Goeli-ROS

Question 1

Where is hydrogen peroxide formed?

Answer 1

In peroxisomes by oxidases.

Question 2

How are ROS used in Phagocytes?

Answer 2

Phagocytes produce free radicals to attack bacteria often through the rapid consumption of O2 (respiratory burst)

Question 3

What are the three main ROS formed?

Answer 3

1. Superoxide- by NADPH oxicase transfers e from NADPH to O2
2. HOCL- made by myeloperoxidase (MPO) only in phagocytic cells of the immune system (Neutrophils)
3. NO- is inducible in response to phagocytosis of bacteria (high conc + 02) = toxic

Question 4

What is the enzyme defect in CGD?

Answer 4

Phagocytes have genetic defects in NADPH oxidase.

Question 5

What happens when NADPH is defective?

Answer 5

If NADPH is defective superoxide isn’t made and the bacteria aren’t killed when ROS are released into the phagosome. This leads to the formation of a granuloma.
*x linked

Question 6

Why do individuals with CGD have greater susceptibility to bacterial and fungal infections?

Answer 6

These kids are specifically more susceptible to catalase + orgs (aspergillus, s. aureus, serratia, etc). Catalase can degrade the small amt of H202 produced by the microb which allows them to survive in the phagosome. If microb is catalase - the small amt of H202 in the phagosome will be enough to kill them.

Question 7

What is the mechanism for ishcemia reperfusion injury?

Answer 7

A lack of oxygen decreases ATP which leads to the loss of mitochondrial ion gradients (increased Na and Ca). This leads to increased superoxide production when O2 becomes available during reperfusion. The ROS in the blood can damage cells.