title: Trimerized apolipoprotein A-I (TripA) forms lipoproteins, activates lecithin: cholesterol acyltransferase, elicits lipid efflux, and is transported through aortic endothelial cells.
abstract: Apolipoprotein A-I (apoA-I) exerts many potentially anti-atherogenic properties and is therefore attractive for prevention and therapy of coronary heart disease. Since induction of apoA-I production by small molecules has turned out as difficult, application of exogenous apoA-I is pursued as an alternative therapeutic option. To counteract fast renal filtration of apoA-I, a trimeric high-molecular weight variant of apoA-I (TripA) was produced by recombinant technology. We compared TripA and apoA-I for important properties in reverse cholesterol transport. Reconstituted high-density lipoproteins (rHDL) containing TripA or apoA-I together with palmitoyl-2-oleyl-phosphatidylcholine (POPC) differed slightly by size. Compared to apoA-I, TripA activated lecithin:cholesterol acyltransferase (LCAT) with similar maximal velocity but concentration leading to half maximal velocity was slightly reduced (K(m)=2.1±0.3μg/mL vs. 0.59±0.06μg/mL). Both in the lipid-free form and as part of rHDL, TripA elicited cholesterol efflux from THP1-derived macrophages with similar kinetic parameters and response to liver-X-receptor activation as apoA-I. Lipid-free TripA is bound and transported by aortic endothelial cells through mechanisms which are competed by apoA-I and TripA and inhibited by knock-down of ATP-binding cassette transporter (ABC) A1. Pre-formed TripA/POPC particles were bound and transported by endothelial cells through mechanisms which are competed by excess native HDL as well as reconstituted HDL containing either apoA-I or TripA and which involve ABCG1 and scavenger receptor B1 (SR-BI). In conclusion, apoA-I and TripA show similar in vitro properties which are important for reverse cholesterol transport. These findings are important for further development of TripA as an anti-atherosclerotic drug.
authors.affiliation: University Hospital, Zurich, Switzerland.
authors.forename: Pascale M
authors.initials: PM
authors.lastname: Ohnsorg
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Mary
authors.forename: Lucia
authors.initials: L
authors.lastname: Rohrer
authors.forename: Michael
authors.initials: M
authors.lastname: Pech
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fingerle
authors.forename: Arnold
authors.initials: A
authors.lastname: von Eckardstein
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016632:Apolipoprotein A-I / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D050197:Atherosclerosis / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D002317:Cardiovascular Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D003327:Coronary Disease / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000378:metabolism; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D002317:Cardiovascular Agents; D008075:Lipoproteins, HDL; D010713:Phosphatidylcholines; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D007862:Phosphatidylcholine-Sterol O-Acyltransferase