Functions of human olfactory mucus and age-dependent changes

Abstract

Odorants are detected by olfactory sensory neurons, which are covered by olfactory mucus. Despite the existence of studies on olfactory mucus, its constituents, functions, and interindividual variability remain poorly understood. Here, we describe a human study that combined the collection of olfactory mucus and olfactory psychophysical tests. Our analyses revealed that olfactory mucus contains high concentrations of solutes, such as total proteins, inorganic elements, and molecules for xenobiotic metabolism. The high concentrations result in a capacity to capture or metabolize a specific repertoire of odorants. We provide evidence that odorant metabolism modifies our sense of smell. Finally, the amount of olfactory mucus decreases in an age-dependent manner. A follow-up experiment recapitulated the importance of the amount of mucus in the sensitive detection of odorants by their receptors. These findings provide a comprehensive picture of the molecular processes in olfactory mucus and propose a potential cause of olfactory decline.

The Latest Cellular and Molecular Mechanisms of COVID-19 on Non-Lung Organs

“…Additionally, non-neuronal cells, such as sustentacular cells and Bowman’s glandular cells, are involved in mucus secretion [ 122 ]. Which owns different functions but most important, olfactory mucus coats the sensory neurons that sense odorants [ 123 ]. RNA sequencing reveals that sustentacular cells, Bowman’s glandular cells, and a limited number of stem cells express ACE-2 and TMPRSS2 significantly, unlike ORN and olfactory bulb cells [ 122 , 124 ].…”

Prediction on Air–Nasal Mucus Partition Coefficients of Odor Compounds

“…Odor molecules inhaled into the nose must first dissolve in the mucus layer that lines the nasal cavity before they can reach the olfactory receptors. − The air–mucus partition coefficient of odorants is a crucial factor in determining the distribution of odorants within the olfactory region of the nose and ultimately influences the ability of the olfactory system to detect and distinguish different odorants. In general, a low air–nasal mucus partition coefficient means that the odorant tends to dissolve readily in the mucus layer and is likely to come into contact with the olfactory receptor cells that are embedded in the mucus.…”