SLAAPAPNEA AND OXIDATIVE STRESS

SLAAPAPNEA AND OXIDATIVE STRESS J. VERBRAECKEN DEPT of PULMONARY MEDICINE AND SLEEP DISORDERS CENTER UNIVERSITYHOSPITAL ANTWERP

Impact Outcome IHD MI Stroke CV death Vascular system= Black Box OSA Confounders: Age Sex Lipids Hypertension Smoking Diabetes Genetics Hypertension Structural and functional vascular changes ? OXIDATIVE STRESS

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

What is oxidative stress ? Definition • State of imbalance: Disturbance in the prooxidant-antioxidant balance in favour of the former. Sies, 1985 Pro-Oxidants Antioxidants

Superoxide Spontaneous or dismutated by SOD Hydrogen peroxide Hydroxyl radical What is oxidative stress ? Chemistry of oxidants/free radicals ROS=Reactive oxygen species Peroxy nitrite

Reactive oxygen species (ROS) Detoxifying enzyme systems Nucleic acid damage, mutation, carcinogenesis Polysaccharide damage, hyaluronic acid, arthritis Membrane damage Lipid peroxidation Protein damage, enzymes, receptors, transporters Oxidative injury to macromolecules LYTIC NON-LYTIC

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 Sources of ROS in OSA

Hypoxia/reoxygenation Alterations in energy (ATP) metabolism Lavie L et al, Sleep Med Rev 2003, 7(1):35-51 Halliwell B Methods Enzymol 1990,186:1-85

Hypoxia/reoxygenation Hypoxia leads to alterations in gene expression ROS VEGF Endothelin-1 EPO HSP Glycolytic enzymes Leptin/Leptin receptor iNOS apoptosis Activation transcription factors NF-B, AP-1 HIF-1 Systemic mediator release – proinflammatory cytokines  TNF, IL-1, … 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

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, … Oxidative stressDefense mechanism: Antioxidative reserve Action: works by keeping the delicate balance between the production of oxidants (ROS) and their catabolism by antioxidants.

Reoxygenation“Respiratory burst”: increased oxygen uptake NADPH Coupling of GSH redox cycle to pentose phosphate pathway

Is there oxidative stress in SAS ? Superoxide release from polymorphonuclear neutrophils (after stimulation with the bacterial tripeptide fMLM and the calcium ionophor A23) Schulz R et al, AJRCCM 2000, 162:566-570

Is there oxidative stress in SAS ?8-Isoprostane in Breath condensate ~AHI ~NC Marker oxidative stress Marker inflammation Arachidonic acid + ROS  isoprostanes Carpagnano G et al Chest 2002, 122:1162-1167

Is there oxidative stress in SAS ?Total ROS production ± PMA by CD11+ and CD64+ cells Basal ROS production Granulocytes Basal ROS production ± PMA Monocytes Controls In OSA: x2.5 x2.7 x1.9 x5 OSA Dyugovskaya L et al, AJRCCM 2002, 165:934-939

Antioxidative capacity in SAS • One night CPAP • No difference in GPx and Catalase Wali S et al, Sleep 1998, 21(3):290-296

Antioxidative capacity in SAS OSA Controls N 17 8 M/F 16/1 4/4 Trolox Equivalent (TEAC) 2.210.6 1.970.52 TEAC > 2 mmol/l 10 3 TEAC < 1.5 mmol/l 1 1 TEAC ~ -AHI Christou K et al, Sleep Med 2003, 4:225-228

Antioxidative capacity in OSA TEAC in OSA before/after CPAP De Backer L, AJRCCM 2003, 167(7):A174

Antioxidative capacity in OSASuperoxide dismutase (SOD) in OSA before/after CPAP De Backer L, AJRCCM 2003, 167(7):A174

Antioxidative capacity in OSA Glutathion peroxidase (GPx) in OSA before/after CPAP De Backer L, AJRCCM 2003, 167(7):A174

Antioxidative capacity in OSA Vit E in OSA before/after CPAP CPAP: 14.5 to 15.4 g/ml Ctrl: 14.2 to 13.8 g/ml

p = 0,0087 0.6 0.5 GSSG equivalents 0.4 Total gluthation 0.3 (nmol/mln cells 0.2 0.1 0.0 Norm O Hyp O H/NO Norm V Hyp V H/N V Antioxidative capacity in OSAGlutathion not affected by exposure to different O2-conditions Manuel-y-Keenoy et al Taormina 2006

Antioxidative capacity in OSA 12 M CPAP Barcelo A et al Eur Respir J 2006, 27: 756-760

Grebe M et al AJRCCM 2006 173 897-901

Links to CVD Abnormal and excessive lipid peroxidation Basal level of lipid peroxidation (TBARs content) Oxidation susceptibility of isolated LDL particles (lag phase) Barcelo A et al, ERJ 2000, 16:644-647

Links to CVD Fatty acid peroxidation:exhaled pentane (and NO) Olopade CO et al Chest 1997, 111:1500-04

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 CVD Studies not supporting the oxidative stress hypothesis

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 Links to CVDPotential damage due to oxidant imbalance:

OSA Hypoxia/Reoxygenation NO NADH-oxidase  xanthine oxidase mitochondrial dysfunction Homocysteine ROS VEGF Endothelin-1 EPO HSP Glycolytic enzymes Activation transcription factors NF-B, AP-1 HIF-1  Systemic mediator release – proinflammatory cytokines  Endothelial cell activation Monocyte neutrophil activation Lymphocyte activation Adhesion molecules expression O2-,H202  Monocyte lymphocyte/endothelial adhesion  Endothelial dysfunction LDL peroxidation L. Lavie Sleep Med Rev 2003 Vascular disease Foam cells

SAS and oxidative stressConclusions • (O)SAS exerts an enhanced intravascular oxidative stress reaction • (O)SAS patients have an increased antıoxidative capacity (SOD, GPx) • CPAP can decrease oxidative stress • CPAP can decrease oxidative capacity (SOD, GPx) • Oxidative stress is linked to CVD (with increased adhesion to endothelial cells)

SLAAPAPNEA AND OXIDATIVE STRESS