Zugl.: Hannover, Univ., Diss., 2009

Reproduction de : Thèse de doctorat : Sciences agronomiques et écosystèmes : Toulouse, INPT : 2008. / Titre provenant de l'écran-titre. Bibliogr. 292 réf.

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Perfluorinated carboxylates (PFCAs) are persistent and ubiquitous in the environment. Humans are exposed to PFCAs through direct and indirect sources, although the relative importance of each is uncertain. Direct sources of PFCAs have been attributed to two primary fluorochemical manufacturing processes: electrochemical fluorination (ECF) and telomerization. A focus of this thesis was to elucidate an additional direct source of PFCAs resulting from the direct fluorination of polyolefin materials. High density polyethylene bottles with varying levels of fluorination were observed to contain significant amounts of PFCAs, particularly those with carbon chain-lengths ≤ C6, marking an unexplored source of PFCA exposure. PFCAs are also produced indirectly from the biotransformation of fluorotelomer-based compounds, such as polyfluoroalkyl phosphate esters (PAPs) and fluorotelomer alcohols (FTOHs). During this transformation process, two predominant classes of metabolic intermediates are formed: the fluorotelomer unsaturated aldehydes (FTUALs) and the fluorotelomer unsaturated carboxylic acids (FTUCAs). Another focus of this thesis was to examine the reactivity of FTUALs and FTUCAs with endogenous nucleophiles such as glutathione (GSH), select amino acids, and model proteins. FTUALs formed adducts with all nucleophiles examined, where those having shorter carbon chain lengths (i.e. 6:2 and 8:2 FTUAL) were more reactive than longer carbon chains (i.e. 10:2 FTUAL). By contrast, FTUCAs had comparably limited reactivity; although FTUCAs showed mild reactivity with GSH, they did not react with any other nucleophiles. In vitro and in vivo experiments were carried out to determine the extent of protein binding formed from the biotransformation of fluorotelomer-based compounds, including the 8:2 FTOH and the 6:2 PAP diester. A significant portion of these biotransformations yielded covalent protein binding at nmol/mg protein concentrations. Protein adducts were observed predominantly in rat liver and also in plasma and kidney. The formation of reactive intermediates may be toxicologically important through protein deactivation. Cellular toxicity of FTUALs was significantly higher compared to PFCAs and the acid metabolic intermediates (i.e. FTUCAs). The EC50 values calculated from dose-response incubations were dependant on chain length and functional group. The work in this thesis examined an unexplored consequence of indirect exposure to PFCAs, potentially impacting the relative importance of PFCA exposure sources.

Perfluorinated carboxylates (PFCAs) are persistent and ubiquitous in the environment. Humans are exposed to PFCAs through direct and indirect sources, although the relative importance of each is uncertain. Direct sources of PFCAs have been attributed to two primary fluorochemical manufacturing processes: electrochemical fluorination (ECF) and telomerization. A focus of this thesis was to elucidate an additional direct source of PFCAs resulting from the direct fluorination of polyolefin materials. High density polyethylene bottles with varying levels of fluorination were observed to contain significant amounts of PFCAs, particularly those with carbon chain-lengths ≤ C6, marking an unexplored source of PFCA exposure. PFCAs are also produced indirectly from the biotransformation of fluorotelomer-based compounds, such as polyfluoroalkyl phosphate esters (PAPs) and fluorotelomer alcohols (FTOHs). During this transformation process, two predominant classes of metabolic intermediates are formed: the fluorotelomer unsaturated aldehydes (FTUALs) and the fluorotelomer unsaturated carboxylic acids (FTUCAs). Another focus of this thesis was to examine the reactivity of FTUALs and FTUCAs with endogenous nucleophiles such as glutathione (GSH), select amino acids, and model proteins. FTUALs formed adducts with all nucleophiles examined, where those having shorter carbon chain lengths (i.e. 6:2 and 8:2 FTUAL) were more reactive than longer carbon chains (i.e. 10:2 FTUAL). By contrast, FTUCAs had comparably limited reactivity; although FTUCAs showed mild reactivity with GSH, they did not react with any other nucleophiles. In vitro and in vivo experiments were carried out to determine the extent of protein binding formed from the biotransformation of fluorotelomer-based compounds, including the 8:2 FTOH and the 6:2 PAP diester. A significant portion of these biotransformations yielded covalent protein binding at nmol/mg protein concentrations. Protein adducts were observed predominantly in rat liver and also in plasma and kidney. The formation of reactive intermediates may be toxicologically important through protein deactivation. Cellular toxicity of FTUALs was significantly higher compared to PFCAs and the acid metabolic intermediates (i.e. FTUCAs). The EC50 values calculated from dose-response incubations were dependant on chain length and functional group. The work in this thesis examined an unexplored consequence of indirect exposure to PFCAs, potentially impacting the relative importance of PFCA exposure sources.

The overall aim of this thesis was to investigate the fate of perfluorinated alkyl compounds (PFCs) in biological systems. During the past several years, it has been shown that wildlife are ubiquitously contaminated with two classes of PFCs, the perfluoroalkyl carboxylates (CxF2x+1C(O)OH, PFCAs) and sulfonates (CxF2x+1SO3H, PFSAs). However, there is still considerable uncertainty regarding how wildlife are accumulating these PFCs, particularly in remote areas such as the Canadian arctic. The potential for fluorotelomer acrylate monomers (CxF2x+1CH2CH2OC(O)CH=CH2, FTAcs) to act as precursors to PFCAs through atmospheric oxidation was investigated using smog chamber experiments. FTAc atmospheric fate is determined by OH radical reaction with a lifetime of approximately 1 day. The sole primary product of this reaction was the 4:2 fluorotelomer glyoxylate which is expected to undergo further atmospheric oxidation or photolysis to ultimately yield PFCAs. Temporal and spatial trends of PFCs in arctic ringed seals and seabirds were investigated to assist in understanding PFC transport mechanisms to remote regions. In ringed seals, perfluorooctane sulfonate (PFOS) levels decreased rapidly, coinciding with the phase out by the major manufacturer. These findings are consistent with volatile precursors as the dominant source of PFCs to arctic wildlife. The bioaccumulation and biotransformation of the 8:2 FTAc was investigated in two complimentary studies with rainbow trout. During the in vivo dietary exposure study, fish rapidly accumulated and biotransformed the 8:2 FTAc, with intermediate metabolites observed within 1 hour of dosing. Perfluorooctanoate (PFOA), perfluorononanoate (PFNA) and perfluoroheptanoate (PFHpA) were formed and accumulated in low yields. The carboxylesterase activity in the trout liver and stomach was investigated using in vivo sub-cellular (S9) incubations. Very high esterase activities were shown with approximately equal efficiency in the stomach and liver. The metabolic pathway of the 8:2 fluorotelomer alcohol (8:2 FTOH) was investigated by separately dosing whole rainbow trout with three intermediate metabolites that represented important branching points. The 7:3 fluorotelomer saturated carboxylate (FTCA) did not form PFOA, but formed PFHpA and the 7:3 fluorotelomer unsaturated carboxylate (FTUCA). The 8:2 FTCA and 8:2 FTUCA did form PFOA, confirming a “beta-like-oxidation” mechanism.

The overall aim of this thesis was to investigate the fate of perfluorinated alkyl compounds (PFCs) in biological systems. During the past several years, it has been shown that wildlife are ubiquitously contaminated with two classes of PFCs, the perfluoroalkyl carboxylates (CxF2x+1C(O)OH, PFCAs) and sulfonates (CxF2x+1SO3H, PFSAs). However, there is still considerable uncertainty regarding how wildlife are accumulating these PFCs, particularly in remote areas such as the Canadian arctic. The potential for fluorotelomer acrylate monomers (CxF2x+1CH2CH2OC(O)CH=CH2, FTAcs) to act as precursors to PFCAs through atmospheric oxidation was investigated using smog chamber experiments. FTAc atmospheric fate is determined by OH radical reaction with a lifetime of approximately 1 day. The sole primary product of this reaction was the 4:2 fluorotelomer glyoxylate which is expected to undergo further atmospheric oxidation or photolysis to ultimately yield PFCAs. Temporal and spatial trends of PFCs in arctic ringed seals and seabirds were investigated to assist in understanding PFC transport mechanisms to remote regions. In ringed seals, perfluorooctane sulfonate (PFOS) levels decreased rapidly, coinciding with the phase out by the major manufacturer. These findings are consistent with volatile precursors as the dominant source of PFCs to arctic wildlife. The bioaccumulation and biotransformation of the 8:2 FTAc was investigated in two complimentary studies with rainbow trout. During the in vivo dietary exposure study, fish rapidly accumulated and biotransformed the 8:2 FTAc, with intermediate metabolites observed within 1 hour of dosing. Perfluorooctanoate (PFOA), perfluorononanoate (PFNA) and perfluoroheptanoate (PFHpA) were formed and accumulated in low yields. The carboxylesterase activity in the trout liver and stomach was investigated using in vivo sub-cellular (S9) incubations. Very high esterase activities were shown with approximately equal efficiency in the stomach and liver. The metabolic pathway of the 8:2 fluorotelomer alcohol (8:2 FTOH) was investigated by separately dosing whole rainbow trout with three intermediate metabolites that represented important branching points. The 7:3 fluorotelomer saturated carboxylate (FTCA) did not form PFOA, but formed PFHpA and the 7:3 fluorotelomer unsaturated carboxylate (FTUCA). The 8:2 FTCA and 8:2 FTUCA did form PFOA, confirming a “beta-like-oxidation” mechanism.

ABSTRACT MORPHINE BIOTRANSFORMATIONS BY MICROBIAL PHENOL OXIDASES Erdural Korkmaz, Beril M.S., Department of Chemical Engineering Supervisor: Prof. Dr. Ufuk Bakir Co-Supervisor: Prof. Dr. Ayhan S. Demir January 2006, 96 pages The objective of this study is to perform morphine biotransformation by using phenol oxidases. Syctalidium thermophilum, Thermomyces lanuginosus and Phanerochaete chrysosporium cells and culture fluid were used as microbial intracellular and extracellular phenol oxidases. Besides the phenol oxidases produced in laboratory, commercial pure phenol oxidases, A. bisporus tyrosinase and laccase, T. versicolor laccase and horseradish peroxidase, were also used in the morphine biotransformation reactions. Morphine biotransformation to pseudo-morphine was achieved by using pure T. versicolor laccase, A.bisporous tyrosinase and laccase. Before utilization of phenol oxidases in morphine biotransformations, the time course of microbial phenol oxidase productions were followed. Maximum phenol oxidase activity of S. thermophilum were detected on the 5th day of cultivation as 0.17 U/ml and the 4th day of cultivation as 0.072 U/ml, respectively. On the other hand, maximum laccase activity of P. chrysosporium was detected on the 8th day of cultivation as 78.5 U/ml. Although phenol oxidases which were obtained from S. thermophilum or T. lanuginosus could not catalyze morphine biotransformation, phenol oxidases including a peroxidase of P. chrysosporium transformed morphine to pseudo-morphine and an unknown product.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 8 uppsatser.