INIBIOLP   05426
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE LA PLATA "PROF. DR. RODOLFO R. BRENNER"
Unidad Ejecutora - UE
artículos
Título:
Tocopherol protects against oxidative damage to lipids of the rod outer segments of the equine retina.
Autor/es:
TERRASA, A.; GUAJARDO, M.H.; MARRA, CARLOS ALBERTO; ZAPATA, GUSTAVO
Revista:
The Veterinary Journal
Editorial:
ELSEVIER SCI LTD
Referencias:
Lugar: Londres; Año: 2009 vol. 182 p. 463 - 468
ISSN:
1090-0233
Resumen:
Oxidative stress is a possible risk factor for eye diseases such as equine uveitis. The free radicals elicited during the inflammatory process often result in pathologic conditions. Polyunsaturated fatty acids (PUFAs) of membranes are the major targets for free radicals  which produce lipid peroxidation. Lipid peroxidation is one of the major events induced by oxidative stress, and it is particularly active in polyunsaturated fatty acid (PUFAs)-rich biomembranes. Due to the fact that damage produced by free radicals in retina membranes affects the visual function and  the ability to scavenge  free radicals of the lipid soluble antioxidants, the of our work was: to quantify lipid soluble antioxidants in equine retina; to determine the fatty acid composition of total lipids isolated from retina equine to evaluate in vitro non-enzymatic lipid peroxidation in equine rod outer segments (ROS) membranes; to determine the fatty acid composition of total lipids isolated from ROS membranes, and their alterations during the oxidative damage and to analyze  a-tocopherol  protecting action. Lipid soluble antioxidants were quantified by HPLC and the fatty acids composition of lipids from retina and ROS membranes were analysed by GLC. The major lipid soluble antioxidants was  a-tocopherol (4,42 ± 0,83 nmol/mg of lipids). Retinoids and carotenoids were detected in appreciable concentration (0,37 ± 0,05 and 0,64 ± 0,31 nmol/mg of lipids respectively). The fatty acids compositions of retina showed a high percentage of PUFAs mainly 22:6n-3 and 20:4n-6. Non-enzymatic lipid peroxidation of the equine ROS membranes, induced by Fe2+-ascorbate pro-oxidizing system, was monitored using chemiluminescence. Light emission (cpm) was measured every 10 min for 180 min in the presence or not of a-tocopherol (a-Toc) in pretreated (0.5 or 1µmol/mg protein) ROS membranes. In the presence of ascorbate, chemiluminescence increased, peaked at 80 min (221,515 ± 10,719 cpm). Then, it declined to its initial values after 180 min. When peroxidation was carried out on a-tocopherol-treated membranes (0.5 mmol/mg protein), chemiluminescence values were significantly decreased (maximum peak -99,104 ± 5,500 cpm- at 60 min).Docosahexaenoic acid (22:6n-3) was the most abundant (20.65 ± 3.20 %) of total fatty acids. After 3 h incubation 95 % of total PUFAs were destroyed by induced peroxidation while in tocopherol-treated ROS the percentage was decreased to 47 and 61 % (0.5 and 1 µmol of a-Toc/mg protein, respectively). The present results shows that the retina has an endogen lipid soluble antioxidant system.. ROS membranes were highly sensitive to oxidative damage since their fatty acid composition was markedly modified during lipid peroxidation process, showing a substantial loss of PUFAs. The protecting role of a-tocopherol as antioxidant was evident, and this fact could be utilized for the treatment of equine ocular diseases in which free radicals are involved.