Aerosolized vitamin D attenuates ozone-induced inflammation and transcriptional responses via membrane antioxidant effects in human bronchial epithelial cells

Ozone exposure increases the risk of infection, worsens lung diseases, and causes systemic health issues. As ambient ozone levels continue to rise globally, effective interventions are needed to reduce these harmful effects. Vitamin D, known for its anti-inflammatory properties, has been inversely linked to various lung conditions, including ozone-induced airway inflammation and reduced lung function. However, oral vitamin D supplementation has shown inconsistent results, possibly due to poor delivery to lung tissues. This study explores a novel approach using vitamin D aerosols to counter ozone-induced damage in primary human bronchial epithelial cells. Cells were pretreated with vitamin D aerosols apically or as a bulk addition basolaterally before ozone exposure at the air-liquid interface. Both treatment routes significantly reduced the ozone-induced secretion of the inflammatory cytokine IL-8. Furthermore, vitamin D suppressed the ozone-induced expression of inflammation- and oxidative stress-related genes, including <i>CXCL8</i>, <i>FFAR2</i>, <i>PTGS2 (</i>COX-2<i>)</i>, and <i>NFKB2</i>. Gene set enrichment analysis indicated that vitamin D reversed ozone-driven pathways related to inflammation, oxidative stress, and immune dysfunction. In addition, vitamin D pretreatment reduced lipid peroxidation, glutathione oxidation, and formation of ozone-derived oxysterols, suggesting a membrane antioxidant effect. These findings support vitamin D's potential as a protective agent against inhaled oxidants and highlight inhaled delivery as a promising therapeutic strategy for treating lung diseases.<b>NEW & NOTEWORTHY</b> Vitamin D aerosols have the potential to protect against exposure to ozone and other inhaled oxidants and prevent the development and exacerbation of lung disease. Here, we show that aerosolized vitamin D treatment decreased ozone-induced oxidative stress and inflammatory responses, as well as decreased production of an oxysterol, β-epoxycholesterol, indicating vitamin D may act as a membrane antioxidant in the airway epithelium.