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1.
Artigo em Inglês | MEDLINE | ID: mdl-31682251

RESUMO

OBJECTIVES: The cephalosporin nitric oxide (NO)-donor prodrug DEA-C3D ('DiEthylAmin-Cephalosporin-3'-Diazeniumdiolate') has been shown to initiate the dispersal of biofilms formed by the Pseudomonas aeruginosa laboratory strain PAO1. In this study, we investigated whether DEA-C3D disperses biofilms formed by clinical cystic fibrosis (CF) isolates of P. aeruginosa and its effect in combination with two antipseudomonal antibiotics, tobramycin and colistin, in vitro. METHODS: ß-Lactamase-triggered release of NO from DEA-C3D was confirmed using a gas-phase chemiluminescence detector. MICs for P. aeruginosa clinical isolates were determined using the broth microdilution method. A crystal violet staining technique and confocal laser scanning microscopy were used to evaluate the effects of DEA-C3D on P. aeruginosa biofilms alone and in combination with tobramycin and colistin. RESULTS: DEA-C3D was confirmed to selectively release NO in response to contact with bacterial ß-lactamase. Despite lacking direct, cephalosporin/ß-lactam-based antibacterial activity, DEA-C3D was able to disperse biofilms formed by three P. aeruginosa clinical isolates. Confocal microscopy revealed that DEA-C3D in combination with tobramycin produces similar reductions in biofilm to DEA-C3D alone, whereas the combination with colistin causes near complete eradication of P. aeruginosa biofilms in vitro. CONCLUSIONS: DEA-C3D is effective in dispersing biofilms formed by multiple clinical isolates of P. aeruginosa and could hold promise as a new adjunctive therapy to patients with CF.

2.
Diabetologia ; 2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31713010

RESUMO

AIMS/HYPOTHESIS: Exposure to sunlight has the potential to suppress metabolic dysfunction and obesity. We previously demonstrated that regular exposure to low-doses of ultraviolet radiation (UVR) reduced weight gain and signs of diabetes in male mice fed a high-fat diet, in part via release of nitric oxide from skin. Here, we explore further mechanistic pathways through which low-dose UVR exerts these beneficial effects. METHODS: We fed mice with a luciferase-tagged Ucp1 gene (which encodes uncoupling protein-1 [UCP-1]), referred to here as the Ucp1 luciferase transgenic mouse ('Thermomouse') a high-fat diet and examined the effects of repeated exposure to low-dose UVR on weight gain and development of metabolic dysfunction as well as UCP-1-dependent thermogenesis in interscapular brown adipose tissue (iBAT). RESULTS: Repeated exposure to low-dose UVR suppressed the development of glucose intolerance and hepatic lipid accumulation via dermal release of nitric oxide while also reducing circulating IL-6 (compared with mice fed a high-fat diet only). Dietary nitrate supplementation did not mimic the effects of low-dose UVR. A single low dose of UVR increased UCP-1 expression (by more than twofold) in iBAT of mice fed a low-fat diet, 24 h after exposure. However, in mice fed a high-fat diet, there was no effect of UVR on UCP-1 expression in iBAT (compared with mock-treated mice) when measured at regular intervals over 12 weeks. More extensive circadian studies did not identify any substantial shifts in UCP-1 expression in mice exposed to low-dose UVR, although skin temperature at the interscapular site was reduced in UVR-exposed mice. The appearance of cells with a white adipocyte phenotype ('whitening') in iBAT induced by consuming the high-fat diet was suppressed by exposure to low-dose UVR in a nitric oxide-dependent fashion. Significant shifts in the expression of important core gene regulators of BAT function (Dio2, increased more than twofold), fatty acid transport (increased Fatp2 [also known as Slc27a2]), lipolysis (decreased Atgl [also known as Pnpla2]), lipogenesis (decreased Fasn) and inflammation (decreased Tnf), and proportions of macrophages (increased twofold) were observed in iBAT of mice exposed to low-dose UVR. These effects were independent of nitric oxide released from skin. CONCLUSIONS/INTERPRETATION: Our results suggest that non-burning (low-dose) UVR suppresses the BAT 'whitening', steatotic and pro-diabetic effects of consuming a high-fat diet through skin release of nitric oxide, with some metabolic and immune pathways in iBAT regulated by UVR independently of nitric oxide.

3.
Am J Clin Nutr ; 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31599928

RESUMO

BACKGROUND: Inorganic nitrate, abundant in leafy green vegetables and beetroot, is thought to have protective health benefits. Adherence to a Mediterranean diet reduces the incidence and severity of coronary artery disease, whereas supplementation with nitrate can improve submaximal exercise performance. Once ingested, oral commensal bacteria may reduce nitrate to nitrite, which may subsequently be reduced to nitric oxide during conditions of hypoxia and in the presence of "nitrite reductases" such as heme- and molybdenum-containing enzymes. OBJECTIVE: We aimed to explore the putative effects of inorganic nitrate and nitrite on mitochondrial function in skeletal muscle. METHODS: Mice were subjected to a nitrate/nitrite-depleted diet for 2 wk, then supplemented with sodium nitrate, sodium nitrite, or sodium chloride (1 g/L) in drinking water ad libitum for 7 d before killing. Skeletal muscle mitochondrial function and expression of uncoupling protein (UCP) 3, ADP/ATP carrier protein (AAC) 1 and AAC2, and pyruvate dehydrogenase (PDH) were assessed by respirometry and Western blotting. Studies were also undertaken in human skeletal muscle biopsies from a cohort of coronary artery bypass graft patients treated with either sodium nitrite (30-min infusion of 10 µmol/min) or vehicle [0.9% (wt:vol) saline] 24 h before surgery. RESULTS: Neither sodium nitrate nor sodium nitrite supplementation altered mitochondrial coupling efficiency in murine skeletal muscle, and expression of UCP3, AAC1, or AAC2, and PDH phosphorylation status did not differ between the nitrite and saline groups. Similar results were observed in human samples. CONCLUSIONS: Sodium nitrite failed to improve mitochondrial metabolic efficiency, rendering this mechanism implausible for the purported exercise benefits of dietary nitrate supplementation. This trial was registered at clinicaltrials.gov as NCT04001283.

4.
Anesth Analg ; 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31609255

RESUMO

Reactive oxygen species (ROS) are essential for cellular signaling and physiological function. An imbalance between ROS production and antioxidant protection results in a state of oxidative stress (OS), which is associated with perturbations in reduction/oxidation (redox) regulation, cellular dysfunction, organ failure, and disease. The pathophysiology of OS is closely interlinked with inflammation, mitochondrial dysfunction, and, in the case of surgery, ischemia/reperfusion injury (IRI). Perioperative OS is a complex response that involves patient, surgical, and anesthetic factors. The magnitude of tissue injury inflicted by the surgery affects the degree of OS, and both duration and nature of the anesthetic procedure applied can modify this. Moreover, the interindividual susceptibility to the impact of OS is likely to be highly variable and potentially linked to underlying comorbidities. The pathological link between OS and postoperative complications remains unclear, in part due to the complexities of measuring ROS- and OS-mediated damage. Exogenous antioxidant use and exercise have been shown to modulate OS and may have potential as countermeasures to improve postoperative recovery. A better understanding of the underlying mechanisms of OS, redox signaling, and regulation can provide an opportunity for patient-specific phenotyping and development of targeted interventions to reduce the disruption that surgery can cause to our physiology. Anesthesiologists are in a unique position to deliver countermeasures to OS and improve physiological resilience. To shy away from a process so fundamental to the welfare of these patients would be foolhardy and negligent, thus calling for an improved understanding of this complex facet of human biology.

5.
Nitric Oxide ; 94: 27-35, 2019 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-31604146

RESUMO

Native highlanders (e.g. Sherpa) demonstrate remarkable hypoxic tolerance, possibly secondary to higher levels of circulating nitric oxide (NO) and increased microcirculatory blood flow. As part of the Xtreme Alps study (a randomised placebo-controlled trial of dietary nitrate supplementation under field conditions of hypobaric hypoxia), we investigated whether dietary supplementation with nitrate could improve NO availability and microvascular blood flow in lowlanders. Plasma measurements of nitrate, nitrite and nitroso species were performed together with measurements of sublingual (sidestream dark-field camera) and forearm blood flow (venous occlusion plethysmography) in 28 healthy adult volunteers resident at 4559 m for 1 week; half receiving a beetroot-based high-nitrate supplement and half receiving an identically-tasting low nitrate 'placebo'. Dietary supplementation increased plasma nitrate concentrations 4-fold compared to the placebo group, both at sea level (SL; 19.2 vs 76.9 µM) and at day 5 (D5) of high altitude (22.9 vs 84.3 µM, p < 0.001). Dietary nitrate supplementation also significantly increased both plasma nitrite (0.78 vs. 0.86 µM SL, 0.31 vs. 0.41 µM D5, p = 0.03) and total nitroso product (11.3 vs. 19.7 nM SL, 9.7 vs. 12.3 nM D5, p < 0.001) levels both at sea level and at 4559 m. However, plasma nitrite concentrations were more than 50% lower at 4559 m compared to sea level in both treatment groups. Despite these significant changes, dietary nitrate supplementation had no effect on any measured read-outs of sublingual or forearm blood flow, even when environmental hypoxia was experimentally reversed using supplemental oxygen. In conclusion, dietary nitrate supplementation does not improve microcirculatory function at 4559 m.

6.
Cardiovasc Res ; 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31372656

RESUMO

AIMS: Under hypoxic conditions, nitrite (NO2-) can be reduced to nitric oxide (NO) eliciting vasorelaxation. However, nitrite also exerts vasorelaxant effects of potential therapeutic relevance under normal physiological conditions via undetermined mechanisms. We therefore sought to investigate the mechanism(s) by which nitrite regulates the vascular system in normoxia and, specifically, whether the biological effects are a result of NO generation (as in hypoxia) or mediated via alternative mechanisms involving classical downstream targets of NO (e.g. effects on protein kinase G1α (PKG1α)). METHODS AND RESULTS: Ex vivo myography revealed that, unlike in thoracic aorta (conduit vessels), the vasorelaxant effects of nitrite in mesenteric resistance vessels from wild-type (WT) mice were NO-independent. Oxidants such as H2O2 promote disulfide formation of PKG1α, resulting in NO-cGMP independent kinase activation. To explore whether the microvascular effects of nitrite were associated with PKG1α oxidation, we used a C42Ser PKG1α knock-in (KI; "redox-dead") mouse that cannot transduce oxidant signals. Resistance vessels from these PKG1α-KI mice were markedly less responsive to nitrite-induced vasodilation. Intraperitoneal (i.p) bolus application of nitrite in conscious WT mice induced a rapid yet transient increase in plasma nitrite and cGMP concentrations followed by prolonged hypotensive effects, as assessed using in vivo telemetry. In the PKG1α-KI mice the blood pressure lowering effects were lower compared to WT. Increased H2O2 concentrations were detected in WT resistance vessel tissue challenged with nitrite. Consistent with this, increased cysteine and glutathione persulfide levels were detected in these vessels by mass spectrometry, matching the temporal profile of nitrite's effects on H2O2 and blood pressure. CONCLUSION: Under physiological conditions, nitrite induces a delayed and long-lasting blood pressure lowering effect, which is NO-independent and occurs via a new redox mechanism involving H2O2, persulfides and PKG1α oxidation/activation. Targeting this novel pathway may provide new prospects for anti-hypertensive therapy. TRANSLATIONAL PERSPECTIVE: Despite current pharmacotherapies and interventional procedures, arterial hypertension remains a global health burden. Thus, novel therapeutic interventions are urgently required. Nitrite exerts vasorelaxant effects of potential therapeutic relevance under normal physiological conditions, yet the mechanism(s) remain unknown. Here, we present evidence of how nitrite lowers blood pressure during normoxia via a novel redox mechanism. This occurs independent of nitric oxide by generating hydrogen peroxide and persulfide formation, which subsequently activates the PKG1α by oxidation. Targeting this novel pathway may provide new prospects for anti-hypertensive therapy and other cardiovascular related diseases.

7.
Circulation ; 139(23): 2664-2667, 2019 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-31157996
8.
Am J Clin Nutr ; 109(6): 1535-1545, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31136659

RESUMO

BACKGROUND: Anthocyanin-rich blueberry intake is associated with reduced type 2 diabetes and cardiovascular disease (CVD) risk in prospective studies, although long-term randomized controlled trials (RCTs) have not been conducted in at-risk populations. OBJECTIVE: In the longest-duration RCT to date, we examined the effect of 6-mo blueberry intake on insulin resistance and cardiometabolic function in metabolic syndrome. METHODS: A double-blind, parallel RCT (n = 115; age 63 ± 7 y; 68% male; body mass index 31.2 ± 3.0 kg/m2) was conducted, which fed 2 dietarily achievable blueberry intakes [equivalent to 1/2 and 1 cup/d (75/150 g)] compared with matched placebo. Insulin resistance was assessed via the homeostasis model assessment of insulin resistance (primary endpoint) and confirmed by [6-6-2H2]-glucose-labeled, 2-step hyperinsulinemic clamp (n = 20). Clinically relevant cardiometabolic endpoints [including flow-mediated dilatation, augmentation index, lipoprotein status (by nuclear magnetic resonance spectroscopy), and nitric oxide (NO)-related metabolite assay] and anthocyanin metabolism were assessed. RESULTS: A daily intake of 1 cup of blueberries improved endothelial function (flow-mediated dilatation: +1.45%; 95% CI: 0.83%, 2.1%; P = 0.003), systemic arterial stiffness (augmentation index: -2.24%; 95% CI: -3.97%, -0.61%; P = 0.04) and attenuated cyclic guanosine monophosphate concentrations. In statin nonusers (n = 71), elevated high-density lipoprotein cholesterol (+0.08 mmol/L; P = 0.03), high-density lipoprotein particle density (+0.48n, ×10-6; P = 0.002) and apolipoprotein A-I (+0.05 g/L; P = 0.01) concentrations were observed following the 1-cup/d intervention. Treatment compliance was 94.1% (wrapper returns) and total concentrations of anthocyanin-derived phenolic acid metabolites significantly increased, dose-dependently, in serum and 24-h urine (P < 0.01 and P < 0.001, respectively). Insulin resistance, pulse wave velocity, blood pressure, NO, and overall plasma thiol status were unaffected. Likewise, a half cup per day had no effect on any biomarkers. CONCLUSIONS: Despite insulin resistance remaining unchanged we show, to our knowledge, the first sustained improvements in vascular function, lipid status, and underlying NO bioactivity following 1 cup blueberries/d. With effect sizes predictive of 12-15% reductions in CVD risk, blueberries should be included in dietary strategies to reduce individual and population CVD risk. This study was registered at clinicaltrials.gov as NCT02035592.

9.
Physiol Rep ; 7(6): e14017, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30916482

RESUMO

Raynaud's phenomenon (RP) is often the first sign of systemic sclerosis (SSc). Molecular mechanisms involved are incompletely understood, but reactive oxygen, nitrogen, and sulfur species are thought to play an important role in the pathogenesis of SSc. Free thiol groups play a protective role against oxidative stress and may represent an attractive therapeutic target. We aimed to investigate the effects of hypothermia-induced vasoconstriction on the responsiveness of redox-related markers. Thirty participants (n = 10/group [SSc, primary Raynaud's phenomenon (PRP), healthy controls (HC)]) were included in this study. Fingertip photoelectric plethysmography was performed during a standardized cooling and recovery experiment. Venous blood was collected at four predetermined time points. Free thiols, NO-derived species (nitros(yl)ated species, nitrite, nitrate), sulfate and endothelin-1 were measured. Lower baseline concentrations of free thiols were observed in PRP and SSc patients (HC: 5.87 [5.41-5.99] µmol/g; PRP: 5.17 [4.74-5.61]; SSc 5.28 [4.75-5.80], P = 0.04). Redox-related markers remained unchanged during cooling. However, an unexpected increase in systemic free thiol concentrations was observed in all groups during the recovery phase. The response of this marker differed between groups, with a higher increase found in SSc patients (HC Δ = 1.30 [1.48-1.17]; PRP Δ = 1.04 [1.06-1.03]; SSc Δ = 1.72 [1.13-1.49], P = 0.04). NO-derived species, sulfate and endothelin-1 levels remained unchanged throughout the recovery phase. This exploratory study sheds light on the rapid responsiveness of systemic free thiol concentrations following reperfusion, which may reflect overall redox balance. The robust response to reperfusion in SSc patients suggests that reductive systems involved in this response are functionally intact in these patients.

10.
Int J Mol Sci ; 20(5)2019 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-30845762

RESUMO

In pregnancy, maternal physiology is subject to considerable adaptations, including alterations in cardiovascular and metabolic function as well as development of immunological tolerance towards the fetus. In an oocyte donation pregnancy, the fetus is fully allogeneic towards the mother, since it carries both oocyte donor antigens and paternal antigens. Therefore, oocyte donation pregnancies result in an immunologically challenging pregnancy, which is reflected by a higher-than-normal risk to develop pre-eclampsia. Based on the allogeneic conditions in oocyte donation pregnancies, we hypothesized that this situation may translate into alterations in concentration of stable readouts of constituents of the reactive species interactome (RSI) compared to normal pregnancies, especially serum free thiols, nitric oxide (NO) and hydrogen sulfide (H2S) related metabolites. Indeed, total free thiol levels and nitrite (NO2-) concentrations were significantly lower whereas protein-bound NO and sulfate (SO42-) concentrations were significantly higher in both oocyte donation and naturally conceived pregnancies complicated by pre-eclampsia. The increased concentrations of nitrite observed in uncomplicated oocyte donation pregnancies suggest that endothelial NO production is compensatorily enhanced to lower vascular tone. More research is warranted on the role of the RSI and bioenergetic status in uncomplicated oocyte donation pregnancies and oocyte donation pregnancies complicated by pre-eclampsia.


Assuntos
Óxido Nítrico/metabolismo , Doação de Oócitos/efeitos adversos , Pré-Eclâmpsia/metabolismo , Compostos de Sulfidrila/metabolismo , Adulto , Estudos de Casos e Controles , Feminino , Fertilização In Vitro , Humanos , Sulfeto de Hidrogênio , Idade Materna , Pessoa de Meia-Idade , Gravidez , Estudos Retrospectivos , Adulto Jovem
11.
Br J Pharmacol ; 2019 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-30924528

RESUMO

BACKGROUND AND PURPOSE: A clinical need exists for targeted, safe, and effective sulfide donors. We recently reported that ammonium tetrathiomolybdate (ATTM) belongs to a new class of sulfide-releasing drugs. Here, we investigated the cellular uptake mechanisms of this drug class compared to sodium hydrosulfide (NaHS) and the effects of a thiometallate tungsten congener of ATTM, ammonium tetrathiotungstate (ATTT). EXPERIMENTAL APPROACH: In vitro H2 S release was determined by headspace gas sampling of vials containing dissolved thiometallates. Thiometallate and NaHS bioactivity was assessed by spectrophotometry-derived sulfhaemoglobin formation. Cellular uptake dependence on the anion exchange protein (AE)-1 was investigated in human red blood cells. ATTM/glutathione interactions were assessed by LC-MS/MS. Rodent pharmacokinetic and pharmacodynamic studies focused on haemodynamics and inhibition of aerobic respiration. KEY RESULTS: ATTM and ATTT both exhibit temperature-, pH-, and thiol-dependence of sulfide release. ATTM/glutathione interactions revealed the generation of inorganic and organic persulfides and polysulfides. ATTM showed greater ex vivo and in vivo bioactivity over ATTT, notwithstanding similar pharmacokinetic profiles. Cellular uptake mechanisms of the two drug classes are distinct; thiometallates show dependence on AE-1, while hydrosulfide itself was unaffected by inhibition of this pathway. CONCLUSIONS AND IMPLICATIONS: The cellular uptake of thiometallates relies upon a plasma membrane ion channel. This advances our pharmacological knowledge of this drug class, and further supports their utility as cell-targeted sulfide donor therapies. Our results indicate that, as a more stable form, ATTT is better suited as a copper chelator. ATTM, a superior sulfide donor, may additionally participate in intracellular redox recycling.

12.
J Sci Med Sport ; 22(7): 852-857, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30745097

RESUMO

OBJECTIVES: Dietary nitrate (NO3-) supplementation and ischaemic preconditioning (IPC) can independently improve exercise performance. The purpose of this study was to explore whether NO3- supplementation, ingested prior to an IPC protocol, could synergistically enhance parameters of exercise. DESIGN: Double-blind randomized crossover trial. METHODS: Ten competitive male cyclists (age 34±6years, body mass 78.9±4.9kg, V⋅O2peak 55±4 mLkgmin-1) completed an incremental exercise test followed by three cycling trials comprising a square-wave submaximal component and a 16.1km time-trial. Oxygen uptake (V⋅O2) and muscle oxygenation kinetics were measured throughout. The baseline (BASE) trial was conducted without any dietary intervention or IPC. In the remaining two trials, participants received 3×5min bouts of lower limb bilateral IPC prior to exercise. Participants ingested NO3--rich gel (NIT+IPC) 90min prior to testing in one trial and a low NO3- placebo in the other (PLA+IPC). Plasma NO3- and nitrite (NO2-) were measured immediately before and after application of IPC. RESULTS: Plasma [NO3-] and [NO2-] were higher before and after IPC in NIT+IPC compared to BASE (P<0.001) but did not differ between BASE and PLA+IPC. There were no differences in V⋅O2 kinetics or muscle oxygenation parameters between trials (all P>0.4). Performance in the time-trial was similar between trials (BASE 1343±72s, PLA+IPC 1350±75s, NIT+IPC 1346±83s, P=0.98). CONCLUSIONS: Pre-exercise IPC did not improve sub-maximal exercise or performance measures, either alone or in combination with dietary NO3- supplementation.


Assuntos
Desempenho Atlético/fisiologia , Precondicionamento Isquêmico/métodos , Nitratos/administração & dosagem , Substâncias para Melhoria do Desempenho/administração & dosagem , Adulto , Ciclismo , Biomarcadores/sangue , Estudos Cross-Over , Método Duplo-Cego , Humanos , Masculino , Nitritos/sangue , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia
13.
Redox Biol ; 21: 101113, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30738322

RESUMO

The chemical and functional interactions between Reactive Oxygen (ROS), Nitrogen (RNS) and Sulfur (RSS) species allow organisms to detect and respond to metabolic and environmental stressors, such as exercise and altitude exposure. Whether redox markers and constituents of this 'Reactive Species Interactome' (RSI) differ in concentration between arterial and venous blood is unknown. We hypothesised that such measurements may provide useful insight into metabolic/redox regulation at the whole-body level and would be consistent between individuals exposed to identical challenges. An exploratory study was performed during the Xtreme Alps expedition in 2010 in which four healthy individuals (2 male, 2 female) underwent paired arterial and central venous blood sampling before, during and after performance of a constant-work-rate cardiopulmonary exercise test, at sea level and again at 4559 m. Unexpectedly, plasma total free thiol and free cysteine concentrations remained substantially elevated at altitude throughout exercise with minimal arteriovenous gradients. Free sulfide concentrations changed only modestly upon combined altitude/exercise stress, whereas bound sulfide levels were lower at altitude than sea-level. No consistent signal indicative of the expected increased oxidative stress and nitrate→nitrite→NO reduction was observed with 4-hydroxynonenal, isoprostanes, nitrate, nitrite, nitroso species and cylic guanosine monophosphate. However, the observed arteriovenous concentration differences revealed a dynamic pattern of response that was unique to each participant. This novel redox metabolomic approach of obtaining quantifiable 'metabolic signatures' to a defined physiological challenge could potentially offer new avenues for personalised medicine.


Assuntos
Biomarcadores/sangue , Metabolômica , Oxirredução , Gasometria , Exercício , Feminino , Humanos , Masculino , Metabolômica/métodos , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico
14.
Can Urol Assoc J ; 2018 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-30472982

RESUMO

INTRODUCTION: Patients suffering from chronic kidney disease (CKD) experience a number of associated comorbidities, including anemia. Relative deficiency in renal erythropoietin (EPO) production is thought to be a primary cause of anemia. Interestingly, CKD patients display low levels of hydrogen sulfide (H2S), an endogenously derived renal oxygen sensor. Previous in vitro experiments have revealed that H2S-deficient renal cell lines produce less EPO than wild-type renal cell lines during hypoxia. METHODS: We postulated that H2S might be a primary mediator of EPO synthesis during hypoxia, which was tested using an in vivo murine model of whole-body hypoxia and in clinical samples obtained from CKD patients. RESULTS: Following a 72-hour period of hypoxia (11% O2), partial H2S knockout mice (lacking the H2S biosynthetic enzyme cystathionine γ-lyase [CSE]) displayed lower levels of hemoglobin, EPO and cystathionine-ß-synthase (CBS) (another H2S biosynthetic enzyme) compared to wild-type mice, all of which was rescued by exogenous H2S supplementation. We also found that anemic CKD patients requiring exogenous EPO exhibited lower urinary thiosulfate levels compared to non-anemic CKD patients of similar CKD classification. CONCLUSIONS: Together, our results confirm an interplay between the actions of H2S during hypoxia and EPO production.

15.
Int J Chron Obstruct Pulmon Dis ; 13: 2739-2749, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30233164

RESUMO

Across Europe, COPD affects 23 million people leading to annual health care costs of ~€25.1 billion. This burden is particularly severe during winter months in association with the peak incidence of exacerbation events. Seasonal variation in the health status of patients with COPD places additional and often critical pressure on already strained health care resources. COPD exacerbations are characterized by worsening day-to-day symptoms of an individual and often triggered by respiratory infections, but the process by which this occurs in a seasonal fashion is likely to be multifactorial. In this review, we discuss recent population studies that highlight the impact of seasonality in COPD and review the proposed biological mechanisms underlying this. An appraisal of the role of the host susceptibility and response, environmental triggers and the biology of respiratory pathogens is detailed. The impact of each aspect is considered, and an integrated model of the context for the whole individual and society in general is explored.

16.
Nitric Oxide ; 80: 82-88, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30179715

RESUMO

Adequate perfusion of the placental vasculature is essential to meet the metabolic demands of fetal growth and development. Lacking neural control, local tissue metabolites, circulating and physical factors contribute significantly to blood flow regulation. Nitric oxide (NO) is a key regulator of fetoplacental vascular tone. Nitrite, previously considered an inert end-product of NO oxidation, has been shown to provide an important source of NO. Reduction of nitrite to NO may be particularly relevant in tissue when the oxygen-dependent NO synthase (NOS) activity is compromised, e.g. in hypoxia. The contribution of this pathway in the placenta is currently unknown. We hypothesised that nitrite vasodilates human placental blood vessels, with enhanced efficacy under hypoxia. Placentas were collected from uncomplicated pregnancies and the vasorelaxant effect of nitrite (10-6-5x10-3 M) was assessed using wire myography on isolated pre-constricted chorionic plate arteries (CPAs) and veins (CPVs) under normoxic (pO2 ∼5%) and hypoxic (pO2 ∼1%) conditions. The dependency on the NO-sGC-cGMP pathway and known nitrite reductase (NiR) activities was also investigated. Nitrite caused concentration-dependent vasorelaxation in both arteries and veins, and this effect was enhanced by hypoxia, significantly in CPVs (P < 0.01) and with a trend in CPAs (P = 0.054). Pre-incubation with NO scavengers (cPTIO and oxyhemoglobin) attenuated (P < 0.01 and P < 0.0001, respectively), and the sGC inhibitor ODQ completely abolished nitrite-mediated vasorelaxation, confirming the involvement of NO and sGC. Inhibition of potential NiR enzymes xanthine oxidoreductase, mitochondrial aldehyde dehydrogenase and mitochondrial bc1 complex did not attenuate vasorelaxation. This data suggests that nitrite may provide an important reservoir of NO bioactivity within the placenta to enhance blood flow when fetoplacental oxygenation is impaired, as occurring in pregnancy diseases such as pre-eclampsia and fetal growth restriction.

17.
Front Physiol ; 9: 1177, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30197602

RESUMO

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by autoimmunity, vasculopathy, and progressive fibrosis typically affecting multiple organs including the skin. SSc often is a lethal disorder, because effective disease-modifying treatment still remains unavailable. Vasculopathy with endothelial dysfunction, perivascular infiltration of mononuclear cells, vascular wall remodeling and rarefaction of capillaries is the hallmark of the disease. Most patients present with vasospastic attacks of the digital arteries referred to as 'Raynaud's phenomenon,' which is often an indication of an underlying widespread vasculopathy. Although autoimmune responses and inflammation are both found to play an important role in the pathogenesis of this vasculopathy, no definite initiating factors have been identified. Recently, several studies have underlined the potential role of oxidative stress in the pathogenesis of SSc vasculopathy thereby proposing a new aspect in the pathogenesis of this disease. For instance, circulating levels of reactive oxygen species (ROS) related markers have been found to correlate with SSc vasculopathy, the formation of fibrosis and the production of autoantibodies. Excess ROS formation is well-known to lead to endothelial cell (EC) injury and vascular complications. Collectively, these findings suggest a potential role of ROS in the initiation and progression of SSc vasculopathy. In this review, we present the background of oxidative stress related processes (e.g., EC injury, autoimmunity, inflammation, and vascular wall remodeling) that may contribute to SSc vasculopathy. Finally, we describe the use of oxidative stress related read-outs as clinical biomarkers of disease activity and evaluate potential anti-oxidative strategies in SSc.

18.
Nitric Oxide ; 80: 52-60, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30114529

RESUMO

BACKGROUND: Endogenous nitric oxide (NO) may contribute to ischemic and anesthetic preconditioning while exogenous NO protects against ischemia-reperfusion (I/R) injury in the heart and other organs. Why those beneficial effects observed in animal models do not always translate into clinical effectiveness remains unclear. To mitigate reperfusion damage a source of NO is required. NO inhalation is known to increase tissue NO metabolites, but little information exists about the lifetime of these species. We therefore sought to investigate the fate of major NO metabolite classes following NO inhalation in mice in vivo. METHODS: C57BL/6J mice were exposed to 80 ppm NO for 1 h. NO metabolites were measured in blood (plasma and erythrocytes) and tissues (heart, liver, lung, kidney and brain) immediately after NO exposure and up to 48 h thereafter. Concentrations of S-nitrosothiols, N-nitrosamines and NO-heme products as well as nitrite and nitrate were quantified by gas-phase chemiluminescence and ion chromatography. In separate experiments, mice breathed 80 ppm NO for 1 h prior to cardiac I/R injury (induced by coronary arterial ligation for 1 h, followed by recovery). After sacrifice, the size of the myocardial infarction (MI) and the area at risk (AAR) were measured. RESULTS: After NO inhalation, elevated nitroso/nitrosyl levels returned to baseline over the next 24 h, with distinct multi-phasic decay profiles in each compartment. S/N-nitroso compounds and NO-hemoglobin in blood decreased exponentially, but remained above baseline for up to 30min, whereas nitrate was elevated for up to 3hrs after discontinuing NO breathing. Hepatic S/N-nitroso species concentrations remained steady for 30min before dropping exponentially. Nitrate only rose in blood, liver and kidney; nitrite tended to be lower in all organs immediately after NO inhalation but fluctuated considerably in concentration thereafter. NO inhalation before myocardial ischemia decreased the ratio of MI/AAR by 30% vs controls (p = 0.002); only cardiac S-nitrosothiols and NO-hemes were elevated at time of reperfusion onset. CONCLUSIONS: Metabolites in blood do not reflect NO metabolite status of any organ. Although NO is rapidly inactivated by hemoglobin-mediated oxidation in the circulation, long-lived tissue metabolites may account for the myocardial preconditioning effects of inhaled NO. NO inhalation may afford similar protection in other organs.

19.
Br J Pharmacol ; 2018 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-29909607

RESUMO

  BACKGROUND AND PURPOSE: Posttranslational modifications of cysteine residues represent a major aspect of redox biology, and their reliable detection is key in providing mechanistic insights. The metastable character of these modifications and cell lysis-induced artifactual oxidation render current state-of-the-art protocols to rely on alkylation-based stabilization of labile cysteine derivatives before cell/tissue rupture. An untested assumption in these procedures is that for all cysteine derivatives, alkylation rates are faster than their dynamic interchange. However, when the interconversion of cysteine derivatives is not rate limiting, electrophilic labelling is under Curtin-Hammett control; hence, the final alkylated mixture may not represent the speciation that prevailed before alkylation. EXPERIMENTAL APPROACH: Buffered aqueous solutions of inorganic, organic, cysteine, GSH and GAPDH polysulfide species were used. Additional experiments in human plasma and serum revealed that monobromobimane can extract sulfide from the endogenous sulfur pool by shifting speciation equilibria, suggesting caution should be exercised when interpreting experimental results using this tool. KEY RESULTS: In the majority of cases, the speciation of alkylated polysulfide/thiol derivatives depended on the experimental conditions. Alkylation perturbed sulfur speciation in both a concentration- and time-dependent manner and strong alkylating agents cleaved polysulfur chains. Moreover, the labelling of sulfenic acids with dimedone also affected cysteine speciation, suggesting that part of the endogenous pool of products previously believed to represent sulfenic acid species may represent polysulfides. CONCLUSIONS AND IMPLICATIONS: We highlight methodological caveats potentially arising from these pitfalls and conclude that current derivatization strategies often fail to adequately capture physiological speciation of sulfur species.

20.
Artigo em Inglês | MEDLINE | ID: mdl-29905081

RESUMO

AIMS: Thiosulfate and sulfate are metabolites of hydrogen sulfide (H2S), a gaseous signaling molecule with cardiovascular (CV) protective properties. Urinary thiosulfate excretion and sulfate excretion are associated with favorable disease outcome in high-risk patient groups. We investigated the relationship between urinary excretion of sulfur metabolites, and risk of CV events and all-cause mortality in the general population. RESULTS: Subjects (n = 6839) of the Prevention of Renal and Vascular End-stage Disease (PREVEND) study were followed prospectively. At baseline, 24-h urinary excretion of thiosulfate and sulfate was determined. Median urinary thiosulfate and sulfate excretion values were 1.27 (interquartile range [IQR] 0.89-2.37) µmol/24 h and 15.7 (IQR 12.0-20.3) mmol/24 h, respectively. Neither thiosulfate nor sulfate excretion showed an independent association with risk of CV events. Sulfate, but not thiosulfate, was inversely associated with risk of all-cause mortality, independent of potential confounders (hazard ratio 0.73 [95% confidence interval 0.63-0.84], p < 0.001). This association appeared most pronounced for normolipidemic subjects (pinteraction = 0.019). INNOVATION: The strong association between sulfate excretion and mortality in the general population emphasizes the (patho)physiological importance of sulfate or its precursor H2S. CONCLUSION: We hypothesize that urinary sulfate excretion, which is inversely associated with all-cause mortality in the general population, holds clinical relevance as a beneficial modulator in health and disease. Antioxid. Redox Signal. 00, 000-000.

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