[Neuroprotection in the treatment of multiple sclerosis]. / Neuroprotektion in der Therapie der Multiplen Sklerose.

Atrophy, the wasting or shrinkage of tissue, of the nervous system is the main feature of neurodegeneration, i.e. the umbrella term for the progressive loss of structure or function of neurons. Loss of neurons due to cell death and axonal degeneration characterize neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease or amyotrophic lateral sclerosis. In these illnesses, it still has to be elucidated to which extent inflammation is part of the pathology. Conversely, in chronic inflammation of the central nervous system (CNS), atrophy has previously also been described and neurodegeneration is discussed as a pathologic feature. The most frequent chronic inflammatory disease of the CNS is multiple sclerosis (MS), which leads to devastating relapsing-remitting symptoms and disability during the relapses, increasingly during the course of disease in patients. Meanwhile it became clear that axons already reveal pathology early in the disease and neurons are affected in the cortex and the spinal cord, albeit to a different extent. The broadening of understanding neurodegenerative aspects of MS pathology demands and creates new therapeutic strategies. Current medication used in MS treatment as well as medications about to be approved are primarily anti-inflammatory therapies. By modulating the immune system and thereby blocking key steps of the pathology, the immunomodulation therapies in MS have a slight impact on disability progression. There is, however, clinical and experimental data concerning the potential neuroprotective properties of novel therapies. Combining anti-inflammatory and direct neuroprotective or even neuroregenerative therapy strategies would be a step forward in the treatment of multiple sclerosis.

Undesired effects of a combinatorial treatment for spinal cord injury--transplantation of olfactory ensheathing cells and BDNF infusion to the red nucleus.

Transplantations of olfactory ensheathing cells (OECs) have been reported to promote axonal regeneration and functional recovery after spinal cord injury, but have demonstrated limited growth promotion of rat rubrospinal axons after a cervical dorsolateral funiculus crush. Rubrospinal neurons undergo massive atrophy after cervical axotomy and show only transient expression of regeneration-associated genes. Cell body treatment with brain-derived neurotrophic factor (BDNF) prevents this atrophy, stimulates regeneration-associated gene expression and promotes regeneration of rubrospinal axons into peripheral nerve transplants. Here, we hypothesized that the failure of rubrospinal axons to regenerate through a bridge of OEC transplants was due to this weak intrinsic cell body response. Hence, we combined BDNF treatment of rubrospinal neurons with transplantation of highly enriched OECs derived from the nasal mucosa and assessed axonal regeneration as well as behavioral changes after a cervical dorsolateral funiculus crush. Each treatment alone as well as their combination prevented the dieback of the rubrospinal axons, but none of them promoted rubrospinal regeneration beyond the lesion/transplantation site. Motor performance in a food-pellet reaching test and forelimb usage during vertical exploration (cylinder test) were more impaired after combining transplantation of OECs with BDNF treatment. This impaired motor performance correlated with lowered sensory thresholds in animals receiving the combinatorial therapy - which were not seen with each treatment alone. Only this combinatorial treatment group showed enhanced sprouting of calcitonin gene-related peptide-positive axons rostral to the lesion site. Hence, some combinatorial treatments, such as OECs with BDNF, may have undesired effects in the injured spinal cord.

Increased expression and activation of poly(ADP-ribose) polymerase (PARP) contribute to retinal ganglion cell death following rat optic nerve transection.

Excessive activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) by free-radical damaged DNA mediates necrotic cell death in injury models of cerebral ischemia-reperfusion and excitotoxicity. We recently reported that secondary retinal ganglion cell (RGC) death following rat optic nerve (ON) transection is mainly apoptotic and can significantly but not entirely be blocked by caspase inhibition. In the present study, we demonstrate transient, RGC-specific PARP activation and increased retinal PARP expression early after ON axotomy. In addition, intravitreal injections of 3-aminobenzamide blocked PARP activation in RGCs and resulted in an increased number of surviving RGCs when compared to control animals 14 days after ON transection. These data indicate that secondary degeneration of a subset of axotomized RGCs results from a necrotic-type cell death mediated by PARP activation and increased PARP expression. Furthermore, PARP inhibition may constitute a relevant strategy for clinical treatment of traumatic brain injury.

Integration of retrograde axonal and nuclear transport mechanisms in neurons: implications for therapeutics.

The elongated morphology of neuronal processes imposes a significant challenge for effective intracellular communication between the neurites and the cell body. This problem is especially acute upon injury, when the cell body must receive accurate and timely information on the site and extent of axonal damage to mount an appropriate response. Recent work has demonstrated that nuclear import factors from the importin (karyopherin) alpha and beta families provide a mechanism for retrograde injury signaling. Importins are found throughout axons and dendrites at significant distances from the cell body, and importin beta protein is increased after nerve lesion by local translation of axonal mRNA. This leads to formation of a high-affinity nuclear localization signal (NLS) binding complex that traffics retrogradely due to an interaction of importin alpha with the motor protein dynein. Disruption of the complex with excess NLS peptides delays regeneration of injured sensory neurons. The dual role of importins in retrograde transport in axons and nuclear import in cell bodies suggests new avenues for manipulating intrinsic regeneration mechanisms in the nervous system and may provide a novel route for drug delivery to the CNS.

BDNF abolishes the survival effect of NT-3 in axotomized Clarke neurons of adult rats.

Neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) have previously been shown to support survival and axonal regeneration in various types of neurons. Also, synergistic neuroprotective effects of these neurotrophins have been reported in descending rubrospinal neurons after cervical spinal cord injury (Novikova et al., [2000] Eur. J. Neurosci. 12:776-780). The present study investigates the effects of intrathecally delivered NT-3 and BDNF on the survival and atrophy of ascending spinocerebellar neurons of Clarke nucleus (CN) after cervical spinal cord injury in adult rats. At 8 weeks after cervical spinal cord hemisection, 40% of the axotomized CN neurons had been lost, and the remaining cells exhibited marked atrophy. Microglial activity was significantly increased in CN of the operated side. Intrathecal infusion of NT-3 for 8 weeks postoperatively resulted in 91% cell survival and a reduction in cell atrophy, but did not reduce microglial activity. In spite of the fact that the CN neurons expressed both TrkC and TrkB receptors, only NT-3 had a neuroprotective effect, whereas BDNF was ineffective. Furthermore, when a combination of BDNF and NT-3 was administered, the neuroprotective effect of NT-3 was lost. The present results indicate a therapeutic potential for NT-3 in the treatment of spinal cord injury, but also demonstrate that in certain neuronal populations the neuroprotection obtained by a combination of neurotrophic factors may be less than that of a single neurotrophin.

Delayed NGF infusion fails to reverse axotomy-induced degeneration of basal forebrain cholinergic neurons in adult p75(LNTR)-deficient mice.

The p75 low-affinity neurotrophin receptor (p75(LNTR)) appears to have various functions that include enhancing nerve growth factor (NGF)-mediated survival by increasing TrkA (high-affinity NGF receptor) efficiency, and mediating apoptosis by acting as a ligand-regulated pro-apoptotic receptor. Here, we investigated the role of p75(LNTR) for adult cholinergic basal forebrain neurons by comparing neuronal responses to injury in control and p75(LNTR)-deficient mice. In both types of mice, approximately 70% of the cholinergic neurons in the ipsilateral medial septum had lost their markers choline acetyltransferase and tyrosine kinase A by 28 days following unilateral transection of the dorsal septohippocampal pathway (fimbria fornix). A 7-day delayed infusion of NGF that started 28 days after the injury resulted in reversal of choline acetyltransferase expression and cell atrophy in control, but not in p75(LNTR)-deficient, mice. This lack of response to delayed NGF treatment in p75(LNTR)-deficient mice was most likely not due to cell death, as all of the septohippocampal neurons, labeled with Fluorogold before the lesion, were present at 28 days post-lesion, similar to control mice. p75(LNTR)-deficient cholinergic neurons can respond to NGF as they were protected by NGF infusions that started immediately after the injury. These observations, the fact that lesioned p75(LNTR)-deficient neurons atrophy faster, and that non-lesioned neurons hypertrophy in response to NGF in control but not in p75(LNTR)-deficient mice, suggest that p75(LNTR) is needed for tyrosine kinase A and NGF signaling efficiency.In conclusion, during adulthood p75(LNTR) appears to play a beneficial role in the response of cholinergic neurons to injury, consistent with the proposed role of p75(LNTR) in the enhancement of TrkA signaling and the transport of neurotrophins by these neurons.

Ovarian steroids reduce apoptosis induced by trophic insufficiency in nerve growth factor-differentiated PC12 cells and axotomized rat facial motoneurons.

Previous studies have demonstrated that ovarian steroids exert neuroprotective effects in a variety of in vitro and in vivo systems. The mechanisms underlying these effects remain poorly understood. In the present study, the neuroprotective effects of estradiol (E(2)) and progesterone (P) were examined in two models of apoptosis induced by growth factor insufficiency: partially nerve growth factor (NGF)-differentiated PC12 cells, after serum and NGF withdrawal; and axotomized immature rat facial motor motoneurons. E(2) and P both increased the survival of trophically withdrawn NGF-differentiated PC12 cells, at physiologically relevant concentrations. However, neither steroid had a significant effect on the survival of PC12 cells that had not been NGF treated. Exposure to NGF had no effect on the expression of estrogen receptor (ER)beta, but markedly increased the levels of ERalpha and altered the expression of the progesterone receptor (PR) from predominantly PR-B in NGF naive cells, to predominantly PR-A after NGF. The survival promoting effects of E(2) and P were blocked by the specific steroid receptor antagonists Faslodex (ICI 182780) and onapristone (ZK98299), respectively. Inhibitors of RNA (actinomycin D) or protein (cycloheximide) synthesis also abrogated the protective effects of both steroids. In immature rats, E(2) and P both significantly increased the numbers of surviving facial motor neurons at 21 days after axotomy. These data demonstrate significant protective effects of E(2) and P in two well-characterized models of apoptosis induced by trophic withdrawal and suggest that, at least in PC12 cells, the effects of the steroids are mediated via interaction with nuclear steroid receptor systems. The lack of steroid responsiveness in NGF-naive PC12 cells despite the presence of abundant ERbeta and PR-B are consistent with the view that ERalpha and PR-A may be particularly important as mediators of the neuroprotective effects of their corresponding hormonal ligands.

Thyroid hormone and retinoids affect motoneuron phenotype and reaction after axotomy in the spinal cord of adult rats.

Motoneuron phenotype in the spinal cord is regulated by an intrinsic genetic program, extrinsic environmental signals and target-derived molecules. Axonal lesions trigger a phenotype switch to foster repair phenomena and axonal re-growth. We have investigated the influence of the long-term treatment with thyroid hormone and all trans retinol palmitate (RA) on motoneuron phenotype and spinal cord reaction to axotomy in adult male rats. Neurochemical markers, investigated by in situ hybridization and immunocytochemistry, included choline acetyltransferase (ChAT), calcitonin gene-related peptide (CGRP) and neurotrophin low affinity receptor p75. Treatment was administered for 56 days and then mid-thigh sciatic axotomy was performed on a number of animals from each experimental groups; the rats were examined 9 days after surgery. The results indicate that: (1) Number and size of ChAT-immunoreactive neurons in the lumbar tract of the spinal cord was reduced in hypothyroid compared to control rats, whereas steady-state level of ChAT mRNA in labelled motoneurons failed to be modified by hypo and hyperthyroidism, but was increased by RA administration; (2) none of the administered treatments did alter CGRP mRNA level, whereas all of them influenced the axotomy-induced changes of motoneuron phenotype; (3) in hyperthyroid rats ChAT mRNA level of lumbar motoneurons not reduced homolateral to lesion while the number of ChAT-IR profiles was pronouncedly reduced; (4) up-regulation of p75 induced by peripheral nerve lesion was reduced in RA-treated rats. These data indicate that the motoneuron phenotype is regulated by transcription factors, which also play a role in phenotype switch regulation after axotomy.

Macrophage invasion into injured cochlear nerve and its modification by methylprednisolone.

Post-traumatic invasion of macrophages into the cochlear nerve of the rat and measurement of how their invasion was modified by the administration of methylprednisolone were investigated for the first time by using a reproducible and quantifiable experimental model of cochlear nerve injury. Two weeks after precise cochlear nerve compression, a massive invasion of ED1 immunostained macrophages was observed at the compressed portion of the cochlear nerve, and this invasion of macrophages was markedly reduced in the rats to which methylprednisolone had been administered during the pre- and post-compression period. Concomitantly, the residual number of spiral ganglion cells was found to be greater in the compression+methylprednisolone group than in the control compression group. The tissue loss observed in the lesion epicenter was also significantly less in the compression+methylprednisolone group than in the control compression group. The results of our present study demonstrated the effectiveness of methylprednisolone treatment to ameliorate trauma induced cochlear nerve degeneration in the acute phase. However, these results may reflect the sum effects of methylprednisolone on macrophages, including both its beneficial effect by inhibiting the negative aspects of macrophages through attenuating macrophage recruitment to the lesion site, and at the same time an undesirable effect by sacrificing the positive aspects of macrophage function. Moreover, one reservation should be added that the protective effects of steroid to injured cochlear nerve may have operated via a pathway not related to macrophage function. Besides macrophages, various cells and factors participate in the process of CNS injury, and their effects may potentially work either positively or negatively with respect to CNS protection and regeneration at each particular time during the on-going process of CNS injury. Therefore, future investigation in CNS injury should be directed toward understanding such complex mechanisms involved in this process.

Insulin-like growth factor I induced survival of axotomized olfactory neurons in the chick.

Insulin-like growth factor 1 (IGF1) receptor is expressed in avian olfactory neurons and IGF1 in the bulb. To explore the function of IGF1 in olfactory system in the chick, we infused IGF1 at the lesion site 0 and 12 h after olfactory axotomy. The animals were killed 1-3 days later. TdT mediated dUTP nick end labeling method and bromodeoxyuridine incorporation allowed the evaluation of programmed cell death and mitotic activity respectively in the olfactory epithelia of IGF1 treated or untreated lesioned animals and controls. IGF1 treatment suppressed the apoptotic wave, stimulated mitosis which peaked within 24 h (instead of 48 h), to return promptly to normal, and transiently maintained the number of calmodulin related kinase II expressing neurons at normal levels. It reveals a long lasting effect of IGF1 on the survival of lesioned olfactory neurons and transient effects on maintenance of differentiation and mitosis stimulation.

Trophic effect of olmesartan, a novel AT1R antagonist, on spinal motor neurons in vitro and in vivo.

Olmesartan is a novel compound which has been shown to exhibit various neuropharmacological effects. For the purpose of clarifying the effect of Olmesartan on spinal motor neurons, we studied the following tests. We studied the effect in vitro of Olmesartan on neurite outgrowth and choline acetyltransferase (ChAT) activity in primary explant cultures of ventral spinal cord (VSCC) of fetal rats. Olmesartan-treated VSCC, compared with control VSCC, had a significant neurite outgrowth and increased activity of ChAT. The effect was dose-related in neurite outgrowth. However, there was no relationship between activity of ChAT andgiven doses of Olmesartan. We examined in vivo the effect of Olmesartan on axotomized spinal motor neuron death in the rat spinal cord. After post-natal unilateral section of sciatic nerve, there was approximately a 50% survival of motor neurons in the fourth lumbar segment. In comparison with vehicle, intraperitoneal injection of Olmesartan for consecutive 14 days reduced spinal motor neuron death. There was no relationship between number of surviving neurons and doses of Olmesartan. These in vitro and in vivo studies showed that Olmesartan has a neurotrophic effect on spinal motor neurons. Our data suggest a potential therapeutic use of Olmesartan in treating diseases that involve degeneration and death of motor neurons, such as motor neuropathy and amyotrophic lateral sclerosis.

Protective effect of interleukin-3 and erythropoietin on motor neuron death after neonatal axotomy.

Several members of hematopoietic factors are known to have neuroprotective effects against axotomized motor neuron death. We carried out a study to determine whether interleukin-3 (IL-3) and erythropoietin (EPO) rescue spinal motor neuron death following axotomy. Unilateral sciatic nerve was transected in neonatal rats. Different doses of IL-3, EPO, or vehicle were administered daily for two weeks by intraperitoneal injection. After treatment, the number of spinal motor neurons was determined at the level of L4 segment In comparison with vehicle, both IL-3 (10 microg kg(-1)) and EPO (5.0 mg kg(-1)) significantly prevented the loss of motor neurons. Protective potentials is the same between them. These results suggest that IL-3 and EPO play a role for motor neuron survival in vivo and suggest the potential use of these hematopoietic factors in treating diseases that involve degeneration and death of motor neurons, such as motor neuropathy and amyotrophic lateral sclerosis.

Spinal cord regeneration induced by a voltage-gated calcium channel agonist.

Regeneration in the central nervous system (CNS) is prohibitive. This is likely due to an interplay of cellular (gene expression, growth factors) and environmental (inhibition by CNS myelin) factors. Calcium supports various intracellular functions, and multiple in vitro studies have shown a role of calcium in axonal growth. In this study, we examine the role of a calcium agonist, S(-)-Bay K 8644, in promoting or impeding CNS growth in vivo, in an effort to understand further the relationship between the voltage-gated L type calcium channel and regeneration. Using a well-established rat spinal cord model of regeneration, we have injected various doses of S(-)-Bay K 8644 (30-240 M) around the injured spinal cord. Our results demonstrate that S(-)-Bay K 8644 enhances regeneration in a dose-dependent fashion. In addition, at very specific concentrations, the same agonist has no effect on or even inhibits regeneration. We conclude that spinal regeneration is highly dependent on intracellular calcium concentration. Furthermore, depending on the dose used, the effect of calcium agonist supplementation on spinal regeneration can be supportive or inhibitory.

Mycoplasma pneumoniae causing nervous system lesion and SIADH in the absence of pneumonia.

A patient was admitted for fever and acute respiratory failure (ARF), rapidly progressive tetraparesis, delirium, behavioral abnormalities, and diplopia. Leukocytosis and a rise in C-reactive protein were present. A syndrome of inappropriate anti-diuretic hormone secretion (SIADH) was also diagnosed. Lumbar puncture yielded colorless CFS with mononuclear pleocytosis and protein rise. Electrodiagnosis revealed demyelinating polyneuropathy and axonal degeneration. Serum IgG and IgM for mycoplasma pneumoniae (MP) was consistent with acute infection, and erythromycin was started with rapid resolution of symptoms. Contrarily to most reports, an associated respiratory disease was not present and SIADH in association with MP has been reported only once, in a patient without direct central nervous system (CNS) involvement. Differential diagnosis and possible pathogenic mechanisms are discussed.

Chondroitinase applied to peripheral nerve repair averts retrograde axonal regeneration.

Antegrade, target-directed axonal regeneration is the explicit goal of nerve repair. However, aberrant and dysfunctional regrowth is commonly observed as well. At the site of surgical nerve coaptation, axonal sprouts encounter fibrotic connective tissue rich in growth-inhibiting chondroitin sulfate proteoglycan that may contribute to misdirection of axonal regrowth. In the present study, we tested the hypothesis that degradation of chondroitin sulfate proteoglycan by application of chondroitinase at the site of nerve repair can decrease aberrant axonal growth. Adult rats received bilateral sciatic nerve transection and end-to-end repair. One nerve was injected with chondroitinase ABC and the contralateral nerve treated with vehicle alone. After 28 weeks, retrograde axonal regeneration was assessed proximal to the repair by scoring neurofilament-immunopositive axons within the nerve (intrafascicular) and outside the nerve proper (extrafascicular). Intrafascicular retrograde axonal growth was equivalent in both control and chondroitinase treatment conditions. In contrast, chondroitinase treatment caused a pronounced (93%) reduction in extrafascicular retrograde axonal growth. The decrease in axon egress from the nerve was coincident with an increase in antegrade regeneration and improved recovery of motor function. Based on these findings, we conclude that chondroitinase applied at the site of nerve transection repair averts dysfunctional extrafascicular retrograde axonal growth.

[Update on pathophysiologic and immunotherapeutic approaches for the treatment of multiple sclerosis]. / Multiple-Sklerose-Update zur Pathophysiologie und neuen immuntherapeutischen Ansätzen.

Multiple sclerosis (MS) is a chronic disabling disease with significant implications for patients and society. The individual disease course is difficult to predict due to the heterogeneity of clinical presentation and of radiologic and pathologic findings. Although its etiology still remains unknown, the last decade has brought considerable understanding of the underlying pathophysiology of MS. In addition to its acceptance as a prototypic inflammatory autoimmune disorder, recent data reveal the importance of primary and secondary neurodegenerative mechanisms such as oligodendrocyte death, axonal loss, and ion channel dysfunction. The deepened understanding of its immunopathogenesis and the limited effectiveness of currently approved disease-modifying therapies have led to a tremendous number of trials investigating potential new drugs. Emerging treatments take into account the different immunopathological mechanisms and strategies, to protect against axonal damage and promote remyelination. This review provides a compilation of novel immunotherapeutic strategies and recently uncovered aspects of known immunotherapeutic agents. The pathogenetic rationale of these novel drugs for the treatment of MS and accompanying preclinical and clinical data are highlighted.

Testosterone treatment attenuates the effects of facial nerve transection on glial fibrillary acidic protein (GFAP) levels in the hamster facial motor nucleus.

Testosterone propionate (TP) administration coincident with facial nerve injury accelerates the recovery rate from facial muscle paralysis in the hamster. One mechanism by which TP could augment peripheral nerve regeneration is through glial fibrillary acidic protein (GFAP) regulation in the facial motor nucleus. In a previous study, axotomy alone induces increases in GFAP mRNA. with TP significantly attenuating the axotomy-induced increases in GFAP mRNA. In the present study, immunoblotting techniques were used to extend our previous GFAP mRNA studies to the protein level. Castrated male hamsters were subjected to a right facial nerve transection, with half of the animals receiving subcutaneous implants of 100% crystalline TP. The left facial motor nucleus of each animal served as an internal control. Postoperative survival times include Days 4, 7, and 14. In non-TP-treated animals, facial nerve transections alone increased GFAP levels at all time points, relative to internal controls. As previously observed at the mRNA level, TP treatment attenuated but did not eliminate the axotomy-induced increase in GFAP levels at all time points tested. These results suggest that the regulatory actions of gonadal steroids on GFAP expression manifested in parallel at the mRNA/protein levels.