Papel de la microglía en la neuroinflamación generada mediante neuraminidasa

Por otra parte, en este trabajo se han desarrollado herramientas para el análisis morfológico objetivo de la microglía. Estas herramientas han permitido la categorización de la población de microglía basándonos en parámetros morfológicos, y el establecimiento de distintos morfotipos asociados a diferentes regiones cerebrales y/o diversos estados de activación. Además, se ha demostrado una correlación entre diferentes parámetros morfológicos y la expresión de la citoquina pro-inflamatoria IL-1β. Estas herramientas de análisis morfológico podrían ser de gran ayuda para la evaluación y el diagnóstico de enfermedades neurodegenerativas o neurológicas en muestras obtenidas post-mortem.Está ampliamente aceptado que en algunas ocasiones la neuroinflamación es un proceso previo al desarrollo de enfermedades neurodegenerativas y que la microglía juega un papel clave en el desarrollo de la misma. En particular, se han descrito complicaciones neurológicas tras infecciones generadas por agentes patógenos que contienen en su estructura neuraminidasa (NA), como es el caso del virus de la gripe. Esta enzima actúa eliminando residuos de ácido siálico terminal de cadenas glucídicas complejas, que frecuentemente presentan glucoproteínas y glucolípidos. La administración intracerebroventricular de NA en animales de laboratorio genera un proceso inflamatorio estéril, que se caracteriza por el reclutamiento de células inmunes periféricas, la activación de la microglía y los astrocitos, y una pérdida parcial del epitelio ependimario. Sin embargo, no se conoce el mecanismo mediante el cual la NA desencadena estos procesos, ni la importancia de la microglía en el desarrollo de los mismos. Los resultados obtenidos en esta tesis han mostrado que la microglía desempeña un papel fundamental en la inflamación inducida por NA. En particular, la NA activa a la microglía a través del receptor Toll-like receptor 4 (TLR4), que es esencial en el inicio de la respuesta inflamatoria generada mediante NA, mientras que el receptor TLR2 también participa pero en menor medida. Por otra parte, también se ha evidenciado que la microglía activada por NA participa en la muerte de los ependimocitos, contribuyendo así a la pérdida del epitelio ependimario. Además, se ha comprobado que en la neuroinflamación inducida por NA la microglía residente desempeña un papel fundamental en comparación con el de los monocitos circulantes infiltrados, los cuales incrementan aún más la virulencia del proceso inflamatorio

Correlation between IL1β expression level and morphological parameters proves the usefulness of morphology measures to predict the degree of activation of microglial cells

It is well known that microglial cells undergo an important change in morphology upon activation, so that form and function are intimately related. Upon activation, microglia cell body enlarges, its ramifications shortens and become thicker. In parallel, a variety of cytokines and inflammatory mediators such as IL1β are released. However the activation process is not all-or-nothing. Rather, cells in subtle activation states or in a deactivation process can occur, so intermediate not obvious phenotypes may appear. Thus, we aimed to correlate the expression level of a well-defined marker of activation, IL1β, with different morphological parameters. To do so, we used an intracerebroventricular injection of neuraminidase to produce an acute inflammation in rats. Brain sections were double-stained with IBA1 to have an image of the whole cell and its ramifications, and with IL1β to assess the level of activation. Images were captured from septofimbria (close to the injection site) and from the hypothalamus. A ratio of IL1β-positive pixels to IBA1-positive pixels was used to estimate the level of IL1β expression for each cell. Single microglial cell images were processed with ImageJ software to obtain outlined and filled shapes, which were used to obtain (by means of FracLac plug in) the following morphological parameters: fractal dimension, lacunarity, area, density and perimeter. All parameters showed a significant correlation with the level of expression of IL1β. This occurred in cells sampled from the two brain areas studied. Density, lacunarity and perimeter resulted as the best predictor parameters of activation, that is, those with a better correlation with the level of expression of IL1β. Area, an extensively used parameter to assess microglial activation, presented the least significant correlation. Thus, objectively measured morphological parameters correlate with the level of expression of IL1β, and could therefore be used as predictors of the activation level of microglial cells.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Neuraminidase-activated microglia compromise the viability of ependymocytes

Neuraminidase (NA) is a sialidase present in the envelope/wall of some virus/bacteria responsible for brain infections, such as flu, mumps or meningitis. The intracerebroventricular injection of NA in the rat brain provokes ependymal detachment and death, and an acute inflammatory process. Although inflammation reverses, ependymal lining is not regenerated. Complement system activation within the CSF contributes to ependymal damage, but is not the only cause (Granados-Duran et al, 2016). Here we aimed to investigate if microglial activation might also play a role. For this purpose we used pure isolated ependymocytes (Grondona et al, 2013) and ventricular wall explants, which were co-cultured with microglial cells, both in basal conditions and with agents that induce microglial activation: NA, LPS, or Pam3CSK4 (synthetic lipopeptide). The viability of the ependymal cells was assessed by trypan blue exclusion. The viability of isolated ependymocytes was reduced when NA or LPS were added to the culture, compared to controls without additives. In the absence of microglia, NA or LPS did not compromise viability significantly, indicating that microglia was involved in ependymocytes death. The addition of NA to cultured explants reduced ependymocytes viability only when microglial cells were present in the culture; a similar reduction was observed when LPS or Pam3CSK4 were added. Conversely, explants cultured in the absence of microglia did not suffer a significant decrease in ependymocytes viability upon NA addition to the medium. We hypothesized that cytokines released by activated microglia, such as IL1β or TNFα, could mediate ependymocytes death. RT-PCR performed in RNA obtained from pure ependymocytes confirmed the presence of IL1β and TNFα receptors in ependymal cells. Nevertheless further experiments are required to confirm this hypothesis. We conclude that microglia activated by NA mediates, at least in part, ependymal cell death, what might be relevant for neuroinflammatory diseases mediated by NA bearing virus/bacteria.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Anxiety and mild microglial activation in the amygdala two weeks after NA-induced neuroinflammation

A single injection of neuraminidase (NA) within the cerebral ventricles (ICV) triggers an acute neuroinflammation. Neurological complications or behavioral alterations have been associated to neuroinflammation. While some of these symptoms decline with time along with inflammation, the possibility of long-term sequelae should be considered. Thus, we aimed to explore if NA-induced neuroinflammation provokes behavioral or neurological disturbances at medium (2 weeks) and long (10 weeks) term. Rats were ICV injected with NA or saline. First, neurological alterations of the sensorimotor reflexes were not found, suggesting that NA does not cause disturbances in major brain functions. While the open field test revealed normal locomotor capacity in the animals injected with NA, however the evaluation of specific behaviors (rearing and rearing with support) pointed out an increased anxiety state 2 weeks after NA administration, but not at long term (10 weeks). A histological study of brain areas related to emotions (amygdala) and stress response (hypothalamic PVN) revealed no significant differences in the number of microglia or astrocytes. Nevertheless, the morphological analysis of microglial cells demonstrated that, in the amygdala of NA injected rats, microglia presented a morphology consistent with a slightly activated state. Such morphological change, which was evident 2 weeks after NA injection, was virtually reverted 10 weeks post-ICV. These results point out that NA injected ICV may cause anxiety in the medium term (while not affecting other functions like sensorimotor functions or the locomotor capacity), a behavioral alteration that is transient and that concurs with a mild inflammation, evidenced by the overexpression of certain genes and, more notably, by the morphological bias of microglial cells located in the amygdala towards an activated profile.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Sudden cessation of fluoxetine before alcohol drinking reinstatement alters microglial morphology and TLR4/inflammatory neuroadaptation in the rat brain

Preclinical studies on the efects of abrupt cessation of selective serotonin reuptake inhibitors (SSRIs), a medication often prescribed in alcohol use disorder (AUD) patients with depression, results in alcohol consumption escalation after resuming drinking. However, a potential neuroinfammatory component on this escalation remains unexplored despite the immunomodulatory role of serotonin. Here, we utilized a rat model of 14-daily administration of the SSRI fuoxetine (10 mg/kg/day) along alcohol self-administration deprivation to study the efects of fuoxetine cessation on neuroinfammation after resuming alcohol drinking. Microglial morphology and infammatory gene expression were analyzed in prelimbic cortex, striatum, basolateral amygdala and dorsal hippocampus. Results indicated that alcohol drinking reinstatement increased microglial IBA1 immunoreactivity and altered morphometric features of activated microglia (fractal dimension, lacunarity, density, roughness, and cell area, perimeter and circularity). Despite alcohol reinstatement, fuoxetine cessation modifed microglial morphology in a brain region-specifc manner, resulting in hyper-ramifed (spatial complexity of branching), reactive (lower heterogeneity and circularity)-like microglia. We also found that microglial cell area correlated with changes in mRNA expression of chemokines (Cx3cl1/fractalkine, Cxcl12/SDF1α, Ccl2/MCP1), cytokines (IL1β, IL6, IL10) and the innate immune toll-like receptor 4 (TLR4) in dorsal hippocampus. Specifcally, TLR4 correlated with microglial spatial complexity assessed by fractal dimension in striatum, suggesting a role in process branching. (...)Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Funding for open access charge: Universidad de Málaga/CBUA. RETICS Red de Trastornos Adictivos, Instituto de Salud Carlos III (ISCIII), Ministerio de Ciencia e Innovación and European Regional Development Funds-European Union (ERDF-EU) (Grant No. RD16/0017/0001); ISCIII, ERDF-EU (Grant No. PI17/02026, Grant No. PI19/01577); Ministerio de Sanidad, Delegación de Gobierno para el Plan Nacional sobre Drogas (Grant No. PND 2020/048, Grant No. PND 2019/040, Grant No. PND 2018/044, Grant No. PND 2018/033); and Consejería de Salud y Familia, Junta de Andalucía (Neuro-RECA, Grant No. RIC-0111–2019). JS (Grant No. CPII17/00024), FJP (Grant No. CPII19/00022) and AS (Grant No. CPII19/00031) hold “Miguel Servet II” research contracts from the National System of Health, ISCIII, ERDF-EU. FJP also holds a “Nicolas Monardes” contract from Servicio Andaluz de Salud, Consejería de Salud y Familia, Junta de Andalucía (Grant No. C1-0049–2019). PR (Grant No. CP19/00068) hold “Miguel Servet I” research contracts from the National System of Health, ISCIII, ERDF-EU. The funding sources had no further role in study design; in the collection, analysis and interpretation of data; in writing of the report; and in the decision to submit the paper for publication

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical science. © The Author(s) 2019. Published by Oxford University Press