Scientists Reveal the Mechanism of Ezetimibe Action in Mouse Small Intestine
Source:
Time: 2012-08-04
Ezetimibe is a clinically prescribed cholesterol-lowering drug, which binds the multiple transmembrane protein Niemann-Pick C1 like1 (NPC1L1) and inhibits NPC1L1 mediated cholesterol absorption. A new study by researchers from Chinese Academy of Sciences shed new light on the mechanism of Ezetimibe action by showing that this drug inhibits cholesterol absorption in mouse small intestine by blocking NPC1L1 and cholesterol internalization.
Dr. SONG Bao-Liang’s and Dr. LI Bo-Liang’s groups from Shanghai Institute of Biochemistry and Cell Biology, CAS found that NPC1L1 mainly presents on the brush border membrane of enterocytes in absence of dietary cholesterol. Dietary cholesterol induces the internalization of NPC1L1 to recycling endosome beneath the brush border. And the internalization of NPC1L1 and cholesterol are impeded by Ezetimibe. For the first time, they demonstrated that in mouse small intestine NPC1L1 facilitates dietary cholesterol to enter enterocytes, and ezetimibe inhibits cholesterol absorption by blocking the internalization of NPC1L1 and cholesterol.
This work has been published online on the Journal of Lipid Research (doi:10.1194/jlr.M027359), with XIE Chang and ZHOU Zhang-Sen as the co-first authors. This research project was funded by the Ministry of Sciences and Technology of China, National Natural Science Foundation of China and Science and Technology Commission of Shanghai Municipality.
AUTHOR CONTACT:
Dr. LI Bo-Liang: blli@sibs.ac.cn
Dr. SONG Bao-Liang: blsong@sibs.ac.cn, Tel./Fax: +86-21-54921649
Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
Figure. Ezetimibe inhibits the internalization of NPC1L1 and cholesterol in mouse intestine.
Twelve-week-old male C57BL/6 mice (six per group) were pretreated with ezetimibe or vehicle before gavaged with cholesterol. 30 minutes later, intestinal samples were excised and subjected to IHC and filipin staining.
(A) Ezetimibe blocked cholesterol-induced endocytosis of NPC1L1. Paraffin embedded sections were applied to IHC staining with anti-NPC1L1 and anti-Villin or anti-Rab11 antibodies.
(B) Ezetimibe blocked dietary cholesterol from entering enterocytes. Frozen sections of mouse intestine were stained with filipin to indicate free cholesterol.
(C) Cholesterol and phospholipids were measured enzymatically. Relative amount of cholesterol was normalized to that of phospholipids.
(D) Male C57BL/6 mice were orally gavaged with vehicle (control) or ezetimibe once daily for 3 days. Then [14C]-cholesterol and [3H]-sitostanol in 150 μl corn oil were orally gavaged. Cholesterol absorption was determined by the fecal ratio method. Values are mean ± STDEV. P values were calculated by ANOVA. **: 0.001<p<0.01.
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