Covalent Protein Modification: An Unignorable Factor for Bisphenol A-Induced Hepatotoxicity

Abstract

Covalent modification of proteins by reactive pollutants/metabolites might trigger various toxicities resulting from the disruption of protein structures and/or functions, which is critical for understanding the mechanism of pollutants-induced toxicity. However, this mechanism has rarely been touched on due to the lack of a methodology. In this research, the protein modification of bisphenol A (BPA) in rats was characterized using a series of liquid chromatography–tandem mass spectrometry (LC–MS) approaches. BPA-modified cysteine (Cys1) was first released from proteins via enzymatic hydrolysis and identified using LC–MS. Moreover, the positive correlation between Cys1 and hepatotoxicity indicated the involvement of protein modification in BPA toxicity. Then, in vitro incubation of BPA with amino acids and protein confirmed that BPA could specifically modify cysteine residues of proteins after bioactivation and provided four additional modification patterns. Finally, 24 BPA-modified proteins were identified from the liver of BPA-exposed rats using proteomic analysis, and they were mainly enriched in oxidative stress-related pathways. The modification on superoxide dismutases, catalase, and glutathione S-transferases disrupted their enzymatic functions, leading to oxidative damage. These results revealed that the covalent protein modification is an unignorable factor for BPA hepatotoxicity. Moreover, the workflow can be applied to identify protein adducts of other emerging contaminants and possible risk.

Application of the Key Characteristics of Carcinogens to Bisphenol A

“…45,46,[56][57][58] BPA can also bind to cysteine residues of proteins and forms protein adducts in the rat in vivo and in a cell-free system. 59 Overall, the evidence for KC1 is consistent across species in vivo and in vitro. In spite of a fairly small data set, the data for KC1 were considered strong during the Committee discussion.…”

Formation and metabolism of 6-(1-acetol)-8-(1-acetol)-rutin in foods and in vivo, and their cytotoxicity

“…Among them, LC-MS/MS analysis was the most promised with much better specificity, less limitation and wider application range ( 38 , 39 ). MRM mode of HPLC-MS/MS analysis has shown advantages for the identification and determination of exogenous substances and their metabolites in complex biological samples especially when the compounds were at extremely low-abundance levels ( 39 , 40 ), and therefore, was applied herein to measure the concentration levels of rutin–MGO adducts in plasma and organs to reveal the formation, metabolism and distribution of adducts in vivo . As shown in Table 3 , 9.40 and 6.40 μg/L of adducts A and B, respectively, were detected in the plasma 15 min after the administration of rutin.…”

Ligand Modification-Free Methods for the Profiling of Protein-Environmental Chemical Interactions

“…30 In such cases, by identifying the covalent chemical modifications of chemicals across the proteome enables systematic target protein determination and thus helps get a better understanding of pollutant-induced toxicities. 31,32 In a recent report, bisphenol A (BPA) was found to specifically modify cysteine residues of proteins and 24 BPA-modified proteins were identified in rat liver to exert oxidative damage. 31 In addition, metal complexes that harbor platinum(II), 33 arsenic, 34 or gold 35 have been reported to covalently interact with target proteins.…”

“…31,32 In a recent report, bisphenol A (BPA) was found to specifically modify cysteine residues of proteins and 24 BPA-modified proteins were identified in rat liver to exert oxidative damage. 31 In addition, metal complexes that harbor platinum(II), 33 arsenic, 34 or gold 35 have been reported to covalently interact with target proteins.…”

“…For example, fluorotelomer unsaturated aldehydes were found to have covalent interactions with proteins in rat liver microsomes and bovine blood plasma, in which, the levels of covalent modification ranged from 20.1 (±2.8)% to 71.3 (±19.5)% and 24.0 (±1.5)% to 82.5 (±14.0)%, respectively . In such cases, by identifying the covalent chemical modifications of chemicals across the proteome enables systematic target protein determination and thus helps get a better understanding of pollutant-induced toxicities. , In a recent report, bisphenol A (BPA) was found to specifically modify cysteine residues of proteins and 24 BPA-modified proteins were identified in rat liver to exert oxidative damage . In addition, metal complexes that harbor platinum­(II), arsenic, or gold have been reported to covalently interact with target proteins.…”