROCK signaling via GPIIb/IIIa 'outside-in' signaling showed that platelets from females produce 3-fold greater levels of phosphorylated protein kinase C (PKC) substrates. There was a 2.5-fold greater level of activated RhoA, and platelet sub-fractionation analysis demonstrated 2.7-fold more RhoA in the membrane fraction of female vs. male platelets. Similarly, there was a 2.8-fold increase in levels of phosphorylated myosin light chain (MLC) in platelets from females vs. males. The increased signaling activity in platelets from females mirrors their greater sensitivity to agonists. These findings further our understanding of the molecular differences between platelets from males and females.

Sex differences in stroke: the contribution of coagulation

Stroke is now the leading cause of adult disability in the United States. Women are disproportionately affected by stroke. Women increasingly outnumber men in the elderly population, the period of highest risk for stroke. However, there is also a growing recognition that fundamental sex differences are present that contribute to differential ischemic sensitivity. In addition, gonadal hormone exposure can impact coagulation and fibrinolysis, key factors in the initiation of thrombosis. In this review we will discuss sex differences in stroke, with a focus on platelets, vascular reactivity and coagulation.

Gender differences in cardiovascular therapy: focus on antithrombotic therapy and percutaneous coronary intervention

The epidemiology of coronary artery disease (CAD) differs between women and men: female cardiac patients are older and have poorer risk profiles than their male counterparts. This results in a preferential exclusion of women from participation in clinical trials, reducing their power to detect differences in performance of cardiovascular therapies in women. In general, all the antiplatelet and anticoagulant medications used in cardiac patients are equally effective in men and women, although women tend to experience a higher relative benefit due to their poorer risk profile. In particular, women with CAD benefit the most from interventional treatment combined with modern antithrombotic drugs. No gender-related differences in the reduction of thromboembolic risk with more potent antithrombotic drugs have been reported. On the other hand, a clear trend to a higher incidence of bleeding complications has been consistently reported in women, which might be related to a more frequent over-dosage of antithrombotic treatment in women than in men. Women are therefore one of the subgroups that might benefit the most from careful dose adjustment of available antithrombotic drugs. However, the development of a gender-based dosage guideline remains an unmet need in cardiology.

Platelet dynamics during natural and pharmacologically induced torpor and forced hypothermia

Hibernation is an energy-conserving behavior in winter characterized by two phases: torpor and arousal. During torpor, markedly reduced metabolic activity results in inactivity and decreased body temperature. Arousal periods intersperse the torpor bouts and feature increased metabolism and euthermic body temperature. Alterations in physiological parameters, such as suppression of hemostasis, are thought to allow hibernators to survive periods of torpor and arousal without organ injury. While the state of torpor is potentially procoagulant, due to low blood flow, increased viscosity, immobility, hypoxia, and low body temperature, organ injury due to thromboembolism is absent. To investigate platelet dynamics during hibernation, we measured platelet count and function during and after natural torpor, pharmacologically induced torpor and forced hypothermia. Splenectomies were performed to unravel potential storage sites of platelets during torpor. Here we show that decreasing body temperature drives thrombocytopenia during torpor in hamster with maintained functionality of circulating platelets. Interestingly, hamster platelets during torpor do not express P-selectin, but expression is induced by treatment with ADP. Platelet count rapidly restores during arousal and rewarming. Platelet dynamics in hibernation are not affected by splenectomy before or during torpor. Reversible thrombocytopenia was also induced by forced hypothermia in both hibernating (hamster) and non-hibernating (rat and mouse) species without changing platelet function. Pharmacological torpor induced by injection of 5'-AMP in mice did not induce thrombocytopenia, possibly because 5'-AMP inhibits platelet function. The rapidness of changes in the numbers of circulating platelets, as well as marginal changes in immature platelet fractions upon arousal, strongly suggest that storage-and-release underlies the reversible thrombocytopenia during natural torpor. Possibly, margination of platelets, dependent on intrinsic platelet functionality, governs clearance of circulating platelets during torpor.

Human platelet microRNA-mRNA networks associated with age and gender revealed by integrated plateletomics

There is little data considering relationships among human RNA, demographic variables, and primary human cell physiology. The platelet RNA and expression-1 study measured platelet aggregation to arachidonic acid, ADP, protease-activated receptor (PAR) 1 activation peptide (PAR1-AP), and PAR4-AP, as well as mRNA and microRNA (miRNA) levels in platelets from 84 white and 70 black healthy subjects. A total of 5911 uniquely mapped mRNAs and 181 miRNAs were commonly expressed and validated in a separate cohort. One hundred twenty-nine mRNAs and 15 miRNAs were differentially expressed (DE) by age, and targets of these miRNAs were over-represented among these mRNAs. Fifty-four mRNAs and 9 miRNAs were DE by gender. Networks of miRNAs targeting mRNAs, both DE by age and gender, were identified. The inverse relationship in these RNA pairs suggests miRNAs regulate mRNA levels on aging and between genders. A simple, interactive public web tool (www.plateletomics.com) was developed that permits queries of RNA levels and associations among RNA, platelet aggregation and demographic variables. Access to these data will facilitate discovery of mechanisms of miRNA regulation of gene expression. These results provide new insights into aging and gender, and future platelet RNA association studies must account for age and gender.

PPARγ activation rescues mitochondrial function from inhibition of complex I and loss of PINK1

Parkinson's disease has long been associated with impaired mitochondrial complex I activity, while several gene defects associated with familial Parkinson's involve defects in mitochondrial function or 'quality control' pathways, causing an imbalance between mitochondrial biogenesis and removal of dysfunctional mitochondria by autophagy. Amongst these are mutations of the gene for PTEN-induced kinase 1 (PINK1) in which mitochondrial function is abnormal. Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear receptor and ligand-dependent transcription factor, regulates pathways of inflammation, lipid and carbohydrate metabolism, antioxidant defences and mitochondrial biogenesis. We have found that inhibition of complex I in human differentiated SHSY-5Y cells by the complex I inhibitor rotenone irreversibly decrease mitochondrial mass, membrane potential and oxygen consumption, while increasing free radical generation and autophagy. Similar changes are seen in PINK1 knockdown cells, in which potential, oxygen consumption and mitochondrial mass are all decreased. In both models, all these changes were reversed by pre-treatment of the cells with the PPARγ agonist, rosiglitazone, which increased mitochondrial biogenesis, increased oxygen consumption and suppressed free radical generation and autophagy. Thus, rosiglitazone is neuroprotective in two different models of mitochondrial dysfunction associated with Parkinson's disease through a direct impact on mitochondrial function.

A place for ultrastructural analysis of platelets in cerebral ischemic research

It is well known that estrogen is neuroprotective through various mechanisms which suggest that sex hormone levels, thrombotic mechanisms, and inflammatory processes are strongly interconnected in predicting the outcome and consequences of cerebral ischemia. Because platelet ultrastructure is altered in conditions like thrombosis and associated with stroke, the question arises whether ultrastructural analyses of platelet morphology may provide further insight into the role of estrogen during ischemic insult. In the current study, a hyperglycemic modification to the two-vessel occlusion model for inducing experimental cerebral ischemia was employed, in order to correlate neural tissue integrity levels between three experimental groups to corresponding platelet ultrastructure so as to determine whether there is an association between cerebral ischemia and the presence of inflammatory or necrotic platelet ultrastructure. It is apparent in the results that under the influence of estrogen in cyclic or intact females, there is lesser neural tissue damage as well as a reduced degree of inflammation evident in platelet activation morphology when compared to males and acyclic or ovariectomized females. It is unmistakable that neural injury is closely shadowed, if not preceded, by inflammatory changes in the coagulation system, particularly manifested in platelet ultrastructure. It is therefore suggested that platelets may indeed be used successfully to follow the progression of events of cerebral ischemia and possibly assist in the assessment of treatment strategies and their effects on hemostasis.

Sex, stroke, and inflammation: the potential for estrogen-mediated immunoprotection in stroke

Stroke is the third leading cause of death and the primary cause of disability in the developed world. Experimental and clinical data indicate that stroke is a sexually dimorphic disease, with males demonstrating an enhanced intrinsic sensitivity to ischemic damage throughout most of their lifespan. The neuroprotective role of estrogen in the female brain is well established, however, estrogen exposure can also be deleterious, especially in older women. The mechanisms for this remain unclear. Our current understanding is based on studies examining estrogen as it relates to neuronal injury, yet cerebral ischemia also induces a robust sterile inflammatory response involving local and systemic immune cells. Despite the potent anti-inflammatory effects of estrogen, few studies have investigated the contribution of estrogen to sex differences in the inflammatory response to stroke. This review examines the potential role for estrogen-mediated immunoprotection in ischemic injury.

Does Gender have an Influence on Platelet Function and the Efficacy of Oral Antiplatelet Therapy?

The underlying pathophysiology of ischemic complications during acute coronary syndrome involves thrombus generation at sites of plaque rupture and endothelial erosion, in which platelet activation and aggregation play major roles. This review discusses whether there are intrinsic differences in thrombogenicity between genders. In trials of acute coronary syndromes with dual antiplatelet therapy strategies, women tend to experience more ischemic events. Controversy exists surrounding the protective role of estrogens in the premenopausal woman. In vitro studies support the attenuation of platelet function by estrogen. Sufficient data support the presence of gender differences in thrombogenicity to promote further investigation in this area.

Gender differences in anticoagulation and antithrombotic therapy

Cardiovascular disease is the main cause of mortality and morbidity worldwide. The rate of thromboembolic events has increased in women but not in men. Large clinical studies support the use of a variety of antithrombotic drugs for the treatment of patients with different cardiovascular diseases. The heterogeneous patient population included in these trials affects the attempt to generalize the study results to subgroups, which are not sufficiently represented in the study population, such as women and other minorities. Gender-related differences in the clinical presentation and outcome seem to relate to differences in platelet biology and coagulation reactions, resulting in different rates of thromboembolic and bleeding events. The effectiveness of antithrombotic therapies and the occurrence of adverse events define the clinical benefit of the treatment for each patient. This chapter gives an overview of the currently available data on gender-differences in anticoagulation and antithrombotic therapy.

Gender differences in platelet aggregation in healthy individuals

This study evaluated gender variability in platelet aggregation in response to common agonists. Platelet aggregation was measured in 36 healthy men and women free of any antiplatelet medication, aged 22-36 years, of Caucasian (White not of Hispanic origin), Hispanic, and African-American not of Hispanic origin. In this ex-vivo study, we investigated platelet aggregation in response to adenosine-5'-diphosphate (ADP), epinephrine (EPI), arachidonic acid (AA) and collagen (COL), using a platelet ionized calcium aggregometer (Chrono-Log Co.). Platelet aggregation response to all tested agonists was higher in females than in males regardless of ethnicity. The most significant differences were observed with collagen (P < 0.01). Among the ethnic groups, Caucasian women were most prone to platelet aggregation. Gender is a determinant of agonist effects on platelet aggregability in healthy subjects.

Inhibition of platelet aggregation by omega-3 polyunsaturated fatty acids is gender specific-Redefining platelet response to fish oils

Existence of gender differences in cardiovascular disease (CVD) following long-chain omega-3 polyunsaturated fatty acid (LCn-3 PUFA) supplementation have suggested that sex hormones play a role in cardio-protection. The objective of this study was to determine gender specific responses in the efficacy of LCn-3 PUFA to inhibit platelet aggregation in vitro. Blood was analyzed for collagen-induced platelet aggregation following pre-incubation with LCn-3 PUFA in healthy adults (n=42). Eicosapentaenoic acid (EPA) was significantly more effective in reducing platelet aggregation compared with docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). When grouped by gender, this differential pattern was followed in males only. In females, DHA, DPA and EPA were all equally effective. Between group analyses (LCn-3 PUFA vs. gender) showed that both DHA and DPA were significantly less effective in males compared with females. EPA was equally effective in reducing platelet aggregation in both groups. These findings show that significant gender differences exist in platelet aggregation in response to various LCn-3 PUFA treatments.

Thrombosis and antithrombotic therapy in women

Sex-based differences in the prevalence and presentation of arterial and venous thrombosis exist, and emerging data indicate that men and women do not accrue equal benefit from antithrombotic therapy. Sex hormones alter procoagulant protein expression and the function of blood and vascular cells. Sex-based differences in platelet function have been reported, and in animal models, sex-based differences in thrombosis have been noted. Here we review plausible mechanisms that may explain how sex functions as a modifier of thrombosis and summarize clinical data on the interaction between sex and response to antithrombotic therapy.