Prospects for the pharmacotherapy of amyotrophic lateral sclerosis : old strategies and new paradigms for the third millennium

Astrocytes and Microglia as Non-cell Autonomous Players in the Pathogenesis of ALS

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that leads to a progressive muscle wasting and paralysis. The pathological phenotypes are featured by severe motor neuron death and glial activation in the lumbar spinal cord. Proposed ALS pathogenic mechanisms include glutamate cytotoxicity, inflammatory pathway, oxidative stress, and protein aggregation. However, the exact mechanisms of ALS pathogenesis are not fully understood yet. Recently, a growing body of evidence provides a novel insight on the importance of glial cells in relation to the motor neuronal damage via the non-cell autonomous pathway. Accordingly, the aim of the current paper is to overview the role of astrocytes and microglia in the pathogenesis of ALS and to better understand the disease mechanism of ALS.

Expression of taurine transporter (TauT) is modulated by heat shock factor 1 (HSF1) in motor neurons of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by progressive paralysis caused by the degeneration of motor neurons throughout the central nervous system. Mutations of the free radical scavenging enzyme Cu/Zn superoxide dismutase 1 (SOD1) are a cause of familial ALS. In the present study, we demonstrated an age-dependent increase in taurine transporter (TauT) immunoreactivity in spinal cord motor neurons of ALS transgenic mice (mutant SOD1 (G93A)) and a similar increase in TauT in spinal motor neurons of patients with ALS. Chromatin immunoprecipitation analysis verified that heat shock factor 1 (HSF1) preferentially occupies the HSF1 binding element in the promoter of TauT under oxidative stress conditions. Knockdown of HSF1 by small interfering RNA reduced the transcriptional activity of TauT. Using [(3)H] taurine, we confirmed that an elevated expression of TauT directly contributes to increased taurine uptake in ALS motor neurons. In addition, we showed that taurine plays an antioxidant role and may prevent motor neuron loss due to oxidative stress in ALS. Our findings suggest that HSF1-induced TauT expression partially protects motor neurons by compensating for constitutive oxidative stress, which is thought to be a key mechanism contributing to the pathogenesis of ALS. Taken together, our results suggest that TauT is a novel pathological marker for stressed motor neurons in ALS and that modulation of TauT and taurine may slow neuronal degeneration in ALS.

Future Perspectives for Brain Pharmacotherapies: Implications of Drug Transport Processes at the Blood-brain Barrier

Years ago, ischemic stroke was regarded as a model disease for the development of neuroprotective therapies by the pharmacological industry. Results were disappointing. There are still no treatments available allowing the rescue of brain tissue once a stroke has occurred. Study failure is not only a problem in the stroke field. In other neurodegenerative conditions and in non-degenerative brain disorders, progress in drug development was also rather scarce until recently. An important factor in drug failure is the blood-brain barrier, which expresses active transporters that eliminate drugs from the brain. These transporters exhibit strong variations between different animals, which make it difficult to predict brain concentrations of drugs over species barriers. This paper claims that more detailed knowledge about: (1) the biology of blood-brain barrier transporters; (2) their regulation in brain disease, (3) the affinity of transporters to candidate drugs; and (4) the accumulation of drugs in brain tissue is needed for the overall success of clinical trials to be improved. An alternative strategy could be the use of disease-modifying treatments that do not have to enter the brain to exert their function. As such, restorative and anti-inflammatory strategies acting at the blood-brain interface might gain therapeutic potential in the future.

Stem cell technology for the study and treatment of motor neuron diseases

Amyotrophic lateral sclerosis and spinal muscular atrophy are devastating neurodegenerative diseases that lead to the specific loss of motor neurons. Recently, stem cell technologies have been developed for the investigation and treatment of both diseases. Here we discuss the different stem cells currently being studied for mechanistic discovery and therapeutic development, including embryonic, adult and induced pluripotent stem cells. We also present supporting evidence for the utilization of stem cell technology in the treatment of amyotrophic lateral sclerosis and spinal muscular atrophy, and describe key issues that must be considered for the transition of stem cell therapies for motor neuron diseases from bench to bedside. Finally, we discuss the first-in-human Phase I trial currently underway examining the safety and feasibility of intraspinal stem cell injections in amyotrophic lateral sclerosis patients as a foundation for translating stem cell therapies for various neurological diseases.

Differential expression of c-Ret in motor neurons versus non-neuronal cells is linked to the pathogenesis of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by selective degeneration of motor neurons throughout the central nervous systems. Non-cell autonomous damage induced by glial cells is linked to the selective susceptibility of motor neurons in ALS, but the mechanisms underlying this phenomenon are not known. We found that the expression of non-phosphorylated and phosphorylated forms (tyrosine (Tyr) residue 905, 1016, and 1062) of c-Ret, a member of the glial cell line-derived neurotrophic factor (GDNF) receptor, are altered in motor neurons of the lumbar spinal cord in ALS transgenic (G93A) mice and ALS (G93A) cell line models. Phosphorylated forms of c-Ret were colocalized with neurofilament aggregates in motor neurons of ALS mice. Consistent with the in vivo data, levels of non-phosphorylated and phosphorylated c-Ret (Tyr 905, 1016, and 1062) were decreased by oxidative stress in motor neuronal cells (NSC-34). Non-phosphorylated and phosphorylated forms of c-Ret immunoreactivity were markedly elevated in active microglia of ALS mice. Our findings suggest that constitutive oxidative stress modulates c-Ret function, thereby reducing GDNF signaling in motor neurons. Furthermore, the induction of c-Ret expression in microglia may contribute to non-cell autonomous cell death of motor neurons by available GDNF in ALS.

Control of neuroinflammation as a therapeutic strategy for amyotrophic lateral sclerosis and other neurodegenerative disorders

Neurodegenerative diseases, Alzheimer's and Parkinson's diseases, and amyotrophic lateral sclerosis (ALS) are progressive and devastating disorders of the nervous system without cure. Although a number of distinct, but not mutually exclusive, mechanisms can affect disease pathogenesis, neuroinflammation stands in common. Neuroinflammatory responses occur as a consequence of oxidative and excitotoxic neuronal damage, mitochondrial dysfunction, and protein aggregation. Thus, it is believed drugs that modulate inflammation may combat disease progression. Such strategies include those commented on in the report by Arie Neymotin et al. demonstrating lenalidomide's anti-inflammatory and neuroprotective responses in the G93A mutant superoxide dismutase-1 mouse model of ALS (Neymotin et al., 2009). While anti-inflammatory interventions may be required, they may not be sufficient to positively affect clinical outcomes. The targeting of combinations of pathogenic events including clearance of disaggregated proteins together with neuroprotective and immune modulatory strategies may all be required to facilitate positive therapeutic outcomes. This may include the targeting of both innate and adaptive neurotoxic immune responses. This commentary is designed to summarize the promises and perils in achieving immunoregulation for brain homeostatic responses and inevitable therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are discussed with a particular focus on ALS.

Inequalities in cervical cancer screening in Eastern Europe: perspectives from Bulgaria and Romania

OBJECTIVES

The incidence of cervical cancer in Eastern Europe has been on the rise, in contrast to the reduction in incidence in most countries of Western Europe. The objectives of the paper are to delineate the inequalities in cervical cancer screening in Romania and Bulgaria and identify explanations for these inequalities.

METHODS

Representative samples of women - 1,099 in Bulgaria and 1,053 in Romania, were interviewed through a structured questionnaire.

RESULTS

We found multiple dimensions of inequalities in cervical cancer prevalence and prevention, including disparities in comparison to other countries, disparities due to socioeconomic status, education, residency and ethnicity, as well as differential barriers faced by women in access to screening and in relationships with providers. We identified mediators of the effects of socio-economic status on screening history.

CONCLUSIONS

The study concludes that the effect of SES on screening is mediated mainly by the structural barriers in accessing the healthcare system, as well as women's perceptions of the multiple costs of the smear. These conclusions are relevant to the development of national screening programs and health promotion in the two countries.

(‐)‐Deprenyl alleviates the degenerative changes induced in the neonatal rat spinal cord by CSF from amyotrophic lateral sclerosis patients

Previous studies from our laboratory suggest the presence of toxic factor(s) in the cerebrospinal fluid (CSF) of patients with amyotrophic lateral sclerosis (ALS) which induces degenerative changes in the spinal cord neurons. The present work was carried out to investigate the role of (-)-deprenyl in attenuating these degenerative changes. CSF samples from ALS and non-ALS neurological patients were injected into the spinal subarachnoid space of 3-day-old rat pups, followed by a single dose (0.01 mg/kg body weight) of (-)-deprenyl, administered 24 h after CSF injection. After a further period of 24 h, the rats were sacrificed and the spinal cord sections were stained with antibodies against phosphorylated neurofilament (NF, SMI-31 antibody) and glial fibrillary acidic protein (GFAP). Activity of lactate dehydrogenase (LDH) was also measured. (-)-Deprenyl injection resulted in a significant (61%) decrease in the number of SMI-31 stained neuronal soma in the ventral horn of the spinal cord of ALS CSF exposed rats. This was accompanied by a reduction in the astrocytes immunoreactive for GFAP. There was also a significant (35%) decrease in the LDH activity following (-)-deprenyl treatment. These results suggest that (-)-deprenyl may confer neuroprotection against the toxic factor(s) present in ALS CSF.

Differential regulation of neuronal and inducible nitric oxide synthase (NOS) in the spinal cord of mutant SOD1 (G93A) ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder characterized by degeneration of motor neurons throughout the central nervous system. Mutations of the free radical scavenging enzyme superoxide dismutase-1 (SOD1) are a cause of familial ALS but it is not known how mutations lead to cell death. Free radicals such as nitric oxide (NO) are thought to play a key pathogenic role. NO is synthesized by NO synthases (NOSs) from arginine, which is a rate-limiting factor for NO production. We found that neuronal NOS (nNOS)-positive motor neurons were depleted while inducible NOS (iNOS)-positive activated glial cells were increased in transgenic mtSOD1 (G93A) ALS mice. iNOS expression was up regulated consistent with the increases of motor neuron loss and glial activation and citrulline and NO levels while nNOS expression was decreased in G93A ALS mice. Administration of l-arginine to G93A mice reduced the severity of motor neuron depletion and glial activation. In treated animals, nNOS expression was preserved while citrulline and NO were reduced, possibly due to reduced activation of glia expressing iNOS. Our findings show that high concentrations of NO correlate with iNOS expression rather than nNOS expression in G93A ALS mice. This suggests that therapy focused on iNOS inhibition might be a fruitful direction for future ALS therapeutic trials.

Linear longitudinal decline in fractional anisotropy in patients with amyotrophic lateral sclerosis: preliminary results

BACKGROUND AND PURPOSE

As potential therapies aimed at halting or slowing the decline in upper motor neuron function in patients with amyotrophic lateral sclerosis (ALS) or primary lateral sclerosis (PLS) are developed, a quantitative method for monitoring response will be necessary. Measurement of fractional anisotropy (FA) using diffusion tensor imaging (DTI) over time should parallel functional decline from upper motor neuron degeneration in these patients.

PATIENTS AND METHODS

Two patients with definite ALS were imaged at 3.0 T and FA values were obtained in the corticospinal tract every 3 months for 1 year. The FA values were compared to normal age-matched controls.

RESULTS

Both patients showed linear decreases in FA values over time with R(2) values ranging from 0.93 to 0.99. The decline became statistically significant over the course of the study. Qualitative decreases in anisotropy were also evident on FA maps.

CONCLUSION

If these trends can be validated in greater numbers of patients, DTI may serve as an objective quantitative biomarker for disease progression in patients with upper motor neuron disease.

Motor neuronal protection by L-arginine prolongs survival of mutant SOD1 (G93A) ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive paralysis due to motor neuron degeneration. Despite the fact that many different therapeutic strategies have been applied to prevent disease progression, no cure or effective therapy is currently available for ALS. We found that L-arginine protects cultured motor neurons from excitotoxic injury. We also found that L-arginine supplementation both prior to and after the onset of motor neuron degeneration in mtSOD1 (G93A) transgenic ALS mice significantly slowed the progression of neuropathology in lumbar spinal cord, delayed onset of motor dysfunction, and prolonged life span. Moreover, L-arginine treatment was associated with preservation of arginase I activity and neuroprotective polyamines in spinal cord motor neurons. Our findings show that L-arginine has potent in vitro and in vivo neuroprotective properties and may be a candidate for therapeutic trials in ALS.

Strategic approaches to developing drug treatments for ALS

Significant progress in understanding the cellular mechanisms of motor neuron degeneration in amyotrophic lateral sclerosis (ALS) has not been matched with the development of therapeutic strategies to prevent disease progression. The multiple potential causes and relative rarity of the disease are two significant factors that make drug development and assessment in clinical trials extremely difficult. We review recent progress in promoting therapeutics into clinical trials and highlight the value of moderate throughput screening for the acceleration and improvement of drug design.

The neuroprotective role of creatine

Significant progress has been made in identifying neuroprotective agents and their translation to patients with neurological disorders. While the direct causative pathways of neurodegeneration remain unclear, they are under great clinical and experimental investigation. There are a number of interrelated pathogenic mechanisms triggering molecular events that lead to neuronal death. One putative mechanism reported to play a prominent role in the pathogenesis of neurological diseases is impaired energy metabolism. If reduced energy stores play a role in neuronal loss, then therapeutic strategies that buffer intracellular energy levels may prevent or impede the neurodegenerative process. Recent studies suggest that impaired energy production promotes neurological disease onset and progression. Sustained ATP levels are critical to cellular homeostasis and may have both direct and indirect influence on pathogenic mechanisms associated with neurological disorders. Creatine is a critical component in maintaining cellular energy homeostasis, and its administration has been reported to be neuroprotective in a wide number of both acute and chronic experimental models of neurological disease. In the context of this chapter, we will review the experimental evidence for creatine supplementation as a neurotherapeutic strategy in patients with neurological disorders, including Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease, as well as in ischemic stroke, brain and spinal cord trauma, and epilepsy.

Sporadic amyotrophic lateral sclerosis as an infectious disease: A possible role of cyanobacteria?

The available epidemiological data for amyotrophic lateral sclerosis (ALS) support an infectious etiology and lead us to propose a new hypothesis. We examined older epidemiological data concerning categories of the population with increased incidence (aged people, people living in rural areas, farmers, breeders), more recent epidemiological reports regarding Italian soccer players, AIDS patients, people living in highly polluted areas, and reports of cases of conjugal and pregnancy-associated ALS. The toxic and infectious hypotheses lead us to suggest a role for cyanobacteria in the production of endogenous beta-N-methylamino-L-alanine. Infection from a cyanobacterium, or another ubiquitous bacterium having similar characteristics, may be the missing clue to the etiology of ALS. We speculate that ubiquitous bacteria secreting toxic amino acids and "colonizing" tissues and organs in the human body might be the common element linking motor neuron diseases in Guam to sporadic ALS in the rest of the world.

Nuclear factor-kappab activation is associated with glutamate-evoked tissue transglutaminase up-regulation in primary astrocyte cultures

We have previously demonstrated that alterations of cell redox state, evoked by glutamate, are associated with tissue transglutaminase increases in primary astrocyte cultures. Furthermore, glutamate exposure activated the nuclear factor (NF)-kappaB pathway, and its effects were significantly reduced by antioxidants. Here, we investigated the possible involvement of activated NF-kappaB pathway in glutamate-evoked tissue transglutaminase up-regulation in primary astrocytes. The presence of DNA binding activity by NF-kappaB in nuclear extracts of astrocytes, treated for 24 hr with glutamate (500 microM) or untreated, was assessed by EMSA, using an oligonucleotide probe containing the NF-kappaB consensus sequence present in the tissue transglutaminase promoter. Supershifting with monoclonal antibodies revealed that activated NF-kappaB dimer complexes were composed of p50 and p65 subunits. Interestingly, the specific NF-kappaB inhibitor SN50 (but not its inactive analogue SN50M), when added to cell cultures 30 min prior to glutamate treatment, was able gradually to reduce glutamate-induced NF-kappaB activation. Western blot analysis confirmed the reduction of the p50 amount in nuclear extracts. Notably, the preincubation with SN50 also diminished glutamate-increased tissue transglutaminase expression, as showed by both RT-PCR and Western blotting. Competition experiments, carried out with an excess of a probe containing the NF-kappaB consensus sequence present in the kappa-light-chain promoter, demonstrated a preferential binding of the tissue transglutaminase specific NF-kappaB probe in the nuclear extracts of glutamate-treated astrocytes compared with untreated astrocytes. These preliminary data suggest that NF-kappaB activation, which has been demonstrated to be involved in astrocyte response to glutamate, could also be associated with the molecular pathway leading to glutamate-evoked tissue transglutaminase up-regulation.

Impaired glutamine metabolism in NMDA receptor hypofunction induced by MK801

Paradoxically, glutamate receptor antagonists have neurotoxic and psychotogenic properties in addition to their neuroprotective potential during excessive glutamate release. In the present study the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK801 was used to examine glial-neuronal interactions in NMDA receptor hypofunction. Rats were given a subanesthetic dose of MK801 together with [1-13C]glucose and [1,2-13C]acetate, and brains were removed 20 min later. Analyses of extracts from cingulate, retrosplenial plus middle frontal cortices (CRFC) and temporal lobe were performed using HPLC and 13C and 1H nuclear magnetic resonance spectroscopy. Hypofunction of the NMDA receptor induced similar changes in both brain areas investigated; however, the changes were most pronounced in the temporal lobe. Generally, only labeling from [1-13C]glucose was affected by MK801. In CRFC and temporal lobe amounts of both labeled and unlabeled glutamine were increased, whereas those of aspartate were decreased. In the CRFC the decrease in labeling of aspartate was greater than the decrease in concentration, leading to decreased 13C enrichment. In temporal lobe, not in CRFC, increased concentrations of glutamate, GABA, succinate, glutathione and inositol were detected together with increased labeling of GABA and succinate from [1-13C]glucose. 13C Enrichment was decreased in glutamate and increased in succinate. The results point towards a disturbance in glutamate-glutamine cycling and thus interaction between neurons and glia, since labeling of glutamate and glutamine from glucose was affected differently.

Into the depths of ataxia

Ataxia is a lethal neurological disease characterized by incoordination, postural abnormalities, difficulties with gait, and problems with clarity of speech. The etiology of ataxia is divided equally between hereditary and sporadic forms. Regardless of cause, the cerebellar cortex is often a target in ataxia. Thus, how a disruption in cerebellar cortex might lead to ataxia is of considerable interest. A report in this issue of the JCI links ataxia to enhanced hyperexcitability of neurons in the deep cerebellar nuclei.