Learning by counting blood platelets in population studies: survey and perspective a long way after Bizzozero

Anti-CXCR2 antibody-coated nanoparticles with an erythrocyte-platelet hybrid membrane layer for atherosclerosis therapy

Atherosclerosis is the leading cause of mortality globally. RBC-platelet hybrid membrane-coated nanoparticles ([RBC-P]NPs), which biologically mimic platelets in vivo, display evidence of anti-atherosclerotic activity. The efficacy of a targeted RBC-platelet hybrid membrane-coated nanoparticles ([RBC-P]NP)-based approach was investigated as a primary preventive measure against atherosclerosis. A ligand-receptor interactome analysis conducted with circulating platelets and monocytes derived from CAD patients and healthy controls identified CXCL8-CXCR2 as a key platelet ligand-monocyte receptor dyad in CAD patients. Based on this analysis, a novel anti-CXCR2 [RBC-P]NP that specifically binds to CXCR2 and blocks the interaction between CXCL8 and CXCR2 was engineered and characterized. Administering anti-CXCR2 [RBC-P]NPs to Western diet-fed Ldlr^-/- mice led to diminished plaque size, necrosis, and intraplaque macrophage accumulation relative to control [RBC-P]NPs or vehicle. Importantly, anti-CXCR2 [RBC-P]NPs demonstrated no adverse bleeding/hemorrhagic effects. A series of in vitro experiments was conducted to characterize anti-CXCR2 [RBC-P]NP's mechanism of action in plaque macrophages. Mechanistically, anti-CXCR2 [RBC-P]NPs inhibited p38α (Mapk14)-mediated, pro-inflammatory M1 skewing and corrected efferocytosis in plaque macrophages. This targeted [RBC-P]NP-based approach, in which the cardioprotective effects of anti-CXCR2 [RBC-P]NP therapy overweighs its bleeding/hemorrhagic risks, could potentially be used to proactively manage atherosclerotic progression in at-risk populations.

A dry immersion model of microgravity modulates platelet phenotype, miRNA signature, and circulating plasma protein biomarker profile

Ground based research modalities of microgravity have been proposed as innovative methods to investigate the aetiology of chronic age-related conditions such as cardiovascular disease. Dry Immersion (DI), has been effectively used to interrogate the sequelae of physical inactivity (PI) and microgravity on multiple physiological systems. Herein we look at the causa et effectus of 3-day DI on platelet phenotype, and correlate with both miRomic and circulating biomarker expression. The miRomic profile of platelets is reflective of phenotype, which itself is sensitive and malleable to the exposome, undergoing responsive transitions in order to fulfil platelets role in thrombosis and haemostasis. Heterogeneous platelet subpopulations circulate at any given time, with varying degrees of sensitivity to activation. Employing a DI model, we investigate the effect of acute PI on platelet function in 12 healthy males. 3-day DI resulted in a significant increase in platelet count, plateletcrit, platelet adhesion, aggregation, and a modest elevation of platelet reactivity index (PRI). We identified 15 protein biomarkers and 22 miRNA whose expression levels were altered after DI. A 3-day DI model of microgravity/physical inactivity induced a prothrombotic platelet phenotype with an unique platelet miRNA signature, increased platelet count and plateletcrit. This correlated with a unique circulating protein biomarker signature. Taken together, these findings highlight platelets as sensitive adaptive sentinels and functional biomarkers of epigenetic drift within the cardiovascular compartment.

Platelet Distribution Width Is Associated with P-Selectin Dependent Platelet Function: Results from the Moli-Family Cohort Study

Defined as an index of platelet size heterogeneity, the platelet distribution width (PDW) is still a poorly characterized marker of platelet function in (sub)clinical disease. We presently validated PDW as a marker of P-selectin dependent platelet activation in the Moli-family cohort. Platelet-bound P-selectin and platelet/leukocyte mixed aggregates were measured by flow cytometry in freshly collected venous blood, both before and after in vitro platelet activation, and coagulation time was assessed in unstimulated and LPS- or TNFα-stimulated whole blood. Closure Times (CT) were measured in a Platelet Function Analyzer (PFA)-100. Multivariable linear mixed effect regression models (with age, sex and platelet count as fixed and family structure as random effect) revealed PDW to be negatively associated with platelet P-selectin, platelet/leukocyte aggregates and von Willebrand factor (VWF), and positively with PFA-100 CT, and LPS- and TNF-α-stimulated coagulation times. With the exception of VWF, all relationships were sex-independent. In contrast, no association was found between mean platelet volume (MPV) and these variables. PDW seems a simple, useful marker of ex vivo and in vitro P-selectin dependent platelet activation. Investigations of larger cohorts will define the usefulness of PDW as a risk predictor of thrombo-inflammatory conditions where activated platelets play a contributing role.

Beyond Haemostasis and Thrombosis: Platelets in Depression and Its Co-Morbidities

Alongside their function in primary haemostasis and thrombo-inflammation, platelets are increasingly considered a bridge between mental, immunological and coagulation-related disorders. This review focuses on the link between platelets and the pathophysiology of major depressive disorder (MDD) and its most frequent comorbidities. Platelet- and neuron-shared proteins involved in MDD are functionally described. Platelet-related studies performed in the context of MDD, cardiovascular disease, and major neurodegenerative, neuropsychiatric and neurodevelopmental disorders are transversally presented from an epidemiological, genetic and functional point of view. To provide a complete scenario, we report the analysis of original data on the epidemiological link between platelets and depression symptoms suggesting moderating and interactive effects of sex on this association. Epidemiological and genetic studies discussed suggest that blood platelets might also be relevant biomarkers of MDD prediction and occurrence in the context of MDD comorbidities. Finally, this review has the ambition to formulate some directives and perspectives for future research on this topic.

Platelet regulation of myeloid suppressor of cytokine signaling 3 accelerates atherosclerosis

Platelets are best known as mediators of hemostasis and thrombosis; however, their inflammatory effector properties are increasingly recognized. Atherosclerosis, a chronic vascular inflammatory disease, represents the interplay between lipid deposition in the artery wall and unresolved inflammation. Here, we reveal that platelets induce monocyte migration and recruitment into atherosclerotic plaques, resulting in plaque platelet-macrophage aggregates. In Ldlr ^-/- mice fed a Western diet, platelet depletion decreased plaque size and necrotic area and attenuated macrophage accumulation. Platelets drive atherogenesis by skewing plaque macrophages to an inflammatory phenotype, increasing myeloid suppressor of cytokine signaling 3 (SOCS3) expression and reducing the Socs1:Socs3 ratio. Platelet-induced Socs3 expression regulates plaque macrophage reprogramming by promoting inflammatory cytokine production (Il6, Il1b, and Tnfa) and impairing phagocytic capacity, dysfunctions that contribute to unresolved inflammation and sustained plaque growth. Translating our data to humans with cardiovascular disease, we found that women with, versus without, myocardial infarction have up-regulation of SOCS3, lower SOCS1:SOCS3, and increased monocyte-platelet aggregate. A second cohort of patients with lower extremity atherosclerosis demonstrated that SOCS3 and the SOCS1:SOCS3 ratio correlated with platelet activity and inflammation. Collectively, these data provide a causative link between platelet-mediated myeloid inflammation and dysfunction, SOCS3, and cardiovascular disease. Our findings define an atherogenic role of platelets and highlight how, in the absence of thrombosis, platelets contribute to inflammation.

Reference Intervals for Platelet Counts in the Elderly: Results from the Prospective SENIORLAB Study

Currently, age- and sex-independent reference limits (RLs) are frequently used to interpret platelet counts in seniors. We aimed to define and validate reference intervals (RIs) for platelet counts within the framework of the prospective SENIORLAB study. Subjectively healthy Swiss individuals aged 60 years and older were prospectively included and followed for morbidity and mortality. Participants who had circumstances known to affect platelet counts were excluded. The obtained RIs were validated with indirect statistical methods. Frequencies of abnormal platelet counts in a population-based setting, including 41.5% of the entire age-specific population of the Principality of Liechtenstein, were compared by using age- and sex-independent RIs and the RLs obtained in the present study. For males (n = 542), 95% RIs for platelet counts were defined as follows: 150–300 × 10⁹/L (60–69 years); 130–300 × 10⁹/L (70–79 years); and 120–300 × 10⁹/L (80 years and above). For females (n = 661), the consolidated age-independent 95% RI was 165–355 × 10⁹/L. These RI values were validated by indirect RI determination of 51,687 (30,392 female/21,295 male) patients of the same age. Age- and sex-independent RIs exhibited imbalanced frequencies of abnormal platelet counts between the two sexes, which were corrected by introducing age- and sex-specific RLs. In conclusion, females have higher platelet counts than males. Whereas the upper RL for males remains constant, the lower RL decreases with age. We propose to abandon the practice of employing sex- and age-independent RL for platelet counts in the elderly.

Cardiovascular Risk Factors and Haematological Indexes of Inflammation in Paralympic Athletes with Different Motor Impairments

Haematological indexes of both inflammation and platelet activation have been suggested as predictive markers of cardiovascular disease (CVD), which has high prevalence in Paralympic athletes (PA). Different mechanisms could play a role in increasing CVD risk in PA with spinal cord injury (PA-SCI), lower limb amputation (PA-LLA), or upper limb impairment (PA-ULI). We compared, in 4 groups of PA competing in power, intermittent (mixed metabolism), and endurance sports, Framingham Risk Score (FRS), metabolic syndrome criteria (MetS-C), inflammation (INFLA) Score, 5 haematological indexes of platelet activation (mean platelet volume (MPV), platelet distribution width (PDW), and the ratios between MPV and platelet (MPVPR), between MPV and lymphocyte (MPVLR), and between PDW and lymphocyte (PDWLR)) and the endogenous antioxidants uric acid (UA) and bilirubin (BR). A retrospective chart review of PA from preparticipation examinations' records (London 2012 and Sochi 2014 Paralympics) was performed. We included 25 PA-SCI (13 with high and 12 with low lesion, PA-SCI-H and PA-SCI-L), 15 PA-LLA, and 10 PA-ULI. FRS and INFLA Score did not differ among groups, but PA-SCI-H had lower HDL, compared to PA-SCI-L and PA-ULI. PA-LLA had more MetS diagnostic criteria with significant higher glucose levels than other groups. PA-SCI-H had significantly lower lymphocytes' count compared to PA-LLA and higher MPV, PDW, MPVPR, MPVLR, and PDWLR. SCI-H had lower BR, haemoglobin, haematocrit, proteins, and creatinine. No interaction was found between the 3 kinds of sitting sports and the 2 groups of health conditions (PA-SCI and PA-LLA). In conclusion, PA-LLA had a higher cardiometabolic risk, whereas PA-SCI-H had a higher platelet-derived cardiovascular risk. Further larger studies are needed to investigate the relationship between indexes of inflammation/oxidation and dietary habit, body composition, and physical fitness/performance in PA with motor impairments.