Microglia-induced Neurotoxicity: A Review of in Vitro Co-culture Models

@#Microglia-induced neurotoxicity occurs when inflammation mediated by microglia causes loss of neuronal structures or functions in the central nervous system implicated in stroke, spinal cord injury, sepsis, neurodegenerative diseases and even psychiatric illnesses. Various co-culture in vitro microglia-induced neurotoxicity (MINT) models have been established to enable an in-depth study of this process and yet there is a dearth of information regarding usages, advantages and limitations of each of the components of this model. In this review, we examined 56 MINTs for the cells, stimuli, parameters, methods of neurotoxicity measurement and formats of co-culture used in their construction. We aim to provide foundational information, overall guideline and framework for the novice researcher to develop his/her own model and for the advancement of improved, novel and more representative MINT models.

Stereotactic injection of shrna GSK-3β-AAV promotes axonal regeneration after spinal cord injury / 华中科技大学学报（医学）（英德文版）

Evidence suggested that glycogen synthase kinase-3β (GSK-3β) is involved in Nogo-66 inhibiting axonal regeneration in vitro, but its effect in vivo was poorly understood. We showed that stereotactic injection of shRNA GSK-3β-adeno associated virus (GSK-3β-AAV) diminished syringomyelia and promoted axonal regeneration after spinal cord injury (SCI), using stereotactic injection of shRNA GSK-3β-AAV (tested with Western blotting and RT-PCR) into the sensorimotor cortex of rats with SCI and by the detection of biotin dextran amine (BDA)-labeled axonal regeneration. We also determined the right position to inject into the sensorimotor cortex. Our findings consolidate the hypothesis that downregulation of GSK-3β promotes axonal regeneration after SCI.

Neuronal damage and neurite change in cell model of intractable epilepsy / 中华神经科杂志

Objective To establish the cell model of intractable epilepsy and to observe its neuronal damage and morphologic change of neurites.Methods The model was established by exposing hippocampal neurons to Mg2+ -free media for 3 hours on days 10 of culture.Expression of lactic acid dehydrogenase (LDH) in supernatant was measured as an index of neuronal damage.The morphologic change of neurons and neurites was observed by optical microscope and scanning electron microscope (SEM).Results Compared to the control group, level of LDH (U/L) was significantly increased in the model group at different time points (3 hours: 4.26 ± 1.28, 6 hours: 6.56 ±2.34 and 24 hours: 16.67 ±3.57, P <0.05).With time prolonging, release of LDH in the model group was gradually increased (F = 39.316,P <0.05).Under optical microscope, neurons of model group migrated closely to each other and neurite connections appeared to be gradually "reticulated" after Mg2+ -free media treatment for 24 hours; and the "reticulated" neurites connections become more obvious after 72 hours.Under SEM, neuronal membrane was rough and had several small depressions, neurites were interlaced in cluster.Conclusions Neuronal damage and morphologic change of neurites are verified in the cell model of intractable epilepsy.

p190RhoGAP and Rap-dependent RhoGAP (ARAP3) inactivate RhoA in response to nerve growth factor leading to neurite outgrowth from PC12 cells

Rat pheochromocytoma (PC12) cells have been used to investigate neurite outgrowth. Nerve growth factor (NGF) has been well known to induce neurite outgrowth from PC12 cells. RhoA belongs to Ras-related small GTP-binding proteins, which regulate a variety of cellular processes, including cell morphology alteration, actin dynamics, and cell migration. NGF suppressed GTP-RhoA levels after 12 h in PC12 cells and was consistently required for a long time to induce neurite outgrowth. Constitutively active (CA)-RhoA suppressed neurite outgrowth from PC12 cells in response to NGF, whereas dominant-negative (DN)-RhoA stimulated it, suggesting that RhoA inactivation is essential for neurite outgrowth. Here, we investigated the mechanism of RhoA inactivation. DN-p190RhoGAP abrogated neurite outgrowth, whereas wild-type (WT)-p190RhoGAP and WT-Src synergistically stimulated it along with accelerating RhoA inactivation, suggesting that p190RhoGAP, which can be activated by Src, is a major component in inhibiting RhoA in response to NGF in PC12 cells. Contrary to RhoA, Rap1 was activated by NGF, and DN-Rap1 suppressed neurite outgrowth, suggesting that Rap1 is also essential for neurite outgrowth. RhoA was co-immunoprecipitated with Rap1, suggesting that Rap1 interacts with RhoA. Furthermore, a DN-Rap-dependent RhoGAP (ARAP3) prevented RhoA inactivation, abolishing neurite formation from PC12 cells in response to NGF. These results suggest that NGF activates Rap1, which, in turn, up-regulates ARAP3 leading to RhoA inactivation and neurite outgrowth from PC12 cells. Taken together, p190RhoGAP and ARAP3 seem to be two main factors inhibiting RhoA activity during neurite outgrowth in PC12 cells in response to NGF.

Nidogen Plays a Role in the Regenerative Axon Growth of Adult Sensory Neurons Through Schwann Cells

We previously reported that nidogen is an extracellular matrix protein regulating Schwann cell proliferation and migration. Since Schwann cells play a critical role in peripheral nerve regeneration, nidogen may play a role in it via regulation of Schwann cells. Here, we demonstrate direct evidence that nidogen induces elongation of regenerative axon growth of adult sensory neurons, and that the effect is Schwann cell dependent. Continuous infusion of recombinant ectodomain of tumor endothelial marker 7, which specifically blocks nidogen function in Schwann cells, suppressed regenerative neurite growth in a sciatic nerve axotomy model. Taken together, it is likely that nidogen is required for proper regeneration of peripheral nerves after injury.

Avaliação clínico-epidemiológica em pacientes multibacilares em uma unidade de referência de hansenologia da amazônia / Clinical and epidemiologycal evaluation of multibacillary patients from a reference center for leprosy in the brazilian amazon

O mycobacterium leprae (bacilo de hansen) possui propriedades imunogênicas especiais, responsáveis pelo alto poder incapacitante da hanseníase. Objetivou-se estudar o perfil clínico-epidemiológico de pacientes hansenianos multibacilares, de acordo com a classificação de madri, correlacionar o índice baciloscópico com o número de troncos afetados pela neurite franca no início e término do tratamento, correlacionar o grau de incapacidade com a forma clínica, à entrada e à saída desses pacientes. Selecionaram-se 158 prontuários de pacientes diagnosticados com hanseníase multibacilar, avaliados pelo exame baciloscópico e neurológico. O estudo foi realizado no centro de referência em dermatologia sanitária dr. Marcelo cândia, em marituba, pará, brasil. Desses pacientes, 52% estavam na faixa etária de 15 a 54 anos, 80,4% eram do sexo masculino, 80% tiveram alta por cura e 84% eram casos novos. A forma clínica predominante foi a dimorfa, com 68% dos casos. A forma virchowiana (mhv) apresentou maior número de pacientes com grau de incapacidade ii. A presença de incapacidade grau zero foi estatisticamente significante na forma dimorfa (mhd), que possui aproximadamente 2,69 vezes maior probabilidade de evoluir para neurite que a mhv. Os nervos periféricos mais afetados foram: o tibial posterior, o ulnar, o fibular e o mediano. Conclui-se que a forma virchowiana tem maior potencial de produção de incapacidades tipo ii, enquanto que os portadores de mhd evoluem mais vezes para neurite; e que não há diferença no acometimento de troncos nervosos em relação ao índice baciloscópico.

Mycobacterium leprae (hansen's baccillus) displays special immunogenic properties responsible by the high incapacitating power of leprae. The aims of this study were to determine the clinical-epidemic profile of multibacillar leprosum patients according to madri's classification, correlate the baciloscopic index with the amount of nerve trunks affected by the classic neuritis prior and post-treatment, and correlate the inability degree of this patient with the clinical form at entrance and outcome. Medical records from 158 selected subjects with multibacilar leprosy from the center of reference in sanitary dermatology dr. Marcelo cândia, in marituba, pará, brazil were accessed to evaluate the baciloscopic and neurological exam. . Fifth two percent of the patients were in the range of 15 to 54 years, 80.4% Were male, 80% reach outcome for cure, and 84% were new cases. The predominant clinical form was dimorfa, comprising 68% of the cases. The virchowian form (mhv) was present in the majority of subjects with degree ii of incapacity, the presence of degree zero of incapacity was statistically significant in the dimorfa form (mhd), whose subjects displayed around 2.69 Fold more chance of evolving with neuritis symptoms than mhv. The most affected peripheric nerves at the moment and during the diagnosis were: tibia posterior, ulnar, fibula, and the median nerve. In conclusion, mhv is at greater potential to develop degree ii of incapacity, whereas mhd barriers more frequently evolve to neuritis, and there is no difference among the nervous trunks affected in regard to the bacterious index.

El neurocitoesqueleto: un nuevo blanco terapéutico para el tratamiento de la depresión

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Summary Postmortem and neuroimaging studies of Major Depressive Disorder patients have revealed changes in brain structure. In particular the reduction in prefrontal cortex and in hippocampus volume has been described. In addition, a variety of cytoarchitectural abnormalities have been described in limbic regions of major depressive patients. Decrease in neuronal density has been reported in the hippocampus, a structure involved in declarative, spatial and contextual memory. This structure undergoes atrophy in depressive illness along with impairment in cognitive function. Several studies suggest that reduction of hyppocampus volume is due to the decreased cell density and diminished axons and dendrites. These changes suggested a disturbance of normal neuronal polarity, established and maintained by elements of the neuronal cytoskeleton. In this review we describe evidence supporting that neuronal cytoskeleton is altered in depression. In addition, we present data indicating that the cytoskeleton can be a potential target in depression treatment. Neurons are structural polarized cells with a highly asymmetric shape. The cytoskeleton plays a key role in maintain the structural polarization in neurons which are differentiated in two structural domains: The somato-dendritic domain and the axonal domain. This differentiated asymmetric shape, depends of the cytoskeletal organization which support, transport and sorts various molecules and organelles in different compartments within the cell. Microtubules determine the asymmetrical shape and axonal structure of neurons and form the tracks for intracellular transport, of crucial importance in axonal flux. Actin microfilaments are involved in force generation during organization of neuronal shape in cellular internal and external movements and participate in growth cone formation. This important cytoskeletal organization preceed the formation of neurites that eventually will differentiated into axons or dendrites, a process that also comprises a dynamic assembly of the three cytoskeletal components. Intermediate filaments are known in neurons as neurofilaments spatially intercalated with microtubules in the axons and facilitate the radial axonal growth and the transport. Neurofilaments also act supporting other components of the cytoskeleton. All changes and movements of the cytoskeletal organization are coordinated by cytoskeletal associated proteins such as the protein tau and the microtubule associated proteins (MAPs). Also, specific interactions of microfilaments, microtubules and filaments which are regulated by extracellular signals take place in modulation of the cytoskeletal rearrangements. The polarized structure and the highly asymmetric shape of neurons are essentials for neuronal physiology and it appears to be lost in patients with a Major Depressive Disorder. Histopathological studies have shown that the hippocampus and frontal cortex of patients with major depressive disorder have diminished soma size, as well as, have decreased dendrites and cellular volume. Dendrite formation depends mainly in microfilaments organization as well as in polarization of the microtubule binding protein MAP2. In addition, there is a decreased synaptic connectivity and an increased oxidative stress, which originates abnormalities in the cytoskeletal structure. These neuronal changes originate alterations in the brain functionality such as decreased cognitive abilities and affective dis-regulations, usually encountered in patients with depression. Therefore, pathologic lesions implicating an altered cytoskeletal organization, may have an important role in decreased cognitive functions, observed in depression, as well as in changes in the brain volume, explained by a lost of neuronal processes such as axons, dendrite processes or dendritic spines, rather than by loss of neuronal or glial cell bodies. This explanation is supported by light immunomicroscopy of brain slices postmortem stained with specific antibodies. Psychological stress which causes oxidative stress has also been suggested to cause a decrease of neuronal volume in the prefrontal cortex, altering the synaptic connections established with the hippocampus. This conclusion was drawn from studies in animal models of psychological stress associated with molecular measurements where defects in the expression of MAP1 and sinaptophysin were found, suggesting that defects in cytoskeletal associated proteins could underlie some cytoarchitectural abnormalities described in depression. Together all the evidence accumulated indicates that major depression illness and bipolar depression are mental disorders that involve loss of axons and dendrites in neurons of the Central Nervous System, that in consequence cause disruption of synaptic connectivity. Thus is possible that depression can be considered as a cytoskeletal disorder, therefore this cellular structure could be a drug target for therapeutic approaches by restoring normal cytoskeleton structure and precluding damage caused by oxygen-reactive species. In this regard, melatonin, the hormone secreted by pineal gland during dark phase of the photoperiod, has two important properties that can be useful in treatment of mental disorders. First, the melatonin is a potent free-radical scavenger and second this hormone governs the assembly of the three main cytoskeletal components modulating the cytoskeletal organization. This notion is supported by direct action of melatonin effects on cytoskeletal organization in neuronal cells. In N1E-115 neuroblastoma cells, melatonin induced a two-fold increase in number of cells with neurites 1 day after plating; the effect lasting up to 4 days. Induction of neurite outgrowths is optimal at 1 nM melatonin and in presence of hormone the cells grew as clusters with long neurites forming a fine network to make contact with adjacent cells. Immunofluorescence of N1E-115 cells cultured under these conditions showed tubulin staining in long neurite processes connecting cells to each other. Neurite formation is a complex process that is critical to establish synaptic connectivity. Neuritogenesis takes place by a dynamic cytoskeletal organization that involves microtubule enlargement, microfilament arrangement, and intermediate- filament reorganization. In particular, it is known that vimentin intermediate filaments are reorganized during initial stages of neurite outgrowth in neuroblastoma cells and cultured hippocampal neurons. Evidence has been published indicating that increase in microtubule assembly participates in neurite formation elicited by melatonin antagonism to calmodulin. Moreover, recently it was reported that melatonin precludes cytoskeletal damage produced by high levels of free radicals produced by hydrogen peroxide, as well as, damage caused by higher doses of the antypsychotics haloperidol and clozapine. N1E-115 cells incubated with either 100 uM hydrogen peroxide, 100 uM haloperidol, or 100 uM clozapine undergo a complete cytoskeletal retraction around the nucleus. By contrast, NIE-115 cells incubated with hydrogen peroxide, clozapine, or haloperidol followed by the nocturnal cerebrospinal fluid concentration of melatonin (100 nM) showed a well preserved cytoskeleton and neuritogenesis. Thus melatonin is a neuroprotective compound, since protects the neurocytoskeletal organization against damage caused by high concentrations of antipsychotics and oxidative stress. As mentioned previously, polarity is intrinsic to neuronal function. In neurons, somatodendritic domain receives and decodes incoming information and axonal domain delivers information to target cells. Progressive loss of neuronal polarity is one of the histopathologic events in depression. Cytoskeletal collapse underlie the lost of structural polarity and it is known that precede neuronal death and disappearance of synaptic connectivity. Drugs that prevent the loss of polarity and cytoskeleton retraction intrinsic to these diseases, as well as damage in cytoskeletal structure produced by oxidative stress can be extremely useful in depression treatment. Melatonin is a potent free-radical scavenger that also acts as a cytoskeleton regulator; thus, we speculate that this hormone could be useful in prevention and alleviation of psychiatry diseases with synaptic connectivity disruption. Clinical trials show that melatonin administration is followed by alleviation of circadian disturbances and cognitive function in various neuropsychiatry diseases. Moreover, in depression, melatonin improves sleep. Thus, as suggestive as this information appears, controlled clinical trials will be necessary to investigate the beneficial effects of melatonin and other drugs in the depression treatment.

Lysophosphatidylcholine suppresses apoptosis and induces neurite outgrowth in PC12 cells through activation of phospholipase D2

Lysophosphatidylcholine (LPC) is a bioactive lipid generated by phospholipase A2-mediated hydrolysis of phosphatidylcholine. In the present study, we demonstrate that LPC stimulates phospholipase D2 (PLD2) activity in rat pheochromocytoma PC12 cells. Serum deprivation induced cell death of PC12 cells, as demonstrated by decreased viability, DNA fragmentation, and increased sub-G1 fraction of cell cycle. LPC treatment protected PC12 cells partially from the cell death and induced neurite outgrowth of the cells. Overexpression of PLD2 drastically enhanced the LPC-induced inhibition of apoptosis and neuritogenesis. Pretreatment of the cells with 1-butanol, a PLD inhibitor, completely abrogated the LPC-induced inhibition of apoptosis and neurite outgrowth in PC12 cells overexpressing PLD2. These results indicate that LPC possesses the neurotrophic effects, such as anti-apoptosis and neurite outgrowth, through activation of PLD2.

Development of ligand-dependent regulatory system and its application to gene therapy of insulin-dependent diabetes mellitus

To develop an inducible expression system, the enhanced artificial nuclear receptors and target reporters were constructed. Artificial nuclear receptors were generated by fusing three domains, consisting of DNA-binding domain (DBD) of GAL4, ligand binding domain (LBD) of progesterone or estrogen receptor, and activation domain (AD) of VP16, sterol regulatory element binding protein (SREBP)-1a, or SREBP-2. The activation domain of SREBP-1a showed most potent transcriptional activity. The maximal level of target reporter gene expression was extremely elevated by the usage of ATP citrate-lyase (ACL) minimal promoter -60/+67 in place of artificial TATA promoter, while the SV40 enhancer severely increased the basal transcription in the absence of ligand. The induction system, developed in the present study, was applied to cell therapy, resulting in successful induction of single-chain insulin analogue (SIA) gene expression to correct the hyperglycemia in diabetic animals. By means of subcutaneous cell therapy, the SIA gene expression rapidly occurred after the local topical application of ligand. These results suggest that our system represents a powerful tool for transcriptional regulation of target gene that can be used for diverse applications, ranging from basic research to gene therapy.

Secretin induces neurite outgrowth of PC12 through cAMP-mitogen-activated protein kinase pathway

The gastrointestinal functions of secretin have been fairly well established. However, its function and mode of action within the nervous system remain largely unclear. To gain insight into this area, we have attempted to determine the effects of secretin on neuronal differentiation. Here, we report that secretin induces the generation of neurite outgrowth in pheochromocytoma PC12 cells. The expressions of Tau and beta-tubulin, neuronal differentiation markers, are increased upon secretin stimulation. In addition, secretin induces sustained mitogen-activated protein kinase (MAPK) activation and also stimulates the cAMP secretion. Moreover, the neurite outgrowth elicited by secretin is suppressed to a marked degree in the presence of either PD98059, a specific MAPK/ERK kinase (MEK) inhibitor, or H89, a specific protein kinase A (PKA) inhibitor. Taken together, these observations demonstrate that secretin induces neurite outgrowth of PC12 cells through cAMP-MAPK pathway, and provide a novel insight into the manner in which secretin participates in neuritogenesis.

Dexamethasone differentiates NG108-15 cells through cyclooxygenase1 induction

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid into prostanoids which participate in various cellular functions including apoptosis, mitogenesis, inflammation, immune modulation and differentiation. Moreover, the synthetic glucocorticoid, dexamethasone has immune modulating and anti-inflammatory effects in vivo. Recently, dexamethasone was found to enhance retinoic acid-induced neuronal differentiation. In this study, we investigated the mechanisms of dexamethasone-mediated neuronal differentiation. Immunoblotting and morphological analysis demonstrated that dexamethasone induced neuronal differentiation through COX 1 induction. This phenomenon was inhibited by indomethacin, a COX inhibitor. In addition, the addition of exogenous prostaglandin E2 (PGE2), a substance produced by the COX-mediated pathway, triggered neurite outgrowth of cells treated with COX inhibitor. Taken together, COX 1 appears to play an important role in dexamethasone-mediated neuronal differentiation.

Multiple Trichodiscoma:the First Case Report in China / 中华皮肤科杂志

Objectives To report the first case of multiple trichodis coma in China.A 31-year-old man presented with multiple,broomcorn grain to r ed bean-sized,skin-colored,firm papules on the right lower extremity for 15 years,and similar lesions on the left knee and lower leg for about one year.T he lesions were asymptomatic.Methods and Results Histopathology showed acanth osis of epidermis,proliferation of fine reticulate collagen fibers and depositi on of focal mucinous proteins in upper dermis.Small blood vessels and nerve fib ers were increased,and proliferation of elastic fibers was localized in the hai r follicles and around some rete ridges.Proliferated hair follicles were seen i n the margins of the lesions and extended down in a collar-like pattern.Ultra structurally,Merkel cell-axon complex was located in the overlying basal lami na of the epidermis.Myelinated nerve fibers were seen in the upper dermis.Bloo d vessel alterations were found under electron microscopy,some basal laminae of blood vessels exhibited laminated structure,proliferation of fibrous component,and thickened wall of blood vessels were observed.Conclusions The disease is rare.It is a hamartoma originated from hair disk.

Extracellular roles of high-mobility-group B1 / 中国病理生理杂志

High-mobility-group B1 (HMGB1), an abundant, highly conserved cellular protein, is widely known as a nuclear DNA-binding protein that stabilizes nucleosome formation, and facilitates gene transcription. Recent studies suggested that HMGB1 could be overexpressed and released from cellular nucleosome upon endotoxin and cytokine stimulation, or other stress challenge including burns, shock, as well as infection. Therefore, extracellular HMGB1 might be involved in the pathogenesis of sepsis and subsequent multiple organ dysfunction syndrome. Moreover, experimental data showed that extracellular HMGB1 might play vital roles in nerves development, tumor metastasis, atherosclerosis and restenosis after vascular damage.