Survival Of Spinal Motor Neurons Research Articles

Intrathecal delivery of AAV-NDNF ameliorates disease progression of ALS mice

Amyotrophic lateral sclerosis (ALS) is a uniformly lethal neurodegenerative disease characterized by progressive deterioration of motor neurons and neuromuscular denervation. Adeno-associated virus (AAV)-mediated delivery of trophic factors is being considered as a potential disease-modifying therapeutic avenue. Here we show a marked effect of AAV-mediated over-expression of neuron-derived neurotrophic factor (NDNF) on SOD1G93A ALS model mice. First, we adopt AAV-PHP.eB capsid to enable widespread expression of target proteins in the brain and spinal cord when delivered intrathecally. Then we tested the effects of AAV-NDNF on SOD1G93A mice at different stages of disease. Interestingly, AAV-NDNF markedly improved motor performance and alleviated weight loss when delivered at early post-symptomatic stage. Injection in the middle post-symptomatic stages still improved the locomotion ability, although it did not alleviate the loss of body weight. Injection in the late stage also extended the life span of SOD1G93A mice. Furthermore, NDNF expression promoted the survival of spinal motoneurons, reduced abnormal protein aggregation, and preserved the innervated neuromuscular functions. We further analyzed the signaling pathways of NDNF expression and found that it activates cell survival and growth-associated mammalian target of rapamycin signaling pathway and downregulates apoptosis-related pathways. Thus, intrathecally AAV-NDNF delivery has provided a potential strategy for the treatment of ALS.

The distribution and function of GDE2, a regulator of spinal motor neuron survival, are disrupted in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the viability of upper and lower motor neurons. Current options for treatment are limited, necessitating deeper understanding of the mechanisms underlying ALS pathogenesis. Glycerophosphodiester phosphodiesterase 2 (GDE2 or GDPD5) is a six-transmembrane protein that acts on the cell surface to cleave the glycosylphosphatidylinositol (GPI)-anchor that tethers some proteins to the membrane. GDE2 is required for the survival of spinal motor neurons but whether GDE2 neuroprotective activity is disrupted in ALS is not known. We utilized a combination of mouse models and patient post-mortem samples to evaluate GDE2 functionality in ALS. Haplogenetic reduction of GDE2 exacerbated motor neuron degeneration and loss in SOD1G93A mice but not in control SOD1WT transgenic animals, indicating that GDE2 neuroprotective function is diminished in the context of SOD1G93A. In tissue samples from patients with ALS, total levels of GDE2 protein were equivalent to healthy controls; however, membrane levels of GDE2 were substantially reduced. Indeed, GDE2 was found to aberrantly accumulate in intracellular compartments of ALS motor cortex, consistent with a disruption of GDE2 function at the cell surface. Supporting the impairment of GDE2 activity in ALS, tandem-mass-tag mass spectrometry revealed a pronounced reduction of GPI-anchored proteins released into the CSF of patients with ALS compared with control patients. Taken together, this study provides cellular and biochemical evidence that GDE2 distribution and activity is disrupted in ALS, supporting the notion that the failure of GDE2-dependent neuroprotective pathways contributes to neurodegeneration and motor neuron loss in disease. These observations highlight the dysregulation of GPI-anchored protein pathways as candidate mediators of disease onset and progression and accordingly, provide new insight into the mechanisms underlying ALS pathogenesis.

Short and long-term neuroprotective effects of cannabidiol after neonatal peripheral nerve axotomy

Neonatal rat sciatic nerve crush mimics obstetric axonotmesis, leading to extensive loss of motor and sensory neurons. The present study aimed to investigate the neuroprotective potential of cannabidiol (CBD) and the role of cannabinoid receptors after sciatic nerve crush in neonatal rats. For that, two-day-old Wistar rats were used, organized into the following experimental groups: sciatic nerve crush plus CBD treatment (CBD), crush plus vehicle treatment (VE), crush + CBD + AM251 treatment (AM251 – CB1 inverse agonist), crush + CBD + AM630 treatment (AM630 – CB2 antagonist). Spinal motoneuron survival was evaluated by Nissl staining of the lumbar spinal cord, 5- and 56-days following injury. CBD treatment enhanced neuronal survival by ~54 % both 5 days and 8 weeks after injury. However, AM251 and AM630 treatment decreased neuronal rescue by 30 % when compared to the CBD group, suggesting that CBD acts partially through such pathways. However, in the long term, only the CB1 blockade reverted CBD positive results. Synaptic preservation was evaluated by anti-synaptophysin immunolabeling. Five days after the lesion, CBD treatment preserved ~35 % of synapses in the ventral horn, and such effect was partially reversed by CB1 inactivation. Additionally, CBD treatment reduced astroglial reaction both at 5 days (39 %, compared to VE) and 8 weeks (31 %, compared to VE) after lesion. The microglial response was acutely reduced by 62 % after CBD treatment. Overall, the results herein show that CBD is neuroprotective, increasing neuronal survival and reducing glial reaction after neonatal axotomy. Such effects require CB1 and CB2 receptors to be effective, in turn influencing neuroprotection, glial reactivity, and functional recovery.

Specific Expression of Glial-Derived Neurotrophic Factor in Muscles as Gene Therapy Strategy for Amyotrophic Lateral Sclerosis.

Glial cell line-derived neurotrophic factor (GDNF) is a powerful neuroprotective growth factor. However, systemic or intrathecal administration of GDNF is associated with side effects. Here, we aimed to avoid this by restricting the transgene expression to the skeletal muscle by gene therapy. To specifically target most skeletal muscles in the mouse model of amyotrophic lateral sclerosis (ALS), SOD1G93A transgenic mice were intravenously injected with adeno-associated vectors coding for GDNF under the control of the desmin promoter. Treated and control SOD1G93A mice were evaluated by rotarod and nerve conduction tests from 8 to 20weeks of age, and then histological and molecular analyses were performed. Muscle-specific GDNF expression delayed the progression of the disease in SOD1G93A female and male mice by preserving the neuromuscular function; increasing the number of innervated neuromuscular junctions, the survival of spinal motoneurons; and reducing glial reactivity in treated SOD1G93A mice. These beneficial actions are attributed to a paracrine protective mechanism from the muscle to the motoneurons by GDNF. Importantly, no adverse secondary effects were detected. These results highlight the potential of muscle GDNF-targeted expression for ALS therapy.

Therapeutic strategies for brachial plexus injury.

Brachial plexus avulsion (BPA), a severe acute peripheral nerve injury in adults, results in total loss of the motor function in the upper limb. Although immediate re-implantation surgery is widely performed to repair this lesion, the motor function cannot be fully restored. The main cause is that the growth velocity of axon is extremely slow in order to re-innervate the target muscles before atrophy develops. Therefore, the survival of spinal motoneurons (MNs) is considered to be a prerequisite for the recovery of motor function. The introduction of survival-proactive agents with anti-oxidative stress and anti-inflammation properties has emerged as a new approach to the motor function recovery following BPA. In the current review, we summarized the treatments of BPA in both mouse and rat models following re-implantation surgery. Furthermore, the pain treatment options following BPA were discussed.

Role of MHC-I Expression on Spinal Motoneuron Survival and Glial Reactions Following Ventral Root Crush in Mice.

Lesions to the CNS/PNS interface are especially severe, leading to elevated neuronal degeneration. In the present work, we establish the ventral root crush model for mice, and demonstrate the potential of such an approach, by analyzing injury evoked motoneuron loss, changes of synaptic coverage and concomitant glial responses in β2-microglobulin knockout mice (β2m KO). Young adult (8–12 weeks old) C57BL/6J (WT) and β2m KO mice were submitted to a L4–L6 ventral roots crush. Neuronal survival revealed a time-dependent motoneuron-like cell loss, both in WT and β2m KO mice. Along with neuronal loss, astrogliosis increased in WT mice, which was not observed in β2m KO mice. Microglial responses were more pronounced during the acute phase after lesion and decreased over time, in WT and KO mice. At 7 days after lesion β2m KO mice showed stronger Iba-1+ cell reaction. The synaptic inputs were reduced over time, but in β2m KO, the synaptic loss was more prominent between 7 and 28 days after lesion. Taken together, the results herein demonstrate that ventral root crushing in mice provides robust data regarding neuronal loss and glial reaction. The retrograde reactions after injury were altered in the absence of functional MHC-I surface expression.

Neuregulin-1 Accelerates Functional Motor Recovery by Improving Motoneuron Survival After Brachial Plexus Root Avulsion in Mice

Brachial plexus root avulsion (BPRA) results in the complete loss of motor function in the upper limb, mainly due to the death of spinal motoneurons (MNs). The survival of spinal MNs is the key to the recovery of motor function. Neuregulin-1 (Nrg1) plays fundamental roles in nervous system development and nerve repair. However, its functional role in BPRA remains unclear. On the basis of our findings that Nrg1 is down-regulated in the ventral horn in a mouse model of BPRA, Nrg1 may be associated with BPRA. Here, we investigated whether recombinant Nrg1β (rNrg1β) can enhance the survival of spinal MNs and improve functional recovery in mice following BPRA. In vitro studies on primary cultured mouse MNs showed that rNrg1β increased the survival rate in a dose-dependent manner, reaching a peak at 5 nM, which increased the survival rate and enhanced the pERK levels in MNs under H2O2-induced oxidative stress. In vivo studies revealed that rNrg1β improved the functional recovery of elbow flexion, promoted the survival of MNs, enhanced the re-innervation of biceps brachii, and decreased the muscle atrophy. These results suggest that Nrg1 may provide a potential therapeutic strategy for root avulsion.

A Stem Cell-Based Screening Platform Identifies Compounds that Desensitize Motor Neurons to Endoplasmic Reticulum Stress.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease selectively targeting motor neurons in the brain and spinal cord. The reasons for differential motor neuron susceptibility remain elusive. We developed a stem cell-based motor neuron assay to study cell-autonomous mechanisms causing motor neuron degeneration, with implications for ALS. A small-molecule screen identified cyclopiazonic acid (CPA) as a stressor to which stem cell-derived motor neurons were more sensitive than interneurons. CPA induced endoplasmic reticulum stress and the unfolded protein response. Furthermore, CPA resulted in an accelerated degeneration of motor neurons expressing human superoxide dismutase 1 (hSOD1) carrying the ALS-causing G93A mutation, compared to motor neurons expressing wild-type hSOD1. A secondary screen identified compounds that alleviated CPA-mediated motor neuron degeneration: three kinase inhibitors and tauroursodeoxycholic acid (TUDCA), a bile acid derivative. The neuroprotective effects of these compounds were validated in human stem cell-derived motor neurons carrying a mutated SOD1 allele (hSOD1A4V). Moreover, we found that the administration of TUDCA in an hSOD1G93A mouse model of ALS reduced muscle denervation. Jointly, these results provide insights into the mechanisms contributing to the preferential susceptibility of ALS motor neurons, and they demonstrate the utility of stem cell-derived motor neurons for the discovery of new neuroprotective compounds.

Genetic ablation of dynactin p150Glued in postnatal neurons causes preferential degeneration of spinal motor neurons in aged mice

BackgroundDynactin p150Glued, the largest subunit of the dynactin macromolecular complex, binds to both microtubules and tubulin dimers through the N-terminal cytoskeleton-associated protein and glycine-rich (CAP-Gly) and basic domains, and serves as an anti-catastrophe factor in stabilizing microtubules in neurons. P150Glued also initiates dynein-mediated axonal retrograde transport. Multiple missense mutations at the CAP-Gly domain of p150Glued are associated with motor neuron diseases and other neurodegenerative disorders, further supporting the importance of microtubule domains (MTBDs) in p150Glued functions. However, most functional studies were performed in vitro. Whether p150Glued is required for neuronal function and survival in vivo is unknown.MethodsUsing Cre-loxP genetic manipulation, we first generated a line of p150Glued knock-in mice by inserting two LoxP sites flanking the MTBD-coding exons 2 to 4 of p150Glued–encoding Dctn1 gene (Dctn1LoxP/), and then crossbred the resulting Dctn1LoxP/ mice with Thy1-Cre mice to generate the bigenic p150Glued (Dctn1LoxP/LoxP; Thy1-Cre) conditional knockout (cKO) mice for the downstream motor behavioral and neuropathological studies.ResultsP150Glued expression was completely abolished in Cre-expressing postnatal neurons, including corticospinal motor neurons (CSMNs) and spinal motor neurons (SMNs), while the MTBD–truncated forms remained. P150Glued ablation did not affect the formation of dynein/dynactin complex in neurons. The p150Glued cKO mice did not show any obvious developmental phenotypes, but exhibited impairments in motor coordination and rearing after 12 months of age. Around 20% loss of SMNs was found in the lumbar spinal cord of 18-month-old cKO mice, in company with increased gliosis, neuromuscular junction (NMJ) disintegration and muscle atrophy. By contrast, no obvious degeneration of CSMNs, striatal neurons, midbrain dopaminergic neurons, cerebellar granule cells or Purkinje cells was observed. Abnormal accumulation of acetylated α-tubulin, and autophagosome/lysosome proteins was found in the SMNs of aged cKO mice. Additionally, the total and cell surface levels of glutamate receptors were also substantially elevated in the p150Glued-depleted spinal neurons, in correlation with increased vulnerability to excitotoxicity.ConclusionOverall, our findings demonstrate that p150Glued is particularly required to maintain the function and survival of SMNs during aging. P150Glued may exert its protective function through regulating the transportation of autophagosomes, lysosomes, and postsynaptic glutamate receptors in neurons.

Neuronal overexpression of human VAPB slows motor impairment and neuromuscular denervation in a mouse model of ALS.

Four mutations in the VAMP/synaptobrevin-associated protein B (VAPB) gene have been linked to amyotrophic lateral sclerosis (ALS) type 8. The mechanism by which VAPB mutations cause motor neuron disease is unclear, but studies of the most common P56S variant suggest both loss of function and dominant-negative sequestration of wild-type protein. Diminished levels of VAPB and its proteolytic cleavage fragment have also been reported in sporadic ALS cases, suggesting that VAPB loss of function may be a common mechanism of disease. Here, we tested whether neuronal overexpression of wild-type human VAPB would attenuate disease in a mouse model of familial ALS1. We used neonatal intraventricular viral injections to express VAPB or YFP throughout the brain and spinal cord of superoxide dismutase (SOD1) G93A transgenic mice. Lifelong elevation of neuronal VAPB slowed the decline of neurological impairment, delayed denervation of hindlimb muscles, and prolonged survival of spinal motor neurons. Collectively, these changes produced a slight but significant extension in lifespan, even in this highly aggressive model of disease. Our findings lend support for a protective role of VAPB in neuromuscular health.

Absence of UCHL 1 function leads to selective motor neuropathy.

ObjectiveThe aim of this study was to investigate the role of ubiquitin C‐terminal hydrolase‐L1 (UCHL1) for motor neuron circuitry and especially in spinal motor neuron (SMN) health, function, and connectivity.MethodsSince mutations in UCHL1 gene leads to motor dysfunction in patients, we investigated the role of UCHL1 on SMN survival, axon health, and connectivity with the muscle, by employing molecular and cellular marker expression analysis and electrophysiological recordings, in healthy wild‐type and Uchl1 nm3419 (UCHL1−/−) mice, which lack all UCHL1 function.ResultsThere is pure motor neuropathy with selective degeneration of the motor, but not sensory axons in the absence of UCHL1 function. Neuromuscular junctions (NMJ) are impaired in muscle groups that are innervated by slow‐twitch or fast‐twitch SMN. However, unlike corticospinal motor neurons, SMN cell bodies remain intact with no signs of elevated endoplasmic reticulum (ER) stress.InterpretationPresence of NMJ defects and progressive retrograde axonal degeneration in the absence of major SMN soma loss suggest that defining pathology as a function of neuron number is misleading and that upper and lower motor neurons utilize UCHL1 function in different cellular events. In line with findings in patients with mutations in UCHL1 gene, our results suggest a unique role of UCHL1, especially for motor neuron circuitry. SMN require UCHL1 to maintain NMJ and motor axon health, and that observed motor dysfunction in the absence of UCHL1 is not due to SMN loss, but mostly due to disintegrated circuitry.

The role of brain-derived neurotrophic factor in bone marrow stromal cell-mediated spinal cord repair.

The ability of intraspinal bone marrow stromal cell (BMSC) transplants to elicit repair is thought to result from paracrine effects by secreted trophic factors including brain-derived neurotrophic factor (BDNF). Here we used gene therapy to increase or silence BDNF production in BMSCs to investigate the role of BDNF in BMSC-mediated neuroprotection. In a spinal cord organotypic culture, BMSC-conditioned medium significantly enhanced spinal motoneuron survival by 64% compared with culture medium only. Only conditioned medium of BDNF-hypersecreting BMSCs sustained this neuroprotective effect. In a rat model of spinal cord contusion, a BDNF-dependent neuroprotective effect was confirmed; only with a subacute transplant of BDNF-hypersecreting BMSCs were significantly more spared motoneurons found at 4 weeks postinjury compared with vehicle controls. Spared nervous tissue volume was improved by 68% with both control BMSCs and BDNF-hypersecreting BMSCs. In addition, blood vessel density in the contusion with BDNF-hypersecreting BMSCs was 35% higher compared with BMSC controls and sixfold higher compared with vehicle controls. BDNF-silenced BMSCs did not survive the first week of transplantation, and no neuroprotective effect was found at 4 weeks after transplantation. Together, our data broaden our understanding of the role of BDNF in BMSC-mediated neuroprotection and successfully exploit BDNF dependency to enhance anatomical spinal cord repair.

Delayed disease onset and extended survival in the SOD1G93A rat model of amyotrophic lateral sclerosis after suppression of mutant SOD1 in the motor cortex.

Sporadic amyotrophic lateral sclerosis (ALS) is a fatal disease with unknown etiology, characterized by a progressive loss of motor neurons leading to paralysis and death typically within 3-5 years of onset. Recently, there has been remarkable progress in understanding inherited forms of ALS in which well defined mutations are known to cause the disease. Rodent models in which the superoxide dismutase-1 (SOD1) mutation is overexpressed recapitulate hallmark signs of ALS in patients. Early anatomical changes in mouse models of fALS are seen in the neuromuscular junctions (NMJs) and lower motor neurons, and selective reduction of toxic mutant SOD1 in the spinal cord and muscle of these models has beneficial effects. Therefore, much of ALS research has focused on spinal motor neuron and NMJ aspects of the disease. Here we show that, in the SOD1(G93A) rat model of ALS, spinal motor neuron loss occurs presymptomatically and before degeneration of ventral root axons and denervation of NMJs. Although overt cell death of corticospinal motor neurons does not occur until disease endpoint, we wanted to establish whether the upper motor neuron might still play a critical role in disease progression. Surprisingly, the knockdown of mutant SOD1 in only the motor cortex of presymptomatic SOD1(G93A) rats through targeted delivery of AAV9-SOD1-shRNA resulted in a significant delay of disease onset, expansion of lifespan, enhanced survival of spinal motor neurons, and maintenance of NMJs. This datum suggests an early dysfunction and thus an important role of the upper motor neuron in this animal model of ALS and perhaps patients with the disease.

Resveratrol Improves Motoneuron Function and Extends Survival in SOD1G93A ALS Mice

Amyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disease that causes progressive paralysis and death due to degeneration of motoneurons in spinal cord, brainstem and motor cortex. Nowadays, there is no effective therapy and patients die 2-5 years after diagnosis. Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural polyphenol found in grapes, with promising neuroprotective effects since it induces expression and activation of several neuroprotective pathways involving Sirtuin1 and AMPK. The objective of this work was to assess the effect of resveratrol administration on SOD1(G93A) ALS mice. We determined the onset of symptoms by rotarod test and evaluated upper and lower motoneuron function using electrophysiological tests. We assessed the survival of the animals and determined the number of spinal motoneurons. Finally, we further investigated resveratrol mechanism of action by means of western blot and immunohistochemical analysis. Resveratrol treatment from 8 weeks of age significantly delayed disease onset and preserved lower and upper motoneuron function in female and male animals. Moreover, resveratrol significantly extended SOD1(G93A) mice lifespan and promoted survival of spinal motoneurons. Delayed resveratrol administration from 12 weeks of age also improved spinal motoneuron function preservation and survival. Further experiments revealed that resveratrol protective effects were associated with increased expression and activation of Sirtuin 1 and AMPK in the ventral spinal cord. Both mediators promoted normalization of the autophagic flux and, more importantly, increased mitochondrial biogenesis in the SOD1(G93A) spinal cord. Taken together, our findings suggest that resveratrol may represent a promising therapy for ALS.

Intracranial Transplant of Olfactory Ensheathing Cells Can Protect Both Upper and Lower Motor Neurons in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease that involves the degeneration of cortical and spinal motor neurons. Mutant SOD1(G93A) rats constitute a good animal model for this pathological condition. We have previously demonstrated that transplantation of neonatal olfactory ensheathing cells (OECs) into the dorsal funiculus of the spinal cord of mutant SOD1(G93A) transgenic rats increases the survival of spinal motor neurons and remyelinates the impaired axons through the pyramidal tract. In the present study, we examine whether intracranial cell implantation could also exert a similar effect on cortical motor neurons and on the lower motor neurons in the spinal cord. We injected OECs from the bulb of 7-day-old GFP green rats into the corona radiata of adult SOD1 mutant rats stereotaxically to observe any changes of the upper motor neurons as well as the lower motor neurons. We found that more motor neurons at both the motor cortices and ventral horns of the spinal cord survived in grafted ALS rats than in control rats. Prolonged survival and behavioral tests including a screen test, hind limb extension, rotarod, and gait control showed that the treated animals were better than the control group. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Motor Unit Survival in Lifelong Runners Is Muscle Dependent

A contributing factor to the loss of muscle mass and strength with adult aging is the reduction in the number of functioning motor units (MUs). Recently, we reported that lifelong competitive runners (master runners = ~66 yr) had greater numbers of MUs in a leg muscle (tibialis anterior) than age-matched recreationally active controls. This suggested that long-term exposure to high levels of physical activity may limit the loss of MU numbers with adult aging. However, it is unknown if this finding is the result of long-term activation of the specifically exercised motoneuron pool (i.e., tibialis anterior) or an overall systemic neuroprotective effect of high levels of physical activity. The purpose was to estimate the number of functioning MUs (MUNEs) in the biceps brachii (an upper body muscle not directly loaded by running) of nine young (27 ± 5 yr) and nine old (70 ± 5 yr) men and nine lifelong competitive master runners (67 ± 4 yr). Decomposition-enhanced spike-triggered averaging was used to measure surface and intramuscular EMG signals during elbow flexion at 10% of maximum voluntary isometric contraction. Derived MUNEs were lower in the biceps brachii of runners (185 ± 69 MUs) and old men (133 ± 69 MUs) than the young (354 ± 113 MUs), but the old and master runners were similar. Although there were no significant differences in MUNE between both older groups in the biceps brachii muscle, with the number of subjects tested here, we cannot eliminate the possibility of some whole-body neuroprotective effect. However, when compared with the remote biceps muscle, a greater influence on age-related spinal motoneuron survival was found in a chronically activated MN pool specific to the exercised muscle.

Activation of phospholipase‐Cγ and protein kinase C signal pathways helps the survival of spinal motoneurons injured by root avulsion

The signaling transduction processes involved in avulsion-induced motoneuron (MN) death have not been elucidated. Using the brachial plexus root avulsion rat model, we showed that avulsion-activated phosphorylation of phospholipase-Cγ (PLCγ) and protein kinase C (PKC) occurred in injured spinal MNs within 72 h of injury. Moreover, some MNs positive for PLCγ and PKC are also positive for avulsion-induced neuronal nitric oxide synthase (nNOS). Inhibition of PLCγ/PKC signal pathway, either with PLCγ inhibitor, 1-[6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl) amino)hexyl]-1H-pyrrole-2,5-dione, or with PLCγ siRNA augmented avulsion-induced MN death. 1-[6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl) amino)hexyl]-1H-pyrrole-2,5-dione also inhibited PKC phosphorylation and exacerbated avulsion-induced reductions in the nNOS protein level in injured spinal segments. Moreover, activation of PLCγ/PKC signal pathway with PKC activator, phorbol-12-myristate-13-acetate, decreased avulsion-induced MN death. The temporal profile of PLCγ/PKC signaling appears to be crucial for the survival of spinal MNs after root avulsion. Our data suggest that PLCγ mediates, while PKC and nNOS are associated with, the avulsion-induced MN death in brachial plexus root avulsion.

Dysregulation of iron homeostasis in the CNS contributes to disease progression in a mouse model of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS), characterized by degeneration of spinal motor neurons, consists of sporadic and familial forms. One cause of familial ALS is missense mutations in the superoxide dismutase 1 (SOD1) gene. Iron accumulation occurs in the CNS of both forms of ALS; however, its contribution to the pathogenesis of ALS is not known. We examined the role of iron in a transgenic mouse line overexpressing the human SOD1(G37R) mutant. We show that multiple mechanisms may underlie the iron accumulation in neurons and glia in SOD1(G37R) transgenic mice. These include dysregulation of proteins involved in iron influx and sensing of intracellular iron; iron accumulation in ventral motor neurons secondary to blockage of anterograde axonal transport; and increased mitochondrial iron load in neurons and glia. We also show that treatment of SOD1(G37R) mice with an iron chelator extends life span by 5 weeks, accompanied by increased survival of spinal motor neurons and improved locomotor function. These data suggest that iron chelator therapy might be useful for the treatment of ALS.

Glatiramer acetate positively influences spinal motoneuron survival and synaptic plasticity after ventral root avulsion

Avulsion of ventral roots induces degeneration of most axotomized motoneurons. At present there are no effective strategies to prevent such neuronal loss and to preserve the affected spinal circuits. Interestingly, changes in the spinal cord network also occur during the course of the experimental model of multiple sclerosis (experimental autoimmune encephalomyelitis—EAE). Glatiramer acetate (GA) significantly reduces the seriousness of the symptoms during the exacerbation of EAE. However, little is known about its effects on motoneurons. In the present study, we investigated whether GA has an influence on synapse plasticity and glial reaction after ventral root avulsion (VRA). Lewis rats were subjected to the avulsion of lumbar ventral roots and treated with GA. The animals were sacrificed after 14 days of treatment and the spinal cords processed for immunohistochemistry. A correlation between the synaptic changes and glial activation was obtained by performing immunolabeling against synaptophysin, GFAP and Iba-1. GA treatment preserved synaptophysin labeling, and significantly reduced the glial reaction in the area surrounding the axotomized motoneurons. After ventral root avulsion, GA treatment was also neuroprotective. The present results indicate that the immunomodulator GA has an influence on the stability of nerve terminals in the spinal cord, which may in turn contribute to future treatment strategies after proximal lesions to spinal motoneurons.

Protective effects of heat shock protein 27 in a model of ALS occur in the early stages of disease progression

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disorder, characterised by progressive motor neuron degeneration and muscle paralysis. Heat shock proteins (HSPs) have significant cytoprotective properties in several models of neurodegeneration. To investigate the therapeutic potential of heat shock protein 27 (HSP27) in a mouse model of ALS, we conducted an extensive characterisation of transgenic mice generated from a cross between HSP27 overexpressing mice and mice expressing mutant superoxide dismutase (SOD1 G93A). We report that SOD1 G93A/HSP27 double transgenic mice showed delayed decline in motor strength, a significant improvement in the number of functional motor units and increased survival of spinal motor neurons compared to SOD1 G93A single transgenics during the early phase of disease. However, there was no evidence of sustained neuroprotection affecting long-term survival. Marked down-regulation of HSP27 protein occurred during disease progression that was not associated with a reduction in HSP27 mRNA, indicating a translational dysfunction due to the presence of mutant SOD1 protein. This study provides further support for the therapeutic potential of HSPs in ALS and other motor neuron disorders.