Characterization of the annual regulation of reproductive and immune parameters on the testis of European sea bass

Abstract

The European sea bass, Dicentrarchus labrax L., is a seasonal gonochoristic species, the males of which are generally mature during their second year of life. It has been demonstrated that cytokines and immune cells play a key role in the testicular development. This reproductive-immune interaction might be very important in the sea bass since several pathogens are able to colonise the gonad and persist in this tissue, altering further reproductive functions and spreading disease. This study aims to investigate the reproductive cycle of 1-year European sea bass males by analysing cell proliferation and apoptosis and the expression profile of some reproductive and immune-related genes in the testis, as well as the serum sex steroid levels. Our data demonstrate that, in 1-year-old European sea bass males, the testis undergoes the spermatogenesis process and that the reproductive and immune parameters analysed varied during the reproductive cycle. In the testis, the highest proliferative rates were recorded at the spermatogenesis stage, while the highest apoptotic rates were recorded at the spawning stage. We have also analysed, for the first time in European sea bass males, the serum levels of 17β-estradiol (E2) and dihydrotestosterone and the gene expression profile of the enzymes implied in their production, determining that at least E2 might be involved in the regulation of the reproductive cycle. Some immune relevant genes, including cytokines, lymphocyte receptors, and anti-viral and anti-bacterial molecules were detected in the testis of naïve European sea bass specimens, and their expression profile was related to the stages of the reproductive cycle, suggesting an important role for the defence of the reproductive tissues.

Transcriptome Dynamics During Turbot Spermatogenesis Predicting the Potential Key Genes Regulating Male Germ Cell Proliferation and Maturation

“…To our knowledge, the present study is the first to investigate spermatogenesis combining male germ cell development with transcriptome in marine fish species. Previous reports related to the process of spermatogenesis in fish mainly focused on morphology descriptions, physiological studies, and the quantity and location of specific genes 11–13 . The large-scale identification of functional genes regulating testis development and spermatogenesis is limited, although omics have been used to investigate biological characteristics such as growth, immunity, sexual dimorphism and sex determination 8–10 .…”

Antimicrobial peptides from fish: beyond the fight against pathogens

“…,b; Valero et al . ,b). Because of its primary structure, disulphide motif and expression pattern, this blood‐derived peptide belongs to a unique family without any resemblance to others (Krause et al .…”

Immune-Endocrine Interactions in the Fish Gonad during Infection: An Open Door to Vertical Transmission

“…In the testicular area of the gonad of the hermaphrodite seasonally breeding gilthead seabream (Sparus aurata), acidophilic granulocytes, macrophages, B and T lymphocytes, and mast cells have been described [49,50]. As occurs in mammals, the testis of gilthead seabream and European sea bass expresses the genes coding for pro-and anti-inflammatory cytokines, chemokines, immunoglobulins, complement factors, antimicrobial peptides (AMPs), immune receptors such as Toll-like receptors (TLRs), and T cell receptor (TCR), as well as molecules involved in the antiviral response [49,51]. In addition, gonadal-specific molecules related with immune-endocrine interactions have been described in other fish species.…”

“…Moreover, the presence of testicular cells in head-kidney acidophilic granulocyte cultures inhibits their phagocytic activity against bacteria [61]. As in mammals, gilthead seabream and European sea bass testis constitutively expresses many cytokines with an expression pattern that depends on the reproductive stage [51,62]. In addition, suppression of cytokine signaling (SOCS)-1 and 3, which act as a negative feedback of cytokine receptor signaling, has been described in the gonad of pufferfish (Tetraodon nigroviridis) [63,64].…”

“…As mentioned above, fish gonads have variable amounts of immune cells, including macrophages, lymphocytes, granulocytes, and mast cells, even though their functioning is not well understood. While their presence and the expression of leucocyte markers, IFN pathway molecules, or cytokines have been described [50,51,62,73], there has been very little in the way of a functional analysis of gonad cells in fish. Besides the molecules described above, AMPs-low weight peptides with amphipathic properties-that are up-regulated upon infection and display a broad-spectrum of antimicrobial functions are also present.…”