Effects of chronic leptin administration on nitric oxide production and immune responsiveness of greenfinches |
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Authors: | Lõhmus Mare Sild Elin Hõrak Peeter Björklund Mats |
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Institution: | a Department for Chemistry, Environment and Feed Hygiene, National Veterinary Institute, Ulls väg 2B, 75189 Uppsala, Sweden;b Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden;c Institute of Ecology and Earth Sciences, Tartu University, Vanemuise 46, 51014 Tartu, Estonia |
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Abstract: | Leptin and nitric oxide (NO) are both important messengers in intra- and intercellular communication systems in vertebrates. Several studies have demonstrated an involvement of both substances in the immune response. Here we tested the effects of chronic leptin and anti-leptin treatments on the NO production and phytohaemagglutinin- (PHA) induced cutaneous inflammatory response in a wild passerine, the greenfinch (Carduelis chloris). Plasma leptin levels of individual birds were consistent in time but could be still temporarily increased by administration of recombinant chicken leptin. Increase of plasma leptin was also induced by administration of anti-leptin, which can be most likely explained by increased endogenous leptin production due to disruption of signalling pathways. Contrary to previous findings in mammals, leptin administration reduced systemic NO production. Leptin increased cutaneous swelling response to PHA. This immune-enhancing effect was observable despite the similar plasma leptin levels of leptin-treated and control birds at the time of measurement of immune responses, i.e., 9 days after start of the treatments. This provides evidence for a delayed or long-term potentiation of the cells and cytokines involved. The effects of leptin administration on NO production and immune responsiveness were age-dependent, which indicates the complexity of underlying regulatory mechanisms. |
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Keywords: | Leptin Nitric oxide Passerine Carduelis chloris Phytohaemagglutinin Cutaneous swelling response Immunomodulation Body mass Age differences |
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