Periyasamy P, Thangaraj A, Guo ML, Hu G, Callen S, Buch S.
PMID: 29760177 | DOI: 10.1523/JNEUROSCI.3474-17.2018
The present study demonstrates HIV-1 Tat-mediated epigenetic downregulation of microglial miR-124 and its association with microglial activation. Exposure of mouse primary microglia isolated from newborn pups of either sex to HIV-1 Tat resulted in decreased expression of primary miR-124-1, primary miR-124-2 as well as the mature miR-124. In parallel, HIV-1 Tat exposure to mouse primary microglial cellsresulted in increased expression of DNA methylation enzymes, such as DNMT1, DNMT3A, and DNMT3B that were also accompanied by increased global DNA methylation. Bisulfite-converted genomic DNA sequencing in the HIV-1 Tat exposed mouse primary microglial cellsfurther confirmed increased DNA methylation of the primary miR-124-1 and primary miR-124-2 promoters. Bioinformatic analyses identified MECP2 as a novel 3'-UTR target of miR-124. This was further validated in mouse primary microglial cells wherein HIV-1 Tat-mediated downregulation of miR-124 resulted in increased expression of MECP2, leading in turn to further repression of miR-124 via the feedback loop. In addition to MECP2, miR-124 also modulated the levels of STAT3 through its binding to the 3'-UTR, leading to microglial activation. Luciferase assays and Ago2 immunoprecipitation determined the direct binding between miR-124 and 3'-UTR of both MECP2 and STAT3. Gene silencing of MECP2 and DNMT1 and overexpression of miR-124 blocked HIV-1 Tat-mediated downregulation of miR-124 and microglial activation. In vitro findings were also confirmed in the basal ganglia of SIV-infected rhesus macaques (both sexes). In summary, our findings demonstrate a novel mechanism of HIV-1 Tat-mediated activation of microglia via downregulation of miR-124, leading ultimately to increased MECP2 and STAT3 signaling.
SIGNIFICANCE STATEMENT
Despite the effectiveness of combination antiretroviral therapy in controlling viremia, the CNS continues to harbor viral reservoirs. The persistence of low-level virus replication leads to the accumulation of early viral proteins including HIV-1 Tat protein. Understanding the epigenetic/molecular mechanism(s) by which viral proteins such as HIV-1 Tat can activate microglia is thus of paramount importance. This study demonstrated HIV-1 Tat-mediated DNA methylation of the miR-124 promoter leads to its downregulation with a concomitant upregulation of the MECP2-STAT3-IL6 resulting in microglial activation. These findings reveal an unexplored epigenetic/molecular mechanism(s) underlying HIV-1 Tat-mediated microglial activation, thereby providing a potential target for the development of therapeutics aimed at ameliorating microglial activation and neuroinflammation in the context of HIV-1 infection.
Timper K, Paeger L, Sánchez-Lasheras C, Varela L, Jais A, Nolte H, Vogt MC, Hausen AC, Heilinger C, Evers N, Pospisilik JA, Penninger JM, Taylor EB, Horvath TL, Kloppenburg P, Brüning JC.
PMID: 30304679 | DOI: 10.1016/j.celrep.2018.09.034
Mitochondrial oxidative phosphorylation (OXPHOS) and substrate utilization critically regulate the function of hypothalamic proopiomelanocortin (POMC)-expressing neurons. Here, we demonstrate that inactivation of apoptosis-inducing factor (AIF) in POMC neurons mildly impairs mitochondrial respiration and decreases firing of POMC neurons in lean mice. In contrast, under diet-induced obese conditions, POMC-Cre-specific inactivation of AIF prevents obesity-induced silencing of POMC neurons, translating into improved glucose metabolism, improved leptin, and insulin sensitivity, as well as increased energy expenditure in AIFΔPOMC mice. On a cellular level, AIF deficiency improves mitochondrial morphology, facilitates the utilization of fatty acids for mitochondrial respiration, and increases reactive oxygen species (ROS) formation in POMC neurons from obese mice, ultimately leading to restored POMC firing upon HFD feeding. Collectively, partial impairment of mitochondrial function shifts substrate utilization of POMC neurons from glucose to fatty acid metabolism and restores their firing properties, resulting in improved systemic glucose and energy metabolism in obesity.
The Journal of clinical investigation
Tu, L;Bean, JC;He, Y;Liu, H;Yu, M;Liu, H;Zhang, N;Yin, N;Han, J;Scarcelli, NA;Conde, KM;Wang, M;Li, Y;Feng, B;Gao, P;Cai, ZL;Fukuda, M;Xue, M;Tong, Q;Yang, Y;Liao, L;Xu, J;Wang, C;He, Y;Xu, Y;
PMID: 37261917 | DOI: 10.1172/JCI163391
Although glucose is the basic fuel essential to maintain the viability and functions of all cells, some neurons, namely glucose-inhibited (GI) neurons, paradoxically increase their firing activities when glucose falls and are inhibited by high glucose. The ionic mechanisms mediating electric responses of GI neurons to glucose fluctuations remain unclear. Here we showed that currents mediated by anoctamin 4 (Ano4) channel are only detected in GI neurons in the ventromedial hypothalamic nucleus (VMH) and are functionally required for their activation in response to low glucose. Genetic disruption of the Ano4 gene in VMH neurons reduced blood glucose and impaired counterregulatory responses during hypoglycemia in mice. Activation of VMHAno4 neurons increased food intake and blood glucose, while chronic inhibition of VMHAno4 neurons ameliorated hyperglycemia in a type 1 diabetic mouse model. Finally, we showed that VMHAno4 neurons represent a unique orexigenic VMH population and transmit a positive valence, while stimulation of non-Ano4 neurons in the VMH suppress feeding and transmit a negative valence. Together, our results indicate that the Ano4 channel and VMHAno4 neurons are potential therapeutic targets for human diseases with abnormal feeding behavior or glucose imbalance.
Becker, K;Weigelt, CM;Fuchs, H;Viollet, C;Rust, W;Wyatt, H;Huber, J;Lamla, T;Fernandez-Albert, F;Simon, E;Zippel, N;Bakker, RA;Klein, H;Redemann, NH;
PMID: 36371417 | DOI: 10.1038/s41598-022-23065-4
Retinopathies are multifactorial diseases with complex pathologies that eventually lead to vision loss. Animal models facilitate the understanding of the pathophysiology and identification of novel treatment options. However, each animal model reflects only specific disease aspects and understanding of the specific molecular changes in most disease models is limited. Here, we conducted transcriptome analysis of murine ocular tissue transduced with recombinant Adeno-associated viruses (AAVs) expressing either human VEGF-A, TNF-α, or IL-6. VEGF expression led to a distinct regulation of extracellular matrix (ECM)-associated genes. In contrast, both TNF-α and IL-6 led to more comparable gene expression changes in interleukin signaling, and the complement cascade, with TNF-α-induced changes being more pronounced. Furthermore, integration of single cell RNA-Sequencing data suggested an increase of endothelial cell-specific marker genes by VEGF, while TNF-α expression increased the expression T-cell markers. Both TNF-α and IL-6 expression led to an increase in macrophage markers. Finally, transcriptomic changes in AAV-VEGF treated mice largely overlapped with gene expression changes observed in the oxygen-induced retinopathy model, especially regarding ECM components and endothelial cell-specific gene expression. Altogether, our study represents a valuable investigation of gene expression changes induced by VEGF, TNF-α, and IL-6 and will aid researchers in selecting appropriate animal models for retinopathies based on their agreement with the human pathophysiology.
Shimbori, C;De Palma, G;Baerg, L;Lu, J;Verdu, EF;Reed, DE;Vanner, S;Collins, SM;Bercik, P;
PMID: 35905313 | DOI: 10.1080/19490976.2022.2105095
Both mast cells and microbiota play important roles in the pathogenesis of Irritable Bowel Syndrome (IBS), however the precise mechanisms are unknown. Using microbiota-humanized IBS mouse model, we show that colonic mast cells and mast cells co-localized with neurons were higher in mice colonized with IBS microbiota compared with those with healthy control (HC) microbiota. In situ hybridization showed presence of IBS, but not control microbiota, in the lamina propria and RNAscope demonstrated frequent co-localization of IBS bacteria and mast cells. TLR4 and H4 receptor expression was higher in mice with IBS microbiota, and in peritoneal-derived and bone marrow-derived mast cells (BMMCs) stimulated with IBS bacterial supernatant, which also increased BMMCs degranulation, chemotaxis, adherence and histamine release. While both TLR4 and H4 receptor inhibitors prevented BMMCs degranulation, only the latter attenuated their chemotaxis. We provide novel insights into the mechanisms, which contribute to gut dysfunction and visceral hypersensitivity in IBS.
Peisker, F;Halder, M;Nagai, J;Ziegler, S;Kaesler, N;Hoeft, K;Li, R;Bindels, EMJ;Kuppe, C;Moellmann, J;Lehrke, M;Stoppe, C;Schaub, MT;Schneider, RK;Costa, I;Kramann, R;
PMID: 35641541 | DOI: 10.1038/s41467-022-30682-0
The cardiac vascular and perivascular niche are of major importance in homeostasis and during disease, but we lack a complete understanding of its cellular heterogeneity and alteration in response to injury as a major driver of heart failure. Using combined genetic fate tracing with confocal imaging and single-cell RNA sequencing of this niche in homeostasis and during heart failure, we unravel cell type specific transcriptomic changes in fibroblast, endothelial, pericyte and vascular smooth muscle cell subtypes. We characterize a specific fibroblast subpopulation that exists during homeostasis, acquires Thbs4 expression and expands after injury driving cardiac fibrosis, and identify the transcription factor TEAD1 as a regulator of fibroblast activation. Endothelial cells display a proliferative response after injury, which is not sustained in later remodeling, together with transcriptional changes related to hypoxia, angiogenesis, and migration. Collectively, our data provides an extensive resource of transcriptomic changes in the vascular niche in hypertrophic cardiac remodeling.
NK-B cell cross talk induces CXCR5 expression on natural killer cells
Rascle, P;Jacquelin, B;Petitdemange, C;Contreras, V;Planchais, C;Lazzerini, M;Dereuddre-Bosquet, N;Le Grand, R;Mouquet, H;Huot, N;Müller-Trutwin, M;
| DOI: 10.1016/j.isci.2021.103109
B cell follicles (BCFs) in lymph nodes (LNs) are generally exempt of CD8+ T and NK cells. African green monkeys (AGMs), a natural host of simian immunodeficiency virus (SIV), display NK cell-mediated viral control in BCF. NK cell migration into BCF in chronically SIVagm-infected AGM is associated with CXCR5+ NK cells. We aimed to identify the mechanism leading to CXCR5 expression on NK cells. We show that CXCR5+ NK cells in LN were induced following SIVagm infection. CXCR5+ NK cells accumulated preferentially in BCF with proliferating B cells. Autologous NK-B cell co-cultures in transwell chambers induced CXCR5+ NK cells. Transcriptome analysis of CXCR5+ NK cells revealed expression of bcl6 and IL6R. IL-6 induced CXCR5 on AGM and human NK cells. IL6 mRNA was detected in LN at higher levels during SIVagm than SIVmac infection and often produced by plasma cells. Our study reveals a mechanism of B cell-dependent NK cell regulation.
The Journal of Neuroscience
Liu, J;Eyring, K;König, G;Kostenis, E;Tsien, R;
| DOI: 10.1523/jneurosci.0921-22.2022
Oxytocin (OXT) and oxytocin receptor (OXTR)-mediated signaling control excitability, firing patterns, and plasticity of hippocampal CA2 pyramidal neurons, which are pivotal in generation of brain oscillations and social memory. Nonetheless, the ionic mechanisms underlying OXTR-induced effects in CA2 neurons are not fully understood. Using slice physiology in a reporter mouse line and interleaved current- and voltage-clamp experiments, we systematically identified the ion channels modulated by OXT signaling in CA2 pyramidal cells (PYRs) in mice of both sexes and explored how changes in channel conductance support altered electrical activity. Activation of OXTRs inhibits an outward potassium current mediated by inward rectifier potassium channels (_I_Kir) and thus favoring membrane depolarization. Concomitantly, OXT signaling also diminishes inward current mediated by hyperpolarization-activated cyclic-nucleotide-gated channels (_I_h), providing a hyperpolarizing drive. The combined reduction in both _I_Kir and _I_h synergistically elevate the membrane resistance and favor dendritic integration while the membrane potential is restrained from quickly depolarizing from rest. As a result, the responsiveness of CA2 PYRs to synaptic inputs is highly sharpened during OXTR activation. Unexpectedly, OXTR signaling also strongly enhances a tetrodotoxin-resistant, voltage-gated sodium current that helps drive the membrane potential to spike threshold and thus promote rhythmic firing. This novel array of OXTR-stimulated ionic mechanisms operates in close coordination and underpins OXT-induced burst firing, a key step in CA2 PYRs’ contribution to hippocampal information processing and broader influence on brain circuitry. Our study deepens our understanding of underpinnings of OXT-promoted social memory and general neuropeptidergic control of cognitive states.
Kraft L, Erdenesukh T, Sauter M, Tschöpe C, Klingel K.
PMID: 30673858 | DOI: 10.1007/s00395-019-0719-0
Coxsackieviruses of group B (CVB) are well-known causes of acute and chronic myocarditis. Chronic myocarditis can evolve into dilated cardiomyopathy (DCM) characterized by fibrosis and cardiac remodeling. Interleukin-1β (IL-1β) plays a decisive role in the induction of the inflammatory response as a consequence of viral replication. In this study, we analyzed the effects of IL-1β neutralization on the transition of acute to chronic myocarditis in a mouse model of CVB3 myocarditis. Mice were treated with an anti-murine IL-1β antibody as a surrogate for Canakinumab at different time points post CVB3 infection. Treatment was performed in the early phase (day 1-14 pi, day 3-14 pi) or at a later stage of myocarditis (day 14-28 pi). Subsequently, the hearts were examined histologically, immunohistochemically and by molecular biology. A significant reduction of viral replication, cardiac damage and inflammation was found after administration of the antibody in the early phase and in the later phase of infection. Furthermore, less collagen I deposition and a considerable reduction of fibrosis were found in antibody-treated mice. Using microarray analysis, a significant upregulation of various extracellular matrix and fibrosis-associated molecules was found in CVB3-infected mice, including TGF-β, TIMP-1 and MMP12, as well as diverse matricellular proteins, whereas, these molecules were significantly downregulated in all IL-1β antibody-treated infected mice. Neutralization of IL-1β at different stages of enteroviral infection prevents the development of chronic viral myocarditis by reducing inflammation, interstitial fibrosis and adverse cardiac remodeling. These findings are relevant for the treatment of patients with acute and chronic myocarditis.
ARCGHR Neurons Regulate Muscle Glucose Uptake
de Lima, JBM;Debarba, LK;Rupp, AC;Qi, N;Ubah, C;Khan, M;Didyuk, O;Ayyar, I;Koch, M;Sandoval, DA;Sadagurski, M;
PMID: 34063647 | DOI: 10.3390/cells10051093
The growth hormone receptor (GHR) is expressed in brain regions that are known to participate in the regulation of energy homeostasis and glucose metabolism. We generated a novel transgenic mouse line (GHRcre) to characterize GHR-expressing neurons specifically in the arcuate nucleus of the hypothalamus (ARC). Here, we demonstrate that ARCGHR+ neurons are co-localized with agouti-related peptide (AgRP), growth hormone releasing hormone (GHRH), and somatostatin neurons, which are activated by GH stimulation. Using the designer receptors exclusively activated by designer drugs (DREADD) technique to control the ARCGHR+ neuronal activity, we demonstrate that the activation of ARCGHR+ neurons elevates a respiratory exchange ratio (RER) under both fed and fasted conditions. However, while the activation of ARCGHR+ promotes feeding, under fasting conditions, the activation of ARCGHR+ neurons promotes glucose over fat utilization in the body. This effect was accompanied by significant improvements in glucose tolerance, and was specific to GHR+ versus GHRH+ neurons. The activation of ARCGHR+ neurons increased glucose turnover and whole-body glycolysis, as revealed by hyperinsulinemic-euglycemic clamp studies. Remarkably, the increased insulin sensitivity upon the activation of ARCGHR+ neurons was tissue-specific, as the insulin-stimulated glucose uptake was specifically elevated in the skeletal muscle, in parallel with the increased expression of muscle glycolytic genes. Overall, our results identify the GHR-expressing neuronal population in the ARC as a major regulator of glycolysis and muscle insulin sensitivity in vivo.
Interleukin-6 In Anca-Associated Vasculitis: Rationale For Successful Treatment with Tocilizumab
Seminars in Arthritis and Rheumatism.
Berti A, Cavalli G, Campochiaro C, Guglielmi B, Baldissera E, Cappio S, Sabbadini MG, Doglioni C, Dagna L.
Abstract
Objective
Microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) are systemic, necrotizing, small-vessel vasculitis associated with circulating anti-neutrophil cytoplasmic autoantibodies (ANCA), and thus called ANCA-associated vasculitides (AAV). Aim of the present study is to evaluate a potential role of interleukin (IL)-6 and its pathway in the pathogenesis of AAV and to review previous evidences of IL-6 in MPA and GPA.
Methods
Blood and histological samples, from 10 untreated myeloperoxidase (MPO)-ANCA/proteinase 3 (PR3)-ANCA positive patients with active AAV were studied. Serum levels of cytokines/chemokines were evaluated by means of a Bio-Plex Multiple Cytokine Assay. IL-6 production at sites of active vasculitis was assessed by means of both immunohistochemistry and in situ hybridization techniques. We also treated a patient with MPA who was resistant or allergic to conventional treatments with a 12-month course of the IL-6 inhibitor tocilizumab, and followed him up for 24 additional months. We also reviewed all the published cases in the English literature of histologically-confirmed MPA or GPA, in which elevated IL-6 serum levels or intralesional IL-6 expression were reported.
Results
IL-6 serum levels were significantly increased in patients with AAV as compared to controls (median, 51.96 pg/mL; range, 34.11 - 84.30; versus 0.68 pg/mL; range, 0.01 – 1.81; P <0.005). Also, IL-6 was expressed and produced at sites of active vasculitis. Treatment with tocilizumab was able to induce a complete and sustained disease remission in a patient with severe multisystemic MPA, as well as normalization of circulating levels of IL-6-associated pro-inflammatory cytokines and chemokines. Previous evidences of IL-6 pathway activation in AAV are scarce. Seven clinical studies for a total of approximately 120 patients, mainly affected by GPA, reported increased serum levels of IL-6.
Conclusion
The finding of an activated IL-6 pathway in patients with AAV, together with the observed effects of tocilizumab monotherapy, provides evidence for a possible central role of IL-6 in the pathogenesis of AAV and suggests its targeting as a potential treatment.
Journal of chemical neuroanatomy
Beebe, NL;Silveira, MA;Goyer, D;Noftz, WA;Roberts, MT;Schofield, BR;
PMID: 36375740 | DOI: 10.1016/j.jchemneu.2022.102189
Neurons in the inferior colliculus (IC), the midbrain hub of the central auditory pathway, send ascending and descending projections to other auditory brain regions, as well as projections to other sensory and non-sensory brain regions. However, the axonal projection patterns of individual classes of IC neurons remain largely unknown. Vasoactive intestinal polypeptide (VIP) is a neuropeptide expressed by subsets of neurons in many brain regions. We recently identified a class of IC stellate neurons that we called VIP neurons because they are labeled by tdTomato (tdT) expression in VIP-IRES-Cre x Ai14 mice. Here, using fluorescence in situ hybridization, we found that tdT+ neurons in VIP-IRES-Cre x Ai14 mice express Vglut2, a marker of glutamatergic neurons, and VIP, suggesting that VIP neurons use both glutamatergic and VIPergic signaling to influence their postsynaptic targets. Next, using viral transfections with a Cre-dependent eGFP construct, we labeled the axonal projections of VIP neurons. As a group, VIP neurons project intrinsically, within the ipsilateral and contralateral IC, and extrinsically to all the major targets of the IC. Within the auditory system, VIP neurons sent axons and formed axonal boutons in higher centers, including the medial geniculate nucleus and the nucleus of the brachium of the IC. Less dense projections terminated in lower centers, including the nuclei of the lateral lemniscus, superior olivary complex, and dorsal cochlear nucleus. VIP neurons also project to several non-auditory brain regions, including the superior colliculus, periaqueductal gray, and cuneiform nucleus. The diversity of VIP projections compared to the homogeneity of VIP neuron intrinsic properties suggests that VIP neurons play a conserved role at the microcircuit level, likely involving neuromodulation through glutamatergic and VIPergic signaling, but support diverse functions at the systems level through their participation in different projection pathways.
