Sunburn: healing phenomenon to be avoided as much as possible

Why does the skin become red and sensitive as a result of excessive sun exposure? And why are red-haired people even more affected by these sunburns? Two in-depth studies lift the veil on the mechanisms involved in the inflammation caused by ultraviolet rays. A paradoxical phenomenon, sunburn is an inflammatory reaction which, by eliminating dead cells and those with genetic alterations, triggers a process of healing of skin cells.

We have known for a long time that the harmful effect of excessive sun exposure is due to UVB rays: by interacting directly with skin cells, these high-energy rays cause inflammation characterized by redness (erythema) and, in some cases, genetic alterations that increase the risk of melanoma. On the other hand, the sequence of events involved in this response of skin cells to UV radiation is still largely misunderstood.

To solve this enigma, American researchers subjected skin cells to UVB rays and examined the formation of molecules capable of activating the production of TNF, an

inflammatory agent suspected of playing an important role in the burning phenomenon associated with prolonged exposure to the sun. They made the astonishing discovery that UVB rays break down small non-coding RNA molecules (which are not translated into proteins) located in the cell nucleus. The irradiated cells release the broken RNA, which prompts nearby healthy cells to manufacture TNF to trigger the inflammatory response to eliminate sun-damaged cells. This inflammatory reaction triggers the healing process by eliminating dead cells as well as those with genetic alterations, before they become cancerous.

In other words, sunburn is the visible (and painful) manifestation of a healing reaction triggered by healthy cells in response to the breaking of RNA molecules caused by UVB rays. However, this mechanism is not perfect and it goes without saying that repeated sunburns increase the risk that damaged cells escape this cleaning process and become cancerous. It is therefore essential to always use protective sun creams or even put on clothing before exposing yourself to the sun, especially in the middle of the day when the radiation is maximum.

Clear skin, redhead, even more precautions to take

These recommendations are particularly important for people who have very pale skin, red hair and freckles.These characteristics are caused by a genetic variation that controls pigment production in the skin Instead of generating eumelanin, a brown/black pigment that blocks UV rays, skin cells called melanocytes produce pheomelamine, which has no protective properties. very important for these people to avoid prolonged exposure to the sun without protection.

Recent research shows that red-haired people have an increased risk of melanoma, even in the absence of UV radiation. noted that he genetic variation leading to the synthesis of red pigment causes increased DNA damage to skin cells and an increased incidence of invasive melanoma, even in the absence of UVB. Pheomelanin is therefore capable of inducing the formation of melanomas by itself, possibly by stimulating a mechanism that causes oxidative stress in skin cells.

Foods to favor

At the level of skin cells. In addition to avoiding unprotected exposure to the sun, red-haired people therefore benefit from adopting certain lifestyle habits that minimize this oxidative stress, for example by abstaining from smoking and eating healthy foods. In this sense, it is interesting to note that green tea, foods rich in carotenoids such as tomatoes, whose lycopene is distributed in the skin, and certain fruits such as pomegranate or grapes all have antioxidant and anti-inflammatory actions. which could help reduce the risk of melanoma in these people.

Source

Bernard JJ et al. Ultraviolet radiation damages self noncoding RNA and is detected by TLR3. NatureMedicine; 18: 1286–1290.

Mitra D et al. An ultraviolet-radiation independent pathway to melanoma carcinogenesis in the red hair/fair skin background. Nature 491: 449-543

Presse Santé strives to transmit health knowledge in a language accessible to all. In NO CASE, the information given can not replace the advice of a health professional.

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