Table_1_Cardiomyocyte Protection by Hibernating Brown Bear Serum: Toward the Identification of New Protective Molecules Against Myocardial Infarction.pdf

Ischemic heart disease remains one of the leading causes of death worldwide. Despite intensive research on the treatment of acute myocardial infarction, no effective therapy has shown clinical success. Therefore, novel therapeutic strategies are required to protect the heart from reperfusion injury. Interestingly, despite physical inactivity during hibernation, brown bears (Ursus arctos) cope with cardiovascular physiological conditions that would be detrimental to humans. We hypothesized that bear serum might contain circulating factors that could provide protection against cell injury. In this study, we sought to determine whether addition of bear serum might improve cardiomyocyte survival following hypoxia–reoxygenation. Isolated mouse cardiomyocytes underwent 45 min of hypoxia followed by reoxygenation. At the onset of reoxygenation, cells received fetal bovine serum (FBS; positive control), summer (SBS) or winter bear serum (WBS), or adult serums of other species, as indicated. After 2 h of reoxygenation, propidium iodide staining was used to evaluate cell viability by flow cytometry. Whereas, 0.5% SBS tended to decrease reperfusion injury, 0.5% WBS significantly reduced cell death, averaging 74.04 ± 7.06% vs. 79.20 ± 6.53% in the FBS group. This cardioprotective effect was lost at 0.1%, became toxic above 5%, and was specific to the bear. Our results showed that bear serum exerts a therapeutic effect with an efficacy threshold, an optimal dose, and a toxic effect on cardiomyocyte viability after hypoxia–reoxygenation. Therefore, the bear serum may be a potential source for identifying new therapeutic molecules to fight against myocardial reperfusion injury and cell death in general.

缺血性心脏病（ischemic heart disease）仍是全球首要致死病因之一。尽管针对急性心肌梗死（acute myocardial infarction）的治疗已开展大量深入研究，但目前尚未有任何有效疗法取得临床成功。因此，亟需开发全新的治疗策略，以保护心脏免受再灌注损伤（reperfusion injury）。有趣的是，冬眠期间缺乏身体活动的棕熊（Ursus arctos）却能耐受对人类而言有害的心血管生理状态。据此我们推测，熊的血清中或许存在循环因子，能够为细胞提供抗损伤保护作用。本研究旨在探究，添加熊血清是否能够提升缺氧-复氧（hypoxia–reoxygenation）处理后心肌细胞（cardiomyocyte）的存活率。我们将分离获取的小鼠心肌细胞施以45分钟缺氧处理，随后进行复氧操作。在复氧开始时，按实验设计分别向细胞加入胎牛血清（fetal bovine serum, FBS；阳性对照）、夏季熊血清（summer bear serum, SBS）、冬季熊血清（winter bear serum, WBS）或其他物种的成年血清。复氧2小时后，采用碘化丙啶（propidium iodide）染色联合流式细胞术（flow cytometry）检测细胞活力。尽管0.5% SBS呈现出降低再灌注损伤的趋势，但0.5% WBS则可显著减少细胞死亡：WBS组的平均细胞死亡率为74.04±7.06%，相较于FBS组的79.20±6.53%更低。该心脏保护作用在浓度为0.1%时消失，浓度高于5%时则会产生毒性，且该效应仅存在于熊的血清中。本研究结果表明，在缺氧-复氧处理后的心肌细胞中，熊血清可发挥具备疗效阈值与最优剂量的治疗作用，同时存在毒性效应。因此，熊血清有望成为筛选新型治疗分子的潜在来源，以对抗心肌再灌注损伤及一般性细胞死亡。