ESR04 - Biomarker integrated analysis of fish stress

Host Institution: UNIPD - Università degli Studi di Padova

This project will focus on stress on fish by anthropic factors associated with hydropower dams. The objective is providing an integrated biological analysis by determining (1) antioxidant enzyme
activities and specific stress indicators; (2) changes in protein gene expression; (3) DNA breaks and apoptotic index.

The hypothalamic-pituitary-interrenal axis is one of the systems that most actively responds to stress. In fact, the cells of the hypothalamus lead to the release of cortisol, with physiological changes of the target organs, which reinforce the action of the catecholamines. However, cortisol has inhibitory effects on the growth of fish, on their reproductive success and on the immune system, which makes it clear how environmental stress can have negative effects on individuals and natural populations. One of the objectives of the project will be to study the variation kinetics of the cortisol blood levels and to correlate them to various types of anthropic stress. It will be important to evaluate how cortisol production correlates with the expression of other genes, such as those that encode Crh and Otp, which regulate the production of cortisol. Another objective of the project will be to evaluate the kinetics of response to the risk of oxidative stress. Cells have an antioxidant defense system, consisting of enzymatic and non-enzymatic molecules that are able to counteract the formation of reactive oxygen species, highly oxidizing molecules whose formation rate can easily increase under conditions stress, generating irreversible damage to biological macromolecules, leading to cellular modifications which are the cause of a wide variety of pathological conditions. Although the defensive role of the antioxidant system has long been known, its activation is so complex and species-specific that it is essential to study its peculiarities in the widest range of organisms. Hence the interest in studying the gene expression of the protein components of the antioxidant system (such as SOD, CAT, Gpx and Prdx) of freshwater fish, evaluating both the accumulation of mRNAs and proteins. Knowledge of cortisol and antioxidant defense induction networks can have an important application impact, perfecting the use of biomarkers and bioindicator organisms in the evaluation of anthropic stress in the freshwater environment. For this purpose, the study of these physiological responses will be related to the analysis of cell damage parameters such as DNA breaks and apoptotic index.

The project will be carried out both in the field and in the laboratory. Field trials will be carried out on rivers, using specimens of specially sampled resident fish species, as well as individuals bred in captivity and appropriately placed in water basins. Cytological, biochemical and biomolecular analyzes will be carried out in the laboratory aimed at studying the physiological responses to fish stress.

Secondment period (to be confirmed): Expected duration: 4 months; Hosting institutions: CBAR (Consorzio di Bonifica Acque Risorgive - Venezia, Italy), IGB (Leibniz Institute of Freshwater Ecology and Inland Fisheries - Berlin, Germany)