title: Increasing cellular level of phosphatidic acid enhances FGF-1 production in long term-cultured rat astrocytes.
abstract: We found in a previous study that both mRNA expression and release of fibroblast growth factor 1 (FGF-1) are greater in rat astrocytes that are long term-cultured for one month (W/M cells) than in the cells cultured for one week (W/W cells). However, FGF-1 does not enhance phosphorylation of Akt, MEK, and ERK in W/M cells, while it does in W/W cells. In this work we studied the mechanism to cause these differences between W/W and W/M cells in culture. As it is known that long term culture generates oxidative stress, we characterized the stresses which W/M cells undergo in comparison with W/W cells. The levels of superoxide dismutase 1 (SOD1) and mitochondrial Bax were higher in W/M cells than in W/W cells. W/M cells recovered their ability to respond to FGF-1 to enhance phosphorylation of Akt, MEK, and ERK in the presence of antioxidants. Oxidative stress induced by hydrogen peroxide (H2O2) had no effect on mRNA expression of FGF-1 in W/W cells, although H2O2 enhances release of FGF-1 from W/W cells without inducing apoptosis. The influence of cell density was studied on mRNA expression of FGF-1 and cellular response to FGF-1, as an increasing cell density is observed in W/M cells. The increasing cell density enhanced mRNA expression of FGF-1 in W/W cells without suppression of responses to FGF-1. The decrease in cell density lowered the FGF-1 mRNA expression in W/M cells without recovery of the response to FGF-1 to enhance phosphorylation of Akt, MEK, and ERK. These findings suggest that oxidative stress attenuate sensitivity to FGF-1 and higher cell density may enhance FGF-1 expression in W/M cells. In addition, we found that the cellular level of phosphatidic acid (PA) increased in H2O2-treated W/W and W/M cells and decreased by the treatment with antioxidants, and that PA enhances the mRNA expression of FGF-1 in the W/W cells. These findings suggest that the increasing PA production may enhance FGF-1 expression to protect astrocytes against oxidative stress induced by long-term culture.
authors.affiliation: Departments of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nagayasu
authors.affiliation: Department of Pharmacy, Shiga University of Medical Science Hospital, Otsu City, Shiga 520-2192, Japan.
authors.forename: Shin-Ya
authors.initials: SY
authors.lastname: Morita
authors.affiliation: Department of Applied Biochemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.affiliation: Bioregulation and Molecular Neurobiology, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Miura
authors.affiliation: Department of Economics, Graduate School of Economics, Nagoya City University, Nagoya 467-8501, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Departments of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Michikawa
authors.affiliation: Departments of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan. Electronic address: jitoh@med.nagoya-cu.ac.jp.
authors.forename: Jin-Ichi
authors.initials: J
authors.lastname: Ito
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D010712:Phosphatidic Acids / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction
chemical_list: D010712:Phosphatidic Acids; D012333:RNA, Messenger; D016220:Fibroblast Growth Factor 1
keywords: Astrocyte; FGF-1 release; Long-term culture; Oxidative stress; Phosphatidic acid