Curbside particulate matter and susceptibility to SARS-CoV-2 infection.

Background: Biologic plausibility for the association between exposure to particulate matter (PM) less than 10 µm in aerodynamic diameter (PM10) and coronavirus disease 2019 (COVID-19) morbidity in epidemiologic studies has not been determined. The upregulation of angiotensin-converting enzyme 2 (ACE2), the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) entry receptor on host cells, by PM10 is a putative mechanism. Objective: We sought to assess the effect of PM10 on SARS-CoV-2 infection of cells in vitro. Methods: PM10 from the curbside of London's Marylebone Road and from exhaust emissions was collected by cyclone. A549 cells, human primary nasal epithelial cells (HPNEpCs), SARS-CoV-2-susceptible Vero-E6 and Calu3 cells were cultured with PM10. ACE2 expression (as determined by median fluorescent intensity) was assessed by flow cytometry, and ACE2 mRNA transcript level was assessed by PCR. The role of oxidative stress was determined by N-acetyl cysteine. The cytopathic effect of SARS-CoV-2 (percentage of infection enhancement) and expression of SARS-CoV-2 genes' open reading frame (ORF) 1ab, S protein, and N protein (focus-forming units/mL) were assessed in Vero-E6 cells. Data were analyzed by either the Mann-Whitney U test or Kruskal-Wallis test with the Dunn multiple comparisons test. Results: Curbside PM10 at concentrations of 10 µg/mL or more increased ACE2 expression in A549 cells (P = .0021). Both diesel PM10 and curbside PM10 in a concentration of 10 µg/mL increased ACE2 expression in HPNEpCs (P = .0022 and P = .0072, respectively). ACE2 expression simulated by curbside PM10 was attenuated by N-acetyl cysteine in HPNEpCs (P = .0464). Curbside PM10 increased ACE2 expression in Calu3 cells (P = .0256). In Vero-E6 cells, curbside PM10 increased ACE2 expression (P = .0079), ACE2 transcript level (P = .0079), SARS-CoV-2 cytopathic effect (P = .0002), and expression of the SARS-CoV-2 genes' ORF1ab, S protein, and N protein (P = .0079). Conclusions: Curbside PM10 increases susceptibility to SARS-COV-2 infection in vitro.

Confocal microscopy 3D imaging and bioreactivity of La Palma volcanic ash particles.

In September 2021 an eruption began of Cumbre Vieja, La Palma (Spain) that lasted 3 months. Previous studies have shown that volcanic ash particles can be associated with adverse effects on human health however, the reasons for this are unclear. Particle shape has been shown to contribute to cellular uptake in prostate cancer cells. Hence we aimed to study 3D structure, elemental composition and effects on cultured lung cells of particles collected from the La Palma volcanic eruption. 3D imaging of PM10 sized and below particles was performed using a LEXT OLS4100 confocal microscope (Olympus Corporation, Japan). A Zeiss EVO 50 (Carl Zeiss AG, Germany) Scanning Electron Microscope (SEM) was used to assess elemental composition. In addition, volcanic particle concentration dose response for pneumococcal adhesion to A549 human alveolar epithelial cells was investigated. Confocal microscopy showed that some PM10 and below sized particles had sharp or angular 3D appearance. SEM x-ray analysis indicated silicate particles with calcium, aluminium and iron. We observed increased colony forming units indicating increased Pneumococcal adhesion due to exposure of cells to volcanic particles. Thus in addition to the toxic nature of some volcanic particles, we suggest that the observed sharp surface particle features may help to explain adverse health effects associated with volcanic eruptions.

Underground railway particulate matter and susceptibility to pneumococcal infection.

BACKGROUND: Concentrations of particulate matter less than 10 microns (PM10) on underground railways are higher than those near urban roads. Traffic-related PM10 increases pneumococcal infection via increasing the expression of platelet-activating factor receptor (PAFR), a receptor co-opted by pneumococci to adhere to cells. To date, it is unknown whether underground railway PM10 increases pneumococcal infection. This study sought to determine the effect of London Underground (LU) PM10 on; i) pneumococcal adhesion to airway cells, and ii) susceptibility to pneumococcal disease. METHODS: A549 cells and human primary airway epithelial cells were cultured with 20 µg/mL PM10 from the Bakerloo (B-PM10) and Jubilee (J-PM10) line platforms of Baker Street station. PAFR expression was assessed by flow cytometry, and pneumococcal adhesion by colony forming unit (CFU) counts. Traffic-related PM10 was collected next to a main road near the station's entrance. The PAFR blocker CV3988 and the antioxidant N-acetyl cysteine were used to assess the role of PAFR-mediated pneumococcal adhesion and oxidative stress respectively. Pneumococcal infection of mice was done after exposure to 3×80 µg doses of intranasal LU-PM10. FINDINGS: In A549 cells, human primary nasal cells, and human primary bronchial epithelial cells, B-PM10 and J-PM10 increased PAFR expression and pneumococcal adhesion. Stimulated adhesion was abrogated by CV3988 and N-acetyl cysteine. Traffic-related PM10 stimulated increased adhesion compared with B-PM10. B-PM10 and J-PM10 increased lung and blood CFU and mortality in mice. Treatment of B-PM10-exposed mice with CV3988 reduced blood CFU. INTERPRETATION: LU-PM10 increases pneumococcal adhesion to airway cells and susceptibility to invasive disease in mice. FUNDING: The Medical College of Saint Bartholomew's Hospital Trust, and the UK Medical Research Council Programme Grant (MR/P011284/1).

Prostaglandin E2 and phagocytosis of inhaled particulate matter by airway macrophages in cystic fibrosis.

BACKGROUND: Exposure to particulate matter (PM) air pollution is associated with adverse health outcomes in children with cystic fibrosis (CF). Airway macrophages (AM) phagocytose and retain inhaled PM in vivo, and the area of carbon in AM reflects both inhaled PM dose and phagocytic function. Since airway prostaglandin-E2 (PGE2) is increased in CF, and PGE2 suppresses AM phagocytosis, we sought evidence for PGE2-mediated suppression of AM phagocytosis of inhaled carbonaceous PM in CF. METHODS: After informed consent, urine was obtained from 20 controls and 24 CF children. In the subgroup of older children, at least one induced sputum was done in 20 controls and 19 CF children. Urinary tetranor PGEM, the major metabolite of PGE2, and sputum PGE2 were measured by mass spectrometry. The area of carbon in AM was determined by image analysis. Exposure to PM was assessed by modelling and personal monitoring. The effect of either PGE2 or CF sputum supernatant on phagocytosis of diesel exhaust particle (DEP) by AM was assessed in vitro. Data were analysed by t-test. RESULTS: Both urinary tetranor PGEM (P<0.05), and sputum PGE2 (P<0.05) were increased in CF . Despite no difference in PM exposure between groups, the area of phagocytosed carbon by AM was decreased in children with CF (P<0.01). PGE2 suppressed phagocytosis of DEP by AM from both controls and CF (P<0.0001). CF sputum supernatant suppressed phagocytosis of DEP by AM (P<0.0001) in a PGE2-dependent manner. CONCLUSION: Increased PGE2 in the CF airway suppresses phagocytosis of inhaled PM by AM.

E-cigarettes and respiratory health: the latest evidence.

The E-cigarette market continues to expand at an alarming rate with thousands of flavours available for purchase and continuously evolving devices. Now that it is a multi-billion dollar industry and one without stringent regulation, there is rising concern over the safety of vaping products. Since June 2019, over 2800 cases of E-cigarette-associated acute lung toxicity have been reported in the USA, over 60 of which resulted in death. Many argue that E-cigarettes offer a safer alternative to smoking, but we are evidently far from fully understanding the potential hazards that they pose to respiratory health. Although the risk of an outbreak in the UK has been considered low due to tighter E-cigarette regulations, we cannot fully eliminate the possibility of similar events occurring in the future. With evidence frequently emerging of the harmful effects of E-cigarettes to pulmonary health, there is an urgent need to define the long-term implications of vaping. Studies show that E-cigarette exposure can disrupt pulmonary homeostasis, with reports of gas exchange disturbance, reduced lung function, increased airway inflammation and oxidative stress, downregulation of immunity, and increased risk of respiratory infection. In this review, the latest research on the effect of E-cigarette use on respiratory health will be presented.

Exposure to diesel exhaust particles increases susceptibility to invasive pneumococcal disease.

BACKGROUND: The World Health Organization estimates that air pollution is responsible for 7 million deaths per annum, with 7% of these attributable to pneumonia. Many of these fatalities have been linked to exposure to high levels of airborne particulates, such as diesel exhaust particles (DEPs). OBJECTIVES: We sought to determine whether exposure to DEPs could promote the progression of asymptomatic nasopharyngeal carriage of Streptococcus pneumoniae to invasive pneumococcal disease. METHODS: We used mouse models and in vitro assays to provide a mechanistic understanding of the link between DEP exposure and pneumococcal disease risk, and we confirmed our findings by using induced sputum macrophages isolated from healthy human volunteers. RESULTS: We demonstrate that inhaled exposure to DEPs disrupts asymptomatic nasopharyngeal carriage of S pneumoniae in mice, leading to dissemination to lungs and blood. Pneumococci are transported from the nasopharynx to the lungs following exposure to DEPs, leading to increased proinflammatory cytokine production, reduced phagocytic function of alveolar macrophages, and consequently, increased pneumococcal loads within the lungs and translocation into blood. These findings were confirmed by using DEP-exposed induced sputum macrophages isolated from healthy volunteers, demonstrating that impaired innate immune mechanisms following DEP exposure are also at play in humans. CONCLUSION: Lung inhaled DEPs increase susceptibility to pneumococcal disease by leading to loss of immunological control of pneumococcal colonisation, increased inflammation, tissue damage, and systemic bacterial dissemination.

Use of cleaner-burning biomass stoves and airway macrophage black carbon in Malawian women.

Exposure to particulate matter (PM) from burning of biomass for cooking is associated with adverse health effects. It is unknown whether or not cleaner burning biomass-fuelled cookstoves reduce the amount of PM inhaled by women compared with traditional open fires. We sought to assess whether airway macrophage black carbon (AMBC) - a marker of inhaled dose of carbonaceous PM from biomass and fossil fuel combustion - is lower in Malawian women using a cleaner burning biomass-fuelled cookstove compared with those using open fires for cooking. AMBC was assessed in induced sputum samples using image analysis and personal exposure to carbon monoxide (CO) and PM were measured using Aprovecho Indoor Air Pollution meters. A fossil-fuel exposed group of UK women was also studied. Induced sputum samples were obtained from 57 women from which AMBC was determined in 31. Median AMBC was 6.87µm2 (IQR 4.47-18.5) and 4.37µm2 (IQR 2.57-7.38) in the open fire (n=11) and cleaner burning cookstove groups (n=20), respectively (p=0.028). There was no difference in personal exposure to CO and PM between the two groups. UK women (n=5) had lower AMBC (median 0.89µm2, IQR 0.56-1.13) compared with both Malawi women using traditional cookstoves (p<0.001) and those using cleaner cookstoves (p=0.022). We conclude that use of a cleaner burning biomass-fuelled cookstove reduces inhaled PM dose in a way that is not necessarily reflected by personal exposure monitoring.

E-cigarette vapour enhances pneumococcal adherence to airway epithelial cells.

E-cigarette vapour contains free radicals with the potential to induce oxidative stress. Since oxidative stress in airway cells increases platelet-activating factor receptor (PAFR) expression, and PAFR is co-opted by pneumococci to adhere to host cells, we hypothesised that E-cigarette vapour increases pneumococcal adhesion to airway cells.Nasal epithelial PAFR was assessed in non-vaping controls, and in adults before and after 5 min of vaping. We determined the effect of vapour on oxidative stress-induced, PAFR-dependent pneumococcal adhesion to airway epithelial cells in vitro, and on pneumococcal colonisation in the mouse nasopharynx. Elemental analysis of vapour was done by mass spectrometry, and oxidative potential of vapour assessed by antioxidant depletion in vitroThere was no difference in baseline nasal epithelial PAFR expression between vapers (n=11) and controls (n=6). Vaping increased nasal PAFR expression. Nicotine-containing and nicotine-free E-cigarette vapour increased pneumococcal adhesion to airway cells in vitro Vapour-stimulated adhesion in vitro was attenuated by the PAFR blocker CV3988. Nicotine-containing E-cigarette vapour increased mouse nasal PAFR expression, and nasopharyngeal pneumococcal colonisation. Vapour contained redox-active metals, had considerable oxidative activity, and adhesion was attenuated by the antioxidant N-acetyl cysteine.This study suggests that E-cigarette vapour has the potential to increase susceptibility to pneumococcal infection.

Immunotoxicity in mice induced by short-term exposure to methoxychlor, parathion, or piperonyl butoxide.

Exposure to environmental agents can compromise numerous immunological functions. Immunotoxicology focuses on the evaluation of the potential adverse effects of xenobiotics on immune mechanisms that can lead to harmful changes in host responses such as: increased susceptibility to infectious diseases and tumorigenesis; the induction of hypersensitivity reactions; or an increased incidence of autoimmune disease. In order to assess the immunosuppressive response to short-term exposure to some commonly used pesticides, the studies here focused on the response of mice after exposures to the organochlorine pesticide methoxychlor, the organophosphorus pesticide parathion, or the agricultural insecticide synergist piperonyl butoxide. In these studies, 7-week-old mice were orally administered (by gavage) methoxychlor, parathion, or piperonyl butoxide daily for five consecutive days. On Day 2, all mice in each group were immunized with sheep red blood cells (SRBC), and their SRBC-specific IgM responses were subsequently assessed. In addition, levels of B-cells in the spleen of each mouse were also analyzed via surface antigen expression. The results of these studies indicated that treatments with these various pesticides induced marked decreases in the production of SRBC-specific IgM antibodies as well as in the expression of surface antigens in IgM- and germinal center-positive B-cells. Based on these outcomes, it is concluded that the short-term exposure protocol was able to detect potential immunosuppressive responses to methoxychlor, parathion, and piperonyl butoxide in situ, and, as a result, may be useful for detecting other environmental chemical-related immunotoxicities.