Antioxidant protection, carotenoids and the costs of immune challenge in greenfinches

Abstract

SUMMARY Costs accompanying immune challenges are believed to play an important role in life-history trade-offs and warranting the honesty of signal traits. We performed an experiment in captive greenfinches (Carduelis chlorisL.) in order to test whether and how humoral immune challenge with non-pathogenic antigen [sheep red blood cells (SRBC)] affects parameters of individual condition including intensity of coccidian infection, estimates of total antioxidant protection, plasma carotenoids and ability to mount a cell-mediated immune response. We also asked whether the potential costs of immune challenge can be alleviated by dietary carotenoid supplementation. None of the treatments affected intensity of coccidiosis. Humoral immune challenge suppressed the cell-mediated response to phytohemagglutinin (PHA), suggesting a trade-off between the uses of different arms of the immune system. Immune challenge reduced body-mass gain, but only among the carotenoid-depleted birds, indicating that certain somatic costs associated with immune system activation can be alleviated by carotenoids. No evidence for oxidative stress-induced immunopathological damages could be found because immune activation did not affect total antioxidant protection or carotenoid levels. Carotenoid supplementation inclined birds to fattening, indicating that lutein interfered with lipid metabolism. Altogether, our results support the hypotheses of biological importance of carotenoids and exemplify the overwhelming complexity of their integrated ecophysiological functions.

Oxidative profile varies with personality in European greenfinches

“…However, the metabolic demands on the study animals were low: temperature was ambient, food abundant and activity (in cages) limited. It is notable that MDA levels in these captive birds were around half those found in wild-caught greenfinches (0.66±0.33 versus 1.23±0.68nmol MDAml -1 plasma) (Hõrak et al, 2006). Wild birds may differ substantially from caged birds in the demands on their antioxidant systems.…”

Carotenoid intake does not mediate a relationship between reactive oxygen species and bright colouration: experimental test in a lizard

“…For example, Blount et al (Blount et al, 2003) demonstrated that carotenoid-treated male zebra finches had better cell-mediated immune function and were more sexually attractive than controls; this was later replicated by others (McGraw and Arida, 2003). However, in humans, large prospective studies have failed to show an effect of ␤-carotene on the health of well-nourished people with a balanced diet (Hughes, 2001) and subsequent analysis of carotenoid-induced protection against oxidative stress in birds have provided similar results (Hõrak et al, 2006;Constantinti et al, 2007). Other studies with a very similar treatment duration to ours (3-4·weeks) suggest that carotenoids may even have directly harmful effects under some conditions [e.g.…”

Carotenoid intake does not affect immune-stimulated oxidative burst in greenfinches

“…Solutions were freshly prepared each evening using filtered (Brita ® Classic; BRITA GmbH, Taunusstein, Germany) tap water and were provided in 50ml doses in opaque dispensers in order to avoid oxidation of carotenoids. Carotenoid dose was determined on the basis of a previous study (Hõrak et al, 2006), in which birds that were supplemented daily with the same dose of lutein circulated approximately 30gml -1 carotenoids after 23days. According to Hõrak et al (Hõrak et al, 2006), plasma carotenoid levels of wild greenfinches in January ranged from 1.5 to 21.6gml Birds were blood sampled on 27 January (i.e.…”