Hormones, age, and sex affect platelet responsiveness in vitro.

BACKGROUND: Female sex confers a survival advantage following severe injury in the setting of trauma-induced coagulopathy, with female platelets having heightened responsiveness likely due to estrogen. The effects of testosterone on platelet biology are unknown, and platelets express both estradiol and androgen receptors on the plasma membrane. We hypothesize testosterone decreases platelet responses in vitro, and there are baseline differences in platelet function and metabolism stratified by sex/age. STUDY DESIGN AND METHODS: Apheresis platelets were collected from: older males (OM) ≥45 years, younger males (YM) <45 years, older females (OF) ≥54 years, and younger females (YF) <54 years, and testosterone and estradiol were measured. Platelets were incubated with testosterone (5.31 ng/ml), estradiol (105 pg/ml) or vehicle and stimulated with buffer, adenosine diphosphate (20 µM), platelet activating factor (2 µM), or thrombin (0.3 U/ml). Aggregation, CD62P surface expression, fibrinogen receptor surface expression, and platelet mitochondrial metabolism were measured. RESULTS: Testosterone significantly inhibited aggregation in OF and OM (p < .05), inhibited CD41a expression in YF, YM, and OM (p < .05), and affected a few of the baseline amounts of CD62P surface expression but not platelet activation to platelet-activating factor and adenosine diphosphate, and variably changed platelet metabolism. DISCUSSION: Platelets have sex- and age-specific aggregation, receptor expression, and metabolism. Testosterone decreases platelet function dependent on the stimulus, age, and sex. Similarly, platelet metabolism has varying responses to sex hormones with baseline metabolic differences dependent upon sex and age.

Molecular and functional characteristics of megakaryocytes and platelets in aging.

PURPOSE OF REVIEW: Advances in medical care and preventive measures have contributed to increasing life expectancy. Therefore, it is critical to expand our understanding of the physiological and pathophysiological adaptations of the hematological system in aging. We highlight and review the findings from recent investigations aimed at understanding the effects of aging on megakaryocytes and platelets. RECENT FINDINGS: Biochemical and transcriptomic studies of megakaryocytes and platelets from older humans and mice have advanced our understanding of the molecular and functional characteristics of megakaryocytes and platelets during aging. These studies have led to the identification of metabolic and inflammatory pathways associated with the generation of hyperreactive platelets that may significantly contribute to the high incidence of thrombosis in aging. SUMMARY: By increasing our research efforts to understand and identify the characteristics of megakaryocytes and platelets in aging, we will increase our potential to develop novel therapies aimed at decreasing the incidence of aging-associated thrombosis. These efforts will also serve as a foundation to better understand the role of megakaryocytes and platelets in other age-related hematological conditions with high thrombotic risk such as clonal hematopoiesis of indeterminate potential and myeloproliferative neoplasms.

A unique phenotype of T-cell acute lymphoblastic leukemia in a patient with GATA2 haploinsufficiency.

Germline or acquired mutations involving the GATA-binding protein gene (GATA2) have been linked to a variety of clinical conditions. In addition, patients harboring GATA2 mutations have a striking predisposition to develop myeloid malignancies, such as myelodysplastic syndrome or acute myeloid leukemia, but not acute lymphoblastic leukemia (ALL). We report here a unique occurrence of early T-cell precursor ALL in a young child with GATA2 haploinsufficiency.

Platelets from blood diversion pouches (DPs) are a suitable alternative for functional, bioenergetic, and metabolomic analyses.

BACKGROUND: The collection of the first blood flow into a diversion pouch (DP) has become widely adopted in blood donation systems to reduce whole-blood unit contamination from skin bacteria. The strict control of pre-analytical variables, such as blood collection and proper anticoagulant selection, is critical to diminish experimental variability when studying different aspects of platelet biology. We hypothesize that the functional, mitochondrial, and metabolomic profiles of platelets isolated from the DP are not different from the ones isolated from standard venipuncture (VP), thus representing a suitable collection method of platelets for experimental purposes. MATERIALS AND METHODS: Whole blood from the blood DP or VP was collected. Platelets were subsequently isolated and washed following standard protocols. Platelet function was assessed by flow cytometry, light transmission aggregometry, clot retraction, and under flow conditions using the total thrombus formation analyzer (T-TAS). Mitochondrial function and the platelet metabolome profiles were determined by the Seahorse extracellular flux analyzer (Agilent, Santa Clara, CA, USA) and ultra-high-pressure liquid chromatography-mass spectrometry metabolomics, respectively. RESULTS: Platelets isolated from VP and the DP have similar functional, mitochondrial, and metabolic profiles with no significant differences between both groups at baseline and upon activation by any of the assays mentioned above. DISCUSSION: The findings of our study support the use of platelets from the DP for performing functional and metabolic studies on platelets from a wide range of blood donors. The DP may serve as an alternative blood collection method to standard VP, allowing the study of diverse aspects of platelet biology, such as age, sex, race, and ethnicity, in many eligible individuals for blood donation.

Erythrocyte mitogen-activated protein kinases mediate hemolytic events under osmotic and oxidative stress and in hemolytic diseases.

p38 MAPKs are key regulators of cellular adaptation to various stress stimuli, however, their role in mediating erythrocyte cell death and hemolysis is largely unknown. We hypothesized that activation of erythrocyte p38 MAPK is a common event in the stimulation of hemolysis, and that inhibition of p38 MAPK pathways could mitigate hemolysis in hemoglobinopathies. We exposed human erythrocytes to diamide-induced oxidative stress or to hypoosmotic shock in the presence or absence of p38 MAPK inhibitors (SCIO469, SB203580, CMPD1) and used immunoblotting to determine MAPK activity and to identify possible downstream effectors of p38 MAPK. We also evaluated the impact of p38 MAPK inhibitors on stress-induced hemolysis or hypoxia-induced sickling in erythrocytes from mouse models of sickle cell disease. We found that human erythrocytes express conventional MAPKs (MKK3, p38 MAPK, MAPKAPK2) and identified differential MAPK activation pathways in each stress condition. Specifically, p38 MAPK inhibition in diamide-treated erythrocytes was associated with decreased phosphorylation of Src tyrosine kinases and Band 3 protein. Conversely, hypoosmotic shock induced MAPKAPK2 and RSK2 phosphorylation, which was inhibited by SCIO469 or CMPD1. Relevant to hemoglobinopathies, sickle cell disease was associated with increased erythrocyte MKK3, p38 MAPK, and MAPKAPK2 expression and phosphorylation as compared with erythrocytes from healthy individuals. Furthermore, p38 MAPK inhibition was associated with decreased hemolysis in response to diamide treatments or osmotic shock, and with decreased erythrocyte sickling under experimental hypoxia. These findings provided insights into MAPK-mediated signaling pathways that regulate erythrocyte function and hemolysis in response to extracellular stressors or human diseases.