Transcriptome analysis provides insights into the function of the cholinergic system in pearl oyster transplantation immunity

Excessive immune response of pearl oyster after transplantation is the main factor that causes its nucleus rejection and death. In this study, to clarify how the cholinergic system regulates the immune response after transplantation, ACh and mecamylamine hydrochloride (nAChR inhibitor) were used to activate or block the cholinergic system of pearl oysters before transplantation. Transcriptomes of hemocytes were constructed at different times (6, 12, 24, and 48 h) after transplantation. Transcriptome analysis showed that the Kyoto Encyclopedia of Genes and Genomes pathway related to inositol phosphate metabolism pathway and Gene Ontology (GO) terms calcium-ion binding were significantly enriched in the differential expression genes of the two comparisons, and calmodulin genes were upregulated at 12-24 h after activation of the cholinergic system. Further experiments showed that ACh treatment significantly induced intracellular Ca2+ concentration. GO terms related to antioxidant activity and superoxide dismutase activity were significantly enriched in the two comparisons. The result of enzyme activity showed that the activities of superoxide dismutase and catalase in serum were significantly upregulated after activation of the cholinergic system but downregulated after blockade of this system. Furthermore, the cholinergic system maybe participate in regulating the DNA replication, cell cycle, mismatch repair, and apoptosis of the hemocytes after transplantation. These results provide new insights into the molecular mechanism of the cholinergic system in regulating the immunity of pearl oyster transplantation and facilitate the development of immunosuppressive agents to improve the effectiveness of cultured pearls.

Automated summary

The excessive immune response of pearl oysters after transplantation is mainly caused by rejection and death. This study investigated how the cholinergic system regulates immune responses post-transplantation and found that activating or blocking the cholinergic system significantly impacted immune responses. Activation of the cholinergic system induced intracellular Ca2+ concentration and enriched genes related to antioxidant and enzymatic activity, while blockade had the opposite effect. These findings shed light on the molecular mechanisms of the cholinergic system in regulating post-transplantation immunity in pearl oysters.