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Localization of 3-nitrotyrosine to rheumatoid and normal synovium
P I Mapp1, R Klocke, D A Walsh
1Department of Medical Sciences, University of Bath, Claverton Down, UK.
Objective:
To determine the localization of 3-nitrotyrosine (3-NT), a footprint marker of peroxynitrite (ONOO-) and other reactive nitrogen species, to the inflamed human synovium and to compare this with normal synovial and nonsynovial tissue of human and animal origin.
Methods:
Monoclonal and polyclonal antibodies were used to investigate for 3-NT, inducible nitric oxide synthase (iNOS), macrophage marker CD68, and the vascular smooth muscle marker alpha-actin by avidin-biotin immunocytochemistry.
Results:
In the inflamed synovium, 3-NT was found in the vascular smooth muscle and macrophages. In normal human synovium, 3-NT was present in the vascular smooth muscle and some lining cells and was not associated with immunoreactivity for iNOS. Similarly, 3-NT could be demonstrated in the vascular smooth muscle cells of normal rats and iNOS knockout mice. It was not present in the vascular smooth muscle of healthy, nonsynovial tissue.
Conclusion:
The synovial vasculature in histologically normal human and naive rodent synovium was alone among the normal tissues studied in exhibiting iNOS-independent immunoreactivity for 3-NT. These findings suggest a physiologic role for ONOO- in normal synovial vascular function.