Effects of oxidative damage of DNA on pathogenesis of pterygium

Background Pterygium is a relatively common eye disease,but its aetiology and pathogenesis remain uncertain.At present,the study on pterygia focuses on understanding its underlying mechanism.Objective This study was to detect the expression of 8-hydroxy-2'-deoxyguaine (8-OHdG),a marker of oxidative damage of DNA,and bcl-2,a gene related with apoptosis,on the pterygium tissue.Methods Thirty pterygium tissue specimens were obtained during the surgery with the primary pterygium 24 cases and recurrent pterygium 6 cases.In addition,20 normal conjunctival specimens from retinal detachment surgery and strabismus surgery were collected.The expressions of 8-OHdG and bcl-2 in pterygium tissue were detected using immunochemistry and compared with the normal conjunctival tissue.The difference in the expressions of 8-OHdG and bcl-2 among different specimens was compared by x2test,and the relationship between 8-OHdG expression and bcl-2 expression was evaluated by Kappa test.Results The positive expressing rate of 8-OHdG in the pterygium tissue was 62.5％ and 83.3％ in the primary and recrudescence pterygium tissue,respectively,but the expression of 8-OHdG was absent in the normal conjunctiva tissue.No significant difference was found in the positive expressing rate of 8-OHdG between primary and recrudescence pterygium tissue(x2 =0.938,P＞0.05).The bcl-2 expressing rate was 90.0％ and 87.5％ in the primary and recrudescence pterygium tissue,respectively.However,that in the normal conjunctival tissue was absent.No significant difference was seen in the bcl-2 expression rate between primary and recrudescence pterygium tissue (x2=0.833,P ＞ 0.05).Of the 27 pterygium tissue with bcl-2 positive expression,8-OHdG showed the positive expression in 20 specimens,and 3 specimens with the bcl-2 negative response were absent reactive to 8-OHdG,showing insignificant difference between them (P＞0.05).The relationship between 8-OHdG expression and bcl-2 expression was concord in a certein extent (Kappa =0.464).Conclusions The upregulation of 8-OHdG in the pterygium tissue indicates that oxidative damage of DNA plays a role in the development of pterygium.Oxidative damage of DNA caused by ultraviolet may be an upriver factor,which induces raising up of expression of bcl-2 and inhibits the apoptosis of normal cells and further proliferation of the conjunctiva tissue,resulting in the genesis and development of pterysium. Key words: Pterygium ;  8-Hydroxy-2'-deoxyguanine ;  Oxidative damage;  Apoptosis related gene/bcl-2