Bezafibrate stimulates canalicular localization of NBD-labeled PC in HepG2 cells by PPARalpha-mediated redistribution of ABCB4.
Fibrates, including bezafibrate (BF), upregulate the expression of ATP binding cassette protein B4 (ABCB4) through gene transcription in mice. To determine the effects of BF on the expression levels of ABCB4 and on the stimulation of biliary phosphatidylcholine (PC) transport in human HepG2 hepatoblastoma cells, mRNA and protein levels as well as subcellular localization were investigated in the cells treated with BF. The canalicular accumulation of a fluorescent PC was assessed by confocal laser scanning microscopy. Treatment with 300 micromol/l BF for 24 h increased levels of ABCB4 mRNA but not protein by up to 151%. BF caused redistribution of ABCB4 into pseudocanaliculi formed between cells. In association with this redistribution, BF accelerated the accumulation of fluorescent PC in bile canaliculi (up to 163% of that in nontreated cells). Suppression of peroxisome proliferator-activated receptor alpha (PPARalpha) expression by either a small interfering RNA duplex or morpholino antisense oligonucleotide attenuated the BF-induced redistribution of ABCB4. These findings suggest that BF may enhance the capacity of human hepatocytes to direct PC into bile canaliculi via PPARalpha-mediated redistribution of ABCB4 to the canalicular membrane. This provides a rationale for the use of BF to improve cholestasis and/or cholangitis that is attributable to hypofunction of ABCB4.
Shoda
Junichi
J
Department of Gastroenterology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba-shi, Ibaraki 305-8575, Japan. shodaj@md.tsukuba.ac.jp
Inada
Yoichi
Y
Tsuji
Atsutoshi
A
Kusama
Hiroshi
H
Ueda
Tetsuya
T
Ikegami
Tadashi
T
Suzuki
Hiroshi
H
Sugiyama
Yuichi
Y
Cohen
David E
DE
Tanaka
Naomi
N
D009327:4-Chloro-7-nitrobenzofurazan; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001629:Bezafibrate / Q000494:pharmacology*; D001648:Bile Canaliculi / Q000378:metabolism*; D045744:Cell Line, Tumor; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D047493:PPAR alpha / Q000502:physiology*; D010713:Phosphatidylcholines / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D014018:Tissue Distribution / Q000187:drug effects
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D047493:PPAR alpha; D010713:Phosphatidylcholines; D012333:RNA, Messenger; C095122:multidrug resistance protein 3; D009327:4-Chloro-7-nitrobenzofurazan; D001629:Bezafibrate