Celecoxib increases SMN and survival in a severe spinal muscular atrophy mouse model via p38 pathway activation

IL-1ra and CCL5, but not IL-10, are promising targets for treating SMA astrocyte-driven pathology

Spinal muscular atrophy (SMA) is a pediatric genetic disorder characterized by the loss of spinal cord motor neurons (MNs). Although the mechanisms underlying MN loss are not clear, current data suggest that glial cells contribute to disease pathology. We have previously found that SMA astrocytes drive microglial activation and MN loss potentially through the upregulation of NF-κB-mediated pro-inflammatory cytokines. In this study, we tested the ability of neutralizing C-C motif chemokine ligand 5 (CCL5) while increasing either interleukin-10 (IL-10) or IL-1 receptor antagonist (IL-1ra) to reduce the pro-inflammatory phenotype of SMA astrocytes. While IL-10 was ineffective, IL-1ra ameliorated SMA astrocyte-driven glial activation and MN loss in induced pluripotent stem cell-derived cultures in vitro. In vivo AAV5 delivered IL-1ra overexpression, and miR-30 small hairpin RNA knockdown of CCL5 made modest but significant improvements in lifespan, weight gain, MN number, and motor function of SMNΔ7 mice. These data identify IL-1ra and CCL5 as possible therapeutic targets for SMA and highlight the importance of glial-targeted therapeutics for neurodegenerative disease.

Recent Progress in Gene-Targeting Therapies for Spinal Muscular Atrophy: Promises and Challenges

Spinal muscular atrophy (SMA) is a severe genetic disorder characterized by the loss of motor neurons, leading to progressive muscle weakness, loss of mobility, and respiratory complications. In its most severe forms, SMA can result in death within the first two years of life if untreated. The condition arises from mutations in the SMN1 (survival of motor neuron 1) gene, causing a deficiency in the survival motor neuron (SMN) protein. Humans possess a near-identical gene, SMN2, which modifies disease severity and is a primary target for therapies. Recent therapeutic advancements include antisense oligonucleotides (ASOs), small molecules targeting SMN2, and virus-mediated gene replacement therapy delivering a functional copy of SMN1. Additionally, recognizing SMA's broader phenotype involving multiple organs has led to the development of SMN-independent therapies. Evidence now indicates that SMA affects multiple organ systems, suggesting the need for SMN-independent treatments along with SMN-targeting therapies. No single therapy can cure SMA; thus, combination therapies may be essential for comprehensive treatment. This review addresses the SMA etiology, the role of SMN, and provides an overview of the rapidly evolving therapeutic landscape, highlighting current achievements and future directions.

Celecoxib attenuates hindlimb unloading-induced muscle atrophy via suppressing inflammation, oxidative stress and ER stress by inhibiting STAT3

Improving inflammation may serve as useful therapeutic interventions for the hindlimb unloading-induced disuse muscle atrophy. Celecoxib is a selective non-steroidal anti-inflammatory drug. We aimed to determine the role and mechanism of celecoxib in hindlimb unloading-induced disuse muscle atrophy. Celecoxib significantly attenuated the decrease in soleus muscle mass, hindlimb muscle function and the shift from slow- to fast-twitch muscle fibers caused by hindlimb unloading in rats. Importantly, celecoxib inhibited the increased expression of inflammatory factors, macrophage infiltration in damaged soleus muscle. Mechanistically, Celecoxib could significantly reduce oxidative stress and endoplasmic reticulum stress in soleus muscle of unloaded rats. Furthermore, celecoxib inhibited muscle proteolysis by reducing the levels of MAFbx, MuRF1, and autophagy related proteins maybe by inhibiting the activation of pro-inflammatory STAT3 pathway in vivo and in vitro. This study is the first to demonstrate that celecoxib can attenuate disuse muscle atrophy caused by hindlimb unloading via suppressing inflammation, oxidative stress and endoplasmic reticulum stress probably, improving target muscle function and reversing the shift of muscle fiber types by inhibiting STAT3 pathways-mediated inflammatory cascade. This study not only enriches the potential molecular regulatory mechanisms, but also provides new potential therapeutic targets for disuse muscle atrophy.

A transcriptomics-based drug repositioning approach to identify drugs with similar activities for the treatment of muscle pathologies in spinal muscular atrophy (SMA) models

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder caused by the reduction of survival of motor neuron (SMN) protein levels. Although three SMN-augmentation therapies are clinically approved that significantly slow down disease progression, they are unfortunately not cures. Thus, complementary SMN-independent therapies that can target key SMA pathologies and that can support the clinically approved SMN-dependent drugs are the forefront of therapeutic development. We have previously demonstrated that prednisolone, a synthetic glucocorticoid (GC) improved muscle health and survival in severe Smn-/-;SMN2 and intermediate Smn2B/- SMA mice. However, long-term administration of prednisolone can promote myopathy. We thus wanted to identify genes and pathways targeted by prednisolone in skeletal muscle to discover clinically approved drugs that are predicted to emulate prednisolone's activities. Using an RNA-sequencing, bioinformatics, and drug repositioning pipeline on skeletal muscle from symptomatic prednisolone-treated and untreated Smn-/-; SMN2 SMA and Smn+/-; SMN2 healthy mice, we identified molecular targets linked to prednisolone's ameliorative effects and a list of 580 drug candidates with similar predicted activities. Two of these candidates, metformin and oxandrolone, were further investigated in SMA cellular and animal models, which highlighted that these compounds do not have the same ameliorative effects on SMA phenotypes as prednisolone; however, a number of other important drug targets remain. Overall, our work further supports the usefulness of prednisolone's potential as a second-generation therapy for SMA, identifies a list of potential SMA drug treatments and highlights improvements for future transcriptomic-based drug repositioning studies in SMA.

Potential Therapeutic Strategies for Skeletal Muscle Atrophy

The maintenance of muscle homeostasis is vital for life and health. Skeletal muscle atrophy not only seriously reduces people's quality of life and increases morbidity and mortality, but also causes a huge socioeconomic burden. To date, no effective treatment has been developed for skeletal muscle atrophy owing to an incomplete understanding of its molecular mechanisms. Exercise therapy is the most effective treatment for skeletal muscle atrophy. Unfortunately, it is not suitable for all patients, such as fractured patients and bedridden patients with nerve damage. Therefore, understanding the molecular mechanism of skeletal muscle atrophy is crucial for developing new therapies for skeletal muscle atrophy. In this review, PubMed was systematically screened for articles that appeared in the past 5 years about potential therapeutic strategies for skeletal muscle atrophy. Herein, we summarize the roles of inflammation, oxidative stress, ubiquitin-proteasome system, autophagic-lysosomal pathway, caspases, and calpains in skeletal muscle atrophy and systematically expound the potential drug targets and therapeutic progress against skeletal muscle atrophy. This review focuses on current treatments and strategies for skeletal muscle atrophy, including drug treatment (active substances of traditional Chinese medicine, chemical drugs, antioxidants, enzyme and enzyme inhibitors, hormone drugs, etc.), gene therapy, stem cell and exosome therapy (muscle-derived stem cells, non-myogenic stem cells, and exosomes), cytokine therapy, physical therapy (electroacupuncture, electrical stimulation, optogenetic technology, heat therapy, and low-level laser therapy), nutrition support (protein, essential amino acids, creatine, β-hydroxy-β-methylbutyrate, and vitamin D), and other therapies (biomaterial adjuvant therapy, intestinal microbial regulation, and oxygen supplementation). Considering many treatments have been developed for skeletal muscle atrophy, we propose a combination of proper treatments for individual needs, which may yield better treatment outcomes.

NSC Physiological Features in Spinal Muscular Atrophy: SMN Deficiency Effects on Neurogenesis

While the U.S. Food and Drug Administration and the European Medicines Evaluation Agency have recently approved new drugs to treat spinal muscular atrophy 1 (SMA1) in young patients, they are mostly ineffective in older patients since many motor neurons have already been lost. Therefore, understanding nervous system (NS) physiology in SMA patients is essential. Consequently, studying neural stem cells (NSCs) from SMA patients is of significant interest in searching for new treatment targets that will enable researchers to identify new pharmacological approaches. However, studying NSCs in these patients is challenging since their isolation damages the NS, making it impossible with living patients. Nevertheless, it is possible to study NSCs from animal models or create them by differentiating induced pluripotent stem cells obtained from SMA patient peripheral tissues. On the other hand, therapeutic interventions such as NSCs transplantation could ameliorate SMA condition. This review summarizes current knowledge on the physiological properties of NSCs from animals and human cellular models with an SMA background converging on the molecular and neuronal circuit formation alterations of SMA fetuses and is not focused on the treatment of SMA. By understanding how SMA alters NSC physiology, we can identify new and promising interventions that could help support affected patients.

Mitochondrial Dysfunction in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by recessive mutations in the SMN1 gene, globally affecting ~8-14 newborns per 100,000. The severity of the disease depends on the residual levels of functional survival of motor neuron protein, SMN. SMN is a ubiquitously expressed RNA binding protein involved in a plethora of cellular processes. In this review, we discuss the effects of SMN loss on mitochondrial functions in the neuronal and muscular systems that are the most affected in patients with spinal muscular atrophy. Our aim is to highlight how mitochondrial defects may contribute to disease progression and how restoring mitochondrial functionality may be a promising approach to develop new therapies. We also collected from previous studies a list of transcripts encoding mitochondrial proteins affected in various SMA models. Moreover, we speculate that in adulthood, when motor neurons require only very low SMN levels, the natural deterioration of mitochondria associated with aging may be a crucial triggering factor for adult spinal muscular atrophy, and this requires particular attention for therapeutic strategies.

Celecoxib alleviates denervation-induced muscle atrophy by suppressing inflammation and oxidative stress and improving microcirculation

The molecular mechanism underlying denervation-induced muscle atrophy is complex and incompletely understood. Our previous results suggested that inflammation may play an important role in the early stages of muscle atrophy. Celecoxib is reported to exert anti-inflammatory effects. Here, we explored the effect of celecoxib on denervation-induced muscle atrophy and sought to identify the mechanism involved. We found that celecoxib treatment significantly increased the wet weight ratio and CSA of the tibialisanteriormuscle. Additionally, celecoxib downregulated the levels of COX-2, inflammatory factors and reduced inflammatory cell infiltration. GO and KEGG pathway enrichment analysis indicated that after 3 days of celecoxib treatment in vivo, the differentially expressed genes (DEGs) were mainly associated with the regulation of immune responses related to complement activation; after 14 days, the DEGs were mainly involved in the regulation of oxidative stress and inflammation-related responses. Celecoxib administration reduced the levels of ROS and oxidative stress-related proteins. Furthermore, we found that celecoxib treatment inhibited the denervation-induced up-regulation of the ubiquitin-proteasome and autophagy-lysosomal systems related proteins; decreased mitophagy in target muscles; and increased levels of MHC. Finally, celecoxib also attenuated microvascular damage in denervated skeletal muscle. Combined, our findings demonstrated that celecoxib inhibits inflammation and oxidative stress in denervated skeletal muscle, thereby suppressing mitophagy and proteolysis, improving blood flow in target muscles, and, ultimately, alleviating denervation-induced muscle atrophy. Our results confirmed that inflammatory responses play a key role in denervation-induced muscle atrophy and highlight a novel strategy for the prevention and treatment of this condition.

Identification of specific gene methylation patterns during motor neuron differentiation from spinal muscular atrophy patient-derived iPSC

Spinal muscular atrophy is a progressive motor neuron disorder caused by deletions or point mutations in the SMN1 gene. It is not known why motor neurons are particularly sensitive to a decrease in SMN protein levels and what factors besides SMN2 underlie the high clinical heterogeneity of the disease. Here we studied the methylation patterns of genes on sequential stages of motor neuron differentiation from induced pluripotent stem cells derived from the patients with SMA type I and II. The genes involved in the regulation of pluripotency, neural differentiation as well as those associated with spinal muscular atrophy development were included. The results show that the PAX6, HB9, CHAT, ARHGAP22, and SMN2 genes are differently methylated in cells derived from SMA patients compared to the cells of healthy individuals. This study clarifies the specificities of the disease pathogenesis and extends the knowledge of pathways involved in the SMA progression.

Targeting the RNA-Binding Protein HuR as Potential Thera-Peutic Approach for Neurological Disorders: Focus on Amyo-Trophic Lateral Sclerosis (ALS), Spinal Muscle Atrophy (SMA) and Multiple Sclerosis

The importance of precise co- and post-transcriptional processing of RNA in the regulation of gene expression has become increasingly clear. RNA-binding proteins (RBPs) are a class of proteins that bind single- or double-chain RNA, with different affinities and selectivity, thus regulating the various functions of RNA and the fate of the cells themselves. ELAV (embryonic lethal/abnormal visual system)/Hu proteins represent an important family of RBPs and play a key role in the fate of newly transcribed mRNA. ELAV proteins bind AU-rich element (ARE)-containing transcripts, which are usually present on the mRNA of proteins such as cytokines, growth factors, and other proteins involved in neuronal differentiation and maintenance. In this review, we focused on a member of ELAV/Hu proteins, HuR, and its role in the development of neurodegenerative disorders, with a particular focus on demyelinating diseases.

Spinal muscular atrophy: From approved therapies to future therapeutic targets for personalized medicine

Spinal muscular atrophy (SMA) is a devastating childhood motor neuron disease that, in the most severe cases and when left untreated, leads to death within the first two years of life. Recent therapeutic advances have given hope to families and patients by compensating for the deficiency in survival motor neuron (SMN) protein via gene therapy or other genetic manipulation. However, it is now apparent that none of these therapies will cure SMA alone. In this review, we discuss the three currently licensed therapies for SMA, briefly highlighting their respective advantages and disadvantages, before considering alternative approaches to increasing SMN protein levels. We then explore recent preclinical research that is identifying and targeting dysregulated pathways secondary to, or independent of, SMN deficiency that may provide adjunctive opportunities for SMA. These additional therapies are likely to be key for the development of treatments that are effective across the lifespan of SMA patients.

Nusinersen, an exon 7 inclusion drug for spinal muscular atrophy: A minireview

Spinal muscular atrophy is an autosomal recessive neuromuscular disease with incidence of 1 in 5000 to 10000 live births and is produced by homozygous deletion of exons 7 and 8 in the SMN1 gene. The SMN1 and SMN2 genes encode the survival motor neuron protein, a crucial protein for the preservation of motor neurons. Use of the newer drug, Nusinersen, from early infancy has shown improvement in clinical outcomes of spinal muscular atrophy patients.

Separating the Wheat from the Chaff: The Use of Upstream Regulator Analysis to Identify True Differential Expression of Single Genes within Transcriptomic Datasets

The development of DNA microarray and RNA-sequencing technology has led to an explosion in the generation of transcriptomic differential expression data under a wide range of biologic systems including those recapitulating the monogenic muscular dystrophies. Data generation has increased exponentially due in large part to new platforms, improved cost-effectiveness, and processing speed. However, reproducibility and thus reliability of data remain a central issue, particularly when resource constraints limit experiments to single replicates. This was observed firsthand in a recent rare disease drug repurposing project involving RNA-seq-based transcriptomic profiling of primary cerebrocortical cultures incubated with clinic-ready blood-brain penetrant drugs. Given the low validation rates obtained for single differential expression genes, alternative approaches to identify with greater confidence genes that were truly differentially expressed in our dataset were explored. Here we outline a method for differential expression data analysis in the context of drug repurposing for rare diseases that incorporates the statistical rigour of the multigene analysis to bring greater predictive power in assessing individual gene modulation. Ingenuity Pathway Analysis upstream regulator analysis was applied to the differentially expressed genes from the Care4Rare Neuron Drug Screen transcriptomic database to identify three distinct signaling networks each perturbed by a different drug and involving a central upstream modulating protein: levothyroxine (DIO3), hydroxyurea (FOXM1), dexamethasone (PPARD). Differential expression of upstream regulator network related genes was next assessed in in vitro and in vivo systems by qPCR, revealing 5× and 10× increases in validation rates, respectively, when compared with our previous experience with individual genes in the dataset not associated with a network. The Ingenuity Pathway Analysis based gene prioritization may increase the predictive value of drug-gene interactions, especially in the context of assessing single-gene modulation in single-replicate experiments.

A high-throughput genome-wide RNAi screen identifies modifiers of survival motor neuron protein

Spinal muscular atrophy (SMA) is a debilitating neurological disorder marked by degeneration of spinal motor neurons and muscle atrophy. SMA results from mutations in survival motor neuron 1 (SMN1), leading to deficiency of survival motor neuron (SMN) protein. Current therapies increase SMN protein and improve patient survival but have variable improvements in motor function, making it necessary to identify complementary strategies to further improve disease outcomes. Here, we perform a genome-wide RNAi screen using a luciferase-based activity reporter and identify genes involved in regulating SMN gene expression, RNA processing, and protein stability. We show that reduced expression of Transcription Export complex components increases SMN levels through the regulation of nuclear/cytoplasmic RNA transport. We also show that the E3 ligase, Neurl2, works cooperatively with Mib1 to ubiquitinate and promote SMN degradation. Together, our screen uncovers pathways through which SMN expression is regulated, potentially revealing additional strategies to treat SMA.

Treatments for spinal muscular atrophy aim to increase survival motor neuron (SMN) protein. Using a genome-wide RNAi screen, McCormack et al. identify modifiers of SMN expression, including genes that are involved in transcription regulation, RNA processing, and protein stability.

AChR β-Subunit mRNAs Are Stabilized by HuR in a Mouse Model of Congenital Myasthenic Syndrome With Acetylcholinesterase Deficiency

Collagen Q (COLQ) is a specific collagen that anchors acetylcholinesterase (AChE) in the synaptic cleft of the neuromuscular junction. So far, no mutation has been identified in the ACHE human gene but over 50 different mutations in the COLQ gene are causative for a congenital myasthenic syndrome (CMS) with AChE deficiency. Mice deficient for COLQ mimic most of the functional deficit observed in CMS patients. At the molecular level, a striking consequence of the absence of COLQ is an increase in the levels of acetylcholine receptor (AChR) mRNAs and proteins in vivo and in vitro in murine skeletal muscle cells. Here, we decipher the mechanisms that drive AChR mRNA upregulation in cultured muscle cells deficient for COLQ. We show that the levels of AChR β-subunit mRNAs are post-transcriptionally regulated by an increase in their stability. We demonstrate that this process results from an activation of p38 MAPK and the cytoplasmic translocation of the nuclear RNA-binding protein human antigen R (HuR) that interacts with the AU-rich element located within AChR β-subunit transcripts. This HuR/AChR transcript interaction induces AChR β-subunit mRNA stabilization and occurs at a specific stage of myogenic differentiation. In addition, pharmacological drugs that modulate p38 activity cause parallel modifications of HuR protein and AChR β-subunit levels. Thus, our study provides new insights into the signaling pathways that are regulated by ColQ-deficiency and highlights for the first time a role for HuR and p38 in mRNA stability in a model of congenital myasthenic syndrome.

Drug Screening and Drug Repositioning as Promising Therapeutic Approaches for Spinal Muscular Atrophy Treatment

Spinal muscular atrophy (SMA) is the most common genetic disease affecting infants and young adults. Due to mutation/deletion of the survival motor neuron (SMN) gene, SMA is characterized by the SMN protein lack, resulting in motor neuron impairment, skeletal muscle atrophy and premature death. Even if the genetic causes of SMA are well known, many aspects of its pathogenesis remain unclear and only three drugs have been recently approved by the Food and Drug Administration (Nusinersen-Spinraza; Onasemnogene abeparvovec or AVXS-101-Zolgensma; Risdiplam-Evrysdi): although assuring remarkable results, the therapies show some important limits including high costs, still unknown long-term effects, side effects and disregarding of SMN-independent targets. Therefore, the research of new therapeutic strategies is still a hot topic in the SMA field and many efforts are spent in drug discovery. In this review, we describe two promising strategies to select effective molecules: drug screening (DS) and drug repositioning (DR). By using compounds libraries of chemical/natural compounds and/or Food and Drug Administration-approved substances, DS aims at identifying new potentially effective compounds, whereas DR at testing drugs originally designed for the treatment of other pathologies. The drastic reduction in risks, costs and time expenditure assured by these strategies make them particularly interesting, especially for those diseases for which the canonical drug discovery process would be long and expensive. Interestingly, among the identified molecules by DS/DR in the context of SMA, besides the modulators of SMN2 transcription, we highlighted a convergence of some targeted molecular cascades contributing to SMA pathology, including cell death related-pathways, mitochondria and cytoskeleton dynamics, neurotransmitter and hormone modulation.

New and Developing Therapies in Spinal Muscular Atrophy: From Genotype to Phenotype to Treatment and Where Do We Stand?

Spinal muscular atrophy (SMA) is a congenital neuromuscular disorder characterized by motor neuron loss, resulting in progressive weakness. SMA is notable in the health care community because it accounts for the most common cause of infant death resulting from a genetic defect. SMA is caused by low levels of the survival motor neuron protein (SMN) resulting from SMN1 gene mutations or deletions. However, patients always harbor various copies of SMN2, an almost identical but functionally deficient copy of the gene. A genotype-phenotype correlation suggests that SMN2 is a potent disease modifier for SMA, which also represents the primary target for potential therapies. Increasing comprehension of SMA pathophysiology, including the characterization of SMN1 and SMN2 genes and SMN protein functions, has led to the development of multiple therapeutic approaches. Until the end of 2016, no cure was available for SMA, and management consisted of supportive measures. Two breakthrough SMN-targeted treatments, either using antisense oligonucleotides (ASOs) or virus-mediated gene therapy, have recently been approved. These two novel therapeutics have a common objective: to increase the production of SMN protein in MNs and thereby improve motor function and survival. However, neither therapy currently provides a complete cure. Treating patients with SMA brings new responsibilities and unique dilemmas. As SMA is such a devastating disease, it is reasonable to assume that a unique therapeutic solution may not be sufficient. Current approaches under clinical investigation differ in administration routes, frequency of dosing, intrathecal versus systemic delivery, and mechanisms of action. Besides, emerging clinical trials evaluating the efficacy of either SMN-dependent or SMN-independent approaches are ongoing. This review aims to address the different knowledge gaps between genotype, phenotypes, and potential therapeutics.

Understanding and targeting the disease-related RNA binding protein human antigen R (HuR)

Altered gene expression is a characteristic feature of many disease states such as tumorigenesis, and in most cancers, it facilitates cancer cell survival and adaptation. Alterations in global gene expression are strongly impacted by post-transcriptional gene regulation. The RNA binding protein (RBP) HuR (ELAVL1) is an established regulator of post-transcriptional gene regulation and is overexpressed in most human cancers. In many cancerous settings, HuR is not only overexpressed, but it is "overactive" as denoted by increased subcellular localization within the cytoplasm. This dysregulation of HuR expression and cytoplasmic localization allows HuR to stabilize and increase the translation of various prosurvival messenger RNA (mRNAs) involved in the pathogenesis of numerous cancers and various diseases. Based on almost 20 years of work, HuR is now recognized as a therapeutic target. Herein, we will review the role HuR plays in the pathophysiology of different diseases and ongoing therapeutic strategies to target HuR. We will focus on three ongoing-targeted strategies: (1) inhibiting HuR's translocation from the nucleus to the cytoplasm; (2) inhibiting the ability of HuR to bind target RNA; and (3) silencing HuR expression levels. In an oncologic setting, HuR has been demonstrated to be critical for a cancer cell's ability to survive a variety of cancer relevant stressors (including drugs and elements of the tumor microenvironment) and targeting this protein has been shown to sensitize cancer cells further to insult. We strongly believe that targeting HuR could be a powerful therapeutic target to treat different diseases, particularly cancer, in the near future. This article is categorized under: RNA in Disease and Development > RNA in Disease NRA Turnover and Surveillance > Regulation of RNA Stability Translation > Translation Regulation.

Drug treatment for spinal muscular atrophy types II and III

BACKGROUND

Spinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron 1 (SMN1) gene on chromosome 5, or a heterozygous deletion in combination with a (point) mutation in the second SMN1 allele. This results in degeneration of anterior horn cells, which leads to progressive muscle weakness. Children with SMA type II do not develop the ability to walk without support and have a shortened life expectancy, whereas children with SMA type III develop the ability to walk and have a normal life expectancy. This is an update of a review first published in 2009 and previously updated in 2011.

OBJECTIVES

To evaluate if drug treatment is able to slow or arrest the disease progression of SMA types II and III, and to assess if such therapy can be given safely.

SEARCH METHODS

We searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, and ISI Web of Science conference proceedings in October 2018. In October 2018, we also searched two trials registries to identify unpublished trials.

SELECTION CRITERIA

We sought all randomised or quasi-randomised trials that examined the efficacy of drug treatment for SMA types II and III. Participants had to fulfil the clinical criteria and have a homozygous deletion or hemizygous deletion in combination with a point mutation in the second allele of the SMN1 gene (5q11.2-13.2) confirmed by genetic analysis. The primary outcome measure was change in disability score within one year after the onset of treatment. Secondary outcome measures within one year after the onset of treatment were change in muscle strength, ability to stand or walk, change in quality of life, time from the start of treatment until death or full-time ventilation and adverse events attributable to treatment during the trial period. Treatment strategies involving SMN1-replacement with viral vectors are out of the scope of this review, but a summary is given in Appendix 1. Drug treatment for SMA type I is the topic of a separate Cochrane Review.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodology.

MAIN RESULTS

The review authors found 10 randomised, placebo-controlled trials of treatments for SMA types II and III for inclusion in this review, with 717 participants. We added four of the trials at this update. The trials investigated creatine (55 participants), gabapentin (84 participants), hydroxyurea (57 participants), nusinersen (126 participants), olesoxime (165 participants), phenylbutyrate (107 participants), somatotropin (20 participants), thyrotropin-releasing hormone (TRH) (nine participants), valproic acid (33 participants), and combination therapy with valproic acid and acetyl-L-carnitine (ALC) (61 participants). Treatment duration was from three to 24 months. None of the studies investigated the same treatment and none was completely free of bias. All studies had adequate blinding, sequence generation and reporting of primary outcomes. Based on moderate-certainty evidence, intrathecal nusinersen improved motor function (disability) in children with SMA type II, with a 3.7-point improvement in the nusinersen group on the Hammersmith Functional Motor Scale Expanded (HFMSE; range of possible scores 0 to 66), compared to a 1.9-point decline on the HFMSE in the sham procedure group (P < 0.01; n = 126). On all motor function scales used, higher scores indicate better function. Based on moderate-certainty evidence from two studies, the following interventions had no clinically important effect on motor function scores in SMA types II or III (or both) in comparison to placebo: creatine (median change 1 higher, 95% confidence interval (CI) -1 to 2; on the Gross Motor Function Measure (GMFM), scale 0 to 264; n = 40); and combination therapy with valproic acid and carnitine (mean difference (MD) 0.64, 95% CI -1.1 to 2.38; on the Modified Hammersmith Functional Motor Scale (MHFMS), scale 0 to 40; n = 61). Based on low-certainty evidence from other single studies, the following interventions had no clinically important effect on motor function scores in SMA types II or III (or both) in comparison to placebo: gabapentin (median change 0 in the gabapentin group and -2 in the placebo group on the SMA Functional Rating Scale (SMAFRS), scale 0 to 50; n = 66); hydroxyurea (MD -1.88, 95% CI -3.89 to 0.13 on the GMFM, scale 0 to 264; n = 57), phenylbutyrate (MD -0.13, 95% CI -0.84 to 0.58 on the Hammersmith Functional Motor Scale (HFMS) scale 0 to 40; n = 90) and monotherapy of valproic acid (MD 0.06, 95% CI -1.32 to 1.44 on SMAFRS, scale 0 to 50; n = 31). Very low-certainty evidence suggested that the following interventions had little or no effect on motor function: olesoxime (MD 2, 95% -0.25 to 4.25 on the Motor Function Measure (MFM) D1 + D2, scale 0 to 75; n = 160) and somatotropin (median change at 3 months 0.25 higher, 95% CI -1 to 2.5 on the HFMSE, scale 0 to 66; n = 19). One small TRH trial did not report effects on motor function and the certainty of evidence for other outcomes from this trial were low or very low. Results of nine completed trials investigating 4-aminopyridine, acetyl-L-carnitine, CK-2127107, hydroxyurea, pyridostigmine, riluzole, RO6885247/RG7800, salbutamol and valproic acid were awaited and not available for analysis at the time of writing. Various trials and studies investigating treatment strategies other than nusinersen (e.g. SMN2-augmentation by small molecules), are currently ongoing.

AUTHORS' CONCLUSIONS

Nusinersen improves motor function in SMA type II, based on moderate-certainty evidence. Creatine, gabapentin, hydroxyurea, phenylbutyrate, valproic acid and the combination of valproic acid and ALC probably have no clinically important effect on motor function in SMA types II or III (or both) based on low-certainty evidence, and olesoxime and somatropin may also have little to no clinically important effect but evidence was of very low-certainty. One trial of TRH did not measure motor function.

Novel therapies hijack the blood-brain barrier to eradicate glioblastoma cancer stem cells

Glioblastoma (GBM) is amongst the most aggressive brain tumors with a dismal prognosis. Despite significant advances in the current multimodality therapy including surgery, postoperative radiotherapy (RT) and temozolomide (TMZ)-based concomitant and adjuvant chemotherapy (CT), tumor recurrence is nearly universal with poor patient outcomes. These limitations are in part due to poor drug penetration through the blood-brain barrier (BBB) and resistance to CT and RT by a small population of cancer cells recognized as tumor-initiating cells or cancer stem cells (CSCs). Though CT and RT kill the bulk of the tumor cells, they fail to affect CSCs, resulting in their enrichment and their development into more refractory tumors. Therefore, identifying the mechanisms of resistance and developing therapies that specifically target CSCs can improve response, prevent the development of refractory tumors and increase overall survival of GBM patients. Small molecule inhibitors that can breach the BBB and selectively target CSCs are emerging. In this review, we have summarized the recent advancements in understanding the GBM CSC-specific signaling pathways, the CSC-tumor microenvironment niche that contributes to CT and RT resistance and the use of novel combination therapies of small molecule inhibitors that may be used in conjunction with TMZ-based chemoradiation for effective management of GBM.

Mechanisms of exercise-induced survival motor neuron expression in the skeletal muscle of spinal muscular atrophy-like mice

Key points

Spinal muscular atrophy (SMA) is a health‐ and life‐limiting neuromuscular disorder caused by a deficiency in survival motor neuron (SMN) protein.

While historically considered a motor neuron disease, current understanding of SMA emphasizes its systemic nature, which requires addressing affected peripheral tissues such as skeletal muscle in particular.

Chronic physical activity is beneficial for SMA patients, but the cellular and molecular mechanisms of exercise biology are largely undefined in SMA.

After a single bout of exercise, canonical responses such as skeletal muscle AMP‐activated protein kinase (AMPK), p38 mitogen‐activated protein kinase (p38) and peroxisome proliferator‐activated receptor γ coactivator 1α (PGC‐1α) activation were preserved in SMA‐like Smn^2B/− animals. Furthermore, molecules involved in SMN transcription were also altered following physical activity. Collectively, these changes were coincident with an increase in full‐length SMN transcription and corrective SMN pre‐mRNA splicing.

This study advances understanding of the exercise biology of SMA and highlights the AMPK–p38–PGC‐1α axis as a potential regulator of SMN expression in muscle.

Abstract

Chronic physical activity is safe and effective in spinal muscular atrophy (SMA) patients, but the underlying cellular events that drive physiological adaptations are undefined. We examined the effects of a single bout of exercise on molecular mechanisms associated with adaptive remodelling in the skeletal muscle of Smn^2B/− SMA‐like mice. Skeletal muscles were collected from healthy Smn^2B/+ mice and Smn^2B/− littermates at pre‐ (postnatal day (P) 9), early‐ (P13) and late‐ (P21) symptomatic stages to characterize SMA disease progression. Muscles were also collected from Smn^2B/− animals exercised to fatigue on a motorized treadmill. Intracellular signalling and gene expression were examined using western blotting, confocal immunofluorescence microscopy, real‐time quantitative PCR and endpoint PCR assays. Basal skeletal muscle AMP‐activated protein kinase (AMPK) and p38 mitogen‐activated protein kinase (p38) expression and activity were not affected by SMA‐like conditions. Canonical exercise responses such as AMPK, p38 and peroxisome proliferator‐activated receptor γ coactivator‐1α (PGC‐1α) activation were observed following a bout of exercise in Smn^2B/− animals. Furthermore, molecules involved in survival motor neuron (SMN) transcription, including protein kinase B (AKT) and extracellular signal‐regulated kinases (ERK)/ETS‐like gene 1 (ELK1), were altered following physical activity. Acute exercise was also able to mitigate aberrant proteolytic signalling in the skeletal muscle of Smn^2B/− mice. Collectively, these changes were coincident with an exercise‐evoked increase in full‐length SMN mRNA expression. This study advances our understanding of the exercise biology of SMA and highlights the AMPK–p38–PGC‐1α axis as a potential regulator of SMN expression alongside AKT and ERK/ELK1 signalling.

Spinal muscular atrophy (SMA) is a health‐ and life‐limiting neuromuscular disorder caused by a deficiency in survival motor neuron (SMN) protein.

While historically considered a motor neuron disease, current understanding of SMA emphasizes its systemic nature, which requires addressing affected peripheral tissues such as skeletal muscle in particular.

Chronic physical activity is beneficial for SMA patients, but the cellular and molecular mechanisms of exercise biology are largely undefined in SMA.

After a single bout of exercise, canonical responses such as skeletal muscle AMP‐activated protein kinase (AMPK), p38 mitogen‐activated protein kinase (p38) and peroxisome proliferator‐activated receptor γ coactivator 1α (PGC‐1α) activation were preserved in SMA‐like Smn^2B/− animals. Furthermore, molecules involved in SMN transcription were also altered following physical activity. Collectively, these changes were coincident with an increase in full‐length SMN transcription and corrective SMN pre‐mRNA splicing.

This study advances understanding of the exercise biology of SMA and highlights the AMPK–p38–PGC‐1α axis as a potential regulator of SMN expression in muscle.

Spinal Muscular Atrophy and Common Therapeutic Advances

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive destructive motor neuron disease which is characterized primarily by the degeneration of α-motor neurons in the ventral gray horn of the spinal cord. It mainly affects children and represents the most common reason of inherited infant mortality.

MATERIAL AND METHODS

We provide an overview of the recent therapeutic strategies for the treatment of SMA together with available and developing therapeutic strategies. For this purpose, Google Scholar and PubMed databases were searched for literature on SMA, therapy and treatment. Titles were reviewed and 96 were selected and assessed in this paper.

RESULT

Over the last two decades, different therapeutic strategies have been proposed for SMA. Some methods are in the pre-clinical, others the clinical phase.

CONCLUSION

By emergence of the new approaches, especially in gene therapy, effective treatment in the close future is probable.

Transcriptomic RNAseq drug screen in cerebrocortical cultures: toward novel neurogenetic disease therapies

Rare monogenic diseases affect millions worldwide; although over 4500 rare disease genotypes are known, disease-modifying drugs are available for only 5% of them. The sheer number of these conditions combined with their rarity precludes traditional costly drug discovery programs. An economically viable alternative is to repurpose established drugs for rare diseases. Many genetic diseases result from increased or decreased protein activity and identification of clinically approved drugs which moderate this pathogenic dosage holds therapeutic potential. To identify such agents for neurogenetic diseases, we have generated genome-wide transcriptome profiles of mouse primary cerebrocortical cultures grown in the presence of 218 blood-brain barrier (BBB) penetrant clinic-tested drugs. RNAseq and differential expression analyses were used to generate transcriptomic profiles; therapeutically relevant drug-gene interactions related to rare neurogenetic diseases identified in this fashion were further analyzed by quantitative reverse transcriptase-polymerase chain reaction, western blot and immunofluorescence. We have created a transcriptome-wide searchable database for easy access to the gene expression data resulting from the cerebrocortical drug screen (Neuron Screen) and have mined this data to identify a novel link between thyroid hormone and expression of the peripheral neuropathy associated gene Pmp22. Our results demonstrate the utility of cerebrocortical cultures for transcriptomic drug screening, and the database we have created will foster further discovery of novel links between over 200 clinic-tested BBB penetrant drugs and genes related to diverse neurologic conditions.

Exercise biology of neuromuscular disorders

Neuromuscular disorders (NMDs) are chronic conditions that affect the neuromuscular system. Many NMDs currently have no cure; however, as more effective therapies become available for NMD patients, these individuals will exhibit improved health and/or prolonged lifespans. As a result, persons with NMDs will likely desire to engage in a more diverse variety of activities of daily living, including increased physical activity or exercise. Therefore, there is a need to increase our knowledge of the effects of acute exercise and chronic training on the neuromuscular system in NMD contexts. Here, we discuss the disease mechanisms and exercise biology of Duchenne muscular dystrophy (DMD), spinal muscular atrophy (SMA), and myotonic dystrophy type 1 (DM1), which are among the most prevalent NMDs in children and adults. Evidence from clinical and preclinical studies are reviewed, with emphasis on the functional outcomes of exercise, as well as on the putative cellular mechanisms that drive exercise-induced remodelling of the neuromuscular system. Continued investigation of the molecular mechanisms of exercise adaptation in DMD, SMA, and DM1 will assist in enhancing our understanding of the biology of these most prevalent NMDs. This information may also be useful for guiding the development of novel therapeutic targets for future pursuit.

Molecular Factors Involved in Spinal Muscular Atrophy Pathways as Possible Disease-modifying Candidates

Spinal Muscular Atrophy (SMA) is a neuromuscular disorder caused by mutations in the SMN1 gene. Being a monogenic disease, it is characterized by high clinical heterogeneity. Variations in penetrance and severity of symptoms, as well as clinical discrepancies between affected family members can result from modifier genes influence on disease manifestation. SMN2 gene copy number is known to be the main phenotype modifier and there is growing evidence of additional factors contributing to SMA severity. Potential modifiers of spinal muscular atrophy can be found among the wide variety of different factors, such as multiple proteins interacting with SMN or promoting motor neuron survival, epigenetic modifications, transcriptional or splicing factors influencing SMN2 expression. Study of these factors enables to reveal mechanisms underlying SMA pathology and can have pronounced clinical application.

Celecoxib treatment improves muscle function in mdx mice and increases utrophin A expression

Duchenne muscular dystrophy (DMD) is a genetic and progressive neuromuscular disorder caused by mutations and deletions in the dystrophin gene. Although there is currently no cure, one promising treatment for DMD is aimed at increasing endogenous levels of utrophin A to compensate functionally for the lack of dystrophin. Recent studies from our laboratory revealed that heparin treatment of mdx mice activates p38 MAPK, leading to an upregulation of utrophin A expression and improvements in the dystrophic phenotype. Based on these findings, we sought to determine the effects of other potent p38 activators, including the cyclooxygenase (COX)-2 inhibitor celecoxib. In this study, we treated 6-wk-old mdx mice for 4 wk with celecoxib. Immunofluorescence analysis of celecoxib-treated mdx muscles revealed a fiber type switch from a fast to a slower phenotype along with beneficial effects on muscle fiber integrity. In agreement, celecoxib-treated mdx mice showed improved muscle strength. Celecoxib treatment also induced increases in utrophin A expression ranging from ∼1.5- to 2-fold in tibialis anterior diaphragm and heart muscles. Overall, these results highlight that activation of p38 in muscles can indeed lead to an attenuation of the dystrophic phenotype and reveal the potential role of celecoxib as a novel therapeutic agent for the treatment of DMD.-Péladeau, C., Adam, N. J., Jasmin, B. J. Celecoxib treatment improves muscle function in mdx mice and increases utrophin A expression.

Gonorazky H, Cohn RD, Campbell C. Treating pediatric neuromuscular disorders: The future is now

Pediatric neuromuscular diseases encompass all disorders with onset in childhood and where the primary area of pathology is in the peripheral nervous system. These conditions are largely genetic in etiology, and only those with a genetic underpinning will be presented in this review. This includes disorders of the anterior horn cell (e.g., spinal muscular atrophy), peripheral nerve (e.g., Charcot-Marie-Tooth disease), the neuromuscular junction (e.g., congenital myasthenic syndrome), and the muscle (myopathies and muscular dystrophies). Historically, pediatric neuromuscular disorders have uniformly been considered to be without treatment possibilities and to have dire prognoses. This perception has gradually changed, starting in part with the discovery and widespread application of corticosteroids for Duchenne muscular dystrophy. At present, several exciting therapeutic avenues are under investigation for a range of conditions, offering the potential for significant improvements in patient morbidities and mortality and, in some cases, curative intervention. In this review, we will present the current state of treatment for the most common pediatric neuromuscular conditions, and detail the treatment strategies with the greatest potential for helping with these devastating diseases.

Muscle-specific expression of the RNA-binding protein Staufen1 induces progressive skeletal muscle atrophy via regulation of phosphatase tensin homolog

Converging lines of evidence have now highlighted the key role for post-transcriptional regulation in the neuromuscular system. In particular, several RNA-binding proteins are known to be misregulated in neuromuscular disorders including myotonic dystrophy type 1, spinal muscular atrophy and amyotrophic lateral sclerosis. In this study, we focused on the RNA-binding protein Staufen1, which assumes multiple functions in both skeletal muscle and neurons. Given our previous work that showed a marked increase in Staufen1 expression in various physiological and pathological conditions including denervated muscle, in embryonic and undifferentiated skeletal muscle, in rhabdomyosarcomas as well as in myotonic dystrophy type 1 muscle samples from both mouse models and humans, we investigated the impact of sustained Staufen1 expression in postnatal skeletal muscle. To this end, we generated a skeletal muscle-specific transgenic mouse model using the muscle creatine kinase promoter to drive tissue-specific expression of Staufen1. We report that sustained Staufen1 expression in postnatal skeletal muscle causes a myopathy characterized by significant morphological and functional deficits. These deficits are accompanied by a marked increase in the expression of several atrophy-associated genes and by the negative regulation of PI3K/AKT signaling. We also uncovered that Staufen1 mediates PTEN expression through indirect transcriptional and direct post-transcriptional events thereby providing the first evidence for Staufen1-regulated PTEN expression. Collectively, our data demonstrate that Staufen1 is a novel atrophy-associated gene, and highlight its potential as a biomarker and therapeutic target for neuromuscular disorders and conditions.

ML372 blocks SMN ubiquitination and improves spinal muscular atrophy pathology in mice

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease and one of the leading inherited causes of infant mortality. SMA results from insufficient levels of the survival motor neuron (SMN) protein, and studies in animal models of the disease have shown that increasing SMN protein levels ameliorates the disease phenotype. Our group previously identified and optimized a new series of small molecules, with good potency and toxicity profiles and reasonable pharmacokinetics, that were able to increase SMN protein levels in SMA patient-derived cells. We show here that ML372, a representative of this series, almost doubles the half-life of residual SMN protein expressed from the SMN2 locus by blocking its ubiquitination and subsequent degradation by the proteasome. ML372 increased SMN protein levels in muscle, spinal cord, and brain tissue of SMA mice. Importantly, ML372 treatment improved the righting reflex and extended survival of a severe mouse model of SMA. These results demonstrate that slowing SMN degradation by selectively inhibiting its ubiquitination can improve the motor phenotype and lifespan of SMA model mice.

Altered mRNA Splicing in SMN-Depleted Motor Neuron-Like Cells

Spinal muscular atrophy (SMA) is an intractable neurodegenerative disease afflicting 1 in 6–10,000 live births. One of the key functions of the SMN protein is regulation of spliceosome assembly. Reduced levels of the SMN protein that are observed in SMA have been shown to result in aberrant mRNA splicing. SMN-dependent mis-spliced transcripts in motor neurons may cause stresses that are particularly harmful and may serve as potential targets for the treatment of motor neuron disease or as biomarkers in the SMA patient population. We performed deep RNA sequencing using motor neuron-like NSC-34 cells to screen for SMN-dependent mRNA processing changes that occur following acute depletion of SMN. We identified SMN-dependent splicing changes, including an intron retention event that results in the production of a truncated Rit1 transcript. This intron-retained transcript is stable and is mis-spliced in spinal cord from symptomatic SMA mice. Constitutively active Rit1 ameliorated the neurite outgrowth defect in SMN depleted NSC-34 cells, while expression of the truncated protein product of the mis-spliced Rit1 transcript inhibited neurite extension. These results reveal new insights into the biological consequence of SMN-dependent splicing in motor neuron-like cells.

Endogenous recovery after brain damage: molecular mechanisms that balance neuronal life/death fate

Neuronal survival depends on multiple factors that comprise a well-fueled energy metabolism, trophic input, clearance of toxic substances, appropriate redox environment, integrity of blood-brain barrier, suppression of programmed cell death pathways and cell cycle arrest. Disturbances of brain homeostasis lead to acute or chronic alterations that might ultimately cause neuronal death with consequent impairment of neurological function. Although we understand most of these processes well when they occur independently from one another, we still lack a clear grasp of the concerted cellular and molecular mechanisms activated upon neuronal damage that intervene in protecting damaged neurons from death. In this review, we summarize a handful of endogenously activated mechanisms that balance molecular cues so as to determine whether neurons recover from injury or die. We center our discussion on mechanisms that have been identified to participate in stroke, although we consider different scenarios of chronic neurodegeneration as well. We discuss two central processes that are involved in endogenous repair and that, when not regulated, could lead to tissue damage, namely, trophic support and neuroinflammation. We emphasize the need to construct integrated models of neuronal degeneration and survival that, in the end, converge in neuronal fate after injury. Under neurodegenerative conditions, endogenously activated mechanisms balance out molecular cues that determine whether neurons contend toxicity or die. Many processes involved in endogenous repair may as well lead to tissue damage depending on the strength of stimuli. Signaling mediated by trophic factors and neuroinflammation are examples of these processes as they regulate different mechanisms that mediate neuronal demise including necrosis, apoptosis, necroptosis, pyroptosis and autophagy. In this review, we discuss recent findings on balanced regulation and their involvement in neuronal death.

Current and emerging treatment options for spinal muscular atrophy

Spinal muscular atrophy is one of the most common inherited neuromuscular conditions; our understanding of the genetic pathology and translational research coming from this insight has made significant progress over the past decade. This short review provides the background of the disease along with the bench to bedside progress of some promising treatment options to develop better understanding of the present state of the disease.

Sodium Channel Inhibitors Reduce DMPK mRNA and Protein

Myotonic dystrophy type 1 (DM1) is caused by an expanded trinucleotide (CTG)n tract in the 3' untranslated region (UTR) of the dystrophia myotonica protein kinase (DMPK) gene. This results in the aggregation of an expanded mRNA forming toxic intranuclear foci which sequester splicing factors. We believe down-regulation of DMPK mRNA represents a potential, and as yet unexplored, DM1 therapeutic avenue. Consequently, a computational screen for agents which down-regulate DMPK mRNA was undertaken, unexpectedly identifying the sodium channel blockers mexiletine, prilocaine, procainamide, and sparteine as effective suppressors of DMPK mRNA. Analysis of DMPK mRNA in C2C12 myoblasts following treatment with these agents revealed a reduction in the mRNA levels. In vivo analysis of CD1 mice also showed DMPK mRNA and protein down-regulation. The role of DMPK mRNA suppression in the documented efficacy of this class of compounds in DM1 is worthy of further investigation.

Spinal Muscular Atrophy Therapeutics: Where do we Stand?

Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder pathologically characterized by the degeneration of motor neurons in the spinal cord and muscle atrophy. Motor neuron loss often results in severe muscle weakness causing affected infants to die before reaching 2 years of age. Patients with milder forms of SMA exhibit slowly progressive muscle weakness over many years. SMA is caused by the loss of SMN1 and the retention of at least 1 copy of a highly homologous SMN2. An alternative splicing event in the pre-mRNA arising from SMN2 results in the production of low levels of functional SMN protein. To date, there are no effective treatments available to treat patients with SMA. However, over the last 2 decades, the development of SMA mouse models and the identification of therapeutic targets have resulted in a promising drug pipeline for SMA. Here, we highlight some of the therapeutic strategies that have been developed to activate SMN2 expression, modulate splicing of the SMN2 pre-mRNA, or replace SMN1 by gene therapy. After 2 decades of translational research, we now stand within reach of a treatment for SMA.

Spinal muscular atrophy: from tissue specificity to therapeutic strategies

Spinal muscular atrophy (SMA) is the most frequent genetic cause of death in infants and toddlers. All cases of spinal muscular atrophy result from reductions in levels of the survival motor neuron (SMN) protein, and so SMN upregulation is a focus of many preclinical and clinical studies. We examine four issues that may be important in planning for therapeutic success. First, neuromuscular phenotypes in the SMNΔ7 mouse model closely match those in human patients but peripheral disease manifestations differ, suggesting that endpoints other than mouse lifespan may be more useful in predicting clinical outcome. Second, SMN plays important roles in multiple central and peripheral cell types, not just motor neurons, and it remains unclear which of these cell types need to be targeted therapeutically. Third, should SMN-restoration therapy not be effective in all patients, blocking molecular changes downstream of SMN reduction may confer significant benefit, making it important to evaluate therapeutic targets other than SMN. Lastly, for patients whose disease progression is slowed, but who retain significant motor dysfunction, additional approaches used to enhance regeneration of the neuromuscular system may be of value.

Drug Discovery Approaches for Rare Neuromuscular Diseases

Rare neuromuscular diseases encompass many diverse and debilitating musculoskeletal disorders, ranging from ultra-orphan conditions that affect only a few families, to the so-called ‘common’ orphan diseases like Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA), which affect several thousand individuals worldwide. Increasingly, pharmaceutical and biotechnology companies, in an effort to improve productivity and rebuild dwindling pipelines, are shifting their business models away from the formerly popular ‘blockbuster’ strategy, with rare diseases being an area of increased focus in recent years. As a consequence of this paradigm shift, coupled with high-profile campaigns by not-for-profit organisations and patient advocacy groups, rare neuromuscular diseases are attracting considerable attention as new therapeutic areas for improved drug therapy. Much pioneering work has taken place to elucidate the underlying pathological mechanisms of many rare neuromuscular diseases. This, in conjunction with the availability of new screening technologies, has inspired the development of several truly innovative therapeutic strategies aimed at correcting the underlying pathology. A survey of medicinal chemistry approaches and the resulting clinical progress for new therapeutic agents targeting this devastating class of degenerative diseases is presented, using DMD and SMA as examples. Complementary strategies using small-molecule drugs and biological agents are included.

Transport rankings of non-steroidal antiinflammatory drugs across blood-brain barrier in vitro models

The aim of this work was to conduct a comprehensive study about the transport properties of NSAIDs across the blood-brain barrier (BBB) in vitro. Transport studies with celecoxib, diclofenac, ibuprofen, meloxicam, piroxicam and tenoxicam were accomplished across Transwell models based on cell line PBMEC/C1-2, ECV304 or primary rat brain endothelial cells. Single as well as group substance studies were carried out. In group studies substance group compositions, transport medium and serum content were varied, transport inhibitors verapamil and probenecid were added. Resulted permeability coefficients were compared and normalized to internal standards diazepam and carboxyfluorescein. Transport rankings of NSAIDs across each model were obtained. Single substance studies showed similar rankings as corresponding group studies across PBMEC/C1-2 or ECV304 cell layers. Serum content, glioma conditioned medium and inhibitors probenecid and verapamil influenced resulted permeability significantly. Basic differences of transport properties of the investigated NSAIDs were similar comparing all three in vitro BBB models. Different substance combinations in the group studies and addition of probenecid and verapamil suggested that transporter proteins are involved in the transport of every tested NSAID. Results especially underlined the importance of same experimental conditions (transport medium, serum content, species origin, cell line) for proper data comparison.

VPAC2 receptor agonist BAY 55-9837 increases SMN protein levels and moderates disease phenotype in severe spinal muscular atrophy mouse models

Background

Spinal Muscular Atrophy (SMA) is one of the most common inherited causes of infant death and is caused by the loss of functional survival motor neuron (SMN) protein due to mutations or deletion in the SMN1 gene. One of the treatment strategies for SMA is to induce the expression of the protein from the homologous SMN2 gene, a rescuing paralog for SMA.

Methods and results

Here we demonstrate the promise of pharmacological modulation of SMN2 gene by BAY 55-9837, an agonist of the vasoactive intestinal peptide receptor 2 (VPAC2), a member of G protein coupled receptor family. Treatment with BAY 55-9837 lead to induction of SMN protein levels via activation of MAPK14 or p38 pathway in vitro. Importantly, BAY 55-9837 also ameliorated disease phenotype in severe SMA mouse models.

Conclusion

Our findings suggest the VPAC2 pathway is a potential SMA therapeutic target.

Gene-environment interactions in severe intraventricular hemorrhage of preterm neonates

Intraventricular hemorrhage (IVH) of the preterm neonate is a complex developmental disorder, with contributions from both the environment and the genome. IVH, or hemorrhage into the germinal matrix of the developing brain with secondary periventricular infarction, occurs in that critical period of time before the 32nd to 33rd wk postconception and has been attributed to changes in cerebral blood flow to the immature germinal matrix microvasculature. Emerging data suggest that genes subserving coagulation, inflammatory, and vascular pathways and their interactions with environmental triggers may influence both the incidence and severity of cerebral injury and are the subject of this review. Polymorphisms in the Factor V Leiden gene are associated with the atypical timing of IVH, suggesting an as yet unknown environmental trigger. The methylenetetrahydrofolate reductase (MTHFR) variants render neonates more vulnerable to cerebral injury in the presence of perinatal hypoxia. The present study demonstrates that the MTHFR 677C>T polymorphism and low 5-min Apgar score additively increase the risk of IVH. Finally, review of published preclinical data suggests the stressors of delivery result in hemorrhage in the presence of mutations in collagen 4A1, a major structural protein of the developing cerebral vasculature. Maternal genetics and fetal environment may also play a role.

Spinal muscular atrophy: development and implementation of potential treatments

In neurodegenerative disorders, effective treatments are urgently needed, along with methods to determine whether treatment worked. In this review, we discuss the rapid progress in the understanding of recessive proximal spinal muscular atrophy and how this is leading to exciting potential treatments of the disease. Spinal muscular atrophy is caused by loss of the survival motor neuron 1 (SMN1) gene and reduced levels of SMN protein. The critical downstream targets of SMN deficiency that result in motor neuron loss are not known. However, increasing SMN levels has a marked impact in mouse models, and these therapeutics are rapidly moving toward clinical trials. Promising preclinical therapies, the varying degree of impact on the mouse models, and potential measures of treatment effect are reviewed. One key issue discussed is the variable outcome of increasing SMN at different stages of disease progression.