Nicotinamide Phosphoribosyltransferase Expression Research Articles

NAMPT-mediated NAD+ biosynthesis suppresses activation of hepatic stellate cells and protects against CCl4-induced liver fibrosis in mice.

Background: Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in the salvage pathway of mammalian nicotinamide adenine dinucleotide (NAD+) biosynthesis. Through its NAD+-biosynthetic activity, NAMPT is able to regulate the development of hepatic steatosis and inflammation induced by diet or alcohol. However, the roles NAMPT plays in the development of liver fibrosis remain obscure.Purpose: To investigate the roles of NAMPT-mediated NAD+biosynthesis in hepatic stellate cell (HSC) activation and liver fibrosis.Research Design: Realtime RT-PCR and western blot analyses were performed to analyze the expression of profibrogenic genes. Sirius red staining was conducted to examine the fibrosis in liver. Mouse liver fibrosis was induced by intraperitoneal injection of carbon tetrachloride (CCl4) 2 times a week for 6 weeks. Adenovirus-mediated NAMPT overexpression or nicotinamide mononucleotide (NMN) administration was carried out to study the effects of elevation of NAD+levels on protecting CCl4-induced liver fibrosis in mice. LX2 cells or primary HSCs were used to study the role of NAMPT overexpression or NMN treatment in reducing profibrogenic gene expression in vitro.ResultsCCl4administration suppresses NAMPT expression in liver and reduces hepatic NAD+content. Tgfβ1 treatment decreases intracellular NAD+levels and NAMPT expression in LX2 cells. Adenovirus-mediated NAMPT overexpression augments liver NAD+levels, inhibits HSC activation and alleviates CCl4-induced liver fibrosis in mice. Administration of NMN also suppresses HSC activation and protects against CCl4-induced liver fibrosis in mice.Conclusions: NAMPT-mediated NAD+biosynthesis inhibits HSC activation and protects against CCl4-induced liver fibrosis.

Evidence of a Synergistic Cross-Talk between the B Cell Receptor (BCR) and Nicotinamide Phosphoribosyl Transferase (NAMPT) in Richter's Syndrome Patient-Derived Xenograft Models: Therapeutic Implications

Background: A rare complication of Chronic Lymphocytic Leukemia (CLL), Richter's Syndrome (RS) represents the transformation of a pre-existing CLL into a Diffuse Large B-cell Lymphoma (DLBCL), generally associated with poor prognosis. Current therapeutic approaches are limited and do not significantly reduce disease progression. For these reasons there is intense investigation to identify potentially druggable molecular circuits, opening the way to innovative combination therapies.Among the several oncogenic signalling pathways that may contribute to disease progression, the B Cell Receptor (BCR) is a main driver and an actionable target. We previously showed that BCR ligation in CLL cells increases expression of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the salvage NAD pathway starting from nicotinamide, a finding in line with the notion of oncogenic-driven metabolic reprogramming. In this context, increased NAMPT expression leading to heightened NAD+ levels could sustain proliferation through the modulation of the activity of several intracellular enzymes, including sirtuins (NAD-dependent deacetylases).Aim: This work explores the connections between BCR signalling and the NAMPT/NAD/sirtuin axis in RS cells, asking the question of whether BCR and NAMPT can be simultaneously targeted.Methods: RS-PDX cells were freshly purified from tumor masses grown in mice and immediately used for short ex-vivo experiments. For in vivo experiments, NSG mice were injected subcutaneously with RS-PDX cells, which were left to engraft until a palpable mass was evident. Mice were then randomized to receive duvelisib, OT82 or a combination of the two for two consecutive weeks. Control mice were similarly treated with vehicle only. Mice were under a niacin-free diet.Results: By using our 4 RS patient-derived xenografts (PDX) models, we invariably observed high levels of NAMPT expression. High levels of NAMPT expression were also observed in 15 primary RS lymph node biopsies analyzed by RNA sequencing. BCR engagement through αIgM polyclonal antibodies significantly up-regulated NAMPT expression, as determined by qRT-PCR and protein analysis, with a concomitant increase in intracellular NAD+ levels. We then asked whether RS cells are sensitive to NAMPT inhibition, alone or in combination with drugs that target the BCR pathway. As most RS patients would likely have been treated during the preceding CLL phase with a BTK inhibitor, possibly developing resistance, we turned to PI3K inhibitors, which are less commonly used for CLL therapy. As NAMPT inhibitors (NAMPTi) we used both FK866 and OT-82, which are validated small molecules. Results indicated that the combination of the dual PI3K-δ/γ inhibitor duvelisib, with either FK866 or OT-82 induces dramatic apoptosis in all 4 models tested, as confirmed by annexinV/PI staining, by caspase 3 activation and by a significant drop in ATP and NAD+ levels. Importantly, two RS-PDX models (RS9737 and RS1316) were fully resistant to NAMPTi used alone, likely due to high levels of nicotinate phosphoribosyltransferase (NAPRT), which is the rate-limiting enzyme in the NAD salvage pathway that starts from nicotinic acid. However, addition of duvelisib, which was mildly effective when used alone, was followed by marked apoptosis even in these two models.Molecular dissection of the pathway showed that the combination of duvelisib and NAMPTi was followed by complete inhibition of the PI3K pathway, which was only partially blocked by duvelisib alone, even at high doses. The connection between NAMPT and PI3K is represented by cytoplasmic sirtuins, particularly SIRT2, which activate AKT through de-acetylation. Immunoprecipitation and two-dimensional gel electrophoresis showed that in the presence of NAMPTi, the amount of acetylated, i.e., inactive, AKT increased considerably. Consistently, treatment of RS-PDX mice with a combination of duvelisib and OT-82 was followed by significantly higher responses and longer animal survival.Conclusions: These results highlight a crosstalk between BCR signalling and NAMPT/sirtuin axis in RS models, showing the increased efficacy of the dual targeting (i.e., PI3K-δ/γ and NAMPT), and supporting this novel and promising therapeutic strategy for the treatment of RS patients. DisclosuresDeaglio: Heidelberg Pharma: Research Funding; Astra Zeneca: Research Funding.

CUL5-Mediated Visfatin (NAMPT) Degradation Blocks Endothelial Proliferation and Angiogenesis via the MAPK/PI3K-AKT Signaling.

Endothelial dysfunction participates in the pathogenesis of various cardiovascular disorders, and dysregulated angiogenesis involves the vascular endothelial growth factor (VEGF)-matrix metalloproteinases (MMP) system. Nicotinamide phosphoribosyltransferase (NAMPT) is known to enhance endothelial function and angiogenesis. The study found that NAMPT overexpression protected human coronary artery endothelial cells (HCAECs) from H2O2-induced injury through promoting cell viability, inhibiting cell apoptosis, enhancing cell motility, and promoting tube formation. Through analyses based on 2 Protein-Protein Interaction databases, Mentha and BioGrid, we identified CUL5 as a protein that may interact with NAMPT, which was then validated by Co-IP experiments. Through interacting with NAMPT, CUL5 inhibited NAMPT expression. In contrast to NAMPT, CUL5 overexpression further aggravated H2O2-induced HCAEC dysfunction. In the meantime, CUL5 overexpression reduced, whereas NAMPT overexpression increased the phosphorylation of p38 and Akt and the protein levels of VEGF and MMP2. More importantly, NAMPT overexpression partially reversed the effects of CUL5 overexpression on H2O2-stimulated HCAECs and the MAPK/phosphatidylinositol 3-kinase-Akt/VEGF/MMP signaling. In conclusion, CUL5 interacts with NAMPT in H2O2-stimulated HCAECs, suppressing cell viability, promoting cell apoptosis, and inhibiting cell mobility and tube formation. NAMPT overexpression protects against H2O2-induced HCAEC dysfunction by promoting cell viability, inhibiting cell apoptosis, and enhancing cell mobility and tube formation.

Dual Roles of Nicotinamide Phosphoribosyltransferase as a Promising Target for Cancer Radiotherapy.

Nicotinamide phosphoribosyltransferase (NAMPT) is the key rate-limiting enzyme in the regulation of nicotinamide adenine dinucleotide (NAD) biosynthesis, and its activity is critical for the replenishment of NAD level as well as cell survival or death. As one of the most important components in the electron transport chain of complex I in mitochondrion, sustained supply of NAD is essential to the maintenance of energy metabolism both in normal and cancer cells. Recent research showed that X-ray radiation sharply downregulated the expression of NAMPT, which may be the main cause of radiation damage in salivary gland. Consistently, upregulation of NAMPT by phenylephrine restored the function and tissue structure of salivary gland, indicating the cytoprotective role of NAMPT in preventing radiation damage in normal tissues of patients with head and neck cancer during radiotherapy. On the other hand, NAMPT downregulation and NAD depletion could induce cell death in oral squamous cell cancer, suggesting that a combination of NAMPT inhibitor and radiotherapy presents a promising therapeutic strategy for cancer treatment. Based on our and other's studies, NAMPT may have dual roles in cancer radiotherapy: the upregulation of NAMPT could serve to suppress radiotherapy complications such as radiation sialadenitis, and combination regimens that involve NAMPT inhibitors may enhance efficacy of radiotherapy for cancer treatment.

α-Mangostin Alleviated Inflammation in Rats With Adjuvant-Induced Arthritis by Disrupting Adipocytes-Mediated Metabolism-Immune Feedback.

A previously identified anti-rheumatic compound α-mangostin (MAN) possesses notable metabolism regulatory properties. In this study, we investigated the immune implication of MAN-altered fat metabolism on adjuvant-induced arthritis (AIA) in rats. Seven days after AIA induction, the rats received oral treatment of MAN at 50 mg/kg/day for 30 days. Metabolic indicators and basic clinical parameters were evaluated using samples collected on day 20 and 38 since immunization. Expression of nicotinamide phosphoribosyltransferase (NAMPT), sirtuin 1 (SIRT1), peroxisome proliferator activated receptor gamma (PPAR-γ), stearoyl-coa desaturase 1 (SCD-1), toll like receptor 4 (TLR4), prostaglandin-endoperoxide synthase 2 (COX-2), (p)-JNK, (p)-p65 and IL-1β were investigated by either RT-qPCR or immunobloting methods. In in vitro experiments, we treated (pre)-adipocytes with monocytes/macrophages and MAN, and investigated the changes of macrophages brought by pre-adipocytes co-culture. Generally, MAN restored the impaired fat anabolism in AIA rats, indicated by increased fat reservoir, leptin and adiponectin secretion, and PPAR-γ and SCD-1 expression. Meanwhile, it decreased circulating IL-1β and IL-6 levels, restored serological lipid profile changes, and relieved oxidative stresses, demonstrating potent therapeutic effects on AIA. AIA rats-derived monocytes inhibited mRNA PPAR-γ and SCD-1 expression in pre-adipocytes. Contrarily, MAN facilitated adipocyte differentiation in vitro, and increased free fatty acids production. It also significantly increased PPAR-γ and SCD-1 expression, which can be abrogated by PPAR-γ inhibitor T0070907. Similarly, lipopolysaccharide-primed macrophages inhibited PPAR-γ expression in the co-cultured pre-adipocytes, which was reversed by MAN. In the same co-culture system, lipopolysaccharide-induced inflammation was amplified by the co-existence of pre-adipocytes. More secretion of IL-1β and IL-6 and higher levels expression of COX-2, p-JNK, p-p65 and TLR4 were observed in lipopolysaccharide-treated macrophages when co-cultured by pre-adipocytes. The intensified inflammatory situation was eased by MAN. The treatment with pre-adipocytes culture medium achieved similar effects. Medium from lipopolysaccharide-treated adipocytes promoted IL-1β, IL-6 and MCP-1 production in separately cultured macrophages, and COX-2, p-JNK, p-p65 and TLR4 expression were increased at the meantime. MAN treatment on pre-adipocytes impaired these changes. It suggests that fat anabolism in AIA rats was deficient due to increased energy expenditure caused by inflammatory conditions. MAN restored fat metabolism homeostasis by up-regulating PPAR-γ, and reshaped secretion profile of adipocytes.

Correction: Epigenetic Regulation of NAMPT by NAMPT-AS Drives Metastatic Progression in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is highly heterogeneous and has a poor prognosis. It is therefore important to identify the underlying molecular mechanisms in order to develop novel therapeutic strategies. Although emerging research has revealed long noncoding RNAs (lncRNA) as vital to carcinogenesis and cancer progression, their functional involvement in TNBC has not been well defined. In this study, we utilized the The Cancer Genome Atlas (TCGA) database and analyzed clinical samples to show that the long noncoding antisense transcript of nicotinamide phosphoribosyltransferase (NAMPT), NAMPT-AS, is upregulated in TNBC and is associated with poor prognosis, lymph node involvement, metastasis, and advanced stage. NAMPT-AS was cotranscribed with NAMPT from a bidirectional promoter, where the distributions of H3K4me3 and H3K27Ac chromatin modifications were enriched based on ENCODE and FANTOM5, suggesting the potential enhancer-RNA characteristics of NAMPT-AS. NAMPT-AS epigenetically regulated the expression of NAMPT in two divergent ways: NAMPT-AS recruited POU2F2 to activate the transcription of NAMPT, and NAMPT-AS acted as a competing endogenous RNA to rescue NAMPT degradation from miR-548b-3p. NAMPT-AS/NAMPT promoted tumor progression and regulated autophagy through the mTOR pathway in vitro and in vivo. In a cohort of 480 breast cancer patients, NAMPT was associated with breast cancer-specific survival and overall survival. These results demonstrate that NAMPT-AS is an oncogenic lncRNA in TNBC that epigenetically activates NAMPT to promote tumor progression and metastasis. Furthermore, these data identify NAMPT-AS/NAMPT as promising therapeutic targets in patients with TNBC. SIGNIFICANCE: Upregulation of the long noncoding antisense RNA of NAMPT gene (NAMPT-AS) is associated with metastasis and poor prognosis in TNBC.

Circular RNA circ_0128846 promotes the progression of osteoarthritis by regulating miR-127-5p/NAMPT axis

BackgroundMounting evidence indicates that circular RNAs (circRNAs) participate in the occurrence and development of various diseases, including osteoarthritis (OA). However, the effects and molecular mechanism of circ_0128846 in OA have not been reported.MethodsThe expression levels of circ_0128846, microRNA-127-5p (miR-127-5p), and nicotinamide phosphoribosyltransferase (NAMPT) were determined by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot assay. Cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was examined by flow cytometry and western blot assay. Inflammatory response and cartilage extracellular matrix (ECM) degradation were evaluated by western blot assay. The relationship between miR-127-5p and circ_0128846 or NAMPT was predicted by bioinformatics tools and verified by dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays.ResultsCirc_0128846 and NAMPT were upregulated and miR-127-5p was downregulated in OA cartilage tissues. Knockdown of circ_0128846 increased cell viability and inhibited apoptosis, inflammation and ECM degradation in OA chondrocytes, while these effects were reversed by downregulating miR-127-5p. Moreover, circ_0128846 positively regulated NAMPT expression by sponging miR-127-5p. Furthermore, miR-127-5p promoted cell viability and suppressed apoptosis, inflammation, and ECM degradation in OA chondrocytes by directly targeting NAMPT.ConclusionCirc_0128846 knockdown might inhibit the progression of OA by upregulating miR-127-5p and downregulating NAMPT, offering a new insight into the potential application of circ_0128846 in OA treatment.

NAD+ oscillation and hypothalamic neuronal functions.

A substantial body of evidence shows the importance of nicotinamide adenine dinucleotide (NAD+) biosynthesis and its regulation in a wide range of cellular metabolism. The expression of nicotinamide phosphoribosyltransferase (NAMPT) is regulated in a circadian manner by the core clock mechanism and NAD+-dependent sirtuins, producing the circadian oscillation of NAD+. The hypothalamus is a critical center for the homeostatic regulation of metabolism, circadian rhythm, and age-associated physiology. The dysfunction of systemic NAD+ biosynthesis over age affects the functions of hypothalamic neurons, causing age-associated metabolic pathophysiologies, including obesity and age-associated diseases. These recent studies suggest that NAD+ oscillation contributes to the hypothalamic function, and its disruption produces circadian and aging-related metabolic disorders. Furthermore, new studies have demonstrated a novel intertissue NAD+-dependent communication as a potential target for preventing and treating such disorders and for extending the health span of humans.

Plasmacytoma variant translocation 1 and nicotinamide phosphoribosyl-transferase long noncoding RNAs promote colorectal cancer

The prevalence of colorectal cancer (CRC) is increasing worldwide. Identifying the mechanisms that cause tumors, and the role of long non-coding RNAs (LncRNAs) in this respect have received much attention in the recent years. This study sought to identify the role of plasmacytoma variant translocation 1 (PVT1) and nicotinamide phosphoribosyltransferase (NAMPT) LncRNAs in development of CRC.The tumoral tissue required to study the expression of PVT1 and NAMPT LncRNAs was obtained from the tumor bank of Imam Khomeini Hospital in Tehran and normal adjacent tissues served as controls. The clinicopathological features of the tumors were recorded, and RNA extraction and cDNA synthesis were performed using the corresponding kits. The reverse-transcription polymerase chain reaction (RT-PCR) was performed using specific PVT1 and NAMPT primers. SPSS version 22 was used to analyze the data.The results showed higher expression of PVT1 and NAMPT LncRNAs in CRC specimens compared with control samples. High expression of PVT1 gene was observed in high-grade tumors. Higher expression of NAMPT was seen when extracapsular nodal extension was absent. Overall survival rate was reduced with higher expression level of NAMPT and PVT1 LncRNAs.The results of the present study revealed the significant role of PVT1 and NAMPT LncRNAs in CRC. However, more research is required to confirm this finding.

NAMPT promotes hepatitis B virus replication and liver cancer cell proliferation through the regulation of aerobic glycolysis.

Nicotinamide phosphoribosyltransferase (NAMPT) is a critical rate-limiting enzyme involved in NAD synthesis that has been shown to contribute to the progression of liver cancer. However, the potential role and mechanism of NAMPT in hepatitis B virus (HBV)-associated liver cancer remain unclear. The present study assessed the expression of NAMPT in HBV-positive and -negative liver cancer cells, and investigated whether HBV-induced NAMPT expression is dependent on HBV X protein (HBx). In addition, the role of NAMPT in HBV replication and transcription, and in HBV-mediated liver cancer cell growth was explored. The effects of NAMPT on the glycolytic pathway were also evaluated. Reverse transcription-quantitative PCR and western blotting results revealed that NAMPT expression levels were significantly higher in HBV-positive liver cancer cells than in HBV-negative liver cancer cells, and this effect was HBx-dependent. Moreover, the activation of NAMPT was demonstrated to be required for HBV replication and transcription. The NAMPT inhibitor FK866 repressed cell survival and promoted cell death in HBV-expressing liver cancer cells, and these effects were attenuated by nicotinamide mononucleotide. Furthermore, the inhibition of NAMPT was associated with decreased glucose uptake, decreased lactate production and decreased ATP levels in HBV-expressing liver cancer cells, indicating that NAMPT may promote the aerobic glycolysis. Collectively, these findings reveal a positive feedback loop in which HBV enhances NAMPT expression and the activation of NAMPT promotes HBV replication and HBV-mediated malignant cell growth in liver cancer. The present study highlights the important role of NAMPT in the regulation of aerobic glycolysis in HBV-mediated liver cancer, and suggests that NAMPT may be a promising treatment target for patients with HBV-associated liver cancer.

Lipopolysaccharide-Induced Microglial Neuroinflammation: Attenuation by FK866.

Alleviating microglia-mediated neuroinflammation bears great promise to reduce neurodegeneration. Nicotinamide phosphoribosyltransferase (NAMPT) may exert cytokine-like effect in the brain. However, it remains unclear about role of NAMPT in microglial inflammation. Also, it remains unknown about effect of NAMPT inhibition on microglial inflammation. In the present study, we observed that FK866 (a specific noncompetitive NAMPT inhibitor) dose-dependently inhibited lipopolysaccharide (LPS)-induced proinflammatory mediator (interleukin (IL)-6, IL-1β, inducible nitric oxide synthase, nitric oxide and reactive species) level increase in BV2 microglia cultures. FK866 also significantly inhibited LPS-induced polarization change in microglia. Furthermore, LPS significantly increased NAMPT expression and nuclear factor kappa B (NF-κB) phosphorylation in microglia. FK866 significantly decreased NAMPT expression and NF-κB phosphorylation in LPS-treated microglia. Finally, conditioned medium from microglia cultures co-treated with FK866 and LPS significantly increased SH-SY5Y and PC12 cell viability compared with conditioned medium from microglia cultures treated with LPS alone. Our study strongly indicates that NAMPT may be a promising target for microglia modulation and NAMPT inhibition may attenuate microglial inflammation.

Polyphenols from Securidaca inappendiculata alleviated acute lung injury in rats by inhibiting oxidative stress sensitive pathways

ObjectiveSecuridaca inappendiculata is a medicinal plant frequently used in the treatment of inflammatory diseases in south China. In this study, we aimed to explore its bioactive constituent which contributes to the anti-inflammatory activity. MethodsPolyphenol-enriched and polyphenol-deprived fractions (PRF and PDF, respectively) were separated from the ethanolic extract by HPD300 macroporous resin-based method, and their anti-inflammatory activities were investigated on a lipopolysaccharide (LPS)-induced acute lung injury (ALI) model in rats. The possible mechanism of action in alleviating acute inflammation was studied using RAW264.7 cells. ResultsBoth Folin-Ciocalteu and 1H nuclear magnetic resonance (NMR) analyses showed that polyphenolic content in PRF was approximately 10 times higher than that of PDF, and this observation reflected in their antioxidative capacities. PRF but not PDF significantly decreased the level of malondialdehyde, suppressed the expression of nicotinamide phosphoribosyltransferase (NAMPT) protein, and improved the severity of ALI in rats. PRF at 10 μg/mL effectively downregulated the expression of proteins NAMPT, HMGB1, TLR4, and p-p65, and scavenged the intracellular reactive oxygen species (ROS) in LPS-primed RAW264.7 cells. N-acetyl-L-cysteine exhibited similar inhibitory effects on ROS production and NAMPT-mediated TLR4/NF-κB activation in vitro, whereas nicotinamide mononucleotide antagonized all the changes induced by PRF during cotreatments. ConclusionAs an antioxidant, PRF exhibited potent anti-inflammatory activity under both in vivo and in vitro conditions by downregulating NAMPT and TLR4/NF-κB. Accordingly, polyphenols were identified as important bioactive constituents in S. inappendiculata targeting oxidative stress-sensitive pro-inflammatory pathways.

Unravelling the Role of LncRNA WT1-AS/miR-206/NAMPT Axis as Prognostic Biomarkers in Lung Adenocarcinoma.

Lung cancer is the world’s highest morbidity and mortality of malignant tumors, with lung adenocarcinoma (LUAD) as a major subtype. The competitive endogenous RNA (ceRNA) regulative network provides opportunities to understand the relationships among different molecules, as well as the regulative mechanisms among them in order to investigate the whole transcriptome landscape in cancer pathology. We designed this work to explore the role of a key oncogene, MYC, in the pathogenesis of LUAD, and this study aims to identify important long noncoding RNA (lncRNA)-microRNA (miRNA)- transcription factor (TF) interactions in non-small cell lung cancer (NSCLC) using a bioinformatics analysis. The Cancer Genome Atlas (TCGA) database, containing mRNA expression data of NSCLC, was used to determine the deferentially expressed genes (DEGs), and the ceRNA network was composed of WT1-AS, miR-206, and nicotinamide phosphoribosyltransferase (NAMPT) bashing on the MYC expression level. The Kaplan–Meier univariate survival analysis showed that these components may be closely related prognostic biomarkers and will become new ideas for NSCLC treatment. Moreover, the high expression of WT1-AS and NAMPT and low expression of miR-206 were associated with a shortened survival in NSCLC patients, which provided a survival advantage. In summary, the current study constructing a ceRNA-based WT1-AS/miR-206/NAMPT axis might be a novel important prognostic factor associated with the diagnosis and prognosis of LUAD.

A Negative Feedback Loop Between NAMPT and TGF-β Signaling Pathway in Colorectal Cancer Cells.

BackgroundNicotinamide phosphoribosyltransferase (NAMPT) and the transforming growth factor-β (TGF-β) signaling pathway play important roles in colorectal tumorigenesis and progress. However, the underlying regulatory mechanisms between NAMPT and TGF-β signaling in colorectal cancer (CRC) remain poorly understood.MethodsPublic data were extracted from the Oncomine database and the PrognoScan database to investigate the mRNA expression and the prognostic value of NAMPT, respectively, in CRC. Western blot tests were performed to detect Smad2, Smad3, p-Smad2, p-Smad3, Smad4 expression in CRC cells transfected with human NAMPT-siRNA or NAMPT-overexpressing plasmid. TGF-β1 concentrations in culture supernatants were assayed using ELISA kits. The effect of TGF-β1 on NAMPT expression was evaluated by quantitative real-time PCR and Western blot. The dual-luciferase reporter assay was employed to confirm the binding of miR-1-3p to NAMPT 3ʹ-UTR. Subsequently, NAMPT levels in HCT116 cells transfected with the mimics and inhibitors of miR-1-3p were detected by quantitative real-time PCR and Western blot.ResultsNAMPT was overexpressed in human CRC and was correlated with short overall survival. NAMPT increased the protein expression levels of components in the TGF-β signaling pathway including Smad2, Smad3, and Smad4. Moreover, NAMPT promoted TGF-β1 secretion. Intriguingly, the TGF-β1 treatment down-regulated NAMPT expression at mRNA and protein levels in CRC cells which were partly through the up-regulation of miR-1-3p that directly bound to the NAMPT 3ʹ-UTR. These outcomes demonstrated that NAMPT was a downstream target of miR-1-3p and there was a negative association between NAMPT and miR-1-3p in CRC.ConclusionThere is a negative feedback loop between NAMPT and the TGF-β signaling pathway in CRC cells, providing new insight into the mechanism underlying the regulatory pathways in CRC.

NAMPT/SIRT1 Attenuate Ang II-Induced Vascular Remodeling and Vulnerability to Hypertension by Inhibiting the ROS/MAPK Pathway.

Hypertension is characterized by endothelial dysfunction, vascular remodeling, and rearrangement of the extracellular matrix. Besides, the pathogenesis of hypertension is closely related to excess generation of reactive oxygen species (ROS). Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in nicotinamide adenine dinucleotide (NAD) biosynthesis that influences the activity of NAD-dependent enzymes, such as sirtuins, which possess NAD-dependent protein deacetylase activity and cleave NAD during the deacetylation cycle. Recently, NAMPT has been shown to play a crucial role in various diseases associated with oxidative stress. However, the function and regulation of NAMPT in hypertension have not been extensively explored. In the present study, we identified NAMPT as a crucial regulator of hypertension, because NAMPT expression was significantly downregulated in both patients with hypertension and experimental animals. NAMPT knockout (NAMPT+/-) mice exhibited a significantly higher blood pressure and ROS levels after stimulation with angiotensin II (Ang II) than wild-type mice, and the administration of recombinant human NAMPT (rhNAMPT) reversed this effect. In vivo, overexpression of NAMPT protected against angiotensin II- (Ang II-) induced hypertension by inhibiting ROS production via sirtuin 1 in mouse aortic endothelial cells (MAECs) and mouse aortic vascular smooth muscle cells (MOVAs). In turn, NAMPT alleviated the ROS-induced mitogen-activated protein kinase (MAPK) pathway. In conclusion, NAMPT might be a novel biomarker and a therapeutic target in hypertension.

NAMPT Over-Expression Recapitulates the BRAF Inhibitor Resistant Phenotype Plasticity in Melanoma.

Simple SummaryMalignant melanoma (MM) is the most fatal skin cancer due to its high metastatic potential. Treatment strategies are dramatically changing due to the introduction of BRAF/MEK inhibitors (i) and immunotherapy; however, multiple resistant mechanisms rapidly occur including metabolic rewiring. This study aimed to establish the driver role of the nicotinamide adenine dinucleotide (NAD)-biosynthetic enzyme nicotinamide phosphoribosyltransferase (NAMPT) in BRAFi resistance development. We defined that NAMPT over-expressing MM cells were strikingly similar to cells that acquired resistance to BRAFi in terms of growth, invasion, and phenotype plasticity. These findings confirmed NAMPT as a key factor in melanoma progression and in the onset of BRAFi resistance in melanoma patients, opening new therapeutic possibilities for this subset of patients.Serine–threonine protein kinase B-RAF (BRAF)-mutated metastatic melanoma (MM) is a highly aggressive type of skin cancer. Treatment of MM patients using BRAF/MEK inhibitors (BRAFi/MEKi) eventually leads to drug resistance, limiting any clinical benefit. Herein, we demonstrated that the nicotinamide adenine dinucleotide (NAD)-biosynthetic enzyme nicotinamide phosphoribosyltransferase (NAMPT) is a driving factor in BRAFi resistance development. Using stable and inducible NAMPT over-expression systems, we showed that forced NAMPT expression in MM BRAF-mutated cell lines led to increased energy production, MAPK activation, colony-formation capacity, and enhance tumorigenicity in vivo. Moreover, NAMPT over-expressing cells switched toward an invasive/mesenchymal phenotype, up-regulating expression of ZEB1 and TWIST, two transcription factors driving the epithelial to mesenchymal transition (EMT) process. Consistently, within the NAMPT-overexpressing cell line variants, we observed an increased percentage of a rare, drug-effluxing stem cell-like side population (SP) of cells, paralleled by up-regulation of ABCC1/MRP1 expression and CD133-positive cells. The direct correlation between NAMPT expression and gene set enrichments involving metastasis, invasiveness and mesenchymal/stemness properties were verified also in melanoma patients by analyzing The Cancer Genome Atlas (TCGA) datasets. On the other hand, CRISPR/Cas9 full knock-out NAMPT BRAFi-resistant MM cells are not viable, while inducible partial silencing drastically reduces tumor growth and aggressiveness. Overall, this work revealed that NAMPT over-expression is both necessary and sufficient to recapitulate the BRAFi-resistant phenotype plasticity.

Notoginseng leaf triterpenes ameliorates mitochondrial oxidative injury via the NAMPT-SIRT1/2/3 signaling pathways in cerebral ischemic model rats

Background: Due to the interrupted blood supply in cerebral ischemic stroke (CIS), ischemic and hypoxia results in neuronal depolarization, insufficient NAD+, excessive levels of ROS, mitochondrial damages, and energy metabolism disorders, which triggers the ischemic cascades. Currently, improvement of mitochondrial functions and energy metabolism is as a vital therapeutic target and clinical strategy. Hence, it is greatly crucial to look for neuroprotective natural agents with mitochondria protection actions and explore the mediated targets for treating CIS. In the previous study, notoginseng leaf triterpenes (PNGL) from Panax notoginseng stems and leaves was demonstrated to have neuroprotective effects against cerebral ischemia/reperfusion injury. However, the potential mechanisms have been not completely elaborate. Methods: The model of middle cerebral artery occlusion and reperfusion (MCAO/R) was adopted to verify the neuroprotective effects and potential pharmacology mechanisms of PNGL in vivo. Antioxidant markers were evaluated by kit detection. Mitochondrial function was evaluated by ATP content measurement, ATPase, NAD and NADH kits. And the transmission electron microscopy (TEM) and pathological staining (H&E and Nissl) were used to detect cerebral morphological changes and mitochondrial structural damages. Western blotting, ELISA and immunofluorescence assay were utilized to explore the mitochondrial protection effects and its related mechanisms in vivo. Results: In vivo, treatment with PNGL markedly reduced excessive oxidative stress, inhibited mitochondrial injury, alleviated energy metabolism dysfunction, decreased neuronal loss and apoptosis, and thus notedly raised neuronal survival under ischemia and hypoxia. Meanwhile, PNGL significantly increased the expression of nicotinamide phosphoribosyltransferase (NAMPT) in the ischemic regions, and regulated its related downstream SIRT1/2/3-MnSOD/PGC-1α pathways. Conclusion: The study finds that the mitochondrial protective effects of PNGL are associated with the NAMPT-SIRT1/2/3-MnSOD/PGC-1α signal pathways. PNGL, as a novel candidate drug, has great application prospects for preventing and treating ischemic stroke.

The Pivotal Role of Nicotinamide Phosphoribosyl Transferase in Chronic Myeloid Leukemia Cells Under Hypoxic Condition

Introduction: ABL tyrosine kinase inhibitors (TKIs) improved outcomes for patients with chronic myeloid leukemia (CML) and Philadelphia chromosome (Ph)-positive leukemia. However, ABL TKIs do not eliminate the leukemia stem cells (LSCs) in the bone marrow, which may represent the most important event in leukemia relapse after TKI discontinuation. Bone marrow is also considered a tissue with limited oxygen supply. Therefore, new approach against leukemia stem cells, which is presented in bone marrow under hypoxia, may improve the outcome of CML patients. Nicotinamide phosphoribosyl transferase (NAMPT) is the rate limiting enzyme of the primary pathway for maintaining cellular NAD+ and that regulates intracellular adenosine triphosphate (ATP) levels in mammalian cells. It has been reported that NAMPT expression is upregulated in several human cancers. Materials and methods: In this study, we established ABL TKI resistantin vitrocell line models (K562 imatinib-R, K562 nilotinib-R, K562 ponatinib-R and Ba/F3 T315I) and used Ph-positive leukemia cell lines. We also investigated whether NAMPT inhibitor could suppress Ph-positive leukemia cells including T315I mutation and ABL TKI resistant under hypoxic condition. Results: In chemical library screen of compounds, NAMPT inhibitor, CHS828 is selected the candidate drug for ABL TKI resistant cells under hypoxic condition. Drug repositioning and repurposing can be an important part of any drug discovery. Therefore, we examined NAMPT efficacy by using Ph-positive leukemia cell lines. We first investigated the NAMPT expression by microarray gene expression data from the online Gene Expression Omnibus (GEO). Gene expression of NAMPT is increased in CML patients compared to normal samples from the public microarray datasets of GSE13159. Protein expression of NAMPT is found in Ph-positive leukemia cell lines including ABL TKI resistant cells. In hypoxia, gene expression of NAMPT was increased in Ph-positive cells compare to normoxic condition. We next examined efficacy of NAMPT inhibitor, CHS828 in Ph-positive leukemia cell lines. We found that CHS828 treatment for 72 h decreased cell viability of Ph-positive cell lines in a dose dependent manner. We also found that CHS828 inhibited the proliferation of ABL TKI resistant cells (K562 imatinib-R, K562 nilotinib-R, K562 ponatinib-R) and T315I mutant Ba/F3 cells under hypoxic condition. The rate of cell cycle progression was delayed and cells were blocked in G2/M phase. Nuclear factor-kappaB (NF-kB) is also implicated in cancer development. CHS828 inhibited constitutive NF-kB activity in the time and dose dependent manner. Intracellular ATP, which is the most important source of energy for cellular reactions, was drastically decreased after CHS828 treatment. NAD+ plays a vital role in diverse cellular processes that govern human health and disease. Intracellular NAD+ was decreased after CHS828 treatment. The wound healing effect was evaluated at 0, 24, 48, and 72 h by using NIH3T3 cells. In wound healing results, CHS828 treatment inhibited cellular migration of NIH3T3 cells. We next investigated the efficacy of ABL TKI and CHS828 against Ph-positive leukemia cell lines. ABL TKI and CHS828 treatment induced cellular growth inhibition compared with each drug alone. Caspase 3/7 activity was also increased after ABL TKIs and CHS828 treatment. ABL TKI and CHS828 reduced the colony formation ability of Ph-positive cells under hypoxic condition. Thein vivoefficacies of one of ABL TKI, ponatinib and CHS828 were evaluated in a mouse xenograft model. Ponatinib and CHS828 inhibited the growth of T315I mutant Ba/F3 cellsin vivomore than the control vehicle. We also found that co-treatment with ponatinib and CHS828 increased mouse survival. Combination treatment with ponatinib and CHS828 was also well tolerated, with no animal deaths in the treated mice. Conclusion: The results of our study indicate that the ABL TKI and CHS828 may be a powerful strategy against Ph-positive cells including ABL TKI resistant cells and provide the promising clinical relevance as a candidate drug for treatment of CML stem cells of the bone marrow microenvironment under hypoxic condition. Disclosures No relevant conflicts of interest to declare.

Notoginseng Leaf Triterpenes Ameliorates OGD/R-Induced Neuronal Injury via SIRT1/2/3-Foxo3a-MnSOD/PGC-1α Signaling Pathways Mediated by the NAMPT-NAD Pathway.

Background Cerebral ischemic stroke (CIS) is a common cerebrovascular disease whose main risks include necrosis, apoptosis, and cerebral infarction. But few therapeutic advances and prominent drugs seem to be of value for ischemic stroke in the clinic yet. In the previous study, notoginseng leaf triterpenes (PNGL) from Panax notoginseng stem and leaf have been confirmed to have neuroprotective effects against mitochondrial damages caused by cerebral ischemia in vivo. However, the potential mechanisms of mitochondrial protection have not been fully elaborated yet. Methods The oxygen and glucose deprivation and reperfusion (OGD/R)-induced SH-SY5Y cells were adopted to explore the neuroprotective effects and the potential mechanisms of PNGL in vitro. Cellular cytotoxicity was measured by MTT, viable mitochondrial staining, and antioxidant marker detection in vitro.Mitochondrial functions were analyzed by ATP content measurement, MMP determination, ROS, NAD, and NADH kit in vitro. And the inhibitor FK866 was adopted to verify the regulation of PNGL on the target NAMPT and its key downstream. Results In OGD/R models, treatment with PNGL strikingly alleviated ischemia injury, obviously preserved redox balance and excessive oxidative stress, inhibited mitochondrial damage, markedly alleviated energy metabolism dysfunction, improved neuronal mitochondrial functions, obviously reduced neuronal loss and apoptosis in vitro, and thus notedly raised neuronal survival under ischemia and hypoxia. Meanwhile, PNGL markedly increased the expression of nicotinamide phosphoribosyltransferase (NAMPT) in the ischemic regions and OGD/R-induced SH-SY5Y cells and regulated the downstream SIRT1/2-Foxo3a and SIRT1/3-MnSOD/PGC-1α pathways. And FK866 further verified that the protective effects of PNGL might be mediated by the NAMPT in vitro. Conclusions The mitochondrial protective effects of PNGL are, at least partly, mediated via the NAMPT-NAD+ and its downstream SIRT1/2/3-Foxo3a-MnSOD/PGC-1α signaling pathways. PNGL, as a new drug candidate, has a pivotal role in mitochondrial homeostasis and energy metabolism therapy via NAMPT against OGD-induced SH-SY5Y cell injury.

Hyperglycemia-reduced NAD+ biosynthesis impairs corneal epithelial wound healing in diabetic mice

ObjectiveNicotinamide adenine dinucleotide (NAD) is an essential molecule participating in multiple physiological and pathophysiological processes. In diabetic cornea, the NAD+-consuming enzyme SIRT1 was down-regulated and contributed to the delayed wound healing. However, the impact of hyperglycemia on corneal NAD+ biosynthesis remained elusive. This study was to investigate the relationship of NAD+ biosynthesis and the delayed corneal wound healing in diabetic mice. MethodsType 1 diabetes mellitus (DM) mice were induced by streptozotocin and corneal epithelial wound healing models were constructed by epithelial scraping. The NAD+ contents of corneal epithelium were measured using the NAD/NADH quantification kit. Expression of key enzymes involved in the NAD+ biosynthesis in type 1 DM mice and type 2 DM patients were analyzed. The nicotinamide phosphoribosyltransferase (NAMPT)-specific siRNA and the selective inhibitor FK866 were used to achieve the blockade of NAMPT, whereas exogenous NAD+ and its precursors were replenished to the corneal epithelial cells and DM mice. ResultsHyperglycemia attenuated NAD+ content and NAMPT expression in the corneal epithelium of both type 1 DM mice and type 2 DM patients. Local knockdown of NAMPT by siRNA or FK866 consistently recapitulated the delayed corneal epithelial wound healing in normal mice. Moreover, NAD+ replenishment recovered the impaired proliferation and migration capacity by either FK866 or high glucose treatment in cultured corneal epithelial cells. Furthermore, in DM mice, NAD+ and its precursors nicotinamide mononucleotide and nicotinamide riboside also facilitated corneal epithelial and nerve regeneration, accompanied with the recovered expression of SIRT1 and phosphorylated EGFR, AKT, and ERK1/2 in epithelium and corneal sensitivity. ConclusionHyperglycemia-reduced NAD+ biosynthesis and contributed to the impaired epithelial wound healing in DM mice. The replenishment of NAD+ and its precursors facilitated diabetic corneal wound healing and nerve regeneration, which may provide a novel therapeutic strategy for the treatment of diabetic corneal complications.