Methylsulfonyl-PCBs (MeSO2-PCBs) are hydrophobic organic contaminants that bioaccumulate in the environment similar to their parent molecules, PCBs. Previously, MeSO2-PCBs have primarily been identified in tissues of birds, humans, and other mammals. However, evidence now supports formation of these metabolites in deepwater sculpin, Myoxocephalus thompsoni, a benthic forage fish predominant in the Great Lakes. The ability of deepwater sculpin to form MeSO2-PCBs is unprecedented for a freshwater fish species and presents a novel biochemical pathway for organochlorine metabolism. Additionally, this appears to be a unique PCB metabolic pathway resulting in a reduction of as much as 10% in the sculpin PCB burden, which is further transformed into another class of organic contaminants in the Great Lakes ecosystem.
"The average concentration ratios of RMeSO 2 -PCBs/RPCBs in northern snakehead (0.00032) were much lower than those examined in plasma of glaucous gull (0.01 in females and 0.007 in males on average) (Verreault et al. 2005) and whole blood of polar bear (0.19 on average) (Sandala et al. 2004). These results indicated that the bioaccumulation or biotransformation of PCBs in fish was much lower than that in birds or mammals perhaps due to the lower CYP2B- like activity (Stapleton et al. 2001). The chiralities of several chiral PCB congeners were analyzed to gain insight into the enantioselective fate process of PCBs. "
[Show abstract][Hide abstract] ABSTRACT: Halogenated organic pollutants (HOPs)—including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), polybromobiphenyls (PBBs), dechlorane plus (DP), tetrabromobisphenol A (TBBPA), and hexabromocyclododecanes (HBCDs) as well as PCB metabolites (methylsulfone [MeSO2-]) and hydroxylated (OH-) PCBs and OH-PBDEs—were determined in the serum of mud carp and northern snakehead from an electronic-waste (e-waste) site in South China. The average concentrations (mean ± SD) of ΣPCBs, ΣPBDEs, ΣOCPs, ΣPBBs, ΣTBBPA, ΣHBCDs, and ΣDP were 1410 ± 324, 70 ± 20, 3.0 ± 0.4, 2.8 ± 0.8, 1.6 ± 0.4, 1.0 ± 0.2, and 0.3 ± 0.03 ng/g wet weight (ww) in mud carp and 6430 ± 781, 468 ± 49, 22.4 ± 1.1, 7.0 ± 0.6, 2.9 ± 2.3, 5.5 ± 1.1, and 4.6 ± 0.6 ng/g ww in northern snakehead, respectively. MeSO2-PCBs, OH-PCBs, and OH-PBDEs were detected at a total concentration of 0.44 ± 0.03 and 9.7 ± 0.3 ng/g ww in mud carp and northern snakehead, respectively. The congener profiles of PCBs, PBDEs, OH/MeSO2-PCBs, and OH-PBDEs were found to be significantly different between the two fish species, possibly as a result of species-specific bioaccumulation and/or metabolism of the HOPs. Chirality of ten PCB congeners and α-HBCD, as well as the f
values of DP in the serum samples, supported the species-specific biotransformation of HOPs. Furthermore, the presence of covaried and counter-varied enantiomeric fractions of PCBs between the two fish species indicated species- and congener-specific enantiomer enrichment of PCBs.
Archives of Environmental Contamination and Toxicology 05/2014; 67(3). DOI:10.1007/s00244-014-0040-8 · 1.90 Impact Factor
"HO-PCBs are susceptible to conjugation reactions resulting in excretion , but a few are retained in blood as a consequence of their high affinity for the thyroid transport protein transthyretin (TTR) (Chauhan et al., 2000; Letcher et al., 2000, 2004). MeSO 2 –PCBs, which are more hydrophobic and resistant to further biodegradation than HO-PCBs, accumulate in lipid-containing tissues such as the liver, lung and kidney and typically represent 5–20% of the total PCBs content in these tissues (Brandt and Bergman, 1987; Bergman et al., 1992, 1994; Letcher et al., 1995, 1998, 2000; Stapleton et al., 2001; Larsson et al., 2002; Sandala et al., 2004). The concentrations of total MeSO 2 –PCBs in tissue samples, which are mainly reported in the fat of marine mammals , are generally in the range of 7–800 ng/g (lipid weight) (Letcher et al., 2000). "
[Show abstract][Hide abstract] ABSTRACT: Some endocrine disrupting chemicals (EDCs) in the environment have been shown to exert their biological effects through interference with steroidogenesis. In this study, the potential effects of four selected polychlorinated biphenyl (PCB) congeners (PCB101, PCB110, PCB126 and PCB149) as well as several of their environmentally-relevant methylsulfonyl-(MeSO2–) PCB metabolites (3′-MeSO2–CB101, 4′-MeSO2–CB101, 4′-MeSO2–CB110, 3′-MeSO2–CB149 and 4′-MeSO2–CB149) on adrenocortical steroidogenesis were evaluated by in vitro bioassay based on the human adrenocortical carcinoma H295R cell line. The PCBs included in the study represented different structures and potential mechanisms of action. Cells were exposed for 48h to 10μM of each PCB congener in the presence or absence of 20% (w/w) of their corresponding MeSO2–PCB metabolite(s). After the chemical treatments, changes in mRNA expression of 11 steroidogenic genes (CYP11A, CYP11B1, CYP11B2, CYP17, CYP19, CYP21, 3β-HSD1, 3β-HSD2, 17β-HSD1, StAR and HMGR) were quantified using molecular beacon-based real-time RT-PCR. Genes coding for enzymes involved in the later or final steps of steroid production (CYP11B1, CYP11B2, CYP19, 3β-HSD1, 3β-HSD2 and 17β-HSD1) were up-regulated to various extents by most PCBs. The greatest transcriptional activations (2.8–29.9-fold) were elicited by PCB110 on CYP11B1, CYP11B2, 3β-HSD2 and CYP19, and PCB149 on CYP11B1, 3β-HSD1 and 17β-HSD1. Increased expression of these steroidogenic genes might ultimately lead to a change in hormonal balance through excessive production of steroid hormones including aldosterone, cortisol and estradiol. In addition, co-treatment with 3′- and 4′-MeSO2–PCB149 resulted in a significant decrease in PCB149-induced 3β-HSD1 and 17β-HSD1 expression. This result indicates that some PCB congeners and their MeSO2-metabolites may affect steroidogenesis via different mechanisms. Overall, these findings suggest that PCBs and PCB metabolites can affect regulation of adrenocortical steroidogenesis.
"CH 3 SO 2 -PCBs are generally referred to as MeSO 2 -PCBs. The numbers of animals and populations where tissue residues of these PCB metabolites have been characterized remains small, but HO-PCBs and MeSO 2 -PCBs are emerging as common contaminant phenomena in wildlife and humans and are of increasing importance in risk assessments of exposure to PCBs (Bennett et al. 2002; Campbell et al. 2003; Chu et al. 2002, 2003; Guvenius et al. 2002; Hoekstra et al. 2003; Hovander et al. 2002; Letcher et al. 2000a, 2000b; Li et al. 2003; Sandala et al., in press; Sandau et al. 2000a, 2000b, 2002; Stapleton et al. 2001). "
[Show abstract][Hide abstract] ABSTRACT: Polychlorinated biphenyls (PCBs) are a widespread class of persistent organic chemicals that accumulate in the environment and humans and are associated with a broad spectrum of health effects. PCB biotransformation has been shown to lead to two classes of PCB metabolites that are present as contaminant residues in the tissues of selected biota: hydroxylated (HO) and methyl sulfone (MeSO2) PCBs. Although these two types of metabolites are related structures, different rules for abbreviation of both classes have emerged. It is important that a standardized nomenclature for the notation of PCB metabolites be universally agreed upon. We suggest that the full chemical name of the PCB metabolite and a shorthand notation should be adopted using the International Union of Pure and Applied Chemistry's chemical name/original Ballschmiter and Zell number of the parent congener, followed by the assignment of the phenyl ring position number of the MeSO2- or HO-substituent. This nomenclature provides a clear, unequivocal set of rules in naming and abbreviating the PCB metabolite structure. Furthermore, this unified PCB metabolite nomenclature approach can be extended to the naming and abbreviation of potential metabolites of structurally analogous contaminants such as HO-polybrominated biphenyls and HO-polybrominated diphenyl ethers.
Environmental Health Perspectives 04/2004; 112(3):291-4. DOI:10.1289/ehp.6409 · 7.98 Impact Factor
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