Protective effects of SR 57746A in central and peripheral models of neurodegenerative disorders in rodents and primates

Short-term social memory deficits in adult female mice exposed to tannery effluent and possible mechanism of action

The accumulated organic residues in tannery-plant courtyards are an eating attraction to small rodents; however, the contact of these animals with these residues may change their social behavior. Thus, the aim of the present study is to investigate whether the exposure to tannery effluent (TE) can damage the social recognition memory of female Swiss mice, as well as to assess whether vitamin C supplementation could provide information about how TE constituents can damage these animals' memory. We have observed that resident females exposed to TE (without vitamin supplementation) did not explore the anogenital region, their body or chased intruding females for shorter time or with lower frequency during the retest session of the social recognition test, fact that indicates social recognition memory deficit in these animals. Such finding is reinforced by the confirmation that there was no change in the animals' olfactory function during the buried food test, or locomotor changes in females exposed to the pollutant. Since no behavioral change was observed in the females exposed to TE and treated with vitamin C (before or after the exposure), it is possible saying that these social cognitive impairments seem to be directly related to the imbalance between the cellular production of reactive oxygen species and the counteracting antioxidant mechanisms (oxidative stress) in female mice exposed to the pollutant (without vitamin supplementation). Therefore, the present study evidences that the direct contact with tannery effluent, even for a short period-of-time, may cause short-term social memory deficits in adult female Swiss mice.

Xaliproden (SR57746A) Induces 5-Ht1A Receptors-Mediated Map Kinase Activation in Pc12 Cells

Neurotrophic growth factors are involved in cell survival. However, natural growth factors have a very limited therapeutic use because of their short half-life. In the present study, we investigated the mechanism of action of a non peptidic neurotrophic drug, Xaliproden, a potential molecule for the treatment of motoneuron diseases, since the transduction pathways of this synthetic 5-HT1A agonist are very poorly understood. Xaliproden does not activate the Trk receptor but causes a rapid increase in the activities of the ERK1 and ERK2 isoforms of MAP kinase, which then rapidly decrease to the basal level. We demonstrate that isoforms of the she adapter protein are phosphorylated independently of each other and are probably not the source of the Xaliproden-induced MAP kinases activation. The inhibitor of Ras farnesylation, FPT-1, and the protein kinase C inhibitors, GF 109203X and chelerythrine, inhibited the Xaliproden-induced MAP kinase activation, suggesting p21Ras and PKC involvement. Moreover, the observations that the 5-HT1A antagonist, pindobind, and pertussis toxin abolished the Xaliproden-induced ERK stimulation suggested that Xaliproden activates the MAP kinase pathways by stimulating the G-protein-coupled receptor, 5-HT1A. These results demonstrated clearly that the non peptidic compound, Xaliproden, exerts its neurotrophic effects through a mechanism of action differing from that of neurotrophins. These findings suggest that this compound does not involve MAPK activation by TrkA receptor stimulation but acts by MAP Kinase pathway by a pertussis toxin-sensitive mechanism involving 5-HT1A receptors, p21 Ras and MEK-1 and by PKC and Akt pathways.

Current and prospective disease-modifying therapies for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a devastating illness of unclear etiology affecting motor neurons. It causes unremitting muscle paralysis, atrophy and death usually within 3 - 5 years from diagnosis. The human and economic costs for those affected are sobering. To date, tremendous efforts have failed to find a cure.

AREAS COVERED

An extensive literature search was undertaken using Medline and the Cochrane Systematic Review and Clinical Trial databases. Riluzole and investigational ALS drugs are discussed. Riluzole is the only approved disease-modifying therapy despite its modest effect on survival. Recent research has produced promising agents aimed at better disease control if not a cure. This review discusses agents targeting neuronal glutamate excitotoxicity, protein misfolding and accumulation, autophagy, apoptosis, mitochondrial dysfunction, free radical oxidative injury, immunomodulation, mutant mRNA counteraction, muscle physiology, neurotrophic factors and stem cell applications. The challenges in ALS drug development are highlighted.

EXPERT OPINION

Riluzole should be used for patients with definite, probable, suspected or possible ALS by World Federation of Neurology diagnostic criteria. Systematic monitoring for hepatic dysfunction, neutropenia and other serious adverse effects should be done routinely as outlined. All ALS patients should consider genetic screening and enrollment in ALS trials guided by the data reviewed.

Literature review and practical aspects on the management of oxaliplatin-associated toxicity

Colorectal cancer is currently a public health priority because it is the second leading cause of cancer deaths in Western countries. Combination regimes of oxaliplatin and infusional fluorouracil/leucovorin or capecitabine have emerged as important options in the palliative and adjuvant treatment of colorectal cancer. Although better tolerated than cisplatin, oxaliplatin displays a characteristic profile of adverse events whose recognition and management are essential for physicians who treat patients with colorectal cancer and other malignancies that benefit from the use of oxaliplatin. Peripheral neuropathy is probably the most frequent and clinically relevant adverse event associated with the use of oxaliplatin, and several measures have been proposed to mitigate this toxicity. Temporary interruption of oxaliplatin before limiting neurotoxicity develops during therapy is a potential approach to avoid the problem of oxaliplatin-associated neuropathy in patients with metastatic colorectal cancer. Calcium and magnesium infusions have no effect on chemotherapy efficacy and also constitute a useful approach in clinical practice. Finally, the incidence and severity of chronic peripheral neuropathy in patients treated with oxaliplatin may be reduced by the use of neuroprotective agents, for example, venlafaxine. Other adverse events, such as gastrointestinal and liver toxicity, thrombocytopenia, and hypersensitivity reactions, are also reviewed in this article, and suggestions are made for their management.

Memória de reconhecimento social em ratos

O paradigma intruso-residente vem sendo intensamente empregado em estudos para avaliar a memória de reconhecimento social em roedores. Tipicamente, ratos adultos (residentes) são expostos a dois encontros de 5 minutos cada com um mesmo intruso juvenil ou com juvenis diferentes; o intervalo entre encontros é usualmente 30 minutos. A quantidade de comportamentos sociais do residente, no segundo encontro, em relação a um intruso familiar é substancialmente menor do que o observado no primeiro encontro, o que não ocorre quando o segundo encontro envolve um juvenil novo; esse resultado caracteriza memória de reconhecimento social. Neste estudo discutimos achados recentes sobre os tipos de comportamentos usualmente incluídos nas categorias social e não-social, a influência da fase temporal, a interferência de rotinas laboratoriais na memória de reconhecimento social, modalidades sensoriais usualmente empregadas por roedores no processamento de informações na memória social e alternativas adicionais para o estudo da socialidade em roedores.

SR 57746A/xaliproden, a non-peptide neurotrophic compound: prospects and constraints for the treatment of nervous system diseases

Neurodegenerative disorders such as Alzheimer's disease or amyotrophic lateral sclerosis as well as peripheral neuropathies are difficult to treat due to a limited range of effective drugs. Neurotrophic growth factors promote neuronal survival and differentiation and could hence be interesting tools to treat these diseases. Their therapeutic use is limited due their short half-life, their inability to cross the BBB and potential side effects including tumor promotion. SR 57746A is a non-peptide, orally active compound that exhibits neuroprotective effects in various model systems in vitro and in vivo. SR 57746A shows--amongst other activities--agonistic activity on 5-HT(1A) receptors. Several clinical trials examined SR 57746A in patients with Alzheimer's disease, amyotrophic lateral sclerosis or chemotherapy-induced peripheral sensory neuropathy. This article reviews the preclinical and clinical data on SR 57746A and points out potential future applications of this compound. However, due to disapointing results in phase III trials, Sanofi-Aventis recently decided to discontinue the development of this drug.

Targeting neuroprotection as an alternative approach to preventing and treating neuropathic pain

Neuropathic pain syndromes arise from dysfunction of the nerve itself, through traumatic or nontraumatic injury. Unlike acute pain syndromes, the pain is long-lasting and does not respond to common analgesic therapies. Drugs that disrupt nerve conduction and transmission or central sensitization, currently the only effective treatments, are only modestly effective for a portion of the patients suffering from neuropathic pain and come with the cost of serious adverse effects. Neurodegeneration, as a reaction to nerve trauma or chronic metabolic or chemical intoxication, appears to be an underlying cause of neuropathic pain. Identifying mechanisms of neurodegeneration and designing neuroprotective therapies is an ambitious goal toward treating or even preventing the development of these disabling disorders.

5-HT1A receptors are involved in the effects of xaliproden on G-protein activation, neurotransmitter release and nociception

BACKGROUND AND PURPOSE

Xaliproden (SR57746A) is a 5-HT(1A) receptor agonist and neurotrophic agent that reduces oxaliplatin-mediated neuropathy in clinical trials. The present study investigated its profile on in vitro transduction, neurochemical responses and acute nociceptive pain tests in rats.

EXPERIMENTAL APPROACH

Xaliproden was tested on models associated with 5-HT(1A) receptor activation including G-protein activation, extracellular dopamine and 5-HT levels measured by microdialysis and formalin-induced pain. Activation of 5-HT(1A) receptors was confirmed by antagonism with WAY100635.

KEY RESULTS

Xaliproden exhibited high affinity for rat (r) and human (h) 5-HT(1A) receptors (pK(i)= 8.84 and 9.00). In [(35)S]GTPgammaS (guanosine 5'-O-(3-[(35)S]thio)triphosphate) assays it activated both hippocampal r5-HT(1A)[pEC(50)/E(MAX) of 7.58/61% (%5-HT)] and recombinant h5-HT(1A) receptors (glioma C6-h5-HT(1A): 7.39/62%; HeLa-h5-HT(1A): 7.24/93%). In functional [(35)S]GTPgammaS autoradiography, xaliproden induced labelling in structures enriched with 5-HT(1A) receptors (hippocampus, lateral septum, prefrontal and entorhinal cortices). Xaliproden inhibited in vivo binding of [(3)H]WAY100635 to 5-HT(1A) receptors in mouse frontal cortex and hippocampus (ID(50): 3.5 and 3.3 mg x kg(-1), p.o. respectively). In rat, it increased extracellular dopamine levels in frontal cortex and reduced hippocampal 5-HT levels (ED(50): 1.2 and 0.7 mg x kg(-1), i.p. respectively). In a rat pain model, xaliproden inhibited paw licking and elevation (ED(50): 1 and 3 mg x kg(-1), i.p. respectively) following formalin injection in the paw. All effects were reversed by pretreatment with WAY100635.

CONCLUSIONS AND IMPLICATIONS

These results indicate that activation of 5-HT(1A) receptors is the principal mechanism of action of xaliproden and provide further support for the utility of 5-HT(1A) receptor activation as an anti-nociceptive strategy.

Taking the next steps in the treatment of Alzheimer's disease: disease-modifying agents

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder in the United States and the number of AD patients is increasing at an alarming rate. There is no cure for AD and the currently available treatments are symptomatic, providing only limited effects on disease pathophysiology and progression. An overwhelming need exists for therapies that can slow or halt this debilitating disease process. Disease modification in AD has been defined from patient-focused, regulatory, and neurobiological perspectives. The latter two of these perspectives rely largely on an interruption of the disease process and a clear demonstration of this interruption. As defined by Cummings, a disease-modifying treatment is a “pharmacologic treatment that retards the underlying process of AD by intervening in the neurobiological processes that constitute the pathology and pathophysiology of the disease and lead to cell death or dysfunction.” By this definition, the burden of confirmatory study is placed on any new treatment for which the claim of “disease modification” is to be made (Slide 1).

Disease-modifying therapies in Alzheimer's disease

Alzheimer's disease (AD) is a chronic, progressive, neurodegenerative disorder that places a substantial burden on patients, their families, and society. The disease affects approximately 5 million individuals in the United States, with an annual cost of care greater than $100 billion. During the past dozen years, several agents have been approved that enhance cognition and global function of AD patients, and recent advances in understanding AD pathogenesis has led to the development of numerous compounds that might modify the disease process. A wide array of antiamyloid and neuroprotective therapeutic approaches are under investigation on the basis of the hypothesis that amyloid beta (A beta) protein plays a pivotal role in disease onset and progression and that secondary consequences of A beta generation and deposition, including tau hyperphosphorylation and neurofibrillary tangle formation, oxidation, inflammation, and excitotoxicity, contribute to the disease process. Interventions in these processes with agents that reduce amyloid production, limit aggregation, or increase removal might block the cascade of events comprising AD pathogenesis. Reducing tau hyperphosphorylation, limiting oxidation and excitotoxicity, and controlling inflammation might be beneficial disease-modifying strategies. Potentially neuroprotective and restorative treatments such as neurotrophins, neurotrophic factor enhancers, and stem cell-related approaches are also under investigation.

Cytotoxic lesions of the hippocampus do not impair social recognition memory in socially housed rats

Socially housed mice with cytotoxic lesions of the hippocampus do not exhibit social recognition memory 30 min following exposure to a juvenile mouse, however the social recognition memory of singly housed rats is unimpaired. The present study tests the hypothesis that social housing of rats could render social recognition memory hippocampally dependent as seen for mice. Rats were housed with juveniles or with adults. Two social recognition one-animal tests paralleling those used with mice were carried out. Seven social discrimination two-animal tests were also given. Sham operated and hippocampally lesioned rats had normal social memory at 30 min whether socially housed for 24, 48 h, 7 or 8 days prior to testing. These findings support other results indicating the hippocampus proper is not required for normal social memory in rats. In a final experiment, rats socially housed in groups of three since weaning, were tested for 30 min and 24 h social memory. Unlike mice, rats socially housed throughout life exhibited social memory only at 30 min, but not at 24 h. Manipulations that extend social memory in rats may be required to render social memory hippocampally dependent or rats and mice may differ in the neural mediation of social memory.

MAPK activation via 5-hydroxytryptamine 1A receptor is involved in the neuroprotective effects of xaliproden

Motoneurons require neurotrophic factors for their survival and their differentiation. Xaliproden (SR57746A) is a synthetic compound that exhibits in vivo and in vitro neurotrophic effects in several experimental studies. Here we demonstrate that neuroprotective effects of Xaliproden on motoneuron cultures are mediated by the activation of the mitogen activated protein kinase pathway. It is inhibited by PD98059, a selective and irreversible inhibitor of MEK1. The activation of this pathway seems to involve two different proteins, the protein kinase C and the Ras. Indeed, we show that Xaliproden is able to activate the MAP kinases ERK1/2 and PKC in motoneurons. In addition, the use of a 5-hydroxytryptamine 1A receptor antagonist, Pindobind and pertussis toxin, inhibits the effect of Xaliproden on motoneuron survival, suggesting the involvement of this G-protein coupled receptor. Morever, 8-OH-DPAT, an agonist of 5-hydroxytryptamine 1A receptor, increases the survival of mouse motoneurons but not by the same extent as BDNF or xaliproden. Since 8-OH-DPAT does not act synergistically with Xaliproden, it is likely that their neuroprotective properties involve a similar pathway. Taken together, these results indicate that neuroprotective effects of Xaliproden on mouse motoneurons are dependent on the mitogen-activated protein kinase activation via 5-hydroxytryptamine 1A receptor.

Therapeutic developments in amyotrophic lateral sclerosis

There is currently no effective treatment for amyotrophic lateral sclerosis (ALS), a devastating disorder of the human nervous system that, due to motoneurone degeneration, causes progressive loss of muscle function and death. The relentless progression of ALS and the uniformly poor prognosis have been unhindered by a variety of therapeutic agents tested in previous clinical studies. Recently, two drugs, namely riluzole and recombinant human insulin-like growth factor-I (IGF-1), have been reported to benefit patients with ALS by improving survival or slowing disease progression. Several other drugs, such as gabapentin and various neurotrophic factors, are being investigated in on-going clinical trials. Therapeutic developments in ALS have been hampered by the fact that the precise cause of the disease remains unknown. In addition, there are considerable variations in disease related characteristics among patients, rendering accurate measurements of disease progression difficult. Advances in theories of pathogenesis, such as genetic factors, glutamate excitotoxicity, oxidative stress, autoimmune mechanism and cytoskeletal abnormality will help guide the development of future therapies. Newer approaches to therapy may include suitable glutamate antagonists, small molecules that augment neurotrophic factor function, and anti-oxidants. Combination therapy of effective agents should be considered.

Quantification of neurotrophin mRNA expression in PMN mouse: modulation by xaliproden

Compounds possessing neurotrophic properties may represent a possible treatment for neurodegenerative disorders such as amyotrophic lateral sclerosis. Xaliproden (SR57746A), an orally-active non-peptide compound, which has been found to exhibit neurotrophic effects in vitro and in vivo, increased the lifespan and delayed the progression of the motor neuron degeneration in PMN mice. We have used a quantitative reverse transcription/polymerase chain reaction amplification technique to study the regulation of neurotrophin mRNA and trk mRNA expression in PMN mice. NGF and NT-3 mRNA are downregulated in PMN mice. These deficiencies can be overcome by a treatment with xaliproden. Such an effect could contribute to neurotrophic effects of xaliproden in vivo and in vitro.

Massive cell death of cerebellar granule neurons accompanied with caspase-3-like protease activation and subsequent motor discoordination after intracerebroventricular injection of vincristine in mice

Vincristine, a microtubule-depolymerizing agent, is known to induce neuronal cell damage. Biochemical, histological and behavioral alterations were investigated after intracerebroventricular injection of vincristine in mice. Intracerebroventricular injection of vincristine caused caspase-3-like protease activation followed by nucleosomal release in the cerebellum. Histological examinations showed that vincristine-induced damage was relatively specific to granule cells in the cerebellum, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling-positive cells were observed among these cells. Chromatin condensation, one of the criteria for apoptosis, was seen on electron microscopy. Behavioral changes, namely head movements, pivoting and backward walking, were observed in parallel with the increase of caspase-3-like protease activity and nucleosomal release. Furthermore, motor function tests (bulb balance test and rotating rod test) showed deficits of motor coordination ability. These observations suggest that intracerebroventricular vincristine causes massive apoptosis of cerebellar granule cells accompanied with caspase-3-like protease activation, leading to motor dysfunction, in this model. These vincristine-treated mice should be a useful in vivo model for examination of neuronal apoptosis, which might be involved in a variety of neurodegenerative diseases.

Magnetic resonance imaging of the neuroprotective effect of xaliproden in rats

RATIONALE AND OBJECTIVES

The neurotrophic effect of Xaliproden has been followed using sequential cerebral magnetic resonance imaging (MRI) in rats with vincristine-induced brain lesion as a model of Alzheimer disease.

METHODS

Nineteen rats received an intraseptal injection of vincristine on day 0, followed by a daily gavage with either the vehicle (Tween-20 1%) (n = 10) or Xaliproden (10 mg/kg) (n = 9). Eight sham-operated controls received a daily gavage with either the vehicle (n = 4) or Xaliproden (n = 4). Brain MR imaging was performed at 4.7 T on a Biospec 47/30 MR system before surgery then 3, 7, 10, and 14 days after surgery.

RESULTS

At day 3 following vincristine injection, an increase in MR signal intensity in the septum was observed on T2-weighted images. This increase was maximal at day 10, and remained stable until day 14. Daily treatment with Xaliproden delayed the appearance of hypersignals until day 7 and reduced by Ca. 50% the magnitude of the increase in signal intensity from day 10. No changes were observed in the hippocampus.

CONCLUSION

Quantitative MRI objectifies noninvasively the neuroprotective effect of Xaliproden on rat brain anatomy.

SSR180575 (7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide), a peripheral benzodiazepine receptor ligand, promotes neuronal survival and repair

In the present study, we have investigated the potential neuroprotective effects of a novel peripheral benzodiazepine binding site (PBR) ligand, 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (SSR180575), in models of central and peripheral neurodegeneration in vivo and its effect on steroid concentrations in plasma and nervous tissue. SSR180575 shows high affinity (IC(50), 2.5-3.5 nM) and selectivity for the rat and human PBR and potently inhibits the in vivo binding of [(3)H]alpidem to PBR in the rat brain and spleen after oral or i.p. administration (ID(50), 0.1-0.3 mg/kg). In an experimental model of motoneuron degeneration induced by facial nerve axotomy in the immature rat, SSR180575 given i.p. or orally for 8 days rescued facial motoneurons, increasing their survival by 40 to 72% at 6 and 10 mg/kg p.o. b.i.d. Moreover, in this model, SSR180575 (10 mg/kg p.o. b.i.d.) increased by 87% the number of motoneurons immunoreactive to peripherin, a type III intermediate filament, whose expression is up-regulated during nerve regeneration. SSR180575 also improved functional recovery in acrylamide-induced neuropathy in the rat when given therapeutically at 2.5 to 10 mg/kg/day p.o. Furthermore, SSR180575 (3 mg/kg i.p. b.i.d.) accelerated functional recovery of the blink reflex after local injury of the facial nerve in the rat. SSR180575 increased pregnenolone accumulation in the brain and sciatic nerve (+100% at 3 mg/kg i.p.), suggesting that its neuroprotective effects are steroid-mediated. These results indicate that PBR ligands (e.g., SSR180575) promote neuronal survival and repair in axotomy and neuropathy models and have potential for the treatment of neurodegenerative diseases (e.g., peripheral neuropathies or amyotrophic lateral sclerosis).

Continuous delivery of neurotrophin 3 by gene therapy has a neuroprotective effect in experimental models of diabetic and acrylamide neuropathies

Neurotrophic factors (NFs) are promising agents for the treatment of peripheral neuropathies such as diabetic neuropathy. However, the value of treatment with recombinant NF is limited by the short half-lives of these molecules, which reduces efficiency, and by their potential toxicity. We explored the use of intramuscular injection of a recombinant adenovirus encoding NT-3 (AdNT-3) to deliver sustained low doses of NT-3. We assessed its effect in two rat models: streptozotocin (STZ)-induced diabetes, a model of early diabetic neuropathy characterized by demyelination, and acrylamide experimental neuropathy, a model of diffuse axonal neuropathy which, like late-onset human diabetic neuropathy, results in a diffuse sensorimotor neuropathy with dysautonomy. Treatment of STZ-diabetic rats with AdNT-3 partially prevented the slowing of motor and sensory nerve conduction velocities (p < 0.01 and p < 0.0001, respectively). Treatment with AdNT-3 of acrylamide-intoxicated rats prevented the slowing of motor and nerve conduction velocities (p < 0.001 and p < 0.0001, respectively) and the decrease in amplitude of compound muscle potentials (p < 0.0001), an index of denervation. Acrylamide-intoxicated rats treated with NT-3 had higher than control levels of muscle choline acetyltransferase activity (p < 0.05), suggesting greater muscle innervation. In addition, treatment of acrylamide-intoxicated rats with AdNT-3 significantly improved behavioral test results. Treatment with AdNT-3 was well tolerated with minimal muscle inflammation and no detectable general side effects. Therefore, our results suggest that NT-3 delivery by adenovirus-based gene therapy is a promising strategy for the prevention of both early diabetic neuropathy and axonal neuropathies, especially late axonal diabetic neuropathy.

Social memory in the rat: circadian variation and effect of circadian rhythm disruption

Disruption of circadian rhythm can impair long-term passive avoidance memory of rats and mice. The present study investigated whether disruption of circadian rhythm can also impair social memory of male rats. Social memory was assessed using the social discrimination test, in which a short-term olfactory memory is formed by social interaction with a juvenile rat during a learning trial. After an intertrial interval, a retrieval trial is performed, in which social memory is expressed as a decreased attention paid to the same juvenile as compared to a new juvenile. First, the social memory at four different time points across the light-dark cycle was measured with an intertrial interval of 10 or 25 min. There was no significant circadian variation of social memory across the light-dark cycle. Subsequently, the effect of a -6 or 12-h phase shift on social memory was studied. These phase shifts were previously found to impair long-term passive avoidance memory. However, no effect of either phase shift was observed in the social discrimination test. It is concluded that the disruption of circadian rhythm had no effect on the social memory of rats. Differences between short-term social memory and long-term passive avoidance memory are discussed in relation to their apparent differential susceptibility to the effects of circadian rhythm disruption.

Effect of the nonpeptide neurotrophic compound SR 57746A on the phenotypic survival of purified mouse motoneurons

1. Neurotrophic factors have been used for the treatment of several neurodegenerative diseases. However, their use is limited by their inability to cross the blood-brain barrier, their short half life and their side effects. SR 57746A is a new orally active compound that exhibits in vivo and in vitro neurotrophic effects in several experimental models. 2. We show here that SR 57746A (1 microM) increases the phenotypic survival of embryonic purified mouse motoneurons in vitro to the same extent as brain-derived neurotrophic factor (100 ng ml-1), and increases the outgrowth and number of their neurites. It acts in a dose-dependent manner up to 1 microM which is the optimal concentration. Above this concentration, its neurotrophic effect decreases. 3. Genistein (10 microM), a protein tyrosine kinase inhibitor, also increases the phenotypic survival and differentiation of mouse motoneurons. It does not act in a synergistic or additive manner with SR 57746A. However, at concentrations equal or superior to 25 microM, it decreases the survival of motoneurons. This suggests that the neurotrophic effect of genistein is due to a favourable alteration of equilibrium between phosphorylated and dephosphorylated states of proteins involved in survival and differentiation of motoneurons. 4. Like genistein, SR 57746A should be used at a critical concentration (1 microM) to exert its optimal effects. Since SR 57746A does not act synergistically with genistein, it is likely that its mechanism of action involves a pathway similar to that affected by this tyrosine kinase inhibitor. 5. At the present time, SR 57746A is the only orally active compound and the only synthetic compound shown to be active on motoneurons in vitro. It should thus be considered as a good candidate for the treatment of motoneuron diseases.

The neuroprotective agent SR 57746A abrogates experimental autoimmune encephalomyelitis and impairs associated blood-brain barrier disruption: implications for multiple sclerosis treatment

Experimental autoimmune encephalomyelitis (EAE) is a T cell autoimmune disorder that is a widely used animal model for multiple sclerosis (MS) and, as in MS, clinical signs of EAE are associated with blood-brain barrier (BBB) disruption. SR 57746A, a nonpeptide drug without classical immunosuppressive properties, efficiently protected the BBB and impaired intrathecal IgG synthesis (two conventional markers of MS exacerbation) and consequently suppressed EAE clinical signs. This compound inhibited EAE-induced spinal cord mononuclear cell invasion and normalized tumor necrosis factor alpha and IFN-gamma mRNA expression within the spinal cord. These data suggested that pharmacological intervention aimed at inhibiting proinflammatory cytokine expression within the central nervous system provided protection against BBB disruption, the first clinical sign of EAE and probably the key point of acute MS attacks. This finding could lead to the development of a new class of compounds for oral therapy of MS, as a supplement to immunosuppressive agents.

Neurotrophic factors and neuro-muscular disease: II. GDNF, other neurotrophic factors, and future directions

This is the second of two reviews in which we discuss the essential aspects of neurotrophic factor neurobiology, the characteristics of each neurotrophic factor, and their clinical relevance to neuromuscular diseases. The previous paper reviewed the neurotrophin family and neuropoietic cytokines. In the present article, we focus on the GDNF family and other neurotrophic factors and then consider future approaches that may be utilized in neurotrophic factor treatment.

Effect of the neuroprotective compound SR57746A on nerve growth factor synthesis in cultured astrocytes from neonatal rat cortex

The neurotrophic factor promoting activity of the neuroprotective compound SR57746A was evaluated in primary cultures of neonatal rat cortical astrocytes by studying the synthesis of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). A concentration- and time-dependent increase of nerve growth factor mRNA was induced by SR57746A (10 nM-1 microM). In these astrocytes, BDNF mRNA contents were increased to a significant but smaller extent, and beta-actin mRNA showed no variation. SR57746A (1 microM) induced increases of both de novo protein translation after 6 h of incubation and NGF release into the extracellular medium after 6-24 h. These effects were preceded by a transient augmentation of junB, c-fos and c-jun mRNA contents. These increases of AP-1 family mRNA were associated with increased nuclear AP-1 binding activity. The results show that SR57746A can increase the synthesis and release of NGF in rat cortical astrocytes. Such effects may contribute to the drug's previously described neuroprotective effects.

SR57746A: a survival factor for motor neurons in vivo

SR57746A(1-[2-(naphth-2-yl)ethy]]-4-(3-trifluoromethyl phenyl)-1,2,5,6-tetrahydropyridine, hydrochloride) is a non-peptide compound which has been shown to exhibit a wide range of neurotrophic effects both in vitro and in vivo. Here we examine the ability of SR57746A on axotomized spinal motor neuron death in the developing rat spinal cord. After postnatal unilateral section of rat sciatic nerve, there was approximately a 50% survival of motor neurons in the fourth lumbar segment (L4). Intraperitoneal injection of SR57746A for consecutive 14 days rescued motor neuron death but did not preserve the motor neuron diameter both on axotomy and non-axotomy side. These results suggest that SR57746A is a survival factor for motor neurons in vivo and may serve as therapeutic agent for damaged motor neurons.

The effect of the nonpeptide neurotrophic compound SR 57746A on the progression of the disease state of the pmn mouse

1. The progressive motor neuronopathy (pmn) mouse is an autosomal recessive mutant, in which the homozygotes suffer caudio-cranial degeneration of motor axons and die several weeks after birth. This strain provides the opportunity of testing potential therapeutic strategies for the treatment of motor neurone diseases such as amyotrophic lateral sclerosis. We have performed a study of the effects on the pmn mouse of SR 57746A, an orally-active, non-peptide compound which has been found to exhibit neurotrophic effects in vitro and in vivo. In order to treat the affected mice from birth, the mothers were administered 2.5 mg kg(-1). p.o., SR 57746A every two days until the weaning of the offspring (at day 20); then the offspring were given every two days a dose of 30 microg kg(-1), p.o., until their death. 2. Affected mice treated with SR 57746A had a lifespan 50% longer than that of the vehicle-treated mice (P=0.01). Compared to vehicle-treated pmn mice, SR 57746A improved the performance of the pmn mice in three different behavioural tasks. SR 57746A also maintained the amplitude of the motor evoked response of the gastrocnemius muscle, reduced the distal motor latency, and delayed the occurrence of the spontaneous denervation activity in this muscle. Histological studies indicated that at 20 days of age the mean surface areas of the fibres of the sciatic nerve were higher in SR 57746A-treated than in vehicle-treated mice. 3. At present, SR 57746A is the only orally active, nonpeptide compound known to be capable of delaying the progression of the motor neurone degeneration in pmn mice.

The non-peptide neuroprotective agents SR 57746A interacts with neurotrophin 3 to induce differentiation in the PC12 cell-line

SR 57746A (1-(2beta-naphthylethyl)-4-(3-trifluoromethylphenyl)-1,2,5,6 -tetrahydropyridine hydrochloride) is a neuroprotective compound which potentiates nerve-growth factor (NGF)-induced differentiation in PC12 cells. We have evaluated the interaction of SR 57746A with the other members of the neurotrophin family in this cell-line. In contrast with NGF, neurotrophin-3 did not increase the differentiation of PC12 cells. However, the association of SR 57746A with neurotrophin-3 significantly increased neurite outgrowth. No significant activity on neurite outgrowth was observed with brain-derived neurotrophic factor or neurotrophin-4, either alone or combined with SR 57746A. These results indicate that as well as potentiating the effect of NGF SR 57746A enables neurotrophin-3, which alone is inactive, to increase the differentiation of these cells.

Inhibition of lysophosphatidic acid-induced neurite retraction and cell rounding by SR 57746A

Rapid neurite retraction and transient rounding of serum-starved NG108-15 and PC12 cells by lysophosphatidic acid (LPA) is retarded and reduced by pre-incubation of the cells with the small non-peptidic molecule, SR 57746A, which exhibits neurotrophic properties. The compound also antagonizes the redistribution of filamentous actin by LPA in both cell types. We hypothesize that the SR 57746A attenuation of LPA-induced effects may account for at least some of the neuroprotective properties of this molecule.

Therapeutic advances in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and rapidly fatal neurodegenerative disease in which both upper and lower motoneurones are involved. The recent discovery of mutations affecting the superoxide dismutase (SOD) gene has given impetus to research on the role of oxidative stress in the pathogenesis of familial ALS, while further evidence for a role of excitotoxicity in the disease process has arisen. In this review, Erik Louvel, Jacques Hugon and Adam Doble discuss these findings and, in addition, describe how a number of large, well-controlled clinical trials have taken place to test potential therapies suggested by different aetiological hypotheses, including immunosuppressive therapies, neurotrophic factors, antioxidants and anti-excitotoxic drugs. These trials have led to the first modest steps in the treatment of this devastating neurological disease.

Muscarinic therapies in Alzheimer's disease; from palliative treatments to disease modification

Cholinergic therapies for Alzheimer's disease (AD) have been developed following painstaking neuropathological and neurochemical studies. Drugs based upon this approach are in development and it is hoped that these compounds will be of some use as palliative therapy. However, increasing evidence from molecular biology suggests that increasing cholinergic neurotransmission might not only alter cognition but also modify disease progression. The evidence that muscarinic-induced increases in protein kinase C activity favourably alter amyloid precursor protein metabolism and tau phosphorylation is reviewed. A unifying hypothesis of AD pathogenesis brings together plaque and tangle formation, suggesting that cholinergic therapies in development may have far-reaching implications as treatments for AD. (Int J Psych Clin Pract 1997; 1: 15-20).

Therapeutic horizons for amyotrophic lateral sclerosis

Recent theories on the pathogenesis of motor neuron disease and research on motor neuron injury have resulted in new putative therapies, which include treatment with various neurotrophic factors, antioxidants and anti-excitotoxicity agents. Clinical and preclinical studies have now provided the first agents that reproducibly alter the course of amyotrophic lateral sclerosis.

Administration of amyloid beta-peptides in the rat medial septum causes memory deficits: reversal by SR 57746A, a non-peptide neurotrophic compound

Different putative toxic amyloid beta (A beta) peptides, beta (1-42), beta (1-40) and beta (25-35), were infused (0.75, 1.5 or 3 nmol) in the rat medial septum. Memory deficits were then investigated using the social recognition test. A significant amnesia was observed 4, 7 and 14 days after intraseptal injection of 3 nmol of beta (1-42), beta-(1-40)- and beta (25-35). Lower amounts of beta (1-42) were inactive except 1.5 nmol that disrupted memory 7 days post-treatment. Used as control, the inverted peptide beta (40-1) and the scrambled beta (25-35) were inactive. Using the prolongation procedure, rats infused with 3 nmol of beta (1-40) were still able to recognize the same juvenile. Finally, a daily treatment with the non-peptide neurotrophic compound SR 57746A (10 mg/kg p.o.) over 21 days, prevented the deficits in short-term memory induced by the intraseptal infusion of 3 nmol of either beta (1-40) or beta (25-35). These findings suggest that A beta fragments could impair short-term memory when infused in the rat medial septum, an effect that is prevented by SR 57746A.

SR 57746A attenuates cytostatic drug-induced reduction of neurite outgrowth in co-cultures of rat dorsal root ganglia and Schwann cells

A co-culture system of intact rat dorsal root ganglia (DRG) with Schwann cells was used to evaluate the potential neurotrophic activity of SR 57746A. Neuritogenesis from DRG was measured with an image analysis system following exposure to different concentrations of SR 57746A. Neurite outgrowth of intact DRG was increased by SR 57746A and this was more obvious in the presence of co-cultured Schwann cells. The neuroprotective properties of SR 57746A were studied in co-cultures of DRG and Schwann cells, in which neuritogenesis was reduced by the cytostatic drugs cisplatin, vincristine and taxol. It was found that neurite outgrowth from DRG treated with cisplatin (3 micrograms/ml) and 10 microM SR 57746A for 3 days was significantly higher than after treatment with cisplatin alone. Similarly, neuritogenesis from DRG treated with taxol (0.01 microgram/ml) or vincristine (0.5 ng/ml) in combination with 10 microM SR 57746A was significantly increased compared to treatment with taxol or vincristine alone. When intact DRG were incubated in vitro with 3 micrograms/ml cisplatin and without Schwann cells, 10 microM SR 57746A also had a neuroprotective effect. These data suggest that SR 57746A has neuroprotective potential and that this effect does not depend solely on the presence of Schwann cells.

Cognitive deficits induced by global cerebral ischaemia: relationship to brain damage and reversal by transplants

The CA1 and hilar fields of the hippocampus are highly vulnerable to lack of oxygen after interruption of blood flow to the brain. Severe anterograde memory loss, seen in a significant proportion of heart attack survivors, has been attributed to selective bilateral ischaemic damage to the hippocampus. Animal models of global ischaemia, induced by extracranial occlusion of the major ascending arteries, enable assessment of the neuropathological and functional consequences of transient interruption of cerebral blood flow, and can inform strategies to reduce or alleviate ischaemic brain damage. This review focuses firstly on the nature of cognitive deficits induced by global ischaemia, how far they are consistent with lesion-based accounts of hippocampal function, and the extent to which these deficits can be correlated with CA1 cell loss. The second focus of the review is to examine the limited evidence for graft-induced recovery of cognitive function in animals subjected to global ischaemia. Recent findings that grafted foetal cells from discrete hippocampal fields follow appropriate laminar routes to form functional connections with host neurons, and that growth factors protect cells from ischaemic damage, have suggested that CA1 or trophic grafts placed in the region of ischaemic CA1 cell loss might restore or protect this vulnerable sector, and reduce cognitive deficits.

Neurotrophic effects of ipsapirone and other 5-HT1A receptor agonists on septal cholinergic neurons in culture

Repeated treatment of primary cultures of fetal rat septal neurons with 5-HT1A receptor agonists (8-OH-DPAT, ipsapirone, gepirone and buspirone) increased choline acetyltransferase activity after 6-7 days in culture. This effect was optimal with ipsapirone (+ 50-80% at 1 microM of the agonist), and could be prevented by potent 5-HT1A receptor antagonists such as (-)-tertatolol and (+)-WAY 100135. Under conditions where they completely suppressed the stimulatory effect of NGF on choline acetyltransferase in these cultures, specific anti-NGF antibodies did not alter the stimulatory effect of ipsapirone, suggesting that a possible release of NGF from some septal cells did not account for the effect of 5-HT1A receptor stimulation. Autoradiographic investigations with [3H]8-OH-DPAT as radioligand and immunocytochemistry with specific anti-choline acetyltransferase antibodies and anti-rat 5-HT1A receptor antibodies showed that 5-HT1A receptors were expressed on septal neurons in culture, notably on the cholinergic neurons identified by their positive staining with anti-choline acetyltransferase antibodies. Detailed morphometrical analysis by computer-assisted imaging revealed that repeated exposure to ipsapirone (1 microM for 7 days) did not influence the survival of cholinergic as well as non-cholinergic neurons, but specifically altered the neuritic tree (i.e. the total length of neurites and the number of branching points) of cholinergic neurons only. These data suggest that under in vitro conditions ipsapirone and other 5-HT1A receptor agonists may exert a direct trophic action on septal cholinergic neurons.