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Objectives: The growing adoption of cochlear implants (CIs) necessitates understanding the factors influencing long-term performance and improved outcomes. This work investigated the long-term effect of early activation of CIs on electrode impedance in a large sample of CI users at different time points. Methods: A retrospective study on 915 ears from CI patients who were implanted between 2015 and 2020. According to their CI audio processor activation time, the patients were categorized into early activation (activated 1 day after surgery, n = 481) and classical activation (activated 4 weeks after surgery, n = 434) groups. Then, the impact of the activation times on the electrode impedance values, along the electrode array contacts, at different time points up to two years was studied and analyzed. Results: The early activation group demonstrated lower impedance values across all the electrode array sections compared to the classical activation at 1 month, 1 year, and 2 years post-implantation. At 1 month, early activation was associated with a reduction of 0.34 kΩ, 0.46 kΩ, and 0.37 kΩ in the apical, middle, and basal sections, respectively. These differences persisted at subsequent intervals. Conclusions: Early activation leads to sustained reductions in the electrode impedance compared to classical activation (CA), suggesting that earlier activation might positively affect long-term CI outcomes.

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[This corrects the article DOI: 10.3389/fimmu.2023.1209898.].

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Introduction: Extracellular vesicles (EVs) are nanometric-membrane-bound sub-cellular structures, which can be recovered from milk. Milk EVs have drawn increasing interest due to their potential biomedical applications, therefore it is important to investigate their impact on key immune cells, such as macrophages. Methods: In this work, the immunomodulatory effects of goat milk EVs on untreated (moMФ) and classically activated (moM1) porcine monocyte-derived macrophages were investigated using flow cytometry, ELISA, and gene expression assays. Results: These particles were efficiently internalized by macrophages and high doses (60 mg protein weight) triggered the upregulation of MHC I and MHC II DR on moMФ, but not on moM1. In moMФ, exposure to low doses (0.6 mg) of mEVs enhanced the gene expression of IL10, EBI3, and IFNB, whereas high doses up-regulated several pro-inflammatory cytokines. These nanosized structures slightly modulated cytokine gene expression on moM1. Accordingly, the cytokine (protein) contents in culture supernatants of moMФ were mildly affected by exposure to low doses of mEVs, whereas high doses promoted the increased release of TNF, IL-8, IL-1a, IL-1b, IL-1Ra, IL-6, IL-10, and IL-12. The cytokines content in moM1 supernatants was not critically affected. Discussion: Overall, our data support a clinical application of these molecules: they polarized macrophages toward an M1-like phenotype, but this activation seemed to be controlled, to prevent potentially pathological over-reaction to stressors.

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Swine are attracting increasing attention as a biomedical model, due to many immunological similarities with humans. However, porcine macrophage polarization has not been extensively analyzed. Therefore, we investigated porcine monocyte-derived macrophages (moMΦ) triggered by either IFN-γ + LPS (classical activation) or by diverse "M2-related" polarizing factors: IL-4, IL-10, TGF-ß, and dexamethasone. IFN-γ and LPS polarized moMΦ toward a proinflammatory phenotype, although a significant IL-1Ra response was observed. Exposure to IL-4, IL-10, TGF-ß, and dexamethasone gave rise to four distinct phenotypes, all antithetic to IFN-γ and LPS. Some peculiarities were observed: IL-4 and IL-10 both enhanced expression of IL-18, and none of the "M2-related" stimuli induced IL-10 expression. Exposures to TGF-ß and dexamethasone were characterized by enhanced levels of TGF-ß2, whereas stimulation with dexamethasone, but not TGF-ß2, triggered CD163 upregulation and induction of CCL23. Macrophages stimulated with IL-10, TGF-ß, or dexamethasone presented decreased abilities to release proinflammatory cytokines in response to TLR2 or TLR3 ligands: IL-10 showed a powerful inhibitory activity for CXCL8 and TNF release, whereas TGF-ß provided a strong inhibitory signal for IL-6 production. While our results emphasized porcine macrophage plasticity broadly comparable to human and murine macrophages, they also highlighted some peculiarities in this species.

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Oral cancer is a common malignancy worldwide, with high disease-related death rates. Oral squamous cell carcinoma (OSCC) accounts for more than 90% of oral tumors, with surgical management remaining the treatment of choice. However, advanced and metastatic OSCC is still incurable. Thus, emphasis has been given lately in understanding the complex role of the oral tumor microenvironment (TME) in OSCC progression, in order to identify novel prognostic biomarkers and therapeutic targets. Tumor associated macrophages (TAMs) constitute a major population of the OSCC TME, with bipolar role in disease progression depending on their activation status (M1 vs. M2). Here, we provide an up to date review of the current literature on the role of macrophages during oral oncogenesis, as well as their prognostic significance in OSCC survival and response to standard treatment regimens. Finally, we discuss novel concepts regarding the potential use of macrophages as targets for OSCC immunotherapeutics and suggest future directions in the field.

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Traumatic brain injury (TBI) causes substantial mortality and long-term disability worldwide. TGFß1 is a unique molecular and functional signature in microglia, but the role of TGFß1 in TBI is not clear. The purpose of this study was to investigate the role of TGFß1 in TBI. The weight dropping device was used to establish TBI model of rats. Hematoxylin eosin staining and Bielschowsky silver staining were used to assess tissue loss. Beam walking and muscle strength tests were used to assess neurological deficits. Immunohistochemical staining was used to assess axonal injures. Western blotting was used to detect expression of related proteins. RT-PCR was used to detect expression of cytokines. Immunofluorescence staining was used to assess the microglia/macrophages activation. We observed obvious axonal injury and microglia/macrophages activation in the peri-lesion cortex. The expression of inflammatory cytokines was markedly high after TBI. The expression of TGFß1 and TGFßRI were significantly reduced after TBI. TGFß1 promoted the functional recovery and alleviated axonal injury 1 day after TBI. TGFß1 promoted microglia/macrophages polarizing to alternative activation and alleviated neuroinflammation. These effects of TGFß1 could be inhibited by LY2109761, the inhibitor of TGFRI/II. These results suggested that TGFß1 played a protective role in axonal injury and could be a potential therapeutic target in early stages following TBI.

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Innate immune responses, particularly activation of macrophages and microglia, are increasingly implicated in CNS disorders. It is now appreciated that the heterogeneity of functions adopted by these cells dictates neuropathophysiology. Research efforts to characterize the range of pro-inflammatory and anti-inflammatory phenotypes and functions adopted by microglia and macrophages are fueled by the potential for inflammatory cells to both exacerbate neurodegeneration and promote repair/disease resolution. The stimulation-based, M1/M2 classification system has emerged over the last decade as a common language to discuss macrophage and microglia heterogeneity across different fields. However, discontinuities between phenotypic markers and function create potential hurdles for the utility of the M1/M2 system in the development of effective immunomodulatory therapeutics for neuroinflammation. A framework to approach macrophage and microglia heterogeneity from a function-based phenotypic approach comes from rapidly emerging evidence that metabolic processes regulate immune cell activation. This concept of immunometabolism, however, is only beginning to unfold in the study of neurodegeneration and has yet to receive much focus in the context of neurotrauma. In this review, we first discuss the current views of macrophage and microglia heterogeneity and limitations of the M1/M2 classification system for neuropathological studies. We then review and discuss the current literature supporting metabolism as a regulator of microglia function in vitro. Lastly, we evaluate the evidence that metabolism regulates microglia and macrophage phenotype in vivo in models of Alzheimer's disease (AD), stroke, traumatic brain injury (TBI) and spinal cord injury (SCI).

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The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CX3CR1+ iPSC-microglia (cultured within a neural environment) and round-shaped CX3CR1- iPSC-macrophages can easily be differentiated from newly established murine CX3CR1eGFP/+CCR2RFP/+ iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CX3CR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon γ or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CX3CR1eGFP/+CCR2RFP/+ mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment.

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BACKGROUND: Functions of astrocytes in the rehabilitation after ischemic stroke, especially their impacts on inflammatory processes, remain controversial. This study uncovered two phenotypes of astrocytes, of which one was helpful, and the other harmful to anoxic neurons after brain ischemia. METHODS: We tested the levels of inflammatory factors including TNF-a, IL-6, IL-10, iNOS, IL-1beta, and CXCL10 in primary astrocytes at 0 h, 6 h, 12 h, 24 h, and 48 h after OGD, grouped the hypoxia astrocytes into iNOS-positive (iNOS(+)) and iNOS-negative (iNOS(-)) by magnetic bead sorting, and then co-cultured the two groups of cells with OGD-treated neurons for 24 h. We further verified the polarization of astrocytes in vivo by detecting the co-localization of iNOS, GFAP, and Iba-1 on MCAO brain sections. Lentivirus overexpressing LCN2 and LCN2 knockout mice (#024630. JAX, USA) were used to explore the role of LCN2 in the functional polarization of astrocytes. 7.0-T MRI scanning and the modified Neurological Severity Score (mNSS) were used to evaluate the neurological outcomes of the mice. RESULTS: After oxygen-glucose deprivation (OGD), iNOS mRNA expression increased to the peak at 6 h in primary astrocytes, but keep baseline expression in LCN2-knockout astrocytes. In mice with transient middle cerebral artery occlusion (tMCAO), LCN2 was proved necessary for astrocyte classical activation. In LCN2 knockout mice with MCAO, no classically activated astrocytes were detected, and smaller infarct volumes and better neurological functions were observed. CONCLUSIONS: The results indicated a novel pattern of astrocyte activation after ischemic stroke and lipocalin-2 (LCN2) plays a key role in polarizing and activating astrocytes.

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Cyanobacterial blooms are an increasing source of environmental toxins that affect both human and animals. After ingestion of cyanobacteria, such as Geitlerinema sp., toxins and lipopolysaccharide (LPS) from this organism induce fever, gastrointestinal illness, and even death. However, little is known regarding the effects of cyanobacterial LPS on human monocytes after exposure to LPS upon ingestion. Based on our previous data using Geitlerinema sp. LPS (which was previously named Oscillatoria sp., a genus belonging to the same order as Geitlerinema), we hypothesized that Geitlerinema sp. LPS would activate human monocytes to proliferate, phagocytose particles, and produce cytokines that are critical for promoting proinflammatory responses in the gut. Our data demonstrate that Geitlerinema sp. LPS induced monocyte proliferation and TNF-α, IL-1, and IL-6 production at high concentrations. In contrast, Geitlerinema sp. LPS is equally capable of inducing monocyte-mediated phagocytosis of FITC-latex beads when compared with Escherichia coli LPS, which was used as a positive control for our experiments. In order to understand the mechanism responsible for the difference in efficacy between Geitlerinema sp. LPS and E. coli LPS, we performed biochemical analysis and identified that Geitlerinema sp. LPS was composed of significantly different sugars and fatty acid side chains in comparison to E. coli LPS. The lipid A portion of Geitlerinema sp. LPS contained longer fatty acid side chains, such as C15:0, C16:0, and C18:0, instead of C12:0 found in E. coli LPS which may explain the decreased efficacy and toxicity of Geitlerinema sp. LPS in comparison to E. coli LPS.

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Macrophages, circulating in the blood or concatenated into different organs and tissues constitute the first barrier against any disease. They are foremost controllers of both innate and acquired immunity, healthy tissue homeostasis, vasculogenesis and congenital metabolism. Two hallmarks of macrophages are diversity and plasticity due to which they acquire a wobbling array of phenotypes. These phenotypes are appropriately synchronized responses to a variety of different stimuli from either the tissue microenvironment or - microbes or their products. Based on the phenotype, macrophages are classified into classically activated/(M1) and alternatively activated/(M2) which are further sub-categorized into M2a, M2b, M2c and M2d based upon gene expression profiles. Macrophage phenotype metamorphosis is the regulating factor in initiation, progression, and termination of numerous inflammatory diseases. Several transcriptional factors and other factors controlling gene expression such as miRNAs contribute to the transformation of macrophages at different points in different diseases. Understanding the mechanisms of macrophage polarization and modulation of their phenotypes to adjust to the micro environmental conditions might provide us a great prospective for designing novel therapeutic strategy. In view of the above, this review summarises the activation of macrophages, the factors intricated in activation along with benefaction of macrophage polarization in response to microbial infections, pulmonary toxicity, lung injury and other inflammatory diseases such as chronic obstructive pulmonary dysplasia (COPD), bronchopulmonary dysplasia (BPD), asthma and sepsis, along with the existing efforts to develop therapies targeting this facet of macrophage biology.

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Macrophages are important in innate and adaptive immunity. Macrophage participation in inflammation or tissue repair is directed by various extracellular signals and mediated by multiple intracellular pathways. Activation of group VIA phospholipase A2 (iPLA2ß) causes accumulation of arachidonic acid, lysophospholipids, and eicosanoids that can promote inflammation and pathologic states. We examined the role of iPLA2ß in peritoneal macrophage immune function by comparing wild type (WT) and iPLA2ß-/- mouse macrophages. Compared with WT, iPLA2ß-/- macrophages exhibited reduced proinflammatory M1 markers when classically activated. In contrast, anti-inflammatory M2 markers were elevated under naïve conditions and induced to higher levels by alternative activation in iPLA2ß-/- macrophages compared with WT. Induction of eicosanoid (12-lipoxygenase (12-LO) and cyclooxygenase 2 (COX2))- and reactive oxygen species (NADPH oxidase 4 (NOX4))-generating enzymes by classical activation pathways was also blunted in iPLA2ß-/- macrophages compared with WT. The effects of inhibitors of iPLA2ß, COX2, or 12-LO to reduce M1 polarization were greater than those to enhance M2 polarization. Certain lipids (lysophosphatidylcholine, lysophosphatidic acid, and prostaglandin E2) recapitulated M1 phenotype in iPLA2ß-/- macrophages, but none tested promoted M2 phenotype. These findings suggest that (a) lipids generated by iPLA2ß and subsequently oxidized by cyclooxygenase and 12-LO favor macrophage inflammatory M1 polarization, and (b) the absence of iPLA2ß promotes macrophage M2 polarization. Reducing macrophage iPLA2ß activity and thereby attenuating macrophage M1 polarization might cause a shift from an inflammatory to a recovery/repair milieu.

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Differences in peritoneal macrophage polarization in mice of opposite lines CBA and C57Bl/6 and the effects of 60 kDa oxidized dextran were studied. Macrophages of C57Bl/6 mice demonstrated a phenotype close to M1, with increasing expression of CD86 costimulatory molecule and unchanged CD206 expression in response to activation. Macrophages of CBA mice demonstrated higher plasticity in response to activating agents; expression of the markers increased irrespectively on stimulated receptor (TLR-4 or mannose receptor) and both CD86 (classical activation) and CD206 (alternative activation) increased. Macrophage response to addition of oxidized dextran (60 kDa) to the culture medium could be characterized as potentiation of their alternative activation: expression of CD86 in CBA mice in response to LPS and LPS+IL-4 and in C57Bl/6 mice in response to IFN-γ and LPS+IFN-γ decreased, while expression of CD206 by intact macrophages of CBA mice and by macrophages stimulated by IFN-γ and IL-4 increased under the effect of 60 kDa oxidized dextran.

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Screening study of the effects of sweet flag (Acorus calamus L.) rhizome and clover (Trifolium pratense L.) aerial part on the production of NO by mouse macrophages was carried out. The polysaccharides were separated by ion exchange chromatography into fractions differing by monomeric composition and ramification type and were used in concentrations of 20, 40, and 100 µg/ml. Four fractions of Acorus calamus L. (PSF-101, PSF-102, PSF-103, and PSF-105), used in different concentrations, moderately stimulated nitrite production by macrophages. Three of five Trifolium pratense L. polysaccharides (PS62-3, PS62-4, and PS62-5) exhibited a significant specific effect on NO production. Rhamnogalactouronans from clover PS63-3 in all concentrations and from PS62-5 in a concentration of 100 µg/ml exhibited the highest activity, comparable to the NO-stimulatory activity of the reference LPS, while polysaccharide PS62-3 in a concentration of 40 µg/ml exhibited even higher activity.

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One of the most striking hallmarks shared by various neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease (AD), and amyotrophic lateral sclerosis, is microglia-mediated neuroinflammation. Increasing evidence indicates that microglial activation in the central nervous system is heterogeneous, which can be categorized into two opposite types: M1 phenotype and M2 phenotype. Depending on the phenotypes activated, microglia can produce either cytotoxic or neuroprotective effects. In this review, we focus on the potential role of M1 and M2 microglia and the dynamic changes of M1/M2 phenotypes that are critically associated with the neurodegenerative diseases. Generally, M1 microglia predominate at the injury site at the end stage of disease, when the immunoresolution and repair process of M2 microglia are dampened. This phenotype transformation is very complicated in AD due to the phagocytosis of regionally distributed ß-amyloid (Aß) plaque and tangles that are released into the extracellular space. The endogenous stimuli including aggregated α-synuclein, mutated superoxide dismutase, Aß, and tau oligomers exist in the milieu that may persistently activate M1 pro-inflammatory responses and finally lead to irreversible neuron loss. The changes of microglial phenotypes depend on the disease stages and severity; mastering the stage-specific switching of M1/M2 phenotypes within appropriate time windows may provide better therapeutic benefit.

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The purpose of this investigation was to test the hypothesis that an in vitro exposure to cyanobacterium Oscillatoria sp. Lipopolysaccharide (LPS) might result in classical and alternative activation of rat neonatal microglia. Using Escherichia coli LPS-primed microglia as a positive control, this study revealed that treatment of rat microglia with Oscillatoria sp. LPS for 17 h in vitro resulted in both classical and alternative activation as well as concomitant pro-inflammatory and anti-inflammatory mediator release, in a concentration-dependent manner: (1) treatment with 0.1-10 000 ng/ml Oscillatoria sp. LPS resulted in minimal lactic dehydrogenase (LDH) release, induced concentration-dependent and statistically significant O2 (-) generation, matrix metalloproteinase-9 (MMP-9) release, generation of the cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and the chemokines macrophage inflammatory protein-2 (MIP-2/CXCL2), interferon γ-induced protein 10 kDa (IP-10/CXCL-10), (MIP-1α/CCL3), monocyte chemotactic protein-1 (MCP-1/CCL2), regulated on activation, normal T cell expressed and secreted (RANTES/CCL5), and the alternative activation cytokine IL-10; (3) in contrast, treatment with 100 000 ng/ml Oscillatoria sp. LPS appeared to damage the microglia cell membrane, because it resulted in minimal O2 (-) generation, statistically significant LDH release, and a decrease in the generation of all the cytokines and chemokines investigated, with the exception of IL-1α and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL1) generation, which was increased. Thus, our results provide experimental support for our working hypothesis, namely that Oscillatoria sp. LPS induces classical and alternative activation of rat brain microglia in vitro in a concentration-dependent manner, namely 0.1-10 000 ng/ml Oscillatoria sp. LPS, when microglia cells were shown to be viable. Furthermore, should cyanobacterium Oscillatoria sp. LPS gain entry into the CNS, our findings suggest that classical and alternative activation of rat brain microglia in vivo, might lead to concomitant mediator release that could result in an interplay between neuroinflammation and neural repair in a concentration-dependent manner.

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Inflammation is a complicated biological process in response to harmful stimuli, which involves the cooperation of immune system and vascular system. Upon pathogen invasion or tissue injury, resident innate immune cells such as macrophages and dendritic cells are activated and release inflammatory mediators, which result in the vasodilation and recruitment of leukocytes, mainly monocytes and neutrophils. As two of the most important inflammation-mediating immune cells, macrophages and neutrophils have long been regarded to have a pro-inflammatory effect. However, increasing evidences suggest the role of macrophage and neutrophil in inflammation is more complicated and diversified than we thought. Differently activated macrophages and neutrophils lead to diverse even opposite activities. Precise understanding of the role of different subpopulations is critical to achieve the effective treatment for inflammatory diseases. In this review, we discuss the two potentially distinct activation routes of macrophages and neutrophils in obesity and diabetes.

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Pro-inflammatory M1 macrophages are critical for defense against intracellular pathogens while alternatively-activated M2 macrophages mediate tissue homeostasis and repair. Whether these distinct activation programs are mutually exclusive or can co-exist within the same cell is unclear. Here, we report the co-existence of these programs in Toxoplasma gondii-elicited inflammatory macrophages. This is independent of parasite expression of the virulence factor ROP16 and host cell expression of signal transducer and activator of transcription 6 (STAT6). Furthermore, this observation was recapitulated by IFN-γ and IL-4 treated bone marrow-derived macrophages in vitro. These results highlight the multi-functionality of macrophages as they respond to diverse microbial and endogenous stimuli.

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Macrophages are key regulators of many organ systems, including innate and adaptive immunity, systemic metabolism, hematopoiesis, vasculogenesis, malignancy, and reproduction. The pleiotropic roles of macrophages are mirrored by similarly diverse cellular phenotypes. A simplified schema classifies macrophages as M1, classically activated macrophages, or M2, alternatively activated macrophages. These cells are characterized by their expression of cell surface markers, secreted cytokines and chemokines, and transcription and epigenetic pathways. Transcriptional regulation is central to the differential speciation of macrophages, and several major pathways have been described as essential for subset differentiation. In this review, we discuss the transcriptional regulation of macrophages.

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