Reactive astrocytes are a hallmark of several neurological diseases in multiple sclerosis and experimental demyelination models. Their morphological alterations are commonly assessed by qualitative histopathology, yet quantitative tools are required to better capture astrocytic heterogeneity and to allow correlations with imaging-derived biomarkers. Here, we present a workflow for the quantitative analysis of Glial Fibrillary Acidic Protein (GFAP) network remodeling in astrocytes in the cuprizone model of demyelination. C57BL/6 mice were intoxicated with cuprizone for 3 or 5 weeks to induce progressive demyelination, microglial activation, and reactive astrogliosis. Brain sections were processed for anti-GFAP immunohistochemistry, and individual astrocytes from the stratum oriens of the hippocampus were digitally reconstructed. Diverse parameters of GFAP topology, including soma size, process length, branching order, convex hull area, and ramification index, were extracted using either the commercial Neurolucida® 360 software or the open-source Simple Neurite Tracer (SNT) plugin in ImageJ. Principal component analysis revealed clear differences between control astrocytes and astrocytes in cuprizone-intoxicated animals, with reactive astrocytes displaying increased numbers of primary processes, enhanced bifurcation, and process complexity. Comparative evaluation of Neurolucida® 360 and SNT demonstrated that both tools are suitable for astrocyte reconstruction, although Neurolucida® 360 enabled faster and more detailed tracing. This protocol provides a reproducible pipeline for the quantitative assessment of astrocyte morphology under control and pathological conditions, thereby supporting future efforts to link cellular remodeling to functional outcomes in neuroinflammatory disease models.

IntroductionRegulatory T-cells (Tregs) are characterized by the expression of Foxp3, a master regulator involved in the development and function of Tregs. Foxp3 expression is dependent on activity of the Treg specific demethylated site (TSDR), which contains a CREB binding site. We aimed to find out how Foxp3 specific CREB deletion affects Treg expression and function.MethodsTregs from Foxp3creCREBfl/fl mice and wild type (CREBfl/fl) mice were analyzed by flow cytometry. Cytokine analysis was performed by flow cytometry, ELISA and RT-qPCR. Gene expression analysis was performed using Affymetrix HTA2 assays, ATAC-sequencing, and Methylation-assays. For functional relevance, a CD4 T cell mediated transfer colitis was performed.Results and discussionFoxp3creCREBfl/fl mice showed increased frequencies of Tregs (CD25+/Foxp3+) in thymus, spleen and peripheral lymph nodes and in nonlymphoid organs including lung and colon, but decreased Foxp3 expression at the single cell level. Despite decreased Foxp3 expression, enhanced expression of the IL- 33 receptor (ST-2), IL-10, IL-13, and CREM was observed. CREB deficient Tregs were highly suppressive in vitro and prevented disease activity in a CD4 T cell mediated transfer colitis in an IL-10 dependent way. Mechanistically CREB fulfils dual roles in Tregs: (1) it promotes Foxp3 expression under Steady state conditions and (2) in cooperation with CREM, CREB restricts chromatin accessibility at the ST2 locus, thereby modulating IL-33 driven immune responses. This dual regulation balances FoxP3-dependent Treg stability with IL-10 mediated suppression of inflammation.

Multiple sclerosis (MS), the most prevalent myelinopathy with unclear etiology, involves mitochondrial dysfunction that critically contributes to oligodendrocyte damage and neurodegeneration. Recent interest has surged around the role of inflammatory non-coding RNAs (ncRNAs) in mitochondrial function, particularly in the context of neurodegenerative diseases (NDs), where neuroinflammation is a hallmark feature. This review highlights the collection and characterization of mitochondrial-related ncRNAs (MRncRNAs) that have been extensively studied in the context of NDs. Through a literature review, we identified 35 MRncRNAs (23 miRNAs, 8 LncRNAs, and 4 circRNAs) across Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS), Alzheimer's disease (AD), and Huntington's disease (HD). Notably, the inflammatory miRNAs miR-34a and miR-146a were commonly dysregulated in both PD and AD, while in HD, only a single miRNA, miR-196a, was identified. As expected, due to the mitochondrial nature of PD, the majority of MRncRNAs (9 miRNAs, 8 lncRNAs, and 3 circRNAs) were associated with this disorder. Further bioinformatic analysis of MRmiRNAs revealed that miR-124-5p, -146a-3p, and -15b-3p target mitochondrial genes more than others, and mRNA of pro-apoptotic protein BCL2L11 is the most targeted. Notably, the link between these MRncRNAs and mitochondrial function in MS remains unidentified. By evaluating upregulated MS-related ncRNAs in patients and comparing them with identified MRncRNAs, we found nine overlapping miRNAs (miR-15b, miR-21, miR-27b, miR-34a, miR-124, miR-137, miR-146a, miR-155, and miR-92a) as well as two shared lncRNAs, MALAT1 and HOTAIR (called MS/MRncRNAs). Further bioinformatic analysis of MS/MRmiRNAs revealed that the autophagy pathway is the most involved. Six of these miRNAs are significantly involved in MR diseases. Notably, miR-34a-5p showed a connection to oligodendrocyte mitochondria, while miR-15b targeted two MR hub genes, SDHC and BCL2. Moreover, several hub proteins (HIF1A, STAT3, MAPK1, GSK3B) targeted by these miRNAs are well-known regulators of inflammatory pathways and mitochondrial homeostasis: These findings highlight the critical roles of ncRNAs in mitochondrial dysfunction and neurodegeneration, emphasizing the urgent need for experimental studies on MRmiRNAs, particularly in the context of MS and other myelinopathies.

Regulatory T cells (Tregs) are gatekeepers of immune homeostasis and characterized by expression of Foxp3, which maintains Treg identity. The cAMP response element binding protein CREB binds the TSDR and influences Foxp3 expression. To understand the functional consequences, we generated mice with a Foxp3-specific knockout of CREB. CREB deficient Tregs expand in vivo but show a reduced Foxp3 expression combined with an enhanced expression of IL-5, IL-13, IL-10, ST2 and CREM. This renders such Tregs highly suppressive in vitro and prevents disease activity in the Th1 model of T cell mediated transfer colitis in an IL-10 dependent way while it enhanced ovalbumin mediated asthma severity. While TSDR methylation was unchanged in CREB deficient Tregs, CREB and CREM directly interact with Foxp3 and deficiency of CREB alters chromatin accessibility at the IL13 and ST2 locus. Additional genetic CREM deficiency reverses the ST2 phenotype. Our data suggest that CREB expression in Tregs is important for the regulation of ST2 mediated balance between type 1 and type 2 immune responses. ### Competing Interest Statement The authors have declared no competing interest.

Objectives: In the early phase of their studies, students are confronted with a number of teaching and learning methods they are usually not familiar with. Beyond, learning in a university environment requires a high degree of self-organization. Thus, the transition from learning in a school environment to university can be challenging for students and associated with adjustment difficulties. We hypothesized that synchronous online lecturing might be able to serve as a thematic superstructure and a curricular guide that can positively influence course perception, motivation and exam outcome.Methods: We investigated this hypothesis in a retrospective approach by comparing results from histology exams (2020 n=411, 2021 n= 423) and questionnaires for course evaluation received from medical and dentistry second semester students of the RWTH Aachen University, Germany, in 2020 (n=113 questionnaire participants) and 2021 (n=106 questionnaire participants). While in 2020, due to the Corona Pandemic, no synchronous online lectures were held, these were reintroduced in 2021.Results: Our results show several differences in between the two study cohorts. Most important findings include a significantly (p<0.001) lower number of students that failed to pass or withdrew from the exam in 2021, an increased motivation to deal with the learning content (p<0.001) and a higher perceived quality of the study materials (p<0.001) in 2021.Conclusion: Our study indicates that synchronous online lectures can be an important tool to help students to accustom to new learning en-vironments and to structure private study. Further studies will now have to show whether live (online) lectures can have the same significance during clinical training.

Spinal cord injury (SCI) results in the production of proinflammatory cytokines due to inflammasome activation. Lipocalin 2 (LCN2) is a small secretory glycoprotein upregulated by toll-like receptor (TLR) signaling in various cells and tissues. LCN2 secretion is induced by infection, injury, and metabolic disorders. In contrast, LCN2 has been implicated as an anti-inflammatory regulator. However, the role of LCN2 in inflammasome activation during SCI remains unknown. This study examined the role of Lcn2 deficiency in the NLRP3 inflammasome-dependent neuroinflammation in SCI. Lcn2−/− and wild-type (WT) mice were subjected to SCI, and locomotor function, formation of the inflammasome complex, and neuroinflammation were assessed. Our findings demonstrated that significant activation of the HMGB1/PYCARD/caspase-1 inflammatory axis was accompanied by the overexpression of LCN2 7 days after SCI in WT mice. This signal transduction results in the cleaving of the pyroptosis-inducing protein gasdermin D (GSDMD) and the maturation of the proinflammatory cytokine IL-1β. Furthermore, Lcn2−/− mice showed considerable downregulation in the HMGB1/NLRP3/PYCARD/caspase-1 axis, IL-1β production, pore formation, and improved locomotor function compared with WT. Our data suggest that LCN2 may play a role as a putative molecule for the induction of inflammasome-related neuroinflammation in SCI.

Multiple sclerosis (MS), an autoimmune-driven, inflammatory demyelinating disease of the central nervous system (CNS), causes irreversible accumulation of neurological deficits to a variable extent. Although there are potent disease-modifying agents for its initial relapsing-remitting phase, immunosuppressive therapies show limited efficacy in secondary progressive MS (SPMS). Although modulation of sphingosine-1 phosphate receptors has proven beneficial during SPMS, the underlying mechanisms are poorly understood. In this project, we followed the hypothesis that siponimod, a sphingosine-1 phosphate receptor modulator, exerts protective effects by direct modulation of glia cell function (i.e., either astrocytes, microglia, or oligodendrocytes). To this end, we used the toxin-mediated, nonautoimmune MS animal model of cuprizone (Cup) intoxication. On the histological level, siponimod ameliorated cuprizone-induced oligodendrocyte degeneration, demyelination, and axonal injury. Protective effects were evident as well using GE180 translocator protein 18-kDa (TSPO) imaging with positron emission tomography (PET)/computed tomography (CT) imaging or next generation sequencing (NGS). Siponimod also ameliorated the cuprizone-induced pathologies in Rag1-deficient mice, demonstrating that the protection is independent of T and B cell modulation. Proinflammatory responses in primary mixed astrocytes/microglia cell cultures were not modulated by siponimod, suggesting that other cell types than microglia and astrocytes are targeted. Of note, siponimod completely lost its protective effects in S1pr5-deficient mice, suggesting direct protection of degenerating oligodendrocytes. Our study demonstrates that siponimod exerts protective effects in the brain in a S1PR5-dependent manner. This finding is not just relevant in the context of MS but in other neuropathologies as well, characterized by a degeneration of the axon-myelin unit.

Abstract Background Spinal cord injury (SCI) induces a multitude of deleterious processes, including neuroinflammation and oxidative stress (OS) which contributed to neuronal damage and demyelination. Recent studies have suggested that increased formation of reactive oxygen species (ROS) and the consequent OS are critical events associated with SCI. However, there is still little information regarding the impact of these events on SCI. Astrocytes are key regulators of oxidative homeostasis in the CNS and astrocytic antioxidant responses promote the clearance of oxidants produced by neurons. Therefore, dysregulation of astrocyte physiology might largely contribute to oxidative damage. Nuclear factor erythroid 2-related factor 2 (Nrf2) is the main transcriptional regulator of cellular anti-oxidative stress responses. Methods In the current study, we hypothesized that astrocytic activation of Nrf2 protects the spinal cord post injury via suppression of neuroinflammation. Thus, using mice line with a GFAP-specific kelch-like ECH-associated protein 1 (Keap1)-deletion, we induced a hyperactivation of Nrf2 in astrocytes and further its effects on SCI outcomes. SCI-induction was performed in mice using the Infinite Horizon Spinal Cord Impactor with a force of 60 kdyn. To assess the quantitative pattern of Nrf2/ARE-activation, we included transgenic ARE-Luc mice. Data were analyzed with GraphPad Prism 8 (GraphPad Software Inc., San Diego, CA, USA). Brown–Forsythe test was performed to test for equal variances and normal distribution was tested with Shapiro–Wilk. Results In ARE-Luc mice, a significant induction of luciferase-activity was observed as early as 1 day post-injury, indicating a functional role of Nrf2-activity at the epicenter of SCI. Furthermore, SCI induced loss of neurons and oligodendrocytes, demyelination and inflammation in wild type mice. The loss of myelin and oligodendrocytes was clearly reduced in Keap1 KO mice. In addition, Keap-1 KO mice showed a significantly better locomotor function and lower neuroinflammation responses compared to wild type mice. Conclusions In summary, our in vivo bioluminescence data showed Nrf2-ARE activation during primary phase of SCI. Furthermore, we found that cell specific hyperactivation of Nrf2 was sufficient to protect the spinal cord against injury which indicate a promising therapeutic approach for SCI-treatment.

Introduction Regulatory T cells (Tregs) are gatekeepers of immune homeostasis and characterized by expression of Foxp3, which maintains Treg identity. The transcriptional activator CREB was shown to stabilize Foxp3 expression in vitro.

Multiple sclerosis (MS) is a central nervous system disease characterized by both degenerative and inflammatory processes. Various mediators are involved in the interplay of degeneration and innate immunity on one hand and peripheral adaptive immunity on the other hand. The secreted protein lipocalin 2 (LCN2) is an inflammatory modulator in a variety of pathologies. Although elevated intrathecal levels of LCN2 have been reported in MS patients, it's functional role is widely unknown. Here, we identified a subpopulation of astrocytes as a source of LCN2 in MS lesions and respective animal models. We investigated the functional role of LCN2 for both autoimmune and degenerative aspects in three MS mouse models including both wild type (WT) and Lcn2-/- mouse strains. While the experimental autoimmune encephalomyelitis (EAE) model reflects primary autoimmunity, the cuprizone model reflects selective oligodendrocyte loss and demyelination. In addition, we included a combinatory Cup/EAE model in which primary cytodegeneration is followed by inflammatory lesions within the forebrain. While in the EAE model, the disease outcome was comparable in between the two mouse strains, cuprizone intoxicated Lcn2-/- animals showed an increased loss of oligodendrocytes. In the Cup/EAE model, Lcn2-/- animals showed increased inflammation when compared to WT mice. Together, our results highlight LCN2 as a potentially protective molecule in MS lesion formation, which might be able to limit loss of oligodendrocytes immune-cell invasion. Despite these findings, it is not yet clear which glial cell phenotype (and to which extent) contributes to the observed neuroprotective effects, that is, microglia and/or astroglia or even endothelial cells in the brain.

The activation of the CXCL12-CXCR4 signaling axis is implicated in the regulation of cell survival, proliferation, and mobilization of bone marrow stem cells into the injured site. We have shown in a previous study that intrathecal administration of CXCL12 reduces spinal cord tissue damage and neuroinflammation and provides functional improvement by reducing inflammasome activity and local inflammatory processes in an experimental spinal cord injury (SCI) rat model. Here, we aimed at investigating whether these neuroprotective effects rely on the control of CXCL12 signaling on microglial activation as microglia cells are known to be the primary immune cells of the brain. LPS induced the expression of the inflammasome components NLRP3, NLRC4 and ASC, the secretion of the cytokines IL-1b and IL-18 and the activation of caspase-1 protease in BV2 cells. Pre-treatment with CXCL12 significantly reduced LPS-induced IL-1b/IL-18 secretion and inflammasome induction. Our results also showed that CXCL12 can suppress caspase-1 activity, which leads to a decrease of SCI-related induction of active IL-1b.

Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by an expanded polyglutamine repeat in the huntingtin gene. The neuropathology of HD is characterized by the decline of a specific neuronal population within the brain, the striatal medium spiny neurons (MSNs). The origins of this extreme vulnerability remain unknown. Human induced pluripotent stem cell (hiPS cell)-derived MSNs represent a powerful tool to study this genetic disease. However, the differentiation protocols published so far show a high heterogeneity of neuronal populations in vitro. Here, we compared two previously published protocols to obtain hiPS cell-derived striatal neurons from both healthy donors and HD patients. Patch-clamp experiments, immunostaining and RT-qPCR were performed to characterize the neurons in culture. While the neurons were mature enough to fire action potentials, a majority failed to express markers typical for MSNs. Voltage-clamp experiments on voltage-gated sodium (Nav) channels revealed a large variability between the two differentiation protocols. Action potential analysis did not reveal changes induced by the HD mutation. This study attempts to demonstrate the current challenges in reproducing data of previously published differentiation protocols and in generating hiPS cell-derived striatal MSNs to model a genetic neurodegenerative disorder in vitro.

Lipocalin 2 (LCN2), an immunomodulator, regulates various cellular processes such as iron transport and defense against bacterial infection. Under pathological conditions, LCN2 promotes neuroinflammation via the recruitment and activation of immune cells and glia, particularly microglia and astrocytes. Although it seems to have a negative influence on the functional outcome in spinal cord injury (SCI), the extent of its involvement in SCI and the underlying mechanisms are not yet fully known. In this study, using a SCI contusion mouse model, we first investigated the expression pattern of Lcn2 in different parts of the CNS (spinal cord and brain) and in the liver and its concentration in blood serum. Interestingly, we could note a significant increase in LCN2 throughout the whole spinal cord, in the brain, liver, and blood serum. This demonstrates the diversity of its possible sites of action in SCI. Furthermore, genetic deficiency of Lcn2 (Lcn2−/−) significantly reduced certain aspects of gliosis in the SCI-mice. Taken together, our studies provide first valuable hints, suggesting that LCN2 is involved in the local and systemic effects post SCI, and might modulate the impairment of different peripheral organs after injury.