Photodamage and Photoaging


What are Photodamage and Photoaging?

Photodamage is damage to skin or DNA caused by exposure to ultraviolet radiation. Similarly, photoaging is the damage done to the skin from a lifetime of prolonged exposure to ultraviolet radiation. They’re essentially interchangeable terms. I’ll use the term photodamage from now on. Ultraviolet radiation (UV rays) comes from the sun and wreaks havoc on our skin. Photodamage can manifest itself on the skin in  many ways. Dermatologists call photodamage any signs of aging caused by the sun’s rays. This can range from wrinkles and leathery texture to the development of both malignant and benign skin cancers. However, photodamage is avoidable.

Some people can’t leave the house without putting on mascara, but I can’t leave the house without putting on sunscreen. However, I’m not a sunscreen saint that lathers up from head to toe every day before putting on my clothes (although I should). I won’t leave the house without sun protection for my face.

Why am I so religious about sun protection? Because I don’t want to be a leather couch later on in life. See leather couch woman depicted below. That’s somewhat of a hyperbole. When it comes to sun damage and aging, prevention is absolutely the best and cheapest option.

signs of photodamage and photoaging

What is the mechanism behind Photodamage?

The sun and DNA are not friends. The sun likes to destroy the orderly way in which DNA is arranged. DNA is the king of the cell. It’s made up of a double helix which forms 2 strands. These strands of DNA are composed of A’s, T’s, G’s, and C’s. On that double helix, A’s can only pair with T’s on the opposite side, and G’s can only pair with C’s on the opposite side. Sun damage induces the formation of pyrimidine dimers. This means that now the T on one side bonded itself to the adjoining T on the same strand and made a weird kink in the DNA.

DNA UV mutation pyrimidine dimer

The generation of pyrimidine dimers.

Fortunately, our bodies have a way of repairing DNA damage. Special enzymes are solely devoted to fixing DNA damage. DNA polymerase is one of these enzymes. It is able to fix DNA into its original code where T goes with A and G goes with C. Unfortunately, DNA repair is not perfect. As time goes on and DNA damage accumulates, mutations will occur. Most importantly, DNA mutations are what lead to cancers and aging. (1) Repair mechanisms don’t work as well the older you get. They are overwhelmed when there are catastrophic amounts of DNA damage. (2) Pyrimidine dimers are the most heavily discussed example of sun-induced damage. There are other forms of sun-induced DNA  damage as well. For instance, reactive oxygen species are also generated by sun damage. These molecules can wreak havoc in your cells.

Does tanning build up resistance to Photodamage?

The redness and darker skin after a sunburn aren’t signs of healthy skin. Skin can’t beat the sun. Tan skin is damaged skin that’s desperately trying to repair itself. The skin becomes red, inflamed, immunosuppressed, and generates pigment as a response to damage. (2) If you’re going to be out in the sun, sunscreen is your best friend.

There is a lot of research to back this up. In one study, researchers irradiated in vitro skin models with UVA and UVB rays. The control group did not receive any sunscreen, and the treatment group was slathered with sunscreen. The results showed that fewer pyrimidine dimers are generated when using a broad-spectrum sunscreen. How many fewer pyrimidine dimers exactly? There were less than 0.1 pyrimidine dimers/mmwhen broad-spectrum sunscreen was used as compared to 1 pyrimidine dimers/mm2 when no sunscreen was used. (3)

Types of Ultraviolet Radiation (UVA, UVB, and Others)

First of all, you’ve probably heard of UVA and UVB rays. UVA and UVB are the ones that cause DNA damage and skin cancer. For this reason, buy sunscreen that’s labeled Broad-Spectrum. This means it covers both the UVA and UVB sides of the ultraviolet spectrum. Don’t be fooled by some of the stuff on the internet that says UVA is for aging, or UVB is for burns. Hence, they’re both bad. UVB is higher energy, but get enough UVA and you’re getting the same result: DNA damage.

Some studies have even implicated visible light and infrared radiation as possible causes of photoaging. (4) Yes, even those fluorescent lights you sit under all day may be causing damage to your skin. There isn’t a lot of research on the subject yet. The only way we have right now to protect against infrared damage is antioxidants. This has been shown to help in in vitro studies and very small in vivo human studies. It doesn’t hurt to use products containing antioxidants like Vitamin E, vitamin C, ubiquinone, ferulic acid, and/or tocopherol just in case.

How will I get enough Vitamin D if I’m not laying out in the sun?

You get enough Vitamin D from the sun walking in the parking lot to and from your car on a regular basis. 15 minutes of total sun exposure a day is enough. The sun is needed (only the UVB rays) to convert 7-dehydrocholesterol to pre-vitamin D3. Pre-Vitamin D goes on in the Vitamin D synthesis pathway until you get the active form used by your body. The active form of Vitamin D is called 1,25-dihydroxycholecalciferol aka 1,25-dihydroxyvitamin D3 aka calcitriol. In sunny countries like Nigeria, people still get Vitamin D deficient Rickets because of inadequate dietary intake. Therefore, the best thing you can do is intake enough Vitamin D from foods. This is preferable to ruining your precious skin with photodamage.

How to Prevent Photodamage

If you’re thinking: “Oh no the rays are going to get me, I need to build a house below ground and avoid the sun like the plague!”

Don’t take it to the extreme. I challenge you to never leave the house without putting on an SPF containing foundation/moisturizer/whatever on your face. If I can convince you to start this one healthy habit, I promise you won’t regret it. Put it on your neck, ears, and the backs of your hands too.

Look for at least SPF 30. I know it’s really hard to find this in most foundations. There are a ton of tinted sunscreens out there that provide coverage like a foundation with the bonus of sun protection. If you’re going through the trouble of putting a bunch of makeup on, do yourself a favor and add sunscreen. It only means you have to wear that much less makeup when you’re older and suffer that many less chemical peels to undo what you’ve done.

Other ways to avoid photodamage include: wearing long sleeved clothing and pants, wide-brimmed hats, staying in the shade, and avoiding sun exposure between the hours of 10AM and 4PM.

How to Treat Photodamage

Finally, many treatment options exist to help undo photodamage. Most modalities aim to increase the sloughing of the photodamaged skin to reveal new healthy skin. As mentioned in my previous post, Tretinoin (Retin-A) is the best medication you can use in my and many experts’ opinions. Other methods, such as chemical peels and laser treatments, are more expensive and painful but usually yield quicker more dramatic results.

What’s your favorite way to prevent photodamage? Leave your comments below!

References

  1. Vink AA, Roza L. Biological consequences of cyclobutane pyrimidine dimers. J Photochem Photobiol B, Biol. 2001;65(2-3):101-4.
  2. Marrot L, Meunier JR. Skin DNA photodamage and its biological consequences. J Am Acad Dermatol. 2008;58(5 Suppl 2):S139-48.
  3. Dehaven C, Hayden PJ, Armento A, Oldach J. DNA photoprotection conveyed by sunscreen. J Cosmet Dermatol. 2014;13(2):99-102.
  4. Grether-beck S, Marini A, Jaenicke T, Krutmann J. Photoprotection of human skin beyond ultraviolet radiation. Photodermatol Photoimmunol Photomed. 2014;30(2-3):167-74.

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