Testosterone immunomodulation in free-living and captive Rhinella icterica male toads

Author(s)

Titon, Stefanny Christie Monteiro ; Junior, Braz Titon ; Assis, Vania Regina ; de Figueiredo, Aymam Cobo ; Floreste, Felipe Rangel ; Lima, Alan Siqueira ; Gomes, Fernando Ribeiro

• Document type: Journal article
• Source: PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES; v. 378, n. 1882, p. 10-pg., 2023-07-31.

Abstract

Testosterone (T) regulates immune function, with both immunostimulatory and immunosuppressive effects on several vertebrates. We investigated the covariation between plasma T and corticosterone (CORT) levels and immunity (plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR)) in free-living Rhinella icterica male toads inside and outside the reproductive season. We found an overall positive correlation between steroids and immune traits, with toads during the reproductive season displaying increased T, CORT and BKA. We also investigated the T transdermal application effects on T, CORT, phagocytosis of blood cells, BKA and NLR in captive toads. Toads were treated with T (1, 10 or 100 mu g) or vehicle (sesame oil) for eight consecutive days. Animals were bled on the first and eighth days of treatment. Increased plasma T was observed on the first and last day of T-treatment, while increased BKA was observed following all T doses on the last day, with a positive correlation between T and BKA. Plasma CORT, NLR and phagocytosis increased on the last day for all T-treated and vehicle groups. Overall, we demonstrated a positive covariation between T and immune traits in the field and T-induced augmented BKA in captive toads, indicating a T immunoenhancing effect in R. icterica males.This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'. (AU)

• FAPESP's process: 14/16320-7 - Impacts of climate/environmental change on the fauna: an integrative approach
• Grantee: Carlos Arturo Navas Iannini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 19/24950-4 - Temporal dynamics of the inflammatory response in amphibians
• Grantee: Fernando Ribeiro Gomes
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/01782-0 - Relations between environmental and physiological conditions of activity and its importance for the distribution alterations of toads with climatic changes
• Grantee: Braz Titon Junior
• Support Opportunities: Scholarships in Brazil - Post-Doctoral