Free radicals and antioxidants

free radicals and antioxidants , effect of free radicals , phases , free radicals in cancer, diabeties and neurodegenerative disease including pathology of each disease.

1. AMAR SHAHEED BABA AJIT SINGH JUJHAR SINGH MEMORIAL COLLEGE OF PHARMACY, BELA ( Ropar ) Pb . Free Radicals & Antioxidants Presented by Navpreet S ingh Dept.Of Pharmacology

2. A free radical is a molecule or molecular fragment that contains one or more unpaired electrons in its outer orbital. Represented by a superscript dot, (R•). Oxidation reactions ensure that molecular oxygen is completely reduced to water. The products of partial reduction of oxygen are highly reactive, called Reactive oxygen species or ROS

3. Superoxide anion radical (O2 -• ) Hydroperoxyl radical (HOO • ) Hydrogen peroxide (H2O2) Hydroxyl radical (OH • ) Lipid peroxide radical (ROO • ) Singlet oxygen ( 1 O2) Nitric oxide (NO • ) Peroxy nitrite (ONOO- • ).

4. H2O2 & singlet oxygen are not free radicals Because of their extreme reactivity, they are included in the group of ROS. Characteristics of ROS: Extreme reactivity. Short life span. Generation of new ROS by chain reaction. Damage to various tissues.

5. Cellular Metabolism Leakage of electrons from ETC Production of H2O2 or O2 by xanthine oxidase & NADPH oxidase. Due to membrane lipid peroxidation Peroxisomal generation-oxidation of O2 & H2O2 During prostaglandin synthesis Production of nitric oxide from arginine During phagocytosis In the oxidation of heme to bile pigments Auto-oxidation (e.g. metal ions, Fe 2+ , Cu 2+ glutathione, ascorbic acid)

6. Environmental effects Result of drug metabolism. Cytochrome P450 related reactions. Due to damage caused by ionizing radiations on tissues (X-rays) Photolysis of O2 by light Photoexcitation of organic molecules Cigarette smoke Alcohol promotes lipid peroxidation.

7. Lipid peroxidation of occurs in 3 stages- initiation, propagation & termination Initiation phase: This step involves the removal of hydrogen atom (H) from polyunsaturated fatty acids (LH), caused by hydroxyl radical. LH + OH - L - + H2O

8. Propagation phase: Under aerobic conditions, the fatty acid radical (L - ) takes up oxygen to form peroxy radical (LOO - ). The latter, in turn, can remove H-atom from another PUFA (LH) to form lipid hydroperoxide (LOOH). LH + OH - LOO - + LH L - + H2O LOOH + L -

9.  The hydroperoxides are capable of further stimulating lipid peroxidation as they can form alkoxy (LO - ) & peroxyl (LOO - ) radicals. 2L O OH LOOH LO - + LO2 - + H2O LO - + LOO - + aldehydes Termination: Lipid peroxidation proceeds as a chain reaction until the PUFA gets oxidized.

10. The products of lipid peroxidation are unstable e.g. carbonyls, esters, alkanes, alkenes, 2-alkenal ,2 ,4- alkadienal, MDA. Malondialdehyde (-CHO-CH2-CHO-) is a marker for the assessment of lipid peroxidation. MDA & other aldehydes react with thiobarbituric acid & produce red-coloured products - thiobarbituric acid reactive substances (TBARS) which can be measured colorimetrically.

11. During the course of phagocytosis, inflammatory cells, particularly the macrophages produce superoxide, by NADPH oxidase. This O2 radical gets converted to H2O2 & then to hypochlorous acid (HCIO). Superoxide radical along with hypochlorous ions brings about bactericidal action.

12. The beneficial affects of the free radicals generated by the body. A large amount of O2 is consumed by macrophages during their bactericidal function, a phenomenon referred to as respiratory burst.

13. Proteins: Free radicals cause oxidation of sulfhydryl groups & modification of certain amino acids (e.g. methionine, cysteine, histidine, tryptophan). ROS may damage proteins by fragmentation, cross-linking & aggregation . Lipids: PUFA are susceptible to damage by free radicals.

14. Carbohydrates: Oxidation of monosaccharides (e .g. glucose) can produce H2O2 & oxoaldehyde. Glycation increases the susceptibility of proteins to the attack by free radicals. E.g. DM . Nucleic acids: Free radicals may cause DNA strand breaks, fragmentation of bases & deoxyribose.

15. FREE RADICALS IN CANCER

16. General pathophysiol o gy of Cancer

17. Impact of free radicals in cell proliferation - Inflammation begins with a reaction to an irritant or infection that is characterized by movement of fluid and white blood cells into extravascular tissue.

18. Cont … This can activate a process called lipid peroxidation and the arachidonic-acid cascade, with the production of cell- proliferation-stimulating eicosanoids. malondialdehyde (MDA) 4- hydroxynonenol (4-HNE) , The free radicals can also damage DNA and modify the structure and function of cancer-related proteins directly. OH•, hydroxyl radical; O2 –•, superoxide; NO•, nitric oxide;

19. Basic fundamental of ROS

20. Role of ROS in development of Cancer  It is well known that species derived from oxygen are cytotoxic and are involved in the etiology of cancer.  Several carcinogens during metabolism exert their effect by producing reactive oxygen species (ROS), It plays a vital role in the process of carcinogenesis  ROS are generated specifically to answer necessary biological functions, whereas in other cases, they indicate byproducts of metabolic processes.  Free radical linked damage of Proteins and DNA has been suggested to play a major role in the development of diseases such as neurodegenerative disorders, arthritis, arteriosclerosis, cancer , and others diseases

21. Role of ROS in development of Cancer  Some researches says reducing and inactivation of antioxidant system, the oxidative stress (OS) in cancer cells is higher , Cancer cells exhibit a higher oxidative stress level compared to normal cells.  Alterations , including rearrangement of DNA sequence , base modification , DNA miscoding lesions , gene amplification , and activation of oncogenes , could be implicated in the initiation stage of several cancers.

22. Free radical damage in DNA and cause Cancer  DNA is a major target of free radicals to damage  The types of damages includes strand breaks (single or double strand breaks), various forms of base damage yielding products such as 8-hydroxyguanosine, thymine glycol etc .  These damages can result mutations that are heritable change in the DNA that can yield cancer in somatic cells.

23. Cont …  Cancer develops through an accumulation of genetic changes. Initiating agents can be Tobacco smoking and chewing, UV rays of sunlight, Radiation, Viruses, Chemical pollutants, etc.  Promoting agents include hormones Example: Androgens for prostate cancer, estrogens for breast cancer and ovarian cancer.

24. FREE RADICALS IN DIABETIES

25. FREE RADICALS IN NEURODEGENERATIVE DISEASE

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