COUNTERVAILING VASCULAR EFFECTS OF ROSIGLITAZONE IN HIGH CARDIOVASCULAR RISK MICE: ROLE OF OXIDATIVE STRESS AND PRMT-1.

In the present study, we tested the hypothesis that the PPARgamma (peroxisome-proliferator-activated receptor gamma) activator rosiglitazone improves vascular structure and function in aged hyperhomocysteinaemic MTHFR (methylene tetrahydrofolate reductase) gene heterozygous knockout (mthfr+/-) mice fed a HCD (high-cholesterol diet), a model of high cardiovascular risk. One-year-old mthfr+/- mice were fed or not HCD (6 mg x kg-1 of body weight x day-1) and treated or not with rosiglitazone (20 mg x kg-1 of body weight x day-1) for 90 days and compared with wild-type mice. Endothelium-dependent relaxation of carotid arteries was significantly impaired (-40%) only in rosiglitazone-treated HCD-fed mthfr+/- mice. Carotid M/L (media-to-lumen ratio) and CSA (cross-sectional area) were increased (2-fold) in mthfr+/- mice fed or not HCD compared with wild-type mice (P<0.05). Rosiglitazone reduced M/L and CSA only in mthfr+/- mice fed a normal diet. Superoxide production was increased in mthfr+/- mice fed HCD treated or not with rosiglitazone, whereas plasma nitrite was decreased by rosiglitazone in mice fed or not HCD. PRMT-1 (protein arginine methyltransferase-1), involved in synthesis of the NO (nitric oxide) synthase inhibitor ADMA (asymmetric omega-NG,NG-dimethylarginine), and ADMA were increased only in rosiglitazone-treated HCD-fed mthfr+/- mice. Rosiglitazone had both beneficial and deleterious vascular effects in this animal model of high cardiovascular risk: it prevented carotid remodelling, but impaired endothelial function in part through enhanced oxidative stress and increased ADMA production in mice at high cardiovascular risk

Defective peroxisomal proliferators activated receptor gamma activity due to dominant-negative mutation synergizes with hypertension to accelerate cardiac fibrosis in mice

Aims Humans with inactivating mutations in peroxisomal proliferators activated receptor gamma (PPARγ) typically develop a complex metabolic syndrome characterized by insulin resistance, diabetes, lipodystrophy, hypertension, and dyslipidaemia which is likely to increase their cardiovascular risk. Despite evidence that the activation of PPARγ may prevent cardiac fibrosis and hypertrophy, recent evidence has suggested that pharmacological activation of PPARγ causes increased cardiovascular mortality. In this study, we investigated the effects of defective PPARγ function on the development of cardiac fibrosis and hypertrophy in a murine model carrying a human dominant‐negative mutation in PPARγ. Methods and results Mice with a dominant‐negative point mutation in PPARγ (P465L) and their wild‐type (WT) littermates were treated with either subcutaneous angiotensin II (AngII) infusion or saline for 2 weeks. Heterozygous P465L and WT mice developed a similar increase in systolic blood pressure, but the mutant mice developed significantly more severe cardiac fibrosis to AngII that correlated with increased expression of profibrotic genes. Both groups similarly increased the heart weight to body weight ratio compared with saline‐treated controls. There were no differences in fibrosis between saline‐treated WT and P465L mice. Conclusion These results show synergistic pathogenic effects between the presence of defective PPARγ and AngII‐induced hypertension and suggest that patients with PPARγ mutation and hypertension may need more aggressive therapeutic measures to reduce the risk of accelerated cardiac fibrosis

食道扁平上皮癌におきてエンドセリンB受容体の高発現は腫瘍の血管新生と予後に関与する

BACKGROUND:The endothelin axis has been shown to have a pivotal role in several human malignancies. The aim of this study was to clarify the clinical importance of endothelin receptor type B (ETBR) in human oesophageal squamous cell carcinoma (OSCC). METHODS:We evaluated ETBR expression in 107 patients with OSCC by immunohistochemistry. Microvessel density (MVD) and lymphatic vessel density were assessed by CD31 and D2-40 immunostaining, respectively. Furthermore, CD4, CD8, and CD45RO+ tumour-infiltrating lymphocytes (TILs) were immunohistochemically analysed.RESULTS:Sixty-one (57%) cases showed high expression of ETBR. Endothelin receptor type B expression was correlated with several clinicopathological factors including tumour differentiation, tumour depth, and lymph node metastasis. The overall and disease-specific survival rates were significantly lower in patients with high ETBR expression than patients with low expression. Furthermore, multivariate analysis revealed that ETBR status was an independent prognostic factor for patient survival. Mechanistic analysis indicated that MVD was significantly higher in tumour tissues with high ETBR expression compared with those with low expression, suggesting that angiogenesis may be a key mechanism in tumour progression and metastasis of OSCC mediated by ETBR expression. By contrast, there were no significant correlations between TILs and ETBR expression.CONCLUSION: Endothelin receptor type B has a pivotal role in oesophageal cancer and may be therapeutic target for this intractable malignancy.博士（医学）・乙第1336号・平成26年5月28

Effect of Cyclosporine and Rifampin on the Pharmacokinetics of Macitentan, a Tissue-Targeting Dual Endothelin Receptor Antagonist

Macitentan is a dual endothelin receptor antagonist under phase 3 investigation in pulmonary arterial hypertension. We investigated the effect of cyclosporine (Cs) and rifampin on the pharmacokinetics of macitentan and its metabolites ACT-132577 and ACT-373898 in healthy male subjects. In addition, in vitro studies were performed to investigate interactions between macitentan and its active metabolite ACT-132577 with human organic anion-transporting polypeptides (OATPs). The clinical study (AC-055-111) was conducted as a two-part, one-sequence, crossover study. Ten subjects in each part received multiple-dose macitentan followed by multiple-dose co-administration of Cs (part A) or rifampin (part B). In the presence of Cs, steady-state area under the plasma concentration–time profiles during a dose interval (AUCτ) for macitentan and ACT-373898 increased 10% and 7%, respectively, and decreased 3% for ACT-132577. Steady-state AUCτ of macitentan and ACT-373898 in the presence of rifampin decreased 79% and 64%, respectively. For ACT-132577, no relevant difference in AUCτ between the two treatments was observed. Macitentan co-administered with Cs or rifampin was well tolerated. The complementary in vitro studies demonstrated no marked differences in uptake rates of macitentan and ACT-132577 between the wild-type and OATP over-expressing cells over the concentration range tested. Concomitant treatment with Cs did not have any clinically relevant effect on the exposure to macitentan or its metabolites, at steady-state. Concomitant treatment with rifampin reduced significantly the exposure to macitentan and its metabolite ACT-373898 at steady-state but did not affect the exposure to the active metabolite ACT-132577 to a clinically relevant extent

The Epidermal Growth Factor Receptor Is Involved in Angiotensin II But Not Aldosterone/Salt-Induced Cardiac Remodelling

Experimental and clinical studies have shown that aldosterone/mineralocorticoid receptor (MR) activation has deleterious effects in the cardiovascular system; however, the signalling pathways involved in the pathophysiological effects of aldosterone/MR in vivo are not fully understood. Several in vitro studies suggest that Epidermal Growth Factor Receptor (EGFR) plays a role in the cardiovascular effects of aldosterone. This hypothesis remains to be demonstrated in vivo. To investigate this question, we analyzed the molecular and functional consequences of aldosterone exposure in a transgenic mouse model with constitutive cardiomyocyte-specific overexpression of a mutant EGFR acting as a dominant negative protein (DN-EGFR). As previously reported, Angiotensin II-mediated cardiac remodelling was prevented in DN-EGFR mice. However, when chronic MR activation was induced by aldosterone-salt-uninephrectomy, cardiac hypertrophy was similar between control littermates and DN-EGFR. In the same way, mRNA expression of markers of cardiac remodelling such as ANF, BNF or β-Myosin Heavy Chain as well as Collagen 1a and 3a was similarly induced in DN-EGFR mice and their CT littermates. Our findings confirm the role of EGFR in AngII mediated cardiac hypertrophy, and highlight that EGFR is not involved in vivo in the damaging effects of aldosterone on cardiac function and remodelling

Treprostinil increases the number and angiogenic potential of endothelial progenitor cells in children with pulmonary hypertension

Background Pulmonary vasodilators in general and prostacyclin therapy in particular, have markedly improved the outcome of patients with pulmonary arterial hypertension (PAH). As endothelial dysfunction is a key feature of PAH, and as endothelial progenitor cells (EPC) may contribute to vascular repair in PAH, we suspected that prostacyclin therapy might enhance EPC numbers and functions. In the present study, objectives were to determine whether EPC may contribute to vasodilator treatment efficacy in PAH. Methods We quantified CD34+ cells, CFU-Hill and ECFC (endothelial colony forming cells) in peripheral blood from children with idiopathic PAH (n = 27) or PAH secondary to congenital heart disease (n = 52). CD34+ were enumerated by flow cytometry, CFU-Hill and ECFC by a culture assay. ECFC grown ex vivo were tested for their angiogenic capacities before and after prostacyclin analog therapy (subcutaneous treprostinil). Results ECFC counts were significantly enhanced in the 8 children treated with treprostinil, while no change was observed in children receiving oral therapy with endothelin antagonists and/or PDE5 inhibitors. CD34+ cell and CFU-Hill counts were unaffected. ECFC from patients treated with treprostinil had a hyperproliferative phenotype and showed enhanced angiogenic potential in a nude mouse preclinical model of limb ischemia. Conclusions ECFC may partly mediate the clinical benefits of prostanoids in pulmonary arterial hypertension

Transgenic Mice Over-Expressing ET-1 in the Endothelial Cells Develop Systemic Hypertension with Altered Vascular Reactivity

Endothelin-1 (ET-1) is a potent vasoconstrictor involved in the regulation of vascular tone and implicated in hypertension. However, the role of small blood vessels endothelial ET-1 in hypertension remains unclear. The present study investigated the effect of chronic over-expression of endothelial ET-1 on arterial blood pressure and vascular reactivity using transgenic mice approach. Transgenic mice (TET-1) with endothelial ET-1 over-expression showed increased in ET-1 level in the endothelial cells of small pulmonary blood vessels. Although TET-1 mice appeared normal, they developed mild hypertension which was normalized by the ETA receptor (BQ123) but not by ETB receptor (BQ788) antagonist. Tail-cuff measurements showed a significant elevation of systolic and mean blood pressure in conscious TET-1 mice. The mice also exhibited left ventricular hypertrophy and left axis deviation in electrocardiogram, suggesting an increased peripheral resistance. The ionic concentrations in the urine and serum were normal in 8-week old TET-1 mice, indicating that the systemic hypertension was independent of renal function, although, higher serum urea levels suggested the occurrence of kidney dysfunction. The vascular reactivity of the aorta and the mesenteric artery was altered in the TET-1 mice indicating that chronic endothelial ET-1 up-regulation leads to vascular tone imbalance in both conduit and resistance arteries. These findings provide evidence for the role of spatial expression of ET-1 in the endothelium contributing to mild hypertension was mediated by ETA receptors. The results also suggest that chronic endothelial ET-1 over-expression affects both cardiac and vascular functions, which, at least in part, causes blood pressure elevation

Pressure Load: The Main Factor for Altered Gene Expression in Right Ventricular Hypertrophy in Chronic Hypoxic Rats

BACKGROUND: The present study investigated whether changes in gene expression in the right ventricle following pulmonary hypertension can be attributed to hypoxia or pressure loading. METHODOLOGY/PRINCIPAL FINDINGS: To distinguish hypoxia from pressure-induced alterations, a group of rats underwent banding of the pulmonary trunk (PTB), sham operation, or the rats were exposed to normoxia or chronic, hypobaric hypoxia. Pressure measurements were performed and the right ventricle was analyzed by Affymetrix GeneChip, and selected genes were confirmed by quantitative PCR and immunoblotting. Right ventricular systolic blood pressure and right ventricle to body weight ratio were elevated in the PTB and the hypoxic rats. Expression of the same 172 genes was altered in the chronic hypoxic and PTB rats. Thus, gene expression of enzymes participating in fatty acid oxidation and the glycerol channel were downregulated. mRNA expression of aquaporin 7 was downregulated, but this was not the case for the protein expression. In contrast, monoamine oxidase A and tissue transglutaminase were upregulated both at gene and protein levels. 11 genes (e.g. insulin-like growth factor binding protein) were upregulated in the PTB experiment and downregulated in the hypoxic experiment, and 3 genes (e.g. c-kit tyrosine kinase) were downregulated in the PTB and upregulated in the hypoxic experiment. CONCLUSION/SIGNIFICANCE: Pressure load of the right ventricle induces a marked shift in the gene expression, which in case of the metabolic genes appears compensated at the protein level, while both expression of genes and proteins of importance for myocardial function and remodelling are altered by the increased pressure load of the right ventricle. These findings imply that treatment of pulmonary hypertension should also aim at reducing right ventricular pressure