NAMPT-mediated salvage synthesis of NAD+ controls morphofunctional changes of macrophages

Protein disulfide isomerase A4 binds to Brucella BtpB and mediates intracellular NAD+/NADH metabolism in RAW264.7 cells

The Toll/interleukin-1 receptor (TIR) signaling domain is distributed widely in mammalian Toll-like receptors and adaptors, plant nucleotide-binding leucine-rich repeat receptors, and specific bacterial virulence proteins. Proteins that possess TIR domain exhibit NADase activity which is distinct from the canonical signaling function of these domains. However, the effects of bacterial TIR domain proteins on host metabolic switches and the underlying mechanism of NADase activity in these proteins remain unclear. Here, we utilized Brucella TIR domain-containing type IV secretion system effector protein, BtpB, to explore the mechanism of NADase activity in host cells. We showed that using ectopic expression BtpB not only generates depletion of NAD+ but also loss of NADH and ATP in RAW264.7 macrophage cells. Moreover, immunoprecipitation-mass spectrometry, co-immunoprecipitation, and confocal microscope assays revealed that BtpB interacted with host protein disulfide isomerase A4 (PDIA4). The Brucella mutant strain deleted the gene for BtpB, significantly decreased PDIA4 expression. Furthermore, our data revealed that PDIA4 played an important role in regulating intracellular NAD+/NADH levels in macrophages, and PDIA4 overexpression restored the decline of intracellular NAD+ and NADH levels induced by Brucella BtpB. The results provide new insights into the metabolic regulatory activity of TIR domain proteins in the critical human and animal pathogen Brucella.

Use of Optical Redox Imaging to Quantify Alveolar Macrophage Redox State in Infants: Proof of Concept Experiments in a Murine Model and Human Tracheal Aspirates Samples

Emerging data indicate that lung macrophages (LM) may provide a novel biomarker to classify disease endotypes in bronchopulmonary dysplasia (BPD), a form of infant chronic lung disease, and that augmentation of the LM phenotype may be a potential therapeutic target. To contribute to this area of research, we first used Optical Redox Imaging (ORI) to characterize the responses to H2O2-induced oxidative stress and caffeine treatment in an in vitro model of mouse alveolar macrophages (AM). H2O2 caused a dose-dependent decrease in NADH and an increase in FAD-containing flavoproteins (Fp) and the redox ratio Fp/(NADH + Fp). Caffeine treatment did not affect Fp but significantly decreased NADH with doses of ≥50 µM, and 1000 µM caffeine treatment significantly increased the redox ratio and decreased the baseline level of mitochondrial ROS (reactive oxygen species). However, regardless of whether AM were pretreated with caffeine or not, the mitochondrial ROS levels increased to similar levels after H2O2 challenge. We then investigated the feasibility of utilizing ORI to examine macrophage redox status in tracheal aspirate (TA) samples obtained from premature infants receiving invasive ventilation. We observed significant heterogeneity in NADH, Fp, Fp/(NADH + Fp), and mitochondrial ROS of the TA macrophages. We found a possible positive correlation between gestational age and NADH and a negative correlation between mean airway pressure and NADH that provides hypotheses for future testing. Our study demonstrates that ORI is a feasible technique to characterize macrophage redox state in infant TA samples and supports further use of this method to investigate lung macrophage-mediated disease endotypes in BPD.

New insight into arginine and tryptophan metabolism in macrophage activation during tuberculosis

Arginine and tryptophan are pivotal in orchestrating cytokine-driven macrophage polarization and immune activation. Specifically, interferon-gamma (IFN-γ) stimulates inducible nitric oxide synthase (iNOS) expression), leading to the conversion of arginine into citrulline and nitric oxide (NO), while Interleukin-4 (IL4) promotes arginase activation, shifting arginine metabolism toward ornithine. Concomitantly, IFN-γ triggers indoleamine 2,3-dioxygenase 1 (IDO1) and Interleukin-4 induced 1 (IL4i1), resulting in the conversion of tryptophan into kynurenine and indole-3-pyruvic acid. These metabolic pathways are tightly regulated by NAD+-dependent sirtuin proteins, with Sirt2 and Sirt5 playing integral roles. In this review, we present novel insights that augment our understanding of the metabolic pathways of arginine and tryptophan following Mycobacterium tuberculosis infection, particularly their relevance in macrophage responses. Additionally, we discuss arginine methylation and demethylation and the role of Sirt2 and Sirt5 in regulating tryptophan metabolism and arginine metabolism, potentially driving macrophage polarization.

Role and Potential Mechanisms of Nicotinamide Mononucleotide in Aging

Nicotinamide adenine dinucleotide (NAD+) has recently attracted much attention due to its role in aging and lifespan extension. NAD+ directly and indirectly affects many cellular processes, including metabolic pathways, DNA repair, and immune cell activities. These mechanisms are critical for maintaining cellular homeostasis. However, the decline in NAD+ levels with aging impairs tissue function, which has been associated with several age-related diseases. In fact, the aging population has been steadily increasing worldwide, and it is important to restore NAD+ levels and reverse or delay these age-related disorders. Therefore, there is an increasing demand for healthy products that can mitigate aging, extend lifespan, and halt age-related consequences. In this case, several studies in humans and animals have targeted NAD+ metabolism with NAD+ intermediates. Among them, nicotinamide mononucleotide (NMN), a precursor in the biosynthesis of NAD+, has recently received much attention from the scientific community for its anti-aging properties. In model organisms, ingestion of NMN has been shown to improve age-related diseases and probably delay death. Here, we review aspects of NMN biosynthesis and the mechanism of its absorption, as well as potential anti-aging mechanisms of NMN, including recent preclinical and clinical tests, adverse effects, limitations, and perceived challenges.

Live-Cell Imaging Quantifies Changes in Function and Metabolic NADH Autofluorescence During Macrophage-Mediated Phagocytosis of Tumor Cells

BACKGROUND

The immune system has evolved to detect foreign antigens and deliver coordinated responses, while minimizing "friendly fire." Until recently, studies investigating the behavior of immune cells were limited to static in vitro measurements. Although static measurements allow for real-time imaging, results are often difficult to translate to an in vivo setting. Multiphoton microscopy is an emerging method to capture spatial information on subcellular events and characterize the local microenvironment. Previous studies have shown that multiphoton microscopy can monitor changes in single-cell macrophage heterogeneity during differentiation. Therefore, there is a need to use multiphoton microscopy to monitor molecular interactions during immunological activities like phagocytosis. Here we investigate the correlation between phagocytic function and changes in endogenous optical reporters during phagocytosis.

METHODS

In vitro autofluorescence imaging of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) was used to detect metabolic changes in macrophages during phagocytosis. More specifically, optical redox ratio, mean NADH fluorescence lifetime and ratio of free to protein-bound NADH were used to quantify changes in metabolism.

RESULTS

Results show that IFN-γ (M1) macrophages showed decreased optical redox ratios and mean NADH lifetime while phagocytosing immunogenic cancer cells compared to metastatic cells. To validate phagocytic function, a fluorescence microscopy-based protocol using a pH-sensitive fluorescent probe was used. Results indicate that M0 and M1 macrophages show similar trends in phagocytic potential.

CONCLUSION

Overall, this work demonstrates that in vitro multiphoton imaging can be used to longitudinally track changes in phagocytosis and endogenous metabolic cofactors.

NAMPT inhibition relieves intestinal inflammation by regulating macrophage activation in experimental necrotizing enterocolitis

Nicotinamide phosphoribosyl transferase (NAMPT) is associated with various NAD+ -consuming enzymatic reactions. The precise role in intestinal mucosal immunity in necrotizing enterocolitis (NEC) is not well defined. Here, we examined whether NAMPT inhibition by the highly specific inhibitor FK866 could alleviate intestinal inflammation during the pathogenesis of NEC. In the present study, we showed that NAMPT expression was upregulated in the human terminal ileum of human infants with NEC. FK866 administration attenuated M1 macrophage polarization and relieved the symptoms of experimental NEC pups. FK866 inhibited intercellular NAD+ levels, macrophage M1 polarization, and the expression of NAD+ -dependent enzymes, such as poly (ADP ribose) polymerase 1 (PARP1) and Sirt6. Consistently, the capacity of macrophages to phagocytose zymosan particles, as well as antibacterial activity, were impaired by FK866, whereas NMN supplementation to restore NAD+ levels reversed the changes in phagocytosis and antibacterial activity. In conclusion, FK866 reduced intestinal macrophage infiltration and skewed macrophage polarization, which is implicated in intestinal mucosal immunity, thereby promoting the survival of NEC pups.

NAD+ metabolism-based immunoregulation and therapeutic potential

Nicotinamide adenine dinucleotide (NAD⁺) is a critical metabolite that acts as a cofactor in energy metabolism, and serves as a cosubstrate for non-redox NAD⁺-dependent enzymes, including sirtuins, CD38 and poly(ADP-ribose) polymerases. NAD⁺ metabolism can regulate functionality attributes of innate and adaptive immune cells and contribute to inflammatory responses. Thus, the manipulation of NAD⁺ bioavailability can reshape the courses of immunological diseases. Here, we review the basics of NAD⁺ biochemistry and its roles in the immune response, and discuss current challenges and the future translational potential of NAD⁺ research in the development of therapeutics for inflammatory diseases, such as COVID-19.

Inhibitory Effects of Ginsenoside Compound K on Lipopolysaccharide-Stimulated Inflammatory Responses in Macrophages by Regulating Sirtuin 1 and Histone Deacetylase 4

Inflammation, an innate immune response mediated by macrophages, has been a hallmark leading to the pathophysiology of diseases. In this study, we examined the inhibitory effects of ginsenoside compound K (CK) on lipopolysaccharide (LPS)-induced inflammation and metabolic alteration in RAW 264.7 macrophages by regulating sirtuin 1 (SIRT1) and histone deacetylase 4 (HDAC4). LPS suppressed SIRT1 while promoting HDAC4 expression, accompanied by increases in cellular reactive oxygen species accumulation and pro-inflammatory gene expression; however, the addition of CK elicited the opposite effects. CK ameliorated the LPS-induced increase in glycolytic genes and abrogated the LPS-altered genes engaged in the NAD+ salvage pathway. LPS decreased basal, maximal, and non-mitochondrial respiration, reducing ATP production and proton leak in macrophages, which were abolished by CK. SIRT1 inhibition augmented Hdac4 expression along with increased LPS-induced inflammatory and glycolytic gene expression, while decreasing genes that regulate mitochondrial biogenesis; however, its activation resulted in the opposite effects. Inhibition of HDAC4 enhanced Sirt1 expression and attenuated the LPS-induced inflammatory gene expression. In conclusion, CK exerted anti-inflammatory and antioxidant properties with the potential to counteract the alterations of energy metabolism, including glycolysis and mitochondrial respiration, through activating SIRT1 and repressing HDAC4 in LPS-stimulated macrophages.

Intracellular NAD+ Depletion Confers a Priming Signal for NLRP3 Inflammasome Activation

Nicotinamide adenine dinucleotide (NAD⁺) is an important cofactor in many redox and non-redox NAD⁺-consuming enzyme reactions. Intracellular NAD⁺ level steadily declines with age, but its role in the innate immune potential of myeloid cells remains elusive. In this study, we explored whether NAD⁺ depletion by FK866, a highly specific inhibitor of the NAD salvage pathway, can affect pattern recognition receptor-mediated responses in macrophages. NAD⁺-depleted mouse bone marrow-derived macrophages (BMDMs) exhibited similar levels of proinflammatory cytokine production in response to LPS or poly (I:C) stimulation compared with untreated cells. Instead, FK866 facilitated robust caspase-1 activation in BMDMs in the presence of NLRP3-activating signals such as ATP and nigericin, a potassium ionophore. However, this FK866-mediated caspase-1 activation was completely abolished in Nlrp3-deficient macrophages. FK866 plus nigericin stimulation caused an NLRP3-dependent assembly of inflammasome complex. In contrast, restoration of NAD⁺ level by supplementation with nicotinamide mononucleotide abrogated the FK866-mediated caspase-1 cleavage. FK866 did not induce or increase the expression levels of NLRP3 and interleukin (IL)-1β but drove mitochondrial retrograde transport into the perinuclear region. FK866-nigericin-induced mitochondrial transport is critical for caspase-1 cleavage in macrophages. Consistent with the in vitro experiments, intradermal coinjection of FK866 and ATP resulted in robust IL-1β expression and caspase-1 activation in the skin of wild-type, but not Nlrp3-deficient mice. Collectively, our data suggest that NAD⁺ depletion provides a non-transcriptional priming signal for NLRP3 activation via mitochondrial perinuclear clustering, and aging-associated NAD⁺ decline can trigger NLRP3 inflammasome activation in ATP-rich environments.

Mitochondrial respiration contributes to the interferon gamma response in antigen-presenting cells

The immunological synapse allows antigen-presenting cells (APCs) to convey a wide array of functionally distinct signals to T cells, which ultimately shape the immune response. The relative effect of stimulatory and inhibitory signals is influenced by the activation state of the APC, which is determined by an interplay between signal transduction and metabolic pathways. While pathways downstream of toll-like receptors rely on glycolytic metabolism for the proper expression of inflammatory mediators, little is known about the metabolic dependencies of other critical signals such as interferon gamma (IFNγ). Using CRISPR-Cas9, we performed a series of genome-wide knockout screens in murine macrophages to identify the regulators of IFNγ-inducible T cell stimulatory or inhibitory proteins MHCII, CD40, and PD-L1. Our multiscreen approach enabled us to identify novel pathways that preferentially control functionally distinct proteins. Further integration of these screening data implicated complex I of the mitochondrial respiratory chain in the expression of all three markers, and by extension the IFNγ signaling pathway. We report that the IFNγ response requires mitochondrial respiration, and APCs are unable to activate T cells upon genetic or chemical inhibition of complex I. These findings suggest a dichotomous metabolic dependency between IFNγ and toll-like receptor signaling, implicating mitochondrial function as a fulcrum of innate immunity.

NAD+-targeting by bacteria: an emerging weapon in pathogenesis

Nicotinamide adenine dinucleotide (NAD+) is a major cofactor in redox reactions in all lifeforms. A stable level of NAD+ is vital to ensure cellular homeostasis. Some pathogens can modulate NAD+ metabolism to their advantage and even utilize or cleave NAD+ from the host using specialized effectors known as ADP-ribosyltransferase toxins and NADases, leading to energy store depletion, immune evasion, or even cell death. This review explores recent advances in the field of bacterial NAD+-targeting toxins, highlighting the relevance of NAD+ modulation as an emerging pathogenesis strategy. In addition, we discuss the role of specific NAD+-targeting toxins in niche colonization and bacterial lifestyle as components of Toxin/Antitoxin systems and key players in inter-bacterial competition. Understanding the mechanisms of toxicity, regulation, and secretion of these toxins will provide interesting leads in the search for new antimicrobial treatments in the fight against infectious diseases.

β-Adrenoceptor regulation of metabolism in U937 derived macrophages

Macrophages have important roles in the immune system including clearing pathogens and wound healing. Metabolic phenotypes in macrophages have been associated with functional phenotypes, where pro-inflammatory macrophages have an increased rate of glycolysis and anti-inflammatory macrophages primarily use oxidative phosphorylation. β-adrenoceptor (βAR) signalling in macrophages has been implicated in disease states such as cancer, atherosclerosis and rheumatoid arthritis. The impact of βAR signalling on macrophage metabolism has not been defined. Using metabolomics and proteomics, we describe the impact of βAR signalling on macrophages treated with isoprenaline. We found that βAR signalling alters proteins involved in cytoskeletal rearrangement and redox homeostasis of the cell. We showed that βAR signalling in macrophages shifts glucose metabolism from glycolysis towards the tricarboxylic acid cycle and pentose phosphate pathways. We also show that βAR signalling perturbs purine metabolism by accumulating adenylate and guanylate pools. Taken together, these results indicate that βAR signalling shifts metabolism to support redox processes and upregulates proteins involved in cytoskeletal changes, which may contribute to βAR effects on macrophage function.

Nicotinamide mononucleotide production by fructophilic lactic acid bacteria

Nicotinamide mononucleotide (NMN), an intermediate in nicotinamide adenine dinucleotide biosynthesis, is recently attracting much attention for its pharmacological and anti-aging efficacies. However, current commercial products containing NMN are very high-priced because efficient and facile methods for industrial NMN production are limited. In this study, aiming for its nutraceutical application, we attempted to screen lactic acid bacteria for intracellular and/or extracellular NMN production. Using a bioassay system with an auxotrophic yeast that requires nicotinamide riboside (NR; dephosphorylated NMN), three candidates were obtained from a library of 174 strains of facultative anaerobic lactic acid bacteria. All three candidates belonged to the genus Fructobacillus and produced NR in the culture media (0.8–1.5 mg/l). Lactic acid bacteria of the genus Fructobacillus are known to use d-fructose as an electron acceptor in anaerobic lactic acid fermentation; addition of d-fructose to the medium caused intracellular accumulation of NMN and NR, but no extracellular production of these compounds was observed. Draft genome sequencing for one of the candidates suggested that nicotinamide phosphoribosyltransferase, which exists commonly in mammals but is less reported in microorganisms, is a key enzyme for NMN and NR production in the fructophilic bacteria.

Macrophages provide a transient muscle stem cell niche via NAMPT secretion

Skeletal muscle regenerates through the activation of resident stem cells. Termed satellite cells, these normally quiescent cells are induced to proliferate by wound-derived signals¹. Identifying the source and nature of these cues has been hampered by an inability to visualize the complex cell interactions that occur within the wound. Here we use muscle injury models in zebrafish to systematically capture the interactions between satellite cells and the innate immune system after injury, in real time, throughout the repair process. This analysis revealed that a specific subset of macrophages 'dwell' within the injury, establishing a transient but obligate niche for stem cell proliferation. Single-cell profiling identified proliferative signals that are secreted by dwelling macrophages, which include the cytokine nicotinamide phosphoribosyltransferase (Nampt, which is also known as visfatin or PBEF in humans). Nampt secretion from the macrophage niche is required for muscle regeneration, acting through the C-C motif chemokine receptor type 5 (Ccr5), which is expressed on muscle stem cells. This analysis shows that in addition to their ability to modulate the immune response, specific macrophage populations also provide a transient stem-cell-activating niche, directly supplying proliferation-inducing cues that govern the repair process that is mediated by muscle stem cells. This study demonstrates that macrophage-derived niche signals for muscle stem cells, such as NAMPT, can be applied as new therapeutic modalities for skeletal muscle injury and disease.

Gold nanoparticles coated with polyvinylpyrrolidone and sea urchin extracellular molecules induce transient immune activation

We report that the immunogenicity of colloidal gold nanoparticles coated with polyvinylpyrrolidone (PVP-AuNPs) in a model organism, the sea urchin Paracentrotus lividus, can function as a proxy for humans for in vitro immunological studies. To profile the immune recognition and interaction from exposure to PVP-AuNPs (1 and 10 μg mL^-1), we applied an extensive nano-scale approach, including particle physicochemical characterisation involving immunology, cellular biology, and metabolomics. The interaction between PVP-AuNPs and soluble proteins of the sea urchin physiological coelomic fluid (blood equivalent) results in the formation of a protein "corona" surrounding the NPs from three major proteins that influence the hydrodynamic size and colloidal stability of the particle. At the lower concentration of PVP-AuNPs, the P. lividus phagocytes show a broad metabolic plasticity based on the biosynthesis of metabolites mediating inflammation and phagocytosis. At the higher concentration of PVP-AuNPs, phagocytes activate an immunological response involving Toll-like receptor 4 (TLR4) signalling pathway at 24 hours of exposure. These results emphasise that exposure to PVP-AuNPs drives inflammatory signalling by the phagocytes and the resolution at both the low and high concentrations of the PVP-AuNPs and provides more details regarding the immunogenicity of these NPs.

NAD+ metabolism and its roles in cellular processes during ageing

Nicotinamide adenine dinucleotide (NAD⁺) is a coenzyme for redox reactions, making it central to energy metabolism. NAD⁺ is also an essential cofactor for non-redox NAD⁺-dependent enzymes, including sirtuins, CD38 and poly(ADP-ribose) polymerases. NAD⁺ can directly and indirectly influence many key cellular functions, including metabolic pathways, DNA repair, chromatin remodelling, cellular senescence and immune cell function. These cellular processes and functions are critical for maintaining tissue and metabolic homeostasis and for healthy ageing. Remarkably, ageing is accompanied by a gradual decline in tissue and cellular NAD⁺ levels in multiple model organisms, including rodents and humans. This decline in NAD⁺ levels is linked causally to numerous ageing-associated diseases, including cognitive decline, cancer, metabolic disease, sarcopenia and frailty. Many of these ageing-associated diseases can be slowed down and even reversed by restoring NAD⁺ levels. Therefore, targeting NAD⁺ metabolism has emerged as a potential therapeutic approach to ameliorate ageing-related disease, and extend the human healthspan and lifespan. However, much remains to be learnt about how NAD⁺ influences human health and ageing biology. This includes a deeper understanding of the molecular mechanisms that regulate NAD⁺ levels, how to effectively restore NAD⁺ levels during ageing, whether doing so is safe and whether NAD⁺ repletion will have beneficial effects in ageing humans.

FK866 alleviates cerebral pyroptosis and inflammation mediated by Drp1 in a rat cardiopulmonary resuscitation model

OBJECTIVES

Dynamin-related protein 1 (Drp1) mediates mitochondrial fission and triggers NLRP3 inflammasome activation. FK866 (a NAMPT inhibitor) exerts a neuroprotective effect in ischemia/reperfusion injury through the suppression of mitochondrial dysfunction. We explored the effects of FK866 on pyroptosis and inflammation mediated by Drp1 in a cardiac arrest/cardiopulmonary resuscitation (CA/CPR) rat model.

METHODS

Healthy male Sprague-Dawley rats were subjected to 7 min CA by trans-esophageal electrical stimulation followed by CPR. The surviving rats were treated with FK866 (a selective inhibitor of NAMPT), Mdivi-1 (Drp1 inhibitor), FK866 + Mdivi-1, or vehicle and then underwent 24 h reperfusion. Hematoxylin and eosin staining and immunohistochemistry (to detect NSE) were used to evaluate brain injury. We performed immunofluorescent staining to analyze NLRP3 and GSDMD expression in microglia or astrocytes and western blot to determine expression of NLRP3, IL-1β, GSDMD, Drp1, and Mfn2. Transmission electron microscopy was used to observe mitochondria.

RESULTS

FK866 significantly decreased pathological damage to brain tissue, inhibited the activation of NLRP3 in microglia or astrocytes, downregulated the expression of NLRP3, IL-1β, GSDMD, p-Drp1 protein, upregulated Mfn2 and improve mitochondrial morphology.

CONCLUSIONS

Our results demonstrated that FK866 protects the brain against ischemia-reperfusion injury in rats after CA/CPR by inhibiting pyroptosis and inflammation mediated by Drp1.

Local Targeting of NAD+ Salvage Pathway Alters the Immune Tumor Microenvironment and Enhances Checkpoint Immunotherapy in Glioblastoma

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic subtypes of malignant glioma are sensitive to selective inhibition of the NAD⁺ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). However, the potential impact of NAD⁺ depletion on the brain tumor microenvironment has not been elaborated. In addition, systemic toxicity of NAMPT inhibition remains a significant concern. Here we show that microparticle-mediated intratumoral delivery of NAMPT inhibitor GMX1778 induces specific immunologic changes in the tumor microenvironment of murine GBM, characterized by upregulation of immune checkpoint PD-L1, recruitment of CD3⁺, CD4⁺, and CD8⁺ T cells, and reduction of M2-polarized immunosuppressive macrophages. NAD⁺ depletion and autophagy induced by NAMPT inhibitors mediated the upregulation of PD-L1 transcripts and cell surface protein levels in GBM cells. NAMPT inhibitor modulation of the tumor immune microenvironment was therefore combined with PD-1 checkpoint blockade in vivo, significantly increasing the survival of GBM-bearing animals. Thus, the therapeutic impacts of NAMPT inhibition extended beyond neoplastic cells, shaping surrounding immune effectors. Microparticle delivery and release of NAMPT inhibitor at the tumor site offers a safe and robust means to alter an immune tumor microenvironment that could potentiate checkpoint immunotherapy for glioblastoma. SIGNIFICANCE: Microparticle-mediated local inhibition of NAMPT modulates the tumor immune microenvironment and acts cooperatively with anti-PD-1 checkpoint blockade, offering a combination immunotherapy strategy for the treatment of GBM.

Nampt-mediated spindle sizing secures a post-anaphase increase in spindle speed required for extreme asymmetry

Meiotic divisions in oocytes are extremely asymmetric and require pre- and post-anaphase-onset phases of spindle migration. The latter induces membrane protrusion that is moulded around the spindle thereby reducing cytoplasmic loss. Here, we find that depleting the NAD biosynthetic enzyme, nicotinamide phosphoribosyl-transferase (Nampt), in mouse oocytes results in markedly longer spindles and compromises asymmetry. By analysing spindle speed in live oocytes, we identify a striking and transient acceleration after anaphase-onset that is severely blunted following Nampt-depletion. Slow-moving midzones of elongated spindles induce cortical furrowing deep within the oocyte before protrusions can form, altogether resulting in larger oocyte fragments being cleaved off. Additionally, we find that Nampt-depletion lowers NAD and ATP levels and that reducing NAD using small molecule Nampt inhibitors also compromises asymmetry. These data show that rapid midzone displacement is critical for extreme asymmetry by delaying furrowing to enable protrusions to form and link metabolic status to asymmetric division.

Meiotic cell division in oocytes is asymmetric and requires microtubule spindle migration after anaphase-onset. Here, the authors show that Nampt, an enzyme of the Nicotinamide adenine dinucleotide (NAD) biosynthetic pathway, contributes to post-anaphase spindle migration and oocyte division asymmetry by controlling spindle length.

Metabolic programming of macrophage functions and pathogens control

Macrophages (Mφ) are central players in mediating proinflammatory and immunomodulatory functions. Unchecked Mφ activities contribute to pathology across many diseases, including those caused by infectious pathogens and metabolic disorders. A fine balance of Mφ responses is crucial, which may be achieved by enforcing appropriate bioenergetics pathways. Metabolism serves as the provider of energy, substrates, and byproducts that support differential Mφ characteristics. The metabolic properties that control the polarization and response of Mφ remain to be fully uncovered for use in managing infectious diseases. Here, we review the various metabolic states in Mφ and how they influence the cell function.

A Systems Vaccinology Approach Reveals the Mechanisms of Immunogenic Responses to Hantavax Vaccination in Humans

Hantavax is an inactivated vaccine for hemorrhagic fever with renal syndrome (HFRS). The immunogenic responses have not been elucidated yet. Here we conducted a cohort study in which 20 healthy subjects were administered four doses of Hantavax during 13-months period. Pre- and post- vaccinated peripheral blood mononuclear cells (PBMCs) and sera were analysed by transcriptomic and metabolomic profilings, respectively. Based on neutralizing antibody titers, subjects were subsequently classified into three groups; non responders (NRs), low responders (LRs) and high responders (HRs). Post vaccination differentially expressed genes (DEGs) associated with innate immunity and cytokine pathways were highly upregulated. DEG analysis revealed a significant induction of CD69 expression in the HRs. High resolution metabolomics (HRM) analysis showed that correlated to the antibody response, cholesteryl nitrolinoleate, octanoyl-carnitine, tyrosine, ubiquinone-9, and benzoate were significantly elevated in HRs, while chenodeoxycholic acid and methyl palmitate were upregulated in NRs and LRs, compared with HRs. Additionally, gene-metabolite interaction revealed upregulated gene-metabolite couplings in, folate biosynthesis, nicotinate and nicotinamide, arachidonic acid, thiamine and pyrimidine metabolism in a dose dependent manner in HR group. Collectively, our data provide new insight into the underlying mechanisms of the Hantavax-mediated immunogenicity in humans.

CCR7 Chemokine Receptor-Inducible lnc-Dpf3 Restrains Dendritic Cell Migration by Inhibiting HIF-1α-Mediated Glycolysis

CCR7 chemokine receptor stimulation induces rapid but transient dendritic cell (DC) migration toward draining lymph nodes, which is critical for the initiation of protective immunity and maintenance of immune homeostasis. The mechanisms for terminating CCR7-mediated DC migration remain incompletely understood. Here we have identified a long non-coding RNA lnc-Dpf3 whose feedback restrained CCR7-mediated DC migration. CCR7 stimulation upregulated lnc-Dpf3 via removing N6-methyladenosine (m⁶A) modification to prevent RNA degradation. DC-specific lnc-Dpf3 deficiency increased CCR7-mediated DC migration, leading to exaggerated adaptive immune responses and inflammatory injuries. Mechanistically, CCR7 stimulation activated the HIF-1α transcription factor pathway in DCs, leading to metabolic reprogramming toward glycolysis for DC migration. lnc-Dpf3 directly bound to HIF-1α and suppressed HIF-1α-dependent transcription of the glycolytic gene Ldha, thus inhibiting DC glycolytic metabolism and migratory capacity. We demonstrate a critical role for CCR7-inducible lnc-Dpf3 in coupling epigenetic and metabolic pathways to feedback-control DC migration and inflammatory responses.

Macrophage metabolism: a wound-healing perspective

Macrophages are a critical component of the innate immune response, and compose the first response to perturbations in tissue homeostasis. Their unique ability to dynamically integrate diverse stimuli underlies their important role in the healing response from first insult to re-establishment of tissue homeostasis. While the roles of macrophages in tissue repair have been well-described in vitro and in vivo, the influence of cellular metabolism on macrophage function during tissue repair remains an unexplored area of immunometabolism. In this review, we will explore the unique metabolic requirements of inflammatory and anti-inflammatory macrophages and the potential contribution of macrophage metabolism to each phase of wound healing.

Efferocytosis Fuels Requirements of Fatty Acid Oxidation and the Electron Transport Chain to Polarize Macrophages for Tissue Repair

During wound injury, efferocytosis fills the macrophage with a metabolite load nearly equal to the phagocyte itself. A timely question pertains to how metabolic phagocytic signaling regulates the signature anti-inflammatory macrophage response. Here we report the metabolome of activated macrophages during efferocytosis to reveal an interleukin-10 (IL-10) cytokine escalation that was independent of glycolysis yet bolstered by apoptotic cell fatty acids and mitochondrial β-oxidation, the electron transport chain, and heightened coenzyme NAD+. Loss of IL-10 due to mitochondrial complex III defects was remarkably rescued by adding NAD+ precursors. This activated a SIRTUIN1 signaling cascade, largely independent of ATP, that culminated in activation of IL-10 transcription factor PBX1. Il-10 activation by the respiratory chain was also important in vivo, as efferocyte mitochondrial dysfunction led to cardiac rupture after myocardial injury. These findings highlight a new paradigm whereby macrophages leverage efferocytic metabolites and electron transport for anti-inflammatory reprogramming that culminates in organ repair.

Nicotinamide Mononucleotide: Exploration of Diverse Therapeutic Applications of a Potential Molecule

Nicotinamide mononucleotide (NMN) is a nucleotide that is most recognized for its role as an intermediate of nicotinamide adenine dinucleotide (NAD+) biosynthesis. Although the biosynthetic pathway of NMN varies between eukaryote and prokaryote, two pathways are mainly followed in case of eukaryotic human-one is through the salvage pathway using nicotinamide while the other follows phosphorylation of nicotinamide riboside. Due to the unavailability of a suitable transporter, NMN enters inside the mammalian cell in the form of nicotinamide riboside followed by its subsequent conversion to NMN and NAD+. This particular molecule has demonstrated several beneficial pharmacological activities in preclinical studies, which suggest its potential therapeutic use. Mostly mediated by its involvement in NAD+ biosynthesis, the pharmacological activities of NMN include its role in cellular biochemical functions, cardioprotection, diabetes, Alzheimer's disease, and complications associated with obesity. The recent groundbreaking discovery of anti-ageing activities of this chemical moiety has added a valuable essence in the research involving this molecule. This review focuses on the biosynthesis of NMN in mammalian and prokaryotic cells and mechanism of absorption along with the reported pharmacological activities in murine model.

Association between serum visfatin levels and atherosclerotic plaque in patients with type 2 diabetes

BACKGROUND

Visfatin is a multifaceted protein that plays an important role in regulating a variety of physiological and pathological processes, including obesity, diabetes and cardiovascular disease. However, circulating visfatin levels in atherosclerosis plaque progression in patients with type 2 diabetes, or its association with the vascular territory affected remain unclear.

METHODS

We evaluated the relationship between visfatin levels and carotid or femoral artery atherosclerosis in Chinese patients with type 2 diabetes. Serum levels of visfatin were measured by enzyme-linked immunosorbent assay (ELISA) in 97 inpatients with type 2 diabetes. Carotid and/or femoral atherosclerotic plaques were detected by B-mode ultrasound.

RESULTS

Serum visfatin levels were elevated in the group with atherosclerotic plaques compared to the control group without plaques [0.68 (0.46-1.58) versus 0.45 (0.23-0.76) ng/mL, respectively, P = 0.0002]. Patients with carotid plaques showed higher visfatin levels than those with or without femoral plaques. Pearson's correlation analysis showed that serum visfatin levels were positively correlated with waist circumference (r = 0.226, P = 0.029), waist-hip ratio (r = 0.221, P = 0.032), TG (r = 0.222, P = 0.030) and number of plaques (r = 0.275, P = 0.009). Logistic regression analysis showed that a higher serum visfatin level was an independent predictor for the presence of atherosclerotic plaques.

CONCLUSIONS

In conclusion, among patients with T2DM, serum visfatin levels were elevated in those with atherosclerotic plaques, especially in patients with carotid atherosclerotic plaques. Serum visfatin may serve as a predictor of atherosclerotic plaques in patients with T2DM.

NAD metabolism fuels human and mouse intestinal inflammation

OBJECTIVE

Nicotinamide phosphoribosyltransferase (NAMPT, also referred to as pre-B cell colony-enhancing factor or visfatin) is critically required for the maintenance of cellular nicotinamide adenine dinucleotide (NAD) supply catalysing the rate-limiting step of the NAD salvage pathway. NAMPT is strongly upregulated in inflammation including IBD and counteracts an increased cellular NAD turnover mediated by NAD-depleting enzymes. These constitute an important mechanistic link between inflammatory, metabolic and transcriptional pathways and NAD metabolism.

DESIGN

We investigated the impact of NAMPT inhibition by the small-molecule inhibitor FK866 in the dextran sulfate sodium (DSS) model of colitis and the azoxymethane/DSS model of colitis-associated cancer. The impact of NAD depletion on differentiation of mouse and human primary monocytes/macrophages was studied in vitro. Finally, we tested the efficacy of FK866 compared with dexamethasone and infliximab in lamina propria mononuclear cells (LPMNC) isolated from patients with IBD.

RESULTS

FK866 ameliorated DSS-induced colitis and suppressed inflammation-associated tumorigenesis in mice. FK866 potently inhibited NAMPT activity as demonstrated by reduced mucosal NAD, resulting in reduced abundances and activities of NAD-dependent enzymes including PARP1, Sirt6 and CD38, reduced nuclear factor kappa B activation, and decreased cellular infiltration by inflammatory monocytes, macrophages and activated T cells. Remarkably, FK866 effectively supressed cytokine release from LPMNCs of patients with IBD. As FK866 was also effective in Rag1^-⁄- mice, we mechanistically linked FK866 treatment with altered monocyte/macrophage biology and skewed macrophage polarisation by reducing CD86, CD38, MHC-II and interleukin (IL)-6 and promoting CD206, Egr2 and IL-10.

CONCLUSION

Our data emphasise the importance of NAD immunometabolism for mucosal immunity and highlight FK866-mediated NAMPT blockade as a promising therapeutic approach in acute intestinal inflammation.

Transcriptional Profiling Suggests Extensive Metabolic Rewiring of Human and Mouse Macrophages during Early Interferon Alpha Responses

Emerging evidence suggests that cellular metabolism plays a critical role in regulating immune activation. Alterations in energy and lipid and amino acid metabolism have been shown to contribute to type I interferon (IFN) responses in macrophages, but the relationship between metabolic reprogramming and the establishment of early antiviral function remains poorly defined. Here, we used transcriptional profiling datasets to develop global metabolic signatures associated with early IFN-α responses in two primary macrophage model systems: mouse bone marrow-derived macrophages (BMM) and human monocyte-derived macrophages (MDM). Short-term stimulation with IFN-α (<4 hours) was associated with significant metabolic rewiring, with >500 metabolic genes altered in mouse and human macrophage models. Pathway and network analysis identified alterations in genes associated with cellular bioenergetics, cellular oxidant status, cAMP/AMP and cGMP/GMP ratios, branched chain amino acid catabolism, cell membrane composition, fatty acid synthesis, and β-oxidation as key features of early IFN-α responses. These changes may have important implications for initial establishment of antiviral function in these cells.

NAMPT: A pleiotropic modulator of monocytes and macrophages

Nicotinamide phosphoribosyltransferase (NAMPT) is the bottleneck enzyme of the NAD salvage pathway and thereby is a controller of intracellular NAD concentrations. It has been long known that the same enzyme can be secreted by a number of cell types and acts as a cytokine, although its receptor is at present unknown. Investigational compounds have been developed that target the enzymatic activity as well as the extracellular action (i.e. neutralizing antibodies). The present contribution reviews the evidence that links intracellular and extracellular NAMPT to myeloid biology, for example governing monocyte/macrophage differentiation, polarization and migration. Furthermore, it reviews the evidence that links this protein to some disorders in which myeloid cells have a prominent role (acute infarct, inflammatory bowel disease, acute lung injury and rheumatoid arthritis) and the data showing that inhibition of the enzymatic activity or the neutralization of the cytokine is beneficial in preclinical animal models.

The Nuclear Receptor LXR Limits Bacterial Infection of Host Macrophages through a Mechanism that Impacts Cellular NAD Metabolism

Macrophages exert potent effector functions against invading microorganisms but constitute, paradoxically, a preferential niche for many bacterial strains to replicate. Using a model of infection by Salmonella Typhimurium, we have identified a molecular mechanism regulated by the nuclear receptor LXR that limits infection of host macrophages through transcriptional activation of the multifunctional enzyme CD38. LXR agonists reduced the intracellular levels of NAD⁺ in a CD38-dependent manner, counteracting pathogen-induced changes in macrophage morphology and the distribution of the F-actin cytoskeleton and reducing the capability of non-opsonized Salmonella to infect macrophages. Remarkably, pharmacological treatment with an LXR agonist ameliorated clinical signs associated with Salmonella infection in vivo, and these effects were dependent on CD38 expression in bone-marrow-derived cells. Altogether, this work reveals an unappreciated role for CD38 in bacterial-host cell interaction that can be pharmacologically exploited by activation of the LXR pathway.

SIRT1 regulates macrophage self-renewal

Mature differentiated macrophages can self-maintain by local proliferation in tissues and can be extensively expanded in culture under specific conditions, but the mechanisms of this phenomenon remain only partially defined. Here, we show that SIRT1, an evolutionary conserved regulator of life span, positively affects macrophage self-renewal ability in vitro and in vivo Overexpression of SIRT1 during bone marrow-derived macrophage differentiation increased their proliferative capacity. Conversely, decrease of SIRT1 expression by shRNA inactivation, CRISPR/Cas9 mediated deletion and pharmacological inhibition restricted macrophage self-renewal in culture. Furthermore, pharmacological SIRT1 inhibition in vivo reduced steady state and cytokine-induced proliferation of alveolar and peritoneal macrophages. Mechanistically, SIRT1 inhibition negatively regulated G1/S transition, cell cycle progression and a network of self-renewal genes. This included inhibition of E2F1 and Myc and concomitant activation of FoxO1, SIRT1 targets mediating cell cycle progression and stress response, respectively. Our findings indicate that SIRT1 is a key regulator of macrophage self-renewal that integrates cell cycle and longevity pathways. This suggests that macrophage self-renewal might be a relevant parameter of ageing.

Selenoprotein MsrB1 promotes anti-inflammatory cytokine gene expression in macrophages and controls immune response in vivo

Post-translational redox modification of methionine residues often triggers a change in protein function. Emerging evidence points to this reversible protein modification being an important regulatory mechanism under various physiological conditions. Reduction of oxidized methionine residues is catalyzed by methionine sulfoxide reductases (Msrs). Here, we show that one of these enzymes, a selenium-containing MsrB1, is highly expressed in immune-activated macrophages and contributes to shaping cellular and organismal immune responses. In particular, lipopolysaccharide (LPS) induces expression of MsrB1, but not other Msrs. Genetic ablation of MsrB1 did not preclude LPS-induced intracellular signaling in macrophages, but resulted in attenuated induction of anti-inflammatory cytokines, such as interleukin (IL)-10 and the IL-1 receptor antagonist. This anomaly was associated with excessive pro-inflammatory cytokine production as well as an increase in acute tissue inflammation in mice. Together, our findings suggest that MsrB1 controls immune responses by promoting anti-inflammatory cytokine expression in macrophages. MsrB1-dependent reduction of oxidized methionine in proteins may be a heretofore unrecognized regulatory event underlying immunity and inflammatory disease, and a novel target for clinical applications.

PARP inhibition in leukocytes diminishes inflammation via effects on integrins/cytoskeleton and protects the blood-brain barrier

Background

Blood-brain barrier (BBB) dysfunction/disruption followed by leukocyte infiltration into the brain causes neuroinflammation and contributes to morbidity in multiple sclerosis, encephalitis, traumatic brain injury, and stroke. The identification of pathways that decreases the inflammatory potential of leukocytes would prevent such injury. Poly(ADP-ribose) polymerase 1 (PARP) controls various genes via its interaction with myriad transcription factors. Selective PARP inhibitors have appeared lately as potent anti-inflammatory tools. Their effects are outside the recognized PARP functions in DNA repair and transcriptional regulation. In this study, we explored the idea that selective inhibition of PARP in leukocytes would diminish their engagement of the brain endothelium.

Methods

Cerebral vascular changes and leukocyte-endothelium interactions were surveyed by intravital videomicroscopy utilizing a novel in vivo model of localized aseptic meningitis when TNFα was introduced intracerebrally in wild-type (PARP^+/+) and PARP-deficient (PARP^−/−) mice. The effects of selective PARP inhibition on primary human monocytes ability to adhere to or migrate across the BBB were also tested in vitro, employing primary human brain microvascular endothelial cells (BMVEC) as an in vitro model of the BBB.

Results

PARP suppression in monocytes diminished their adhesion to and migration across BBB in vitro models and prevented barrier injury. In monocytes, PARP inactivation decreased conformational activation of integrins that plays a key role in their tissue infiltration. Such changes were mediated by suppression of activation of small Rho GTPases and cytoskeletal rearrangements in monocytes. In vitro observations were confirmed in vivo showing diminished leukocyte-endothelial interaction after selective PARP suppression in leukocytes accompanied by BBB protection. PARP knockout animals demonstrated a substantial diminution of inflammatory responses in brain microvasculature and a decrease in BBB permeability.

Conclusions

These results suggest PARP inhibition in leukocytes as a novel approach to BBB protection in the setting of endothelial dysfunction caused by inflammation-induced leukocyte engagement.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0729-x) contains supplementary material, which is available to authorized users.

Increased expression of NAMPT in PBMC from patients with acute coronary syndrome and in inflammatory M1 macrophages

AIM

The aim of the present study were to elucidate the role of NAMPT in atherosclerosis, by examine NAMPT expression in peripheral blood mononuclear cells (PBMC) in patients with coronary artery disease (CAD) and healthy controls and by examining the regulation and effect of NAMPT on macrophage polarization, hypothesizing that it could influence the polarization to inflammatory and resolving macrophages.

METHOD AND RESULTS

We analyzed RNA levels of NAMPT in PBMC from CAD and healthy controls and found NAMPT to be increased in PBMC from patients with acute coronary syndrome (n = 39) compared to healthy controls (n = 20) and patients with stable CAD (n = 22). Within the PBMC NAMPT was correlated to several inflammatory cytokines and the antioxidant enzyme superoxide dismutase 2. In vitro cell experiments revealed that NAMPT is increased both intracellular and extracellular in inflammatory M1 macrophages compared to in anti-inflammatory M2 macrophages. In addition, inhibiting NAMPT enzymatic activity inhibited M1 polarization in macrophages.

CONCLUSION

Based on our in vivo and in vitro findings we suggest that NAMPT could contribute to systemic and plaque inflammation in atherosclerotic disorders at least partly through effect on macrophages.

Nicotinamide phosphorybosiltransferase overexpression in thyroid malignancies and its correlation with tumor stage and with survivin/survivin DEx3 expression

Nicotinamide phosphorybosiltransferase (NAMPT) plays an important role in the regulation of cellular growth, angiogenesis, and apoptosis in mammalian cells. NAMPT overexpression has been recently found in colorectal, breast, prostatic, gastric, esophageal, pancreatic cancers, and specific NAMPT inhibitors might be adjuvant therapeutic modalities. In this study, we analyzed NAMPT expression in 40 malignant and in 67 benign thyroid tissue samples using qPCR. We also investigated relationships between NAMPT expression and survivin/survivin splicing variants DEx3 and 2B expressions. NAMPT expression was significantly higher in thyroid cancers (P < 0.0001), and it was positively correlated with tumor stage (P = 0.0012; r = 0.493). NAMPT expression was significantly higher in tumors staged pT3 or pT4 (16 cases) than in tumors staged pT1 or pT2 (24 cases) (P = 0.0106). Metastases to the lymph nodes were found in 12 out of 40 cases, and NAMPT expression was higher in the metastatic group (P = 0.0258). Multifocality was not associated with higher NAMPT expression (P = 0.3451). NAMPT expression in thyroid cancers significantly correlated with survivin and with survivin splice variant DEx3 expressions (P < 0.0001; r = 0.624 and P = 0.0239; r = 0.357, respectively). There was no correlation between NAMPT and survivin 2B expressions (P = 0.3508). This is the first study demonstrating NAMPT overexpression in thyroid malignancies using quantitative RT-PCR. Moreover, it shows that NAMPT is upregulated in patients with more advanced tumor stage and metastatic disease which may prove to be clinically relevant. Further studies are needed to explain the role of NAMPT in thyroid cancer biology and the possible use of NAMPT inhibitors in thyroid cancer.

NAMPT inhibitor and metabolite protect mouse brain from cryoinjury through distinct mechanisms

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme in the biosynthesis of nicotinamide adenine dinucleotide (NAD). In the brain, NAMPT is primarily expressed in neurons and can prevent neuronal degeneration. NAMPT is also highly expressed in inflammatory cells, and is responsible for their activation. Since inflammation following traumatic brain injury enhances neuronal damage, we assessed the effects of nicotinamide mononucleotide (NMN), the direct NAMPT metabolite, and FK866, a potent NAMPT inhibitor, on brain injury in a cryoinjury mouse model. Twenty-four hours after brain cryoinjury, the density of neuron and the level of NAD decreased. Both NMN and FK866 alleviated the neuronal loss and decreased the lesion volume. NMN prevented the cryoinjury-induced decrease of NAD level, and FK866 decreased it further. On day 14 after cryoinjury, further neuronal loss occurred, astrocytes and Iba1-positive macrophage/microglia activated, and the NAD level increased. At this time-point, NAMPT expression was strongly induced in Iba1-positive macrophages/microglia in the lesion core. NMN and FK866 also alleviated the neuronal loss and decreased the lesion volume. In addition, FK866 significantly attenuated the activation of astrocytes and Iba1-positive macrophages/microglia, and decreased the NAD, while NMN had no such effects. Taken together, both FK866 and NMN attenuate traumatic brain injury. However, FK866 acts via the inhibition of the NAMPT activity in inflammatory cells resulting in the inhibition of inflammation, whereas NMN is effective via replenishing NAD.