A fly that rests on the arm, a hair that falls on the shoulders, a piece of clothing that moves. Sometimes just the touch of a small object on the skin is enough to trigger a strong itchy sensation. Today, a research team from the Scripps Research Institute in California has identified a new possible mechanism behind this phenomenon. The key would be found in a protein, called Piezo1, which, acting as a biological sensor, immediately detects when the skin is touched or touched and sends a signal to the brain.
The discovery of the Nobel
The discovery, for now on animals, is the work of the team led by Ardem Patapoutianwinner in 2021 – together with David Julius – of the Nobel Prize for Medicine, thanks to the discoveries on this protein and on its “sister” Piezo2. Although very initial, today’s results, published in Naturecould pave the way for new studies on anti-itch drugs, for example to be used in some patients suffering from eczema.
Itching: chemical or mechanical?
Since 2010, Patapoutian’s group has been studying sensory processes related to the sensation of one’s body in space, the need to urinate and itching. The identification of the two Piezo1 and Piezo2 receptors, linked to the perception of temperature and touch, earned him the Nobel Prize, in 2021, together with Julius. In recent times the group has focused on itching, distinguishing a more “chemical” itch, generated by the release of substances such as histamine and typical of allergic reactions, and another more “mechanical”, stimulated by contact or touching objects on the skin. The first, the chemical one, is more closely linked to the activation of the Piezo2 receptor. While the second, mechanical, would be associated with the Piezo1 protein, as the authors demonstrate today.
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The itch switch
To study the phenomenon, the scientists monitored the reaction of mice exposed to skin contact with thin filaments; all in combination with cell culture experiments. The result? In animals in which the Piezo1 protein was particularly present and active, the itching sensation and scratching behaviors were more marked. In contrast, mice with a reduced amount of the protein tended to scratch much less. “Just like a switch,” he explains Giacomo Koch, director of the laboratory of Experimental Neuropsychophysiology at the Santa Lucia Irccs Foundation, “once activated, the Piezo1 protein triggers a series of physiological processes through which the signal is communicated first to peripheral neurons, and then to the brain”. This is where the scratching begins.
Two channels of itch activation
“The study is valuable”, comments Koch, who is also Professor of Physiology at the University of Ferrara – not involved in the work, “since he identifies a new possible mechanism of itching, the mechanical one. The two activation channels, the chemical and mechanical ones are therefore different “. They are different but not completely disjoint. In fact, as mechanical itching decreased or increased, the “chemical” itch decreased or increased in animals – a proof of how, once activated, the two different pathways can mix and coexist.
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New strategies against itching
The authors of the work on Nature they then used a compound that serves to block Piezo1 in order to try to figure out if it could relieve the itch. The outcome is again favorable: in mice with a manifestation comparable to eczema, with this strategy the itching subsided. “The result is of interest”, adds Koch, “given that it identifies a new possible avenue for researching new therapeutic options, possibly to be allocated to patients suffering from itch”. The results, however, are very initial. “This is because they are obtained on animals”, explains the expert, “and because the chosen compound is not highly specific for the receptor considered”. As we know, the road to experimentation is long.
Itching, from prevention to remedies
From stress to pre-existing pathologies, from contact with irritants to allergens, the causes of itching are many and often coexistent. “There is no single itch, the chemical mechanisms can be numerous and coexistent,” he stresses Eleonora Nucera, director of the Allergy Service at the Agostino Gemelli Irccs University Polyclinic Foundation. “Some dermatological diseases, for example, have the release of histamine in common with allergic ones. There is also an itch not related to histamine, such as neurological and hepatic pruritus.” If the itching is persistent and the causes are not clear, it is advisable to go to the doctor, first of all that of the family, for more information.
Dermatitis: the answers to itching are online
In summer, then, the skin is more exposed and more subject to insect bites, especially mosquitoes. “Again, histamine is produced,” Nucera adds. “To prevent and protect ourselves we can apply insect-repellent sprays, even for children. Or, in some cases, in people with hyper-reactivity, supplementation with vitamin B1 can be recommended, since this component generates a skin odor. unpleasant for mosquitoes “.