PKM2: A Potential Regulator of Rheumatoid Arthritis via Glycolytic and Non-Glycolytic Pathways

Single-cell characterisation of tissue homing CD4 + and CD8 + T cell clones in immune-mediated refractory arthritis

BACKGROUND

Immune-mediated arthritis is a group of autoinflammatory diseases, where the patient's own immune system attacks and destroys synovial joints. Sustained remission is not always achieved with available immunosuppressive treatments, warranting more detailed studies of T cell responses that perpetuate synovial inflammation in treatment-refractory patients.

METHODS

In this study, we investigated CD4 + and CD8 + T lymphocytes from the synovial tissue and peripheral blood of patients with treatment-resistant immune-mediated arthritis using paired single-cell RNA and TCR-sequencing. To gain insights into the trafficking of clonal families, we compared the phenotypes of clones with the exact same TCRß amino acid sequence between the two tissues.

RESULTS

Our results show that both CD4 + and CD8 + T cells display a more activated and inflamed phenotype in the synovial tissue compared to peripheral blood both at the population level and within individual T cell families. Furthermore, we found that both cell subtypes exhibited clonal expansion in the synovial tissue.

CONCLUSIONS

Our findings suggest that the local environment in the synovium drives the proliferation of activated cytotoxic T cells, and both CD4 + and CD8 + T cells may contribute to tissue destruction and disease pathogenesis.

Glycolysis: an emerging regulator of osteoarthritis

Osteoarthritis (OA) has been a leading cause of disability in the elderly and there remains a lack of effective therapeutic approaches as the mechanisms of pathogenesis and progression have yet to be elucidated. As OA progresses, cellular metabolic profiles and energy production are altered, and emerging metabolic reprogramming highlights the importance of specific metabolic pathways in disease progression. As a crucial part of glucose metabolism, glycolysis bridges metabolic and inflammatory dysfunctions. Moreover, the glycolytic pathway is involved in different areas of metabolism and inflammation, and is associated with a variety of transcription factors. To date, it has not been fully elucidated whether the changes in the glycolytic pathway and its associated key enzymes are associated with the onset or progression of OA. This review summarizes the important role of glycolysis in mediating cellular metabolic reprogramming in OA and its role in inducing tissue inflammation and injury, with the aim of providing further insights into its pathological functions and proposing new targets for the treatment of OA.

Silencing PKM2 Attenuates Brain Injury Induced by Status Epilepticus by Inhibiting the AKT/mTOR Pathway and the NLRP3 Inflammasome

PKM2 is a glycolytic pyruvate kinase isoenzyme, and its role in neurological diseases has been published. However, the role and mechanism of PKM2 in the process of status epilepticus have not been reported. The purpose of this study is to explore the role and mechanism of PKM2 in epilepsy. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to explore the expression of PKM2 in cells. Enzyme-linked immunosorbent assay kits were used to evaluate the level of inflammatory factors. An epilepsy model was established by intraperitoneal injection of lithium chloride in rats. Various behavioural assays were conducted to explore the learning ability and cognitive level of rats. PKM2 expression was upregulated in Mg2+-induced hippocampal neurons. PKM2 inhibition ameliorated Mg2+-induced hippocampal neuronal inflammation and reduced neuronal apoptosis. In addition, PKM2 silencing inhibited the metabolic dysfunction of Mg2+-induced hippocampal neurons. Subsequent experiments showed that the Akt/mTOR pathway and NLRP3 inflammasome are involved in PKM2-mediated neuronal regulation. More importantly, PKM2 inhibition could alleviate status epilepticus in rats. PKM2 inhibition attenuates Mg2+-induced hippocampal neuronal inflammation, apoptosis and metabolic dysfunction and improves the cognitive ability of rats. Therefore, PKM2 may be an important target for epilepsy treatment.

Recent Advances on PKM2 Inhibitors and Activators in Cancer Applications

Metabolic reprogramming of cells, from the normal mode of glucose metabolism named glycolysis, is a pivotal characteristic of impending cancerous cells. Pyruvate kinase M2 (PKM2), an important enzyme that catalyzes the final rate-limiting stage during glycolysis, is highly expressed in numerous types of tumors and aids in development of favorable conditions for the survival of tumor cells. Increasing evidence has suggested that PKM2 is one of promising targets for innovative drug discovery, especially for the developments of antitumor therapeutics. Herein, we systematically summarize the recent advancement on PKM2 modulators including inhibitors and activators in cancer applications. We also discussed the classifications of pyruvate kinases in mammals and the biological functions of PKM2 in this review. We do hope that this review would provide a comprehensive understanding of the current research on PKM2 modulators, which may benefit the development of more potent PKM2-related drug candidates to treat PKM2-associated diseases including cancers in future.

Association between glycolysis markers and prognosis of liver cancer: a systematic review and meta-analysis

BACKGROUND

In recent years, the capacity of tumor cells to maintain high levels of glycolysis, even in the presence of oxygen, has emerged as one of the main metabolic traits and garnered considerable attention. The purpose of this meta-analysis is to investigate the prognostic value of glycolysis markers in liver cancer.

METHODS

PubMed, Embase, and Cochrane Library databases were searched for articles on glycolytic marker expression levels associated with the prognosis of liver cancer until April 2023. Stata SE14.0 was used to calculate the aggregate hazard ratios and 95% confidence intervals.

RESULTS

Thirty-five studies were included. The worse overall survival (OS) (P < 0.001), disease-free survival (DFS) (P = 0.001), recurrence-free survival (RFS) (P = 0.004), and time to recurrence (TTR) (P < 0.001) were significantly associated with elevated expression of glycolysis markers. Higher expression of PKM2 (P < 0.001), STMN1 (P = 0.002), MCT4 (P < 0.001), GLUT1 (P = 0.025), HK-2 (P < 0.001), and CA9 (P < 0.001) were significantly related to shorter OS. Increased levels of PKM2 (P < 0.001), CA9 (P = 0.005), and MCT4 (P < 0.001) were associated with worse DFS. Elevated PKM2 expression (P = 0.002) was also associated with poorer RFS in hepatocellular carcinoma patients. GLUT2 expression was not correlated with the prognosis of liver cancer (P = 0.134).

CONCLUSIONS

Elevated expression of glycolysis markers was associated with worse OS, DFS, RFS, and TTR in patients with liver cancer. Therefore, these glycolysis markers could serve as potential prognostic markers and therapeutic targets in liver cancer.

TRIAL REGISTRATION

PROSPERO registration: CRD42023469645.

Targeting glycolytic pathway in fibroblast-like synoviocytes for rheumatoid arthritis therapy: challenges and opportunities

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by hyperplastic synovium, pannus formation, immune cell infiltration, and potential articular cartilage damage. Notably, fibroblast-like synoviocytes (FLS), especially rheumatoid arthritis fibroblast-like synoviocytes (RAFLS), exhibit specific overexpression of glycolytic enzymes, resulting in heightened glycolysis. This elevated glycolysis serves to generate ATP and plays a pivotal role in immune regulation, angiogenesis, and adaptation to hypoxia. Key glycolytic enzymes, such as hexokinase 2 (HK2), phosphofructose-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), and pyruvate kinase M2 (PKM2), significantly contribute to the pathogenic behavior of RAFLS. This increased glycolysis activity is regulated by various signaling pathways.

MATERIALS AND METHODS

A comprehensive literature search was conducted to retrieve relevant studies published from January 1, 2010, to the present, focusing on RAFLS glycolysis, RA pathogenesis, glycolytic regulation pathways, and small-molecule drugs targeting glycolysis.

CONCLUSION

This review provides a thorough exploration of the pathological and physiological characteristics of three crucial glycolytic enzymes in RA. It delves into their putative regulatory mechanisms, shedding light on their significance in RAFLS. Furthermore, the review offers an up-to-date overview of emerging small-molecule candidate drugs designed to target these glycolytic enzymes and the upstream signaling pathways that regulate them. By enhancing our understanding of the pathogenic mechanisms of RA and highlighting the pivotal role of glycolytic enzymes, this study contributes to the development of innovative anti-rheumatic therapies.

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.

Dexamethasone inhibits IL-8 via glycolysis and mitochondria-related pathway to regulate inflammatory pain

BACKGROUND

Dexamethasone (Dexa) has been recently found to exert an analgesic effect, whose action is closely related to IL-8. However, whether dexamethasone induces antinociception via glycolysis and mitochondria-related pathways is still unclear.

METHODS

Right hind paw inflammatory pain in mice was induced by intraplantar injection of Freund's Complete Adjuvant (FCA). Von Frey test was then used to measure the paw withdrawal threshold. The detection of glycolysis and mitochondrial pathway-related proteins and IL-8 were determined by Western blot and ELISA. The potential interaction between Dexa and fructose-1,6-bisphosphate (FBP, a PKM2 activator) was examined by simulation predictions using molecular docking.

RESULTS

Intrathecal administration of Dexa (20 µg/20 µL) had an obvious analgesic effect in FCA-treated mice, which was counteracted by the glycolysis inhibitor 2-deoxyglucose (2-DG, 5 mg/20 µL) or the mitochondria-related pathway inhibitor oligomycin complex (Oligo, 5 µg/20 µL). In the glycolysis pathway, Dexa decreased GLUT3 and had no impact on HIF-1α expression during FCA-induced inflammation. Additionally, Dexa further increased the PKM2 level, accompanied by the formation of hydrogen bonds between Dexa and the PKM2 activator fructose-1,6-bisphosphate (FBP). In the mitochondrial pathway, Dexa downregulated the expression of Mfn2 protein but not the PGC-1α and SIRT-1 levels in the spinal cord. Moreover, both 2-DG and Oligo decreased Mfn2 expression. Finally, IL-8 level was reduced by the single or combined administration of Dexa, 2-DG, and Oligo.

CONCLUSION

Dexa attenuated IL-8 expression via glycolysis and mitochondrial pathway-related proteins, thus mediating the analgesic effect during inflammatory pain.

Sarsasapogenin, a principal active component absorbed into blood of total saponins of Anemarrhena, attenuates proliferation and invasion in rheumatoid arthritis fibroblast-like synoviocytes through downregulating PKM2 inhibited pathological glycolysis

Increased glycolytic in fibroblast-like synoviocytes (FLS) of rheumatoid arthritis (RA) not only contributes to early-stage disease pathogenesis but leads to sustained proliferation of FLS. Given the importance of PKM2 in glycolysis and apoptosis, PKM2 is considered a potential therapeutic and drug discovery target in RA. Total saponins of anemarrhena (TSA), a class of steroid saponins, originated from Anemarrhena asphodeloides Bge. In this study, we verified that 200 mg/kg TSA could significantly alleviate inflammation and the pathological characteristics of RA and inhibit synovial hyperplasia in AA rats. We confirmed that sarsasapogenin (SA) was the principal active ingredient absorbed into the blood of TSA by the UPLC/Q Exactive MS test. Then we used TNF-α-induced MH7A to get the conclusion that 20 μM SA could effectively inhibit the glycolysis by inhibiting the activity of PKM2 tetramer and glucose uptake. Moreover, 20 μM SA could suppress proliferation, migration, invasion, and cytokine release of FLS, interfere with the growth cycle of FLS, and induce FLS apoptosis by depressing the phosphorylation of PKM2. At last, In-1, a potent inhibitor of the PKM2 was used to reverse verify the above results. Taken together, the key mechanisms of SA on RA treatment through downregulating the activity of PKM2 tetramer and phosphorylation of PKM2 inhibited pathological glycolysis and induced apoptosis to exert inhibition on the proliferation and invasion of RA FLS.

Metabolic profile of mesenchymal stromal cells and macrophages in the presence of polyethylene particles in a 3D model

BACKGROUND

Continuous cross talk between MSCs and macrophages is integral to acute and chronic inflammation resulting from contaminated polyethylene particles (cPE); however, the effect of this inflammatory microenvironment on mitochondrial metabolism has not been fully elucidated. We hypothesized that (a) exposure to cPE leads to impaired mitochondrial metabolism and glycolytic reprogramming and (b) macrophages play a key role in this pathway.

METHODS

We cultured MSCs with/without uncommitted M0 macrophages, with/without cPE in 3-dimensional gelatin methacrylate (3D GelMA) constructs/scaffolds. We evaluated mitochondrial function (membrane potential and reactive oxygen species-ROS production), metabolic pathways for adenosine triphosphate (ATP) production (glycolysis or oxidative phosphorylation) and response to stress mechanisms. We also studied macrophage polarization toward the pro-inflammatory M1 or the anti-inflammatory M2 phenotype and the osteogenic differentiation of MSCs.

RESULTS

Exposure to cPE impaired mitochondrial metabolism of MSCs; addition of M0 macrophages restored healthy mitochondrial function. Macrophages exposed to cPE-induced glycolytic reprogramming, but also initiated a response to this stress to restore mitochondrial biogenesis and homeostatic oxidative phosphorylation. Uncommitted M0 macrophages in coculture with MSC polarized to both M1 and M2 phenotypes. Osteogenesis was comparable among groups after 21 days.

CONCLUSION

This work confirmed that cPE exposure triggers impaired mitochondrial metabolism and glycolytic reprogramming in a 3D coculture model of MSCs and macrophages and demonstrated that macrophages cocultured with MSCs undergo metabolic changes to maintain energy production and restore homeostatic metabolism.

Role of Moonlighting Proteins in Disease: Analyzing the Contribution of Canonical and Moonlighting Functions in Disease Progression

The term moonlighting proteins refers to those proteins that present alternative functions performed by a single polypeptide chain acquired throughout evolution (called canonical and moonlighting, respectively). Over 78% of moonlighting proteins are involved in human diseases, 48% are targeted by current drugs, and over 25% of them are involved in the virulence of pathogenic microorganisms. These facts encouraged us to study the link between the functions of moonlighting proteins and disease. We found a large number of moonlighting functions activated by pathological conditions that are highly involved in disease development and progression. The factors that activate some moonlighting functions take place only in pathological conditions, such as specific cellular translocations or changes in protein structure. Some moonlighting functions are involved in disease promotion while others are involved in curbing it. The disease-impairing moonlighting functions attempt to restore the homeostasis, or to reduce the damage linked to the imbalance caused by the disease. The disease-promoting moonlighting functions primarily involve the immune system, mesenchyme cross-talk, or excessive tissue proliferation. We often find moonlighting functions linked to the canonical function in a pathological context. Moonlighting functions are especially coordinated in inflammation and cancer. Wound healing and epithelial to mesenchymal transition are very representative. They involve multiple moonlighting proteins with a different role in each phase of the process, contributing to the current-phase phenotype or promoting a phase switch, mitigating the damage or intensifying the remodeling. All of this implies a new level of complexity in the study of pathology genesis, progression, and treatment. The specific protein function involved in a patient's progress or that is affected by a drug must be elucidated for the correct treatment of diseases.

Polyene phosphatidylcholine ameliorates synovial inflammation: involvement of PTEN elevation and glycolysis suppression

BACKGROUND

Synovial inflammation, characterized by the activation of synovial fibroblasts (SFs), is a crucial factor to drive the progression of rheumatoid arthritis (RA). Polyene phosphatidylcholine (PPC), the classic hepatoprotective drug, has been reported to ameliorate arthritis in animals. However, the molecular mechanism remains poorly understood. METHODS AND RESULTS: Using in vitro primary synovial fibroblast (SFs) culture system, we revealed that phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, mediates the anti-inflammatory effect of PPC in lipopolysaccharide (LPS)-stimulated primary SFs. PPC decreased the production of TNF-α and IL-6 production while elevating the level of IL-10 and TGF-β. Furthermore, PPC up-regulated the expression of PTEN, but inhibited the expression of p-AKT (ser473) and PI3K-p85α. Moreover, pre-treatment of SF1670 (the inhibitor of PTEN) or 740Y-P (the agonist of AKT/PI3K pathways) partially abrogated the anti-inflammatory effect of PPC. In addition, PPC could inhibit the expression of GLUT4, a key transporter of glucose that fuels the glycolysis, which is accompanied by the expression downregualtion of glycolytic enzymes PFKFB3 and PKM2. Furthermore, PPC could reduce ROS production and mitochondrial membrane potential in LPS-stimulated SFs and MH7A cell line.

CONCLUSION

The present study supported that PPC can alleviate synovial inflammation, which involves in the elevation of PTEN and blockage of glycolysis.

Rheumatoid arthritis and mitochondrial homeostasis: The crossroads of metabolism and immunity

Rheumatoid arthritis is an autoimmune disease characterized by chronic symmetric synovial inflammation and erosive bone destruction. Mitochondria are the main site of cellular energy supply and play a key role in the process of energy metabolism. They possess certain self-regulatory and repair capabilities. Mitochondria maintain relative stability in number, morphology, and spatial structure through biological processes, such as biogenesis, fission, fusion, and autophagy, which are collectively called mitochondrial homeostasis. An imbalance in the mitochondrial homeostatic environment will affect immune cell energy metabolism, synovial cell proliferation, apoptosis, and inflammatory signaling. These biological processes are involved in the onset and development of rheumatoid arthritis. In this review, we found that in rheumatoid arthritis, abnormal mitochondrial homeostasis can mediate various immune cell metabolic disorders, and the reprogramming of immune cell metabolism is closely related to their inflammatory activation. In turn, mitochondrial damage and homeostatic imbalance can lead to mtDNA leakage and increased mtROS production. mtDNA and mtROS are active substances mediating multiple inflammatory pathways. Several rheumatoid arthritis therapeutic agents regulate mitochondrial homeostasis and repair mitochondrial damage. Therefore, modulation of mitochondrial homeostasis would be one of the most attractive targets for the treatment of rheumatoid arthritis.

The Sarcoplasmic Protein Profile of Breast Muscle in Turkeys in Response to Different Dietary Ratios of Limiting Amino Acids and Clostridium perfringens-Induced Inflammation

In this study, the effects of the Arginine/Lysine (Arg/Lys) ratio in low- and high-methionine (Met) diets on the sarcoplasmic protein profile of breast muscles from turkeys reared under optimal or challenge (Clostridium perfringens infection) conditions were determined. One-day-old Hybrid Converter female turkey poults (216 in total) obtained from a commercial hatchery on hatching day, and on the basis of their average initial body weight were randomly allocated to 12 pens (4 m² each; 2.0 m × 2.0 m) containing litter bedding and were reared over a 42-day experimental period. Diets with high levels of Lys contained approximately 1.80% and 1.65% Lys and were offered in two successive feeding periods (days 1–28 and days 29–42). The supplemental levels of Lys were consistent with the nutritional specifications for birds at their respective ages as established in the Management Guidelines for Raising Commercial Turkeys. The experiment was based on a completely randomized 3 × 2 × 2 factorial design with three levels of Arg (90%, 100% and 110%) relative to the content of dietary Met (30 or 45%) and without (−) or with (+) C. perfringens challenge at 34, 36, or 37 d of age. Meat samples were investigated in terms of pH, color, and sarcoplasmic protein profile. The experimental factors did not influence meat quality but the dietary Arg content affected meat color. The sarcoplasmic protein profile was influenced by all studied factors, and glycolytic enzymes were the most abundant. This study evidenced strong association between the challenge conditions and the involvement of glycolytic enzymes in cell metabolism, particularly in inflammatory processes, and DNA replication and maintenance in turkeys. The results showed an effect of C. perfringens infection and feeding with different doses of Arg and Met may lead to significant consequences in cell metabolism.

Assessment of disease activity in patients with rheumatoid arthritis using plasma tumour M2-pyruvate kinase test

Background

Pyruvate kinase M2 (PKM2) is an enzyme that regulates the final process of glycolysis and exists in tetrameric and dimeric forms. The dimeric form of PKM2, also known as tumour M2-PK, increases when aerobic glycolysis is augmented, a feature observed in rheumatoid arthritis (RA). We investigated whether plasma tumour M2-PK is elevated in patients with RA and whether its levels correlate with disease activity.

Methods

Plasma levels of tumour M2-PK were measured for patients with RA (n=151), those with osteoarthritis (OA) (n=37), and controls (n=37). We evaluated the association between plasma tumour M2-PK and continuous variables using Pearson’s correlation analysis, and multivariate logistic regression analysis to determine the association between plasma tumour M2-PK and disease activity status. Knee synovial tissue blocks from patients with RA and OA were subjected to real-time quantitative PCR (qPCR) using two different primers for PKM2 and tumour M2-PK immunohistochemical (IHC) staining.

Results

The tumour M2-PK level significantly correlated with the disease activity score in 28 joints (DAS28)-erythrocyte sedimentation rate (ESR) (r=0.546, p<0.001) and DAS28-C-reactive protein (CRP) (r=0.589, p<0.001). Moreover, repeat testing of tumour M2-PK levels in 20 patients revealed a significant decline in tumour M2-PK levels after reduction in inflammation (p<0.001). Area under the receiver operating characteristic curve (AUROC) analysis demonstrated that upon incorporation of tumour M2-PK, ESR, and CRP, the area under the curve was 0.962 for distinguishing moderate/high from remission/low disease activity. Adjusted logistic regression also revealed that a tumour M2-PK >43.9 U/mL (OR 3.672, p=0.042) independently predicted moderate/high disease activity status. Furthermore, tumour M2-PK levels in patients with RA were significantly higher than in those with OA and controls (all p<0.001). However, no differences were found in PKM2 expression in RA and OA synovial tissues as assessed by qPCR, and IHC analysis revealed negligible tumour M2-PK expression in the synovial tissues.

Conclusion

Circulating plasma tumour M2-PK levels may be a clinically useful indicator for evaluating disease activity and RA diagnosis.

Research progress on the role of PKM2 in the immune response

Pyruvate kinase (PK) is a key enzyme that catalyzes the dephosphorylation of phosphoenolpyruvate (PEP) into pyruvate, and is responsible for the production of ATP during glycolysis. As another important isozyme of PK, pyruvate kinase M2 (PKM2) exists in cells with high levels of nucleic acid synthesis, such as normal proliferating cells (e.g., lymphocytes and intestinal epithelial cells), embryonic cells, adult stem cells, and tumor cells. With further research, PKM2, as an important regulator of cellular pathophysiological activity, has attracted increasing attention in the process of autoimmune response and inflammatory. In this re]view, we examine the contribution of PKM2 to the human immune response. Further studies on the immune mechanisms of PKM2 are expected to provide more new ideas and drug targets for immunotherapy of inflammatory and autoimmune diseases, guiding drug development and disease treatment.

Plasma Pyruvate Kinase M2 as a marker of vascular inflammation in giant cell arteritis

OBJECTIVES

GCA is a large vessel vasculitis in which metabolically active immune cells play an important role. GCA diagnosis is based on CRP/ESR and temporal artery biopsies (TABs), in combination with 18F-fluorodeoxyglucose ([18F]FDG)-PET/CT relying on enhanced glucose uptake by glycolytic macrophages. Here, we studied circulating Pyruvate Kinase M2 (PKM2), a glycolytic enzyme, as a possible systemic marker of vessel wall inflammation in GCA.

METHODS

Immunohistochemical detection of PKM2 was performed on inflamed (n = 12) and non-inflamed (n = 4) TABs from GCA patients and non-GCA (n = 9) patients. Dimeric PKM2 levels were assessed in plasma of GCA patients (n = 44), age-matched healthy controls (n = 41), metastatic melanoma patients (n = 7) and infection controls (n = 11). CRP, ESR and macrophage markers calprotectin and YKL-40 were correlated with plasma PKM2 levels. To detect the cellular source of plasma PKM2 in tissue, double IF staining was performed on inflamed GCA TABs. [18F]FDG-PET scans of 23 GCA patients were analysed and maximum standard uptake values and target to background ratios were calculated.

RESULTS

PKM2 is abundantly expressed in TABs of GCA patients. Dimeric PKM2 plasma levels were elevated in GCA and correlated with CRP, ESR, calprotectin and YKL-40 levels. Elevated plasma PKM2 levels were downmodulated by glucocorticoid treatment. PKM2 was detected in both macrophages and T cells at the site of vascular inflammation. Circulating PKM2 levels correlated with average target to background ratios PET scores.

CONCLUSION

Elevated plasma PKM2 levels reflect active vessel inflammation in GCA and may assist in disease diagnosis and in disease monitoring.

Lactate metabolism in rheumatoid arthritis: Pathogenic mechanisms and therapeutic intervention with natural compounds

BACKGROUND

Rheumatoid arthritis (RA) is a common chronic and systemic autoimmune disease characterized by persistent inflammation and hyperplasia of the synovial membrane, the degradation of cartilage, and the erosion of bones in diarthrodial joints. The inflamed joints of patients with RA have been recognized to be a site of hypoxic microenvironment which results in an imbalance of lactate metabolism and the accumulation of lactate. Lactate is no longer considered solely a metabolic waste product of glycolysis, but also a combustion aid in the progression of RA from the early stages of inflammation to the late stages of bone destruction.

PURPOSE

To review the pathogenic mechanisms of lactate metabolism in RA and investigate the potential of natural compounds for treating RA linked to the regulation of imbalance in lactate metabolism.

METHODS

Research advances in our understanding of lactate metabolism in the pathogenesis of RA and novel pharmacological approaches of natural compounds by targeting lactate metabolic signaling were comprehensively reviewed and deeply discussed.

RESULTS

Lactate produced by RA synovial fibroblasts (RASFs) acts on targeted cells such as T cells, macrophages, dendritic cells and osteoclasts, and affects their differentiation, activation and function to accelerate the development of RA. Many natural compounds show therapeutic potential for RA by regulating glycolytic rate-limiting enzymes to limit lactate production, and affecting monocarboxylate transporter and acetyl-CoA carboxylase to inhibit lactate transport and conversion.

CONCLUSION

Regulation of imbalance in lactate metabolism offers novel therapeutic approaches for RA, and natural compounds capable of targeting lactate metabolic signaling constitute potential candidates for development of drugs RA.

Podocyte specific deletion of PKM2 ameliorates LPS-induced podocyte injury through beta-catenin

BACKGROUND

Acute kidney injury (AKI) is associated with a severe decline in kidney function caused by abnormalities within the podocytes' glomerular matrix. Recently, AKI has been linked to alterations in glycolysis and the activity of glycolytic enzymes, including pyruvate kinase M2 (PKM2). However, the contribution of this enzyme to AKI remains largely unexplored.

METHODS

Cre-loxP technology was used to examine the effects of PKM2 specific deletion in podocytes on the activation status of key signaling pathways involved in the pathophysiology of AKI by lipopolysaccharides (LPS). In addition, we used lentiviral shRNA to generate murine podocytes deficient in PKM2 and investigated the molecular mechanisms mediating PKM2 actions in vitro.

RESULTS

Specific PKM2 deletion in podocytes ameliorated LPS-induced protein excretion and alleviated LPS-induced alterations in blood urea nitrogen and serum albumin levels. In addition, PKM2 deletion in podocytes alleviated LPS-induced structural and morphological alterations to the tubules and to the brush borders. At the molecular level, PKM2 deficiency in podocytes suppressed LPS-induced inflammation and apoptosis. In vitro, PKM2 knockdown in murine podocytes diminished LPS-induced apoptosis. These effects were concomitant with a reduction in LPS-induced activation of β-catenin and the loss of Wilms' Tumor 1 (WT1) and nephrin. Notably, the overexpression of a constitutively active mutant of β-catenin abolished the protective effect of PKM2 knockdown. Conversely, PKM2 knockdown cells reconstituted with the phosphotyrosine binding-deficient PKM2 mutant (K433E) recapitulated the effect of PKM2 depletion on LPS-induced apoptosis, β-catenin activation, and reduction in WT1 expression.

CONCLUSIONS

Taken together, our data demonstrates that PKM2 plays a key role in podocyte injury and suggests that targetting PKM2 in podocytes could serve as a promising therapeutic strategy for AKI.

TRIAL REGISTRATION

Not applicable. Video abstract.

The enhanced mitochondrial dysfunction by cantleyoside confines inflammatory response and promotes apoptosis of human HFLS-RA cell line via AMPK/Sirt 1/NF-κB pathway activation

OBJECTIVE

Cantleyoside (CA) is a kind of iridoid glycosides in Pterocephalus hookeri (C. B. Clarke) Höeck. The purpose of this study was to investigate the effects of CA on human rheumatoid arthritis fibroblast synovial cells (HFLS-RA).

METHODS

Cell proliferation of HFLS-RA was assessed by CCK-8. ELISA was used to detect cytokines NO, TNF-α, IL-1β/6, MCP-1, MMP-1/3/9 and metabolism-related ATPase activities and ATP levels. JC-1, DCFH-DA, Fluo-3 AM and Calcein AM probes were used to detect mitochondrial membrane potential (MMP), reactive oxygen species (ROS), Ca²⁺ and mitochondrial permeability conversion pore (MPTP), respectively. Isolated mitochondria assay was used to detect mitochondrial swelling. Oxygen consumption rate (OCR), extracellular acidification rate (ECAR) and real-time ATP production were measured using a Seahorse analyzer. Apoptosis was detected by TUNEL and Hoechst staining. Western blot was used to detect the expressions of AMPK/p-AMPK, Sirt 1, IκBα, NF-κB p65/p-NF-κB p65, Bcl-2 and Bax. Cytoplasmic nuclear isolation was also performed to detect the translocation of NF-κB.

RESULTS

CA significantly suppressed cell proliferation and the levels of NO, TNF-α, IL-1β/6, MCP-1 and MMP-1/3/9 in HFLS-RA. In addition, CA promoted the apoptosis of HFLS-RA by increasing TUNEL and Hoechst positive cells and the ratio of Bax/Bcl-2. Inhibition of energy metabolism in HFLS-RA by CA reduced OCR, ECAR and real-time ATP generation rate. Importantly, CA promoted p-AMPK and Sirt 1 expression, inhibited IκBα degradation to reduce p-NF-κB and translocation.

CONCLUSION

The results suggest that CA activates the AMPK/Sirt 1/NF-κB pathway by promoting mitochondrial dysfunction, thereby exerting anti-inflammatory and pro-apoptotic effects.

Thermal and wine processing enhanced Clematidis Radix et Rhizoma ameliorate collagen Ⅱ induced rheumatoid arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Clematidis Radix et Rhizoma, a kind of traditional Chinese medicine, is derived from Clematis chinensis Osbeck, Clematis hexapetala Pall. and Clematis manshurica Rupr. This herb shows great effects on expelling wind and dispelling dampness in ancient and it has anti-inflammatory and analgesic activity in modern clinical application.

AIM OF THE STUDY

This experiment aimed to research anti-rheumatoid arthritis effect of crude and wine processed RC based on glycolysis metabolism to provide new ideas treating RA.

MATERIALS AND METHODS

Network pharmacology was applied to preliminarily forecast the potential pathways of common targets of RC and RA. RAW264.7 macrophages were induced by LPS, NO production, glucose uptake, lactate production, ROS and MMP were detected as instructions in vitro. ELISA was used to measure the content of HK2, PKM2 and LDHA involving in glycolysis process. Gut microbiota was analyzed by 16S rRNA gene amplicon sequencing in CIA rats.

RESULTS

Crude and wine processed RC had good anti-inflammatory effect by reducing NO in RAW264.7 macrophages and ameliorating inflammatory infiltration and cartilage surface erosion in CIA rats. Whether in LPS-induced macrophages or CIA rats, crude and wine processed RC could inhibit glycolysis by down-regulating the expression of PKM2, causing less glucose uptake and lactic acid, which lead to less ROS and higher MMP to normal. PI3K-AKT and HIF-1α pathways were deduced to possibly play a crucial part in controlling glycolysis metabolism by network pharmacology analysis. Besides, it was displayed that Firmicutes and Bacteroidetes were prominent gut microbiota in CIA rats feces. CC-H and PZ-H groups could both increase the relative abundance of Firmicutes and decrease Bacteroidetes. These microbiota also played a role in RA pathological process via involving in energy metabolism, carbohydrate metabolism and immune system.

CONCLUSION

Crude and wine processed RC have a good influence in ameliorating rheumatoid arthritis by inhibiting glycolysis and modulating gut microbiota together.

Noncoding RNAs in the Glycolysis of Ovarian Cancer

Energy metabolism reprogramming is the characteristic feature of tumors. The tumorigenesis, metastasis, and drug resistance of ovarian cancer (OC) is dependent on energy metabolism. Even under adequate oxygen conditions, OC cells tend to convert glucose to lactate, and glycolysis can rapidly produce ATP to meet their metabolic energy needs. Non-coding RNAs (ncRNAs) interact directly with DNA, RNA, and proteins to function as an essential regulatory in gene expression and tumor pathology. Studies have shown that ncRNAs regulate the process of glycolysis by interacting with the predominant glycolysis enzyme and cellular signaling pathway, participating in tumorigenesis and progression. This review summarizes the mechanism of ncRNAs regulation in glycolysis in OC and investigates potential therapeutic targets.

Immunoregulatory effects of Lactococcus lactis-derived extracellular vesicles in allergic asthma

Background

Probiotics have been shown to prevent various allergic diseases by producing extracellular vesicles (EVs). However, the role of EVs in allergic asthma has not yet been completely determined.

Methods

Gut microbial composition, mainly genera related to probiotics, was investigated in allergic asthmatic mice. Moreover, EVs were isolated from Lactococcus lactis (L. lactis, a selected bacterium) and EV proteins were identified by peptide mass fingerprinting. EV functions in immune responses were evaluated in vivo or ex vivo. Furthermore, the levels of specific IgG antibodies (an alternative marker for EV quantification) to L. lactis‐EVs were measured by ELISA in the sera of 27 asthmatic patients and 26 healthy controls.

Results

Allergic asthmatic mice showed a lower proportion of Lactococcus compared to healthy mice. L. lactis was cultured and its EVs abundantly contained pyruvate kinase. When allergic asthmatic mice were intranasally treated with EVs, airway hyperresponsiveness, eosinophil number, cytokine secretion, and mucus production were significantly decreased. Moreover, L. lactis‐EV treatment shifted immune responses from Th2 to Th1 by stimulating dendritic cells to produce IL‐12. In addition, significantly lower levels of serum specific IgG4 (but not IgG1) to L. lactis‐EVs were noted in asthmatic patients than in healthy controls. A positive correlation between the levels of EV‐specific IgG4 and FEV₁ (%), but a negative correlation between the levels of EV‐specific IgG4 and IL‐13 were observed.

Conclusion

These findings suggest that L. lactis‐EVs may have immune‐regulating effects on airway inflammation mediated by dendritic cell activation, providing a potential benefit for allergic asthma.

α-Mangostin Alleviated HIF-1α-Mediated Angiogenesis in Rats With Adjuvant-Induced Arthritis by Suppressing Aerobic Glycolysis

A previously validated anti-rheumatic compound α-mangostin (MAN) shows significant metabolism regulatory effects. The current study aimed to clarify whether this property contributed to its inhibition on synovial angiogenesis. Male wistar rats with adjuvant-induced arthritis (AIA) were orally treated by MAN for 32 days. Afterwards, biochemical parameters and cytokines in plasma were determined by corresponding kits, and glycometabolism-related metabolites were further accurately quantified by LC-MS method. Anti-angiogenic effects of MAN were preliminarily assessed by joints based-immunohistochemical examination and matrigel plug assay. Obtained results were then validated by experiments in vitro. AIA-caused increase in circulating transforming growth factor beta, interleukin 6, hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in blood and local HIF-1α/VEGF expression in joints was abrogated by MAN treatment, and pannus formation within matrigel plugs implanted in AIA rats was inhibited too. Scratch and transwell assays revealed the inhibitory effects of MAN on human umbilical vein endothelial cells (HUVECs) migration. Furthermore, MAN inhibited tubule formation capability of HUVECs and growth potential of rat arterial ring-derived endothelial cells in vitro. Meanwhile, MAN eased oxidative stress, and altered glucose metabolism in vivo. Glycolysis-related metabolites including glucose 6-phosphate, fructose 6-phosphate, 3-phosphoglyceric acid and phosphoenolpyruvic acid in AIA rats were decreased by MAN, while the impaired pyruvate-synthesizing capability of lactate dehydrogenase (LDH) was recovered. Consistently, MAN restored lipopolysaccharide-elicited changes on levels of glucose and LDH in HUVECs culture system, and exerted similar effects with LDH inhibitor stiripentol on glycometabolism and VEGF production as well as tubule formation capability of HUVECs. These evidences show that MAN treatment inhibited aerobic glycolysis in AIA rats, which consequently eased inflammation-related hypoxia, and hampered pathological neovascularization.

Metabolomics in Autoimmune Diseases: Focus on Rheumatoid Arthritis, Systemic Lupus Erythematous, and Multiple Sclerosis

The metabolomics approach represents the last downstream phenotype and is widely used in clinical studies and drug discovery. In this paper, we outline recent advances in the metabolomics research of autoimmune diseases (ADs) such as rheumatoid arthritis (RA), multiple sclerosis (MuS), and systemic lupus erythematosus (SLE). The newly discovered biomarkers and the metabolic mechanism studies for these ADs are described here. In addition, studies elucidating the metabolic mechanisms underlying these ADs are presented. Metabolomics has the potential to contribute to pharmacotherapy personalization; thus, we summarize the biomarker studies performed to predict the personalization of medicine and drug response.

New potential therapeutic approaches targeting synovial fibroblasts in rheumatoid arthritis

Synovial cells play a key role in joint destruction during chronic inflammation. In particular, activated synovial fibroblasts (SFs) undergo intrinsic alterations leading to an aggressive phenotype mediating cartilage destruction and bone erosion in rheumatoid arthritis (RA). Recent research has revealed a number of targets to control arthritogenic changes in SFs. Therefore, identification of SF phenotypes, control of epigenetic changes, modulation of cellular functions, or regulation of the activity of cation channels and different signaling pathways has been investigated. Although many of these approaches have shown efficacy in vitro and in animal models of RA, further research is needed to select the most relevant targets for drug development. This review is focused on the role of SFs as a potential strategy to discover novel therapeutic targets in RA aimed at preserving joint architecture and function.

Paraquat promotes acute lung injury in rats by regulating alveolar macrophage polarization through glycolysis

The present study investigates whether paraquat (PQ) regulates polarization of alveolar macrophages through glycolysis and promotes the occurrence of acute lung injury in rats. In vivo, the PQ intraperitoneal injection was used to construct a model of acute lung injury in rats. In vitro, the study measured the effect of different concentrations of PQ on the viability of the alveolar macrophages, and explored the polarization and glycolysis metabolism of alveolar macrophages at different time points after PQ intervention. Compared with the normal control (NC) group, the lung pathological damage in rats increased gradually after PQ poisoning, reaching a significant degree at 48 h after poisoning. The PQ-poisoned rat serum showed increased expressions of interleukin-6 (IL-6), tumor necrosis factor- α (TNF-α), and M1 macrophage marker, iNOS, while the expression of interleukin-10 (IL-10) and M2 macrophage marker, Arg1, decreased. The toxic effect of PQ on alveolar macrophages was dose- and time-dependent. Compared with the NC group, IL-6 and TNF-α in the cell supernatant gradually increased after PQ intervention, while the IL-10 content gradually decreased. The PQ intervention in alveolar macrophages increased the expression of intracellular glycolysis rate-limiting enzyme pyruvate kinase isozymes M1/M2 (PKM1/M2), lactate, lactate/pyruvate ratio, and the polarization of alveolar macrophage towards M1. Inhibition of cellular glycolysis significantly reduced the PQ-induced alveolar macrophage polarization to M1 type. Thus, PQ induced increased polarization of lung macrophages toward M1 and decreased polarization toward M2, promoting acute lung injury. Therefore, it can be concluded that PQ regulates the polarization of alveolar macrophages through glycolysis.

Norisoboldine Attenuates Sepsis-Induced Acute Lung Injury by Modulating Macrophage Polarization via PKM2/HIF-1α/PGC-1α Pathway

This study aimed to investigate the effect of norisopoldine (NOR) on acute lung injury in septic mice. Lipopolysaccharide (LPS) was used to establish sepsis induced acute lung injury (ALI) in mice. The dry and wet weight of mice lung was detected, and the pathological changes of lung were observed by hematoxylin and eosin (H&E) staining. Bronchoalveolar lavage fluid (BALF) was detected. Inflammatory factors in BALF were detected by enzyme-linked immunosorbent assay (ELISA). The polarization of macrophages in lung tissue was detected by flow cytometry. The markers of M1 and M2 macrophages were detected by RT-PCR. LPS induced RAW264.7 cells were treated with NOR. Inflammatory response, macrophage polarization, glycolysis, and M2 pyruvate kinase (PKM2)/hypoxia inducible factor-1α (HIF-1α)/peroxisome proliferator activated receptor-γ co-activator 1-α (PGC-1α) signaling pathway were detected. NOR could effectively alleviate sepsis induced ALI, and reduce the number of total cells, total protein concentration, neutrophils, macrophages in BALF. NOR decreased the level of inflammatory factors and promoted macrophages from M1 to M2 type in vivo and vitro. Moreover, NOR could activated PKM2, and inhibited PKM2 from cytoplasm to nuclear, attenuated HIF-1α expression, and increased PGC-1α and peroxisome proliferator-activated receptor (PPAR)-γ expression. In addition, NOR inhibited glycolysis and promoted oxidative phosphorylation in RAW264.7 cells. Furthermore, PKM2 inhibitors could reverse the effect of NOR on PKM2/HIF-1α/PGC-1α signaling pathway in RAW264.7 cells. NOR alleviated sepsis induced AIL in mice, inhibited the inflammatory response, promote M2 polarization of macrophages through regulating PKM2/HIF-1α/PGC-1α signaling pathway.

2-Deoxy-D-glucose Alleviates Collagen-Induced Arthritis of Rats and Is Accompanied by Metabolic Regulation of the Spleen and Liver

Rheumatoid arthritis (RA) is significantly associated with glycolysis. This study used 2-deoxy-D-glucose (2-DG), an inhibitor of glycolysis, to treat rats with collagen-induced arthritis (CIA) and investigate the metabolic regulatory mechanism of glycolysis in the disease. 2-DG significantly alleviated CIA. Metabolomics and transcriptomics, as well as their integrative analysis, detected significant changes in the pathways of bile secretion, cholesterol and linoleic acid metabolism in the plasma, liver and spleen during the CIA process and the opposite changes following 2-DG treatment, whereas the expression of the genes regulating these metabolic pathways were changed only in the spleen. In the rat liver, levels of (S)-5-diphosphomevalonic acid in the terpenoid backbone biosynthesis pathway were significantly decreased during CIA progression and increased following 2-DG treatment, and levels of taurochenodeoxycholic acid in the pentose and glucuronate interconversions pathway showed the opposite results. In the spleen, levels of 3-methoxy-4-hydroxyphenylglycol glucuronide in bile secretion and 12(S)-leukotriene B4 in arachidonic acid metabolism were significantly decreased during CIA progression and increased following 2-DG treatment. The changes in the gene-metabolite network of bile secretion in the spleen correlated with a decreased plasma L-acetylcarnitine level in CIA rats and an increase following 2-DG treatment. Our analysis suggests the involvement of spleen and liver metabolism in CIA under the control of glycolysis.

Pharmacological Effects of Polyphenol Phytochemicals on the JAK-STAT Signaling Pathway

The JAK-STAT signaling pathway is a common pathway of many cytokine signal transductions, closely related to cell proliferation, apoptosis, differentiation, and inflammatory response. It is essential for inhibiting the inflammatory response, initiating innate immunity, and coordinating adaptive immune mechanisms. Owing to the nature of this pathway and its potential cross-epitopes with multiple alternative pathways, the long-term efficacy of monotherapy-based adaptive targeting therapy is limited, and the majority of drugs targeting STATs are still in the preclinical phase. Meanwhile, curcumin, quercetin, and several kinds of plant polyphenol chemicals play roles in multiple sites of the JAK-STAT pathway to suppress abnormal activation. Polyphenol compounds have shown remarkable effects by acting on the JAK-STAT pathway in anti-inflammatory, antitumor, and cardiovascular disease control. This review summarizes the pharmacological effects of more than 20 kinds of phytochemicals on JAK-STAT signaling pathway according to the chemical structure of polyphenolic phytochemicals.

Metabolic enzymes function as epigenetic modulators: A Trojan Horse for chromatin regulation and gene expression

Epigenetic modification is a fundamental biological process in living organisms, which has significant impact on health and behavior. Metabolism refers to a set of life-sustaining chemical reactions, including the uptake of nutrients, the subsequent conversion of nutrients into energy or building blocks for organism growth, and finally the clearance of redundant or toxic substances. It is well established that epigenetic modifications govern the metabolic profile of a cell by modulating the expression of metabolic enzymes. Strikingly, almost all the epigenetic modifications require substrates produced by cellular metabolism, and a large proportion of metabolic enzymes can transfer into nucleus to locally produce substrates for epigenetic modification, thereby providing an alternative link between metabolism, epigenetic modification and gene expression. Here, we summarize the recent literature pertinent to metabolic enzymes functioning as epigenetic modulators in the regulation of chromatin architecture and gene expression.

Multiple functions of pyruvate kinase M2 in various cell types

Glucose metabolism is a mechanism by which energy is produced in form of adenosine triphosphate (ATP) by mitochondria and precursor metabolites are supplied to enable the ultimate enrichment of mature metabolites in the cell. Recently, glycolytic enzymes have been shown to have unconventional but important functions. Among these enzymes, pyruvate kinase M2 (PKM2) plays several roles including having conventional metabolic enzyme activity, and also being a transcriptional regulator and a protein kinase. Compared with the closely related PKM1, PKM2 is highly expressed in cancer cells and embryos, whereas PKM1 is dominant in mature, differentiated cells. Posttranslational modifications such as phosphorylation and acetylation of PKM2 change its cellular functions. In particular, PKM2 can translocate to the nucleus, where it regulates the transcription of many target genes. It is notable that PKM2 also acts as a protein kinase to phosphorylate several substrate proteins. Besides cancer cells and embryonic cells, astrocytes also highly express PKM2, which is crucial for lactate production via expression of lactate dehydrogenase A (LDHA), while mature neurons predominantly express PKM1. The lactate produced in cancer cells promotes tumor progress and that in astrocytes can be supplied to neurons and may act as a major source for neuronal ATP energy production. Thereby, we propose that PKM2 along with its different posttranslational modifications has specific purposes for a variety of cell types, performing unique functions.

The role of metabolism in chondrocyte dysfunction and the progression of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by low-grade inflammation and high levels of clinical heterogeneity. Aberrant chondrocyte metabolism is a response to changes in the inflammatory microenvironment and may play a key role in cartilage degeneration and OA progression. Under conditions of environmental stress, chondrocytes tend to adapt their metabolism to microenvironmental changes by shifting from one metabolic pathway to another, for example from oxidative phosphorylation to glycolysis. Similar changes occur in other joint cells, including synoviocytes. Switching between these pathways is implicated in metabolic alterations that involve mitochondrial dysfunction, enhanced anaerobic glycolysis, and altered lipid and amino acid metabolism. The shift between oxidative phosphorylation and glycolysis is mainly regulated by the AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) pathways. Chondrocyte metabolic changes are likely to be a feature of different OA phenotypes. Determining the role of chondrocyte metabolism in OA has revealed key features of disease pathogenesis. Future research should place greater emphasis on immunometabolism and altered metabolic pathways as a means to understand the pathophysiology of age-related OA. This knowledge will advance the development of new drugs against therapeutic targets of metabolic significance.

Pristane promotes anaerobic glycolysis to facilitate proinflammatory activation of macrophages and development of arthritis

Pristane-induced arthritis (PIA) could be adoptively transferred by splenic T cells in rats, and innate immunity should play critical roles in T cell activation. However, in pre-clinical stage, the activation mechanism of innate cells like macrophages remains unclear. Here we found that PIA was dependent on macrophages since cell depletion alleviated disease severity. Splenic macrophages of PIA rats showed M1 phenotypic shifting. The quantitative proteomics analysis suggested that macrophages initiated metabolic reprogramming with the conversion of aerobic oxidation to glycolysis in response to pristane in vivo. Notably, macrophages treated with pristane showed mitochondrial dysregulation and increased glycolysis flux and enzyme activity. Additionally, TNFα production, strongly associating with the glycolysis enzyme Ldha/Ldhb, could be reduced as glycolysis was inhibited or be enhanced as citrate cycle was blocked. This work provides detailed insights into the molecular mechanisms of pristane-mediated metabolic reprogramming in macrophages and suggests a new therapeutic strategy for arthritic disorders.

Disease-Specific Autoantibodies Induce Trained Immunity in RA Synovial Tissues and Its Gene Signature Correlates with the Response to Clinical Therapy

Much evidence suggests that trained immunity is inappropriately activated in the synovial tissue in rheumatoid arthritis (RA), but the underlying mechanism remains unclear. Here, we describe how RA-specific autoantibody deposits can train human monocytes to exert the hyperactive inflammatory response, particularly via the exacerbated release of tumor necrosis factor α (TNFα). Comparative transcriptomic analysis by plate-bound human IgG (cIgG) or β-glucan indicated that metabolic shift towards glycolysis is a crucial mechanism for trained immunity. Moreover, the cIgG-trained gene signatures were enriched in synovial tissues from patients with ACPA- (anticitrullinated protein antibody-) positive arthralgia and undifferentiated arthritis, and early RA and established RA bore a great resemblance to the myeloid pathotype, suggesting a historical priming event in vivo. Additionally, the expression of the cIgG-trained signatures is higher in the female, older, and ACPA-positive populations, with a predictive role in the clinical response to infliximab. We conclude that RA-specific autoantibodies can train monocytes in the inflamed lesion as early as the asymptomatic stage, which may not merely improve understanding of disease progression but may also suggest therapeutic and/or preventive strategies for autoimmune diseases.

Deoxyshikonin Inhibits Viability and Glycolysis by Suppressing the Akt/mTOR Pathway in Acute Myeloid Leukemia Cells

Deoxyshikonin was reported to exhibit an anti-tumor effect in colorectal cancer. However, no studies are available to illustrate the effect of deoxyshikonin on acute myeloid leukemia (AML). The effects of deoxyshikonin on viability, apoptosis, caspase-3/7 activity, and cytochrome (Cyt) C expression were evaluated by Cell Counting Kit-8 assay, flow cytometry analysis, caspase-3/7 activity assay, and western blot analysis, respectively. Glucose consumption and lactate production were measured to determine the glycolysis level. The expression of pyruvate kinase M2 (PKM2) was detected by quantitative real-time polymerase chain reaction and western blot analysis. The results showed that deoxyshikonin inhibited cell viability and increased the apoptotic rate, the caspase-3/7 activity, and the Cyt C protein level in AML cells in a dose-dependent manner. Additionally, deoxyshikonin concentration-dependently decreased glucose consumption, lactate production, and PKM2 expression in AML cells. Deoxyshikonin inactivated the protein kinase B (Akt)/mammalian target of the rapamycin (mTOR) pathway. The activation of the Akt/mTOR pathway reversed the effects of deoxyshikonin on viability, apoptosis, and glycolysis in AML cells. In conclusion, deoxyshikonin dampened the viability and the glycolysis of AML cells by suppressing PKM2 via inactivation of the Akt/mTOR signaling.

Emerging Roles and Therapeutic Interventions of Aerobic Glycolysis in Glioma

Glioma is the most common type of intracranial malignant tumor, with a great recurrence rate due to its infiltrative growth, treatment resistance, intra- and intertumoral genetic heterogeneity. Recently, accumulating studies have illustrated that activated aerobic glycolysis participated in various cellular and clinical activities of glioma, thus influencing the efficacy of radiotherapy and chemotherapy. However, the glycolytic process is too complicated and ambiguous to serve as a novel therapy for glioma. In this review, we generalized the implication of key enzymes, glucose transporters (GLUTs), signalings and transcription factors in the glycolytic process of glioma. In addition, we summarized therapeutic interventions via the above aspects and discussed promising clinical applications for glioma.

Human herpesvirus 6A promotes glycolysis in infected T cells by activation of mTOR signaling

Human herpesvirus 6 (HHV-6) is an important immunosuppressive and immunomodulatory virus worldwide. However, whether and how HHV-6 infection influences the metabolic machinery of the host cell to provide the energy and biosynthetic resources for virus propagation remains unknown. In this study, we identified that HHV-6A infection promotes glucose metabolism in infected T cells, resulting in elevated glycolytic activity with an increase of glucose uptake, glucose consumption and lactate secretion. Furthermore, we explored the mechanisms involved in HHV-6A-mediated glycolytic activation in the infected T cells. We found increased expressions of the key glucose transporters and glycolytic enzymes in HHV-6A-infected T cells. In addition, HHV-6A infection dramatically activated AKT-mTORC1 signaling in the infected T cells and pharmacological inhibition of mTORC1 blocked HHV-6A-mediated glycolytic activation. We also found that direct inhibition of glycolysis by 2-Deoxy-D-glucose (2-DG) or inhibition of mTORC1 activity in HHV-6A-infected T cells effectively reduced HHV-6 DNA replication, protein synthesis and virion production. These results not only reveal the mechanism of how HHV-6 infection affects host cell metabolism, but also suggest that targeting the metabolic pathway could be a new avenue for HHV-6 therapy.