Integrated transcriptomic and proteomic analysis of heat exposure on heart tissue in rats

Background: Deaths due to heat stroke have surged in recent years in Japan. While the long-term sequelae of heat stroke in its survivors are well understood, our previous studies suggest that heat exposure may cause fatal organ damage before the systemic inflammatory response is triggered. In this study we aimed to provide a comprehensive analysis of cytokines and other signaling factors in sera and myocardial tissues in a rat model of heat stress. Methods: Male Wistar rats were anesthetized and subjected to heat stress (37.0°C, 100% humidity; n = 8) to induce heat stroke (Heat group, n = 4) or normal temperatures (Control group, n = 4) for 90 min, followed by collection of blood sera and heart tissue samples. A multiplex assay system was used to analyze serum markers. Heart tissue was subjected to multiplex RNA sequencing and gene cascade analysis, and combined with iTRAQ (isobaric tags for relative and absolute quantitation) protein pathway analysis. Results: There were significantly higher levels of five interleukins (IL-1α, IL-2, IL-6, IL-17A, IL-18), fractalkine, interferon-γ-inducible protein-10, leptin, tumor necrosis factor α, and vascular endothelial growth factor, and significantly lower levels of LIX and RANTES, in the sera of the Heat group compared with the Control group. From the 2,741 genes that showed a significant difference in myocardial mRNA expression between the groups, we identified 48 transcription factors and 34 binding regions. Pathway analysis identified the involvement of key node proteins including protein kinase C isoforms, calmodulin-dependent protein kinase II, and protein interacting with C-kinase (PICK1). Conclusion: This model of heat stress in rats triggered changes in the mRNA and protein levels of many genes involved in cardiac function, primarily affecting the activity of ion channels and mitogen-activated protein kinase.