Regulation of LRRK2 Expression Points to a Functional Role in Human Monocyte Maturation

Genetic variants of Leucine-Rich Repeat Kinase 2 (LRRK2) are associated with a significantly enhanced risk for Parkinson disease, the second most common human neurodegenerative disorder. Despite major efforts, our understanding of LRRK2 biological function and regulation remains rudimentary. In the present study we analyze LRRK2 mRNA and protein expression in sub-populations of human peripheral blood mononuclear cells (PBMCs). LRRK2 mRNA and protein was found in circulating CD19+ B cells and in CD14+ monocytes, whereas CD4+ and CD8+ T cells were devoid of LRRK2 mRNA. Within CD14+ cells the CD14+CD16+ sub-population of monocytes exhibited high levels of LRRK2 protein, in contrast to CD14+CD16- cells. However both populations expressed LRRK2 mRNA. As CD14+CD16+ cells represent a more mature subset of monocytes, we monitored LRRK2 expression after in vitro treatment with various stress factors known to induce monocyte activation. We found that IFN-γ in particular robustly increased LRRK2 mRNA and protein levels in monocytes concomitant with a shift of CD14+CD16− cells towards CD14+CD16+cells. Interestingly, the recently described LRRK2 inhibitor IN-1 attenuated this shift towards CD14+CD16+ after IFN-γ stimulation. Based on these findings we speculate that LRRK2 might have a role in monocyte maturation. Our results provide further evidence for the emerging role of LRRK2 in immune cells and regulation at the transcriptional and translational level. Our data might also reflect an involvement of peripheral and brain immune cells in the disease course of PD, in line with increasing awareness of the role of the immune system in PD

Trophic macrophages in development and disease

Specialized phagocytes are found in the most primitive multicellular organisms. Their roles in homeostasis and in distinguishing self from non-self have evolved with the complexity of organisms and their immune systems. Equally important, but often overlooked, are the roles of macrophages in tissue development. As discussed in this Review, these include functions in branching morphogenesis, neuronal patterning, angiogenesis, bone morphogenesis and the generation of adipose tissue. In each case, macrophage depletion impairs the formation of the tissue and compromises its function. I argue that in several diseases, the unrestrained acquisition of these developmental macrophage functions exacerbates pathology. For example, macrophages enhance tumour progression and metastasis by affecting tumour-cell migration and invasion, as well as angiogenesis

Targeting dendritic cells to treat multiple sclerosis

Multiple sclerosis (MS) is considered to be a predominantly T-cell-mediated disease, and emerging evidence indicates that dendritic cells have a critical role in the initiation and progression of this debilitating condition. Dendritic cells are specialized antigen-presenting cells that can prime naive T cells and modulate adaptive immune responses. Their powerful biological functions indicate that these cells can be exploited by immunotherapeutic approaches. Therapies that inhibit the immunogenic actions of dendritic cells through the blockade of proinflammatory cytokine production and T cell co-stimulatory pathways are currently being pursued. Furthermore, novel strategies that can regulate dendritic cell development and differentiation and harness the tolerogenic capacity of these cells are also being developed. Here, we evaluate the prospects of these future therapeutic strategies, which focus on dendritic cells and dendritic cell-related targets to treat MS

Acute in vivo exposure to interferon-γ enables resident brain dendritic cells to become effective antigen presenting cells

Dendritic cells (DC) are the professional antigen presenting cells (APC) that bridge the innate and adaptive immune system. Previously, in a CD11c/EYFP transgenic mouse developed to study DC functions, we anatomically mapped and phenotypically characterized a discrete population of EYFP+ cells within the microglia that we termed brain dendritic cells (bDC). In this study, we advanced our knowledge of the function of these cells in the CD11c/EYFP transgenic mouse and its chimeras, using acute stimuli of stereotaxically inoculated IFNγ or IL-4 into the CNS. The administration of IFNγ increased the number of EYFP+bDC but did not recruit peripheral DC into the CNS. IFNγ, but not IL-4, upregulated the expression levels of major histocompatibility class II (MHC-II). In addition, IFNγ-activated EYFP+bDC induced antigen-specific naïve CD4 T cells to proliferate and secrete Th1/Th17 cytokines. Activated bDC were also able to stimulate naïve CD8 T cells. Collectively, these data reveal the Th1 cytokine IFNγ, but not the Th2 cytokine IL4, induces bDC to up-regulate MHC-II and become competent APC

Mineralocorticoid and glucocorticoid receptors differentially regulate NF-kappaB activity and pro-inflammatory cytokine production in murine BV-2 microglial cells

ABSTRACT:; Microglia, the resident macrophage-like cells in the brain, regulate innate immune responses in the CNS to protect neurons. However, excessive activation of microglia contributes to neurodegenerative diseases. Corticosteroids are potent modulators of inflammation and mediate their effects by binding to mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Here, the coordinated activities of GR and MR on the modulation of the nuclear factor-κB (NF-κB) pathway in murine BV-2 microglial cells were studied.; BV-2 cells were treated with different corticosteroids in the presence or absence of MR and GR antagonists. The impact of the glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) was determined by incubating cells with 11-dehydrocorticosterone, with or without selective inhibitors. Expression of interleukin-6 (IL-6), tumor necrosis factor receptor 2 (TNFR2), and 11β-HSD1 mRNA was analyzed by RT-PCR and IL-6 protein expression by ELISA. NF-κB activation and translocation upon treatment with various corticosteroids were visualized by western blotting, immunofluorescence microscopy, and translocation assays.; GR and MR differentially regulate NF-κB activation and neuroinflammatory parameters in BV-2 cells. By converting inactive 11-dehydrocorticosterone to active corticosterone, 11β-HSD1 essentially modulates the coordinated action of GR and MR. Biphasic effects were observed for 11-dehydrocorticosterone and corticosterone, with an MR-dependent potentiation of IL-6 and tumor necrosis factor-α (TNF-α) expression and NF-κB activation at low/moderate concentrations and a GR-dependent suppression at high concentrations. The respective effects were confirmed using the MR ligand aldosterone and the antagonist spironolactone as well as the GR ligand dexamethasone and the antagonist RU-486. NF-κB activation could be blocked by spironolactone and the inhibitor of NF-κB translocation Cay-10512. Moreover, an increased expression of TNFR2 was observed upon treatment with 11-dehydrocorticosterone and aldosterone, which was reversed by 11β-HSD1 inhibitors and/or spironolactone and Cay-10512.; A tightly coordinated GR and MR activity regulates the NF-κB pathway and the control of inflammatory mediators in microglia cells. The balance of GR and MR activity is locally modulated by the action of 11β-HSD1, which is upregulated by pro-inflammatory mediators and may represent an important feedback mechanism involved in resolution of inflammation

Feminized Behavior and Brain Gene Expression in a Novel Mouse Model of Klinefelter Syndrome

Klinefelter Syndrome is the most common sex chromosome aneuploidy in men and is characterized by the presence of an additional X chromosome (XXY). In some Klinefelter males, certain traits may be feminized or shifted from the male-typical pattern towards a more female-typical one. Among them might be partner choice, one of the most sexually dimorphic traits in the animal kingdom. We investigated the extent of feminization in XXY male mice (XXYM) in partner preference and gene expression in the bed nucleus of the stria terminalis/preoptic area and the striatum in mice from the Sex Chromosome Trisomy model. We tested for partner preference using a three-chambered apparatus in which the test mouse was free to choose between stimulus animals of either sex. We found that partner preference in XXYM was feminized. These differences were likely due to interactions of the additional X chromosome with the Y. We also discovered genes that differed in expression in XXYM vs. XYM. Some of these genes are feminized in their expression pattern. Lastly, we also identified genes that differed only between XXYM vs. XYM and not XXM vs. XYM. Genes that are both feminized and unique to XXYM vs. XYM represent strong candidates for dissecting the molecular pathways responsible for phenotypes present in KS/XXYM but not XXM. In sum, our results demonstrated that investigating behavioral and molecular feminization in XXY males can provide crucial information about the pathophysiology of Klinefelter Syndrome and may aid our understanding of sex differences in brain and behavior