Effects of the angiotensin II type-1 receptor antagonist telmisartan on endothelial activation induced by advanced glycation endproducts

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1 Effects of the angiotensin II type-1 receptor antagonist telmisartan on endothelial activation induced by advanced glycation endproducts Serena Del Turco, Teresa Navarra, Giuseppina Basta, Raffaele De Caterina # CNR Institute of Clinical Physiology, Pisa, Italy,# G. d Annunzio University, Chieti, Italy

2 Background I Angiotensin and cardiovascular disease Vasoconstriction Aldosterone synthesis VSMC tone Oxidative stress NADPH oxidase ROS LOX-1 Angiotensin II Inflammation Leukocyte infiltration Permeability Activation of signaling (NF-κB ) Endothelial dysfunction NO production Vasoconstriction Platelet aggregation Adhesion molecule expression, Growth factor and cytokine release 1 Tissue remodeling Proliferation of VSMC MMP activation

3 Background II Ang II, AT 1 R and endothelial dysfunction Ang II AT 1 R Endothelial cell NADPH Oxidase Gq enos CAM ROS NO ERK ET-1 expression VSMC growth contraction NF-κB VCAM-1 ICAM-1 E-Selectin ONOO - DNA damage Vasorelaxation Vascular protection Endothelial dysfunction

4 Background III ARBs and ACE-inhibitors Angiotensinogen Renin Ang I (1-10) Bradykinin ACE ACE inhibitors LOSARTAN TELMISARTAN OLMESARTAN ARBs Ang II (1-8) Kinin fragment AT 1 -receptor (detrimental effects) AT 2 -receptor (beneficial effects)

5 Background IV Pleiotropic effects of telmisartan agonist of PPAR-γ amelioration of Insulin resistence improvement of lipid profile favorable fat redistribution beneficial effects on: - vascular function - cardiac remodeling - renal function

6 Aim of the study We hypothesize that part of the anti-atherogenic properties of ARBs are mediated by a reversal of specific (Ang-II-mediated) and nonspecific (TNF-α- or AGEs-mediated) induction of endothelial dysfunction. We studied the anti-inflammatory and anti-oxidant effects of telmisartan on adhesion molecule expression in an in vitro system mimicking the vascular milieu in inflammatory and diabetic conditions.

7 Methods Cell culture and experimental design Cultured human umbilical vein endothelial cells (HUVEC) were pretreated with or without telmisartan (TEL) (10, 100 μmol/l) for 30 minutes, and then stimulated with AGEs (200 μmol/l) or TNF-α (20 ng/ml) for 18h to induce vascular adhesion molecule-1 (VCAM-1) and intercellular molecule-1 (ICAM-1), and for 10h to induce E-Selectin expression. Losartan and its active metabolite EXP-3174 (both at 10, 100 μmol/l), were used as control. Detection of adhesion molecule expression Assay of cell surface adhesion molecules was carried out by cell surface enzyme immunoassay (EIA) using mouse anti-human antibody against VCAM-1, ICAM-1 and E- Selectin. Detection of intracellular ROS generation Generation of intracellular ROS (mostly hydrogen peroxide) was assessed by carboxydi-chloro-fluoresceinediacetate (DCHF-DA) fluorescence.

8 VCAM-1 expression (OD mu, mean SD) VCAM-1 expression (OD mu, mean SD) Results I Telmisartan reduced VCAM-1 expression induced by TNF-α..and by AGEs (TEL 0 μmol/l) (TEL 10 μmol/l) (TEL 100 μmol/l) TNF-α (10 ng/ml) P<0.001 vs stimulation with TNF-α (TEL 0 μmol/l) (TEL 10 μmol/l) (TEL 100 μmol/l) P<0.001 vs stimulation with AGEs AGEs (200 μg/ml)

9 E-Selectin expression (OD mu, mean SD)v E-Selectin expression (OD mu, mean SD) Results II Telmisartan increased E-Selectin expression after TNF-α stimulation but prevented its induction by AGEs 0 (TEL 0 μmol/l) (TEL 10 μmol/l) (TEL 100 μmol/l) + TNF-α (10 ng/ml) 1 2 P<0.001 vs stimulation with TNF-α (TEL 0 μmol/l) (TEL 10 μmol/l) (TEL 100 μmol/l) + AGEs (200 μg/ml) 1 2 P<0.001 vs stimulation with AGEs

10 Results III 1. Telmisartan did not affect ICAM-1 expression induced by AGEs or TNF-α; 2. Loosartan, a hydrophilic ARB, and its active metabolite, EXP3174, a compound with anti-inflammatory properties, did not influence adhesion molecule expression induced by TNF-a or AGEs.

11 Intracellular ROS production (Fluorescence intensity a.u., mean±sd) Results IV Telmisartan (10 μmol/l) prevented the increase of intracellular ROS after AGEs stimulation but not after TNF-α stimulation. (A) control + TEL (10 µmol/l) (B) 100 TEL (0 µmol/l) TEL (10 µmol/l) P< AGEs (200 µg/ml) TNF-a (10 ng/ml) AGEs (200 µg/ml) + TNF-a (10 ng/ml)

12 Conclusions Our results demonstrate that telmisartan: - has peculiar regulatory mechanisms on adhesion molecule expression induced by either AGEs or TNF-α; - AT1R antagonism was not involved in the inhibitory effect madiated by TEL and highlighting the peculiar nature of TEL among ARBs; - such anti-inflammatory properties may disclose a role for this drug in the pro-atherogenic vascular milieu occurring in diabetes