title: Triacylglycerol deposition with group IVC phospholipase A2 expression in oleate- and linoleate-stimulated Huh-7 hepatocytes.
abstract: The accumulation of hepatocellular triacylglycerol (TG), a major symptom of fatty liver, is associated with the excessive incorporation of exogenous free fatty acids into hepatocytes, the free fatty acids inducing an increase in TG bearing acyl chains derived from not only themselves but also endogenous fatty acids. However, the mechanisms responsible for the supply of endogenous fatty acids, which are mainly esterified into phospholipids, remain unclear. In the present study, we examined the possible involvement of intracellular phospholipase A(2) (PLA(2))s including group IVA, IVC, VIA, and VIB PLA(2)s, which catalyze the release of endogenous fatty acids, in the deposition of TG in hepatocytes. Stimulation of human hepatoma Huh-7 cells with oleate or linoleate for 48 h increased TG contents time-dependently. Under the conditions, increased expression of group IVC PLA(2) mRNA and protein was observed at 6-12 h and 24-48 h after the stimulation, respectively. However, mRNA levels of group IVA, VIA, or VIB PLA(2) did not change. When cells were treated with methyl arachidonyl fluorophosphonate used as an inhibitor of group IVC PLA(2), the fatty acid-induced deposition of TG was partially but significantly suppressed at 48 h, although no significant inhibition was observed at 24 h. Overexpression of wild-type group IVC PLA(2) but not a catalytically inactive mutant of group IVC PLA(2) tended to increase cellular TG levels. The present findings suggest that stimulation of Huh-7 hepatocytes with free fatty acids induces the expression of group IVC PLA(2), which is involved in the fatty acid-induced deposition of TG.
authors.affiliation: Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607–8414, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ishihara
authors.forename: Kengo
authors.initials: K
authors.lastname: Tachibana
authors.forename: Asuka
authors.initials: A
authors.lastname: Kuroda
authors.forename: Ayano
authors.initials: A
authors.lastname: Terakawa
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Baba
authors.forename: Shiho
authors.initials: S
authors.lastname: Kanai
authors.forename: Satoshi
authors.initials: S
authors.lastname: Akiba
mesh_terms: D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005234:Fatty Liver / Q000378:metabolism*; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D008041:Linoleic Acids / Q000378:metabolism*; D009829:Oleic Acids / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D005230:Fatty Acids, Nonesterified; D008041:Linoleic Acids; D009829:Oleic Acids; D012333:RNA, Messenger; D014280:Triglycerides; D054513:Group IV Phospholipases A2