Caldwell Aaron R, Oki Kentaro, Ward Shauna M, Ward Jermaine A, Mayer Thomas A, Plamper Mark L, King Michelle A, Leon Lisa R
Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.
Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee.
J Appl Physiol (1985). 2021 Nov 1;131(5):1469-1485. doi: 10.1152/japplphysiol.00160.2021. Epub 2021 Sep 16.
The purpose of the study was to determine if repeated exertional heat injuries (EHIs) worsen the inflammatory response. We assessed the impact of a single EHI bout (EHI0) or two separate EHI episodes separated by 1 (EHI1), 3 (EHI3), and 7 (EHI7) days in male C57BL/6J mice ( = 236). To induce EHI, mice underwent a forced running protocol until loss of consciousness or core temperature reached ≥ 42.7°C. Blood and tissue samples were obtained 30 min, 3 h, 1 day, or 7 days after the EHI. We observed that mice undergoing repeated EHI (EHI1, EHI3, and EHI7) had longer running distances before collapse (∼528 m), tolerated higher core temperatures (∼0.18°C higher) before collapse, and had higher minimum core temperature (indicative of injury severity) during recovery relative to EHI0 group (∼2.18°C higher; all < 0.05). Heat resilience was most pronounced when latency was shortest between EHI episodes (i.e., thermal load and running duration highest in EHI1), suggesting the response diminishes with longer recoveries between EHI events. Furthermore, mice experiencing a second EHI exhibited increased serum and liver HSP70, and lower corticosterone, FABP2, MIP-1β, MIP-2, and IP-10 relative to mice experiencing a single EHI typically at 30 min to 3 h after EHI. Our findings indicate that an EHI event may initiate some adaptive processes that provide acute heat resilience to subsequent EHI conditions. Mice undergoing repeated exertional heat injuries, within 1 wk of an initial heat injury, appear to have some protective adaptations. During the second exertional heat injury, mice were able to run longer and sustain higher body temperatures before collapse. Despite this, the mice undergoing a second exertional heat injury were more resilient to the heat as evidenced by attenuated minimum body temperature, higher HPS70 (serum and liver), lower corticosterone, and lower FABP2.
本研究的目的是确定反复的运动性热损伤（EHI）是否会加剧炎症反应。我们评估了单次EHI发作（EHI0）或两次间隔1天（EHI1）、3天（EHI3）和7天（EHI7）的单独EHI发作对雄性C57BL/6J小鼠（n = 236）的影响。为诱导EHI，小鼠接受强制跑步方案，直至意识丧失或核心体温达到≥42.7°C。在EHI后30分钟、3小时、1天或7天采集血液和组织样本。我们观察到，与EHI0组相比，经历反复EHI（EHI1、EHI3和EHI7）的小鼠在崩溃前的跑步距离更长（约528米），在崩溃前能耐受更高的核心体温（约高0.18°C），并且在恢复期间的最低核心体温更高（表明损伤严重程度）（约高2.18°C；所有P < 0.05）。当EHI发作之间的潜伏期最短时（即EHI1中的热负荷和跑步持续时间最高），热适应能力最为明显，这表明随着EHI事件之间恢复时间的延长，这种反应会减弱。此外，与单次EHI的小鼠相比，经历第二次EHI的小鼠通常在EHI后30分钟至3小时血清和肝脏中的HSP70增加，而皮质酮、FABP2、MIP-1β、MIP-2和IP-10降低。我们的研究结果表明，一次EHI事件可能会启动一些适应性过程，为随后的EHI情况提供急性热适应能力。在初次热损伤后1周内经历反复运动性热损伤的小鼠似乎有一些保护性适应。在第二次运动性热损伤期间，小鼠在崩溃前能够跑得更远并维持更高的体温。尽管如此，经历第二次运动性热损伤的小鼠对热的适应能力更强，这表现为最低体温降低、HPS70（血清和肝脏）升高、皮质酮降低和FABP2降低。
