Nishizawa Junichiro, Nakai Akira, Komeda Masashi, Ban Toshihiko, Nagata Kazuhiro
Department of Cardiovascular Surgery, Faculty of Medicine, Kyoto University, Kyoto, Japan.
Cardiovasc Res. 2002 Aug 1;55(2):341-8. doi: 10.1016/s0008-6363(02)00404-2.
The rapid induction of heat shock proteins (HSPs) by cardiac overload has been shown using in vivo models and it is assumed that HSPs are involved in myocardial protection against cardiac overload. However, the mechanisms for the induction of heat shock response by cardiac overload remain unclear. We examined whether increased preload as mechanical stress directly induces heat shock gene expression.
Rat hearts were isolated and perfused with Krebs-Henseleit buffer by the Langendorff method. Whole-cell extracts were prepared for gel mobility shift assay using oligonucleotides containing the heat shock element. We examined the induction of the DNA-binding activity of heat shock transcription factor (HSF), by which the transcription of heat shock genes is mainly regulated, during increased preload of left ventricle (LV) or perfusion with the buffer containing epinephrine, norepinephrine, angiotensin II, or vasopressin.
In preloaded hearts, with LVEDP of both 30 and 50 mmHg, the DNA-binding activity of HSF1 was detected at 10 min, and increased at 20 and 60 min. At any time point, the activity with LVEDP of 50 mmHg was stronger than that with LVEDP of 30 mmHg. However, none of these hypertensive agents activated the DNA-binding activities of HSF. In afterloaded hearts, with the perfusion of norepinephrine, the activation of HSF was not induced.
Our findings demonstrate that increased preload as mechanical stress directly induces the activation of HSF1 in the LV-overloaded heart.
利用体内模型已证实心脏负荷过重可快速诱导热休克蛋白（HSPs）产生，并且推测HSPs参与了心肌对心脏负荷过重的保护作用。然而，心脏负荷过重诱导热休克反应的机制仍不清楚。我们研究了作为机械应力的前负荷增加是否直接诱导热休克基因表达。
采用Langendorff法分离大鼠心脏，并用Krebs-Henseleit缓冲液灌注。使用含有热休克元件的寡核苷酸制备全细胞提取物用于凝胶迁移率变动分析。我们检测了在左心室（LV）前负荷增加或用含有肾上腺素、去甲肾上腺素、血管紧张素II或血管加压素的缓冲液灌注期间，热休克转录因子（HSF）的DNA结合活性的诱导情况，热休克基因的转录主要受HSF调控。
在前负荷增加的心脏中，当左心室舒张末压（LVEDP）分别为30和50 mmHg时，HSF1的DNA结合活性在10分钟时被检测到，并在20和60分钟时增加。在任何时间点，LVEDP为50 mmHg时的活性都强于LVEDP为30 mmHg时的活性。然而，这些升压药均未激活HSF的DNA结合活性。在增加后负荷的心脏中，用去甲肾上腺素灌注未诱导HSF的激活。
我们的研究结果表明，作为机械应力的前负荷增加直接诱导左心室负荷过重心脏中HSF1的激活。
