Pyruvate kinase M2 regulates Hif-1α activity and IL-1β induction and is a critical determinant of the warburg effect in LPS-activated macrophages

Sirt5-mediated polarization and metabolic reprogramming of macrophage sustain brain function following ischemic stroke

Ischemic stroke has become the leading cause of morbidity and mortality in adults. Reperfusion may initiate inflammatory response and cause damage to brain. Macrophage is supposed to be the major contributor of neuroinflammation and immune response. Hypersuccinylation correlates with neuropathological process post cerebral ischemia, rendering the possibility of functional role of succinylation in regulating recovery from injury. Here we reported that ischemic stroke causes upregulation of global protein succinylation dramatically. Mechanically, Sirt5 expression is repressed upon ischemic stroke, which exerts a crucial role in orchestrating global protein succinylation level. Furthermore, deficiency of Sirt5 enhances infiltration, M1 polarization and metabolic programming of macrophage in response to stroke via succinylation of Pkm2. Physiologically, depletion of Sirt5 enlarges damage region of brain during stroke. Utilization of Sirt5 agonist resveratrol efficiently ameliorates the destructive effects induced by stroke, thereby supporting recovery from brain injury. Our study not only reveal a heretofore unrecognized mechanism underlying the relation between stroke and protein succinylation, but also shed light on clinical potential for management of stroke injury via targeting protein succinylation.

New insights on metabolic reprogramming in macrophage plasticity

Macrophages are the first line of defense in the innate immune system. Macrophages have two subtypes: classically activated macrophages (M1) and alternatively activated macrophages (M2), with different phenotypes and functions. They play a critical role in defending against pathogens and maintaining internal homeostasis. Macrophages have great plasticity in their biological characteristics. Although the regulation of macrophage plasticity has not been fully elucidated, accumulated evidence supports that microenvironmental differences are the root cause for macrophage differentiation into different subtypes. These differences alter macrophage plasticity by modulating key metabolites, activating downstream gene transcription, and influencing phagocytosis, cytokine secretion, and immune regulation. Herein, we systematically summarize metabolic reprogramming, including glucose, lipid, amino acid, ion, vitamin, nucleotide, and butyrate metabolism, as key regulators affecting macrophage polarization, providing new insights for developing targeted drugs that modulate macrophage plasticity.

GLUT1-mediated HMGB1 O-GlcNAcylation drives hyperglycemia-Induced neutrophil extracellular trap networks formation via TLR4 signaling and exacerbates fibroblast inflammation

Neutrophil extracellular traps (NETs) exacerbate fibroblast inflammatory injury in hyperglycemic conditions, yet the role of glucose metabolism and O-linked N-acetylglucosamine (O-GlcNAc) glycosylation in this process remains unclear. Here, we investigate how glucose transporter protein 1 (GLUT1)-dependent glucose uptake regulates O-GlcNAcylation of high-mobility group box 1 (HMGB1) to drive NET formation and fibroblast inflammation. Mouse peripheral blood neutrophils (MPBN) were treated with high glucose (25 mM) and phorbol ester (PMA) to induce NETs. Co-culture of NETs with mouse fibroblasts (L929) reduced fibroblast viability by 1.1 fold and migration by 1.2 fold within 24 h, while upregulating pro-inflammatory cytokines (Tumor Necrosis Factor-α (TNF-α): +1.3-fold; Interleukin-1β (IL-1β): +1.1-fold; Interleukin-6 (IL-6): +1.1-fold) and suppressing collagen synthesis (Collagen I (COL-I): - 1.7-fold; Collagen III (COL-III): -2.5-fold). Critically, high glucose elevated GLUT1 expression in MPBN (+ 1.2-fold), further amplified under co-culture conditions(+ 1.2-fold). Functional assays using GLUT1 knockdown confirmed that GLUT1 activity was essential for glucose uptake and subsequent O-GlcNAc modification of HMGB1, stabilizing its expression. Enhanced O-GlcNAcylation of high-mobility group box 1 (HMGB1) directly promoted NET formation, evidenced by elevated markers (Citrullinated histone H3 (Cit-H3): +1.6-fold; Myeloperoxidase (MPO): +1.2-fold; Circulating free DNA (cfDNA): +2-fold) and activation of c-Jun N-terminal kinase (JNK)/p38 phosphorylation. These effects were abolished by toll-like receptor 4 (TLR4) inhibition, linking HMGB1-TLR4 signaling to NET-driven inflammation. Mechanistically, GLUT1 knockdown reduced HMGB1 O-GlcNAcylation and reversed NET-induced fibroblast dysfunction. Our findings provide direct evidence that hyperglycemia enhances GLUT1 expression and activity, driving HMGB1 O-GlcNAcylation to maintain NETs formation through TLR4, which promotes fibroblast inflammatory injury. This pathway highlights a metabolic-inflammation axis relevant to diabetic complications.

Association between circulating inflammatory proteins and gout: A Mendelian randomization study

Clinical studies have consistently demonstrated that inflammation is a critical factor in the pathophysiology and progression of gout. This study aims to explore the causal relationship between CIPs and gout, utilizing MR in conjunction with meta-analyses. We utilized genetic data pertaining to gout from the GWAS which involved 3576 cases and 147,221 control participants. A total of 132 CIPs were extracted from the GWAS data to identify SNPs associated with gout. The primary analytical approach was the IVW method. Sensitivity analyses indicated no pleiotropy or heterogeneity. The IVW results revealed that several CIPs were associated with gout in European populations. The analysis results indicate that FGF-21, MMP-1, G-CSF, and IFN-γ are involved in the pathogenesis of gout, and gout may influence the expression of CXCL1, IL-1Ra, and TNF-α. Consequently, targeted research focusing on specific CIPs could provide a promising strategy for the treatment and prevention of gout, offering potential therapeutic targets for the underlying inflammatory mechanisms of the disease.

Hypoxia-driven angiogenesis and metabolic reprogramming in vascular tumors

Hypoxia is a hallmark of the tumor microenvironment (TME), and it plays a crucial role in the occurrence and progression in vascular tumors. Under hypoxic conditions, hypoxia-inducible factor 1-alpha (HIF-1α) is stabilized, inducing changes in the expression of various target genes involved in angiogenesis, metabolism, and cell survival. This includes the upregulation of pro-angiogenic factors like VEGF, which promotes the formation of dysfunctional blood vessels, contributing to the worsening of the hypoxic microenvironment. At the same time, hypoxia induces a metabolic shift toward glycolysis, even in the presence of oxygen, supporting tumor cell survival and proliferation by providing necessary energy and biosynthetic precursors. This review discusses the molecular mechanisms by which hypoxia regulates angiogenesis and metabolic reprogramming in vascular tumors, highlighting the intricate link between these processes, and explores potential therapeutic strategies to target these pathways in order to develop effective treatment strategies for patients.

Macrophage immunometabolism dysregulation and inflammatory disorders

Macrophages are innate immune cells which are involved in triggering inflammation. Growing evidence shows that, macrophages respond to intracellular and extracellular cues which makes them adopt either anti-inflammatory or pro-inflammatory functions and phenotypes. Immunometabolism has been identified as one of the prominent factors which contributes massively towards the cessation and the development of inflammation as an immune response to infections and autoimmune diseases. However, when inflammation is poorly regulated, it leads to dire consequences. This illustrates that, understanding the role of immunometabolism in the regulation of inflammation, is paramount. In view of this, the review investigated the role of metabolic pathways such as: glycolysis, tricarboxylic acid cycle, pentose phosphate pathway, fatty acid oxidation, amino acid metabolism in macrophage reprogramming. The role of the intermediates and enzymes associated with these metabolic pathways in the regulation of, macrophage reprogramming and polarisation or activation was also reviewed. It was unveiled that, manipulating metabolic intermediates and enzymes could impact cellular immunometabolism. This eventually influences macrophage reprogramming and thus influences the generation of either a pro-inflammatory or anti-inflammatory response.

Lactate-mediated metabolic reprogramming of tumor-associated macrophages: implications for tumor progression and therapeutic potential

The tumor microenvironment (TME) is characterized by distinct metabolic adaptations that not only drive tumor progression but also profoundly influence immune responses. Among these adaptations, lactate, a key metabolic byproduct of aerobic glycolysis, accumulates in the TME and plays a pivotal role in regulating cellular metabolism and immune cell function. Tumor-associated macrophages (TAMs), known for their remarkable functional plasticity, serve as critical regulators of the immune microenvironment and tumor progression. Lactate modulates TAM polarization by influencing the M1/M2 phenotypic balance through diverse signaling pathways, while simultaneously driving metabolic reprogramming. Furthermore, lactate-mediated histone and protein lactylation reshapes TAM gene expression, reinforcing their immunosuppressive properties. From a therapeutic perspective, targeting lactate metabolism has shown promise in reprogramming TAMs and enhancing anti-tumor immunity. Combining these metabolic interventions with immunotherapies may further augment treatment efficacy. This review underscores the crucial role of lactate in TAM regulation and tumor progression, highlighting its potential as a promising therapeutic target in cancer treatment.

Fruit of Physalis angulata L. and anti-inflammatory potential: An in silico, in vitro, and in vivo study focusing on PFKFB3

BACKGROUND

Sepsis-associated lung injury (SALI) is a disease characterised by inflammation. The fruit of Physalis angulata L. has been employed as a premium, novel, nutritious, healthcare "herbal fruit", which can be processed into juice, preserved fruit, canned food, and so forth.

PURPOSE

The objective of this study is to examine the impact of the fruit of Physalis angulata L. on the inhibition of inflammation in sepsis-associated lung injury and to elucidate the underlying mechanisms.

METHODS

The active components of fruit of Physalis angulata L. were analysed using HPLC-MS/MS. A comprehensive investigation was conducted to elucidate the effects and regulatory mechanisms of fruit of Physalis angulata L. on sepsis-associated lung injury and M1 polarisation of macrophage in mice subjected to acute LPS treatment. The renoprotective effect of fruit of Physalis angulata L. on LPS-treated mice was evaluated by measuring tissue damage and inflammation. In addition, we employed RNA-seq methodologies to analyse the principal regulatory targets of fruit of Physalis angulata L.. Furthermore, the expression of key proteins and markers of inflammation and glucose metabolism, as well as the levels of key indicators related to M1 polarisation of macrophage, were examined by immunoblotting, immunohistochemistry, immunoprecipitation, quantitative real-time PCR (qPCR) and specific probes.

RESULTS

In murine models, the ethanol extract of the fruit of Physalis angulata L. (EPAF) has been demonstrated to effectively inhibit structural damage and inflammation in the lung tissue of a murine model of LPS-induced acute lung injury. In terms of its mechanism of action, EPAF may inhibit M1 polarisation of macrophage and excessive inflammation by modulating the acetylation and phosphorylation of PFKFB3. This in turn affects glycolysis and the subsequent activation of NF-κB, HIF-1α and STAT3 in macrophages. Furthermore, the capacity of EPAF to markedly diminish LPS-induced lung injury in a murine model indicates that it may serve as a promising adjunctive therapy for acute lung Injury.

CONCLUSION

These suggest that fruit of Physalis angulata L. alleviates sepsis-associated lung injury through suppressing M1 polarization of macrophage via regulation of PFKFB3.

HIF-1α regulated GLUT1-mediated glycolysis enhances Treponema pallidum-induced cytokine responses

Syphilis, caused by Treponema pallidum (Tp), represents a significant public health challenge. The clinical manifestations of syphilis are attributed to local inflammatory responses induced by Tp, notably monocyte infiltration into local lesions and the secretion of inflammatory cytokines. However, the mechanisms driving cytokine production in response to Tp infection remain largely unknown. Given that increased glycolysis is associated with inflammatory responses, we aimed to investigate the role of glycolysis in Tp-induced secretion of inflammatory cytokines. In this study, we found that Tp promotes the secretion of inflammatory cytokines IL-6, IL-8, and CCL2 from monocytes while enhancing glycolysis through increased GLUT1 plasma membrane expression and glucose uptake. Importantly, inhibiting glycolysis and GLUT1 reduced the Tp-induced secretion of monocyte inflammatory cytokines. Additionally, Tp significantly increased HIF-1α expression and induced its nuclear translocation, thereby promoting glycolysis by upregulating the expression of GLUT1 and LDHA glycolytic enzymes. Knockdown of HIF-1α inhibits Tp-induced monocyte cytokine secretion, highlighting the crucial role of HIF-1α-mediated glycolysis in the cytokine response to Tp. Also, expression of HIF-1α and an increase in glycolysis were confirmed in patients with syphilis. In conclusion, we demonstrated that HIF-1α-regulated GLUT1-mediated glycolysis enhances inflammatory cytokine secretion following Tp infection. Our findings not only elucidate the mechanism of glycolysis in Tp-induced inflammatory responses in monocytes but also contribute to the development of a potential biomarker in syphilis diagnosis and treatment.

Tissue-Resident Macrophages in Cardiovascular Diseases: Heterogeneity and Therapeutic Potential

Tissue-resident macrophages (TRMs) play a crucial role in maintaining tissue homeostasis and regulating immune responses. In recent years, an increasing number of studies have highlighted their central role in cardiovascular diseases. This review provides a comprehensive overview of TRMs, with a particular emphasis on cardiac resident macrophages (CRMs), discussing their origin, heterogeneity, and functions in various cardiovascular diseases. We conduct an in-depth analysis of macrophage subpopulations based on C-C Chemokine Receptor Type 2 (CCR2) receptor expression, elucidating the role of CCR2+ macrophages in promoting fibrosis and cardiac remodeling, while highlighting the protective functions of CCR2- macrophages in suppressing inflammation and promoting tissue repair. In atherosclerosis, we focus on the role of metabolic reprogramming in regulating macrophage polarization, revealing how metabolic pathways influence the balance between pro-inflammatory M1 and anti-inflammatory M2 macrophages, thereby affecting plaque stability and disease progression. By summarizing the roles of these macrophage subpopulations in myocardial infarction, heart failure, and other diseases, we propose potential therapeutic strategies aimed at modulating different macrophage subtypes. These include targeting the CCR2 signaling pathway to mitigate inflammation and fibrosis, and metabolic reprogramming to restore the balance between M1 and M2 macrophages. Finally, we highlight the need for future research to focus on the functional diversity and molecular mechanisms of human TRMs to develop novel immunotherapeutic strategies and improve the prognosis of cardiovascular diseases.

Immunometabolism of tumor-associated macrophages: A therapeutic perspective

Tumor-associated macrophages (TAMs) play a pivotal role in the tumor microenvironment (TME), actively contributing to the formation of an immunosuppressive niche that fosters tumor progression. Consequently, there has been a growing interest in targeting TAMs as a promising avenue for cancer therapy. Recent advances in the field of immunometabolism have shed light on the influence of metabolic adaptations on macrophage physiology in the context of cancer. Here, we discuss the key metabolic pathways that shape the phenotypic diversity of macrophages. We place special emphasis on how metabolic reprogramming impacts the activation status of TAMs and their functions within the TME. Additionally, we explore alterations in TAM metabolism and their effects on phagocytosis, production of cytokines/chemokines and interaction with cytotoxic T and NK immune cells. Moreover, we examine the application of nanomedical approaches to target TAMs and assess the clinical significance of modulating the metabolism of TAMs as a strategy to develop new anti-cancer therapies. Taken together, in this comprehensive review article focusing on TAMs, we provide invaluable insights for the development of effective immunotherapeutic strategies and the enhancement of clinical outcomes for cancer patients.

VSIG4 Promotes Tumour-Associated Macrophage M2 Polarization and Immune Escape in Colorectal Cancer via Fatty Acid Oxidation Pathway

BACKGROUND

V-set and immunoglobulin domain containing 4 (VSIG4) is a B7-family-related protein almost exclusively expressed on macrophages. The difference in its expression mediates the dynamic transformation of the polarization state of macrophages, but the underlying mechanism is still unclear. We sought to reveal the correlation between VSIG4 and the polarization of tumour-associated macrophages (TAMs) and the immune escape of tumour cells in colorectal cancer (CRC).

METHODS

THP-1 monocyte-derived macrophages expressing different levels of VSIG4 were used for in vitro investigations. In addition, the co-culture system was used to verify the effect of tumour cells on the expression of VSIG4 in macrophages, and the effect of VSIG4 expression level on tumour cells in turn. Subcutaneous xenograft models evaluated the tumour growth inhibition efficacy of VSIG4 blockade as monotherapy and combined with immune checkpoint inhibitors (ICIs).

RESULTS

CRC cells secreted lactate to promote VSIG4 expression in macrophages. On the contrary, VSIG4 promoted macrophage M2 polarization and induced malignant progression of tumour cells by promoting M2 macrophage secretion of heparin-bound epidermal growth factor. In vivo experiments confirmed that knockdown VSIG4 inhibited tumour growth and improved the efficacy of ICIs therapy. Mechanistically, lactate secreted by CRC cells promoted its expression by influencing the epigenetic modification of VSIG4 in macrophages. In addition, VSIG4 enhanced the fatty acid oxidation (FAO) of macrophages and upregulated PPAR-γ expression by activating the JAK2/STAT3 pathway, which ultimately induced M2 polarization of macrophages. Downregulation of VSIG4 or blocking of FAO reversed the M2 polarization process of macrophages.

CONCLUSIONS

Our findings provide a molecular basis for VSIG4 to influence TAMs polarization by regulating the reprogramming of FAO, suggesting that targeting VSIG4 in macrophages could enhance the ICIs efficacy and represent a new combination therapy strategy for immunotherapy of CRC.

KEY POINTS

Colorectal cancer cells secrete lactate to upregulate VSIG4 in macrophages via the H3K18la-METTL14-m6A axis. VSIG4 promotes fatty acid oxidation of macrophages and drives its M2-type polarization. These VSIG4-expressing M2 macrophages promote tumour progression and an immunosuppressive microenvironment. Inhibition of VSIG4 expression can synergistically enhance the therapeutic effect of anti-PD-1 antibody.

Hypoxia-reduced YAP phosphorylation enhances expression of Mucin5AC in nasal epithelial cells of chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is an upper respiratory disease characterized by persistent inflammation of the nasal mucosa. However, the mechanism of abnormal Mucin5AC expression by CRSwNP epithelial cells is not fully understood.

OBJECTIVE

We investigated the potential role of yes-associated protein (YAP) underlying the mechanism of excessive epithelial Mucin5AC expression in CRSwNP in a hypoxic model.

METHODS

Tissue biopsies of CRSwNP (n = 60), chronic rhinosinusitis without nasal polyps (CRSsNP) (n = 9) and healthy controls (n = 30) were investigated together with a well-established hypoxic model of primary human nasal epithelial cells (hNECs). The expression levels of hypoxia inducible factor (HIF)-1α and YAP, and the effect of the signaling axis on mucus secretion in hNECs were analyzed.

RESULTS

We observed a significant elevated expression levels of YAP in patients with CRSwNP and CRSsNP compared to controls. In addition, HIF-1α expression of CRSwNP was higher than that of control group. Under hypoxic conditions, HIF-1α was found to regulate the upregulation of YAP in hNECs. Further investigations revealed that HIF-1α facilitated the activation and nuclear localization of active-YAP by reducing the phosphorylation of YAP. This mechanism appeared to be linked to HIF-1α-mediated inhibition of LATS 1 phosphorylation and subsequent YAP degradation. HIF-1α was shown to promote the expression of P63 and the levels of Mucin5AC in hNECs by enhancing YAP activation.

CONCLUSION

Our findings indicated that hypoxia enhances YAP activation by decreasing p-LATS 1 and YAP phosphorylation. This has the potential to impact on the proliferation of basal cells and the differentiation of goblet cells in CRSwNP, ultimately leading to a pathological condition characterized by excessive Mucin5AC expression.

Roles of circadian clocks in macrophage metabolism: implications in inflammation and metabolism of lipids, glucose, and amino acids

Macrophages are essential immune cells that play crucial roles in inflammation and tissue homeostasis and are important regulators of metabolic processes, such as the metabolism of glucose, lipids, and amino acids. The regulation of macrophage metabolism by circadian clock genes has been emphasized in many studies. Changes in metabolic profiles occurring after the perturbation of macrophage circadian cycles may underlie the etiology of several diseases. Specifically, chronic inflammatory disorders, such as atherosclerosis, diabetes, cardiovascular diseases, and liver dysfunction, are associated with poor macrophage metabolism. Developing treatment approaches that target metabolic and immunological ailments requires an understanding of the complex relationships among clock genes, disease etiology, and macrophage metabolism. This review explores the molecular mechanisms through which clock genes regulate lipid, amino acid, and glucose metabolism in macrophages and discusses their potential roles in the development and progression of metabolic disorders. The findings underscore the importance of maintaining circadian homeostasis in macrophage function as a promising avenue for therapeutic intervention in diseases involving metabolic dysregulation, given its key roles in inflammation and tissue homeostasis. Moreover, reviewing the therapeutic implications of circadian rhythm in macrophages can help minimize the side effects of treatment. Novel strategies may be beneficial in treating immune-related diseases caused by shifted and blunted circadian rhythms via light exposure, jet lag, seasonal changes, and shift work or disruption to the internal clock (such as stress or disease).

PKM2 regulates osteoclastogenesis by affecting osteoclast precursor cell fusion via downregulation of OC-STAMP and DC-STAMP

Osteoporosis is a common bone disease that has become a serious public health problem with the aging of population. Osteoclasts are the only cells in body that can resorb bone, whose dysfunction is closely related to osteoporosis. Pyruvate kinase M2 (PKM2) is one of the essential rate-limiting enzymes in the process of glycolysis. This study aimed to elucidate the role of PKM2 in osteoclastogenesis and bone resorption. Bone marrow-derived macrophages were transfected with adenovirus to knock down the expression of PKM2 gene or treated with the PKM2 activators, DASA-58 and TEPP-46. Osteoclast formation was detected by tartrate-resistant acid phosphatase staining, osteoclast-specific gene and protein expression was detected by RT-quantitative PCR and Western blotting, and the effect of DASA-58 on osteoclast gene expression at the transcriptional level was examined by RNA sequencing. The results showed that knockdown of PKM2 by adenoviral transfection or treatment with PKM2 activators, DASA-58 and TEPP-46, inhibited osteoclast differentiation and suppressed the expression of osteoclast-associated genes in bone marrow-derived macrophages. Furthermore, PKM2 activators, DASA-58 and TEPP-46, could inhibit several signaling pathways in osteoclasts; knockdown of PKM2 or treatment with PKM2 activators, DASA-58 and TEPP-46, both affected osteoclast precursor cell fusion by inhibiting the expression of osteoclast stimulatory transmembrane protein (OC-STAMP) and dendritic cell-specific transmembrane protein (DC-STAMP). Therefore, PKM2 is closely related to osteoclast differentiation and formation, and the development of new therapeutic strategies targeting the PKM2 gene in osteoclasts may be feasible for the prevention and treatment of osteoporosis.

Astragalin alleviates lipopolysaccharide-induced depressive-like behavior in mice by preserving blood-brain barrier integrity and suppressing neuroinflammation

Astragalin (AST) is a flavonoid glycoside commonly found in edible plants and medicinal herbs with a variety of therapeutic effects. This study aimed to investigate whether AST protects the integrity of the blood-brain barrier (BBB) and inhibits neuroinflammation, thereby alleviating depressive-like behaviors. LPS-stimulated cultured cells and LPS-induced BBB disruption and depressive-like behavior mice models were employed. We founded that AST inhibited LPS-induced inflammatory responses in microglial BV2 cells and protected SH-SY5Y cells from inflammatory injury. In mice, AST effectively ameliorated LPS-induced depressive-like behaviors, which was attributed to its ability to maintain BBB integrity and inhibit inflammatory damage caused by LPS invasion. Furthermore, AST suppressed LPS-induced activation of glial cells, protecting neuronal dendritic spines, synapses, and mitochondria from inflammatory damage. It also reduced the elevation of pro-inflammatory factors such as TNF-α, IL-1β, and IL-6, and normalized the aberrant activation of inflammatory signaling pathways, including RIPK1/RIPK3/MLKL and mTOR/NF-κB. In conclusion, AST protects BBB integrity and brain tissue from inflammatory damage, offering new insights for drug development and clinical interventions in systemic inflammatory responses, such as sepsis-induced encephalitis.

MicroRNA-122 regulates inflammatory and autophagic proteins by downregulating pyruvate kinase M2 in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the serious global health concerns, leading to non-alcoholic steatohepatitis (NASH), and to hepatocellular carcinoma (HCC). Despite its prevalence, the molecular mechanisms regulating NAFLD progression remain elusive. The present study aims to determine role of microRNA-122-mediated regulation of pyruvate kinase M2 (PKM2) on regulating inflammatory and autophagic proteins during the pathogenesis of NAFLD. Huh7 cells were incubated with free fatty acids (FFAs) or transfected with single guide RNA to PKM2 containing CRISPR-Cas9 system or miR-122 for up to 72 h. C57BL/6 mice were fed with sham-operated control, choline sufficient L-amino acid defined (CSAA) or choline-deficient L-amino acid defined (CDAA) diet for 6, 18, 32 and 54 weeks. The RNA or protein was isolated from the Huh7 cells and the liver tissue of the mice. RT-PCR was performed for miR-122 expression and Western blots were performed for PKM2, iNOS, COX2, Beclin-1, Atg7 and LC3-II. FFAs induced the expression of PKM2, iNOS and COX2, while decreased the expression of miR-122, Beclin-1, Atg7 and LC3-II. Overexpression of miR-122 resulted in decreased PKM2, iNOS and COX2 and increased Beclin-1, Atg7 and LC3-II. Silencing of PKM2 led to decreased iNOS and COX2 and increased Beclin-1, Atg7 and LC3-II. In CDAA fed-mice, there was a significant increase in PKM2, iNOS and COX2 and decreased miR-122, Beclin-1, Atg7 and LC3-II. The data showed that FFAs downregulated miR-122 expression, which resulted in the upregulation of PKM2, which in turn upregulated inflammatory proteins and downregulated autophagic proteins during the pathogenesis of NAFLD.

Metabolic reprogramming in hepatocellular carcinoma: mechanisms of immune evasion and therapeutic implications

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide, with limited treatment options for advanced stages. Metabolic reprogramming is a hallmark of cancer, enabling tumor cells to adapt to the harsh tumor microenvironment (TME) and evade immune surveillance. This review involves the role of metabolic reprogramming in HCC, focusing on the dysregulation of glucose, lipid, and amino acid metabolism, and its impact on immune evasion. Key metabolic pathways, such as the Warburg effect, fatty acid synthesis, and glutaminolysis, are discussed, along with their influence on tumor-associated macrophages (TAMs) and immune cell function. Targeting these metabolic alterations presents a promising therapeutic approach to enhance immunotherapy efficacy and improve HCC patient outcomes.

Macrophage PKM2 depletion ameliorates hepatic inflammation and acute liver injury in mice

Introduction

Pyruvate kinase M2 (PKM2), the rate-limiting enzyme of glycolysis, plays a critical role in macrophage activation and a broad spectrum of chronic liver diseases. However, whether PKM2 contributes to the pathogenesis of acute liver injury (ALI) remains largely unexplored.

Methods

PKM2 expression was assessed in human and mouse ALI livers. Macrophage-specific PKM2 knockout mice were challenged by two independent ALI models, induced by acetaminophen (APAP) and lipopolysaccharide/D-galactosamine (LPS/D-GalN), to explore the role and regulatory mechanism of macrophage PKM2 in ALI progression.

Results

By bioinformatic screening and analysis of ALI liver, we found that PKM2 was significantly upregulated in the liver tissues of ALI patients and mice. Immunofluorescence staining further demonstrated that PKM2 was markedly upregulated in macrophages during ALI progression. Notably, macrophage PKM2 depletion effectively alleviated APAP- and LPS/D-GalN-induced ALI, as demonstrated by ameliorated immune cells infiltration, pro-inflammatory mediators, and hepatocellular cell death. PKM2-deficient macrophages showed M2 anti-inflammatory polarization in vivo and in vitro. Furthermore, PKM2 deletion limited HIF-1α signaling and aerobic glycolysis of macrophages, which thereby attenuated macrophage pro-inflammatory activation and hepatocyte injury. Pharmacological PKM2 antagonist efficiently ameliorated liver injury and prolonged the survival of mice in APAP-induced ALI model.

Discussion

Our study highlights the pivotal role of macrophage PKM2 in advancing ALI, and therapeutic targeting of PKM2 may serve as a novel strategy to combat ALI.

MIF tautomerase inhibitor TE-11 prevents inflammatory macrophage activation and glycolytic reprogramming while reducing leukocyte migration and improving Crohn's disease-like colitis in male mice

Background & aims

Crohn's disease (CD) is a chronic inflammatory disorder primarily affecting the gastrointestinal tract. Leukocyte recruitment, M1 macrophage polarization and associated metabolic reprogramming are hallmarks of its pathomechanism. Here, we tested TE-11, a potent MIF tautomerase inhibitor (IC50 = 5.63 μmol/dm3) in experimental Crohn's disease in male mice, in leukocyte recruitment and in inflammatory M1 macrophage activation.

Methods

2,4,6-trinitrobenzenesulfonic acid-(TNBS)-induced colitis was utilized as a CD-model in male mice. We performed macroscopic scoring and cytokine measurements. We also analyzed MIF-induced leukocyte migration and evaluated apoptosis. LPS+IFN-γ-induced RAW264.7 cells were applied as a M1 macrophage model. We performed qPCR, ROS and nitrite determinations, ELISA measurements, mitochondrial oxygen consumption rate and extracellular acidification rate determinations.

Results

TE-11 improved mucosal damage, reduced inflammation score and concentration of IL-1β and IL-6 in the colon. It inhibited MIF-induced human blood eosinophil and neutrophil migration and counteracted the anti-apoptotic effect of MIF. In macrophages, MIF inhibition prevented M1 polarization by downregulating HIF-1α gene expression in LPS+IFN-γ-activated cells. Additionally, the molecule reduced mRNA transcription and protein expression of chemokine CCL-2 and cytokine IL-6 while further increasing SOD2 gene transcription and decreased ROS and nitrite production in macrophages. During inflammatory metabolic reprogramming, TE-11 prevented LPS+IFN-γ-induced metabolic shift from OXPHOS to glycolysis. Similarly to anti-inflammatory M2 cells, TE-11 improved mitochondrial energy production by increasing basal respiration, ATP production, coupling efficiency, maximal respiration and spare respiratory capacity.

Conclusion

Comprehensively, TE-11, a MIF tautomerase inhibitor ameliorates CD-like colitis, reduces MIF-induced eosinophil and neutrophil migration and prevents M1 polarization and associated metabolic reprogramming; therefore, it may prove beneficial as a potential drug candidate regarding CD therapy.

Lactate metabolism and acute kidney injury

ABSTRACT

Acute kidney injury (AKI) is a common clinically critical syndrome in hospitalized patients with high morbidity and mortality. At present, the mechanism of AKI has not been fully elucidated, and no therapeutic drugs exist. As known, glycolytic product lactate is a key metabolite in physiological and pathological processes. The kidney is an important gluconeogenic organ, where lactate is the primary substrate of renal gluconeogenesis in physiological conditions. During AKI, altered glycolysis and gluconeogenesis in kidneys significantly disturb the lactate metabolic balance, which exert impacts on the severity and prognosis of AKI. Additionally, lactate-derived posttranslational modification, namely lactylation, is novel to AKI as it could regulate gene transcription of metabolic enzymes involved in glycolysis or Warburg effect. Protein lactylation widely exists in human tissues and may severely affect non-histone functions. Moreover, the strategies of intervening lactate metabolic pathways are expected to bring a new dawn for the treatment of AKI. This review focused on renal lactate metabolism, especially in proximal renal tubules after AKI, and updated recent advances of lactylation modification, which may help to explore potential therapeutic targets against AKI.

Targeting mTOR in myeloid cells prevents infection-associated inflammation

Infections, cancer, and trauma can cause life-threatening hyperinflammation. In the present study, using single-cell RNA sequencing of circulating immune cells, we found that the mammalian target of rapamycin (mTOR) pathway plays a critical role in myeloid cell regulation in COVID-19 patients. Previously, we developed an mTOR-inhibiting nanobiologic (mTORi-nanobiologic) that efficiently targets myeloid cells and their progenitors in the bone marrow. In vitro, we demonstrated that mTORi-nanobiologics potently inhibit infection-associated inflammation in human primary immune cells. Next, we investigated the in vivo effect of mTORi-nanobiologics in mouse models of hyperinflammation and acute respiratory distress syndrome. Using 18F-FDG uptake and flow cytometry readouts, we found mTORi-nanobiologic therapy to efficiently reduce hematopoietic organ metabolic activity and inflammation to levels comparable to those of healthy control animals. Together, we show that regulating myelopoiesis with mTORi-nanobiologics is a compelling therapeutic strategy to prevent deleterious organ inflammation in infection-related complications.

The role of PKM2-mediated metabolic reprogramming in the osteogenic differentiation of BMSCs under diabetic periodontitis conditions

BACKGROUND

Diabetes mellitus (DM) and periodontitis have a bidirectional relationship, with each being a high-risk factor for the other. Prolonged hyperglycemia exacerbates periodontal inflammation and disrupts bone homeostasis. Pyruvate kinase M2 (PKM2), a key enzyme in glycolysis, is involved in metabolic reprogramming, but its role in osteogenesis under high-glucose (HG) inflammatory conditions remains largely unknown. This study aimed to investigate the effects of HG and inflammation on bone marrow mesenchymal stem cells (BMSCs) under indirect co-culture conditions and to explore how PKM2 regulates metabolism and mitochondrial function during osteogenic differentiation in HG inflammatory environments, elucidating its role in diabetic periodontitis (DP).

METHODS

Expose BMSCs to conditioned medium (CM) collected from RAW264.7 cells stimulated with HG and/or lipopolysaccharide (LPS). BMSCs functionality was assessed using CCK8, EdU, Annexin V-PI apoptosis assay, alkaline phosphatase (ALP), and Alizarin Red S (ARS) staining. Metabolic characteristics were evaluated through Seahorse assays, lactate production, glucose uptake, and ATP measurements. Mitochondrial function was assessed via JC-1, and ROS staining, Mito-Tracker staining, and transmission electron microscopy (TEM). Gene and protein expression were analyzed by quantitative real-time PCR and western blotting. In vivo therapeutic effects of shikonin were validated via micro-CT and histological staining in a diabetic periodontitis mouse model.

RESULTS

In vitro experiments demonstrated that HG inflammatory conditions impaired the survival of BMSCs, suppressed osteogenic differentiation, and induced metabolic reprogramming. This reprogramming was characterized by enhanced glycolysis, impaired oxidative phosphorylation (OXPHOS), abnormal upregulation of PKM2 expression, and mitochondrial dysfunction accompanied by morphological alterations. Shikonin effectively reversed these adverse effects by inhibiting PKM2 tetramerization, rescuing the loss of osteogenic function in BMSCs. The therapeutic potential of shikonin was confirmed in the diabetic periodontitis mouse model.

CONCLUSION

PKM2 impairs the osteogenesis of BMSCs by affecting metabolism and mitochondrial function, suggesting it as a potential therapeutic target for diabetic periodontitis.

Dimethyl fumarate modulates M1/M2 macrophage polarization to ameliorate periodontal destruction by increasing TUFM-mediated mitophagy

Periodontitis is a common oral disease characterized by progressive alveolar bone resorption and inflammation of the periodontal tissues. Dimethyl fumarate (DMF) has been used in the treatment of various immune-inflammatory diseases due to its excellent anti-inflammatory and antioxidant functions. Here, we investigated for the first time the therapeutic effect of DMF on periodontitis. In vivo studies showed that DMF significantly inhibited periodontal destruction, enhanced mitophagy, and decreased the M1/M2 macrophage ratio. In vitro studies showed that DMF inhibited macrophage polarization toward M1 macrophages and promoted polarization toward M2 macrophages, with improved mitochondrial function, inhibited oxidative stress, and increased mitophagy in RAW 264.7 cells. Furthermore, DMF increased intracellular mitochondrial Tu translation elongation factor (TUFM) levels to maintain mitochondrial homeostasis, promoted mitophagy, and modulated macrophage polarization, whereas TUFM knockdown decreased the protective effect of DMF. Finally, mechanistic studies showed that DMF increased intracellular TUFM levels by protecting TUFM from degradation via the ubiquitin-proteasomal degradation pathway. Our results demonstrate for the first time that DMF protects mitochondrial function and inhibits oxidative stress through TUFM-mediated mitophagy in macrophages, resulting in a shift in the balance of macrophage polarization, thereby attenuating periodontitis. Importantly, this study provides new insights into the prevention of periodontitis.

Inhibition of colorectal cancer cell growth by downregulation of M2-PK and reduction of aerobic glycolysis by clove active ingredients

Exploring the anti-tumor molecular mechanisms of traditional Chinese medicines has become an important strategy to develop novel anti-tumor drugs in the clinic. Several pharmacological studies have reported the antioxidant, antibacterial, anti-inflammatory, and anti-tumor effects of clove. Previously, we have shown that the active fraction from clove (AFC) can inhibit the growth of tumor cells, particularly colon cancer cells, in vitro. However, the mechanism of action regarding the anti-colon cancer activity of AFC, especially in aerobic glycolysis, has not been adequately investigated. In this study, we found that AFC significantly inhibited the growth of five types of colon cancer cells, downregulated the mRNA and protein levels of M2-type pyruvate kinase (PKM2), and reduced aerobic glycolysis capacity. Transfection of PKM2-siRNA mimicked the inhibitory effects of AFC on aerobic glycolysis in colon cancer cells. Furthermore, the highly expressed, tumor-specific targets c-myc and cyclin D1 in cells were also found to be downregulated following the action of AFC. In the HCT116 cell xenograft nude mice models, the results after AFC administration were consistent with those of the cellular experiments, while AFC caused less liver injury and weight loss than the conventional chemotherapeutic agent 5- fluorouracil (5-FU). In conclusion, AFC inhibits colon cancer growth by downregulating PKM2 to inhibit aerobic glycolysis and reduce the tumor-specific high expression of c-myc and cyclin D1. Future work should explore how it downregulates pyruvate kinase (PK) in the first place, along with the intrinsic mechanism between the downregulation of PKM2 and the downregulation of c-myc.

Indole-3-propionic acid alleviates DSS-induced colitis in mice through macrophage glycolipid metabolism

Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease for which current therapeutic approaches still face many dilemmas, and targeting macrophage polarization and metabolism for the treatment of this disease is a potentially effective strategy. The gut microbial metabolite indole-3-propionic acid (IPA) has favorable anti-inflammatory and antioxidant effects and plays a role in a variety of disease models. IPA is effective in the treatment of UC, but the underlying mechanisms have not been well explored. In the present study, we investigated the mechanisms by which IPA ameliorates colitis in mice from the perspective of macrophage polarization and metabolism. In this study, mice colitis was induced by sodium dextran sulfate and treated with oral IPA. RAW264.7 cells were induced by LPS to polarize into M1 macrophages and treated with IPA. The results showed that IPA could improve colitis by inhibiting M1 polarization of colonic macrophages and promoting M2 polarization. The inhibition of IPA on M1 macrophages was verified in vitro through JNK/MAPK pathway, which inhibited the glycolysis of macrophages. IPA promotes macrophage M2 polarization and enhances fatty acid oxidation through upregulating of CPT1A and ACSL1, which may be related to the activation of PPAR-γ. In summary, IPA can improve colitis by regulating macrophage glucose and lipid metabolism, and targeting intestinal macrophage metabolism may be an effective target for the treatment of UC.

Tumor Microenvironment Lactate: Is It a Cancer Progression Marker, Immunosuppressant, and Therapeutic Target?

The "Warburg effect" is a term coined a century ago for the preferential use of glycolysis over aerobic respiration in tumor cells for energy production, even under aerobic conditions. Although this is a less efficient mechanism of generating energy from glucose, aerobic glycolysis, in addition to the canonical anaerobic glycolysis, is an effective means of lactate production. The abundant waste product, lactate, yielded by the dual glycolysis in a tumor, has been discovered to be a major biomolecule that drives cancer progression. Lactate is a metabolic energy source that, via cell membrane lactate transporters, shuttles in and out of cancer cells as well as cancer cell-associated stromal cells and immune cells within the tumor microenvironment (TME). Additionally, lactate serves as a pH tuner, signaling ligand and transducer, epigenetic and gene transcription regulator, TME modifier, immune suppressor, chemoresistance modulator, and prognostic marker. With such broad functionalities, the production-consumption-reproduction of TME lactate fuels tumor growth and dissemination. Here, we elaborate on the lactate sources that contribute to the pool of lactate in the TME, the functions of TME lactate, the influence of the TME lactate on immune cell function and local tissue immunity, and anticancer therapeutic approaches adopting lactate manipulations and their efficacies. By scrutinizing these properties of the TME lactate and others that have been well addressed in the field, it is expected that a better weighing of the influence of the TME lactate on cancer development, progression, prognosis, and therapeutic efficacy can be achieved.

Metabolic reprogramming of macrophages by a nano-sized opsonization strategy to restore M1/M2 balance for osteoarthritis therapy

Osteoarthritis is a chronic and progressive joint disease accompanied by cartilage degeneration and synovial inflammation. It is associated with an imbalance of synovial macrophage M1/M2 ratio tilting more towards the pro-inflammatory M1 than the anti-inflammatory M2. The M1-macrophages rely on aerobic glycolysis for energy whereas the M2-macrophages derive energy from oxidative phosphorylation. Therefore, inhibiting aerobic glycolysis to induce metabolic reprogramming of macrophages and consequently promote the shift from M1 type to M2 type is a therapeutic strategy for osteoarthritis. Here we developed a macrophage-targeting strategy based on opsonization, using nanoparticles self-assembled to incorporate Chrysin (an anti-inflammatory flavonoid) and V-9302 (an inhibitor of glutamine uptake), and the outer layer modified by immunoglobulin IgG by electrostatic adsorption into IgG/Fe-CV NPs. In vitro studies showed that IgG/Fe-CV NPs effectively target M1 macrophages and inhibit HIF-1α and GLUT-1 essential for aerobic glycolysis and promote polarization from M1 to M2-type macrophages. In vivo, IgG/Fe-CV NPs inhibit inflammation and protect against cartilage damage. The metabolic reprogramming strategy with IgG/Fe-CV NPs to shift macrophage polarization from inflammatory to anti-inflammatory phenotype by inhibiting aerobic glycolysis and glutamine delivery may open up new avenues to treat osteoarthritis.

PKM2-mediated metabolic reprogramming of microglia in neuroinflammation

Microglia, the resident immune cells of the central nervous system, undergo metabolic reprogramming during neuroinflammation, playing a crucial role in the pathogenesis of neurological disorders such as Parkinson's disease. This review focuses on Pyruvate Kinase M2 (PKM2), a key glycolytic enzyme, and its impact on microglial metabolic reprogramming and subsequent neuroinflammation. We explore the regulatory mechanisms governing PKM2 activity, its influence on microglial activation and immune responses, and its contribution to the progression of various neurological diseases. Finally, we highlight the therapeutic potential of targeting PKM2 as a novel strategy for treating neuroinflammation-driven neurological disorders. This review provides insights into the molecular mechanisms of PKM2 in neuroinflammation, aiming to inform the development of future therapeutic interventions.

HIF-1 regulates mitochondrial function in bone marrow-derived macrophages but not in tissue-resident alveolar macrophages

HIF-1α plays a critical role in shaping macrophage phenotype and effector function. We have previously shown that tissue-resident alveolar macrophages (TR-AMs) have extremely low glycolytic capacity at steady-state but can shift toward glycolysis under hypoxic conditions. Here, we generated mice with tamoxifen-inducible myeloid lineage cell specific deletion of Hif1a (Hif1afl/fl:LysM-CreERT2+/-) and from these mice, we isolated TR-AMs and bone marrow-derived macrophages (BMDMs) in which Hif1a is deleted. We show that TR-AM HIF-1α is required for the glycolytic shift under prolyl hydroxylase inhibition but is dispensable at steady-state for inflammatory effector function. In contrast, HIF-1α deletion in BMDMs led to diminished glycolytic capacity at steady-state and reduced inflammatory capacity, but higher mitochondrial function. Gene set enrichment analysis revealed enhanced c-Myc transcriptional activity in Hif1a-/- BMDMs, and upregulation of gene pathways related to ribosomal biogenesis and cellular proliferation. We conclude that HIF-1α regulates mitochondrial function in BMDMs but not in TR-AMs. The findings highlight the heterogeneity of HIF-1α function in distinct macrophage populations and provide new insight into how HIF-1α regulates gene expression, inflammation, and metabolism in different types of macrophages.

PKM2 crotonylation reprograms glycolysis in VSMCs, contributing to phenotypic switching

Post-translational modifications (PTMs) of pyruvate kinase M2 (PKM2) play a vital role in regulating its activity and function. Recently, we found PKM2 can undergo crotonylation in vascular smooth muscle cell (VSMC) phenotypic switching. However, the role of PKM2 crotonylation remains unknown. Here, we verify a crucial role of PKM2 crotonylation in VSMC metabolic reprogramming. In PDGF-BB-induced synthetic VSMCs, PKM2 crotonylation was upregulated and promotes its nuclear translocation, thereby facilitating the expression of Glut1 and Ldha. Furthermore, crotonylation facilitated the dimeric formation of PKM2. Then we identified the highly conserved crotonylation site at K305 across different species. The crotonylation of PKM2 was compromised by PKM2 K305 mutation, resulting in the suppression of PKM2 dimeric configuration and nuclear relocation, and ultimately reducing glycolysis rate. Furthermore, PKM2 K305 crotonylation was necessary for VSMC phenotypic switching in vitro and intimal hyperplasia in vivo via infection of PKM2 recombinant adenovirus. In summary, PKM2 K305 crotonylation facilitates VSMC aerobic glycolysis by enhancing PKM2 dimeric form.

Pyruvate kinase M2 activation reprograms mitochondria in CD8 T cells, enhancing effector functions and efficacy of anti-PD1 therapy

Mitochondria regulate T cell functions and response to immunotherapy. We show that pyruvate kinase M2 (PKM2) activation enhances mitochondria-dependent effector functions in CD8 and chimeric antigen receptor (CAR)-T cells. Multi-omics and 13C-glucose tracer studies showed that PKM2 agonism alters one-carbon metabolism, decreasing methionine levels, resulting in hypomethylated nuclear and mitochondrial DNA and enhancing mitochondrial biogenesis and functions. PKM2 activation increased the recall responses and anti-tumor functions of CD8 T cells, enhancing adoptive cell therapy. In preclinical models, the PKM2 agonist induced CD8 T cell-dependent anti-tumor responses that synergized with anti-programmed death 1 (PD1) therapy. Immunologically, PKM2 agonists boosted the activation of effector T cells while reducing FoxP3+ T regulatory (Treg) cells in the tumors. The anti-PD1 combination enhanced the frequency of tumor-specific activated CD8 T cells. Together, PKM2 agonism increased mitochondrial functions supporting cell cytotoxicity. Hence, pharmacological targeting of PKM2 can be a clinically viable strategy for enhancement of adoptive cell therapy, in situ anti-tumor immune responses, and immune checkpoint blockade therapy. VIDEO ABSTRACT.

Redefining Macrophage Heterogeneity in Atherosclerosis: A Focus on Possible Therapeutic Implications

Atherosclerosis is a lipid disorder where modified lipids (especially oxidized LDL) induce macrophage foam cell formation in the aorta. Its pathogenesis involves a continuum of persistent inflammation accompanied by dysregulated anti-inflammatory responses. Changes in the immune cell status due to differences in the lesional microenvironment are crucial in terms of plaque development, its progression, and plaque rupture. Ly6Chi monocytes generated through both medullary and extramedullary cascades act as one of the major sources of plaque macrophages and thereby foam cells. Both monocytes and monocyte-derived macrophages also participate in pathological events in atherosclerosis-associated multiple organ systems through inter-organ communications. For years, macrophage phenotypes M1 and M2 have been shown to perpetuate inflammatory and resolution responses; nevertheless, such a dualistic classification is too simplistic and contains severe drawbacks. As the lesion microenvironment is enriched with multiple mediators that possess the ability to activate macrophages to diverse phenotypes, it is obvious that such cells should demonstrate substantial heterogeneity. Considerable research in this regard has indicated the presence of additional macrophage phenotypes that are exclusive to atherosclerotic plaques, namely Mox, M4, Mhem, and M(Hb) type. Furthermore, although the concept of macrophage clusters has come to the fore in recent years with the evolution of high-dimensional techniques, classifications based on such 'OMICS' approaches require extensive functional validation as well as metabolic phenotyping. Bearing this in mind, the current review provides an overview of the status of different macrophage populations and their role during atherosclerosis and also outlines possible therapeutic implications.

Polychlorinated biphenyls induce immunometabolic switch of antiinflammatory macrophages toward an inflammatory phenotype

Polychlorinated biphenyls (PCBs) are a group of environmental toxicants associated with increased risk of diabetes, obesity, and metabolic syndrome. These metabolic disorders are characterized by systemic and local inflammation within adipose tissue, the primary site of PCB accumulation. These inflammatory changes arise when resident adipose tissue macrophages undergo phenotypic plasticity-switching from an antiinflammatory to an inflammatory phenotype. Thus, we sought to assess whether PCB exposure drives macrophage phenotypic switching. We investigated how human monocyte-derived macrophages polarized toward an M1, M2a, or M2c phenotype were impacted by exposure to Aroclor 1254, a PCB mixture found at high levels in school air. We showed that PCB exposure not only exacerbates the inflammatory phenotype of M1 macrophages but also shifts both M2a and M2c cells toward a more inflammatory phototype in both a dose- and time-dependent manner. Additionally, we show that PCB exposure leads to significant metabolic changes. M2 macrophages exposed to PCBs exhibit increased reliance on aerobic glycolysis and reduced capacity for fatty acid and amino acid oxidation-both indicators of an inflammatory macrophage phenotype. Collectively, these results demonstrate that PCBs promote immunometabolic macrophage plasticity toward a more M1-like phenotype, thereby suggesting that PCBs exacerbate metabolic diseases by altering the inflammatory environment in adipose tissue.

The glycolytic enzyme PKM2 regulates inflammatory osteoclastogenesis by modulating STAT3 phosphorylation

Periodontitis is a prevalent chronic inflammatory disease characterized by alveolar bone resorption mediated by osteoclasts. Pyruvate kinase M2 (PKM2), a key enzyme in glycolysis and pyruvate metabolism, has recently been recognized for its regulatory roles beyond metabolism, including gene expression and protein kinase activity. However, its exact role in osteoclastogenesis remains unclear. This study investigates the function of PKM2 in inflammatory osteoclastogenesis and explores its potential as a therapeutic target for periodontitis. Using murine bone marrow-derived macrophages (BMMs) stimulated with lipopolysaccharides (LPS) to mimic inflammatory conditions in vitro, we analyzed PKM2 expression and glycolytic activity during osteoclastogenesis through bioinformatics, tartrate-resistant acid phosphatase (TRAP) staining, phalloidin staining, quantitative real-time PCR (RT-qPCR), and Western blotting. Glycolysis was inhibited using 2-deoxy-D-glucose (2-DG), while TEPP-46 was used to activate PKM2. In a mouse model of periodontitis, the effects of TEPP-46 on alveolar bone loss were evaluated using micro-computed tomography, immunohistochemistry, TRAP staining, and hematoxylin-eosin (HE) staining. The results demonstrated that LPS significantly enhanced osteoclastogenesis and glycolysis, increasing PKM2 expression in osteoclasts. Inhibiting glycolysis with 2-DG suppressed osteoclast formation and osteoclast-related gene expression under inflammatory conditions. TEPP-46 treatment reduced nuclear dimeric PKM2 levels, decreased phosphorylated signal transducer and activator of transcription three (p-STAT3) expression, and inhibited osteoclastogenesis and osteoclast-related gene expression. Co-immunoprecipitation confirmed an interaction between nuclear dimeric PKM2 and p-STAT3. In vivo, TEPP-46 effectively reduced alveolar bone loss by preventing PKM2 nuclear translocation and STAT3 phosphorylation. These findings reveal that PKM2 regulates inflammatory osteoclastogenesis through modulation of glycolysis and STAT3 signaling, highlighting its potential as a therapeutic target for periodontitis.

Metabolic Reprogramming in Stromal and Immune Cells in Rheumatoid Arthritis and Osteoarthritis: Therapeutic Possibilities

Metabolic reprogramming of stromal cells, including fibroblast-like synoviocytes (FLS) and chondrocytes, as well as osteoclasts (OCs), are involved in the inflammatory and degenerative processes underlying rheumatoid arthritis (RA) and osteoarthritis (OA). In RA, FLS exhibit mTOR activation, enhanced glycolysis and reduced oxidative phosphorylation, fuelling inflammation, angiogenesis, and cartilage degradation. In OA, chondrocytes undergo metabolic rewiring, characterised by mTOR and NF-κB activation, mitochondrial dysfunction, and increased glycolysis, which promotes matrix metalloproteinase production, extracellular matrix (ECM) degradation, and angiogenesis. Macrophage-derived immunometabolites, including succinate and itaconate further modulate stromal cell function, acting as signalling molecules that modulate inflammatory and catabolic processes. Succinate promotes inflammation whilst itaconate is anti-inflammatory, suppressing inflammatory joint disease in models. Itaconate deficiency also correlates inversely with disease severity in RA in humans. Emerging evidence highlights the potential of targeting metabolic processes as promising therapeutic strategies for connective tissue disorders.

The multiple functions and mechanisms of long non-coding RNAs in regulating breast cancer progression

Breast cancer (BC) is a malignant tumor that has the highest morbidity and mortality rates in the female population, and its high tendency to metastasize is the main cause of poor clinical prognosis. Long non-coding RNAs (lncRNAs) have been extensively documented to exhibit aberrant expression in various cancers and influence tumor progression via multiple molecular pathways. These lncRNAs not only modulate numerous aspects of gene expression in cancer cells, such as transcription, translation, and post-translational modifications, but also play a crucial role in the reprogramming of energy metabolism by regulating metabolic regulators, which is particularly significant in advanced BC. This review examines the characteristics and mechanisms of lncRNAs in regulating BC cells, both intracellularly (e.g., cell cycle, autophagy) and extracellularly (e.g., tumor microenvironment). Furthermore, we explore the potential of specific lncRNAs and their regulatory factors as molecular markers and therapeutic targets. Lastly, we summarize the application of lncRNAs in the treatment of advanced BC, aiming to offer novel personalized therapeutic options for patients.

Roles of TLR4 in macrophage immunity and macrophage-pulmonary vascular/lymphatic endothelial cell interactions in sepsis

In sepsis, acute lung injury (ALI) is a severe complication and a leading cause of death, involving complex mechanisms that include cellular and molecular interactions between immune and lung parenchymal cells. In recent decades, the role of Toll-like receptor 4 (TLR4) in mediating infection-induced inflammation has been extensively studied. However, how TLR4 facilitates interactions between innate immune cells and lung parenchymal cells in sepsis remains to be fully understood. This study aims to explore the role of TLR4 in regulating macrophage immunity and metabolism in greater depth. It also seeks to reveal how changes in these processes affect the interaction between macrophages and both pulmonary endothelial cells (ECs) and lymphatic endothelial cells (LECs). Using TLR4 knockout mice and the combined approaches of single-cell RNA sequencing and experimental validation, we demonstrate that in sepsis, TLR4-deficient macrophages upregulate Abca1, enhance cholesterol efflux, and reduce glycolysis, promoting M2 polarization and attenuating inflammation. These metabolic and phenotypic shifts significantly affect their interactions with pulmonary ECs and LECs. Mechanistically, we uncovered that TLR4 operates through multiple pathways in endothelial dysfunction: macrophage TLR4 mediates inflammatory damage to ECs/LECs, while endothelial TLR4 both directly sensitizes cells to lipopolysaccharide-induced injury and determines their susceptibility to macrophage-derived inflammatory signals. These findings reveal the complex role of TLR4 in orchestrating both immune-mediated and direct endothelial responses during sepsis-induced ALI, supporting that targeting TLR4 on multiple cell populations may present an effective therapeutic strategy.

The Intestinal Macrophage-Intestinal Stem Cell Axis in Inflammatory Bowel Diseases: From Pathogenesis to Therapy

The gut plays a crucial role in digestion and immunity, so its balance is essential to overall health. This balance relies on dynamic interactions between intestinal epithelial cells, immune cells, and crypt stem cells. Inflammatory bowel disease (IBD), which consists of ulcerative colitis and Crohn's disease, is a chronic relapsing inflammatory disease of the gastrointestinal tract closely related to immune dysfunction. Stem cells, known for their ability to self-renew and differentiate, play an important role in repairing damaged intestinal epithelium and maintaining homeostasis in vivo. Macrophages are key gatekeepers of intestinal immune homeostasis and have a significant impact on IBD. Current research has focused on the link between epithelial cells and stem cells, but interactions with macrophages, which have been recognized as attractive targets for the development of new therapeutic approaches to disease, have been less explored. Recently, the developing field of immunometabolism has reinforced that metabolic reprogramming is a key determinant of macrophage function and subsequent disease progression. The aim of this review is to explore the role of the macrophage-stem cell axis in the maintenance of intestinal homeostasis and to summarize potential approaches to treating IBD by manipulating the cellular metabolism of macrophages, as well as the main opportunities and challenges faced. In summary, our overview provides a framework for understanding the critical role of macrophage immunometabolism in maintaining gut health and potential therapeutic targets.

Sulfur dioxide controls M1 macrophage polarization by sulphenylation of prolyl hydroxylase 2 at cysteine 260

M1 macrophage polarization plays a pivotal role in inflammation-related diseases. However, the endogenous regulatory factors and mechanisms underlying M1 macrophage polarization have not been entirely clarified. This study aimed to explore whether endogenous sulfur dioxide (SO2) is involved in M1 macrophage polarization and its mechanism. In the study, we found that the endogenous SO2/aspartate aminotransferase1 (AAT1) pathway was downregulated during M1 polarization of macrophages induced by lipopolysaccharide (LPS) stimulation, and supplementation with SO2 donors or AAT1 overexpression restored SO2 content, suppressed protein expression of inducible nitric oxide synthase, restrained mRNA level of M1 phenotype-related genes tumor necrosis factor α, interleukin-1β and interleukin-12β and decreased the CD86 expression. In addition, AAT1-knockdowned macrophages exhibited reduced level of hypoxia-inducible factor-1α (HIF-1α) hydroxylation, elevated HIF-1α protein level, and polarization into M1-type, while supplementation with SO2 reversed the above effects. Mechanistically, SO2 maintained prolyl hydroxylase (PHD) activity in a thiol-dependent manner. SO2 maintained PHD2 activity by sulphenylating PHD2 at Cys260, thereby reducing HIF-1α protein levels and subsequently inhibiting M1 macrophage polarization. Besides, SO2 enhanced PHD2 sulphenylation, inhibited M1 macrophage polarization, and alleviated lung damage in a mouse model of LPS-induced acute lung injury. These results suggested that downregulation of the endogenous SO2/AAT1 pathway was a pivotal mechanism for M1 macrophage polarization. SO2 maintained PHD2 activity via sulphenylation of Cys260, and promoted HIF-1α hydroxylation and degradation, thereby impeding M1 macrophage polarization.

Immunomodulatory role of the stem cell circadian clock in muscle repair

Circadian rhythms orchestrate physiological processes such as metabolism, immune function, and tissue regeneration, aligning them with the optimal time of day (TOD). This study identifies an interplay between the circadian clock within muscle stem cells (SCs) and their capacity to modulate the immune microenvironment during muscle regeneration. We reveal that the SC clock triggers TOD-dependent inflammatory gene transcription after injury, particularly genes related to neutrophil activity and chemotaxis. These responses are driven by cytosolic regeneration of the signaling metabolite nicotinamide adenine dinucleotide (oxidized form) (NAD+), as enhancing cytosolic NAD+ regeneration in SCs is sufficient to induce inflammatory responses that influence muscle regeneration. Mononuclear single-cell sequencing of the regenerating muscle niche further implicates the cytokine CCL2 in mediating SC-neutrophil cross-talk in a TOD-dependent manner. Our findings highlight the intersection between SC metabolic shifts and immune responses within the muscle microenvironment, dictated by circadian rhythms, and underscore the potential for targeting circadian and metabolic pathways to enhance tissue regeneration.

Unraveling the Complex Nexus of Macrophage Metabolism, Periodontitis, and Associated Comorbidities

BACKGROUND

Periodontitis is recognized as one of the most prevalent oral dysbiotic inflammatory diseases, ultimately leading to the irreversible destruction of periodontal tissues. Macrophages play a pivotal role in the development and progression of periodontitis, and the feasibility of targeting them therapeutically has been established. Since metabolic switching significantly contributes to macrophage regulation, conducting an in-depth review of macrophage metabolism in periodontitis may serve as the foundation for developing innovative treatments.

SUMMARY

This paper has been carefully reviewed to provide a comprehensive overview of the roles played by macrophages in periodontitis and associated comorbidities. Initially, detailed presentations on the metabolic reprogramming of macrophages, including glucose, lipid, and amino acid metabolism, were provided. Subsequently, dominating macrophage phenotype and metabolism under lipopolysaccharide (LPS) stimulation or during periodontitis were presented with emphasize on critical molecules involved. Furthermore, in recognition of the close association between periodontitis and several comorbidities, the interaction among macrophage metabolism, periodontitis, and related metabolic diseases, was thoroughly discussed.

KEY MESSAGES

Through the examination of current research on macrophage metabolic reprogramming induced by periodontitis, this review provides potential immunometabolic therapeutic targets for the future and raises many important, yet unstudied, subjects for follow-up.

BACKGROUND

Periodontitis is recognized as one of the most prevalent oral dysbiotic inflammatory diseases, ultimately leading to the irreversible destruction of periodontal tissues. Macrophages play a pivotal role in the development and progression of periodontitis, and the feasibility of targeting them therapeutically has been established. Since metabolic switching significantly contributes to macrophage regulation, conducting an in-depth review of macrophage metabolism in periodontitis may serve as the foundation for developing innovative treatments.

SUMMARY

This paper has been carefully reviewed to provide a comprehensive overview of the roles played by macrophages in periodontitis and associated comorbidities. Initially, detailed presentations on the metabolic reprogramming of macrophages, including glucose, lipid, and amino acid metabolism, were provided. Subsequently, dominating macrophage phenotype and metabolism under lipopolysaccharide (LPS) stimulation or during periodontitis were presented with emphasize on critical molecules involved. Furthermore, in recognition of the close association between periodontitis and several comorbidities, the interaction among macrophage metabolism, periodontitis, and related metabolic diseases, was thoroughly discussed.

KEY MESSAGES

Through the examination of current research on macrophage metabolic reprogramming induced by periodontitis, this review provides potential immunometabolic therapeutic targets for the future and raises many important, yet unstudied, subjects for follow-up.

Macrophages in graft-versus-host disease (GVHD): dual roles as therapeutic tools and targets

Graft-versus-host disease remains one of the most formidable barriers to the complete success of hematopoietic stem cell transplantation that has emerged as the curative approach for many hematopoietic malignancies because it affects quality of life and overall survival. Macrophages are among the important members of the immune system, which perform dual roles in GVHD as both therapeutic tools and targets. This review epitomizes the multifunctional role of macrophages in the pathophysiology of both acute and chronic GVHD. Macrophages play an important role in the early phase of GVHD because of their recruitment and infiltration into target organs. Furthermore, they polarize into two functionally different phenotypes, including M1 and M2. In the case of acute GVHD, most macrophages express the M1 phenotype characterized by the production of pro-inflammatory cytokines that contribute to tissue damage. In contrast, in chronic GVHD, macrophages tend toward the M2 phenotype associated with the repair of tissues and fibrosis. A critical balance among these phenotypes is central to the course and severity of GVHD. Further interactions of macrophages with other lymphocytes such as T cells, B cells, and fibroblast further determine the course of GVHD. Macrophage interaction associated with alloreactive T cells promotes inflammation. This is therefore important in inducing injuries of tissues during acute GVHD. Interaction of macrophages, B cell, fibroblast, and CD4+ T cells promotes fibrosis during chronic GVHD and, hence, the subsequent dysfunction of organs. These are some insights, while several challenges remain. First, the impact of the dominant cytokines in GVHD on the polarization of macrophages is incompletely characterized and sometimes controversial. Second, the development of targeted therapies able to modulate macrophage function without systemic side effects remains an area of ongoing investigation. Future directions involve the exploration of macrophage-targeted therapies, including small molecules, antibodies, and nanotechnology, which modulate macrophage behavior and improve patient outcomes. This underlines the fact that a profound understanding of the dual role of macrophages in GVHD is essential for developing new and more effective therapeutic strategies. Targeting macrophages might represent one avenue for decreasing the incidence and severity of GVHD and improving the success and safety of HSCT.

TEPP-46 inhibits glycolysis to promote M2 polarization of microglia after ischemic stroke

Following an ischemic stroke, neuroinflammation is triggered and is often typified by microglial activation. According to recent research, increased glycolysis metabolism frequently occurs when microglia become activated in an inflammatory response. In this study, we found that the PKM2 expression of microglia was gradually increased during the activation of microglia in ischemic stroke. TEPP-46, the activator of PKM2, enhanced the M2 polarization and promoted phagocytosis of microglia both in vivo and in vitro. Meanwhile, TEPP-46 administration ameliorated neuroinflammation and neuronal injuries and reduced the infarct volume of tMCAO mice. Mechanistically, we demonstrated that TEPP-46 suppressed the nuclear translocation of PKM2 and the interaction of PKM2 and HIF-1α, and inhibited glycolysis of microglia. According to our research, PKM2 modulation in microglia may be a viable therapeutic approach to lessen neuroinflammation following ischemic stroke, and TEPP-46 may be able to polarize microglia from an M1 to an M2 phenotype after ischemia/reperfusion damage.

Links Between Cellular Energy Metabolism and Pain Sensation

One of the functions of organism cells is to maintain energy homeostasis to promote metabolism and adapt to the environment. The 3 major pathways of cellular energy metabolism are glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (OXPHOS). Neurons, astrocytes, and microglia are crucial in allodynia, hyperalgesia, and sensitization in nociceptive pathways. This review focused on these 3 major cellular energy metabolism pathways, aiming to elucidate the relationship between neurocyte and pain sensation and present the reprogramming of energy metabolism on pain, as well as the cellular and molecular mechanism underlying various forms of pain. The clinical and preclinical drugs involved in pain treatment and molecular mechanisms via cellular energy metabolism were also discussed.

Highly expressed VGLL3 in keloid fibroblasts promotes glycolysis and collagen production via the activation of Wnt/β-catenin signaling

PURPOSE

This study investigated the effects and related mechanisms of Vestigial-like family member 3 (VGLL3) on keloid fibroblast (KF) proliferation, apoptosis, collagen production, and glycolysis.

METHODS

Western blot, qRT-PCR, and immunohistochemistry were used for determining VGLL3 expression. KF viability, proliferation, and apoptosis were assessed using CCK-8 assay, EdU assay, and flow cytometry. Changes in the protein expression levels of α-SMA, fibronectin, collagen I, and collagen III were examined utilizing western blotting. The pathways related to VGLL3 were analyzed using Gene Set Enrichment Analysis. Changes in glycolysis were assessed by measuring oxygen consumption rate (OCR), extracellular acidification rate (ECAR), glucose uptake, and lactate production. WNT2 and β-catenin protein levels were measured using western blotting.

RESULTS

VGLL3 was upregulated in human keloid tissues. In KFs, overexpression of VGLL3 inhibited cell apoptosis, promoted cell proliferation and protein expression of α-SMA, fibronectin, collagen I, and collagen III. Moreover, it reduced OCR level, and increased the levels of ECAR, glucose uptake, and lactate production. On the other hand, the knockdown of VGLL3 had the opposite effect. WNT2 and β-catenin protein levels were enhanced by overexpression of VGLL3 and reduced by VGLL3 knockdown. Silencing of WNT2 reversed the effects of VGLL3 on apoptosis, proliferation, collagen production, and glycolysis in KFs.

CONCLUSIONS

VGLL3 promoted glycolysis in KFs and keloid progression, which was achieved through the activation of Wnt signaling pathway. Therefore, targeting VGLL3 may be a promising therapeutic strategy for the treatment of keloids.

The role of HIF-1α in hypoxic metabolic reprogramming in osteoarthritis

The joint dysfunction caused by osteoarthritis (OA) is increasingly becoming a major challenge in global healthcare, and there is currently no effective strategy to prevent the progression of OA. Therefore, better elucidating the relevant mechanisms of OA occurrence and development will provide theoretical basis for formulating new prevention and control strategies. Due to long-term exposure of cartilage tissue to the hypoxic microenvironment of joints, metabolic reprogramming changes occur. Hypoxia-inducible factor-1alpha (HIF-1α), as a core gene regulating hypoxia response in vivo, plays an important regulatory role in the hypoxic metabolism of chondrocytes. HIF-1α adapts to the hypoxic microenvironment by regulating metabolic reprogramming changes such as glycolysis, oxidative phosphorylation (OXPHOS), amino acid metabolism, and lipid metabolism in OA chondrocytes. In addition, HIF-1α also regulates macrophage polarization and synovial inflammation, chondrocytes degeneration and extracellular matrix (ECM) degradation, subchondral bone remodeling and angiogenesis in the hypoxic microenvironment of OA, and affects the pathophysiological progression of OA. Consequently, the regulation of chondrocytes metabolic reprogramming by HIF-1α has become an important therapeutic target for OA. Therefore, this article reviews the mechanism of hypoxia affecting chondrocyte metabolic reprogramming, focusing on the regulatory mechanism of HIF-1α on chondrocyte metabolic reprogramming, and summarizes potential effective ingredients or targets targeting chondrocyte metabolic reprogramming, in order to provide more beneficial basis for the prevention and treatment of clinical OA and the development of effective drugs.

Sweet regulation - The emerging immunoregulatory roles of hexoses

BACKGROUND

It is widely acknowledged that dietary habits have profound impacts on human health and diseases. As the most important sweeteners and energy sources in human diets, hexoses take part in a broad range of physiopathological processes. In recent years, emerging evidence has uncovered the crucial roles of hexoses, such as glucose, fructose, mannose, and galactose, in controlling the differentiation or function of immune cells.

AIM OF REVIEW

Herein, we reviewed the latest research progresses in the hexose-mediated modulation of immune responses, provided in-depth analyses of the underlying mechanisms, and discussed the unresolved issues in this field.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Owing to their immunoregulatory effects, hexoses affect the onset and progression of various types of immune disorders, including inflammatory diseases, autoimmune diseases, and tumor immune evasion. Thus, targeting hexose metabolism is becoming a promising strategy for reversing immune abnormalities in diseases.

Pro-inflammatory macrophages produce mitochondria-derived superoxide by reverse electron transport at complex I that regulates IL-1β release during NLRP3 inflammasome activation

Macrophages stimulated by lipopolysaccharide (LPS) generate mitochondria-derived reactive oxygen species (mtROS) that act as antimicrobial agents and redox signals; however, the mechanism of LPS-induced mitochondrial superoxide generation is unknown. Here we show that LPS-stimulated bone-marrow-derived macrophages produce superoxide by reverse electron transport (RET) at complex I of the electron transport chain. Using chemical biology and genetic approaches, we demonstrate that superoxide production is driven by LPS-induced metabolic reprogramming, which increases the proton motive force (∆p), primarily as elevated mitochondrial membrane potential (Δψm) and maintains a reduced CoQ pool. The key metabolic changes are repurposing of ATP production from oxidative phosphorylation to glycolysis, which reduces reliance on F1FO-ATP synthase activity resulting in a higher ∆p, while oxidation of succinate sustains a reduced CoQ pool. Furthermore, the production of mtROS by RET regulates IL-1β release during NLRP3 inflammasome activation. Thus, we demonstrate that ROS generated by RET is an important mitochondria-derived signal that regulates macrophage cytokine production.

Macrophage energy metabolism in cardiometabolic disease

In a rapidly expanding body of literature, the major role of energy metabolism in determining the response and polarization status of macrophages has been examined, and it is currently a very active area of research. The metabolic flux through different metabolic pathways in the macrophage is interconnected and complex and could influence the polarization of macrophages. Earlier studies suggested glucose flux through cytosolic glycolysis is a prerequisite to trigger the pro-inflammatory phenotypes of macrophages while proposing that fatty acid oxidation is essential to support anti-inflammatory responses by macrophages. However, recent studies have shown that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully defined yet. In this review, we systematically reviewed and summarized the literature regarding the role of energy metabolism in controlling macrophage activity and how that might be altered in cardiometabolic diseases, namely heart failure, obesity, and diabetes. We critically appraised the experimental studies and methodologies in the published studies. We also highlighted the challenging concepts in macrophage metabolism and identified several research questions yet to be addressed in future investigations.