Jessica H. Hartman

Background: Chronic ethanol use drives numerous neurological dysfunctions. Ethanol in the brain is mainly metabolized into acetaldehyde by catalase and cytochrome P450 2E1 (Cyp2e1), and acetaldehyde does not freely cross the blood–brain barrier. While Cyp2e1 is a well‐known enzyme in liver toxicology, how central nervous system (CNS)‐expressed Cyp2e1 contributes to ethanol toxicity is unknown. Methods: We investigated the effects of Cyp2e1‐driven ethanol metabolism in the brain of male and female global Cyp2e1 knockout (KO) and wild‐type (WT) 129S1/SvImJ mice. RNA‐seq was completed on the medial prefrontal cortex (mPFC), the dorsal and ventral hippocampus, and cerebellum to see whether there are baseline differences in gene expression between WT and KO mice. To investigate acute functional tolerance (AFT), we evaluated blood ethanol concentrations (BECs) of mice on a fixed‐speed rotarod after two consecutive ethanol doses. Next, we used the chronic intermittent ethanol (CIE) exposure model to study dependence‐induced escalation of drinking. After the study, catalase protein expression was analyzed in the mPFC, hippocampus, and cerebellum. Results: Transcriptomic pathway analysis in ethanol‐naïve mice revealed differences in ethanol‐important pathways in both male and female Cyp2e1‐KO mice. Glyoxylase‐1 ( Glo1 ) was downregulated in KO animals. Both WT and Cyp2e1‐KO mice had a similar AFT. However, after both injections, Cyp2e1‐KO mice had to reach a lower BEC to balance on the rotarod ( p < 0.001), indicating increased sensitivity to ethanol intoxication. In the drinking study, Cyp2e1‐KO mice drank more than WT controls during baseline drinking sessions ( p < 0.01, n = 8–9). After CIE exposure, only Cyp2e1‐KO mice significantly escalated their drinking ( p < 0.001, n = 16–17). Catalase levels were not significantly higher in KO mice in the brain regions studied regardless of condition. Conclusions: This study reveals an important role for Cyp2e1 in ethanol‐related behaviors and highlights a need to better understand the effects of ethanol and its metabolites in mediating ethanol drinking and sensitivity.

Polyploid cells contain more than two copies of each chromosome. Polyploidy has important roles in development, evolution, and tissue regeneration/repair, and can arise as a programmed polyploidization event or be triggered by stress. Cancer cells are often polyploid. C. elegans nematodes are typically diploid, but stressors such as heat shock and starvation can trigger the production of tetraploid offspring. In this study, we utilized a recently published protocol to generate stable tetraploid strains of C. elegans and compared their physiological traits and sensitivity to two DNA-damaging chemotherapeutic drugs, cisplatin and doxorubicin. As prior studies have shown, tetraploid worms are approximately 30% longer, shorter-lived, and have a smaller brood size than diploids. We investigated the reproductive defect further, determining that tetraploid worms have a shorter overall germline length, a higher rate of germ cell apoptosis, more aneuploidy in oocytes and offspring, and larger oocytes and embryos. We also found that tetraploid worms are modestly protected from growth delay from the chemotherapeutics but are similarly or more sensitive to reproductive toxicity. Transcriptomic analysis revealed differentially expressed pathways that may contribute to sensitivity to stress. This study reveals phenotypic consequences of whole-animal tetraploidy that make C. elegans an excellent model for ploidy differences.

Polyploid cells contain more than two copies of each chromosome. Polyploidy has important roles in development, evolution, and tissue regeneration/repair, and can arise as a programmed polyploidization event or be triggered by stress. Cancer cells are often polyploid. C. elegans nematodes are typically diploid, but stressors such as heat shock and starvation can trigger the production of tetraploid offspring. In this study, we utilized a recently published protocol to generate stable tetraploid strains of C. elegans and compared their physiological traits and sensitivity to two DNA-damaging chemotherapeutic drugs, cisplatin and doxorubicin. As prior studies have shown, tetraploid worms are approximately 30% longer, shorter-lived, and have a smaller brood size than diploids. We investigated the reproductive defect further, determining that tetraploid worms have a shorter overall germline length, a higher rate of germ cell apoptosis, more aneuploidy in oocytes and offspring, and larger oocytes and embryos. We also found that tetraploid worms are modestly protected from growth delay from the chemotherapeutics but are similarly or more sensitive to reproductive toxicity. Transcriptomic analysis revealed differentially expressed pathways that may contribute to sensitivity to stress. Overall, this study reveals the phenotypic consequences of whole-animal tetraploidy in C. elegans .

Cytochrome P450 2E1 (CYP2E1) is pivotal in hepatotoxicity induced by alcohol abuse and different xenobiotics. In this setting, CYP2E1 generates reactive metabolites inducing oxidative stress, mitochondrial dysfunction and cell death. In addition, this enzyme appears to play a role in the progression of obesity-related fatty liver to nonalcoholic steatohepatitis. Indeed, increased CYP2E1 activity in nonalcoholic fatty liver disease (NAFLD) is deemed to induce reactive oxygen species overproduction, which in turn triggers oxidative stress, necroinflammation and fibrosis. In 1997, Avadhani’s group reported for the first time the presence of CYP2E1 in rat liver mitochondria, and subsequent investigations by other groups confirmed that mitochondrial CYP2E1 (mtCYP2E1) could be found in different experimental models. In this review, we first recall the main features of CYP2E1 including its role in the biotransformation of endogenous and exogenous molecules, the regulation of its expression and activity and its involvement in different liver diseases. Then, we present the current knowledge on the physiological role of mtCYP2E1, its contribution to xenobiotic biotransformation as well as the mechanism and regulation of CYP2E1 targeting to mitochondria. Finally, we discuss experimental investigations suggesting that mtCYP2E1 could have a role in alcohol-associated liver disease, xenobiotic-induced hepatotoxicity and NAFLD.