Coronary Artery Vasodilation Research Articles

Asymmetric Dimethylarginine (ADMA) in Cardiovascular Disease, Cardiac Ischemia/reperfusion Injury, and Ischemic Non-obstructive Coronary Artery Disease: Biochemical and Pharmacological Implications

: Several studies have shown that high plasma concentrations of asymmetric dimethylarginine (ADMA), a known endogenous competitive inhibitor of endothelial nitric oxide synthase (eNOS), correlate with the severity of coronary artery disease (CAD), with worsening of cardiac ischemia/reperfusion (I/R) injury and coronary atherosclerosis. It is believed that it may be an important risk factor for myocardial infarction. ADMA, when in high concentrations, can determine a significant decrease in the synthesis and bioavailability of NO (Nitric oxide) and therefore alter the mechanisms of regulation of coronary vasodilation and vasomotor function of epicardial coronary arteries. Higher serum ADMA concentration is associated with worsening of post-ischemic remodeling since coronary angiogenesis, vasculogenesis, and collateral coronary growth are seriously impaired. In addition, there are reasons to believe that elevated plasma ADMA levels are related to the development of diseases affecting coronary microcirculation, such as ischemic non-obstructive coronary artery disease (INOCA). With the aim of providing the pharmacologist engaged in the design and discovery of new ADMA-lowering drugs with a complete examination of the subject, in this review, we discuss the most important studies related to the correlations between serum ADMA levels and cardiovascular diseases mentioned above. In addition, we critically discuss the main aspects of enzymology, synthesis, and metabolism of ADMA as a prerequisite for understanding the molecular mechanisms through which high concentrations of ADMA could contribute to promoting cardiovascular diseases. ADMA represents a new target for pharmacological modulation of cardiovascular endothelial function and therefore, there is a possibility of using selective pharmacological ADMA lowering drugs in cardiovascular disease with endothelial dysfunction and high plasma ADMA levels.

Methylglyoxal induces endothelial cell apoptosis and coronary microvascular dysfunction through regulating AR-cPLA2 signaling

ObjectiveSince diabetic patients with coronary microvascular dysfunction (CMD) exhibit high cardiac mortality and women have higher prevalence of non-obstructive coronary artery disease than men, we tried to expand the limited understanding about the etiology and the sex difference of diabetic CMD. Approach and resultsAccumulated methylglyoxal (MGO) due to diabetes promotes vascular damage and it was used for mimicking diabetic status. Flow cytometry analysis and isometric tension measurement were performed to evaluate coronary artery endothelial injury. MGO induced apoptosis of coronary endothelial cells, accompanied by downregulation of androgen receptor (AR). Lentivirus-mediated stable expression of AR in coronary endothelial cells increased anti-apoptotic Bcl-2 expression and attenuated MGO-induced cell apoptosis. cPLA2 activation was the downstream of AR downregulation by MGO treatment. Moreover, MGO also activated cPLA2 rapidly to impair endothelium-dependent vasodilation of coronary arteries from mice. Reactive oxygen species (ROS) overproduction was demonstrated to account for MGO-mediated cPLA2 activation and endothelial dysfunction. Importantly, AR blockade increased endothelial ROS production whereas AR activation protected coronary artery endothelial vasodilatory function from the MGO-induced injury. Although galectin-3 upregulation was confirmed by siRNA knockdown in endothelial cells not to participate in MGO-induced endothelial apoptosis, pharmacological inhibitor of galectin-3 further enhanced MGO-triggered ROS generation and coronary artery endothelial impairment. ConclusionsOur data proposed the AR downregulation-ROS overproduction-cPLA2 activation pathway as one of the mechanisms underlying diabetic CMD and postulated a possible reason for the sex difference of CMD-related angina. Meanwhile, MGO-induced galectin-3 activation played a compensatory role against coronary endothelial dysfunction.

Sex-specific differences in the mechanisms for enhanced thromboxane A2-mediated vasoconstriction in adult offspring exposed to prenatal hypoxia

BackgroundPrenatal hypoxia, a common pregnancy complication, leads to impaired cardiovascular outcomes in the adult offspring. It results in impaired vasodilation in coronary and mesenteric arteries of the adult offspring, due to reduced nitric oxide (NO). Thromboxane A2 (TxA2) is a potent vasoconstrictor increased in cardiovascular diseases, but its role in the impact of prenatal hypoxia is unknown. To prevent the risk of cardiovascular disease by prenatal hypoxia, we have tested a maternal treatment using a nanoparticle-encapsulated mitochondrial antioxidant (nMitoQ). We hypothesized that prenatal hypoxia enhances vascular TxA2 responses in the adult offspring, due to decreased NO modulation, and that this might be prevented by maternal nMitoQ treatment.MethodsPregnant Sprague–Dawley rats received a single intravenous injection (100 µL) of vehicle (saline) or nMitoQ (125 µmol/L) on gestational day (GD)15 and were exposed to normoxia (21% O2) or hypoxia (11% O2) from GD15 to GD21 (term = 22 days). Coronary and mesenteric arteries were isolated from the 4-month-old female and male offspring, and vasoconstriction responses to U46619 (TxA2 analog) were evaluated using wire myography. In mesenteric arteries, L-NAME (pan-NO synthase (NOS) inhibitor) was used to assess NO modulation. Mesenteric artery endothelial (e)NOS, and TxA2 receptor expression, superoxide, and 3-nitrotyrosine levels were assessed by immunofluorescence.ResultsPrenatal hypoxia resulted in increased U46619 responsiveness in coronary and mesenteric arteries of the female offspring, and to a lesser extent in the male offspring, which was prevented by nMitoQ. In females, there was a reduced impact of L-NAME in mesenteric arteries of the prenatal hypoxia saline-treated females, and reduced 3-nitrotyrosine levels. In males, L-NAME increased U46619 responses in mesenteric artery to a similar extent, but TxA2 receptor expression was increased by prenatal hypoxia. There were no changes in eNOS or superoxide levels.ConclusionsPrenatal hypoxia increased TxA2 vasoconstrictor capacity in the adult offspring in a sex-specific manner, via reduced NO modulation in females and increased TP expression in males. Maternal placental antioxidant treatment prevented the impact of prenatal hypoxia. These findings increase our understanding of how complicated pregnancies can lead to a sex difference in the programming of cardiovascular disease in the adult offspring.Graphical

Novel nitric oxide donors are coronary vasodilators that also bind to the papain-like protease of SARS-CoV-2

Several investigational nitric oxide donors were originally created to correct vascular endothelial dysfunction in cardiovascular diseases. These 48 compounds contain an urea-like moiety attached to the well-known NO donors isosorbide 2- and 5-mononitrate. CR-0305 and CR-0202 were synthesized and found to be nontoxic in the cell lines HMEC-1, A549/hACE2 and VeroE6. CR-0305 induced vasodilation in human coronary arteries ex vivo. Since NO can also have antiviral properties, a study of drug-protein interactions with SARS-CoV-2 was undertaken using in silico modeling. CR-0305 experimentally outperformed the other compounds, including CR-0202, in binding the catalytic site of SARS-CoV-2 papain-like protease (PLpro). PLpro is a primary target for therapeutic inhibition of SARS-CoV-2 as it mediates viral replication and modulates host innate immune responses. CR-0305 is predicted to sit firmly in the PLpro catalytic pocket as confirmed by molecular dynamics simulations, wherein stability of binding to the catalytic site of PLpro induces a conformational change in the BL2 loop to a more closed conformation as observed previously with GRL0617. Surface plasmon resonance was performed with CR-0305 and CR-0202 to characterize binding affinity to purified SARS-CoV-2 PLpro protein. CR-0305 and CR-0202 also inhibited SARS-CoV-2 infection compared to vehicle as measured by virus N protein staining with a specific antibody in A549-ACE2 and VeroE6 cells at 20 µM. CR-0305 is a coronary vasodilator that appears to bind to the catalytic site of the PLpro of SARS-CoV-2 while targeting delivery of antiviral NO to cells infected by SARS-CoV-2, suggesting multiple indications for future development.

Sorbs2 Deficiency and Vascular BK Channelopathy in Diabetes.

Vascular large conductance Ca2+-activated K+ (BK) channel, composed of the α-subunit (BK-α) and the β1-subunit (BK-β1), is a key determinant of coronary vasorelaxation and its function is impaired in diabetic vessels. However, our knowledge of diabetic BK channel dysregulation is incomplete. The Sorbs2 (Sorbin homology [SoHo] and Src homology 3 [SH3] domains-containing protein 2), is ubiquitously expressed in arteries, but its role in vascular pathophysiology is unknown. The role of Sorbs2 in regulating vascular BK channel activity was determined using patch-clamp recordings, molecular biological techniques, and in silico analysis. Sorbs2 is not only a cytoskeletal protein but also an RNA-binding protein that binds to BK channel proteins and BK-α mRNA, regulating BK channel expression and function in coronary smooth muscle cells. Molecular biological studies reveal that the SH3 domain of Sorbs2 is necessary for Sorbs2 interaction with BK-α subunits, while both the SH3 and SoHo domains of Sorbs2 interact with BK-β1 subunits. Deletion of the SH3 or SoHo domains abolishes the Sorbs2 effect on the BK-α/BK-β1 channel current density. Additionally, Sorbs2 is a target gene of the Nrf2 (nuclear factor erythroid-2-related factor 2), which binds to the promoter of Sorbs2 and regulates Sorbs2 expression in coronary smooth muscle cells. In vivo studies demonstrate that Sorbs2 knockout mice at 4 months of age display a significant decrease in BK channel expression and function, accompanied by impaired BK channel Ca2+-sensitivity and BK channel-mediated vasodilation in coronary arteries, without altering their body weights and blood glucose levels. Importantly, Sorbs2 expression is significantly downregulated in the coronary arteries of db/db type 2 diabetic mice. Sorbs2, a downstream target of Nrf2, plays an important role in regulating BK channel expression and function in vascular smooth muscle cells. Vascular Sorbs2 is downregulated in diabetes. Genetic knockout of Sorbs2 manifests coronary BK channelopathy and vasculopathy observed in diabetic mice, independent of obesity and glucotoxicity.

Alkaloids as Vasodilator Agents: a Review.

The pathophysiology of hypertension is often associated with endothelial dysfunction and the impairment of endothelium-dependent vasodilation mechanisms, as well as alterations in vascular smooth muscle (VSM) tone. Natural products, particularly alkaloids, have received increased attention in the search for new vasodilator agents. This review aims to summarize the noteworthy results from ex-vivo and in-vitro studies that explored the vasodilatory effects of some selected alkaloids (Berberine, Sinomenine, (S)-Reticuline, Neferine, Nuciferine, Villocarine A, 8-Oxo-9-Dihydromakonakine, Harmaline, Harman, and Capsaicin) and the underlying mechanisms implicated. The results obtained from the literature revealed that these selected alkaloids exhibited vasodilation in various vascular models, including mesenteric, carotid, and coronary arteries, thoracic aorta, and cultured HUCECs and VSMCs. Furthermore, most of these alkaloids induced vasodilation through endothelium-dependent and endothelium-independent mechanisms, which were primarily mediated by activating eNOS/NO/sGC/cGMP pathway, opening various potassium (K+ ) channels, or modulating calcium (Ca2+) channels. Additionally, several alkaloids exerted vasodilatory effects through multiple mechanism pathways. Moreover, different alkaloids demonstrated the ability to protect endothelial function by reducing oxidative stress, endoplasmic reticulum and inflammation. In conclusion, this class of secondary metabolites holds interesting therapeutic potential in the prevention and treatment of cardiovascular diseases (CVD), particularly hypertension.

Exercise protects aged mice against coronary endothelial senescence via FUNDC1-dependent mitophagy

Vascular aging contributes to adverse changes in organ function and is a significant indicator of major cardiac events. Endothelial cells (ECs) participate in aging-provoked coronary vascular pathology. Regular exercise is associated with preservation of arterial function with aging in humans. However, the molecular basis is not well understood. The present study was aimed to determine the effects of exercise on coronary endothelial senescence and whether mitochondrial clearance regulator FUN14 domain containing 1 (FUNDC1)-related mitophagy and mitochondrial homeostasis were involved. In mouse coronary arteries, FUNDC1 levels showed gradually decrease with age. Both FUNDC1 and mitophagy levels in cardiac microvascular endothelial cells (CMECs) were significantly reduced in aged mice and were rescued by exercise training. Exercise also alleviated CMECs senescence as evidenced by senescence associated β-galactosidase activity and aging markers, prevented endothelial abnormal cell migration, proliferation, and eNOS activation in CMECs from aged mice, and improved endothelium-dependent vasodilation of coronary artery, reduced myocardial neutrophil infiltration and inflammatory cytokines evoked by MI/R, restored angiogenesis and consequently alleviated MI/R injury in aging. Importantly, FUNDC1 deletion abolished the protective roles of exercise and FUNDC1 overexpression in ECs with adeno-associated virus (AAV) reversed endothelial senescence and prevented MI/R injury. Mechanistically, PPARγ played an important role in regulating FUNDC1 expressions in endothelium under exercise-induced laminar shear stress. In conclusion, exercise prevents endothelial senescence in coronary arteries via increasing FUNDC1 in a PPARγ-dependent manner, and subsequently protects aged mice against MI/R injury. These findings highlight FUNDC1-mediated mitophagy as potential therapeutic target that prevents endothelial senescence and myocardial vulnerability.

Sustained release of dipyridamole from collagen membranes

Commercial collagen membranes that are used as bioresorbable barrier membranes in guided bone regeneration do not contain active ingredients to promote bone regeneration. The emerging efforts to repurpose old drugs produced mounting scientific evidence that dipyridamole (DIPY), which inhibits platelet aggregation and serves as a coronary artery vasodilator, also exhibits therapeutic effects to promote bone healing/regeneration. The therapeutic effect of DIPY on bone healing/regeneration occurs via G-protein coupled adenosine (P1) receptors of the purinergic family. In this study, we investigated the feasibility of synthesizing collagen membranes for sustained release of DIPY, with the ultimate purpose of using them as tools to promote bone regeneration. The synthesized membranes were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a universal mechanical testing machine. We conducted an in vitro release experiment to evaluate the release kinetics of DIPY from these membranes. The chemical and physical characterization confirmed the successful synthesis of DIPY-containing collagen membranes, namely DCM-1 and DCM-2. Both membranes had weaker tensile strength than other commercial collagen membranes, although both supported continuous release of DIPY. The in vitro release of DIPY from DCM-1 continued for at least 30 days in phosphate buffer saline (pH 7.4) at 37 °C, while DCM-2 achieved sustained release of DIPY for more than 10 weeks. These results warrant the further evaluation of DIPY-containing collagen membranes for their potential applications in guided bone regeneration after optimization of their mechanical strength.

A historical literature review of coronary microvascular obstruction and intra-myocardial hemorrhage as functional/structural phenomena.

The analysis of experimental data demonstrates that platelets and neutrophils are involved in the no-reflow phenomenon, also known as microvascular obstruction (MVO). However, studies performed in the isolated perfused hearts subjected to ischemia/reperfusion (I/R) do not suggest the involvement of microembolization and microthrombi in this phenomenon. The intracoronary administration of alteplase has been found to have no effect on the occurrence of MVO in patients with acute myocardial infarction. Consequently, the major events preceding the appearance of MVO in coronary arteries are independent of microthrombi, platelets, and neutrophils. Endothelial cells appear to be the target where ischemia can disrupt the endothelium-dependent vasodilation of coronary arteries. However, reperfusion triggers more pronounced damage, possibly mediated by pyroptosis. MVO and intra-myocardial hemorrhage contribute to the adverse post-infarction myocardial remodeling. Therefore, pharmacological agents used to treat MVO should prevent endothelial injury and induce relaxation of smooth muscles. Ischemic conditioning protocols have been shown to prevent MVO, with L-type Ca 2+ channel blockers appearing the most effective in treating MVO.

The Long-Term Effects of Prenatal Hypoxia on Coronary Artery Function of the Male and Female Offspring.

Prenatal hypoxia predisposes the offspring to the development of cardiovascular (CV) dysfunction in adult life. Using a rat model, we assessed the effect of prenatal hypoxia on vasoconstrictive and vasodilative mechanisms in left anterior descending coronary arteries of 4- and 9.5-month-old offspring. Endothelium-dependent relaxation to methylcholine and vasoconstriction responses to endothelin-1 (ET-1) were assessed by wire myography. Prenatal hypoxia impaired endothelium-dependent vasodilation in 4- and 9.5-month-old offspring. Inhibition of nitric oxide (NO) synthase prevented coronary artery relaxation in all groups. Inhibition of prostaglandin H synthase (PGHS) improved relaxation in prenatally hypoxic males and tended to improve vasorelaxation in females, suggesting that impaired vasodilation was mediated via increased PGHS-dependent vasoconstriction. An enhanced contribution of endothelium-dependent hyperpolarization to coronary artery vasodilation was observed in prenatally hypoxic males and females. No changes in endothelial NO synthase (eNOS) and PGHS-1 expressions were observed, while PGHS-2 expression was decreased in only prenatally hypoxic males. At 4 months, ET-1 responses were similar between groups, while ETB inhibition (with BQ788) tended to decrease ET-1-mediated responses in only prenatally hypoxic females. At 9.5 months, ET-1-mediated responses were decreased in only prenatally hypoxic females. Our data suggest that prenatal hypoxia has long-term similar effects on the mechanisms of impaired endothelium-dependent vasodilation in coronary arteries from adult male and female offspring; however, coronary artery contractile capacity is impaired only in prenatally hypoxic females. Understanding the mechanistic pathways involved in the programming of CV disease may allow for the development of therapeutic interventions.

Mechanisms of Metformin Improving vasodilation of coronary artery in Type 2 Diabetic Rats

In recent years, the incidence of type 2 diabetes has gradually increased. Coronary artery-related disease is one of the most common and serious complications of this. Endothelial dysfunction has become a risk factor for cardiovascular disease in patients with coronary heart disease. In this study, the protective effect of metformin on coronary artery in type 2 diabetic rats was investigated.

Mechanisms of Metformin Improving vasodilation of coronary artery in Type 2 Diabetic Rats

In recent years, the incidence of type 2 diabetes has gradually increased. Coronary artery-related disease is one of the most common and serious complications of this. Endothelial dysfunction has become a risk factor for cardiovascular disease in patients with coronary heart disease. In this study, the protective effect of metformin on coronary artery in type 2 diabetic rats was investigated.

Signaling and structures underpinning conducted vasodilation in human and porcine intramyocardial coronary arteries.

BackgroundAdequate blood flow into coronary micro-arteries is essential for myocardial function. Here we assess the mechanisms responsible for amplifying blood flow into myogenically-contracting human and porcine intramyocardial micro-arteries ex vivo using endothelium-dependent and -independent vasodilators.MethodsHuman and porcine atrial and ventricular small intramyocardial coronary arteries (IMCAs) were studied with pressure myography and imaged using confocal microscopy and serial section/3-D reconstruction EM.Results3D rendered ultrastructure images of human right atrial (RA-) IMCAs revealed extensive homo-and hetero-cellular contacts, including to longitudinally-arranged smooth muscle cells (l-SMCs) found between the endothelial cells (ECs) and radially-arranged medial SMCs (r-SMCs). Local and conducted vasodilatation followed focal application of bradykinin in both human and porcine RA-IMCAs, and relied on hyperpolarization of SMCs, but not nitric oxide. Bradykinin initiated asynchronous oscillations in endothelial cell Ca2+ in pressurized RA-IMCAs and, as previously shown in human RA-IMCAs, hyperpolarized porcine arteries. Immunolabelling showed small- and intermediate-conductance Ca2+-activated K+ channels (KCa) present in the endothelium of both species, and concentration-dependent vasodilation to bradykinin followed activation of these KCa channels. Extensive electrical coupling was demonstrated between r-SMCs and l-SMCs, providing an additional pathway to facilitate the well-established myoendothelial coupling. Conducted dilation was still evident in a human RA-IMCA with poor myogenic tone, and heterocellular contacts were visible in the 3D reconstructed artery. Hyperpolarization and conducted vasodilation was also observed to adenosine which, in contrast to bradykinin, was sensitive to combined block of ATP-sensitive (KATP) and inwardly rectifying (KIR) K+ channels.ConclusionsThese data extend our understanding of the mechanisms that coordinate human coronary microvascular blood flow and the mechanistic overlap with porcine IMCAs. The unusual presence of l-SMCs provides an additional pathway for rapid intercellular signaling between cells of the coronary artery wall. Local and conducted vasodilation follow hyperpolarization of the ECs or SMCs, and contact-coupling between l-SMCs and r-SMCs likely facilitates this vasodilation.

Determining the Association Between Density of Muscarinic Acetylcholine Receptor M3 in Myocardium and Tunica Media of Coronary Vasculature and Self‐Reported Disease States

Myocardial infarction causes parasympathetic dysfunction in cardiovascular tissue, where central parasympathetic drive decreases but local acetylcholine levels are unchanged. However, muscarinic acetylcholine receptor M3 (AChM3R) is shown to have mediating effects in cardiac tissue and vasculature, such as regulation of heart rate and vasodilation of coronary arteries. The objective of this study is to determine the association between AChM3R levels in the heart wall and in the coronary vasculature with self‐reported disease states from cadaver donor records.Biopsies of the left anterior descending (LAD) artery and the underlying anterior interventricular septum (AIVS) were taken from 14 cadavers as opportunity samples. A 5 mm biopsy of the LAD and its underlying AIVS were harvested 2.54‐3.81cm from the bifurcation point of the left coronary artery, depending on the tissue integrity of the cadaver specimen. The tissues were immunostained for AChM3R (CHRM3 NB100‐58975 at 1:2000) and visualized using a DAB chromogen. Slides were digitally scanned into a virtual image at 20x using the Motic Easyscan (Motic, Inc.). Images were segmented for tunica media and myocardium using Adobe Photoshop CS (Adobe, Inc.). We developed code in Python to calculate the strong positive and positive staining of the tissues. The number of pixels stained was normalized to the tissue area. The donors from which tissue was biopsied were classified into cardiovascular, cerebrovascular, Alzheimer’s disease dementia (AD), or both cerebrovascular and AD disease categories based on self‐reported donor declarations. We used SPSS (v27, IBM, Inc.) to run a Pearson correlation to determine the association of staining positivity in the anatomical regions and a MANOVA to determine significant differences in the amount of pixel positivity in the tunica media and myocardium as a function of disease classification.Strong positive and positive staining of the myocardium were not correlated with strong positive in the tunica media. There was a significant, strong, and positive relationship between strong myocardium staining and positive tunica media staining (r =.727, n=14, p=.003) as well as positive myocardium and positive tunica media staining (r=.674, n=14, p=.008). There is no significant difference between the amount of AChM3R staining and disease classification.The lack of correlation between strong positive in the tunica media and positive and strong positive in the myocardium suggests that changes in the AChM3R of coronary vascular smooth muscle are independent of the AChM3R state in the heart wall. However, significant correlation between strong positive in the myocardium and positive in the tunica media indicates that changes in AChM3R in the myocardium could be dependent on the presence of a baseline amount of AChM3R in the coronary vascular smooth muscle. Categorization of donor disease states may be too broad to provide statistical significance. Many donors reported co‐morbid diseases, which could have affected the influence of cardiovascular disease and dementia on AChM3R modulation. These findings highlight that interventions targeting parasympathetic dysfunction of coronary vasculature may leave the underlying heart wall unaffected. Future studies should consider cardiovascular disease diagnoses to assess AChM3R distribution in the heart wall and coronary vasculature.

Activation of APJ Receptors by CMF‐019, but not Apelin, Causes Endothelium‐Dependent Relaxation of Spontaneously Hypertensive Rat Coronary Arteries

Hypertension is a major risk factor for coronary artery disease, but the pathophysiological mechanisms linking these diseases are not completely understood. Apelin is a novel vasoactive adipokine. Receptors for apelin (APJ receptors) are G‐protein‐coupled receptors and are widely expressed throughout the cardiovascular system. APJ receptors can also signal via G‐protein‐independent pathways, including G‐protein‐coupled‐receptor kinase 2 (GRK2), which inhibits nitric oxide synthase (eNOS) activity and nitric oxide (NO) production in endothelial cells. Apelin causes endothelium‐dependent, NO‐mediated relaxation of coronary arteries from normotensive animals, but the effects of activating APJ receptor signaling pathways in hypertensive coronary arteries are unknown. Since endothelium‐dependent relaxations are often blunted in arteries from hypertensive animals, we tested the hypothesis that apelin‐induced relaxation is impaired in coronary arteries from spontaneously hypertensive rats (SHR). Moreover, we hypothesized that endothelium‐dependent relaxations in response to CMF‐019, an APJ receptor G‐protein biased agonist with little effect on GRK2, would be unaffected in SHR coronary arteries. Western blot and RT‐qPCR analysis demonstrated that APJ receptor protein and mRNA expression did not differ between normotensive WKY (Wistar‐Kyoto) and SHR coronary arteries. eNOS protein expression was also similar between SHR and WKY coronary arteries, but GRK2 expression was significantly increased in SHR coronary endothelial cells, as compared to WKY. In myograph studies, apelin (10‐9‐10‐6 M) caused endothelium‐dependent relaxation of isolated WKY coronary arterial rings (pD2= 7.00 ± 0.11; Emax= 54 ± 4% relaxation; n=6), but had no effect in arteries from SHR. By contrast, CMF‐019 (10‐9‐10‐6 M)‐induced relaxation did not differ between normotensive and hypertensive coronary arteries. The relaxation response to CMF‐019 was abolished by the APJ receptor antagonist, F13A (10‐7 M), by removal of the endothelium, and by inhibition of eNOS with nitro‐ L‐arginine (3 x 10‐5 M). Moreover, the GRK2 inhibitor, CMPD 101 (3 x 10‐5 M), partially restored the relaxation response to apelin in SHR coronary arteries (pD2= 6.56 ± 0.22; Emax= 46 ± 6% relaxation; n=6). Immunoblot analysis of SHR coronary endothelial cells demonstrated that CMF‐019 (10‐7 M) significantly increased eNOS phosphorylation whereas apelin (10‐7 M) had no effect. We conclude that apelin failed to cause relaxation in hypertensive coronary arteries, likely due to impaired eNOS activity resulting from APJ receptor signaling via the GRK2 pathway and decreased eNOS phosphorylation. APJ receptor activation by the biased agonist, CMF‐019, caused similar endothelium‐dependent relaxations in WKY and SHR coronary arteries. Thus, APJ receptor‐biased agonists, such as CMF‐019, may be more effective than apelin in causing vasodilation of hypertensive coronary arteries.

Protective role of activating PPARγ in advanced glycation end products-induced impairment of coronary artery vasodilation via inhibiting p38 phosphorylation and reactive oxygen species production

Advanced glycation end products (AGEs) can damage voltage-gated K+ (Kv) channels and attenuate coronary artery vasodilation, but the underlying mechanisms remain unclear. The aim of this study was to investigate the role and potential mechanism of PPARγ in AGEs-induced Kv 1 channels impairment. We used both primary rat coronary smooth muscle cells (CSMCs) in vitro and Zucker Diabetic Fatty (ZDF) rat model in vivo. Overexpression of the Pparg gene by lentivirus vector (LV-Pparg) was used to transfect CSMCs for upregulation PPARγ. Kv 1.2 and Kv 1.5 currents were measured by patch clamp. The vascular tone of coronary artery was evaluated by isometric force measurements. The proteins expression of Kv1.2 and Kv1.5 channel were detected by western blot. PPARγ was detected by immunofluorescence and western blot. Oxidative stress markers including superoxide dismutase (SOD), glutathione peroxidase (GPx) and malondialdehyde (MDA) were detected by enzyme linked immunosorbent assay (ELISA). The phosphorylation of p38 mitogen-activated protein kinase (MAPK) and total p38 expression were detected by western blot. The intracellular ROS levels were measured by the fluorescent dye 2’,7’- dichlorofluorescein diacetate (DCFDA) and a cellular ROS assay kit. We found that activating PPARγ via LV-Pparg (100 MOI, 5 × 108 TU/mL) prevented AGEs (100 μg/mL) -mediated impairment of Kv 1.2 and Kv 1.5 channels activity and improved the reduction of Kv 1.2 and Kv 1.5 protein expression in CSMCs. Isometric force measurements showed that activating PPARγ by pioglitazone (10 mg/kg/d, intragastric administration) improved the impairment of coronary artery vasodilation, and western blot analysis showed that activating PPARγ increased the Kv 1.2 and Kv 1.5 protein expression, while inhibiting PPARγ by GW9662 (10 mg/kg/d, intraperitoneal injection) attenuated these effects in ZDF rats. Furthermore, LV-Pparg overexpression PPARγ attenuated NADPH oxidase activity, which was shown as the reduction of the NOX2 and p22phox expression by western blot analysis, decreased the MDA production and increased the SOD and GPx activities by ELISA, finally led to reduce AGEs-mediated ROS production. Moreover, activating PPARγ by LV-Pparg inhibited AGEs-induced phosphorylation of p38 MAPK, by which could reduce AGEs-mediated NOX2, p22phox expression and ROS production, while CSMCs treatment with SB203580 (10 μmol/L), a p38 MAPK inhibitor, attenuated these effects. Activating PPARγ plays a protective role in AGEs-induced impairment of coronary artery vasodilation by inhibiting p38 phosphorylation to attenuate NOX2 and p22phox expression and further decrease oxidative stress induced by ROS overproduction.

Marjoram extract prevents ischemia reperfusion-induced myocardial damage and exerts anti-contractile effects in aorta segments of male wistar rats

Ethnopharmacological relevanceMarjoram (Origanum majorana L.) is an herb traditionally used as a medicine in different countries, as Morocco and Iran, because of its beneficial cardiovascular effects. Some studies suggest that these effects are due, at least in part, to the presence of phenolic compounds such as rosmarinic acid (RA) and luteolin. Aim of the studyTo analyze the possible cardiprotective effects of a marjoram extract (ME) reducing myocardial damage after coronary ischemia-reperfusion (IR) and its possible antihypertensive effects reducing the response of aorta segments to the vasoconstrictors noradrenaline (NA) and endothelin-1 (ET-1). Materials and methodsMale Wistar rats (300g) were used. After sacrifice, the heart was immediately removed and mounted in a perfusion system (Langendorff). The aorta was carefully dissected and cut in 2 mm segments to perform vascular reactivity experiments. ResultsIn the heart, ME perfusion after IR reduced heart rate and prevented IR-induced decrease of cardiac contractility, possibly through vasodilation of coronary arteries and through the upregulation of antioxidant markers in the myocardium that led to reduced apoptosis of cardiomyocytes. In the aorta, ME decreased the vasoconstrictor response to NA and ET-1 and exerted a potent anti-inflammatory and antioxidant effect. Neither RA nor 6-hydroxi-luteolin-O-glucoside, major compounds of this ME, were effective in improving cardiac contractility after IR or attenuating vasoconstriction to NA and ET-1 in aorta segments. ConclusionIn conclusion, ME reduces the myocardial damage induced by IR and the contractile response to vasoconstrictors in the aorta. Thus, it may be useful for the treatment of cardiovascular diseases such as myocardial infarction and hypertension.

Myocardial Blood Flow Control by Oxygen Sensing Vascular Kvβ Proteins.

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Abstract 15033: Chronic Inhibition of Mitochondrial Reactive Oxygen Species Protects Against Endothelial SK Channel Dysfunction in Diabetes

Introduction: Oxidative stress plays an important role in the development of pathological condition in diabetes. Persistent oxidative stress during diabetes may result in impaired endothelium-independent vasodilation, by reducing small-conductance Ca 2+ -activated K + (SK) channel activity. The mitochondria are main sources of reactive oxygen species (ROS) in diabetes, and mitochondria-targeted antioxidant mito-TEMPO (MT) prevents ROS generation has been found in a variety of disorders. However, few studies are available on the dysfunction of vasodilation and endothelial SK channels in diabetes after a chronic use of MT. Purpose: We investigated the chronic administration of MT on vasodilation in coronary arteries, and endothelial SK channel activity with or without diabetes. Methods: MT (1mg/kg) was applied to diabetic and health mice (n = 6/group) for 1 month. In-vitro relaxation response of pre-contracted arteries was examined in the presence or absence of the vasodilatory agents. Isolated endothelium was studied using whole-cell patch clamp recording SK channels currents. Results: Coronary arteries dilation was decreased in diabetic mice compared with that in health ( p <0.05). After one month treatment with MT, coronary arteries dilation was significantly improved when compared with that in non-treatment diabetic mice ( p <0.05). Interestingly, coronary arteries dilation was no significantly changed in health mice whether to treat with MT or not. Similar changes were seen in patch clamp recording, impaired currents of SK channels in endothelial cells of diabetic mice were significantly improved after chronic treatment with MT ( p <0.05, Fig) and currents of SK channels were no changed in health mice whether to treat with MT or not. Conclusions: MT appears to improve coronary endothelial function/dilation by protection of SK channel activity in diabetes, and administration of MT may be a novel strategy to treat vascular complications in diabetes.

Role of peroxisome proliferators-activated receptor-gamma in advanced glycation end product-mediated functional loss of voltage-gated potassium channel in rat coronary arteries

Abstract Background Voltage-gated K+ (Kv) channels in coronary artery smooth muscle cells (CSMCs), especially the major specific Kv1 subfamily, contribute to coronary artery vasodilation. Advanced glycation end products (AGEs) have been strongly implicated in diabetes-related cardiovascular complications. Our previous study showed AGEs can impair Kv channel-mediated coronary vasodilation by reducing Kv channel activity. However, its underlying mechanism remains unclear. Purpose Here, we used isolated rat small coronary arteries (RSCAs) and primary CSMCs to investigate the effect of AGEs on Kv channel-mediated coronary vasodilation and the possible involvement of peroxisome proliferators-activated receptor (PPAR)-γ pathway. Methods RSCAs and primary CSMCs were isolated, cultured and treated with bovine serum albumin (BSA), AGE-BSA, alagrebrium (ALA, AGE cross-linking breaker), pioglitazone (PIO) and/or GW9662, and then divided into the following groups: DMEM, BSA, AGE, AGE+ALA, AGE+PIO, and AGE+PIO+GW9662. Kv channel-mediated coronary vasodilation was analyzed using wire myograph. Histology and immunohistochemistry of RSCAs were performed. Western blot was used to detect the protein expression of RAGE, the major Kv1 channel subunits expressed in CSMCs (Kv1.2/1.5), PPAR-γ, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX-2). Results AGEs markedly reduced forskolin-induced Kv channel-mediated vasodilation of RSCAs by interacting with the receptor for AGEs (RAGE), and ALA or PIO significantly reversed this effect. In both RSCAs and primary CSMCs, AGEs decreased Kv1.2 and Kv1.5 channel protein expression, inhibited PPAR-γ expression, increased RAGE and NOX-2 expression. Treatment with ALA or PIO partially reversed the effects of AGEs on Kv1.2/Kv1.5 expression, accompanied by elevation of PPAR-γ level and diminished oxidative stress. Conclusion AGE/RAGE axis-induced inhibition of PPAR-γ pathway and enhancement of oxidative stress may contribute to AGEs-mediated Kv channel dysfunction and coronary vasodilation in RSCAs. Our results may provide new insights into developing therapeutic strategies to manage diabetic vasculature. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Natural Science Foundation of China; Natural Science Foundation of Beijing (7172059)