Episode 50.
Sun Tans vs Sun Burns

Question:

Key Points:

• As of 2021, as a civilization, we do not know for sure all of the things that determine whether a person tans vs burns, but we assume it mostly has to do with people's genes.
• In Episode 12: Can Babies Be Born with Pink Hair? we discussed the different Melanin that our bodies produce to create hair color. Pheomelanin produces red or yellow pigments and Eumelanin produces black or brown pigments
• We have genes which indicate how much red vs yellow pheomelanin is produced, how much black vs brown eumelanin is produced, and how much eumelanin vs pheomelanin is produced.
• Melanocytes produce melanin essentially the same for hair color as skin color by packaging it into a melanosome
• The Melanocytes live just above the "basement membrane" which is the barier between the epidermis (top layer of skin) and the dermis (the lower layer of skin)
• Melanin, specifically eumelanin, converts UV radiation into heat. Eumelanin is able to effectively convert over 99.9% of UV radiation that hits it into heat.
• Human skin has light receptors, similar to those in the eye, which triggers melanocytes to increase the production of melanin within about 2 hours from exposure to UV-B radiation
• Exposure to UV-A radiation causes the cell to move the melanosomes that are already there to the periphery (outside) of the skin cells which mean that you will quickly get a little bit darker. Once that radiation is removed, the melanosomes start floating around the cell again, so the tan quickly fades.
• When UV radiation does not hit a melanosome, then it will hit something else in the cell. The thing that is most important in the cell not to be damaged is the DNA.
• DNA can get damaged by having a UV ray hit it directly or by hitting anything else in the cell which releases a charged oxygen atom which then goes and bonds with and corrupts the DNA
• When the DNA of our cells gets damaged, then we have multiple enzymes which go to work to try to repair the cell.
• When there is too much damage to the cell to be repaired, the cell self-destructs.
• Our immune system detects the damage to the cells (and the self-destruciton) and sends in anti-bodies and white blood cells.
• It is actually our immune system's response which causes the sunburn: redness, swelling, etc
• If our cell does not self-destruct, there is potential for cancer
• Our bodies need some amount of UV radiation in order to convert 7-dehydrocholesterol into vitamin D.
• Therefore, the melanocytes are trying to provide an appropriate amount of melanin to balance protection to the DNA vs the production of vitamin D.
• The main gene for our melanin production is MC1R. This deals with what types of melanin are produced: red vs yellow, brown vs black, and eumelanin vs pheomelanin
• The ASIP can down-modify the amount of eumelanin produced
• OCA2 defines how to make a p-protein which is used to move melanin from the melanocytes to the cells that need it. (One type of albinoism is where the person makes melanin but does not make this p-protein, so then cells don't have any melanin even though the body is able to produce it
• IRF4 deals with adaptive responses from our immune system, which can allow it to not over-react to the UV radiation
• CYP1B1 deals with our ability to create the enxyme which corrects issues in our DNA
• AYR deals with creating an enzyme that does transcription of DNA, so a better value of this gene allows for tanning to be more likely because the DNA repair happens more quickly
• TRPS1 deals with turning genes on and off, which, naturally, influences burning vs tanning because it can choose which genes to utilize
• Our sweat is made of water and water can reflect up to 80% of UV rays, so it can act as a defense
• Damaged skin, such as 2nd degree burns, can cause damage to a melanocyte, which means that they can no longer produce the melanin needed to protect the next potential sunburn