Neuregulin-1 beta 1 is implicated in pathogenesis of multiple sclerosis.

Multiple sclerosis is characterized by immune mediated neurodegeneration that results in progressive, life-long neurological and cognitive impairments. Yet, the endogenous mechanisms underlying multiple sclerosis pathophysiology are not fully understood. Here, we provide compelling evidence that associates dysregulation of neuregulin-1 beta 1 (Nrg-1ß1) with multiple sclerosis pathogenesis and progression. In the experimental autoimmune encephalomyelitis model of multiple sclerosis, we demonstrate that Nrg-1ß1 levels are abated within spinal cord lesions and peripherally in the plasma and spleen during presymptomatic, onset and progressive course of the disease. We demonstrate that plasma levels of Nrg-1ß1 are also significantly reduced in individuals with early multiple sclerosis and is positively associated with progression to relapsing-remitting multiple sclerosis. The functional impact of Nrg-1ß1 downregulation preceded disease onset and progression, and its systemic restoration was sufficient to delay experimental autoimmune encephalomyelitis symptoms and alleviate disease burden. Intriguingly, Nrg-1ß1 therapy exhibited a desirable and extended therapeutic time window of efficacy when administered prophylactically, symptomatically, acutely or chronically. Using in vivo and in vitro assessments, we identified that Nrg-1ß1 treatment mediates its beneficial effects in EAE by providing a more balanced immune response. Mechanistically, Nrg-1ß1 moderated monocyte infiltration at the blood-CNS interface by attenuating chondroitin sulphate proteoglycans and MMP9. Moreover, Nrg-1ß1 fostered a regulatory and reparative phenotype in macrophages, T helper type 1 (Th1) cells and microglia in the spinal cord lesions of EAE mice. Taken together, our new findings in multiple sclerosis and experimental autoimmune encephalomyelitis have uncovered a novel regulatory role for Nrg-1ß1 early in the disease course and suggest its potential as a specific therapeutic target to ameliorate disease progression and severity.

LAR and PTPσ receptors are negative regulators of oligodendrogenesis and oligodendrocyte integrity in spinal cord injury.

Following spinal cord injury (SCI), the population of mature oligodendrocytes undergoes substantial cell death; promoting their preservation and replacement is a viable strategy for preserving axonal integrity and white matter repair in the injured spinal cord. Dramatic upregulation of matrix chondroitin sulfate proteoglycans (CSPGs) is shown to pose an obstacle to endogenous repair processes, and targeting CSPGs improves functional recovery after SCI. However, the cellular and molecular mechanisms underlying the inhibitory effects of CSPGs remain largely undefined. Modulation of CSPGs specific signaling receptors, leukocyte common antigen-related (LAR), and protein tyrosine phosphatase-sigma (PTPσ) allows us to uncover the role and mechanisms of CSPGs in regulating oligodendrocytes in SCI. Here, utilizing specific functionally blocking peptides in a clinically relevant model of contusive/compressive SCI in the rat, we demonstrate that inhibition of PTPσ and LAR receptors promotes oligodendrogenesis by endogenous precursor cells, attenuates caspase 3-mediated cell death in mature oligodendrocytes, and preserves myelin. In parallel in vitro systems, we have unraveled that CSPGs directly induce apoptosis in populations of neural precursor cells and oligodendrocyte progenitor cells and limit their ability for oligodendrocyte differentiation, maturation, and myelination. These negative effects of CSPGs are mediated through the activation of both LAR and PTPσ receptors and the downstream Rho/ROCK pathway. Thus, we have identified a novel inhibitory role for PTPσ and LAR in regulating oligodendrocyte differentiation and apoptosis in the injured adult spinal cord and a new feasible therapeutic strategy for optimizing endogenous cell replacement following SCI.

Neuregulin-1 promotes remyelination and fosters a pro-regenerative inflammatory response in focal demyelinating lesions of the spinal cord.

Oligodendroglial cell death and demyelination are hallmarks of neurotrauma and multiple sclerosis that cause axonal damage and functional impairments. Remyelination remains a challenge as the ability of endogenous precursor cells for oligodendrocyte replacement is hindered in the unfavorable milieu of demyelinating conditions. Here, in a rat model of lysolecithin lysophosphatidyl-choline (LPC)-induced focal demyelination, we report that Neuregulin-1 (Nrg-1), an important factor for oligodendrocytes and myelination, is dysregulated in demyelinating lesions and its bio-availability can promote oligodendrogenesis and remyelination. We delivered recombinant human Nrg-1ß1 (rhNrg-1ß1) intraspinally in the vicinity of LPC demyelinating lesion in a sustained manner using poly lactic-co-glycolic acid microcarriers. Availability of Nrg-1 promoted generation and maturation of new oligodendrocytes, and accelerated endogenous remyelination by both oligodendrocyte and Schwann cell populations in demyelinating foci. Importantly, Nrg-1 enhanced myelin thickness in newly remyelinated spinal cord axons. Our complementary in vitro studies also provided direct evidence that Nrg-1 significantly promotes maturation of new oligodendrocytes and facilitates their transition to a myelinating phenotype. Nrg-1 therapy remarkably attenuated the upregulated expression chondroitin sulfate proteoglycans (CSPGs) specific glycosaminoglycans in the extracellular matrix of demyelinating foci and promoted interleukin-10 (IL-10) production by immune cells. CSPGs and IL-10 are known to negatively and positively regulate remyelination, respectively. We found that Nrg-1 effects are mediated through ErbB2 and ErbB4 receptor activation. Our work provides novel evidence that dysregulated levels of Nrg-1 in demyelinating lesions of the spinal cord pose a challenge to endogenous remyelination, and appear to be an underlying cause of myelin thinning in newly remyelinated axons.

Neuregulin-1 elicits a regulatory immune response following traumatic spinal cord injury.

BACKGROUND: Spinal cord injury (SCI) triggers a robust neuroinflammatory response that governs secondary injury mechanisms with both degenerative and pro-regenerative effects. Identifying new immunomodulatory therapies to promote the supportive aspect of immune response is critically needed for the treatment of SCI. We previously demonstrated that SCI results in acute and permanent depletion of the neuronally derived Neuregulin-1 (Nrg-1) in the spinal cord. Increasing the dysregulated level of Nrg-1 through acute intrathecal Nrg-1 treatment enhanced endogenous cell replacement and promoted white matter preservation and functional recovery in rat SCI. Moreover, we identified a neuroprotective role for Nrg-1 in moderating the activity of resident astrocytes and microglia following injury. To date, the impact of Nrg-1 on immune response in SCI has not yet been investigated. In this study, we elucidated the effect of systemic Nrg-1 therapy on the recruitment and function of macrophages, T cells, and B cells, three major leukocyte populations involved in neuroinflammatory processes following SCI. METHODS: We utilized a clinically relevant model of moderately severe compressive SCI in female Sprague-Dawley rats. Nrg-1 (2 µg/day) or saline was delivered subcutaneously through osmotic mini-pumps starting 30 min after SCI. We conducted flow cytometry, quantitative real-time PCR, and immunohistochemistry at acute, subacute, and chronic stages of SCI to investigate the effects of Nrg-1 treatment on systemic and spinal cord immune response as well as cytokine, chemokine, and antibody production. RESULTS: We provide novel evidence that Nrg-1 promotes a pro-regenerative immune response after SCI. Bioavailability of Nrg-1 stimulated a regulatory phenotype in T and B cells and augmented the population of M2 macrophages in the spinal cord and blood during the acute and chronic stages of SCI. Importantly, Nrg-1 fostered a more balanced microenvironment in the injured spinal cord by attenuating antibody deposition and expression of pro-inflammatory cytokines and chemokines while upregulating pro-regenerative mediators. CONCLUSION: We provide the first evidence of a significant regulatory role for Nrg-1 in neuroinflammation after SCI. Importantly, the present study establishes the promise of systemic Nrg-1 treatment as a candidate immunotherapy for traumatic SCI and other CNS neuroinflammatory conditions.

Perturbing chondroitin sulfate proteoglycan signaling through LAR and PTPσ receptors promotes a beneficial inflammatory response following spinal cord injury.

BACKGROUND: Traumatic spinal cord injury (SCI) results in upregulation of chondroitin sulfate proteoglycans (CSPGs) by reactive glia that impedes repair and regeneration in the spinal cord. Degradation of CSPGs is known to be beneficial in promoting endogenous repair mechanisms including axonal sprouting/regeneration, oligodendrocyte replacement, and remyelination, and is associated with improvements in functional outcomes after SCI. Recent evidence suggests that CSPGs may regulate secondary injury mechanisms by modulating neuroinflammation after SCI. To date, the role of CSPGs in SCI neuroinflammation remains largely unexplored. The recent discovery of CSPG-specific receptors, leukocyte common antigen-related (LAR) and protein tyrosine phosphatase-sigma (PTPσ), allows unraveling the cellular and molecular mechanisms of CSPGs in SCI. In the present study, we have employed parallel in vivo and in vitro approaches to dissect the role of CSPGs and their receptors LAR and PTPσ in modulating the inflammatory processes in the acute and subacute phases of SCI. METHODS: In a clinically relevant model of compressive SCI in female Sprague Dawley rats, we targeted LAR and PTPσ by two intracellular functionally blocking peptides, termed ILP and ISP, respectively. We delivered ILP and ISP treatment intrathecally to the injured spinal cord in a sustainable manner by osmotic mini-pumps for various time-points post-SCI. We employed flow cytometry, Western blotting, and immunohistochemistry in rat SCI, as well as complementary in vitro studies in primary microglia cultures to address our questions. RESULTS: We provide novel evidence that signifies a key immunomodulatory role for LAR and PTPσ receptors in SCI. We show that blocking LAR and PTPσ reduces the population of classically activated M1 microglia/macrophages, while promoting alternatively activated M2 microglia/macrophages and T regulatory cells. This shift was associated with a remarkable elevation in pro-regenerative immune mediators, interleukin-10 (IL-10), and Arginase-1. Our parallel in vitro studies in microglia identified that while CSPGs do not induce an M1 phenotype per se, they promote a pro-inflammatory phenotype. Interestingly, inhibiting LAR and PTPσ in M1 and M2 microglia positively modulates their inflammatory response in the presence of CSPGs, and harnesses their ability for phagocytosis and mobilization. Interestingly, our findings indicate that CSPGs regulate microglia, at least in part, through the activation of the Rho/ROCK pathway downstream of LAR and PTPσ. CONCLUSIONS: We have unveiled a novel role for LAR and PTPσ in regulating neuroinflammation in traumatic SCI. Our findings provide new insights into the mechanisms by which manipulation of CSPG signaling can promote recovery from SCI. More importantly, this work introduces the potential of ILP/ISP as a viable strategy for modulating the immune response following SCI and other neuroinflammatory conditions of the central nervous system.

Neuregulin-1 positively modulates glial response and improves neurological recovery following traumatic spinal cord injury.

Spinal cord injury (SCI) results in glial activation and neuroinflammation, which play pivotal roles in the secondary injury mechanisms with both pro- and antiregeneration effects. Presently, little is known about the endogenous molecular mechanisms that regulate glial functions in the injured spinal cord. We previously reported that the expression of neuregulin-1 (Nrg-1) is acutely and chronically declined following traumatic SCI. Here, we investigated the potential ramifications of Nrg-1 dysregulation on glial and immune cell reactivity following SCI. Using complementary in vitro approaches and a clinically-relevant model of severe compressive SCI in rats, we demonstrate that immediate delivery of Nrg-1 (500 ng/day) after injury enhances a neuroprotective phenotype in inflammatory cells associated with increased interleukin-10 and arginase-1 expression. We also found a decrease in proinflammatory factors including IL-1ß, TNF-α, matrix metalloproteinases (MMP-2 and 9) and nitric oxide after injury. In addition, Nrg-1 modulates astrogliosis and scar formation by reducing inhibitory chondroitin sulfate proteoglycans after SCI. Mechanistically, Nrg-1 effects on activated glia are mediated through ErbB2 tyrosine phosphorylation in an ErbB2/3 heterodimer complex. Furthermore, Nrg-1 exerts its effects through downregulation of MyD88, a downstream adaptor of Toll-like receptors, and increased phosphorylation of Erk1/2 and STAT3. Nrg-1 treatment with the therapeutic dosage of 1.5 µg/day significantly improves tissue preservation and functional recovery following SCI. Our findings for the first time provide novel insights into the role and mechanisms of Nrg-1 in acute SCI and suggest a positive immunomodulatory role for Nrg-1 that can harness the beneficial properties of activated glia and inflammatory cells in recovery following SCI.

Myelin basic protein cleaves cell adhesion molecule L1 and promotes neuritogenesis and cell survival.

The cell adhesion molecule L1 is a Lewis(x)-carrying glycoprotein that plays important roles in the developing and adult nervous system. Here we show that myelin basic protein (MBP) binds to L1 in a Lewis(x)-dependent manner. Furthermore, we demonstrate that MBP is released by murine cerebellar neurons as a sumoylated dynamin-containing protein upon L1 stimulation and that this MBP cleaves L1 as a serine protease in the L1 extracellular domain at Arg(687) yielding a transmembrane fragment that promotes neurite outgrowth and neuronal survival in cell culture. L1-induced neurite outgrowth and neuronal survival are reduced in MBP-deficient cerebellar neurons and in wild-type cerebellar neurons in the presence of an MBP antibody or L1 peptide containing the MBP cleavage site. Genetic ablation of MBP in shiverer mice and mutagenesis of the proteolytically active site in MBP or of the MBP cleavage site within L1 as well as serine protease inhibitors and an L1 peptide containing the MBP cleavage site abolish generation of the L1 fragment. Our findings provide evidence for novel functions of MBP in the nervous system.

Biotechnological interventions in Withania somnifera (L.) Dunal.

Withania somnifera is one of the most valued plants and is extensively used in Indian, Unani, and African systems of traditional medicine. It possess a wide array of therapeutic properties including anti-arthritic, anti-aging, anti-cancer, anti-inflammatory, immunoregulatory, chemoprotective, cardioprotective, and recovery from neurodegenerative disorders. With the growing realization of benefits and associated challenges in the improvement of W. somnifera, studies on exploration of genetic and chemotypic variations, identification and characterization of important genes, and understanding the secondary metabolites production and their modulation has gained significant momentum. In recent years, several in vitro and in vivo preclinical studies have facilitated the validation of therapeutic potential of the phytochemicals derived from W. somnifera and have provided necessary impetus for gaining deeper insight into the mechanistic aspects involved in the mode of action of these important pharmaceutically active constituents. The present review highlights some of the current developments and future prospects of biotechnological intervention in this important medicinal plant.

Gemini imidazolium surfactants: synthesis and their biophysiochemical study.

New gemini imidazolium surfactants 9-13 have been synthesized by a regioselective epoxy ring-opening reaction under solvent-free conditions. The surface properties of these new gemini surfactants were evaluated by surface tension and conductivity measurements. These surfactants have been found to have low critical micelle concentration (cmc) values as compared to other categories of gemini cationic surfactants and also showed the tendency to form premicellar aggregates in solution at sufficiently low concentration below their cmc values. The thermal degradation of these surfactants was determined by thermograviometry analysis (TGA). These new cationic surfactants have a good DNA binding capability as determined by agarose gel electrophoresis and ethidium bromide exclusion experiments. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line.

Water extract of ashwagandha leaves limits proliferation and migration, and induces differentiation in glioma cells.

Root extracts of Withania somnifera (Ashwagandha) are commonly used as a remedy for a variety of ailments and a general tonic for overall health and longevity in the Indian traditional medicine system, Ayurveda. We undertook a study to investigate the anti-proliferative and differentiation-inducing activities in the water extract of Ashwagandha leaves (ASH-WEX) by examining in glioma cells. Preliminary detection for phytochemicals was performed by thin-layer chromatography. Cytotoxicity was determined using trypan blue and MTT assays. Expression level of an hsp70 family protein (mortalin), glial cell differentiation marker [glial fibrillary acidic protein (GFAP)] and neural cell adhesion molecule (NCAM) were analyzed by immunocytochemistry and immunoblotting. Anti-migratory assay was also done using wound-scratch assay. Expression levels of mortalin, GFAP and NCAM showed changes, subsequent to the treatment with ASH-WEX. The data support the existence of anti-proliferative, differentiation-inducing and anti-migratory/anti-metastasis activities in ASH-WEX that could be used as potentially safe and complimentary therapy for glioma.

Neuroendocrine plasticity in GnRH release is disrupted by valproic acid treatment of cycling rats.

Valproic acid (VPA) has been used for > 30 years in the treatment of epilepsy and is now one of the most frequently prescribed anti-epileptic drugs (AEDs) worldwide. Its chronic use has been associated with hyperandrogenism and polycystic ovaries in women with epilepsy and thus suggests change in normal levels of estrogens--the gonadal steroids in females. We have tested the hypothesis whether AEDs that exert anticonvulsive effects via key molecules of the gamma amino butyric acid (GABAergic) system, have inhibitory effects on the hypothalamo-hypophyseal-gonadal (HPG) axis at the level of hypothalamic gonadotropin releasing hormone (GnRH) synthesis and/or release and thereby affect reproductive health. Three-month old female Wistar rats were given VPA (i.p.) at a dose of 300 mg/Kg once a day for 12 weeks; the control group received an equivalent volume of vehicle. Glutamic acid decarboxylase (GAD), glial fibrillary acidic protein (GFAP) and their mRNA expression in the median eminence arcuate region (ME-ARC) of the hypothalamus were upregulated in the VPA treated group. By contrast, polysialyltransferase (PST) mRNA which is the enzyme responsible for the polysialylation of neural cell adhesion molecule (NCAM), a plasticity marker, was found to be downregulated. These results support our hypothesis that VPA disrupts normal neuronal-glial plasticity in the hypothalamus and can thereby cause reproductive neuroendocrine disorders in female patients treated for epilepsy, bipolar disorder or migraine.

Mechanisms and repair strategies for white matter degeneration in CNS injury and diseases.

White matter degeneration is an important pathophysiological event of the central nervous system that is collectively characterized by demyelination, oligodendrocyte loss, axonal degeneration and parenchymal changes that can result in sensory, motor, autonomic and cognitive impairments. White matter degeneration can occur due to a variety of causes including trauma, neurotoxic exposure, insufficient blood flow, neuroinflammation, and developmental and inherited neuropathies. Regardless of the etiology, the degeneration processes share similar pathologic features. In recent years, a plethora of cellular and molecular mechanisms have been identified for axon and oligodendrocyte degeneration including oxidative damage, calcium overload, neuroinflammatory events, activation of proteases, depletion of adenosine triphosphate and energy supply. Extensive efforts have been also made to develop neuroprotective and neuroregenerative approaches for white matter repair. However, less progress has been achieved in this area mainly due to the complexity and multifactorial nature of the degeneration processes. Here, we will provide a timely review on the current understanding of the cellular and molecular mechanisms of white matter degeneration and will also discuss recent pharmacological and cellular therapeutic approaches for white matter protection as well as axonal regeneration, oligodendrogenesis and remyelination.

Availability of neuregulin-1beta1 protects neurons in spinal cord injury and against glutamate toxicity through caspase dependent and independent mechanisms.

Spinal cord injury (SCI) causes sensorimotor and autonomic impairment that partly reflects extensive, permanent loss of neurons at the epicenter and penumbra of the injury. Strategies aimed at enhancing neuronal protection are critical to attenuate neurodegeneration and improve neurological recovery after SCI. In rat SCI, we previously uncovered that the tissue levels of neuregulin-1beta 1 (Nrg-1ß1) are acutely and persistently downregulated in the injured spinal cord. Nrg-1ß1 is well-known for its critical roles in the development, maintenance and physiology of neurons and glia in the developing and adult spinal cord. However, despite this pivotal role, Nrg-1ß1 specific effects and mechanisms of action on neuronal injury remain largely unknown in SCI. In the present study, using a clinically-relevant model of compressive/contusive SCI in rats and an in vitro model of glutamate toxicity in primary neurons, we demonstrate Nrg-1ß1 provides early neuroprotection through attenuation of reactive oxygen species, lipid peroxidation, necrosis and apoptosis in acute and subacute stages of SCI. Mechanistically, availability of Nrg-1ß1 following glutamate challenge protects neurons from caspase-dependent and independent cell death that is mediated by modulation of mitochondria associated apoptotic cascades and MAP kinase and AKT signaling pathways. Altogether, our work provides novel insights into the role and mechanisms of Nrg-1ß1 in neuronal injury after SCI and introduces its potential as a new neuroprotective target for this debilitating neurological condition.

Acute upregulation of bone morphogenetic protein-4 regulates endogenous cell response and promotes cell death in spinal cord injury.

Traumatic spinal cord injury (SCI) elicits a cascade of secondary injury mechanisms that induce profound changes in glia and neurons resulting in their activation, injury or cell death. The resultant imbalanced microenvironment of acute SCI also negatively impacts regenerative processes in the injured spinal cord. Thus, it is imperative to uncover endogenous mechanisms that drive these acute injury events. Here, we demonstrate that the active form of bone morphogenetic protein-4 (BMP4) is robustly and transiently upregulated in acute SCI in rats. BMP4 is a key morphogen in neurodevelopment; however, its role in SCI is not fully defined. Thus, we elucidated the ramification of BMP4 upregulation in a preclinical model of compressive/contusive SCI in the rat by employing noggin, an endogenous antagonist of BMP ligands, and LDN193189, an intracellular inhibitor of BMP signaling. In parallel, we studied cell-specific effects of BMP4 on neural precursor cells (NPCs), oligodendrocyte precursor cells (OPCs), neurons and astrocytes in vitro. We demonstrate that activation of BMP4 inhibits differentiation of spinal cord NPCs and OPCs into mature myelin-expressing oligodendrocytes, and acute blockade of BMPs promotes oligodendrogenesis, oligodendrocyte preservation and remyelination after SCI. Importantly, we report for the first time that BMP4 directly induces caspase-3 mediated apoptosis in neurons and oligodendrocytes in vitro, and noggin and LDN193189 remarkably attenuate caspase-3 activation and lipid peroxidation in acute SCI. BMP4 also enhances the production of inhibitory chondroitin sulfate proteoglycans (CSPGs) in activated astrocytes in vitro and after SCI. Interestingly, our work reveals that despite the beneficial effects of BMP inhibition in acute SCI, neither noggin nor LDN193189 treatment resulted in long-term functional recovery. Collectively, our findings suggest a role for BMP4 in regulating acute secondary injury mechanisms following SCI, and a potential target for combinatorial approaches to improve endogenous cell response and remyelination.

Effect of the alcoholic extract of Ashwagandha leaves and its components on proliferation, migration, and differentiation of glioblastoma cells: combinational approach for enhanced differentiation.

Ashwagandha (Withania somnifera) is widely used in the Indian traditional system of medicine, Ayurveda. Although it is claimed to have a large variety of health-promoting effects, including therapeutic effects on stress and disease, the mechanisms of action have not yet been determined. In the present study, we aimed to investigate the growth inhibition and differentiation potential of the alcoholic extract of Ashwagandha leaves (i-Extract), its different constituents (Withaferin A, Withanone, Withanolide A) and their combinations on glioma (C6 and YKG1) cell lines. Withaferin A, Withanone, Withanolide A and i-Extract markedly inhibited the proliferation of glioma cells in a dose-dependent manner and changed their morphology toward the astrocytic type. Molecular analysis revealed that the i-Extract and some of its components caused enhanced expression of glial fibrillary acidic protein, change in the immunostaining pattern of mortalin from perinuclear to pancytoplasmic, delay in cell migration, and increased expression of neuronal cell adhesion molecules. The data suggest that the i-Extract and its components have the potential to induce senescence-like growth arrest and differentiation in glioma cells. These assays led us to formulate a unique combination formula of i-Extract components that caused enhanced differentiation of glial cells.

Neuregulin-1/ErbB network: An emerging modulator of nervous system injury and repair.

Neuregulin-1 (Nrg-1) is a member of the Neuregulin family of growth factors with essential roles in the developing and adult nervous system. Six different types of Nrg-1 (Nrg-1 type I-VI) and over 30 isoforms have been discovered; however, their specific roles are not fully determined. Nrg-1 signals through a complex network of protein-tyrosine kinase receptors, ErbB2, ErbB3, ErbB4 and multiple intracellular pathways. Genetic and pharmacological studies of Nrg-1 and ErbB receptors have identified a critical role for Nrg-1/ErbB network in neurodevelopment including neuronal migration, neural differentiation, myelination as well as formation of synapses and neuromuscular junctions. Nrg-1 signaling is best known for its characterized role in development and repair of the peripheral nervous system (PNS) due to its essential role in Schwann cell development, survival and myelination. However, our knowledge of the impact of Nrg-1/ErbB on the central nervous system (CNS) has emerged in recent years. Ongoing efforts have uncovered a multi-faceted role for Nrg-1 in regulating CNS injury and repair processes. In this review, we provide a timely overview of the most recent updates on Nrg-1 signaling and its role in nervous system injury and diseases. We will specifically highlight the emerging role of Nrg-1 in modulating the glial and immune responses and its capacity to foster neuroprotection and remyelination in CNS injury. Nrg-1/ErbB network is a key regulatory pathway in the developing nervous system; therefore, unraveling its role in neuropathology and repair can aid in development of new therapeutic approaches for nervous system injuries and associated disorders.

Neuregulin-1 Fosters Supportive Interactions between Microglia and Neural Stem/Progenitor Cells.

Microglia play diverse roles in homeostasis and pathology of the central nervous system (CNS). Their response to injury or insult is critical for initiating neuroinflammation and tissue damage as well as resolution of inflammation and wound healing. Changes to the microenvironment of microglia appear to be a key determinant of their phenotype and their role in the endogenous repair process in the injured or diseased CNS. Our recent findings have identified a positive role for neuregulin-1 (Nrg-1) in regulating immune response in spinal cord injury and focal demyelinating lesions. We show that increasing the tissue availability of Nrg-1 after injury can promote endogenous repair by modulating neuroinflammation. In the present study, we sought to elucidate the specific role of Nrg-1 in regulating microglial activity and more importantly their influence on the behavior of neural stem/progenitor cells (NPCs). Using injury-relevant in vitro systems, we demonstrate that Nrg-1 attenuates the expression of proinflammatory mediators in activated microglia. Moreover, we provide novel evidence that availability of Nrg-1 can restore the otherwise suppressed phagocytic ability of proinflammatory microglia. Interestingly, the presence of Nrg-1 in the microenvironment of proinflammatory microglia mitigates their inhibitory effects on NPC proliferation. Nrg-1 treated proinflammatory microglia also augment mobilization of NPCs, while they had no influence on their suppressive effects on NPC differentiation. Mechanistically, we show that Nrg-1 enhances the interactions of proinflammatory microglia and NPCs, at least in part, through reduction of TNF-α expression in microglia. These findings provide new insights into the endogenous regulation of microglia-NPC interactions and identify new potential targets for optimizing this important crosstalk during the regenerative process after CNS injury and neuroinflammatory conditions.

A Fragment of Adhesion Molecule L1 Binds to Nuclear Receptors to Regulate Synaptic Plasticity and Motor Coordination.

Proteolytic cleavage of the neuronal isoform of the murine cell adhesion molecule L1, triggered by stimulation of the cognate L1-dependent signaling pathways, results in the generation and nuclear import of an L1 fragment that contains the intracellular domain, the transmembrane domain, and part of the extracellular domain. Here, we show that the LXXLL and FXXLF motifs in the extracellular and transmembrane domain of this L1 fragment mediate the interaction with the nuclear estrogen receptors α (ERα) and ß (ERß), peroxisome proliferator-activated receptor γ (PPARγ), and retinoid X receptor ß (RXRß). Mutations of the LXXLL motif in the transmembrane domain and of the FXXLF motif in the extracellular domain disturb the interaction of the L1 fragment with these nuclear receptors and, when introduced by viral transduction into mouse embryos in utero, result in impaired motor coordination, learning and memory, as well as synaptic connectivity in the cerebellum, in adulthood. These impairments are similar to those observed in the L1-deficient mouse. Our findings suggest that the interplay of nuclear L1 and distinct nuclear receptors is associated with synaptic contact formation and plasticity.

Proteolytic cleavage of transmembrane cell adhesion molecule L1 by extracellular matrix molecule Reelin is important for mouse brain development.

The cell adhesion molecule L1 and the extracellular matrix protein Reelin play crucial roles in the developing nervous system. Reelin is known to activate signalling cascades regulating neuronal migration by binding to lipoprotein receptors. However, the interaction of Reelin with adhesion molecules, such as L1, has remained poorly explored. Here, we report that full-length Reelin and its N-terminal fragments N-R2 and N-R6 bind to L1 and that full-length Reelin and its N-terminal fragment N-R6 proteolytically cleave L1 to generate an L1 fragment with a molecular mass of 80 kDa (L1-80). Expression of N-R6 and generation of L1-80 coincide in time at early developmental stages of the cerebral cortex. Reelin-mediated generation of L1-80 is involved in neurite outgrowth and in stimulation of migration of cultured cortical and cerebellar neurons. Morphological abnormalities in layer formation of the cerebral cortex of L1-deficient mice partially overlap with those of Reelin-deficient reeler mice. In utero electroporation of L1-80 into reeler embryos normalised the migration of cortical neurons in reeler embryos. The combined results indicate that the direct interaction between L1 and Reelin as well as the Reelin-mediated generation of L1-80 contribute to brain development at early developmental stages.

Withania somnifera Suppresses Tumor Growth of Intracranial Allograft of Glioma Cells.

Gliomas are the most frequent type of primary brain tumor in adults. Their highly proliferative nature, complex cellular composition, and ability to escape therapies have confronted investigators for years, hindering the advancement toward an effective treatment. Agents that are safe and can be administered as dietary supplements have always remained priority to be most feasible for cancer therapy. Withania somnifera (ashwagandha) is an essential ingredient of Ayurvedic preparations and is known to eliminate cancer cells derived from a variety of peripheral tissues. Although our previous studies have addressed the in vitro anti-proliferative and differentiation-inducing properties of ashwagandha on neuronal cell lines, in vivo studies validating the same are lacking. While exploring the mechanism of its action in vitro, we observed that the ashwagandha water extract (ASH-WEX) induced the G2/M phase blockade and caused the activation of multiple pro-apoptotic pathways, leading to suppression of cyclin D1, bcl-xl, and p-Akt, and reduced the expression of polysialylated form of neural cell adhesion molecule (PSA-NCAM) as well as the activity of matrix metalloproteinases. ASH-WEX reduced the intracranial tumor volumes in vivo and suppressed the tumor-promoting proteins p-nuclear factor kappa B (NF-κB), p-Akt, vascular endothelial growth factor (VEGF), heat shock protein 70 (HSP70), PSA-NCAM, and cyclin D1 in the rat model of orthotopic glioma allograft. Reduction in glial fibrillary acidic protein (GFAP) and upregulation of mortalin and neural cell adhesion molecule (NCAM) expression specifically in tumor-bearing tissue further indicated the anti-glioma efficacy of ASH-WEX in vivo. Combining this enhanced understanding of the molecular mechanisms of ASH-WEX in glioma with in vivo model system offers new opportunities to develop therapeutic strategy for safe, specific, and effective formulations for treating brain tumors.