-
The Journal of Physiology Nov 2020Preclinical models have demonstrated that nitric oxide is a key component of neurovascular coupling; this has yet to be translated to humans. We conducted two separate...
KEY POINTS
Preclinical models have demonstrated that nitric oxide is a key component of neurovascular coupling; this has yet to be translated to humans. We conducted two separate protocols utilizing intravenous infusion of a nitric oxide synthase inhibitor and isovolumic haemodilution to assess the influence of nitric oxide on neurovascular coupling in humans. Isovolumic haemodilution did not alter neurovascular coupling. Intravenous infusion of a nitric oxide synthase inhibitor reduced the neurovascular coupling response by ∼30%, indicating that nitric oxide is integral to neurovascular coupling in humans.
ABSTRACT
Nitric oxide is a vital neurovascular signalling molecule in preclinical models, yet the mechanisms underlying neurovascular coupling (NVC) in humans have yet to be elucidated. To investigate the contribution of nitric oxide to NVC in humans, we utilized a visual stimulus paradigm to elicit an NVC response in the posterior cerebral circulation. Two distinct mechanistic interventions were conducted on young healthy males: (1) NVC was assessed during intravenous infusion of saline (placebo) and the non-selective competitive nitric oxide synthase inhibitor N -monomethyl-l-arginine (l-NMMA, 5 mg kg bolus & subsequent 50 μg kg min maintenance dose; n = 10). The order of infusion was randomized, counterbalanced and single blinded. A subset of participants in this study (n = 4) underwent a separate intervention with phenylephrine infusion to independently consider the influence of blood pressure changes on NVC (0.1-0.6 μg kg min constant infusion). (2) NVC was assessed prior to and following isovolumic haemodilution, whereby 20% of whole blood was removed and replaced with 5% human serum albumin to reduce haemoglobin concentration (n = 8). For both protocols, arterial and internal jugular venous blood samples were collected at rest and coupled with volumetric measures of cerebral blood flow (duplex ultrasound) to quantify resting cerebral metabolic parameters. l-NMMA elicited a 30% reduction in the peak (P = 0.01), but not average (P = 0.11), NVC response. Neither phenylephrine nor haemodilution influenced NVC. Nitric oxide signalling is integral to NVC in humans, providing a new direction for research into pharmacological treatment of humans with dementia.
Topics: Cerebrovascular Circulation; Enzyme Inhibitors; Humans; Male; Neurovascular Coupling; Nitric Oxide; omega-N-Methylarginine
PubMed: 32785972
DOI: 10.1113/JP280162 -
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 -
Molecules (Basel, Switzerland) May 2020(QM)-a member of the Fagaceae family-has been used as traditional medicine in Korea, China and Mongolia as a treatment for inflammation of oral, genital or anal mucosa...
(QM)-a member of the Fagaceae family-has been used as traditional medicine in Korea, China and Mongolia as a treatment for inflammation of oral, genital or anal mucosa and for external inflammation of skin. To treat acne vulgaris (AV), we evaluated the inhibition of inflammatory cytokines (IL-6 and IL-8) of QM leaf extract (QML) and its main compound, pedunculagin (PD) in vitro and 5α-reductase inhibitory activity by western blotting. As results, QML and PD showed potent NO production inhibitory activity compared with the positive control (PC), NG-monomethyl-L-arginine (L-NMMA). QML and PD was also showed the decreases of IL-6 and IL-8 compared with the PC, EGCG and exhibited potent 5α-reductase type 1 inhibitory activities compared with the PC, dutasteride.
Topics: 5-alpha Reductase Inhibitors; Acne Vulgaris; Anti-Inflammatory Agents; Cell Line; Cholestenone 5 alpha-Reductase; Down-Regulation; Humans; Interleukin-6; Interleukin-8; Lipopolysaccharides; Medicine, Traditional; Nitric Oxide; Plant Extracts; Plant Leaves; Quercus; Tannins; omega-N-Methylarginine
PubMed: 32380665
DOI: 10.3390/molecules25092154 -
Oxidative Medicine and Cellular... 2020() is one of the most important agents of dermatophyte infection in humans. The aim of this experiment was to evaluate the effect of HaCaT cells on , investigate the...
() is one of the most important agents of dermatophyte infection in humans. The aim of this experiment was to evaluate the effect of HaCaT cells on , investigate the responsible mechanism of action, and explore the role of reactive oxygen species (ROS) and nitric oxide (NO) in the inhibition of growth by HaCaT cells. The viability of fungi treated with HaCaT cells alone and with HaCaT cells combined with pretreatment with the NADPH oxidase inhibitor (DPI) or the nitric oxide synthase (NOS) inhibitor L-NMMA was determined by enumerating the colony-forming units. NOS, ROS, and NO levels were quantified using fluorescent probes. The levels of the NOS inhibitor asymmetric dimethylarginine (ADMA) were determined by enzyme-linked immunosorbent assay (ELISA). Micromorphology was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, fungal keratinase activity was assessed by measuring dye release from keratin azure. In vitro fungal viability, keratinase activity, and ADMA content decreased after HaCaT cell intervention, whereas the levels of ROS, NO, and NOS increased. The micromorphology was abnormal. Fungi pretreated with DPI and L-NMMA exhibited opposite effects. HaCaT cells inhibited the growth and pathogenicity of in vitro. A suggested mechanism is that ROS and NO play an important role in the inhibition of growth by HaCaT cells.
Topics: Arginine; Catecholamines; Cell Line; Enzyme Inhibitors; Humans; Imidazolines; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; NADPH Oxidases; Nitric Oxide; Nitric Oxide Synthase; Peptide Hydrolases; Reactive Oxygen Species; Trichophyton; omega-N-Methylarginine
PubMed: 32104540
DOI: 10.1155/2020/8548619 -
Annals of Biomedical Engineering Apr 2020tDCS has been used to treat various brain disorders and its mechanism of action (MoA) was found to be neuronal polarization. Since the blood-brain barrier (BBB) tightly...
tDCS has been used to treat various brain disorders and its mechanism of action (MoA) was found to be neuronal polarization. Since the blood-brain barrier (BBB) tightly regulates the neuronal microenvironment, we hypothesized that another MoA of tDCS is direct vascular activation by modulating the BBB structures to increase its permeability (P). To test this hypothesis, we used high resolution multiphoton microscopy to determine P of the cerebral microvessels in rat brain. We found that 20 min 0.1-1 mA tDCS transiently increases P to a small solute, sodium fluorescein (MW 376) and to a large solute, Dextran-70k, with a much higher increase in P to the large solute. By pretreating the vessel with a nitric oxide synthase inhibitor, we revealed that the tDCS-induced increase in P is NO dependent. A transport model for the BBB was further employed to predict the structural changes by the tDCS. Comparing model predictions with the measured data suggests that tDCS increases P by temporarily disrupting the structural components forming the paracellular pathway of the BBB. That the transient and reversible increase in the BBB permeability also suggests new applications of tDCS such as a non-invasive approach for brain drug delivery through the BBB.
Topics: Animals; Blood-Brain Barrier; Dextrans; Drug Delivery Systems; Female; Fluorescein; Nitric Oxide Synthase; Permeability; Rats, Sprague-Dawley; Transcranial Direct Current Stimulation; omega-N-Methylarginine
PubMed: 31916126
DOI: 10.1007/s10439-020-02447-7 -
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 -
Microcirculation (New York, N.Y. : 1994) Oct 2019To determine the ability of renal contrast-enhanced ultrasonography (CEUS) to detect acute drug-induced changes in renal perfusion (using the glucagon-like... (Randomized Controlled Trial)
Randomized Controlled Trial
Assessment of real-time and quantitative changes in renal hemodynamics in healthy overweight males: Contrast-enhanced ultrasonography vs para-aminohippuric acid clearance.
OBJECTIVE
To determine the ability of renal contrast-enhanced ultrasonography (CEUS) to detect acute drug-induced changes in renal perfusion (using the glucagon-like peptide (GLP)-1 receptor agonist exenatide and nitric oxide [NO]-synthase inhibitor L-N -monomethyl arginine [l-NMMA]), and assess its correlation with gold standard-measured effective renal plasma flow in humans.
METHODS
In this prespecified exploratory analysis of a placebo-controlled cross-over study, renal hemodynamics was assessed in 10 healthy overweight males (aged 20-27 years; BMI 26-31 kg/m ) over two separate testing days; during placebo (isotonic saline) and subsequent exenatide infusion (Day-A), and during l-NMMA, and subsequent exenatide plus l-NMMA infusion (Day-B). Renal cortical microvascular blood flow was estimated following microbubble infusion and CEUS destruction-refilling-sequences. Renal cortical microvascular blood flow was compared with simultaneously measured effective renal plasma flow in humans, derived from para-aminohippuric acid-clearance methodology.
RESULTS
On Day-A, effective renal plasma flow increased by 68 [26-197] mL/min/1.73 m during exenatide vs placebo infusion (+17%; P = .015). In parallel, exenatide increased renal cortical microvascular blood flow, from 2.42 × 10 [6.54 × 10 -4.66 × 10 ] AU to 4.65 × 10 [2.96 × 10 -7.74 × 10 ] AU (+92%; P = .027). On Day-B, effective renal plasma flow and renal cortical microvascular blood flow were reduced by l-NMMA, with no significant effect of concomitant exenatide on renal hemodynamic-indices assessed by either technique. Effective renal plasma flow correlated with renal cortical microvascular blood flow on Day-A (r = .533; P = .027); no correlation was found on Day-B.
CONCLUSIONS
Contrast-enhanced ultrasonography can detect acute drug-induced changes human renal hemodynamics. CEUS-assessed renal cortical microvascular blood flow moderately associates with effective renal plasma flow, particularly when perfusion is in normal-to-high range. Renal CEUS cannot replace effective renal plasma flow measurements, but may be a complementary tool to characterize regional kidney perfusion.
Topics: Adult; Blood Flow Velocity; Contrast Media; Humans; Kidney; Male; Microcirculation; Overweight; Pilot Projects; Ultrasonography; omega-N-Methylarginine
PubMed: 31313410
DOI: 10.1111/micc.12580 -
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 -
Journal of the American Society For... Jul 2019Arginine methylation is a common protein post-translational modification (PTM) that plays a key role in eukaryotic cells. Three distinct types of this modification are...
Arginine methylation is a common protein post-translational modification (PTM) that plays a key role in eukaryotic cells. Three distinct types of this modification are found in mammals: asymmetric NN-dimethylarginine (aDMA), symmetric NN-dimethylarginine (sDMA), and an intermediate N-monomethylarginine (MMA). Elucidation of regulatory mechanisms of arginine methylation in living organisms requires precise information on both the type of the modified residues and their location inside the protein amino acid sequences. Despite mass spectrometry (MS) being the method of choice for analysis of multiple protein PTMs, unambiguous characterization of protein arginine methylation may not be always straightforward. Indeed, frequent internal basic residues of Arg methylated tryptic peptides hamper their sequencing under positive ion mode collision-induced dissociation (CID), the standardly used tandem mass spectrometry method, while the relative stability of the aDMA and sDMA side chains under alternative non-ergodic electron-based fragmentation techniques, electron-capture and electron transfer dissociations (ECD and ETD), may impede differentiation between the isobaric residues. Here, for the first time, we demonstrate the potential of the negative ion mode collision-induced dissociation MS for analysis of protein arginine methylation and present data revealing that the negative polarity approach can deliver both an unambiguous identification of the arginine methylation type and extensive information on the modified peptide sequences.
Topics: Amino Acid Sequence; Arginine; Peptides; Protein Processing, Post-Translational; Proteins; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; omega-N-Methylarginine
PubMed: 30915654
DOI: 10.1007/s13361-019-02176-9 -
Pflugers Archiv : European Journal of... Jul 2019Nitric oxide (NO) is involved in skeletal muscle glucose uptake during exercise and also in the increase in insulin sensitivity after exercise. Given that neuronal...
Nitric oxide (NO) is involved in skeletal muscle glucose uptake during exercise and also in the increase in insulin sensitivity after exercise. Given that neuronal nitric oxide synthase (NOS) isoform mu (nNOSμ) is a major isoform of NOS in skeletal muscle, we examined if the increase in skeletal muscle insulin-stimulated glucose uptake 3.5 h following ex vivo contraction of extensor digitorum longus (EDL) is reduced in muscles from nNOSμ and nNOSμ mice compared with nNOSμ mice. 3.5 h post-contraction/basal, muscles were exposed to saline or insulin (120μU/ml) with or without the presence of the NOS inhibitor NG-monomethyl-L-arginine (L-NMMA) during the last 30 min and glucose uptake was determined by radioactive tracers. Skeletal muscle insulin-stimulated glucose uptake from nNOSμ, nNOSμ and nNOSμ mice increased approximately twofold 3.5 h following ex vivo contraction when compared to rest. L-NMMA significantly attenuated this increase in muscle insulin-stimulated glucose uptake by around 50%, irrespective of genotype. Low levels of NOS activity were detected in muscles from nNOSμ mice. In conclusion, NO mediates increases in mouse skeletal muscle insulin response following ex vivo contraction independently of nNOSμ.
Topics: Animals; Biological Transport; Enzyme Inhibitors; Glucose; Insulin; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Contraction; Muscle, Skeletal; Neurons; Nitric Oxide; Nitric Oxide Synthase Type I; Physical Conditioning, Animal; omega-N-Methylarginine
PubMed: 30900045
DOI: 10.1007/s00424-019-02268-1