Fibrin clot structure is affected by levels of particulate air pollution exposure in patients with venous thrombosis

Air pollution and venous thromboembolism: current knowledge and future perspectives

Air pollution, comprising a variable mixture of gaseous and solid particulate material, represents a serious, unmet, global health issue. The Global Burden of Disease study reported that 12% of all deaths occurring in 2019 were related to ambient air pollution, with particulate matter often considered to be the leading cause of harm. As of 2024, over 90% of the world's population are exposed to excessive amounts of particulate matter, based on WHO maximum exposure level guidelines. A substantial body of evidence supports a link between air pollution and cardiovascular disease, with around half of ambient pollution-related deaths thought to be secondary to cardiovascular causes. A possible association between particulate matter and venous thromboembolism has been less clear, but in the past decade, several studies have added to the available literature. In this Review, we discuss the current epidemiological evidence linking air pollution to the development of venous thrombotic events. We consider mechanisms promoting a thromboinflammatory phenotype in these individuals, including platelet dysfunction, dysregulated fibrinolysis, and enhanced thrombin generation. Given the relevance to global health, we also discuss possible strategies required to mitigate the impact of air pollution on human health worldwide.

How Dendrimers Impact Fibrin Clot Formation, Structure, and Properties

Polyamidoamine (PAMAM) dendrimers, with their unique structural versatility and tunable surface functionalities, have emerged as promising nanomaterials for a wide range of biomedical applications. However, their in vivo use raises concerns, as unintended interactions between dendrimers and blood components could disrupt the delicate hemostatic balance and lead to serious complications like bleeding or thrombosis. In this study, we explored the impact of low-generation PAMAM dendrimers on the kinetics of fibrin clot formation, along with their influence on the structure, properties, and resistance to lysis of the resulting clots. For this purpose, we employed a multilevel characterization approach using purified fibrinogen, human plasma, and whole blood to assess the effects of four dendrimer types: G2-NH2, G4-NH2, G3.5-COOH, and G4-OH. Among the main findings, both G2-NH2 and G4-NH2 significantly impaired thrombin generation and delayed clot formation, with G4-NH2 also promoting fibrin aggregation, increasing clot permeability, and accelerating clot lysis. When present at high concentrations, G4-OH also affected critical clotting parameters, delaying thrombin generation and prolonging clotting time. Notably, the prolongation of clotting time by G4-OH was evident in both human plasma and whole blood. Interestingly, G3.5-COOH showed potential as a safer option since it induced minimal alterations across most tested metrics. These results will be important for guiding the rational design of dendrimers and identifying safe concentrations for future clinical applications.

Diesel exhaust particles exposure exacerbates pro-thrombogenic plasma features ex-vivo after cerebral ischemia and accelerates tPA-induced clot-lysis in hypertensive subjects

The combustion of fossil fuels, mainly by diesel engines, generates Diesel Exhaust Particles (DEP) which are the main source of Particulate Matter (PM), a major air pollutant in urban areas. These particles are a risk factor for stroke with 5.6% of cases attributed to PM exposure. Our aim was to evaluate the effect of DEP exposure on clot formation and lysis in the context of stroke. An ex-vivo clot formation and lysis turbidimetric assay has been conducted in human and mouse plasma samples from ischemic stroke or control subjects exposed to DEP or control conditions. Experimental DEP exposure was achieved by nasal instillation in mice, or by ex-vivo exposure in human plasma. Results show consistent pro-thrombogenic features in plasma after human ischemic stroke and mouse cerebral ischemia (distal MCAo), boosted by the presence of DEP. Otherwise, thrombolysis times were increased after ischemia in chronically exposed mice but not in the DEP exposed group. Finally, subjects living in areas with high PM levels presented accelerated thrombolysis compared to those living in low polluted areas. Overall, our results point at a disbalance of the thrombogenic/lytic system in presence of DEP which could impact on ischemic stroke onset, clot size and thrombolytic treatment.

Exploring the Microbial Community Structure in the Chicken House Environment by Metagenomic Analysis

The environmental conditions of chicken houses play an important role in the growth and development of these animals. The chicken house is an essential place for the formation of microbial aerosols. Microbial aerosol pollution and transmission can affect human and animal health. In this work, we continuously monitored fine particulate matter (PM2.5) in the chicken house environment for four weeks and studied the microbial community structure in the aerosols of the chicken house environment through metagenomic sequencing. Our results found that bacteria, fungi, viruses, and archaea were the main components of PM2.5 in the chicken house environment, accounting for 89.80%, 1.08%, 2.06%, and 0.49%, respectively. Conditional pathogens are a type of bacteria that poses significant harm to animals themselves and to farm workers. We screened ten common conditional pathogens and found that Staphylococcus had the highest relative abundance, while Clostridium contained the most microbial species, up to 456. Basidiomycetes and Ascomycota in fungi showed dramatic changes in relative abundance, and other indexes showed no significant difference. Virulence factors (VF) are also a class of molecules produced by pathogenic microbes that can cause host diseases. The top five virulence factors were found in four groups: FbpABC, HitABC, colibactin, acinetobactin, and capsule, many of which are used for the iron uptake system. In the PM2.5 samples, eight avian viruses were the most significant discoveries, namely Fowl aviadovirus E, Fowl aviadovirus D, Avian leukosis virus, Avian endogenous retrovirus EAV-HP, Avian dependent parvovirus 1, Fowl adenovus, Fowl aviadovirus B, and Avian sarcoma virus. The above results significantly improve our understanding of the microbial composition of PM2.5 in chicken houses, filling a gap on virus composition; they also indicate a potential threat to poultry and to human health. This work provides an important theoretical basis for animal house environmental monitoring and protection.

PM2.5 induces alterations in gene expression profile of platelet-derived extracellular vesicles and mediates cardiovascular injury in rats

Platelet-derived extracellular vesicles (P-EVs), as the most abundant vesicles in blood, have been proven to play cardinal roles in cardiovascular injury. RNAs (especially miRNAs) carried by P-EVs can be transferred to the receptor, which plays a critical role in regulating vascular endothelial function. PM2.5 is one of the most well-known risk factors that cause cardiovascular disease. Therefore, the objective of the current study was to explore whether exposure to PM2.5 would alter the gene expression profile of P-EVs, and to further elucidate the role of RNAs (especially miRNAs) carried by P-EVs in cardiovascular injury induced by PM2.5 exposure. P-EVs were isolated from the platelet-rich plasma which was exposed and unexposed to PM2.5, and the differentially expressed target genes were evaluated using whole-transcriptome gene sequencing. Rats were treated with P-EVs under different exposure conditions (a protein concentration of 50 µg/mL) and an equal volume of normal saline. The pathological damage of the thoracic aorta and cardiac tissue was evaluated and the coagulation function of the rats was detected. The differentially expressed genes were shown to be mainly concentrated in inflammation, angiogenesis, and apoptosis-related pathways. Moreover, P-EVs extracted from PM2.5-exposed plasma had the potential to trigger an inflammatory response, impair vascular endothelial function, disrupt the normal coagulation process, and promote a prothrombotic state. Our study indicated that PM2.5 induces cardiovascular injury in rats by interfering with the gene expression of P-EVs. It will provide new targets for studying the mechanism involved in PM2.5-induced cardiovascular injury.

Effects of air pollution on human health - Mechanistic evidence suggested by in vitro and in vivo modelling

Airborne particulate matter (PM) comprises both solid and liquid particles, including carbon, sulphates, nitrate, and toxic heavy metals, which can induce oxidative stress and inflammation after inhalation. These changes occur both in the lung and systemically, due to the ability of the small-sized PM (i.e. diameters ≤2.5 μm, PM_2.5) to enter and circulate in the bloodstream. As such, in 2016, airborne PM caused ∼4.2 million premature deaths worldwide. Acute exposure to high levels of airborne PM (eg. during wildfires) can exacerbate pre-existing illnesses leading to hospitalisation, such as in those with asthma and coronary heart disease. Prolonged exposure to PM can increase the risk of non-communicable chronic diseases affecting the brain, lung, heart, liver, and kidney, although the latter is less well studied. Given the breadth of potential disease, it is critical to understand the mechanisms underlying airborne PM exposure-induced disorders. Establishing aetiology in humans is difficult, therefore, in-vitro and in-vivo studies can provide mechanistic insights. We describe acute health effects (e.g. exacerbations of asthma) and long term health effects such as the induction of chronic inflammatory lung disease, and effects outside the lung (e.g. liver and renal change). We will focus on oxidative stress and inflammation as this is the common mechanism of PM-induced disease, which may be used to develop effective treatments to mitigate the adverse health effect of PM exposure.

Reducing particulates in indoor air can improve the circulation and cardiorespiratory health of old people: A randomized, double-blind crossover trial of air filtration

Exposure to indoor air particulate pollution increases respiratory and cardiovascular morbidity and mortality, especially in the elderly. To assess a short-term, indoor air filtration's potential benefit on circulatory and cardiopulmonary health among healthy older people, a randomized, double-blind crossover trial was conducted with 24 healthy residents of an aged-care center in Chongqing, China in 2020. Each room received a high-efficiency particulate air filter air purifier and a placebo air purifier for two days. Fifteen circulatory system biomarkers of inflammation, coagulation, and oxidative stress; lung function; blood pressure (BP); heart rate (HR) and fractional exhaled nitric oxide (FeNO) were measured end of each two days. Indoor air particulate pollution was monitored throughout the study period. Linear mixed-effect models were used to associate health outcome variables with indoor particles. This intervention study demonstrated that air filtration was associated with significantly decreased concentrations of inflammatory and coagulation biomarkers, but not of biomarkers of oxidative stress and lung function. Just 48 h of air filtration can improve the cardiopulmonary health of the elderly. Air purifiers may be a public health measure that can be taken to improve circulatory and cardiopulmonary health among older people.

Engineering of magnetic nanoparticles as magnetic particle imaging tracers

Magnetic particle imaging (MPI) has recently emerged as a promising non-invasive imaging technique because of its signal linearly propotional to the tracer mass, ability to generate positive contrast, low tissue background, unlimited tissue penetration depth, and lack of ionizing radiation. The sensitivity and resolution of MPI are highly dependent on the properties of magnetic nanoparticles (MNPs), and extensive research efforts have been focused on the design and synthesis of tracers. This review examines parameters that dictate the performance of MNPs, including size, shape, composition, surface property, crystallinity, the surrounding environment, and aggregation state to provide guidance for engineering MPI tracers with better performance. Finally, we discuss applications of MPI imaging and its challenges and perspectives in clinical translation.

The contribution of PM2.5 to cardiovascular disease in China

China is experiencing rapid urbanization and industrialization with correspondingly high levels of air pollution. Although the harm of PM2.5 has been long reported, it is only quite recently that there is increasing concern in China for its possible adverse health effects on cardiovascular disease. We reviewed the epidemiologic evidence of potential health effects of PM2.5 on cardiovascular disease reported from recent studies in China (2013 onwards). There is clear evidence for the contribution of PM2.5 to cardiovascular outcomes, including mortality, ischemic heart disease, and stroke from studies based in various regions in China. This evidence adds to the global evidence that PM2.5 contributes to adverse cardiovascular health risk and highlights the need for improved air quality in China.

Dense and dangerous: The tissue plasminogen activator-resistant fibrinolysis shutdown phenotype is due to abnormal fibrin polymerization

BACKGROUND

Both hyperfibrinolysis and fibrinolysis shutdown can occur after severe trauma. The subgroup of trauma patients with fibrinolysis shutdown resistant to tissue plasminogen activator (t-PA)-mediated fibrinolysis have increased mortality. Fibrin polymerization and structure may influence fibrinolysis subgroups in trauma, but fibrin architecture has not been characterized in acutely injured subjects. We hypothesized that fibrin polymerization measured in situ will correlate with fibrinolysis subgroups.

METHODS

Blood samples were collected from trauma patients and noninjured controls. We selected samples across a range of fibrinolysis phenotypes (shutdown, physiologic, hyperfibrinolysis) and t-PA sensitivities (sensitive, physiologic, resistant) determined by thrombelastography. Plasma clots were created in situ with fluorescent fibrinogen and imaged using confocal microscopy for analysis of clot architecture in three dimensions. For each clot, we quantified the fiber resolvability, a metric of fiber distinctness or clarity, by mapping the variance of fluorescence intensity relative to background fluorescence. We also determined clot porosity by measuring the size and distribution of the gaps between fibrin fibers in three-dimensional space. We compared these measures across fibrinolysis subgroups.

RESULTS

Fiber resolvability was significantly lower in all trauma subgroups compared with controls (n = 35 and 5, respectively; p < 0.05). We observed markedly different patterns of fibrin architecture among trauma patients stratified by fibrinolysis subgroup. Subjects with t-PA-resistant fibrinolysis shutdown exhibited abnormal, densely packed fibrin clots nearly devoid of pores. Individuals with t-PA-hypersensitive fibrinolysis shutdown had highly irregular clots with pores as large as 2500 μm to 20,000 μm, versus 78 μm to 1250 μm in noninjured controls.

CONCLUSION

Fiber resolvability was significantly lower in trauma patients than controls, and subgroups of fibrinolysis differ in the porosity of the fibrin clot structure. The dense fibrin network in the t-PA-resistant group may prevent access to plasmin, suggesting a mechanism for thrombotic morbidity after injury.

Correlation between short-term air pollution exposure and unprovoked lung embolism. Prospective observational (Contamina-TEP Group)

BACKGROUND

The aim was to analyze the temporal relationship between short-term air pollution exposure and acute symptomatic unprovoked pulmonary embolism (PE).

PATIENTS/METHODS

We performed a prospective, multicenter study in consecutive patients diagnosed with acute symptomatic unprovoked PE from February 2012 to January 2013. We analyzed demographic and clinical data, patients' addresses, meteorological and air pollutants data (PM₁₀, SO₂, CO, NO₂, ozone emission data). We considered the number of days the patient had symptoms, and the study period constituted the previous 30 days. Likewise, the mean annual data of the reference season were calculated as well as the data of the 30-day study period corresponding to the same dates in the previous 3 years in order to obtain the monthly mean of the different pollutants for each period.

RESULTS

A total of 162 patients with acute symptomatic PE were recruited (43.2% unprovoked PE). The air pollutants could be determined in 50% of the patients with unprovoked PE, and a final analysis was performed in 35 patients. In the multiple comparison analysis to verify a possible correlation between the study period and the annual median, only NO₂ showed a statistically significant association (p = 0.009). When comparing the study period with the previous 3 years, only NO₂ maintained a statistically significant association for the 3 study periods.

CONCLUSIONS

We found a relationship between short-term exposure to NO₂ and the presence of unprovoked PE.

Effect of particulate matter-bound metals exposure on prothrombotic biomarkers: A systematic review

Environmental pollution is an important modifiable determinant for preventing cardiovascular diseases. Acute exposure to air pollution is linked to severe adverse cardiovascular events, including venous thromboembolism risk. The adverse health effects seem to arise from blood-borne metals and transition metal components from exposure to particulate matter that, when breathed, passes through the lungs into the heart and the blood stream. Pollution affects health via mechanisms including oxidative stress and inflammation, and metals may have a detrimental effect on both the blood cells, particularly platelets, and circulation. Some evidences demonstrates atherotrombotic consequences of acute and chronic exposure to air pollution, but few studies have examined exposure effects on the prothrombotic biomarkers leading to venous thromboembolism. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology, we performed a systematic review (14 papers) of the past twelve years, focusing on the relationship between inhalable airborne metal exposures and coagulative biomarker disorders leading to lower limb venous thromboembolisms, e.g., deep vein thrombosis. Results support the hypothesis that exposure to inhalable metals, as elemental compounds in particulate matter, cause changes or activation of a number of human prothrombotic hemostatic biomarkers.

Improving fibrinolysis in venous thromboembolism: impact of fibrin structure

Introduction. Fibrinolysis is of key importance in maintaining vessel patency. Impaired fibrinolysis associated with more compact fibrin structure has been shown in patients with venous thromboembolism (VTE), including deep-vein thrombosis and pulmonary embolism (PE). Currently, recombinant or modified plasminogen activators are the only commonly available thrombolytic agents. However, they are fraught with side effects and suboptimal effectiveness. Areas covered. Based on the available literature, the current evidence linking fibrinolysis with VTE and potential therapeutic targets among fibrinolysis proteins are presented. Expert opinion. Prolonged clot lysis time has been reported as a new predictor of first-time and recurrent VTE, including PE. Anticoagulant therapy, including non-vitamin K antagonist oral anticoagulants, has a favorable impact on fibrinolysis in VTE patients. Several VTE risk factors are also related to lower efficiency of fibrinolysis and their treatment improve fibrinolysis, in part by alterations to fibrin properties. There is an increasing number of studies aiming at developing novel profibrinolytic therapeutic agents for treatment of VTE patients, mostly targeting the antifibrinolytic proteins, i.e. antiplasmin, plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor.