Proteomic analysis of carp seminal plasma provides insights into the immune response to bacterial infection of the male reproductive system.

Aeromonas salmonicida is recognized as a significant bacterial pathogen in ulcerative disease of cyprinid fish. However, the mechanism of immunity to these bacteria in common carp is still not well understood, especially the immune regulation in the gonad to bacterial infection. The aims of our study were to analyze changes in the seminal plasma proteome following A. salmonicida infection in carp males. The observed pathological changes in the tissue (liver, spleen, kidney and testis) morphology and upregulation of immune-related genes (tnfa2, il6a) confirmed the successful infection challenge. Using mass spectrometry-based label-free quantitative proteomics, we identified 1402 seminal plasma proteins, and 44 proteins (20 up- and 24 downregulated) were found to be differentially abundant between infected and control males. Most differentially abundant proteins were involved in the immune response mechanisms, such as acute phase response, complement activation and coagulation, inflammation, lipid metabolism, cell-cell and cell-matrix adhesion, creatine-phosphate biosynthesis and germ cell-Sertoli cell junction signaling. Bacterial infection also caused profound changes in expression of selected genes in the testis and hematopoietic organs, which contributed to changes in seminal proteins. The altered seminal proteins and bacterial proteins in seminal plasma may serve as valuable markers of infection in the testis.

2D-DIGE proteomic analysis of blood plasma reveals changes in immune- and stress-associated proteins following hormonal stimulation of carp males.

In carp aquaculture, hormonal manipulation with an analog of GnRH (Ovopel) and carp pituitary extract (CPE), which act at different levels of the hypothalamic-pituitary-gonadal axis, is a routine practice to enhance sperm production. Our recent studies revealed that hormonal stimulation of male carp was associated with changes in the seminal plasma proteome, including blood origin proteins. Here, we explored whether Ovopel and CPE could affect the blood proteome of male carp. Both preparations induced increases in semen volume, total number of sperm, and testosterone level. However, hormonal stimulation did not affect the plasma cortisol and glucose levels. A comparative proteomic analysis of carp blood plasma between the control (PBS) and the hormonally treated males revealed significant changes (>1.2 <-1.2-fold change, P < 0.05) in the abundance of 30 spots (14 up- and 16 downregulated) and 44 spots (28 up- and 16 downregulated) upon CPE and Ovopel treatment, respectively. The most significantly affected pathways were acute phase response signaling, the coagulation system, LXR/RXR and FXR/RXR activation; however, there were different sets of proteins in Ovopel- and CPE-treated males. The majority of differentially abundant proteins were involved in the regulation of the immune defense response, the response to stress, and complement activation. Moreover hormonal stimulation with CPE markedly increased the bactericidal activity of blood and both preparations caused profound changes in gene expression in hematopoietic organs. This work is important in understanding the biological processes behind the protein-based response to hormonal stimulation of sperm production in fish.