Reactive Phenotype Research Articles

Pharmacological inhibition of astrocytic transglutaminase 2 facilitates the expression of a neurosupportive astrocyte reactive phenotype in association with increased histone acetylation.

Astrocytes play critical roles in supporting structural and metabolic homeostasis in the central nervous system (CNS). CNS injury leads to the development of a range of reactive phenotypes in astrocytes whose molecular determinants are poorly understood. Finding ways to modulate astrocytic injury responses and leverage a pro-recovery phenotype holds promise in treating CNS injury. Recently, it has been demonstrated that ablation of astrocytic transglutaminase 2 (TG2) modulates the phenotype of reactive astrocytes in a way that improves neuronal injury outcomes both in vitro and in vivo. In an in vivo mouse model, pharmacological inhibition of TG2 with the irreversible inhibitor VA4 phenocopies the neurosupportive effects of TG2 deletion in astrocytes. In this study, we provide insights into the mechanisms by which TG2 deletion or inhibition result in a more neurosupportive astrocytic phenotype. Using a neuron-astrocyte co-culture model, we show that VA4 treatment improves the ability of astrocytes to support neurite outgrowth on an injury-relevant matrix. To better understand how pharmacologically altering TG2 affects its ability to regulate reactive astrocyte phenotypes, we assessed how VA4 inhibition impacts TG2s interaction with Zbtb7a, a transcription factor we have previously identified as a functionally relevant TG2 nuclear interactor. The results of these studies demonstrate that VA4 significantly decreases the interaction of TG2 and Zbtb7a. TG2s interactions with Zbtb7a, as well as a wide range of other transcription factors and chromatin regulatory proteins, suggest that TG2 may act as an epigenetic regulator to modulate gene expression. To begin to understand if TG2-mediated epigenetic modification may impact astrocytic phenotypes in our models, we interrogated the effect of TG2 deletion and VA4 treatment on histone acetylation and found significantly greater acetylation in both experimental groups. Consistent with these findings, previous RNA-sequencing and our present proteomic analysis also supported a predominant transcriptionally suppressive role of TG2 in astrocytes. Our proteomic data additionally unveiled pronounced changes in lipid and antioxidant metabolism in astrocytes with TG2 deletion or inhibition, which likely contribute to the enhanced neurosupportive function of these astrocytes.

TLR4-mediated chronic neuroinflammation has no effect on tangle pathology in a tauopathy mouse model.

Alzheimer's disease (AD) is marked by the accumulation of fibrillary aggregates composed of pathological tau protein. Although neuroinflammation is frequently observed in conjunction with tau pathology, current preclinical evidence does not sufficiently establish a direct causal role in tau tangle formation. This study aimed to evaluate whether chronic Toll-like receptor 4 (TLR4) stimulation, induced by a high dose of lipopolysaccharide (LPS, 5 mg/kg), exacerbates neurofibrillary tangle (NFT) pathology in a transgenic mouse model of tauopathy that expresses human truncated 151-391/3R tau, an early feature of sporadic AD. We utilized a transgenic mouse model of tauopathy subjected to chronic TLR4 stimulation via weekly intraperitoneal injections of LPS over nine consecutive weeks. Neurofibrillary tangle formation, microglial activation, and tau hyperphosphorylation in the brainstem and hippocampus were assessed through immunohistochemistry, immunofluorescence, and detailed morphometric analysis of microglia. Chronic LPS treatment led to a significant increase in the number of Iba-1+ microglia in the LPS-treated group compared to the sham group (p < 0.0001). Notably, there was a 1.5- to 1.7-fold increase in microglia per tangle-bearing neuron in the LPS-treated group. These microglia exhibited a reactive yet exhausted phenotype, characterized by a significant reduction in cell area (p < 0.0001) without significant changes in other morphometric parameters, such as perimeter, circumference, solidity, aspect ratio, or arborization degree. Despite extensive microglial activation, there was no observed reduction in tau hyperphosphorylation or a decrease in tangle formation in the brainstem, where pathology predominantly develops in this model. These findings suggest that chronic TLR4 stimulation in tau-transgenic mice results in significant microglial activation but does not influence tau tangle formation. This underscores the complexity of the relationship between neuroinflammation and tau pathology, indicating that additional mechanisms may be required for neuroinflammation to directly contribute to tau tangle formation.

Astrocytic DLL4-NOTCH1 signaling pathway promotes neuroinflammation via the IL-6-STAT3 axis

Under neuroinflammatory conditions, astrocytes acquire a reactive phenotype that drives acute inflammatory injury as well as chronic neurodegeneration. We hypothesized that astrocytic Delta-like 4 (DLL4) may interact with its receptor NOTCH1 on neighboring astrocytes to regulate astrocyte reactivity via downstream juxtacrine signaling pathways. Here we investigated the role of astrocytic DLL4 on neurovascular unit homeostasis under neuroinflammatory conditions. We probed for downstream effectors of the DLL4-NOTCH1 axis and targeted these for therapy in two models of CNS inflammatory disease. We first demonstrated that astrocytic DLL4 is upregulated during neuroinflammation, both in mice and humans, driving astrocyte reactivity and subsequent blood-brain barrier permeability and inflammatory infiltration. We then showed that the DLL4-mediated NOTCH1 signaling in astrocytes directly drives IL-6 levels, induces STAT3 phosphorylation promoting upregulation of astrocyte reactivity markers, pro-permeability factor secretion and consequent blood-brain barrier destabilization. Finally we revealed that blocking DLL4 with antibodies improves experimental autoimmune encephalomyelitis symptoms in mice, identifying a potential novel therapeutic strategy for CNS autoimmune demyelinating disease. As a general conclusion, this study demonstrates that DLL4-NOTCH1 signaling is not only a key pathway in vascular development and angiogenesis, but also in the control of astrocyte reactivity during neuroinflammation.

Reactive astrocytes generated from human iPSC are pro-inflammatory and display altered metabolism

Astrocytes are the most abundant type of glial cell in the central nervous system and they play pivotal roles in both normal health and disease. Their dysfunction is detrimental to many brain related pathologies. Under pathological conditions, such as Alzheimer's disease, astrocytes adopt an activated reactive phenotype which can contribute to disease progression. A prominent risk factor for many neurodegenerative diseases is neuroinflammation which is the purview of glial cells, such as astrocytes and microglia. Human in vitro models have the potential to reveal relevant disease specific mechanisms, through the study of individual cell types such as astrocytes or the addition of specific factors, such as those secreted by microglia. The aim of this study was to generate human cortical astrocytes, in order to assess their protein and gene expression, examine their reactivity profile in response to exposure to the microglial secreted factors IL-1α, TNFα and C1q and assess their functionality in terms of calcium signalling and metabolism. The successfully differentiated and stimulated reactive astrocytes display increased IL-6, RANTES and GM-CSF secretion, and increased expression of genes associated with reactivity including, IL-6, ICAM1, LCN2, C3 and SERPINA3. Functional assessment of these reactive astrocytes showed a delayed and sustained calcium response to ATP and a concomitant decrease in the expression of connexin–43. Furthermore, it was demonstrated these astrocytes had an increased glycolytic capacity with no effect on oxidative phosphorylation. These findings not only increase our understanding of astrocyte reactivity but also provides a functional platform for drug discovery.

Exploring neuroglial signaling: diversity of molecules implicated in microglia-to-astrocyte neuroimmune communication.

Effective communication between different cell types is essential for brain health, and dysregulation of this process leads to neuropathologies. Brain glial cells, including microglia and astrocytes, orchestrate immune defense and neuroimmune responses under pathological conditions during which interglial communication is indispensable. Our appreciation of the complexity of these processes is rapidly increasing due to recent advances in molecular biology techniques, which have identified numerous phenotypic states of both microglia and astrocytes. This review focuses on microglia-to-astrocyte communication facilitated by secreted neuroimmune modulators. The combinations of interleukin (IL)-1α, tumor necrosis factor (TNF), plus complement component C1q as well as IL-1β plus TNF are already well-established microglia-derived stimuli that induce reactive phenotypes in astrocytes. However, given the large number of inflammatory mediators secreted by microglia and the rapidly increasing number of distinct functional states recognized in astrocytes, it can be hypothesized that many more intercellular signaling molecules exist. This review identifies the following group of cytokines and gliotransmitters that, while not established as interglial mediators yet, are known to be released by microglia and elicit functional responses in astrocytes: IL-10, IL-12, IL-18, transforming growth factor (TGF)-β, interferon (IFN)-γ, C-C motif chemokine ligand (CCL)5, adenosine triphosphate (ATP), l-glutamate, and prostaglandin E2 (PGE2). The review of molecular mechanisms engaged by these mediators reveals complex, partially overlapping signaling pathways implicated in numerous neuropathologies. Additionally, lack of human-specific studies is identified as a significant knowledge gap. Further research on microglia-to-astrocyte communication is warranted, as it could discover novel interglial signaling-targeted therapies for diverse neurological disorders.

MTOR activation induces endolysosomal remodeling and nonclassical secretion of IL-32 via exosomes in inflammatory reactive astrocytes

Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo–IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states and was upregulated in astrocytes in multiple sclerosis lesions. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.

IBS stress reactivity phenotype is associated with blood transcriptome profiles and microstructural and functional brain changes.

Clinical evidence suggests significant interindividual differences in stress reactivity (SR), but biological mechanisms and therapeutic implications of these differences are poorly understood. We aimed to identify the biological basis of increased SR by investigating associations between a psychometric-based phenotype with blood transcriptomics profiles of increased sympathetic nervous system (SNS) activation and brain imaging phenotypes in irritable bowel syndrome (IBS) participants and healthy controls (HCs). A cross-sectional observational study design, transcriptomics profiling, multimodal brain imaging, and psychosocial assessments were obtained in 291 female and male IBS participants and HCs. Prior to analyses, unsupervised clustering was applied to derive high and low SR subgroups across participants based on two measures of SR. General linear models tested for SR group differences in clinical and biological parameters. Exploratory analyses examined associations between SR group-specific brain alterations and gene expression. The high, compared to low SR group showed greater cyclic AMP response element-binding protein (CREB) gene expression consistent with tonic SNS activity and proinflammatory changes in whole blood. Brain imaging showed neuroplastic changes in the high SR group consistent with an upregulation of ascending arousal systems and sensory processing and integration regions, and functional connectivity changes in the central autonomic network. SR moderated the sex difference in extraintestinal symptoms. The findings support a model of tonically increased SNS activity as a plausible risk factor for increased autonomic reactivity to psychosocial stressors and low grade immune activation in both IBS and HCs, with a greater prevalence in IBS. These findings may have important implications for personalized treatment interventions in IBS.

Early nuclear phenotypes and reactive transformation in human iPSC-derived astrocytes from ALS patients with SOD1 mutations.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive death of motor neurons (MNs). Glial cells play roles in MN degeneration in ALS. More specifically, astrocytes with mutations in the ALS-associated gene Cu/Zn superoxide dismutase 1 (SOD1) promote MN death. The mechanisms by which SOD1-mutated astrocytes reduce MN survival are incompletely understood. To characterize the impact of SOD1 mutations on astrocyte physiology, we generated astrocytes from human induced pluripotent stem cell (iPSC) derived from ALS patients carrying SOD1 mutations, together with control isogenic iPSCs. We report that astrocytes harboring SOD1(A4V) and SOD1(D90A) mutations exhibit molecular and morphological changes indicative of reactive astrogliosis when compared to isogenic astrocytes. We show further that a number of nuclear phenotypes precede, or coincide with, reactive transformation. These include increased nuclear oxidative stress and DNA damage, and accumulation of the SOD1 protein in the nucleus. These findings reveal early cell-autonomous phenotypes in SOD1-mutated astrocytes that may contribute to the acquisition of a reactive phenotype involved in alterations of astrocyte-MN communication in ALS.

Induction of astrocyte reactivity promotes neurodegeneration in human pluripotent stem cell models

Reactive astrocytes are known to exert detrimental effects upon neurons in several neurodegenerative diseases, yet our understanding of how astrocytes promote neurotoxicity remains incomplete, especially in human systems. In this study, we leveraged human pluripotent stem cell (hPSC) models to examine how reactivity alters astrocyte function and mediates neurodegeneration. hPSC-derived astrocytes were induced to a reactive phenotype, at which point they exhibited a hypertrophic profile and increased complement C3 expression. Functionally, reactive astrocytes displayed decreased intracellular calcium, elevated phagocytic capacity, and decreased contribution to the blood-brain barrier. Subsequently, co-culture of reactive astrocytes with a variety of neuronal cell types promoted morphological and functional alterations. Furthermore, when reactivity was induced in astrocytes from patient-specific hPSCs (glaucoma, Alzheimer's disease, and amyotrophic lateral sclerosis), the reactive state exacerbated astrocytic disease-associated phenotypes. These results demonstrate how reactive astrocytes modulate neurodegeneration, significantly contributing to our understanding of a role for reactive astrocytes in neurodegenerative diseases.

Delayed administration of interleukin-4 coacervate alleviates the neurotoxic phenotype of astrocytes and promotes functional recovery after a contusion spinal cord injury

Objective. Macrophages and astrocytes play a crucial role in the aftermath of a traumatic spinal cord injury (SCI). Infiltrating macrophages adopt a pro-inflammatory phenotype while resident astrocytes adopt a neurotoxic phenotype at the injury site, both of which contribute to neuronal death and inhibit axonal regeneration. The cytokine interleukin-4 (IL-4) has shown significant promise in preclinical models of SCI by alleviating the macrophage-mediated inflammation and promoting functional recovery. However, its effect on neurotoxic reactive astrocytes remains to be elucidated, which we explored in this study. We also studied the beneficial effects of a sustained release of IL-4 from an injectable biomaterial compared to bolus administration of IL-4.Approach. We fabricated a heparin-based coacervate capable of anchoring and releasing bioactive IL-4 and tested its efficacyin vitroandin vivo. Main results. We show that IL-4 coacervate is biocompatible and drives a robust anti-inflammatory macrophage phenotype in culture. We also show that IL-4 and IL-4 coacervate can alleviate the reactive neurotoxic phenotype of astrocytes in culture. Finally, using a murine model of contusion SCI, we show that IL-4 and IL-4 coacervate, injected intraspinally 2 d post-injury, can reduce macrophage-mediated inflammation, and alleviate neurotoxic astrocyte phenotype, acutely and chronically, while also promoting neuroprotection with significant improvements in hindlimb locomotor recovery. We observed that IL-4 coacervate can promote a more robust regenerative macrophage phenotypein vitro, as well as match its efficacyin vivo,compared to bolus IL-4.Significance. Our work shows the promise of coacervate as a great choice for local and prolonged delivery of cytokines like IL-4. We support this by showing that the coacervate can release bioactive IL-4, which acts on macrophages and astrocytes to promote a pro-regenerative environment following a SCI leading to robust neuroprotective and functional outcomes.

PEDF-34 attenuates neurological deficit and suppresses astrocyte-dependent neuroinflammation by modulating astrocyte polarization via 67LR/JNK/STAT1 signaling pathway after subarachnoid hemorrhage in rats

BackgroundReactive astrocytes participate in various pathophysiology after subarachnoid hemorrhage (SAH), including neuroinflammation, glymphatic–lymphatic system dysfunction, brain edema, BBB disruption, and cell death. Astrocytes transform into two new reactive phenotypes with changed morphology, altered gene expression, and secretion profiles, termed detrimental A1 and beneficial A2. This study investigates the effect of 67LR activation by PEDF-34, a PEDF peptide, on neuroinflammation and astrocyte polarization after the experimental SAH.MethodsA total of 318 male adult Sprague-Dawley rats were used in experiments in vivo, of which 272 rats were subjected to the endovascular perforation model of SAH and 46 rats underwent sham surgery. 67LR agonist (PEDF-34) was administrated intranasally 1 h after SAH. 67LR-specific inhibitor (NSC-47924) and STAT1 transcriptional activator (2-NP) were injected intracerebroventricularly 48 h before SAH. Short- and long-term neurological tests, brain water content, immunostaining, Nissl staining, western blot, and ELISA assay were performed. In experiments in vitro, primary astrocyte culture with hemoglobin (Hb) stimulation was used to mimic SAH. The expression of the PEDF-34/67LR signaling pathway and neuro-inflammatory cytokines were assessed using Western blot, ELISA, and immunohistochemistry assays both in vivo and in vitro.ResultsEndogenous PEDF and 67LR expressions were significantly reduced at 6 h after SAH. 67LR was expressed in astrocytes and neurons. Intranasal administration of PEDF-34 significantly reduced brain water content, pro-inflammatory cytokines, and short-term and long-term neurological deficits after SAH. The ratio of p-JNK/JNK and p-STAT1/STAT1 and the expression of CFB and C3 (A1 astrocytes marker), significantly decreased after PEDF-34 treatment, along with fewer expression of TNF-α and IL-1β at 24 h after SAH. However, 2-NP (STAT1 transcriptional activator) and NSC-47924 (67LR inhibitor) reversed the protective effects of PEDF-34 in vivo and in vitro by promoting A1 astrocyte polarization with increased inflammatory cytokines.ConclusionPEDF-34 activated 67LR, attenuating neuroinflammation and inhibiting astrocyte A1 polarization partly via the JNK/STAT1 pathway, suggesting that PEDF-34 might be a potential treatment for SAH patients.Graphical

HB-EGF activates EGFR to induce reactive neural stem cells in the mouse hippocampus after seizures.

Hippocampal seizures mimicking mesial temporal lobe epilepsy cause a profound disruption of the adult neurogenic niche in mice. Seizures provoke neural stem cells to switch to a reactive phenotype (reactive neural stem cells, React-NSCs) characterized by multibranched hypertrophic morphology, massive activation to enter mitosis, symmetric division, and final differentiation into reactive astrocytes. As a result, neurogenesis is chronically impaired. Here, using a mouse model of mesial temporal lobe epilepsy, we show that the epidermal growth factor receptor (EGFR) signaling pathway is key for the induction of React-NSCs and that its inhibition exerts a beneficial effect on the neurogenic niche. We show that during the initial days after the induction of seizures by a single intrahippocampal injection of kainic acid, a strong release of zinc and heparin-binding epidermal growth factor, both activators of the EGFR signaling pathway in neural stem cells, is produced. Administration of the EGFR inhibitor gefitinib, a chemotherapeutic in clinical phase IV, prevents the induction of React-NSCs and preserves neurogenesis.

Activity-induced reactivity of astrocytes impairs cognition.

Glial cells such as astrocytes can modulate neuronal signaling. Astrocytes can also acquire a reactive phenotype that correlates with cognitive impairments in brain diseases. A study in PLOS Biology shows that prolonged activation of astrocytes can trigger both cognitive impairments and a reactive astrocyte phenotype.

Delivery of TGFβ3 from Magnetically Responsive Coaxial Fibers Reduces Spinal Cord Astrocyte Reactivity In Vitro.

A spinal cord injury (SCI) compresses the spinal cord, killing neurons and glia at the injury site and resulting in prolonged inflammation and scarring that prevents regeneration. Astrocytes, the main glia in the spinal cord, become reactive following SCI and contribute to adverse outcomes. The anti-inflammatory cytokine transforming growth factor beta 3 (TGFβ3) has been shown to mitigate astrocyte reactivity; however, the effects of prolonged TGFβ3 exposure on reactive astrocyte phenotype have not yet been explored. This study investigates whether magnetic core-shell electrospun fibers can be used to alter the release rate of TGFβ3 using externally applied magnetic fields, with the eventual application of tailored drug delivery based on SCI severity. Magnetic core-shell fibers are fabricated by incorporating superparamagnetic iron oxide nanoparticles (SPIONs) into the shell and TGFβ3 into the core solution for coaxial electrospinning. Magnetic field stimulation increased the release rate of TGFβ3 from the fibers by 25% over 7 days and released TGFβ3 reduced gene expression of key astrocyte reactivity markers by at least twofold. This is the first study to magnetically deliver bioactive proteins from magnetic fibers and to assess the effect of sustained release of TGFβ3 on reactive astrocyte phenotype.

Mapping the landscape of histomorphological cancer phenotypes using self-supervised learning on unannotated pathology slides

Cancer diagnosis and management depend upon the extraction of complex information from microscopy images by pathologists, which requires time-consuming expert interpretation prone to human bias. Supervised deep learning approaches have proven powerful, but are inherently limited by the cost and quality of annotations used for training. Therefore, we present Histomorphological Phenotype Learning, a self-supervised methodology requiring no labels and operating via the automatic discovery of discriminatory features in image tiles. Tiles are grouped into morphologically similar clusters which constitute an atlas of histomorphological phenotypes (HP-Atlas), revealing trajectories from benign to malignant tissue via inflammatory and reactive phenotypes. These clusters have distinct features which can be identified using orthogonal methods, linking histologic, molecular and clinical phenotypes. Applied to lung cancer, we show that they align closely with patient survival, with histopathologically recognised tumor types and growth patterns, and with transcriptomic measures of immunophenotype. These properties are maintained in a multi-cancer study.

The Use of Guanfacine to Mediate Anxiety-related Reactivity and Reduce Associated Agonistic Behavior in Two Pigtail Macaques (Macaca nemestrina).

Guanfacine, an α ₂adrenoceptor agonist, has been used to successfully treat self-injurious behavior in nonhuman primates, including macaques (Macaca mulatta) and baboons (Papio anubis). It does so by facilitating a correction to the dopaminergic system that mediates a reduction in impulsivity and reactivity. Given this, we assessed the potential efficacy of guanfacine to treat socially directed agonistic behavior in primates with an apparent reactive behavioral phenotype. We present data from 2 pigtail macaques (Macaca nemestrina): an intact adult male housed in a breeding group, and an experimentally naive adult female living in a research setting with her social partner. Baseline behavioral assessments suggested that both macaques showed extreme responses to external stressors that triggered them to aggress social partners often leading to wounding that required veterinary intervention. Both animals were tracked during the course of 1 y. Once treated regularly with guanfacine, both animals showed significant reduction in their agonistic behavior and the rate at which they wounded other animals. Indeed, in the year since the female has been treated with guanfacine she has never wounded her cagemate. By collecting regular and detailed behavioral observations on the male in the breeding colony, we were able to identify triggers for his aggression and to track the behavioral changes evidenced after guanfacine treatment. These data supported our hypothesis that his aggression reflected extreme reactivity to external stressors, rather than general anxiety. Importantly, we saw only a limited and short-lived reduction in the male's affiliative behavioral rates, and thus guanfacine had no sedative effect, but did successfully reduce his reactivity and resultant agonism and wounding.

Montelukast improves disease outcome in SOD1G93A female mice by counteracting oligodendrocyte dysfunction and aberrant glial reactivity.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron (MN) loss and consequent muscle atrophy, for which no effective therapies are available. Recent findings reveal that disease progression is fuelled by early aberrant neuroinflammation and the loss of oligodendrocytes with neuroprotective and remyelinating properties. On this basis, pharmacological interventions capable of restoring a pro-regenerative local milieu and re-establish proper oligodendrocyte functions may be beneficial. Here, we evaluated the in vivo therapeutic effects of montelukast (MTK), an antagonist of the oligodendroglial G protein-coupled receptor 17 (GPR17) and of cysteinyl-leukotriene receptor 1 (CysLT1R) receptors on microglia and astrocytes, in the SOD1G93A ALS mouse model. We chronically treated SOD1G93A mice with MTK, starting from the early symptomatic disease stage. Disease progression was assessed by behavioural and immunohistochemical approaches. Oral MTK treatment significantly extended survival probability, delayed body weight loss and ameliorated motor functionalityonly in female SOD1G93A mice. Noteworthy, MTK significantly restored oligodendrocyte maturation and induced significant changes in the reactive phenotype and morphological features of microglia/macrophages and astrocytes in the spinal cord of female SOD1G93A mice, suggesting enhanced pro-regenerative functions. Importantly, concomitant MN preservation has been detected after MTK administration. No beneficial effects were observed in male mice, highlighting a sex-based difference in the protective activity of MTK. Our results provide the first preclinical evidence indicating that repurposing of MTK, a safe and marketed anti-asthmatic drug, may be a promising sex-specific strategy for personalized ALS treatment.

Systemic LPS Administration Stimulates the Activation of Non-Neuronal Cells in an Experimental Model of Spinal Muscular Atrophy.

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by deficiency of the survival motor neuron (SMN) protein. Although SMA is a genetic disease, environmental factors contribute to disease progression. Common pathogen components such as lipopolysaccharides (LPS) are considered significant contributors to inflammation and have been associated with muscle atrophy, which is considered a hallmark of SMA. In this study, we used the SMNΔ7 experimental mouse model of SMA to scrutinize the effect of systemic LPS administration, a strong pro-inflammatory stimulus, on disease outcome. Systemic LPS administration promoted a reduction in SMN expression levels in CNS, peripheral lymphoid organs, and skeletal muscles. Moreover, peripheral tissues were more vulnerable to LPS-induced damage compared to CNS tissues. Furthermore, systemic LPS administration resulted in a profound increase in microglia and astrocytes with reactive phenotypes in the CNS of SMNΔ7 mice. In conclusion, we hereby show for the first time that systemic LPS administration, although it may not precipitate alterations in terms of deficits of motor functions in a mouse model of SMA, it may, however, lead to a reduction in the SMN protein expression levels in the skeletal muscles and the CNS, thus promoting synapse damage and glial cells' reactive phenotype.

Pharmacological activation of LANCL2 provides immunometabolic support for the restoration of cognitive function markers in a mouse model of Alzheimer’s disease

Abstract LANCL2 is a member of a three-protein family of receptors that acts as the mammalian receptor for abscisic acid (ABA). LANCL2 expression is significantly diminished both with the brains of 3xTg mice as well as human patients with Alzheimer’s disease. Immunologically, LANCL2 expression is closely associated with regulatory CD4+ T cells and their suppressive capacity as well as within microglia. Treatment of mice with ABA improved spatial memory and reduced amyloid beta load. To study the effects of LANCL2 activation in vivo, we created a novel agonist. After 12 weeks of daily oral treatment at 20 mg/kg, LANCL2 activation significantly reduced inflammatory immune cells including neutrophils, Th17 and Th1 cells in 3xTg mice relative to vehicle control. Further, treatment with LANCL2 agonists reduced the expression of key markers in the brain associated with impaired cognitive function to levels observed within age-matched, negative control WT mice. Activation of LANCL2 prevents the polarization of microglia into a reactive phenotype and supports the metabolic demands of amyloid beta phagocytosis. LANCL2 drugs can combat Alzheimer’s disease progression, given that reactive microglia polarization not only diminishes microglial phagocytic capacity but also increases the production of inflammatory cytokines. The LANCL2 pathway’s transformative potential merits development as a promising therapeutic mechanism for Alzheimer's disease and diverse age-related cognitive impairment.

Interaction of high-fat diet and brain trauma alters adipose tissue macrophages and brain microglia associated with exacerbated cognitive dysfunction

Obesity increases the morbidity and mortality of traumatic brain injury (TBI). Detailed analyses of transcriptomic changes in the brain and adipose tissue were performed to elucidate the interactive effects between high-fat diet-induced obesity (DIO) and TBI. Adult male mice were fed a high-fat diet (HFD) for 12 weeks prior to experimental TBI and continuing after injury. High-throughput transcriptomic analysis using Nanostring panels of the total visceral adipose tissue (VAT) and cellular components in the brain, followed by unsupervised clustering, principal component analysis, and IPA pathway analysis were used to determine shifts in gene expression patterns and molecular pathway activity. Cellular populations in the cortex and hippocampus, as well as in VAT, during the chronic phase after combined TBI-HFD showed amplification of central and peripheral microglia/macrophage responses, including superadditive changes in selected gene expression signatures and pathways. Furthermore, combined TBI and HFD caused additive dysfunction in Y-Maze, Novel Object Recognition (NOR), and Morris water maze (MWM) cognitive function tests. These novel data suggest that HFD-induced obesity and TBI can independently prime and support the development of altered states in brain microglia and VAT, including the disease-associated microglia/macrophage (DAM) phenotype observed in neurodegenerative disorders. The interaction between HFD and TBI promotes a shift toward chronic reactive microglia/macrophage transcriptomic signatures and associated pro-inflammatory disease-altered states that may, in part, underlie the exacerbation of cognitive deficits. Thus, targeting of HFD-induced reactive cellular phenotypes, including in peripheral adipose tissue immune cell populations, may serve to reduce microglial maladaptive states after TBI, attenuating post-traumatic neurodegeneration and neurological dysfunction.