The role of itaconate in host defense and inflammation

Redox Regulation of Immunometabolism in Microglia Underpinning Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness among the working-age population. Microglia, resident immune cells in the retina, are recognized as crucial drivers in the DR process. Microglia activation is a tightly regulated immunometabolic process. In the early stages of DR, the M1 phenotype commonly shifts from oxidative phosphorylation to aerobic glycolysis for energy production. Emerging evidence suggests that microglia in DR not only engage specific metabolic pathways but also rearrange their oxidation-reduction (redox) system. This redox adaptation supports metabolic reprogramming and offers potential therapeutic strategies using antioxidants. Here, we provide an overview of recent insights into the involvement of reactive oxygen species and the distinct roles played by key cellular antioxidant pathways, including the NADPH oxidase 2 system, which promotes glycolysis via enhanced glucose transporter 4 translocation to the cell membrane through the AKT/mTOR pathway, as well as the involvement of the thioredoxin and nuclear factor E2-related factor 2 antioxidant systems, which maintain microglia in an anti-inflammatory state. Therefore, we highlight the potential for targeting the modulation of microglial redox metabolism to offer new concepts for DR treatment.

When Our Best Friend Becomes Our Worst Enemy: The Mitochondrion in Trauma, Surgery, and Critical Illness

Common for major surgery, multitrauma, sepsis, and critical illness, is a whole-body inflammation. Tissue injury is able to trigger a generalized inflammatory reaction. Cell death causes release of endogenous structures termed damage associated molecular patterns (DAMPs) that initiate a sterile inflammation. Mitochondria are evolutionary endosymbionts originating from bacteria, containing molecular patterns similar to bacteria. These molecular patterns are termed mitochondrial DAMPs (mDAMPs). Mitochondrial debris released into the extracellular space or into the circulation is immunogenic and damaging secondary to activation of the innate immune system. In the circulation, released mDAMPS are either free or exist in extracellular vesicles, being able to act on every organ and cell in the body. However, the role of mDAMPs in trauma and critical care is not fully clarified. There is a complete lack of knowledge how they may be counteracted in patients. Among mDAMPs are mitochondrial DNA, cardiolipin, N-formyl peptides, cytochrome C, adenosine triphosphate, reactive oxygen species, succinate, and mitochondrial transcription factor A. In this overview, we present the different mDAMPs, their function, release, targets, and inflammatory potential. In light of present knowledge, the role of mDAMPs in the pathophysiology of major surgery and trauma as well as sepsis, and critical care is discussed.

Itaconate impairs immune control of Plasmodium by enhancing mtDNA-mediated PD-L1 expression in monocyte-derived dendritic cells

Severe forms of malaria are associated with systemic inflammation and host metabolism disorders; however, the interplay between these outcomes is poorly understood. Using a Plasmodium chabaudi model of malaria, we demonstrate that interferon (IFN) γ boosts glycolysis in splenic monocyte-derived dendritic cells (MODCs), leading to itaconate accumulation and disruption in the TCA cycle. Increased itaconate levels reduce mitochondrial functionality, which associates with organellar nucleic acid release and MODC restraint. We hypothesize that dysfunctional mitochondria release degraded DNA into the cytosol. Once mitochondrial DNA is sensitized, the activation of IRF3 and IRF7 promotes the expression of IFN-stimulated genes and checkpoint markers. Indeed, depletion of the STING-IRF3/IRF7 axis reduces PD-L1 expression, enabling activation of CD8+ T cells that control parasite proliferation. In summary, mitochondrial disruption caused by itaconate in MODCs leads to a suppressive effect in CD8+ T cells, which enhances parasitemia. We provide evidence that ACOD1 and itaconate are potential targets for adjunct antimalarial therapy.

Zinc glycinate alleviates LPS-induced inflammation and intestinal barrier disruption in chicken embryos by regulating zinc homeostasis and TLR4/NF-κB pathway

The effect of an immune challenge induced by a lipopolysaccharide (LPS) exposure on systemic zinc homeostasis and the modulation of zinc glycinate (Zn-Gly) was investigated using a chicken embryo model. 160 Arbor Acres broiler fertilized eggs were randomly divided into 4 groups: CON (control group, injected with saline), LPS (LPS group, injected with 32 µg of LPS saline solution), Zn-Gly (zinc glycinate group, injected with 80 µg of zinc glycinate saline solution) and Zn-Gly+LPS (zinc glycinate and LPS group, injected with the same content of zinc glycinate and LPS saline solution). Each treatment consisted of eight replicates of five eggs each. An in ovo feeding procedure was performed at 17.5 embryonic day and samples were collected after 12 hours. The results showed that Zn-Gly attenuated the effects of LPS challenge-induced upregulation of pro-inflammatory factor interleukin 1β (IL-1β) level (P =0.003). The LPS challenge mediated zinc transporter proteins and metallothionein (MT) to regulate systemic zinc homeostasis, with increased expression of the jejunum zinc export gene zinc transporter protein 1 (ZnT-1) and elevated expression of the import genes divalent metal transporter 1 (DMT1), Zrt- and Irt-like protein 3 (Zip3), Zip8 and Zip14 (P < 0.05). A similar trend could be observed for the zinc transporter genes in the liver, which for ZnT-1 mitigated by Zn-Gly supplementation (P =0.01). Liver MT gene expression was downregulated in response to the LPS challenge (P =0.004). These alterations caused by LPS resulted in decreased serum and liver zinc levels and increased small intestinal, muscle and tibial zinc levels. Zn-Gly reversed the elevated expression of the liver zinc finger protein A20 induced by the LPS challenge (P =0.025), while Zn-Gly reduced the gene expression of the pro-inflammatory factors IL-1β and IL-6, decreased toll-like receptor 4 (TLR4) and nuclear factor kappa-B p65 (NF-κB p65) (P < 0.05). Zn-Gly also alleviated the LPS-induced downregulation of the intestinal barrier gene Claudin-1. Thus, LPS exposure prompted the mobilization of zinc transporter proteins and MT to perform the remodeling of systemic zinc homeostasis, Zn-Gly participated in the regulation of zinc homeostasis and inhibited the production of pro-inflammatory factors through the TLR4/NF-κB pathway, attenuating the inflammatory response and intestinal barrier damage caused by an immune challenge.

Gene expression response to Salmonella Typhimurium in the cecal tonsil reveals a potential mechanism of resistance in chickens

Salmonella has been one of the most important factors restricting the development of the poultry industry and also poses great threat to public health. To get insight into molecular alterations that occur during bacterial infection, we sequenced the cecal tonsil transcriptome in 2 chicken breeds (Beijing-You and Cobb) known to have differing resistance to Salmonella. The 28-day-old chickens were orally challenged by 1.83 × 1011 CFU Salmonella Typhimurium, and the cecal tonsil transcriptome was sequenced 3 d postinfection. Analysis identified 201 and 170 differentially expressed genes response to Salmonella in 2 chicken breeds, respectively. They were involved in the Toll-like receptor signaling pathway and activated the production of pro-inflammatory cytokines and chemokines. The protein-protein interaction (PPI) network suggested MMP9 as a crucial protein that may be involved in extracellular matrix breakdown and leukocyte migration in the resistant breed (Beijing-You). Meanwhile, in susceptible chickens (Cobb), ACOD1 was the key gene in the PPI network and might promote the expression of genes related to oxidative stress response and gastrointestinal tract function. These findings provide insight into the differing resistance of these 2 chicken breeds.

Monocyte immunometabolic reprogramming in human pregnancy: contribution of trophoblast cells

Immunometabolism research is uncovering the relationship between metabolic features and immune cell functions in physiological and pathological conditions. Normal pregnancy entails a fine immune and metabolic regulation of the maternal-fetal interaction to assist the energetic demands of the fetus with immune homeostasis maintenance. Here, we determined the immunometabolic status of monocytes of pregnant women compared with nonpregnant controls and its impact on monocyte anti-inflammatory functions such as efferocytosis. Monocytes from pregnant women (16-20 wk) and nonpregnant age-matched controls were studied. Single cell-based metabolic assays using freshly isolated monocytes from both groups were carried out in parallel with functional assays ex vivo to evaluate monocyte efferocytic capacity. On the other hand, various in vitro metabolic assays with human monocytes or monocyte-derived macrophages were designed to explore the effect of trophoblast cells in the profiles observed. We found that pregnancy alters monocyte metabolism and function. An increased glucose dependency and enhanced efferocytosis were detected in monocytes from pregnant women at resting states, compared with nonpregnant controls. Furthermore, monocytes display a reduced glycolytic response when stimulated with lipopolysaccharide (LPS). The metabolic profiling of monocytes at this stage of pregnancy was comparable with the immunometabolic phenotypes of human monocytes treated in vitro with human first trimester trophoblast cell conditioned media. These findings suggest that immunometabolic mechanisms are involved in the functional shaping of monocytes during pregnancy with a contribution of trophoblast cells. Results provide new clues for future hypotheses regarding pregnancies complicated by metabolic disorders.NEW & NOTEWORTHY Immunometabolism stands as a novel perspective to understand the complex regulation of the immune response and to provide small molecule-based therapies. By applying this approach to study monocytes during pregnancy, we found that these cells have a unique activation pattern. They rely more on glycolysis and show increased efferocytosis/IL-10 production, but they do not have the typical proinflammatory responses. We also present evidence that trophoblast cells can shape monocytes into this distinct immunometabolic profile.

IRG1 restrains M2 macrophage polarization and suppresses intrahepatic cholangiocarcinoma progression via the CCL18/STAT3 pathway

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant and aggressive cancer whose incidence and mortality continue to increase, whereas its prognosis remains dismal. Tumor-associated macrophages (TAMs) promote malignant progression and immune microenvironment remodeling through direct contact and secreted mediators. Targeting TAMs has emerged as a promising strategy for ICC treatment. Here, we revealed the potential regulatory function of immune responsive gene 1 (IRG1) in macrophage polarization. We found that IRG1 expression remained at a low level in M2 macrophages. IRG1 overexpression can restrain macrophages from polarizing to the M2 type, which results in inhibition of the proliferation, invasion, and migration of ICC, whereas IRG1 knockdown exerts the opposite effects. Mechanistically, IRG1 inhibited the tumor-promoting chemokine CCL18 and thus suppressed ICC progression by regulating STAT3 phosphorylation. The intervention of IRG1 expression in TAMs may serve as a potential therapeutic target for delaying ICC progression.

Early metabolic markers as predictors of respiratory complications in preterm infants with bronchopulmonary dysplasia

BACKGROUND

Bronchopulmonary dysplasia (BPD), a common complication of premature birth, exerts considerable impact on the respiratory health of infants. This study aimed to identify the role of plasma metabolites in predicting respiratory outcomes in BPD-afflicted infants.

METHODS

This was a case-control study including 15 BPD premature infants and 15 gestational age and birth weight matched no-BPD preterm infants. Plasma samples, obtained at 36 weeks postmenstrual age (PMA), were subjected to a comprehensive analysis of over 300 metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The respiratory outcomes of the infants were collected with the first 2 years of corrected postnatal age.

RESULTS

The analysis revealed a significant upregulation of urea and downregulation of nine metabolites in BPD infants, including oxalacetic acid, cis-aconitic acid, itaconic acid, betaine, L-asparagine, L-alanine, picolinic acid, inositol, and purine (p < 0.05). These metabolites primarily pertained to the citrate cycle (TCA cycle), glyoxylate and dicarboxylate metabolism, and alanine, aspartate, and glutamate metabolism. Furthermore, seven metabolites demonstrated substantial predictive capacity for respiratory readmissions within the first two years of corrected postnatal age, achieving an area under curve (AUC) exceeding or equal to 0.8. These included chenodeoxycholic acid, dehydrolithocholic acid, glucaric acid, D-glucuronic acid, gamma-glutamylvaline, mevalonic acid, and 3-ureidopropionic acid.

CONCLUSIONS

This study identified ten distinct plasma metabolites at 36 weeks PMA that differentiate BPD infants from their non-BPD counterparts, implicating three major metabolic pathways. Additionally, seven metabolites showed strong predictive value for heightened risk of respiratory readmission within two years, underscoring their potential utility in clinical prognostication and management strategies for BPD.

The aconitate decarboxylase 1/itaconate pathway modulates immune dysregulation and associates with cardiovascular disease markers in SLE

Objective

The Krebs cycle enzyme Aconitate Decarboxylase 1 (ACOD1) mediates itaconate synthesis in myeloid cells.. Previously, we reported that administration of 4-octyl itaconate abrogated lupus phenotype in mice. Here, we explore the role of the endogenous ACOD1/itaconate pathway in the development of murine lupus as well as their relevance in premature cardiovascular damage in SLE.

Methods

We characterized Acod1 protein expression in bone marrow-derived macrophages and human monocyte-derived macrophages, following a TLR7 agonist (imiquimod, IMQ). Wild type and Acod1-/- mice were exposed to topical IMQ for 5 weeks to induce an SLE phenotype and immune dysregulation was quantified. Itaconate serum levels were quantified in SLE patients and associated to cardiometabolic parameters and disease activity.

Results

ACOD1 was induced in mouse bone marrow-derived macrophages (BMDM) and human monocyte-derived macrophages following in vitro TLR7 stimulation. This induction was partially dependent on type I Interferon receptor signaling and specific intracellular pathways. In the IMQ-induced mouse model of lupus, ACOD1 knockout (Acod1-/-) displayed disruptions of the splenic architecture, increased serum anti-dsDNA and proinflammatory cytokine levels, enhanced kidney immune complex deposition and proteinuria, when compared to the IMQ-treated WT mice. Consistent with these results, Acod1-/- BMDM exposed to IMQ showed higher proinflammatory features in vitro. Itaconate levels were decreased in SLE serum compared to healthy control sera, in association with specific perturbed cardiometabolic parameters and subclinical vascular disease.

Conclusion

These findings suggest that the ACOD1/itaconate pathway plays important immunomodulatory and vasculoprotective roles in SLE, supporting the potential therapeutic role of itaconate analogs in autoimmune diseases.

Aerobic glycolysis of bronchial epithelial cells rewires Mycoplasma pneumoniae pneumonia and promotes bacterial elimination

The immune response to Mycoplasma pneumoniae infection plays a key role in clinical symptoms. Previous investigations focused on the pro-inflammatory effects of leukocytes and the pivotal role of epithelial cell metabolic status in finely modulating the inflammatory response have been neglected. Herein, we examined how glycolysis in airway epithelial cells is affected by M. pneumoniae infection in an in vitro model. Additionally, we investigated the contribution of ATP to pulmonary inflammation. Metabolic analysis revealed a marked metabolic shift in bronchial epithelial cells during M. pneumoniae infection, characterized by increased glucose uptake, enhanced aerobic glycolysis, and augmented ATP synthesis. Notably, these metabolic alterations are orchestrated by adaptor proteins, MyD88 and TRAM. The resulting synthesized ATP is released into the extracellular milieu via vesicular exocytosis and pannexin protein channels, leading to a substantial increase in extracellular ATP levels. The conditioned medium supernatant from M. pneumoniae-infected epithelial cells enhances the secretion of both interleukin (IL)-1β and IL-18 by peripheral blood mononuclear cells, partially mediated by the P2X7 purine receptor (P2X7R). In vivo experiments confirm that addition of a conditioned medium exacerbates pulmonary inflammation, which can be attenuated by pre-treatment with a P2X7R inhibitor. Collectively, these findings highlight the significance of airway epithelial aerobic glycolysis in enhancing the pulmonary inflammatory response and aiding pathogen clearance.

Itaconate stabilizes CPT1a to enhance lipid utilization during inflammation

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 Acod1 knockout mice that are deficient in synthesizing itaconate, we aimed to understand the metabolic role of itaconate in the liver and systemically during sepsis. We find itaconate aids in lipid metabolism during sepsis. Specifically, Acod1 KO mice develop a heightened level of hepatic steatosis when induced with polymicrobial sepsis. Proteomics analysis reveals enhanced expression of enzymes involved in fatty acid oxidation in following 4-octyl 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 Acod1 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.

The cGAS-STING pathway: a therapeutic target in diabetes and its complications

Diabetic wound healing (DWH) represents a major complication of diabetes where inflammation is a key impediment to proper healing. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway has emerged as a central mediator of inflammatory responses to cell stress and damage. However, the contribution of cGAS-STING activation to impaired healing in DWH remains understudied. In this review, we examine the evidence that cGAS-STING-driven inflammation is a critical factor underlying defective DWH. We summarize studies revealing upregulation of the cGAS-STING pathway in diabetic wounds and discuss how this exacerbates inflammation and senescence and disrupts cellular metabolism to block healing. Partial pharmaceutical inhibition of cGAS-STING has shown promise in damping inflammation and improving DWH in preclinical models. We highlight key knowledge gaps regarding cGAS-STING in DWH, including its relationships with endoplasmic reticulum stress and metal-ion signaling. Elucidating these mechanisms may unveil new therapeutic targets within the cGAS-STING pathway to improve healing outcomes in DWH. This review synthesizes current understanding of how cGAS-STING activation contributes to DWH pathology and proposes future research directions to exploit modulation of this pathway for therapeutic benefit.

ACOD1 deficiency offers protection in a mouse model of diet-induced obesity by maintaining a healthy gut microbiota

Aconitate decarboxylase 1 (ACOD1) is the enzyme synthesizing itaconate, an immuno-regulatory metabolite tuning host-pathogen interactions. Such functions are achieved by affecting metabolic pathways regulating inflammation and microbe survival. However, at the whole-body level, metabolic roles of itaconate remain largely unresolved. By using multiomics-integrated approaches, here we show that ACOD1 responds to high-fat diet consumption in mice by promoting gut microbiota alterations supporting metabolic disease. Genetic disruption of itaconate biosynthesis protects mice against obesity, alterations in glucose homeostasis and liver metabolic dysfunctions by decreasing meta-inflammatory responses to dietary lipid overload. Mechanistically, fecal metagenomics and microbiota transplantation experiments demonstrate such effects are dependent on an amelioration of the intestinal ecosystem composition, skewed by high-fat diet feeding towards obesogenic phenotype. In particular, unbiased fecal microbiota profiling and axenic culture experiments point towards a primary role for itaconate in inhibiting growth of Bacteroidaceae and Bacteroides, family and genus of Bacteroidetes phylum, the major gut microbial taxon associated with metabolic health. Specularly to the effects imposed by Acod1 deficiency on fecal microbiota, oral itaconate consumption enhances diet-induced gut dysbiosis and associated obesogenic responses in mice. Unveiling an unrecognized role of itaconate, either endogenously produced or exogenously administered, in supporting microbiota alterations underlying diet-induced obesity in mice, our study points ACOD1 as a target against inflammatory consequences of overnutrition.

Anti-Necroptotic Effects of Itaconate and its Derivatives

Itaconate is an unsaturated dicarboxylic acid that is derived from the decarboxylation of the Krebs cycle intermediate cis-aconitate and has been shown to exhibit anti-inflammatory and anti-bacterial/viral properties. But the mechanisms underlying itaconate's anti-inflammatory activities are not fully understood. Necroptosis, a lytic form of regulated cell death (RCD), is mediated by receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL) signaling. It has been involved in the pathogenesis of organ injury in many inflammatory diseases. In this study, we aimed to explore whether itaconate and its derivatives can inhibit necroptosis in murine macrophages, a mouse MPC-5 cell line and a human HT-29 cell line in response to different necroptotic activators. Our results showed that itaconate and its derivatives dose-dependently inhibited necroptosis, among which dimethyl itaconate (DMI) was the most effective one. Mechanistically, itaconate and its derivatives inhibited necroptosis by suppressing the RIPK1/RIPK3/MLKL signaling and the oligomerization of MLKL. Furthermore, DMI promoted the nuclear translocation of Nrf2 that is a critical regulator of intracellular redox homeostasis, and reduced the levels of intracellular reactive oxygen species (ROS) and mitochondrial superoxide (mtROS) that were induced by necroptotic activators. Consistently, DMI prevented the loss of mitochondrial membrane potential induced by the necroptotic activators. In addition, DMI mitigated caerulein-induced acute pancreatitis in mice accompanied by reduced activation of the necroptotic signaling in vivo. Collectively, our study demonstrates that itaconate and its derivatives can inhibit necroptosis by suppressing the RIPK1/RIPK3/MLKL signaling, highlighting their potential applications for treating necroptosis-associated diseases.

Polyguluronate alleviates ulcerative colitis by targeting the gut commensal Lactobacillus murinus and its anti-inflammatory metabolites

Polyguluronate (PG) is a fermentable polysaccharide from edible algae. The present study was designed to investigate the therapeutic effect of PG on ulcerative colitis (UC) and its underlying mechanisms. Our results suggest that oral intake of PG attenuates UC and improves gut microbiota dysbiosis by promoting the growth of Lactobacillus spp. in dextran sulfate sodium-fed mice. Five different species of Lactobacillus were isolated from the feces of PG-treated mice and L. murinus was identified to have the best anti-colitis effect, suggesting a critical role for L. murinus in mediating the therapeutic effect of PG. Furthermore, PG was degraded potentially by the beta-glucuronidase from L. murinus and adding PG to the culture medium of L. murinus remarkably increased its production of anti-inflammatory metabolites, including itaconic acid, cis-11,14-eicosadienoic acid, and 3-amino-3-(2-chlorophenyl)-propionic acid. Additionally, L. salivarius, a human intestine-derived PG-utilizing species that is closely related to L. murinus, was also demonstrated to have potent anti-colitis effects, suggesting that it is a candidate target of PG in the human gut. Altogether, our study illustrates an unprecedented application of PG in the treatment of UC and establishes the basis for understanding its therapeutic effect from the perspective of L. murinus and its metabolites.

4-octyl itaconate inhibits high glucose induced renal tubular epithelial cell fibrosis through TGF-β-ROS pathway

Diabetic kidney disease (DKD) is one of the most serious complications of diabetes and has become the leading cause of end-stage kidney disease, causing serious health damage and a huge economic burden. Tubulointerstitial fibrosis play important role in the development of DKD. Itaconate, a macrophage-specific metabolite, has been reported to have anti-oxidant, anti-inflammatory effects. However, it is unknown whether it perform anti-fibrotic effect in renal tubular epithelial cells. In this current study, we observed that in human renal tubular epithelial cells (HK2), high glucose induced an increase in transforming growth factor β (TGF-β) production, and upregulated the expressions of fibronectin and collagen I through the TGF-β receptor as verified by administration of TGF-β receptor blocker LY2109761. Treatment with 4-octyl itaconate (4-OI), a derivant of itaconic acid, reduced the TGF-β production induced by high glucose and inhibited the pro-fibrotic effect of TGF-β in a dose-dependent manner. In addition, we found that 4-OI exerted its anti-fibrotic effect by inhibiting the excessive production of ROS induced by high glucose and TGF-β. In summary, 4-OI could ameliorate high glucose-induced pro-fibrotic effect in HK2 cell, and blocking the expression of TGF-β and reducing the excessive ROS production may be involved in its anti-fibrotic effect.

The mitochondrial thiolase ACAT1 regulates monocyte/macrophage type I interferon via epigenetic control

Lipid-derived acetyl-CoA is shown to be the major carbon source for histone acetylation. However, there is no direct evidence demonstrating lipid metabolic pathway contribututions to this process. Mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1) catalyzes the final step of ß-oxidation, the aerobic process catabolizing fatty acids (FA) into acetyl-CoA. To investigate this in the context of immunometabolism, we generated macrophage cell line lacking ACAT1. 13C-carbon tracing combined with mass spectrometry confirmed incorporation of FA-derived carbons into histone H3 and this incorporation was reduced in ACAT1 KO macrophage cells. RNA-seq identified a subset of genes downregulated in ACAT1 KO cells including STAT1/2 and interferon stimulated genes (ISGs). CHIP analysis demonstrated reduced acetyl-H3 binding to STAT1 promoter/enhancer regions. Increasing histone acetylation rescued STAT1/2 expression in ACAT1 KO cells. Concomitantly, ligand triggered IFNβ release was blunted in ACAT1 KO cells and rescued by reconstitution of ACAT1. Furthermore, ACAT1 promotes FA-mediated histone acetylation in an acetylcarnitine shuttle-dependent manner. In patients with obesity, levels of ACAT1 and histone acetylation are abnormally elevated. Thus, our study identified a novel link between ACAT1 mediated FA metabolism and epigenetic modification on STAT1/2 that uncovers a regulatory role of lipid metabolism in innate immune signaling and opens novel avenues for interventions in human diseases such as obesity.

Identification of apoptosis-related gene signatures as potential biomarkers for differentiating active from latent tuberculosis via bioinformatics analysis

Background

Apoptosis is associated with the pathogenesis of Mycobacterium tuberculosis infection. This study aims to identify apoptosis-related genes as biomarkers for differentiating active tuberculosis (ATB) from latent tuberculosis infection (LTBI).

Methods

The tuberculosis (TB) datasets (GSE19491, GSE62525, and GSE28623) were downloaded from the Gene Expression Omnibus (GEO) database. The diagnostic biomarkers differentiating ATB from LTBI were identified by combining the data of protein-protein interaction network, differentially expressed gene, Weighted Gene Co-Expression Network Analysis (WGCNA), and receiver operating characteristic (ROC) analyses. Machine learning algorithms were employed to validate the diagnostic ability of the biomarkers. Enrichment analysis for biomarkers was established, and potential drugs were predicted. The association between biomarkers and N6-methyladenosine (m6A) or 5-methylated cytosine (m5C) regulators was evaluated.

Results

Six biomarkers including CASP1, TNFSF10, CASP4, CASP5, IFI16, and ATF3 were obtained for differentiating ATB from LTBI. They showed strong diagnostic performances, with area under ROC (AUC) values > 0.7. Enrichment analysis demonstrated that the biomarkers were involved in immune and inflammation responses. Furthermore, 24 drugs, including progesterone and emricasan, were predicted. The correlation analysis revealed that biomarkers were positively correlated with most m6A or m5C regulators.

Conclusion

The six ARGs can serve as effective biomarkers differentiating ATB from LTBI and provide insight into the pathogenesis of Mycobacterium tuberculosis infection.

Small organic molecules containing amorphous calcium phosphate: synthesis, characterization and transformation

As the primary solid phase, amorphous calcium phosphate (ACP) is a pivotal precursor in cellular biomineralization. The intrinsic interplay between ACP and Howard factor underscores the significance of understanding their association for advancing biomimetic ACP development. While organic compounds play established roles in biomineralization, this study presents the synthesis of ACP with naturally occurring organic compounds (ascorbate, glutamate, and itaconate) ubiquitously found in mitochondria and vital for bone remodeling and healing. The developed ACP with organic compounds was meticulously characterized using XRD, FTIR, and solid-state 13C and 31P NMR. The morphological analysis revealed the characteristic spherical morphology with particle size close to 20 nm of all synthesized ACP variants. Notably, the type of organic compound strongly influences true density, specific surface area, particle size, and transformation. The in vitro analysis was performed with MC3T3-E1 cells, indicating the highest cell viability with ACP_ASC (ascorbate), followed by ACP_ITA (itaconate). The lowest cell viability was observed with 10 %w/v of ACP_GLU (glutamate); however, 1 %w/v of ACP_GLU was cytocompatible. Further, the effect of small organic molecules on the transformation of ACP to low crystalline apatite (Ap) was examined in Milli-Q® water, PBS, and α-MEM.

Mitochondrial-derived vesicles in metabolism, disease, and aging

Mitochondria are central hubs of cellular metabolism and are tightly connected to signaling pathways. The dynamic plasticity of mitochondria to fuse, divide, and contact other organelles to flux metabolites is central to their function. To ensure bona fide functionality and signaling interconnectivity, diverse molecular mechanisms evolved. An ancient and long-overlooked mechanism is the generation of mitochondrial-derived vesicles (MDVs) that shuttle selected mitochondrial cargoes to target organelles. Just recently, we gained significant insight into the mechanisms and functions of MDV transport, ranging from their role in mitochondrial quality control to immune signaling, thus demonstrating unexpected and diverse physiological aspects of MDV transport. This review highlights the origin of MDVs, their biogenesis, and their cargo selection, with a specific focus on the contribution of MDV transport to signaling across cell and organ barriers. Additionally, the implications of MDVs in peroxisome biogenesis, neurodegeneration, metabolism, aging, and cancer are discussed.

4-Octyl Itaconate Alleviates Airway Eosinophilic Inflammation by Suppressing Chemokines and Eosinophil Development

4-Octyl itaconate (4-OI) is a derivative of the Krebs cycle-derived metabolite itaconate and displays an array of antimicrobial and anti-inflammatory properties through modifying cysteine residues within protein targets. We have found that 4-OI significantly reduces the production of eosinophil-targeted chemokines in a variety of cell types, including M1 and M2 macrophages, Th2 cells, and A549 respiratory epithelial cells. Notably, the suppression of these chemokines in M1 macrophages was found to be NRF2-dependent. In addition, 4-OI can interfere with IL-5 signaling and directly affect eosinophil differentiation. In a model of eosinophilic airway inflammation in BALB/c mice, 4-OI alleviated airway resistance and reduced eosinophil recruitment to the lungs. Our findings suggest that itaconate derivatives could be promising therapeutic agents for the treatment of eosinophilic asthma.

Carbon metabolism in the regulation of macrophage functions

Carbon metabolism, including one-carbon (1C) metabolism and central carbon metabolism (CCM), provides energy for the cell and generates metabolites with signaling activities. The regulation of macrophage polarization involves complex signals and includes an epigenetic level. Epigenetic modifications through changes in carbon metabolism allow macrophages to respond in a timely manner to their environment and adapt to metabolic demands during macrophage polarization. Here we summarize the current understanding of the crosstalk between carbon metabolism and epigenetic modifications in macrophages under physiological conditions and in the tumor microenvironment (TME) and provide targets and further directions for macrophage-associated diseases.

Itaconate inhibits CD103 + T RM cells and alleviates hepatobiliary injury in mouse models of primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic progressive liver disease characterized by the infiltration of intrahepatic tissue-resident memory CD8 + T cells (T RM ). Itaconate has demonstrated therapeutic potential in modulating inflammation. An unmet need for PSC is the reduction of biliary inflammation, and we hypothesized that itaconate may directly modulate pathogenic T RM .

APPROACH AND RESULTS

The numbers of intrahepatic CD103 + T RM were evaluated by immunofluorescence in PSC (n = 32), and the serum levels of itaconate in PSC (n = 64), primary biliary cholangitis (PBC) (n = 60), autoimmune hepatitis (AIH) (n = 49), and healthy controls (n = 109) were determined by LC-MS/MS. In addition, the frequencies and immunophenotypes of intrahepatic T RM using explants from PSC (n = 5) and healthy donors (n = 6) were quantitated by flow cytometry. The immunomodulatory properties of 4-octyl itaconate (4-OI, a cell-permeable itaconate derivative) on CD103 + T RM were studied in vitro. Finally, the therapeutic potential of itaconate was studied by the administration of 4-OI and deficiency of immune-responsive gene 1 (encodes the aconitate decarboxylase producing itaconate) in murine models of PSC. Intrahepatic CD103 + T RM was significantly expanded in PSC and was positively correlated with disease severity. Serum itaconate levels decreased in PSC. Importantly, 4-OI inhibited the induction and effector functions of CD103 + T RM in vitro. Mechanistically, 4-OI blocked DNA demethylation of RUNX3 in CD8 + T cells. Moreover, 4-OI reduced intrahepatic CD103 + T RM and ameliorated liver injury in murine models of PSC.

CONCLUSIONS

Itaconate exerted immunomodulatory activity on CD103 + T RM in both in vitro and murine PSC models. Our study suggests that targeting pathogenic CD103 + T RM with itaconate has therapeutic potential in PSC.

Metabolic Enzymes in Viral Infection and Host Innate Immunity

Metabolic enzymes are central players for cell metabolism and cell proliferation. These enzymes perform distinct functions in various cellular processes, such as cell metabolism and immune defense. Because viral infections inevitably trigger host immune activation, viruses have evolved diverse strategies to blunt or exploit the host immune response to enable viral replication. Meanwhile, viruses hijack key cellular metabolic enzymes to reprogram metabolism, which generates the necessary biomolecules for viral replication. An emerging theme arising from the metabolic studies of viral infection is that metabolic enzymes are key players of immune response and, conversely, immune components regulate cellular metabolism, revealing unexpected communication between these two fundamental processes that are otherwise disjointed. This review aims to summarize our present comprehension of the involvement of metabolic enzymes in viral infections and host immunity and to provide insights for potential antiviral therapy targeting metabolic enzymes.

Profiling whole-tissue metabolic reprogramming during cutaneous poxvirus infection and clearance

IMPORTANCE

Human poxvirus infections have caused significant public health burdens both historically and recently during the unprecedented global Mpox virus outbreak. Although vaccinia virus (VACV) infection of mice is a commonly used model to explore the anti-poxvirus immune response, little is known about the metabolic changes that occur in vivo during infection. We hypothesized that the metabolome of VACV-infected skin would reflect the increased energetic requirements of both virus-infected cells and immune cells recruited to sites of infection. Therefore, we profiled whole VACV-infected skin using untargeted mass spectrometry to define the metabolome during infection, complementing these experiments with flow cytometry and transcriptomics. We identified specific metabolites, including nucleotides, itaconic acid, and glutamine, that were differentially expressed during VACV infection. Together, this study offers insight into both virus-specific and immune-mediated metabolic pathways that could contribute to the clearance of cutaneous poxvirus infection.

Itaconate suppresses atherosclerosis by activating a Nrf2-dependent antiinflammatory response in macrophages in mice

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. Deletion of Acod1 in myeloid cells exacerbated inflammation and atherosclerosis in vivo and resulted in an elevated frequency of a specific subset of M1-polarized proinflammatory macrophages in the atherosclerotic aorta. Importantly, Acod1 levels were inversely correlated with clinical occlusion in atherosclerotic human aorta specimens. Treating mice with the itaconate derivative 4-octyl itaconate attenuated inflammation and atherosclerosis induced by high cholesterol. Mechanistically, we found that the antioxidant transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), was required for itaconate to suppress macrophage activation induced by oxidized lipids in vitro and to decrease atherosclerotic lesion areas in vivo. Overall, our work shows that itaconate suppresses atherogenesis by inducing Nrf2-dependent inhibition of proinflammatory responses in macrophages. Activation of the itaconate pathway may represent an important approach to treat atherosclerosis.

Itaconate promotes hepatocellular carcinoma progression by epigenetic induction of CD8+ T-cell exhaustion

Itaconate is a well-known immunomodulatory metabolite; however, its role in hepatocellular carcinoma (HCC) remains unclear. Here, we find that macrophage-derived itaconate promotes HCC by epigenetic induction of Eomesodermin (EOMES)-mediated CD8+ T-cell exhaustion. Our results show that the knockout of immune-responsive gene 1 (IRG1), responsible for itaconate production, suppresses HCC progression. Irg1 knockout leads to a decreased proportion of PD-1+ and TIM-3+ CD8+ T cells. Deletion or adoptive transfer of CD8+ T cells shows that IRG1-promoted tumorigenesis depends on CD8+ T-cell exhaustion. Mechanistically, itaconate upregulates PD-1 and TIM-3 expression levels by promoting succinate-dependent H3K4me3 of the Eomes promoter. Finally, ibuprofen is found to inhibit HCC progression by targeting IRG1/itaconate-dependent tumor immunoevasion, and high IRG1 expression in macrophages predicts poor prognosis in HCC patients. Taken together, our results uncover an epigenetic link between itaconate and HCC and suggest that targeting IRG1 or itaconate might be a promising strategy for HCC treatment.

Metabolite itaconate in host immunoregulation and defense

Metabolic states greatly influence functioning and differentiation of immune cells. Regulating the metabolism of immune cells can effectively modulate the host immune response. Itaconate, an intermediate metabolite derived from the tricarboxylic acid (TCA) cycle of immune cells, is produced through the decarboxylation of cis-aconitate by cis-aconitate decarboxylase in the mitochondria. The gene encoding cis-aconitate decarboxylase is known as immune response gene 1 (IRG1). In response to external proinflammatory stimulation, macrophages exhibit high IRG1 expression. IRG1/itaconate inhibits succinate dehydrogenase activity, thus influencing the metabolic status of macrophages. Therefore, itaconate serves as a link between macrophage metabolism, oxidative stress, and immune response, ultimately regulating macrophage function. Studies have demonstrated that itaconate acts on various signaling pathways, including Keap1-nuclear factor E2-related factor 2-ARE pathways, ATF3-IκBζ axis, and the stimulator of interferon genes (STING) pathway to exert antiinflammatory and antioxidant effects. Furthermore, several studies have reported that itaconate affects cancer occurrence and development through diverse signaling pathways. In this paper, we provide a comprehensive review of the role IRG1/itaconate and its derivatives in the regulation of macrophage metabolism and functions. By furthering our understanding of itaconate, we intend to shed light on its potential for treating inflammatory diseases and offer new insights in this field.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

Uncoupling protein 2 modulates polarization and metabolism of human primary macrophages via glycolysis and the NF‑κB pathway

Metabolic abnormalities, particularly the M1/M2 macrophage imbalance, play a critical role in the development of various diseases, leading to severe inflammatory responses. The present study aimed to investigate the role of uncoupling protein 2 (UCP2) in regulating macrophage polarization, glycolysis, metabolic reprogramming, reactive oxygen species (ROS) and inflammation. Primary human macrophages were first polarized into M1 and M2 subtypes, and these two subtypes were infected by lentivirus-mediated UCP2 overexpression or knockdown, followed by enzyme-linked immunosorbent assay, reverse transcription-quantitative PCR, western blotting and flow cytometry to analyze the effects of UCP2 on glycolysis, oxidative phosphorylation (OXPHOS), ROS production and cytokine secretion, respectively. The results demonstrated that UCP2 expression was suppressed in M1 macrophages and increased in M2 macrophages, suggesting its regulatory role in macrophage polarization. UCP2 overexpression decreased macrophage glycolysis, increased OXPHOS, decreased ROS production, and led to the conversion of M1 polarization to M2 polarization. This process involved NF-κB signaling to regulate the secretion profile of cytokines and chemokines and affected the expression of key enzymes of glycolysis and a key factor for maintaining mitochondrial homeostasis (nuclear respiratory factor 1). UCP2 knockdown in M2 macrophages exacerbated inflammation and oxidative stress by promoting glycolysis, which was attenuated by the glycolysis inhibitor 2-deoxyglucose. These findings highlight the critical role of UCP2 in regulating macrophage polarization, metabolism, inflammation and oxidative stress through its effects on glycolysis, providing valuable insights into potential therapeutic strategies for macrophage-driven inflammatory and metabolic diseases.

The yin and yang of itaconate metabolism and its impact on the tumor microenvironment

The tumor microenvironment (TME) consists of a network of metabolically interconnected tumor and immune cell types. Macrophages influence the metabolic composition within the TME, which directly impacts the metabolic state and drug response of tumors. The accumulation of oncometabolites, such as succinate, fumarate, and 2-hydroxyglutarate, represents metabolic vulnerabilities in cancer that can be targeted therapeutically. Immunometabolites are emerging as metabolic regulators of the TME impacting immune cell functions and cancer cell growth. Here, we discuss recent discoveries on the potential impact of itaconate on the TME. We highlight how itaconate influences metabolic pathways relevant to immune responses and cancer cell proliferation. We also consider the therapeutic implications of manipulating itaconate metabolism as an immunotherapeutic strategy to constrain tumor growth.

Elastomeric Polyesters in Cardiovascular Tissue Engineering and Organs-on-a-Chip

Cardiovascular tissue constructs provide unique design requirements due to their functional responses to substrate mechanical properties and cyclic stretching behavior of cardiac tissue that requires the use of durable elastic materials. Given the diversity of polyester synthesis approaches, an opportunity exists to develop a new class of biocompatible, elastic, and immunomodulatory cardiovascular polymers. Furthermore, elastomeric polyester materials have the capability to provide tailored biomechanical synergy with native tissue and hence reduce inflammatory response in vivo and better support tissue maturation in vitro. In this review, we highlight underlying chemistry and design strategies of polyester elastomers optimized for cardiac tissue scaffolds. The major advantages of these materials such as their tunable elasticity, desirable biodegradation, and potential for incorporation of bioactive compounds are further expanded. Unique fabrication methods using polyester materials such as micromolding, 3D stamping, electrospinning, laser ablation, and 3D printing are discussed. Moreover, applications of these biomaterials in cardiovascular organ-on-a-chip devices and patches are analyzed. Finally, we outline unaddressed challenges in the field that need further study to enable the impactful translation of soft polyesters to clinical applications.

Influence of Microbiota-Related Metabolites Associated with Inflammation and Sepsis on the Peroxidase Activity of Cyclooxygenase in Healthy Human Monocytes and Acute Monocytic Leukemia Cells

The human microbiota produces metabolites that can enter the bloodstream and exert systemic effects on various functions in both healthy and pathological states. We have studied the participation of microbiota-related metabolites in bacterial infection by examining their influence on the activity of cyclooxygenase (COX) as a key enzyme of inflammation. The influence of aromatic microbial metabolites, derivatives of phenylalanine (phenylpropionic acid, PPA), tyrosine (4-hydroxyphenyllactic acid, HPLA), and tryptophan (indolacetic acids, IAA), the concentrations of which in the blood change notably during sepsis, was evaluated. Also, the effect of itaconic acid (ITA) was studied, which is formed in macrophages under the action of bacterial lipopolysaccharides (LPS) and appears in the blood in the early stages of infection. Metabiotic acetyl phosphate (AcP) as a strong acetylating agent was also tested. The activity of COX was measured via the TMPD oxidation colorimetric assay using the commercial pure enzyme, cultured healthy monocytes, and the human acute monocytic leukemia cell line THP-1. All metabolites in the concentration range of 100-500 μM lowered the activity of COX. The most pronounced inhibition was observed on the commercial pure enzyme, reaching up to 40% in the presence of AcP and 20-30% in the presence of the other metabolites. On cell lysates, the effect of metabolites was preserved, although it significantly decreased, probably due to their interaction with other targets subject to redox-dependent and acetylation processes. The possible contribution of the redox-dependent action of microbial metabolites was confirmed by assessing the activity of the enzyme in the presence of thiol reagents and in model conditions, when the COX-formed peroxy intermediate was replaced with tert-butyl hydroperoxide (TBH). The data show the involvement of the microbial metabolites in the regulation of COX activity, probably due to their influence on the peroxidase activity of the enzyme.

The multifaceted roles of activating transcription factor 3 (ATF3) in inflammatory responses - Potential target to regulate neuroinflammation in acute brain injury

Activating transcription factor 3 (ATF3) is one of the most important transcription factors that respond to and exert dual effects on inflammatory responses. Recently, the involvement of ATF3 in the neuroinflammatory response to acute brain injury (ABI) has been highlighted. It functions by regulating neuroimmune activation and the production of neuroinflammatory mediators. Notably, recent clinical evidence suggests that ATF3 may serve as a potential ideal biomarker of the long-term prognosis of ABI patients. This mini-review describes the essential inflammation modulatory roles of ATF3 in different disease contexts and summarizes the regulatory mechanisms of ATF3 in the ABI-induced neuroinflammation.

4-Octyl itaconate inhibits inflammation to attenuate psoriasis as an agonist of oxeiptosis

Psoriasis is a highly prevalent chronic disease associated with a substantial social and economic burden. Oxeiptosis is a programmed cell death that occurs when cells are in a state of high oxidative stress, which has a potent anti-inflammatory effect. However, there is still no research on oxeiptosis in psoriasis, and the agonists or antagonists of oxeiptosis remain an unclear field. Here, we found that oxeiptosis of keratinocytes was inhibited in psoriasis lesions. KEAP1, as the upstream molecular component of oxeiptosis, is highly expressed in psoriasis lesions. Knockdown of KEAP1 in HaCaT cells caused oxeiptosis in the condition of M5 cocktail stimulation. Next, we found that the cell-permeable derivative of itaconate, 4-octylitaconate (OI) promoted oxeiptosis of keratinocytes by inhibiting KEAP1 and then activating PGAM5 which are two upstream molecular components of oxeiptosis. At the same time, OI can reduce the expression of inflammatory cytokines induced by M5 cocktail stimulation in vitro. Similarly, we found that OI can alleviate IMQ-induced psoriatic lesions in mice and downregulate the levels of inflammatory cytokines in psoriatic lesions. In summary, our findings suggest that oxeiptosis of keratinocytes was inhibited in psoriasis and OI can significantly inhibit inflammation and alleviate psoriasis as an agonist of oxeiptosis, indicating that oxeiptosis may be involved in regulating the progression of psoriasis, which may provide new therapeutic targets for psoriasis treatment.

Ethanol Extract of Rosa rugosa Ameliorates Acetaminophen-Induced Liver Injury via Upregulating Sirt1 and Subsequent Potentiation of LKB1/AMPK/Nrf2 Cascade in Hepatocytes

Acetaminophen (APAP)-induced liver injury is a common hepatic disease resulting from drug abuse. Few targeted treatments are available clinically nowadays. The flower bud of Rosa rugosa has a wide range of biological activities. However, it is unclear whether it alleviates liver injury caused by APAP. Here, we prepared an ethanol extract of Rosa rugosa (ERS) and analyzed its chemical profile. Furthermore, we revealed that ERS significantly ameliorated APAP-induced apoptosis and ferroptosis in AML-12 hepatocytes and dampened APAP-mediated cytotoxicity. In AML-12 cells, ERS elevated Sirt1 expression, boosted the LKB1/AMPK/Nrf2 axis, and thereby crippled APAP-induced intracellular oxidative stress. Both EX527 and NAM, which are chemically unrelated inhibitors of Sirt1, blocked ERS-induced activation of LKB1/AMPK/Nrf2 signaling. The protection of ERS against APAP-triggered toxicity in AML-12 cells was subsequently abolished. As expression of LKB1 was knocked down, ERS still upregulated Sirt1 but failed to activate AMPK/Nrf2 cascade or suppress cytotoxicity provoked by APAP. Results of in vivo experiments showed that ERS attenuated APAP-caused hepatocyte apoptosis and ferroptosis and improved liver injury and inflammation. Consistently, ERS boosted Sirt1 expression, increased phosphorylations of LKB1 and AMPK, and promoted Nrf2 nuclear translocation in the livers of APAP-intoxicated mice. Hepatic transcriptions of HO-1 and GCLC, which are downstream antioxidant genes of Nrf2, were also significantly increased in response to ERS. Our results collectively indicated that ERS effectively attenuates APAP-induced liver injury by activating LKB1/AMPK/Nrf2 cascade. Upregulated expression of Sirt1 plays a crucial role in ERS-mediated activation of LKB1.

Itaconate inhibits SYK through alkylation and suppresses inflammation against hvKP induced intestinal dysbiosis

Hypervirulent Klebsiella pneumoniae (hvKP) is a highly lethal opportunistic pathogen that elicits more severe inflammatory responses compared to classical Klebsiella pneumoniae (cKP). In this study, we investigated the interaction between hvKP infection and the anti-inflammatory immune response gene 1 (IRG1)-itaconate axis. Firstly, we demonstrated the activation of the IRG1-itaconate axis induced by hvKP, with a dependency on SYK signaling rather than STING. Importantly, we discovered that exogenous supplementation of itaconate effectively inhibited excessive inflammation by directly inhibiting SYK kinase at the 593 site through alkylation. Furthermore, our study revealed that itaconate effectively suppressed the classical activation phenotype (M1 phenotype) and macrophage cell death induced by hvKP. In vivo experiments demonstrated that itaconate administration mitigated hvKP-induced disturbances in intestinal immunopathology and homeostasis, including the restoration of intestinal barrier integrity and alleviation of dysbiosis in the gut microbiota, ultimately preventing fatal injury. Overall, our study expands the current understanding of the IRG1-itaconate axis in hvKP infection, providing a promising foundation for the development of innovative therapeutic strategies utilizing itaconate for the treatment of hvKP infections.

Exosomal MicroRNAs: An Emerging Important Regulator in Acute Lung Injury

Acute lung injury (ALI) is a clinically life-threatening form of respiratory failure with a mortality of 30%-40%. Acute respiratory distress syndrome is the aggravated form of ALI. Exosomes are extracellular lipid vesicles ubiquitous in human biofluids with a diameter of 30-150 nm. They can serve as carriers to convey their internal cargo, particularly microRNA (miRNA), to the target cells involved in cellular communication. In disease states, the quantities of exosomes and the cargo generated by cells are altered. These exosomes subsequently function as autocrine or paracrine signals to nearby or distant cells, regulating various pathogenic processes. Moreover, exosomal miRNAs from multiple stem cells can provide therapeutic value for ALI by regulating different signaling pathways. In addition, changes in exosomal miRNAs of biofluids can serve as biomarkers for the early diagnosis of ALI. This study aimed to review the role of exosomal miRNAs produced by different sources participating in various pathological processes of ALI and explore their potential significance in the treatment and diagnosis.

Ketogenesis promotes tolerance to Pseudomonas aeruginosa pulmonary infection

Pseudomonas aeruginosa is a common cause of pulmonary infection. As a Gram-negative pathogen, it can initiate a brisk and highly destructive inflammatory response; however, most hosts become tolerant to the bacterial burden, developing chronic infection. Using a murine model of pneumonia, we demonstrate that this shift from inflammation to disease tolerance is promoted by ketogenesis. In response to pulmonary infection, ketone bodies are generated in the liver and circulate to the lungs where they impose selection for P. aeruginosa strains unable to display surface lipopolysaccharide (LPS). Such keto-adapted LPS strains fail to activate glycolysis and tissue-damaging cytokines and, instead, facilitate mitochondrial catabolism of fats and oxidative phosphorylation (OXPHOS), which maintains airway homeostasis. Within the lung, P. aeruginosa exploits the host immunometabolite itaconate to further stimulate ketogenesis. This environment enables host-P. aeruginosa coexistence, supporting both pathoadaptive changes in the bacteria and the maintenance of respiratory integrity via OXPHOS.

Neutrophils resist ferroptosis and promote breast cancer metastasis through aconitate decarboxylase 1

Metastasis causes breast cancer-related mortality. Tumor-infiltrating neutrophils (TINs) inflict immunosuppression and promote metastasis. Therapeutic debilitation of TINs may enhance immunotherapy, yet it remains a challenge to identify therapeutic targets highly expressed and functionally essential in TINs but under-expressed in extra-tumoral neutrophils. Here, using single-cell RNA sequencing to compare TINs and circulating neutrophils in murine mammary tumor models, we identified aconitate decarboxylase 1 (Acod1) as the most upregulated metabolic enzyme in mouse TINs and validated high Acod1 expression in human TINs. Activated through the GM-CSF-JAK/STAT5-C/EBPβ pathway, Acod1 produces itaconate, which mediates Nrf2-dependent defense against ferroptosis and upholds the persistence of TINs. Acod1 ablation abates TIN infiltration, constrains metastasis (but not primary tumors), bolsters antitumor T cell immunity, and boosts the efficacy of immune checkpoint blockade. Our findings reveal how TINs escape from ferroptosis through the Acod1-dependent immunometabolism switch and establish Acod1 as a target to offset immunosuppression and improve immunotherapy against metastasis.

Tissue-specific macrophage immunometabolism

Macrophages are phagocytic cells distributed across tissues that sustain homeostasis by constantly probing their local environment. Upon perturbations, macrophages rewire their energy metabolism to execute their immune programs. Intensive research in the field of immunometabolism highlights cell-intrinsic immunometabolites such as succinate and itaconate as immunomodulatory signals. A role for cell-extrinsic stimuli now emerges with evidence for signals that shape macrophages' metabolism in a tissue-specific manner. In this review, we will cover macrophage immunometabolism in the gut, a complex metabolic and immunologically active tissue. During homeostasis, gut macrophages are constantly exposed to pro-inflammatory ligands from the microbiota, and in contrast, are balanced by microbiota-derived anti-inflammatory metabolites. Given their extensive metabolic changes during activation, spatial analyses of the tissue will allow the characterization of metabolic niches of macrophage in the gut. Identifying metabolic perturbations of macrophage subsets during chronic inflammation and infection can direct future tissue-specific metabolotherapies.

Influence of intestinal microecology in the development of gout or hyperuricemia and the potential therapeutic targets

Gout and hyperuricemia are common metabolic diseases. Patients with purine metabolism disorder and/or decreased uric acid excretion showed increased uric acid levels in the blood. The increase of uric acid in the blood leads to the deposition of urate crystals in tissues, joints, and kidneys, and causes gout. Recent studies have revealed that imbalance of the intestinal microecology is closely related to the occurrence and development of hyperuricemia and gout. Disorder of the intestinal flora often occurs in patients with gout, and high purine and high fructose may induce the disorder of intestinal flora. Short-chain fatty acids and endotoxins produced by intestinal bacteria are closely related to the inflammatory response of gout. This article summarizes the characteristics of intestinal microecology in patients or animal models with hyperuricemia or gout, and explores the relationship between intestinal microecology and gout or hyperuricemia from the aspect of the intestinal barrier, intestinal microorganisms, intestinal metabolites, and intestinal immune system. We also review the current status of hyperuricemia treatment by targeting intestinal microecology.

Suppression of HIV and cocaine-induced neurotoxicity and inflammation by cell penetrable itaconate esters

HIV-associated neurological disorder (HAND) is a serious complication of HIV infection, marked by neurotoxicity induced by viral proteins like Tat. Substance abuse exacerbates neurocognitive impairment in people living with HIV. There is an urgent need for effective therapeutic strategies to combat HAND comorbid with Cocaine Use Disorder (CUD). Our analysis of the HIV and cocaine-induced transcriptomes in primary cortical cultures revealed a significant overexpression of the macrophage-specific gene, aconitate decarboxylase 1 (Acod1), caused by the combined insults of HIV and cocaine. ACOD1 protein converts the tricarboxylic acid intermediate cis-aconitate into itaconate during the activation of inflammation. The itaconate produced facilitates cytokine production and subsequently activates anti-inflammatory transcription factors, shielding macrophages from infection-induced cell death. While the role of itaconate' in limiting inflammation has been studied in peripheral macrophages, its immunometabolic function remains unexplored in HIV and cocaine-exposed microglia. We assessed in this model system the potential of 4-octyl-itaconate (4OI), a cell-penetrable esterified form of itaconate known for its potent anti-inflammatory properties and potential therapeutic applications. We administered 4OI to primary cortical cultures exposed to Tat and cocaine. 4OI treatment increased the number of microglial cells in both untreated and Tat±Cocaine-treated cultures and also reversed the morphological altercations induced by Tat and cocaine. In the presence of 4OI, microglial cells also appeared more ramified, resembling the quiescent microglia. Consistent with these results, 4OI treatment inhibited the secretion of the proinflammatory cytokines IL-1α, IL-1β, IL-6, and MIP1-α induced by Tat and cocaine. Transcriptome profiling further determined that Nrf2 target genes such as NAD(P)H quinone oxidoreductase 1 (Nqo1), Glutathione S-transferase Pi (Gstp1), and glutamate cysteine ligase catalytic (Gclc), were most significantly activated in Tat-4OI treated cultures, relative to Tat alone. Further, genes associated with cytoskeleton dynamics in inflammatory microglia were downregulated by 4OI treatment. Together, the results strongly suggest 4-octyl-itaconate holds promise as a potential candidate for therapeutic development aimed at addressing HAND coupled with CUD comorbidities.

Succinate metabolism: a promising therapeutic target for inflammation, ischemia/reperfusion injury and cancer

Succinate serves as an essential circulating metabolite within the tricarboxylic acid (TCA) cycle and functions as a substrate for succinate dehydrogenase (SDH), thereby contributing to energy production in fundamental mitochondrial metabolic pathways. Aberrant changes in succinate concentrations have been associated with pathological states, including chronic inflammation, ischemia/reperfusion (IR) injury, and cancer, resulting from the exaggerated response of specific immune cells, thereby rendering it a central area of investigation. Recent studies have elucidated the pivotal involvement of succinate and SDH in immunity beyond metabolic processes, particularly in the context of cancer. Current scientific endeavors are concentrated on comprehending the functional repercussions of metabolic modifications, specifically pertaining to succinate and SDH, in immune cells operating within a hypoxic milieu. The efficacy of targeting succinate and SDH alterations to manipulate immune cell functions in hypoxia-related diseases have been demonstrated. Consequently, a comprehensive understanding of succinate's role in metabolism and the regulation of SDH is crucial for effectively targeting succinate and SDH as therapeutic interventions to influence the progression of specific diseases. This review provides a succinct overview of the latest advancements in comprehending the emerging functions of succinate and SDH in metabolic processes. Furthermore, it explores the involvement of succinate, an intermediary of the TCA cycle, in chronic inflammation, IR injury, and cancer, with particular emphasis on the mechanisms underlying succinate accumulation. This review critically assesses the potential of modulating succinate accumulation and metabolism within the hypoxic milieu as a means to combat various diseases. It explores potential targets for therapeutic interventions by focusing on succinate metabolism and the regulation of SDH in hypoxia-related disorders.

Microglia-dependent neuroprotective effects of 4-octyl itaconate against rotenone-and MPP+-induced neurotoxicity in Parkinson's disease

Chronic neuroinflammation is implicated in the pathogenesis of Parkinson's disease (PD), one of the most common neurodegenerative diseases. Itaconate, an endogenous metabolite derived from the tricarboxylic acid cycle via immune-responsive gene 1 activity, may mediate anti-inflammatory responses by activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant pathway. This study investigates the neuroprotective potential of 4-octyl itaconate (OI), a cell-permeable derivative of itaconate, in cellular models of PD. OI not only suppressed lipopolysaccharide-induced proinflammatory cascades of inducible nitric oxide synthase, cyclooxygenase-2, and cytokines release in mouse BV2 microglial cells but also activated the Nrf2 signaling pathway and its downstream targets in these cells. Conditioned medium derived from OI-treated BV2 cells protected against rotenone- and MPP+-induced neurotoxicity in Neuro 2A cells. Overall, our findings support the anti-inflammatory neuroprotective potential of OI in PD.

Metabolic Reprogramming via ACOD1 depletion enhances function of human induced pluripotent stem cell-derived CAR-macrophages in solid tumors

The pro-inflammatory state of macrophages, underpinned by their metabolic condition, is essentially affecting their capacity of combating tumor cells. Here we find, via a pooled metabolic gene knockout CRISPR screen that KEAP1 and ACOD1 are strong regulators of the pro-inflammatory state in macrophages. We show that ACOD1 knockout macrophages, generated in our induced pluripotent stem cell-derived CAR-macrophage (CAR-iMAC) platform, are strongly and persistently polarized toward the pro-inflammatory state, which manifests in increased reactive oxygen species (ROS) production, more potent phagocytosis and enhanced cytotoxic functions against cancer cells in vitro. In ovarian or pancreatic cancer mouse models, ACOD1-depleted CAR-iMACs exhibit enhanced capacity in repressing tumors, leading to increased survival. In addition, combining ACOD1-depleted CAR-iMACs with immune checkpoint inhibitors (ICI), such as anti-CD47 or anti-PD1 antibodies, result in even stronger tumor suppressing effect. Mechanistically, the depletion of ACOD1 reduces levels of the immuno-metabolite itaconate, allowing KEAP1 to prevent NRF2 from entering the nucleus to activate an anti-inflammatory program. This study thus lays down the proof of principle for targeting ACOD1 in myeloid cells for cancer immunotherapy and introduces metabolically engineered human iPSC-derived CAR-iMACs cells with enhanced polarization and anti-tumor functions in adoptive cell transfer therapies.

Getting fat and stressed: Effects of dietary intake of titanium dioxide nanoparticles in the liver of turbot Scophthalmus maximus

The extensive use of nanomaterials, including titanium dioxide nanoparticles (TiO2 NPs), raises concerns about their persistence in ecosystems. Protecting aquatic ecosystems and ensuring healthy and safe aquaculture products requires the assessment of the potential impacts of NPs on organisms. Here, we study the effects of a sublethal concentration of citrate-coated TiO2 NPs of two different primary sizes over time in flatfish turbot, Scophthalmus maximus (Linnaeus, 1758). Bioaccumulation, histology and gene expression were assessed in the liver to address morphophysiological responses to citrate-coated TiO2 NPs. Our analyses demonstrated a variable abundance of lipid droplets (LDs) in hepatocytes dependent on TiO2 NPs size, an increase in turbot exposed to smaller TiO2 NPs and a depletion with larger TiO2 NPs. The expression patterns of genes related to oxidative and immune responses and lipid metabolism (nrf2, nfκb1, and cpt1a) were dependent on the presence of TiO2 NPs and time of exposure supporting the variance in hepatic LDs distribution over time with the different NPs. The citrate coating is proposed as the likely catalyst for such effects. Thus, our findings highlight the need to scrutinize the risks associated with exposure to NPs with distinct properties, such as primary size, coatings, and crystalline forms, in aquatic organisms.

Mitochondrial PGAM5-Drp1 signaling regulates the metabolic reprogramming of macrophages and regulates the induction of inflammatory responses

Macrophages play a critical role in the regulation of inflammation and tissue homeostasis. In addition to their vital functions for cell survival and physiology, mitochondria play a crucial role in innate immunity as a platform for the induction of inflammatory responses by regulating cell signaling and dynamics. Dynamin-related protein 1 (Drp1) plays a role in the induction of inflammatory responses and the subsequent development of various diseases. PGAM5 (phosphoglycerate mutase member 5) is a mitochondrial outer membrane phosphatase that dephosphorylates its substrate, Drp1. Previous studies showed that PGAM5 regulates the phosphorylation of Drp1 for the activation of NKT cells and T cells. However, it is not clear how PGAM5 regulates Drp1 activity for the induction of inflammation in macrophages. Here, we demonstrate that PGAM5 activity regulates the dephosphorylation of Drp1 in macrophages, leading to the induction of proinflammatory responses in macrophages. In TLR signaling, PGAM5 regulates the expression and production of inflammatory cytokines by regulating the activation of downstream signaling pathways, including the NF-κB and MAPK pathways. Upon LPS stimulation, PGAM5 interacts with Drp1 to form a complex, leading to the production of mtROS. Furthermore, PGAM5-Drp1 signaling promotes the polarization of macrophages toward a proinflammatory phenotype. Our study further demonstrates that PGAM5-Drp1 signaling promotes metabolic reprogramming by upregulating glycolysis and mitochondrial metabolism in macrophages. Altogether, PGAM5 signaling is a linker between alterations in Drp1-mediated mitochondrial dynamics and inflammatory responses in macrophages and may be a target for the treatment of inflammatory diseases.

Methylglyoxal suppresses microglia inflammatory response through NRF2-IκBζ pathway

Methylglyoxal (MGO) is a highly reactive metabolite generated by glycolysis. Although abnormal accumulation of MGO has been reported in several autoimmune diseases such as multiple sclerosis and rheumatoid arthritis, the role of MGO in autoimmune diseases has not yet been fully investigated. In this study, we found that the intracellular MGO levels increased in activated immune cells, such as microglia and lymphocytes. Treatment with MGO inhibited inflammatory cell accumulation in the spinal cord and ameliorated the clinical symptoms in EAE mice. Further analysis indicated that MGO suppressed M1-polarization of microglia cells and diminished their inflammatory cytokine production. MGO also inhibited the ability of microglial cells to recruit and activate lymphocytes by decreasing chemokine secretion and expression of co-stimulatory molecules. Furthermore, MGO negatively regulated glycolysis by suppressing glucose transporter 1 expression. Mechanically, we found that MGO could activate nuclear factor erythroid 2-related factor 2 (NRF2) pathway and NRF2 could bind to the promoter of IκBζ gene and suppressed its transcription and subsequently pro-inflammatory cytokine production. In conclusion, our results showed that MGO acts as an immunosuppressive metabolite by activating the NRF2-IκBζ.