Abstract
Purpose: :
To investigate the modifications of glycoproteins from the Bruch’s membrane such as fibronectin, vitronectin, and laminin, when it is exposed to either glycolaldehyde or nitration. This will serve as a model system for aging and inflammation in age-related ocular diseases.
Methods: :
Model peptides were reacted with glycolaldehyde or sodium nitrite. Tryptic digestion was performed before analyzing via LC-MS (Thermo Finnigan, LCQ Advantage, Surveyor; Surveyor LC with PDA detectors, quadrupole ion trap mass analyzer, electrospray ion source).
Results: :
Modifications of the fibronectin and vitronectin with glycolaldehyde occurred on lysine and arginine residues via the Maillard reaction resulting in an increased mass of 42. Modifications from nitrite to fibronectin and laminin, preferentially occurred at either tyrosine and/or lysine sites. When nitration occurs at the tyrosine residue, it produces 3-nitrotyrosine sites with a increased mass multiple of 45. At the lysine residues, the nitrite induces nitrosative deamination to produce two products, either an OH substitution or an alkene, increasing the mass by 1 or decreasing the mass by 17, respectively.
Conclusions: :
The model system identified sites of modification in fibronectin, vitronectin, and laminin either from glycolaldehyde or nitrite. These types of model systems can aid in the identification of these modifications in vivo. They’re essential to advance the mechanism of eye diseases.
Keywords: age-related macular degeneration • inflammation • aging