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Metabolic landscape and rewiring in normal hematopoiesis, leukemia and aging

Recent advancements in metabolism research have demonstrated its critical roles in a lot of critical biological processes, including stemness maintenance, cell differentiation, proliferation, and function. Hematopoiesis is the fundamental cell differentiation process with the production of millions of red blood cells per second in carrying oxygen and white blood cells in fighting infection and cancers. The differentiation processes of hematopoietic stem and progenitor cells (HSPCs) are accompanied by significant metabolic reprogramming. In hematological malignancy, metabolic reprogramming is also essential to the malignant hematopoiesis processes. The metabolic rewiring is driven by distinct molecular mechanisms that meet the specific demands of different target cells. Leukemic cells, for instance, adopt unique metabolic profiles to support their heightened energy needs for survival and proliferation. Moreover, aging HSPCs exhibit altered energy consumption compared to their younger counterparts, often triggering protective mechanisms at the cellular level. In this review, we provide a comprehensive analysis of the metabolic processes involved in hematopoiesis and the metabolic rewiring that occurs under adverse conditions. In addition, we highlight current research directions and discuss the potential of targeting metabolic pathways for the management of hematological malignancies and aging.

Baicalin Modulates Glycolysis via the PKC/Raf/MEK/ERK and PI3K/AKT Signaling Pathways to Attenuate IFN-I-Induced Neutrophil NETosis

Type I interferon (IFN-I), a pivotal component of the host's innate antiviral immune system, can induce the formation of neutrophil extracellular traps (NETs) and facilitate inflammatory responses. Baicalin exhibits a range of pharmacological activities, including anti-inflammatory and immunomodulatory effects. It has been reported that neutrophil glycolysis plays a pivotal role in the formation of NETs and the regulation of inflammatory response in immune modulation, regulated by IFN-I. However, it remains unclear whether baicalin regulates IFN-I-induced NETs formation through glycolysis. In this study, we induced the formation of NETs in vitro using IFN-I and observed that baicalin significantly reduced the formation of IFN-I-induced NETs. Furthermore, baicalin inhibited the production of pro-inflammatory cytokines, specifically interleukin-1 beta (IL-1β) and interleukin-6 (IL-6), as well as the generation of reactive oxygen species (ROS) and chemotactic responses. Our findings further indicated that baicalin could inhibit both lactic acid and ATP levels in IFN-I-induced neutrophils, as well as the expression of glycolytic-related proteins, including HK2, HK3, PKM2, and LDHA. Moreover, following the administration of glycolytic agonists insulin, it was observed that heightened glycolytic activity significantly augmented NETs formation and the release of inflammatory cytokines, potentially regulated by PKC/Raf/MEK/ERK and PI3K/AKT signaling pathways. In conclusion, our findings indicated that baicalin may exert inhibitory effects on IFN-I-induced NETs formation and inflammatory cytokine production by modulating glycolysis, thereby providing further evidence for the potential clinical application of baicalin in the treatment of IFN-I-related inflammatory diseases.

Mitochondrial metabolism is rapidly re-activated in mature neutrophils to support stimulation-induced response

Introduction

Neutrophils are highly abundant innate immune cells that are constantly produced from myeloid progenitors in the bone marrow. Differentiated neutrophils can perform an arsenal of effector functions critical for host defense. This study aims to quantitatively understand neutrophil mitochondrial metabolism throughout differentiation and activation, and to elucidate the impact of mitochondrial metabolism on neutrophil functions.

Methods

To study metabolic remodeling throughout neutrophil differentiation, murine ER-Hoxb8 myeloid progenitor-derived neutrophils and human induced pluripotent stem cell-derived neutrophils were assessed as models. To study the metabolic remodeling upon neutrophil activation, differentiated ER-Hoxb8 neutrophils and primary human neutrophils were activated with various stimuli, including ionomycin, monosodium urate crystals, and phorbol 12-myristate 13-acetate. Characterization of cellular metabolism by isotopic tracing, extracellular flux analysis, metabolomics, and fluorescence-lifetime imaging microscopy revealed dynamic changes in mitochondrial metabolism.

Results

As neutrophils mature, mitochondrial metabolism decreases drastically, energy production is offloaded from oxidative phosphorylation, and glucose oxidation through the TCA cycle is substantially reduced. Nonetheless, mature neutrophils retain the capacity for mitochondrial metabolism. Upon stimulation with certain stimuli, TCA cycle is rapidly activated. Mitochondrial pyruvate carrier inhibitors reduce this re-activation of the TCA cycle and inhibit the release of neutrophil extracellular traps. Treatment with these inhibitors also impacts neutrophil redox status, migration, and apoptosis without significantly changing overall bioenergetics.

Conclusions

Together, these results demonstrate that mitochondrial metabolism is dynamically remodeled and plays a significant role in neutrophils. Furthermore, these findings point to the therapeutic potential of mitochondrial pyruvate carrier inhibitors in a range of conditions where dysregulated neutrophil response drives inflammation and contributes to pathology.

High fat diet feeding impairs neutrophil phagocytosis, bacterial killing, and neutrophil-induced hematopoietic regeneration

The prevalence of obesity and metabolic diseases have risen significantly over the past decades. Chronic inflammation in obesity is a link between obesity and secondary disease. While macrophages and monocytes are known to contribute to metabolic disease risk during diet exposure, little is known about the contribution of neutrophils. We assessed the impact of obesity on neutrophils using a 16-week model of diet-induced obesity. Bone marrow (BM) neutrophils significantly expanded with chronic high-fat diet (HFD), significantly decreased TNFɑ protein release, and impaired neutrophil regenerative function compared to normal diet (ND) neutrophils. scRNAseq and flow cytometry demonstrated HFD neutrophil heterogeneity and validated that these cells do not have elevated expression of proinflammatory genes without secondary stimulation. HFD neutrophils showed elevated expression of genes associated with lipid metabolism-acyl-CoA thioesterase 1 (Acot1), carnitine palmitoyltransferase 1a (Cpt1a), and perilipin 2 (Plin2). Consistent with the importance of lipid metabolism in driving dysfunction, neutrophils from HFD-fed animals and neutrophils treated with palmitate had impaired bacterial phagocytosis and killing responses. These data shed light on the complex regulation of intracellular lipids and the role of metabolism on neutrophil function during homeostasis and disease.

Metabolic phenotype of bovine blood-derived neutrophils is altered in milk

In a healthy udder, immune cells from the peripheral bloodstream migrate into mammary tissue in low numbers to provide baseline immune surveillance, without triggering inflammation. In bovine intramammary inflammation, on the other hand, high amounts of leukocytes are recruited, causing severe inflammation. We were interested in leukocyte subpopulations and functional differences between blood- and milk-derived neutrophils from healthy and inflamed udder quarters. In this context, we found a distinct leukocyte subpopulation profile dependent on the health status of mammary gland quarters, with a predominant T cells population in heathy mammary gland quarters and a shift to macrophages and granulocytes in inflammation. Further, we detected divergent expression of major histocompatibility complex class II and interleukin 2 receptor CD25 on the surface of milk- and blood-derived neutrophils, pointing to antigen presentation and immune modulatory properties. Moreover, we observed differences in production of reactive oxygen species, deviant early and late apoptosis and functional changes in these cells, pointing to an altered metabolic phenotype in milk cells dependent on the health status of mammary gland quarters. These findings provide insights into the functional adaptations of neutrophils in different environments, highlighting the importance of metabolic alterations for immune cell function.

Melezitose inhibited glycolytic pathway and enhances anti-Crohn's disease activity via binding to PGK1

ETHNOPHARMACOLOGY RELEVANCE

Alhagi honey is a light yellow sugar granule formed by concentrating the liquid secreted by Alhagi branches and leaves. It is a traditional Uygur medicine often used to treat abdominal pain, diarrhea, dysentery, and other conditions. Modern research has indicated that the main active components of Alhagi honey are oligosaccharides and polysaccharides. Our previous research had identified that the extract of Alhagi honey exhibits good anti-inflammatory pharmacological activity, however, its efficacy against Crohn's disease (CD) remains to be elucidated.

AIM OF THE STUDY

To determine the efficacy of the extract of Alhagi honey in CD and to explore its potential targets and mechanisms.

MATERIALS AND METHODS

Mel (melitriose) is extracted from dried Alhagi honey. In vivo, 2.5% 2,4,6-trinitrobenzenesulfonic acid (TNBS, At a dosage of 100 mg/kg) is used as an enema to induce CD-like changes in the rat colon. Over the subsequent fortnight, the modeled rats were treated with Mel via gavage. The histopathological alterations and repair ability of colonic injury in the colon tissue were evaluated using hematoxylin and eosin (H&E), Masson's trichrome, and immunofluorescence staining. Additionally, the amelioration of inflammatory responses in the colon was assessed using enzyme-linked immunosorbent assay (ELISA). The reparative capacity of Mel on inflammation was evaluated by inducing inflammation in RAW264.7 cells with lipopolysaccharide (LPS). The Drug Affinity Responsive Target Stability (DARTS) experiment was used to explore the relevant targets of action. Furthermore, network pharmacology was used to investigate the mechanism of action of Mel, to further validate its effects at the cellular level.

RESULTS

In the CD rat model, treatment with Mel significantly improved colonic mucosal damage and inflammatory infiltration. It also demonstrated a reduced collagen fiber deposition, thereby ameliorating fibrotic changes in colonic tissue. Furthermore, Mel decreased the expression of pro-inflammatory factors and increased the expression of anti-inflammatory factors in colonic tissue and cell supernatants. Further research confirmed that Mel influences the glycolytic pathway by binding to phosphoglycerate kinase 1 (PGK1) and suppressing its activity, leading to reduced production of adenosine triphosphate (ATP) and its metabolites, 2-phosphoglycerate (2-PG), 3-phosphoglycerate (3-PG); thus, playing a role in anti-inflammation and promotion of repair. This mechanism was further validated using the PGK1 inhibitor NG52, which also demonstrated a reduction in the production of ATP, 2-PG, and 3-PG.

CONCLUSIONS

This study revealed that Mel exerts its anti-inflammatory and reparative capabilities in vitro and in vivo by inhibiting the activity of the key glycolytic enzyme PGK1, leading to reduced production of ATP and its products 2-PG and 3-PG, thereby ameliorating the symptoms of CD. It can emerge as a promising candidate for CD treatment.

Cellular immune responses of bovine polymorphonuclear neutrophils to Calicophoron daubneyi

Calicophoron daubneyi infections have increased in Europe, being more frequent than fasciolosis in some areas. Infection occurs once definitive hosts ingest encysted metacercariae present on vegetation. Following excystation, juvenile flukes penetrate the small intestinal mucosa and migrate into the rumen where adults mature. Throughout the somatic migration, juveniles come across different microenvironments and tissues and encounter host leukocytes. Besides phagocytosis, production of reactive oxygen species (ROS) and degranulation, polymorphonuclear neutrophils also cast neutrophil extracellular traps (NETs), which can entrap several parasite species, including the closely related liver fluke Fasciola hepatica. In this study, we analyzed whether in vitro exposure of bovine neutrophils to C. daubneyi antigen (CdAg) and eggs triggered neutrophils activation and NET formation. Results on scanning electron microscopy (SEM) and immunofluorescence analyses show weak formation of short spread NETs upon CdAg stimulation, corroborated by increased extracellular DNA measurements. Likewise, early NETosis was confirmed via nuclear area expansion assays. Bovine neutrophil stimulation with CdAg 100 µg/mL concentration led to a significant increase in oxygen consumption rates (p = 0.0152) and extracellular acidification rates (p = 0.0022), while lower concentrations of CdAg (10 µg/mL) failed to induce neutrophil activation, suggesting a dose dependent response. Both intra- and extracellular ROS production was not affected by any CdAg concentration here studied. Bovine neutrophil total adenosine triphosphate concentration significantly decreased after exposure to CdAg 100 µg/mL, in line to the observed with the positive control (phorbol myristate acetate/ionomycin). In summary, C. daubneyi activates bovine neutrophils with rather weak responses, which might suggest that the release of C. daubneyi-specific molecules (i.e. excretory-secretory antigens, proteases, or nucleases) could interfere with neutrophil-related effector mechanisms. Further ex vivo analyses will clarify if such mechanisms are also involved in pathogenesis of paramphistomosis by demonstrating neutrophil recruitment into affected intestinal mucosa.

Ceramide Complex Ameliorates Metabolically Driven Neutrophil Senescence by Regulating Apoptosis via the cGAS-STING Pathway

Background: Population aging is increasingly recognized as a major global challenge. Researchers have identified a correlation between aging and immunosenescence, leading to dysfunction of the immune system. As a crucial component of the innate immune system, age-related changes in neutrophils have garnered significant attention from researchers, but the underlying mechanisms remain unclear. This study aims to comprehensively evaluate the senescence status and potential mechanisms of neutrophils, and to identify targets for delaying or even reversing senescence. Methods: Blood routine tests and Luminex Multiplex Cytokine Analysis were employed to assess inflammation levels in mice. Flow cytometry and an agarose chemotaxis model were used to evaluate baseline biological functions and stress responses of neutrophils. Transmission electron microscopy and flow cytometry were utilized to compare mitochondrial ultrastructure and function. Metabolomic analysis was performed to examine metabolic patterns. qPCR, Western blotting, and flow cytometry were used to investigate the potential mechanisms of ceramide intervention on neutrophils. Results: Our findings indicate that aged mice exhibit considerable variability in delayed apoptosis among bone marrow neutrophils, alongside a notable reduction in baseline functionality and stress response capabilities. Metabolomic analysis revealed a marked decrease in ceramide levels within aged neutrophils. In vitro ceramide intervention revitalized neutrophil functionality and partially inhibited delayed apoptosis, facilitating the efficient elimination of senescent neutrophils. The underlying mechanism behind these effects might be attributed to ceramide's modulation of mitochondrial permeability, which in turn influences the activation of the cGAS-STING pathway, as well as its regulatory role in maintaining the equilibrium of pro-apoptotic Bcl-2 protein levels. Conclusions: This investigation proficiently assessed neutrophil senescence in terms of both biological functionalities and intrinsic diversity, while concurrently exploring the feasibility and primary mechanisms through which ceramide intervention impacts neutrophil senescence at the levels of signaling pathways, protein expression, and cellular microarchitecture. These findings provide novel insights into evaluating and potentially intervening in immune senescence, with implications for organismal aging.

Mitochondrial metabolism is rapidly re-activated in mature neutrophils to support stimulation-induced response

Neutrophils are highly abundant innate immune cells that are constantly produced from myeloid progenitors in the bone marrow. Differentiated neutrophils can perform an arsenal of effector functions critical for host defense. This study aims to quantitatively understand neutrophil mitochondrial metabolism throughout differentiation and activation, and to elucidate the impact of mitochondrial metabolism on neutrophil functions. To study metabolic remodeling throughout neutrophil differentiation, murine ER-Hoxb8 myeloid progenitor-derived neutrophils and human induced pluripotent stem cell-derived neutrophils were assessed as models. To study the metabolic remodeling upon neutrophil activation, differentiated ER-Hoxb8 neutrophils and primary human neutrophils were activated with various stimuli, including ionomycin, MSU crystals, and PMA. Characterization of cellular metabolism by isotopic tracing, extracellular flux analysis, metabolomics, and fluorescence-lifetime imaging microscopy revealed dynamic changes in mitochondrial metabolism. As neutrophils mature, mitochondrial metabolism decreases drastically, energy production is fully offloaded from oxidative phosphorylation, and glucose oxidation through TCA cycle is substantially reduced. Nonetheless, mature neutrophils retain the capacity for mitochondrial metabolism. Upon stimulation with certain stimuli, TCA cycle is rapidly activated. Mitochondrial pyruvate carrier inhibitors reduce this re-activation of the TCA cycle and inhibit the release of neutrophil extracellular traps. Mitochondrial metabolism also impacts neutrophil redox status, migration, and apoptosis without significantly changing overall bioenergetics. Together, these results demonstrate that mitochondrial metabolism is dynamically remodeled and plays a significant role in neutrophil function and fate. Furthermore, these findings point to the therapeutic potential of mitochondrial pyruvate carrier inhibitors in a range of conditions where dysregulated neutrophil response drives inflammation and contributes to pathology.

Early downmodulation of tumor glycolysis predicts response to fasting-mimicking diet in triple-negative breast cancer patients

In preclinical experiments, cyclic fasting-mimicking diets (FMDs) showed broad anticancer effects in combination with chemotherapy. Among different tumor types, triple-negative breast cancer (TNBC) is exquisitely sensitive to FMD. However, the antitumor activity and efficacy of cyclic FMD in TNBC patients remain unclear. Here, we show that a severely calorie-restricted, triweekly, 5-day FMD regimen results in excellent pathologic complete response (pCR) rates (primary endpoint) and long-term clinical outcomes (secondary endpoints) when combined with preoperative chemotherapy in 30 patients with early-stage TNBC enrolled in the phase 2 trial BREAKFAST. Bulk and single-cell RNA sequencing analysis revealed that highly glycolytic cancer cells, myeloid cells, and pericytes from tumors achieving pCR undergo a significant, early downmodulation of pathways related to glycolysis and pyruvate metabolism. Our findings pave the wave for conducting larger clinical trials to investigate the efficacy of cyclic FMD in early-stage TNBC patients and to validate early changes of intratumor glycolysis as a predictor of clinical benefit from nutrient restriction. This study was registered at Clinicaltrials.gov (NCT04248998).

Remifentanil Ameliorates Lipopolysaccharide-Induced Neuroinflammation by Regulating the Phosphatidylinositol 3-Kinase/Serine-Threonine Protein Kinase/Hypoxia-Inducible Factor 1 Alpha Pathway

There has been scarce research on the potential neuroprotective effects of remifentanil (REM) in septic individuals. We aimed to investigate the role and underlying mechanism of REM in LPS-induced neuroinflammation. Thirty-two rats were randomly divided to control, lipopolysaccharide (LPS), LPS + REM, and REM groups. Depending on the group, 4 h after intraperitoneal administration of LPS or saline, REM or saline was infused intravenously for 40 min. Following the sacrification, blood samples and brain tissues were collected for analysis. Brain tissues (prefrontal cortex, cerebellum, and hippocampus) were stained with hematoxylin and eosin, caspase-3 (Cas-3), and tumor necrosis factor alpha (TNF-α). Quantitative reverse transcription-polymerase chain reaction analysis was used to detect claudin-5 (CLDN5), zonula occludens-1 (ZO-1), phosphatidylinositol 3-kinase (PI3K), serine-threonine protein kinase (AKT), and hypoxia-inducible factor 1 alpha (HIF-1α) gene expression levels. Histopathologic and immunohistochemical analyses showed that REM treatment improved LPS-induced histological changes. REM does not reduce TOS and OSI levels or increase TAS levels, suggesting that it is ineffective through oxidative stress. LPS-induced changes in gene expression levels (PI3K, AKT, HIF-1α, and CLDN5) were also reversed by REM. REM was found to prevent neuroinflammation, and apoptosis by restoring blood-brain barrier, and regulating the PI3K/AKT/HIF-1α pathway. These findings suggest that REM is protective against neuroinflammation.

Exploring glycolytic enzymes in disease: potential biomarkers and therapeutic targets in neurodegeneration, cancer and parasitic infections

Glycolysis, present in most organisms, is evolutionarily one of the oldest metabolic pathways. It has great relevance at a physiological level because it is responsible for generating ATP in the cell through the conversion of glucose into pyruvate and reducing nicotinamide adenine dinucleotide (NADH) (that may be fed into the electron chain in the mitochondria to produce additional ATP by oxidative phosphorylation), as well as for producing intermediates that can serve as substrates for other metabolic processes. Glycolysis takes place through 10 consecutive chemical reactions, each of which is catalysed by a specific enzyme. Although energy transduction by glucose metabolism is the main function of this pathway, involvement in virulence, growth, pathogen-host interactions, immunomodulation and adaptation to environmental conditions are other functions attributed to this metabolic pathway. In humans, where glycolysis occurs mainly in the cytosol, the mislocalization of some glycolytic enzymes in various other subcellular locations, as well as alterations in their expression and regulation, has been associated with the development and progression of various diseases. In this review, we describe the role of glycolytic enzymes in the pathogenesis of diseases of clinical interest. In addition, the potential role of these enzymes as targets for drug development and their potential for use as diagnostic and prognostic markers of some pathologies are also discussed.

Glucose Metabolism Reprogramming of Immune Cells in the Microenvironment of Pancreatic and Hepatobiliary Cancers

BACKGROUND AND AIM

Pancreatic and hepatobiliary cancers are increasing in prevalence and contribute significantly to cancer-related mortality worldwide. Emerging therapeutic approaches, particularly immunotherapy, are gaining attention for their potential to harness the patient's immune system to combat these tumors. Understanding the role of immune cells in the tumor microenvironment (TME) and their metabolic reprogramming is key to developing more effective treatment strategies. This review aims to explore the relationship between immune cell function and glucose metabolism in the TME of pancreatic and hepatobiliary cancers.

METHODS

This review synthesizes current research on the metabolic adaptations of immune cells, specifically focusing on glucose metabolism within the TME of pancreatic and hepatobiliary cancers. We examine the mechanisms by which immune cells influence tumor progression through metabolic reprogramming and how these interactions can be targeted for therapeutic purposes.

RESULTS

Immune cells in the TME undergo significant metabolic changes, with glucose metabolism playing a central role in modulating immune responses. These metabolic shifts not only affect immune cell function but also influence tumor behavior and progression. The unique metabolic features of immune cells in pancreatic and hepatobiliary cancers provide new opportunities for targeting immune responses to combat these malignancies more effectively.

CONCLUSION

Understanding the complex relationship between immune cell glucose metabolism and tumor progression in the TME of pancreatic and hepatobiliary cancers offers promising therapeutic strategies. By modulating immune responses through targeted metabolic interventions, it may be possible to improve the efficacy of immunotherapies and better combat these aggressive cancers.

Proteomic analysis reveals dysregulation of peripheral blood neutrophils in patients with Multiple Sclerosis

Multiple Sclerosis (MS) is a complex auto-inflammatory disease affecting the brain and spinal cord, which results in axonal de-myelination and symptoms including fatigue, pain, and difficulties with vision and mobility. The involvement of the immune system in the pathology of MS is well established, particularly the adaptive T cell response, and there has been a particular focus on the IL-17-producing subset of Th17 cells and their role in driving disease. However, the importance of innate immune cells has not been so well characterized. Here we focussed on neutrophils, which are innate immune cells and rapid responders to inflammation, and which have recently been linked to other chronic autoimmune conditions. Multiple strands of evidence in patients with MS and in mice with the experimental autoimmune encephalomyelitis MS model suggest neutrophils may play a role in driving MS inflammation. Here, we performed proteomic analysis on neutrophils from patients with MS and healthy donors, revealing striking differences. In particular, granule proteins were significantly more abundant in the MS neutrophils compared to the healthy controls, with a particular overabundance of proteins in primary and secondary granules. In addition, members of the MAVS signalling pathway were differently regulated compared to healthy donor cells. Finally, we find that MS neutrophils do not suppress T cell activation equivalently to healthy neutrophils, and in particular are unable to suppress expression of CD161 on the T cells, indicative of a suppression of Th17 differentiation. We propose that neutrophil dysregulation in MS may contribute to dysfunctional T cell responses.

Pathophysiological Role of Neutrophil Extracellular Traps in Diet-Induced Obesity and Metabolic Syndrome in Animal Models

The global pandemic of obesity poses a serious health, social, and economic burden. Patients living with obesity are at an increased risk of developing noncommunicable diseases or to die prematurely. Obesity is a state of chronic low-grade inflammation. Neutrophils are first to be recruited to sites of inflammation, where they contribute to host defense via phagocytosis, degranulation, and extrusion of neutrophil extracellular traps (NETs). NETs are web-like DNA structures of nuclear or mitochondrial DNA associated with cytosolic antimicrobial proteins. The primary function of NETosis is preventing the dissemination of pathogens. However, neutrophils may occasionally misidentify host molecules as danger-associated molecular patterns, triggering NET formation. This can lead to further recruitment of neutrophils, resulting in propagation and a vicious cycle of persistent systemic inflammation. This scenario may occur when neutrophils infiltrate expanded obese adipose tissue. Thus, NETosis is implicated in the pathophysiology of autoimmune and metabolic disorders, including obesity. This review explores the role of NETosis in obesity and two obesity-associated conditions-hypertension and liver steatosis. With the rising prevalence of obesity driving research into its pathophysiology, particularly through diet-induced obesity models in rodents, we discuss insights gained from both human and animal studies. Additionally, we highlight the potential offered by rodent models and the opportunities presented by genetically modified mouse strains for advancing our understanding of obesity-related inflammation.

Effects of the pan-caspase inhibitor Q-VD-OPh on human neutrophil lifespan and function

Human neutrophils are abundant, short-lived leukocytes that turn over at a rate of approximately 1011 cells/day via a constitutive apoptosis program. Certain growth factors, inflammatory mediators and infectious agents can delay apoptosis or induce neutrophils to die by other mechanisms. Nonetheless, a large body of data demonstrates that apoptosis of untreated neutrophils typically ensues within 24 hours of cell isolation and in vitro culture. At the molecular level apoptosis is driven by executioner caspase-3, and during this process cell proinflammatory capacity and host defense functions are downregulated. We undertook the current study to determine the extent to which human neutrophil viability and function could be prolonged by treatment with the non-toxic, irreversible, pan-caspase inhibitor Q-VD-OPh. Our data demonstrate that a single 10 μM dose of this drug was sufficient to markedly prolong cell lifespan. Specifically, we show that apoptosis was prevented for at least 5 days as indicated by analysis of nuclear morphology, DNA fragmentation, and phosphatidylserine externalization together with measurements of procaspase-3 processing and caspase activity. Conversely, mitochondrial depolarization declined despite abundant Myeloid Cell Leukemia 1 (MCL-1). At the same time, glutathione levels were maintained and Q-VD-OPh prevented age-associated increases mitochondrial oxidative stress. Regarding functional capacity, we show that phagocytosis, NADPH oxidase activity, chemotaxis, and degranulation were maintained following Q-VD-OPh treatment, albeit to somewhat different extents. Thus, a single 10 μM dose of Q-VD-OPh can sustain human neutrophil viability and function for at least 5 days.

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.

Pregnancy Entails a Metabolic Rewiring of Maternal Circulating Neutrophils

Immunometabolism is an emerging growing field that focuses on the role of cellular metabolism in the regulation of immune cell function and fate. Thus, proliferation, differentiation, activation, and function of immune cell populations are modulated by reprogramming their fueling and metabolic pathways. Pregnancy entails a fine immune and metabolic regulation of the maternal-fetal interaction to assist the energetic demands of the fetus where trophoblast cells have a central role. Maternal neutrophil functional shaping by trophoblast cells has been proposed though their metabolic conditioning during pregnancy has not been studied yet. Here, we explored the effects of trophoblast-derived factors on the metabolic rewiring of neutrophils from nonpregnant women and its impact on central functions like reactive oxygen species (ROS) production, neutrophil extracellular trap (NET) release, and migration. In parallel, the immunometabolic status and function of neutrophils isolated from pregnant women (16-20 weeks) was compared with nonpregnant age-matched control samples. Trophoblast-derived factors induced glucose uptake and lipid droplet accumulation without activating ROS production or NET release. Conditioned media from trophoblast cells also inhibited PMA-induced NETosis partly by impairing glucose uptake in neutrophils. In turn, neutrophils from pregnant women had increased basal ROS production, lipid accumulation, and glucose uptake compared to neutrophils from nonpregnant women, accompanied by a higher release of PMA-induced NETs. Interestingly, PMA-induced NETs was blocked by a fatty acid oxidation inhibitor in neutrophils from pregnant women indicating the contribution of fatty acid metabolism to neutrophil activity during pregnancy. Results are consistent with immunometabolic mechanisms underlying the functional shaping of neutrophils during pregnancy and point out the contribution of trophoblast-derived factors to their metabolic profiling. These findings provide novel immunometabolic clues to understand immune homeostasis maintenance during pregnancy and raise the clinical potential of monitoring neutrophil metabolism during normal and complicated pregnancies.

Correlation between lncRNAs with human molecular chaperons in cancer immunopathogenesis and drug resistance

The development of cancer immunology heavily relies on the interaction between long non-coding RNAs (lncRNAs) and molecular chaperones. By participating in gene regulation, lncRNAs interact with molecular chaperones, which play a critical role in protein folding and stress responses, to influence oncogenic pathways. This interaction has an impact on both the immune cells within the tumor microenvironment and the tumor cells themselves. Understanding these mechanisms provides valuable insights into innovative approaches for diagnosis and treatment. Targeting the lncRNA-chaperone axis has the potential to strengthen anti-tumor immunity and enhance cancer treatment outcomes. Further research is necessary to uncover specific associations, identify biomarkers, and develop personalized therapies aimed at disrupting this axis, which could potentially revolutionize cancer diagnosis and treatment.

Metabolism: a potential regulator of neutrophil fate

Neutrophils are essential components of the innate immune system that defend against the invading pathogens, such as bacteria, viruses, and fungi, as well as having regulatory roles in various conditions, including tissue repair, cancer immunity, and inflammation modulation. The function of neutrophils is strongly related to their mode of cell death, as different types of cell death involve various cellular and molecular alterations. Apoptosis, a non-inflammatory and programmed type of cell death, is the most common in neutrophils, while other modes of cell death, including NETOsis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis, have specific roles in neutrophil function regulation. Immunometabolism refers to energy and substance metabolism in immune cells, and profoundly influences immune cell fate and immune system function. Intercellular and intracellular signal transduction modulate neutrophil metabolism, which can, in turn, alter their activities by influencing various cell signaling pathways. In this review, we compile an extensive body of evidence demonstrating the role of neutrophil metabolism in their various forms of cell death. The review highlights the intricate metabolic characteristics of neutrophils and their interplay with various types of cell death.

Metabolic landscape in venous thrombosis: insights into molecular biology and therapeutic implications

The findings of the last decade suggest a complex link between inflammatory cells, coagulation, and the activation of platelets and their synergistic interaction to promote venous thrombosis. Inflammation is present throughout the process of venous thrombosis, and various metabolic pathways of erythrocytes, endothelial cells, and immune cells involved in venous thrombosis, including glucose metabolism, lipid metabolism, homocysteine metabolism, and oxidative stress, are associated with inflammation. While the metabolic microenvironment has been identified as a marker of malignancy, recent studies have revealed that for cancer thrombosis, alterations in the metabolic microenvironment appear to also be a potential risk. In this review, we discuss how the synergy between metabolism and thrombosis drives thrombotic disease. We also explore the great potential of anti-inflammatory strategies targeting venous thrombosis and the complex link between anti-inflammation and metabolism. Furthermore, we suggest how we can use our existing knowledge to reduce the risk of venous thrombosis.

Single cell autofluorescence imaging reveals immediate metabolic shifts of neutrophils with activation across biological systems

Neutrophils, the most abundant leukocytes in human peripheral circulation, are crucial for the innate immune response. They are typically quiescent but rapidly activate in response to infection and inflammation, performing diverse functions such as oxidative burst, phagocytosis, and NETosis, which require significant metabolic adaptation. Deeper insights into such metabolic changes will help identify regulation of neutrophil functions in health and diseases. Due to their short lifespan and associated technical challenges, the metabolic processes of neutrophils are not completely understood. This study uses optical metabolic imaging (OMI), which entails optical redox ratio and fluorescence lifetime imaging microscopy of intrinsic metabolic coenzymes NAD(P)H and FAD to assess the metabolic state of single neutrophils. Primary human neutrophils were imaged in vitro under a variety of activation conditions and metabolic pathway inhibitors, while metabolic and functional changes were confirmed with mass spectrometry, oxidative burst, and NETosis measurements. Our findings show that neutrophils undergo rapid metabolic remodeling to a reduced redox state indicated by changes in NAD(P)H lifetime and optical redox ratio, with a shift to an oxidized redox state during activation. Additionally, single cell OMI analysis reveals a heterogeneous metabolic response across neutrophils and human donors to live pathogen infection ( Pseudomonas aeruginosa and Toxoplasma gondii ). Finally, consistent OMI changes with activation were confirmed between in vitro human and in vivo zebrafish larvae neutrophils. This study demonstrates the potential of OMI as a versatile tool for studying neutrophil metabolism and underscores its use across different biological systems, offering insights into neutrophil metabolic activity and function at a single cell level.

Simvastatin ameliorates adverse pregnancy by inhibiting glycolysis-related NETs in obstetrical antiphospholipid syndrome

AIMS

Some patients with Obstetric Antiphospholipid Syndrome (OAPS) still experience miscarriage and placental dysfunction after routine treatment, which is related to an abnormal increase in neutrophil extracellular traps (NETs). The labeling of statins has been revised to remove the contraindication for use during pregnancy. Our aim is to investigate the effect of Simvastatin on pregnancy outcomes in OAPS and its correlation mechanisms with NETs.

MAIN METHODS

The effect of Simvastatin on pregnancy outcomes was observed. The effect of simvastatin on the function and apoptosis of neutrophils has evaluated. The effect of Simvastatin to NETs and the changes in oxidative stress levels were observed. Different groups of NETs were extracted to intervene the HTR8-Svneo.RNA-seq analysis of the mechanism of which Simvastatin reduces NETs. Seahorse experiment detected the effect of Simvastatin on neutrophil glycolysis levels. Fluorescence co-localization and flow cytometry and Co-IP were used to verify relevant mechanisms.

KEY FINDINGS

In the OAPS mice, Simvastatin can reduce embryo absorption rate, reshape placental blood flow perfusion. Simultaneously reducing the production of NETs both in vivo and vitro, remolding oxidative stress. Simvastatin can improve neutrophil dysfunction caused by aPL-IgG. The reduction of NETs improved HTR8-Svneo's dysfunction. The intervention of Simvastatin on neutrophils under the stimulation of aPL-IgG showed a signature in glycolytic. The key rate limiting enzyme PKM2 in glycolysis interacts with Cit-H2b and PI3K/AKT signaling pathway.

SIGNIFICANCE

Our study providing basic theoretical support for the treatment of OAPS with Simvastatin.

Metabolic pathways fueling the suppressive activity of myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSC) are considered an aberrant population of immature myeloid cells that have attracted considerable attention in recent years due to their potent immunosuppressive activity. These cells are typically absent or present in very low numbers in healthy individuals but become abundant under pathological conditions such as chronic infection, chronic inflammation and cancer. The immunosuppressive activity of MDSC helps to control excessive immune responses that might otherwise lead to tissue damage. This same immunosuppressive activity can be detrimental, particularly in cancer and chronic infection. In the cancer setting, tumors can secrete factors that promote the expansion and recruitment of MDSC, thereby creating a local environment that favors tumor progression by inhibiting the effective immune responses against cancer cells. This has made MDSC a target of interest in cancer therapy, with researchers exploring strategies to inhibit their function or reduce their numbers to improve the efficacy of cancer immunotherapies. In the context of chronic infections, MDSC can lead to persistent infections by suppressing protective immune responses thereby preventing the clearance of pathogens. Therefore, targeting MDSC may provide a novel approach to improve pathogen clearance during chronic infections. Ongoing research on MDSC aims to elucidate the exact processes behind their expansion, recruitment, activation and suppressive mechanisms. In this context, it is becoming increasingly clear that the metabolism of MDSC is closely linked to their immunosuppressive function. For example, MDSC exhibit high rates of glycolysis, which not only provides energy but also generates metabolites that facilitate their immunosuppressive activity. In addition, fatty acid metabolic pathways, such as fatty acid oxidation (FAO), have been implicated in the regulation of MDSC suppressive activity. Furthermore, amino acid metabolism, particularly arginine metabolism mediated by enzymes such as arginase-1, plays a critical role in MDSC-mediated immunosuppression. In this review, we discuss the metabolic signature of MDSC and highlight the therapeutic implications of targeting MDSC metabolism as a novel approach to modulate their immunosuppressive functions.

TNF inhibitors target a mevalonate metabolite/TRPM2/calcium signaling axis in neutrophils to dampen vasculitis in Behçet's disease

TNF inhibitors have been used to treat autoimmune and autoinflammatory diseases. Here we report an unexpected mechanism underlying the therapeutic effects of TNF inhibitors in Behçet's disease (BD), an autoimmune inflammatory disorder. Using serum metabolomics and peripheral immunocyte transcriptomics, we find that polymorphonuclear neutrophil (PMN) from patients with BD (BD-PMN) has dysregulated mevalonate pathway and subsequently increased farnesyl pyrophosphate (FPP) levels. Mechanistically, FPP induces TRPM2-calcium signaling for neutrophil extracellular trap (NET) and proinflammatory cytokine productions, leading to vascular endothelial inflammation and damage. TNF, but not IL-1β, IL-6, IL-18, or IFN-γ, upregulates TRPM2 expression on BD-PMN, while TNF inhibitors have opposite effects. Results from mice with PMN-specific FPP synthetase or TRPM2 deficiency show reduced experimental vasculitis. Meanwhile, analyses of public datasets correlate increased TRPM2 expressions with the clinical benefits of TNF inhibitors. Our results thus implicate FPP-TRPM2-TNF/NETs feedback loops for inflammation aggravation, and novel insights for TNF inhibitor therapies on BD.

Lazy neutrophils - a lack of DGAT1 reduces the chemotactic activity of mouse neutrophils

BACKGROUND

Neutrophils are key players in the innate immune system, actively migrating to sites of inflammation in the highly energetic process of chemotaxis. In this study, we focus on the role of acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1), an enzyme that catalyzes the synthesis of triglycerides, the major form of stored energy, in neutrophil chemotaxis.

METHODS AND RESULTS

Using a mouse model of psoriasis, we show that DGAT1-deficiency reduces energy-demanding neutrophil infiltration to the site of inflammation, but this inhibition is not caused by decreased glycolysis and reduced ATP production by neutrophils lacking DGAT1. Flow cytometry and immunohistochemistry analysis demonstrate that DGAT1 also does not influence lipid accumulation in lipid droplets during inflammation. Interestingly, as has been shown previously, a lack of DGAT1 leads to an increase in the concentration of retinoic acid, and here, using real-time PCR and publicly-available next-generation RNA sequencing datasets, we show the upregulation of retinoic acid-responsive genes in Dgat1KO neutrophils. Furthermore, supplementation of WT neutrophils with exogenous retinoic acid mimics DGAT1-deficiency in the inhibition of neutrophil chemotaxis in in vitro transwell assay.

CONCLUSIONS

These results suggest that impaired skin infiltration by neutrophils in Dgat1KO mice is a result of the inhibitory action of an increased concentration of retinoic acid, rather than impaired lipid metabolism in DGAT1-deficient mice.

Osteocalcin-expressing neutrophils from skull bone marrow exert immunosuppressive and neuroprotective effects after TBI

Neutrophils from skull bone marrow (Nskull) are activated under some brain stresses, but their effects on traumatic brain injury (TBI) are lacking. Here, we find Nskull infiltrates brain tissue quickly and persistently after TBI, which is distinguished by highly and specifically expressed osteocalcin (OCN) from blood-derived neutrophils (Nblood). Reprogramming of glucose metabolism by reducing glycolysis-related enzyme glyceraldehyde 3-phosphate dehydrogenase expression is involved in the antiapoptotic and proliferative abilities of OCN-expressing Nskull. The transcription factor Fos-like 1 governs the specific gene profile of Nskull including C-C motif chemokine receptor-like 2 (CCRL2), arginase 1 (Arg1), and brain-derived neurotrophic factor (BDNF) in addition to OCN. Selective knockout of CCRL2 in Nskull demonstrates that CCRL2 mediates its recruitment, whereas high Arg1 expression is consistent with its immunosuppressive effects on Nblood, and the secretion of BDNF facilitating dendritic growth contributes to its neuroprotection. Thus, our findings provide insight into the roles of Nskull in TBI.

Activation induces shift in nutrient utilization that differentially impacts cell functions in human neutrophils

Neutrophils utilize a variety of metabolic sources to support their crucial functions as the first responders in innate immunity. Here, through in vivo and ex vivo isotopic tracing, we examined the contributions of different nutrients to neutrophil metabolism under specific conditions. Human peripheral blood neutrophils, in contrast to a neutrophil-like cell line, rely on glycogen storage as a major metabolic source under resting state but rapidly switch to primarily using extracellular glucose upon activation with various stimuli. This shift is driven by a substantial increase in glucose uptake, enabled by rapidly increased GLUT1 on cell membrane, that dominates the simultaneous increase in gross glycogen cycling capacity. Shifts in nutrient utilization impact neutrophil functions in a function-specific manner: oxidative burst depends on glucose utilization, whereas NETosis and phagocytosis can be flexibly supported by either glucose or glycogen, and neutrophil migration and fungal control are enhanced by the shift from glycogen utilization to glucose utilization. This work provides a quantitative and dynamic understanding of fundamental features in neutrophil metabolism and elucidates how metabolic remodeling shapes neutrophil functions, which has broad health relevance.

Diagnostic accuracy of the neutrophil-to-lymphocyte ratio and the platelet-to-lymphocyte ratio in rheumatoid arthritis: a systematic review and meta-analysis

Existing challenges with the early diagnosis of rheumatoid arthritis (RA) and active disease, mainly by non-rheumatologists, have prompted the search for novel biomarkers. Elevations in indices derived from blood cell counts, e.g., the neutrophil-to-lymphocyte ratio (NLR) and the platelet-to-lymphocyte ratio (PLR), have been reported in RA patients. However, their diagnostic accuracy has not been comprehensively assessed. Therefore, we conducted a systematic review and meta-analysis of studies reporting the sensitivity and specificity of the NLR and PLR, obtained by receiver operating characteristic (ROC) curve analysis, for the presence of RA and active disease. We searched electronic databases from inception to 15 March 2024 and assessed the risk of bias using the JBI Critical Appraisal Checklist (PROSPERO registration number: CRD42024533546). In 15 studies, the NLR exhibited acceptable accuracy for the presence of RA (area under the curve, AUC = 0.76, 95% CI 0.72 to 0.80) and active disease (AUC = 0.70, 95% CI 0.66 to 0.74). The PLR exhibited good accuracy for the presence of RA (AUC = 0.80, 95% CI 0.76 to 0.83). There were insufficient studies to assess the accuracy of the PLR for the presence of active disease. Our systematic review and meta-analysis suggests that the NLR and the PLR are promising biomarkers of RA (NLR and PLR) and active disease (NLR). Further research is required to investigate whether the NLR and PLR can significantly enhance the capacity to diagnose RA and active disease in clinical practice.

Metabolic regulation of neutrophil functions in homeostasis and diseases

Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.

Dietary fats as regulators of neutrophil plasticity: an update on molecular mechanisms

PURPOSE OF REVIEW

Contemporary guidelines for the prevention of cardio-metabolic diseases focus on the control of dietary fat intake, because of their adverse metabolic effects. Moreover, fats alter innate immune defenses, by eliciting pro-inflammatory epigenetic mechanisms on the long-living hematopoietic cell progenitors which, in the bone marrow, mainly give rise to short-living neutrophils. Nevertheless, the heterogenicity of fats and the complexity of the biology of neutrophils pose challenges in the understanding on how this class of nutrients could contribute to the development of cardio-metabolic diseases via specific molecular mechanisms activating the inflammatory response.

RECENT FINDINGS

The knowledge on the biology of neutrophils is expanding and there are now different cellular networks orchestrating site-specific reprogramming of these cells to optimize the responses against pathogens. The innate immune competence of neutrophil is altered in response to high fat diet and contributes to the development of metabolic alterations, although the precise mechanisms are still poorly understood.

SUMMARY

Defining the different molecular mechanisms involved in the fat-neutrophil crosstalk will help to reconcile the sparse data about the interaction of dietary fats with neutrophils and to tailor strategies to target neutrophils in the context of cardio-metabolic diseases.

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.

Intersection of the microbiome and immune metabolism in lupus

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

Involvement of tumor immune microenvironment metabolic reprogramming in colorectal cancer progression, immune escape, and response to immunotherapy

Metabolic reprogramming is a k`ey hallmark of tumors, developed in response to hypoxia and nutrient deficiency during tumor progression. In both cancer and immune cells, there is a metabolic shift from oxidative phosphorylation (OXPHOS) to aerobic glycolysis, also known as the Warburg effect, which then leads to lactate acidification, increased lipid synthesis, and glutaminolysis. This reprogramming facilitates tumor immune evasion and, within the tumor microenvironment (TME), cancer and immune cells collaborate to create a suppressive tumor immune microenvironment (TIME). The growing interest in the metabolic reprogramming of the TME, particularly its significance in colorectal cancer (CRC)-one of the most prevalent cancers-has prompted us to explore this topic. CRC exhibits abnormal glycolysis, glutaminolysis, and increased lipid synthesis. Acidosis in CRC cells hampers the activity of anti-tumor immune cells and inhibits the phagocytosis of tumor-associated macrophages (TAMs), while nutrient deficiency promotes the development of regulatory T cells (Tregs) and M2-like macrophages. In CRC cells, activation of G-protein coupled receptor 81 (GPR81) signaling leads to overexpression of programmed death-ligand 1 (PD-L1) and reduces the antigen presentation capability of dendritic cells. Moreover, the genetic and epigenetic cell phenotype, along with the microbiota, significantly influence CRC metabolic reprogramming. Activating RAS mutations and overexpression of epidermal growth factor receptor (EGFR) occur in approximately 50% and 80% of patients, respectively, stimulating glycolysis and increasing levels of hypoxia-inducible factor 1 alpha (HIF-1α) and MYC proteins. Certain bacteria produce short-chain fatty acids (SCFAs), which activate CD8+ cells and genes involved in antigen processing and presentation, while other mechanisms support pro-tumor activities. The use of immune checkpoint inhibitors (ICIs) in selected CRC patients has shown promise, and the combination of these with drugs that inhibit aerobic glycolysis is currently being intensively researched to enhance the efficacy of immunotherapy.

TREM1 facilitates the development of gastric cancer through regulating neutrophil extracellular traps-mediated macrophage polarization

Triggering receptor expressed on myeloid cell 1 (TREM1) elevation is associated with the unfavorable prognosis of gastric cancer (GC) patients. This work uncovered the effects and mechanism of TREM1 in GC. IHC staining examined TREM1 expression in GC tissues. TREM1-knockout and TREM1 knock-in mice were generated prior to the construction of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced GC mice model. H&E staining detected the pathological alternations of gastric tissues. IHC staining tested Ki67 expression. Wright-Giemsa staining performed neutrophil counting and flow cytometry analysis measured neutrophil infiltration. ELISA analyzed serum and tissue myeloperoxidase (MPO) levels and serum MPO-DNA levels. Immunofluorescence, Western blotting and related kits detected NETs formation. Immunofluorescence and IHC staining evaluated macrophage polarization. In MNNG-treated GES-1 cells and phorbal myristate acetate (PMA)-treated neutrophils, TREM1 expression was also examined. CCK-8 method and Western blotting assayed cell proliferation. Western blotting and immunofluorescence detected NETs formation. Flow cytometry analysis detected the changes of macrophage typing. TREM1 was overexpressed in tumor tissues, MNNG-treated GES-1 cells and PMA-treated neutrophils. TREM1 deficiency hindered tumor growth, reduced neutrophil infiltration, NETs formation and stimulated M1 macrophage polarization in MNNG-induced GC models. Neutrophil extracellular traps (NETs) degrader DNase-1 countervailed the impacts of TREM1 on MNNG-induced GC models in vivo. Collectively, TREM1 knockdown obstructed NETs-mediated M2 macrophage polarization to hamper GC progression.

Immune cells crosstalk Pathways, and metabolic alterations in Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) presents a challenging progression characterized by lung tissue scarring and abnormal extracellular matrix deposition. This review examines the influence of immune responses, emphasizing their complex role in initiating and perpetuating fibrosis. It highlights how metabolic pathways modulate immune cell function during IPF. Immune cell modulation holds promise in managing pulmonary fibrosis (PF). Inhibiting neutrophil recruitment and monitoring mast cell levels offer insights into PF progression. Low-dose IL-2 therapy and regulation of fibroblast recruitment present potential therapeutic avenues, while the role of innate lymphoid cells (ILC2s) in allergic lung inflammation sheds light on disease mechanisms. The review focuses on metabolic reprogramming's role in shaping immune cell function during IPF progression. While some immune cells use glycolysis for pro-inflammatory responses, others favor fatty acid oxidation for regulatory functions. Targeting specialized pro-resolving lipid mediators (SPMs) presents significant potential for managing fibrotic disorders. Additionally, it highlights the pivotal role of amino acid metabolism in synthesizing serine and glycine as crucial regulators of collagen production and exploring the interconnectedness of lipid metabolism, mitochondrial dysfunction, and adipokines in driving fibrotic processes. Moreover, the review discusses the impact of metabolic disorders such as obesity and diabetes on lung fibrosis. Advocating for a holistic approach, it emphasizes the importance of considering this interplay between immune cell function and metabolic pathways in developing effective and personalized treatments for IPF.

Neutrophil glucose flux as a therapeutic target in antiphospholipid syndrome

Neutrophil hyperactivity and neutrophil extracellular trap release (NETosis) appear to play important roles in the pathogenesis of the thromboinflammatory autoimmune disease known as antiphospholipid syndrome (APS). The understanding of neutrophil metabolism has advanced tremendously in the past decade, and accumulating evidence suggests that a variety of metabolic pathways guide neutrophil activities in health and disease. Our previous work characterizing the transcriptome of APS neutrophils revealed that genes related to glycolysis, glycogenolysis, and the pentose phosphate pathway (PPP) were significantly upregulated. Here, we found that neutrophils from patients with APS used glycolysis more avidly than neutrophils from people in the healthy control group, especially when the neutrophils were from patients with APS with a history of microvascular disease. In vitro, inhibiting either glycolysis or the PPP tempered phorbol myristate acetate- and APS IgG-induced NETosis, but not NETosis triggered by a calcium ionophore. In mice, inhibiting either glycolysis or the PPP reduced neutrophil reactive oxygen species production and suppressed APS IgG-induced NETosis ex vivo. When APS-associated thrombosis was evaluated in mice, inhibiting either glycolysis or the PPP markedly suppressed thrombosis and circulating NET remnants. In summary, these data identify a potential role for restraining neutrophil glucose flux in the treatment of APS.

13C-metabolic flux analysis reveals metabolic rewiring in HL-60 neutrophil-like cells through differentiation and immune stimulation

Neutrophils are innate immune cells and the first line of defense for the maintenance of homeostasis. However, our knowledge of the metabolic rewiring associated with their differentiation and immune stimulation is limited. Here, quantitative 13C-metabolic flux analysis was performed using HL-60 cells as the neutrophil model. A metabolic model for 13C-metabolic flux analysis of neutrophils was developed based on the accumulation of 13C in intracellular metabolites derived from 13C-labeled extracellular carbon sources and intracellular macromolecules. Aspartate and glutamate in the medium were identified as carbon sources that enter central carbon metabolism. Furthermore, the breakdown of macromolecules, estimated to be fatty acids and nucleic acids, was observed. Based on these results, a modified metabolic model was used for 13C-metabolic flux analysis of undifferentiated, differentiated, and lipopolysaccharide (LPS)-activated HL-60 cells. The glucose uptake rate and glycolytic flux decreased with differentiation, whereas the tricarboxylic acid (TCA) cycle flux remained constant. The addition of LPS to differentiated HL-60 cells activated the glucose uptake rate and pentose phosphate pathway (PPP) flux levels, resulting in an increased rate of total NADPH regeneration, which could be used to generate reactive oxygen species. The flux levels of fatty acid degradation and synthesis were also increased in LPS-activated HL-60 cells. Overall, this study highlights the quantitative metabolic alterations in multiple pathways via the differentiation and activation of HL-60 cells using 13C-metabolic flux analysis.

Diabetes Primes Neutrophils for Neutrophil Extracellular Trap Formation through Trained Immunity

Neutrophils are primed for neutrophil extracellular trap (NET) formation during diabetes, and excessive NET formation from primed neutrophils compromises wound healing in patients with diabetes. Here, we demonstrate that trained immunity mediates diabetes-induced NET priming in neutrophils. Under diabetic conditions, neutrophils exhibit robust metabolic reprogramming comprising enhanced glycolysis via the pentose phosphate pathway and fatty acid oxidation, which result in the accumulation of acetyl-coenzyme A. Adenosine 5'-triphosphate-citrate lyase-mediated accumulation of acetyl-coenzyme A and histone acetyltransferases further induce the acetylation of lysine residues on histone 3 (AcH3K9, AcH3K14, and AcH3K27) and histone 4 (AcH4K8). The pharmacological inhibition of adenosine 5'-triphosphate-citrate lyase and histone acetyltransferases completely inhibited high-glucose-induced NET priming. The trained immunity of neutrophils was further confirmed in neutrophils isolated from patients with diabetes. Our findings suggest that trained immunity mediates functional changes in neutrophils in diabetic environments, and targeting neutrophil-trained immunity may be a potential therapeutic target for controlling inflammatory complications of diabetes.

Stress hyperglycaemia following trauma - a survival benefit or an outcome detriment?

PURPOSE OF REVIEW

Stress hyperglycaemia occur often in critically injured patients. To gain new consideration about it, this review compile current as well as known immunological and biochemical findings about causes and emergence.

RECENT FINDINGS

Glucose is the preferred energy substrate for fending immune cells, reparative tissue and the cardiovascular system following trauma. To fulfil these energy needs, the liver is metabolically reprogrammed to rebuild glucose from lactate and glucogenic amino acids (hepatic insulin resistance) at the expenses of muscles mass and - to a less extent - fat tissue (proteolysis, lipolysis, peripheral insulin resistance). This inevitably leads to stress hyperglycaemia, which is evolutionary preserved and seems to be an essential and beneficial survival response. It is initiated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs), intensified by immune cells itself and mainly ruled by tumour necrosis factor (TNF)α and catecholamines with lactate and hypoxia inducible factor (HIF)-1α as intracellular signals and lactate as an energy shuttle. Important biochemical mechanisms involved in this response are the Warburg effect as an efficient metabolic shortcut and the extended Cori cycle.

SUMMARY

Stress hyperglycaemia is beneficial in an acute life-threatening situation, but further research is necessary, to prevent trauma patients from the detrimental effects of persisting hyperglycaemia.

AIRE is expressed in breast cancer TANs and TAMs to regulate the extrinsic apoptotic pathway and inflammation

The autoimmune regulator (AIRE) is a transcriptional regulator expressed in the thymus and is necessary for maintaining immunological self-tolerance. Extrathymic AIRE expression is rare, and a role for AIRE in tumor-associated innate immune cells has not yet been established. In this study, we show that AIRE is expressed in human pro-tumor neutrophils. In breast cancer, AIRE was primarily located to tumor-associated neutrophils (TANs), and to a lesser extent to tumor-associated macrophages (TAMs) and tumor cells. Expression of AIRE in TAN/TAMs, but not in cancer cells, was associated with an adverse prognosis. We show that the functional role for AIRE in neutrophils and macrophages is to regulate expression of immune mediators and the extrinsic apoptotic pathway involving the Fas/TNFR death receptors and cathepsin G. Here, we propose that the role for AIRE in TAN/TAMs in breast tumors is to regulate cell death and inflammation, thus promoting tumor progression.

Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis

Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.

Granulocytic myeloid-derived suppressor cell activity during biofilm infection is regulated by a glycolysis/HIF1a axis

Staphylococcus aureus is a leading cause of biofilm-associated prosthetic joint infection (PJI). A primary contributor to infection chronicity is an expansion of granulocytic myeloid-derived suppressor cells (G-MDSCs), which are critical for orchestrating the antiinflammatory biofilm milieu. Single-cell sequencing and bioinformatic metabolic algorithms were used to explore the link between G-MDSC metabolism and S. aureus PJI outcome. Glycolysis and the hypoxia response through HIF1a were significantly enriched in G-MDSCs. Interfering with both pathways in vivo, using a 2-deoxyglucose nanopreparation and granulocyte-targeted Hif1a conditional KO mice, respectively, attenuated G-MDSC-mediated immunosuppression and reduced bacterial burden in a mouse model of S. aureus PJI. In addition, single-cell RNA-Seq (scRNA-Seq) analysis of granulocytes from PJI patients also showed an enrichment in glycolysis and hypoxia-response genes. These findings support the importance of a glycolysis/HIF1a axis in promoting G-MDSC antiinflammatory activity and biofilm persistence during PJI.

Dinner date: Neisseria gonorrhoeae central carbon metabolism and pathogenesis

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, is a human-adapted pathogen that does not productively infect other organisms. The ongoing relationship between N. gonorrhoeae and the human host is facilitated by the exchange of nutrient resources that allow for N. gonorrhoeae growth in the human genital tract. What N. gonorrhoeae 'eats' and the pathways used to consume these nutrients have been a topic of investigation over the last 50 years. More recent investigations are uncovering the impact of N. gonorrhoeae metabolism on infection and inflammatory responses, the environmental influences driving N. gonorrhoeae metabolism, and the metabolic adaptations enabling antimicrobial resistance. This mini-review is an introduction to the field of N. gonorrhoeae central carbon metabolism in the context of pathogenesis. It summarizes the foundational work used to characterize N. gonorrhoeae central metabolic pathways and the effects of these pathways on disease outcomes, and highlights some of the most recent advances and themes under current investigation. This review ends with a brief description of the current outlook and technologies under development to increase understanding of how the pathogenic potential of N. gonorrhoeae is enabled by metabolic adaptation.

Overcoming the limitations of immunotherapy in pancreatic ductal adenocarcinoma: Combining radiotherapy and metabolic targeting therapy

As a novel anticancer therapy, immunotherapy has demonstrated robust efficacy against a few solid tumors but poor efficacy against pancreatic ductal adenocarcinoma (PDAC). This poor outcome is primarily attributable to the intrinsic cancer cell resistance and T-cell exhaustion, which is also the reason for the failure of conventional therapy. The present review summarizes the current PDAC immunotherapy avenues and the underlying resistance mechanisms. Then, the review discusses synergistic combination therapies, such as radiotherapy (RT) and metabolic targeting. Research suggests that RT boosts the antigen of PDAC, which facilitates the anti-tumor immune cell infiltration and exerts function. Metabolic reprogramming contributes to restoring the exhausted T cell function. The current review will help in tailoring combination regimens to enhance the efficacy of immunotherapy. In addition, it will help provide new approaches to address the limitations of the immunosuppressive tumor microenvironment (TME) by examining the relationship among immunotherapy, RT, and metabolism targeting therapy in PDAC.

Redox processes are major regulators of leukotriene synthesis in neutrophils exposed to bacteria Salmonella typhimurium; the way to manipulate neutrophil swarming

Neutrophils play a primary role in protecting our body from pathogens. When confronted with invading bacteria, neutrophils begin to produce leukotriene B4, a potent chemoattractant that, in cooperation with the primary bacterial chemoattractant fMLP, stimulates the formation of swarms of neutrophils surrounding pathogens. Here we describe a complex redox regulation that either stimulates or inhibits fMLP-induced leukotriene synthesis in an experimental model of neutrophils interacting with Salmonella typhimurium. The scavenging of mitochondrial reactive oxygen species by mitochondria-targeted antioxidants MitoQ and SkQ1, as well as inhibition of their production by mitochondrial inhibitors, inhibit the synthesis of leukotrienes regardless of the cessation of oxidative phosphorylation. On the contrary, antioxidants N-acetylcysteine and sodium hydrosulfide promoting reductive shift in the reversible thiol-disulfide system stimulate the synthesis of leukotrienes. Diamide that oxidizes glutathione at high concentrations inhibits leukotriene synthesis, and the glutathione precursor S-adenosyl-L-methionine prevents this inhibition. Diamide-dependent inhibition is also prevented by diphenyleneiodonium, presumably through inhibition of NADPH oxidase and NADPH accumulation. Thus, during bacterial infection, maintaining the reduced state of glutathione in neutrophils plays a decisive role in the synthesis of leukotriene B4. Suppression of excess leukotriene synthesis is an effective strategy for treating various inflammatory pathologies. Our data suggest that the use of mitochondria-targeted antioxidants may be promising for this purpose, whereas known thiol-based antioxidants, such as N-acetylcysteine, may dangerously stimulate leukotriene synthesis by neutrophils during severe pathogenic infection.

A metabolic perspective of the neutrophil life cycle: new avenues in immunometabolism

Neutrophils are the most abundant innate immune cells. Multiple mechanisms allow them to engage a wide range of metabolic pathways for biosynthesis and bioenergetics for mediating biological processes such as development in the bone marrow and antimicrobial activity such as ROS production and NET formation, inflammation and tissue repair. We first discuss recent work on neutrophil development and functions and the metabolic processes to regulate granulopoiesis, neutrophil migration and trafficking as well as effector functions. We then discuss metabolic syndromes with impaired neutrophil functions that are influenced by genetic and environmental factors of nutrient availability and usage. Here, we particularly focus on the role of specific macronutrients, such as glucose, fatty acids, and protein, as well as micronutrients such as vitamin B3, in regulating neutrophil biology and how this regulation impacts host health. A special section of this review primarily discusses that the ways nutrient deficiencies could impact neutrophil biology and increase infection susceptibility. We emphasize biochemical approaches to explore neutrophil metabolism in relation to development and functions. Lastly, we discuss opportunities and challenges to neutrophil-centered therapeutic approaches in immune-driven diseases and highlight unanswered questions to guide future discoveries.

E-cigarette vapor renders neutrophils dysfunctional due to filamentous actin accumulation

BACKGROUND

Electronic cigarette (e-cigarette) use continues to rise despite concerns of long-term effects, especially the risk of developing lung diseases such as chronic obstructive pulmonary disease. Neutrophils are central to the pathogenesis of chronic obstructive pulmonary disease, with changes in phenotype and function implicated in tissue damage.

OBJECTIVE

We sought to measure the impact of direct exposure to nicotine-containing and nicotine-free e-cigarette vapor on human neutrophil function and phenotype.

METHODS

Neutrophils were isolated from the whole blood of self-reported nonsmoking, nonvaping healthy volunteers. Neutrophils were exposed to 40 puffs of e-cigarette vapor generated from e-cigarette devices using flavorless e-cigarette liquids with and without nicotine before functions, deformability, and phenotype were assessed.

RESULTS

Neutrophil surface marker expression was altered, with CD62L and CXCR2 expression significantly reduced in neutrophils treated with e-cigarette vapor containing nicotine. Neutrophil migration to IL-8, phagocytosis of Escherichia coli and Staphylococcus aureus pHrodo bioparticles, oxidative burst response, and phorbol 12-myristate 13-acetate-stimulated neutrophil extracellular trap formation were all significantly reduced by e-cigarette vapor treatments, independent of nicotine content. E-cigarette vapor induced increased levels of baseline polymerized filamentous actin levels in the cytoplasm, compared with untreated controls.

CONCLUSIONS

The significant reduction in effector neutrophil functions after exposure to high-power e-cigarette devices, even in the absence of nicotine, is associated with excessive filamentous actin polymerization. This highlights the potentially damaging impact of vaping on respiratory health and reinforces the urgency of research to uncover the long-term health implications of e-cigarettes.

The metabolic basis of inherited neutropenias

Neutrophils are the shortest-lived blood cells, which requires a prodigious degree of proliferation and differentiation to sustain physiologically sufficient numbers and be poised to respond quickly to infectious emergencies. More than 107 neutrophils are produced every minute in an adult bone marrow-a process that is tightly regulated by a small group of cytokines and chemical mediators and dependent on nutrients and energy. Like granulocyte colony-stimulating factor, the primary growth factor for granulopoiesis, they stimulate signalling pathways, some affecting metabolism. Nutrient or energy deficiency stresses the survival, proliferation, and differentiation of neutrophils and their precursors. Thus, it is not surprising that monogenic disorders related to metabolism exist that result in neutropenia. Among these are pathogenic mutations in HAX1, G6PC3, SLC37A4, TAFAZZIN, SBDS, EFL1 and the mitochondrial disorders. These mutations perturb carbohydrate, lipid and/or protein metabolism. We hypothesize that metabolic disturbances may drive the pathogenesis of a subset of inherited neutropenias just as defects in DNA damage response do in Fanconi anaemia, telomere maintenance in dyskeratosis congenita and ribosome formation in Diamond-Blackfan anaemia. Greater understanding of metabolic pathways in granulopoiesis will identify points of vulnerability in production and may point to new strategies for the treatment of neutropenias.

Perturbational phenotyping of human blood cells reveals genetically determined latent traits associated with subsets of common diseases

Although genome-wide association studies (GWAS) have successfully linked genetic risk loci to various disorders, identifying underlying cellular biological mechanisms remains challenging due to the complex nature of common diseases. We established a framework using human peripheral blood cells, physical, chemical and pharmacological perturbations, and flow cytometry-based functional readouts to reveal latent cellular processes and performed GWAS based on these evoked traits in up to 2,600 individuals. We identified 119 genomic loci implicating 96 genes associated with these cellular responses and discovered associations between evoked blood phenotypes and subsets of common diseases. We found a population of pro-inflammatory anti-apoptotic neutrophils prevalent in individuals with specific subsets of cardiometabolic disease. Multigenic models based on this trait predicted the risk of developing chronic kidney disease in type 2 diabetes patients. By expanding the phenotypic space for human genetic studies, we could identify variants associated with large effect response differences, stratify patients and efficiently characterize the underlying biology.