Up-regulation of low density lipoprotein receptor by a novel isobenzofranone derivative, MD-700.
Stimulatory effects of a novel isobenzofranone, MD-700, on low density lipoprotein (LDL) receptor activity were investigated in vitro and in vivo. MD-700 at 0.03 microg/ml elevated the expression of LDL receptor in HepG2 cells within 4 h. Corresponding to this, uptake of fluorescent labeled-LDL (3,3'-dioctadecylindocarbocyanine-LDL) by the cells increased linearly in time- and dose-dependent manner by MD-700 for up to 12 h. In the experiment using HepG2 cells transiently transfected with promoter-luciferase gene constructs, MD-700 increased luciferase activity in a dose-dependent manner from 0.03 to 0.1 microg/ml. In contrast, luciferase activity was not stimulated by MD-700 in construct with a deleted sterol regulatory element (SRE)-1, suggesting importance of SRE-1 in stimulation of the LDL receptor gene promoter by MD-700. Binding experiments on liver membranes from MD-700-treated hamsters showed about a 60% increase in 125I-labeled LDL binding. A Scatchard plot revealed that MD-700 increased the maximal binding without affecting binding affinity. In contrast to findings with an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, pravastatin, MD-700 had no effect on the sterol synthesis in hamster liver homogenates. These results suggest that MD-700 stimulates the expression of LDL receptor, presumably in a manner independent of change in sterol metabolism, and thereby promotes LDL clearance. Hypocholesterolemic actions of MD-700 in hamsters were then examined. MD-700 lowered serum cholesterol levels in hamsters fed normal chow or a high-fat diet. Fractionation of serum lipoproteins demonstrated that MD-700 selectively decreased LDL and very low density lipoprotein cholesterol. Dose-dependent decrease in serum cholesterol was also seen in hypercholesterolemic rats. Thus, the hypocholesterolemic action of MD-700 may be attributed to up-regulation of the LDL receptor, based on stimulation of the transcription of the LDL receptor gene. Although pravastatin stimulates LDL uptake and lowers serum cholesterol in a manner similar to that seen with MD-700, the mechanism responsible for hypocholesterolemic action appears to differ.
Murakami
S
S
Medicinal Research Laboratories, Taisho Pharmaceutical Co. Ltd., Ohmiya, Japan. s12867@ccm.taisho.co.jp
Nitanai
I
I
Uchida
S
S
Kondo-Ohta
Y
Y
Asami
Y
Y
Kondo
K
K
Sato
M
M
Kawashima
A
A
Hara
H
H
Tomisawa
K
K
Mei
H B
HB
Xiang
C Z
CZ
D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D015152:Blotting, Northern; D002232:Carbocyanines / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000096:biosynthesis; D006224:Cricetinae; D017931:DNA Primers / Q000737:chemistry; D004195:Disease Models, Animal; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008077:Lipoproteins, LDL / Q000187:drug effects / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000187:drug effects / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D008297:Male; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism*; D013261:Sterols / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
C104226:3-hydroxy-3-methyl-1(3H)-isobenzofuranone; D001572:Benzofurans; D002232:Carbocyanines; D017931:DNA Primers; D005456:Fluorescent Dyes; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011973:Receptors, LDL; D013261:Sterols; C024286:3,3'-dioctadecylindocarbocyanine; D002784:Cholesterol