Transcriptome analysis reveals the mechanism of cortisol through GR regulating the expression of inflammatory cytokines in Siberian sturgeon (Acipenser baerii) after LPS treatment in vitro

Cortisol can impact the transcription of downstream inflammation and immune-related genes via the glucocorticoid receptor (GR), thereby influencing the immune response and maintaining the homeostatic balance of the host. However, there is a lack of research on the mechanisms by which cortisol affects the immune response of Siberian sturgeon (Acipenser baerii) through GR. In this study, an anti-inflammatory state of Siberian sturgeon was established by the combined treatment of head kidney (HK) leukocytes with LPS + cortisol. Subsequently, the inflammation-related genes of the AbGR antagonistic group (LPS + cortisol + RU-486) and the AbGR non-antagonistic group (LPS + cortisol) were compared by qRT-PCR and high-throughput sequencing methods. Furthermore, an AP-1 agonist ASLAN003 was used to detect the regulatory effect of the AP-1 gene on inflammatory cytokines. The results showed that cortisol downregulated the expressions of il-1β, il-6, il-8, tnf-α, and il-17c that were induced by LPS, while simultaneously promoting the expressions of tgf-β1. Moreover, this pattern was reversed by adding RU486. When analyzing the differentially expressed genes in the transcriptome sequencing of HK leukocytes in AbGR antagonistic group, 261 significantly down-regulated genes and 194 significantly up-regulated genes were annotated. Furthermore, 26 differentially expressed genes related to inflammation in AbGR antagonistic group were enriched, and the key nuclear transcription factor AP-1 for regulating inflammation function of AbGR was selected based on the enrichment factor and p-value for subsequent research. In the HK leukocytes after cortisol + ASLAN003 treatment, the expressions of fosl1 and jund that were induced by ASLAN003 were significantly down-regulated after cortisol treatment. In this situation, the expression of tgf-β1 was significantly increased, and the expression of tnf-α was significantly decreased after cortisol treatment. Therefore, this study demonstrated that cortisol inhibits the expression of AP-1 through GR in Siberian sturgeon, and then regulates the generation of the inflammatory response.