Project description:The human pathogen Helicobacter pylori (Hp) colonizes the gastric epithelium as a unique niche in the stomach. Infections commonly occur in childhood and persist lifelong, leading in some cases to adenocarcinoma and MALT lymphoma. Several studies define mammalian microRNAs as key regulators of the immune system and of carcinogenesis processes. Here, we show Hp infection induces miR-155 expression in epithelial and hematopoietic cells in vitro and in vivo. This induction is mediated by at least two main bacterial virulence factors, the vacuolating toxin (VacA) and the gamma-glutamyl transpeptidase (GGT) in an LPS independent manner. Using adenylate cyclases agonists and inhibitor, we demonstrated that the miR-155 microRNA regulatory cascade in Hp infection involves the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, the study showed that a knock-down of the Foxp3 transcription factor in T cells abolishes miR-155 expression. Together, these findings are the first demonstration of a direct interconnection between the regulatory T cell development factor Foxp3 and a microRNA. This study supports the link between Hp infection, regulation of cellular immunity, inflammation and cancer development.
Project description:The human pathogen Helicobacter pylori (Hp) colonizes the gastric epithelium as a unique niche in the stomach. Infections commonly occur in childhood and persist lifelong, leading in some cases to adenocarcinoma and MALT lymphoma. Several studies define mammalian microRNAs as key regulators of the immune system and of carcinogenesis processes. Here, we show Hp infection induces miR-155 expression in epithelial and hematopoietic cells in vitro and in vivo. This induction is mediated by at least two main bacterial virulence factors, the vacuolating toxin (VacA) and the gamma-glutamyl transpeptidase (GGT) in an LPS independent manner. Using adenylate cyclases agonists and inhibitor, we demonstrated that the miR-155 microRNA regulatory cascade in Hp infection involves the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, the study showed that a knock-down of the Foxp3 transcription factor in T cells abolishes miR-155 expression. Together, these findings are the first demonstration of a direct interconnection between the regulatory T cell development factor Foxp3 and a microRNA. This study supports the link between Hp infection, regulation of cellular immunity, inflammation and cancer development. A color-swap dye reversal experimental setting was applied. Ratio profiles comprising single hybridizations were combined in an error-weighted fashion to create ratio experiments. A two-fold change expression cut off for ratio experiments was applied together with anti-correlation of ratio profiles rendering the microarray analysis set highly significant (P-value > 0.01), robust and reproducible.
Project description:Amongst the most severe clinical outcomes of life-long infections with Helicobacter pylori is the development of peptic ulcers and gastric adenocarcinoma--diseases often associated with an increase of regulatory T cells. Understanding H. pylori-driven regulation of T cells is therefore of crucial clinical importance. Several studies have defined mammalian microRNAs as key regulators of the immune system and of carcinogenic processes. Hence, we aimed here to identify H. pylori-regulated miRNAs, mainly in human T cells. MicroRNA profiling of non-infected and infected human T cells revealed H. pylori infection triggers miR-155 expression in vitro and in vivo. By using single and double H. pylori mutants and the corresponding purified enzymes, the bacterial vacuolating toxin A (VacA) and gamma-glutamyl transpeptidase (GGT) plus lipopolysaccharide (LPS) tested positive for their ability to regulate miR-155 and Foxp3 expression in human lymphocytes; the latter being considered as the master regulator and marker of regulatory T cells. RNAi-mediated knockdown (KD) of the Foxp3 transcription factor in T cells abolished miR-155 expression. Using adenylate cyclase inhibitors, the miR-155 induction cascade was shown to be dependent on the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, we found that miR-155 directly targets the protein kinase A inhibitor alpha (PKIalpha) mRNA in its 3'UTR, indicative of a positive feedback mechanism on the cAMP pathway. Taken together, our study describes, in the context of an H. pylori infection, a direct link between Foxp3 and miR-155 in human T cells and highlights the significance of cAMP in this miR-155 induction cascade.
Project description:Regulatory T cells have been shown to adopt a catabolic metabolic programme with increased capacity for fatty acid oxidation fuelled oxidative phosphorylation (OXPHOS). The role of Foxp3 in this metabolic shift is poorly understood. Here we show that Foxp3 was sufficient to induce a significant increase in the spare respiratory capacity of the cell, the extra OXPHOS capacity available to a cell to increased demands on energy in response to work. Foxp3-expressing cells were enhanced in their ability to utilise palmitate for respiration and in addition the activity of electron transport complexes I, II and IV were enhanced following Foxp3 expression. ATP was secreted by both T effector and regulatory T cells and was reduced by mitochondrial respiration inhibitors. Thus Foxp3 imparts a selective advantage in ATP generation capacity to the cell and may exploit this as a source of adenosine for functional immunomodulation. In order to explore possible mechanisms for these differences in metabolism we conducted a comparative quantitative proteomics study to compare the contribution of TGFβ and the transcription factor Foxp3 to the Treg proteome. We used quantitative mass spectrometry to examine differences between proteomes of nuclear and cytoplasmic Foxp3-containing T cells and Foxp3 positive iTreg and Foxp3 negative activated CD4 T cells in addition to human peripheral blood natural Treg. Gene set enrichment analysis of our proteomic datasets demonstrated that Foxp3 drives a significant up regulation of several members of the mitochondrial electron transport chain.
Project description:Factors that increase cAMP levels can induce lineage-specific differentiation of glioma cells into astrocyte-like cells. However, the differentiation pattern and underlying mechanisms remain unclear. Here, we find that cAMP/PKA/CREB1-induced miR-221/222 suppression contributes to the neuron-like differentiation of gliomas. cAMP agonists selectively induced neuron- and astrocyte-like but not oligodendrocyte-like differentiation of C6 glioma cells. PKA inhibitors and CREB1 knockout blocked neuron-like differentiation of glioma cells. cAMP inhibited miR-221/222 in a PKA/CREB1 dependent manner. Importantly, both in vitro and in vivo assays demonstrated that transcriptional suppression of miR-221/222 is required for neuronal differentiation of glioma cells. Our findings suggest that increasing cAMP levels can induce bidirectional differentiation of glioma cells. Furthermore, the miR-221/222 cluster acts as an epigenetic brake during glioma differentiation. Factors that increase cAMP levels can induce lineage-specific differentiation of glioma cells into astrocyte-like cells. However, the differentiation pattern and underlying mechanisms remain unclear. Here, we find that cAMP/PKA/CREB1-induced miR-221/222 suppression contributes to the neuron-like differentiation of gliomas. cAMP agonists selectively induced neuron- and astrocyte-like but not oligodendrocyte-like differentiation of C6 glioma cells. PKA inhibitors and CREB1 knockout blocked neuron-like differentiation of glioma cells. cAMP inhibited miR-221/222 in a PKA/CREB1 dependent manner. Importantly, both in vitro and in vivo assays demonstrated that transcriptional suppression of miR-221/222 is required for neuronal differentiation of glioma cells. Our findings suggest that increasing cAMP levels can induce bidirectional differentiation of glioma cells. Furthermore, the miR-221/222 cluster acts as an epigenetic brake during glioma differentiation.
Project description:Mammalian microRNAs (miRNAs) are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the sufficiency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the mir-155-induced GM populations displayed pathological features characteristic of myeloid neoplasia. Extending possible relevance to human disease, miR-155 was overexpressed in the bone marrow of patients with acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during inflammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of inflammatory stress. Keywords: genetic modification
Project description:Factors that increase cAMP levels can induce lineage-specific differentiation of glioma cells into astrocyte-like cells. However, the differentiation pattern and underlying mechanisms remain unclear. Here, we find that cAMP/PKA/CREB1-induced miR-221/222 suppression contributes to the neuron-like differentiation of gliomas. cAMP agonists selectively induced neuron- and astrocyte-like but not oligodendrocyte-like differentiation of C6 glioma cells. PKA inhibitors and CREB1 knockout blocked neuron-like differentiation of glioma cells. cAMP inhibited miR-221/222 in a PKA/CREB1 dependent manner. Importantly, both in vitro and in vivo assays demonstrated that transcriptional suppression of miR-221/222 is required for neuronal differentiation of glioma cells. Our findings suggest that increasing cAMP levels can induce bidirectional differentiation of glioma cells. Furthermore, the miR-221/222 cluster acts as an epigenetic brake during glioma differentiation.
Project description:Regulatory T (Treg) cells expressing the lineage-defining transcription factor Foxp3 are essential for the maintenance of immune tolerance. Foxp3 expression can be induced in a subset of developing self-reactive thymocytes to yield thymic Treg (tTreg) cells, critical for tolerance against self-antigens. Alternatively, activation of mature naïve T cells under non-inflammatory conditions can drive the differentiation of peripherally-induced Treg (pTreg) cells, thought to contribute to tolerance against commensal microbes and dietary antigens. While Foxp3 is indispensable for tTreg cell development and function, its role in pTreg cells has remained unknown. Here, we used a genetic fate mapping approach to characterize polyclonal pTreg cells induced by microbial colonization. We found that expression of a pTreg cell-specific gene expression program was initiated in the mesenteric lymph node (mLN) in a Foxp3-independent manner. Moreover, in contrast to Treg cells in secondary lymphoid tissues, colonic microbiota-dependent pTreg cells did not depend on Foxp3 for their fitness or lineage commitment and were capable of suppressing colonic effector T cell expansion in a Foxp3-independent manner. Rather, Foxp3 was required in a cell-intrinsic manner to limit IL-17 production and to prevent the expansion of intestinal mast cells. Our results suggest that, extrathymic Foxp3 induction likely acts as a mechanism to fine-tune the activity of Th17-like cells with Foxp3-independent regulatory functions.
Project description:Regulatory T (Treg) cells expressing the lineage-defining transcription factor Foxp3 are essential for the maintenance of immune tolerance. Foxp3 expression can be induced in a subset of developing self-reactive thymocytes to yield thymic Treg (tTreg) cells, critical for tolerance against self-antigens. Alternatively, activation of mature naïve T cells under non-inflammatory conditions can drive the differentiation of peripherally-induced Treg (pTreg) cells, thought to contribute to tolerance against commensal microbes and dietary antigens. While Foxp3 is indispensable for tTreg cell development and function, its role in pTreg cells has remained unknown. Here, we used a genetic fate mapping approach to characterize polyclonal pTreg cells induced by microbial colonization. We found that expression of a pTreg cell-specific gene expression program was initiated in the mesenteric lymph node (mLN) in a Foxp3-independent manner. Moreover, in contrast to Treg cells in secondary lymphoid tissues, colonic microbiota-dependent pTreg cells did not depend on Foxp3 for their fitness or lineage commitment and were capable of suppressing colonic effector T cell expansion in a Foxp3-independent manner. Rather, Foxp3 was required in a cell-intrinsic manner to limit IL-17 production and to prevent the expansion of intestinal mast cells. Our results suggest that, extrathymic Foxp3 induction likely acts as a mechanism to fine-tune the activity of Th17-like cells with Foxp3-independent regulatory functions.
Project description:Regulatory T (Treg) cells expressing the X-linked lineage-defining transcription factor (TF) Foxp3 are essential for preventing fatal autoimmunity. During thymic differentiation, Foxp3 expression is induced in a subset of developing self-reactive thymocytes yielding thymic Treg (tTreg) cells, critical for enforcing tolerance to “self”. In the periphery, Foxp3 induction in mature naïve CD4 T cells activated under particular conditions results in extrathymic generation of Treg (pTreg) cells, thought to contribute to tolerance against commensal microbiota and dietary antigens. While Foxp3 is indispensable for tTreg cell differentiation and function, its role in pTreg cells has remained unknown. Here, we used complementary genetic approaches to characterize pTreg cells induced by microbial colonization and elucidate a role for Foxp3 in these cells. We found that a pTreg cell-specific gene expression program was installed in the gut-draining mesenteric lymph nodes (mLN) in a Foxp3-independent manner. In contrast to tTreg cells residing in the secondary lymphoid tissues, colonic microbiota-dependent pTreg cells did not depend on Foxp3 for their fitness or lineage commitment and were capable of preventing colonic effector T cell expansion in a Foxp3-independent manner. Rather, Foxp3 acted in a cell intrinsic manner to limit IL-17 production and was critical for the suppression of rampant intestinal mastocytosis. Thus, in contrast to tTreg cells, whose functionality is entirely Foxp3-dependent, Foxp3 expression plays a notably nuanced role in pTreg cells and acts to fine-tune the activity of IL-17 producing cells with Foxp3-independent regulatory functions.