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Environmental variations and toxicological responses
Aquatic Toxicology 127 (2013) 1
Contents lists available at SciVerse ScienceDirect
Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox
Editorial
Environmental variations and toxicological responses
While toxicological testing has as its outset that one should be able to get the same result regardless of where testing is done, the effects of chemicals in nature are influenced by the local environmental conditions. This being the case, an ecotoxicologist must always consider how an animal responds to its normal environment and natural environmental changes, and how the responses to natural environments affect either the behaviour of a chemical or the responses of an organism to the chemical. Taking into account the natural fluctuations in the responses requires a solid knowledge of pathways (mechanisms) involved in environmental adaptation and how these may interact with chemical responses. A good example of a mechanism involved in natural responses to environmental variation is the regulation of transcription of many genes by hypoxia-inducible factor (HIF) in oxygen-dependent manner (Nikinmaa and Rees, 2005). The HIF␣ proteins respond to oxygen level, and after dimer formation with ARNT bind to DNA and direct transcription of oxygen-dependent genes. Interaction with chemicals released to the environment comes from two facts: first, the HIF␣ proteins belong to the same protein family as aryl hydrocarbon receptor (AhR), the major receptor for organic environmental toxicants (Bracken et al., 2003), and, second, compete for ARNT dimer formation with AhR (Nikinmaa and Rytkönen, 2011). The latter competition has been shown to affect the xenobiotic response (Hofer et al., 2004). Natural environment and xenobiotic responses interact also in the function of cytochrome P450 enzymes: they are, e.g., involved both in toxicant responses and natural steroid metabolism. Another important interaction between the natural environment and toxic responses relates to metal toxicology. The biotic ligand model (BLM) which seeks to take into account water quality properties in estimating the toxicity of metals (Niyogi and Wood, 2004) is approved by several regulatory authorities. However, while the model works quite well with freshwater fish, its utility is markedly affected by environmental salinity. This is probably because the salt uptake pathways and their regulation are markedly affected by salinity (Blanchard and Grosell, 2006). One could add many more examples to the list of interactions between responses to natural environment and environmental chemicals. In addition to the interaction of natural environmental changes and environmental chemicals, many present environmental questions relate to toxicant behaviour. For example, how will the
0166-445X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquatox.2012.03.012
changes of UV radiation affect the responses of sea surface organisms to toxicants or how do the changes modify toxicant structure? Similarly, what is the effect of increasing temperature due to climate change on contamination responses of aquatic organisms. The authors of this issue have addressed some aspects of environmental variations that need to be taken into account when aquatic toxicological studies are carried out. The articles clearly show the importance of integrating the biology of organisms in their natural environment to their toxicological responses. We hope that this issue is useful and helps future authors of Aquatic Toxicology to consider responses to natural environment in their mechanistic studies. References Blanchard, J., Grosell, M., 2006. Copper toxicity across salinities from freshwater to seawater in the euryhaline fish Fundulus heteroclitus: is copper an ionoregulatory toxicant in high salinities? Aquat. Toxicol. 80, 131–139. Bracken, C.P., Whitelaw, M.L., Peet, D.J., 2003. The hypoxia-inducible factors: key transcriptional regulators of hypoxic responses. Cell. Mol. Life Sci. 60, 1376–1393. Hofer, T., Pohjanvirta, R., Spielmann, P., Viluksela, M., Buchmann, D.P., Wenger, R.H., Gassmann, M., 2004. Simultaneous exposure of rats to dioxin and carbon monoxide reduces the xenobiotic but not the hypoxic response. Biol. Chem. 385, 291–294. Nikinmaa, M., Rees, B.B., 2005. Oxygen-dependent gene expression in fishes. Am. J. Physiol. Regul. Integr. Comp. Physiol. 288, R1079–R1090. Nikinmaa, M., Rytkönen, K.T., 2011. Functional genomics in aquatic toxicology – do not forget the function. Aquat. Toxicol. 105S, 16–24. Niyogi, S., Wood, C.M., 2004. Biotic ligand model, a flexible tool for developing site-specific water quality guidelines for metals. Environ. Sci. Technol. 38, 6177–6192.
Mikko Nikinmaa ∗ Department of Biology, University of Turku, FI-20014 Turku, Finland Ron Tjeerdema Department of Environmental Toxicology, University of California at Davis, Davis, CA 95616-8501, USA ∗ Corresponding
author. Tel.: +358 2 3335731. E-mail addresses: mikko.nikinmaa@utu.fi (M. Nikinmaa), [email protected] (R. Tjeerdema)
Contents lists available at SciVerse ScienceDirect
Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox
Editorial
Environmental variations and toxicological responses
While toxicological testing has as its outset that one should be able to get the same result regardless of where testing is done, the effects of chemicals in nature are influenced by the local environmental conditions. This being the case, an ecotoxicologist must always consider how an animal responds to its normal environment and natural environmental changes, and how the responses to natural environments affect either the behaviour of a chemical or the responses of an organism to the chemical. Taking into account the natural fluctuations in the responses requires a solid knowledge of pathways (mechanisms) involved in environmental adaptation and how these may interact with chemical responses. A good example of a mechanism involved in natural responses to environmental variation is the regulation of transcription of many genes by hypoxia-inducible factor (HIF) in oxygen-dependent manner (Nikinmaa and Rees, 2005). The HIF␣ proteins respond to oxygen level, and after dimer formation with ARNT bind to DNA and direct transcription of oxygen-dependent genes. Interaction with chemicals released to the environment comes from two facts: first, the HIF␣ proteins belong to the same protein family as aryl hydrocarbon receptor (AhR), the major receptor for organic environmental toxicants (Bracken et al., 2003), and, second, compete for ARNT dimer formation with AhR (Nikinmaa and Rytkönen, 2011). The latter competition has been shown to affect the xenobiotic response (Hofer et al., 2004). Natural environment and xenobiotic responses interact also in the function of cytochrome P450 enzymes: they are, e.g., involved both in toxicant responses and natural steroid metabolism. Another important interaction between the natural environment and toxic responses relates to metal toxicology. The biotic ligand model (BLM) which seeks to take into account water quality properties in estimating the toxicity of metals (Niyogi and Wood, 2004) is approved by several regulatory authorities. However, while the model works quite well with freshwater fish, its utility is markedly affected by environmental salinity. This is probably because the salt uptake pathways and their regulation are markedly affected by salinity (Blanchard and Grosell, 2006). One could add many more examples to the list of interactions between responses to natural environment and environmental chemicals. In addition to the interaction of natural environmental changes and environmental chemicals, many present environmental questions relate to toxicant behaviour. For example, how will the
0166-445X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquatox.2012.03.012
changes of UV radiation affect the responses of sea surface organisms to toxicants or how do the changes modify toxicant structure? Similarly, what is the effect of increasing temperature due to climate change on contamination responses of aquatic organisms. The authors of this issue have addressed some aspects of environmental variations that need to be taken into account when aquatic toxicological studies are carried out. The articles clearly show the importance of integrating the biology of organisms in their natural environment to their toxicological responses. We hope that this issue is useful and helps future authors of Aquatic Toxicology to consider responses to natural environment in their mechanistic studies. References Blanchard, J., Grosell, M., 2006. Copper toxicity across salinities from freshwater to seawater in the euryhaline fish Fundulus heteroclitus: is copper an ionoregulatory toxicant in high salinities? Aquat. Toxicol. 80, 131–139. Bracken, C.P., Whitelaw, M.L., Peet, D.J., 2003. The hypoxia-inducible factors: key transcriptional regulators of hypoxic responses. Cell. Mol. Life Sci. 60, 1376–1393. Hofer, T., Pohjanvirta, R., Spielmann, P., Viluksela, M., Buchmann, D.P., Wenger, R.H., Gassmann, M., 2004. Simultaneous exposure of rats to dioxin and carbon monoxide reduces the xenobiotic but not the hypoxic response. Biol. Chem. 385, 291–294. Nikinmaa, M., Rees, B.B., 2005. Oxygen-dependent gene expression in fishes. Am. J. Physiol. Regul. Integr. Comp. Physiol. 288, R1079–R1090. Nikinmaa, M., Rytkönen, K.T., 2011. Functional genomics in aquatic toxicology – do not forget the function. Aquat. Toxicol. 105S, 16–24. Niyogi, S., Wood, C.M., 2004. Biotic ligand model, a flexible tool for developing site-specific water quality guidelines for metals. Environ. Sci. Technol. 38, 6177–6192.
Mikko Nikinmaa ∗ Department of Biology, University of Turku, FI-20014 Turku, Finland Ron Tjeerdema Department of Environmental Toxicology, University of California at Davis, Davis, CA 95616-8501, USA ∗ Corresponding
author. Tel.: +358 2 3335731. E-mail addresses: mikko.nikinmaa@utu.fi (M. Nikinmaa), [email protected] (R. Tjeerdema)