Role Of Macrophages On The Benefits Of O??G On Susceptibility To Infection Following Exercise Stress

Abstract

Exhaustive exercise has been associated with increased risk for respiratory infection. Oat β-glucan (OβG), a soluble fiber with mild immunostimulant activity, can offset the decrease in macrophage (MΦ) antiviral resistance and increased risk of infection associated with exercise stress. PURPOSE To determine the role of lung MΦs on the benefits of OβG on susceptibility to infection following exercise stress. METHODS Exercise mice were run to fatigue on a treadmill for 3 consecutive days prior to infection. OβG was fed in the drinking water for 10 consecutive days prior to infection. Mice were administered 100μl of clodronate (Ex-H2O-CL2MDP, Ex-OβG-CL2MDP, Con-H2O-CL2MDP and Con-OβG-CL2MDP) or phosphate buffered saline (Ex-H2OPBS, Ex-OβG-PBS, Con-H2O-PBS and Con-OβG-PBS) encapsulated in liposomes, via an intra-nasal route on the 1st day of exercise and the 4th day following infection. MΦs ingest the liposomes and are killed by the clodronate through apoptosis. This procedure has previously been found to deplete approximately 75% of lung MΦs. Fifteen minutes following exercise or rest on the last day of training, mice were intranasally inoculated with HSV-1 (1.28 × 105 PFUs). They were monitored twice daily for morbidity, mortality and symptom severity for 21 days. RESULTS As we have previously shown, exercise increased morbidity, mortality and symptom severity versus control, and this increase was attenuated in OβG fed animals. MΦ depletion negated the beneficial effects of OβG. CONCLUSION These data suggest that MΦs play an important role in the mechanism whereby OβG exerts its beneficial effects on reducing susceptibility to infection following exhaustive exercise. Funded by the American College of Sports Medicine.