Radiation-induced skin injury (RISI) commonly occur in cancer patients who received radiotherapy and is one of the first clinical symptoms after suffering from nuclear exposure. Oxidative damage is the major causes of RISI. Nuclear factor erythroid 2-related factor 2 (Nrf2) is considered as a key mediator of the cellular antioxidant response. However, whether Nrf2 can alleviate RISI after high-dose irradiation remains unknown. In this study, we demonstrated that Nrf2-deficient (Nrf2 -/-) mice were susceptible to high-dose irradiation and adenovirus-mediated overexpression of Nrf2 (ad-Nrf2) protected against radiation in skin cells. Overexpression of Nrf2 attenuated the severity of skin injury after high-dose electron beam irradiation. To uncover the mechanisms of Nrf2 involved in RISI, mRNA sequencing technology was performed to analyze the mRNA expression profiles of Ad-Nrf2 skin cells following radiation. The results revealed that a total of 127 genes were significantly changed, 55 genes were upregulated, and 72 genes were downregulated after Nrf2 overexpression. GSEA showed that Nrf2 was associated with positive regulation of genes involved in the reactive oxygen species pathway after radiation. Taken together, this study illustrated the role of Nrf2 in RISI and provided potentially strategies for ameliorating RISI.

Free radicals generated by oxidative stress cause damage that can contribute to numerous chronic diseases. Mammalian cells respond to this damage by increased transcription of cytoprotective phase II genes, which are regulated by NRF2. Previously, it has been shown that NRF2 protein levels increase after oxidative stress because its negative regulator, KEAP1, loses its ability to bind NRF2 and cause its proteasome-mediated degradation during oxidative stress. Here, we show that CRIF1, a protein previously known as cell cycle regulator and transcription cofactor, is also able to negatively regulate NRF2 protein stability. However, in contrast to KEAP1, which regulates NRF2 stability only under normal reducing conditions, CRIF1 regulates NRF2 stability and its target gene expression under both reducing and oxidative stress conditions. Thus, CRIF1-NRF2 interactions and their consequences are redox-independent. In addition, we found that CRIF1, unlike KEAP1 (which only interacts with N-terminal region of NRF2), physically interacts with both N- and C-terminal regions of NRF2 and promotes NRF2 ubiquitination and subsequent proteasome-mediated NRF2 protein degradation.

We investigated the association of redox regulator Nuclear factor erythroid 2-related factor 2 (Nrf2) and inflammatory cytokines as well as clinical remission in patients with recent onset type 2 diabetes (DM). Blood was collected from 180 DM patients (105 males/75 females) and 150 control subjects (86 males/64 females). Blood glucose, HbA1c, lipid profile and Nrf2 levels were determined along with circulatory cytokines in study subjects. The data were adjusted with confounding factors such as age and sex using multiple logistic regression analysis. We found that Th1/Th2 and oxidative stress markers were significantly elevated, whereas Nrf2 and its downstream targets were decreased in peripheral blood mononuclear cells (PBMCs) of DM subjects when compared with control. The circulatory levels of Nrf2 showed a positive correlation with Th2 cytokines and negative correlation to Th1 cytokines. Further, the impaired insulin secretion in pancreatic β-cells observed due to cytokine stress has been restored by activation of Nrf2 as assessed by glucose-stimulated insulin secretion (GSIS). This study identifies Nrf2 plays a central role in skewing Th1 and Th2 dominance in the progression of diabetes.

Cereblon is a protein encoded by the CRBN gene, which has been associated with human autosomal recessive nonsyndromic mental retardation. However, little is known about the regulation of CRBN expression. Following exposure of mouse neuroblastoma N2A cells to hypoxia/reoxygenation (H/R), mRNA and protein expression of CRBN were increased. To better understand how CRBN expression is regulated, the promoter region of the mouse CRBN gene was characterized functionally. Deletion mutations and site-directed mutagenesis led to the identification of a functional NF-E2-related factor 2 (Nrf2)-binding site. Electrophoretic mobility shift analysis indicated that Nrf2 binds to a putative binding site in the CRBN promoter. Nrf2 overexpression and tert-butylhydroquinone treatment enhanced CRBN protein expression. These results imply that Nrf2 stimulates CRBN gene transcription under H/R conditions in neuronal cells.

TGF-β plays a key role in the development of renal fibrosis. Suppressing the TGF-β signaling pathway is a possible therapeutic approach for preventing this disease, and reports have suggested that Nrf2 protects against renal fibrosis by inhibiting TGF-β signaling. This study examines whether dimethylfumarate (DMF), which stimulates Nrf2, prevents renal fibrosis via the Nrf2-mediated suppression of TGF-β signaling. Results showed that DMF increased nuclear levels of Nrf2, and both DMF and adenovirus-mediated overexpression of Nrf2 (Ad-Nrf2) decreased PAI-1, alpha-smooth muscle actin (α-SMA), fibronectin and type 1 collagen expression in TGF-β-treated rat mesangial cells (RMCs) and renal fibroblast cells (NRK-49F). Additionally, DMF and Ad-Nrf2 repressed TGF-β-stimulated Smad3 activity by inhibiting Smad3 phosphorylation, which was restored by siRNA-mediated knockdown of Nrf2 expression. However, downregulation of the antioxidant response element (ARE)-driven Nrf2 target genes such as NQO1, HO-1 and glutathione S-transferase (GST) did not reverse the inhibitory effect of DMF on TGF-β-induced upregulation of profibrotic genes or extracellular matrix proteins, suggesting an ARE-independent anti-fibrotic activity of DMF. Finally, DMF suppressed unilateral ureteral obstruction (UUO)-induced renal fibrosis and α-SMA, fibronectin and type 1 collagen expression in the obstructed kidneys from UUO mice, along with increased and decreased expression of Nrf2 and phospho-Smad3, respectively. In summary, DMF attenuated renal fibrosis via the Nrf2-mediated inhibition of TGF-β/Smad3 signaling in an ARE-independent manner, suggesting that DMF could be used to treat renal fibrosis.

β-amyloid peptide (Aβ), a major component of senile plaques, plays important roles in neuropathology of Alzheimer's disease (AD). An array of in vitro and in vivo data indicates that Aβ-induced neuronal death is mediated by oxidative stress. In this study, we aimed to investigate effects of sulforaphane (SUL), an isothiocyanate in cruciferous vegetables, on Aβ-induced oxidative cell death in SH-SY5Y cells. Cells treated with Aβ(25-35) exhibited decreased cell viability and underwent apoptosis as determined by MTT assay and TUNEL, respectively. Aβ(25-35)-induced cytotoxicity and apoptotic characteristics such as activation of c-JNK, dissipation of mitochondrial membrane potential, altered expression of Bcl-2 family proteins, and DNA fragmentation were effectively attenuated by SUL pretreatment. The antiapoptotic activity of SUL seemed to be mediated by inhibition of intracellular accumulation of reactive oxygen species and oxidative damages. SUL exerted antioxidant potential by upregulating expression of antioxidant enzymes including γ-glutamylcysteine ligase, NAD(P)H:quinone oxidoreductase-1, and heme oxygenase-1 via activation of NF-E2-related factor 2(Nrf2). The protective effect of SUL against Aβ(25-35)-induced apoptotic cell death was abolished by siRNA of Nrf2. Taken together, the results suggest that pharmacologic activation of Nrf2 signaling pathway by SUL might be a practical prevention and/or protective treatment for the management of AD.

Heat shock increases skin temperature during sun exposure and some evidence indicates that it may be involved in skin aging. The antioxidant response mediated by the transcription factor NF-E2-related factor 2 (Nrf2) is a critically important cellular defense mechanism that serves to limit skin aging. We investigated the effects of heat shock on collagenase expression when the antioxidant defense system was downregulated by knockdown of Nrf2. GSH and collagenases were analyzed, and the expression of inducible Nrf2, HO-1, and NQO1 was measured. HS68 cells were transfected with small interfering RNA against Nrf2. Heat shock induced the downregulation of Nrf2 in both the cytosol and nucleus and reduced the expression of HO-1, GSH, and NQO1. In addition, heat-exposed Nrf2-knockdown cells showed significantly increased levels of collagenase protein and decreased levels of procollagen. Our data suggest that Nrf2 plays an important role in protection against heat shock-induced collagen breakdown in skin.

Cinnamaldehyde (CN) is an activator of NF-E2-related factor 2 (Nrf2), which has the potential to reduce endothelial dysfunction, oxidative stress and inflammation in metabolic disorders. Our main purpose was to evaluate the effects of CN on vascular dysfunction in metabolic syndrome rats. Normal Wistar (W) rats were divided into eight groups: (1) Wistar (W) rats; (2) W rats fed with a high-fat diet (WHFD); (3) W rats fed with a sucrose diet (WS); (4) WHFD fed with a sucrose diet (WHFDS); (5) W treated with CN (WCn); (6) WS treated with CN (WSCn); (7) WHFD treated with CN (WHFDCn); (8) WHFDS treated with CN (WHFDSCn). CN treatment with 20 mg/kg/day was administered for 8 weeks. Evaluation of metabolic profile, inflammation, endothelial function, oxidative stress, eNOS expression levels and Nrf2 activation was performed. The metabolic dysfunction was greatly exacerbated in the WHFDS rats, accompanied by significantly higher levels of vascular oxidative stress, inflammation, and endothelial dysfunction. In addition, the WHFDS rats displayed significantly reduced activity of Nrf2 at the vascular level. CN significantly reverted endothelial dysfunction in the aortas and the mesenteric arteries. In addition, CN significantly decreased vascular oxidative damage, inflammation at vascular and perivascular level and up-regulated Nrf2 activity in the arteries of WHFDS rats. Cinnamaldehyde, an activator of Nrf2, can be used to improve metabolic profile, and to revert endothelial dysfunction in obesity and metabolic syndrome.

Sulforaphane is an activator of transcription factor NF-E2-related factor-2 (nrf2) that regulates gene expression through the promoter antioxidant response element (ARE). Nrf2 regulates the transcription of a battery of protective and metabolic enzymes. The aim of this study was to assess whether activation of nrf2 by sulforaphane in human microvascular endothelial cells prevents metabolic dysfunction in hyperglycemia.

Serine racemase (SR) synthesizes l-type serine to its enantimor, d-serine which participates in physiological processes and in pathological conditions. In the central nervous system, SR is highly expressed in neurons and astrocytes but expressed at relatively lower amount in microglia. However, the mechanism by which SR is highly expessed in neurons is hitherto unknown. We report that the SR mRNA and protein levels in Neuro-2a were increased by valproic acid (VPA), a neuron differentiation stimulator as well as a histone deacetylase inhibitor. SR proximal promoter contained nine putative Sp-binding elements and in the exon 1, three putative anti-oxidant elements (AREs) were conservative among human, rat, and mouse genome. The promoter constructs including 5'-, 3'-fragment, and full length fragment from mouse were individually cloned into a luciferase reporter. Using dual-luciferase assay, the promoter harboring 3'-fragment contained much lower activity than the construct containing 5'-fragment which was though resistant to VPA induction, relative to 3'-fragment. Overexpression of Sp4 or Nrf2 increased whereas knockdown of either decreased Srr mRNA and SR protein. Using site-directed mutagenesis, mutation of Sp-binding elements or AREs in the constructs significantly decreased luciferase activity of the corresponding promoter construct. With chromatin immunoprecipitation, Sp4 was demonstrated to interact directly with the Sp-binding elements whereas Nrf2 bound AREs in Srr mRNA promoter. Altogether, our study highlights that Sp4 controls constitutive expression of SR in neuron and VPA mediates SR expression in N2A cells which is associated with its effect on neuron differentiation, that is, the effect is mediated via Nrf2.

BACKGROUND This study aimed to investigate the effects of SIN on ankle fracture and the underlying mechanisms in MG-63 cells. MATERIAL AND METHODS qRT-PCR and ELISA assay were used to detect the mRNA and protein levels of cytokines in peripheral blood of children with or without ankle fracture. The expression and activity of antioxidant and detoxifying enzymes were detected by ELISA assay. Pretreated MG-63 cells with/without SIN were stimulated with 1 μg/ml bradykinin (BK). A CCK-8 kit was used to detect the cell viability. The cytokines produced from MG-63 cells were detected by Western blotting and qRT-PCR. Moreover, Western blotting was used to detect the levels of p-p38 and p-NF-κB (p65), and the activation level of the Nrf2 signaling pathway was examined by qRT-PCR and Western blotting. RESULTS In this study, we found that compared with the healthy children, the mRNA and protein levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) were significantly upregulated in children with ankle fracture. In addition, the expression and activity of antioxidant and detoxifying enzymes were imbalanced in children with ankle fracture. SIN treatment did not have a cytotoxic effect on MG-63 cells. SIN dose-dependently suppressed BK-induced upregulation of IL-1β, IL-6, TNF-α, p-p38, and p-NF-κB (p65). Furthermore, SIN dramatically inhibited oxidative stress induced by BK via balancing the expression and activity of antioxidant and detoxifying enzymes and inhibited the activation of Nrf2 signaling. CONCLUSIONS SIN might be a potential agent for the treatment of ankle fracture through reducing inflammatory response and oxidative stress.

To investigate the role of hepatic 18-carbon fatty acids (FA) accumulation in regulating CYP2A5/2A6 and the significance of Nrf2 in the process during hepatocytes steatosis, Nrf2-null, and wild type mice fed with high-fat diet (HFD), and Nrf2 silenced or over expressed HepG2 cells administered with 18-carbon FA were used. HE and Oil Red O staining were used for mice hepatic pathological examination. The mRNA and protein expressions were measured with real-time PCR and Western blot. The results showed that hepatic CYP2A5 and Nrf2 expression levels were increased in HFD fed mice accompanied with hepatic 18-carbon FA accumulation. The Nrf2 expression was increased dose-dependently in cells administered with increasing concentrations of stearic acid, oleic acid, and alpha-linolenic acid. The Nrf2 expression was dose-dependently decreased in cells treated with increasing concentrations of linoleic acid, but the Nrf2 expression level was still found higher than the control cells. The CYP2A6 expression was increased dose-dependently in increasing 18-carbon FA treated cells. The HFD-induced up-regulation of hepatic CYP2A5 in vivo and the 18-carbon FA treatment induced up-regulation of CYP2A6 in HepG2 cells were, respectively, inhibited by Nrf2 deficiency and Nrf2 silencing. While the basal expression of mouse hepatic CYP2A5 was not impeded by Nrf2 deletion. Nrf2 over expression improved the up-regulation of CYP2A6 induced by 18-carbon FA. As the classical target gene of Nrf2, GSTA1 mRNA relative expression was increased in Nrf2 over expressed cells and was decreased in Nrf2 silenced cells. In presence or absence of 18-carbon FA treatment, the change of CYP2A6 expression level was similar to GSTA1 in Nrf2 silenced or over expressed HepG2 cells. It was concluded that HFD-induced hepatic 18-carbon FA accumulation contributes to the up-regulation of CYP2A5/2A6 via activating Nrf2. However, the CYP2A5/2A6 expression does not only depend on Nrf2.

Selenium has been reported to induce the expression of some cytoprotective enzymes, which may account for its chemoprotective and chemopreventive effects. However, it remains largely unresolved whether these effects are exerted by selenium itself or mediated by its metabolite(s). In the present study, methylseleninic acid (MSeA), a monomethylated selenium, induced the expression of NAD(P)H:quinone oxidoreductase-1 (NQO-1) in human Chang liver cells. Expression of NQO-1 and other antioxidant/stress response genes is primarily regulated by the transcription factor NF-E2-related factor2 (Nrf2). Exposure of human Chang liver cells to MSeA (3 μM) increased nuclear translocation of Nrf2 and binding to antioxidant response elements. Silencing Nrf2 markedly reduced the MSeA-induced NQO-1 expression. In comparison with embryonic fibroblasts from Nrf2 wild-type mice, those from Nrf2 knockout mice failed to induce NQO-1 expression when treated with MSeA. Moreover, MSeA treatment enhanced ubiquitination of Keap1, but repressed Nrf2 ubiquitination. Pretreatment of cells with dithiothreitol abrogated the MSeA-induced NQO-1 expression, suggesting that MSeA causes Keap1 thiol modification. MSeA-induced NQO-1 upregulation was attenuated in cells harbouring the mutant Keap1 in which the cysteine 151 residue was replaced by serine. Oral administration of MSeA (1 mg/kg) by gavage to mice induced hepatic NQO-1 expression. Similar to MSeA, methylselenol generated from selenomethionine by methioninase activity induced NQO-1 expression. In conclusion, MSeA, the immediate precursor of methylselenol, upregulates the expression of NQO-1 via the Keap1-Nrf2 signaling. The above findings suggest that biological activities of selenium are dependent on the nature of the metabolites as well as the type of ingested selenium formulations.

Statin has been known not only as their cholesterol-lowering action but also on their pleiotropic effects including anti-inflammatory and anti-oxidant as well as anti-cancer effect. Nrf2 (NF-E2-related factor 2) is a transcription factor to activate cellular antioxidant response to oxidative stress. There are little known whether statins affect activation of Nrf2 and Nrf2 signaling pathway in colon cancer cells. We investigated whether simvastatin stimulates the expression of Nrf2 and nuclear translocation of Nrf2 and which signal pathway is involved in the expression of Nrf2 and antioxidant enzymes. We investigated the effect of simvastatin on the expression of Nrf2 and nuclear translocation of Nrf2 in two human colon cancer cell lines, HT-29 and HCT 116 through cell proliferation assay, Western blotting and immunocytochemical analysis. We evaluated which signal pathway such as ERK or PI3K pathway affect Nrf2 activation and whether simvastatin induces antioxidant enzymes (heme oxygenase-1 (HO-1), NAD(P)H: quinine oxidoreductase 1 (NQO1), γ-glutamate-cysteine ligase catalytic subunit (GCLC)). We demonstrated simvastatin-induced dose-dependent up-regulation of Nrf2 expression and stimulated Nrf2 nuclear translocation in colon cancer cells. We also demonstrated that simvastatin-induced anti-oxidant enzymes (HO-1, NQO1, and GCLC) in HT-29 and HCT 116 cells. PI3K/Akt inhibitor (LY294002) and ERK inhibitor (PD98059) suppressed simvastatin-induced Nrf2 and HO-1 expression in both HT-29 and HCT 116 cells. This study shows that simvastatin induces the activation and nuclear translocation of Nrf2 and the expression of various anti-oxidant enzymes via ERK and PI3K/Akt pathway in colon cancer cells.

Alzheimer's disease (AD) is a common dementia affecting a vast number of individuals and significantly impairing quality of life. Despite extensive research in animal models and numerous promising treatment trials, there is still no curative treatment for AD. Astrocytes, the most common cell type of the central nervous system, have been shown to play a role in the major AD pathologies, including accumulation of amyloid plaques, neuroinflammation, and oxidative stress. Here, we show that inflammatory stimulation leads to metabolic activation of human astrocytes and reduces amyloid secretion. On the other hand, the activation of oxidative metabolism leads to increased reactive oxygen species production especially in AD astrocytes. While healthy astrocytes increase glutathione (GSH) release to protect the cells, Presenilin-1-mutated AD patient astrocytes do not. Thus, chronic inflammation is likely to induce oxidative damage in AD astrocytes. Activation of NRF2, the major regulator of cellular antioxidant defenses, encoded by the NFE2L2 gene, poses several beneficial effects on AD astrocytes. We report here that the activation of NRF2 pathway reduces amyloid secretion, normalizes cytokine release, and increases GSH secretion in AD astrocytes. NRF2 induction also activates the metabolism of astrocytes and increases the utilization of glycolysis. Taken together, targeting NRF2 in astrocytes could be a potent therapeutic strategy in AD.

NF-E2-related factor 2 (NRF2) regulates a battery of antioxidative and phase II drug metabolizing/detoxifying genes through binding to the antioxidant response elements (ARE). NRF2-ARE signaling plays a central role in protecting cells from a wide spectrum of reactive toxic species including reactive oxygen/nitrogen species (RONS). 4-hydroxylnonenal (4-HNE) is a major end product from lipid peroxidation of omega-6 polyunsaturated fatty acids (PUFA) induced by oxidative stress, and it is highly reactive to nucleophilic sites in DNA and proteins, causing cytotoxicity and genotoxicity. In this study, we examined the role of NRF2 in regulating the 4-HNE induced gene expression of antioxidant and detoxifying enzymes.

BACKGROUND Diabetic nephropathy (DN) is a disease characterized by oxidative stress and apoptosis of renal tubular epithelial cells driven by hyperglycemia. Apigenin is a flavonoid compound that possesses potent anti‑apoptotic properties. The present study aimed to explore the protective effects and underlying mechanisms of apigenin on renal tubular epithelial cells exposed to hyperglycemia. MATERIAL AND METHODS Human renal epithelial cell HK-2 were incubated to D-glucose to establish in vitro DN model. The cell viability, lactate dehydrogenase (LDH) release, apoptosis and oxidative stress were evaluated. qRT-PCR was performed to determine the mRNA levels of NF-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Western blot analysis was performed to measure the protein expressions of Nrf2. RESULTS In HK-2 cells, high glucose reduced cell viability in a concentration- and time-dependent manner. Apigenin suppressed the decrease in cell viability and increase in supernatant LDH release at 100 and 200 μM after 48-h treatment. Apigenin reduced apoptotic rate and pro-inflammatory cytokines production. Apigenin suppressed oxidative stress and increased mRNA expressions of Nrf2 and HO-1. Inhibition of Nrf2 using small interfering RNA (siRNA), or cotreatment with LY294002, an inhibitor of PI3K/Akt, abolished the protective effect on high glucose-induced injury, oxidative stress, and pro-inflammatory cytokines production by apigenin. LY294002 also attenuated the increase in Nrf2 protein by apigenin in high glucose-treated HK-2 cells. CONCLUSIONS Apigenin protects renal tubular epithelial cells against high glucose-induced injury through suppression of oxidative stress and inflammation via activation of the Nrf2 pathway.

Oxidative stress-induced retinal pigment epithelial (RPE) cell damage is an important factor in the pathogenesis of age-related macular degeneration (AMD). Previous studies have shown that RTA 408, a synthetic triterpenoid compound, potently activates Nrf2. This study aimed to investigate the protective effects of RTA 408 in cultured RPE cells during oxidative stress and to determine the effects of RTA 408 on Nrf2 and its downstream target genes. Primary human RPE cells were pretreated with RTA 408 and then incubated in 200μM H2O2 for 6h. Cell viability was measured with the WST-8 assay. Apoptosis was quantitatively measured by annexin V/propidium iodide (PI) double staining and Hoechst 33342 fluorescent staining. Reduced (GSH) and oxidized glutathione (GSSG) were measured using colorimetric assays. Nrf2 activation and its downstream effects on phase II enzymes were examined by Western blot. Treatment of RPE cells with nanomolar ranges (10 and 100nM) of RTA 408 markedly attenuated H2O2-induced viability loss and apoptosis. RTA 408 pretreatment significantly protected cells from oxidative stress-induced GSH loss, GSSG formation and decreased ROS production. RTA 408 activated Nrf2 and increased the expression of its downstream genes, such as HO-1, NQO1, SOD2, catalase, Grx1, and Trx1. Consequently, the enzyme activities of NQO1, Grx1, and Trx1 were fully protected by RTA 408 pretreatment under oxidative stress. Moreover, knockdown of Nrf2 by siRNA significantly reduced the cytoprotective effects of RTA 408. In conclusion, our data suggest that RTA 408 protect primary human RPE cells from oxidative stress-induced damage by activating Nrf2 and its downstream genes.

Cytarabine (Ara-C) and Daunorubicin (Dnr) forms the backbone of acute myeloid leukemia (AML) therapy. Drug resistance and toxic side effects pose a major threat to treatment success and hence alternate less toxic therapies are warranted. NF-E2 related factor-2 (Nrf2), a master regulator of antioxidant response is implicated in chemoresistance in solid tumors. However, little is known about the role of Nrf2 in AML chemoresistance and the effect of pharmacological inhibitor brusatol in modulating this resistance. Primary AML samples with high ex-vivo IC50 to Ara-C, ATO, Dnr had significantly high NRF2 RNA expression. Gene-specific knockdown of NRF2 improved sensitivity to these drugs in resistant AML cell lines by decreasing the expression of downstream antioxidant targets of Nrf2 by compromising the cell's ability to scavenge the ROS. Treatment with brusatol, a pharmacological inhibitor of Nrf2, improved sensitivity to Ara-C, ATO, and Dnr and reduced colony formation capacity. AML cell lines stably overexpressing NRF2 showed increased resistance to ATO, Dnr and Ara-C and increased expression of downstream targets. This study demonstrates that Nrf2 could be an ideal druggable target in AML, more so to the drugs that function through ROS, suggesting the possibility of using Nrf2 inhibitors in combination with chemotherapeutic agents to modulate drug resistance in AML.

Radiotherapy produces excessive reactive oxygen species (ROS), which can lead to DNA damage and apoptosis in tumor cells, thereby killing malignant cells. Chlorogenic acid (CGA) is a well-known antioxidant in coffee due to its strong ability to remove ROS. However, the effect of CGA on radiotherapeutic efficacy remains unclear. In this study, we showed that CGA could hinder the therapeutic effect of radiotherapy by inhibiting radiation-induced apoptosis and DNA damage via scavenging excessive ROS and activating the NF-E2-related factor 2 (Nrf2) antioxidant system in hepatocellular carcinoma (HCC) cells and a murine model. The knockdown of Nrf2 reversed CGA-mediated radiation resistance in HCC cells. In conclusion, CGA might be a potential tumor-protective compound upon irradiation and reduce the efficacy of radiotherapy via ROS scavenging and Nrf2 activation.