iTRAQ-based proteomic identification of cyclophilin as a candidate mediator for cyclosporin A-mediated immunomodulation in pearl oysters Pinctada fucata martensii.

Transplantation surgery induces severe immune stress in pearl oysters Pinctada fucata martensii, yet effective immunomodulatory strategies remain limited. This study establishes a proteomics-guided strategy for immunomodulation by identifying cyclophilin as a candidate mediator through iTRAQ-based quantitative analysis and validating cyclosporin A (CsA) through serum immune indicator and transcriptome analysis. Serum iTRAQ analysis identified 1069 differentially expressed proteins following transplantation, among which cyclophilin exhibited significant up-regulation and was selected as a candidate target for therapeutic intervention. Dose-response assays determined 3.9 × 10-3 mol/L as the optimal concentration, which significantly suppressed TNF-α levels under LPS stimulation (P < 0.05). At this concentration, CsA pre-treatment markedly decreased circulating IL-17 concentrations, while it enhanced SOD and CAT enzymatic activities (P < 0.05). Transcriptome analysis revealed that CsA treatment was associated with upregulation of HIF-1 and Notch signaling pathway-related genes, concomitant with alleviation of LPS-induced downregulation in DNA replication and cell cycle pathways. Furthermore, CsA significantly inhibited hemocyte apoptosis compared to the control group (P < 0.05). These findings demonstrate that iTRAQ-based proteomic screening enables rational target identification for immunomodulation, and CsA exerts protective effects associated with altered expression of HIF-1/Notch pathway-related genes and apoptosis inhibition. These findings provide a molecular basis for developing immunomodulatory strategies in pearl oyster aquaculture.