Glioblastoma (GBM) is the most common and malignant brain tumor in adult humans. Recent studies have demonstrated a link between the composition of the gut microbiota and glioma progression. Here, we describe that the growth of glioma in mice is inversely correlated with the relative abundance of the anaerobic bacterium Muribaculum intestinale in the feces. We found that M. intestinale administration: 1) induced an inflammatory environment in the gut; 2) reduced glioma growth; 3) increased the pro-inflammatory profile of tumor-associated microglial cells and the frequency of CD8+ T cells; and 4) increased the peripheral TNF-α levels. The effects induced by M. intestinale administration were significantly attenuated upon toll-like receptor 2 (TLR2) silencing using TLR2-targeting siRNA. As a pattern-recognition receptor, TLR2 detects microbial-associated molecular patterns and orchestrates host immune responses to infection. Collectively, these data demonstrate that M. intestinale induces a pro-inflammatory response in glioma bearing mice, inhibiting tumor growth via TLR2-dependent signaling.

Sleep pressure reflects the brain's homeostatic need to sleep, but the mechanisms underlying its regulation remain poorly understood. In mice, a subset of cortical inhibitory neuronal nitric oxide synthase (nNOS) positive interneurons tunes the electroencephalographic slow wave activity in the delta band (<4 Hz), marker of sleep pressure. Here, we demonstrate that in mice the natural killer (NK) cells and innate lymphoid cells (ILC)1 depletion inhibits nNOS+ interneurons and EEG delta activity reducing the time spent in the non-rapid eye movement (NREM) sleep. The optogenetic re-activation of nNOS+ interneurons in the cingulate cortex of NK cell/ILC1-depleted mice rescues the EEG delta activity, confirming the link between innate immune cells-nNOS+ interneurons-sleep pressure. Finally, we demonstrated that meningeal NK/ILC1 cells produce IFN-γ in a circadian independent manner and that IFN-γ blockade in vivo mimics the effect of NK cell depletion in mice. These findings provide insights into the complex network involved in sleep regulation and further support the contribution of the innate immune system on sleep pressure.

The heterotrimeric G proteins are ubiquitous membrane-bound complexes specialized in the transduction of receptor-mediated extracellular signals into intracellular responses. Mutations in the G protein subunit alpha O1 (Gαo), encoded by GNAO1, have been associated with neurodevelopmental disorders characterized by prominent movement disorder with or without epilepsy. The Gnao1[C215Y]/+ mouse model recapitulates key features of the human disease, with a relatively mild phenotype, normal viability and late onset movement abnormalities, detectable in specific motor tasks. Here we report functional alterations in cortical layer V pyramidal neurons from Gnao1[C215Y]/+ mice, with reduction of the inward currents (Ih) and impairment of the GABAB-mediated outward current. We propose an adeno-associated virus (AAV)-based gene therapy aimed at overexpressing the wild-type form of Gαo by intracerebroventricular injection in newborn heterozygous Gnao1[C215Y]/ + mice. Our results demonstrate that overexpression of the wild-type protein mitigates behavioral abnormalities and restores functional neuronal deficits in young adult mice, thereby supporting the development of AAV-mediated gene augmentation strategies to counteract the effects of GNAO1 variants in patients. The potential of gene supplementation therapy is further supported by data from genetically modified C. elegans strains carrying not only the relatively mild C215Y variant but also a panel of goa-1/GNAO1 mutations associated with more severe phenotypes, suggesting a broader potential of this therapeutic strategy.

Several lines of evidence have shown that platelet-derived factors are key molecules in brain-body communication in pathological conditions. Here, we identify platelets as key actors in the modulation of fear behaviors in mice through the control of inhibitory neurotransmission and plasticity in the hippocampus. Interfering with platelet number or activation reduces hippocampal serotonin (5-HT) and modulates fear learning and memory in mice, and this effect is reversed by serotonin replacement by serotonin precursor (5-HTP)/benserazide. In addition, we unravel that natural killer (NK) cells participate in this mechanism, regulating interleukin13 (IL-13) levels in the gut, with effects on serotonin production by enterochromaffin cells and uptake by platelets. Both NK cells and platelet depletion reduce the activation of hippocampal inhibitory neurons and increase the long-term potentiation of synaptic transmission. Understanding the role of platelets in the modulation of neuro-immune interactions offers additional tools for the definition of the molecular and cellular elements involved in the growing field of brain-body communication.

Weight loss is a common early sign in amyotrophic lateral sclerosis (ALS) patients and negatively correlates with survival. In different cancers and metabolic disorders, high levels of serum growth differentiation factor 15 (GDF15) contribute to a decrease of food intake and body weight, acting through GDNF family receptor alpha-like (GFRAL). Here we report that GDF15 is highly expressed in the peripheral blood of ALS patients and in the hSOD1G93A mouse model and that GFRAL is upregulated in the brainstem of hSOD1G93A mice. We demonstrate that the localized GFRAL silencing by shRNA in the area postrema/nucleus tractus solitarius of hSOD1G93A mice induces weight gain, reduces adipose tissue wasting, ameliorates the motor function and muscle atrophy and prolongs the survival time. We report that microglial cells could be involved in mediating these effects because their depletion with PLX5622 reduces brainstem GDF15 expression, weight loss and the expression of lipolytic genes in adipose tissue. Altogether these results reveal a key role of GDF15-GFRAL signaling in regulating weight loss and the alteration of and lipid metabolism in the early phases of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no effective therapy, causing progressive loss of motor neurons in the spinal cord, brainstem, and motor cortex. Regardless of its genetic or sporadic origin, there is currently no cure for ALS or therapy that can reverse or control its progression. In the present study, taking advantage of a human superoxide dismutase-1 mutant (hSOD1-G93A) mouse that recapitulates key pathological features of human ALS, we investigated the possible role of voltage-gated potassium channel Kv1.3 in disease progression. We found that chronic administration of the brain-penetrant Kv1.3 inhibitor, PAP-1 (40 mg/Kg), in early symptomatic mice (i) improves motor deficits and prolongs survival of diseased mice (ii) reduces astrocyte reactivity, microglial Kv1.3 expression, and serum pro-inflammatory soluble factors (iii) improves structural mitochondrial deficits in motor neuron mitochondria (iv) restores mitochondrial respiratory dysfunction. Taken together, these findings underscore the potential significance of Kv1.3 activity as a contributing factor to the metabolic disturbances observed in ALS. Consequently, targeting Kv1.3 presents a promising avenue for modulating disease progression, shedding new light on potential therapeutic strategies for ALS.

In recent years, biomedical research efforts aimed to unravel the mechanisms involved in motor neuron death that occurs in amyotrophic lateral sclerosis (ALS). While the main causes of disease progression were first sought in the motor neurons, more recent studies highlight the gliocentric theory demonstrating the pivotal role of microglia and astrocyte, but also of infiltrating immune cells, in the pathological processes that take place in the central nervous system microenvironment. From this point of view, microglia-astrocytes-lymphocytes crosstalk is fundamental to shape the microenvironment toward a pro-inflammatory one, enhancing neuronal damage. In this review, we dissect the current state-of-the-art knowledge of the microglial dialogue with other cell populations as one of the principal hallmarks of ALS progression. Particularly, we deeply investigate the microglia crosstalk with astrocytes and immune cells reporting in vitro and in vivo studies related to ALS mouse models and human patients. At last, we highlight the current experimental therapeutic approaches that aim to modulate microglial phenotype to revert the microenvironment, thus counteracting ALS progression.

The mechanisms of communication between the brain and the immune cells are still largely unclear. Here, we characterize the populations of resident natural killer (NK) cells and innate lymphoid cells (ILC) 1 in the meningeal dura layer of adult mice. We describe that ILC1/NK cell-derived interferon-γ and acetylcholine can contribute to the modulation of brain homeostatic functions, shaping synaptic neuronal transmission and neurotransmitter levels with effects on mice behavior. In detail, the interferon-γ plays a role in the formation of non-spatial memory, tuning the frequency of GABAergic neurotransmission on cortical pyramidal neurons, while the acetylcholine is a mediator involved in the modulation of brain circuitries that regulate anxiety-like behavior. These findings disclose mechanisms of immune-to-brain communication that modulate brain functions under physiological conditions.

Duchenne muscular dystrophy (DMD) is an X-linked disease, caused by a mutant dystrophin gene, leading to muscle membrane instability, followed by muscle inflammation, infiltration of pro-inflammatory macrophages and fibrosis. The calcium-activated potassium channel type 3.1 (KCa3.1) plays key roles in controlling both macrophage phenotype and fibroblast proliferation, two critical contributors to muscle damage. In this work, we demonstrate that pharmacological blockade of the channel in the mdx mouse model during the early degenerative phase favors the acquisition of an anti-inflammatory phenotype by tissue macrophages and reduces collagen deposition in muscles, with a concomitant reduction of muscle damage. As already observed with other treatments, no improvement in muscle performance was observed in vivo. In conclusion, this work supports the idea that KCa3.1 channels play a contributing role in controlling damage-causing cells in DMD. A more complete understanding of their function could lead to the identification of novel therapeutic approaches.

Neuroinflammation is one of the main hallmarks of amyotrophic lateral sclerosis (ALS). Recently, peripheral immune cells were discovered as pivotal players that promptly participate in this process, speeding up neurodegeneration during progression of the disease. In particular, infiltrating T cells and natural killer cells release inflammatory cytokines that switch glial cells toward a pro-inflammatory/detrimental phenotype, and directly attack motor neurons with specific ligand-receptor signals. Here, we assessed the presence of lymphocytes in the spinal cord of sporadic ALS patients. Furthermore, we demonstrate that blocking the extravasation of immune cells in the central nervous system using Natalizumab (NAT), an antibody for the α4 integrin, reduces the level of interferon-γ in the spinal cord of ALS mouse models, such as the hSOD1G93A and TDP43A315T mice, modifying microglia and astrocytes phenotype, increasing motor neuron number and prolonging the survival time. Taken together, our results establish a central role for the immune cells as drivers of inflammation in ALS.

Many epigenetic modifications occur in glioma, in particular the histone-deacetylase class proteins play a pivotal role in glioma development, driving the proliferation rate and the invasiveness of tumor cells, and modulating the tumor microenvironment. In this study, we evaluated the role of the histone deacetylase HDAC8 in the regulation of the immune response in glioma and tumor growth. We found that inhibition of HDAC8 by the specific inhibitor PCI-34051 reduces tumor volume in glioma mouse models. We reported that HDAC8 modulates the viability and the migration of human and murine glioma cells. Interestingly, HDAC8 inhibition increases the acetylation of alpha-tubulin, suggesting this epigenetic modification controls glioma migration. Furthermore, we identify HDAC8 as a key molecule that supports a poorly immunogenic tumor microenvironment, modulating microglial phenotype and regulating the gene transcription of NKG2D ligands that trigger the Natural Killer cell-mediated cytotoxicity of tumor cells. Altogether, these results identify HDAC8 as a key actor in glioma growth and tumor microenvironment, and pave the way to a better knowledge of the molecular mechanisms of immune escape in glioma.

Abstract Background Intracellular Ca2+ modulates several microglial activities, such as proliferation, migration, phagocytosis, and inflammatory mediator secretion. Extracellular ATP, the levels of which significantly change during epileptic seizures, activates specific receptors leading to an increase of intracellular free Ca2+ concentration ([Ca2+]i). Here, we aimed to functionally characterize human microglia obtained from cortices of subjects with temporal lobe epilepsy, focusing on the Ca2+-mediated response triggered by purinergic signaling. Methods Fura-2 based fluorescence microscopy was used to measure [Ca2+]i in primary cultures of human microglial cells obtained from surgical specimens. The perforated patch-clamp technique, which preserves the cytoplasmic milieu, was used to measure ATP-evoked Ca2+-dependent whole-cell currents. Results In human microglia extracellular ATP evoked [Ca2+]i increases depend on Ca2+ entry from the extracellular space and on Ca2+ mobilization from intracellular compartments. Extracellular ATP also induced a transient fivefold potentiation of the total transmembrane current, which was completely abolished when [Ca2+]i increases were prevented by removing external Ca2+ and using an intracellular Ca2+ chelator. TRAM-34, a selective KCa3.1 blocker, significantly reduced the ATP-induced current potentiation but did not abolish it. The removal of external Cl− in the presence of TRAM-34 further lowered the ATP-evoked effect. A direct comparison between the ATP-evoked mean current potentiation and mean Ca2+ transient amplitude revealed a linear correlation. Treatment of microglial cells with LPS for 48 h did not prevent the ATP-induced Ca2+ mobilization but completely abolished the ATP-mediated current potentiation. The absence of the Ca2+-evoked K+ current led to a less sustained ATP-evoked Ca2+ entry, as shown by the faster Ca2+ transient kinetics observed in LPS-treated microglia. Conclusions Our study confirms a functional role for KCa3.1 channels in human microglia, linking ATP-evoked Ca2+ transients to changes in membrane conductance, with an inflammation-dependent mechanism, and suggests that during brain inflammation the KCa3.1-mediated microglial response to purinergic signaling may be reduced.

Several types of cancer grow differently depending on the environmental stimuli they receive. In glioma, exposure to an enriched environment (EE) increases the overall survival rate of tumor-bearing mice, acting on the cells that participate to define the tumor microenvironment. In particular, environmental cues increase the microglial production of interleukin (IL)-15 which promotes a pro-inflammatory (antitumor) phenotype of microglia and the cytotoxic activity of natural killer (NK) cells, counteracting glioma growth, thus representing a virtuous mechanism of interaction between NK cells and microglia. To mimic the effect of EE on glioma, we investigated the potential of creating engineered microglia as the source of IL-15 in glioma. We demonstrated that microglia modified with recombinant adeno-associated virus serotype 2 (rAAV2) carrying IL-15 (rAAV2-IL-15), to force the production of IL-15, are able to increase the NK cells viability in coculture. Furthermore, the intranasal delivery of rAAV2-IL-15 microglia triggered the interplay with NK cells in vivo, enhancing NK cell recruitment and pro-inflammatory microglial phenotype in tumor mass of glioma-bearing mice, and ultimately counteracted tumor growth. This approach has a high potential for clinical translatability, highlighting the therapeutic efficacy of forced IL-15 production in microglia: the delivery of engineered rAAV2-IL-15 microglia to boost the immune response paves the way to design a new perspective therapy for glioma patients.

The growing interest in the role of microglia in the progression of many neurodegenerative diseases is developing in an ever-expedited manner, in part thanks to emergent new tools for studying the morphological and functional features of the CNS. The discovery of specific biomarkers of the microglia phenotype could find application in a wide range of human diseases, and creates opportunities for the discovery and development of tailored therapeutic interventions. Among these, recent studies highlight the pivotal role of the potassium channels in regulating microglial functions in physiological and pathological conditions such as Alzheimer's Disease, Parkinson's Disease, and Amyotrophic Lateral Sclerosis. In this review, we summarize the current knowledge of the involvement of the microglial potassium channels in several neurodegenerative diseases and their role as modulators of microglial homeostasis and dysfunction in CNS disorders.

Background and Purpose Amyotrophic lateral sclerosis (ALS) patients exhibit dysfunctional energy metabolism and weight loss, which is negatively correlated with survival, together with neuroinflammation. However, the possible contribution of neuroinflammation to deregulations of feeding behaviour in ALS has not been studied in detail. We here investigated if microglial K Ca 3.1 is linked to hypothalamic neuroinflammation and affects feeding behaviours in ALS mouse models. Experimental Approach hSOD1 G93A and TDP43 A315T mice were treated daily with 120 mg·kg −1 of TRAM‐34 or vehicle by intraperitoneal injection from the presymptomatic until the disease onset phase. Body weight and food intake were measured weekly. The later by weighing food provided minus that left in the cage. RT‐PCR and immunofluorescence analysis were used to characterize microglia phenotype and the main populations of melanocortin neurons in the hypothalamus of hSOD1 G93A and age‐matched non‐tg mice. The cannabinoid–opioid interactions in feeding behaviour of hSOD1 G93A mice were studied using an inverse agonist and an antagonist of the cannabinoid receptor CB 1 (rimonabant) and μ‐opioid receptors (naloxone), respectively. Key Results We found that treatment of hSOD1 G93A mice with the K Ca 3.1 inhibitor TRAM‐34 (i), attenuates the pro‐inflammatory phenotype of hypothalamic microglia, (ii) increases food intake and promotes weight gain, (iii) increases the number of healthy pro‐opiomelanocortin (POMC) neurons and (iv), changes the expression of cannabinoid receptors involved in energy homeostasis. Conclusion and Implications Using ALS mouse models, we describe defects in the hypothalamic melanocortin system that affect appetite control. These results reveal a new regulatory role for K Ca 3.1 to counteract weight loss in ALS.

In amyotrophic lateral sclerosis (ALS), immune cells and glia contribute to motor neuron (MN) degeneration. We report the presence of NK cells in post-mortem ALS motor cortex and spinal cord tissues, and the expression of NKG2D ligands on MNs. Using a mouse model of familial-ALS, hSOD1 G93A , we demonstrate NK cell accumulation in the motor cortex and spinal cord, with an early CCL2-dependent peak. NK cell depletion reduces the pace of MN degeneration, delays motor impairment and increases survival. This is confirmed in another ALS mouse model, TDP43 A315T . NK cells are neurotoxic to hSOD1 G93A MNs which express NKG2D ligands, while IFNγ produced by NK cells instructs microglia toward an inflammatory phenotype, and impairs FOXP3 + /Treg cell infiltration in the spinal cord of hSOD1 G93A mice. Together, these data suggest a role of NK cells in determining the onset and progression of MN degeneration in ALS, and in modulating Treg recruitment and microglia phenotype.

Recent studies described a critical role for microglia in amyotrophic lateral sclerosis (ALS), where these CNS- resident immune cells participate in the establishment of an in fl ammatory microenvironment that contributes to motor neuron degeneration. Understanding the mechanisms leading to microglia activation in ALS could help to identify speci fi c molecular pathways which could be targeted to reduce or delay motor neuron degeneration and muscle paralysis in patients. The intermediate-conductance calcium-activated potassium channel KCa3.1 has been reported to modulate the “ pro-in fl ammatory ” phenotype of microglia in di ff erent pathological conditions. We here investigated the e ff ects of blocking KCa3.1 activity in the hSOD1 G93A ALS mouse model, which recapitulates many features of the human disease. We report that treatment of hSOD1 G93A mice with a selective KCa3.1 inhibitor, 1-[(2-chlorophenyl)diphenylmethyl]-1 H -pyrazole (TRAM-34), attenuates the “ pro-in fl ammatory ” phenotype of mi- croglia in the spinal cord, reduces motor neuron death, delays onset of muscle weakness, and increases survival. Speci fi cally, inhibition of KCa3.1 channels slowed muscle denervation, decreased the expression of the fetal acetylcholine receptor γ subunit and reduced neuromuscular junction damage. Taken together, these results demonstrate a key role for KCa3.1 in driving a pro-in fl ammatory microglia phenotype in ALS.

Recent studies described a critical role for microglia in amyotrophic lateral sclerosis (ALS), where these CNS-resident immune cells participate in the establishment of an inflammatory microenvironment that contributes to motor neuron degeneration. Understanding the mechanisms leading to microglia activation in ALS could help to identify specific molecular pathways which could be targeted to reduce or delay motor neuron degeneration and muscle paralysis in patients. The intermediate-conductance calcium-activated potassium channel KCa3.1 has been reported to modulate the "pro-inflammatory" phenotype of microglia in different pathological conditions. We here investigated the effects of blocking KCa3.1 activity in the hSOD1G93AALS mouse model, which recapitulates many features of the human disease. We report that treatment of hSOD1G93A mice with a selective KCa3.1 inhibitor, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), attenuates the "pro-inflammatory" phenotype of microglia in the spinal cord, reduces motor neuron death, delays onset of muscle weakness, and increases survival. Specifically, inhibition of KCa3.1 channels slowed muscle denervation, decreased the expression of the fetal acetylcholine receptor γ subunit and reduced neuromuscular junction damage. Taken together, these results demonstrate a key role for KCa3.1 in driving a pro-inflammatory microglia phenotype in ALS.

Object: Although several epidemiological studies show a clear association between late-life dementia/sporadic Alzheimer's disease (AD) and hypertension, little is known about the effects of chronic hypertension on AD neuropathological changes. Recent evidence indicate that inflammation is a common pathophysiological trait of both hypertension and AD. Therefore, we hypothesize that hypertension could promote a recruitment of the neuroinflammatory response, through activation of microglia, the brain resident macrophages and favor the onset and progression of late-life dementia/sporadic AD. Design and Method: To explore the possible dynamic interaction among hypertension, inflammation and amyloid deposition, a typical trait of AD pathology, we focused on a particular mouse model of arterial hypertension, obtained by transverse aortic coarctation (TAC), selectively imposing a pressure overload to the cerebral circulation. Results and Conclusions: The analysis of Aβ, the main component of AD senile plaques, revealed that a significant deposition of Aβin brain parenchyma and around blood vessels started four weeks after TAC. Thus, we investigated the relevance of neuroinflammation in the onset and/or progression of the amyloid-related pathology analyzing 3-week TAC mice, an early time preceding Aβ deposition, and 8-week TAC mice, when Aβis overt. We found early microglial activation in 3-week TAC mice, suggesting a neuroinflammatory reaction preceding evident Aβ deposition and triggered by hypertension per se. Concomitantly, important pro-inflammatory cytokines, typically involved in AD, were clearly up-regulated. This response was even more pronounced at a later time with clear brain Aβ deposition. Finally, we stimulated the immune system with a LPS challenge, a strategy described to be able to modulate neuroinflammation. Remarkably, we found that LPS strongly reduced TAC-induced parenchymal and perivascular Aβ deposition, thus indicating that modulation of neuroinflammation can be a novel target to prevent or limit hypertension-induced AD-related neurodegenerative processes.