Protein adducts formation

The QSAR data show that glucuronidation can be either a detoxification or bioactivation mechanism, depending chemical structure. For N SAIDs, it appears to be mostly a detoxification mechanism. Nonetheless, the toxicity of acyl glucuronide and glucoside adducts (espedally as it relates to isomerization and protein adduct formation) must be considered when designing carboxylic acids [38]... 

Within cells, sulfur mustard forms adducts with DNA, primarily those described in Toxicity of sulfur mustard, above. Adducts can also be formed with nucleophilic sites of amino acids and proteins. Contrary to DNA adducts, there is no specific mechanism to reverse protein adduct formation. For this reason, there is a strong forensic interest in the detection of protein adducts of sulfur mustard as these may provide evidence of sulfur mustard exposure for prolonged periods after the incident. 

The concentration of crosslinked red blood cell spectrin has been suggested as a marker of nerve protein crosslinking damage that leads to slower conduction velocities and abnormal nerves due to protein adduct formation initially with dithiocarbamates which decompose to form isothiocyanate adducts (Valentine et al. 1993). These latter adducts can then cause the actual crosslinking of both spectrin and nerve protein. 

P450 3A and 2C forms in secondary metabolism and drug-protein adduct formation. Drug Metab Dispos 28(8) 945—950, 2000. 

Dingley KH, Curtis KD, Nowell S, Felton JS, Lang NP, Turteltaub KW. DNA and protein adduct formation in the colon and blood of humans after exposure to a dietary-relevant dose of 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine. Cancer Epidemiol Biomarkers Prev 1999 8 507-512. 

The techniques described in this chapter can be of use to the optimization of lead compounds during drug discovery processes. However, the link between drug-protein adduct formation and toxicity has not been well defined. Additional considerations should be taken, such as therapeutic area and clinical doses. It has been suggested that a 10 mg daily dose rarely results in drug-related adverse effects (Uetrecht, 1999). Thus, the propensity of bioactivation should only be considered as one of the factors in the selection of developmental drug candidates. 

We perceived the need for sensitive assays that do not rely on the use of radioisotopes or extensive analytical methodology and that could accurately detect protein-bound acetaminophen in biological fluids in the presence of unbound acetaminophen. To this end, we recently developed sensitive avidin biotin-amplified ELISA (A-B ELISA) and particle concentration fluorescence immunoassays (PCFIA) which use antiserum specific for the major acetaminophen-protein adduct associated with toxicity (13-16). These assays are new tools to study the relation between formation of the 3-Cys-A protein adduct and acetaminophen-induced toxicity. In this report we review how these assays were developed, validated in laboratory animals, and used to quantify 3-Cys-A protein adduct formation in human acetaminophen overdose patients. 

Park, B.K., et al.. Drug bioactivation and protein adduct formation in the pathogenesis of drug-induced toxicity. Chem Biol Interact, 2011. 192(1-2) p. 30-6. 

Notley et al. (2002) investigated the P450 forms responsible for covalent drug-protein adduct formation and the possibility that covalent adduct formation might occur via alternative pathways to catechol formation. Recombinant P450 3A4 catalysed... 

Exposure of protein amino groups to MDA (formed by the degradation of lipid peroxides) or to oxygen radicals directly, generated by transition metals and hydrogen peroxide, induce fluorescence indistinguishable from that attributed to Amadori-adduct formation (Chio and Tappel, 1969), and leads to the formation of cross-links (Lunec a al., 1985). 

Enzyme-adduct formation has also been successfully achieved with the Erbl and 2 (receptor tyrosine kinases from EGFR subfamily) [19, 20], suggesting that the tethered library-screening approach would also be amenable to protein kinases. 

Bolton, J. L. Le Blanc, J. C. Y. Siu, K. W. M. Reaction of quinone methides with proteins analysis of myoglobin adduct formation by electrospray mass spectrometry. Biol. Mass... 

A characteristic feature of ESMS is the detection of multiply charged analytes. Macromolecules, such as proteins have multiple sites where protonation or deprotonation (the two most common charge inducing mechanisms in electrospray—other routes to charge induction include, ionization through adduct formation, through gas-phase reactions, and through electrochemical oxidation or reduction) occur. These are desorbed effectively in ESMS and... 

An additional question relating to sites of modification is the possible influence of DNA binding proteins and the conformational changes they induce in DNA as it forms chromatin, which in turn may influence available binding sites for adduct formation. Several studies have investigated the distribution of DNA adducts in chromatin (95-102). although no clear answer for the influence of these proteins has yet emerged. 

Aflatoxin Bi (AFB) is a mold metabolite which has been observed to be acutely toxic and carcinogenic to a wide variety of animals (5,6) and has been implicated in human primary hepatic carcinoma (7, 8). Diets deficient in protein have been reported to increase the susceptibility of mammals to acute AFB toxicity and the induction of cancer (2, 9, 10, 11, 12, 13). Increased dietary proteins have increased the carcinogenic activity of AFB fed to rats (1 4) and trout (15.). Supportive of this latter finding has been the reported direct relationship between dietary protein content and AFB-DNA adduct formation in vivo in rats (16, 17). 

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]. 

Exposure. Exposure to 1,3-DNB is currently measured indirectly by determining levels of methemoglobin in the blood (Donovan 1990). However, increased methemoglobin formation is not a specific response to 1,3-DNB exposure and may occur after exposure to other nitrobenzene compounds such as the other two isomers of dinitrobenzene. Determination of methemoglobin levels is widely used and is a reliable detection method. Very few methods are available for direct evaluation of 1,3-DNB levels, and they are not extensively used, probably because of the relatively rapid rate of conversion of 1,3-DNB to its degradation products (Cossum and Rickert 1985). Preliminary data suggested that the formation of adducts of 1,3,5-TNB with tissue DNA and/or with blood proteins may be useful as markers for exposure to 1,3,5-TNB (Reddy et al. 1991). Further research with both 1,3-DNB and 1,3,5-TNB in the area of adduct formation could provide valuable additional information. 

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