Hydrogen Sulfide (H2S) Theory

Question 1

The later work of Olsen et al nominated H2S as the potential oxygen sensor

Answer 1

inducing K+ channel closure on type I glomus cells of the CB (Olsen, 2006)

Question 2

H2S is constitutivrly generated from cysteine by enzymes….

Answer 2

Cystathionine-β-synthase (CBS)
Cystathionine-γ-lyase (CSE)

Question 3

In normoxic conditions

Answer 3

H2S readily oxidised by mitochondria to produce sulfate

Question 4

In hypoxic conditions

Answer 4

cytosolic H2S concentration increases due to lack of mitochondrial oxidation

Question 5

Potential oxygen sensitive elements identified

Answer 5

in both CBS and CSE enzymes

Question 6

Exogenous application of H2S

Answer 6

has been shown to mimic hypoxic conditions, with effects on pulmonary arterial resistance in cows and sea lions (model organisms)

Question 7

H2S endogenously produced by tissues however

Answer 7

currently no method to measure intracellular H2S levels directly

Question 8

Recent studies have indicated an increase in H2S does not….

Answer 8

modulate ion channels (Kim, 2015)

Question 9

Knockout of H2S producing enzymes…

Answer 9

has no effect on acute oxygen sensing in CB (Wang, 2017)

Question 10

Relationship between elevated H2S and how this would contribute to K+ channel inhibition

Answer 10

Requires further elucidation

Question 11

Prabhakar 2013

Answer 11

Combining HO-2 theory with that of H2S
Crosstalk between CO and H2S in acute oxygen sensing is something to further explore