Therapeutisches Potenzial von natürlich synthetisierten entzündungshemmenden Mediatoren bei neuroinflammatorischen Prozessen

The central nervous system (CNS) requires special and robust protection against damage, partly it can not regenerate. Various protective mechanisms, including the blood-brain barrier (BBB), ensure a controlled microenvironment and safeguard against external threats. For many decades, the brain was considered an immune privileged organ. However, extensive research has shown that neuroimmune interactions occur both during pathological events and under homeostatic conditions. Peripheral infections influencing brain function underscore the interplay between the brain and peripheral immunity. While acute infections, even if they are localized in the periphery and not in the brain itself, activate the brain's resident immune cells, the microglia, to defend the host, prolonged and uncontrolled inflammation can disrupt the homeostatic balance and cause neuronal damage. Chronic immune activation is increasingly recognized as a contributing factor to the development of neurodegenerative diseases such as Alzheimer's disease, which has an alarmingly increasing prevalence. Consequently, targeting inflammatory signaling pathways offers potential therapeutic strategies for various neuropathological conditions by mitigating inflammation. Itaconate, a metabolite derived from the tricarboxylic acid cycle (TCA) cycle metabolite, is produced in macrophages during inflammation and has been demonstrated to significantly affect immune responses. Both itaconate and its recently identified isomer mesaconate, serve as immunomodulators with anti-inflammatory effects. However, most research has focused on their chemically modified variants and their peripheral effects, leaving their impact on the CNS largely unexplored. Therefore, this study investigated whether itaconate and mesaconate alleviate the inflammation in the brain, triggered by lipopolysaccharide (LPS) or influenza-A virus (IAV) infection. The results indicate that both metabolites possess the capacity to attenuate LPS-induced neuroinflammation, as evidenced by lower levels of inflammatory mediators, decreased microglial reactivity and enhanced synaptic plasticity, but showed limited efficacy in the IAV infection model. Additionally, the study presented here explored the impact of the immune-responsive gene 1 (Irg1)-deletion, and its respective lack of endogenous itaconate production, on LPS-induced neuroinflammation. Comparing IRG1-knockout (KO) mice with wild type (WT) mice revealed only a slight increase in neuroinflammation in the former, suggesting a limited anti-inflammatory effect of endogenous itaconate in the brain. Finally, this study examined the effects of interleukin-37 (IL-37), another anti-inflammatory molecule, on LPS-induced neuroinflammation. Despite its known anti-inflammatory properties, pretreatment of mice with recombinant IL-37 had no preventive effect on LPS-induced neuroinflammatory processes, suggesting that more attention needs to be paid to the treatment regimen with anti-inflammatory agents. Overall, the results of this thesis decipher the potential therapeutic strategies against neuroinflammation.Das zentrale Nervensystem (ZNS) bedarf speziellen Schutz gegen Schädigungen, den vor allem die Blut-Hirn-Schranke gewährleistet. Sie sichert eine kontrollierte Mikroumgebung und schützt vor externen Bedrohungen. Früher als immunprivilegiert betrachtet, zeigt die Forschung heute, dass das Gehirn unter normalen und pathologischen Bedingungen neuroimmunologische Wechselwirkungen aufweist. Periphere Infektionen beeinflussen die Gehirnfunktion und verdeutlichen die komplexe Verbindung zwischen dem Gehirn und dem Immunsystem. Starke oder chronische Entzündungen können die im Gehirn ansässigen Immunzellen, die Mikroglia, aktivieren und homöostatische Prozesse stören. Zudem zeigten jüngste Erkenntnisse, dass diese neuroinflammatorischen Prozesse zu neurodegenerativen Erkrankungen wie Alzheimer beitragen. Entzündungshemmende Therapien bieten daher vielversprechende Behandlungsansätze für verschiedene neuropathologische Zustände. Kürzlich wurde gezeigt, dass Itaconat, ein Metabolit aus dem Tricarbonsäurezyklus in aktivierten Makrophagen heraufreguliert wird und eine wichtige Rolle in der Immunantwort spielt. Darüber hinaus haben sich sowohl Itaconat, als auch sein kürzlich entdecktes Isomer Mesaconat, als wirksame Immunmodulatoren mit entzündungshemmenden Eigenschaften erwiesen. Die meisten Studien konzentrieren sich allerdings auf chemisch modifizierte Derivate von Itaconat und ihre peripheren Effekte, wodurch ihre Auswirkungen auf das ZNS weitgehend unerforscht bleiben. In der hier präsentierten Studie wurde erforscht, ob Itaconat und Mesaconat neuroinflammatorische Reaktionen, verursacht durch Lipopolysaccharid (LPS) oder das Influenza-A-Virus (IAV), im Gehirn mildern können. Die Ergebnisse zeigen, dass beide Metabolite Entzündungsprozesse im LPS-Modell reduzieren, was sich in einer Verringerung von Entzündungsmediatoren, geringerer Mikroglia-Reaktivität, und erhaltender synaptischer Plastizität manifestiert, welche in den Kontrollen ohne Metabolitverabreichung stark eingeschränkt war. Allerdings blieb ein vergleichbarer Effekt im gewählten IAV-Modell weitgehend aus. Die Studie untersucht außerdem, wie sich das Fehlen endogener Itaconat-Produktion auf LPS-induzierte Neuroinflammation auswirkt. Der Vergleich von Irg1-defizienten Mäusen, die kein Itaconat produzieren, mit Wildtyp-Mäusen (WT) zeigt nur einen leichten Anstieg der Neuroinflammation bei Ersteren im Vergleich zu den WT, was die begrenzte präventive Wirkung von endogenem Itaconat im ZNS nahelegt. Zuletzt wurde die Wirkung von Interleukin-37 (IL-37), einem weiteren entzündungshemmenden Molekül, auf die LPS-induzierte Neuroinflammation untersucht. Obwohl IL-37 für seine entzündungshemmenden Eigenschaften bekannt ist, ergab die Vorbehandlung von LPS-exponierten Mäusen mit einer rekombinanten Form von IL-37 keine signifikante Veränderung der Entzündungsreaktionen im Gehirn, was ein begrenztes therapeutisches Potential andeutet. Die Ergebnisse dieser Arbeit liefern insgesamt einen Einblick in potenzielle therapeutische Strategien zur Bekämpfung von Neuroinflammation

Forschendes Lernen als „eine Haltung, die imstande ist, das Zweifelhafte zu genießen“: Zur Produktivität des pragmatistischen Lern- und Forschungsbegriffs am Beispiel des Gegenstands Mehrsprachigkeit im Fachgebiet Deutsch als Zweitsprache des Lehramtsstudiums

Ohm U. Forschendes Lernen als „eine Haltung, die imstande ist, das Zweifelhafte zu genießen“: Zur Produktivität des pragmatistischen Lern- und Forschungsbegriffs am Beispiel des Gegenstands Mehrsprachigkeit im Fachgebiet Deutsch als Zweitsprache des Lehramtsstudiums. In: Basten M, Mertens C, Schöning A, Wolf E, eds. Forschendes Lernen in der Lehrer/innenbildung. Implikationen für Wissenschaft und Praxis. Münster: Waxmann; 2020: 229-236

Fast Regulation of GABA(A)R Diffusion Dynamics by Nogo-A Signaling

Precisely controlling the excitatory and inhibitory balance is crucial for the stability and information-processing ability of neuronal networks. However, the molecular mechanisms maintaining this balance during ongoing sensory experiences are largely unclear. We show that Nogo-A signaling reciprocally regulates excitatory and inhibitory transmission. Loss of function for Nogo-A signaling through S1PR2 rapidly increases GABAAR diffusion, thereby decreasing their number at synaptic sites and the amplitude of GABAergic mIPSCs at CA3 hippocampal neurons. This increase in GABAAR diffusion rate is correlated with an increase in Ca2+ influx and requires the calcineurin-mediated dephosphorylation of the γ2 subunit at serine 327. These results suggest that Nogo-A signaling rapidly strengthens inhibitory GABAergic transmission by restricting the diffusion dynamics of GABAARs. Together with the observation that Nogo-A signaling regulates excitatory transmission in an opposite manner, these results suggest a crucial role for Nogo-A signaling in modulating the excitation and inhibition balance to restrict synaptic plasticity

Fast Regulation of GABAR Diffusion Dynamics by Nogo-A Signaling.

Precisely controlling the excitatory and inhibitory balance is crucial for the stability and information-processing ability of neuronal networks. However, the molecular mechanisms maintaining this balance during ongoing sensory experiences are largely unclear. We show that Nogo-A signaling reciprocally regulates excitatory and inhibitory transmission. Loss of function for Nogo-A signaling through S1PR2 rapidly increases GABAAR diffusion, thereby decreasing their number at synaptic sites and the amplitude of GABAergic mIPSCs at CA3 hippocampal neurons. This increase in GABAAR diffusion rate is correlated with an increase in Ca2+ influx and requires the calcineurin-mediated dephosphorylation of the γ2 subunit at serine 327. These results suggest that Nogo-A signaling rapidly strengthens inhibitory GABAergic transmission by restricting the diffusion dynamics of GABAARs. Together with the observation that Nogo-A signaling regulates excitatory transmission in an opposite manner, these results suggest a crucial role for Nogo-A signaling in modulating the excitation and inhibition balance to restrict synaptic plasticity

IL-37 expression reduces acute and chronic neuroinflammation and rescues cognitive impairment in an Alzheimer's disease mouse model

The anti-inflammatory cytokine interleukin-37 (IL-37) belongs to the IL-1 family but is not expressed in mice. We used a human IL-37 (hIL-37tg) expressing mouse, which has been subjected to various models of local and systemic inflammation as well as immunological challenges. Previous studies reveal an immunomodulatory role of IL-37, which can be characterized as an important suppressor of innate immunity. Here, we examined the functions of IL-37 in the central nervous system and explored the effects of IL-37 on neuronal architecture and function, microglial phenotype, cytokine production and behavior after inflammatory challenge by intraperitoneal LPS-injection. In wild-type mice, decreased spine density, activated microglial phenotype and impaired long-term potentiation (LTP) were observed after LPS injection, whereas hIL-37tg mice showed no impairment. In addition, we crossed the hIL-37tg mouse with an animal model of Alzheimer’s disease (APP/PS1) to investigate the anti-inflammatory properties of IL-37 under chronic neuroinflammatory conditions. Our results show that expression of IL-37 is able to limit inflammation in the brain after acute inflammatory events and prevent loss of cognitive abilities in a mouse model of AD

Influenza vaccine is able to prevent neuroinflammation triggered by H7N7 IAV infection

Influenza A virus (IAV) subtypes are a major cause of illness and mortality worldwide and pose a threat to human health. Although IAV infection is considered a self-limiting respiratory syndrome, an expanded spectrum of cerebral manifestations has been reported following IAV infection. Neurotropic IAVs, such as the H7N7 subtype, are capable of invading the central nervous system (CNS) and replicating in brain cells, resulting in microglia-induced neuroinflammation. Microglial cells, the brain's resident immune cells, are instrumental in the inflammatory response to viral infection. While activation of microglia is important to initially contain the virus, excessive activation of these cells leads to neuronal damage. Previous studies have shown that acute and even long-term IAV-induced neuroinflammation leads to CNS damage. Therefore, the search for possible preventive or therapeutic strategies is of great importance. In this study, we investigated the potential effect of vaccination against acute neuroinflammation induced by H7N7 infection and subsequent neuronal damage in the hippocampus, a particularly vulnerable brain region, comparing young and aged mice. Immunosenescence is one of the striking pathophysiological changes during mammalian aging that leads to "inflammaging" and critically limits the protection by vaccines in the elderly. The results suggest that formalin-inactivated H7N7 vaccine has a preventive effect against the inflammatory responses in the periphery and also in the CNS after H7N7 infection. Cytokine and chemokine levels, increased microglial density, and cell volume after H7N7 infection were all attenuated by vaccination. Further structural analysis of microglial cells also revealed a change in branching complexity after H7N7 infection, most likely reflecting the neuroprotective effect of the vaccination. In addition, synapse loss was prevented in vaccinated mice. Remarkably, engulfment of post-synaptic compartments by microglia can be proposed as the underlying mechanism for spine loss triggered by H7N7 infection, which was partially modulated by vaccination. Although young mice showed better protection against neuroinflammation and the resulting deleterious neuronal effects upon vaccination, a beneficial role of the vaccine was also observed in the brains of older mice. Therefore, vaccination can be proposed as an important strategy to prevent neurological sequelae of H7N7 infection

SiMeEx, a simplified method for metabolite extraction of adherent mammalian cells

A reliable method for metabolite extraction is central to mass spectrometry-based metabolomics. However, existing methods are lengthy, mostly due to the step of scraping cells from cell culture vessels, which restricts metabolomics in broader application such as lower cell numbers and high-throughput studies. Here, we present a simplified metabolite extraction (SiMeEx) method, to efficiently and quickly extract metabolites from adherent mammalian cells. Our method excludes the cell scraping step and therefore allows for a more efficient extraction of polar metabolites in less than 30 min per 12-well plate. We demonstrate that SiMeEx achieves the same metabolite recovery as using a standard method containing a scraping step, in various immortalized and primary cells. Omitting cell scraping does not compromise the performance of non-targeted and targeted GC-MS analysis, but enables metabolome analysis of cell culture on smaller well sizes down to 96-well plates. Therefore, SiMeEx demonstrates advantages not only on time and resources, but also on the applicability in high-throughput studies