Abstract
Circular RNAs (circRNAs) have vital roles in great variety of biological processes. However, expression levels and functions of circRNAs related to heat acclimation (HA) are poorly understood. This study is the first time an in-depth circRNA expression profiling were used to investigate circRNA–miRNA interactions in HA rats in order to further comprehend the mechanisms underlying HA. CircRNA expression profile was performed in rats’ hypothalamus of HA and control group with microarray assays and their functions were predicted by using Bioinformatics analysis. Differential circRNAs and their regulated downstream miRNAs and mRNAs were quantitatively validated by means of quantitative polymerase chain reaction in real-time (RT-qPCR). Enzyme-linked immunosorbent assay (ELISA) was then applied to predict the expression of proteins. In total, 53 circRNAs were expressed distinctively between the HA and Control; up- and down-regulation of circRNAs were 28 and 25, respectively, in HA (fold change > 1.5, P < 0.05). Three circRNAs and two miRNAs and three predicted mRNAs were obviously regulated after validated by RT-qPCR in HA rats. Two proteins expression were proportional to their mRNA changes. Further analysis demonstrates that circRNAs closest to HA can be categorized into three signal pathways: including rno_circRNA_014301-vs-rno-miR-3575-vs-Hif-1α, rno_circRNA_014301-vs-rno-miR-3575-vs-Lppr4, and rno_circRNA_010393-vs-rno-miR-20b-3p-vs-Mfap4 in hypoxia response pathways, substance/energy metabolism, and inflammatory response pathways. Our findings implicate that many circRNAs regulate expressions of genes that interact with each other to exert their functions during HA.
Highlights
Heat acclimation results in a multitude of positive adaptations, including elevated whole-body sweat rate and body plasma volume in conjunction with reduced core temperature and heart rate (Schwimmer et al, 2004; Dervisevik et al, 2011)
Using the information obtained from microarray analysis, we aimed to identify the regulatory genes and pathways as well as their targeted genes involved in heat acclimation (HA) to obtain the indepth understanding of molecular mechanism underlying HA, which can serve as an experimental basis for the targeted activation of HA
Prolonged heat exposure resulted in a prominent decrease of rectal temperature (Tre) in the HA group (Figure 1C)
Summary
Heat acclimation results in a multitude of positive adaptations, including elevated whole-body sweat rate and body plasma volume in conjunction with reduced core temperature and heart rate (Schwimmer et al, 2004; Dervisevik et al, 2011). Temperature threshold for thermal injury is generally associated with the increment of inducible cytoprotective networks which includes several components of essential acclimation, such as HIF-1, HSP70, and HSF1. In the same vein, Schwimmer et al (2006) have examined mRNA expression in HA, heat-stressed rats using a cDNA array of stress genes and substantiated (in addition to changes in HSPs) enhancements of antiapoptotic and antioxidative networks by demonstrating the upregulation of gene transcripts associated with cell cycle in the hypothalamus of long-term HA rats (Horowitz et al, 2004). There is limited information regarding molecular mechanisms underlying HA and division of specific essential HA pathways
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