Water Rewarming After Seawater Hypothermia Mitigates IL-1β in Both Intestinal Tissue and Blood

In this study, the rat models of severe hypothermia induced by seawater immersion were established in artificial seawater immersion at 15°C for 5 hours. With the rewarming measurement of 37°C water bath, the rewarming effects were evaluated by monitoring basic vital signs and dynamically detecting intestinal inflammation cytokines. Fifty Sprague–Dawley rats were randomly divided into five groups including the control group (group C), hypothermia group (group H), 2-hour rewarming group (group R2), 6-hour rewarming group (group R6), and 12-hour rewarming group (group R12), with 10 in each group. The basic vital signs of rats (i.e., core temperature, respiration, heart rate, and muscle tremor) were constantly recorded. The inflammatory factors were detected in the intestinal tissue via a protein chip GSR-CAA-67 of Innopsys, and the verification by reverse transcription-quantitative polymerase chain reaction. The levels of cytokines (interleukin IL-1β, IL-6, and IL-10) were detected from blood samples collected at the end of the observation period via enzyme-linked immunosorbent assay. The expression landscape of IL-1β in the intestinal tissue was validated by immunohistochemistry. Five hours of immersion in artificial seawater at 15°C successfully induced severe hypothermia of rats. After 2 hours of constant water bath rewarming at 37°C, the basic vital signs recovered to the normal level and maintained stably as well as the acute inflammatory reaction alleviated effectively, which indicated that 37°C of water immersion rewarming had the potential to be a suitable method for early treatment of water immersion hypothermia. After the process of hypothermia, several inflammatory cytokines of rats in rewarming groups changed distinctly with IL-1β, showing the most significant variations compared with group C, which confirmed IL-1β as a potential monitoring biomarker referring to the therapeutic effect of rewarming for severe hypothermia caused by seawater immersion.