Cellular and molecular studies of adaptive survival responses induced by mild heat stress at 40°C in mammalian cells

应激反应途径使细胞能够感知和应对不利的环境变化。亚致死剂量的不同应激（活性氧（ROS）、热休克、环境毒素）可以诱导适应性生存反应，使细胞和生物体在面对不利刺激时能够继续正常功能。适应性反应由一组强大的抗凋亡基因（热休克蛋白 (Hsp)、抗氧化剂）介导，这些基因可抵御多种毒性应激并使细胞能够生存。适应性反应可以抵消应激引起的脂质、蛋白质和 DNA 损伤和/或增加对此类损伤的耐受性。如果适应性反应不能保护细胞，则受损细胞将通过细胞凋亡和/或坏死性凋亡而被消除。 我们发现，40°C 诱导的适应性生存反应可以保护哺乳动物细胞免受 ROS 和 43C 热休克等毒性应激的影响。除了热休克蛋白之外，抗氧化剂和内质网应激蛋白也被这种适应性反应上调。然而，40°C 时引发的这种适应性反应的机制尚不完全清楚。 长期目标：我们正在进行的研究旨在进一步阐明轻度耐热性的细胞和分子基础，这是一种在暴露于 40°C 低温非致命温度的细胞中诱导的适应性生存反应。耐热性可以保护细胞免受各种环境压力的不利影响，我的假设是，40°C 低剂量热压力的预处理会诱导多重防御系统，保护细胞免受更具攻击性的压力和环境毒素的不利影响。细胞对压力和毒素的常见反应是增加超氧化物和 H2O2 等 ROS 的产生。 我们的具体短期目标是： 1. 确定 40°C 的轻度热休克是否会增加 ROS，从而诱导适应性生存反应。 2. 确定 Nrf2 信号通路在适应性生存反应 (40C) 中的作用以及该通路与 ER 应激和 Hsf1（热休克因子 1）介导的应激反应之间的可能联系。 3. 确定在 40°C 预处理的细胞中，42-43°C 诱导细胞存活反应（ER 应激、自噬）和细胞死亡（细胞凋亡）之间的阈值是否发生改变。 了解细胞适应压力环境的机制将为人类和野生动物接触有毒污染物的大量研究提供信息，识别更敏感的生物标志物进行毒理学风险评估，并展示如何利用适应性生存反应的治愈能力来防止和修复压力引起的生物系统损害。有了这些知识，我们将开发新的策略（例如增强内源性生存反应）来保护生物体免受有毒物质的侵害，并减缓或阻止老龄化人口的功能障碍。

Stress response pathways allow cells to sense and respond to adverse environmental changes. Sub-lethal doses of different stresses (reactive oxygen species (ROS), heat shock, environmental toxins) can induce adaptive survival responses that allow cells and organisms to continue normal function in the face of an adverse stimulus. Adaptive responses are mediated by a core group of powerful anti-apoptotic genes (heat shock proteins (Hsp), antioxidants) that protect against diverse toxic stresses and enable the cell to survive. An adaptive response could counteract stress-induced damage to lipids, proteins and DNA and/or increase tolerance to such damage. If the adaptive response cannot protect the cell, then the damaged cell would be eliminated by apoptosis and/or necroptosis. We found that an adaptive survival response induced at 40C protected mammalian cells against toxic stresses such as ROS and 43C heat shock. In addition to Hsps, antioxidants and ER stress proteins were upregulated by this adaptive response. However, mechanisms underlying this adaptive response induced at 40C are not entirely understood. Long-term goals: Our ongoing research aims to further clarify the cellular and molecular basis of mild thermotolerance, an adaptive survival response induced in cells exposed to a low, non-lethal temperature of 40C. Thermotolerance protects cells against adverse effects of a variety of environmental stresses and my hypothesis is that preconditioning by low-dose heat stress at 40C induces multiple defense systems that protect cells against adverse effects of more aggressive stresses and environmental toxins. A common response of cells to stresses and toxins is increased production of ROS such as superoxide and H2O2. Our specific short-term objectives are to: 1. Determine whether mild heat shock at 40C increases ROS, which then induce the adaptive survival response. 2. Establish the role of the Nrf2 signaling pathway in the adaptive survival response (40C) and possible links between this pathway and the ER stress- and Hsf1 (heat shock factor 1)-mediated stress responses. 3. Determine if the threshold between induction of cell survival responses (ER stress, autophagy) and cell death (apoptosis) at 42-43ºC is altered in preconditioned cells at 40C. Understanding of mechanisms involved in cellular adaptation to stressful environments will inform the multitude of investigations on exposure of humans and wildlife to toxic pollutants, identify more sensitive biomarkers for toxicological risk assessment and demonstrate how to utilize the healing capacity of the adaptive survival response to protect against and repair stress-induced damage to biological systems. Armed with this knowledge, novel strategies (e.g. boost endogenous survival responses) will be developed to protect living organisms against toxic agents and to slow or halt dysfunction in our aging population.