Pre-B-cell-colony-enhancing factor is critically involved in thrombin-induced lung endothelial cell barrier dysregulation

eNAMPT is a novel therapeutic target for mitigation of coronary microvascular disease in type 2 diabetes

AIMS/HYPOTHESIS

Individuals with diabetes are at high risk of cardiovascular complications, which significantly increase morbidity/mortality. Coronary microvascular disease (CMD) is recognised as a critical contributor to the increased cardiac mortality observed in people with diabetes. Therefore, there is an urgent need for treatments that are specific to CMD. eNAMPT (extracellular nicotinamide phosphoribosyltransferase) is a damage-associated molecular pattern and TLR4 ligand, whose plasma levels are elevated in people with diabetes. This study was thus designed to investigate the pathogenic role of intracellular nicotinamide phosphoribosyltransferase (iNAMPT) and eNAMPT in promoting the development of CMD in a preclinical murine model of type 2 diabetes.

METHODS

An inducible type 2 diabetic mouse model was generated by a single injection of low-dose streptozocin (75 mg/kg, i.p.) combined with a high-fat diet for 16 weeks. The in vivo effects of i/eNAMPT inhibition on cardiac endothelial cell (CEC) function were evaluated by using Nampt+/- heterozygous mice, chronic administration of eNAMPT-neutralising monoclonal antibody (mAb) or use of an NAMPT enzymatic inhibitor (FK866).

RESULTS

As expected, diabetic wild-type mice exhibited significantly lower coronary flow velocity reserve (CFVR), a determinant of coronary microvascular function, compared with control wild-type mice. eNAMPT plasma levels or expression in CECs were significantly greater in diabetic mice than in control mice. Furthermore, in comparison with diabetic wild-type mice, diabetic Nampt+/- heterozygous mice showed markedly improved CFVR, accompanied by increased left ventricular capillary density and augmented endothelium-dependent relaxation (EDR) in the coronary artery. NAMPT inhibition by FK866 or an eNAMPT-neutralising mAb significantly increased CFVR in diabetic mice. Furthermore, administration of the eNAMPT mAb upregulated expression of angiogenesis- and EDR-related genes in CECs from diabetic mice. Treatment with either eNAMPT or NAD+ significantly decreased CEC migration and reduced EDR in coronary arteries, partly linked to increased production of mitochondrial reactive oxygen species.

CONCLUSIONS/INTERPRETATION

These data indicate that increased i/eNAMPT expression contributes to the development of diabetic coronary microvascular dysfunction, and provide compelling support for eNAMPT inhibition as a novel and effective therapeutic strategy for CMD in diabetes.

The role of adipokines in osteoporosis management: a mini review

The prevalence of osteoporosis has been on the rise globally. With ageing populations, research has sought therapeutic solutions in novel areas. One such area is that of the adipokines. Current literature points to an important role for these chemical mediators in relation to bone metabolism. Well-established adipokines have been broadly reported upon. These include adiponectin and leptin. However, other novel adipokines such as visfatin, nesfatin-1, meteorin-like protein (Metrnl), apelin and lipocalin-2 are starting to be addressed pre-clinically and clinically. Adipokines hold pro-inflammatory and anti-inflammatory properties that influence the pathophysiology of various bone diseases. Omentin-1 and vaspin, two novel adipokines, share cardioprotective effects and play essential roles in bone metabolism. Studies have reported bone-protective effects of omentin-1, whilst others report negative associations between omentin-1 and bone mineral density. Lipocalin-2 is linked to poor bone microarchitecture in mice and is even suggested to mediate osteoporosis development from prolonged disuse. Nesfatin-1, an anorexigenic adipokine, has been known to preserve bone density. Animal studies have demonstrated that nesfatin-1 treatment limits bone loss and increases bone strength, suggesting exogenous use as a potential treatment for osteopenic disorders. Pre-clinical studies have shown adipokine apelin to have a role in bone metabolism, mediated by the enhancement of osteoblast genesis and the inhibition of programmed cell death. Although many investigations have reported conflicting findings, sufficient literature supports the notion that adipokines have a significant influence on the metabolism of bone. This review aims at highlighting the role of novel adipokines in osteoporosis while also discussing their potential for treating osteoporosis.

Extracellular nicotinamide phosphoribosyltransferase: role in disease pathophysiology and as a biomarker

Nicotinamide phosphoribosyltransferase (NAMPT) plays a central role in mammalian cell metabolism by contributing to nicotinamide adenine dinucleotide biosynthesis. However, NAMPT activity is not limited to the intracellular compartment, as once secreted, the protein accomplishes diverse functions in the extracellular space. Extracellular NAMPT (eNAMPT, also called visfatin or pre-B-cell colony enhancing factor) has been shown to possess adipocytokine, pro-inflammatory, and pro-angiogenic activities. Numerous studies have reported the association between elevated levels of circulating eNAMPT and various inflammatory and metabolic disorders such as obesity, diabetes, atherosclerosis, arthritis, inflammatory bowel disease, lung injury and cancer. In this review, we summarize the current state of knowledge on eNAMPT biology, proposed roles in disease pathogenesis, and its potential as a disease biomarker. We also briefly discuss the emerging therapeutic approaches for eNAMPT inhibition.

Linkage of NAMPT promoter variants to eNAMPT secretion, plasma eNAMPT levels, and ARDS severity

BACKGROUND AND OBJECTIVES

eNAMPT (extracellular nicotinamide phosphoribosyltransferase), a novel DAMP and TLR4 ligand, is a druggable ARDS therapeutic target with NAMPT promoter SNPs associated with ARDS severity. This study assesses the previously unknown influence of NAMPT promoter SNPs on NAMPT transcription, eNAMPT secretion, and ARDS severity.

METHODS AND DESIGN

Human lung endothelial cells (ECs) transfected with NAMPT promoter luciferase reporters harboring SNPs G-1535A, A-1001 C, and C-948A, were exposed to LPS or LPS/18% cyclic stretch (CS) and NAMPT promoter activity, NAMPT protein expression, and secretion assessed. NAMPT genotypes and eNAMPT plasma measurements (Days 0/7) were assessed in two ARDS cohorts (DISCOVERY n = 428; ALVEOLI n = 103).

RESULTS

Comparisons of minor allelic frequency (MAF) in both ARDS cohorts with the 1000 Human Genome Project revealed the G-1535A and C-948A SNPs to be significantly associated with ARDS in Blacks compared with controls and trended toward significance in non-Hispanic Whites. LPS-challenged and LPS/18% CS-challenged EC harboring the -1535G wild-type allele exhibited significantly increased NAMPT promoter activity (compared with -1535A) with the -1535G/-948A diplotype exhibiting significantly increased NAMPT promoter activity, NAMPT protein expression, and eNAMPT secretion compared with the -1535A/-948 C diplotype. Highly significant increases in Day 0 eNAMPT plasma values were observed in both DISCOVERY and ALVEOLI ARDS cohorts (compared with healthy controls). Among subjects surviving to Day 7, Day 7 eNAMPT values were significantly increased in Day 28 non-survivors versus survivors. The protective -1535A SNP allele drove -1535A/-1001A and -1535A/-948 C diplotypes that confer significantly reduced ARDS risk (compared with -1535G, -1535G/-1001 C, -1535G/-948A), particularly in Black ARDS subjects. NAMPT SNP comparisons within the two ARDS cohorts did not identify significant association with either APACHE III scores or plasma eNAMPT levels.

CONCLUSION

NAMPT SNPs influence promoter activity, eNAMPT protein expression/secretion, plasma eNAMPT levels, and ARDS severity. NAMPT genotypes are a potential tool for stratification in eNAMPT-focused ARDS clinical trials.

eNAMPT/TLR4 inflammatory cascade activation is a key contributor to SLE Lung vasculitis and alveolar hemorrhage

Rationale

Effective therapies to reduce the severity and high mortality of pulmonary vasculitis and diffuse alveolar hemorrhage (DAH) in patients with systemic lupus erythematosus (SLE) is a serious unmet need. We explored whether biologic neutralization of eNAMPT (extracellular nicotinamide phosphoribosyl-transferase), a novel DAMP and Toll-like receptor 4 ligand, represents a viable therapeutic strategy in lupus vasculitis.

Methods

Serum was collected from SLE subjects (n = 37) for eNAMPT protein measurements. In the preclinical pristane-induced murine model of lung vasculitis/hemorrhage, C57BL/6 J mice (n = 5-10/group) were treated with PBS, IgG (1 mg/kg), or the eNAMPT-neutralizing ALT-100 mAb (1 mg/kg, IP or subcutaneously (SQ). Lung injury evaluation (Day 10) included histology/immuno-histochemistry, BAL protein/cellularity, tissue biochemistry, RNA sequencing, and plasma biomarker assessment.

Results

SLE subjects showed highly significant increases in blood NAMPT mRNA expression and eNAMPT protein levels compared to healthy controls. Preclinical pristane-exposed mice studies showed significantly increased NAMPT lung tissue expression and increased plasma eNAMPT levels accompanied by marked increases in alveolar hemorrhage and lung inflammation (BAL protein, PMNs, activated monocytes). In contrast, ALT-100 mAb-treated mice showed significant attenuation of inflammatory lung injury, alveolar hemorrhage, BAL protein, tissue leukocytes, and plasma inflammatory cytokines (eNAMPT, IL-6, IL-8). Lung RNA sequencing showed pristane-induced activation of inflammatory genes/pathways including NFkB, cytokine/chemokine, IL-1β, and MMP signaling pathways, each rectified in ALT-100 mAb-treated mice.

Conclusions

These findings highlight the role of eNAMPT/TLR4-mediated inflammatory signaling in the pathobiology of SLE pulmonary vasculitis and alveolar hemorrhage. Biologic neutralization of this novel DAMP appears to serve as a viable strategy to reduce the severity of SLE lung vasculitis.

Progress in non-viral localized delivery of siRNA therapeutics for pulmonary diseases

Emerging therapies based on localized delivery of siRNA to lungs have opened up exciting possibilities for treatment of different lung diseases. Localized delivery of siRNA to lungs has shown to result in severalfold higher lung accumulation than systemic route, while minimizing non-specific distribution in other organs. However, to date, only 2 clinical trials have explored localized delivery of siRNA for pulmonary diseases. Here we systematically reviewed recent advances in the field of pulmonary delivery of siRNA using non-viral approaches. We firstly introduce the routes of local administration and analyze the anatomical and physiological barriers towards effective local delivery of siRNA in lungs. We then discuss current progress in pulmonary delivery of siRNA for respiratory tract infections, chronic obstructive pulmonary diseases, acute lung injury, and lung cancer, list outstanding questions, and highlight directions for future research. We expect this review to provide a comprehensive understanding of current advances in pulmonary delivery of siRNA.

Endothelial eNAMPT amplifies pre-clinical acute lung injury: efficacy of an eNAMPT-neutralising monoclonal antibody

RATIONALE

The severe acute respiratory syndrome coronavirus 2/coronavirus disease 2019 pandemic has highlighted the serious unmet need for effective therapies that reduce acute respiratory distress syndrome (ARDS) mortality. We explored whether extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a ligand for Toll-like receptor (TLR)4 and a master regulator of innate immunity and inflammation, is a potential ARDS therapeutic target.

METHODS

Wild-type C57BL/6J or endothelial cell (EC)-cNAMPT -/- knockout mice (targeted EC NAMPT deletion) were exposed to either a lipopolysaccharide (LPS)-induced ("one-hit") or a combined LPS/ventilator ("two-hit")-induced acute inflammatory lung injury model. A NAMPT-specific monoclonal antibody (mAb) imaging probe (99mTc-ProNamptor) was used to detect NAMPT expression in lung tissues. Either an eNAMPT-neutralising goat polyclonal antibody (pAb) or a humanised monoclonal antibody (ALT-100 mAb) were used in vitro and in vivo.

RESULTS

Immunohistochemical, biochemical and imaging studies validated time-dependent increases in NAMPT lung tissue expression in both pre-clinical ARDS models. Intravenous delivery of either eNAMPT-neutralising pAb or mAb significantly attenuated inflammatory lung injury (haematoxylin and eosin staining, bronchoalveolar lavage (BAL) protein, BAL polymorphonuclear cells, plasma interleukin-6) in both pre-clinical models. In vitro human lung EC studies demonstrated eNAMPT-neutralising antibodies (pAb, mAb) to strongly abrogate eNAMPT-induced TLR4 pathway activation and EC barrier disruption. In vivo studies in wild-type and EC-cNAMPT -/- mice confirmed a highly significant contribution of EC-derived NAMPT to the severity of inflammatory lung injury in both pre-clinical ARDS models.

CONCLUSIONS

These findings highlight both the role of EC-derived eNAMPT and the potential for biologic targeting of the eNAMPT/TLR4 inflammatory pathway. In combination with predictive eNAMPT biomarker and NAMPT genotyping assays, this offers the opportunity to identify high-risk ARDS subjects for delivery of personalised medicine.

Molecular Mechanisms of Vascular Damage During Lung Injury

A variety of pulmonary and systemic insults promote an inflammatory response causing increased vascular permeability, leading to the development of acute lung injury (ALI), a condition necessitating hospitalization and intensive care, or the more severe acute respiratory distress syndrome (ARDS), a disease with a high mortality rate. Further, COVID-19 pandemic-associated ARDS is now a major cause of mortality worldwide. The pathogenesis of ALI is explained by injury to both the vascular endothelium and the alveolar epithelium. The disruption of the lung endothelial and epithelial barriers occurs in response to both systemic and local production of pro-inflammatory cytokines. Studies that evaluate the association of genetic polymorphisms with disease risk did not yield many potential therapeutic targets to treat and revert lung injury. This failure is probably due in part to the phenotypic complexity of ALI/ARDS, and genetic predisposition may be obscured by the multiple environmental and behavioral risk factors. In the last decade, new research has uncovered novel epigenetic mechanisms that control ALI/ARDS pathogenesis, including histone modifications and DNA methylation. Enzyme inhibitors such as DNMTi and HDACi may offer new alternative strategies to prevent or reverse the vascular damage that occurs during lung injury. This review will focus on the latest findings on the molecular mechanisms of vascular damage in ALI/ARDS, the genetic factors that might contribute to the susceptibility for developing this disease, and the epigenetic changes observed in humans, as well as in experimental models of ALI/ADRS.

Direct Extracellular NAMPT Involvement in Pulmonary Hypertension and Vascular Remodeling. Transcriptional Regulation by SOX and HIF-2α

We previously demonstrated involvement of NAMPT (nicotinamide phosphoribosyltransferase) in pulmonary arterial hypertension (PAH) and now examine NAMPT regulation and extracellular NAMPT's (eNAMPT's) role in PAH vascular remodeling. NAMPT transcription and protein expression in human lung endothelial cells were assessed in response to PAH-relevant stimuli (PDGF [platelet-derived growth factor], VEGF [vascular endothelial growth factor], TGF-β1 [transforming growth factor-β1], and hypoxia). Endothelial-to-mesenchymal transition was detected by SNAI1 (snail family transcriptional repressor 1) and PECAM1 (platelet endothelial cell adhesion molecule 1) immunofluorescence. An eNAMPT-neutralizing polyclonal antibody was tested in a PAH model of monocrotaline challenge in rats. Plasma eNAMPT concentrations, significantly increased in patients with idiopathic pulmonary arterial hypertension, were highly correlated with indices of PAH severity. eNAMPT increased endothelial-to-mesenchymal transition, and each PAH stimulus significantly increased endothelial cell NAMPT promoter activity involving transcription factors STAT5 (signal transducer and activator of transcription 5), SOX18 (SRY-box transcription factor 18), and SOX17 (SRY-box transcription factor 17), a PAH candidate gene newly defined by genome-wide association study. The hypoxia-induced transcription factor HIF-2α (hypoxia-inducible factor-2α) also potently regulated NAMPT promoter activity, and HIF-2α binding sites were identified between -628 bp and -328 bp. The PHD2 (prolyl hydroxylase domain-containing protein 2) inhibitor FG-4592 significantly increased NAMPT promoter activity and protein expression in an HIF-2α-dependent manner. Finally, the eNAMPT-neutralizing polyclonal antibody significantly reduced monocrotaline-induced vascular remodeling, PAH hemodynamic alterations, and NF-κB activation. eNAMPT is a novel and attractive therapeutic target essential to PAH vascular remodeling.

Nicotinamide phosphoribosyltransferase purification using SUMO expression system

Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in the salvage pathway required for nicotinamide adenine dinucleotide synthesis. The secreted NAMPT protein serves as a master regulatory cytokine involved in activation of evolutionarily conserved inflammatory networks. Appreciation of the role of NAMPT as a damage-associated molecular pattern protein (DAMP) has linked its activities to several disorders via Toll-like receptor 4 (TLR4) binding and inflammatory cascade activation. Information is currently lacking concerning the precise mode of the NAMPT protein functionality due to limited availability of purified protein for use in in vitro and in vivo studies. Here we report successful NAMPT expression using the pET-SUMO expression vector in E. coli strain SHuffle containing a hexa-His tag for purification. The Ulp1 protease was used to cleave the SUMO and hexa-His tags, and the protein was purified by immobilized-metal affinity chromatography. The protein yield was ~4 mg/L and initial biophysical characterization of the protein using circular dichroism revealed the secondary structural elements, while dynamic light scattering demonstrated the presence of oligomeric units. The NAMPT-SUMO showed a predominantly dimeric protein with functional enzymatic activity. Finally, we report NAMPT solubilization in n-dodecyl-β-d-maltopyranoside (DDM) detergent in monomeric form, thus enhancing the opportunity for further structural and functional investigations.

Genomic and Genetic Approaches to Deciphering Acute Respiratory Distress Syndrome Risk and Mortality

Significance: Acute respiratory distress syndrome (ARDS) is a severe, highly heterogeneous critical illness with staggering mortality that is influenced by environmental factors, such as mechanical ventilation, and genetic factors. Significant unmet needs in ARDS are addressing the paucity of validated predictive biomarkers for ARDS risk and susceptibility that hamper the conduct of successful clinical trials in ARDS and the complete absence of novel disease-modifying therapeutic strategies. Recent Advances: The current ARDS definition relies on clinical characteristics that fail to capture the diversity of disease pathology, severity, and mortality risk. We undertook a comprehensive survey of the available ARDS literature to identify genes and genetic variants (candidate gene and limited genome-wide association study approaches) implicated in susceptibility to developing ARDS in hopes of uncovering novel biomarkers for ARDS risk and mortality and potentially novel therapeutic targets in ARDS. We further attempted to address the well-known health disparities that exist in susceptibility to and mortality from ARDS. Critical Issues: Bioinformatic analyses identified 201 ARDS candidate genes with pathway analysis indicating a strong predominance in key evolutionarily conserved inflammatory pathways, including reactive oxygen species, innate immunity-related inflammation, and endothelial vascular signaling pathways. Future Directions: Future studies employing a system biology approach that combines clinical characteristics, genomics, transcriptomics, and proteomics may allow for a better definition of biologically relevant pathways and genotype-phenotype connections and result in improved strategies for the sub-phenotyping of diverse ARDS patients via molecular signatures. These efforts should facilitate the potential for successful clinical trials in ARDS and yield a better fundamental understanding of ARDS pathobiology.

Visfatin Connection: Present and Future in Osteoarthritis and Osteoporosis

Musculoskeletal pathologies (MSPs) such as osteoarthritis (OA) and osteoporosis (OP), are a set of disorders that cause severe pain, motion difficulties, and even permanent disability. In developed countries, the current incidence of MSPs reaches about one in four adults and keeps escalating as a consequence of aging and sedentarism. Interestingly, OA and OP have been closely related to similar risk factors, including aging, metabolic alterations, and inflammation. Visfatin, an adipokine with an inflammatory and catabolic profile, has been associated with several OA and OP metabolic risk factors, such as obesity, insulin resistance, and type II diabetes. Furthermore, visfatin has been associated with the innate immune receptor toll-like receptor 4 (TLR4), which plays a key role in cartilage and bone inflammatory and catabolic responses. Moreover, visfatin has been related to several OA and OP pathologic features. The aim of this work is to bring together basic and clinical data regarding the common role of visfatin in these pathologies and their major shared risk factors. Finally, we discuss the pitfalls of visfatin as a potential biomarker and therapeutic target in both pathologies.

Circulating visfatin levels in the second and third trimester of pregnancies with gestational diabetes: a systematic review

INTRODUCTION

There are multiple published conflicting associations of the adipocytokine visfatin with gestational diabetes. In this study, we attempted to investigate this relationship via a systematic review of the published literature.

EVIDENCE ACQUISITION

Literature retrieval using PubMed, Google Scholar, Scopus and Hydi databases followed by article selection and data extraction were conducted. Relevant studies published up to June 2018 were included. In total, 29 cohorts that were published in 27 articles were analyzed. Three studies carried out in early pregnancy were excluded. A total of 2365 individuals, with 1069 gestational diabetes (GDM) cases and 1296 controls from studies describing visfatin in the second or third trimester of gestation were included.

EVIDENCE SYNTHESIS

The difference in visfatin levels between women with GDM and the controls in the second and third trimester was measured by weighted mean difference (WMD) and 95% confidence intervals (CI). Heterogeneity was inspected by using both subgroup and meta-regression analysis. Analysis was restricted to studies describing singleton pregnancies. The quality of included studies was assessed by the Newcastle-Ottawa Scale.

CONCLUSIONS

No significant difference in circulating visfatin levels in GDM during the second trimester of pregnancy (WMD -0.30 ng/mL, 95% CI: -2.06, 1.45, SE=0.895, P=0.733) was detected. Meta-analysis of the studies in the third trimester revealed a significant negative effect, that was however driven by only one study. This finding limits the meaningful interpretation of the pooled analysis. Significant heterogeneity was identified between studies, and meta-regression analysis showed that homeostatic model assessment for insulin resistance contributes significantly to heterogeneity. In conclusion, our findings suggest that peripheral blood visfatin concentration cannot be robustly associated with gestational diabetes status in the second and third trimesters of pregnancy.

Novel Mechanism for Nicotinamide Phosphoribosyltransferase Inhibition of TNF-α-mediated Apoptosis in Human Lung Endothelial Cells

Nicotinamide phosphoribosyltransferase (NAMPT) exists as both intracellular NAMPT and extracellular NAMPT (eNAMPT) proteins. eNAMPT is secreted into the blood and functions as a cytokine/enzyme (cytozyme) that activates NF-κB signaling via ligation of Toll-like receptor 4 (TLR4), further serving as a biomarker for inflammatory lung disorders such as acute respiratory distress syndrome. In contrast, intracellular NAMPT is involved in nicotinamide mononucleotide synthesis and has been implicated in the regulation of cellular apoptosis, although the exact mechanisms for this regulation are poorly understood. We examined the role of NAMPT in TNF-α-induced human lung endothelial cell (EC) apoptosis and demonstrated that reduced NAMPT expression (siRNA) increases EC susceptibility to TNF-α-induced apoptosis as reflected by PARP-1 cleavage and caspase-3 activation. In contrast, overexpression of NAMPT served to reduce degrees of TNF-α-induced EC apoptosis. Inhibition of nicotinamide mononucleotide synthesis by FK866 (a selective NAMPT enzymatic inhibitor) failed to alter TNF-α-induced human lung EC apoptosis, suggesting that NAMPT-dependent NAD⁺ generation is unlikely to be involved in regulation of TNF-α-induced EC apoptosis. We next confirmed that TNF-α-induced EC apoptosis is attributable to NAMPT secretion into the EC culture media and subsequent eNAMPT ligation of TLR4 on the EC membrane surface. Silencing of NAMPT expression, direct neutralization of secreted eNAMPT by an NAMPT-specific polyclonal antibody (preventing TLR4 ligation), or direct TLR4 antagonism all served to significantly increase EC susceptibility to TNF-α-induced EC apoptosis. Together, these studies provide novel insights into NAMPT contributions to lung inflammatory events and to novel mechanisms of EC apoptosis regulation.

Essential Role of Visfatin in Lipopolysaccharide and Colon Ascendens Stent Peritonitis-Induced Acute Lung Injury

Acute lung injury (ALI) is a life-threatening syndrome characterized by acute and severe hypoxemic respiratory failure. Visfatin, which is known as an obesity-related cytokine with pro-inflammatory activities, plays a role in regulation of inflammatory cytokines. The mechanisms of ALI remain unclear in critically ill patients. Survival in ALI patients appear to be influenced by the stress generated by mechanical ventilation and by ALI-associated factors that initiate the inflammatory response. The objective for this study was to understand the mechanisms of how visfatin regulates inflammatory cytokines and promotes ALI. The expression of visfatin was evaluated in ALI patients and mouse sepsis models. Moreover, the underlying mechanisms were investigated using human bronchial epithelial cell lines, BEAS-2B and NL-20. An increase of serum visfatin was discovered in ALI patients compared to normal controls. Results from hematoxylin and eosin (H&E) and immunohistochemistry staining also showed that visfatin protein was upregulated in mouse sepsis models. Moreover, lipopolysaccharide (LPS) induced visfatin expression, activated the STAT3/NFκB pathway, and increased the expression of pro-inflammatory cytokines, including IL1-β, IL-6, and TNF-α in human bronchial epithelial cell lines NL-20 and BEAS-2B. Co-treatment of visfatin inhibitor FK866 reversed the activation of the STAT3/NFκB pathway and the increase of pro-inflammatory cytokines induced by LPS. Our study provides new evidence for the involvement of visfatin and down-stream events in acute lung injury. Further studies are required to confirm whether the anti-visfatin approaches can improve ALI patient survival by alleviating the pro-inflammatory process.

Epigenetic regulation of NfatC1 transcription and osteoclastogenesis by nicotinamide phosphoribosyl transferase in the pathogenesis of arthritis

Nicotinamide phosphoribosyltransferase (NAMPT) functions in NAD synthesis, apoptosis, and inflammation. Dysregulation of NAMPT has been associated with several inflammatory diseases, including rheumatoid arthritis (RA). The purpose of this study was to investigate NAMPT’s role in arthritis using mouse and cellular models. Collagen-induced arthritis (CIA) in DBA/1J Nampt^+/− mice was evaluated by ELISA, micro-CT, and RNA-sequencing (RNA-seq). In vitro Nampt loss-of-function and gain-of-function studies on osteoclastogenesis were examined by TRAP staining, nascent RNA capture, luciferase reporter assays, and ChIP-PCR. Nampt-deficient mice presented with suppressed inflammatory bone destruction and disease progression in a CIA mouse model. Nampt expression was required for the epigenetic regulation of the Nfatc1 promoter and osteoclastogenesis. Finally, RNA-seq identified 690 differentially expressed genes in whole ankle joints which associated (P < 0.05) with Nampt expression and CIA. Selected target was validated by RT-PCR or functional characterization. We have provided evidence that NAMPT functions as a genetic risk factor and a potential therapeutic target to RA.

Up-regulation of SFTPB expression and attenuation of acute lung injury by pulmonary epithelial cell-specific NAMPT knockdown

Although a deficiency of surfactant protein B (SFTPB) has been associated with lung injury, SFTPB expression has not yet been linked with nicotinamide phosphoribosyltransferase (NAMPT), a potential biomarker of acute lung injury (ALI). The effects of Nampt in the pulmonary epithelial cell on both SFTPB expression and lung inflammation were investigated in a LPS-induced ALI mouse model. Pulmonary epithelial cell-specific knockdown of Nampt gene expression, achieved by the crossing of Nampt gene exon 2 floxed mice with mice expressing epithelial-specific transgene Cre or by the use of epithelial-specific expression of anti-Nampt antibody cDNA, significantly attenuated LPS-induced ALI. Knockdown of Nampt expression was accompanied by lower levels of bronchoalveolar lavage (BAL) neutrophil infiltrates, total protein and TNF-α levels, as well as lower lung injury scores. Notably, Nampt knockdown was also associated with significantly increased BAL SFTPB levels relative to the wild-type control mice. Down-regulation of NAMPT increased the expression of SFTPB and rescued TNF-α-induced inhibition of SFTPB, whereas overexpression of NAMPT inhibited SFTPB expression in both H441 and A549 cells. Inhibition of NAMPT up-regulated SFTPB expression by enhancing histone acetylation to increase its transcription. Additional data indicated that these effects were mainly mediated by NAMPT nonenzymatic function via the JNK pathway. This study shows that pulmonary epithelial cell-specific knockdown of NAMPT expression attenuated ALI, in part, via up-regulation of SFTPB expression. Thus, epithelial cell-specific knockdown of Nampt may be a potential new and viable therapeutic modality to ALI.-Bi, G., Wu, L., Huang, P., Islam, S., Heruth, D. P., Zhang, L. Q., Li, D.-Y., Sampath, V., Huang, W., Simon, B. A., Easley, R. B., Ye, S. Q. Up-regulation of SFTPB expression and attenuation of acute lung injury by pulmonary epithelial cell-specific NAMPT knockdown.

Promotion of anoxia-reoxygenation-induced inflammation and permeability enhancement by nicotinamide phosphoribosyltransferase-activated MAPK signaling in human umbilical vein endothelial cells

Previous studies have demonstrated that nicotinamide phosphoribosyltransferase (NAMPT) promoted inflammation and permeability of vascular endothelial cells following cardiopulmonary bypass (CPB). In addition, mitogen-activated protein kinase (MAPK) signaling was activated and contributed to these cell responses. However, the mechanism by which NAMPT regulates cellular inflammation and permeability remains unknown, and whether NAMPT regulates MAPK signaling during this process is also not clear. The present study established an anoxia-reoxygenation (A-R) model using human umbilical vein endothelial cells (HUVECs) and investigated the regulation of MAPK signaling by NAMPT by using small RNA transfection, ELISA and western blot analysis. The results demonstrated that A-R significantly induced the expression levels of NAMPT and cellular permeability-associated proteins, and the release of several inflammatory factors. Furthermore, calcium and MAPK signaling were evidently increased. When the A-R cells were transfected with NAMPT small interfering RNA, the expression of cellular permeability-associated proteins was downregulated, the release of inflammatory factors was decreased, and calcium and MAPK signaling was blocked. These data suggest that NAMPT may activate MAPK signaling to promote A-R-induced inflammation and permeability enhancement of HUVECs. Therefore, the current study indicates that NAMPT may be a potential drug target for A-R-induced endothelial cell injury subsequent to CPB.

Characterization of the visfatin gene and its expression pattern and effect on 3T3-L1 adipocyte differentiation in chickens

Visfatin is a newly identified adipocytokine that plays an important role in the determination of fat traits. In this study, we investigated the characterization of visfatin and the relationship between gene expression and chicken development to provide a theoretical basis for studying visfatin functions. The main results are summarized as follows: The 1482-bp full coding sequence of the visfatin gene of silky fowl was obtained and found to encode 493 amino acids. This gene contains 26 phosphorylation sites and a conserved domain of the NAPRTase family but no signal peptide sequence. It exhibits six functional motifs, including an amidation site. In chickens, visfatin is a highly conserved protein. The highest expression of visfatin was found in breast muscle and the lowest in bone marrow. There was no difference in expression between visceral fat and subcutaneous fat. However, the expression of visfatin in the bone marrow, liver, kidneys, and subcutaneous and visceral fat of broiler chickens was significantly higher than that in silky fowl (P<0.05). Visfatin mRNA levels in the bone marrow decreased with development (P<0.05) but increased in the liver and leg muscle. Visfatin gene expression in the liver, heart and bone marrow did not differ in silky fowl according to sex. A visfatin fusion protein caused a significant increase in the expression of adipocyte differentiation markers (PPARγ, aP2, C/EBPα, and FAS) compared with the control group and a decrease compared with the insulin group. Taken together, the results of the present study contribute to a better understanding of the expression and role of the visfatin gene in chickens.

MC-PPEA as a new and more potent inhibitor of CLP-induced sepsis and pulmonary inflammation than FK866

Our previous study indicated that overexpression of nicotinamide phosphoribosyltransferase (NAMPT) aggravated acute lung injury, while knockdown of NAMPT expression attenuated ventilator-induced lung injury. Recently, we found that meta-carborane-butyl-3-(3-pyridinyl)-2E-propenamide (MC-PPEA, MC4), in which the benzoylpiperidine moiety of FK866 has been replaced by a carborane, displayed a 100-fold increase in NAMPT inhibition over FK866. Here, we determined the effects of MC4 and FK866 on cecal ligation and puncture (CLP) surgery-induced sepsis in C57BL/6J mice. MC4 showed stronger inhibitory effects than FK866 on CLP-induced mortality, serum tumor necrosis factor α (TNFα) levels, pulmonary myeloperoxidase activity, alveolar injury, and interleukin 6 and interleukin1β messenger RNA levels. In vitro cell permeability and electric cell-substrate impedance sensing assays demonstrated that MC4 inhibited TNFα- and thrombin-mediated pulmonary endothelial cell permeability better than FK866. MC4 also exerted more potent effects than FK866, at concentrations as low as 0.3 nM, to attenuate TNFα-mediated intracellular cytokine expression, nicotinamide adenine dinucleotide (NAD+) and its reduced form NADH levels, and nuclear factor kappa B p65 phosphorylation and nuclear translocation in A549 cells. Our results strongly suggest that the newly developed MC4 is a more potent suppressor of CLP-induced pulmonary inflammation and sepsis than FK866, with potential clinical application as a new treatment agent for sepsis and inflammation.

Nicotinamide Phosphoribosyltransferase Promotes Pulmonary Vascular Remodeling and Is a Therapeutic Target in Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension is a severe and progressive disease, a hallmark of which is pulmonary vascular remodeling. Nicotinamide phosphoribosyltransferase (NAMPT) is a cytozyme that regulates intracellular nicotinamide adenine dinucleotide levels and cellular redox state, regulates histone deacetylases, promotes cell proliferation, and inhibits apoptosis. We hypothesized that NAMPT promotes pulmonary vascular remodeling and that inhibition of NAMPT could attenuate pulmonary hypertension.

METHODS

Plasma, mRNA, and protein levels of NAMPT were measured in the lungs and isolated pulmonary artery endothelial cells from patients with pulmonary arterial hypertension and in the lungs of rodent models of pulmonary hypertension. Nampt^+/- mice were exposed to 10% hypoxia and room air for 4 weeks, and the preventive and therapeutic effects of NAMPT inhibition were tested in the monocrotaline and Sugen hypoxia models of pulmonary hypertension. The effects of NAMPT activity on proliferation, migration, apoptosis, and calcium signaling were tested in human pulmonary artery smooth muscle cells.

RESULTS

Plasma and mRNA and protein levels of NAMPT were increased in the lungs and isolated pulmonary artery endothelial cells from patients with pulmonary arterial hypertension, as well as in lungs of rodent models of pulmonary hypertension. Nampt^+/- mice were protected from hypoxia-mediated pulmonary hypertension. NAMPT activity promoted human pulmonary artery smooth muscle cell proliferation via a paracrine effect. In addition, recombinant NAMPT stimulated human pulmonary artery smooth muscle cell proliferation via enhancement of store-operated calcium entry by enhancing expression of Orai2 and STIM2. Last, inhibition of NAMPT activity attenuated monocrotaline and Sugen hypoxia-induced pulmonary hypertension in rats.

CONCLUSIONS

Our data provide evidence that NAMPT plays a role in pulmonary vascular remodeling and that its inhibition could be a potential therapeutic target for pulmonary arterial hypertension.

Nicotinamide Phosphoribosyltransferase Attenuates Methotrexate Response in Juvenile Idiopathic Arthritis and In Vitro

Variability in response to methotrexate (MTX) in the treatment of juvenile idiopathic arthritis (JIA) remains unpredictable and poorly understood. Based on previous studies implicating an interaction between nicotinamide phosphoribosyltransferase (NAMPT) expression and MTX therapy in inflammatory arthritis, we hypothesized that increased NAMPT expression would be associated with reduced therapeutic response to MTX in patients with JIA. A significant association was found between increased plasma concentrations of NAMPT and reduced therapeutic response in patients with JIA treated with MTX. Inhibition of NAMPT in cell culture by either siRNA‐based gene silencing or pharmacological inhibition with FK‐866 was found to result in a fourfold increase in the pharmacological activity of MTX. Collectively, these findings provide evidence that NAMPT inhibits the pharmacological activity of MTX and may represent a predictive biomarker of response, as well as a therapeutic target, in the treatment of JIA with MTX.

A critical role of nicotinamide phosphoribosyltransferase in human telomerase reverse transcriptase induction by resveratrol in aortic smooth muscle cells

Aging is the predominant risk factor for cardiovascular diseases and contributes to a considerably more severe outcome in patients with acute myocardial infarction. Resveratrol, a polyphenol found in red wine, is a caloric restriction mimetic with potential anti-aging properties which has emerged as a beneficial nutraceutical for patients with cardiovascular disease. Although resveratrol is widely consumed as a nutritional supplement, its mechanism of action remains to be elucidated fully. Here, we report that resveratrol activates human nicotinamide phosphoribosyltransferase (NAMPT), SIRT4 and telomerase reverse transcriptase (hTERT) in human aortic smooth muscle cells. Similar observations were obtained in resveratrol treated C57BL/6J mouse heart and liver tissues. Resverotrol can also augment telomerase activity in both human pulmonary microvascular endothelial cells and A549 cells. Blocking NAMPT and SIRT4 expression prevents induction of hTERT in human aortic smooth muscle cells while overexpression of NAMPT elevates the telomerase activity induced by resveratrol in A549 cells. Together, these results identify a NAMPT-SIRT4-hTERT axis as a novel mechanism by which resveratrol may affect the anti-aging process in human aortic smooth muscle cells, mouse hearts and other cells. These findings enrich our understanding of the positive effects of resveratrol in human cardiovascular diseases.

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.

FK866 compromises mitochondrial metabolism and adaptive stress responses in cultured cardiomyocytes

AIM

FK866 is an inhibitor of the NAD(+) synthesis rate-limiting enzyme nicotinamide phosphoribosyltransferase (NAMPT). Using FK866 to target NAD(+) synthesis has been proposed as a treatment for inflammatory diseases and cancer. However, use of FK866 may pose cardiovascular risks, as NAMPT expression is decreased in various cardiomyopathies, with low NAD(+) levels playing an important role in cardiovascular disease progression. In addition, low NAD(+) levels are associated with cardiovascular risk conditions such as aging, dyslipidemia, and type II diabetes mellitus. The aim of this work was to study the effects of FK866-induced NAD(+) depletion on mitochondrial metabolism and adaptive stress responses in cardiomyocytes.

METHODS AND RESULTS

FK866 was used to deplete NAD(+) levels in cultured rat cardiomyocytes. Cell viability, mitochondrial metabolism, and adaptive responses to insulin, norepinephrine, and H2O2 were assessed in cardiomyocytes. The drop in NAD(+) induced by FK866 decreased mitochondrial metabolism without changing cell viability. Insulin-stimulated Akt phosphorylation, glucose uptake, and H2O2-survival were compromised by FK866. Glycolytic gene transcription was increased, whereas cardiomyocyte hypertrophy induced by norepinephrine was prevented. Restoring NAD(+) levels via nicotinamide mononucleotide administration reestablished mitochondrial metabolism and adaptive stress responses.

CONCLUSION

This work shows that FK866 compromises mitochondrial metabolism and the adaptive response of cardiomyocytes to norepinephrine, H2O2, and insulin.

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)‑1β, IL‑6 and IL‑8 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.

Nicotinamide exacerbates hypoxemia in ventilator-induced lung injury independent of neutrophil infiltration

Background

Ventilator-induced lung injury is a form of acute lung injury that develops in critically ill patients on mechanical ventilation and has a high degree of mortality. Nicotinamide phosphoribosyltransferase is an enzyme that is highly upregulated in ventilator-induced lung injury and exacerbates the injury when given exogenously. Nicotinamide (vitamin B3) directly inhibits downstream pathways activated by Nicotinamide phosphoribosyltransferase and is protective in other models of acute lung injury.

Methods

We administered nicotinamide i.p. to mice undergoing mechanical ventilation with high tidal volumes to study the effects of nicotinamide on ventilator-induced lung injury. Measures of injury included oxygen saturations and bronchoalveolar lavage neutrophil counts, protein, and cytokine levels. We also measured expression of nicotinamide phosophoribosyltransferase, and its downstream effectors Sirt1 and Cebpa, Cebpb, Cebpe. We assessed the effect of nicotinamide on the production of nitric oxide during ventilator-induced lung injury. We also studied the effects of ventilator-induced lung injury in mice deficient in C/EBPε.

Results

Nicotinamide treatment significantly inhibited neutrophil infiltration into the lungs during ventilator-induced lung injury, but did not affect protein leakage or cytokine production. Surprisingly, mice treated with nicotinamide developed significantly worse hypoxemia during mechanical ventilation. This effect was not linked to increases in nitric oxide production or alterations in expression of Nicotinamide phosphoribosyl transferase, Sirt1, or Cebpa and Cebpb. Cebpe mRNA levels were decreased with either nicotinamide treatment or mechanical ventilation, but mice lacking C/EBPε developed the same degree of hypoxemia and ventilator-induced lung injury as wild-type mice.

Conclusions

Nicotinamide treatment during VILI inhibits neutrophil infiltration of the lungs consistent with a strong anti-inflammatory effect, but paradoxically also leads to the development of significant hypoxemia. These findings suggest that pulmonary neutrophilia is not linked to hypoxemia in ventilator-induced lung injury, and that nicotinamide exacerbates hypoxemia during VILI.

Nicotinamide phosphoribosyltransferase inhibitor is a novel therapeutic candidate in murine models of inflammatory lung injury

We previously identified the intracellular nicotinamide phosphoribosyltransferase (iNAMPT, aka pre-B-cell colony enhancing factor) as a candidate gene promoting acute respiratory distress syndrome (ARDS) and ventilator-induced lung injury (VILI) with circulating nicotinamide phosphoribosyltransferase potently inducing NF-κB signaling in lung endothelium. iNAMPT also synthesizes intracellular nicotinamide adenine dinucleotide (iNAD) in response to extracellular oxidative stress, contributing to the inhibition of apoptosis via ill-defined mechanisms. We now further define the role of iNAMPT activity in the pathogenesis of ARDS/VILI using the selective iNAMPT inhibitor FK-866. C57/B6 mice were exposed to VILI (40 ml/kg, 4 h) or LPS (1.5 mg/kg, 18 h) after osmotic pump delivery of FK-866 (100 mg/kg/d, intraperitoneally). Assessment of total bronchoalveolar lavage (BAL) protein, polymorphonuclear neutrophil (PMN) levels, cytokine levels (TNF-α, IL-6, IL-1α), lung iNAD levels, and injury scores revealed that FK-866-mediated iNAMPT inhibition successfully reduced lung tissue iNAD levels, BAL injury indices, inflammatory cell infiltration, and lung injury scores in LPS- and VILI-exposed mice. FK-866 further increased lung PMN apoptosis, as reflected by caspase-3 activation in BAL PMNs. These findings support iNAMPT inhibition via FK-866 as a novel therapeutic agent for ARDS via enhanced apoptosis in inflammatory PMNs.

Beyond single-nucleotide polymorphisms: genetics, genomics, and other 'omic approaches to acute respiratory distress syndrome

This article summarizes the contributions of high-throughput genomic, proteomic, metabolomic, and gene expression investigations to the understanding of inherited or acquired risk for acute respiratory distress syndrome (ARDS). Although not yet widely applied to a complex trait like ARDS, these techniques are now routinely used to study a variety of disease states. Omic applications hold great promise for identifying novel factors that may contribute to ARDS pathophysiology or may be appropriate for further development as biomarkers or surrogates in clinical studies. Opportunities and challenges of different techniques are discussed, and examples of successful applications in non-ARDS fields are used to illustrate the potential use of each technique.

Visfatin levels in patients with severe pneumonia

BACKGROUND

As a cytokine highly expressed in internal organs, visfatin could be used as a biomarker of systemic inflammation response for chronic obstructive pulmonary diseases, but few studies have reported the use of visfatin in severe pneumonia. The present study was undertaken to determine the plasma levels of visfatin in patients with severe pneumonia.

METHODS

A total of 70 patients, including 40 patients with severe pneumonia (group A) and 30 patients with non severe pneumonia (group B) who had been admitted to the ICU from June 2009 to June 2010, were enrolled in this prospective study. And another 30 healthy physical examinees served as healthy controls (group C). Patients were excluded if they suffered from severe diseases of the heart, brain and kidney, cancers, autoimmune diseases, or received special treatment in the latest month. The plasma levels of visfatin, IL-6, IL-8 and TNF-α were measured by ELISA, while the level of CRP was determined by immuneturbidimetry, and the routine blood test was performed. Blood gas analysis and Acute Physiology and Chronic Health Evaluation II (APACHE II) were performed in patients with pneumonia. Comparisons between the groups were conducted by Student's t test, ANOVA or nonparametric test. Correlation analysis was carried out by Pearson's correlation test or Spearman's rank-order correlation test.

RESULTS

The plasma level of visfatin in group A was significantly higher than that in groups B and C (P<0.001), and the level of visfatin in group B was significantly higher than that in group C (P<0.001). The plasma level of visfatin was positively correlated with CRP, TNF-α, APACHE II and PMN% in patients with severe pneumonia (rho =0.653, r=0.554, r=0.558, r=0.484, respectively, P<0.05 for all), while it was negatively correlated with PaO2 and PaO2/FiO2 (rho =-0.422, r=-0.543, respectively, P<0.05 for all).

CONCLUSION

Visfatin may be involved in the systematic inflammation response in patients with severe pneumonia as a pro-inflammatory cytokine, and it is valuable in assessing the severity of pneumonia..

Mechanical stress induces pre-B-cell colony-enhancing factor/NAMPT expression via epigenetic regulation by miR-374a and miR-568 in human lung endothelium

Increased lung vascular permeability and alveolar edema are cardinal features of inflammatory conditions such as acute respiratory distress syndrome (ARDS) and ventilator-induced lung injury (VILI). We previously demonstrated that pre-B-cell colony-enhancing factor (PBEF)/NAMPT, the proinflammatory cytokine encoded by NAMPT, participates in ARDS and VILI inflammatory syndromes. The present study evaluated posttranscriptional regulation of PBEF/NAMPT gene expression in human lung endothelium via 3'-untranslated region (UTR) microRNA (miRNA) binding. In silico analysis identified hsa-miR-374a and hsa-miR-568 as potential miRNA candidates. Increased PBEF/NAMPT transcription (by RT-PCR) and expression (by Western blotting) induced by 18% cyclic stretch (CS) (2 h: 3.4 ± 0.06 mRNA fold increase (FI); 10 h: 1.5 ± 0.06 protein FI) and by LPS (4 h: 3.8 ± 0.2 mRNA FI; 48 h: 2.6 ± 0.2 protein FI) were significantly attenuated by transfection with mimics of hsa-miR-374a or hsa-miR-568 (40-60% reductions each). LPS and 18% CS increased the activity of a PBEF/NAMPT 3'-UTR luciferase reporter (2.4-3.25 FI) with induction reduced by mimics of each miRNA (44-60% reduction). Specific miRNA inhibitors (antagomirs) for each PBEF/NAMPT miRNA significantly increased the endogenous PBEF/NAMPT mRNA (1.4-3.4 ± 0.1 FI) and protein levels (1.2-1.4 ± 0.1 FI) and 3'-UTR luciferase activity (1.4-1.7 ± 0.1 FI) compared with negative antagomir controls. Collectively, these data demonstrate that increased PBEF/NAMPT expression induced by bioactive agonists (i.e., excessive mechanical stress, LPS) involves epigenetic regulation with hsa-miR-374a and hsa-miR-568, representing novel therapeutic strategies to reduce inflammatory lung injury.

Pre-B cell colony enhancing factor (PBEF), a cytokine with multiple physiological functions

Pre-B cell colony enhancing factor (PBEF) is regarded as a proinflammatory cytokine. Named for its first discovered function as a pre-B cell colony enhancing factor, it has since been found to have many other functions relating to cell metabolism, inflammation, and immune modulation. It has also been found to have intracellular and extracellular forms, with the two overlapping in function. Most of the intracellular functions of PBEF are due to its role as a nicotinamide phosphoribosyltransferase (Nampt). It has been found in human endothelial cells, where it is able to induce angiogenesis through upregulation of VEGF and VEGFR and secretion of MCP-1. In human umbilical endothelial cells, PBEF increases levels of the protease MMP 2/9. PBEF has also been found in a variety of immune cells other than B cells and has been shown to inhibit apoptosis of macrophages. Extracellular PBEF has been shown to increase inflammatory cytokines, such as TNF-α, IL-1β, IL-16, and TGF-β1, and the chemokine receptor CCR3. PBEF also increases the production of IL-6, TNF-α, and IL-1β in CD14(+) monocyctes, macrophages, and dendritic cells, enhances the effectiveness of T cells, and is vital to the development of both B and T lymphocytes. The purpose of this review is to summarize the recent advances in PBEF research.

Elevated plasma visfatin concentrations in patients with community-acquired pneumonia

Visfatin has been associated with some inflammatory disease. This study aimed to compare plasma visfatin levels in patients with community-acquired pneumonia and healthy controls and to furthermore investigate the relationship between their concentrations and 30-day mortality in patients. Plasma visfatin concentrations were measured in 176 patients and 95 healthy controls. The admission visfatin levels were significantly increased in all patients, survivals and non-survivals with community-acquired pneumonia compared with healthy control individuals, associated with pneumonia severity index score, Acute Physiology and Chronic Health Evaluation II score, white blood cell count, and plasma C-reactive protein level, and identified as an independent predictor for 30-day mortality. Its predictive value was similar to those of pneumonia severity index score and Acute Physiology and Chronic Health Evaluation II score. However, visfatin did not statistically significantly improve the predictive values of pneumonia severity index score and Acute Physiology and Chronic Health Evaluation II score. Thus, higher plasma visfatin level correlates with disease severity and markers of system inflammation and represent a novel biomarker for predicting 30-day mortality in patients with community-acquired pneumonia.

Characterization of chicken visfatin gene: cDNA cloning, tissue distribution, and promoter analysis

Here we report the cloning and characterization of chicken visfatin (also called pre-B cell enhancing factor; PBEF, or nicotinamide phosphoribosyltransferase; Nampt) gene. Sequence analyses revealed that the coding region of visfatin is 1,482 bp in length and encodes a protein of 493 amino acids, which shares high amino acid sequence identity not only to visfatin of human (94%), rat (94%), carp (89%), and zebrafish (89%), but also to Nampt of sponge (58%) and cyanobacterium (48%). The reverse transcription PCR assay and Northern-blot analysis demonstrated that visfatin was widely expressed in all chicken tissues examined. Using a dual luciferase reporter system, we further demonstrated that the cloned 1,372-bp fragment upstream of the putative translation start site (ATG) displayed the maximal promoter activity in cultured CHO, DF-1, and HEK293 cells, whereas the removal of its 5'-region (1,075 bp) or 3'-region (297 bp) could only partially reduce its promoter activity, implying that visfatin gene transcription was likely controlled by multiple promoters near the translation start site. Taken together, results from present study will contribute to our better understanding of the expression and roles of visfatin gene in chickens.

Pleiotropic functions of pre-B-cell colony-enhancing factor (PBEF) revealed by transcriptomics of human pulmonary microvascular endothelial cells treated with PBEFsiRNA

This study profiled transcriptomes of human pulmonary microvascular endothelial cells (HMVEC-L) treated with pre-B-cell colony-enhancing factor (PBEF) siRNA or scrambled RNA to gain insight into transcriptional regulations of PBEF on the endothelial function using the Affymetrix GeneChips HG-U133 plus 2. Several important themes are emerged from this study. First, PBEF affected expressions of multiple genes in the endothelium. Expression of 373 genes was increased and 64 genes decreased by at least 1.3-fold in the PBEFsiRNA-treated HMVEC-L versus the scramble RNA control. Second, the microarray results confirmed previous reports of PBEF-mediated gene expressions in some pathways but provided a more complete repertoire of molecules in those pathways. Third, most of the affected canonical pathways have not previously been reported to be PBEF responsive. Fourth, network analysis supports that PBEF has pleiotropic functions. Our first transcriptome analysis of human pulmonary microvascular endothelial cells treated with PBEFsiRNA has provided important insights into the transcriptional regulation of gene expression in HMVEC-L cells by PBEF. Further in-depth analysis of these transcriptional regulations may shed light on molecular mechanisms underlying PBEF-mediated endothelial functions and dysfunctions in various diseases and provide new leads of therapeutic targets to those diseases.

RNA-seq reveals novel transcriptome of genes and their isoforms in human pulmonary microvascular endothelial cells treated with thrombin

The dysregulation of vascular endothelial cells by thrombin has been implicated in the development of a number of pathologic disorders such as inflammatory conditions, cancer, diabetes, coronary heart disease. However, transcriptional regulation of vascular endothelial cells by thrombin is not completely understood. In the present study, Illumina RNA-seq was used to profile the transcriptome in human pulmonary microvascular endothelial cells (HMVEC-L) treated with thrombin for 6 h to gain insight into thrombin's direct effects on the endothelial function. Out of 100 million total reads from a paired end sequencing assay, 91–94% of the reads were aligned to over 16,000 genes in the reference human genome. Thrombin upregulated 150 known genes and 480 known isoforms, and downregulated 2,190 known genes and 3,574 known isoforms by at least 2 fold. Of note, thrombin upregulated 1,775 previously unknown isoforms and downregulated 12,202 previously unknown isoforms by at least 2 fold. Many genes displayed isoform specific differential expression levels and different usage of transcriptional start sites after the thrombin treatment. The cross comparisons between our RNA-seq data and those of DNA microarray analysis of either 6 h thrombin treated HUVEC or 5 h TNFα treated HMVEC have provided a significant overlapping list of differentially expressed genes, supporting the robust utility of our dataset. Further in-depth follow-up analysis of the transcriptional regulation reported in this study may shed light on molecular pathogenic mechanisms underlying thrombin mediated endothelial dysfunction in various diseases and provide new leads of potential therapeutic targets.

Inhibition of pre-B cell colony-enhancing factor attenuates inflammation and apoptosis induced by pandemic H1N1 2009 in lung endothelium

The recent pandemic influenza A (H1N1 2009) virus infection has caused acute lung injury in susceptible population resulting in high mortality in ICU patients. In this report, we observed the effect of pre-B cell colony-enhancing factor (PBEF) on the inflammation and apoptosis in H1N1-infected human pulmonary microvascular endothelial cells (HPMECs). We constructed an in vitro HPMEC monolayer model. The results showed that H1N1 2009 induced the increased expression of inflammatory cytokines (IL-6/IL-8/TNF-α/IP-10) and apoptosis factors (FasL/TRAIL) in infected HPMECs. However, PBEF silencing with siRNA inhibited the expression of some inflammatory cytokines and decreased the apoptosis mediated by FasL. We conclude that PBEF might be partially responsible for the localized inflammatory response to H1N1 2009 in the lung microvascular endothelium and the H1N1-induced endothelial cell apoptosis probably through the FasL-mediated pathway.

Pre-B-cell colony-enhancing factor and its clinical correlates with acute lung injury and sepsis

BACKGROUND

Pre-B-cell colony-enhancing factor (PBEF) is a potential biomarker for acute lung injury (ALI) in sepsis. We aimed to determine the clinical correlates for elevated plasma PBEF upon ICU admission for severe sepsis and the usefulness of PBEF to predict ALI development and sepsis mortality.

METHODS

This is a prospective cohort of patients admitted to the medical ICU with severe sepsis. Patients without available blood samples or who were not enrolled within 24 h of admission were excluded. Plasma collected within 24 h of ICU admission was measured for PBEF concentrations by enzyme-linked immunosorbent assay. Patients were followed for ALI development as defined by the American-European Consensus Conference and for all-cause hospital mortality.

RESULTS

Between September 30, 2008, and March 10, 2009, 113 patients were enrolled, and 50 (44%) developed ALI. Elevated PBEF levels significantly correlated with higher APACHE (Acute Physiology and Chronic Health Evaluation) III scores (R(2) = 0.08, P = .003) and failure to reach early sepsis goals within 6 h of severe sepsis (P = .003). PBEF did not differ by ALI status (P = .58). The mortality rate was 46%. Nonsurvivors had higher PBEF levels than survivors (2.53 ng/mL; interquartile range [IQR], 1.07-8.16 vs 1.44 ng/mL; IQR, 0.84-2.81; P = .02). After adjusting for severity of illness, PBEF levels were no longer significantly associated with mortality (OR, 1.44 per 10-fold increase; 95% CI, 0.69-3.03, P = .34).

CONCLUSIONS

In this study, elevated PBEF did not correlate with lung injury in sepsis. However, it was associated with sepsis mortality mainly due to its association with greater severity of illness on ICU admission.

[Acute lung injury and acute respiratory distress syndrome: a genomic perspective]

Genomics have allowed important advances in the knowledge of the etiology and pathogenesis of complex disease entities such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Genomic medicine aims to personalize and optimize diagnosis, prognosis and treatment by determining the influence of genetic polymorphisms in specific diseases. The scientific community must cope with the important challenge of securing rapid transfer of knowledge to clinical practice, in order to prevent patients from becoming exposed to unnecessary risks. In the present article we describe the main concepts of genomic medicine pertaining to ALI/ARDS, and its currently recognized clinical applications.

Genomics of Acute Lung Injury and Vascular Barrier Dysfunction

Acute lung injury (ALI) is a devastating ­syndrome of diffuse alveolar damage that develops via a variety of local and systemic insults such as sepsis, trauma, ­pneumonia, and aspiration. It is interestingly to note that only a subset of individuals exposed to potential ALI-inciting insults develop the disorder and the severity of the disease varies from complete resolution to death. In addition, ALI susceptibility and severity are also affected by ethnicity as evidenced by the higher mortality rates observed in African-American ALI patients compared with other ethnic groups in the USA. Moreover, marked differences in strain-specific ALI responses to inflammatory and injurious agents are observed in preclinical animal models. Together, these observations strongly indicate genetic components to be involved in the pathogenesis of ALI. The identification of genes contributing to ALI would potentially provide a better understanding of ALI pathobiology, yield novel biomarkers, identify individuals or populations at risk, and prove useful for the development of novel and individualized therapies. Genome-wide searches in animal models have identified a number of quantitative trait loci that associate with ALI susceptibility. In this chapter, we utilize a systems biology approach combining cellular signaling pathway analysis with population- based association studies to review established and suspected candidate genes that contribute to dysfunction of endothelial cell barrier integrity and ALI susceptibility.

Nicotinamide Phosphoribosyltransferase in Human Diseases

Nicotinamide phosphoribosyltransferase (NAMPT) was first reported as a pre-B-cell colony enhancing factor in 1994 with little notice, but it has received increasing attention in recent years due to accumulating evidence indicating that NAMPT is a pleiotropic protein such as a growth factor, a cytokine, an enzyme and a visfatin. Now, NAMPT has been accepted as an official name of this protein. Because of NAMPT's multiple functions in a variety of physiological processes, their dysregulations have been implicated in the pathogenesis of a number of human diseases or conditions such as acute lung injury, aging, atherosclerosis, cancer, diabetes, rheumatoid arthritis and sepsis. This review will cover the current understanding of NAMPT's structure and functions with an emphasis on recent progress of nicotinamide phosphoribosyltransferase's pathological roles in various human diseases and conditions. Future directions on exploring its Terra incognita will be offered in the end.

Effects of age on the synergistic interactions between lipopolysaccharide and mechanical ventilation in mice

Children have a lower incidence and mortality from acute lung injury (ALI) than adults, and infections are the most common event associated with ALI. To study the effects of age on susceptibility to ALI, we investigated the responses to microbial products combined with mechanical ventilation (MV) in juvenile (21-d-old) and adult (16-wk-old) mice. Juvenile and adult C57BL/6 mice were treated with inhaled Escherichia coli 0111:B4 lipopolysaccharide (LPS) and MV using tidal volume = 15 ml/kg. Comparison groups included mice treated with LPS or MV alone and untreated age-matched control mice. In adult animals treated for 3 hours, LPS plus MV caused synergistic increases in neutrophils (P < 0.01) and IgM in bronchoalveolar lavage fluid (P = 0.03) and IL-1β in whole lung homogenates (P < 0.01) as compared with either modality alone. Although juvenile and adult mice had similar responses to LPS or MV alone, the synergistic interactions between LPS and MV did not occur in juvenile mice. Computational analysis of gene expression array data suggest that the acquisition of synergy with increasing age results, in part, from the loss of antiapoptotic responses and the acquisition of proinflammatory responses to the combination of LPS and MV. These data suggest that the synergistic inflammatory and injury responses to inhaled LPS combined with MV are acquired with age as a result of coordinated changes in gene expression of inflammatory, apoptotic, and TGF-β pathways.

Plasma and myocardial visfatin expression changes are associated with therapeutic hypothermia protection during murine hemorrhagic shock/resuscitation

AIM

Cytokine production during hemorrhagic shock (HS) could affect cardiac function during the hours after resuscitation. Visfatin is a recently described protein that functions both as a proinflammatory plasma cytokine and an intracellular enzyme within the nicotinamide adenine dinucleotide (NAD(+)) salvage pathway. We developed a mouse model of HS to study the effect of therapeutic hypothermia (TH) on hemodynamic outcomes and associated plasma and tissue visfatin content.

METHODS

Mice were bled and maintained at a mean arterial pressure (MAP) of 35 mmHg. After 30 min, animals (n=52) were randomized to normothermia (NT, 37+/-0.5 degrees C) or TH (33+/-0.5 degrees C) followed by rewarming at 60 min following resuscitation. After 90 min of HS (S90), mice were resuscitated and monitored for 180 min (R180). Visfatin, interleukin 6 (IL-6), keratinocyte-derived chemokine (KC), tumor necrosis factor-alpha (TNF-alpha), and myoglobin were measured by ELISA.

RESULTS

Compared to NT, TH animals exhibited improved R180 survival (23/26 [88.5%] vs. 13/26 [50%]; p=0.001). Plasma visfatin, IL-6, KC, and TNF-alpha increased by S90 in both groups (p<0.05). TH attenuated S90 plasma visfatin and, after rewarming, decreased R180 plasma IL-6, KC, and myoglobin (p<0.05) relative to NT. Heart and gut KC increased at S90 while IL-6 increases were delayed until R180 (p<0.05). NT produced sustained elevations of myocardial KC but decreased visfatin by R180, effects abrogated by TH (p<0.05).

CONCLUSIONS

In a mouse model of HS, TH improves hemodynamics and alters plasma and tissue proinflammatory cytokines including the novel cytokine visfatin. TH modulation of cytokines may attenuate cardiac dysfunction following HS.

Maternal plasma concentration of the pro-inflammatory adipokine pre-B-cell-enhancing factor (PBEF)/visfatin is elevated in pregnant patients with acute pyelonephritis

PROBLEM

Visfatin/pre-B-cell-enhancing factor (PBEF) has been implicated in the regulation of the innate immune system, as well as in glucose metabolism. Specifically, visfatin plays a requisite role in delayed neutrophil apoptosis in patients with sepsis. The aim of this study was to determine whether pyelonephritis during pregnancy is associated with changes in maternal plasma visfatin concentration in normal weight and overweight/obese patients.

METHOD OF STUDY

This cross-sectional study included the following groups: (1) normal pregnant women (n = 200) and (2) pregnant women with pyelonephritis (n = 40). Maternal plasma visfatin concentrations were determined by ELISA. Non-parametric statistics was used for analyses.

RESULTS

(1) The median maternal plasma visfatin concentration was significantly higher in patients with pyelonephritis than in those with a normal pregnancy; (2) among overweight/obese pregnant women, those with pyelonephritis had a significantly higher median plasma visfatin concentration than women with a normal pregnancy; and (3) pyelonephritis was independently associated with higher maternal plasma visfatin concentrations after adjustment for maternal age, pre-gestational body mass index, smoking status, gestational age at sampling, and birthweight.

CONCLUSION

Acute pyelonephritis during pregnancy is associated with a high circulating maternal visfatin concentration. These findings suggest that visfatin/PBEF may play a role in the regulation of the complex and dynamic crosstalk between inflammation and metabolism during pregnancy.

Visfatin gene expression in chickens is sex and tissue dependent

The present study investigated the expression of visfatin mRNA in various tissues of male and female broiler chickens. We also studied the effect of leptin, cerulenin, and food deprivation, known effectors of energy balance and insulin action, on visfatin gene expression in chickens. Using reverse transcription polymerase chain reaction (RT-PCR) and Northern blot analysis, we detected chicken visfatin mRNA transcript in the kidney, hypothalamus, gizzard, liver, pancreas, proventriculus, breast and leg muscle, ovary, testis, lung, intestine, adipose tissue, and heart. Expression of the visfatin gene in various tissues of male and female chickens was determined by real-time quantitative PCR and found to be tissue and sex dependent. In both sexes, compared to other tissues, the visfatin gene is highly expressed in the muscle. Females exhibited greater (P<0.001) abundance of visfatin mRNA in adipose tissue compared to males, whereas compared to females, males showed greater (P<0.05) visfatin mRNA abundance in the kidney. Also, the regulation of visfatin gene expression by leptin, cerulenin, and food deprivation is tissue specific. Leptin decreased (P<0.05) visfatin mRNA abundance in the liver and hypothalamus, but not in muscle. In contrast, cerulenin increased (P<0.01) visfatin gene expression in the liver and in muscle, but not in the hypothalamus. Interestingly, visfatin mRNA levels increased (P<0.05) in the liver after 24-h food deprivation, but not in muscle or in the hypothalamus of genetically selected fat and lean line chickens. Our results showed that the visfatin gene is ubiquitously expressed in chickens with greater abundance in muscle, and that it is regulated in a tissue-specific manner by energy balance-related factors.