Autophagy, lithium, and amyotrophic lateral sclerosis

The beneficial role of autophagy in multiple sclerosis: Yes or No?

Multiple sclerosis (MS) is a chronic progressive demyelinating disease of the central nervous system (CNS) due to an increase of abnormal peripherally auto-reactive T lymphocytes which elicit autoimmunity. The main pathophysiology of MS is myelin sheath damage by immune cells and a defect in the generation of myelin by oligodendrocytes. Macroautophagy/autophagy is a critical degradation process that eliminates dysfunctional or superfluous cellular components. Autophagy has the property of a double-edged sword in MS in that it may have both beneficial and detrimental effects on MS neuropathology. Therefore, this review illustrates the protective and harmful effects of autophagy with regard to this disease. Autophagy prevents the progression of MS by reducing oxidative stress and inflammatory disorders. In contrast, over-activated autophagy is associated with the progression of MS neuropathology and in this case the use of autophagy inhibitors may alleviate the pathogenesis of MS. Furthermore, autophagy provokes the activation of different immune and supporting cells that play an intricate role in the pathogenesis of MS. Autophagy functions in the modulation of MS neuropathology by regulating cell proliferation related to demyelination and remyelination. Autophagy enhances remyelination by increasing the activity of oligodendrocytes, and astrocytes. However, autophagy induces demyelination by activating microglia and T cells. In conclusion, specific autophagic activators of oligodendrocytes, and astrocytes, and specific autophagic inhibitors of dendritic cells (DCs), microglia and T cells induce protective effects against the pathogenesis of MS.Abbreviations: ALS: amyotrophic lateral sclerosis; APCs: antigen-presenting cells; BBB: blood-brain barrier; CSF: cerebrospinal fluid; CNS: central nervous system; DCs: dendritic cells; EAE: experimental autoimmune encephalomyelitis; ER: endoplasmic reticulum; LAP: LC3-associated phagocytosis; MS: multiple sclerosis; NCA: non-canonical autophagy; OCBs: oligoclonal bands; PBMCs: peripheral blood mononuclear cells; PD: Parkinson disease; ROS: reactive oxygen species; UPR: unfolded protein response.

Therapeutic targeting of ALS pathways: Refocusing an incomplete picture

Numerous potential amyotrophic lateral sclerosis (ALS)-relevant pathways have been hypothesized and studied preclinically, with subsequent translation to clinical trial. However, few successes have been observed with only modest effects. Along with an improved but incomplete understanding of ALS as a neurodegenerative disease is the evolution of more sophisticated and diverse in vitro and in vivo preclinical modeling platforms, as well as clinical trial designs. We highlight proposed pathological pathways that have been major therapeutic targets for investigational compounds. It is likely that the failures of so many of these therapeutic compounds may not have occurred because of lack of efficacy but rather because of a lack of preclinical modeling that would help define an appropriate disease pathway, as well as a failure to establish target engagement. These challenges are compounded by shortcomings in clinical trial design, including lack of biomarkers that could predict clinical success and studies that are underpowered. Although research investments have provided abundant insights into new ALS-relevant pathways, most have not yet been developed more fully to result in clinical study. In this review, we detail some of the important, well-established pathways, the therapeutics targeting them, and the subsequent clinical design. With an understanding of some of the shortcomings in translational efforts over the last three decades of ALS investigation, we propose that scientists and clinicians may choose to revisit some of these therapeutic pathways reviewed here with an eye toward improving preclinical modeling, biomarker development, and the investment in more sophisticated clinical trial designs.

UNC13A in amyotrophic lateral sclerosis: from genetic association to therapeutic target

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with limited treatment options and an incompletely understood pathophysiology. Although genomewide association studies (GWAS) have advanced our understanding of the disease, the precise manner in which risk polymorphisms contribute to disease pathogenesis remains unclear. Of relevance, GWAS have shown that a polymorphism (rs12608932) in the UNC13A gene is associated with risk for both ALS and frontotemporal dementia (FTD). Homozygosity for the C-allele at rs12608932 modifies the ALS phenotype, as these patients are more likely to have bulbar-onset disease, cognitive impairment and FTD at baseline as well as shorter survival. UNC13A is expressed in neuronal tissue and is involved in maintaining synaptic active zones, by enabling the priming and docking of synaptic vesicles. In the absence of functional TDP-43, risk variants in UNC13A lead to the inclusion of a cryptic exon in UNC13A messenger RNA, subsequently leading to nonsense mediated decay, with loss of functional protein. Depletion of UNC13A leads to impaired neurotransmission. Recent discoveries have identified UNC13A as a potential target for therapy development in ALS, with a confirmatory trial with lithium carbonate in UNC13A cases now underway and future approaches with antisense oligonucleotides currently under consideration. Considering UNC13A is a potent phenotypic modifier, it may also impact clinical trial outcomes. This present review describes the path from the initial discovery of UNC13A as a risk gene in ALS to the current therapeutic options being explored and how knowledge of its distinct phenotype needs to be taken into account in future trials.

Lithium engages autophagy for neuroprotection and neuroplasticity: translational evidence for therapy

Here an overview is provided on therapeutic/neuroprotective effects of Lithium (Li⁺) in neurodegenerative and psychiatric disorders focusing on the conspicuous action of Li⁺ through autophagy. The effects on the autophagy machinery remain the key molecular mechanisms to explain the protective effects of Li⁺ for neurodegenerative diseases, offering potential therapeutic strategies for the treatment of neuropsychiatric disorders and emphasizes a crossroad linking autophagy, neurodegenerative disorders, and mood stabilization. Sensitization by psychostimulants points to several mechanisms involved in psychopathology, most also crucial in neurodegenerative disorders. Evidence shows the involvement of autophagy and metabotropic Glutamate receptors-5 (mGluR5) in neurodegeneration due to methamphetamine neurotoxicity as well as in neuroprotection, both in vitro and in vivo models. More recently, Li⁺ was shown to modulate autophagy through its action on mGluR5, thus pointing to an additional way of autophagy engagement by Li⁺ and to a substantial role of mGluR5 in neuroprotection related to neural e neuropsychiatry diseases. We propose Li⁺ engagement of autophagy through the canonical mechanisms of autophagy machinery and through the intermediary of mGluR5.

The role of autophagy-lysosomal pathway in motor neuron diseases

Motor neuron diseases (MNDs) include a broad group of diseases in which neurodegeneration mainly affects upper and/or lower motor neurons (MNs). Although the involvement of specific MNs, symptoms, age of onset, and progression differ in MNDs, the main pathogenic mechanism common to most MNDs is represented by proteostasis alteration and proteotoxicity. This pathomechanism may be directly related to mutations in genes encoding proteins involved in the protein quality control system, particularly the autophagy-lysosomal pathway (ALP). Alternatively, proteostasis alteration can be caused by aberrant proteins that tend to misfold and to aggregate, two related processes that, over time, cannot be properly handled by the ALP. Here, we summarize the main ALP features, focusing on different routes utilized to deliver substrates to the lysosome and how the various ALP pathways intersect with the intracellular trafficking of membranes and vesicles. Next, we provide an overview of the mutated genes that have been found associated with MNDs, how these gene products are involved in different steps of ALP and related processes. Finally, we discuss how autophagy can be considered a valid therapeutic target for MNDs treatment focusing on traditional autophagy modulators and on emerging approaches to overcome their limitations.

Transient increase in recurrent inhibition in amyotrophic lateral sclerosis as a putative protection from neurodegeneration

AIM

Adaptive mechanisms in spinal circuits are likely involved in homeostatic responses to maintain motor output in amyotrophic lateral sclerosis. Given the role of Renshaw cells in regulating the motoneuron input/output gain, we investigated the modulation of heteronymous recurrent inhibition.

METHODS

Electrical stimulations were used to activate recurrent collaterals resulting in the Hoffmann reflex depression. Inhibitions from soleus motor axons to quadriceps motoneurons, and vice versa, were tested in 38 patients and matched group of 42 controls.

RESULTS

Compared with controls, the mean depression of quadriceps reflex was larger in patients, while that of soleus was smaller, suggesting that heteronymous recurrent inhibition was enhanced in quadriceps but reduced in soleus. The modulation of recurrent inhibition was linked to the size of maximal direct motor response and lower limb dysfunctions, suggesting a significant relationship with the integrity of the target motoneuron pool and functional abilities. No significant link was found between the integrity of motor axons activating Renshaw cells and the level of inhibition. Enhanced inhibition was particularly observed in patients within the first year after symptom onset and with slow progression of lower limb dysfunctions. Normal or reduced inhibitions were mainly observed in patients with motor weakness first in lower limbs and greater dysfunctions in lower limbs.

CONCLUSION

We provide the first evidence for enhanced recurrent inhibition and speculate that Renshaw cells might have transient protective role on motoneuron by counteracting hyperexcitability at early stages. Several mechanisms likely participate including cortical influence on Renshaw cell and reinnervation by slow motoneurons.

Lithium promotes recovery after spinal cord injury

Lithium is associated with oxidative stress and apoptosis, but the mechanism by which lithium protects against spinal cord injury remains poorly understood. In this study, we found that intraperitoneal administration of lithium chloride (LiCl) in a rat model of spinal cord injury alleviated pathological spinal cord injury and inhibited expression of tumor necrosis factor α, interleukin-6, and interleukin 1 β. Lithium inhibited pyroptosis and reduced inflammation by inhibiting Caspase-1 expression, reducing the oxidative stress response, and inhibiting activation of the Nod-like receptor protein 3 inflammasome. We also investigated the neuroprotective effects of lithium intervention on oxygen/glucose-deprived PC12 cells. We found that lithium reduced inflammation, oxidative damage, apoptosis, and necrosis and up-regulated nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 in PC12 cells. All-trans retinoic acid, an Nrf2 inhibitor, reversed the effects of lithium. These results suggest that lithium exerts anti-inflammatory, anti-oxidant, and anti-pyroptotic effects through the Nrf2/heme oxygenase-1 pathway to promote recovery after spinal cord injury. This study was approved by the Animal Ethics Committee of Xi’an Jiaotong University (approval No. 2018-2053) on October 23, 2018.

Inflammatory myopathies: shedding light on promising agents and combination therapies in clinical trials

INTRODUCTION

Due to new insights into the pathogenesis of inflammatory myopathies - in short myositis - and the urgent need for new treatment options in patients who are refractory to standard therapy, multiple novel drugs have been developed and studied in clinical trials. In light of this exciting development, a critical evaluation of the present data is necessary in order to identify the best pathway to future treatment of inflammatory myopathies.

AREAS COVERED

This review focuses on the current evidence from clinical trials in myositis and encompasses dermatomyositis, polymyositis, necrotizing myopathy, antisynthetase-syndrome, overlap myositis, and inclusion body myositis. The results of studies on new therapeutic agents are summarized, in particular larger cohort studies and randomized trials from recent years. When such data were not available, earlier and smaller representative studies were included instead.

EXPERT OPINION

Current studies in most myositis subtypes have shown positive effects of novel biologicals such as abatacept, sifalimumab, JAK-Inhibitors as well as known agents such as rituximab, but further studies are needed to confirm these observations. In inclusion body myositis, the eagerly awaited recent therapeutic trials have missed their primary endpoints, except for the phase 2 study with rapamycin, which has demonstrated significant improvements in secondary endpoints. Future trials will also need to focus on combination therapies of multiple immunomodulatory agents.

Update on Myositis Therapy: from Today's Standards to Tomorrow's Possibilities

Inflammatory myopathies, in short, myositis, are heterogeneous disorders that are characterized by inflammation of skeletal muscle and weakness of arms and legs. Research over the past few years has led to a new understanding regarding the pathogenesis of myositis. The new insights include different pathways of the innate and adaptive immune response during the pathogenesis of myositis. The importance of non-inflammatory mechanisms such as cell stress and impaired autophagy has been recently described. New target-specific drugs for myositis have been developed and are currently being tested in clinical trials. In this review, we discuss the mechanisms of action of pharmacological standards in myositis and provide an outlook of future treatment approaches.

Translational evidence for lithium-induced brain plasticity and neuroprotection in the treatment of neuropsychiatric disorders

Increasing evidence indicates lithium (Li+) efficacy in neuropsychiatry, pointing to overlapping mechanisms that occur within distinct neuronal populations. In fact, the same pathway depending on which circuitry operates may fall in the psychiatric and/or neurological domains. Li+ restores both neurotransmission and brain structure unveiling that psychiatric and neurological disorders share common dysfunctional molecular and morphological mechanisms, which may involve distinct brain circuitries. Here an overview is provided concerning the therapeutic/neuroprotective effects of Li+ in different neuropsychiatric disorders to highlight common molecular mechanisms through which Li+ produces its mood-stabilizing effects and to what extent these overlap with plasticity in distinct brain circuitries. Li+ mood-stabilizing effects are evident in typical bipolar disorder (BD) characterized by a cyclic course of mania or hypomania followed by depressive episodes, while its efficacy is weaker in the opposite pattern. We focus here on neural adaptations that may underlie psychostimulant-induced psychotic development and to dissect, through the sensitization process, which features are shared in BD and other psychiatric disorders, including schizophrenia. The multiple functions of Li+ highlighted here prove its exceptional pharmacology, which may help to elucidate its mechanisms of action. These may serve as a guide toward a multi-drug strategy. We propose that the onset of sensitization in a specific BD subtype may predict the therapeutic efficacy of Li+. This model may help to infer in BD which molecular mechanisms are relevant to the therapeutic efficacy of Li+.

Hyperoside alleviates epilepsy-induced neuronal damage by enhancing antioxidant levels and reducing autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum perforatum L. (genus Hypericum, family Hypericaceae), a plant commonly used in traditional Chinese medicine, is believed to confer a wide range of benefits, including fever reduction, detoxification, calming, and pain relief via decoctions of its stems and leaves. Hyperoside (HYP), a natural compound extracted from Hypericum perforatum L., has been shown to demonstrate a wide array of bioactivities including antioxidative, anti-inflammatory, and anti-apoptotic effects. In this study, we investigated the effects of HYP on epilepsy-induced neuronal damage in mice and the associated regulatory factors.

AIM OF THE STUDY

This study examined the potential therapeutic use of HYP for the treatment of neuronal damage in a mouse model of epilepsy and explored the relationships of the potential neuroprotective effects of HYP pretreatment with antioxidant levels and autophagy.

MATERIALS AND METHODS

ICR mice were randomly divided into six groups: sham group, sham-HYP group, KA group, KA-HYP group, KA-HYP-DDC group and KA-CQ group. Immunohistochemical staining was used to assess changes in NeuN, IBA-1, and GFAP expression in the CA3 region of the hippocampus. Immunofluorescence staining was used to assess the effects of HYP on the number of autophagosomes that accumulated in neurons in the hippocampal CA3 region. The levels of SOD1, SOD2, LC3I/II, Beclin1, and PI3K/AKT and MAPK signaling-related proteins were detected by Western blot.

RESULTS

Pretreatment with 50 mg/kg HYP protected against epilepsy-induced neuronal damage in the hippocampal CA3 region. Additionally, HYP enhanced antioxidant levels and reduced the levels of autophagy-related proteins via the PI3K/AKT and MAPK pathways.

CONCLUSION

HYP protected the hippocampal CA3 region against epilepsy-induced neuronal damage via enhancing antioxidant levels and reducing autophagy. The mechanism of action may be related to the maintenance of antioxidant levels and the suppression of autophagy via the PI3K/Akt and MAPK pathways.

Quantitative Ultrastructural Morphometry and Gene Expression of mTOR-Related Mitochondriogenesis within Glioblastoma Cells

In glioblastoma (GBM) cells, an impairment of mitochondrial activity along with autophagy suppression occurs. Autophagy suppression in GBM promotes stemness, invasion, and poor prognosis. The autophagy deficit seems to be due, at least in part, to an abnormal up-regulation of the mammalian target of rapamycin (mTOR), which may be counteracted by pharmacological mTORC1 inhibition. Since autophagy activation is tightly bound to increased mitochondriogenesis, a defect in the synthesis of novel mitochondria is expected to occur in GBM cells. In an effort to measure a baseline deficit in mitochondria and promote mitochondriogenesis, the present study used two different GBM cell lines, both featuring mTOR hyperactivity. mTORC1 inhibition increases the expression of genes and proteins related to autophagy, mitophagy, and mitochondriogenesis. Autophagy activation was counted by RT-PCR of autophagy genes, LC3- immune-fluorescent puncta and immune-gold, as well as specific mitophagy-dependent BNIP3 stoichiometric increase in situ, within mitochondria. The activation of autophagy-related molecules and organelles after rapamycin exposure occurs concomitantly with progression of autophagosomes towards lysosomes. Remarkably, mitochondrial biogenesis and plasticity (increased mitochondrial number, integrity, and density as well as decreased mitochondrial area) was long- lasting for weeks following rapamycin withdrawal.

CB2R orchestrates neuronal autophagy through regulation of the mTOR signaling pathway in the hippocampus of developing rats with status epilepticus

Neuronal loss and gliosis are the major pathological changes after status epilepticus (SE). The authors' previous study revealed the time-dependent changes of cannabinoid receptor type 2 (CB2R) in hippocampal neurons of developing rats after SE, which were accompanied by a decrease in the number of neurons. Meanwhile, growing evidence indicates that CB2R stimulation exerts anti-convulsant properties in seizure models. However, the activation of CB2R in neuronal repair in response to the damage after SE is still unclear. In this experiment, a highly-selective CB2R agonist JWH133 and antagonist AM630 were administered to determine the activity of CB2R in neuronal autophagy and apoptosis of the post-SE repair in developing rats. The present results revealed that activation of CB2R by JWH133, not only obviously lowered the success rate, 24-h death rate and the Racine stage in the model, but also extended the latency period to SE. In addition, compared with the vehicle control group, CB2R activation increased neuronal autophagy and the expression of phosphorylated-mammalian target of rapamycin (p-mTOR)/mTOR, Beclin-1, and LC3II/LC3I while decreasing the expression of p-Unc-51-like autophagy-activating kinase 1 (ULK-1)/ULK1, p62, and cleaved caspase-3. These results were dose-dependent and were especially evident in the high-dose group, and interestingly the opposite results were obtained in the AM630 group. Thus, CB2R orchestrates neuronal autophagy through regulation of the mTOR signaling pathway in the hippocampus of developing rats with SE. These findings might provide an important basis for further investigation of the therapeutic role of CB2R in ameliorating epilepsy-related neuronal damage.

Motor Neurons Pathology After Chronic Exposure to MPTP in Mice

The neurotoxin 1-methyl,4-phenyl-1,2,3,6-tetrahydropiridine (MPTP) is widely used to produce experimental parkinsonism in rodents and primates. Among different administration protocols, continuous or chronic exposure to small amounts of MPTP is reported to better mimic cell pathology reminiscent of Parkinson's disease (PD). Catecholamine neurons are the most sensitive to MPTP neurotoxicity; however, recent studies have found that MPTP alters the fine anatomy of the spinal cord including motor neurons, thus overlapping again with the spinal cord involvement documented in PD. In the present study, we demonstrate that chronic exposure to low amounts of MPTP (10 mg/kg daily, × 21 days) significantly reduces motor neurons in the ventral lumbar spinal cord while increasing α-synuclein immune-staining within the ventral horn. Spinal cord involvement in MPTP-treated mice extends to Calbindin D28 KDa immune-reactive neurons other than motor neurons within lamina VII. These results were obtained in the absence of significant reduction of dopaminergic cell bodies in the Substantia Nigra pars compacta, while a slight decrease was documented in striatal tyrosine hydroxylase immune-staining. Thus, the present study highlights neuropathological similarities between dopaminergic neurons and spinal motor neurons and supports the pathological involvement of spinal cord in PD and experimental MPTP-induced parkinsonism. Remarkably, the toxic threshold for motor neurons appears to be lower compared with nigral dopaminergic neurons following a chronic pattern of MPTP intoxication. This sharply contrasts with previous studies showing that MPTP intoxication produces comparable neuronal loss within spinal cord and Substantia Nigra.

Molecular Mechanisms Linking ALS/FTD and Psychiatric Disorders, the Potential Effects of Lithium

Altered proteostasis, endoplasmic reticulum (ER) stress, abnormal unfolded protein response (UPR), mitochondrial dysfunction and autophagy impairment are interconnected events, which contribute to the pathogenesis of amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD). In recent years, the mood stabilizer lithium was shown to potentially modify ALS/FTD beyond mood disorder-related pathology. The effects of lithium are significant in ALS patients carrying genetic variations in the UNC13 presynaptic protein, which occur in ALS/FTD and psychiatric disorders as well. In the brain, lithium modulates a number of biochemical pathways involved in synaptic plasticity, proteostasis, and neuronal survival. By targeting UPR-related events, namely ER stress, excitotoxicity and autophagy dysfunction, lithium produces plastic effects. These are likely to relate to neuroprotection, which was postulated for mood and motor neuron disorders. In the present manuscript, we try to identify and discuss potential mechanisms through which lithium copes concomitantly with ER stress, UPR and autophagy dysfunctions related to UNC13 synaptic alterations and aberrant RNA and protein processing. This may serve as a paradigm to provide novel insights into the neurobiology of ALS/FTD featuring early psychiatric disturbances.

Redox-Related Neuronal Death and Crosstalk as Drug Targets: Focus on Epilepsy

Cell death has a vital role in embryonic development and organismal homeostasis. Biochemical, pharmacological, behavioral, and electrophysiological evidences support the idea that dysregulation of cell death programs are involved in neuropathological conditions like epilepsy. The brain is particularly vulnerable to oxidative damage due to higher oxygen consumption and lower endogenous antioxidant defense than other bodily organ. Thus, in this review, we focused on the comprehensive summarization of evidence for redox-associated cell death pathways including apoptosis, autophagy, necroptosis, and pyroptosis in epilepsy and the oxidative stress-related signaling in this process. We specially proposed that the molecular crosstalk of various redox-linked neuronal cell death modalities might occur in seizure onset and/or epileptic conditions according to the published data. Additionally, abundance of polyunsaturated fatty acids in neuronal membrane makes the brain susceptible to lipid peroxidation. This presumption was then formalized in the proposal that ferroptosis, a novel type of lipid reactive oxygen species (ROS)-dependent regulatory cell death, is likely to be a critical mechanism for the emergence of epileptic phenotype. Targeting ferroptosis process or combination treatment with multiple cell death pathway inhibitors may shed new light on the therapy of epilepsy.

Mitochondrial DNA copy number is associated with psychosis severity and anti-psychotic treatment

Mitochondrial pathology has been implicated in the pathogenesis of psychotic disorders. A few studies have proposed reduced leukocyte mitochondrial DNA (mtDNA) copy number in schizophrenia and bipolar disorder type I, compared to healthy controls. However, it is unknown if mtDNA copy number alteration is driven by psychosis, comorbidity or treatment. Whole blood mtDNA copy number was determined in 594 psychosis patients and corrected for platelet to leukocyte count ratio (mtDNAcn_res). The dependence of mtDNAcn_res on clinical profile, metabolic comorbidity and antipsychotic drug exposure was assessed. mtDNAcn_res was reduced with age (β = −0.210, p < 0.001), use of clozapine (β = −0.110,p = 0.012) and risperidone (β = −0.109,p = 0.014), dependent on prescribed dosage (p = 0.006 and p = 0.026, respectively), and the proportion of life on treatment (p = 0.006). Clozapine (p = 0.0005) and risperidone (p = 0.0126) had a reducing effect on the mtDNA copy number also in stem cell-derived human neurons in vitro at therapeutic plasma levels. For patients not on these drugs, psychosis severity had an effect (β = −0.129, p = 0.017), similar to age (β = −0.159, p = 0.003) and LDL (β = −0.119, p = 0.029) on whole blood mtDNAcn_res. Further research is required to determine if mtDNAcn_res reflects any psychosis-intrinsic mitochondrial changes.

mTOR-Related Brain Dysfunctions in Neuropsychiatric Disorders

The mammalian target of rapamycin (mTOR) is an ubiquitously expressed serine-threonine kinase, which senses and integrates several intracellular and environmental cues to orchestrate major processes such as cell growth and metabolism. Altered mTOR signalling is associated with brain malformation and neurological disorders. Emerging evidence indicates that even subtle defects in the mTOR pathway may produce severe effects, which are evident as neurological and psychiatric disorders. On the other hand, administration of mTOR inhibitors may be beneficial for a variety of neuropsychiatric alterations encompassing neurodegeneration, brain tumors, brain ischemia, epilepsy, autism, mood disorders, drugs of abuse, and schizophrenia. mTOR has been widely implicated in synaptic plasticity and autophagy activation. This review addresses the role of mTOR-dependent autophagy dysfunction in a variety of neuropsychiatric disorders, to focus mainly on psychiatric syndromes including schizophrenia and drug addiction. For instance, amphetamines-induced addiction fairly overlaps with some neuropsychiatric disorders including neurodegeneration and schizophrenia. For this reason, in the present review, a special emphasis is placed on the role of mTOR on methamphetamine-induced brain alterations.

Lithium promotes recovery of neurological function after spinal cord injury by inducing autophagy

Lithium promotes autophagy and has a neuroprotective effect on spinal cord injury (SCI); however, the underlying mechanisms remain unclear. Therefore, in this study, we investigated the effects of lithium and the autophagy inhibitor 3-methyladenine (3-MA) in a rat model of SCI. The rats were randomly assigned to the SCI, lithium, 3-MA and sham groups. In the 3-MA group, rats were intraperitoneally injected with 3-MA (3 mg/kg) 2 hours before SCI. In the lithium and 3-MA groups, rats were intraperitoneally injected with lithium (LiCl; 30 mg/kg) 6 hours after SCI and thereafter once daily until sacrifice. At 2, 3 and 4 weeks after SCI, neurological function and diffusion tensor imaging indicators were remarkably improved in the lithium group compared with the SCI and 3-MA groups. The Basso, Beattie and Bresnahan locomotor rating scale score and fractional anisotropy values were increased, and the apparent diffusion coefficient value was decreased. Immunohistochemical staining showed that immunoreactivities for Beclin-1 and light-chain 3B peaked 1 day after SCI in the lithium and SCI groups. Immunoreactivities for Beclin-1 and light-chain 3B were weaker in the 3-MA group than in the SCI group, indicating that 3-MA inhibits lithium-induced autophagy. Furthermore, NeuN⁺ neurons were more numerous in the lithium group than in the SCI and 3-MA groups, with the fewest in the latter. Our findings show that lithium reduces neuronal damage after acute SCI and promotes neurological recovery by inducing autophagy. The neuroprotective mechanism of action may not be entirely dependent on the enhancement of autophagy, and furthermore, 3-MA might not completely inhibit all autophagy pathways.

Autophagy and Its Impact on Neurodegenerative Diseases: New Roles for TDP-43 and C9orf72

Autophagy is a catabolic mechanism where intracellular material is degraded by vesicular structures called autophagolysosomes. Autophagy is necessary to maintain the normal function of the central nervous system (CNS), avoiding the accumulation of misfolded and aggregated proteins. Consistently, impaired autophagy has been associated with the pathogenesis of various neurodegenerative diseases. The proteins TAR DNA-binding protein-43 (TDP-43), which regulates RNA processing at different levels, and chromosome 9 open reading frame 72 (C9orf72), probably involved in membrane trafficking, are crucial in the development of neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS) and Frontotemporal Lobar Degeneration (FTLD). Additionally, recent studies have identified a role for these proteins in the control of autophagy. In this manuscript, we review what is known regarding the autophagic mechanism and discuss the involvement of TDP-43 and C9orf72 in autophagy and their impact on neurodegenerative diseases.

Protein Quality Control and the Amyotrophic Lateral Sclerosis/Frontotemporal Dementia Continuum

Protein homeostasis, or proteostasis, has an important regulatory role in cellular function. Protein quality control mechanisms, including protein folding and protein degradation processes, have a crucial function in post-mitotic neurons. Cellular protein quality control relies on multiple strategies, including molecular chaperones, autophagy, the ubiquitin proteasome system, endoplasmic reticulum (ER)-associated degradation (ERAD) and the formation of stress granules (SGs), to regulate proteostasis. Neurodegenerative diseases are characterized by the presence of misfolded protein aggregates, implying that protein quality control mechanisms are dysfunctional in these conditions. Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative diseases that are now recognized to overlap clinically and pathologically, forming a continuous disease spectrum. In this review article, we detail the evidence for dysregulation of protein quality control mechanisms across the whole ALS-FTD continuum, by discussing the major proteins implicated in ALS and/or FTD. We also discuss possible ways in which protein quality mechanisms could be targeted therapeutically in these disorders and highlight promising protein quality control-based therapeutics for clinical trials.

Lithium protects dopaminergic cells from rotenone toxicity via autophagy enhancement

Background

Previous studies have indicated that enhancement of autophagy lysosome pathway may be beneficial for Parkinson’s disease (PD), in which aberrant accumulation of aggregated/misfolded proteins and mitochondrial dysfunction are considered as crucial pathogenesis. Recently, a number of studies have suggested the neuroprotective effects of lithium in models of several neurodegenerative diseases including PD. However, the exact mechanisms underlying this neuroprotection remain unclear. In our study, rotenone-exposed SH-SY5Y cells were used as an in vitro parkinsonian model to assess the autophagy-enhancing effect of lithium and the underlying mechanisms were further investigated.

Results

Similar to the common used autophagy enhancer rapamycin (Rap, 0.2 μM), lithium (LiCl, 10 mM) significantly recovered the shrinkage of SH-SY5Y cells, and alleviated rotenone-induced cell apoptosis, mitochondrial membrane potential reduction and reactive oxygen species accumulation. Furthermore, the protective effects induced by LiCl were partially blocked by the co-treatment of autophagy inhibitors such as 3-methyladenine (3-MA, 10 mM) or chloroquine (CHL, 10 μM). Moreover, 3-MA or Chl suppressed LiCl-induced autophagy in the immunoblot assay. In addition, the co-localization of LC3 and mitochondria and the preservation of mitochondrial function within LiCl-treated cells were observed, confirming that the damaged mitochondria were cleared through autophagy (mitophagy).

Conclusions

These findings suggested that lithium exerted neuroprotection against rotenone-induced injuries partially through the autophagy pathway. Pharmacologically induction of autophagy by lithium may represent a novel therapeutic strategy as a disease-modifier in PD.

Compartment-dependent mitochondrial alterations in experimental ALS, the effects of mitophagy and mitochondriogenesis

Amyotrophic lateral sclerosis (ALS) is characterized by massive loss of motor neurons. Data from ALS patients and experimental models indicate that mitochondria are severely damaged within dying or spared motor neurons. Nonetheless, recent data indicate that mitochondrial preservation, although preventing motor neuron loss, fails to prolong lifespan. On the other hand, the damage to motor axons plays a pivotal role in determining both lethality and disease course. Thus, in the present article each motor neuron compartment (cell body, central, and peripheral axons) of G93A SOD-1 mice was studied concerning mitochondrial alterations as well as other intracellular structures. We could confirm the occurrence of ALS-related mitochondrial damage encompassing total swelling, matrix dilution and cristae derangement along with non-pathological variations of mitochondrial size and number. However, these alterations occur to a different extent depending on motor neuron compartment. Lithium, a well-known autophagy inducer, prevents most pathological changes. However, the efficacy of lithium varies depending on which motor neuron compartment is considered. Remarkably, some effects of lithium are also evident in wild type mice. Lithium is effective also in vitro, both in cell lines and primary cell cultures from the ventral spinal cord. In these latter cells autophagy inhibition within motor neurons in vitro reproduced ALS pathology which was reversed by lithium. Muscle and glial cells were analyzed as well. Cell pathology was mostly severe within peripheral axons and muscles of ALS mice. Remarkably, when analyzing motor axons of ALS mice a subtotal clogging of axoplasm was described for the first time, which was modified under the effects of lithium. The effects induced by lithium depend on several mechanisms such as direct mitochondrial protection, induction of mitophagy and mitochondriogenesis. In this study, mitochondriogenesis induced by lithium was confirmed in situ by a novel approach using [2-³H]-adenosine.

Impairment of the autophagic flux in astrocytes intoxicated by trimethyltin

Autophagy is a lysosomal catabolic route for protein aggregates and damaged organelles which in different stress conditions, such as starvation, generally improves cell survival. An impairment of this degradation pathway has been reported to occur in many neurodegenerative processes. Trimethyltin (TMT) is a potent neurotoxin present as an environmental contaminant causing tremors, seizures and learning impairment in intoxicated subjects. The present data show that in rat primary astrocytes autophagic vesicles (AVs) appeared after few hours of TMT treatment. The analysis of the autophagic flux in TMT-treated astrocytes was consistent with a block of the late stages of autophagy and was accompanied by a progressive accumulation of the microtubule associated protein light chain 3 (LC3) and of p62/SQSTM1. Interestingly, an increased immunoreactivity for p62/SQSTM1 was also observed in hippocampal astrocytes detected in brain slices of TMT-intoxicated rats. The time-lapse recordings of AVs in EGFP-mCherry-LC3B transfected astrocytes demonstrated a reduced mobility of autophagosomes after TMT exposure respect to control cells. The observed block of the autophagic flux cannot be overcome by known autophagy inducers such as rapamycin or 0.5mM lithium. Although ineffective when used at 0.5mM, lithium at higher concentrations (2mM) was able to protect astrocyte cultures from TMT toxicity. This effect correlated well with its ability to determine the phosphorylation/inactivation of glycogen kinase synthase-3β (GSK-3β).

Ultrastructural studies of ALS mitochondria connect altered function and permeability with defects of mitophagy and mitochondriogenesis

The key role of mitochondria in patients affected by amyotrophic lateral sclerosis (ALS) is well documented by electron microscopy studies of motor neurons within spinal cord and brainstem. Nonetheless, recent studies challenged the role of mitochondria placed within the cell body of motor neuron. In fact, it was demonstrated that, despite preservation of mitochondria placed within this compartment, there is no increase in the lifespan of transgenic mouse models of ALS. Thus, the present mini-review comments on morphological findings of mitochondrial alterations in ALS patients in connection with novel findings about mitochondrial dynamics within various compartments of motor neurons. The latter issue was recently investigated in relationship with altered calcium homeostasis and autophagy, which affect mitochondria in ALS. In fact, it was recently indicated that a pathological mitophagy, mitochondriogenesis and calcium homeostasis produce different ultrastructural effects within specific regions of motor neurons. This might explain why specific compartments of motor neurons possess different thresholds to mitochondrial damage. In particular, it appears that motor axons represent the most sensitive compartment which undergoes the earliest and most severe alterations in the course of ALS. It is now evident that altered calcium buffering is compartment-dependent, as well as mitophagy and mitochondriogenesis. On the other hand, mitochondrial homeostasis strongly relies on calcium handling, the removal of altered mitochondria through the autophagy flux (mitophagy) and the biogenesis of novel mitochondria (mitochondriogenesis). Thus, recent findings related to altered calcium storage and impaired autophagy flux in ALS may help to understand the occurrence of mitochondrial alterations as a hallmark in ALS patients. At the same time, the compartmentalization of such dysfunctions may be explained considering the compartments of calcium dynamics and autophagy flux within motor neurons.

Notch pathway is activated in cell culture and mouse models of mutant SOD1-related familial amyotrophic lateral sclerosis, with suppression of its activation as an additional mechanism of neuroprotection for lithium and valproate

Amyotrophic lateral sclerosis (ALS) is an idiopathic and lethal neurodegenerative disease that currently has no effective treatment. A recent study found that the Notch signaling pathway was up-regulated in a TAR DNA-binding protein-43 (TDP-43) Drosophila model of ALS. Notch signaling acts as a master regulator in the central nervous system. However, the mechanisms by which Notch participates in the pathogenesis of ALS have not been completely elucidated. Recent studies have shown that the mood stabilizers lithium and valproic acid (VPA) are able to regulate Notch signaling. Our study sought to confirm the relationship between the Notch pathway and ALS and whether the Notch pathway contributes to the neuroprotective effects of lithium and VPA in ALS. We found that the Notch pathway was activated in in vitro and in vivo models of ALS, and suppression of Notch activation with a Notch signaling inhibitor, N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) and Notch1 siRNA significantly reduced neuronal apoptotic signaling, as evidenced by the up-regulation of Bcl-2 as well as the down-regulation of Bax and cytochrome c. We also found that lithium and VPA suppressed the Notch activation associated with the superoxide dismutase-1 (SOD1) mutation, and the combination of lithium and VPA produced a more robust effect than either agent alone. Our findings indicate that the Notch pathway plays a critical role in ALS, and the neuroprotective effects of lithium and VPA against mutant SOD1-mediated neuronal damage are at least partially dependent on their suppression of Notch activation.

Autophagy and neurodegenerative disorders

Accumulation of aberrant proteins and inclusion bodies are hallmarks in most neurodegenerative diseases. Consequently, these aggregates within neurons lead to toxic effects, overproduction of reactive oxygen species and oxidative stress. Autophagy is a significant intracellular mechanism that removes damaged organelles and misfolded proteins in order to maintain cell homeostasis. Excessive or insufficient autophagic activity in neurons leads to altered homeostasis and influences their survival rate, causing neurodegeneration. The review article provides an update of the role of autophagic process in representative chronic and acute neurodegenerative disorders.

Inclusion body myositis

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of rare disorders that share many similarities. In addition to sporadic inclusion body myositis (IBM), these include dermatomyositis, polymyositis, and autoimmune necrotizing myopathy. IBM is the most common IIM after age 50 years. Muscle histopathology shows endomysial inflammatory exudates surrounding and invading nonnecrotic muscle fibers often accompanied by rimmed vacuoles and protein deposits. It is likely that IBM is has a prominent degenerative component. This article reviews the evolution of knowledge in IBM, with emphasis on recent developments in the field, and discusses ongoing clinical trials.

Microglia centered pathogenesis in ALS: insights in cell interconnectivity

Amyotrophic lateral sclerosis (ALS) is the most common and most aggressive form of adult motor neuron (MN) degeneration. The cause of the disease is still unknown, but some protein mutations have been linked to the pathological process. Loss of upper and lower MNs results in progressive muscle paralysis and ultimately death due to respiratory failure. Although initially thought to derive from the selective loss of MNs, the pathogenic concept of non-cell-autonomous disease has come to the forefront for the contribution of glial cells in ALS, in particular microglia. Recent studies suggest that microglia may have a protective effect on MN in an early stage. Conversely, activated microglia contribute and enhance MN death by secreting neurotoxic factors, and impaired microglial function at the end-stage may instead accelerate disease progression. However, the nature of microglial–neuronal interactions that lead to MN degeneration remains elusive. We review the contribution of the neurodegenerative network in ALS pathology, with a special focus on each glial cell type from data obtained in the transgenic SOD1G93A rodents, the most widely used model. We further discuss the diverse roles of neuroinflammation and microglia phenotypes in the modulation of ALS pathology. We provide information on the processes associated with dysfunctional cell–cell communication and summarize findings on pathological cross-talk between neurons and astroglia, and neurons and microglia, as well as on the spread of pathogenic factors. We also highlight the relevance of neurovascular disruption and exosome trafficking to ALS pathology. The harmful and beneficial influences of NG2 cells, oligodendrocytes and Schwann cells will be discussed as well. Insights into the complex intercellular perturbations underlying ALS, including target identification, will enhance our efforts to develop effective therapeutic approaches for preventing or reversing symptomatic progression of this devastating disease.

Plastic changes in the spinal cord in motor neuron disease

In the present paper, we analyze the cell number within lamina X at the end stage of disease in a G93A mouse model of ALS; the effects induced by lithium; the stem-cell like phenotype of lamina X cells during ALS; the differentiation of these cells towards either a glial or neuronal phenotype. In summary we found that G93A mouse model of ALS produces an increase in lamina X cells which is further augmented by lithium administration. In the absence of lithium these nestin positive stem-like cells preferentially differentiate into glia (GFAP positive), while in the presence of lithium these cells differentiate towards a neuron-like phenotype (βIII-tubulin, NeuN, and calbindin-D28K positive). These effects of lithium are observed concomitantly with attenuation in disease progression and are reminiscent of neurogenetic effects induced by lithium in the subependymal ventricular zone of the hippocampus.

Reduced Renshaw recurrent inhibition after neonatal sciatic nerve crush in rats

Renshaw recurrent inhibition (RI) plays an important gated role in spinal motion circuit. Peripheral nerve injury is a common disease in clinic. Our current research was designed to investigate the change of the recurrent inhibitory function in the spinal cord after the peripheral nerve crush injury in neonatal rat. Sciatic nerve crush was performed on 5-day-old rat puppies and the recurrent inhibition between lateral gastrocnemius-soleus (LG-S) and medial gastrocnemius (MG) motor pools was assessed by conditioning monosynaptic reflexes (MSR) elicited from the sectioned dorsal roots and recorded either from the LG-S and MG nerves by antidromic stimulation of the synergist muscle nerve. Our results demonstrated that the MSR recorded from both LG-S or MG nerves had larger amplitude and longer latency after neonatal sciatic nerve crush. The RI in both LG-S and MG motoneuron pools was significantly reduced to virtual loss (15-20% of the normal RI size) even after a long recovery period upto 30 weeks after nerve crush. Further, the degree of the RI reduction after tibial nerve crush was much less than that after sciatic nerve crush indicatig that the neuron-muscle disconnection time is vital to the recovery of the spinal neuronal circuit function during reinnervation. In addition, sciatic nerve crush injury did not cause any spinal motor neuron loss but severally damaged peripheral muscle structure and function. In conclusion, our results suggest that peripheral nerve injury during neonatal early development period would cause a more sever spinal cord inhibitory circuit damage, particularly to the Renshaw recurrent inhibition pathway, which might be the target of neuroregeneration therapy.

Oxidative stress and autophagic alteration in brainstem of SOD1-G93A mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease involving both upper and lower motor neurons. The mechanism of motor neuron degeneration is still unknown. Although many studies have been performed on spinal motor neurons, few have been reported on brainstem and its motor nuclei. The aim of this study was to investigate oxidative stress and autophagic changes in the brainstem and representative motor nuclei of superoxide dismutase 1 (SOD1)-G93A mouse model of ALS. The expression levels of cluster of differentiation molecule 11b (CD11b), glial fibrillary acidic protein, glutamate-cysteine ligase catalytic subunit, heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, voltage-dependent anion-selective channel protein 1, Sequestosome 1/p62 (p62), microtubule-associated protein 1 light chain 3B (LC3), and SOD1 proteins in brainstem were examined by Western blot analysis. Immunohistochemistry and immunofluorescence were performed to identify the cellular localization of SOD1, p62, and LC3B, respectively. The results showed that there were progressive asctrocytic proliferation and microglial activation, induction of antioxidant proteins, and increased p62 and LC3II expression in brainstem of SOD1-G93A mice. Additionally, SOD1 and p62 accumulated in hypoglossal, facial, and red nuclei, but not in oculomotor nucleus. Furthermore, electron microscope showed increased autophagic vacuoles in affected brainstem motor nuclei. Our results indicate that brainstem share similar gliosis, oxidative stress, and autophagic changes as the spinal cord in SOD1-G93A mice. Thus, SOD1 accumulation in astrocytes and neurons, oxidative stress, and altered autophagy are involved in motor neuron degeneration in the brainstem, similar to the motor neurons in spinal cord. Therefore, therapeutic trials in the SOD1G93A mice need to target the brainstem in addition to the spinal cord.

Spinal inhibitory circuits and their role in motor neuron degeneration

In the spinal cord neuronal activity is controlled by the balance between excitatory and inhibitory neurotransmission, mediated mainly by the neurotransmitters glutamate and GABA/glycine, respectively. Alterations of this equilibrium have been associated with spinal motor neuron hyperexcitability and degeneration, which can be induced by excitotoxicity or by decreasing inhibitory neurotransmission. Here we review the ventral horn neuronal network and the possible involvement of inhibitory circuits in the mechanisms of degeneration of motor neurons characteristic of amyotrophic lateral sclerosis (ALS). Whereas glutamate mediated excitotoxicity seems to be an important factor, recent experimental and histopathological evidence argue in favor of a decreased activity of the inhibitory circuits controlling motor neuron excitability, mainly the recurrent inhibition exerted by Renshaw cells. A decreased Renshaw cell activity may be caused by cell loss or by a reduction of its inhibitory action secondary to a decreased excitation from cholinergic interneurons. Ultimately, inhibitory failure by either mechanism might lead to motor neuron degeneration, and this suggests inhibitory circuits and Renshaw cells as pharmacologic targets for ALS treatment.

Inclusion body myositis

Sporadic inclusion body myositis (IBM) is the most common idiopathic inflammatory myopathy (IIM) after age 50 years. It presents with chronic insidious proximal leg and distal arm asymmetric muscle weakness. Despite similarities with polymyositis (PM), it is likely that IBM is primarily a degenerative disorder rather than inflammatory muscle disease. IBM is associated with a modest degree of creatine kinase (CK) elevation and an electromyogram (EMG) demonstrates a chronic irritative myopathy. Muscle histopathology demonstrates endomysial inflammatory exudates surrounding and invading non-necrotic muscle fibers often times accompanied by rimmed vacuoles. We review IBM with emphasis on recent developments in the field and discuss ongoing clinical trials.

Alterations in the motor neuron-renshaw cell circuit in the Sod1(G93A) mouse model

Motor neurons become hyperexcitable during progression of amyotrophic lateral sclerosis (ALS). This abnormal firing behavior has been explained by changes in their membrane properties, but more recently it has been suggested that changes in premotor circuits may also contribute to this abnormal activity. The specific circuits that may be altered during development of ALS have not been investigated. Here we examined the Renshaw cell recurrent circuit that exerts inhibitory feedback control on motor neuron firing. Using two markers for Renshaw cells (calbindin and cholinergic nicotinic receptor subunit alpha2 [Chrna2]), two general markers for motor neurons (NeuN and vesicular acethylcholine transporter [VAChT]), and two markers for fast motor neurons (Chondrolectin and calcitonin-related polypeptide alpha [Calca]), we analyzed the survival and connectivity of these cells during disease progression in the Sod1(G93A) mouse model. Most calbindin-immunoreactive (IR) Renshaw cells survive to end stage but downregulate postsynaptic Chrna2 in presymptomatic animals. In motor neurons, some markers are downregulated early (NeuN, VAChT, Chondrolectin) and others at end stage (Calca). Early downregulation of presynaptic VAChT and Chrna2 was correlated with disconnection from Renshaw cells as well as major structural abnormalities of motor axon synapses inside the spinal cord. Renshaw cell synapses on motor neurons underwent more complex changes, including transitional sprouting preferentially over remaining NeuN-IR motor neurons. We conclude that the loss of presynaptic motor axon input on Renshaw cells occurs at early stages of ALS and disconnects the recurrent inhibitory circuit, presumably resulting in diminished control of motor neuron firing. J. Comp. Neurol. 521:1449-1469, 2013. © 2012 Wiley Periodicals, Inc.

Differentiation of CD133+ stem cells from amyotrophic lateral sclerosis patients into preneuron cells

Improvements in quality of life and life expectancy have been observed in amyotrophic lateral sclerosis (ALS) patients transplanted with CD133(+) stem cells into their frontal motor cortices. However, questions have emerged about the capacity of cells from these patients to engraft and differentiate into neurons. The objective of this work was to evaluate the in vitro capacity of CD133(+) stem cells from 13 ALS patients to differentiate into neuron lineage. Stem cells were obtained through leukapheresis and cultured in a control medium or a neuroinduction medium for 2-48 hours. Expression of neuronal genes was analyzed by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical techniques. Fluorescence microscopy demonstrated that CD133(+) stem cells from ALS patients incubated for 48 hours in a neuroinduction medium increased the detection of neuronal proteins such as nestin, β-tubulin III, neuronal-specific enolase, and glial fibrillary acidic protein. RT-PCR assays demonstrated an increase in the expression of β-tubulin III, nestin, Olig2, Islet-1, Hb9, and Nkx6.1. No correlation was found between age, sex, or ALS functional scale and the CD133(+) stem cell response to the neuroinduction medium. We conclude that CD133(+) stem cells from ALS patients, like the stem cells of healthy subjects, are capable of differentiating into preneuron cells.

Mutation in TECPR2 reveals a role for autophagy in hereditary spastic paraparesis

We studied five individuals from three Jewish Bukharian families affected by an apparently autosomal-recessive form of hereditary spastic paraparesis accompanied by severe intellectual disability, fluctuating central hypoventilation, gastresophageal reflux disease, wake apnea, areflexia, and unique dysmorphic features. Exome sequencing identified one homozygous variant shared among all affected individuals and absent in controls: a 1 bp frameshift TECPR2 deletion leading to a premature stop codon and predicting significant degradation of the protein. TECPR2 has been reported as a positive regulator of autophagy. We thus examined the autophagy-related fate of two key autophagic proteins, SQSTM1 (p62) and MAP1LC3B (LC3), in skin fibroblasts of an affected individual, as compared to a healthy control, and found that both protein levels were decreased and that there was a more pronounced decrease in the lipidated form of LC3 (LC3II). siRNA knockdown of TECPR2 showed similar changes, consistent with aberrant autophagy. Our results are strengthened by the fact that autophagy dysfunction has been implicated in a number of other neurodegenerative diseases. The discovered TECPR2 mutation implicates autophagy, a central intracellular mechanism, in spastic paraparesis.

Autophagy and neuronal cell death in neurological disorders

Autophagy is implicated in the pathogenesis of major neurodegenerative disorders although concepts about how it influences these diseases are still evolving. Once proposed to be mainly an alternative cell death pathway, autophagy is now widely viewed as both a vital homeostatic mechanism in healthy cells and as an important cytoprotective response mobilized in the face of aging- and disease-related metabolic challenges. In Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, and other diseases, impairment at different stages of autophagy leads to the buildup of pathogenic proteins and damaged organelles, while defeating autophagy's crucial prosurvival and antiapoptotic effects on neurons. The differences in the location of defects within the autophagy pathway and their molecular basis influence the pattern and pace of neuronal cell death in the various neurological disorders. Future therapeutic strategies for these disorders will be guided in part by understanding the manifold impact of autophagy disruption on neurodegenerative diseases.

Clinical recognition and management of amyotrophic lateral sclerosis: the nurse's role

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, causes a progressive wasting and loss of the upper and lower motor neurons that facilitate the movement of body parts. At onset, ALS patients may show symptoms such as muscle weakness, atrophy, hyperreflexia, or bulbar symptoms such as dysphagia or dysarthria. Deterioration progresses rapidly, and the later stages of ALS are characterized by severely limited mobility and respiratory failure, which is the primary cause of death. There is no specific diagnostic test for ALS, and there are a number of other conditions that may resemble ALS, making a diagnosis difficult. The variability of the initial presentation combined with the broad differential diagnosis may result in significant delays in diagnosis or, in some cases, misdiagnosis, which in turn have a negative impact on patient outcomes. There is no cure for ALS; however, many of the symptoms are treatable, and the physical and psychological symptoms are best managed through the efforts of a coordinated, multidisciplinary team. Nurses play a critical role in the clinical management of ALS and may be involved in coordinating the activities of the team, facilitating treatment, and helping patients and caregivers in making informed treatment and end-of-life decisions. Drug therapy for ALS is currently limited to riluzole; however, patients may be treated with a number of nonpharmacologic methods on the basis of their symptoms. A number of other treatment modalities, such as stem-cell-based therapy or gene therapy, and an array of neuroprotective clinical trials are currently under development for the treatment of ALS. Nurses may also have a key role in these various ALS studies.

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.