Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology
Expression profiles of seven glutathione S-transferase (GST) genes from Venerupis philippinarum exposed to heavy metals and benzo[a]pyrene
Introduction
Aquatic organisms are frequently exposed to numerous environmental pollutants including polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Rainbow, 1995, Xue and Warshawsky, 2005, Wan et al., 2009). Heavy metals such as copper (Cu) and cadmium (Cd) can induce excessive production of reactive oxygen species (ROS) in cells, which cause oxidative modification of the major cellular macromolecules (Cecconi et al., 2002). Benzo[a]pyrene (B[a]P) is an extensively studied prototype of PAH and has been diffused into marine environment as an persistent organic pollutant, inducing cytotoxic, mutagenic and carcinogenic effects in various animal species (Gonzalez and Gelboin, 1994). In recent years, research on the gene expression of some detoxification and antioxidant enzymes has been recognized as a powerful tool to assess the ecotoxicological effects of certain chemicals (Woo et al., 2009, Won et al., 2011).
Glutathione S-transferases (GSTs, EC 2.5.1.18) are a superfamily of multifunctional phase II enzymes primarily involved in detoxification of both endogenous and exogenous electrophiles. Generally, the detoxification mechanisms of GSTs lie in the conjugation of reduced glutathione with toxic compounds or their metabolites to increase the hydrophilicity and facilitate the excretion of toxicants (Ketterer et al., 1983). Moreover, GSTs have been found to play a critical role in mitigating oxidative stress in all life forms (Lee et al., 2008), and GST activities have been widely used as potential biomarkers for the monitoring of environmental pollution as well (Hoarau et al., 2002, Shailaja and D'Silva, 2003, Cunha et al., 2007).
GSTs have been found in all the prokaryotic and eukaryotic organisms investigated so far, in which they have three intra-cellular locations: in the cytosol, in mitochondria, and in microsomes (Hayes et al., 2005). Currently, at least 15 different classes of GSTs (alpha, beta, delta, epsilon, kappa, lambda, mu, omega, phi, pi, sigma, tau, theta, zeta, and rho) have been identified from numerous phylogenetically diverse organisms based on the differences in structural, catalytic and immunological characters (Hayes et al., 2005). In the previous studies, the mRNA expression of multiple specific GSTs had been investigated in several aquatic organisms after exposure to environmental pollutants (Boutet et al., 2004, Lee et al., 2008, Wan et al., 2008a, Li et al., 2009, Kim et al., 2010, Nail and Choi, 2011, Won et al., 2011). These studies provided the possibility to explore the correlation of specific GST responses with the detoxification of various toxicants, which were perhaps useful to evaluate the potential of different GST isoforms as molecular biomarkers to monitor marine environmental pollution. However, phylogenetically diverse organisms do not always respond similarly with regard to the transcriptional response of GSTs, therefore it is necessary to analyze the expression profiles of these genes across species.
Manila clam, Venerupis philippinarum is widely distributed and occurs at high densities around the heavily polluted Bohai Sea (Liang et al., 2004). It has been listed as a sentinel organism in “Mussel Watch Programs” launched in China. Our previous studies had demonstrated that this species exhibited distinct biochemical and genetic responses when exposed to heavy metals and B[a]P (Liu et al., 2011, Wang et al., 2011, Zhang et al., 2011a, Zhang et al., 2011b), possessing the requisite features of a promising indicator species. Because GST isoenzymes were considered useful biomarkers in mollusk species (Boutet et al., 2004, Hoarau et al., 2006, Wan et al., 2008a, Wan et al., 2008b, Wan et al., 2009), investigation on the expression profiles of VpGSTs isoforms to specific environmental pollutants would be helpful to identify potential biomarkers for future environmental biomonitoring. To our knowledge, only one GST-pi gene was cloned and characterized from V. philippinarum (Xu et al., 2010). However, information about different classes of VpGSTs and their expression profiles to various toxicants exposure is currently unavailable. In this study, we reported the identification, characterization and distribution of seven VpGSTs from our ESTs database. To further identify promising VpGST isoforms as biomarkers, the expression patterns of seven VpGSTs were also investigated after exposure to three typical environmental contaminants in the Bohai Sea.
Section snippets
Clams and treatments
The clams V. philippinarum (shell length: 3.0–4.0 cm, Zebra pedigrees) were purchased from local aqufarm and acclimatized in aerated seawater (33 parts per thousand) at 25 °C for 10 days before exposures. During the acclimatization period, the clams were fed with Chlorella vulgaris Beij, and the water was totally exchanged daily. After the acclimatization, the clams were randomly divided into eight flat-bottomed rectangular tanks, each containing 50 individuals in 20 L seawater.
For the exposure
Identification and classification of VpGSTs genes
Seven different GST transcripts were identified from the V. philippinarum EST database and the full-length cDNAs were cloned by RACE approaches. Based on the deduced amino acid identities and phylogenetic analysis with other GSTs, the V. philippinarum GSTs were classified into five different classes, including three in Sigma (VpGSTS1, VpGSTS2, VpGSTS3) and one each in Omega (VpGSTO), Mu (VpGSTM), Rho (VpGSTR) and the microsomal GST isoenzyme (VpGSTMi). The cDNA and deduced amino acid sequences
Discussion
The molecular biological approach in studying potential biomarker has been widely used as a reliable means to conduct environmental monitoring studies (Hoarau et al., 2006, Rhee et al., 2007). 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
Conclusions
In summary, we characterized seven GST genes in V. philippinarum and also examined their potential as biomarkers for heavy metals and B[a]P contamination. The expressions of VpGSTs transcript appeared to be selectively up- or down-regulated, which enhanced our understanding of the antioxidant roles of VpGSTs and their biomarker application. Of them, VpGSTS2, VpGSTS3, VpGSTM and VpGSTR exhibited significant up-regulation, indicating its good biomarker potential for Cu or B[a]P pollution in
Acknowledgements
This research was supported by The 100 Talents Program of the Chinese Academy of Sciences and Key Laboratory of Fisheries Genetic Resources & Aquaculture, Chinese Academy of Fisheries Sciences and the Key Laboratory of Marine Spill Oil Identification and Damage Assessment Technology (201115),and State Oceanic Administration.
References (52)
- et al.
Activation of rat liver microsomal glutathione S-transferase by hydrogen peroxide: role for protein–dimer formation
Arch. Biochem. Biophys.
(2002) - et al.
Acute effects of benzo[a]pyrene on digestive gland enzymatic biomarkers and DNA damage on mussel Mytilus galloprovincialis
Ecotoxicol. Environ. Saf.
(2010) - et al.
Isolation and characterization of glutathione S-transferases isozyme from the Northen quahog, Mercinaria mercinaria
J. Protein Chem.
(2002) - et al.
Identification, characterization, and crystal structure of the omega class glutathione transferases
J. Biol. Chem.
(2000) - et al.
Characterization and expression of four mRNA sequences encoding glutathione S-transferases pi, mu, omega, and sigma classes in the Pacific oyster Crassostrea gigas exposed to hydrocarbons and pesticides
Mar. Biol.
(2004) - et al.
Oxidative modification of aldose reductase induced by copper ion. Definition of the metal–protein interaction mechanism
J. Biol. Chem.
(2002) - et al.
Effects of copper and cadmium on cholinesterase and glutathione S-transferase activities of two marine gastropods (Monodonta lineata and Nucella lapillus)
Comp. Biochem. Physiol. C
(2007) - et al.
Molecular cloning and characterization of a glutathione S-transferase from largemouth bass (Micropterus salmoides) liver that is involved in the detoxification of 4-hydroxynonenal
Biochem. Pharmacol.
(2004) - et al.
Identification, sequencing and expression of selenium-dependent glutathione peroxidase transcript in the freshwater bivalve Unio tumidus exposed to Aroclor 1254
Comp. Biochem. Physiol. C
(2006) - et al.
The acute effects of microcystin LR on the transcription of nine glutathione S-transferase genes in common carp Cyprinus carpio L
Aquat. Toxicol.
(2006)
cDNA cloning and mRNA expression of heat shock protein 90 gene in the haemocytes of Zhikong scallop Chlamys farreri
Comp. Biochem. Physiol. B
Role of human cytochrome P450 in the metabolic activation of chemical carcinogens and toxins
Drug Metab. Rev.
The effect of cyanobacterial crude extract on the transcription of GST mu, GST kappa and GST rho in different organs of goldfish (Carassius auratus)
Aquat. Toxicol.
Glutathione transferases
Annu. Rev. Pharmacol. Toxicol.
Cloning and expression of a GST-pi gene in Mytilus galloprovincialis. Attempt to use the GST-pi transcript as a biomarker of pollution
Comp. Biochem. Physiol. C
Purification and partial characterization of glutathione S-transferases from the clam Ruditapes decussatus
Eur. J. Biochem.
Multiple roles of microsomal glutathione transferase 1 in cellular protection: a mechanistic study
Free Radic. Biol. Med.
The role of glutathione in detoxication
Environ. Health Perspect.
Expression profiles of seven glutathione S-transferase (GST) genes in cadmium-exposed river pufferfish (Takifugu obscurus)
Comp. Biochem. Physiol. C
Expression of glutathione S-transferase (GST) genes in the marine copepod Tigriopus japonicus exposed to trace metals
Aquat. Toxicol.
Cloning and expression of alpha class glutathione S-transferase gene from the small hermaphroditic fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae)
Mar. Pollut. Bull.
Molecular cloning and characterization of θ-class glutathione S-transferase (GST-T) fromthe hermaphroditic fish Rivulus marmoratus and biochemical comparisons with α-class glutathione S-transferase (GST-A)
Biochem. Biophys. Res. Commun.
Identification and characterization of eleven glutathione S-transferase genes from the aquatic midge Chironomus tentans (Diptera: Chironomidae)
Insect Biochem. Mol. Biol.
Evaluation of mollusks as biomonitors to investigate heavy metal contaminations along the Chinese Bohai Sea
Sci. Total. Environ.
Molecular cloning and characterization of alpha-class glutathione S-transferase gene from the liver of silver carp, bighead carp, and other major Chinese freshwater fishes
J. Biochem. Mol. Toxicol.
Toxicological responses to acute mercury exposure for three species of Manila clam Ruditapes philippinarum by NMR-based metabolomics
Environ. Toxicol. Pharmacol.
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