Project description:The rate-limiting step in glutathione (GSH) synthesis is controlled by glutamate-cysteine ligase catalytic subunit. GSH is reported to buffer oxidative stress. In the absence of GSH, the antioxidant transcription factor Nrf2 is reported to be stabilized. The liver has the highest levels of GSH, but its impact on liver homeostasis is unclear. To investigate this, we induced a liver-specific deletion of Gclc (Gclc f/f), Nrf2 (Nrf2 f/f), or Gclc-Nrf2 (Gclc f/f Nrf2 f/f) by injecting my via tail-vein with AAV-TBG-Cre, which induces recombination specifically in hepatocytes.
Project description:The rate-limiting step in glutathione (GSH) synthesis is controlled by glutamate-cysteine ligase catalytic subunit. To investigate the impact of GSH in vivo, we induced a deletion of Gclc using a Gclcf/f Rosa26-CreERT2 mouse model and harvested liver tissue for analysis.
Project description:Addition of liver-specific Keap1 deletion to mice harboring mutant K-ras and p53 accelerated cholangiocarcinoma formation, with hallmarks of Nrf2 activation.
Project description:Background: NRF2 is an essential cytoprotective transcription factor inducing antioxidant response element (ARE)-bearing genes. However, association of NRF2 with lung development has not been examined. Human lungs are not fully developed until 2-3 years of and they are fully matured at about 8 years. Murine lungs at birth are immature (at saccular stage of lung development) and have been used to study developmental lung disorders. Methods: To investigate (1) the transcriptome changes during lung development and (2) the role of NRF2 in lung development and maturation in mice, lungs were harvested from Nrf2-deficient (Nrf2-/-) and wild-type (Nrf2+/+) mouse embryos, neonates and adults. Microarray and pathway analysis determined NRF2-directed mechanisms underlying lung development and maturation. Results: Nrf2 mRNA expression was peack at embryonic days E17.5-E18.5 (immediately before birth) probably to increase antioxidant apparatus to prepare against high O2 environment after birth. The pseudoglandular phase lungs (E13-E15) are undergoing vigorous cell proliferation under the control of high-fidelity DNA damage repair system. Fetal lungs (E13.5-E17.5) are lack in immune system, xenobiotic metabolism, and tissue damage genes. After birth at postnatal day 1 (PND1), lung cell division is quiescent but transporters and lipid metabolism are activated. When lung enters alveolar phase (PND4), cell proliferation is resumed. Mature lungs (PND14-P42) have heightened networks of host defense systems (immunity, antioxidants) and cellular injury and abnormality (e.g., glucose metabolism disorder). Nrf2 deletion in fetal lung (E13.5-E17.5) altered developmental, immunity, and metabolism genes, and it may have affected lung branching. Nrf2 deletion affected lung transcriptome changes the most at E17.5 when Nrf2 message level is maximum (E17.5-E18.5). Nrf2 deletion in newborn lung (PND0) decreased cell cycle progress and DNA damage repair. Nrf2 deletion in neonatal lung (PND1-4) enhanced tissue injury/cell death and inhibited developmental cell differentiation. Nrf2 deletion in matured mouse lung (PND42) affected not only antioxidant pathway but also immune responses and connective tissue cell migrations. Conclusion: Overall, NRF2 plays multiple roles in underdeveloped lungs and associated with lung morphogenesis, immunity, cell cycle progress, tissue differentiation and metabolism as well as cellular defense. Results provide putative molecular mechanisms of NRF2-directed lung morphogenesis and maturation.
Project description:To identify Nrf1-dependent and Nrf2-dependent genes in the liver, we examined the gene expression profiles of Nrf1 Alb-CKO, Nrf2 knockout and Keap1 knockdown mouse livers by microarray analyses. Total RNAs from Nrf1dN/-::Alb-Cre, Nrf1dN/+, Nrf2-/-, Nrf2+/+, Keap1KD/- and Keap1KD/+ mouse livers were used for the microarray analyses.
Project description:Background & Aims: Inflammation in chronic liver diseases induces oxidative stress and thus may contribute to progression of liver injury, fibrosis, and carcinogenesis. The KEAP1/NRF2 axis is a major regulator of cellular redox balance. In the present study, we investigated whether the KEAP1/NRF2 system is involved in liver disease progression in human and mice. Methods: The clinical relevance of oxidative stress was investigated in a well-characterized cohort of NAFLD patients (n=63) by liver RNA sequencing and correlated with histological and clinical parameters. For functional analysis hepatocyte-specific NEMO knock-out (NEMO∆hepa) mice were crossed with hepatocyte-specific KEAP1 knock-out (KEAP1∆hepa) mice. Results: Immunohistochemical analysis of human liver sections showed increased oxidative stress and high NRF2 expression in patients with chronic liver disease. RNA sequencing of liver samples in a human pediatric NAFLD cohort revealed a significant increase of NRF2 activation correlating with the grade of inflammation, but not with the grade of steatosis, which could be confirmed in a second adult NASH cohort. In mice, microarray analysis revealed that KEAP1 deletion induces NRF2 target genes involved in glutathione metabolism and xenobiotic stress (e.g., Nqo1). Furthermore, deficiency of one of the most important antioxidants, glutathione (GSH), in NEMO∆hepa livers was rescued after deleting KEAP1. As a consequence, NEMO∆hepa/KEAP1∆hepa livers showed reduced apoptosis compared to NEMO∆hepa livers as well as a dramatic downregulation of genes involved in cell cycle regulation and DNA replication. Consequently, NEMO∆hepa/KEAP1∆hepa compared to NEMOΔhepa livers displayed decreased fibrogenesis, lower tumor incidence, reduced tumor number, and decreased tumor size. Conclusions: NRF2 activation in NASH patients correlates with the grade of inflammation, but not steatosis. Functional analysis in mice demonstrated that NRF2 activation in chronic liver disease is protective by ameliorating fibrogenesis, initiation and progression of hepatocellular carcinogenesis.
Project description:The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates an array of cytoprotective genes, yet studies in transgenic mice have led to conflicting reports on its role in liver regeneration. We aimed to test the hypothesis that pharmacological activation of Nrf2 would enhance liver regeneration. Wild type (WT) and Nrf2 null mice were administered bardoxolone methyl (CDDO-Me), a potent activator of Nrf2 that has entered clinical development, and then subjected to partial hepatectomy (PHx). CDDO-Me enhanced the rate of restoration of liver volume and improved liver function (multispectral optoacoustic imaging in wild type, but not Nrf2 null, mice following two-thirds partial hepatectomy. These effects were associated with an increase in hepatocyte hypertrophy and proliferation, the suppression of immune and inflammatory signals, and metabolic remodeling in the remnant liver tissue.
Project description:Nrf2 antioxidant signaling is involved in liver protection, but this generalization overlooks conflicting studies indicating that Nrf2 effects are not necessarily hepatoprotective. The role of Nrf2/HO-1 in cholestatic liver injury (CLI) remains poorly defined. Here, we report that Nrf2/HO-1 activation exacerbates liver injury rather than exerts a protective effect in CLI. Inhibiting HO-1 or ameliorating bilirubin transport alleviates liver injury in CLI models. Nrf2 knockout confers hepatoprotection in CLI mice, whereas in non-CLI mice, Nrf2 knockout aggravates liver damage. In the CLI setting, oxidative stress activates Nrf2/HO-1, leads to bilirubin accumulation, and impairs mitochondrial function. High levels of bilirubin reciprocally upregulate the activation of Nrf2 and HO-1, while antioxidant and mitochondria-targeted SOD2 overexpression attenuate the toxicity of bilirubin. Additionally, the expression of Nrf2 and HO-1 is significantly elevated in serum of patients with CLI. These results reveal an unrecognized function of Nrf2 signaling in exacerbating liver injury in cholestatic disease.