Endothelium-derived Contracting Factor Research Articles

Pathogenic Mechanisms of Pulmonary Arterial Hypertension: Homeostasis Imbalance of Endothelium-Derived Relaxing and Contracting Factors.

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease. Sustained pulmonary vasoconstriction and concentric pulmonary vascular remodeling contribute to the elevated pulmonary vascular resistance and pulmonary artery pressure in PAH. Endothelial cells regulate vascular tension by producing endothelium-derived relaxing factors (EDRFs) and endothelium-derived contracting factors (EDCFs). Homeostasis of EDRF and EDCF production has been identified as a marker of the endothelium integrity. Impaired synthesis or release of EDRFs induces persistent vascular contraction and pulmonary artery remodeling, which subsequently leads to the development and progression of PAH. In this review, the authors summarize how EDRFs and EDCFs affect pulmonary vascular homeostasis, with special attention to the recently published novel mechanisms related to endothelial dysfunction in PAH and drugs associated with EDRFs and EDCFs.

Effect of Nonsteroidal Mineralocorticoid Receptor Blocker Esaxerenone on Vasoreactivity to an Endothelial Stimulator in Superior Mesenteric Arteries of Type 2 Diabetic Goto-Kakizaki Rat.

Endothelial dysfunction contributes to cardiometabolic disorders, including hypertension, obesity, and type 2 diabetes. Esaxerenone is a selective, nonsteroidal, high-affinity mineralocorticoid receptor blocker recently approved in Japan for the treatment of hypertension. Although imbalanced signaling between vasorelaxant and vasocontractile factors induced by endothelial stimulation is often observed in type 2 diabetic vessels, the effects of esaxerenone on endothelium-dependent responses in type 2 diabetes remain unclear. The aim of this study was to investigate the effect of esaxerenone on endothelium-dependent responses in superior mesenteric arteries isolated from type 2 diabetic Goto-Kakizaki (GK) rats. It was found that esaxerenone (3 mg/kg/d for 4 weeks, per os (p.o.)) partially ameliorated acetylcholine (ACh)-induced endothelium-derived hyperpolarizing factor (EDHF)-type relaxation and NS309, a potent activator of small- and intermediate-conductance Ca2+-activated K+ channels, -induced relaxation, and reduced ACh-induced endothelium-derived contracting factor (EDCF)-mediated contraction. These results suggest that esaxerenone ameliorates endothelial function through increased EDHF signaling and suppressed EDCF signaling.

Pathophysiology and Outcomes of Endothelium Function in Coronary Microvascular Diseases: A Systematic Review of Randomized Controlled Trials and Multicenter Study.

Coronary macrovascular disease is a concept that has been well-studied within the literature and has long been the subject of debates surrounding coronary artery bypass grafting (CABG) vs. Percutaneous Coronary Intervention (PCI). ISCHEMIA trial reported no statistical difference in the primary clinical endpoint between initial invasive management and initial conservative management, while in the ORBITA trial PCI did not improve angina frequency score significantly more than placebo, albeit PCI resulted in more patient-reported freedom from angina than placebo. However, these results did not prove the superiority of the PCI against OMT, therefore do not indicate the benefit of PCI vs. the OMT. Please rephrase the sentence. We reviewed the role of different factors responsible for endothelial dysfunction from recent randomized clinical trials (RCTs) and multicentre studies. A detailed search strategy was performed using a dataset that has previously been published. Data of pooled analysis include research articles (human and animal models), CABG, and PCI randomized controlled trials (RCTs). Details of the search strategy and the methods used for data pooling have been published previously and registered with Open-Source Framework. The roles of nitric oxide (NO), endothelium-derived contracting factors (EDCFs), and vasodilator prostaglandins (e.g., prostacyclin), as well as endothelium-dependent hyperpolarization (EDH) factors, are crucial for the maintenance of vasomotor tone within the coronary vasculature. These homeostatic mechanisms are affected by sheer forces and other several factors that are currently being studied, such as vaping. The role of intracoronary testing is crucial when determining the effects of therapeutic medications with further studies on the horizon. The true impact of coronary microvascular dysfunction (CMD) is perhaps underappreciated, which supports the role of medical therapy in determining outcomes. Ongoing trials are underway to further investigate the role of therapeutic agents in secondary prevention.

Endothelium-dependent contraction: The non-classical action of endothelial prostacyclin, its underlying mechanisms, and implications.

Although commonly thought to produce prostacyclin (prostaglandin I2 ; PGI2 ) that evokes vasodilatation and protects vessels from the development of diseases, the endothelial cyclooxygenase (COX)-mediated metabolism has also been found to release substance(s) called endothelium-derived contracting factor(s) (EDCF) that causes endothelium-dependent contraction and implicates in endothelial dysfunction of disease conditions. Various mechanisms have been proposed for the process; however, the major endothelial COX metabolite PGI2 , which has been classically considered to activate the I prostanoid receptor (IP) that mediates vasodilatation and opposes the effects of thromboxane (Tx) A2 produced by COX in platelets, emerges as a major EDCF in health and disease conditions. Our recent studies from genetically altered mice further suggest that vasomotor reactions to PGI2 are collectively modulated by IP, the vasoconstrictor Tx-prostanoid receptor (TP; the prototype receptor of TxA2 ) and E prostanoid receptor-3 (EP3; a vasoconstrictor receptor of PGE2 ) although with differences in potency and efficacy; a contraction to PGI2 reflects activities of TP and/or EP3 outweighing that of the concurrently activated IP. Here, we discuss the history of endothelium-dependent contraction, evidences that support the above hypothesis, proposed mechanisms for the varied reactions to endothelial PGI2 synthesis as well as the relation of its dilator activity to the effect of another NO-independent vasodilator mechanism, the endothelium-derived hyperpolarizing factor. Also, we address the possible pathological and therapeutic implications as well as questions remaining to be resolved or limitations of our above findings obtained from genetically altered mouse models.

Contributions of Rho-kinase and AMP-related kinase signaling pathways to responses mediated by endothelium-derived contracting factors in diabetic rat aorta.

Diabetes-induced endothelial damage leads to vascular dysfunction. The current study investigated the effects of short-term (4-week) streptozotocin (STZ)-induced diabetes on responses mediated by endothelium-derived contracting factors (EDCFs) as well as possible contributions of Rho-kinase and AMP-activated kinase (AMPK) signaling pathways. The effects of STZ-diabetes on vascular function were examined in isolated thoracic aorta preparations of 30-week-old rats (n = 27). The diabetes-associated changes in vascular function were studied with calcium ionophore A23187, acetylcholine, Rho-kinase inhibitor Y27632 ((R)-(+)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride), and AMPK activator AICAR (5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside). The phosphorylation of acetyl-CoA carboxylase, AMPK, and phospholamban and the protein levels of sarcoplasmic/endoplasmic Ca2+-ATPase 2 (SERCA2) and Rho-associated protein kinase (ROCKII) were measured in aortic preparations. Although the acetylcholine-mediated relaxation responses were preserved in 4-week STZ-induced diabetes, the increased activation of the Rho-kinase pathway was demonstrated via twofold enhancement in A23187-mediated contractile responses and significantly augmented protein levels of ROCKII. The AICAR-activated AMPK-mediated relaxation response was also augmented ∼4-fold in diabetic rats, without any alteration in phospholamban phosphorylation; further, this relaxation response suppressed A23187-mediated contraction in both groups. Diabetic rats showed an increase in AICAR-induced AMPK-mediated vasorelaxation and a 2.5-fold elevation of phosphorylated AMPK levels. These results indicate a possible compensation between hyperglycemia-induced endothelium-dependent hypercontractility and AMPK-mediated vasorelaxation in diabetes.

Decreased contraction induced by endothelium-derived contracting factor in prolonged treatment of rat renal artery with endoplasmic reticulum stress inducer

Recent evidence suggests that endoplasmic reticulum (ER) stress is involved in the regulation of various physiological functions, including those of the vascular system. However, the relationship between ER stress and vascular function is poorly understood. The endothelial cells control the vascular tone by releasing endothelium-derived relaxing factors and contracting factors (EDCFs). We hypothesized that tunicamycin, an inducer of ER stress, modifies endothelium-dependent contraction and prostaglandins (PGs), a major class of EDCFs, induced contractions in the rat renal artery in rats. An organ-culture technique was used to purely investigate the effects of ER stress on the vascular tissue. We observed that tunicamycin treatment (20μg/mL for 23 ± 1h) did not affect acetylcholine (ACh)-induced relaxation and decreased EDCF-mediated contractions under nitric oxide synthase (NOS) inhibition induced by ACh, ATP, or A23187 (a calcium ionophore) in the renal arteries. Under NOS inhibition, U46619 (a thromboxane A2 mimetic)- and beraprost (a prostacyclin analog)-induced contractions were also decreased in the renal arteries of the tunicamycin-treated group (vs. vehicle), while PGE2- and PGF2α-induced contractions were similar between the groups. Tunicamycin treatment slightly enhanced the contractions induced by phenylephrine, an α1 adrenoceptor ligand. Isotonic high-K+-induced contractions were similar between the vehicle- and tunicamycin-treated groups. Another ER stress inducer, thapsigargin (4μmol/L for 23 ± 1h), also caused substantial reduction of ACh-induced EDCF-mediated contraction (vs. vehicle-treated group). In the cultured renal arteries, tunicamycin and thapsigargin increased the expression of binding immunoglobulin protein (BiP), an ER stress marker. In conclusion, ER stress induction directly affects renal arterial function, especially in reducing EDCF-mediated contractions.

TRPV4 (Transient Receptor Potential Vanilloid 4) Mediates Endothelium-Dependent Contractions in the Aortas of Hypertensive Mice.

The role of TRPV4 (transient receptor potential vanilloid 4) in regulating vascular contraction in hypertensive mice is poorly established. We tested the hypothesis that TRPV4 regulates endothelium-dependent contractions in aortas from hypertensive mice through the activation of cytosolic cPLA2 (phospholipase A2) and COX2 (cyclooxygenase 2) and identified the possible endothelium-derived contracting factor generated by COX2. Using myography, we demonstrated that GSK1016790A (a TRPV4 agonist) and acetylcholine (ACh) trigger endothelium-dependent contractions in aortas from hypertensive mice, and the contractions were abolished with TRPV4 deletion. PLA2 assay and Western blotting showed that cPLA2 activity was higher in salt-induced hypertension and HC067047 or a Ca2+ chelator inhibited cPLA2 activity. Contractions induced by TRPV4 and ACh were inhibited by the cPLA2 inhibitor or removal of extracellular Ca2+ COX2 expression was enhanced in the endothelium from hypertensive mice and contractions induced by TRPV4 or ACh were inhibited by the COX2 inhibitor. Enzyme immunoassay showed that the release of prostaglandin F2α (PGF2α) was increased in hypertensive mice. GSK1016790A or ACh triggered the release of PGF2α and this was inhibited by HC067047, the cPLA2 inhibitor, and COX2 inhibitor. GSK1016790A, ACh, and PGF2α induced contractions were significantly reduced by S18886 in salt-induced hypertensive mice. The present study demonstrates that PGF2α generated by COX2 in the endothelium is the most likely endothelium-derived contracting factor underlying endothelium-dependent, TRPV4-mediated contraction in hypertensive mice. This contraction involved increased intracellular Ca2+ concentrations and cPLA2 activity. These results suggested an important role of TRPV4 in endothelium-dependent contraction in mice during hypertension.

Contribution of Rho-kinase and Adenosine Monophosphate-Activated Protein Kinase Signaling Pathways to Endothelium-Derived Contracting Factors Responses.

Vascular tonus is controlled by endothelium-derived relaxing factor (EDRF), endothelium-derived hyperpolarizing factor (EDHF) and endothelium-derived contracting factor (EDCF) under physiological circumstances. In pathological conditions, impairment of endothelium-derived relaxation can be caused by both decrease in EDRF release and increase in EDCF release. The increase in EDCF is observed with diseases such as hypertension and diabetes. The contribution of Rho-kinase and activated protein kinase (AMPK), which have opposite effects, to the increased EDCF responses was investigated. Rho-kinases are the effectors of Rho which is one of the small guanosine triphosphate-binding proteins. They increase cytosolic Ca+2 concentration and cause vascular smooth muscle to contract, keeping myosin light chain (MLC) in phosphorylated state by affecting myosin phosphatase target subunit which dephosphorylates the MLC. The activities of Rho-kinases increase with the increase of EDCF function. AMPK is the energy sensor of the cell. It provides a vasculoprotective effect by causing endothelium-dependent and endothelium-independent relaxation in smooth muscle. In contrast to Rho-kinase pathway activity, AMPK pathway activity decreases with diseases in which the EDCF function increases. In cases such as diabetes and hypertension that endothelial function impairs toward vasocontraction, it is considered that evaluating Rho-kinase and AMPK pathways which mediate contraction and relaxation in vascular smooth muscle respectively, would provide clues on choosing therapeutic target for pathologies in which endothelial dysfunction is observed.

“Endothelial Protector Drugs” and Diabetes: Is there a Role for these Drugs?

Diabetic vasculopathy, including macro and micro vascular disorders, is the leading cause of morbidity and mortality in patients with type 1 (T1) and type 2 (T2) diabetes mellitus (DM) [1]. A lot of researches pointed out that endothelial dysfunction, characterized by an imbalance between Endothelium-Derived Relaxing Factors (EDRFs) and endothelium-derived contracting factors (EDCFs) play a central role on the development and progression of diabetic vasculopathy [2-5]. Endothelial dysfunction and inflammation, as indicated by abnormal flow-dependent vasodilatation and by increased circulating levels of adhesion molecules (ICAM-1 and E-selectin) are known to occur in T2DM and seems to be an important predictor in systemic atherogenesis [6]. Both hyperglycemia and insulin administration increasing circulating levels of endothelin-1 (ET-1), an endothelial cell (EC)-derived potent vasoconstrictor peptide with mitogenic, pro-oxidative and pro-inflammatory properties that have shown to be extremely relevant to the pathophysiology of diabetic vasculopathy [7-10]. Circulating and local levels of ET-1 are increased in diabetic animal models and diabetic patients [1,11,12].

A vasoconstrictor response to COX-1-mediated prostacyclin synthesis in young rat renal arteries that increases in prehypertensive conditions.

This study aimed to determine whether prostacyclin (PGI2) functions as an endothelium-derived contracting factor (EDCF) in young rat renal arteries, and, if so, we wanted to examine the underlying mechanism(s) and how it changes in prehypertensive conditions. Vessels from Wistar-Kyoto (WKY) and prehypertensive spontaneously hypertensive rats (SHRs) of 25-28 days of age were isolated for functional and biochemical analyses. Result showed that following NO synthase (NOS) inhibition PGI2 and the thromboxane-prostanoid (TP) receptor agonist U-46619 evoked contractions in young WKY renal arteries that were similar to those in prehypertensive SHRs. Meanwhile, the endothelial muscarinic receptor agonist ACh evoked an endothelium-dependent contraction under NOS-inhibited conditions and a production of the PGI2 metabolite 6-keto-PGF1α; both were sensitive to cyclooxygenase (COX) and/or COX-1 inhibition but higher in prehypertensive SHRs than in young WKYs. Interestingly, in WKY renal arteries PGI2 did not evoke relaxation even after TP receptor antagonism that diminished the contraction evoked by the agonist. Indeed, PGI2 (IP) receptors were not detected in the vessel with Western blot. Moreover, we noted that treatment with the nonselective COX inhibitor indomethacin, which was started at the prehypertensive stage, blunted the elevation of systolic blood pressure and reduced the heart-to-body ratio in SHR within 2 mo of treatment. These results demonstrate that due to scarcity of IP receptors, PGI2, which is derived mainly from COX-1-mediated metabolism, acts as an EDCF in young WKY renal arteries, and it increases in prehypertensive conditions. Also, our data revealed that COX inhibition starting from the prehypertensive stage has an antihypertensive effect in young SHRs.

Abstract 642: Wy14643 and Fenofibrate Reduce Acetylcholine-induced Contractions in Spontaneously Hypertensive Rat Aortae

Introduction and hypothesis: Hypertension is associated with endothelial dysfunction, which is defined as an imbalanced release of endothelium-derived relaxing factors (EDRF) and endothelium-derived contracting factors (EDCF). Oxidative stress contributes to endothelial dysfunction by increasing the production of EDCF. Research studies have demonstrated that peroxisome proliferator-activated receptor alpha agonists, Wy14643 (WY) and fenofibrate (FF), improve endothelial function. Therefore, we assessed the hypothesis that WY and FF inhibited acetylcholine-induced endothelium-dependent contractions through reduction of oxidative stress in aortae of spontaneously hypertensive rats (SHR). Method: Thoracic aortic rings, with and without endothelium, were isolated from 40-44 weeks old male SHR and their normotensive counterparts, Wistar Kyoto rats (WKY). They were suspended in organ chambers for isometric tension recording. Responses to the endothelium-dependent vasoactive agent, acetylcholine (10 -8 - 10 -4 M), and to the oxidizing agent, hydrogen peroxide (10 -8 - 10 -4 M), were examined in the presence of N ω -nitro-L-arginine methyl ester (L-NAME, 3*10 -4 M; nitric oxide synthase inhibitor). Results: Acetylcholine caused significantly greater contractions in aortic rings, with endothelium, of SHR than in those of WKY. The contraction was significantly inhibited by the combination of Tiron (10 -3 M; intracellular superoxide anion scavenger) and DETCA (10 -4 M; superoxide dismutase inhibitor), suggesting that the reactive oxygen species, hydrogen peroxide, was involved in vascular dysfunction in hypertension. Both WY (10 -5 M) and FF (10 -5 M) significantly inhibited contractions to acetylcholine in SHR aorta, suggesting that they may reduce the amount of hydrogen peroxide or inhibit its downstream signaling. Moreover, they inhibited contractions induced by hydrogen peroxide in SHR aortic rings with, but not in those without, endothelium, indicating that their inhibitory effect was endothelium-dependent. Conclusion: The peroxisome proliferator-activated receptor alpha agonists act on the endothelium to reduce acetylcholine-induced contractions that are mediated by hydrogen peroxide in aortae of hypertensive rats.

Abstract 335: Prostaglandin I 2 Receptor Blockade Contracts Rat Renal Arteries and Facilitates Endothelium-Dependent Contractions.

Endothelium-dependent contractions are augmented in human hypertension and in isolated preparations, including renal arteries, from hypertensive animals. Renal vasomotor tone is essential in the regulation of arterial blood pressure and renal arteries are highly sensitive to vasoconstrictor prostanoids including prostacyclin, identified as endothelium-derived contracting factor (EDCF) activating thromboxane prostanoid (TP) receptors. However, the mechanisms underlying increased EDCF responses in hypertension are not completely resolved. Isometric tension was measured, in wire myographs, in renal arterial rings from spontaneously hypertensive (SHR) and age (38-52 weeks)-matched Wistar Kyoto (WKY) rats. Responses were compared under control conditions and after incubation with indomethacin (10 -5 mol/L, cyclooxygenase inhibitor), ketanserin (10 -6 mol/L, 5-HT 2 receptor antagonist), CAY10441 (10 -6 mol/L, prostaglandin I 2 [IP] receptor antagonist), and S18886 (10 -7 mol/L, TP receptor antagonist). All experiments were performed in the presence of L-NAME (3 x 10 -4 mol/L) to exclude effects of endothelium-derived NO. Surprisingly, CAY10441 (10 -10 to 10 -6 mol/L) contracted renal arterial rings from both strains; the contraction at the highest concentration was significantly larger in SHR (15±0.7 mN) than in WKY (10±1.5 mN) preparations ( n =10, P <0.05). This phenomenon was blunted by indomethacin, ketanserin, but not S18886. After washout and re-incubation, EDCF responses to acetylcholine (10 -8 to 10 -4 mol/L) were similar between SHR and WKY preparations in the presence of CAY10441 ( E max 72.6±5.3% and 67.4±3.8% KCl, n =8), but significantly larger than under control conditions ( n =4-8, P <0.05). S18886 prevented EDCF responses in the absence but not in the presence of CAY10441. Contractions to prostacyclin [in the presence of indomethacin] were facilitated by CAY10441 in rings from both strains and no longer prevented by S18886, although the TP receptor antagonist abolished contractions to U46619 (10 -11 to 3 x 10 -6 mol/L). These data suggest that: a) inhibitory IP receptors reduce renal vasomotor tone; b) IP and TP receptors form heterodimers; and c) endogenous serotonin contributes to the action of prostacyclin in rat renal arteries.

Resveratrol attenuates endothelium‐dependent cyclooxygenase‐mediated contractile activity in the carotid artery of spontaneously hypertensive rats (855.6)

The objective of this study was to determine the chronic and acute effects of resveratrol (RSV) on endothelial function and endothelium‐derived contracting factor (EDCF) signaling using common carotid artery (CCA) isolated from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Acetylcholine (Ach)‐stimulated endothelium‐dependent relaxation in pre‐contracted CCA was impaired in SHR (max. 53±6% vs. 86±6% in WKY) caused by competitive cyclooxygenase (COX)‐mediated contraction at high [Ach]. Chronic (28‐day) treatment in vivo (via drinking water) with a moderate RSV dose (Mod‐RSV, ~0.075 mg/kg/day) was without effect on Ach‐stimulated relaxation, or Ach‐stimulated contraction and associated prostaglandin (PG) production in quiescent CCA, in either strain. In contrast, in SHR but not WKY, a chronic high RSV dose (High‐RSV, ~7.5 mg/kg/day) improved Ach‐stimulated relaxation (max. 99±5% vs. 53±6% in No‐RSV SHR), and attenuated Ach‐stimulated contraction (55±5% vs. 68±5% in No‐RSV SHR) and associated PG production (189±30 vs. 519±93 pg/ml in No‐RSV SHR) (all p<0.05). High‐RSV also reduced mean arterial pressure in SHR (159±6 vs. 176±6 mmHg in No‐RSV SHR; p<0.05). In separate experiments, acute (30 min) in vitro treatment (in‐bath pre‐incubation) with 20µM RSV (RSV‐20µM) nearly abolished Ach‐stimulated contraction and greatly attenuated the associated PG production in SHR and WKY CCA (all p<0.05). Taken altogether, these experiments demonstrate that RSV can reverse endothelial dysfunction caused by EDCF activity by a signaling mechanism predominately involving the attenuation of COX‐derived PG production.Grant Funding Source: Supported by NSERC Canada RGPIN 238342

Interactions between thromboxane A2, thromboxane/prostaglandin (TP) receptors, and endothelium-derived hyperpolarization

Endothelium-dependent smooth muscle hyperpolarization (EDH) increasingly predominates over endothelium-derived nitric oxide (NO) as a participant in vasodilation as vessel size decreases. Its underlying nature is highly variable between vessel types, species, disease states, and exact experimental conditions, and is variably mediated by one or more transferable endothelium-derived hyperpolarizing factors and/or the electrotonic spread of endothelial hyperpolarization into the media via gap junctions. Although generally regarded (and studied) as a mechanism that is independent of NO and prostanoids, evidence has emerged that the endothelium-derived contracting factor and prostanoid thromboxane A2 can modulate several signalling components central to EDH, and therefore potentially curtail vasodilation through mechanisms that are distinct from those putatively involved in direct smooth muscle contraction. Notably, vascular production of thromboxane A2 is elevated in a number of cardiovascular disease states that promote endothelial dysfunction. This review will therefore discuss the mechanisms through which thromboxane A2 interacts with and modulates EDH, and will also consider the implications of such cross-talk in vasodilator control in health and disease.

Abstract 643: Heterozygous Endothelial Endothelin-1 Overexpression Potentiates Endothelium-Dependent Contractions in the Carotid Arteries of Obese Mice

Elevated plasma levels of the vasoconstrictor peptide endothelin-1 (ET-1) are associated with cardiovascular risk factors such as obesity, diabetes and hypertension, in which endothelium-dependent contractions are prominent. Exogenous ET-1 promotes the release of endothelium-derived contracting factors (EDCF), but the role of endogenously produced ET-1 in these processes is unknown. Therefore, mice with tie-1 promoter driven endothelium-restricted heterozygous overexpression of ppET-1 (TET+/-) and WT littermates were kept on standard chow as lean controls or administered a high fat diet for 30 weeks to induce obesity. At sacrifice, fasting glucose levels were significantly elevated in obese animals (8.3±0.3 vs. 5.3±0.2 mmol/l in lean controls, n =6, P <0.001). Isometric tension was measured in aortic and carotid arterial rings in wire myographs. In phenylephrine-contracted aortic rings, endothelium-dependent and −independent relaxations to acetylcholine and sodium nitroprusside, respectively, were unaltered between groups. In carotid arteries, the potency of phenylephrine to evoke contractions was greater in preparations from obese TET+/- mice ( pD 2 6.71±0.07 vs. lean TET+/- 6.34±0.13, n =5-6, P <0.05), whereas there was no change in the contractile response to the α 1 -adrenergic agonist by diet-induced obesity in WT littermates. The augmented EDCF responses to acetylcholine of quiescent carotid arterial rings of obese animals were further potentiated by TET+/- ( E max 51.3±1.1% vs. 40.6±1.3% KCl in WT obese, n =6, P <0.001). The production of 6-keto PGF 1α − the stable metabolite of prostacyclin − was increased significantly in preparations from obese TET+/- mice (238.4±30.0 vs. 127.0±12.7 pg/mL in obese WT littermates, n =4-6, P <0.05). In the presence of L-NAME, TP receptor activation by U46619 was more effective in obese TET+/- ( E max 151.8±5.4% vs. 126.1±4.7% KCl in WT obese, n =4-6, P <0.05). Overall, TET+/- had no effect on relaxations in obese animals, but contractile responses − EDCF-mediated ones in particular − were facilitated. The present results suggest that this is due to an increased production of vasoconstrictor prostanoids possibly combined with an augmented responsiveness of the underlying vascular smooth muscle.

Enhanced uridine adenosine tetraphosphate-induced contraction in renal artery from type 2 diabetic Goto-Kakizaki rats due to activated cyclooxygenase/thromboxane receptor axis

The dinucleotide uridine adenosine tetraphosphate (Up4A), which has both purine and pyrimidine moieties, was reported as a novel endothelium-derived contracting factor. Recently, growing evidence has suggested that Up4A plays an important role in regulation of the cardiovascular function. We previously demonstrated that Up4A-induced vasoconstrictions are altered in arteries from DOCA-salt hypertensive rats. We have assessed responses to Up4A shown by renal arteries from type 2 diabetic Goto-Kakizaki (GK) rats (42-46weeks old) and identified the molecular mechanisms involved. Concentration-dependent contractions to Up4A were greater in renal arterial rings from the GK than age-matched control Wistar group. In both groups, the inhibition of nitric oxide synthase (with N (G)-nitro-L-arginine) increased the response to Up4A, whereas the inhibition of cyclooxygenase (COX) (with indomethacin) decreased the response. Specific inhibitors of COX-1 (valeroyl salicylate) and COX-2 (NS398), a thromboxane (TX) receptor (TP) antagonist (SQ29548), and P2 receptor antagonist (suramin) also decreased the response to Up4A. Protein expressions of COXs in renal arteries were greater in the GK than Wistar group. The production of TXB2 (a metabolite of TXA2) by Up4A did not differ between these groups. Concentration-dependent contractions to U46619, an agonist of the TP receptor, were greater in renal arteries from the GK than Wistar group. The expression of P2X1 and P2Y2 receptors did not differ between these groups. These results suggest that enhancement of the Up4A-induced contraction in renal arteries from GK rats may be attributable to the increased activation of COXs/TP receptor signaling.

Uridine adenosine tetraphosphate is a novel vasodilator in the coronary microcirculation which acts through purinergic P1 but not P2 receptors

Uridine adenosine tetraphosphate (Up4A) has been identified as an endothelium-derived contracting factor, which acts through purinergic P2X and P2Y receptors. Since the coronary vascular actions of Up4A are unknown, we investigated the vasoactive profile of Up4A in coronary microvessels, and studied the involvement of purinergic receptor subtypes. Studies were performed in isolated porcine coronary small arteries (diameter∼250μm), with and without endothelial denudation, mounted on a Mulvany wire myograph. Purinergic receptor expression was assessed by real-time PCR. Up4A (10−9–10−5M) failed to induce contraction at basal tone, but produced concentration-dependent vasorelaxation in precontracted microvessels. Up4A was slightly less potent than adenosine, ATP, and ADP in producing vasorelaxation, but significantly more potent than UTP and UDP. mRNA expression of P2X4, P2Y1, P2Y2, P2Y4, P2Y6 and A2A, but not P2X1, receptors was observed. Up4A-induced vasodilation was unaffected by non-selective P2 receptor antagonist PPADS, P2X1 antagonist MRS2159, P2Y1 antagonist MRS2179 and P2Y6 antagonist MRS2578, but was markedly attenuated by non-selective P1 receptor antagonist 8PT and A2A antagonist SCH58261. Up4A-induced vasodilation was not affected by ectonucleotidase inhibitor ARL67156, suggesting that A2A stimulation was not the result of Up4A breakdown to adenosine. Up4A-induced vasodilation was blunted in denuded vessels; additional A2A receptor blockade further attenuated Up4A-induced vasodilation, suggesting that A2A receptor-mediated vasodilation is only partly endothelium-dependent. In conclusion, Up4A exerts a vasodilator rather than a vasoconstrictor influence in coronary microvessels, which is mediated via A2A receptors and is partly endothelium-dependent.

Study on the beneficial effect of dual peroxisome proliferator-activated receptor agonist WY14643 on vascular endothelium

Objective The present study aimed to determine whether or not dual paroxysm proliferator-activated receptor (PPAR) agonist,WY14643,improved the dysfunctioned vascular endothelium in hypertension by reducing endothelium-derived contracting factors ( EDCFs ),and to explore the molecular mechanism it was involved in.Methods Isometric tension in isolated thoracic aortic rings of spontaneously hypertensive rats was recorded.Endothelium-dependent contractions evoked by acetylcholine in the presence of L NAME were reduced by fenofibrate.Cyclooxygenase 1 ( COX1 ) activities were determined by analyzing the peroxidase activity of cyclooxygenase colorimetrically by using ELISA kit.Results Compared to the control group,WY14643 significantly decreased the vasoconstriction in aorta of the SHR rats(P=0.014).PPARα antagonist MK866 enhanced the vascular contractility of SHR rats that were incubated with 10.0μmol/L WY14643( P=0.021 ).PPARΥ antagonist GW9662 did not significantly affect the vascular contractility of SHR rats that were incubated with 10.0 μmol/L WY14643( P=0.061 ).The levels of serum PGFlα(P=0.012),2α( P =0.019) and TXB2(P=0.023) in SHR rats incubated with 10.0 μmol/L WY14643 were significantly lower than the control group,respectively.Under the condition of the existence of vascular endothelium,the expression of COX-1 in SHR rats incubated with WY14643 was significantly lower than that in SHR rats incubated without WY14643 (P=0.017).Conclusions Those data showed that WY14643 reduced the release of EDCFs,it suggests that WY14643 protects against vascular diseases through the PPAR activators in spontaneous hypertension. Key words: Peroxisome proliferator-activated receptors/agonists; Cyclooxygenase 1/metabolism; Endothelins/metabolism; Hypertension; Rats

Thyroid hormone affects both endothelial and vascular smooth muscle cells in rat arteries

SAR, China, Peopleˈs Republic of The effect of thyroid hormone on vascular cells is controversial. The present study investigated in isolated arteries [with and without endothelium; suspended for isometric tension measurement] whether or not thyroid hormone causes relaxations in, or alleviates endothelial dysfunction in diabetic animals.Triiodothyronine, (T3) did not relax aortae of control rats with or without endothelium but caused endothelium‐independent decreases in tension in mesenteric arteries, suggesting an endothelium‐independent vasodilator effect of the hormone.In femoral arteries of rats with streptozotocin‐induced Type 1 diabetes, A23187 caused the release of endothelium‐derived contracting factors (EDCF). After four weeks of chronic treatment with T3, the contractions to A23187 of preparations with endothelium were unchanged, but those without endothelium were augmented, suggesting that the release of EDCF was reduced. Thus, thyroid hormone affects both endothelial and vascular smooth muscle cells in rat arteries.

Reduction of contractions to phenylephrine by L‐NAME in the carotid artery of mice with endothelial overexpression of endothelin‐1

The release of endothelium‐derived contracting factors (EDCF) is increased by exogenous endothelin‐1 (ET‐1). Experiments were designed to determine whether or not endothelial overexpression of ET‐1 affects vascular responsiveness. Carotid artery rings with endothelium of control mice and mice with endothelial overexpression of ET‐1 (TET‐1) were contracted with the α1‐adrenoceptor agonist phenylephrine in the absence or presence of the eNOS inhibitor L‐NAME and exposed to acetylcholine. After washout, the rings were contracted with increasing concentrations of the TP receptor agonist U46619. EDCF‐mediated increases in tension caused by acetylcholine were augmented in TET‐1 arteries compared to controls both in the absence and presence of LNAME. In the presence of the latter, TET‐1 rings showed stronger contractions to U46619 than controls. By contrast, contractions to phenylephrine were reduced by L‐NAME in TET‐1 arteries with a rightward shift and loss of the sigmoidal shape of the concentration‐response curve. These results imply a role of endothelial ET‐1 in EDCF‐mediated contractions and indicate an increased TXA2 receptor signaling in vascular smooth muscle cells. They do not provide an explanation for the decreased response to α1‐adrenergic activation in TET‐1 arteries in the absence of NO. Sponsored by the Swiss National Science Foundation and the Hong Kong Research Grant Council.