Killifish metallothionein messenger RNA expression following temperature perturbation and cadmium exposure

Abstract

Metallothionein (MT), a cysteine-rich metal binding protein, is considered to play an essential role in the regulation of intracellular metals. Induction of MT in mammalian and nonmammalian tissues following heavy metal exposure may serve as a defense mechanism and a biomarker of environmental exposure to chemical stressors such as toxic metals. In this study, MT messenger RNA (mRNA) expression was characterized in male and female nonspawning and spawning killifish (Fundulus heteroclitus) following an 8-day exposure to specific sublethal stressors, which included temperature perturbation (26ЊC or 10ЊC) and/or 6 ppb of waterborne cadmium chloride (CdCl 2 ). Hepatic, gill, and intestinal MT mRNA, expressed as copy number per microgram of total RNA, was assessed by reverse transcriptase-polymerase chain reaction and electrochemiluminescence using winter flounder (Pleuronectes americanus) MT complementary DNA primers. Liver, gill, and intestine MT mRNA expression was significantly (P Ͻ 0.05) increased in nonspawning killifish exposed to 26ЊC compared with those exposed to 19ЊC (control). In addition, a significant (P Ͻ 0.05) increase in gill MT mRNA induction was observed in nonspawning killifish exposed to 6 ppb of waterborne CdCl 2 compared with controls. The results of this study demonstrate significant MT mRNA induction in nonspawning killifish following short-term exposure to physiological and chemical stressors. Thus, further research may be necessary before the use of killifish MT mRNA induction as a biomarker of environmental chemical stress exposure alone.

Evaluation of the gene expression changes in Nile tilapia (Oreochromis niloticus) as affected by the bio-removal of toxic textile dyes from aqueous solution in small-scale bioreactor

“…MTs are cysteine-rich metal-binding proteins that play an essential role in the regulation of intracellular metal concentration (Chang 1995). Moreover, it is known that the expression of its transcript, generally present at basal levels, is increased also after other physiological sub-lethal stressor (Van Cleef-Toedt et al 2001). Our experiments demonstrated that MT mRNA increases, both in liver and brain, after exposure to industrial Direct violet, green, and brown dye water as well as benzene compared to the control group.…”

Transcriptomic analyses in a benthic fish exposed to contaminated estuarine sediments through laboratory and in situ bioassays

“…This difference between laboratory and field assays is most likely caused by two main factors: (i) the differential bioavailability of metals and (ii) increased induction of MT by oxidative stress originated by organic contaminant detoxification processes. In fact, MT mRNA up-regulation has been found to change as consequence of different types of stressors in fish liver, from thermal (van Cleef-Toedt et al 2001) to oxidative stress, with MTs being nowadays recognized scavengers for ROS (Tamai et al 1993;Andrews 2000;Laity and Andrews 2007). Oxidative radicals produced as a consequence of CYP activity on organic toxicants may have triggered MT1 up-regulation, thus explaining the higher transcription in the livers of fish exposed to sediment C 2 (most contaminated by organic contaminants) in the field for 28 days when compared to animals exposed to sediment C 1 (most metal-contaminated).…”

Evaluation of environmental impact on natural populations of the Mediterranean killifish Aphanius fasciatus by quantitative RNA biomarkers

“…In this work, we develop mRNA markers for monitoring A. fasciatus exposure to different kinds of pollutants, using known DNA sequences from evolutionarily related species (mainly Cyprinodonts and Percomorphs). Genes used in this analysis included the main metal-responsive metallothionein (MT) gene (Cheung et al, 2004;Navarro et al, 2009;Schlenk et al, 1995;Tom et al, 2004;Van Cleef-Toedt et al, 2001), the egg-forming, liver-expressed vitellogenin (Vtg), a known marker for estrogens (Barucca et al, 2006;Denslow et al, 2001;Garcia-Reyero et al, 2004), the dioxin-like responsive Cytochrome P4501A (CYP1A, Chung-Davidson et al, 2004;Craft et al, 2001;Quirós et al, 2007a;Quirós et al, 2007b), the oxidative stress-related gene Superoxide dismutase (SOD, Cho et al, 2006;Gonzalez et al, 2006;Pandey et al, 2003), and the protein chaperone HSP70, which are involved in the processing of missfolded proteins due to different kinds of stress (Carnevali and Maradonna, 2003;Maradonna and Carnevali, 2007;Schroder et al, 2000;Varo et al, 2002). In addition, probes for two housekeeping genes (ß actin and the elongation translation factor EF1)…”