Inhibition of prostaglandin synthesis during polystyrene microsphere-induced pulmonary embolism in the rat

Science-based evidence on pathways and effects of human exposure to micro- and nanoplastics

Human exposure to plastic particles has raised great concern among all relevant stakeholders involved in the protection of human health due to the contamination of the food chain, surface waters, and even drinking water as well as due to their persistence and bioaccumulation. Now more than ever, it is critical that we understand the biological fate of plastics and their interaction with different biological systems. Because of the ubiquity of plastic materials in the environment and their toxic potential, it is imperative to gain reliable, regulatory-relevant, science-based data on the effects of plastic micro- and nanoparticles (PMNPs) on human health in order to implement reliable risk assessment and management strategies in the circular economy of plastics. This review presents current knowledge of human-relevant PMNP exposure doses, pathways, and toxic effects. It addresses difficulties in properly assessing plastic exposure and current knowledge gaps and proposes steps that can be taken to underpin health risk perception, assessment, and mitigation through rigorous science-based evidence. Based on the existing scientific data on PMNP adverse health effects, this review brings recommendations on the development of PMNP-specific adverse outcome pathways (AOPs) following the AOP Users' Handbook of the Organisation for Economic Cooperation and Development (OECD).

Acute Pulmonary Embolism and Immunity in Animal Models

Venous thromboembolism, encompassing acute pulmonary embolism (APE) and deep vein thrombosis (DVT), is a potentially fatal disease with complex pathophysiology. Traditionally, the Virchow triad provided a framework for understanding the pathogenic contributors to thrombus formation, which include endothelial dysfunction, alterations in blood flow and blood hypercoagulability. In the last years, it has become apparent that immunity plays a central role in thrombosis, interacting with classical prothrombotic mechanisms, oxidative stress and vascular factors. Thrombosis amplifies inflammation, and exaggerated inflammatory processes can trigger thrombosis mainly due to the activation of leukocytes, platelets, and endothelial cells. APE-related endothelium injury is a major trigger for immune system activation. Endothelium is also a key component mediating inflammatory reaction and it is relevant to maintain vascular permeability. Exaggerated right ventricular wall stress and overload, with coexisting systemic hypotension and hypoxemia, result in myocardial injury and necrosis. Hypoxia, tissue factor activation and cytokine storm are engaged in the thrombo-inflammatory processes. Thrombus development is characterized by inflammatory state vascular wall caused mainly by an early extravasation of leukocytes and intense selectins and cytokines production. Nevertheless, immunity of DVT is well described, little is known about potential chemokine and cellular differences between thrombus that develops in the vein and thrombus that detaches and lodges in the pulmonary circulation being a cause of APE. There is a paucity of data considering inflammatory state in the pulmonary artery wall during an acute episode of pulmonary embolism. The main aim of this review is to summarize the knowledge of immunity in acute phase of pulmonary embolism in experimental models.

Atmospheric Microplastics: Perspectives on Origin, Abundances, Ecological and Health Risks

Microplastic (MP) pollution has aroused a tremendous amount of public and scientific interest worldwide. MPs are found widely ranging from terrestrial to aquatic ecosystems primarily due to the over-exploitation of plastic products and unscientific disposal of plastic waste. There is a large availability of scientific literature on MP pollution in the terrestrial and aquatic ecosystems, especially the marine environments; however, only recently has greater scientific attention been focused on the presence of MPs in the air and its retrospective health implications. Besides, atmospheric transport has been reported to be an important pathway of transport of MPs to the pristine regions of the world. From a health perspective, existing studies suggest that airborne MPs are priority pollutant vectors, that may penetrate deep into the body through inhalation leading to adverse health impacts such as neurotoxicity, cancer, respiratory problems, cytotoxicity, and many more. However, their effects on indoor and outdoor air quality, and on human health are not yet clearly understood due to the lack of enough research studies on that and the non-availability of established scientific protocols for their characterization. This scientific review entails important information concerning the abundance of atmospheric MPs worldwide within the existing literature. A thorough comparison of existing sampling and analytical protocols has been presented. Besides, this review has unveiled the areas of scientific concern especially air quality monitoring which requires immediate attention, with the information gaps to be filled have been addressed.

Alleviation of neurotoxicity induced by polystyrene nanoplastics by increased exocytosis from neurons

Nanoplastics (NPs) are potentially toxic and pose a health risk as they can induce an inflammatory response and oxidative stress at cellular and organismal levels. Humans can be exposed to NPs through various routes, including ingestion, inhalation, and skin contact. Notably, uptake into the body via inhalation could result in brain accumulation, which may occur directly across the blood-brain barrier or via other routes. NPs that accumulate in the brain may be endocytosed into neurons, inducing neurotoxicity. Recently, we demonstrated that exposure to polystyrene (PS)-NPs reduces the viability of neurons. We have also reported that inhibiting the retrograde transport of PS-NPs by histone deacetylase 6 (HDAC6) prevents their intracellular accumulation and promotes their export in mouse embryonic fibroblasts. However, whether HDAC6 inhibition can improve neuronal viability by increasing exocytosis of PS-NPs from neurons remains unknown. In this study, mice were intranasally administered fluorescent PS-NPs (PS-YG), which accumulated in the brain and showed potential neurotoxic effects. In cultured neurons, the HDAC6 inhibitor ACY-1215 reduced the fluorescence signal detected from PS-YG, suggesting that the removal of PS-YG from neurons was promoted. Therefore, these results suggest that blocking the retrograde transport of PS-NPs using an HDAC6 inhibitor can alleviate the neurotoxic effects of PS-NPs that enter the brain.

The rationale, design, and methods of a trial to evaluate the efficacy and safety of oxygen therapy in patients with intermediate-risk acute pulmonary embolism

BACKGROUND

In patients with intermediate-risk pulmonary embolism (PE), reversal of hypoxic vasoconstriction could constitute a target for treatment that protects the right ventricular (RV) function until endogenous fibrinolysis occurs. The Air vs oxygen for Intermediate-Risk pulmonary embolism (AIR) trial aims to assess the effect of oxygen therapy in patients with intermediate-risk acute PE who do not have hypoxemia at baseline.

METHODS AND ANALYSES

AIR is a prospective, multicenter, randomized, open-label, parallel-group, proof-of-concept trial. A total of 90 patients hospitalized with intermediate-risk PE and an oxygen saturation of 90% or higher at baseline will be randomized in a 1:1 fashion to receive supplemental oxygen or ambient air. The primary outcome is a RV/LV diameter ratio equal or less than 1.0 on echocardiography measured 48 hours after the start of treatment. Secondary efficacy outcomes are the numerical change in the ratio of the RV to the LV diameter measured 48 hours and 7 days after the start of treatment, with respect to the baseline ratio measured at randomization. Clinical adverse events will be also collected.

RESULTS

Enrollment started in July 2019 and is expected to proceed until 2022. Median age of the first 50 patients was 74 years (interquartile range, 61-81), and 50% were female.

CONCLUSIONS

This multicenter trial will provide information about the value of supplemental oxygen in patients with intermediate-risk acute PE who do not have hypoxemia at baseline. The results will contribute to research that may assist patients with intermediate-risk PE in the future.

Microplastics: A Matter of the Heart (and Vascular System)

Plastic use dramatically increased over the past few years. Besides obvious benefits, the consequent plastic waste and mismanagement in disposal have caused ecological problems. Plastic abandoned in the environment is prone to segregation, leading to the generation of microplastics (MPs) and nanoplastics (NPs), which can reach aquatic and terrestrial organisms. MPs/NPs in water can access fish's bodies through the gills, triggering an inflammatory response in loco. Furthermore, from the gills, plastic fragments can be transported within the circulatory system altering blood biochemical parameters and hormone levels and leading to compromised immunocompetence and angiogenesis. In addition, it was also possible to observe an unbalanced ROS production, damage in vascular structure, and enhanced thrombosis. MPs/NPs led to cardiotoxicity, pericardial oedema, and impaired heart rate in fish cardiac tissue. MPs/NPs effects on aquatic organisms pose serious health hazards and ecological consequences because they constitute the food chain for humans. Once present in the mammalian body, plastic particles can interact with circulating cells, eliciting an inflammatory response, with genotoxicity and cytotoxicity of immune cells, enhanced haemolysis, and endothelium adhesion. The interaction of MPs/NPs with plasma proteins allows their transport to distant organs, including the heart. As a consequence of plastic fragment internalisation into cardiomyocytes, oxidative stress was increased, and metabolic parameters were altered. In this scenario, myocardial damage, fibrosis and impaired electrophysiological values were observed. In summary, MPs/NPs are an environmental stressor for cardiac function in living organisms, and a risk assessment of their influence on the cardiovascular system certainly merits further analysis.

Are Ingested or Inhaled Microplastics Involved in Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) has emerged as the predominant cause of chronic liver injury; however, the mechanisms underlying its progression have not been fully elucidated. Pathophysiological studies have stated that NAFLD is significantly influenced by dietary and environmental factors that could participate in the development of NAFLD through different mechanisms. Currently, "plastic pollution" is one of the most challenging environmental problems worldwide since several plastics have potential toxic or endocrine disputing properties. Specifically, the intake of microplastics (MPs) and nanoplastics (NPs) in water or diet and/or the inhalation from suspended particles is well established, and these particles have been found in human samples. Laboratory animals exposed to MPs develop inflammation, immunological responses, endocrine disruptions, and alterations in lipid and energy metabolism, among other disorders. MPs additives also demonstrated adverse reactions. There is evidence that MPs and their additives are potential "obesogens" and could participate in NAFLD pathogenesis by modifying gut microbiota composition or even worsen liver fibrosis. Although human exposure to MPs seems clear, their relationship with NAFLD requires further study, since its prevention could be a possible personalized therapeutic strategy. Adequate mitigation strategies worldwide, reducing environmental pollution and human exposure levels of MPs, could reduce the risk of NAFLD.

Microplastic ingestion from atmospheric deposition during dining/drinking activities

Human-health risks from microplastics have attracted considerable attention, but little is known about human-exposure pathways and intensities. Recent studies posited that inhalation of atmospheric microplastics was the dominant human-exposure pathway. Herein, our study identified that atmospheric microplastics ingested from deposition during routine dining/drinking activities represent another important exposure pathway. We measured abundances of atmospheric-deposited microplastics of up to 10⁵ items m^-2 d^-1 in dining/drinking venues, with 90% smaller than 100 µm and a dominance of amorphous fragments rather than fibers. Typical work-life scenarios projected an annual ingestion of 1.9 × 10⁵ to 1.3 × 10⁶ microplastics through atmospheric deposition on diet, with higher exposure rates for indoor versus outdoor dining/drinking settings. Ingestion of atmospheric-deposited microplastics through diet was similar in magnitude to presumed inhalation exposure, but 2-3 orders of magnitude greater than direct ingestion from food sources. Simple mitigation strategies (e.g., covering and rinsing dishware) can substantially reduce the exposure of atmospheric deposition microplastics through diet.

Effects of polystyrene nanoplastics on endothelium senescence and its underlying mechanism

Global plastic use has increased rapidly, and environmental pollution associated with nanoplastics (NPs) has been a growing concern recently. However, the impact and biological mechanism of NPs on the cardiovascular system are not well characterized. This study aimed to assess the possibility that NPs exposure promotes premature endothelial cell (EC) senescence in porcine coronary artery ECs and, if so, to elucidate the underlying mechanism. Treatment of ECs with NPs promoted the acquisition of senescence markers, senescence-associated β-galactosidase activity, and p53, p21, and p16 protein expression, resulting in the inhibition of proliferation. In addition, NPs impaired endothelium-dependent vasorelaxation associated with decreased endothelial nitric oxide synthase (eNOS) expression. NPs enhanced reactive oxygen species formation in ECs, and increased oxidative stress levels were associated with the induction of NADPH oxidases expression, followed by the subsequent downregulation of Sirt1 expression. The characteristics of EC senescence and dysfunction caused by NPs are prevented by an antioxidant (N-acetylcysteine), an NADPH oxidase inhibitor (apocynin), and a Sirt1 activator (resveratrol). These findings indicate that NPs induced premature EC senescence, at least in part, through the redox-sensitive eNOS/Sirt1 signaling pathway. This study suggested the effects and underlying mechanism of NPs on the cardiovascular system, which may provide pharmacological targets to prevent NPs-associated cardiovascular diseases.

From properties to toxicity: Comparing microplastics to other airborne microparticles

Microplastic (MP) debris is considered as a potentially hazardous material. It is omnipresent in our environment, and evidence that MP is also abundant in the atmosphere is increasing. Consequently, the inhalation of these particles is a significant exposure route to humans. Concerns about potential effects of airborne MP on human health are rising. However, currently, there are not enough studies on the putative toxicity of airborne MP to adequately assess its impact on human health. Therefore, we examined potential drivers of airborne MP toxicity. Physicochemical properties like size, shape, ζ-potential, adsorbed molecules and pathogens, and the MP's bio-persistence have been proposed as possible drivers of MP toxicity. Since their role in MP toxicity is largely unknown, we reviewed the literature on toxicologically well-studied non-plastic airborne microparticles (asbestos, silica, soot, wood, cotton, hay). We aimed to link the observed health effects and toxicology of these microparticles to the abovementioned properties. By comparing this information with studies on the effects of airborne MP, we analyzed possible mechanisms of airborne MP toxicity. Thus, we provide a basis for a mechanistic understanding of airborne MP toxicity. This may enable the assessment of risks associated with airborne MP pollution, facilitating effective policymaking and product design.

Polystyrene micro-/nanoplastics induced hematopoietic damages via the crosstalk of gut microbiota, metabolites, and cytokines

Micro-/nanoplastics (MNPLs), novel environmental pollutants, widely exist in the environment and life and bring health risks. Previous studies have shown that NMPLs can penetrate bone marrow, but whether they cause hematopoietic damage remains uncertain. In this study, C57BL/6J mice were treated with polystyrene MNPLs (PS-MNPLs, 10 μm, 5 μm and 80 nm) at 60 μg doses for 42 days by intragastric administration. We evaluated the hematopoietic toxicity induced by MNPLs and potential mechanisms via combining 16S rRNA, metabolomics, and cytokine chips. The results demonstrated that PS-MNPLs induced hematopoietic toxicity, which was manifested by the disorder of bone marrow cell arrangement, the reduction in colony-forming, self-renewal and differentiation capacity, and the increased proportion of lymphocytes. PS-MNPLs also disrupted the homeostasis of the gut microbiota, metabolism, and inflammation, all of which were correlated with hematotoxicity, suggesting that abnormal gut microbiota-metabolite-cytokine axes might be the crucial pathways in MNPLs-induced hematopoietic injury. In conclusion, our study systematically demonstrated that multi-scale PS-MNPLs induced hematopoietic toxicity via the crosstalk of gut microbiota, metabolites, and cytokines and provided valuable insights into MNPLs toxicity, which was conducive to health risk assessment and informed policy decisions regarding PS-MNPLs.

Rodent models of pulmonary embolism and chronic thromboembolic pulmonary hypertension

Pulmonary embolism (PE) is the third most prevalent cardiovascular disease. It is associated with high in-hospital mortality and the development of acute and chronic complications. New approaches aimed at improving the prognosis of patients with PE are largely dependent on reliable animal models. Mice, rats, hamsters, and rabbits, are currently most commonly used for PE modeling because of their ethical acceptability and economic feasibility. This article provides an overview of the main approaches to PE modeling, and the advantages and disadvantages of each method. Special attention is paid to experimental endpoints, including morphological, functional, and molecular endpoints. All approaches to PE modeling can be broadly divided into three main groups: 1) induction of thromboembolism, either by thrombus formation in vivo or by injection of in vitro prepared blood clots; 2) introduction of particles of non-thrombotic origin; and 3) surgical procedures. The choice of a specific model and animal species is determined based on the objectives of the study. Rodent models of chronic thromboembolic pulmonary hypertension (CTEPH), which is the most devastating complication of PE, are also described. CTEPH models are especially challenging because of insufficient knowledge about the pathogenesis and high fibrinolytic activity of rodent plasma. The CTEPH model should demonstrate a persistent increase in pulmonary artery pressure and stable reduction of the vascular bed due to recurrent embolism. Based on the analysis of available evidence, one might conclude that currently, there is no single optimal method for modeling PE and CTEPH.

Characteristics, Toxic Effects, and Analytical Methods of Microplastics in the Atmosphere

Microplastics (MPs) (including nanoplastics (NPs)) are pieces of plastic smaller than 5 mm in size. They are produced by the crushing and decomposition of large waste plastics and widely distributed in all kinds of ecological environments and even in organisms, so they have been paid much attention by the public and scientific community. Previously, several studies have reviewed the sources, occurrence, distribution, and toxicity of MPs in water and soil. By comparison, the review of atmospheric MPs is inadequate. In particular, there are still significant gaps in the quantitative analysis of MPs and the mechanisms associated with the toxic effects of inhaled MPs. Thus, this review summarizes and analyzes the distribution, source, and fate of atmospheric MPs and related influencing factors. The potential toxic effects of atmospheric MPs on animals and humans are also reviewed in depth. In addition, the common sampling and analysis methods used in existing studies are introduced. The aim of this paper is to put forward some feasible suggestions on the research direction of atmospheric MPs in the future.

Neurotoxic potential of polystyrene nanoplastics in primary cells originating from mouse brain

Polystyrene (PS) and chemically modified compounds in the PS family have long been used in commercial and industrial fields. However, it is poorly understood whether nanoscale-PS microplastic or PS nanoplastic exposure leads to perturbations in fundamental cellular functions, such as proliferation, differentiation, and apoptosis. Herein, we cultured three types of primary cells, including mouse embryonic fibroblasts (MEFs), mixed neuronal cells isolated from embryonic cortex, and cortical astrocytes, and investigated the effects of their exposure to PS nanoplastics with a 100 nm diameter. Although PS nanoplastic exposure did not affect the viability of MEFs or astrocytes, it significantly reduced the viability of mixed neuronal cells. Consistent with the observed effect on cellular viability, levels of the apoptosis marker, cleaved caspase-3, were elevated exclusively in mixed neuronal cells. To investigate whether cells uptake PS nanoplastics into the cytoplasm, we exposed MEFs and neurons to fluorescent PS latex beads and monitored fluorescence over time. We found that PS nanoplastics were deposited and accumulated in the cytoplasm in a concentration-dependent manner. Although astrocytes were not apoptotic upon exposure to PS nanoplastics, they underwent reactive astrocytosis, with increased levels of lipocalin-2 and proinflammatory cytokines. Therefore, our findings suggested that the vulnerability of cells to the deposition and accumulation of PS nanoplastics in the cytoplasm was dependent on cell type. Furthermore, based on our data from primary cells originating from mouse brains, we suggest that reactive astrocytosis may contribute to the neuronal apoptosis seen in defective neurons with PS nanoplastics accumulated in the cell body.

Animal models of right heart failure

Right heart failure may be the ultimate cause of death in patients with acute or chronic pulmonary hypertension (PH). As PH is often secondary to other cardiovascular diseases, the treatment goal is to target the underlying disease. We do however know, that right heart failure is an independent risk factor, and therefore, treatments that improve right heart function may improve morbidity and mortality in patients with PH. There are no therapies that directly target and support the failing right heart and translation from therapies that improve left heart failure have been unsuccessful, with the exception of mineralocorticoid receptor antagonists. To understand the underlying pathophysiology of right heart failure and to aid in the development of new treatments we need solid animal models that mimic the pathophysiology of human disease. There are several available animal models of acute and chronic PH. They range from flow induced to pressure overload induced right heart failure and have been introduced in both small and large animals. When initiating new pre-clinical or basic research studies it is key to choose the right animal model to ensure successful translation to the clinical setting. Selecting the right animal model for the right study is hence important, but may be difficult due to the plethora of different models and local availability. In this review we provide an overview of the available animal models of acute and chronic right heart failure and discuss the strengths and limitations of the different models.

A Review of Microplastics in Table Salt, Drinking Water, and Air: Direct Human Exposure

The ubiquity of microplastics in aquatic and terrestrial environments and related ecological impacts have gained global attention. Microplastics have been detected in table salt, drinking water, and air, posing inevitable human exposure risk. However, rigorous analytical methods for detection and characterization of microplastics remain scarce. Knowledge about the potential adverse effects on human health via dietary and respiratory exposures is also limited. To address these issues, we reviewed 46 publications concerning abundances, potential sources, and analytical methods of microplastics in table salt, drinking water, and air. We also summarized probable translocation and accumulation pathways of microplastics within human body. Human body burdens of microplastics through table salt, drinking water, and inhalation were estimated to be (0-7.3)×10⁴, (0-4.7)×10³, and (0-3.0)×10⁷ items per person per year, respectively. The intake of microplastics via inhalation, especially via indoor air, was much higher than those via other exposure routes. Moreover, microplastics in the air impose threats to both respiratory and digestive systems through breathing and ingestion. Given the lifetime inevitable exposure to microplastics, we urgently call for a better understanding of the potential hazards of microplastics to human health.

Near-Infrared Light-Induced Sequential Shape Recovery and Separation of Assembled Temperature Memory Polymer Microparticles

Light-induced, shape-changing polymeric microparticles have many applications. Here, the near-infrared (NIR)-light-triggered sequential recovery and separation of assembled large and small polymer microparticles using cross-linked blends of poly(ethylene-vinyl acetate) and trans-polyisoprene as temperature memory polymers as well as two NaYF₄ based up-conversion nanoparticles (UCPs) to provide luminescent and photothermal effects are reported. Under irradiation of NIR light with a low light power density, small particles assembled onto the compressed large one recover first due to the low switching temperature (T_sw ) arising from the temperature-memory effect. The small particles can separate from the underlying large particle in flowing aqueous media. The recovery of the large particle occurs at a high power density. Two UCPs of NaYF₄ : 20Yb, 0.2Tm, 5Gd and NaYF₄ : 18Yb, 2Er, 5Gd facilitate the detection of small and large microparticles via providing blue and green light emissions, respectively. This work can expand the applications of light-induced shape-changing polymer microparticles in the biomedical field, controlled catalysis, microfluidic devices, and so on.

Pulmonary vasodilation in acute pulmonary embolism - a systematic review

Acute pulmonary embolism is the third most common cause of cardiovascular death. Pulmonary embolism increases right ventricular afterload, which causes right ventricular failure, circulatory collapse and death. Most treatments focus on removal of the mechanical obstruction caused by the embolism, but pulmonary vasoconstriction is a significant contributor to the increased right ventricular afterload and is often left untreated. Pulmonary thromboembolism causes mechanical obstruction of the pulmonary vasculature coupled with a complex interaction between humoral factors from the activated platelets, endothelial effects, reflexes and hypoxia to cause pulmonary vasoconstriction that worsens right ventricular afterload. Vasoconstrictors include serotonin, thromboxane, prostaglandins and endothelins, counterbalanced by vasodilators such as nitric oxide and prostacyclins. Exogenous administration of pulmonary vasodilators in acute pulmonary embolism seems attractive but all come with a risk of systemic vasodilation or worsening of pulmonary ventilation-perfusion mismatch. In animal models of acute pulmonary embolism, modulators of the nitric oxide-cyclic guanosine monophosphate-protein kinase G pathway, endothelin pathway and prostaglandin pathway have been investigated. But only a small number of clinical case reports and prospective clinical trials exist. The aim of this review is to give an overview of the causes of pulmonary embolism-induced pulmonary vasoconstriction and of experimental and human investigations of pulmonary vasodilation in acute pulmonary embolism.

Environmental exposure to microplastics: An overview on possible human health effects

Microplastics are ubiquitous environmental contaminants leading to inevitable human exposure. Even so, little is known about the effects of microplastics in human health. Thus, in this work we review the evidence for potential negative effects of microplastics in the human body, focusing on pathways of exposure and toxicity. Exposure may occur by ingestion, inhalation and dermal contact due to the presence of microplastics in products, foodstuff and air. In all biological systems, microplastic exposure may cause particle toxicity, with oxidative stress, inflammatory lesions and increased uptake or translocation. The inability of the immune system to remove synthetic particles may lead to chronic inflammation and increase risk of neoplasia. Furthermore, microplastics may release their constituents, adsorbed contaminants and pathogenic organisms. Nonetheless, knowledge on microplastic toxicity is still limited and largely influenced by exposure concentration, particle properties, adsorbed contaminants, tissues involved and individual susceptibility, requiring further research.

Inhibition of the cyclophilin A-CD147 interaction attenuates right ventricular injury and dysfunction after acute pulmonary embolism in rats

Acute pulmonary embolism (APE)-induced inflammation contributes to cardiomyocyte injury and dysfunction in the right ventricle (RV) of the heart. The interactions of cyclophilin A with its ligand extracellular matrix metalloproteinase inducer (EMMPRIN or CD147) may be involved in this inflammatory process. To this end, here we induced APE by intravenous injections of microspheres in Sprague-Dawley rats. We found that after the APE, cyclophilin A and CD147 levels increased synchronously in RV tissue following APE and peaked at 24 h. The cyclophilin A inhibitor cyclosporine A attenuated the APE-induced cyclophilin A levels, and a monoclonal antibody of CD147 (anti-CD147) abrogated the elevation of CD147 in the RV but not the increase of cyclophilin A. Importantly, treatment with cyclosporine A, anti-CD147, or both attenuated APE-induced increases in RV systolic pressure, plasma cardiac troponin-I (cTnI) concentrations, the RV/left ventricle diameter ratio, and the Tei index, measured by echocardiography 24 h after APE induction. These beneficial effects were associated with reduced RV neutrophil infiltration and prevention of matrix metalloproteinase 9 (MMP-9) and MMP-2 activation. These findings suggested that inhibiting the cyclophilin A-CD147 interaction attenuates APE-associated RV cardiomyocyte injury and dysfunction by suppressing inflammation. We further proposed that cyclophilin A and CD147 might participate in APE-induced pathological processes by partly activating the ERK1/2 kinase-nuclear factor-κB pathway. We conclude that the cyclophilin A-CD147 interaction may represent a potential therapeutic target for managing APE.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

The effect of nitric oxide inhalation on heart and pulmonary circulation in rabbits with acute massive pulmonary embolism

The aim of the present study was to investigate the effect of nitric oxide inhalation (NOI) on cardiac troponin I (CTnI) levels and mean pulmonary arterial pressure (mPAP) in rabbits with acute massive pulmonary embolism (AMPE). Thirty rabbits were used as animal models for AMPE and received different treatments. A total of 4 h after successful modeling, the control group (CON, n=10) received conventional thrombolysis, whereas the treatment group (TRE, n=10) received conventional thrombolysis plus NOI. The experimental group (EXP, n=10) did not receive any treatments. Myocardial necrosis was pathologically confirmed in all 30 rabbits. In group EXP, the post-AMPE CTnI peak level was 0.42±0.12 µg/l, was achieved in 18.8±4.5 h and remained positive for 38.6±5.2 h (≥0.1 µg/l). These values were lower in group TRE when compared with those in groups CON and EXP (P<0.05). Group TRE exhibited significantly reduced mPAP at 24, 28, 32, and 34 h (P<0.05) when compared with group CON. AMPE-induced cardiac impairment was more severe in group EXP when compared with groups CON and TRE. The present findings indicated that the CTnI peak was significantly correlated with the corresponding mPAP. Furthermore, the results suggested NOI may reduce mPAP and CTnI peak levels, with protective effects against AMPE-induced myocardial damage in rabbits.

Airborne microplastics: Consequences to human health?

Microplastics have recently been detected in atmospheric fallout in Greater Paris. Due to their small size, they can be inhaled and may induce lesions in the respiratory system dependent on individual susceptibility and particle properties. Even though airborne microplastics are a new topic, several observational studies have reported the inhalation of plastic fibers and particles, especially in exposed workers, often coursing with dyspnea caused by airway and interstitial inflammatory responses. Even though environmental concentrations are low, susceptible individuals may be at risk of developing similar lesions. To better understand airborne microplastics risk to human health, this work summarizes current knowledge with the intention of developing awareness and future research in this area.

Differential effect of mild and severe pulmonary embolism on the rat lung transcriptome

BACKGROUND

Pulmonary thromboembolism (PTE) is a common diagnosis and a leading cause of cardiovascular morbidity and mortality. A growing literature has associated PE with systemic inflammation, and global hyper-coagulability, which contribute to lung remodeling and clot recurrence. The source and mechanism of inflammation remains unstudied. In humans, inhibition of cholesterol synthesis with statins decreases biomarkers of inflammation. We test the differential effect of pulmonary vascular occlusion during mild and severe pulmonary embolism on the lung transcriptome.

METHODS

Experimental PE was induced in adult male rats by injection of 25 micron polystyrene microspheres into the jugular vein. The effect of Mild PE, (2-h right ventricular systolic pressure [RVSP] normal, 18-h RVSP 44 mmHg) and Severe PE (2-h RVSP > 50 mmHg; 18-h RVSP 44 mmHg) on lungs was assessed by measuring transcriptome-wide changes in gene expression by DNA microarrays.

RESULTS

Severe PE was associated with a large change in lung gene expression and in the expression of KEGG pathways and other gene functional annotation groups. Mild PE was also associated with a large number of significant changes in gene expression and in the expression of KEGG pathways and gene functional annotation groups, even after only 2 h of PE. Up-regulated pathways included increased adipocytokine, chemokine and cytokine signaling as well as cholesterol synthesis.

CONCLUSIONS

Mild PE without acute pulmonary hypertension (PH) increased lung gene expression of inflammatory pathways, including increased cholesterol synthesis. These data indicate that even mild persistent pulmonary vascular occlusion is capable of inciting an inflammatory response from the lung. These data imply the detrimental effect of unresolved pulmonary obstruction from PE.

Leukocyte expression of heme oxygenase-1 [hmox1] varies inversely with severity of tricuspid regurgitation in acute pulmonary embolism

OBJECTIVE

Pulmonary embolism (PE) can cause intracardiac hemolysis and increased plasma hemoglobin and arginase-1, which can worsen pulmonary vasoconstriction. We test the hypothesis that patients with PE that causes tricuspid regurgitation (TR), indicative of higher pulmonary arterial pressures, have decreased leukocyte expression of hmox-1 compared with patients with PE and no TR and patients without PE.

DESIGN

Prospective, noninterventional study.

PATIENTS

Normotensive patients with suspected PE (n=87) who underwent CT pulmonary angiography and transthoracic Doppler-echocardiography.

MEASUREMENTS

Significant TR was defined as a jet velocity >2.7m/s. Leukocyte expression of hmox-1, haptoglobin, haptoglobin related gene, the haptoglobin receptor, CD163 and cox-2 genes were assessed by quantitative rtPCR, and the hmox-1 promoter was examined for the -413 A→T SNP and GT repeat polymorphisms.

RESULTS

Of the 44 (50%) with PE+, 22 had TR+, and their mean pulmonary vascular occlusion (39±32%) did not differ significantly from patients who were TR- (28±26%, P=0.15). Patients with PE+ and TR+ had significantly lower expression of hmox-1 and haptoglobin genes than patients without PE+ and no TR. Expression of hmox-1 varied inversely with TR velocity (r(2)=0.45, P<0.001) for PE+ (n=22) but not patients without PE. Hmox-1 expression did not vary significantly with genotype. Cox-2 did not differ between groups and had no correlation with TR.

CONCLUSIONS

Severity of TR varied inversely with hmox-1 expression, suggesting that hmox-1 expression affects pulmonary vascular reactivity after PE.

Pilot study of a protocol to administer inhaled nitric oxide to treat severe acute submassive pulmonary embolism

OBJECTIVE

Inhaled nitric oxide has been reported to benefit patients with acute pulmonary embolism (PE). To date, all published literature has derived from case reports or case series conducted without a structured protocol. Here we report the results of a phase I trial with a predefined clinical protocol to treat patients with CT-demonstrated, submassive PE and moderate to severe dyspnoea.

METHODS

Patients were recruited from the emergency department of an academic teaching hospital. Informed consent and the entire treatment protocol was administered by a study physician. Nitric oxide was administered using a commercial device (Inovent) and a custom-made non-rebreathing face mask. The NO concentration was increased at 1 ppm/min (parts per million) until a maximum of 25 ppm and continued for 120 min and then weaned at 1 ppm/min. Dyspnoea was assessed with the Borg score, oxygenation by pulse oximetry, and haemodynamic status by shock index (HR/SBP).

RESULTS

Eight patients were enrolled. All patients tolerated the entire protocol without adverse events, and all had decreased numerical Borg score by >50%. The changes from baseline to 155 min were as follows: Borg score 7.5±2.5 to 2.3±1.9 (p=0.06, Signed rank test), SaO2% 93±5 to 97±3 and shock index 1.0±0.11 to 0.86±0.09. No patient experienced worsening during weaning.

CONCLUSIONS

Inhaled NO reduced dyspnoea without adverse events in eight patients with severe submassive PE. This protocol can serve as the basis for a phase II trial or for a compassionate use protocol.

A soluble guanylate cyclase stimulator, BAY 41-8543, preserves right ventricular function in experimental pulmonary embolism

Pulmonary embolism (PE) increases pulmonary vascular resistance, causing right ventricular (RV) dysfunction, and poor clinical outcome. Present studies test if the soluble guanylate cyclase stimulator BAY 41-8543 reduces pulmonary vascular resistance and protects RV function. Experimental PE was induced in anesthetized, male Sprague-Dawley rats by infusing 25 μm polystyrene microspheres (1.95 million/100 g body wt, right jugular vein) producing moderate PE. Pulmonary artery vascular resistance, estimated as RVPSP/CO, increased 3-fold after 5 h of PE. Treatment with BAY 41-8543 (50 μg/kg, I.V.; given at the time of PE induction) normalized this index by reducing RVPSP and markedly increasing CO, via preservation of heart rate and stroke volume. Ex vivo RV heart function showed minimal changes at 5 h of PE, but decreased significantly after 18 h of PE, including peak systolic pressure (PSP, Control 39 ± 1 mmHg vs. 19 ± 3 PE), +dP/dt (1192 ± 93 mmHg/s vs. 444 ± 64) and -dP/dt (-576 ± 60 mmHg/s vs. -278 ± 40). BAY 41-8543 significantly improved all three indices of RV heart function (PSP 35 ± 3.5, +dP/dt 1129 ± 100, -dP/dt -568 ± 87). Experimental PE produced increased PVR and RV dysfunction, which were ameliorated by treatment with BAY 41-8543. Thus, there is vasodilator reserve in this model of experimental PE that can be exploited to reduce the stress upon the heart and preserve RV contractile function.

Right ventricular responses to massive and submassive pulmonary embolism

It is critically important to quickly recognize and treat acute pulmonary embolism (PE). Submassive and massive PEs are associated with right ventricular (RV) dysfunction and may culminate in RV failure, cardiac arrest, and death. A rapid and coordinated diagnostic and management approach can maximize success and save lives.

Up-regulation of arginase II contributes to pulmonary vascular endothelial cell dysfunction during experimental pulmonary embolism

Pulmonary embolism (PE) causes pulmonary hypertension by mechanical obstruction and constriction of non-obstructed vasculature. We tested if experimental PE impairs pulmonary vascular endothelium-dependent dilation via activation of arginase II. Experimental PE was induced in male Sprague-Dawley rats by infusing 25 μm microspheres in the right jugular vein, producing moderate pulmonary hypertension. Shams received vehicle injection. Pulmonary arterial rings were isolated after 18 h and isometric tensions were determined. Dilations were induced with acetylcholine, calcium ionophore A23187 or nitroglycerin (NTG) in pre-contracted rings (phenylephrine). Protein expression was assessed by Western blot and immunohistochemistry. Arginase activity was inhibited by intravenous infusion of N(w)-hydroxy-nor-l-arginine (nor-NOHA). l-Arginine supplementation was also given. Endothelium-dependent dilation responses were significantly reduced in PE vs. vehicle-treated animals (ACh: 50 ± 9% vs. 93 ± 3%; A23187: 19 ± 7% vs. 85 ± 7%, p < 0.05), while endothelium-independent dilations (NTG) were unchanged. Endothelial nitric oxide synthase (eNOS) protein content was unchanged by PE. Expression of arginase II increased 4.5-fold and immunohistochemistry revealed increased arginase II staining. Nor-NOHA treatment and l-arginine supplementation significantly improved pulmonary artery ring endothelium-dependent dilation in PE (ACh: 58 ± 6% PE, 88 ± 6% PE + nor-NOHA, 84 ± 4% PE + l-arginine). Experimental PE impairs endothelium-dependent pulmonary artery dilation, while endothelium-independent dilation remains unchanged. The data support the conclusion that up-regulation of arginase II protein expression contributes to pulmonary artery endothelial dysfunction in this model of experimental PE.

Gene expression of ANP, BNP and ET-1 in the heart of rats during pulmonary embolism

Aims

Atrial natriuretic petide (ANP), brain natriuretic peptide (BNP) and endothelin-1 (ET-1) may reflect the severity of right ventricular dysfunction (RVD) in patients with pulmonary embolism (PE). The exact nature and source of BNP, ANP and ET-1 expression and secretion following PE has not previously been studied.

Methods and Results

Polystyrene microparticles were injected to induce PE in rats. Gene expression of BNP, ANP and ET-1 were determined in the 4 cardiac chambers by quantitative real time polymerase chain reaction (QPCR). Plasma levels of ANP, BNP, ET-1 and cardiac troponin I (TNI) were measured in plasma. PE dose-dependently increased gene expression of ANP and BNP in the right ventricle (RV) and increased gene expression of ANP in the right atrium (RA). In contrast PE dose-dependently decreased BNP gene expression in both the left ventricle (LV) and the left atrium (LA). Plasma levels of BNP, TNI and ET-1 levels dose-dependently increased with the degree of PE.

Conclusion

We found a close correlation between PE degree and gene-expression of ANP, and BNP in the cardiac chambers with a selective increase in the right chambers of the heart.

The present data supports the idea of natriuretic peptides as valuable biomarkers of RVD in PE.

Threshold size for optimal passive pulmonary targeting and retention of rigid microparticles in rats

The relationship between microparticle (MP) size and lung targeting efficiency, intra-lung distribution and retention time was systematically studied after intravenous administration of rigid fluorescent polystyrene MPs of various sizes (2, 3, 6 and 10 microm) to Sprague Dawley rats. Total fluorescence was assessed and it was found that 2 microm and 3 microm MPs readily passed through the lung to the liver and spleen while 10 microm MPs were completely entrapped in the lung for the one-week duration of the study. Approximately 84% of 6 microm MPs that were initially entrapped in the lung were cleared over the next 2 days and 15% were cleared over the remaining 5 days. A Caliper IVIS 100 small animal imaging system confirmed that 3 microm MPs were not retained in the lung but that 6 microm and 10 microm MPs were widely distributed throughout the lung. Moreover, histologic examination showed MP entrapment in capillaries but not arterioles. These studies suggest that for rigid MPs the optimal size range required to achieve transient but highly efficiently targeting to pulmonary capillaries after IV injection is >6 microm but <10 microm in rats and that systemic administration of optimally sized MPs may be an efficient alternative to currently used inhalation-based delivery to the lung.

Development and comparison of a minimally-invasive model of autologous clot pulmonary embolism in Sprague-Dawley and Copenhagen rats

Background

Experimental models of pulmonary embolism (PE) that produce pulmonary hypertension (PH) employ many different methods of inducing acute pulmonary occlusion. Many of these models induce PE with intravenous injection of exogenous impervious objects that may not completely reproduce the physiological properties of autologous thromboembolism. Current literature lacks a simple, well-described rat model of autlogous PE. Objective: Test if moderate-severity autologous PE in Sprague-Dawley (SD) and Copenhagen (Cop) rats can produce persistent PH.

Methods

blood was withdrawn from the jugular vein, treated with thrombin-Ca⁺⁺ and re-injected following pretreatment with tranexamic acid. Hemodynamic values, clot weights and biochemical measurements were performed at 1 and 5 days.

Results

Infusion of clot significantly increased the right ventricular peak systolic pressure to 45-55 mm Hg, followed by normalization within 24 hours in SD rats, and within 5 days in COP rats. Clot lysis was 95% (24 hours) and 97% (5 days) in SD rats and was significantly lower in COP rats (70%, 24 hours; 87% 5 days). Plasma D-dimer was elevated in surgical sham animals and was further increased 8 hours after pulmonary embolism. Neither strain showed a significant increase in bronchoalveolar chemotactic activity, myeloperoxidase activity, leukocyte infiltration, or chemokine accumulation, indicating that there was no significant pulmonary inflammation.

Conclusions

Both SD and COP rats exhibited near complete fibrinolysis of autologous clot PE within 5 days. Neither strain developed persistent PH. Experimental models of PE designed to induce sustained PH and a robust inflammatory response appear to require significant, persistent pulmonary vascular occlusion.

Rapid clearance of circulating haptoglobin from plasma during acute pulmonary embolism in rats results in HMOX1 up-regulation in peripheral blood leukocytes

BACKGROUND

Acute pulmonary embolism (PE) causes pulmonary hypertension (PH) via several mechanisms including pulmonary vasospasm. We hypothesize that PE with associated PH leads to alterations in plasma protein concentrations indicative of disease severity and prognosis.

OBJECTIVE

To identify plasma proteins altered in abundance by PE in rats.

METHODS

Plasma samples were obtained from rats at 2, 6 and 18 h after experimental PE produced with intrajugular injection of polystyrene beads at three different levels of severity (mild, moderate and severe). Total plasma protein was separated using two-dimensional sodium dodecylsulfate-polyacrylamide gel electrophoresis (2D SDS-PAGE) and candidate protein spots altered in expression by PE were identified by mass spectroscopy. Haptoglobin identity and amount was verified by western blot analysis.

RESULTS

The PE model produced a dose-dependent increase in right ventricular systolic pressure (RVSP) (mmHg) at 2 h: mild 39+/-1.7, moderate 40+/-1.8 and severe 51+/-1.3 mmHg, coincident with significant increases in free plasma (hemoglobin). Combined 2D SDS-PAGE and Western blot analysis indicated time- and dose-dependant loss of plasma haptoglobin levels in response to acute PE. Haptoglobin (HP) was essentially absent from plasma within 2 h of severe PE. Clearance of HP from plasma was accompanied by increased expression of heme oxygenase-1 (hmox1) in peripheral blood leukocytes and in HMOX1 enzyme activity in the liver.

CONCLUSIONS

PE that causes pulmonary hypertension is associated with haptoglobin depletion and up-regulation of HMOX1 enzyme.

Right ventricular heart failure from pulmonary embolism: key distinctions from chronic pulmonary hypertension

BACKGROUND

The right ventricle normally operates as a low pressure, high-flow pump connected to a high-capacitance pulmonary vascular circuit. Morbidity and mortality in humans with pulmonary hypertension (PH) from any cause is increased in the presence of right ventricular (RV) dysfunction, but the differences in pathology of RV dysfunction in chronic versus acute occlusive PH are not widely recognized.

METHODS AND RESULTS

Chronic PH that develops over weeks to months leads to RV concentric hypertrophy without inflammation that may progress slowly to RV failure. In contrast, pulmonary embolism (PE) results in an abrupt vascular occlusion leading to increased pulmonary artery pressure within minutes to hours that causes immediate deformation of the RV. RV injury is secondary to mechanical stretch, shear force, and ischemia that together provoke a cytokine and chemokine-mediated inflammatory phenotype that amplifies injury.

CONCLUSIONS

This review will briefly describe causes of pulmonary embolism and chronic PH, models of experimental study, and pulmonary vascular changes, and will focus on mechanisms of right ventricular dysfunction, contrasting mechanisms of RV adaptation and injury in these 2 settings.

Transcriptional changes in right ventricular tissues are enriched in the outflow tract compared with the apex during chronic pulmonary embolism in rats

Moderate to severe pulmonary embolism (PE) can cause pulmonary arterial hypertension and right ventricular (RV) heart damage. Previous studies from our laboratory indicate that the basal outflow tract of the RV is injured and has acute inflammation followed by tissue remodeling while the apex appears normal. The present studies examine transcription responses to chronic PE in RV apex and outflow tracts using DNA microarrays to identify transcription responses by region. Changes predominated in the RV outflow tract (8,575 genes showed >/=1.5-fold expression change). Gene ontology and KEGG analyses indicated a significant decrease in genes involved in cellular respiration and energy metabolism and increases in inflammatory cell adhesion molecules and extracellular matrix proteins. Signal pathways for wound healing such as fibroblast growth factor, collagen synthesis, and CCN proteins (named for the first three members of the family: cysteine-rich protein 61, connective tissue growth factor, and nephroblastoma overexpressed gene) were strongly upregulated. In comparison, few genes (422) showed significant change in the RV apex tissue. Apex-selective genes included two genes affecting metabolism and a stretch-sensitive transcription factor (ankyrin repeat domain 1). We conclude that the RV outflow tract is subject to strong proinflammatory and profibrotic remodeling transcriptional responses in chronic PE. Severe loss of genes involved in cellular respiration is consistent with previous histology indicating a shift in cell types present within the outflow tract tissue away from highly energy-dependant cardiomyocytes to less metabolically active cells during remodeling. The apex region of the RV had few compensating adaptations.

Transcriptional profile of right ventricular tissue during acute pulmonary embolism in rats

Acute pulmonary embolism (PE) is the third leading cause of cardiovascular death in the United States. Moderate to severe PE can cause pulmonary arterial hypertension (PH) with resultant right ventricular (RV) heart damage. The mechanisms leading to RV failure after PE are not well defined, although it is becoming clear that PH-induced inflammatory responses are involved. We previously demonstrated profound neutrophil-mediated inflammation and RV dysfunction during PE that was associated with increased expression of several chemokine genes. However, a complete assessment of transcriptional changes in RVs during PE is still lacking. We have now used DNA microarrays to assess the alterations in gene expression in RV tissue during acute PE/PH in rats. Key results were confirmed with real-time RT-PCR. Nine CC-chemokine genes (CCL-2, -3, -4, -6, -7, -9, -17, -20, -27), five CXC-chemokine genes (CXCL-1, -2, -9, -10, -16), and the receptors CCR1 and CXCR4 were upregulated after 18 h of moderate PE, while one C-chemokine (XCL-1) and one CXC-chemokine (CXCL-12) were downregulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated increased expression of many inflammatory genes. There was also a major shift in the expression of components of metabolic pathways, including downregulation of fatty acid transporters and oxidative enzymes, a change in glucose transporters, and upregulation of stretch-sensing and hypoxia-inducible transcription factors. This pattern suggests an extensive shift in cardiac physiology favoring the expression of the “fetal gene program.”

Inhibition of thromboxane a synthase activity enhances steroidogenesis and steroidogenic acute regulatory gene expression in MA-10 mouse Leydig cells

The cyclooxygenase-2 (COX2)-dependent inhibition of Leydig cell steroidogenesis has been demonstrated. To understand the mechanism for this effect of COX2, the present study examined the role of an enzyme downstream of COX2, namely thromboxane A synthase (TBXAS), in steroidogenesis. Inhibition of TBXAS activity with the inhibitor furegrelate induced a concentration-dependent increase in cAMP-induced steroidogenic acute regulatory (StAR) protein in MA-10 mouse Leydig cells. The increase in StAR protein occurred concomitantly with a significant increase in steroid hormone production. Similar results were obtained in StAR promoter activity assays and RT-PCR analyses of StAR mRNA levels, suggesting that inhibition of TBXAS activity enhanced StAR gene transcription. These observations were corroborated when TBXAS expression was specifically inhibited by RNA interference. Although the RNA interference reduced mRNA levels of TBXAS, it increased StAR mRNA levels, StAR protein, and steroidogenesis. Additional studies indicated that inhibition of TBXAS activity reduced DAX-1 protein, a repressor in StAR gene transcription. In the absence of cAMP, inhibition of TBXAS activity did not induce a significant increase in steroid hormone and StAR protein. However, addition of a low level of cAMP analogs dramatically increased steroidogenesis. Lastly, inhibition of protein kinase A activity essentially abolished the steroidogenic effect of the TBXAS inhibitor. Thus, the results from the present study suggest that a minimal level of protein kinase A activity is required for the steroidogenic effect of the TBXAS inhibitor and that inhibition of TBXAS activity or its expression increase the steroidogenic sensitivity of MA-10 mouse Leydig cells to cAMP stimulation.

Measurement of expired carbon dioxide, oxygen and volume in conjunction with pretest probability estimation as a method to diagnose and exclude pulmonary venous thromboembolism

BACKGROUND

The classical alveolar pCO(2)-pO(2) relationship predicts that pulmonary embolism (PE) causes a low ratio of pCO(2)/pO(2) at end expiration. Our purpose was to define a simple protocol to collect expired pCO(2)/pO(2) to diagnose PE. Emergency department patients with suspected PE were enrolled. Clinical pretest probabilities for PE were estimated prior to diagnostic testing using the Canadian score and clinicians' unstructured estimate. Patients provided three 30-s periods of tidal breathing, separated by three deep exhalations. Expired pCO(2), pO(2) and breath volume were measured. All patients underwent standardized objective testing for PE including 90-day follow-up. Diagnosis (PE+) required anticoagulation for image-proven PE within 90 days.

RESULTS

Of 200 patients enrolled, 178 were included in final analysis (24 PE+). The mean coefficient of variability for the deep-exhaled and end-tidal pCO(2)/pO(2) ratios were 6.8 +/- 6.7 and 7.5 +/- 6.8%, respectively. Mean pCO(2)/pO(2) ratios were stable throughout the collection periods in both methods. When compared with the deep-exhaled ratio, the end-tidal mean ratio demonstrated slightly better diagnostic utility by the area under the receiver operating characteristic curve. The end-tidal ratios were divided into four interval likelihood ratios and coupled with pretest probability from the two methods to generate three sets of posttest probabilities. Receiver operating characteristic analysis demonstrated good overall diagnostic performance (areas under the curves >0.88) for both posttest probability sets.

CONCLUSION

This preliminary work demonstrates that the end-tidal pCO(2)/pO(2) averaged from 30 s of breathing can produce clinically relevant likelihood ratios for the diagnosis and exclusion of PE.

Cardiac inflammation contributes to right ventricular dysfunction following experimental pulmonary embolism in rats

Acute right ventricular (RV) failure following pulmonary embolism (PE) is a strong predictor of poor clinical outcome. Present studies test for an association between RV failure from experimental PE, inflammation, and upregulated chemokine expression. Additional experiments test if neutrophil influx contributes to RV dysfunction. PE was induced in male rats by infusing 24 microm microspheres (right jugular vein) producing mild hypertension (1.3 million beads/100 g, PE1.3), or moderately severe hypertension (2.0 million beads/100 g, PE2.0). Additional rats served as vehicle sham (0.01% Tween 20, Veh). In vivo RV peak systolic pressures (RVPSP) increased significantly, and then declined following PE2.0 (51 +/- 1 mm Hg 2 h; 49 +/- 1, 6 h; 44 +/- 1, 18 h). RV generated pressure of isolated, perfused hearts was significantly reduced in PE2.0 compared with PE1.3 or Veh. MCP-1 protein (ELISA) was elevated 21-fold and myeloperoxidase activity 95-fold in RV of PE2.0 compared with Veh or PE1.3. CINC-1, CINC-2, MIP-2, MCP-1, and MIP-1alpha mRNA also increased in RV of PE2.0. Histological analysis revealed massive accumulation of neutrophils (selective esterase stain) and monocyte/macrophages (CD68, ED-1) in RV of PE2.0 hearts in regions of myocyte damage. Electron microscopy showed myocyte necrosis and phagocytosis by inflammatory cells. LV function was normal and did not show increased inflammation after PE2.0. Treatment with anti-PMN antibody reduced RV MPO activity and prevented RV dysfunction. Conclusions-PE with moderately severe pulmonary hypertension (PE2.0) resulted in selective RV dysfunction, which was associated with increased chemokine expression, and infiltration of both neutrophils and monocyte/macrophages, indicating that a robust immune response occurred with RV damage following experimental PE. Experimental agranulocytosis reduced RV, suggesting that neutrophil influx contributed to RV damage.