TNF-alpha-induced optic nerve degeneration and nuclear factor-kappaB p65.
OBJECTIVE
To characterize a model of optic nerve axonal degeneration induced by tumor necrosis factor (TNF)-alpha and to determine the role of nuclear factor (NF)-kappaB p65 in axonal degeneration.


METHODS
Groups of rats were euthanatized at 1 day, 1 or 2 weeks, or 1 or 2 months after intravitreal injection of TNF-alpha. Morphometric analyses of neurofilament- or Thy-1-positive cells, retinal ganglion cells (flat preparations stained with cresyl violet or retrograde labeling with a neurotracer), the number of axons, immunostaining for myelin basic protein, and TUNEL assays were performed. Levels of NF-kappaB p65 protein in retina and optic nerve were determined by Western blot analysis and immunohistochemistry. The effects of antisense oligodeoxynucleotide (AS ODN) against NF-kappaB p65 and helenalin, an inhibitor of NF-kappaB p65 activation, on TNF-alpha-induced optic nerve degeneration were determined by counting the number of axons.


RESULTS
Intravitreal injections of TNF-alpha induced obvious axonal loss and extensive degeneration of the axons from 2 weeks to 2 months after injection, whereas significant retinal ganglion cell loss was noted only at 2 months after injection. NF-kappaB p65 was increased in the optic nerve but not in the retina and was found to colocalize with ED-1 and Iba1, markers of microglia. Inhibition of NF-kappaB p65 with AS ODN or helenalin significantly ameliorated the effects of TNF-alpha-mediated axonal loss.


CONCLUSIONS
TNF-alpha causes axonal degeneration with probable delayed loss of retinal ganglion cell bodies. NF-kappaB p65 may play a pivotal role in axonal degeneration, with the possible involvement of microglial cells.
Department of Ophthalmology, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. kitaoka@marianna-u.ac.jp
Yasushi
Y
Kitaoka
Yuka
Y
Kitaoka
Jacky M K
JM
Kwong
Fred N
FN
Ross-Cisneros
Jiantao
J
Wang
Rong Kung
RK
Tsai
Alfredo A
AA
Sadun
Tim T
TT
Lam
D000818:Animals; D001369:Axons / Q000378:metabolism; D015153:Blotting, Western; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007267:Injections; D008297:Male; D004676:Myelin Basic Protein / Q000378:metabolism; D009410:Nerve Degeneration / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D009900:Optic Nerve / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D012160:Retina / Q000378:metabolism; D012717:Sesquiterpenes / Q000494:pharmacology; D045789:Sesquiterpenes, Guaiane; D051996:Transcription Factor RelA / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*; D014822:Vitreous Body
D004676:Myelin Basic Protein; D020319:Oligodeoxyribonucleotides, Antisense; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; C001329:helenalin