Endothelium-dependent Research Articles

Abstract 10955: The Effects of Acute and Chronic Selective Phosphodiesterase 1 Inhibition in Associated Smooth Muscle Cell-Specific Aging Features

Introduction: Aging-related vascular smooth muscle cell (VSMC) remodeling plays an essential role in cardiovascular diseases. Reduced NO-cGMP pathway signalling is a major feature and pathogenic mechanism underlying VSMC dysfunction. Recently, we found that phosphodiesterase (PDE) 1, an enzyme that hydrolyzes and inactivates the cyclic nucleotides cAMP and cGMP, is a potential treatment target for restoring age-related deficits in VSMC signalling. We here tested the effects of PDE1 inhibition in SMC-specific Ercc1 DNA repair mutant mice, a model of isolated, accelerated SMC aging. Design and Method: SM22α Cre+ Ercc1 fl/- (SMC-KO) and SM22α Cre+ Ercc1 fl/+ littermate (SMC-LM) mice receive either vehicle or the PDE1 inhibitor lenrispodun (dose 40mg/kg/day) in drinking water for 8 weeks. Reactive hyperemia was measured in-vivo at the age of 14 and 25 weeks. Mice were sacrificed at 26 weeks. The endothelium-dependent (ED) and -independent (EI) relaxation of the thoracic aorta was assessed by wire myography. Moreover, we investigated the effect of PDE1 inhibition on the expression of selected PDEs involved in the vasculature by qPCR. Results: Reactive hyperemia was dramatically reduced in vehicle-treated SMC-KO vs. SMC-LM at the age of 25 weeks (P=0.0002) but was preserved in lenrispodun-treated SMC-KO mice. In vehicle-treated SMC-KO mice, the ED and EI relaxations were greatly diminished compared to SMC-LM (ED: 23.92±4.34 vs. 68.04±4.86, P<0.0001; EI: 57.93±5.31 vs. 87.43±4.01, P=0.0004). Acute administration of lenrispodun in the organ bath improved both ED and EI responses (ED: 38.61±4.04, P=0.001; EI 69.99±4.29 P=0.01) while the relaxations remained unchanged after chronic lenrispodun treatment. In addition, lenrispodun upregulated PDE1a mRNA expression in SMC-KO, while no changes were observed in other PDEs. Conclusions: PDE1 inhibition may therapeutically be useful in restoring age-related vascular dysfunction by preserving microvascular function and potentiating NO-cGMP signaling. Yet, its chronic effects might be counteracted by the upregulation of PDE1a in vasculature. These results warrant further pharmacodynamic profiling of PDE enzyme regulation during chronic PDE1 inhibitor treatment.

Abstract 9317: Soluble Guanylate Cyclase Activator Treatment Improves Vasomotor Function in an Accelerated-Ageing Mouse Model

Introduction: Vascular ageing is a key driver of cardiovascular diseases. Mice with partial deletion of the repair enzyme gene Ercc1 ( Ercc1 Δ/- ) display accelerated vascular ageing which is associated with decreased nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling, oxidative stress, inflammation, and cellular senescence. Restoring this pathway could be an effective treatment opportunity for vascular ageing. We therefore, investigated the therapeutic potential of the sGC activator BAY 56-6544, which can activate oxidized and heme-free sGC in Ercc1 Δ/- mice. Design and Method: Ercc1 Δ/- and wild-type (WT) mice received either vehicle or BAY 54-6544 chow for 8 weeks. Blood pressure (BP) and in-vivo vasodilation (reactive hyperemia: RH) were measured at 15 and 16 weeks respectively. Mice were sacrificed at 17 weeks. Thoracic aorta (TA) endothelium-dependent (ED) and -independent (EI) relaxations were assessed (wire-myograph). Afterwards, we investigated the expression level of senescent markers p16 and p21 and inflammatory markers Il-6 and Ccl2 in aorta by qPCR. Results: BP was similar in all groups. RH was decreased in Ercc1 Δ/- vs. WT (P=0.03) and significantly improved after BAY 54-6544 treatment to the same level as in WT. In vehicle-treated Ercc1 Δ/- mice maximal NO-mediated relaxation in TA to acetylcholine (ED) and sodium nitroprusside (EI) were decreased as compared to WT (ED: 46.97±7.04 vs. 72.33±3.03, P=0.0001; EI: 75.47±5.27 vs. 88.30±3.64, P=0.02). Although BAY 54-6544 treatment did not improve ED response significantly, it improved EI relaxation in Ercc1 Δ/- to the same level as in WT (EI 88.54±3.26). EI response in BAY 54-6544-treated WT was the same as in vehicle-treated one (86.98±3.56). mRNA expression of p16, p21 and Ccl2 were significantly higher in vehicle-treated Ercc1 Δ/- , whereas BAY 54-6544 treatment could attenuate this increase. Conclusion: DNA repair deficiency in Ercc1 Δ/- mice causes a disruption of NO-sGC-cGMP signaling and a decrease of vasodilator response. Treatment with the BAY 54-6544 improved NO-mediated vasodilation and attenuated vascular senescence and inflammation markers. Thus, BAY 54-6544 could be a potential therapeutic treatment to attenuate vascular ageing.

Impaired endothelium-dependent and endothelium-independent systemic vasodilatory reserve in pulmonary hypertension regardless the clinical group: A generalized dysfunction beyond the pulmonary arteries?

Endothelium-dependent (ED) and endothelium-independent (EI) flow-mediated vasodilatation (FMD) have been used as measures of systemic arterial vasodilatory reserve. In this study, we aimed to assess both ED-FMD and EI-FMD in different groups with pulmonary hypertension (PH), and to investigate the relationship of these measures with clinical, echocardiographic, and invasive parameters of diseases severity and targeted treatment status. Our study population comprised 41 patients with PH [28 (68.2%) women, age 46.3±19.6 years] including idiopathic pulmonary arterial hypertension, Eisenmenger syndrome, and chronic thromboembolic PH in whom diagnosis were confirmed in accordance with current guidelines and 17 age and sex-matched healthy controls. The brachial artery (BA) was used for assessment of FMD with Duplex ultrasound, and serial changes in diameter were recorded at baseline, 1, and 3 minutes after termination of 2-minute external occlusive compression for ED-FMD, and after sublingual intake of glycerol trinitrate for EI-FMD, respectively. Compared with controls, overall the PH group showed significantly lower ED-FMD (0.65±0.21 vs. 0.30±0.23 and 0.65±0.18 vs. 0.24±0.21) and EI-FMD (0.67±0.15 vs. 0.37±0.25 and 0.75±0.20 vs. 0.32±0.24) responses at 1st and 3rd min (p<0.001 for all). All these changes in the values of ED-FMD and EI-FMD were comparable among the PH subgroups. Neither ED-FMD nor EI-FMD were correlated with measures of PH severity and targeted therapy (TT) status (p>0.05). Our results suggest an impaired BA vasodilatory reserve in patients with PH regardless of the clinical subgroup. Although these findings seem to be consistent with systemic dysfunction, acute FMD may not reflect the severity of PH and cannot be used as a potential surrogate for outcome in this setting.

DNA REPAIR DEFECT IN SMOOTH MUSCLE CELL REPRODUCES FEATURES OF AGE-RELATED VASCULAR DISEASE IN MICE

Objective: DNA damage and repair responses have been implicated in age-related vascular disease. Evidence in mice shows that deletion of the Ercc1 gene, encoding an endonuclease that participates in several DNA repair systems, leads to features of accelerated ageing. It is not known from which cell type the vascular aging effect of Ercc1 deletion originates. A possibility is local DNA damage in vascular smooth muscle cells (VSMC). We determined features of vascular aging in a mouse model with specific Ercc1 deletion in smooth muscle cells (SMC-KO). Design and method: 12 SMC-KO and 13 Wild-type (WT) littermates were generated using alpha SM22-Cre driven cre-lox deletion of Ercc1. Blood pressure (BP) and in vivo vasodilation (reactive hyperemia: RH) were measured at the age of 22 and 23 weeks respectively. Mice were sacrificed at 24 weeks. Thoracic aorta and iliac artery endothelium-dependent (ED) and –independent (EI) relaxation were assessed (wire myograph). Results: There was no significant difference in BP between WT and SMC-KO. RH was decreased in SMC-KO vs. WT by 73% (P = 0.008). In SMC-KO mice maximal relaxation in iliac arteries to acetylcholine (ED) and sodium nitroprusside donor (EI) were decreased as compared to WT (ED: 48.04 ± 6.80 vs. 86.16 ± 3.68, P = 0.001; EI: 79.84 ± 4.04 vs. 93.78 ± 2.13, P = 0.022). In aorta similar observations were made (ED: 17.11 ± 2.29 vs. 73.42 ± 4.29, P = 0.0001; EI 55.87 ± 4.77 vs. 69.01 ± 5.17, p = 0.007). When added in the organ bath ITI-214 acutely increased aortic EI relaxation both in WT (from 69.01 ± 5.17 to 80.53 ± 2.05, P = 0.006) and SMC-KO (from 55.87 ± 4.77 to 67.17 ± 3.70, P = 0.084). Conclusions: Local DNA damage in SMC causes a decrease of vasodilator responses. This effect is blood pressure-independent. Given that responses to sodium nitroprusside, a nitric oxide (NO) donor, and PDE1, a cGMP-metabolising enzyme, were both involved, most probably a decline of NO-cGMP signalling is involved.

Прогнозирование состояния пациенток с преэклампсией на основании показателей эндотелийзависимой вазодилатации

Aim: to determine prognostic criteria of severe preeclampsia based on the assessment of endothelium-dependent (ED) flow-mediated dilation (FMD) of the brachial artery (BA). Patients and Methods: 97 pregnant women (&gt;28 weeks of pregnancy) with moderate preeclampsia were enrolled. These women were retrospectively divided into two groups. Group 1 included 42 pregnant women (mean age 30.0±0.5 years) in whom the severity of preeclampsia increased after treatment. Group 2 included 55 pregnant women (mean age 31.0±0.7 years) whose severity of preeclampsia did not increase after treatment. Group 3 (control group) included 20 women with a healthy pregnancy. ED FMD of BA was assessed by vascular ultrasound using a reactive hyperemia test. In addition, BA diameter and peak systolic velocity (PSV) 15 sec and 1 min after cuff deflation were measured. These measurements were performed at enrollment and after one week (or in feeling worse). Results: healthy pregnancy was characterized by a gradual increase in BA diameter in response to cuff inflation (by 15.7% and 23.9% after 15 sec and 1 min, respectively, at baseline and by 17.8% and 21.3% after 15 sec and 1 min, respectively, after one week). In pregnant women with preeclampsia, baseline changes in BA diameter were less significant. Meanwhile, after one week, a reduction in BA diameter was reported in group 1, and close-to-normal BA diameter was reported in group 2. In group 3, BA PSV increased by 5.2% and 16% in 15 sec and 1 min, respectively, after cuff inflation. In pregnant women with preeclampsia, BA PSV, in contrast, was reduced (more significant after 1 min). Conclusion: increased BA diameter and PSV by less than 10% 15 sec and 1 min after cuff inflation indicate endothelial dysfunction. A negative pattern of changes in these parameters suggests an unfavorable course of preeclampsia and its transition to severe disease. KEYWORDS: preeclampsia, endothelial dysfunction, vasodilation, brachial artery, peak systolic velocity, prognosis. FOR CITATION: Shavaeva R.Kh., Murashko A.V., Zuev V.M. et al. Predicting preeclampsia course based on endothelium-dependent dilation. Russian Journal of Woman and Child Health. 2021;4(4):317–321 (in Russ.). DOI: 10.32364/2618-8430-2021-4-4-317-321.

Role of Chronic Stress and Exercise on Microvascular Function in Metabolic Syndrome

The present study examined the effect of unpredictable chronic mild stress (UCMS) on peripheral microvessel function in healthy and metabolic syndrome (MetS) rodents and whether exercise training could prevent the vascular dysfunction associated with UCMS. Lean and obese (model of MetS) Zucker rats (LZR and OZR) were exposed to 8 wk of UCMS, exercise (Ex), UCMS + Ex, or control conditions. At the end of the intervention, gracilis arterioles (GA) were isolated and hung in a pressurized myobath to assess endothelium-dependent (EDD) and endothelium-independent (EID) dilation. Levels of nitric oxide (NO) and reactive oxygen species (ROS) were measured through 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate and dihydroethidium staining, respectively. Compared with LZR controls, EDD and EID were lower (P = 0.0001) in LZR-UCMS. The OZR-Ex group had a higher EDD (P = 0.0001) and EID (P = 0.003) compared with OZR controls, whereas only a difference in EDD (P = 0.01) was noted between the LZR-control and LZR-Ex groups. Importantly, EDD and EID were higher in the LZR (P = 0.0001; P = 0.02) and OZR (P = 0.0001; P = 0.02) UCMS + Ex groups compared with UCMS alone. Lower NO bioavailability and higher ROS were noted in the LZR-UCMS group (P = 0.0001), but not OZR-UCMS, compared with controls. The Ex and UCMS-Ex groups had higher NO bioavailability (P = 0.0001) compared with the control and UCMS groups, but ROS levels remained high. The comorbidity between UCMS and MetS does not exacerbate the effects of one another on GA EDD responses, but does lead to the development of other vasculopathy adaptations, which can be partially explained by alterations in NO and ROS production. Importantly, exercise training alleviates most of the negative effects of UCMS on GA function.

Omega 3 Polyunsaturated Fatty Acids Improve Endothelial Dysfunction in Chronic Renal Failure: Role of eNOS Activation and of Oxidative Stress.

Background: Endothelial dysfunction is a key vascular alteration in chronic kidney disease (CKD). Omega 3 (n-3) polyunsaturated fatty acids (PUFA) reduce vascular oxidative stress and inflammation. We investigated whether n-3 PUFA could reverse endothelial dysfunction in CKD by improving endothelial nitric oxide synthase (eNOS) function and oxidative stress. Methods: 5/6 nephrectomized male Wistar rats (CKD; n = 10) and sham operated animals (SHAM; n = 10) were treated for 6 weeks with standard diet. An additional group of CKD rats were fed an n-3 PUFA enriched diet (CKD + PUFA; n = 10). We then measured endothelium-dependent (EDD) and -independent vasodilation, markers of endothelial function and of oxidative stress in thoracic aortas. Results: Compared to SHAM, in CKD aortas EDD and eNOS expression were reduced (p < 0.05) and 3-nitrotyrosine levels were increased, while expression of NADPH oxidase subunits NOX4 and p22phox was similar. In-vitro incubation with Tiron failed to reverse endothelial dysfunction in CKD. In CKD + PUFA, EDD improved (p < 0.05) compared with CKD rats, while blockade of eNOS by L-NAME worsened EDD. These effects were accompanied by increased (p < 0.05) eNOS and reduced (p < 0.05) expression of NOX4 and 3-nitrotyrosine levels. Conclusion: Collectively, these findings indicate that n-3 PUFA improve endothelial dysfunction by restoring NO bioavailability in CKD.

Adaptation to hypoxia prevents endothelial dysfunction of coronary and non‐coronary blood vessels during myocardial ischemia and reperfusion injury

Prior adaptation to intermittent hypoxia (AIH) is cardioprotective during myocardial ischemia‐reperfusion injury (IR). This study investigated the possibility that AIH would lessen endothelial dysfunction (EDF) in rat hearts during IR. AIH was performed in a normobaric chamber (5–8 cycles/d for 20 d, FIO2 9.5–10% for 5–10 min/cycle, with intervening 4‐min normoxia). Endothelium‐dependent (ED) function of coronary blood vessels was evaluated by the flow response to acetylcholine (ACH) in Langendorf isolated hearts after in vitro IR. Also, ED relaxation of noradrenaline‐precontracted isolated aortic rings was evaluated by response to ACH after in situ myocardial IR. With no IR, coronary flow and response to ACH were similar in hearts of non‐AIH (n=9) and AIH (n=10) rats. IR injury decreased ED dilation of coronary arteries to 10.4±1.7% of the pre‐IR response to ACH in non‐AIH (n=10) rats and to 76±20% in AIH (n=9) rats (p&lt;0.05). In the aorta, IR reduced ED relaxation from 45±4% (n=8) of the precontraction magnitude to 9.7±1.2% (n=10) in non‐AIH rats and to 30±3% (n=10) in AIH (p&lt;0.05). Therefore, 1) IR heart injury induced EDF of both coronary and remote, non‐coronary blood vessels; and 2) AIH blunted EDF of both coronary and noncoronary vessels. These data suggest that adaptation to hypoxia is not only cardioprotective but also vasoprotective during myocardial IR injury. Supported by RFBR grant 10–04‐00980.

Estrogen-induced relaxation of the rat tail artery is attenuated in rats with pulmonary hypertension

The mechanisms involved in the effects of estrogen on arterial smooth muscle contractility are very complex and not fully clarified. Therefore, the aim of this paper was to examine the mechanisms of estrogen-induced relaxation of the rat tail artery and, specifically, how pulmonary hypertension affects this action. We used male rats and performed experiments on isolated tail arteries in a control group and a group with pulmonary hypertension (PAH) induced by monocrotaline (60mg/kg b.w. ip). The pD value (–log ECo) of phenylephrine significantly decreased in the presence of 20µM of 17β-estradiol (5.4±0.13 vs. 4.9±0.12, p<0.05, n=6). Estrogen-induced relaxation of a phenylephrine-precontracted tail artery has two components: endothelium-dependent (ED) and endothelium-independent (EI). The estrogen effect was independent of ATP-sensitive K+ channels, vasoactive prostanoids and nitric oxide. PAH augmented the maximal effect of phenylephrine on the tail artery contractility but did not affect estrogen-induced ED-relaxation. However, the EI component of relaxation induced by estrogen was completely abolished in tail arteries obtained from animals with pulmonary hypertension. Pulmonary hypertension affects the sensitivity of the rat tail artery to phenylephrine and estrogen, leading to impairment of EI mechanisms of relaxation. Further experiments are required to elucidate the molecular mechanisms of this phenomenon.

Na+/H+ exchange inhibition with cariporide prevents alterations of coronary endothelial function in streptozotocin-induced diabetes

Hyperglycemia encountered during diabetes triggers abnormalities of vascular function associated with cell acidosis and calcium overload. The purpose of this study was to determine, whether Na+/H+ exchanger (NHE-1) inhibition by cariporide protects coronary cells against the deleterious effect of hyperglycemia in the rat. In vivo hyperglycemia was triggered by streptozotocin injection. One week after, the glycemia was checked and the control and diabetic animals were treated or not with cariporide (2.5 mg/kg/day) for two weeks. Glycemia was again estimated and the hearts were perfused according to the Langendorff mode at forced flow. The left ventricle developed pressure (LVDP) and heart rate (HR) were determined with a latex balloon inserted into the left ventricle. Coronary pressure was artificially increased to 130 mmHg by infusing a thromboxane A2 analogue (U46619). This allowed the evaluation of endothelium-dependent (EDD) and endothelium-independent (EID) dilatation through bolus injections of carbamoylcholin and sodium nitroprusside, respectively. Releases of lactate and pyruvate in the coronary effluents were also determined. Diabetes did not modified LVDP, but reduced HR (-15%). This was associated with a marked decrease in EDD (-56%) and EID (-30%), while the cytosolic redox potential (estimated as the lactate/pyruvate ratio) was reduced. NHE-1 inhibition restored EDD and the lactate/pyruvate ratio without improving EID and HR. The present findings indicate that NHE-1 exchanger inhibition by cariporide protects the coronary endothelium against the deleterious effects of hyperglycemia.

Effect of coenzyme Q10 administration on endothelial function and extracellular superoxide dismutase in patients with ischaemic heart disease: a double-blind, randomized controlled study

This randomized controlled study was designed to determine whether oral coenzyme Q(10) (CoQ(10)) supplementation (100 mg tid) was able to improve extracellular superoxide dismutase (ecSOD) activity and endothelium-dependent (ED) vasodilation in patients with coronary artery disease (CAD). ecSOD, a major antioxidant enzyme system of the vessel wall, is reduced in patients with CAD. Moreover, there is a strong correlation between endothelium-bound ecSOD and the ED dilation of conduit arteries. CoQ(10) has been recently shown to improve the ED relaxation in diabetic patients. Thirty-eight CAD patients (33 M/5 F, mean age 55 +/- 4 years, ejection fraction 57.5 +/- 8%) were randomized into two groups. One group (n = 19) received CoQ(10) orally at doses of 300 mg/day for 1 month, whereas the other group received a placebo. On entry and after 1 month, all patients underwent brachial artery ED assessment, cardiopulmonary exercise test, and the measurement of endothelium-bound ecSOD activity. A total of 33 patients completed the study. ecSOD, ED relaxation, as well as peak VO(2) and O(2) pulse increases in the CoQ(10)-treated group were statistically greater vs. the variations in the placebo group. In particular, improvements elicited by CoQ(10) supplementation were remarkable in subjects presenting low initial endothelium-bound ecSOD and thus more prone to oxidative stress. Improvements in the ED relaxation and endothelium-bound ecSOD activity might be related to CoQ(10) capability of enhancing endothelial functionality by counteracting nitric oxide oxidation. The enhancement of peak VO(2) and of O(2) pulse is likely due to the bioenergetic effect of CoQ(10); on the other end, the improved VO(2) could also depend on the observed enhanced peripheral endothelial function.

Uncoupling of Oxidative Phosphorylation in Vascular Function in Aging.

Aging is a risk factor for the development of CVD and is characterized by a reduced vascular reactivity and increased free radical generation (ROS). The uncoupling of oxidative phosphorylation (OXPHOS) reduces ROS generation. We hypothesized that endothelium-dependent (EDD) and endothelium-independent (EIND) dilation is linked to mitochondrial uncoupling. Isometric tension experiments were performed in Fisher 344 (F344, 15–16 months) rat aortic rings. Acetylcholine (Ach, 10 μM, n=13 rings) caused 10% vasodilation (n= 19). The EIND dilation was tested with MAHMA NONO-ate (10μM) and rings responded with 46% (n= 13, P<0.05) relaxation. FCCP (1 μM) a chemical uncoupler of OXPHOS had no effects on neither EDD nor EIND (n=6, ns). Bay 41–2272 (10 μM), stimulator of soluble guanylate cyclase (sGC) improved relaxation to Ach, and arteries responded with 56% (n=6, P<0.05) relaxation; relaxation to MAHMA was at 71% (n=6, P<0.05). The expression of uncoupling protein UCP-2 in heart and aorta of F344 was increased by 30% (3 hearts, 3 aortas, n=2), respectively; the expression of UCP-3 was increased by 3-fold (n=3) in F344 hearts as compare to age matched controls. Taken together, a decline in vascular function is consistent with progressive oxidative stress. The oxidative modification of proteins could be responsible for a lack of activation of a negative feedback via the uncoupling of OXPHOS and reduction in ROS levels.

Vasodilator effect of the extracts and some coumarins from the stem bark of Mammea africana (Guttiferae)

CH 2Cl 2 fraction obtained from the stem bark of Mammea africana inhibited noradrenaline (NA) or KCl-induced contraction in isolated guinea pig and rat aorta. The vasorelaxant potency of the CH 2Cl 2 fraction of Mammea africana was diminished by a pre-treatment with Nitro- l-arginine methyl ester ( l-NAME), an inhibitor of NO synthase, which was however not affected by indomethacin pre-treatment. These findings indicated that the vasorelaxant effect of Mammea africana may be partially endothelium dependent, mediated by nitric oxide and that vasoactive prostanoids might not be contributing to the vasorelaxation effect. Three bioactive compounds were isolated from this CH 2Cl 2 fraction and identified as 4- n-propylcoumarins ( 1) (mammea B/BB), 4-phenylcoumarins ( 2) (mammea A/AA or mammeisin) and (B/BA) ( 3) and might involved in the vasorelaxant effect of the extract. The mechanisms of the vasorelaxant effect might therefore be multiple, including endothelium dependence and the mechanisms, which interfere with the liberation of Ca 2+ into the muscle cell.

Point: Release of an endothelium-derived vasoconstrictor and RhoA/Rho kinase-mediated calcium sensitization of smooth muscle cell contraction are/are not the main effectors for full and sustained hypoxic pulmonary vasoconstriction

The ability of an organism, or an organ therein, to respond appropriately to episodes of hypoxia is a key evolutionary determinant. In mammalian lungs, the response to acute hypoxia involves constriction of the intrapulmonary arteries (IPA) in the hypoxic region of the lung. This response, termed

Effect of whole wild blueberries on endothelium‐dependent (ED) vasodilation in spontaneously hypertensive rats (SHR)

Effect of whole wild blueberries on endothelium‐dependent (ED) vasodilation in spontaneously hypertensive rats (SHR)

Efeitos da metformina na disfunção endotelial da circulação renal induzida pela hiperglicemia em coelhos não diabéticos

To assess the effects of metformin (Met) on the endothelial dysfunction of the renal circulation of non-diabetic rabbits acutely induced by levels of glucose usually observed in diabetic patients in daily clinical practice. Isolated perfused kidneys from non-diabetic rabbits were exposed for 3 h to normal (100 mg/dl--control group) or high (270 mg/dl) D-glucose with or without Met (100 microM). The glucose levels used correspond to 2 h post-breakfast median values (272 mg/dl) obtained from a cohort of 780 type 2 diabetic (DM2) outpatients seen in our service. Vascular reactivity was evaluated with endothelium-dependent (ED) [acetylcholine-ACh] and independent (EI) [sodium nitroprusside-SNP] vasodilating agents. Kidneys perfused with high glucose had ED maximal vasodilation blunted in comparison to controls (respectively 25 +/- 3 and 41 +/- 3%; p < 0.01). A 3 h Met infusion restored the vasodilating effect of ACh in the renal circulation in the presence of high glucose, no different from controls (respectively 43 +/- 1.5 vs. 41 +/- 3% p > 0.05). Met did not affect maximum vasodilation induced by ACh in the presence of normal glucose levels. Finally, renal vasodilation induced by SNP was not modified by simultaneous infusion of glucose and Met. Acute hyperglycemia corresponding to the range observed in patients with DM2 induces endothelial dysfunction in the renal circulation of normal rabbits. Acute treatment with Met was able to protect the renal circulation against the effects of high glucose. The mechanisms involved in this protector effect deserve further investigation.

INVOLVEMENT OF ENDOTHELIAL CYCLO‐OXYGENASE METABOLITES IN NORADRENALINE‐INDUCED CONTRACTION OF RAT CORONARY ARTERY

1. Noradrenaline (NA; 0.3 micromol/L) caused a contraction of the rat coronary artery that markedly increased in the presence of the nitric oxide synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME; 100 micromol/L) and arachidonic acid (1 micromol/L; P < 0.05). 2. The present experiments attempted to elucidate the endothelium dependency of the contraction and to pharmacologically characterize the factors involved in the contraction induced by NA (0.3 micromol/L) in the presence of L-NAME and arachidonic acid in ring preparations of the rat coronary artery. 3. The NA (0.3 micromol/L)-induced contraction was attenuated by a chemical remover of the endothelium (saponin at concentrations of 0.1 and 0.4 mg/mL) in a concentration-dependent manner (P < 0.05). 4. The cyclo-oxygenase (COX)-1 inhibitor flurbiprofen (0.01-1 micromol/L) and the COX-2 inhibitor nimesulide (0.01-1 micromol/L) attenuated the NA-induced contraction in a concentration-dependent manner and the inhibitory effect of flurbiprofen was significantly more potent than that of nimesulide (P < 0.05). The 5-lipoxigenase inhibitor ZM-230487 (1 micromol/L) did not affect the NA-induced contraction. 5. The thromboxane A2 (TXA2) synthetase inhibitor OKY-046 (30 micromol/L) and the TXA2 antagonist S-1452 (0.1-10 micromol/L) did not attenuate the NA-induced contraction. 6. These results indicate that the contraction induced by NA in the rat coronary artery in the presence of L-NAME and arachidonic acid is endothelium dependent and is due to endothelial COX metabolites of arachidonic acid.

PRETREATMENT WITH INTRAVENOUS ASCORBIC ACID PRESERVES ENDOTHELIAL FUNCTION DURING ACUTE HYPERGLYCAEMIA (R1)

1. Acute hyperglycaemia may impair endothelial function. Ascorbic acid (AA), administered intra-arterially, has been reported to improve endothelium-dependent vasodilatation during a forearm hyperglycaemic clamp. Using a randomized, double-blind, placebo-controlled, cross-over study, we investigated the potential for intravenous ascorbic acid to modify the endothelial response to acute systemic hyperglycaemia in humans. 2. Nine healthy male volunteers were recruited from the hospital staff. Endothelial function was determined by measuring the forearm blood flow responses to intrabrachial infusions of endothelium-dependent (ED) and endothelium-independent (EID) vasodilators. The endothelial function index (EFI) was derived from the ratio of ED and EID vasodilatation. Haemodynamic and endothelial function measurements were performed at baseline and then repeated 2 h after a systemic hyperglycaemic clamp (14 mmol/L). The subjects, studied on two separate occasions, were randomized to placebo or 2 g intravenous ascorbic acid prior to the initiation of hyperglycaemia. 3. After systemic hyperglycaemia with placebo pretreatment, the EFI fell from 1.08 +/- 0.21 to 0.74 +/- 0.13 (difference (95% confidence interval): 0.34 (0.20, 0.47); P < 0.001). When subjects were pretreated with ascorbic acid, the EFI was not affected by hyperglycaemia (1.11 +/- 0.21 to 1.12 +/- 0.17; P = 0.938). This difference between placebo and ascorbic acid was significant (P < 0.001). Plasma ascorbate concentrations decreased during hyperglycaemia and correlated directly with the reduction in the EFI (r = 0.798; P < 0.001). 4. Pretreatment with an intravenous bolus of ascorbic acid can prevent endothelial dysfunction during acute systemic hyperglycaemia. Therefore, ascorbic acid may have potential therapeutic use in clinical situations where acute hyperglycaemia may be a complication.

Effects of short-term moderate exercise training on sexual function in male patients with chronic stable heart failure

Background Patients with chronic heart failure (CHF) have sexual dysfunction that impairs quality of life. Recent trials have demonstrated that exercise training (ET) improves quality of life (QOL) of CHF patients, but it is not established whether this benefit may be associated with an improvement in sexual dysfunction. Objective To determine whether ET can improve sexual dysfunction in patients with CHF. Methods We prospectively studied 59 male patients (57±9 years) with stable CHF in sinus rhythm and without prostatic disease. Patients were randomized into two groups. A group (T, n=30) underwent supervised cycle ergometer ET at 60% of peak VO 2, three times a week, 60 min each session, for 8 weeks. A group (NT, n=29) was not exercised. Medications were not changed during the study. On study entry and at 8 weeks all patients underwent a symptom-limited cardiopulmonary exercise testing, brachial artery endothelium-dependent (ED) and endothelium-independent (EI) vasomotor responses, QOL and sexual activity profile assessment (SAP) by questionnaire. Results At 8 weeks, no changes were observed in control patients. In trained patients, however, peak VO 2 improved by 18% ( P<0.005) and was correlated with QOL ( r=0.80; P<0.001). Flow-mediated dilation improved in trained patients (from 2.29±1.13% to 5.04±1.7%, P=0.0001), while EI dilation (after 0.3 mg sublingual NTG) did not. In group T, all three domains (i.e. Domain 1=relationship with the partner; Domain 2=quality of penile erection; Domain 3=personal wellness) were significantly improved from baseline (total score patients: from 3.49±3.4 to 6.17±3.2, P<0.001; partners: from 2.47±2.7 to 4.87±2.5, P<0.001). Pre-post training change in SAP total score was correlated with changes in coronary risk profile ( r=−0.49; P=0.01), peak VO 2 ( r=0.67; P<0.001) and QOL ( r=0.73; P=0.01). Multivariate analysis selected the improvement in ED-vasomotor response as the strongest independent predictor of SAP improvement ( r=0.63, P<0.001). Conclusions In stable CHF, cycle ergometer ET significantly improves brachial artery endothelial dysfunction, suggesting a systemic effect of leg exercise. This benefit was correlated with improvements in sexual activity.

Non-invasive evaluation of endothelial function in hypertensive elderly patients

Impaired endothelium-dependent vasomotion is a diffuse disease process resulting in abnormal regulation of blood vessel tone and loss of several atheroprotective effects of the normal endothelium. The aim of the present study was to investigate the effects of aging and hypertension on endothelial function. Sixty-six geriatric subjects with ages over 60 (48 hypertensive and 18 healthy) and 40 middle-aged subjects (16 hypertensive and 24 healthy) were included in the study. Systemic vascular endothelial function was evaluated through measuring brachial arterial vasodilation, a physiologic answer to reactive hyperemia occured with increased blood flow in the vessel after transient ischemia (flow-mediated dilation, FMD%), and with carotid artery intima-media thickness (IMT) measurement, using high-resolution ultrasonography. Endothelial independent vasodilation was also measured after administration of sublingual isosorbide dinitrate (isosorbide dinitrate mediated dilation, IDNMD%). FMD% was significantly decreased in elderly and/or hypertensive (HT) patients (geriatric HT: 9.5 ± 4.7%, geriatric non-HT: 12.7 ± 5.5%, middle-aged HT: 12.9 ± 4.3% and middle-aged non-HT: 18.9 ± 8.1%) (geriatric HT versus geriatric non-HT ( P = 0.02), geriatric HT versus middle-aged HT ( P = 0.01), geriatric non-HT versus middle-aged non-HT ( P = 0.008)). Both FMD% and IDNMD% were inversely correlated with age, baseline vessel diameter and carotid artery intima-media thickness. FMD% was also inversely correlated with diastolic blood pressure. No correlation was found between FMD% and systolic blood pressure, serum cholesterol and triglyceride levels. Endothelium dependent (EDD) and independent dilatation of large arteries decreased with aging even in the healthy elderly, and FMD further declined in HT elderly patients, indicating that age and hypertension independently impair endothelial function. Positive correlations with age and hypertension, and significant inverse correlation with FMD, makes carotid artery IMT a possible indicator of endothelial function.