title: Protein Oxidation Levels After Different Corneal Collagen Cross-Linking Methods.
abstract: OBJECTIVE
  To evaluate advanced oxidation protein products (AOPP) levels, superoxide dismutase (SOD) enzyme activity, and total sulfhydryl (TSH) levels in rabbit corneas after different corneal collagen cross-linking (CXL) methods.
  
  
  METHODS
  Eighteen eyes of 9 adult New Zealand rabbits were divided into 3 groups of 6 eyes. The standard CXL group was continuously exposed to UV-A at a power setting of 3 mW/cm for 30 minutes. The accelerated CXL (A-CXL) group was continuously exposed to UV-A at a power setting of 30 mW/cm for 3 minutes. The pulse light-accelerated CXL (PLA-CXL) group received UV-A at a power setting of 30 mW/cm for 6 minutes of pulsed exposure (1 second on, 1 second off). Corneas were obtained after 1 hour of UV-A exposure, and 360-degree keratotomy was performed. SOD enzyme activity, AOPP, and TSH levels were measured in the corneal tissues.
  
  
  RESULTS
  Compared with the standard CXL and A-CXL groups (133.2 ± 8.5 and 140.2 ± 6.2 μmol/mg, respectively), AOPP levels were found to be significantly increased in the PLA-CXL group (230.7 ± 30.2 μmol/mg) (P = 0.005 and 0.009, respectively). SOD enzyme activities and TSH levels did not differ between the groups (P = 0.167 and 0.187, respectively).
  
  
  CONCLUSIONS
  CXL creates covalent bonds between collagen fibers because of reactive oxygen species. This means that more oxygen concentration during the CXL method will produce more reactive oxygen species and, thereby, AOPP. This means that in which CXL method occurs in more oxygen concentration that will produce more reactive oxygen species and thereby AOPP. This study demonstrated that PLA-CXL results in more AOPP formation than did standard CXL and A-CXL.
authors.affiliation: *Department of Medical Biochemistry, Faculty of Medicine, Mugla Sitki Koçman University, Mugla, Turkey; †Department of Ophthalmology, Ataturk Training and Research Hospital, Ankara, Turkey; ‡Department of Vitreoretinal Surgery, National Centre of Ophthalmology named after academician Zarifa Aliyeva, Baku, Azerbaijan; §Department of Ophthalmology, Faculty of Medicine, Gazi University, Ankara, Turkey; and ¶Department of Medical Biochemistry, Faculty of Medicine, Gazi University, Ankara, Turkey.
authors.forename: Ummuhani Ozel
authors.initials: UO
authors.lastname: Turkcu
authors.forename: Nilay
authors.initials: N
authors.lastname: Yuksel
authors.forename: Sahin
authors.initials: S
authors.lastname: Novruzlu
authors.forename: Duygu
authors.initials: D
authors.lastname: Yalinbas
authors.forename: Ayse
authors.initials: A
authors.lastname: Bilgihan
authors.forename: Kamil
authors.initials: K
authors.lastname: Bilgihan
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004195:Disease Models, Animal; D018384:Oxidative Stress / Q000502:physiology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011817:Rabbits; D012256:Riboflavin / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D014792:Visual Acuity
chemical_list: D000975:Antioxidants; D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D013438:Sulfhydryl Compounds; D003094:Collagen; D013482:Superoxide Dismutase; D012256:Riboflavin