A small-molecule PI3Kα activator for cardioprotection and neuroregeneration

Harnessing the potential beneficial effects of kinase signalling through the generation of direct kinase activators remains an underexplored area of drug development1-5. This also applies to the PI3K signalling pathway, which has been extensively targeted by inhibitors for conditions with PI3K overactivation, such as cancer and immune dysregulation. Here we report the discovery of UCL-TRO-1938 (referred to as 1938 hereon), a small-molecule activator of the PI3Kα isoform, a crucial effector of growth factor signalling. 1938 allosterically activates PI3Kα through a distinct mechanism by enhancing multiple steps of the PI3Kα catalytic cycle and causes both local and global conformational changes in the PI3Kα structure. This compound is selective for PI3Kα over other PI3K isoforms and multiple protein and lipid kinases. It transiently activates PI3K signalling in all rodent and human cells tested, resulting in cellular responses such as proliferation and neurite outgrowth. In rodent models, acute treatment with 1938 provides cardioprotection from ischaemia-reperfusion injury and, after local administration, enhances nerve regeneration following nerve crush. This study identifies a chemical tool to directly probe the PI3Kα signalling pathway and a new approach to modulate PI3K activity, widening the therapeutic potential of targeting these enzymes through short-term activation for tissue protection and regeneration. Our findings illustrate the potential of activating kinases for therapeutic benefit, a currently largely untapped area of drug development.

Bisphenol-A exposure leads to neurotoxicity through upregulating the expression of histone deacetylase 2 in vivo and in vitro

Bisphenol-A (BPA), an environmental endocrine disruptor, is toxic to the central nervous system. Although recent studies have shown BPA-induced neurotoxicity, it is far from clear what precisely epigenetic mechanisms are involved in BPA-induced cognitive deficits. In this study, pheochromocytoma (PC12) cells were treated with BPA at 1 μM for 36 h in vitro. In vivo, C57BL/6 mice were administered to BPA at a dose of 1 mg/kg/day for 10 weeks. The results showed that 1 μM BPA exposure for 36 h impaired neurite outgrowth of PC12 cells through decreasing the primary and secondary branches. Besides, BPA exposure decreased the level of Ac-H3K9 (histone H3 Lys9 acetylation) by upregulating the expression of HDAC2 (histone deacetylases 2) in PC12 cells. Furthermore, treatment of both TSA (Trichostatin A, inhibitor of the histone deacetylase) and shHDAC2 plasmid (HDAC2 knockdown construct) resulted in amelioration neurite outgrowth deficits induced by BPA. In addition, it was shown that repression of HDAC2 could markedly rescue the spine density impairment in the hippocampus and prevent the cognitive impairment caused by BPA exposure in mice. Collectively, HDAC2 plays an essential role in BPA-induced neurotoxicity, which provides a potential molecular target for medical intervention.

Human Sensory Neuron-like Cells and Glycated Collagen Matrix as a Model for the Screening of Analgesic Compounds

Increased collagen-derived advanced glycation end-products (AGEs) are consistently related to painful diseases, including osteoarthritis, diabetic neuropathy, and neurodegenerative disorders. We have recently developed a model combining a two-dimensional glycated extracellular matrix (ECM-GC) and primary dorsal root ganglion (DRG) that mimicked a pro-nociceptive microenvironment. However, culturing primary cells is still a challenge for large-scale screening studies. Here, we characterized a new model using ECM-GC as a stimulus for human sensory-like neurons differentiated from SH-SY5Y cell lines to screen for analgesic compounds. First, we confirmed that the differentiation process induces the expression of neuron markers (MAP2, RBFOX3 (NeuN), and TUBB3 (β-III tubulin), as well as sensory neuron markers critical for pain sensation (TRPV1, SCN9A (Nav1.7), SCN10A (Nav1.8), and SCN11A (Nav1.9). Next, we showed that ECM-GC increased c-Fos expression in human sensory-like neurons, which is suggestive of neuronal activation. In addition, ECM-GC upregulated the expression of critical genes involved in pain, including SCN9A and TACR1. Of interest, ECM-GC induced substance P release, a neuropeptide widely involved in neuroinflammation and pain. Finally, morphine, the prototype opiate, decreased ECM-GC-induced substance P release. Together, our results suggest that we established a functional model that can be useful as a platform for screening candidates for the management of painful conditions.

NME1 Protects Against Neurotoxin-, α-Synuclein- and LRRK2-Induced Neurite Degeneration in Cell Models of Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease characterised by the progressive degeneration of midbrain dopaminergic neurons, coupled with the intracellular accumulation of α-synuclein. Axonal degeneration is a central part of the pathology of PD. While the majority of PD cases are sporadic, some are genetic; the G2019S mutation in leucine-rich repeat kinase 2 (LRRK2) is the most common genetic form. The application of neurotrophic factors to protect dopaminergic neurons is a proposed experimental therapy. One such neurotrophic factor is growth differentiation factor (GDF)5. GDF5 is a dopaminergic neurotrophic factor that has been shown to upregulate the expression of a protein called nucleoside diphosphate kinase A (NME1). However, whether NME1 is neuroprotective in cell models of axonal degeneration of relevance to PD is unknown. Here we show that treatment with NME1 can promote neurite growth in SH-SY5Y cells, and in cultured dopaminergic neurons treated with the neurotoxin 6-hydroxydopamine (6-OHDA). Similar effects of NME1 were found in SH-SY5Y cells and dopaminergic neurons overexpressing human wild-type α-synuclein, and in stable SH-SY5Y cell lines carrying the G2019S LRRK2 mutation. We found that the effects of NME1 require the RORα/ROR2 receptors. Furthermore, increased NF-κB-dependent transcription was partially required for the neurite growth-promoting effects of NME1. Finally, a combined bioinformatics and biochemical analysis of the mitochondrial oxygen consumption rate revealed that NME1 enhanced mitochondrial function, which is known to be impaired in PD. These data show that recombinant NME1 is worthy of further study as a potential therapeutic agent for axonal protection in PD.

Phenotypic Screening Following Transcriptomic Deconvolution to Identify Transcription Factors Mediating Axon Growth Induced by a Kinase Inhibitor

After injury to the central nervous system (CNS), both neuron-intrinsic limitations on regenerative responses and inhibitory factors in the injured CNS environment restrict regenerative axon growth. Instances of successful axon regrowth offer opportunities to identify features that differentiate these situations from that of the normal adult CNS. One such opportunity is provided by the kinase inhibitor RO48, which dramatically enhances neurite outgrowth of neurons in vitro and substantially increased contralateral sprouting of corticospinal tract neurons when infused intraventricularly following unilateral pyramidotomy. The authors present here a transcriptomic deconvolution of RO48-associated axon growth, with the goal of identifying transcriptional regulators associated with axon growth in the CNS. Through the use of RNA sequencing (RNA-seq) and transcription factor binding site enrichment analysis, the authors identified a list of transcription factors putatively driving differential gene expression during RO48-induced neurite outgrowth of rat hippocampal neurons in vitro. The 82 transcription factor motifs identified in this way included some with known association to axon growth regulation, such as Jun, Klf4, Myc, Atf4, Stat3, and Nfatc2, and many with no known association to axon growth. A phenotypic loss-of-function screen was carried out to evaluate these transcription factors for their roles in neurite outgrowth; this screen identified several potential outgrowth regulators. Subsequent validation suggests that the Forkhead box (Fox) family transcription factor Foxp2 restricts neurite outgrowth, while FoxO subfamily members Foxo1 and Foxo3a promote neurite outgrowth. The authors' combined transcriptomic-phenotypic screening strategy therefore allowed identification of novel transcriptional regulators of neurite outgrowth downstream of a multitarget kinase inhibitor.

Human iPSC-derived neurons reveal early developmental alteration of neurite outgrowth in the late-occurring neurodegenerative Wolfram syndrome

Recent studies indicate that neurodegenerative processes that appear during childhood and adolescence in individuals with Wolfram syndrome (WS) occur in addition to early brain development alteration, which is clinically silent. Underlying pathological mechanisms are still unknown. We have used induced pluripotent stem cell-derived neural cells from individuals affected by WS in order to reveal their phenotypic and molecular correlates. We have observed that a subpopulation of Wolfram neurons displayed aberrant neurite outgrowth associated with altered expression of axon guidance genes. Selective inhibition of the ATF6α arm of the unfolded protein response prevented the altered phenotype, although acute endoplasmic reticulum stress response-which is activated in late Wolfram degenerative processes-was not detected. Among the drugs currently tried in individuals with WS, valproic acid was the one that prevented the pathological phenotypes. These results suggest that early defects in axon guidance may contribute to the loss of neurons in individuals with WS.

Adhesion of Neurons and Glial Cells with Nanocolumnar TiN Films for Brain-Machine Interfaces

Coupling of cells to biomaterials is a prerequisite for most biomedical applications; e.g., neuroelectrodes can only stimulate brain tissue in vivo if the electric signal is transferred to neurons attached to the electrodes' surface. Besides, cell survival in vitro also depends on the interaction of cells with the underlying substrate materials; in vitro assays such as multielectrode arrays determine cellular behavior by electrical coupling to the adherent cells. In our study, we investigated the interaction of neurons and glial cells with different electrode materials such as TiN and nanocolumnar TiN surfaces in contrast to gold and ITO substrates. Employing single-cell force spectroscopy, we quantified short-term interaction forces between neuron-like cells (SH-SY5Y cells) and glial cells (U-87 MG cells) for the different materials and contact times. Additionally, results were compared to the spreading dynamics of cells for different culture times as a function of the underlying substrate. The adhesion behavior of glial cells was almost independent of the biomaterial and the maximum growth areas were already seen after one day; however, adhesion dynamics of neurons relied on culture material and time. Neurons spread much better on TiN and nanocolumnar TiN and also formed more neurites after three days in culture. Our designed nanocolumnar TiN offers the possibility for building miniaturized microelectrode arrays for impedance spectroscopy without losing detection sensitivity due to a lowered self-impedance of the electrode. Hence, our results show that this biomaterial promotes adhesion and spreading of neurons and glial cells, which are important for many biomedical applications in vitro and in vivo.

Akt and MAPK/ERK signaling regulate neurite extension in adult neural progenitor cells but do not directly mediate disruption of cytoskeletal structure and neurite dynamics by low-level silver nanoparticles

Silver nanoparticles (AgNPs) are an environmental contaminant of emerging concern. Ionic and colloidal silver has long been used for its antimicrobial properties, but with the development of engineered AgNPs, these are increasingly incorporated in the manufacture of nano-enhanced products. AgNPs are released into the environment from manufacturing plants and they can be shed from products during use and after disposal. This can lead to chronic low-level environmental exposure in animals. Unlike traditional forms of silver, the unique physical properties of AgNPs allow them to bypass biological barriers and enter tissues, like the brain, where they can bioaccumulate. Thus, it is important to understand if low-level AgNPs induce physiological changes in brain cells. Previously we found that 1.0 μg/mL AgNP exposure resulted in disruption of f-actin organization and neurite collapse in cultured differentiating adult neural stem cells, and that interaction with β-catenin signaling was involved. Here, we report that AgNP exposure may interact with pAkt signaling irreversibly or indirectly to disrupt cytoskeleton and inhibit neurite extension. Furthermore, the MAPK/ERK signaling pathway is not a target for AgNP-mediated dysregulation. Environmental exposure to low-level AgNPs therefore appears to target specific cellular mechanisms to alter brain cell physiology. Understanding these underlying mechanisms is important for decisions regulating the use and disposal of manufactured AgNPs.

Quinacrine and Niclosamide Promote Neurite Growth in Midbrain Dopaminergic Neurons Through the Canonical BMP-Smad Pathway and Protect Against Neurotoxin and α-Synuclein-Induced Neurodegeneration

Parkinson's disease is a neurodegenerative disorder characterised by nigrostriatal dopaminergic degeneration, and intracellular α-synuclein aggregation. Current pharmacological treatments are solely symptomatic so there is a need to identify agents that can slow or stop dopaminergic degeneration. One proposed class of therapeutics are neurotrophic factors which promote the survival of nigrostriatal dopaminergic neurons. However, neurotrophic factors need to be delivered directly to the brain. An alternative approach may be to identify pharmacological agents which can reach the brain to stimulate neurotrophic factor expression and/or their signalling pathways in dopaminergic neurons. BMP2 is a neurotrophic factor that is expressed in the human substantia nigra; exogenous BMP2 administration protects against dopaminergic degeneration in in vitro models of PD. In this study, we investigated the neurotrophic potential of two FDA-approved drugs, quinacrine and niclosamide, that are modulators of BMP2 signalling. We report that quinacrine and niclosamide, like BMP2, significantly increased neurite length, as a readout of neurotrophic action, in SH-SY5Y cells and dopaminergic neurons in primary cultures of rat ventral mesencephalon. We also show that these effects of quinacrine and niclosamide require the activation of BMP-Smad signalling. Finally, we demonstrate that quinacrine and niclosamide are neuroprotective against degeneration induced by the neurotoxins, MPP+ and 6-OHDA, and by viral-mediated overexpression of α-synuclein in vitro. Collectively, this study identifies two drugs, that are safe for use in patients' to 'are approved for human use, that exert neurotrophic effects on dopaminergic neurons through modulation of BMP-Smad signalling. This rationalises the further study of drugs that target the BMP-Smad pathway as potential neuroprotective pharmacotherapy for Parkinson's disease.

CYLD deficiency causes auditory neuropathy due to reduced neurite outgrowth

BACKGROUND

Auditory neuropathy is a cause of hearing loss that has been studied in a number of animal models. Signal transmission from hair cells to spiral ganglion neurons plays an important role in normal hearing. CYLD is a microtubule-binding protein, and deubiquitinase involved in the regulation of various cellular processes. In this study, we used Cyld knockout (KO) mice and nerve cell lines to examine whether CYLD is associated with auditory neuropathy.

METHODS

Hearing of Cyld KO mice was studied using the TDT RZ6 auditory physiology workstation. The expression and localization of CYLD in mouse cochlea and cell lines were examined by RT-PCR, immunoblotting, and immunofluorescence. CYLD expression was knocked down in SH-SY5Y cells by shRNAs and in PC12 and N2A cells by siRNAs. Nerve growth factor and retinoic acid were used to induce neurite outgrowth, and the occurrence and length of neurites were statistically analyzed between knockdown and control groups.

RESULTS

Cyld KO mice had mild hearing impairment. Moreover, CYLD was widely expressed in mouse cochlear tissues and different nerve cell lines. Knocking down CYLD significantly reduced the length and proportion of neurites growing from nerve cells.

CONCLUSIONS

The abnormal hearing of Cyld KO mice might be caused by a decrease in the length and number of neurites growing from auditory nerve cells in the cochlea, suggesting that CYLD is a key protein affecting hearing.

Exposure to human relevant mixtures of halogenated persistent organic pollutants (POPs) alters neurodevelopmental processes in human neural stem cells undergoing differentiation

Halogenated persistent organic pollutants (POPs) like perfluorinated alkylated substances (PFASs), brominated flame retardants (BFRs), organochlorine pesticides and polychlorinated biphenyls (PCBs) are known to cause cancer, immunotoxicity, neurotoxicity and interfere with reproduction and development. Concerns have been raised about the impact of POPs upon brain development and possibly neurodevelopmental disorders. The developing brain is a particularly vulnerable organ due to dynamic and complex neurodevelopmental processes occurring early in life. However, very few studies have reported on the effects of POP mixtures at human relevant exposures, and their impact on key neurodevelopmental processes using human in vitro test systems. Aiming to reduce this knowledge gap, we exposed mixed neuronal/glial cultures differentiated from neural stem cells (NSCs) derived from human induced pluripotent stem cells (hiPSCs) to reconstructed mixtures of 29 different POPs using concentrations comparable to Scandinavian human blood levels. Effects of the POP mixtures on neuronal proliferation, differentiation and synaptogenesis were evaluated using in vitro assays anchored to common key events identified in the existing developmental neurotoxicity (DNT) adverse outcome pathways (AOPs). The present study showed that mixtures of POPs (in particular brominated and chlorinated compounds) at human relevant concentrations increased proliferation of NSCs and decreased synapse number. Based on a mathematical modelling, synaptogenesis and neurite outgrowth seem to be the most sensitive DNT in vitro endpoints. Our results indicate that prenatal exposure to POPs may affect human brain development, potentially contributing to recently observed learning and memory deficits in children.

Phenolic and Steroidal Metabolites from the Cultivated Edible Inonotus hispidus Mushroom and Their Bioactivities

A chemical study on the fruiting bodies of cultivated edible mushroom Inonotus hispidus resulted in 14 metabolites including three new hispolon congeners, named inonophenols A-B and one new lanostane triterpenoid, named inonoterpene A. These structures were identified by NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and electronic circular dichroism (ECD) data analysis. All metabolites were assessed for neurotrophic, anti-inflammatory, and antioxidative activities. Among them, inonophenols B and C were the most active in promoting PC-12 cell neurite outgrowth at a concentration of 10 μM. The phenolic derivatives reduced NO generation by lipopolysaccharide (LPS)-induced BV-2 microglial cells by suppressing the expression of toll-like receptor-4 (TLR-4) and the nuclear factor-kappa-B (NF-κB) signaling pathway as well as the inflammatory mediators including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, the phenolics showed antioxidant effects in DPPH scavenging assay with the IC₅₀ values of 9.82-21.43 μM. These findings showed that I. hispidus may be a new source of neurotrophic and protective agents against neurodegenerative disorders.

PPAR gamma agonist leriglitazone improves frataxin-loss impairments in cellular and animal models of Friedreich Ataxia

Friedreich ataxia (FRDA), the most common autosomal recessive ataxia, is characterized by degeneration of the large sensory neurons and spinocerebellar tracts, cardiomyopathy, and increased incidence in diabetes. The underlying pathophysiological mechanism of FRDA, driven by a significantly decreased expression of frataxin (FXN), involves increased oxidative stress, reduced activity of enzymes containing iron‑sulfur clusters (ISC), defective energy production, calcium dyshomeostasis, and impaired mitochondrial biogenesis, leading to mitochondrial dysfunction. The peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcriptional factor playing a key role in mitochondrial function and biogenesis, fatty acid storage, energy metabolism, and antioxidant defence. It has been previously shown that the PPARγ/PPARγ coactivator 1 alpha (PGC-1α) pathway is dysregulated when there is frataxin deficiency, thus contributing to FRDA pathogenesis and supporting the PPARγ pathway as a potential therapeutic target. Here we assess whether MIN-102 (INN: leriglitazone), a novel brain penetrant and orally bioavailable PPARγ agonist with an improved profile for central nervous system (CNS) diseases, rescues phenotypic features in cellular and animal models of FRDA. In frataxin-deficient dorsal root ganglia (DRG) neurons, leriglitazone increased frataxin protein levels, reduced neurite degeneration and α-fodrin cleavage mediated by calpain and caspase 3, and increased survival. Leriglitazone also restored mitochondrial membrane potential and partially reversed decreased levels of mitochondrial Na+/Ca2+ exchanger (NCLX), resulting in an improvement of mitochondrial functions and calcium homeostasis. In frataxin-deficient primary neonatal cardiomyocytes, leriglitazone prevented lipid droplet accumulation without increases in frataxin levels. Furthermore, leriglitazone improved motor function deficit in YG8sR mice, a FRDA mouse model. In agreement with the role of PPARγ in mitochondrial biogenesis, leriglitazone significantly increased markers of mitochondrial biogenesis in FRDA patient cells. Overall, these results suggest that targeting the PPARγ pathway by leriglitazone may provide an efficacious therapy for FRDA increasing the mitochondrial function and biogenesis that could increase frataxin levels in compromised frataxin-deficient DRG neurons. Alternately, leriglitazone improved the energy metabolism by increasing the fatty acid β-oxidation in frataxin-deficient cardiomyocytes without elevation of frataxin levels. This could be linked to a lack of significant mitochondrial biogenesis and cardiac hypertrophy. The results reinforced the different tissue requirement in FRDA and the pleiotropic effects of leriglitazone that could be a promising therapy for FRDA.

Abnormal neuronal morphology and altered synaptic proteins are restored by oxytocin in autism-related SHANK3 deficient model

Oxytocin has been suggested as a potential therapeutic agent in autism and other neuropsychiatric conditions. Although, the link between the deficit in "SH3 domain and ankyrin repeat containing protein 3" (SHANK3) and autism spectrum disorders is highly studied topic, developmental mechanisms are still poorly understood. In this study, we clearly confirm that SHANK3 deficiency is accompanied with abnormalities in neurite number and length, which are reversed by oxytocin treatment (1 μM, 48h) in primary hippocampal neurons. Transient silencing for the SHANK3 gene (siSHANK3) in neuron-like cell line (SH-SY5Y) revealed a significant decrease in the expression levels of Neurexins 1α, 1β, 2α and 2β. Oxytocin treatment compensated reduced levels of Synapsin I, PSD95 and Neuroligin 3 in siSHANK3 cells suggesting a marked potential of oxytocin to ameliorate defects present in conditions of SHANK3 deficiency. Further analysis of hippocampal tissue revealed that oxytocin application (0.1 μg/μl, s.c. at P2 and P3 day) affects levels of synaptic proteins and GTPases in both WT and SHANK3 deficient mice on day P5. Oxytocin stimulated the mRNA expression of RhoB and Rac1 in both WT and SHANK3 deficient mice. Our data suggest that autism relevant synaptic pathologies could be reversed by oxytocin treatment.

A dual inhibitor targeting HMG-CoA reductase and histone deacetylase mitigates neurite degeneration in LRRK2-G2019S parkinsonism

Parkinson's disease (PD) is among the most common neurodegenerative disorders, and its etiology involves both genetic and environmental factors. The leucine-rich repeat kinase (LRRK2) G2019S mutation is the most common genetic cause of familial and sporadic PD. Current treatment is limited to dopaminergic supplementation, as no disease-modifying therapy is available yet. Recent evidence reveals that HMG-CoA reductase (HMGR) inhibitors (statins) exert neuroprotection through anti-neuroinflammatory effects, and histone deacetylase (HDAC) inhibitors mitigate neurodegeneration by promoting the transcription of neuronal survival factors. We designed and synthesized a dual inhibitor, statin hydroxamate JMF3086, that simultaneously inhibits HMGR and HDAC, and examined its neuroprotective effects on LRRK2-G2019S parkinsonism. JMF3086 restored dopaminergic neuron loss in aged LRRK2-G2019S flies and rescued neurite degeneration in primary hippocampal and dopaminergic neurons isolated from transgenic LRRK2-G2019S mice. The molecular mechanisms included downregulation of ERK1/2 phosphorylation, increased anti-apoptotic Akt phosphorylation, and inhibition of GSK3β activity to maintain cytoskeletal stability in stably transfected LRRK2-G2019S SH-SY5Y human dopaminergic cells. JMF3086 also promoted a-tubulin acetylation and kinesin-1 expression, facilitating antegrade mitochondrial transport in axons. Our findings demonstrate that JMF3086 exerted beneficial effects on restoring LRRK2-G2019S neurite degeneration by maintaining microtubule stability. This dual-target compound may be a promising mechanism-based therapy for PD.

SP6616 as a Kv2.1 inhibitor efficiently ameliorates peripheral neuropathy in diabetic mice

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes severely afflicting the patients, while there is yet no effective medication against this disease. As Kv2.1 channel functions potently in regulating neurological disorders, the present work was to investigate the regulation of Kv2.1 channel against DPN-like pathology of DPN model mice by using selective Kv2.1 inhibitor SP6616 (ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate) as a probe.

METHODS

STZ-induced type 1 diabetic mice with DPN (STZ mice) were defined at 12 weeks of age (4 weeks after STZ injection) through behavioral tests, and db/db (BKS Cg-m+/+Leprdb/J) type 2 diabetic mice with DPN (db/db mice) were at 18 weeks of age. SP6616 was administered daily via intraperitoneal injection for 4 weeks. The mechanisms underlying the amelioration of SP6616 on DPN-like pathology were investigated by RT-PCR, western blot and immunohistochemistry technical approaches against diabetic mice, and verified against the STZ mice with Kv2.1 knockdown in dorsal root ganglion (DRG) tissue by injection of adeno associated virus AAV9-Kv2.1-RNAi. Amelioration of SP6616 on the pathological behaviors of diabetic mice was assessed against tactile allodynia, thermal sensitivity and motor nerve conduction velocity (MNCV).

FINDINGS

SP6616 treatment effectively ameliorated the threshold of mechanical stimuli, thermal sensitivity and MNCV of diabetic mice. Mechanism research results indicated that SP6616 suppressed Kv2.1 expression, increased the number of intraepidermal nerve fibers (IENFs), improved peripheral nerve structure and vascular function in DRG tissue. In addition, SP6616 improved mitochondrial dysfunction through Kv2.1/CaMKKβ/AMPK/PGC-1α pathway, repressed inflammatory response by inhibiting Kv2.1/NF-κB signaling and alleviated apoptosis of DRG neuron through Kv2.1-mediated regulation of Bcl-2 family proteins and Caspase-3 in diabetic mice.

INTERPRETATION

Our work has highly supported the beneficial of Kv2.1 inhibition in ameliorating DPN-like pathology and highlighted the potential of SP6616 in the treatment of DPN.

FUNDING

Please see funding sources.

Hippocampal neural stem cells are more susceptible to the neurotoxin BMAA than primary neurons: effects on apoptosis, cellular differentiation, neurite outgrowth, and DNA methylation

Developmental exposure to the environmental neurotoxin β-N-methylamino-L-alanine (BMAA), a proposed risk factor for neurodegenerative disease, can induce long-term cognitive impairments and neurodegeneration in rats. While rodent studies have demonstrated a low transfer of BMAA to the adult brain, this toxin is capable to cross the placental barrier and accumulate in the fetal brain. Here, we investigated the differential susceptibility of primary neuronal cells and neural stem cells from fetal rat hippocampus to BMAA toxicity. Exposure to 250 µM BMAA induced cell death in neural stem cells through caspase-independent apoptosis, while the proliferation of primary neurons was reduced only at 3 mM BMAA. At the lowest concentrations tested (50 and 100 µM), BMAA disrupted neural stem cell differentiation and impaired neurite development in neural stem cell-derived neurons (e.g., reduced neurite length, the number of processes and branches per cell). BMAA induced no alterations of the neurite outgrowth in primary neurons. This demonstrates that neural stem cells are more susceptible to BMAA exposure than primary neurons. Importantly, the changes induced by BMAA in neural stem cells were mitotically inherited to daughter cells. The persistent nature of the BMAA-induced effects may be related to epigenetic alterations that interfere with the neural stem cell programming, as BMAA exposure reduced the global DNA methylation in the cells. These findings provide mechanistic understanding of how early-life exposure to BMAA may lead to adverse long-term consequences, and potentially predispose for neurodevelopmental disorders or neurodegenerative disease later in life.

ReN VM spheroids in matrix: A neural progenitor three-dimensional in vitro model reveals DYRK1A inhibitors as potential regulators of radio-sensitivity

INTRODUCTION

Pre-clinical testing of small molecules for therapeutic development across many pathologies relies on the use of in-vitro and in-vivo models. When designed and implemented well, these models serve to predict the clinical outcome as well as the toxicity of the evaluated therapies. The two-dimensional (2D) reductionist approach where cells are incubated in a mono-layer on hard plastic microtiter plates is relatively inexpensive but not physiologically relevant. In contrast, well developed and applied three dimensional (3D) in vitro models could be employed to bridge the gap between 2D in vitro primary screening and expensive in vivo rodent models by incorporating key features of the tissue microenvironment to explore differentiation, cortical development, cancers and various neuronal dysfunctions. These features include an extracellular matrix, co-culture, tension and perfusion and could replace several hundred rodents in the drug screening validation cascade.

METHODS

Human neural progenitor cells from middle brain (ReN VM, Merck Millipore, UK) were expanded as instructed by the supplier (Merck Millipore, UK), and then seeded in 96-well low-attachment plates (Corning, UK) to form multicellular spheroids followed by adding a Matrigel layer to mimic extracellular matrix around neural stem cell niche. ReN VM cells were then differentiated via EGF and bFGF deprivation for 7 days and were imaged at day 7. Radiotherapy was mimicked via gamma-radiation at 2Gy in the absence and presence of selected DYRK1A inhibitors Harmine, INDY and Leucettine 41 (L41). Cell viability was measured by AlamarBlue assay. Immunofluorescence staining was used to assess cell pluripotency marker SOX2 and differentiation marker GFAP.

RESULTS

After 7 days of differentiation, neuron early differentiation marker (GFAP, red) started to be expressed among the cells expressing neural stem cell marker SOX2 (green). Radiation treatment caused significant morphology change including the reduced viability of the spheroids. These spheroids also revealed sensitizing potential of DYRK1A inhibitors tested in this study, including Harmine, INDY and L41.

DISCUSSION & CONCLUSIONS

Combined with the benefit of greatly reducing the issues associated with in vivo rodent models, including reducing numbers of animals used in a drug screening cascade, cost, ethics, and potential animal welfare burden, we feel the well-developed and applied 3D neural spheroid model presented in this study will provide a crucial tool to evaluate combinatorial therapies, optimal drug concentrations and treatment dosages.

Troxerutin flavonoid has neuroprotective properties and increases neurite outgrowth and migration of neural stem cells from the subventricular zone

Troxerutin (TRX) is a water-soluble flavonoid which occurs commonly in the edible plants. Recent studies state that TRX improves the functionality of the nervous system and neutralizes Amyloid-ß induced neuronal toxicity. In this study, an in vitro assay based upon Neural stem cell (NSCs) isolated from the subventricular zone of the postnatal balb/c mice was established to explore the impact of TRX on individual neurogenesis processes in general and neuroprotective effect against ß-amyloid 1-42 (Aß42) induced inhibition in differentiation in particular. NSCs were identified exploiting immunostaining of the NSCs markers. Neurosphere clonogenic assay and BrdU/Ki67 immunostaining were employed to unravel the impact of TRX on proliferation. Differentiation experiments were carried out for a time span lasting from 48 h to 7 days utilizing ß-tubulin III and GFAP as neuronal and astrocyte marker respectively. Protective effects of TRX on Aß42 induced depression of NSCs differentiation were determined after 48 h of application. A neurosphere migration assay was carried out for 24 h in the presence and absence of TRX. Interestingly, TRX enhanced neuronal differentiation of NSCs in a dose-dependent manner after 48 h and 7 days of incubation and significantly enhanced neurite growth. A higher concentration of TRX also neutralized the inhibitory effects of Aß42 on neurite outgrowth and length after 48 h of incubation. TRX significantly stimulated cell migration. Overall, TRX not only promoted NSCs differentiation and migration but also neutralized the inhibitory effects of Aß42 on NSCs. TRX, therefore, offers an interesting lead structure from the perspective of drug design especially to promote neurogenesis in neurological disorders i.e. Alzheimer's disease.

Melatonin alters neuronal architecture and increases cysteine-rich protein 1 signaling in the male mouse hippocampus

Neuronal plasticity describes changes in structure, function, and connections of neurons. The hippocampus, in particular, has been shown to exhibit considerable plasticity regarding both physiological and morphological functions. Melatonin, a hormone released by the pineal gland, promotes cell survival and dendrite maturation of neurons in the newborn brain and protects against neurological disorders. In this study, we investigated the effect of exogenous melatonin on neuronal architecture and its possible mechanism in the hippocampus of adult male C57BL/6 mice. Melatonin treatment significantly increased the total length and complexity of dendrites in the apical and basal cornu ammonis (CA) 1 and in the dentate gyrus in mouse hippocampi. Spine density in CA1 apical dendrites was increased, but no significant differences in other subregions were observed. In primary cultured hippocampal neurons, the length and arborization of neurites were significantly augmented by melatonin treatment. Additionally, western blot and immunohistochemical analyses in both in vivo and in vitro systems revealed significant increases in the level of cysteine-rich protein 1 (crp-1) protein, which is known to be involved in dendritic branching in mouse hippocampal neurons after melatonin treatment. Our results suggest that exogenous melatonin leads to significant alterations of neuronal micromorphometry in the adult hippocampus, possibly via crp-1 signaling.

Self-Assembling Peptide Scaffold Carrying Neural-Cell Adhesion Molecule-Derived Mimetic-Peptide Transplantation Promotes Proliferation and Stimulates Neurite Extension by Modulating Tau Phosphorylation and Calpain/Glycogen Synthase Kinase 3 beta (GSK-3β) in Neurons

BACKGROUND Self-assembling peptide scaffolds have been extensively applied in tissue engineering. Many investigations have modified self-assembling peptide scaffolds by integrating functional motifs, with promising applications. This study aimed to generate a novel RADA16 self-assembling peptide scaffold integrating a neural-cell adhesion molecule-derived mimetic-peptide (SIDRVEPYSSTAQ) and evaluated the effects on neuron proliferation. MATERIAL AND METHODS A 37-amino-acids peptide of RADA16-activation motif containing neural-cell adhesion molecule-derived mimetic-peptide (SIDRVEPYSSTAQ) was synthesized and self-assembled into a scaffold. Dorsal root ganglion (DRG) and spinal cord motor neurons (SCMN) were primarily isolated and identified. Neurons (DRG and SCMN) were divided into FRM, FRM-MP, and FRM-MP-LiCl groups. The adherence ability of neurons was evaluated using toluidine blue staining. Proliferation and apoptosis of neurons were assessed using CCK-8 and flow cytometry assay, respectively. Immunofluorescence assay was used to measure neurite extension. Western blot assay was used to assess GSK-3ß/p-GSK-3ß, Tau/p-Tau, and calpain expression in neurons. RESULTS FRM-MP-LiCl released multiple-peptide with higher efficiency. FRM-MP-LiCl significantly enhanced proliferation and inhibited apoptosis compared to FRM and FRM-MP groups (p.

The Antioxidant, Anti-Inflammatory, and Neuroprotective Properties of the Synthetic Chalcone Derivative AN07

Chalcones belong to a class of biologically active polyphenolic natural products. As a result of their simple chemical nature, they are easily synthesized and show a variety of promising biological activities. 2-Hydroxy-4′-methoxychalcone (AN07) is a synthetic chalcone derivate with potential anti-atherosclerosis effects. In this study, we demonstrated the novel antioxidant, anti-inflammatory, and neuroprotective effects of AN07. In RAW 264.7 macrophages, AN07 attenuated lipopolysaccharide (LPS)-induced elevations in reactive oxygen species (ROS) level and oxidative stress via down-regulating gp91^phox expression and stimulating the antioxidant system of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) pathways, which were accompanied by increased glutathione (GSH) levels. Additionally, AN07 attenuated LPS-induced inflammatory factors, including NO, inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and phosphorylated inhibitor of nuclear factor kappa B-alpha (p-IκBα) in RAW 264.7 macrophages. However, the effects of AN07 on promoting nuclear Nrf2 levels and decreasing COX-2 expressions were significantly abrogated by the peroxisome proliferator-activated receptor-γ (PPARγ) antagonist GW9662. In human dopaminergic SH-SY5Y cells treated with or without methylglyoxal (MG), a toxic endogenous by-product of glycolysis, AN07 up-regulated neurotrophic signals including insulin-like growth factor 1 receptor (IGF-1R), p-Akt, p-GSK3β, glucagon-like peptide 1 receptor (GLP-1R), and brain-derived neurotrophic factor (BDNF). AN07 attenuated MG-induced apoptosis by up-regulating the B-cell lymphoma 2 (Bcl-2) protein and down-regulating the cytosolic expression of cytochrome c. AN07 also attenuated MG-induced neurite damage via down-regulating the Rho-associated protein kinase 2 (ROCK2)/phosphorylated LIM kinase 1 (p-LIMK1) pathway. Moreover, AN07 ameliorated the MG-induced down-regulation of neuroprotective Parkinsonism-associated proteins parkin, pink1, and DJ-1. These findings suggest that AN07 possesses the potentials to be an anti-inflammatory, antioxidant, and neuroprotective agent

Effect of (m)RVD-hemopressin against Aβ1-42-induced apoptosis and inhibition of neurite outgrowth in SH-SY5Y cells

Alzheimer's disease (AD) is a serious neurodegenerative disease. Senile plaques (SPs) in the extracellular space and neurofibrillary tangles (NFTs) in the intracellular areas of the brain are two typical features of AD. SPs and NFTs are composed of amyloid-β (Aβ) aggregates and hyperphosphorylated Tau, respectively. (m)RVD-hemopressin (RVD), which is derived from mouse brain peptide, binds to the cannabinoid 1 receptor (CB1R) as an agonist. Our previous study indicated that RVD reversed Aβ1-42-induced memory impairment in mice. Here, we investigated the underlying molecular mechanism of RVD on Aβ1-42-induced neurotoxicity in retinoic acid-differentiated human neuroblastoma SH-SY5Y cells. Cell viability and neurite outgrowth were investigated by live cell imaging and analysis instrument. We found that RVD reversed Aβ1-42-induced Tau phosphorylation, apoptosis and suppression of neurite outgrowth and the synapse-associated protein postsynaptic density protein 95 (PSD-95) by inhibiting the activity of protein kinase A (PKA) and glycogen synthase kinase 3β (GSK-3β). Combined treatment with AM251 (a CB1R antagonist) blocked the effects of RVD. In conclusion, RVD may be a potential therapeutic agent for the treatment of cognitive dysfunctions, such as Alzheimer's disease.

The Mixture of Gotu Kola, Cnidium Fruit, and Goji Berry Enhances Memory Functions by Inducing Nerve-Growth-Factor-Mediated Actions Both In Vitro and In Vivo

Nerve growth factor (NGF), a typical neurotrophin, has been characterized by the regulation of neuronal cell differentiation and survival involved in learning and memory functions. NGF has a main role in neurite extension and synapse formation by activating the cyclic adenosine monophosphate-response-element-binding protein (CREB) in the hippocampus. The purpose of this study was to determine whether a mixture of Gotu Kola, Cnidium fruit, and Goji berry (KYJ) enhances memory function by inducing NGF-mediated actions both in vitro and in vivo. The KYJ combination increased NGF concentration and neurite length in C6 glioma and N2a neuronal cells, respectively. Additionally, we discovered memory-enhancing effects of KYJ through increased NGF-mediated synapse maturation, CREB phosphorylation, and cell differentiation in the mouse hippocampus. These findings suggest that this combination may be a potential nootropic cognitive enhancer via the induction of NGF and NGF-dependent activities.

Meridianins and Lignarenone B as Potential GSK3β Inhibitors and Inductors of Structural Neuronal Plasticity

Glycogen Synthase Kinase 3 (GSK3) is an essential protein, with a relevant role in many diseases such as diabetes, cancer and neurodegenerative disorders. Particularly, the isoform GSK3β is related to pathologies such as Alzheimer's disease (AD). This enzyme constitutes a very interesting target for the discovery and/or design of new therapeutic agents against AD due to its relation to the hyperphosphorylation of the microtubule-associated protein tau (MAPT), and therefore, its contribution to neurofibrillary tangles (NFT) formation. An in silico target profiling study identified two marine molecular families, the indole alkaloids meridianins from the tunicate genus Aplidium, and lignarenones, the secondary metabolites of the shelled cephalaspidean mollusc Scaphander lignarius, as possible GSK3β inhibitors. The analysis of the surface of GSK3β, aimed to find possible binding regions, and the subsequent in silico binding studies revealed that both marine molecular families can act over the ATP and/or substrate binding regions. The predicted inhibitory potential of the molecules from these two chemical families was experimentally validated in vitro by showing a ~50% of increased Ser9 phosphorylation levels of the GSK3β protein. Furthermore, we determined that molecules from both molecular families potentiate structural neuronal plasticity in vitro. These results allow us to suggest that meridianins and lignarenone B could be used as possible therapeutic candidates for the treatment of GSK3β involved pathologies, such as AD.

NeuroHeal Treatment Alleviates Neuropathic Pain and Enhances Sensory Axon Regeneration

Peripheral nerve injury (PNI) leads to the loss of motor, sensory, and autonomic functions, and often triggers neuropathic pain. During the last years, many efforts have focused on finding new therapies to increase axonal regeneration or to alleviate painful conditions. Still only a few of them have targeted both phenomena. Incipient or aberrant sensory axon regeneration is related to abnormal unpleasant sensations, such as hyperalgesia or allodynia. We recently have discovered NeuroHeal, a combination of two repurposed drugs; Acamprosate and Ribavirin. NeuroHeal is a neuroprotective agent that also enhances motor axon regeneration after PNI. In this work, we investigated its effect on sensory fiber regeneration and PNI-induced painful sensations in a rat model of spare nerve injury and nerve crush. The follow up of the animals showed that NeuroHeal treatment reduced the signs of neuropathic pain in both models. Besides, the treatment favored sensory axon regeneration, as observed in dorsal root ganglion explants. Mechanistically, the effects observed in vivo may improve the resolution of cell-protective autophagy. Additionally, NeuroHeal treatment modulated the P2X4-BDNF-KCC2 axis, which is an essential driver of neuropathic pain. These data open a new therapeutic avenue based on autophagic modulation to foster endogenous regenerative mechanisms and reduce the appearance of neuropathic pain in PNI.

Gαq-mediated calcium dynamics and membrane tension modulate neurite plasticity

The formation and disruption of synaptic connections during development are a fundamental step in neural circuit formation. Subneuronal structures such as neurites are known to be sensitive to the level of spontaneous neuronal activity, but the specifics of how neurotransmitter-induced calcium activity regulates neurite homeostasis are not yet fully understood. In response to stimulation by neurotransmitters such as acetylcholine, calcium responses in cells are mediated by the Gαq/phospholipase Cβ (PLCβ)/phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) signaling pathway. Here, we show that prolonged Gαq stimulation results in the retraction of neurites in PC12 cells and the rupture of neuronal synapses by modulating membrane tension. To understand the underlying cause, we dissected the behavior of individual components of the Gαq/PLCβ/PI(4,5)P2 pathway during retraction and correlated these with the retraction of the membrane and cytoskeletal elements impacted by calcium signaling. We developed a mathematical model that combines biochemical signaling with membrane tension and cytoskeletal mechanics to show how signaling events are coupled to retraction velocity, membrane tension, and actin dynamics. The coupling between calcium and neurite retraction is shown to be operative in the Caenorhabditis elegans nervous system. This study uncovers a novel mechanochemical connection between Gαq/PLCβ /PI(4,5)P2 that couples calcium responses with neural plasticity.

A Unique GSK-3β inhibitor B10 Has a Direct Effect on Aβ, Targets Tau and Metal Dyshomeostasis, and Promotes Neuronal Neurite Outgrowth

Due to the complicated pathogenesis of Alzheimer's disease (AD), the development of multitargeted agents to simultaneously interfere with multiple pathological processes of AD is a potential choice. Glycogen synthase kinase-3β (GSK-3β) plays a vital role in the AD pathological process. In this study, we discovered a novel 1H-pyrrolo[2,3-b]pyridine derivative B10 as a GSK-3β inhibitor that features with a quinolin-8-ol moiety to target the metal dyshomeostasis of AD. B10 potently inhibited GSK-3β with an IC₅₀ of 66 ± 2.5 nM. At the concentration of 20 μM, B10 increased β-catenin abundance (β-catenin/GAPDH: 0.83 ± 0.086 vs. 0.30 ± 0.016), phosphorylated GSK-3β at Ser9 (p-GSK-3β/GAPDH: 0.53 ± 0.045 vs. 0.35 ± 0.012), and decreased the phosphorylated tau level (p-tau/GAPDH: 0.33 ± 0.065 vs. 0.83 ± 0.061) in SH-SY5Y cells. Unlike other GSK-3β inhibitors, B10 had a direct effect on Aβ by inhibiting Aβ_1-42 aggregation and promoting the Aβ_1-42 aggregate disassociation. It selectively chelated with Cu²⁺, Zn²⁺, Fe^3+, and Al³⁺, and targeted AD metal dyshomeostasis. Moreover, B10 effectively increased the mRNA expression of the recognized neurogenesis markers, GAP43, N-myc, and MAP-2, and promoted the differentiated neuronal neurite outgrowth, possibly through the GSK-3β and β-catenin signal pathways. Therefore, B10 is a potent and unique GSK-3β inhibitor that has a direct on Aβ and serves as a multifunctional anti-AD agent for further investigations.

Surface-Anchored Graphene Oxide Nanosheets on Cell-Scale Micropatterned Poly(d,l-lactide-co-caprolactone) Conduits Promote Peripheral Nerve Regeneration

Regeneration and functional recovery of peripheral nerves remain formidable due to the inefficient physical and chemical cues in the available nerve guidance conduits (NGCs). Introducing micropatterns and bioactive substances into the inner wall of NGCs can effectively regulate the behavior of Schwann cells, the elongation of axons, and the phenotype of macrophages, thereby aiding the regeneration of injured nerve. In this study, linear micropatterns with ridges and grooves of 3/3, 5/5, 10/10, and 30/30 μm were created on poly(d,l-lactide-co-caprolactone) (PLCL) films following with surface aminolysis and electrostatic adsorption of graphene oxide (GO) nanosheets. The GO-modified micropatterns could significantly accelerate the collective migration of Schwann cells (SCs) and migration of SCs from their spheroids in vitro. Moreover, the SCs migrated directionally along the stripes with a fastest rate on the 3/3-GO film that had the largest cell adhesion force. The neurites of N2a cells were oriented along the micropatterns, and the macrophages tended to differentiate into the M2 type on the 3/3-GO film judged by the higher expression of Arg 1 and IL-10. The systematic histological and functional assessments of the regenerated nerves at 4 and 8 weeks post-surgery in vivo confirmed that the 3/3-GO NGCs had better performance to promote the nerve regeneration, and the CMAP, NCV, wet weight of gastrocnemius muscle, positive S100β and NF200 area percentages, and average myelinated axon diameter were more close to those of the autograft group at 8 weeks. This type of NGCs thus has a great potential for nerve regeneration.

Growth hormone increases dendritic spine density in primary hippocampal cell cultures

OBJECTIVE

Growth hormone (GH) is widely known for its peripheral effects during growth and development. However, numerous reports also suggest that GH exert pro-cognitive, restorative, and protective properties in the brain. In in vitro studies, the detection of dendritic spines, small protrusions extending from axons, can act as a marker for cognition-related function as spine formation is considered to be associated with learning and memory. Here we show that an acute 24-hour treatment of GH can increase dendritic spine density in primary hippocampal cell cultures.

DESIGN

Primary hippocampal cells were harvested from embryonic Wistar rats and cultured for 14 days. Cells were treated with supra-physiological doses of GH (10-1000 nM) and subjected to a high-throughput screening protocol. Images were acquired and analyzed using automated image analysis and the number of spines, spines per neurite length, neurite length, and mean area of spines, was reported.

RESULTS

GH treatment (1000 nM) increased the number of dendritic spines by 83% and spines per neurite length by 82% when compared to control. For comparison BDNF, a known inducer of spine densities, produced statistically non-significant increase in this setting.

CONCLUSION

The results was found significant using the highest supra-physiological dose of GH, and the present study further confirms a potential role of the hormone in the treatment of cognitive dysfunction.

Enduring effects of juvenile social isolation on physiological properties of medium spiny neurons in nucleus accumbens

RATIONALE

Juvenile social isolation (SI) and neglect is associated with a wide range of psychiatric disorders. While dysfunction of the corticolimbic pathway is considered to link various abnormal behaviors in SI models of schizophrenia, the enduring effects of early social deprivation on physiological properties of medium spiny neurons (MSNs) in nucleus accumbens (NAc) are not well understood.

OBJECTIVES

This study investigated the impacts of juvenile SI on locomotor activity to methamphetamine (METH) and neurophysiological characteristics of MSNs in the core of NAc.

METHODS

Socially isolated C57BL/6 mice experienced single housing for 4 weeks on postnatal day (PND) 21. The locomotor response to METH (1.0 mg/kg) was observed in both socially isolated and group-housed mice at PND 56. The effects of juvenile SI on the excitatory synaptic events in MSNs and the intrinsic excitability of MSNs in NAc core were investigated in other batches during PND 63-70.

RESULTS

Socially isolated mice showed locomotor hypersensitivity to METH, although the expression of locomotor sensitization to METH in socially isolated mice was not different from group-housed mice. The recordings from MSNs of SI-reared mice exhibited higher frequency and smaller amplitude of miniature/spontaneous excitatory postsynaptic current than those from group-reared mice. Moreover, SI resulted in increased intrinsic excitability of MSNs in adult mice.

CONCLUSIONS

These results demonstrate neuronal hyperactivity in the NAc of socially isolated mice, which could contribute to locomotor hypersensitivity to METH. Furthermore, the findings indicate a biological link between early negative life events and the vulnerability to psychostimulant-induced psychosis in adulthood.

Pigment Epithelium-Derived Factor Promotes Axon Regeneration and Functional Recovery After Spinal Cord Injury

Although neurons in the adult mammalian CNS are inherently incapable of regeneration after injury, we previously showed that exogenous delivery of pigment epithelium-derived factor (PEDF), a 50-kDa neurotrophic factor (NTF), promoted adult retinal ganglion cell neuroprotection and axon regeneration. Here, we show that PEDF and other elements of the PEDF pathway are highly upregulated in dorsal root ganglion neurons (DRGN) from regenerating dorsal column (DC) injury paradigms when compared with non-regenerating DC injury models. Exogenous PEDF was neuroprotective to adult DRGN and disinhibited neurite outgrowth, whilst overexpression of PEDF after DC injury in vivo promoted significant DC axon regeneration with enhanced electrophysiological, sensory, and locomotor function. Our findings reveal that PEDF is a novel NTF for adult DRGN and may represent a therapeutically useful factor to promote functional recovery after spinal cord injury.

BDNF, NT-3 and Trk receptor agonist monoclonal antibodies promote neuron survival, neurite extension, and synapse restoration in rat cochlea ex vivo models relevant for hidden hearing loss

Neurotrophins and their mimetics are potential treatments for hearing disorders because of their trophic effects on spiral ganglion neurons (SGNs) whose connections to hair cells may be compromised in many forms of hearing loss. Studies in noise or ototoxin-exposed animals have shown that local delivery of NT-3 or BDNF has beneficial effects on SGNs and hearing. We evaluated several TrkB or TrkC monoclonal antibody agonists and small molecules, along with BDNF and NT-3, in rat cochlea ex vivo models. The TrkB agonists BDNF and a monoclonal antibody, M3, had the greatest effects on SGN survival, neurite outgrowth and branching. In organotypic cochlear explants, BDNF and M3 enhanced synapse formation between SGNs and inner hair cells and restored these connections after excitotoxin-induced synaptopathy. Loss of these synapses has recently been implicated in hidden hearing loss, a condition characterized by difficulty hearing speech in the presence of background noise. The unique profile of M3 revealed here warrants further investigation, and the broad activity profile of BDNF observed underpins its continued development as a hearing loss therapeutic.

Micropatterned nanolayers immobilized with nerve growth factor for neurite formation of PC12 cells

BACKGROUND

Nerve regeneration is important for the treatment of degenerative diseases and neurons injured by accidents. Nerve growth factor (NGF) has been previously conjugated to materials for promotion of neurogenesis.

MATERIALS AND METHODS

Photoreactive gelatin was prepared by chemical coupling of gelatin with azidobenzoic acid (P-gel), and then NGF was immobilized on substrates in the presence or absence of micropatterned photomasks. UV irradiation induced crosslinking reactions of P-gel with itself, NGF, and the plate for immobilization.

RESULTS

By adjustment of the P-gel concentration, the nanometer-order height of micropatterns was controlled. NGF was quantitatively immobilized with increasing amounts of P-gel. Immobilized NGF induced neurite outgrowth of PC12 cells, a cell line derived from a pheochromocytoma of the rat adrenal medulla, at the same level as soluble NGF. The immobilized NGF showed higher thermal stability than the soluble NGF and was repeatedly used without loss of biological activity. The 3D structure (height of the formed micropattern) regulated the behavior of neurite guidance. As a result, the orientation of neurites was regulated by the stripe pattern width.

CONCLUSION

The micropattern-immobilized NGF nanolayer biochemically and topologically regulated neurite formation.

Protein profiling of SH-SY5Y neuroblastoma cells: The effect of rhein

4,5-Dihydroxyanthraquinone-2-carboxylic acid (Rhein) has been shown to have various physiological and pharmacological properties including anticancer activity and modulatory effects on bioenergetics. In this study, we explored the impact of rhein on protein profiling of undifferentiated (UC) and differentiated (DC) SH-SY5Y cells. Besides that, the cellular morphology and expression of differentiation markers were investigated to determine the effect of rhein on retinoic acidinduced neuronal cell differentiation. Using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ ionization-time-of-flight mass spectrometry we evaluated the changes in the proteome of both UC and DC SH-SY5Y cells after 24 h treatment with rhein. Validation of selected differentially expressed proteins and the assessment of neuronal differentiation markers were performed by western blotting. Proteomic analysis revealed significant changes in the abundance of 15 proteins linked to specific cellular processes such as cytoskeleton structure and regulation, mitochondrial function, energy metabolism, protein synthesis and neuronal plasticity. We also observed that the addition of rhein to the cultured cells during differentiation resulted in a significantly reduced neurite outgrowth and decreased expression of neuronal markers. These results indicate that rhein may strongly interfere with the differentiation process of SH-SY5Y neuroblastoma cells and is capable of inducing marked proteomic changes in these cells.

Development of a neurotoxicity assay that is tuned to detect mitochondrial toxicants

Many neurotoxicants affect energy metabolism in man, but currently available test methods may still fail to predict mito- and neurotoxicity. We addressed this issue using LUHMES cells, i.e., human neuronal precursors that easily differentiate into mature neurons. Within the NeuriTox assay, they have been used to screen for neurotoxicants. Our new approach is based on culturing the cells in either glucose or galactose (Glc-Gal-NeuriTox) as the main carbohydrate source during toxicity testing. Using this Glc-Gal-NeuriTox assay, 52 mitochondrial and non-mitochondrial toxicants were tested. The panel of chemicals comprised 11 inhibitors of mitochondrial respiratory chain complex I (cI), 4 inhibitors of cII, 8 of cIII, and 2 of cIV; 8 toxicants were included as they are assumed to be mitochondrial uncouplers. In galactose, cells became more dependent on mitochondrial function, which made them 2-3 orders of magnitude more sensitive to various mitotoxicants. Moreover, galactose enhanced the specific neurotoxicity (destruction of neurites) compared to a general cytotoxicity (plasma membrane lysis) of the toxicants. The Glc-Gal-NeuriTox assay worked particularly well for inhibitors of cI and cIII, while the toxicity of uncouplers and non-mitochondrial toxicants did not differ significantly upon glucose ↔ galactose exchange. As a secondary assay, we developed a method to quantify the inhibition of all mitochondrial respiratory chain functions/complexes in LUHMES cells. The combination of the Glc-Gal-NeuriTox neurotoxicity screening assay with the mechanistic follow up of target site identification allowed both, a more sensitive detection of neurotoxicants and a sharper definition of the mode of action of mitochondrial toxicants.

The Protective Effects of Levetiracetam on a Human iPSCs-Derived Spinal Muscular Atrophy Model

Spinal muscular atrophy (SMA) is an inherited disease characterized by progressive motor neuron death and subsequent muscle weakness and is caused by deletion or mutation of survival motor neuron (SMN) 1 gene. Protecting spinal motor neuron is an effective clinical strategy for SMA. The purpose of this study was to investigate the potential effect of an anti-epileptic drug levetiracetam on SMA. In the present study, we used differentiated spinal motor neurons (MNs) from SMA patient-derived induced pluripotent stem cells (SMA-iPSCs) to investigate the effect of levetiracetam. Levetiracetam promoted neurite elongation in SMA-iPSCs-MNs. TUNEL-positive spinal motor neurons were significantly reduced by levetiracetam in SMA-iPSCs-MNs. In addition, the expression level of cleaved-caspase 3 was decreased by levetiracetam in SMA-iPSCs-MNs. Furthermore, levetiracetam improved impaired mitochondrial function in SMA-iPSCs-MNs. On the other hand, levetiracetam did not affect the expression level of SMN protein in SMA-iPSCs-MNs. These findings indicate that levetiracetam has a neuroprotective effect for SMA.

Short-term fish oil supplementation applied in presymptomatic stage of Alzheimer's disease enhances microglial/macrophage barrier and prevents neuritic dystrophy in parietal cortex of 5xFAD mouse model

Dystrophic neurites and activated microglia are one of the main neuropathological characteristics of Alzheimer's disease (AD). Although the use of supplements with omega-3 fatty acids has been associated with reduced risk and lessened AD pathology, it still remains elusive whether such a treatment could affect dystrophic neurites (DNs) formation and microglia/macrophage behavior in the early phase of disease. We analyzed the effects of short-term (3 weeks) fish oil supplementation on DNs formation, tau hyperphosphorylation, Amyloid-beta peptide 1–42 (Aβ42) levels and microglial/macrophage response to AD pathology in the parietal cortex of 4-month-old 5xFAD mice, a mouse model of AD. The present study shows for the first time that short-term FO supplementation applied in presymptomatic stage of AD, alters the behaviour of microglia/macrophages prompting them to establish a physical barrier around amyloid plaques. This barrier significantly suppresses DNs formation through the reduction of both Aβ content and tau hyperphosphorylation. Moreover, the short-term FO treatment neither suppresses inflammation nor enhances phagocytic properties of microglia/macrophages in the response to Aβ pathology, the effects most commonly attributed to the fish oil supplementation. Our findings suggest that fish oil consumption may play an important role in modulating microglial/macrophage response and ameliorating the AD pathology in presymptomatic stage of Alzheimer's disease.

Impact of topical anti-fibrotics on corneal nerve regeneration in vivo

Recent work in vitro has shown that fibroblasts and myofibroblasts have opposing effects on neurite outgrowth by peripheral sensory neurons. Here, we tested a prediction from this work that dampening the fibrotic response in the early phases of corneal wound healing in vivo could enhance reinnervation after a large, deep corneal injury such as that induced by photorefractive keratectomy (PRK). Since topical steroids and Mitomycin C (MMC) are often used clinically for mitigating corneal inflammation and scarring after PRK, they were ideal to test this prediction. Twenty adult cats underwent bilateral, myopic PRK over a 6 mm optical zone followed by either: (1) intraoperative MMC (n = 12 eyes), (2) intraoperative prednisolone acetate (PA) followed by twice daily topical application for 14 days (n = 12 eyes), or (3) no post-operative treatment (n = 16 eyes). Anti-fibrotic effects of MMC and PA were verified optically and histologically. First, optical coherence tomography (OCT) performed pre-operatively and 2, 4 and 12 weeks post-PRK was used to assess changes in corneal backscatter reflectivity. Post-mortem immunohistochemistry was then performed at 2, 4 and 12 weeks post-PRK, using antibodies against α-smooth muscle actin (α-SMA). Finally, immunohistochemistry with antibodies against βIII-tubulin (Tuj-1) was performed in the same corneas to quantify changes in nerve distribution relative to unoperated, control cat corneas. Two weeks after PRK, untreated corneas exhibited the greatest amount of staining for α-SMA, followed by PA-treated and MMC-treated eyes. This was matched by higher OCT-based stromal reflectivity values in untreated, than PA- and MMC-treated eyes. PA treatment appeared to slow epithelial healing and although normal epithelial thickness was restored by 12 weeks-post-PRK, intra-epithelial nerve length only reached ∼1/6 normal values in PA-treated eyes. Even peripheral cornea (outside the ablation zone) exhibited depressed intra-epithelial nerve densities after PA treatment. Stromal nerves were abundant under the α-SMA zone, but appeared to largely avoid it, creating an area of sub-epithelial stroma devoid of nerve trunks. In turn, this may have led to the lack of sub-basal and intra-epithelial nerves in the ablation zone of PA-treated eyes 4 weeks after PRK, and their continuing paucity 12 weeks after PRK. Intra-operative MMC, which sharply decreased α-SMA staining, was followed by rapid restoration of nerve densities in all corneal layers post-PRK compared to untreated corneas. Curiously, stromal nerves appeared unaffected by the development of large, stromal, acellular zones in MMC-treated corneas. Overall, it appears that post-PRK treatments that were most effective at reducing α-SMA-positive cells in the early post-operative period benefited nerve regeneration the most, resulting in more rapid restoration of nerve densities in all corneal layers of the ablation zone and of the corneal periphery.

Low sulfated heparins target multiple proteins for central nervous system repair

The lack of endogenous repair following spinal cord injury (SCI) accounts for the frequent permanent deficits for which effective treatments are absent. Previously, we demonstrated that low sulfated modified heparin mimetics (LS-mHeps) attenuate astrocytosis, suggesting they may represent a novel therapeutic approach. mHeps are glycomolecules with structural similarities to resident heparan sulfates (HS), which modulate cell signaling by both sequestering ligands, and acting as cofactors in the formation of ligand-receptor complexes. To explore whether mHeps can affect the myelination and neurite outgrowth necessary for repair after SCI, we created lesioned or demyelinated neural cell co-cultures and exposed them with a panel of mHeps with varying degrees and positions of their sulfate moieties. LS-mHep7 enhanced neurite outgrowth and myelination, whereas highly sulfated mHeps (HS-mHeps) had attenuating effects. LS-mHeps had no effects on myelination or neurite extension in developing, uninjured myelinating cultures, suggesting they might exert their proregenerating effects by modulating or sequestering inhibitory factors secreted after injury. To investigate this, we examined conditioned media from cultures using chemokine arrays and conducted an unbiased proteomics approach by applying TMT-LC/MS to mHep7 affinity purified conditioned media from these cultures. Multiple protein factors reported to play a role in damage or repair mechanisms were identified, including amyloid betaA4. Amyloid beta peptide (1-42) was validated as an important candidate by treating myelination cultures and shown to inhibit myelination. Thus, we propose that LS-mHeps exert multiple beneficial effects on mechanisms supporting enhanced repair, and represent novel candidates as therapeutics for CNS damage.

Promoting the Outgrowth of Neurites on Electrospun Microfibers by Functionalization with Electrosprayed Microparticles of Fatty Acids

Controlling the outgrowth of neurites is important for enhancing the repair of injured nerves and understanding the development of nervous systems. Herein we report a simple strategy for enhancing the outgrowth of neurites through a unique integration of topographical guidance and a chemical cue. We use electrospray to easily functionalize the surface of a substrate with microparticles of natural fatty acids at a controllable density. Through a synergistic effect from the surface roughness arising from the microparticles and the chemical cue offered by the fatty acids, the outgrowth of neurites from PC12 cells is greatly enhanced. We also functionalize the surfaces of uniaxially aligned, electrospun microfibers with the microparticles and further demonstrate that the substrates can guide and enhance directional outgrowth of neurites from both PC12 multicellular spheroids and chick embryonic dorsal root ganglia bodies.

D3T acts as a pro-oxidant in a cell culture model of diabetes-induced peripheral neuropathy

Diabetes mellitus is one of the most common chronic diseases in the United States and peripheral neuropathy (PN) affects at least 50% of diabetic patients. Medications available for patients ameliorate symptoms (pain), but do not protect against cellular damage and come with severe side effects, leading to discontinued use. Our research group uses differentiated SH-SY5Y cells treated with advanced glycation end products (AGE) as a model to mimic diabetic conditions and to study the mechanisms of oxidative stress mediated cell damage and antioxidant protection. N-acetylcysteine (NAC), a common antioxidant supplement, was previously shown by our group to fully protect against AGE-induced damage. We have also shown that 3H-1,2-dithiole-3-thione (D3T), a cruciferous vegetable constituent and potent inducer of nuclear factor (erythroid-derived 2)- like 2 (Nrf2), can significantly increase cellular GSH concentrations and protect against oxidant species-induced cell death. Paradoxically, D3T conferred no protection against AGE-induced cell death or neurite degeneration. In the present study we establish a mechanism for this paradox by showing that D3T in combination with AGE increased oxidant species generation and depleted GSH via inhibition of glutathione reductase (GR) activity and increased expression of the NADPH generating enzyme glucose-6-phosphate dehydrogenase (G6PD). Blocking NADPH generation with the G6PD inhibitor dehydroepiandrosterone was found to protect against AGE-induced oxidant species generation, loss of viability, and neurite degeneration. It further reversed the D3T potentiation effect under AGE-treated conditions. Collectively, these results suggest that strategies aimed at combating oxidative stress that rely on upregulation of the endogenous antioxidant defense system via Nrf2 may backfire and promote further damage in diabetic PN.

Neuronal survival of DRG neurons after neurite transection in vitro promotes by nerve growth factor and brain derived neurotrophic factor

Neurotrophic factors are growth factors that promote neuronal survival, regulate synaptic function and neurotransmitter release, and promote the plasticity and growth of axons in the peripheral and central nervous systems. This study focused on the roles of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in the survival of adult dorsal root ganglion (DRG) neurons following axotomy. To investigate this, we cultured adult mouse DRG neurons and administered NGF or BDNF to the culture medium at different doses before transection. After determining the optimal doses of NGF and BDNF, these factors were then applied in combination. Axotomy was performed using a precise laser beam and neuronal death was visualized through cell observer microscopy system, by adding propidium iodide to the culture medium. The results demonstrate that the optimal doses of NGF and BDNF for neuronal survival are 150 ng/mL and 50 ng/mL, respectively. The highest level of neuronal survival was observed in the cells treated with a combination of NGF and BDNF. In conclusion, NGF and BDNF have a positive effect, both individually and in combination, on the survival of DRG neurons following neurite transection.

Medicinal Leech CNS as a Model for Exosome Studies in the Crosstalk between Microglia and Neurons

In healthy or pathological brains, the neuroinflammatory state is supported by a strong communication involving microglia and neurons. Recent studies indicate that extracellular vesicles (EVs), including exosomes and microvesicles, play a key role in the physiological interactions between cells allowing central nervous system (CNS) development and/or integrity. The present report used medicinal leech CNS to investigate microglia/neuron crosstalk from ex vivo approaches as well as primary cultures. The results demonstrated a large production of exosomes from microglia. Their incubation to primary neuronal cultures showed a strong interaction with neurites. In addition, neurite outgrowth assays demonstrated microglia exosomes to exhibit significant neurotrophic activities using at least a Transforming Growth Factor beta (TGF-β) family member, called nGDF (nervous Growth/Differentiation Factor). Of interest, the results also showed an EV-mediated dialog between leech microglia and rat cells highlighting this communication to be more a matter of molecules than of species. Taken together, the present report brings a new insight into the microglia/neuron crosstalk in CNS and would help deciphering the molecular evolution of such a cell communication in brain.

Oxytocin alters the morphology of hypothalamic neurons via the transcription factor myocyte enhancer factor 2A (MEF-2A)

Oxytocin (OT) has gained attention not only as anxiolytic drug and as potential treatment option for autistic children; it also acts as a growth and differentiation factor in neuronal cells. While behavioral effects of OT have been studied in detail, knowledge about the cellular effects of OT is relatively sparse. In this study, we present evidence for three hypotheses: 1) OT leads to neurite retraction in hypothalamic neurons via the OT receptor (OTR) 2) The transcription factor MEF-2A is a central regulator of OT-induced neurite retraction, and 3) The MAPK pathway is critical for OT-induced MEF-2A activation. Incubation of rat hypothalamic H32 cells with 10 nM to 1 μM OT, vasopressin, and the specific OTR agonist TGOT, over the course of 12 h resulted in a time-dependent, significant retraction of neurites. In addition, the size of the nuclear compartment increased, whereas the overall cell size remained unchanged. OT treatment for 10 h increased the cellular viability significantly, and this effect could be blocked by a specific OTR antagonist, providing evidence for a specific and pro-active effect of OT on neurite retraction, and not as an unspecific side effect of apoptosis. The molecular mechanism that controls OT-induced neurite retraction includes a reduced phosphorylation of the transcription factor MEF-2A at Serine 408 (S408). This dephosphorylation is under the control of the OTR-coupled MAPK pathway, as blocking MEK1/2 by U0126 inhibited MEF-2A activation and subsequent neurite retraction. The siRNA-mediated knockdown of MEF-2A prevented the OT-induced neurite retraction, providing direct evidence for a role of MEF-2A in morphological alterations induced by OT treatment. In summary, the present study reveals a previously unknown OTR-coupled MAPK-MEF-2A pathway, which is responsible for OT-induced neurite retraction of hypothalamic neurons.

The effect of rho kinase inhibition on morphological and electrophysiological maturity in iPSC-derived neurons

Induced pluripotent stem cell (iPSC)-derived neurons permit the study of neurogenesis and neurological disease in a human setting. However, the electrophysiological properties of iPSC-derived neurons are consistent with those observed in immature cortical neurons, including a high membrane resistance depolarized resting membrane potential and immature firing properties, limiting their use in modeling neuronal activity in adult cells. Based on the proven association between inhibiting rho kinase (ROCK) and increased neurite complexity, we seek to determine if short-term ROCK inhibition during the first 1-2 weeks of differentiation would increase morphological complexity and electrophysiological maturity after several weeks of differentiation. While inhibiting ROCK resulted in increased neurite formation after 24 h, this effect did not persist at 3 and 6 weeks of age. Additionally, there was no effect of ROCK inhibition on electrophysiological properties at 2-3, 6, or 12 weeks of age, despite an increase in evoked and spontaneous firing and a more hyperpolarized resting membrane potential over time. These results indicate that while there is a clear effect of time on electrophysiological maturity, ROCK inhibition did not accelerate maturity.

Differences in Neuritogenic Activity and Signaling Activation of Madecassoside, Asiaticoside, and Their Aglycones in Neuro-2a cells

Madecassoside (MS) and asiaticoside (AS) along with their aglycones, madecassic acid (MA) and asiatic acid (AA), are considered the major neuroactive triterpenoid constituents of Centella asiatica. In this study, we aimed to compare MS, AS, MA, and AA for their neurite outgrowth activities and mechanisms in Neuro-2a cells. Immunofluorescent cell staining showed MS and AS significantly increased the percentage of neurite-bearing cells (%NBC) and the neurite length with higher potency than MA and AA. The triterpenoid glycosides induced sustained extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) phosphorylation, while their aglycones activated only transient signaling of ERK1/2. Suppression of ERK1/2 activation significantly abolished not only cAMP response element-binding protein (CREB) phosphorylation but also the increment of %NBC and neurite length in MS- and AS-treated cells. Inhibition of ERK phosphorylation did not produce similar blockage of CREB activation and neurite outgrowth in MA- and AA-treated cells. On the other hand, inactivation of protein kinase B (Akt) resulted in a suppression of neurite lengthening in all studied triterpenoids. This is the first study discerning the different signaling pathways of neurite outgrowth activity induced by C. asiatica triterpenoid glycosides and aglycones. Neurite outgrowth activity of the glycosides MS and AS was found to involve the activation of sustained ERK phosphorylation leading to CREB activation, while ERK activation was not associated with MA- and AA-induced neurite outgrowth. In addition, Akt activation was evident to be more involved in neurite elongation process.

Aligning Synthetic Hippocampal Neural Circuits via Self-Rolled-Up Silicon Nitride Microtube Arrays

Directing neurons to form predetermined circuits with the intention of treating neurological disorders and neurodegenerative diseases is a fundamental goal and current challenge in neuroengineering. Until recently, only neuronal aggregates were studied and characterized in culture, which can limit information gathered to populations of cells. In this study, we use a substrate constructed of arrays of strain-induced self-rolled-up membrane 3D architectures. This results in changes in the neuronal architecture and altered growth dynamics of neurites. Hippocampal neurons from postnatal rats were cultured at low confluency (∼250 cells mm^-2) on an array of transparent rolled-up microtubes (μ-tubes; 4-5 μm diameter) of varying topographical arrangements. Neurite growth on the μ-tubes was characterized and compared to controls in order to establish a baseline for alignment imposed by the topography. Compared to control substrates, neurites are significantly more aligned toward the 0° reference on the μ-tube array. Pitch (20-60 and 100 μm) and μ-tube length (30-80 μm) of array elements were also varied to investigate their impact on neurite alignment. We found that alignment was improved by the gradient pitch arrangement and with longer μ-tubes. Application of this technology will enhance the ability to construct intentional neural circuits through array design and manipulation of individual neurons and can be adapted to address challenges in neural repair, reinnervation, and neuroregeneration.

Calpain Inhibition Increases SMN Protein in Spinal Cord Motoneurons and Ameliorates the Spinal Muscular Atrophy Phenotype in Mice

Spinal muscular atrophy (SMA), a leading genetic cause of infant death, is caused by the loss of survival motor neuron 1 (SMN1) gene. SMA is characterized by the degeneration and loss of spinal cord motoneurons (MNs), muscular atrophy, and weakness. SMN2 is the centromeric duplication of the SMN gene, whose numbers of copies determine the intracellular levels of SMN protein and define the disease onset and severity. It has been demonstrated that elevating SMN levels can be an important strategy in treating SMA and can be achieved by several mechanisms, including promotion of protein stability. SMN protein is a direct target of the calcium-dependent protease calpain and induces its proteolytic cleavage in muscle cells. In this study, we examined the involvement of calpain in SMN regulation on MNs. In vitro experiments showed that calpain activation induces SMN cleavage in CD1 and SMA mouse spinal cord MNs. Additionally, calpain 1 knockdown or inhibition increased SMN level and prevent neurite degeneration in these cells. We examined the effects of calpain inhibition on the phenotype of two severe SMA mouse models. Treatment with the calpain inhibitor, calpeptin, significantly improved the lifespan and motor function of these mice. Our observations show that calpain regulates SMN level in MNs and calpeptin administration improves SMA phenotype demonstrating the potential utility of calpain inhibitors in SMA therapy.