Involvement of eNAMPT/TLR4 signaling in murine radiation pneumonitis: protection by eNAMPT neutralization.

Therapeutic strategies to prevent or reduce the severity of radiation pneumonitis are a serious unmet need. We evaluated extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a damage-associated molecular pattern protein (DAMP) and Toll-Like Receptor 4 (TLR4) ligand, as a therapeutic target in murine radiation pneumonitis. Radiation-induced murine and human NAMPT expression was assessed in vitro, in tissues (IHC, biochemistry, imaging), and in plasma. Wild type C57Bl6 mice (WT) and Nampt+/- heterozygous mice were exposed to 20Gy whole thoracic lung irradiation (WTLI) with or without weekly IP injection of IgG1 (control) or an eNAMPT-neutralizing polyclonal (pAb) or monoclonal antibody (mAb). BAL protein/cells and H&E staining were used to generate a WTLI severity score. Differentially-expressed genes (DEGs)/pathways were identified by RNA sequencing and bioinformatic analyses. Radiation exposure increases in vitro NAMPT expression in lung epithelium (NAMPT promoter activity) and NAMPT lung tissue expression in WTLI-exposed mice. Nampt+/- mice and eNAMPT pAb/mAb-treated mice exhibited significant histologic attenuation of WTLI-mediated lung injury with reduced levels of BAL protein and cells, and plasma levels of eNAMPT, IL-6,  and IL-1ß. Genomic and biochemical studies from WTLI-exposed lung tissues highlighted dysregulation of NFkB/cytokine and MAP kinase signaling pathways which were rectified by eNAMPT mAb treatment. The eNAMPT/TLR4 pathway is essentially involved in radiation pathobiology with eNAMPT neutralization an effective therapeutic strategy to reduce the severity of radiation pneumonitis.

Sirtuin 1, Visfatin and IL-27 Serum Levels of Type 1 Diabetic Females in Relation to Cardiovascular Parameters and Autoimmune Thyroid Disease.

The loss of cardioprotection observed in premenopausal, diabetic women may result from the interplay between epigenetic, metabolic, and immunological factors. The aim of this study was to evaluate the concentration of sirtuin 1, visfatin, and IL-27 in relation to cardiovascular parameters and Hashimoto's disease (HD) in young, asymptomatic women with type 1 diabetes mellitus (T1DM). Thyroid ultrasound, carotid intima-media thickness (cIMT) measurement, electrocardiography, and echocardiography were performed in 50 euthyroid females with T1DM (28 with HD and 22 without concomitant diseases) and 30 controls. The concentrations of serum sirtuin 1, visfatin and IL-27 were assessed using ELISA. The T1DM and HD group had higher cIMT (p = 0.018) and lower left ventricular global longitudinal strain (p = 0.025) compared to females with T1DM exclusively. In women with a double diagnosis, the sirtuin 1 and IL-27 concentrations were non-significantly higher than in other groups and significantly positively correlated with each other (r = 0.445, p = 0.018) and thyroid volume (r = 0.511, p = 0.005; r = 0.482, p = 0.009, respectively) and negatively correlated with relative wall thickness (r = -0.451, p = 0.016; r = -0.387, p = 0.041, respectively). These relationships were not observed in the control group nor for the visfatin concentration. These results suggest that sirtuin 1 and IL-27 contribute to the pathogenesis of early cardiac dysfunction in women with T1DM and HD.

NAD+ metabolism, stemness, the immune response, and cancer.

NAD+ was discovered during yeast fermentation, and since its discovery, its important roles in redox metabolism, aging, and longevity, the immune system and DNA repair have been highlighted. A deregulation of the NAD+ levels has been associated with metabolic diseases and aging-related diseases, including neurodegeneration, defective immune responses, and cancer. NAD+ acts as a cofactor through its interplay with NADH, playing an essential role in many enzymatic reactions of energy metabolism, such as glycolysis, oxidative phosphorylation, fatty acid oxidation, and the TCA cycle. NAD+ also plays a role in deacetylation by sirtuins and ADP ribosylation during DNA damage/repair by PARP proteins. Finally, different NAD hydrolase proteins also consume NAD+ while converting it into ADP-ribose or its cyclic counterpart. Some of these proteins, such as CD38, seem to be extensively involved in the immune response. Since NAD cannot be taken directly from food, NAD metabolism is essential, and NAMPT is the key enzyme recovering NAD from nicotinamide and generating most of the NAD cellular pools. Because of the complex network of pathways in which NAD+ is essential, the important role of NAD+ and its key generating enzyme, NAMPT, in cancer is understandable. In the present work, we review the role of NAD+ and NAMPT in the ways that they may influence cancer metabolism, the immune system, stemness, aging, and cancer. Finally, we review some ongoing research on therapeutic approaches.

NAD+ Metabolism Maintains Inducible PD-L1 Expression to Drive Tumor Immune Evasion.

NAD+ metabolism is implicated in aging and cancer. However, its role in immune checkpoint regulation and immune evasion remains unclear. Here, we find nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD+ biogenesis, drives interferon γ (IFNγ)-induced PD-L1 expression in multiple types of tumors and governs tumor immune evasion in a CD8+ T cell-dependent manner. Mechanistically, NAD+ metabolism maintains activity and expression of methylcytosine dioxygenase Tet1 via α-ketoglutarate (α-KG). IFNγ-activated Stat1 facilitates Tet1 binding to Irf1 to regulate Irf1 demethylation, leading to downstream PD-L1 expression on tumors. Importantly, high NAMPT-expressing tumors are more sensitive to anti-PD-L1 treatment and NAD+ augmentation enhances the efficacy of anti-PD-L1 antibody in immunotherapy-resistant tumors. Collectively, these data delineate an NAD+ metabolism-dependent epigenetic mechanism contributing to tumor immune evasion, and NAD+ replenishment combined with PD-(L)1 antibody provides a promising therapeutic strategy for immunotherapy-resistant tumors.

Dingxin recipe alleviates atherosclerosis injury in ApoE-knockout mice via downregulation of visfatin expression and inhibition of the visfatin-induced inflammatory response.

OBJECTIVE: To further elucidate the mechanism underlying the anti-atherosclerotic effect of Dingxin recipe (DXR). METHODS: Fifty 6-week-old male ApoE-/- mice were randomly divided into the following groups: model, simvastatin (5 mg·kg－1·d－1), DXR low-dose (9.30 g·kg－1·d－1), DXR middle-dose (18.59 g·kg－1·d－1) and DXR high-dose (37.18 g·kg－1·d－1) (n = 10). Ten male C57BL/6J mice were used as the control group. All ApoE-/- mice were fed a high-fat diet (HFD) and the control mice received a common diet. After HFD for 12 weeks, the mice were treated with DXR or simvastatin for another 12 weeks. The expression of inflammatory cytokines and visfatin was determined in serum and atherosclerotic lesions by enzyme-linked immunosorbent assay. Visfatin expression was also assessed in aortic atherosclerotic plaques. Cultured vessel endothelial cells (VECs) were pretreated with DXR sera prior to visfatin. The effects of DXR were analyzed to elucidate its protective mechanism against visfatin-induced inflammation in VECs. RESULTS: DXR regulated blood lipids and reduced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), intercellular adhesion molecules-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and visfatin expression in ApoE-/- mice, particularly at the higher doses. The areas of atherosclerotic lesions in the DXR groups were significantly smaller than those in the model group. DXR alleviated visfatin-induced VEC injury via downregulation of TNF-α, IL-6, ICAM-1 and VCAM-1 through mitogen-activated protein kinase pathways. CONCLUSION: DXR alleviated atherosclerosis injury via downregulation of visfatin expression and inhibition of the visfatin-induced inflammatory response in VECs.

Bioactive fractions from Securidaca inappendiculata alleviated collagen-induced arthritis in rats by regulating metabolism-related signaling.

Securidaca inappendiculata is a xanthone rich medicinal plant that has been used in the treatment of inflammation and autoimmune diseases like rheumatoid arthritis (RA) for centuries; however, the material base and mechanism of action responsible for its anti-arthritis effect still remains elusive. The objective of this study is to evaluate the therapeutic effects of xanthone-enriched extract of the plant against collagen-induced arthritis (CIA) in rats and explore the underlying mechanisms. The xanthone-deprived fraction (XDF) and xanthone-rich fraction (XRF) were obtained by using a resin adsorption coupled with acid-base treatment method, and their chemical composition difference was characterized by UPLC-MS/MS analysis. Effects of the two on CIA were analyzed using radiographic, histological, and immunohistochemical analyses. The results indicated that XRF alleviated joint structures destructions with the higher efficacy than XDF, and decreased levels of TNF-α, IL-6, and anti-cyclic citrullinated peptide antibody in CIA rats significantly. Furthermore, XRF inhibited nicotinamide phosphoribosyl transferase (NAMPT) mediated fat biosynthesis and utilization indicated by clinical evidences and metabonomics analysis, which thereby disrupted energy-metabolism feedback. In addition, Toll-like Receptor 4 and High Mobility Group Protein 1 expressions were downregulated in XRF-treated CIA rats. Collective evidences suggest NAMPT could be an ideal target for RA treatments and reveal a novel antirheumatic mechanism of S. inappendiculata by regulating NAMPT controlled fat metabolism.

Visfatin and Rheumatoid Arthritis: Pathogenetic Implications and Clinical Utility.

OBJECTIVE: Analysis and generalization of data related to visfatin involvement in the pathogenesis of inflammation at various stages of rheumatoid arthritis. DATA SYNTHESIS: Visfatin is an adipocytokine which has also been identified in non-adipose tissues. It influences directly on the maturation of B cells, which are involved in autoantibody production and T cell activation. Visfatin can promote inflammation via regulation of pro-inflammatory cytokines including TNF, IL-1ß and IL-6. The concentration of circulating visfatin in rheumatoid arthritis patients is higher compared to healthy individuals. Several studies suggest that visfatin level is associated with rheumatoid arthritis activity, and its elevation may precede clinical signs of the relapse. In murine collagen-induced arthritis, visfatin levels were also found to be elevated both in inflamed synovial cells and in joint vasculature. Visfatin blockers have been shown to confer fast and long-term attenuation of pathological processes; however, most of their effects are transient. Other factors responsible for hyperactivation of the immune system can participate in this process at a later stage. Treatment of rheumatoid arthritis with a combination of these blockers and inhibitors of other mediators of inflammation can potentially improve treatment outcomes compared to current therapeutic strategies. Recent advances in the treatment of experimental arthritis in mice as well as the application of emerging treatment strategies obtained from oncology for rheumatoid arthritis management could be a source of novel adipokine-mediated anti-rheumatic drugs. CONCLUSION: The ongoing surge of interest in anticytokine therapy makes further study of visfatin highly relevant as it may serve as a base for innovational RA treatment.

Potential role of adipose tissue and its hormones in burns and critically III patients.

Obesity has become a world-wide pandemic and is considered a major risk factor for various diseases. Despite this, recent intriguing clinical observations have been made suggesting that being overweight has some advantages. Overweight and some obese patients were reported to have significantly lower all-cause mortality, described as the 'obesity paradox'. This phenomenon resulted in increased research aimed at investigating the influence of adipose tissue on outcomes of various clinical states including critical illness. In this review, we summarise research findings on the effect burn injury and trauma-related critical illness have on adipose tissue and discuss potential mechanisms by which adipose tissue influences outcomes in burn and other critically ill patients. Burn injury and critical illness influence adipose tissue functionally and morphologically, with circulating levels of fat derived hormones, adipokines, altered in patients following injury and/or critical illness. As adipokines regulate a variety of processes including inflammation and metabolism, this disruption in the adipokine axis may explain the obesity paradox phenomenon observed in critically ill patients. We conclude that further research on the influence of individual adipokines on prognosis in burn and critically ill patients and the mechanisms involved is required to increase understanding of their therapeutic potential.

Switch of NAD Salvage to de novo Biosynthesis Sustains SIRT1-RelB-Dependent Inflammatory Tolerance.

A typical inflammatory response sequentially progresses from pro-inflammatory, immune suppressive to inflammatory repairing phases. Although the physiological inflammatory response resolves in time, severe acute inflammation usually sustains immune tolerance and leads to high mortality, yet the underlying mechanism is not completely understood. Here, using the leukemia-derived THP-1 human monocytes, healthy and septic human peripheral blood mononuclear cells (PBMC), we report that endotoxin dose-dependent switch of nicotinamide adenine dinucleotide (NAD) biosynthesis pathways sustain immune tolerant status. Low dose endotoxin triggered nicotinamide phosphoribosyltransferase (NAMPT)-dependent NAD salvage activity to adapt pro-inflammation. In contrast, high dose endotoxin drove a shift of NAD synthesis pathway from early NAMPT-dependent NAD salvage to late indoleamine 2,3-dioxygenase-1 (IDO1)-dependent NAD de novo biosynthesis, leading to persistent immune suppression. This is resulted from the IDO1-dependent expansion of nuclear NAD pool and nuclear NAD-dependent prolongation of sirtuin1 (SIRT1)-directed epigenetics of immune tolerance. Inhibition of IDO1 activity predominantly decreased nuclear NAD level, which promoted sequential dissociations of immunosuppressive SIRT1 and RelB from the promoter of pro-inflammatory TNF-α gene and broke endotoxin tolerance. Thus, NAMPT-NAD-SIRT1 axis adapts pro-inflammation, but IDO1-NAD-SIRT1-RelB axis sustains endotoxin tolerance during acute inflammatory response. Remarkably, in contrast to the prevention of sepsis death of animal model by IDO1 inhibition before sepsis initiation, we demonstrated that the combination therapy of IDO1 inhibition by 1-methyl-D-tryptophan (1-MT) and tryptophan supplementation rather than 1-MT administration alone after sepsis onset rescued sepsis animals, highlighting the translational significance of tryptophan restoration in IDO1 targeting therapy of severe inflammatory diseases like sepsis.

Podocyte NLRP3 Inflammasome Activation and Formation by Adipokine Visfatin.

BACKGROUND/AIMS: NLRP3 inflammasome activation has been reported to be an early mechanism responsible for glomerular inflammation and injury in obese mice. However, the precise mechanism of obesity-induced NLRP3 inflammasome activation remains unknown. The present study explored whether adipokine visfatin mediates obesity-induced NLRP3 inflammasome activation and consequent podocyte injury. METHODS: Inflammasome formation and immunofluorescence expressions were quantified by confocal microscopy. Caspase-activity, IL-1ß production and VEGF concentrations were measured by ELISA. RESULTS: Confocal microscopic analysis showed that visfatin treatment increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1 in podocytes indicating the formation of NLRP3 inflammasomes. This visfatin-induced NLRP3 inflammasome formation was abolished by pretreatment of podocytes with Asc siRNA. Correspondingly, visfatin treatment significantly increased the caspase-1 activity and IL-1ß production in podocytes, which was significantly attenuated by Asc siRNA transfection. Further RT-PCR and confocal microscopic analysis demonstrated that visfatin treatment significantly decreased the podocin expression (podocyte damage). Podocytes pretreatment with Asc siRNA or caspase-1 inhibitor, WEHD attenuated this visfatin-induced podocin reduction. Furthermore, Asc siRNA transfection was found to preserve podocyte morphology by maintaining the distinct arrangement of F-actin fibers normally lost in response to visfatin. It also prevented podocyte dysfunction by restoring visfatin-induced suppression of VEGF production and secretion. CONCLUSION: Visfatin induces NLRP3 inflammasome activation in podocytes and thereby resulting in podocyte injury.

Minor compounds from virgin olive oil attenuate LPS-induced inflammation via visfatin-related gene modulation on primary human monocytes.

We have analyzed the effects of minor compounds found in the unsaponifiable fraction (UF) and in the phenolic fraction (PF) of virgin olive oil (VOO) on LPS-induced inflammatory response via visfatin modulation in human monocytes. For this purpose, monocytes were incubated with UF and PF at different concentrations and the pro-inflammatory stimulus LPS for 24 hr; squalene (SQ) and hydroxytyrosol (HTyr), the main components in UF and PF, respectively, were also used. The relative expression of both pro-inflammatory and anti-inflammatory genes, as well as other genes related to the NAD+-biosynthetic pathway was evaluated by RT-qPCR; and the secretion of some of these markers was assessed by ELISA procedures. We found that UF, SQ, PF, and HTyr prevented from LPS-induced dysfunctional gene expression and secretion via visfatin-related gene modulation in human monocytes. These findings unveil a potential beneficial role for minor compounds of VOO in the prevention of inflammatory-disorders. PRACTICAL APPLICATION: In this project, potential health benefits of VOO micronutrients (unsaponifiable and phenolic compounds) were confirmed through anti-inflammatory assays. Our results reveal new interesting researching goals concerning nutrition by considering the role of bioactive VOO compounds in the prevention and progress of diseases related to inflammation.

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 relationship between visfatin, liver inflammation, and acute phase reactants in chronic viral hepatitis B.

Chronic viral hepatitis B (CHB) is an important cause of morbidity and mortality. Adipokine stimulation might play an important role in the pathogenesis of chronic inflammation. The aim of this study was to evaluate serum visfatin concentrations and the relationship between visfatin, fibrosis, liver inflammation, and acute phase reactants in CHB patients.The sampling universe of the study consisted of 41 CHB patients and 25 healthy controls. All patients had positive hepatitis B surface antigen (Hepatitis e antigen (HBeAg) positive n: 7, n: 34 HBeAg negative) for at least 6 months and detectable serum HBV DNA. Serum visfatin concentrations were significantly higher in the CHB patients [18.0 ± 10.9 ng dL(-1)] than in the healthy controls [9.4 ± 1.6 ng dL(-1)] [P < 0.001]. On the other hand, fibrinogen and haptoglobin concentrations were significantly lower in CHB patients. A strong negative correlation was observed between serum visfatin concentration, haptoglobin, and fibrinogen levels; however, there was no significant correlation between visfatin, glucose, alanine aminotransferase, aspartate aminotransferase, BMI, Knodell score, fibrosis score, hepatitis B virus DNA, sedimentation, and C-reactive protein. Visfatin concentrations were elevated and visfatin was negatively correlated with haptoglobin and fibrinogen levels in CHB patients.

The role of visfatin (PBEF/Nampt) in pregnancy complications.

Visfatin (PBEF/Nampt) is an adipocytokine that exerts pleiotropic effects within the human body, particularly affecting its metabolism and immunity. Visfatin was originally identified as being secreted by peripheral blood lymphocytes acting as a pre-B-cell colony-enhancing factor (PBEF). However, it was subsequently reported to be expressed in almost every tissue of the human body, with visceral fat deposits being the main source of visfatin. In addition to its secreted form, visfatin may also be found intracellularly where it functions as a nicotinamide phosphoribosyltransferase (Nampt). Visfatin maternal plasma concentrations increase during pregnancy, suggesting its important role in this complicated process. Alterations in visfatin level also take place in patients during pregnancy complications. This review focuses on the ones that most commonly occur in connection with visfatin: preterm labor, pre-eclampsia and gestational diabetes mellitus. The review aims to provide a better understanding of the role of visfatin during pregnancy and the causes of its alteration in maternal plasma, highlighting the potential use of visfatin as a diagnostic marker of pregnancy complications in the future.

Unique Toll-Like Receptor 4 Activation by NAMPT/PBEF Induces NFκB Signaling and Inflammatory Lung Injury.

Ventilator-induced inflammatory lung injury (VILI) is mechanistically linked to increased NAMPT transcription and circulating levels of nicotinamide phosphoribosyl-transferase (NAMPT/PBEF). Although VILI severity is attenuated by reduced NAMPT/PBEF bioavailability, the precise contribution of NAMPT/PBEF and excessive mechanical stress to VILI pathobiology is unknown. We now report that NAMPT/PBEF induces lung NFκB transcriptional activities and inflammatory injury via direct ligation of Toll-like receptor 4 (TLR4). Computational analysis demonstrated that NAMPT/PBEF and MD-2, a TLR4-binding protein essential for LPS-induced TLR4 activation, share ~30% sequence identity and exhibit striking structural similarity in loop regions critical for MD-2-TLR4 binding. Unlike MD-2, whose TLR4 binding alone is insufficient to initiate TLR4 signaling, NAMPT/PBEF alone produces robust TLR4 activation, likely via a protruding region of NAMPT/PBEF (S402-N412) with structural similarity to LPS. The identification of this unique mode of TLR4 activation by NAMPT/PBEF advances the understanding of innate immunity responses as well as the untoward events associated with mechanical stress-induced lung inflammation.

PBEF promotes the apoptosis of pulmonary microvascular endothelial cells and regulates the expression of inflammatory factors and AQP1 through the MAPK pathways.

Pre-B cell colony-enhancing factor (PBEF) has been shown to have a variety of biological functions. Studies have proven that PBEF plays a functional role in acute lung injury (ALI). Therefore, in this study, we aimed to confirm the importance of PBEF in ALI. The effects of PBEF overexpression on the apoptosis of human pulmonary microvascular endothelial cells (HPMECs) were analyzed by flow cytometry, and the results indicated that PBEF promoted the apoptosis of HPMECs, which aggravated the development of ALI. Comparative experiments involving increasing and decreasing PBEF expression demonstrated that PBEF promoted the expression of inflammatory factors, such as interleukin (IL)­1ß, IL­6 and IL­8 in the HPMECs , thus intensifying the inflammatory response. PBEF also inhibited the expression of aquaporin 1 (AQP1), which caused a dysfunction and imbalance in water transport. Moreover, we also found that tumor necrosis factor (TNF)­α promoted the expression of PBEF in the HPMECs. After blocking the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways, we found that PBEF regulated the expression of inflammatory factors and AQP1, mainly through the MAPK pathways. Taken together, these results demonstrate that the increase in intracellular PBEF expression promoted the apoptosis of HPMECs and the expression of inflammatory factors and thus enhanced the inflammatory response and inhibited the expression of AQP1, which resulted in abnormal water transport, diminishing the regulatory effects of AQP1 on water transport.

Adipokines influence the inflammatory balance in autoimmunity.

Over the past few decades, our understanding of the role of adipose tissue has changed dramatically. Far from simply being a site of energy storage or a modulator of the endocrine system, adipose tissue has emerged as an important regulator of multiple important processes including inflammation. Adipokines are a diverse family of soluble mediators with a range of specific actions on the immune response. Autoimmune diseases are perpetuated by chronic inflammatory responses but the exact etiology of these diseases remains elusive. While researchers continue to investigate these causes, millions of people continue to suffer from chronic diseases. To this end, an increased interest has developed in the connection between adipose tissue-secreted proteins that influence inflammation and the onset and perpetuation of autoimmunity. This review will focus on recent advances in adipokine research with specific attention on a subset of adipokines that have been associated with autoimmune diseases.

Targeting NAMPT for Therapeutic Intervention in Cancer and Inflammation: Structure-Based Drug Design and Biological Screening.

Nicotinamide phosphoribosyltransferase (NAMPT) is a rate limiting enzyme that plays an important role in the synthesis of nicotinamide adenine dinucleotide (NAD) via a salvage pathway. Along with a role in bioenergetics, NAMPT regulates the activity of proteins such as SIRT-1 that utilize NAD as a cofactor. As NAD metabolism is usually high in diseased conditions, it has been hypothesized and proven that NAMPT is over expressed in various cancers and inflammatory disorders. Inhibitors targeting NAMPT could therefore be useful in treating disorders arising from aberrant NAMPT signalling. In this study, inhibitors against NAMPT were designed using an energy-based pharmacophore strategy and evaluated for efficacy in cellular assays. Besides reducing cellular pools of NAD and NMN, NAMPT inhibitors decreased concentrations of reactive oxygen species as well as mRNA levels of TNFα and IL6, thereby implicating their potential in alleviating the inflammatory process. In addition, reduced NAD levels corroborated with an induction of apoptosis in prostate cancer cell lines.

Extracellular visfatin has nicotinamide phosphoribosyltransferase enzymatic activity and is neuroprotective against ischemic injury.

AIM: Visfatin, a novel adipokine, is predominantly produced by visceral adipose tissue and exists in intracellular and extracellular compartments. The intracellular form of visfatin is proved to be nicotinamide phosphoribosyltransferase (NAMPT) and exhibits neuroprotection through maintaining intracellular NAD(+) pool. However, whether extracellular form of visfatin has NAMPT activity and the effect of extracellular visfatin in cerebral ischemia are unknown. METHODS AND RESULTS: Plasma concentrations of visfatin, NAD(+) , and ATP were increased in mice upon cerebral ischemia. Cultured glia, but not neuron, was able to secrete visfatin. Oxygen-glucose deprivation (OGD) stress increased the secretion of visfatin from glia. Extracellular recombinant mouse wild-type visfatin, but not mouse H247A-mutant enzymatic-dead visfatin, had NAMPT enzymatic function in vitro. Treatment of wild-type visfatin, but not H247A-mutant enzymatic-dead visfatin, significantly attenuated detrimental effect of OGD on the cell viability and apoptosis in both cultured mouse neuron and glia. Treatment of neutralizing antibody, abolished the protective effect of extracellular visfatin on cell viability, but failed to block the antiapoptotic effect of extracellular visfatin. At last, we observed that plasma visfatin concentrations decreased in 6-month-old but not 3-month-old SHR-SP compared with that in age-matched Wistar-Kyoto rats. Inhibition of NAMPT enzymatic function of visfatin (by FK866) accelerated the occurrence of stroke in SHR-SP. CONCLUSIONS: Extracellular visfatin has NAMPT enzymatic activity and maybe be neuroprotective just as intracellular visfatin in cerebral ischemic injury.