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Redox Biology Sep 2019L-N-Nitro arginine methyl ester (L-NAME) has been widely applied for several decades in both basic and clinical research as an antagonist of nitric oxide synthase (NOS)....
L-N-Nitro arginine methyl ester (L-NAME) has been widely applied for several decades in both basic and clinical research as an antagonist of nitric oxide synthase (NOS). Herein, we show that L-NAME slowly releases NO from its guanidino nitro group. Daily pretreatment of rats with L-NAME potentiated mesenteric vasodilation induced by nitrodilators such as nitroglycerin, but not by NO. Release of NO also occurred with the NOS-inactive enantiomer D-NAME, but not with L-arginine or another NOS inhibitor L-NMMA, consistent with the presence or absence of a nitro group in their structure and their nitrodilator-potentiating effects. Metabolic conversion of the nitro group to NO-related breakdown products was confirmed using isotopically-labeled L-NAME. Consistent with Fenton chemistry, transition metals and reactive oxygen species accelerated the release of NO from L-NAME. Both NO production from L-NAME and its nitrodilator-potentiating effects were augmented under inflammation. NO release by L-NAME can confound its intended NOS-inhibiting effects, possibly by contributing to a putative intracellular NO store in the vasculature.
Topics: Animals; Arginine; Enzyme Inhibitors; Female; Mesenteric Arteries; Mice; Myography; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroglycerin; RAW 264.7 Cells; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Sheep; Stereoisomerism; Vasodilation; Vasodilator Agents; omega-N-Methylarginine
PubMed: 31200239
DOI: 10.1016/j.redox.2019.101238 -
Microcirculation (New York, N.Y. : 1994) Apr 2020The aim of this study was to investigate whether the effects on local blood flow and metabolic changes observed in the skin after an endogenous systemic increase in... (Clinical Trial)
Clinical Trial
OBJECTIVE
The aim of this study was to investigate whether the effects on local blood flow and metabolic changes observed in the skin after an endogenous systemic increase in insulin are mediated by the endothelial nitric oxide pathway, by administering the nitric oxide synthase inhibitor N -monomethyl l-arginine using microdialysis.
METHODS
Microdialysis catheters, perfused with N -monomethyl l-arginine and with a control solution, were inserted intracutaneously in 12 human subjects, who received an oral glucose load to induce a systemic hyperinsulinemia. During microdialysis, the local blood flow was measured by urea clearance and by laser speckle contrast imaging, and glucose metabolites were measured.
RESULTS
After oral glucose intake, microvascular blood flow and glucose metabolism were both significantly suppressed in the N -monomethyl l-arginine catheter compared to the control catheter (urea clearance: P < .006, glucose dialysate concentration: P < .035). No significant effect of N -monomethyl l-arginine on microvascular blood flow was observed with laser speckle contrast imaging (P = .81).
CONCLUSION
Local delivery of N -monomethyl l-arginine to the skin by microdialysis reduces microvascular blood flow and glucose delivery in the skin after oral glucose intake, presumably by decreasing local insulin-mediated vasodilation.
Topics: Adult; Blood Flow Velocity; Blood Glucose; Female; Glucose Tolerance Test; Humans; Male; Microcirculation; Microdialysis; Regional Blood Flow; omega-N-Methylarginine
PubMed: 31628700
DOI: 10.1111/micc.12597 -
Clinical Physiology and Functional... Jul 2021Flow-mediated vasodilatation (FMD) has become one of the most widely assessed parameters to analyse endothelial and vascular function in cardiovascular medicine. The... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Flow-mediated vasodilatation (FMD) has become one of the most widely assessed parameters to analyse endothelial and vascular function in cardiovascular medicine. The degree of contribution of nitric oxide (NO) to FMD is inconclusive and varies widely depending on the device used. In this study, we used a semi-automatic ultrasound device to analyse to what extent basal NO activity contributes to FMD of the brachial artery.
METHODS
FMD was assessed with the UNEX EF device in a cross-over single blinded randomized study at baseline and then during infusion of either a NO-synthase-inhibitor (NG-monomethyl-L-arginine (L-NMMA)) or saline. The analysis was repeated after 1 week with the alternative infusion of L-NMMA or saline. All measurements were analysed both automatically and by a technician manually.
RESULTS
In total, 25 healthy men subjects completed the study. Diastolic blood pressure and heart rate significantly changed during infusion of L-NMMA. Infusion of L-NMMA reduced FMD significantly (-37%, p = 0.002). Saline solution had no effect on FMD (+14%, p = 0.392). Change in FMD was significantly different between the groups (ΔFMD vs. ΔFMD , p = 0.032). There was a statistically significant correlation between automatically analysed results and those obtained by an experienced technician (FMD : r = 0.822, p < 0.001; FMD : r = 0.645, p = 0.007).
CONCLUSION
The influence of NO on FMD is approximately 40% if assessed using the UNEX EF. Prior to use FMD as a marker of endothelial dysfunction, we should explore different methods including various duration of forearm ischaemia to increase NO dependency of FMD.
Topics: Brachial Artery; Humans; Male; Nitric Oxide; Regional Blood Flow; Vasodilation; omega-N-Methylarginine
PubMed: 33621423
DOI: 10.1111/cpf.12696 -
Behavioural Brain Research Mar 2022Nitric oxide (NO)-dependent pathways may play a significant role in the decline of synaptic and cognitive functions in Alzheimer's disease (AD). However, whether NO in...
Nitric oxide impairs spatial learning and memory in a rat model of Alzheimer's disease via disturbance of glutamate response in the hippocampal dentate gyrus during spatial learning.
Nitric oxide (NO)-dependent pathways may play a significant role in the decline of synaptic and cognitive functions in Alzheimer's disease (AD). However, whether NO in the hippocampal dentate gyrus (DG) is involved in the spatial learning and memory impairments of AD by affecting the glutamate (Glu) response during these processes is not well-understood. Here, we prepared an AD rat model by long-term i.p. of D-galactose into ovariectomized rats, and then the effects of L-NMMA (a NO synthase inhibitor) on Glu concentration and amplitude of field excitatory postsynaptic potential (fEPSP) were measured in the DG region during the Morris water maze (MWM) test in freely-moving rats. During the MWM test, compared with the sham group, the escape latency was increased in the place navigation trial, and the percentage of time spent in target quadrant and the number of platform crossings were decreased in the spatial probe trial, in addition, the increase of fEPSP amplitude in the DG was significantly attenuated in AD group rats. L-NMMA significantly attenuated the spatial learning and memory impairment in AD rats, and reversed the inhibitory effect of AD on increase of fEPSP amplitude in the DG during the MWM test. In sham group rats, the Glu level in the DG increased significantly during the MWM test, and this response was markedly enhanced in AD rats. Furthermore, the response of Glu in the DG during spatial learning was recovered by microinjection of L-NMMA into the DG. Our results suggest that NO in the DG impairs spatial learning and memory and related synaptic plasticity in AD rats, by disturbing the Glu response during spatial learning.
Topics: Alzheimer Disease; Animals; Behavior, Animal; Dentate Gyrus; Disease Models, Animal; Enzyme Inhibitors; Excitatory Postsynaptic Potentials; Female; Glutamic Acid; Maze Learning; Nitric Oxide; Nitric Oxide Synthase; Ovariectomy; Rats; Rats, Sprague-Dawley; omega-N-Methylarginine
PubMed: 35033612
DOI: 10.1016/j.bbr.2022.113750 -
Clinical Hemorheology and... 2022Exercise-induced impairment of blood fluidity is considered to be associated with thrombosis development. However, the effects of L-arginine on blood fluidity after...
BACKGROUND
Exercise-induced impairment of blood fluidity is considered to be associated with thrombosis development. However, the effects of L-arginine on blood fluidity after exercise remain unclear.
OBJECTIVE
We investigated the mechanisms of impaired blood fluidity after high-intensity exercise, and examined whether L-arginine improves exercise-induced blood fluidity impairment in vitro.
METHODS
Ten healthy male participants performed 15 minutes of ergometer exercise at 70% of their peak oxygen uptake levels. Blood samples were obtained before and after exercise. L-arginine and NG-monomethyl-L-arginine acetate (L-NMMA)-a nitric oxide (NO) synthase inhibitor-were added to the post-exercise blood samples. Using Kikuchi's microchannel method, we measured the blood passage time, percentage of obstructed microchannels, and the number of adherent white blood cells (WBCs) on the microchannel terrace.
RESULTS
Exercise increased the hematocrit levels. The blood passage times, percentage of obstructed microchannels, and the number of adherent WBCs on the microchannel terrace increased after exercise; however, they decreased in a dose-dependent manner after the addition of L-arginine. L-NMMA inhibited the L-arginine-induced decrease in blood passage time.
CONCLUSIONS
High-intensity exercise impairs blood fluidity by inducing hemoconcentration along with increasing platelet aggregation and WBC adhesion. The L-arginine-NO pathway improves blood fluidity impairment after high-intensity exercise in vitro.
Topics: Humans; Male; omega-N-Methylarginine; Nitric Oxide; Arginine; Exercise; Leukocytes; Platelet Aggregation
PubMed: 35599472
DOI: 10.3233/CH-211201 -
Tissue & Cell Dec 2021Puerarin regulates the osteoblast differentiation of umbilical cord mesenchymal stem cells. This study, hereby, explored the effects of puerarin on the osteogenic...
Puerarin regulates the osteoblast differentiation of umbilical cord mesenchymal stem cells. This study, hereby, explored the effects of puerarin on the osteogenic differentiation of dental follicle cells (DFCs) for the first time. Rat DFCs (rDFCs) were isolated and identified. After the rDFCs were treated by Puerarin and cultured in osteogenic induction medium, the viability, osteogenic differentiation, and the activities of alkaline phosphatase (ALP) and nitric oxide (NO) were detected. Besides, the secretion of cyclic guanosine monophosphate (cGMP) and expressions of collagen I, osteocalcin (OC), osteopontin (OPN), runt-related transcription factor 2 (RUNX2), soluble guanylate cyclase (SGC), and protein kinase G 1 (PKG-1) were further determined or quantified. Puerarin enhanced the viability and osteogenic differentiation, and increased the activities of ALP, NO, and cGMP and the expressions of Collagen I, OC, OPN, RUNX2, SGC, and PKG-1 in rDFCs. After the co-treatment with puerarin and L-NMMA (NO synthase inhibitor), the promotive effects of Puerarin on cell viability, osteogenic differentiation, and the expressions of collagen I, OC, OPN, RUNX2, SGC, and PKG-1 in rDFCs were reversed by L-NMMA. Puerarin boosted the osteogenic differentiation of rDFCs by activating the NO pathway.
Topics: Alkaline Phosphatase; Animals; Animals, Newborn; Cell Differentiation; Cell Survival; Cells, Cultured; Collagen Type I; Core Binding Factor Alpha 1 Subunit; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Dental Sac; Guanylate Cyclase; Isoflavones; Nitric Oxide; Osteocalcin; Osteogenesis; Osteopontin; Rats, Sprague-Dawley; Solubility; omega-N-Methylarginine; Rats
PubMed: 34371290
DOI: 10.1016/j.tice.2021.101601 -
American Journal of Physiology.... Dec 2023Animal data indicate that insulin triggers a robust nitric oxide synthase (NOS)-mediated dilation in cerebral arteries similar to the peripheral tissue vasodilation...
Animal data indicate that insulin triggers a robust nitric oxide synthase (NOS)-mediated dilation in cerebral arteries similar to the peripheral tissue vasodilation observed in healthy adults. Insulin's role in regulating cerebral blood flow (CBF) in humans remains unclear but may be important for understanding the links between insulin resistance, diminished CBF, and poor brain health outcomes. We tested the hypothesis that an oral glucose challenge (oral glucose tolerance test, OGTT), which increases systemic insulin and glucose, would acutely increase CBF in healthy adults due to NOS-mediated vasodilation, and that changes in CBF would be greater in anterior regions where NOS expression or activity may be greater. In a randomized, single-blind approach, 18 young healthy adults (24 ± 5 yr) underwent magnetic resonance imaging (MRI) with a placebo before and after an OGTT (75 g glucose), and 11 of these adults also completed an -monomethyl-l-arginine (l-NMMA) visit. Four-dimensional (4-D) flow MRI quantified macrovascular CBF and arterial spin labeling (ASL) quantified microvascular perfusion. Subjects completed baseline imaging with a placebo (or l-NMMA), then consumed an OGTT followed by MRI scans and blood sampling every 10-15 min for 90 min. Contrary to our hypothesis, total CBF ( = 0.17) and global perfusion ( > 0.05) did not change at any time point up to 60 min after the OGTT, and no regional changes were detected. l-NMMA did not mediate any effect of OGTT on CBF. These data suggest that insulin-glucose challenge does not acutely alter CBF in healthy adults.
Topics: Adult; Animals; Humans; omega-N-Methylarginine; Glucose Tolerance Test; Enzyme Inhibitors; Single-Blind Method; Nitric Oxide Synthase; Cerebrovascular Circulation; Glucose; Insulin
PubMed: 37842740
DOI: 10.1152/ajpregu.00169.2022 -
The American Journal of Pathology Dec 2021Bone homeostasis depends on the balance between bone resorption by osteoclasts (OCs) and bone formation by osteoblasts. Bone resorption can become excessive under...
Bone homeostasis depends on the balance between bone resorption by osteoclasts (OCs) and bone formation by osteoblasts. Bone resorption can become excessive under various pathologic conditions, including rheumatoid arthritis. Previous studies have shown that OC formation is promoted under hypoxia. However, the precise mechanisms behind OC formation under hypoxia have not been elucidated. The present study investigated the role of inducible nitric oxide synthase (iNOS) in OC differentiation under hypoxia. Primary bone marrow cells obtained from mice were stimulated with receptor activator of NF-κB ligand and macrophage colony-stimulating factor to induce OC differentiation. The number of OCs increased in culture under hypoxia (oxygen concentration, 5%) compared with that under normoxia (oxygen concentration, 20%). iNOS gene and protein expression increased in culture under hypoxia. Addition of an iNOS inhibitor under hypoxic conditions suppressed osteoclastogenesis. Addition of a nitric oxide donor to the normoxic culture promoted osteoclastogenesis. Furthermore, insulin-like growth factor 2 expression was significantly altered in both iNOS inhibition experiments and nitric oxide donor experiments. These data might provide clues to therapies for excessive osteoclastogenesis under several hypoxic pathologic conditions, including rheumatoid arthritis.
Topics: Animals; Bone Resorption; Cell Differentiation; Cell Hypoxia; Cells, Cultured; Enzyme Induction; Hypoxia; Male; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase Type II; Osteoclasts; Osteogenesis; Oxygen; Signal Transduction; omega-N-Methylarginine
PubMed: 34560064
DOI: 10.1016/j.ajpath.2021.08.014 -
Journal of the American Heart... Aug 2020Background Basal release of nitric oxide (NO) from the vascular endothelium regulates the tone of muscular arteries and resistance vasculature. Effects of NO on muscular... (Randomized Controlled Trial)
Randomized Controlled Trial
Background Basal release of nitric oxide (NO) from the vascular endothelium regulates the tone of muscular arteries and resistance vasculature. Effects of NO on muscular arteries could be particularly important during exercise when shear stress may stimulate increased NO synthesis. Methods and Results We investigated acute effects of NO synthase inhibition on exercise hemodynamics using N-monomethyl-l-arginine (l-NMMA), a nonselective NO synthase -inhibitor. Healthy volunteers (n=10, 5 female, 19-33 years) participated in a 2-phase randomized crossover study, receiving l-NMMA (6 mg/kg, iv over 5 minutes) or placebo before bicycle exercise (25-150 W for 12 minutes). Blood pressure, cardiac output (measured by dilution of soluble and inert tracers) and femoral artery diameter were measured before, during, and after exercise. At rest, l-NMMA reduced heart rate (by 16.2±4.3 bpm relative to placebo, <0.01), increased peripheral vascular resistance (by 7.0±1.4 mmHg per L/min, <0.001), mean arterial blood pressure (by 8.9±3.5 mmHg, <0.05), and blunted an increase in femoral artery diameter that occurred immediately before exercise (change in diameter: 0.14±0.04 versus 0.32±0.06 mm after l-NMMA and placebo, <0.01). During/after exercise l-NMMA had no significant effect on peripheral resistance, cardiac output, or on femoral artery diameter. Conclusions These results suggest that NO plays little role in modulating muscular artery function during exercise but that it may mediate changes in muscular artery tone immediately before exercise.
Topics: Adult; Arterial Pressure; Arteries; Cardiac Output; Cross-Over Studies; Enzyme Inhibitors; Exercise; Exercise Test; Female; Femoral Artery; Humans; Male; Muscle, Skeletal; Nitric Oxide; Nitric Oxide Synthase; Placebos; Pulse Wave Analysis; Vascular Resistance; Vasodilation; Young Adult; omega-N-Methylarginine
PubMed: 32781940
DOI: 10.1161/JAHA.119.013849 -
Microbial Pathogenesis Oct 2023The CXCL8/CXCR1 axis in conjoint with the free radicals and anti-oxidants dictates the severity of inflammation caused by the bacteria, Staphylococcus aureus. S.aureus...
Pyrrolidine dithiocarbamate in combination with L-N-monomethyl arginine alleviates Staphylococcus aureus infection via regulation of CXCL8/CXCR1 axis in peritoneal macrophages in vitro.
The CXCL8/CXCR1 axis in conjoint with the free radicals and anti-oxidants dictates the severity of inflammation caused by the bacteria, Staphylococcus aureus. S.aureus mediated inflammatory processes is regulated by NF-κB and its product, iNOS. The objective of this study was to examine the effects of inhibition of NF-κB and iNOS on CXCL8/CXCR1, alteration in M1/M2 polarization of macrophages and associated inflammatory responses during S.aureus infection in vitro. For this, the murine peritoneal macrophages were pretreated with NF-κB inhibitor, Pyrrolidine dithiocarbamate (PDTC) and iNOS inhibitor, L-N-monomethyl arginine (LNMMA), either alone or in combination, followed by time-dependent S.aureus infection. The chemotactic migrations of macrophages were determined by the agarose spot assay. The iNOS, NF-κB and CXCR1 protein expressions were evaluated. The ROS level (superoxide, HO, NO) and antioxidant activities (SOD, CAT, GSH, arginase) were measured. The intra-macrophage phagoctyic activity had been analyzed by confocal microscopy. S.aureus activated macrophages showed increased iNOS expression that symbolizes M1 characterization of macrophages. The results suggest that the combination treatment of LNMMA + PDTC was effective in diminution of CXCL8 production and CXCR1 expression through downregulation of NF-κB and iNOS signaling pathway. Consequently, there was decrement in macrophage migration, reduced ROS generation, elevated antioxidant enzyme activity as well as bacterial phagocytosis at 90 min post bacterial infection. The increased arginase activity further proves the switch from pro-inflammatory M1 to anti-inflammatory M2 polarization of macrophages. Concludingly, the combination of PDTC + LNMMA could resolve S.aureus mediated inflammation through mitigation of CXCL8/CXCR1 pathway switching from M1 to M2 polarization.
Topics: Mice; Animals; Macrophages, Peritoneal; Staphylococcus aureus; omega-N-Methylarginine; Antioxidants; Reactive Oxygen Species; NF-kappa B; Hydrogen Peroxide; Arginase; Cytokines; Staphylococcal Infections; Receptors, Interleukin-8A; Inflammation
PubMed: 37567327
DOI: 10.1016/j.micpath.2023.106294