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Hydrogen sulfide and meningitis Hydrogen sulfide and meningitis

Hydrogen sulfide and meningitis - PowerPoint Presentation

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Uploaded On 2017-10-05

Hydrogen sulfide and meningitis - PPT Presentation

Supplemental Digital Content 2 The subarachnoid space and adjacent brain is depicted Bacteria blue cocci take up cysteine Cys from cerebrospinal or interstitial fluid which is further enriched by phagocytes ID: 593394

methb cys pmn activated cys methb activated pmn depicted bacteria nitrite cells muscle smooth cytochrome oxygen radius dilatation dipyridamole

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Slide1

Hydrogen sulfide and meningitis

Supplemental Digital Content 2. The subarachnoid space and adjacent brain is depicted. Bacteria (blue

cocci

) take up

cysteine

(

Cys

) from cerebrospinal or interstitial fluid, which is further enriched by phagocytes (

polymorphonuclear

neutrophils

(PMN),

monocytes

, microglia) exporting

Cys

into their extracellular environment when activated. Bacteria metabolize

Cys

through one of 3 metabolic pathways (CBS, CSE, 3MST – see discussion) to elaborate H

2

S, a toxicant gas that diffuses freely. A gradient of H

2

S gas (green) is depicted permeating CSF, brain tissue and blood vessels. H

2

S inactivates the oxidative burst of

polymorphonuclear

(PMN) cells and kills all cells (phagocytes,

glia

, neurons) within a defined radius. Within neuronal mitochondria, the terminal

cytochrome

c

oxidase

complex (E) uses H

2

S as a poor substrate. H

2

S also binds the intermediate state (E*) to inhibit electron transport non-competitively and reversibly. Sites of action of other gases (HCN, CO, NO and O

2

) are also depicted, with kind permission from Springer

Science+Business

Media from reference 6, Figure 1. Within the radius of high concentrations of H

2

S, mitochondrial respiration ceases in all resident cells and necrosis ensues. Within vessels, H

2

S acts similarly to NO on vascular smooth muscle, causing dilatation. At high levels of H

2

S, refractory dilatation occurs. During treatment for H

2

S intoxication, hyperbaric oxygen directly oxidizes H

2

S and also boosts

cytochrome

c

oxidase

activity, restoring mitochondrial function and also consuming H

2

S as substrate.

Dipyridamole

potentiates production of nitric oxide (NO), which spontaneously, and through interaction with hemoglobin, decomposes to nitrite (NO

2

-

) and nitrate. Nitrite, generated endogenously or administered, interacts with H

2

S to form NO, and also causes

methemoglobin

(

metHb

) formation.

MetHb

actively scavenges H

2

S to form

sulfmethemoglobin

.Slide2

Cys

Cys

Cys

H

2

S

H

2

S

Activated microglia

Activated monocyte

Activated PMN

NO

metHb

S-metHb

Vascular smooth muscle

Arachnoid mater

Pia

mater

NO

2

-

Endothelial cell

Neuron: E

E*ER

H

2

S

HCN

H

2

S producing

bacteria

NO

CO

H

2

0 0

2

H

2

S

S

Hyperbaric oxygen

Dipyridamole, or

Nitrite (NO

2

-

)