Turkiye Klinikleri Journal of Ophthalmology

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Yaşa Bağlı Maküla Dejenerasyonu Etiyopatogenezinde Oksidatif Stres ve Antioksidanların Rolü
ROLE OF ANTIOXIDANTS AND OXIDATIVE STRESS IN THE ETHIOPATHOGENESIS OF AGE-RELATED MACULAR DEGENERATION
Özlem YENİCEa, Sezen ÇAKIRa, Haluk KAZOKOĞLUa
aGöz Hastalıkları AD, Marmara Üniversitesi Tıp Fakültesi, İSTANBUL
Turkiye Klinikleri J Ophthalmol. 2007;16(2):114-21
Article Language: TR
Full Text
ÖZET
 Son yıllarda yaşa bağlı maküla dejenerasyonu (YBMD)'nin patogenezinde oksidatif stresin önemli rol oynadığı bildirilmektedir. Retina oksidatif strese hassastır. Göz için güneş ışığına maruz kalma en önemli oksijen radikali oluşma nedenidir. Retina vücuttaki metabolik aktivitesi en yüksek dokulardan biridir ve önemli bir oksijen radikali oluşum yeridir. Reaktif oksijen medyatörleri (ROM), hücresel metabolizmanın veya fotokimyasal reaksiyonların sonucunda meydana gelebilir. Bu anlamda retina reaktif oksijen türlerinin oluşumu için uygun bir ortam teşkil eder. Öncelikle, retinadaki oksijen tüketimi diğer bütün dokulardan daha fazladır. İkinci olarak retina yüksek oranda ışınlanmaya uğrayan bir dokudur. Üçüncü olarak fotoreseptör dış segment zarları kolaylıkla okside olup hücreye zararlı zincir reaksiyonu meydana getirebilecek şekilde poliansatüre yağ asitlerinden zengin bir yapıya sahiptir. Dördüncü olarak nörosensöriyel retina ve retina pigment epiteli (RPE), yüksek miktarda ışığa duyarlı maddeler içermektedir. Ayrıca bunlara ilave olarak RPE'deki fagositozun kendisi de ROM oluşumu ile sonuçlanabilen oksidatif bir olaydır. Yaşlanma için en yaygın hipotez, serbest radikallere bağlı hücrelerde oksidatif hasar gelişmesidir. Bu hipoteze göre, serbest radikalleri parçalayan enzimler (süperoksitler ve peroksitler gibi) yaşa bağlı hasardan hücreleri korurlar. Zamanla oksidatif stresin birikimiyle geriye dönüşümsüz doku hasarı oluşur ve yaşlılığın fenotipik değişiklikleri görülür. Genetik veya çevresel faktörler gibi risk faktörleri varlığında oksidatif stres patolojik değişikliklerle sonuçlanır. Retinada oksidasyondan korunmak için antioksidan savunma mekanizmaları mevcuttur. Serbest radikalleri ve peroksitleri parçalayan retina pigment epitelinin, katalaz ve süperoksit dismutaz gibi enzimleri ayrıca antioksidan vitamin olarak askorbik asit (vitamin C), ?-tokoferol (vitamin E) ve karotenoidleri (lutein ve zeoksantin) içerdiği bilinmektedir. Bu derlemede, tüm bu mekanizmaların özetlenmesi ve son yıllarda vitaminler ve YBMD hakkındaki yayınların sunulması amaçlanmıştır.

Anahtar Kelimeler: Maküla dejenerasyonu; antioksidanlar; vitaminler
ABSTRACT
 Recently, oxidative stress has been implicated in the pathogenesis of age-related macular degeneration (AMD). Retina is very sensitive to oxidative stress. In eye, exposure to sun light is the most important mechanism for formation of oxygen radicals. Retina is one of the organs with highest metabolic activity and a common place for formation of oxygen radicals. Reactive oxygen mediatörs (ROM) may occur as the byproducts of cellular metabolism and photochemical reactions. Retina is an ideal environment fort the generation of reactive oxygen species for several reasons. Primarily, oxygen consumption by the retina is much greater than by any other tissue. Secondly, the retina is subject to high levels of cumulative irradiation. Third, photoreceptor outer segment membranes are rich in polyunsaturated fatty acids, which are readily oxidized and which can initiate a cytotoxic chain-reaction. Fourth, the neurosensory retina and the retina pigment epithelium (RPE) contain abundant number of photosensitizers. Additional to all these, the process of phagocytosis by the RPE is itself an oxidative stress and results in the generation of ROI. Oxidative damage to cells by free radicals is a widely accepted hypothesis for aging. According to this hypothesis, enzymes that destroy free radicals (superoxides and peroxides) as protect cells against age-related damage. Irreversible tissue damage caused by such oxidative processes accumulates in time which we observe the phenotypic changes of aging. Oxidative stress results in pathological changes in the presence of genetic and environmental risk factors. In retina there are some antioxidant mechanisms for protection against oxidative stress. Retina pigment epithelium which degrades free radicals and peroxides includes several enzymes including catalase and superoxide dismutase and antioxidant vitamins such as ascorbic acid (vitamin C), ?-tocopherol (vitamin E) and carotenoids (lutein ve zeoxanthine). We aimed to summarize all the mechanisms of antioxidation and present recent literature about vitamins and AMD.

Keywords: Macular degeneration; antioxidants; vitamins

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30.03.2014

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