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BMC Nephrology Mar 2017Tolvaptan is a selective vasopressin receptor antagonist. Nitric Oxide (NO) promotes renal water and sodium excretion, but the effect is unknown in the nephron's... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Tolvaptan is a selective vasopressin receptor antagonist. Nitric Oxide (NO) promotes renal water and sodium excretion, but the effect is unknown in the nephron's principal cells. In a dose-response study, we measured the effect of tolvaptan on renal handling of water and sodium and systemic hemodynamics, during baseline and NO-inhibition with L-NMMA (L-NG-monomethyl-arginine).
METHODS
In a randomized, placebo-controlled, double blind, cross over study, 15 healthy subjects received tolvaptan 15, 30 and 45 mg or placebo. L-NMMA was given as a bolus followed by continuous infusion during 60 min. We measured urine output (UO), free water clearance (C), fractional excretion of sodium (FE), urinary aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma vasopressin (p-AVP) and central blood pressure (cBP).
RESULTS
During baseline, FE was unchanged. Tolvaptan decreased u-ENaC dose-dependently and increased p-AVP threefold, whereas u-AQP2 was unchanged. During tolvaptan with NO-inhibition, UO and C decreased dose-dependently. FE decreased dose-independently and u-ENaC remained unchanged. Central BP increased equally after all treatments.
CONCLUSIONS
During baseline, fractional excretion of sodium was unchanged. During tolvaptan with NO-inhibition, renal water excretion was reduced dose dependently, and renal sodium excretion was reduced unrelated to the dose, partly via an AVP dependent mechanism. Thus, tolvaptan antagonized the reduction in renal water and sodium excretion during NO-inhibition. Most likely, the lack of decrease in AQP2 excretion by tolvaptan could be attributed to a counteracting effect of the high level of p-AVP.
TRIAL REGISTRATION
Clinical Trial no: NCT02078973 . Registered 1 March 2014.
Topics: Adult; Benzazepines; Blood Pressure; Body Water; Cross-Over Studies; Dose-Response Relationship, Drug; Double-Blind Method; Glomerular Filtration Rate; Humans; Kidney; Nitric Oxide; Placebo Effect; Sodium; Tolvaptan; Water-Electrolyte Balance; omega-N-Methylarginine
PubMed: 28288570
DOI: 10.1186/s12882-017-0501-1 -
Diabetes & Vascular Disease Research May 2017RhoA/Rho-associated kinase and arginase are implicated in vascular complications in diabetes. This study investigated whether RhoA/Rho-associated kinase and arginase... (Comparative Study)
Comparative Study
AIM
RhoA/Rho-associated kinase and arginase are implicated in vascular complications in diabetes. This study investigated whether RhoA/Rho-associated kinase and arginase inhibition protect from myocardial ischaemia-reperfusion injury in type 1 diabetes and the mechanisms behind these effects.
METHODS
Rats with streptozotocin-induced type 1 diabetes and non-diabetic rats were subjected to 30 min myocardial ischaemia and 2 h reperfusion after being randomized to treatment with (1) saline, (2) RhoA/Rho-associated kinase inhibitor hydroxyfasudil, (3) nitric oxide synthase inhibitor N-monomethyl-l-arginine monoacetate followed by hydroxyfasudil, (4) arginase inhibitor N-omega-hydroxy-nor-l-arginine, (5) N-monomethyl-l-arginine monoacetate followed by N-omega-hydroxy-nor-l-arginine or (6) N-monomethyl-l-arginine monoacetate given intravenous before ischaemia.
RESULTS
Myocardial arginase activity, arginase 2 expression and RhoA/Rho-associated kinase activity were increased in type 1 diabetes ( p < 0.05). RhoA/Rho-associated kinase inhibition and arginase inhibition significantly reduced infarct size in diabetic and non-diabetic rats ( p < 0.001). The cardioprotective effects of hydroxyfasudil and N-omega-hydroxy-nor-l-arginine in diabetes were abolished by nitric oxide synthase inhibition. RhoA/Rho-associated kinase inhibition attenuated myocardial arginase activity in diabetic rats via a nitric oxide synthase-dependent mechanism.
CONCLUSION
Inhibition of either RhoA/Rho-associated kinase or arginase protects from ischaemia-reperfusion injury in rats with type 1 diabetes via a nitric oxide synthase-dependent pathway. These results suggest that inhibition of RhoA/Rho-associated kinase and arginase constitutes a potential therapeutic strategy to protect the diabetic heart against ischaemia-reperfusion injury.
Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Arginase; Arginine; Cytoprotection; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Drug Therapy, Combination; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide Synthase; Protein Kinase Inhibitors; Rats, Sprague-Dawley; Signal Transduction; omega-N-Methylarginine; rho GTP-Binding Proteins; rho-Associated Kinases
PubMed: 28183205
DOI: 10.1177/1479164116687935 -
Journal of Bacteriology Apr 2017Dimethylarginine dimethylaminohydrolases (DDAHs) catalyze the hydrolysis of methylarginines to yield l-citrulline and methylamines as products. DDAHs and their central...
Dimethylarginine dimethylaminohydrolases (DDAHs) catalyze the hydrolysis of methylarginines to yield l-citrulline and methylamines as products. DDAHs and their central roles in methylarginine metabolism have been characterized for eukaryotic cells. While DDAHs are known to exist in some bacteria, including and , the physiological importance and genetic regulation of bacterial DDAHs remain poorly understood. To provide some insight into bacterial methylarginine metabolism, this study focused on identifying the key elements or factors regulating DDAH expression in PAO1. First, results revealed that can utilize , -dimethyl-l-arginine (ADMA) as a sole source of nitrogen but not carbon. Second, expression of the gene was observed to be induced in the presence of methylarginines, including -monomethyl-l-arginine (l-NMMA) and ADMA. Third, induction of the gene was shown to be achieved through a mechanism consisting of the putative enhancer-binding protein PA1196 and the alternative sigma factor RpoN. Both PA1196 and RpoN were essential for the expression of the gene in response to methylarginines. On the basis of the results of this study, PA1196 was given the name DdaR, for imethylarginine imethylminohydrolase egulator. Interestingly, DdaR and its target gene are conserved only among strains, suggesting that this particular species has evolved to utilize methylarginines from its environment. Methylated arginine residues are common constituents of eukaryotic proteins. During proteolysis, methylarginines are released in their free forms and become accessible nutrients for bacteria to utilize as growth substrates. In order to have a clearer and better understanding of this process, we explored methylarginine utilization in the metabolically versatile bacterium PAO1. Our results show that the transcriptional regulator DdaR (PA1196) and the sigma factor RpoN positively regulate expression of dimethylarginine dimethylaminohydrolases (DDAHs) in response to exogenous methylarginines. DDAH is the central enzyme of methylarginine degradation, and its transcriptional regulation by DdaR-RpoN is expected to be conserved among strains.
Topics: Amidohydrolases; Arginine; Bacterial Proteins; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Pseudomonas aeruginosa; RNA Polymerase Sigma 54; omega-N-Methylarginine
PubMed: 28167521
DOI: 10.1128/JB.00001-17 -
Journal of the National Cancer Institute Jun 2017Metaplastic breast cancer is one of the most therapeutically challenging forms of breast cancer because of its highly heterogeneous and chemoresistant nature. We have...
BACKGROUND
Metaplastic breast cancer is one of the most therapeutically challenging forms of breast cancer because of its highly heterogeneous and chemoresistant nature. We have previously demonstrated that ribosomal protein L39 (RPL39) and its gain-of-function mutation A14V have oncogenic activity in triple-negative breast cancer and this activity may be mediated through inducible nitric oxide synthase (iNOS). The function of RPL39 and A14V in other breast cancer subtypes is currently unknown. The objective of this study was to determine the role and mechanism of action of RPL39 in metaplastic breast cancer.
METHODS
Both competitive allele-specific and droplet digital polymerase chain reaction were used to determine the RPL39 A14V mutation rate in metaplastic breast cancer patient samples. The impact of RPL39 and iNOS expression on patient overall survival was estimated using the Kaplan-Meier method. Co-immunoprecipitation and immunoblot analyses were used for mechanistic evaluation of RPL39.
RESULTS
The RPL39 A14V mutation rate was 97.5% (39/40 tumor samples). High RPL39 (hazard ratio = 0.71, 95% confidence interval = 0.55 to 0.91, P = 006) and iNOS expression (P = 003) were associated with reduced patient overall survival. iNOS inhibition with the pan-NOS inhibitor N-methyl-L-arginine acetate decreased in vitro proliferation and migration, in vivo tumor growth in both BCM-4664 and BCM-3807 patient-derived xenograft models (P = 04 and P = 02, respectively), and in vitro and in vivo chemoresistance. Mechanistically, RPL39 mediated its cancer-promoting actions through iNOS signaling, which was driven by the RNA editing enzyme adenosine deaminase acting on RNA 1.
CONCLUSION
NOS inhibitors and RNA editing modulators may offer novel treatment options for metaplastic breast cancer.
Topics: Adenosine Deaminase; Animals; Cell Line, Tumor; Cell Movement; Cell Proliferation; Down-Regulation; Enzyme Inhibitors; Female; Humans; Kaplan-Meier Estimate; Metaplasia; Mice; Mutation Rate; Neoplasm Transplantation; Nitrates; Nitric Oxide Synthase Type II; Nitrites; RNA, Small Interfering; RNA-Binding Proteins; Ribosomal Proteins; STAT3 Transcription Factor; Signal Transduction; Survival Rate; Triple Negative Breast Neoplasms; Ubiquitin C; omega-N-Methylarginine
PubMed: 28040796
DOI: 10.1093/jnci/djw292 -
Scientific Reports Dec 2016IFN alfacon-1 (Infergen) is a synthetic form of Interferon (IFN)-α2b. Infergen has immunomodulatory activity and is effective against hepatitis C virus. However, the...
IFN alfacon-1 (Infergen) is a synthetic form of Interferon (IFN)-α2b. Infergen has immunomodulatory activity and is effective against hepatitis C virus. However, the effect of Infergen (IFG) on Mycobacterium tuberculosis (Mtb) has not yet been reported. Therefore, for the first time, we have studied the influence of IFG in constraining the survival of Mtb in human macrophages. We observed that IFG significantly enhanced the maturation and activation of macrophages. Further, it substantially augmented the secretion of IL-6, nitric oxide (NO) and antigen uptake. Moreover, macrophages exhibited remarkably higher bactericidal activity, as evidenced by reduction in the Mtb growth. Infergen-mediated mechanism was different from the type-1 interferons; since it worked through the activation of NF-κB, phosphorylation of STAT-3 and Akt-PI3K that improved the bactericidal activity through autophagy and NO release. In future, IFG immunotherapy can be a novel strategy for treating patients and controlling TB.
Topics: Autophagy; B7-1 Antigen; B7-2 Antigen; Cell Line; Cell Proliferation; Cytokines; HLA-DR Antigens; Humans; Interferon-alpha; Interleukin-6; Leukocytes, Mononuclear; Macrophages; Microscopy, Confocal; Mycobacterium tuberculosis; Nitric Oxide; Nitric Oxide Synthase Type II; Phosphorylation; Recombinant Proteins; T-Lymphocytes; THP-1 Cells; Tuberculosis; omega-N-Methylarginine
PubMed: 28000752
DOI: 10.1038/srep39492 -
Scientific Reports Aug 2016This study was conducted to investigate the effects of oxytocin (OT) on visceral hypersensitivity/pain and mast cell degranulation and the underlying mechanisms. We...
This study was conducted to investigate the effects of oxytocin (OT) on visceral hypersensitivity/pain and mast cell degranulation and the underlying mechanisms. We found that oxytocin receptor (OTR) was expressed in colonic mast cells in humans and rats, as well as in human mast cell line-1 (HMC-1), rat basophilic leukemia cell line (RBL-2H3) and mouse mastocytoma cell line (P815). OT decreased 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced visceral hypersensitivity, colonic mast cell degranulation and histamine release after mast cell degranulation in rats. Also, OT attenuated the compound 48/80 (C48/80)-evoked histamine release in P815 cells and inward currents, responsible for the mast cell degranulation, in HMC-1, RBL-2H3 and P815 cells. Moreover, these protective effects of OT against visceral hypersensitivity and mast cell degranulation were eliminated by coadministration of OTR antagonist atosiban or a nonselective inhibitor of nitric oxide synthase (NOS), NG-Methyl-L-arginine acetate salt (L-NMMA). Notably, OT evoked a concentration-dependent increase of intracellular Ca(2+) in HMC-1, RBL-2H3 and P815 cells, which was responsible for the activation of neuronal NOS (NOS1) and endothelial NOS (NOS3). Our findings strongly suggest that OT might exert the antinociception on colonic hypersensitivity through inhibition of mast cell degranulation via Ca(2+)-NOS pathway.
Topics: Analgesics; Animals; Calcium; Cell Degranulation; Cell Line; Colitis; Colon; Evoked Potentials; Histamine Release; Humans; Male; Mast Cells; Microscopy, Confocal; Nitric Oxide Synthase; Oxytocin; Patch-Clamp Techniques; Rats; Rats, Wistar; Receptors, Oxytocin; Signal Transduction; Trinitrobenzenesulfonic Acid; Vasotocin; omega-N-Methylarginine
PubMed: 27538454
DOI: 10.1038/srep31452 -
Circulation. Arrhythmia and... Aug 2016Syncope is a sudden transient loss of consciousness and postural tone with spontaneous recovery; the most common form is vasovagal syncope (VVS). During VVS,...
BACKGROUND
Syncope is a sudden transient loss of consciousness and postural tone with spontaneous recovery; the most common form is vasovagal syncope (VVS). During VVS, gravitational pooling excessively reduces central blood volume and cardiac output. In VVS, as in hemorrhage, impaired adrenergic vasoconstriction and venoconstriction result in hypotension. We hypothesized that impaired adrenergic responsiveness because of excess nitric oxide can be reversed by reducing nitric oxide.
METHODS AND RESULTS
We recorded cardiopulmonary dynamics in supine syncope patients and healthy volunteers (aged 15-27 years) challenged with a dose-response using the α1-agonist phenylephrine (PE), with and without the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine, monoacetate salt (L-NMMA). Systolic and diastolic pressures among control and VVS were the same, although they increased after L-NMMA and saline+PE (volume and pressor control for L-NMMA). Heart rate was significantly reduced by L-NMMA (P<0.05) for control and VVS compared with baseline, but there was no significant difference in heart rate between L-NMMA and saline+PE. Cardiac output and splanchnic blood flow were reduced by L-NMMA for control and VVS (P<0.05) compared with baseline, while total peripheral resistance increased (P<0.05). PE dose-response for splanchnic flow and resistance were blunted for VVS compared with control after saline+PE, but enhanced after L-NMMA (P<0.001). Postsynaptic α1-adrenergic vasoconstrictive impairment was greatest in the splanchnic vasculature, and splanchnic blood flow was unaffected by PE. Forearm and calf α1-adrenergic vasoconstriction were unimpaired in VVS and unaffected by L-NMMA.
CONCLUSIONS
Impaired postsynaptic α1-adrenergic vasoconstriction in young adults with VVS can be corrected by nitric oxide synthase inhibition, demonstrated with our use of L-NMMA.
Topics: Adolescent; Adult; Cardiac Output; Enzyme Inhibitors; Female; Heart Rate; Humans; Male; Nitric Oxide Synthase; Phenylephrine; Splanchnic Circulation; Syncope, Vasovagal; Treatment Outcome; Vascular Resistance; Vasoconstriction; omega-N-Methylarginine
PubMed: 27444639
DOI: 10.1161/CIRCEP.115.003828 -
Cardiovascular Diabetology May 2016Impaired vasoreactivity is often observed in subjects with metabolic syndrome, a condition that includes the presence of a specific cluster of risk factors for obesity...
BACKGROUND
Impaired vasoreactivity is often observed in subjects with metabolic syndrome, a condition that includes the presence of a specific cluster of risk factors for obesity and cardiovascular disease. However, hierarchical causes in the impaired vasoreactivity have not been clarified. We evaluated the impact of individual metabolic risk components or its clustering under the condition of insulin resistance on endothelial and smooth muscle cell function.
METHODS
Vascular reactivity to acetylcholine (Ach), with or without nitric oxide synthase (NOS) inhibitor N (G)-monomethyl-L-arginine (L-NMMA), or sodium nitroprusside (SNP) by forearm venous occlusion plethysmography and insulin sensitivity index (M mg/kg/min) in euglycemic clamp were measured in men without (n = 18, control group) or with (n = 19, metabolic syndrome group) metabolic syndrome.
RESULTS
(1) Ach-induced maximal forearm blood flow (maxFBF) was impaired in subjects with metabolic syndrome. In particular, the NOS-dependent component of Ach-induced maxFBF was selectively decreased, while the NOS-independent component remained relatively unchanged. (2) Ach-induced maxFBF and ∆Ach-induced maxFBF with L-NMMA were correlated with waist circumference, glucose, and triglycerides, and most strongly correlated with visceral fat area, adiponectin, and M. (3) Multivariate regression analysis indicated that individual metabolic risk components explained Ach-induced maxFBF by 4-21 %. Clustering of all metabolic risk components increased this to 35 %, and the presence of metabolic syndrome explained 30 %, indicating that defining metabolic syndrome can effectively predict impairment of endothelial dysfunction.
CONCLUSIONS
Endothelial dysfunction was correlated with individual metabolic risk components, but more strongly with clustering of the components under a condition with low insulin sensitivity. We suggest that in subjects with metabolic syndrome, endothelial function is impaired by multiple cardiovascular risk factors exclusively when under the condition of insulin insensitivity and also that defining metabolic syndrome can effectively predict impairment of endothelial dysfunction.
Topics: Acetylcholine; Adult; Aged; Cardiovascular Diseases; Endothelium, Vascular; Forearm; Humans; Male; Middle Aged; Myocytes, Smooth Muscle; Nitroprusside; Obesity; Regional Blood Flow; Risk Factors; Vasodilation; Vasodilator Agents; omega-N-Methylarginine
PubMed: 27188597
DOI: 10.1186/s12933-016-0394-5 -
American Journal of Physiology. Heart... Jun 2016Nitric oxide (NO) at different concentrations may promote or inhibit tumor growth and metastasis under various conditions. To test the hypothesis that tumor cells prefer...
Nitric oxide (NO) at different concentrations may promote or inhibit tumor growth and metastasis under various conditions. To test the hypothesis that tumor cells prefer to adhere to the locations with a higher endothelial NO production in intact microvessels under physiological flows and to further test that inhibiting NO production decreases tumor cell adhesion, we used intravital fluorescence microscopy to measure NO production and tumor cell adhesion in postcapillary venules of rat mesentery under normal and reduced flow conditions, and in the presence of an endothelial nitric oxide synthase (eNOS) inhibitor, N(G)-monomethyl-l-arginine (l-NMMA). Rats (SD, 250-300 g) were anesthetized. A midline incision (∼2 inch) was made in the abdominal wall, and the mesentery was taken out from the abdominal cavity and spread over a coverslip for the measurement. An individual postcapillary venule (35-50 μm) was first loaded with 4,5-diaminofluorescein diacetate (DAF-2 DA), a fluorescent indictor for NO. Then the DAF-2 intensity was measured for 30 min under a normal or reduced flow velocity, with and without perfusion with MDA-MB-231 breast cancer cells, and in the presence of l-NMMA. We found that tumor cells prefer to adhere to the microvessel locations with a higher NO production such as curved portions. Inhibition of eNOS by l-NMMA attenuated the flow-induced NO production and reduced tumor cell adhesion. We also found that l-NMMA treatment for ∼40 min reduced microvessel permeability to albumin. Our results suggest that inhibition of eNOS is a good approach to preventing tumor cell adhesion to intact microvessels under physiological flows.
Topics: Animals; Breast Neoplasms; Cell Adhesion; Cell Line, Tumor; Enzyme Inhibitors; Female; Humans; Mesentery; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; omega-N-Methylarginine
PubMed: 27059076
DOI: 10.1152/ajpheart.00109.2016 -
Nitric Oxide : Biology and Chemistry Apr 2016Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases that limits nitric oxide bioavailability and can increase production of NOS... (Review)
Review
Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases that limits nitric oxide bioavailability and can increase production of NOS derived reactive oxidative species. Increased plasma ADMA is a one of the strongest predictors of mortality in patients who have had a myocardial infarction or suffer from chronic left heart failure, and is also an independent risk factor for several other conditions that contribute to heart failure development, including hypertension, coronary artery disease/atherosclerosis, diabetes, and renal dysfunction. The enzyme responsible for ADMA degradation is dimethylarginine dimethylaminohydrolase-1 (DDAH1). DDAH1 plays an important role in maintaining nitric oxide bioavailability and preserving cardiovascular function in the failing heart. Here, we examine mechanisms of abnormal NO production in heart failure, with particular focus on the role of ADMA and DDAH1.
Topics: Amidohydrolases; Animals; Arginine; Heart Failure; Humans; Nitric Oxide; Nitric Oxide Synthase; Peroxynitrous Acid; Signal Transduction; Superoxides; omega-N-Methylarginine
PubMed: 26923818
DOI: 10.1016/j.niox.2016.02.006