Response of selenium-dependent glutathione peroxidase in the freshwater bivalve Anodonta woodiana exposed to 2,4-dichlorophenol,2,4,6-trichlorophenol and pentachlorophenol.

2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) pose a health risk to aquatic organism and humans, and are recognized as persistent priority pollutants. Selenium dependent glutathione peroxidase (Se-GPx) belongs to the family of selenoprotein, which acts mainly as an antioxidant role in the cellular defense system. In the current study, a Se-GPx full length cDNA was cloned from Anodonta woodiana and named as AwSeGPx. It had a characteristic codon at 165TGA167 that corresponds to selenocysteine(Sec) amino acid as U44. The full length cDNA consists of 870 bp, an open reading frame (ORF) of 585 bp encoded a polypeptide of 195 amino in which conserved domain (68LGFPCNQF75) and a glutathione peroxide-1 GPx active site (32GKVILVENVASLUGTT47) were observed. Additionally, the eukaryotic selenocysteine insertion sequence (SECIS) was conserved in the 3'UTR. The AwSeGPx amino acid sequence exhibited a high similarity with that of other Se-GPx. Real-time PCR analysis revealed that AwSeGPx mRNA had a widely distribution, but the highest level was observed in hepatopancreas. AwSeGPx mRNA expression was significantly up-regulated in hepatopancreas, gill and hemocytes after 2,4-DCP, 2,4,6-TCP and PCP exposure. Under similar environment, clams A. woodiana showed a more sensitive to PCP than that of 2,4-DCP and 2,4,6-TCP. These results indicate that AwSeGPx plays a protective role in eliminating oxidative stress derived from 2,4-DCP, 2,4,6-TCP and PCP treatment.

Molecular cloning, characterization, and the response of Cu/Zn superoxide dismutase and catalase to PBDE-47 and -209 from the freshwater bivalve Anodonta woodiana.

Polybrominated diphenyl ethers-47 (PBDE-47) and -209 are significant components of total PBDEs in water and can catalyze the production of reactive oxygen species (ROS) in the organisms. Anti-oxidant enzymes play an important role in scavenging the high level of ROS. In the current study, two full-length cDNAs of Cu/Zn superoxide dismutase (CuZnSODs) and catalase (CAT) were isolated from freshwater bivalve Anodonta woodiana by rapid amplification of cDNA ends approach and respectively named as AwSOD and AwCAT. The nucleotide sequence of AwSOD cDNA had an open reading frame (ORF) of 465 bp encoding a polypeptide of 155 amino acids in which signature 1 GKHGFHVHEFGDNT and signature 2 GNAGARSACGVI of SODs were observed. Deduced amino acid sequence of AwSOD showed a significant similarity with that of CuZnSODs. AwCAT had an ORF 1536 bp encoding a polypeptide of 512 amino acids which contains a conserved catalytic site motif, and a proximal heme-ligand signature motif of CATs. The time-course expressions of AwSOD and AwCAT in hepatopancreas were measured by quantitative real-time PCR. Expressions of AwSOD and AwCAT showed a significant up-regulation in groups at a low concentration treatment of PBDE-47, a biphasic pattern in groups with a high concentration treatment. Administration of PBDE-209 could result in an up-regulation of AwSOD and AwCAT expressions with time- and dose-dependent matter. These results indicate that up-regulations of AwSOD and AwCAT expression of hepatopancreas of freshwater bivalve A. woodiana contribute to eliminate oxidative stress derived from PBDE-47 and -209 treated.