Clofibric acid down-regulation of metallothionein IIA in HepG2 human hepatoma cells

Transcriptional responses of Daphnia magna exposed to Akaki river water

Pollution of the aquatic environment is a global problem, with industrial waste, farming effluents, sewage, and wastewater as the main contributors. Many pollutants are biologically active at low concentrations, resulting in sublethal effects, which makes it a highly complex situation and difficult to assess. In many places, such as the Akaki river in Ethiopia, the pollution situation has resulted in streams with minimal presence of invertebrates or vertebrates. As it is difficult to perform a complete chemical analysis of the waters, the present study focused on using gene expression analysis as a biological end point to determine the effects of Akaki river contaminants. The present study was conducted using the small planktonic crustacean Daphnia magna with toxicogenomic molecular markers. Daphnia magna neonates were exposed to Akaki water samples collected from two different sites on the river and analyzed for mortality and expression of genes involved in different biological pathways. Despite the poor quality of Akaki river water, 48 h acute toxicity tests showed no mortality. Interestingly, analysis of sublethal toxicogenomic responses showed that exposure to Akaki water altered the expression of 25 out of 37 genes involved in metal regulation, immune response, oxidative stress, respiration, reproduction, and development. The toxicogenomic data gives insight into the mechanisms involved in causing potential adverse effects to aquatic biota harboring the Akaki river system.

Behaviour and biomarkers of oxidative stress in Gambusia holbrooki after acute exposure to widely used pharmaceuticals and a detergent

Pharmaceuticals are continuously dispersed into the environment, as a result of human and veterinary use, and have become a relevant environmental concern. In the present study, the acute toxicity of three therapeutic agents (diazepam, clofibrate, and clofibric acid) and a detergent, sodium dodecylsulphate (SDS), to the euryhaline fish Gambusia holbrooki was evaluated. Special attention was devoted to oxidative stress parameters. G. holbrooki males, captured in the estuary of the Minho River (NW Portugal), were exposed for 96 h to the selected compounds. The following oxidative stress biomarkers were evaluated in gills and liver tissues: reduced and oxidised glutathione, lipid peroxidation, and several antioxidant enzymes, namely (1) total and selenium-dependent glutathione peroxidase (GPx), (2) glutathione reductase (GRed), (3) copper-zinc superoxide dismutase (Cu-ZnSOD) and manganese superoxide dismutase (MnSOD), and (4) glutathione-S-transferases (GSTs). In the particular case of diazepam, swimming behaviour was also evaluated. The obtained results indicate an overall diminished oxidative stress response caused by SDS and diazepam. Oxidative-based alterations were observed after exposure to clofibrate and clofibric acid, with modifications of several enzymatic activities. Diazepam caused evident behavioural changes: animals showed dark pigmentation and also abnormal postures, namely lethargy and anomalous movement.

Modifications of nuclear architecture and chromatin organization in ataxia telangiectasia cells are coupled to changes of gene transcription

Ataxia telangiectasia (AT) is a rare genetic disorder caused by mutations of ATM gene. ATM kinase is a "master controller" of DNA-damage response and signal transducer of external stimuli. The complex role of ATM may explain the pleiotropic phenotype characteristic of AT syndrome, only partially. In our hypothesis, the multi-faceted phenotype of AT patients might depend on specific chromatin reorganization, which then reflects on the cellular transcription. We analyzed three lymphoblastoid cell-lines isolated from AT patients and one healthy control. The three-dimensional reconstruction disclosed marked changes of nuclear morphology and architecture in AT cells. When chromatin condensation was analyzed by differential scanning calorimetry, a remodeling was observed at the level of fiber folding and nucleosome conformation. Despite the structural differences, chromatin did not exhibit modifications of the average acetylation status in comparison to the control. Moreover, AT cells presented significant alterations in the transcription of genes involved in cell-cycle regulation and stress response. In AT3RM cells, the average chromatin decondensation went with the upregulation of c-fos, c-jun, and c-myc and downregulation of metallothioneins, p21 and p53. AT9RM and AT44RM cells were instead characterized by an increased chromatin condensation and presented a different transcription unbalance. Whereas in AT44RM all the considered genes were downregulated, in AT3RM the three oncogenes and metallothioneins were upregulated, but p53 and p21 were downregulated.

Depletion of Kupffer cell function by gadolinium chloride attenuates thioacetamide-induced hepatotoxicity. Expression of metallothionein and HSP70

Kupffer cell function plays an important role in drug-induced liver injury. Thus, gadolinium chloride (GD), by selectively inactivating Kupffer cells, can alleviate drug-induced hepatotoxicity. The effect of GD was studied in reference to metallothionein and heat shock proteins expression in an in vivo model of liver necrosis induced by thioacetamide. Rats, pre-treated or not with GD (0.1 mmol/kg), were intraperitoneally injected with thioacetamide (6.6 mmol/kg), and samples of blood and liver were obtained at 0, 12, 24, 48, 72 and 96 hr. Parameters related to liver damage, Kupffer cell function, microsomal FAD monooxygenase activity, oxidative stress, and the expression of metallothionein and HSP70 were determined. GD significantly reduced serum myeloperoxidase activity and serum concentration of TNF alpha and IL-6, increased by thioacetamide. The extent of necrosis, the degree of oxidative stress and lipoperoxidation and microsomal FAD monooxygenase activity were significantly diminished by GD. The effect of GD induced noticeable changes in the expression of both metallothionein and HSP70, compared to those induced by thioacetamide. We conclude that GD pre-treatment reduces thioacetamide-induced liver injury and enhances the expression of metallothionein and HSP70. This effect, parallel to reduced levels of serum cytokines and myeloperoxidase activity, demonstrates that Kupffer cells are involved in thioacetamide-induced liver injury, the degree of contribution being approximately 50%.