Ascorbic Acid Attenuates Hyperoxia-Compromised Host Defense against Pulmonary Bacterial Infection

Area of Science:

• Pulmonary Medicine
• Immunology
• Nutritional Science

Background:

• Supraphysiological oxygen (hyperoxia) impairs macrophage phagocytosis via increased reactive oxygen species (ROS) and high-mobility group box protein B1 (HMGB1).
• This impairment increases susceptibility to bacterial infections like ventilator-associated pneumonia (VAP).

Purpose of the Study:

• To investigate if ascorbic acid (AA) can mitigate hyperoxia-induced host defense compromise.
• To determine AA's effect on macrophage function and bacterial infection during hyperoxia.

Main Methods:

• C57BL/6 mice exposed to hyperoxia (≥98% O2) and inoculated with Pseudomonas aeruginosa, with simultaneous AA administration.
• RAW 264.7 macrophage-like cells incubated with AA prior to hyperoxic exposure (95% O2).

Main Results:

• AA (50 mg/kg) significantly improved bacterial clearance and reduced airway HMGB1 in mice.
• AA stabilized macrophage phagocytic activity in a concentration-dependent manner.
• AA decreased intracellular ROS production and extracellular HMGB1 accumulation in macrophages.

Conclusions:

• Ascorbic acid supplementation can prevent or attenuate ventilator-associated pneumonia development.
• AA enhances macrophage function, offering a therapeutic strategy for hyperoxia-induced immune compromise.