Metabolic Reprogramming Mediated by the mTORC2-IRF4 Signaling Axis Is Essential for Macrophage Alternative Activation

Wogonin Attenuates Atherosclerosis via KLF11-Mediated Suppression of PPARα-YAP1-Driven Glycolysis and Enhancement of ABCA1/G1-Mediated Cholesterol Efflux

Atherosclerosis, a chronic inflammatory disorder and leading cause of cardiovascular disease, is characterized by macrophage-derived inflammation and foam cell formation. Emerging evidence suggests that metabolic reprogramming of macrophages represents a promising therapeutic approach for atherosclerosis management. In this study, the therapeutic potential of wogonin, a bioactive flavonoid isolated from Scutellaria baicalensis, in modulating macrophage metabolism and attenuating atherogenesis is investigated. Wogonin reduces lesion size and plaque vulnerability, accompanied by a reduction in foam cell formation and inflammation. Mechanistically, wogonin reprogrammes macrophage metabolism from glycolysis to fatty acid oxidation (FAO) by activating the PPARα-CPT1α pathway and acts as a mitochondrial protector by activating PPARα. Wogonin also promotes the KLF11 expression and KLF11 knockout exacerbated atherosclerosis and abolishes the inhibitory effect of wogonin on glycolysis and atherosclerosis. KLF11 forms a transcriptional complex with PPARα and YAP1, serving both as a brake on PPARα-YAP1-mediated glycolysis and a transcriptional activator of ABCA1/G1. Collectively, wogonin reprograms macrophage metabolism from glycolysis to FAO through activation of the PPARα-KLF11-YAP1 pathway, thereby reducing inflammation and foam cell formation, ultimately attenuating atherogenesis.

Exosomes Derived From Human Gingival Mesenchymal Stem Cells Induce Metabolic Reprogramming of Inflammatory Macrophages

AIM

To investigate the influence and mechanism of exosomes derived from human gingival mesenchymal stem cells (GMSC-Exo) regulating macrophage polarisation through metabolic reprogramming.

MATERIALS AND METHODS

Human acute monocytic leukaemia cells (THP-1)-derived macrophages were treated with GMSC-Exo or Porphyromonas gingivalis lipopolysaccharide (P.g-LPS) in vitro. Metabolic inhibitors were used to study the role of metabolic reprogramming in GMSC-Exo-induced polarisation, while the hypoxia-inducible factor-1 alpha (HIF-1α) modulators were employed to explore the HIF-1α signalling pathway's impact on macrophage metabolic reprogramming. The impact of GMSC-Exo on periodontitis and macrophage metabolism was assessed using a rat model in vivo.

RESULTS

In vitro experiments confirmed that GMSC-Exo promoted the polarisation of macrophages from pro-inflammatory M1 type (classically activated) to anti-inflammatory M2 type (alternatively activated) by promoting metabolic reprogramming (glycolysis to oxidative phosphorylation). In this process, the activation of the HIF-1α signalling pathway was inhibited. In vivo experiments revealed that GMSC-Exo could regulate the inflammatory microenvironment of periodontal tissue and the metabolic pattern of macrophages.

CONCLUSION

By inhibiting the activation of HIF-1α signalling pathway, GMSC-Exo trigger metabolic reprogramming in macrophages, thereby regulating the macrophage transformation from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. This change enhances the local inflammatory environment, aiding tissue repair and regeneration.

Reprogramming and targeting of cholesterol metabolism in tumor-associated macrophages

Cholesterol, as a major component of cell membranes, is closely related to the metabolic regulation of cells and organisms; tumor-associated macrophages play an important push role in tumor progression. We know that tumor-associated macrophages are polarized from macrophages, and the abnormalities of cholesterol metabolism that may be induced during their polarization are worth discussing. This manuscript focuses on metabolic abnormalities in tumor-associated macrophages, and first provides a basic summary of the regulatory mechanisms of abnormal macrophage polarization. Subsequently, it comprehensively describes the features of abnormal glucose, lipid and cholesterol metabolism in TAMs as well as the different regulatory pathways. Then, the paper also discusses the link between abnormal cholesterol metabolism in TAMs and tumors, chronic diseases and aging. Finally, the paper summarizes cancer therapeutic strategies targeting cholesterol metabolism that are already in clinical trials, as well as nanomaterials capable of targeting cholesterol metabolism that are in the research stage, in the hope of providing value for the design of targeting materials. Overall, elucidating metabolic abnormalities in tumor-associated macrophages, particularly cholesterol metabolism, could provide assistance in tumor therapy and the design of targeted drugs.

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).

Artesunate Inhibits Neointimal Hyperplasia by Promoting IRF4 Associated Macrophage Polarization

Vascular restenosis is a serious clinical issue initiated and aggravated by macrophage inflammation, with no effective treatments available, in cardiovascular and autoimmune diseases. However, the untapped mechanisms and new targets that can regulate macrophage polarization and vascular restenosis remain elusive. The research identifies interferon regulatory factor 4 (IRF4) expression as crucial in macrophage polarization during arterial restenosis. Myeloid-specific Irf4 deficiency and overexpression experiments showed that IRF4 promoted M2 macrophage polarization, inhibited M1 macrophage transitions, and disrupted the interaction between macrophages and vascular smooth muscle cells to reduce neointimal hyperplasia by directly upregulating krüppel like factor 4 (KLF4) expression. Artesunate, an FDA-approved drug, is screened as a potent activator of IRF4 expression in M2 polarization, and its treatment attenuated arterial restenosis in rodents and non-human primates. The findings reveal a significant protective role of IRF4 in the development of neointimal hyperplasia by regulating macrophage polarization, and artesunate may be proposed as a novel therapy for vascular restenosis.

Phosphatidylethanolamine species with n-3 and n-6 fatty acids modulate macrophage lipidome and attenuate responses to LPS stimulation

Phospholipids are increasingly recognized as key regulators of biological processes, including macrophage polarization and function. Among these, phosphatidylethanolamine (PE), a major constituent of cell membranes, is pivotal in maintaining cellular structure and function, yet the mechanisms through which native PE species influence macrophage immunometabolism remain largely unexplored. This study investigates the effects of two native PE species, PE 18:0/22:6 and PE 18:0/20:4, on the lipidome of resting and LPS-activated macrophages. Using C18 HPLC-MS/MS, we identified 337 lipid molecular species across 15 lipid subclasses, 332 of which varied significantly among conditions. Both PE 18:0/22:6 and PE 18:0/20:4 supplementation modulated the macrophage lipidome without inducing a pro-inflammatory phenotype under basal conditions. Notably, supplementation with PE 18:0/22:6 and PE 18:0/20:4 significantly increased lipid classes such as PE, PE O-, SM, CL, PG, LPE and PS, producing unique lipid profiles. Pre-treatment with PE 18:0/22:6 and PE 18:0/20:4 partially attenuated LPS-induced lipidomic changes, significantly reducing lipid classes like PC, including PC O- and PC P-, and Cer, which are typically linked to inflammation. While PE 18:0/20:4, from an individual lipid species perspective, may promote certain lipid profiles compatible with pro-inflammatory signaling pathways, particularly under inflammatory conditions, PE 18:0/22:6 seems to foster a lipid profile more supportive of inflammation resolution. This behaviour of PE 18:0/22:6 and PE 18:0/20:4 highlights the intricate complexity of lipid-mediated immunomodulation and emphasizes the critical role of cellular context in determining the functional outcomes of phospholipid supplementation in macrophage lipid metabolism and immune responses.

The Dual Roles of Lamin A/C in Macrophage Mechanotransduction

Cellular mechanotransduction is a complex physiological process that integrates alterations in the external environment with cellular behaviours. In recent years, the role of the nucleus in mechanotransduction has gathered increased attention. Our research investigated the involvement of lamin A/C, a component of the nuclear envelope, in the mechanotransduction of macrophages under compressive force. We discovered that hydrostatic compressive force induces heterochromatin formation, decreases SUN1/SUN2 levels, and transiently downregulates lamin A/C. Notably, downregulated lamin A/C increased nuclear permeability to yes-associated protein 1 (YAP1), thereby amplifying certain effects of force, such as inflammation induction and proliferation inhibition. Additionally, lamin A/C deficiency detached the linker of nucleoskeleton and cytoskeleton (LINC) complex from nuclear envelope, consequently reducing force-induced DNA damage and IRF4 expression. In summary, lamin A/C exerted dual effects on macrophage responses to mechanical compression, promoting certain outcomes while inhibiting others. It operated through two distinct mechanisms: enhancing nuclear permeability and impairing intracellular mechanotransmission. The results of this study support the understanding of the mechanisms of intracellular mechanotransduction and may assist in identifying potential therapeutic targets for mechanotransduction-related diseases.

Insulin‑like growth factor 2 in spermatogenesis dysfunction (Review)

Spermatogenesis dysfunction is characterized by abnormal morphology, destruction, atrophy of seminiferous tubules, blocked differentiation of spermatogenic cells, decreased sperm count and increased sperm abnormalities. Inflammation, oxidative stress, endoplasmic reticulum stress and obesity are important factors leading to spermatogenesis dysfunction. It has been demonstrated that insulin‑like growth factor 2 (IGF2) is closely related to the aforementioned factors. In the present review, the relationship between IGF2 and inflammation, oxidative stress, ER stress and obesity was investigated, providing theoretical and experimental evidence on the role of IGF2 in the prevention and treatment of spermatogenesis dysfunction of male infertility.

The Evolving Role of Macrophage Metabolic Reprogramming in Obesity

Recent research has extensively explored the critical role of energy metabolism in shaping the inflammatory response and polarization of macrophages in obesity. This rapidly growing field emphasizes the need to understand the connection between metabolic processes that support macrophage polarization in obesity. Although most published research in this area has focused on glucose and fatty acids, how the flux through other metabolic pathways (such as ketone and amino acid oxidation) in macrophages is altered in obesity is not well defined. This review summarizes the main alterations in uptake, storage, and oxidation of oxidative substrates (glucose, fatty acids, ketone bodies, and amino acids) in macrophages and how these alterations are linked to macrophage polarization and contribution to augmented inflammatory markers in obesity. The review also discusses how oxidative substrates could modulate macrophage energy metabolism and inflammatory responses via feeding into other nonoxidative pathways (such as the pentose phosphate pathway, triacylglycerol synthesis/accumulation), via acting as signalling molecules, or via mediating post-translational modifications (such as O-GlcNAcylation or β-hydroxybutyrylation). The review also identifies several critical unanswered questions regarding the characteristics (functional and metabolic) of macrophages from different origins (adipose tissue, skeletal muscle, bone marrow) in obesity and how these characteristics contribute to early vs late phases of obesity. We also identified a number of new therapeutic targets that could be evaluated in future investigations. Targeting macrophage metabolism in obesity is an exciting and active area of research with significant potential to help identify new treatments to limit the detrimental effects of inflammation in obesity.

Crosstalk between metabolism and epigenetics during macrophage polarization

Macrophage polarization is a dynamic process driven by a complex interplay of cytokine signaling, metabolism, and epigenetic modifications mediated by pathogens. Upon encountering specific environmental cues, monocytes differentiate into macrophages, adopting either a pro-inflammatory (M1) or anti-inflammatory (M2) phenotype, depending on the cytokines present. M1 macrophages are induced by interferon-gamma (IFN-γ) and are characterized by their reliance on glycolysis and their role in host defense. In contrast, M2 macrophages, stimulated by interleukin-4 (IL-4) and interleukin-13 (IL-13), favor oxidative phosphorylation and participate in tissue repair and anti-inflammatory responses. Metabolism is tightly linked to epigenetic regulation, because key metabolic intermediates such as acetyl-coenzyme A (CoA), α-ketoglutarate (α-KG), S-adenosylmethionine (SAM), and nicotinamide adenine dinucleotide (NAD+) serve as cofactors for chromatin-modifying enzymes, which in turn, directly influences histone acetylation, methylation, RNA/DNA methylation, and protein arginine methylation. These epigenetic modifications control gene expression by regulating chromatin accessibility, thereby modulating macrophage function and polarization. Histone acetylation generally promotes a more open chromatin structure conducive to gene activation, while histone methylation can either activate or repress gene expression depending on the specific residue and its methylation state. Crosstalk between histone modifications, such as acetylation and methylation, further fine-tunes macrophage phenotypes by regulating transcriptional networks in response to metabolic cues. While arginine methylation primarily functions in epigenetics by regulating gene expression through protein modifications, the degradation of methylated proteins releases arginine derivatives like asymmetric dimethylarginine (ADMA), which contribute directly to arginine metabolism-a key factor in macrophage polarization. This review explores the intricate relationships between metabolism and epigenetic regulation during macrophage polarization. A better understanding of this crosstalk will likely generate novel therapeutic insights for manipulating macrophage phenotypes during infections like tuberculosis and inflammatory diseases such as diabetes.

Elevation of Plasma IL-15 and RANTES as Potential Biomarkers of Healing in Chronic Venous Ulcerations: A Pilot Study

Chronic wounds present a large burden to our healthcare system and are typically marked by a failure to transition out of the inflammatory phase of wound healing. Venous leg ulcers (VLUs) represent the largest portion of chronic wounds. A pilot study of eleven (11) patients with VLUs seen over a 12-week period was undertaken utilizing RNA sequencing of wound biopsies and plasma cytokine levels to determine if biomarkers could be identified that would distinguish between wounds which heal versus those that do not. Chronic wounds were found to have increased expression of genes relating to epithelial-to-mesenchymal transition (EMT), cartilage and bone formation, and regulation of apical junction. Plasma cytokine levels showed predictive potential for IL-15 and RANTES, which were found to increase over time in patients with healed wounds. Further research is needed to validate these biomarkers as well as additional study of other chronic wound models, such as diabetic foot ulcers (DFUs).

Tissue macrophages: origin, heterogenity, biological functions, diseases and therapeutic targets

Macrophages are immune cells belonging to the mononuclear phagocyte system. They play crucial roles in immune defense, surveillance, and homeostasis. This review systematically discusses the types of hematopoietic progenitors that give rise to macrophages, including primitive hematopoietic progenitors, erythro-myeloid progenitors, and hematopoietic stem cells. These progenitors have distinct genetic backgrounds and developmental processes. Accordingly, macrophages exhibit complex and diverse functions in the body, including phagocytosis and clearance of cellular debris, antigen presentation, and immune response, regulation of inflammation and cytokine production, tissue remodeling and repair, and multi-level regulatory signaling pathways/crosstalk involved in homeostasis and physiology. Besides, tumor-associated macrophages are a key component of the TME, exhibiting both anti-tumor and pro-tumor properties. Furthermore, the functional status of macrophages is closely linked to the development of various diseases, including cancer, autoimmune disorders, cardiovascular disease, neurodegenerative diseases, metabolic conditions, and trauma. Targeting macrophages has emerged as a promising therapeutic strategy in these contexts. Clinical trials of macrophage-based targeted drugs, macrophage-based immunotherapies, and nanoparticle-based therapy were comprehensively summarized. Potential challenges and future directions in targeting macrophages have also been discussed. Overall, our review highlights the significance of this versatile immune cell in human health and disease, which is expected to inform future research and clinical practice.

Lysosomes in the immunometabolic reprogramming of immune cells in atherosclerosis

Lysosomes have a central role in the disposal of extracellular and intracellular cargo and also function as metabolic sensors and signalling platforms in the immunometabolic reprogramming of macrophages and other immune cells in atherosclerosis. Lysosomes can rapidly sense the presence of nutrients within immune cells, thereby switching from catabolism of extracellular material to the recycling of intracellular cargo. Such a fine-tuned degradative response supports the generation of metabolic building blocks through effectors such as mTORC1 or TFEB. By coupling nutrients to downstream signalling and metabolism, lysosomes serve as a crucial hub for cellular function in innate and adaptive immune cells. Lysosomal dysfunction is now recognized to be a hallmark of atherogenesis. Perturbations in nutrient-sensing and signalling have profound effects on the capacity of immune cells to handle cholesterol, perform phagocytosis and efferocytosis, and limit the activation of the inflammasome and other inflammatory pathways. Strategies to improve lysosomal function hold promise as novel modulators of the immunoinflammatory response associated with atherosclerosis. In this Review, we describe the crosstalk between lysosomal biology and immune cell function and polarization, with a particular focus on cellular immunometabolic reprogramming in the context of atherosclerosis.

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.

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.

The GATA-3-dependent transcriptome and tumor microenvironment are regulated by eIF4E and XPO1 in T-cell lymphomas

ABSTRACT

The transcription factor GATA-binding protein 3 (GATA-3) and the transcriptional program it regulates have emerged as oncogenic drivers across diverse T-cell lymphomas (TCLs), many of which are resistant to conventional chemotherapeutic agents and characterized by recurrent losses of key tumor suppressor genes, including TP53 and PTEN, both of which are clients of the nuclear export protein XPO1. Here, we demonstrated that XPO1 is highly expressed by malignant T cells expressing GATA-3 and by lymphoma-associated macrophages (LAMs) within their tumor microenvironment (TME). Using complementary genetically engineered mouse models, we demonstrated that TP53- and/or phosphate and tensin homolog (PTEN)-deficient TCLs, and LAMs within their TME, are sensitive to the selective exportin-1 (XPO1) antagonist selinexor. In an effort to identify TP53- and PTEN-independent mechanisms, we used complementary and orthogonal approaches to investigate the role of eIF4E and XPO1-dependent messenger RNA nuclear export in these TCLs. We identified a novel role for eIF4E/XPO1 in exporting GATA-3 and GATA-3-dependent transcripts from the nucleus in TCLs, and in the export of therapeutically relevant transcripts, including colony-stimulating factor-1 receptor, from LAMs. Therefore, XPO1 antagonism, by impairing oncogenic transcriptional programs in TCLs and depleting LAMs from their TME, is a novel approach to target 2 independent dependencies in a group of therapeutically challenging TCLs.

Blimp-1 orchestrates macrophage polarization and metabolic homeostasis via purine biosynthesis in sepsis

Sepsis is a life-threatening condition characterized by a dysregulated immune response to infection, leading to systemic inflammation and organ dysfunction. Macrophage polarization plays a critical role in pathogenesis of sepsis, and the influence of B lymphocyte-induced maturation protein-1 (Blimp-1) on this polarization is an underexplored yet pivotal aspect. This study aimed to elucidate the role of Blimp-1 in macrophage polarization and metabolism during sepsis. Using a murine cecal ligation and puncture model, we observed elevated Blimp-1 expression in M2 macrophages. Knockdown of Blimp-1 by macrophage-targeted adeno-associated virus in this model resulted in decreased survival rates, exacerbated tissue damage, and impaired M2 polarization, underscoring its protective role in sepsis. In vitro studies with bone marrow-derived macrophage (BMDM), RAW264.7, and THP-1 cells further demonstrated Blimp-1 promotes M2 polarization and modulates key metabolic pathways. Metabolomics and dual-luciferase assays revealed Blimp-1 significantly influences purine biosynthesis and the downstream Ornithine cycle, which are essential for M2 macrophage polarization. In vitro studies with BMDM further suggested that the purine biosynthesis and Ornithine cycle metabolic regulation is involved in Blimp-1's effects on M2 macrophage polarization, and mediates Blimp-1's impact on septic mice. Our findings unveil a novel mechanism by which Blimp-1 modulates macrophage polarization through metabolic regulation, presenting potential therapeutic targets for sepsis. This study highlights the significance of Blimp-1 in orchestrating macrophage responses and metabolic adaptations in sepsis, offering valuable insights into its role as a critical regulator of immune and metabolic homeostasis.

mTOR/HIF-1α pathway-mediated glucose reprogramming and macrophage polarization by Sini decoction plus ginseng soup in ALF

BACKGROUND

Acute liver failure (ALF) has a high mortality rate, and despite treatment advancements, long-term outcomes remain poor.

PURPOSE

This study explores the therapeutic targets and pathways of Sini Decoction plus Ginseng Soup (SNRS) in ALF using bioinformatics and network pharmacology, focusing on its impact on macrophage polarization through glucose metabolism reprogramming. The efficacy of SNRS was validated in an LPS/D-GalN-induced ALF model, and its optimal concentration was determined for in vitro macrophage intervention.

STUDY DESIGN AND METHODS

Differentially expressed genes (DEGs) in HBV-induced and acetaminophen-induced ALF were identified from GEO datasets. The correlation between target gene expression and immune cell infiltration in ALF liver tissue was analyzed. AST, ALT, TNF-α, HMGB1, IL-1β, IL-6, and IL-10 levels were measured, and liver histopathology was assessed. Macrophage polarization was analyzed via immunofluorescence, flow cytometry, and Western blot. Glycolysis-related enzymes and metabolites, including HK2, PFK-1, PKM2, and LDHA, were quantified. Cellular ultrastructure was examined by transmission electron microscopy.

RESULTS

Five key glycolysis-regulating genes (HK2, CDK1, SOD1, VEGFA, GOT1) were identified, with significant involvement in the HIF-1 signaling pathway. Immune infiltration was markedly higher in ALF liver tissue. SNRS improved survival, reduced ALT/AST levels, alleviated liver injury, and modulated macrophage polarization by decreasing CD86 and increasing CD163 expression. In vitro, SNRS inhibited LPS-induced inflammatory cytokine release, lactate production, p-mTOR/mTOR ratio, and HIF-1α expression.

CONCLUSION

SNRS modulates macrophage polarization and glucose metabolism reprogramming via the mTOR/HIF-1α pathway, showing promise as a treatment for ALF.

Immunomodulatory effect of efferocytosis at the maternal-fetal interface

Efferocytosis is a mechanism by which phagocytes efficiently clear apoptotic cells, averting their secondary necrosis and the subsequent release of potentially immunogenic or cytotoxic substances that can trigger strong immune and inflammatory responses. During efferocytosis, the metabolic pathways of phagocytes are transformed, which, along with the catabolism of apoptotic cargo, can affect their function and inflammatory state. Extensive apoptosis occurs during placental development, and some studies reported the immunomodulatory effects of efferocytosis at the maternal-fetal interface. The dysregulation of efferocytosis is strongly linked to pregnancy complications such as preeclampsia and recurrent spontaneous abortion. In this review, we discuss the mechanisms of efferocytosis and its relationships with metabolism and inflammation. We also highlight the roles of professional and non-professional phagocytes in efferocytosis at the maternal-fetal interface and their impact on pregnancy outcomes and explore relevant regulatory factors. These insights are expected to guide future basic research and clinical strategies for identifying efferocytosis-related molecules as potential predictors or therapeutic targets in obstetric diseases.

Mitochondria complex III-generated superoxide is essential for IL-10 secretion in macrophages

Mitochondrial electron transport chain (ETC) function modulates macrophage biology; however, mechanisms underlying mitochondria ETC control of macrophage immune responses are not fully understood. Here, we report that mutant mice with mitochondria ETC complex III (CIII)-deficient macrophages exhibit increased susceptibility to influenza A virus (IAV) and LPS-induced endotoxic shock. Cultured bone marrow-derived macrophages (BMDMs) isolated from these mitochondria CIII-deficient mice released less IL-10 than controls following TLR3 or TLR4 stimulation. Unexpectedly, restoring mitochondrial respiration without generating superoxide using alternative oxidase (AOX) was not sufficient to reverse LPS-induced endotoxic shock susceptibility or restore IL-10 release. However, activation of protein kinase A (PKA) rescued IL-10 release in mitochondria CIII-deficient BMDMs following LPS stimulation. In addition, mitochondria CIII deficiency did not affect BMDM responses to interleukin-4 (IL-4) stimulation. Thus, our results highlight the essential role of mitochondria CIII-generated superoxide in the release of anti-inflammatory IL-10 in response to TLR stimulation.

Lipid metabolism in myeloid cell function and chronic inflammatory diseases

Immune cells adapt their metabolism in response to their differentiation and activation status to meet the energy demands for an appropriate immune response. Recent studies have elucidated that during immune cell metabolic reprogramming, lipid metabolism, including lipid uptake, de novo lipid synthesis and fatty acid oxidation, undergoes significant alteration, resulting in dynamic changes in the quantity and quality of intracellular lipids. Given that lipids serve as an energy source and structural components of cellular membranes, they have important implications for physiological function. Myeloid cells, which are essential in bridging innate and adaptive immunity, are sensitive to these changes. Dysregulation of lipid metabolism in myeloid cells can result in immune dysfunction, chronic inflammation and impaired resolution of inflammation. Understanding the mechanism by which lipids regulate immune cell function might provide novel therapeutic insights into chronic inflammatory diseases, including metabolic diseases, autoimmune diseases and cancer. (143 words).

The metabolic cofactor Coenzyme A enhances alternative macrophage activation via MyD88-linked signaling

Metabolites and metabolic co-factors can shape the innate immune response, though the pathways by which these molecules adjust inflammation remain incompletely understood. Here we show that the metabolic cofactor Coenzyme A (CoA) enhances IL-4 driven alternative macrophage activation [m(IL-4)] in vitro and in vivo. Unexpectedly, we found that perturbations in intracellular CoA metabolism did not influence m(IL-4) differentiation. Rather, we discovered that exogenous CoA provides a weak TLR4 signal which primes macrophages for increased receptivity to IL-4 signals and resolution of inflammation via MyD88. Mechanistic studies revealed MyD88-linked signals prime for IL-4 responsiveness, in part, by reshaping chromatin accessibility to enhance transcription of IL-4-linked genes. The results identify CoA as a host metabolic co-factor that influences macrophage function through an extrinsic TLR4-dependent mechanism, and suggests that damage-associated molecular patterns (DAMPs) can prime macrophages for alternative activation and resolution of inflammation.

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.

Innate immune response to bone fracture healing

The field of osteoimmunology has primarily focused on fracture healing in isolated musculoskeletal injuries. The innate immune system is the initial response to fracture, with inflammatory macrophages, cytokines, and neutrophils arriving first at the fracture hematoma, followed by an anti-inflammatory phase to begin the process of new bone formation. This review aims to first discuss the current literature and knowledge gaps on the immune responses governing single fracture healing by encompassing the individual role of macrophages, neutrophils, cytokines, mesenchymal stem cells, bone cells, and other immune cells. This paper discusses the interactive effects of these cellular responses underscoring the field of osteoimmunology. The critical role of the metabolic environment in guiding the immune system properties will be highlighted along with some effective therapeutics for fracture healing in the context of osteoimmunology. However, compared to isolated fractures, which frequently heal well, long bone fractures in over 30 % of polytrauma patients exhibit impaired healing. Clinical evidence suggests there may be distinct physiologic and inflammatory pathways altered in polytrauma resulting in nonunion. Nonunion is associated with worse patient outcomes and increased societal healthcare costs. The dysregulated immunomodulatory/inflammatory response seen in polytrauma may lead to this increased nonunion rate. This paper will investigate the differences in immune response between isolated and polytrauma fractures. Finally, future directions for fracture studies are explored with consideration of the emerging roles of newly discovered immune cell functions in fracture healing, the existing challenges and conflicting results in the field, the translational potential of these studies in clinic, and the more complex nature of polytrauma fractures that can alter cell functions in different tissues.

Reprogramming macrophage metabolism following myocardial infarction: A neglected piece of a therapeutic opportunity

Given the global prevalence of myocardial infarction (MI) as the leading cause of mortality, there is an urgent need to devise novel strategies that target reducing infarct size, accelerating cardiac tissue repair, and preventing detrimental left ventricular (LV) remodeling. Macrophages, as a predominant type of innate immune cells, undergo metabolic reprogramming following MI, resulting in alterations in function and phenotype that significantly impact the progression of MI size and LV remodeling. This article aimed to delineate the characteristics of macrophage metabolites during reprogramming in MI and elucidate their targets and functions in cardioprotection. Furthermore, we summarize the currently proposed regulatory mechanisms of macrophage metabolic reprogramming and identify the regulators derived from endogenous products and natural small molecules. Finally, we discussed the challenges of macrophage metabolic reprogramming in the treatment of MI, with the goal of inspiring further fundamental and clinical research into reprogramming macrophage metabolism and validating its potential therapeutic targets for MI.

Testicular immunity

The testis is a unique environment where immune responses are suppressed to allow the development of sperm that possess autoimmunogenic antigens. There are several contributors responsible for testicular immune privilege, including the blood-testis barrier, testicular immune cells, immunomodulation by Sertoli cells, and high levels of steroid hormones. Despite multiple mechanisms in place to regulate the testicular immune environment, pathogens that disrupt testicular immunity can lead to long-term effects such as infertility. If testicular immunity is disturbed, autoimmune reactions can also occur, leading to aberrant immune cell infiltration and subsequent attack of autoimmunogenic germ cells. Here we discuss cellular and molecular factors underlying testicular immunity and how testicular infection or autoimmunity compromise immune privilege. We also describe infections and autoimmune diseases that impact the testis. Further research into testicular immunity will reveal how male fertility is maintained and will help update therapeutic strategies for infertility and other testicular disorders.

Thermogenic Adipocytes Promote M2 Macrophage Polarization through CNNM4-Mediated Mg Secretion

M2 macrophages promote adipose tissue thermogenesis which dissipates energy in the form of heat to combat obesity. However, the regulation of M2 macrophages by thermogenic adipocytes is unclear. Here, it is identified magnesium (Mg) as a thermogenic adipocyte-secreted factor to promote M2 macrophage polarization. Mg transporter Cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) induced by ADRB3-PKA-CREB signaling in thermogenic adipocytes during cold exposure mediates Mg efflux and Mg in turn binds to the DFG motif in mTOR to facilitate mTORC2 activation and M2 polarization in macrophages. In obesity, downregulation of CNNM4 expression inhibits Mg secretion from thermogenic adipocytes, which leads to decreased M2 macrophage polarization and thermogenesis. As a result, CNNM4 overexpression in adipocytes or Mg supplementation in adipose tissue ameliorates obesity by promoting thermogenesis. Importantly, an Mg wire implantation (AMI) approach is introduced to achieve adipose tissue-specific long-term Mg supplement. AMI promotes M2 macrophage polarization and thermogenesis and ameliorates obesity in mice. Taken together, a reciprocal regulation of thermogenic adipocytes and M2 macrophages important for thermogenesis is identified, and AMI is offered as a promising strategy against obesity.

High TCTA expression is an adverse prognostic biomarker in acute myeloid leukemia

BackgroundAcute myeloid leukemia (AML) prognosis varies greatly, underscoring the need for novel biomarkers to improve patient stratification. T-cell leukemia translocation-associated gene (TCTA) has emerged as a potential player in hematological malignancies, yet its role in AML remains unexplored.ObjectiveTo investigate the prognostic significance of TCTA in AML and elucidate its functional mechanisms.MethodsRNA sequencing data from 173 AML patients (TCGA) and 70 normal controls (GTEx) were analyzed. Patients were categorized into high and low TCTA expression groups. Bioinformatics tools assessed Gene Ontology, KEGG pathways, and immune infiltration and constructed a nomogram predicting 1-5-year overall survival (OS).ResultsHigh TCTA expression correlated with significantly reduced OS (P < 0.001), with multivariate analysis identifying TCTA expression alongside age and cytogenetic risk as independent OS predictors. Receiver operating characteristic analysis validated TCTA's diagnostic potential. Enrichment analyses implicated TCTA in pathways critical to AML, such as hematopoiesis, p53 signaling, and DNA methylation, with a notable association with natural killer (NK) cell activity.ConclusionsElevated TCTA expression signifies poor prognosis in AML, positioning it as a promising prognostic biomarker. Its involvement in key AML-related pathways highlights TCTA's functional relevance and potential as a therapeutic target in AML management.

The HDAC6 inhibitor AVS100 (SS208) induces a pro-inflammatory tumor microenvironment and potentiates immunotherapy

Histone deacetylase 6 (HDAC6) inhibition is associated with an increased pro-inflammatory tumor microenvironment and antitumoral immune responses. Here, we show that the HDAC6 inhibitor AVS100 (SS208) had an antitumoral effect in SM1 melanoma and CT26 colon cancer models and increased the efficacy of anti-programmed cell death protein 1 treatment, leading to complete remission in melanoma and increased response in colon cancer. AVS100 treatment increased pro-inflammatory tumor-infiltrating macrophages and CD8 effector T cells with an inflammatory and T cell effector gene signature. Acquired T cell immunity and long-term protection were evidenced as increased immunodominant T cell clones after AVS100 treatment. Last, AVS100 showed no mutagenicity, toxicity, or adverse effects in preclinical good laboratory practice studies, part of the package that has led to US Food and Drug Administration clearance of an investigational new drug application for initiating clinical trials. This would be a first-in-human combination therapy of pembrolizumab with HDAC6 inhibition for locally advanced or metastatic solid tumors.

Multiomics reveals age-dependent metabolic reprogramming of macrophages by wound bed niche secreted signals

The cellular metabolism of macrophages depends on tissue niches and can control macrophage inflammatory or resolving phenotypes. Yet, the identity of signals within tissue niches that control macrophage metabolism is not well understood. Here, using single-cell RNA sequencing of macrophages in early mouse wounds, we find that, rather than gene expression of canonical inflammatory or resolving polarization markers, metabolic gene expression defines distinct populations of early wound macrophages. Single-cell secretomics and transcriptomics identify inflammatory and resolving cytokines expressed by early wound macrophages, and we show that these signals drive metabolic inputs and mitochondrial metabolism in an age-dependent manner. We show that aging alters the metabolome of early wound macrophages and rewires their metabolism from mitochondria to glycolysis. We further show that macrophage-derived Chi3l3 and IGF-1 can induce metabolic inputs and mitochondrial mass/metabolism in aged and bone marrow-derived macrophages. Together, these findings reveal that macrophage-derived signals drive the mitochondrial metabolism of macrophages within early wounds in an age-dependent manner and have implications for inflammatory diseases, chronic injuries, and age-related inflammatory diseases.

In Brief

This study reveals that macrophage subsets in early inflammatory stages of skin wound healing are defined by their metabolic profiles rather than polarization phenotype. Using single-cell secretomics, we establish key macrophage cytokines that comprise the in vivo wound niche and drive mitochondrial-based metabolism. Aging significantly alters macrophage heterogeneity and increases glycolytic metabolism, which can be restored to OxPHOS-based metabolism with young niche cytokines. These findings highlight the importance of the tissue niche in driving macrophage phenotypes, with implications for aging-related impairments in wound healing.

Highlights

Single cell transcriptional analysis reveals that reveals that metabolic gene expression identifies distinct macrophage populations in early skin wounds.Single-cell secretomic data show that young macrophages contribute to the wound bed niche by secreting molecules such as IGF-1 and Chi3l3.Old wound macrophages display altered metabolomics, elevated glycolytic metabolism and glucose uptake, and reduced lipid uptake and mitochondrial mass/metabolism.Chi3l3 but not IGF-1 secretion is altered in macrophages in an age dependent manner.Chi3l3 can restore mitochondrial mass/metabolism in aged macrophages.

SPP1+ TAM Regulates the Metastatic Colonization of CXCR4+ Metastasis-Associated Tumor Cells by Remodeling the Lymph Node Microenvironment

Lymph node metastasis, the initial step in distant metastasis, represents a primary contributor to mortality in patients diagnosed with oral squamous cell carcinoma (OSCC). However, the underlying mechanisms of lymph node metastasis in OSCC remain incompletely understood. Here, the transcriptomes of 56 383 single cells derived from paired tissues of six OSCC patients are analyzed. This study founds that CXCR4+ epithelial cells, identified as highly malignant disseminated tumor cells (DTCs), exhibited a propensity for lymph node metastasis. Importantly, a distinct subset of tumor-associated macrophages (TAMs) characterized by exclusive expression of phosphoprotein 1 (SPP1) is discovered. These TAMs may remodel the metastatic lymph node microenvironment by potentially activating fibroblasts and promoting T cell exhaustion through SPP1-CD44 and CD155-CD226 ligand-receptor interactions, thereby facilitating colonization and proliferation of disseminated tumor cells. The research advanced the mechanistic understanding of metastatic tumor microenvironment (TME) and provided a foundation for the development of personalized treatments for OSCC patients with metastasis.

mTORC2: A neglected player in aging regulation

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a pivotal role in various biological processes, through integrating external and internal signals, facilitating gene transcription and protein translation, as well as by regulating mitochondria and autophagy functions. mTOR kinase operates within two distinct protein complexes known as mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which engage separate downstream signaling pathways impacting diverse cellular processes. Although mTORC1 has been extensively studied as a pro-proliferative factor and a pro-aging hub if activated aberrantly, mTORC2 received less attention, particularly regarding its implication in aging regulation. However, recent studies brought increasing evidence or clues for us, which implies the associations of mTORC2 with aging, as the genetic elimination of unique subunits of mTORC2, such as RICTOR, has been shown to alleviate aging progression in comparison to mTORC1 inhibition. In this review, we first summarized the basic characteristics of mTORC2, including its protein architecture and signaling network. We then focused on reviewing the molecular signaling regulation of mTORC2 in cellular senescence and organismal aging, and proposed the multifaceted regulatory characteristics under senescent and nonsenescent contexts. Next, we outlined the research progress of mTOR inhibitors in the field of antiaging and discussed future prospects and challenges. It is our pleasure if this review article could provide meaningful information for our readers and call forth more investigations working on this topic.

Mitochondrial metabolism regulated macrophage phenotype in myocardial infarction

Cardiovascular disease (CVD) remains the leading cause of death worldwide, with myocardial infarction (MI) being the primary contributor to mortality and disability associated with CVD. Reperfusion therapies are widely recognized as effective strategies for treating MI. However, while intended to restore blood flow, the reperfusion processes paradoxically initiate a series of pathophysiological events that worsen myocardial injury, resulting in ischemia-reperfusion (I/R) injury. Therefore, there is a pressing need for new treatment strategies to reduce the size of MI and enhance cardiac function post-infarction. Macrophages are crucial for maintaining homeostasis and mitigating undesirable remodeling following MI. Extensive research has established a strong link between cellular metabolism and macrophage function. In the context of MI, macrophages undergo adaptive metabolic reprogramming to mount an immune response. Moreover, mitochondrial metabolism in macrophages is evident, leading to significant changes in their metabolism. Therefore, we need to delve deeper into summarizing and understanding the relationship and role between mitochondrial metabolism and macrophage phenotype, and summarize existing treatment methods. In this review, we explore the role of mitochondria in shaping the macrophage phenotype and function. Additionally, we summarize current therapeutic strategies aimed at modulating mitochondrial metabolism of macrophages, which may offer new insights treating of MI.

Oxidative phosphorylation and fatty acid oxidation in slow-aging mice

Oxidative metabolism declines with aging in humans leading to multiple metabolic ailments and subsequent inflammation. In mice, there is evidence of age-related suppression of fatty acid oxidation and oxidative phosphorylation in the liver, heart, and muscles. Many interventions that extend healthy lifespan of mice have been developed, including genetic, pharmacological, and dietary interventions. In this article, we review the literature on oxidative metabolism changes in response to those interventions. We also discuss the molecular pathways that mediate those changes, and their potential as targets for future longevity interventions.

The aryl hydrocarbon receptor shapes monocyte transcriptional responses to interleukin-4 by prolonging STAT6 binding to promoters

Cytokines induce functional and metabolic adaptations in immune cells, typically through transcriptional responses that can be influenced by other extracellular signals and by intracellular factors. The binding of the cytokine interleukin-4 (IL-4) to its receptor induces the phosphorylation and activation of the transcription factor STAT6. The aryl hydrocarbon receptor (AhR), a transcription factor activated by various endogenous and microbe-derived metabolites, modulates the responses of immune cells to danger signals or inflammatory mediators such as cytokines. Here, we investigated cross-talk between the AhR and signaling stimulated by IL-4 in human and mouse monocytes. AhR activation was required for a subset of IL-4-induced transcriptional responses and inhibited the IL-4-induced metabolic switch to fatty acid β-oxidation. The promoters of the genes that were induced by IL-4 in an AhR-dependent manner lacked canonical AhR binding sites, implying a nongenomic mechanism of AhR action. Mechanistically, AhR activation reduced the activity of SHP-1, a phosphatase that targets and inhibits STAT6, and prolonged STAT6 phosphorylation and binding to specific target loci, thus extending the duration of STAT6 activity. Our results identify AhR as a key player in the molecular control of responses to IL-4 in monocytes and suggest a nongenomic mechanism through which AhR ligands may influence the functional responses of cells to IL-4.

Smart Hydrogel Dressing Enhances the Healing of Chronic Infectious Diabetic Wounds through Dual-Barrier Drug Delivery Action

Chronic diabetic wounds struggle to heal due to drug-resistant bacterial infections, oxidative stress microenvironment, and immune dysfunction. At present, the disease has become a huge clinical challenge. Multifunctional hydrogels with antibacterial, antioxidant, and anti-inflammatory properties are becoming an emerging trend in the treatment of chronic wounds. However, matching different bioactive functions with the wound healing process to sequentially exert antibacterial, antioxidant, anti-inflammatory, and immunomodulatory functions remains a significant challenge. In this research, a hydrogel dressing with bactericidal and anti-inflammatory properties was synthesized by crafting a pH/ROS-responsive scaffold from phenylboronic acid-grafted hyaluronic acid (HA-PBA) and 4-arm-PEG-dopamine (4A-PEG-Dopa), employing dynamic borate ester bonds. This structure was then infused with the antimicrobial peptide (AMP) and ROS-sensitive micelle mPEG-TK-PLGA loaded with quercetin (QC). This dressing embodied a dual-barrier drug delivery mechanism, engineered for the prolonged and consistent liberation of QC. In the experiment, the hydrogel dissociated within the acidic microenvironment of diabetic wounds, thereby liberating the encapsulated micelles and AMP. Upon further dissociation, the micelles release QC due to the ROS-abundant microenvironment, which could relieve oxidative stress and encourage M2 polarization of macrophage via the Akt/STAT6 signaling pathway. Therefore, this smart delivery system, developed through our innovative approach, holds promise for treating chronic infectious diabetic wounds.

ABBV-744 alleviates LPS-induced neuroinflammation via regulation of BATF2-IRF4-STAT1/3/5 axis

Suppression of neuroinflammation using small molecule compounds targeting the key pathways in microglial inflammation has attracted great interest. Recently, increasing attention has been gained to the role of the second bromodomain (BD2) of the bromodomain and extra-terminal (BET) proteins, while its effect and molecular mechanism on microglial inflammation has not yet been explored. In this study, we evaluated the therapeutic effects of ABBV-744, a BD2 high selective BET inhibitor, on lipopolysaccharide (LPS)-induced microglial inflammation in vitro and in vivo, and explored the key pathways by which ABBV-744 regulated microglia-mediated neuroinflammation. We found that pretreatment of ABBV-744 concentration-dependently inhibited the expression of LPS-induced inflammatory mediators/enzymes including NO, TNF-α, IL-1β, IL-6, iNOS, and COX-2 in BV-2 microglial cells. These effects were validated in LPS-treated primary microglial cells. Furthermore, we observed that administration of ABBV-744 significantly alleviated LPS-induced activation of microglia and transcriptional levels of pro-inflammatory factors TNF-α and IL-1β in mouse hippocampus and cortex. RNA-Sequencing (RNA-seq) analysis revealed that ABBV-744 induced 508 differentially expressed genes (DEGs) in LPS-stimulated BV-2 cells, and gene enrichment and gene expression network analysis verified its regulation on activated microglial genes and inflammatory pathways. We demonstrated that pretreatment of ABBV-744 significantly reduced the expression levels of basic leucine zipper ATF-like transcription factor 2 (BATF2) and interferon regulatory factor 4 (IRF4), and suppressed JAK-STAT signaling pathway in LPS-stimulated BV-2 cells and mice, suggesting that the anti-neuroinflammatory effect of ABBV-744 might be associated with regulation of BATF2-IRF4-STAT1/3/5 pathway, which was confirmed by gene knockdown experiments. This study demonstrates the effect of a BD2 high selective BET inhibitor, ABBV-744, against microglial inflammation, and reveals a BATF2-IRF4-STAT1/3/5 pathway in regulation of microglial inflammation, which might provide new clues for discovery of effective therapeutic strategy against neuroinflammation.

Transcriptional control of metabolism by interferon regulatory factors

Interferon regulatory factors (IRFs) comprise a family of nine transcription factors in mammals. IRFs exert broad effects on almost all aspects of immunity but are best known for their role in the antiviral response. Over the past two decades, IRFs have been implicated in metabolic physiology and pathophysiology, partly as a result of their known functions in immune cells, but also because of direct actions in adipocytes, hepatocytes, myocytes and neurons. This Review focuses predominantly on IRF3 and IRF4, which have been the subject of the most intense investigation in this area. IRF3 is located in the cytosol and undergoes activation and nuclear translocation in response to various signals, including stimulation of Toll-like receptors, RIG-I-like receptors and the cGAS-STING pathways. IRF3 promotes weight gain, primarily by inhibiting adipose thermogenesis, and also induces inflammation and insulin resistance using both weight-dependent and weight-independent mechanisms. IRF4, meanwhile, is generally pro-thermogenic and anti-inflammatory and has profound effects on lipogenesis and lipolysis. Finally, new data are emerging on the role of other IRF family members in metabolic homeostasis. Taken together, data indicate that IRFs serve as critical yet underappreciated integrators of metabolic and inflammatory stress.

The mitochondrial pyruvate carrier regulates adipose glucose partitioning in female mice

OBJECTIVE

The mitochondrial pyruvate carrier (MPC) occupies a critical node in intermediary metabolism, prompting interest in its utility as a therapeutic target for the treatment of obesity and cardiometabolic disease. Dysregulated nutrient metabolism in adipose tissue is a prominent feature of obesity pathophysiology, yet the functional role of adipose MPC has not been explored. We investigated whether the MPC shapes the adaptation of adipose tissue to dietary stress in female and male mice.

METHODS

The impact of pharmacological and genetic disruption of the MPC on mitochondrial pathways of triglyceride assembly (lipogenesis and glyceroneogenesis) was assessed in 3T3L1 adipocytes and murine adipose explants, combined with analyses of adipose MPC expression in metabolically compromised humans. Whole-body and adipose-specific glucose metabolism were subsequently investigated in male and female mice lacking adipocyte MPC1 (Mpc1AD-/-) and fed either standard chow, high-fat western style, or high-sucrose lipid restricted diets for 24 weeks, using a combination of radiolabeled tracers and GC/MS metabolomics.

RESULTS

Treatment with UK5099 or siMPC1 impaired the synthesis of lipids and glycerol-3-phosphate from pyruvate and blunted triglyceride accumulation in 3T3L1 adipocytes, whilst MPC expression in human adipose tissue was negatively correlated with indices of whole-body and adipose tissue metabolic dysfunction. Mature adipose explants from Mpc1AD-/- mice were intrinsically incapable of incorporating pyruvate into triglycerides. In vivo, MPC deletion restricted the incorporation of circulating glucose into adipose triglycerides, but only in female mice fed a zero fat diet, and this associated with sex-specific reductions in tricarboxylic acid cycle pool sizes and compensatory transcriptional changes in lipogenic and glycerol metabolism pathways. However, whole-body adiposity and metabolic health were preserved in Mpc1AD-/- mice regardless of sex, even under conditions of zero dietary fat.

CONCLUSIONS

These findings highlight the greater capacity for mitochondrially driven triglyceride assembly in adipose from female versus male mice and expose a reliance upon MPC-gated metabolism for glucose partitioning in female adipose under conditions of dietary lipid restriction.

Crosstalk between macrophages and immunometabolism and their potential roles in tissue repair and regeneration

Immune metabolism is a result of many specific metabolic reactions, such as glycolysis, the tricarboxylic acid (TCA) pathway, the pentose phosphate pathway (PPP), mitochondrial oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), fatty acid biosynthesis (FAs) and amino acid pathways, which promote cell proliferation and maintenance with structural and pathological energy to regulate cellular signaling. The metabolism of macrophages produces many metabolic intermediates that play important regulatory roles in tissue repair and regeneration. The metabolic activity of proinflammatory macrophages (M1) mainly depends on glycolysis and the TCA cycle system, but anti-inflammatory macrophages (M2) have intact functions of the TCA cycle, which enhances FAO and is dependent on OXPHOS. However, the metabolic mechanisms of macrophages in tissue repair and regeneration have not been well investigated. Thus, we review how three main metabolic mechanisms of macrophages, glucose metabolism, lipid metabolism, and amino acid metabolism, regulate tissue repair and regeneration.

Immunomodulation of Macrophages in Diabetic Wound Individuals by Structurally Diverse Bioactive Phytochemicals

Diabetes-related ulcers and slow-healing wounds pose a significant health risk to individuals due to their uncertain causes. Mortality rates for diabetes foot ulcers (DFUs) range from 10% after 16 months to 24% after five years. The use of bioactive phytochemicals can play a key role in healing wounds in a predictable time. Recent literature has demonstrated that various natural substances, including flavonoids, saponins, phenolic compounds, and polysaccharides, play key roles at different stages of the wound-healing process through diverse mechanisms. These studies have categorized the compounds according to their characteristics, bioactivities, and modes of action. In this study, we evaluated the role of natural compounds derived from plant sources that have been shown to play a crucial role in immunomodulation. Macrophages are closely involved in immunomodulation within the wound microenvironment and are key players in efferocytosis, inflammation resolution, and tissue regeneration, all of which contribute to successful wound healing. Phytochemicals and their derivatives have shown capabilities in immune regulation, including macrophage migration, nitric oxide synthase inhibition, lymphocyte and T-cell stimulation, cytokine activation, natural killer cell enhancement, and the regulation of NF-κβ, TNF-α, and apoptosis. In this review, we have studied the role of phytochemicals in immunomodulation for the resolution of diabetic wound inflammation.

Metabolic reprogramming of macrophages in cancer therapy

Cancer presents a significant global public health challenge. Within the tumor microenvironment (TME), macrophages are the most abundant immune cell population. Tumor-associated macrophages (TAMs) undergo metabolic reprogramming through influence of the TME; thus, by manipulating key metabolic pathways such as glucose, lipid, or amino acid metabolism, it may be possible to shift TAMs towards an antitumor state, enhancing the immune response against tumors. Here, we highlight the metabolic reprogramming of macrophages as a potential approach for cancer immunotherapy. We explore the major pathways involved in the metabolic reprogramming of TAMs and offer new and valuable insights on the current technologies utilized for TAM reprogramming, including genome editing, antibodies, small molecules, nanoparticles and other in situ editing strategies.

Transcriptional profiling of lung macrophages following ozone exposure in mice identifies signaling pathways regulating immunometabolic activation

Macrophages play a key role in ozone-induced lung injury by regulating both the initiation and resolution of inflammation. These distinct activities are mediated by pro-inflammatory and anti-inflammatory/proresolution macrophages which sequentially accumulate in injured tissues. Macrophage activation is dependent, in part, on intracellular metabolism. Herein, we used RNA-sequencing (seq) to identify signaling pathways regulating macrophage immunometabolic activity following exposure of mice to ozone (0.8 ppm, 3 h) or air control. Analysis of lung macrophages using an Agilent Seahorse showed that inhalation of ozone increased macrophage glycolytic activity and oxidative phosphorylation at 24 and 72 h post-exposure. An increase in the percentage of macrophages in S phase of the cell cycle was observed 24 h post ozone. RNA-seq revealed significant enrichment of pathways involved in innate immune signaling and cytokine production among differentially expressed genes at both 24 and 72 h after ozone, whereas pathways involved in cell cycle regulation were upregulated at 24 h and intracellular metabolism at 72 h. An interaction network analysis identified tumor suppressor 53 (TP53), E2F family of transcription factors (E2Fs), cyclin-dependent kinase inhibitor 1A (CDKN1a/p21), and cyclin D1 (CCND1) as upstream regulators of cell cycle pathways at 24 h and TP53, nuclear receptor subfamily 4 group a member 1 (NR4A1/Nur77), and estrogen receptor alpha (ESR1/ERα) as central upstream regulators of mitochondrial respiration pathways at 72 h. To assess whether ERα regulates metabolic activity, we used ERα-/- mice. In both air and ozone-exposed mice, loss of ERα resulted in increases in glycolytic capacity and glycolytic reserve in lung macrophages with no effect on mitochondrial oxidative phosphorylation. Taken together, these results highlight the complex interaction between cell cycle, intracellular metabolism, and macrophage activation which may be important in the initiation and resolution of inflammation following ozone exposure.

UK5099 Inhibits the NLRP3 Inflammasome Independently of its Long-Established Target Mitochondrial Pyruvate Carrier

Targeting NLRP3 inflammasome has been recognized as a promising therapeutic strategy for the treatment of numerous common diseases. UK5099, a long-established inhibitor of mitochondrial pyruvate carrier (MPC), is previously found to inhibit macrophage inflammatory responses independent of MPC expression. However, the mechanisms by which UK5099 inhibit inflammatory responses remain unclear. Here, it is shown that UK5099 is a potent inhibitor of the NLRP3 inflammasome in both mouse and human primary macrophages. UK5099 selectively suppresses the activation of the NLRP3 but not the NLRC4 or AIM2 inflammasomes. Of note, UK5099 retains activities on NLRP3 in macrophages devoid of MPC expression, indicating this inhibitory effect is MPC-independent. Mechanistically, UK5099 abrogates mitochondria-NLRP3 interaction and in turn inhibits the assembly of the NLRP3 inflammasome. Further, a single dose of UK5099 persistently reduces IL-1β production in an endotoxemia mouse model. Importantly, structure modification reveals that the inhibitory activities of UK5099 on NLRP3 are unrelated to the existence of the activated double bond within the UK5099 molecule. Thus, this study uncovers a previously unknown molecular target for UK5099, which not only offers a new candidate for the treatment of NLRP3-driven diseases but also confounds its use as an MPC inhibitor in immunometabolism studies.

MSR1-dependent efferocytosis improved ischemia-reperfusion injury following aged-donor liver transplantation in mice by regulating the pro-resolving polarisation of macrophages

Compared with young liver donors, aged liver donors are more susceptible to ischemia-reperfusion injury (IRI) following transplantation, which may be related to excessive inflammatory response and macrophage dysfunction, but the specific mechanism is unclear. Macrophage scavenger receptor 1 (MSR1) is a member of the scavenger receptor family, and plays an important regulatory role in inflammation response and macrophage function regulation. But its role in IRI following aged-donor liver transplantation is still unclear. This study demonstrates that MSR1 expression is decreased in macrophages from aged donor livers, inhibiting their efferocytosis and pro-resolving polarisation. Decreased MSR1 is responsible for the more severe IRI suffered by aged donor livers. Overexpression of MSR1 using F4/80-labelled AAV9 improved intrahepatic macrophage efferocytosis and promoted pro-resolving polarisation, ultimately ameliorating IRI following aged-donor liver transplantation. In vitro co-culture experiments further showed that overexpression of MSR1 promoted an increase in calcium concentration, which further activated the PI3K-AKT-GSK3β pathway, and induced the upregulation of β-catenin. Overall, MSR1-dependent efferocytosis promoted the pro-resolving polarisation of macrophages through the PI3K-AKT-GSK3β pathway-induced up-regulating of β-catenin leading to improved IRI following aged-donor liver transplantation.

Unlocking the potential: Targeting metabolic pathways in the tumor microenvironment for Cancer therapy

Cancer incidence and mortality are increasing and impacting global life expectancy. Metabolic reprogramming in the tumor microenvironment (TME) is intimately related to tumorigenesis, progression, metastasis and drug resistance. Tumor cells drive metabolic reprogramming of other cells in the TME through metabolic induction of cytokines and metabolites, and metabolic substrate competition. Consequently, this boosts tumor cell growth by providing metabolic support and facilitating immunosuppression and angiogenesis. The metabolic interplay in the TME presents potential therapeutic targets. Here, we focus on the metabolic reprogramming of four principal cell subsets in the TME: CAFs, TAMs, TILs and TECs, and their interaction with tumor cells. We also summarize medications and therapies targeting these cells' metabolic pathways, particularly in the context of immune checkpoint blockade therapy.

The Effects of Hypoxia on the Immune-Metabolic Interplay in Liver Cancer

M2-like macrophages promote tumor growth and cancer immune evasion. This study used an in vitro model to investigate how hypoxia and tumor metabolism affect macrophage polarization. Liver cancer cells (HepG2 and VX2) and macrophages (THP1) were cultured under hypoxic (0.1% O2) and normoxic (21% O2) conditions with varying glucose levels (2 g/L or 4.5 g/L). Viability assays and extracellular pH (pHe) measurements were conducted over 96 hours. Macrophages were exposed to the tumor-conditioned medium (TCM) from the cancer cells, and polarization was assessed using arginase and nitrite assays. GC-MS-based metabolic profiling quantified TCM meta-bolites and correlated them with M2 polarization. The results showed that pHe in TCMs decreased more under hypoxia than normoxia (p < 0.0001), independent of glucose levels. The arginase assay showed hypoxia significantly induced the M2 polarization of macrophages (control group: p = 0.0120,0.1%VX2-TCM group: p = 0.0149, 0.1%HepG2-TCM group: p < 0.0001, 0.1%VX2-TCMHG group: p = 0.0001, and 0.1%HepG2-TCMHG group: p < 0.0001). TCMs also induced M2 polarization under normoxic conditions, but the strongest M2 polarization occurred when both tumor cells and macrophages were incubated under hypoxia with high glucose levels. Metabolomics revealed that several metabolites, particularly lactate, were correlated with hypoxia and M2 polarization. Under normoxia, elevated 2-amino-butanoic acid (2A-BA) strongly correlated with M2 polarization. These findings suggest that targeting tumor hypoxia could mitigate immune evasion in liver tumors. Lactate drives acidity in hypoxic tumors, while 2A-BA could be a therapeutic target for overcoming immunosuppression in normoxic conditions.

Cellular metabolism changes in atherosclerosis and the impact of comorbidities

Cell activation and nutrient dysregulation are common consequences of atherosclerosis and its preceding risk factors, such as hypertension, dyslipidemia, and diabetes. These diseases may also impact cellular metabolism and consequently cell function, and the other way around, altered cellular metabolism can impact disease development and progression through altered cell function. Understanding the contribution of altered cellular metabolism to atherosclerosis and how cellular metabolism may be altered by co-morbidities and atherosclerosis risk factors could support the development of novel strategies to lower the risk of CVD. Therefore, we briefly review disease pathogenesis and the principles of cell metabolic pathways, before detailing changes in cellular metabolism in the context of atherosclerosis and comorbidities. In the hypoxic, inflammatory and hyperlipidemic milieu of the atherosclerotic plaque riddled with oxidative stress, metabolism shifts to increase anaerobic glycolysis, the pentose-phosphate pathway and amino acid use. We elaborate on metabolic changes for macrophages, neutrophils, vascular endothelial cells, vascular smooth muscle cells and lymphocytes in the context of atherosclerosis and its co-morbidities hypertension, dyslipidemia, and diabetes. Since causal relationships of specific key genes in a metabolic pathway can be cell type-specific and comorbidity-dependent, the impact of cell-specific metabolic changes must be thoroughly explored in vivo, with a focus on also systemic effects. When cell-specific treatments become feasible, this information will be crucial for determining the best metabolic intervention to improve atherosclerosis and its interplay with co-morbidities.

Suppression of SENP3 enhances macrophage alternative activation by mediating IRF4 de-SUMOylation in ESCC progression

Esophageal cancer is common worldwide, with ESCC being the most frequent tumor in East Asia. Tumor-associated macrophages are an important component of the ESCC microenvironment. SUMOylation is a post-translational modification of proteins, and SUMO-specific proteases (SENPs) play an important role in de-SUMOylation. In human patients, we discovered that the levels of SENP3 were upregulated in the tumor-associated macrophages. Furthermore, the loss of SENP3 enhanced the alternative activation of macrophages in the 4-NQO-induced ESCC mice model. This is the first study to identify SENP3-mediated macrophage polarization via the de-SUMOylation of interferon regulatory factor 4 (IRF4) at the K349 site. Alternative activation of macrophages increases the migration and invasion potential of ESCC cells and promotes their progression in vivo. Moreover, patients with relatively low SENP3 expression in macrophages exhibit higher primary PET SUVmax value and lymph node metastasis rates. In summary, this study revealed that SENP3-mediated IRF4 de-SUMOylation is crucial for the alternative activation of macrophages and influences the progression of ESCC.

Citric Acid: A Nexus Between Cellular Mechanisms and Biomaterial Innovations

Citrate-based biodegradable polymers have emerged as a distinctive biomaterial platform with tremendous potential for diverse medical applications. By harnessing their versatile chemistry, these polymers exhibit a wide range of material and bioactive properties, enabling them to regulate cell metabolism and stem cell differentiation through energy metabolism, metabonegenesis, angiogenesis, and immunomodulation. Moreover, the recent US Food and Drug Administration (FDA) clearance of the biodegradable poly(octamethylene citrate) (POC)/hydroxyapatite-based orthopedic fixation devices represents a translational research milestone for biomaterial science. POC joins a short list of biodegradable synthetic polymers that have ever been authorized by the FDA for use in humans. The clinical success of POC has sparked enthusiasm and accelerated the development of next-generation citrate-based biomaterials. This review presents a comprehensive, forward-thinking discussion on the pivotal role of citrate chemistry and metabolism in various tissue regeneration and on the development of functional citrate-based metabotissugenic biomaterials for regenerative engineering applications.