N-nitrosodiethylamine genotoxicity evaluation: a cytochrome P450 induction study in rat hepatocytes

Abstract

ABSTRACT. In rats, N-nitrosodiethylamine (NDEA) induces tumors mainly in the liver. This could be because various enzymes are responsible for the metabolic activation of NDEA, besides the hepatic NDEA metabolizing enzyme, CYP2E1. We examined NDEA genotoxicity and cytotoxicity in primary cultures of female rat hepatocytes; we also looked at how it affected CYP mRNA expression. Single incubation with 0.9% NaCl resulted in a mean of 0.2% apoptotic cells, which doubled with 105 µg NDEA/mL. The frequency of necrosis with NDEA treatment was also doubled. Besides the cytotoxic effects, there was also a 4-fold decrease in mitotic index and a 3-fold decrease in the percentage of cells with micronuclei. A significant increase in micronucleus cells when hepatocytes were incubated with 2.1 µg NDEA/mL suggests that DNA repair was inactive. The chromosomal aberration evaluation revealed a discrete dose-response curve. Treatment with NDEA 2341 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 10 (4): 2340-2348 (2011) N-nitrosodiethylamine and cytochrome P450 induction induced increases in CYP mRNA: CYP2B2 (1.8 times) and CYP2E1 (1.6 times) with non-cytotoxic NDEA concentrations (0.21-21 µg/mL). CYP2B1 mRNA levels decreased at 0.21 µg NDEA/mL (2.5-fold), while CYP4A3 mRNA decreased 1.3-fold. NDEA treatment at 2.1 µg/ mL induced a 1.9-fold increase in CYP3A1 mRNA. Understanding the cumulative effects in target cells during precarcinogenesis is crucial to understanding the mode of action of potential carcinogens and in order to develop comprehensive chemical toxicity profiles.

Garlic Oil Attenuated Nitrosodiethylamine-Induced Hepatocarcinogenesis by Modulating the Metabolic Activation and Detoxification Enzymes

“…In the current study, NDEA treatment was found to dramatically reduce the activities, mRNA and protein levels of CYP2E1 and CYP1A2. In a recently published in vitro study, the CYP2E1 mRNA levels were decreased when rat hepatocytes were treated with non-cytotoxic concentrations of NDEA (0.21-21 μg/ml), while decreased mRNA levels of CYP2E1 was observed when hepatocytes were treated with higher dose of NDEA (100 μg/ml) 36. Therefore, it may be speculated that low dose of NDEA might induce the expression of CYP2E1, while high dose of NDEA could inhibit expression of CYP2E1.…”

Development of a Medium-term Animal Model Using <i>gpt</i> Delta Rats to Evaluate Chemical Carcinogenicity and Genotoxicity

“…In this model, DEN was selected because correlations between the administration of DEN and the induction of GST-P foci in the rat liver have been extensively reported 23 , 24 , 25 , 26 . However, the dose of DEN should be as low as possible to avoid any effects on the metabolism of the test chemical because DEN has been shown to influence various parameters, including the induction of cytochrome P450 (CYP) and glutathione S-transferase 27 , 28 . We took advantage of the rapid induction of cell proliferation following PH because genotoxic compounds can effectively induce gene mutations under conditions of high cell proliferation 4 .…”

Carcinogenesis: Failure of resolution of inflammation?

“…Also, N-nitroso compounds such as NDMA activate ras oncogenes, which play a pro-tumorigenic role in the development of various cancers (e.g., colon) ( Tricker & Preussmann, 1991 ). DNA damage induced by NDEA increases micronuclei due to DNA breakage that could not be repaired, leading to an increase in chromosomal aberrations, and apoptotic cell death which can lead to cancer ( Aiub et al, 2011 ; Fishbein et al, 2020 ). Thus, carcinogens can initiate tumor growth via genotoxic mechanisms in synergy with nongenotoxic processes including cell death, inflammation, oxidative stress, angiogenesis and tissue injury.…”