DD Ultraviolet Damage and Repair Flashcards

1
Q

UVR (UVB+UVA) damage to skin includes:

A

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

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2
Q

UVB radiation

A

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.

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3
Q

Vitamin D synthesis via sunlight (UVR)

A

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

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4
Q

UVA physiological changes

A

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
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5
Q

UVB physiological changes

A

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

-high energy

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6
Q

UVC

A

Filtered out by ozone typically

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7
Q

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

A

UVB >UVA with non melanoma skin cancer,

UVB=UVA in melanoma

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8
Q

Particularly for UVR, main types of DNA damage are

A

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

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9
Q

Negative effects of UVA

A

Oxidative damage
Base modification
Bbasic sites
Strand breaks

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10
Q

Negative effects of UVB

A

Cell cycle changes
Mutations
Cyclopuridine dimers
Photoproducts

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11
Q

Melanocytes

A

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.

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12
Q

Outcome of DNA Damage

A
  • Repair of Damage
  • Induction of Apoptosis
  • Gene Mutation
  • Carcinogenesis initiation, transformation and progression
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13
Q

What does UVR induce?

A
  1. Leukocyte migration into the skin
  2. Inflammation
  3. Immunosuppression
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14
Q

UVR Induced Immunosuppression

A
  • 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
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15
Q

Is UVR immunosuppression inhibited by high melanin content?

A

no.

it potentiates induction of NMSC (non-melanoma skin cancer)

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16
Q

Xeroderma Pigmentosum

A

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
Q

Defenses against Reactive Oxygen in the Epidermis

A
  • Peroxidases and catalases
  • Superoxide dysmutase
  • Glutathione reductase
  • Thioredoxin reductase
18
Q

Melanocytes are situated in which layer of the skin

A

Basal

19
Q

Photocarcinogenesis Cascade

A
  1. UV Exposure
  2. DNA Damage
  3. Formation of Mutations
  4. Multistage Carcinogenesis
    Initiation
    Promotion
    Transformation
20
Q

Sunscreen typically refers to what?

A

UVB rating

-best sunscreen uses both UVB and UVA protection