Project description:The eye is highly susceptible to inflammation-mediated tissue damage evoked during bacterial infection. We observed the itaconate as one of the highly induced metabolites in mouse retina and activated macrophages, yet its functional significance remains unknown in ocular infections.
Project description:The eye is highly susceptible to inflammation-mediated tissue damage evoked during bacterial infection. However, mechanisms regulating inflammation to protect the eye remain elusive. Here, we used integrated metabolomics and transcriptomics to show that the immunomodulatory metabolite itaconate and immune-responsive gene 1 (Irg1) are induced in bacterial (Staphylococcus aureus)-infected mouse eyes, bone-marrow-derived macrophages (BMDMs), and Müller glia. Itaconate levels are also elevated in the vitreous of patients with bacterial endophthalmitis. Irg1 deficiency in mice led to increased ocular pathology. Conversely, intraocular administration of itaconate protects both Irg1 -/- and wild-type mice from bacterial endophthalmitis by reducing inflammation, bacterial burden, and preserving retinal architecture and visual function. Notably, itaconate exerts synergistic effects with antibiotics. The protective, anti-inflammatory effects of itaconate are mediated via activation of NRF2/HO-1 signaling and inhibition of NLRP3 inflammasome. Collectively, our study demonstrates the Irg1/itaconate axis is a regulator of intraocular inflammation and provides evidence for using itaconate, along with antibiotics, to treat bacterial infections.
Project description:Remodeling of the tricarboxylic acid (TCA) cycle is a metabolic adaptation mechanism accompanying inflammatory macrophage activation. During this process, endogenous metabolites can adopt regulatory roles that govern specific aspects of inflammatory response, as recently shown for succinate, which regulates the downstream pro-inflammatory IL-1β-HIF1a axis. Itaconate is one of the most highly induced metabolites in activated macrophages, yet its functional significance remains unknown. Here, we show that itaconate modulates macrophage metabolism and effector functions via its effect on succinate dehydrogenase, by inhibiting conversion of succinate to fumarate. Through this action, itaconate exerts anti-inflammatory effects when administered in vitro and in vivo during macrophage activation and ischemia-reperfusion injury. Using newly generated Irg1-/- mice, which lack the ability to produce itaconate, we show that endogenous itaconate regulates succinate levels and function, changes in mitochondrial respiration, and inflammatory cytokine production during macrophage activation. These studies highlight itaconate as a major physiological regulator of the global metabolic rewiring and effector functions of inflammatory macrophages. Experiment 1: mature WT BMDM were treated for 12h with 0.25 mM dimethyl itaconate (DI) or vehicle (Unst) and then stimulated with LPS (E. coli 0111:B4; 100 ng/ml, 4h) (DI+LPS; LPS); Experiment 2: mature Irg1-/- BMDM were stimulated with LPS (E. coli 0111:B4; 100 ng/ml) and murine recombinant IFNg (50 ng/ml) for 24h.
Project description:One primary metabolic manifestation of inflammation is the diversion of cis-aconitate within the tricarboxylic acid (TCA) cycle to synthesize the immunometabolite itaconate. Itaconate is well established to possess immunomodulatory and metabolic effects within myeloid cells and lymphocytes, however, its effects in other organ systems during sepsis remain less clear. Utilizing Irg1 knockout mice that are deficient in synthesizing itaconate, we aimed at understanding the metabolic role of itaconate in the liver and systemically during sepsis. We find itaconate aids in lipid metabolism during sepsis. Specifically, Irg1 KO mice develop a heightened level of hepatic steatosis when induced with polymicrobial sepsis. Proteomics analysis reveal enhanced expression of enzymes involved in fatty acid oxidation in following 4-ocytl itaconate (4-OI) treatment in vitro. Downstream analysis reveals itaconate stabilizes the expression of the mitochondrial fatty acid uptake enzyme CPT1a, mediated by its hypoubiquitination. Chemoproteomic analysis revealed itaconate interacts with proteins involved in protein ubiquitination as a potential mechanism underlying its stabilizing effect on CPT1a. From a systemic perspective, we find itaconate deficiency triggers a hypothermic response following endotoxin stimulation, potentially mediated by brown adipose tissue (BAT) dysfunction. Finally, by use of metabolic cage studies, we demonstrate Irg1 KO mice rely more heavily on carbohydrates versus fatty acid sources for systemic fuel utilization in response to endotoxin treatment. Our data reveal a novel metabolic role of itaconate in modulating fatty acid oxidation during polymicrobial sepsis.
Project description:This dataset was generated to confirm that +130 and +146 Da adducts observed in LPS-stimulated macrophages were produced by the itaconate metabolite. To this end, model proteins (bovine serum albumin and human KEAP1) were reacted in vitro with itaconate, and the correspondent adducts were analyzed by LC-MSMS
Project description:Itaconate is an immunoregulatory metabolite produced by the mitochondrial enzyme immune-responsive gene 1 (IRG1) in inflammatory macrophages. We recently identified an important mechanism by which itaconate is released from inflammatory macrophages. However, it remains unknown whether extracellular itaconate is taken up by non-myeloid cells to exert immunoregulatory functions. Here, we used a custom-designed CRISPR screen to identify the dicarboxylate transporter solute carrier family 13 member 3 (SLC13A3) as an itaconate importer and to characterize the role of SLC13A3 in itaconate-improved hepatic antibacterial innate immunity. Functionally, liver-specific deletion of Slc13a3 impairs hepatic antibacterial innate immunity in vivo and in vitro. Mechanistically, itaconate uptake via SLC13A3 induces transcription factor EB (TFEB)-dependent lysosomal biogenesis and subsequently improves antibacterial innate immunity in murine hepatocytes. These findings identify SLC13A3 as a key itaconate importer in murine hepatocytes and will aid in the development of potent itaconate-based antibacterial therapeutics.
Project description:Ocular melanoma is a common primary malignant ocular tumor in adults with limited effective treatments, so novel therapeutic approaches are desperately needed. Epigenetic regulation plays an important role in tumor development. The SWI/SNF chromatin remodeling complex and bromodomain and extraterminal domain (BET) family proteins are epigenetic regulators involved in several cancers. We aimed to screen a candidate small molecule inhibitor targeting the SWI/SNF complex or BET proteins and investigate its effect and mechanism in ocular melanoma. Colony formation assays were applied to select the most effective candidate inhibitor (JQ-1). We observed phenotypes caused by knockdown of the corresponding gene and synergistic effects with BRD inhibitor (BRDi) treatment and SWI/SNF complex knockdown. We further validated the efficacy of JQ-1 in 10 ocular melanoma cell lines and a mouse xenograft model. The effect of JQ-1 on ocular melanoma cell cycle and apoptosis was analyzed with flow cytometry. We performed RNA sequencing in 2 pairs of ocular melanoma cell lines treated with JQ-1 and control cells treated with DMSO. Gene set enrichment analysis (GSEA) was performed for pathway analysis of the differentially expressed genes (DEGs). We also validated the correlations of DEGs with BRD4 and patient outcomes. Overall, JQ-1 may act downstream of BRD4 and suppress ocular melanoma growth by inducing G1 cell cycle arrest.
Project description:Itaconate has emerged as a critical immunoregulatory metabolite. Here, we examined the therapeutic potential of itaconate in atherosclerosis. We found that both itaconate and the enzyme that synthesizes it, aconitate decarboxylase 1 (Acod1, also known as “immune-responsive gene 1”/IRG1) are upregulated during atherogenesis in mice. Here we analzyed the anatomy of atherosclerotic plaques from wildtype and Acod1-/- mice through single cell RNA-seq.
Project description:Analysis of gene expression in human PBMCs infected with influenza A virus or Mock and treated with Itaconic acid, Dimethyl itaconate or 4-Octyl itaconate to investigate the effects itaconate have on transcriptional response in human PBMCs. We particularly looked at anti-inflammatory effects of itaconate in inflammation followed by Influenza A virus infection.
Project description:In colorectal cancer therapy anti-angiogenic strategies have become a cornerstone of treatment regimens in the metastatic setting. Addition of bevacizumab to conventional chemotherapeutic combination regimens has improved the median overall survival of advanced colorectal cancer patients by approximately 5 months. Selecting patients, who will benefit from anti-angiogenic approaches, would be highly desirable in order to optimize treatment strategies. Changes in ocular blood flow may be an attractive biomarker for predicting treatment response. In light of the given alternative first line treatment options such a predictive biomarker would be of clinical benefit. In the proposed study the investigators will assess potential changes in the ocular blood flow of mCRC patients after treatment with standard of care anti-angiogenic/cytotoxic therapy as an early predictive marker of treatment response as assessed by standard CT-scan