Kana Maruyama

Disturbance of vasodilation via protease-activated receptor 2 in SHRSP.Z-Leprfa/IzmDmcr rats with metabolic syndrome

Protease-activated receptor-2 (PAR2) activation causes vascular inflammation and vasodilation, but its role in metabolic syndrome (MetS) remains uncertain. Therefore, we examined whether the PAR2-induced vasodilation of SHRSP.Z-Lepr(fa)/IzmDmcr rats (SHRSP.ZF) is impaired and if so, whether administering telmisartan is protective. PAR2-activating peptide, 2-furoyl-LIGRLO-amide (2fly), relaxed the isolated superior and first-order branches of mesenteric arteries (MAs) from Wistar-Kyoto rats (WKY) and SHRSP.ZF. Superior-MA relaxation by 2fly was less in SHRSP.ZF than in WKY. Relaxation of first-order MAs by 2fly was the same in SHRSP.ZF and WKY. NO synthase inhibitor partially reduced 2fly-induced relaxation of superior and first-order MAs in SHRSP.ZF and WKY; inhibition of relaxation was proportionately larger in SHRSP.ZF. In SHRSP.ZF, nitroprusside-induced relaxation and the expression of soluble guanylyl cyclase decreased. In SHRSP.ZF, telmisartan reversed these abnormalities, and decreased blood pressure and serum levels of thiobarbituric acid reactive substances, an index of oxidative stress. Vasodilation via PAR2 activation was preserved in small-caliber MAs, in contrast to large-caliber MAs, even when MetS reduced NO-dependent relaxation mechanisms. NO and non-NO relaxing factor(s) contributed to PAR2-mediated relaxation in MAs, and the balance between factors may be altered to preserve vasodilation in MetS. Telmisartan prevented vascular dysfunction in MetS by protecting arteries against oxidative stress.

Chronic oxidative-nitrosative stress impairs coronary vasodilation in metabolic syndrome model rats

Metabolic syndrome (MetS) is a combination of clinical disorders that together increase the risk for cardiovascular disease and diabetes. SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP.ZF) rats with MetS show impaired nitric oxide-mediated relaxation in coronary and mesenteric arteries, and angiotensin II receptor type 1 blockers protect against dysfunction and oxidative-nitrosative stress independently of metabolic effects. We hypothesize that superoxide contributes to functional deterioration in SHRSP.ZF rats. To test our hypothesis, we studied effects of treatment with tempol, a membrane-permeable radical scavenger, on impaired vasodilation in SHRSP.ZF rats. Tempol did not alter body weight, high blood pressure, or metabolic abnormalities, but prevented impairment of acetylcholine-induced and nitroprusside-induced vasodilation in the coronary and mesenteric arteries. Furthermore, tempol reduced the levels of serum thiobarbituric acid reactive substance (TBARS) and 3-nitrotyrosine content in mesenteric arteries. Systemic administration of tempol elevated the expression of soluble guanylate cyclase (sGC) above basal levels in mesenteric arteries of SHRSP.ZF rats. However, acute treatment with tempol or ebselen, a peroxynitrite scavenger, did not ameliorate impaired relaxation of isolated mesenteric arteries. No nitration of tyrosine residues in sGC was observed; however, sGC mRNA expression levels in the arteries of SHRSP.ZF rats were lower than those in the arteries of Wistar-Kyoto rats. Levels of Thr(496)- and Ser(1177)-phosphorylated endothelial nitric oxide synthase (eNOS) were lower in arteries of SHRSP.ZF rats, and acetylcholine decreased Thr(496)-phosphorylated eNOS levels. These results indicated that prolonged superoxide production, leading to oxidative-nitrosative stress, was associated with impaired vasodilation in SHRSP.ZF rats with MetS. Down-regulated sGC expression may be linked to dysfunction, while reduced NO bioavailability/eNOS activity and modified sGC activity due to superoxide production were excluded as pivotal mechanisms.

Characterization and Functions of Protease-Activated Receptor 2 in Obesity, Diabetes, and Metabolic Syndrome: A Systematic Review

Proteinase-activated receptor 2 (PAR2) is a cell surface receptor activated by serine proteinases or specific synthetic compounds. Interest in PAR2 as a pharmaceutical target for various diseases is increasing. Here we asked two questions relevant to endothelial dysfunction and diabetes: How is PAR2 function affected in blood vessels? What role does PAR2 have in promoting obesity, diabetes, and/or metabolic syndrome, specifically via the endothelium and adipose tissues? We conducted a systematic review of the published literature in PubMed and Scopus (July 2015; search terms: par2, par-2, f2lr1, adipose, obesity, diabetes, and metabolic syndrome). Seven studies focused on PAR2 and vascular function. The obesity, diabetes, or metabolic syndrome animal models differed amongst studies, but each reported that PAR2-mediated vasodilator actions were preserved in the face of endothelial dysfunction. The remaining studies focused on nonvascular functions and provided evidence supporting the concept that PAR2 activation promoted obesity. Key studies showed that PAR2 activation regulated cellular metabolism, and PAR2 antagonists inhibited adipose gain and metabolic dysfunction in rats. We conclude that PAR2 antagonists for treatment of obesity indeed show early promise as a therapeutic strategy; however, endothelial-specific PAR2 functions, which may offset mechanisms that produce vascular dysfunction in diabetes, warrant additional study.

A maternal high salt diet disturbs cardiac and vascular function of offspring

AIMS High salt intake is an environmental factor that promotes increased blood pressure. We previously demonstrated that high salt diet causes aggravation of hypertension and impaired vasodilation in response to nitric oxide (NO) in young spontaneously hypertensive rats (SHR), which exhibit low sensitivity to salt in adulthood. Changes in offspring blood pressure and cardiovascular structures have been reported. However, it remains unclear to what extent a maternal high salt intake may affect cardiac and/or vascular function in offspring. Therefore, we investigated influence of exposure to a maternal high salt diet during gestation and lactation on offsprings cardiac and arterial functions in SHR. MAIN METHODS SHR dams were fed either a high salt diet or a control diet. After weaning, the offspring were fed the high salt diet or control diet for 8weeks. KEY FINDINGS Compared with offspring of control diet-fed dams, at 12weeks of age, offspring of the high-salt diet-fed dams had lower blood pressure, heart rate, indices of both left ventricular systolic and diastolic function, and a decreased aortic vasodilation response to NO. Postnatal high salt intake did not affect blood pressure, vasodilatory response, or cardiac function in offspring of high-salt diet-fed dams. Neither maternal nor postnatal dietary salt altered levels of lipid peroxide, superoxide dismutase, or angiotensinogen mRNA in serum and ventricle of the offspring. SIGNIFICANCE Exposure to high maternal dietary salt induces cardiac and vascular dysfunction in offspring. These results point to the possible importance of avoiding excess dietary salt during gestation and lactation.

Panax notoginseng saponins ameliorate impaired arterial vasodilation in SHRSP.Z‐Leprfa/lzmDmcr rats with metabolic syndrome

Panax notoginseng saponins (PNS) are major components of Panax notoginseng, a herb with established clinical efficacy against vascular diseases. SHRSP.Z‐Leprfa/IzmDmcr (SHRSP.ZF) rats, a new animal model for metabolic syndrome, display an impaired vasorelaxation response in aortas and mesenteric arteries that is mediated by nitric oxide (NO). This study investigated whether PNS and its components can ameliorate this vascular dysfunction in SHRSP.ZF rats. In an in vitro study, in the presence or absence of PNS and its components, vasodilation in response to nitroprusside was determined from myographs under isometric tension conditions in aortas and mesenteric arteries from male SHRSP.ZF rats at 18–20 weeks of age. In an in vivo study, PNS (30 mg/kg per day) was orally administered to SHRSP.ZF rats from 8 to 20 weeks of age. In vitro treatment with PNS and Ginsenoside Rb1 increased nitroprusside‐induced relaxation of aortas and mesenteric arteries in SHRSP.ZF rats. The PNS‐induced increase was not affected by a nitric oxide (NO) synthase inhibitor or endothelium denudation. Relaxation in response to a cell‐permeable cGMP analogue was increased by PNS, but cGMP accumulation by nitroprusside was not altered. In vivo treatment with PNS in SHRSP.ZF rats lowered blood pressure and increased relaxation and the expression of soluble guanylyl cyclase protein in arteries, without affecting metabolic abnormalities. These results indicate that PNS causes an increase in vasodilation in response to NO and a decrease in blood pressure, resulting in protection against vascular dysfunction in SHRSP.ZF rats. PNS might be beneficial in alleviating impaired vasodilation in metabolic syndrome.

Enhanced Nitric Oxide Synthase Activation via Protease-Activated Receptor 2 Is Involved in the Preserved Vasodilation in Aortas from Metabolic Syndrome Rats

Endothelium-dependent vasodilation via protease-activated receptor 2 (PAR2) is preserved in mesenteric arteries from SHRSP.Z-Leprfa/IzmDmcr rats (SHRSP.ZF) with metabolic syndrome even though nitric oxide (NO)-mediated vasodilation is attenuated. Therefore, we examined the PAR2 mechanisms underlying metabolic syndrome-resistant vasodilation in SHRSP.ZF aortas with ageing. In isolated aortas, the PAR2 agonist 2-furoyl-LIGRLO-amide (2fly) caused vasodilation that was sustained in male SHRSP.ZF until 18 weeks of age, but was attenuated afterwards compared with age-matched Wistar-Kyoto rats (controls) at 23 weeks. In contrast, acetylcholine-induced vasodilation was impaired in SHRSP.ZF already at 18 weeks of age. Treatments of aortas with inhibitors of NO synthase and soluble guanylate cyclase abolished the sustained 2fly- and residual acetylcholine-induced vasodilation in SHRSP.ZF at 18 weeks of age. In the aortas of SHRSP.ZF, 8-bromo-cGMP-induced vasodilation, NO production and cGMP accumulation elicited by 2fly were not different from in the controls. PAR2 agonist increased phospho-Ser1177-eNOS protein content only in SHRSP.ZF aortas. These results indicate that vasodilation mediated by PAR2 is sustained even though NO-dependent relaxation is attenuated with ageing/exposure to metabolic disorders in large-caliber arteries from SHRSP.ZF. PAR2 stimulation of NO production via an additional pathway that targets phosphorylation of Ser1177-eNOS suggests a regulatory mechanism for sustaining agonist-mediated vasodilation in metabolic syndrome.

Functional Relationship between Arterial Tissue and Perivascular Adipose Tissue in Metabolic Syndrome.

Metabolic syndrome is a complex of disorders that includes visceral obesity, insulin resistance, hypertension, and dyslipidemia. It is characterized by an increased risk for serious cardiovascular events. Adipocytes are now recognized to contribute to the development of cardiovascular complications in metabolic syndrome via the release of several bioactive substances (adipocytokines). Obesity induces an increase in the volume of perivascular adipose tissue (PVAT), which is located outside the blood vessels. In recent years, PVAT has been reported to produce/release vasoactive adipocytokines. Thus, PVAT can modulate vasomotor function by releasing vasorelaxing/vasocontracting factors, resulting in the development of cardiovascular disease due to metabolic syndrome. By using animal models (SHR/NDmcr-cp rats, SHRSP.Z-Lepr(fa)/IzmDmcr rats, and B6.BKS (D)-Lepr(fa)/J mice), we have demonstrated that chronic oxidative-nitrative stress is closely linked to the development of vascular dysfunction in response to nitric oxide (NO) in resistant arteries with increasing age/exposure to metabolic abnormalities. Further, our recent findings have led us to believe that PVAT helps in the regulation of vasodilation to compensate for the impaired vasodilation observed in pathophysiological conditions in the mesenteric arteries of SHRSP.Z-Lepr(fa)/IzmDmcr rats. However, a breakdown of the compensatory system occurs with long-term exposure to metabolic abnormalities. We propose the concept of the functional regulation of vascular tissue by PVAT in metabolic syndrome.

Age-related changes to vascular protease-activated receptor 2 in metabolic syndrome: A relationship between oxidative stress, receptor expression and endothelium-dependent vasodilation.

Protease-activated receptor 2 (PAR2) is expressed in vascular endothelium. Nitric oxide (NO) - cyclic GMP-mediated vasodilation in response to 2-furoyl-LIGRLO-amide (2fLIGRLO), a PAR2-activating peptide, is impaired in aortas from aged SHRSP.Z-Leprfa/IzmDmcr (SHRSP.ZF) rats with metabolic syndrome. Here we investigated mechanisms linking PAR2s vascular effects to phenotypic characteristics of male SHRSP.ZF rats at 10, 20, and 30 weeks of age. We found vasodilation responses to either 2fLIGRLO or enzyme-mediated PAR2 activation by trypsin were sustained until 20 weeks and lessened at 30 weeks. PAR2 protein and mRNA levels were lower in aortas at 30 weeks than at 10 and 20 weeks. PAR2-mediated responses positively correlated with PAR2 protein and mRNA levels. Decreased cGMP accumulation in the presence of 2fLIGRLO paralleled the decreased relaxations elicited by nitroprusside and the cGMP analog 8-pCPT-cGMP, and the less soluble guanylyl cyclase protein at 30 weeks. 2fLIGRLO-induced relaxation was negatively correlated with serum thiobarbituric acid reactive substances, an index of oxidative stress, which increased with age. Forward stepwise data regression supported a model of age-related decreases in PAR2 function resulting from decreased PAR2 mRNA and increased oxidative stress. We conclude that decreased responsiveness of aortic smooth muscle to NO and downregulation of receptor expression impair PAR2 functions at later stages of metabolic syndrome in SHRSP.ZF rats.

Abnormal amounts of intracellular calcium regulatory proteins in SHRSP.Z-Leprfa/IzmDmcr rats with metabolic syndrome and cardiac dysfunction

Metabolic syndrome is known to increase the risk of abnormal cardiac structure and function, which are considered to contribute to increased incidence of cardiovascular disease and mortality. We previously demonstrated that ventricular hypertrophy and diastolic dysfunction occur in SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP fatty) rats with metabolic syndrome. The aim of this study was to investigate the possible mechanisms underlying abnormal heart function in SHRSP fatty rats. The amount of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) 2a, phospholamban (PLB) protein, and Ser(16)-phosphorylated PLB was decreased in cardiomyocytes from SHRSP fatty rats compared with those from control Wistar-Kyoto rats at 18 weeks of age, and the PLB-to-SERCA2a ratio was increased. Left ventricular developed pressure was unchanged, and coronary flow rate and maximum rate of left ventricular pressure decline (-dP/dt) was decreased in SHRSP fatty rats. Treatment with telmisartan reversed the abnormalities of PLB amount, coronary flow rate, and -dP/dt in SHRSP fatty rats. These results indicate that abnormal amounts of intracellular Ca(2+) regulatory proteins in cardiomyocytes, leading to reduced intracellular Ca(2+) reuptake into the sarcoplasmic reticulum, may play a role in the diastolic dysfunction in SHRSP fatty rats and that these effects are partially related to decreased coronary circulation. Telmisartan may be beneficial in protecting against disturbances in cardiac function associated with metabolic syndrome.

Royal jelly increases peripheral circulation by inducing vasorelaxation through nitric oxide production under healthy conditions

AIMS Royal jelly (RJ) has a variety of reported biological activities, including vasorelaxation and blood pressure-lowering effects. Although functional foods are positively used for health, the effects of RJ on the cardiovascular system in healthy individuals have not been well studied. Therefore, we investigated the mechanisms underlying the vasorelaxation effects of RJ in healthy control rats to evaluate whether the peripheral circulation was increased. MAIN METHODS We used fresh RJ to examine the vasorelaxation effects and related mechanisms in Wistar rats using organ bath techniques. Furthermore, we measured changes in tail blood circulation, systolic blood pressure (sBP), and heart rate (HR) after the oral administration of RJ to control rats and nitro-l-arginine methyl ester (l-NAME)-treated rats (0.5 mg/ml dissolved in distilled drinking water for 1 week). Concentrations of acetylcholine (ACh) in the RJ were measured using a commercial kit. KEY FINDINGS RJ caused vasorelaxation of isolated rat aortas and superior mesenteric arteries, and this effect was inhibited by atropine (10-5 M, 15 min) or L-NAME (10-4 M, 20 min) and endothelium-denuded arterial ring preparations. Oral RJ increased tail blood flow and mass in control rats 1 h after treatment without affecting velocity, sBP, or HR. These effects were not observed in L-NAME-treated rats. RJ contained approximately 1000 μg/g of ACh. SIGNIFICANCE The present study demonstrated that RJ is composed of muscarinic receptor agonist(s), likely ACh, and induces vasorelaxation through nitric oxide (NO) production from the vascular endothelium of healthy rats, leading to increased tail blood circulation. Thus, fresh RJ may improve peripheral circulation in healthy individuals.