Efeitos da hiperóxia sobre o pulmão de ratos Wistar

Abstract

Objective: To study the effects of short-term exposure to high oxygen concentrations (hyperoxia) on Wistar rat lungs. Methods: Animals were divided into three groups exposed to hyperoxia for 10', 30' and 90' (O10', O30', O90', respectively), together with a control group (exposed to room air). The animals were sacrificed 24 h after exposure. Bronchoalveolar lavage was performed, and the lungs were removed for histological and stereological analysis. Results: In the O10', O30', and O90' groups, respectively and in comparison with the controls, we observed an increase in the numbers of macrophages (2169.9 ± 118.0, 1560.5 ± 107.0, and 1467.6 ± 39.0 vs. 781.3 ± 78.3) and neutrophils (396.3 ± 35.4, 338.4 ± 17.3, and 388.7 ± 11.7 vs. 61.6 ± 4.2), concomitant with an increase in oxidative damage (143.0 ± 7.8%, 180.4 ± 5.6%, and 235.0 ± 13.7 vs. 100.6 ± 1.7%). The histological and stereological analyses revealed normal alveoli and alveolar septa in the controls (83.51 ± 1.20% and 15 ± 1.21%), in the O10' group (81.32 ± 0.51% and 16.64 ± 0.70%), and in the O30' group (78.75 ± 0.54% and 17.73 ± 0.26%). However, in the O90' group, inflammatory cell infiltration was observed in the alveoli and alveolar septa. Red blood cells extravasated from capillaries to the alveoli (59.06 ± 1.22%), with evidence of congestion, hemorrhage, and septal edema (35.15 ± 0.69%). Conclusion: Hyperoxia for 90' caused injury of the lung parenchyma, resulting in oxidative damage and inflammatory cell infiltration.

Hyperoxia-Induced Lung Injury Is Dose Dependent in Wistar Rats

“…The present study sought to determine the concentration-dependent effect of HILI. Because of our interest in the pathophysiological mechanisms leading to HILI, we investigated a time period and range of oxygen concentrations based on results of a previous study by our group [25]. In the present study, we confirmed an undesirable effect of oxygen administered to rats at high concentrations (50%, 75%, or 100%) over 90 minutes.…”

“…In order to expose the animals to hyperoxia, an acrylic inhalation chamber was used (length = 30 cm, width = 20 cm, and height = 15 cm) as described by us previously [25]. The oxygen was acquired from White Martins (White Martins Praxair, São Paulo, Brazil).…”

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

“…Airway inflammation was induced by intranasal introduction of 50 μL of 1% ovalbumin, followed by challenge with 2.5% nebulized methacholine for 20 min. After the methacholine challenge, the animals were exposed to hyperoxic conditions in an inhalation chamber (length = 30 cm, width = 20 cm, and height = 15 cm) as previously described 11,17,19. Medical-grade oxygen was purchased from White Martins (Praxair, Inc., São Paulo, Brazil).…”

“…Paradoxically, hyperoxia alone induces pulmonary inflammation, characterized by an influx of neutrophils and macrophages into airways 10, increased expression of cytokines IL-6, TGF-β, and IFNγ 11–14, pulmonary edema, epithelial and endothelial cells death 15, apoptosis, oxidative stress, damage to extracellular matrix proteins 16,17, and DNA 18 and lipid peroxidation 19. The hyperoxia-induced oxidative stress is characterized by a redox imbalance with increased levels of reactive oxygen species (ROS), such as superoxide anion (O 2 − ) and hydroxyl radical (OH Ÿ ), and reactive nitrogen species (NOS) nitrite and peroxide (ONOO − ) 20–25.…”

Ventilation of rats with room air is more adequate than ventilation with pure oxygen

“…However, some deleterious effects have already been triggered and they can be detected through PaO2/FiO2 ratio in the present study. High concentration of oxygen is a known cause of iatrogenic effects on lung parenchyma and time of exposure seems to be a crucial factor in the process of hyperoxia-induced lung injury (VALENÇA et al, 2004). Andrade et al (2014) show that although using short-term control mechanical ventilation with protective low tidal volume, hyperoxia has great impact on increasing inflammation and on decreasing diaphragmatic contractile function in rats.…”