Olfactory receptors (ORs) are expressed in the olfactory epithelium of the nose to detect common odorants in the environment, they have also been mapped outside of the olfactory system in other human tissues, including the testis, lung, intestine, skin, heart, and blood.  However, the function of the majority of ORs in non-olfactory tissues remains unclear, leaving much to be uncovered in regards to these neuron-like cells scattered throughout the body, and manual body regulation.  Now, a literature review from researchers at Ruhr-Universität Bochum provides the most up-to-date overview of receptors detected so far and their functions within the human body.  The team states understanding the molecular and cellular mechanisms of action of extra nasal ORs will ultimately lead to their clinical utility.  The opensource study is published in the journal Physiological Reviews.  

Previous studies have shown ORs fulfill important functions in tissues outside of the nose with researchers successfully describing the role of olfactory receptors in more than 20 different types of human tissue.  Using up to date DNA sequencing it was shown that five to eighty different types of olfactory receptors can be found per tissue.  Olfactory receptors outside the nose act as chemoreceptors being activated by a specific molecule to stimulate the cells to multiply, move, or release specific chemical transmitters.  ORs also have the ability to switch on different signaling pathways in cells, including those controlling apoptosis.

The current lit review elaborates potential clinical applications, such as cancer diagnosis and therapy, and discusses the steps researchers could take to ensure the full potential of ORs.  The team states cancer cells often contain specific ORs in large amounts, extremely dissimilar to those found in healthy cells.  They go on to hypothesize ORs could be used as specific markers in cancer diagnosis as well as oncology-based therapeutics, particularly in intestinal or bladder cancer whose cells are easily accessible for odorants.

It was found applications in the field of wellness and healthcare are also viable, with skin regeneration, intestinal digestion, and hair growth regulated by olfactory receptors.  The lab notes this OR therapeutic method is already being applied to tissue repair and the promotion of healthy digestion.  They go on to add in order to exploit the ORs’ potential in the areas outlined ongoing in-depth research is crucial, with the activating odorants of only about fifty of the 350 known human olfactory receptors identified to date.

The team surmises they have provided an up-to-date review of the occurrence of human ORs outside of the nose with a focus on their effects on various human tissues.  For the future, the researchers state it is essential to decode additional olfactory receptors, to identify the relevant signaling pathways, and to shed light on the function of receptors in the human body.

Source: Ruhr-Universität Bochum

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