Infection, inflammation and exercise in cystic fibrosis

Abstract

Regular exercise is positively associated with health. It has also been suggested to exert anti-inflammatory effects. In healthy subjects, a single exercise session results in immune cell activation, which is characterized by production of immune modulatory peptides (e.g. IL-6, IL-8), a leukocytosis and enhanced immune cell functions. Upon cessation of exercise, immune activation is followed by a tolerizing phase, characterized by a reduced responsiveness of immune cells. Regular exercise of moderate intensity and duration has been shown to exert anti-inflammatory effects and is associated with a reduced disease incidence and viral infection susceptibility. Specific exercise programs may therefore be used to modify the course of chronic inflammatory and infectious diseases such as cystic fibrosis (CF).Patients with CF suffer from severe and chronic pulmonary infections and inflammation, leading to obstructive and restrictive pulmonary disease, exercise intolerance and muscle cachexia. Inflammation is characterized by a hyper-inflammatory phenotype. Patients are encouraged to engage in exercise programs to maintain physical fitness, quality of life, pulmonary function and health.In this review, we present an overview of available literature describing the association between regular exercise, inflammation and infection susceptibility and discuss the implications of these observations for prevention and treatment of inflammation and infection susceptibility in patients with CF.

Figure 1

Exercise-related immune responses. A single exercise session leads to immune activation and improved immune effector functions (left, upper panel), indicated by enhanced circulating levels of immune cells with an activated phenotype and enhanced production of immune modulatory peptides. Upon cessation of the exercise session, immune activation is followed by a tolerizing phase, which is characterized by reduced immune effector functions (left, lower panel). Immune cell levels return to normal or even below normal when the exercise session has been of high intensity and/ or duration. Immune cell responsiveness is reduced, indicated by a diminished production of immune modulatory peptides upon stimulation with ligands. Long-term changes induced by regular exercise result in immune dampening and improved immune effector functions, indicated by a reduced disease incidence and infection susceptibility (right).

Figure 2

Effect of exercise in inflammation in patients with cystic fibrosis, possible mechanisms. It can be hypothesized that a single exercise session in patients with cystic fibrosis leads to a more pronounced immune activation, since both a single exercise session and cystic fibrosis lead to immune activation. A single exercise session in healthy subjects also leads to improved immune effector functions, therefore improved anti-bacterial immunity induced by exercise in patients with CF may also be hypothesized (left). Regular moderate exercise results in immune dampening and improved immune effector functions, which may therefore reduce chronic inflammation in CF and improve anti-bacterial defence mechanisms.