Increase in circulating ACE-positive endothelial microparticles during acute lung injury

Endothelium-Derived Extracellular Vesicles Expressing Intercellular Adhesion Molecules Reflect Endothelial Permeability and Sepsis Severity

BACKGROUND

Currently, clinical indicators for evaluating endothelial permeability in sepsis are unavailable. Endothelium-derived extracellular vesicles (EDEVs) are emerging as biomarkers of endothelial injury. Platelet endothelial cell adhesion molecule (PECAM) and vascular endothelial (VE)-cadherin are constitutively expressed endothelial intercellular adhesion molecules that regulate intercellular adhesion and permeability. Herein, we investigated the possible association between EDEVs expressing intercellular adhesion molecules (PECAM+ or VE-cadherin+ EDEVs) and endothelial permeability and sepsis severity.

METHODS

Human umbilical vein endothelial cells (HUVECs) were stimulated with tumor necrosis factor alpha (TNF-α) directly or after pretreatment with permeability-modifying reagents such as angiopoietin-1, prostacyclin, or vascular endothelial growth factor (VEGF) to alter TNF-α-induced endothelial hyperpermeability. Endothelial permeability was measured using the dextran assay or transendothelial electrical resistance. Additionally, a prospective cross-sectional observational study was conducted to analyze circulating EDEV levels in patients with sepsis. EDEVs were examined in HUVEC culture supernatants or patient plasma (nonsepsis, n = 30; sepsis, n = 30; septic shock, n = 42) using flow cytometry. The Wilcoxon rank-sum test was used for comparisons between 2 groups. Comparisons among 3 or more groups were performed using the Steel-Dwass test. Spearman's test was used for correlation analysis. Statistical significance was set at P < .05.

RESULTS

TNF-α stimulation of HUVECs significantly increased EDEV release and endothelial permeability. Pretreatment with angiopoietin-1 or prostacyclin suppressed the TNF-α-induced increase in endothelial permeability and inhibited the release of PECAM+ and VE-cadherin+ EDEVs. In contrast, pretreatment with VEGF increased TNF-α-induced endothelial permeability and the release of PECAM+ and VE-cadherin+ EDEVs. However, pretreatment with permeability-modifying reagents did not affect the release of EDEVs expressing inflammatory stimulus-inducible endothelial adhesion molecules such as E-selectin, intracellular adhesion molecule-1, or vascular cell adhesion molecule-1. The number of PECAM+ EDEVs on admission in the septic-shock group (232 [124, 590]/μL) was significantly higher (P = .043) than that in the sepsis group (138 [77,267]/μL), with an average treatment effect of 98/μL (95% confidence interval [CI], 2-270/μL), and the number of VE-cadherin+ EDEVs in the septic-shock group (173 [76,339]/μL) was also significantly higher (P = .004) than that in the sepsis group (81 [42,159]/μL), with an average treatment effect (ATE) of 79/μL (95% CI, 19-171/μL); these EDEV levels remained elevated until day 5.

CONCLUSIONS

EDEVs expressing intercellular adhesion molecules (PECAM+ or VE-cadherin+ EDEVs) may reflect increased endothelial permeability and could be valuable diagnostic and prognostic markers for sepsis.

Insight into endothelial cell-derived extracellular vesicles in cardiovascular disease: Molecular mechanisms and Clinical implications

The endothelium is crucial in regulating vascular function. Extracellular vesicles (EVs) serve as membranous structures released by cells to facilitate intercellular communication through the delivery of nucleic acids, lipids, and proteins to recipient cells in an paracrine or endocrine manner. Endothelial cell-derived EVs (EndoEVs) have been identified as both biomarkers and significant contributors to the occurrence and progression of cardiovascular disease (CVD). The impact of EndoEVs on CVD is complex and contingent upon the condition of donor cells, the molecular cargo within EVs, and the characteristics of recipient cells. Consequently, elucidating the underlying molecular mechanisms of EndoEVs is crucial for comprehending their contributions to CVD. Moreover, a thorough understanding of the composition and function of EndoEVs is imperative for their potential clinical utility. This review aims provide an up-to-date overview of EndoEVs in the context of physiology and pathophysiology, as well as to discuss their prospective clinical applications.

Endothelial extracellular vesicles induce acute lung injury via follistatin-like protein 1

Cardiopulmonary bypass has been speculated to elicit systemic inflammation to initiate acute lung injury (ALI), including acute respiratory distress syndrome (ARDS), in patients after cardiac surgery. We previously found that post-operative patients showed an increase in endothelial cell-derived extracellular vesicles (eEVs) with components of coagulation and acute inflammatory responses. However, the mechanism underlying the onset of ALI owing to the release of eEVs after cardiopulmonary bypass, remains unclear. Plasma plasminogen-activated inhibitor-1 (PAI-1) and eEV levels were measured in patients with cardiopulmonary bypass. Endothelial cells and mice (C57BL/6, Toll-like receptor 4 knockout (TLR4-/-) and inducible nitric oxide synthase knockout (iNOS-/-)) were challenged with eEVs isolated from PAI-1-stimulated endothelial cells. Plasma PAI-1 and eEVs were remarkably enhanced after cardiopulmonary bypass. Plasma PAI-1 elevation was positively correlated with the increase in eEVs. The increase in plasma PAI-1 and eEV levels was associated with post-operative ARDS. The eEVs derived from PAI-1-stimulated endothelial cells could recognize TLR4 to stimulate a downstream signaling cascade identified as the Janus kinase 2/3 (JAK2/3)-signal transducer and activator of transcription 3 (STAT3)-interferon regulatory factor 1 (IRF-1) pathway, along with iNOS induction, and cytokine/chemokine production in vascular endothelial cells and C57BL/6 mice, ultimately contributing to ALI. ALI could be attenuated by JAK2/3 or STAT3 inhibitors (AG490 or S3I-201, respectively), and was relieved in TLR4-/- and iNOS-/- mice. eEVs activate the TLR4/JAK3/STAT3/IRF-1 signaling pathway to induce ALI/ARDS by delivering follistatin-like protein 1 (FSTL1), and FSTL1 knockdown in eEVs alleviates eEV-induced ALI/ARDS. Our data thus demonstrate that cardiopulmonary bypass may increase plasma PAI-1 levels to induce FSTL1-enriched eEVs, which target the TLR4-mediated JAK2/3/STAT3/IRF-1 signaling cascade and form a positive feedback loop, leading to ALI/ARDS after cardiac surgery. Our findings provide new insight into the molecular mechanisms and therapeutic targets for ALI/ARDS after cardiac surgery.

The Proteome of Extracellular Vesicles Released from Pulmonary Microvascular Endothelium Reveals Impact of Oxygen Conditions on Biotrauma

The lung can experience different oxygen concentrations, low as in hypoxia, high as under supplemental oxygen therapy, or oscillating during intermittent hypoxia as in obstructive sleep apnea or intermittent hypoxia/hyperoxia due to cyclic atelectasis in the ventilated patient. This study aimed to characterize the oxygen-condition-specific protein composition of extracellular vesicles (EVs) released from human pulmonary microvascular endothelial cells in vitro to decipher their potential role in biotrauma using quantitative proteomics with bioinformatic evaluation, transmission electron microscopy, flow cytometry, and non-activated thromboelastometry (NATEM). The release of vesicles enriched in markers CD9/CD63/CD81 was enhanced under intermittent hypoxia, strong hyperoxia and intermittent hypoxia/hyperoxia. Particles with exposed phosphatidylserine were increased under intermittent hypoxia. A small portion of vesicles were tissue factor-positive, which was enhanced under intermittent hypoxia and intermittent hypoxia/hyperoxia. EVs from treatment with intermittent hypoxia induced a significant reduction of Clotting Time in NATEM analysis compared to EVs isolated after normoxic exposure, while after intermittent hypoxia/hyperoxia, tissue factor in EVs seems to be inactive. Gene set enrichment analysis of differentially expressed genes revealed that EVs from individual oxygen conditions potentially induce different biological processes such as an inflammatory response under strong hyperoxia and intermittent hypoxia/hyperoxia and enhancement of tumor invasiveness under intermittent hypoxia.

Endothelial-Related Biomarkers in Evaluation of Vascular Function During Progression of Sepsis After Severe Trauma: New Potential Diagnostic Tools in Sepsis

Purpose

This study aimed to investigate the changes in endothelial-related biomarkers and their relationship with the incidence and prognosis of patients with sepsis after severe trauma.

Methods

A total of 37 severe trauma patients admitted to our hospital from Jan. to Dec. 2020 were enrolled in our research. All enrolled patients were divided into the sepsis and the non-sepsis groups. Endothelial progenitor cells (EPCs), circulating endothelial cells (CECs), and endothelial microparticles (EMPs) were detected on admission time; 24-48 hours and 48-72 hours after admission respectively. Demographic data, Acute Physiology, Chronic Health Evaluation (APACHE) II, and Sequential Organ Failure Assessment (SOFA) score were calculated every 24 h of admission to assess the severity of organ dysfunction. Receiver operating characteristic (ROC) curves were drawn to compare the areas under the curve (AUC) of endothelial-related biomarkers for the diagnosis of sepsis.

Results

The incidence rate of sepsis was 45.95% in all patients. The SOFA score in the sepsis group was significantly higher than that in the non-sepsis group (2 points vs 0 points, P<0.01). The number of EPCs, CECs, and EMPs all rose quickly in the early phase after trauma. The number of EPCs was similar in both groups, but the number of CECs and EMPs in the Sepsis Group was much higher than in the non-Sepsis Group (all P<0.01). Logistic regression analysis showed that the occurrence of sepsis was closely related to the expression of 0-24h CECs and 0-24h EMPs. The AUC ROC for CECs in different time periods were 0.815, 0.877, and 0.882, respectively (all P<0.001). The AUC ROC for EMPs in 0-24h was 0.868 (P=0.005).

Conclusion

The expression of EMPs was higher in early severe trauma, and high levels of EMPs were significantly higher in patients with early sepsis and poor prognosis.

Potential of extracellular vesicles for early prediction of severity and potential risk stratification in critical inflammatory diseases

Some acute inflammatory diseases are often exacerbated during or after hospitalization, leading to some severe manifestations like systemic inflammatory response syndrome, multiple organ failure, and high mortality. Early clinical predictors of disease severity are urgently needed to optimize patient management for better prognosis. The existing clinical scoring system and laboratory tests cannot circumvent the problems of low sensitivity and limited specificity. Extracellular vesicles (EVs) are heterogeneous nanosecretory vesicles containing various biomolecules related to immune regulation, inflammation activation, and inflammation-related complications. This review provides an overview of EVs as inflammatory mediators, inflammatory signaling pathway regulators, promoters of inflammatory exacerbation, and markers of severity and prognosis. Currently, although relevant biomarkers are clinically available or are in the preclinical research stage, searching for new markers and detection methods is still warranted, as the problems of low sensitivity/specificity, cumbersome laboratory operation and high cost still plague clinicians. In-depth study of EVs might open a door in the search for novel predictors.

THE ROLES OF EXTRACELLULAR VESICLES IN SEPSIS AND SYSTEMIC INFLAMMATORY RESPONSE SYNDROME

ABSTRACT

Sepsis is a life-threatening organ dysfunction, caused by dysregulation of the host response to infection. To understand the underlying mechanisms of sepsis, the vast spectrum of extracellular vesicles (EVs) is gaining importance in this research field. A connection between EVs and sepsis was shown in 1998 in an endotoxemia pig model. Since then, the number of studies describing EVs as markers and mediators of sepsis increased steadily. Extracellular vesicles in sepsis could be friends and foes at the same time depending on their origin and cargo. On the one hand, transfer of EVs or outer membrane vesicles can induce sepsis or systemic inflammatory response syndrome with comparable efficiency as well-established methods, such as cecal ligation puncture or lipopolysaccharide injection. On the other hand, EVs could provide certain therapeutic effects, mediated via reduction of reactive oxygen species, inflammatory cytokines and chemokines, influence on macrophage polarization and apoptosis, as well as increase of anti-inflammatory cytokines. Moreover, EVs could be helpful in the diagnosis of sepsis. Extracellular vesicles of different cellular origin, such as leucocytes, macrophages, platelets, and granulocytes, have been suggested as potential sepsis biomarkers. They ensure the diagnosis of sepsis earlier than classical clinical inflammation markers, such as C-reactive protein, leucocytes, or IL-6. This review summarizes the three roles of EVs in sepsis-mediator/inducer, biomarker, and therapeutic tool.

Extracellular vesicles participate in the pathogenesis of sepsis

Sepsis is one of the leading causes of mortality worldwide and is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The early diagnosis and effective treatment of sepsis still face challenges due to its rapid progression, dynamic changes, and strong heterogeneity among different individuals. To develop novel strategies to control sepsis, a better understanding of the complex mechanisms of sepsis is vital. Extracellular vesicles (EVs) are membrane vesicles released from cells through different mechanisms. In the disease state, the number of EVs produced by activated or apoptotic cells and the cargoes they carry were altered. They regulated the function of local or distant host cells in autocrine or paracrine ways. Current studies have found that EVs are involved in the occurrence and development of sepsis through multiple pathways. In this review, we focus on changes in the cargoes of EVs in sepsis, the regulatory roles of EVs derived from host cells and bacteria, and how EVs are involved in multiple pathological processes and organ dysfunction in sepsis. Overall, EVs have great application prospects in sepsis, such as early diagnosis of sepsis, dynamic monitoring of disease, precise therapeutic targets, and prevention of sepsis as a vaccine platform.

Inflammatory indices obtained from routine blood tests show an inflammatory state associated with disease progression in engineered stone silicosis patients

Patients with silicosis caused by occupational exposure to engineered stone (ES) present a rapid progression from simple silicosis (SS) to progressive massive fibrosis (PMF). Patient classification follows international rules based on radiology and high-resolution computed tomography (HRCT), but limited studies, if any, have explored biomarkers from routine clinical tests that can be used as predictors of disease status. Our objective was thus to investigate circulating biomarker levels and systemic inflammatory indices in ES silicosis patients whose exposure to ES dust ended several years ago. Ninety-one adult men, ex-workers in the manufacturing of ES, 53 diagnosed with SS and 38 with PMF, and 22 healthy male volunteers (HC) as controls not exposed to ES dust, were recruited. The following circulating levels of biomarkers like lactate dehydrogenase (LDH), angiotensin-converting-enzyme (ACE), protein C reactive (PCR), rheumatoid factor, alkaline phosphatase and fibrinogen were obtained from clinical reports after being measured from blood samples. As biochemical markers, only LDH (HC = 262 ± 48.1; SS = 315.4 ± 65.4; PMF = 337.6 ± 79.3 U/L), ACE (HC = 43.1 ± 18.4; SS = 78.2 ± 27.2; PMF = 86.1 ± 23.7 U/L) and fibrinogen (HC = 182.3 ± 49.1; SS = 212.2 ± 43.5; PMF = 256 ± 77.3 U/L) levels showed a significant sequential increase, not been observed for the rest of biomarkers, in the HC → SS → PMF direction. Moreover, several systemic inflammation indices neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-lymphocyte ratio (PLR), systemic inflammation response index (SIRI), systemic immune-inflammation index (SII), aggregate index of systemic inflammation (AISI) derived from whole blood cell counts showed significant differences between the HC, SS and PMF groups. All these biomarkers were analyzed using receiver operating characteristic (ROC) curves, and the results provided moderately high sensitivity and specificity for discriminating between ES silicosis patient groups and healthy controls. Our study reveals that some inflammatory biomarkers, easily available from routine blood analysis, are present in ES silicosis patients even several years after cessation of exposure to ES silica dust and they could help to know the progression of the disease.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

Size Distribution of Microparticles: A New Parameter to Predict Acute Lung Injury After Cardiac Surgery With Cardiopulmonary Bypass

Background

Acute lung injury (ALI) is a common complication after cardiac surgery with cardiopulmonary bypass (CPB). No precise way, however, is currently available to predict its occurrence. We and others have demonstrated that microparticles (MPs) can induce ALI and were increased in patients with ALI. However, whether MPs can be used to predict ALI after cardiac surgery with CPB remains unknown.

Methods

In this prospective study, 103 patients undergoing cardiac surgery with CPB and 53 healthy subjects were enrolled. MPs were isolated from the plasma before, 12 h after, and 3 d after surgery. The size distributions of MPs were measured by the LitesizerTM 500 Particle Analyzer. The patients were divided into two subgroups (ALI and non-ALI) according to the diagnosis of ALI. Descriptive and correlational analyzes were conducted between the size distribution of MPs and clinical data.

Results

Compared to the non-ALI group, the size at peak and interquartile range (IQR) of MPs in patients with ALI were smaller, but the peak intensity of MPs is higher. Multivariate logistic regression analysis indicated that the size at peak of MPs at postoperative 12 h was an independent risk factor for ALI. The area under the curve (AUC) of peak diameter at postoperative 12 h was 0.803. The best cutoff value of peak diameter to diagnose ALI was 223.05 nm with a sensitivity of 88.0% and a negative predictive value of 94.5%. The AUC of IQR at postoperative 12 h was 0.717. The best cutoff value of IQR to diagnose ALI was 132.65 nm with a sensitivity of 88.0% and a negative predictive value of 92.5%. Combining these two parameters, the sensitivity reached 92% and the negative predictive value was 96%.

Conclusions

Our findings suggested that the size distribution of MPs could be a novel biomarker to predict and exclude ALI after cardiac surgery with CPB.

Lymphatic and Blood Endothelial Extracellular Vesicles: A Story Yet to Be Written

Extracellular vesicles (EVs), such as exosomes, microvesicles, and apoptotic bodies, are cell-derived, lipid bilayer-enclosed particles mediating intercellular communication and are therefore vital for transmitting a plethora of biological signals. The vascular endothelium substantially contributes to the circulating particulate secretome, targeting important signaling pathways that affect blood cells and regulate adaptation and plasticity of endothelial cells in a paracrine manner. Different molecular signatures and functional properties of endothelial cells reflect their heterogeneity among different vascular beds and drive current research to understand varying physiological and pathological effects of blood and lymphatic endothelial EVs. Endothelial EVs have been linked to the development and progression of various vascular diseases, thus having the potential to serve as biomarkers and clinical treatment targets. This review aims to provide a brief overview of the human vasculature, the biology of extracellular vesicles, and the current knowledge of endothelium-derived EVs, including their potential role as biomarkers in disease development.

Pulmonary perfusion imaging and delayed imaging to measure pulmonary capillary permeability in pulmonary contusion

PURPOSE

Explore the application value of pulmonary perfusion imaging and delayed imaging for evaluating pulmonary capillary permeability.

MATERIALS AND METHODS

After establishing a rat model of pulmonary contusion, changes in the metabolic index of technetium-99m macroaggregated albumin (99mTC-MAA) in the lungs of model rats were evaluated for two consecutive days. 99mTC-MAA metabolic indices of rat lungs with pulmonary contusion of varying severity (mild, moderate, and severe) were correlated with lung wet/dry weight ratio (W/D) and Evans blue extravasation. Finally, the method was validated in patients with pulmonary contusion and one healthy volunteer.

RESULTS

The 99mTC-MAA metabolic index was 23.56% ± 2.44% in healthy control (HC) rat lung, 8.56% ± 3.42% immediately after lung contusion (d0), 8.35% ± 3.20% after 1 day (d1), and 17.45% ± 6.44% after 2 days (d2); indices at d0 and d1 were significantly higher than those at HC (P < 0.05). The metabolic index of 99mTC-MAA in lung had significant negative correlations with W/D (r = -0.8025; P = 0.0092) and Evans blue extravasation (r = -0.9356; P = 0.0002). Metabolic and oxygenation indices of 99mTC-MAA exhibited a significant positive linear correlation in patients with pulmonary contusion (r = 0.8925; P = 0.0416).

CONCLUSION

Pulmonary perfusion and delayed imaging of 99mTC-MAA have potential value for evaluating pulmonary capillary permeability.

Procoagulant Microvesicles in COVID-19 Patients: Possible Modulators of Inflammation and Prothrombotic Tendency

Background

The hypercoagulability and thrombotic tendency in coronavirus disease 2019 (COVID-19) is multifactorial, driven mainly by inflammation, and endothelial dysfunction. Elevated levels of procoagulant microvesicles (MVs) and tissue factor–bearing microvesicles (TF-bearing MVs) have been observed in many diseases with thrombotic tendency. The current study aimed to measure the levels of procoagulant MVs and TF-bearing MVs in patients with COVID-19 and healthy controls and to correlate their levels with platelet counts, D-Dimer levels, and other proposed calculated inflammatory markers.

Materials and Methods

Forty ICU-admitted patients with COVID-19 and 37 healthy controls were recruited in the study. Levels of procoagulant MVs and TF-bearing MVs in the plasma of the study population were measured using enzyme linked immunosorbent assay.

Results

COVID-19 patients had significantly elevated levels of procoagulant MVs and TF-bearing MVs as compared with healthy controls (P<0.001). Procoagulant MVs significantly correlated with TF-bearing MVs, D-dimer levels, and platelet count, but not with calculated inflammatory markers (neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, and platelet/neutrophil ratio).

Conclusion

Elevated levels of procoagulant MVs and TF-bearing MVs in patients with COVID-19 are suggested to be (i) early potential markers to predict the severity of COVID-19 (ii) a novel circulatory biomarker to evaluate the procoagulant activity and severity of COVID-19.

Upregulation of leukocyte immunoglobulin-like receptor B4 on interstitial macrophages in COPD; their possible protective role against emphysema formation

Background

Leukocyte immunoglobulin-like receptor B4 (LILRB4) is one of the inhibitory receptors in various types of immune cells including macrophages. Previous reports suggested that LILRB4 could be involved in a negative feedback system to prevent excessive inflammatory responses. However, its role has been unclear in chronic obstructive pulmonary disease (COPD), in which macrophages play a crucial role in the pathogenesis. In this study, we aimed to examine the changes of LILRB4 on macrophages both in the lung specimens of COPD patients and the lungs of a mouse emphysema model. We then tried to compare the differences in both inflammation and emphysematous changes of the model between wild-type and LILRB4-deficient mice in order to elucidate the role of LILRB4 in the pathogenesis of COPD.

Methods

We prepared single-cell suspensions of resected lung specimens of never-smokers (n = 21), non-COPD smokers (n = 16), and COPD patients (n = 14). The identification of LILRB4-expressing cells and the level of LILRB4 expression were evaluated by flow cytometry. We analyzed the relationships between the LILRB4 expression and clinical characteristics including respiratory function. In the experiments using an elastase-induced mouse model of emphysema, we also analyzed the LILRB4 expression on lung macrophages. We compared inflammatory cell accumulation and emphysematous changes induced by elastase instillation between wild-type and LILRB4-deficient mice.

Results

The levels of surface expression of LILRB4 are relatively high on monocyte linage cells including macrophages in the human lungs. The percentage of LILRB4⁺ cells in lung interstitial macrophages was increased in COPD patients compared to non-COPD smokers (p = 0.018) and correlated with the severity of emphysematous lesions detected by CT scan (r_s = 0.559, p < 0.001), whereas the amount of smoking showed no correlation with LILRB4 expression. Increased LILRB4 on interstitial macrophages was also observed in elastase-treated mice (p = 0.008). LILRB4-deficient mice showed severer emphysematous lesions with increased MMP-12 expression in the model.

Conclusions

LILRB4 on interstitial macrophages was upregulated both in human COPD lungs and in a mouse model of emphysema. This upregulated LILRB4 may have a protective effect against emphysema formation, possibly through decreasing MMP-12 expression in the lungs.

COVID-19 Infection and Circulating Microparticles-Reviewing Evidence as Microthrombogenic Risk Factor for Cerebral Small Vessel Disease

Severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) due to novel coronavirus disease 2019 (COVID-19) has affected the global society in numerous unprecedented ways, with considerable morbidity and mortality. Both direct and indirect consequences from COVID-19 infection are recognized to give rise to cardio- and cerebrovascular complications. Despite current limited knowledge on COVID-19 pathogenesis, inflammation, endothelial dysfunction, and coagulopathy appear to play critical roles in COVID-19-associated cerebrovascular disease (CVD). One of the major subtypes of CVD is cerebral small vessel disease (CSVD) which represents a spectrum of pathological processes of various etiologies affecting the brain microcirculation that can trigger subsequent neuroinflammation and neurodegeneration. Prevalent with aging, CSVD is a recognized risk factor for stroke, vascular dementia, and Alzheimer's disease. In the background of COVID-19 infection, the heightened cellular activations from inflammations and oxidative stress may result in elevated levels of microthrombogenic extracellular-derived circulating microparticles (MPs). Consequently, MPs could act as pro-coagulant risk factor that may serve as microthrombi for the vulnerable microcirculation in the brain leading to CSVD manifestations. This review aims to appraise the accumulating body of evidence on the plausible impact of COVID-19 infection on the formation of microthrombogenic MPs that could lead to microthrombosis in CSVD manifestations, including occult CSVD which may last well beyond the pandemic era.

Microparticles in COVID-19 as a link between lung injury extension and thrombosis

Among the distinctive features of coronavirus disease 2019 (COVID-19), numerous reports have stressed the importance of vascular damage associated with coagulopathy onset [1]. Histological analysis of pulmonary vessels in patients with COVID-19 revealed severe endothelial injury associated with intracellular severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and disrupted endothelial cell membranes together with widespread thrombosis and occlusion of alveolar capillaries. Microparticles (MPs) shed by apoptotic/stimulated cells of various cellular lineages, including platelets, leukocytes, macrophages or endothelial cells, are reliable markers of vascular damage [2] released upon pro-inflammatory conditions and behave as active participants in the early steps of clot formation [3]. Circulating MPs promote procoagulant responses due to the exposure of tissue factor, the physiological activator of the coagulation cascade, and of negatively charged phospholipids, such as phosphatidylserine, required for the assembly of the tenase and prothrombinase coagulation complexes ultimately leading to thrombin generation, through which they can precisely be quantified [4]. MPs carry angiotensin-converting enzyme (ACE)1 and upregulate ACE1 expression in neighbouring endothelial cells [5]. By contrast, exosomes were recently reported to convey ACE2, the cell-entry receptor for SARS-CoV-2 [4], in the vasculature [6]. ACE2 converts angiotensin II (Ang II) into angiotensin 1–7 (Ang 1–7), which by virtue of its actions on the Mas receptor, limits the noxious effects of Ang II. Pioneering data have demonstrated that the renin–angiotensin system has a crucial role in severe acute injury and that ACE2 has a protective role in acute lung injury mediated by SARS-CoV [7]. According to this paradigm, the loss of ACE2 function following binding by SARS-CoV-2 may contribute to unopposed Ang II accumulation that further exacerbates tissue injury and promotes inflammation, MPs release and thrombosis. During SARS-CoV-2 infection, we hypothesised that various factors including inflammatory burden, Ang II, altered shear stress and hypoxic vasoconstriction, could enhance MPs shedding by various cell lineages including the alveolar vascular endothelium and contribute to clot formation.

Procoagulant microparticles are associated with the extent of lung injuries in #COVID19 and pulmonary thrombosishttps://bit.ly/3eX2LPc

Extracellular Vesicles and Citrullinated Histone H3 in Coronavirus Disease 2019 Patients

OBJECTIVES

 Pulmonary thrombus formation is a hallmark of coronavirus disease 2019 (COVID-19). A dysregulated immune response culminating in thromboinflammation has been described, but the pathomechanisms remain unclear.

METHODS

 We studied 41 adult COVID-19 patients with positive results on reverse-transcriptase polymerase-chain-reaction assays and 37 sex- and age-matched healthy controls. Number and surface characteristics of extracellular vesicles (EVs) and citrullinated histone H3 levels were determined in plasma upon inclusion by flow cytometry and immunoassay.

RESULTS

 In total, 20 patients had severe and 21 nonsevere disease. The number of EV (median [25th, 75th percentile]) was significantly higher in patients compared with controls (658.8 [353.2, 876.6] vs. 435.5 [332.5, 585.3], geometric mean ratio [95% confidence intervals]: 2.6 [1.9, 3.6]; p < 0.001). Patients exhibited significantly higher numbers of EVs derived from platelets, endothelial cells, leukocytes, or neutrophils than controls. EVs from alveolar-macrophages and alveolar-epithelial cells were detectable in plasma and were significantly higher in patients. Intercellular adhesion molecule-1-positive EV levels were higher in patients, while no difference between tissue factor-positive and angiotensin-converting enzyme-positive EV was seen between both groups. Levels of EV did not differ between patients with severe and nonsevere COVID-19. Citrullinated histone H3 levels (ng/mL, median [25th, 75th percentile]) were higher in patients than in controls (1.42 [0.6, 3.4] vs. 0.31 [0.1, 0.6], geometric mean ratio: 4.44 [2.6, 7.7]; p < 0.001), and were significantly lower in patients with nonsevere disease compared with those with severe disease.

CONCLUSION

 EV and citrullinated histone H3 are associated with COVID-19 and could provide information regarding pathophysiology of the disease.

Extracellular vesicles: Their emerging roles in the pathogenesis of respiratory diseases

Alveoli are the basic structure of the lungs, consisting of various types of parenchymal and bone marrow-derived cells including alveolar macrophages. These various types of cells have several important functions; thus, communication between these cells plays an important role in homeostasis as well as in the pathophysiology of diseases in the lungs. For a better understanding of the pathophysiology of lung diseases, researchers have isolated each type of lung cell to investigate the changes in their gene expressions, including their humoral factor or adhesion molecules, to reveal the intercellular communication among these cells. In particular, investigations during the past decade have focused on extracellular vesicles, which are lipid bilayer delimited vesicles released from a cell that can move among various cells and transfer substances, including microRNAs, mRNAs and proteins, thus, functioning as intercellular messengers. Extracellular vesicles can be classified into three general groups: apoptotic bodies, exosomes, and microparticles. Extracellular vesicles, especially exosomes and microparticles, are attracting increasing attention from pulmonologists as tools for understanding pathogenesis and disease diagnosis. Here, we review studies, including our own, on exosomes and microparticles and their roles in both lung homeostasis and the pathogenesis of lung diseases such as idiopathic pulmonary fibrosis, chronic obstructive lung diseases, and acute respiratory distress syndrome. This review also addresses the roles of extracellular vesicles in COVID-19, the current global public health crisis.

Intercellular Communication by Vascular Endothelial Cell-Derived Extracellular Vesicles and Their MicroRNAs in Respiratory Diseases

Respiratory diseases and their comorbidities, such as cardiovascular disease and muscle atrophy, have been increasing in the world. Extracellular vesicles (EVs), which include exosomes and microvesicles, are released from almost all cell types and play crucial roles in intercellular communication, both in the regulation of homeostasis and the pathogenesis of various diseases. Exosomes are of endosomal origin and range in size from 50 to 150 nm in diameter, while microvesicles are generated by the direct outward budding of the plasma membrane in size ranges of 100-2,000 nm in diameter. EVs can contain various proteins, metabolites, and nucleic acids, such as mRNA, non-coding RNA species, and DNA fragments. In addition, these nucleic acids in EVs can be functional in recipient cells through EV cargo. The endothelium is a distributed organ of considerable biological importance, and disrupted endothelial function is involved in the pathogenesis of respiratory diseases such as chronic obstructive pulmonary disease, pulmonary hypertension, and acute respiratory distress syndrome. Endothelial cell-derived EVs (EC-EVs) play crucial roles in both physiological and pathological conditions by traveling to distant sites through systemic circulation. This review summarizes the pathological roles of vascular microRNAs contained in EC-EVs in respiratory diseases, mainly focusing on chronic obstructive pulmonary disease, pulmonary hypertension, and acute respiratory distress syndrome. Furthermore, this review discusses the potential clinical usefulness of EC-EVs as therapeutic agents in respiratory diseases.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

COVID-19-driven endothelial damage: complement, HIF-1, and ABL2 are potential pathways of damage and targets for cure

COVID-19 pandemia is a major health emergency causing hundreds of deaths worldwide. The high reported morbidity has been related to hypoxia and inflammation leading to endothelial dysfunction and aberrant coagulation in small and large vessels. This review addresses some of the pathways leading to endothelial derangement, such as complement, HIF-1α, and ABL tyrosine kinases. This review also highlights potential targets for prevention and therapy of COVID-19-related organ damage and discusses the role of marketed drugs, such as eculizumab and imatinib, as suitable candidates for clinical trials.

COVID-19 Related Coagulopathy: A Distinct Entity?

The coronavirus disease 2019 (COVID-19) pandemic has impacted healthcare communities across the globe on an unprecedented scale. Patients have had diverse clinical outcomes, but those developing COVID-19-related coagulopathy have shown a disproportionately worse outcome. This narrative review summarizes current evidence regarding the epidemiology, clinical features, known and presumed pathophysiology-based models, and treatment guidance regarding COVID-19 coagulopathy.