Niemann-Pick C1-Like 1 (NPC1L1) is expressed in 
human liver, but its mechanism of action and how it is regulated 
in this tissue is not well-understood.  Herein, we decided to 
examine the effects of the inhibitor of NPC1L1, ezetimibe, in the 
presence and absence of a low cholesterol medium (MITO+ 
medium), on the expression of NPC1L1 in the human hepatocyte
like C3A cell line.  It was demonstrated that ezetimibe and 
MITO+ medium were able to independently decrease NPC1L1 
protein expression while increased the mRNA expression of this 
transporter.  Treating with ezetimibe and MITO+ medium 
together additively decreased NPC1L1 protein levels, but their 
effects on NPC1L1 mRNA expression were counteracting.  
Cycloheximide studies showed that these treatments enhanced the 
stability of the NPC1L1 protein in an additive manner, supporting 
the possibility that the translation efficiency of the NPC1L1 
mRNA was decreased under these conditions or that the factors 
required to degrade the NPC1L1 transporter were inhibited by the 
presence of cycloheximide.  In addition, the data confirmed that 
growing the cells in flasks coated with poly-D-lysine (should 
induce polarization) was required for maximum expression levels 
of NPC1L1 protein but not for localization of this transporter to 
the apical membrane.  The information derived from this research 
is critical to our understanding of the role of hepatic NPC1L1 in 
removing cholesterol from the bile and in cholesterol homeostasis 
in general.