Ultraviolet Damage and Repair

Question 1

Which type of UV light is responsible for most of the negative physiological effects?

Answer 1

UVB, although UVA can also cause DNA damage

Question 2

UVA is ______ than UVB.

Answer 2

longer (it can thus penetrate deeper into the skin and affect fibroblasts and connective tissue)

Question 3

Why don’t we worry about UVC and solar light with shorter wavelengths than UVB?

Answer 3

Because the middle and upper atmosphere scatter it

Question 4

_____ light induces vitamin D synthesis.

Answer 4

UVB

Question 5

List the five main categories of UVR’s effects on skin.

Answer 5

(1) vitamin D synthesis; (2) damage to DNA, RNA, proteins, and lipids; (3) apoptosis; (4) pro-inflammatory effects; and (5) induction of innate defenses

Question 6

_____ is the most effective UV light at inducing ROS generation and immunosuppression.

Answer 6

UVA

Question 7

UVB acts primarily on _________.

Answer 7

Langerhans cells, keratinocytes, and melanocytes

Question 8

What is the precursor molecule in vitamin D synthesis?

Answer 8

7-dehydrocholesterol

Question 9

Other than thymine dimerization, what does UVR do to DNA?

Answer 9

Pyrimidine 6,4 pyrimidone formation (UVB), and hydroxyguanosine formation (UVA and singlet oxygen)

Question 10

By what two mechanisms does UVR induce immunosuppression?

Answer 10

(1) stimulating the immune-regulatory molecules, such as IL10; and (2) decrease in Langerhans proliferation

Question 11

What pro-inflammatory molecules are released by UVR?

Answer 11

IL-1, TNF-alph, prostaglandins, leukotrienes, and histamine

Question 12

List four ways that the skin can protect itself against UV damage.

Answer 12

DNA repair, apoptosis of excessively damaged cells, ROS defense, and melanin

Question 13

Where are melanocytes located?

Answer 13

Stratum basalis

Question 14

Thioredoxin reductase is an ________.

Answer 14

enzyme that protects against reactive oxygen species