DD Ultraviolet Damage and Repair Flashcards Preview

BL DD final > DD Ultraviolet Damage and Repair > Flashcards

Flashcards in DD Ultraviolet Damage and Repair Deck (20):
1

UVR (UVB+UVA) damage to skin includes:

1) Damage to RNA, DNA, lipids, and proteins.
2) Pro-inflammatory effects
3) Immunosuppressive effects
4) Induction of innate defenses
5) Induction of apoptosis
6) Vitamin D synthesis

2

UVB radiation

Main cause of sunburn and tanning on skin, as well as Vit D3 formation.

UVB contributes to higher carcinogenesis than at larger wavelengths such as UVA.

3

Vitamin D synthesis via sunlight (UVR)

Cholecalciferol (VitD3) and ergocalciferol (VitD2) (also available through diet) --> converted to active form in liver and kidney (Di-hydroxy Vitamin D3)

4

UVA physiological changes

premature aging, loose skin, wrinkles, dark patches, and DNA damage
□ Used in tanning beds; most effective at inducing ROS and immunosuppression.
□ Penetrates deeper into dermis, thus act on fibroblasts and CT b/c of longer wavelength.

- low energy

5

UVB physiological changes

DNA damage, sunburn, and eye damage.
□ Act principally on keratinocytes, melanocytes, and Langerhans cells (DC of skin) b/c of shorter wavelengths

-high energy

6

UVC

Filtered out by ozone typically

7

Which, UVB or UVA is most associated with skin cancer?

UVB >UVA with non melanoma skin cancer,

UVB=UVA in melanoma

8

Particularly for UVR, main types of DNA damage are

§ Thymine dimer (UVB)
§ Pyrimidine-6-4-pyrimidone (UVB)
§ Hydroxyguanosine (UVA and singlet oxygen)

9

Negative effects of UVA

Oxidative damage
Base modification
Bbasic sites
Strand breaks

10

Negative effects of UVB

Cell cycle changes
Mutations
Cyclopuridine dimers
Photoproducts

11

Melanocytes

Functional “slaves” to keratinocytes that produce melanosomes that contain melanin.

• Increased melanogenesis occurs in response to UVR. Keratinocytes detect UVR, signal melanocytes to increase melanin production.

12

Outcome of DNA Damage

- Repair of Damage
- Induction of Apoptosis
- Gene Mutation
- Carcinogenesis initiation, transformation and progression

13

What does UVR induce?

1. Leukocyte migration into the skin
2. Inflammation
3. Immunosuppression

14

UVR Induced Immunosuppression

- UVR decrease in Langerhans Cell populations
-UVR induction of inhibitory cytokine network:
IL10, TH2 cytokine pattern
-Tolerance induced by Suppressor cells
Treg (CD4+CD25+)
NKT cells

15

Is UVR immunosuppression inhibited by high melanin content?

no.
it potentiates induction of NMSC (non-melanoma skin cancer)

16

Xeroderma Pigmentosum

is a 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

17

Defenses against Reactive Oxygen in the Epidermis

-Peroxidases and catalases
-Superoxide dysmutase
-Glutathione reductase
-Thioredoxin reductase

18

Melanocytes are situated in which layer of the skin

Basal

19

Photocarcinogenesis Cascade

1. UV Exposure
2. DNA Damage
3. Formation of Mutations
4. Multistage Carcinogenesis
Initiation
Promotion
Transformation

20

Sunscreen typically refers to what?

UVB rating

-best sunscreen uses both UVB and UVA protection