OBJECTIVES: To investigate the effects of hyperoxia on the expression of N-methyl-D-aspartate receptor 1 (NMDAR1) and its synapse-associated molecules, including cannabinoid receptor 1 (CB1R), postsynaptic density 95 (PSD95), and synapsin (SYN), in the hippocampus of neonatal rats. METHODS: One-day-old Sprague-Dawley neonatal rats were randomly divided into a hyperoxia group and a control group (n=8 per group). The hyperoxia group was exposed to 80% ± 5% oxygen continuously, while the control group was exposed to room air, for 7 days. At 1, 3, and 7 days after hyperoxia exposure, hematoxylin and eosin (HE) staining was used to observe histopathological changes in the brain. The expression levels of NMDAR1, CB1R, PSD95, and SYN proteins and mRNAs in the hippocampus were detected by immunohistochemistry, Western blotting, and quantitative real-time PCR. RESULTS: After 7 days of hyperoxia exposure, the hyperoxia group showed decreased neuronal density and disordered arrangement in brain tissue. Compared with the control group, after 1 day of hyperoxia exposure, CB1R mRNA and both NMDAR1 and CB1R protein expression in the hyperoxia group were significantly downregulated, while SYN protein expression was significantly upregulated (P<0.05). After 3 days, mRNA expression of NMDAR1, CB1R, and SYN was significantly decreased (P<0.05); NMDAR1 and CB1R protein expression was significantly downregulated (P<0.05), while PSD95 and SYN protein expression was significantly upregulated (P<0.05). After 7 days of hyperoxia, the protein expression of NMDAR1 and CB1R was significantly upregulated (P<0.05). CONCLUSIONS Continuous hyperoxia exposure induces time-dependent changes in the expression levels of NMDAR1 and its synapse-associated molecules in the hippocampus of neonatal rats.
Animals ; Receptors, N-Methyl-D-Aspartate/genetics* ; Rats, Sprague-Dawley ; Hippocampus/pathology* ; Rats ; Animals, Newborn ; Receptor, Cannabinoid, CB1/genetics* ; Hyperoxia/metabolism* ; Disks Large Homolog 4 Protein/genetics* ; Synapsins/genetics* ; Synapses ; Male ; Female ; RNA, Messenger/analysis*

OBJECTIVE: To investigate the expression and possible regulatory mechanism of miR-34a in the lung tissue of neonatal rat model of bronchopulmonary dysplasia (BPD) induced by hyperoxia. METHODS: In the study, 80 newborn SD rats were randomly divided into hyperoxia group (FiO₂=60%) and air group (FiO₂=21%) within 2 hours after birth, 40 rats per group. Lung tissue samples of the SD rats in each group were extracted on the 1st, 7th, 14th and 21st days after birth, and the pathological changes of lung tissue were observed under light microscope after HE staining. The number of radial alveolar counts (RAC) and the mean alveolar diameter (MAD) and the thickness of alveolar septal thickness (AST) were measured to evaluate the development of alveoli. Real-time fluorescence quantitative PCR was used to detect the expression of miR-34a, angiopoietin-1 (Ang-1) and tyrosine kinase receptor-2 (Tie-2) in lung tissue of rats in hyperoxia group and air group at different time points. Enzyme-linked immunosorbent assay (ELISA) was used to detect the proteins expression of Ang-1 and Tie-2 in the lung tissues of the two groups at different time points. RESULTS: The weight of rats in the hyperoxia group on the 7th, 14th and 21st days after birth was significantly lower than that in the air group (P all < 0.05). With the prolongation of oxygen exposure, the number of alveoli decreased, the volume increased, the structure simplified, the alveolar cavity enlarged obviously and the alveolar septum thickened in the hyperoxia group. On the 7th, 14th and 21st days after birth, the RAC in the hyperoxia group was significantly lower than that in the air group (P all < 0.05). Compared with the air group, MAD and AST increased significantly on the 7th, 14th and 21st days after birth in the hyperoxia group, and the difference was statistically significant (P all < 0.05). The expression level of miR-34a in lung tissue of hyperoxia group was significantly higher than that of air group on the 7th, 14th and 21st days after birth, and the difference was statistically significant (P all < 0.05). Compared with the air group at the same time point, the expression levels of Ang-1 and Tie-2 mRNA and protein in the hyperoxia group were lower than those in the air group on the 14th and 21st days after birth (P all < 0.05). CONCLUSION The new BPD model of newborn SD rats can be successfully established by continuous exposure to 60% hyperoxia. The expression of miR-34a was up-regulated in the lung tissue of the new BPD model of neonatal rats. MiR-34a may play an important role in the occurrence and development of BPD by regulating Ang-1/Tie-2 signal pathway.
Animals ; MicroRNAs/metabolism* ; Bronchopulmonary Dysplasia/genetics* ; Hyperoxia/metabolism* ; Rats, Sprague-Dawley ; Animals, Newborn ; Rats ; Angiopoietin-1/genetics* ; Disease Models, Animal ; Receptor, TIE-2/genetics* ; Lung/pathology* ; Male

Objective To explore the phenotypic conversion of regulatory T cells (Tregs) in the lungs of mice with bronchopulmonary dysplasia (BPD)-affected mice. Methods A total of 20 newborn C57BL/6 mice were divided into air group and hyperoxia group, with 10 mice in each group. The BPD model was established by exposing the newborn mice to hyperoxia. Lung tissues from five mice in each group were collected on postnatal days 7 and 14, respectively. Histopathological changes of the lung tissues was detected by HE staining. The expression level of surfactant protein C (SP-C) in the lung tissues was examined by Western blot analysis. Flow cytometry was performed to assess the proportion of FOXP3⁺ Tregs and RORγt⁺FOXP3⁺ Tregs in CD4⁺ lymphocytes. The concentrations of interleukin-17A (IL-17A) and IL-6 in lung homogenate were measured by using ELISA. Spearman correlation analysis was used to analyze the correlation between FOXP3⁺Treg and the expression of SP-C and the correlation between RORγt⁺FOXP3⁺ Tregs and the content of IL-17A and IL-6. Results The hyperoxia group exhibited significantly decreased levels of SP-C and radical alveolar counts in comparison to the control group. The proportion of FOXP3⁺Tregs was reduced and that of RORγt⁺FOXP3⁺Tregs was increased. IL-17A and IL-6 concentrations were significantly increased. SP-C was positively correlated with the expression level of RORγt⁺FOXP3⁺ Tregs. RORγt⁺FOXP3⁺ Tregs and IL-17A and IL-6 concentrations were also positively correlated. Conclusion The number of FOXP3⁺ Tregs in lung tissue of BPD mice is decreased and converted to RORγt⁺ FOXP3⁺ Tregs, which may be involved in hyperoxy-induced lung injury.
Animals ; Mice ; Mice, Inbred C57BL ; Bronchopulmonary Dysplasia ; T-Lymphocytes, Regulatory ; Interleukin-17 ; Nuclear Receptor Subfamily 1, Group F, Member 3 ; Hyperoxia ; Interleukin-6 ; Forkhead Transcription Factors ; Lung

OBJECTIVE: To investigate the effect of hyperoxia on intestinal metabolomics in mice. METHODS: Sixteen 8-week-old male C57BL/6 mice were randomly divided into hyperoxia group and control group, with 8 mice in each group. The hyperoxia group was exposed to 80% oxygen for 14 days. Mice were anesthetized and euthanized, and cecal contents were collected for untargeted metabolomics analysis by liquid chromatography-mass spectrometry (LC-MS) combined detection. Orthogonal partial least square discriminant analysis (OPLS-DA), volcano plot analysis, heat map analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the effects of hyperoxia on metabolism. RESULTS: (1) OPLS-DA analysis showed that R²Y was 0.967 and Q² was 0.796, indicating that the model was reliable. (2) Volcano plot and heat map analysis showed significant statistical differences in the expression levels of metabolites between the two groups, with 541 up-regulated metabolites, 64 down-regulated metabolites, and 907 no differences, while the elevated 5-hydroxy-L-lysine was the most significant differential metabolite induced by high oxygen. (3) KEGG pathway enrichment analysis showed that porphyrin and chlorophyll metabolism (P = 0.005), lysine degradation (P = 0.047), and aromatic compound degradation (P = 0.024) were the targets affected by hyperoxia. (4) Differential analysis of metabolic products through KEGG enrichment pathway showed that hyperoxia had a significant impact on the metabolism of porphyrin and chlorophyll, lysine, and aromatic compounds such as benzene and o-cresol. CONCLUSIONS Hyperoxia significantly induces intestinal metabolic disorders. Hyperoxia enhances the metabolism of porphyrins and chlorophyll, inhibits the degradation of lysine, and delays the degradation of aromatic compounds such as benzene and o-cresol.
Mice ; Male ; Animals ; Lysine ; Hyperoxia ; Benzene ; Mice, Inbred C57BL ; Metabolic Diseases ; Oxygen ; Chlorophyll ; Porphyrins ; Biomarkers/metabolism*

OBJECTIVE: To study whether wedelolactone can reduce hyperoxia-induced acute lung injury (HALI) by regulating ferroptosis, and provide a basic theoretical basis for the drug treatment of HALI. METHODS: A total of 24 C57BL/6J mice were randomly divided into normal oxygen control group, HALI model group and wedelolactone pretreatment group, with 8 mice in each group. Mice in wedelolactone pretreatment group were treated with wedelolactone 50 mg/kg intraperitoneally for 6 hours, while the other two groups were not given with wedelolactone. After that, the HALI model was established by maintaining the content of carbon dioxide < 0.5% and oxygen > 90% in the molding chamber for 48 hours, and the normal oxygen control group was placed in indoor air. After modeling, the mice were sacrificed and lung tissues were collected. The lung histopathological changes were observed under light microscope and pathological scores were performed to calculate the ratio of lung wet/dry mass (W/D). The levels of tumor necrosis factor-α (TNF-α), interleukins (IL-6, IL-1β), superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH) in lung tissues of mice in each group were determined. The protein expression of glutathione peroxidase 4 (GPX4) in lung tissue was detected by Western blotting. RESULTS: Under light microscope, the alveolar structure of HALI model group was destroyed, and a large number of neutrophils infiltrated the alveolar and interstitial lung, and the interstitial lung was thickened. The pathological score of lung injury (score: 0.75±0.02 vs. 0.11±0.01) and the ratio of lung W/D (6.23±0.34 vs. 3.68±0.23) were significantly higher than those in the normal oxygen control group (both P < 0.05). Wedelolactone pretreated mice had clear alveolar cavity and lower neutrophil infiltration and interstitial thickness than HALI group. Pathological scores (score: 0.43±0.02 vs. 0.75±0.02) and W/D ratio (4.56±0.12 vs. 6.23±0.34) were significantly lower than HALI group (both P < 0.05). Compared with the normal oxygen control group, the levels of SOD (kU/g: 26.41±4.25 vs. 78.64±3.95) and GSH (mol/g: 4.51±0.33 vs. 12.53±1.25) in HALI group were significantly decreased, while the levels of MDA (mmol/g: 54.23±4.58 vs. 9.65±1.96), TNF-α (μg/L: 96.32±3.67 vs. 11.65±2.03), IL-6 (ng/L: 163.35±5.89 vs. 20.56±3.63) and IL-1β (μg/L: 72.34±4.64 vs. 15.64±2.47) were significantly increased, and the protein expression of GPX4 (GPX4/β-actin: 0.44±0.02 vs. 1.00±0.09) was significantly decreased (all P < 0.05). Compared with the HALI group, the levels of SOD (kU/g: 53.28±3.69 vs. 26.41±4.25) and GSH (mol/g: 6.73±0.97 vs. 12.53±1.25) were significantly higher in the wedelolactone pretreatment group, and the levels of MDA (mmol/g: 25.36±1.98 vs. 54.23±4.58), TNF-α (μg/L: 40.25±4.13 vs. 96.32±3.67), IL-6 (ng/L: 78.32±4.65 vs. 163.35±5.89), and IL-1β (μg/L: 30.65±3.65 vs. 72.34±4.64) were significantly lower (all P < 0.05), and protein expression of GPX4 was significantly higher (GPX4/β-actin: 0.68±0.04 vs. 0.44±0.02, P < 0.05). CONCLUSIONS Wedelolactone attenuates HALI injury by regulating ferroptosis.
Mice ; Animals ; Hyperoxia ; Ferroptosis ; Tumor Necrosis Factor-alpha ; Interleukin-6 ; Actins ; Mice, Inbred C57BL ; Acute Lung Injury/drug therapy* ; Lung ; Oxygen ; Superoxide Dismutase

Our previous studies have shown that calcitonin gene-related peptide (CGRP) exerts protective effects on the acute lung injury induced by oxidative stress. This study was aimed to investigate whether autophagy was involved in the protection of CGRP against oxidative stress-induced lung injury in neonatal rats. Newborn Sprague-Dawley (SD) rats were randomly divided into five groups: Control group, oxidative stress model group (Model group), Model + CGRP group, Model + CGRP + Rapamycin (an autophagy agonist) group, and Model + CGRP + LY294002 (an autophagy inhibitor) group. The model of hyperoxia-induced lung injury was established by continuous inhalation of oxygen (FiO₂ = 90%-95%) for 14 days in neonatal SD rats. Pathological changes of lung tissue were observed by hematoxylin and eosin (HE) staining, and mean linear intercept (MLI) was measured. The quantitative changes of autophagic vesicles (AV) in type II alveolar epithelial cells (AECII) were measured under the transmission electron microscope. The protein expressions of Caspase-3, Bcl-2, mTOR, and Beclin-1 in lung tissue lysates were detected by Western blot. The results showed that, compared to the Model group at the same time point, the number of AV in AECII and the expression level of Beclin-1 protein of the lung tissue were increased, while the expression level of mTOR protein was decreased, with alleviated pathological changes, reduced MLI value and Caspase-3 protein expression level, increased Bcl-2 protein expression level in the lung tissue of Model + CGRP group. In addition, we found that the protective effect of CGRP on hyperoxia-induced lung injury could be enhanced by autophagy activator Rapamycin and abolished by autophagy inhibitor LY294002. Together, these findings indicate that CGRP could attenuate hyperoxia-induced lung injury in neonatal rats by enhancing autophagy.
Acute Lung Injury/pathology* ; Animals ; Animals, Newborn ; Autophagy ; Calcitonin/metabolism* ; Calcitonin Gene-Related Peptide/metabolism* ; Caspase 3/metabolism* ; Hyperoxia/pathology* ; Lung/pathology* ; Lung Injury/prevention & control* ; Oxidative Stress ; Proto-Oncogene Proteins c-bcl-2/metabolism* ; Rats ; Rats, Sprague-Dawley ; Sirolimus/pharmacology*

Animals ; Cecum/microbiology* ; Hyperoxia/blood* ; Microbiota ; Rats

OBJECTIVES: To study the role of adrenomedullin (ADM) in hyperoxia-induced lung injury by examining the effect of ADM on the expression of calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein 2 (RAMP2), extracellular signal-regulated kinase (ERK), and protein kinase B (PKB) in human pulmonary microvascular endothelial cells (HPMECs) under different experimental conditions. METHODS: HPMECs were randomly divided into an air group and a hyperoxia group ( RESULTS: Compared with the air group, the hyperoxia group had significant increases in the mRNA and protein expression levels of ADM, CRLR, RAMP2, ERK1/2, and PKB ( CONCLUSIONS ERK1/2 and PKB may be the downstream targets of the ADM signaling pathway. ADM mediates the ERK/PKB signaling pathway by regulating CRLR/RAMP2 and participates in the protection of hyperoxia-induced lung injury.
Adrenomedullin/genetics* ; Endothelial Cells ; Humans ; Hyperoxia/complications* ; Lung Injury ; Receptor Activity-Modifying Proteins

OBJECTIVES: To study the role of the low-density lipoprotein receptor-related protein 1 (LRP1)-proline-rich tyrosine kinase 2 phosphorylation (pPyk2)-matrix metalloproteinases 9 (MMP9) pathway in hyperoxia-induced lung injury in neonatal rats. METHODS: A total of 16 neonatal rats were randomly placed in chambers containing room air (air group) or 95% medical oxygen (hyperoxia group) immediately after birth, with 8 rats in each group. All of the rats were sacrificed on day 8 of life. Hematoxylin and eosin staining was used to observe the pathological changes of lung tissue. ELISA was used to measure the levels of soluble LRP1 (sLRP1) and MMP9 in serum and bronchoalveolar lavage fluid (BALF). Western blot was used to measure the protein expression levels of LRP1, MMP9, Pyk2, and pPyk2 in lung tissue. RT-PCR was used to measure the mRNA expression levels of LRP1 and MMP9 in lung tissue. RESULTS: The hyperoxia group had significantly higher levels of sLRP1 and MMP9 in serum and BALF than the air group ( CONCLUSIONS The activation of the LRP1-pPyk2-MMP9 pathway is enhanced in hyperoxia-induced lung injury in neonatal rats, which may be involved in the pathogenesis of bronchopulmonary dysplasia.
Animals ; Animals, Newborn ; Hyperoxia/complications* ; Lung ; Lung Injury/etiology* ; Matrix Metalloproteinase 9/genetics* ; Rats

OBJECTIVE: To study the expression and significance of ubiquitin-specific protease 7 (USP7) and the key factors of the Wnt signaling pathway in the lung tissue of preterm rats after hyperoxia exposure. METHODS: A total of 180 preterm neonatal Wistar rats were randomly divided into an air control group, an air intervention group, a hyperoxia control group, and a hyperoxia intervention group, with 45 rats in each group. Lung injury was induced by hyperoxia exposure in the hyperoxia groups. The preterm rats in the intervention groups were given intraperitoneal injection of the USP7 specific inhibitor P5091 (5 mg/kg) every day. The animals were sacrificed on days 3, 5, and 9 of the experiment to collect lung tissue specimens. Hematoxylin-eosin staining was used to observe the pathological changes of lung tissue. RT-PCR and Western blot were used to measure the mRNA and protein expression levels of USP7 and the key factors of the Wnt signaling pathway β-catenin and α-smooth muscle actin (α-SMA) in lung tissue. RESULTS: The air groups had normal morphology and structure of lung tissue; on days 3 and 5, the hyperoxia control group showed obvious alveolar compression and disordered structure, with obvious inflammatory cells, erythrocyte diapedesis, and interstitial edema. On day 9, the hyperoxia control group showed alveolar structural disorder and obvious thickening of the alveolar septa. Compared with the hyperoxia control group at the corresponding time points, the hyperoxia intervention group had significantly alleviated disordered structure, inflammatory cell infiltration, and bleeding in lung tissue. At each time point, the hyperoxia groups had a significantly lower radial alveolar count (RAC) than the corresponding air groups ( CONCLUSIONS Hyperoxia exposure can activate the Wnt/β-catenin signaling pathway, and USP7 may participate in hyperoxic lung injury through the Wnt/β-catenin signaling pathway. The USP7 specific inhibitor P5091 may accelerate the degradation of β-catenin by enhancing its ubiquitination, reduce lung epithelial-mesenchymal transition, and thus exert a certain protective effect against hyperoxic lung injury.
Animals ; Animals, Newborn ; Hyperoxia/physiopathology* ; Lung/physiopathology* ; Random Allocation ; Rats ; Rats, Wistar ; Thiophenes/pharmacology* ; Ubiquitin-Specific Peptidase 7/metabolism* ; Ubiquitin-Specific Proteases ; Wnt Signaling Pathway