TY  - JOUR
AB  - Retinitis pigmentosa (RP), an inherited retinal disease, affects 1,5 million people worldwide. The initial mutation-driven photoreceptor degeneration leads to chronic inflammation, characterized by Müller cell activation and upregulation of CD44. CD44 is a cell surface transmembrane glycoprotein and the primary receptor for hyaluronic acid. It is involved in many pathological processes, but little is known about CD44's retinal functions. CD44 expression is also increased in Müller cells from our Pde6bSTOP/STOP RP mouse model. To gain a more detailed understanding of CD44's role in healthy and diseased retinas, we analyzed Cd44-/- and Cd44-/-Pde6bSTOP/STOP mice, respectively. The loss of CD44 led to enhanced photoreceptor degeneration, reduced retinal function, and increased inflammatory response. To understand the underlying mechanism, we performed proteomic analysis on isolated Müller cells from Cd44-/- and Cd44-/-Pde6bSTOP/STOP retinas and identified a significant downregulation of glutamate transporter 1 (SLC1A2). This downregulation was accompanied by higher glutamate levels, suggesting impaired glutamate homeostasis. These novel findings indicate that CD44 stimulates glutamate uptake via SLC1A2 in Müller cells, which in turn, supports photoreceptor survival and function.
AU  - Ayten, M.*
AU  - Straub, T.*
AU  - Kaplan, L.*
AU  - Hauck, S.M.
AU  - Grosche, A.*
AU  - Koch, S.F.*
C1  - 71409
C2  - 56130
CY  - Campus, 4 Crinan St, London N1 9xw, England
TI  - CD44 signaling in Müller cells impacts photoreceptor function and survival in healthy and diseased retinas.
JO  - J. Neuroinflamm.
VL  - 21
IS  - 1
PB  - Bmc
PY  - 2024
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - BACKGROUND: Specific microglia responses are thought to contribute to the development and progression of neurodegenerative diseases, including Parkinson's disease (PD). However, the phenotypic acquisition of microglial cells and their role during the underlying neuroinflammatory processes remain largely elusive. Here, according to the multiple-hit hypothesis, which stipulates that PD etiology is determined by a combination of genetics and various environmental risk factors, we investigate microglial transcriptional programs and morphological adaptations under PARK7/DJ-1 deficiency, a genetic cause of PD, during lipopolysaccharide (LPS)-induced inflammation. METHODS: Using a combination of single-cell RNA-sequencing, bulk RNA-sequencing, multicolor flow cytometry and immunofluorescence analyses, we comprehensively compared microglial cell phenotypic characteristics in PARK7/DJ-1 knock-out (KO) with wildtype littermate mice following 6- or 24-h intraperitoneal injection with LPS. For translational perspectives, we conducted corresponding analyses in human PARK7/DJ-1 mutant induced pluripotent stem cell (iPSC)-derived microglia and murine bone marrow-derived macrophages (BMDMs). RESULTS: By excluding the contribution of other immune brain resident and peripheral cells, we show that microglia acutely isolated from PARK7/DJ-1 KO mice display a distinct phenotype, specially related to type II interferon and DNA damage response signaling, when compared with wildtype microglia, in response to LPS. We also detected discrete signatures in human PARK7/DJ-1 mutant iPSC-derived microglia and BMDMs from PARK7/DJ-1 KO mice. These specific transcriptional signatures were reflected at the morphological level, with microglia in LPS-treated PARK7/DJ-1 KO mice showing a less amoeboid cell shape compared to wildtype mice, both at 6 and 24 h after acute inflammation, as also observed in BMDMs. CONCLUSIONS: Taken together, our results show that, under inflammatory conditions, PARK7/DJ-1 deficiency skews microglia towards a distinct phenotype characterized by downregulation of genes involved in type II interferon signaling and a less prominent amoeboid morphology compared to wildtype microglia. These findings suggest that the underlying oxidative stress associated with the lack of PARK7/DJ-1 affects microglia neuroinflammatory responses, which may play a causative role in PD onset and progression.
AU  - Lind-Holm Mogensen, F.*
AU  - Sousa, C.*
AU  - Ameli, C.*
AU  - Badanjak, K.*
AU  - Pereira, S.L.*
AU  - Muller, A.*
AU  - Kaoma, T.*
AU  - Coowar, D.*
AU  - Scafidi, A.*
AU  - Poovathingal, S.K.*
AU  - Tziortziou, M.*
AU  - Antony, P.M.A.*
AU  - Nicot, N.*
AU  - Ginolhac, A.*
AU  - Vogt Weisenhorn, D.M.
AU  - Wurst, W.
AU  - Poli, A.*
AU  - Nazarov, P.V.*
AU  - Skupin, A.*
AU  - Grünewald, A.*
AU  - Michelucci, A.*
C1  - 71191
C2  - 55926
CY  - Campus, 4 Crinan St, London N1 9xw, England
TI  - PARK7/DJ-1 deficiency impairs microglial activation in response to LPS-induced inflammation.
JO  - J. Neuroinflamm.
VL  - 21
IS  - 1
PB  - Bmc
PY  - 2024
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - Diabetic retinopathy (DR) is considered a primarily microvascular complication of diabetes. Müller glia cells are at the centre of the retinal neurovascular unit and play a critical role in DR. We therefore investigated Müller cell-specific signalling pathways that are altered in DR to identify novel targets for gene therapy. Using a multi-omics approach on purified Müller cells from diabetic db/db mice, we found the mRNA and protein expression of the glucocorticoid receptor (GR) to be significantly decreased, while its target gene cluster was down-regulated. Further, oPOSSUM TF analysis and ATAC- sequencing identified the GR as a master regulator of Müller cell response to diabetic conditions. Cortisol not only increased GR phosphorylation. It also induced changes in the expression of known GR target genes in retinal explants. Finally, retinal functionality was improved by AAV-mediated overexpression of GR in Müller cells. Our study demonstrates an important role of the glial GR in DR and implies that therapeutic approaches targeting this signalling pathway should be aimed at increasing GR expression rather than the addition of more ligand.
AU  - Pfaller, A.M.*
AU  - Kaplan, L.*
AU  - Moreira Carido Pereira, M.
AU  - Grassmann, F.*
AU  - Díaz-Lezama, N.*
AU  - Ghaseminejad, F.*
AU  - Wunderlich, K.A.*
AU  - Glänzer, S.*
AU  - Bludau, O.*
AU  - Pannicke, T.*
AU  - Weber, B.H.F.*
AU  - Koch, S.F.*
AU  - Bonev, B.
AU  - Hauck, S.M.
AU  - Grosche, A.*
C1  - 69860
C2  - 55288
CY  - Campus, 4 Crinan St, London N1 9xw, England
TI  - The glucocorticoid receptor as a master regulator of the Müller cell response to diabetic conditions in mice.
JO  - J. Neuroinflamm.
VL  - 21
IS  - 1
PB  - Bmc
PY  - 2024
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - Background: Ligand-driven modulation of the mitochondrial translocator protein 18 kDa (TSPO) was recently described to dampen the neuroinflammatory response of microglia in a retinal light damage model resulting in protective effects on photoreceptors. We characterized the effects of the TSPO ligand XBD173 in the postischemic retina focusing on changes in the response pattern of the major glial cell types of the retina-microglia and Muller cells.Methods: Retinal ischemia was induced by increasing the intraocular pressure for 60 min followed by reperfusion of the tissue in mice. On retinal cell types enriched via immunomagnetic separation expression analysis of TSPO, its ligand diazepam-binding inhibitor (DBI) and markers of glial activation were performed at transcript and protein level using RNA sequencing, qRT-PCR, lipid chromatography-mass spectrometry, and immunofluorescent labeling. Data on cell morphology and numbers were assessed in retinal slice and flatmount preparations. The retinal functional integrity was determined by electroretinogram recordings.Results: We demonstrate that TSPO is expressed by Muller cells, microglia, vascular cells, retinal pigment epithelium (RPE) of the healthy and postischemic retina, but only at low levels in retinal neurons. While an alleviated neurodegeneration upon XBD173 treatment was found in postischemic retinae as compared to vehicle controls, this neuroprotective effect of XBD173 is mediated putatively by its action on retinal glia. After transient ischemia, TSPO as a marker of activation was upregulated to similar levels in microglia as compared to their counterparts in healthy retinae irrespective of the treatment regimen. However, less microglia were found in XBD173-treated postischemic retinae at 3days post-surgery (dps) which displayed a more ramified morphology than in retinae of vehicle-treated mice indicating a dampened microglia activation. Muller cells, the major retinal macroglia, show upregulation of the typical gliosis marker GFAP. Importantly, glutamine synthetase was more stably expressed in Muller glia of XBD173-treated postischemic retinae and homeostatic functions such as cellular volume regulation typically diminished in gliotic Muller cells remained functional.Conclusions: In sum, our data imply that beneficial effects of XBD173 treatment on the postischemic survival of inner retinal neurons were primarily mediated by stabilizing neurosupportive functions of glial cells.
AU  - Mages, K.*
AU  - Grassmann, F.*
AU  - Jägle, H.*
AU  - Rupprecht, R.*
AU  - Weber, B.H.F.*
AU  - Hauck, S.M.
AU  - Grosche, A.*
C1  - 55536
C2  - 46397
CY  - Campus, 4 Crinan St, London N1 9xw, England
TI  - The agonistic TSPO ligand XBD173 attenuates the glial response thereby protecting inner retinal neurons in a murine model of retinal ischemia.
JO  - J. Neuroinflamm.
VL  - 16
IS  - 1
PB  - Bmc
PY  - 2019
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - Astrocytosis is a reactive process involving cellular, molecular, and functional changes to facilitate neuronal survival, myelin preservation, blood brain barrier function and protective glial scar formation upon brain insult. The overall pro-or anti-inflammatory impact of reactive astrocytes appears to be driven in a context- and disease-driven manner by modulation of astrocytic Ca2+ homeostasis and activation of Ca2+/calmodulin-activated serine/threonine phosphatase calcineurin. Here, we aimed to assess whether calcineurin is dispensable for astrocytosis in the hypothalamus driven by prolonged high fat diet (HFD) feeding. Global deletion of calcineurin A beta (gene name: Ppp3cb) led to a decrease of glial fibrillary acidic protein (GFAP)positive cells in the ventromedial hypothalamus (VMH), dorsomedial hypothalamus (DMH), and arcuate nucleus (ARC) of mice exposed chronically to HFD. The concomitant decrease in Iba1-positive microglia in the VMH further suggests a modest impact of Ppp3cb deletion on microgliosis. Pharmacological inhibition of calcineurin activity by Fk506 had no impact on IBA1-positive microglia in hypothalami of mice acutely exposed to HFD for 1 week. However, Fk506-treated mice displayed a decrease in GFAP levels in the ARC. In vivo effects could not be replicated in cell culture, where calcineurin inhibition by Fk506 had no effect on astrocytic morphology, astrocytic cell death, GFAP, and vimentin protein levels or microglia numbers in primary hypothalamic astrocytes and microglia co-cultures. Further, adenoviral overexpression of calcineurin subunit Ppp3r1 in primary glia culture did not lead to an increase in GFAP fluorescence intensity. Overall, our results point to a prominent role of calcineurin in mediating hypothalamic astrocytosis as response to acute and chronic HFD exposure. Moreover, discrepant findings in vivo and in cell culture indicate the necessity of studying astrocytes in their "natural" environment, i.e., preserving an intact hypothalamic microenvironment with neurons and non-neuronal cells in close proximity.
AU  - Pfuhlmann, K.
AU  - Schriever, S.C.
AU  - Legutko, B.
AU  - Baumann, P.
AU  - Harrison, L.
AU  - Kabra, D.G.*
AU  - Baumgart, E.V.
AU  - Tschöp, M.H.
AU  - García-Cáceres, C.
AU  - Pfluger, P.T.
C1  - 52991
C2  - 44375
CY  - London
TI  - Calcineurin A beta deficiency ameliorates HFD-induced hypothalamic astrocytosis in mice.
JO  - J. Neuroinflamm.
VL  - 15
IS  - 1
PB  - Biomed Central Ltd
PY  - 2018
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - BACKGROUND: Müller glial cells are important regulators of physiological function of retina. In a model disease of retinal inflammation and spontaneous recurrent uveitis in horses (ERU), we could show that retinal Müller glial cells significantly change potassium and water channel protein expression during autoimmune pathogenesis. The most significantly changed channel protein in neuroinflammatory ERU was aquaporin 11 (AQP11). Aquaporins (AQP, 13 members) are important regulators of water and small solute transport through membranes. AQP11 is an unorthodox member of this family and was assigned to a third group of AQPs because of its difference in amino acid sequence (conserved sequence is only 11 %) and especially its largely unknown function. METHODS: In order to gain insight into the distribution, localization, and function of AQP11 in the retina, we first developed a novel monoclonal antibody for AQP11 enabling quantification, localization, and functional studies. RESULTS: In the horse retina, AQP11 was exclusively expressed at Müller glial cell membranes. In uveitic condition, AQP11 disappeared from gliotic Müller cells concomitant with glutamine synthase. Since function of AQP11 is still under debate, we assessed the impact of AQP11 channel on cell volume regulation of primary Müller glial cells under different osmotic conditions. We conclude a concomitant role for AQP11 with AQP4 in water efflux from these glial cells, which is disturbed in ERU. This could probably contribute to swelling and subsequent severe complication of retinal edema through impaired intracellular fluid regulation. CONCLUSIONS: Therefore, AQP11 is important for physiological Müller glia function and the expression pattern and function of this water channel seems to have distinct functions in central nervous system. The significant reduction in neuroinflammation points to a crucial role in pathogenesis of autoimmune uveitis.
AU  - Deeg, C.A.*
AU  - Amann, B.*
AU  - Lutz, K.*
AU  - Hirmer, S.*
AU  - Lutterberg, K.*
AU  - Kremmer, E.
AU  - Hauck, S.M.
C1  - 48466
C2  - 41159
CY  - London
TI  - Aquaporin 11, a regulator of water efflux at retinal Müller glial cell surface decreases concomitant with immune-mediated gliosis.
JO  - J. Neuroinflamm.
VL  - 13
IS  - 1
PB  - Biomed Central Ltd
PY  - 2016
SN  - 1742-2094
ER  - 

TY  - JOUR
AB  - BACKGROUND: The paracaspase mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is crucial for lymphocyte activation through signaling to the transcription factor NF-κB. Besides functioning as a scaffold signaling protein, MALT1 also acts as a cysteine protease that specifically cleaves a number of substrates and contributes to specific T cell receptor-induced gene expression. Recently, small molecule inhibitors of MALT1 proteolytic activity were identified and shown to have promising anticancer properties in subtypes of B cell lymphoma. However, information on the therapeutic potential of small compound inhibitors that target MALT1 protease activity in autoimmunity is still lacking. METHODS: The present study aimed to elucidate whether MALT1 protease inhibitors are also useful in the treatment of lymphocyte-mediated autoimmune pathologies such as multiple sclerosis (MS). For this, we studied the therapeutic potential of a recently identified inhibitor of MALT1 protease activity, the phenothiazine derivative mepazine, in the context of experimental autoimmune encephalomyelitis (EAE), the main animal model for MS. RESULTS: We demonstrate that administration of mepazine prophylactically or after disease onset, can attenuate EAE. Importantly, while complete absence of MALT1 affects the differentiation of regulatory T (Treg) cells in vivo, the MALT1 protease inhibitor mepazine did not affect Treg development. CONCLUSIONS: Altogether, these data indicate that small molecule inhibitors of MALT1 not only hold great promise for the treatment of B cell lymphomas but also for autoimmune disorders such as MS.
AU  - Mc Guire, C.*
AU  - Elton, L.*
AU  - Wieghofer, P.*
AU  - Staal, J.*
AU  - Voet, S.*
AU  - Demeyer, A.*
AU  - Nagel, D.
AU  - Krappmann, D.
AU  - Prinz, M.*
AU  - Beyaert, R.*
AU  - van Loo, G.*
C1  - 31839
C2  - 34799
CY  - London
TI  - Pharmacological inhibition of MALT1 protease activity protects mice in a mouse model of multiple sclerosis.
JO  - J. Neuroinflamm.
VL  - 11
IS  - 1
PB  - Biomed Central Ltd
PY  - 2014
SN  - 1742-2094
ER  -