Selective impairment of slow axonal transport after optic nerve injury in adult rats

Abstract

To investigate cellular responses of injured mammalian CNS neurons, we examined the slow transport of cytoskeletal proteins in rat retinal ganglion cell (RGC) axons within the ocular stump of optic nerves that were crushed intracranially. RGC proteins were labeled by an intravitreal injection of 35S-methionine, and optic nerves were examined by SDS PAGE at different times after injury. In one group of rats, the RGC proteins were labeled 1 week after crushing. From 14 to 67 d after axotomy, the labeling of tubulin and neurofilaments was reduced in relation to other labeled proteins and to the labeling of tubulin and neurofilaments in the intact optic nerve of controls. To determine whether this reduction in labeling was due to an alteration in axonal transport after axotomy, we prelabeled RGC proteins 1 week before crushing. In such experiments, the rate of slow axonal transport of tubulin and neurofilaments decreased approximately 10-fold from 6 to 60 d after injury. Our results cannot be due only to the retrograde degeneration of RGCs and injured axons caused by axotomy in the optic nerve, because fast axonal protein transport and the fluorescent labeling of many axons were preserved in the ocular stumps of these optic nerves. This selective failure of the slow axonal transport of tubulin and neurofilaments may affect the renewal of the cytoskeleton and contribute to the gradual degeneration of RGCs that is observed after axotomy. The alterations in slow transport we document here differ from the enhanced rates we previously reported when injured RGC axons regenerated along peripheral nerve segments grafted to the ocular stump of transected optic nerves (McKerracher et al., 1990).

Application of Rho Antagonist to Neuronal Cell Bodies Promotes Neurite Growth in Compartmented Cultures and Regeneration of Retinal Ganglion Cell Axons in the Optic Nerve of Adult Rats

“…Our experiments confirmed a previous report that slow axonal transport is almost completely stopped after an intracranial crush of the optic nerve (McKerracher et al, 1990). Typically, RGCs do not regenerate with intracranial injury, even when a PN graft is provided (Richardson et al, 1982;You et al, 2000).…”

“…Axonal transport in normal and injured optic nerve of adult rat has been well described (McQuarrie et al, 1986(McQuarrie et al, , 1989McKerracher et al, 1990) and is detected by examining the movement of 35 Smethionine-labeled proteins along 2 mm optic nerve segments. In uninjured optic nerve, the rate of slow axonal transport of neurofilament, as detected by the 150 kDa middle neurofilament subunit (NF-M), is ϳ0.5 mm/d (McQuarrie et al, 1986), and the transport rate decreases significantly when the optic nerve is crushed intracranially near the optic chiasma (McKerracher et al, 1990).…”

“…In uninjured optic nerve, the rate of slow axonal transport of neurofilament, as detected by the 150 kDa middle neurofilament subunit (NF-M), is ϳ0.5 mm/d (McQuarrie et al, 1986), and the transport rate decreases significantly when the optic nerve is crushed intracranially near the optic chiasma (McKerracher et al, 1990). To determine whether C3-07 had an impact on slow axonal transport, the optic nerve was crushed 6 d after labeling, a time when tubulin and neurofilament proteins enter the optic nerve (Fig.…”

Anatomical and Molecular Responses Triggered in the Retina by Axonal Injury

“…The levels of NF transcripts decrease after different retinal injuries, such as ischemia, excitotoxicity or optic nerve injury (McKerracher et al, 1990a(McKerracher et al, , 1990bChidlow et al, 2005b;Agudo et al, 2008). This regulation correlates, after optic nerve transection, with an impairment of the axonal transport if the RGCs are committed to death, but not if RGCs are allowed to regenerate along peripheral nerve grafts (McKerracher et al, 1990a(McKerracher et al, , 1990bVidal-Sanz et al, 1991, 2000. In healthy retinas pNFH expression is circumscribed to the mature portion of the intrarretinal axons, i.e.…”

Temporal changes in beta-tubulin and neurofilament mRNA levels after transection of adult rat retinal ganglion cell axons in the optic nerve

“…Other events may also play a role in regulating the axonal cytoskeleton, such as protein phosphorylation (Nixon and Logvinenko, 1986;De Waegh et al, 1992). While such changes in the regulation of the cytoskeleton have been described in axotomized neurons that regenerate naturally, thcrc arc differences in the expression of cytoskeletal proteins after injury to nerve cells that do not regrow in the CNS environment (McKerracher et al, 1990b;Tetzlaff et al, 1991;McKcrracher and Hirscheimer, 1992). To investigate molecular changes in tubulin and NF expression after injury in the CNS, retinal ganglion cells (RGCs) were examined after cutting their axons in the optic nerve because several degenerative and rcgenerative responses have been well characterized in this CNS neuronal projection (rcvicwcd by Aguayo et al,I99 I a,b).…”