Hyperoxia promotes polarization of the immune response in ovalbumin-induced airway inflammation, leading to a TH17 cell phenotype.

Previous studies have demonstrated that hyperoxia-induced stress and oxidative damage to the lungs of mice lead to an increase in IL-6, TNF-α, and TGF-ß expression. Together, IL-6 and TGF-ß have been known to direct T cell differentiation toward the TH17 phenotype. In the current study, we tested the hypothesis that hyperoxia promotes the polarization of T cells to the TH17 cell phenotype in response to ovalbumin-induced acute airway inflammation. Airway inflammation was induced in female BALB/c mice by intraperitoneal sensitization and intranasal introduction of ovalbumin, followed by challenge methacholine. After the methacholine challenge, animals were exposed to hyperoxic conditions in an inhalation chamber for 24 h. The controls were subjected to normoxia or aluminum hydroxide dissolved in phosphate buffered saline. After 24 h of hyperoxia, the number of macrophages and lymphocytes decreased in animals with ovalbumin-induced airway inflammation, whereas the number of neutrophils increased after ovalbumin-induced airway inflammation. The results showed that expression of Nrf2, iNOS, T-bet and IL-17 increased after 24 of hyperoxia in both alveolar macrophages and in lung epithelial cells, compared with both animals that remained in room air, and animals with ovalbumin-induced airway inflammation. Hyperoxia alone without the induction of airway inflammation lead to increased levels of TNF-α and CCL5, whereas hyperoxia after inflammation lead to decreased CCL2 levels. Histological evidence of extravasation of inflammatory cells into the perivascular and peribronchial regions of the lungs was observed after pulmonary inflammation and hyperoxia. Hyperoxia promotes polarization of the immune response toward the TH17 phenotype, resulting in tissue damage associated with oxidative stress, and the migration of neutrophils to the lung and airways. Elucidating the effect of hyperoxia on ovalbumin-induced acute airway inflammation is relevant to preventing or treating asthmatic patients that require oxygen supplementation to reverse the hypoxemia.

Alterações da histoarquitetura pulmonar de camundongos neonatos expostos à hiperóxia / Alterations in the pulmonary histoarchitecture of neonatal mice exposed to hyperoxia

OBJETIVOS: Analisar os efeitos da exposição à hiperóxia (100% de oxigênio) sobre a histoarquitetura pulmonar de camundongos neonatos. MÉTODOS: Camundongos neonatos da linhagem Balb/c foram expostos à hiperóxia (GH) (100% de oxigênio) (n = 10) em uma câmara (15 x 20 x 30 cm) por 24 horas, com fluxo de 2 L/min. O grupo controle (GC) (n = 10) foi exposto a normóxia em um mesmo tipo de câmara e pelo mesmo tempo. Após a exposição, os animais foram sacrificados por decapitação, os pulmões foram removidos para análise histológica e processados de acordo com a rotina do laboratório. Cortes de 3 µm de espessura foram corados com hematoxilina e eosina (H&E). A análise morfométrica foi realizada com o objetivo de analisar macrófagos presentes na luz alveolar, densidade de superfície (Sv) de trocas gasosas, densidade de volume (Vv) de parênquima pulmonar e áreas de atelectasias. RESULTADOS: Foi verificada diminuição do número de macrófagos alveolares (MØ) no GH (GH = 0,08±0,01 MØ/mm²; GC = 0,18±0,03 MØ/mm²; p = 0,0475), Sv de troca gasosa no GH (GH = 8,08 ± 0,12 mm² /mm³; GC = 8,65 ± 0,20 mm² /mm³; p = 0,0233), Vv de parênquima pulmonar no GH (GH = 54,7/33,5/83,5 %/mm²; GC = 75/56,7/107,9 %/mm²; p < 0.0001) quando comparado com o GC. Entretanto, houve aumento de áreas de atelectasias no GH (GH = 17,5/11,3/38,4 atelectasia/mm²; GC = 14/6,1/24,4 atelectasia/mm²; p = 0,0166) quando comparado com o GC. CONCLUSÃO: Nossos resultados indicam que a hiperóxia promoveu alterações na histoarquitetura pulmonar, aumentando áreas de atelectasia e hemorragia alveolar difusa.

OBJECTIVES: To analyze the effects of exposure to hyperoxia (100% oxygen) on the lung histoarchitecture of neonatal mice. METHODS: Neonatal Balb/c mice were exposed to hyperoxia (HG) (100% oxygen) (n = 10) in a chamber (15 x 20 x 30 cm) for 24 horas ours with a flow of 2 L/min. The control group (CG) (n = 10) was exposed to normoxia in the same type of chamber and for the same time. After exposure, the animals were euthanized by decapitation; the lungs were removed and processed for histological examination according to the laboratory routine. Three-mm thick sections were stained with hematoxylin and eosin (H&E). The morphometric analysis was performed with in order to analyze the macrophages present in the alveolar lumen, surface density (Sv) of gas exchange, volume density (Vv) of lung parenchyma, and areas of atelectasis. RESULTS: A decrease in the number of alveolar macrophages (MØ) was observed in the HG (HG = 0.08±0.01 MØ/mm², CG = 0.18±0.03 MØ/mm², p = 0.0475), Sv of gas exchange in HG (HG = 8.08±0.12 mm² /mm³, CG = 8.65±0.20 mm² /mm³, p = 0.0233), Vv of lung parenchyma in HG (HG = 54.7/33.5/83.5%/ mm²; CG = 75/56.7/107.9%/mm², p < 0.0001) when compared with the CG. However, there was an increase in areas of atelectasis in HG (HG = 17.5/11.3/38.4 atelectasis/mm², CG = 14/6.1/24.4 atelectasis/mm², p = 0.0166) when compared with the CG. CONCLUSION: The present results indicate that hyperoxia caused alterations in lung histoarchitecture, increasing areas of atelectasis and diffuse alveolar hemorrhage.

Alterations in the pulmonary histoarchitecture of neonatal mice exposed to hyperoxia.

OBJECTIVES: To analyze the effects of exposure to hyperoxia (100% oxygen) on the lung histoarchitecture of neonatal mice. METHODS: Neonatal Balb/c mice were exposed to hyperoxia (HG) (100% oxygen) (n= 10) in a chamber (15 x 20 x 30 cm) for 24 hours with a flow of 2 L/min. The control group (CG) (n = 10) was exposed to normoxia in the same type of chamber and for the same time. After exposure, the animals were euthanized by decapitation; the lungs were removed and processed for histological examination according to the laboratory routine. Three-mm thick sections were stained with hematoxylin and eosin (H&E). The morphometric analysis was performed with in order to analyze the macrophages present in the alveolar lumen, surface density (Sv) of gas exchange, volume density (Vv) of lung parenchyma, and areas of atelectasis. RESULTS: A decrease in the number of alveolar macrophages (MØ) was observed in the HG (HG = 0.08 ±0.01 MØ/mm(2), CG = 0.18 ± 0.03 MØ/mm(2), p=0.0475), Sv of gas exchange in HG (HG = 8.08 ± 0.12 mm(2)/mm(3), CG=8.65 ± 0.20mm(2)/mm(3), p = 0.0233), Vv of lung parenchyma in HG (HG = 54.7/33.5/83.5%/mm(2); CG = 75/56.7/107.9%/mm(2), p<0.0001) when compared with the CG. However, there was an increase in areas of atelectasis in HG (HG = 17.5/11.3/38.4 atelectasis/mm(2), CG = 14/6.1/24.4 atelectasis/mm(2), p=0.0166) when compared with the CG. CONCLUSION: The present results indicate that hyperoxia caused alterations in lung histoarchitecture, increasing areas of atelectasis and diffuse alveolar hemorrhage.

Time course of inflammation, oxidative stress and tissue damage induced by hyperoxia in mouse lungs.

In this study our aim was to investigate the time courses of inflammation, oxidative stress and tissue damage after hyperoxia in the mouse lung. Groups of BALB/c mice were exposed to 100% oxygen in a chamber for 12, 24 or 48 h. The controls were subjected to normoxia. The results showed that IL-6 increased progressively after 12 (P < 0.001) and 24 h (P < 0.001) of hyperoxia with a reduction at 48 h (P < 0.01), whereas TNF-α increased after 24 (P < 0.001) and 48 h (P < 0.001). The number of macrophages increased after 24 h (P < 0.001), whereas the number of neutrophils increased after 24 h (P < 0.01) and 48 h (P < 0.001). Superoxide dismutase activity decreased in all groups exposed to hyperoxia (P < 0.01). Catalase activity increased only at 48 h (P < 0.001). The reduced glutathione/oxidized glutathione ratio decreased after 12 h (P < 0.01) and 24 h (P < 0.05). Histological evidence of lung injury was observed at 24 and 48 h. This study shows that hyperoxia initially causes an inflammatory response at 12 h, resulting in inflammation associated with the oxidative response at 24 h and culminating in histological damage at 48 h. Knowledge of the time course of inflammation and oxidative stress prior to histological evidence of acute lung injury can improve the safety of oxygen therapy in patients.