Metabolic and Epigenetic Coordination of T Cell and Macrophage Immunity

Pyruvate Carboxylase in Macrophages Aggravates Atherosclerosis by Regulating Metabolism Reprogramming to Promote Inflammatory Responses Through the Hypoxia-Inducible Factor-1 Signaling Pathway

Atherosclerosis (AS) is a major cause of cardiovascular diseases, driven by chronic inflammation and macrophage polarization toward a proinflammatory phenotype. Pyruvate carboxylase (PC), a mitochondrial enzyme involved in glucose metabolism, is implicated in various metabolic disorders; however, its role in AS remains unclear. This study aims to investigate the role and mechanism of PC on macrophages in AS. PC is upregulated in macrophages of humans and mice with AS. Myeloid cell-specific PC knockout mice are generated to investigate the effects of PC deletion on atherosclerotic plaque formation. Myeloid cell-specific PC deficiency mitigates high-fat diet-induced atherosclerotic lesions in apolipoprotein E knockout mice and mice injected with adeno-associated virus-PCSK9DY. PC deletion enhances mitochondrial respiration and reduces glycolytic activity, thereby reducing reactive oxygen species overproduction and mitochondrial damage in macrophages. PC activates the hypoxia-inducible factor-1 (HIF-1) signaling pathway through macrophage metabolic reprogramming. PC induces nuclear translocation of HIF-1α in atherosclerotic aortic roots by preventing HIF-1α from proteasome degradation. HIF-1α stabilizer reverses the anti-inflammatory effect of macrophage-PC ablation in atherogenesis; however, inhibiting HIF-1α suppresses the proinflammatory macrophage phenotype induced by PC overexpression. This study indicates that macrophage PC aggravates AS through macrophage metabolic reprogramming, promoting inflammatory responses in macrophages through the HIF-1 signaling pathway.

Succinate-loaded tumor cell-derived microparticles reprogram tumor-associated macrophage metabolism

The tumor microenvironment predominantly polarizes tumor-associated macrophages (TAMs) toward an M2-like phenotype, thereby inhibiting antitumor immune responses. This process is substantially affected by metabolic reprogramming; however, reeducating TAMs to enhance their antitumor capabilities through metabolic remodeling remains a challenge. Here, we show that tumor-derived microparticles loaded with succinate (SMPs) can remodel the metabolic state of TAMs. SMPs promote classical M1-like polarization of macrophages by enhancing glycolysis and attenuating the tricarboxylic acid (TCA) cycle in a protein succinylation-dependent manner. Mechanistically, succinate is delivered into the mitochondria and nucleus by SMPs, leading to succinylation of isocitrate dehydrogenase 2 (IDH2) and histone H3K122 within the lactate dehydrogenase A (Ldha) promoter region. Our findings provide a distinct approach for TAM polarization using cell membrane-derived microparticles loaded with endogenous metabolites, a platform that may be used more broadly for posttranslational modification-based tumor immunotherapy.

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

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

Metabolic reprogram and T cell differentiation in inflammation: current evidence and future perspectives

T cell metabolism and differentiation significantly shape the initiation, progression, and resolution of inflammatory responses. Upon activation, T cells undergo extensive metabolic shifts to meet distinct functional demands across various inflammatory stages. These metabolic alterations are not only critical for defining different T cell subsets, but also for sustaining their activity in inflammatory environments. Key signaling pathways-including mTOR, HIF-1α, and AMPK regulate these metabolic adaptions, linking cellular energy states with T cell fate decisions. Insights into the metabolic regulation of T cells offer potential therapeutic strategies to manipulate T cell function, with implications for treating autoimmune diseases, chronic inflammation, and cancer by targeting specific metabolic pathways.

Single cell immunoprofile of synovial fluid in rheumatoid arthritis with TNF/JAK inhibitor treatment

Numerous patients with rheumatoid arthritis (RA) manifest severe syndromes, including elevated synovial fluid volumes (SF) with abundant immune cells, which can be controlled by TNF/JAK inhibitors. Here, we apply single-cell RNA sequencing (scRNA-seq) and subsequent validations in SF from RA patients. These analyses of synovial tissue show reduced density of SF-derived pathogenic cells (e.g., SPP1+ macrophages and CXCL13+CD4+ T cells), altered gene expression (e.g., SPP1 and STAT1), molecular pathway changes (e.g., JAK/STAT), and cell-cell communications in drug-specific manners in samples from patients pre-/post-treated with adalimumab/tofacitinib. Particularly, SPP1+ macrophages exhibit pronounced communication with CXCL13+CD4+ T cells, which are abolished after treatment and correlate with treatment efficacy. These pathogenic cell types alone or in combination can augment inflammation of fibroblast-like synoviocytes in vitro, while conditional Spp1 knocking-out reduces RA-related cytokine expression in collagen-induced arthritis mice models. Our study shows the functional role of SF-derived pathogenic cells in progression and drug-specific treatment outcomes in RA.

Metabolism-epigenetic interaction-based bone and dental regeneration: From impacts and mechanisms to treatment potential

Metabolic pathways exhibit fluctuating activities during bone and dental loss and defects, suggesting a regulated metabolic plasticity. Skeletal remodeling is an energy-demanding process related to altered metabolic activities. These metabolic changes are frequently associated with epigenetic modifications, including variations in the expression or activity of enzymes modified through epigenetic mechanisms, which directly or indirectly impact cellular metabolism. Metabolic reprogramming driven by bone and dental conditions alters the epigenetic landscape by modulating the activities of DNA and histone modification enzymes at the metabolite level. Epigenetic mechanisms modulate the expression of metabolic genes, consequently influencing the metabolome. The interplay between epigenetics and metabolomics is crucial in maintaining bone and dental homeostasis by preserving cell proliferation and pluripotency. This review, therefore, aims to examine the effects of metabolic reprogramming in bone and dental-related cells on the regulation of epigenetic modifications, particularly acetylation, methylation, and lactylation. We also discuss the effects of chromatin-modifying enzymes on metabolism and the potential therapeutic benefits of dietary compounds as epigenetic modulators. In this review, we highlight the inconsistencies in current research findings and suggest potential approaches to translate fundamental insights into clinical treatments for bone and tooth diseases.

Short-chain fatty acids in viral infection: the underlying mechanisms, opportunities, and challenges

Viral infections can cause cellular pathway derangements, cell death, and immunopathological responses, leading to host inflammation. Short-chain fatty acids (SCFAs), produced by the microbiota, have emerged as a potential therapeutic for viral infections due to their ability to modulate these processes. However, SCFAs have been reported to have both beneficial and detrimental effects, necessitating a comprehensive understanding of the underlying mechanisms. This review highlights the complex mechanisms underlying SCFAs' effects on viral infection outcomes. We also emphasize the importance of considering how SCFAs' activities may differ under diverse contexts, including but not limited to target cells with different metabolic wiring, different viral causes of infection, the target organism/cell's nutrient availability and/or energy balance, and hosts with varying microbiome compositions.

Microenvironmental β-TrCP negates amino acid transport to trigger CD8+ T cell exhaustion in human non-small cell lung cancer

CD8+ T cell exhaustion (Tex) has been widely acknowledged in human cancer, while the underlying mechanisms remain unclear. Here, we demonstrate that reduced amino acid (aa) metabolism and mTOR inactivation are accountable for Tex in human non-small cell lung cancer (NSCLC). NSCLC cells impede the T cell-intrinsic transcription of SLC7A5 and SLC38A1, disrupting aa transport and consequently leading to mTOR inactivation. Further, the ubiquitination of YAP1 protein is the basis for NSCLC-mediated transcriptional inhibition of aa transporters. Mechanistically, NSCLC cells transfer β-TrCP-containing exosomes into T cells, inducing YAP1 ubiquitination and Tex. Consequently, inhibiting cancer-associated β-TrCP effectively restores the anti-tumor immune response of CD8+ T cells and curtails tumor growth in NSCLC patient-derived organoids. Together, our findings highlight a β-TrCP-dependent mechanism in steering intrinsic metabolic adaptation and CD8+ Tex, emphasizing microenvironmental β-TrCP as an immune checkpoint for therapeutic exploration against human NSCLC.

Global Trends in Research of Amino Acid Metabolism in T Lymphocytes in Recent 15 Years: A Bibliometric Analysis

Amino acid metabolism in T cells determines the therapeutic efficacy of T-cell-targeting drugs. To assess the direction of amino acid metabolism in T cells and construct related knowledge structure, we performed a bibliometric analysis aiming at amino acid metabolism in T cells utilizing studies publicized in recent 15 years. Three hundred thirty-seven related studies were downloaded from the Web of Science Core Collection (WoSCC), and the information on countries, institutes, and authors was collected and analyzed. In addition, the present research status and future trends were explored according to the results yielded from the analysis of cited references and keywords. This study revealed that publications regarding amino acid metabolism in T cells gradually increased each year. The USA is the top producer and most influential country in this field. Recent research has focused on the correlation between the metabolism of several amino acids and regulatory T cells (Tregs) and CD8+ T cells. Overall, this research offers a comprehensive exhibition on the field of amino acid metabolism in T cells, which will help researchers to study this domain more effectively and intuitively.

Immune senescence: A key player in cancer biology

With the rapid development of immunological techniques in recent years, our understanding of immune senescence has gradually deepened, but the role of immune senescence in cancer biology remains incompletely elucidated. Understanding these mechanisms and interactions is crucial for the development of tumor biology. This review examines five key areas: the classification and main features of immune senescence, factors influencing immune cell senescence in cancer, the reciprocal causal cycle between immune senescence and malignancy, and the potential of immune senescence as a target for cancer immunotherapy.

Spatial heterogeneity and prognostic significance of TAMs and TILs infiltrates in different staging esophageal squamous carcinoma

BACKGROUND

The prognostic value and clinical relevance of tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs) in esophageal squamous cell carcinoma (ESCC) remain unclear.

AIMS

To investigate the prognostic value and functional involvement of TILs in ESCC.

METHODS

We included 40 patients across different stages of ESCC from Xinjiang. Multiplex fluorescent immunohistochemistry characterized TILs and TAMs. TILs in different tumor regions were quantified and correlated with overall survival (OS) using log-rank test and Cox regression analyses.

RESULTS

Invasive ESCC exhibited increased CD4 T cells and Tregs compared to carcinoma in situ, with a higher Tregs/CD4 T cells ratio (p < 0.05). TAMs, primarily in stromal regions, were significantly associated with Foxp3+ cells (p < 0.05). Higher infiltration of stromal TAMs and a higher CD4/CD8 T cells ratio correlated with poorer OS, while a higher CD8 T/Foxp3+ cells ratio indicated better survival. Multivariate Cox analysis revealed TNM stage, tumor length, and stromal CD4/CD8 T cells ratio as independent prognostic factors (p < 0.05). An immune prognostic risk score-based nomogram was constructed to predict patient outcomes.

CONCLUSIONS

The spatial distribution and abundance of TILs significantly correlated with prognosis, providing a useful immune classification for ESCC.

Prognostic characteristics and drug sensitivity analysis of hepatocellular carcinoma based on histone modification-related genes: a multi-omics integrated study revealing potential therapeutic targets and individualized treatment strategies

Background

Hepatocellular carcinoma (HCC) ranks among the most prevalent and lethal malignancies worldwide. Histone modifications (HMs) play a pivotal role in the initiation and progression of HCC. However, our understanding of HMs in HCC remains limited due to the disease's heterogeneity and the complexity of HMs.

Methods

We integrated multi-omics data from multiple cohorts, including single-cell RNA sequencing, bulk RNA sequencing, and clinical information. Weighted gene co-expression network analysis (WGCNA) and consensus clustering were employed to identify histone-related genes. We developed a histone modification-related signature (HMRS) using 117 machine learning methods. Comprehensive analyses of molecular characteristics, immune landscape, and drug sensitivity associated with the HMRS were performed.

Results

Through integrative analysis, we defined 110 histone-related genes and identified 45 HCC-HM-related genes (HCC-HMRgenes). The HMRS demonstrated robust prognostic value across multiple cohorts. Patients with high HMRS scores exhibited distinct genomic alterations, including higher tumor heterogeneity and TP53 mutations. The high-risk group showed enrichment in cell cycle, DNA repair, and metabolic pathways. Immune landscape analysis revealed significant differences in immune cell infiltration and pathway activities between high- and low-risk groups. Drug sensitivity prediction suggested potential therapeutic strategies for different risk groups.

Conclusion

Our study provides a comprehensive understanding of HMs in HCC and establishes a robust prognostic signature. The HMRS not only stratifies patients into distinct risk groups but also offers insights into underlying molecular mechanisms, immune characteristics, and potential therapeutic strategies, paving the way for personalized medicine in HCC.

Metabolomics Dysfunction in Replicative Senescence of Periodontal Ligament Stem Cells Regulated by AMPK Signaling Pathway

Periodontal ligament mesenchymal stem cells (PDLSCs) are a promising cell resource for stem cell-based regenerative medicine in dentistry, but they inevitably acquire a senescent phenotype after prolonged in vitro expansion. The key regulators of PDLSCs during replicative senescence remain unclear. Here, we sought to elucidate the role of metabolomic changes in determining the cellular senescence of PDLSCs. PDLSCs were cultured to passages 4, 10, and 20. The senescent phenotypes of PDLSCs were detected, and metabolomics analysis was performed. We found that PDLSCs manifested senescence phenotype during passaging. Metabolomics analysis showed that the metabolism of replicative senescence in PDLSCs varied significantly. The AMP-activated protein kinase (AMPK) signaling pathway was closely related to adenosine monophosphate (AMP) levels. The AMP:ATP ratio increased in senescent PDLSCs; however, the levels of p-AMPK, FOXO1 and FOXO3a decreased with senescence. We treated PDLSCs with an activator of the AMPK pathway (AICAR) and observed that the phosphorylated AMPK level at P20 PDLSCs was partially restored. These data delineate that the metabolic process of PDLSCs is active in the early stage of senescence and attenuated in the later stages of senescence; however, the sensitivity of AMPK phosphorylation sites is impaired, causing senescent PDLSCs to fail to respond to changes in energy metabolism.

AMBRA1 controls the translation of immune-specific genes in T lymphocytes

T cell receptor (TCR) engagement causes a global cellular response that entrains signaling pathways, cell cycle regulation, and cell death. The molecular regulation of mRNA translation in these processes is poorly understood. Using a whole-genome CRISPR screen for regulators of CD95 (FAS/APO-1)-mediated T cell death, we identified AMBRA1, a protein previously studied for its roles in autophagy, E3 ubiquitin ligase activity, and cyclin regulation. T cells lacking AMBRA1 resisted FAS-mediated cell death by down-regulating FAS expression at the translational level. We show that AMBRA1 is a vital regulator of ribosome protein biosynthesis and ribosome loading on select mRNAs, whereby it plays a key role in balancing TCR signaling with cell cycle regulation pathways. We also found that AMBRA1 itself is translationally controlled by TCR stimulation via the CD28-PI3K-mTORC1-EIF4F pathway. Together, these findings shed light on the molecular control of translation after T cell activation and implicate AMBRA1 as a translational regulator governing TCR signaling, cell cycle progression, and T cell death.

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.

In silico design and evaluation of a multiepitope vaccine targeting the nucleoprotein of Puumala orthohantavirus

The Puumala orthohantavirus is present in the body of the bank vole (Myodes glareolus). Humans infected with this virus may develop hemorrhagic fever accompanying renal syndrome. In addition, the infection may further lead to the failure of an immune system completely. The present study aimed to propose a possible vaccine by employing bioinformatics techniques to identify B and T-cell antigens. The best multi-epitope of potential immunogenicity was generated by combining epitopes. Additionally, the linkers EAAAK, AAY, and GPGPG were utilized in order to link the epitopes successfully. Further, C-ImmSim was used to perform in silico immunological simulations upon the vaccine. For the purpose of conducting expression tests in Escherichia coli, the chimeric protein construct was cloned using Snapgene into the pET-9c vector. The designed vaccine showed adequate results, evidenced by the global population coverage and favorable immune response. The developed vaccine was found to be highly effective and to have excellent population coverage in a number of computer-based assessments. This work is fully dependent on the development of nucleoprotein-based vaccines, which would constitute a significant step forward if our findings were used in developing a global vaccination to combat the Puumala virus.

Ecnomotopic olfactory receptors in metabolic regulation

Olfactory receptors are seven-transmembrane G-protein-coupled receptors on the cell surface. Over the past few decades, evidence has been mounting that olfactory receptors are not unique to the nose and that their ectopic existence plays an integral role in extranasal diseases. Coupled with the discovery of many natural or synthetic odor-compound ligands, new roles of ecnomotopic olfactory receptors regulating blood glucose, obesity, blood pressure, and other metabolism-related diseases are emerging. Many well-known scientific journals have called for attention to extranasal functions of ecnomotopic olfactory receptors. Thus, the prospect of ecnomotopic olfactory receptors in drug target research has been greatly underestimated. Here, we have provided an overview for the role of ecnomotopic olfactory receptors in metabolic diseases, focusing on their effects on various metabolic tissues, and discussed the possible molecular biological and pathophysiological mechanisms, which provide the basis for drug development and clinical application targeting the function of ecnomotopic olfactory receptors via literature machine learning and screening.

Mitochondrial DNA Programs Lactylation of cGAS to Induce IFN Responses in Patients with Systemic Lupus Erythematosus

Mitochondrial DNA (mtDNA) is frequently released from mitochondria, activating cGAS-STING signaling and inducing type I IFNs (IFN-Is) in systemic lupus erythematosus (SLE). Meanwhile, whether and how the glycolytic pathway was involved in such IFN-I responses in human SLE remain unclear. In this study, we found that monocytes from SLE patients exerted robust IFN-I generation and elevated level of cytosolic mtDNA. Transfection of mtDNA into THP-1 macrophages was efficient in inducing IFN-I responses, together with the strong glycolytic pathway that promoted lactate production, mimicking the SLE phenotype. Blockade of lactate generation abrogated such IFN-I responses and, vice versa, exogenous lactate enhanced the IFN-I generation. Mechanistically, lactate promoted the lactylation of cGAS, which inhibited its binding to E3 ubiquitination ligase MARCHF5, blocking cGAS degradation and leading to strong IFN-I responses. In accordance, targeting lactate generation alleviated disease development in humanized SLE chimeras. Collectively, cytosolic mtDNA drives metabolic adaption toward the glycolytic pathway, promoting lactylation of cGAS for licensing IFN-I responses in human SLE and thereby assigning the glycolytic pathway as a promising therapeutic target for SLE.

Targeting tumour metabolism in melanoma to enhance response to immune checkpoint inhibition: A balancing act

Immune checkpoint inhibition has transformed the treatment landscape of advanced melanoma and long-term survival of patients is now possible. However, at least half of the patients do not benefit sufficiently. Metabolic reprogramming is a hallmark of cancer cells and may contribute to both tumour growth and immune evasion by the tumour. Preclinical studies have indeed demonstrated that modulating tumour metabolism can reduce tumour growth while improving the functionality of immune cells. Since metabolic pathways are commonly shared between immune and tumour cells, it is essential to understand how modulating tumour metabolism in patients influences the intricate balance of pro-and anti-tumour immune effects in the tumour microenvironment. The key question is whether modulating tumour metabolism can inhibit tumour cell growth as well as facilitate an anti-tumour immune response. Here, we review current knowledge on the effect of tumour metabolism on the immune response in melanoma. We summarise metabolic pathways in melanoma and non-cancerous cells in the tumour microenvironment and discuss models and techniques available to study the metabolic-immune interaction. Finally, we discuss clinical use of these techniques to improve our understanding of how metabolic interventions can tip the balance towards a favourable, immune permissive microenvironment in melanoma patients.

Remodeling the hepatic immune microenvironment and demolishing T cell traps to enhance immunotherapy efficacy in liver metastasis

Immune checkpoint inhibitors (ICIs) exhibit compromised therapeutic efficacy in many patients with advanced cancers, particularly those with liver metastases. Much of this incapability can be ascribed as an irresponsiveness resulting from the "cold" hepatic tumor microenvironment that acts as T cell "traps" for which there currently lack countermeasures. We report a novel nanomedicine that converts the hepatic immune microenvironment to a "hot" phenotype by targeting hepatic macrophage-centric T cell elimination. Using the nanomedicine, composed of KIRA6 (an endothelium reticulum stress inhibitor), α-Tocopherol nanoemulsions, and anti-PD1 antibodies, we found its potency in murine models of orthotopic colorectal tumors and hepatic metastases, restoring immune responses and enhancing anti-tumor effects. A post-treatment scrutiny of the immune microenvironment landscape in the liver reveals repolarization of immunosuppressive hepatic macrophages, upregulation of Th1-like effector CD4+ T cells, and rejuvenation of dendritic cells along with CD8+ T cells. These findings suggest adaptations of liver-centric immune milieu modulation strategies to improve the efficacy of ICIs for a variety of "cold" tumors and their liver metastases.

IRF5 mediates adaptive immunity via altered glutamine metabolism, mTORC1 signaling and post-transcriptional regulation following T cell receptor activation

Although dynamic alterations in transcriptional, translational, and metabolic programs have been described in T cells, the factors and pathways guiding these molecular shifts are poorly understood, with recent studies revealing a disassociation between transcriptional responses and protein expression following T cell receptor (TCR) stimulation. Previous studies identified interferon regulatory factor 5 (IRF5) in the transcriptional regulation of cytokines, chemotactic molecules and T effector transcription factors following TCR signaling. In this study, we identified T cell intrinsic IRF5 regulation of mTORC1 activity as a key modulator of CD40L protein expression. We further demonstrated a global shift in T cell metabolism, with alterations in glutamine metabolism accompanied by shifts in T cell populations at the single cell level due to loss of Irf5. T cell conditional Irf5 knockout mice in a murine model of experimental autoimmune encephalomyelitis (EAE) demonstrated protection from clinical disease with conserved defects in mTORC1 activity and glutamine regulation. Together, these findings expand our mechanistic understanding of IRF5 as an intrinsic regulator of T effector function(s) and support the therapeutic targeting of IRF5 in multiple sclerosis.

The significance of CD16+ monocytes in the occurrence and development of chronic thromboembolic pulmonary hypertension: insights from single-cell RNA sequencing

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious pulmonary vascular disease characterized by residual thrombi in the pulmonary arteries and distal pulmonary microvascular remodeling. The pathogenesis of CTEPH remains unclear, but many factors such as inflammation, immunity, coagulation and angiogenesis may be involved. Monocytes are important immune cells that can differentiate into macrophages and dendritic cells and play an important role in thrombus formation. However, the distribution, gene expression profile and differentiation trajectory of monocyte subsets in CTEPH patients have not been systematically studied. This study aims to reveal the characteristics and functions of monocytes in CTEPH patients using single-cell sequencing technology, and to provide new insights for the diagnosis and treatment of CTEPH.

Methods

Single-cell RNA sequencing (scRNA-seq) were performed to analyze the transcriptomic features of peripheral blood mononuclear cells (PBMCs) from healthy controls, CTEPH patients and the tissues from CTEPH patients after the pulmonary endarterectomy (PEA). We established a CTEPH rat model with chronic pulmonary embolism caused by repeated injection of autologous thrombi through a central venous catheter, and used flow cytometry to detect the proportion changes of monocyte subsets in CTEPH patients and CTEPH rat model. We also observed the infiltration degree of macrophage subsets in thrombus tissue and their differentiation relationship with peripheral blood monocyte subsets by immunofluorescence staining.

Results

The results showed that the monocyte subsets in peripheral blood of CTEPH patients changed significantly, especially the proportion of CD16+ monocyte subset increased. This monocyte subset had unique functional features at the transcriptomic level, involving processes such as cell adhesion, T cell activation, coagulation response and platelet activation, which may play an important role in pulmonary artery thrombus formation and pulmonary artery intimal remodeling. In addition, we also found that the macrophage subsets in pulmonary endarterectomy tissue of CTEPH patients showed pro-inflammatory and lipid metabolism reprogramming features, which may be related to the persistence and insolubility of pulmonary artery thrombi and the development of pulmonary hypertension. Finally, we also observed that CD16+ monocyte subset in peripheral blood of CTEPH patients may be recruited to pulmonary artery intimal tissue and differentiate into macrophage subset with high expression of IL-1β, participating in disease progression.

Conclusion

CD16+ monocytes subset had significant gene expression changes in CTEPH patients, related to platelet activation, coagulation response and inflammatory response. And we also found that these cells could migrate to the thrombus and differentiate into macrophages with high expression of IL-1β involved in CTEPH disease progression. We believe that CD16+ monocytes are important participants in CTEPH and potential therapeutic targets.

Fasting hyperglycaemia and fatty liver drive colorectal cancer: a retrospective analysis in 1145 patients

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents the hepatic manifestation of increased adiposopathy, whose pathogenetic features have been proposed as tumourigenic triggers for colorectal cancer (CRC). We aim to identify specific metabolic signatures involved in CRC development that may be used as non-invasive biomarkers, paving the way for specific and personalized strategies of CRC prevention and early detection.

METHODS

We retrospectively assessed CRC onset during a time frame of 8 years in a cohort of 1145 out-patients individuals who had previously been evaluated for Metabolic Syndrome.

RESULTS

28 patients developed CRC. No association between CRC development and visceral and general obesity was detected, while baseline fasting plasma glucose (FPG) and non-invasive liver fibrosis scores were significantly higher in patients with CRC, compared to those who did not develop cancer. Liver steatosis and MASLD were more frequently diagnosed in patients who developed CRC compared to no cancer developers. Canonical correlations among metabolic biomarkers were not present in CRC developers, differently from no cancer group. In ROC analysis, FPG and non-invasive scores also showed good sensitivity and specificity in predicting colon cancer. We then calculated ORs for metabolic biomarkers, finding that higher FPG and non-invasive scores were associated with an increased risk of developing CRC.

CONCLUSION

MASLD and increased FPG may play a role in the clinical background of CRC, bringing to light the fascinating possibility of a reversed gut-liver axis communication in the pathogenesis of CRC. Thus, the use of non-invasive scores of fatty liver may be helpful to predict the risk of CRC and serve as novel prognostic factors for prevention and therapeutic strategies.

Metabolic flux in macrophages in obesity and type-2 diabetes

Recent literature extensively investigates the crucial role of energy metabolism in determining the inflammatory response and polarization status of macrophages. This rapidly expanding area of research highlights the importance of understanding the link between energy metabolism and macrophage function. The metabolic pathways in macrophages are intricate and interdependent, and they can affect the polarization of macrophages. Previous studies suggested that glucose flux through cytosolic glycolysis is necessary to trigger pro-inflammatory phenotypes of macrophages, and fatty acid oxidation is crucial to support anti-inflammatory responses. However, recent studies demonstrated that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully understood yet. How the metabolic flux through different metabolic pathways (glycolysis, glucose oxidation, fatty acid oxidation, ketone oxidation, and amino acid oxidation) is altered by obesity- and type 2 diabetes (T2D)-associated insulin resistance is also not fully defined. This mini-review focuses on the impact of insulin resistance in obesity and T2D on the metabolic flux through the main metabolic pathways in macrophages, which might be linked to changes in their inflammatory responses. We closely evaluated the experimental studies and methodologies used in the published research and highlighted priority research areas for future investigations.

Targeting NPM1 Epigenetically Promotes Postinfarction Cardiac Repair by Reprogramming Reparative Macrophage Metabolism

BACKGROUND

Reparative macrophages play a crucial role in limiting excessive fibrosis and promoting cardiac repair after myocardial infarction (MI), highlighting the significance of enhancing their reparative phenotype for wound healing. Metabolic adaptation orchestrates the phenotypic transition of macrophages; however, the precise mechanisms governing metabolic reprogramming of cardiac reparative macrophages remain poorly understood. In this study, we investigated the role of NPM1 (nucleophosmin 1) in the metabolic and phenotypic shift of cardiac macrophages in the context of MI and explored the therapeutic effect of targeting NPM1 for ischemic tissue repair.

METHODS

Peripheral blood mononuclear cells were obtained from healthy individuals and patients with MI to explore NPM1 expression and its correlation with prognostic indicators. Through RNA sequencing, metabolite profiling, histology, and phenotype analyses, we investigated the role of NPM1 in postinfarct cardiac repair using macrophage-specific NPM1 knockout mice. Epigenetic experiments were conducted to study the mechanisms underlying metabolic reprogramming and phenotype transition of NPM1-deficient cardiac macrophages. The therapeutic efficacy of antisense oligonucleotide and inhibitor targeting NPM1 was then assessed in wild-type mice with MI.

RESULTS

NPM1 expression was upregulated in the peripheral blood mononuclear cells from patients with MI that closely correlated with adverse prognostic indicators of MI. Macrophage-specific NPM1 deletion reduced infarct size, promoted angiogenesis, and suppressed tissue fibrosis, in turn improving cardiac function and protecting against adverse cardiac remodeling after MI. Furthermore, NPM1 deficiency boosted the reparative function of cardiac macrophages by shifting macrophage metabolism from the inflammatory glycolytic system to oxygen-driven mitochondrial energy production. The oligomeric NPM1 recruited histone demethylase KDM5b to the promoter of Tsc1 (TSC complex subunit 1), the mTOR (mechanistic target of rapamycin kinase) complex inhibitor, reduced histone H3K4me3 modification, and inhibited TSC1 expression, which then facilitated mTOR-related inflammatory glycolysis and antagonized the reparative function of cardiac macrophages. The in vivo administration of antisense oligonucleotide targeting NPM1 or oligomerization inhibitor NSC348884 substantially ameliorated tissue injury and enhanced cardiac recovery in mice after MI.

CONCLUSIONS

Our findings uncover the key role of epigenetic factor NPM1 in impeding postinfarction cardiac repair by remodeling metabolism pattern and impairing the reparative function of cardiac macrophages. NPM1 may serve as a promising prognostic biomarker and a valuable therapeutic target for heart failure after MI.

Effects of Iron Status on Adaptive Immunity and Vaccine Efficacy: A Review

Vaccines can prevent infectious diseases, but their efficacy varies, and factors impacting vaccine effectiveness remain unclear. Iron deficiency is the most common nutrient deficiency, affecting >2 billion individuals. It is particularly common in areas with high infectious disease burden and in groups that are routinely vaccinated, such as infants, pregnant women, and the elderly. Recent evidence suggests that iron deficiency and low serum iron (hypoferremia) not only cause anemia but also may impair adaptive immunity and vaccine efficacy. A report of human immunodeficiency caused by defective iron transport underscored the necessity of iron for adaptive immune responses and spurred research in this area. Sufficient iron is essential for optimal production of plasmablasts and IgG responses by human B-cells in vitro and in vivo. The increased metabolism of activated lymphocytes depends on the high-iron acquisition, and hypoferremia, especially when occurring during lymphocyte expansion, adversely affects multiple facets of adaptive immunity, and may lead to prolonged inhibition of T-cell memory. In mice, hypoferremia suppresses the adaptive immune response to influenza infection, resulting in more severe pulmonary disease. In African infants, anemia and/or iron deficiency at the time of vaccination predict decreased response to diphtheria, pertussis, and pneumococcal vaccines, and response to measles vaccine may be increased by iron supplementation. In this review, we examine the emerging evidence that iron deficiency may limit adaptive immunity and vaccine responses. We discuss the molecular mechanisms and evidence from animal and human studies, highlight important unknowns, and propose a framework of key research questions to better understand iron-vaccine interactions.

A new era of cancer immunotherapy: combining revolutionary technologies for enhanced CAR-M therapy

Significant advancements have been made in the application of chimeric antigen receptor (CAR)-T treatment for blood cancers during the previous ten years. However, its effectiveness in treating solid tumors is still lacking, necessitating the exploration of alternative immunotherapies that can overcome the significant challenges faced by current CAR-T cells. CAR-based immunotherapy against solid tumors shows promise with the emergence of macrophages, which possess robust phagocytic abilities, antigen-presenting functions, and the ability to modify the tumor microenvironment and stimulate adaptive responses. This paper presents a thorough examination of the latest progress in CAR-M therapy, covering both basic scientific studies and clinical trials. This study examines the primary obstacles hindering the realization of the complete potential of CAR-M therapy, as well as the potential strategies that can be employed to overcome these hurdles. With the emergence of revolutionary technologies like in situ genetic modification, synthetic biology techniques, and biomaterial-supported gene transfer, which provide a wider array of resources for manipulating tumor-associated macrophages, we suggest that combining these advanced methods will result in the creation of a new era of CAR-M therapy that demonstrates improved efficacy, safety, and availability.

Immuno-metabolic reprogramming of T cell: a new frontier for pharmacotherapy of Rheumatoid arthritis

Rheumatoid arthritis (RA) is a persistent autoimmune condition characterized by ongoing inflammation primarily affecting the synovial joint. This inflammation typically arises from an increase in immune cells such as neutrophils, macrophages, and T cells (TC). TC is recognized as a major player in RA pathogenesis. The involvement of HLA-DRB1 and PTPN-2 among RA patients confirms the TC involvement in RA. Metabolism of TC is maintained by various other factors like cytokines, mitochondrial proteins & other metabolites. Different TC subtypes utilize different metabolic pathways like glycolysis, oxidative phosphorylation and fatty acid oxidation for their activation from naive TC (T0). Although all subsets of TC are not deleterious for synovium, some subsets of TC are involved in joint repair using their anti-inflammatory properties. Hence artificially reprogramming of TC subset by interfering with their metabolic status poised a hope in future to design new molecules against RA.

Methyltransferase Setd2 prevents T cell-mediated autoimmune diseases via phospholipid remodeling

Coordinated metabolic reprogramming and epigenetic remodeling are critical for modulating T cell function and differentiation. However, how the epigenetic modification controls Th17/Treg cell balance via metabolic reprogramming remains obscure. Here, we find that Setd2, a histone H3K36 trimethyltransferase, suppresses Th17 development but promotes iTreg cell polarization via phospholipid remodeling. Mechanistically, Setd2 up-regulates transcriptional expression of lysophosphatidylcholine acyltransferase 4 (Lpcat4) via directly catalyzing H3K36me3 of Lpcat4 gene promoter in T cells. Lpcat4-mediated phosphatidylcholine PC(16:0,18:2) generation in turn limits endoplasmic reticulum stress and oxidative stress. These changes decrease HIF-1α transcriptional activity and thus suppress Th17 but enhance Treg development. Consistent with this regulatory paradigm, T cell deficiency of Setd2 aggravates neuroinflammation and demyelination in experimental autoimmune encephalomyelitis due to imbalanced Th17/Treg cell differentiation. Overall, our data reveal that Setd2 acts as an epigenetic brake for T cell-mediated autoimmunity through phospholipid remodeling, suggesting potential targets for treating neuroinflammatory diseases.

A review on regulation of DNA methylation during post-myocardial infarction

Myocardial infarction (MI) imposes a huge medical and economic burden on society, and cardiac repair after MI involves a complex series of processes. Understanding the key mechanisms (such as apoptosis, autophagy, inflammation, and fibrosis) will facilitate further drug development and patient treatment. Presently, a substantial body of evidence suggests that the regulation of epigenetic processes contributes to cardiac repair following MI, with DNA methylation being among the notable epigenetic factors involved. This article will review the research on the mechanism of DNA methylation regulation after MI to provide some insights for future research and development of related drugs.

Examining Chronic Inflammation, Immune Metabolism, and T Cell Dysfunction in HIV Infection

Chronic Human Immunodeficiency Virus (HIV) infection remains a significant challenge to global public health. Despite advances in antiretroviral therapy (ART), which has transformed HIV infection from a fatal disease into a manageable chronic condition, a definitive cure remains elusive. One of the key features of HIV infection is chronic immune activation and inflammation, which are strongly associated with, and predictive of, HIV disease progression, even in patients successfully treated with suppressive ART. Chronic inflammation is characterized by persistent inflammation, immune cell metabolic dysregulation, and cellular exhaustion and dysfunction. This review aims to summarize current knowledge of the interplay between chronic inflammation, immune metabolism, and T cell dysfunction in HIV infection, and also discusses the use of humanized mice models to study HIV immune pathogenesis and develop novel therapeutic strategies.

Metabolic reprogramming in skin wound healing

Metabolic reprogramming refers to the ability of a cell to alter its metabolism in response to different stimuli and forms of pressure. It helps cells resist external stress and provides them with new functions. Skin wound healing involves the metabolic reprogramming of nutrients, such as glucose, lipids, and amino acids, which play vital roles in the proliferation, differentiation, and migration of multiple cell types. During the glucose metabolic process in wounds, glucose transporters and key enzymes cause elevated metabolite levels. Glucose-mediated oxidative stress drives the proinflammatory response and promotes wound healing. Reprogramming lipid metabolism increases the number of fibroblasts and decreases the number of macrophages. It enhances local neovascularization and improves fibrin stability to promote extracellular matrix remodelling, accelerates wound healing, and reduces scar formation. Reprogramming amino acid metabolism affects wound re-epithelialization, collagen deposition, and angiogenesis. However, comprehensive reviews on the role of metabolic reprogramming in skin wound healing are lacking. Therefore, we have systematically reviewed the metabolic reprogramming of glucose, lipids, and amino acids during skin wound healing. Notably, we identified their targets with potential therapeutic value and elucidated their mechanisms of action.

Diesel exhaust particles induce polarization state-dependent functional and transcriptional changes in human monocyte-derived macrophages

Macrophage populations exist on a spectrum between the proinflammatory M1 and proresolution M2 states and have demonstrated the ability to reprogram between them after exposure to opposing polarization stimuli. Particulate matter (PM) has been repeatedly linked to worsening morbidity and mortality following respiratory infections and has been demonstrated to modify macrophage function and polarization. The purpose of this study was to determine whether diesel exhaust particles (DEP), a key component of airborne PM, would demonstrate polarization state-dependent effects on human monocyte-derived macrophages (hMDMs) and whether DEP would modify macrophage reprogramming. CD14+CD16- monocytes were isolated from the blood of healthy human volunteers and differentiated into macrophages with macrophage colony-stimulating factor (M-CSF). Resulting macrophages were left unpolarized or polarized into the proresolution M2 state before being exposed to DEP, M1-polarizing conditions (IFN-γ and LPS), or both and tested for phagocytic function, secretory profile, gene expression patterns, and bioenergetic properties. Contrary to previous reports, we observed a mixed M1/M2 phenotype in reprogrammed M2 cells when considering the broader range of functional readouts. In addition, we determined that DEP exposure dampens phagocytic function in all polarization states while modifying bioenergetic properties in M1 macrophages preferentially. Together, these data suggest that DEP exposure of reprogrammed M2 macrophages results in a highly inflammatory, highly energetic subpopulation of macrophages that may contribute to the poor health outcomes following PM exposure during respiratory infections.NEW & NOTEWORTHY We determined that reprogramming M2 macrophages in the presence of diesel exhaust particles (DEP) results in a highly inflammatory mixed M1/M2 phenotype. We also demonstrated that M1 macrophages are particularly vulnerable to particulate matter (PM) exposure as seen by dampened phagocytic function and modified bioenergetics. Our study suggests that PM causes reprogrammed M2 macrophages to become a highly energetic, highly secretory subpopulation of macrophages that may contribute to negative health outcomes observed in humans after PM exposure.

PKM2 promotes proinflammatory macrophage activation in ankylosing spondylitis

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

Novel insights into the role of acetyl-CoA producing enzymes in epigenetic regulation

Inflammation-dependent changes in gene expression programs in innate immune cells, such as macrophages, involve extensive reprogramming of metabolism. This reprogramming is essential for the production of metabolites required for chromatin modifications, such as acetyl-CoA, and regulate their usage and availability impacting the macrophage epigenome. One of the most transcriptionally induced proinflammatory mediator is nitric oxide (NO), which has been shown to inhibit key metabolic enzymes involved in the production of these metabolites. Recent evidence indicates that NO inhibits mitochondrial enzymes such as pyruvate dehydrogenase (PDH) in macrophages induced by inflammatory stimulus. PDH is involved in the production of acetyl-CoA, which is essential for chromatin modifications in the nucleus, such as histone acetylation. In addition, acetyl-CoA levels in inflamed macrophages are regulated by ATP citrate lyase (ACLY) and citrate transporter SLC25A1. Interestingly, acetyl-CoA producing enzymes, such as PDH and ACLY, have also been reported to be present in the nucleus and to support the local generation of cofactors such as acetyl-CoA. Here, we will discuss the mechanisms involved in the regulation of acetyl-CoA production by metabolic enzymes, their inhibition by prolonged exposure to inflammation stimuli, their involvement in dynamic inflammatory expression changes and how these emerging findings could have significant implications for the design of novel therapeutic approaches.

Immune Regulation of the Liver Through the PCSK9/CD36 Pathway During Heart Transplant Rejection

BACKGROUND

PCSK9 (proprotein convertase subtilisin/kexin 9), which is mainly secreted by the liver, is not only a therapeutic target for hyperlipidemia and cardiovascular disease, but also has been implicated in the immune regulation of infections and tumors. However, the role of PCSK9 and the liver in heart transplant rejection (HTR) and the underlying mechanisms remain unclear.

METHODS

We assessed serum PCSK9 expression in both murine and human recipients during HTR and investigated the effect of PCSK9 ablation on HTR by using global knockout mice and a neutralizing antibody. Moreover, we performed multiorgan histological and transcriptome analyses, and multiomics and single-cell RNA-sequencing studies of the liver during HTR, as well. We further used hepatocyte-specific Pcsk9 knockout mice to investigate whether the liver regulated HTR through PCSK9. Last, we explored the regulatory effect of the PCSK9/CD36 pathway on the phenotype and function of macrophages in vitro and in vivo.

RESULTS

Here, we report that murine and human recipients have high serum PCSK9 levels during HTR. PCSK9 ablation prolonged cardiac allograft survival and attenuated the infiltration of inflammatory cells in the graft and the expansion of alloreactive T cells in the spleen. Next, we demonstrated that PCSK9 was mainly produced and significantly upregulated in the recipient liver, which also showed a series of signaling changes, including changes in the TNF-α (tumor necrosis factor α) and IFN-γ (interferon γ) signaling pathways and the bile acid and fatty acid metabolism pathways. We found mechanistically that TNF-α and IFN-γ synergistically promoted PCSK9 expression in hepatocytes through the transcription factor SREBP2 (sterol regulatory element binding protein 2). Moreover, in vitro and in vivo studies indicated that PCSK9 inhibited CD36 expression and fatty acid uptake by macrophages and strengthened the proinflammatory phenotype, which facilitated their ability to promote proliferation and IFN-γ production by donor-reactive T cells. Last, we found that the protective effect of PCSK9 ablation against HTR is dependent on the CD36 pathway in the recipient.

CONCLUSIONS

This study reveals a novel mechanism for immune regulation by the liver through the PCSK9/CD36 pathway during HTR, which influences the phenotype and function of macrophages and suggests that the modulation of this pathway may be a potential therapeutic target to prevent HTR.

Intrahepatic macrophage reprogramming associated with lipid metabolism in hepatitis B virus-related acute-on-chronic liver failure

BACKGROUND

Acute-on-chronic liver failure (ACLF) is a severe syndrome with high short-term mortality, but the pathophysiology still remains largely unknown. Immune dysregulation and metabolic disorders contribute to the progression of ACLF, but the crosstalk between immunity and metabolism during ACLF is less understood. This study aims to depict the immune microenvironment in the liver during ACLF, and explore the role of lipid metabolic disorder on immunity.

METHODS

Single-cell RNA-sequencing (scRNA-seq) was performed using the liver non-parenchymal cells (NPCs) and peripheral blood mononuclear cells (PBMCs) from healthy controls, cirrhosis patients and ACLF patients. A series of inflammation-related cytokines and chemokines were detected using liver and plasma samples. The lipid metabolomics targeted free fatty acids (FFAs) in the liver was also detected.

RESULTS

The scRNA-seq analysis of liver NPCs showed a significant increase of monocytes/macrophages (Mono/Mac) infiltration in ACLF livers, whereas the resident Kupffer cells (KCs) were exhausted. A characterized TREM2⁺ Mono/Mac subpopulation was identified in ACLF, and showed immunosuppressive function. Combined with the scRNA-seq data from PBMCs, the pseudotime analysis revealed that the TREM2⁺ Mono/Mac were differentiated from the peripheral monocytes and correlated with lipid metabolism-related genes including APOE, APOC1, FABP5 and TREM2. The targeted lipid metabolomics proved the accumulation of unsaturated FFAs associated with α-linolenic acid (α-LA) and α-LA metabolism and beta oxidation of very long chain fatty acids in the ACLF livers, indicating that unsaturated FFAs might promote the differentiation of TREM2⁺ Mono/Mac during ACLF.

CONCLUSIONS

The reprogramming of macrophages was found in the liver during ACLF. The immunosuppressive TREM2⁺ macrophages were enriched in the ACLF liver and contributed to the immunosuppressive hepatic microenvironment. The accumulation of unsaturated FFAs in the ACLF liver promoted the reprogramming of the macrophages. It might be a potential target to improve the immune deficiency of ACLF patients through regulating lipid metabolism.

Immunosenescence: molecular mechanisms and diseases

Infection susceptibility, poor vaccination efficacy, age-related disease onset, and neoplasms are linked to innate and adaptive immune dysfunction that accompanies aging (known as immunosenescence). During aging, organisms tend to develop a characteristic inflammatory state that expresses high levels of pro-inflammatory markers, termed inflammaging. This chronic inflammation is a typical phenomenon linked to immunosenescence and it is considered the major risk factor for age-related diseases. Thymic involution, naïve/memory cell ratio imbalance, dysregulated metabolism, and epigenetic alterations are striking features of immunosenescence. Disturbed T-cell pools and chronic antigen stimulation mediate premature senescence of immune cells, and senescent immune cells develop a proinflammatory senescence-associated secretory phenotype that exacerbates inflammaging. Although the underlying molecular mechanisms remain to be addressed, it is well documented that senescent T cells and inflammaging might be major driving forces in immunosenescence. Potential counteractive measures will be discussed, including intervention of cellular senescence and metabolic-epigenetic axes to mitigate immunosenescence. In recent years, immunosenescence has attracted increasing attention for its role in tumor development. As a result of the limited participation of elderly patients, the impact of immunosenescence on cancer immunotherapy is unclear. Despite some surprising results from clinical trials and drugs, it is necessary to investigate the role of immunosenescence in cancer and other age-related diseases.

Lactate mediated metabolic crosstalk between cancer and immune cells and its therapeutic implications

Metabolism is central to energy generation and cell signaling in all life forms. Cancer cells rely heavily on glucose metabolism wherein glucose is primarily converted to lactate even in adequate oxygen conditions, a process famously known as "the Warburg effect." In addition to cancer cells, Warburg effect was found to be operational in other cell types, including actively proliferating immune cells. According to current dogma, pyruvate is the end product of glycolysis that is converted into lactate in normal cells, particularly under hypoxic conditions. However, several recent observations suggest that the final product of glycolysis may be lactate, which is produced irrespective of oxygen concentrations. Traditionally, glucose-derived lactate can have three fates: it can be used as a fuel in the TCA cycle or lipid synthesis; it can be converted back into pyruvate in the cytosol that feeds into the mitochondrial TCA; or, at very high concentrations, accumulated lactate in the cytosol may be released from cells that act as an oncometabolite. In immune cells as well, glucose-derived lactate seems to play a major role in metabolism and cell signaling. However, immune cells are much more sensitive to lactate concentrations, as higher lactate levels have been found to inhibit immune cell function. Thus, tumor cell-derived lactate may serve as a major player in deciding the response and resistance to immune cell-directed therapies. In the current review, we will provide a comprehensive overview of the glycolytic process in eukaryotic cells with a special focus on the fate of pyruvate and lactate in tumor and immune cells. We will also review the evidence supporting the idea that lactate, not pyruvate, is the end product of glycolysis. In addition, we will discuss the impact of glucose-lactate-mediated cross-talk between tumor and immune cells on the therapeutic outcomes after immunotherapy.

HIV-Differentiated Metabolite N-Acetyl-L-Alanine Dysregulates Human Natural Killer Cell Responses to Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) has latently infected over two billion people worldwide (LTBI) and caused ~1.6 million deaths in 2021. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared with HIV- LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals. Plasma samples collected from healthy and HIV-infected individuals were investigated using liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using the online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, and quantitative reverse-transcription PCR (qRT-PCR) were performed using standard procedures to determine the surface markers, cytokines, and other signaling molecule expressions. Seahorse extra-cellular flux assays were used to measure mitochondrial oxidative phosphorylation and glycolysis. Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared with healthy donors. One of the HIV-upregulated metabolites, N-acetyl-L-alanine (ALA), inhibits pro-inflammatory cytokine IFN-γ production by the NK cells of LTBI+ individuals. ALA inhibits the glycolysis of LTBI+ individuals' NK cells in response to Mtb. Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK-cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV-Mtb interaction and providing insights into the implication of nutrition intervention and therapy for HIV-Mtb co-infected patients.

An optimized reporter of the transcription factor hypoxia-inducible factor 1α reveals complex HIF-1α activation dynamics in single cells

Immune cells adopt a variety of metabolic states to support their many biological functions, which include fighting pathogens, removing tissue debris, and tissue remodeling. One of the key mediators of these metabolic changes is the transcription factor hypoxia-inducible factor 1α (HIF-1α). Single-cell dynamics have been shown to be an important determinant of cell behavior; however, despite the importance of HIF-1α, little is known about its single-cell dynamics or their effect on metabolism. To address this knowledge gap, here we optimized a HIF-1α fluorescent reporter and applied it to study single-cell dynamics. First, we showed that single cells are likely able to differentiate multiple levels of prolyl hydroxylase inhibition, a marker of metabolic change, via HIF-1α activity. We then applied a physiological stimulus known to trigger metabolic change, interferon-γ, and observed heterogeneous, oscillatory HIF-1α responses in single cells. Finally, we input these dynamics into a mathematical model of HIF-1α-regulated metabolism and discovered a profound difference between cells exhibiting high versus low HIF-1α activation. Specifically, we found cells with high HIF-1α activation are able to meaningfully reduce flux through the tricarboxylic acid cycle and show a notable increase in the NAD+/NADH ratio compared with cells displaying low HIF-1α activation. Altogether, this work demonstrates an optimized reporter for studying HIF-1α in single cells and reveals previously unknown principles of HIF-1α activation.

A comprehensive molecular profiling approach reveals metabolic alterations that steer bone tissue regeneration

Bone regeneration after fracture is a complex process with high and dynamic energy demands. The impact of metabolism on bone healing progression and outcome, however, is so far understudied. Our comprehensive molecular profiling reveals that central metabolic pathways, such as glycolysis and the citric acid cycle, are differentially activated between rats with successful or compromised bone regeneration (young versus aged female Sprague-Dawley rats) early in the inflammatory phase of bone healing. We also found that the citric acid cycle intermediate succinate mediates individual cellular responses and plays a central role in successful bone healing. Succinate induces IL-1β in macrophages, enhances vessel formation, increases mesenchymal stromal cell migration, and potentiates osteogenic differentiation and matrix formation in vitro. Taken together, metabolites-here particularly succinate-are shown to play central roles as signaling molecules during the onset of healing and in steering bone tissue regeneration.

Bio-inspired glycosylated nano-hydroxyapatites enhance endogenous bone regeneration by modulating macrophage M2 polarization

A macrophage-associated immune response is vital in bone regeneration. Mannose receptor (MR), a macrophage pattern-recognition receptor, is crucial for the maintenance of immune homeostasis. Here, we designed MR-targeted glycosylated nano-hydroxyapatites (GHANPs) to reprogram macrophages into polarized M2s, promoting bone regeneration by improving the osteoimmune microenvironment. The prepared GHANPs induced macrophage M2 polarization, which then promoted osteoblastic differentiation of stem cells. Further, the mechanistic study showed that GHANPs might influence macrophage polarization by modulating cell metabolism, including enhancing mitochondrial oxidative phosphorylation and activating autophagy. Finally, a rat cranial defect model was used to verify the effect of GHANPs on endogenous bone regeneration in vivo, revealing that GHANPs promoted bone regeneration within the defect and increased the ratio of M2/M1 macrophages in early bone repair. Our results indicate that the MR-targeted macrophage M2 polarization strategy is promising in endogenous bone regeneration. STATEMENT OF SIGNIFICANCE: Macrophage is a pivotal immunity component for bone regeneration. A switch to M2 macrophage has been considered to contribute to osteogenesis. For inducing macrophage M2 polarization, an effective strategy to overcome off-target effects and insufficient specificity is a critical challenge. The mannose receptor on the surface of macrophages has been involved in regulating macrophage directional polarization. The glucomannan presented on the nano-hydroxyapatite rods acts as ligands targeting macrophage mannose receptors to promote their M2 polarization, improving the immunomicroenvironment and achieving bone regeneration. This approach has the advantage of easy preparation, specific regulation, and safety.

Git1-PGK1 interaction achieves self-protection against spinal cord ischemia-reperfusion injury by modulating Keap1/Nrf2 signaling

Spinal cord ischemia-reperfusion (IR) injury (SCIRI) is a significant secondary injury that causes damage to spinal cord neurons, leading to the impairment of spinal cord sensory and motor functions. Excessive reactive oxygen species (ROS) production is considered one critical mechanism of neuron damage in SCIRI. Nonetheless, the molecular mechanisms underlying the resistance of neurons to ROS remain elusive. Our study revealed that the deletion of Git1 in mice led to poor recovery of spinal cord motor function after SCIRI. Furthermore, we discovered that Git1 has a beneficial effect on neuron resistance to ROS production. Mechanistically, Git1 interacted with PGK1, regulated PGK1 phosphorylation at S203, and affected the intermediate products of glycolysis in neurons. The influence of Git1 on glycolysis regulates the dimerization of Keap1, which leads to changes in Nrf2 ubiquitination and plays a role in resisting ROS. Collectively, we show that Git1 regulates the Keap1/Nrf2 axis to resist ROS in a PGK1-dependent manner and thus is a potential therapeutic target for SCIRI.

HIV-differentiated metabolite N-Acetyl-L-Alanine dysregulates human natural killer cell responses to Mycobacterium tuberculosis infection

Background

Mycobacterium tuberculosis ( Mtb ) has latently infected over two billion people worldwide (LTBI) and causes 1.8 million deaths each year. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared to the HIV-LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals.

Methods

Plasma samples collected from healthy and HIV-infected individuals were investigated by liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using an online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, quantitative reverse transcription PCR (qRT-PCR) were performed by standard procedure to determine the surface markers, cytokines and other signaling molecule expression. Seahorse extra cellular flux assays were used to measure the mitochondrial oxidative phosphorylation and glycolysis.

Results

Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared to healthy donors. One of the HIV-upregulated metabolites, N-Acetyl-L-Alanine (ALA), inhibits pro-inflammatory cytokine IFN-□ production by NK cells of LTBI+ individuals. ALA inhibits glycolysis of LTBI+ individuals' NK cells in response to Mtb .

Conclusions

Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV- Mtb interaction and providing the implication of nutrition intervention and therapy for HIV- Mtb co-infected patients.

Gut Microbiota-Derived Glutamine Attenuates Liver Ischemia/Reperfusion Injury via Macrophage Metabolic Reprogramming

BACKGROUND & AIMS

Many studies have revealed crucial roles of the gut microbiota and its metabolites in liver disease progression. However, the mechanism underlying their effects on liver ischemia/reperfusion (I/R) injury remain largely unknown. Here, we investigate the function of gut microbiota and its metabolites in liver I/R injury.

METHODS

C57BL/6 mice was pretreated with an antibiotic cocktail. Then, we used multi-omics detection methods including 16s rRNA sequencing, ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) to explore the changes of gut microbiota and metabolites in both feces and portal blood to reveal the mechanism of their protective effect in liver I/R injury.

RESULTS

We found that antibiotic pretreatment (ABX) could significantly reduce the severity of I/R-induced hepatic injury, and this effect could be transferred to germ-free mice by fecal microbiota transplantation (FMT), suggesting a protective role of the gut microbiota depletion. During I/R, the rates of serum α-ketoglutarate (αKG) production and glutamate reduction, downstream products of gut microbiota-derived glutamine, were more significant in the ABX mice. Then, we showed that αKG could promote alternative (M2) macrophage activation through oxidative phosphorylation, and oligomycin A could inhibit M2 macrophage polarization and reversed this protective effect.

CONCLUSIONS

These findings show that the gut microbiota and its metabolites play critical roles in hepatic I/R injury by modulating macrophage metabolic reprogramming. Potential therapies that target macrophage metabolism, including antibiotic therapies and novel immunometabolism modulators, can be exploited for the treatment of liver I/R injury.

Targeting glycolysis for cancer therapy using drug delivery systems

There is close crosstalk between cancer metabolism and immunity. Cancer metabolism regulation is a promising therapeutic target for cancer immunotherapy. Warburg effect is characterized by abnormal glucose metabolism that includes common features of increased glucose uptake and lactate production. The aerobic glycolysis can reprogram the cancer cells and promote the formation of a suppressive immune microenvironment. As a case in point, lactate plays an essential role in tumorigenesis, which is the end product of glycolysis as well as serves as a fuel supporting cancer cell survival. Meanwhile, it is also an important immune regulator that drives immunosuppression in tumors. Immunometabolic therapy is to intervene tumor metabolism and regulate the related metabolites that participate in the innate and acquired immunity, thereby reinstalling the immune balance and eliciting anticancer immune responses. In this contribution to the Orations - New Horizons of the Journal of controlled Release I will provide an overview of glucose metabolism in tumors and its effects on drug resistance and tumor metastasis, and present the advance of glycolysis-targeting therapy strategies with drug delivery techniques, as well as discuss the challenges in glycolysis-targeting immunometabolic therapy.

Metabolic control of innate lymphoid cells in health and disease

Innate lymphoid cells (ILCs) are a family of predominantly tissue-resident lymphocytes that critically orchestrate immunity, inflammation, tolerance and repair at barrier surfaces of the mammalian body. Heterogeneity among ILC subsets is comparable to that of adaptive CD4⁺ T helper cell counterparts, and emerging studies demonstrate that ILC biology is also dictated by cellular metabolism that adapts bioenergetic requirements during activation, proliferation or cytokine production. Accumulating evidence in mouse models and human samples indicates that ILCs exhibit profound roles in shaping states of metabolic health and disease. Here we summarize and discuss our current knowledge of the cell-intrinsic and cell-extrinsic metabolic factors controlling ILC responses, as well as highlight contributions of ILCs to organismal metabolism. It is expected that continued research in this area will advance our understanding of how to manipulate ILCs or their metabolism for therapeutic strategies that benefit human health.