Stanford University, Hopkins Marine Station, Pacific Grove, California.
Am J Physiol Regul Integr Comp Physiol. 2013 Nov 1;305(9):R1010-20. doi: 10.1152/ajpregu.00254.2013. Epub 2013 Sep 4.
Little is known about the mechanisms underpinning thermal plasticity of vertebrate hearts. Bluefin tuna hearts offer a unique model to investigate processes underlying thermal acclimation. Their hearts, while supporting an endothermic physiology, operate at ambient temperature, and are presented with a thermal challenge when migrating to different thermal regimes. Here, we examined the molecular responses in atrial and ventricular tissues of Pacific bluefin tuna acclimated to 14°C, 20°C, and 25°C. Quantitative PCR studies showed an increase in sarcoplasmic reticulum Ca(2+) ATPase gene expression with cold acclimation and an induction of Na(+)/Ca(2+)-exchanger gene at both cold and warm temperatures. These data provide evidence for thermal plasticity of excitation-contraction coupling gene expression in bluefin tunas and indicate an increased capacity for internal Ca(2+) storage in cardiac myocytes at 14°C. Transcriptomic analysis showed profound changes in cardiac tissues with acclimation. A principal component analysis revealed that temperature effect was greatest on gene expression in warm-acclimated atrium. Overall data showed an increase in cardiac energy metabolism at 14°C, potentially compensating for cold temperature to optimize bluefin tuna performance in colder oceans. In contrast, metabolic enzyme activity and gene expression data suggest a decrease in ATP production at 25°C. Expression of genes involved in protein turnover and molecular chaperones was also decreased at 25°C. Expression of genes involved in oxidative stress response and programmed cell death suggest an increase in oxidative damage and apoptosis at 25°C, particularly in the atrium. These findings provide insights into molecular processes that may characterize cardiac phenotypes at upper thermal limits of teleosts.
关于脊椎动物心脏热塑性的机制知之甚少。蓝鳍金枪鱼心脏为研究热驯化过程提供了一个独特的模型。它们的心脏虽然支持吸热生理，但在环境温度下运行，当迁移到不同的热区时会面临热挑战。在这里，我们研究了适应 14°C、20°C 和 25°C 的太平洋蓝鳍金枪鱼心房和心室组织的分子反应。定量 PCR 研究表明，冷驯化时肌浆网 Ca2+-ATP 酶基因表达增加，冷温和温暖时 Na+/Ca2+-交换器基因诱导。这些数据为蓝鳍金枪鱼兴奋-收缩偶联基因表达的热塑性提供了证据，并表明在 14°C 时心肌细胞内 Ca2+储存能力增加。转录组分析显示，适应过程中心脏组织发生了深刻变化。主成分分析表明，温度对温暖适应心房的基因表达影响最大。总体数据显示，14°C 时心脏能量代谢增加，可能补偿低温，优化蓝鳍金枪鱼在较冷海洋中的表现。相比之下，代谢酶活性和基因表达数据表明，25°C 时 ATP 产量下降。涉及蛋白质周转和分子伴侣的基因表达也在 25°C 时下降。氧化应激反应和程序性细胞死亡相关基因的表达表明，25°C 时氧化损伤和细胞凋亡增加，特别是在心房。这些发现为可能表征硬骨鱼类热上限心脏表型的分子过程提供了深入了解。
