Cell signaling in smell loss (hyposmia)

Perception of odors depends upon detection of olfactory stimuli by olfactory receptors. This detection depends upon the complex processes of cellular signaling. Cytokines are chemical moieties which play a critical role in cell signaling. Cytokines are part of the cellular components which comprise and control olfactory receptor function. Cytokines which play this role in olfaction are found in nasal mucus. This control mechanism involves both proinflammatory and anti‐inflammatory components. In order to understand these complex events we measured levels of cytokines in nasal mucus in patients with smell loss (hyposmia) and compared these levels with those in saliva, blood plasma and urine. We measured several cytokines including IL‐1α, IL‐1β, IL‐2, IL‐1ra, IL‐6, IL‐10, IFN‐α, IFN‐β, TNF‐α and TRAIL in patients with hyposmia by use of a sensitive spectrocolorimetric immunoassay. Results in nasal mucus indicated a physiological balance occurs between proinflammatory and anti‐inflammatory cytokines in these patients with significantly higher levels of anti‐inflammatory cytokines (IL‐1ra, IL‐10) than proinflammatory cytokines (IL‐1α, IL‐1β, TNF‐α). These results indicate that there are important physiological mechanisms in nasal mucus which control this balance, thereby controlling the homeostasis in the nasal cavity and thereby controlling olfactory receptor function, in part through control of the level of inflammation in hyposmic patients. Clinical use of knowledge of this balance between pro‐ and anti‐inflammatory cytokines emphasizes the importance of presence of these cytokines in nasal mucus and the roles they may play in correction of hyposmia in these patients.