Iron-dependent human platelet activation and hydroxyl radical formation: involvement of protein kinase C

C-type lectin-like receptor-2 in platelets mediates ferric chloride-induced platelet activation and attenuates ferroptosis of endothelial cells

BACKGROUND

An iron overload status induces ferroptosis, an iron-dependent nonapoptotic cell death, in various pathological conditions. We previously reported that hemin (heme), protoporphyrin-IX with ferric iron, activates platelets via C-type lectin-like receptor-2 (CLEC-2) and glycoprotein VI/FcRγ, but protoporphyrin-IX alone blocks CLEC-2-dependent platelet activation. Therefore, we hypothesized that free iron has the ability to activate platelets.

OBJECTIVES

This study aimed to elucidate platelet activation mechanisms of iron (ferric chloride), including the identification of signaling pathways and receptors, and to examine whether platelets regulate ferroptosis.

METHODS

Platelet aggregometry, platelet activation marker expression, and protein phosphorylation were examined in ferric chloride-stimulated human and murine platelets. Inhibitors of platelet activation signaling pathways and receptor-deleted platelets were utilized to identify the responsible signaling pathway and receptor. The effect of platelets on ferroptosis of endothelial cells was investigated in vitro.

RESULTS

Ferric chloride induced platelet activation dependent on Src family kinase pathways in humans and mice. Ferric chloride-induced platelet aggregation was almost lost in CLEC-2-depleted murine platelets and wild-type platelets preincubated with recombinant CLEC-2 proteins. Furthermore, coculture of wild-type platelets, but not CLEC-2-deficient platelets, attenuated ferroptosis of endothelial cells in vitro.

CONCLUSION

Ferric chloride activates platelets via CLEC-2 and Src family kinase pathways, and platelets have a protective role in the ferroptosis of endothelial cells dependent on CLEC-2.

Association of Higher Hemoglobin Level With Significant Carotid Artery Plaque in the General Population

Objective

Serum hemoglobin (Hb) level affects the viscosity of blood. Several studies have reported that Hb level is associated with adverse cardiovascular outcome. However, there is a paucity of evidence on the association between serum Hb level and the risk of subclinical atherosclerosis. Thus, the objective of this study was to investigate the relationship between Hb level and risk of carotid plaque in a health checkup cohort.

Methods

This retrospective study analyzed a total of 3,805 individuals without history of cardiovascular disease (CVD) who underwent carotid ultrasonography (USG) between January 2016 and June 2018. Participants were divided into 4 groups based on Hb quartiles in each of male and female. Carotid plaque score was calculated based on USG reports. Multivariable logistic regression analysis was performed for each index of quartile groups regarding the risk of carotid plaque.

Results

Of 3,805 individuals (mean age, 52.62±10.25 years; 2,674 [70.28%] males), mean Hb level was 15.11±0.75 g/dL in male and 13.35±0.74 g/dL in female. When the Q1 group was compared to the Q4, increasing quartile of Hb was associated with the presence of significant carotid plaque (plaque score ≥3) in male (adjusted odds ratio [OR], 1.538; 95% confidence interval [CI], 1.182-2.001; p=0.001) and female (adjusted OR, 1.749; 95% CI, 1.058-2.676; p=0.01).

Conclusion

A high Hb level is associated with an increased risk of carotid plaques in individuals without history of CVD. This finding may support the need for early screening of CVD in individuals with high Hb levels.

The Combination of Uric Acid and Hemoglobin Levels Predicts the Incident Risk of Ischemic Heart Disease More Than Uric Acid Alone in Non-Diabetic Koreans: A Longitudinal Study Using National Health Insurance Data

Uric acid has been related to cardiovascular disease (CVD). Recently, slightly elevated hemoglobin (Hb) was also shown to be associated with CVD. We retrospectively investigated the joint effect of uric acid and elevated Hb by comparing normal-range uric acid alone on incident ischemic heart disease (IHD) risk in a large cohort of non-diabetic Korean adults using National Health Insurance data. We assessed 16,786 participants without diabetes (8595 men and 8191 women) using extensive cohort data. High Hb was defined as ≥16.4 g/dL in men and 13.8 g/dL in women (>75th percentile). We analyzed the data using two different methods. First, the participants were divided into quartiles according to uric acid levels. Second, subjects were also divided into quartiles: reference (group 1), high uric acid and normal Hb (group 2), normal uric acid and high Hb (group 3), and normal uric acid and high Hb (group 4). We evaluated hazard ratios (HRs) with 95% confidence intervals (CIs) for IHD using multivariate Cox regression analysis over a 50-month follow-up. During the follow-up, 345 (1.9%) participants developed IHD. In the analysis using both uric acid and Hb, compared with the reference group, the HRs for IHD were 1.37 (95% CI, 1.01-1.86) in the second group, 1.63 (95% CI, 1.21-2.21) in the third group, and 1.86 (95% CI, 1.30-2.67) in the fourth group after adjusting for IHD risk factors. Subsequently, patients with high uric acid are more likely to develop incident IHD than control patients. Moreover, we confirmed the joint effects of high uric acid and high hemoglobin on incident IHD. Awareness of these interactions is essential for clinicians. Risk factor management and screening for IHD are part of the routine management of patients with high uric acid and Hb.

Haemoglobin levels as a predictor for the occurrence of future cardiovascular events in adults-Sex-dependent results from the EPIC trial

BACKGROUND

The impact of hemoglobin levels on the occurrence of future health events remains equivocal. Due to its integral role in human hemostasis, both, high and low hemoglobin levels may play a significant role in the development of future cardiovascular (CV) events in otherwise healthy adults.

METHODS

Data from the European Prospective Investigation into Cancer (EPIC)-InterAct cohort was analyzed. In 13.648 individuals, physical activity, body mass index, family history of cardiovascular events, kidney function, smoking status, blood pressure and LDL levels were modelled to concomitant hemoglobin levels and correlated to the occurrence of clinically-overt cardiovascular events and death over a 21-year period. (Sex specific) cox regression analysis were used to develop hazard ratios (HRs) for CV events and all-cause mortality.

RESULTS

Anemia (hemoglobin (HGB) levels < 13.0 g/dl in men and < 12.0 g/dl in non-pregnant women) were associated with an increased all-cause mortality in men but not in women (HR anemia in men 1.4 (1.2; 1.6)) p=<0.0001).This was particularly visible with increasing age. Various sex specific Cox regression models, accounting for several CV risk factors confirmed these results. The incidence of future CV events and myocardial infarction was significantly influenced by underlying HGB levels in men with increasing age but not in women.

CONCLUSION

The influence of HGB levels on future cardiovascular events is sex-dependent. In men, presenting with anemia at baseline, the overall survival probability was impaired with increasing age. After adjusting for several CV risk factors, abnormal hemoglobin levels could be identified as a risk factor for the development of clinically-apparent future CV events in men. None of these effects were observed in women.

Platelets at the Vessel Wall in Non-Thrombotic Disease

Platelets are small, anucleate entities that bud from megakaryocytes in the bone marrow. Among circulating cells, platelets are the most abundant cell, traditionally involved in regulating the balance between thrombosis (the terminal event of platelet activation) and hemostasis (a protective response to tissue injury). Although platelets lack the precise cellular control offered by nucleate cells, they are in fact very dynamic cells, enriched in preformed RNA that allows them the capability of de novo protein synthesis which alters the platelet phenotype and responses in physiological and pathological events. Antiplatelet medications have significantly reduced the morbidity and mortality for patients afflicted with thrombotic diseases, including stroke and myocardial infarction. However, it has become apparent in the last few years that platelets play a critical role beyond thrombosis and hemostasis. For example, platelet-derived proteins by constitutive and regulated exocytosis can be found in the plasma and may educate distant tissue including blood vessels. First, platelets are enriched in inflammatory and anti-inflammatory molecules that may regulate vascular remodeling. Second, platelet-derived microparticles released into the circulation can be acquired by vascular endothelial cells through the process of endocytosis. Third, platelets are highly enriched in mitochondria that may contribute to the local reactive oxygen species pool and remodel phospholipids in the plasma membrane of blood vessels. Lastly, platelets are enriched in proteins and phosphoproteins which can be secreted independent of stimulation by surface receptor agonists in conditions of disturbed blood flow. This so-called biomechanical platelet activation occurs in regions of pathologically narrowed (atherosclerotic) or dilated (aneurysmal) vessels. Emerging evidence suggests platelets may regulate the process of angiogenesis and blood flow to tumors as well as education of distant organs for the purposes of allograft health following transplantation. This review will illustrate the potential of platelets to remodel blood vessels in various diseases with a focus on the aforementioned mechanisms.

The enhancement of mechanical properties and uniform degradation of electrodeposited Fe-Zn alloys by multilayered design for biodegradable stent applications

Pure Fe is a potential biodegradable stent material due to its better biocompatibility and mechanical properties, but its degradation rate needs to be improved. Alloying with Zn to form Fe-Zn alloy is anticipated to meet the degradation rate requirements while retaining the iron's inherent properties. Therefore, Fe-Zn alloys with monolayered and multilayered structures were prepared by electrodeposition. The alloys' composition, microstructure, mechanical properties, in vitro degradation and biocompatibility were assessed. Results showed that the Zn content ranged from 2.1 wt% to 11.6 wt%. After annealing at 450°C, all the alloys consisted of α(Fe) solid solution and Zn-rich B2 ordered coherent phase, except for the alloy with 11.6 wt% Zn content, in which a Fe₃Zn₁₀ phase appeared. The layered structure consisted of alternating columnar-grain and nano-grain layers, which compensated for the intrinsic brittleness of electrodeposited metals and improved the galvanic effect of the alloy, thus increasing the strength and plasticity and changing the corrosion from localized to uniform while augmenting the corrosion rate. The yield strength of the multilayered alloy exceeded 350 MPa, its elongation was more than 20%, and its corrosion rate obtained by immersion test in Hank's solution reached 0.367 mm·y^-1. Fe-Zn alloys with lower Zn content had good cytocompatibility with the human umbilical vein endothelial cells and good blood compatibility. The above results verified that the multilayered Fe-Zn alloy prepared by electrodeposition presented enhanced mechanical properties, higher degradation rate, uniform degradation mechanism and good biocompatibility. It should be qualified for the application of biodegradable stents. STATEMENT OF SIGNIFICANCE: A potential biodegradable Fe-Zn alloy, which is difficult to be obtained by the metallurgical method, was prepared by electrodeposition to solve the low degradation rate of iron-based biomaterials. A multilayered microstructure design composed of alternating columnar-grain and nano-grain layers was achieved by changing the electrical parameters. The layered design compensated for the intrinsic poor plasticity of electrodeposited metals. It increased the galvanic effect of the alloy, thus augmenting the corrosion rate and changing the corrosion mode of the alloy from localized to uniform corrosion. The yield strength of multilayered alloy exceeded 350 MPa; its elongation was more than 20%. Moreover, the layered alloy had good cytocompatibility and blood compatibility. It indicates that the alloy is qualified for biodegradable stent application.

Deferiprone, an iron chelator, alleviates platelet hyperactivity in patients with β-thalassaemia/HbE

Background

Hyperfunctional platelets play important roles in thromboembolism in patients with β-thalassaemia/ haemoglobin E (β-thal/HbE). Our previous study revealed ex vivo inhibitory effects of deferiprone on normal platelets. Herein, we aimed to investigate the in vivo effects on platelets in patients with β-thal/HbE.

Methods

A prospective, self-controlled clinical study on 30 patients with β-thal/HbE who had received therapeutic deferiprone (20.8-94.5 mg/kg/day) was conducted. The study included a 4-week washout period followed by 4 and 12 weeks of deferiprone treatment. Platelet aggregation was performed by a turbidimetric method. Levels of deferiprone and soluble platelet (sP)-selectin in serum were measured by high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) kit, respectively.

Results

The washout period significantly enhanced platelet hyperactivity both in patients who had undergone splenectomy and in those who had not. At 2 hours following the administration of a single dose of deferiprone, platelet sensitivity to ADP and arachidonic acid was significantly reduced. The inhibitory effects of deferiprone were gradually increased over the period of 4 and 12 weeks. Deferiprone also depressed sP-selectin levels, but the effect was stable over longer follow-up periods. Correlation analysis demonstrated the relationship between serum levels of deferiprone, sP-selectin, and platelet activities induced by ADP and arachidonic acid.

Conclusion

We first demonstrated the in vivo antiplatelet effect and benefit of short-term treatment of deferiprone in patients with β-thal/HbE. The impact on thrombotic outcomes deserves further study.

Melatonin: Potential avenue for treating iron overload disorders

Iron overload as a highly risk factor, can be found in almost all human chronic and common diseases. Iron chelators are often used to treat iron overload; however, patient adherence to these chelators is poor due to obvious side effects and other disadvantages. Numerous studies have shown that melatonin has a high iron chelation ability and direct free radical scavenging activity, and can inhibit the lipid peroxidation process caused by iron overload. Therefore, melatonin may become potential complementary therapy for iron overload-related disorders due to its iron chelating and antioxidant activities. Here, the research progress of iron overload is reviewed and the therapeutic potential of melatonin in the treatment of iron overload is analyzed. In addition, studies related to the protective effects of melatonin on oxidative damage induced by iron overload are discussed. This review provides a foundation for preventing and treating iron homeostasis disorders with melatonin.

Platelet reactivity and platelet count in women with iron deficiency treated with intravenous iron

Background

Iron deficiency anemia (IDA) and heavy menstrual bleeding are prevalent, interrelated issues impacting over 300 million premenopausal women worldwide. IDA is generally associated with increased platelet counts; however, the effects of IDA and its correction on platelet function in premenopausal women remain unknown.

Objectives

We sought to determine how IDA and intravenous iron affect platelet count and platelet function in premenopausal women.

Methods

Hematologic indices were assessed in a multicenter, retrospective cohort of 231 women repleted with intravenous iron. Pre- and postinfusion blood samples were then obtained from a prospective cohort of 13 women to analyze the effect of intravenous iron on hematologic parameters as well as platelet function with flow cytometry and platelet aggregation assays under physiologic shear.

Results

Following iron replacement, anemia improved, and mean platelet counts decreased by 26.5 and 16.0 K/mm³ in the retrospective and prospective cohorts, respectively. Replacement reduced baseline platelet surface P-selectin levels while enhancing platelet secretory responses to agonists, including collagen-related peptide and ADP. Platelet adhesion and aggregation on collagen under physiologic shear also significantly increased following repletion.

Conclusion

We find that intravenous iron improves anemia while restoring platelet counts and platelet secretory responses in premenopausal women with iron deficiency. Our results suggest that iron deficiency as well as iron replacement can have a range of effects on platelet production and function. Consequently, platelet reactivity profiles should be further examined in women and other groups with IDA where replacement offers a promising means to improve anemia as well as quality of life.

Predictive value of hemoglobin level on early neurological outcomes in acute ischemic stroke

BACKGROUND

Few studies have examined the association between hemoglobin (Hb) levels and early neurological changes following acute ischemic stroke (AIS). The present research investigated whether higher or lower Hb level on admission was associated with early neurological deterioration (END) in AIS patients. Furthermore, we evaluated the predictive effect of Hb concentration on stable or improving outcome.

METHODS

In this prospective cohort study, a total of 1330 patients admitted within 24 hours after AIS onset were finally involved in the analysis. We classified participants into four groups according to baseline Hb levels: ≤120, 121-140, 141-160, and >160 g/L. The risk of END was accessed by means of logistic regression analysis, and tendency of improvement and stability by multinomial logit analysis. We further evaluated the pattern and magnitude of association of Hb as a continuous variable and END by multivariate logistic regression analysis of restricted cubic spline.

RESULTS

Compared with the reference group, hemoglobin >160 g/L was associated with END (OR, 95%CI; 2.149, 1.314-3.512) and severe END (OR, 95% CI as 2.317, 1.351-3.976 and 2.810,1.589-4.968, respectively). Comparatively, higher Hb level also independently predicted improving (OR, 95% CI; 0.322, 0.170-0.609) and stable (OR, 95% CI; 0.371, 0.205-0.673) outcome. Similar results were found when restricted to anterior circulation ischemic stroke after adjustment of variables including large vessel disease.

CONCLUSIONS

We concluded that patients with higher baseline Hb level are at significantly higher risk for END, and less likely to reach stable or improving status at the early stage of stroke.

High haemoglobin levels and mortality in males with intracerebral haemorrhage: a retrospective cohort study

OBJECTIVES

To examine the association between high haemoglobin levels and outcomes in intracerebral haemorrhage (ICH) in a multicentre cohort study.

DESIGN

Prospective multicentre cohort study.

SETTINGS

21 tertiary hospitals across mainland China.

PARTICIPANTS

A total of 5318 consecutive in-hospital spontaneous ICH patients were recruited between January 2012 and June 2016.

PRIMARY AND SECONDARY OUTCOME MEASURES

Haemoglobin levels were measured on admission. Binary or ordinary logistic regression was used to evaluate the independent relationship of haemoglobin level with clinical outcomes at 3 months, measured as death or disability. Restricted cubic spline regression was fitted to examine the potential non-linear shape of the dose-response curve between the whole haemoglobin levels and 3-month poor outcomes.

RESULTS

A total of 5031 patients with ICH were analysed (64.3% male; mean age (SD), 57.8 (15.2) years). We found that the highest haemoglobin quintile was associated with poor outcomes 3 months in males (adjusted OR (aOR) 1.65, 95% CI 1.21 to 2.25) but not in females, which was also observed in the pooled analysis of three subcohorts in male patients (average aOR 1.70, 95% CI 1.23 to 2.33). The spline regression suggested a non-linear association between haemoglobin levels and outcomes and a linear relationship was observed between an elevated haemoglobin level and 3-month disability/death in males (haemoglobin level per 10 g/L: aOR 1.24, 95% CI 1.10 to 1.40, p<0.001), which was mediated by larger haematoma volume (effect size: 0.115, 95% CI 0.012 to 0.231).

CONCLUSIONS

This study found a sex-specific association between an elevated haemoglobin level and poor 3-month outcomes, which might be mediated by larger haematoma volume.

Iron and platelets: A subtle, under-recognized relationship

The role of iron in the formation and functioning of erythrocytes, and to a lesser degree of white blood cells, is well established, but the relationship between iron and platelets is less documented. Physiologically, iron plays an important role in hematopoiesis, including thrombopoiesis; iron levels direct, together with genetic factors, the lineage commitment of megakaryocytic/erythroid progenitors toward either megakaryocyte or erythroid progenitors. Megakaryocytic iron contributes to cellular machinery, especially energy production in platelet mitochondria. Thrombocytosis, possibly favoring vascular thrombosis, is a classical feature observed with abnormally low total body iron stores (mainly due to blood losses or decreased duodenal iron intake), but thrombocytopenia can also occur in severe iron deficiency anemia. Iron sequestration, as seen in inflammatory conditions, can be associated with early thrombocytopenia due to platelet consumption and followed by reactive replenishment of the platelet pool with possibility of thrombocytosis. Iron overload of genetic origin (hemochromatosis), despite expected mitochondrial damage related to ferroptosis, has not been reported to cause thrombocytopenia (except in case of high degree of hepatic fibrosis), and iron-related alteration of platelet function is still a matter of debate. In acquired iron overload (of transfusional and/or dyserythropoiesis origin), quantitative or qualitative platelet changes are difficult to attribute to iron alone due to the interference of the underlying hematological conditions; likewise, hematological improvement, including increased blood platelet counts, observed under iron oral chelation is likely to reflect mechanisms other than the sole beneficial impact of iron depletion.

Shear and Integrin Outside-In Signaling Activate NADPH-Oxidase 2 to Promote Platelet Activation

[Figure: see text].

Surrogate Markers of Subclinical Atherosclerosis and Its Associated Factors in Patients with β-Thalassemia Major

β-Thalassemia major (β-TM) is a severe genetic hemoglobin (Hb) disorder with cardiovascular complications such as atherosclerosis due to transfusion-dependent iron overload. We aimed to determine the associated factors with surrogate markers of subclinical atherosclerosis in these patients. Sixty subjects with β-TM referred to the Thalassemia Clinic of the Iranian Blood Transfusion Organization (IBTO) were included in our study. The blood samples were collected for laboratory measurements. The carotid intima-media thickness (CIMT), was measured by ultrasonography, and ankle-brachial index (ABI) was calculated. The multivariate linear analysis was performed to determine the appropriate indicators of subclinical atherosclerosis in β-TM. There was no significant difference in baseline characteristics between the study groups. In multivariate linear analysis, age and systolic blood pressure (SBP) were negatively associated with inverse-transformed CIMT [unstandardized β coefficient (B): -0.024, 95% confidence interval (95% CI): -0.032- -0.010, p < 0.001; B: -0.009, 95% CI: -0.017- -0.001, p 0.031, respectively]. There was also a significant correlation between the serum level of high-density lipoprotein cholesterol (HDL-C) and insulin with higher ABI, after adjustment for confounding variables (B: 0.003; 95% CI: 0.000-0.005; p = 0.030, and B: 0.004, 95% CI: 0.000-0.009, p = 0.037, respectively). Our results show that advancing age and increased SBP, HDL-C and insulin, associated with higher CIMT or ABI, are appropriate indicators of subclinical atherosclerosis in β-TM patients.

Extrusion-based 3D printed biodegradable porous iron

Extrusion-based 3D printing followed by debinding and sintering is a powerful approach that allows for the fabrication of porous scaffolds from materials (or material combinations) that are otherwise very challenging to process using other additive manufacturing techniques. Iron is one of the materials that have been recently shown to be amenable to processing using this approach. Indeed, a fully interconnected porous design has the potential of resolving the fundamental issue regarding bulk iron, namely a very low rate of biodegradation. However, no extensive evaluation of the biodegradation behavior and properties of porous iron scaffolds made by extrusion-based 3D printing has been reported. Therefore, the in vitro biodegradation behavior, electrochemical response, evolution of mechanical properties along with biodegradation, and responses of an osteoblastic cell line to the 3D printed iron scaffolds were studied. An ink formulation, as well as matching 3D printing, debinding and sintering conditions, was developed to create iron scaffolds with a porosity of 67%, a pore interconnectivity of 96%, and a strut density of 89% after sintering. X-ray diffracometry confirmed the presence of the α-iron phase in the scaffolds without any residuals from the rest of the ink. Owing to the presence of geometrically designed macropores and random micropores in the struts, the in vitro corrosion rate of the scaffolds was much improved as compared to the bulk counterpart, with 7% mass loss after 28 days. The mechanical properties of the scaffolds remained in the range of those of trabecular bone despite 28 days of in vitro biodegradation. The direct culture of MC3T3-E1 preosteoblasts on the scaffolds led to a substantial reduction in living cell count, caused by a high concentration of iron ions, as revealed by the indirect assays. On the other hand, the ability of the cells to spread and form filopodia indicated the cytocompatibility of the corrosion products. Taken together, this study shows the great potential of extrusion-based 3D printed porous iron to be further developed as a biodegradable bone substituting biomaterial.

Rho GTPase regulation of reactive oxygen species generation and signalling in platelet function and disease

Platelets are master regulators and effectors of haemostasis with increasingly recognized functions as mediators of inflammation and immune responses. The Rho family of GTPase members Rac1, Cdc42 and RhoA are known to be major components of the intracellular signalling network critical to platelet shape change and morphological dynamics, thus playing a major role in platelet spreading, secretion and thrombus formation. Initially linked to the regulation of actomyosin contraction and lamellipodia formation, recent reports have uncovered non-canonical functions of platelet RhoGTPases in the regulation of reactive oxygen species (ROS), where intrinsically generated ROS modulate platelet function and contribute to thrombus formation. Platelet RhoGTPases orchestrate oxidative processes and cytoskeletal rearrangement in an interconnected manner to regulate intracellular signalling networks underlying platelet activity and thrombus formation. Herein we review our current knowledge of the regulation of platelet ROS generation by RhoGTPases and their relationship with platelet cytoskeletal reorganization, activation and function.

Centrality of G6PD in COVID-19: The Biochemical Rationale and Clinical Implications

Introduction: COVID-19 is a novel and devastating disease. Its manifestations vary from asymptomatic to lethal. Moreover, mortality rates differ based on underlying health conditions and ethnicity. We investigated the biochemical rationale behind these observations using machine reasoning by the sci.AI system (https://sci.ai/). Facts were extracted and linked from publications available in nlm.nih.gov and Europe PMC to form the dataset which was validated by medical experts. Results: Based on the analysis of experimental and clinical data, we synthesized detailed biochemical pathways of COVID-19 pathogenesis which were used to explain epidemiological and clinical observations. Clinical manifestations and biomarkers are highlighted to monitor the course of COVID-19 and navigate treatment. As depicted in the Graphical Abstract, SARS-CoV-2 triggers a pro-oxidant (PO) response leading to the production of reactive oxygen species (ROS) as a normal innate defense. However, SARS-CoV-2's unique interference with the antioxidant (AO) system, through suppression of nitric oxide (NO) production in the renin- angiotensin-aldosterone system (RAAS), leads to an excessive inflammatory PO response. The excessive PO response becomes critical in cohorts with a compromised AO system such as patients with glucose-6-phosphate dehydrogenase deficiency (G6PDd) where NO and glutathione (GSH) mechanisms are impaired. G6PDd develops in patients with metabolic syndrome. It is mediated by aldosterone (Ald) which also increases specifically in COVID-19. Conclusion: G6PD is essential for an adequate immune response. Both G6PDd and SARS-CoV-2 compromise the AO system through the same pathways rendering G6PDd the Achilles' heel for COVID-19. Thus, the evolutionary antimalarial advantage of the G6PDd cohort can be a disadvantage against SARS-CoV-2.

Relation of Hypoalbuminemia to Response to Aspirin in Patients With Stable Coronary Artery Disease

Serum albumin (SA) level is a powerful cardiovascular prognostic marker, suggested to be involved in regulation of platelet function. High on-aspirin platelet reactivity (HAPR) is associated with increased risk for deleterious cardiovascular events. The aim of the present study was to evaluate the association between HAPR and albumin levels in patients with stable coronary artery disease (CAD) treated with aspirin. Patients with known stable CAD, who were taking aspirin (75 to 100 mg qd) regularly for at least 1 month, were screened for the present study. Exclusion criteria: cancer, sepsis or acute infection, active inflammatory/rheumatic disease, recent major surgery, chronic liver failure, the administration of other antiplatelet drugs, nonadherence with aspirin and thrombocytopenia. Blood was drawn from the participants and sent for SA level and platelet function test (VerifyNow). HAPR was defined as aspirin reaction units (ARU) >550. Overall 116 patients were analyzed; age 69 ± 10, 28% women. Twenty (17%) were hypoalbuminemic (≤3.5 g/dl). Hypoalbuminemic patients had similar characteristics to the normal albumin group except mildly higher creatinine in the former. SA levels were significantly lower in the hypoalbuminemic group (3.2 ± 0.2 g/dl vs 4.2 ± 0.4 g/dl, respectively, p <0.001) whereas mean ARU was significantly higher compared with the normal albumin group (548 ± 45 vs 444 ± 66 ARU, respectively, p <0.001). A significant inverse association was observed between SA and ARU with (R² = 0.67, p <0.001). Multivariate analysis adjusted for potential confounders found that albumin ≤3.5 is the strongest predictor of HAPR in patients with stable CAD (hazards ratio 4.9, 95% confidence interval 2.2 to 32, p = 0.002). In conclusion, hypoalbuminemia is strongly associated with HAPR in patients with stable CAD.

Antiplatelet activity of deferiprone through cyclooxygenase-1 inhibition

Thalassemia patients are susceptible to both iron overload and thromboembolism. Deferiprone is an iron chelator that shows an antiplatelet activity and thus may alleviate platelet hyperactivation in thalassemia. Therefore, this study aimed to characterize the inhibitory effects and mechanisms of deferiprone on normal human platelets. The results illustrated that deferiprone inhibited platelet aggregation at the iron chelating concentrations (0.08-0.25 mmol/l). Deferiprone inhibited human platelet aggregation stimulated by arachidonic acid and ADP more potently than epinephrine and collagen, with the IC₅₀ of 0.24 mmol/l and 0.25 mmol/l vs. 3.36 mmol/l and 3.73 mmol/l, respectively. Interestingly, deferiprone significantly inhibited COX-1 activity, with the IC₅₀ of 0.33 mmol/l, and slightly increased cAMP level at the high concentration of 4 mmol/l. Moreover, the results from molecular docking showed that deferiprone interacted closely with key residues in the peroxidase active site of COX-1. These results suggested that deferiprone possessed antiplatelet activity mainly through the inhibition of COX-1 activity.

Moderate morning rise in blood pressure has lowest risk of stroke but only in women

BACKGROUND

The morning period which is recognized as the highest risk for cardiovascular events is associated with a surge in blood pressure (BP). However, it is unclear what aspect of this rise is important.

AIM

To determine whether the rate of rise (RoR), the magnitude (day night difference) or the product [BP power (BPPower)] is associated with increased cardiovascular risk.

METHODS

We developed a logistic equation method to fit individual 24-h patterns of BP to determine RoR, amplitude and BPPower using the ambulatory recordings from the Ohasama study including 564 men and 971 women (16.6 years follow-up).

RESULTS

Men had a higher risk of cardiovascular events than women (24, 16%, P < 0.001). Age and night BP were strong linear risk predictors. In men sorting risk by quintiles of BPPower (adjusted for age, night BP, smoking status) revealed no clear linear or nonlinear pattern. However, in women BPPower had a U-shaped relationship with the lowest risk being the 2-3rd quintile for all cardiovascular events (Pquadratic = 0.01) including cardiovascular death (Pquadratic = 0.03) and nonfatal stroke (Pquadratic = 0.02). A similar but less clear trend was observed with the RoR but only stroke (infarct) reached significance (Pquadratic = 0.03) while sorting by range showed a U shaped pattern for combined cardiovascular events (Pquadratic = 0.04).

CONCLUSION

These findings suggest that the morning BPPower is an important independent risk factor for predicting cardiovascular events and stroke but only in women with median levels having the lowest risk.

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD40L (Spearman's rank correlation coefficient [r_s ], -0.33; P < 0.001), sNox2-dp (r_s , -0.57; P < 0.0001), and urinary excretion of isoprostanes (r_s, -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2α-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation.

Hemoglobin level and three-month clinical outcomes among ischemic stroke patients with elevated systolic blood pressure

BACKGROUND

Previous studies have reported that extreme low and high hemoglobin levels are positively associated with the risk of ischemic stroke. However, there are few reports on the relationship between hemoglobin at acute phase and clinical outcomes after ischemic stroke and the results of their association to date are inconsistent. We aimed to investigate the association between them in a large prospective cohort of ischemic stroke patients.

METHODS

Baseline hemoglobin levels were measured in 3881 patients with acute ischemic stroke. The primary outcome was defined as composite outcome of major disability and death (modified Rankin Scale score ≥ 3) at 3 months after stroke onset. Secondary outcomes were separately those of major disability and death.

RESULTS

Compared with the lowest quartile of hemoglobin, the multivariate adjusted odds ratios (95% confidence intervals) associated with the highest quartile were 1.38 (1.03-1.86), 1.49 (1.11-1.99), 0.79 (0.41-1.52) for primary outcome, major disability and death, respectively. Multiple-adjusted spline regression model showed linear associations of hemoglobin levels with primary outcome (P for linearity =0.037) and major disability (P for linearity =0.004). Subgroup analyses further confirmed the positive association between high hemoglobin and poor prognosis of ischemic stroke.

CONCLUSIONS

Elevated hemoglobin levels in the acute phase were associated with poor prognosis at 3 months after ischemic stroke. Further prospective studies from other samples of ischemic stroke patients are needed to validate our findings.

Hematocrit and the incidence of stroke: a prospective, population-based cohort study

Background and purpose

Whether higher hematocrit levels could increase the incidence of stroke has always been full of controversy. This study aimed to explore the association between hematocrit and the incidence of stroke in the Chinese population.

Subjects and methods

The Kailuan study is a prospective longitudinal cohort study on risk factors and events of chronic diseases. Using a multivariable Cox proportional hazards analysis, we examined the association between baseline hematocrit values and the incidence of stroke in the Kailuan cohort (93,299 participants).

Results

A total of 3,624 participants developed stroke during the 9-year follow-up period. In Cox regression models adjusted for demographic information and for clinical variables, there was a significant association between baseline hematocrit levels and the incidence of stroke. The highest hematocrit quartile (quartile 5: men, hematocrit >48.6%; women, hematocrit >43.2%) was associated with a higher incidence of stroke (HR 1.17, 95% CI 1.04–1.31, P for trend =0.0016) compared with the lowest hematocrit quartile (quartile 1: men, hematocrit <41.5%; women, hematocrit <36.6%). In the analysis of ischemic stroke, intracerebral hemorrhage separately, similar association was observed in ischemic stroke, but there were no statistical differences in intracerebral hemorrhage.

Conclusion

Higher hematocrit levels are associated with a higher incidence of stroke in the Chinese population.

Mitochondrial functioning abnormalities observed in blood platelets of chronic smoke-exposed guinea pigs - a pilot study

Background

COPD represents a major global health issue, which is often accompanied by cardiovascular diseases. A considerable body of evidence suggests that cardiovascular risk is elevated by the activation of blood platelets, which in turn is exacerbated by inflammation. As reactive oxygen species are believed to be an important factor in platelet metabolism and functioning, the aim of our study was to perform a complex assessment of mitochondrial function in platelets in chronic smoke exposed animals with COPD-like lung lesions.

Materials and methods

Eight-week-old, male Dunkin Hartley guinea pigs (the study group) were exposed to the cigarette smoke from commercial unfiltered cigarettes (0.9 mg/cig of nicotine content) or to the air without cigarette smoke (control group), using the Candela Constructions^® exposure system. The animals were exposed for 4 hours daily, 5 days a week, with 2×70 mL puff/minute, until signs of dyspnea were observed. The animals were bled, and isolated platelets were used to monitor blood platelet respiration. The mitochondrial respiratory parameters of the platelets were monitored in vitro based on continuous recording of oxygen consumption by high-resolution respirometry.

Results

An elevated respiration trend was observed in the LEAK-state (adjusted for number of platelets) in the smoke-exposed animals: 6.75 (5.09) vs 2.53 (1.28) (pmol O₂/[s ⋅ 110⁸ platelets]); bootstrap-boosted P_1α=0.04. The study group also demonstrated lowered respiration in the ET-state (normalized for protein content): 12.31 (4.84) vs 16.48 (1.72) (pmol O₂/[s ⋅ mg of protein]); bootstrap-boosted P_1α=0.049.

Conclusion

Our results suggest increased proton and electron leak and decreased electron transfer system capacity in platelets from chronic smoke-exposed animals. These observations may also indicate that platelets play an important role in the pathobiology of COPD and its comorbidities and may serve as a background for possible therapeutic targeting. However, these preliminary outcomes should be further validated in studies based on larger samples.

Association of Hemoglobin Concentration and Its Change With Cardiovascular and All-Cause Mortality

Background

Anemia is thought to increase mortality risks, but the effects of high hemoglobin concentration on survival are unclear. The effect of change in hemoglobin concentrations on survival in the general population is also unknown. This study aimed to examine the effect of hemoglobin concentrations and their changes on cardiovascular and all‐cause mortality risks.

Methods and Results

We retrospectively analyzed a cohort from the NHIS‐HEALS (National Health Insurance Service–National Health Screening Cohort) database, including 170 078 men and 122 116 women without cardiovascular diseases, aged >40 years at baseline, with hemoglobin concentrations available for both first and second health examinations. We assessed 2 independent variables: “One‐time” hemoglobin concentrations and changes in hemoglobin from first to second examination. Participants were followed up for a median of 8 years to determine mortality related to myocardial infarction, stroke, all cardiovascular diseases, and all causes. Hemoglobin concentrations showed a U‐ or J‐shaped association with cardiovascular and all‐cause mortality after adjusting for cardiovascular risk factors. When anemic men achieved normal hemoglobin concentrations, the all‐cause mortality risk decreased, with an adjusted hazard ratio of 0.67 (95% confidence interval, 0.59–0.77), in comparison with those whose anemia persisted. Both increases and decreases of hemoglobin concentration outside the normal range elevated all‐cause mortality risk (adjusted hazard ratio: 1.39 [95% confidence interval, 1.28–1.49] and 1.10 [95% confidence interval, 1.01–1.20], respectively), compared with persistent normal hemoglobin concentrations. The trend was similar in women but was less significant.

Conclusions

Low or high hemoglobin concentrations were associated with elevated cardiovascular and all‐cause mortality. Reaching and maintaining hemoglobin concentrations within the normal range correlated with decreased all‐cause mortality.

Macrophage extracellular trap formation promoted by platelet activation is a key mediator of rhabdomyolysis-induced acute kidney injury

Rhabdomyolysis is a serious syndrome caused by skeletal muscle injury and the subsequent release of breakdown products from damaged muscle cells into systemic circulation. The muscle damage most often results from strenuous exercise, muscle hypoxia, medications, or drug abuse and can lead to life-threatening complications, such as acute kidney injury (AKI). Rhabdomyolysis and the AKI complication can also occur during crush syndrome, an emergency condition that commonly occurs in victims of natural disasters, such as earthquakes, and man-made disasters, such as wars and terrorism. Myoglobin released from damaged muscle is believed to trigger renal dysfunction in this form of AKI. Recently, macrophages were implicated in the disease pathogenesis of rhabdomyolysis-induced AKI, but the precise molecular mechanism remains unclear. In the present study, we show that macrophages released extracellular traps (ETs) comprising DNA fibers and granule proteins in a mouse model of rhabdomyolysis. Heme-activated platelets released from necrotic muscle cells during rhabdomyolysis enhanced the production of macrophage extracellular traps (METs) through increasing intracellular reactive oxygen species generation and histone citrullination. Here we report, for the first time to our knowledge, this unanticipated role for METs and platelets as a sensor of myoglobin-derived heme in rhabdomyolysis-induced AKI. This previously unknown mechanism might be targeted for treatment of the disease. Finally, we found a new therapeutic tool for prevention of AKI after rhabdomyolysis, which might rescue some sufferers of this pathology.

The role of iron in the pathogenesis of atherosclerosis

Ferritin and increased iron stores first appeared on the list of cardiovascular risk factors more than 30 years ago and their causal role in the pathogenesis of atherosclerosis has been heavily discussed since the early 1990s. It seems that besides traditional factors such as hyperlipoproteinemia, hypertension, diabetes mellitus, obesity, physical inactivity, smoking and family history, high iron stores represent an additional parameter that could modify individual cardiovascular risk. The role of iron in the pathogenesis of atherosclerosis was originally primarily associated with its ability to catalyze the formation of highly reactive free oxygen radicals and the oxidation of atherogenic lipoproteins. Later, it became clear that the mechanism is more complex. Atherosclerosis is a chronic fibroproliferative inflammatory process and iron, through increased oxidation stress as well as directly, can control both native and adaptive immune responses. Within the arterial wall, iron affects all of the cell types that participate in the atherosclerotic process (monocytes/macrophages, endothelial cells, vascular smooth muscle cells and platelets). Most intracellular iron is bound in ferritin, whereas redox-active iron forms labile iron pool. Pro-inflammatory and anti-inflammatory macrophages within arterial plaque differ with regard to the amount of intracellular iron and most probably with regard to their labile iron pool. Yet, the relation between plasma ferritin and intracellular labile iron pool has not been fully clarified. Data from population studies document that the consumption of meat and lack of physical activity contribute to increased iron stores. Patients with hereditary hemochromatosis, despite extreme iron storage, do not show increased manifestation of atherosclerosis probably due to the low expression of hepcidin in macrophages.

Iron and peripheral arterial disease: revisiting the iron hypothesis in a different light

The relationship between iron status and atherosclerosis has long been a topic of debate in the literature. Despite more than 25 years of research, there is no consensus regarding a causal relationship. To date, the vast majority of studies have focused on iron burden with respect to a hypothesized role in the onset and progression of coronary artery disease. However, the effect of iron in the coronary arterial system may differ mechanistically and therefore clinically from its effect in the peripheral arterial system. This review will summarize the biochemical, pathologic, animal, and clinical research data with respect to iron and atherosclerosis. This background will be expanded upon to provide insights into ongoing studies and paths for future investigations into the role of iron and peripheral arterial disease.

Hemoglobin Concentration and Risk of Incident Stroke in Community-Living Adults

BACKGROUND AND PURPOSE

In previous observational studies, hemoglobin concentrations have been associated with an increased risk of stroke. However, these studies were limited by a relatively low number of stroke events, making it difficult to determine whether the association of hemoglobin and stroke differed by demographic or clinical factors.

METHODS

Using Cox proportional hazards analysis and Kaplan-Meier plots, we examined the association of baseline hemoglobin concentrations with incident stroke in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a cohort of black and white adults aged ≥45 years.

RESULTS

A total of 518 participants developed stroke over a mean 7±2 years of follow-up. There was a statistically significant interaction between hemoglobin and sex (P=0.05) on the risk of incident stroke. In Cox regression models adjusted for demographic and clinical variables, there was no association of baseline hemoglobin concentration with incident stroke in men, whereas in women, the lowest (<12.4 g/dL) and highest (>14.0 g/dL) quartiles of hemoglobin were associated with higher risk of stroke when compared with the second quartile (12.4-13.2 g/dL; quartile 1: hazard ratio, 1.59; 95% confidence interval, 1.09-2.31; quartile 2: referent; quartile 3: hazard ratio, 0.91; 95% confidence interval, 0.59-1.38; quartile 4: hazard ratio, 1.59; 95% confidence interval, 1.08-2.35). Similar results were observed in models stratified by hemoglobin and sex and when hemoglobin was modeled as a continuous variable using restricted quadratic spline regression.

CONCLUSIONS

Lower and higher hemoglobin concentrations were associated with a higher risk of incident stroke in women. No such associations were found in men.

Accelerating degradation rate of pure iron by zinc ion implantation

Pure iron has been considered as a promising candidate for biodegradable implant applications. However, a faster degradation rate of pure iron is needed to meet the clinical requirement. In this work, metal vapor vacuum arc technology was adopted to implant zinc ions into the surface of pure iron. Results showed that the implantation depth of zinc ions was about 60 nm. The degradation rate of pure iron was found to be accelerated after zinc ion implantation. The cytotoxicity tests revealed that the implanted zinc ions brought a slight increase on cytotoxicity of the tested cells. In terms of hemocompatibility, the hemolysis of zinc ion implanted pure iron was lower than 2%. However, zinc ions might induce more adhered and activated platelets on the surface of pure iron. Overall, zinc ion implantation can be a feasible way to accelerate the degradation rate of pure iron for biodegradable applications.

Differential Roles of the NADPH-Oxidase 1 and 2 in Platelet Activation and Thrombosis

OBJECTIVE

Reactive oxygen species (ROS) are known to regulate platelet activation; however, the mechanisms of ROS production during platelet activation remain unclear. Platelets express different isoforms of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) oxidases (NOXs). Here, we investigated the role of NOX1 and NOX2 in ROS generation and platelet activation using NOX1 and NOX2 knockout mice.

APPROACH AND RESULTS

NOX1(-/Y) platelets showed selective defects in G-protein-coupled receptor-mediated platelet activation induced by thrombin and thromboxane A2 analog U46619, but were not affected in platelet activation induced by collagen-related peptide, a glycoprotein VI agonist. In contrast, NOX2(-/-) platelets showed potent inhibition of collagen-related peptide-induced platelet activation, and also showed partial inhibition of thrombin-induced platelet activation. Consistently, production of ROS was inhibited in NOX1(-/Y) platelets stimulated with thrombin, but not collagen-related peptide, whereas NOX2(-/-) platelets showed reduced ROS generation induced by collagen-related peptide or thrombin. Reduced ROS generation in NOX1/2-deficient platelets is associated with impaired activation of Syk and phospholipase Cγ2, but minimally affected mitogen-activated protein kinase pathways. Interestingly, laser-induced arterial thrombosis was impaired but the bleeding time was not affected in NOX2(-/-) mice. Wild-type thrombocytopenic mice injected with NOX2(-/-) platelets also showed defective arterial thrombosis, suggesting an important role for platelet NOX2 in thrombosis in vivo but not hemostasis.

CONCLUSIONS

NOX1 and NOX2 play differential roles in different platelet activation pathways and in thrombosis. ROS generated by these enzymes promotes platelet activation via the Syk/phospholipase Cγ2/calcium signaling pathway.

Atherosclerotic cardiovascular disease: a review of initiators and protective factors

Atherosclerotic cardiovascular disease (CVD) is a collective term comprising of a group of disorders of the heart and blood vessels. These diseases are the largest cause of morbidity and premature death worldwide. Coronary heart disease and cerebrovascular disease (stroke) are the most frequently occurring diseases. The two major initiators involved in the development of atherosclerotic CVD are vascular production of reactive oxygen species (ROS) and lipid oxidation. In atherosclerosis development, ROS is associated with rapid loss of anti-inflammatory and anti-atherogenic activities of the endothelium-derived nitric oxide (NO(·)) resulting in endothelial dysfunction. In part involving activation of the transcription factor NF-κB, ROS have been involved in signaling cascades leading to vascular pro-inflammatory and pro-thrombotic gene expression. ROS is also a potent activator of matrix metalloproteinases (MMPs), which indicate plaque destabilization and rupture. The second initiator involved in atherosclerotic CVD is the oxidation of low-density lipoproteins (LDL). Oxidation of LDL in vessel wall leads to an inflammatory cascade that activates atherogenic pathway leading to foam cell formation. The accumulation of foam cells leads to fatty streak formation, which is the earliest visible atherosclerotic lesion. In contrast, the cardiac sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2a) and hepatic apolipoprotein E (apoE) expression can improve cardiovascular function. SERCA2a regulates the cardiac contractile function by lowering cytoplasmic calcium levels during relaxation, and affecting NO(·) action in vascular cells, while apoE is a critical ligand in the plasma clearance of triglyceride- and cholesterol-rich lipoproteins.

Study on the interaction between Fe3+and fibrinogen and its influence on the polymerization behavior of fibrin networks

The interactions between fibrinogen molecule and Fe³⁺were studied and applied to explicate the polymerization behavior of fibrinogen mediated with Fe³⁺. Overloading Fe³⁺in the fibrinogen solution will accelerate the amorphous aggregation of fibrin.

The stability of blood fatty acids during storage and potential mechanisms of degradation: A review

Fatty acids in blood samples, particularly polyunsaturated fatty acids (PUFAs), are susceptible to degradation through peroxidation reactions during long-term storage. Storage of blood samples is necessary in almost all studies and is crucial for larger clinical studies and in field research settings where it is not plausible for analytical infrastructure. Despite this, PUFA stability during blood storage is often overlooked. This review introduces and discusses lipid peroxidation and popular strategies employed to prevent or minimize peroxidation reactions during fatty acid analysis. Further, an in-depth examination of fatty acid stability during storage of blood is discussed in detail for all blood fractions including plasma/serum, erythrocytes and whole blood stored both in cryovials and on chromatography paper before discussing the associated mechanisms of degradation during storage. To our knowledge this is the first review of its kind and will provide researchers with the necessary information to confidently store blood samples for fatty acid analysis.

Oxidative stress-related mechanisms affecting response to aspirin in diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a major cardiovascular risk factor. Persistent platelet activation plays a key role in atherothrombosis in T2DM. However, current antiplatelet treatments appear less effective in T2DM patients vs nondiabetics at similar risk. A large body of evidence supports the contention that oxidative stress, which characterizes DM, may be responsible, at least in part, for less-than-expected response to aspirin, with multiple mechanisms acting at several levels. This review discusses the pathophysiological mechanisms related to oxidative stress and contributing to suboptimal aspirin action or responsiveness. These include: (1) mechanisms counteracting the antiplatelet effect of aspirin, such as reduced platelet sensitivity to the antiaggregating effects of NO, due to high-glucose-mediated oxidative stress; (2) mechanisms interfering with COX acetylation especially at the platelet level, e.g., lipid hydroperoxide-dependent impaired acetylating effects of aspirin; (3) mechanisms favoring platelet priming (lipid hydroperoxides) or activation (F2-isoprostanes, acting as partial agonists of thromboxane receptor), or aldose-reductase pathway-mediated oxidative stress, leading to enhanced platelet thromboxane A2 generation or thromboxane receptor activation; (4) mechanisms favoring platelet recruitment, such as aspirin-induced platelet isoprostane formation; (5) modulation of megakaryocyte generation and thrombopoiesis by oxidative HO-1 inhibition; and (6) aspirin-iron interactions, eventually resulting in impaired pharmacological activity of aspirin, lipoperoxide burden, and enhanced generation of hydroxyl radicals capable of promoting protein kinase C activation and platelet aggregation. Acknowledgment of oxidative stress as a major contributor, not only of vascular complications, but also of suboptimal response to antiplatelet agents in T2DM, may open the way to designing and testing novel antithrombotic strategies, specifically targeting oxidative stress-mediated mechanisms of less-than-expected response to aspirin.

The role of Nox1 and Nox2 in GPVI-dependent platelet activation and thrombus formation

Background

Activation of the platelet-specific collagen receptor, glycoprotein (GP) VI, induces intracellular reactive oxygen species (ROS) production; however the relevance of ROS to GPVI-mediated platelet responses remains unclear.

Objective

The objective of this study was to explore the role of the ROS-producing NADPH oxidase (Nox)1 and 2 complexes in GPVI-dependent platelet activation and collagen-induced thrombus formation.

Methods and results

ROS production was measured by quantitating changes in the oxidation-sensitive dye, H₂DCF-DA, following platelet activation with the GPVI-specific agonist, collagen related peptide (CRP). Using a pharmacological inhibitor specific for Nox1, 2-acetylphenothiazine (ML171), and Nox2 deficient mice, we show that Nox1 is the key Nox homolog regulating GPVI-dependent ROS production. Nox1, but not Nox2, was essential for CRP-dependent thromboxane (Tx)A₂ production, which was mediated in part through p38 MAPK signaling; while neither Nox1 nor Nox2 was significantly involved in regulating CRP-induced platelet aggregation/integrin α_IIbβ₃ activation, platelet spreading, or dense granule and α-granule release (ATP release and P-selectin surface expression, respectively). Ex-vivo perfusion analysis of mouse whole blood revealed that both Nox1 and Nox2 were involved in collagen-mediated thrombus formation at arterial shear.

Conclusion

Together these results demonstrate a novel role for Nox1 in regulating GPVI-induced ROS production, which is essential for optimal p38 activation and subsequent TxA₂ production, providing an explanation for reduced thrombus formation following Nox1 inhibition.

•

Nox1, but not Nox2 mediates GPVI-induced ROS production.

•

GPVI-specific, CRP-activated platelet aggregation, spreading, secretion and α_IIbβ₃ activation is Nox1/2-independent.

•

GPVI-induced thromboxane A2 production is ROS-dependent, which is mediated by p38 signaling.

•

Collagen-induced ROS production and aggregation is Nox1-dependent.

•

Both Nox1 and Nox2 regulate collagen-induced thrombus formation at arterial shear.

Mechanisms of hemolysis-associated platelet activation

BACKGROUND

Intravascular hemolysis occurs after blood transfusion, in hemolytic anemias, and in other conditions, and is associated with hypercoagulable states. Hemolysis has been shown to potently activate platelets in vitro and in vivo, and several mechanisms have been suggested to account for this, including: (i) direct activation by hemoglobin (Hb); (ii) increase in reactive oxygen species (ROS); (iii) scavenging of nitric oxide (NO) by released Hb; and (iv) release of intraerythrocytic ADP.

OBJECTIVE

To elucidate the mechanism of hemolysis-mediated platelet activation.

METHODS

We used flow cytometry to detect PAC-1 binding to activated platelets for in vitro experiments, and a Siemens' Advia 120 hematology system to assess platelet aggregation by using platelet counts from in vivo experiments in a rodent model.

RESULTS

We found that Hb did not directly activate platelets. However, ADP bound to Hb could cause platelet activation. Furthermore, platelet activation caused by shearing of red blood cells (RBCs) was reduced in the presence of apyrase, which metabolizes ADP to AMP. The use of ROS scavengers did not affect platelet activation. We also found that cell-free Hb enhanced platelet activation by abrogating the inhibitory effect of NO on platelet activation. In vivo infusions of ADP and purified (ADP-free) Hb, as well as hemolysate, resulted in platelet aggregation, as shown by decreased platelet counts.

CONCLUSION

Two primary mechanisms account for RBC hemolysis-associated platelet activation: ADP release, which activates platelets; and cell-free Hb release, which enhances platelet activation by lowering NO bioavailability.

Iron, human growth, and the global epidemic of obesity

Iron is an essential nutrient utilized in almost every aspect of cell function and its availability has previously limited life. Those same properties which allow iron to function as a catalyst in the reactions of life also present a threat via generation of oxygen-based free radicals. Accordingly; life exists at the interface of iron-deficiency and iron-sufficiency. We propose that: (1) human life is no longer positioned at the limits of iron availability following several decades of fortification and supplementation and there is now an overabundance of the metal among individuals of many societies; (2) this increased iron availability exerts a positive effect on growth by targeting molecules critical in regulating the progression of the cell cycle; there is increased growth in humans provided greater amounts of this metal; and indices of obesity can positively correlate with body stores of iron; and (3) diseases of obesity reflect this over-abundance of iron. Testing potential associations between iron availability and both obesity and obesity-related diseases in populations will be difficult since fortification and supplementation is so extensively practiced.

Mannitol-adenine-phosphate: a novel solution for intraoperative blood salvage

BACKGROUND

Intraoperative blood salvage (IBS) procedures include washing with normal saline (NS), which may deplete red blood cell (RBC) nutrients. The mannitol-adenine-phosphate (MAP) solution, commonly used for RBC preservation, provides glycolytic substrates; therefore, MAP should be a better solution than NS in IBS. In this study, we determined whether using MAP could reduce washing-associated RBC damage and destruction.

STUDY DESIGN AND METHODS

Adenine nucleotide contents, RBC morphology, and plasma free hemoglobin (PF-Hb) level of RBCs treated with NS or MAP solution were compared under three conditions: (1) 4-hour preservation of fresh blood from healthy volunteers, (2) collection from the shed blood of patients, and 3) incubation of the collected shed blood with plasma.

RESULTS

Adenine nucleotide level and RBC elongation index were greater and PF-Hb level was lower in MAP groups than NS groups (p < 0.05) after preservation and incubation. In NS, RBCs lost their deformability and became stomatocytes, and even RBC "ghosts" 48 hours after incubation, while they remained normal in MAP solution.

CONCLUSION

The MAP solution helps preserve RBC morphology and function, and reduces hemolysis, possibly due to improved energy production. Therefore, MAP should replace NS during IBS.

Iron stores in regular blood donors in Lagos, Nigeria

Background

Apart from challenging the bone marrow to increase its red cell production, thereby producing more blood for the donor, regular blood donation has been shown to have several benefits, one of which is preventing accumulation of body iron which can cause free radical formation in the body. This study was carried out to assess body iron stores in regular blood donors.

Methods

A total of 52 regular (study) and 30 first-time (control) volunteer blood donors were studied prospectively. Twenty milliliters of venous blood was drawn from each subject, 5 mL of which was put into sodium ethylenediamine tetra-acetic acid specimen bottles for a full blood count, including red blood cell indices. The remaining sample was allowed to clot in a plain container, and the serum was then retrieved for serum ferritin, serum iron, and serum transferrin receptor measurement by enzyme-linked immunosorbent assay.

Results

Mean hemoglobin and packed cell volume in the study group (13.47 ± 2.36 g/dL and 42.00 ± 7.10, respectively, P = 0.303) were not significantly higher than in the control group (12.98 ± 1.30 g/dL and 39.76 ± 4.41, respectively, P = 0.119). Mean serum ferritin was 102.46 ± 80.26 ng/mL in the control group and 41.46 ± 40.33 ng/mL in the study group (P = 0.001). Mean serum ferritin for women in the study group (28.02 ± 25.00 ng/mL) was significantly lower than for women in the control group (56.35 ± 34.03 ng/mL, P = 0.014). Similarly, men in the study group had a lower mean serum ferritin (48.57 ± 45.17 ng/mL) than men in the control group (145.49 ± 87.74 ng/mL, P = 0.00). The mean serum transferrin receptor value was higher in the study group (1.56 ± 0.88 μg/mL) than in the control group (1.19 ± 0.38 μg/mL, P = 0.033).

Conclusion

These findings suggest that hemoglobin concentration, packed cell volume, and serum iron levels are not significantly affected by regular blood donation and that regular blood donors appear to have reduced iron stores compared with controls.

Seasonal influences on CAPs exposures: differential responses in platelet activation, serum cytokines and xenobiotic gene expression

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 μg/m(3) of CAPs in the winter and 21.7 μg/m3 CAPs in the summer, in a size range less than 2.5 μm for 6 h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.

Non transferrin bound iron: nature, manifestations and analytical approaches for estimation

Iron is an essential trace element and plays a number of vital roles in biological system. It also leads the chains of pathological actions if present in excess and/or present in free form. Major portion of iron in circulation is associated with transferrin, a classical iron transporter, which prevent the existence of free iron. The fraction of iron which is free of transferrin is known as "non transferrin bound iron". Along with the incidence in iron over loaded patient non transferrin bound iron has been indicated in patients without iron overload. It has been suggested as cause as well as consequence in a number of pathological conditions. The major organs influenced by iron toxicity are heart, pancreas, kidney, organs involved in hematopoiesis etc. The most commonly suggested way for iron mediated pathogenesis is through increased oxidative stress and their secondary effects. Generation of free oxygen radicals by iron has been well documented in Fenton chemistry and Haber-Weiss reaction. Non transferrin bound iron has obvious chance to generate the free reactive radicals as it is not been shielded by the protective carrier protein apo transferrin. The nature of non transferrin bound iron is not clear at present time but it is definitely a group of heterogenous iron forms free from transferrin and ferritin. A variety of analytical approaches like colorimetry, chromatography, fluorimetry etc. have been experimented in different research laboratories for estimation of non transferrin bound iron. However the universally accepted gold standard method which can be operated in pathological laboratories is still to be developed.

The evaluation of carotid intima-media thickness in children with beta-thalassaemia major

BACKGROUND

Cardiovascular complications and vascular changes are common in patients with beta-thalassaemia major. The aim of this study is to investigate the common carotid artery intima-media thickness in children.

METHODS

The study population was consisted of 33 thalassaemic children (22 boys and 11 girls, with a median age of 8 years) and 30 healthy children for control (12 girls and 18 boys, with a median age of 8 years) who were matched for age and gender. Common carotid artery intima-media thickness of the children was measured.

RESULTS

The patients' age at diagnosis ranged from 0.25 to 2 years, with a median of 0.6 months. Their disease duration ranged from 4 to 13.75 years, with a median of 6.5 years. The patients' median common carotid artery intima-media thickness was significantly higher than controls - that is, 0.87 versus 0.74, with a p-value less than 0.005. The mean common carotid artery intima-media thickness value was positively correlated with disease duration (r = 0.535), with a p-value less than 0.01 and ferritin level (r = 0.501), with a p-value less than 0.01.

CONCLUSION

Owing to the nature of the disease, patients with beta-thalassaemia major should be considered to have an increased risk of early vascular alteration and atherosclerosis. For this reason, common carotid artery intima-media thickness measurement can be recommended as a non-invasive and early diagnostic method.

Platelet function alterations and their relation to P-selectin (CD62P) expression in children with iron deficiency anemia

Iron deficiency anemia (IDA) may cause platelet aggregation dysfunction and this can be reversed by iron therapy. On the other hand, it has been reported that the platelet fractions carrying the platelet activation markers, CD62P and CD63, are increased in thalassemic patients and there is a significant correlation between the increased levels of soluble P-selectin and free iron in sickle cell disease. This study was performed to investigate the alterations of platelet functions and whether iron deficiency results in diminished expression of activation marker (P-selectin; CD62P) leading to platelet aggregation dysfunction in children with IDA. Hemoglobin, erythrocyte indices (mean erythrocyte volume and red blood cell distribution width), serum levels of iron, transferrin and ferritin, platelet aggregation tests (with ADP, collagen, and ristocetin), PFA-100 closure time, and CD62P expression were evaluated in fasting blood samples of 22 children with IDA and 20 children without anemia. CD62P expression was detected by flow cytometry in normal and 5 μmol/l ADP-activated platelets. Mean closure times were longer in the patient group than control. In platelet aggregation tests, mean values of maximum aggregation times by ristocetin, ADP, and collagen were also more prolonged in patient group. Ristocetin-induced maximum aggregation rates (amplitude) were significantly higher in patients. However, ADP and collagen induction did not produce the same effect. CD62P expressions were significantly higher on activated platelets of the patient group, although they were similar in both groups before activation by ADP. These findings suggest that platelet aggregation and adhesion have been delayed in children with IDA; however, platelet function abnormalities are not associated with CD62P expression on platelet surface.