Benefits of oat β-glucan on respiratory infection following exercise stress:: role of lung macrophages

Benefits of oat beta-glucan on respiratory infection following exercise stress: role of lung macrophages. Am J Physiol Regul Integr Comp Physiol 294: R1593-R1599, 2008. First published March 19, 2008; doi:10.1152/ajpregu.00562.2007.-Exercise stress is associated with an increased risk for upper respiratory tract infection (URTI). We have shown that consumption of the soluble oat fiber beta-glucan (O beta G) can offset the increased risk for infection and decreased macrophage antiviral resistance following stressful exercise; however, the direct role of macrophages is unknown. This study examined the effect of macrophage depletion on the benefits of orally administered O beta G on susceptibility to infection ( morbidity, symptom severity, and mortality) following exercise stress. CL2MDP ( Ex-H2O-CL2MDP, Ex-O beta G-CL2MDP, Con-H2O-CL2MDP, Con-O beta G-CL2MDP)encapsulated liposomes were administered intranasally to deplete macrophages, and PBS ( Ex-H2O-PBS,Ex-O beta G-PBS, Con-H2O-PBS, Con-O beta G-PBS)-encapsulated liposomes were given to macrophage-intact groups. Ex mice ran to volitional fatigue on a treadmill for 3 consecutive days, and O beta G mice were fed a solution of 50% O beta G in their drinking water for 10 consecutive days before infection. Fifteen minutes following the final bout of Ex or rest, mice were intranasally inoculated with 50 mu l of a standardized dose of herpes simplex virus-1. Ex increased morbidity ( P < 0.001) and symptom severity ( P < 0.05) but not mortality ( P = 0.09). The increase in morbidity and symptom severity was blocked by O beta G consumption for 10 consecutive days before exercise and infection [morbidity ( P < 0.001) and symptom severity ( P < 0.05)]. Depletion of macrophages negated the beneficial effects of O beta G on reducing susceptibility to infection following exercise stress, as evidenced by an increase in morbidity ( P < 0.01) and symptom severity ( P < 0.05). Results indicate that lung macrophages are at least partially responsible for mediating the beneficial effects of O beta G on susceptibility to respiratory infection following exercise stress.