Fatty acid metabolism and brain mitochondrial performance of juvenile Nile tilapia (Oreochromis niloticus) exposed to the water-accommodated fraction of Maya crude oil.

Crude oil and its derivatives are still the primary source of energy for humankind. However, during its transportation and treatment, spills of this resource can occur in aquatic environments. Nile tilapia is one of the most globally widespread fish species. This species is even found in brackish water due to its tolerance to salinity and pollution. In this study, the performance of brain cells (mitochondrial membrane potential [ΔΨm], calcium [Ca2+] and O2 and H2O2 levels) exposed to crude oil was assessed. In addition, fatty acid metabolism (cholesterol concentration and fatty acid synthase [FAS], acyl CoA-oxidase [AOX] and catalase [CAT] activities) in the brain, heart, liver and intestine of Nile tilapia exposed to the water-accommodated fraction (WAF) of 0.01, 0.1 or 1 g/L Maya crude oil (MCO) for 96 h were evaluated. After exposure, in brain cells, there were only increases in ROS and slight reductions in ΔΨm. Exposure to WAF of MCO induced and increased the levels of cholesterol and altered FAS and AOX activities in all examined tissues. The brain is the most susceptible organ to alterations in the activity of fatty acid metabolic enzymes and cholesterol levels relative to the heart, liver and intestine. The correlation between inhibition of the activity of CAT and AOX suggests a possible reduction in the proliferation and size of peroxisomes. Most biomarkers were significantly altered in the brains of Nile tilapia exposed to the WAF containing 1 g/L MCO in comparison to the control.

Proteomic analysis of oxidized proteins in the brain and liver of the Nile tilapia (Oreochromis niloticus) exposed to a water-accommodated fraction of Maya crude oil.

Crude oil (CO) is a super mixture of chemical compounds whose toxic effects are reported in fish species according to international guidelines. In the current study a proteomic analysis of oxidized proteins (ox) was performed on the brain and liver of Nile tilapia exposed to WAF obtained from relevant environmental loads (0.01, 0.1 and 1.0 g/L) of Maya CO. Results have shown that oxidation of specific proteins was a newly discovered organ-dependent process able to disrupt key functions in Nile tilapia. In control fish, enzymes involved on aerobic metabolism (liver aldehyde dehydrogenase and brain dihydrofolate reductase) and liver tryptophan--tRNA ligase were oxidized. In WAF-treated liver specimens, fructose-bisphosphate aldolase (FBA), ß-galactosidase (ß-GAL) and dipeptidyl peptidase 9 (DPP-9) were detected in oxidized form. oxDPP-9 could be favorable by reducing the risk associated with altered glucose metabolism, the opposite effects elicited by oxFBA and oxß-GAL. oxTrypsin showed a clear adverse effect by reducing probably the hepatocyte capacity to achieve proteolysis of oxidized proteins as well as for performing the proper digestive function. Additionally, enzyme implicated in purine metabolism adenosine (deaminase) was oxidized. Cerebral enzymes of mitochondrial respiratory chain complex (COX IV, COX5B), of glycosphingolipid biosynthesis (ß-N-acetylhexosaminidase), involved in catecholamines degradation (catechol O-methyltransferase), and microtubule cytoskeleton (stathmin) were oxidized in WAF-treated specimens. This response suggests, in the brain, an adverse scenario for the mitochondrial respiration process and for ATP provision as for ischemia/reoxygenation challenges. Proteomic analysis of oxidized proteins is a promising tool for monitoring environmental quality influenced by hydrocarbons dissolved in water.

Lipid metabolism and pro-oxidant/antioxidant balance of Halamphora oceanica from the Gulf of Mexico exposed to water accommodated fraction of Maya crude oil.

Diatoms play key roles in primary production and carbon fixation at a global scale and in some cases these species live on marine ecosystems impacted by crude oil (CO) spills. Halamphora oceanica, a new diatom species from the Southwest of the Gulf of Mexico was isolated and cultured in the laboratory and was exposed to water accommodated fraction (WAF) of different Maya CO loads at 0.01, 0.1, 1 and 10g/L by 96h. A battery of biomarkers involved in oxidative stress (O2•, H2O2, TBARS, ROOH, RC=O, SOD, CAT, GPx), biotransformation and conjugation (total CYP450 activity and GST) moreover fatty acid (FA) metabolism (FA levels, fatty-acid synthase and acyl-CoA oxidase) were measured. Obtained results suggest that increases of PAHs in the medium (below to EC50) acts as external forces able to turn-on regulatory mechanisms on H. oceanica involved in both, on the PAHs uptake and changing its aerobic metabolism to anaerobic metabolism. However, the growth of this microalgae species evaluated as chlorophyll "a" and pheophytin levels increased as the WAF concentration indicating that PAHs and other hydrosoluble hydrocarbons were used as carbon and energy sources by unidentified enzymes not evaluated in the current study. Our hypothesis was also corroborated by IBRv2. In the current study, we suppose the change from aerobic to anaerobic metabolism as a strategy for Halamphora oceanica survival exposed to petroleum hydrocarbons.

Oxidative stress response in the skin mucus layer of Goodea gracilis (Hubbs and Turner, 1939) exposed to crude oil: A non-invasive approach.

The skin of the fish is the foremost target of oxidative stress due to the generation of Reactive Oxygen Species (ROS) originated in the environment and in the skin itself. In this study, a non-destructive assay was developed to evaluate the effects of crude oil (0.0001-0.1mg/L, 96h) on oxidative stress response in the Skin Mucus Layer (SML) of the dusky splitfin goodeid (Goodea gracilis). The response in the SML was compared with recognized target organs through the Integrated Biomarker Response (IBRv2) and a slight addition to the method was proposed. Crude oil was extremely toxic and elicited a clear induction of ROS in the SML, as in the brain, liver and muscle. By the exposure to crude, a significant change in the activities of Superoxide Dismutase (SOD), Catalase (CAT), Glutathione Peroxidase (GPx) as well as on lipid peroxidation (TBARS) and carbonyl protein (RCO) levels was detected. Also, increases in the activity of EROD were found. The general IBRv2 proposed in this study (gIBRv2) showed that oil causes the higher oxidative response in the SML (60.049) under different concentrations of petroleum, which was greater in the brain (56.749), muscle (56.561) and liver (55.775). The results of the study revealed an organ-specific antioxidant defense response that was dependent on the load of petroleum. These results contributed to the understanding of the complexity of oxidative stress response in fish exposed to crude oil using the Skin Mucus Layer as a target for environmental monitoring studies.