Trimerized apolipoprotein A-I (TripA) forms lipoproteins, activates lecithin:cholesterol acyltransferase, elicits lipid efflux, and is transported through aortic endothelial cells

• Published in: Biochimica et biophysica acta 2011-12, Vol.1811 (12), p.1115-1123
• Main Authors: Ohnsorg, Pascale M., Mary, Jean-Luc, Rohrer, Lucia, Pech, Michael, Fingerle, Jürgen, von Eckardstein, Arnold
• Format: Article
• Language: English
• Subjects: ABC transporters; ABCA1; Animals; Aorta - cytology; Aorta - drug effects; Aorta - metabolism; apolipoprotein A-I; Apolipoprotein A-I - chemistry; Apolipoprotein A-I - metabolism; Apolipoprotein A-I - pharmacology; Atherosclerosis - drug therapy; Atherosclerosis - metabolism; Atherosclerosis - pathology; ATP-Binding Cassette Transporters - antagonists & inhibitors; ATP-Binding Cassette Transporters - metabolism; Cardiovascular Agents - chemistry; Cardiovascular Agents - metabolism; Cardiovascular Agents - pharmacology; Cattle; cholesterol; Cholesterol efflux; coronary disease; Coronary Disease - drug therapy; Coronary Disease - metabolism; Coronary Disease - pathology; drugs; endothelial cells; Endothelial Cells - cytology; Endothelial Cells - drug effects; Endothelial Cells - metabolism; Endothelium; filtration; Gene Silencing; High-density lipoprotein; Humans; Kinetics; Lipoproteins, HDL - chemistry; Lipoproteins, HDL - metabolism; macrophages; Phosphatidylcholine-Sterol O-Acyltransferase - metabolism; Phosphatidylcholines - metabolism; Protein Binding; Protein Transport - drug effects; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Recombinant Proteins - pharmacology; Reverse cholesterol transport; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; therapeutics; Transcytosis
• ISSN: 1388-1981; 0006-3002; 1879-2618
• DOI: 10.1016/j.bbalip.2011.09.001

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 (Km=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. ► Apolipoprotein A-I (apoA-I) and HDL exert potentially anti-atherogenic properties. ► Trimerized apoA-(TripA) is a potentially therapeutic mimetic of apoA-I and HDL. ► TripA resembles apoA-I by LCAT and cholesterol efflux stimulating properties. ► TripA resembles apoA-I by binding and transport through endothelial cells.