Altered expression of platelet proteins and calpain activity mediate hypoxia-induced prothrombotic phenotype

Development of a super-hydrophilic anaerobic tube for the optimization of platelet-rich fibrin

Horizontal platelet-rich fibrin (H-PRF) contains a variety of bioactive growth factors and cytokines that play a key role in the process of tissue healing and regeneration. The blood collection tubes used to produce Solid-PRF (plasmatrix (PM) tubes) have previously been shown to have a great impact on the morphology, strength and composition of the final H-PRF clot. Therefore, modification to PM tubes is an important step toward the future optimization of PRF. To this end, we innovatively modified the inner wall surface of the PM tubes with plasma and adjusted the gas environment inside the PM tubes to prepare super-hydrophilic anaerobic plasmatrix tubes (SHAP tubes). It was made anaerobic for the preparation of H-PRF with the aim of improving mechanical strength and bioactivity. The findings demonstrated that an anaerobic environment stimulated platelet activation within the PRF tubes. After compression, the prepared H-PRF membrane formed a fibrous cross-linked network with high fracture strength, ideal degradation characteristics, in addition to a significant increase in size. Thereafter, the H-PRF membranes prepared by the SHAP tubes significantly promoted collagen synthesis of gingival fibroblast and the mineralization of osteoblasts while maintaining excellent biocompatibility, and advantageous antibacterial properties. In conclusion, the newly modified PRF tubes had better platelet activation properties leading to better mechanical strength, a longer degradation period, and better regenerative properties in oral cell types including gingival fibroblast and alveolar osteoblasts. It also improves the success rate of H-PRF preparation in patients with coagulation dysfunction and expands the clinical application scenario.

Diagnostic significance of complete blood cell count and hemogram-derived markers for neonatal sepsis at Southwest Public Hospitals, Ethiopia

BACKGROUND

Neonatal sepsis is defined as an infection-related condition characterized by signs and symptoms of bacteremia within the first month of life. It is the leading cause of mortality and morbidity among newborns. While several studies have been conducted in other parts of world to assess the usefulness of complete blood count parameters and hemogram-derived markers as early screening tools for neonatal sepsis, the associations between sepsis and its complications with these blood parameters are still being investigated in our setting and are not yet part of routine practice.

AIM

To evaluate the diagnostic significance of complete blood cell count hemogram-derived novel markers for neonatal sepsis among neonates attending public hospitals in the southwest region of Oromia, Ethiopia, through a case control study.

METHODS

A case control study was conducted from October 2021 to October 2023 Sociodemographic, clinical history, and laboratory test results data were collected using structured questionnaires. The collected data were entered into Epi-data 3.1 version and exported to SPSS-25 for analysis. Chi-square, independent sample t-test, and receiver operator characteristics curve of curve were used for analysis. A P-value of less than 0.05 was considered statistically significant.

RESULTS

In this study, significant increases were observed in the following values in the case group compared to the control group: In white blood cell (WBC) count, neutrophils, monocyte, mean platelet volume (MPV), neutrophils to lymphocyte ratio, monocyte to lymphocyte ratio (MLR), red blood cell width to platelet count ratio (RPR), red blood width coefficient variation, MPV to RPR, and platelet to lymphocyte ratio. Regarding MLR, a cut-off value of ≥ 0.26 was found, with a sensitivity of 68%, a specificity of 95%, a positive predictive value (PPV) of 93.2%, and a negative predictive value (NPV) of 74.8%. The area under the curve (AUC) was 0.828 (P < 0.001). For WBC, a cut-off value of ≥ 11.42 was identified, with a sensitivity of 55%, a specificity of 89%, a PPV of 83.3%, and a NPV of 66.4%. The AUC was 0.81 (P < 0.001). Neutrophils had a sensitivity of 67%, a specificity of 81%, a PPV of 77.9%, and a NPV of 71.1%. The AUC was 0.801, with a cut-off value of ≥ 6.76 (P = 0.001). These results indicate that they were excellent predictors of neonatal sepsis diagnosis.

CONCLUSION

The findings of our study suggest that certain hematological parameters and hemogram-derived markers may have a potential role in the diagnosis of neonatal sepsis.

Poly (ADP-ribose) Polymerase-1 modulations in the genesis of thrombosis

Thrombosis, a coagulation disorder, occurs due to altered levels of coagulation, fibrinolytic and immune factors, which are otherwise known to maintain hemostasis in normal physiological conditions. Here, we review the direct and indirect participation of a multifunctional nuclear enzyme poly (ADP-ribose) polymerase-1 (PARP1) in the expression of key genes and cellular processes involved in thrombotic pathogenesis. PARP1 biological activities range from maintenance of genomic integrity, chromatin remodeling, base excision DNA repair, stress responses to cell death, angiogenesis and cell cycle pathways. However, under homeostatic imbalances, PARP1 activities are linked with the pathogenesis of diseases, including cancer, aging, neurological disorders, and cardiovascular diseases. Disease-associated distressed cells employ a variety of PARP-1 functions such as oxidative damage exacerbations, cellular energetics and apoptosis pathways, regulation of inflammatory mediators, promotion of endothelial dysfunction, and ERK-mediated signaling in pathogenesis. Thrombosis is one such pathogenesis that comprises exacerbation of coagulation cascade due to biochemical alterations in endothelial cells, platelet activation, overexpression of adhesion molecules, cytokines release, and leukocyte adherence. Thus, the activation of endothelial and inflammatory cells in thrombosis implicates a potential role of PARP1 activation in thrombogenesis. This review article explores the direct impact of PARP1 activation in the etiology of thrombosis and discusses PARP1-mediated endothelial dysfunction, inflammation, and epigenetic regulations in the disease manifestation. Understanding PARP1 functions associated with thrombosis may elucidate novel pathogenetic mechanisms and help in better disease management through newer therapeutic interventions targeting PARP1 activity.

Pre-chemoradiotherapy high platelet counts predict jaw osteoradionecrosis in locally advanced nasopharyngeal carcinoma patients

INTRODUCTION

This retrospective study aimed to investigate if pretreatment platelet (PLT) levels can predict the risk of osteoradionecrosis of the jaw (ORNJ) in patients with locally advanced nasopharyngeal carcinoma (LA-NPC) who received concurrent chemoradiotherapy (CCRT).

MATERIAL &METHODS

ORNJ instances were identified from LA-NPC patients' pre- and post-CCRT oral exam records. All pretreatment PLT values were acquired on the first day of CCRT. Receiver operating characteristic curve analysis was used to determine the optimal PLT cutoff that divides patients into two subgroups with distinctive ORNJ rates. The primary outcome measure was the association between pretreatment PLT values and ORNJ incidence rates.

RESULTS

The incidence of ORNJ was 8.8 % among the 240 LA-NPC patients analyzed. The ideal pre-CCRT PLT cutoff which divided the patients into two significantly different ORNJ rate groups was 285,000 cells/µL (PLT ≤ 285,000 cells/µL (N = 175) vs. PLT > 285,000 cells/µL (N = 65)). A comparison of the two PLT groups revealed that the incidence of ORNJ was substantially higher in patients with PLT > 285,000 cells/L than in those with PLT≤285,000 cells/L (26.2% vs. 2.3 %; P < 0.001). The presence of pre-CCRT ≥3 tooth extractions, any post-CCRT tooth extractions, mean mandibular dose ≥ 34.1 Gy, mandibular V57.5 Gy ≥ 34.7 %, and post-CCRT tooth extractions > 9 months after CCRT completion were also associated with significantly increased ORNJ rates. A multivariate Cox regression analysis demonstrated that each characteristic had an independent significance on ORNJ rates after CCRT.

CONCLUSION

An affordable and easily accessible novel biomarker, PLT> 285,000 cells/L, may predict substantially higher ORNJ rates after definitive CCRT in individuals with LA-NPC.

Under the dual effect of inflammation and pulmonary fibrosis, CTD-ILD patients possess a greater susceptibility to VTE

As an autoimmune disease, the persistent systemic inflammatory response associated with connective tissue disease (CTD) is involved in the development of venous thromboembolism (VTE). However, clinical data showed that the risk of VTE in patients differed between subtypes of CTD, suggesting that different subtypes may have independent mechanisms to promote the development of VTE, but the specific mechanism lacks sufficient research at present. The development of pulmonary fibrosis also contributes to the development of VTE, and therefore, patients with CTD-associated interstitial lung disease (CTD-ILD) may be at higher risk of VTE than patients with CTD alone or patients with ILD alone. In addition, the activation of the coagulation cascade response will drive further progression of the patient's pre-existing pulmonary fibrosis, which will continue to increase the patient's risk of VTE and adversely affect prognosis. Currently, the treatment for CTD-ILD is mainly immunosuppressive and antirheumatic therapy, such as the use of glucocorticoids and janus kinase-inhibitors (JAKis), but, paradoxically, these drugs are also involved in the formation of patients' coagulation tendency, making the clinical treatment of CTD-ILD patients with a higher risk of developing VTE challenging. In this article, we review the potential risk factors and related mechanisms for the development of VTE in CTD-ILD patients to provide a reference for clinical treatment and prevention.

Therapeutic implication of MicroRNA-320a antagonist in attenuating blood clots formed during venous thrombosis

Venous thrombosis (VT) is a complex multi-factorial disease and a major health concern worldwide. Its clinical implications include deep vein thrombosis (DVT) and pulmonary embolism (PE). VT pathogenesis involves intricate interplay of various coagulants and anti-coagulants. Growing evidences from epidemiological studies have shown that many non-coding microRNAs play significant regulatory role in VT pathogenesis by modulating expressions of large number of gene involved in blood coagulation. Present study aimed to investigate the effect of human micro RNA (hsa-miR)-320a antagonist on thrombus formation in VT. Surgery was performed on Sprague-Dawley (SD) rats, wherein the inferior vena cava (IVC) was ligated to introduce DVT. Animals were divided into four groups (n = 5 in each group); Sham controls (Sham), IVC ligated-DVT (DVT), IVC ligated-DVT + transfection reagent (DVT-NC) and IVC ligated-DVT + miR320a antagonist (DVT-miR-320a antagonist). IVC was dissected after 6 h and 24 h of surgery to estimate thrombus weight and coagulatory parameters such as levels of D-dimer, clotting time and bleeding time. Also, ELISA based biochemical assays were formed to assess toxicity of miRNA antagonist in animals. Our experimental analysis demonstrated that there was a marked reduction in size of thrombus in hsa-miR-320a antagonist treated animals, both at 6 h and 24 h. There was a marked reduction in D-dimer levels in hsa-miR-320a antagonist treated animals. Also, blood clotting time was delayed and bleeding time was increased significantly in hsa-miR-320a antagonist treated rats compared to the non-treated and Sham rats. There was no sign of toxicity in treated group compared to control animals. Hsa-miR-320a antagonist could be promising therapeutic target for management of VT.

Exercise and hypoxia-induced hypercoagulability is counterbalanced in women in part by decreased platelet reactivity

Hypoxia plays an important role in several pathologies, e.g. chronic obstructive pulmonary disease and obstructive sleep apnea syndrome, and is linked to an increased thrombosis risk. Furthermore, oxygen deprivation is associated with hypercoagulability. In this study, we investigated the effect of gender and exercise on the coagulation potential under hypoxic conditions at high altitude by assessing thrombin generation (TG) and platelet activation. Hereto, ten healthy volunteers were included (50 % male, median age of 27.5 years). The measurements were conducted first at sea level and then twice at high altitude (3883 m), first after a passive ascent by cable car and second after an active ascent by a mountain hike. As expected, both the passive and active ascent resulted in a decreased oxygen saturation and an increased heart rate at high altitude. Acute mountain sickness symptoms were observed independently of the ascent method. After the active ascent, platelet, white blood cell and granulocyte count were increased, and lymphocytes were decreased, without a gender-related difference. FVIII and von Willebrand factor were significantly increased after the active ascent for both men and women. Platelet activation was reduced and delayed under hypobaric conditions, especially in women. TG analysis showed a prothrombotic trend at high altitude, especially after the active ascent. Women had a hypercoagulable phenotype, compared to men at all 3 timepoints, indicated by a higher peak height and endogenous thrombin potential (ETP), and shorter lag time and time-to-peak. In addition, ETP and peak inhibition by thrombomodulin was lower in women after the active ascent, compared to men. Interestingly, data normalisation for subject baseline values indicated an opposing effect of altitude-induced hypoxia on α2-macroglobulin levels and TG lag time between men and women, decreasing in men and increasing in women. We conclude that hypoxia increases TG, as well as FVIII and VWF levels in combination with exercise. In contrast, platelets lose their responsiveness at high altitude, which is most pronounced after heavy exercise. Women had a more pronounced prothrombotic phenotype compared to men, which we theorize is counterbalanced under hypobaric conditions by decreased platelet activation.

Intense exercise at high altitude causes platelet loss across the brain in humans

Platelets are known primarily for their role in blood clotting; however, it is becoming clear that they play diverse roles beyond that of haemostasis. Exercise has been shown to activate platelets and stimulate neurogenesis, neuroplasticity and improve cognitive function, highlighting a potentially powerful link between platelet function and brain health. Despite this clear link between platelets and the brain, very little is known about the behaviour of platelets through the cerebral circulation in humans. We examined platelet concentration across the brain in exercising humans at sea level (340 m) and high altitude (6-8 days at 3800 m; a stimulus known to modify platelet function). During intense exercise at sea level, platelet concentration increased similarly by 27 ± 17% in the arterial and internal jugular venous circulations (exercise: P < 0.001, interaction: P = 0.262), indicating no uptake or release of platelets into/from the brain. At high altitude, resting platelet concentrations were similar to sea level values in both the arterial and jugular venous circulations (P = 0.590); however, intense exercise at high altitude caused a 31 ± 35% decrease in platelet concentration across the brain (P = 0.016). This divergent response across the brain was not observed in any other haematological or metabolic variables. These data highlight a unique situation where the combination of intense exercise and high altitude hypoxia cause a decrease in platelet concentration across the cerebral circulation. The physiological implications and mechanisms that might influence platelet function across the brain during exercise at high altitude remain to be established. KEY POINTS: Platelets are known primarily for their role in blood clotting; however, it is becoming clear that they play diverse roles beyond that of haemostasis. Exercise has been shown to activate platelets, which in turn stimulate neurogenesis, neuroplasticity and improve cognitive function, highlighting a powerful link between platelet function and brain health. At sea level, platelet concentration in blood going into and out of the brain was similar at rest, during maximal exercise and in recovery from exercise. During maximal exercise at high altitude, platelet concentration was 31% lower in the blood exiting the brain; the final destination of these platelets is unknown. The physiological implications and mechanisms that might influence platelet function across the cerebral circulation during exercise at high altitude remain to be established.

Vibro-Acoustic Platelet Activation: An Additive Mechanism of Prothrombosis with Applicability to Snoring and Obstructive Sleep Apnea

Introduction: Obstructive sleep apnea (OSA) and loud snoring are conditions with increased cardiovascular risk and notably an association with stroke. Central in stroke are thrombosis and thromboembolism, all related to and initiaing with platelet activation. Platelet activation in OSA has been felt to be driven by biochemical and inflammatory means, including intermittent catecholamine exposure and transient hypoxia. We hypothesized that snore-associated acoustic vibration (SAAV) is an activator of platelets that synergizes with catecholamines and hypoxia to further amplify platelet activation. Methods: Gel-filtered human platelets were exposed to snoring utilizing a designed vibro-acoustic exposure device, varying the time and intensity of exposure and frequency content. Platelet activation was assessed via thrombin generation using the Platelet Activity State assay and scanning electron microscopy. Comparative activation induced by epinephrine and hypoxia were assessed individually as well as additively with SAAV, as well as the inhibitory effect of aspirin. Results: We demonstrate that snore-associated acoustic vibration is an independent activator of platelets, which is dependent upon the dose of exposure, i.e., intensity x time. In snoring, acoustic vibrations associated with low-frequency sound content (200 Hz) are more activating than those associated with high frequencies (900 Hz) (53.05% vs. 22.08%, p = 0.001). Furthermore, SAAV is additive to both catecholamines and hypoxia-mediated activation, inducing synergistic activation. Finally, aspirin, a known inhibitor of platelet activation, has no significant effect in limiting SAAV platelet activation. Conclusion: Snore-associated acoustic vibration is a mechanical means of platelet activation, which may drive prothrombosis and thrombotic risk clinically observed in loud snoring and OSA.

Apoptosis is one cause of thrombocytopenia in patients with high-altitude polycythemia

High-altitude polycythemia (HAPC) can occur in individuals who are intolerant to high-altitude hypoxia. In patients with HAPC, erythrocytosis is often accompanied by a decrease in platelet count. Chronic hypoxia can increase the incidence of arteriovenous thrombosis and the risk of bleeding during antithrombotic treatment due to thrombocytopenia; therefore, understanding the cause of thrombocytopenia can reduce the risk of treatment-related bleeding. In this study, we examined platelet production and apoptosis to understand the cause of thrombocytopenia in patients with HAPC. The classification of myeloid-derived megakaryocytes (MKs) in HAPC patients was mainly granular MKs rather than mature MKs, suggesting impaired differentiation and maturation. However, the total number of MKs and newly generated reticulated platelets in the peripheral blood increased, indicating sufficient platelet generation in HAPC thrombocytopenia. Increased platelet apoptosis may be one of the causes of thrombocytopenia. Platelet activation and GP1bα pathway activation induced by thrombin and von Willebrand factor can lead to platelet apoptosis. Platelet production was not reduced in patients with HAPC, whereas platelet apoptosis was associated with thrombocytopenia. These findings provide a rationale for considering the bleeding risk in HAPC patient while treating thrombotic diseases.

Longitudinal study on blood and biochemical indexes of Tibetan and Han in high altitude area

Objective

This study aims to review the blood routine and biochemical indicators of the plateau population for three consecutive years, and analyze the impact of the plateau on these blood indicators of the Tibetan population and the Han immigrant population.

Method

These parameters were extracted from the Laboratory Department of Ali District People's Hospital in Tibet from January 2019 to December 2021, including blood routine, liver and kidney function, blood lipids, myocardial enzyme spectrum, and rheumatic factor indicators. Changes in these parameters were analyzed over 3 consecutive years according to inclusion and exclusion criteria.

Result

A total of 114 Tibetans and 93 Hans participated in the study. These parameters were significantly different between Tibetan and Han populations. Red blood cells (RBC), hemoglobin (HGB), hematocrit (HCT), mean hemoglobin content (MCH), mean corpuscular hemoglobin concentration (MCHC), white blood cells (WBC), lymphocytes (LYMPH) and monocytes (MONO) were significantly higher in Hans than Tibetans (p < 0.05). Biochemically, total bilirubin (TBIL), direct bilirubin (DBIL), albumin (ALB), urea nitrogen (Urea), creatinine (Cr), uric acid (UA), glucose (GLU), triglycerides (TG) and creatine kinase isoenzyme (CKMB) were significantly higher in Hans than Tibetans; aspartate aminotransferase (AST), glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), antistreptolysin (ASO), and C-reactive protein (CRP) were significantly higher in Tibetans than Hans (p < 0.05). There were no obvious continuous upward or downward trend of the parameters for 3 consecutive years.

Conclusion

In high-altitude areas, Han immigrants have long-term stress changes compared with Tibetans. The main differences are reflected in the blood system, liver and kidney functions, etc., which provide basic data for further research on the health status of plateau populations.

PATHOPHYSIOLOGICAL MECHANISMS OF DEEP VEIN THROMBOSIS

Deep venous thrombosis is a frequent multifactorial disease and most of the time is triggered by the interaction between acquired risk factors, particularly immobility, and hereditary risk factors such as thrombophilias. The mechanisms underlying deep venous thrombosis are not fully elucidated; however, in recent years the role of venous flow, endothelium, platelets, leukocytes, and the interaction between inflammation and hemostasis has been determined. Alteration of venous blood flow produces endothelial activation, favoring the adhesion of platelets and leukocytes, which, through tissue factor expression and neutrophil extracellular traps formation, contribute to the activation of coagulation, trapping more cells, such as red blood cells, monocytes, eosinophils, lymphocytes. The coagulation factor XI-driven propagation phase of blood coagulation plays a major role in venous thrombus growth, but a minor role in hemostasis. In this work, the main mechanisms involved in the pathophysiology of deep vein thrombosis are described.

Effects of Hypobaric Hypoxia on Coagulation in Healthy Subjects Exposed to 3,500 m Altitude

Kammerer, Tobias, Anna Walzl, Thomas Müller, Philipp Groene, Giulia Roveri, Rachel Turner, Johanna Roche, Hannes Gatterer, Christoph Siebenmann, and Simon T. Schäfer. Effects of hypobaric hypoxia on coagulation in healthy subjects exposed to 3,500 m altitude. High Alt Med Biol. 24:94-103, 2023. Background: Hypoxia is discussed as a trigger for prothrombotic changes both in intensive care and high altitude medicine. This research study aimed to evaluate the effect of isolated hypobaric hypoxia (HH) on coagulation in females in a highly standardized setting. Methods: Twelve healthy female subjects were studied under HH (equivalent to 3,500 m) and normoxia (NX) during two 4-day sojourns, in a strictly controlled crossover design. Nutrition, fluid intake, hormonal status (i.e., menstrual cycle variation), and physical stress were standardized. Functional coagulation and blood lysis were measured by viscoelastometry and compared between HH and NX. In addition, plasma-based coagulation tests (PBCTs), namely prothrombin time, activated partial thromboplastin time, fibrinogen, factor VIII coagulation activity (FVIII:C), von Willebrand factor antigen (vWF:Ag), and von Willebrand factor ristocetin cofactor activity (vWF:RCo) were measured. Results: Neither for Viscoelastic Haemostatic Assays nor for PBCTs significant changes were found for HH compared with NX (all p > 0.05). Specifically, the lysis ability, as well as clotting time, clot formation, clot amplitude, and maximum clot firmness unchanged were similar between HH and NX. This also applied to all other variables. Conclusion: We demonstrate that moderate HH per se has no influence on blood coagulation in healthy females.

The Associations of Platelet Activation and Coagulation Parameters with Obstructive Sleep Apnoea: A Large-Scale Observational Study

OBJECTIVES

Obstructive sleep apnoea (OSA) is associated with an increased risk of cardiovascular disease, with alterations in coagulability suspected as the mediating factor. This study explored blood coagulability and breathing-related parameters during sleep in patients with OSA.

DESIGN

Cross-sectional observational study. Setting. Shanghai Sixth People's Hospital. Participants. 903 patients diagnosed by standard polysomnography. Main Outcome and Measures. The relationships between coagulation markers and OSA were evaluated using Pearson's correlation, binary logistic regression, and restricted cubic spline (RCS) analyses.

RESULTS

The platelet distribution width (PDW) and activated partial thromboplastin time (APTT) decreased significantly with increasing OSA severity (both p < 0.001). PDW was positively associated with the apnoea-hypopnea index (AHI), oxygen desaturation index (ODI), and microarousal index (MAI) (ß = 0.136, p < 0.001; ß = 0.155, p < 0.001; and ß = 0.091, p = 0.008, respectively). APTT was negatively correlated with AHI (ß = -0.128, p < 0.001) and ODI (ß = -0.123, p = 0.001). PDW was negatively correlated with percentage of sleep time with oxygen saturation below 90%(CT90) (ß = -0.092, p = 0.009). The minimum arterial oxygen saturation (SaO₂) correlated with PDW (ß = -0.098, p = 0.004), APTT (ß = 0.088, p = 0.013), and prothrombin time (PT) (ß = 0.106, p = 0.0003). ODI was risk factors for PDW abnormalities (odds ratio (OR) = 1.009, p = 0.009) after model adjustment. In the RCS, a nonlinear dose-effect relationship was demonstrated between OSA and the risk of PDW and APTT abnormalities.

CONCLUSION

Our study revealed nonlinear relationships between PDW and APTT, and AHI and ODI, in OSA, with AHI and ODI increasing the risk of an abnormal PDW and thus also the cardiovascular risk. This trial is registered with ChiCTR1900025714.

Does living at high altitude increase the risk of bleeding events after total knee arthroplasty? A retrospective cohort study

OBJECTIVE

Post-operative bleeding after total knee arthroplasty (TKA) is a frequent cause of post-operative complications. This study compared blood loss and indicators of coagulation and fibrinolysis between TKA patients living at low or high altitudes.

METHODS

We retrospectively analyzed 120 patients at our institution who underwent primary TKA from May 2019 to March 2020, and we divided them into those living in areas about 500 m or > 3000 m above sea level. We compared the primary outcome of total blood loss between them. We also compared them in terms of several secondary outcomes: coagulation and fibrinolysis parameters, platelet count, reduction in hemoglobin, hidden blood loss, intra-operative blood loss, transfusion rate, and incidence of thromboembolic events and other complications.

RESULTS

Total blood loss was significantly higher in the high-altitude group than in the low-altitude group (mean, 748.2 mL [95% CI, 658.5-837.9] vs 556.6 mL [95% CI, 496.0-617.1]; p = 0.001). The high-altitude group also showed significantly longer activated partial thromboplastin time, prothrombin time, and thrombin time before surgery and on post-operative day one, as well as increased levels of fibrinogen/fibrin degradation product on post-operative days one and three. Ecchymosis was significantly more frequent in the high-altitude group (41.7 vs 21.7%; relative risk (RR) = 1.923 [95% CI, 1.091-3.389]; p = 0.019). The two groups showed similar transfusion rates, and none of the patients experienced venous thromboembolism, pulmonary embolism, or infection.

CONCLUSION

High altitude may alter coagulation and fibrinolysis parameters in a way that increases risk of blood loss after TKA. Such patients may benefit from special management to avoid bleeding events.

The impact of platelets on pulmonary microcirculation throughout COVID-19 and its persistent activating factors

Patients with COVID-19 often have hypoxemia, impaired lung function, and abnormal imaging manifestations in acute and convalescent stages. Alveolar inflammation, pulmonary vasculitis, and thromboembolism synergistically damage the blood-air barrier, resulting in increased pulmonary permeability and gas exchange disorders. The incidence of low platelet counts correlates with disease severity. Platelets are also involved in the impairment of pulmonary microcirculation leading to abnormal lung function at different phases of COVID-19. Activated platelets lose the ability to protect the integrity of blood vessel walls, increasing the permeability of pulmonary microvasculature. High levels of platelet activation markers are observed in both mild and severe cases, short and long term. Therefore, the risk of thrombotic events may always be present. Vascular endothelial injury, immune cells, inflammatory mediators, and hypoxia participate in the high reactivity and aggregation of platelets in various ways. Microvesicles, phosphatidylserine (PS), platelets, and coagulation factors are closely related. The release of various cell-derived microvesicles can be detected in COVID-19 patients. In addition to providing a phospholipid surface for the synthesis of intrinsic factor Xase complex and prothrombinase complex, exposed PS also promotes the decryption of tissue factor (TF) which then promotes coagulant activity by complexing with factor VIIa to activate factor X. The treatment of COVID-19 hypercoagulability and thrombosis still focuses on early intervention. Antiplatelet therapy plays a role in relieving the disease, inhibiting the formation of the hypercoagulable state, reducing thrombotic events and mortality, and improving sequelae. PS can be another potential target for the inhibition of hypercoagulable states.

Impact of high altitude on the incidence of postoperative venous thromboembolism and its genetic susceptibility: A meta-analysis and systematic review

BACKGROUND

The effect of high-altitude (HA) on venous thromboembolism (VTE) and its mechanism remains ambiguous. To clarify this, we aimed to conduct a meta-analysis and systematic review to evaluate the incidence of VTE at HA and comparatively low altitude (LA) and figure out the intrinsic risk factors such as susceptibility genes of patients with VTE at HA.

METHODS

We selected studies that explored the risk factors for HA and VTE by searching PubMed, Embase, and Web of Science to analyze the impact of HA on VTE. All relevant studies before August 2021 were screened using the terms ([high altitude] OR [plateau] OR [mountain]) AND ([venous thromboembolism] OR [deep vein thrombosis] OR [pulmonary embolism]). Latest studies on the gene of HA-VTE patients were also summarized and analyzed.

RESULTS

Fifteen studies were eventually assessed, and the overall numbers of subjects with and without VTE were 1475 and 286,926 respectively. The overall incidence of VTE, deep vein thrombosis (DVT) and pulmonary embolism (PE) in the HA group was significantly higher than that in the LA group (P < 0.01). The overall incidence of VTE, DVT and PE in the HA group was significantly higher than that in the LA group at 30 days post operation (P < 0.05, P < 0.05 and P < 0.01, respectively). At 90 days post operation, incidence of VTE and PE in the HA group was higher than that in the LA group (P < 0.01and P < 0.01, respectively), but there was no difference in the incidence of DVT (P = 0.07). Regarding endogenous factors, the analysis of genes in patients with HA-VTE revealed numerous targeted genes such as ANG, ACE, lncRNA-LINC00 659/UXT-AS1 and GP4.

CONCLUSIONS

We observed a significant association between HA and the overall incidence of VTE and that at 30/90 days post operation, indicating that HA may be a risk factor for VTE.

Epidemiology and pathophysiology of vascular thrombosis in acclimatized lowlanders at high altitude: A prospective longitudinal study

BACKGROUND

Previous literature suggests that thrombosis is more common in lowlanders sojourning at high altitude (HA) compared to near-sea-level. Though the pathophysiology is partly understood, little is known of its epidemiology. To elucidate this, an observational prospective longitudinal study was conducted in healthy soldiers sojourning for months at HA.

METHODS

A total of 960 healthy male subjects were screened in the plains, of which 750 ascended, to altitudes above 15,000ft (4,472m). Clinical examination, haemogram, coagulogram, markers of inflammation and endothelial dysfunction, were studied at three time points during ascent and descent. The diagnosis of thrombosis was confirmed radiologically in all cases where a thrombotic event was suspected clinically. Subjects developing thrombosis at HA were labelled as Index Cases (ICs) and compared to a nested cohort of the healthy subjects (comparison group,(CG)) matched for altitude of stay.

FINDINGS

Twelve and three subjects, developed venous (incidence: 5,926/105 person-years) and arterial (incidence: 1,482/105 person-years) thrombosis at HA, respectively. The ICs had enhanced coagulation (FVIIa: p<0.001; FXa: p<0.001) and decreased levels of natural anticoagulants (thrombomodulin, p=0.016; tissue factor pathway inhibitor [TFPI]: p<0.001) and a trend to dampened fibrinolysis (tissue plasminogen activator tPA; p=0.078) compared to CG. ICs also exhibited statistically significant increase in the levels of endothelial dysfunction and inflammation markers (vascular cell adhesion molecule-1[VCAM-1], intercellular adhesion molecule-1 [ICAM-1], vascular endothelial growth factor receptor 3 [VEGFR-3], P-Selectin, CD40 ligand, soluble C-reactive protein and myeloperoxidase: p<0.001).

INTERPRETATION

The incidence of thrombosis in healthy subjects at HA was higher than that reported in literature at near sea-level. This was associated with inflammation, endothelial dysfunction, a prothrombotic state and dampened fibrinolysis.

FUNDING

Research grants from the Armed Forces Medical Research Committee, Office of the Director General of Armed Forces Medical Services (DGAFMS) & Defence Research and Development Organization (DRDO), Ministry of Defence, India.

Proteomic and clinical biomarkers for acute mountain sickness in a longitudinal cohort

Ascending to high-altitude by non-high-altitude natives is a well-suited model for studying acclimatization to extreme environments. Acute mountain sickness (AMS) is frequently experienced by visitors. The diagnosis of AMS mainly depends on a self-questionnaire, revealing the need for reliable biomarkers for AMS. Here, we profiled 22 AMS symptom phenotypes, 65 clinical indexes, and plasma proteomic profiles of AMS via a combination of proximity extension assay and multiple reaction monitoring of a longitudinal cohort of 53 individuals. We quantified 1069 proteins and validated 102 proteins. Via differential analysis, machine learning, and functional association analyses. We found and validated that RET played an important role in the pathogenesis of AMS. With high-accuracies (AUCs > 0.9) of XGBoost-based models, we prioritized ADAM15, PHGDH, and TRAF2 as protective, predictive, and diagnostic biomarkers, respectively. Our findings shed light on the precision medicine for AMS and the understanding of acclimatization to high-altitude environments.

Potential acute mountain sickness diagnostic, predictive, protective biomarkers are established using plasma proteomic, clinical and symptom phenotype data with machine learning approaches in a longitudinal cohort of 53 individuals.

The key role of Calpain in COVID-19 as a therapeutic strategy

COVID-19 is one of the viral diseases that has caused many deaths and financial losses to humans. Using the available information, this virus appears to activate the host cell-death mechanism through Calpain activation. Calpain inhibition can stop its downstream cascade reactions that cause cell death. Given the main roles of Calpain in the entry and pathogenicity of the SARS-CoV-2, its inhibition can be effective in controlling the COVID-19. This review describes how the virus activates Calpain by altering calcium flow. When Calpain was activated, the virus can enter the target cell. Subsequently, many complications of the disease, such as inflammation, cytokine storm and pulmonary fibrosis, are caused by virus-activated Calpain function. Calpain inhibitors appear to be a potential drug to control the disease and prevent death from COVID-19.

Pulmonary Embolism at Extreme High Altitude: A Study of Seven Cases

Wu, Jialin, Xiaobo Han, Haiwen Ke, Li Wang, Kun Wang, Jianli Zhang, Jun Tang, Wei Yan, Guangjun Wang, and Peng Jiang. Pulmonary embolism at extreme high altitude: A study of seven cases. High Alt Med Biol. XX:000-000, 2022. Background: The incidence of venous thromboembolism (VTE) is high in high-altitude (HA) areas. We analyzed cases of pulmonary embolism (PE) in extreme HA areas to explore the epidemiological characteristics and risk factors of PE in these regions. Methods: Seven cases of PE occurring in an extreme HA region were prospectively collected at an HA (3,800 m) hospital from May to November 2020. All patients resided 5,000 m above sea level and were diagnosed with PE using computed tomography pulmonary angiography. Results: Seven patients (24 ± 3.6 years old) had symptom onset at a mean altitude of 5,200 ± 200 m, and the duration spent at HA ranged from 8 to 210 days (99.29 ± 77.31 days). Cough, expectoration, chest tightness, fever, shortness of breath, and chest pain were the most common symptoms. Six of the seven patients were initially diagnosed with pulmonary inflammation, and four were diagnosed with high-altitude pulmonary edema using computed tomography or X-ray. Most patients presented with an increased concentration of inflammatory cells and high initial D-dimer levels. Conclusions: In this study, a retrospective analysis of PE case data in extreme HA areas suggested that PE was underdiagnosed owing to misdiagnosis or masking by HA-associated disease.

UNUSUAL CAUSE OF BRANCH RETINAL ARTERY OCCLUSION: POLYCYTHEMIA IN A TRANSGENDER MAN FROM UNREGULATED TESTOSTERONE USE

PURPOSE

We report a transgender patient with branch retinal artery occlusion who had secondary polycythemia from unregulated testosterone injections and review the literature on the mechanisms of supraphysiologic and standard doses of testosterone causing a hypercoagulable state.

METHODS

Case report.

RESULTS

A 45-year-old Chinese transgender man with no medical history presented with a 1-week history of a scotoma in his left eye vision. Ophthalmologic examination revealed retinal pallor and edema along the superotemporal arteriole in the left eye. Optical coherence tomography showed increased thickness of the inner retinal layers of the superotemporal retina. Fluorescein angiography demonstrated an arm-retina time of 1 minute and 43 seconds, with no vascular sheathing and capillary fallout. A diagnosis of left superotemporal branch retinal artery occlusion was made. Initial blood tests revealed a hemoglobin level of 19.3 g/dL (11.8-14.6 g/dL), hematocrit of 62% (34.3-43.0%), and erythrocytes of 6.56 × 1012/L (3.7-4.8 × 1012/L). He revealed later that he had been on weekly testosterone injections (testosterone enanthate 250-mg depot injection) since 2011. He was also exposed to a moderately high altitude, when his symptoms occurred, raising the possibility of worsening hypercoagulability resulting in his thrombotic event.

CONCLUSION

To the best of our knowledge, this is the first documented case of a trans man who developed branch retinal artery occlusion after self-administering supraphysiological doses of testosterone. In a young patient with no history of cardiovascular risk factors who develops retinal arterial occlusion, other causes such as hypercoagulable syndromes must be excluded. This case warns of the dangers of unregulated testosterone use, especially at supraphysiologic doses, and the risks of thrombotic events from secondary polycythemia.

A guide to molecular and functional investigations of platelets to bridge basic and clinical sciences

Platelets have been shown to be associated with pathophysiological process beyond thrombosis, demonstrating critical additional roles in homeostatic processes, such as immune regulation, and vascular remodeling. Platelets themselves can have multiple functional states and can communicate and regulate other cells including immune cells and vascular smooth muscle cells, to serve such diverse functions. Although traditional platelet functional assays are informative and reliable, they are limited in their ability to unravel platelet phenotypic heterogeneity and interactions. Developments in methods such as electron microscopy, flow cytometry, mass spectrometry, and 'omics' studies, have led to new insights. In this Review, we focus on advances in platelet biology and function, with an emphasis on current and promising methodologies. We also discuss technical and biological challenges in platelet investigations. Using coronavirus disease 2019 (COVID-19) as an example, we further describe the translational relevance of these approaches and the possible 'bench-to-bedside' utility in patient diagnosis and care.

The Influence of Environmental Hypoxia on Hemostasis—A Systematic Review

Humans have been ascending to high altitudes for centuries, with a growing number of professional- and leisure-related sojourns occurring in this millennium. A multitude of scientific reports on hemostatic disorders at high altitude suggest that hypoxia is an independent risk factor. However, no systematic analysis of the influence of environmental hypoxia on coagulation, fibrinolysis and platelet function has been performed. To fill this gap, we performed a systematic literature review, including only the data of healthy persons obtained during altitude exposure (&lt;60 days). The results were stratified by the degree of hypoxia and sub-categorized into active and passive ascents and sojourns. Twenty-one studies including 501 participants were included in the final analysis. Since only one study provided relevant data, no conclusions regarding moderate altitudes (1,500–2,500 m) could be drawn. At high altitude (2,500–5,400 m), only small pathophysiological changes were seen, with a possible impact of increasing exercise loads. Elevated thrombin generation seems to be balanced by decreased platelet activation. Viscoelastic methods do not support increased thrombogenicity, with fibrinolysis being unaffected by high altitude. At extreme altitude (5,400–8,850 m), the limited data showed activation of coagulation in parallel with stimulation of fibrinolysis. Furthermore, multiple confounding variables at altitude, like training status, exercise load, fluid status and mental stress, prevent definitive conclusions being drawn on the impact of hypoxia on hemostasis. Thus, we cannot support the hypothesis that hypoxia triggers hypercoagulability and increases the risk of thromboembolic disorders, at least in healthy sojourners.

Soluble P-Selectin and von Willebrand Factor Rise in Healthy Volunteers Following Non-exertional Ascent to High Altitude

Reduced oxygen tensions experienced at high altitudes are thought to predispose to thrombosis, yet there are few studies linking hypoxia, platelet activation, and thrombosis. Reports of platelet phenotypes in hypoxia are inconsistent, perhaps due to differing degrees of hypoxia experienced and the duration of exposure. This study aimed to investigate the relationship between soluble P-selectin, a marker of platelet activation, and von Willebrand factor (vWF) on exposure to hypoxia. We measured plasma concentrations of P-selectin and vWF in sixteen healthy volunteers before, during and after the APEX 2 expedition. APEX 2 consisted of a non-exertional ascent to 5,200 m, followed by 7 consecutive days at high altitude. We showed that high altitude significantly increased mean plasma P-selectin and vWF compared to pre-expedition levels. Both plasma marker levels returned to baseline post-expedition. We found a strong positive correlation between vWF and P-selectin, but no association between P-selectin and platelet count. Our results are consistent with previous work showing evidence of platelet activation at high altitude and demonstrate that the rise in P-selectin is not simply due to an increase in platelet count. As vWF and P-selectin could be derived from either platelets or endothelial cells, further work assessing more specific markers of endothelial activation is proposed to provide insight into the source of these potential pro-thrombotic biomarkers at altitude.

Genomic Diversity Profiling and Breed-Specific Evolutionary Signatures of Selection in Arunachali Yak

Arunachali yak, the only registered yak breed of India, is crucial for the economic sustainability of pastoralist Monpa community. This study intended to determine the genomic diversity and to identify signatures of selection in the breed. Previously available double digest restriction-site associated DNA (ddRAD) sequencing data of Arunachali yak animals was processed and 99,919 SNPs were considered for further analysis. The genomic diversity profiled based on nucleotide diversity, π (π = 0.041 in 200 bp windows), effective population size, Ne (Ne = 83) and Runs of homozygosity (ROH) (predominance of shorter length ROHs) was found to be optimum. Subsequently, 207 regions were identified to be under selective sweeps through de-correlated composite of multiple signals (DCMS) statistic which combined three individual test statistics viz. π, Tajima’s D and |iHS| in non-overlapping 100 kb windows. Mapping of these regions revealed 611 protein-coding genes including KIT, KITLG, CDH12, FGG, FGA, FGB, PDGFRA, PEAR1, STXBP3, olfactory receptor genes (OR5K3, OR5H6 and OR1E1) and taste receptor genes (TAS2R1, TAS2R3 and TAS2R4). Functional annotation highlighted that biological processes like platelet aggregation and sensory perception were the most overrepresented and the associated regions could be considered as breed-specific signatures of selection in Arunachali yak. These findings point towards evolutionary role of natural selection in environmental adaptation of Arunachali yak population and provide useful insights for pursuing genome-wide association studies in future.

Indicators of Hypoxia Tolerance as Determined by Cellular Elements of Rat Blood

Although hypoxia tolerance is mainly determined genetically, it is important to study individual variability of animal organisms in order to identify the factors that underlie their tolerance to hypoxic exposure. We investigated blood cell counts and coagulograms in Wistar rats as predictors allowing the animal population to be split into hypoxia-tolerant and hypoxia-intolerant individuals. The validity of the specific predictors’ choice was proved by a coincidence between the population split in accordance with the detected individual parameters and the results of testing animals in a decompression chamber at a rarefaction corresponding to the “rise to an altitude” of 11500 m above sea level. Circulating blood cells were quantitatively assessed by eighteen indicators before and after hypoxic exposure. The differences between animals low-tolerant (LT), high-tolerant (HT), and medium-tolerant (MT) to hypoxia were determined by five indicators: white blood cell count (WBC), granulocyte count (Gran#), red blood cell count (RBC), reticulocyte count/percent (RTC), and mean corpuscular hemoglobin (MCH). The RBC, RTC, and MCH values in HT rats were significantly higher than in LT animals (by 1.4, 1.9, and 1.1 times, respectively). The WBC and Gran# values in HT rats were lower than in LT individuals. The hypoxia tolerance indices (HTI) were calculated using the original formula. It was established that in LT rats, the HTI ≤ 0.203, in HT rats ≥ 0.335, and in MT rats < 0.335 but > 0.203. After testing in a decompression chamber, the activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) decreased, but the fibrinogen level increased. LT rats were characterized by the lowest APTT, TT, and PT values and the highest values of the fibrinogen level. Our results indicate that one of the most important mechanisms underlying a high hypoxia tolerance in rats consists in sustaining reciprocal relationships between the complex of RBC indicators, which tend to increase under hypoxia, and Gran# indicators, which tend to decrease after hypoxic exposure.

Practical Considerations of Dissolved Oxygen Levels for Platelet Function under Hypoxia

Investigating human platelet function in low-oxygen environments is important in multiple settings, including hypobaric hypoxia (e.g., high altitude), sea level hypoxia-related disease, and thrombus stability. These studies often involve drawing blood from which platelets are isolated and analysed at atmospheric conditions or re-exposed to low oxygen levels in hypoxia chambers before testing. However, it remains unknown how the in vitro handling of the samples itself changes their dissolved oxygen concentration, which might affect platelet function and experimental results. Here, we prepared healthy donor platelet-rich plasma and washed platelet (WP) suspensions and exposed them to 2% oxygen. We found that the use of hypoxia pre-equilibrated tubes, higher platelet concentrations (>2 × 10⁸/mL versus 2 × 10⁷/mL), smaller volumes (600 µL versus 3 mL), and presence of plasma reduced the time for samples to reach 2% oxygen. Notably, oxygen levels decreased below 2% in most suspensions, but also in WP maintained at atmospheric 21% oxygen. Additionally, platelet spreading on fibrinogen was decreased when using hypoxic fibrinogen-coated culture plates regardless of the oxygen percentage (2% or 21%) in which platelet incubation took place. Thus, sample handling and experimental conditions should be carefully monitored in platelet-hypoxia studies as they might compromise results interpretation and comparison across studies.

Pathogenic Basis of Thromboinflammation and Endothelial Injury in COVID-19: Current Findings and Therapeutic Implications

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic with a great impact on social and economic activities, as well as public health. In most patients, the symptoms of COVID-19 are a high-grade fever and a dry cough, and spontaneously resolve within ten days. However, in severe cases, COVID-19 leads to atypical bilateral interstitial pneumonia, acute respiratory distress syndrome, and systemic thromboembolism, resulting in multiple organ failure with high mortality and morbidity. SARS-CoV-2 has immune evasion mechanisms, including inhibition of interferon signaling and suppression of T cell and B cell responses. SARS-CoV-2 infection directly and indirectly causes dysregulated immune responses, platelet hyperactivation, and endothelial dysfunction, which interact with each other and are exacerbated by cardiovascular risk factors. In this review, we summarize current knowledge on the pathogenic basis of thromboinflammation and endothelial injury in COVID-19. We highlight the distinct contributions of dysregulated immune responses, platelet hyperactivation, and endothelial dysfunction to the pathogenesis of COVID-19. In addition, we discuss potential therapeutic strategies targeting these mechanisms.

Stroke-Related Mortality at Different Altitudes: A 17-Year Nationwide Population-Based Analysis From Ecuador

Introduction: Worldwide, more than 5.7% of the population reside above 1,500 m of elevation. It has been hypothesized that acute short-term hypoxia exposure could increase the risk of developing a stroke. Studies assessing the effect of altitude on stroke have provided conflicting results, some analyses suggest that long-term chronic exposure could be associated with reduced mortality and lower stroke incidence rates.

Methods: An ecological analysis of all stroke hospital admissions, mortality rates, and disability-adjusted life years in Ecuador was performed from 2001 to 2017. The cases and population at risk were categorized in low (<1,500 m), moderate (1,500–2,500 m), high (2,500–3,500 m), and very high altitude (3,500–5,500 m) according to the place of residence. The derived crude and direct standardized age-sex adjusted mortality and hospital admission rates were calculated.

Results: A total of 38,201 deaths and 75,893 stroke-related hospital admissions were reported. High altitude populations (HAP) had lower stroke mortality in men [OR: 0.91 (0.88–0.95)] and women [OR: 0.83 (0.79–0.86)]. In addition, HAP had a significant lower risk of getting admitted to the hospital when compared with the low altitude group in men [OR: 0.55 (CI 95% 0.54–0.56)] and women [OR: 0.65 (CI 95% 0.64–0.66)].

Conclusion: This is the first epidemiological study that aims to elucidate the association between stroke and altitude using four different elevation ranges. Our findings suggest that living at higher elevations offers a reduction or the risk of dying due to stroke as well as a reduction in the probability of being admitted to the hospital. Nevertheless, this protective factor has a stronger effect between 2,000 and 3,500 m.

Diet and redox state in maintaining skeletal muscle health and performance at high altitude

High altitude exposure leads to compromised physical performance with considerable weight loss. The major stressor at high altitude is hypobaric hypoxia which leads to disturbance in redox homeostasis. Oxidative stress is a well-known trigger for many high altitude illnesses and regulates several key signaling pathways under stressful conditions. Altered redox homeostasis is considered the prime culprit of high altitude linked skeletal muscle atrophy. Hypobaric hypoxia disturbs redox homeostasis through increased RONS production and compromised antioxidant system. Increased RONS disturbs the cellular homeostasis via multiple ways such as inflammation generation, altered protein anabolic pathways, redox remodeling of RyR1 that contributed to dysregulated calcium homeostasis, enhanced protein degradation pathways via activation calcium-regulated protein, calpain, and apoptosis. Ultimately, all the cellular signaling pathways aggregately result in skeletal muscle atrophy. Dietary supplementation of phytochemicals could become a safe and effective intervention to ameliorate skeletal muscle atrophy and enhance the physical performance of the personnel who are staying at high altitude regions. The present evidence-based review explores few dietary supplementations which regulate several signaling mechanisms and ameliorate hypobaric hypoxia induced muscle atrophy and enhances physical performance. However, a clinical research trial is required to establish proof-of-concept.

In situ Pulmonary Artery Thrombosis: A Previously Overlooked Disease

Pulmonary thromboembolism (PTE) is the third leading cause of death in cardiovascular diseases. PTE is believed to be caused by thrombi detached from deep veins of lower extremities. The thrombi travel with systemic circulation to the lung and block pulmonary arteries, leading to sudden disruption of hemodynamics and blood gas exchange. However, this concept has recently been challenged by accumulating evidence demonstrating that de novo thrombosis may be formed in pulmonary arteries without deep venous thrombosis. On the other hand, chronic thromboembolic pulmonary hypertension (CTEPH), a subtype of pulmonary hypertension, could have different pathogenesis than traditional PTE. Therefore, this article summarized and compared the risk factors, the common and specific pathogenic mechanisms underlying PTE, in situ pulmonary artery thrombosis, and CTEPH at molecular and cellular levels, and suggested the therapeutic strategies to these diseases, aiming to facilitate understanding of pathogenesis, differential diagnosis, and precision therapeutics of the three pulmonary artery thrombotic diseases.

Sanguinarine Attenuates Collagen-Induced Platelet Activation and Thrombus Formation

Sanguinarine, a benzophenanthridine alkaloid, has been described to have an antiplatelet activity. However, its antithrombotic effect and the mechanism of platelet inhibition have not thoroughly been explored. The current study found that sanguinarine had an inhibitory effect on thrombus formation. This inhibitory effect was quite evident both in the flow-chamber assays as well as in a murine model of FeCl₃-induced carotid artery thrombosis. Further investigations also revealed that sanguinarine inhibited the collagen-induced human platelet aggregation and granule release. At the same time, it also prevented platelet spreading and adhesion to immobilized fibrinogen. The molecular mechanisms of its antiplatelet activity were found to be as follows: 1. Reduced phosphorylation of the downstream signaling pathways in collagen specific receptor GPVI (Syk-PLCγ2 and PI3K-Akt-GSK3β); 2. Inhibition of collagen-induced increase in the intracellular Ca²⁺ concentration ([Ca²⁺]i); 3. Inhibition of integrin αIIbβ3 outside-in signaling via reducing β3 and Src (Tyr-416) phosphorylation. It can be concluded that sanguinarine inhibits collagen-induced platelet activation and reduces thrombus formation. This effect is mediated via inhibiting the phosphorylation of multiple components in the GPVI signaling pathway. Current data also indicate that sanguinarine can be of some clinical value to treat cardiovascular diseases involving an excess of platelet activation.

"Silent Hypoxemia" Leads to Vicious Cycle of Infection, Coagulopathy and Cytokine Storm in COVID-19: Can Prophylactic Oxygen Therapy Prevent It?

Humankind is facing its worst pandemic of the twenty-first century, due to infection of a novel coronavirus named as SARS-CoV2, started from Wuhan in China. Till now, 15 million people are infected, causing more than 600,000 deaths. The disease, commonly known as, COVID-19, was initially thought to be associated with ARDS only, but later on revealed to have many unexplained and atypical clinical features like coagulopathy and cytokinemia, leading to multi-organ involvements. The patients also suffer from 'Silent Hypoxemia', where there is no immediate respiratory signs and symptoms even though alarmingly low SpO₂ level. We hypothesize that this covert hypoxemia may lead to molecular changes exacerbating coagulopathy and cytokine storm in COVID19 patients, which again, in turn, causes a vicious cycle of more hypoxemia/hypoxia and progression of the infection to more severe stages through HIF-1α dependent pathway. Although molecular mechanisms are yet to be substantiated by scientific evidence, hypoxemia remains an independent worsening factor in serious COVID 19 patients. Keeping all in mind, we propose that even in the early and asymptomatic cases, prophylactic oxygen therapy to be initiated to break the vicious cycle and to reduce the mortality in COVID 19 to save precious human lives.

Coagulation and Fibrinolysis in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a common disease which is characterised by repetitive collapse of the upper airways during sleep resulting in chronic intermittent hypoxaemia and frequent microarousals, consequently leading to sympathetic overflow, enhanced oxidative stress, systemic inflammation, and metabolic disturbances. OSA is associated with increased risk for cardiovascular morbidity and mortality, and accelerated coagulation, platelet activation, and impaired fibrinolysis serve the link between OSA and cardiovascular disease. In this article we briefly describe physiological coagulation and fibrinolysis focusing on processes which could be altered in OSA. Then, we discuss how OSA-associated disturbances, such as hypoxaemia, sympathetic system activation, and systemic inflammation, affect these processes. Finally, we critically review the literature on OSA-related changes in markers of coagulation and fibrinolysis, discuss potential reasons for discrepancies, and comment on the clinical implications and future research needs.

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

Thrombocytopathies: Not Just Aggregation Defects-The Clinical Relevance of Procoagulant Platelets

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.

Platelet activation contributes to hypoxia-induced inflammation

Inflammation is central to the pathogenesis of pulmonary vascular remodeling and pulmonary hypertension (PH). Inflammation precedes remodeling in preclinical models, thus supporting the concept that changes in immunity drive remodeling in PH. Platelets are recognized as mediators of inflammation, but whether platelets contribute to hypoxia-driven inflammation has not been studied. We utilized a murine hypoxia model to test the hypothesis that platelets drive hypoxia-induced inflammation. We evaluated male and female 9-wk-old normoxic and hypoxic mice and in selected experiments included hypoxic thrombocytopenic mice. Thrombocytopenic mice were generated with an anti-GP1bα rat IgG antibody. We also performed immunostaining of lung sections from failed donor controls and patients with idiopathic pulmonary arterial hypertension. We found that platelets are increased in the lungs of hypoxic mice and hypoxia induces platelet activation. Platelet depletion prevents hypoxia-driven increases in the proinflammatory chemokines CXCL4 and CCL5 and attenuates hypoxia-induced increase in plasma CSF-2. Pulmonary interstitial macrophages are increased in the lungs of hypoxic mice; this increase is prevented in thrombocytopenic mice. To determine the potential relevance to human disease, lung sections from donors and patients with advanced idiopathic pulmonary arterial hypertension (iPAH) were immunostained for the platelet-specific protein CD41. We observed iPAH lungs had a two-fold increase in CD41, compared with controls. Our data provide evidence that the platelet count is increased in the lungs and activated in mice with hypoxia-induced inflammation and provides rationale for the further study of the potential contribution of platelets to inflammatory mediated vascular remodeling and PH.

Redox modification of ryanodine receptor contributes to impaired Ca2+ homeostasis and exacerbates muscle atrophy under high altitude

At extreme altitude, prolonged and severe hypoxia menaces human function and survival, and also associated with profound loss of muscle mass which results into a debilitating critical illness of skeletal muscle atrophy. Hypobaric hypoxia altered redox homeostasis and impaired calcium ion handling in skeletal muscles. Dysregulated Ca²⁺ homeostasis and activated calpain is the prime stressor in high altitude hypoxia while the reason for subsequent abnormal release of pathological Ca²⁺ into cytoplasm is largely unexplored. The present study identified the redox remodeling in the Ca²⁺ release channel, Ryanodine Receptor (RyR1) owing to its hypernitrosylation state in skeletal muscles in chronic hypobaric hypoxia exposed rats. RyR1-hypernitrosylation decreases the binding of FKBP12/calstabin-1 and other complexes from the channel, causing "leakiness" in RyR1 ion-channel. A strong RyR1 stabilizer, S107 enhanced binding affinity of FKBP12 with hypernitrosylated RyR1, reduced Sarco(endo)plasmic reticulum (SR) Ca²⁺ leak and improved muscle strength and function under chronic hypoxia. Administration of S107 inhibited the skeletal muscle damage, maintained ultrastructure of sarcomere and sarcolemmal integrity. Histological analysis proved the increase in cross-sectional area of myofibers. Further, the number of apoptotic cells was also reduced by S107 treatment. Conclusively, we proposed that the redox remodeling of RyR1 (hypernitrosylated-RyR1) might be responsible for dysregulated Ca²⁺ homeostasis which consequently impaired muscle strength and function in response to chronic hypoxic stress. Reduced SR Ca²⁺ leak and enhanced binding affinity of FKBP12 may provide a novel therapeutic avenue in ameliorating skeletal muscle atrophy at high altitude.

Hematologic Profiles of Ethiopian Preterm Infants With Clinical Diagnoses of Early-Onset Sepsis, Perinatal Asphyxia, and Respiratory Distress Syndrome

Objective. To determine the hematologic profile of preterm infants with regard to different diseases. Methods. A prospective, cross-sectional, observational study, conducted in 5 hospitals in Ethiopia from July 2016 to May 2018. Preterm babies <7 days of age were included and investigated with complete blood counts (CBC) and other investigations, accordingly. Results. Out of 4919 preterms, 3852 (78.3%) were admitted to a newborn intensive care unit, and of these, 68.3% had a CBC performed. The mean values of hemoglobin, white blood cell (WBC) and platelet counts were 17.9 mg/dL; 12 685 cells/mm³, and 159 340 cells/mm³, respectively. Early onset neonatal sepsis (EONS) 1433 (37%), asphyxia 266 (6.9%), and respiratory distress syndrome (RDS) 1738 (45.3%) were common reasons for admission. The WBC count was <5000 cells/mm³ for 8.8%, 9.0%, and 11.1% of neonates with EONS, asphyxia and RDS, respectively. The hemoglobin value was <7 mg/dL for 0.6%, 1.7%, and 0.4% of preterm infants with EONS, asphyxia, and RDS, respectively. The platelet count was <50 000 cells/mm³ for 16.8%, 17.7%, and 19.8% of preterms admitted with a diagnosis of EONS, asphyxia, and RDS, respectively. Conclusion. WBC and platelet counts were the most common to be associated with EONS, asphyxia, and RDS. Further study is recommended to determine the effect of abnormal hematologic profile on the outcome of preterm babies.

Venous thrombosis at altitude presents with distinct biochemical profiles: a comparative study from the Himalayas to the plains

High-altitude (HA) hypoxia exposure is believed to induce venous thromboembolism (VTE) in otherwise healthy individuals, although this needs to be fully established. The present study aims to ascertain the role of HA exposure in aggravating any predisposition toward VTE and to explore whether the etiology of HA-induced VTE is different from that of VTE closer to sea level. We compared manifestation-matched male VTE patients from HA (HAPs) and VTE patients from the plains closer to sea level (SLPs) for 54 parameters, including coagulation-related, fibrinolytic, and thrombophilic variables, as well as markers for stress and inflammatory response and platelet and endothelial activation. Our results established an association between HA hypoxia and VTE in alterations of primarily hemostatic variables. Approximately 96% of HAPs presented with ≥10 altered parameters out of 54 studied compared with 7% of SLPs. Elevated platelet count, von Willebrand factor, and clotting factors and altered coagulation exhibited significant associations with VTE events and altitude exposure (all P < .05). Additionally, most VTEs at HA were associated with younger age groups, unlike those on the plains. A receiver operator characteristic curve analysis revealed differences between HAPs and SLPs for CD40 ligand (area under the curve [AUC], 0.90; 95% confidence interval [CI], 0.84-0.96]), P-selectin (0.79; 0.70-0.88), platelet factor-4 (0.90; 0.84-0.96), intracellular adhesion molecule-1 (0.86; 0.79-0.93), vascular cell adhesion molecule-1 (0.97; 0.95-0.99), vascular endothelial growth factor (0.87; 0.8-0.94), FLT4 (0.94; 0.89-0.99), and Toll-like receptor-2 (0.98; 0.96-1.0) (all P < .05). In conclusion, this study suggests that HA exposure perturbs the molecules associated with vascular integrity and contributes to the early onset of VTE.

Immunothrombosis and thromboinflammation in host defense and disease

Platelets are increasingly being recognized for playing roles beyond thrombosis and hemostasis. Today we know that they mediate inflammation by direct interactions with innate immune cells or secretion of cytokines/chemokines. Here we review their interactions with neutrophils and monocytes/macrophages in infection and sepsis, stroke, myocardial infarction and venous thromboembolism. We discuss new roles for platelet surface receptors like GPVI or GPIb and also look at platelet contributions to the formation of neutrophil extracellular traps (NETs) as well as to deep vein thrombosis during infection, e.g. in COVID-19 patients.

Pulmonary Artery Thrombosis: A Diagnosis That Strives for Its Independence

According to a widespread theory, thrombotic masses are not formed in the pulmonary artery (PA) but result from migration of blood clots from the venous system. This concept has prevailed in clinical practice for more than a century. However, a new technologic era has brought forth more diagnostic possibilities, and it has been shown that thrombotic masses in the PA could, in many cases, be found without any obvious source of emboli. Chronic obstructive pulmonary disease, asthma, sickle cell anemia, emergency and elective surgery, viral pneumonia, and other conditions could be complicated by PA thrombosis development without concomitant deep vein thrombosis (DVT). Different pathologies have different causes for local PA thrombotic process. As evidenced by experimental results and clinical observations, endothelial and platelet activation are the crucial mechanisms of this process. Endothelial dysfunction can impair antithrombotic function of the arterial wall through downregulation of endothelial nitric oxide synthase (eNOS) or via stimulation of adhesion receptor expression. Hypoxia, proinflammatory cytokines, or genetic mutations may underlie the procoagulant phenotype of the PA endothelium. Both endotheliocytes and platelets could be activated by protease mediated receptor (PAR)- and receptors for advanced glycation end (RAGE)-dependent mechanisms. Hypoxia, in particular induced by high altitudes, could play a role in thrombotic complications as a trigger of platelet activity. In this review, we discuss potential mechanisms of PA thrombosis in situ.

Cytokine and chemokine regulation of venous thromboembolism

Morbidity and mortality from venous thromboembolism (VTE), which refers to deep vein thrombosis and pulmonary embolism, have a substantial effect on the global burden of disease. The field of venous thrombosis research has been dramatically changed over the past 10 years with the improvement of animal models that shed some light on the interaction between inflammation and thrombosis. Important recent advances provided evidence of the implication of the innate immune system in venous thrombosis. In this review, we highlighted the cytokines and chemokines that regulate mechanisms of thrombus formation and resolution. Cytokines are pleiotropic, redundant, and multifunctional endogenous mediators orchestrating the inflammatory responses leading to thrombus formation or resolution. The use of experimental models has revealed the pro-thrombotic activity of some cytokines including interferon-γ, interleukin (IL)-6, chemokine ligand 2, IL-17A, IL-9, IL-1β, and transforming growth factor-β. Other cytokines such as IL-10, tumor necrosis factor-α, and IL-8 appear to promote thrombus resolution in late phase of venous thromboembolism. The purpose of this review is to bring together the current knowledge regarding the cytokines and chemokines that have been involved in thrombosis formation and resolution. We postulate that an imbalance between pro-thrombotic and anti-thrombotic cytokines/chemokines may be involved in the pathophysiology of VTE. However, in-depth basic and clinical research in venous thrombosis is still require to fully understand the precise mechanism of action of these cytokines.

Impact of respiratory symptoms and oxygen saturation on the risk of incident venous thromboembolism-the Tromsø study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with risk of venous thromboembolism (VTE). It remains unknown whether individual respiratory symptoms and lowered oxygen saturation (SpO2), individually and in combination with COPD, affect the risk of VTE.

OBJECTIVES

To investigate whether measures of respiratory impairments including respiratory symptoms and SpO2, individually and combined with COPD, were associated with an increased risk of VTE.

METHODS

Spirometry, SpO2, and self-reported respiratory symptoms were collected in 8686 participants from the fifth (2001-2002) and sixth (2007-2008) surveys of the Tromsø Study. Incident VTE events were registered from the date of inclusion to December 31, 2016. Cox regression models with exposures and confounders as time-varying covariates (for repeated measurements) were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for VTE.

RESULTS

During a median follow-up of 9.1 years, 330 participants developed incident VTE. Subjects with SpO2 ≤ 96% (lowest 20th percentile) had a 1.5-fold higher risk of VTE (adjusted HR, 1.48; 95% CI, 1.13-1.93) compared with those with SpO2 ≥ 98%. Severe respiratory symptoms (dyspnea, cough, and phlegm) were associated with a 1.4- to 2.0-fold higher risk of VTE compared with no such symptoms. COPD, combined with respiratory symptoms or lowered SpO2, had an additive effect on the VTE risk.

CONCLUSIONS

Lowered SpO2 and severe respiratory symptoms were associated with increased VTE risk. COPD combined with respiratory impairments had an additive effect on VTE risk, and may suggest particular attention on VTE preventive strategies in COPD patients with respiratory impairments.

CD154 Induces Interleukin-6 Secretion by Kidney Tubular Epithelial Cells under Hypoxic Conditions: Inhibition by Chloroquine

Inflammation is a major contributor to tubular epithelium injury in kidney disorders, and the involvement of blood platelets in driving inflammation is increasingly stressed. CD154, the ligand of CD40, is one of the mediators supporting platelet proinflammatory properties. Although hypoxia is an essential constituent of the inflammatory reaction, if and how platelets and CD154 regulate inflammation in hypoxic conditions remain unclear. Here, we studied the control by CD154 of the proinflammatory cytokine interleukin- (IL-) 6 secretion in short-term oxygen (O₂) deprivation conditions, using the HK-2 cell line as a kidney tubular epithelial cell (TEC) model. IL-6 secretion was markedly stimulated by CD154 after 1 to 3 hours of hypoxic stress. Both intracellular IL-6 expression and secretion were stimulated by CD154 and associated with a strong upregulation of IL-6 mRNA and increased transcription. Searching for inhibitors of CD154-mediated IL-6 production by HK-2 cells in hypoxic conditions, we observed that chloroquine, a drug that has been repurposed as an anti-inflammatory agent, alleviated this induction. Therefore, CD154 is a potent early stimulus for IL-6 secretion by TECs in O₂ deprivation conditions, a mechanism likely to take part in the deleterious inflammatory consequences of platelet activation in kidney tubular injury. The inhibition of CD154-induced IL-6 production by chloroquine suggests the potential usefulness of this drug as a therapeutic adjunct in conditions associated with acute kidney injury.

Hypoxia Modulates Platelet Purinergic Signalling Pathways

BACKGROUND

 Hypoxia resulting from ascent to high-altitude or pathological states at sea level is known to increase platelet reactivity. Previous work from our group has suggested that this may be adenosine diphosphate (ADP)-specific. Given the clinical importance of drugs targeting ADP pathways, research into the impact of hypoxia on platelet ADP pathways is highly important.

METHODS

 Optimul aggregometry was performed on plasma from 29 lowland residents ascending to 4,700 m, allowing systematic assessment of platelet reactivity in response to several platelet agonists. Aggregometry was also performed in response to ADP in the presence of inhibitors of the two main ADP receptors, P2Y₁ and P2Y₁₂ (MRS2500 and cangrelor, respectively). Phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a key determinant of platelet aggregation, was analysed using the VASPFix assay.

RESULTS

 Hypobaric hypoxia significantly reduced the ability of a fixed concentration of cangrelor to inhibit ADP-induced aggregation and increased basal VASP phosphorylation. However, in the absence of P2Y receptor inhibitors, we did not find evidence of increased platelet sensitivity to any of the agonists tested and found reduced sensitivity to thrombin receptor-activating peptide-6 amide.

CONCLUSION

 Our results provide evidence of increased P2Y₁ receptor activity at high altitude and suggest down-regulation of the P2Y₁₂ pathway through increased VASP phosphorylation. These changes in ADP pathway activity are of potential therapeutic significance to high-altitude sojourners and hypoxic sea level patients prescribed platelet inhibitors and warrant further investigation.