Unraveling the NRF2 confusion: Distinguishing nuclear respiratory factor 2 from nuclear erythroid factor 2.

In recent years, the acronym NRF2 has garnered significant attention in scientific discourse. However, this attention has occasionally led to confusion due to the existence of two distinct proteins sharing the same acronym: Nuclear Respiratory Factor 2 (NRF2), also known as GA-binding protein transcription factor subunit alpha (GABPA), and Nuclear Factor Erythroid 2-related Factor 2 (NFE2L2 or NRF2). This confusion has been highlighted in various scientific forums, including PubPeer and anonymous reader comments, where the confusion between the two proteins has been expressed. In this article, we aim to elucidate the disparities between these two proteins. Both are transcription factors that play pivotal roles in cellular homeostasis and response to stress, with some overlapping functional aspects. Nuclear Factor Erythroid 2-related Factor 2 (NFE2L2) is a key regulator of the antioxidant response element (ARE) pathway. It functions by binding to antioxidant response elements in the promoters of target genes, thereby orchestrating the expression of various cytoprotective enzymes and proteins involved in detoxification, redox balance, and cellular defense against oxidative stress. Conversely, Nuclear Respiratory Factor 2 (GABPA) is primarily associated with the regulation of mitochondrial biogenesis, in relation to PGC1α, and maintaining cellular energy metabolism. It is important to recognize and differentiate between these two proteins to avoid misconceptions and misinterpretations in scientific literature and discussions. Our laboratories (Arubala P Reddy and P. Hemachandra Reddy) focued on Nuclear Respiratory Factor 2 (NRF2), but not on Nuclear Factor Erythroid 2-related Factor 2 (NFE2L2). We hope that the facts, figures, and discussions presented in this article will clarify the current controversy regarding the sizes, structural features, and functional aspects of these proteins.

Novel Keap1-Nrf2 Protein-Protein Interaction Inhibitor UBE-1099 Ameliorates Progressive Phenotype in Alport Syndrome Mouse Model.

Background: Bardoxolone methyl activates nuclear factor erythroid 2-related factor 2 (Nrf2) via covalent binding and irreversible inhibition of Kelch-like ECH-associated protein 1 (Keap1), the negative regulator of Nrf2. Ongoing clinical trials of bardoxolone methyl show promising effects for patients with CKD. However, the direct inhibition of Keap1-Nrf2 protein-protein interaction (PPI) as an approach to activate Nrf2 is less explored. Methods: We developed a noncovalent Nrf2 activator UBE-1099, which highly selectively inhibits Keap1-Nrf2 PPI, and evaluated its efficacy on the progressive phenotype in an Alport syndrome mouse model (Col4a5-G5X). Results: Similar to bardoxolone methyl, UBE-1099 transiently increased proteinuria and reduced plasma creatinine in Alport mice. Importantly, UBE-1099 improved the glomerulosclerosis, renal inflammation, and fibrosis, and prolonged the life span of Alport mice. UBE-1099 ameliorated the dysfunction of Nrf2 signaling in the renal tissue of Alport mice. Moreover, transcriptome analysis in the glomerulus showed that UBE-1099 induced the expression of genes associated with the cell cycle and cytoskeleton, which may explain its unique mechanism of improvement such as glomerular morphologic change. Conclusions: UBE-1099 significantly ameliorates the progressive phenotype in Alport mice. Our results revealed the efficacy of Keap1-Nrf2 PPI inhibitor for glomerulosclerosis and present a potential therapeutic drug for CKD.

Lysine-Specific Demethylase 1 Affects the Progression of Papillary Thyroid Carcinoma via HIF1α and microRNA-146a.

CONTEXT: Lysine-specific demethylase 1 (LSD1) stabilizes hypoxia-inducible factor 1α (HIF1α) to advance tumor progression, while HIF1α functions as a transcription factor to increase the expression of microRNA-146a (miR-146a). OBJECTIVE: We aim to investigate whether LSD1 affects the development of papillary thyroid carcinoma (PTC) via HIF1α and miR-146a. DESIGN: In vitro assays were performed with Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines. In vivo assays were conducted with established xenograft tumors in nude mice. SETTING: This study was conducted at our lab. PATIENTS AND MATERIALS: PTC tissues and corresponding adjacent normal tissues were obtained from 45 patients hospitalized in Sun Yat-Sen Memorial Hospital. Assays were conducted using Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines, as well as 50 male BALB/c nude mice. INTERVENTION: Cells were transfected with sh-LSD1, sh-GABPA, oe-LSD1, oe-HIF1α, miR-146a mimic, and miR-146a inhibitor. In addition, K1 cells expressing lv-oe-LSD1, lv-miR-146a inhibitor, lv-oe-LSD1 or miR-146a inhibitor were injected into the right side of the mice. LSD1 gene and protein expression patterns were analyzed in 45 clinical PTC tissue samples. MAIN OUTCOME MEASURE: Expression of LSD1, HIF1α, miR-146a, and GA-binding protein transcription factor alpha (GABPA), as well as their effects on PTC. RESULTS: LSD1 was highly expressed in clinical PTC tissues. LSD1 stabilized HIF1α and inhibited the degradation of its ubiquitin proteasome. HIF1α was enriched in the promoter region of miR-146a, an upregulated miRNA in PTC. HIF1α increased miR-146a expression to promote PTC progression in vitro, which was achieved by inhibiting GABPA, a target gene of miR-146a. LSD1 upregulated miR-146a to enhance the development and metastasis of PTC in nude mice. CONCLUSION: Our results show that LSD1 functions as an oncogene in PTC by upregulating HIF1α and miR-146a, elucidating an understanding of undefined mechanisms associated with tumor progression in PTC.

Emerging role of microRNAs in lipid metabolism.

microRNAs (miRNAs or miRs) are small non-coding RNAs that are involved in post-transcriptional regulation of their target genes in a sequence-specific manner. Emerging evidence demonstrates that miRNAs are critical regulators of lipid synthesis, fatty acid oxidation and lipoprotein formation and secretion. Dysregulation of miRNAs disrupts gene regulatory network, leading to metabolic syndrome and its related diseases. In this review, we introduced epigenetic and transcriptional regulation of miRNAs expression. We emphasized on several representative miRNAs that are functionally involved into lipid metabolism, including miR-33/33(⁎), miR122, miR27a/b, miR378/378(⁎), miR-34a and miR-21. Understanding the function of miRNAs in lipid homeostasis may provide potential therapeutic strategies for fatty liver disease.

Sevoflurane post-conditioning increases nuclear factor erythroid 2-related factor and haemoxygenase-1 expression via protein kinase C pathway in a rat model of transient global cerebral ischaemia.

BACKGROUND: The antioxidant mechanism of sevoflurane post-conditioning-induced neuroprotection remains unclear. We determined whether sevoflurane post-conditioning induces nuclear factor erythroid 2-related factor (Nrf2, a master transcription factor regulating antioxidant defence genes) and haemoxygenase-1 (HO-1, an antioxidant enzyme) expression, and whether protein kinase C (PKC) is involved in Nrf2 activation, in a rat model of transient global cerebral ischaemia/reperfusion (I/R) injury. METHODS: Eighty-six rats were assigned to five groups: sham (n=6), control (n=20), sevoflurane post-conditioning (two cycles with 2 vol% sevoflurane inhalation for 10 min, n=20), chelerythrine (a PKC inhibitor; 5 mg kg(-1) i.v. administration, n=20), and sevoflurane post-conditioning plus chelerythrine (n=20). The levels of nuclear Nrf2 and cytoplasmic HO-1 were assessed 1 or 7 days after ischaemia (n=10 each, apart from the sham group, n=3). RESULTS: On day 1 but not day 7 post-ischaemia, Nrf2 and HO-1 expression were significantly higher in the sevoflurane post-conditioning group than in the control group. Chelerythrine administration reduced the elevated Nrf2 and HO-1 expression induced by sevoflurane post-conditioning. CONCLUSIONS: Sevoflurane post-conditioning increased Nrf2/HO-1 expression via PKC signalling in the early phase after transient global cerebral I/R injury, suggesting that activation of antioxidant enzymes may be responsible for sevoflurane post-conditioning-induced neuroprotection in the early phase after cerebral I/R injury.

Nuclear factor E2-related factor 2 dependent overexpression of sulfiredoxin and peroxiredoxin III in human lung cancer.

BACKGROUND/AIMS: Oxidative stress results in protein oxidation and is implicated in carcinogenesis. Sulfiredoxin (Srx) is responsible for the enzymatic reversal of inactivated peroxiredoxin (Prx). Nuclear factor E2-related factor 2 (Nrf2) binds to antioxidant responsive elements and upregulates the expression of Srx and Prx during oxidative stress. We aimed to elucidate the biological functions and potential roles of Srx in lung cancer. METHODS: To study the roles of Srx and Prx III in lung cancer, we compared the protein levels of Nrf2, Prxs, thioredoxin, and Srx in 40 surgically resected human lung cancer tissues using immunoblot and immunohistochemical analyses. Transforming growth factor-ß(1), tumor necrosis factor-α, and camptothecin treatment were used to examine Prx III inactivation in Mv1Lu mink lung epithelial cells and A549 lung cancer cells. RESULTS: Prx I and Prx III proteins were markedly overexpressed in lung cancer tissues. A significant increase in the oxidized form of a cysteine sulfhydryl at the catalytic site of Prxs was found in carcinogenic lung tissue compared to normal lung tissue. Densitometric analyses of immunoblot data revealed significant Srx expression, which was higher in squamous cell carcinoma tissue (60%, 12/20) than in adenocarcinoma (20%, 4/20). Also, Nrf2 was present in the nuclear compartment of cancer cells. CONCLUSIONS: Srx and Prx III proteins were markedly overexpressed in human squamous cell carcinoma, suggesting that these proteins may play a protective role against oxidative injury and compensate for the high rate of mitochondrial metabolism in lung cancer.

Nuclear factor E2-related factor 2 Dependent Overexpression of Sulfiredoxin and Peroxiredoxin III in Human Lung Cancer

BACKGROUND/AIMS: Oxidative stress results in protein oxidation and is implicated in carcinogenesis. Sulfiredoxin (Srx) is responsible for the enzymatic reversal of inactivated peroxiredoxin (Prx). Nuclear factor E2-related factor 2 (Nrf2) binds to antioxidant responsive elements and upregulates the expression of Srx and Prx during oxidative stress. We aimed to elucidate the biological functions and potential roles of Srx in lung cancer. METHODS: To study the roles of Srx and Prx III in lung cancer, we compared the protein levels of Nrf2, Prxs, thioredoxin, and Srx in 40 surgically resected human lung cancer tissues using immunoblot and immunohistochemical analyses. Transforming growth factor-beta1, tumor necrosis factor-alpha, and camptothecin treatment were used to examine Prx III inactivation in Mv1Lu mink lung epithelial cells and A549 lung cancer cells. RESULTS: Prx I and Prx III proteins were markedly overexpressed in lung cancer tissues. A significant increase in the oxidized form of a cysteine sulfhydryl at the catalytic site of Prxs was found in carcinogenic lung tissue compared to normal lung tissue. Densitometric analyses of immunoblot data revealed significant Srx expression, which was higher in squamous cell carcinoma tissue (60%, 12/20) than in adenocarcinoma (20%, 4/20). Also, Nrf2 was present in the nuclear compartment of cancer cells. CONCLUSIONS: Srx and Prx III proteins were markedly overexpressed in human squamous cell carcinoma, suggesting that these proteins may play a protective role against oxidative injury and compensate for the high rate of mitochondrial metabolism in lung cancer.