Inflammatory changes such as subepithelial edema and excessive inflammatory cell infiltration have been observed in uvular tissues of obstructive sleep apnea (OSA) subjects. The levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin-6 are elevated in the serum of apneic patients and have been proposed as mediators of muscle weakness. TNF-α has been shown to affect diaphragm contractility in mice and rabbit in vivo.
To assess total and compartmental TNF-α expression in uvular tissues of apneic and nonapneic patients.
Uvular tissues were collected from 14 snorers without sleep disorders breathing, 14 subjects with OSA (OSA 1 group) whose body mass index (BMI) was similar to that of snorers, and 12 additional obese OSA subjects (OSA 2 group) who underwent an uvulopalatopharyngoplasty. Sections were examined using immunohistochemistry and Western blot analysis. TNF-α expression was evaluated in the musculus uvulae (MU), epithelial layer, and perimuscular tissues from proximal uvular sections.
TNF-α was more highly expressed in whole uvular protein extracts of apneic groups than in snorers ([mean ± SEM] snorers, 100.5 ± 3.0%; OSA 1 group, 127.1 ± 6.9%; OSA 2 group, 140.7 ± 11.0%; p = 0.01). In the muscular area, TNF-α levels were higher in the more obese OSA subjects than in the other two groups (snorers, 100.3 ± 3%; OSA 1 group, 107.4 ± 0.7%; OSA 2 group, 124.1 ± 4.2%; p = 0.007). In the muscular area, TNF-α was correlated with BMI, but no relationship was found with the apnea-hypopnea index.
We conclude that MU is the major TNF-α source in uvular tissue and that TNF-α is more highly expressed in the heaviest OSA patients compared to less obese OSA patients and nonapneic snorers.