O-28: Molecular basis for the insurmountable AT-1 receptor antagonism of telmisartan

In vitro studies have shown that telmisartan is an insurmountable angiotensin II AT-1 receptor antagonist. In this study we have investigated the molecular basis of this insurmountable antagonism. The association and dissociation kinetics of telmisartan to angiotensin AT-1 receptors were measured using an in vitro radio-receptor binding assay. These radioligand binding studies were conducted either directly on rat vascular (aorta) smooth muscle cells (RVSMC) expressing solely the AT-1 receptor or on membrane preparation obtained from the same cells. The specific binding of3H-telmisartan to the surface of living RVSMC or membranes was saturable. From these data, a Kd value of 1.7 nM was estimated. Scatchard analysis of the3H-telmisartan binding on RVSMC indicated the existence of a single class of binding sites. The affinity of telmisartan for AT-1 receptor is only poorly affected by the presence of proteins (0.4% of rat plasma proteins) in the binding buffer, indicating that no great competition between telmisartan binding to its specific AT-1 receptor and to non-specific proteins binding sites occurs. In association experiments, the specific binding of3H-telmisartan increases quickly and reaches equilibrium within less than 1 hour, with an association rate constant calculated to be 0.006 min-1nM-1. Telmisartan dissociates very slowly from the AT-1 receptor, either in RVSMC membrane preparation or in living cells with a dissociation rate constant of ca. 0.01 min-1 resulting in a dissociation half-life (t1/2) of about 60 min, which is comparable to the previously published data for candesartan in bovine adrenal cortical membranes and almost 5 times slower than that of 125I-angiotensin II binding (t1/2=12 min). In contrast to candesartan that has been shown to re-associate with the AT-1 receptor, telmisartan does not appear to re-associate. Indeed, when the dissociation of labeled-telmisartan from AT-1 receptors was induced by washing the cells with cold-binding buffer, followed by addition of fresh binding buffer containing either cold telmisartan, Ang II or losartan, or nothing, no difference were observed in the dissociation rate constants measured with telmisartan whatever the composition of the binding buffer after removal of labeled-telmisartan. In conclusion, these results suggest that the insurmountable antagonism of telmisartan is due mainly to its very slow dissociation from angiotensin AT-1 receptor

De « l’excellence » territoriale en général et en particulier. Les campus des métiers et des qualifications de l’action « Territoires d’innovation pédagogique »

Introduction Créé dans le cadre de la Loi d’orientation et de programmation pour la refondation de l’École de la République du 8 juillet 2013, le campus des métiers et des qualifications (CMQ) est un label qui, selon la définition du ministère de l’Éducation nationale, « permet d'identifier, sur un territoire donné, un réseau d'acteurs qui interviennent en partenariat pour développer une large gamme de formations professionnelles, technologiques et générales, relevant de l'enseignement second..

Assessment of angiotensin II receptor blockade in humans using a standardized angiotensin II receptor-binding assay

An in vitro angiotensin II (AngII) receptor-binding assay was developed to monitor the degree of receptor blockade in standardized conditions. This in vitro method was validated by comparing its results with those obtained in vivo with the injection of exogenous AngII and the measurement of the AngII-induced changes in systolic blood pressure. For this purpose, 12 normotensive subjects were enrolled in a double-blind, four-way cross-over study comparing the AngII receptor blockade induced by a single oral dose of losartan (50 mg), valsartan (80 mg), irbesartan (150 mg), and placebo. A significant linear relationship between the two methods was found (r = 0.723, n = 191, P < .001). However, there exists a wide scatter of the in vivo data in the absence of active AngII receptor blockade. Thus, the relationship between the two methods is markedly improved (r = 0.87, n = 47, P < .001) when only measurements done 4 h after administration of the drugs are considered (maximal antagonist activity observed in vivo) suggesting that the two methods are equally effective in assessing the degree of AT-1 receptor blockade, but with a greatly reduced variability in the in vitro assay. In addition, the pharmacokinetic/pharmacodynamic analysis performed with the three antagonists suggest that the AT-1 receptor-binding assay works as a bioassay that integrates the antagonistic property of all active drug components of the plasma. This standardized in vitro-binding assay represents a simple, reproducible, and precise tool to characterize the pharmacodynamic profile of AngII receptor antagonists in human

Digging deeper into lymphatic vessel formation in vitro and in vivo

Background Abnormal lymphatic vessel formation (lymphangiogenesis) is associated with different pathologies such as cancer, lymphedema, psoriasis and graft rejection. Lymphatic vasculature displays distinctive features than blood vasculature, and mechanisms underlying the formation of new lymphatic vessels during physiological and pathological processes are still poorly documented. Most studies on lymphatic vessel formation are focused on organism development rather than lymphangiogenic events occurring in adults. We have here studied lymphatic vessel formation in two in vivo models of pathological lymphangiogenesis (corneal assay and lymphangioma). These data have been confronted to those generated in the recently set up in vitro model of lymphatic ring assay. Ultrastructural analyses through Transmission Electron Microscopy (TEM) were performed to investigate tube morphogenesis, an important differentiating process observed during endothelial cell organization into capillary structures

Does Plasminogen Activator Inhibitor-1 Drive Lymphangiogenesis?

The purpose of this study is to explore the function of plasminogen activator inhibitor-1 (PAI-1) during pathological lymphangiogenesis. PAI-1, the main physiological inhibitor of plasminogen activators is involved in pathological angiogenesis at least by controlling extracellular proteolysis and by regulating endothelial cell survival and migration. Protease system's role in lymphangiogenesis is unknown yet. Thus, based on its important pro-angiogenic effect, we hypothesized that PAI-1 may regulate lymphangiogenesis associated at least with metastatic dissemination of cancer cells. To address this issue, we studied the impact of PAI-1 deficiency in various murine models of tumoral lymphangiogenesis. Wild-type PAI-1 proficient mice were used as controls. We provide for the first time evidence that PAI-1 is dispensable for tumoral lymphangiogenesis associated with breast cancers either induced by mammary carcinoma cell injection or spontaneously appearing in transgenic mice expressing the polyomavirus middle T antigen (PymT) under the control of a mouse mammary tumor virus long-terminal repeat promoter (MMTV-LTR). We also investigated inflammation-related lymphatic vessel recruitment by using two inflammatory models. PAI-1 deficiency did neither affect the development of lymphangioma nor burn-induced corneal lymphangiogenesis. These novel data suggest that vascular remodelling associated with lymphangiogenesis and angiogenesis involve different molecular determinants. PAI-1 does not appear as a potential therapeutic target to counteract pathological lymphangiogenesis

Higher sensitivity of Adamts12-deficient mice to tumor growth and angiogenesis.

ADAMTS (a disintegrin and metalloproteinase domain with thrombospondin motifs) constitute a family of endopeptidases related to matrix metalloproteinases. These proteases have been largely implicated in tissue remodeling and angiogenesis associated with physiological and pathological processes. To elucidate the in vivo functions of ADAMTS-12, we have generated a knockout mouse strain (Adamts12−/−) in which Adamts12 gene was deleted. The mutant mice had normal gestations and no apparent defects in growth, life span and fertility. By applying three different in vivo models of angiogenesis (malignant keratinocyte transplantation, Matrigel plug and aortic ring assays) to Adamts12−/− mice, we provide evidence for a protective effect of this host enzyme toward angiogenesis and cancer progression. In the absence of Adamts-12, both the angiogenic response and tumor invasion into host tissue were increased. Complementing results were obtained by using medium conditioned by cells overexpressing human ADAMTS-12, which inhibited vessel outgrowth in the aortic ring assay. This angioinhibitory effect of ADAMTS-12 was independent of its enzymatic activity as a mutated inactive form of the enzyme was similarly efficient in inhibiting endothelial cell sprouting in the aortic ring assay than the wild-type form. Altogether, our results show that ADAMTS-12 displays antiangiogenic properties and protect the host toward tumor progression

Associations of body mass index and waist circumference with: energy intake and percentage energy from macronutrients, in a cohort of australian children

Background: It is evident from previous research that the role of dietary composition in relation to the development of childhood obesity remains inconclusive. Several studies investigating the relationship between body mass index (BMI), waist circumference (WC) and/or skin fold measurements with energy intake have suggested that the macronutrient composition of the diet (protein, carbohydrate, fat) may play an important contributing role to obesity in childhood as it does in adults. This study investigated the possible relationship between BMI and WC with energy intake and percentage energy intake from macronutrients in Australian children and adolescents

Amyloid pathology and vascular risk are associated with distinct patterns of cerebral white matter hyperintensities:A multicenter study in 3132 memory clinic patients

INTRODUCTION: White matter hyperintensities (WMH) are associated with key dementia etiologies, in particular arteriolosclerosis and amyloid pathology. We aimed to identify WMH locations associated with vascular risk or cerebral amyloid-β1-42 (Aβ42)-positive status. METHODS: Individual patient data (n = 3,132; mean age 71.5 ± 9 years; 49.3% female) from 11 memory clinic cohorts were harmonized. WMH volumes in 28 regions were related to a vascular risk compound score (VRCS) and Aß42 status (based on cerebrospinal fluid or amyloid positron emission tomography), correcting for age, sex, study site, and total WMH volume.RESULTS: VRCS was associated with WMH in anterior/superior corona radiata (B = 0.034/0.038, p &lt; 0.001), external capsule (B = 0.052, p &lt; 0.001), and middle cerebellar peduncle (B = 0.067, p &lt; 0.001), and Aß42-positive status with WMH in posterior thalamic radiation (B = 0.097, p &lt; 0.001) and splenium (B = 0.103, p &lt; 0.001). DISCUSSION: Vascular risk factors and Aß42 pathology have distinct signature WMH patterns. This regional vulnerability may incite future studies into how arteriolosclerosis and Aß42 pathology affect the brain's white matter. Highlights: Key dementia etiologies may be associated with specific patterns of white matter hyperintensities (WMH). We related WMH locations to vascular risk and cerebral Aβ42 status in 11 memory clinic cohorts. Aβ42 positive status was associated with posterior WMH in splenium and posterior thalamic radiation. Vascular risk was associated with anterior and infratentorial WMH. Amyloid pathology and vascular risk have distinct signature WMH patterns.</p