MAPK pathways mediate hyperoxia-induced oncotic cell death in lung epithelial cells

Area of Science:

• Pulmonary Medicine
• Cell Biology
• Molecular Mechanisms of Disease

Background:

• Cell injury and death in pulmonary epithelium are key in acute lung injury pathogenesis.
• Hyperoxia exposure can lead to significant lung tissue damage.

Purpose of the Study:

• To investigate the molecular mechanisms driving cell death in lung epithelium under hyperoxia.
• To differentiate between apoptotic and oncotic cell death pathways induced by hyperoxia.

Main Methods:

• Exposure of MLE-12 cells to 95% oxygen (hyperoxia).
• Assay for caspase-3 activity and phosphatidylserine translocation to distinguish apoptosis from oncosis.
• Analysis of transcription factor AP-1 and mitogen-activated protein kinase (MAPK) pathways (p38 and JNK).
• Inhibition of AP-1, p38, and JNK pathways to assess their role in cell survival.

Main Results:

• Hyperoxia induced cell death characterized by swelling and mitochondrial dysfunction, consistent with oncosis, not apoptosis.
• Sustained activation of AP-1, p38, and JNK was observed in hyperoxia-exposed cells.
• Inhibiting AP-1, p38, or JNK significantly enhanced MLE-12 cell survival during hyperoxia.
• Oxidative apoptosis induced by hydrogen peroxide also involved AP-1, JNK, and p38 pathways.

Conclusions:

• Hyperoxia triggers a programmed oncosis in lung epithelial cells mediated by AP-1, JNK, and p38 MAPK.
• Despite different downstream events, both hyperoxic oncosis and oxidative apoptosis share upstream signaling pathways.
• Targeting these shared upstream pathways (AP-1, JNK, p38) may offer therapeutic strategies for hyperoxic lung injury.