title: Blockade of scavenger receptor class B type I raises high density lipoprotein cholesterol levels but exacerbates atherosclerotic lesion formation in apolipoprotein E deficient mice.
abstract: Recent accumulating evidence supports the concept that raising high-density lipoprotein (HDL) may represent an additional therapeutic target for prevention of cardiovascular disease. Scavenger receptor class B type I plays a critical role in plasma HDL cholesterol concentration and structure. This study investigated the effect of scavenger receptor class B type I blockade by a synthetic scavenger receptor class B type I blocker on plasma lipids and atherosclerosis lesion formation in apolipoprotein E (apoE)-deficient mice. N-[4-(4-tert-Butoxycarbonylpiperazin-1-yl)phenyl]-(2-chloro-5-nitrophenyl)carboxamide (R-138329), a novel scavenger receptor class B type I blocker, was identified by screening with a half-maximal inhibitory potency (IC50 value) of around 1 microM in scavenger receptor class B type I-expressing COS-1 cells. Male apoE-deficient mice were fed a chow diet with or without R-138329 (0.01-0.10%, approximately 10-100 mg kg(-1), n = 9 or 10) for 12 weeks. Compared with control, treatment with R-138329 at 0.10% caused significant (P < 0.05) increases in plasma HDL cholesterol levels, and decreases in non-HDL cholesterol and triglyceride levels. Furthermore, R-138329 at 0.01% significantly increased the extent of atherosclerotic lesion formation in the aorta by 98% (P < 0.05), while favourable changes in plasma lipid parameters were achieved. The results of quantitative analysis of atherosclerosis lesion areas were: control, 102691 +/-22871 microm(2) (n = 10); R-138329 0.01%, 119792+/-30842 microm(2) (n = 9); R-138329 0.03%, 141346+/-21934 microm(2) (n = 10); and R-138329 0.10% 203732+/- 36326 microm(2) (n = 10). To clarify the mechanistic basis underlying this preferential deterioration, we examined the potential impact on closely related cellular functions. Further studies revealed that the active metabolite of R-138329 inhibited scavenger receptor class B type I-mediated cholesterol efflux. This study demonstrates for the first time pharmacological blockade of scavenger receptor class B type I in apoE-deficient mice. Blockade of scavenger receptor class B type I deteriorates atherosclerotic lesion formation in apoE-deficient mice even though it favourably affects plasma lipid parameters such as raising HDL cholesterol and decreasing non-HDL cholesterol. These results provide new insights for pharmaceutical industry research and development issues.
authors.affiliation: Pharmacology and Molecular Biology Research Laboratories, Sankyo Co., Ltd, Tokyo, Japan. kitaya@sankyo.co.jp
authors.forename: Ken
authors.initials: K
authors.lastname: Kitayama
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Koji
authors.initials: K
authors.lastname: Abe
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakabayashi
authors.forename: Tomiichiro
authors.initials: T
authors.lastname: Oda
authors.forename: Toshimori
authors.initials: T
authors.lastname: Inaba
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Amemiya
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency* / Q000235:genetics; D050197:Atherosclerosis / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D008076:Cholesterol, HDL / Q000097:blood / Q000378:metabolism*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015394:Molecular Structure; D010879:Piperazines / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D051122:Scavenger Receptors, Class B / Q000037:antagonists & inhibitors*; D014162:Transfection
chemical_list: D001057:Apolipoproteins E; D008076:Cholesterol, HDL; C521768:N-(4-(4-tert-butoxycarbonylpiperazin-1-yl)phenyl)-(2-chloro-5-nitrophenyl)carboxamide; D010879:Piperazines; C521770:R-154716; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B