Ganglioside-induced acceleration of axonal transport following nerve crush injury in the rat

Effect of estrogen on vagal afferent projections to the brainstem in the female

The effects of 17β-estradiol (E) on the distribution and density of brainstem projections of small or large diameter primary vagal afferents were investigated in Wistar rats using transganglionic transport of wheat germ agglutinin- (WGA; preferentially transported by non-myelinated afferent C-fibers; 2%), or cholera toxin B-subunit- (CTB, 5%; preferentially transported by large myelinated afferent A-fibers) conjugated horseradish peroxidase (HRP) in combination with the tetramethylbenzidine method in age matched ovariectomized (OVX) only or OVX and treated with E (OVX+E; 30 pg/ml plasma) females for 12 weeks. Additionally, these projections were compared to aged matched males. Unilateral microinjection of WGA-HRP into the nodose ganglion resulted in dense anterograde labeling bilaterally, with an ipsilateral predominance in several subnuclei of the nucleus of the solitary tract (NTS) and in area postrema that was greatest in OVX+E animals compared to OVX only and males. Moderately dense anterograde labeling was also observed in paratrigeminal nucleus (PAT) of the OVX+E animals. CTB-HRP produced less dense anterograde labeling in the NTS complex, but had a wider distribution within the brainstem including the area postrema, dorsal motor nucleus of the vagus, PAT, the nucleus ambiguus complex and ventrolateral medulla in all groups. The distribution of CTB-HRP anterograde labeling was densest in OVX+E, less dense in OVX only females and least dense in male rats. Little, if any, labeling was found within PAT in males using either WGA-or CTB-HRP. Taken together, these data suggest that small, non-myelinated (WGA-labeled) and large myelinated (CTB-labeled) diameter vagal afferents projecting to brainstem autonomic areas are differentially affected by circulating levels of estrogen. These effects of estrogen on connectivity may contribute to the sex differences observed in central autonomic mechanisms between gender, and in females with and without estrogen.

Translational spinal cord injury research: preclinical guidelines and challenges

Advances in the neurobiology of spinal cord injury (SCI) have prompted increasing attention to opportunities for moving experimental strategies towards clinical applications. Preclinical studies are the centerpiece of the translational process. A major challenge is to establish strategies for achieving optimal translational progression while minimizing potential repetition of previous disappointments associated with clinical trials. This chapter reviews and expands upon views pertaining to preclinical design reported in recently published opinion surveys. Subsequent discussion addresses other preclinical considerations more specifically related to current and potentially imminent cellular and pharmacological approaches to acute/subacute and chronic SCI. Lastly, a retrospective and prospective analysis examines how guidelines currently under discussion relate to select examples of past, current, and future clinical translations. Although achieving definition of the "perfect" preclinical scenario is difficult to envision, this review identifies therapeutic robustness and independent replication of promising experimental findings as absolutely critical prerequisites for clinical translation. Unfortunately, neither has been fully embraced thus far. Accordingly, this review challenges the notion "everything works in animals and nothing in humans", since more rigor must first be incorporated into the bench-to-bedside translational process by all concerned, whether in academia, clinical medicine, or corporate circles.

Current status of clinical trials for acute spinal cord injury

Acute spinal cord injury (ASCI) occurs as a result of physical disruption of spinal cord axons through the epicenter of injury leading to deficits in motor, sensory, and autonomic function. This is a debilitating neurological disorder common in young adults that often requires life-long therapy and rehabilitative care, placing a significant burden on our healthcare system. While no cure exists, research has identified various pharmacological compounds that specifically antagonize primary and secondary mechanisms contributing to the etiology of ASCI. Several compounds including methylprednisolone (MPSS), GM-1 ganglio-side, thyrotropin releasing hormone (TRH), nimodipine, and gacyclidine have been tested in prospective randomized clinical trials of ASCI. MPSS and GM-1 ganglioside have shown evidence of modest benefits. Clearly trials of improved neuroprotective agents are required. Promising potential therapies for ASCI include riluzole, minocycline, erythropoietin, and the fusogen polyethylene glycol, as well as mild hypothermia.

Cholinergic deficits in aged rat spinal cord: restoration by GM1 ganglioside

Cholinergic neurons of spinal cord are central for the processing of motor, autonomic, and sensory modalities. Aging is associated with a variety of motor and autonomic symptoms that might be attributed, in part, to impaired spinal cord function. We found that cholinergic neurochemistry is diminished in the spinal cord of 22-24-month-old rats compared with 3-month-old rats. Choline acetyltransferase, high-affinity choline transport and hemicholinium-3 binding to the choline carrier were reduced in the aged spinal cord. The activity of the choline transporter and the hemicholinium-3 binding were decreased in all spinal segments, cervical, thoracic, lumbar and sacral. Hemicholinium-3 binding was reduced in ventral and dorsal horns along all spinal segments. The activity of choline acetyltransferase was decreased only in cervical and lumbar cord. Treatment of aged animals with GM1 induced the recovery of the presynaptic cholinergic markers in the aged spinal cord.

Promotion of sciatic nerve regeneration in rats by a new neurotrophic pyrimidine derivative MS-430

1. The effects of a new neurotrophic pyrimidine derivative of MS-430 on nerve regeneration was examined using Wistar rats whose left sciatic nerve had been subjected to controlled injury. 2. The functional recovery and the packing density of common peroneal nerve axons were significantly enhanced with the administration of 3 mg/kg/day of MS-430. 3. These results suggest that MS-430 is a promising candidate as a neurotrophic drug for clinical use.

Electrophysiological evaluation of the effects of naftidrofuryl on skeletal muscle reinnervation in the rat

The effects of naftidrofuryl on the reinnervation of the rat gastrocnemius muscle after its denervation by localized freezing of the sciatic nerve were tested with electrophysiological techniques. Daily intraperitoneal injections of 30 mg/kg of naftidrofuryl do not increase the rate of axonal regeneration since early signs of reinnervation appeared as in controls around the 10th day after surgery. However, axonal sprouting is markedly increased since the percentage of muscle fibers with polyneuronal innervations was almost twice as high as in controls at the 15 and 21 day postoperative stages. The promoting effects of naftidrofuryl on polyneuronal innervation which gives rise to a redundant innervation during the first period of reinnervation constitutes an improvement of motor function which might be efficient for treatment of nerve injury and neuropathies.

Gangliosides--a new therapeutic agent against stroke and Alzheimer's disease

Gangliosides are glycosphingolipids localized to the outer leaflet of the plasma membrane of vertebrate cells. The highest ganglioside concentration of any organ is found in the mammalian brain, where the gangliosides are enriched in the neuronal membrane, particularly in the synapses. There are four major brain gangliosides with the same neutral tetrasaccharide core to which one to three sialic acids are linked--the simplest being the GM1-ganglioside. These gangliosides have been shown to have neuritogenic and neuronotrophic activity and to facilitate repair of neuronal tissue after mechanical, biochemical or toxic injuries. Mixtures of native bovine brain gangliosides were adopted for pharmacological use in the treatment of peripheral nerve damage, and GM1-ganglioside has been applied for the treatment of CNS injuries and diseases. Beneficial effects of GM1 have been documented in the treatment of stroke and spinal cord injuries, particularly when the treatment has been initiated within a few hours of the acute event. Continuous intraventricular infusion of GM1 has recently been shown to have a significant beneficial effect in Alzheimer disease of early onset (AD Type I).

Ganglioside function in the development and repair of the nervous system. From basic science to clinical application

Gangliosides play important roles in the normal physiological operations of the nervous system, in particular that of the brain. Changes in ganglioside composition occur in the mammalian brain not only during development, but also in aging and in several neuropathological situations. Gangliosides may modulate the ability of the brain to modify its response to cues or signals from the microenvironment. For example, cultured neurons are known to respond to exogenous ganglioside with changes characteristic of cell differentiation. Gangliosides can amplify the responses of neurons to extrinsic protein factors (neuronotrophic factors) that are normal constituents of the neuron's environment. The systemic administration of monosialoganglioside also potentiates trophic actions in vivo and improves neural responses following various types of injury to the adult mammalian central nervous system. The possible molecular mechanism(s) underlying the ganglioside effects may reflect an action in modulating ligand-receptor linked transfer of information across the plasma membrane of the cell.

Effect of crush lesion on radiolabelling of ganglioside in rat peripheral nerve

Left sciatic nerves of adult male Sprague-Dawley rats were crushed and allowed to recover for 0, 1, 2, 4, 7, or 14 days. At each of these times both L-5 dorsal root ganglia were injected with 100 microCi of [3H]glucosamine. Two days later, dorsal root ganglia, lumbosacral trunks, and sciatic nerves were removed bilaterally. The amounts of radiolabelled ganglioside in crushed lumbosacral trunks were consistently higher than in the controls, with the largest difference occurring within 2 days from simultaneous crush and injection to killing (specimens labelled day 0). The largest difference in the amount of radiolabelled ganglioside between crushed and control sciatic nerve (4-9 days from crush to killing) occurred later than that of lumbosacral trunk, but no significant difference occurred within the first 3 days following crush. There was only a slightly higher radioactivity in gangliosides totalled from all three anatomical specimens of crushed than in control nerves. The neutral nonganglioside lipid and acid-precipitable fraction followed patterns of synthesis and accumulation similar to those of the gangliosides. These findings indicate that after nerve crush gangliosides, glucosamine-labelled neutral nonganglioside lipids, and glycoproteins accumulate close to the proximal end of the regenerating axon. This accumulation could serve as a reservoir to increase the ganglioside concentration in the growth cone membrane.

Gangliosides in the nervous system during development and regeneration

Gangliosides are present in nervous tissues of echinoderms and chordates, but the amounts and patterns differ widely. There are changes in the ganglioside contents of nervous tissues during development in most animals studied. To a large extent, regional differences and changes with development and degeneration in ganglioside composition reflect changing and different proportions of cellular types and subcellular organelles within the tissue. GM1 and GM4 are enriched in myelin; GD1a may be a marker for dendritic arborization. During regeneration of fish optic nerve and rat sciatic nerve there is an increased amount of ganglioside proximal to the regenerating axon tips, which may largely be a result of accumulation. This could provide a relatively large reservoir of ganglioside to become incorporated into the sprouting axolemma. Gangliosides added exogenously to growth medium can induce neuritogenesis of several types of neurons. The mechanisms of this action are unknown but may be related to nerve growth factor, microskeletal organization, membrane fluidity, and other factors. Gangliosides injected into young animals affect brain development, but further studies are required to determine these effects more specifically. Ganglioside administration increases the number of sprouts in regenerating peripheral nerves, but does not seem to accelerate axonal elongation. Parenterally administered gangliosides alter the recovery of brain tissue from a variety of types of lesions, and clinical trials are in progress to determine if they are of benefit in human neurological disorders. The biochemical mechanisms of these in vivo ganglioside effects are poorly understood, but may involve modulation of several enzyme systems as well as other properties of neural membranes, such as fluidity. It is possible that gangliosides may play similar roles and operate through some of the same mechanisms in developing and regenerating nervous tissues.

Denervation-induced collateral sprouting: no case for tracing methods

Sprouting of axonal collaterals is assumed to represent a major feature of the regenerative capacity of the CNS. Following the denervation of a brain region, synaptic contact sites become free and are replaced by sprouted collaterals of intact afferents of this area. During the last three years, numerous studies have been published which have used anatomical tracing methods to demonstrate this morphological consequence of lesions. This paper criticizes the use of tracing methods in this research field because of the striking problems in quantifying the altered connectivity of a denervated structure. This critique is illustrated by summarizing the studies on the lesion-induced morphological effects within the nigro-striatal system which has become a paradigmatic neuronal circuit for the study of neuronal and functional reorganization. It is concluded that anatomical tracing methods seem to be inappropriate in studying denervation-induced collateral sprouting.

Ganglioside-induced regeneration and reestablishment of axonal continuity in spinal cord-transected rats

In this study we examined the effect of chronic GM-1 ganglioside treatment on the reestablishment of axonal continuity and functional recovery in spinal cord-transected rats. Previous studies have shown that chronic treatment with GM-1 ganglioside is effective in producing regeneration of lesioned mesostriatal dopaminergic neurons in the central nervous system [1, 2]. In addition, GM-1 ganglioside advances peripheral nerve regeneration following nerve crush injury [12]. Axonal continuity was determined by the ability of the spinal cord to transport horseradish peroxidase across the region of transection. Comparisons between ganglioside-treated and saline-treated controls showed that ganglioside treatment resulted in the reestablishment of axonal continuity between the spinal cord distal to the level of the transection and the brainstem. Saline-treated controls showed little evidence of axonal continuity between these two regions. Thus gangliosides induce reestablishment of axonal continuity and thereby could advance functional recovery in rats following spinal cord transection.

Effects of isaxonine on skeletal muscle reinnervation in the rat: an electrophysiologic evaluation

Electrophysiologic detection of the first signs of gastrocnemius muscle reinnervation shows that after a single localized freezing of the rat sciatic nerve, isaxonine does not significantly increase the rate of axonal regeneration. However, this drug does significantly enhance axonal sprouting, as it induces an increase of 50% in the number of muscle fibers with multiple innervation 10-30 days after freezing. After 30 days, the proportion of multiinnervated fibers decreases in both the control and isaxonine-treated rats, and the differences between them gradually disappear.

Quantitation of the in vitro neuroblastoma response to exogenous, purified gangliosides

Individual ganglioside species (possessing the gangliotetrose oligosaccharide) were purified from bovine brain gray matter and applied in varying concentrations to the culture medium of mouse neuroblastoma cells (N2A) in vitro. After 48 hr of incubation, the cells were stained, and the neuritogenic response quantitated with a video analysis system, employing a program to measure three parameters of neuroblastoma differentiation: neurites per cell (sprouting), neurite length (extension), and degree of neurite branching (arborization). All the individual gangliosides tested promoted neurite extension in a dose-dependent fashion. Asialogangliosides ("neutral" glycosphingolipids) were without effect, which suggests that sialic acid (N-acetylneuraminic acid) is necessary to elicit this cellular response. With increasing concentrations of GM1 (5 to 500 micrograms/ml), the average cellular neurite length increased significantly, whereas the number of neurites per cell decreased. With the trisialoganglioside GT1b, neurite length did not increase to the extent seen with GM1, but an increase in the number of neurites per cell (sprouting) and branch points per neurite (arborization) was observed. These results suggest that the in vitro neuronal response to exogenous gangliosides may combine specific responses to individual species making up the total.

Gangliosides stimulate protein synthesis, growth, and axon number of regenerating limb buds

When a newt limb is amputated and begins to regrow, regenerating axons exert a neurotrophic influence on the limb regeneration process. Previous studies have shown that direct manipulation of limb nerves, by electrical stimulation or a conditioning lesion, elevates protein synthesis, increases neurotization and accelerates growth of the limb bud. Since exogenously supplied gangliosides accelerate axonal sprouting in regenerating nerves, we wanted to know whether gangliosides would similarly affect limb regeneration. To test this, regrowing limb buds were either infused with or immersed into gangliosides, or animals were injected intraperitoneally with gangliosides. Infused gangliosides elevated protein synthesis in limb buds 15% and increased the number of axons in limb buds 45% by 6 hours after infusion. Regenerating limb bud morphogenesis was initiated 3-4 days earlier in animals receiving i.p. injections of gangliosides every 12 hours. Similarly, limbs immersed daily in gangliosides began regrowth sooner than contralateral controls and this advantage was maintained throughout the period of observation. These findings indicate that treatment with gangliosides has a salutary effect on limb regeneration.

Biology of gangliosides: neuritogenic and neuronotrophic properties

Research on the biologic function of gangliosides has accelerated in recent years following discovery of their pronounced effects when administered exogenously to neurons in culture and in vivo. These effects are of two principal types: 1) neuronotrophic, concerned primarily with survival and maintenance of the neuron, and 2) neuritogenic, involving significant increase in the number, length, and/or branching of neuronal processes. Such neurite-promoting activity has been observed in primary cultures of neurons from brain and ganglia as well as transformed lines of neuronal origin. These phenomena may be related to the remarkable growth of aberrant secondary neurites, often accompanied by synaptogenesis, observed in the gangliosidoses. Several in vivo studies have shown exogenously administered gangliosides to aid nervous system repair in both the CNS and PNS, although it is not clear in some cases whether the observed effects should be attributed to neuronotrophic or neuritogenic effects (or both). This article attempts to briefly review the principal developments that have occurred in this area of ganglioside research over the past several years. It also presents for consideration some of the tentative hypotheses put forward concerning mechanism of action.

Ganglioside changes in the regenerating goldfish optic system: comparison with glycoproteins and phospholipids

Axonally transported radioactivity in sialoglycoconjugates, labeled by intraocular injection of [3H]N-acetylmannosamine, increased significantly during regeneration of goldfish optic axons at 30 degrees C. Ganglioside radioactivity showed the largest increase--approximately eightfold--in the optic nerve tract at 8 days after optic nerve crush while sialoglycoprotein radioactivity increased fourfold under the same conditions. As regeneration proceeded the magnitude of the increase in the nerve tract diminished for both glycoconjugates. In the optic tectum, however, transported radioactivities remained approximately twofold higher than controls between 15 and 25 days postcrush. The zwitterionic fraction of glycerophospholipids, labeled by intraocular injection of [14C]glycerol, also showed large increases during regeneration, but the acidic glycerophospholipids showed only modest increases. Thus while membrane components in general were elevated during the early stages of regeneration, the most pronounced increases occurred in gangliosides and certain glycerophospholipids. The significance of these changes in the regeneration process remain to be determined.

Effects of ganglioside treatments on lesion-induced behavioral impairments and sprouting in the CNS

Recent findings suggest that exogenous gangliosides improve recovery of a learned behavior (alternation in a T-maze) which is thought to be related to sprouting after lesions of the entorhinal cortex. In the present investigation, we studied an unlearned behavior (the open-field hyperactivity resulting from bilateral entorhinal lesions) to evaluate whether ganglioside treatments reduce the severity of initial postlesion impairments or improve recovery. We also examined whether the treatments enhance the sprouting of septodenate fibers which parallels the recovery of open-field activity. The typical behavioral changes induced by bilateral entorhinal lesions include hyperactivity, reduced habituation of activity, and a gradual time-dependent return toward control levels. We found that rats treated with total brain gangliosides (30 mg/kg) showed a smaller lesion-induced increase, consistently lower levels, and greater within-session habituation of activity than did saline-treated counterparts. Control rats treated with gangliosides did not exhibit a reduction in activity, suggesting that the effect was on lesion-induced hyperactivity rather than on activity, per se. Ganglioside-treated rats showed a slight, but consistently smaller lesion-induced sprouting response by the septodentate pathway than did untreated counterparts at all postlesion intervals examined (3, 5, 7, and 10 days). The present findings indicate that ganglioside treatments reduce the severity of the initial behavioral effects after entorhinal lesions without enhancing the sprouting by septodentate fibers.

Treatment of painful diabetic polyneuropathy with mixed gangliosides

We studied 18 patients with painful diabetic neuropathy in a double-blind study of 40 mg per day of mixed gangliosides. Diabetes control was maintained throughout by analysis of serum glucose and glycosylated hemoglobin levels. Median motor and sensory, and peroneal motor conductions we evaluated in placebo and treated groups before and after a treatment period of three months. All conductions were performed by one technician on a TECA-4 EMG machine with surface temperature controlled at 37 degrees C. There was a definite improvement in nerve conductions in the treated group, particularly noted in the median sensory conductions. We have demonstrated a difference between right and left-sided conductions in the same patients confirming that this illness, at least from an electrophysiological point of view is asymmetric. Clinical improvement was variable but when present was dramatic. Side effects of this drug were minimal. Half of the patient complained of a transient increase in pain during the first two weeks of treatment. No patient stopped the drug because of this complaint. We conclude that in this three-month study mixed gangliosides caused a significant improvement in some nerve conductions without significant side effects. Further studies seem warranted to determine the nature and extent of this effect.