Project description:The innate immune regulator stimulator of interferon genes (STING) mediates self-DNA sensing and leads to the induction of type I interferons and inflammatory cytokines, which promotes the progression of various inflammatory and autoimmune diseases. Innate immune system plays a critical role in regulating obesity-induced islet dysfunction, whereas the potential effect of STING signaling remains unclear. Here, we demonstrate that STING is mainly expressed and activated in islet macrophages upon high-fat diet (HFD) feeding. Knocking-out STING alleviates HFD-induced islet inflammation by inhibiting the expression of pro-inflammatory cytokines and infiltration of macrophages. Mechanically, palmitic acid incubation promotes mitochondrial DNA leakage into the cytosol and subsequently activates cyclic AMP-GMP synthase (cGAS)-STING pathway in macrophages. Additionally, STING activation in macrophages impairs glucose-stimulated insulin secretion by mediating the engulfment of β cell insulin secretory granules. Genetically or pharmacologically inhibiting STING activation boosts insulin secretion and hyperglycemia. Together, these findings reveal a regulatory mechanism in controlling the islet inflammation and insulin secretion in diet-induced obesity and suggest that selective blocking of the STING activation maybe a promising strategy for treating type 2 diabetes.
Project description:Chronic stimulation of innate immune pathways by microbial agents or damaged tissue is known to promote inflammation-driven tumorigenesis by unclarified mechanisms1-3. Here we demonstrate that mutagenic 7,12-dimethylbenz(a)anthracene (DMBA), etoposide or cisplatin induces nuclear DNA leakage into the cytosol to intrinsically activate STING (Stimulator of Interferon Genes) dependent cytokine production. Inflammatory cytokine levels were subsequently augmented in a STING-dependent extrinsic manner by infiltrating phagocytes purging dying cells. Consequently, STING-/- mice, or wild type mice adoptively transferred with STING-/- bone marrow, were almost completely resistant to DMBA-induced skin carcinogenesis compared to their wild type counterparts. Our data emphasizes, for the first time, a role for STING in the induction of cancer, sheds significant insight into the causes of inflammation-driven carcinogenesis, and may provide therapeutic strategies to help prevent malignant disease Total RNA obtained from DMBA or acetone treated wild type (WT) or STING deficient (SKO) mouse skin or skin tumor was examined for gene expression.
Project description:Chronic stimulation of innate immune pathways by microbial agents or damaged tissue is known to promote inflammation-driven tumorigenesis by unclarified mechanisms1-3. Here we demonstrate that mutagenic 7,12-dimethylbenz(a)anthracene (DMBA), etoposide or cisplatin induces nuclear DNA leakage into the cytosol to intrinsically activate STING (Stimulator of Interferon Genes) dependent cytokine production. Inflammatory cytokine levels were subsequently augmented in a STING-dependent extrinsic manner by infiltrating phagocytes purging dying cells. Consequently, STING-/- mice, or wild type mice adoptively transferred with STING-/- bone marrow, were almost completely resistant to DMBA-induced skin carcinogenesis compared to their wild type counterparts. Our data emphasizes, for the first time, a role for STING in the induction of cancer, sheds significant insight into the causes of inflammation-driven carcinogenesis, and may provide therapeutic strategies to help prevent malignant disease Total RNA obtained from wild type murine embryonic fibroblasts (WT MEFs), STING deficient MEFs (SKO), Trex1 deficient MEFs (TKO), and both STING and Trex1 deficient MEFs (STKO) treated with DMBA and examined cytokine production by these cells.
Project description:Inflammation is a key component of the pathogenesis of obesity-associated type 2 diabetes (T2D). However, the nature of T2D-associated islet inflammation and its impacts on T2D-associated beta cell abnormalities remain poorly defined. Using both diet-induced and genetically modified T2D animal models, we explore immune components of islet inflammation and define their roles in regulating beta cell function and proliferation. Our studies show that T2D-associated islet inflammation is uniquely dominated by macrophages, without the involvement of adaptive immune cells. We identify two islet macrophage populations, characterized by their distinct phenotypes, anatomical distributions and functional properties. Obesity induces a local expansion of intra-islet macrophages, independent of the replenishment from circulating monocytes. In contrast, the abundance of peri-islet macrophages is negligibly affected by obesity. Functionally, intra-islet macrophages impair beta cell function in a cell-cell contact dependent manner. In contrast, both intra- and peri-islet macrophage populations are able to promote beta cell proliferation. Together, these data provide a definitive view of the genesis of T2D-associated islet inflammation and define specific roles of islet macrophages in regulating beta cell function and proliferation.
Project description:Lysosomes are essential organelles for cellular homeostasis. Defective lysosomes are associated with many human diseases, such as lysosomal storage disorders (LSD). How the cell detects lysosomal defects and then restores lysosomal function remain incompletely understood. Here, we show that STING mediates a common neuroinflammatory gene signature in three distinct lysosomal storage disorders, Galctwi/twi, Ppt1-/-, and Cln7-/-. Transcriptomic analysis of Galctwi/twi brain tissue revealed that STING also mediates the expression of a broad panel of lysosomal genes that are part of the CLEAR (Coordinated Lysosomal Expression and Regulation) signaling pathway, which is regulated by transcriptional factor EB (TFEB). Immunohistochemical and single-nucleus RNA-seq analysis show that STING regulates lysosomal gene expression in microglia in LSD mice. Mechanistically, we show that STING activation in both human and mouse cells leads to TFEB dephosphorylation, nuclear translocation, and expression of target lysosomal genes. In addition, STING-mediated TFEB activation requires its proton channel function, the V-ATPase-ATG5-ATG8 cascade, and is independent of immune signaling. Functionally, we show that the STING-proton channel-TFEB axis plays a role in facilitating lysosomal repair. Together, our data identify STING-TFEB as a lysosomal quality control and recovery mechanism that responds to both genetic and chemically induced lysosomal dysfunction.