Matrix metalloproteinase-2 (MMP-2) regulates astrocyte motility in connection with the actin cytoskeleton and integrins

Non-neoplastic astrocytes: key players for brain tumor progression

Astrocytes are highly plastic cells whose activity is essential to maintain the cerebral homeostasis, regulating synaptogenesis and synaptic transmission, vascular and metabolic functions, ions, neuro- and gliotransmitters concentrations. In pathological conditions, astrocytes may undergo transient or long-lasting molecular and functional changes that contribute to disease resolution or exacerbation. In recent years, many studies demonstrated that non-neoplastic astrocytes are key cells of the tumor microenvironment that contribute to the pathogenesis of glioblastoma, the most common primary malignant brain tumor and of secondary metastatic brain tumors. This Mini Review covers the recent development of research on non-neoplastic astrocytes as tumor-modulators. Their double-edged capability to promote cancer progression or to represent potential tools to counteract brain tumors will be discussed.

Involvement of the peroxisome proliferator-activated receptor gamma (Pparγ) and matrix metalloproteinases-2 and -9 (Mmp-2 and -9) in the mechanism of action of di(2-ethylhexyl)phthalate (DEHP) in cultured mouse brain astrocytes and neurons

Di(2-ethylhexyl)phthalate (DEHP) is one of the most widely used phthalates in industry. It has been shown that, after entering the body, DEHP has the ability to cross the blood-placenta and blood-brain barriers. One of the proposed mechanisms of action of DEHP is the activation of peroxisome proliferator-activated receptors (PPARs). Many different functions of PPARγ in cells have been demonstrated, one of which is the modulation of the activation of matrix metalloproteinases (MMPs). The aim of this study was to investigate the role of Pparγ, Mmp-2, and Mmp-9 in the mechanism of action of DEHP. The experiments were performed on in vitro primary murine neurons and astrocytes. The results showed that DEHP has a pro-apototic effect on neurons, causing an increase in caspase-3 activity and in the number of apoptotic bodies. However, in astrocytes, the increase in caspase-3 activity was not related to the apoptosis process, as no increase in the formation of apoptotic bodies was observed. Moreover, DEHP increased the proliferation of astrocytes, which was confirmed by the increase in the amount and expression of the Ki-67 protein. In astrocytes, DEHP decreased the expression of the Pparγ and Mmp-9 proteins but increased the expression of the Mmp-2 protein. In DEHP neurons, it increased the expression of the Pparγ protein but decreased the expression of the Mmp-2 and Mmp-9 proteins.

Identification of the matrix metalloproteinase (MMP) gene family in Japanese flounder (Paralichthys olivaceus): Involved in immune response regulation to temperature stress and Edwardsiella tarda infection

The Matrix metalloproteinase (MMP) gene family is responsible for regulating the degradation of Extra Cellular Matrix (ECM) proteins, which are important for physiological processes such as wound healing, tissue remodeling, and stress response. Although MMPs have been studied in many species, their role in immune response in Japanese flounder (Paralichthys olivaceus) is still not fully understood. This study conducted a comprehensive analysis of MMPs in flounder, including gene structures, evolutionary relationships, conserved domains, molecular evolution, and expression patterns. Analysis revealed that MMP genes could be grouped into 17 subfamilies and were evolutionarily conserved and functionally-constrained. Meanwhile, MMP genes were found to express in different embryonic and larval stages and might play the role of sentinel in healthy tissues. Furthermore, expression profiling showed that MMPs had diverse functions in environmental stress, with 60% (9/15) and 73% (11/15) of MMPs showing differential expression patterns under temperature stress and Edwardsiella tarda (E. tarda) infection, respectively. These findings provide a useful resource for understanding the immune functions of MMP genes in Japanese flounder.

The Role of Extracellular Matrix in Human Neurodegenerative Diseases

The dense neuropil of the central nervous system leaves only limited space for extracellular substances free. The advent of immunohistochemistry, soon followed by advanced diagnostic tools, enabled us to explore the biochemical heterogeneity and compartmentalization of the brain extracellular matrix in exploratory and clinical research alike. The composition of the extracellular matrix is critical to shape neuronal function; changes in its assembly trigger or reflect brain/spinal cord malfunction. In this study, we focus on extracellular matrix changes in neurodegenerative disorders. We summarize its phenotypic appearance and biochemical characteristics, as well as the major enzymes which regulate and remodel matrix establishment in disease. The specifically built basement membrane of the central nervous system, perineuronal nets and perisynaptic axonal coats can protect neurons from toxic agents, and biochemical analysis revealed how the individual glycosaminoglycan and proteoglycan components interact with these molecules. Depending on the site, type and progress of the disease, select matrix components can either proactively trigger the formation of disease-specific harmful products, or reactively accumulate, likely to reduce tissue breakdown and neuronal loss. We review the diagnostic use and the increasing importance of medical screening of extracellular matrix components, especially enzymes, which informs us about disease status and, better yet, allows us to forecast illness.

The emerging role of furin in neurodegenerative and neuropsychiatric diseases

Furin is an important mammalian proprotein convertase that catalyzes the proteolytic maturation of a variety of prohormones and proproteins in the secretory pathway. In the brain, the substrates of furin include the proproteins of growth factors, receptors and enzymes. Emerging evidence, such as reduced FURIN mRNA expression in the brains of Alzheimer's disease patients or schizophrenia patients, has implicated a crucial role of furin in the pathophysiology of neurodegenerative and neuropsychiatric diseases. Currently, compared to cancer and infectious diseases, the aberrant expression of furin and its pharmaceutical potentials in neurological diseases remain poorly understood. In this article, we provide an overview on the physiological roles of furin and its substrates in the brain, summarize the deregulation of furin expression and its effects in neurodegenerative and neuropsychiatric disorders, and discuss the implications and current approaches that target furin for therapeutic interventions. This review may expedite future studies to clarify the molecular mechanisms of furin deregulation and involvement in the pathogenesis of neurodegenerative and neuropsychiatric diseases, and to develop new diagnosis and treatment strategies for these diseases.

Potential neurotoxic activity of diverse molecules released by astrocytes

Astrocytes are the main support cells of the central nervous system. They also participate in neuroimmune reactions. In response to pathological and immune stimuli, astrocytes transform to reactive states characterized by increased release of inflammatory mediators. Some of these molecules are neuroprotective and inflammation resolving while others, including reactive oxygen species (ROS), nitric oxide (NO), matrix metalloproteinase (MMP)- 9, L-glutamate, and tumor necrosis factor α (TNF), are well-established toxins known to cause damage to surrounding cells and tissues. We hypothesized that similar to microglia, the brain immune cells, reactive astrocytes can release a broader set of diverse molecules that are potentially neurotoxic. A literature search was conducted to identify such molecules using the following two criteria: 1) evidence of their expression and secretion by astrocytes and 2) direct neurotoxic action. This review describes 14 structurally diverse molecules as less-established astrocyte neurotoxins, including C-X-C motif chemokine ligand (CXCL)10, CXCL12/CXCL12(5-67), FS-7-associated surface antigen ligand (FasL), macrophage inflammatory protein (MIP)- 2α, TNF-related apoptosis inducing ligand (TRAIL), pro-nerve growth factor (proNGF), pro-brain-derived neurotrophic factor (proBDNF), chondroitin sulfate proteoglycans (CSPGs), cathepsin (Cat)B, group IIA secretory phospholipase A₂ (sPLA₂-IIA), amyloid beta peptides (Aβ), high mobility group box (HMGB)1, ceramides, and lipocalin (LCN)2. For some of these molecules, further studies are required to establish either their direct neurotoxic effects or the full spectrum of stimuli that induce their release by astrocytes. Only limited studies with human-derived astrocytes and neurons are available for most of these potential neurotoxins, which is a knowledge gap that should be addressed in the future. We also summarize available evidence of the role these molecules play in select neuropathologies where reactive astrocytes are a key feature. A comprehensive understanding of the full spectrum of neurotoxins released by reactive astrocytes is key to understanding neuroinflammatory diseases characterized by the adverse activation of these cells and may guide the development of novel treatment strategies.

Protease Responsive Nanogels for Transcytosis across the Blood-Brain Barrier and Intracellular Delivery of Radiopharmaceuticals to Brain Tumor Cells

Despite profound advances in treatment approaches, gliomas remain associated with very poor prognoses. The residual cells after incomplete resection often migrate and proliferate giving a seed for highly resistant gliomas. The efficacy of chemotherapeutic drugs is often strongly limited by their poor selectivity and the blood brain barrier (BBB). Therefore, the development of therapeutic carrier systems for efficient transport across the BBB and selective delivery to tumor cells remains one of the most complex problems facing molecular medicine and nano-biotechnology. To address this challenge, a stimuli sensitive nanogel is synthesized using pre-polymer approach for the effective delivery of nano-irradiation. The nanogels are cross-linked via matrix metalloproteinase (MMP-2,9) substrate and armed with Auger electron emitting drug 5-[¹²⁵ I]Iodo-4"-thio-2"-deoxyuridine ([¹²⁵ I]ITdU) which after release can be incorporated into the DNA of tumor cells. Functionalization with diphtheria toxin receptor ligand allows nanogel transcytosis across the BBB at tumor site. Functionalized nanogels efficiently and increasingly explore transcytosis via BBB co-cultured with glioblastoma cells. The subsequent nanogel degradation correlates with up-regulated MMP2/9. Released [¹²⁵ I]ITdU follows the thymidine salvage pathway ending in its incorporation into the DNA of tumor cells. With this concept, a highly efficient strategy for intracellular delivery of radiopharmaceuticals across the challenging BBB is presented.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

Deficiency in MT5-MMP Supports Branching of Human iPSCs-Derived Neurons and Reduces Expression of GLAST/S100 in iPSCs-Derived Astrocytes

For some time, it has been accepted that the β-site APP cleaving enzyme 1 (BACE1) and the γ-secretase are two main players in the amyloidogenic processing of the β-amyloid precursor protein (APP). Recently, the membrane-type 5 matrix metalloproteinase (MT5-MMP/MMP-24), mainly expressed in the nervous system, has been highlighted as a new key player in APP-processing, able to stimulate amyloidogenesis and also to generate a neurotoxic APP derivative. In addition, the loss of MT5-MMP has been demonstrated to abrogate pathological hallmarks in a mouse model of Alzheimer’s disease (AD), thus shedding light on MT5-MMP as an attractive new therapeutic target. However, a more comprehensive analysis of the role of MT5-MMP is necessary to evaluate how its targeting affects neurons and glia in pathological and physiological situations. In this study, leveraging on CRISPR-Cas9 genome editing strategy, we established cultures of human-induced pluripotent stem cells (hiPSC)-derived neurons and astrocytes to investigate the impact of MT5-MMP deficiency on their phenotypes. We found that MT5-MMP-deficient neurons exhibited an increased number of primary and secondary neurites, as compared to isogenic hiPSC-derived neurons. Moreover, MT5-MMP-deficient astrocytes displayed higher surface area and volume compared to control astrocytes. The MT5-MMP-deficient astrocytes also exhibited decreased GLAST and S100β expression. These findings provide novel insights into the physiological role of MT5-MMP in human neurons and astrocytes, suggesting that therapeutic strategies targeting MT5-MMP should be controlled for potential side effects on astrocytic physiology and neuronal morphology.

Modeling invasion patterns in the glioblastoma battlefield

Glioblastoma is the most aggressive tumor of the central nervous system, due to its great infiltration capacity. Understanding the mechanisms that regulate the Glioblastoma invasion front is a major challenge with preeminent potential clinical relevances. In the infiltration front, the key features of tumor dynamics relate to biochemical and biomechanical aspects, which result in the extension of cellular protrusions known as tumor microtubes. The coordination of metalloproteases expression, extracellular matrix degradation, and integrin activity emerges as a leading mechanism that facilitates Glioblastoma expansion and infiltration in uncontaminated brain regions. We propose a novel multidisciplinary approach, based on in vivo experiments in Drosophila and mathematical models, that describes the dynamics of active and inactive integrins in relation to matrix metalloprotease concentration and tumor density at the Glioblastoma invasion front. The mathematical model is based on a non-linear system of evolution equations in which the mechanisms leading chemotaxis, haptotaxis, and front dynamics compete with the movement induced by the saturated flux in porous media. This approach is able to capture the relative influences of the involved agents and reproduce the formation of patterns, which drive tumor front evolution. These patterns have the value of providing biomarker information that is related to the direction of the dynamical evolution of the front and based on static measures of proteins in several tumor samples. Furthermore, we consider in our model biomechanical elements, like the tissue porosity, as indicators of the healthy tissue resistance to tumor progression.

Glioblastoma (GB) is a type of brain cancer that originated from glial cells. The infiltrative nature of GB cells is a key feature for understanding its aggressiveness and resistance to current treatments. Cellular protrusions, named as Tumor Microtubes (TMs) in GB, mediate the interaction between tumor and healthy tissue and the processes leading GB invasion. These protrusions are also responsible for several cell communication pathways (e.g. Hedgehog or WNT). We have developed a multidisciplinary approach, which combined biological biomarker measurements performed in Drosophila GB with a novel mathematical model, to determine the interactions between proteases, integrins, and TM dynamics. The resulting model is able to predict the formation and infiltration of GB fronts, and, therefore, the directionality, aggressiveness, and progression of the tumor.

Hydrogels for 3D Neural Tissue Models: Understanding Cell-Material Interactions at a Molecular Level

The development of 3D neural tissue analogs is of great interest to a range of biomedical engineering applications including tissue engineering of neural interfaces, treatment of neurodegenerative diseases and in vitro assessment of cell-material interactions. Despite continued efforts to develop synthetic or biosynthetic hydrogels which promote the development of complex neural networks in 3D, successful long-term 3D approaches have been restricted to the use of biologically derived constructs. In this study a poly (vinyl alcohol) biosynthetic hydrogel functionalized with gelatin and sericin (PVA-SG), was used to understand the interplay between cell-cell communication and cell-material interaction. This was used to probe critical short-term interactions that determine the success or failure of neural network growth and ultimately the development of a useful model. Complex primary ventral mesencephalic (VM) neural cells were encapsulated in PVA-SG hydrogels and critical molecular cues that demonstrate mechanosensory interaction were examined. Neuronal presence was constant over the 10 day culture, but the astrocyte population decreased in number. The lack of astrocytic support led to a reduction in neural process outgrowth from 24.0 ± 1.3 μm on Day 7 to 7.0 ± 0.1 μm on Day 10. Subsequently, purified astrocytes were studied in isolation to understand the reasons behind PVA-SG hydrogel inability to support neural network development. It was proposed that the spatially restrictive nature (or tight mesh size) of PVA-SG hydrogels limited the astrocytic actin polymerization together with a cytoplasmic-nuclear translocation of YAP over time, causing an alteration in their cell cycle. This was confirmed by the evaluation of p27/Kip1 gene that was found to be upregulated by a twofold increase in expression at both Days 7 and 10 compared to Day 3, indicating the quiescent stage of the astrocytes in PVA-SG hydrogel. Cell migration was further studied by the quantification of MMP-2 production that was negligible compared to 2D controls, ranging from 2.7 ± 2.3% on Day 3 to 5.3 ± 2.9% on Day 10. This study demonstrates the importance of understanding astrocyte-material interactions at the molecular level, with the need to address spatial constraints in the 3D hydrogel environment. These findings will inform the design of future hydrogel constructs with greater capacity for remodeling by the cell population to create space for cell migration and neural process extension.

Signatures of the Consolidated Response of Astrocytes to Ischemic Factors In Vitro

Whether and under what conditions astrocytes can mount a collective network response has recently become one of the central questions in neurobiology. Here, we address this problem, investigating astrocytic reactions to different biochemical stimuli and ischemic-like conditions in vitro. Identifying an emergent astrocytic network is based on a novel mathematical approach that extracts calcium activity from time-lapse fluorescence imaging and estimates the connectivity of astrocytes. The developed algorithm represents the astrocytic network as an oriented graph in which the nodes correspond to separate astrocytes, and the edges indicate high dynamical correlations between astrocytic events. We demonstrate that ischemic-like conditions decrease network connectivity in primary cultures in vitro, although calcium events persist. Importantly, we found that stimulation under normal conditions with 10 µM ATP increases the number of long-range connections and the degree of corresponding correlations in calcium activity, apart from the frequency of calcium events. This result indicates that astrocytes can form a large functional network in response to certain stimuli. In the post-ischemic interval, the response to ATP stimulation is not manifested, which suggests a deep lesion in functional astrocytic networks. The blockade of Connexin 43 during ischemic modeling preserves the connectivity of astrocytes in the post-hypoxic period.

Parallel Murine and Human Plaque Proteomics Reveals Pathways of Plaque Rupture

RATIONALE

Plaque rupture is the proximate cause of most myocardial infarctions and many strokes. However, the molecular mechanisms that precipitate plaque rupture are unknown.

OBJECTIVE

By applying proteomic and bioinformatic approaches in mouse models of protease-induced plaque rupture and in ruptured human plaques, we aimed to illuminate biochemical pathways through which proteolysis causes plaque rupture and identify substrates that are cleaved in ruptured plaques.

METHODS AND RESULTS

We performed shotgun proteomics analyses of aortas of transgenic mice with macrophage-specific overexpression of urokinase (SR-uPA^+/0 mice) and of SR-uPA^+/0 bone marrow transplant recipients, and we used bioinformatic tools to evaluate protein abundance and functional category enrichment in these aortas. In parallel, we performed shotgun proteomics and bioinformatics studies on extracts of ruptured and stable areas of freshly harvested human carotid plaques. We also applied a separate protein-analysis method (protein topography and migration analysis platform) to attempt to identify substrates and proteolytic fragments in mouse and human plaque extracts. Approximately 10% of extracted aortic proteins were reproducibly altered in SR-uPA^+/0 aortas. Proteases, inflammatory signaling molecules, as well as proteins involved with cell adhesion, the cytoskeleton, and apoptosis, were increased. ECM (Extracellular matrix) proteins, including basement-membrane proteins, were decreased. Approximately 40% of proteins were altered in ruptured versus stable areas of human carotid plaques, including many of the same functional categories that were altered in SR-uPA^+/0 aortas. Collagens were minimally altered in SR-uPA^+/0 aortas and ruptured human plaques; however, several basement-membrane proteins were reduced in both SR-uPA^+/0 aortas and ruptured human plaques. Protein topography and migration analysis platform did not detect robust increases in proteolytic fragments of ECM proteins in either setting.

CONCLUSIONS

Parallel studies of SR-uPA^+/0 mouse aortas and human plaques identify mechanisms that connect proteolysis with plaque rupture, including inflammation, basement-membrane protein loss, and apoptosis. Basement-membrane protein loss is a prominent feature of ruptured human plaques, suggesting a major role for basement-membrane proteins in maintaining plaque stability.

Investigating the ameliorative effect of alpha-mangostin on development and existing pain in a rat model of neuropathic pain

Mangosteen fruit has been used for various disorders, including pain. The effects of alpha-mangostin, the main component of mangosteen, on the neuropathic pain caused by chronic constriction injury (CCI) were evaluated in rats. In treatment groups, alpha-mangostin (10, 50, 100 mg/kg/day, i.p.) was administered from Day 0, the day of surgery, for 14 days. The degree of heat hyperalgesia, cold, and mechanical allodynia was assessed on Days 0, 3, 5, 7, 10, and 14. The lumbar spinal cord levels of MDA, GSH, inflammatory markers (TLR-4, TNF-α, MMP2, COX2, IL-1β, iNOS, and NO), apoptotic markers (Bcl-2, Bax, and caspase-3) were measured by western blot on Days 7 and 14. Rats in the CCI group showed thermal hyperalgesia, cold, and mechanical allodynia on Days 3-14. All concentrations of alpha-mangostin alleviated CCI-induced behavioral alterations. MDA level augmented and GSH level decreased in the CCI group and alpha-mangostin (50, 100 mg/kg) reversed the alterations. An enhancement in the levels of all inflammatory markers, Bax, and caspase-3 was shown on Days 7 and 14, which was controlled by alpha-mangostin (50 mg/kg). The detected antinociceptive effects of alpha-mangostin may be mediated through antioxidant, anti-inflammatory, and antiapoptotic properties.

Matrix Metalloproteinases as New Targets in Alzheimer's Disease: Opportunities and Challenges

Although matrix metalloproteinases (MMPs) are implicated in the regulation of numerous physiological processes, evidence of their pathological roles have also been obtained in the last decades, making MMPs attractive therapeutic targets for several diseases. Recent discoveries of their involvement in central nervous system (CNS) disorders, and in particular in Alzheimer's disease (AD), have paved the way to consider MMP modulators as promising therapeutic strategies. Over the past few decades, diverse approaches have been undertaken in the design of therapeutic agents targeting MMPs for various purposes, leading, more recently, to encouraging developments. In this article, we will present recent examples of inhibitors ranging from small molecules and peptidomimetics to biologics. We will also discuss the scientific knowledge that has led to the development of emerging tools and techniques to overcome the challenges of selective MMP inhibition.

A neuroglia-based interpretation of glaucomatous neuroretinal rim thinning in the optic nerve head

Neuroretinal rim thinning (NRR) is a characteristic glaucomatous optic disc change. However, the precise mechanism of the rim thinning has not been completely elucidated. This review focuses on the structural role of the glioarchitecture in the formation of the glaucomatous NRR thinning. The NRR is a glia-framed structure, with honeycomb geometry and mechanically reinforced astrocyte processes along the transverse plane. When neural damage selectively involves the neuron and spares the glia, the gross structure of the tissue is preserved. The disorganization and loss of the glioarchitecture are the two hallmarks of optic nerve head (ONH) remodeling in glaucoma that leads to the thinning of NRR tissue upon axonal loss. This is in contrast to most non-glaucomatous optic neuropathies with optic disc pallor where hypertrophy of the glioarchitecture is associated with the seemingly absent optic disc cupping. Arteritic anterior ischemic optic neuropathy is an exception where pan-necrosis of ONH tissue leads to NRR thinning. Milder ischemia indicates selective neuronal loss that spares glia in non-arteritic anterior ischemic optic neuropathy. The biological reason is the heterogeneous glial response determined by the site, type, and severity of the injury. The neuroglial interpretation explains how the cellular changes underlie the clinical findings. Updated understandings on glial responses illustrate the mechanical, microenvironmental, and microglial modulation of activated astrocytes in glaucoma. Findings relevant to the possible mechanism of the astrocyte death in advanced glaucoma are also emerging. Ultimately, a better understanding of glaucomatous glial response may lead to glia-targeting neuroprotection in the future.

Matrix metalloproteinase signals following neurotrauma are right on cue

Neurotrauma, a term referencing both traumatic brain and spinal cord injuries, is unique to neurodegeneration in that onset is clearly defined. From the perspective of matrix metalloproteinases (MMPs), there is opportunity to define their temporal participation in injury and recovery beginning at the level of the synapse. Here we examine the diverse roles of MMPs in the context of targeted insults (optic nerve lesion and hippocampal and olfactory bulb deafferentation), and clinically relevant focal models of traumatic brain and spinal cord injuries. Time-specific MMP postinjury signaling is critical to synaptic recovery after focal axonal injuries; members of the MMP family exhibit a signature temporal profile corresponding to axonal degeneration and regrowth, where they direct postinjury reorganization and synaptic stabilization. In both traumatic brain and spinal cord injuries, MMPs mediate early secondary pathogenesis including disruption of the blood-brain barrier, creating an environment that may be hostile to recovery. They are also critical players in wound healing including angiogenesis and the formation of an inhibitory glial scar. Experimental strategies to reduce their activity in the acute phase result in long-term neurological recovery after neurotrauma and have led to the first clinical trial in spinal cord injured pet dogs.

Sensory deafferentation modulates and redistributes neurocan in the rat auditory brainstem

INTRODUCTION

Cochlear ablation causing sensory deafferentation (SD) of the cochlear nucleus triggers complex re-arrangements in the cellular and molecular communication networks of the adult mammalian central auditory system. Participation of the extracellular matrix (ECM) in these processes is not well understood.

METHODS

We investigated consequences of unilateral SD for the expression and distribution of the chondroitin sulfate proteoglycans, neurocan (Ncan) and aggrecan (Agg), alongside various plasticity markers in the auditory brainstem of the adult rat using immunohistochemical techniques.

RESULTS

In the deafferented ventral cochlear nucleus (VCN), Ncan expression increased massively within 3 postoperative days (POD), but rapidly decreased thereafter. Agg showed a similar but less pronounced progression. Decrease in Ncan was spatially and temporally related to the re-innervation of VCN documented by the emergence of growth-associated protein Gap43 contained in nerve fibers and presynaptic boutons. Concurrently, astrocytes grew and expressed matrix metalloproteinase-2 (MMP2), an enzyme known to emerge only under re-innervation of VCN. MMP2 is capable of cleaving both Ncan and Agg when released. A transient modulation of the ECM in the central inferior colliculus on the side opposite to SD occurred by POD1. Modulations of glutamatergic synapses and Gap43 expression were detected, reflecting state changes of the surrounding tissue induced by transsynaptic effects of SD.

CONCLUSIONS

The ECM variously participates in adaptive responses to sudden deafness by SD on several levels along the central auditory pathway, with a striking spatial and temporal relationship of Ncan modulation to astrocytic activation and to synaptogenesis.

MMPs in learning and memory and neuropsychiatric disorders

Matrix metalloproteinases (MMPs) are a group of over twenty proteases, operating chiefly extracellularly to cleave components of the extracellular matrix, cell adhesion molecules as well as cytokines and growth factors. By virtue of their expression and activity patterns in animal models and clinical investigations, as well as functional studies with gene knockouts and enzyme inhibitors, MMPs have been demonstrated to play a paramount role in many physiological and pathological processes in the brain. In particular, they have been shown to influence learning and memory processes, as well as major neuropsychiatric disorders such as schizophrenia, various kinds of addiction, epilepsy, fragile X syndrome, and depression. A possible link connecting all those conditions is either physiological or aberrant synaptic plasticity where some MMPs, e.g., MMP-9, have been demonstrated to contribute to the structural and functional reorganization of excitatory synapses that are located on dendritic spines. Another common theme linking the aforementioned pathological conditions is neuroinflammation and MMPs have also been shown to be important mediators of immune responses.

Zika Virus Infection Disrupts Astrocytic Proteins Involved in Synapse Control and Axon Guidance

The first human Zika virus (ZIKV) outbreak was reported in Micronesia in 2007, followed by one in Brazil in 2015. Recent studies have reported cases in Europe, Oceania and Latin America. In 2016, ZIKV transmission was also reported in the US and the World Health Organization declared it a Public Health Emergency of International Concern. Because various neurological conditions are associated with ZIKV, such as microcephaly, Guillain-Barré syndrome, and other disorders of both the central and peripheral nervous systems, including encephalopathy, (meningo)encephalitis and myelitis, and because of the lack of reliable patient diagnosis, numerous ongoing studies seek to understand molecular mechanisms underlying ZIKV pathogenesis. Astrocytes are one of the most abundant cells in the CNS. They control axonal guidance, synaptic signaling, neurotransmitter trafficking and maintenance of neurons, and are targeted by ZIKV. In this study, we used a newly developed multiplexed aptamer-based technique (SOMAScan) to examine > 1300 human astrocyte cell proteins. We identified almost 300 astrocyte proteins significantly dysregulated by ZIKV infection that span diverse functions and signaling pathways, including protein translation, synaptic control, cell migration and differentiation.

Astrocyte Mechano-Activation by High-Rate Overpressure Involves Alterations in Structural and Junctional Proteins

Primary blast neurotrauma represents a unique injury paradigm characterized by high-rate overpressure effects on brain tissue. One major hallmark of blast neurotrauma is glial reactivity, notably prolonged astrocyte activation. This cellular response has been mainly defined in primary blast neurotrauma by increased intermediate filament expression. Because the intermediate filament networks physically interface with transmembrane proteins for junctional support, it was hypothesized that cell junction regulation is altered in the reactive phenotype as well. This would have implications for downstream transcriptional regulation via signal transduction pathways like nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Therefore, a custom high-rate overpressure simulator was built for in vitro testing using mechanical conditions based on intracranial pressure measurements in a rat model of blast neurotrauma. Primary rat astrocytes were exposed to isolated high-rate mechanical stimulation to study cell junction dynamics in relation to their mechano-activation. First, a time course for "classical" features of reactivity was devised by evaluation of glial fibrillary acidic protein (GFAP) and proliferating cell nuclear antigen (PCNA) expression. This was followed by gene and protein expression for both gap junction (connexins) and anchoring junction proteins (integrins and cadherins). Signal transduction analysis was carried out by nuclear localization of two molecules, NF-κB p65 and mitogen-activated protein kinase (MAPK) p38. Results indicated significant increases in connexin-43 expression and PCNA first at 24 h post-overpressure (p < 0.05), followed by structural reactivity (via increased GFAP, p < 0.05) corresponding to increased anchoring junction dynamics at 48 h post-overpressure (p < 0.05). Moreover, increased phosphorylation of focal adhesion kinase (FAK) was observed in addition to increased nuclear localization of both p65 and p38 (p < 0.05) during the period of structural reactivity. To evaluate the transcriptional activity of p65 in the nucleus, electrophoretic mobility shift assay was conducted for a binding site on the promoter region for intracellular adhesion molecule-1 (ICAM-1), an antagonist of tight junctions. A significant increase in the interaction of nuclear proteins with the NF-κB site on the ICAM-1 corresponded to increased gene and protein expression of ICAM-1 (p < 0.05). Altogether, these results indicate multiple targets and corresponding signaling pathways which involve cell junction dynamics in the mechano-activation of astrocytes following high-rate overpressure.

Oleoylethanolamide inhibits glial activation via moudulating PPARα and promotes motor function recovery after brain ischemia

Glial activation and scar formation impede the neurological function recovery after cerebral ischemia. Oleoylethanolamide (OEA), a bioactive lipid mediator, shows neuroprotection against acute brain ischemia, however, its long-term effect, especially on glial scar formation, has not been characterized. In this research, we investigate the effect of OEA on glial activation and scar formation after cerebral ischemia in vitro and in vivo experiments. Glial scar formation in vitro model was induced by transforming growth factor β1 (TGF-β1) in C6 glial cell culture, and experiment model in vivo was induced by middle cerebral artery occlusion (MCAO) in mice. The protein expressions of the markers of glial activation (S100β, GFAP, or pSmads) and glial scar (neurocan) were detected by Western blot and/or immunofluorescence staining; To evaluate the role of PPARɑ in the effect of OEA on glial activation, the PPARɑ antagonist GW6471 was used. Behavior tests were used to assay the effect of OEA on motor function recovery 14 days after brain ischemia in mice. Our results show that OEA (10-50 μM) concentration-dependently inhibited the upregulation of S100β, GFAP, pSmads and neurocan induced by TGF-β1 in C6 glial cells. At the same time, OEA promoted the protein expression and nuclear transportation of PPARɑ in glial cells. PPARα antagonist GW6471 abolished the effect of OEA on glial activation. In addition, we found that delay administration of OEA inhibited the astrocyte activation and promoted the recovery of motor function after brain ischemia in mice. These results indicate that OEA may be developed into a new candidate for attenuating astrocytic scar formation and improving motor function after ischemic stroke.

ROCK Inhibitor Y27632 Induced Morphological Shift and Enhanced Neurite Outgrowth-Promoting Property of Olfactory Ensheathing Cells via YAP-Dependent Up-Regulation of L1-CAM

Olfactory ensheathing cells (OECs) are heterogeneous in morphology, antigenic profiles and functions, and these OEC subpopulations have shown different outcomes following OEC transplantation for central nervous system (CNS) injuries. Morphologically, OECs are divided into two subpopulations, process-bearing (Schwann cells-like) and flattened (astrocytes-like) OECs, which could switch between each other and are affected by extracellular and intracellular factors. However, neither the relationship between the morphology and function of OECs nor their molecular mechanisms have been clarified. In the present study, we first investigated morphological and functional differences of OECs under different cytokine exposure conditions. It demonstrated that OECs mainly displayed a process-bearing shape under pro-inflammatory conditions (lipopolysaccharide, LPS), while they displayed a flattened shape under anti-inflammatory conditions [interleukin-4 (IL-4) and transforming growth factor-β1 (TGF-β1)]. The morphological changes were partially reversible and the Rho-associated coiled-coil-containing protein kinase (ROCK)/F-actin pathway was involved. Functionally, process-bearing OECs under pro-inflammatory conditions showed increased cellular metabolic activity and a higher migratory rate when compared with flattened OECs under anti-inflammatory conditions and significantly promoted neurite outgrowth and extension. Remarkably, the morphological shift towards process-bearing OECs induced by ROCK inhibitor Y27632 enhanced the neurite outgrowth-promoting property of OECs. Furthermore, as the downstream of the ROCK pathway, transcriptional co-activator Yes-associated protein (YAP) mediated morphological shift and enhanced the neurite outgrowth-promoting property of OECs through upregulating the expression of the neural adhesion molecule L1-CAM. Our data provided evidence that OECs with specific shapes correspond to specific functional phenotypes and opened new insights into the potential combination of OECs and small-molecule ROCK inhibitors for the regeneration of CNS injuries.

Spinal Cord Injury Scarring and Inflammation: Therapies Targeting Glial and Inflammatory Responses

Deficits in neuronal function are a hallmark of spinal cord injury (SCI) and therapeutic efforts are often focused on central nervous system (CNS) axon regeneration. However, secondary injury responses by astrocytes, microglia, pericytes, endothelial cells, Schwann cells, fibroblasts, meningeal cells, and other glia not only potentiate SCI damage but also facilitate endogenous repair. Due to their profound impact on the progression of SCI, glial cells and modification of the glial scar are focuses of SCI therapeutic research. Within and around the glial scar, cells deposit extracellular matrix (ECM) proteins that affect axon growth such as chondroitin sulfate proteoglycans (CSPGs), laminin, collagen, and fibronectin. This dense deposition of material, i.e., the fibrotic scar, is another barrier to endogenous repair and is a target of SCI therapies. Infiltrating neutrophils and monocytes are recruited to the injury site through glial chemokine and cytokine release and subsequent upregulation of chemotactic cellular adhesion molecules and selectins on endothelial cells. These peripheral immune cells, along with endogenous microglia, drive a robust inflammatory response to injury with heterogeneous reparative and pathological properties and are targeted for therapeutic modification. Here, we review the role of glial and inflammatory cells after SCI and the therapeutic strategies that aim to replace, dampen, or alter their activity to modulate SCI scarring and inflammation and improve injury outcomes.

Sphingosine 1-Phosphate Receptor 1 Is Required for MMP-2 Function in Bone Marrow Mesenchymal Stromal Cells: Implications for Cytoskeleton Assembly and Proliferation

Bone marrow-derived mesenchymal stromal cell- (BM-MSC-) based therapy is a promising option for regenerative medicine. An important role in the control of the processes influencing the BM-MSC therapeutic efficacy, namely, extracellular matrix remodelling and proliferation and secretion ability, is played by matrix metalloproteinase- (MMP-) 2. Therefore, the identification of paracrine/autocrine regulators of MMP-2 function may be of great relevance for improving BM-MSC therapeutic potential. We recently reported that BM-MSCs release the bioactive lipid sphingosine 1-phosphate (S1P) and, here, we demonstrated an impairment of MMP-2 expression/release when the S1P receptor subtype S1PR1 is blocked. Notably, active S1PR1/MMP-2 signalling is required for F-actin structure assembly (lamellipodia, microspikes, and stress fibers) and, in turn, cell proliferation. Moreover, in experimental conditions resembling the damaged/regenerating tissue microenvironment (hypoxia), S1P/S1PR1 system is also required for HIF-1α expression and vinculin reduction. Our findings demonstrate for the first time the trophic role of S1P/S1PR1 signalling in maintaining BM-MSCs' ability to modulate MMP-2 function, necessary for cytoskeleton reorganization and cell proliferation in both normoxia and hypoxia. Altogether, these data provide new perspectives for considering S1P/S1PR1 signalling a pharmacological target to preserve BM-MSC properties and to potentiate their beneficial potential in tissue repair.

Matrix Metalloproteinases in Bone Resorption, Remodeling, and Repair

Matrix metalloproteinases (MMPs) are the major protease family responsible for the cleavage of the matrisome (global composition of the extracellular matrix (ECM) proteome) and proteins unrelated to the ECM, generating bioactive molecules. These proteins drive ECM remodeling, in association with tissue-specific and cell-anchored inhibitors (TIMPs and RECK, respectively). In the bone, the ECM mediates cell adhesion, mechanotransduction, nucleation of mineralization, and the immobilization of growth factors to protect them from damage or degradation. Since the first description of an MMP in bone tissue, many other MMPs have been identified, as well as their inhibitors. Numerous functions have been assigned to these proteins, including osteoblast/osteocyte differentiation, bone formation, solubilization of the osteoid during bone resorption, osteoclast recruitment and migration, and as a coupling factor in bone remodeling under physiological conditions. In turn, a number of pathologies, associated with imbalanced bone remodeling, arise mainly from MMP overexpression and abnormalities of the ECM, leading to bone osteolysis or bone formation. In this review, we will discuss the functions of MMPs and their inhibitors in bone cells, during bone remodeling, pathological bone resorption (osteoporosis and bone metastasis), bone repair/regeneration, and emergent roles in bone bioengineering.

The Unwanted Cell Migration in the Brain: Glioma Metastasis

Cell migration is identified as a highly orchestrated process. It is a fundamental and essential phenomenon underlying tissue morphogenesis, wound healing, and immune response. Under dysregulation, it contributes to cancer metastasis. Brain is considered to be the most complex organ in human body containing many types of neural cells with astrocytes playing crucial roles in monitoring both physiological and pathological functions. Astrocytoma originates from astrocytes and its most malignant type is glioblastoma multiforme (WHO Grade IV astrocytoma), which is capable to infiltrate widely into the neighboring brain tissues making a complete resection of tumors impossible. Very recently, we have reviewed the mechanisms for astrocytes in migration. Given the fact that astrocytoma shares many histological features with astrocytes, we therefore attempt to review the mechanisms for glioma cells in migration and compare them to normal astrocytes, hoping to obtain a better insight into the dysregulation of migratory mechanisms contributing to their metastasis in the brain.

2-Chloroethanol Induced Upregulation of Matrix Metalloproteinase-2 in Primary Cultured Rat Astrocytes Via MAPK Signal Pathways

This study was to explore the mechanisms underlying 1,2-dichloroethane (1,2-DCE) induced brain edema by focusing on alteration of matrix metalloproteinase-2 (MMP-2) in rat astrocytes induced by 2-chloroethanol (2-CE), an intermediate metabolite of 1,2-DCE in vivo. Protein and mRNA levels of MMP-2, and the phosphorylated protein levels of p38 MAPK (p-p38), extracellular signal regulated protein kinase (p-ERK1/2) and c-Jun N-terminal kinase (p-JNK1/2) in astrocytes were examined by immunostaining, western blot or real-time RT-PCR analysis. Findings from this study disclosed that protein levels of MMP-2 were upregulated by 2-CE in astrocytes. Meanwhile, protein levels of p-p38, p-ERK1/2 and p-JNK1/2 were also increased apparently in the cells treated with 2-CE. Moreover, pretreatment of astrocytes with SB202190 (inhibitor of p38 MAPK), U0126 (inhibitor of ERK1/2) or SP600125 (inhibitor of JNK1/2) could suppress the upregulated expression of p-p38, p-ERK1/2, and p-JNK1/2. In response to suppressed protein levels of p-p38 and p-JNK1/2, the protein levels of MMP-2 also decreased significantly, indicating that activation of MAPK signal pathways were involved in the mechanisms underlying 2-CE-induced upregulation of MMP-2 expression.

Integrins in synapse regulation

Integrins are a large family of extracellular matrix (ECM) receptors. In the developing and adult brain, many integrins are present at high levels at synapses. The tetrapartite structure of synapses - which comprises presynaptic and postsynaptic neurons, the ECM and glial processes - places synaptic integrins in an excellent position to sense dynamic changes in the synaptic environment and use this information to coordinate further changes in synapse structure and function that will shape neural circuit properties. Recent developments in our understanding of the cellular and physiological roles of integrins, which range from control of neural process outgrowth and synapse formation to regulation of synaptic plasticity and memory, enable us to attempt a synthesis of synaptic integrin function.

Implication of Hypothalamus in Alleviating Spinal Cord Injury-Induced Neuropathic Pain

Neuropathic pain (NP) is common among spinal cord injury (SCI) patients, and there remain clinical difficulties in treating NP due to the lack of understanding of underlying mechanisms. Extracellular proteins, such as matrix metalloproteinase and β-catenin, have been shown to be activated in the spinal cord regions following an injury, and may play a key role in contributing to NP states. While these extracellular proteins have been used as therapeutic targets in the spinal cord, there has also been evidence of up-regulation in the hypothalamus following a SCI. We hypothesize that the hypothalamus is involved in regulating NP following a SCI, and hence should be researched further to determine if it is a viable target for future therapeutic treatments.

The multifaceted role of metalloproteinases in physiological and pathological conditions in embryonic and adult brains

Matrix metalloproteinases (MMPs) are a large family of ubiquitous extracellular endopeptidases, which play important roles in a variety of physiological and pathological conditions, from the embryonic stages throughout adult life. Their extraordinary physiological "success" is due to concomitant broad substrate specificities and strict regulation of their expression, activation and inhibition levels. In recent years, MMPs have gained increasing attention as significant effectors in various aspects of central nervous system (CNS) physiology. Most importantly, they have been recognized as main players in a variety of brain disorders having different etiologies and evolution. A common aspect of these pathologies is the development of acute or chronic neuroinflammation. MMPs play an integral part in determining the result of neuroinflammation, in some cases turning its beneficial outcome into a harmful one. This review summarizes the most relevant studies concerning the physiology of MMPs, highlighting their involvement in both the developing and mature CNS, in long-lasting and acute brain diseases and, finally, in nervous system repair. Recently, a concerted effort has been made in identifying therapeutic strategies for major brain diseases by targeting MMP activities. However, from this revision of the literature appears clear that MMPs have multifaceted functional characteristics, which modulate physiological processes in multiple ways and with multiple consequences. Therefore, when choosing MMPs as possible targets, great care must be taken to evaluate the delicate balance between their activation and inhibition and to determine at which stage of the disease and at what level they become active in order maximize chances of success.

Matrix Metalloproteinases During Axonal Regeneration, a Multifactorial Role from Start to Finish

By proteolytic cleavage, matrix metalloproteinases (MMPs) not only remodel the extracellular matrix (ECM) but they also modify the structure and activity of other proteinases, growth factors, signaling molecules, cell surface receptors, etc. Their vast substrate repertoire adds a complex extra dimension of biological control and turns MMPs into important regulatory nodes in the protease web. In the central nervous system (CNS), the detrimental impact of elevated MMP activities has been well-described for traumatic injuries and many neurodegenerative diseases. Nonetheless, there is ample proof corroborating MMPs as fine regulators of CNS physiology, and well-balanced MMP activity is instrumental to development, plasticity, and repair. In this manuscript, we review the emerging evidence for MMPs as beneficial modulators of axonal regeneration in the mammalian CNS. By exploring the multifactorial causes underlying the inability of mature axons to regenerate, and describing how MMPs can help to overcome these hurdles, we emphasize the benign actions of these Janus-faced proteases.

Niclosamide induces colorectal cancer apoptosis, impairs metastasis and reduces immunosuppressive cells in vivo

Colorectal cancer (CRC) is one of the most common malignancies with considerable metastatic potential, explaining the need for new candidates that inhibit tumor growth and metastasis.

Astrocytic CCAAT/Enhancer-Binding Protein Delta Contributes to Glial Scar Formation and Impairs Functional Recovery After Spinal Cord Injury

After spinal cord injury, inflammatory reaction induces the aggregation of astrocytes to form a glial scar that eventually blocks axonal regeneration. Transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ) is a regulatory protein of genes responsive to inflammatory factors, but its role in glial scar formation after spinal cord injury remains unknown. By using a model of moderate spinal cord contusion injury at the mid-thoracic level, we found that C/EBPδ was expressed mostly in the reactive astrocytes bordering the lesion in wild-type mice from 7 days after the injury. C/EBPδ-deficient mice showed reduced glial scar formation, more residual white matter, and better motor function recovery compared with wild-type mice 28 days after the injury. Upon interleukin (IL)-1β stimulation in vitro, the increased expression of C/EBPδ in reactive astrocytes inhibited RhoA expression and, subsequently, the ability of astrocyte migration. However, these reactive astrocytes also produced an increased amount of matrix metalloproteinase-3, which promoted the migration of non-IL-1β-treated, inactive astrocytes. Although the involvement of other non-astroglial C/EBPδ cannot be entirely excluded, our studies suggest that astrocytic C/EBPδ is integral to the inflammatory cascades leading to glial scar formation after spinal cord injury.

Extracellular environment contribution to astrogliosis-lessons learned from a tissue engineered 3D model of the glial scar

Glial scars are widely seen as a (bio)mechanical barrier to central nervous system regeneration. Due to the lack of a screening platform, which could allow in-vitro testing of several variables simultaneously, up to now no comprehensive study has addressed and clarified how different lesion microenvironment properties affect astrogliosis. Using astrocytes cultured in alginate gels and meningeal fibroblast conditioned medium, we have built a simple and reproducible 3D culture system of astrogliosis mimicking many features of the glial scar. Cells in this 3D culture model behave similarly to scar astrocytes, showing changes in gene expression (e.g., GFAP) and increased extra-cellular matrix production (chondroitin 4 sulfate and collagen), inhibiting neuronal outgrowth. This behavior being influenced by the hydrogel network properties. Astrocytic reactivity was found to be dependent on RhoA activity, and targeting RhoA using shRNA-mediated lentivirus reduced astrocytic reactivity. Further, we have shown that chemical inhibition of RhoA with ibuprofen or indirectly targeting RhoA by the induction of extracellular matrix composition modification with chondroitinase ABC, can diminish astrogliosis. Besides presenting the extracellular matrix as a key modulator of astrogliosis, this simple, controlled and reproducible 3D culture system constitutes a good scar-like system and offers great potential in future neurodegenerative mechanism studies, as well as in drug screenings envisaging the development of new therapeutic approaches to minimize the effects of the glial scar in the context of central nervous system disease.

Spinal cord injury induced neuropathic pain: Molecular targets and therapeutic approaches

Neuropathic pain, especially that resulting from spinal cord injury, is a tremendous clinical challenge. A myriad of biological changes have been implicated in producing these pain states including cellular interactions, extracellular proteins, ion channel expression, and epigenetic influences. Physiological consequences of these changes are varied and include functional deficits and pain responses. Developing therapies that effectively address the cause of these symptoms require a deeper knowledge of alterations in the molecular pathways. Matrix metalloproteinases and tissue inhibitors of metalloproteinases are two promising therapeutic targets. Matrix metalloproteinases interact with and influence many of the studied pain pathways. Gene expression of ion channels and inflammatory mediators clearly contributes to neuropathic pain. Localized and time dependent targeting of these proteins could alleviate and even prevent neuropathic pain from developing. Current therapeutic options for neuropathic pain are limited primarily to analgesics targeting the opioid pathway. Therapies directed at molecular targets are highly desirable and in early stages of development. These include transplantation of exogenously engineered cell populations and targeted gene manipulation. This review describes specific molecular targets amenable to therapeutic intervention using currently available delivery systems.

Early detection of structural abnormalities and cytoplasmic accumulation of TDP-43 in tissue-engineered skins derived from ALS patients

Amyotrophic lateral sclerosis (ALS) is an adult-onset disease characterized by the selective degeneration of motor neurons in the brain and spinal cord progressively leading to paralysis and death. Current diagnosis of ALS is based on clinical assessment of related symptoms. The clinical manifestations observed in ALS appear relatively late in the disease course after degeneration of a significant number of motor neurons. As a result, the identification and development of disease-modifying therapies is difficult. Therefore, novel strategies for early diagnosis of neurodegeneration, to monitor disease progression and to assess response to existing and future treatments are urgently needed. Factually, many neurological disorders, including ALS, are accompanied by skin changes that often precede the onset of neurological symptoms. Aiming to generate an innovative human-based model to facilitate the identification of predictive biomarkers associated with the disease, we developed a unique ALS tissue-engineered skin model (ALS-TES) derived from patient’s own cells. The ALS-TES presents a number of striking features including altered epidermal differentiation, abnormal dermo-epidermal junction, delamination, keratinocyte infiltration, collagen disorganization and cytoplasmic TDP-43 inclusions. Remarkably, these abnormal skin defects, uniquely seen in the ALS-derived skins, were detected in pre-symtomatic C9orf72-linked ALS patients carrying the GGGGCC DNA repeat expansion. Consequently, our ALS skin model could represent a renewable source of human tissue, quickly and easily accessible to better understand the physiopathological mechanisms underlying this disease, to facilitate the identification of disease-specific biomarkers, and to develop innovative tools for early diagnosis and disease monitoring.

Neuropathic pain: role of inflammation, immune response, and ion channel activity in central injury mechanisms

Neuropathic pain (NP) is a significant and disabling clinical problem with very few therapeutic treatment options available. A major priority is to identify the molecular mechanisms responsible for NP. Although many seemingly relevant pathways have been identified, more research is needed before effective clinical interventions can be produced. Initial insults to the nervous system, such as spinal cord injury (SCI), are often compounded by secondary mechanisms such as inflammation, the immune response, and the changing expression of receptors and ion channels. The consequences of these secondary effects myriad and compound those elicited by the primary injury. Chronic NP syndromes following SCI can greatly complicate the clinical treatment of the primary injury and result in high comorbidity. In this review, we will describe physiological outcomes associated with SCI along with some of the mechanisms known to contribute to chronic NP development.

Expression of matrix metalloproteinases (MMP-2, MMP-9) and their inhibitors (TIMP-1, TIMP-2) in canine testis, epididymis and semen

This study aims to investigate the role of matrix metalloproteinases (MMPs) in determining semen quality and to evaluate the expression and cellular localization of MMP-2, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 in the testes, epididymis and ejaculated spermatozoa. Gelatinase activities between normal (n = 21) and abnormal (n = 25) semen samples showed a significant, sixfold increase in proMMP-2 and MMP-2 activity in high than low sperm concentration samples (p < 0.001). ProMMP-9 and MMP-9 levels were significantly elevated in samples with low sperm counts compared to those with high sperm density (p < 0.001). High levels of proMMP-2 and MMP-2 were associated with high sperm motility (≥70%, p < 0.001). Sperm-rich fraction showed significantly (eight-fold) higher proMMP-9 enzymatic activity compared with prostatic fraction. The mRNA expressions of MMP-2, MMP-9, TIMP-1 and TIMP-2 were confirmed in testicular and epididymal tissues. Immunohistochemical staining illustrated the MMP-2-specific strong immunoreactivity in the head of mature spermatids during spermatogenesis, whereas MMP-9, TIMP-1 and TIMP-2 were absent in these cells. Matrix metalloproteinase-9 immunoreactivity was observed in the spermatocyte and round spermatid, whereas TIMP-1 was only exhibited in the residual bodies. Immunolabeling of epididymal and ejaculated sperm demonstrated MMP-2 localization along acrosomal region of sperm, while MMP-9, TIMP-1 and TIMP-2 localization was merely limited to the flagella. In conclusion, spermatozoa initially acquire MMP-2 during their formation at testicular level, and the presence of this protein persists through the epididymal transit and up to ejaculate. The enzymatic activity of MMP-2 and MMP-9 may serve as an alternative biomarker in determining semen quality.

Differential spatio-temporal regulation of MMPs in the 5xFAD mouse model of Alzheimer's disease: evidence for a pro-amyloidogenic role of MT1-MMP

Matrix metalloproteinases (MMPs) are pleiotropic endopeptidases involved in a variety of neurodegenerative/neuroinflammatory processes through their interactions with a large number of substrates. Among those, the amyloid precursor protein (APP) and the beta amyloid peptide (Aβ) are largely associated with the development of Alzheimer’s disease (AD). However, the regulation and potential contribution of MMPs to AD remains unclear. In this study, we investigated the evolution of the expression of MMP-2, MMP-9, and membrane-type 1-MMP (MT1-MMP) in the hippocampus at different stages of the pathology (asymptomatic, prodromal-like and symptomatic) in the 5xFAD transgenic mouse AD model. In parallel we also followed the expression of functionally associated factors. Overall, the expression of MMP-2, MMP-9, and MT1-MMP was upregulated concomitantly with the tissue inhibitor of MMPs-1 (TIMP-1) and several markers of inflammatory/glial response. The three MMPs exhibited age- and cell-dependent upregulation of their expression, with MMP-2 and MMP-9 being primarily located to astrocytes, and MT1-MMP to neurons. MMP-9 and MT1-MMP were also prominently present in amyloid plaques. The levels of active MT1-MMP were highly upregulated in membrane-enriched fractions of hippocampus at 6 months of age (symptomatic phase), when the levels of APP, its metabolites APP C-terminal fragments (CTFs), and Aβ trimers were the highest. Overexpression of MT1-MMP in HEK cells carrying the human APP Swedish mutation (HEKswe) strongly increased β-secretase derived C-terminal APP fragment (C99) and Aβ levels, whereas MMP-2 overexpression nearly abolished Aβ production without affecting C99. Our data consolidate the emerging idea of a regulatory interplay between MMPs and the APP/Aβ system, and demonstrate for the first time the pro-amyloidogenic features of MT1-MMP. Further investigation will be justified to evaluate this MMP as a novel potential therapeutic target in AD.

MMPs: a novel drug target for schizophrenia

INTRODUCTION

Schizophrenia, a multifactorial disorder, is associated with dopaminergic hyperactivity, dysregulated glutamatergic neurotransmission, neuroinflammation and extracellular matrix (ECM) disturbances. MMPs, a group of structurally related proteolytic enzymes, are responsible for remodeling of ECM that maintains synaptic functions and blood-brain barrier (BBB) patency. Overstimulation of MMPs by neuroinflammation triggers ECM abnormalities that directly or indirectly alter neuronal functions like synaptic plasticity and damage to BBB. MMP-mediated ECM abnormality plays a central role in the pathogenesis of schizophrenia.

AREAS COVERED

The current review discusses the mechanistic involvement of MMPs in the pathogenesis of schizophrenia and briefly gives an overview on the recent studies on various MMP modulators.

EXPERT OPINION

Overexpression of MMPs and imbalance between MMP versus tissue inhibitors of metalloproteinase are associated with various ECM disturbances in the schizophrenic brain. Therefore, MMPs can be projected as potential therapeutic target for treatment and/or prevention of positive, negative and cognitive symptoms of schizophrenia. From past decade, scientific community is focusing on broad spectrum MMP modulators as potential therapeutic moieties for prevention of plethora of neurological, cardiovascular and pulmonary diseases. In future, specific MMP modulators should be tailored to regulate ECM integrity and explored for their pharmacotherapeutic potential in schizophrenia.

Time dependent integration of matrix metalloproteinases and their targeted substrates directs axonal sprouting and synaptogenesis following central nervous system injury

Over the past two decades, many investigators have reported how extracellular matrix molecules act to regulate neuroplasticity. The majority of these studies involve proteins which are targets of matrix metalloproteinases. Importantly, these enzyme/substrate interactions can regulate degenerative and regenerative phases of synaptic plasticity, directing axonal and dendritic reorganization after brain insult. The present review first summarizes literature support for the prominent role of matrix metalloproteinases during neuroregeneration, followed by a discussion of data contrasting adaptive and maladaptive neuroplasticity that reveals time-dependent metalloproteinase/substrate regulation of postinjury synaptic recovery. The potential for these enzymes to serve as therapeutic targets for enhanced neuroplasticity after brain injury is illustrated with experiments demonstrating that metalloproteinase inhibitors can alter adaptive and maladaptive outcome. Finally, the complexity of metalloproteinase role in reactive synaptogenesis is revealed in new studies showing how these enzymes interact with immune molecules to mediate cellular response in the local regenerative environment, and are regulated by novel binding partners in the brain extracellular matrix. Together, these different examples show the complexity with which metalloproteinases are integrated into the process of neuroregeneration, and point to a promising new angle for future studies exploring how to facilitate brain plasticity.

Matrix metalloproteinases, new insights into the understanding of neurodegenerative disorders

Matrix metalloproteinases (MMPs) are a subfamily of zinc-dependent proteases that are responsible for degradation and remodeling of extracellular matrix proteins. The activity of MMPs is tightly regulated at several levels including cleavage of prodomain, allosteric activation, compartmentalization and complex formation with tissue inhibitor of metalloproteinases (TIMPs). In the central nervous system (CNS), MMPs play a wide variety of roles ranging from brain development, synaptic plasticity and repair after injury to the pathogenesis of various brain disorders. Following general discussion on the domain structure and the regulation of activity of MMPs, we emphasize their implication in various brain disorder conditions such as Alzheimer’s disease, multiple sclerosis, ischemia/reperfusion and Parkinson’s disease. We further highlight accumulating evidence that MMPs might be the culprit in Parkinson’s disease (PD). Among them, MMP-3 appears to be involved in a range of pathogenesis processes in PD including neuroinflammation, apoptosis and degradation of α-synuclein and DJ-1. MMP inhibitors could represent potential novel therapeutic strategies for treatments of neurodegenerative diseases.

Cypermethrin induces astrocyte damage: role of aberrant Ca(2+), ROS, JNK, P38, matrix metalloproteinase 2 and migration related reelin protein

Cypermethrin is a synthetic type II pyrethroid, derived from a natural pyrethrin of the chrysanthemum plant. Cypermethrin-mediated neurotoxicity is well studied; however, relatively less is known of its effect on astrocyte development and migration. Astrocytes are the major components of blood brain barrier (BBB), and astrocyte damage along with BBB dysfunction impair the tight junction (TJ) proteins resulting in altered cell migration and neurodegeneration. Here, we studied the mechanism of cypermethin mediated rat astrocyte damage and BBB disruption, and determined any change in expression of proteins associated with cell migration. Through MTT assay we found that cypermethrin reduced viability of cultured rat astrocytes. Immunolabelling with astrocyte marker, glial fibrillary acidic protein, revealed alteration in astrocyte morphology. The astrocytes demonstrated an enhanced release of intracellular Ca(++) and ROS, and up-regulation in p-JNK and p-P38 levels in a time-dependent manner. Cypermethrin disrupted the BBB (in vivo) in developing rats and attenuated the expression of the extracellular matrix molecule (ECM) and claudin-5 in cultured astrocytes. We further observed an augmentation in the levels of matrix metalloproteinase 2 (MMP2), known to modulate cellular migration and disrupt the developmental ECM and BBB. We observed an increase in the levels of reelin, involved in cell migration, in cultured rat astrocytes. The reelin receptor, α3β1integrin, and a mammalian cytosolic protein Disabled1 (Dab1) were also up-regulated. Overall, our study demonstrates that cypermethrin induces astrocyte injury via modulation in Ca(++), ROS, JNK and P38 pathways, which may alter MMP expression and reelin dependent astrocyte migration during brain development.

Matrix metalloproteinase 2 and membrane type 1 matrix metalloproteinase co-regulate axonal outgrowth of mouse retinal ganglion cells

Restoration of correct neural activity following central nervous system (CNS) damage requires the replacement of degenerated axons with newly outgrowing, functional axons. Unfortunately, spontaneous regeneration is largely lacking in the adult mammalian CNS. In order to establish successful regenerative therapies, an improved understanding of axonal outgrowth and the various molecules influencing it, is highly needed. Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteases that were sporadically reported to influence axon outgrowth. Using an ex vivo retinal explant model, we were able to show that broad-spectrum MMP inhibition reduces axon outgrowth of mouse retinal ganglion cells (RGCs), implicating MMPs as beneficial factors in axonal regeneration. Additional studies, using more specific MMP inhibitors and MMP-deficient mice, disclosed that both MMP-2 and MT1-MMP, but not MMP-9, are involved in this process. Furthermore, administration of a novel antibody to MT1-MMP that selectively blocks pro-MMP-2 activation revealed a functional co-involvement of these proteinases in determining RGC axon outgrowth. Subsequent immunostainings showed expression of both MMP-2 and MT1-MMP in RGC axons and glial cells. Finally, results from combined inhibition of MMP-2 and β1-integrin were suggestive for a functional interaction between these molecules. Overall, our data indicate MMP-2 and MT1-MMP as promising axonal outgrowth-promoting molecules. Axonal regeneration in the central nervous system is lacking in adult mammals, thereby impeding recovery from injury to the nervous system. Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteases that were sporadically reported to influence axon outgrowth. Inhibition of specific MMPs reduced neurite outgrowth from mouse retinal explants. Our data indicate MMP-2 and MT1-MMP as promising axonal outgrowth-promoting molecules and show a possible link between MMP-2 and β1-integrin in axon outgrowth.

Defining the role of mesenchymal stromal cells on the regulation of matrix metalloproteinases in skeletal muscle cells

Recent studies indicate that mesenchymal stromal cell (MSC) transplantation improves healing of injured and diseased skeletal muscle, although the mechanisms of benefit are poorly understood. In the present study, we investigated whether MSCs and/or their trophic factors were able to regulate matrix metalloproteinase (MMP) expression and activity in different cells of the muscle tissue. MSCs in co-culture with C2C12 cells or their conditioned medium (MSC-CM) up-regulated MMP-2 and MMP-9 expression and function in the myoblastic cells; these effects were concomitant with the down-regulation of the tissue inhibitor of metalloproteinases (TIMP)-1 and -2 and with increased cell motility. In the single muscle fiber experiments, MSC-CM administration increased MMP-2/9 expression in Pax-7(+) satellite cells and stimulated their mobilization, differentiation and fusion. The anti-fibrotic properties of MSC-CM involved also the regulation of MMPs by skeletal fibroblasts and the inhibition of their differentiation into myofibroblasts. The treatment with SB-3CT, a potent MMP inhibitor, prevented in these cells, the decrease of α-smooth actin and type-I collagen expression induced by MSC-CM, suggesting that MSC-CM could attenuate the fibrogenic response through mechanisms mediated by MMPs. Our results indicate that growth factors and cytokines released by these cells may modulate the fibrotic response and improve the endogenous mechanisms of muscle repair/regeneration.

Prognostic significance of α5β1-integrin expression in cervical cancer

The purpose of this study was to evaluate the association of expression of α5β1-integrin with clinicopathologic features and prognosis in cervical cancer. Levels of α5β1-integrin in normal cervical mucosa and cervical cancer tissue were detected with immunohistochemistry. Survival analysis by the Kaplan-Meier method was performed to assess prognostic significance. α5β1-integrin expression was detected in 84.6% (143/169) cervical cancer samples, significantly different from that in normal cervical mucosa (P < 0.05). Positive expression rates of α5β1-integrin in patients with poor histologic differentiation, lymph node metastasis, and recurrence were elevated. Using Kaplan-Meier analysis, a comparison of survival curves of low versus high expression of α5β1-integrin revealed a highly significant difference in human cervical cancer cases (P < 0.05), suggesting that overexpression of α5β1-integrin is associated with a worse prognosis.The α5β1-integrin promotes angiogenesis and associates with lymph node metastasis, vascular invasion and poor prognosis of cervical cancer. The current study indicated that α5β1-integrin may be an independent prognostic factor for cervical cancer patients.