Blockade of scavenger receptor class B type I raises high density lipoprotein cholesterol levels but exacerbates atherosclerotic lesion formation in apolipoprotein E deficient mice

• Published in: Journal of pharmacy and pharmacology Vol. 58; no. 12; p. 1629
• Main Authors: Kitayama, Ken, Nishizawa, Tomohiro, Abe, Koji, Wakabayashi, Kenji, Oda, Tomiichiro, Inaba, Toshimori, Amemiya, Yoshiya
• Format: Journal Article
• Language: English
• Published: England 01.12.2006
• Subjects: Animals; Apolipoproteins E - deficiency; Apolipoproteins E - genetics; Atherosclerosis - metabolism; Atherosclerosis - pathology; Atherosclerosis - prevention & control; Cell Line; Cercopithecus aethiops; Cholesterol, HDL - blood; Cholesterol, HDL - metabolism; COS Cells; Disease Models, Animal; Dose-Response Relationship, Drug; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Structure; Piperazines - chemistry; Piperazines - pharmacology; Piperazines - therapeutic use; Scavenger Receptors, Class B - antagonists & inhibitors; Transfection
• ISSN: 0022-3573; 2042-7158
• DOI: 10.1211/jpp.58.12.0010

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.