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So. You're probably one of those people that thinks us humans only smell with our noses. But you'd be wrong.
A team of biologist eggheads at Ruhr University Bochum in Germany have turned the age-old, nose-centric notion of smell decidedly upside-down. It turns out that our olfactory receptors—which are responsible for the detection of odor molecules and transmit nerve impulses to the brain—don't just reside in our schnozes. In fact, they've discovered that 15 of these stink-sensing receptors that previously were thought only to be in the nose, are actually found in our skin cells as well. Humans have about 350 different kinds of olfactory receptors, which before you get cocky, is seriously nothing in comparison to most vertebrates. Some of whom use their sense of smell for hunting, finding food and eluding hungry predators; mice, for example, have more than 1,000 smell sensors.
If that isn't weird enough, the scientists also discovered that exposing one of these receptors to a synthetic sandalwood odor—known as Sandalore—set off a "cascade of molecular signals" that induces healing in injured tissue.
Lead researcher Dr. Hanns HattIn explains that in a series of human tests, skin abrasions exposed to the presence of Sandalore healed 30% faster than damaged skin left to its own devices. Hattin believes these findings could have a sweeping impact on the development of everything from dermatology and cosmetics to helping those in the wake of physical trauma.
How It Works
Apparently olfactory receptors comprise the largest subset of G protein-coupled receptors, which in turn, constitute a large protein family of receptors that are able to sense molecules outside the cell, and activate cellular responses. These G proteins are involved in everything from odors and pheromones to hormones, light-sensitive compounds, and neurotransmitters.
I like to think of them as a highly dedicated, omnipresent SWAT team that is poised and ready to react at any time.
New York Times writer Alex Stone opts for utilizing a lock and key metaphor for the olfactory receptors; the odor molecule—be it Thanksgiving dinner, your lovers neck-nook or fetid garbage—serves as the key to the receptor's lock:
"Only certain molecules fit with certain receptors. When the right molecule comes along and alights on the matching receptor, it sets in motion an elaborate choreography of biochemical reactions. Inside the nose, this culminates in a nerve signal being sent to brain, which we perceive as odor. But the same apparatus can fulfill other biological functions as well."
Dr. Hatt has been huffing out this seemingly peculiar situation since 2003 when he first discovered that olfactory receptors were found inside testes—serving as chemical homing device—guiding those ever-confused sperm cells toward an unfertilized egg; these days Hatt believes every organ in the body may possess olfactory receptors including the brain, colon, heart, liver and lungs. In 2009 he published a paper that proved that cancerous prostate cells, when exposed to beta-ionone (an odor found in roses and violets) the spreading of the sinister cells was inhibited. The theory is that the exposure to said smells successfully switched off "errant genes."
He has since identified olfactory receptors in several other organs, including the liver, heart, lungs, colon and brain. In fact, genetic evidence suggests that nearly every organ in the body contains olfactory receptors.
In 2009, for instance, Dr. Hatt and his team reported that exposing olfactory receptors in the human prostate to beta-ionone, a primary odor compound in violets and roses, appeared to inhibit the spread of prostate cancer cells by switching off errant genes.
"As the outermost barrier of the body, the skin is exposed to multiple environmental factors, including temperature, humidity, mechanical stress, and chemical stimuli such as odorants that are often used in cosmetic articles. Keratinocytes, the major cell type of the epidermal layer, express a variety of different sensory receptors that enable them to react to various environmental stimuli and process information in the skin." — Journal of Investigative Dermatology
And it turns out, our whole body being able to smell is not that strange after all. Dr. Hatt says that odor receptors are actually one of the oldest chemical sensors in the human body, evolutionarily, and can detect a multitude of compounds not just those wafting about in the wind. They enable our body to react to all kinds of stimuli to keep our vessel in tip top shape; in fact, Jennifer Pluznick, an assistant professor of physiology at Johns Hopkins University discovered that mice kidneys "employ well-designed chemosensors" which regulate all the necessary excretions, playing a "physiologically critical role" in renal function.
The body is a bona fide blur of mystery and wonder—keep it comin' science, keep it comin'.
