Hexokinase Is an Innate Immune Receptor for the Detection of Bacterial Peptidoglycan

The phagosome-mediated anti-bacterial immunity is governed by the proton-activated chloride channel in peritoneal macrophages

Phagosome degradation is an evolutionally conserved and highly effective innate immune response against pathogen infections. The success of this process relies on the ability of phagocytes to regulate the maturation of phagosomes. However, the underlying molecular mechanisms and its roles in shaping downstream immune activation remain poorly understood. Here, we identify the proton-activated chloride (PAC) channel as a key negative regulator of phagosome maturation. PAC deletion enhanced phagosomal acidification and protease activities, leading to augmented bacterial killing in large peritoneal macrophages (LPMs) upon peritoneal Escherichia coli infection in mice. Surprisingly, phagosome bacterial degradation also stimulated STING-IRF3-interferon responses and inflammasome activation in LPMs, both of which are enhanced upon PAC deletion. The increased inflammasome activation and pyroptosis induced an unexpected release of cleaved gasdermin D, which localized to the surface of bacteria in the peritoneum and further contributed to their killing. Finally, enhanced bacterial clearance by PAC-deficient LPMs reduced proinflammatory immune cell infiltration and overall peritoneal inflammation, resulting in improved survival in mice. Our study thus provides new insights into the molecular mechanism of phagosome maturation and the dynamics of host defense response following phagosome-mediated bacterial degradation in peritoneal macrophages. It also highlights the potential of targeting the PAC channel as a therapeutic strategy for treating bacterial infections.

Gut microbial-derived N-acetylmuramic acid alleviates colorectal cancer via the AKT1 pathway

BACKGROUND

Gut microbial metabolites are recognised as critical effector molecules that influence the development of colorectal cancer (CRC). Peptidoglycan fragments (PGFs) produced by microbiota play a crucial role in maintaining intestinal homeostasis, but their role in CRC remains unclear.

OBJECTIVE

Here, we aimed to explore the potential contribution of PGFs in intestinal tumourigenesis.

DESIGN

The relative abundance of peptidoglycan synthase and hydrolase genes was assessed by metagenomic analysis. Specific PGFs in the faeces and serum of CRC patients were quantified using targeted mass spectrometry. The effects of PGF on intestinal tumourigenesis were systematically evaluated using various murine models of CRC and organoids derived from CRC patients. Downstream molecular targets were screened and evaluated using proteome microarray, transcriptome sequencing and rescue assays.

RESULTS

Metagenomic analysis across seven independent cohorts (n=1121) revealed a comprehensive reduction in peptidoglycan synthase gene relative abundance in CRC patients. Targeted mass spectrometry identified significant depletion of a specific PGF, N-acetylmuramic acid (NAM) in CRC patients, which decreased as tumours progressed (p<0.001). NAM significantly inhibits intestinal tumourigenesis in various models, including Apc Min/+, AOM/DSS-treated and MC38 tumour-bearing mice. Additionally, NAM inhibits the growth of patient-derived CRC organoids in a concentration-dependent manner. Mechanistically, NAM inhibits the activation of AKT1 by directly binding to it and blocking its phosphorylation, which is a partial mediator of NAM's anticancer effects.

CONCLUSION

The PGF NAM protects against intestinal tumourigenesis by targeting the AKT1 signalling pathway. NAM may serve as a novel potential preventive and therapeutic biomarker against CRC.

Shape-Shifting Mechanisms: Integrative Multi-Omics Insights Into Candida albicans Morphogenesis

The ability of Candida albicans to switch among yeast, hyphal, and pseudohyphal forms underlies its adaptability and pathogenicity. While cAMP-dependent signaling has long been considered central to hyphal growth, recent multi-omics studies show that cAMP-independent mechanisms also drive morphological changes. Basal PKA activity, cyclin-dependent kinases (e.g., Cdc28), and other regulators can promote shape-shifting even without classical cAMP pathways. In addition, N-acetylglucosamine (GlcNAc) acts as a potent signal that induces hyphal growth independently of its metabolic role, directly connecting environmental cues to morphological states. By integrating transcriptomic, proteomic, and phosphoproteomic data, this review exposes the intricate networks controlling C. albicans morphogenesis. A clearer understanding of these complex regulatory circuits lays the groundwork for future studies that employ advanced multi-omics analyses. Such approaches will help elucidate how these pathways converge, how they respond to changing environments, and how they might be harnessed or disrupted to influence fungal behavior.

The critical role of NLRP3 in drug resistance of cancers: Focus on the molecular mechanisms and possible therapeutics

Nod-like receptor protein 3 (NLRP3) is a member of the leucine-rich repeat-containing protein (NLR) canonical inflammasome family. It regulates the pathophysiology of cancer by facilitating immune responses and apoptotic proteins. Furthermore, it has been observed that chemotherapy activates NLRP3 in human malignancies. The secretion of IL-1β and IL-22 to promote cancer spread may be triggered by NLRP3 activation. Furthermore, earlier studies have exhibited that NLRP3 may cause medication resistance when used in cancer treatments given that cell viability may be regulated by NLRP3 depletion. Additionally, clinical studies have demonstrated correlation between NLRP3 expression, lymphogenesis, and cancer metastasis. Various NLRP3 agonists may cause the EMT process, stimulate IL-1β and Wnt/β-catenin signaling, and alter miRNA function in drug-resistant cells. This review seeks to clarify the possibility involvement of NLRP3-related pathways in the control of cancer cells' resistance to widely used treatment approaches, such as chemotherapy. In the end, an improved perception of the corresponding mechanisms behind NLRP3's tumor-supporting activities will help NLRP3-based treatments advance in the future.

Knockout of hexokinase 2 regulates mitochondrial dysfunction and activates the NLRP3 signal pathway in the rumen epithelial cells of dairy cows

Hexokinase 2 (HK2) plays a vital role in mitochondrial homeostasis; however, the molecular mechanisms underlying its involvement in high-concentrate diet-induced damage in the ruminal epithelium of dairy cows are poorly understood. This study aimed to explore the regulatory role of HK2 in mitochondrial function and responses to inflammation in the rumen of dairy cows fed a high-concentrate diet. Our results showed that, compared with a low-concentrate (LC) diet, feeding a high-concentrate (HC) diet increased oxidative stress and reduced relative antioxidant gene expression levels and enzyme activities in the ruminal epithelium. Furthermore, the expression of genes related to mitochondrial biosynthesis and structure decreased in the HC group, concomitant with nuclear oligomerization domain (NOD)-like receptor 3 (NLRP3) signaling pathway activation, which compromised normal rumen epithelium function. Meanwhile, transcription results showed the same trend in HK2-knockout bovine rumen epithelial cells (HK2KO BRECs) related to wild-type (WT) BRECs. Notably, the knockout of HK2 aggravated mitochondrial dysfunction, resulting in the impairment of mitochondrial morphology and quality, a reduction in mitochondrial membrane potential (MMP), mitochondrial permeability transition pore (MPTP) opening, increased reactive oxygen species (ROS) generation, and decreased expression of antioxidant genes. These changes led to upregulating genes and proteins in the NLRP3 pathway and activating proinflammatory response. In addition, metabolomic results showed that knockout HK2 altered the glycerophospholipid metabolic pathway. This study provides new strategies for mitigating high-concentrate diet-induced injury in the ruminal epithelium of dairy cows.

The alterations of ocular surface metabolism and the related immunity inflammation in dry eye

Background

Dry eye disease (DED) stands as a prominent ocular condition of global prevalence, emerging as a growing concern within public health. However, the underlying mechanisms involved in its pathogenesis remain largely unknown. In recent years, with the development of metabolomics, numerous studies have reported alterations in ocular surface metabolism in DED and offered fresh perspectives on the development of DED.

Main text

The metabolic changes of the ocular surface of DED patients are closely intertwined with the cellular metabolism process and immune inflammation changes. This article expounds upon the correlation between ocular surface metabolism and immune inflammation alterations in DED in terms of glycolysis, lipid metabolism, amino acid metabolism, cellular signaling pathways, and immune inflammation regulation.

Conclusions

The alterations in ocular surface metabolism of patients with dry eye are closely associated with their inflammatory status. Our work contributes novel insights into the pathogenesis of dry eye diseases and offers innovative molecular targets for diagnosing, detecting, and managing DED patients.

Mitochondria complex III-generated superoxide is essential for IL-10 secretion in macrophages

Mitochondrial electron transport chain (ETC) function modulates macrophage biology; however, mechanisms underlying mitochondria ETC control of macrophage immune responses are not fully understood. Here, we report that mutant mice with mitochondria ETC complex III (CIII)-deficient macrophages exhibit increased susceptibility to influenza A virus (IAV) and LPS-induced endotoxic shock. Cultured bone marrow-derived macrophages (BMDMs) isolated from these mitochondria CIII-deficient mice released less IL-10 than controls following TLR3 or TLR4 stimulation. Unexpectedly, restoring mitochondrial respiration without generating superoxide using alternative oxidase (AOX) was not sufficient to reverse LPS-induced endotoxic shock susceptibility or restore IL-10 release. However, activation of protein kinase A (PKA) rescued IL-10 release in mitochondria CIII-deficient BMDMs following LPS stimulation. In addition, mitochondria CIII deficiency did not affect BMDM responses to interleukin-4 (IL-4) stimulation. Thus, our results highlight the essential role of mitochondria CIII-generated superoxide in the release of anti-inflammatory IL-10 in response to TLR stimulation.

Acute suppression of mitochondrial ATP production prevents apoptosis and provides an essential signal for NLRP3 inflammasome activation

How mitochondria reconcile roles in functionally divergent cell death pathways of apoptosis and NLRP3 inflammasome-mediated pyroptosis remains elusive, as is their precise role in NLRP3 activation and the evolutionarily conserved physiological function of NLRP3. Here, we have shown that when cells were challenged simultaneously, apoptosis was inhibited and NLRP3 activation prevailed. Apoptosis inhibition by structurally diverse NLRP3 activators, including nigericin, imiquimod, extracellular ATP, particles, and viruses, was not a consequence of inflammasome activation but rather of their effects on mitochondria. NLRP3 activators turned out as oxidative phosphorylation (OXPHOS) inhibitors, which we found to disrupt mitochondrial cristae architecture, leading to trapping of cytochrome c. Although this effect was alone not sufficient for NLRP3 activation, OXPHOS inhibitors became triggers of NLRP3 when combined with resiquimod or Yoda-1, suggesting that NLRP3 activation requires two simultaneous cellular signals, one of mitochondrial origin. Therefore, OXPHOS and apoptosis inhibition by NLRP3 activators provide stringency in cell death decisions.

Genome-wide screen based on 2DG activated NLRP3 inflammasome reveals the priming signal of TLR2/4 to IKKβ but not IKKα

NLRP3 inflammasome activation is a pivotal area of research in innate immunity, yet the precise priming and activation signal remain unclear. In this study, we demonstrate that glycolysis inhibitor 2-Deoxy-D-glucose (2DG) triggers NLRP3-driven pyroptosis in human leukemia monocyte THP-1 cells by interfering glycosylation rather than glycolysis, which occurs independent of potassium efflux but requires the involvement of glycolysis rate-limiting enzyme PFKP. Using a CRISPR-Cas9 mediated large-scale screen, with 2DG as a new tool for probing NLRP3 activation, we identified that TLR2, rather than TLR4, initiates a rapid and robust priming signal for NLRP3 inflammasome activation. Importantly, both TLR2 and TLR4 depend entirely on MyD88, but not TRIF, for signal transduction. Furthermore, we discovered that TAK1, IKKβ and NEMO, but not IKKα, are essential for the priming signal. Additionally, we observed that deficiency in the linear ubiquitin assembly complex (LUBAC) subunits HOIP and HOIL-1, but not SHARPIN, is sufficient to inhibit 2DG-induced pyroptotic cell death. Collectively, our study reveals some common mechanism in the NLRP3 priming signals, as well as specific mechanisms upstream of NLRP3 triggered by 2DG, and underscores the potential of 2DG as a trigger to facilitate further detailed analysis of the underlying mechanisms of NLRP3 inflammasome activation. One Sentence Summary: Priming signal by IKKβ is essential for NLRP3 activation.

A Review on the Extraction, Structural Characterization, Function, and Applications of Peptidoglycan

Peptidoglycan (PGN) is the primary component of bacterial cell walls, consisting of linear glycan chains formed by alternating linkages of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) through glycosidic bonds. It exhibits biological activity in various aspects, making it a biologically significant macromolecule with extensive industrial application. This review aims to explore the latest research advancements in the extraction techniques, structural characterization, functions, and applications of PGN. The review compares the advantages and limitations of traditional chemical lysis methods with modern mechanical-assisted and bio-assisted extraction techniques, discusses chemical composition analysis techniques and structural characterization methods of PGN. The review emphasizes the potential of PGN in immune modulation, specific recognition, and adsorption functions. Furthermore, the review examines potential applications of PGN in vaccine development, the livestock industry, the removal of harmful substances, and protein bioprocessing. In the end, based on the current development trend, future research directions for PGN are proposed, including in-depth studies on the mechanisms of PGN in different hosts and its immunomodulatory effects in various disease models. It is expected that a comprehensive reference framework for the research and application of PGN will be provided through this review, offering ideas and directions for further development and utilization.

Mechanism of action of the nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome and its regulation in liver injury

ABSTRACT

Nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) is a cytosolic pattern recognition receptor that recognizes multiple pathogen-associated molecular patterns and damage-associated molecular patterns. It is a cytoplasmic immune factor that responds to cellular stress signals, and it is usually activated after infection or inflammation, forming an NLRP3 inflammasome to protect the body. Aberrant NLRP3 inflammasome activation is reportedly associated with some inflammatory diseases and metabolic diseases. Recently, there have been mounting indications that NLRP3 inflammasomes play an important role in liver injuries caused by a variety of diseases, specifically hepatic ischemia/reperfusion injury, hepatitis, and liver failure. Herein, we summarize new research pertaining to NLRP3 inflammasomes in hepatic injury, hepatitis, and liver failure. The review addresses the potential mechanisms of action of the NLRP3 inflammasome, and its regulation in these liver diseases.

Monocyte uptake of polymeric peptidoglycan is bimodal and governed by complement C3 and C4 opsonins

Peptidoglycans (PGNs) are structural polymers of the bacterial cell wall and a common microbial molecular pattern encountered by the immune system daily. Low levels of PGNs are constitutively present in the systemic circulation in humans and rise during inflammatory pathologies. Since all known PGN sensors are intracellular, PGN internalization is a prerequisite for the initiation of cellular immune responses. Here, we report the mechanisms controlling the recognition and uptake of polymeric PGNs by circulating human mononuclear phagocytes. We found that complement C3 and C4 opsonins govern PGN recognition and internalization, but no single opsonin is indispensable because of multiple uptake redundancies. We observed a bimodal internalization of polymeric PGNs with distinct requirements for complement C4. At low PGN concentrations, C3 mediated PGN recognition by surface receptors while the efficient internalization of PGN polymers critically required C4. Supraphysiologic PGN concentrations triggered a secondary uptake modality that was insensitive to C4 and mediated instead by C3 engagement of complement receptors 1 and 3. To our knowledge, this is the first description of nonoverlapping C3 and C4 opsonophagocytoses working in parallel. Controlling these uptake mechanisms has the potential to modulate PGN clearance or the dysregulated immune responses during bacterial infections.

Metabolism: a potential regulator of neutrophil fate

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

The role of the interplay between macrophage glycolytic reprogramming and NLRP3 inflammasome activation in acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a severe respiratory condition associated with elevated morbidity and mortality. Understanding their complex pathophysiological mechanisms is crucial for developing new preventive and therapeutic strategies. Recent studies highlight the significant role of inflammation involved in ALI/ARDS, particularly the hyperactivation of the NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome in macrophages. This activation drives pulmonary inflammation by releasing inflammatory signalling molecules and is linked to metabolic reprogramming, marked by increased glycolysis and reduced oxidative phosphorylation. However, the relationship between NLRP3 inflammasome activation and macrophage glycolytic reprogramming in ALI/ARDS, as well as the molecular mechanisms regulating these processes, remain elusive. This review provides a detailed description of the interactions and potential mechanisms linking NLRP3 inflammasome activation with macrophage glycolytic reprogramming, proposing that glycolytic reprogramming may represent a promising therapeutic target for mitigating inflammatory responses in ALI/ARDS. KEY POINTS: NLRP3 inflammasome activation is pivotal in mediating the excessive inflammatory response in ALI/ARDS. Glycolytic reprogramming regulates NLRP3 inflammasome activation. Therapeutic potential of targeting glycolytic reprogramming to inhibit NLRP3 inflammasome activation in ALI/ARDS.

Targeting glycolysis for neuroprotection in early LPS-induced neuroinflammation

Neuroinflammation is a pathophysiological feature of numerous neurological and psychiatric disorders. The immune response in the central nervous system, driven by microglia and astrocytes, leads to metabolic reprogramming towards aerobic glycolysis, a phenomenon known as the Warburg effect. The control of metabolic reprogramming via immunomodulation may represent a potential therapeutic target for providing protection against neuroinflammation, which contributes to neuronal dysfunction and death in several neurological disorders. For this purpose, we investigated putative neuroprotective effects of the downregulation of aerobic glycolysis using the 3PO inhibitor, and the downregulation of neuroinflammation using MCC950, in the early LPS-induced neuroinflammation model. The LPS-induced shift towards glycolysis, inflammatory and glial changes (IL-1β, NF-κB, COX2, Iba1, GFAP) were reversed by 3PO, which improved animal behavior. Additionally, MCC950 (an NLRP3 inhibitor) downregulated TLR4/Akt/p38 MAPK/NF-κB/STAT3 signaling, expressions of COX2 and IL-1β, and the astrocyte reactivity (decreasing GFAP) induced by early neuroinflammation, resulting in low glucose uptake. Our data support the occurrence of the Warburg effect during early neuroinflammation and suggest potential new approaches for the treatment of brain injury, given the role of neuroinflammation in such events.

The role of glycolysis in tumorigenesis: From biological aspects to therapeutic opportunities

Glycolytic metabolism generates energy and intermediates for biomass production. Tumor-associated glycolysis is upregulated compared to normal tissues in response to tumor cell-autonomous or non-autonomous stimuli. The consequences of this upregulation are twofold. First, the metabolic effects of glycolysis become predominant over those mediated by oxidative metabolism. Second, overexpressed components of the glycolytic pathway (i.e. enzymes or metabolites) acquire new functions unrelated to their metabolic effects and which are referred to as "moonlighting" functions. These functions include induction of mutations and other tumor-initiating events, effects on cancer stem cells, induction of increased expression and/or activity of oncoproteins, epigenetic and transcriptional modifications, bypassing of senescence and induction of proliferation, promotion of DNA damage repair and prevention of DNA damage, antiapoptotic effects, inhibition of drug influx or increase of drug efflux. Upregulated metabolic functions and acquisition of new, non-metabolic functions lead to biological effects that support tumorigenesis: promotion of tumor initiation, stimulation of tumor cell proliferation and primary tumor growth, induction of epithelial-mesenchymal transition, autophagy and metastasis, immunosuppressive effects, induction of drug resistance and effects on tumor accessory cells. These effects have negative consequences on the prognosis of tumor patients. On these grounds, it does not come to surprise that tumor-associated glycolysis has become a target of interest in antitumor drug discovery. So far, however, clinical results with glycolysis inhibitors have fallen short of expectations. In this review we propose approaches that may allow to bypass some of the difficulties that have been encountered so far with the therapeutic use of glycolysis inhibitors.

Type I IFN drives unconventional IL-1β secretion in lupus monocytes

Opsonization of red blood cells that retain mitochondria (Mito+ RBCs), a feature of systemic lupus erythematosus (SLE), triggers type I interferon (IFN) production in macrophages. We report that monocytes (Mos) co-produce IFN and mature interleukin-1β (mIL-1β) upon Mito+ RBC opsonization. IFN expression depended on cyclic GMP-AMP synthase (cGAS) and RIG-I-like receptors' (RLRs) sensing of Mito+ RBC-derived mitochondrial DNA (mtDNA) and mtRNA, respectively. Interleukin-1β (IL-1β) production was initiated by the RLR antiviral signaling adaptor (MAVS) pathway recognition of Mito+ RBC-derived mtRNA. This led to the cytosolic release of Mo mtDNA, which activated the inflammasome. Importantly, mIL-1β secretion was independent of gasdermin D (GSDMD) and pyroptosis but relied on IFN-inducible myxovirus-resistant protein 1 (MxA), which facilitated the incorporation of mIL-1β into a trans-Golgi network (TGN)-mediated secretory pathway. RBC internalization identified a subset of blood Mo expressing IFN-stimulated genes (ISGs) that released mIL-1β and expanded in SLE patients with active disease.

Esculetin rebalances M1/M2 macrophage polarization to treat sepsis-induced acute lung injury through regulating metabolic reprogramming

Sepsis-induced acute lung injury (SALI) is characterized by a high incidence and mortality rate, which has caused a serious medical burden. The pharmacological effects of esculetin (ELT), such as antibacterial and anti-inflammatory actions, have been widely confirmed. However, the therapeutic effects and mechanisms of ELT on SALI still need to be further clarified. In this study, we first evaluated the therapeutic potential of ELT on a caecal ligation and puncture (CLP) induced septic rat model, particularly in the treatment of acute lung injury. Afterwards, we explored the effect of ELT on macrophage polarization in vivo and in vitro. Then, we investigated the anti-inflammatory mechanism of ELT based on modulating the metabolic reprogramming of macrophage (the effect on glycolysis in M1, and the effect on fatty acid β-oxidation in M2). In addition, macrophage metabolic inhibitors (glycolysis inhibitor: 2-DG, and fatty acid β-oxidation inhibitor: etomoxir) were used to verify the regulatory effect of ELT on macrophage metabolic reprogramming. Our results proved that ELT intervention could effectively improve the survival rate of SALI rats and ameliorate pathological injury. Next, we found that ELT intervention inhibited M1 polarization and promoted M2 polarization of macrophages in vivo and in vitro, including the downregulation of M1-related markers (CD86, iNOS), the decrease of pro-inflammatory factors (nitric oxide, IL-1β, IL-6, and TNF-α), the upregulation of M2-related markers (CD206, ARG-1), the increase of immunomodulatory factors (IL-4 and IL-10). Subsequently, seahorse analysis showed that ELT intervention inhibited the glycolytic capacity in M1, and promoted the ability of fatty acid β-oxidation in M2. Besides, ELT intervention inhibited the level of glycolysis product (lactic acid), and the expression of glycolysis-related genes (Glut1, Hk2, Pfkfb1, Pkm and Ldha) and promoted the expression of fatty acid β-oxidation related genes (Cpt1a, Cpt2, Acox1). In addition, we found that the inhibitory effect of ELT on M1 polarization was comparable to that of 2-DG, while intervention with etomoxir abolished the promoting effect of ELT on M2 polarization. ELT inhibited the inflammatory response in SALI by correcting macrophage polarization (inhibiting M1 and promoting M2). The mechanism of ELT on macrophage polarization was associated with regulating metabolic reprogramming (inhibiting glycolysis in M1 and promoting fatty acid β-oxidation in M2).

MCC950 as a promising candidate for blocking NLRP3 inflammasome activation: A review of preclinical research and future directions

The NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome is a key component of the innate immune system that triggers inflammation and pyroptosis and contributes to the development of several diseases. Therefore, blocking the activation of the NLRP3 inflammasome has therapeutic potential for the treatment of these diseases. MCC950, a selective small molecule inhibitor, has emerged as a promising candidate for blocking NLRP3 inflammasome activation. Ongoing research is focused on elucidating the specific targets of MCC950 as well as assessfing its metabolism and safety profile. This review discusses the diseases that have been studied in relation to MCC950, with a focus on stroke, Alzheimer's disease, liver injury, atherosclerosis, diabetes mellitus, and sepsis, using bibliometric analysis. It then summarizes the potential pharmacological targets of MCC950 and discusses its toxicity. Furthermore, it traces the progression from preclinical to clinical research for the treatment of these diseases. Overall, this review provides a solid foundation for the clinical therapeutic potential of MCC950 and offers insights for future research and therapeutic approaches.

Target modulation of glycolytic pathways as a new strategy for the treatment of neuroinflammatory diseases

Neuroinflammation is an innate and adaptive immune response initiated by the release of inflammatory mediators from various immune cells in response to harmful stimuli. While initially beneficial and protective, prolonged or excessive neuroinflammation has been identified in clinical and experimental studies as a key pathological driver of numerous neurological diseases and an accelerant of the aging process. Glycolysis, the metabolic process that converts glucose to pyruvate or lactate to produce adenosine 5'-triphosphate (ATP), is often dysregulated in many neuroinflammatory disorders and in the affected nerve cells. Enhancing glucose availability and uptake, as well as increasing glycolytic flux through pharmacological or genetic manipulation of glycolytic enzymes, has shown potential protective effects in several animal models of neuroinflammatory diseases. Modulating the glycolytic pathway to improve glucose metabolism and ATP production may help alleviate energy deficiencies associated with these conditions. In this review, we examine six neuroinflammatory diseases-stroke, Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and depression-and provide evidence supporting the role of glycolysis in their treatment. We also explore the potential link between inflammation-induced aging and glycolysis. Additionally, we briefly discuss the critical role of glycolysis in three types of neuronal cells-neurons, microglia, and astrocytes-within physiological processes. This review highlights the significance of glycolysis in the pathology of neuroinflammatory diseases and its relevance to the aging process.

Macrophage polarization and metabolic reprogramming in abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is a macrovascular disease with high morbidity and mortality in the elderly. The limitation of the current management is that most patients can only be followed up until the AAA diameter increases to a threshold, and surgical intervention is recommended. The development of preventive and curative drugs for AAA is urgently needed. Macrophage-mediated immune inflammation is one of the key pathological links in the occurrence and development of AAA.

AIMS

This review article aims to evaluate the impact of immunometabolism on macrophage biology and its role in AAA.

METHODS

We analyze publications focusing on the polarization and metabolic reprogramming in macrophages as well as their potential impact on AAA, and summarize the potential interventions that are currently available to regulate these processes.

RESULTS

The phenotypic and functional changes in macrophages are accompanied by significant alterations in metabolic pathways. The interaction between macrophage polarization and metabolic pathways significantly influences the progression of AAA.

CONCLUSION

Macrophage polarization is a manifestation of the gross dichotomy of macrophage function into pro-inflammatory killing and tissue repair, that is, classically activated M1 macrophages and alternatively activated M2 macrophages. Macrophage functions are closely linked to metabolic changes, and the emerging field of immunometabolism is providing unique insights into the role of macrophages in AAA. It is essential to further investigate the precise metabolic changes and their functional consequences in AAA-associated macrophages.

When the Host Encounters the Cell Wall and Vice Versa

Peptidoglycan (PGN) and associated surface structures such as secondary polymers and capsules have a central role in the physiology of bacteria. The exoskeletal PGN heteropolymer is the major determinant of cell shape and allows bacteria to withstand cytoplasmic turgor pressure. Thus, its assembly, expansion, and remodeling during cell growth and division need to be highly regulated to avoid compromising cell survival. Similarly, regulation of the assembly impacts bacterial cell shape; distinct shapes enhance fitness in different ecological niches, such as the host. Because bacterial cell wall components, in particular PGN, are exposed to the environment and unique to bacteria, these have been coopted during evolution by eukaryotes to detect bacteria. Furthermore, the essential role of the cell wall in bacterial survival has made PGN an important signaling molecule in the dialog between host and microbes and a target of many host responses. Millions of years of coevolution have resulted in a pivotal role for PGN fragments in shaping host physiology and in establishing a long-lasting symbiosis between microbes and the host. Thus, perturbations of this dialog can lead to pathologies such as chronic inflammatory diseases. Similarly, pathogens have devised sophisticated strategies to manipulate the system to enhance their survival and growth.

Hexokinase 2 expression in apical enterocytes correlates with inflammation severity in patients with inflammatory bowel disease

BACKGROUND

Inflammation is characterized by a metabolic switch promoting glycolysis and lactate production. Hexokinases (HK) catalyze the first reaction of glycolysis and inhibition of epithelial HK2 protected from colitis in mice. HK2 expression has been described as elevated in patients with intestinal inflammation; however, there is conflicting data from few cohorts especially with severely inflamed individuals; thus, systematic studies linking disease activity with HK2 levels are needed.

METHODS

We examined the relationship between HK2 expression and inflammation severity using bulk transcriptome data derived from the mucosa of thoroughly phenotyped inflammatory bowel disease (IBD) patients of two independent cohorts including both subtypes Crohn's disease (CD) and ulcerative colitis (UC). Publicly available single-cell RNA sequencing data were analyzed, and immunofluorescence staining on colonic biopsies of unrelated patients with intestinal inflammation was performed to confirm the RNA-based findings on cellular and protein level.

RESULTS

HK2 expression gradually increased from mild to intermediate inflammation, yet strongly declined at high inflammation scores. Expression of epithelial marker genes also declined at high inflammation scores, whereas that of candidate immune marker genes increased, indicating a cellular remodeling of the mucosa during inflammation with an infiltration of HK2-negative immune cells and a loss of terminal differentiated epithelial cells in the apical epithelium-the main site of HK2 expression. Normalizing for the enterocyte loss clearly identified epithelial HK2 expression as gradually increasing with disease activity and remaining elevated at high inflammation scores. HK2 protein expression was mostly restricted to brush border enterocytes, and these cells along with HK2 levels vanished with increasing disease severity.

CONCLUSIONS

Our findings clearly define dysregulated epithelial HK2 expression as an indicator of disease activity in intestinal inflammation and suggest targeted HK2-inhibition as a potential therapeutic avenue.

Decoding Cancer through Silencing the Mitochondrial Gatekeeper VDAC1

Mitochondria serve as central hubs for regulating numerous cellular processes that include metabolism, apoptosis, cell cycle progression, proliferation, differentiation, epigenetics, immune signaling, and aging. The voltage-dependent anion channel 1 (VDAC1) functions as a crucial mitochondrial gatekeeper, controlling the flow of ions, such as Ca2+, nucleotides, and metabolites across the outer mitochondrial membrane, and is also integral to mitochondria-mediated apoptosis. VDAC1 functions in regulating ATP production, Ca2+ homeostasis, and apoptosis, which are essential for maintaining mitochondrial function and overall cellular health. Most cancer cells undergo metabolic reprogramming, often referred to as the "Warburg effect", supplying tumors with energy and precursors for the biosynthesis of nucleic acids, phospholipids, fatty acids, cholesterol, and porphyrins. Given its multifunctional nature and overexpression in many cancers, VDAC1 presents an attractive target for therapeutic intervention. Our research has demonstrated that silencing VDAC1 expression using specific siRNA in various tumor types leads to a metabolic rewiring of the malignant cancer phenotype. This results in a reversal of oncogenic properties that include reduced tumor growth, invasiveness, stemness, epithelial-mesenchymal transition. Additionally, VDAC1 depletion alters the tumor microenvironment by reducing angiogenesis and modifying the expression of extracellular matrix- and structure-related genes, such as collagens and glycoproteins. Furthermore, VDAC1 depletion affects several epigenetic-related enzymes and substrates, including the acetylation-related enzymes SIRT1, SIRT6, and HDAC2, which in turn modify the acetylation and methylation profiles of histone 3 and histone 4. These epigenetic changes can explain the altered expression levels of approximately 4000 genes that are associated with reversing cancer cells oncogenic properties. Given VDAC1's critical role in regulating metabolic and energy processes, targeting it offers a promising strategy for anti-cancer therapy. We also highlight the role of VDAC1 expression in various disease pathologies, including cardiovascular, neurodegenerative, and viral and bacterial infections, as explored through siRNA targeting VDAC1. Thus, this review underscores the potential of targeting VDAC1 as a strategy for addressing high-energy-demand cancers. By thoroughly understanding VDAC1's diverse roles in metabolism, energy regulation, mitochondrial functions, and other cellular processes, silencing VDAC1 emerges as a novel and strategic approach to combat cancer.

Metabolic reprogramming of the inflammatory response in the nervous system: the crossover between inflammation and metabolism

Metabolism is a fundamental process by which biochemicals are broken down to produce energy (catabolism) or used to build macromolecules (anabolism). Metabolism has received renewed attention as a mechanism that generates molecules that modulate multiple cellular responses. This was first identified in cancer cells as the Warburg effect, but it is also present in immunocompetent cells. Studies have revealed a bidirectional influence of cellular metabolism and immune cell function, highlighting the significance of metabolic reprogramming in immune cell activation and effector functions. Metabolic processes such as glycolysis, oxidative phosphorylation, and fatty acid oxidation have been shown to undergo dynamic changes during immune cell response, facilitating the energetic and biosynthetic demands. This review aims to provide a better understanding of the metabolic reprogramming that occurs in different immune cells upon activation, with a special focus on central nervous system disorders. Understanding the metabolic changes of the immune response not only provides insights into the fundamental mechanisms that regulate immune cell function but also opens new approaches for therapeutic strategies aimed at manipulating the immune system.

Cortisol affects macrophage polarization by inducing miR-143/145 cluster to reprogram glucose metabolism and by promoting TCA cycle anaplerosis

Chronic stress can have adverse consequences on human health by disrupting the hormonal balance in our body. Earlier, we observed elevated levels of cortisol, a primary stress hormone, and some exosomal microRNAs in the serum of patients with breast cancer. Here, we investigated the role of cortisol in microRNA induction and its functional consequences. We found that cortisol induced the expression of miR-143/145 cluster in human monocyte (THP1 and U937)-derived macrophages but not in breast cancer cells. In silico analysis identified glucocorticoid-response element in the upstream CARMN promoter utilized by the miR-143/145 cluster. Enhanced binding of glucocorticoid-receptor (GR) upon cortisol exposure and its regulatory significance was confirmed by chromatin-immunoprecipitation and promoter-reporter assays. Further, cortisol inhibited IFNγ-induced M1 polarization and promoted M2 polarization, and these effects were suppressed by miR-143-3p and miR-145-5p inhibitors pretreatment. Cortisol-treated macrophages exhibited increased oxygen-consumption rate (OCR) to extracellular-acidification rate (ECAR) ratio, and this change was neutralized by functional inhibition of miR-143-3p and miR-145-5p. HK2 and ADPGK were confirmed as the direct targets of miR-143-3p and miR-145-5p, respectively. Interestingly, silencing of HK2 and ADPGK inhibited IFNγ-induced M1 polarization but failed to induce M2 polarization, since it suppressed both ECAR and OCR, while OCR was largely sustained in cortisol-treated M2-polarized macrophages. We found that cortisol treatment sustained OCR by enhancing fatty acid and glutamine metabolism through upregulation of CPT2 and GLS, respectively, to support M2 polarization. Thus, our findings unfold a novel mechanism of immune suppression by cortisol and open avenues for preventive and therapeutic interventions.

The glycolytic metabolite methylglyoxal covalently inactivates the NLRP3 inflammasome

The NLRP3 inflammasome promotes inflammation in disease, yet the full repertoire of mechanisms regulating its activity is not well delineated. Among established regulatory mechanisms, covalent modification of NLRP3 has emerged as a common route for the pharmacological inactivation of this protein. Here, we show that inhibition of the glycolytic enzyme phosphoglycerate kinase 1 (PGK1) results in the accumulation of methylglyoxal, a reactive metabolite whose increased levels decrease NLRP3 assembly and inflammatory signaling in cells. We find that methylglyoxal inactivates NLRP3 via a non-enzymatic, covalent-crosslinking-based mechanism, promoting inter- and intraprotein MICA (methyl imidazole crosslink between cysteine and arginine) posttranslational linkages within NLRP3. This work establishes NLRP3 as capable of sensing a host of electrophilic chemicals, both exogenous small molecules and endogenous reactive metabolites, and suggests a mechanism by which glycolytic flux can moderate the activation status of a central inflammatory signaling pathway.

The genetic advantage of healthy centenarians: unraveling the central role of NLRP3 in exceptional healthspan

Despite extensive research into extending human healthspan (HS) and compressing morbidity, the mechanisms underlying aging remain elusive. However, a better understanding of the genetic advantages responsible for the exceptional HS of healthy centenarians (HC), who live in good physical and mental health for one hundred or more years, could lead to innovative health-extending strategies. This review explores the role of NLRP3, a critical component of innate immunity that significantly impacts aging. It is activated by pathogen-associated signals and self-derived signals that increase with age, leading to low-grade inflammation implicated in age-related diseases. Furthermore, NLRP3 functions upstream in several molecular aging pathways, regulates cellular senescence, and may underlie the robust health observed in HC. By targeting NLRP3, mice exhibit a phenotype akin to that of HC, the HS of monkeys is extended, and aging symptoms are reversed in humans. Thus, targeting NLRP3 could offer a promising approach to extend HS. Additionally, a paradigm shift is proposed. Given that the HS of the broader population is 30 years shorter than that of HC, it is postulated that they suffer from a form of accelerated aging. The term 'auto-aging' is suggested to describe accelerated aging driven by NLRP3.

Tethering of hexokinase 2 to mitochondria promotes resistance of liver cancer cells to natural killer cell cytotoxicity

Hexokinases (HKs) control the first step of glucose catabolism. A switch of expression from liver HK (glucokinase, GCK) to the tumor isoenzyme HK2 is observed in hepatocellular carcinoma progression. Our prior work revealed that HK isoenzyme switch in hepatocytes not only regulates hepatic metabolic functions but also modulates innate immunity and sensitivity to Natural Killer (NK) cell cytotoxicity. This study investigates the impact of HK2 expression and its mitochondrial binding on the resistance of human liver cancer cells to NK-cell-induced cytolysis. We have shown that HK2 expression induces resistance to NK cell cytotoxicity in a process requiring mitochondrial binding of HK2. Neither HK2 nor GCK expression affects target cells' ability to activate NK cells. In contrast, mitochondrial binding of HK2 reduces effector caspase 3/7 activity both at baseline and upon NK-cell activation. Furthermore, HK2 tethering to mitochondria enhances their resistance to cytochrome c release triggered by tBID. These findings indicate that HK2 mitochondrial binding in liver cancer cells is an intrinsic resistance factor to cytolysis and an escape mechanism from immune surveillance.

Microsporidia secretory effectors and their roles in pathogenesis

Microsporidia, a group of unicellular eukaryotic parasites, rely intensely on secretory effectors for successful invasion and proliferation within host cells. This review focuses on the identification, characterization, and functional roles of effectors, including secretory proteins and microRNAs. The adhesion proteins like the Ricin-B-lectin facilitate initial invasion, which binds to the host cell surface. Once inside, microsporidia deploy a range of effectors to modulate host immune responses, such as serpin proteins, and redirect host cell metabolism to meet the parasite's nutritional needs through hexokinase. Some effectors such as microRNAs, alter the host gene expression to create a more favorable intracellular parasitic environment. In conclusion, the secretory effectors of microsporidia play a pivotal role spanning from host cell invasion to intracellular establishment. In the future, more effectors secreted by microsporidia will be studied, which will not only help to elucidate the molecular mechanism of pathogenic manipulation of the host but also help to provide the potential targets for anti-parasitic treatments.

mRNA vaccines in tumor targeted therapy: mechanism, clinical application, and development trends

Malignant tumors remain a primary cause of human mortality. Among the various treatment modalities for neoplasms, tumor vaccines have consistently shown efficacy and promising potential. These vaccines offer advantages such as specificity, safety, and tolerability, with mRNA vaccines representing promising platforms. By introducing exogenous mRNAs encoding antigens into somatic cells and subsequently synthesizing antigens through gene expression systems, mRNA vaccines can effectively induce immune responses. Katalin Karikó and Drew Weissman were awarded the 2023 Nobel Prize in Physiology or Medicine for their great contributions to mRNA vaccine research. Compared with traditional tumor vaccines, mRNA vaccines have several advantages, including rapid preparation, reduced contamination, nonintegrability, and high biodegradability. Tumor-targeted therapy is an innovative treatment modality that enables precise targeting of tumor cells, minimizes damage to normal tissues, is safe at high doses, and demonstrates great efficacy. Currently, targeted therapy has become an important treatment option for malignant tumors. The application of mRNA vaccines in tumor-targeted therapy is expanding, with numerous clinical trials underway. We systematically outline the targeted delivery mechanism of mRNA vaccines and the mechanism by which mRNA vaccines induce anti-tumor immune responses, describe the current research and clinical applications of mRNA vaccines in tumor-targeted therapy, and forecast the future development trends of mRNA vaccine application in tumor-targeted therapy.

Fatty acid synthesis promotes inflammasome activation through NLRP3 palmitoylation

Despite its significance, the role of lipid metabolism in NLRP3 inflammasome remains elusive. Here, we reveal a critical role for fatty acid synthase (FASN) in NLRP3 inflammasome activation. We demonstrate that pharmacological or genetic depletion of FASN dampens NLRP3 activation in primary mouse and human macrophages and in mice. This disruption in NLRP3 activation is contingent upon FASN activity. Accordingly, abolishing cellular palmitoylation, a post-translational modification in which the FASN product palmitate is reversibly conjugated to cysteine residues of target proteins, blunts inflammasome signaling. Correspondingly, an acyl-biotin exchange assay corroborated NLRP3 palmitoylation. Mechanistically, Toll-like receptor (TLR) ligation introduces palmitoylation at NLRP3 Cys898, permitting NLRP3 translocation to dispersed trans-Golgi network (dTGN) vesicles, the site of inflammasome assembly, upon NLRP3 activation. Accordingly, the NLRP3 Cys898 mutant exhibits reduced palmitoylation, limited translocation to the dTGN compartment, and diminished inflammasome activation. These results underscore mechanistic insights through which lipid metabolism licenses NLRP3 inflammasome assembly and activation.

Impaired microglial glycolysis promotes inflammatory responses after intracerebral haemorrhage via HK2-dependent mitochondrial dysfunction

INTRODUCTION

Intracerebral haemorrhage (ICH) is a devastating disease that leads to severe neurological deficits. Microglia are the first line of defence in the brain and play a crucial role in neurological recovery after ICH, whose activities are primarily driven by glucose metabolism. However, little is known regarding the status of glucose metabolism in microglia and its interactions with inflammatory responses after ICH.

OBJECTIVES

This study investigated microglial glycolysis and its mechanistic effects on microglial inflammation after ICH.

METHODS

We explored the status of glucose metabolism in the ipsilateral region and in fluorescence-activated-cell-sorting-isolated (FACS-isolated) microglia via 2-deoxy-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) analyses and gamma emission, respectively. Energy-related targeted metabolomics, along with 13C-glucose isotope tracing, was utilised to analyse glycolytic products in microglia. Mitochondrial membrane potential and mitochondrial reactive oxygen species (MitoROS) accumulation was assessed by flow cytometry. Behavioural, western blotting, gene regulation, and enzymatic activity analyses were conducted with a focus on microglia.

RESULTS

Neurological dysfunction was strongly correlated with decreased FDG-PET signals in the perihaematomal region, where microglial uptake of FDG was reduced. The decreased quantity of glucose-6-phosphate (G-6-P) in microglia was attributed to the downregulation of glucose transporter 1 (GLUT1) and hexokinase 2 (HK2). Enhanced inflammatory responses were driven by HK2 suppression via decreased mitochondrial membrane potential, which could be rescued by MitoROS scavengers. HK inhibitors aggravated neurological injury by suppressing FDG uptake and enhancing microglial inflammation in ICH mice.

CONCLUSION

These findings indicate an unexpected metabolic status in pro-inflammatory microglia after ICH, consisting of glycolysis impairment caused by the downregulation of GLUT1 and HK2. Additionally, HK2 suppression promotes inflammatory responses by disrupting mitochondrial function, providing insight into the mechanisms by which inflammation may be facilitated after ICH and indicating that metabolic enzymes as potential targets for ICH treatment.

Excitotoxicity, Oxytosis/Ferroptosis, and Neurodegeneration: Emerging Insights into Mitochondrial Mechanisms

Mitochondrial dysfunction plays a pivotal role in the development of age-related diseases, particularly neurodegenerative disorders. The etiology of mitochondrial dysfunction involves a multitude of factors that remain elusive. This review centers on elucidating the role(s) of excitotoxicity, oxytosis/ferroptosis and neurodegeneration within the context of mitochondrial bioenergetics, biogenesis, mitophagy and oxidative stress and explores their intricate interplay in the pathogenesis of neurodegenerative diseases. The effective coordination of mitochondrial turnover processes, notably mitophagy and biogenesis, is assumed to be critically important for cellular resilience and longevity. However, the age-associated decrease in mitophagy impedes the elimination of dysfunctional mitochondria, consequently impairing mitochondrial biogenesis. This deleterious cascade results in the accumulation of damaged mitochondria and deterioration of cellular functions. Both excitotoxicity and oxytosis/ferroptosis have been demonstrated to contribute significantly to the pathophysiology of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's Disease (HD), Amyotrophic Lateral Sclerosis (ALS) and Multiple Sclerosis (MS). Excitotoxicity, characterized by excessive glutamate signaling, initiates a cascade of events involving calcium dysregulation, energy depletion, and oxidative stress and is intricately linked to mitochondrial dysfunction. Furthermore, emerging concepts surrounding oxytosis/ferroptosis underscore the importance of iron-dependent lipid peroxidation and mitochondrial engagement in the pathogenesis of neurodegeneration. This review not only discusses the individual contributions of excitotoxicity and ferroptosis but also emphasizes their convergence with mitochondrial dysfunction, a key driver of neurodegenerative diseases. Understanding the intricate crosstalk between excitotoxicity, oxytosis/ferroptosis, and mitochondrial dysfunction holds potential to pave the way for mitochondrion-targeted therapeutic strategies. Such strategies, with a focus on bioenergetics, biogenesis, mitophagy, and oxidative stress, emerge as promising avenues for therapeutic intervention.

Intracellular acidification and glycolysis modulate inflammatory pathway in senescent cells

Senescent cells accumulate in various organs with ageing, and its accumulation induces chronic inflammation and age-related physiological dysfunctions. Several remodelling of intracellular environments have been identified in senescent cells, including enlargement of cell/nuclear size and intracellular acidification. Although these alterations of intracellular environments were reported to be involved in the unique characteristics of senescent cells, the contribution of intracellular acidification to senescence-associated cellular phenotypes is poorly understood. Here, we identified that the upregulation of TXNIP and its paralog ARRDC4 as a hallmark of intracellular acidification in addition to KGA-type GLS1. These genes were also upregulated in response to senescence-associated intracellular acidification. Neutralization of the intracellular acidic environment ameliorated not only senescence-related upregulation of TXNIP, ARRDC4 and KGA but also inflammation-related genes, possibly through suppression of PDK-dependent anaerobic glycolysis. Furthermore, we found that expression of the intracellular acidification-induced genes, TXNIP and ARRDC4, correlated with inflammatory gene expression in heterogeneous senescent cell population in vitro and even in vivo, implying that the contribution of intracellular pH to senescence-associated cellular features, such as SASP.

Therapeutic targeting of immunometabolism reveals a critical reliance on hexokinase 2 dosage for microglial activation and Alzheimer's progression

Neuroinflammation is a prominent feature of Alzheimer's disease (AD). Activated microglia undergo a reprogramming of cellular metabolism necessary to power their cellular activities during disease. Thus, selective targeting of microglial immunometabolism might be of therapeutic benefit for treating AD. In the AD brain, the levels of microglial hexokinase 2 (HK2), an enzyme that supports inflammatory responses by promoting glycolysis, are significantly increased. In addition, HK2 displays non-metabolic activities that extend its inflammatory role beyond glycolysis. The antagonism of HK2 affects microglial phenotypes and disease progression in a gene-dose-dependent manner. HK2 complete loss fails to improve pathology by exacerbating inflammation, while its haploinsufficiency reduces pathology in 5xFAD mice. We propose that the partial antagonism of HK2 is effective in slowing disease progression by modulating NF-κB signaling through its cytosolic target, IKBα. The complete loss of HK2 affects additional inflammatory mechanisms related to mitochondrial dysfunction.

NLRP3 inflammasome signalling in Alzheimer's disease

Every year, 10 million people develop dementia, the most common of which is Alzheimer's disease (AD). To date, there is no way to prevent cognitive decline and therapies are limited. This review provides a neuroimmunological perspective on the progression of AD, and discusses the immune-targeted therapies that are in preclinical and clinical trials that may impact the development of this disease. Specifically, we look to the role of the NLRP3 inflammasome, its triggers in the brain and how its activation can contribute to the progression of dementia. We summarise the range of inhibitors targeting the NLRP3 inflammasome and its downstream pathways that are under investigation, and discuss future therapeutic perspectives for this devastating condition.

Is Methylglyoxal a Potential Biomarker for the Warburg Effect Induced by the Lipopolysaccharide Neuroinflammation Model?

Methylglyoxal (MG) is considered a classical biomarker of diabetes mellitus and its comorbidities. However, a role for this compound in exacerbated immune responses, such as septicemia, is being increasingly observed and requires clarification, particularly in the context of neuroinflammatory responses. Herein, we used two different approaches (in vivo and acute hippocampal slice models) to investigate MG as a biomarker of neuroinflammation and the neuroimmunometabolic shift to glycolysis in lipopolysaccharide (LPS) inflammation models. Our data reinforce the hypothesis that LPS-induced neuroinflammation stimulates the cerebral innate immune response by increasing IL-1β, a classical pro-inflammatory cytokine, and the astrocyte reactive response, via elevating S100B secretion and GFAP levels. Acute neuroinflammation promotes an early neuroimmunometabolic shift to glycolysis by elevating glucose uptake, lactate release, PFK1, and PK activities. We observed high serum and cerebral MG levels, in association with a reduction in glyoxalase 1 detoxification activity, and a close correlation between serum and hippocampus MG levels with the systemic and neuroinflammatory responses to LPS. Findings strongly suggest a role for MG in immune responses.

Evaluation of secretome biomarkers in glioblastoma cancer stem cells: A bioinformatics analysis

BACKGROUND

Glioblastoma (GBM) is a malignant brain tumor that frequently occurs alongside other central nervous system (CNS) conditions. The secretome of GBM cells contains a diverse array of proteins released into the extracellular space, influencing the tumor microenvironment. These proteins can serve as potential biomarkers for GBM due to their involvement in key biological processes, exploring the secretome biomarkers in GBM research represents a cutting-edge strategy with significant potential for advancing diagnostic precision, treatment monitoring, and ultimately improving outcomes for patients with this challenging brain cancer.

AIM

This study was aimed to investigate the roles of secretome biomarkers and their pathwayes in GBM through bioinformatics analysis.

METHODS AND RESULTS

Using data from the Gene Expression Omnibus and the Cancer Genome Atlas datasets-where both healthy and cancerous samples were analyzed-we used a quantitative analytical framework to identify differentially expressed genes (DEGs) and cell signaling pathways that might be related to GBM. Then, we performed gene ontology studies and hub protein identifications to estimate the roles of these DEGs after finding disease-gene connection networks and signaling pathways. Using the GEPIA Proportional Hazard Model and the Kaplan-Meier estimator, we widened our analysis to identify the important genes that may play a role in both progression and the survival of patients with GBM. In total, 890 DEGs, including 475 and 415 upregulated and downregulated were identified, respectively. Our results revealed that SQLE, DHCR7, delta-1 phospholipase C (PLCD1), and MINPP1 genes are highly expressed, and the Enolase 2 (ENO2) and hexokinase-1 (HK1) genes are low expressions.

CONCLUSION

Hence, our findings suggest novel mechanisms that affect the occurrence of GBM development, growth, and/or establishment and may also serve as secretory biomarkers for GBM prognosis and possible targets for therapy. So, continued research in this field may uncover new avenues for therapeutic interventions and contribute to the ongoing efforts to combat GBM effectively.

NLRP3 promotes allergic responses to birch pollen extract in a model of intranasal sensitization

Introduction & Objective

Allergic sensitization is an essential step in the development of allergic airway inflammation to birch pollen (BP); however, this process remains to be fully elucidated. Recent scientific advances have highlighted the importance of the allergen context. In this regard, microbial patterns (PAMPs) present on BP have attracted increasing interest. As these PAMPs are recognized by specialized pattern recognition receptors (PRRs), this study aims at investigating the roles of intracellular PRRs and the inflammasome regulator NLRP3.

Methods

We established a physiologically relevant intranasal and adjuvant-free sensitization procedure to study BP-induced systemic and local lung inflammation.

Results

Strikingly, BP-sensitized Nlrp3-deficient mice showed significantly lower IgE levels, Th2-associated cytokines, cell infiltration into the lung, mucin production and epithelial thickening than their wild-type counterparts, which appears to be independent of inflammasome formation. Intriguingly, bone-marrow chimera revealed that expression of NLRP3 in the hematopoietic system is required to trigger an allergic response.

Conclusion

Overall, this study identifies NLRP3 as an important driver of BP-induced allergic immune responses.

Interleukin-6 classic and trans-signaling utilize glucose metabolism reprogramming to achieve anti- or pro-inflammatory effects

Interleukin (IL)-6 has anti- and pro-inflammatory functions, controlled by IL-6 classic and trans-signaling, respectively. Differences in the downstream signaling mechanism between IL-6 classic and trans-signaling have not been identified. Here, we report that IL-6 activates glycolysis to regulate the inflammatory response. IL-6 regulates glucose metabolism by forming a complex containing signal-transducing activators of transcription 3 (STAT3), hexokinase 2 (HK2), and voltage-dependent anion channel 1 (VDAC1). The IL-6 classic signaling directs glucose flux to oxidative phosphorylation (OxPhos), while IL-6 trans-signaling directs glucose flux to anaerobic glycolysis. Classic IL-6 signaling promotes STAT3 translocation into mitochondria to interact with pyruvate dehydrogenase kinase-1 (PDK1), leading to pyruvate dehydrogenase α (PDHA) dissociation from PDK1. As a result, PDHA is dephosphorylated, and STAT3 is phosphorylated at Ser727. By contrast, IL-6 trans-signaling promotes the interaction of sirtuin 2 (SIRT2) and lactate dehydrogenase A (LDHA), leading to the dissociation of STAT3 from SIRT2. As a result, LDHA is deacetylated, and STAT3 is acetylated and phosphorylated at Tyr705. IL-6 classic signaling promotes the differentiation of regulatory T cells via the PDK1/STAT3/PDHA axis, whereas IL-6 trans-signaling promotes the differentiation of Th17 cells via the SIRT2/STAT3/LDHA axis. Conclusion: IL-6 classic signaling generates anti-inflammatory functions by shifting energy metabolism to OxPhos, while IL-6 trans-signaling generates pro-inflammatory functions by shifting energy metabolism to anaerobic glycolysis.

Profiling phagosome proteins identifies PD-L1 as a fungal-binding receptor

Phagocytosis is the process by which myeloid phagocytes bind to and internalize potentially dangerous microorganisms1. During phagocytosis, innate immune receptors and associated signalling proteins are localized to the maturing phagosome compartment, forming an immune information processing hub brimming with microorganism-sensing features2-8. Here we developed proximity labelling of phagosomal contents (PhagoPL) to identify proteins localizing to phagosomes containing model yeast and bacteria. By comparing the protein composition of phagosomes containing evolutionarily and biochemically distinct microorganisms, we unexpectedly identified programmed death-ligand 1 (PD-L1) as a protein that specifically enriches in phagosomes containing yeast. We found that PD-L1 directly binds to yeast upon processing in phagosomes. By surface display library screening, we identified the ribosomal protein Rpl20b as a fungal protein ligand for PD-L1. Using an auxin-inducible depletion system, we found that detection of Rpl20b by macrophages cross-regulates production of distinct cytokines including interleukin-10 (IL-10) induced by the activation of other innate immune receptors. Thus, this study establishes PhagoPL as a useful approach to quantifying the collection of proteins enriched in phagosomes during host-microorganism interactions, exemplified by identifying PD-L1 as a receptor that binds to fungi.

Multifaceted mitochondria in innate immunity

The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.

The septin modifier, forchlorfenuron, activates NLRP3 via a potassium-independent mitochondrial axis

The Nod-like receptor protein 3 (NLRP3) inflammasome is activated by stimuli that induce perturbations in cell homeostasis, which commonly converge on cellular potassium efflux. NLRP3 has thus emerged as a sensor for ionic flux. Here, we identify forchlorfenuron (FCF) as an inflammasome activator that triggers NLRP3 signaling independently of potassium efflux. FCF triggers the rearrangement of septins, key cytoskeletal proteins that regulate mitochondrial function. We report that FCF triggered the rearrangement of SEPT2 into tubular aggregates and stimulated SEPT2-independent NLRP3 inflammasome signaling. Similar to imiquimod, FCF induced the collapse of the mitochondrial membrane potential and mitochondrial respiration. FCF thereby joins the imidazoquinolines as a structurally distinct class of molecules that triggers NLRP3 inflammasome signaling independent of potassium efflux, likely by inducing mitochondrial damage.

Metabolism-inflammasome crosstalk shapes innate and adaptive immunity

Inflammasomes are a central component of innate immunity and play a vital role in regulating innate immune response. Activation of inflammasomes is also indispensable for adaptive immunity, modulating the development and response of adaptive immunity. Recently, increasing studies have shown that metabolic alterations and adaptations strongly influence and regulate the differentiation and function of the immune system. In this review, we will take a holistic view of how inflammasomes bridge innate and adaptive (especially T cell) immunity and how inflammasomes crosstalk with metabolic signals during the immune responses. And, special attention will be paid to the metabolic control of inflammasome-mediated interactions between innate and adaptive immunity in disease. Understanding the metabolic regulatory functions of inflammasomes would provide new insights into future research directions in this area and may help to identify potential targets for inflammasome-associated diseases and broaden therapeutic avenues.

Strategies of bacterial detection by inflammasomes

Mammalian innate immunity is regulated by pattern-recognition receptors (PRRs) and guard proteins, which use distinct strategies to detect infections. PRRs detect bacterial molecules directly, whereas guards detect host cell manipulations by microbial virulence factors. Despite sensing infection through different mechanisms, both classes of innate immune sensors can activate the inflammasome, an immune complex that can mediate cell death and inflammation. Inflammasome-mediated immune responses are crucial for host defense against many bacterial pathogens and prevent invasion by non-pathogenic organisms. In this review, we discuss the mechanisms by which inflammasomes are stimulated by PRRs and guards during bacterial infection, and the strategies used by virulent bacteria to evade inflammasome-mediated immunity.

Pattern-Recognition Receptors and Immunometabolic Reprogramming: What We Know and What to Explore

BACKGROUND

Evolutionarily, immune response is a complex mechanism that protects the host from internal and external threats. Pattern-recognition receptors (PRRs) recognize MAMPs, PAMPs, and DAMPs to initiate a protective pro-inflammatory immune response. PRRs are expressed on the cell membranes by TLR1, 2, 4, and 6 and in the cytosolic organelles by TLR3, 7, 8, and 9, NLRs, ALRs, and cGLRs. We know their downstream signaling pathways controlling immunoregulatory and pro-inflammatory immune response. However, the impact of PRRs on metabolic control of immune cells to control their pro- and anti-inflammatory activity has not been discussed extensively.

SUMMARY

Immune cell metabolism or immunometabolism critically determines immune cells' pro-inflammatory phenotype and function. The current article discusses immunometabolic reprogramming (IR) upon activation of different PRRs, such as TLRs, NLRs, cGLRs, and RLRs. The duration and type of PRR activated, species studied, and location of immune cells to specific organ are critical factors to determine the IR-induced immune response.

KEY MESSAGE

The work herein describes IR upon TLR, NLR, cGLR, and RLR activation. Understanding IR upon activating different PRRs is critical for designing better immune cell-specific immunotherapeutics and immunomodulators targeting inflammation and inflammatory diseases.

Oxidative Stress and Neurodegeneration: Insights and Therapeutic Strategies for Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative condition marked by the gradual deterioration of dopaminergic neurons in the substantia nigra. Oxidative stress has been identified as a key player in the development of PD in recent studies. In the first part, we discuss the sources of oxidative stress in PD, including mitochondrial dysfunction, dopamine metabolism, and neuroinflammation. This paper delves into the possibility of mitigating oxidative stress as a potential treatment approach for PD. In addition, we examine the hurdles and potential of antioxidant therapy, including the challenge of delivering antioxidants to the brain and the requirement for biomarkers to track oxidative stress in PD patients. However, even if antioxidant therapy holds promise, further investigation is needed to determine its efficacy and safety in PD treatment.

The Glycolytic Metabolite Methylglyoxal Covalently Inactivates the NLRP3 Inflammasome

The NLRP3 inflammasome promotes inflammation in disease, yet the full repertoire of mechanisms regulating its activity are not well delineated. Among established regulatory mechanisms, covalent modification of NLRP3 has emerged as a common route for pharmacological inactivation of this protein. Here, we show that inhibition of the glycolytic enzyme PGK1 results in the accumulation of methylglyoxal, a reactive metabolite whose increased levels decrease NLRP3 assembly and inflammatory signaling in cells. We find that methylglyoxal inactivates NLRP3 via a non-enzymatic, covalent crosslinking-based mechanism, promoting inter- and intra-protein MICA posttranslational linkages within NLRP3. This work establishes NLRP3 as capable of sensing a host of electrophilic chemicals, both exogenous small molecules and endogenous reactive metabolites, and suggests a mechanism by which glycolytic flux can moderate the activation status of a central inflammatory signaling pathway.

Bacterial peptidoglycan acts as a digestive signal mediating host adaptation to diverse food resources in C. elegans

Food availability and usage is a major adaptive force for the successful survival of animals in nature, yet little is known about the specific signals that activate the host digestive system to allow for the consumption of varied foods. Here, by using a food digestion system in C. elegans, we discover that bacterial peptidoglycan (PGN) is a unique food signal that activates animals to digest inedible food. We identified that a glycosylated protein, Bacterial Colonization Factor-1 (BCF-1), in the gut interacts with bacterial PGN, leading to the inhibition of the mitochondrial unfolded protein response (UPRmt) by regulating the release of Neuropeptide-Like Protein (NLP-3). Interestingly, activating UPRmt was found to hinder food digestion, which depends on the innate immune p38 MAPK/PMK-1 pathway. Conversely, inhibiting PMK-1 was able to alleviate digestion defects in bcf-1 mutants. Furthermore, we demonstrate that animals with digestion defects experience reduced natural adaptation capabilities. This study reveals that PGN-BCF-1 interaction acts as "good-food signal" to promote food digestion and animal growth, which facilitates adaptation of the host animals by increasing ability to consume a wide range of foods in their natural environment.