Background/Objectives: Shenfu Decoction (SFD) is a traditional Chinese herbal formula composed of Panax ginseng and Aconitum carmichaelii that can revive and counteract shock. However, how SFD can mitigate hypothermia caused by seawater immersion is poorly understood. Methods: Three commonly used ratios of SFD (Panax ginseng:Aconitum carmichaelii = 1:1, 1:2, 2:1) were prepared, and their chemical properties were analyzed with UPLC-Q-TOF-MS. A rat model of hypothermia caused by seawater immersion at 15 °C was utilized. Survival analysis was used to evaluate the prophylactic effect of single intragastric administration of SFD with different ratios and doses on the survival time of rats, and to identify the optimal intervention conditions. Network pharmacology analysis based on the absorbed constituents of SFD was performed to preliminarily predict the underlying mechanisms, which were subsequently validated using RT-PCR, Western blotting, ELISA, and H&E staining. Results: SFD contained 54 compounds, including ginsenosides and aconitine alkaloids, whose relative concentrations varied across different ratios of SFD. Animal studies showed that pretreatment of SFD (1:1) administered at a dose of 1.35 g/kg was very effective in increasing rats’ survival time in hypothermia and slowed down core body temperature decline. Based on the 28 plasma-absorbed compounds of SFD, network pharmacology identified 503 targets, enriched in cAMP and MAPK signaling pathways. SFD (1:1, 1.35 g/kg) resulted in larger lipid droplets in brown adipose tissue (BAT) and enhanced the respiratory metabolic rate in seawater-immersion-induced hypothermia rats. Furthermore, its thermogenic effect is likely associated with the upregulation of uncoupling protein 1 (UCP1) via activating p38 MAPK/PGC1α/PPARγ and NE-(β3-AR)-cAMP-PKA pathways. Conclusions: The results of this study demonstrate that a single prophylactic administration of the traditional Chinese medicine formula SFD prior to cold seawater exposure significantly prolongs the survival time of rats. This effect is associated with the upregulation of UCP1 and the subsequent enhancement of thermogenesis in BAT. These findings highlight the great potential of SFD as a promising intervention for the management of hypothermia.

Cold seawater immersion is a critical lethal risk in maritime accidents and military operations, frequently inducing fatal myocardial dysfunction. However, the mechanisms underlying this seawater immersion hypothermia-induced cardiac injury remain poorly defined. This study aimed to elucidate the pathological progression and underlying mechanisms of myocardial injury induced by cold seawater immersion. A male SD rat model was immersed in 15 °C seawater for 2 h. Echocardiography, transmission electron microscopy, transcriptomics, and Western blot were performed to assess cardiac function, mitochondrial ultrastructure, and molecular mechanisms. Cold stress triggered progressive bradycardia (~480 to ~100 bpm) with initial Frank–Starling compensation, followed by decompensation with reduced cardiac output and impaired diastolic function. Mitochondrial ultrastructural damage preceded histological lesions and was accompanied by elevated cardiac injury markers (cTnT, CK-MB, BNP). Cardiac tissue exhibited upregulated TNF-α, IL-1β, and IL-6, while transcriptomic analysis revealed enrichment of inflammatory pathways (TNF, NF-κB) and coordinated upregulation of pattern recognition receptors including scavenger receptor, Toll-like receptor, and NOD-like receptor families. The Western blot confirmed NF-κB activation, NLRP3 inflammasome assembly, and the N-terminal fragment of gasdermin D (GSDMD-NT) accumulation, indicating pyroptotic cell death. These findings demonstrate that cold seawater stress disrupts mitochondrial homeostasis and activates the NF-κB/NLRP3/pyroptosis cascade, contributing to inflammatory cardiomyocyte death and cardiac decompensation. This mechanistic insight may inform therapeutic strategies for seawater immersion hypothermia.