15166-50-4

Tetrachloroethene (PCE), a common industrial solvent and environmental contaminant, is primarily used in the dry-cleaning industry. The toxicity of PCE has been linked to vision disorders, renal and hepatic cancer, and autoimmune diseases. Although the mechanism of toxicity is not fully understood, PCE forms trichloroacylated protein adducts in tissues where toxicity is known to occur. These adducts may be responsible for toxicity by altering the function of cellular proteins. Using Western blot analysis, formation of trichloroacylated protein adducts has been reported. To determine the localization of the adducts in a specific zone of a tissue, immunohistochemical staining was used in the study. An antiserum to trichloroacylated proteins was raised in rabbits and its specificity was established by enzyme-linked immunosorbent assay (ELISA). Female MRL-Ipr/Ipr and MRL +/+ mice were treated with PCE using a single 5-mmol/kg dose over 24 h or on every fourth day for 6 wk (total 20 doses). Formation of trichloroacylated protein adducts was observed in the liver, and localized to the centrilobular zones. Intensity and circumference of the staining around the central vein were much greater in subchronically treated mice than in acutely treated mice. No immunochemical reactivity was observed in any of the other tissues examined. This study shows that hepatic trichloroacylated protein adducts are localized in a region of the liver where PCE-mediated toxicity is known to occur. Immunohistochemical localization of these adducts and its association with PCE-induced toxicity support the contention that adducts may contribute to toxicity.

Antibodies directed against chemical specific protein modifications are valuable tools to detect and comparatively quantify protein modifications. Both Nε-(dichloroacetyl)-L-lysine and N(ε)(trichloroacety)]-L-lysine have been detected as modified amino acids in liver and kidneys of rats treated with perchloroethene (PER) after proteolysis. These protein modifications are formed by the interaction of reactive metabolites formed from PER with proteins. In this study we developed monospecific antibodies to dichloroacetylated and to trichloroacetylated amino acids to detect modified proteins in the target organs of PER toxicity. These antibodies were prepared by immunization of rabbits with modified keyhole limpet hemocyanin (KLH) coupled with either the dichloroacetyl or trichtoroacetyl moiety. Enzyme- linked immunosorbent assays (ELISA) indicated that the polyclonal rabbit sera recognized dichloroacetylated or trichloroacetylated rabbit serum albumin (RSA), but not unmodified protein. Therefore, we further purified rabbit antisera on either N(ε)-(dichloroacetyl)-L-lysine or N(ε)- (trichloroacetyl)-L-lysine immobilized to immunoaffinity columns to obtain monospecific antibodies. The potential of these antibodies in the detection of di- and trichloroacetylated proteins and their selectivity for the desired dichloroacetyl or trichloroacetyl group was demonstrated in competitive enzyme-linked immunosorbent assays with several structurally related compounds. Anti-dichloroacetyl (anti-DCA) antibody binding to dichloroacetylated RSA was inhibited by N(ε)-(dichloroacetyl)L-lysine with an IC50 value of 150 μM whereas inhibition by N(ε)-(monochloroacetyl)-L- lysine and N(ε)-(trichloroacetyl)-L-lysine showed an IC50 value of 100 mM. The binding of the antitrichloroacetyl (anti-TCA) antibody to trichloroacetylated RSA was inhibited by N(ε)-(dichloroacetyl)-L-lysine with an IC50 value of 80 mM. The inhibition by N(ε)-(trichloroacetyl)-L-lysine was again 3 orders of magnitude stronger resulting in an IC50 value of 90 μM. N(ε)-(acetyl)-L-lysine and unmodified RSA did not effect antibody binding to the chemically modified antigen. The antibodies were also successfully applied to detect modified proteins in subcellular fractions of liver and kidney from PER treated rats demonstrated in immunoblot. Protein adduct formation from different PER metabolism pathways was confirmed by the observation that the majority of dichloroacetylated proteins were located in kidney mitochondria and trichloroacetylated proteins were located in liver microsomes.

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A new efficient synthesis of α-amino acids from allyl alcohol derivatives via an acetimidate rearrangement has been developed.