Mechanisms involved in the death of steatotic WIF-B9 hepatocytes co-exposed to benzo[a]pyrene and ethanol: a possible key role for xenobiotic metabolism and nitric oxide

Abstract

We previously demonstrated that co-exposing pre-steatotic hepatocytes to benzo[a]pyrene (B[a]P), a carcinogenic environmental pollutant, and ethanol, favored cell death. Here, the intracellular mechanisms underlying this toxicity were studied. Steatotic WIF-B9 hepatocytes, obtained by a 48hsupplementation with fatty acids, were then exposed to B[a]P/ethanol (10 nM/5 mM, respectively) for 5 days. Nitric oxide (NO) was demonstrated to be a pivotal player in the cell death caused by the coexposure in steatotic hepatocytes. Indeed, by scavenging NO, CPTIO treatment of co-exposed steatotic cells prevented not only the increase in DNA damage and cell death, but also the decrease in the activity of CYP1, major cytochrome P450s of B[a]P metabolism. This would then lead to an elevation of B[a]P levels, thus possibly suggesting a long-lasting stimulation of the transcription factor AhR. Besides, as NO can react with superoxide anion to produce peroxynitrite, a highly oxidative compound, the use of FeTPPS to inhibit its formation indicated its participation in DNA damage and 1 equal supervision 2 cell death, further highlighting the important role of NO. Finally, a possible key role for AhR was pointed out by using its antagonist, CH-223191. Indeed it prevented the elevation of ADH activity, known to participate to the ethanol production of ROS, notably superoxide anion. The transcription factor, NFB, known to be activated by ROS, was shown to be involved in the increase in iNOS expression. Altogether, these data strongly suggested cooperative mechanistic interactions between B[a]P via AhR and ethanol via ROS production, to favor cell death in the context of prior steatosis.

Quercetin and Isorhamnetin Attenuate Benzo[a]pyrene-Induced Toxicity by Modulating Detoxification Enzymes through the AhR and NRF2 Signaling Pathways

“…Xenobiotic detoxification metabolism consists of three phases. The phase I enzymes such as cytochrome P450 family 1 subfamily A member 1 (CYP1A1) and cytochrome P450 family 1 subfamily B member 1 (CYP1B1) introduce oxygen molecules to xenobiotic compounds [ 10 ]. The converted compounds are then conjugated to glutathione (GSH), sulfate, or glucuronic acid by phase II enzymes such as glutathione S-transferase alpha 1 (GSTA1) and glutathione S-transferase pi 1 (GSTP1).…”

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

“…Finally, recent investigations of different experimental models of MAFLD suggested that benzo[a]pyrene exposure might even further aggravate the progression of steatosis to steatohepatitis induced by ethanol [176,[213][214][215]. Potential mechanisms involved in such progression include overproduction of ROS and nitric oxide [176,214], mitochondrial dysfunction [176], increased expression of proinflammatory cytokines [213] and plasma membrane remodeling [215].…”

Extracellular vesicles released by polycyclic aromatic hydrocarbons-treated hepatocytes trigger oxidative stress in recipient hepatocytes by delivering iron

“…For instance, benzo(a)pyrene (BP) can promote ROS production in liver cells both in vitro [24,25] and in vivo [26], leading to oxidative damages such as lipid peroxidation in cultured liver cells [27,28] or in mice liver [29], as well as DNA oxidation in hepatocytes [30] or in rat liver [31]. Those oxidative damages were demonstrated to be responsible for cell death in liver [27,28,32,33]. Pyrene (PYR) can also trigger ROS production in hepatocytes along with a decrease in the expression of antioxidant enzymes, thus leading to a loss of viability [34].…”

“…Oxidative stress measurement in hepatocytes ROS production. Intracellular ROS production was evaluated using dihydroethidium (DHE), as previously described[33]. Briefly, after treatment by hepatocyte-derived EVs, recipient cells were incubated with 25 μM DHE for 1 h at 37°C.…”