ATP binding cassette transporter gene expression in rat liver progenitor cells.
OBJECTIVE
Liver regeneration after severe liver damage depends in part on proliferation and differentiation of hepatic progenitor cells (HPCs). Under these conditions they must be able to withstand the toxic milieu of the damaged liver. ATP binding cassette (ABC) transporters are cytoprotective efflux pumps that may contribute to the preservation of these cells. The aim of this study was to determine the ABC transporter phenotype of HPCs.


METHODS
HPC activation was studied in rats treated with 2- acetylaminofluorene (2-AAF) followed by partial hepatectomy (PHx). ABC transporter gene expression was determined by real time detection reverse transcription-polymerase chain reaction in isolated HPCs, hepatocytes, cholangiocytes, and cultured progenitor cell-like RLF phi 13 cells and by immunohistochemistry of total liver samples. ABC transporter efflux activity was studied in RLF phi 13 cells by flow cytometry.


RESULTS
2-AAF/PHx treated animals showed increased hepatic mRNA levels of the genes encoding multidrug resistance proteins Mdr1b, Mrp1, and Mrp3. Immunohistochemistry demonstrated expression of Mrp1 and Mrp3 proteins in periportal progenitor cells and of the Mdr1b protein in periportal hepatocytes. Freshly isolated Thy-1 positive cells and cultured RLF phi 13 progenitor cells highly expressed Mrp1 and Mrp3 mRNA while the hepatocyte specific transporters Mdr2, Bsep, Mrp2, and Mrp6 were only minimally expressed. Blocking Mrp activity by MK-571 resulted in accumulation of the Mrp specific substrate carboxyfluorescein in RLF phi 13 cells.


CONCLUSIONS
HPCs express high levels of active Mrp1 and Mrp3. These may have a cytoprotective role in conditions of severe hepatotoxicity.
Ros
J E
JE
Groningen University Institute for Drug Exploration (GUIDE), Centre for the Study of Liver, Digestive, and Metabolic Diseases, University Hospital Groningen, 9700 RB Groningen, the Netherlands.
Roskams
T A D
TA
Geuken
M
M
Havinga
R
R
Splinter
P L
PL
Petersen
B E
BE
LaRusso
N F
NF
van der Kolk
D M
DM
Kuipers
F
F
Faber
K N
KN
Müller
M
M
Jansen
P L M
PL
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000032:analysis; D018528:ATP-Binding Cassette Transporters / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D005434:Flow Cytometry / Q000379:methods; D015870:Gene Expression; D019450:Genes, MDR / Q000235:genetics; D007150:Immunohistochemistry / Q000379:methods; D008099:Liver / Q000166:cytology*; D008297:Male; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013047:Specific Pathogen-Free Organisms; D013234:Stem Cells / Q000378:metabolism*
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger; C095122:multidrug resistance protein 3; C421109:multidrug resistance-associated protein 1