ABSTRACT
Dideoxyosones (DDOs) are intermediates in the synthesis of advanced glycation endproducts (AGEs), such as pentosidine and glucosepane. Although the formation of pentosidine and glucosepane in the human lens has been firmly established, the formation of DDOs has not been demonstrated. The aim of this study was to develop a reliable method to detect DDOs in lens proteins. A specific DDO trapping agent, biotinyl-diaminobenzene (3,4-diamino-N-(3-[5-(2-oxohexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanoyl]aminopropyl)benzamide) (BDAB) was added during in vitro protein glycation or during protein extraction from human lenses. In vitro glycated human lens protein showed strong reaction in monomeric and polymeric crosslinked proteins by Western blot and ELISA. Glycation of BSA in the presence of BDAB resulted in covalent binding of BDAB to the protein and inhibited pentosidine formation. Mass spectrometric analysis of lysozyme glycated in the presence of BDAB showed the presence of quinoxalines at lysine residues at positions K1, K33, K96, and K116. The ELISA results indicated that cataractous lens proteins contain significantly higher levels of DDO than non-cataractous lenses (101.9±67.8 vs. 31.7±19.5AU/mg protein, p<0.0001). This study provides first direct evidence of DDO presence in human tissue proteins and establishes that AGE crosslink synthesis in the human lens occurs via DDO intermediates.
Subject(s)
Cataract/metabolism , Crystallins/chemistry , Glycation End Products, Advanced/analysis , Lens, Crystalline/chemistry , Adult , Amino Acid Sequence , Animals , Blotting, Western/methods , Cattle , Crystallins/metabolism , Enzyme-Linked Immunosorbent Assay/methods , Glycation End Products, Advanced/metabolism , Glycosylation , Humans , Lens, Crystalline/metabolism , Lysine/chemistry , Lysine/metabolism , Mass Spectrometry/methods , Molecular Sequence Data , Reproducibility of Results , Young AdultABSTRACT
Post-operative capsular opacification (PCO) is a multifactorial physiological consequence of cataract surgery. Opacification involving the central posterior capsule has a significant impact on high and low contrast acuity and low contrast sensitivity. The assessment of PCO on cadaver eyes, experimental studies and culture models and in clinical studies has provided an understanding of its pathogenesis. The proliferation, migration and abnormal differentiation of residual lens epithelial cells and fibers in the capsular bag have been implicated in the pathogenesis of PCO. The incidence and severity of PCO correlates to the use of surgical techniques, intraocular lens (IOL) optic edge designs and IOL materials. This article summarizes the clinical studies with recommendations for retarding the development of central PCO. It discusses experiments with pharmacological agents broadly categorized as anti-inflammatory, immuno-modulating, antiproliferative, antiadhering and antitransdifferentiating agents for the prevention of PCO. These studies will remain critical for future endeavors undertaken for the eradication of PCO.
