Life after death? Exploring biochemical and molecular changes following organismal death in green turtles, Chelonia mydas (Linnaeus, 1758)

Green turtles, Chelonia mydas, have been included in biomonitoring efforts given its status as an endangered species. Many studies, however, rely on samples from stranded animals, raising the question of how death affects important biochemical and molecular biomarkers. The goal of this study was to investigate post mortem fluctuations in the antioxidant response and metabolism of carbohydrates in the liver of C. mydas. Liver samples were obtained from six green turtles which were submitted to rehabilitation and euthanized due to the impossibility of recovery. Samples were collected immediately after death (t = 0) and at various time intervals (1, 2, 3, 4, 5, 6, 12, 18 and 24 h post mortem), frozen in liquid nitrogen and stored at -80 °C. The activities of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH) were analyzed, as were the levels of lipid peroxidation, glycogen concentration, RNA integrity (RNA IQ) and transcript levels of carbonic anhydrase and pyruvate carboxylase genes. Comparison between post mortem intervals showed a temporal stability for all the biomarkers evaluated, suggesting that changes in biochemical and molecular parameters following green turtle death are not immediate, and metabolism may remain somewhat unaltered up to 24 h after death. Such stability may be associated with the overall lower metabolism of turtles, especially under an oxygen deprivation scenario such as organismal death. Overall, this study supports the use of biomarkers in sea turtles sampled within a period of 24 h post mortem for biomonitoring purposes, though it is recommended that post mortem fluctuations of particular biomarkers be evaluated prior to their application, given that proteins may show varying degrees of susceptibility to proteolysis.

Is gene transcription in mussel gills altered after exposure to Ag nanoparticles?

Nanotechnology is a rapid field of development with the enhancement of the production of different types of nanoparticles (NPs) applied in several industrial and commercial applications which increase the risk of their presence in the aquatic environment. Ag NPs have a wide application in everyday life products. However, there is concern about the exposure effects on aquatic organisms to these NPs. Therefore, this study aims to assess gene transcription alterations in mussels Mytilus galloprovincialis gills exposed for 2 weeks to Ag NPs (42 ± 10 nm, 10 μg.L(-1)). The genes were selected based on previous biomarkers and proteomic results and included superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), caspase 3/7-1 (CAS), cathepsin L (CATH), heat-shock protein 70 (HSP 70), cytochrome P450 4YA (CYP 4YA), the elongation factor (EF1), actin and α- tubulin. No significant changes in gene transcription profiles were observed after exposure of M. galloprovincialis to Ag NPs for 15 days. The lack of significant gene transcription responses is in light with previous results obtained for mussels exposed to these NPs and may be related to the fact that enzyme kinetics and relative abundance of proteins (increase of antioxidant enzymes and metalllothioneins (MTs) with the time of exposure) do not always directly reflect their relative mRNA levels. Nevertheless, their overall expression maintenance may signify that, at end of the exposure period (15 days), the transcription of the respective genes is no longer required, pointing out to a possible adaptation effect to nanoparticles or due to the levels of Ag NPs accumulated in this tissue at this exposure time. This study highlights that gene transcription application and role as an additional and/or alternative end point approach is important to understand the mode of action of these emergent contaminants in aquatic organisms. However, in future studies, the time window needs to be adjusted, as genes are likely to respond earlier to the nanoparticle exposure.

Effects of active pharmaceutical ingredients mixtures in mussel Mytilus galloprovincialis

Active pharmaceutical ingredients (APIs) are emergent environmental contaminants widely detected in surface waters as result of incomplete waste water treatment plant (WWTP) removal processes and improper disposal. The assessment of potential effects of APIs on non-target organisms is still scarce since besides presenting multiple chemical structures, properties and modes of action, these compounds occur as complex mixtures. This study comprises a 15-day exposure of mussels Mytilus galloprovincialis to mixtures (at environmentally relevant nominal concentrations) of non-steroidal inflammatory drugs ibuprofen (IBU) and diclofenac (DCF) (250 ng L(-1) each) and selective serotonin reuptake inhibitor (SSRI) fluoxetine (FLX) (75 ng L(-1)) (MIX 1) along with the addition of classical pro-oxidant copper (Cu) (5 μg L(-1)) (MIX 2). The goals included the assessment of oxidative stress, neurotoxic and endocrine effects on this sentinel species applying both a multibiomarker and gene expression (here and later gene expression is taken as synonym to gene transcription, although it is acknowledged that it is also affected by, e.g. translation, and mRNA and protein stability) analysis approaches. The results revealed a swifter antioxidant response in digestive glands than in gills induced by MIX 1, nevertheless the presence of Cu in MIX 2 promoted a higher lipid peroxidation (LPO) induction. Neither mixture altered acetylcholinesterase (AChE) activity, while both triggered the formation of vitellogenin-like proteins in females confirming the xenoestrogenic effect of mixtures. All these results varied with respect to those obtained in previous single exposure essays. Moreover, RT-PCR analysis revealed a catalase (CAT) and CYP4Y1 gene expression down- and upregulation, respectively, with no significant changes in mRNA levels of genes encoding superoxide dismutase (SOD) and glutathione-S-transferase (GST). Finally, this study highlights variable tissue and time-specific biomarker responses and gene expression alterations, which along with several interactions between each mixture component on each biomarker confirm the susceptibility of mussels to API mixtures.

Differential gene expression in Poecilia vivipara exposed to diesel oil water accommodated fraction

Diesel fuel is a potential contaminant of estuarine and mangrove areas, particularly because it is the main fuel used in small boats and larger vessels. The aim of this work was to identify genes differentially expressed in the liver of Poecilia vivipara (Guppy) exposed to 10% diesel fuel water accommodated fraction (WAF), employing the subtractive suppressive hybridization (SSH) method. The results showed 27 differentially expressed gene fragments, 12 up-regulated and 15 down-regulated. Among the up-regulated genes were CYP1A, UDPGT1a, ABCC4, Methyltransferase and Apolipoprotein A1. Down-regulated genes included Vitellogenins, C1 Inhibitor and Complement Component 3c. The identified genes are associated with different metabolic functions like biotransformation, membrane transport and immune system, indicating the susceptibility and/or molecular responses of this organism to the toxic effects elicited by diesel fuel WSF.