Protein adduction

K. Mizutani, T. Electronic and structural requirements for metabolic activation of butylated hydroxytoluene analogs to their quinone methides, intermediates responsible for lung toxicity in mice. Biol. Pharm. Bull. 1997, 20, 571-573. (c) McCracken, P. G. Bolton, J. L. Thatcher, G. R. J. Covalent modification of proteins and peptides by the quinone methide from 2-rm-butyl-4,6-dimethylphenol selectivity and reactivity with respect to competitive hydration. J. Org. Chem. 1997, 62, 1820-1825. (d) Reed, M. Thompson, D. C. Immunochemical visualization and identification of rat liver proteins adducted by 2,6-di- m-butyl-4-methylphenol (BHT). Chem. Res. Toxicol. 1997, 10, 1109-1117. (e) Lewis, M. A. Yoerg, D. G. Bolton, J. L. Thompson, J. Alkylation of 2 -deoxynucleosides and DNA by quinone methides derived from 2,6-di- m-butyl-4-methylphenol. Chem. Res. Toxicol. 1996, 9, 1368-1374. 

In contrast to the lability of certain dN adducts formed by the BHT metabolite above, amino acid and protein adducts formed by this metabolite were relatively stable.28,29 The thiol of cysteine reacted most rapidly in accord with its nucleophilic strength and was followed in reactivity by the a-amine common to all amino acids. This type of amine even reacted preferentially over the e-amine of lysine.28 In proteins, however, the e-amine of lysine and thiol of cysteine dominate reaction since the vast majority of a-amino groups are involved in peptide bonds. Other nucleophilic side chains such as the carboxylate of aspartate and glutamate and the imidazole of histidine may react as well, but their adducts are likely to be too labile to detect as suggested by the relative stability of QMs and the leaving group ability of the carboxylate and imidazole groups (see Section 9.2.3). 

Lemercier, J.-N. Meier, B. Gomez, J. D. Thompson, J. A. Inhibition of glutathione S-transferase Pl-1 in mouse lung epithelial cells by the tumor promoted 2,6,di-tert-butyl-4-methylene-2,5-cylcohexadienone (BHT-quinone methide) protein adducts investigated by electrospray mass spectrometry. Chem. Res. Toxicol. 2004, 17, 1675-1683. 

Reed, M. Thompson, D. C. Immunochemical visualization and identification of rat liver proteins adducted by 2,6-di-terf-butyl-4-methylphenol (BHT). Chem. Res. Toxicol. 1997, 10, 1109-1117. 

Gu, XR, Meer, SG, Miyagi, M, Raybom, ME, Hollyfield, JG, Crabb, JW, and Salomon, RG, 2003. Carboxyethylpyrrole protein adducts and autoantibodies, biomarkers for age-related macular degeneration. J Biol Chem 278, 42027-42035. 

Beauchamp, C.O., Gonias, S.L., Menapace, D.P., and Pizzo, S.V. (1983) A new procedure for the synthesis of polyethylene glycol-protein adducts Effects on function, receptor recognition, and clearance of superoxide dismutase, lactoferrin, and a2macroglobulin. Anal. Biochem. 131, 25-33. 

This paper will focus on methods that are based on the analysis of long-lived protein adducts of CW agents which are detectable weeks or even months after exposure. Examples of real exposure incidents will be described. 

In the case of sulfur mustard, analysis of low molecular weight urinary metabolites suffers from the same drawback as in the case of anticholinesterases, i.e., these products are rapidly excreted and provide therefore limited retrospectivity. Similarly, the in vivo lifetime of DNA adducts of sulfur mustard are less than those of protein adducts due to repair of DNA damage. 

Blood Protein adduct Albumin peptide LC-MS-MS Whole blood treated with known phosgene concentrations Specific and sensitive LOD luM Standards not easily available... 

Evans, D.C. et al., Drug-protein adducts An industry perspective on minimizing the potential for drug bioactivation in drug discovery and development, Chem. Res. Toxicol., 17, 3, 2004. 

A further remarkable finding in the hydrolysis of aflatoxin B1 exo-8,9-epoxide is the relative instability of the dihydrodiol, which under basic conditions exists in equilibrium with an aflatoxin dialdehyde, more precisely a furofuran-ring-opened oxy anionic a-hydroxy dialdehyde (10.134, Fig. 10.30). The dihydrodiol is the predominant or exclusive species at pH < 7, whereas this is true for the dialdehyde at pH >9, the pK value of the equilibrium being 8.2 [204], The dialdehyde is known to form Schiff bases with primary amino groups leading to protein adducts. However, the slow rate of dialdehyde formation at physiological pH and its reduction by rat and human aldo-keto reductases cast doubts on the toxicological relevance of this pathway [206]. 

Covalent protein adducts of quinones are formed through Mchael-type addihon reachon with protein sulfhydryl groups or glutathione. Metabolic activahon of several toxins (e.g., naphthalene, pentachlorophenol, and benzene) into quinones has been shown to result in protein quinone adducts (Lin et al, 1997 Rappaport et al, 1996 Zheng et al., 1997). Conversion of substituted hydroquinones such as p-aminophenol-hydroquinone and 2-bromo-hydroquinone to their respective glutathione S-conjugates must occur to allow bioactivation into nephrotoxic metabolites (Dekant, 1993). Western blot analysis of proteins from the kidneys of rats treated with 2-bromo-hydroquinone has revealed three distinct protein adducts conjugated to quinone-thioethers (Kleiner et al, 1998). 

Immunochemical detection of quinol-thioether-deiived protein adducts. Chem. Res. Toxicol. 11 1283-1290... 

The modified Florence program is well-suited for fitting the experimental NMRD profiles for slowly-rotating complexes of gadolinium(HI), an S = 7/2 ion characterized by relatively low ZFS, whose electron spin relaxation can be considered to be in the Redfield limit. An example of fitting an NMRD profile for aqueous protons, using different methods, for a protein adduct of a Gd(HI) chelate capable of accommodating one water molecule in the first coordination sphere, is displayed in Fig. 11. Other examples will be provided in Chapter 3. 

The NMRD profile of the protein adduct shows a largely increased relaxivity, with the dispersion moved at about 1 MHz and a relaxivity peak in the high field region. This shape is clearly related to the fact that the field dependent electron relaxation time is now the correlation time for proton relaxation even at low fields. The difference in relaxivities before and after the dispersion is in this case very small, and therefore the profile cannot be well fit with the SBM theory, and the presence of a small static ZFS must be taken into account 103). The best fit parameters obtained with the Florence NMRD program are D = 0.01 cm , A = 0.017 cm , t = 18x10 s, and xji =0.56 X 10 s. Such values are clearly in agreement with those obtained with fast-motion theory 101). 

Late clinical Metabolites react with protein Protein adduct acts as... 

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