NF-κB-mediated regulation of rat CYP2E1 by two independent signaling pathways

Abstract

Cytochrome P450 2E1 (CYP2E1) plays an important role in both alcohol-induced and immune-mediated liver injury. However, the mechanism underlying CYP2E1 transcriptional regulation has not been clarified. This study focused on the NF-κB-mediated transcriptional regulation of rat CYP2E1 by two independent signaling pathways in alcohol-induced and immune-mediated liver injury rat models. Male Sprague-Dawley rats were used in pharmacokinetic, molecular pharmacology, and morphology experiments. A rat model of alcohol-induced liver injury (AL) was established by feeding an ethanol-containing diet (42 g/kg/day) for 5 weeks as indicated. A rat immune-mediated liver injury (IM) model was established by the sequential injection of bacillus Calmette-Guérin (BCG, 125 mg/kg, once) via the tail vein after test day 21 and 10 μg/kg LPS 13 days later. HPLC, real-time PCR, western blot and ELISA analyses were performed. CYP2E1 expression was enhanced during the process of alcohol-induced liver injury (increased by 56%, P < 0.05) and significantly reduced during that of immune-mediated liver injury (reducedby52%, P < 0.05). NF-κB was activated in both the AL and IM groups (increased by 56% and76%, respectively, P < 0.05). Compared to those in the livers of AL model rats, the interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and iNOS levels in IM model rat livers were increased (increased by 26%, 21% and 101%, respectively, P < 0.05). The differential changes in CYP2E1 in the processes of alcohol-induced and immune-mediated liver injury may result from the differential expression of inflammatory cytokines and iNOS after NF-κB activation, leading to the NF-κB-mediated transcriptional regulation of rat CYP2E1 by two independent signaling pathways.

Involvement of NF-κB in the reversal of CYP3A down-regulation induced by sea buckthorn in BCG-induced rats

“…Our study as well as those of others [9] found that during BCG-induced immune liver injury, a large number of inflammatory cells infiltrated the liver, while Kupffer cells released high levels of IL-1β and TNF-α, and activated NF-κB. Immunological liver injury is an immune response [4,5,11]. Liver cells become damaged during immune-induced clearance of viruses, which serves as an integral component in the pathogenesis of viral hepatitis, cirrhosis and hepatocellular carcinoma [33,34].…”

“…Hence, activated NF-κB regulates various downstream inflammatory cytokines, oxidative enzymes, and iNOS, and affects liver injury [ 13 – 15 ]. Our previous work confirmed the activation of NF-κB during BCG-induced immune liver injury and its regulation of CYP2E1 [ 4 , 5 ]. It is, therefore, highly plausible that NF-κB may regulate CYP3A in this process.…”

“…We also found that during BCG-induced immune liver injury, a large amount of iNOS is induced which catalyzes the production of large amounts of NO, generates nitrifying stress [ 4 ], and activates NF-κB since NF-κB is more sensitive to inflammatory reactions and oxidative nitrification [ 5 ]. Importantly, an NF-κB activation site is located between the CYP3A promoter nucleotide sequences 2326 and 2297, and hence, NF-κB inhibits the transcription of CYP3A [ 38 , 39 ].…”

“…This kind of immune liver injury is primarily caused by specific antiviral T cell-mediated cellular immunity [3]. Specifically, a large number of monocytes and lymphocytes infiltrate the parenchymal cells of the liver where Kupffer cells release many inflammatory cytokines, thereby inducing liver inflammation and leading to disrupted liver functions including dysfunction of drug metabolism [4,5].…”

“…Cytochrome P450 3A (CYP3A) is a predominant human liver monooxygenase responsible for metabolizing more than half of the drugs in use today [8]. Inflammatory stimuli and viral infections downregulate hepatic cytochrome P450 protein, which increases exposure to parent drugs by reducing their clearance and/or enhancing their bioavailability [5,9]. As a result, the incidence of adverse reactions increases and drug treatment efficacy decreases.…”