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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 -
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 -
Alcoholism, Clinical and Experimental... Apr 2019Maternal consumption of alcohol produces abnormalities in the developing fetus and can contribute to an increased incidence of many cardiovascular-related diseases. The...
BACKGROUND
Maternal consumption of alcohol produces abnormalities in the developing fetus and can contribute to an increased incidence of many cardiovascular-related diseases. The first goal of this study was to determine whether in utero exposure to alcohol influences reactivity of cerebral arterioles in adult (12 to 15 weeks old) rats. The second goal of this study was to examine whether in utero exposure to alcohol increased the susceptibility of the brain to damage following an ischemic event in adult rats.
METHODS
We fed Sprague Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy (21 to 23 days). In the first series of studies, we examined reactivity of cerebral arterioles to endothelial nitric oxide synthase (eNOS)- (adenosine diphosphate [ADP]) and neuronal nitric oxide synthase (nNOS)-dependent N-methyl-D-aspartate (NMDA, and NOS-independent agonists in adult rats before and during application of l-NMMA. In another series of studies, we examined infarct volume following middle cerebral artery occlusion in adult offspring exposed to alcohol in utero. In both series of studies, we also determined the role for an increase in oxidative stress by feeding dams apocynin for the duration of their pregnancy.
RESULTS
We found that in utero exposure to alcohol reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in adult rats. In addition, treatment of the dams with apocynin prevented this impairment in cerebral vascular function. We also found that in utero exposure to alcohol worsened brain damage following ischemia/reperfusion in adult rats and that treatment of dams with apocynin prevented this increase in brain damage following ischemia/reperfusion.
CONCLUSIONS
We suggest that our findings may have important implications for the pathogenesis of brain abnormalities associated with fetal alcohol exposure.
Topics: Acetophenones; Adenosine Diphosphate; Animals; Arterioles; Brain; Enzyme Inhibitors; Ethanol; Excitatory Amino Acid Agonists; Female; Infarction; Infarction, Middle Cerebral Artery; Male; N-Methylaspartate; Nitroglycerin; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Reperfusion Injury; omega-N-Methylarginine
PubMed: 30748017
DOI: 10.1111/acer.13979 -
Diabetes, Obesity & Metabolism Feb 2019The associations between arginine-based metabolites and incident type 2 diabetes (T2D) are unknown. We employed a case-cohort design, nested within the PREDIMED trial,... (Observational Study)
Observational Study
The associations between arginine-based metabolites and incident type 2 diabetes (T2D) are unknown. We employed a case-cohort design, nested within the PREDIMED trial, to examine six plasma metabolites (arginine, citrulline, ornithine, asymmetric dimethylarginine [ADMA], symmetric dimethylarginine [SDMA] and N-monomethyl-l-arginine [NMMA]) among 892 individuals (251 cases) for associations with incident T2D and insulin resistance. Weighted Cox models with robust variance were used. The 1-year changes in arginine (adjusted hazard ratio [HR] per SD 0.68, 95% confidence interval [CI] 0.49, 0.95; Q4 vs. Q1 0.46, 95% CI 0.21, 1.04; P trend = 0.02) and arginine/ADMA ratio (adjusted HR per SD 0.73, 95% CI 0.51, 1.04; Q4 vs. Q1 0.52, 95% CI 0.22, 1.25; P trend = 0.04) were associated with a lower risk of T2D. Positive changes of citrulline and ornithine, and negative changes in SDMA and arginine/(ornithine + citrulline) were associated with concurrent 1-year changes in homeostatic model assessment of insulin resistance. Individuals in the low-fat-diet group had a higher risk of T2D for 1-year changes in NMMA than individuals in Mediterranean-diet groups (P interaction = 0.02). We conclude that arginine bioavailability is important in T2D pathophysiology.
Topics: Aged; Aged, 80 and over; Arginine; Case-Control Studies; Citrulline; Cohort Studies; Diabetes Mellitus, Type 2; Diet, Fat-Restricted; Diet, Mediterranean; Female; Humans; Incidence; Insulin Resistance; Male; Middle Aged; Ornithine; Risk Factors; omega-N-Methylarginine
PubMed: 30146690
DOI: 10.1111/dom.13514 -
Hypertension (Dallas, Tex. : 1979) Sep 2018Renal denervation (RDN) has been shown to restore endogenous neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) and reduce sympathetic drive...
Renal denervation (RDN) has been shown to restore endogenous neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) and reduce sympathetic drive during chronic heart failure (CHF). The purpose of the present study was to assess the contribution of afferent renal nerves to the nNOS-mediated sympathetic outflow within the PVN in rats with CHF. CHF was induced in rats by ligation of the left coronary artery. Four weeks after surgery, selective afferent RDN (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal arteries. Seven days after intervention, nNOS protein expression, nNOS immunostaining signaling, and diaphorase-positive stained cells were significantly decreased in the PVN of CHF rats, changes that were reversed by A-RDN. A-RDN reduced basal lumbar sympathetic nerve activity in rats with CHF (8.5%±0.5% versus 17.0%±1.2% of max). Microinjection of nNOS inhibitor L-NMMA (L-N-monomethyl arginine citrate) into the PVN produced a blunted increase in lumbar sympathetic nerve activity in rats with CHF. This response was significantly improved after A-RDN (Δ lumbar sympathetic nerve activity: 25.7%±2.4% versus 11.2%±0.9%). Resting afferent renal nerves activity was substantially increased in CHF compared with sham rats (56.3%±2.4% versus 33.0%±4.7%). These results suggest that intact afferent renal nerves contribute to the reduction of nNOS in the PVN. A-RDN restores nNOS and thus attenuates the sympathoexcitation. Also, resting afferent renal nerves activity is elevated in CHF rats, which may highlight a crucial neural mechanism arising from the kidney in the maintenance of enhanced sympathetic drive in CHF.
Topics: Afferent Pathways; Animals; Capsaicin; Chronic Disease; Denervation; Enzyme Inhibitors; Heart Failure; Kidney; Male; Nitric Oxide Synthase Type I; Paraventricular Hypothalamic Nucleus; Rats, Sprague-Dawley; Sensory System Agents; Sympathetic Nervous System; omega-N-Methylarginine
PubMed: 30012866
DOI: 10.1161/HYPERTENSIONAHA.118.11071 -
Nitric Oxide : Biology and Chemistry Aug 2018Patients with chronic kidney disease have an increased cardiovascular morbidity and mortality. It has been recognized that the traditional cardiovascular risk factors... (Review)
Review
Patients with chronic kidney disease have an increased cardiovascular morbidity and mortality. It has been recognized that the traditional cardiovascular risk factors could only partially explain the increased cardiovascular morbidity and mortality in patients with chronic kidney disease. Asymmetric dimethylarginine (ADMA) and N-monomethy l-arginine (L-NMMA) are endogenous inhibitors of nitric oxide synthases that attenuate nitric oxide production and enhance reactive oxidative specie generation. Increased plasma ADMA and/or L-NMMA are strong and independent risk factor for chronic kidney disease, and various cardiovascular diseases such as hypertension, coronary artery disease, atherosclerosis, diabetes, and heart failure. Both ADMA and L-NMMA are also eliminated from the body through either degradation by dimethylarginine dimethylaminohydrolase-1 (DDAH1) or urine excretion. This short review will exam the literature of ADMA and L-NMMA degradation and urine excretion, and the role of chronic kidney diseases in ADMA and L-NMMA accumulation and the increased cardiovascular disease risk. Based on all available data, it appears that the increased cardiovascular morbidity in chronic kidney disease may relate to the dramatic increase of systemic ADMA and L-NMMA after kidney failure.
Topics: Amidohydrolases; Animals; Arginine; Endothelium, Vascular; Heart Failure; Humans; Nitric Oxide Synthase; Renal Insufficiency, Chronic; Risk Factors; Signal Transduction; omega-N-Methylarginine
PubMed: 29928990
DOI: 10.1016/j.niox.2018.06.004 -
Clinical Cancer Research : An Official... Mar 2018Chemoresistance in triple-negative breast cancer (TNBC) is associated with the activation of a survival mechanism orchestrated by the endoplasmic reticulum (EnR) stress...
Chemoresistance in triple-negative breast cancer (TNBC) is associated with the activation of a survival mechanism orchestrated by the endoplasmic reticulum (EnR) stress response and by inducible nitric oxide synthase (iNOS). Our aim was to determine the effects of pharmacologic NOS inhibition on TNBC. TNBC cell lines, SUM-159PT, MDA-MB-436, and MDA-MB-468, were treated with docetaxel and NOS inhibitor (L-NMMA) for 24, 48, and 72 hours. Apoptosis was assessed by flow cytometry using Annexin-V and propidium iodide. Western blot was used to assess ER stress and apoptosis, and rtPCR was used to evaluate s-XBP1. TNBC patient-derived xenografts (PDX) were treated either with vehicle, docetaxel, or combination therapy (NOS inhibition + docetaxel). Mouse weight and tumor volumes were recorded twice weekly. Docetaxel concentration was determined using mass spectrometry. To quantify proliferation and apoptosis, PDX tumor samples were stained using Ki67 and TUNEL assay. L-NMMA ameliorated the iNOS upregulation associated with docetaxel. Apoptosis increased when TNBC cells were treated with combination therapy. In TNBC PDXs, combination therapy significantly reduced tumor volume growth and increased survival proportions. In the BCM-5998 PDX model, intratumoral docetaxel concentration was higher in mice receiving combination therapy. Coupling docetaxel with NOS inhibition increased EnR-stress response via coactivation of ATF4 and CHOP, which triggered the pASK1/JNK proapoptotic pathway, promoting cleavage of caspases 3 and 9. iNOS is a critical target for docetaxel resistance in TNBC. Pharmacologic inhibition of NOS enhanced chemotherapy response in TNBC PDX models. Combination therapy may improve prognosis and prevent relapse in TNBC patients who have failed conventional chemotherapy. .
Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Docetaxel; Drug Synergism; Female; Humans; JNK Mitogen-Activated Protein Kinases; MAP Kinase Kinase Kinase 5; MAP Kinase Signaling System; Mice; Mice, SCID; Nitric Oxide Synthase Type II; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays; omega-N-Methylarginine
PubMed: 29301832
DOI: 10.1158/1078-0432.CCR-17-1437 -
The Journal of Physiology Dec 2017People with insulin resistance or type 2 diabetes can substantially increase their skeletal muscle glucose uptake during exercise and insulin sensitivity after exercise....
KEY POINTS
People with insulin resistance or type 2 diabetes can substantially increase their skeletal muscle glucose uptake during exercise and insulin sensitivity after exercise. Skeletal muscle nitric oxide (NO) is important for glucose uptake during exercise, although how prior exercise increases insulin sensitivity is unclear. In the present study, we examined whether NO is necessary for normal increases in skeletal muscle insulin sensitivity after contraction ex vivo in mouse muscle. The present study uncovers, for the first time, a novel role for NO in the insulin sensitizing effects of ex vivo contraction, which is independent of blood flow.
ABSTRACT
The factors regulating the increase in skeletal muscle insulin sensitivity after exercise are unclear. We examined whether nitric oxide (NO) is required for the increase in insulin sensitivity after ex vivo contractions. Isolated C57BL/6J mouse EDL muscles were contracted for 10 min or remained at rest (basal) with or without the NO synthase (NOS) inhibition (N -monomethyl-l-arginine; l-NMMA; 100 μm). Then, 3.5 h post contraction/basal, muscles were exposed to saline or insulin (120 μU ml ) with or without l-NMMA during the last 30 min. l-NMMA had no effect on basal skeletal muscle glucose uptake. The increase in muscle glucose uptake with insulin (57%) was significantly (P < 0.05) greater after prior contraction (140% increase). NOS inhibition during the contractions had no effect on this insulin-sensitizing effect of contraction, whereas NOS inhibition during insulin prevented the increase in skeletal muscle insulin sensitivity post-contraction. Soluble guanylate cyclase inhibition, protein kinase G (PKG) inhibition or cyclic nucleotide phosphodiesterase inhibition each had no effect on the insulin-sensitizing effect of prior contraction. In conclusion, NO is required for increases in insulin sensitivity several hours after contraction of mouse skeletal muscle via a cGMP/PKG independent pathway.
Topics: 2',3'-Cyclic-Nucleotide Phosphodiesterases; Animals; Cells, Cultured; Cyclic GMP-Dependent Protein Kinases; Glucose; Guanylate Cyclase; Insulin; Male; Mice; Mice, Inbred C57BL; Muscle Contraction; Muscle Fibers, Skeletal; Nitric Oxide; Nitric Oxide Synthase; Signal Transduction; omega-N-Methylarginine
PubMed: 29071734
DOI: 10.1113/JP275133