LPS‐induced immunomodulation and hormonal variation over time in toads

Abstract

The inflammatory response is a complex process that relies on interactions among multiple endocrine and immune modulators. Studies incorporating time-related and integrative endocrine and immune responses to an immune challenge might shed light on the characterization of the phases of the inflammatory response in anurans. The present study investigated time-related changes (1, 3, 6, and 18 h post-challenge) in plasma corticosterone (CORT), melatonin (MEL) and testosterone (T) levels, phagocytosis percentage (PP), plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR) following a lipopolysaccharide (LPS) immune challenge in Rhinella diptycha toads.Our results showed the response to LPS injection was characterized by increased CORT, PP, BKA, and NLR, with a concomitant decrease in plasma MEL and T. Increased CORT was more pronounced at 6 and 18 h, while increased NLR was observed only 18 h post-LPS injection. Meanwhile, plasma MEL and T decreased independently of the time post-LPS injection. Additionally, toads in better body condition showed higher BKA and PP in the LPS-treated group, regardless of the time postinjection. Our results show that toads (R. diptycha) were sensitive to the LPS challenge, mounting an inflammatory response, which started quickly (after 1 h) and developed over time and was influenced by body condition. These results demonstrate a time-related hormonal and immune variation as a consistent pattern of activation of the immune system, as well as of hypothalamicpituitary-adrenal/interrenal and immune-pineal axes following an immune challenge more deeply studied in mammals, suggesting the evolutionary conservation of the regulatory mechanisms for tetrapod vertebrates.

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

“…Moreover, Titon Junior et al . [64] demonstrated that body index was positively associated with BKA and percentage phagocytosis after lipopolysaccharide injection in R. diptycha . Herein, potential interactions between body condition and T-induced immunomodulation were not found in T-treated R. icterica toads.…”

“…In addition, individuals of R. icterica maintaining body index under long-term captivity also showed a positive association between T and percentage phagocytosis [43]. Moreover, Titon Junior et al [64] demonstrated that body index was positively associated with BKA and percentage phagocytosis after lipopolysaccharide injection in R. diptycha. Herein, potential interactions between body condition and T-induced immunomodulation were not found in T-treated R. icterica toads.…”

Introduction to the special issue Amphibian immunity: stress, disease and ecoimmunology

“…Stress-driven immunomodulation has gained more attention in ectothermic vertebrates in the last decades [25,27,39,[56][57][58][59][60][61][62], with implications on the stress-induced protective and harmful effects on several immune functions. As observed in other vertebrates, the amphibian immune system is subjected to stressors and its endocrine mediators, including glucocorticoid-induced immunomodulation [27,28,31,32,63,64].…”

Efeitos de uma infecção simulada no comportamento alimentar e locomotor de anuros.

“…A ação específica do LPS no organismo de anuros é pouco esclarecida em detalhes na literatura, mas já foi observado que anuros injetados com LPS apresentam em seus níveis plasmáticos glicocorticóides e moléculas pró-inflamatórias como as citocinas (IL-1β, IL-6, TNF-α), que desencadeiam uma resposta inflamatória e levam as alterações comportamentais comentadas Junior et al, 2021;.…”