Meeting Abstract
Glucocorticoids and melatonin show integrated and complex immunomodulatory effects described for mammals, but underexplored in amphibians. In this context, the oligonucleotides development to quantify gene expression of molecules mediating inflammatory processes in amphibians is an innovative way to explore the relationships among molecular biology, stress physiology and immune response in these animals. In this study, toads (Rhinella diptycha) received an intraperitoneal injection of saline (APBS) or lipopolysaccharide (LPS; 2mg/kg). Six hours post-injection, toads were bled to measure corticosterone (CORT), testosterone (T), and melatonin (MEL) plasma levels, neutrophil/lymphocyte ratio (NL), and bacterial killing ability (BKA). Then, toads were killed by decapitation and lavage fluid and spleens were collected to measure phagocytosis from peritoneal leukocytes (PP) and quantify gene expression (IL1β, IL6, IL10, IFN-γ and C1s), respectively. As partial results, we found increased CORT (p=0.05) and a trend of increased NL and decreased MEL, T and PP in response to LPS. We found IL6 and IL10 upregulation in LPS-injected toads compared to saline-injected (p≤0.05). These results show toads responded to LPS within this timeframe by secreting cytokines related with immune cells attraction to inflammatory site (IL6), but also secreting anti-inflammatory cytokines (IL10), which would inhibit pro-inflammatory cytokines such as IL1β and IFN-γ. Even without significant differences in most physiological variables for these preliminary results, the patterns found were expected for an inflammatory stimulus: increased circulating CORT (activation of hypothalamus-pituitary-interrenal axis) and decreased circulating MEL (possible activation of immune-pineal axis).
