Rodent of the Week: Smelling signs of illness

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You’ve probably heard of dogs that seem to smell a disease, such as a cancerous tumor, in their owners. Scientists say they may have figured out why some animals have disease-sniffing abilities.

Research published online this week in the journal Nature identified some new receptors on olfactory cells in mice that appear to establish this unique talent. Previous studies have shown that mice have smell receptors in their noses that pick up the scents of a mate, food or even emotions like fear. Mice are also known to avoid their sick friends. In the new study, scientists at the University of Geneva in Switzerland examined the mouse genome to look for receptor proteins in the olfactory system. They found five receptors from a family of proteins known as formyl peptide receptors. Formyl peptide receptors are known to exist in the immune system. They detect chemicals given off by germs in order to help the immune system attack those pathogens. What the researchers found was that the newly identified olfactory receptors do the same for pathogens outside the body or in another animal.

In the study, they placed the olfactory mouse receptor neurons in a dish and exposed the neurons to disease-causing bacteria and the urine of sick mice. Some of the neurons responded to the chemicals by sending off electrical charges, which indicates recognition.

These disease-sniffing sensors are found in a part of the brain that also identifies chemicals called pheromones, which are important to mating. The area is linked to the brain’s emotional center, which is probably why mice react quickly to the threat of disease or to the perfect mate

Alas, these receptors have only been found in gerbils, rats and mice. There’s no evidence that humans have formyl peptide receptors anywhere but in the immune system. But the research could open a new avenue in molecular medicine for detecting, or sniffing out, disease.

-- Shari Roan

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