Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation

Oxidative stress activates the TRPM2-Ca2+-NLRP3 axis to promote PM2.5-induced lung injury of mice

PM_2.5, a main particulate air pollutant, poses a serious hazard to human health. The exposure to PM_2.5 increases mortality and morbidity of many respiratory diseases such as asthma, chronic obstructive pulmonary diseases and even lung cancer. The contribution of reactive oxygen species (ROS) in the PM_2.5-induced acute lung injury process was confirmed in our previous research, but the molecular mechanism based for it remains unclarified. In this research, ROS-induced lung injury after exposure to PM_2.5 was explored in vivo and in vitro. The in vivo study indicated that N-acetyl-L-cysteine (NAC) could attenuate the accumulation of inflammatory cells, the thickening of alveolar wall and the degree of lung injury. Furthermore, we found ROS could regulate the intracellular Ca²⁺ level, expression of the Transient Receptor Potential Melastatin 2 (TRPM2), NLRP3 and its downstream inflammatory factors in vivo. In vitro experiments with A549 cells and primary type II alveolar epithelium cells (SD cells) showed that ROS induced by PM_2.5 exposure could mediate intracellular Ca²⁺ mobilization via TRPM2, with a subsequent activation of NLRP3. In our present study, we demonstrated the contribution of the ROS-TRPM2-Ca²⁺-NLRP3 pathway in PM_2.5-induced acute lung injury and offered a potential therapeutical target valid for related pathology.

Particulate Matter Decreases Intestinal Barrier-Associated Proteins Levels in 3D Human Intestinal Model

(1) Background: The gastrointestinal tract (GI) tract is one of the main organs exposed to particulate matter (PM) directly through ingestion of contaminated food or indirectly through inhalation. Previous studies have investigated the effects of chronic PM exposure on intestinal epithelia in vitro using Caco-2 cells and in vivo using mice. In this study, we hypothesized that chronic PM exposure would increase epithelial permeability and decrease barrier function due to altered redox homeostasis, which alters levels and/or localization of barrier-associated proteins in human three-dimensional (3D) intestinal tissues. (2) Methods: Transepithelial electrical resistance (TEER) in tissues exposed to 50, 100, 150, 250, and 500 µg/cm² of PM for 1 week and 2 weeks was analyzed. Levels and localization of tight junction proteins zonula occludens protein 1 (ZO-1) and claudin-1 and desmosome-associated desmocollin were analyzed using immunofluorescence. As a marker of oxidative stress, levels of 4-hydroxy-nonenal (4HNE) adducts were measured. (3) Results: No differences in TEER measurements were observed between exposed and un-exposed tissues. However, increased levels of 4HNE adducts in exposed tissues were observed. Additionally, decreased levels of ZO-1, claudin-1, and desmocollin were demonstrated. (4) Conclusion: These data suggest that chronic PM exposure results in an increase of oxidative stress; modified levels of barrier-associated proteins could possibly link to GI tract inflammatory conditions.

Calpain proteolytic systems counteract endothelial cell adaptation to inflammatory environments

Vascular endothelial cells (ECs) make up the innermost surface of arteries, veins, and capillaries, separating the remaining layers of the vessel wall from circulating blood. Under non-inflammatory conditions, ECs are quiescent and form a robust barrier structure; however, exposure to inflammatory stimuli induces changes in the expression of EC proteins that control transcellular permeability and facilitate angiogenic tube formation. Increasing evidence suggests that dysfunction in intracellular proteolytic systems disturbs EC adaptation to the inflammatory environment, leading to vascular disorders such as atherosclerosis and pathological angiogenesis. Recent work has highlighted the contribution of the calpain–calpastatin stress-responsive intracellular proteolytic system to adaptation failure in ECs. In this review, we summarize our current knowledge of calpain–calpastatin-mediated physiologic and pathogenic regulation in ECs and discuss the molecular basis by which disruption of this system perturbs EC adaptation to the inflammatory environment.

Traffic-related particulate matter affects behavior, inflammation, and neural integrity in a developmental rodent model

Recent studies indicate that exposure to airborne particulate matter (PM) is associated with cognitive delay, depression, anxiety, autism, and neurodegenerative diseases; however, the role of PM in the etiology of these outcomes is not well-understood. Therefore, there is a need for controlled animal studies to better elucidate the causes and mechanisms by which PM impacts these health outcomes. We assessed the effects of gestational and early life exposure to traffic-related PM on social- and anxiety-related behaviors, cognition, inflammatory markers, and neural integrity in juvenile male rats. Gestating and lactating rats were exposed to PM from a Boston (MA, USA) traffic tunnel for 5 h/day, 5 days/week for 6 weeks (3 weeks gestation, 3 weeks lactation). The target exposure concentration for the fine fraction of nebulized PM, measured as PM2.5, was 200 μg/m3. To assess anxiety and cognitive function, F1 male juveniles underwent elevated platform, cricket predation, nest building, social behavior and marble burying tests at 32-60 days of age. Upon completion of behavioral testing, multiple cytokines and growth factors were measured in these animals and their brains were analyzed with diffusion tensor MRI to assess neural integrity. PM exposure had no effect on litter size or weight, or offspring growth; however, F1 litters developmentally exposed to PM exhibited significantly increased anxiety (p = 0.04), decreased cognition reflected in poorer nest-organization (p = 0.04), and decreased social play and allogrooming (p = 0.003). MRI analysis of ex vivo brains revealed decreased structural integrity of neural tissues in the anterior cingulate and hippocampus in F1 juveniles exposed to PM (p < 0.01, p = 0.03, respectively). F1 juvenile males exposed to PM also exhibited significantly decreased plasma levels of both IL-18 (p = 0.03) and VEGF (p = 0.04), and these changes were inversely correlated with anxiety-related behavior. Chronic exposure of rat dams and their offspring to traffic-related PM during gestation and lactation decreases social behavior, increases anxiety, impairs cognition, decreases levels of inflammatory and growth factors (which are correlated with behavioral changes), and disrupts neural integrity in the juvenile male offspring. Our findings add evidence that exposure to traffic-related air pollution during gestation and lactation is involved in the etiology of autism spectrum disorder and other disorders which include social and cognitive deficits and/or increased anxiety.

Inhibitory functions of maslinic acid on particulate matter-induced lung injury through TLR4-mTOR-autophagy pathways

Particulate matter (PM), the collection of all liquid and solid particles suspended in air, includes both organic and inorganic particles, many of which are health-hazards. PM particles with a diameter equal to or less than 2.5 μm (PM_2.5) is a form of air pollutant that causes significant lung damage when inhaled. Maslinic acid (MA) prevents oxidative stress and pro-inflammatory cytokine generation, but there is little information available regarding its role in PM-induced lung injury. Therefore, the purpose of this study was to determine the protective activity of MA against PM_2.5-induced lung injury. The mice were divided into seven groups (n = 10 each): a mock control group, an MA control (0.8 mg/kg mouse body weight) group, an opted PM_2.5 produced from diesel (10 mg/kg mouse body weight) group, a diesel PM_2.5+MA (0.2, 0.4, 0.6, and 0.8 mg/kg mouse body weight) groups. Mice were treated with MA via tail-vein injection 30 min after the intratracheal instillation of a diesel PM_2.5. Changes in the wet/dry weight ratio of the lung tissue, total protein/total cell and lymphocyte counts, inflammatory cytokines in the bronchoalveolar lavage fluid (BALF), vascular permeability, and histology were monitored in diesel PM_2.5-treated mice. The results showed that MA reduced pathological lung injury, the wet/dry weight ratio of the lung tissue, and hyperpermeability caused by diesel PM_2.5. MA also inhibited diesel PM_2.5-induced myeloperoxidase (MPO) activity in the lung tissue, decreased the levels of diesel PM_2.5-induced inflammatory cytokines, including tumor necrosis factor (TNF)-α and interleukin (IL)-1β, reduced nitric oxide (NO) and total protein in the BALF, and effectively attenuated diesel PM_2.5-induced increases in the number of lymphocytes in the BALF. In addition, MA increased the protein phosphorylation of the mammalian target of rapamycin (mTOR) and dramatically suppressed diesel PM_2.5-stimulated expression of toll-like receptor 4 (TLR4), MyD88, and the autophagy-related proteins LC3 II and Beclin 1. In conclusion, these findings indicate that MA has a critical anti-inflammatory effect due to its ability to regulate both the TLR4-MyD88 and mTOR-autophagy pathways and may thus be a potential therapeutic agent against diesel PM_2.5-induced lung injury.

New Approach Methods to Evaluate Health Risks of Air Pollutants: Critical Design Considerations for In Vitro Exposure Testing

Air pollution consists of highly variable and complex mixtures recognized as major contributors to morbidity and mortality worldwide. The vast number of chemicals, coupled with limitations surrounding epidemiological and animal studies, has necessitated the development of new approach methods (NAMs) to evaluate air pollution toxicity. These alternative approaches include in vitro (cell-based) models, wherein toxicity of test atmospheres can be evaluated with increased efficiency compared to in vivo studies. In vitro exposure systems have recently been developed with the goal of evaluating air pollutant-induced toxicity; though the specific design parameters implemented in these NAMs-based studies remain in flux. This review aims to outline important design parameters to consider when using in vitro methods to evaluate air pollutant toxicity, with the goal of providing increased accuracy, reproducibility, and effectiveness when incorporating in vitro data into human health evaluations. This review is unique in that experimental considerations and lessons learned are provided, as gathered from first-hand experience developing and testing in vitro models coupled to exposure systems. Reviewed design aspects include cell models, cell exposure conditions, exposure chambers, and toxicity endpoints. Strategies are also discussed to incorporate in vitro findings into the context of in vivo toxicity and overall risk assessment.

Exosomes derived from HeLa cells break down vascular integrity by triggering endoplasmic reticulum stress in endothelial cells

Exosomes play a critical role in intercellular communication since they contain signalling molecules and genetic materials. During tumorigenesis, tumour-derived exosomes have been demonstrated to promote tumour angiogenesis and metastasis. However, how the exosomes facilitate tumour metastasis is not clear. Here we explored the effect of HeLa cell-derived exosomes (Exo^HeLa) on endothelial tight junctions (TJ) and the related mechanisms. After human umbilical vein endothelial cells (HUVEC) were treated with Exo^HeLa, TJ proteins zonula occludens-1 (ZO-1) and Claudin-5 in HUVEC were significantly reduced as compared with that treated with exosomes from human cervical epithelial cells, while mRNA levels of ZO-1 and Claudin-5 remained unchanged. Consequently, permeability of endothelial monolayer was increased after the treatment with Exo^HeLa. Injection of Exo^HeLa into mice also increased vascular permeability and tumour metastasis in vivo. Neither knocking down of Dicer nor use of inhibitors of microRNAs targeting at mRNAs of ZO-1 and Claudin-5 could block the inhibitory effect of Exo^HeLa on ZO-1 and Claudin-5. The expression of genes involved in endoplasmic reticulum (ER) stress was significantly increased in HUVECs after treated with Exo^HeLa. Inhibition of ER stress by knocking down protein kinase RNA-like endoplasmic reticulum kinase prevented the down-regulation of ZO-1 and Claudin-5 by Exo^HeLa. Our study found that HeLa cell-derived exosomes promote metastasis by triggering ER stress in endothelial cells and break down endothelial integrity. Such effect of exosomes is microRNA-independent.

Oral Co-Exposures to zinc oxide nanoparticles and CdCl2 induced maternal-fetal pollutant transfer and embryotoxicity by damaging placental barriers

Synergistic toxicity from multiple environmental pollutants poses greater threat to humans, especially to susceptible pregnant population. Here we evaluated combined toxicity from environment pollutants zinc oxide nanoparticles (ZnO NPs) and cadmium chloride (CdCl₂) using two pregnant mice models established by oral administration during peri-implantation or organogenesis period. We found that exposures to combined pollutants only at organogenesis stage induced higher fetal deformity rate compared to co-exposures at peri-implantation stage. We further discovered that surface charge of ZnO NPs were modified after Cd²⁺ adsorption and the resulting nanoadducts caused more severe damages in placental barriers by causing shed endothelial cells and decreased expressions of tight junction proteins ZO1, occludin, claudin-4 and claudin-8. These cellular and molecular events enhanced maternal-fetal transfer of both pollutants and aggravated embryotoxicity. Our findings help elucidate synergistic embryotoxicity by nanoparticle/pollutant adducts and establish proper safety criteria for pregnant population in an era that nanotechnology-based products are widely used.

Particulate Matter 2.5 Causes Deficiency in Barrier Integrity in Human Nasal Epithelial Cells

Purpose

The effect of air pollution-related particulate matter (PM) on epithelial barrier function and tight junction (TJ) expression in human nasal mucosa has not been studied to date. This study therefore aimed to assess the direct impact of PM with an aerodynamic diameter less than 2.5 μm (PM2.5) on the barrier function and TJ molecular expression of human nasal epithelial cells.

Methods

Air-liquid interface cultures were established with epithelial cells derived from noninflammatory nasal mucosal tissue collected from patients undergoing paranasal sinus surgery. Confluent cultures were exposed to 50 or 100 µg/mL PM2.5 for up to 72 hours, and assessed for 1) epithelial barrier integrity as measured by transepithelial resistance (TER) and permeability of fluorescein isothiocyanate (FITC) 4 kDa; 2) expression of TJs using real-time quantitative polymerase chain reaction and immunofluorescence staining, and 3) proinflammatory cytokines by luminometric bead array or enzyme-linked immunosorbent assay.

Results

Compared to control medium, 50 and/or 100 µg/mL PM2.5-treatment 1) significantly decreased TER and increased FITC permeability, which could not be restored by budesonide pretreatment; 2) significantly decreased the expression of claudin-1 messenger RNA, claudin-1, occludin and ZO-1 protein; and 3) significantly increased production of the cytokines interleukin-8, TIMP metallopeptidase inhibitor 1 and thymic stromal lymphopoietin.

Conclusions

Exposure to PM2.5 may lead to loss of barrier function in human nasal epithelium through decreased expression of TJ proteins and increased release of proinflammatory cytokines. These results suggest an important mechanism of susceptibility to rhinitis and rhinosinusitis in highly PM2.5-polluted areas.

Polyhexamethylene Guanidine Phosphate Damages Tight Junctions and the F-Actin Architecture by Activating Calpain-1 via the P2RX7/Ca2+ Signaling Pathway

Polyhexamethylene guanidine phosphate (PHMG-p), a member of the polymeric guanidine family, has strong antimicrobial activity and may increase the risk of inflammation-associated pulmonary fibrosis. However, the effect of PHMG-p on the barrier function of the bronchial epithelium is unknown. Epithelial barrier functioning is maintained by tight junctions (TJs); damage to these TJs is the major cause of epithelial barrier breakdown during lung inflammation. The present study showed that, in BEAS-2B human bronchial epithelial cells, exposure to PHMG-p reduced the number of TJs and the E-cadherin level and impaired the integrity of the F-actin architecture. Furthermore, exposure to PHMG-p stimulated the calcium-dependent protease calpain-1, which breaks down TJs. However, treatment with the calpain-1 inhibitor, ALLN, reversed the PHMG-p-mediated impairment of TJs and the F-actin architecture. Furthermore, exposure to PHMG-p increased the intracellular Ca²⁺ level via P2X purinoreceptor 7 (P2RX7) and inhibition of P2RX7 abolished the PHMG-p-induced calpain-1 activity and protein degradation and increased the intracellular Ca²⁺ level. Although exposure to PHMG-p increased the extracellular ATP level, hydrolysis of extracellular ATP by apyrase did not influence its detrimental effect on bronchial epithelial cells. These results implicate the impairment of TJs and the F-actin architecture in the pathogenesis of pulmonary diseases.

Reactive Oxygen Species-Dependent Calpain Activation Contributes to Airway and Pulmonary Vascular Remodeling in Chronic Obstructive Pulmonary Disease

Aims: Airway and pulmonary vascular remodeling is an important pathological feature in the pathogenesis of chronic obstructive pulmonary disease (COPD). Tobacco smoke (TS) induces the production of large amounts of reactive oxygen species (ROS) in COPD lungs. We investigated how ROS lead to airway and pulmonary vascular remodeling in COPD. Results: We used in vitro bronchial and pulmonary artery smooth muscle cells (BSMCs and PASMCs), in vivo TS-induced COPD rodent models, and lung tissues of COPD patients. We found that H2O2 and TS extract (TSE) induced calpain activation in BSMCs and PASMCs. Calpain activation was elevated in smooth muscle of bronchi and pulmonary arterioles in COPD patients and TS-induced COPD rodent models. Calpain inhibition attenuated H2O2- and TSE-induced collagen synthesis and proliferation of BSMCs and PASMCs. Exposure to TS causes increases in airway resistance, right ventricular systolic pressure (RVSP), and thickening of bronchi and pulmonary arteries. Calpain inhibition by smooth muscle-specific knockout of calpain and the calpain inhibitor MDL28170 attenuated increases in airway resistance, RVSP, and thickening of bronchi and pulmonary arteries. Moreover, smooth muscle-specific knockout of calpain did not reduce TS-induced emphysema in the mouse model, but MDL28170 did reduce TS-induced emphysema in the rat model. Innovation: This study provides the first evidence that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling in TS-induced COPD. Calpain might be a novel therapeutic target for the treatment of COPD. Conclusion: These results indicate that ROS-induced calpain activation contributes to airway and pulmonary vascular remodeling and pulmonary hypertension in COPD.

TRPM2 channel: A novel target for alleviating ischaemia-reperfusion, chronic cerebral hypo-perfusion and neonatal hypoxic-ischaemic brain damage

The transient receptor potential melastatin-related 2 (TRPM2) channel, a reactive oxygen species (ROS)-sensitive cation channel, has been well recognized for being an important and common mechanism that confers the susceptibility to ROS-induced cell death. An elevated level of ROS is a salient feature of ischaemia-reperfusion, chronic cerebral hypo-perfusion and neonatal hypoxia-ischaemia. The TRPM2 channel is expressed in hippocampus, cortex and striatum, the brain regions that are critical for cognitive functions. In this review, we examine the recent studies that combine pharmacological and/or genetic interventions with using in vitro and in vivo models to demonstrate a crucial role of the TRPM2 channel in brain damage by ischaemia-reperfusion, chronic cerebral hypo-perfusion and neonatal hypoxic-ischaemia. We also discuss the current understanding of the underlying TRPM2-dependent cellular and molecular mechanisms. These new findings lead to the hypothesis of targeting the TRPM2 channel as a potential novel therapeutic strategy to alleviate brain damage and cognitive dysfunction caused by these conditions.

Methylglyoxal Disrupts Paranodal Axoglial Junctions via Calpain Activation

Nodes of Ranvier and associated paranodal and juxtaparanodal domains along myelinated axons are essential for normal function of the peripheral and central nervous systems. Disruption of these domains as well as increases in the reactive carbonyl species methylglyoxal are implicated as a pathophysiology common to a wide variety of neurological diseases. Here, using an ex vivo nerve exposure model, we show that increasing methylglyoxal produces paranodal disruption, evidenced by disorganized immunostaining of axoglial cell-adhesion proteins, in both sciatic and optic nerves from wild-type mice. Consistent with previous studies showing that increase of methylglyoxal can alter intracellular calcium homeostasis, we found upregulated activity of the calcium-activated protease calpain in sciatic nerves after methylglyoxal exposure. Methylglyoxal exposure altered clusters of proteins that are known as calpain substrates: ezrin in Schwann cell microvilli at the perinodal area and zonula occludens 1 in Schwann cell autotypic junctions at paranodes. Finally, treatment with the calpain inhibitor calpeptin ameliorated methylglyoxal-evoked ezrin loss and paranodal disruption in both sciatic and optic nerves. Our findings strongly suggest that elevated methylglyoxal levels and subsequent calpain activation contribute to the disruption of specialized axoglial domains along myelinated nerve fibers in neurological diseases.

Particulate matter disrupts airway epithelial barrier via oxidative stress to promote Pseudomonas aeruginosa infection

Background

Airborne particulate matter (PM) is associated with increasing susceptibility to respiratory bacterial infection. Tight junctions (TJs) are protein complexes that form airway epithelial barrier against infection. This study aimed to investigate the effects of PM on the airway TJs in response to infection.

Methods

The cytotoxicity of PM to BEAS-2B was evaluated. The reactive oxygen species (ROS) production was measured by the flow cytometry. Colony forming units (CFUs) assay and confocal microscopy were utilized to evaluate the number of bacteria. Immunofluorescence and western blot assay were conducted to detect the expressions of TJs proteins. Animal models were used to investigate the role of TJs in PM-induced lung injury upon bacterial infection.

Results

In vitro, PM decreased cell viability, increased ROS production, and increased the number of intracellular bacteria accompanying by the degradation of TJs. N-acetylcysteine (NAC) significantly reversed the PM-induced bacterial invasion and PM-induced disruption of TJs. In vivo, PM increases bacteria-infected lung injury, lung bacteria burden and blood bacterial dissemination, which was closely correlated to the degradation of TJs.

Conclusions

PM disrupts TJs via oxidative stress to promote bacterial infection.

Fine particulate matter (PM2.5) inhibits ciliogenesis by increasing SPRR3 expression via c-Jun activation in RPE cells and skin keratinocytes

Exposure to fine particulate matter (PM) with diameter <2.5 µm (PM2.5) causes epithelium injury and endothelial dysfunction. Primary cilia are sensory organelles that transmit extracellular signals into intracellular biochemical responses and have roles in physiology. To date, there have been no studies investigating whether PM2.5 affects primary cilia in skin. We addressed this in the present study using normal human epidermal keratinocytes (NHEKs) and retinal pigment epithelium (RPE) cells. We found that formation of primary cilium is increased in differentiated NHEKs. However, treatment with PM2.5 blocked increased ciliogenesis in NHEKs and RPE cells. Furthermore, PM2.5 transcriptionally upregulated small proline rich protein 3 (SPRR3) expression by activating c-Jun, and ectopic expression of SPRR3 inhibits suppressed the ciliogenesis. Accordingly, treatment with c-Jun activator (anisomycin) induced SPRR3 expression, whereas the inhibitor (SP600125) recovered the ciliated cells and cilium length in PM2.5-treated cells. Moreover, c-Jun inhibitor suppressed upregulation of SPRR3 in PM2.5-treated cells. Taken together, our finding suggested that PM2.5 inhibits ciliogenesis by increasing SPRR3 expression via c-Jun activation in RPE cells and keratinocytes.

Indoor nanoscale particulate matter-induced coagulation abnormality based on a human 3D microvascular model on a microfluidic chip

BACKGROUND

A growing body of evidence shows that indoor concentrations of airborne particles are often higher than is typically encountered outdoors. Since exposure to indoor PM2.5 is thought to be associated with cardiovascular disease, the health impacts of indoor air pollution need to be explored. Based on animal models, ambient particulate matter has been proved to promote coagulation which is very likely involved in the pathogenic development of cardiovascular disease. However, animal models are insufficient to predict what will happen with any certainty in humans. For this reason, the precise pathogenic mechanisms behind the development of cardiovascular disease in humans have not yet been determined.

RESULTS

We generated a 3D functional human microvascular network in a microfluidic device. This model enables human vascular endothelial cells to form tissue-like microvessels that behave very similarly to human blood vessels. The perfusable microvasculature allows the delivery of particles introduced into these generated human-like microvessels to follow the fluid flow. This exposure path effectively simulates the dynamic movement of airborne nanoscale particles (ANPs) within human vessels. In this study, we first identified the existence of ANPs in indoor air pollution. We then showed that ANPs could activate endothelial cells via ROS induced inflammation, and further resulted in abnormal expression of the coagulation factors (TF, TM and t-PA) involved in coagulation cascades. In addition, we found that a protein could cover ANPs, and this biointeraction could interfere with heparan sulfate (HS). Human organotypic 3D microvessel models provide a bridge for how research outcomes can translate to humans.

CONCLUSIONS

The 3D human microvessel model was used to determine the physiological responses of human vessels to ANP stimulation. Based on the obtained data, we concluded that ANPs not only disrupts normal coagulation functions, but also act directly on anticoagulant factors in human vessels. These experimental observations provide a potential biological explanation for the epidemiologically established link between ANPs and coagulation abnormality. This organ-on-chip model may provide a bridge from in vitro results to human responses.

Sphingolipids Signaling in Lamellipodia Formation and Enhancement of Endothelial Barrier Function

Sphingolipids, first described in the brain in 1884, are important structural components of biological membranes of all eukaryotic cells. In recent years, several lines of evidence support the critical role of sphingolipids such as sphingosine, sphingosine-1-phosphate (S1P), and ceramide as anti- or pro-inflammatory bioactive lipid mediators in a variety of human pathologies including pulmonary and vascular disorders. Among the sphingolipids, S1P is a naturally occurring agonist that exhibits potent barrier enhancing property in the endothelium by signaling via G protein-coupled S1P1 receptor. S1P, S1P analogs, and other barrier enhancing agents such as HGF, oxidized phospholipids, and statins also utilize the S1P/S1P1 signaling pathway to generate membrane protrusions or lamellipodia, which have been implicated in resealing of endothelial gaps and maintenance of barrier integrity. A better understanding of sphingolipids mediated regulation of lamellipodia formation and barrier enhancement of the endothelium will be critical for the development of sphingolipid-based therapies to alleviate pulmonary disorders such as sepsis-, radiation-, and mechanical ventilation-induced acute lung injury.

Airborne particulate matter increases MUC5AC expression by downregulating Claudin-1 expression in human airway cells

CLB_2.0, a constituent of PM, induces secretion of multiple cytokines and chemokines that regulate airway inflammation. Specifically, IL-6 upregulates CLB_2.0-induced MUC5AC and MUC1 expression. Interestingly, of the tight junction proteins examined, claudin-1 expression was inhibited by CLB_2.0. While the overexpression of claudin-1 decreased CLB_2.0-induced MUC5AC expression, it increased the expression of the anti-inflammatory mucin, MUC1. CLB_2.0-induced IL-6 secretion was mediated by ROS. The ROS scavenger N-acetylcysteine inhibited CLB_2.0-induced IL-6 secretion, thereby decreasing the CLB_2.0-induced MUC5AC expression, whereas CLB_2.0-induced MUC1 expression increased. CLB_2.0 activated the ERK1/2 MAPK via a ROS-dependent pathway. ERK1/2 downregulated the claudin-1 and MUC1 expressions, whereas it dramatically increased CLB_2.0-induced MUC5AC expression. These findings suggest that CLB_2.0-induced ERK1/2 activation acts as a switch for regulating inflammatory conditions though a ROS-dependent pathway. Our data also suggest that secreted IL-6 regulates CLB_2.0-induced MUC5AC and MUC1 expression via ROS-mediated downregulation of claudin-1 expression to maintain mucus homeostasis in the airway.

Association of polycyclic aromatic hydrocarbons exposure with atherosclerotic cardiovascular disease risk: A role of mean platelet volume or club cell secretory protein

BACKGROUND

Inflammation may play an important role in the association between exposure to polycyclic aromatic hydrocarbons (PAHs) and atherosclerotic cardiovascular disease (ASCVD) risk. However, the underlying mechanisms remain unclear.

OBJECTIVES

To investigate the association of PAHs exposure with ASCVD risk and effects of mean platelet volume (MPV) or Club cell secretory protein (CC16) on the association.

METHODS

A total of 2022 subjects (689 men and 1333 women) were drawn from the baseline Wuhan residents of the Wuhan-Zhuhai Cohort study. Data on demography and the physical examination were obtained from each participant. Urinary monohydroxy PAH metabolites (OH-PAHs) levels were measured by a gas chromatography-mass spectrometry. We estimated the association between each OH-PAHs and the 10-year ASCVD risk or coronary heart disease (CHD) risk using logistic regression models, and further analyze the mediating effect of MPV or plasma CC16 on the association by using structural equation modeling.

RESULTS

The results of multiple logistic regression models showed that some OH-PAHs were positively associated with ASCVD risk but not CHD risk, including 2-hydroxyfluoren (β = 1.761; 95% CI: 1.194-2.597), 9-hydroxyfluoren (β = 1.470; 95% CI: 1.139-1.898), 1-hydroxyphenanthrene (β = 1.480; 95% CI: 1.008-2.175) and ΣOH-PAHs levels (β = 1.699; 95% CI: 1.151-2.507). The analysis of structural equation modeling shows that increased MPV and increased plasma CC16 levels contributed 13.6% and 15.1%, respectively, to the association between PAHs exposure and the 10-year ASCVD risk (p < 0.05).

CONCLUSIONS

Exposure to PAHs may increase the risk of atherosclerosis, which was partially mediated by MPV or CC16.

PM2.5-induced oxidative stress increases intercellular adhesion molecule-1 expression in lung epithelial cells through the IL-6/AKT/STAT3/NF-κB-dependent pathway

BACKGROUND

Epidemiological studies have shown that ambient air pollution is closely associated with increased respiratory inflammation and decreased lung function. Particulate matters (PMs) are major components of air pollution that damages lung cells. However, the mechanisms remain to be elucidated. This study examines the effects of PMs on intercellular adhesion molecule-1 (ICAM-1) expression and the related mechanisms in vitro and in vivo.

RESULT

The cytotoxicity, reactive oxygen species (ROS) generation, and monocyte adherence to A549 cells were more severely affected by treatment with O-PMs (organic solvent-extractable fraction of SRM1649b) than with W-PMs (water-soluble fraction of SRM1649b). We observed a significant increase in ICAM-1 expression by O-PMs, but not W-PMs. O-PMs also induced the phosphorylation of AKT, p65, and STAT3. Pretreating A549 cells with N-acetyl cysteine (NAC), an antioxidant, attenuated O-PMs-induced ROS generation, the phosphorylation of the mentioned kinases, and the expression of ICAM-1. Furthermore, an AKT inhibitor (LY294002), NF-κB inhibitor (BAY11-7082), and STAT3 inhibitor (Stattic) significantly down-regulated O-PMs-induced ICAM-1 expression as well as the adhesion of U937 cells to epithelial cells. Interleukin-6 (IL-6) was the most significantly changed cytokine in O-PMs-treated A549 cells according to the analysis of the cytokine antibody array. The IL-6 receptor inhibitor tocilizumab (TCZ) and small interfering RNA for IL-6 significantly reduced ICAM-1 secretion and expression as well as the reduction of the AKT, p65, and STAT3 phosphorylation in O-PMs-treated A549 cells. In addition, the intratracheal instillation of PMs significantly increased the levels of the ICAM-1 and IL-6 in lung tissues and plasma in WT mice, but not in IL-6 knockout mice. Pre-administration of NAC attenuated those PMs-induced adverse effects in WT mice. Furthermore, patients with chronic obstructive pulmonary disease (COPD) had higher plasma levels of ICAM-1 and IL-6 compared to healthy subjects.

CONCLUSION

These results suggest that PMs increase ICAM-1 expression in pulmonary epithelial cells in vitro and in vivo through the IL-6/AKT/STAT3/NF-κB signaling pathway.

Cardiovascular effects of air pollution

Air pollution is composed of particulate matter (PM) and gaseous pollutants, such as nitrogen dioxide and ozone. PM is classified according to size into coarse particles (PM₁₀), fine particles (PM_2.5) and ultrafine particles. We aim to provide an original review of the scientific evidence from epidemiological and experimental studies examining the cardiovascular effects of outdoor air pollution. Pooled epidemiological studies reported that a 10μg/m³ increase in long-term exposure to PM_2.5 was associated with an 11% increase in cardiovascular mortality. Increased cardiovascular mortality was also related to long-term and short-term exposure to nitrogen dioxide. Exposure to air pollution and road traffic was associated with an increased risk of arteriosclerosis, as shown by premature aortic and coronary calcification. Short-term increases in air pollution were associated with an increased risk of myocardial infarction, stroke and acute heart failure. The risk was increased even when pollutant concentrations were below European standards. Reinforcing the evidence from epidemiological studies, numerous experimental studies demonstrated that air pollution promotes a systemic vascular oxidative stress reaction. Radical oxygen species induce endothelial dysfunction, monocyte activation and some proatherogenic changes in lipoproteins, which initiate plaque formation. Furthermore, air pollution favours thrombus formation, because of an increase in coagulation factors and platelet activation. Experimental studies also indicate that some pollutants have more harmful cardiovascular effects, such as combustion-derived PM_2.5 and ultrafine particles. Air pollution is a major contributor to cardiovascular diseases. Promotion of safer air quality appears to be a new challenge in cardiovascular disease prevention.

Particulate matter disrupts human lung endothelial cell barrier integrity via Rho-dependent pathways

Increased exposure to ambient particulate matter (PM) is associated with elevated morbidity and mortality in patients with cardiopulmonary diseases and cancer. We and others have shown that PM induces lung microvascular barrier dysfunction which potentially enhances the systemic toxicity of PM. However, the mechanisms by which PM disrupts vascular endothelial integrity remain incompletely explored. We hypothesize that PM induces endothelial cell (EC) cytoskeleton rearrangement via Rho GTPase-dependent pathways to facilitate vascular hyperpermeability. Fine PM induced time-dependent activation of cytoskeletal machinery with increases in myosin light chain (MLC) phosphorylation and EC barrier disruption measured by transendothelial electrical resistance (TER), events attenuated by the Rho-dependent kinase (ROCK) inhibitor Y-27632 or the reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC). Both Y-27632 and NAC prevented PM-induced stress fiber formation and phospho-MLC accumulation in human lung ECs. PM promotes rapid accumulation of Rho-GTP. This event is attenuated by NAC or knockdown of RhoA (siRNA). Consistent with ROCK activation, PM induced phosphorylation of myosin light chain phosphatase (MYPT) at Thr850, a post-translational modification known to inhibit phosphatase activity. Furthermore, PM activates the guanine nucleotide exchange factor (GEF) for Rho, p115, with p115 translocation to the cell periphery, in a ROS-dependent manner. Together these results demonstrate that fine PM induces EC cytoskeleton rearrangement via Rho-dependent pathways that are dependent upon the generation of oxidative stress. As the disruption of vascular integrity further contributes to cardiopulmonary physiologic derangements, these findings provide pharmacologic targets for prevention of PM-induced cardiopulmonary toxicity.

Pneumococcal infection of respiratory cells exposed to welding fumes; Role of oxidative stress and HIF-1 alpha

Welders are more susceptible to pneumococcal pneumonia. The mechanisms are yet unclear. Pneumococci co-opt the platelet activating factor receptor (PAFR) to infect respiratory epithelial cells. We previously reported that exposure of respiratory cells to welding fumes (WF), upregulates PAFR-dependent pneumococcal infection. The signaling pathway for this response is unknown, however, in intestinal cells, hypoxia-inducible factor-1 α (HIF 1α) is reported to mediate PAFR-dependent infection. We sought to assess whether oxidative stress plays a role in susceptibility to pneumococcal infection via the platelet activating factor receptor. We also sought to evaluate the suitability of nasal epithelial PAFR expression in welders as a biomarker of susceptibility to infection. Finally, we investigated the generalisability of the effect of welding fumes on pneumococcal infection and growth using a variety of different welding fume samples. Nasal epithelial PAFR expression in welders and controls was analysed by flow cytometry. WF were collected using standard methodology. The effect of WF on respiratory cell reactive oxygen species production, HIF-1α expression, and pneumococcal infection was determined using flow cytometry, HIF-1α knockdown and overexpression, and pneumococcal infection assays. We found that nasal PAFR expression is significantly increased in welders compared with controls and that WF significantly increased reactive oxygen species production, HIF-1α and PAFR expression, and pneumococcal infection of respiratory cells. In unstimulated cells, HIF-1α knockdown decreased PAFR expression and HIF-1α overexpression increased PAFR expression. However, in knockdown cells pneumococcal infection was paradoxically increased and in overexpressing cells infection was unaffected. Nasal epithelial PAFR expression may be used as a biomarker of susceptibility to pneumococcal infection in order to target individuals, particularly those at high risk such as welders, for the pneumococcal vaccine. Expression of HIF-1α in unexposed respiratory cells inhibits basal pneumococcal infection via PAFR-independent mechanisms.

Redox-Dependent Calpain Signaling in Airway and Pulmonary Vascular Remodeling in COPD

The calcium-dependent cytosolic, neutral, thiol endopeptidases, calpains, perform limited cleavage of their substrates thereby irreversibly changing their functions. Calpains have been shown to be involved in several physiological processes such as cell motility, proliferation, cell cycle, signal transduction, and apoptosis. Overactivation of calpain or mutations in the calpain genes contribute to a number of pathological conditions including neurodegenerative disorders, rheumatoid arthritis, cancer, and lung diseases. High concentrations of reactive oxygen and nitrogen species (RONS) originated from cigarette smoke or released by numerous cell types such as activated inflammatory cells and other respiratory cells cause oxidative and nitrosative stress contributing to the pathogenesis of COPD. RONS and calpain play important roles in the development of airway and pulmonary vascular remodeling in COPD. Published data show that increased RONS production is associated with increased calpain activation and/or elevated calpain protein level, leading to epithelial or endothelial barrier dysfunction, neovascularization, lung inflammation, increased smooth muscle cell proliferation, and deposition of extracellular matrix protein. Further investigation of the redox-dependent calpain signaling may provide future targets for the prevention and treatment of COPD.

Attenuation of Blood-Brain Barrier Breakdown and Hyperpermeability by Calpain Inhibition

Blood-brain barrier (BBB) breakdown and the associated microvascular hyperpermeability followed by brain edema are hallmark features of several brain pathologies, including traumatic brain injuries (TBI). Recent studies indicate that pro-inflammatory cytokine interleukin-1β (IL-1β) that is up-regulated following traumatic injuries also promotes BBB dysfunction and hyperpermeability, but the underlying mechanisms are not clearly known. The objective of this study was to determine the role of calpains in mediating BBB dysfunction and hyperpermeability and to test the effect of calpain inhibition on the BBB following traumatic insults to the brain. In these studies, rat brain microvascular endothelial cell monolayers exposed to calpain inhibitors (calpain inhibitor III and calpastatin) or transfected with calpain-1 siRNA demonstrated attenuation of IL-1β-induced monolayer hyperpermeability. Calpain inhibition led to protection against IL-1β-induced loss of zonula occludens-1 (ZO-1) at the tight junctions and alterations in F-actin cytoskeletal assembly. IL-1β treatment had no effect on ZO-1 gene (tjp1) or protein expression. Calpain inhibition via calpain inhibitor III and calpastatin decreased IL-1β-induced calpain activity significantly (p < 0.05). IL-1β had no detectable effect on intracellular calcium mobilization or endothelial cell viability. Furthermore, calpain inhibition preserved BBB integrity/permeability in a mouse controlled cortical impact model of TBI when studied using Evans blue assay and intravital microscopy. These studies demonstrate that calpain-1 acts as a mediator of IL-1β-induced loss of BBB integrity and permeability by altering tight junction integrity, promoting the displacement of ZO-1, and disorganization of cytoskeletal assembly. IL-1β-mediated alterations in permeability are neither due to the changes in ZO-1 expression nor cell viability. Calpain inhibition has beneficial effects against TBI-induced BBB hyperpermeability.

Nonmuscle myosin light chain kinase activity modulates radiation-induced lung injury

Radiotherapy as a primary treatment for thoracic malignancies induces deleterious effects, such as acute or subacute radiation-induced lung injury (RILI). Although the molecular etiology of RILI is controversial and likely multifactorial, a potentially important cellular target is the lung endothelial cytoskeleton that regulates paracellular gap formation and the influx of macromolecules and fluid to the alveolar space. Here we investigate the central role of a key endothelial cytoskeletal regulatory protein, the nonmuscle isoform of myosin light chain kinase (nmMLCK), in an established murine RILI model. Our results indicate that thoracic irradiation significantly augmented nmMLCK protein expression and enzymatic activity in murine lungs. Furthermore, genetically engineered mice harboring a deletion of the nmMLCK gene (nmMLCK(-/-) mice) exhibited protection from RILI, as assessed by attenuated vascular leakage and leukocyte infiltration. In addition, irradiated wild-type mice treated with two distinct MLCK enzymatic inhibitors, ML-7 and PIK (peptide inhibitor of kinase), also demonstrated attenuated RILI. Taken together, these data suggests a key role for nmMLCK in vascular barrier regulation in RILI and warrants further examination of RILI strategies that target nmMLCK.

Exposure to concentrated ambient fine particulate matter disrupts vascular endothelial cell barrier function via the IL-6/HIF-1α signaling pathway

Exposure to concentrated ambient fine particulate matter (PM2.5) has been associated with cardiovascular diseases (CVDs). The barrier function of vascular endothelial cells is critical for the development of CVDs. Here, we employed human umbilical vein endothelial cells to clarify the function of ambient PM2.5 pollution in the regulation of membrane permeability of vascular endothelial cells. The results show that a high concentration of PM2.5, which mainly includes heavy metals and polycyclic aromatic hydrocarbons, induces barrier dysfunction of vascular endothelial cells. This was mediated in part by promoting IL‐6 expression, which then increases the transcriptional activity of HIF‐1α by promoting its translocation to the nucleus. Our findings indicate that concentrated PM2.5 can destroy membrane integrity and promote permeability in vascular endothelial cells, thereby contributing to the development of CVDs.

Sulfur Dioxide Contributes to the Cardiac and Mitochondrial Dysfunction in Rats

Epidemiological studies have demonstrated an association between sulfur dioxide (SO2) and an increase of morbidity and mortality of cardiovascular diseases, such as ischemic heart disease, heart failure, and arrhythmia. Mitochondrion is the most sensitive organelle in myocardium of animals exposed to SO2 Here we study the molecular characterization of mitochondrial dysfunction in cardiac muscles of rat after SO2 exposure. We found that the cytochrome c oxidase (COX) activity, mitochondrial membrane potential (ΔΨm), ATP contents, mitochondrial DNA (mtDNA) contents, and mRNA expression of complexes IV and V subunits encoded by mtDNA were decreased after NaHSO3 treatment in vitro or SO2 inhalation in vivo The mitochondrial dysfunctions were accompanied by depressions of co-activator of peroxisome proliferator activated receptor gamma (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A (TFAM) mRNA and protein. We observed swollen mitochondria and lower amounts of cristae in hearts of rats after 3.5 mg/m(3) SO2 inhalation for 30 days. Interestingly, NaHSO3 induced mitochondrial dysfunctions marked by ΔΨm and ATP reduction could be inhibited by an antioxidant N-acetyl-L-cysteine (NALC), accompanied by the restoration of transcriptional factors expressions. The cardiac mitochondrial dysfunctions could also be alleviated by overexpression of TFAM. SO2 induced abnormal left ventricular function was restored by NALC in vivo Our findings demonstrate that SO2 induces cardiac and mitochondrial dysfunction. And inhibition of reactive oxygen species and enhancing the transcriptional network controlling mitochondrial biogenesis can mitigate the SO2-induced mitochondrial dysfunction.

Predilection of contralateral upper lung metastasis in upper lobe lung adenocarcinoma patients

BACKGROUND

Lung cancer with lung to lung metastasis is common. The objective of this study was to investigate the association among the distribution of contralateral lung metastases versus primary lung tumor location, clinical characteristics, and epidermal growth factor receptor (EGFR) mutations status.

METHODS

The study included treatment-naïve stage IV lung adenocarcinoma with contralateral lung metastases from 2012 through 2013.

RESULTS

In total, 103 patients were enrolled after excluding lung cancer with histology other than adenocarcinoma, synchronous multiple primary lung cancers, or other active malignancy. The median age was 65 years (range, 28-93 years); 47 male patients (45.6%); 69 non-smoker (NS) patients (67.0%); 68 Eastern Cooperative Oncology Group performance status (ECOG PS) 0-1 patients (66.0%); 38 M1a patients (38.9%); and 60 EGFR mutation patients (58.3%). There were 51 cases (49.5%) with primary lung cancer located over upper lobes. Among them, 36 (70.6%) had contralateral upper lung predominance metastasis, 9 (17.6%) had lower lung predominance, and 6 (11.8%) had equal distribution. Among the 52 lower lobe tumors, 17 (32.7%), 19 (36.5%), and 16 (30.8%) had upper, lower lung predominance, and equal distribution metastasis, respectively. Univariate analysis showed only male gender and primary tumor location over upper lobes were significantly associated with contralateral upper lung predominance metastases. After multivariate analysis, only primary tumor location over upper lobes was significantly associated with contralateral upper lung predominance metastases (adjusted OR 5.49, 95% CI, 2.15-14.03, P<0.001).

CONCLUSIONS

Upper lobe lung adenocarcinoma was significantly associated with contralateral upper lung predominance metastases. Further research is needed to elucidate the mechanisms underlying this phenomenon.

Pulmonary instillation of MWCNT increases lung permeability, decreases gp130 expression in the lungs, and initiates cardiovascular IL-6 transsignaling

Pulmonary instillation of multiwalled carbon nanotubes (MWCNT) has the potential to promote cardiovascular derangements, but the mechanisms responsible are currently unclear. We hypothesized that exposure to MWCNT would result in increased epithelial barrier permeability by 24 h postexposure and initiate a signaling process involving IL-6/gp130 transsignaling in peripheral vascular tissue. To test this hypothesis we assessed the impact of 1 and 10 μg/cm(2) MWCNT on transepithelial electrical resistance (TEER) and expression of barrier proteins and cell activation in vitro using normal human bronchial epithelial primary cells. Parallel studies using male Sprague-Dawley rats instilled with 100 μg MWCNT measured bronchoalveolar lavage (BAL) differential cell counts, BAL fluid total protein, and lung water-to-tissue weight ratios 24 h postexposure and quantified serum concentrations of IL-6, soluble IL-6r, and soluble gp130. Aortic sections were examined immunohistochemically for gp130 expression, and gp130 mRNA/protein expression was evaluated in rat lung, heart, and aortic tissue homogenates. Our in vitro findings indicate that 10 μg/cm(2) MWCNT decreased the development of TEER and zonula occludens-1 expression relative to the vehicle. In rats MWCNT instillation increased BAL protein, lung water, and induced pulmonary eosinophilia. Serum concentrations of soluble gp130 decreased, aortic endothelial expression of gp130 increased, and expression of gp130 in the lung was downregulated in the MWCNT-exposed group. We propose that pulmonary exposure to MWCNT can manifest as a reduced epithelial barrier and activator of vascular gp130-associated transsignaling that may promote susceptibility to cardiovascular derangements.

The Effect of Therapeutic Blockades of Dust Particles-Induced Ca²⁺ Signaling and Proinflammatory Cytokine IL-8 in Human Bronchial Epithelial Cells

Bronchial epithelial cells are the first barrier of defense against respiratory pathogens. Dust particles as extracellular stimuli are associated with inflammatory reactions after inhalation. It has been reported that dust particles induce intracellular Ca(2+) signal, which subsequently increases cytokines production such as interleukin- (IL-) 8. However, the study of therapeutic blockades of Ca(2+) signaling induced by dust particles in human bronchial epithelial cells is poorly understood. We investigated how to modulate dust particles-induced Ca(2+) signaling and proinflammatory cytokine IL-8 expression. Bronchial epithelial BEAS-2B cells were exposed to PM10 dust particles and subsequent mediated intracellular Ca(2+) signaling and reactive oxygen species signal. Our results show that exposure to several inhibitors of Ca(2+) pathway attenuated the PM10-induced Ca(2+) response and subsequent IL-8 mRNA expression. PM10-mediated Ca(2+) signal and IL-8 expression were attenuated by several pharmacological blockades such as antioxidants, IP3-PLC blockers, and TRPM2 inhibitors. Our results show that blockades of PLC or TRPM2 reduced both of PM10-mediated Ca(2+) signal and IL-8 expression, suggesting that treatment with these blockades should be considered for potential therapeutic trials in pulmonary epithelium for inflammation caused by environmental events such as seasonal dust storm.

"TRP inflammation" relationship in cardiovascular system

Despite considerable advances in the research and treatment, the precise relationship between inflammation and cardiovascular (CV) disease remains incompletely understood. Therefore, understanding the immunoinflammatory processes underlying the initiation, progression, and exacerbation of many cardiovascular diseases is of prime importance. The innate immune system has an ancient origin and is well conserved across species. Its activation occurs in response to pathogens or tissue injury. Recent studies suggest that altered ionic balance, and production of noxious gaseous mediators link to immune and inflammatory responses with altered ion channel expression and function. Among plausible candidates for this are transient receptor potential (TRP) channels that function as polymodal sensors and scaffolding proteins involved in many physiological and pathological processes. In this review, we will first focus on the relevance of TRP channel to both exogenous and endogenous factors related to innate immune response and transcription factors related to sustained inflammatory status. The emerging role of inflammasome to regulate innate immunity and its possible connection to TRP channels will also be discussed. Secondly, we will discuss about the linkage of TRP channels to inflammatory CV diseases, from a viewpoint of inflammation in a general sense which is not restricted to the innate immunity. These knowledge may serve to provide new insights into the pathogenesis of various inflammatory CV diseases and their novel therapeutic strategies.

Induction of size-dependent breakdown of blood-milk barrier in lactating mice by TiO2 nanoparticles

This study aims to investigate the potential nanotoxic effects of TiO₂ nanoparticles (TNPs) to dams and pups during lactation period. TiO₂ nanoparticles are accumulated in mammary glands of lactating mice after i.v. administration. This accumulation of TiO₂ NP likely causes a ROS-induced disruption of tight junction of the blood-milk barrier as indicated by the loss of tight junction proteins and the shedding of alveolar epithelial cells. Compared to larger TNPs (50 nm), smaller ones (8 nm) exhibit a higher accumulation in mammary glands and are more potent in causing perturbations to blood-milk barrier. An alarming finding is that the smaller TNPs (8 nm) are transferred from dams to pups through breastfeeding, likely through the disrupted blood-milk barrier. However, during the lactation period, the nutrient quality of milk from dams and the early developmental landmarks of the pups are not affected by above perturbations.

HIV-1/cocaine induced oxidative stress disrupts tight junction protein-1 in human pulmonary microvascular endothelial cells: role of Ras/ERK1/2 pathway

Intravenous drug use (IVDU) is the major risk factor in the development of HIV-related pulmonary arterial hypertension (HRPAH); however, the pathogenesis of HRPAH in association with IVDU has yet to be characterized. Endothelial injury is considered to be an initiating factor for pulmonary vascular remodeling in animal models of PAH. Our previous study shows that simultaneous exposure to HIV-Trans-activator of transcription (Tat) and cocaine exacerbates both disruption of tight junction proteins and permeability of human pulmonary artery endothelial cells compared with either treatment alone. We here now demonstrate that this HIV-Tat and cocaine mediated endothelial dysfunction accompanies with increase in hydrogen peroxide and superoxide radicals generation and involves redox sensitive signaling pathway. Pretreatment with antioxidant cocktail attenuated the cocaine and Tat mediated disassembly of Zonula Occludens (ZO)-1 and enhancement of endothelial monolayer permeability. Furthermore, inhibition of NADPH oxidase by apocynin or siRNA-mediated knockdown of gp-91(phox) abolished the Tat/cocaine-induced reactive oxygen species (ROS) production, suggesting the NADPH oxidase mediated generation of oxidative radicals. In addition, ROS dependent activation of Ras and ERK1/2 Kinase was observed to be mediating the TJP-1 disassembly, and endothelial dysfunction in response to cocaine and Tat exposure. In conclusion, our findings demonstrate that Tat/cocaine -mediated production of ROS activate Ras/Raf/ERK1/2 pathway that contributes to disruption of tight junction protein leading to pulmonary endothelial dysfunction associated with pulmonary vascular remodeling.

Activation of transient receptor potential ankyrin-1 (TRPA1) in lung cells by wood smoke particulate material

Cigarette smoke, diesel exhaust, and other combustion-derived particles activate the calcium channel transient receptor potential ankyrin-1 (TRPA1), causing irritation and inflammation in the respiratory tract. It was hypothesized that wood smoke particulate and select chemical constituents thereof would also activate TRPA1 in lung cells, potentially explaining the adverse effects of wood and other forms of biomass smoke on the respiratory system. TRPA1 activation was assessed using calcium imaging assays in TRPA1-overexpressing HEK-293 cells, mouse primary trigeminal neurons, and human adenocarcinoma (A549) lung cells. Particles from pine and mesquite smoke were less potent agonists of TRPA1 than an equivalent mass concentration of an ethanol extract of diesel exhaust particles; pine particles were comparable in potency to cigarette smoke condensate, and mesquite particles were the least potent. The fine particulate (PM < 2.5 μm) of wood smoke were the most potent TRPA1 agonists and several chemical constituents of wood smoke particulate, 3,5-ditert-butylphenol, coniferaldehyde, formaldehyde, perinaphthenone, agathic acid, and isocupressic acid, were TRPA1 agonists. Pine particulate activated TRPA1 in mouse trigeminal neurons and A549 cells in a concentration-dependent manner, which was inhibited by the TRPA1 antagonist HC-030031. TRPA1 activation by wood smoke particles occurred through the electrophile/oxidant-sensing domain (i.e., C621/C641/C665/K710), based on the inhibition of cellular responses when the particles were pretreated with glutathione; a role for the menthol-binding site of TRPA1 (S873/T874) was demonstrated for 3,5-ditert-butylphenol. This study demonstrated that TRPA1 is a molecular sensor for wood smoke particulate and several chemical constituents thereof, in sensory neurons and A549 cells, suggesting that TRPA1 may mediate some of the adverse effects of wood smoke in humans.