| 1. |
- Carlström, Mattias, et al.
(författare)
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Cross-talk Between Nitrate-Nitrite-NO and NO Synthase Pathways in Control of Vascular NO Homeostasis
- 2015
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Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert Inc. - 1523-0864 .- 1557-7716. ; 23:4, s. 295-306
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Inorganic nitrate and nitrite from endogenous and dietary sources have emerged as alternative substrates for nitric oxide (NO) formation in addition to the classic L-arginine NO synthase (NOS)-dependent pathway. Here, we investigated a potential cross-talk between these two pathways in the regulation of vascular function. Results: Long-term dietary supplementation with sodium nitrate (0.1 and 1mmol kg(-1) day(-1)) in rats caused a reversible dose-dependent reduction in phosphorylated endothelial NOS (eNOS) (Ser1177) in aorta and a concomitant increase in phosphorylation at Thr495. Moreover, eNOS-dependent vascular responses were attenuated in vessels harvested from nitrate-treated mice or when nitrite was acutely added to control vessels. The citrulline-to-arginine ratio in plasma, as a measure of eNOS activity, was reduced in nitrate-treated rodents. Telemetry measurements revealed that a low dietary nitrate dose reduced blood pressure, whereas a higher dose was associated with a paradoxical elevation. Finally, plasma cyclic guanosine monophosphate increased in mice that were treated with a low dietary nitrate dose and decreased with a higher dose. Innovation and Conclusions: These results demonstrate the existence of a cross-talk between the nitrate-nitrite-NO pathway and the NOS-dependent pathway in control of vascular NO homeostasis. Antioxid. Redox Signal. 23, 295-306.
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| 2. |
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| 3. |
- Gao, Xiang, et al.
(författare)
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Adenosine A1 receptor-dependent and independent pathways in modulating renal vascular responses to angiotensin II
- 2015
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 213:1, s. 268-276
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Renal afferent arterioles are the effector site for autoregulation of glomerular perfusion and filtration. There is synergistic interaction between angiotensin II (ANG II) and adenosine (Ado) in regulating arteriolar contraction, however, the mechanisms are not clear. In this context, this study investigated the contribution of A1 receptor dependent and independent signaling mechanisms.METHODS: Isolated perfused afferent arterioles from transgenic mice (A1+/+ and A1-/-) were used for vascular reactivity studies. Cultured vascular smooth muscle cells (VSMC) were used for phosphorylation studies of signaling proteins that induce arteriolar contraction.RESULTS: Maximal arteriolar contraction to ANG II was attenuated in A1-/- (22%) compared with A1+/+ (40%). Simultaneous incubation with low dose Ado (10-8 mol/L) enhanced ANG II-induced contraction in A1+/+ (58%), but also in A1-/- (42%). An Ado transporter inhibitor (NBTI) abolished this synergistic effect in A1-/-, but not in wild-type mice. Incubation with Ado+ANG II increased p38 phosphorylation in aortic VSMC from both genotypes, but treatment with NBTI only blocked phosphorylation in A1-/-. Combination of ANG II+Ado also increased MLC phosphorylation in A1+/+ but not significantly in A1-/-, and NBTI had no effects. In agreement, Ado+ANG II-induced phosphorylation of p38 and MLC in rat preglomerular VSMC was not affected by NBTI. However, during pharmacological inhibition of the A1 receptor simultaneous treatment with NBTI reduced phosphorylation of both p38 and MLC to control levels.CONCLUSION: Interaction between ANG II and Ado in VSMC normally involves A1 receptor signaling, but this can be compensated by receptor independent actions that phosphorylate p38 MAPK and MLC.
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| 4. |
- Gao, Xiang, et al.
(författare)
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NADPH Oxidase in the Renal Microvasculature Is a Primary Target for Blood Pressure-Lowering Effects by Inorganic Nitrate and Nitrite
- 2015
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Ingår i: Hypertension. - 0194-911X .- 1524-4563. ; 65:1, s. 161-
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Tidskriftsartikel (refereegranskat)abstract
- Renal oxidative stress and nitric oxide (NO) deficiency are key events in hypertension. Stimulation of a nitrate-nitrite-NO pathway with dietary nitrate reduces blood pressure, but the mechanisms or target organ are not clear. We investigated the hypothesis that inorganic nitrate and nitrite attenuate reactivity of renal microcirculation and blood pressure responses to angiotensin II (ANG II) by modulating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and NO bioavailability. Nitrite in the physiological range (10(-7)-10(-5) mol/L) dilated isolated perfused renal afferent arterioles, which were associated with increased NO. Contractions to ANG II (34%) and simultaneous NO synthase inhibition (56%) were attenuated by nitrite (18% and 26%). In a model of oxidative stress (superoxide dismutase-1 knockouts), abnormal ANG II-mediated arteriolar contractions (90%) were normalized by nitrite (44%). Mechanistically, effects of nitrite were abolished by NO scavenger and xanthine oxidase inhibitor, but only partially attenuated by inhibiting soluble guanylyl cyclase. Inhibition of NADPH oxidase with apocynin attenuated ANG II-induced contractility (35%) similar to that of nitrite. In the presence of nitrite, no further effect of apocynin was observed, suggesting NADPH oxidase as a possible target. In preglomerular vascular smooth muscle cells and kidney cortex, nitrite reduced both basal and ANG II-induced NADPH oxidase activity. These effects of nitrite were also abolished by xanthine oxidase inhibition. Moreover, supplementation with dietary nitrate (10(-2) mol/L) reduced renal NADPH oxidase activity and attenuated ANG II-mediated arteriolar contractions and hypertension (99+/-2-146+/-2 mm Hg) compared with placebo (100+/-3-168+/-3 mm Hg). In conclusion, these novel findings position NADPH oxidase in the renal microvasculature as a prime target for blood pressure-lowering effects of inorganic nitrate and nitrite.
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| 5. |
- Peleli, Maria, et al.
(författare)
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Enhanced XOR activity in eNOS-deficient mice Effects on the nitrate-nitrite-NO pathway and ROS homeostasis
- 2016
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 99, s. 472-484
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Tidskriftsartikel (refereegranskat)abstract
- Xanthine oxidoreductase (XOR) is generally known as the final enzyme in purine metabolism and as a source of reactive oxygen species (ROS). In addition, this enzyme has been suggested to mediate nitric oxide (NO) formation via reduction of inorganic nitrate and nitrite. This NO synthase (NOS)-independent pathway for NO generation is of particular importance during certain conditions when NO bioavailability is diminished due to reduced activity of endothelial NOS (eNOS) or increased oxidative stress, including aging and cardiovascular disease. The exact interplay between NOS- and XOR-derived NO generation is not fully elucidated yet. The aim of the present study was to investigate if eNOS deficiency is associated with changes in XOR expression and activity and the possible impact on nitrite, NO and ROS homeostasis. Plasma levels of nitrate and nitrite were similar between eNOS deficient (eNOS(-/-)) and wildtype (wt) mice. XOR activity was upregulated in eNOS(-/-) compared with wt, but not in nNOS(-/-), iNOS(-/-) or wt mice treated with the non-selective NOS inhibitor L-NAME. Following an acute dose of nitrate, plasma nitrite increased more in eNOS(-/-) compared with wt, and this augmented response was abolished by the selective XOR inhibitor febuxostat. Livers from eNOS(-/-) displayed higher nitrite reducing capacity compared with wt, and this effect was attenuated by febuxostat. Dietary supplementation with nitrate increased XOR expression and activity, but concomitantly reduced superoxide generation. The latter effect was also seen in vitro after nitrite administration. Treatment with febuxostat elevated blood pressure in eNOS(-/-), but not in wt mice. A high dose of dietary nitrate reduced blood pressure in na ve eNOS(-/-) mice, and again this effect was abolished by febuxostat. In conclusion, eNOS deficiency is associated with an upregulation of XOR facilitating the nitrate-nitrite-NO pathway and decreasing the generation of ROS. This interplay between XOR and eNOS is proposed to play a significant role in NO homeostasis and blood pressure regulation.
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| 6. |
- Peleli, Maria, et al.
(författare)
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In adenosine A(2B) knockouts acute treatment with inorganic nitrate improves glucose disposal, oxidative stress, and AMPK signaling in the liver
- 2015
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Rationale: Accumulating studies suggest that nitric oxide (NO) deficiency and oxidative stress are central pathological mechanisms in type 2 diabetes (T2D). Recent findings demonstrate therapeutic effects by boosting the nitrate-nitrite-NO pathway, which is an alternative pathway for NO formation. This study aimed at investigating the acute effects of inorganic nitrate on glucose and insulin signaling in adenosine A2B receptor knockout mice (A(2B)(-/-), a genetic mouse model of impaired metabolic regulation. Methods: Acute effects of nitrate treatment were investigated in aged wild-type (WT) and A(2B)(-/-) mice. One hour after injection with nitrate (0.1 mmol/kg, i.p.) or placebo, metabolic regulation was evaluated by intraperitoneal glucose and insulin tolerance tests. NADPH oxidase-mediated superoxide production and AMPK phosphorylation were measured in livers obtained from non-treated or glucose-treated mice, with or without prior nitrate injection. Plasma was used to determine insulin resistance (HOMA-IR) and NO signaling. Results: A(2B)(-/-) displayed increased body weight, reduced glucose clearance, and attenuated overall insulin responses compared with age-matched WT mice. Nitrate treatment increased circulating levels of nitrate, nitrite and cGMP in the A(2B)(-/-), and improved glucose clearance. In WT mice, however, nitrate treatment did not influence glucose clearance. HOMA-IR increased following glucose injection in the A(2B)(-/-), but remained at basal levels in mice pretreated with nitrate. NADPH oxidase activity in livers from A(2B)(-/-), but not WT mice, was reduced by nitrate treatment. Livers from A(2B)(-/-) displayed reduced AMPK phosphorylation compared with WT mice, and this was increased by nitrate treatment. Finally, injection with the anti-diabetic agent metformin induced similar therapeutic effects in the A(2B)(-/-) as observed with nitrate. Conclusion: The A(2B)(-/-) mouse is a genetic mouse model of metabolic syndrome. Acute treatment with nitrate improved the metabolic profile in it, at least partly via reduction in oxidative stress and improved AMPK signaling in the liver.
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| 7. |
- Porpino, Suenia K. P., et al.
(författare)
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Nitric oxide generation by the organic nitrate NDBP attenuates oxidative stress and angiotensin II-mediated hypertension
- 2016
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Ingår i: British Journal of Pharmacology. - : Wiley. - 0007-1188 .- 1476-5381. ; 173:14, s. 2290-2302
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Tidskriftsartikel (refereegranskat)abstract
- Background and PurposeNO deficiency and oxidative stress are crucially involved in the development or progression of cardiovascular disease, including hypertension and stroke. We have previously demonstrated that acute treatment with the newly discovered organic nitrate, 2-nitrate-1,3-dibuthoxypropan (NDBP), is associated with NO-like effects in the vasculature. This study aimed to further characterize the mechanism(s) and to elucidate the therapeutic potential in a model of hypertension and oxidative stress. Experimental ApproachA combination of ex vivo, in vitro and in vivo approaches was used to assess the effects of NDBP on vascular reactivity, NO release, NADPH oxidase activity and in a model of hypertension. Key ResultsEx vivo vascular studies demonstrated NDBP-mediated vasorelaxation in mesenteric resistance arteries, which was devoid of tolerance. In vitro studies using liver and kidney homogenates revealed dose-dependent and sustained NO generation by NDBP, which was attenuated by the xanthine oxidase inhibitor febuxostat. In addition, NDBP reduced NADPH oxidase activity in the liver and prevented angiotensin II-induced activation of NADPH oxidase in the kidney. In vivo studies showed that NDBP halted the progression of hypertension in mice with chronic angiotensin II infusion. This was associated with attenuated cardiac hypertrophy, and reduced NADPH oxidase-derived oxidative stress and fibrosis in the kidney and heart. Conclusion and ImplicationsThe novel organic nitrate NDBP halts the progression of angiotensin II-mediated hypertension. Mechanistically, our findings suggest that NDBP treatment is associated with sustained NO release and attenuated activity of NADPH oxidase, which to some extent requires functional xanthine oxidase.
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| 8. |
- Yang, Ting, et al.
(författare)
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Abrogation of adenosine A(1) receptor signalling improves metabolic regulation in mice by modulating oxidative stress and inflammatory responses
- 2015
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 58:7, s. 1610-1620
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis Adenosine is an important regulator of metabolism; however, the role of the A(1) receptor during ageing and obesity is unclear. The aim of this study was to investigate the effects of A(1) signalling in modulating metabolic function during ageing. Methods Age-matched young and aged A (1) (also known as Adora1)-knockout (A (1) (-/-)) and wild-type (A (1) (+/+)) mice were used. Metabolic regulation was evaluated by body composition, and glucose and insulin tolerance tests. Isolated islets and islet arterioles were used to detect islet endocrine and vascular function. Oxidative stress and inflammation status were measured in metabolic organs and systemically. Results Advanced age was associated with both reduced glucose clearance and insulin sensitivity, as well as increased visceral adipose tissue (VAT) in A (1) (+/+) compared with A (1) (-/-) mice. Islet morphology and insulin content were similar between genotypes, but relative changes in in vitro insulin release following glucose stimulation were reduced in aged A (1) (+/+) compared with A (1) (-/-) mice. Islet arteriolar responses to angiotensin II were stronger in aged A (1) (+/+) mice, this being associated with increased NADPH oxidase activity. Ageing resulted in multiple changes in A (1) (+/+) compared with A (1) (-/-) mice, including enhanced NADPH oxidase-derived O-2 (-) formation and NADPH oxidase isoform 2 (Nox2) protein expression in pancreas and VAT; elevated levels of circulating insulin, leptin and proinflammatory cytokines (TNF-alpha, IL-1 beta, IL-6 and IL-12); and accumulation of CD4(+) T cells in VAT. This was associated with impaired insulin signalling in VAT from aged A (1) (+/+) mice. Conclusions/interpretation These studies emphasise that A(1) receptors regulate metabolism and islet endocrine and vascular functions during ageing, including via the modulation of oxidative stress and inflammatory responses, among other things.
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| 9. |
- Yang, Ting, et al.
(författare)
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Genetic Abrogation of Adenosine A(3) Receptor Prevents Uninephrectomy and High Salt-Induced Hypertension
- 2016
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Ingår i: Journal of the American Heart Association. - 2047-9980. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- Background - Early-life reduction in nephron number (uninephrectomy [UNX]) and chronic high salt (HS) intake increase the risk of hypertension and chronic kidney disease. Adenosine signaling via its different receptors has been implicated in modulating renal, cardiovascular, and metabolic functions as well as inflammatory processes; however, the specific role of the A(3) receptor in cardiovascular diseases is not clear. In this study, gene-modified mice were used to investigate the hypothesis that lack of A(3) signaling prevents the development of hypertension and attenuates renal and cardiovascular injuries following UNX in combination with HS (UNX-HS) in mice.Methods and Results - Wild-type (A(3)(+/+)) mice subjected to UNX-HS developed hypertension compared with controls (mean arterial pressure 106 +/- 3 versus 82 +/- 3 mm Hg; P<0.05) and displayed an impaired metabolic phenotype (eg, increased adiposity, reduced glucose tolerance, hyperinsulinemia). These changes were associated with both cardiac hypertrophy and fibrosis together with renal injuries and proteinuria. All of these pathological hallmarks were significantly attenuated in the A(3)(-/-) mice. Mechanistically, absence of A(3) receptors protected from UNX-HS-associated increase in renal NADPH oxidase activity and Nox2 expression. In addition, circulating cytokines including interleukins 1 beta, 6, 12, and 10 were increased in A(3)(+/+) following UNX-HS, but these cytokines were already elevated in naive A(3)(-/-) mice and did not change following UNX-HS.Conclusions - Reduction in nephron number combined with chronic HS intake is associated with oxidative stress, chronic inflammation, and development of hypertension in mice. Absence of adenosine A(3) receptor signaling was strongly protective in this novel mouse model of renal and cardiovascular disease.
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| 10. |
- Zollbrecht, Christa, et al.
(författare)
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Nitrite-mediated reduction of macrophage NADPH oxidase activity is dependent on xanthine oxidoreductase-derived nitric oxide but independent of S-nitrosation
- 2016
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Ingår i: Redox Biology. - : Elsevier BV. - 2213-2317. ; 10, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- Background: Inorganic nitrite has shown beneficial effects in cardiovascular and metabolic diseases partly via attenuation of NADPH-oxidase (NOX)-mediated oxidative stress. However, the exact mechanisms are still unclear. Here we investigated the role of S-nitrosation or altered expression of NOX subunits, and the role of xanthine oxidoreductase (XOR) in nitrite-derived nitric oxide (NO) production. Methods: Mouse macrophages were activated with LPS in the presence or absence of nitrite. NOX activity was measured by lucigenin-dependent chemiluminescence. Gene and protein expression of NOX2 subunits and XOR were investigated using qPCR and Western Blot. S-nitrosation of Nox2 and p22phox was studied with a Biotin Switch assay. Uric acid levels in cell culture medium were analyzed as a measure of XOR activity, and NO production was assessed by DAF-FM fluorescence. Results: NOX activity in activated macrophages was significantly reduced by nitrite. Reduced NOX activity was not attributed to decreased NOX gene expression. However, protein levels of p47phox and p67phox subunits were reduced by nitrite in activated macrophages. Protein expression of Nox2 and p22phox was not influenced by this treatment and neither was their S-nitrosation status. Increased uric acid levels after nitrite and diminished NO production during XOR-inhibition with febuxostat suggest that XOR is more active during nitrite-treatment of activated macrophages and plays an important role in the bioactivation of nitrite. Conclusions: Our findings contribute to the mechanistic understanding about the therapeutic effects associated with nitrite supplementation in many diseases. We show that nitrite-mediated inhibition of NOX activity cannot be explained by S-nitrosation of the NOX enzyme, but that changes in NOX2 expression and XOR function may contribute.
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