Integrated Transcriptomic Analysis Uncovers the Protective Effects of Berberine Hydrochloride in Enhancing Hepatic Caecum Response of Branchiostoma belcheri (Chinese lancelet) to Aeromonas hydrophila.

Berberine hydrochloride (BH), the derivative component of Coptidis chinensis, is widely used to treat bacterial infections due to its notable antibacterial properties. However, the underlying molecular mechanisms of its therapeutic effects remain largely unexplored. This study employed transcriptome sequencing to investigate berberine hydrochloride's therapeutic efficacy and molecular responses in Branchiostoma belcheri infected with Aeromonas hydrophila. In this study, B. belcheri was first exposed to 200 mg/L berberine hydrochloride (BH) for 24 h, and then infected with A. hydrophila. After 48 h, transcriptome differential expression analysis was performed to compare the transcriptomic changes with the control group. A total of 2,478 differentially expressed genes (DEGs) were identified. Enrichment analysis revealed that these DEGs are involved in key pathways such as metabolism, cellular processes, signal transduction, and immune functions. Berberine hydrochloride treatment activated pathways including retinol metabolism, proteasome function, oxidative phosphorylation, lysosome, phagosome, and glutathione metabolism. RT-PCR validation confirmed the upregulation of immune-related genes such as TUBA, RAB5A, CTSL, GST, GPX4, G6PD, ND1, COX2, FECH, and LYP3A across these seven pathways. Notably, the glutathione metabolism, phagocytosis, and oxidative phosphorylation pathways appear to be central in regulating BH-mediated protection against A. hydrophila infection in B. belcheri. Moreover, BH significantly enhanced the activity of glutathione-related pathways, including GST, GSH, GPX, and GSSG in the hepatic caecum, activating oxidative defence systems and modulating immune-related responses in B. belcheri under A. hydrophila exposure. These results provide new insights into the potential role of BH in enhancing immune and oxidative stress responses in lancelets, which may have implications for its application in aquaculture.