A new method to determine tissue specific tissue factor thrombomodulin activities: endotoxin and particulate air pollution induced disbalance

Breath Biopsy Reveals Systemic Immunothrombosis and Its Resolution through Bioorthogonal Dendritic Nanoprobes

Immunothrombosis, an inflammation-dependent activation of the coagulation cascade, leads to microthrombi formations in small vessels. It is a dreaded complication of COVID-19 and a major cause of respiratory failure. Due to their size and disseminated nature, microthrombi are currently undetectable. Here, noninvasive detection of a volatile reporter in the exhaled air is introduced for assessment of systemic immunothrombosis. A dendritic nanoprobe, containing high loading of a thrombin-sensitive substrate, is selectively cleaved by thrombin, resulting in release of a synthetic bioorthogonal volatile organic compound (VOC). The VOC is quantitated in the exhaled air biopsies via gas chromatography-mass spectrometry (GC-MS), allowing near real-time assessment of systemic immunothrombosis. The VOC detection can be further improved with more rapid and sensitive MS-based technologies. The amount of the VOC in the exhaled air decreases with resolution of the microvascular inflammation and intravascular fibrin depositions. Through conjugation of the thrombin-sensitive peptide with a rhodol derivative, a novel thrombin-sensitive fluorescent nanoprobe is developed for intravital visualization of thrombin activity in actively growing thrombi. These results establish unprecedented detection of thrombin activity in vivo, addressing this unmet medical need. This novel approach facilitates diagnosis of immunothrombosis in diseases such as diabetic complications, disseminated intravascular coagulation, and COVID-19.

Effects of Particulate Matter on Inflammation and Thrombosis: Past Evidence for Future Prevention

Ambient air pollution has become a common problem worldwide. Exposure to pollutant particles causes many health conditions, having a particular impact on pulmonary and cardiovascular disease. Increased understanding of the pathological processes related to these conditions may facilitate the prevention of the adverse impact of air pollution on our physical health. Evidence from in vitro, in vivo, and clinical studies has consistently shown that exposure to particulate matter could induce the inflammatory responses such as IL-6, TNF-α, IL-1β, as well as enhancing the oxidative stress. These result in vascular injury, adhesion molecule release, platelet activation, and thrombin generation, ultimately leading to a prothrombotic state. In this review, evidence on the effects of particulate matter on inflammation, oxidative stress, adhesion molecules, and coagulation pathways in enhancing the risk of thrombosis is comprehensively summarized and discussed. The currently available outcomes of interventional studies at a cellular level and clinical reports are also presented and discussed.

[Inhibitory Effects of Dabigatran on Airway Inflammation Induced by Lipopolysaccharide in Mice]

Asthma and chronic obstructive pulmonary disease (COPD) are characterised by chronic inflammation in the lung that is associated with airway obstruction. Inhaled therapy with a combination of corticosteroid and a long-acting β₂-agonist is an effective anti-inflammatory medicine for asthma, but in patients with severe asthma and COPD fails to completely control these symptoms with current therapies. The inflammatory process in these diseases, which involves activation of the coagulation and fibrinolytic system in the lung, offers the opportunity for alternative anti-inflammatory therapies. In this study, we investigated the effects of anti-coagulants on lipopolysaccharide (LPS)-induced airway inflammation in mice. A/J mice were exposed to LPS, a bacterial endotoxin, intranasally and accumulation of inflammatory cells, TNF-α, C-X-C motif chemokine (CXCL) 1, and osteopontin in bronchoalveolar lavage fluid (BALF) was monitored by flow cytometry and an enzyme-linked immunosorbent assay. LPS exposure induced airway neutrophilia and accumulation of TNF-α, CXCL1, and osteopontin in BALF. This LPS-induced airway inflammation was not relieved using a corticosteroid, fluticasone propionate (FP), or a direct inhibitor of Factor Xa, rivaroxaban. In contrast, a direct thrombin inhibitor, dabigatran, inhibited LPS-induced airway neutrophilia and decreased inflammatory cytokine production in a dose dependent manner. Furthermore, combination of dabigatran and FP elicited stronger inhibition of LPS-induced airway inflammation. Therefore, these results suggest that dabigatran could be an effective new therapy for severe respiratory diseases.

Particulate matter phagocytosis induces tissue factor in differentiating macrophages

Airborne exposure to particulate matter with diameter < 10 mcM (PM10) has been linked to an increased risk of thromboembolic events, but the mechanisms are not completely understood. The aim of this study was to evaluate the effect of PM10 phagocytosis on the release of procoagulant molecules in human differentiating macrophages, and that of PM10 inhalation in an experimental model in rats. Human monocytes were separated from the peripheral blood by the lymphoprep method, differentiated in vitro and treated with standard PM10 or vehicle. Sprague-Dawley rats were instilled intratracheally with PM10 or vehicle alone. The outcome was expression of proinflammatory genes and of tissue factor (TF). In human differentiating macrophages, PM10 exposure upregulated inflammatory genes, but most consistently induced TF mRNA and protein levels, but not TF protein inhibitor, resulting in increased TF membrane expression and a procoagulant phenotype. Differentiation towards the anti-inflammatory M2 phenotype inhibited PM10 -mediated TF expression. TF induction required phagocytosis of PM10 , whereas phagocytosis of inert particles was less effective. PM10 phagocytosis was associated with a gene expression profile consistent with intracellular retention of iron, inducing oxidative stress. Both PM10 and iron activated the stress kinases ERK1/2 pathway, involved in the induction of TF expression. In rats, alveolar exposure to PM10 was associated with pulmonary recruitment of inflammatory cells and resulted in local, but not systemic, induction of TF expression, which was sufficient to increase circulating TF levels. In conclusion, TF induction by differentiating lung macrophages, activated following phagocytosis, contributes to the increased risk of thromboembolic complications associated with PM10 exposure.

Vascular and thrombogenic effects of pulmonary exposure to Libby amphibole

Exposure to Libby amphibole (LA) asbestos is associated with increased incidences of human autoimmune disease and mortality related to cardiovascular diseases. However, the systemic and vascular impacts are less well examined because of the dominance of pulmonary disease. It was postulated that regardless of the type of exposure scenario, LA exposure might produce systemic and vascular inflammogenic and thrombotic alterations in healthy and cardiovascular compromised rat models. Samples from three independent studies were examined. In the first study, male Wistar Kyoto (WKY), spontaneously hypertensive (SH), and SH heart failure (SHHF) rats were intratracheally instilled once with 0 (vehicle), 0.25, or 1 mg/rat of LA. In the second study, F344 rats were instilled with vehicle or LA at 0.5, 1.5, or 5 mg/rat. In the third study, F344 rats were instilled with the same mass concentrations of LA delivered by biweekly multiple instillations over 3 mo to simulate an episodic subchronic exposure. Complete blood count, platelet aggregation, serum cytokines, and biomarkers of systemic and aortic effects were examined. LA reduced adenosine diphosphate (ADP)-induced platelet aggregation and decreased circulating platelets in WKY (1 mg/rat) and F344 (5 mg/rat) at the 3-mo time point but did not do so in SH or SHHF rats. A decline in circulating lymphocytes with age appeared to be exacerbated by LA exposure in F344 rats but the differences were not significant. Aorta mRNA expression for biomarkers of oxidative stress (HO-1, LOX-1), inflammation (MIP-2), and thrombosis (tPA, PAI-1, vWf) were increased at baseline in SH and SHHF relative to WKY. LA exposure upregulated several of these biomarkers and also those involved in aortic contractility of WKY rats at 3 mo, suggesting thrombogenic, vasocontractile, and oxidative stress-mediated impairments. The aorta changes in F344 rats were less remarkable than changes noted in WKY following LA exposure. In conclusion, exposure to LA decreased circulating platelets and platelet coagulability while increasing the expression of oxidative stress, thrombosis, and vasoconstriction biomarkers in the aorta of healthy rats. These changes were similar to those noted at baseline in SH and SHHF rats, suggesting that LA-induced pulmonary injury might increase the risk of developing cardiovascular disease in healthy individuals.

Pulmonary and cardiovascular effects of traffic-related particulate matter: 4-week exposure of rats to roadside and diesel engine exhaust particles

Traffic-related particulate matter (PM) may play an important role in the development of adverse health effects, as documented extensively in acute toxicity studies. However, rather little is known about the impacts of prolonged exposure to PM. We hypothesized that long-term exposure to PM from traffic adversely affects the pulmonary and cardiovascular system through exacerbation of an inflammatory response. To examine this hypothesis, Fisher F344 rats, with a mild pulmonary inflammation at the onset of exposure, were exposed for 4 weeks, 5 days/week for 6 h a day to: (a) diluted diesel engine exhaust (PM(DEE)), or: (b) near roadside PM (PM(2.5)). Ultrafine particulates, which are largely present in diesel soot, may enter the systemic circulation and directly or indirectly trigger cardiovascular effects. Hence, we assessed the effects of traffic-related PM on pulmonary inflammation and activity of procoagulants, vascular function in arteries, and cytokine levels in the heart 24 h after termination of the exposures. No major adverse health effects of prolonged exposure to traffic-related PM were detected. However, some systemic effects due to PM(DEE) exposure occurred including decreased numbers of white blood cells and reduced von Willebrand factor protein in the circulation. In addition, lung tissue factor activity is reduced in conjunction with reduced lung tissue thrombin generation. To what extent these alterations contribute to thrombotic effects and vascular diseases remains to be established. In conclusion, prolonged exposure to traffic-related PM in healthy animals may not be detrimental due to various biological adaptive response mechanisms.

Factor XII activation is essential to sustain the procoagulant effects of particulate matter

BACKGROUND

Particulate matter (PM) is a key component of ambient air pollution and has been associated with an increased risk of thrombotic events and mortality. The underlying mechanisms remain unclear.

OBJECTIVES

 To study the mechanisms of PM-driven procoagulant activity in human plasma and to investigate mainly, the coagulation driven by ultrafine particles (UFPs; < 0.1 μm) in genetically modified mice.

METHODS

Thrombin generation in response to PM of different sizes was assessed in normal human platelet-poor plasma, as well as in plasmas deficient in the intrinsic pathway proteases factors XII (FXII) or XI (FXI). In addition, UFPs were intratracheally instilled in wild-type (WT) and FXII-deficient (FXII(-/-) ) mice and plasma thrombin generation was analyzed in plasma from treated mice at 4 and 20 h post-exposure.

RESULTS

In normal human plasma, thrombin generation was enhanced in the presence of PM, whereas PM-driven thrombin formation was completely abolished in FXII- and FXI-deficient plasma. UFPs induced a transient increase in tissue factor (TF)-driven thrombin formation at 4 h post-instillation in WT mice compared with saline instillation. Intratracheal instillation of UFPs resulted in a procoagulant response in WT mice plasma at 20 h, whereas it was entirely suppressed in FXII(-/-) mice.

CONCLUSIONS

 Overall, the data suggest that PM promotes its early procoagulant actions mostly through the TF-driven extrinsic pathway of coagulation, whereas PM-driven long lasting thrombogenic effects are predominantly mediated via formation of activated FXII. Hence, FXII-driven thrombin formation may be relevant to an enhanced thrombotic susceptibility upon chronic exposure to PM in humans.

The procoagulant effects of fine particulate matter in vivo

Inhalation of fine particulate matter (<2.5 μm; fine PM) has been shown to increase the risk for cardiovascular events. In this letter, we reappraise the role of tissue factor (TF) antigen and we also summarize changes in measured coagulation proteins in humans and rodents by other studies with fine PM. By considering all studies including ours, we conclude that monitoring the overall coagulation state by measuring capacity assays such as thrombin generation, and quantification of TF activity would be more suitable than determining single coagulation proteins (such as TF antigen) in order to better assess the systemic prothrombotic effects of fine PM.

The relationship of air pollution and surrogate markers of endothelial dysfunction in a population-based sample of children

Background

This study aimed to assess the relationship of air pollution and plasma surrogate markers of endothelial dysfunction in the pediatric age group.

Methods

This cross-sectional study was conducted in 2009-2010 among 125 participants aged 10-18 years. They were randomly selected from different areas of Isfahan city, the second large and air-polluted city in Iran. The association of air pollutants' levels with serum thrombomodulin (TM) and tissue factor (TF) was determined after adjustment for age, gender, anthropometric measures, dietary and physical activity habits.

Results

Data of 118 participants was complete and was analyzed. The mean age was 12.79 (2.35) years. The mean pollution standards index (PSI) value was at moderate level, the mean particular matter measuring up to 10 μm (PM₁₀) was more than twice the normal level. Multiple linear regression analysis showed that TF had significant relationship with all air pollutants except than carbon monoxide, and TM had significant inverse relationship with ozone. The odds ratio of elevated TF was significantly higher in the upper vs. the lowest quartiles of PM₁₀, ozone and PSI. The corresponding figures were in opposite direction for TM.

Conclusions

The relationship of air pollutants with endothelial dysfunction and pro-coagulant state can be an important factor in the development of atherosclerosis from early life. This finding should be confirmed in future longitudinal studies. Concerns about the harmful effects of air pollution on children's health should be considered a top priority for public health policy; it should be underscored in primordial and primary prevention of chronic diseases.