DNA Hypomethylation-Mediated Upregulation of GADD45B Facilitates Airway Inflammation and Epithelial Cell Senescence in COPD

Academic Background

Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous disease characterized by chronic airway inflammation and irreversible airflow limitation, and it is one of the leading causes of death worldwide. Although smoking is considered the primary risk factor for COPD, its exact pathological mechanisms remain incompletely understood. In recent years, the driving role of cellular senescence in COPD has gradually gained attention, as senescent cells exacerbate airway inflammation and lung function decline by secreting inflammatory factors and altering the microenvironment. The Growth Arrest and DNA Damage-Inducible (GADD45) family of proteins plays an important role in inflammation and cellular senescence, but its specific role in COPD remains unclear.

This study aims to explore the expression and role of the GADD45 family in COPD, particularly the mechanism of GADD45B in airway inflammation and cellular senescence. By revealing the regulatory mechanisms of GADD45B in COPD, this research provides potential new targets for the prevention and treatment of COPD.

Source of the Paper

This paper was authored by Yuan Zhan, Qian Huang, Zhesong Deng, and others, with the research team affiliated with the Department of Respiratory and Critical Care Medicine at Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, the Department of Respiratory Medicine at Qinghai University Affiliated Hospital, and several other institutions. The study was published in Volume 68 of the Journal of Advanced Research in 2025, with pages 201-214.

Research Process and Results

1. Upregulation of GADD45B in COPD Patients and Model Mice

The study first analyzed gene expression data from COPD patients (GSE38974 dataset) using bioinformatics, revealing that GADD45B is significantly upregulated in COPD patients and positively correlated with inflammation- and senescence-related genes. Subsequently, the research team collected 62 clinical samples (including 20 non-smokers, 20 smokers, and 22 COPD patients) and validated the high expression of GADD45B in the bronchial epithelium of COPD patients through qPCR, Western blot, and immunohistochemistry. Additionally, mouse experiments confirmed that GADD45B expression was significantly increased in wild-type mice exposed to cigarette smoke (CS).

2. GADD45B Promotes CSE-Induced Inflammation and Cellular Senescence in Human Bronchial Epithelial Cells (HBE)

To investigate the role of GADD45B in bronchial epithelial cells, the research team performed RNA sequencing on GADD45B-overexpressing HBE cells and found that the differentially expressed genes (DEGs) were mainly enriched in biological processes related to inflammation and cellular senescence. Subsequent experiments showed that overexpression of GADD45B significantly increased the release of inflammatory factors (such as IL-6, IL-8, and IL-1β) in HBE cells and upregulated the expression of senescence markers (such as p16 and p21). Conversely, knockdown of GADD45B alleviated CSE-induced inflammation and cellular senescence.

3. p38 Phosphorylation Mediates GADD45B-Induced Inflammation, While FOS Mediates Cellular Senescence

The study further explored the mechanisms by which GADD45B regulates inflammation and cellular senescence. Overexpression of GADD45B increased p38 phosphorylation, and the p38 inhibitor SB202190 significantly alleviated GADD45B-induced inflammatory responses. However, p38 phosphorylation did not affect GADD45B-induced cellular senescence. RNA sequencing and protein interaction analysis indicated that GADD45B promotes cellular senescence by interacting with the FOS protein. The FOS inhibitor T-5224 significantly alleviated GADD45B-induced cellular senescence, further validating this mechanism.

4. GADD45B Deficiency Improves Lung Function, Lung Injury, and Inflammation in CS-Exposed Mice

To validate the role of GADD45B in vivo, the research team constructed a GADD45B knockout mouse model. The results showed that GADD45B deficiency significantly improved lung function in CS-exposed mice and alleviated emphysema and airway inflammation. Additionally, GADD45B deficiency reduced the expression of senescence markers in the bronchial epithelium of CS-exposed mice, further confirming the regulatory role of GADD45B in cellular senescence.

5. CS-Induced DNA Hypomethylation Enhances GADD45B Expression

The study further investigated how CS regulates GADD45B expression. Through target bisulfite sequencing (TBS), the research team found that CS exposure significantly reduced DNA methylation levels in the promoter region of GADD45B. Treatment of HBE cells and mouse experiments with the demethylating drug 5-azacytidine (5-Aza) demonstrated that DNA hypomethylation is an important mechanism for CS-induced upregulation of GADD45B.

Conclusions and Significance

This study found that CS promotes the expression of GADD45B in bronchial epithelial cells by reducing DNA methylation levels in the GADD45B promoter. GADD45B directly promotes the release of inflammatory factors through p38 phosphorylation and promotes cellular senescence by interacting with FOS, further exacerbating inflammatory responses. These findings reveal the critical role of GADD45B in the pathogenesis of COPD and provide potential new targets for COPD treatment.

Research Highlights

1. Key Finding: First revealed the regulatory mechanisms of GADD45B in COPD, particularly its role in inflammation and cellular senescence.
2. Innovative Methods: Multi-dimensional validation of the function and mechanisms of GADD45B through RNA sequencing, TBS, and knockout mouse models.
3. Application Value: GADD45B as a potential therapeutic target for COPD provides a theoretical basis for developing novel therapies for COPD.

Other Valuable Information

The limitations of this study include the incomplete elucidation of the specific mechanisms of the interaction between GADD45B and FOS, necessitating further gene editing experiments and molecular biology research. Additionally, the role of GADD45B in other cell types (such as alveolar epithelial cells and immune cells) remains to be explored.