Sciatic nerve axotomy in aged rats: response of motoneurons and the effect of GM1 ganglioside treatment

Transdermal monosialoganglioside with laser in the treatment of spinal cord lesion in rats

OBJECTIVES:

To evaluate the effects of monosialoganglioside (GM1) administered transdermally with laser in the recovery of spinal cord injury in rats.

METHODS:

Forty male Wistar rats underwent spinal cord contusion using the NYU Impactor. In Group 1, the rats received 0,2 ml of saline intraperitoneally daily; in Group 2, GM1 was administered intraperitoneally at a concentration of 30 mg/kg per day; in Group 3, rats were treated daily with laser at low temperature on the skin, and in Group 4, the daily laser session also contained GM1. All the groups were treated for 42 days. The animals were evaluated by the Basso, Baettie and Bresnahan (BBB) functional scale on days 7, 14, 21, 28, 35 and 42 after the injury, and by histopathology and motor evoked potential after 42 days of injury.

RESULTS:

The animals in Group 4 had higher BBB scores compared with the other groups. There were no differences between the groups, or in the comparisons over time. Histological evaluation showed no differences, and no differences were found in the motor evoked potential tests either.

CONCLUSION:

GM1 associated with the use of low-temperature laser shows no superior functional, neurological or histological results in the treatment of spinal cord lesions in rats. Evidence Level I, Experimental, Controlled, Animal Study.

Expression of tyrosine kinase receptors in cultured dorsal root ganglion neurons in the presence of monosialoganglioside and skeletal muscle cells

The neurotrophic factor-like activity of monosialoganglioside (GM1) has been shown to activate tyrosine kinase receptors (Trk). Targets of neuronal innervation play a vital role in regulating the survival and differentiation of innervating neurotrophin-responsive neurons. Both GM1 and target skeletal muscle (SKM) cells are essential for the maintenance of the function of neurons. However, much less is known about the effects of GM1 or/and target SKM cells on the expression of Trk receptors in dorsal root ganglion (DRG) neurons. Here we have tested what extent to the expression of TrkA, TrkB, and TrkC receptors in primary cultured of DRG neurons in absence or presence of GM1 or/and SKM cells. In this experiment, we found that: (1) GM1 promoted expression of TrkA and TrkB but not TrkC in primary cultured DRG neurons; (2) target SKM cells promoted expression of TrkC but not TrkA and TrkB in neuromuscular cocultures without GM1 treatment; and (3) GM1 and target SKM cells had additional effects on expression of these three Trk receptors. The results of the present study offered new clues for a better understanding of the association of GM1 and target SKM on the expression of Trk receptors.

Nitroxidergic system in human trigeminal ganglia neurons: a quantitative evaluation

The trigeminal ganglia are involved in transmission of orofacial sensitivity. The free radical gas nitric oxide (NO) has recently been found to function as a messenger molecule in both central and peripheral trigeminal primary afferent neurons. NO is produced within neurons mainly by two enzymes: a constitutive (neuronal) form of NO synthase (nNOS) or an inducible form of NOS (iNOS). The aim of the study was to evaluate the distribution of trigeminal neurons according to size (small, medium and large neurons) and to correlate the percentage of NOS-immunopositive neurons with regard to neuronal size. The results showed a significant relationship between the percentage of nNOS-immunopositive neurons and the size of neurons. Evaluation of the percentage of nNOS-immunopositive neurons showed that they constitute about 50% of the total number of neurons and that they are represented mainly as large-sized neurons. The iNOS immunolabelling was very faint in all neuronal types. Since the nitroxidergic system is well represented in human trigeminal ganglia, this study indicates that it could play a relevant role in trigeminal neurotransmission.

Co-administration of monosialoganglioside and skeletal muscle cells on dorsal root ganglion neuronal phenotypes in vitro

The neuropeptide-immunoreactive (IR) and neurofilament-IR neurons are two major phenotypical classes in dorsal root ganglion (DRG). Targets of neuronal innervation play a vital role in regulating the survival and differentiation of innervating neurotrophin-responsive neurons. Monosialoganglioside (GM1) has been considered to have a neurotrophic factor-like activity. Both GM1 and target skeletal muscle (SKM) cells are essential for the maintenance of the function of neurons. However, whether target SKM cells and GM1, alone or associated, generate neuropeptide or neurofilament expression remains unclear. The aim of the present study is to investigate the effects of GM1 or/and SKM on DRG neuronal phenotypes. DRG neurons containing the neuropeptide substance P (SP) and neurofilament 200 (NF-200) were quantified using immunofluorescent labeling in cultures of DRG, which was dissected out at times before (at embryonic days 12.5, E12.5) and after (at E19.5) sensory neurons contact peripheral targets in vivo. DRG neurons were cultured in absence or presence of GM1 or/and SKM cells. In this experiment, we found that: (1) GM1 promoted expression of SP and NF-200 in E12.5 DRG cultures; (2) SKM cells promoted expression of NF-200 but not SP in E12.5 DRG cultures; (3) GM1 and target SKM cells had additive effects on expression of SP and NF-200 in E12.5 DRG cultures; and (4) SKM or/and GM1 did not have effects on expression of SP and NF-200 in E19.5 DRG cultures. These results suggested that GM1 could influence DRG, two major neuronal phenotypes, before sensory neurons contact peripheral targets in vivo. Target SKM cells could only influence neurofilament-expressed neuronal phenotype before sensory neurons contact peripheral targets in vivo. GM1 and SKM cells had the additive effects on two major DRG neuronal classes, which express neuropeptide or neurofilament when DRG cells were harvested before sensory neurons contact peripheral targets in vivo. These results offered new clues for a better understanding of the association of GM1 or/and SKM with neuronal phenotypes.

The neuroprotective effects of NGF combined with GM1 on injured spinal cord neurons in vitro

Monosialoganglioside (GM1) has been considered to have a neurotrophic factor-like activity. Nerve growth factor (NGF), a member of the neurotrophin family, is essential for neuronal survival, differentiation and maturation. The aim of the present study was to investigate whether co-administration of GM1 and NGF reverses glutamate (Glu) neurotoxicity in primary cultured rat embryonic spinal cord neurons. Spinal cord neurons were exposed to Glu (2 mmol/l), Glu (2 mmol/l) plus GM1 (10 mg/ml), Glu (2 mmol/l) plus NGF (10 ng/ml), Glu (2 mmol/l) plus GM1 (5 mg/ml) and NGF (5 ng/ml) and then processed for detecting intracellular concentrations of Ca2+([Ca2+]i) by confocal laser scanning microscopy and growth associated protein 43 (GAP43) mRNA by RT-PCR. The fluorescent intensity in Glu plus GM1 and NGF incubated neurons was the lowest as compared with that in other groups. The expression of GAP43 mRNA in Glu plus GM1 and NGF incubated neurons was the highest as compared with that in other groups. These results implicated that GM1 and NGF have synergistic neuroprotective effects on spinal cord neurons with excitotoxicity induced by Glu in vitro.

Alterations of AQP2 expression in trigeminal ganglia in a murine inflammation model

Aquaporins (AQPs) are small membrane channel proteins involved in osmoregulation. To date, only AQP1, AQP2, AQP4 and AQP9 have been found in the nervous system. Generally, they are involved in water movement in nervous tissue, nevertheless, recent data would suggest the involvement of AQPs in neurotransmission. In this work, we have evaluated the expression of AQP1 and AQP2 in the trigeminal ganglia of mice in an animal model of perioral acute inflammatory pain using immunohistochemistry and immunoblotting analysis. Our data have shown for the first time, the alteration of AQP2 expression in trigeminal ganglia in acute inflammatory pain showing increased and intracellular redistribution of AQP2 mainly in small-sized neurons and Schwann cells. Apart from this, the AQP1 expression remained unaltered. On the whole, these data support the hypothesis that AQP2 is involved in pain transmission in the peripheral nervous system.

GM1 and NGF modulate Ca2+ homeostasis and GAP43 mRNA expression in cultured dorsal root ganglion neurons with excitotoxicity induced by glutamate

Monosialoganglioside (GM1) has been considered to have a neurotrophic factor-like activity. Nerve growth factor (NGF), a member of the neurotrophin family, is essential for neuronal survival, differentiation and maturation. The aim of the present study was to investigate whether co-administration of GM1 and NGF reverses glutamate (Glu) neurotoxicity in primary cultured rat embryonic dorsal root ganglion (DRG) neurons. DRG neurons were exposed to Glu (2 mmol/1), Glu (2 mmol/1) plus GM1 (10 microg/ml), Glu (2 mmol/l) plus NGF (10 ng/ml), Glu (2 mmol/l) plus GM1 (5 microg/ml) and NGF (5 ng/ml) and then processed for detecting intracellular concentrations of Ca2+ ([Ca2+] i) by confocal laser scanning microscopy and growth-associated protein 43 (GAP43) mRNA by RT-PCR. The fluorescent intensity in Glu plus GM1 and NGF incubated neurons was the lowest as compared with that in other groups. The expression of GAP43 mRNA in Glu plus GM1 and NGF incubated neurons was the highest as compared with that in other groups. These results implicated that GM1 and NGF have synergistic neuroprotective effects on DRG neurons with excitotoxicity induced by Glu in vitro.

Effects of cochlear ablation on choline acetyltransferase activity in the rat cochlear nucleus and superior olive

Using microdissection and quantitative microassay, choline acetyltransferase (ChAT) activity was mapped in the cochlear nucleus (CN) and in the source nuclei of the olivocochlear bundle, the lateral superior olive and ventral nucleus of the trapezoid body. In control rats, gradients of ChAT activity were found within the major subdivisions of the CN and in the lateral superior olive. These gradients correlated with the known tonotopic organizations, with higher activities corresponding to locations representing higher sound frequencies. No gradient was found in the ventral nucleus of the trapezoid body. In rats surviving 7 days or 1 or 2 months after cochlear ablation, ChAT activity was increased 1 month after ablation in the anteroventral CN by 30-50% in most parts of the lesion-side and by 40% in the contralateral ventromedial part. ChAT activity in the lesion-side posteroventral CN was increased by approximately 40-50% at all survival times. Little change was found in the dorsal CN. Decreases of ChAT activity were also found ipsilaterally in the lateral superior olive and bilaterally in the ventral nucleus of the trapezoid body. Our results suggest that cholinergic neurons are involved in plasticity within the CN and superior olive following cochlear lesions.

Histochemical and immunohistochemical evaluation of gingival collagen and metalloproteinases in peri-implantitis

The extra-cellular matrix of the gingival tissue plays an important role in the homeostasis of dental implants. In this work we have studied immunohistochemically the distribution of collagen I-III-IV-V, tenascin, metalloproteinases (MMP) 1-3-8-13 and TIMP-1 in three groups of patients: (1) subjects with natural teeth (healthy periodontal tissue), (2) subjects with normal peri-implant mucosa and (3) subjects with clinically evident peri-implantitis. The immunolabelling for collagen I-III-IV showed a similar pattern in all three groups. The labelling for collagen V increased in lamina propria of healthy peri-implant tissue and peri-implantitis. Tenascin immunolabelling in healthy and peri-implant tissues was scattered in lamina propria. In peri-implantitis tenascin immunolabelling increased mainly near to the basal lamina. The MMP-1-3-8 and TIMP-1 immunolabelling were very faint and localized in the stroma in all three groups. In healthy and peri-implant tissues MMP-13 immunolabelling was found in the lamina propria whereas in peri-implantitis MMP-13 immunolabelling was also in epithelium. On the whole, these data suggest that in the extracellular matrix of peri-implantitis there are alterations of collagen V, tenascin and MMP-13 patterns.

GM1 and ERK signaling in the aged brain

We investigated the ability of GM1 to induce phosphorylation/activation of the extracellular-regulated protein kinases (ERKs) in the striatum, hippocampus and frontal cortex of aged male Sprague-Dawley rats. Three different treatment paradigms were used: a single application of GM1 to brain slices in situ, a single intracerebroventricular (icv) administration of GM1 in vivo, and chronic administration of GM1 in vivo. In situ, GM1 induced a rapid and transient activation of ERK1 and ERK 2 in both young and aged rats, and a similar effect was observed after stimulation with the neurotrophins NGF and BDNF. The aged brain appeared to respond more robustly to neurotrophic stimulation with the pERK2 response being significantly greater in the hippocampus and frontal cortex. Acute icv administration of GM1 resulted in short-lasting phosphorylation of ERKs in both aged groups, while chronic administration of GM1 induced a protracted phosphorylation of ERKs. Following chronic GM1 treatment, pERK2 levels in the aged hippocampus were elevated over young control animals. In agreement with reports that GM1 phosphorylates TrkA in vitro or in situ, treatment with GM1 increased the phosphorylation of TrkA in hippocampus of both young and aged animals. These observations indicate that the aged brain maintains the ability to respond to neurotrophic stimuli and put forward the proposition that the ERK cascade is associated with the action(s) of GM1 ganglioside in vivo.