Outline-O2 discovery-O2 sensing -O2 utilization

Non-shivering Thermogenesis-Brown fat-Amino-acids

Oxygen The capable electron acceptor

Oxygenic Photosynthesis

consists of two photosystems, I and II

4e-

O2 + 4H+

2H2O

Photosystem II performs only when Photosystem I is present to dispose e-

Chlorophyll

NADP/NADPH

e- tp chain

Photosystem I

Light(4 photons)

Chlorophyll Chlorophyll + e-

Photosystem II

ADPATP

e- tp chain

Light(4 photons)

Chlorophyll

+ 1.1 V

An-oxygenic Photosynthesis

Either Photosystem I or Photosystem II

Never both.

Source of electrons :

Molecular Hydrogen

or

Inorganic molecules such as (S2).

An-oxygenic species

Heliobacillus

ChlorobiumH2S

S2

S2

H2S

Type I

Type I

Type I

Type II

Chlorobium

Heliobacillus

Loss of type II

Protocyanobacterium

e-

e-

e-

e-

H2S

S2

S2

H2S

Type I

Type I

Type I

Type II

Chlorobium

Heliobacillus

Loss of type II

Protocyanobacterium

e-

e-

e-

e-

Modified from Allen & Martin, Nature 2004

Protocyanobacterium

An-oxygenic Photosynthesis

Is there anything like Protocyanobacteria today?

Allen & Martin, Nature, 2007

Oscillatoria limnetica, a true cyanobacterium, turns off its genes for Photosystem II in the

presence of H2S and thus reverts from

Oxygenic to An-oxygenic Photosynthesis

Discovery of Oxygen

1674Mayow:Demonstrated that only one part of air was necessary for life. That part was removed both by respiration and by fire ”Nitro ariel spirits” (NAS)

NAS

NA

S

NASNASNAS

NAS

NAS

NAS

NAS

NAS

H2O

NAS NAS

NASNAS NAS

The Phlogiston Theory

All combustible materials contain a ”phlogiston” that escape during burning

Discovery of Oxygen

Priestley’s experiment, August, 1774.

2Hg + ”Air” + heat 2HgO

2HgO + intense heat 2Hg+ ”Air”

Reported to the Royal Society, March 1775 and demonstrated that a mouse survived better in ”Air” from heated HgO.Called it both ”Dephlogisticated air” and ”Fire Air”.

Discovery of Oxygen

Scheele, also a Phlogistonist, did the same experiments already 1773.

Sent a letter to Lavoisier in September 1774.

No response; the letter was lost.

Lavoisier denied having seen the letter.

Priestley visited Lavoisier in October, 1774 and discussed his experiment.

Lavoisier repeated and confirmed.

Lavoisier published and called the air ”eminently breathable air”.

He never referred to Priestley or Scheele. Several years later Lavoiser

called this ”air” - Oxygen.

John W SeveringhausActa Anaesth Scand, 2002

Discovery of Oxygen

It was re-discovered by

E. Grimaux in 1890 in a collection of

papers that belonged to MarieAnne Lavoisier.

Grimaux published the text but the original

was lost again.

Re-re-discovered, however, in 1993, when donated

to Archives de l’Académie de Sciences

What about Scheeles letter ?

John W SeveringhausActa Anaesth Scand, 2002

Discovery of Oxygen

Who should goto Stockholm

December 10?

From the hands of ....

...His Majesty The King

Hence,Scheele and Priestley discovered ”Fire Air”

Lavoisier repeated the experiments. Understood the physiological role of ”Fire Air” and later called it Oxygen.

Oxygen Sensing

In all oxygen consuming mammalian cells the transcriptionfactor Hypoxia Inducible Factor, HIF, is a key regulator

The Discovery of HIF opened up for delineation of molecular mechanisms of oxygen regulated gene expression

Gregg Semenza, Cell, 1999

Oxygen Sensing

Cellular Hypoxia stabilizes HIF-1

HIF-1 is capable of activating over 70 genes

In response to hypoxia which

mediates adaptive

physiological responses

such as

Angiogenesis

Erythropoieses

Glycolysis

Gregg Semenza, 2006

Oxygen Sensing

Acute response to hypoxia occurs in seconds or few minutes and involves pre-excisting proteins.

Chronic response to hypoxia occurs in a few minutes or more involves gene expression and synthesis of new proteins

Gregg Semenza, Progress in Biophysics and Molecular Biology, 2006

hyperoxia preferred hypoxiafr

actio

nso

f an

imal

s

20 18 16 14 12 10 8 6 4 2 0

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00

% oxygenhyperoxia preferred hypoxia

frac

tions

of a

nim

als

20 18 16 14 12 10 8 6 4 2 0

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00

% oxygen

Oxygen Sensing

Bargmann, 2006

Genes encode for various soluable Guanylyl Cyclases (sGC) which bind oxygen

Oxygen 0% 21% Oxygen

1 2 3 4 5 6 7 8 9

bins Oxygen 0% 21% Oxygen

1 2 3 4 5 6 7 8 91 2 3 4 5 6 7 8 9

bins

lessons from a 1mm worm and sGC

These locomotion patterns varies with the sGC’s.Hence, sGC is an important oxygen sensor

Oxygen SensingH

IF-1

pro

lyl h

ydro

xyla

tion Normoxia

HIF-1

Fe2+

-ketogluterate

Prolylhydoxylases

HIF-1VHL-protein

UbiguitinationProteosomedegrading

HIF-1inactivated

Hypoxia

HIF-1Prolyl

hydoxylasesinhibited

HIF-1no binding to VHL-protein

HIF-1 stabilized and activates

genes

Oxygen Utilization

Two Aspects Non-Shivering Thermogenesis

1. The Brown Adipose Tissue, BAT

2. Amino Acids, AA, as fuels for heat production

Oxygen Utilization

Neonatal patho-physiology

Organ development - immaturity

Temperature balance-BAT

Oxygen Utilization

birth

Nor

epin

ephr

ine

(nm

ol/l)

parturitionafter birth

Lagercrantz et al 1994

100 80 60 40 30 20 10

5

2

1

0.5

0.2

Oxygen Utilization

3 6 9 cmcervixdilatation

1/2 2 24 h20 25 30 35 w gestational age

Norepinephrine during normal delivery

Isolated brown fat cells respondto norepinephrine with increased

O2 consumption: thermogenesis

Oxygen Utilization

ACß3 cAMP

PK

acyl-CoA FFA

acyl-carn

acyl-CoA ß-oxidation CAC

ATP

respiratorychain

proton circuit

H+

cell membrane

NE

HSL

thermogenin

mitochondrial membrane

ß3

lipiddroplet

Oxygen Utilization

NENE

oxygen electrode

oxygen electrode

Oxygen Utilization

400

0

NE

2 min

O

Control cells

min . cell400

0

NE

2 min

fmol O

Control cells

min cell

Oxygen Utilization

Control

+3% halothane

Oxygen Utilization

Halothane and other volatile anesthetic

agents inhibit oxygen utilization in BAT,

reduce heat production and hence

thermogenesis.

This leads to thermoregulatory problems

in newborns during surgery

Oxygen Utilization

Where is the effect located ?

Oxygen Utilization

ACß3

cAMP

PK

acyl-CoA FFA

acyl-carn

acyl-CoA ß-oxidation CAC

ATP

respiratorychain

proton circuit

H+

cell membrane

NE

HSL

thermogenin

mitochondrial membrane

ß3

lipiddroplet

Oxygen Utilization

Cold-acclimated hamster as a modelfor the newborn child

Oxygen Utilization

Cold-acclimated hamster as a modelfor the newborn child

Oxygen Utilization

Oxygen Utilization

10 53 12 49

NE NE

ml O2

kg0.75 • min

Oxygen consumption in awake hamster

10 min

910510Female hamster28 w old, cold-adapted 10 wbw. 0.220 kg

1% O2

10 53 12 49

NE NE

ml O2

kg0.75 • min

Oxygen consumption in awake hamster

10 min

910510Female hamster28 w old, cold-adapted 10 wbw. 0.220 kg

1% O2

RMR-1 RMR-2 RMR-3 NE-2 NE-1

NENE-2

-1

0

% O2

B. Halothane

3% 1.5% halothane

10 min

Oxygen Utilization

Hibernation in Medicine

Anti-arrhythmics?

Organ protection?

Oxygen Utilization

Where is the defibrillator?

Hibernation in Medicine

Anti-arrhythmics

Oxygen Utilization

Neonates almost never develop ventricular fibrillation just like hedge-hogs, ground squirrels and other hibernators

Hibernation in Medicine

Anti-arrhythmics

Several explanatory mechanisms such as different:

• pattern of adrenergic innervation

• melting points for lipids

• enzyme temperature activity curves

• handling of intracellular Ca2+

• increased size and nos. of connexin-43 gap junctions

Oxygen Utilization

O2 dependent

oxidative phosphorylation produces ATPthat is consumed within seconds

When O2 drops, oxidative phosphorylation

becomes less efficient and free radicals are produced

Protection from this is a clinical target

with implications on surgical procedures,

trauma, organ preservation/transplantation

Oxygen Utilization Hibernation in Medicine

Organ protection

SCIENCE, 2005

H2S Induces a Suspended Animation-like State In Mice

Eric Blackstone, 1,2 Mike Morrison, 2 Mark B. Roth2*

Oxygen Utilization

80 ppm H2S for six hours

CO2 production and O2 consumption dropped

Oxygen UtilizationHibernation in Medicine

Organ protection

120

100

80

60

40

20

0- 5 minutes + 5 minutes - 6 hours + 1 hour discovery

Carbon Dioxide Production Oxygen Consumption

%

120

100

80

60

40

20

0- 5 minutes + 5 minutes - 6 hours + 1 hour discovery

Carbon Dioxide Production Oxygen Consumption

%Core body temperature decreased to 12oC

Recovery after six hours

Follow-up normal

Hibernation in MedicineOrgan protection

Roth and Nystul ”showed that hibernation states can be induced on demand on animals that do not

naturally hibernate” – using H2S!!

Oxygen Utilization

Scientific American June 2005

H2S reduces oxidative phosphorylation due to a specific,

potent and reversible binding to complex IV (cytocrome c oxidase) preventing oxygen from binding

Oxygen UtilizationHibernation in Medicine

Organ protection

Beauchamp Jr 1984

H2S blocks cells from using O2 and

triggers suspended animation in mice

Oxygen UtilizationHibernation in Medicine

Organ protection

Oxygen UtilizationHibernation in Medicine

Organ protection

Allen & Martin, Nature, 2007

Oscillatoria limnetica, a true cyanobacterium, turns off its genes for Photosystem II in the

presence of H2S and thus reverts from

Oxygenic to An-oxygenic Photosynthesis

An-oxygenic Photosynthesis

Either Photosystem I or Photosystem II

Never both.

Source of electrons :

Molecular Hydrogen

or

Inorganic molecules such as (S2).

An-oxygenic species

Heliobacillus

ChlorobiumH2S

S2

S2

H2S

Type I

Type I

Type I

Type II

Chlorobium

Heliobacillus

Loss of type II

Protocyanobacterium

e-

e-

e-

e-

H2S

S2

S2

H2S

Type I

Type I

Type I

Type II

Chlorobium

Heliobacillus

Loss of type II

Protocyanobacterium

e-

e-

e-

e-

Modified from Allen & Martin, Nature 2004

4e-

O2 + 4H+

2H2O

4e-

O2 + 4H+

2H2O

With regard to ischemia-reperfusion:

The shift into ”suspended animation”, using

H2S, is an interesting mechanism that might

be clinically useful

Oxygen UtilizationHibernation in Medicine

Organ protection

Amino acid-induced thermogenesis

during anesthesia

Oxygen Utilization

Adminstration of oral protein or i.v. amino acids in the awake state is accompanied by approximately 20 % rise in energy expenditure and heat production

AWAKE

Oxygen Utilization

Brundin & Wahren, Metabolism 43, 1994

The thermic effect ofi.v. amino acids is normal or supranormal in the spinal man

TETRAPLEGIA

Oxygen Utilization

Aksnäs et al., Clin Physiol 15, 1995

0

50

100

150

Con

trol

148

0

50

100

150

Con

trol

148

Con

trol

148 Am

ino

acid

s

84

Am

ino

acid

s

84

0

25

50

75C

ontr

ol

47

0

25

50

75C

ontr

ol

47

Con

trol

47

Am

ino

acid

s

26

Am

ino

acid

s

26

21

4

Am

ino

acid

s

4

Am

ino

acid

sA

min

oac

ids

VO2, mL/min

During AnesthesiaDuring Anesthesia AwakeAwake

Watts (J/s)

Oxygen Utilization

Is the heat produced in

- Splanchnic

or

- Extra Splanchnic Tissue ?Oxygen Utilization

70

50

30

10

0

60

40

20

Awakesubjects

Whole body

Splanchnic

Wat

ts

Oxygen Utilization

During anesthesiaand surgery

At awakening Awakesubjects

70

50

30

10

0

60

40

20

Whole body

Splanchnic

Amino acid-induced thermogenesis in whole body and splanchnic region

During anesthesiaand surgery

At awakening Awakesubjects

70

50

30

10

0

60

40

20

Whole body

Splanchnic

Amino acid-induced thermogenesis in whole body and splanchnic region

Oxygen Utilization

What happens in the skeletal muscle cell ?

Is it un-coupling of respiration from ATP synthesis ?

Skeletal muscleUCP 2 and UCP 3 Expression of UCP 2 & 3 mRNAincreased in Tetraplegia

Hjeltnes et al. Diabetologia 1999

Mitochondrial membrane

UCP 1.

Neonates&

Hibernators

BAT

UCP 3 may be a determinant of EEand metabolic efficiency

Schrauwen et al. Diabetes 1999

Oxygen Utilization

Speculations

Release of central inhibition ? Un-coupling in skeletal muscle?

Oxygen Utilization

Normal,awake Spinal, awake Normal, anesthetized

20% >20% 5 fold

CrewAnette EbberydRingvor Hägglöf

Ingeborg Gottlieb-Inacio

Oxygen Consumption – Heat Production

Jan NedergaardBarbara CannonKerstin OlssonEric GrigsbyDonna Meyer

Eva SelldenJohn Wahren