Analysis of C3 Suggests Three Periods of Positive Selection Events and Different Evolutionary Patterns between Fish and Mammals

BACKGROUND: The third complement component (C3) is a central protein of the complement system conserved from fish to mammals. It also showed distinct characteristics in different animal groups. Striking features of the fish complement system were unveiled, including prominent levels of extrahepatic expression and isotypic diversity of the complement components. The evidences of the involvement of complement system in the enhancement of B and T cell responses found in mammals indicated that the complement system also serves as a bridge between the innate and adaptive responses. For the reasons mentioned above, it is interesting to explore the evolutionary process of C3 genes and to investigate whether the huge differences between aquatic and terrestrial environments affected the C3 evolution between fish and mammals. METHODOLOGY/PRINCIPAL FINDINGS: Analysis revealed that these two groups of animals had experienced different evolution patterns. The mammalian C3 genes were under purifying selection pressure while the positive selection pressure was detected in fish C3 genes. Three periods of positive selection events of C3 genes were also detected. Two happened on the ancestral lineages to all vertebrates and mammals, respectively, one happened on early period of fish evolutionary history. CONCLUSIONS/SIGNIFICANCE: Three periods of positive selection events had happened on C3 genes during history and the fish and mammals C3 genes experience different evolutionary patterns for their distinct living environments

Effects of Chronic Cortisol Administration on Global Expression of GR and the Liver Transcriptome in Sparus aurata

The present work was designed to assess the effects of artificially increased high plasma cortisol levels induced by slow-release cortisol implants on the mRNA abundance of the glucocorticoid receptor (GR) in different organs of Sparus aurata (Gilthead sea bream), as well as to evaluate global transcriptional changes in the liver, using the Aquagenomics S. aurata oligo-nucleotide microarray technology. For that purpose, groups of fish were intraperitoneally injected with implants containing two different concentrations of cortisol (50 or 200 μg/g body weight). Blood and organs were sampled after 7 and 14 days of cortisol implantation. Only fish with 200 μg/g implants exhibited a significant rise in plasma cortisol. Thus, we evaluated the expression of the GR in different organs in these fish 7 and 14 days post-implantation. GR mRNA abundance was upregulated in head kidney and heart of fish at both sampling times. In liver and muscle, GR mRNA abundance was upregulated after 14 days, whereas in gills, the GR mRNA transcript was upregulated earlier, at day 7. These results suggest that increased plasma cortisol induced by a slow-release implant of cortisol mimics the overall effects of stress and affects the expression of GR mRNA in a time- and organ-specific manner. Data obtained with the Aquagenomics S. aurata oligo-nucleotide microarray allowed the identification of a total of 491 cortisol-responsive transcripts and highlight the strong intensity of transcriptional modulation in liver of fish implanted with cortisol after 7 days, in contrast to that observed at day 14. Transcriptional remodeling highlighted a significant activity in carbohydrate metabolism mainly in the gluconeogenic pathway linked to downregulation of inflammatory and immune response processes in implanted fish

Interactive effects of a high-quality protein diet and high stocking density on the stress response and some innate immune parameters of Senegalese sole Solea senegalensis

Amino acids (AA) regulate key metabolic pathways, including some immune responses. Therefore, this study aimed to assess whether an increased availability of dietary AA can mitigate the expected increase in plasma cortisol and metabolites levels due to high stocking density and its subsequent immunosuppression. Senegalese sole (Solea senegalensis) were maintained at low stocking density (LSD; 3.5 kg m−2) or high stocking density (HSD; 12 kg m−2) for 18 days. Additionally, both treatments were fed a control or a high protein (HP) diet (LSD, LSD HP, HSD and HSD HP). The HP diet slightly increased the levels of digestible indispensable AA, together with tyrosine and cysteine. HSD was effective in inducing a chronic stress response after 18 days of treatment since fish held at HSD presented higher plasma cortisol, glucose and lactate levels. Moreover, this increase in stress indicators translated in a decrease in plasma lysozyme, alternative complement pathway (ACP) and peroxidase activities, suggesting some degree of immunosuppression. Interestingly, while plasma glucose and lactate levels in HSD HP specimens decreased to similar values than LSD fish, plasma lysozyme, ACP and peroxidase activities increased, with even higher values than LSD groups for ACP activity. It is suggested that the HP diet may be used as functional feed since it may represent a metabolic advantage during stressful events and may counteract immunosuppression in sole