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.
Kitaoka
Yasushi
Y
Department of Ophthalmology, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. kitaoka@marianna-u.ac.jp
Kitaoka
Yuka
Y
Kwong
Jacky M K
JM
Ross-Cisneros
Fred N
FN
Wang
Jiantao
J
Tsai
Rong Kung
RK
Sadun
Alfredo A
AA
Lam
Tim T
TT
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