title: Interactions of VIP with rigid phospholipid bilayers: implications for vasoreactivity.
abstract: The purpose of this study was to determine whether vasoactive intestinal peptide (VIP), a pleiotropic amphipathic peptide, interacts with rigid liposomes composed of gel phase phospholipids. We found that incubation of VIP with small unilamellar gel phase liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and egg phosphatidylglycerol (ePG) for 2h at room temperature had no significant effects on VIP secondary structure. Moreover, suffusion of VIP (0.01, 0.1 and 1.0nmol) incubated in saline or with DPPC/ePG liposomes (size, 30 and 100nm) for 2h at room temperature or 4 degrees C onto the intact hamster cheek pouch microcirculation elicited a similar concentration-dependent vasodilation except for 0.01nmol VIP (P<0.05). By contrast, incubation of VIP with gel phase liposomes overnight at 4 degrees C significantly potentiated vasodilation evoked by all three concentrations of the peptide in comparison to aqueous VIP (P<0.05). VIP-induced vasodilation was liposome size-independent. The ratio of VIP to phospholipids in DPPC/ePG liposomes was concentration-independent. Collectively, these data indicate that short-term interactions of VIP with rigid phospholipid bilayers are limited resulting in only modest effects on VIP vasoreactivity in vivo.
authors.affiliation: Department of Biopharmaceutical Sciences, University of Illinois at Chicago, IL 60612, Chicago, USA.
authors.forename: Hayat
authors.initials: H
authors.lastname: Onyüksel
authors.forename: Beena
authors.initials: B
authors.lastname: Ashok
authors.forename: Sumeet
authors.initials: S
authors.lastname: Dagar
authors.forename: Varun
authors.initials: V
authors.lastname: Sethi
authors.forename: Israel
authors.initials: I
authors.lastname: Rubinstein
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001160:Arterioles / Q000187:drug effects; D002610:Cheek / Q000098:blood supply; D002942:Circular Dichroism; D006224:Cricetinae; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008297:Male; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D013696:Temperature; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010715:Phosphatidylglycerols; D010743:Phospholipids; D015060:1,2-Dipalmitoylphosphatidylcholine; D014660:Vasoactive Intestinal Peptide