Modulation of bronchial epithelial cell barrier function by in vitro ozone exposure

Ozone exposure affects airway epithelia, but the specific mechanisms remain unclear. Peripheral airway epithelial cells are vulnerable to ozone, which may impair their barrier function. Prior research has shown that ozone induces inflammation and alters permeability in these regions. However, the direct impact of ozone on epithelial cells is not fully understood. Establishing how ozone interacts with epithelial barriers is essential for understanding airway disease progression. Existing studies focus on systemic effects rather than localized cellular responses. This gap motivated researchers to examine ozone's direct influence on bronchial epithelial cells. The need for targeted in vitro models led to this investigation.

This study aimed to assess how ozone exposure directly affects bronchial epithelial cell barrier function. Researchers focused on paracellular permeability and electrical resistance in cultured canine bronchial epithelial cells. The goal was to determine whether ozone exposure alters these parameters in a dose-dependent manner. They also sought to identify potential protective agents against ozone-induced damage. The study tested the effects of antioxidants and cytoskeletal stabilizers on ozone-induced changes. A key question was whether these effects are reversible or progressive over time. The experimental design allowed for precise measurement of permeability shifts. The findings could clarify how ozone contributes to airway dysfunction.

Canine bronchial epithelial cells were cultured at an air interface to mimic in vivo conditions. Cells were exposed to ozone at 0.2, 0.5, or 0.8 ppm for 3 hours or to filtered air. Mannitol flux was measured to assess paracellular permeability changes. Transcellular electrical resistance was monitored to evaluate barrier integrity. Vitamin E and vitamin A were used to test antioxidant protection against ozone effects. Phalloidin, an actin polymerizing agent, was applied to assess cytoskeletal involvement. Permeability measurements were repeated at 18 hours post-exposure to track reversibility. The experimental setup allowed for dose-response and time-dependent analysis.

Mannitol flux increased by 461%, 774%, and 1172% at ozone concentrations of 0.2, 0.5, and 0.8 ppm, respectively. Transcellular resistance decreased in a dose-dependent manner following ozone exposure. Pretreatment with vitamin E or vitamin A reduced permeability increases by 33% and 34%, respectively. Phalloidin pretreatment inhibited ozone-induced permeability changes by 34% and 25% at 0.5 and 0.8 ppm. Permeability increases at 0.2 and 0.5 ppm were partially reversed by 18 hours post-exposure. The 0.8 ppm ozone effect worsened by 42% at this time point. These findings suggest a direct oxidative effect on epithelial cells. The reversibility of effects depends on ozone concentration.

Ozone exposure directly impairs bronchial epithelial cell barrier function in a dose-dependent manner. The observed increases in permeability suggest a paracellular disruption mechanism. Antioxidants like vitamin E and vitamin A can partially mitigate ozone-induced damage. Cytoskeletal disruption appears to play a role in ozone-induced permeability changes. The reversibility of effects varies with ozone concentration and time post-exposure. Higher ozone levels may lead to progressive barrier dysfunction. These results align with the hypothesis of direct oxidative effects on epithelial cells. The findings support the role of antioxidants in protecting against ozone-induced damage.