Endothelium-dependent hyperpolarization. Beyond nitric oxide and cyclic GMP

Perivascular Adipose Tissue and Uterine Artery Adaptations to Pregnancy

Pregnancy is characterized by longitudinal maternal, physiological adaptations to support the development of a fetus. One of the cardinal maternal adaptations during a healthy pregnancy is a progressive increase in uterine artery blood flow. This facilitates sufficient blood supply for the development of the placenta and the growing fetus. Regional hemodynamic changes in the uterine circulation, such as a vast reduction in uterine artery resistance, are mainly facilitated by changes in uterine artery reactivity and myogenic tone along with remodeling of the uterine arteries. These regional changes in vascular reactivity have been attributed to pregnancy-induced adaptations of cell-to-cell communication mechanisms, with an emphasis on the interaction between endothelial and vascular smooth muscle cells. Perivascular adipose tissue (PVAT) is considered the fourth layer of the vascular wall and contributes to the regulation of vascular reactivity in most vascular beds and most species. This review focuses on mechanisms of uterine artery reactivity and the role of PVAT in pregnancy-induced maternal vascular adaptations, with an emphasis on the uterine circulation.

Adverse Clinical Effects Associated With Non-catecholamine Pharmacologic Agents for Treatment of Vasoplegic Syndrome in Adult Cardiac Surgery

Vasoplegic syndrome is a relatively common complication that can happen during and after major adult cardiac surgery. It is associated with a higher rate of complications, including postoperative renal failure, longer duration of mechanical ventilation, and intensive care unit stay, as well as increased mortality. The underlying pathophysiology of vasoplegic syndrome is that of profound vascular hyporesponsiveness, and involves a complex interplay among inflammatory cytokines, cellular surface receptors, and nitric oxide (NO) production. The pharmacotherapy approaches for the treatment of vasoplegia include medications that increase vascular smooth muscle contraction via increasing cytosolic calcium in myocytes, reduce the vascular effects of NO and inflammation, and increase the biosynthesis of and vascular response to norepinephrine. Clinical trials have demonstrated the clinical efficacy of non-catecholamine pharmacologic agents in the treatment of vasoplegic syndrome. With an increase in their use today, it is important for clinicians to understand the adverse clinical outcomes and patient risk profiles associated with these agents, which will allow better-tailored medical therapy.

Effects of single and multiple sessions of lower body diastole-synchronized compressions using a pulsating pneumatic suit on endothelium function and metabolic parameters in patients with type 2 diabetes: two controlled cross-over studies

BACKGROUND

Endothelium function is often impaired in patients with type 2 diabetes. We hypothesized that by improving endothelial function using diastole-synchronized compressions/decompressions (DSCD) to the lower body may improve the metabolic profile. The objective of this research was to evaluate the effects of single and multiple DSCD sessions on microcirculation, endothelium function and metabolic parameters of patients with type 2 diabetes.

METHODS

Two monocentric, controlled, randomized cross-over studies (Study 1 and Study 2) were performed. In Study 1, 16 patients received one 20 min DSCD and one simulated (control) session at 2 week intervals; continuous glucose monitoring and cutaneous blood flow were recorded continuously before, during and after DSCD or Control session; other vascular assessments were performed before and after DSCD and control sessions. In Study 2, 38 patients received 60 min DSCD sessions three times/week for three months followed by a 4-6 week washout and 3 month control period (without simulated sessions); vascular, metabolic, body composition, physical activity and quality of life assessments were performed before and after 3 months.

RESULTS

Both studies showed significant, multiplex effects of DSCD sessions. In Study 1, cutaneous blood flow and endothelium function increased, and plasma and interstitial glucose levels after a standard breakfast decreased after DSCD sessions. In Study 2, cutaneous endothelium function improved, LDL-cholesterol and non-HDL cholesterol decreased, extra-cell water decreased and SF-36 Vitality score increased after 3 months of DSCD sessions.

CONCLUSIONS

Our findings support the beneficial effect of DSCD on the endothelium and show concomitant beneficial metabolic and vitality effects. Future clinical trials need to test whether DSCD use translates into a preventive measure against microvascular diabetic complications and its progression. Trial registration ClinicalTrials.gov identifiers: NCT02293135 and NCT02359461.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

Sandwiching Phosphorene with Iron Porphyrin Monolayer for High Stability and Its Biomimetic Sensor to Sensitively Detect Living Cell Released NO

Instability of 2D phosphorene material is the major obstacle for its broad applications. Herein phosphorene is sandwiched with self-assembled iron porphyrin monolayers on both sides (I-Phene) to significantly enhance stability. Iron porphyrin has strong interaction with phosphorene through formation of PFe bonds. The sandwich structure offers excellent stability of phosphorene by both-sided monolayer protections for an intact phosphorene structure more than 40 days under ambient conditions. Meanwhile, the electron transfer between iron porphyrin and phosphorene result in a high oxidation state of Fe, making I-Phene biomimetic sensitivity toward oxidation of nitric oxide (NO) for 2.5 and 4.0 times higher than phosphorene and iron-porphyrin alone, respectively. Moreover, I-Phene exhibits excellent selectivity, a wide detection range, and a low detection limit at a low oxidation potential of 0.82 V, which is comparable with the reported noble metal based biomimetic sensors while ranking the best among all non-noble biomimetic ones. I-Phene is further used for real-time monitoring NO released from cells. This work provides effective approach against phosphorene degrading for outstanding stability, which has universal significance for its various important applications, and holds a great promise for a highly sensitive biomimetic sensor in live-cell assays.

Differential hyperpolarization to substance P and calcitonin gene-related peptide in smooth muscle versus endothelium of mouse mesenteric artery

OBJECTIVE

We sought to define how sensory neurotransmitters substance P and calcitonin gene-related peptide (CGRP) affect membrane potential of vascular smooth muscle and endothelium.

METHODS

Microelectrodes recorded membrane potential of smooth muscle from pressurized mouse mesenteric arteries (diameter, ~150 µm) and in endothelial tubes.

RESULTS

Resting potential was similar (~ -45 mV) for each cell layer. Substance P hyperpolarized smooth muscle and endothelium ~ -15 mV; smooth muscle hyperpolarization was abolished by endothelial disruption or NO synthase inhibition. Blocking K_Ca channels (apamin + charybdotoxin) attenuated hyperpolarization in both cell types. CGRP hyperpolarized endothelium and smooth muscle ~ -30 mV; smooth muscle hyperpolarization was independent of endothelium. Blocking K_Ca channels prevented hyperpolarization to CGRP in endothelium but not smooth muscle. Inhibiting K_ATP channels with glibenclamide or genetic deletion of K_IR 6.1 attenuated hyperpolarization in smooth muscle but not endothelium. Pinacidil (K_ATP channel agonist) hyperpolarized smooth muscle more than endothelium (~ -35 vs. ~ -20 mV).

CONCLUSIONS

Calcitonin gene-related peptide elicits greater hyperpolarization than substance P. Substance P hyperpolarizes both cell layers through K_Ca channels and involves endothelium-derived NO in smooth muscle. Endothelial hyperpolarization to CGRP requires K_Ca channels, while K_ATP channels mediate hyperpolarization in smooth muscle. Differential K⁺ channel activation in smooth muscle and endothelium through sensory neurotransmission may selectively tune mesenteric blood flow.

A cellular nitric oxide sensor based on porous hollow fiber with flow-through configuration

Nitric oxide plays important transmission and regulation roles in the human body, but its in-vitro concentration is extremely low with a short half-life. In this work, we developed a three-dimensional 'flow-through' configuration based on polysulfone hollow fiber (PHF) for efficient detection of cell released NO. The PHF served as the substrate for cell culture as well as the base layer of the working electrode. The carbon nanotubes-gold nanoparticles (CNT-AuNPs) composites uniformly wrapped around the PHF as the sensing layer. The CNT provided a large specific surface area, which allowed uniform distribution and high loading of AuNPs, thus enhancing the electrocatalytic activity synergistically. Compared with the conventional flow-by configuration, such configuration resulted in a higher surface area per unit volume and enhanced NO molecule capture efficiency. The CNT-AuNPs PHF sensor showed a low detection limit (91 nM), high stability, selectivity, and biocompatibility. We utilized it for real-time in-situ detection of NO released by human lung cancer cell H1299 under drug stimulation. Furthermore, owing to the unique PHF structure, we performed long-term monitoring of NO release under the treatment of Lipopolysaccharide, Nitroglycerin and Aminoguanidine, which helps to understand the kinetic process of cellular drug response.

Current Knowledge on the Vascular Effects of Menthol

Menthol is a monoterpene alcohol, widely used in several food and healthcare products for its particular odor and flavor. For some decades, menthol has been known to act on the vasculature directly in the endothelium and vascular smooth muscle, with recent studies showing that it also evokes an indirect vascular response via sensory fibers. The mechanisms underlying menthol's vascular action are complex due to the diversity of cellular targets, to the interplay between signaling pathways and to the variability in terms of response. Menthol can evoke either a perfusion increase or decrease in vivo in different vascular territories, an observation that warrants a critical discussion. Menthol vascular actions in vivo seem to depend on whether the vascular territory under analysis has been directly provoked with menthol or is located deep/distant to the application site. Menthol increases perfusion of directly provoked skin regions due to a complex interplay of increased nitric oxide (NO), endothelium-derived hyperpolarization factors (EDHFs) and sensory nerve responses. In non-provoked vascular beds menthol decreases perfusion which might be attributed to heat-conservation sympathetically-mediated vasoconstriction, although an increase in tissue evaporative heat loss due the formulation ethanol may also play a role. There is increasing evidence that several of menthol's cellular targets are involved in cardiovascular diseases, such as hypertension. Thus menthol and pharmacologically-similar drugs can play important preventive and therapeutic roles, which merits further investigation.

Inflammation and Peripheral Arterial Disease

Peripheral arterial disease (PAD) is an atherosclerotic disease closely associated with high morbidity and mortality in cardiac events. Inflammation is crucial in atherosclerosis both at triggering and in progression. Numerous inflammatory biomarkers (cytokines, matrix metalloproteinases (MMPs), selectin, intracellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) C-reactive protein (CRP), fibrinogen) have been measured in atherosclerotic diseases including PAD. This paper summarizes the data on the inflammatory biomarkers for PAD pathophysiology and highlights the most useful markers in monitoring PAD outcomes.

Recovery of blood flow regulation in microvascular resistance networks during regeneration of mouse gluteus maximus muscle

KEY POINTS

Skeletal muscle regenerates after injury, however the recovery of its microvascular supply is poorly understood. We injured the gluteus maximus muscle in mice aiming to investigate the recovery of blood flow regulation in microvascular resistance networks. We hypothesized that blood flow regulation recovers in concert with myofibre regeneration. Microvascular perfusion ceased within 1 day post injury and was restored at 5 days coincident with the appearance of new myofibres; however, the resistance network was dilated and unresponsive to vasoactive agents. Spontaneous vasomotor tone, endothelium-dependent dilatation and adrenergic vasoconstriction increased at 10 days in concert with myofibre regeneration. Vasomotor control recovered at 21 days, when regenerated myofibres matured and active force production stabilized. Functional vasodilatation in response to muscle contraction recovered at 35 days. Physiological integrity of microvascular smooth muscle and endothelium recovers in parallel with myofibre regeneration. Additional time is required to restore the efficacy of signalling between myofibres and microvascular networks controlling their oxygen supply.

ABSTRACT

Myofibre regeneration after skeletal muscle injury is well-studied, although little is known about how microvascular perfusion is restored. The present study aimed to evaluate the recovery of blood flow regulation during skeletal muscle regeneration. In anaesthetized male C57BL/6J mice (aged 4 months), the gluteus maximus muscle (GM) was injured by local injection of barium chloride solution (1.2%, 75 μL). Functional integrity of the resistance network was evaluated at 5, 10, 21 and 35 days post-injury vs. Control by measuring internal diameter of feed arteries, first-, second- and third-order arterioles supplying the GM using intravital microscopy. The resting diameters of all branch orders were significantly greater (P < 0.05) than Control at 5 and 10 days and recovered to Control by 21 days, as did spontaneous vasomotor tone. Vasodilatation to ACh and vasoconstriction to phenylephrine (10^-9 to 10^-5  m) were absent at 5 days, increased at 10 days and recovered to Control by 21 days; reactivity improved in a distal-to-proximal gradient. Across branch orders, functional vasodilatation to single tetanic contraction (100 Hz, 500 ms) and to rhythmic twitch contractions (4 Hz, 30 s) was impaired at 5 days, improved through 21 days and was not different from Control at 35 days. Peak force development (g) was 60% of Control at 10 days and recovered by 21 days. Diminished vasomotor tone during the initial stages of regeneration promotes tissue perfusion as myofibre recovery begins. Recovery of tone and vasomotor responses to agonists occur in concert with myofibre regeneration. Delayed recovery of functional vasodilatation indicates that additional time is required to restore signalling between contracting myofibres and their vascular supply.

Gene expression changes in the retina after systemic administration of aldosterone

PURPOSE

Retinal ganglion cell (RGC) loss associated with thinning of the retinal nerve fiber layer without elevated intraocular pressure (IOP) occurs after the systemic administration of aldosterone. Since it is important to determine the mechanism of cell death independent of the IOP, we examined gene expression changes in the retina after the systemic administration of aldosterone.

METHODS

Following subcutaneous implantation of an osmotic minipump into the mid-scapular region of rats, we administered an 80 μg/kg/day dose of aldosterone. Differences in the gene expression in the retina between normal rats and aldosterone-treated rats were investigated using microarrays. Real-time PCR was used to confirm the differential expression.

RESULTS

Analysis of the microarray data sets revealed the upregulation of 24 genes and the downregulation of 24 genes of key apoptosis-specific genes. Real-time PCR revealed 4 genes (Cdkn1a, Tbox5, Pf4, Vdr) were upregulated while 12 genes (Acvr1c, Asns, Bard1, Card9, Crh, Fcgr1a, Inhba, Kcnh8, Lck, Phlda1, Ptprc, Sh3rf1) were downregulated.

CONCLUSIONS

Significant increases and decreases were noted in several genes after the systemic administration of aldosterone. Further studies will need to be undertaken in order to definitively clarify the role of these genes in the eyes of animals with normal-tension glaucoma.

Intrauterine and lactational exposure to fluoxetine enhances endothelial modulation of aortic contractile response in adult female rats

The study aimed to evaluate if maternal exposure to fluoxetine (FLX) during pregnancy and lactation would result in altered aortic reactivity in adult offspring. We also sought to understand the role of endothelium derived relaxing factors in aortic response. Wistar rats (75–80 days old), whose progenitors had received FLX (5 mg/kg, FLX offspring) or tap water (control offspring) during pregnancy and lactation were anesthetized, after which the aorta was removed and cut into two rings, one with (Endo+) and the other without (Endo-) endothelium. Concentration-effect curves for acetylcholine (ACh), sodium nitroprusside (SNP), and phenylephrine (Phe) were performed. The vasodilation to ACh and SNP was similar between control and FLX groups in both male and female offspring. In male rats, the response to Phe was similar between the FLX and control groups on Endo+ and Endo- rings. The response to Phe was reduced on Endo+ rings from female FLX when compared with the control group. The endothelium removal, as well as L-NAME, indomethacin, and tranylcypromine incubation corrected the reduced Phe-induced contraction in the aorta from the female FLX group. On the other hand, catalase, NS-398, and L-NIL did not interfere with the vasoconstriction. The aortic level of nitric oxide (NO) was higher in the female FLX than the control group. Although endothelial NO synthase isoform and cyclooxygenase (COX)-1 expressions were similar between the groups, there was a notable increment in neuronal NO synthase expression in the aorta of FLX-exposed female rats, suggesting an important role of this enzyme in the higher levels of NO. Our results show that developmental exposure to FLX causes sex-specific alteration in aortic function through a mechanism involving endothelial factors, probably NO and COX-1 products.

Communication Is Key: Mechanisms of Intercellular Signaling in Vasodilation

Thirty years ago, Robert F. Furchgott concluded that nitric oxide, a compound traditionally known to be a toxic component of fuel exhaust, is in fact released from the endothelium, and in a paracrine fashion, induces relaxation of underlying vascular smooth muscle resulting in vasodilation. This discovery has helped pave the way for a more thorough understanding of vascular intercellular and intracellular communication that supports the process of regulating regional perfusion to match the local tissue oxygen demand. Vasoregulation is controlled not only by endothelial release of a diverse class of vasoactive compounds such as nitric oxide, arachidonic acid metabolites, and reactive oxygen species, but also by physical forces on the vascular wall and through electrotonic conduction through gap junctions. Although the endothelium is a critical source of vasoactive compounds, paracrine mediators can also be released from surrounding parenchyma such as perivascular fat, myocardium, and cells in the arterial adventitia to exert either local or remote vasomotor effects. The focus of this review will highlight the various means by which intercellular communication contributes to mechanisms of vasodilation. Paracrine signaling and parenchymal influences will be reviewed as well as regional vessel communication through gap junctions, connexons, and myoendothelial feedback. More recent modes of communication such as vesicular and microRNA signaling will also be discussed.

Menthol-Induced Cutaneous Vasodilation Is Preserved in Essential Hypertensive Men and Women

BACKGROUND

Menthol is a selective transient receptor potential melastatin 8 (TRPM8) channel agonist that induces cutaneous vasodilation in young, normotensive men and women through nitric oxide synthase (NOS)-, endothelium-derived hyperpolarizing factor (EDHF)-, and sensory nerve-mediated mechanisms. Microvascular dysfunction is present in essential hypertension and whether menthol induces vasodilation is men and women with essential hypertension is equivocal.

METHODS

Four intradermal microdialysis fibers were placed in the forearm of 9 essential hypertensive and 10 age-matched normotensive control subjects. Sites were pretreated with lactated Ringer's (control), l-NAME (NOS inhibited), TEA (EDHF inhibited), and lidocaine (sensory nerve inhibited). The microdialysis fibers were then perfused with 7 increasing doses of menthol (0.1-500 mM). Red cell flux in response to menthol was measured with laser Doppler flowmetry. Data were normalized to mean arterial pressure and presented as a percentage of site-specific maximum vasodilation (%CVCmax).

RESULTS

At the control site, menthol caused vasodilation in both the normotensive and hypertensive groups (menthol doses 100, 250, and 500 mM; all P < 0.05 compared to baseline). There were no differences between groups (P = 0.58, main effect). There was no effect of either NOS or sensory nerve inhibition on menthol-induced vasodilation in the normotensive group; however, menthol-induced vasodilation was attenuated with NOS and sensory nerve inhibition in the hypertensive group. EDHF inhibition attenuated menthol-induced vasodilation in both groups.

CONCLUSIONS

Menthol-induced vasodilation has NO, EDHF, and sensory nerve components. Menthol-induced cutaneous vasodilation is preserved in hypertensive subjects. However, the hypertensive subjects exhibited a loss of redundant vasodilator systems.

Dynamin 3 suppresses growth and induces apoptosis of hepatocellular carcinoma cells by activating inducible nitric oxide synthase production

Dynamin 3 (DNM3) is candidate tumor suppressor against hepatocellular carcinoma (HCC). Downregulation of DNM3 is more frequently identified in HCC tissues than in normal liver tissues. However, the mechanism underlying DNM3-mediated inhibition of HCC remains unclear. The present study demonstrated that DNM3 expression was decreased in human HCC tissues and cell lines. The downregulation of DNM3 promoted cell proliferation by increasing cell cycle-associated proteins, including cyclin D1, cyclin-dependent kinase (CDK) 2 and CDK4. The upregulation of DNM3 induced HCC cell apoptosis and inhibited tumor growth. The present study also revealed that overexpression of DNM3 induced nitric oxide (NO) production and intracellular reactive oxygen species (ROS) accumulation. DNM3 overexpression also increased the protein expression level of inducible nitric oxide synthase (iNOS) in HCC cells and subcutaneous HCC tumor xenografts. The inhibition of iNOS by L-canavanine attenuated the DNM3-induced ROS accumulation and apoptotic cell death. In conclusion, the results indicate that DNM3 overexpression may induce apoptosis and inhibit tumor growth of HCC by activating iNOS production and the subsequent NO-ROS signaling pathways.

Mechanisms and time course of menthol-induced cutaneous vasodilation

Menthol is a vasoactive compound that is widely used in topical analgesic agents. Menthol induces cutaneous vasodilation, however the underlying mechanisms are unknown. Determining the rates of appearance and clearance of menthol in the skin is important for optimizing topical treatment formulation and dosing. The purpose of this study was to determine the mechanisms contributing to menthol-mediated cutaneous vasodilation and to establish a time course for menthol appearance/clearance in the skin. Ten young (23±1years, 5 males 5 females) subjects participated in two protocols. In study 1, four intradermal microdialysis fibers were perfused with increasing doses of menthol (0.1-500mM) and inhibitors for nitric oxide (NO), endothelium derived hyperpolarizing factors (EDHFs), and sensory nerves. Skin blood flow was measured with laser Doppler flowmetry and normalized to %CVC_max. In study 2, two intradermal microdialysis fibers were perfused with lactated Ringer's solution. 0.017mL·cm^-2 of a 4% menthol gel was placed over each fiber. 5μL samples of dialysate from the microdialysis fibers were collected every 30min and analyzed for the presence of menthol with high performance gas chromatography/mass spectrometry. Skin blood flow (laser speckle contrast imaging) and subjective ratings of menthol sensation were simultaneously obtained with dialysate samples. In study 1, menthol induced cutaneous vasodilation at all doses ≥100mM (all p<0.05). However, inhibition of either NO, EDHFs, or sensory nerves fully inhibited menthol-mediated vasodilation (all p>0.05). In study 2, significant menthol was detected in dialysate 30min post menthol application (0.89ng, p=0.0002). Relative to baseline, cutaneous vasodilation was elevated from minutes 15-45 and ratings of menthol sensation were elevated from minute 5-60 post menthol application (all p<0.05). Menthol induces cutaneous vasodilation in the skin through multiple vasodilator pathways, including NO, EDHF, and sensory nerves. Topical menthol is detectable in the skin within 30min and is cleared by 60min. Skin blood flow and perceptual measures follow a similar time course as menthol appearance/clearance.

Essential Role of Smooth Muscle STIM1 in Hypertension and Cardiovascular Dysfunction

OBJECTIVES

Chronic hypertension is the most critical risk factor for cardiovascular disease, heart failure, and stroke.

APPROACH AND RESULTS

Here we show that wild-type mice infused with angiotensin II develop hypertension, cardiac hypertrophy, perivascular fibrosis, and endothelial dysfunction with enhanced stromal interaction molecule 1 (STIM1) expression in heart and vessels. All these pathologies were significantly blunted in mice lacking STIM1 specifically in smooth muscle (Stim1(SMC-/-)). Mechanistically, STIM1 upregulation during angiotensin II-induced hypertension was associated with enhanced endoplasmic reticulum stress, and smooth muscle STIM1 was required for endoplasmic reticulum stress-induced vascular dysfunction through transforming growth factor-β and nicotinamide adenine dinucleotide phosphate oxidase-dependent pathways. Accordingly, knockout mice for the endoplasmic reticulum stress proapoptotic transcriptional factor, CCAAT-enhancer-binding protein homologous protein (CHOP(-/-)), were resistant to hypertension-induced cardiovascular pathologies. Wild-type mice infused with angiotensin II, but not Stim1(SMC-/-) or CHOP(-/-) mice showed elevated vascular nicotinamide adenine dinucleotide phosphate oxidase activity and reduced phosphorylated endothelial nitric oxide synthase, cGMP, and nitrite levels.

CONCLUSIONS

Thus, smooth muscle STIM1 plays a crucial role in the development of hypertension and associated cardiovascular pathologies and represents a promising target for cardiovascular therapy.

Prevalence of Coronary Microvascular Dysfunction Among Patients With Chest Pain and Nonobstructive Coronary Artery Disease

OBJECTIVES

This study assessed the prevalence of coronary microvascular abnormalities in patients presenting with chest pain and nonobstructive coronary artery disease (CAD).

BACKGROUND

Coronary microvascular abnormalities mediate ischemia and can lead to an increased risk of cardiovascular events.

METHODS

Using an intracoronary Doppler guidewire, endothelial-dependent microvascular function was examined by evaluating changes in coronary blood flow in response to acetylcholine, whereas endothelial-independent microvascular function was examined by evaluating changes in coronary flow velocity reserve in response to intracoronary adenosine. Patients were divided into 4 groups depending on whether they had a normal (+) or abnormal (-) coronary blood flow (CBF) in response to acetylcholine (Ach) and a normal (+) or abnormal (-) coronary flow velocity reserve (CFR) in response to adenosine (Adn): CBFAch+, CFRAdn+ (n = 520); CBFAch-, CFRAdn+ (n = 478); CBFAch+, CFRAdn- (n = 173); and CBFAch-, CFRAdn- (n = 268).

RESULTS

Two-thirds of all patients had some sort of microvascular dysfunction. Women were more prevalent in each group (56% to 82%). Diabetes was uncommon in all groups (7% to 12%), whereas hypertension and hyperlipidemia were relatively more prevalent in each group, although rates for most conventional cardiovascular risk factors did not differ significantly between groups. There were no significant differences in the findings of noninvasive functional testing between groups. In a multivariable analysis, age was the only variable that independently predicted abnormal microvascular function.

CONCLUSIONS

Patients with chest pain and nonobstructive CAD have a high prevalence of coronary microvascular abnormalities. These abnormalities correlate poorly with conventional cardiovascular risk factors and are dissociated from the findings of noninvasive functional testing.

Endothelial Dysfunction in Human Diabetes Is Mediated by Wnt5a-JNK Signaling

OBJECTIVE

Endothelial dysfunction is linked to insulin resistance, inflammatory activation, and increased cardiovascular risk in diabetes mellitus; however, the mechanisms remain incompletely understood. Recent studies have identified proinflammatory signaling of wingless-type family member (Wnt) 5a through c-jun N-terminal kinase (JNK) as a regulator of metabolic dysfunction with potential relevance to vascular function. We sought to gain evidence that increased activation of Wnt5a-JNK signaling contributes to impaired endothelial function in patients with diabetes mellitus.

APPROACH AND RESULTS

We measured flow-mediated dilation of the brachial artery and characterized freshly isolated endothelial cells by protein expression, eNOS activation, and nitric oxide production in 85 subjects with type 2 diabetes mellitus (n=42) and age- and sex-matched nondiabetic controls (n=43) and in human aortic endothelial cells treated with Wnt5a. Endothelial cells from patients with diabetes mellitus displayed 1.3-fold higher Wnt5a levels (P=0.01) along with 1.4-fold higher JNK activation (P<0.01) without a difference in total JNK levels. Higher JNK activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction (r=0.53, P=0.02). Inhibition of Wnt5a and JNK signaling restored insulin and A23187-mediated eNOS activation and improved nitric oxide production in endothelial cells from patients with diabetes mellitus. In endothelial cells from nondiabetic controls, rWnt5a treatment inhibited eNOS activation replicating the diabetic endothelial phenotype. In human aortic endothelial cells, Wnt5a-induced impairment of eNOS activation and nitric oxide production was reversed by Wnt5a and JNK inhibition.

CONCLUSIONS

Our findings demonstrate that noncanonical Wnt5a signaling and JNK activity contribute to vascular insulin resistance and endothelial dysfunction and may represent a novel therapeutic opportunity to protect the vasculature in patients with diabetes mellitus.

Extracellular matrix fibronectin initiates endothelium-dependent arteriolar dilatation via the heparin-binding, matricryptic RWRPK sequence of the first type III repeat of fibrillar fibronectin

KEY POINTS

The local arteriolar dilatation produced by contraction of skeletal muscle is dependent upon multiple signalling mechanisms. In addition to the many metabolic signals that mediate this vasodilatation, we show here that the extracellular matrix protein fibronectin also contributes to the response. This vasodilatory signal requires the heparin-binding matricryptic RWRPK sequence in the first type III repeat of fibrillar fibronectin. The fibronectin-dependent component of the integrated muscle contraction-dependent arteriolar vasodilatation is coupled through an endothelial cell-dependent signalling pathway. Recent studies in contracting skeletal muscle have shown that functional vasodilatation in resistance arterioles has an endothelial cell (EC)-dependent component, and, separately have shown that the extracellular matrix protein fibronectin (FN) contributes to functional dilatation in these arterioles. Here we test the hypotheses that (i) the matricryptic heparin-binding region of the first type III repeat of fibrillar FN (FNIII1H) mediates vasodilatation, and (ii) this response is EC dependent. Engineered FN fragments with differing (defined) heparin- and integrin-binding capacities were applied directly to resistance arterioles in cremaster muscles of anaesthetized (pentobarbital sodium, 65 mg kg(-1)) mice. Both FNIII1H,8-10 and FNIII1H induced dilatations (12.2 ± 1.7 μm, n = 12 and 17.2 ± 2.4 μm, n = 14, respectively) whereas mutation of the active sequence (R(613) WRPK) of the heparin binding region significantly diminished the dilatation (3.2 ± 1.8 μm, n = 10). Contraction of skeletal muscle fibres via electrical field stimulation produced a vasodilatation (19.4 ± 1.2 μm, n = 12) that was significantly decreased (to 7.0 ± 2.7 μm, n = 7, P < 0.05) in the presence of FNIII1Peptide 6, which blocks extracellular matrix (ECM) FN and FNIII1H signalling. Furthermore, FNIII1H,8-10 and FNIII1H applied to EC-denuded arterioles failed to produce any dilatation indicating that endothelium was required for the response. Finally, FNIII1H significantly increased EC Ca(2+) (relative fluorescence 0.98 ± 0.02 in controls versus 1.12 ± 0.05, n = 17, P < 0.05). Thus, we conclude that ECM FN-dependent vasodilatation is mediated by the heparin-binding (RWRPK) sequence of FNIII1 in an EC-dependent manner. Importantly, blocking this signalling sequence decreased the dilatation to skeletal muscle contraction, indicating that there is a physiological role for this FN-dependent mechanism.

The role of endothelial mechanosensitive genes in atherosclerosis and omics approaches

Atherosclerosis is the leading cause of morbidity and mortality in the U.S., and is a multifactorial disease that preferentially occurs in regions of the arterial tree exposed to disturbed blood flow. The detailed mechanisms by which d-flow induces atherosclerosis involve changes in the expression of genes, epigenetic patterns, and metabolites of multiple vascular cells, especially endothelial cells. This review presents an overview of endothelial mechanobiology and its relation to the pathogenesis of atherosclerosis with special reference to the anatomy of the artery and the underlying fluid mechanics, followed by a discussion of a variety of experimental models to study the role of fluid mechanics and atherosclerosis. Various in vitro and in vivo models to study the role of flow in endothelial biology and pathobiology are discussed in this review. Furthermore, strategies used for the global profiling of the genome, transcriptome, miR-nome, DNA methylome, and metabolome, as they are important to define the biological and pathophysiological mechanisms of atherosclerosis. These "omics" approaches, especially those which derive data based on a single animal model, provide unprecedented opportunities to not only better understand the pathophysiology of atherosclerosis development in a holistic and integrative manner, but also to identify novel molecular and diagnostic targets.

Vascular nitric oxide: Beyond eNOS

As the first discovered gaseous signaling molecule, nitric oxide (NO) affects a number of cellular processes, including those involving vascular cells. This brief review summarizes the contribution of NO to the regulation of vascular tone and its sources in the blood vessel wall. NO regulates the degree of contraction of vascular smooth muscle cells mainly by stimulating soluble guanylyl cyclase (sGC) to produce cyclic guanosine monophosphate (cGMP), although cGMP-independent signaling [S-nitrosylation of target proteins, activation of sarco/endoplasmic reticulum calcium ATPase (SERCA) or production of cyclic inosine monophosphate (cIMP)] also can be involved. In the blood vessel wall, NO is produced mainly from l-arginine by the enzyme endothelial nitric oxide synthase (eNOS) but it can also be released non-enzymatically from S-nitrosothiols or from nitrate/nitrite. Dysfunction in the production and/or the bioavailability of NO characterizes endothelial dysfunction, which is associated with cardiovascular diseases such as hypertension and atherosclerosis.

Molecular mechanisms of renal blood flow autoregulation

Diabetes and hypertension are the leading causes of chronic kidney disease and their incidence is increasing at an alarming rate. Both are associated with impairments in the autoregulation of renal blood flow (RBF) and greater transmission of fluctuations in arterial pressure to the glomerular capillaries. The ability of the kidney to maintain relatively constant blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure is mediated by the myogenic response of afferent arterioles working in concert with tubuloglomerular feedback that adjusts the tone of the afferent arteriole in response to changes in the delivery of sodium chloride to the macula densa. Despite intensive investigation, the factors initiating the myogenic response and the signaling pathways involved in the myogenic response and tubuloglomerular feedback remain uncertain. This review focuses on current thought regarding the molecular mechanisms underlying myogenic control of renal vascular tone, the interrelationships between the myogenic response and tubuloglomerular feedback, the evidence that alterations in autoregulation of RBF contributes to hypertension and diabetes-induced nephropathy and the identification of vascular therapeutic targets for improved renoprotection in hypertensive and diabetic patients.

Nitric Oxide Contributes to Vasomotor Tone in Hypertensive African Americans Treated With Nebivolol and Metoprolol

Endothelial dysfunction is more prevalent in African Americans (AAs) compared with whites. The authors hypothesized that nebivolol, a selective β1 -antagonist that stimulates nitric oxide (NO), will improve endothelial function in AAs with hypertension when compared with metoprolol. In a double-blind, randomized, crossover study, 19 AA hypertensive patients were randomized to a 12-week treatment period with either nebivolol 10 mg or metoprolol succinate 100 mg daily. Forearm blood flow (FBF) was measured using plethysmography at rest and after intra-arterial infusion of acetylcholine and sodium nitroprusside to estimate endothelium-dependent and independent vasodilation, respectively. Physiologic vasodilation was assessed during hand-grip exercise. Measurements were repeated after NO blockade with L-N(G) -monomethylarginine (L-NMMA) and after inhibition of endothelium-derived hyperpolarizing factor (EDHF) with tetraethylammonium chloride (TEA). NO blockade with L-NMMA produced a trend toward greater vasoconstriction during nebivolol compared with metoprolol treatment (21% vs 12% reduction in FBF, P=.06, respectively). This difference was more significant after combined administration of L-NMMA and TEA (P<.001). Similarly, there was a contribution of NO to exercise-induced vasodilation during nebivolol but not during metoprolol treatment. There were significantly greater contributions of NO and EDHF to resting vasodilator tone and of NO to exercise-induced vasodilation with nebivolol compared with metoprolol in AAs with hypertension.

CYP2J2 overexpression ameliorates hyperlipidemia via increased fatty acid oxidation mediated by the AMPK pathway

OBJECTIVE

The study aims to investigate the effect of cytochrome P450 2J2 (CYP2J2) overexpression on hyperlipidemia in mice and further to explore its effect on fatty acid oxidation in vivo and in vitro.

METHODS

The effects and mechanisms of endothelial-specific CYP2J2 transgene (Tie2-CYP2J2-Tr) on lipid and fatty acid metabolism were investigated in high-fat diet (HFD) -treated mice. HepG2, LO2 cells, and HUVECs were exposed to 0.4 mM free fatty acid (FFA) for 24 h and used as a model to investigate the roles of CYP2J2 overexpression and epoxyeicosatrienoic acids (EETs) on fatty acid β-oxidation in vitro.

RESULTS

Tie2-CYP2J2-Tr mice had significantly lower plasma and liver triglycerides, lower liver cholesterol and fatty acids, and reduced HFD-induced lipid accumulation. CYP2J2 overexpression resulted in activation of the hepatic and endothelial AMPKα, increased ACC phosphorylation, and increased expression of CPT-1 and PPARα, which were all reduced by HFD treatment. In FFA-treated HepG2, LO2, and HUVECs, both CYP2J2 overexpression and EETs significantly decreased lipid accumulation and increased fatty acid oxidation via activating the AMPK and PPARα pathways.

CONCLUSIONS

Endothelial-specific CYP2J2 overexpression alleviates HFD-induced hyperlipidemia in vivo. CYP2J2 ameliorates FFA-induced dyslipidemia via increased fatty acid oxidation mediated by the AMPK and PPARα pathways.

Nitric oxide, vasodilation and the red blood cell

Since the identification of the elusive endothelium-derived relaxing factor as nitric oxide (NO), much attention has been devoted to understanding its physiological effects. NO is a free radical with many roles, and owing to its neutral charge and high diffusion capacity, it appears NO is involved in every mammalian biological system. Most attention has been focused on the NO generating pathways within the endothelium; however, the recent discovery of a NO synthase (NOS)-like enzyme residing in red blood cells (RBC) has increased our understanding of the blood flow and oxygen delivery modulation by RBC. In the present review, pathways of NO generation are summarized, with attention to those residing within RBC. While the bioactivity of RBC-derived NO is still debated due to its generation within proximity of NO scavengers, current theories for NO export from RBC are explored, which are supported by recent findings demonstrating an extracellular response to RBC-derived NO. The importance of NO in the active regulation of RBC deformability is discussed in the context of the subsequent effects on blood fluidity, and the complex interplay between blood rheology and NO are summarized. This review provides a summary of recent advances in understanding the role played by RBC in NO equilibrium and vascular regulation.

Au nanoparticles-3D graphene hydrogel nanocomposite to boost synergistically in situ detection sensitivity toward cell-released nitric oxide

In situ detection of nitric oxide (NO) released from living cells has become very important in studies of some critical physiological and pathological processes, but it is still very challenging due to the low concentration and fast decay of NO. A nanocomposite of Au nanoparticles deposited on three-dimensional graphene hydrogel (Au NPs-3DGH) was prepared through a facile one-step approach by in situ reduction of Au(3+) on 3DGH to build a unique sensing film for a strong synergistic effect, in which the highly porous 3DGH offers a large surface area while Au NPs uniformly deposited on 3DGH efficiently catalyze the electrochemical oxidation of NO for sensitive detection of NO with excellent selectivity, fast response, and low detection limit. The sensor was further used to in situ detect NO released from living cells under drug stimulation, showing significant difference between normal and tumor cells under drug stimulation.

Molecular targets of antihypertensive peptides: understanding the mechanisms of action based on the pathophysiology of hypertension

There is growing interest in using functional foods or nutraceuticals for the prevention and treatment of hypertension or high blood pressure. Although numerous preventive and therapeutic pharmacological interventions are available on the market, unfortunately, many patients still suffer from poorly controlled hypertension. Furthermore, most pharmacological drugs, such as inhibitors of angiotensin-I converting enzyme (ACE), are often associated with significant adverse effects. Many bioactive food compounds have been characterized over the past decades that may contribute to the management of hypertension; for example, bioactive peptides derived from various food proteins with antihypertensive properties have gained a great deal of attention. Some of these peptides have exhibited potent in vivo antihypertensive activity in both animal models and human clinical trials. This review provides an overview about the complex pathophysiology of hypertension and demonstrates the potential roles of food derived bioactive peptides as viable interventions targeting specific pathways involved in this disease process. This review offers a comprehensive guide for understanding and utilizing the molecular mechanisms of antihypertensive actions of food protein derived peptides.

Tranilast increases vasodilator response to acetylcholine in rat mesenteric resistance arteries through increased EDHF participation

Background and Purpose

Tranilast, in addition to its capacity to inhibit mast cell degranulation, has other biological effects, including inhibition of reactive oxygen species, cytokines, leukotrienes and prostaglandin release. In the current study, we analyzed whether tranilast could alter endothelial function in rat mesenteric resistance arteries (MRA).

Experimental Approach

Acetylcholine-induced relaxation was analyzed in MRA (untreated and 1-hour tranilast treatment) from 6 month-old Wistar rats. To assess the possible participation of endothelial nitric oxide or prostanoids, acetylcholine-induced relaxation was analyzed in the presence of L-NAME or indomethacin. The participation of endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced response was analyzed by preincubation with TRAM-34 plus apamin or by precontraction with a high K⁺ solution. Nitric oxide (NO) and superoxide anion levels were measured, as well as vasomotor responses to NO donor DEA-NO and to large conductance calcium-activated potassium channel opener NS1619.

Key Results

Acetylcholine-induced relaxation was greater in tranilast-incubated MRA. Acetylcholine-induced vasodilation was decreased by L-NAME in a similar manner in both experimental groups. Indomethacin did not modify vasodilation. Preincubation with a high K⁺ solution or TRAM-34 plus apamin reduced the vasodilation to ACh more markedly in tranilast-incubated segments. NO and superoxide anion production, and vasodilator responses to DEA-NO or NS1619 remained unmodified in the presence of tranilast.

Conclusions and Implications

Tranilast increased the endothelium-dependent relaxation to acetylcholine in rat MRA. This effect is independent of the nitric oxide and cyclooxygenase pathways but involves EDHF, and is mediated by an increased role of small conductance calcium-activated K+ channels.

Maternal nutrient restriction during pregnancy impairs an endothelium-derived hyperpolarizing factor-like pathway in sheep fetal coronary arteries

The mechanisms underlying developmental programming are poorly understood but may be associated with adaptations by the fetus in response to changes in the maternal environment during pregnancy. We hypothesized that maternal nutrient restriction during pregnancy alters vasodilator responses in fetal coronary arteries. Pregnant ewes were fed a control [100% U.S. National Research Council (NRC)] or nutrient-restricted (60% NRC) diet from days 50 to 130 of gestation (term = 145 days); fetal tissues were collected at day 130. In coronary arteries isolated from control fetal lambs, relaxation to bradykinin was unaffected by nitro-l-arginine (NLA). Iberiotoxin or contraction with KCl abolished the NLA-resistant response to bradykinin. In fetal coronary arteries from nutrient-restricted ewes, relaxation to bradykinin was fully suppressed by NLA. Large-conductance, calcium-activated potassium channel (BKCa) currents did not differ in coronary smooth muscle cells from control and nutrient-restricted animals. The BKCa openers, BMS 191011 and NS1619, and 14,15-epoxyeicosatrienoic acid [a putative endothelium-derived hyperpolarizing factor (EDHF)] each caused fetal coronary artery relaxation and BKCa current activation that was unaffected by maternal nutrient restriction. Expression of BKCa-channel subunits did not differ in fetal coronary arteries from control or undernourished ewes. The results indicate that maternal undernutrition during pregnancy results in loss of the EDHF-like pathway in fetal coronary arteries in response to bradykinin, an effect that cannot be explained by a decreased number or activity of BKCa channels or by decreased sensitivity to mediators that activate BKCa channels in vascular smooth muscle cells. Under these conditions, bradykinin-induced relaxation is completely dependent on nitric oxide, which may represent an adaptive response to compensate for the absence of the EDHF-like pathway.

Vascular origin of vildagliptin-induced skin effects in Cynomolgus monkeys: pathomechanistic role of peripheral sympathetic system and neuropeptide Y

The purpose of this article is to characterize skin lesions in cynomolgus monkeys following vildagliptin (dipeptidyl peptidase-4 inhibitor) treatment. Oral vildagliptin administration caused dose-dependent and reversible blister formation, peeling and flaking skin, erosions, ulcerations, scabs, and sores involving the extremities at ≥5 mg/kg/day and necrosis of the tail and the pinnae at ≥80 mg/kg/day after 3 weeks of treatment. At the affected sites, the media and the endothelium of dermal arterioles showed hypertrophy/hyperplasia. Skin lesion formation was prevented by elevating ambient temperature. Vildagliptin treatment also produced an increase in blood pressure and heart rate likely via increased sympathetic tone. Following treatment with vildagliptin at 80 mg/kg/day, the recovery time after lowering the temperature in the feet of monkeys and inducing cold stress was prolonged. Ex vivo investigations showed that small digital arteries from skin biopsies of vildagliptin-treated monkeys exhibited an increase in neuropeptide Y-induced vasoconstriction. This finding correlated with a specific increase in NPY and in NPY1 receptors observed in the skin of vildagliptin-treated monkeys. Present data provide evidence that skin effects in monkeys are of vascular origin and that the effects on the NPY system in combination with increased peripheral sympathetic tone play an important pathomechanistic role in the pathogenesis of cutaneous toxicity.

Effects of DL-homocysteine thiolactone on cardiac contractility, coronary flow, and oxidative stress markers in the isolated rat heart: the role of different gasotransmitters

Considering the adverse effects of DL-homocysteine thiolactone hydrochloride (DL-Hcy TLHC) on vascular function and the possible role of oxidative stress in these mechanisms, the aim of this study was to assess the influence of DL-Hcy TLHC alone and in combination with specific inhibitors of important gasotransmitters, such as L-NAME, DL-PAG, and PPR IX, on cardiac contractility, coronary flow, and oxidative stress markers in an isolated rat heart. The hearts were retrogradely perfused according to the Langendorff technique at a 70 cm H₂O and administered 10 μM DL-Hcy TLHC alone or in combination with 30 μM L-NAME, 10 μM DL-PAG, or 10 μM PPR IX. The following parameters were measured: dp/dt max, dp/dt min, SLVP, DLVP, MBP, HR, and CF. Oxidative stress markers were measured spectrophotometrically in coronary effluent through TBARS, NO₂, O₂⁻, and H₂O₂ concentrations. The administration of DL-Hcy TLHC alone decreased dp/dt max, SLVP, and CF but did not change any oxidative stress parameters. DL-Hcy TLHC with L-NAME decreased CF, O₂⁻, H₂O₂, and TBARS. The administration of DL-Hcy TLHC with DL-PAG significantly increased dp/dt max but decreased DLVP, CF, and TBARS. Administration of DL-Hcy TLHC with PPR IX caused a decrease in dp/dt max, SLVP, HR, CF, and TBARS.

Peripheral circulation

Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.

Inducible endothelium-derived hyperpolarizing factor: role of the 15-lipoxygenase-EDHF pathway

Endothelium-derived hyperpolarizing factors (EDHFs) regulate vascular tone by contributing to the vasorelaxations to shear stress and endothelial agonists such as bradykinin and acetylcholine. 15(S)-Hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA) and 11(R),12(S),15(S)-trihydroxyeicosatrienoic acid (11,12,15-THETA) are endothelial metabolites of the 15-lipoxygenase (15-LO) pathway of arachidonic acid metabolism and are EDHFs. 11,12,15-THETA activates small conductance, calcium-activated potassium channels on smooth muscle cells causing membrane hyperpolarization, and relaxation. Expression levels of 15-LO in the endothelium regulate the activity of the 15-LO/15-H-11,12-EETA/11,12,15-THETA pathway and its contribution to vascular tone. Regulation of its expression is by transcriptional, translational, and epigenetic mechanisms. Hypoxia, hypercholesterolemia, atherosclerosis, anemia, estrogen, interleukins, and possibly other hormones increase 15-LO expression. An increase in 15-LO results in increased synthesis of 15-H-11,12-EETA and 11,12,15-THETA, increased membrane hyperpolarization, and enhanced contribution to relaxation by endothelial agonists. Thus, the 15-LO pathway represents the first example of an inducible EDHF. In addition to 15-LO metabolites, a number of chemicals have been identified as EDHFs and their contributions to vascular tone vary with species and vascular bed. The reason for multiple EDHFs has evaded explanation. However, EDHF functioning as constitutive EDHFs or inducible EDHFs may explain the need for chemically and biochemically distinct pathways for EDHF activity and the variation in EDHFs between species and vascular beds. This new EDHF classification provides a framework for understanding EDHF activity in physiological and pathological conditions.

Reactive hyperemia occurs via activation of inwardly rectifying potassium channels and Na+/K+-ATPase in humans

RATIONALE

Reactive hyperemia (RH) in the forearm circulation is an important marker of cardiovascular health, yet the underlying vasodilator signaling pathways are controversial and thus remain unclear.

OBJECTIVE

We hypothesized that RH occurs via activation of inwardly rectifying potassium (KIR) channels and Na(+)/K(+)-ATPase and is largely independent of the combined production of the endothelial autocoids nitric oxide (NO) and prostaglandins in young healthy humans.

METHODS AND RESULTS

In 24 (23±1 years) subjects, we performed RH trials by measuring forearm blood flow (FBF; venous occlusion plethysmography) after 5 minutes of arterial occlusion. In protocol 1, we studied 2 groups of 8 subjects and assessed RH in the following conditions. For group 1, we studied control (saline), KIR channel inhibition (BaCl2), combined inhibition of KIR channels and Na(+)/K(+)-ATPase (BaCl2 and ouabain, respectively), and combined inhibition of KIR channels, Na(+)/K(+)-ATPase, NO, and prostaglandins (BaCl2, ouabain, L-NMMA [N(G)-monomethyl-L-arginine] and ketorolac, respectively). Group 2 received ouabain rather than BaCl2 in the second trial. In protocol 2 (n=8), the following 3 RH trials were performed: control; L-NMMA plus ketorolac; and L-NMMA plus ketorolac plus BaCl2 plus ouabain. All infusions were intra-arterial (brachial). Compared with control, BaCl2 significantly reduced peak FBF (-50±6%; P<0.05), whereas ouabain and L-NMMA plus ketorolac did not. Total FBF (area under the curve) was attenuated by BaCl2 (-61±3%) and ouabain (-44±12%) alone, and this effect was enhanced when combined (-87±4%), nearly abolishing RH. L-NMMA plus ketorolac did not impact total RH FBF before or after administration of BaCl2 plus ouabain.

CONCLUSIONS

Activation of KIR channels is the primary determinant of peak RH, whereas activation of both KIR channels and Na(+)/K(+)-ATPase explains nearly all of the total (AUC) RH in humans.

[Vasodilator effect of oroxylin A on thoracic aorta isolated from rats]

OBJECTIVE

To investigate the vasodilator effect and the endothelium-dependent mechanism of oroxylin A in thoracic aorta isolated from rats.

METHODS

Thoracic aorta was isolated from Wistar rats. After pretreatment with norepinephrine or KCl, the effects of oroxylin A at different concentrations were detected on isolated vascular rings prepared from rats' thoracic aorta. The response of thoracic aortic ring was evaluated in the presence and absence of endothelium, and NG-nitro-L-arginine methyl ester (L-NAME), a specific inhibitor of nitric oxide synthase.

RESULTS

Oroxylin A (10 and 100 μmol/L) caused vasodilation on endothelium-intact aortic rings pretreated with norepinephrine (1 μmol/L) and KCl (60 mmol/L) compared with the control (P<0.05, P<0.01). The vasodilation function of 10 and 100 μmol/L oroxylin A on the endothelium-denuded aorta rings was significantly lower than that on the endothelium-intact aorta rings (P<0.05, P<0.01). L-NAME pretreatment significantly attenuated the effect of 100 μmol/L oroxylin A on endothelium-intact aorta rings (P<0.05, P<0.01).

CONCLUSION

Oroxylin A can induce the relaxation of the aorta ring in endothelium-dependent manner. Nitric oxide may be involved in the endothelium-dependent effect of oroxylin A.

Apelin is decreased with human preterm and term labor and regulates prolabor mediators in human primary amnion cells

A critical role of proinflammatory mediators including cytokines, prostaglandins, and extracellular matrix remodeling enzymes in the processes of human labor and delivery, at term and preterm, has been demonstrated. In nongestational tissues, apelin plays an important role in a number of physiologic processes, including the regulation of inflammation. However, the role and regulation of apelin and the apelin receptor (APJ) in human gestational tissues are not known. The aims of this study were to determine the effect of (i) preterm and term labor on apelin and APJ expression in human gestational tissues and (ii) apelin small interfering RNA (siRNA) knockdown in human primary amnion cells on prolabor mediators. Human placenta and fetal membranes were collected from term nonlaboring women and women after spontaneous labor and delivery. Preterm and term spontaneous labor were associated with significantly lower apelin expression in fetal membranes. On the other hand, there was no effect of labor on APJ expression and no effect of term labor on placental apelin or APJ expression. Transfection of primary amnion cells with apelin siRNA was associated with significantly increased interleukin (IL)-1β-induced IL-6 and IL-8 release and cyclooxygenase-2 messenger RNA (mRNA) expression and resultant prostaglandin E2 and prostaglandin F2α release. There was no effect of apelin siRNA on matrix metalloproteinase (MMP)-9 mRNA expression and pro MMP-9 release. In summary, human labor downregulates apelin expression in human fetal membranes. Furthermore, a role of apelin in the regulation of proinflammatory and prolabor mediators in human fetal membranes is supported by our studies.

iNOS-selective inhibitors for cancer prevention: promise and progress

Nitric oxide (NO) is involved in various physiological functions and its role in tumorigenesis has been well studied. A large majority of human and experimental tumors appear to progress owing to NO resulting from iNOS, further stimulated by proinflammatory cytokines. Conversely, in some cases, NO is associated with induction of apoptosis and tumor regression. This dichotomy of NO is largely explained by the complexity of signaling pathways in tumor cells, which respond to NO very differently depending on its concentration. In addition, NO alters many signaling pathways through chemical modifications, such as the addition of S-nitrosothiols and nitrosotyrosine to target proteins altering various biological pathways. Hence, iNOS inhibitors are designed and developed to inhibit various organ site cancers including the colon. Here, we review iNOS expression, generation of NO, involvement of NO in altering signaling pathways, and iNOS select inhibitors and their possible use for the prevention and treatment of various cancers.

Endothelin-1 and endothelin receptor gene variants and their association with negative outcomes following aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating disease that affects approximately 30,000 people a year in the United States. Delayed cerebral ischemia (DCI) and cerebral vasospasm (CV) are common complications after aSAH. In addition, aSAH patients have a high risk of poor long-term outcomes. Endothelin-1 (ET-1), a potent vasoconstrictor, or its two types of receptors, ET receptor A (ETA) and ET receptor B (ETB), may play a role in the pathogenesis of DCI and CV. Genetic variations within the ET-1, ETA, or ETB genes may also account for variance observed in the outcomes of aSAH patients. The purpose of this study was to describe the distribution of the Lys198Asn polymorphism, a known functional SNP in the ET-1 gene, and tagging SNPs of the ET-1, ETA, and ETB genes in individuals recovering from aSAH. This study also investigated the relationships among the ET polymorphisms, DCI, and global functional outcomes measured at 3 and 6 months after aSAH. Participants included individuals aged 18-75 years with a diagnosis of aSAH. There was a trend found between the variant allele of an ET-1 SNP (rs6912834) and angiographic vasospasm. There were also associations found between two ETB SNPs (rs9574124 and rs3027111) and poor outcomes as measured by the Glasgow Outcome scale at 3 months. These findings support the role of ET-1 and ETB in recovery following aSAH.

RGD-peptide functionalized graphene biomimetic live-cell sensor for real-time detection of nitric oxide molecules

It is always challenging to construct a smart functional nanostructure with specific physicochemical properties to real time detect biointeresting molecules released from live-cells. We report here a new approach to build a free-standing biomimetic sensor by covalently bonding RGD-peptide on the surface of pyrenebutyric acid functionalized graphene film. The resulted graphene biofilm sensor comprises a well-packed layered nanostructure, in which the RGD-peptide component provides desired biomimetic properties for superior human cell attachment and growth on the film surface to allow real-time detection of nitric oxide, an important signal yet short-life molecule released from the attached human endothelial cells under drug stimulations. The film sensor exhibits good flexibility and stability by retaining its original response after 45 bending/relaxing cycles and high reproducibility from its almost unchanged current responses after 15 repeated measurements, while possessing high sensitivity, good selectivity against interferences often existing in biological systems, and demonstrating real time quantitative detection capability toward nitric oxide molecule released from living cells. This study not only demonstrates a facial approach to fabricate a smart nanostructured graphene-based functional biofilm, but also provides a powerful and reliable platform to the real-time study of biointeresting molecules released from living cells, thus rendering potential broad applications in neuroscience, screening drug therapy effect, and live-cell assays.

Combined contribution of endothelial relaxing autacoides in the rat femoral artery response to CPCA: an adenosine A2 receptor agonist

We examined the contribution of endothelial relaxing factors and potassium channels in actions of CPCA, potent adenosine A(2) receptor agonist, on isolated intact male rat femoral artery (FA). CPCA produced concentration-dependent relaxation of FA, which was notably, but not completely, reduced after endothelial denudation. DPCPX, A(1) receptor antagonist, had no significant effect, while SCH 58261 (A(2A) receptor antagonist) notably reduced CPCA-evoked effect. Pharmacological inhibition of nitric oxide synthase or cyclooxygenase comparably reduced CPCA-evoked action, still in a lesser degree than after denudation. In the presence of buffer with high K(+) (100  mM), CPCA-produced relaxations were almost abolished. TEA (nonselective K(Ca) blocker), glibenclamide (K(ATP) blocker), Ba(++) (K(IR) blocker), or ouabain (Na(+)/K(+)-ATPase inhibitor) did not change CPCA-induced relaxation. Concentration-response curve for CPCA was significantly shifted to the right after the incubation of apamin (SK channel blocker). CPCA produced concentration-dependent relaxation of FA that was partly dependent on endothelial cells. Endothelium-related portion of CPCA-elicited effect was mediated by combined action of endothelial NO, prostacyclin, and EDHF after activation of endothelial A(2A) receptors. Small conductance K(Ca) channels were involved in this action.

Epoxides and soluble epoxide hydrolase in cardiovascular physiology

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites that importantly contribute to vascular and cardiac physiology. The contribution of EETs to vascular and cardiac function is further influenced by soluble epoxide hydrolase (sEH) that degrades EETs to diols. Vascular actions of EETs include dilation and angiogenesis. EETs also decrease inflammation and platelet aggregation and in general act to maintain vascular homeostasis. Myocyte contraction and increased coronary blood flow are the two primary EET actions in the heart. EET cell signaling mechanisms are tissue and organ specific and provide significant evidence for the existence of EET receptors. Additionally, pharmacological and genetic manipulations of EETs and sEH have demonstrated a contribution for this metabolic pathway to cardiovascular diseases. Given the impact of EETs to cardiovascular physiology, there is emerging evidence that development of EET-based therapeutics will be beneficial for cardiovascular diseases.