ABCA1, ABCG1 and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines.
BACKGROUND
Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism.


RESULTS
By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines.


CONCLUSIONS
Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR.
Sporstøl
Marita
M
Programme for Cell Biology, Department of Molecular Biosciences, University of Oslo, Norway. marita.sporstol@imbv.uio.no
Mousavi
Seyed Ali
SA
Eskild
Winnie
W
Roos
Norbert
N
Berg
Trond
T
D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D003907:Dexamethasone / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051122:Scavenger Receptors, Class B / Q000378:metabolism*
C577836:ABCA1 protein, human; C419353:ABCG1 protein, human; D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D007328:Insulin; D011965:Receptors, Glucocorticoid; D051122:Scavenger Receptors, Class B; D003907:Dexamethasone; D002784:Cholesterol