Global lactylome reveals lactylation-dependent mechanisms underlying TH17 differentiation in experimental autoimmune uveitis

Signaling balance of MCTs and GPR81 controls lactate-induced metabolic function and cell death in skeletal muscle cells through Ranbp3l/Nfat5 and Atf4

Lactate, a byproduct of pyruvate in the glycolytic pathway, has been recognized as a signaling molecule and a regulator of gene expression. In skeletal muscles, lactate is dynamically regulated during exercise and influences muscular function, including myogenic differentiation and metabolism. The effects of lactate vary depending on lactate levels, which are influenced by exercise intensity, type, and duration. Furthermore, the effects of lactate on cellular signaling are different during the stages of myogenic differentiation. However, the distribution of lactate signaling in terms of lactate concentration, signaling types, and myogenesis has not been fully elucidated. In this study, we investigated the dual effects of lactate on myogenic differentiation and viability using C2C12 cells and C57BL/6 mice. Low levels of lactate treatment promoted myogenesis in the early stage of C2C12 differentiation, while high lactate concentrations or treatment with 3,5-DHBA, a GPR81 agonist, impaired cell viability during late myogenic differentiation. Transcriptomic analysis and knockdown experiments revealed that lactate promotes myogenesis and muscular metabolic functions through the induction of Ranbp3l and Nfat5 expressions. On the other hand, the detrimental effects of lactate on cell survival are mediated by the GPR81-induced PI3K-Akt/ERK-Atf4 axis. GPR81 signaling also feeds forward the expression of Hcar1 via Akt and ERK. These dual actions of lactate on skeletal muscle were also observed in vivo through lactate or 3,5-DHBA injections and exercise training models. Our study concludes that maintaining a balance in lactate signaling is crucial for regulating skeletal muscle phenotypes in response to exercise and lactate treatments.

Research progress on the regulatory role of lactate and lactylation in tumor microenvironment

The tumor microenvironment (TME) arises from the dynamic interactions between tumor cells and the surrounding medium, including a variety of cell types and extracellular components, which have an important impact on the genesis and development of tumors. A key player in TME is lactate, a metabolic byproduct of glycolysis, which serves as a significant energy source. Lactate has direct implications on the survival and differentiation of immune cells, the metabolic reprogramming and progression of tumor cells. Moreover, lactylation, a unique post-translational modification, exerts a regulatory effect on TME by affecting gene transcription via adding lactate groups to both histone and non-histone proteins. This review systematically and comprehensively synthesizes emerging evidence on how the lactate-lactylation axis drives immune evasion, therapy resistance, and TME remodeling, highlighting the therapeutic targets related to lactate and lactylation that dismantle this metabolic-epigenetic crosstalk.

Histone lactylation-augmented IRF4 is implicated in arsenite-induced liver fibrosis via modulating Th17 cell differentiation

Arsenic, a ubiquitous environmental toxicant, has been implicated in causing liver fibrosis through chronic exposure. Histone lactylation is involved in various inflammatory diseases, among which liver fibrosis is included, and is also closely related to the regulation of immune cells. This work focuses on the mechanisms of histone lactylation and Th17 cell differentiation in arsenite-induced liver fibrosis through animal and cellular experiments. Chronic arsenite exposure of mice led to liver fibrosis, elevated glycolysis in liver, and increased lactate levels in both serum and liver, which promoted Th17 cell differentiation of CD4+ T cells and increased IL-17A secretion. Treatment with oxamate, a lactate dehydrogenase inhibitor, suppressed Th17 cell differentiation and alleviated fibrosis in the liver. For HepG2 cells, arsenite exposure enhanced glycolysis and lactate levels, leading to increased global lactylation (Kla), H3K18la, interferon-regulatory factor 4 (IRF4), retinoic acid receptor-related orphan receptor gamma t (RORγt), and IL-17A expression and secretion in co-cultured Jurkat cells. Furthermore, in Jurkat cells, reducing lactate production and transport decreased these protein levels, suppressed Th17 cell differentiation, decreased IL-17A secretion, and ultimately inhibited the activation of hepatic stellate cells (HSCs). These results indicate that lactate derived from hepatocytes promotes Th17 cell differentiation by upregulating IRF4 through H3K18la, thereby enhancing IL-17A secretion and the activation of HSCs, contributing to arsenite-induced liver fibrosis. Our work reveals a new mechanism of histone lactylation in arsenite-induced liver fibrosis and offers a fresh perspective for the development of strategies for prevention and treatment of this condition.

Spatial alteration of metabolites in diabetic cortical cataracts: New insight into lactate

This study aimed to use metabolomics to accurately reveal alterations in metabolites and potential regulatory mechanisms in patients with diabetic cortical cataracts (DCC). We first collected cortical samples from different pathological areas of the same lens in DCC patients for metabolomics. Then, we used transcriptomic analysis to study lactate's effect on gene expression in human lens epithelial cells (HLECs). An in vitro rat lens culture assay evaluated lactate's impact on lens transparency, and WB and immunofluorescence assessed lactate-induced apoptosis and oxidative damage in rat LECs. Furthermore, CHIP sequencing and LC-MS identified H3K18la separately modified genes and potential lactylation proteins in HLECs. Immunoprecipitation validated lactylation levels of proteins. Our findings identified 11 upregulated and 18 downregulated metabolites in the opacity zone of LFCs (OZ-LFCs) compared to the clear zone (CZ-LFCs) in DCC patients. We confirmed the differential lactate content between OZ-LFCs and CZ-LFCs and, through transcriptomic analysis, discovered that lactate affects gene expression, protein metabolism, and DNA repair in primary Human Lens epithelial cells (HLECs). Lactate-induced apoptosis and DNA repair hastened lens opacity in a high-sugar rat lens culture model. Lactylation-MS and H3K18la-ChIP sequencing revealed 591 H3K18la-modified genes and 953 lactylation proteins in HLECs. PKM2 and NPM1 lactylation was confirmed through immunoprecipitation. These findings improve our grasp of spatial dynamics in DCC patient metabolomics and suggest a new research path into lactylation modification to understand lactate's role in cataract formation.

Lactylation and Ischemic Stroke: Research Progress and Potential Relationship

Ischemic stroke is caused by interrupted cerebral blood flow and is a leading cause of mortality and disability worldwide. Significant advancements have been achieved in comprehending the pathophysiology of stroke and the fundamental mechanisms responsible for ischemic damage. Lactylation, as a newly discovered post-translational modification, has been reported to participate in several physiological and pathological processes. However, research on lactylation and ischemic stroke is scarce. This review summarized the current function of protein lactylation in other diseases or normal physiological processes and explored their potential link with the pathophysiological process and the reparative mechanism of ischemic stroke. We proposed that neuroinflammation, regulation of metabolism, regulation of messenger RNA translation, angiogenesis, and neurogenesis might be the bridge linking lactylation and ischemic stroke. Our study provided a novel perspective for comprehending the role of protein lactylation in the pathophysiological processes underlying ischemic stroke. Lactylation might be a promising target in drug development of ischemic stroke.

Lactate metabolism and lactylation in breast cancer: mechanisms and implications

As the end-product of glycolysis, lactate serves as a regulator of protein lactylation in addition to being an energy substrate, metabolite, and signaling molecule in cancer. The reprogramming of glucose metabolism and the Warburg effect in breast cancer results in extensive lactate production and accumulation, making it likely that lactylation in tumor tissue is also abnormal. This review summarizes evidence on lactylation derived from studies of lactate metabolism and disease, highlighting the role of lactate in the tumor microenvironment of breast cancer and detailing the levels of lactylation and cancer-promoting mechanisms across various tumors. The roles of lactate and lactylation, along with potential intervention mechanisms, are presented and discussed, offering valuable insights for future research on the role of lactylation in tumors.

SIRT3 Functions as an Eraser of Histone H3K9 Lactylation to Modulate Transcription for Inhibiting the Progression of Esophageal Cancer

Lysine lactylation (Kla) links lactate metabolism to epigenetic regulation, playing a key role in modulation of gene expression in tumor and immune microenvironment. Our recent study shows that HBO1-mediated histone H3K9la activates the transcription of genes encoding tumorigenesis, suggesting the potential significance of intervening in this Kla site for tumor therapy. Evidence so far indicates that traditional deacetylases can catalyze the removal of Kla; however, the precise demodifying enzyme to histone H3K9la in vivo and functional consequence remain elusive. Herein, we combined an antibody-based proximity labeling approach with mass spectrometry analysis to identify SIRT3 as a major binder to histone H3K9la and showed the specific catalysis of SIRT3 for the removal of lactylation. Molecular docking further revealed the molecular mechanism of the binding of histone H3K9la to SIRT3. More importantly, SIRT3 can specifically modulate gene transcription by regulating H3K9la, inhibiting the progression of esophageal squamous cancer cells. Together, our work identifies the specific delactylase of H3K9la and reveals an H3K9la-mediated molecular mechanism catalyzed by SIRT3 for gene transcription regulation in esophageal squamous cancer cells, and our findings provide an opportunity to investigate the physiological significance of Kla controlled by SIRT3 in cancer.

Global Profiling of Lactylation Proteomics and Specific Lactylated Site Validation in Rheumatoid Arthritis Patients

Protein lactylation is a novel post-translational modification that has rarely been investigated in rheumatoid arthritis (RA). This study aimed to explore lactylation proteomics in RA patients and validate sorted candidate lactylation sites. Synovial tissues from ten RA and six osteoarthritis (OA) patients were subjected to lactylation proteomics via affinity enrichment and LC-MS/MS. Four candidate lactylated modification sites were validated by immunoprecipitation. Totally, 566 sites and 250 proteins with lactylated modifications in RA patients and 548 sites and 220 proteins with lactylated modifications in OA patients were identified. By comparison, 24 upregulated but 2 downregulated lactylated modification sites and 18 upregulated but 1 downregulated lactylated modification protein were discovered in RA patients versus OA patients. The dysregulated lactylated proteins were mainly enriched in biological processes such as positive regulation of plasma membrane repair by GO analysis; pathways such as neutrophil extracellular trap formation by KEGG analysis; and two metabolism-related items by COG/KOG analysis. Immunoprecipitation confirmed that FTH1-K69la (P = 0007) and PKM2-K166la (P = 0.003), but not ANXA2-K115la (P = 0.127) or ANXA5-K76la (P = 0.361), were more abundant in RA patients versus OA patients. Moreover, FTH1-K69la was positively correlated with erythrocyte sedimentation rate (ESR) in RA patients (P = 0.037). Conclusively, this study describes a general landscape of lactylation proteomics in the RA.

Do the monocyte-derived dendritic cells exert a pivotal role in the early onset of experimental autoimmune uveitis?

BACKGROUND

Eyes are recognized as immunological privileged site. However, the onset of autoimmune uveitis (AU) prompts an influx of dendritic cells (DCs) into the retinas, tasked with presenting auto-antigens, thereby exacerbating the inflammatory response. Monocyte-derived DCs (moDCs) implicated in various autoimmune disorders, but their specific involvement in AU remains unclear. This study aims to investigate the constitution and dynamics of retinal DCs subsequent to the induction of experimental autoimmune uveitis (EAU).

METHODS

In our study, an EAU model was established in C57BL/6J mice, and prednisolone acetate (PA) eye drops were administrated unilaterally to the right eye from 5 days post-immunization (dpi). The infiltration of Gr-1+CD115+CD11c-MHC-II- cells (monocytes), Gr-1+CD115+CD11c+MHC-II+ cells (moDCs) and Gr-1-CD115-CD11c+MHC-II+ cells (conventional dendritic cells, cDCs) within retina were detected by flow cytometry and immunofluorescence stain at 7, 10, 13, and 16 dpi. Additionally, the protein expression and mRNA expression of pivotal cytokines associated with moDCs and inflammation were analysed by western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively.

RESULTS

Our findings unveiled a notable rise in moDCs infiltration and differentiation from 7 to 13 dpi. The administration of PA eye drops did not yield a significant variance in either the quantity or the differentiation rate of moDCs. Throughout the initial stages of EAU, the expression of GM-CSF remained consistent, while TGF-β1 exhibited a sustained increase until 13 dpi in the control group and until 10 dpi following PA treatment. Anti-inflammatory cytokines Il-10 and Il-4 displayed no significant increase until 16 dpi after PA administration.

CONCLUSIONS

Our results indicate that moDCs exhibited an earlier and more substantial infiltration into the inflamed retina compared to cDCs. This heightened presence of moDCs appeared to play a dominant role in the presentation of auto-antigens during the initial stages of EAU, consequently contributing to the exaggerated autoimmune response within the ocular milieu. The administration of PA exhibited no discernible impact on either the differentiation or the infiltration of moDCs.

The emerging role of protein L-lactylation in metabolic regulation and cell signalling

L-Lactate has emerged as a crucial metabolic intermediate, moving beyond its traditional view as a mere waste product. The recent discovery of L-lactate-driven protein lactylation as a post-translational modification has unveiled a pathway that highlights the role of lactate in cellular signalling. In this Perspective, we explore the enzymatic and metabolic mechanisms underlying protein lactylation and its impacts on both histone and non-histone proteins in the contexts of physiology and diseases. We discuss growing evidence suggesting that this modification regulates a wide range of cellular functions and is involved in various physiological and pathological processes, such as cell-fate determination, development, cardiovascular diseases, cancer and autoimmune disorders. We propose that protein lactylation acts as a pivotal mechanism, integrating metabolic and signalling pathways to enable cellular adaptation, and highlight its potential as a therapeutic target in various diseases.

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.

CD4+ T-cell metabolism in the pathogenesis of Sjogren's syndrome

The abnormal effector function of CD4+ T cells plays a key role in the pathogenesis of Sjogren's syndrome (SS) and its associated systematic autoimmune response. Cellular metabolism, including glucose metabolism, lipid metabolism and amino acid metabolism, supports proliferation, migration, survival and differentiation into distinct CD4+ T-cell subsets. Different subtypes of T cells have significantly different demands for related metabolic processes, which enables us to finely regulate CD4+ T cells through different metabolic processes in autoimmune diseases such as SS. In this review, we summarize the effects of disturbances in distinct metabolic processes, such as glycolysis, fatty acid metabolism, glutamine decomposition, mitochondrial dynamics, and ferroptosis, on how to support the effector functions of CD4+ T cells in the SS. We also discuss potential drugs with high value in the treatment of SS through metabolic normalization in CD4+ T cells. Finally, we propose possible directions for future targeted therapy for immunometabolism in SS.

Global Profiling of Protein Lactylation in Human Hippocampi

PURPOSE

The hippocampus has long been associated with cognition and memory function, the implications of lysine lactylation (Kla), a recently identified post-translational modification (PTM), in the role of the hippocampus remain largely unexplored.

EXPERIMENTAL DESIGN

An LC-MS/MS bottom-up proteomics analysis of three human hippocampal tissue samples was applied to profile the lactylation map in human hippocampi under normal physiological conditions.

RESULTS

We identified 2579 quantifiable Class I lactylated sites in 853 proteins, of which contained four types of modification motifs. Cellular localization analysis implies that a majority of lactylated proteins were distributed in the cytoplasm. Functional enrichment analysis showed that lactylated proteins were mainly involved in energy metabolic pathways. In addition, we found that the lactylation on histones exhibits a certain degree of conservation across different tissues. Compared with previously reported lactylation databases, 213 lactylated proteins were identified for the first time in this study.

CONCLUSION AND CLINICAL RELEVANCE

The first global lactylated proteins atlas of human hippocampi was reported in this study. Our work provides a reliable foundation for further research on lactylation in the hippocampus under physiological conditions.

Serpina3k lactylation protects from cardiac ischemia reperfusion injury

Lactate produced during ischemia-reperfusion injury is known to promote lactylation of proteins, which play controversial roles. By analyzing the lactylomes and proteomes of mouse myocardium during ischemia-reperfusion injury using mass spectrometry, we show that both Serpina3k protein expression and its lactylation at lysine 351 are increased upon reperfusion. Both Serpina3k and its human homolog, SERPINA3, are abundantly expressed in cardiac fibroblasts, but not  in cardiomyocytes. Biochemically, lactylation of Serpina3k enhances protein stability. Using Serpina3k knockout mice and mice overexpressing its lactylation-deficient mutant, we find that Serpina3k protects from cardiac injury in a lysine 351 lactylation-dependent manner. Mechanistically, ischemia-reperfusion-stimulated fibroblasts secrete Serpina3k/SERPINA3, and protect cardiomyocytes from reperfusion-induced apoptosis in a paracrine fashion, partially through the activation of cardioprotective reperfusion injury salvage kinase and survivor activating factor enhancement pathways. Our results demonstrate the pivotal role of protein lactylation in cardiac ischemia-reperfusion injury, which may hold therapeutic value.

Non-histone lactylation: unveiling its functional significance

Lactylation, a newly discovered protein posttranslational modification (PTM) in 2019, primarily occurs on lysine residues. Lactylation of histones was initially identified, and subsequent studies have increasingly demonstrated its widespread presence on non-histone proteins. Recently, high-throughput proteomics studies have identified a large number of lactylated proteins and sites, revealing their global regulatory role in disease development. Notably, this modification is catalyzed by lactyltransferase and reversed by delactylase, with numerous new enzymes, such as AARS1/2, reported to be involved. Specifically, these studies have revealed how lactylation exerts its influence through alterations in protein spatial conformation, molecular interactions, enzyme activity and subcellular localization. Indeed, lactylation is implicated in various physiological and pathological processes, including tumor development, cardiovascular and cerebrovascular diseases, immune cell activation and psychiatric disorders. This review provides the latest advancements in research on the regulatory roles of non-histone protein lactylation, highlighting its crucial scientific importance for future studies.

Lactate-induced protein lactylation in cancer: functions, biomarkers and immunotherapy strategies

Lactate, long viewed as a byproduct of glycolysis and metabolic waste. Initially identified within the context of yogurt fermentation, lactate's role extends beyond culinary applications to its significance in biochemical processes. Contemporary research reveals that lactate functions not merely as the terminal product of glycolysis but also as a nexus for initiating physiological and pathological responses within the body. Lysine lactylation (Kla), a novel post-translational modification (PTM) of proteins, has emerged as a pivotal mechanism by which lactate exerts its regulatory influence. This epigenetic modification has the potential to alter gene expression patterns, thereby impacting physiological and pathological processes. Increasing evidence indicates a correlation between lactylation and adverse prognosis in various malignancies. Consequently, this review article aims to encapsulate the proteins that interact with lactate, elucidate the role of lactylation in tumorigenesis and progression, and explore the potential therapeutic targets afforded by the modulation of lactylation. The objective of this review is to clarify the oncogenic significance of lactylation and to provide a strategic framework for future research directions in this burgeoning field.

Infection-induced lysine lactylation enables herpesvirus immune evasion

Aerobic glycolysis is a hallmark of many viral infections, leading to substantial accumulation of lactate. However, the regulatory roles of lactate during viral infections remain poorly understood. Here, we report that human cytomegalovirus (HCMV) infection leverages lactate to induce widespread protein lactylation and promote viral spread. We establish that lactyllysine is enriched in intrinsically disordered regions, regulating viral protein condensates and immune signaling transduction. Dynamic lactylation of immune factors suppresses immunity, a feature we show to be shared for HCMV and herpes simplex virus 1 infections, through regulation of RNA binding protein 14 and interferon-γ-inducible protein 16 (IFI16). K90 lactylation of the viral DNA sensor IFI16 inhibits recruitment of the DNA damage response kinase DNA-PK, preventing IFI16-driven virus gene repression and cytokine induction. Together, we characterize global protein lactylation dynamics during virus infection, finding that virus-induced lactate contributes to its immune evasion through direct inhibition of immune signaling pathways.

ENO2-Regulated Glycolysis in Endothelial Cells Contributes to FGF2-Induced Retinal Neovascularization

Purpose

Ocular neovascularization is a major cause of blindness. Although fibroblast growth factor-2 (FGF2) has been implicated in the pathophysiology of angiogenesis, the underlying mechanisms remain incompletely understood. The purpose of this study was to investigate the role of FGF2 in retinal neovascularization and elucidate its underlying mechanisms.

Methods

The oxygen-induced retinopathy mouse model was used to study the pathogenesis of retinal neovascularization. Immunofluorescence was used to quantify the neovascularization in retina. Data-independent acquisition proteomics were performed to quantify differentially expressed proteins in human retinal microvascular endothelial cells stimulated with FGF2 and associated pathways were analyzed. We carried out qRT-PCR and Western Blot assays to detect the expression of genes at mRNA and protein levels. The angiogenesis abilities of human retinal microvascular endothelial cells were measured by transwell, EdU and tube formation assays.

Results

FGF2 was significantly upregulated in retinal tissues of the oxygen-induced retinopathy mouse model and it markedly enhanced tube formation, migration, and proliferation abilities of human retinal microvascular endothelial cells in vitro. The proteomic analysis identified 287 differentially expressed proteins in endothelial cells in response to FGF2 stimulation, characterized by a notable upregulation of the glycolysis pathway, among which we confirmed that the enolase 2 (ENO2) levels were elevated after FGF2 stimulation, and its knockdown resulted in diminished glycolytic activity and impaired angiogenic processes. Furthermore, the use of the ENO2 inhibitor AP-Ⅲ-a4 alleviated angiogenesis in vivo and in vitro.

Conclusions

Our findings underscore the pivotal role of ENO2-mediated glycolysis in FGF2-induced angiogenesis, suggesting that ENO2 may serve as a promising therapeutic target for managing pathological neovascularization.

Lactylation in health and disease: physiological or pathological?

Lactate is an indispensable substance in various cellular physiological functions and plays regulatory roles in different aspects of energy metabolism and signal transduction. Lactylation (Kla), a key pathway through which lactate exerts its functions, has been identified as a novel posttranslational modification (PTM). Research indicates that Kla is an essential balancing mechanism in a variety of organisms and is involved in many key cellular biological processes through different pathways. Kla is closely related to disease development and represents a potential and important new drug target. In line with existing reports, we searched for newly discovered Kla sites on histone and nonhistone proteins; reviewed the regulatory mechanisms of Kla (particularly focusing on the enzymes directly involved in the reversible regulation of Kla, including "writers" (modifying enzymes), "readers" (modification-binding enzymes), and "erasers" (demodifying enzymes); and summarized the crosstalk between different PTMs to help researchers better understand the widespread distribution of Kla and its diverse functions. Furthermore, considering the "double-edged sword" role of Kla in both physiological and pathological contexts, this review highlights the "beneficial" biological functions of Kla in physiological states (energy metabolism, inflammatory responses, cell fate determination, development, etc.) and its "detrimental" pathogenic or inducive effects on pathological processes, particularly malignant tumors and complex nontumor diseases. We also clarify the molecular mechanisms of Kla in health and disease, and discuss its feasibility as a therapeutic target. Finally, we describe the detection technologies for Kla and their potential applications in diagnosis and clinical settings, aiming to provide new insights for the treatment of various diseases and to accelerate translation from laboratory research to clinical practice.

New Posttranslational Modification Lactylation Brings New Inspiration for the Treatment of Rheumatoid Arthritis

Lactic acid (LA) is an essential glycolytic metabolite and energy source in the body, which is present in high levels in the synovial fluid of patients with rheumatoid arthritis (RA) and is a reliable indicator for identifying inflammatory arthritis. LA not only acts as an inflammatory amplifier in RA, recent studies have found that novel posttranslational modification (PTM) lactylation mediated by LA may also play a key role in RA. Single-cell sequencing showed that the RA lactylation score of patients with RA was significantly increased, and core lactylation-promoting genes, including NDUFB3, NGLY1, and other genes, were found to be potential biomarkers of RA. More studies have shown that lactylation can regulate genes in various cells, such as fibroblast-like synoviocytes (FLSs) and macrophages, thus playing a special role in the development and occurrence of autoimmune diseases, neurological diseases, and cancer diseases. In this paper, we review the research on lactylation in RA-related cells and mechanisms and bring new insights into the pathogenesis, diagnosis, and treatment of RA.

Lactate and Lactylation: Dual Regulators of T-Cell-Mediated Tumor Immunity and Immunotherapy

Lactate and its derivative, lactylation, play pivotal roles in modulating immune responses within the tumor microenvironment (TME), particularly in T-cell-mediated cancer immunotherapy. Elevated lactate levels, a hallmark of the Warburg effect, contribute to immune suppression through CD8+ T cell functionality and by promoting regulatory T cell (Treg) activity. Lactylation, a post-translational modification (PTM), alters histone and non-histone proteins, influencing gene expression and further reinforcing immune suppression. In the complex TME, lactate and its derivative, lactylation, are not only associated with immune suppression but can also, under certain conditions, exert immunostimulatory effects that enhance cytotoxic responses. This review describes the dual roles of lactate and lactylation in T-cell-mediated tumor immunity, analyzing how these factors contribute to immune evasion, therapeutic resistance, and immune activation. Furthermore, the article highlights emerging therapeutic strategies aimed at inhibiting lactate production or disrupting lactylation pathways to achieve a balanced regulation of these dual effects. These strategies offer new insights into overcoming tumor-induced immune suppression and hold the potential to improve the efficacy of cancer immunotherapies.

Ocular immune-related diseases: molecular mechanisms and therapy

Ocular immune-related diseases, represent a spectrum of conditions driven by immune system dysregulation, include but not limit to uveitis, diabetic retinopathy, age-related macular degeneration, Graves' ophthalmopathy, etc. The molecular and cellular mechanisms underlying these diseases are typically dysfunctioned immune responses targeting ocular tissues, resulting in inflammation and tissue damage. Recent advances have further elucidated the pivotal role of different immune responses in the development, progression, as well as management of various ocular immune diseases. However, there is currently a relative lack of connection between the cellular mechanisms and treatments of several immune-related ocular diseases. In this review, we discuss recent findings related to the immunopathogenesis of above-mentioned diseases. In particular, we summarize the different types of immune cells, inflammatory mediators, and associated signaling pathways that are involved in the pathophysiology of above-mentioned ophthalmopathies. Furthermore, we also discuss the future directions of utilizing anti-inflammatory regime in the management of these diseases. This will facilitate a better understanding of the pathogenesis of immune-related ocular diseases and provide new insights for future treatment approaches.

Lactylation of Hdac1 regulated by Ldh prevents the pluripotent-to-2C state conversion

BACKGROUND

Cellular metabolism regulates the pluripotency of embryonic stem cells (ESCs). Yet, how metabolism regulates the transition among different pluripotent states remains elusive. It has been shown that protein lactylation, which uses lactate, a metabolic product of glycolysis, as a substrate, plays a critical role in various biological events. Here we focused on that glycolysis regulates the conversion between ESCs and 2-cell-like cells (2CLCs) through protein lactylation.

METHODS

RNA-seq revealed the activation of 2-cell (2C) genes by suppression of Ldh. Stable isotope labeling by amino acids in cell culture (SILAC) coupled with lactylated peptide enrichment and quantitative mass spectrometric analysis was carried out to investigate the mechanism how protein lactylation regulates the pluripotent-to-2C transition. And we focused on Hdac1. Lactylation of Hdac1 required for silencing 2C genes was proved by quantitative reverse-transcription PCR (qRT-PCR), immunofluorescence (IF), Western blot and chimeric embryos. Chromatin immunoprecipitation coupled with sequencing (ChIP-seq) and in vitro deacetylation assay confirmed lactylation of Hdac1 promoting its binding at 2C genes and enhancing its deacetylase activity, thereby facilitating the removal of H3K27ac and the silencing of 2C genes.

RESULTS

We found that inhibition or depletion of Ldha, the enzyme converting pyruvate to lactate, leads to the activation of 2C genes, as well as reduced global lactylation in ESCs. To investigate the mechanism how protein lactylation regulates the pluripotent-to-2C transition, quantitative lactylome analysis was performed, and 1716 lactylated proteins were identified. We then focused on Hdac1, a histone deacetylase involved in the silencing of 2C genes. Lactylation of Hdac1 promotes its binding at 2C genes and enhances its deacetylase activity, thus facilitating the removal of H3K27ac and the silencing of 2C genes.

CONCLUSIONS

In summary, our study reveals a mechanistic link between cellular metabolism and pluripotency regulation through protein lactylation. Our research is the first time to reveal that quantitative lactylome analysis in mouse ESCs. We found that lactylated Hdac1 promotes its binding at 2C genes and enhances its deacetylase activity, thus facilitating the removal of H3K27ac and the silencing of 2C genes.

Lactate-mediated lactylation in human health and diseases: Progress and remaining challenges

BACKGROUND

Lactate was once considered as metabolic waste for a long time. In 2019, Professor Zhao Yingming's team from the University of Chicago found that lactate could also be used as a substrate to induce histone lactylation and regulate gene expression. Since then, researchers have discovered that lactate-mediated lactylation play important regulatory roles in various physiological and pathological processes.

AIM OF REVIEW

In this review, we aim to discuss the roles and mechanisms of lactylation in human health and diseases, as well as the effects of lactylation on proteins and metabolic modulators targeting lactylation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we emphasize the crucial regulatory roles of lactylation in the development of numerous physiological and pathological processes. Of relevance, we discuss the current issues and challenges pertaining to lactylation. This review provides directions and a theoretical basis for future research and clinical translation of lactylation.

Microglial-mediated immune mechanisms in autoimmune uveitis: Elucidating pathogenic pathways and targeted therapeutics

This review offers a comprehensive examination of the role of microglia in the pathogenesis of autoimmune uveitis, an inflammatory eye disease with significant potential for vision impairment. Central to our discussion is the dual nature of microglial cells, which act as both protectors and potential perpetrators in the immune surveillance of the retina. We explore the mechanisms of microglial activation, highlighting the key signaling pathways involved, such as NF-κB, JAK/STAT, MAPK, and PI3K/Akt. The review also delves into the genetic and environmental factors influencing microglial behavior, underscoring their complex interaction in disease manifestation. Advanced imaging techniques and emerging biomarkers for microglial activation, pivotal in diagnosing and monitoring the disease, are critically assessed. Additionally, we discuss current and novel therapeutic strategies targeting microglial activity, emphasizing the shift towards more precise and personalized interventions. This article aims to provide a nuanced understanding of microglial dynamics in autoimmune uveitis, offering insights into potential avenues for effective treatment and management.

The role of nonhistone lactylation in disease

In 2019, a novel post-translational modification termed lactylation was identified, which established a connection among lactate, transcriptional regulation and epigenetics. Lactate, which is traditionally viewed as a metabolic byproduct, is now recognized for its significant functional role, including modulating the tumor microenvironment, engaging in signaling and interfering in immune regulation. While research on lactylation (KLA) is advancing, the focus has primarily been on histone lactylation. This paper aims to explore the less-studied area of nonhistone lactylation, highlighting its involvement in certain diseases and physiological processes. Additionally, the clinical relevance and potential implications of nonhistone lactylation will be discussed.

Transcription factor EGR2 alleviates autoimmune uveitis via activation of GDF15 to modulate the retinal microglial phenotype

Uveitis is a vision-threatening disease primarily driven by a dysregulated immune response, with retinal microglia playing a pivotal role in its progression. Although the transcription factor EGR2 is known to be closely associated with uveitis, including Vogt-Koyanagi-Harada disease and Behcet's disease, and is essential for maintaining the dynamic homeostasis of autoimmunity, its exact role in uveitis remains unclear. In this study, diminished EGR2 expression was observed in both retinal microglia from experimental autoimmune uveitis (EAU) mice and inflammation-induced human microglia cell line (HMC3). We constructed a mice model with conditional knockout of EGR2 in microglia and found that EGR2 deficiency resulted in increased intraocular inflammation. Meanwhile, EGR2 overexpression downregulated the expression of inflammatory cytokines as well as cell migration and proliferation in HMC3 cells. Next, RNA sequencing and ChIP-PCR results indicated that EGR2 directly bound to its downstream target growth differentiation factor 15 (GDF15) and further regulated GDF15 transcription. Furthermore, intravitreal injection of GDF15 recombinant protein was shown to ameliorate EAU progression in vivo. Meanwhile, knockdown of GDF15 reversed the phenotype of EGR2 overexpression-induced microglial inflammation in vitro. In summary, this study highlighted the protective role of the transcription factor EGR2 in AU by modulating the microglial phenotype. GFD15 was identified as a downstream target of EGR2, providing a unique target for uveitis treatment.

Lactate's impact on immune cells in sepsis: unraveling the complex interplay

Lactate significantly impacts immune cell function in sepsis and septic shock, transcending its traditional view as just a metabolic byproduct. This review summarizes the role of lactate as a biomarker and its influence on immune cell dynamics, emphasizing its critical role in modulating immune responses during sepsis. Mechanistically, key lactate transporters like MCT1, MCT4, and the receptor GPR81 are crucial in mediating these effects. HIF-1α also plays a significant role in lactate-driven immune modulation. Additionally, lactate affects immune cell function through post-translational modifications such as lactylation, acetylation, and phosphorylation, which alter enzyme activities and protein functions. These interactions between lactate and immune cells are central to understanding sepsis-associated immune dysregulation, offering insights that can guide future research and improve therapeutic strategies to enhance patient outcomes.

Overview of dendritic cells and related pathways in autoimmune uveitis

Dendritic cells (DCs) play a crucial role in bridging innate and adaptive immune responses. They are widely distributed in various tissues and organs, including the eyes. In the ocular context, permanent DCs are present at the peripheral edge of the retina and the peripapillary area in an immature state. However, during the inflammatory process, DCs become activated and contribute to the development of uveitis. This review focuses on introducing the characteristics and status of DC-induced uveitis, exploring factors that can influence the status of DCs, and discussing feasible methods for treating DCs in both experimental autoimmune uveitis animal models and humans. It emphasizes the importance of further research on molecular pathways and signaling pathways that regulate the function of DCs. For example, investigating molecules such as cytotoxic T-lymphocyte-associated protein 4, which inhibits the B7-CD28 co-stimulatory interaction, can help improve immune homeostasis. The aim is to identify new therapeutic targets and develop targeted strategies for DCs, such as DC vaccine therapy or the use of immune modulators. These approaches can be tailored to the immune characteristics and disease manifestations of individual patients, enabling personalized treatment strategies. This may include the personalized design and precise medication of DC therapy, with the ultimate goal of improving treatment efficacy while minimizing adverse reactions.

A lactate-responsive gene signature predicts the prognosis and immunotherapeutic response of patients with triple-negative breast cancer

Background

Increased glycolytic activity and lactate production are characteristic features of triple-negative breast cancer (TNBC). The aim of this study was to determine whether a subset of lactate-responsive genes (LRGs) could be used to classify TNBC subtypes and predict patient outcomes.

Methods

Lactate levels were initially measured in different breast cancer (BC) cell types. Subsequently, MDA-MB-231 cells treated with 2-Deoxy-d-glucose or l-lactate were subjected to RNA sequencing (RNA-seq). The gene set variation analysis algorithm was utilized to calculate the lactate-responsive score, conduct a differential analysis, and establish an association with the extent of immune infiltration. Consensus clustering was then employed to classify TNBC patients. Tumor immune dysfunction and exclusion, cibersort, single-sample gene set enrichment analysis, and EPIC, were used to compare the tumor-infiltrating immune cells between TNBC subtypes and predict the response to immunotherapy. Furthermore, a prognostic model was developed by combining 98 machine learning algorithms, to assess the predictive significance of the LRG signature. The predictive value of immune infiltration and the immunotherapy response was also assessed. Finally, the association between lactate and various anticancer drugs was examined based on expression profile similarity principles.

Results

We found that the lactate levels of TNBC cells were significantly higher than those of other BC cell lines. Through RNA-seq, we identified 14 differentially expressed LRGs in TNBC cells under varying lactate levels. Notably, this LRG signature was associated with interleukin-17 signaling pathway dysregulation, suggesting a link between lactate metabolism and immune impairment. Furthermore, the LRG signature was used to categorize TNBC into two distinct subtypes, whereby Subtype A was characterized by immunosuppression, whereas Subtype B was characterized by immune activation.

Conclusion

We identified an LRG signature in TNBC, which could be used to predict the prognosis of patients with TNBC and gauge their response to immunotherapy. Our findings may help guide the precision treatment of patients with TNBC.

Advances in the interaction of glycolytic reprogramming with lactylation

Lactylation is a novel post-translational modification (PTM) involving proteins that is induced by lactate accumulation. Histone lysine lactylation alters chromatin spatial configuration, influencing gene transcription and regulating the expression of associated genes. This modification plays a crucial role as an epigenetic regulatory factor in the progression of various diseases. Glycolytic reprogramming is one of the most extensively studied forms of metabolic reprogramming, recognized as a key hallmark of cancer cells. It is characterized by an increase in glycolysis and the inhibition of the tricarboxylic acid (TCA) cycle, accompanied by significant lactate production and accumulation. The two processes are closely linked by lactate, which interacts in various physiological and pathological processes. On the one hand, lactylation levels generally correlate positively with the extent of glycolytic reprogramming, being directly influenced by the lactate concentration produced during glycolytic reprogramming. On the other hand, lactylation can also regulate glycolytic pathways by affecting the transcription and structural functions of essential glycolytic enzymes. This review comprehensively outlines the mechanisms of lactylation and glycolytic reprogramming and their interactions in tumor progression, immunity, and inflammation, with the aim of elucidating the relationship between glycolytic reprogramming and lactylation.

Histone H3K18 and Ezrin Lactylation Promote Renal Dysfunction in Sepsis-Associated Acute Kidney Injury

Histone lactylation is a metabolic stress-related histone modification. However, the role of histone lactylation in the development of sepsis-associated acute kidney injury (SA-AKI) remains unclear. Here, histone H3K18 lactylation (H3K18la) is elevated in SA-AKI, which is reported in this study. Furthermore, this lactate-dependent histone modification is enriched at the promoter of Ras homolog gene family member A (RhoA) and positively correlated with the transcription. Correction of abnormal lactate levels resulted in a reversal of abnormal histone lactylation at the promoter of RhoA. Examination of related mechanism revealed that histone lactylation promoted the RhoA/Rho-associated protein kinase (ROCK) /Ezrin signaling, the activation of nuclear factor-κB (NF-κB), inflammation, cell apoptosis, and aggravated renal dysfunction. In addition, Ezrin can undergo lactylation modification. Multiple lactylation sites are identified in Ezrin and confirmed that lactylation mainly occurred at the K263 site. The role of histone lactylation is revealed in SA-AKI and reportes a novel post-translational modification in Ezrin. Its potential role in regulating inflammatory metabolic adaptation of renal proximal tubule epithelial cells is also elucidated. The results provide novel insights into the epigenetic regulation of the onset of SA-AKI.

Lactylation: The emerging frontier in post-translational modification

Lactate, a metabolic byproduct, has gained recognition as a highly influential signaling molecule. Lactylation, an emerging form of post-translational modification derived from lactate, plays a crucial role in numerous cellular processes such as inflammation, embryonic development, tumor proliferation, and metabolism. However, the precise molecular mechanisms through which lactylation governs these biological functions in both physiological and pathological contexts remain elusive. Hence, it is imperative to provide a comprehensive overview of lactylation in order to elucidate its significance in biological processes and establish a foundation for forthcoming investigations. This review aims to succinctly outline the process of lactylation modification and the characterization of protein lactylation across diverse organisms. Additionally, A summary of the regulatory mechanisms of lactylation in cellular processes and specific diseases is presented. Finally, this review concludes by delineating existing research gaps in lactylation and proposing primary directions for future investigations.

A feedback loop driven by H3K9 lactylation and HDAC2 in endothelial cells regulates VEGF-induced angiogenesis

BACKGROUND

Vascular endothelial growth factor (VEGF) is one of the most powerful proangiogenic factors and plays an important role in multiple diseases. Increased glycolytic rates and lactate accumulation are associated with pathological angiogenesis.

RESULTS

Here, we show that a feedback loop between H3K9 lactylation (H3K9la) and histone deacetylase 2 (HDAC2) in endothelial cells drives VEGF-induced angiogenesis. We find that the H3K9la levels are upregulated in endothelial cells in response to VEGF stimulation. Pharmacological inhibition of glycolysis decreases H3K9 lactylation and attenuates neovascularization. CUT& Tag analysis reveals that H3K9la is enriched at the promoters of a set of angiogenic genes and promotes their transcription. Interestingly, we find that hyperlactylation of H3K9 inhibits expression of the lactylation eraser HDAC2, whereas overexpression of HDAC2 decreases H3K9 lactylation and suppresses angiogenesis.

CONCLUSIONS

Collectively, our study illustrates that H3K9la is important for VEGF-induced angiogenesis, and interruption of the H3K9la/HDAC2 feedback loop may represent a novel therapeutic method for treating pathological neovascularization.

YY1 Lactylation Aggravates Autoimmune Uveitis by Enhancing Microglial Functions via Inflammatory Genes

Activated microglia in the retina are essential for the development of autoimmune uveitis. Yin-Yang 1 (YY1) is an important transcription factor that participates in multiple inflammatory and immune-mediated diseases. Here, an increased YY1 lactylation in retinal microglia within in the experimental autoimmune uveitis (EAU) group is observed. YY1 lactylation contributed to boosting microglial activation and promoting their proliferation and migration abilities. Inhibition of lactylation suppressed microglial activation and attenuated inflammation in EAU. Mechanistically, cleavage under targets & tagmentation （CUT&Tag） analysis revealed that YY1 lactylation promoted microglial activation by regulating the transcription of a set of inflammatory genes, including STAT3, CCL5, IRF1, IDO1, and SEMA4D. In addition, p300 is identified as the writer of YY1 lactylation. Inhibition of p300 decreased YY1 lactylation and suppressed microglial inflammation in vivo and in vitro. Collectively, the results showed that YY1 lactylation promoted microglial dysfunction in autoimmune uveitis by upregulating inflammatory cytokine secretion and boosting cell migration and proliferation. Therapeutic effects can be achieved by targeting the lactate/p300/YY1 lactylation/inflammatory genes axis.

Regulation of newly identified lysine lactylation in cancer

Metabolic reprogramming is a typical hallmark of cancer. Enhanced glycolysis in tumor cells leads to the accumulation of lactate, which is traditionally considered metabolic waste. With the development of high-resolution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), the lactate-derived, lysine lactylation(Kla), has been identified. Kla can alter the spatial configuration of chromatin and regulate the expression of corresponding genes. Metabolic reprogramming and epigenetic remodeling have been extensively linked. Accumulating studies have subsequently expanded the framework on the key roles of this protein translational modification (PTM) in tumors and have provided a new concept of cancer-specific regulation by Kla.

Basic Mechanisms of Immunometabolites in Shaping the Immune Response

BACKGROUND

Innate immune cells play a crucial role in responding to microbial infections, but their improper activation can also drive inflammatory disease. For this reason, their activation state is governed by a multitude of factors, including the metabolic state of the cell and, more specifically, the individual metabolites which accumulate intracellularly and extracellularly. This relationship is bidirectional, as innate immune cell activation by pathogen-associated molecular patterns causes critical changes in cellular metabolism.

SUMMARY

In this review, we describe the emergence of various "immunometabolites." We outline the general characteristics of these immunometabolites, the conditions under which they accumulate, and their subsequent impact on immune cells. We delve into well-studied metabolites of recent years, such as succinate and itaconate, as well as newly emerging immunometabolites, such as methylglyoxal.

KEY MESSAGES

We hope that this review may be used as a framework for further studies dissecting the mechanisms by which immunometabolites regulate the immune system and provide an outlook to harnessing these mechanisms in the treatment of inflammatory diseases.