4-Amino-2-chlorophenol: Comparative in vitro nephrotoxicity and mechanisms of bioactivation

Abstract

Chlorinated anilines are nephrotoxicants both in vivo and in vitro. The mechanism of chloroaniline nephrotoxicity may occur via more than one mechanism, but aminochlorophenol metabolites appear to contribute to the adverse in vivo effects. The purpose of this study was to compare the nephrotoxic potential of 4-aminophenol (4-AP), 4-amino-2-chlorophenol (4-A2CP), 4-amino-3-chlorophenol (4-A3CP) and 4-amino-2,6-dichlorophenol (4-A2,6DCP) using isolated renal cortical cells (IRCC) from male Fischer 344 rats as the model and to explore renal bioactivation mechanisms for 4-A2CP. For these studies, IRCC (~4×106 cells/ml) were incubated with an aminophenol (0.5 or 1.0 mM) or vehicle for 60 min at 37° C with shaking. In some experiments, cells were pretreated with an antioxidant or cytochrome P450 (CYP), flavin monooxygenase (FMO), peroxidase or cyclooxygenase inhibitor prior to 4-A2CP (1.0 mM). Lactate dehydrogenase (LDH) release served as a measure of cytotoxicity. The order of decreasing nephrotoxic potential in IRCC was 4-A2,6-DCP > 4-A2CP > 4-AP > 4-A3CP. The cytotoxicity induced by 4-A2CP was reduced by pretreatment with the peroxidase inhibitor mercaptosuccinic acid, and some antioxidants (ascorbate, glutathione, N-acetyl-L-cysteine) but not by others (α-tocopherol, DPPD). In addition, pretreatment with the iron chelator deferoxamine, several CYP inhibitors (except for the general CYP inhibitor piperonyl butoxide), FMO inhibitors or indomethacin (a cyclooxygenase inhibitor) failed to attenuate 4-A2CP cytotoxicity. These results demonstrate that the number and ring position of chloro groups can influence the nephrotoxic potential of 4-aminochlorophenols. In addition, 4-A2CP may be bioactivated by cyclooxygenase and peroxidases, and free radicals appear to play a role in 4-A2CP cytotoxicity.

Nephrotoxic Potential of Putative 3,5-Dichloroaniline (3,5-DCA) Metabolites and Biotransformation of 3,5-DCA in Isolated Kidney Cells from Fischer 344 Rats

“…3,5-DCPHA proved to be the most toxic metabolite tested, and it is likely that 3,5-DCPHA is a major contributor to 3,5-DCA nephrotoxicity, directly to kidney cells and/or indirectly via hematotoxicity. It is also likely that multiple enzyme systems are capable of forming 3,5-DCPHA from 3,5-DCA, and these enzyme systems may also be forming other 3,5-DCA nephrotoxic metabolites [ 46 , 47 ]. N-Oxidation of aniline compounds has been shown to be catalyzed by CYPs, flavin monooxygenases (FMOs), peroxidases and prostaglandin synthetase [ 48 , 49 , 50 , 51 ].…”

Voltammetric behavior of HeLa cells on a carbon nanotube/ionic liquid modified electrode for cytotoxicity evaluation of chlorophenols

“…In recent years, the in vitro toxicity testing technique has been approved as an alternative to the whole-animal test. [4][5][6] Some assays including neutral red assay, methyl tetrazolium (MTT) assay, lactate dehydrogenase leakage assay and deoxyribonucleic acid fragmentation assay have been used in the cytotoxicity evaluation of CPs. [7][8][9] However, these marking methods have several disadvantages, such as the complexity of operation, high cost, and time-consumption.…”