We explained in previous posts the mechanisms by which melanocytes synthesize melanin to protect our skin from solar ultraviolet radiation. This melanin is packaged and migrates to the outermost layers of our skin causing the sun tanning typical of summertime. If we are exposed to a large amount of ultraviolet radiation, melanin cannot absorb all the energy arriving at our body and it can damage some biomolecules in our cells resulting in an inflammatory process that becomes apparent in the redness our skin presents when it is burned. Despite sunburns usually heal without scars, I’m sure many of us have heard the sentence “the skin has memory”. This sentence typically refers to the long-term consequences that this damage can cause in our skin. Do you know how cells save this “memory”?
When the molecule receiving UV radiation is DNA, it can cause alterations in its sequence, that means, mutations. Cells have mechanisms able to repair those mutations or to promote programed cell death if the DNA damage is too much. That explains why skin peels off after sunburned: the most damaged layer in the skin dies, detaches and it is substituted by new cells (1).
However, some cells are able to escape these control mechanisms and survive with mutated DNA. Those mutations will be present in their daughter cells and from them to their daughters and so on until the percentage of damaged cells in the skin could be significant.
When cells with mutated DNA are exposed again to intense UV radiation, the process repeats. Thus, as time goes by and after successive UV exposures and sunburns, it is possible that there are cells that accumulate a great number of mutations. When that happens, cells can turn into malignant cells able to proliferate in an uncontrolled way giving rise to skin tumors (2).
Dermatologists and skin experts use the term “memory” to express that ability cells have to accumulate mutations in their DNA sequence until the damage is too high and it can result in a skin disease. It is important to note that part of the damage our body gets during a sunburn remains with us forever. The skin can “remember” by the mutations the moments it has suffered. For these reasons, it is so important to protect our skin from sun radiation, try to avoid maxim radiations hours (especially during summer), apply sun block and have a well moisturized skin.
- Gaddameedhi S, Selby CP, Kemp MG, Ye R, Sancar A. The circadian clock controls sunburn apoptosis and erythema in mouse skin. J Invest Dermatol. 2015;135(4):1119–1127.
- Rastrelli M, Tropea S, Rossi CR, Alaibac M. Melanoma: epidemiology, risk factors, pathogenesis, diagnosis and classification. In Vivo. 2014 Nov-Dec;28(6):1005-11.