Hyperoxia-induced lung injury increases CDKN1A levels in a newborn rat model of bronchopulmonary dysplasia

A rat model establishment of bronchopulmonary dysplasia-related lung & brain injury within 28 days after birth

PURPOSE

Lung injury associated with bronchopulmonary dysplasia (BPD) and its related neurodevelopmental disorders have garnered increasing attention in the context of premature infants. Establishing a reliable animal model is essential for delving into the underlying mechanisms of these conditions.

METHODS

Newborn rats were randomly assigned to two groups: the hyperoxia-induced BPD group and the normoxia (NO) group. For the BPD group, they were nurtured in a hyperoxic environment with a high oxygen inspired fraction (0.85) from birth until day 14 within 28 days postnatally. In contrast, the NO group consisted of newborn rats that were nurtured in a normoxic environment with a standard oxygen inspired fraction (0.21) for 28 days postnatally. Various pathological sections of both lung and brain tissues were examined. TUNEL staining, immunofluorescence assays, and functional tests were performed, and the results were meticulously analyzed to assess the impact of hyperoxia environments on the developing organs.

RESULTS

In the newborn rats of the BPD group, a significant reduction in alveolar number coupled with enlargement was observed, alongside severe fibrosis, collagen deposition, and constriction of bronchi and vascular lumens. This was accompanied by an accumulation of inflammatory cells and a marked deterioration in lung function compared to the NO group (P < 0.05). Additionally, a decrease in neuronal count, an increase in neuronal apoptosis, proliferation of neuroglia cells, and demyelination were noted, and poorer performance in the Morris water maze test within the BPD group (P < 0.05).

CONCLUSION

The BPD-rats model was established successfully. Lung injury in the BPD group evident across the bronchi to the alveoli and pulmonary vessels, which was associated with deteriorated lung function at postnatal day 14. Concurrently, brain injury extended from the cerebral cortex to the hippocampus, which was associated with impaired performance in orientation navigation and spatial probe tests at postnatal day 28.

P311 knockdown alleviates hyperoxia-induced injury by inactivating the Smad3 signaling pathway in type II alveolar epithelial cells

P311 is associated with alveolar formation and development. However, the role and possible mechanism of P311 in hyperoxia-induced injury in type II alveolar epithelial cells (AEC II) need to be elucidated. In our study, rat AEC II (RLE-6TN) were exposure to normoxia (21% O₂ and 5% CO₂) or hyperoxia (95% O₂ and 5% CO₂) for 24 h, followed by determination of P311 expression. After knockdown of P311 and hyperoxic treatment, cell viability, cell cycle progression, apoptosis and the Smad3 signaling pathway were examined. Rat AEC II were pretreated with SIS3 HCl for 4 h and then subjected to P311 overexpression plasmid transfection and hyperoxic exposure. Then, cell viability, apoptosis and the Smad3 signaling pathway were determined. The results showed that hyperoxic exposure significantly elevated P311 levels in rat AEC II. P311 knockdown increased cell viability, accelerated cell cycle progression and inhibited apoptosis, as well as suppression of the Smad3 signaling pathway in hyperoxia-exposed AEC II. Additionally, we found that P311 overexpression enhanced the effects of hyperoxia. Interestingly, SIS3 HCl incubation blocked the effects of P311 overexpression on rat AEC II function under hyperoxic condition, as evidenced by an increase in cell viability, and suppressions of apoptosis and the Smad3 signaling pathway. These results indicate that P311 knockdown may ameliorate hyperoxia-induced injury by inhibiting the Smad3 signaling pathway in rat AEC II. P311 may be a novel target for the treatment of hyperoxia-induced lung injury and even bronchopulmonary dysplasia (BPD).

RNA Sequencing Analyses Reveal the Potential Mechanism of Pulmonary Injury Induced by Gallium Arsenide Particles in Human Bronchial Epithelioid Cells

Extensive use of gallium arsenide (GaAs) has led to increased exposure to humans working in the semiconductor industry. This study employed physicochemical characterization of GaAs obtained from a workplace, cytotoxicity analysis of damage induced by GaAs in 16HBE cells, RNA-seq and related bioinformatic analysis, qRT-PCR verification and survival analysis to comprehensively understand the potential mechanism leading to lung toxicity induced by GaAs. We found that GaAs-induced abnormal gene expression was mainly related to the cellular response to chemical stimuli, the regulation of signalling, cell differentiation and the cell cycle, which are involved in transcriptional misregulation in cancer, the MAPK signalling pathway, the TGF-β signalling pathway and pulmonary disease-related pathways. Ten upregulated genes (FOS, JUN, HSP90AA1, CDKN1A, ESR1, MYC, RAC1, CTNNB1, MAPK8 and FOXO1) and 7 downregulated genes (TP53, AKT1, NFKB1, SMAD3, CDK1, E2F1 and PLK1) related to GaAs-induced pulmonary toxicity were identified. High expression of HSP90AA1, RAC1 and CDKN1A was significantly associated with a lower rate of overall survival in lung cancers. The results of this study indicate that GaAs-associated toxicities affected the misregulation of oncogenes and tumour suppressing genes, activation of the TGF-β/MAPK pathway, and regulation of cell differentiation and the cell cycle. These results help to elucidate the molecular mechanism underlying GaAs-induced pulmonary injury.