Impact of multiple stressors (stress hormones, environmental pollution and hydrostatic pressure) on marine mammals using precision-cut adipose tissue slices from northern elephant seals

Details

Supervisors

Debier, Cathy ; Rees, Jean-François

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Marine mammals are constantly facing multiple stressors. These stresses can be of natural origin such as hydrostatic pressure or predation or of anthropic origin such as environmental pollution or underwater noise. Some of these disturbances are chronic, i.e persistent over time. This is the case for hydrostatic pressure because some species spend most of their time in deep dives. This is also the case for environmental pollution and acoustic disturbance, both of which are persistent in their habitat today. These stressors are likely to disrupt the functions of the adipose tissue, an endocrine organ involved in essential processes such as energy storage and insulation. In addition, it is an accessible organ that can be easily sampled on wild animals. The goal of this master thesis was to study the impact of multiple stressors, individually and in combination, on adipose tissue of marine mammals. For this purpose, the precision-cut adipose tissue slices model was used on northern elephant seal (Mirounga angustirostri). This is a novel in vitro model of tissue culture that enables to study multiple treatments on reproductible tissue samples under controlled conditions. Northern elephant seals represent a particularly interesting model for the purpose of this study because of its large layer of accessible subcutaneous adipose tissue. Its coastal access during specific periods of its life cycle also facilitates the sampling activity. In addition, this species presents a unique robustness to handling and sampling compared to other marine mammals. The pig was used as a second model for the development of the pressurization system. The experiment lasted for 45 hours. During the first 36 hours, adipose slices were exposed to cortisol (2 µM) to mimic hormonal response to chronic stress and a mixture of persistent organic pollutants (including DDE, a mixture of PCBs - Aroclor 1254 – and two PBDEs – PBDEs-47and-99) that was representative of the pollution to which marine mammals are exposed. During that period, culture media were renewed every 12 hours. For the last 9 hours of culture, epinephrine (100 nm) was added to mimic an acute stress. Samples also underwent pressure cycles up to 50 bars for 2 hours. On the pig model, results showed that : i) the pressurization had not impact on the tissue viability and ii) the pressurization decreased the induced lipolysis. Further investigations would be interesting to understand the cause of this decrease. It may be due to an impact of pressure on enzymatic activities, on membrane receptors or on membrane transporters. On the NES model, results demonstrated that : i) all the stressors (cortisol, POPs and high hydrostatic pressure) had no impact on the tissue viability and ii) the cryotubes placement decreased the lipolysis. The most likely hypothesis is that the adipose tissue has undergone hypoxia. An optimal system for oxygenation of culture media could be interesting to develop and calibrate.