Aging-dependent mitochondrial bioenergetic impairment in the skeletal muscle of NNT-deficient mice.

Overall health relies on features of skeletal muscle that generally decline with age, partly due to mechanisms associated with mitochondrial redox imbalance and bioenergetic dysfunction. Previously, aged mice genetically devoid of the mitochondrial NAD(P)+ transhydrogenase (NNT, encoded by the nicotinamide nucleotide transhydrogenase gene), an enzyme involved in mitochondrial NADPH supply, were shown to exhibit deficits in locomotor behavior. Here, by using young, middle-aged, and older NNT-deficient (Nnt-/-) mice and age-matched controls (Nnt+/+), we aimed to investigate how muscle bioenergetic function and motor performance are affected by NNT expression and aging. Mice were subjected to the wire-hang test to assess locomotor performance, while mitochondrial bioenergetics was evaluated in fiber bundles from the soleus, vastus lateralis and plantaris muscles. An age-related decrease in the average wire-hang score was observed in middle-aged and older Nnt-/- mice compared to age-matched controls. Although respiratory rates in the soleus, vastus lateralis and plantaris muscles did not significantly differ between the genotypes in young mice, the rates of oxygen consumption did decrease in the soleus and vastus lateralis muscles of middle-aged and older Nnt-/- mice. Notably, the soleus, which exhibited the highest NNT expression level, was the muscle most affected by aging, and NNT loss. Additionally, histology of the soleus fibers revealed increased numbers of centralized nuclei in older Nnt-/- mice, indicating abnormal morphology. In summary, our findings suggest that NNT expression deficiency causes locomotor impairments and muscle dysfunction during aging in mice.

Lack of NAD(P)+ transhydrogenase activity in patients with primary adrenal insufficiency due to NNT variants.

BACKGROUND: Pathogenic variants in the nicotinamide nucleotide transhydrogenase gene (NNT) are a rare cause of primary adrenal insufficiency (PAI), as well as functional impairment of the gonads. OBJECTIVE: Despite the description of different homozygous and compound heterozygous NNT variants in PAI patients, the extent to which the function and expression of the mature protein are compromised remains to be clarified. DESIGN: The activity and expression of mitochondrial NAD(P)+ transhydrogenase (NNT) were analyzed in blood samples obtained from patients diagnosed with PAI due to genetically confirmed variants of the NNT gene (n = 5), heterozygous carriers as their parents (n = 8), and healthy controls (n = 26). METHODS: NNT activity was assessed by a reverse reaction assay standardized for digitonin-permeabilized peripheral blood mononuclear cells (PBMCs). The enzymatic assay was validated in PBMC samples from a mouse model of NNT absence. Additionally, the PBMC samples were evaluated for NNT expression by western blotting and reverse transcription quantitative polymerase chain reaction and for mitochondrial oxygen consumption. RESULTS: NNT activity was undetectable (<4% of that of healthy controls) in PBMC samples from patients, independent of the pathogenic genetic variant. In patients' parents, NNT activity was approximately half that of the healthy controls. Mature NNT protein expression was lower in patients than in the control groups, while mRNA levels varied widely among genotypes. Moreover, pathogenic NNT variants did not impair mitochondrial bioenergetic function in PBMCs. CONCLUSIONS: The manifestation of PAI in NNT-mutated patients is associated with a complete lack of NNT activity. Evaluation of NNT activity can be useful to characterize disease-causing NNT variants.

The C-terminal tail of polycystin-1 suppresses cystic disease in a mitochondrial enzyme-dependent fashion.

Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent potentially lethal monogenic disorder. Mutations in the PKD1 gene, which encodes polycystin-1 (PC1), account for approximately 78% of cases. PC1 is a large 462-kDa protein that undergoes cleavage in its N and C-terminal domains. C-terminal cleavage produces fragments that translocate to mitochondria. We show that transgenic expression of a protein corresponding to the final 200 amino acid (aa) residues of PC1 in two Pkd1-KO orthologous murine models of ADPKD suppresses cystic phenotype and preserves renal function. This suppression depends upon an interaction between the C-terminal tail of PC1 and the mitochondrial enzyme Nicotinamide Nucleotide Transhydrogenase (NNT). This interaction modulates tubular/cyst cell proliferation, the metabolic profile, mitochondrial function, and the redox state. Together, these results suggest that a short fragment of PC1 is sufficient to suppress cystic phenotype and open the door to the exploration of gene therapy strategies for ADPKD.

Long-Term Follow-Up of Three Family Members with a Novel NNT Pathogenic Variant Causing Primary Adrenal Insufficiency.

Nicotinamide nucleotide transhydrogenase (NNT) deficiency causes primary adrenal insufficiency (PAI) and possibly some extra-adrenal manifestations. A limited number of these patients were previously described. We present the clinical and genetic characteristics of three family members with a biallelic novel pathogenic variant in the NNT gene. The patients were followed until the ages of 21.6, 20.2, and 4.2 years. PAI was diagnosed in the eldest two brothers after an Addisonian crisis and the third was diagnosed at the age of 4.5 months in the asymptomatic stage due to the genetic screening of family members. Whole exome sequencing with a targeted interpretation of variants in genes related to PAI was performed in all the patients. The urinary steroid metabolome was determined by gas chromatography-mass spectrometry in the asymptomatic patient. The three patients, who were homozygous for c.1575dup in the NNT gene, developed isolated glucocorticoid deficiency. The urinary steroid metabolome showed normal excretion of cortisol metabolites. The adolescent patients had slow pubertal progression with low-normal testicular volume, while testicular endocrine function was normal. Bone mineral density was in the range for osteopenia in both grown-up siblings. Echocardiography revealed no structural or functional heart abnormalities. This article is among the first with a comprehensive and chronologically-detailed description of patients with NNT deficiency.

Mitochondrial NAD(P)+ Transhydrogenase: From Molecular Features to Physiology and Disease.

Significance: Proton-translocating NAD(P)+ transhydrogenase, also known as nicotinamide nucleotide transhydrogenase (NNT), catalyzes a reversible reaction coupling the protonmotive force across the inner mitochondrial membrane and hydride (H-, a proton plus two electrons) transfer between the mitochondrial pools of NAD(H) and NADP(H). The forward NNT reaction is a source of NADPH in the mitochondrial matrix, fueling antioxidant and biosynthetic pathways with reductive potential. Despite the greater emphasis given to the net forward reaction, the reverse NNT reaction that oxidizes NADPH also occurs in physiological and pathological conditions. Recent Advances: NNT (dys)function has been linked to various metabolic pathways and disease phenotypes. Most of these findings have been based on spontaneous loss-of-function Nnt mutations found in the C57BL/6J mouse strain (NntC57BL/6J mutation) and disease-causing Nnt mutations in humans. The present review focuses on recent advances based on the mouse NntC57BL/6J mutation. Critical Issues: Most studies associating NNT function with disease phenotypes have been based on comparisons between different strains of inbred mice (with or without the NntC57BL/6J mutation), which creates uncertainties over the actual contribution of NNT in the context of other potential genetic modifiers. Future Directions: Future research might contribute to understanding the role of NNT in pathological conditions and elucidate how NNT regulates physiological signaling through its forward and reverse reactions. The importance of NNT in redox balance and tumor cell proliferation makes it a potential target of new therapeutic strategies for oxidative-stress-mediated diseases and cancer. Antioxid. Redox Signal. 36, 864-884.

Nicotinamide nucleotide transhydrogenase mutation analysis in Chinese patients with thyroid dysgenesis.

Thyroid dysgenesis (TD) accounts for 80% cases of congenital hypothyroidism, which is the most common neonatal disorder. Until now, the gene mutations have been reported associated with TD can only account for 5% cases, suggesting the genetic heterogeneity of the pathology. Nicotinamide nucleotide transhydrogenase (NNT) plays a crucial role in regulating redox homeostasis, patients carrying NNT mutations have been described with a clinical phenotype of hypothyroidism. As TD risk is increased in the context of several syndromes and redox homeostasis is vital for thyroid development and function, NNT might be a candidate gene involved in syndromic TD. Therefore, we performed target sequencing (TS) in 289 TD patients for causative mutations in NNT and conducted functional analysis of the gene mutations. TS and Sanger sequence were used to screen the novel mutations. For functional analysis, we performed western blot, measurement of NADPH/NADPtotal and H2 O2 generation, cell proliferation, and wounding healing assay. As a result, three presumably pathogenic mutations (c.811G > A, p.Ala271Ser; c.2078G > A, p.Arg693His; and c.2581G > A, p.Val861Met) in NNT had been identified. Our results showed the damaging effect of NNT mutations on stability and catalytic activity of proteins and redox balance of cells. In conclusion, our findings provided novel insights into the role of the NNT isotype in thyroid physiopathology and broaden the spectrum of pathogenic genes associated with TD. However, the pathogenic mechanism of NNT in TD is still need to be investigated in further study.

LncRNA NNT-AS1 regulates proliferation, ECM accumulation and inflammation of human mesangial cells induced by high glucose through miR-214-5p/smad4.

BACKGROUND: LncRNA NNT-AS1 (NNT-AS1) has been extensively studied as the causative agent in propagation and progression of lung and bladder cancers, and cholangiocarcinoma. However, its significance in proliferation and inflammation of diabetic nephropathy is enigmatic. This study focuses on the molecular mechanisms followed by NNT-AS1 to establish diabetic nephropathy (DN) and its potential miRNA target. METHODS: Bioinformatics analysis to identify potential miRNA target of NNT-AS1 and smad4 transcription factor was conducted using LncBase and TargetScan, and was subsequently confirmed by luciferase reporter assay. Relative quantitative expression of NNT-AS1 in human glomerular mesangial cells (HGMCs) was detected through quantitative real-time PCR and WB analysis. Cell proliferation was detected through CCK-8 assay, whereas, ELISA was conducted to evaluate the expression of inflammatory cytokines. Following this, relative expression of miR-214-5p and smad4 were confirmed through qRT-PCR and western blot analysis. RESULTS: Results from the experiments manifested up-regulated levels of NNT-AS1 and smad4 in the blood samples of DN patients as well as in HGMCs, whereas, downregulated levels of miR-214-5p were measured in the HGMCs suggesting the negative correlation between NNT-AS1 and miR-214-5p. Potential binding sites of NNT-AS1 showed miR-214-5p as its direct target and NNT-AS1 as potential absorber for this microRNA, in turn increasing the expression of transcription factor smad4. CONCLUSION: The data suggests that NNT-AS1 can be positively used as a potential biomarker and indicator of DN and causes extracellular matrix (ECM) accumulation and inflammation of human mesangial cells.

Loss of Nnt Increases Expression of Oxidative Phosphorylation Complexes in C57BL/6J Hearts.

Nicotinamide nucleotide transhydrogenase (NNT) is a proton pump in the inner mitochondrial membrane that generates reducing equivalents in the form of NAPDH, which can be used for anabolic pathways or to remove reactive oxygen species (ROS). A number of studies have linked NNT dysfunction to cardiomyopathies and increased risk of atherosclerosis; however, biallelic mutations in humans commonly cause a phenotype of adrenal insufficiency, with rare occurrences of cardiac dysfunction and testicular tumours. Here, we compare the transcriptomes of the hearts, adrenals and testes from three mouse models: the C57BL/6N, which expresses NNT; the C57BL/6J, which lacks NNT; and a third mouse, expressing the wild-type NNT sequence on the C57BL/6J background. We saw enrichment of oxidative phosphorylation genes in the C57BL/B6J in the heart and adrenal, possibly indicative of an evolved response in this substrain to loss of Nnt. However, differential gene expression was mainly driven by mouse background with some changes seen in all three tissues, perhaps reflecting underlying genetic differences between the C57BL/B6J and -6N substrains.

Undesirable effects of chemical inhibitors of NAD(P)+ transhydrogenase on mitochondrial respiratory function.

NAD(P)+ transhydrogenase (NNT) is located in the inner mitochondrial membrane and catalyzes a reversible hydride transfer between NAD(H) and NADP(H) that is coupled to proton translocation between the intermembrane space and mitochondrial matrix. NNT activity has an essential role in maintaining the NADPH supply for antioxidant defense and biosynthetic pathways. In the present report, we evaluated the effects of chemical compounds used as inhibitors of NNT over the last five decades, namely, 4-chloro-7-nitrobenzofurazan (NBD-Cl), N,N'-dicyclohexylcarbodiimide (DCC), palmitoyl-CoA, palmitoyl-l-carnitine, and rhein, on NNT activity and mitochondrial respiratory function. Concentrations of these compounds that partially inhibited the forward and reverse NNT reactions in detergent-solubilized mouse liver mitochondria significantly impaired mitochondrial respiratory function, as estimated by ADP-stimulated and nonphosphorylating respiration. Among the tested compounds, NBD-Cl showed the best relationship between NNT inhibition and low impact on respiratory function. Despite this, NBD-Cl concentrations that partially inhibited NNT activity impaired mitochondrial respiratory function and significantly decreased the viability of cultured Nnt-/- mouse astrocytes. We conclude that even though the tested compounds indeed presented inhibitory effects on NNT activity, at effective concentrations, they cause important undesirable effects on mitochondrial respiratory function and cell viability.

Nicotinamide nucleotide transhydrogenase (NNT) regulates mitochondrial ROS and endothelial dysfunction in response to angiotensin II.

Endothelial dysfunction is a critical, initiating step in the development of hypertension (HTN) and mitochondrial reactive oxygen species (ROS) are important contributors to endothelial dysfunction. Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) in the nicotinamide nucleotide transhydrogenase (Nnt) gene that are associated with endothelial dysfunction and increased risk for HTN. NNT is emerging as an important enzyme that regulates mitochondrial NADPH levels and mitochondrial redox balance by supporting the thiol dependent peroxidase systems in the mitochondria. We have previously shown that the absence of NNT in C57Bl/6J animals promotes a more severe hypertensive phenotype through reductions in •NO and endothelial dependent vessel dilation. However, the impact of NNT on human endothelial cell function remains unclear. We utilized NNT directed shRNA in human aortic endothelial cells to test the hypothesis that NNT critically regulates mitochondrial redox balance and endothelial function in response to angiotensin II (Ang II). We demonstrate that NNT expression and activity are elevated in response to the mitochondrial dysfunction and oxidative stress associated with Ang II treatment. Knockdown of NNT led to a significant elevation of mitochondrial ROS production and impaired glutathione peroxidase and glutathione reductase activities associated with a reduction in the NADPH/NADP+ ratio. Loss of NNT also promoted mitochondrial dysfunction, disruption of the mitochondrial membrane potential, and impaired ATP production in response to Ang II. Finally, we observed that, while the loss of NNT augmented eNOS phosphorylation at Ser1177, neither eNOS activity nor nitric oxide production were similarly increased. The results from these studies clearly demonstrate that NNT is critical for the maintenance of mitochondrial redox balance and mitochondrial function. Loss of NNT and disruption of redox balance leads to oxidative stress that compromises eNOS activity that could have a profound effect on the endothelium dependent regulation of vascular tone.

Flux through mitochondrial redox circuits linked to nicotinamide nucleotide transhydrogenase generates counterbalance changes in energy expenditure.

Compensatory changes in energy expenditure occur in response to positive and negative energy balance, but the underlying mechanism remains unclear. Under low energy demand, the mitochondrial electron transport system is particularly sensitive to added energy supply (i.e. reductive stress), which exponentially increases the rate of H2O2 (JH2O2) production. H2O2 is reduced to H2O by electrons supplied by NADPH. NADP+ is reduced back to NADPH by activation of mitochondrial membrane potential-dependent nicotinamide nucleotide transhydrogenase (NNT). The coupling of reductive stress-induced JH2O2 production to NNT-linked redox buffering circuits provides a potential means of integrating energy balance with energy expenditure. To test this hypothesis, energy supply was manipulated by varying flux rate through ß-oxidation in muscle mitochondria minus/plus pharmacological or genetic inhibition of redox buffering circuits. Here we show during both non-ADP- and low-ADP-stimulated respiration that accelerating flux through ß-oxidation generates a corresponding increase in mitochondrial JH2O2 production, that the majority (∼70-80%) of H2O2 produced is reduced to H2O by electrons drawn from redox buffering circuits supplied by NADPH, and that the rate of electron flux through redox buffering circuits is directly linked to changes in oxygen consumption mediated by NNT. These findings provide evidence that redox reactions within ß-oxidation and the electron transport system serve as a barometer of substrate flux relative to demand, continuously adjusting JH2O2 production and, in turn, the rate at which energy is expended via NNT-mediated proton conductance. This variable flux through redox circuits provides a potential compensatory mechanism for fine-tuning energy expenditure to energy balance in real time.

Long noncoding RNA NNT-AS1 functions as an oncogene in breast cancer via repressing ZFP36 expression.

Breast cancer is one of the most common cancers in women. This study focuses on the effects of Long non-coding RNAs (lncRNAs) NNT-AS1 on breast cancer cell growth and metastasis. Fifty-six pairs of breast cancer (BC) tissues and matched paracarcinoma tissues were obtained. The BC cell lines and normal human breast cell line were employed. NNT-AS1 in BC cells was knocked down by shRNA. Cell counting kit-8 assay (CCK-8), colony formation assay, cell cycle analysis, cell apoptosis analysis, cound healing assay, Transwell assay, cioinformatics analysis, Western blot analysis and Xenograft model were used. Quantitative real-time polymerase chain reaction (qRT-PCR) assay indicated that expression of NNT-AS1 was obviously upregulated in breast cancer tissues compared with adjacent tissues (n=56). Knockdown of NNT-AS1 could attenuate breast cancer cell viability, proliferation, invasion and migration, as well as promote cell apoptosis and induce cell cycle arrest at G0/G1 phase. ZFP36 was directly combined with NNT-AS1, and silencing of ZFP36 could rescue tumor suppression role by downregulating NNT-AS1 on cell proliferation and metastasis. Knockdown of NNT-AS1 could suppress cell growth and metastasis via interacting with ZFP36 in vivo. This study demonstrated that knockdown of NNT-AS1 had tumor-suppressive effect on breast cancer progression and metastasis via interacting with ZFP36 in vitro and in vivo, which provides a new insight into the treatment and prognosis evaluation of breast cancer.

Nicotinamide Nucleotide Transhydrogenase (Nnt) is Related to Obesity in Mice.

The C57BL/6J (B6J) mouse strain has been widely used as a control strain for the study of metabolic diseases and diet induced obesity (DIO). B6J mice carry a spontaneous deletion mutation in the nicotinamide nucleotide transhydrogenase (Nnt) gene eliminating exons 7-11, resulting in expression of a truncated form of Nnt, an enzyme that pumps protons across the inner mitochondrial membrane. It has been proposed that this mutation in B6J mice is associated with epigonadal fat mass and altered sensitivity to diet induced obesity. To define the role of Nnt in the development of diet induced obesity, we generated first backcross (BC1) hybrids of wild type Nnt C57BL/6NTac and mutated Nnt C57BL/6JRj [(C57BL/6NTac×C57BL/6JRj)F1×C57BL/6NTac]. Body weight gain and specific fat-pad depot mass were measured in BC1 hybrids under high fat diet conditions. Both sexes of BC1 hybrids indicate that mice with Nnt wild type allele are highly sensitive to DIO and exhibit higher relative fat mass. In summary, our data indicate that the Nnt mutation in mice is associated with sensitivity to DIO and fat mass.

Mitochondrial NAD(P)+ Transhydrogenase is Unevenly Distributed in Different Brain Regions, and its Loss Causes Depressive-like Behavior and Motor Dysfunction in Mice.

NAD(P)+ transhydrogenase (NNT) links redox states of the mitochondrial NAD(H) and NADP(H) via a reaction coupled to proton-motive force across the inner mitochondrial membrane. NNT is believed to be ubiquitously present in mammalian cells, but its expression may vary substantially in different tissues. The present study investigated the tissue distribution and possible roles of NNT in the mouse brain. The pons exhibited high NNT expression/activity, and immunohistochemistry revealed intense NNT labeling in neurons from brainstem nuclei. In some of these regions, neuronal NNT labeling was strongly colocalized with enzymes involved in the biosynthesis of 5-hydroxytryptamine (5-HT) and nitric oxide (NO), which directly or indirectly require NADPH. Behavioral tests were performed in mice lacking NNT activity (Nnt-/-, mice carrying the mutated NntC57BL/6J allele from the C57BL/6J strain) and the Nnt+/+ controls. Our data demonstrated that aged Nnt-/- mice (18-20 months old), but not adult mice (3-4 months old), showed an increased immobility time in the tail suspension test that was reversed by fluoxetine treatment, providing evidence of depressive-like behavior in these mice. Aged Nnt-/- mice also exhibited behavioral changes and impaired locomotor activity in the open field and rotarod tests. Despite the colocalization between NNT and NO synthase, the S-nitrosation and cGMP levels were independent of the Nnt genotype. Taken together, our results indicated that NNT is unevenly distributed throughout the brain and associated with 5-THergic and NOergic neurons. The lack of NNT led to alterations in brain functions related to mood and motor behavior/performance in aged mice.

Mylk3 null C57BL/6N mice develop cardiomyopathy, whereas Nnt null C57BL/6J mice do not.

The C57BL/6J and C57BL/6N mice have well-documented phenotypic and genotypic differences, including the infamous nicotinamide nucleotide transhydrogenase (Nnt) null mutation in the C57BL/6J substrain, which has been linked to cardiovascular traits in mice and cardiomyopathy in humans. To assess whether Nnt loss alone causes a cardiovascular phenotype, we investigated the C57BL/6N, C57BL/6J mice and a C57BL/6J-BAC transgenic rescuing NNT expression, at 3, 12, and 18 mo. We identified a modest dilated cardiomyopathy in the C57BL/6N mice, absent in the two B6J substrains. Immunofluorescent staining of cardiomyocytes revealed eccentric hypertrophy in these mice, with defects in sarcomere organisation. RNAseq analysis identified differential expression of a number of cardiac remodelling genes commonly associated with cardiac disease segregating with the phenotype. Variant calling from RNAseq data identified a myosin light chain kinase 3 (Mylk3) mutation in C57BL/6N mice, which abolishes MYLK3 protein expression. These results indicate the C57BL/6J Nnt-null mice do not develop cardiomyopathy; however, we identified a null mutation in Mylk3 as a credible cause of the cardiomyopathy phenotype in the C57BL/6N.

Long non-coding RNA NNT-AS1 promotes cholangiocarcinoma cells proliferation and epithelial-to-mesenchymal transition through down-regulating miR-203.

BACKGROUND: Cholangiocarcinoma (CCA) is a serious malignant tumor. Long non-coding RNA NNT-AS1 (NNT-AS1) takes crucial roles in several tumors. So, we planned to research the roles and underlying mechanism of NNT-AS1 in CCA. RESULTS: NNT-AS1 overexpression was appeared in CCA tissues and cell lines. Proliferation was promoted by NNT-AS1 overexpression in CCLP1 and TFK1 cells. Besides, NNT-AS1 overexpression reduced E-cadherin level and raised levels of N-cadherin, vimentin, Snail and Slug. However, the opposite trend was occurred by NNT-AS1 knockdown. Further, NNT-AS1 overexpression promoted phosphatidylinositol 3 kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK)1/2 pathways. MiR-203 was sponged by NNT-AS1 and miR-203 mimic reversed the above promoting effects of NNT-AS1. Additionally, insulin-like growth factor type 1 receptor (IGF1R) and zinc finger E-box binding homeobox 1 (ZEB1) were two potential targets of miR-203. CONCLUSION: NNT-AS1 promoted proliferation, EMT and PI3K/AKT and ERK1/2 pathways in CCLP1 and TFK1 cells through down-regulating miR-203. METHODS: CCLP1 and TFK1 cells were co-transfected with pcDNA-NNT-AS1 and miR-203 mimic. Bromodeoxyuridine (BrdU), flow cytometry, quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot were employed to detect roles and mechanism of NNT-AS1. Interaction between NNT-AS1 and miR-203 or miR-203 and target genes was examined through luciferase activity experiment.

LncRNA NNT-AS1 regulates the progression of lung cancer through the NNT-AS1/miR-3666/E2F2 axis.

OBJECTIVE: Lung cancer is the main burden on human health, with high mortality and poor prognosis. The involvement of long non-coding RNAs (lncRNAs) in the development of cancer has attracted wide attention. This study aimed to investigate the role and novel mechanisms of lncRNA nicotinamide nucleotide transhydrogenase antisense RNA 1 (NNT-AS1) in the progression of lung cancer. MATERIALS AND METHODS: Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed to detect the expression of NNT-AS1, microRNA-3666 (miR-3666), and E2F transcription factor 2 (E2F2). 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay was used to analyze cell proliferation. Flow cytometry was carried out to investigate cell apoptosis. Transwell assay was conducted to observe cell invasion. The interaction between miR-3666 and NNT-AS1 or E2F2 was predicted by bioinformatics tool starBase v2.0 and verified by Dual-Luciferase reporter assay. The protein level of E2F2 was quantified by Western blot. RESULTS: NNT-AS1 and E2F2 were upregulated, but miR-3666 was downregulated in lung cancer tissues and cells. NNT-AS1 knockdown attenuated proliferation and invasion but enhanced apoptosis of lung cancer cells, while miR-3666 inhibition reversed these effects. It was confirmed that miR-3666 was a target of NNT-AS1 and it directly interacted with E2F2. The inhibitory proliferation and invasion, and acceleratory apoptosis of lung cancer cells, caused by miR-3666 enrichment, were overturned by E2F2 overexpression. Furthermore, E2F2 was regulated by NNT-AS1 through miR-3666. CONCLUSIONS: NNT-AS1 participated in the progression of lung cancer through NNT-AS1/miR-3666/E2F2 regulatory axis at least in part. Our study supplied a promising strategy for the treatment of lung cancer.

LncRNA NNT-AS1 promotes non-small cell lung cancer progression through regulating miR-22-3p/YAP1 axis.

BACKGROUND: Lung cancer is the leading cause of cancer-related mortality worldwide. Studies have demonstrated that long noncoding RNA nicotinamide nucleotide transhydrogenase-antisense RNA1 (NNT-AS1) functioned as an oncogene in most malignancies, including non-small cell lung cancer (NSCLC). This study aimed to investigate the underlying mechanisms of NNT-AS1 in NSCLC progression. METHODS: The levels of NNT-AS1, miR-22-3p and Yes-associated protein (YAP1) were detected by qRT-PCR in NSCLC tissues and cells. Kaplan-Meier analysis was conducted to analyze the correlation between NNT-AS1 expression and overall survival of NSCLC patients. Cell proliferation was evaluated by MTT assay. Cell migration and invasion were assessed using transwell assay. The protein levels of YAP1 and EMT-related proteins were detected by western blot. The molecular mechanism was predicted by starBase2.0 and validated by dual-luciferase reporter assay or RNA pull-down assay. Xenograft analysis was carried out to analyze tumor growth in vivo. RESULTS: We found that the levels of NNT-AS1 and YAP1 were enhanced, while miR-22-3p expression was decreased in NSCLC tissues and cells. High NNT-AS1 expression was correlated with poor prognosis. NNT-AS1 knockdown impeded proliferation, migration, invasion and EMT of NSCLC cells. NNT-AS1 targeted miR-22-3p, and YAP1 was a target of miR-22-3p in NSCLC cells. Furthermore, NNT-AS1 facilitated the progression of NSCLC by regulating miR-22-3p/YAP1 axis. NNT-AS1 knockdown repressed tumor growth in vivo. CONCLUSION: NNT-AS1 facilitated proliferation, migration, invasion and EMT of NSCLC cells by sponging miR-22-3p and regulating YAP1 expression, which might provide a potential biomarker and therapeutic target for NSCLC.