Oxidant Mechanisms in Response to Ambient Air Particles Beatriz González-Flecha

1. Oxidant Mechanisms in Response to Ambient Air Particles • Beatriz González-Flecha • Department of Environmental Health • Harvard School of Public Health • Boston, MA, USA

2. Oxygen toxicity: early evidence Mice Mice Drosophila Rats Paramecia Rats Paramecia

3. Oxygen poisoning and X-irradiation: A mechanism in common R. Gershman et al. Nature, 1954 First demonstration of the involvement of oxygen free radicals in the mechanism of oxygen toxicity

4. Oxygen Free Radicals = Reactive Oxygen Species (ROS) e- e- e- e- O2-. H2O2 HO• H2O O2 Superoxide anion Hydrogen peroxide Hydroxyl radical • Produced in association to aerobic • metabolism (1952)(1970’s) • Able to promote cell proliferation and • enzyme induction at sublethal • concentrations (1962)(1990) • Toxic at high concentrations (1954) • (1970’s)

5. Main sources of ROS in mammalian tissues Intracellular source Species 1. Mitochondrial Respiratory Chain Ubiquinone O2-. NADH dehydrogrenase O2-. 2. Enoplasmic Reticulum NADH-cytochrome reductase O2-. or H2O2 Cytochrome P450 O2-. Cytochrome b5 O2-. 3. Plasma Membrane Lipoxygenase 1O2 Prostaglandin synthase 1O2 NADH oxidase (PMN) O2-. 4. Cytosol a) soluble enzymes and proteins Hemoglobin O2-. Xanthine oxidase O2-. b) small molecules Flavins O2-. or H2O2 Thiols O2-.

6. Radical Chain Protective mechanisms O 2 SOD 10 -11 M •- O O + H O 2 2 2 2 Catalase 10 -7 M H O O + H O 2 2 2 2 • HO Carotene 10 -13 M 1 O O 2 2 Modified from Chance et al. Physiol. Rev. 59, 527-605 (1979).

7. Radical Chain Protective mechanisms O 2 SOD Damage to cellular components •- O O + H O 2 2 2 2 Catalase H O O + H O 2 2 2 2 • HO Carotene 1 O O 2 2 Modified from Chance et al. Physiol. Rev. 59, 527-605 (1979).

8. Pulmonary Responses to Oxygen 20% O2Normoxia 85% O2Adaptive responses: Proliferation of epithelial cells Induction of antioxidant enzymes 100 % O2Damage to the lung epithelium Inflammation Edema Post-100% O2Reparative responses: Epithelial remodeling Enzyme induction

9. Cellular Responses to ROS ROS concentration

10. Health Effects of Ambient Air Particles

11. 1943- Los Angeles, CA Visibility 3 Blocks. Numerous complaints watery eyes, nausea, & respiratory discomfort

12. 20 People and 1,000's animals dead, 6,000 ill

13. 1952- London, England 4,000 Dead

14. Ambient air particles have intrinsic toxicity Particle pollution, and not other pollutants, leads to increased death across much of the USA (HEI:www.healtheffects.org.news)

15. Particle Sources • Anthropogenic sources • Transportation • Power plants • Incinerators • Wood burning • Natural Sources • Volcanoes • Erosion • Forest fires • Sea spray • Soil • Biological (pollen, spores)

16. Ambient Air Particles and Oxidants • CAPs increase luminol-enhanced chemiluminescence, and the oxidation of redox-sensitive fluorescent markers in PMN and alveolar macrophages in vitro • Quinone radicals were detected in air particles @ 1010 per mg • PM inhalation induces anti-oxidant enzymes • Oxidants induce expression of pro-inflammatory cytokines

17. Mechanism of Pulmonary Oxidative Stress and Toxicity by PM • Particle/cell interactions • Direct action on intracellular sources of ROS • Potentiation by macrophage-derived cytokines • TNF-alpha, IL-8, etc.

18. Cardiac Effects of PM Neural mechanisms sympathetic/parasympathetic stimulation of the heart Inflammatory mechanisms release of cytokine/chemokine into circulation Direct action on the heart Soluble components (inorganic and organic) Insoluble (ultrafine/fine particles)

19. Summary • The health effects of PM in humans as well as the biological effects of CAPs in animal and cell models are well documented • The existing evidence strongly suggests that ROS are involved in the initiation steps of the mechanistic pathways leading from PM exposure to inflammatory effects and cardiopulmonary toxicity • The cellular mechanisms of PM toxicity are currently under investigation