Biologists have found out why the skin reddens and itchs with sunburn

Damaged skin cells with sunburn secrete a large number of deformed signal RNA molecules that penetrate healthy cells and cause them to produce proteins that cause inflammation and other characteristic signs of "reloading" - redness and painful sensitivity, scientists say in an article published in the journal Nature Medicine .

"Some diseases, in particular psoriasis, are treated with ultraviolet irradiation.The main problem of this therapy is an increased likelihood of developing skin cancer.With our discovery, we can get the positive effects of UV irradiation without the actual irradiation.In addition, we can now block this mechanism to protect the body of especially sensitive people, for example, patients with lupus, from ultraviolet, "- said the head of the group of biologists Richard Gallo (Richard Gallo) from the University of California in San Diego (USA).

Gallo and his colleagues studied the effects of ultraviolet irradiation on human skin cultures and on the skin of healthy mice.

During the first experiment, biologists grew several cultures of skin cells, divided them into two groups and irradiated half of them with ultraviolet for a minute. The power of such radiation simulates a strong sunburn, with some cells in the test tubes either dying, or irreversibly damaged. Some time after irradiation, scientists cleared the nutrient medium from the cells and added it to test tubes with healthy cultures.

This led to unusual consequences - healthy cells began to secrete a large number of protein molecules, TNF-alpha and interleukin-6. These compounds belong to a class of anti-inflammatory proteins that stimulate the metabolism, transferring healthy cells to the "emergency" regime and triggering mechanisms of self-destruction in damaged cells.

Biologists analyzed the contents of the extract from the nutrient medium in which the irradiated cells lived and found a number of deformed signal RNA molecules. According to Gallo and his colleagues, these molecules were combined with special protein outgrowths on the walls of healthy cells - the receptors of the congenital immune system TLR-3. This receptor belongs to the class of so-called Toll-like receptors, which control the protective reaction to certain types of bacteria and the appearance of cancer cells.

Scientists synthesized artificial RNA molecules, similar to those that produce healthy cells and irradiated them with ultraviolet light. They added the resulting molecules to the nutrient medium to healthy cells and followed their reaction. Synthetic RNAs produced the same effect as their natural counterparts.

In the following experiment, Gallo and his colleagues neutralized this effect by removing the TLR-3 receptor gene from the mouse genome. According to scientists, disabling this gene made the skin of rodents insensitive to ultraviolet radiation and injections of damaged RNA, - redness of the skin was absent, as healthy cells ceased to release anti-inflammatory proteins.

As biologists note, preparations based on RNA molecules can be used as a "replacement" of irradiation in some types of therapy.

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