W3: Sublethal Injury and Adaptation

Question 1

What is the most damaging free radical?

Answer 1

Hydroxyl radical: OH

Question 2

What are examples of ROS (reactive oxygen species)

Answer 2

Free radicals: hydroxyl radical

Other reactive species: hydrogen peroxide

Question 3

What is the primary location of ROS generation?

Answer 3

Mitochondria

Question 4

Where is the major continuous source of ROS?

Answer 4

Mitochondria

Question 5

Describe the Fenton reaction. Where does it occur?

Answer 5

Iron turns hydrogen peroxide into hydroxyl radical; mitochondria

Question 6

The longer the ROS lives, the more/less damage there is.

Answer 6

Less (longer lived means less reactive; inverse relationship)

Question 7

Cysteine residues are especially susceptible to ROS because of theirf __ group.

Answer 7

SH (S-S cross linking)

Question 8

What are amino acids susceptible to adduct formation (addition product) from ROS?

Answer 8

Lysine, cysteine, tyrosine

Question 9

What are 4 effects of ROS on protein?

Answer 9

S-S cross-linking,
adduct formation (addition product),
protein unfolding,
protein scission (splitting apart)

Question 10

What are 6 effects of ROS on lipids?

Answer 10

ROS lipid propagation of ROS
lipid cross-linking
lipid scission
membrane fluidity

FAO
4-HNE formation (carbonylation)

Question 11

PUFA –ROS–> PUFA-OOH —> 4-HNE –> attachment of protein (___)

Answer 11

Carbonylation

ROS effect on lipid

Question 12

When PUFA is oxidized by ROS, ___ carbonylation occurs, attaching ____ to the FA.

Answer 12

4-HNE, proteins

Question 13

_____ is usually the starting ROS. But much of cell damage is result of ____ diffusing throughout and being converted to the highly reactive ____ radical.

Answer 13

Superoxide, H2O2, hydroxyl

Question 14

Lipid peroxidation byproduct ___ causes ___, a covalent modification of lipid by adding protein.

Answer 14

4-HNE, carbonylation

Question 15

__ % of acetaminophen usually gets excreted by ___ but __% yield superoxide and reactive/toxic intermediate (NAPQI).

Answer 15

95, hepatocyte, 5

common clinically

Question 16

What vitamins function as free radical quenchers?

Answer 16

E - reduces (redox) lipid peroxide radicals***

C - reduce (redox) vitamin E and quenches free radicals

A - may quench singlet oxygen

Question 17

A reduced _____ is a major cellular anti-oxidant that quenches oxygen free radicals.

Answer 17

Glutathione (GSH)

Reduced glutathione (GSH) - by reductase (replenish GSH)
Oxidized glutathione (GSSG) - by peroxidase (convert H2O2 to H2O)

Question 18

__to __ ratio is an indicator of cellular oxidative stress (redox state). Increase in ___ indicates to oxidative stress.

Answer 18

GSSG/GSH, GSSG

Question 19

___ can treat acetaminophen toxicity because it is converted to ___ in ___, reducing the toxic intermediate (NAPQI).

Answer 19

NAC (N-acetylcysteine), glutathione, hepatocytes

Question 20

Acetaminophen detoxification: ___ –> GSH in the liver, which creates non-toxic NAPQI conjugate.

Answer 20

NAC (N-acetylcysteine)

Question 21

Vit E/C replenishes vit E/C.

Answer 21

C (water) replenishes E (fat).

Question 22

Fava beans incur no cell injury to normal cells but can damage ___ when there is not enough enzyme ___ to replenish ___.

Answer 22

RBC, G6P-DH, NADPH

this is because G6P-DH is the only enzyme producing NADPH in RBC

Question 23

Glutathione __ replenishes GSH with help of NADPH, which is dependent on enzyme___ in the RBC.

Answer 23

Reductase, G6P-DH

Question 24

In RBC, ___ is the only enzyme that produces NADPH.

Answer 24

G6P-DH

Question 25

In G6P-DH deficient red cell, fava bean can lead to acute hemolytic anemia due to build up of ___.

Answer 25

Hydrogen peroxide (H2O2)

Question 26

In UPR (unfolded protein response), ubiquination of misfolded protein leads to degradation inside ___.

Answer 26

Proteasome (ubiquitin-proteasome pathway)

Question 27

Autophagy is activated when two instances occur:

Answer 27

Damaged organelle recognition Nutrient deprivation states

Question 28

Inside the cell, organelle __ detects misfolded proteins through three sensory molecules that communicate with the nucleus to activate genes.

Answer 28

ER (sensory molecules: PERK, IRE1, ATF6)

Question 29

UPR (unfolded protein response): Detection of misfolded proteins by ER promotes two actions:

Answer 29

1) Activate trxn of genes to handle the damage | 2) Deactivate cell division

Question 30

DNA damage response: Proteins that sense DNA damage promote recruitment of other proteins to induce 2 cellular responses:

Answer 30

1) Cell cycle arrest (inhibition of replication) | 2) Apoptosis (if severe)

Question 31

Cell stress leads to apoptosis, it will enter intrinsic/extrinsic pathway of apoptosis.

Answer 31

Intrinsic (mitochondrial)

Question 32

Intrinsic pathway of apoptosis involves release of ___ from mitochondria, leading to activation of ___ cascade. It is also associated with __ family.

Answer 32

Cytochrome c, caspase, Bcl-2

Question 33

What is Nrf2 and what does it do?

Answer 33

Nuclear factor E2-related factor 2; a redox sensitive TF that increase trxn of protective genes under cellular stress

Question 34

What is Keap and it's function?

Answer 34

Sensory protein that ubiquinates (degrades) Nrf2.

Question 35

Default: when ROS is low, Nrf2 is activated/degraded.

Answer 35

Degraded (by proteasome)

Question 36

Keap is inactivated when ROS level is low/high, leading to activation/degradation of Nrf2.

Answer 36

High, activation

Question 37

Keap is an enzyme that adds/detaches ubiquitin to Nrf2, leading to Nrf2 activation/degradation.

Answer 37

Adds (ubiquitin ligase), degradation

Question 38

Why are antioxidant supplements not shown to work?

Answer 38

May be because ROS lead to redox signaling of adaptive and protective activities. Although antioxidants may inhibit damage caused by ROS, it may also block beneficial signaling pathway activated by ROS.

Question 39

Major free radical produced by cells is O2/H2O2/OH, which is relatively unreactive with DNA, lipid, and protein.

Answer 39

O2 - superoxide radical

Question 40

O2/H2O2 diffuses well across the membrane and can introduce radicals from cytoplasm to nucleus

Answer 40

H2O2

Question 41

ROS ___ is made during FAO by peroxisomes.

Answer 41

H2O2

Question 42

OH radical is formed when ___ reacts with ___.

Answer 42

Iron (Fe), hydrogen peroxide (H2O2) Fenton Reaction

Question 43

Strength: superoxide radical < hydrogen peroxide < hydroxyl radical. Write their chemical equation.

Answer 43

Rad O2, H2O2, rad OH

Question 44

Two reactive nitrogen species (RNS) are:

Answer 44

Peroxynitrite Nitrogen dioxide radical

Question 45

Three important metabolites for antioxidant defense mechanisms include:

Answer 45

Glutathione, tocopherol (vit E), ascorbic acid (vit C)

Question 46

Name the 5 most important enzymes for antioxidant defense mechanism (hint: 3 categories):

Answer 46

SOD*, catalase* (hydrogen peroxide) glutathione peroxidase*, glutathione reductase (glutathione) heme oxygenase (free iron)

Question 47

Glutathione ___ replenishes GSH, and Glutathione ___ makes ___ and H2O from H2O2.

Answer 47

Reductase, peroxidase, GSSG

Question 48

___ carbonylation covalently modifies proteins which can affect major biochemical processes, including gene expression, protein secretion and function, and signal transduction.

Answer 48

4-HNE (4-hydroxyl-nonenol)

Question 49

4-HNE carbonylation can occur with the following residues (aa):

Answer 49

His, Cys, Lys

Question 50

ROS leads to oxidative modification of DNA via (2)

Answer 50

base pair mismatching | DNA strand breakage

Question 51

__ of FA allow propagation of ROS in membranes (which changes the composition)

Answer 51

polyunsaturated double bonds

Question 52

What is the treatment for acetaminophen toxicity? How?

Answer 52

NAC (N-acetylcysteine) NAC is converted to glutathione in the liver!

Question 53

the symptom of acute hemolytic anemia due to fava bean

Answer 53

enlarged spleen due to increased hemolytic lysis

Question 54

ROS is directly detected by

Answer 54

Nrf2