Pentoxifylline suppression of TNF-α mediated axonal degeneration in the rabbit optic nerve

Abstract

In AIDS patientsl axonal degeneration in the optic nerve occurs as a histopathological manifestation of the optic neuropathy. Direct infection of neurons by HIV is unlikely, and the axonal injury may be an indirect effect mediated by cytotoxic factors such as tumor necrosis factor-alpha (TNF-α) which we have previously demonstrated to cause axonal degeneration in the rabbit optic nerve. To test the suppressive effects of pentoxifylline in preventing TNF-a-mediated axonal degenerationl we applied pentoxifylline to an established rabbit model that demonstrates an AIDS-like optic neuropathy using intravitreal TNF-α injections. Degenerated axonal profiles were numerous in control rabbit optic nerve (mean 1879) and reduced in rabbits receiving the medium dose of pentoxifylline (300 mg PO BIOI mean 4391 p < 0.001) and the highest dose of pentoxifylline (600 mg PO BIOI mean 120, P< 0.007). High dose pentoxifylline reduced TNF-α-induced axonal losses to less than 10% that seen without pentoxifylline pretreatment. Lower doses of pentoxifylline had a lesser but significant protective effect. Our results suggest that TNF-amediated axonal degeneration can be suppressed by high doses of pentoxifylline. Pentoxifylline may therefore be useful in AIDS patients demonstrating neurological or neuro-ophthalmological symptoms. [Neural Res 1997; 19: 551-554]