Entry, dispersion and differentiation of microglia in the developing central nervous system

Microglial cells within the developing central nervous system (CNS) originate from mesodermic precursors of hematopoietic lineage that enter the nervous parenchyma from the meninges, ventricular space and/or blood stream. Once in the nervous parenchyma, microglial cells increase in number and disperse throughout the CNS; these cells finally differentiate to become fully ramified microglial cells. In this article we review present knowledge on these phases of microglial development and the factors that probably influence them

Personality characteristics in specialist and generalist intimate partner violence perpetrators

Intimate partner violence (IPV) is one of the most common types of violence against women. Although personality disorders have been associated with IPV, perpetration research regarding personality according to the classification specialist/generalist IPV perpetrators is scarce. The general aim of this study was to describe personality in a large sample of IPV Spanish male perpetrators considering their classification (special ist vs. generalist). Participants were 1093 men convicted of IPV crimes whose ages ranged from 18 to 76 years old (M = 40.15; SD = 10.32). Of them, 554 men were classified as specialist perpetrators and 539 men were classified as generalist perpetrators. Participants completed questionnaires regarding sociodemographic and violence aspects as well as the Spanish version of the Millon Clinical Multiaxial Inventory III. Generalist perpetrators showed higher means in nearly all the personal ity disorders scales compared to specialist perpetrators. Prevalence rates in the majority of personality disorders were lower than 5%. Higher scores on the avoidant, histrionic, and self-defeating scales and lower scores on the aggressive, borderline, and drug dependence scales were related to being a specialist perpetrator. This study contributes to a better understanding of personality among generalist and specialist perpetrators.Consejería de Economía y Conocimiento, Junta de Andalucía, Grant/Award Number: Project: B-CTS-493-UGR18Ministerio de Ciencia e Innovacion, Agencia Estatal de Investigación. Gobierno de España, Grant/Award Numbers: Project: PID2019-111565GB-I00, Project: PID2019.110041GB/AEI/10.13039/50110001103

Microglia and Microglia-Like Cells: Similar but Different

We want to thank all people for fighting in the front line of the COVID-19 pandemic, during which most parts of this article was written. We also acknowledge the task of the reviewers who contributed to improve the quality of this article.Microglia are the tissue-resident macrophages of the central nervous parenchyma. In mammals, microglia are thought to originate from yolk sac precursors and posteriorly maintained through the entire life of the organism. However, the contribution of microglial cells from other sources should also be considered. In addition to “true” or “bonafide” microglia, which are of embryonic origin, the so-called “microglia-like cells” are hematopoietic cells of bone marrow origin that can engraft the mature brain mainly under pathological conditions. These cells implement great parts of the microglial immune phenotype, but they do not completely adopt the “true microglia” features. Because of their pronounced similarity, true microglia and microglia-like cells are usually considered together as one population. In this review, we discuss the origin and development of these two distinct cell types and their differences. We will also review the factors determining the appearance and presence of microglia-like cells, which can vary among species. This knowledge might contribute to the development of therapeutic strategies aiming at microglial cells for the treatment of diseases in which they are involved, for example neurodegenerative disorders like Alzheimer’s and Parkinson’s diseases.University of Granada, Spain, and FEDER-Junta de Andalucía, Spain (grant number A1-CTS-324- UGR18

Onset of microglial entry into developing quail retina coincides with increased expression of active caspase-3 and is mediated by extracellular ATP and UDP

Microglial cell precursors located in the area of the base of the pecten and the optic nerve head (BP/ONH) start to enter the retina of quail embryos at the 7 th day of incubation (E7), subsequently colonizing the entire retina by central-to-peripheral tangential migration, as previously shown by our group. The present study demonstrates a precise chronological coincidence of the onset of microglial cell entry into the retina with a striking increase in death of retinal cells, as revealed by their active caspase-3 expression and TUNEL staining, in regions dorsal to the BP/ONH area, suggesting that dying retinal cells would contribute to the microglial cell inflow into the retina. However, the molecular mechanisms involved in this inflow are currently unclear. Extracellular nucleotides, such as ATP and UDP, have previously been shown to favor migration of microglia towards brain injuries because they are released by apoptotic cells and stimulate both chemotaxis and chemokinesis in microglial cells via signaling through purinergic receptors. Hence, we tested here the hypothesis that ATP and UDP play a role in the entry and migration of microglial precursors into the developing retina. For this purpose, we used an experimental model system based on organotypic cultures of E6.5 quail embryo retina explants, which mimics the entry and migration of microglial precursors in the in situ developing retina. Inhibition of purinergic signaling by treating retina explants with either apyrase, a nucleotide-hydrolyzing enzyme, or suramin, a broad spectrum antagonist of purinergic receptors, significantly prevents the entry of microglial cells into the retina. In addition, treatment of retina explants with either exogenous ATP or UDP results in significantly increased numbers of microglial cells entering the retina. In light of these findings, we conclude that purinergic signaling by extracellular ATP and UDP is necessary for the entry and migration of microglial cells into the embryonic retina by inducing chemokinesis in these cells

Switching Roles: Beneficial Effects of Adipose Tissue-Derived Mesenchymal Stem Cells on Microglia and Their Implication in Neurodegenerative Diseases

This research was funded by the Andalusian Government, Spain (grant no. P20-01255 to M.D. and FEDER program grant no. A1-CTS-324-UGR18 to M.R.S.) and by the Spanish Ministry for Economy and Competition, Spain (grant no. SAF2017-85602-R and PID2020-119638RB-I00, both to E.G.-R.). A.I.S.-C. was the awardee of a Research Starting Fellowship for master´s students at the University of Granada, Spain. The APC was funded by MDPI.Neurological disorders, including neurodegenerative diseases, are often characterized by neuroinflammation, which is largely driven by microglia, the resident immune cells of the central nervous system (CNS). Under these conditions, microglia are able to secrete neurotoxic substances, provoking neuronal cell death. However, microglia in the healthy brain carry out CNS-supporting functions. This is due to the ability of microglia to acquire different phenotypes that can play a neuroprotective role under physiological conditions or a pro-inflammatory, damaging one during disease. Therefore, therapeutic strategies focus on the downregulation of these neuroinflammatory processes and try to re-activate the neuroprotective features of microglia. Mesenchymal stem cells (MSC) of different origins have been shown to exert such effects, due to their immunomodulatory properties. In recent years, MSC derived from adipose tissue have been made the center of attention because of their easy availability and extraction methods. These cells induce a neuroprotective phenotype in microglia and downregulate neuroinflammation, resulting in an improvement of clinical symptoms in a variety of animal models for neurological pathologies, e.g., Alzheimer’s disease, traumatic brain injury and ischemic stroke. In this review, we will discuss the application of adipose tissue-derived MSC and their conditioned medium, including extracellular vesicles, in neurological disorders, their beneficial effect on microglia and the signaling pathways involved.Andalusian Government, Spain P20-01255FEDER program grant no. A1-CTS-324-UGR18Spanish Ministry for Economy and Competition, Spain (grant no. SAF2017-85602-R and PID2020-119638RB-I00)Research Starting Fellowship for master´s students at the University of Granada, SpainMDP

Expression of Inducible Nitric Oxide Synthase (iNOS) in Microglia of the Developing Quail Retina

Inducible nitric oxide synthase (iNOS), which produce large amounts of nitric oxide (NO), is induced in macrophages and microglia in response to inflammatory mediators such as LPS and cytokines. Although iNOS is mainly expressed by microglia that become activated in different pathological and experimental situations, it was recently reported that undifferentiated amoeboid microglia can also express iNOS during normal development. The aim of this study was to investigate the pattern of iNOS expression in microglial cells during normal development and after their activation with LPS by using the quail retina as model. iNOS expression was analyzed by iNOS immunolabeling, western-blot, and RT-PCR. NO production was determined by using DAR-4M AM, a reliable fluorescent indicator of subcellular NO production by iNOS. Embryonic, postnatal, and adult in situ quail retinas were used to analyze the pattern of iNOS expression in microglial cells during normal development. iNOS expression and NO production in LPS-treated microglial cells were investigated by an in vitro approach based on organotypic cultures of E8 retinas, in which microglial cell behavior is similar to that of the in situ retina, as previously demonstrated in our laboratory. We show here that amoeboid microglia in the quail retina express iNOS during normal development. This expression is stronger in microglial cells migrating tangentially in the vitreal part of the retina and is downregulated, albeit maintained, when microglia differentiate and become ramified. LPS treatment of retina explants also induces changes in the morphology of amoeboid microglia compatible with their activation, increasing their lysosomal compartment and upregulating iNOS expression with a concomitant production of NO. Taken together, our findings demonstrate that immature microglial cells express iNOS during normal development, suggesting a certain degree of activation. Furthermore, LPS treatment induces overactivation of amoeboid microglia, resulting in a significant iNOS upregulation.This work was supported by grants from Ministerio de Economía y Competitividad, Spain (BFU2010-19981) and Junta de Andalucía, Spain (P07-CVI-03008)

The endoplasmic reticulum Ca2+-ATPase SERCA2b is upregulated in activated microglia and its inhibition causes opposite effects on migration and phagocytosis

This is the peer reviewed version of the following article: Morales-Ropero JM, Arroyo-Urea S, Neubrand VE, Martín-Oliva D, Marín-Teva JL, Cuadros MA, Vangheluwe P, Navascués J, Mata AM, Sepúlveda MR. The endoplasmic reticulum Ca2+ -ATPase SERCA2b is upregulated in activated microglia and its inhibition causes opposite effects on migration and phagocytosis. Glia. 2021 Apr;69(4):842-857, which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/glia.23931. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.The accepted version is under embargo until April 2022.Activation of microglia is an early immune response to damage in the brain. Although a key role for Ca2+ as trigger of microglial activation has been considered, little is known about the molecular scenario for regulating Ca2+ homeostasis in these cells. Taking into account the importance of the endoplasmic reticulum as a cellular Ca2+ store, the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2b) is an interesting target to modulate intracellular Ca2+ dynamics. We found upregulation of SERCA2b in activated microglia of human brain with Alzheimer´s disease and we further studied the participation of SERCA2b in microglial functions by using the BV2 murine microglial cell line and primary microglia isolated from mouse brain. To trigger microglia activation, we used the bacterial lipopolysaccharide (LPS), which is known to induce an increase of cytosolic Ca2+. Our results showed an upregulated expression of SERCA2b in LPS-induced activated microglia likely associated to an attempt to restore the increased cytosolic Ca2+ concentration. We analyzed SERCA2b contribution in microglial migration by using the specific SERCA inhibitor thapsigargin in scratch assays. Microglial migration was strongly stimulated with thapsigargin, even more than with LPS-induction, but delayed in time. However, phagocytic capacity of microglia was blocked in the presence of the SERCA inhibitor, indicating the importance of a tight control of cytosolic Ca2+ in these processes. All together, these results provide for the first time compelling evidence for SERCA2b as a major player regulating microglial functions, affecting migration and phagocytosis in an opposite manner.Grant mP_BS_35-2014 from CEI BioTic GranadaPP2016-PJI05 from University of GranadaA1-CTS-324-UGR18 from FEDER-Junta de Andalucía, SpainPP2016-PIP08 from University of GranadaBFU2017-85723-P from Spanish Ministry of Economy and Competitiveness co-financed with FEDERG044212N from Flanders Research Foundatio

P2X4 receptors in activated C8-B4 cells of cerebellar microglial origin

We investigated the properties and regulation of P2X receptors in immortalized C8-B4 cells of cerebellar microglial origin. Resting C8-B4 cells expressed virtually no functional P2X receptors, but largely increased functional expression of P2X4 receptors within 2–6 h of entering the activated state. Using real-time polymerase chain reaction, we found that P2X4 transcripts were increased during the activated state by 2.4-fold, but this increase was not reflected by a parallel increase in total P2X4 proteins. In resting C8-B4 cells, P2X4 subunits were mainly localized within intracellular compartments, including lysosomes. We found that cell surface P2X4 receptor levels increased by ∼3.5-fold during the activated state. This change was accompanied by a decrease in the lysosomal pool of P2X4 proteins. We next exploited our findings with C8-B4 cells to investigate the mechanism by which antidepressants reduce P2X4 responses. We found little evidence to suggest that several antidepressants were antagonists of P2X4 receptors in C8-B4 cells. However, we found that moderate concentrations of the same antidepressants reduced P2X4 responses in activated microglia by affecting lysosomal function, which indirectly reduced cell surface P2X4 levels. In summary, our data suggest that activated C8-B4 cells express P2X4 receptors when the membrane insertion of these proteins by lysosomal secretion exceeds their removal, and that antidepressants indirectly reduce P2X4 responses by interfering with lysosomal trafficking