The underlying mechanism of cardiac injury in exertional heat stroke rats based on the scRNA-seq analysis.

Heat dissipation relies on an intact cardiovascular system to dilate cutaneous blood vessels and increase cardiac output. However, the heart becomes a vulnerable organ and is susceptible to cardiac arrhythmias, functional failure, and focal myocardial necrosis in a hyperthermic state. In particular, individuals with cardiovascular dysfunction are at a much higher risk of exertional heat stroke (EHS). This study aimed to investigate and validate the cell signaling pathways and key genes associated with EHS. The findings are intended to elucidate the mechanisms underlying cardiac injury and to provide a theoretical basis for the early identification of biomarkers for cardiac injury in EHS. A total of 310 differentially expressed genes (DEGs) were identified across all cell types between the two groups using the SeuratFindMarkers function with the logfc. threshold = 0.25, adjusted P value = 0.05 (Bonferroni correction), and min. pct = 0.1. Of these, 18 genes with substantial variability were chosen for further verification. Finally, RT-qPCR and immunohistochemistry tests verified that Hspa8 and Hspe1 were further up-regulated, while Id1, Ndufa4, and Cd36 were down-regulated. These screened hypervariable genes play different roles in heat stress-induced mitochondrial and myocardial mechanical damage, protein misfolding, and may serve as potential biomarkers in the mechanism of cardiac injury or play an important role in the functional pathway described above.