Glycolysis in Innate Immune Cells Contributes to Autoimmunity

Decoding microglial immunometabolism: a new frontier in Alzheimer's disease research

Alzheimer's disease (AD) involves a dynamic interaction between neuroinflammation and metabolic dysregulation, where microglia play a central role. These immune cells undergo metabolic reprogramming in response to AD-related pathology, with key genes such as TREM2, APOE, and HIF-1α orchestrating these processes. Microglial metabolism adapts to environmental stimuli, shifting between oxidative phosphorylation and glycolysis. Hexokinase-2 facilitates glycolytic flux, while AMPK acts as an energy sensor, coordinating lipid and glucose metabolism. TREM2 and APOE regulate microglial lipid homeostasis, influencing Aβ clearance and immune responses. LPL and ABCA7, both associated with AD risk, modulate lipid processing and cholesterol transport, linking lipid metabolism to neurodegeneration. PPARG further supports lipid metabolism by regulating microglial inflammatory responses. Amino acid metabolism also contributes to microglial function. Indoleamine 2,3-dioxygenase controls the kynurenine pathway, producing neurotoxic metabolites linked to AD pathology. Additionally, glucose-6-phosphate dehydrogenase regulates the pentose phosphate pathway, maintaining redox balance and immune activation. Dysregulated glucose and lipid metabolism, influenced by genetic variants such as APOE4, impair microglial responses and exacerbate AD progression. Recent findings highlight the interplay between metabolic regulators like REV-ERBα, which modulates lipid metabolism and inflammation, and Syk, which influences immune responses and Aβ clearance. These insights offer promising therapeutic targets, including strategies aimed at HIF-1α modulation, which could restore microglial function depending on disease stage. By integrating metabolic, immune, and genetic factors, this review underscores the importance of microglial immunometabolism in AD. Targeting key metabolic pathways could provide novel therapeutic strategies for mitigating neuroinflammation and restoring microglial function, ultimately paving the way for innovative treatments in neurodegenerative diseases.

LT-α Facilitates the Aerobic Glycolysis and M1 Polarization of Macrophages by Activating the NF-κB Signaling Pathway in Intervertebral Disc Degeneration

Purpose

Injury and inflammatory activate and polarize macrophages in intervertebral disc degeneration (IVDD). Further research needs to be carried to explore the mechanisms that regulate macrophage polarization, providing new insights and targets for IVDD treatment. The aim of our study was to evaluate the influence of LT-α on aerobic glycolysis (AG) and polarization in macrophages.

Methods

M0 macrophages were achieved by stimulating THP-1 cells with PMA. M1 macrophages were obtained by IFN-γ and LPS stimulation in M0 macrophages. Energy metabolomics, AG and apoptosis related protein expression, migration and invasion measurement, proliferation was analyzed. Polarization of macrophages, AG associated genes expression, macrophage recruitment was evaluated. NF-κB signaling was ascertained by laser confocal and Western blotting.

Results

The propanoate metabolism pathway was enriched in LT-α overexpressing M0 macrophages, and various energy metabolites were detected. Glucose absorption, lactic acid production, and levels of AG proteins were strikingly increased in LT-α overexpression macrophages and remarkably repressed in LT-α knockdown macrophages, accompanied by activated and inactivated NF-κB signaling, respectively. Suppressed migration and invasion ability, restrained proliferation, activated AG, and enhanced apoptosis were observed in nucleus pulposus (NP) cells treated by LT-α overexpressed macrophages, accompanied by reduced macrophage recruitment, with opposite results when treated by LT-α knockdown macrophages. The enhanced M1 polarization and activated AG in LT-α overexpression macrophages were abolished by co-culturing with NF-κB inhibitor.

Conclusion

LT-α facilitates the AG and M1 polarization of macrophages via activating the NF-κB signaling pathway.

Advanced Machine Learning for Comparative Synovial Fluid Analysis in Osteoarthritis and Rheumatoid Arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are joint diseases that share similar clinical features but have different etiologies, making a differential diagnosis particularly challenging. Background/Objectives: Utilizing advanced machine learning (ML) techniques on metabolomic data, this study aimed to identify key metabolites in synovial fluid (SF) that could aid in distinguishing between OA and RA. Methods: Metabolite data from the MetaboLights database (MTBLS564), analyzed using nuclear magnetic resonance (NMR), were processed using normalization, a principal component analysis (PCA), and a partial least squares discriminant analysis (PLS-DA) to reveal prominent clustering. Results: Decision forests and random forest classifiers, optimized using genetic algorithms (GAs), highlighted a selection of a few metabolites-primarily glutamine, pyruvate, and proline-with significant discriminative power. A Shapley additive explanations (SHAP) analysis confirmed these metabolites to be pivotal predictors, offering a streamlined approach for clinical diagnostics. Conclusions: Our findings suggest that a minimal set of key metabolites can effectively be relied upon to distinguish between OA and RA, supported by an optimized ML model achieving high accuracy. This workflow could streamline diagnostic efficiency and enhance clinical decision-making in rheumatology.

Inorganic pyrophosphatase 1: a key player in immune and metabolic reprogramming in ankylosing spondylitis

The relationships among immune cells, metabolites, and AS events were analyzed via Mendelian randomization (MR), and potential immune cells and metabolites were identified as risk factors for AS. Their relationships were subjected to intermediary MR analysis to identify the final immune cells and metabolites. The vertebral bone marrow blood samples from three patients with and without AS were subjected to 10× single-cell sequencing to further elucidate the role of immune cells in AS. The key genes were screened via expression quantitative trait loci (eQTLs) and MR analyses. The metabolic differences between the two groups were compared through single-cell metabolism analysis. Two subgroups of differentiated (CD)8+ memory T cells and naive B cells were obtained from the combined results of intermediary MR analysis and AS single-cell analysis. After the verification of key genes, inorganic pyrophosphatase 1 (PPA1) was identified as the hub gene, as it is differentially expressed in CD8+ memory T cells and can affect the metabolism of T cells in AS by affecting the expression of ferulic acid (FA)4 sulfate, which participates in the cellular immunity in AS.

The General Principle of the Warburg Effect as a Possible Approach for Cancer Immunotherapy: The Regulatory Effect of Plant Extracts Could Change the Game

The interpretation of the biochemistry of immune metabolism could be considered an attractive scientific field of biomedicine research. In this review, the role of glycolysis in macrophage polarization is discussed together with mitochondrial metabolism in cancer cells. In the first part, the focus is on the Warburg effect and redox metabolism during macrophage polarization, cancer development, and management of the immune response by the cancer cells. The second part addresses the possibility of impacts on the Warburg effect through targeting peroxisome proliferator-activated receptors (PPARs). This could be an activator of native immune responses. Because of the reported serious adverse effects of using synthetic ligands for PPARs in combination with chemotherapeutics, searches for less toxic and more active PPAR inhibitors, as well as blocking undesirable cellular PPAR-dependent processes, are in progress. On the other hand, recent research in modern immunotherapy has focused on the search for gentle immune-modulating natural compounds with harmless synergistic chemotherapeutic efficacy that can be used as an adjuvant. It is a well-known fact that the plant kingdom is a source of important therapeutic agents with multifaceted effectiveness. One of these is the known association with PPAR activities. In this regard, the secondary metabolites extracted from plants could change the game.

Sex-based differences in persistent lung inflammation following influenza infection of juvenile outbred mice

Children are susceptible to influenza infections and can experience severe disease presentation due to a lack of or limited pre-existing immunity. Despite the disproportionate impact influenza has on this population, there is a lack of focus on pediatric influenza research, particularly when it comes to identifying the pathogenesis of long-term outcomes that persist beyond the point of viral clearance. In this study, juvenile outbred male and female mice were infected with influenza and analyzed following viral clearance to determine how sex impacts the persistent inflammatory responses to influenza. It was found that females maintained a broader cytokine response in the lung following clearance of influenza, with innate, type I and type II cytokine signatures in almost all mice. Males, on the other hand, had higher levels of IL-6 and other macrophage-related cytokines, but no evidence of a type I or type II response. The immune landscape was similar in the lungs between males and females postinfection, but males had a higher regulatory T cell to TH1 ratio compared with female mice. Cytokine production positively correlated with the frequency of TH1 cells and exudate macrophages, as well as the number of cells in the bronchoalveolar lavage fluid. Furthermore, female lungs were enriched for metabolites involved in the glycolytic pathway, suggesting glycolysis is higher in female lungs compared with males after viral clearance. These data suggest juvenile female mice have persistent and excessive lung inflammation beyond the point of viral clearance, whereas juvenile males had a more immunosuppressive phenotype.NEW & NOTEWORTHY This study identifies sex-based differences in persistent lung inflammation following influenza infection in an outbred, juvenile animal model of pediatric infection. These findings indicate the importance of considering sex and age as variable in infectious disease research.

Genomic Deletion of PFKFB3 Decreases In Vivo Tumorigenesis

Rapidly proliferative processes in mammalian tissues including tumorigenesis and embryogenesis rely on the glycolytic pathway for energy and biosynthetic precursors. The enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) plays an important regulatory role in glycolysis by activating the key rate-limiting glycolytic enzyme, 6-phosphofructo-1-kinase (PFK-1). We have previously determined that decreased PFKFB3 expression reduced glycolysis and growth in transformed cells in vitro and suppressed xenograft growth in vivo. In earlier studies, we created a constitutive knockout mouse to interrogate the function of PFKFB3 in vivo but failed to generate homozygous offspring due to the requirement for PFKFB3 for embryogenesis. We have now developed a novel transgenic mouse model that exhibits inducible homozygous pan-tissue Pfkfb3 gene deletion (Pfkfb3fl/fl). We have induced Pfkfb3 genomic deletion in these mice and found that it effectively decreased PFKFB3 expression and activity. To evaluate the functional consequences of Pfkfb3 deletion in vivo, we crossed Cre-bearing Pfkfb3fl/fl mice with oncogene-driven tumor models and found that Pfkfb3 deletion markedly decreased their glucose uptake and growth. In summary, our studies reveal a critical regulatory function for PFKFB3 in glycolysis and tumorigenesis in vivo and characterize an effective and powerful model for further investigation of its role in multiple biological processes.

Regulation of macrophage polarization by targeted metabolic reprogramming for the treatment of lupus nephritis

Lupus nephritis (LN) is a severe and common manifestation of systemic lupus erythematosus (SLE) that is frequently identified with a poor prognosis. Macrophages play an important role in its pathogenesis. Different macrophage subtypes have different effects on lupus-affected kidneys. Based on their origin, macrophages can be divided into monocyte-derived macrophages (MoMacs) and tissue-resident macrophages (TrMacs). During nephritis, TrMacs develop a hybrid pro-inflammatory and anti-inflammatory functional phenotype, as they do not secrete arginase or nitric oxide (NO) when stimulated by cytokines. The infiltration of these mixed-phenotype macrophages is related to the continuous damage caused by immune complexes and exposure to circulating inflammatory mediators, which is an indication of the failure to resolve inflammation. On the other hand, MoMacs differentiate into M1 or M2 cells under cytokine stimulation. M1 macrophages are pro-inflammatory and secrete pro-inflammatory cytokines, while the M2 main phenotype is essentially anti-inflammatory and promotes tissue repair. Conversely, MoMacs undergo differentiation into M1 or M2 cells in response to cytokine stimulation. M1 macrophages are considered pro-inflammatory cells and secrete pro-inflammatory mediators, whereas the M2 main phenotype is primarily anti-inflammatory and promotes tissue repair. Moreover, based on cytokine expression, M2 macrophages can be further divided into M2a, M2b, and M2c phenotypes. M2a and M2c have anti-inflammatory effects and participate in tissue repair, while M2b cells have immunoregulatory and pro-inflammatory properties. Further, memory macrophages also have a role in the advancement of LN. Studies have demonstrated that the polarization of macrophages is controlled by multiple metabolic pathways, such as glycolysis, the pentose phosphate pathway, fatty acid oxidation, sphingolipid metabolism, the tricarboxylic acid cycle, and arginine metabolism. The changes in these metabolic pathways can be regulated by substances such as fish oil, polyenylphosphatidylcholine, taurine, fumaric acid, metformin, and salbutamol, which inhibit M1 polarization of macrophages and promote M2 polarization, thereby alleviating LN.

Exploring the Potential of Glycolytic Modulation in Myeloid-Derived Suppressor Cells for Immunotherapy and Disease Management

Recent advancements in various technologies have shed light on the critical role of metabolism in immune cells, paving the way for innovative disease treatment strategies through immunometabolism modulation. This review emphasizes the glucose metabolism of myeloid-derived suppressor cells (MDSCs), an emerging pivotal immunosuppressive factor especially within the tumor microenvironment. MDSCs, an immature and heterogeneous myeloid cell population, act as a double-edged sword by exacerbating tumors or mitigating inflammatory diseases through their immune-suppressive functions. Numerous recent studies have centered on glycolysis of MDSC, investigating the regulation of altered glycolytic pathways to manage diseases. However, the specific changes in MDSC glycolysis and their exact functions continue to be areas of ongoing discussion yet. In this paper, we review a range of current findings, including the latest research on the alteration of glycolysis in MDSCs, the consequential functional alterations in these cells, and the outcomes of attempts to modulate MDSC functions by regulating glycolysis. Ultimately, we will provide insights into whether these research efforts could be translated into clinical applications.

The Exploitation of the Glycosylation Pattern in Asthma: How We Alter Ancestral Pathways to Develop New Treatments

Asthma has reached epidemic levels, yet progress in developing specific therapies is slow. One of the main reasons for this is the fact that asthma is an umbrella term for various distinct subsets. Due to its high heterogeneity, it is difficult to establish biomarkers for each subset of asthma and to propose endotype-specific treatments. This review focuses on protein glycosylation as a process activated in asthma and ways to utilize it to develop novel biomarkers and treatments. We discuss known and relevant glycoproteins whose functions control disease development. The key role of glycoproteins in processes integral to asthma, such as inflammation, tissue remodeling, and repair, justifies our interest and research in the field of glycobiology. Altering the glycosylation states of proteins contributing to asthma can change the pathological processes that we previously failed to inhibit. Special emphasis is placed on chitotriosidase 1 (CHIT1), an enzyme capable of modifying LacNAc- and LacdiNAc-containing glycans. The expression and activity of CHIT1 are induced in human diseased lungs, and its pathological role has been demonstrated by both genetic and pharmacological approaches. We propose that studying the glycosylation pattern and enzymes involved in glycosylation in asthma can help in patient stratification and in developing personalized treatment.

The causes and consequences of trained immunity in myeloid cells

Conventionally, immunity in humans has been classified as innate and adaptive, with the concept that only the latter type has an immunological memory/recall response against specific antigens or pathogens. Recently, a new concept of trained immunity (a.k.a. innate memory response) has emerged. According to this concept, innate immune cells can exhibit enhanced responsiveness to subsequent challenges, after initial stimulation with antigen/pathogen. Thus, trained immunity enables the innate immune cells to respond robustly and non-specifically through exposure or re-exposure to antigens/infections or vaccines, providing enhanced resistance to unrelated pathogens or reduced infection severity. For example, individuals vaccinated with BCG to protect against tuberculosis were also protected from malaria and SARS-CoV-2 infections. Epigenetic modifications such as histone acetylation and metabolic reprogramming (e.g. shift towards glycolysis) and their inter-linked regulations are the key factors underpinning the immune activation of trained cells. The integrated metabolic and epigenetic rewiring generates sufficient metabolic intermediates, which is crucial to meet the energy demand required to produce proinflammatory and antimicrobial responses by the trained cells. These factors also determine the efficacy and durability of trained immunity. Importantly, the signaling pathways and regulatory molecules of trained immunity can be harnessed as potential targets for developing novel intervention strategies, such as better vaccines and immunotherapies against infectious (e.g., sepsis) and non-infectious (e.g., cancer) diseases. However, aberrant inflammation caused by inappropriate onset of trained immunity can lead to severe autoimmune pathological consequences, (e.g., systemic sclerosis and granulomatosis). In this review, we provide an overview of conventional innate and adaptive immunity and summarize various mechanistic factors associated with the onset and regulation of trained immunity, focusing on immunologic, metabolic, and epigenetic changes in myeloid cells. This review underscores the transformative potential of trained immunity in immunology, paving the way for developing novel therapeutic strategies for various infectious and non-infectious diseases that leverage innate immune memory.

Soluble TREM2 triggers microglial dysfunction in neuromyelitis optica spectrum disorders

Microglia-mediated neuroinflammation contributes to acute demyelination in neuromyelitis optica spectrum disorders (NMOSD). Soluble triggering receptor expressed on myeloid cells 2 (sTREM2) in the CSF has been associated with microglial activation in several neurodegenerative diseases. However, the basis for this immune-mediated attack and the pathophysiological role of sTREM2 in NMOSD remain to be elucidated. Here, we performed Mendelian randomization analysis and identified a genetic association between increased CSF sTREM2 and NMOSD risk. CSF sTREM2 was elevated in patients with NMOSD and was positively correlated with neural injury and other neuroinflammation markers. Single-cell RNA sequencing of human macrophage/microglia-like cells in CSF, a proxy for microglia, showed that increased CSF sTREM2 was positively associated with microglial dysfunction in patients with NMOSD. Furthermore, we demonstrated that sTREM2 is a reliable biomarker of microglial activation in a mouse model of NMOSD. Using unbiased transcriptomic and lipidomic screens, we identified that excessive activation, overwhelmed phagocytosis of myelin debris, suppressed lipid metabolism and enhanced glycolysis underlie sTREM2-mediated microglial dysfunction, possibly through the nuclear factor kappa B (NF-κB) signalling pathway. These molecular and cellular findings provide a mechanistic explanation for the genetic association between CSF sTREM2 and NMOSD risk and indicate that sTREM2 could be a potential biomarker of NMOSD progression and a therapeutic target for microglia-mediated neuroinflammation.

PKM2 promotes proinflammatory macrophage activation in ankylosing spondylitis

Macrophages play a critical role in ankylosing spondylitis by promoting autoimmune tissue inflammation through various effector functions. The inflammatory potential of macrophages is highly influenced by their metabolic environment. Here, we demonstrate that glycolysis is linked to the proinflammatory activation of human blood monocyte-derived macrophages in ankylosing spondylitis. Specifically, ankylosing spondylitis macrophages produced excessive inflammation, including TNFα, IL1β, and IL23, and displayed an overactive status by exhibiting stronger costimulatory signals, such as CD80, CD86, and HLA-DR. Moreover, we found that patient-derived monocyte-derived M1-type macrophages (M1 macrophages) exhibited intensified glycolysis, as evidenced by a higher extracellular acidification rate. Upregulation of PKM2 and GLUT1 was observed in ankylosing spondylitis-derived monocytes and monocyte-derived macrophages, especially in M1 macrophages, indicating glucose metabolic alteration in ankylosing spondylitis macrophages. To investigate the impact of glycolysis on macrophage inflammatory ability, we treated ankylosing spondylitis M1 macrophages with 2 inhibitors: 2-deoxy-D-glucose, a glycolysis inhibitor, and shikonin, a PKM2 inhibitor. Both inhibitors reduced proinflammatory function and reversed the overactive status of ankylosing spondylitis macrophages, suggesting their potential utility in treating the disease. These data place PKM2 at the crosstalk between glucose metabolic changes and the activation of inflammatory macrophages in patients with ankylosing spondylitis.

The mechanism of dendritic cell-T cell crosstalk in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterised by joint pain and swelling, synovial hyperplasia, cartilage damage, and bone destruction. The mechanisms of dendritic cell (DC) and T cell-mediated crosstalk have gradually become a focus of attention. DCs regulate the proliferation and differentiation of CD4+ T cell subtypes through different cytokines, surface molecules, and antigen presentation. DC-T cell crosstalk also blocks antigen presentation by DCs, ultimately maintaining immune tolerance. DC-T cell crosstalk mainly involves chemokines, surface molecules (TonEBP, NFATc1), the PD-L1/PD-1 signalling axis, and the TGF-β signalling axis. In addition, DC-T cell crosstalk in RA is affected by glycolysis, reactive oxygen species, vitamin D, and other factors. These factors lead to the formation of an extremely complex regulatory network involving various mechanisms. This article reviews the key immune targets of DC-T cell crosstalk and elucidates the mechanism of DC-T cell crosstalk in RA to provide a basis for the treatment of patients with RA.

Insights into the pathogenic role of neutrophils in systemic lupus erythematosus

PURPOSE OF REVIEW

Although dysregulated adaptive immune response has been considered as the main culprit for systemic lupus erythematosus (SLE), emerging studies have indicated that innate immunity, functioning upstream of adaptive immunity, acts as an important trigger of autoimmune diseases and promotes SLE development. Here, we have reviewed the most recent findings to highlight the influence of neutrophils on SLE pathogenesis.

RECENT FINDINGS

Neutrophils participate in SLE development mainly via promoting self-antigen exposure and autoantibody production, advocating the release of type I interferons (IFNs) and other pro-inflammatory cytokines, and mediating systemic tissue injury. A recent study revealed that neutrophil ferroptosis exerts a strong pathogenic effect in SLE, and that dysregulated innate immunity is adequate to disrupt the homeostasis of immune tolerance.

SUMMARY

Insights into the pathogenic role of neutrophils in SLE will contribute to a more comprehensive understanding of this disease and may propose novel clinical targets for accurate diagnosis and precision medicine.

SIRT2-PFKP interaction dysregulates phagocytosis in macrophages with acute ethanol-exposure

Alcohol abuse, reported by 1/8th critically ill patients, is an independent risk factor for death in sepsis. Sepsis kills over 270,000 patients/year in the US. We reported that the ethanol-exposure suppresses innate-immune response, pathogen clearance, and decreases survival in sepsis-mice via sirtuin 2 (SIRT2). SIRT2 is an NAD+-dependent histone-deacetylase with anti-inflammatory properties. We hypothesized that in ethanol-exposed macrophages, SIRT2 suppresses phagocytosis and pathogen clearance by regulating glycolysis. Immune cells use glycolysis to fuel increased metabolic and energy demand of phagocytosis. Using ethanol-exposed mouse bone marrow- and human blood monocyte-derived macrophages, we found that SIRT2 mutes glycolysis via deacetylating key glycolysis regulating enzyme phosphofructokinase-platelet isoform (PFKP), at mouse lysine 394 (mK394, human: hK395). Acetylation of PFKP at mK394 (hK395) is crucial for PFKP function as a glycolysis regulating enzyme. The PFKP also facilitates phosphorylation and activation of autophagy related protein 4B (Atg4B). Atg4B activates microtubule associated protein 1 light chain-3B (LC3). LC3 is a driver of a subset of phagocytosis, the LC3-associated phagocytosis (LAP), which is crucial for segregation and enhanced clearance of pathogens, in sepsis. We found that in ethanol-exposed cells, the SIRT2-PFKP interaction leads to decreased Atg4B-phosphorylation, decreased LC3 activation, repressed phagocytosis and LAP. Genetic deficiency or pharmacological inhibition of SIRT2 reverse PFKP-deacetylation, suppressed LC3-activation and phagocytosis including LAP, in ethanol-exposed macrophages to improve bacterial clearance and survival in ethanol with sepsis mice.