Differential effects of intense exercise and pollution on the airways in a murine model

Exercise-induced bronchoconstriction (EIB) is a transient airway narrowing, occurring during or shortly after intensive exercise. It is highly prevalent in non-asthmatic outdoor endurance athletes suggesting an important contribution of air pollution in the development of EIB. Therefore, more research is necessary to investigate the combination of exercise and pollutants on the airways.

Balbc/ByJ mice were intranasally challenged 5 days a week for 3 weeks with saline or 0.2 mg/ml diesel exhaust particles (DEP), prior to a daily incremental running session or non-exercise session. Once a week, the early ventilatory response was measured and lung function was determined at day 24. Airway inflammation and cytokine levels were evaluated in bronchoalveolar lavage fluid. Furthermore, innate lymphoid cells, dendritic cells and tight junction mRNA expression were determined in lung tissue.

Submaximal exercise resulted in acute alterations of the breathing pattern and significantly improved FEV_0.1 at day 24. DEP exposure induced neutrophilic airway inflammation, accompanied with increased percentages of CD11b⁺ DC in lung tissue and pro-inflammatory cytokines, such as IL-13, MCP-1, GM-CSF and KC. Occludin and claudin-1(Cldn-1) expression were respectively increased and decreased by DEP exposure. Whereas, exercise increased Cldn-3 and Cldn-18 expression. Combining exercise and DEP exposure resulted in significantly increased SP-D levels in the airways.

DEP exposure induced typical airway neutrophilia, DC recruitment and pro-inflammatory cytokine production. Whereas, intensive exercise induced changes of the breathing pattern. The combination of both triggers resulted in a dysregulation of tight junction expression, suggesting that intensive exercise in polluted environments can induce important changes in the airway physiology and integrity.