Towards a navigational logic for graphical structures

One of the main advantages of the Logic of Nested Conditions, defined by Habel and Pennemann, for reasoning about graphs, is its generality: this logic can be used in the framework of many classes of graphs and graphical structures. It is enough that the category of these structures satisfies certain basic conditions. In a previous paper [14], we extended this logic to be able to deal with graph properties including paths, but this extension was only defined for the category of untyped directed graphs. In addition it seemed difficult to talk about paths abstractly, that is, independently of the given category of graphical structures. In this paper we approach this problem. In particular, given an arbitrary category of graphical structures, we assume that for every object of this category there is an associated edge relation that can be used to define a path relation. Moreover, we consider that edges have some kind of labels and paths can be specified by associating them to a set of label sequences. Then, after the presentation of that general framework, we show how it can be applied to several classes of graphs. Moreover, we present a set of sound inference rules for reasoning in the logic.Peer ReviewedPostprint (author's final draft

A logic of graph conditions extended with paths

In this paper we tackle the problem of extending the logic of nested graph conditions with paths. This means, for instance, that we may state properties about the existence of paths between some given nodes. As a main contribution, a sound and complete tableau method is defined for reasoning about this kind of properties.Peer ReviewedPostprint (published version

Microglial responses in the human Alzheimer’s disease frontal cortex

The continuing failure to develop an effective treatment for Alzheimer’s disease (AD) reveals the complexity for this pathology. Increasing evidence indicates that neuroinflammation involving particularly microglial cells contributes to AD pathogenesis. The actual view, based on the findings in APP based models, gives a cytotoxic/proinflammatory role to activated microglia. However, we have previously reported a limited activation and microglial degeneration in the hippocampus of AD patients in contrast with that observed in amyloidogenic models. Here, we evaluated the microglial response in a different region of AD brains, the frontal cortex. Post mortem tissue from controls (Braak 0-II) and AD patients (Braak V-VI) including familial cases, were obtained from Spain Neurological Tissue Banks. Cellular (immunohistochemistry and image analysis) and molecular (qPCR and western blots) approaches were performed. Frontal cortex of AD patients (Braak V-VI) showed strong microglial activation similar to that observed in amyloidogenic mice. These strongly activated microglial cells, predominantly located surrounding amyloid plaques, could drive the AD pathology and, in consequence, could be implicated in the pathology progression. Furthermore, different microglial responses were observed between sporadic and familial AD cases. These findings in the frontal cortex were highly in contrast to the attenuated activation and degenerative morphology displayed by microglial cells in the hippocampus of AD patients. Regional differences in the microglial response suggest different functional states of microglial cells in a region-specific manner. All together, these data provide a better understanding of the immunological mechanisms underlying AD progression and uncover new potential therapeutic targets to fight this devastating neurodegenerative disease.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Supported by PI18/01557 (AG) and PI18/01556 (JV) grants from ISCiii of Spain co-financed by FEDER funds from European Unio

Decoding damage-associated microglia in post mortem hippocampus of Alzheimer’s disease patients

The relationship between Alzheimer’s disease (AD) and neuroinflammation has become stronger since the identification of several genetic risk factors related to microglial function. Though the role of microglial cells in the development/progression of AD is still unknown, a dysfunctional response has recently gained support. In this sense, we have reported an attenuated microglial activation associated to amyloid plaques in the hippocampus of AD patients, including a prominent degenerative process of the microglial population in the dentate gyrus, which was in contrast to the exacerbated microglial response in amyloidogenic models. This microglial degeneration could compromise their normal role of surveying the brain environment and respond to the damage. Here, we have further analyzed the phenotypic profile displayed by the damage-associated microglial cells by immunostaining and qPCR in the hippocampus of postmortem samples of AD patients (Braak V-VI) and control cases (Braak 0-II). Damage-associated microglial cells of Braak V-VI individuals were clustered around amyloid plaques and expressed Iba1, CD68, Trem2, TMEM119 and CD45high. A subset of these cells also expressed ferritin. On the contrary, these microglia down-regulated homeostatic markers, such as Cx3cr1 and P2ry12. The homeostatic and ramified microglial cells of non-demented Braak II cases were characterized by Iba1, CX3CR1, P2ry12, TMEM119 and CD45low expression. The dynamic of the microglial molecular phenotypes associated to AD pathology needs to be considered for better understand the disease complexity and, therefore, guarantee clinical success. Correcting dysregulated brain inflammatory responses might be a promising avenue to prevent/slow cognitive decline.Universidad de Málaga. Campus de excelencia Internacional-Andalucía Tech. Supported by PI18/01557 (AG) and PI18/01556 (JV) grants from ISCiii of Spain co-financed by FEDER funds from European Union

Analyzing hippocampal synaptic damage and glial response in a mouse model of tauopathy

Tau pathology is highly related to synaptic and neuronal loss, leading to cognitive decline and dementia in Alzheimer’s disease (AD) and other tauopathies. Tau transgenic mice are widely used to investigate the specific contribution of this protein to AD since they reproduce the synaptic and cognitive dysfunction in parallel to an age-dependent accumulation of hyperphosphorylated forms of tau (phospho-tau). The aim of this study was to investigate the progression of tau aggregation and analyze its relationship with microglial activation and synaptic damage within the hippocampus of a transgenic tau model. 2, 6, 9, 12 and 18 month-old THY-Tau22 transgenic and WT mice were analyzed. Tau pathology was assessed by western blotting and immunohistochemistry (AT8, AT100). Confocal microscopy was used to study microglial/phospho-tau relationship, and Thioflavin-S staining to evidence fibrillar aggregates. Levels of general (Synaptophysin) and subtype-specific (ChAT, VGAT, VGLUT-1) synaptic proteins were determined by WB and immunohistochemistry. Inflammatory markers were assessed by quantitative PCR (CD45, CD68, TREM2), immunohistochemistry (Iba-1) and image analysis. Tau pathology was detectable in the hippocampus from 2 months of age and increased progressively during aging. Presynaptic protein levels were significantly decreased from 9-12 months compared to age-matched WT mice. Even though some inflammatory markers were slightly increased in the hippocampus, microglial reactivity was found to be generally attenuated and some cells even exhibited reduction in their prolongations and a clear degenerative phenotype at advanced ages similar to that seen in the hippocampus of AD patients. Finally, this model could be a relevant tool to further understand the specific role of tau in both microglial response and synaptic pathology in AD.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Disentangling the contribution of tau and abeta pathologies in transgenic models of Alzheimer's disease

AIMS: Amyloid-beta (Abeta) deposits and intraneuronal hyperphosphorylated tau are major pathological hallmarks of Alzheimer’s disease (AD). The coexistence of these aggregates in AD brains leads to synaptic dysfunction, neuronal loss and cognitive decline. Failures in protein homeostasis, along with defective glial responses, have been identified as pathological mechanisms linked to this disorder. Thus, our main objective is to better understand the differential impact of Abeta- and tau-aggregates to these processes in the hippocampus of AD models. METHODS: We analyzed APP- (APPSL/PS1M146L) and Tau- (ThyTau22 and hP301S) based models from 2 to 18 months of age. Tau and Abeta pathologies were assessed by western blotting and immunohistochemistry. Confocal microscopy was used to study microglia/aggregates relationship. Levels of synaptic proteins, autophagy and inflammatory markers were determined by quantitative PCR, WB and immunohistochemistry. RESULTS: Tau and Abeta pathologies initiated as early as 2 months of age and increased progressively with aging. Even though only APP/PS1 hippocampus showed dystrophic neurites positive to proteostatic and presynaptic markers, their protein levels were altered in both types of models from 6-9 months compared to age-matched WT mice. Inflammatory markers and microglial reactivity were barely increased in the hippocampus of ThyTau mice in contrast to P301S and APP/PS1 mice which displayed a prominent microglial response. CONCLUSIONS: Clarifying the effects of Abeta and tau separately would indeed enable the development of novel therapeutic strategies and drugs targeting pathways related to these proteinopathies. Supported by grants FIS PI15/00796 and PI15/00957 co-financed by FEDER funds from European Union, by Junta de Andalucia Proyecto de Excelencia CTS385 2035 and by grant PPIT.UMA.B1/2017.26Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Abeta from APP/PS1 Alzheimer mice hippocampus induced synaptic damage in vivo and in vitro

We aim to investigate the effects of Abeta from young APP/PS1 mouse model of Alzheimer`s disease (AD) on the synaptic integrity, as the loss of synapses strongly correlates with cognitive deficits in patients. Plaque-associated abnormal swellings of neuronal processes represent the first indicator of disease development and might compromise neuronal integrity and synaptic function. Here, we examined the synaptic nature of dystrophic neurites, and the reduction of both synapses and vesicles density in presynaptic terminals along with the progressive accumulation of autophagic structures and Abeta within hippocampal synaptosomes during the aging. We analysed both the direct synaptotoxic effect of plaques in the hippocampus of this model and also the repercussion of the soluble (S1) fraction in neuronal cultures. Hippocampal synapses were observed under both optic and electron microscopy. Synapses and vesicle density were quantified in periplaque and control (plaque-free) areas by electron microscopy. Primary neuronal cultures were incubated for 48 hours with 6-month-old APP/PS1 and wild-type S1 fractions. In addition, Abeta immunodepletion was carried out with different anti-Abeta antibodies and the levels of synaptic proteins were measured by Western-blot (WB). Both synapse number and synaptic-vesicles density were significantly decreased in young APP/PS1 mice, close to the Abeta deposits, in several hippocampal layers. Importantly, there was a correlation between the synaptic deficiencies and the distance to plaques, which presented oligomeric forms in their periphery. Some presynaptic elements were abnormally swollen, containing autophagic vesicles. In addition, we found by WB a decrease in several hippocampal synaptic markers as early as 4 months of age in this model, and also in neuronal cultures incubated with S1 fractions. Significantly, the neuronal reduction in VGLUT was reversed after Abeta immunodepletion. Plaque-associated oligomeric Abeta induced an early deleterious effect on synapses that correlates with memory deficits in young APP/PS1 mice. Moreover, soluble Abeta derived from these transgenic mice reduced synaptic protein content in vitro, which was restored after immunodepletion of Abeta species. Therefore, this model produced synaptotoxic Abeta and may represent a valuable tool to test novel treatments to protect synapses as an early therapeutic approach for AD.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Microtubule stabilization reduces amyloid pathology and improves synaptic/memory deficits in APP/PS1 mice

Aims: Cognitive decline in Alzheimer's disease (AD) is highly related to synaptic/neuronal loss. Tau hyperphosphorylation destabilizes microtubules leading to axonal transport failure and generation of dystrophic neurites, thus contributing to synaptic dysfunction. The effect of microtubule stabilization on amyloid-beta pathology has not been assessed in vivo yet. This study evaluated the effect of the microtubule-stabilizing agent, Epothilone D (EpoD) in the pathology of an amyloidogenic mouse model. Methods: APP751SL/PS1M146L mice (3-month-old) were treated weekly with intraperitoneal injections of EpoD (2 mg/kg) or vehicle for 3 months. For memory performance, animals were tested on the objectrecognition, Y-maze and Morris water maze. Hippocampal proteinopathies were quantified by image analysis after immunostaining. Somatostatin (SOM)-numerical density was calculated by stereology. APPswe-N2a cells were treated with EpoD 100nM for 12/24 hours. Protein levels were analysed by Western/dot-blot. Results: EpoD-treated mice improved their performance of cognitive tests, while hippocampal phospho-tau and Ab (especially oligomers) accumulation decreased, together with synaptic/neuritic pathology. Remarkably, EpoD exerted a neuroprotective effect on SOM-interneurons, a highly AD-vulnerable GABAergic subpopulation. Conclusions: EpoD improved microtubule dynamics and axonal transport in an AD-like context, reducing tau and Ab accumulation and promoting neuronal and cognitive protection, underlining the cross-talk between cytoskeleton pathology and proteinopathy. Therefore, microtubule-stabilizing drugs could be candidates for slowing AD at both tau and Ab pathologies.Supported by PI18/01557 (to AG) and PI18/01556 (to JV) grants from ISCiii of Spain, co-financed by FEDER funds (European Union), CIBERNED collaborative grant (to AG and JV), and by PPIT.UMA.B1.2017/26 grant (to RSV). Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.

Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes

Plasma lipid profiles discriminate bacterial from viral infection in febrile children

Fever is the most common reason that children present to Emergency Departments. Clinical signs and symptoms suggestive of bacterial infection are often non-specific, and there is no definitive test for the accurate diagnosis of infection. The 'omics' approaches to identifying biomarkers from the host-response to bacterial infection are promising. In this study, lipidomic analysis was carried out with plasma samples obtained from febrile children with confirmed bacterial infection (n = 20) and confirmed viral infection (n = 20). We show for the first time that bacterial and viral infection produces distinct profile in the host lipidome. Some species of glycerophosphoinositol, sphingomyelin, lysophosphatidylcholine and cholesterol sulfate were higher in the confirmed virus infected group, while some species of fatty acids, glycerophosphocholine, glycerophosphoserine, lactosylceramide and bilirubin were lower in the confirmed virus infected group when compared with confirmed bacterial infected group. A combination of three lipids achieved an area under the receiver operating characteristic (ROC) curve of 0.911 (95% CI 0.81 to 0.98). This pilot study demonstrates the potential of metabolic biomarkers to assist clinicians in distinguishing bacterial from viral infection in febrile children, to facilitate effective clinical management and to the limit inappropriate use of antibiotics