NFE2L2 Knockout Cell Line (HEK 293)

Oxidative stress underlies a number of pathological conditions, including cancer, neurodegeneration, and aging. Antioxidant-rich foods help maintain cellular redox homeostasis and mitigate oxidative stress, but the underlying mechanisms are not clear. For example, sulforaphane (SFN), an electrophilic compound that is enriched in cruciferous vegetables such as broccoli, is a potent inducer of cellular antioxidant responses. NFE2L2/NRF2 (nuclear factor, erythroid 2 like 2), a transcriptional factor that controls the expression of multiple detoxifying enzymes through antioxidant response elements (AREs), is a proposed target of SFN. is a target gene of TFEB (transcription factor EB), a master regulator of autophagic and lysosomal functions, which we show here to be potently activated by SFN. SFN induces TFEB nuclear translocation via a Ca-dependent but MTOR (mechanistic target of rapamycin kinase)-independent mechanism through a moderate increase in reactive oxygen species (ROS). Activated TFEB then boosts the expression of genes required for autophagosome and lysosome biogenesis, which are known to facilitate the clearance of damaged mitochondria. Notably, TFEB activity is required for SFN-induced protection against both acute oxidant bursts and chronic oxidative stress. Hence, by simultaneously activating macroautophagy/autophagy and detoxifying pathways, natural compound SFN may trigger a self-defense cellular mechanism that can effectively mitigate oxidative stress commonly associated with many metabolic and age-related diseases. ANOVA: analyzes of variance; AREs: antioxidant response elements; Baf-A1: bafilomycin A; BHA: butylhydroxyanisole; CAT: catechin hydrate; CCCP: carbonyl cyanide m- chlorophenylhydrazone; CLEAR: coordinated lysosomal expression and regulation; DCFH-DA: 2',7'-dichlorofluorescin diacetate; FBS: fetal bovine serum; GFP: green fluorescent protein; HMOX1/HO-1: heme oxygenase 1; KD: knockdown; KEAP1: kelch like ECH associated protein 1; KO: knockout; LAMP1: lysosomal associated membrane protein 1; MCOLN1/TRPML1: mucolipin 1; ML-SA1: mucolipin-specific synthetic agonist 1; ML-SI3: mucolipin-specific synthetic inhibitor 3; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NFE2L2/NRF2: nuclear factor: erythroid 2 like 2; NPC: Niemann-Pick type C; PBS: phosphate-buffered saline; PPP2/PP2A: protein phosphatase 2; Q-PCR: real time polymerase chain reaction; ROS: reactive oxygen species; RPS6KB1/S6K1/p70S6K: ribosomal protein S6 kinase B1; SFN: sulforaphane; TFEB: transcription factor EB; WT, wild-type.

Activation of nuclear-factor-E2-related factor 2 (Nrf2) signaling can protect human osteoblasts from dexamethasone-induced oxidative injury. DDB1 and CUL4 associated factor 1 (DCAF1) is a novel ubiquitin E3 ligase for Nrf2 protein degradation. We identified a novel DCAF1-targeting miRNA, miR-3175. RNA pull-down, Argonaute 2 RNA-immunoprecipitation, and RNA fluorescent in situ hybridization results confirmed a direct binding between miR-3175 and DCAF1 mRNA in primary human osteoblasts. DCAF1 3'-untranslated region luciferase activity and its expression were significantly decreased after miR-3175 overexpression but were augmented with miR-3175 inhibition in human osteoblasts and hFOB1.19 osteoblastic cells. miR-3175 overexpression activated Nrf2 signaling, causing Nrf2 protein stabilization, antioxidant response (ARE) activity increase, and transcription activation of Nrf2-dependent genes in human osteoblasts and hFOB1.19 cells. Furthermore, dexamethasone-induced oxidative injury and apoptosis were largely attenuated by miR-3175 overexpression in human osteoblasts and hFOB1.19 cells. Importantly, shRNA-induced silencing or CRISPR/Cas9-mediated Nrf2 knockout abolished miR-3175 overexpression-induced osteoblast cytoprotection against dexamethasone. Conversely, DFAC1 knockout, by the CRISPR/Cas9 method, activated the Nrf2 cascade and inhibited dexamethasone-induced cytotoxicity in hFOB1.19 cells. Importantly, miR-3175 expression was decreased in necrotic femoral head tissues of dexamethasone-taking patients, where DCAF1 mRNA was upregulated. Together, silencing DCAF1 by miR-3175 activated Nrf2 signaling to inhibit dexamethasone-induced oxidative injury and apoptosis in human osteoblasts.

Uropathogenic Escherichia coli (UPEC) cause urinary tract infections (UTIs) by invading urothelial cells. In response, the host mounts an inflammatory response to expel bacteria. Here, we show that the NF-E2-related factor 2 (NRF2) pathway is activated in response to UPEC-triggered reactive oxygen species (ROS) production. We demonstrate the molecular sequence of events wherein NRF2 activation in urothelial cells reduces ROS production, inflammation, and cell death, promotes UPEC expulsion, and reduces the bacterial load. In contrast, loss of NRF2 leads to increased ROS production, bacterial burden, and inflammation, both in vitro and in vivo. NRF2 promotes UPEC expulsion by regulating transcription of the RAB-GTPase RAB27B. Finally, dimethyl fumarate, a US Food and Administration-approved NRF2 inducer, reduces the inflammatory response, increases RAB27B expression, and lowers bacterial burden in urothelial cells and in a mouse UTI model. Our findings elucidate mechanisms underlying the host response to UPEC and provide a potential strategy to combat UTIs.

Chronic endoplasmic reticulum (ER) stress in hepatocytes plays a role in the pathogenesis of nonalcoholic fatty liver disease. Therefore, given the association between oxidative stress, mitochondrial dysfunction, and ER stress, our study investigated the role of NRF2-mediated SIRT3 activation in ER stress. SIRT3, a sirtuin, was predicted as the target of NRF2 based on bioinformatic analyses and animal experiments. Nrf2 abrogation diminished mitochondrial DNA content in hepatocytes with Ppargc1α and Cpt1a inhibition, whereas its overexpression enhanced oxygen consumption. Further, chromatin immunoprecipitation and luciferase reporter assays indicated that NRF2 induced SIRT3 through the antioxidant responsive element (ARE) sites comprising the -641 to -631 bp and -419 to -409 bp regions. In tunicamycin-induced ER stress conditions and liver injury animal models following ER stress, NRF2 levels were highly correlated with SIRT3. Nrf2 deficiency enhanced the tunicamycin-mediated induction of CHOP, which was attenuated by Sirt3 overexpression. Further, Sirt3 delivery to hepatocytes in Nrf2 knockout mice prevented tunicamycin from increasing mortality by decreasing ER stress. SIRT3 was upregulated in livers of patients with nonalcoholic liver diseases, whereas lower SIRT3 expression coincided with more severe disease conditions. Taken together, our findings indicated that NRF2-mediated SIRT3 induction protects hepatocytes from ER stress-induced injury, which may contribute to the inhibition of liver disease progression.