Journal of Neuroscience, Vol 4, 1516-1526, Copyright © 1984 by Society for Neuroscience
3,4-Dimethyl-2,5-hexanedione impairs the axonal transport of neurofilament proteins
JW Griffin, DC Anthony, KE Fahnestock, PN Hoffman and DG Graham
Accumulations of neurofilaments are observed in a variety of neurological
disorders, and their pathogenesis is a fundamental problem of
neuropathology. 2,5-Hexanedione (HD) neurotoxicity provides an extensively
studied model of axonal neurofibrillary changes in which the pathogenetic
mechanisms have been conjectural. Chronic exposure to HD results in
neurofilament-filled swellings in the distal regions of large axons of
exposed humans and experimental animals. In this report we describe the
changes produced by a potent analogue of HD, 3,4- dimethyl-2,5-hexanedione
( DMHD ), in slow axonal transport in the rat sciatic motor axons. Young
rats received 0.6 mmol/kg of DMHD for 5 days before [35S]methionine was
injected into the lumbar ventral horns. Slow axonal transport of the
neurofilament proteins, tubulin, and selected slow component b (SCb)
proteins in DMHD -treated animals was compared to the profiles found in
age-matched control animals. DMHD administration reduced the rate of
transport of the neurofilament proteins 75 to 90%, while tubulin and the
SCb proteins were only modestly retarded. No alterations in electrophoretic
mobilities of slowly transported proteins were found, nor were any proteins
accelerated in transport. These findings were systematically compared to
the changes produced by administration of beta,beta'- immino -
dipropionitrile (IDPN) (2.0 gm/kg, i.p.), an agent known to impair
neurofilament transport. Although slightly less severe, the changes
produced by DMHD were nearly identical to those of IDPN. In correlative
morphological studies, the neurofilamentous changes were also comparable.
The results indicate that DMHD and IDPN share the capacity to interfere
selectively with neurofilament transport and thereby share pathogenetic
mechanisms. DMHD provides a new agent for exploration of the organization
and transport of the neuronal cytoskeleton.