MMP-3 secreted from endothelial cells of blood vessels after spinal cord injury activates microglia, leading to oligodendrocyte cell death

Ferroptosis in the neurovascular unit after spinal cord injury

The mechanisms of secondary injury following spinal cord injury are complicated. The role of ferroptosis, which is a newly discovered form of regulated cell death in the neurovascular unit(NVU), is increasingly important. Ferroptosis inhibitors have been shown to improve neurovascular homeostasis and attenuate secondary spinal cord injury(SCI). This review focuses on the mechanisms of ferroptosis in NVU cells and NVU-targeted therapeutic strategies according to the stages of SCI, and analyzes possible future research directions.

Microglial PCGF1 alleviates neuroinflammation associated depressive behavior in adolescent mice

Epigenetics plays a crucial role in regulating gene expression during adolescent brain maturation. In adolescents with depression, microglia-mediated chronic neuroinflammation may contribute to the activation of cellular signaling cascades and cause central synapse loss. However, the exact mechanisms underlying the epigenetic regulation of neuroinflammation leading to adolescent depression remain unclear. In this study, we found that the expression of polycomb group 1 (PCGF1), an important epigenetic regulator, was decreased both in the plasma of adolescent major depressive disorder (MDD) patients and in the microglia of adolescent mice in a mouse model of depression. We demonstrated that PCGF1 alleviates neuroinflammation mediated by microglia in vivo and in vitro, reducing neuronal damage and improving depression-like behavior in adolescent mice. Mechanistically, PCGF1 inhibits the transcription of MMP10 by upregulating RING1B/H2AK119ub and EZH2/H3K27me3 in the MMP10 promoter region, specifically inhibiting microglia-mediated neuroinflammation. These results provide valuable insights into the pathogenesis of adolescent depression, highlighting potential links between histone modifications, neuroinflammation and nerve damage. Potential mechanisms of microglial PCGF1 regulates depression-like behavior in adolescent mice. Microglial PCGF1 inhibits NF-κB/MAPK pathway activation through regulation of RING1B/H2AK119ub and EZH2/H3K27me3 in the MMP10 promoter region, which attenuates neuroinflammation and ameliorates depression-like behaviors in adolescent mice.

TRPM7 Mediates BSCB Disruption After Spinal Cord Injury by Regulating the mTOR/JMJD3 Axis in Rats

After spinal cord injury (SCI), secondary injuries including blood cells infiltration followed by the production of inflammatory mediators are led by blood-spinal cord barrier (BSCB) breakdown. Therefore, preventing BSCB damage could alleviate the secondary injury progresses after SCI. Recently, we reported that transient receptor potential melastatin 7 channel (TRPM7) expression is increased in vascular endothelial cells after injury and thereby mediates BSCB disruption. However, the mechanism by which TRPM7 regulates BSCB disruption has not been examined yet. In current research, we show that TRPM7 mediates BSCB disruption via mammalian target of rapamycin (mTOR) pathway after SCI in rats. After contusion injury at T9 level of spinal cord, mTOR pathway was activated in the endothelial cells of blood vessels and TRPM7 was involved in the activation of mTOR pathway. BSCB disruption, MMP-2/9 activation, and blood cell infiltration after injury were alleviated by rapamycin, a mTOR signaling inhibitor. Rapamycin also conserved the level of tight junction proteins, which were decreased after SCI. Furthermore, mTOR pathway regulated the expression and activation of histone H3K27 demethylase JMJD3, known as a key epigenetic regulator mediating BSCB damage after SCI. In addition, rapamycin inhibited JMJD3 expression, the loss of tight junction molecules, and MMP-2/9 expression in bEnd.3, a brain endothelial cell line, after oxygen-glucose deprivation/reoxygenation. Thus, our results suggest that TRPM7 contributes to the BSCB disruption by regulating JMJD3 expression through the mTOR pathway after SCI.

Immunomodulatory roles of metalloproteinases in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, autoimmune pathology characterized by persistent synovial inflammation and gradually advancing bone destruction. Matrix metalloproteinases (MMPs), as a family of zinc-containing enzymes, have been found to play an important role in degradation and remodeling of extracellular matrix (ECM). MMPs participate in processes of cell proliferation, migration, inflammation, and cell metabolism. A growing number of persons have paid attention to their function in inflammatory and immune diseases. In this review, the details of regulation of MMPs expression and its expression in RA are summarized. The role of MMPs in ECM remodeling, angiogenesis, oxidative and nitrosative stress, cell migration and invasion, cytokine and chemokine production, PANoptosis and bone destruction in RA disease are discussed. Additionally, the review summarizes clinical trials targeting MMPs in inflammatory disease and discusses the potential of MMP inhibition in the therapeutic context of RA. MMPs may serve as biomarkers for drug response, pathology stratification, and precision medicine to improve clinical management of rheumatoid arthritis.

Matrix Metalloproteinases Inhibitors in Cancer Treatment: An Updated Review (2013-2023)

Matrix metalloproteinases (MMPs) are identifiable members of proteolytic enzymes that can degrade a wide range of proteins in the extracellular matrix (ECM). MMPs can be categorized into six groups based on their substrate specificity and structural differences: collagenases, gelatinases, stromelysins, matrilysins, metalloelastase, and membrane-type MMPs. MMPs have been linked to a wide variety of biological processes, such as cell transformation and carcinogenesis. Over time, MMPs have been evaluated for their role in cancer progression, migration, and metastasis. Accordingly, various MMPs have become attractive therapeutic targets for anticancer drug development. The first generations of broad-spectrum MMP inhibitors displayed effective inhibitory activities but failed in clinical trials due to poor selectivity. Thanks to the evolution of X-ray crystallography, NMR analysis, and homology modeling studies, it has been possible to characterize the active sites of various MMPs and, consequently, to develop more selective, second-generation MMP inhibitors. In this review, we summarize the computational and synthesis approaches used in the development of MMP inhibitors and their evaluation as potential anticancer agents.

Microglia and the Blood-Brain Barrier: An External Player in Acute and Chronic Neuroinflammatory Conditions

Microglia are the resident immune cells of the central nervous system that guarantee immune surveillance and exert also a modulating role on neuronal synaptic development and function. Upon injury, microglia get activated and modify their morphology acquiring an ameboid phenotype and pro- or anti-inflammatory features. The active role of microglia in blood-brain barrier (BBB) function and their interaction with different cellular components of the BBB-endothelial cells, astrocytes and pericytes-are described. Here, we report the specific crosstalk of microglia with all the BBB cell types focusing in particular on the involvement of microglia in the modulation of BBB function in neuroinflammatory conditions that occur in conjunction with an acute event, such as a stroke, or in a slow neurodegenerative disease, such as Alzheimer's disease. The potential of microglia to exert a dual role, either protective or detrimental, depending on disease stages and environmental conditioning factors is also discussed.

Implications of microglial heterogeneity in spinal cord injury progression and therapy

Microglia are widely distributed in the central nervous system (CNS), where they aid in the maintenance of neuronal function and perform key auxiliary roles in phagocytosis, neural repair, immunological control, and nutrition delivery. Microglia in the undamaged spinal cord is in a stable state and serve as immune monitors. In the event of spinal cord injury (SCI), severe changes in the microenvironment and glial scar formation lead to axonal regeneration failure. Microglia participates in a series of pathophysiological processes and behave both positive and negative consequences during this period. A deep understanding of the characteristics and functions of microglia can better identify therapeutic targets for SCI. Technological innovations such as single-cell RNA sequencing (Sc-RNAseq) have led to new advances in the study of microglia heterogeneity throughout the lifespan. Here,We review the updated studies searching for heterogeneity of microglia from the developmental and pathological state, survey the activity and function of microglia in SCI and explore the recent therapeutic strategies targeting microglia in the CNS injury.

The Interplay between Ghrelin and Microglia in Neuroinflammation: Implications for Obesity and Neurodegenerative Diseases

Numerous studies have shown that microglia are capable of producing a wide range of chemokines to promote inflammatory processes within the central nervous system (CNS). These cells share many phenotypical and functional characteristics with macrophages, suggesting that microglia participate in innate immune responses in the brain. Neuroinflammation induces neurometabolic alterations and increases in energy consumption. Microglia may constitute an important therapeutic target in neuroinflammation. Recent research has attempted to clarify the role of Ghre signaling in microglia on the regulation of energy balance, obesity, neuroinflammation and the occurrence of neurodegenerative diseases. These studies strongly suggest that Ghre modulates microglia activity and thus affects the pathophysiology of neurodegenerative diseases. This review aims to summarize what is known from the current literature on the way in which Ghre modulates microglial activity during neuroinflammation and their impact on neurometabolic alterations in neurodegenerative diseases. Understanding the role of Ghre in microglial activation/inhibition regulation could provide promising strategies for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

Microglia: The Hub of Intercellular Communication in Ischemic Stroke

Communication between microglia and other cells has recently been at the forefront of research in central nervous system (CNS) disease. In this review, we provide an overview of the neuroinflammation mediated by microglia, highlight recent studies of crosstalk between microglia and CNS resident and infiltrating cells in the context of ischemic stroke (IS), and discuss how these interactions affect the course of IS. The in-depth exploration of microglia-intercellular communication will be beneficial for therapeutic tools development and clinical translation for stroke control.

Research advances of biomaterials-based microenvironment-regulation therapies for repair and regeneration of spinal cord injury

Traumatic spinal cord injury (SCI) usually results in restricted behaviour recovery and even life-changing paralysis, accompanied with numerous complications. Pathologically, the initial injuries trigger a series of secondary injuries, leading to an expansion of lesion site, a mass of neuron loss, and eventual failure of endogenous axon regeneration. As the advances rapidly spring up in regenerative medicine and tissue engineering biomaterials, regulation of these secondary injuries becomes possible, shedding a light on normal functional restoration. The successful tissue regeneration lies in proper regulation of the inflammatory microenvironment, including the inflammatory immune cells and inflammatory factors that lead to oxidative stress, inhibitory glial scar and neuroexcitatory toxicity. Specifically, the approaches based on microenvironment-regulating biomaterials have shown great promise in the repair and regeneration of SCI. In this review, the pathological inflammatory microenvironments of SCI are discussed, followed by the introduction of microenvironment-regulating biomaterials in terms of their impressive therapeutic effect in attenuation of secondary inflammation and promotion of axon regrowth. With the emphasis on regulating secondary events, the biomaterials for SCI treatment will become promising for clinical applications.

Hypoxia response element-directed expression of bFGF in dental pulp stem cells improve the hypoxic environment by targeting pericytes in SCI rats

Cell-based transplantation strategies possess great potential for spinal cord injury (SCI) repair. Basic fibroblast growth factor (bFGF) has been reported to have multiple neuro-promoting effects on developing and adult nervous system of mammals and considered a promising therapy for nerve injury following SCI. Human dental pulp stem cells (DPSCs) are abundant stem cells with low immune rejection, which can be considered for cell replacement therapy. The purpose of this study was to investigate the roles of DPSCs which express bFGF under the regulation of five hypoxia-responsive elements (5HRE) using an adeno-associated virus (AAV-5HRE-bFGF-DPSCs) in SCI repairing model. In this study, DPSCs were revealed to differentiate into CD13⁺ pericytes and up-regulate N-cadherin expression to promote the re-attachment of CD13⁺ pericytes to vascular endothelial cells. The re-attachment of CD13⁺ pericytes to vascular endothelial cells subsequently increased the flow rate of blood in microvessels via the contraction of protuberance. As a result, increased numbers of red blood cells carried more oxygen to the damaged area and the local hypoxia microenvironment in SCI was improved. Thus, this study represents a step forward towards the potential use of AAV-5HRE-bFGF-DPSCs in SCI treatment in clinic.

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) 5HRE-bFGF-DPSCs secrete bFGF in a hypoxia dependent manner, making the administration more precise.

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CD13+ pericyte regulate vascular diameter and promote the recovery of hypoxia microenvironment via DDC-5HT-5HT-1B in SCI.

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5HRE-bFGF-DPSCs can differentiate into CD13+ pericyte to compensate for the mass death of CD13+ pericyte after SCI.

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5HRE-bFGF-DPSCs promote CD13+ pericyte adhesion to vascular endothelial cell by secreting bFGF through N-cadherin.

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5HRE-bFGF-DPSCs promote the recovery of SCI by restoring hypoxic microenvironment and inhibit autophagy pathway.

Acylated Ghrelin as a Multi-Targeted Therapy for Alzheimer's and Parkinson's Disease

Much thought has been given to the impact of Amyloid Beta, Tau and Alpha-Synuclein in the development of Alzheimer's disease (AD) and Parkinson's disease (PD), yet the clinical failures of the recent decades indicate that there are further pathological mechanisms at work. Indeed, besides amyloids, AD and PD are characterized by the culminative interplay of oxidative stress, mitochondrial dysfunction and hyperfission, defective autophagy and mitophagy, systemic inflammation, BBB and vascular damage, demyelination, cerebral insulin resistance, the loss of dopamine production in PD, impaired neurogenesis and, of course, widespread axonal, synaptic and neuronal degeneration that leads to cognitive and motor impediments. Interestingly, the acylated form of the hormone ghrelin has shown the potential to ameliorate the latter pathologic changes, although some studies indicate a few complications that need to be considered in the long-term administration of the hormone. As such, this review will illustrate the wide-ranging neuroprotective properties of acylated ghrelin and critically evaluate the hormone's therapeutic benefits for the treatment of AD and PD.

Metformin: A Prospective Alternative for the Treatment of Chronic Pain

Metformin (biguanide) is a drug widely used for the treatment of type 2 diabetes. This drug has been used for 60 years as a highly effective antihyperglycemic agent. The search for the mechanism of action of metformin has produced an enormous amount of research to explain its effects on gluconeogenesis, protein metabolism, fatty acid oxidation, oxidative stress, glucose uptake, autophagy and pain, among others. It was only up the end of the 1990s and beginning of this century that some of its mechanisms were revealed. Metformin induces its beneficial effects in diabetes through the activation of a master switch kinase named AMP-activated protein kinase (AMPK). Two upstream kinases account for the physiological activation of AMPK: liver kinase B1 and calcium/calmodulin-dependent protein kinase kinase 2. Once activated, AMPK inhibits the mechanistic target of rapamycin complex 1 (mTORC1), which in turn avoids the phosphorylation of p70 ribosomal protein S6 kinase 1 and phosphatidylinositol 3-kinase/protein kinase B signaling pathways and reduces cap-dependent translation initiation. Since metformin is a disease-modifying drug in type 2 diabetes, which reduces the mTORC1 signaling to induce its effects on neuronal plasticity, it was proposed that these mechanisms could also explain the antinociceptive effect of this drug in several models of chronic pain. These studies have highlighted the efficacy of this drug in chronic pain, such as that from neuropathy, insulin resistance, diabetic neuropathy, and fibromyalgia-type pain. Mounting evidence indicates that chronic pain may induce anxiety, depression and cognitive impairment in rodents and humans. Interestingly, metformin is able to reverse some of these consequences of pathological pain in rodents. The purpose of this review was to analyze the current evidence about the effects of metformin in chronic pain and three of its comorbidities (anxiety, depression and cognitive impairment).

High Glucose and Hypoxia-Mediated Damage to Human Brain Microvessel Endothelial Cells Induces an Altered, Pro-Inflammatory Phenotype in BV-2 Microglia In Vitro

Diabetes is strongly linked to the development of Alzheimer’s disease (AD), though the mechanisms for this enhanced risk are unclear. Because vascular inflammation is a consistent feature of both diabetes and AD, the cerebral microcirculation could be a key target for the effects of diabetes in the brain. The goal of this study is to explore whether brain endothelial cells, injured by diabetes-related insults, glucose and hypoxia, can affect inflammatory and activation processes in microglia in vitro. Human brain microvascular endothelial cells (HBMVECs) were either treated with 5 mM glucose (control), 30 mM glucose (high glucose), exposed to hypoxia, or exposed to hypoxia plus high glucose. HBMVEC-conditioned medium was then used to treat BV-2 microglia. Alterations in microglia phenotype were assessed through measurement of nitric oxide (NO), cytokine production, microglial activation state markers, and microglial phagocytosis. HBMVECs were injured by exposure to glucose and/or hypoxia, as assessed by release of LDH, interleukin (IL)-1β, and reactive oxygen species (ROS). HBMVECs injured by glucose and hypoxia induced increases in microglial production of NO, tumor necrosis factor-α (TNFα) and matrix metalloproteinase (MMP)-9. Injured HBMVECs significantly increased microglial expression of CD11c and CLEC7A, and decreased expression of the homeostatic marker P2RY12. Finally, bead uptake by BV-2 cells, an index of phagocytic ability, was elevated by conditioned media from injured HBMVECs. The demonstration that injury to brain endothelial cells by diabetic-associated insults, glucose and hypoxia, promotes microglial inflammation supports the idea that the cerebral microcirculation is a critical locus for the deleterious effects of diabetes in the AD brain.

Sodium Tanshinone IIA Silate Exerts Microcirculation Protective Effects against Spinal Cord Injury In Vitro and In Vivo

Spinal cord microcirculation involves functioning endothelial cells at the blood spinal cord barrier (BSCB) and maintains normal functioning of spinal cord neurons, axons, and glial cells. Protection of both the function and integrity of endothelial cells as well as the prevention of BSCB disruption may be a strong strategy for the treatment of spinal cord injury (SCI) cases. Sodium Tanshinone IIA silate (STS) is used for the treatment of coronary heart disease and improves microcirculation. Whether STS exhibits protective effects for SCI microcirculation is not yet clear. The purpose of this study is to investigate the protective effects of STS on oxygen-glucose deprivation- (OGD-) induced injury of spinal cord endothelial cells (SCMECs) in vitro and to explore effects on BSCB and neurovascular protection in vivo. SCMECs were treated with various concentrations of STS (1 μM, 3 μM, and 10 μM) for 24 h with or without OGD-induction. Cell viability, tube formation, migration, and expression of Notch signaling pathway components were evaluated. Histopathological evaluation (H&E), Nissl staining, BSCB permeability, and the expression levels of von Willebrand Factor (vWF), CD31, NeuN, and Notch signaling pathway components were analyzed. STS was found to improve SCMEC functions and reduce inflammatory mediators after OGD. STS also relieved histopathological damage, increased zonula occludens-1 (ZO-1), inhibited BSCB permeability, rescued microvessels, protected motor neuromas, and improved functional recovery in a SCI model. Moreover, we uncovered that the Notch signaling pathway plays an important role during these processes. These results indicated that STS protects microcirculation in SCI, which may be used as a therapeutic strategy for SCI in the future.

Matrix metalloproteinases shape the oligodendrocyte (niche) during development and upon demyelination

The oligodendrocyte lineage cell is crucial to proper brain function. During central nervous system development, oligodendrocyte progenitor cells (OPCs) migrate and proliferate to populate the entire brain and spinal cord, and subsequently differentiate into mature oligodendrocytes that wrap neuronal axons in an insulating myelin layer. When damage occurs to the myelin sheath, OPCs are activated and recruited to the demyelinated site, where they differentiate into oligodendrocytes that remyelinate the denuded axons. The process of OPC attraction and differentiation is influenced by a multitude of factors from the cell's niche. Matrix metalloproteinases (MMPs) are powerful and versatile enzymes that do not only degrade extracellular matrix proteins, but also cleave cell surface receptors, growth factors, signaling molecules, proteases and other precursor proteins, leading to their activation or degradation. MMPs are markedly upregulated during brain development and upon demyelinating injury, where their broad functions influence the behavior of neural progenitor cells (NPCs), OPCs and oligodendrocytes. In this review, we focus on the role of MMPs in (re)myelination. We will start out in the developing brain with describing the effects of MMPs on NPCs, OPCs and eventually oligodendrocytes. Then, we will outline their functions in oligodendrocyte process extension and developmental myelination. Finally, we will review their potential role in demyelination, describe their significance in remyelination and discuss the evidence for a role of MMPs in remyelination failure, focusing on multiple sclerosis. In conclusion, MMPs shape the oligodendrocyte (niche) both during development and upon demyelination, and thus are important players in directing the fate and behavior of oligodendrocyte lineage cells throughout their life cycle.

Perspectives and New Aspects of Metalloproteinases' Inhibitors in the Therapy of CNS Disorders: From Chemistry to Medicine

Matrix metalloproteinases (MMPs) play a key role in remodeling of the extracellular matrix (ECM) and, at the same time, influence cell differentiation, migration, proliferation, and survival. Their importance in a variety of human diseases including cancer, rheumatoid arthritis, pulmonary emphysema and fibrotic disorders has been known for many years but special attention should be paid on the role of MMPs in the central nervous system (CNS) disorders. Till now, there are not many well documented physiological MMP target proteins in the brain but only some pathological ones. Numerous neurodegenerative diseases are a consequence of or result in disturbed remodeling of brain ECM, therefore proper action of MMPs as well as control of their activity may play crucial roles in the development of these diseases. In the present review, we discuss the role of metalloproteinase inhibitors, from the wellknown natural endogenous tissue inhibitors of metalloproteinases (TIMPs) to the exogenous synthetic ones like (4-phenoxyphenylsulfonyl)methylthiirane (SB-3CT), tetracyclines, batimastat (BB-94) and FN-439. As the MMP-TIMP system has been well described in physiological development as well as in pathological conditions mainly in neoplastic diseases, the knowledge about the enzymatic system in mammalian brain tissue still remains poorly understood in this context. Therefore, we focus on MMPs inhibition in the context of the physiological function of the adult brain as well as pathological conditions including neurodegenerative diseases, brain injuries, and others.

Direct and indirect effects of lipids on microglia function

Microglia are key players in brain function by maintaining brain homeostasis across lifetime. They participate to brain development and maturation through their ability to release neurotrophic factors, to remove immature synapses or unnecessary neural progenitors. They modulate neuronal activity in healthy adult brains and they also orchestrate the neuroinflammatory response in various pathophysiological contexts such as aging and neurodegenerative diseases. One of the main features of microglia is their high sensitivity to environmental factors, partly via the expression of a wide range of receptors. Recent data pinpoint that dietary fatty acids modulate microglia function. Both the quantity and the type of fatty acid are potent modulators of microglia physiology. The present review aims at dissecting the current knowledge on the direct and indirect mechanisms (focus on gut microbiota and hormones) through which fatty acids influence microglial physiology. We summarize main discoveries from in vitro and in vivo models on fatty acid-mediated microglial modulation. All these studies represent a promising field of research that could promote using nutrition as a novel therapeutic or preventive tool in diseases involving microglia dysfunctions.

Dysfunction of Cerebrovascular Endothelial Cells: Prelude to Vascular Dementia

Vascular dementia (VaD) is the second most common type of dementia after Alzheimer's disease (AD), characterized by progressive cognitive impairment, memory loss, and thinking or speech problems. VaD is usually caused by cerebrovascular disease, during which, cerebrovascular endothelial cells (CECs) are vulnerable. CEC dysfunction occurs before the onset of VaD and can eventually lead to dysregulation of cerebral blood flow and blood-brain barrier damage, followed by the activation of glia and inflammatory environment in the brain. White matter, neuronal axons, and synapses are compromised in this process, leading to cognitive impairment. The present review summarizes the mechanisms underlying CEC impairment during hypoperfusion and pathological role of CECs in VaD. Through the comprehensive examination and summarization, endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) signaling pathway, Ras homolog gene family member A (RhoA) signaling pathway, and CEC-derived caveolin-1 (CAV-1) are proposed to serve as targets of new drugs for the treatment of VaD.

Microglia in the Neurovascular Unit: Blood-Brain Barrier-microglia Interactions After Central Nervous System Disorders

Over the past few decades, microglial cells have been regarded as the main executor of inflammation after acute and chronic central nervous system (CNS) disorders, responding rapidly to exogenous stimuli during acute trauma or infections, or signals released by cells undergoing cell death during conditions such as stroke, Alzheimer's disease (AD) and Parkinson's disease (PD). Barriers of the nervous system, and in particular the blood-brain barrier (BBB), play a key role in the normal physiological and cognitive functions of the brain. Being at the interface between the central and peripheral compartment, the BBB is regarded as a sensor of homeostasis, and any disruption within the brain or the systemic compartment triggers BBB dysfunction and neuroinflammation, both contributing to the pathogenesis of cerebrovascular disease. This involves a dynamic response mediated by all components of the neurovascular unit (NVU), and ongoing research suggests that BBB-microglia interaction is critical to dictate the microglial response to NVU injury. The present review aims to give an up-to-date account of the emerging critical role of BBB-microglia interactions during neuroinflammation, and how these could be targeted for the therapeutic treatment of major central inflammatory disease.

Microglia: Housekeeper of the Central Nervous System

Microglia, of myeloid origin, play fundamental roles in the control of immune responses and the maintenance of central nervous system homeostasis. These cells, just like peripheral macrophages, may be activated into M1 pro-inflammatory or M2 anti-inflammatory phenotypes by appropriate stimuli. Microglia do not respond in isolation, but form part of complex networks of cells influencing each other. This review addresses the complex interaction of microglia with each cell type in the brain: neurons, astrocytes, cerebrovascular endothelial cells, and oligodendrocytes. We also highlight the participation of microglia in the maintenance of homeostasis in the brain, and their roles in the development and progression of age-related neurodegenerative disorders.

Associations between serum ghrelin and knee symptoms, joint structures and cartilage or bone biomarkers in patients with knee osteoarthritis

OBJECTIVE

The roles of ghrelin in knee osteoarthritis (OA) are unclear. This study aimed to examine cross-sectional associations of ghrelin with knee symptoms, joint structures and cartilage or bone biomarkers in patients with knee OA.

METHODS

This study included 146 patients with symptomatic knee OA. Serum levels of ghrelin and cartilage or bone biomarkers including cartilage oligomeric matrix protein (COMP), cross linked C-telopeptide of type I collagen (CTXI), cross linked N-telopeptide of type I collagen (NTXI), N-terminal procollagen III propeptide (PIIINP), and matrix metalloproteinase (MMP)-3, 10, 13 were measured using Enzyme-linked immunosorbent assay (ELISA). Knee symptoms were assessed using the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Infrapatellar fat pad (IPFP) volume, IPFP signal intensity alternation, cartilage defects, bone marrow lesions (BMLs) and effusion-synovitis were assessed using the (MRI). Osteophytes and joint space narrowing (JSN) were assessed using the Osteoarthritis Research Society International atlas.

RESULTS

After adjustment for potential confounders, ghrelin quartiles were positively associated with knee symptoms including pain, stiffness, dysfunction and total score (quartile 4 vs 1: β 24.19, 95% CI 8.13-40.25). Ghrelin quartiles were also significantly associated with increased IPFP signal intensity alteration (quartile 4 vs 1: OR 3.57, 95% CI 1.55-8.25) and NTXI, PIIINP, MMP3 and MMP13. Ghrelin was not significantly associated with other joint structures and biomarkers.

CONCLUSIONS

Serum levels of ghrelin were significantly associated with increased knee symptoms, IPFP signal intensity alteration and serum levels of MMP3, MMP13, NTXI and PIIINP, suggesting that ghrelin may have a role to play in knee OA.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Beneficial effects of early hemostasis on spinal cord injury in the rat

STUDY DESIGN

Experimental study.

OBJECTIVES

To investigate the effect of early hemostasis on spinal cord injury (SCI).

SETTING

Fourth Military Medical University, Xi'an, China.

METHODS

Sprague Dawley rats were used. Hematoxylin and eosin (HE) staining was performed to observe hemorrhage at different time points (2, 6, 12, 24 and 48 h) after SCI to determine the time window of hemostatic drug administration (n=3 per time point). Three different concentrations of Etamsylate (0.025, 0.05 and 0.1 g kg-1) were administered immediately and 5 and 10 h after SCI to evaluate the effective dosage (n=6 per group). Another 82 rats were then randomly divided into two groups, Etamsylate group (0.1 g kg-1, n=41) and glucose control group (n=41). Nissl staining was performed to observe neurons at 10 days post injury. Immunohistochemistry, western blot and quantitative real-time PCR were performed to detect tissue necrosis at 7 d.p.i., the activation of astrocytes and microglia/macrophages and lesion cavity at 10 d.p.i. Basso-Beattie-Bresnahan scoring and rump height index assay were used to examine locomotion recovery.

RESULTS

Early hemostasis reduced the lesion area and tissue necrosis, enhanced neuronal survival, alleviated the activation of microglia/macrophages and astrocytes and facilitated functional recovery after spinal cord contusion in rats. Early hemostasis decreased hemorrhage area and lesion area after spinal cord transection in rats.

CONCLUSION

The present study demonstrated that early hemostasis has beneficial effects on SCI in the rat. It has the potential to be translated into clinical practice.

Jmjd3 mediates blood-spinal cord barrier disruption after spinal cord injury by regulating MMP-3 and MMP-9 expressions

The disruption of the blood-spinal cord barrier (BSCB) by matrix metalloprotease (MMP) activation is a detrimental event that leads to blood cell infiltration, inflammation, and apoptosis, thereby contributing to permanent neurological disability after spinal cord injury (SCI). However, the molecular mechanisms underlying Mmp gene regulation have not been fully elucidated. Here, we demonstrated the critical role of histone H3K27 demethylase Jmjd3 in the regulation of Mmp gene expression and BSCB disruption using in vitro cellular and in vivo animal models. We found that Jmjd3 up-regulation, in cooperation with NF-κB, after SCI is required for Mmp-3 and Mmp-9 gene expressions in injured vascular endothelial cells. In addition, Jmjd3 mRNA depletion inhibited Mmp-3 and Mmp-9 gene expressions and significantly attenuated BSCB permeability and the loss of tight junction proteins. These events further led to improved functional recovery, along with decreased hemorrhage, blood cell infiltration, inflammation, and cell death of neurons and oligodendrocytes after SCI. Thus, our findings suggest that Jmjd3 regulation may serve as a potential therapeutic intervention for preserving BSCB integrity following SCI.

Functions and mechanisms of microglia/macrophages in neuroinflammation and neurogenesis after stroke

Microglia/macrophages are the major immune cells involved in the defence against brain damage. Their morphology and functional changes are correlated with the release of danger signals induced by stroke. These cells are normally responsible for clearing away dead neural cells and restoring neuronal functions. However, when excessively activated by the damage-associated molecular patterns following stroke, they can produce a large number of proinflammatory cytokines that can disrupt neural cells and the blood-brain barrier and influence neurogenesis. These effects indicate the important roles of microglia/macrophages in the pathophysiological processes of stroke. However, the modifiable and adaptable nature of microglia/macrophages may also be beneficial for brain repair and not just result in damage. These distinct roles may be attributed to the different microglia/macrophage phenotypes because the M1 population is mainly destructive, while the M2 population is neuroprotective. Additionally, different gene expression signature changes in microglia/macrophages have been found in diverse inflammatory milieus. These biofunctional features enable dual roles for microglia/macrophages in brain damage and repair. Currently, it is thought that the proper inflammatory milieu may provide a suitable microenvironment for neurogenesis; however, detailed mechanisms underlying the inflammatory responses that initiate or inhibit neurogenesis remain unknown. This review summarizes recent progress concerning the mechanisms involved in brain damage, repair and regeneration related to microglia/macrophage activation and phenotype transition after stroke. We also argue that future translational studies should be targeting multiple key regulating molecules to improve brain repair, which should be accompanied by the concept of a "therapeutic time window" for sequential therapies.

D-allose protects the blood brain barrier through PPARγ-mediated anti-inflammatory pathway in the mice model of ischemia reperfusion injury

Our early experiments confirmed that D-allose was closely involved in the blood brain barrier (BBB) protection from ischemia reperfusion (IR) injury, but the regulatory mechanism is not fully defined. In this study, we aimed to investigate the role of D-allose in the protection of BBB integrity and the relevant mechanisms involved in the mice model of middle cerebral artery occlusion and reperfusion (MCAO/Rep). D-allose was intravenously injected via a tail vein (0.2mg/g and 0.4mg/g, 1h before ischemia), GW9662 was intraperitoneal injected to the mice (4mg/kg) before inducing ischemia 24h. Pretreatment with D-allose ameliorated the neurological deficits, infarct volume and brain edema in brains of MCAO/Rep mice. D-allose inhibited cell apoptosis in the mice model of MCAO/Rep. We observed that D-allose remarkably decreased BBB permeability and prevented the reduction of ZO-1, Occludin and Claudin-5 in mice brains with MCAO/Rep injury. D-allose also repressed the levels of TNF-α, NF-κB, interleukin (IL)-1β and IL-8 in inflammatory responses. The increases of intercellular adhesion molecular-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and CD11b/CD18 were significantly inhibited by D-allose during the MCAO/Rep injury. And D-allose decreased the L-selectin and P-selectin levels after MCAO/Rep. Moreover, D-allose induced up-regulation of peroxisome proliferator-activated receptor γ (PPARγ), and down-regulation of TNF-α and NF-κB after MCAO/Rep, which were abolished by utilization of GW9662. In conclusion, we provided evidences that D-allose may has therapeutic potential against brain IR injury through attenuating BBB disruption and the inflammatory response via PPARγ-dependent regulation of NF-κB.

Intracellular Cleavage of the Cx43 C-Terminal Domain by Matrix-Metalloproteases: A Novel Contributor to Inflammation?

The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell-cell transfer of metabolic and electric signals. GJs are formed by connexin (Cx) proteins of which Cx43 is most widespread in the human body. Beyond its role in direct intercellular communication, Cx43 also forms nonjunctional hemichannels (HCs) in the plasma membrane that mediate the release of paracrine signaling molecules in the extracellular environment. Both HC and GJ channel function are regulated by protein-protein interactions and posttranslational modifications that predominantly take place in the C-terminal domain of Cx43. Matrix metalloproteases (MMPs) are a major group of zinc-dependent proteases, known to regulate not only extracellular matrix remodeling, but also processing of intracellular proteins. Together with Cx43 channels, both GJs and HCs, MMPs contribute to acute inflammation and a small number of studies reports on an MMP-Cx43 link. Here, we build further on these reports and present a novel hypothesis that describes proteolytic cleavage of the Cx43 C-terminal domain by MMPs and explores possibilities of how such cleavage events may affect Cx43 channel function. Finally, we set out how aberrant channel function resulting from cleavage can contribute to the acute inflammatory response during tissue injury.