SLAAPAPNEA AND OXIDATIVE STRESS

SLAAPAPNEA AND

OXIDATIVE STRESSJ. VERBRAECKEN

DEPT of PULMONARY MEDICINE AND SLEEP DISORDERS CENTER

UNIVERSITY HOSPITAL ANTWERP

Impact Outcome

Vascular system= Black Box

Structural and functional vascular changes

IHD

MI

Stroke

CV death

Hypertension

OSA

Confounders:AgeSexLipidsHypertensionSmokingDiabetesGenetics OXIDATIVE STRESS

?

1) What is oxidative stress?2) Is there oxidative stress in SAS ?3) Antioxidative capacity in SAS ?4) Links to vascular disease !?

SAS and oxidative stress

What is oxidative stress ? Definition

State of imbalance: Disturbance in the prooxidant-antioxidant balance in favour of the former.

Sies, 1985 Pro-Oxidants Antioxidants

What is oxidative stress ? Chemistry of oxidants/free radicals

Superoxide

Hydroxyl radical

Peroxy nitrite

Hydrogen peroxide

Spontaneous or dismutated by SOD

ROS=Reactive oxygen species

Oxidative injury to macromolecules

Reactive oxygen species (ROS)

Nucleic acid damage, mutation, carcinogenesis

Membrane damage Lipid peroxidation

Protein damage, enzymes, receptors, transporters

Polysaccharide damage, hyaluronic acid, arthritis

Detoxifying enzyme systems

LYTIC

NON-LYTIC

Sources of ROS in OSA

Normal oxygen transport– NADPH oxidase– Mitochondria (ETC, semi-

ubiquinon) Induction of enzyme

systems by hypoxia/reoxygenation– Xanthine Oxidase– Cyclooxygenase– Lipooxygenase– NO synthase– Haem oxygenase

Inflammatory leucocytes Cardiac tissues and vascular

cells Oxidation of small molecules:

– glucose – homocysteine

Hypoxia/reoxygenation Alterations in energy (ATP) metabolism

Lavie L et al, Sleep Med Rev 2003, 7(1):35-51Halliwell B Methods Enzymol 1990,186:1-85

Hypoxia/reoxygenation Hypoxia leads to alterations in gene expression

Activation of hypoxia-inducible factor 1 (HIF-1)Increased expression of hypoxia dependent genes

Forsythe JA et al, Mol Cell Biol 1996; 16:4604-4613. Huang L et al J Biol Chem 1996, 271:32253-9. Kallio P et al Proc Natl Acad Sci USA 1997:5667-72. Huang L et al, Proc Natl Acad Sci USA 1998, 95:7987-92

ROS

Activation transcription factors

NF-B, AP-1 HIF-1

VEGF Endothelin-1 EPO HSP Glycolytic enzymes Leptin/Leptin receptor iNOS apoptosisSystemic mediator release – proinflammatory cytokines

TNF, IL-1, …

Oxidative stress Defense mechanism: Antioxidative reserve

Antioxidant enzymes– Glutathion peroxidase (GPx)– Catalase– Superoxide dismutase (SOD)

Nonenzymatic antioxidants (radical scavengers): – Vit E– Vit A (Beta carotene)– Vit C (ascorbic acid)– Glutathion– Selenium– Albumin, ceruloplasmin,

bilirubine, uric acid, …

Action: works by keeping the delicate balance between the production of oxidants (ROS) and their catabolism by antioxidants.

Reoxygenation“Respiratory burst”: increased oxygen uptake

Coupling of GSH redox cycle to pentose phosphate pathway

NADPH

1) What is oxidative stress?2) Is there oxidative stress in SAS ?3) Antioxidative capacity in SAS ?4) Links to vascular disease !?

SAS and oxidative stress

Is there oxidative stress in SAS ? Superoxide release from polymorphonuclear neutrophils

Schulz R et al, AJRCCM 2000, 162:566-570

(after stimulation with the bacterial tripeptide fMLM and the calcium ionophor A23)

Is there oxidative stress in SAS ?8-Isoprostane in Breath condensate

Carpagnano G et al Chest 2002, 122:1162-1167

Marker oxidative stress Marker inflammation

Arachidonic acid + ROS isoprostanes

~AHI

~NC

Is there oxidative stress in SAS ? Total ROS production ± PMA by CD11+ and CD64+ cells

Granulocytes

Monocytes

Controls

OSADyugovskaya L et al, AJRCCM 2002, 165:934-939

x1.9 x5 x2.5 x2.7In OSA:

Basal ROS production

Basal ROS production ± PMA

1) What is oxidative stress?2) Is there oxidative stress in SAS ?3) Antioxidative capacity in SAS ?4) Links to vascular disease !?

SAS and oxidative stress

Antioxidative capacity in SAS

Wali S et al, Sleep 1998, 21(3):290-296

One night CPAP

No difference in GPx and Catalase

Antioxidative capacity in SAS

OSA Controls

N 17 8M/F 16/1 4/4Trolox Equivalent (TEAC) 2.210.6 1.970.52TEAC > 2 mmol/l 10 3TEAC < 1.5 mmol/l 1 1

Christou K et al, Sleep Med 2003, 4:225-228

TEAC ~ -AHI

Antioxidative capacity in OSA TEAC in OSA before/after CPAP

Changes in TEAC after CPAP therapy

Baseline After 1 month0

1

2

TEAC in CPAP groupTEAC in control group

p=0.08 (Paired T test)

Time

mM

Tro

lox

eq

Changes in TEAC after1 month CPAP therapy

TEAC before TEAC after0.75

1.00

1.25

1.50

1.75

Timem

M T

rolo

x Eq

De Backer L, AJRCCM 2003, 167(7):A174

Antioxidative capacity in OSASuperoxide dismutase (SOD) in OSA before/after CPAP

Changes in SOD during 1 month CPAP therapy

SOD before SOD after0

50

100

150

200

p<0.0001 (Paired T test)

Time

U/m

l

Changes in SOD before and after1 month CPAP therapy

Baseline After 1 month0

100

200

SOD in CPAP groupSOD in control group

p=0.0064(ANOVA)

NS(ANOVA)

Time

U/m

l

De Backer L, AJRCCM 2003, 167(7):A174

Antioxidative capacity in OSA Glutathion peroxidase (GPx) in OSA before/after CPAP

Changes in GPx after CPAP therapy

Baseline After 1 month0

5000

10000

15000

GPx in CPAP groupGPx in control group

p<0.001( Paired T test)

Time

U/L

Changes in GPx after1 month CPAP therapy

GPx before GPx after0

2500

5000

7500

10000

12500

15000

17500

p<0.001 (Paired T test)

Time

U/m

l

De Backer L, AJRCCM 2003, 167(7):A174

Changes in vit E after CPAP therapy

Baseline After 1 month0

10

20Vit E in CPAP groupVit E in control group

Time

µg/m

lAntioxidative capacity in OSA

Vit E in OSA before/after CPAP

CPAP: 14.5 to 15.4 g/mlCtrl: 14.2 to 13.8 g/ml

Antioxidative capacity in OSA Glutathion not affected by exposure to different O2-conditions

Norm O

Hyp O

H/N O

Norm V

Hyp V

H/N V

0.0

0.1

0.2

0.3

0.4

0.5

0.6p = 0,0087

Tota

l glu

that

ion

(nm

ol/m

ln c

ells

GSS

G e

quiv

alen

ts

Manuel-y-Keenoy et al Taormina 2006

Barcelo A et al Eur Respir J 2006, 27: 756-760

Antioxidative capacity in OSA

12 M CPAP

Grebe M et al AJRCCM 2006 173 897-901

1) What is oxidative stress?2) Is there oxidative stress in SAS ?3) Antioxidative capacity in SAS ?4) Links to vascular disease !?

SAS and oxidative stress

Links to CVD Abnormal and excessive lipid peroxidation

Basal level of lipid peroxidation (TBARs content)

Barcelo A et al, ERJ 2000, 16:644-647

Oxidation susceptibility of isolated LDL particles (lag phase)

Links to CVD Fatty acid peroxidation: exhaled pentane (and NO)

Olopade CO et al Chest 1997, 111:1500-04

Links to CVD Studies not supporting the oxidative stress hypothesis

Wali S et al, Sleep 1998, 21(3):290-296– Oxidative stress in vitro– Normal lipid peroxidation– Normal GPx– Normal catalase– CPAP: no influence

(one night)

Öztürk L et al, Clin Chim Acta 2003,332:83-88– Normal glutathion– Normal lipid peroxidation– Normal osmotic fragility of RBC– Limited number of patients

Svatikova et al, Eur Heart J 2005,26:2435-2439– Normal oxLDL– Normal lipid peroxidation– Normal plasma 8-isoprostane

Links to CVDPotential damage due to oxidant imbalance:

Expression of vascular adhesion molecules ICAM-1

» Ohga E et al, JAP 1999 VCAM-1, ICAM-1, E-selectine

» Chin K et al AMJ 2000 ICAM-A, IL-8, MCP-1

» Ohga E et al, JAP 2003 Proliferation of vascular smooth

muscle cells/proliferation of microvasculature (angiogenesis) VEGF: Gozal D Sleep 2002 VEGF: Schultz R AJRCCM 2002 VEGF: Imagawa S Blood 2001

Aggregation and activation of platelets, decreased fibrinolytic activity

– Sanner B et al, ERJ 2000– Arnulf I et al, JAMA 2002

Enhanced oxidation of LDL– Lipid peroxides - >>> foam cells

» Barcelo A et al, ERJ 2000 Break down of NO to peroxynitrate

NO+ O2- >>>>>>> OONO-

Induction of proinflammatory cytokines TNF, IL-6, IL-8

Increased expression of hypoxia dependent genes

OSA Hypoxia/Reoxygenation

NADH-oxidase xanthine oxidase mitochondrial dysfunction Homocysteine

ROS

Activation transcription factors HIF-1NF-B, AP-1VEGF Endothelin-1 EPO HSP Glycolytic enzymes

Systemic mediator release – proinflammatory cytokines

Monocyte neutrophil activation Lymphocyte activation Endothelial cell activation

Adhesion molecules expression

Monocyte lymphocyte/endothelial adhesion

Endothelial dysfunction

NO

Vascular disease

LDL peroxidation

Foam cells

O2-,H202

L. Lavie Sleep Med Rev 2003

SAS and oxidative stressConclusions

1) (O)SAS exerts an enhanced intravascular oxidative stress reaction

2) (O)SAS patients have an increased antıoxidative capacity (SOD, GPx)

3) CPAP can decrease oxidative stress4) CPAP can decrease oxidative capacity

(SOD, GPx)5) Oxidative stress is linked to CVD (with increased

adhesion to endothelial cells)