Reaktive oksygenmetabolitter i sykdomsutvikling

1. Reaktive oksygenmetabolitter i sykdomsutvikling

2. What are free radicals? Molecules with one, unpaired electrone in the outer shell Superoxide (O2�), hydrogen peroxide (H2O2), hydroxyl ion (OH-�), nitrogen oxide (NO�) Highly reactive, initiate chain reactions

3. Cellular Sources of Free Radicals

4. NADPH oxidase and phagocytosis

5. Free Radical Scavengers

6. Cellular Free Radical Targets

7. DNA damage

8. Amino acid modifications

9. Protein modifications

10. Signal proteins modified by ROS Receptors; activateds EGFR PDGFaR PDGF�R Signal mediators; activated Ras (Cys) Src Jak EGFR Erk Jnk P38 BMK Ca increase P66Shc

11. ROS production induced by growth factors

12. Redox sensitive targets in signaling cascades

13. Rac1 � Erk cross-talk: Effects on proliferation

14. ROS-aktiverbare transkripsjonsfaktorer HIF-1: I familie med aryl hydrocarbon-reseptor. Hypoksi aktiverer HIF-1, som bl.a. induserer erytropoietin

15. ROS and chromatin regulation ROS may influence histone acetylation and phosphorylation by ADP-ribosylation via MAP kinases. Increased acetylation of H3 and H4 is observed

16. Redox regulation of immune responces ROS increase T-cell activation IL2 production by antigenically or mitogenically stimulated T-cells is augmented

17. ROS in programmed cell death ROS induce apoptosis in various cell types Hydrogen peroxide induce CD95-independent apoptosis which requires mitochondrial ROS production and activation of NFkB NO induce apoptosis in some cells, but many cells are resitant and low NO concentations may provide protection by inhibiting certain caspases. APO-1/Fas/CD95 ligands induce ROS production TNFa induce cell death through ROS production in mitochondria and/or NADPH oxidase

18. Ageing �The age-related degenerative process is to a large extent the consequence of free radical damage� In Caenorhabditis elegans, the daf-2 mutation causes longevity by increasing Mn-SOD expression. Catalase is required to extend the life span in daf-C and clk-1 mutants of C. elegans Mice carrying a mutation in the p66shc protein were found to have an increased life span associated with increased resistance to oxidative stress Mitochondrial genome may be particularly susceptible to oxidative damage during aging. Mitochondrial DNA deletion mutations may contribute to the fiber atrophy that causes sarcopenia.

19. Cancer The carcinogens nickel and asbestos induce ROS ROS DNA damage has also been detected in PAH-exposed cells H-Ras and mox1 mutations associated with increased ROS production ROS cause mutagenic DNA lesions (8-oxo-G) Mitogenic stimulation through intracellular signal activation

20. Diabetes Hyperglycemia is associated with increased ROS production May contribute to vascular complications; PKC and NFkB activation, glycation end products Hyperglycemia enhances cell-mediated low-density lipoprotein (LDL) peroxidation in endothelial cells. Treatment with antioxidants ameliorates diabetic complications including the dysfunction of endothelial cells or increased platelet aggregation

21. Atherosclerosis ROS induces expression of focal adhesion kinase and intercellular adhesion molecules (ICAM-1). Artery wall invasion by monocytes and T lymphocytes is an early event in the development of atherosclerotic lesions. Monocytes, macrophages, and smooth muscle cells possess the scavenger receptor for oxidized LDL. Binding of oxidized LDL activates monocytes The process may be further enhanced by cytokines and other factors such as TNF, interleukin-1b, angiotensin II, and interferon-g, which induce superoxide production by the membrane-bound NADPH oxidase in endothelial cells

22. Neurodegeneration Significant amount of lipid peroxidation and increased levels of 4-hydroxynonenal detected in Altzheimer brains. ROS were found to mediate amyloid b-protein damage. Amyotrophic lateral sclerosis affects motor neurons in the spinal cord and brain stem. 10% of the cases are inherited (autosomal dominant). One-fifth of these carry mutations in the Cu/Zn-SOD gene. Mutant SOD transgenic mice developed a pathology and clinical phenotype similar to familial ALS patients. Mutation in the Cu/Zn-SOD gene causes neuronal death by apoptosis through sequential activation of caspase-1 and caspase-3. Transmissible spongiform encephalopathies (including BSA) are characterized by the conversion of the cellular form of the prion protein (PrPC) into a conformationally modified protease-resistant isoform called PrPSc. PrPC may play a role in the control of the oxidative state of the cell through regulation of the copper transport and/or through a modification of Cu/Zn-SOD activity. Prion infected neuronal cells displayed a higher sensitivity to oxidative stress and increased lipid peroxidation over noninfected cells.

23. Rheumatoid Arthritis RA is a systemic autoimmune disease characterized by chronic joint inflammation with infiltration of macrophages and activated T cells. Production of ROS at the site of inflammation may contribute decisively to the pathogenesis of this disease. T cells isolated from RA synovial fluid are characterized by a decreased intracellular GSH level and the �primed� CD45RO phenotype. These T cells exhibit severely impaired phosphorylation of the adaptor protein linker for T-cell activation (LAT). Migration of monocytes and lymphocytes into the synovium is mediated by the abnormal expression of adhesion molecules (ELAM-1, VCAM-1, ICAM-1, and ICAM-2). This may be mediated by abnormal induction of redox-sensitive signaling pathways.

24. Ischemia and Reperfusion Injury (IR) IR are serious complications in organ transplantation, myocardial infarction, and stroke. Massive ROS production has been identified as an important causative factor. Rac1-regulated NAD(P)H oxidase has been shown to be critically involved in ROS production in a mouse model of hepatic IR injury. Inhibition of neutrophil adhesion to the endothelium attenuates the tissue damage. Antioxidant treatment ameliorates leukocyte adhesion and heart injury in the postischemic period. Treatment with a synthetic SOD mimetic ameliorated tissue damage in a rat IR model. Experimental IR in the rat heart was found to be associated with activation of the redox-responsive trancription factors NF-kB and AP-1 and the MAPKs JNK and p38. This activation may account for inflammatory responses and apoptotic cell death in the affected tissue.

25. Conclusions ROS are physiological second messengers, activated from Rac1/NADPH oxidase and inducing MAPK and transcription factor activation An increased ROS load may activate several intracellular signalling pathways; contributing to cellular damage or conferring cell survival ROS has been implicated in a long series of diseases, but their molecular involvements are poorly defined Dietary interventions with antioxidants have not shown consistent effects