Molecular Biomarkers: Their significance and application in marine pollution monitoring

Abstract

This paper presents an overview of the significance of the use of molecular biomarkers as diagnostic and prognostic tools for marine pollution monitoring. In order to assess the impact of highly persistent pollutants such as polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDD), polychlorinated dibenzo-furans (PCDF), polynuclear aromatic hydrocarbons (PAH), tributyltin (TBT) and other toxic metals on the marine ecosystem a suite of biomarkers are being extensively used worldwide. Among the various types of biomarkers, the following have received special attention: cytochrome P4501A induction, DNA integrity, acetylcholinesterase activity and metallothionein induction. These biomarkers are being used to evaluate exposure of various species of sentinel marine organisms (e.g. mussels, clams, oysters, snails, fishes, etc.) to and the effect of various contaminants (organic xenobiotics and metals) using different molecular approaches [biochemical assays, enzyme linked immuno-sorbent assays (ELISA), spectrophotometric, fluorometric measurement, differential pulsed polarography, liquid chromatography, atomic absorption spectrometry]. The induction of the biotransformation enzyme, cytochrome P4501A in fishes (Callionymus lyra, Limanda limanda, Serranus sp., Mullus barbatus) and mussels (Dreissena polymorpha) by various xenobiotic contaminants such as PCBs, PAHs, PCDs is used as a biomarker of exposure to such organic pollutants. The induction of cytochrome P4501A is involved in chemical carcinogenesis through catalysis of the covalent bonding of organic contaminants to a DNA strand leading to formation of DNA adduct. Measurement of the induction of cytochrome P4501A in terms of EROD (7-ethoxy resorufin O-deethylase) activity is successfully used as a potential biomarker of exposure to xenobiotic contaminants in marine pollution monitoring. In order to assess the impact of neurotoxic compounds on marine environment the evaluation of acetylcholinesterase activity in marine organisms is used as a biomarker of exposure to neurotoxic agents such as organophosphorus, carbamate pesticides etc. Metallothioneins (MTs) are induced by toxic metals such as Cd, Hg, and Cu by chelation through cysteine residues and are used in both vertebrates and invertebrates as a biomarker of metal exposure. The measurement of the levels of DNA integrity in marine organisms such as Sea stars (Asterias rubens) from the North Sea and the marine snails (Planaxis sulcatus) from the Arabian Sea along the Goa coast exposed to environmental xenobiotic contaminants clearly indicated the extent and the nature of pollution at the sampling sites along coastal environment.

Expression profiles of seven glutathione S-transferase (GST) genes from Venerupis philippinarum exposed to heavy metals and benzo[a]pyrene

“…Owing to the sensitive response of mRNA expression to diverse forms of stressors, changes in mRNA expression of cytochrome P450, glutathione S-transferases, superoxide dismutase, heat shock proteins, metallothioneins and vitellogenin have been frequently used for the diagnosis of environmental contamination (Hoarau et al, 2006;Sarkar et al, 2006;Gao et al, 2007). Since GST play important roles in detoxification pathways and in the oxidative stress response, GSTs have been investigated widely in ecotoxicology and marine pollution assessment (Boutet et al, 2004;Hoarau et al, 2006;Rhee et al, 2007;Lee et al, 2008;Wan et al, 2008aWan et al, , 2008bWan et al, , 2009Kim et al, 2010;Nail and Choi, 2011;Won et al, 2011).…”

Identification and expression profile of a new cytochrome P450 isoform (CYP414A1) in the hepatopancreas of Venerupis (Ruditapes) philippinarum exposed to benzo[a]pyrene, cadmium and copper

“…Thus it is necessary to assess the toxicological effects of contaminants with biomarker discovery for the environmental monitoring. Recently, xenobiotic metabolizing enzymes (XMEs) reflecting the effects of contaminations on resident biota have been employed to monitor environmental pollutants (Sarkar et al, 2006). To our knowledge, researches on the expression and regulation of XMEs in mollusks, especially for CYPs, are still deficient compared with those in vertebrates and insects.…”

Quantitative profiling of mRNA expression of glutathione S‐transferase superfamily genes in various tissues of bighead carp (Aristichthys nobilis)

“…Measurement of enzyme activities or expression of GST transcripts in fish has been used as biomarker of exposure to xenobiotics [19,20,21]. Fu and Xie.…”