Abstract: BACKGROUND: When exercising in a cold environment, the body’s inflammatory response is affected by both low temperature and exercise intervention, and its impact and mechanism remain to be explored.
OBJECTIVE: To explore the effects and mechanisms of cold water swimming on inflammatory response of rats based on transcriptome sequencing technology.
METHODS: 40 male SD rats were randomly divided into room temperature control group, room temperature swimming group, cold water control group, and cold water swimming group, with 10 rats in each group. The room temperature control group had no intervention and was free to eat. The room temperature swimming group received swimming at 30 min/time, 6 times/week, for 5 weeks; the water temperature was (28±2) °C, and the water depth was 35 cm. In the cold water control group, the rats were placed in a water tank with a depth of 3 cm; the water temperature was (18±2) °C, and they were free to move. The cold water swimming group received swimming at 30 min/time, 6 times/week, for 5 weeks; the water temperature was (18±2) °C, and the water depth was 35 cm. Enzyme-linked immunosorbent assay was used to detect the levels of serum interleukin-6, tumor necrosis factor-α, and high-sensitivity C-reactive protein. Based on the transcriptome sequencing results, differentially expressed genes were screened to draw Venn diagrams and heat maps, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were performed. The protein-protein interaction network was used to screen core genes. RT-qPCR was used to detect the mRNA expression of IRF7, OAS2, and OASL in rat spleen tissue.
RESULTS AND CONCLUSION: (1) The ELISA results showed that compared with the room temperature control group, the levels of various inflammatory indicators in the room temperature swimming group and the cold water swimming group were significantly increased (P < 0.05), and there was no significant difference in the cold water control group. Compared with the room temperature swimming group, there was no significant difference in the expression of inflammatory indicators in the cold water swimming group. Compared with the cold water control group, the expressions of interleukin-6 and tumor necrosis factor-α in the cold water swimming group showed an upward trend, and high-sensitivity C-reactive protein increased significantly (P < 0.05). (2) Transcriptome analysis: Venn diagram showed that there were 39 differentially expressed genes affected by the dual factors of temperature and exercise intervention. Cluster heat map analysis results showed that the overall gene expression trends of the room temperature swimming group and the cold water swimming group were similar, and the cold water control group showed an opposite trend. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis results showed that differentially expressed genes were enriched in the immune system, locomotion, nucleic acid-binding transcription factor activity, NOD-like receptor signaling pathways and other pathways. The number of genes enriched in the NOD-like receptor signaling pathway was relatively large, and the q value was small, which may be a key pathway. The protein-protein interaction network screened out IRF7, OAS2, OASL, IFIT2, IFIT3 and other core genes. (3) RT-qPCR verification results showed that compared with the room temperature control group, the expressions of IRF7, OAS2 and OASL were significantly increased in the room temperature swimming group and the cold water swimming group (P < 0.01), and there was no significant difference in the cold water control group. Compared with the cold water control group, the expression of each gene was significantly increased in the cold water swimming group (P < 0.01). (4) It is concluded that cold water swimming can promote inflammatory response, and its mechanism may be regulated through the NOD-like receptor signaling pathway.

Key words: cold water swimming, inflammatory response, transcriptome, NOD-like receptor signaling pathway, differentially expressed gene, engineered tissue construction