Impaired Vasodilatory Response Research Articles

Increased oxidative stress alters coronary microvascular tone in exercising swine with multiple comorbidities

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Cardiovascular Alliance Background/Objectives We have previously shown, in female swine that the combination of three cardiovascular risk factors (diabetes mellitus (DM), hypercholestolemia (HC) and chronic kidney disease (CKD)) induces systemic inflammation, oxidative stress, coronary endothelial dysfunction and impaired myocardial perfusion due to impaired nitric oxide (NO) bioavailability. In the present study we hypothesized that the reduced bioavailability of nitric oxide (NO) is the result of increased production of reactive oxygen species (ROS) and ROS scavenging will restore myocardial oxygen balance thereby improving myocardial perfusion. Methods 12 female swine, with DM (streptozotocin 3x50mg/kg iv), CKD (renal embolization), and HC (high fat, high sugar, high salt diet) and 9 female healthy swine on normal pig chow (Normal) were included. The effect of ROS scavenging on the coronary microvascular tone control was studied in vivo, at rest and during graded treadmill exercise before and after infusion of the ROS scavengers (MPG+Tempol). Additionally, vasodilation to bradykinin was studied in the presence of MPG and TEMPOL and after subsequent addition to catalase, in isolated left ventricle small coronary arteries, in vitro using wire-myography. Results 6 months of DM+HC+CKD resulted in hyperglycemia (18.0±1.3 vs 8.4±0.9mmol/L), hypercholesterolemia (13.4±2.1 vs 1.7±0.1mmol/l), renal dysfunction (plasma creatinine: 166±9 vs 119±3µmol/l), and systemic inflammation (TNFα: 63±8 vs 41±4pg/ml, all P<0.05) associated with impaired endothelium-dependent vasodilator response to bradykinin in vitro. Furthermore, myocardial oxidative stress was increased in DM+HC+CKD animals (8-isoprostane 13±1 vs 10±1pg/ml) and total antioxidant capacity was reduced (0.67±0.02 vs 0.72±0.01nmol Trolox eq./mg protein, both P<0.05). Surprisingly, in vivo ROS scavenging resulted in an even further increase in myocardial oxygen extraction in DM+HC+CKD while it had no effect in Normal, indicating the involvement of a vasodilator ROS (most likely H2O2) in the control of coronary microvascular tone. This was supported by increased activity of catalase in the myocardium of DM+HC+CKD animals (44±3 vs 31±4nmol/min/ml, both P<0.05) and the vascular relaxation response to bradykinin when catalase was added on top of the ROS scavenging in vitro. Conclusion In swine exposed for 6 months to multiple comorbidities, impaired myocardial perfusion is mediated by a loss of NO bioavailability due to increased oxidative stress which was partially compensated by increased H2O2-mediated coronary vasodilation.

IMPAIRED BETA-ADRENERGIC VASODILATOR FUNCTION IN HYPERTENSIVE PATIENTS WITH SYMPTOMS OF DEPRESSION

Objective: Hypertension and depression are amongst the most common chronic physical and mental conditions worldwide. The two conditions cluster, however the mechanisms underlying the association are not well understood. Hypertension complicated by affective disorders may be characterised by high sympathetic activity. We investigated whether symptoms of depression may be associated with impaired endothelium-dependent beta2-adrenergic vasodilator responses. Design and method: Hypertensive subjects with no previous history of diabetes or cardiovascular disease were recruited from the hypertension outpatient service at St. Thomas’ Hospital, London. Detailed medical history and baseline characteristics including blood pressure (BP), heart rate (HR), routine biochemistry including C-reactive protein (CRP) and low-density lipoprotein (LDL) were obtained during a single study visit. Plasma concentrations of normetadrenaline were measured as a marker of resting sympathetic activity. Depression symptom severity was assessed using the Patient Health Questionnaire-9 (PHQ-9). The pulse wave response to the beta2-adrenergic vasodilator salbutamol (PWRS) was assessed using radial tonometry to measure the change in augmentation index after inhalation of 200μg salbutamol from a metered dose inhaler with spacer device. Results: 100 subjects (62% male, mean ± SD age 41.0±11.6 years) were recruited. 79% were on pharmacological treatment for hypertension. Mean PHQ-9 depression score was 8.8±6.2, consistent with a high prevalence of depression. After adjusting for confounders (age, sex, smoking status, body mass index, BP, HR, CRP, LDL, treatment for hypertension), PWRS was significantly related to depression score (Beta= 0.447, P=0.002). Depression score was also significantly associated with plasma concentrations of normetadrenaline (Beta= 0.605, P<0.001) and after adjusting for plasma normetadrenaline level, the association between PWRS and depression score was no longer significant (Beta= 0.343, P=0.102). Conclusions: These results suggest that in hypertensive subjects with depression, an impaired endothelium-dependent beta2-adrenergic vasodilator response is mediated by a high level of sympathetic activity which could contribute to cardiovascular complications.

High-fat diet causes endothelial dysfunction in the mouse ophthalmic artery

Obesity is a significant health concern that leads to impaired vascular function and subsequent abnormalities in various organs. The impact of obesity on ocular blood vessels, however, remains largely unclear. In this study, we examined the hypothesis that obesity induced by high-fat diet produces vascular endothelial dysfunction in the ophthalmic artery. Mice were subjected to a high-fat diet for 20 weeks, while age-matched controls were maintained on a standard diet. Reactivity of isolated ophthalmic artery segments was assessed in vitro. Reactive oxygen species (ROS) were quantified in cryosections by dihydroethidium (DHE) staining. Redox gene expression was determined in ophthalmic artery explants by real-time PCR. Furthermore, the expression of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), the receptor for advanced glycation end products (RAGE), and of the lectin-like oxidized low-density-lipoprotein receptor-1 (LOX-1) was determined in cryosections using immunofluorescence microscopy. Ophthalmic artery segments from mice on a high-fat diet exhibited impaired vasodilation responses to the endothelium-dependent vasodilator acetylcholine, while endothelium-independent responses to nitroprusside remained preserved. DHE staining intensity in the vascular wall was notably stronger in mice on a high-fat diet. Messenger RNA expression for NOX2 was elevated in the ophthalmic artery of mice subjected to high fat diet. Likewise, immunostainings revealed increased expression of NOX2 and of RAGE, but not of LOX-1. These findings suggest that a high-fat diet triggers endothelial dysfunction by inducing oxidative stress in the ophthalmic artery via involvement of RAGE and NOX2.

Human Omentin-1 Administration Ameliorates Hypertensive Complications without Affecting Hypertension in Spontaneously Hypertensive Rats.

Hypertension is one of the major risk factors for cardiovascular diseases and is caused by various abnormalities including the contractility of blood vessels. Spontaneously hypertensive rats (SHR), whose systemic blood pressure increases with aging, are a frequently used animal model for investigating essential hypertension and related complications in humans due to the damage of several organs. Human omentin-1 is an adipocytokine consisting of 313 amino acids. Serum omentin-1 levels decreased in hypertensive patients compared with normotensive controls. Furthermore, omentin-1 knockout mice showed elevated blood pressure and impaired endothelial vasodilation. Taken together, we hypothesized that adipocytokine, human omentin-1 may improve the hypertension and its complications including heart and renal failure in the aged SHR (65-68-weeks-old). SHR were subcutaneously administered with human omentin-1 (18 μg/kg/day, 2 weeks). Human omentin-1 had no effect on body weight, heart rate, and systolic blood pressure in SHR. The measurement of isometric contraction revealed that human omentin-1 had no influence on the enhanced vasocontractile or impaired vasodilator responses in the isolated thoracic aorta from SHR. On the other hand, human omentin-1 tended to improve left ventricular diastolic failure and renal failure in SHR. In summary, human omentin-1 tended to improve hypertensive complications (heart and renal failure), while it had no influence on the severe hypertension in the aged SHR. The further study of human omentin-1 may lead to the development of therapeutic agents for hypertensive complications.

Hyperoxaluria Induces Endothelial Dysfunction in Preglomerular Arteries: Involvement of Oxidative Stress.

Urolithiasis is a worldwide problem and a risk factor for kidney injury. Oxidative stress-associated renal endothelial dysfunction secondary to urolithiasis could be a key pathogenic factor, similar to obesity and diabetes-related nephropathy. The aim of the present study was to characterize urolithiasis-related endothelial dysfunction in a hyperoxaluria rat model of renal lithiasis. Experimental approach: Endothelial dysfunction was assessed in preglomerular arteries isolated from control rats and in which 0.75% ethylene glycol was administered in drinking water. Renal interlobar arteries were mounted in microvascular myographs for functional studies; superoxide generation was measured by chemiluminescence and mRNA and protein expression by RT-PCR and immunofluorescence, respectively. Selective inhibitors were used to study the influence of the different ROS sources, xanthine oxidase, COX-2, Nox1, Nox2 and Nox4. Inflammatory vascular response was also studied by measuring the RNAm expression of NF-κB, MCP-1 and TNFα by RT-PCR. Results: Endothelium-dependent vasodilator responses were impaired in the preglomerular arteries of the hyperoxaluric group along with higher superoxide generation in the renal cortex and vascular inflammation developed by MCP-1 and promoted by NF-κB. The xanthine oxidase inhibitor allopurinol restored the endothelial relaxations and returned superoxide generation to basal values. Nox1 and Nox2 mRNA were up-regulated in arteries from the hyperoxaluric group, and Nox1 and Nox2 selective inhibitors also restored the impaired vasodilator responses and normalized NADPH oxidase-dependent higher superoxide values of renal cortex from the hyperoxaluric group. Conclusions: The current data support that hyperoxaluria induces oxidative stress-mediated endothelial dysfunction and inflammatory response in renal preglomerular arteries which is promoted by the xanthine oxidase, Nox1 and Nox2 pathways.

Nicotine Alters cAMP Signaling in Arterial Myocytes

Arterial myocytes receive many inputs from sympathetic nerves that regulate vascular reactivity by activating GS protein‐coupled receptors (GSPCRs). The ubiquitous second messenger 3′,5′‐ cyclic adenosine monophosphate (cAMP) is synthesized by adenylyl cyclases (ACs) in response to the activation of various GSPCRs and plays a critical role in integrating the myriad of signals elicited. Importantly, arterial myocyte cAMP signaling has been traditionally linked with relaxation. We found that arterial myocytes from mice exposed to secondhand smoke (SHS) had an attenuated cAMP synthesis in response to the β‐adrenergic receptor (βAR) agonist isoproterenol (ISO) (unpublished data), which could alter vascular reactivity. Tobacco smoke contains over 7,000 chemicals, including nicotine. Nicotine, the primary addictive component in tobacco cigarettes is a strong sympathomimetic with significant vasoactive effects and have been shown to alter cellular cAMP production. However, how nicotine impacts cAMP signaling in the vasculature, particularly in arterial myocytes, and the implications of these changes in vascular reactivity are unclear. We are tackling this knowledge gap by expressing a FRET‐based cAMP biosensor in cultured arterial myocytes to determine cAMP signaling in response to nicotine/cotinine. We also developed a mouse expressing a new cAMP sensor specifically in SM (CamperSM) to investigate cAMP dynamics in native VSM/arteries. We hypothesize that nicotine impairs receptor‐mediated cAMP signaling in arterial myocytes leading to altered vascular reactivity. Our data using unpassaged arterial myocytes expressing a cytosolic FRET‐based cAMP sensor exposed to cotinine (the primary metabolite of nicotine) show a reduction in ISOinduced cAMP production. Similar results were observed in arterial myocytes from CAMPERSM mice infused with nicotine. These results suggest similar effects of cotinine in vitro or nicotine in vivo on βAR‐mediated cAMP synthesis in arterial myocytes. Intriguingly, we found that inhibition of phosphodiesterases rescue cAMP synthesis in CAMPERSM arterial myocytes exposed to nicotine. We correlated the nicotine‐induced reduction in arterial myocytes cAMP synthesis with impaired vasodilation in response to ISO. Our data suggest that nicotine impairs receptormediated cAMP signaling in arterial myocytes leading to altered vascular reactivity. Nicotineinduced cAMP dysregulation leading to altered arterial myocytes excitability could be an underlying factor contributing to cardiovascular disease in individuals exposed to SHS and users of nicotine containing products.

Rho‐related BTB Domain‐containing Protein 1 Reverses Established Arterial Stiffness in Angiotensin II‐treated Mice

Rho‐related BTB domain‐containing protein 1 (RhoBTB1) is associated with blood pressure in GWAS studies, but its function is not well‐understood. The level of RhoBTB1 mRNA was decreased in mice treated with angiotensin II (Ang‐II) concomitant with hypertension, arterial stiffness, and impaired vasodilation. Here, we tested the hypothesis that restoration of RhoBTB1 would reverse hypertension, arterial stiffness, and improve vasodilation response caused by Ang‐II infusion. Genetic complementation of RhoBTB1 in the vasculature was achieved by expressing a smooth muscle‐specific, tamoxifen‐inducible RhoBTB1 transgene (S‐RhoBTB1 mice). Mice expressing smooth muscle‐specific, tamoxifen‐inducible Cre‐recombinase without RhoBTB1 (ISM‐Cre mice) were used as genotype control. ISM‐Cre and S‐RhoBTB1 mice received 6 weeks of Ang‐II infusion, but their transgene was not activated until two weeks after the initiation of Ang‐II treatment. Meanwhile, vehicle‐treated ISM‐Cre and S‐RhoBTB1 mice were used as control. Blood pressure was continuously recorded by radiotelemetry during the entire protocol. Pulse wave velocity (PWV) and aortic compliance assay were used to evaluate arterial stiffness both during and at the end of the protocol. Vasodilation was measured in isolated carotid and mesenteric arteries using wire myography. In vehicle‐treated mice, aortic RhoBTB1 expression was increased in S‐RhoBTB1 mice compared to ISM‐Cre mice. Ang‐II significantly decreased the level of RhoBTB1 in the aorta of ISM‐Cre mice whereas S‐RhoBTB1 mice normalized this effect. At baseline, overexpressing RhoBTB1 in the vasculature had no significant effect on any phenotype. Before transgene activation, Ang‐II increased blood pressure, arterial stiffness, and impaired vasodilation in response to acetylcholine and sodium nitroprusside in both ISM‐Cre and S‐RhoBTB1 mice. Remarkably, in Ang‐II‐treated mice, RhoBTB1 restoration restored arterial stiffness nearly back to baseline without rescuing either hypertension or vasodilation. Since arterial stiffness is often observed to go hand‐in‐hand with hypertension, the current phenotype is particularly interesting as it provides novel insight into the cause‐effect relationship between arterial stiffness and hypertension. Next, we utilized RNA‐seq and biochemical assays to investigate the mechanism by which RhoBTB1 reversed arterial stiffness. Classical contributors of arterial stiffness, for instance, collagen, elastin, and vascular smooth muscle remodeling, were not altered by RhoBTB1 restoration. However, actin polymerization was elevated by Ang‐II and normalized upon RhoBTB1 restoration, as evident by both immunoblotting and fluorescent labeling. In conclusion, we identified a novel function of RhoBTB1 and showed its importance in protecting from and reversing arterial stiffness.

The Role of Vasospasm and Microcirculatory Dysfunction in Fluoropyrimidine-Induced Ischemic Heart Disease

Cardiovascular diseases and cancer are the leading cause of morbidity and mortality globally. Cardiotoxicity from chemotherapeutic agents results in substantial morbidity and mortality in cancer survivors and patients with active cancer. Cardiotoxicity induced by 5-fluorouracil (5-FU) has been well established, yet its incidence, mechanisms, and manifestation remain poorly defined. Ischemia secondary to coronary artery vasospasm is thought to be the most frequent cardiotoxic effect of 5-FU. The available evidence of 5-FU-induced epicardial coronary artery spasm and coronary microvascular dysfunction suggests that endothelial dysfunction or primary vascular smooth muscle dysfunction (an endothelial-independent mechanism) are the possible contributing factors to this form of cardiotoxicity. In patients with 5-FU-related coronary artery vasospasm, termination of chemotherapy and administration of nitrates or calcium channel blockers may improve ischemic symptoms. However, there are variable results after administration of nitrates or calcium channel blockers in patients treated with 5-FU presumed to have myocardial ischemia, suggesting mechanisms other than impaired vasodilatory response. Clinicians should investigate whether chest pain and ECG changes can reasonably be attributed to 5-FU-induced cardiotoxicity. More prospective data and clinical randomized trials are required to understand and mitigate potentially adverse outcomes from 5-FU-induced cardiotoxicity.

Postcontractile blood oxygenation level-dependent (BOLD) response in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is characterized by a progressive replacement of muscle by fat and fibrous tissue, muscle weakness, and loss of functional abilities. Impaired vasodilatory and blood flow responses to muscle activation have also been observed in DMD and associated with mislocalization of neuronal nitric oxide synthase mu (nNOSμ) from the sarcolemma. The objective of this study was to determine whether the postcontractile blood oxygen level-dependent (BOLD) MRI response is impaired in DMD and correlated with established markers of disease severity in DMD, including MRI muscle fat fraction (FF) and clinical functional measures. Young boys with DMD (n = 16, 5-14 yr) and unaffected controls (n = 16, 5-14 yr) were evaluated using postcontractile BOLD, FF, and functional assessments. The BOLD response was measured following five brief (2 s) maximal voluntary dorsiflexion contractions, each separated by 1 min of rest. FFs from the anterior compartment lower leg muscles were quantified via chemical shift-encoded imaging. Functional abilities were assessed using the 10 m walk/run and the 6-min walk distance (6MWD). The peak BOLD responses in the tibialis anterior and extensor digitorum longus were reduced (P < 0.001) in DMD compared with controls. Furthermore, the anterior compartment peak BOLD response correlated with function (6MWD ρ = 0.87, P < 0.0001; 10 m walk/run time ρ = -0.78, P < 0.001) and FF (ρ = -0.52, P = 0.05). The reduced postcontractile BOLD response in DMD may reflect impaired microvascular function. The relationship observed between the postcontractile peak BOLD response and functional measures and FF suggests that the BOLD response is altered with disease severity in DMD.NEW & NOTEWORTHY This study examined the postcontractile blood oxygen level-dependent (BOLD) response in boys with Duchenne muscular dystrophy (DMD) and unaffected controls, and correlated this measure to markers of disease severity. Our findings indicate that the postcontractile BOLD response is impaired in DMD after brief muscle contractions, is correlated to disease severity, and may be valuable to implement in future studies to evaluate treatments targeting microvascular function in DMD.

Impaired Adenosine‐Mediated Coronary Vasodilation in Swine with Repetitive Pressure Overload‐Induced Heart Failure with Preserved Ejection Fraction

Objective We recently demonstrated that swine subjected to 2-weeks of intermittent repetitive pressure overload (RPO) develop cardiac phenotypic characteristics of heart failure with preserved ejection fraction (HFpEF), including a reduction in left ventricular (LV) diastolic compliance, myocyte hypertrophy, and interstitial fibrosis without an increase in LV mass. The objective of the present study was to determine if this pattern of myocardial remodeling is accompanied by alterations in coronary microvascular function or structure that contribute to an impaired vasodilator response to adenosine (ADO). Methods Regional myocardial blood flow (BF) was assessed via administration of fluorescent microspheres at rest and during ADO vasodilation in swine subjected to 2-weeks of RPO (300 µg/min phenylephrine (PE), 30 min/day; n=5) and normal controls (n=5). Adenosine (ADO)-mediated vasodilation was initially assessed at a submaximal dose (0.15 mg/kg/min), followed by a maximal vasodilating dose (0.90 mg/kg/min) with concomitant PE to maintain arterial blood pressure. Post-mortem histological evaluation of myocardial tissue samples was performed in separate groups of swine subjected to 2-weeks of RPO (n=8) and normal controls (n=5) to assess arteriolar density (α-smooth muscle actin staining) and structural remodeling (wall thickness/lumen diameter ratio). Results Submaximal ADO produced a significant ~60% rise in myocardial BF in normal controls, but this response was completely attenuated in the RPO group (Figure; A). The impaired vasodilator response to submaximal ADO in the RPO group was not explained by hemodynamic factors, as heart rate (RPO vs. control: 102±5 vs. 95±4 beats/min; p=0.29) and mean arterial pressure (71±3 vs. 67±5 mmHg; p=0.55) were similar between groups. However, group differences in ADO-induced vasodilation were abolished by administration of maximal ADO, which elicited a comparable ~4-fold rise in myocardial BF in normal controls and the RPO group. Arteriolar density (Figure; B) and arteriolar wall thickness/lumen diameter (Figure; C) were not different between groups, further supporting abnormal microvascular function as the primary mechanism underlying the impaired response to submaximal ADO after RPO. Conclusions These results indicate that RPO-induced HFpEF is characterized by an impairment in ADO-mediated coronary vasodilation that may compromise myocardial perfusion during episodes of increased metabolic demand. The absence of histopathological evidence of arteriolar structural remodeling along with a preserved vasodilator response to maximal ADO indicate that a functional abnormality is primarily responsible for the impaired responsiveness to ADO in this setting. Further studies are necessary to evaluate the contribution of endothelium-dependent vs. endothelium-independent factors, as well as whether therapeutic interventions targeting RPO-induced coronary microvascular dysfunction may prevent or reverse adverse myocardial remodeling and diastolic dysfunction in HFpEF.

L-Citrulline ameliorates the attenuation of acetylcholine-induced vasodilation of retinal arterioles in diabetic rats

In our previous study, we found that the vasodilation of retinal arterioles induced by acetylcholine and BMS-191011, a large-conductance Ca2+-activated K+ (BKCa) channel opener, were diminished in diabetic rats. Currently, few agents ameliorate the impaired vasodilator responses of retinal blood vessels. Our recent finding that the intravenous infusion of L-citrulline dilated retinal arterioles, suggests that L-citrulline could be a potential therapeutic agent for circulatory disorders of the retina. In this study, we determined the effect of an oral L-citrulline treatment on impaired acetylcholine- and BMS-191011-induced vasodilation in the retinal arterioles of diabetic rats. To induce diabetes, rats were administered an intravenous dose of streptozotocin (65 mg/kg) and a 5% D-glucose solution as drinking water. The L-citrulline (2 g/kg/day) and L-arginine (2 g/kg/day) treatments commenced either 15 days before or just after the streptozotocin injection and continued throughout the experimental period. A 29-day treatment with L-citrulline, but not L-arginine, significantly ameliorated the impaired acetylcholine- and BMS-191011-induced retinal vasodilation in diabetic rats without affecting their plasma glucose levels. The 2-week L-citrulline treatment tended to ameliorate the dysfunction of the acetylcholine-induced retinal vasodilation in diabetic rats. In conclusion, these results showed that the retinal blood vessel dysfunction induced by diabetes mellitus could be prevented by the long-term administration of L-citrulline and suggest that the latter could play a potentially prophylactic role in diabetic retinopathy.

Assessment of Cerebral Vasomotor Reactivity in Patients With Primary Open-angle Glaucoma and Ocular Hypertension Using the Breath-Holding Index.

Patients with ocular hypertension (OHT) do not show impaired cerebral vasodilation responses to hypercapnia but patients with primary open-angle glaucoma (POAG) do. Impaired vasoreactivity in patients with POAG may have neuronal or vascular origins and increase stroke risk. To investigate changes in cerebral blood flow and cerebral vasomotor reactivity using the breath-holding index in patients with POAG and OHT, to examine whether these parameters contribute to the risk of ischemic stroke. Thirty patients with POAG, 30 patients with OHT, and 30 age- and sex-matched healthy control subjects were included in this university hospital-based, cross-sectional, and observational study. Eyes with a greater degree of visual field loss and/or more severe optic disc damage were selected for the study in patients with POAG, whereas in patients with OHT and controls, the study eye was chosen randomly. The mean blood flow velocity and breath-holding index were measured in the middle cerebral artery ipsilaterally in patient and control groups, by using transcranial Doppler ultrasonography. The mean blood flow velocity and breath-holding indexes were significantly lower in patients with POAG than in the control group (all P<0.05). In the OHT group, the mean blood flow velocity and breath-holding indexes were not different from those in the control group. Patients with POAG have impaired vasodilation response to hypercapnia. Presumably, the neuronal changes and deterioration of the endothelium-mediated vasodilatation in patients with glaucoma may disrupt the regulation of arteries and potentially present functional insufficiency on vasoreactivity. Moreover, impaired cerebral vascular regulation may contribute to the increased risk of stroke in patients with POAG.

Glycated hemoglobin and subsequent risk of microvascular and macrovascular complications

Diabetes mellitus (DM) is a global health problem and its prevalence is constantly increasing over the past several decades. Measurement of glycated hemoglobin (HbA1c) is widely accepted as indicator of long-term glycemic exposure and used as tool for the diagnosis and management of DM. Patients with DM are at heightened risk of both microvascular and macrovascular complications which affect the several organs including skin, heart, brain, eyes, and kidneys. There is a common etiology between hyperglycemia and vascular diseases. The mechanism of pathogenesis starts with formation and accumulation of advanced glycation end product, impaired vasodilatory response, smooth muscle cell dysfunction, overproduction of endothelial growth factors, chronic inflammation, hemodynamic dysregulation, impaired fibrinolytic activity, and enhanced platelet aggregation. These events decrease the diameter of the vessel and initiate the lesion of the vessel wall followed by local ischemia and tissue damage.

Myeloid GRK2 Regulates Obesity-Induced Endothelial Dysfunction by Modulating Inflammatory Responses in Perivascular Adipose Tissue.

Perivascular adipose tissue (PVAT) is increasingly being regarded as an important endocrine organ that directly impacts vessel function, structure, and contractility in obesity-associated diseases. We uncover here a role for myeloid G protein-coupled receptor kinase 2 (GRK2) in the modulation of PVAT-dependent vasodilation responses. GRK2 expression positively correlates with myeloid- (CD68) and lymphoid-specific (CD3, CD4, and CD8) markers and with leptin in PVAT from patients with abdominal aortic aneurysms. Using mice hemizygous for GRK2 in the myeloid lineage (LysM-GRK2+/−), we found that GRK2 deficiency in myeloid cells allows animals to preserve the endothelium-dependent acetylcholine or insulin-induced relaxation, which is otherwise impaired by PVAT, in arteries of animals fed a high fat diet (HFD). Downregulation of GRK2 in myeloid cells attenuates HFD-dependent infiltration of macrophages and T lymphocytes in PVAT, as well as the induction of tumor necrosis factor-α (TNFα) and NADPH oxidase (Nox)1 expression, whereas blocking TNFα or Nox pathways by pharmacological means can rescue the impaired vasodilator responses to insulin in arteries with PVAT from HFD-fed animals. Our results suggest that myeloid GRK2 could be a potential therapeutic target in the development of endothelial dysfunction induced by PVAT in the context of obesity.

Despite Blocking Doxorubicin-Induced Vascular Damage, Quercetin Ameliorates Its Antibreast Cancer Activity.

Quercetin is a naturally occurring flavonol present in many foods. Doxorubicin is an effective anticancer agent despite its dose-limiting cardiovascular toxicity. Herein, we investigated the potential protective effects of quercetin against doxorubicin-induced vascular toxicity and its effect on the therapeutic cytotoxic profile of doxorubicin in breast cancer cell lines. The incubation of isolated aortic rings with doxorubicin produced concentration-dependent exaggeration of vasoconstriction responses to phenylephrine but impaired vasodilation responses to acetylcholine. Coincubation with quercetin completely blocked the exaggerated vasoconstriction responses and the impaired vasodilation. In addition, doxorubicin incubation increased reactive oxygen species generation from the isolated aorta, while coincubation with quercetin inhibited ROS generation back to normal values. On the other hand, quercetin in combination with doxorubicin, doubled the IC50 of doxorubicin alone in MCF-7 cells from 0.4 ± 0.03 to 0.8 ± 0.06 μM. To a lesser extent, the IC50 of doxorubicin did not change after combination with quercetin in MDA-MB-231 cells. These findings indicate a significant antagonistic interaction between quercetin and doxorubicin in the aforementioned cell lines. Only in T47D cells, quercetin combination with doxorubicin was an additive interaction (CI − value = 1.17). Yet, quercetin significantly impaired the immediate phase of intracellular ROS generation by doxorubicin within breast cancer cells from 125.2 ± 3.6% to 102.5 ± 3.9% of control cells. Using annexin-V/FITC staining technique, the quercetin/doxorubicin combination showed a significantly lower percent of apoptotic cells compared to doxorubicin alone treated cells. Cell cycle distribution in breast cancer cells was performed using DNA content flowcytometry after propidium iodide staining. Quercetin induced significant accumulation of cells in the S phase as well as in the G2/M phase within both MCF-7 and MDA-MB-231 cell lines and interfered with doxorubicin-induced cell cycle effects. Interestingly, quercetin was found to inhibit the P-glycoprotein ATPase subunit with a consequent enhanced intracellular concentration of doxorubicin in MDA-MB-231 and T47D cells. In conclusion, quercetin, despite its potent vascular protective activity against doxorubicin, was found to influence doxorubicin-induced antibreast cancer effects via pharmacodynamic as well as cellular pharmacokinetic aspects.

Clinical significance of endothelial vasodilatory function evaluated by EndoPAT in patients with systemic sclerosis.

Endothelial dysfunction is a hallmark of vasculopathy associated with systemic sclerosis (SSc). Reactive hyperemia peripheral arterial tonometry is a rapid and non-invasive technique to assess peripheral microvascular endothelial function by measuring changes in digital pulse volume during reactive hyperemia. Low scores of the reactive hyperemia index (RHI) imply an impaired vasodilatory response and, accordingly, impaired endothelial and vascular health. To investigate the clinical significance of the RHI in SSc patients, RHI values were measured in 43 SSc patients and 10 healthy controls. In diffuse cutaneous SSc (dcSSc) patients, RHI values were significantly decreased compared with healthy controls, and inversely correlated with disease duration. In total SSc patients, there was a significant inverse correlation between RHI values and skin score, and interstitial lung disease was associated with the decrease in RHI values. Among vascular symptoms, the current and past history of digital ulcers was seen more frequently in patients with decreased RHI values than in those with normal RHI values. Although no SSc patients had pulmonary arterial hypertension, an inverse correlation was evident between RHI values and mean pulmonary arterial pressure measured by right heart catheterization. These results indicate that the decrease in RHI values is associated with skin fibrosis, interstitial lung disease, digital ulcers and pulmonary vascular involvement leading to pulmonary arterial hypertension, supporting the canonical idea that endothelial dysfunction is a critical event underlying the development of tissue fibrosis and vascular complications in SSc.

Clapping jumping jacks to improve endothelial function in obese adults: if you're happy and you NO it, clap your hands.

Clapping jumping jacks to improve endothelial function in obese adults: if you're happy and you NO it, clap your hands.

未熟児網膜症モデルラットにおいて内皮依存性網膜血管拡張反応が減弱する

未熟児網膜症モデルラットにおいて内皮依存性網膜血管拡張反応が減弱する

Pharmacological Targeting of KCa Channels to Improve Endothelial Function in the Spontaneously Hypertensive Rat

Systemic hypertension is a major risk factor for the development of cardiovascular disease and is often associated with endothelial dysfunction. KCa2.3 and KCa3.1 channels are expressed in the vascular endothelium and contribute to stimulus-evoked vasodilation. We hypothesized that acute treatment with SKA-31, a selective activator of KCa2.x and KCa3.1 channels, would improve endothelium-dependent vasodilation and transiently lower mean arterial pressure (MAP) in male, spontaneously hypertensive rats (SHRs). Isolated vascular preparations exhibited impaired vasodilation in response to bradykinin (i.e., endothelial dysfunction) compared with Wistar controls, which was associated with decreased bradykinin receptor expression in mesenteric arteries. In contrast, similar levels of endothelial KCa channel expression were observed, and SKA-31 evoked vasodilation was comparable in vascular preparations from both strains. Addition of a low concentration of SKA-31 (i.e., 0.2–0.3 μM) failed to augment bradykinin-induced vasodilation in arteries from SHRs. However, responses to acetylcholine were enhanced. Surprisingly, acute bolus administration of SKA-31 in vivo (30 mg/kg, i.p. injection) modestly elevated MAP compared with vehicle injection. In summary, pharmacological targeting of endothelial KCa channels in SHRs did not readily reverse endothelial dysfunction in situ, or lower MAP in vivo. SHRs thus appear to be less responsive to endothelial KCa channel activators, which may be related to their vascular pathology.

Insulin resistance is associated with subclinical vascular disease in humans.

Insulin resistance is associated with subclinical vascular disease that is not justified by conventional cardiovascular risk factors, such as smoking or hypercholesterolemia. Vascular injury associated to insulin resistance involves functional and structural damage to the arterial wall that includes impaired vasodilation in response to chemical mediators, reduced distensibility of the arterial wall (arterial stiffness), vascular calcification, and increased thickness of the arterial wall. Vascular dysfunction associated to insulin resistance is present in asymptomatic subjects and predisposes to cardiovascular diseases, such as heart failure, ischemic heart disease, stroke, and peripheral vascular disease. Structural and functional vascular disease associated to insulin resistance is highly predictive of cardiovascular morbidity and mortality. Its pathogenic mechanisms remain undefined. Prospective studies have demonstrated that animal protein consumption increases the risk of developing cardiovascular disease and predisposes to type 2 diabetes (T2D) whereas vegetable protein intake has the opposite effect. Vascular disease linked to insulin resistance begins to occur early in life. Children and adolescents with insulin resistance show an injured arterial system compared with youth free of insulin resistance, suggesting that insulin resistance plays a crucial role in the development of initial vascular damage. Prevention of the vascular dysfunction related to insulin resistance should begin early in life. Before the clinical onset of T2D, asymptomatic subjects endure a long period of time characterized by insulin resistance. Latent vascular dysfunction begins to develop during this phase, so that patients with T2D are at increased cardiovascular risk long before the diagnosis of the disease.