1. RADICALES LIBRES ESPECIES REACTIVAS DE OXIGENO (ROS) Y DE NITROGENO
3. ROS
4. ¿Dónde se produce normalmente ROS?
5. ROS production - I Mitochondria ATP generating organelles E.T.C. system common to all life
electron leak - birds, bats, other mammals State 3 and 4
Turtles, ischemia/reperfusion 90% ROS are generated here
Membrane potential and ROS production
70% Japanese centanarians have mutation in complex 190% ROS are generated here
Membrane potential and ROS production
70% Japanese centanarians have mutation in complex 1
6. ROS production - II
7. Efectos de los ROS sobre las moléculas biológicas
9. Radical Mediated Cleavage of Peptide Bonds Instead of forming carbonyl adduct products, ROS can directly cleave and oxidize the peptide bond.
Table 1 illustrates the four most common types of radical mediated cleavages and the corresponding products.
Table 1
10. Deamidation, Racemization and Isomerization of Protein Residues Besides introducing carbonyl groups into the protein, ROS are also responsible for deamidation, racemization and isomerization of residues.
Gln and Asn residues deamidate and racemize about their C alpha atoms to the D-isomers.
Asymmetric side chains of Thr and Ile residues convert from the L-isomer to the D-isomer.
Spontaneous prolyl cis-trans isomerization occurs.
11. Modified Proteins Which Are Not Degraded The previous slides dealt with chemical modifications which lead to protein degradation, but not all aberrant proteins are recognized by degradation systems in the cells.
For example, modified proteins in eye lens are not recognized.
Therefore, modified lens proteins accumulate over a lifetime with deleterious effects to vision.
Chemically modified lens proteins lead to the formation of cataracts.
15. Hydroperoxides - Sources
16. Fate of Hydrogen Peroxide
17. Hydroperoxides & Cellular Oxidative Damage
18. Mecanismos anti-oxidantes
20. Reaccion de la Superoxido Dismutasa
24. Cellular Defense Mechanisms to Prevent ROS Buildup. Due to the oxygen rich environment in which proteins exist, reactions with ROS are unavoidable.
Superoxide dismutase and glutathione peroxidase are natural antioxidants present in organisms which eliminate some ROS.
Glutathione peroxidase catalyzes the reduction of peroxide by oxidizing glutathione (GSH) to GSSG.
25. Trypanothione metabolism in trypanosomatids
26. Defense against ROS
37. Radicales de nitrogeno
41. 1885 1955
43. El estrés oxidativo y su relaciòn con el envejecimiento
44. La Hipòtesis de la Tasa de Vida “La tasa metabòlica de una especie determina su expectativa de vida”
45. Relaciòn entre metabolismo y envejecimiento En 1957 Denham Harman propone la teorìa de envejecimiento por radicales libres
En 1969 se identifica la superoxido dismutasa (SOD)
Se unifica empiricamente el concepto de “a mayor tasa metabòlica, mayor producciòn de ROS, menor tiempo de vida”
Se corrige y se simplifica la correlaciòn ROS y longevidad
46. Los oxidantes contribuyen al desarrollo del fenotipo de senescencia Fibroblastos crecidos en baja tensiòn de O2 viven mas tiempo
Fibroblastos crecidos en baja tensiòn de O2 reducen su tiempo de vida y presentan acortamiento de telomeros mas ràpido
H2O2 detienen el crecimiento celular y muestran senescencia
Efecto de Ras puede ser revertido por anti oxidantes permeables
47. Mitochondrial respiratory Chain
increased oxygen consumption produces more O2.- and H2O2.
Xanthine oxidase
Insufficient blood flow (hypoxia) leads to degradation of ATP to hypoxanthine producing O2.- and H2O2 .
Neutrophil (PMN)
Respiratory burst by NADPH oxidase
IL-1, IL-6 and TNF-? increases adhesion molecules and PMN infiltration
Lipoxygenase/cycloxygenase
Activated by cytokines, hormones and toxins
48. Source of Free Radicals in Skeletal Muscle An acute bout of exercise in rats increases ROS production in skeletal muscle.
Aged rats generates more ROS at rest and during exercise (15 m/min, 0%) at the same relative workload as young rats (25 m/min, 10%).
Both mitochondria and NADPH oxidase are sources of ROS in young muscle during exercise.
For aged muscle, mitochondria seem to be the main source.
ROS generation is also increased in the heart.
With 2 mM pyruvate and 2 mM malate as mitochondrial respiration substrates
Replace pyr-
malate wiith
1.7 mM ADP, 0.1 mM NADPH and Fe+3
Ji & Bejma J.A.P. (1999)
49. p53 puede presentar un loop de retroalimentacion pro-apoptotica
50. Control + Peroxido de hidrògeno
51. Antioxidant activity vs Lipid (LDL) Peroxidation
52. ROS manipulation Dietary supplementation Very mixed results except in particular cases such as Vitamin E and ischemea/reperfusion
Dietary Restriction (up to 50% LS extension) Less evidence of oxidative damage Metabolic rate unaltered Mitochondria characteristics – lipid membrane, less ROS with same membrane potential
Exercise (up to 10% LS extension) Acute can lead to immune response and damage Depletion of Vitamin E Training generally beneficial with more mitochondria produced
53. “Es casi un milagro que los mètodos modernos de enseñanza no hayan estrangulado aùn enteramente la sagrada curiosidad de la investigaciòn; para lo cual èsta pequeña planta, necesita mas que nada, ademàs de estimulaciòn, libertad
54. The problem with vitamin C antioxidant or pro-oxidant ?
55. 1 All antioxidants may be prooxidants 2 Regulated antioxidant system - Redox 3 Other natural agents – OVERDOSES?
