Introduction: Respiratory infections caused by rhinovirus exacerbate inflammatory diseases such as chronic obstructive pulmonary disease. Exercise training is proposed to have anti-inflammatory effects that may limit infection-induced airway inflammation.
Aim: Our aim was to examine the effects of exercise training on airway inflammation in a rhinovirus infection model.
Methods: Sixteen-week-old female C57BL/6 mice were randomised to one of four experimental groups (n=6 per group): Control (no exercise) + UV-Inactivated Rhinovirus (C-UV); Exercise training + UV-Inactivated Rhinovirus (E-UV); Control + Rhinovirus (C-RV); Exercise training + Rhinovirus (E-RV). The exercise training groups completed sixty minutes of treadmill running at 50% maximal speed, five days per week, for a total of eight weeks. Controls remained in their cages (exposed to room air) in the treadmill room during exercise sessions. Minor group rhinovirus serotype-A1 (RV-A1) (2.5×106 median TCID50) or UV-Inactivated RV-A1 was administered intranasally 24 hours following exercise training or control. Bronchoalveolar lavage (BAL) samples were harvested and processed for inflammatory cells 24 hours later. Between-group differences were analysed by ANOVA with Benjamini-Hochberg correction for multiple comparisons.
Results: Our data reveal significant effects of exercise training on baseline airway inflammation but not during rhinovirus infection. Statistically significant differences between groups were observed for BAL neutrophils (cells/mL:p=0.001; %:p=0.002), lymphocytes (cells/mL:p=0.009) and macrophages (%:p=0.001). Mean absolute BAL neutrophil count in E-UV was 12-to-30-fold lower than C-UV (p=0.214), C-RV (p=0.006) and E-RV (p=0.004). Mean absolute BAL lymphocyte was 4-fold lower in E-UV than C-RV (p=0.001). Mean relative BAL neutrophil count in E-UV was lower than C-UV (-11.5%,p=0.086), C-RV (-23.5%,p=0.002) and E-RV (-29.0%,p<0.001). Mean relative BAL macrophage count in E-UV was greater than C-UV (13.3%,p=0.062), C-RV (26.4%,p=0.001) and E-RV (31.8%,p<0.001).
Conclusion: Exercise training favourably modifies airway inflammation, particularly neutrophil count, which may be an important mechanism in regulation of the immune system with ageing and inflammatory diseases.