UV Radiation and DNA repair

Question 1

__________ radiation is responsible for most of the effects of the sunlight on the body?

Answer 1

uv-b

Question 2

___ radiation is the main cause of sunburn and tanning

Answer 2

uv-b

Question 3

___ radiation is main cause of formation of VitD3

Answer 3

uv-b

Question 4

UV-B penetration

Answer 4

not fa - most is absorbed in the superficial tissue layers of 0.1mm depth

Question 5

UVR effects on skin (6)

Answer 5

damage to DNA/RNA/protein/lipid

pro-inflammatory effects

immunosuppressive effects

induction of innate defense

induction of apoptosis

vitD synthesis

Question 6

Most skin cancers are caused by?

Answer 6

UVA and UVB UV rays

Question 7

UVB biological consequences?

Answer 7

eye problems

sunburns

Question 8

UVB penetration?

Answer 8

just epidermis

Question 9

UVA biological consequences?

Answer 9

dartk patches
wrinkles
loose skin
premature aging

Question 10

UVA penetration?

Answer 10

through dermis

Question 11

Erythema action spectrum is highest at?

Answer 11

low wavelength UVB (290nm) - so most sunburn is UVB dependent

Question 12

melanoma

Answer 12

UVA and UVB

Question 13

DNA damage primarily

Answer 13

UVB

Question 14

NMSC?

Answer 14

mainly UVB

Question 15

Erythema?

Answer 15

mainly UVB

Question 16

Immune suppression?

Answer 16

mainly UVA

Question 17

UVB affected cells?

Answer 17

kertinocytes
melanocytes
langerhaans

Question 18

UVA affected cells

Answer 18

In addition to those in epidermis (kertinocyte, melanocyte, langerhaans)
also those in dermis
- fibroblast
- vessle and CT damage

Question 19

what is present in skin that is converted to vitD3

Answer 19

7-dehydrocholesterol

Question 20

DNA damage indueced by UVR?
Thymine dimer?

Pyrimidine-6-4-pyrimidone?

Hydroxyguanosine (free radicals)?

Answer 20

UVB

UVB

UVA

Question 21

mainly responsible for oxidative damage and base modifications?

Answer 21

UVA

Question 22

mainly responsible for strand breaks / mutation / cell cycle changes

Answer 22

UVB

Question 23

Outcome of DNA damage to skin (3)

Answer 23

repair
induction of apoptosis
gene mutation
–> carcinogenesis initiation, transformtion, progression

Question 24

basal and apoptosis

Answer 24

more resistant

Question 25

What contributes to the erythema and oedema you seen in sunburn?

Answer 25

leukocyte extravasation and migration to the inflammatory sunburn cytokines are induced by UVR

Question 26

UVR induces inflammation by?

Answer 26

mediated by primary and secondary cytokines as well as lipids - erythema and sunburn cells potentiate other types of cutaneous inflammation (adhesion molcules, induction, cytoine and chemokine release)

Question 27

Important mediators released by UVR | Primary cytokines?

Answer 27

IL-1a / TNF-a

Question 28

Important mediators released by UVR | Secondary cytokines?

Answer 28

IL-6, IL-8, IL-10, GM-CSF

Question 29

How does DNA damage via UVR cause immune suppression

Answer 29

via preferentially stimulating TH2 --> cytokine IL10 TNFalpha --> suupress cell induction?

Question 30

UVR and langerhaans

Answer 30

reduces langerhaans cell population

Question 31

UVR and inhibitory cytokine

Answer 31

IL10 / TH2

Question 32

Is UVR immunosuppression inhibited by high melanin content?

Answer 32

No - so it will not be affected by black vs white

Question 33

What does UVR immunosuppression potentiate?

Answer 33

induction of NMSC

Question 34

Skin defenses against UVR? (4)

Answer 34

DNA repair Apoptosis Defenses against ROS Melanin

Question 35

________________ is a family of diseases in which genetic defects lead to premature aging of the skin and fatal induction of UVR induced skin cancer

Answer 35

xeroderma pigmentosum

Question 36

What activates DNA repair enzymes following exposure to UVR

Answer 36

p53 activation by UVR

Question 37

Defenses against ROS in epidermis?

Answer 37

peroxidase and catalase superoxide dysmutase glutathione reductase thioredoxin reductase

Question 38

albinism | defective?

Answer 38

tyrosinase

Question 39

tyrosinase

Answer 39

converts tyrosine to dopa which is beginning of melanin production cascade

Question 40

Who knows to make more melanin?

Answer 40

surrounding keratinocytes are principle detectors of UVR adn they signal melanocytes to increase melanin production as well as melanocyte proliferation

Question 41

SPF refers to?

Answer 41

UVB rating