UV damage and repair Flashcards
UVR effects on the skin
- damage to the DA, RNA, lipids and proteins
- pro-inflammatory effects
- immunosuppression
- induction of the innate immune system
- induction of apoptosis
- Vitamin D synthesis
Describe vitamin D metabolism in the skin
- UV (specifically UVB) induces synthesis of Vitamin D3 and D2 in the epidermis. These are then transported to the liver and kidney and activated.
- Vitamin supplements contain both D2 and D3, mainly D2 (which is less active). There is some controversy over whether the benefits of UV exposure can be fully supplied with vitamin supplementation
Define SPF, what increasing or decreasing SPF means, and the rationale for the use of sunscreen agents
- SPF: sun-protective factor for UVB alone. Should have UVA also.
- Good sunscreens: UVA has a longer-lasting effect.
- Parsol 1789 (avobenzone) = good ingredient (lasting UVA protection)
- Neutrogena Helioplex = current gold standard
- SPF15 is not sufficient especially for photosensitive, skiers, cancer risk patients, etc- want at least SPF 30. Avoid noontime exposure.
UVA effects
goes fully into the dermis
- dark patches
- wrinkles
- loose skin
- premature aging
- DNA damage
UVB
barely into the dermis
- sunburn
- eye problems
- DNA damage
-also Vit D synthesis
skin defenses against UVR
- DNA Repair
- Apoptosis of Cells with DNA Damage
- Defenses Against Reactive Oxygen
- Melanin
melanocytets
deposit melanin in to kertinocytes
Increased melanogenesis occurs in response to
UVR. Surrounding keratinocytes are principle detectors of UVR, and they signal melanocytes to increase melanin production as well as melanocyte proliferation. Many genes are involved that are known to assist with melanin biogenesis.
Melanin
is synthesized within intracellular organelles known as melanosomes. The process of melanin polymerization results in generation of free radicals that have the capability of damaging cells, hence the need for limiting melanin biosynthesis to melanosomes
list the skin diseases caused by UVR
skin cancer (melanoma and non-melanoma) -photodermatoses (XE, idiopathic, chem photosensitivity (drug induced, porphhyria) photoaggrevated dermatoses - psoriasis and atopic dermatitis)
