Brown Kyle E, Broadhurst Kimberly A, Mathahs M Meleah, Weydert Jamie
Iowa City Veterans Administration Medical Center, Division of Gastroenterology-Hepatology, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City 52242, USA.
Toxicol Appl Pharmacol. 2007 Sep 1;223(2):180-6. doi: 10.1016/j.taap.2007.05.011. Epub 2007 May 25.
Oxidative stress can trigger a cellular stress response characterized by induction of antioxidants, acute phase reactants (APRs) and heat shock proteins (HSPs), which are presumed to play a role in limiting tissue damage. In rodents, hepatic iron overload causes oxidative stress that results in upregulation of antioxidant defenses with minimal progressive liver injury. The aim of this study was to determine whether iron overload modulates expression of other stress-responsive proteins such as APRs and HSPs that may confer protection against iron-induced damage in rodent liver.
Male rats received repeated injections of iron dextran or dextran alone over a 6-month period. Hepatic transcript levels for a panel of APRs and HSPs were quantitated by real-time PCR and protein expression was evaluated by Western blot and immunohistochemistry.
Hepatic iron concentrations were increased >50-fold in the iron-loaded rats compared to controls. Iron loading resulted in striking increases in mRNAs for Hsp32 (heme oxygenase-1; 12-fold increase vs. controls) and metallothionein-1 and -2 (both increased approximately 6-fold). Transcripts for alpha1-acid glycoprotein, the major rat APR, were increased approximately 3-fold, while expression of other classical APRs was unaltered. Surprisingly, although mRNA levels for the HSPs were not altered by iron, the abundance of Hsp25, Hsp70 and Hsp90 proteins was uniformly reduced in the iron-loaded livers, as were levels of NAD(P)H:quinone oxidoreductase 1, an Hsp70 client protein.
Chronic iron administration elicits a unique pattern of stress protein expression. These alterations may modulate hepatic responses to iron overload, as well as other injury processes.
氧化应激可引发细胞应激反应，其特征为抗氧化剂、急性期反应物（APR）和热休克蛋白（HSP）的诱导，这些物质被认为在限制组织损伤中发挥作用。在啮齿动物中，肝脏铁过载会导致氧化应激，从而使抗氧化防御上调，同时肝脏损伤进展极小。本研究的目的是确定铁过载是否会调节其他应激反应蛋白（如APR和HSP）的表达，这些蛋白可能对啮齿动物肝脏中铁诱导的损伤具有保护作用。
雄性大鼠在6个月内反复注射右旋糖酐铁或单独注射右旋糖酐。通过实时PCR定量一组APR和HSP的肝脏转录水平，并通过蛋白质印迹和免疫组织化学评估蛋白质表达。
与对照组相比，铁负荷大鼠的肝脏铁浓度增加了50倍以上。铁负荷导致Hsp32（血红素加氧酶-1；与对照组相比增加12倍）以及金属硫蛋白-1和-2（两者均增加约6倍）的mRNA显著增加。大鼠主要的APR——α1-酸性糖蛋白的转录本增加了约3倍，而其他经典APR的表达未改变。令人惊讶的是，尽管铁对HSP的mRNA水平没有影响，但铁负荷肝脏中Hsp25、Hsp70和Hsp90蛋白的丰度均一致降低，NAD(P)H:醌氧化还原酶1（一种Hsp70的客户蛋白）的水平也降低。
长期给予铁会引发独特的应激蛋白表达模式。这些改变可能会调节肝脏对铁过载以及其他损伤过程的反应。
