Target cells for cytochrome P450-catalysed irreversible binding of 7,12-dimethylbenz[a]anthracene (DMBA) in rodent adrenal glands

Abstract

7,12-Dimethylbenz[a]anthracene (DMBA) is an adrenocorticolytic agent that causes apoplexy (haemorrhage) and massive necrosis in the adrenal cortex in rat. Several explanations regarding the origin of toxicity have been proposed. Huggins and Morii (J Exp Med 114:741-60, 1961) suggested that the cells of the inner adrenal cortex are the primary target, whereas Horváth and Kovács (Pathol Eur 8:43-59, 1973) suggested the vascular endothelium as being the origin of toxicity. In the present study, cultured precision-cut tissue slices were used to localize target cells for irreversible [(3)H]DMBA binding in rat and mouse adrenal cortex. The sites of binding were confirmed by autoradiography in vivo. Irreversible [(3)H]DMBA binding was confined to zona fasciculata/reticularis cells in rat (but not in mouse) adrenal cortex. Pronounced binding was observed in clusters of cells (focal binding), localized predominantly in zona reticularis of rat. [(3)H]DMBA binding in zona fasciculata/reticularis cells was inhibited by the cytochrome p450 1A/B (CYP1A/B) inhibitors ellipticine, alpha-naphthoflavone, and 1-ethynylpyrene. The CYP11B1-inhibitor metyrapone did not reduce [(3)H]DMBA binding. In CYP1-induced (PCB 126-treated) rats and mice, intense irreversible [(3)H]DMBA binding was found also in endothelial cells of the adrenal cortex. The endothelial binding was abolished by the CYP1 inhibitors but remained unaffected by metyrapone. We conclude that the metabolic activation in adrenal parenchymal cells is presumably catalysed by CYP1B1, whereas CYP1A1 presumably catalyses the activation in endothelial cells. We suggest that the adrenocorticolytic effect of DMBA is the result of a dual mode of action, targeting both endothelial and parenchymal cells in the rat adrenal cortex.

Organochlorines Affect the Steroid Hormone Cortisol in Free-Ranging Polar Bears (Ursus maritimus) at Svalbard, Norway

“…The results after micro-autoradiography revealed irreversible o,p-DDD-derived binding to the glucocorticoid producing interrenal cells. Steroid hydroxylases, affected by organochlorines seem to hinder the catalytic conversion of 11-deoxycortisol to cortisol (Jönsson et al, 1993;Lund, 1994;Lindhe et al, 2002aLindhe et al, , 2002b. Walsh and Stocco (2000) reported steroidogenesis inhibited by lindane, based on the reduction of the steroidogenic enzyme (StAR) expression.…”

Functional Characterization of Human Cytochrome P450 2S1 Using a Synthetic Gene-Expressed Protein inEscherichia coli

“…The K m and rate of 7,8-diol-9,10-H 2 -BaP formation were calculated based on the r7,t8,t9,c10-tetrol standard: K m , 23 Ϯ 6 M; turnover, 1.6 min Ϫ1 (Table 1). DMBA is a potent carcinogen that induces many types of cancer, adrenocorticolytic, and immunosuppression in mice and other species (Lindhe et al, 2002;Gao et al, 2005). Its toxicity and carcinogenicity depends on CYP1 family en- zymes (Nebert and Russell, 2002).…”

Effect of 7,12-Dimethylbenz(α)anthracene on the Expression of miR-330, miR-29a, miR-9-1, miR-9-3 and the mTORC1 Gene in CBA/Ca Mice

“…7,12-dimethylbenz(α) anthracene (DMBA) is a commonly occuring environmental polycyclic aromatic hydrocarbon that, acting as a mutagene, is capable of exerting a carcinogenic effect, that can be tested both in cell culture and in vivo animal models (15,16). DMBA is activated by cytochrome P450 metabolizing enzymes (17,18), and then it may participate in the early stages of carcinogenesis, i.e. in the initiation and the promotion (19).…”