Banca de DEFESA: Marina Minari Rocha de Carvalho

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Marina Minari Rocha de Carvalho
DATE: 30/11/2022
TIME: 09:00
LOCAL: Videoconferência
TITLE:

Redox metabolism in Hymeniacidon heliophila (Porifera, Demospongiae) under influence of the tide cycle and solar radiation

KEY WORDS:

aerial exposure; ultraviolet radiation; antioxidant enzymes; Porifera; oxidative stress; glutathione.

PAGES: 90
BIG AREA: Ciências Biológicas
AREA: Biologia Geral
SUMMARY:

Many animals endure seasonal conditions associated with oxidative stress when oxygen is limited or unable to be extracted by organisms due to environmental conditions. Examples include frogs that freeze during the winter and stay in a hypometabolic state, and marine invertebrates from coastal environments that face aerial exposure during the tide cycle. Some well-known mechanisms that can explain hypoxia tolerance are (i) high constitutive levels of antioxidants, (ii) tolerance to oxidative damage and (iii) preparation for oxidative stress (POS). The latter has been demonstrated in 9 different animal phyla and consists in the upregulation of endogenous antioxidants during environmental stress, so the animal can be in a favorable redox balance during reoxygenation, when a high production of oxyradicals is expected. With the antioxidant system working consistently, oxidative damage (including DNA damage, protein oxidation, and lipid peroxidation) can be minimized. Currently, one of the biggest challenges related to POS’s research is its evolutionary origin, in which the most basal animals proved to be POS positive are two species of cnidarians. The Porifera phylum, whose origin is estimated to be more than 800 million years ago, is a good biological model for the evolutionary analysis of the POS mechanism. Therefore, this research aimed to verify whether the sponge Hymeniacidon heliophila, which daily goes through tidal aerial exposure, fits the POS criteria. The sponge H. heliophila is commonly found in the southern region of Brazil, inhabiting coastal environments, rarely seen submerged throughout the whole day. The species developed several adaptations that allow it to survive the functional hypoxia caused by the low tide, and one of such adaptations could be POS. Moreover, besides the hypoxic stressor, ultraviolet radiation (UV) has been recently suggested to be a trigger of POS. In this line of work, our research group analyzed POS in mussels Brachidontes solisianus, which also inhabit coastal environments. The findings indicate that B. solisianus uses POS in response to air exposure and UV radiation. Considering these two stressors, expeditions were made along the coast of São Sebastião (SP) to collect sponges H. heliophila. To verify the occurrence of POS in the field under totally natural environmental conditions, day and night samplings were made, with submerged and exposed sponges (high and low tides), on 3 different days. The sponges were scraped from the rocks, cleaned with water, and frozen in liquid N2, preserving the animal's biochemistry at the time of sampling. Then, whole-body homogenates were used to measure the activity of antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase, total and selenium-dependent glutathione peroxidase, and glutathione transferase), levels of glutathione (total GSH, GSSG, and GSH/GSSG), and oxidative damage (TBARS and carbonyl proteins) of sponges under different environmental conditions (UV radiation, temperature, and relative humidity). We also compared the redox effect of air exposure during the day and night. This dissertation discusses the role of redox metabolism and POS as part of the biochemical adaptations of H. heliophila sponges to survive and cope with tidal and solar radiation stresses.

BANKING MEMBERS:
Externo à Instituição - MÁRCIO REIS CUSTÓDIO - USP
Interno - 404930 - CARLOS ANDRE ORNELAS RICART
Presidente - 1189637 - MARCELO HERMES LIMA
Interno - 1661623 - RICARDO HENRIQUE KRUGER