The role of nitric oxide in uveitis
D. J. Parks, M. K. Cheung, C. C. Chan and F. G. Roberge
Laboratory of Immunology, National Eye Institute, National Institutes of Health, Betheda, MD.
OBJECTIVE: To evaluate the possible role played by nitric oxide in the
pathogenesis of uveitis. METHODS: Uveitis was induced in rats with
subcutaneous lipopolysaccharide. Lipopolysaccharide stimulates nitric oxide
production from L-arginine. The animals were treated with
NG-nitro-L-arginine methyl ester, an L-arginine analogue acting as a
specific inhibitor of nitric oxide synthesis. Ocular inflammation was
evaluated by measuring protein concentration and leukocyte number in the
aqueous humor of one eye, and by histopathologic examination of the
contralateral eye. RESULTS: Aqueous humor protein levels were reduced 73%
to 82% and cellular infiltration was almost abrogated in
NG-nitro-L-arginine methyl ester-treated rats compared with controls. The
histopathologic examination also showed a similar inhibition of uveal
tissue inflammation in treated rats. CONCLUSION: By inhibiting nitric oxide
synthesis, NG-nitro-L-arginine methyl ester inhibits the induction of
endotoxin-induced uveitis in the rat. This observation demonstrates that
nitric oxide is an important mediator of anterior uveitis in this model
system and suggests that nitric oxide may also be implicated in human
uveitis.
