Activity Of Nicotinamide Adenine Dinucleotide Research Articles

NAD/NAMPT and mTOR Pathways in Melanoma: Drivers of Drug Resistance and Prospective Therapeutic Targets.

Malignant melanoma represents the most fatal skin cancer due to its aggressive behavior and high metastatic potential. The introduction of BRAF/MEK inhibitors and immune-checkpoint inhibitors (ICIs) in the clinic has dramatically improved patient survival over the last decade. However, many patients either display primary (i.e., innate) or develop secondary (i.e., acquired) resistance to systemic treatments. Therapeutic resistance relies on the rewiring of multiple processes, including cancer metabolism, epigenetics, gene expression, and interactions with the tumor microenvironment that are only partially understood. Therefore, reliable biomarkers of resistance or response, capable of facilitating the choice of the best treatment option for each patient, are currently missing. Recently, activation of nicotinamide adenine dinucleotide (NAD) metabolism and, in particular, of its rate-limiting enzyme nicotinamide phosphoribosyltransferase (NAMPT) have been identified as key drivers of targeted therapy resistance and melanoma progression. Another major player in this context is the mammalian target of rapamycin (mTOR) pathway, which plays key roles in the regulation of melanoma cell anabolic functions and energy metabolism at the switch between sensitivity and resistance to targeted therapy. In this review, we summarize known resistance mechanisms to ICIs and targeted therapy, focusing on metabolic adaptation as one main mechanism of drug resistance. In particular, we highlight the roles of NAD/NAMPT and mTOR signaling axes in this context and overview data in support of their inhibition as a promising strategy to overcome treatment resistance.

Nicotinamide mononucleotide ameliorates adriamycin-induced renal damage by epigenetically suppressing the NMN/NAD consumers mediated by Twist2

The activation of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, Sirt1, after the administration of nicotinamide mononucleotide (NMN) suppresses many diseases. However, the role of NMN and Sirt1 in focal glomerulosclerosis (FSGS) has not yet been elucidated. This study aimed to assess the protective effect of NMN treatment in mice with adriamycin (ADR)-induced FSGS. Transient short-term NMN treatment was administered to 8-week-old ADR- or saline-treated BALB/c mice (Cont group) for 14 consecutive days. NMN alleviated the increase in urinary albumin excretion in the ADR-treated mice. NMN treatment mitigated glomerulosclerosis and ameliorated the reduced Sirt1 expression and elevated Claudin-1 expression in the kidneys of the mice. Moreover, this treatment improved the decrease in histone methylation and the expression level of Dnmt1 and increased the concentration of NAD+ in the kidney. Dnmt1 epigenetically suppressed the expression of the NMN-consuming enzyme nicotinamide mononucleotide adenyltransferase1 (Nmnat1) by methylating the E-box in the promoter region and repressing the NAD-consuming enzyme PARP1. Additionally, NMN downregulated the expression of Nmnat1 in the ADR-treated mice. Short-term NMN treatment in FSGS has epigenetic renal protective effects through the upregulation of Sirt1 and suppression of the NAD and NMN consumers. The present study presents a novel treatment paradigm for FSGS.

Enhanced nitrate removal by biochar supported nano zero-valent iron (nZVI) at biocathode in bioelectrochemical system (BES)

In this study, activated biochar (BC), nano zero-valent iron (nZVI) and biochar supported nano zero-valent iron (BC-nZVI) were used to remove cathodic nitrate in bioelectrochemical system (BES). With an initial NO3–-N concentration of 100 mg/L, it was found that the complete nitrate removal could be observed within 28 h for the group of BC-nZVI, whereas the accumulated ammonia reached 63.33 mg/L. Meanwhile, nitrate removal reaction rate constants reached 0.171, 0.110, 0.023 and only 0.010 h−1 for BC-nZVI, nZVI, BC and the Control groups, respectively. Besides, enzymatic activity of nicotinamide adenine dinucleotide (NADH) and nitrous oxide reductase (NOS) of the BC-nZVI group reached the peak faster than three other groups. As a carrier for nZVI, loading of nZVI onto BC could increase the surface area of BC-nZVI other than nZVI for microbial aggregation, while embedded nZVI would contribute to the granulation of sludge and nitrate reduction. Moreover, Cyclic Voltammetry (CV) and chronoamperometry (CA) indicated that BC-nZVI group obtain better electrochemical performances. Importantly, it was found that not only abundances of microbial genus, but relative abundances of those iron mediated enzymes responsible for electro-consuming, hydrogen production and preferential ammonia accumulated nitrate removal could all be enriched. Therefore, BC-nZVI could be implemented to enhance the nitrate removal at biocathode in BES.

NAMPT/SIRT2-mediated inhibition of the p53-p21 signaling pathway is indispensable for maintenance and hematopoietic differentiation of human iPS cells

BackgroundNicotinamide phosphoribosyltransferase (NAMPT) regulates cellular functions through the protein deacetylation activity of nicotinamide adenine dinucleotide (NAD+)-dependent sirtuins (SIRTs). SIRTs regulate functions of histones and none-histone proteins. The role of NAMPT/SIRT pathway in the regulation of maintenance and differentiation of human-induced pluripotent stem (iPS) cells is not fully elucidated.MethodsWe evaluated the effects of specific inhibitors of NAMPT or SIRT2 on the pluripotency, proliferation, survival, and hematopoietic differentiation of human iPS cells. We also studied the molecular mechanism downstream of NAMPT/SIRTs in iPS cells.ResultsWe demonstrated that NAMPT is indispensable for the maintenance, survival, and hematopoietic differentiation of iPS cells. We found that inhibition of NAMPT or SIRT2 in iPS cells induces p53 protein by promoting its lysine acetylation. This leads to activation of the p53 target, p21, with subsequent cell cycle arrest and induction of apoptosis in iPS cells. NAMPT and SIRT2 inhibition also affect hematopoietic differentiation of iPS cells in an embryoid body (EB)-based cell culture system.ConclusionsOur data demonstrate the essential role of the NAMPT/SIRT2/p53/p21 signaling axis in the maintenance and hematopoietic differentiation of iPS cells.

The genomic effects of cell phone exposure on the reproductive system

Humans are exposed to increasing levels of electromagnetic fields (EMF) at various frequencies as technology advances. In this context, improving understanding of the biological effects of EMF remains an important, high priority issue. Although a number of studies in this issue and elsewhere have focused on the mechanisms of the oxidative stress caused by EMF, the precise understanding of the processes involved remains to be elucidated. Due to unclear results among the studies, the issue of EMF exposure in the literature should be evaluated at the genomic level on the reproductive system. Based on this requirement, a detail review of recently published studies is necessary. The main objectives of this study are to show differences between negative and positive effect of EMF on the reproductive system of animal and human. Extensive review of literature has been made based on well known data bases like Web of Science, PubMed, MEDLINE, Google Scholar, Science Direct, Scopus. This paper reviews the current literature and is intended to contribute to a better understanding of the genotoxic effects of EMF emitted from mobile phones and wireless systems on the human reproductive system, especially on fertility. The current literature reveals that mobile phones can affect cellular functions via non-thermal effects. Although the cellular targets of global system for mobile communications (GSM)-modulated EMF are associated with the cell membrane, the subject is still controversial. Studies regarding the genotoxic effects of EMF have generally focused on DNA damage. Possible mechanisms are related to ROS formation due to oxidative stress. EMF increases ROS production by enhancing the activity of nicotinamide adenine dinucleotide (NADH) oxidase in the cell membrane. Further detailed studies are needed to elucidate DNA damage mechanisms and apoptotic pathways during oogenesis and spermatogenesis in germ cells exposed to EMF.

Nrf2 activation attenuates the early suppression of mitochondrial respiration due to the α-synuclein overexpression

Backgroundα-synuclein (SNCA) accumulation in the substantia nigra is one of the characteristic pathologies of Parkinson's disease (PD). A53T missense mutations in the SNCA gene has been proved to enhance the expression of SNCA and accelerate the onset of PD. Mitochondrial dysfunction in SNCA aggregation has been under debate for decades but the causal relationship remains uncertain. At a later stage of PD, the cellular dysfunctions are complicated and multiple factors are tangled. Our aim here is to investigate the mitochondrial functional changes and clarify the main causal mechanism at earlier-stage of PD. MethodsWe used the mutant A53T SNCA-expressed neuro 2a (N2a) cells without detectable cell death to investigate: 1) whether SNCA overexpression impairs the mitochondrial respiration and biogenesis. 2) The role of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signal in SNCA–induced mitochondria dysfunction. ResultsAccompanying with the increment of SNCA, reactive oxygen species (ROS) accumulation was increased. The maximal respiratory capacity was suppressed. Meanwhile, mitochondrial complex 1 activity and the activity of nicotinamide adenine dinucleotide (NADH) cytochrome C reductase (NCCR) were decreased. Moreover, the mitochondrial DNA (mtDNA) copy number was decreased. On the other hand, the nuclear peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), Nrf2, and the cytosolic mitochondrial transcription factor A (TFAM) were increased at an early stage and declined thereafter. Above factors triggered by SNCA were reversed by tBHQ, a Nrf2 activator. ConclusionThese results suggested that at an early stage, SNCA-overexpressed increase mtROS accumulation, mitochondrial dysfunction and mtDNA decrement. Nrf2, PGC-1α and TFAM were upregulated to compromise mitochondrial dysfunction. tBHQ effectively reversed the SNCA-induced mitochondrial dysfunction.

S-Adenosyl-L-Homocysteine Hydrolase Inhibition by a Synthetic Nicotinamide Cofactor Biomimetic

S-adenosyl-L-homocysteine (SAH) hydrolases (SAHases) are involved in the regulation of methylation reactions in many organisms and are thus crucial for numerous cellular functions. Consequently, their dysregulation is associated with severe health problems. The SAHase-catalyzed reaction is reversible and both directions depend on the redox activity of nicotinamide adenine dinucleotide (NAD+) as a cofactor. Therefore, nicotinamide cofactor biomimetics (NCB) are a promising tool to modulate SAHase activity. In the present in vitro study, we investigated 10 synthetic truncated NAD+ analogs against a SAHase from the root-nodulating bacterium Bradyrhizobium elkanii. Among this set of analogs, one was identified to inhibit the SAHase in both directions. Isothermal titration calorimetry (ITC) and crystallography experiments suggest that the inhibitory effect is not mediated by a direct interaction with the protein. Neither the apo-enzyme (i.e., deprived of the natural cofactor), nor the holo-enzyme (i.e., in the NAD+-bound state) were found to bind the inhibitor. Yet, enzyme kinetics point to a non-competitive inhibition mechanism, where the inhibitor acts on both, the enzyme and enzyme-SAH complex. Based on our experimental results, we hypothesize that the NCB inhibits the enzyme via oxidation of the enzyme-bound NADH, which may be accessible through an open molecular gate, leaving the enzyme stalled in a configuration with oxidized cofactor, where the reaction intermediate can be neither converted nor released. Since the reaction mechanism of SAHase is quite uncommon, this kind of inhibition could be a viable pharmacological route, with a low risk of off-target effects. The NCB presented in this work could be used as a template for the development of more potent SAHase inhibitors.

Nicotinamide mononucleotide inhibits JNK activation to reverse Alzheimer disease

Amyloid-β (Aβ) oligomers have been accepted as major neurotoxic agents in the therapy of Alzheimer’s disease (AD). It has been shown that the activity of nicotinamide adenine dinucleotide (NAD+) is related with the decline of Aβ toxicity in AD. Nicotinamide mononucleotide (NMN), the important precursor of NAD+, is produced during the reaction of nicotinamide phosphoribosyl transferase (Nampt). This study aimed to figure out the potential therapeutic effects of NMN and its underlying mechanisms in APPswe/PS1dE9 (AD-Tg) mice. We found that NMN gave rise to a substantial improvement in behavioral measures of cognitive impairments compared to control AD-Tg mice. In addition, NMN treatment significantly decreased β-amyloid production, amyloid plaque burden, synaptic loss, and inflammatory responses in transgenic animals. Mechanistically, NMN effectively controlled JNK activation. Furthermore, NMN potently progressed nonamyloidogenic amyloid precursor protein (APP) and suppressed amyloidogenic APP by mediating the expression of APP cleavage secretase in AD-Tg mice. Based on our findings, it was suggested that NMN substantially decreases multiple AD-associated pathological characteristically at least partially by the inhibition of JNK activation.

Oxidant and antioxidant status in Saccharomyces cerevisiae exposed to antifungal ketoconazole

Abstract In this study, production of intracellular reactive oxygen species (ROS) and nitric oxide (NO ),the activities of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, superoxide dismutase (SOD) and catalase (CAT) and levels of membrane lipid peroxidation (LPO) in ketoconazole-treated Saccharomyces cerevisiae were investigated in a dose- and time-dependent manner. Hydrogen peroxide, total ROS and hydroxyl radical levels in 150–250 μM ketoconazole-treated cells were increased with increasing concentrations, which reached 4.30, 4.24 and 2.41 times their controls, respectively. Superoxide anion and NO radical levels increased dose-dependently up to the fourth hour and then dropped under the controls at 150–225 μM, while decreasing continuously at 250 μM. The highest levels were 2.23 and 3.43 times their controls, respectively. While NADH-NADPH oxidases and SOD activities increased with increasing time at 150–225 μM, extremely induced initial activities decreased throughout incubation at 250 μM. CAT activities were increased dose- and time-dependently up to the fourth hour and the activity reached 3.57 times the control. The highest LPO level was 2.28 times the control at 250 μM, because of the oxidative stress. The results showed that although the antioxidant system was effectively triggered, it couldn’t prevent S. cerevisiae from ketoconazole-induced oxidative stress.

Gypenosides attenuate cholesterol-induced DNA damage by inhibiting the production of reactive oxygen species in human umbilical vein endothelial cells.

Previous studies have demonstrated that DNA damage induces atherosclerosis and that oxidative stress has an important role in DNA damage. Gypenosides (Gps), the main ingredient of Gynostemma Pentaphylla (Thunb.) Makino, have been recognized as specific antioxidants and have previously been reported to inhibit high‑fat diet‑induced atherosclerosis in rats. However, whether or not Gps attenuate DNA damage through their antioxidant effects remains to be elucidated. The current study was performed to clarify whether or not Gps can inhibit cholesterol‑induced DNA damage through antioxidation. The present study provided new insights into the pharmacological effects of Gps on atherosclerosis. HUVECs were treated with Gps at various concentrations (1, 10 and 100 µg/ml) for 1 h. The protective effects of Gps on cholesterol‑induced DNA damage were determined using immunofluorescence, western blotting, reverse‑transcription quantitative polymerase chain reaction and flow cytometry. Pretreatment with Gps (1, 10 and 100 µg/ml) effectively attenuated cholesterol‑induced DNA damage in HUVECs by inhibiting phosphorylation of H2AX, a member of the histone family. Furthermore, Gps (100 µg/ml) pretreatment inhibited cholesterol‑induced transcription and activity of nicotinamide adenine dinucleotide phosphate‑oxidase 4 and reduced intracellular ROS levels. In conclusion, Gps attenuated cholesterol‑induced DNA damage by inhibiting ROS production in HUVECs, suggesting that the inhibitory effect of Gps on atherogenesis is correlated with the alleviation of DNA damage.

Ethanol increases matrix metalloproteinase-12 expression via NADPH oxidase-dependent ROS production in macrophages

Matrix metalloproteinase-12 (MMP-12), an enzyme responsible for degradation of extracellular matrix, plays an important role in the progression of various diseases, including inflammation and fibrosis. Although most of those are pathogenic conditions induced by ethanol ingestion, the effect of ethanol on MMP-12 has not been explored. In the present study, we investigated the effect of ethanol on MMP-12 expression and its potential mechanisms in macrophages. Here, we demonstrated that ethanol treatment increased MMP-12 expression in primary murine peritoneal macrophages and RAW 264.7 macrophages at both mRNA and protein levels. Ethanol treatment also significantly increased the activity of nicotinamide adenine dinucleotide (NADPH) oxidase and the expression of NADPH oxidase-2 (Nox2). Pretreatment with an anti-oxidant (N-acetyl cysteine) or a selective inhibitor of NADPH oxidase (diphenyleneiodonium chloride (DPI)) prevented ethanol-induced MMP-12 expression. Furthermore, knockdown of Nox2 by small interfering RNA (siRNA) prevented ethanol-induced ROS production and MMP-12 expression in RAW 264.7 macrophages, indicating a critical role for Nox2 in ethanol-induced intracellular ROS production and MMP-12 expression in macrophages. We also showed that ethanol-induced Nox2 expression was suppressed by transient transfection with dominant negative IκB-α plasmid or pretreatment with Bay 11-7082, a selective inhibitor of NF-κB, in RAW 264.7 macrophages. In addition, ethanol-induced Nox2 expression was also attenuated by treatment with a selective inhibitor of p38 MAPK, suggesting involvement of p38 MAPK/NF-κB pathway in ethanol-induced Nox2 expression. Taken together, these results demonstrate that ethanol treatment elicited increase in MMP-12 expression via increase in ROS production derived from Nox2 in macrophages.

Electrophilic and Reactive Oxygen Species Detoxification Potentials of Chalcone Dimers is Mediated by Redox Transcription Factor Nrf‐2

Nuclear erythroid related factor-2 (Nrf2), a redox-transcription factor, plays a critical role in the detoxification of electrophilic and reactive oxygen species that halt various biochemical and molecular processes. This makes it a candidate for regulation by polyphenols. This study investigates the capability of chalcone dimers (lophirones B and C) to induce expressions and activities of cytoprotective enzymes. Chalcone dimers administration to rats not only induced the Nrf2, but also suppressed cytoplasmic Kelch-like ECH-associated protein 1 (Keap1) expressions. In addition, the chalcone dimers significantly (p < 0.05) increased the expressions and activities of nicotinamide adenine dinucleotide and reduced quinone oxidoreductase-1, glutathione-S-transferase, epoxide hydrolase and uridyl glucuronosyl transferase in rat liver. Also, activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in rat liver increased significantly (p < 0.05). Overall, lophirones B and C increased the expressions and activities of cytoprotective proteins in rat liver possibly through the reduction of cytoplasmic Keap1 expression, leading to the nuclear translocation of Nrf2.

Metabolic changes in the lymphocytes during influenza

Aim. To assess the nature and intensity of metabolic processes in lymphocytes of patients with influenza according to the activity of intracellular enzymes in comparison to the severity of the disease. Methods. Determined were the enzymatic parameters of lymphocytes of 45 patients aged 18 to 42 years with a diagnosis of «influenza». Two groups of patients were formed: with moderate (24 patients) and severe (21 patients) course of the disease. Used as controls were the values the activity of intracellular enzymes of lymphocytes of 37 practically healthy individuals of comparable age. Results. In patients with a moderately severe course of the influenza compared with the controls noted was a significant increase in activity of glucose-6-phosphate dehydrogenase (3.17±0.53 and 2.74±0.31 mkE/10 000 cells, p 0.05) and glycerol-3-phosphate dehydrogenase (57.33±±5.65 and 0.84±0.16 mkE/10 000 cells respectively, p 0.001). The activity of lactate dehydrogenase was lower in patients than in controls (0.40±0.08 and 0.84±0.08 mkE/10 000 cells respectively, p 0.001). Indicators of nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate dependant isocitrate dehydrogenases in lymphocytes of patients were lower than in the controls: the first indicator in the patients was 0.17±0.02 mkE/10 000 cells, in controls - 1.95±0.25 mkE/10 000 cells (p 0.001), and for the second indicator these values were respectively 0.09±0.01 and 31.02±±2.20 mkE/10 000 cells (p 0.001). In patients with a moderately severe course of influenza the activity of nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate dependant glutamate dehydrogenases was significantly higher compared with healthy individuals: 63.67±5.32 and 0.34±0.06 mkE/10 000 cells, 1.45±0.18 and 0.11±0.02 mkE/10 000 cells respectively (p 0.001). The activity of nicotinamide adenine dinucleotide dependant malate dehydrogenase in patients was equal to 86.46±12.30 mkE/10 000 cells (in the control group 84.16±13.70 mkE/10 000 cells), and the activity of nicotinamide adenine dinucleotide phosphate dependant malate dehydrogenase was equal to 1.34±±0.25 mkE/10 000 cells (in the control group 0.33±0.07 mkE/10 000 cells, p 0.001). The activity of glutathione reductase was also higher in patients with the moderately severe course of the influenza: 5.86±0.25 mkE/10 000 cells, while the value in healthy individuals was 1.28±0.30 mkE/10 000 cells (p 0.001). In the group of patients with a severe course of influenza the activity of almost all (except for glucose-6-phosphate dehydrogenase) enzymes was higher than during the moderately severe course of disease. Conclusion. At the peak of the diseases noted were opposite changes in the activity of reactions of the pentose phosphate cycle and glycolysis. With a high functional load on the cells there is a significant reduction in the intensity of the reactions of the initial phase of the tricarboxylic acid cycle, which reduces the energy efficiency of the cycle, while the intense influx of metabolites to supply the tricarboxylic acid cycle with substrates of the amino acid metabolism provides enhanced transport of amino acids into the lymphocytes.

Optical analysis of lactate dehydrogenase and glucose by CdTe quantum dots and their dual simultaneous detection

Biomolecules detection by size-controlled quantum dots (QDs) was promising in developing clinic diagnostic techniques. In this work, a novel bioanalytical platform was developed to detect the activity of nicotinamide adenine dinucleotide (NAD) dependent enzyme, lactate dehydrogenase (LDH), and the concentration of glucose by the changes of fluorescence intensities of the QDs based on the electron transfer between QDs and sensitive biomolecules. The fluorescence intensities of the QDs was firstly quenched by NAD and then intensified with increasing amounts of the LDH because of the consumption of the NAD by the biocatalyzed reaction. Also the glucose led to the decline of fluorescence due to the formation of hydrogen peroxide (H 2O 2) which was the product of the glucose reacting with the glucose oxidase (GOD). The linear calibration plots of the activity of LDH and glucose were obtained from 250 to 6000 U/L and 1.67 to 6.67 mM, respectively. The detection system was also successfully applied to detect LDH and glucose in human serum samples. This analysis process was very convenient and simple because the QDs need not to be modified by any organic or biological molecules before they were used into the system. Moreover, the established method had great potential in detection of the physiological level of some biomolecules in clinical diagnostics of various diseases.

Hungry for life

Hungry for life

Inhibition of the nicotinamide adenine dinucleotide-oxidoreductase reaction by herbicides and fungicides of various structures

The effect of herbicides (basagran, zenkor, kusagard, roundup, setoxidim, and lontrel and lontrel complexes with some doubly charged metal ions) and fungicides (tachigaren and tilt) on the activity of nicotinamide adenine dinucleotide (NADH)-oxidoreductase from the methylotroph Methylococcus capsulatus (strain M) was studied. All the herbicides and fungicides inhibit the enzyme, differing in the degree and type of inhibition. The inhibition constants K i for these compounds and for lontrel complexes were determined. A correlation between the K i values and the complexation constants of these pesticides with NADH was established. The studied compounds are toxic.

Deoxycorticosterone stimulates the activity of nicotinamide adenine dinucleotide phosphate-diaphorase/nitric oxide synthase immunoreactivity in hypothalamic nuclei of rats

Mineralocorticoids (MC) play an important role in development of salt appetite. Part of this effect involves the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, in which MC treatment increases arginine vasopressin (AVP) synthesis and release. Since the AVP system is also modulated by nitric oxide (NO), we studied if deoxycorticosterone acetate (DOCA) treatment changed the number of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) active neurons and neuronal NO synthase (nNOS)-immunoreactive (IR) cells in the PVN and SON. After four injections of DOCA (10 mg/rat per day), rats developed a salt appetite and increased NADPH-d active and nNOS-IR neurons in both nuclei. A single DOCA injection did not change salt consumption or nNOS-IR cells, but increased the number of NADPH-d positive neurons in the PVN only. Therefore, while acute MC treatment stimulated the activity of pre-existing enzyme, chronic steroid treatment recruited additional neurons showing nNOS immunoreactivity/NADPH-d activity. These data suggest a role for NO produced in the PVN and SON in DOCA stimulatory effects on AVP mRNA and salt appetite.

Looking for drug targets for the treatment of neurological disease — a focus on lipid and cholesterol pathways

Amyloid-β (Aβ) oligomers have been accepted as major neurotoxic agents in the therapy of Alzheimer’s disease (AD). It has been shown that the activity of nicotinamide adenine dinucleotide (NAD+) is related with the decline of Aβ toxicity in AD. Nicotinamide mononucleotide (NMN), the important precursor of NAD+, is produced during the reaction of nicotinamide phosphoribosyl transferase (Nampt). This study aimed to figure out the potential therapeutic effects of NMN and its underlying mechanisms in APPswe/PS1dE9 (AD-Tg) mice. We found that NMN gave rise to a substantial improvement in behavioral measures of cognitive impairments compared to control AD-Tg mice. In addition, NMN treatment significantly decreased β-amyloid production, amyloid plaque burden, synaptic loss, and inflammatory responses in transgenic animals. Mechanistically, NMN effectively controlled JNK activation. Furthermore, NMN potently progressed nonamyloidogenic amyloid precursor protein (APP) and suppressed amyloidogenic APP by mediating the expression of APP cleavage secretase in AD-Tg mice. Based on our findings, it was suggested that NMN substantially decreases multiple AD-associated pathological characteristically at least partially by the inhibition of JNK activation.

Increased NAD(P)H oxidase-mediated superoxide production in renovascular hypertension: Evidence for an involvement of protein kinase C

Angiotensin II infusion has been shown to cause hypertension and endothelial dysfunction and to increase superoxide (O-.2) production in vascular tissue, mainly via an activation of nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-dependent oxidase, the most significant O-.2 source in endothelial and/or smooth muscle cells. With these studies, we sought to determine whether endothelial dysfunction in renovascular hypertension is secondary to an activation of these oxidases. Endothelial function in aortas from rats with two kidney-one clip (2K-1C) hypertension and age-matched controls was assessed using isometric tension studies in organ chambers. Changes in vascular O-.2 production were measured using lucigenin-enhanced chemiluminescence and electron spin resonance spectroscopy. In hypertensive animals, relaxation to endothelium-dependent (acetylcholine) and endothelium-independent nitrovasodilators (nitroglycerin) was impaired. Constriction to a direct activator of protein kinase C (PKC) phorbol ester 12,13 dibutyrate (PDBu) was enhanced, and vascular O-.2 was significantly increased compared with controls. Vascular O-.2 was normalized by the PKC inhibitor calphostin C, by the inhibitor of flavin-dependent oxidases, diphenylene iodonium, and recombinant heparin-binding superoxide dismutase, whereas inhibitors of the xanthine oxidase (oxypurinol), nitric oxide synthase (NG-nitro-l-arginine) and mitochondrial NADH dehydrogenase (rotenone) were ineffective. Studies of vascular homogenates demonstrated that the major source of O-.2 was a NAD(P)H-dependent oxidase. Incubation of intact tissue with PDBu markedly increased O-. 2, the increase being significantly stronger in vessels from hypertensive animals as compared with vessels from controls. Endothelial dysfunction was improved by preincubation of vascular tissue with superoxide dismutase and calphostin C. We therefore conclude that renovascular hypertension in 2K-1C rats is associated with increased vascular O-.2 leading to impaired vasodilator responses to endogenous and exogenous nitrovasodilators. Increased vascular O-.2 is likely secondary to a PKC-mediated activation of a membrane-associated NAD(P)H-dependent oxidase.

Mitochondrial respiratory enzymes are a major target of iron toxicity in rat heart cells

Our previous studies in iron-loaded rat heart cells showed that in vitro iron loading results in peroxidative injury, manifested in a marked decrease in rate and amplitude of heart cell contractility and rhythmicity, which is correctable by treatment with deferoxamine (DF). In the present studies we explored the role of mitochondrial damage in myocardial iron toxicity. Iron loading by 24-hour incubation with 0.36 mmol/L ferric ammonium citrate resulted in a decrease in the activity of nicotinamide adenine dinucleotide (NADH)-cytochrome c oxidoreductase (complex I+III) to 35.3% ± 11.2% of the value in untreated controls; of succinate-cytochrome c oxidoreductase (complex II+III) to 57.4% ± 3.1%; and of succinate dehydrogenase to 63.5% ± 12.6% ( p < 0.001 in all cases). The decrease in activity of other mitochondrial enzymes, including NADH-ferricyanide reductase, succinate ubiquinone oxidoreductase (complex II), cytochrome c oxidase (complex IV), and ubiquinol cytochrome c oxidoreductase (complex III), was less impressive and ranged from 71.5% ± 15.8% to 91.5% ± 14.6% of controls. That the observed loss of respiratory enzyme activity was a specific effect of iron toxicity was clearly demonstrated by the complete restoration of enzyme activities by in vitro iron chelation therapy. Sequential treatment with iron and doxorubicin caused a loss of complex I+III and complex II+III activity that was greater than that seen with either agent alone but was only partially correctable by DF treatment. Alterations in cellular adenosine triphosphate measurements paralleled very closely the changes observed in respiratory complex activity. These findings demonstrate for the first time the impairment of cardiac mitochondrial respiratory enzyme activity caused by iron loading at conditions formerly shown to produce severe abnormalities in contractility and rhythmicity.