Influence of ethynylestradiol and trenbolone acetate on the immune system of rainbow trout, Oncorhynchus mykiss

Abstract

In vertebrates, sex hormones act on the reproductive system but also affect the functioning of several non-reproductive tissues, notably the immune system. In teleost fish, reported adverse effects of endocrine disrupting chemicals (EDC) include population decline, inhibition of reproductive function, and disruption of the nervous and immune systems. Although much is know about the end effects of EDC exposure, less is known about the mechanisms induced by the endocrine disruptors on the immunity.
The main goal of this thesis was to improve the understanding of the mechanisms by which exogenous endocrine compounds could disrupt the immune system of juvenile male rainbow trout, Oncorhynchus mykiss, through in vivo exposures to two endocrine disruptive compounds, one estrogenic (17α-ethynylestradiol) and one androgenic (trenbolone acetate).
To achieve this goal, we investigated, first, the major tissues linked to immunity targeted by EDC in order to select the more relevant organs that will be used during the in vivo approach. To do that, the ERα was quantified and located by quantitative real-time PCR, western blot and immunohistochemistry in variety of organs linked to immunity. Secondly, fish were exposed 17α-ethynylestradiol in concentrations ranging from environmental to pharmaceutical doses for 1, 7 and 21 days. Finally, to examine whether xenoandrogens affect the immune system, by applying an experimental design similar to the one used for xenoestrogens. Juvenile male rainbow trout were exposed to two pharmaceutical doses of trenbolone acetate.
The results of ERα characterization supported the hypothesis that estrogenic compounds could modulate the immunity in rainbow trout. The ERɑ1 was observed into each organ investigated and we highlighted a co-expression of ER and several immune actors. This observation is an important indication that estrogenic compounds could modulate the immune system in rainbow trout. This disruption of immune mechanisms by estrogenic compounds was further confirmed by an in vivo exposure of trout juveniles to EE2. Indeed, the immune capacity of the skin seems to be intensifying by EE2 as well as plasma humoral innate immunity, given that both plasma myeloperoxidase and lysozyme activity increased with EE2. This pollutant causes a redistribution of leucocyte population. Both populations investigated, i.e. lymphocytes + thrombocytes and neutrophils, were modulated. Moreover, several results suggest that an enhancement of the adaptive immunity may occurs. The results obtained following a treatment with trenbolone acetate are quite different from those EE2.

Concerning the influence of androgenic compounds on the immune mechanisms in rainbow trout, the results differed from those obtained withEE2. The plasma humoral innate immnité was modulated because a decrease of lysozyme activity and changes time-dependent occur for complement activity. No effect on TbA were observed on the cellular innate immunity. The effect of TbA on hepatic inflammatory response is rather confuse because only one expression of cytokines investigated was down-regulated.

Date of Award	26 Jan 2015
Original language	English
Awarding Institution	University of Namur
Supervisor	Patrick Kestemont (Supervisor), Eric Depiereux (Jury), Robert Mandiki (Jury), Stéphane BETOULLE (Jury), C. Rougeot (Jury), Sylvain Milla (Jury) & Eric Muraille (Jury)