Age-related NADH oxidase (arNOX)-catalyzed oxidative damage to skin proteins
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Age-related NADH oxidase (arNOX), a cell surface-located hydroquinone oxidase capable of superoxide generation, appears at age 30 and increases with age thereafter. The ectodomain of arNOX is shed from the cell surface into body fluids including sera and saliva where its activity was measured spectrophotometrically using a reduction of ferricytochrome c as a measure of superoxide generation. The autofluorescence of advanced glycation end products correlates with epidermal arNOX activity as well. To demonstrate protein cross-linking, a fluorescence-labeled analog of tyrosine, tyramine, that would react with proteins carrying arNOX-generated tyrosyl radicals was used. The assay demonstrated the potential for arNOX-induced oxidative damage (dityrosine formation) to human collagen and elastin and to other surface proteins of intact human embryo fibroblasts and frozen sections from epidermal punch biopsies. The findings support a role for arNOX as a major source of oxidative damage leading to cross-linking of skin proteins.
KeywordsAge-related ECTO-NADH oxidase Skin aging Advanced glycation end products Collagen Reactive oxygen
We thank Debby Parisi, Michael Kim, and Brittany Kiefner for providing technical assistance and Carol Bain, Tracy Weigand, and Dr. Paul Snyder, Department of Pathology, Purdue University School of Veterinary Medicine, for assistance in the preparation and analysis of the frozen tissue sections and Peggy Runck for the preparation of the manuscript.
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