E. Hall et al., Overexpression of CYP27 in hepatic and extrahepatic cells: role in the regulation of cholesterol homeostasis, AM J P-GAST, 281(1), 2001, pp. G293-G301
Citations number
39
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
In the liver, sterol 27-hydroxylase (CYP27) participates in the classic and
alternative pathways of bile acid biosynthesis from cholesterol (Chol). In
extrahepatic tissues, CYP27 converts intracellular Chol to 27-hydroxychole
sterol (27OH-Chol), which may regulate the activity of 3-hydroxy-3-methylgl
utaryl CoA reductase (HMG-CoA-R). This study attempts to better define the
role of CYP27 in the maintenance of Chol homeostasis in hepatic and extrahe
patic cells by overexpressing CYP27 in Hep G2 cells and Chinese hamster ova
ry (CHO) cells through infection with a replication-defective recombinant a
denovirus encoding for CMV-CYP27. After infection, CYP27 mRNA and protein l
evels increased dramatically. CYP27 specific activity also increased two- t
o fourfold in infected cells (P less than or equal to 0.02), with a marked
increase in conversion of [C-14]Chol to [C-14]27OH-Chol (similar to 150%; P
less than or equal to 0.01). Accumulation of 27OH-Chol in CHO cells was as
sociated with a 50% decrease in HMG-CoA-R specific activity (P less than or
equal to 0.02). In infected Hep G2 cells, the significant increase in bile
acid synthesis (46%; P less than or equal to 0.006), which prevented the a
ccumulation of intracellular 27OH-Chol, resulted in increased HMG-CoA-R act
ivity (183%; P less than or equal to 0.02). Overexpression of CYP27 in Hep
G2 cells also increased acyl CoA-cholesterol acyltransferase (71%, P less t
han or equal to 0.02) and decreased cholesteryl ester hydrolase (55%, P les
s than or equal to 0.02). In conclusion, CYP27 generates different physiolo
gical responses depending on cell type and presence or absence of bile acid
biosynthetic pathways.