Lambrecht R W, Cable J W, Pepe J A, Bonkovsky H L
Department of Medicine, University of Massachusetts Medical Center, Worcester 01655.
Biochem Pharmacol. 1994 Apr 29;47(9):1669-76. doi: 10.1016/0006-2952(94)90546-0.
Recent work showed that the combination of 50 microM glutethimide plus 50 microM ferric nitrilotriacetate (FeNTA) synergistically induces heme oxygenase (HO) activity in cultured chick embryo liver cells (Cable et al., Biochem Biophys Res Commun 168: 176-181, 1990). This synergistic induction is due to increased heme synthesis, which then acts to increase HO gene transcription. The aim of the current studies was to characterize the effects on hepatic heme metabolism of (3,5,5-trimethylhexanoyl)ferrocene (TMH-ferrocene), which causes hepatic iron-loading in rats. Unlike FeNTA, TMH-ferrocene alone maximally induced HO activity at 5-10 microM TMH-ferrocene. At higher concentrations, HO activities declined, as did total cellular protein synthesis. Induction of HO was maximal after a 12-hr exposure to TMH-ferrocene, similar to induction by glutethimide plus FeNTA. The effect of TMH-ferrocene on HO could not be ascribed to greater cellular uptake of iron, since cell-associated iron levels were higher after FeNTA than after TMH-ferrocene treatment. TMH-ferrocene (up to 20 microM) did not induce delta-aminolevulinic acid synthase activity. Uroporphyrin accumulation in cells treated with TMH-ferrocene was minimal, but the combination of TMH-ferrocene and glutethimide caused a synergistic increase in uroporphyrin accumulation, similar to treatment with glutethimide plus FeNTA. 4,6-Dioxoheptanoic acid, an inhibitor of heme synthesis, blocked the induction of HO caused by glutethimide and FeNTA, but did not decrease the induction of HO by TMH-ferrocene. TMH-ferrocene-mediated induction of HO does not appear to be due to lipid peroxidation, since malondialdehyde formation was greater for ferrocene (a structural analog of TMH-ferrocene that does not induce HO) than for TMH-ferrocene. Furthermore, the anti-oxidant, butylated hydroxyanisole, which prevented lipid peroxidation, decreased HO induced by glutethimide plus FeNTA, but butylated hydroxyanisole did not affect HO induced by TMH-ferrocene. We conclude that, unlike the combination of glutethimide plus FeNTA, TMH-ferrocene induces HO activity by a mechanism that is independent of cellular heme synthesis.
近期研究表明，50微摩尔的格鲁米特与50微摩尔的次氮基三乙酸铁（FeNTA）联合使用可协同诱导培养的鸡胚肝细胞中的血红素加氧酶（HO）活性（Cable等人，《生物化学与生物物理研究通讯》168：176 - 181，1990）。这种协同诱导是由于血红素合成增加，进而作用于增加HO基因转录。当前研究的目的是表征（3,5,5 - 三甲基己酰基）二茂铁（TMH - 二茂铁）对肝脏血红素代谢的影响，该物质会导致大鼠肝脏铁负荷增加。与FeNTA不同，单独使用TMH - 二茂铁在5 - 10微摩尔TMH - 二茂铁时可最大程度地诱导HO活性。在更高浓度下，HO活性下降，总细胞蛋白质合成也下降。暴露于TMH - 二茂铁12小时后HO诱导达到最大值，这与格鲁米特加FeNTA的诱导情况相似。TMH - 二茂铁对HO的作用不能归因于细胞对铁的摄取增加，因为FeNTA处理后细胞相关铁水平高于TMH - 二茂铁处理后。TMH - 二茂铁（高达20微摩尔）不会诱导δ - 氨基 - γ - 酮戊酸合酶活性。TMH - 二茂铁处理的细胞中尿卟啉积累极少，但TMH - 二茂铁与格鲁米特的组合导致尿卟啉积累协同增加，这与格鲁米特加FeNTA的处理情况相似。4,6 - 二氧庚酸，一种血红素合成抑制剂，可阻断格鲁米特和FeNTA引起的HO诱导，但不会降低TMH - 二茂铁对HO的诱导。TMH - 二茂铁介导的HO诱导似乎不是由于脂质过氧化，因为二茂铁（TMH - 二茂铁的结构类似物，不诱导HO）的丙二醛形成比TMH - 二茂铁更大。此外，抗氧化剂丁基羟基茴香醚可防止脂质过氧化，它会降低格鲁米特加FeNTA诱导的HO，但不会影响TMH - 二茂铁诱导的HO。我们得出结论，与格鲁米特加FeNTA的组合不同，TMH - 二茂铁通过一种独立于细胞血红素合成的机制诱导HO活性。
