Misty Hyman, Cathy Seiler

Olympic gold-medal swimmer Misty Hyman, left, and Dr. Cathy Seiler getting ready to swim.

In this two part series, I partner with my friend, Olympic gold medalist Misty Hyman, winner of the women's 200 meter butterfly in the 2000 Australian games.  Misty currently coaches private lessons, leads swim clinics, and gives motivational speeches around the world.  Misty was also recently named the senior assistant coach for the Arizona State University swim team. In her spare time, Misty extends her passion for swimming into the community as a spokesperson for FitPHX and encouraging everyone to learn how to swim.

Swimmers, as opposed to scientists, spend a lot of time outside.  Whether in the pool, by the pool, or in and around the beach, swimmers have a thing for the outdoors. With the outdoors, comes the sun.  With the sun, comes the possibility of a sunburn. And in Phoenix, where there are nearly 300 days a year with sun, a sunburn is even more likely. We all know that you should wear sunscreen to avoid getting a sunburn, but most people don't know what a sunburn is or why you want to avoid it.  That's what I'm going to talk about today.

So what is sunburn? Sunburn is a response to the UV light of the sun.  The UV light is a damaging agent to DNA, the genetic code within each of your cells responsible for making your cell function properly. If there is a lot of DNA damage caused by the UV light - if you are in the sun for too long - this is a trigger for these damaged skin cells to commit suicide in a process called apoptosis. Before your cells die, this damage induces an inflammatory response, which is what causes the redness and the heat that accompany a sunburn. A few days after the sunburn, your skin starts to peel - this is the layer of skin cells that committed suicide peeling away from your body.  To summarize - sunburn is essentially a form of radiation poisoning to the skin that kills an entire layer of skin cells because the DNA was too damaged for the cells to live.

Now as you and I both know, you don't always get a sunburn when you lay in the sun (or a tanning bed, which also using UV light and has the same affect as the sun's UV rays). Instead you could tan.  Tanning is a defense mechanism of your cells against the DNA damage caused by the sun's UV rays.  How does it work?  The UV triggers special cells in your skin called melanocytes to redistribute or darken a pigment called melanin.  This pigment absorbs the UV light and protects the DNA from the damaging effect of UV.  If you are naturally darker skinned or already tan, the melanin absorbs the UV light so you are less likely to damage your DNA and less likely to sunburn.  But this doesn't mean that you should just spend all of your time "working on your tan."  The melanin isn't a fail safe UV protector and DNA damage still occurs.

Now that you know how sunburn and tanning works, maybe you're thinking about how you're out in the sun all the time, but you don't get burned or you burn every once in a while but not all the time, so you must be okay. Maybe not.  When the UV light damages your DNA and you don't burn, your cells still have to repair this DNA damage.  If the DNA damage isn't repaired, you could end up with permanent mutations in the DNA of of your skin cells. These mutations may change the function of a protein and affect how your skin cells function.  Let's say for example that you get a mutation in a gene that prevents your skin cells from dying next time they are hit with too much UV from the sun. The next time you get a sunburn, this cell will get damaged, it won't die, and it will grow and divide with this mutation. Mutations then have the opportunity to accumulate and at a certain point will have enough mutations that the cells grow out of control and form skin cancer.

This can all be avoided in a number of ways.  You could become a scientist and never have the time to go outside because you're always in the lab (or in my case, because your office is in the basement).  Since that likely won't happen, you do have the option to avoid UV exposure by covering your skin with light clothing, a hat, or sunscreen. You can also avoid spending long periods of time in the sun or limit your exposure to times of day where the UV rays are not as strong (when the UV Index is low).  Either way, the DNA mutations accumulate over a lifetime of exposure, so decreasing exposure or protecting your skin at any age will provide an added benefit and decrease your risk of skin cancer.

Misty's Message: In fourth grade, Misty did a science project on sunscreen and won the elementary school science fair.  Clearly, avoiding sunburn has been an interest of hers from early on.  Her advice is still the same as her science fair conclusions in the fourth grade: "No matter what time of day it is, you should always wear your sunscreen especially when you're in the pool." The one exception is swimming at midnight - then you're okay.

Dr. Cathy Seiler is the Program Manager for the tissue biorepository at St. Joseph's Hospital and Barrow Neurological Institute. She has her BA in Biochemistry and Molecular Biology from Boston University and PhD in the Biological Sciences from Cold Spring Harbor Laboratory. Her research and teaching focuses on genetics, cancer, and personalized medicine. Find her on Facebook at www.facebook.com/thingsitellmymom

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