Ultraviolet Radiation and DNA Repair

Question 1

Peak time of biologic effectiveness of UVR

Answer 1

noon

Question 2

Lift UVR effect on skin

Answer 2

-Damage to DNA, RNA, lipids, proteins
-Pro-inflammatory effects
-Induction of apoptosis
-Vitamin D synthesis
Immunosuppressive effects
-Induction of innate defenses

Question 3

Role of UVR in vitD synthesis

Answer 3

UVR induces the non-enzymatic synthesis of cholecalciferol (VitD3) and ergocalciferol (VitD2). -Both converted to active form in liver and kidney

Question 4

DNA Damage Induced by UVR

Answer 4

-Thymine dimer
(cyclobutane pyrimidine dimer) : UVB
-Pyrimidine-6-4 pyrimidone: UVB
–Hydroxyguanosine (UVA and singlet oxygen)

Question 5

Proinflammtory effects of UVR

Answer 5

mediated by primary and secondary cytokines and lipid mediators.

• Erythema,
• sunburn cells,
• potentiation of other types of cutaneous inflammation

Question 6

UVR Induced Immunosuppression

Answer 6

-UVR decrease in Langerhans Cell populations
-UVR induction of inhibitory cytokine network
-Tolerance induced by Suppressor cells
Treg & NKT cells

Question 7

T or F: UVR Immunosuppression Not inhibited by high melanin content

Answer 7

True

Question 8

Xeroderma Pigmentosum

Answer 8

family of diseases in which genetic defects in DNA repair lead to premature aging of the skin and fatal induction of UVR-induced skin cancers

Question 9

list UV Induced Skin Cancers

Answer 9

melanoma, BCC, SCC

Question 10

list Photodermatoses

Answer 10

-Idiopathic probably immunologic
Solar urticaria, PMLE, actinic prurigo
-DNA repair Defects Xeroderma pigmentosum
--Chemical photosensitivity Drug induced
Porphyria
-Photoaggrevated dermatoses
Psoriasis
Atopic Dermatitis

Question 11

Define SPF

Answer 11

Sun Protective Factor refers to UVB rating. Best sunscreen block: both UVB and UVA. Factor by which burning is prolonged