CREB1 controls mitochondrial dysfunction in 1-nitropyrene-mediated apoptosis of human bronchial cells and lung injury

Airborne pollutants, particularly nitro-polycyclic aromatic hydrocarbons (nitro-PAHs), are significant contributors to respiratory diseases. Among these, 1-NP, a nitro-PAH prevalent in diesel exhaust particles (DEPs), is known to induce lung damage. While studies on the respiratory toxicity of 1-NP remain limited, the underlying molecular mechanisms, particularly the roles of mitochondrial dysfunction and toxicity-related gene expression in lung cell death, are even less understood. To address this gap, this study aims to elucidate the relationship between 1-NP-induced lung cell death, mitochondrial dysfunction, and gene expression. In vitro assays were used to assess mitochondrial dysfunction and apoptotic markers in human bronchial epithelial cells, while phosphoproteomic analysis and in vivo murine models were employed to investigate the role of CREB1 phosphorylation in 1-NP toxicity. This study demonstrated an increase in apoptotic cells using Annexin V/PI staining and the activation of apoptotic proteins, such as caspase-3 and PARP, following a 24-h exposure to 1-NP. Notably, the mitochondrial cristae disruption occurred, accompanied by elevated expression of cytochrome c and Bid. Additionally, exposure of human bronchial epithelial cells to 1-NP led to significant mitochondrial dysfunction, characterized by decreased oxygen consumption rate and membrane potential, increased mitochondrial reactive oxygen species (ROS), and upregulated voltage-dependent anion channel 1 (VDAC1) expression. Phosphoproteomic analysis revealed that CREB1 phosphorylation protects against 1-NP toxicity. In contrast, CREB1 knockdown exacerbated mitochondrial respiratory disruption and apoptotic cell death, rendering cells more susceptible to 1-NP exposure. Furthermore, intranasal exposure to 1-NP in a murine model significantly elevated chemokine CCL2 levels in bronchoalveolar lavage fluid along with IL-1β and CXCL1 expression in lung tissue compared to the controls. Additionally, 1-NP exposure induced lung collapse, fibrosis, and mucin hyperexpression, along with increased expression of CREB1, cleaved caspase-3, VDAC1, and 8-OHdG, indicating oxidative DNA damage. This study demonstrates that 1-NP exposure induces CREB1 phosphorylation, mitochondrial dysfunction, cell death, and lung pathologies, highlighting the potential of this model for developing pharmaceutical interventions targeting respiratory diseases.