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Published on: September 29, 2008
Increased expression of CHOP and LC3B in newborn rats with bronchopulmonary dysplasia
Mengyun Li1, Bingting Pan1, Yongyan Shi1
1Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China.
Insights
Bronchopulmonary dysplasia (BPD) in newborn rats impairs lung development. The study found that C/EBP homologous protein (CHOP) and microtubule-associated protein light chain 3 beta (LC3B) are upregulated and may jointly contribute to BPD pathogenesis.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Developmental Biology
Background:
- Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants, leading to significant long-term health issues.
- Current treatments for BPD have limited efficacy, highlighting the need for a deeper understanding of its underlying mechanisms.
- Key cellular pathways involved in BPD pathogenesis, particularly endoplasmic reticulum stress and autophagy, require further investigation.
Purpose of the Study:
- To investigate the role of C/EBP homologous protein (CHOP), activating transcription factor 4 (ATF4), and microtubule-associated protein light chain 3 beta (LC3B) in neonatal rats with induced BPD.
- To examine the interaction and co-localization between CHOP and LC3B in lung tissues of BPD model rats.
- To elucidate the impact of BPD on alveolar development and type II alveolar epithelial cell (AECII) ultrastructure.
Main Methods:
- Induction of BPD in newborn rats using hyperoxia (80-85% FiO2) and comparison with control rats (21% FiO2).
- Assessment of alveolar development via radial alveolar count (RAC) and alveolar septum thickness.
- Ultrastructural analysis using transmission electron microscopy (TEM) and evaluation of protein and mRNA expression of CHOP, ATF4, and LC3B via immunohistochemistry, western blot, and RT-qPCR.
- Co-localization studies using immunofluorescence and correlation analysis between CHOP and LC3B protein levels.
Main Results:
- BPD model rats exhibited impaired alveolarization compared to controls.
- TEM revealed damage to AECII lamellar bodies, endoplasmic reticulum (ER) dilation, and autophagy in BPD lungs at day 14.
- Protein levels of ATF4, CHOP, and LC3B were significantly increased between days 7 and 14 in BPD rats, while mRNA levels of CHOP and LC3B were decreased.
- CHOP and LC3B were co-localized in lung cells, and their protein levels showed a positive correlation, suggesting a joint role.
Conclusions:
- BPD induces significant ultrastructural damage in AECII cells, including ER dilation and autophagosome formation.
- The upregulation of CHOP and LC3B proteins, along with their co-localization and positive correlation, indicates their potential joint involvement in BPD development.
- Further research into the interplay between ER stress (CHOP) and autophagy (LC3B) could offer novel therapeutic targets for BPD.
Abstract:
Bronchopulmonary dysplasia (BPD) seriously affects the health and prognosis of children, but the efficacy of treatments is poor. The present study aimed to examine the effects of C/EBP homologous protein (CHOP), activating transcription factor 4 (ATF4) and microtubule‑associated protein light chain 3β (LC3B), and the interaction between CHOP and LC3B, in newborn rats with BPD. At 1, 7, 14 and 21 days, the rats in the model [fraction of inspired oxygen (FiO2)=80‑85%] and control groups (FiO2=21%) were randomly sacrificed, and lung samples were collected. Alveolar development was evaluated according to the radial alveolar count (RAC) and alveolar septum thickness. Ultrastructural changes were observed by transmission electron microscopy (TEM), the expression levels of CHOP, ATF4 and LC3B were determined by immunohistochemistry, and western blot and reverse transcription‑quantitative polymerase chain reaction analyses. The co‑localization of CHOP and LC3B in lung tissues was determined by immunofluorescence. The results showed that, compared with the control group, alveolarization arrest was present in the model group. The TEM observations revealed that, at 14 days, type II alveolar epithelial cell (AECII) lamellar bodies were damaged, with an apparent dilation of the endoplasmic reticulum (ER) and autophagy in cells within the model group. Between days 7 and 14, the protein levels of ATF4, CHOP and LC3B were significantly increased in the model group. The mRNA levels of CHOP and LC3B were lower at days 7‑21. CHOP and LC3B were co‑localized in the cells of the lung tissues at day 14 in the model group. Pearson's correlation analysis showed that the protein levels of CHOP and LC3B‑II were positively correlated in the model groups. As in previous studies, the present study demonstrated that BPD damaged the AECII cells, which exhibited detached and sparse microvilli and the vacuolization of lamellar bodies. In addition, it was found that the ER was dilated, with autophagosomes containing ER and other organelles in AECII cells; the expression levels of CHOP and LC3B‑II were upregulated. CHOP and LC3B‑II may have joint involvement in the occurrence and development of BPD.
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