Hydrogen peroxide localization in experimental optic neuritis
J. Guy, E. A. Ellis and N. A. Rao
Department of Ophthalmology, University of Florida, College of Medicine, Gainesville 32610.
The association of reactive oxygen species to altered permeability of the
blood-brain barrier in acute experimental encephalomyelitis was
investigated by ultrastructural cytochemical localization of hydrogen
peroxide (H2O2) to sites in the optic nerve previously identified by
extravasation of intravascular horseradish peroxidase. Using a modified
cerium method, we found electron-dense cerium-derived H2O2 reaction product
was localized to the perivascular space at the lamina retinalis, lamina
choroidalis, and lamina scleralis. In the optic nerve head, electron-dense
reaction product was observed in the presence of intravascular leukocytes,
although adjacent perivascular and interstitial inflammatory cells at this
site were scant. In the myelinated retrobulbar optic nerve, cerium-derived
H2O2 reaction product was seen in the intravascular space of blood vessels
and surrounding perivascular and interstitial foci of inflammatory cells.
Reaction product was also observed in the extracellular space adjacent to
the plasmalemma of axons and glial cells in the optic nerve head and
retrobulbar nerve. The perivascular and intravascular distribution of
cerium-derived reaction product suggests that H2O2 may play a role in the
pathogenesis of altered vascular permeability in experimental optic
neuritis and supports our previous observations of suppression of
blood-brain barrier permeability by detoxification of H2O2 with the
exogenous administration of antioxidant enzymes.
