title: Thermal, dynamic and structural properties of drug AT1 antagonist olmesartan in lipid bilayers.
abstract: It is proposed that AT1 antagonists (ARBs) exert their biological action by inserting into the lipid membrane and then diffuse to the active site of AT1 receptor. Thus, lipid bilayers are expected to be actively involved and play a critical role in drug action. For this reason, the thermal, dynamic and structural effects of olmesartan alone and together with cholesterol were studied using differential scanning calorimetry (DSC), 13C magic-angle spinning (MAS) nuclear magnetic resonance (NMR), cross-polarization (CP) MAS NMR, and Raman spectroscopy as well as small- and wide angle X-ray scattering (SAXS and WAXS) on dipalmitoyl-phosphatidylcholine (DPPC) multilamellar vesicles. 13C CP/MAS spectra provided direct evidence for the incorporation of olmesartan and cholesterol in lipid bilayers. Raman and X-ray data revealed how both molecules modify the bilayer's properties. Olmesartan locates itself at the head-group region and upper segment of the lipid bilayers as 13C CP/MAS spectra show that its presence causes significant chemical shift changes mainly in the A ring of the steroidal part of cholesterol. The influence of olmesartan on DPPC/cholesterol bilayers is less pronounced. Although, olmesartan and cholesterol are residing at the same region of the lipid bilayers, due to their different sizes, display distinct impacts on the bilayer's properties. Cholesterol broadens significantly the main transition, abolishes the pre-transition, and decreases the membrane fluidity above the main transition. Olmesartan is the only so far studied ARB that increases the gauche:trans ratio in the liquid crystalline phase. These significant differences of olmesartan may in part explain its distinct pharmacological profile.
authors.affiliation: Department of Chemistry, University of Patras, Patras 26500, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Ntountaniotis
authors.forename: Gregor
authors.initials: G
authors.lastname: Mali
authors.forename: Simona Golic
authors.initials: SG
authors.lastname: Grdadolnik
authors.forename: Maria
authors.initials: M
authors.lastname: Halabalaki
authors.forename: Halabalaki
authors.initials: H
authors.lastname: Maria
authors.forename: Alexios-Leandros
authors.initials: AL
authors.lastname: Skaltsounis
authors.forename: Constantinos
authors.initials: C
authors.lastname: Potamitis
authors.forename: Eleni
authors.initials: E
authors.lastname: Siapi
authors.forename: Petros
authors.initials: P
authors.lastname: Chatzigeorgiou
authors.forename: Michael
authors.initials: M
authors.lastname: Rappolt
authors.forename: Thomas
authors.initials: T
authors.lastname: Mavromoustakos
mesh_terms: D002152:Calorimetry, Differential Scanning; D007093:Imidazoles / Q000737:chemistry*; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D044139:Receptor, Angiotensin, Type 2; D012542:Scattering, Radiation; D013059:Spectrum Analysis, Raman; D013777:Tetrazoles / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D008051:Lipid Bilayers; D044139:Receptor, Angiotensin, Type 2; D013777:Tetrazoles; C437965:olmesartan