The Role of NF– B p65 in TNF––Induced Optic Nerve Degeneration

Abstract

Abstract: : Purpose: We previously showed an increased expression of NF–Κ B p65 in TNF–α–induced optic nerve degeneration. The purpose of this study was to examine its role in the degenerative process. Methods: Rats were euthanized at 1 day, 1, 2 weeks, 1 or 2 months after TNF–α (1–10 ng) intravitreal injection. Morphometric analysis of cells in the retinal ganglion cell layer (RGCL) and axon counting in optic nerve were performed. Immunohistochemistry was performed with antibodies against NF–Κ B p65, TNF–receptor 1 (R1), TNF–receptor 2 (R2), ED–1 or neurofilament. Results: Morphometry of cells in the RGCL showed a delayed loss (only significant at 2 months) as compared to the loss of axons in the optic nerve, which showed significant loss in 2 weeks. NF–Κ B p65 immunoreactivity was colocalized with TNF–R1, TNF–R2 or ED–1, a marker of microglia/phagocytic cells, in the optic nerve. Inhibition of NF–Κ B p65 with antisense oligodeoxynucleotide or helenalin, an inhibitor of NF–Κ B p65 binding to DNA, significantly ameliorated the loss of axon number after TNF–α injection. Conclusions: Intravitreal TNF–α caused axonal degeneration with delayed loss of retinal cell bodies. TNF–R1 and TNF–R2 may be involved in NF–Κ B p65 activation. Microglial cells with upregulation of NF–Κ B p65 may contribute to TNF–α–induced axonal degeneration of optic nerve.

Keywords: neuro-ophthalmology: optic nerve • neuroprotection • immunohistochemistry