PURPOSE:Nasal mucosal immune suppression, induced by long-term high-intensity training, could lead to an increasing risk of upper respiratory tract infections. This study aimed to examine the effect of laser irradiation on nasal mucosa structure and nasal immune function.
METHODS:40 male Sprague Dawley rats, aged 8 weeks, were randomly divided into 4 groups: Control (C), Exercise (E), E + Low power laser (EL, 1 mw, 6.79 J/cm2), and E + High power laser (EH, 2 mw,13.58 J/cm2). The rats in all E-related groups went through an incremental treadmill exercise protocol: 6 days/week, 30 min/day; 10 m/min velocity during wk1, 20 m/min for wk2, with 5 m/min/wk increment in the following weeks. The laser treatments were He-Ne laser (2 h after exercise, 2 min) at two irradiation point (each side of the nasal ala). Pre- and post-6-week intervention, Structure of mucosa of nose was observed by HE staining, sIgA concentration of nasopharyngeal washing were examined by ELISA, and the expression of CD4+ and CD8+ T lymphocytes of nasal mucosa were analyzed by immunohistochemistry.
RESULTS: 1) Following changes (p<0.01) occurred in Exercise group after 6-wk exercise: nasal mucosa was seriously damaged, cilia layer of free edge essentially fell off, and the decline of sIgA (↓57%, ES=0.77) level and ratio of CD4+/CD8+ (↓41%, ES=0.53) were observed in nasal mucosa. 2) Compared with E group, the structure of nasal mucosa were obviously improved in EL group. In addition, the sIgA concentration (↑107%, p<0.01, ES=0.55), CD4+ cells (↑127%, p<0.01, ES=0.59), and ratio of CD4+/CD8+ (↑40%, p<0.05, ES=0.36) of nasal mucosa were enhanced markedly in EL group Compared with that of E group. 3) However, compared with E group, the EH treatment did not show significant effects as those by the EL group (p > 0.05), with the following changes: sIgA (↑40%, ES=0.29), CD8+ (↓12%, ES=0.13), and ratio of CD4+/CD8+ (↓20%, ES=0.15).
CONCLUSIONS: The long-term high-intensity exercise training would lead to destruction of nasal mucosa structure and the declining of nasal immune function. Low energy laser irradiation, especially EL treatment, had a beneficial effect on nasal mucosa immune function.