Pharmacological elevation of lactate alleviates sepsis via histone lactylation-induced IL-10 production.

Sepsis is the major cause of death in intensive care units. We previously found that intermedin (IMD), a calcitonin family peptide, can protect against sepsis by dynamically repairing vascular endothelial junctions and can ameliorate the inflammatory response by inhibiting the infiltration of macrophages in peripheral tissues. The effects of IMD on inflammatory and immune responses indicate that IMD may play a role in immunity. However, whether IMD affects immune cell development, differentiation and response to infection remains unclear. IMD-knockout (Adm2-/-) mice were generated in our previous work. Wild-type and IMD-KO mice were subjected to sham or cecal ligation and puncture (CLP) surgery, and bone marrow cells were obtained for RNA sequencing (RNA-Seq) analysis. The RNA-Seq results were verified by real-time RT-PCR. The effect of IMD KO or IMD rescue on the septic mice was explored using mild and severe infection models induced by CLP surgery at different levels of severity, and the survival outcomes were analyzed using Kaplan-Meier curves and the log-rank test. The mechanism underlying the effects of IMD in T/B cell proliferation and differentiation were investigated by PCR, Western blot (WB), and cell proliferation assays and flow cytometry analysis. RNA-Seq showed that IMD-KO mice exhibited a primary immunosuppression phenotype characterized by a marked decrease in the expression of T- and B-cell function-related genes. This immunosuppression made the IMD-KO mice vulnerable to pathogenic invasion, and even mild infection killed nearly half of the IMD-KO mice. Supplementation with the IMD peptide restored the expression of T/B-cell-related genes and significantly reduced the mortality rate of the IMD-KO mice. IMD is likely to directly promote T- and B-cell proliferation through ERK1/2 phosphorylation, stimulate T-cell differentiation via Ilr7/Rag1/2-controled T cell receptor (TCR) recombination, and activate B cells via Pax5, a transcription factor that activates at least 170 genes needed for B-cell functions. Together with previous findings, our results indicate that IMD may play a protective role in sepsis via three mechanisms: protecting the vascular endothelium, reducing the inflammatory response, and activating T/B-cell proliferation and differentiation. Our study may provide the first identification of IMD as a calcitonin peptide that plays an important role in the adaptive immune response by activating T/B cells and provides translational opportunities for the design of immunotherapies for sepsis and other diseases associated with primary immunodeficiency.

Sepsis is a severe system inflammatory response syndrome in response to infection. The vascular endothelium cells play a key role in sepsis-induced organ dysfunction. The heat shock protein 70 (HSP70) has been reported to play an anti-inflammatory role and protect from sepsis. The present study is aimed at finding the function of HSP70 against sepsis in vascular endothelium cells. Lipopolysaccharide (LPS) and HSP70 agonist and inhibitor were used to treat HUVEC. Cell permeability was measured by transepithelial electrical resistance (TEER) assay and FITC-Dextrans. Cell junction protein levels were measured by western blot. Mice were subjected to cecal ligation and puncture (CLP) to establish a sepsis model and were observed for survival. After LPS incubation, HSP70 expression was decreased in HUVEC. LPS induced the inhibition of cell viability and the increases of IL-1β, IL-6, and TNF-α. Furthermore, cell permeability was increased and cell junction proteins (E-cadherin, occludin, and ZO-1) were downregulated after treatment with LPS. However, HSP70 could reverse these effects induced by LPS in HUVEC. In addition, LPS-induced elevated phosphorylation of p38 can be blocked by HSP70. On the other hand, we found that inhibition of HSP70 had similar effects as LPS and these effects could be alleviated by the inhibitor of p38. Subsequently, HSP70 was also found to increase survival of sepsis mice in vivo. In conclusion, HSP70 plays a protective role in sepsis by maintenance of the endothelial permeability via regulating p38 signaling.

Ischemic retinal diseases are major causes of blindness worldwide and are characterized by pathological angiogenesis. Epigenetic alterations in response to metabolic shifts in endothelial cells (ECs) suffice to underlie excessive angiogenesis. Lactate accumulation and its subsequent histone lactylation in ECs contribute to vascular disorders. However, the regulatory mechanism of establishing and sustaining lactylation modification remains elusive. Here, we showed that lactate accumulation induced histone lactylations on H3K9 and H3K18 in neovascular ECs in the proliferative stage of oxygen-induced retinopathy. Joint CUT&Tag and scRNA-seq analyses identified Prmt5 as a target of H3K9la and H3K18la in isolated retinal ECs. EC-specific deletion of Prmt5 since the early stage of revascularization suppressed a positive feedback loop of lactate production and histone lactylation, thus inhibiting neovascular tuft formation. Mechanistically, the C-terminal intrinsically disorder region (IDR) of the transmembrane semaphorin 6A (SEMA6A) forms liquid-liquid phase separation condensates to recruit RHOA and P300, facilitating P300 phosphorylation and histone lactylation cycle. Deletion of endothelial Sema6A reduced H3K9la and H3K18la at the promoter of PRMT5 and diminished its expression. The induction of histone lactylation by SEMA6A-IDR and its pro-angiogenic effect were abrogated by deletion of Prmt5. Our study illustrates a sustainable histone lactylation machinery driven by phase separation-dependent lactyltransferase activation in dysregulated vascularization.

Lactate-Mediated Histone H3K9 Lactylation Facilitates Tumorigenesis of T-Cell Lymphoma Via Activation of SFXN1 Expression

Inflammation resolution and cardiac repair initiation after myocardial infarction (MI) require timely activation of reparative signals. Histone lactylation confers macrophage homeostatic gene expression signatures via transcriptional regulation. However, the role of histone lactylation in the repair response post-MI remains unclear. We aimed to investigate whether histone lactylation induces reparative gene expression in monocytes early and remotely post-MI. Single-cell transcriptome data indicated that reparative genes were activated early and remotely in bone marrow and circulating monocytes before cardiac recruitment. Western blotting and immunofluorescence staining revealed increases in histone lactylation levels, including the previously identified histone H3K18 lactylation in monocyte-macrophages early post-MI. Through joint CUT&Tag and RNA-sequencing analyses, we identified Lrg1, Vegf-a, and IL-10 as histone H3K18 lactylation target genes. The increased modification and expression levels of these target genes post-MI were verified by chromatin immunoprecipitation-qPCR and reverse transcription-qPCR. We demonstrated that histone lactylation regulates the anti-inflammatory and pro-angiogenic dual activities of monocyte-macrophages by facilitating reparative gene transcription and confirmed that histone lactylation favors a reparative environment and improves cardiac function post-MI. Furthermore, we explored the potential positive role of monocyte histone lactylation in reperfused MI. Mechanistically, we provided new evidence that monocytes undergo metabolic reprogramming in the early stage of MI and demonstrated that dysregulated glycolysis and MCT1 (monocarboxylate transporter 1)-mediated lactate transport promote histone lactylation. Finally, we revealed the catalytic effect of IL (interleukin)-1β-dependent GCN5 (general control non-depressible 5) recruitment on histone H3K18 lactylation and elucidated its potential role as an upstream regulatory element in the regulation of monocyte histone lactylation and downstream reparative gene expression post-MI. Histone lactylation promotes early remote activation of the reparative transcriptional response in monocytes, which is essential for the establishment of immune homeostasis and timely activation of the cardiac repair process post-MI.

Introduction: Cardiac hypertrophy is characterized by significant metabolic changes, notably an increase in glycolysis. Histone lactylation, a post-translational modification influenced by the glycolytic state of cells, plays a crucial role in regulating gene transcription. However, the relationship between histone lactylation and cardiac hypertrophy remains unclear. Research Questions: This study aims to elucidate the effects and underlying mechanisms of histone lactylation in the progression of cardiac hypertrophy induced by pressure overload. Methods and Results: We observed an increase in histone lactylation levels in hypertrophic hearts from both humans and mice. To investigate further, male mice underwent transverse aortic constriction (TAC) to induce cardiac hypertrophy, followed by either an intraperitoneal injection of Oxamate (an LDHA inhibitor) to reduce histone lactylation or sodium lactate to increase it. Reducing histone lactylation protected the hearts from TAC-induced hypertrophy and fibrosis, preserving cardiac function, while increased histone lactylation exacerbated cardiac hypertrophy and fibrosis, impairing cardiac function. Cardiomyocyte-specific deletion of LDHA also led to a reduction in cardiac hypertrophy. In vitro experiments showed that inhibiting histone lactylation reduced the expression of hypertrophic markers and the hypertrophic growth of cardiomyocytes stimulated by phenylephrine. Using co-immunoprecipitation, we confirmed that P300 and GCN5 are the transferases mediating histone lactylation in cardiomyocytes. Mechanistic studies using the CUT&Tag technique revealed lactate-dependent histone modification was enriched at the promoter of TGFB2, activating its transcription. Inhibiting cardiac-specific TGFB2 expression through adeno-associated viral delivery of shRNA reduced TAC-induced cardiac hypertrophy. Furthermore, TGFB2 overexpression induced a hypertrophic phenotype in cardiomyocytes and activated the PI3K/AKT/mTOR pathways. This hypertrophic phenotype, induced by TGFB2 overexpression, was suppressed by inhibitors of PI3K or AKT. Conclusion: Our findings reveal a critical role for histone lactylation in the development of pathological cardiac hypertrophy by regulating TGFB2 expression and the PI3K/AKT/mTOR pathway.

Plasma gelsolin is a circulating actin-binding protein that serves a protective role against tissue injuries. Depletion of plasma gelsolin in systemic inflammation may contribute to adverse outcomes. We examined the role of plasma gelsolin in animal models of sepsis. Animal and laboratory experiments. Academic research laboratory. Adult male mice. Mice subjected to endotoxin or cecal ligation and puncture (CLP) were treated with exogenous plasma gelsolin or placebo. We document the depletion of plasma gelsolin (25-50% of normal) in murine models of sepsis associated with the presence of circulating actin within 6 hrs of septic challenge. Repletion of plasma gelsolin leads to solubilization of circulating actin aggregates and significantly reduces mortality in endotoxemic mice (survival rates were 88% in the gelsolin group vs. 0% in the saline group, p < .001) and in CLP-challenged mice (survival rates were 30% in the gelsolin group vs. 0% in the saline group, p = .001). Plasma gelsolin repletion also shifted the cytokine profile of endotoxemic mice toward anti-inflammatory (plasma interleukin-10 levels were 205 +/- 108 pg/mL in the gelsolin group vs. 39 +/- 29 pg/mL in the saline group, p = .02). We propose that circulation of particulate actin is a marker for sepsis-induced cell injury, that plasma gelsolin has a crucial protective role in sepsis, and that gelsolin replacement represents a potential therapy for this common lethal condition.

Obesity is a risk factor for sepsis morbidity and mortality, whereas the hypothalamic–pituitary–adrenal (HPA) axis plays a protective role in the body's defence against sepsis. Sepsis induces a profound systemic immune response and cytokines serve as excellent markers for sepsis as they act as mediators of the immune response. Evidence suggests that the adipokine leptin may play a pathogenic role in sepsis. Mouse endotoxaemic models present with elevated leptin levels and exogenously added leptin increased mortality whereas human septic patients have elevated circulating levels of the soluble leptin receptor (Ob-Re). Evidence suggests that leptin can inhibit the regulation of the HPA axis. Thus, leptin may suppress the HPA axis, impairing its protective role in sepsis. We hypothesised that leptin would attenuate the HPA axis response to sepsis. We investigated the direct effects of an i.p. injection of 2 mg/kg leptin on the HPA axis response to intraperitoneally injected 25 μg/kg lipopolysaccharide (LPS) in the male Wistar rat. We found that LPS potently activated the HPA axis, as shown by significantly increased plasma stress hormones, ACTH and corticosterone, and increased plasma interleukin 1β (IL1β) levels, 2 h after administration. Pre-treatment with leptin, 2 h before LPS administration, did not influence the HPA axis response to LPS. In turn, LPS did not affect plasma leptin levels. Our findings suggest that leptin does not influence HPA function or IL1β secretion in a rat model of LPS-induced sepsis, and thus that leptin is unlikely to be involved in the acute-phase endocrine response to bacterial infection in rats.

Cardiac hypertrophy is accompanied by profound metabolic remodeling, including enhanced glycolysis. Histone lactylation, a posttranslational modification linked to glycolytic activity, has been shown to regulate gene transcription. However, its role in cardiac hypertrophy remains unclear. Histone lactylation was assessed in failing human and mouse hearts. Male mice subjected to transverse aortic constriction were treated with oxamate (an LDHA [lactate dehydrogenase A] inhibitor) or sodium lactate to modulate histone lactylation. Cardiomyocyte-specific Ldha deletion was also evaluated. In vitro, phenylephrine-stimulated neonatal rat ventricular myocytes were used to examine the effects of lactylation inhibition. Potential histone lactylation transferases were identified by coimmunoprecipitation. Promoter-specific histone lactylation was analyzed by Cleavage Under Targets and Tagmentation and ChIP quantitative polymerase chain reaction, and transcriptional regulation was further evaluated by nascent RNA-seq. TGFB2 (transforming growth factor β2) function was investigated using AAV-shRNA knockdown and lentiviral overexpression in combination with pharmacological inhibition of PI3K (phosphoinositide 3-kinase) or AKT (protein kinase B). Histone lactylation was elevated in failing human and mouse hearts. Reducing lactylation attenuated transverse aortic constriction-induced hypertrophy and fibrosis, preserving cardiac function, whereas increasing lactylation exacerbated pathological remodeling. In vitro, inhibition of lactylation suppressed phenylephrine-induced cardiomyocyte hypertrophy. P300 and GCN5 (general control non-derepressible 5) were identified as candidate lactylation transferases. Cleavage Under Targets and Tagmentation revealed lactate-dependent enrichment of H3K18la (histone H3 lysine 18 lactylation) at the TGFB2 promoter, correlating with increased TGFB2 expression. Cardiac-specific Tgfb2 knockdown reversed the prohypertrophic effects of histone lactylation in vivo, while Tgfb2 overexpression promoted cardiomyocyte hypertrophy via PI3K/AKT/mTOR (mechanistic target of rapamycin) signaling. Pharmacological inhibition of PI3K or AKT attenuated this effect. Histone lactylation promotes pathological cardiac hypertrophy and heart failure by upregulating TGFB2 and activating PI3K/AKT/mTOR signaling. These findings identify histone lactylation as an epigenetic link between metabolic reprogramming and hypertrophic signaling, and suggest it as a potential therapeutic target for pathological cardiac remodeling.

Lactate-triggered histone lactylation contributes to podocyte epithelial-mesenchymal transition in diabetic nephropathy in mice.

Dietary Selenium deficiency activates the NLRP3 inflammasome to induce gallbladder pyroptosis by regulating glycolysis and histone lactylation through ROS/HIF-1α pathway.

Apelin is the native ligand for the G protein-coupled receptor APJ. Numerous studies have demonstrated that the Apelin/APJ system has positive inotropic, anti-inflammatory, and anti-apoptotic effects and regulates fluid homeostasis. The Apelin/APJ system has been demonstrated to play a protective role in sepsis and may serve as a promising therapeutic target for the treatment of sepsis. Better understanding of the mechanisms of the effects of the Apelin/APJ system will aid in the development of novel drugs for the treatment of sepsis. In this review, we provide a brief overview of the physiological role of the Apelin/APJ system and its role in sepsis.

Long-term histone lactylation connects metabolic and epigenetic rewiring in innate immune memory.

Vascular smooth muscle cells (VSMCs) undergo phenotypic changes during the development of aortic aneurysm and dissection (AAD). Metabolism shifts from oxidative phosphorylation to glycolysis. Recent studies suggest that epigenetics plays a crucial role in AAD. The epigenetic regulation of histone lactylation was analyzed in the aorta of patients with aortic aneurysm and in a murine model of AAD. Histone lactylation was also studied in VSMCs treated with angiotensin II. The epigenetic pathway involving H4K16 lactylation (H4K16la) was explored in vitro and in vivo. To examine the role of H4K16la in AAD formation, mice lacking Pdk1 or Kat7 in VSMCs were created. Mice were treated with pharmacological inhibitors of Pdk1 or Kat7. The levels of blood lactate, aortic lactate, and aortic H4K16la were compared between patients with aortic aneurysm and controls. Histone lactylation (H4K16la) was increased in the aortic tissues of patients with AAD and mice. Enhanced histone lactylation was linked to increased pyruvate dehydrogenase kinase 1 (PDK1) transcription, which accelerated lactate production in VSMCs. A positive feedback loop was identified involving H4K16la, PDK1, and lactate; this pathway alters the metabolism and phenotype of VSMCs. KAT7 (lysine acetyltransferase 7) was found to be a histone lactyltransferase for histone lactylation in VSMCs. Genetic or pharmacological inhibition of PDK1 or KAT7 decreased AAD injury by disrupting the H4K16la/PDK1/lactate pathway. Patients with AAD have elevated lactate in blood and aortic tissues and elevated H4K16la in aortic tissues compared with control patients. Histone lactylation changes the metabolism and phenotype of VSMC in AAD. Inhibition of PDK1 or KAT7 may be a novel approach to treat or prevent AAD.

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor which is classified as a long-pentraxin in the pentraxin family. It is known to play an important role in innate immunity, inflammatory regulation, and female fertility. PTX3 is synthesized by specific cells, primarily in response to inflammatory signals. Among these various cells, neutrophils have a unique PTX3 production system. Neutrophils store PTX3 in neutrophil-specific granules and then the stored PTX3 is released and localizes in neutrophil extracellular traps (NETs). Although certain NET components have been identified, such as histones and anti-microbial proteins, the detailed mechanisms by which NETs localize, as well as capture and kill microbes, have not been fully elucidated. PTX3 is a candidate diagnostic marker of infection and vascular damage. In severe infectious diseases such as sepsis, the circulating PTX3 concentration increases greatly (up to 100 ng/mL, i.e., up to 100-fold of the normal level). Even though it is clearly implied that PTX3 plays a protective role in sepsis and certain other disorders, the detailed mechanisms by which it does so remain unclear. A proteomic study of PTX3 ligands in septic patients revealed that PTX3 forms a complex with certain NET component proteins. This suggests a role for PTX3 in which it facilitates the efficiency of anti-microbial protein pathogen clearance by interacting with both pathogens and anti-microbial proteins. We discuss the possible relationships between PTX3 and NET component proteins in the host protection afforded by the innate immune response. The PTX3 complex has the potential to be a highly useful diagnostic marker of sepsis and other inflammatory diseases.