Function Of Resistance Arteries Research Articles

Paying the Toll for Inflammation

Paying the Toll for Inflammation

Endothelial Dysfunction of Conduit Arteries in Patients with Repaired Coarctation of the Aorta.

Adult patients with repaired coarctation of the aorta (r-CoA) show high prevalence of late hypertension, but the exact mechanisms of this phenomenon are unknown. Endothelial dysfunction has been implicated in this paradoxical hypertension. We evaluated the endothelial function of both conduit and resistance arteries by using flow-mediated dilation (FMD) and digital peripheral artery tonometry (PAT).Seventeen patients with r-CoA and one patient with repaired interrupted aortic arch (r-CoA group) aged 22.0 ± 6.9 years (5 females) underwent FMD of the right brachial artery, PAT of the right finger, blood marker tests, ambulatory blood pressure monitoring, echocardiography, carotid ultrasonography, and brachio-ankle pulse wave velocity measurement. The median age at aortic arch reconstruction was 2.0 months (interquartile range: 15 days to 7.0 years). Results were compared with 17 age-matched healthy subjects (control group).Eight (44%) patients of the r-CoA group were hypertensive (5 received antihypertensive drugs). Patients in the r-CoA group showed significantly lower FMD (3.8 ± 1.5 versus 6.6 ± 2.5%, P < 0.001), larger intima-media thickness (0.63 ± 0.17 versus 0.47 ± 0.09 mm, P = 0.001), and higher left ventricular mass index (91.4 ± 24.6 versus 73.4 ± 17.3 g/m2, P = 0.017) than those in the control group. There were no significant differences in PAT (refractory hyperemia index, 1.86 ± 0.43 versus 1.99 ± 0.59, P = 0.48) and brachio-ankle pulse wave velocity between the two groups.Vascular dysfunction in r-CoA patients, particularly endothelial dysfunction, tends to occur more significantly in conduit arteries than in resistance arteries.

Linoleic acid reduces vascular reactivity and improves the vascular dysfunction of the small mesentery in hypertension

We aimed to investigate the effect of linoleic acid (LA) treatment on the blood pressure and function of mesenteric resistance arteries (MRA) in spontaneous hypertensive rats (SHR). Male SHR were treated daily with LA (15 mg/kg) or vehicle (control) for 15 days. Compared with controls, LA treatment decreased blood pressure and showed the following in MRA: (1) increased lumen and external diameter, (2) decreased wall:lumen ratio and wall thickness, (3) decreased stiffness and (4) less collagen deposition. LA treatment reduced the contractile response to phenylephrine, although there were no changes observed in MRA in regard to the acetylcholine or sodium nitroprusside responses. Incubation with L-NAME left-shifted the reactivity to phenylephrine only in the MRA treated group, suggesting that LA treatment can improve NO bioavailability. This result was accompanied by an increase “in situ” NO production. Incubation with tiron decreased vascular reactivity to phenylephrine in MRA in LA rats, which was accompanied by decreased superoxide anion production. Moreover, incubation with indomethacin (non-selective COX inhibitor, 10 μM), NS 398 (COX-2 specific inhibitor, 1 μM), furegrelate (TXA2 synthase inhibitor, 1 μM), SQ 29.548 (TP receptor antagonist, 1 μM) and SC 19220 (EP1 receptor antagonist, 10 μM) reduced the vasoconstrictor responses to phenylephrine in MRA in the treated group. These results were accompanied by a reduction in COX-2 protein expression. In conclusion, these findings show that LA treatment decreases blood pressure. In addition, the improvement of endothelial dysfunction and structural changes in this hypertension model may be responsible for the reduction in blood pressure.

FGF23 impairs peripheral microvascular function in renal failure.

Cardiovascular diseases account for ~50% of mortality in patients with chronic kidney disease (CKD). Fibroblast growth factor 23 (FGF23) is independently associated with endothelial dysfunction and cardiovascular mortality. We hypothesized that CKD impairs microvascular endothelial function and that this can be attributed to FGF23. Mice were subjected to partial nephrectomy (5/6Nx) or sham surgery. To evaluate the functional role of FGF23, non-CKD mice received FGF23 injections and CKD mice received FGF23-blocking antibodies after 5/6Nx surgery. To examine microvascular function, myocardial perfusion in vivo and vascular function of gracilis resistance arteries ex vivo were assessed in mice. 5/6Nx surgery blunted ex vivo vasodilator responses to acetylcholine, whereas responses to sodium nitroprusside or endothelin were normal. In vivo FGF23 injections in non-CKD mice mimicked this endothelial defect, and FGF23 antibodies in 5/6Nx mice prevented endothelial dysfunction. Stimulation of microvascular endothelial cells with FGF23 in vitro did not induce ERK phosphorylation. Increased plasma asymmetric dimethylarginine concentrations were increased by FGF23 and strongly correlated with endothelial dysfunction. Increased FGF23 concentration did not mimic impaired endothelial function in the myocardium of 5/6Nx mice. In conclusion, impaired peripheral endothelium-dependent vasodilatation in 5/6Nx mice is mediated by FGF23 and can be prevented by blocking FGF23. These data corroborate FGF23 as an important target to combat cardiovascular disease in CKD. NEW & NOTEWORTHY In the present study, we provide the first evidence that fibroblast growth factor 23 (FGF23) is a cause of peripheral endothelial dysfunction in a model of early chronic kidney disease (CKD) and that endothelial dysfunction in CKD can be prevented by blockade of FGF23. This pathological effect on endothelial cells was induced by long-term exposure of physiological levels of FGF23. Mechanistically, increased plasma asymmetric dimethylarginine concentrations were strongly associated with this endothelial dysfunction in CKD and were increased by FGF23.

Sustained conduction of vasomotor responses in rat mesenteric arteries in a two-compartment invitro set-up.

AimConduction of vasomotor responses may contribute to long‐term regulation of resistance artery function and structure. Most previous studies have addressed conduction of vasoactivity only during very brief stimulations. We developed a novel set‐up that allows the local pharmacological stimulation of arteries in vitro for extended periods of time and studied the conduction of vasomotor responses in rat mesenteric arteries under those conditions.MethodsThe new in vitro set‐up was based on the pressure myograph. The superfusion chamber was divided halfway along the vessel into two compartments, allowing an independent superfusion of the arterial segment in each compartment. Local and remote cumulative concentration‐response curves were obtained for a range of vasoactive agents. Additional experiments were performed with the gap junction inhibitor 18β‐glycyrrhetinic acid and in absence of the endothelium.ResultsPhenylephrine‐induced constriction and acetylcholine‐induced dilation were conducted over a measured distance up to 2.84 mm, and this conduction was maintained for 5 minutes. Conduction of acetylcholine‐induced dilation was inhibited by 18β‐glycyrrhetinic acid, and conduction of phenylephrine‐induced constriction was abolished in absence of the endothelium. Constriction in response to high K+ was not conducted. Absence of remote stimulation dampened the local response to phenylephrine.ConclusionThis study demonstrates maintained conduction of vasoactive responses to physiological agonists in rat mesenteric small arteries likely via gap junctions and endothelial cells, providing a possible mechanism for the sustained functional and structural control of arterial networks.

Importance of mechanical signals in promoting exercise-induced improvements in vasomotor function of aged skeletal muscle resistance arteries.

Current research indicates that vasomotor responses are altered with aging in skeletal muscle resistance arteries. The changes in vasomotor function are characterized by impaired vasodilator and vasoconstrictor responses. The detrimental effects of aging on vasomotor function are attenuated in some vascular beds after a program of endurance exercise training. The signals associated with exercise responsible for inducing improvements in vasomotor function have been proposed to involve short-duration increases in intraluminal shear stress and/or pressure during individual bouts of exercise. Here, we review evidence that increases in shear stress and pressure, within a range believed to present in these arteries during exercise, promote healthy vasomotor function in aged resistance arteries. We conclude that available research is consistent with the interpretation that short-duration mechanical stimulation, through increases in shear stress and pressure, contributes to the beneficial effects of exercise on vasomotor function in aged skeletal muscle resistance arteries.

Klf4 has an unexpected protective role in perivascular cells within the microvasculature.

Recent smooth muscle cell (SMC) lineage-tracing studies have revealed that SMCs undergo remarkable changes in phenotype during development of atherosclerosis. Of major interest, we demonstrated that Kruppel-like factor 4 (KLF4) in SMCs is detrimental for overall lesion pathogenesis, in that SMC-specific conditional knockout of the KLF4 gene ( Klf4) resulted in smaller, more-stable lesions that exhibited marked reductions in the numbers of SMC-derived macrophage- and mesenchymal stem cell-like cells. However, since the clinical consequences of atherosclerosis typically occur well after our reproductive years, we sought to identify beneficial KLF4-dependent SMC functions that were likely to be evolutionarily conserved. We tested the hypothesis that KLF4-dependent SMC transitions play an important role in the tissue injury-repair process. Using SMC-specific lineage-tracing mice positive and negative for simultaneous SMC-specific conditional knockout of Klf4, we demonstrate that SMCs in the remodeling heart after ischemia-reperfusion injury (IRI) express KLF4 and transition to a KLF4-dependent macrophage-like state and a KLF4-independent myofibroblast-like state. Moreover, heart failure after IRI was exacerbated in SMC Klf4 knockout mice. Surprisingly, we observed a significant cardiac dilation in SMC Klf4 knockout mice before IRI as well as a reduction in peripheral resistance. KLF4 chromatin immunoprecipitation-sequencing analysis on mesenteric vascular beds identified potential baseline SMC KLF4 target genes in numerous pathways, including PDGF and FGF. Moreover, microvascular tissue beds in SMC Klf4 knockout mice had gaps in lineage-traced SMC coverage along the resistance arteries and exhibited increased permeability. Together, these results provide novel evidence that Klf4 has a critical maintenance role within microvascular SMCs: it is required for normal SMC function and coverage of resistance arteries. NEW & NOTEWORTHY We report novel evidence that the Kruppel-like factor 4 gene ( Klf4) has a critical maintenance role within microvascular smooth muscle cells (SMCs). SMC-specific Klf4 knockout at baseline resulted in a loss of lineage-traced SMC coverage of resistance arteries, dilation of resistance arteries, increased blood flow, and cardiac dilation.

Impact of Aerobic Capacity, Age and Duration of Disease on Arterial Function in Individuals with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system associated with vascular dysfunction and increased risk of cardiovascular disease and mortality. Aerobic capacity (VO2peak) and age are strong predictors of arterial function in a healthy cohort; however, we know very little about the role of VO2peak, disease duration, and age on vasculature in those with MS.PurposeTo evaluate the role of fitness, duration of disease since diagnosis (Dx) and age on arterial function in individuals with MS.Methods56 individuals (Male: 15, 46±12 yrs, BMI: 29.0±6.8) with MS were divided into young (≤50 years) or older (&gt;50 years) groups. The age groups were further delineated by length of Dx, defined as short (≤10 years) or long (&gt;10 years). Brachial blood pressure (BP) was obtained after a 10 minute rest. Resistance artery function was assessed using strain gauge plethysmography. Reactive hyperemia was calculated as the absolute change between resting and peak flow. Carotid artery stiffness was assessed by ultrasound (Beta‐Stiffness Index (β), Elastic Modulus (Ep) and Arterial Compliance (AC)). A maximal incremental cycle test was performed to assess VO2peak.ResultsSee Table. Older adults with MS had higher systolic and mean BP (p&lt;0.05). Length of Dx and age did not influence resistance vessel function (p&gt;0.05), however, VO2peak was associated with peak forearm blood flow and peak conductance. Young and older adults with MS exhibited differential responses in large artery stiffness with disease progression, even after controlling for fitness level (β, Ep, AC) (interactions, p&lt;0.05). Older adults had higher arterial stiffness (β, Ep, AC) with shorter disease duration compared to young. However, with longer disease duration, there was no difference between younger and older adults (p&gt;0.05). β and Ep in older adults decreased with progression of MS (p&lt;0.05). Disease duration did not affect arterial stiffness in young adults (p&gt;0.05).ConclusionIt appears greater fitness can improve resistance artery function in the MS population. Fitness does not influence large artery stiffness in MS, but with age and duration of disease β and Ep are counterintuitively reduced. These findings require further investigation to elucidate the effects of age, VO2peak and length of Dx on vascular function in MS.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Phosphodiesterase-3 inhibitor cilostazol reverses endothelial dysfunction with ageing in rat mesenteric resistance arteries

Ageing impairs endothelial function, which is considered a hallmark of the development of cardiovascular diseases in elderly. Cilostazol, a phosphodiesterase-3 inhibitor, has antiplatelet, antithrombotic and protective effects on endothelial cells. Here, we hypothesized that cilostazol could improve endothelial function in mesenteric resistance arteries (MRA) from old rats. Using eight-week cilostazol-treated (100mg/kg/day) or untreated 72-week-old Wistar rats, we evaluate the relaxation to acetylcholine, sodium nitroprusside (SNP), forskolin and isoproterenol and the noradrenaline-induced contraction in MRA. Superoxide anion and nitric oxide (NO) was measured by dihydroethidium- and diaminofluorescein-2-emitted fluorescence, respectively. Normotensive old rats had impaired acetylcholine-induced NO- and EDHF-mediated relaxation and increased noradrenaline vasoconstriction than young rats. This age-associated endothelial dysfunction was restored by cilostazol treatment. Relaxation to SNP, forskolin or isoproterenol remained unmodified by cilostazol. Diaminofluorescein-2-emitted fluorescence was increased while dihydroethidium-emitted was decreased by cilostazol, indicating increased NO and reduced superoxide generation, respectively. Cilostazol improves endothelial function in old MRA without affecting blood pressure. This protective effect of cilostazol could be attributed to reduced oxidative stress, increased NO bioavailability and EDHF-type relaxation. Although these results are preliminary, we believe that should stimulate further interest in cilostazol as an alternative for the treatment of age-related vascular disorders.

High-Intensity Exercise Enhances Conduit Artery Vascular Function in Older Adults.

Modulation of vascular function follows an exercise intensity-dependent pattern in young adults. This study aimed to investigate the potential intensity-dependent effects of an acute bout of exercise on conduit and resistance artery function in healthy older adults. Eleven healthy older adults (five males/six females, 66 ± 1 yr) completed 30 min of recumbent cycling at 50%-55% (low intensity) and 75%-80% (high intensity) of their age-predicted HRmax on two separate study visits. Doppler ultrasound measures of brachial artery flow-mediated dilation (FMD) and reactive hyperemia were taken at baseline, 10 min postexercise, and 1 h postexercise. In addition, cardiovascular hemodynamics and brachial shear rate were measured every 5 min during exercise. Brachial artery FMD was enhanced 10 min after high-intensity exercise (4.8% ± 0.2% to 9.1% ± 0.3%, P < 0.01), but not low-intensity (4.7% ± 0.2% to 6.2% ± 0.3%, P = 0.54) exercise. Peak and total (area under the curve) blood flow during reactive hyperemia (measures of resistance artery function) were enhanced 10 min postexercise for both intensities (peak low intensity, 372 ± 31 to 444 ± 37 mL·min; peak high intensity, 391 ± 30 to 455 ± 28 mL·min; total low intensity, 142 ± 16 to 205 ± 20 mL; total high intensity, 158 ± 14 to 240 ± 25 mL; main effect of time for both, P < 0.05). However, the magnitude of change in peak and the total blood flow were not different between exercise intensities (interaction effect; P = 0.56 and P = 0.97, respectively). Independent of exercise intensity, FMD returned to baseline 1 h after exercise (high, 5.9% ± 0.3%; low, 5.1% ± 0.1%; both P > 0.05). Our data indicate that high-intensity exercise acutely enhances conduit artery function in healthy older adults. In addition, an acute bout of exercise enhances resistance artery function independent of intensity.

Shaker-related voltage-gated K+ channel expression and vasomotor function in human coronary resistance arteries.

KV channels are important regulators of vascular tone, but the identity of specific KV channels involved and their regulation in disease remain less well understood. We determined the expression of KV 1 channel subunits and their role in cAMP-mediated dilation in coronary resistance arteries from subjects with and without CAD. HCAs from patients with and without CAD were assessed for mRNA and protein expression of KV 1 channel subunits with molecular techniques and for vasodilator response with isolated arterial myography. Assays of mRNA transcripts, membrane protein expression, and vascular cell-specific localization revealed abundant expression of KV 1.5 in vascular smooth muscle cells of non-CAD HCAs. Isoproterenol and forskolin, two distinct cAMP-mediated vasodilators, induced potent dilation of non-CAD arterioles, which was inhibited by both the general KV blocker 4-AP and the selective KV 1.5 blocker DPO-1. The cAMP-mediated dilation was reduced in CAD and was accompanied by a loss of or reduced contribution of 4-AP-sensitive KV channels. KV 1.5, as a major 4-AP-sensitive KV 1 channel expressed in coronary VSMCs, mediates cAMP-mediated dilation in non-CAD arterioles. The cAMP-mediated dilation is reduced in CAD coronary arterioles, which is associated with impaired 4-AP-sensitive KV channel function.

Relationship between impaired forearm endothelial function and osteoporosis in Tunisian postmenopausal women: Serum lipids or others factors?

AimsRecent research suggests that bone loss and vascular endothelial dysfunction are functionally interwoven in postmenopausal women. The aim of our study was to assess the relationship between forearm endothelial function and bone mineral density in postmenopausal women. MethodsWe studied the endothelial function of resistance arteries of the forearm in 113 Tunisians postmenopausal women, 75 with normal bone mineral density (BMD) and 38 with osteoporosis. Skin blood flow (SBF) was measured by laser Doppler during three cumulative doses of acetylcholine by iontophoresis (endothelium dependent vasodilatation: EDV) and after local heating (endothelium independent vasodilatation: EIV). Dual-energy X-ray absorptiometry was used to measure BMD of the hip and lumbar spine (L1–L4). Resultswomen with normal BMD had a higher maximal EDV (415,9±410%) than those with osteoporosis (111±135%) (P=.03), even after adjusting for a variety of confounding factors (age, body mass index, years since the start of menopause, weekly exercise and cardiovascular diseases). For the EIV, no difference was detected between the two groups. In addition, we found no difference in serum lipid, lipoprotein and apolipoprotein concentrations, between the two groups. In multivariate regression analysis, the EDV was correlated only with lumbar spine BMD (p=,026). Conclusionour study supports the hypothesis that postmenopausal women with osteoporosis have a weak forearm endothelial function.

Calcium and electrical dynamics in lymphatic endothelium.

Endothelial cell function in resistance arteries integrates Ca2+ signalling with hyperpolarization to promote relaxation of smooth muscle cells and increase tissue blood flow. Whether complementary signalling occurs in lymphatic endothelium is unknown. Intracellular calcium and membrane potential were evaluated in endothelial cell tubes freshly isolated from mouse collecting lymphatic vessels of the popliteal fossa. Resting membrane potential measured using intracellular microelectrodes averaged ∼-70mV. Stimulation of lymphatic endothelium by acetylcholine or a TRPV4 channel agonist increased intracellular Ca2+ with robust depolarization. Findings from Trpv4-/- mice and with computational modelling suggest that the initial mobilization of intracellular Ca2+ leads to influx of Ca2+ and Na+ through TRPV4 channels to evoke depolarization. Lymphatic endothelial cells lack the Ca2+ -activated K+ channels present in arterial endothelium to generate endothelium-derived hyperpolarization. Absence of this signalling pathway with effective depolarization may promote rapid conduction of contraction along lymphatic muscle during lymph propulsion. Subsequent to a rise in intracellular Ca2+ ([Ca2+ ]i ), hyperpolarization of the endothelium coordinates vascular smooth muscle relaxation along resistance arteries during blood flow control. In the lymphatic vasculature, collecting vessels generate rapid contractions coordinated along lymphangions to propel lymph, but the underlying signalling pathways are unknown. We tested the hypothesis that lymphatic endothelial cells (LECs) exhibit Ca2+ and electrical signalling properties that facilitate lymph propulsion. To study electrical and intracellular Ca2+ signalling dynamics in lymphatic endothelium, we excised collecting lymphatic vessels from the popliteal fossa of mice and removed their muscle cells to isolate intact LEC tubes (LECTs). Intracellular recording revealed a resting membrane potential of ∼-70mV. Acetylcholine (ACh) increased [Ca2+ ]i with a time course similar to that observed in endothelium of resistance arteries (i.e. rapid initial peak with a sustained 'plateau'). In striking contrast to the endothelium-derived hyperpolarization (EDH) characteristic of arteries, LECs depolarized (>15mV) to either ACh or TRPV4 channel activation. This depolarization was facilitated by the absence of Ca2+ -activated K+ (KCa ) channels as confirmed with PCR, persisted in the absence of extracellular Ca2+ , was abolished by LaCl3 and was attenuated ∼70% in LECTs from Trpv4-/- mice. Computational modelling of ion fluxes in LECs indicated that omitting K+ channels supports our experimental results. These findings reveal novel signalling events in LECs, which are devoid of the KCa activity abundant in arterial endothelium. Absence of EDH with effective depolarization of LECs may promote the rapid conduction of contraction waves along lymphatic muscle during lymph propulsion.

The acute effect of black tea consumption on resistance artery endothelial function in healthy subjects. A randomized controlled trial

Black tea is a main source of flavonoids in the Western diet and has been associated with reduced risk for cardiovascular disease, possibly through lowering blood pressure. These effects may be mediated through improving endothelial function of resistance arteries. The aim of this study was therefore to examine the acute impact of black tea on forearm resistance artery endothelial function in healthy, normotensive middle-aged subjects. Twenty middle-aged men and women (age-range 45-75 years) were recruited into a double-blind, randomized, placebo-controlled crossover intervention study. Forearm resistance artery blood flow (FBF, measured using venous occlusion plethysmography) in response to incremental doses of acetylcholine, sodium nitroprusside and L-NG-monomethyl arginine were determined 2h after consumption of either black tea containing ∼400mg flavonoids (equivalent to 2-3 cups of tea) or a taste- and color-matched placebo. The mean FBF-response to acetylcholine after tea consumption was 23% higher compared to the response after placebo (95% CI:-20%,+88%), but this difference did not reach statistical significance (P=0.32). No significant differences in the FBF-responses to sodium nitroprusside and L-NG-monomethyl arginine were found between the tea and placebo interventions (P=0.96 and 0.74, respectively). Correcting FBF for changes in blood pressure did not alter the outcomes. We found no evidence that acute intake of black tea significantly altered endothelium-dependent vasodilation of forearm resistance arteries in healthy middle-aged subjects. Interventions with a longer duration of tea ingestion are required to further explore the (long-term) impact of tea flavonoids on blood pressure regulatory mechanisms. This trial was registered at clinicaltrials.gov as NCT02328339.

Abstract P286: Circulating Lipoxin A4 Causes Resolution of Inflammation via Estrogen Receptor Activation, While Mitochondria N-Formyl Peptides Induce Inflammation via Formyl Peptide Receptor in Hypertension

Recently, we observed that mitochondrial components have inflammatogenic proprieties and that their fragments are elevated in the circulation of spontaneously hypertensive rats (SHR). Also, infusion of mitochondrial N-formyl peptides (F-MITs) into rats induces inflammation and vascular dysfunction via formyl peptide receptor (FPR) activation. In contrast, Lipoxin A4 (LXA4), a mediator of resolution of inflammation, also binds FPR. However, LXA4-FPR-dependent effects seem to be opposite from F-MITs. We first hypothesized that LXA4 is decreased in SHR. We collected plasma from male SHR and Wistar Kyoto rats (WKY) (12 weeks old) and LXA4 was extracted via hydrophobic, reverse-phase, silica-based column. Our initial hypothesis was refuted, since LXA4 was increased in SHR (WKY: 0.33±0.05 vs. SHR: 0.79±0.08 ng/ml, p&lt;0.05). As a result, we inhibited LXA4 synthesis in SHR with a 5-lipoxygenase (5-LOX) inhibitor Zileuton (10mg/kg/day i.p.) for 10 days. 5-LOX blockade did not change blood pressure (BP), but did cause a deterioration of vascular function in intrarenal and mesenteric resistance arteries in SHR. On the other hand, the blockade of FPR in SHR for 10 days with Cyclosporin H (CsH) and WRW4 (0.1 mg/kg/day) reduced BP (telemetry: SHR+control: 151±7.2 vs. SHR+CsH+WRW4: 138±0.4 mmHg, p&lt;0.05) and left ventricle mass. FPR blockade also ameliorated acetylcholine-induced relaxation of intrarenal (Emax: SHR+control: 10±5 vs. SHR+CsH+WRW4: 28±6 %, p&lt;0.05) and mesenteric resistance arteries (Emax: SHR+vehicle: 74±10 vs. SHR+CsH+WRW4: 99±0.6 %, p&lt;0.05). From these data, we suggest that LXA4 does not act on FPR to promote resolution of inflammation. We believe that another factor binds FPR (e.g., F-MITs) and leads to vascular damage in SHR. In support of this, we observed that LXA4 phosphorylates estrogen receptor (ER) alpha Ser118 in aortic vascular smooth muscle cells (VSMC) and ER antagonist ICI-182 (100nM), but not FPR antagonist, abolishes these responses. On the other hand, FMITs increased phosphoERK 1/2 in VSMC and FPR antagonists blocked this increase. In conclusion, FMITs and LXA4 have opposite effects in SHR. LXA4 induces resolution of inflammation, possibly via ER activation, and F-MITs lead to damage via FPR activation.

Aluminum exposure at human dietary levels promotes vascular dysfunction and increases blood pressure in rats: A concerted action of NAD(P)H oxidase and COX-2.

Aluminum (Al) is a non-essential metal and a significant environmental contaminant and is associated with a number of human diseases including cardiovascular disease. We investigated the effects of Al exposure at doses similar to human dietary levels on the cardiovascular system over a 60day period. Wistar male rats were divided into two major groups and received orally: 1) Low aluminum level - rats were subdivided and treated for 60days as follows: a) Untreated - ultrapure water; b) AlCl3 at a dose of 8.3mg/kg bw for 60days, representing human Al exposure by diet; and 2) High aluminum level - rats were subdivided and treated for 42days as follows: C) Untreated - ultrapure water; d) AlCl3 at 100mg/kg bw for 42days, representing a high level of human exposure to Al. Effects on systolic blood pressure (SBP) and vascular function of aortic and mesenteric resistance arteries (MRA) were studied. Endothelium and smooth muscle integrity were evaluated by concentration-response curves to acetylcholine (ACh) and sodium nitroprusside. Vasoconstrictor responses to phenylephrine (Phe) in the presence and absence of endothelium and in the presence of the NOS inhibitor L-NAME, the potassium channels blocker TEA, the NAD(P)H oxidase inhibitor apocynin, superoxide dismutase (SOD), the non-selective COX inhibitor indomethacin and the selective COX-2 inhibitor NS 398 were analyzed. Vascular reactive oxygen species (ROS), lipid peroxidation and total antioxidant capacity, were measured. The mRNA expressions of eNOS, NAD(P)H oxidase 1 and 2, SOD1, COX-2 and thromboxane A2 receptor (TXA-2 R) were also investigated. Al exposure at human dietary levels impaired the cardiovascular system and these effects were almost the same as Al exposure at much higher levels. Al increased SBP, decreased ACh-induced relaxation, increased response to Phe, decreased endothelial modulation of vasoconstrictor responses, the bioavailability of nitric oxide (NO), the involvement of potassium channels on vascular responses, as well as increased ROS production from NAD(P)H oxidase and contractile prostanoids mainly from COX-2 in both aorta and mesenteric arteries. Al exposure increased vascular ROS production and lipid peroxidation as well as altered the antioxidant status in aorta and MRA. Al decreased vascular eNOS and SOD1 mRNA levels and increased the NAD(P)H oxidase 1, COX-2 and TXA-2 R mRNA levels. Our results point to an excess of ROS mainly from NAD(P)H oxidase after Al exposure and the increased vascular prostanoids from COX-2 acting in concert to decrease NO bioavailability, thus inducing vascular dysfunction and increasing blood pressure. Therefore, 60-day chronic exposure to Al, which reflects common human dietary Al intake, appears to pose a risk for the cardiovascular system.

151 Nox5 induces vascular dysfunction and arterial remodelling independently of blood pressure elevation in ang ii-infused nox5-expressing mice

Nox5 is a unique Ca2+-sensitive Nox isoform that is expressed in human vascular smooth muscle cells (VSMC). Although Nox5 has been implicated in diabetic nephropathy, its role in vascular function...

Chronic administration of sodium nitrite prevents hypertension and protects arterial endothelial function by reducing oxidative stress in angiotensin II-infused mice

AimEndothelial dysfunction accompanied by an increase in oxidative stress is a key event leading to hypertension. As dietary nitrite has been reported to exert antihypertensive effect, the present study investigated whether chronic oral administration of sodium nitrite improves vascular function in conduit and resistance arteries of hypertensive animals with elevated oxidative stress. MethodsSodium nitrite (50mg/L) was given to angiotensin II-infused hypertensive C57BL/6J (eight to ten weeks old) mice for two weeks in the drinking water. Arterial systolic blood pressure was measured using the tail-cuff method. Vascular responsiveness of isolated aortae and renal arteries was studied in wire myographs. The level of nitrite in the plasma and the cyclic guanosine monophosphate (cGMP) content in the arterial wall were determined using commercially available kits. The production of reactive oxygen species (ROS) and the presence of proteins (nitrotyrosine, NOx-2 and NOx-4) involved in ROS generation were evaluated with dihydroethidium (DHE) fluorescence and by Western blotting, respectively. ResultsChronic administration of sodium nitrite for two weeks to mice with angiotensin II-induced hypertension decreased systolic arterial blood pressure, reversed endothelial dysfunction, increased plasma nitrite level as well as vascular cGMP content. In addition, sodium nitrite treatment also decreased the elevated nitrotyrosine and NOx-4 protein level in angiotensin II-infused hypertensive mice. ConclusionsThe present study demonstrates that chronic treatment of hypertensive mice with sodium nitrite improves impaired endothelium function in conduit and resistance vessels in addition to its antihypertensive effect, partly through inhibition of ROS production.

Dual NEP/ECE inhibition improves endothelial function in mesenteric resistance arteries of 32-week-old SHR.

Endothelin 1 (ET-1), a potent vasoconstrictor, pro-mitogenic and pro-inflammatory peptide, may promote development of endothelial dysfunction and arterial remodeling. ET-1 can be formed through cleavage of big-ET-1 by endothelin-converting enzyme (ECE) or neutral endopeptidase (NEP). We investigated whether chronic treatment with the novel dual NEP/ECE inhibitor SOL1 improves functional and structural properties of resistance-sized arteries of 32-week-old male spontaneously hypertensive rats (SHR). SHR received a chronic 4-week treatment with SOL1, losartan or hydralazine. We then compared effects of inhibition of NO synthase (NOS) (100 μM l-NAME), blockade of ETA- and ETB-receptors (10 μM bosentan) and stimulation of the endothelium with 0.001-10 μM acetylcholine (ACh) in isolated third-order mesenteric resistance arteries. Losartan and hydralazine significantly lowered blood pressure. Losartan decreased the media-to-lumen ratio of resistance arteries. l-NAME (1) increased arterial contractile responses to K+ (5.9-40 mM) in the losartan, SOL1 and vehicle group and (2) increased the sensitivity to phenylephrine (PHE; 0.16-20 μM) in the SOL1 group but not in the losartan, hydralazine and vehicle group. Relaxing responses to ACh in the absence or presence of l-NAME during contractions induced by either 10 μM PHE or 40 mM K+ were not altered by any in vivo treatment. Acute treatment with bosentan did, however, significantly improve maximal relaxing responses involving endothelium-derived nitric oxide and -hyperpolarizing factors in the SOL1 group but not in the losartan, hydralazine or vehicle group. Thus, chronic inhibition of NEP/ECE improved basal endothelial function but did not alter blood pressure, resistance artery structure and stimulated endothelium-dependent relaxing responses in 32-week-old SHR.

A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice.

Background and PurposeThe cofactor tetrahydrobiopterin (BH4) is a critical regulator of endothelial NOS (eNOS) function, eNOS‐derived NO and ROS signalling in vascular physiology. To determine the physiological requirement for de novo endothelial cell BH4 synthesis for the vasomotor function of resistance arteries, we have generated a mouse model with endothelial cell‐specific deletion of Gch1, encoding GTP cyclohydrolase 1 (GTPCH), an essential enzyme for BH4 biosynthesis, and evaluated BH4‐dependent eNOS regulation, eNOS‐derived NO and ROS generation.Experimental ApproachThe reactivity of mouse second‐order mesenteric arteries was assessed by wire myography. High performance liquid chromatography was used to determine BH4, BH2 and biopterin. Western blotting was used for expression analysis.Key Results Gch1 fl/flTie2cre mice demonstrated reduced GTPCH protein and BH4 levels in mesenteric arteries. Deficiency in endothelial cell BH4 leads to eNOS uncoupling, increased ROS production and loss of NO generation in mesenteric arteries of Gch1 fl/flTie2cre mice. Gch1 fl/flTie2cre mesenteric arteries had enhanced vasoconstriction to U46619 and phenylephrine, which was abolished by L‐NAME. Endothelium‐dependent vasodilatations to ACh and SLIGRL were impaired in mesenteric arteries from Gch1 fl/flTie2cre mice, compared with those from wild‐type littermates. Loss of eNOS‐derived NO‐mediated vasodilatation was associated with increased eNOS‐derived H2O2 and cyclooxygenase‐derived vasodilator in Gch1 fl/flTie2cre mesenteric arteries.Conclusions and ImplicationsEndothelial cell Gch1 and BH4‐dependent eNOS regulation play pivotal roles in maintaining vascular homeostasis in resistance arteries. Therefore, targeting vascular Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of microvascular dysfunction in patients with cardiovascular disease.