Glial Reaction Research Articles

Tumor necrosis factor-α-induced protein 8-like 2 alleviates morphine antinociceptive tolerance through reduction of ROS-mediated apoptosis and MAPK/NF-κB signaling pathways

Chronic morphine tolerance is a repulsive barrier to the clinical treatment of pain. Whereas the underlying molecular mechanisms of morphine tolerance remain unknown. Here, we proposed that tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) is an essential control point regarding the progression of chronic morphine antinociceptive tolerance. We found that TIPE2 levels in the lumbar spinal cord were significantly downregulated in the morphine tolerance mouse model. Specifically, decreased TIPE2 by morphine tolerance was primarily expressed in spinal neurons, while increased expression of spinal TIPE2 distinctly attenuated the chronic morphine antinociceptive tolerance and tolerance-associated hyperalgesia. We also observed that increased expression of spinal TIPE2 significantly reduced morphine tolerance-induced neuronal ROS production and apoptosis, along with the activation of MAPKs and NF-κB signaling pathways. Moreover, the increased TIPE2 expression inhibited neuronal activation and glial reactivity in the spinal dorsal horn after chronic morphine exposure. Additionally, TIPE2 overexpression in cultured SH-SY5Y cells significantly suppressed ROS production and apoptosis in response to morphine challenge. Therefore, we can conclude that the upregulation of spinal TIPE2 may attenuate the morphine antinociceptive tolerance via TIPE2-dependent downregulation of neuronal ROS, inhibition of neuronal apoptosis, suppression of MAPKs and NF-κB activation. TIPE2 may be a potential strategy for preventing morphine tolerance in the future studies and clinical settings.

Mini-review: Enteric glial cell reactions to inflammation and potential therapeutic implications for GI diseases, motility disorders, and abdominal pain

Enteric glial cells are emerging as critical players in the regulation of intestinal motility, secretion, epithelial barrier function, and gut homeostasis in health and disease. Enteric glia react to intestinal inflammation by converting to a ‘reactive glial phenotype’ and enteric gliosis, contributing to neuroinflammation, enteric neuropathy, bowel motor dysfunction and dysmotility, diarrhea or constipation, ‘leaky gut’, and visceral pain. The focus of the minireview is on the impact of inflammation on enteric glia reactivity in response to diverse insults such as intestinal surgery, ischemia, infections (C. difficile infection, HIV-Tat-induced diarrhea, endotoxemia and paralytic ileus), GI diseases (inflammatory bowel diseases, diverticular disease, necrotizing enterocolitis, colorectal cancer) and functional GI disorders (postoperative ileus, chronic intestinal pseudo-obstruction, constipation, irritable bowel syndrome). Significant progress has been made in recent years on molecular pathogenic mechanisms of glial reactivity and enteric gliosis, resulting in enteric neuropathy, disruption of motility, diarrhea, visceral hypersensitivity and abdominal pain. There is a growing number of glial molecular targets with therapeutic implications that includes receptors for interleukin-1 (IL-1R), purines (P2X2R, A2BR), PPARα, lysophosphatidic acid (LPAR1), Toll-like receptor 4 (TLR4R), estrogen-β receptor (ERβ) adrenergic α-2 (α-2R) and endothelin B (ETBR), connexin-43 / Colony-stimulating factor 1 signaling (Cx43/CSF1) and the S100β/RAGE signaling pathway. These exciting new developments are the subject of the minireview. Some of the findings in pre-clinical models may be translatable to humans, raising the possibility of designing future clinical trials to test therapeutic application(s). Overall, research on enteric glia has resulted in significant advances in our understanding of GI pathophysiology.

Extremely Low-Frequency Electromagnetic Stimulation (ELF-EMS) Improves Neurological Outcome and Reduces Microglial Reactivity in a Rodent Model of Global Transient Stroke.

Extremely low-frequency electromagnetic stimulation (ELF-EMS) was demonstrated to be significantly beneficial in rodent models of permanent stroke. The mechanism involved enhanced cerebrovascular perfusion and endothelial cell nitric oxide production. However, the possible effect on the neuroinflammatory response and its efficacy in reperfusion stroke models remains unclear. To evaluate ELF-EMS effectiveness and possible immunomodulatory response, we studied neurological outcome, behavior, neuronal survival, and glial reactivity in a rodent model of global transient stroke treated with 13.5 mT/60 Hz. Next, we studied microglial cells migration and, in organotypic hippocampal brain slices, we assessed neuronal survival and microglia reactivity. ELF-EMS improved the neurological score and behavior in the ischemia-reperfusion model. It also improved neuronal survival and decreased glia reactivity in the hippocampus, with microglia showing the first signs of treatment effect. In vitro ELF-EMS decreased (Lipopolysaccharide) LPS and ATP-induced microglia migration in both scratch and transwell assay. Additionally, in hippocampal brain slices, reduced microglial reactivity, improved neuronal survival, and modulation of inflammation-related markers was observed. Our study is the first to show that an EMF treatment has a direct impact on microglial migration. Furthermore, ELF-EMS has beneficial effects in an ischemia/reperfusion model, which indicates that this treatment has clinical potential as a new treatment against ischemic stroke.

Inhaled molecular hydrogen reduces hippocampal neuroinflammation, glial reactivity and ameliorates memory impairment during systemic inflammation

Sepsis is associated with numerous physiological and biochemical abnormalities that result in a life-threatening condition. The involvement of the Central Nervous System (CNS) during sepsis has received considerable attention, especially the hippocampus which plays a key role in the learning and memory processes. The increased interest in this limbic region during systemic inflammation (SI) is related to the number of sepsis survivor patients who have cognitive impairments. A single injection of lipopolysaccharide (LPS)-induced systemic inflammation is the most commonly used murine endotoxemia model because it replicates several pathophysiological changes observed in severe sepsis. Molecular hydrogen (H2) has been used as an anti-inflammatory therapeutic strategy to prevent neuroinflammation. However, the mechanisms by which inhaled H2 mitigate memory loss during SI remains unknown. To understand how H2 acts in the hippocampus, the current study focused on specific mechanisms that may be involved in reducing neuroinflammation in rats during SI. We hypothesized that inhaled H2 decreases LPS-induced hippocampal pro-inflammatory cytokines surges and this effect is associated with reduced memory loss. Using different and integrative approaches, i.e., from hippocampal cells electrophysiology to animal behavior, we report that inhaled H2 decreased LPS-induced peripheral and hippocampal inflammation, decreased microglial and astrocytic activation, lessen memory loss without affecting long-term potentiation (LTP). To our knowledge, this is the first evidence showing that inhaled H2 reduces hippocampal microglial and glial cells inflammation, which may be associated with a reduced memory impairment induced by SI.

Brief Oxygen Exposure after Traumatic Brain Injury Hastens Recovery and Promotes Adaptive Chronic Endoplasmic Reticulum Stress Responses.

Traumatic brain injury (TBI) is a major public health concern, particularly in adolescents who have a higher mortality and incidence of visual pathway injury compared to adult patients. Likewise, we have found disparities between adult and adolescent TBI outcomes in rodents. Most interestingly, adolescents suffer a prolonged apneic period immediately post-injury, leading to higher mortality; therefore, we implemented a brief oxygen exposure paradigm to circumvent this increased mortality. Adolescent male mice experienced a closed-head weight-drop TBI and were then exposed to 100% O2 until normal breathing returned or recovered in room air. We followed mice for 7 and 30 days and assessed their optokinetic response; retinal ganglion cell loss; axonal degeneration; glial reactivity; and retinal ER stress protein levels. O2 reduced adolescent mortality by 40%, improved post-injury visual acuity, and reduced axonal degeneration and gliosis in optical projection regions. ER stress protein expression was altered in injured mice, and mice given O2 utilized different ER stress pathways in a time-dependent manner. Finally, O2 exposure may be mediating these ER stress responses through regulation of the redox-sensitive ER folding protein ERO1α, which has been linked to a reduction in the toxic effects of free radicals in other animal models of ER stress.

Orally Induced High Serum Level of Trimethylamine N-oxide Worsened Glial Reaction and Neuroinflammation on MPTP-Induced Acute Parkinson's Disease Model Mice.

Neuroinflammation mediated by brain glial cells is one of the pathological drivers of Parkinson's disease (PD). Recent studies have shown that higher circulating trimethylamine N-oxide (TMAO, a gut microbiota-derived metabolite) can induce neuroinflammation and are strongly related to a variety of central nervous system diseases and adverse brain events. Herein, we explored the effect of pre-existing higher circulating TMAO on dopamine system and neuroinflammation in acute PD model mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP). TMAO pretreatment was given by adding 3% (w/v) TMAO to drinking water of mice for 21days to induce higher circulating TMAO status, then mice were administered with MPTP (20mg/kg, i.p) for four times in one day to construct an acute PD model mice and treated with TMAO continuously until the end of the experiment. Results demonstrated that TMAO treatment significantly increased serum TMAO levels. Moreover, high serum TMAO significantly increased activation of microglia and astrocytes both in striatum and in substantia nigra. And strikingly, high serum TMAO significantly promoted the metabolism of striatal dopamine (DA) of PD model mice, although it had no significant effect on the number of dopaminergic neurons or the content of DA. Furthermore, immunofluorescence, ELISA, and RT-qPCR results of the hippocampus also showed that high serum TMAO significantly promoted the activation of microglia and astrocytes in the dentate gyrus, increased the levels of TNF-α and IL-1β, and upregulated gene expression of M1 microglia-related markers (including CD16, CD32, and iNOS) and A2 astrocyte-related markers (including S100a10, Ptx3, and Emp1) in mRNA levels. In summary, we found that pre-existing high serum levels of TMAO worsened the PD-related brain pathology by promoting DA metabolism, aggravating neuroinflammation and regulating glial cell polarization.

Glial cell reactivity drives cognitive decline in LDLr‐/‐ mice: experimental evidences

AbstractBackgroundFamilial hypercholesterolemia (FH) is a clinical condition characterized by increased plasma cholesterol levels, due to a mutation in the gene encoding the low‐density lipoprotein receptor (LDLr) in cells [Brown and Goldstein, 1984]. Importantly, clinical evidence indicates that FH negatively affects cognition and favors the development of neuropathologies [Ariza et al., 2016; Zambón et al, 2010], however, the mechanisms behind this relationship are still not fully understood. In this study we aimed to investigate the role of glial cell reactivity on the cognitive deficits related to the FH, as well as the possible neuroprotective effect of a pharmacological inhibitor of microglial cell activation.MethodFirstly, male 3‐months‐old and 14‐months‐old C57BL/6 wild‐type and LDLr knockout mice (LDLr‐/‐) mice brains were prepared for the evaluation of glial cell morphology by immunofluorescence. In addition, the mice’s hippocampus was removed to measure the immune content of synaptic and tight‐junctions proteins. Moreover, male and female 6‐months‐old C57BL/6 wild‐type and LDLr‐/‐ mice were treated with minocycline (50 mg/kg) or vehicle (saline) for four weeks. Afterwards, mice were submitted to behavioral tests.ResultMiddle‐aged LDLr‐/‐ mice (14‐months‐old) exhibited increased microgliosis in hippocampus, which was correlated with morphological change of microglial cells and astrocytes in this same brain region. Also, middle‐aged LDLr‐/‐ mice presented a reduction in the immune content of synaptophysin‐1 in the hippocampus. Moreover, young adult (3‐months‐old) LDLr‐/‐ mice exhibited reduced immune content of PSD95 in the hippocampus. Finally, the administration of minocycline to 6‐months‐old LDLr‐/‐ mice ameliorated the performance of hypercholesterolemic mice in hippocampal‐dependent memory tasks, without modifying their locomotor activity and metabolic parameters.ConclusionTaken together, our results demonstrated that FH alters the glial cell reactivity, which was associated with changes in synaptic proteins in the hippocampus. In addition, the pharmacological modulation of microglial cell reactivity ameliorated the hippocampal‐dependent memory in LDLr‐/‐ mice, suggesting that increased glial cell reactivity is a key event for HF‐related cognitive deficits.

Scientific and Regulatory Policy Committee Points to Consider: Sampling, Processing, Evaluation, Interpretation, and Reporting of Test Article-Related Ganglion Pathology for Nonclinical Toxicity Studies.

Certain biopharmaceutical products consistently affect dorsal root ganglia, trigeminal ganglia, and/or autonomic ganglia. Product classes targeting ganglia include antineoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, and anti-nerve growth factor agents. This article outlines "points to consider" for sample collection, processing, evaluation, interpretation, and reporting of ganglion findings; these points are consistent with published best practices for peripheral nervous system evaluation in nonclinical toxicity studies. Ganglion findings often occur as a combination of neuronal injury (e.g., degeneration, necrosis, and/or loss) and/or glial effects (e.g., increased satellite glial cell cellularity) with leukocyte accumulation (e.g., mononuclear cell infiltration or inflammation). Nerve fiber degeneration and/or glial reactions may be seen in nerves, dorsal spinal nerve roots, spinal cord, and occasionally brainstem. Interpretation of test article (TA)-associated effects may be confounded by incidental background changes or experimental procedure-related changes and limited historical control data. Reports should describe findings at these sites, any TA relationship, and the criteria used for assigning severity grades. Contextualizing adversity of ganglia findings can require a weight-of-evidence approach because morphologic changes of variable severity occur in ganglia but often are not accompanied by observable overt in-life functional alterations detectable by conventional behavioral and neurological testing techniques.

Chronic glial activation causes cholinergic cell loss in the basal forebrain during pathological aging

AbstractBackgroundNeuroinflammation, described by chronic glial reactivation lead to gradual neurodegeneration during pathological aging, contributing to disorders like Alzheimer’s disease (AD). Cholinergic cell loss in the basal forebrain (BF) including the medial septum (MS) is associated with AD; however the underlying mechanism is still unknown. Hence, this study investigated the effects of aging and chronic neuroinflammation on the MS cholinergic cell numbers and morphology.MethodAged, 12 and 24 months WT and GFAP‐IL6 mice (presenting IL‐6 overexpression under the GFAP promoter, resulting in chronic glial activation) were used. Immunohistochemistry combined with unbiased stereology and 3D morphology analysis were used to estimate the number and morphology of Iba1+ microglia and ChAT+ cholinergic cells in the MS. Transcriptomic analysis of the MS was performed using qPCR.ResultStereological estimation of MS microglia number displayed a significant 25% increase in GFAP‐IL6 mice compared to control WT (12M). A significant 30% increase was obtained for GFAP‐IL6 (24M) mice compared to control (24M). Furthermore, a significant 23% increase in microglia was described for GFAP‐IL6 (24M) compared to the GFAP‐IL6 (12M) mice. A significant 28% and 38% decrease in microglial 3D surface area, and volume respectively were observed between WT and GFAP‐IL (12M) mice, as well as 26% and 34% decrease respectively between WT (12M) and (24M), resembling reactive microglial morphology. Meanwhile, cholinergic cell number displayed a significant 31% decrease in GFAP‐IL6 (12M) mice compared to WT (12M). While a significant 30% decrease was displayed in GFAP‐IL6 (24M) mice compared to WT (24M) mice. There was a tendency for the cholinergic cell number to decrease with ageing among control and GFAP‐IL6 cohorts. Cholinergic cell morphology displayed significant 58% and 67% reduction in the 3D dendritic field surface area, and volume respectively between WT (12M) and GFAP‐IL (12M) mice, as well as 41% and 46% decrease respectively between WT (12M) and (24M), displaying patterns like neuronal degeneration.ConclusionThese findings demonstrate a significant impact of both aging and chronic glial activation alone on cholinergic cell number and morphology in the MS, resembling the cholinergic cell loss in AD, which can exacerbate throughout ageing leading to neurodegenerative impairments.

Sustained and potent analgesia with negligible side effects enabled by adaptive individualized granular stimulation in rat brainstem

Objectives. To clarify if an adaptive current stimulation protocol, in which current amplitude is modulated during continuous stimulation, provides better efficacy than constant current stimulation protocol with respect to analgesia caused by individualized stimulation in rat periaqueductal gray matter (PAG) /dorsal raphe nuclei (DRN). Approach. Ultrathin microelectrodes adapted for recording (n = 6) and stimulation (n = 16) were implanted in rat primary somatosensory cortex and PAG/DRN, respectively. In each animal included (n = 12), a subset of PAG/DRN microelectrodes (n = 1–3 per animal) was selected that on simultaneous stimulation blocked nociceptive withdrawal reflexes in awake unrestrained animals without noticeable side effects. Analgesic effects were subsequently assessed from both nociceptive withdrawal reflexes and intracortical pain-related responses on CO2 laser hind paw stimulation. The analgesic effects of adaptive current PAG/DRN stimulation comprising incremental increases of 5 μA/microelectrode (initial median current 30 μA/microelectrode) when effects declined were compared to the effects of constant current stimulation. Behavioral effects and brain state related changes were analyzed using quantitative movement analysis and electrocorticography (recorded on top of the dura mater), respectively. Tissue reactions and probe placement in PAG/DRN were assessed with immunohistochemistry. Main results. Powerful and sustained (4 h) analgesia was achieved with the adaptive current protocol within a rather wide area of PAG/DRN. Analgesic after-effects were seen for up to 30 min. Behavioral and brain state related side effects were minimal. Moreover, 6 weeks after implantation, there were no traces of bleedings, only small glial reactions and small but not statistically significant loss of neurons nearby indicating that the microelectrode stimulation employed is biocompatible. Significance. The results indicate that sustained and powerful analgesia with minimal side effects can be achieved by granular and individualized stimulation in PAG/DRN using an adaptive current stimulation protocol. This microelectrode technology and stimulation paradigm thus has the potential of providing a highly efficient and safe pain therapy.

Preclinical investigation in FAAH inhibition as a neuroprotective therapy for frontotemporal dementia using TDP-43 transgenic male mice

BackgroundFrontotemporal dementia (FTD) is a heterogeneous group of early onset and progressive neurodegenerative disorders, characterized by degeneration in the frontal and temporal lobes, which causes deterioration in cognition, personality, social behavior and language. Around 45% of the cases are characterized by the presence of aggregates of the RNA-binding protein TDP-43.MethodsIn this study, we have used a murine model of FTD that overexpresses this protein exclusively in the forebrain (under the control of the CaMKIIα promoter) for several biochemical, histological and pharmacological studies focused on the endocannabinoid system.ResultsThese mice exhibited at postnatal day 90 (PND90) important cognitive deficits, signs of emotional impairment and disinhibited social behaviour, which were, in most of cases, maintained during the first year of life of these animals. Motor activity was apparently normal, but FTD mice exhibited higher mortality. Their MRI imaging analysis and their ex-vivo histopathological evaluation proved changes compatible with atrophy (loss of specific groups of pyramidal neurons: Ctip2- and NeuN-positive cells) and inflammatory events (astroglial and microglial reactivities) in both cortical (medial prefrontal cortex) and subcortical (hippocampus) structures at PND90 and also at PND365. The analysis of the endocannabinoid system in these mice proved a decrease in the hydrolysing enzyme FAAH in the prefrontal cortex and the hippocampus, with an increase in the synthesizing enzyme NAPE-PLD only in the hippocampus, responses that were accompanied by modest elevations in anandamide and related N-acylethanolamines. The potentiation of these elevated levels of anandamide after the pharmacological inactivation of FAAH with URB597 resulted in a general improvement in behaviour, in particular in cognitive deterioration, associated with the preservation of pyramidal neurons of the medial prefrontal cortex and the CA1 layer of the hippocampus, and with the reduction of gliosis in both structures.ConclusionsOur data confirmed the potential of elevating the endocannabinoid tone as a therapy against TDP-43-induced neuropathology in FTD, limiting glial reactivity, preserving neuronal integrity and improving cognitive, emotional and social deficits.

Intrathecal administration of conditioned serum from different species resolves Chemotherapy-Induced neuropathic pain in mice via secretory exosomes

Chemotherapy-induced peripheral neuropathy (CIPN) is the most prevalent neurological complication of chemotherapy for cancer, and has limited effective treatment options. Autologous conditioned serum (ACS) is an effective biologic therapy used by intra-articular injection for patients with osteoarthritis. However, ACS has not been systematically tested in the treatment of peripheral neuropathies such as CIPN. It has been generally assumed that the analgesic effect of this biologic therapy results from augmented concentrations of anti-inflammatory cytokines and growth factors. Here we report that a single intrathecal injection of human conditioned serum (hCS) produced long-lasting inhibition of paclitaxel chemotherapy-induced neuropathic pain (mechanical allodynia) in mice, without causing motor impairment. Strikingly, the analgesic effect of hCS in our experiments was maintained even 8 weeks after the treatment, compared with non-conditioned human serum (hNCS). Furthermore, the hCS transfer-induced pain relief in mice was fully recapitulated by rat or mouse CS transfer to mice of both sexes, indicating cross-species and cross-sex effectiveness. Mechanistically, CS treatment blocked the chemotherapy-induced glial reaction in the spinal cord and improved nerve conduction. Compared to NCS, CS contained significantly higher concentrations of anti-inflammatory and pro-resolving mediators, including IL-1Ra, TIMP-1, TGF-β1, and resolvins D1/D2. Intrathecal injection of anti-TGF-β1 and anti-Il-1Ra antibody transiently reversed the analgesic action of CS. Nanoparticle tracking analysis revealed that rat conditioned serum contained a significantly greater number of exosomes than NCS. Importantly, the removal of exosomes by high-speed centrifugation largely diminished the CS-produced pain relief, suggesting a critical involvement of small vesicles (exosomes) in the beneficial effects of CS. Together, our findings demonstrate that intrathecal CS produces a remarkable resolution of neuropathic pain mediated through a combination of small vesicles/exosomes and neuroimmune/neuroglial modulation.

Evaluation of Photobiomodulation and Boldine as Alternative Treatment Options in Two Diabetic Retinopathy Models.

Diabetic retinopathy causes progressive and irreversible damage to the retina through activation of inflammatory processes, overproduction of oxidative species, and glial reactivity, leading to changes in neuronal function and finally ischemia, edema, and hemorrhages. Current treatments are invasive and mostly applied at advanced stages, stressing the need for alternatives. To this end, we tested two unconventional and potentially complementary non-invasive treatment options: Photobiomodulation, the stimulation with near-infrared light, has shown promising results in ameliorating retinal pathologies and insults in several studies but remains controversial. Boldine, on the other hand, is a potent natural antioxidant and potentially useful to prevent free radical-induced oxidative stress. To establish a baseline, we first evaluated the effects of diabetic conditions on the retina with immunofluorescence, histological, and ultrastructural analysis in two diabetes model systems, obese LepRdb/db mice and organotypic retinal explants, and then tested the potential benefits of photobiomodulation and boldine treatment in vitro on retinal explants subjected to high glucose concentrations, mimicking diabetic conditions. Our results suggest that the principal subcellular structures affected by these conditions were mitochondria in the inner segment of photoreceptors, which displayed morphological changes in both model systems. In retinal explants, lactate metabolism, assayed as an indicator of mitochondrial function, was altered, and decreased photoreceptor viability was observed, presumably as a consequence of increased oxidative-nitrosative stress. The latter was reduced by boldine treatment in vitro, while photobiomodulation improved mitochondrial metabolism but was insufficient to prevent retinal structural damage caused by high glucose. These results warrant further research into alternative and complementary treatment options for diabetic retinopathy.

Hexanucleotide repeat expansions in C9orf72 alter microglial responses and prevent a coordinated glial reaction in ALS (P1-6.002)

<h3>Objective:</h3> Neuroinflammation is an important hallmark in amyotrophic lateral sclerosis (ALS). Experimental evidence has highlighted a role of microglia in the modulation of motor neuron degeneration. However, the exact contribution of microglia to both sporadic and genetic forms of ALS is still unclear. <h3>Background:</h3> Single nuclei (sn) RNA sequencing is an interesting approach to study transcriptional changes at the cellular level in human tissues from patients with neurodegenerative disorders. For this study we included motor cortex and spinal cord samples from 5 patients with ALS caused by a C9orf72 hexanucleotide repeat expansion (HRE), from 5 patients with sporadic ALS (mutations in C9orf72, SOD1, TARDBP and FUS excluded) and from 5 control individuals. <h3>Design/Methods:</h3> We generated single nuclei profiles of spinal cord and motor cortex from sporadic and <i>C9orf72</i> ALS patients, as well as controls. We particularly focused on the transcriptomic responses of both microglia and astrocytes. <h3>Results:</h3> We confirmed that <i>C9orf72</i> is highly expressed in microglia and shows a diminished expression as a result of the HRE. This resulted in an impaired response to disease, with specific deficits in phagocytic and lysosomal transcriptional pathways. Astrocytes also displayed a dysregulated response in <i>C9orf72</i> ALS patients, remaining in a homeostatic state. This suggesting that <i>C9orf72</i> HRE alters a coordinated glial response, which ultimately would increase the risk for developing ALS. <h3>Conclusions:</h3> Our results indicate that <i>C9orf72</i> HRE results in a selective microglial loss-of-function, likely impairing microglial-astrocyte communication and preventing a global glial response. This is relevant as it indicates that sporadic and familial forms of ALS may present a different cellular substrate, which is of great importance for patient stratification and selecting treatments. <b>Disclosure:</b> Dr. Masrori has received research support from European Academy of Neurology. An immediate family member of Miss Bijnens has received personal compensation in the range of $0-$499 for serving as a Consultant for Lundbeck . The institution of Miss Bijnens has received research support from University of Antwerp . Dr. Davie has nothing to disclose. Suresh Kumar Poovathingal has nothing to disclose. Miss Storm has nothing to disclose. Nicole Hersmus has nothing to disclose. Laura Fumagalli has nothing to disclose. The institution of Ludo Van Den Bosch has received research support from FWO-Vlaanderen. The institution of Ludo Van Den Bosch has received research support from Muscular Dystrophy Association (MDA). The institution of Ludo Van Den Bosch has received research support from American ALS Association (ALSA). The institution of Ludo Van Den Bosch has received research support from Thierry Latran Foundation. The institution of Ludo Van Den Bosch has received research support from Target ALS. The institution of Ludo Van Den Bosch has received research support from ABMM. Mark Fiers has nothing to disclose. Dietmar Thal has nothing to disclose. Prof. Mancuso has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Sanofi. The institution of Dr. Van Damme has received research support from CSL Behring.

Remote damage after spinal cord injury

After spinal cord injury pathological changes in the lesion site and adjacent segments are described in detail. Data are accumulating on the tissue response in the areas of the spinal cord and even the brain distant from the epicentre of spinal cord injury. The concept of plasticity and post-traumatic responses in remote lumbar regions, which contain a specific circuits of interneurons known as the central pattern generator, is particularly important for the recovery of motor function. Among the factors influencing the plasticity of neuronal connections and regenerative potential in the area remote from the lesion epicentre, myeloid infiltration, microglial reactivity, neuroinflammation, and molecular rearrangements of the extracellular matrix are only beginning to be systematically studied. After thoracic spinal cord injury rapid responses develop in the lumbar cord that are characteristic of disintegration of the axons of the descending tracts. These shifts are accompanied by glial reactivity, synapse elimination, imbalance between excitation and inhibition, and disruption of connections in neural networks. This severity of these remote changes depends on the type and severity of the injury, which determines the different involvement and degree of destruction of the descending motor pathways. The review presents an analysis of experimental data on the responses and reorganization of the neural network in the lumbar spinal cord after injury in the proximal regions. The lesional biomarkers are of particular interest as a possible cause of pathological changes in distant areas. These molecules are released from dying cells at the epicenter of injury, appear in the cerebrospinal fluid, and acting as injury-associated molecular patterns and alarmins, can exert a neurotoxic effect in areas remote from the epicenter of injury.

Differential activation of spinal and parabrachial glial cells in a neuropathic pain model.

The clinical burden faced by chronic pain patients is compounded by affective comorbidities, such as depression and anxiety disorders. Emerging evidence suggests that reactive glial cells in the spinal cord dorsal horn play a key role in the chronification of pain, while supraspinal glia are important for psychological aspects of chronic pain. The lateral parabrachial nucleus (LPBN) in the brainstem is a key node in the ascending pain system, and is crucial for the emotional dimension of pain. Yet, whether astrocytes and microglia in the LPBN are activated during chronic pain is unknown. Here, we evaluated the occurrence of glial activation in the LPBN of male Sprague-Dawley rats 1, 4, and 7 weeks after inducing a chronic constriction injury (CCI) of the sciatic nerve, a prevalent neuropathic pain model. CCI animals developed mechanical and thermal hypersensitivity that persisted for at least 4 weeks, and was mostly reversed after 7 weeks. Using immunohistochemical staining and confocal imaging, we found that CCI caused a strong increase in the expression of the astrocytic marker GFAP and the microglial marker Iba1 in the ipsilateral spinal dorsal horn, with peak expression observed 1 week post-injury. Moreover, morphology analysis revealed changes in microglial phenotype, indicative of microglia activation. In contrast, CCI did not induce any detectable changes in either astrocytes or microglia in the LPBN, at any time point. Thus, our results indicate that while neuropathic pain induces a robust glial reaction in the spinal dorsal horn, it fails to activate glial cells in the LPBN.

Alpha Synuclein: Neurodegeneration and Inflammation.

Alpha-Synuclein (α-Syn) is one of the most important molecules involved in the pathogenesis of Parkinson's disease and related disorders, synucleinopathies, but also in several other neurodegenerative disorders with a more elusive role. This review analyzes the activities of α-Syn, in different conformational states, monomeric, oligomeric and fibrils, in relation to neuronal dysfunction. The neuronal damage induced by α-Syn in various conformers will be analyzed in relation to its capacity to spread the intracellular aggregation seeds with a prion-like mechanism. In view of the prominent role of inflammation in virtually all neurodegenerative disorders, the activity of α-Syn will also be illustrated considering its influence on glial reactivity. We and others have described the interaction between general inflammation and cerebral dysfunctional activity of α-Syn. Differences in microglia and astrocyte activation have also been observed when in vivo the presence of α-Syn oligomers has been combined with a lasting peripheral inflammatory effect. The reactivity of microglia was amplified, while astrocytes were damaged by the double stimulus, opening new perspectives for the control of inflammation in synucleinopathies. Starting from our studies in experimental models, we extended the perspective to find useful pointers to orient future research and potential therapeutic strategies in neurodegenerative disorders.

Glial Reaction in a Neuroinflammatory Model of Parkinson's Disease.

Sixty and 90 days after unilateral intranigral injection of LPS to Wistar rats (10 μg), activation of microglia, neuronal death, and formation of synuclein-positive inclusions were observed in the substantia nigra, but not in dopaminergic neurons. Astrocytes were characterized by increased expression of gliofibrillary protein GFAP, vimentin, complement protein C3, aquaporin-4, and connexin-43. At later stages, GFAP expression decreased, but the distribution of aquaporin-4 and connexin-43 remained disordered, and neuronal degeneration deteriorated. Thus, reactive changes in astrocytes after LPS administration can cause long-term disturbances of the neurogliovascular coupling. The observed functional and morphological alterations in the astroglia can be the cause of progressive disturbances in the substantia nigra.

Chronic juvenile stress exacerbates neurobehavioral dysfunction and neuroinflammation following traumatic brain injury in adult mice.

Chronic stress in adolescence may affect brain maturation and predispose individuals to psychiatric disorders in adulthood. However, whether chronic juvenile stress influences vulnerability to nonpsychiatric brain injuries, such as traumatic brain injury (TBI), remains unclear. Therefore, we hypothesized that juvenile stress-related neuronal circuit disturbances could aggravate brain damage following TBI in adulthood. For chronic stress, we used an unpredictable chronic mild stress (UCMS) procedure for 5 weeks in adolescent mice. This was followed by a controlled cortical impact (CCI) injury to evaluate the influence of chronic juvenile stress on brain damage progression following TBI in adult mice. Mice underwent UCMS alone, UCMS followed by CCI, CCI alone, or sham operation. We characterized neurobehavioral deficits (Barnes maze, open field, and light-dark tests), neuroinflammation (ionized calcium-binding adapter molecule 1 [Iba-1], glial fibrillary acidic protein [GFAP], and neuron-specific nuclear protein [NeuN] immunoreactivity), and apoptosis (B-cell lymp [Bcl-2], Bcl-2-associated X protein [Bax], and procaspase-3 immunoreactivity). Following CCI, mice exposed to UCMS showed decreased spatial learning and memory in the Barnes maze test compared with unstressed mice. A significant increase in Iba-1, GFAP, and Bax/Bcl-2 immunostaining levels was observed in the mice exposed to UCMS followed by CCI compared with the CCI-only mice. In contrast, a significant decrease in NeuN immunostaining levels was observed in the UCMS with CCI group compared with the CCI alone group. Chronic stress in a juvenile mouse model aggravates neurobehavioral impairments and potentiates glial reactivity, neuronal injury, and apoptosis following moderate-to-severe TBI that occurs in adulthood. The present study suggests that juvenile chronic stress may influence poor outcomes following TBI in later adulthood.

Social adversity during juvenile age but not adulthood increases susceptibility to an immune challenge later in life

Adverse experiences in early life can increase mental vulnerability to immune challenges experienced later in life, which may induce the development of stress-related psychopathologies. Here, we investigated whether the combined effect of both events is higher if the first adverse experience occurs when the brain is still in development. Therefore, male Wistar rats were exposed to repeated social defeat (RSD, first hit) during juvenile age or adulthood and to an immune challenge consisting of a single injection of lipopolysaccharide (LPS, second hit) in adulthood. Control animals were not exposed to RSD, but only to the LPS challenge. Translocator protein density, a marker for reactive microglia, microglia cell density and plasma corticosterone levels were measured using in vivo [11C]PBR28 positron emission tomography, iba1 immunostaining, and corticosterone ELISA, respectively. Anhedonia, social behavior and anxiety were measured with the sucrose preference, social interaction, and open field tests, respectively. Rats exposed to RSD during juvenile age exhibited enhanced anhedonia and social interaction dysfunction after an immune challenge in adulthood. This enhanced susceptibility was not observed in rats exposed to RSD during adulthood. In addition, exposure to RSD synergistically increased microglia cell density and glial reactivity to the LPS challenge. This increase in microglia cell density and reactivity to the LPS challenge was more pronounced in rats exposed to RSD during juvenile age than in adulthood. Exposure to RSD alone in juvenile age or adulthood induced similar short-term anhedonia, a long-lasting increase in plasma corticosterone and microglial activity, but no change in anxiety and social behavior. Our findings indicate that exposure to social stress during juvenile age, but not adulthood, primes the immune system and increases the sensitivity to an immune challenge experienced later in life. This suggests that juvenile social stress can have more deleterious effects in the long term than similar stress in adulthood.