Effects of Endotoxin and Psychological Stress on Redox Physiology, Immunity and Feather Corticosterone in Greenfinches

Abstract

Assessment of costs accompanying activation of immune system and related neuroendocrine pathways is essential for understanding the selective forces operating on these systems. Here we attempted to detect such costs in terms of disruption to redox balance and interference between different immune system components in captive wild-caught greenfinches (Carduelis chloris). Study birds were subjected to an endotoxin-induced inflammatory challenge and temporary exposure to a psychological stressor (an image of a predator) in a 2*2 factorial experiment. Injection of bacterial endotoxin resulted in up-regulation of two markers of antioxidant protection – erythrocyte glutathione, and plasma oxygen radical absorbance (OXY). These findings suggest that inflammatory responses alter redox homeostasis. However, no effect on markers of oxidative damage to proteins or DNA in erythrocytes could be detected. We found no evidence that the endotoxin injection interfered with antibody production against Brucella abortus antigen or the intensity of chronic coccidiosis. The hypothesis of within-immune system trade-offs as a cost of immunity was thus not supported in our model system. We showed for the first time that administration of endotoxin can reduce the level of corticosterone deposited into feathers. This finding suggests a down-regulation of the corticosterone secretion cascade due to an endotoxin-induced immune response, a phenomenon that has not been reported previously. Exposure to the predator image did not affect any of the measured physiological parameters.

Ambient temperature, body condition and sibling rivalry explain feather corticosterone levels in developing black kites

“…Detectable CORT levels have been reported in the feathers of all avian species analysed so far (c. 35 species), representing a diverse range of orders, habitats, ecological contexts, body sizes, trophic positions and behaviours (e.g. Bortolotti et al 2008;Kouwenberg et al 2013;Legagneux et al 2013;Meitern et al 2013). Such generalized trait underscores the potential for conducting similar analyses to the ones applied in this study on other wild birds, thereby opening the door further to the use of feathers as widespread indicator tools in conservation.…”

“…; Meitern et al . ). Such generalized trait underscores the potential for conducting similar analyses to the ones applied in this study on other wild birds, thereby opening the door further to the use of feathers as widespread indicator tools in conservation.…”

Beyond corticosterone: The acute stress response increases DNA damage in house sparrows

“…These studies have used DNA damage to assess the effects of longer term stressors, including environmental pollution, radiation exposure, and captivity. A minority of studies have also examined the impacts of short‐term stressors—including immune activation (Meitern et al, 2013), cold exposure (Stier, Massemin, & Criscuolo, 2014), and restraint (Malandrakis et al, 2016; Stier et al, 2019)—on DNA damage. In this study, we tested the hypothesis that DNA damage increases acutely in the whole blood of house sparrows when exposed to standardized restraint stress.…”

Exogenous and endogenous corticosterone in feathers

“…fCORT has been shown to increase with stress (Fairhurst et al 2011, decrease with stress (Meitern et al 2013, Patterson et al 2015, or remain unchanged (this study). This indicates that it is imperative that researchers take care in interpreting fCORT levels in wild birds.…”

“…Many more studies have made use of fCORT in an ecological context, relating fCORT to, for example, food quality, immunity, sexual coloration, or carry-over effects between life history stages (Lendvai et al 2013, Sild et al 2014, Harms et al 2015. However, there have been relatively few studies where experimentally induced stress has been related to fCORT levels (Fairhurst et al 2011, Meitern et al 2013, Patterson et al 2015. Of these, two experiments examined the effects on fCORT of major nutritional deprivation in developing young , Patterson et al 2015.…”