COVID-19 induces more pronounced extracellular matrix deposition than other causes of ARDS.

BACKGROUND: Lung fibrosis is a major concern in severe COVID-19 patients undergoing mechanical ventilation (MV). Lung fibrosis frequency in post-COVID syndrome is highly variable and even if the risk is proportionally small, many patients could be affected. However, there is still no data on lung extracellular matrix (ECM) composition in severe COVID-19 and whether it is different from other aetiologies of ARDS. METHODS: We have quantified different ECM elements and TGF-ß expression in lung tissue of 28 fatal COVID-19 cases and compared to 27 patients that died of other causes of ARDS, divided according to MV duration (up to six days or seven days or more). In COVID-19 cases, ECM elements were correlated with lung transcriptomics and cytokines profile. RESULTS: We observed that COVID-19 cases presented significant increased deposition of collagen, fibronectin, versican, and TGF-ß, and decreased decorin density when compared to non-COVID-19 cases of similar MV duration. TGF-ß was precociously increased in COVID-19 patients with MV duration up to six days. Lung collagen was higher in women with COVID-19, with a transition of upregulated genes related to fibrillogenesis to collagen production and ECM disassembly along the MV course. CONCLUSIONS: Fatal COVID-19 is associated with an early TGF-ß expression lung environment after the MV onset, followed by a disordered ECM assembly. This uncontrolled process resulted in a prominent collagen deposition when compared to other causes of ARDS. Our data provides pathological substrates to better understand the high prevalence of pulmonary abnormalities in patients surviving COVID-19.

LPS Response Is Impaired by Urban Fine Particulate Matter.

Fine particulate matter (PM2.5) is a complex mixture of components with diverse chemical and physical characteristics associated with increased respiratory and cardiovascular diseases mortality. Our study aimed to investigate the effects of exposure to concentrated PM2.5 on LPS-induced lung injury onset. BALB/c male mice were exposed to either filtered air or ambient fine PM2.5 in an ambient particle concentrator for 5 weeks. Then, an acute lung injury was induced with nebulized LPS. The animals were euthanized 24 h after the nebulization to either LPS or saline. Inflammatory cells and cytokines (IL-1ß, IL-4, IL-5, IL-6, IL-10, IL-17, TNF) were assessed in the blood, bronchoalveolar lavage fluid (BALF), and lung tissue. In addition, lung morphology was assessed by stereological methods. Our results showed that the PM+LPS group showed histological evidence of injury, leukocytosis with increased neutrophils and macrophages, and a mixed inflammatory response profile, with increased KC, IL-6, IL-1ß, IL-4, and IL-17. Our analysis shows that there is an interaction between the LPS nebulization and PM2.5 exposure, differently modulating the inflammatory response, with a distinct response pattern as compared to LPS or PM2.5 exposure alone. Further studies are required to explain the mechanism of immune modulation caused by PM2.5 exposure.

Diesel exhaust exposure intensifies inflammatory and structural changes associated with lung aging in mice.

Life expectancy is increasing worldwide. Lung aging is a process marked by changes in multiple morphological, physiological and age-related biomarkers (e.g., sirtuins) and is influenced by external factors, such as air pollution. Hence, the elderly are considered more vulnerable to the air pollution hazards. We hypothesized that diesel exhaust (DE) exposure intensifies changes in lung inflammatory and structural parameters in aging subjects. Two- and fifteen-month-old mice were exposed to DE for 30 days. Lung function was measured using the forced oscillation method. The inflammatory profile was evaluated in the bronchoalveolar lavage fluid (BALF) and blood, and lung volumes were estimated by stereology. Antioxidant enzyme activity was evaluated by spectrophotometry, sirtuin 1 (SIRT1), sirtuin 2 (SIRT2) and sirtuin 6 (SIRT6) expression was assessed by reverse transcription polymerase chain reaction (RT-PCR), and levels of the sirtuin proteins were evaluated by immunohistochemical staining in lung tissues. Older mice presented decreased pulmonary resistance and elastance, increased macrophage infiltration and decreased tumor necrosis factor (TNF) and interleukin 10 (IL-10) levels in the BALF, reduced activities of the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GR), and increased activity glutathione S-transferase (GST); increased lung volumes with decreased elastic fiber and increased airway collagen content. SIRT1 gene expression was decreased in older animals, but protein levels were increased. DE exposure increased macrophage infiltration and oxidative stress in the lungs of animals of both ages. SIRT6 gene expression was decreased by DE exposure, with increased protein levels. In older animals, DE affected lung structure and collagen content. Lung aging features, such as decreased antioxidant reserves, lower IL-10 expression, and decreased SIRT1 levels may predispose subjects to exacerbated responses after DE exposure. Our data support the hypothesis that strategies designed to reduce ambient air pollution are an important step towards healthy aging.

Air pollution impairs recovery and tissue remodeling in a murine model of acute lung injury.

Evidence regarding the impact of air pollution on acute respiratory distress syndrome (ARDS) is limited, and most studies focus on ARDS onset. Our study aimed to evaluate whether exposure to fine particulate matter interferes with lung recovery and remodeling in a murine model of acute lung injury. Forty-eight mice received nebulized LPS or the vehicle (controls). Blood, BALF, lungs and spleen were collected after 5 weeks of exposure to either PM2.5 (PM and LPS + PM group) or filtered air (control and LPS5w groups). Inflammatory cells and cytokines were assessed in the blood, BALF, lungs and spleen. Stereological analyses and remodeling assessments were performed by histology. The LPS + PM group showed increased BALF leukocytes, characterized by increased macrophages, increased IL-1ß and IL-6 levels, anemia and thrombocytopenia. Moreover, we also observed septal thickening, decreased alveolar air space total volume and, septa surface density. Finally, regarding tissue remodeling, we observed elastosis of the lung parenchyma, and unlike in the LPS5w group, we did not observe fibrosis in the LPS + PM group. In conclusion, the delayed inflammation resolution due to subchronic exposure to PM2.5 could be influenced by low systemic and local lymphocyte counts, which lead to impaired lung injury recovery and tissue remodeling.

Inflammation response, oxidative stress and DNA damage caused by urban air pollution exposure increase in the lack of DNA repair XPC protein.

Air pollution represents a considerable threat to health worldwide. The São Paulo Metropolitan area, in Brazil, has a unique composition of atmospheric pollutants with a population of nearly 20 million people and 9 million passenger cars. It is long known that exposure to particulate matter less than 2.5 µm (PM2.5) can cause various health effects such as DNA damage. One of the most versatile defense mechanisms against the accumulation of DNA damage is the nucleotide excision repair (NER), which includes XPC protein. However, the mechanisms by which NER protects against adverse health effects related to air pollution are largely unknown. We hypothesized that reduction of XPC activity may contribute to inflammation response, oxidative stress and DNA damage after PM2.5 exposure. To address these important questions, XPC knockout and wild type mice were exposed to PM2.5 using the Harvard Ambient Particle concentrator. Results from one-single exposure have shown a significant increase in the levels of anti-ICAM, IL-1ß, and TNF-α in the polluted group when compared to the filtered air group. Continued chronic PM2.5 exposure increased levels of carbonylated proteins, especially in the lung of XPC mice, probably as a consequence of oxidative stress. As a response to DNA damage, XPC mice lungs exhibit increased γ-H2AX, followed by severe atypical hyperplasia. Emissions from vehicles are composed of hazardous substances, with polycyclic aromatic hydrocarbons (PAHs) and metals being most frequently cited as the major contributors to negative health impacts. This analysis showed that benzo[b]fluoranthene, 2-nitrofluorene and 9,10-anthraquinone were the most abundant PAHs and derivatives. Taken together, these findings demonstrate the participation of XPC protein, and NER pathway, in the protection of mice against the carcinogenic potential of air pollution. This implicates that DNA is damaged directly (forming adducts) or indirectly (Reactive Oxygen Species) by the various compounds detected in urban PM2.5.

Pre- and postnatal exposure of mice to concentrated urban PM2.5 decreases the number of alveoli and leads to altered lung function at an early stage of life.

Gestational exposure to air pollution is associated with negative outcomes in newborns and children. In a previous study, we demonstrated a synergistic negative effect of pre- and postnatal exposure to PM2.5 on lung development in mice. However, the means by which air pollution affects development of the lung have not yet been identified. In this study, we exposed pregnant BALB/c mice and their offspring to concentrated urban PM2.5 (from São Paulo, Brazil; target dose 600 µg/m3 for 1 h daily). Exposure was started on embryonic day 5.5 (E5.5, time of placental implantation). Lung tissue of fetuses and offspring was submitted to stereological and transcriptomic analyses at E14.5 (pseudoglandular stage of lung development), E18.5 (saccular stage) and P40 (postnatal day 40, alveolarized lung). Additionally, lung function and cellularity of bronchoalveolar lavage (BAL) fluid were studied in offspring animals at P40. Compared to control animals that were exposed to filtered air throughout gestation and postnatal life, PM-exposed mice exhibited higher lung elastance and a lower alveolar number at P40 whilst the total lung volume and cellularity of BAL fluid were not affected. Glandular and saccular structures of fetal lungs were not altered upon gestational exposure; transcriptomic signatures, however, showed changes related to DNA damage and its regulation, inflammation and regulation of cell proliferation. A differential expression was validated at E14.5 for the candidates Sox8, Angptl4 and Gas1. Our data substantiate the in utero biomolecular effect of gestational exposure to air pollution and provide first-time stereological evidence that pre- and early life-postnatal exposure compromise lung development, leading to a reduced number of alveoli and an impairment of lung function in the adult mouse.

Early and late pulmonary effects of nebulized LPS in mice: An acute lung injury model.

BACKGROUND AND OBJECTIVE: Acute respiratory distress syndrome (ARDS) has a high mortality rate of 35-46% depending on its severity. Animal models are crucial to better understand the pathophysiology of diseases, including ARDS. This study presents a feasible animal model of acute lung injury (ALI) using nebulized lipopolysaccharide (LPS) in a non-invasive approach, focusing on its short and long-term effects. METHODS: Mice received nebulized LPS or vehicle only (control group). Blood, BALF and lung tissue were collected 24 hours (LPS 24h) or 5 weeks (LPS 5w) after the nebulized LPS-induced lung injury. Inflammatory cytokines were assessed in the blood serum, BALF and lung tissue. Stereological analyses and remodeling changes were assessed by histology and immunohistochemistry at the specified time points. RESULTS: The LPS 24h group showed increased pro-inflammatory cytokine levels, intense cell influx, increased total septal volume, septal thickening and decreased surface density of the alveolar septa. The LPS 5w group showed persistent lung inflammation, septal thickening, increased total lung volume, accentuated collagen deposition, especially of collagen type I, and decreased MMP-2 protein expression. CONCLUSION: We present a feasible, reproducible and non-invasive nebulized-LPS animal model that allows the assessment of both the acute and late phases of acute lung injury. The presence of lung remodeling with collagen deposition after 5 weeks makes it useful to study the pathophysiology, complications, and possible therapeutic intervention studies that aim to understand and reduce pulmonary fibrosis in the late phases of ALI.

Respirometria e emissão de metano por ovinos alimentados com capim-elefante cortado com diferentes idades / Respirometry and methane emissions by sheep fed elephantgrass at different cutting ages

Objetivou-se com este trabalho mensurar a respirometria e a emissão de metano entérico por ovinos alimentados com o capim-elefante cortado aos 56, 84 e 112 dias de crescimento. Foram utilizados 18 carneiros adultos sem raça definida, com peso médio de 34,7 ± 6 kg alojados em gaiolas de estudo de metabolismo. A mensuração dos gases foi realizada através de uma câmara respirométrica de fluxo aberto. O delineamento experimental utilizado foi inteiramente casualizado, com seis repetições, e as médias foram comparadas pelo teste SNK (P<0,05). Os animais alimentados com o capim colhido após 56 dias de rebrotação consumiram mais oxigênio e produziram mais dióxido de carbono e metano. As produções de calor variaram 87,19 a 143,57 Kcal/kg 0,75/dia. O coeficiente respiratório foi semelhante entre os tratamentos, com valor médio de 0,98. A produção de metano variou entre 11,74 e 22,51 g/dia, havendo redução com o aumento da idade da planta forrageira. Quando expressa em g/kg0,75/dia, a produção deste gás foi superior para animais que receberam o capim-elefante-verde cortado aos 56 dias de idade (1,53 g/kg 0,75/dia). A emissão de metano (g) por quilo de matéria seca (MS) e de fibra insolúvel em detergente neutro (FDN) consumido para o capim colhido mais novo (56 dias) foi superior à do capim colhido no estádio mais avanço de maturação (112 dias). Porém, as emissões de metano em gramas por quilo de MS digestível (27,2 g/kg) e FDN digestível (44,4 g/kg) foram semelhantes para os capins colhidos nas diferentes idades de corte. A emissão diária de metano (g/kg 0,75/dia) foi maior em animais alimentados com a planta forrageira colhida mais nova, enquanto que se expressa em gramas por quilo de MS ou FDN digestível a emissão deste gás não sofreu influência do capim-elefante no momento do corte.

The aim of this work was to determinate the respirometry and enteric methane emission from sheep fed fresh elephant grass cut at 56, 84 and 112 days of regrowth. Eighteen crossbred sheep (34.7 ± 6 kg) individually housed in metabolic crates were used in this experiment. The gases measurements were accomplished with an open circuit respirometric chamber. The experimental design was completely randomized with three treatments (grass regowth age) and six repetitions (sheep). The data were subjected to ANOVA and means were compared by SNK test (P<0.05). The animals fed with elephant grass harvested at 56 days of regrowth had higher oxygen uptake and carbon dioxide and methane emissions. Heat production ranged from 87.19 to 143.57 Kcal/kg 0.75/day. The respiratory quotients were similar (P>0.05) among treatments, averaging 0.98. Methane emissions ranged from 11.74 to 22.51 g/day. When expressed in g/kg 0.75/day, methane emissions were higher for sheep fed fresh elephant grass with 56 days of regrowth (1.53 g/kg 0.75/day). Methane emissions expressed in g/kg of dry matter (DM) intake or neutral detergent fiber (NDF) intake were higher (P<0.05) for the grass harvested with 56 days of regrowth compared to the grass harvested in more advanced stage of maturity (112 days). However, methane emissions in g/kg of digestible DM (27.2 g/kg) and digestible NDF (44.4 g/kg) were similar among treatments. While daily methane emissions (g/kg 0.75/day) were higher in sheep fed fresh elephant grass harvested with 56 days of regrowth, it was not affected by regrowth age when expressed as g/kg of digestible DM or digestible NDF.