Cytokines gene expression alterations in Rhinella toads following an immune challenge with lipopolysaccharide (LPS)

• Grant number: 20/00370-6
• Support Opportunities: Scholarships in Brazil - Master
• Effective date (Start): July 01, 2020
• Effective date (End): January 31, 2022
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Felipe Rangel Floreste
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 14/16320-7 - Impacts of climate/environmental change on the fauna: an integrative approach, AP.PFPMCG.TEM

Abstract

In the last decades, amphibian populations around the world have experimented an aggravated decline. Among the probable causes, we can highlight climate change, pollution, habitat fragmentation and introduction of invasive species. Such alterations may be perceived as chronic stressors, impair the immune function and potentialize the exposure to pathogens, resulting in higher mortality rates. The contact of amphibians with this environmental instability can lead to an increase in the secretion of glucocorticoid hormones. The elevation of glucocorticoids in the circulation may also affect the circulating of other hormones, for example, decreasing testosterone and melatonin plasmatic concentrations. Moreover, glucocorticoid hormones have a complex immuno-modulatory effect according to the temporal pattern of the hypothalamus-pituitary-interrenal (HPI) axis activation. Inside of this context, it is fundamental a better understanding of the endogenous immune processes in amphibians and the modulation by glucocorticoid hormones on their immune function. The general objective of this project is to evaluate the temporal dynamics of the plasma hormones corticosterone, testosterone and melatonin and the gene expression of cytokines that participate in activating and regulating the inflammatory response in anurans following an immune challenge. Therefore, we used lipopolysaccharide (LPS) in order to mimic a bacterial infection in Rhinella diptycha toads while tracking cytokines expression in the spleen and plasmatic concentrations of corticosterone, testosterone and melatonin. So far, our preliminary results demonstrate a complex temporal variation pattern of the plasmatic concentrations of corticosterone, testosterone and melatonin, as well as the immune parameters in response to LPS. Similarly, we predict to find a compatible temporal pattern of the cytokines expression. Thus, we expect higher expression of pro-inflammatory cytokines in the earlier measurements after injection, decreasing as the expression of regulatory and anti-inflammatory cytokines accentuates in the later measurements leading to the resolution of the inflammatory process. (AU)