Involvement of Iba1 in membrane ruffling and phagocytosis of macrophages/microglia

Effects of social dominance and acute social stress on morphology of microglia and structural integrity of the medial prefrontal cortex

Chronic stress increases activity of the brain's innate immune system and impairs function of the medial prefrontal cortex (mPFC). However, whether acute stress triggers similar neuroimmune mechanisms is poorly understood. Across four studies, we used a Syrian hamster model to investigate whether acute stress drives changes in mPFC microglia in a time-, subregion-, and social status-dependent manner. We found that acute social defeat increased expression of ionized calcium binding adapter molecule 1 (Iba1) in the infralimbic (IL) and prelimbic (PL) and altered the morphology Iba1+ cells 1, 2, and 7 days after social defeat. We also investigated whether acute defeat induced tissue degeneration and reductions of synaptic plasticity 2 days post-defeat. We found that while social defeat increased deposition of cellular debris and reduced synaptophysin immunoreactivity in the PL and IL, treatment with minocycline protected against these cellular changes. Finally, we tested whether a reduced conditioned defeat response in dominant compared to subordinate hamsters was associated with changes in microglia reactivity in the IL and PL. We found that while subordinate hamsters and those without an established dominance relationships showed defeat-induced changes in morphology of Iba1+ cells and cellular degeneration, dominant hamsters showed resistance to these effects of social defeat. Taken together, these findings indicate that acute social defeat alters microglial morphology, increases markers of tissue degradation, and impairs structural integrity in the IL and PL, and that experience winning competitive interactions can specifically protect the IL and reduce stress vulnerability.

Diverse Efficacy of Dimethyl Fumarate in Alleviating the Late Streptozotocin-Induced Cognitive Impairment and Neuropathological Features in Rat

Our previous study showed that dimethyl fumarate (DMF) treatment performed within three weeks after intracerebroventricular (ICV) injection of streptozotocin (STZ) attenuated spatial memory impairment, hippocampal neurodegeneration, and neuroinflammation in rats. The present study is aimed at verifying the hypothesis that DMF alleviates late effects of STZ (6 months after ICV injection) which reflects advanced stage of the Alzheimer's disease (AD) in human patients. Spatial memory was assessed with Morris water maze (MWM), general brain level of amyloid β (Aβ) and p-tau was measured by western blot, immunofluorescent labelling of active microglia (IBA1), Aβ and p-tau and histological assay of neurodegeneration (Fluoro-Jade C) were performed in hippocampus and cortex. Two-week oral therapy with DMF normalized spatial memory disrupted by STZ but had no influence on general brain level of Aβ and p-tau. However, immunofluorescence showed local reduction of Aβ aggregates number in parietal cortex and p-tau+ cells in CA2 hippocampal area. Microgliosis was alleviated by DMF in CA1 area and parietal cortex. DMF-treated STZ injected rats showed higher number of Aβ containing microglia than untreated group in CA2 and frontal cortex, which may be the result of increased phagocytic activity in these areas after DMF treatment. STZ-induced neurodegeneration was alleviated by DMF in dentate gyrus and frontal cortex. In conclusion DMF treatment exerts beneficial effect on spatial memory in the rat model of late stage of AD, but weakly influences neuropathological features, as only local reduction in number of Aβ aggregates, p-tau containing cells, neurodegeneration, and microgliosis was found.

Co-localization and co-expression of Olfml3 with Iba1 in brain of mice

Olfml3 is a microglia-specific protein whose role in neuroinflammation is elusive. In silico analysis was conducted to characterize the Olfml3 protein, followed by molecular docking and MD simulation to check possible interaction with Iba1. Further, expression and co-localization analysis was performed in the LPS-induced neuroinflammatory mice brains. Results suggest that Olfml3 physically interacts with Iba1. Olfml3 and Iba1 expression increases during neuroinflammation in mice brains. Olfml3 was observed to co-localize with Iba1, and the number of Olfml3 and Iba1 dual-positive cells increased in the brain of the neuroinflammatory mice model. Thus, Olfml3 could potentially participate in microglia functions by interacting with Iba1.

Mammalian Inner Ear-Resident Immune Cells-A Scoping Review

BACKGROUND

Several studies have demonstrated the presence of resident immune cells in the healthy inner ear.

AIM

This scoping review aimed to systematize this knowledge by collecting the data on resident immune cells in the inner ear of different species under steady-state conditions.

METHODS

The databases PubMed, MEDLINE (Ovid), CINAHL (EBSCO), and LIVIVO were used to identify articles. Systematic reviews, experimental studies, and clinical data in English and German were included without time limitations.

RESULTS

The search yielded 49 eligible articles published between 1979 and 2022. Resident immune cells, including macrophages, lymphocytes, leukocytes, and mast cells, have been observed in various mammalian inner ear structures under steady-state conditions. However, the physiological function of these cells in the healthy cochlea remains unclear, providing an opportunity for basic research in inner ear biology.

CONCLUSIONS

This review highlights the need for further investigation into the role of these cells, which is crucial for advancing the development of therapeutic methods for treating inner ear disorders, potentially transforming the field of otolaryngology and immunology.

H7N7 viral infection elicits pronounced, sex-specific neuroinflammatory responses in vitro

Influenza A virus (IAV) infection can increase the risk of neuroinflammation, and subsequent neurodegenerative diseases. Certain IAV strains, such as avian H7N7 subtype, possess neurotropic properties, enabling them to directly invade the brain parenchyma and infect neurons and glia cells. Host sex significantly influences the severity of IAV infections. Studies indicate that females of the reproductive age exhibit stronger innate and adaptive immune responses to IAVs compared to males. This heightened immune response correlates with increased morbidity and mortality, and potential neuronal damage in females. Understanding the sex-specific neurotropism of IAV and associated mechanisms leading to adverse neurological outcomes is essential. Our study reveals that primary hippocampal cultures from female mice show heightened interferon-β and pro-inflammatory chemokine secretion following neurotropic IAV infection. We observed sex-specific differences in microglia activation: both sexes showed a transition into a hyper-ramified state, but only male-derived microglia exhibited an increase in amoeboid-shaped cells. These disparities extended to alterations in neuronal morphology. Neurons derived from female mice displayed increased spine density within 24 h post-infection, while no significant change was observed in male cultures. This aligns with sex-specific differences in microglial synaptic pruning. Data suggest that amoeboid-shaped microglia preferentially target postsynaptic terminals, potentially reducing neuronal hyperexcitability. Conversely, hyper-ramified microglia may focus on presynaptic terminals, potentially limiting viral spread. In conclusion, our findings underscore the utility of primary hippocampal cultures, incorporating microglia, as an effective model to study sex-specific, virus-induced effects on brain-resident cells.

Microglia undergo disease-associated transcriptional activation and CX3C motif chemokine receptor 1 expression regulates neurogenesis in the aged brain

Adult neurogenesis continues throughout life but declines dramatically with age and in neurodegenerative disorders such as Alzheimer's disease. In parallel, microglia become activated resulting in chronic inflammation in the aged brain. A unique type of microglia, suggested to support neurogenesis, exists in the subventricular zone (SVZ), but little is known how they are affected by aging. We analyzed the transcriptome of aging microglia and identified a unique neuroprotective activation profile in aged SVZ microglia, which is partly shared with disease-associated microglia (DAM). CX3C motif chemokine receptor 1 (CX3CR1) is characteristically expressed by brain microglia where it directs migration to targets for phagocytosis. We show that Cx3cr1 expression, as in DAM, is downregulated in old SVZ microglia and that heterozygous Cx3cr1 mice have increased proliferation and neuroblast number in the aged SVZ but not in the dentate gyrus, identifying CX3CR1 signaling as a novel age and brain region-specific regulator of neurogenesis.

4'-fluorocannabidiol associated with capsazepine restrains L-DOPA-induced dyskinesia in hemiparkinsonian mice: Contribution of anti-inflammatory and anti-glutamatergic mechanisms

We tested the efficacy of 4'-fluorocannabidiol (4'-F-CBD), a semisynthetic cannabidiol derivative, and HU-910, a cannabinoid receptor 2 (CB2) agonist in resolving l-DOPA-induced dyskinesia (LID). Specifically, we were interested in studying whether these compounds could restrain striatal inflammatory responses and rescue glutamatergic disturbances characteristic of the dyskinetic state. C57BL/6 mice were rendered hemiparkinsonian by unilateral striatal lesioning with 6-OHDA. Abnormal involuntary movements were then induced by repeated i.p. injections of l-DOPA + benserazide. After LID was installed, the effects of a 3-day treatment with 4'-F-CBD or HU-910 in combination or not with the TRPV1 antagonist capsazepine (CPZ) or CB2 agonists HU-308 and JWH015 were assessed. Immunostaining was conducted to investigate the impacts of 4'-F-CBD and HU-910 (with CPZ) on inflammation and glutamatergic synapses. Our results showed that the combination of 4'-F-CBD + CPZ, but not when administered alone, decreased LID. Neither HU-910 alone nor HU-910+CPZ were effective. The CB2 agonists HU-308 and JWH015 were also ineffective in decreasing LID. Both combination treatments efficiently reduced microglial and astrocyte activation in the dorsal striatum of dyskinetic mice. However, only 4'-F-CBD + CPZ normalized the density of glutamate vesicular transporter-1 (vGluT1) puncta colocalized with the postsynaptic density marker PSD95. These findings suggest that 4'-F-CBD + CPZ normalizes dysregulated cortico-striatal glutamatergic inputs, which could be involved in their anti-dyskinetic effects. Although it is not possible to rule out the involvement of anti-inflammatory mechanisms, the decrease in striatal neuroinflammation markers by 4'-F-CBD and HU-910 without an associated reduction in LID indicates that they are insufficient per se to prevent LID manifestations.

Effects of environmentally relevant concentration of short-chain chlorinated paraffins on BV2 microglia activation and lipid metabolism, implicating altered neurogenesis

Short-chain chlorinated paraffins (SCCPs), a class of persistent organic pollutants, have been found to cause diverse organ and systemic toxicity. However, little is known about their neurotoxic effects. In this study, we exposed BV2, a mouse microglia cell line, to environmentally relevant concentration of SCCPs (1 μg/L, 10 μg/L, 100 μg/L) for 24 h to investigate their impacts on the nervous system. Our observations revealed that SCCPs induced the activation of BV2 microglia, as indicated by altered morphology, stimulated cell proliferation, enhanced phagocytic and migratory capabilities. Analysis at the mRNA level confirmed the activation status, with the downregulation of TMEM119 and Tgfbr1, and upregulation of Iba1 and CD11b. The upregulated expression of genes such as cenpe, mki67, Axl, APOE and LPL also validated alterations in cell functions. Moreover, BV2 microglia presented an M2 alternative phenotype upon SCCPs exposure, substantiated by the reduction of NF-κB, TNF-α, IL-1β, and the elevation of TGF-β. Additionally, SCCPs caused lipid metabolic changes in BV2 microglia, characterized by the upregulations of long-chain fatty acids and acylcarnitines, reflecting an enhancement of β-oxidation. This aligns with our findings of increased ATP production upon SCCPs exposure. Intriguingly, cell activation coincided with elevated levels of omega-3 polyunsaturated fatty acids. Furthermore, activated microglial medium remarkably altered the proliferation and differentiation of mouse neural stem cells. Collectively, exposure to environmentally relevant concentrations of SCCPs resulted in activation and lipid metabolic alterations in BV2 microglia, potentially impacting neurogenesis. These findings provide valuable insights for further research on the neurotoxic effect of SCCPs.

In the Murine and Bovine Maternal Mammary Gland Signal Transducer and Activator of Transcription 3 is Activated in Clusters of Epithelial Cells around the Day of Birth

Signal transducers and activators of transcription (STAT) proteins regulate mammary development. Here we investigate the expression of phosphorylated STAT3 (pSTAT3) in the mouse and cow around the day of birth. We present localised colocation analysis, applicable to other mammary studies requiring identification of spatially congregated events. We demonstrate that pSTAT3-positive events are multifocally clustered in a non-random and statistically significant fashion. Arginase-1 expressing cells, consistent with macrophages, exhibit distinct clustering within the periparturient mammary gland. These findings represent a new facet of mammary STAT3 biology, and point to the presence of mammary sub-microenvironments.

Molecular Aspects Involved in the Mechanisms of Bothrops jararaca Venom-Induced Hyperalgesia: Participation of NK1 Receptor and Glial Cells

Accidents caused by Bothrops jararaca (Bj) snakes result in several local and systemic manifestations, with pain being a fundamental characteristic. The inflammatory process responsible for hyperalgesia induced by Bj venom (Bjv) has been studied; however, the specific roles played by the peripheral and central nervous systems in this phenomenon remain unclear. To clarify this, we induced hyperalgesia in rats using Bjv and collected tissues from dorsal root ganglia (DRGs) and spinal cord (SC) at 2 and 4 h post-induction. Samples were labeled for Iba-1 (macrophage and microglia), GFAP (satellite cells and astrocytes), EGR1 (neurons), and NK1 receptors. Additionally, we investigated the impact of minocycline, an inhibitor of microglia, and GR82334 antagonist on Bjv-induced hyperalgesia. Our findings reveal an increase in Iba1 in DRG at 2 h and EGR1 at 4 h. In the SC, markers for microglia, astrocytes, neurons, and NK1 receptors exhibited increased expression after 2 h, with EGR1 continuing to rise at 4 h. Minocycline and GR82334 inhibited venom-induced hyperalgesia, highlighting the crucial roles of microglia and NK1 receptors in this phenomenon. Our results suggest that the hyperalgesic effects of Bjv involve the participation of microglial and astrocytic cells, in addition to the activation of NK1 receptors.

Time-course analysis of liver and serum galectin-3 in acute liver injury after alpha-galactosylceramide injection

Galectin-3 is a beta-galactoside-binding lectin that plays important roles in diverse physiological functions, such as cell proliferation, apoptosis, and mRNA splicing. This protein is expressed on inflammatory cells and acts as a local inflammatory mediator. Recently, galectin-3 has been detected in several diseases, such as chronic liver, heart, and kidney diseases, diabetes, viral infection, autoimmune and neurodegenerative diseases, and tumors, and its role as a biomarker has attracted attention. Alpha-galactosylceramide is an artificially synthesized sphingolipid that can induce acute liver injury via the natural killer T pathway. However, the pathophysiological roles and kinetics of galectin-3 in acute liver injury are not fully understood. This study aimed to elucidate the expression and time course of galectin-3 in liver tissues during acute liver injury following alpha-galactosylceramide injection. Animals were histologically examined on days 1, 2, 4, and 7 after intraperitoneal injection of alpha-galactosylceramide, and the expressions of galectin-3 and ionized calcium-binding adaptor molecule 1 were analyzed. Notably, galectin-3 formed characteristic cluster foci, particularly on day 2 after injection. Cluster formation was not observed in chronic liver disease. Simultaneously, ionized calcium-binding adaptor molecule 1-positive cells were observed in the cluster foci. Serum galectin-3 levels increased on day 2 of treatment and correlated well with the number of galectin-3-positive cell clusters in the liver. Moreover, galectin-3 expression was an important mediator of the early phase of liver injury after alpha-galactosylceramide injection. These results suggest that serum galectin-3 may be a biomarker for the early diagnosis of acute liver injury and that clusters of galectin-3-positive cells may be a specific finding in acute liver injury.

Adjuvants influence the immune cell populations present at the injection site granuloma induced by whole-cell inactivated paratuberculosis vaccines in sheep

Vaccination is the most effective tool for paratuberculosis control. Currently, available vaccines prevent the progression of clinical disease in most animals but do not fully protect them against infection and induce the formation of an injection site granuloma. The precise mechanisms that operate in response to vaccination and granuloma development, as well as the effect that adjuvants could trigger, have not been fully investigated. Therefore, this study aimed to investigate the injection site granulomas induced by two inactivated paratuberculosis vaccines, which differ in the adjuvant employed. Two groups of 45-day-old lambs were immunized with two commercially available vaccines-one (n = 4) with Gudair® and the other (n = 4) with Silirum®. A third group (n = 4) was not vaccinated and served as control. The peripheral humoral response was assessed throughout the study by a commercial anti-Mycobacterium avium subspecies paratuberculosis (Map) antibody indirect ELISA, and the cellular immune response was assessed similarly by the IFN-γ release and comparative intradermal tests. The injection site granulomas were measured during the experiment and sampled at 75 days post-vaccination (dpv) when the animals were euthanized. The tissue damage, antigen and adjuvant distribution, and the presence and amount of immune cells were then determined and assessed by immunohistochemical methods. Antibodies against Map antigens; a general macrophage marker (Iba1), M1 (iNOS), and M2 (CD204) macrophages; T (CD3), B (CD20), and γδ T lymphocytes, proteins MHC-II and NRAMP1, and cytokines IL-4, IL-10, TNF, and IFN-γ were employed. Silirum® elicited a stronger peripheral cellular immune response than Gudair®, while the latter induced larger granulomas and more tissue damage at the site of injection. Additionally, adjuvant and Map antigen distribution throughout the granulomatous inflammatory infiltrate, as well as the NRAMP1 cell expression, which is linked to antigen phagocytosis, were highly irregular. In Silirum® induced granulomas, a higher number of MHC-II and TNF-expressing cells and a lower number of M2 macrophages suggested an improved antigen presentation, which could be due to the better antigen distribution and reduced tissue damage induced by this vaccine.

Noninvasive imaging of rat-derived microglia and its reactivity to inflammatory molecules via acoustic impedance microscopy

PURPOSE

Microglia, the brain's immune cells, play important roles in neuronal differentiation, survival, and death. The function of microglia is deeply related to the morphologies; however, it is too complex to observe conventionally and identify the condition of living microglia using optical microscopes. Herein, we proposed a new method to observe living cultured microglia and their reactivity to inflammation via the acoustic impedance mode of a scanning acoustic microscope.

METHODS

Primary cultured microglia collected from rat pups exposed to acetamiprid, an insecticide, in utero were observed with both acoustic interface impedance mode (C-mode) and transparent three-dimensional impedance mode (B-mode).

RESULTS

We characterized microglia into four types based on the results obtained from acoustic impedance, cytoskeletal information, and laser confocal imaging. Biphasic acoustic observation using B-mode and C-mode gave us information regarding the dynamic morphologies of living microglia treated with adenosine triphosphate (ATP) (600 μmol/L), which reflects distress signals from inflamed neurons. Acetamiprid exposure induced microglia response even in the neonatal period. ATP stimulus altered the shape and thickness of microglia with a change in the bulk modulus of the cell. Three-dimensional alteration with ATP stimulus could be observed only after biphasic acoustic observation using B-mode and C-mode. This acoustic observation was consistent with confocal observation using anti-Iba-1 and P2Y12 immunocytochemistry.

CONCLUSION

This study demonstrated the adequacy of using a scanning acoustic microscope in analyzing microglia's shape, motility, and response to inflammation.

Roles in Innate Immunity

Microglia are best known as the resident phagocytes of the central nervous system (CNS). As a resident brain immune cell population, microglia play key roles during the initiation, propagation, and resolution of inflammation. The discovery of resident adaptive immune cells in the CNS has unveiled a relationship between microglia and adaptive immune cells for CNS immune-surveillance during health and disease. The interaction of microglia with elements of the peripheral immune system and other CNS resident cells mediates a fine balance between neuroprotection and tissue damage. In this chapter, we highlight the innate immune properties of microglia, with a focus on how pattern recognition receptors, inflammatory signaling cascades, phagocytosis, and the interaction between microglia and adaptive immune cells regulate events that initiate an inflammatory or neuroprotective response within the CNS that modulates immune-mediated disease exacerbation or resolution.

Development and characterisation of mgTHP-1, a novel in vitro model for neural macrophages with microglial characteristics

Neuroinflammation is primarily characterised by activation of the brain's resident macrophages - the microglia. However, other central nervous system (CNS) cells also contribute to this response, including the astrocytes and endothelial cells. In addition, there is infiltration into the CNS of peripherally derived immune cells. Together these cells mediate inflammation by the production of cytokines, chemokines, reactive oxygen species, and secondary messengers, and enacting of the appropriate response to those signals. However, deciphering the specific contributions of each cell type has been challenging. Studying CNS cell biology is often challenging, as the isolation of primary cells is not always feasible, and differentiation towards microglia-like cells is complex. Here, we demonstrate a novel method whereby THP-1 monocytic cells are differentiated into neural macrophage cells with microglia-like cell characteristics. The cells, designated mgTHP-1, show typical morphological and gene expression patterns of resident CNS macrophages and functionally respond to inflammatory stimuli by producing inflammatory cytokines. Furthermore, with the addition of Vicenin-2 (an anti-inflammatory flavonoid) such responses can be reversed. This novel cell model will allow further investigations, and hence insights, into the neuroinflammatory mechanisms associated with CNS diseases.

Potential Anti-Toxoplasmosis Efficiency of Phoenix dactylifera Extracts Loaded on Selenium Nanoparticles

Background

Toxoplasmosis is a parasitic disease caused by Toxoplasma gondii that infects humans and many types of mammals and birds.

Objective

To investigate the effect of selenium nanoparticles (SeNPs) and Phoenix dactylifera (Pd) extracts loaded on SeNPs as a new agent to combat chronic T. gondii infections in murine model as an alternative method to standard Spiramycin drug therapy.

Methods

A total of 64 female mice were randomly divided into eight groups: GI: Normal control, GII: Positive control, GIII: infected and treated with Spiramycin, GIV: infected and treated with SeNPs, GV: infected and treated with aqueous extract of Pd, GVI: infected and treated with methanolic extract of Pd, GVII: infected and treated with aqueous extract of Pd loaded on SeNPs, GVIII: infected and treated with methanolic extract of Pd loaded on SeNPs. Date palm (P. dactylifera) fruits were identified and collected from the farms of Saudi Arabia. Preparation and characterization of SeNPs were done. The parasitological, histopathological examinations and biochemical changes were evaluated in all groups.

Results

Parasitological results showed significant differences in GVII in comparison to GII while GVIII showed significant differences in comparison to GII and GIII. The histopathological section of the cerebral cortex showed obvious alterations in the infected compared with untreated control groups. Aqueous and methanolic extracts of P. dactylifera loaded on SeNPs treatment showed improvement that indicated by few perivascular cuffing with few inflammatory cell infiltrations. Few granule cells with mild intracellular vacuolation and edema few deformed neurons with deep pyknotic nuclei. Microglia cells expression of Iba-1 and inflammatory cytokines (IL-4, IL-10 and INF-γ) in serum of all groups was higher in GII and lowest in GVIII followed by GVII.

Conclusion

SeNPs and P. dactylifera extracts loaded on SeNPs could be a potent agent to combat T. gondii infections.

Synaptamide modulates glial and neurotransmitter activity in the spinal cord during neuropathic pain

N-docosahexaenoylethanolamine, or synaptamide, is an endogenous metabolite of docosahexaenoic acid that is known for synaptogenic and neurogenic effects. In our previous studies we have shown that synaptamide attenuates neuropathic pain, facilitates remyelination, and reduces neuroinflammation after the chronic constriction injury (CCI) of the sciatic nerve in rats. In the current study, we show that daily synaptamide administration (4 mg/kg/day) within 14 days post-surgery: (1) decreases micro- and astroglia activity in the dorsal and ventral horns of the lumbar spinal cord; (2) modulates pro-inflammatory (IL1β, IL6) and anti-inflammatory (IL4, IL10) cytokine level in the serum and spinal cord; (3) leads to a rise in synaptamide and anandamide concentration in the spinal cord; (4) enhances IL10, CD206 and N-acylethanolamine-hydrolyzing acid amidase synthesis in macrophage cell culture following LPS-induced inflammation. Thus, the ability of synaptamide to modulate glial and cytokine activity indicates its potential for implementation in the treatment peripheral nerve injury.

Agarperoxinols A and B: Two Unprecedented Tricyclic 6/6/7 Rearranged Humulene-Type Sesquiterpenoids That Attenuated the Neuroinflammation in LPS-Stimulated Microglial Models

Agarperoxinols A and B (1-2), two naturally occurring humulene-type sesquiterpenoids with an unprecedented tricyclic 6/6/7 ring, were discovered from the agarwood of Aquilaria malaccensis. Their structures were unambiguously determined by various spectroscopic data, experimental ECD calculations, and single-crystal X-ray diffraction analysis. Agarperoxinol B showed significant and dose-dependent neuroinflammatory inhibitory effects on various proinflammatory mediators, including NO, TNF-α, IL-6, and IL-1β, and suppressed iNOS and COX-2 enzymes in LPS-activated microglial cells. A mechanistic study demonstrated that agarperoxinol B remarkably inhibited the phosphorylation of the Akt and JNK signaling pathways. Agarperoxinol B also significantly reduced the expression of the microglial markers Iba-1, COX-2, and TNF-α in the mouse cerebral cortex. Our findings introduce a bioactive compound from natural products that decreases proinflammatory factor production and has application for the treatment of neurodegenerative diseases.

Glial Cells of the Central Nervous System: A Potential Target in Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is one of the most common diseases of the male urological system while the etiology and treatment of CP/CPPS remain a thorny issue. Cumulative research suggested a potentially important role of glial cells in CP/CPPS. This narrative review retrospected literature and grasped the research process about glial cells and CP/CPPS. Three types of glial cells showed a crucial connection with general pain and psychosocial symptoms. Microglia might also be involved in lower urinary tract symptoms. Only microglia and astrocytes have been studied in the animal model of CP/CPPS. Activated microglia and reactive astrocytes were found to be involved in both pain and psychosocial symptoms of CP/CPPS. The possible mechanism might be to mediate the production of some inflammatory mediators and their interaction with neurons. Glial cells provide a new insight to understand the cause of complex symptoms of CP/CPPS and might become a novel target to develop new treatment options. However, the activation and action mechanism of glial cells in CP/CPPS needs to be further explored.

Thiamine and benfotiamine: Focus on their therapeutic potential

Thiamine, also known as vitamin B1, is an essential nutrient that plays a crucial role in energy metabolism and overall health. It is a water-soluble vitamin that plays an important role in the conversion of carbohydrates into energy in the body. Thiamine is essential for the proper functioning of the nervous system, heart and muscles. Thiamine deficiency is a life-threatening disease that leads to various disorders and lesions in the nerves and brain, at least in vertebrates. Several thiamine precursors with higher bioavailability have been developed to compensate for thiamine deficiency, including benfotiamine. Benfotiamine is more bioavailable and has higher tissue penetration than thiamine. Studies have shown its antioxidant and anti-inflammatory potential in activated immune and glial cells. It also improves complications observed in type 2 diabetes and has beneficial effects in mouse models of neurodegenerative disease. Benfotiamine represents an off-the-shelf agent used to support nerve health, promote healthy aging and support glucose metabolism. Accordingly, the present review aimed to provide an overview of the neuroprotective effects of thiamine/benfotiamine in the context of inflammation and oxidative stress.

Switching Rat Resident Macrophages from M1 to M2 Phenotype by Iba1 Silencing Has Analgesic Effects in SNL-Induced Neuropathic Pain

Resident macrophages from dorsal root ganglia are important for the development of traumatic-induced neuropathic pain. In the first 5-7 days after a traumatic sciatic nerve injury (i.e., spinal nerve ligation (SNL), spared nerve injury (SNI), sciatic nerve transection or sciatic nerve ligation and transection), Ionized binding adapter protein 1 (Iba1) (+) resident macrophages cluster around dorsal root ganglia neurons, possibly contributing to nerve injury-induced hypersensitivity. Since infiltrating macrophages gradually recruited to the lesion site peak at about 7 days, the first few days post-lesion offer a window of opportunity when the contribution of Iba1 (+) resident macrophages to neuropathic pain pathogenesis could be investigated. Iba1 is an actin cross-linking cytoskeleton protein, specifically located only in macrophages and microglia. In this study, we explored the contribution of rat Iba1 (+) macrophages in SNL-induced neuropathic pain by using intra-ganglionic injections of naked Iba1-siRNA, delivered at the time the lesion occurred. The results show that 5 days after Iba1 silencing, Iba1 (+) resident macrophages are switched from an M1 (pro-inflammatory) phenotype to an M2 (anti-inflammatory) phenotype, which was confirmed by a significant decrease of M1 markers (CD32 and CD86), a significant increase of M2 markers (CD163 and Arginase-1), a reduced secretion of pro-inflammatory cytokines (IL-6, TNF-α and IL-1β) and an increased release of pro-regenerative factors (BDNF, NGF and NT-3) which initiated the regrowth of adult DRG neurites and reduced SNL-induced neuropathic pain. Our data show for the first time, that it is possible to induce macrophages towards an anti-inflammatory phenotype by interacting with their cytoskeleton.

Effect of Oleoylethanolamide-Based Dietary Supplement on Systemic Inflammation in the Development of Alimentary-Induced Obesity in Mice

The complex effect of oleoylethanolamide-based dietary supplement (OEA-DS) was studied in a model of diet-induced obesity in mice. Physiological, biochemical, and immunohistochemical methods were used to reveal differences in the changes in the weight of experimental animals, morphological changes in the spleen tissues, and changes in the cytokine expression profile in the spleen, blood plasma, and macrophage cell culture. First, it is shown that a hypercaloric diet high in carbohydrates and cholesterol led to the development of systemic inflammation, accompanied by organ morphological changes and increased production of proinflammatory cytokines. In parallel, the use of OEA-DS reduced the intensity of cellular inflammatory reactions, accompanied by a decrease in markers of cellular inflammation and proliferation, such as CD68, Iba-1, and Ki67 in the spleen tissue, and stabilized the level of proinflammatory cytokines (IL-1β, IL-6, TNFα) both in animals and in cell culture. In addition, in the macrophage cell culture (RAW264.7), it was shown that OEA-DS also suppressed the production of reactive oxygen species and nitrites in LPS-induced inflammation. The results of this study indicate the complex action of OEA-DS in obesity, which includes a reduction of systemic inflammation.

Myelodysplastic neoplasm-associated U2AF1 mutations induce host defense defects by compromising neutrophil chemotaxis

Myelodysplastic neoplasm (MDS) is a hematopoietic stem cell disorder that may evolve into acute myeloid leukemia. Fatal infection is among the most common cause of death in MDS patients, likely due to myeloid cell cytopenia and dysfunction in these patients. Mutations in genes that encode components of the spliceosome represent the most common class of somatically acquired mutations in MDS patients. To determine the molecular underpinnings of the host defense defects in MDS patients, we investigated the MDS-associated spliceosome mutation U2AF1-S34F using a transgenic mouse model that expresses this mutant gene. We found that U2AF1-S34F causes a profound host defense defect in these mice, likely by inducing a significant neutrophil chemotaxis defect. Studies in human neutrophils suggest that this effect of U2AF1-S34F likely extends to MDS patients as well. RNA-seq analysis suggests that the expression of multiple genes that mediate cell migration are affected by this spliceosome mutation and therefore are likely drivers of this neutrophil dysfunction.

Ceftriaxone ameliorates hippocampal synapse loss by inhibiting microglial/macrophages activation in glial glutamate transporter-1 dependent manner in the APP/PS1 mouse model of Alzheimer's disease

Synapse loss is a major contributor to cognitive dysfunction in Alzheimer's disease (AD). Impairments in the expression and/or glutamate uptake activity of glia glutamate transporter-1 (GLT-1) contribute to synapse loss in AD. Hence, targeting the restoration of GLT-1 activity may have potential for alleviating synapse loss in AD. Ceftriaxone (Cef) can upregulate the expression and glutamate uptake activity of GLT-1 in many disease models, including those for AD. The present study investigated the effects of Cef on synapse loss and the role of GLT-1 using APP/PS1 transgenic and GLT-1 knockdown APP/PS1 AD mice. Furthermore, the involvement of microglia in the process was investigated due to its important role in synapse loss in AD. We found that Cef treatment significantly ameliorated synapse loss and dendritic degeneration in APP/PS1 AD mice, evidenced by an increased dendritic spine density, decreased dendritic beading density, and upregulated levels of postsynaptic density protein 95 (PSD95) and synaptophysin. The effects of Cef were suppressed by GLT-1 knockdown in GLT-1^+/-/APP/PS1 AD mice. Simultaneously, Cef treatment inhibited ionized calcium binding adapter molecule 1 (Iba1) expression, decreased the proportion of CD11b⁺CD45^hi cells, declined interleukin-6 (IL-6) content, and reduced the co-expression of Iba1 with PSD95 or synaptophysin in APP/PS1 AD mice. In conclusion, Cef treatment ameliorated synapse loss and dendritic degeneration in APP/PS1 AD mice in a GLT-1-dependent manner, and the inhibitory effect of Cef on the activation of microglia/macrophages and their phagocytosis for synaptic elements contributed to the mechanism.

Effects of Therapeutic Hypothermia on Macrophages in Mouse Cochlea Explants

Globally, over the next few decades, more than 2.5 billion people will suffer from hearing impairment, including profound hearing loss, and millions could potentially benefit from a cochlea implant. To date, several studies have focused on tissue trauma caused by cochlea implantation. The direct immune reaction in the inner ear after an implantation has not been well studied. Recently, therapeutic hypothermia has been found to positively influence the inflammatory reaction caused by electrode insertion trauma. The present study aimed to evaluate the hypothermic effect on the structure, numbers, function and reactivity of macrophages and microglial cells. Therefore, the distribution and activated forms of macrophages in the cochlea were evaluated in an electrode insertion trauma cochlea culture model in normothermic and mild hypothermic conditions. In 10-day-old mouse cochleae, artificial electrode insertion trauma was inflicted, and then they were cultured for 24 h at 37 °C and 32 °C. The influence of mild hypothermia on macrophages was evaluated using immunostaining of cryosections using antibodies against IBA1, F4/80, CD45 and CD163. A clear influence of mild hypothermia on the distribution of activated and non-activated forms of macrophages and monocytes in the inner ear was observed. Furthermore, these cells were located in the mesenchymal tissue in and around the cochlea, and the activated forms were found in and around the spiral ganglion tissue at 37 °C. Our findings suggest that mild hypothermic treatment has a beneficial effect on immune system activation after electrode insertion trauma.

Dysfunctional Autophagy, Proteostasis, and Mitochondria as a Prelude to Age-Related Macular Degeneration

Retinal pigment epithelial (RPE) cell dysfunction is a key driving force of AMD. RPE cells form a metabolic interface between photoreceptors and choriocapillaris, performing essential functions for retinal homeostasis. Through their multiple functions, RPE cells are constantly exposed to oxidative stress, which leads to the accumulation of damaged proteins, lipids, nucleic acids, and cellular organelles, including mitochondria. As miniature chemical engines of the cell, self-replicating mitochondria are heavily implicated in the aging process through a variety of mechanisms. In the eye, mitochondrial dysfunction is strongly associated with several diseases, including age-related macular degeneration (AMD), which is a leading cause of irreversible vision loss in millions of people globally. Aged mitochondria exhibit decreased rates of oxidative phosphorylation, increased reactive oxygen species (ROS) generation, and increased numbers of mitochondrial DNA mutations. Mitochondrial bioenergetics and autophagy decline during aging because of insufficient free radical scavenger systems, the impairment of DNA repair mechanisms, and reductions in mitochondrial turnover. Recent research has uncovered a much more complex role of mitochondrial function and cytosolic protein translation and proteostasis in AMD pathogenesis. The coupling of autophagy and mitochondrial apoptosis modulates the proteostasis and aging processes. This review aims to summarise and provide a perspective on (i) the current evidence of autophagy, proteostasis, and mitochondrial dysfunction in dry AMD; (ii) current in vitro and in vivo disease models relevant to assessing mitochondrial dysfunction in AMD, and their utility in drug screening; and (iii) ongoing clinical trials targeting mitochondrial dysfunction for AMD therapeutics.

Toward discovering a novel family of peptides targeting neuroinflammatory states of brain microglia and astrocytes

Microglia are immune-derived cells critical to the development and healthy function of the brain and spinal cord, yet are implicated in the active pathology of many neuropsychiatric disorders. A range of functional phenotypes associated with the healthy brain or disease states has been suggested from in vivo work and were modeled in vitro as surveying, reactive, and primed sub-types of primary rat microglia and mixed microglia/astrocytes. It was hypothesized that the biomolecular profile of these cells undergoes a phenotypical change as well, and these functional phenotypes were explored for potential novel peptide binders using a custom 7 amino acid-presenting M13 phage library (SX7) to identify unique peptides that bind differentially to these respective cell types. Surveying glia were untreated, reactive were induced with a lipopolysaccharide treatment, recovery was modeled with a potent anti-inflammatory treatment dexamethasone, and priming was determined by subsequently challenging the cells with interferon gamma. Microglial function was profiled by determining the secretion of cytokines and nitric oxide, and expression of inducible nitric oxide synthase. After incubation with the SX7 phage library, populations of SX7-positive microglia and/or astrocytes were collected using fluorescence-activated cell sorting, SX7 phage was amplified in Escherichia coli culture, and phage DNA was sequenced via next-generation sequencing. Binding validation was done with synthesized peptides via in-cell westerns. Fifty-eight unique peptides were discovered, and their potential functions were assessed using a basic local alignment search tool. Peptides potentially originated from proteins ranging in function from a variety of supportive glial roles, including synapse support and pruning, to inflammatory incitement including cytokine and interleukin activation, and potential regulation in neurodegenerative and neuropsychiatric disorders.

AIF1: Function and Connection with Inflammatory Diseases

Macrophages are a type of immune cell distributed throughout all tissues of an organism. Allograft inflammatory factor 1 (AIF1) is a calcium-binding protein linked to the activation of macrophages. AIF1 is a key intracellular signaling molecule that participates in phagocytosis, membrane ruffling and F-actin polymerization. Moreover, it has several cell type-specific functions. AIF1 plays important roles in the development of several diseases: kidney disease, rheumatoid arthritis, cancer, cardiovascular diseases, metabolic diseases and neurological disorders, and in transplants. In this review, we present a comprehensive review of the known structure, functions and role of AIF1 in inflammatory diseases.

The Flavonoid Agathisflavone Directs Brain Microglia/Macrophages to a Neuroprotective Anti-Inflammatory and Antioxidant State via Regulation of NLRP3 Inflammasome

Agathisflavone, purified from Cenostigma pyramidale (Tul.) has been shown to be neuroprotective in in vitro models of glutamate-induced excitotoxicity and inflammatory damage. However, the potential role of microglial regulation by agathisflavone in these neuroprotective effects is unclear. Here we investigated the effects of agathisflavone in microglia submitted to inflammatory stimulus in view of elucidating mechanisms of neuroprotection. Microglia isolated from cortices of newborn Wistar rats were exposed to Escherichia coli lipopolysaccharide (LPS, 1 µg/mL) and treated or not with agathisflavone (1 µM). Neuronal PC12 cells were exposed to a conditioned medium from microglia (MCM) treated or not with agathisflavone. We observed that LPS induced microglia to assume an activated inflammatory state (increased CD68, more rounded/amoeboid phenotype). However, most microglia exposed to LPS and agathisflavone, presented an anti-inflammatory profile (increased CD206 and branched-phenotype), associated with the reduction in NO, GSH mRNA for NRLP3 inflammasome, IL1-β, IL-6, IL-18, TNF, CCL5, and CCL2. Molecular docking also showed that agathisflavone bound at the NLRP3 NACTH inhibitory domain. Moreover, in PC12 cell cultures exposed to the MCM previously treated with the flavonoid most cells preserved neurites and increased expression of β-tubulin III. Thus, these data reinforce the anti-inflammatory activity and the neuroprotective effect of agathisflavone, effects associated with the control of NLRP3 inflammasome, standing out it as a promising molecule for the treatment or prevention of neurodegenerative diseases.

Purinergic P2X7 receptor-mediated inflammation precedes PTSD-related behaviors in rats

Clinical evidence has linked increased peripheral pro-inflammatory cytokines with post-traumatic stress disorder (PTSD) symptoms. However, whether inflammation contributes to or is a consequence of PTSD is still unclear. Previous research shows that stress can activate purinergic P2X7 receptors (P2X7Rs) on microglia to induce inflammation and behavioral changes. In this investigation, we examined whether P2X7Rs contribute to the development of PTSD-like behaviors induced by single prolonged stress (SPS) exposure in rats. Consistent with the literature, exposing adult male and female rats to SPS produced a PTSD-like phenotype of impaired fear extinction and extinction of cue-induced center avoidance one week after exposure. Next, we examined if inflammation precedes the behavioral manifestations. Three days after SPS exposure, increased inflammatory cytokines were found in the blood and hippocampal microglia showed increased expression of the P2X7R, IL-1β, and TNF-α, suggesting increased peripheral and central inflammation before the onset of impaired fear extinction. In addition, SPS-exposed animals with impaired fear extinction recall also had more Iba1-positive microglia expressing the P2X7R in the ventral hippocampus. To determine whether P2X7Rs contribute to the PTSD-related behaviors induced by SPS exposure, we gave ICV infusions of the P2X7R antagonist, A-438079, for one week starting the day of SPS exposure. Blocking P2X7Rs prevented the SPS-induced impaired fear extinction and extinction of cue-induced center avoidance in male and female rats, suggesting that SPS activates P2X7Rs which increase inflammation to produce a PTSD-like phenotype.

Microglial CD68 and L-ferritin upregulation in response to phosphorylated-TDP-43 pathology in the amyotrophic lateral sclerosis brain

Microglia, the innate immune cells of the brain, are activated by damage or disease. In mouse models of amyotrophic lateral sclerosis (ALS), microglia shift from neurotrophic to neurotoxic states with disease progression. It remains unclear how human microglia change relative to the TAR DNA-binding protein 43 (TDP-43) aggregation that occurs in 97% of ALS cases. Here we examine spatial relationships between microglial activation and TDP-43 pathology in brain tissue from people with ALS and from a TDP-43-driven ALS mouse model. Post-mortem human brain tissue from the Neurological Foundation Human Brain Bank was obtained from 10 control and 10 ALS cases in parallel with brain tissue from a bigenic NEFH-tTA/tetO-hTDP-43∆NLS (rNLS) mouse model of ALS at disease onset, early disease, and late disease stages. The spatiotemporal relationship between microglial activation and ALS pathology was determined by investigating microglial functional marker expression in brain regions with low and high TDP-43 burden at end-stage human disease: hippocampus and motor cortex, respectively. Sections were immunohistochemically labelled with a two-round multiplexed antibody panel against; microglial functional markers (L-ferritin, HLA-DR, CD74, CD68, and Iba1), a neuronal marker, an astrocyte marker, and pathological phosphorylated TDP-43 (pTDP-43). Single-cell levels of microglial functional markers were quantified using custom analysis pipelines and mapped to anatomical regions and ALS pathology. We identified a significant increase in microglial Iba1 and CD68 expression in the human ALS motor cortex, with microglial CD68 being significantly correlated with pTDP-43 pathology load. We also identified two subpopulations of microglia enriched in the ALS motor cortex that were defined by high L-ferritin expression. A similar pattern of microglial changes was observed in the rNLS mouse, with an increase first in CD68 and then in L-ferritin expression, with both occurring only after pTDP-43 inclusions were detectable. Our data strongly suggest that microglia are phagocytic at early-stage ALS but transition to a dysfunctional state at end-stage disease, and that these functional states are driven by pTDP-43 aggregation. Overall, these findings enhance our understanding of microglial phenotypes and function in ALS.

Effects of Whole-Body Vibration and Manually Assisted Locomotor Therapy on Neurotrophin-3 Expression and Microglia/Macrophage Mobilization Following Thoracic Spinal Cord Injury in Rats

Microglial cells play an important role in neuroinflammation and secondary damages after spinal cord injury (SCI). Progressive microglia/macrophage inflammation along the entire spinal axis follows SCI, and various factors may determine the microglial activation profile. Neurotrophin-3 (NT-3) is known to control the survival of neurons, the function of synapses, and the release of neurotransmitters, while also stimulating axon plasticity and growth. We examined the effects of whole-body vibration (WBV) and forms of assisted locomotor therapy, such as passive flexion-extension (PFE) therapy, at the neuronal level after SCI, with a focus on changes in NT-3 expression and on microglia/macrophage reaction, as they play a major role in the reconstitution of CNS integrity after injury and they may critically account for the observed structural and functional benefits of physical therapy. More specifically, the WBV therapy resulted in the best overall functional recovery when initiated at day 14, while inducing a decrease in Iba1 and the highest increase in NT-3. Therefore, the WBV therapy at the 14th day appeared to be superior to the PFE therapy in terms of recovery. Functional deficits and subsequent rehabilitation depend heavily upon the inflammatory processes occurring caudally to the injury site; thus, we propose that increased expression of NT-3, especially in the dorsal horn, could potentially be the mediator of this favorable outcome.

Curcumin promotes microglial M2 polarization and suppresses chronic constriction: Injury-induced neuropathic pain in a rat model of peripheral neuropathy

OBJECTIVES

Glia (i.e., astrocyte and microglia) activation in the central nervous system plays a critical role in developing neuropathic pain. Microglia can be activated into proinflammatory (M1) and anti-inflammatory (M2) phenotypes. Switching microglial polarization from M1 to M2 phenotypes represents a novel therapeutic strategy for neuropathic pain. Curcumin has been widely used for its anti-inflammatory and immunomodulatory effects. This study investigated effects of curcumin on astrocyte activation and microglia polarization in the cuneate nucleus (CN) and development of neuropathic pain behavior after chronic constriction injury (CCI) of the median nerve.

METHODS

Rats were fed with curcumin once daily at a dose of 40, 80, or 120 mg/kg 30 min before and until 7 d after median nerve CCI. Subsequently, mechanical allodynia and thermal hyperalgesia were evaluated using von Frey filaments and plantar tests, respectively. The levels of astrocyte marker, monoclonal glial fibrillary acidic protein; microglia marker, ionized calcium-binding adapter molecule 1; M1 marker, CD86; and M2 marker, CD206 in the cuneate nucleus were determined. Enzyme-linked immunosorbent assay was applied to measure cytokine concentrations.

RESULTS

Curcumin administration dose-dependently reduced mechanical allodynia and thermal hyperalgesia and decreased monoclonal glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 immunoreactivity in the ipsilateral cuneate nucleus after CCI. On ultrastructural observation, curcumin treatment was associated with fewer features of activated astrocytes and microglia. Furthermore, CCI rats given curcumin exhibited a decline in CD86 immunoreactivity and proinflammatory cytokine levels but an increase in CD206 immunoreactivity and release of anti-inflammatory cytokines.

CONCLUSIONS

In our findings, curcumin switches microglial phenotypes from M1 to M2 by suppressing astrocytic activation, reducing proinflammatory cytokine release, promoting anti-inflammatory cytokine production, and contributing to relief of neuropathic pain.

Increased adipose catecholamine levels and protection from obesity with loss of Allograft Inflammatory Factor-1

Recent studies implicate macrophages in regulation of thermogenic, sympathetic neuron-mediated norepinephrine (NE) signaling in adipose tissues, but understanding of such non-classical macrophage activities is incomplete. Here we show that male mice lacking the allograft inflammatory factor-1 (AIF1) protein resist high fat diet (HFD)-induced obesity and hyperglycemia. We link this phenotype to higher adipose NE levels that stem from decreased monoamine oxidase A (MAOA) expression and NE clearance by AIF1-deficient macrophages, and find through reciprocal bone marrow transplantation that donor Aif1-/- vs WT genotype confers the obesity phenotype in mice. Interestingly, human sequence variants near the AIF1 locus associate with obesity and diabetes; in adipose samples from participants with obesity, we observe direct correlation of AIF1 and MAOA transcript levels. These findings identify AIF1 as a regulator of MAOA expression in macrophages and catecholamine activity in adipose tissues - limiting energy expenditure and promoting energy storage - and suggest how it might contribute to human obesity.

Microglia in Human Postmortem Brain Samples: Quantitative Ultrastructural Analysis of Scanning Electron Microscopy Images

In this protocol, we describe the specific steps required to prepare human postmortem brain samples for ultrastructural microglial analysis. A detailed procedure is provided to improve the ultrastructural quality of the samples, using aldehyde fixatives followed by immunoperoxidase staining of allograft inflammatory factor 1 (AIF1, also known as IBA1), a marker of myeloid cells, and cluster of differentiation 68 (CD68), a marker of phagolysosomal activity. Additionally, we describe an osmium-thiocarbohydrazide-osmium (OTO) post-fixation method that preserves and increases the contrast of cellular membranes in human postmortem brain samples, as well as the steps necessary to acquire scanning electron microscopy (SEM) images of microglial cell bodies. In the last section, we cover the quantitative analysis of various microglial cytoplasmic organelles and their interactions with other parenchymal elements.

Cytoskeletal Responses and Aif-1 Expression in Caco-2 Monolayers Exposed to Phorbol-12-Myristate-13-Acetate and Carnosine

The dis(re)organization of the cytoskeletal actin in enterocytes mediates epithelial barrier dys(re)function, playing a key role in modulating epithelial monolayer's integrity and remodeling under transition from physiological to pathological states. Here, by fluorescence-based morphological and morphometric analyses, we detected differential responses of cytoskeletal actin in intestinal epithelial Caco-2 cell monolayers at two different stages of their spontaneous differentiation, i.e., undifferentiated cells at 7 days post-seeding (dps) and differentiated enterocyte-like cells at 21 dps, upon challenge in vitro with the inflammation-mimicking stimulus of phorbol-12-myristate-13-acetate (PMA). In addition, specific responses were found in the presence of the natural dipeptide carnosine detecting its potential counteraction against PMA-induced cytoskeletal alterations and remodeling in differentiated Caco-2 monolayers. In such an experimental context, by both immunocytochemistry and Western blot assays in Caco-2 monolayers, we identified the expression of the allograft inflammatory factor 1 (AIF-1) as protein functionally related to both inflammatory and cytoskeletal pathways. In 21 dps monolayers, particularly, we detected variations of its intracellular localization associated with the inflammatory stimulus and its mRNA/protein increase associated with the differentiated 21 dps enterocyte-like monolayer compared to the undifferentiated cells.

Characterization of microglia/macrophage phenotypes in the spinal cord following intervertebral disc herniation

Dogs frequently suffer from traumatic spinal cord injury (SCI). Most cases of SCI have a favorable prognosis but 40-50% of dogs with paraplegia and absence of nociception do not regain ambulatory abilities, eventually leading to euthanasia. Microglia and infiltrating macrophages play a crucial role in inflammatory process after SCI. However, little is known about microglia/macrophage phenotypes representing a potential target for future therapeutic strategies. In the present study, the microglia/macrophage phenotype was characterized by immunohistochemistry in the morphologically unaltered canine spinal cord (10 control dogs) and during acute and subacute SCI (1-4 and 5-10 days post injury, 9 and 8 dogs, respectively) using antibodies directed against IBA1, MAC387, MHC-II, lysozyme, EGR2, myeloperoxidase, CD18, CD204 and lectin from Griffonia simplicifolia (BS-1). The expression of these markers was also analyzed in the spleen as reference for the phenotype of histiocytic cells. Histological lesions were absent in controls. In acute SCI, 4 dogs showed mild to moderate hemorrhages, 2 dogs bilateral gray matter necrosis and 6 dogs mild multifocal axonal swellings and myelin sheath dilation. One dog with acute SCI did not show histological alterations except for few dilated myelin sheaths. In subacute SCI, variable numbers of gitter cells, axonal changes and dilated myelin sheaths were present in all dogs and large areas of tissue necrosis in 2 dogs. Neuronal chromatolysis was found in 3 dogs with acute and subacute SCI, respectively. In control dogs, microglia/macrophage constitutively expressed IBA1 and rarely other markers. In acute SCI, a similar marker expression was found except for an increase in MAC387-positive cells in the spinal cord white matter due to an infiltration of few blood-borne macrophages. In subacute SCI, increased numbers of microglia/macrophages expressed CD18, CD204 and MHC-II in the gray matter SCI indicating enhanced antigen recognition, processing and presentation as well as cell migration and phagocytosis during this stage. Interestingly, only CD204-positive cells were upregulated in the white matter, which might be related to gray-white matter heterogeneity of microglia as previously described in humans. The present findings contribute to the understanding of the immunological processes during SCI in a large animal model for human SCI.

A novel automated morphological analysis of Iba1+ microglia using a deep learning assisted model

There is growing evidence for the key role of microglial functional state in brain pathophysiology. Consequently, there is a need for efficient automated methods to measure the morphological changes distinctive of microglia functional states in research settings. Currently, many commonly used automated methods can be subject to sample representation bias, time consuming imaging, specific hardware requirements and difficulty in maintaining an accurate comparison across research environments. To overcome these issues, we use commercially available deep learning tools Aiforia^® Cloud (Aifoira Inc., Cambridge, MA, United States) to quantify microglial morphology and cell counts from histopathological slides of Iba1 stained tissue sections. We provide evidence for the effective application of this method across a range of independently collected datasets in mouse models of viral infection and Parkinson's disease. Additionally, we provide a comprehensive workflow with training details and annotation strategies by feature layer that can be used as a guide to generate new models. In addition, all models described in this work are available within the Aiforia^® platform for study-specific adaptation and validation.

Immunological Markers for Central Nervous System Glia

Glial cells in the central nervous system (CNS) are composed of oligodendrocytes, astrocytes and microglia. They contribute more than half of the total cells of the CNS, and are essential for neural development and functioning. Studies on the fate specification, differentiation, and functional diversification of glial cells mainly rely on the proper use of cell- or stage-specific molecular markers. However, as cellular markers often exhibit different specificity and sensitivity, careful consideration must be given prior to their application to avoid possible confusion. Here, we provide an updated overview of a list of well-established immunological markers for the labeling of central glia, and discuss the cell-type specificity and stage dependency of their expression.

Effect of water-soluble fullerenes on macrophage surface ultrastructure revealed by scanning ion conductance microscopy

C₆₀-fullerenes have unique potential in antiviral, drug delivery, photodynamic therapy and other biomedical applications. However, little is known about their effects on macrophage surface morphology and ultrastructure. Here by using contact-free scanning ion conductance microscopy (SICM), we investigated the effects of two water-soluble fullerenes on the surface ultrastructure and function of macrophages. The results showed that these fullerenes would be a promising phagocytosis inhibitor and SICM would be an excellent tool to study the morphological information of adhesive and fragile samples.

Nanoscale morphological changes of macrophages characterized by contact-free SICM and their relationship with phagocytosis after C₆₀-fullerene treatment demonstrate they are a potential phagocytosis inhibitor.

Isolation driven changes in Iba1-positive microglial morphology are associated with social recognition memory in adults and adolescents

Microglia are critical for regulation of neuronal circuits that mature from adolescence to adulthood. The morphological complexity and process length of microglia can indicate different activation states. These states are sensitive to a variety of environmental and stress conditions. Microglia are sensitive to many factors that also regulate social behavior, and in turn, microglial manipulations can impact social function. Brief social isolation is one factor that can lead to robust social changes. Here, we explored the role of microglia in the effects of brief social isolation on social recognition memory. Using morphological measures of Iba1 to index microglial intensity, complexity, and process length, we identified different effects of brief isolation on microglial complexity in the basal region of the amygdala between adults and adolescents alongside overall increases in intensity of Iba1 in several cortical brain regions. Short-term social recognition memory is sensitive to the amount of social engagement, and provides an opportunity to test if social engagement produced by brief isolation enhances social learning in a manner that relies on microglia. We found that brief isolation facilitated social interaction across ages but had opposing effects on short-term social recognition. Isolation increased novel partner investigation in adolescents, which is consistent with better social recognition, but increased familiar partner investigation in adults. Depletion of microglia with PLX3397 prevented these effects of brief isolation in adolescents, and reduced them in adults. These results suggest that distinct changes in microglial function driven by the social environment may differentially contribute to subsequent social recognition memory during development.

Partial Endothelial Nitric Oxide Synthase Deficiency Exacerbates Cognitive Deficit and Amyloid Pathology in the APPswe/PS1ΔE9 Mouse Model of Alzheimer’s Disease

Increasing evidence implicates endothelial dysfunction in the pathogenesis of Alzheimer’s disease (AD). Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is essential in maintaining cerebrovascular function and can modulate the production and clearance of amyloid beta (Aβ). APPswe/PSdE1 (APP/PS1) mice display age-related Aβ accumulation and memory deficits. In order to make the model more clinically relevant with an element of endothelial dysfunction, we generated APP/PS1/eNOS+/− mice by crossing complete eNOS deficient (eNOS−/−) mice and APP/PS1 mice. APP/PS1/eNOS+/− mice at 8 months of age displayed a more severe spatial working memory deficit relative to age-matched APP/PS1 mice. Moreover, immunohistochemistry and immunoblotting revealed significantly increased Aβ plaque load in the brains of APP/PS1/eNOS+/− mice, concomitant with upregulated BACE-1 (hence increased Aβ production), downregulated insulin-degrading enzyme (hence reduced Aβ clearance) and increased immunoreactivity and expression of microglia. The present study, for the first time, demonstrated that partial eNOS deficiency exacerbated behavioral dysfunction, Aβ brain deposition, and microglial pathology in APP/PS1 mice, further implicating endothelial dysfunction in the pathogenesis of AD. The present findings also provide the scientific basis for developing preventive and/or therapeutic strategies by targeting endothelial dysfunction.

Microglia as a Hub for Suicide Neuropathology: Future Investigation and Prevention Targets

Suicide is a complex public health challenge associated worldwide with one death every 40 s. Research advances in the neuropathology of suicidal behaviors (SB) have defined discrete brain changes which may hold the key to suicide prevention. Physiological differences in microglia, the resident immune cells of the brain, are present in post-mortem tissue samples of individuals who died by suicide. Furthermore, microglia are mechanistically implicated in the outcomes of important risk factors for SB, including early-life adversity, stressful life events, and psychiatric disorders. SB risk factors result in inflammatory and oxidative stress activities which could converge to microglial synaptic remodeling affecting susceptibility or resistance to SB. To push further this perspective, in this Review we summarize current areas of opportunity that could untangle the functional participation of microglia in the context of suicide. Our discussion centers around microglial state diversity in respect to morphology, gene and protein expression, as well as function, depending on various factors, namely brain region, age, and sex.

Targeting IFN-λ Signaling Promotes Recovery from Central Nervous System Autoimmunity

Type III IFNs (IFNLs) are newly discovered cytokines, acting at epithelial and other barriers, that exert immunomodulatory functions in addition to their primary roles in antiviral defense. In this study, we define a role for IFNLs in maintaining autoreactive T cell effector function and limiting recovery in a murine model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis. Genetic or Ab-based neutralization of the IFNL receptor (IFNLR) resulted in lack of disease maintenance during experimental autoimmune encephalomyelitis, with loss of CNS Th1 effector responses and limited axonal injury. Phenotypic effects of IFNLR signaling were traced to increased APC function, with associated increase in T cell production of IFN-γ and GM-CSF. Consistent with this, IFNL levels within lesions of CNS tissues derived from patients with MS were elevated compared with MS normal-appearing white matter. Furthermore, expression of IFNLR was selectively elevated in MS active lesions compared with inactive lesions or normal-appearing white matter. These findings suggest IFNL signaling as a potential therapeutic target to prevent chronic autoimmune neuroinflammation.

Tumor-Associated Macrophages in Gliomas—Basic Insights and Treatment Opportunities

Simple Summary

Macrophages are a specialized immune cell type found in both invertebrates and vertebrates. Versatile in functionality, macrophages carry out important tasks such as cleaning cellular debris in healthy tissues and mounting immune responses during infection. In many cancer types, macrophages make up a significant portion of tumor tissue, and these are aptly called tumor-associated macrophages. In gliomas, a group of primary brain tumors, these macrophages are found in very high frequency. Tumor-associated macrophages can promote glioma development and influence the outcome of various therapeutic regimens. At the same time, these cells provide various potential points of intervention for therapeutic approaches in glioma patients. The significance of tumor-associated macrophages in the glioma microenvironment and potential therapeutic targets are the focus of this review.

Abstract

Glioma refers to a group of primary brain tumors which includes glioblastoma (GBM), astrocytoma and oligodendroglioma as major entities. Among these, GBM is the most frequent and most malignant one. The highly infiltrative nature of gliomas, and their intrinsic intra- and intertumoral heterogeneity, pose challenges towards developing effective treatments. The glioma microenvironment, in addition, is also thought to play a critical role during tumor development and treatment course. Unlike most other solid tumors, the glioma microenvironment is dominated by macrophages and microglia—collectively known as tumor-associated macrophages (TAMs). TAMs, like their homeostatic counterparts, are plastic in nature and can polarize to either pro-inflammatory or immunosuppressive states. Many lines of evidence suggest that immunosuppressive TAMs dominate the glioma microenvironment, which fosters tumor development, contributes to tumor aggressiveness and recurrence and, very importantly, impedes the therapeutic effect of various treatment regimens. However, through the development of new therapeutic strategies, TAMs can potentially be shifted towards a proinflammatory state which is of great therapeutic interest. In this review, we will discuss various aspects of TAMs in the context of glioma. The focus will be on the basic biology of TAMs in the central nervous system (CNS), potential biomarkers, critical evaluation of model systems for studying TAMs and finally, special attention will be given to the potential targeted therapeutic options that involve the TAM compartment in gliomas.

Co-expression patterns of microglia markers Iba1, TMEM119 and P2RY12 in Alzheimer's disease

Microglia have been identified as key players in Alzheimer's disease pathogenesis, and other neurodegenerative diseases. Iba1, and more specifically TMEM119 and P2RY12 are gaining ground as presumedly more specific microglia markers, but comprehensive characterization of the expression of these three markers individually as well as combined is currently missing. Here we used a multispectral immunofluorescence dataset, in which over seventy thousand microglia from both aged controls and Alzheimer patients have been analysed for expression of Iba1, TMEM119 and P2RY12 on a single-cell level. For all markers, we studied the overlap and differences in expression patterns and the effect of proximity to β-amyloid plaques. We found no difference in absolute microglia numbers between control and Alzheimer subjects, but the prevalence of specific combinations of markers (phenotypes) differed greatly. In controls, the majority of microglia expressed all three markers. In Alzheimer patients, a significant loss of TMEM119⁺-phenotypes was observed, independent of the presence of β-amyloid plaques in its proximity. Contrary, phenotypes showing loss of P2RY12, but consistent Iba1 expression were increasingly prevalent around β-amyloid plaques. No morphological features were conclusively associated with loss or gain of any of the markers or any of the identified phenotypes. All in all, none of the three markers were expressed by all microglia, nor can be wholly regarded as a pan- or homeostatic marker, and preferential phenotypes were observed depending on the surrounding pathological or homeostatic environment. This work could help select and interpret microglia markers in previous and future studies.

Mycobacterium vaccae immunization in rats ameliorates features of age-associated microglia activation in the amygdala and hippocampus

Aging and reduced exposure to environmental microbes can both potentiate neuroinflammatory responses. Prior studies indicate that immunization with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), in aged rats limits neuroimmune activation and cognitive impairments. However, the mechanisms by which M. vaccae immunization ameliorates age-associated neuroinflammatory “priming” and whether microglia are a primary target remain unclear. Here, we investigated whether M. vaccae immunization protects against microglia morphological changes in response to aging. Adult (3 mos) and aged (24 mos) Fisher 344 × Brown Norway rats were immunized with either M. vaccae or vehicle once every week for 3 weeks. Aging led to elevated Iba1 immunoreactivity, microglial density, and deramification of microglia processes in the hippocampus and amygdala but not other brain regions. Additionally, aged rats exhibited larger microglial somas in the dorsal hippocampus, suggestive of a more activated phenotype. Notably, M. vaccae treatment ameliorated indicators of microglia activation in both the amygdala and hippocampus. While changes in morphology appeared to be region-specific, gene markers indicative of microglia activation were upregulated by age and lowered in response to M. vaccae in all brain regions evaluated. Taken together, these data suggest that peripheral immunization with M. vaccae quells markers of age-associated microglia activation.

Cortical Dysplasia in Rats Provokes Neurovascular Alterations, GLUT1 Dysfunction, and Metabolic Disturbances That Are Sustained Post-Seizure Induction

Focal cortical dysplasia (FCD) is associated with blood-brain barrier (BBB) dysfunction in patients with difficult-to-treat epilepsy. However, the underlying cellular and molecular factors in cortical dysplasia (CD) associated with progressive neurovascular challenges during the pro-epileptic phase, post-seizure, and during epileptogenesis remain unclear. We studied the BBB function in a rat model of congenital (in utero radiation-induced, first hit) CD and longitudinally examined the cortical brain tissues at baseline and the progressive neurovascular alterations, glucose transporter-1 (GLUT1) expression, and glucose metabolic activity at 2, 15, and 30 days following a second hit using pentylenetetrazole-induced seizure. Our study revealed through immunoblotting, immunohistochemistry, and biochemical analysis that (1) altered vascular density and prolongation of BBB albumin leakages in CD rats continued through 30 days post-seizure; (2) CD brain tissues showed elevated matrix metalloproteinase-9 levels at 2 days post-seizure and microglial overactivation through 30 days post-seizure; (3) BBB tight junction protein and GLUT1 levels were decreased and neuronal monocarboxylate transporter-2 (MCT2) and mammalian target of rapamycin (mTOR) levels were increased in the CD rat brain: (4) ATPase activity is elevated and a low glucose/high lactate imbalance exists in CD rats; and (5) the mTOR pathway is activated and MCT2 levels are elevated in the presence of high lactate during glucose starvation in vitro. Together, this study suggests that BBB dysfunction, including decreased GLUT1 expression and metabolic disturbance, may contribute to epileptogenesis in this CD rat model through multiple mechanisms that could be translated to FCD therapy in medically refractory epilepsy.

Post-weaning Social Isolation in Male and Female Prairie Voles: Impacts on Central and Peripheral Immune System

The socially monogamous prairie vole (Microtus ochrogaster) offers a unique opportunity to examine the impacts of adolescent social isolation on the brain, immune system, and behavior. In the current study, male and female prairie voles were randomly assigned to be housed alone or with a same-sex cagemate after weaning (i.e., on postnatal day 21-22) for a 6-week period. Thereafter, subjects were tested for anxiety-like and depressive-like behaviors using the elevated plus maze (EPM) and Forced Swim Test (FST), respectively. Blood was collected to measure peripheral cytokine levels, and brain tissue was processed for microglial density in various brain regions, including the Nucleus Accumbens (NAcc), Medial Amygdala (MeA), Central Amygdala (CeA), Bed Nucleus of the Stria Terminalis (BNST), and Paraventricular Nucleus of the Hypothalamus (PVN). Sex differences were found in EPM and FST behaviors, where male voles had significantly lower total arm entries in the EPM as well as lower latency to immobility in the FST compared to females. A sex by treatment effect was found in peripheral IL-1β levels, where isolated males had a lower level of IL-1β compared to cohoused females. Post-weaning social isolation also altered microglial density in a brain region-specific manner. Isolated voles had higher microglial density in the NAcc, MeA, and CeA, but lower microglial density in the dorsal BNST. Cohoused male voles also had higher microglial density in the PVN compared to cohoused females. Taken together, these data suggest that post-weaning social housing environments can alter peripheral and central immune systems in prairie voles, highlighting a potential role for the immune system in shaping isolation-induced alterations to the brain and behavior.