Oxidative stress-induced endothelial dysfunction drives mechanical and infectious lung injury: Therapeutic potential of kaempferol in males.

Mechanical ventilation (MV) remains an essential life-support strategy for patients with respiratory failure or critical illness. However, the mechanical stress generated during MV can lead to ventilator-induced lung injury (VILI). By integrating population-level epidemiology with bulk microarray and single-cell transcriptomic profiling, we identified a convergent pathogenic program shared by MV- and sepsis-associated lung injury, characterized by persistent oxidative stress and widespread endothelial dysfunction. In the National Health and Nutrition Examination Survey (NHANES), higher dietary intake of kaempferol, a plant-derived flavonol, was associated with improved pulmonary function in men. Ingenuity Pathway Analysis (IPA) results showed that NADPH oxidase (NOX) in the plasma membrane is the direct target of kaempferol. AlphaFold Protein Structure Database and cryo-electron microscopy (cryo-EM) resolved NOX2 structure, combined with molecular docking, suggest a direct interaction between kaempferol and NOX2. We also found that MV led to elevated reactive oxygen species (ROS) and induced endothelial dysfunction in various regions of the lung. Of note, kaempferol alleviated abnormal mechanical stress-induced ROS and endothelial barrier disruption by inactivating NOX2-Calcium-calmodulin-dependent protein kinase II (CaMKII)- Extracellular signal-regulated protein kinase 1/2 (ERK1/2) axis both in vivo and in vitro. Besides, kaempferol also improved survival rate and alleviated acute lung injury in cecal ligation and puncture (CLP)-induced septic mice via inhibiting the NOX2-CaMKII-ERK1/2 signaling pathway. These findings highlight the therapeutic potential of kaempferol in attenuating MV-associated lung injury and alleviating pre-existing inflammatory damage to the lung.