Itaconate is a lysosomal inducer that promotes antibacterial innate immunity

The cGAS-STING pathway activates transcription factor TFEB to stimulate lysosome biogenesis and pathogen clearance

Induction of autophagy is an ancient function of the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway through which autophagic cargoes are delivered to lysosomes for degradation. However, whether lysosome function is also modulated by the cGAS-STING pathway remains unknown. Here, we discovered that the cGAS-STING pathway upregulated lysosomal activity by stimulating lysosome biogenesis independently of the downstream protein kinase TANK-binding kinase 1 (TBK1). STING activation enhanced lysosome biogenesis through inducing the nuclear translocation of transcription factor EB (TFEB) as well as its paralogs transcription factor E3 (TFE3) and microphthalmia-associated transcription factor (MITF). STING-induced lipidation of GABA type A receptor-associated protein (GABARAP), an autophagy-related protein, on STING vesicles was responsible for TFEB activation. Membrane-bound GABARAP sequestered the GTPase-activating protein folliculin (FLCN) and FLCN-interacting protein (FNIP) complex to block its function toward the Rag GTPases Ras-related GTP-binding C and D (RagC and RagD), abolishing mechanistic target of rapamycin (mTOR) complex 1 (mTORC1)-dependent phosphorylation and inactivation of TFEB. Functionally, STING-induced lysosome biogenesis within cells facilitated the clearance of cytoplasmic DNA and invading pathogens. Thus, our findings reveal that induction of lysosome biogenesis is another important function of the cGAS-STING pathway.

Itaconate and its derivatives as anti-pathogenic agents

Pathogenic microorganisms and viruses cause outbreaks and pandemics that affect millions of people worldwide. Despite recent advances in pharmacology and medicine, the ability of infectious diseases to spread in the modern era is accelerating due to various factors contributing to increased human-to-human and human-animal contacts. With the global rise of drug resistance among pathogens and frequently occurring viral outbreaks, alternative drugs and therapies that specifically inhibit microbial virulence or regulate immune responses are attracting growing interest. The present review focuses on itaconate and its derivatives as potential anti-pathogenic agents. It summarizes the current state of research on itaconate metabolism in bacteria, fungi and mammals. This is followed by a comprehensive review of recent advances studying itaconate and its derivatives as anti-inflammatory, immunoregulatory, antimicrobial and antiviral compounds, along with their mechanisms of action. Finally, the review emphasises the existing challenges and future research directions for the application of itaconate and its derivatives as anti-pathogenic agents.

Itaconate transporter SLC13A3 confers immunotherapy resistance via alkylation-mediated stabilization of PD-L1

Itaconate is a metabolite catalyzed by cis-aconitate decarboxylase (ACOD1), which is mainly produced by activated macrophages and secreted into the extracellular environment to exert complex bioactivity. In the tumor microenvironment, itaconate is concentrated and induces an immunosuppressive response. However, whether itaconate can be taken up by tumor cells and its mechanism of action remain largely unclear. Here, we identified solute carrier family 13 member 3 (SLC13A3) as a key protein transporting extracellular itaconate into cells, where it elevates programmed cell death ligand 1 (PD-L1) protein levels and decreases the expression of immunostimulatory molecules, thereby promoting tumor immune evasion. Mechanistically, itaconate alkylates the cysteine 272 residue on PD-L1, antagonizing PD-L1 ubiquitination and degradation. Consequently, SLC13A3 inhibition enhances the efficacy of anti-CTLA-4 (cytotoxic T lymphocyte-associated antigen-4) immunotherapy and improves the overall survival rate in syngeneic mouse tumor models. Collectively, our findings identified SLC13A3 as a key transporter of itaconate and revealed its immunomodulatory role, providing combinatorial strategies to overcome immunotherapy resistance in tumors.

Preclinical insights into the potential of itaconate and its derivatives for liver disease therapy

Annually, approximately 3.5 % of the world's population dies of cirrhosis or liver cancer, and the burden of liver disease is steadily expanding owing to multiple factors such as alcohol consumption, irrational diets, viral transmission, and exposure to drugs and toxins. However, the lack of effective therapies and the adverse effects of some medications remain a threat to the management of liver disease. Recently, immunometabolism, as an emerging discipline, appears to be the focus of unprecedented research. As a natural metabolite that regulates cellular functions, itaconate is a crucial bridge connecting metabolism and immune response. Remodeling immune function through metabolic modulation may be a promising alternative for disease intervention strategies. In this review, we first briefly describe the historical origin of itaconate and the development of its derivatives. This was followed by a review of the molecular mechanisms by which itaconate regulated immune-metabolic responses. Furthermore, we analyzed the effects of itaconate regulation on immune cells of the hepatic system. Finally, we summarized the experimental evidence for itaconate and its derivatives in the therapeutic application of liver diseases. Itaconate is potentially an invaluable component of emerging therapeutic strategies for liver disease.

Inducible antibacterial responses in macrophages

Macrophages destroy bacteria and other microorganisms through phagocytosis-coupled antimicrobial responses, such as the generation of reactive oxygen species and the delivery of hydrolytic enzymes from lysosomes to the phagosome. However, many intracellular bacteria subvert these responses, escaping to other cellular compartments to survive and/or replicate. Such bacterial subversion strategies are countered by a range of additional direct antibacterial responses that are switched on by pattern-recognition receptors and/or host-derived cytokines and other factors, often through inducible gene expression and/or metabolic reprogramming. Our understanding of these inducible antibacterial defence strategies in macrophages is rapidly evolving. In this Review, we provide an overview of the broad repertoire of antibacterial responses that can be engaged in macrophages, including LC3-associated phagocytosis, metabolic reprogramming and antimicrobial metabolites, lipid droplets, guanylate-binding proteins, antimicrobial peptides, metal ion toxicity, nutrient depletion, autophagy and nitric oxide production. We also highlight key inducers, signalling pathways and transcription factors involved in driving these different antibacterial responses. Finally, we discuss how a detailed understanding of the molecular mechanisms of antibacterial responses in macrophages might be exploited for developing host-directed therapies to combat antibiotic-resistant bacterial infections.

The cell autonomous and non-autonomous roles of itaconate in immune response

Itaconate which is discovered as a mammalian metabolite possessing antimicrobial and immunoregulatory activity has attracted much attention in the field of immunometabolism. Itaconate is synthesized by myeloid cells under conditions of pathogen infection and sterile inflammation. In addition to regulating immune response of myeloid cells, itaconate secreted from myeloid cells can also be taken up by non-myeloid cells to exert immunoregulatory effects in a cell non-autonomous manner. In this review, we recap the discovery of itaconate as a distinct immunologic regulator and effector, describe the development of itaconate biosensor, and detail the recent findings that decipher the mechanism underlying intercellular transport of itaconate. Based on these knowledges, we propose itaconate is a messenger transmitting immunologic signals from myeloid cells to other types of cells during host inflammation and immune defense.

Itaconate mechanism of action and dissimilation in Mycobacterium tuberculosis

Itaconate, an abundant metabolite produced by macrophages upon interferon-γ stimulation, possesses both antibacterial and immunomodulatory properties. Despite its crucial role in immunity and antimicrobial control, its mechanism of action and dissimilation are poorly understood. Here, we demonstrate that infection of mice with Mycobacterium tuberculosis increases itaconate levels in lung tissues. We also show that exposure to itaconate inhibits M. tuberculosis growth in vitro, in macrophages, and mice. We report that exposure to sodium itaconate (ITA) interferes with the central carbon metabolism of M. tuberculosis. In addition to the inhibition of isocitrate lyase (ICL), we demonstrate that itaconate inhibits aldolase and inosine monophosphate (IMP) dehydrogenase in a concentration-dependent manner. Previous studies have shown that Rv2498c from M. tuberculosis is the bona fide (S)-citramalyl-CoA lyase, but the remaining components of the pathway remain elusive. Here, we report that Rv2503c and Rv3272 possess itaconate:succinyl-CoA transferase activity, and Rv2499c and Rv3389c possess itaconyl-CoA hydratase activity. Relative to the parental and complemented strains, the ΔRv3389c strain of M. tuberculosis was attenuated for growth in itaconate-containing medium, in macrophages, mice, and guinea pigs. The attenuated phenotype of ΔRv3389c strain of M. tuberculosis is associated with a defect in the itaconate dissimilation and propionyl-CoA detoxification pathway. This study thus reveals that multiple metabolic enzymes are targeted by itaconate in M. tuberculosis. Furthermore, we have assigned the two remaining enzymes responsible for the degradation of itaconic acid into pyruvate and acetyl-CoA. Finally, we also demonstrate the importance of enzymes involved in the itaconate dissimilation pathway for M. tuberculosis pathogenesis.

LincR-PPP2R5C regulates the PP2A signaling pathway in the macrophage-myofibroblast transition in a mouse model of epidural fibrosis

Low back pain after spine surgery is a major complication due to excessive epidural fibrosis, which compresses the lumbar nerve. Macrophage-myofibroblast transition (MMT) promoted epidural fibrosis in a mouse laminectomy model. Previously, we demonstrated that LincR-PPP2R5C regulated CD4 + T-cell differentiation. Here, we aimed to explore the roles and mechanisms of LincR-PPP2R5C in macrophages in epidural fibrosis. In M2 macrophages, the level of LincR-PPP2R5C was significantly decreased. Upon overexpression, LincR-PPP2R5C induced M1-macrophage polarization and reduced MMT. In contrast, LincR-PPP2R5C deficiency promoted M2-macrophage polarization and increased MMT. Mechanistically, LincR-PPP2R5C modulated the expression of α-SMA in macrophages via the PP2A signaling pathway. In vivo, LincR-PPP2R5C deficiency aggravated epidural fibrosis by enhancing MMT in a mouse model of laminectomy, and this effect was abolished in mice with macrophage depletion. Our study shed light on the effects of LincR-PPP2R5C on macrophage differentiation and MMT in epidural fibrosis.

Itaconic acid ameliorates necrotizing enterocolitis through the TFEB-mediated autophagy-lysosomal pathway

Excessive autophagy has been implicated in the pathogenesis of necrotizing enterocolitis (NEC), yet the molecular underpinnings of the autophagy-lysosomal pathway (ALP) in NEC are not well characterized. This study aimed to elucidate alterations within the ALP in NEC by employing RNA sequencing on intestinal tissues obtained from affected infants. Concurrently, we established animal and cellular models of NEC to assess the therapeutic efficacy of itaconic acid (ITA). Our results indicate that the ALP is significantly disrupted in NEC. Notably, ITA was found to modulate the ALP, enhancing autophagic flux and lysosomal function, which consequently alleviated NEC symptoms. Further analysis revealed that ITA's beneficial effects are mediated through the promotion of TFEB nuclear translocation, thereby augmenting the ALP. These findings suggest that targeting the ALP with ITA to modulate TFEB activity may represent a viable therapeutic approach for NEC.

Itaconate facilitates viral infection via alkylating GDI2 and retaining Rab GTPase on the membrane

Metabolic reprogramming of host cells plays critical roles during viral infection. Itaconate, a metabolite produced from cis-aconitate in the tricarboxylic acid cycle (TCA) by immune responsive gene 1 (IRG1), is involved in regulating innate immune response and pathogen infection. However, its involvement in viral infection and underlying mechanisms remain incompletely understood. Here, we demonstrate that the IRG1-itaconate axis facilitates the infections of VSV and IAV in macrophages and epithelial cells via Rab GTPases redistribution. Mechanistically, itaconate promotes the retention of Rab GTPases on the membrane via directly alkylating Rab GDP dissociation inhibitor beta (GDI2), the latter of which extracts Rab GTPases from the membrane to the cytoplasm. Multiple alkylated residues by itaconate, including cysteines 203, 335, and 414 on GDI2, were found to be important during viral infection. Additionally, this effect of itaconate needs an adequate distribution of Rab GTPases on the membrane, which relies on Rab geranylgeranyl transferase (GGTase-II)-mediated geranylgeranylation of Rab GTPases. The single-cell RNA sequencing data revealed high expression of IRG1 primarily in neutrophils during viral infection. Co-cultured and in vivo animal experiments demonstrated that itaconate produced by neutrophils plays a dominant role in promoting viral infection. Overall, our study reveals that neutrophils-derived itaconate facilitates viral infection via redistribution of Rab GTPases, suggesting potential targets for antiviral therapy.

Polydatin-Mediated Inhibition of HSP90α Disrupts NLRP3 Complexes and Alleviates Acute Pancreatitis

The NLRP3 inflammasome plays a critical role in various inflammatory conditions. However, despite extensive research in targeted drug development for NLRP3, including MCC950, clinical success remains elusive. Here, we discovered that the activated NLRP3 inflammasome complex (disc-NLRP3) and the activating mutation L351P exhibited resistance to MCC950. Through investigations using the small-molecule compound polydatin, HSP90α was found to stabilize both the resting (cage-NLRP3) and activated state (disc-NLRP3) of NLRP3 complexes, sustaining its activation. Our mechanistic studies revealed that polydatin specifically targets HSP90α, binding to it directly and subsequently interfering with the HSP90α-NLRP3 interaction. This disruption leads to the dissipation of cage-NLRP3, disc-NLRP3 complexes and NLRP3 L351P. Importantly, genetic and pharmacological inactivation of HSP90α effectively reduced NLRP3 inflammasome activation and alleviated cerulein-induced acute pancreatitis. These therapeutic effects highlight the clinical potential of HSP90α inhibition. Our findings demonstrate that HSP90α is crucial for the stability of both the resting and activated states of the NLRP3 inflammasome during its sustained activation, and targeting HSP90α represents a promising therapeutic strategy for diseases driven by the NLRP3 inflammasome.

A low-molecular-weight α-glucan from edible fungus Agaricus blazei Murrill activates macrophage TFEB-mediated antibacterial defense to combat implant-associated infection

Implant-associated infection (IAI) is a prevalent and potentially fatal complication of orthopaedic surgery. Boosting antibacterial immunity, particularly the macrophage-mediated response, presents a promising therapeutic approach for managing persistent infections. In this study, we successfully isolated and purified a homogeneous and neutral water-soluble polysaccharide, designated as AM-1, from the edible fungus Agaricus blazei Murrill. Structure analysis revealed that AM-1 (Mw = 3.87 kDa) was a low-molecular-weight glucan characterized by a primary chain of →4)-α-D-Glcp-(1 → and side chains that were linked at the O-6 and O-3 positions. In vivo assays showed that AM-1 effectively attenuated the progression of infection and mitigated infectious bone destruction in IAI mouse models. Mechanistically, AM-1 promotes intracellular autophagy-lysosomal biogenesis by inducing the nuclear translocation of transcription factor EB, finally enhancing the bactericidal capabilities and immune-modulatory functions of macrophages. These findings demonstrate that AM-1 significantly alleviates the progression of challenging IAIs as a presurgical immunoenhancer. Our research introduces a novel therapeutic strategy that employs natural polysaccharides to combat refractory infections.

4-Octyl itaconate attenuates renal tubular injury in db/db mice by activating Nrf2 and promoting PGC-1α-mediated mitochondrial biogenesis

Objectives: The aim of this study was to investigate the mechanism of itaconate's potential effect in diabetic kidney disease.

Methods: Renal immune responsive gene 1 (IRG1) levels were measured in db/db mice and streptozotocin (STZ) + high-fat diet (HFD)-induced diabetic mice. Irg1 knockout mice were generated. db/db mice were treated with 4-octyl itaconate (4-OI, 50 mg/kg), a derivative of itaconate, for 4 weeks. Renal function and morphological changes were investigated. Ultrastructural alterations were determined by transmission electron microscopy.

Results: Renal IRG1 levels were reduced in two diabetic models. STZ+HFD-treated Irg1 knockout mice exhibited aggravated renal tubular injury and worsened renal function. Treatment with 4-OI lowered urinary albumin-to-creatinine ratio and blood urea nitrogen levels, and restored renal histological changes in db/db mice. It improved mitochondrial damage, increased expressions of peroxisome-proliferator-activated receptor γ coactivator-1α (PGC-1α) and mitochondrial transcription factor A (TFAM) in the renal cortex of db/db mice. These were confirmed in vitro; 4-OI improved high glucose-induced abnormal mitochondrial morphology and TFAM expression in HK-2 cells, effects that were inhibited by PGC-1α silencing. Moreover, 4-OI reduced the number of apoptotic cells in the renal cortex of db/db mice. Further study showed that 4-OI increased renal Nrf2 expression and decreased oxidative stress levels in db/db mice. In HK-2 cells, 4-OI decreased high glucose-induced mitochondrial ROS production, which was reversed by Nrf2 silencing. Nrf2 depletion also inhibited 4-OI-mediated regulation of PGC-1α, TFAM, and mitochondrial apoptotic protein expressions.

Conclusions: 4-OI attenuates renal tubular injury in db/db mice by activating Nrf2 and promoting PGC-1α-mediated mitochondrial biogenesis.

Targeting GSDME-mediated macrophage polarization for enhanced antitumor immunity in hepatocellular carcinoma

Despite the notable efficacy of anti-PD1 therapy in the management of hepatocellular carcinoma (HCC) patients, resistance in most individuals necessitates additional investigation. For this study, we collected tumor tissues from nine HCC patients receiving anti-PD1 monotherapy and conducted RNA sequencing. These findings revealed significant upregulation of GSDME, which is predominantly expressed by tumor-associated macrophages (TAMs), in anti-PD1-resistant patients. Furthermore, patients with elevated levels of GSDME+ macrophages in HCC tissues presented a poorer prognosis. The analysis of single-cell sequencing data and flow cytometry revealed that the suppression of GSDME expression in nontumor cells resulted in a decrease in the proportion of M2-like macrophages within the tumor microenvironment (TIME) of HCC while concurrently augmenting the cytotoxicity of CD8 + T cells. The non-N-terminal fragment of GSDME within macrophages combines with PDPK1, thereby activating the PI3K-AKT pathway and facilitating M2-like polarization. The small-molecule Eliprodil inhibited the increase in PDPK1 phosphorylation mediated by GSDME site 1. The combination of Eliprodil and anti-PD1 was effective in the treatment of both spontaneous HCC in c-Myc + /+;Alb-Cre + /+ mice and in a hydrodynamic tail vein injection model, which provides a promising strategy for novel combined immunotherapy.

Metabolomics analysis of rice fermented by medicinal fungi providing insights into the preparation of functional food

Rice, a primary staple food, may be improved in value via fermentation. Here, ten medicinal basidiomycetous fungi were separately applied for rice fermentation. After preliminary screening, Ganoderma boninense, Phylloporia pulla, Sanghuangporus sanghuang and Sanghuangporus weigelae were selected for further LC-MS based determination of the changes in metabolic profile after their fermentation with rice, and a total of 261, 296, 312, and 355 differential compounds were identified, respectively. Most of these compounds were up-regulated and involved in the metabolic pathways of amino acid metabolism, lipid metabolism, carbohydrate metabolism and the biosynthesis of other secondary metabolites. Sanghuangporus weigelae endowed the rice with the highest nutritional and bioactive values. The metabolic network of the identified differential compounds in rice fermented by S. weigelae illustrated their close relationships. In summary, this study provides insights into the preparation and application of potential functional food via the fermentation of rice with medicinal fungi.

Itaconate uptake via SLC13A3 improves hepatic antibacterial innate immunity

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 mouse hepatocytes. These findings identify SLC13A3 as a key itaconate importer in mouse hepatocytes and will aid in the development of potent itaconate-based antibacterial therapeutics.

METABOLIC AND BIOENERGETIC ALTERATIONS ARE ASSOCIATED WITH INFECTION SUSCEPTIBILITY IN SURVIVORS OF SEVERE TRAUMA: AN EXPLORATORY STUDY

ABSTRACT

Background : Trauma and blood loss are frequently associated with organ failure, immune dysfunction, and a high risk of secondary bacterial lung infections. We aim to test if plasma metabolomic flux and monocyte bioenergetics are altered in association with trauma and related secondary infections. Methods : Plasma samples were collected from trauma patients at three time points: days 0, 3, and 7 postadmission. Metabolites (140) were measured in plasma from trauma survivors ( n = 24) and healthy control individuals (HC, n = 10). Further analysis within the trauma cohort included subsets of trauma/infection-negative (TIneg, n = 12) and trauma/infection-positive patients (TIpos, n = 12). The bioenergetic profile in monocytes was determined using mitochondrial and glycolytic stress tests. Results : In the trauma cohort, significant alterations were observed in 29 metabolites directly affecting 11 major metabolic pathways, while 34 metabolite alterations affected 8 pathways in 9, versus TIneg patients. The most altered metabolic pathways included protein synthesis, the urea cycle/arginine metabolism, phenylalanine, tyrosine, tryptophan biosynthesis, and carnitine compound family. In monocytes from trauma patients, reduced mitochondrial indices and loss of glycolytic plasticity were consistent with an altered profile of plasma metabolites in the tricarboxylic acid cycle and glycolysis. Conclusions : Our study highlights that the metabolic profile is significantly and persistently affected by trauma and related infections. Among trauma survivors, metabolic alterations in plasma were associated with reduced monocyte bioenergetics. These exploratory findings establish a groundwork for future clinical studies aimed at enhancing our understanding of the interplay between metabolic/bioenergetic alterations associated with trauma and secondary bacterial infections.

Itaconate drives mtRNA-mediated type I interferon production through inhibition of succinate dehydrogenase

Itaconate is one of the most highly upregulated metabolites in inflammatory macrophages and has been shown to have immunomodulatory properties. Here, we show that itaconate promotes type I interferon production through inhibition of succinate dehydrogenase (SDH). Using pharmacological and genetic approaches, we show that SDH inhibition by endogenous or exogenous itaconate leads to double-stranded mitochondrial RNA (mtRNA) release, which is dependent on the mitochondrial pore formed by VDAC1. In addition, the double-stranded RNA sensors MDA5 and RIG-I are required for IFNβ production in response to SDH inhibition by itaconate. Collectively, our data indicate that inhibition of SDH by itaconate links TCA cycle modulation to type I interferon production through mtRNA release.

Targeting lysosomal quality control as a therapeutic strategy against aging and diseases

Previously, lysosomes were primarily referred to as the digestive organelles and recycling centers within cells. Recent discoveries have expanded the lysosomal functional scope and revealed their critical roles in nutrient sensing, epigenetic regulation, plasma membrane repair, lipid transport, ion homeostasis, and cellular stress response. Lysosomal dysfunction is also found to be associated with aging and several diseases. Therefore, function of macroautophagy, a lysosome-dependent intracellular degradation system, has been identified as one of the updated twelve hallmarks of aging. In this review, we begin by introducing the concept of lysosomal quality control (LQC), which is a cellular machinery that maintains the number, morphology, and function of lysosomes through different processes such as lysosomal biogenesis, reformation, fission, fusion, turnover, lysophagy, exocytosis, and membrane permeabilization and repair. Next, we summarize the results from studies reporting the association between LQC dysregulation and aging/various disorders. Subsequently, we explore the emerging therapeutic strategies that target distinct aspects of LQC for treating diseases and combatting aging. Lastly, we underscore the existing knowledge gap and propose potential avenues for future research.

Cancer cell-intrinsic biosynthesis of itaconate promotes tumor immunogenicity

The Krebs cycle byproduct itaconate has recently emerged as an important metabolite regulating macrophage immune functions, but its role in tumor cells remains unknown. Here, we show that increased tumor-intrinsic cis-aconitate decarboxylase (ACOD1 or CAD, encoded by immune-responsive gene 1, Irg1) expression and itaconate production promote tumor immunogenicity and anti-tumor immune responses. Furthermore, we identify thimerosal, a vaccine preservative, as a specific inducer of IRG1 expression in tumor cells but not in macrophages, thereby enhancing tumor immunogenicity. Mechanistically, thimerosal induces itaconate production through a ROS-RIPK3-IRF1 signaling axis in tumor cells. Further, increased IRG1/itaconate upregulates antigen presentation-related gene expression via promoting TFEB nuclear translocation. Intratumoral injection of thimerosal induced itaconate production, activated the tumor immune microenvironment, and inhibited tumor growth in a T cell-dependent manner. Importantly, IRG1 deficiency markedly impaired tumor response to thimerosal treatment. Furthermore, itaconate induction by thimerosal potentiates the anti-tumor efficacy of adoptive T-cell therapy and anti-PD1 therapy in a mouse lymphoma model. Hence, our findings identify a new role for tumor intrinsic IRG1/itaconate in promoting tumor immunogenicity and provide a translational means to increase immunotherapy efficacy.

Classical swine fever virus inhibits serine metabolism-mediated antiviral immunity by deacetylating modified PHGDH

Classical swine fever virus (CSFV), an obligate intracellular pathogen, hijacks cellular metabolism to evade immune surveillance and facilitate its replication. The precise mechanisms by which CSFV modulates immune metabolism remain largely unknown. Our study reveals that CSFV infection disrupts serine metabolism, which plays a crucial role in antiviral immunity. Notably, we discovered that CSFV infection leads to the deacetylation of PHGDH, a key enzyme in serine metabolism, resulting in autophagic degradation. This deacetylation impairs PHGDH's enzymatic activity, reduces serine biosynthesis, weakens innate immunity, and promotes viral proliferation. Molecularly, CSFV infection induces the association of HDAC3 with PHGDH, leading to deacetylation at the K364 site. This modification attracts the E3 ubiquitin ligase RNF125, which facilitates the addition of K63-linked ubiquitin chains to PHGDH-K364R. Subsequently, PHGDH is targeted for lysosomal degradation by p62 and NDP52. Furthermore, the deacetylation of PHGDH disrupts its interaction with the NAD+ substrate, destabilizing the PHGDH-NAD complex, impeding the active site, and thereby inhibiting de novo serine synthesis. Additionally, our research indicates that deacetylated PHGDH suppresses the mitochondria-MAVS-IRF3 pathway through its regulatory effect on serine metabolism, leading to decreased IFN-β production and enhanced viral replication. Overall, our findings elucidate the complex interplay between CSFV and serine metabolism, revealing a novel aspect of viral immune evasion through the lens of immune metabolism.

IMPORTANCE

Classical swine fever (CSF) seriously restricts the healthy development of China's aquaculture industry, and the unclear pathogenic mechanism and pathogenesis of classical swine fever virus (CSFV) are the main obstacle to CSF prevention, control, and purification. Therefore, it is of great significance to explore the molecular mechanism of CSFV and host interplay, to search for the key signaling pathways and target molecules in the host that regulate the replication of CSFV infection, and to elucidate the mechanism of action of host immune dysfunction and immune escape due to CSFV infection for the development of novel CSFV vaccines and drugs. This study reveals the mechanism of serine metabolizing enzyme post-translational modifications and antiviral signaling proteins in the replication of CSFV and enriches the knowledge of CSFV infection and immune metabolism.

The role and therapeutic potential of itaconate in lung disease

Lung diseases triggered by endogenous or exogenous factors have become a major concern, with high morbidity and mortality rates, especially after the coronavirus disease 2019 (COVID-19) pandemic. Inflammation and an over-activated immune system can lead to a cytokine cascade, resulting in lung dysfunction and injury. Itaconate, a metabolite produced by macrophages, has been reported as an effective anti-inflammatory and anti-oxidative stress agent with significant potential in regulating immunometabolism. As a naturally occurring metabolite in immune cells, itaconate has been identified as a potential therapeutic target in lung diseases through its role in regulating inflammation and immunometabolism. This review focuses on the origin, regulation, and function of itaconate in lung diseases, and briefly discusses its therapeutic potential.

Future applications of host direct therapies for infectious disease treatment

New and emerging pathogens, such as SARS-CoV2 have highlighted the requirement for threat agnostic therapies. Some antibiotics or antivirals can demonstrate broad-spectrum activity against pathogens in the same family or genus but efficacy can quickly reduce due to their specific mechanism of action and for the ability of the disease causing agent to evolve. This has led to the generation of antimicrobial resistant strains, making infectious diseases more difficult to treat. Alternative approaches therefore need to be considered, which include exploring the utility of Host-Directed Therapies (HDTs). This is a growing area with huge potential but difficulties arise due to the complexity of disease profiles. For example, a HDT given early during infection may not be appropriate or as effective when the disease has become chronic or when a patient is in intensive care. With the growing understanding of immune function, a new generation of HDT for the treatment of disease could allow targeting specific pathways to augment or diminish the host response, dependent upon disease profile, and allow for bespoke therapeutic management plans. This review highlights promising and approved HDTs that can manipulate the immune system throughout the spectrum of disease, in particular to viral and bacterial pathogens, and demonstrates how the advantages of HDT will soon outweigh the potential side effects.

Itaconate induces tolerance of Staphylococcus aureus to aminoglycoside antibiotics

INTRODUCTION

Staphylococcus aureus is one of the chief pathogens that cause chronic and recurrent infections. Failure of the antibiotics to curb the infections contributes to relapse and is an important reason for the high mortality rate. Treatment failure may also be due to antibiotic tolerance. Accumulating evidence suggests that t the host immune environment plays an important role in inducing antibiotic tolerance of S. aureus, but research in this area has been limited.

METHODS

In this study,the minimum inhibitory concentration (MIC) of the antibiotics against S. aureus was determined using the standard broth microdilution method.The study evaluated whether itaconate induces antibiotic tolerance in S. aureus through an antibiotic bactericidal activity assay.The effect of itaconate on the growth of S. aureus was evaluated by monitoring the growth of S. aureus in medium supplemented with itaconate. Additionally, RNA sequencing and metabolomics analyses were used to determine transcriptional and metabolic changes in S. aureus when exposed to itaconate.

RESULTS AND DISCUSSION

According to the study,we found that the immune metabolite itaconate can induce tolerance in both methicillin-resistant and -susceptible S. aureus to aminoglycosides. When S. aureus was exposed to itaconate, its growth slowed down and transcriptomic and metabolomic alterations associated with decreased energy metabolism, including the tricarboxylate cycle, glycolysis, pyruvate metabolism, and arginine biosynthesis, were observed. These changes are associated with aminoglycoside tolerance. This study highlights the role of immune signaling metabolites in bacterial antibiotic tolerance and suggests new strategies to improve antibiotic treatment by modulating the host immune response and stimulating the metabolism of bacteria.

Neurodegenerative diseases reflect the reciprocal roles played by retroelements in regulating memory and immunity

Tetrapod endogenous retroelements (ERE) encode proteins that have been exapted to perform many roles in development and also in innate immunity, including GAG (group specific antigen) proteins from the ERE long terminal repeat (LTR) family, some of which can assemble into viral-like capsids (VLCs) and transmit mRNA across synapses. The best characterized member of this family is ARC (activity-regulated cytoskeletal gene), that is involved in memory formation. Other types of EREs, such as LINES and SINES (long and short interspersed elements), have instead been exapted for immune defenses against infectious agents. These immune EREs identify host transcripts by forming the unusual left-handed Z-DNA and Z-RNA conformations to enable self/nonself discrimination. Elevated levels of immune EREs in the brain are associated with neurodegenerative disease. Here I address the question of how pathways based on immune EREs are relate to the memory EREs that mediate neural plasticity. I propose that during infection and in other inflammatory states, ERE encoded GAG capsids deliver interferon-induced immune EREs that rapidly inhibit translation of viral RNAs in the dendritic splines by activation of protein kinase R (PKR). The response limits transmission of viruses and autonomously replicating elements, while protecting bystander cells from stress-induced cell death. Further, the PKR-dependent phosphorylation of proteins, like tau, disrupts the endocytic pathways exploited by viruses to spread to other cells. The responses come at a cost. They impair memory formation and can contribute to pathology by increasing the deposition of amyloid beta.

The association of appendectomy with prognosis and tumor-associated macrophages in patients with colorectal cancer

The vermiform appendix plays an important role in colorectal immunity and the homeostasis of the gut microbiome. We aimed to evaluate the prognostic value of prior appendectomy for patients with colorectal cancer (CRC). This study revealed that prior appendectomy is an independent risk factor for the prognosis of patients with CRC, based on a multicentral CRC cohort. We further demonstrated that appendectomy induced a poor prognosis of CRC through the depletion of M1 macrophage cells in AOM-induced mice, which was confirmed in age-, sex-, and location-matched patients' cohorts and orthotopic model models with the CT26 cell line. Poor responses to anti-PD-1 immunotherapy were detected in patients with CRC with appendectomy, and cetuximab is an effective treatment for patients with appendectomy-associated colorectal cancer (APD-CRC) to improve their prognosis. Our study will provide a reference for developing treatment plans for a considerable number of patients with APD-CRC, which is of great clinical significance.

Toward decoding spatiotemporal signaling activities of reactive immunometabolites with precision immuno-chemical biology tools

Immune-cell reprogramming driven by mitochondria-derived reactive electrophilic immunometabolites (mt-REMs-e.g., fumarate, itaconate) is an emerging phenomenon of major biomedical importance. Despite their localized production, mt-REMs elicit significantly large local and global footprints within and across cells, through mechanisms involving electrophile signaling. Burgeoning efforts are being put into profiling mt-REMs' potential protein-targets and phenotypic mapping of their multifaceted inflammatory behaviors. Yet, precision indexing of mt-REMs' first-responders with spatiotemporal intelligence and locale-specific function assignments remain elusive. Highlighting the latest advances and overarching challenges, this perspective aims to stimulate thoughts and spur interdisciplinary innovations to address these unmet chemical-biotechnological needs at therapeutic immuno-signaling frontiers.

Metabolic regulation of the host-fungus interaction: from biological principles to therapeutic opportunities

Fungal infections present a significant global public health concern, impacting over 1 billion individuals worldwide and resulting in more than 3 million deaths annually. Despite considerable progress in recent years, the management of fungal infections remains challenging. The limited development of novel diagnostic and therapeutic approaches is largely attributed to our incomplete understanding of the pathogenetic mechanisms involved in these diseases. Recent research has highlighted the pivotal role of cellular metabolism in regulating the interaction between fungi and their hosts. In response to fungal infection, immune cells undergo complex metabolic adjustments to meet the energy demands necessary for an effective immune response. A comprehensive understanding of the metabolic circuits governing antifungal immunity, combined with the integration of individual host traits, holds the potential to inform novel medical interventions for fungal infections. This review explores recent insights into the immunometabolic regulation of host-fungal interactions and the infection outcome and discusses how the metabolic repurposing of immune cell function could be exploited in innovative and personalized therapeutic approaches.

Systemic knockout of Tmem175 results in aberrant differentiation but no effect on hematopoietic reconstitution

Lysosomes play crucial roles in regulating cell metabolism, and K+ channels are critical for controlling various aspects of lysosomal function. Additionally, lysosomal activity is essential for maintaining the quiescence of hematopoietic stem cells (HSCs) under both steady-state and stress conditions. Tmem175 is a lysosomal potassium channel protein. To further investigate the role of K+ channels in HSCs, our study employed knockout mice to examine the function of Tmem175. Our research findings demonstrate that the deletion of Tmem175 does not disrupt the functionality of HSCs in both stable and stressed conditions, including irradiation and intraperitoneal 5-FU injections. However, we did observe that the absence of Tmem175 impairs the long-term differentiation capacity of HSCs into myeloid differentiated subpopulation cells（In this paper, it is referred to simply as M cells）in HSC transplantation test, while promoting their differentiation into T cells. This suggests that Tmem175 plays a role in the lineage differentiation of HSCs without being essential for their self-renewal or long-term regenerative capabilities.

Gut bacterial type III secretion systems aggravate colitis in mice and serve as biomarkers of Crohn's disease

BACKGROUND

Mesenteric adipose tissue (mAT) hyperplasia, known as creeping fat, is a pathologic characteristic of Crohn's disease (CD). In our previously reported cohort, we observed that Achromobacter pulmonis was the most abundant and prevalent bacteria cultivated from creeping fat.

METHODS

A whole genomic sequencing and identification of T3SS orthologs of mAT-derived A. pulmonis were used. A functional type III secretion system (T3SS) mediated the pathogenic potential of A. pulmonis in vitro and in mouse colitis model. Furthermore, a T3SS Finder pipeline was introduced to evaluate gut bacterial T3SS orthologs in the feces of CD patients, ulcerative colitis and colorectal cancer patients.

FINDINGS

Here, we reveal that mAT-derived A. pulmonis possesses a functional T3SS, aggravates colitis in mice via T3SS, and exhibits T3SS-dependent cytotoxicity via a caspase-independent mechanism in macrophages and epithelial cells, which demonstrated the pathogenic potential of the T3SS-harboring A. pulmonis. Metagenomic analyses demonstrate an increased abundance of Achromobacter in the fecal of Crohn's disease patients compared to healthy controls. A comprehensive comparison of total microbial vT3SS abundance in various intestine diseases demonstrated that the specific enrichment of vT3SS genes was shown in fecal samples of CD, neither ulcerative colitis nor colorectal cancer patients, and ten T3SS gene-based biomarkers for CD were discovered and validated in a newly recruited CD cohort. Furthermore, treatment with exclusive enteral nutrition (EEN), an intervention that improves CD patient symptomatology, was found associated with a significant reduction in the prevalence of T3SS genes in fecal samples.

INTERPRETATION

These findings highlight the pathogenic significance of T3SSs in the context of CD and identify specific T3SS genes that could potentially function as biomarkers for diagnosing and monitoring the clinical status of CD patients.

FUNDING

This work is supported by the National Key Research and Development Program of China (2020YFA0907800), the China Postdoctoral Science Foundation (2023M744089), the National Natural Science Foundation of China (32000096), the Shenzhen Science and Technology Programs (KQTD20200820145822023, RCIC20231211085944057, and ZDSYS20220606100803007), National Key Clinical Discipline, Guangdong Provincial Clinical Research Center for Digestive Diseases (2020B1111170004), Qingfeng Scientific Research Fund of the China Crohn's & Colitis Foundation (CCCF) (CCCF-QF-2022B71-1), and the Sixth Affiliated Hospital, Sun Yat-sen University Clinical Research 1010 Program 1010CG(2023)-08. These funding provided well support for this research work, which involved data collection, analysis, interpretation, patient recruitment and so on.

CD146-dependent macrophage infiltration promotes epidural fibrosis via the Erdr1/ERK/CCR2 pathway

Low back pain due to epidural fibrosis is a major complication after spine surgery. Macrophages infiltrate the wound area post laminectomy, but the role of macrophages in epidural fibrosis remains largely elusive. In a mouse model of laminectomy, macrophage depletion decreased epidural fibrosis. CD146, an adhesion molecule involved in cell migration, is expressed by macrophages. CD146-defective macrophages exhibited impaired migration, which was mediated by reduced expression of CCR2 and suppression of the MAPK/ERK signaling pathway. CD146-defective macrophages suppress the MAPK/ERK signaling pathway by increasing Erdr1. In vivo, CD146 deficiency decreased macrophage infiltration and reduced extracellular matrix deposition in wound tissues. Moreover, the anti-CD146 antibody AA98 suppressed macrophage infiltration and epidural fibrosis. Taken together, these findings demonstrated that CD146 deficiency alleviates epidural fibrosis by decreasing the migration of macrophages via the Erdr1/ERK/CCR2 pathway. Blocking CD146 and macrophage infiltration may help alleviate epidural fibrosis.

Intersection of the microbiome and immune metabolism in lupus

Systemic lupus erythematosus is a complex autoimmune disease resulting from a dysregulation of the immune system that involves gut dysbiosis and an altered host cellular metabolism. This review highlights novel insights and expands on the interactions between the gut microbiome and the host immune metabolism in lupus. Pathobionts, invasive pathogens, and even commensal microbes, when in dysbiosis, can all trigger and modulate immune responses through metabolic reprogramming. Changes in the microbiota's global composition or individual taxa may trigger a cascade of metabolic changes in immune cells that may, in turn, reprogram their functions. Factors contributing to dysbiosis include changes in intestinal hypoxia, competition for glucose, and limited availability of essential nutrients, such as tryptophan and metal ions, all of which can be driven by host metabolism changes. Conversely, the accumulation of some host metabolites, such as itaconate, succinate, and free fatty acids, could further influence the microbial composition and immune responses. Overall, mounting evidence supports a bidirectional relationship between host immunometabolism and the microbiota in lupus pathogenesis.

Versatile Underwater Pressure Sensitive Adhesive: UV Curing Synthesis and Substrate-Independent Adhesion

The demand for underwater pressure sensitive adhesives (PSAs) is rapidly increasing in fields such as underwater engineering and biomedicine. However, the achievement of underwater adhesion of PSAs remains a challenge because of the hydration layer that hinders the interaction between the adhesive and the substrate. Herein, a new type of underwater PSA was synthesized by the copolymerization of hydrophobic unsaturated poly(1,2-butylene oxide) (UPBO) and hydrophilic itaconic acid monomers using solvent-free ultraviolet curing. The PSA has demonstrated substrate-independent underwater adhesion strengths ranging from 108 to 141 kPa on both hydrophilic (glass, wood, steel) and hydrophobic (PET, PMMA, PTFE) substrates. The underwater adhesion performance of PSA remains stable during 30 adhesion-detachment cycles and incubation in water for 20 days. Notably, PSA shows cytocompatibility, antimicrobial, and degradable properties and can be used for rapid hemostasis of skin wounds. Experimental characterizations confirm that the process of underwater adhesion is achieved by hydrophobic alkyl side chains of the PBO chain segments, which repel water at the adhesive-substrate interface. This study should provide both practical and facile design strategies for multifunctional underwater PSAs that can be used in a variety of applications.

Itaconate in host inflammation and defense

Immune cells undergo rapid and extensive metabolic changes during inflammation. In addition to contributing to energetic and biosynthetic demands, metabolites can also function as signaling molecules. Itaconate (ITA) rapidly accumulates to high levels in myeloid cells under infectious and sterile inflammatory conditions. This metabolite binds to and regulates the function of diverse proteins intracellularly to influence metabolism, oxidative response, epigenetic modification, and gene expression and to signal extracellularly through binding the G protein-coupled receptor (GPCR). Administration of ITA protects against inflammatory diseases and blockade of ITA production enhances antitumor immunity in preclinical models. In this article, we review ITA metabolism and its regulation, discuss its target proteins and mechanisms, and conjecture a rationale for developing ITA-based therapeutics to treat inflammatory diseases and cancer.

Neddylation activated TRIM25 desensitizes triple-negative breast cancer to paclitaxel via TFEB-mediated autophagy

BACKGROUND

Paclitaxel (PTX) treatment resistance is an important factor leading to poor prognosis in triple-negative breast cancer (TNBC), therefore there is an urgent need to identify new target for combination therapy. Neddylation is a post-translational process that introduces a ubiquitin-like protein called neural precursor cell expressed developmentally downregulated protein 8 (NEDD8). Previous studies have found that neddylation is activated in multiple tumors, but its relationship with PTX chemotherapy sensitivity has not been reported.

METHODS

Differences in UBC12 and NEDD8 expression levels between PTX-sensitive and PTX-insensitive TNBC tissues were validated using public databases and immunohistochemistry. The in vitro and in vivo functional experiments were used to observe the effect of neddylation inhibition combined with PTX therapy on tumor progression. Co-IP, western blot and PCR assays were used to investigate the molecular mechanisms. Molecular docking was used to simulate the protein binding of UBC12 and TRIM25. Molecular dynamics simulation was used to observe the changes in TRIM25 protein conformation.

RESULTS

We found that in TNBC that is insensitive to PTX, NEDD8 and NEDD8 conjugating enzyme UBC12 are highly expressed. Treatment with the NEDD8-activating enzyme (NAE) inhibitor mln4924 or knockdown of UBC12 significantly increased the sensitivity of the tumor to PTX, and this increase in sensitivity is related to UBC12-mediated autophagy activation. Mechanistically, UBC12 can transfer NEDD8 to E3 ubiquitin ligase tripartite motif containing 25 (TRIM25) at K117. Molecular dynamics simulations indicate that the neddylation modification of TRIM25 reduces steric hindrance in its RING domain, facilitating the binding of TRIM25 and ubiquitylated substrates. Subsequently, TRIM25 promotes the nuclear translocation of transcription factor EB (TFEB) and transcription of autophagy related genes by increasing K63-polyubiquitination of TFEB, thereby reducing tumor sensitivity to PTX.

CONCLUSIONS

Neddylation is activated in PTX-insensitive TNBC. Specifically, autophagy gene transcriptional activation mediated by the UBC12/TRIM25/TFEB axis reduces TNBC sensitivity to PTX. Neddylation suppression combination with PTX treatment shows a synergistic anti-tumor effect.

Itaconic acid regulation of TFEB-mediated autophagy flux alleviates hyperoxia-induced bronchopulmonary dysplasia

BACKGROUND

Premature infants often require oxygen supplementation, which can elicit bronchopulmonary dysplasia (BPD) and lead to mitochondrial dysfunction. Mitochondria play important roles in lung development, in both normal metabolism and apoptosis. Enhancing our comprehension of the underlying mechanisms in BPD development can facilitate the effective treatments.

METHODS

Plasma samples from BPD and non-BPD infants were collected at 36 weeks post-menstrual age and used for metabolomic analysis. Based on hyperoxia-induced animal and cell models, changes in mitophagy and apoptosis were evaluated following treatment with itaconic acid (ITA). Finally, the mechanism of action of ITA in lung development was comprehensively demonstrated through rescue strategies and administration of corresponding inhibitors.

RESULTS

An imbalance in the tricarboxylic acid (TCA) cycle significantly affected lung development, with ITA serving as a significant metabolic marker for the outcomes of lung development. ITA improved the morphological changes in BPD rats, promoted SP-C expression, and inhibited the degree of alveolar type II epithelial cells (AEC II) apoptosis. Mechanistically, ITA mainly promotes the nuclear translocation of transcription factor EB (TFEB) to facilitate dysfunctional mitochondrial clearance and reduces apoptosis in AEC II cells by regulating autophagic flux.

CONCLUSION

The metabolic imbalance in the TCA cycle is closely related to lung development. ITA can improve lung development by regulating autophagic flux and promote the nuclear translocation of TFEB, implying its potential therapeutic utility in the treatment of BPD.

Redox regulation of macrophages

Redox signaling, a mode of signal transduction that involves the transfer of electrons from a nucleophilic to electrophilic molecule, has emerged as an essential regulator of inflammatory macrophages. Redox reactions are driven by reactive oxygen/nitrogen species (ROS and RNS) and redox-sensitive metabolites such as fumarate and itaconate, which can post-translationally modify specific cysteine residues in target proteins. In the past decade our understanding of how ROS, RNS, and redox-sensitive metabolites control macrophage function has expanded dramatically. In this review, we discuss the latest evidence of how ROS, RNS, and metabolites regulate macrophage function and how this is dysregulated with disease. We highlight the key tools to assess redox signaling and important questions that remain.

Fumarate hydratase as a metabolic regulator of immunity

Tricarboxylic acid (TCA) cycle metabolites have been implicated in modulating signalling pathways in immune cells. Notable examples include succinate and itaconate, which have pro- and anti-inflammatory roles, respectively. Recently, fumarate has emerged as having specific roles in macrophage activation, regulating the production of such cytokines as interleukin (IL)-10 and type I interferons (IFNs). Fumarate hydratase (FH) has been identified as a control point. Notably, FH loss in different models and cell types has been found to lead to DNA and RNA release from mitochondria which are sensed by cytosolic nucleic acid sensors including retinoic acid-inducible gene (RIG)-I, melanoma differentiation-associated protein (MDA)5, and cyclic GMP-AMP synthase (cGAS) to upregulate IFN-β production. These findings may have relevance in the pathogenesis and treatment of diseases associated with decreased FH levels such as systemic lupus erythematosus (SLE) or FH-deficient kidney cancer.

Mitochondria, Autophagy and Inflammation: Interconnected in Aging

In this manuscript, I discuss the direct link between abnormalities in inflammatory responses, mitochondrial metabolism and autophagy during the process of aging. It is focused on the cytosolic receptors nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) and cyclic GMP-AMP synthase (cGAS); myeloid-derived suppressor cells (MDSCs) expansion and their associated immunosuppressive metabolite, methyl-glyoxal, all of them negatively regulated by mitochondrial autophagy, biogenesis, metabolic pathways and its distinct metabolites.

Multifaceted mitochondria in innate immunity

The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.

Acod1 expression in cancer cells promotes immune evasion through the generation of inhibitory peptides

Targeting programmed cell death protein 1 (PD-1) is an important component of many immune checkpoint blockade (ICB) therapeutic approaches. However, ICB is not an efficacious strategy in a variety of cancer types, in part due to immunosuppressive metabolites in the tumor microenvironment. Here, we find that αPD-1-resistant cancer cells produce abundant itaconate (ITA) due to enhanced levels of aconitate decarboxylase (Acod1). Acod1 has an important role in the resistance to αPD-1, as decreasing Acod1 levels in αPD-1-resistant cancer cells can sensitize tumors to αPD-1 therapy. Mechanistically, cancer cells with high Acod1 inhibit the proliferation of naive CD8+ T cells through the secretion of inhibitory factors. Surprisingly, inhibition of CD8+ T cell proliferation is not dependent on the secretion of ITA but is instead a consequence of the release of small inhibitory peptides. Our study suggests that strategies to counter the activity of Acod1 in cancer cells may sensitize tumors to ICB therapy.

Urolithin A inhibits breast cancer progression via activating TFEB-mediated mitophagy in tumor macrophages

INTRODUCTION

Urolithin A (UA) is a naturally occurring compound that is converted from ellagitannin-like precursors in pomegranates and nuts by intestinal flora. Previous studies have found that UA exerts tumor-suppressive effects through antitumor cell proliferation and promotion of memory T-cell expansion, but its role in tumor-associated macrophages remains unknown.

OBJECTIVES

Our study aims to reveal how UA affects tumor macrophages and tumor cells to inhibit breast cancer progression.

METHODS

Observe the effect of UA treatment on breast cancer progression though in vivo and in vitro experiments. Western blot and PCR assays were performed to discover that UA affects tumor macrophage autophagy and inflammation. Co-ip and Molecular docking were used to explore specific molecular mechanisms.

RESULTS

We observed that UA treatment could simultaneously inhibit harmful inflammatory factors, especially for InterleuKin-6 (IL-6) and tumor necrosis factor α (TNF-α), in both breast cancer cells and tumor-associated macrophages, thereby improving the tumor microenvironment and delaying tumor progression. Mechanistically, UA induced the key regulator of autophagy, transcription factor EB (TFEB), into the nucleus in a partially mTOR-dependent manner and inhibited the ubiquitination degradation of TFEB, which facilitated the clearance of damaged mitochondria via the mitophagy-lysosomal pathway in macrophages under tumor supernatant stress, and reduced the deleterious inflammatory factors induced by the release of nucleic acid from damaged mitochondria. Molecular docking and experimental studies suggest that UA block the recognition of TFEB by 1433 and induce TFEB nuclear localization. Notably, UA treatment demonstrated inhibitory effects on tumor progression in multiple breast cancer models.

CONCLUSION

Our study elucidated the anti-breast cancer effect of UA from the perspective of tumor-associated macrophages. Specifically, TFEB is a crucial downstream target in macrophages.

Targeting NAD+ Metabolism to Modulate Autoimmunity and Inflammation

NAD+ biology is involved in controlling redox balance, functioning as a coenzyme in numerous enzymatic reactions, and is a cofactor for Sirtuin enzymes and a substrate for multiple regulatory enzyme reactions within and outside the cell. At the same time, NAD+ levels are diminished with aging and are consumed during the development of inflammatory and autoimmune diseases linked to aberrant immune activation. Direct NAD+ augmentation via the NAD+ salvage and Priess-Handler pathways is being investigated as a putative therapeutic intervention to improve the healthspan in inflammation-linked diseases. In this review, we survey NAD+ biology and its pivotal roles in the regulation of immunity and inflammation. Furthermore, we discuss emerging studies evaluate NAD+ boosting in murine models and in human diseases, and we highlight areas of research that remain unresolved in understanding the mechanisms of action of these nutritional supplementation strategies.

ABCG2 is an itaconate exporter that limits antibacterial innate immunity by alleviating TFEB-dependent lysosomal biogenesis

Itaconate is a metabolite that synthesized from cis-aconitate in mitochondria and transported into the cytosol to exert multiple regulatory effects in macrophages. However, the mechanism by which itaconate exits from macrophages remains unknown. Using a genetic screen, we reveal that itaconate is exported from cytosol to extracellular space by ATP-binding cassette transporter G2 (ABCG2) in an ATPase-dependent manner in human and mouse macrophages. Elevation of transcription factor TFEB-dependent lysosomal biogenesis and antibacterial innate immunity are observed in inflammatory macrophages with deficiency of ABCG2-mediated itaconate export. Furthermore, deficiency of ABCG2-mediated itaconate export in macrophages promotes antibacterial innate immune defense in a mouse model of S. typhimurium infection. Thus, our findings identify ABCG2-mediated itaconate export as a key regulatory mechanism that limits TFEB-dependent lysosomal biogenesis and antibacterial innate immunity in inflammatory macrophages, implying the potential therapeutic utility of blocking itaconate export in treating human bacterial infections.

Lysosomes as coordinators of cellular catabolism, metabolic signalling and organ physiology

Every cell must satisfy basic requirements for nutrient sensing, utilization and recycling through macromolecular breakdown to coordinate programmes for growth, repair and stress adaptation. The lysosome orchestrates these key functions through the synchronised interplay between hydrolytic enzymes, nutrient transporters and signalling factors, which together enable metabolic coordination with other organelles and regulation of specific gene expression programmes. In this Review, we discuss recent findings on lysosome-dependent signalling pathways, focusing on how the lysosome senses nutrient availability through its physical and functional association with mechanistic target of rapamycin complex 1 (mTORC1) and how, in response, the microphthalmia/transcription factor E (MiT/TFE) transcription factors exert feedback regulation on lysosome biogenesis. We also highlight the emerging interactions of lysosomes with other organelles, which contribute to cellular homeostasis. Lastly, we discuss how lysosome dysfunction contributes to diverse disease pathologies and how inherited mutations that compromise lysosomal hydrolysis, transport or signalling components lead to multi-organ disorders with severe metabolic and neurological impact. A deeper comprehension of lysosomal composition and function, at both the cellular and organismal level, may uncover fundamental insights into human physiology and disease.

The evolutionary tug-of-war of macrophage metabolism during bacterial infection

The function and phenotype of macrophages are intimately linked with pathogen detection. On sensing pathogen-derived signals and molecules, macrophages undergo a carefully orchestrated process of polarization to acquire pathogen-clearing properties. This phenotypic change must be adequately supported by metabolic reprogramming that is now known to support the acquisition of effector function, but also generates secondary metabolites with direct microbicidal activity. At the same time, bacteria themselves have adapted to both manipulate and take advantage of macrophage-specific metabolic adaptations. Here, we summarize the current knowledge on macrophage metabolism during infection, with a particular focus on understanding the 'arms race' between host immune cells and bacteria during immune responses.

Control of immune cell signaling by the immuno-metabolite itaconate

Immune cell activation triggers signaling cascades leading to transcriptional reprogramming, but also strongly impacts on the cell's metabolic activity to provide energy and biomolecules for inflammatory and proliferative responses. Macrophages activated by microbial pathogen-associated molecular patterns and cytokines upregulate expression of the enzyme ACOD1 that generates the immune-metabolite itaconate by decarboxylation of the TCA cycle metabolite cis-aconitate. Itaconate has anti-microbial as well as immunomodulatory activities, which makes it attractive as endogenous effector metabolite fighting infection and restraining inflammation. Here, we first summarize the pathways and stimuli inducing ACOD1 expression in macrophages. The focus of the review then lies on the mechanisms by which itaconate, and its synthetic derivatives and endogenous isomers, modulate immune cell signaling and metabolic pathways. Multiple targets have been revealed, from inhibition of enzymes to the post-translational modification of many proteins at cysteine or lysine residues. The modulation of signaling proteins like STING, SYK, JAK1, RIPK3 and KEAP1, transcription regulators (e.g. Tet2, TFEB) and inflammasome components (NLRP3, GSDMD) provides a biochemical basis for the immune-regulatory effects of the ACOD1-itaconate pathway. While the field has intensely studied control of macrophages by itaconate in infection and inflammation models, neutrophils have now entered the scene as producers and cellular targets of itaconate. Furthermore, regulation of adaptive immune responses by endogenous itaconate, as well as by exogenously added itaconate and derivatives, can be mediated by direct and indirect effects on T cells and antigen-presenting cells, respectively. Taken together, research in ACOD1-itaconate to date has revealed its relevance in diverse immune cell signaling pathways, which now provides opportunities for potential therapeutic or preventive manipulation of host defense and inflammation.

A small-molecule degrader selectively inhibits the growth of ALK-rearranged lung cancer with ceritinib resistance

Anaplastic lymphoma kinase (ALK) is a highly responsive therapeutic target for ALK-rearranged non-small cell lung cancer (NSCLC). However, patients with this cancer invariably relapse because of the development of ALK inhibitor resistance resulting from mutations within the ALK tyrosine kinase domain. Herein, we report the discovery of dEALK1, a small-molecule degrader of EML4-ALK fusion proteins, with capability of overcoming resistance to ALK inhibitor ceritinib. dEALK1 induces rapid and selective degradation of wild-type (WT) EML4-ALK and mutated EML4-ALKs acquiring resistance to ceritinib, leading to inhibition of cell proliferation and increase of apoptosis in NSCLC cells expressing WT EML4-ALK or ceritinib-resistant EML4-ALK mutants in vitro. Furthermore, dEALK1 also exerts a potent antitumor activity against EML4-ALK-positive xenograft tumors without or with harboring ceritinib-resistant EML4-ALK mutations in vivo. Our study suggests that dEALK1-induced degradation of EML4-ALK fusion proteins is a promising therapeutic strategy for treatment of ALK-rearranged lung cancer with ceritinib resistance.

Electrophilic metabolites targeting the KEAP1/NRF2 partnership

Numerous electrophilic metabolites are formed during cellular activity, particularly under conditions of oxidative, inflammatory and metabolic stress. Among them are lipid oxidation and nitration products, and compounds derived from amino acid and central carbon metabolism. Here we focus on one cellular target of electrophiles, the Kelch-like ECH associated protein 1 (KEAP1)/nuclear factor erythroid 2 p45-related factor 2 (NRF2) partnership. Many of these reactive compounds modify C151, C273 and/or C288 within KEAP1. Other types of modifications include S-lactoylation of C273, N-succinylation of K131, and formation of methylimidazole intermolecular crosslink between two KEAP1 monomers. Modified KEAP1 relays the initial signal to transcription factor NRF2 and its downstream targets, the ultimate effectors that provide means for detoxification, adaptation and survival. Thus, by non-enzymatically covalently modifying KEAP1, the electrophilic metabolites discussed here serve as chemical signals connecting metabolism with stress responses.

TFEB and TFE3 cooperate in regulating inorganic arsenic-induced autophagy-lysosome impairment and immuno-dysfunction in primary dendritic cells

Arsenic (As) is a prevalent and hazardous environmental toxicant associated with cancer and various health problems, which has been shown suppressive effects on dendritic cells (DCs). Autophagy is essential for the innate and adaptive immune responses of DCs, and the transcription factors TFEB and TFE3 are key regulators of autophagic and lysosomal target genes. However, the detrimental alterations of the autophagy-lysosome pathway in As-exposed DCs and the possible coordinating roles of TFEB and TFE3 in the immune dysfunction of this cell are less understood. In this paper, we found that As exposure significantly impaired lysosomal number, lysosomal acidic environment, and lysosomal membrane permeabilization, which might lead to blocked autophagic flux in cultured DCs. Furthermore, our results confirmed that TFEB or TFE3 knockdown exacerbated the disorders of lysosome and the blockade of autophagic flux in As-exposed DCs, and also enhanced the inhibitory expression of co-stimulatory molecules Cd80 and Cd83; adhesion molecule Icam1; cytokines TNF-α, IL-1β, and IL-6; chemokine receptor Ccr7; and antigen-presenting molecules MHC II and MHC I. By contrast, overexpression of TFEB or TFE3 partially alleviated the above-mentioned impairment of DCs by inorganic As exposure. In conclusion, these findings reveal a previously unappreciated inhibition of lysosome-mediated degradation and damage of lysosomal membrane integrity leading to dysregulated autophagy and impaired immune functions of DCs by arsenicals, and also suggest TFEB and TFE3 as potential therapeutic targets for ameliorating As toxicity.