Endogenous and Exogenous Modulation of Nrf2 Mediated Oxidative Stress Response in Bovine Granulosa Cells: Potential Implication for Ovarian Function
Nrf2 is a redox sensitive transcription factor regulating the expression of antioxidant genes as defense mechanism against various stressors. The aim of this study is to investigate the potential role of noncoding miRNAs as endogenous and quercetin as exogenous regulators of Nrf2 pathway in bovine granulosa cells. For this cultured granulosa cells were used for modulation of miRNAs (miR-28, 153 and miR-708) targeting the bovine Nrf2 and supplementation of quercentin to investigate the regulatory mechanisms of the Nrf2 antioxidant system. Moreover, cultured cells were treated with hydrogen peroxide to induce oxidative stress in those cells. Our results showed that, oxidative stress activated the expression of Nrf2 as a defense mechanism, while suppressing the expression of those miRNAs. Overexpression of those miRNAs resulted in downregulation of Nrf2 expression resulted in higher ROS accumulation, reduced mitochondrial activity and cellular proliferation. Quercetin supplementation showed its protective role against oxidative stress induced by H₂O₂ by inducing the expression of antioxidant enzymes. In conclusion, this study highlighted the involvement of miR-153, miR-28 and miR-708 in regulatory network of Nrf2 mediated antioxidant system in bovine granulosa cells function. Furthermore, quercetin at a low dose played a protective role in bovine granulosa cells against oxidative stress damage.
Resveratrol and Quercetin Administration Improves Antioxidant DEFENSES and reduces Fatty Liver in Metabolic Syndrome Rats
Mixtures of resveratrol (RSV) + quercetin (QRC) have antioxidant properties that probably impact on fatty liver in metabolic syndrome (MS) individuals. Here, we study the effects of a mixture of RSV + QRC on oxidative stress (OS) and fatty liver in a rat model of MS. Weanling male Wistar rats were separated into four groups ( = 8): MS rats with 30% sucrose in drinking water plus RSV + QRC (50 and 0.95 mg/kg/day, respectively), MS rats without treatment, control rats (C), and C rats plus RSV + QRC. MS rats had increased systolic blood pressure, triglycerides, insulin levels, insulin resistance index homeostasis model (HOMA), adiponectin, and leptin. The RSV + QRC mixture compensated these variables to C values ( < 0.01) in MS rats. Lipid peroxidation and carbonylation were increased in MS. Total antioxidant capacity and glutathione (GSH) were decreased in MS and compensated in MS plus RVS + QRC rats. Catalase, superoxide dismutase isoforms, peroxidases, glutathione-S-transferase, glutathione reductase, and the expression of Nrf2 were decreased in MS and reversed in MS plus RVS + QRC rats ( < 0.01). In conclusion, the mixture of RSV + QRC has benefic effects on OS in fatty liver in the MS rats through the improvement of the antioxidant capacity and by the over-expression of the master factor Nrf2, which increases the antioxidant enzymes and GSH recycling.
Luteolin Shifts Oxaliplatin-Induced Cell Cycle Arrest at G₀/G₁ to Apoptosis in HCT116 Human Colorectal Carcinoma Cells
Certain antioxidative flavonoids are known to activate nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates cellular antioxidants and detoxifying response and is reportedly highly activated in many types of cancers. Few studies on the potential undesired effects of flavonoid intake during chemotherapy have been conducted, yet Nrf2 activators could favor cancer cell survival by attenuating chemotherapeutic efficiency. This study aimed to examine if luteolin, an Nrf2 activator, hinders chemotherapeutic activity of oxaliplatin, a potent anticancer agent for colorectal cancer, in HCT116 cells. Luteolin treatment strongly increased the transcriptional activity of the antioxidant response element in HCT116 cells and induced the protein expression of heme oxygenase-1, which were indicative of its Nrf2-inducing potential. Intriguingly, 25 μM luteolin reduced cell viability through apoptotic induction, which was intensified in p53-expressing cells while 1 μM oxaliplatin caused cell cycle arrest at G₀/G₁-phase via the p53/p21-dependent mechanism. Moreover, luteolin treatment was found to reduce oxaliplatin-treated p53-null cell viability and colony counts further, thereby demonstrating an additional effect of luteolin in the killing of human colorectal tumor HCT116 cells not expressing functional p53 protein. The findings suggest that luteolin can induce p53-mediated apoptosis regardless of oxaliplatin treatment and may eliminate oxaliplatin-resistant p53-null colorectal cells.
Luteolin promotes apoptotic cell death via upregulation of Nrf2 expression by DNA demethylase and the interaction of Nrf2 with p53 in human colon cancer cells
Luteolin, a dietary flavone, modulates various signaling pathways involved in carcinogenesis. In this study, we investigated the molecular mechanism that underlies the apoptotic effects of luteolin mediated by DNA demethylation of the nuclear factor erythroid 2-related factor 2 (Nrf2) promoter and the interaction of Nrf2 and p53, a tumor suppressor, in human colon cancer cells. Luteolin increased the expression of apoptosis-related proteins and antioxidant enzymes. In DNA methylation, luteolin inhibited the expression of DNA methyltransferases, a transcription repressor, and increased the expression and activity of ten-eleven translocation (TET) DNA demethylases, a transcription activator. Methyl-specific polymerase chain reaction and bisulfite genomic sequencing indicated that luteolin decreased the methylation of the Nrf2 promoter region, which corresponded to the increased mRNA expression of Nrf2. In addition, luteolin increased TET1 binding to the Nrf2 promoter, as determined using a chromatin immunoprecipitation (ChIP) assay. TET1 knockdown decreased the percentages of luteolin-treated cells in sub-G phase and cells with fragmented nuclei. Furthermore, complex formation between p53 and Nrf2 was involved in the apoptotic effects of luteolin. These results provide insight into the mechanism that underlies the anticancer effects of luteolin on colon cancer, which involve the upregulation of Nrf2 and its interaction with the tumor suppressor.
Sequestosome 1/p62-related pathways as therapeutic targets in hepatocellular carcinoma
Protein sequestosome 1/p62 (p62) plays a crucial role in vital complex and interacting signaling pathways in normal and neoplastic cells. P62 is involved in autophagy, defense against oxidative stress via activation of the Keap1/Nrf2 system, in protein aggregation and sequestration, and in apoptosis. Autophagy contributes to cell survival and proliferation by eliminating damaged organelles, potentially toxic protein aggregates and invading microorganisms, and by providing nutrients under starvation conditions. The same holds true for oxidative stress defense, which may prevent genomic alterations and tumor initiation but also protect established tumor cells and promote tumor progression. Cross-talk between autophagy and apoptosis is regulated by a signaling network with the involvement of p62. Areas covered: The review deals with structure, function, and regulation of p62 and its role in liver carcinogenesis. Emphasis is placed on mechanisms leading to overexpression of p62 and its accumulation as inclusion bodies in HCC and on the impact of p62-dependent signaling pathways in tumor cells with the aim to explore the possible role of p62 as the therapeutic target. Expert opinion: Depending on the context, targeting p62 or interference with related pathways, such as autophagy, is a potential therapeutic strategy in HCC. However, the heterogeneity of this tumor entity and the complexity and mutual interactions of the p62-dependent pathways involved are challenges for a targeted therapy since interference with p62-mediated regulatory processes could result likewise in inhibition of tumorigenesis and in its promotion and thus provoke harmful side effects. Therapy-related patient stratification based on reliable markers to better define pathogenic principles of the tumor is a necessity when this type of treatment is considered.
Berberine protects immortalized line of human melanocytes from HO-induced oxidative stress via activation of Nrf2 and Mitf signaling pathway
Oxidative stress plays important roles in the pathogenesis of vitiligo. The removal of hydrogen peroxided (HO) has been established to be beneficial to vitiligo patients. Berberine (BBR), a natural isoquinoline alkaloid, has antioxidant activity, however, whether BBR can defend human melanocytes against oxidative injury remains to be elucidated.
The in vitro and in vivo depigmenting activity of Coenzyme Q10 through the down-regulation of α-MSH signaling pathways and induction of Nrf2/ARE-mediated antioxidant genes in UVA-irradiated skin keratinocytes
Coenzyme CoQ10 (CoQ10), a ubiquinone compound, has been reported to inhibit tyrosinase activity and melanin production in melanoma B16F10 cells. However, the molecular mechanism underlying this inhibitory effect is poorly understood. In this paper we aimed to investigate the molecular mechanisms involved in the anti-melanogenic activity of CoQ10 (1-2 μM) in UVA (5 J/cm)-irradiated keratinocyte HaCaT cells and α-MSH stimulated B16-F10 cells. It was observed that CoQ10 suppressed p53/POMC, α-MSH production as well as inhibited ROS generation in UVA-irradiated keratinocyte HaCaT cells. CoQ10 down-regulated the melanin synthesis in α-MSH-stimulated B16-F10 cells by suppressing the MITF expression by down regulating the cAMP mediated CREB signaling cascades. Furthermore, in vivo evidence demonstrated the inhibitory effect of CoQ10 on endogenous pigmentation in zebrafish. Increased nuclear Nrf2 translocation accompanied by the induction of HO-1 and γ-GCLC genes were observed in CoQ10 treated keratinocyte HaCaT cells. Notably, silencing of Nrf2 (siRNA transfection) significantly diminished CoQ10-mediated anti-melanogenic activity, as evidenced by impaired antioxidant HO-1 gene, uncontrolled ROS generation, and α-MSH production following UVA irradiation. To conclude, CoQ10 is an effective de-pigmention or skin-whitening agent and could be used in cosmetics for topical application.
Alpha lipoic acid inhibits oxidative stress-induced apoptosis by modulating of Nrf2 signalling pathway after traumatic brain injury
Alpha lipoic acid (ALA) is a powerful antioxidant which has been widely used in the treatment of different system diseases, such as cardiovascular and cerebrovascular diseases. But, there are few studies that refer to protective effects and potential mechanisms on traumatic brain injury (TBI). This study was carried out to investigate the neuroprotective effect following TBI and illuminate the underlying mechanism. Weight drop-injured model in rats was induced by weight-drop. ALA was administrated via intraperitoneal injection after TBI. Neurologic scores were examined following several tests. Neurological score was performed to measure behavioural outcomes. Nissl staining and TUNEL were performed to evaluate the neuronal apoptosis. Western blotting was engaged to analyse the protein content of the Nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream protein factors, including hemeoxygenase-1 (HO-1) and quinine oxidoreductase-1 (NQO1). ALA treatment alleviated TBI-induced neuron cell apoptosis and improved neurobehavioural function by up-regulation of Nrf2 expression and its downstream protein factors after TBI. This study presents new perspective of the mechanisms responsible for the neuronal apoptosis of ALA, with possible involvement of Nrf2 pathway.
A preclinical evaluation of thiostrepton, a natural antibiotic, in nasopharyngeal carcinoma
Background Thiostrepton, a natural antibiotic, has recently been shown to be a potential anticancer drug for certain cancers, but its study in nasopharyngeal carcinoma (NPC) is still limited. The aims of this study were to investigate the anticancer effect of thiostrepton on NPC cells and to explore its underlying mechanism. Methods The effects of thiostrepton on the proliferation, migration, and invasion of NPC cells were investigated by a WST-1 assay, wound healing assay, and cell invasion assay, respectively. Microarrays were conducted and further analyzed by Ingenuity Pathways Analysis (IPA) to determine the molecular mechanism by which thiostrepton affects NPC cells. Results Our results showed that thiostrepton reduced NPC cell viability in a dose-dependent manner. Thiostrepton inhibited the migration and invasion of NPC cells in wound healing and cell invasion assays. The microarray data analyzed by IPA indicated the top 5 ingenuity canonical pathways, which were unfolded protein response, NRF2-mediated oxidative stress response, retinoate biosynthesis I, choline biosynthesis III, and pancreatic adenocarcinoma signaling. Conclusion Thiostrepton effectively suppressed NPC cell proliferation, migration, and invasion, likely by several mechanisms. Thiostrepton may be a potential therapeutic agent for treating NPC in the future.
Identification of Nrf2/STAT3 axis in induction of apoptosis through sub-G cell cycle arrest mechanism in HT-29 colon cancer cells
We investigated the role of stattic as an adjuvant molecule to increase the cytotoxicity of 5-fluorouracil (5-FU) through specific inhibition of molecular targets, signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid 2-related factor 2 (Nrf2) in HT-29 colon cancer cells. Cytotoxicity and apoptotic effects were investigated by methylthiazolyldiphenyl-tetrazolium bromide assay and flow cytometry analysis, respectively. Real-time polymerase chain reaction was applied to assess the messenger RNA (mRNA) level of STAT3, Nrf2, and apoptotic genes including Bax, Bcl-xl, and Bcl-2. The antitumor effect of 5-FU in combination with stattic induced synergistic effect in HT-29 cells with combination indexes (CIs) 0.49. Flow cytometric results related to apoptotic confirmed that there was up to 40% increase in the population of apoptotic cells in HT-29 colon cancer cells incubated with 5-FU and stattic compared with control groups. Our data from gene expression determined a substantial diminish in the mRNA levels of the Nrf2 and antiapoptotic gene Bcl-2 along with a noticeable increase in the level of the proapoptotic Bax in HT-29 colon cells that underwent cotreatment with 5-FU and stattic (P < 0.05). Moreover, the results exhibited that stattic can be used as adjuvant chemotherapy besides the 5-FU. This therapeutic approach in colon cancer could mediate 5-FU chemoresistance via modulating therapeutic targets (ie, STAT3 and Nrf2 pathways) and decreased 5-FU-related adverse effects.
Keap1-Nrf2 System Plays an Important Role in Invariant Natural Killer T Cell Development and Homeostasis
Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) proteins work in concert to regulate the levels of reactive oxygen species (ROS). The Keap1-Nrf2 antioxidant system also participates in T cell differentiation and inflammation, but its role in innate T cell development and functions remains unclear. We report that T cell-specific deletion of Keap1 results in defective development and reduced numbers of invariant natural killer T (NKT) cells in the thymus and the peripheral organs in a cell-intrinsic manner. The frequency of NKT2 and NKT17 cells increases while NKT1 decreases in these mice. Keap1-deficient NKT cells show increased rates of proliferation and apoptosis, as well as increased glucose uptake and mitochondrial function, but reduced ROS, CD122, and Bcl2 expression. In NKT cells deficient in Nrf2 and Keap1, all these phenotypic and metabolic defects are corrected. Thus, the Keap1-Nrf2 system contributes to NKT cell development and homeostasis by regulating cell metabolism.
Rooibos (Aspalathus linearis) and honeybush (Cyclopia species) modulate the oxidative stress associated injury of diesel exhaust particles in human umbilical vein endothelial cells
Previous evidence show foods and beverages rich in polyphenolic compounds to have favourable effects on the cardiovascular system.
The protective role of IL-1Ra on intestinal ischemia reperfusion injury by anti-oxidative stress via Nrf2/HO-1 pathway in rat
Intestinal ischemia reperfusion injury is a frequent clinical damage, in which the oxidative stress and inflammation play an important role. Interleukin-1 receptor antagonist (IL-1Ra) is a natural anti-inflammatory factor, however, its effect on intestinal ischemia reperfusion injury remains unclear.
[Protective effect of raspberry extract on ConA-induced acute liver injuryin mice]
In this experiment,the antioxidant capacity of raspberry extract and the protective effect on liver injury induced by ConA in mice were investigated. Balb/C male mice were randomly divided into six groups: normal group,model group,bicyclol control group( 200 mg·kg~(-1)),low-dose raspberry extract group( 200 mg·kg~(-1)),middle-dose raspberry extract group( 400 mg·kg~(-1)),and highdose raspberry extract group( 800 mg·kg~(-1)). Each group was intragastrically administered with drugs according to the body weight once a day. Seven days later,all of the groups except for the normal group were treated with ConA( 20 mg·kg~(-1)) through tail vein injection to establish the acute liver injury model. The mice were put to death 8 hours later. The organ indexes were calculated. These rum levels of ALT,AST and LDH and the activities of SOD,CAT,GSH and MDA in liver tissue were detected. HE staining was used to observe the pathological changes of liver tissue in mice. Western blot was used to detect the expressions of Bax,Bcl-2,Nrf2 and Keap-1. The antioxidant capacity of raspberry extract was measured by CAA assay. The results showed that,raspberry extract had a strong antioxidant capacity. Simultaneously,compared with the model group,raspberry extract can significantly improve the pathological conditions of liver,and significantly reduce ALT,AST and LDH activities in serum of liver injury mice( P<0. 01). The activities of SOD,CAT in liver homogenate supernatant were significantly increased in the high-dose group,the content of GSH increased,while the content of MDA was sharply declined in the high-dose group( P<0. 01). Meanwhile,raspberry extract down-regulated the expressions of Bax and Keap-1 and up-regulated the expressions of Bcl-2 and Nrf2. CAA showed that the compound raspberry extract had a strong antioxidant capacity. Therefore,raspberry extract has an obvious protective effect on acute liver injury induced by ConA in mice.
[Effect of maternal exposure to Curcumae Rhizoma during pregnancy on neurodevelopment and apoptosis mechanism in offspring]
Curcumae Rhizoma is a Chinese medicinal herb that is contraindicated during pregnancy. Cold-congelation and blood-stasis are corresponding syndromes to Curcumae Rhizoma. Whether syndrome-based treatment is associated with developmental neurotoxicity of Curcumae Rhizoma remains to be unclear. To verify the theory of traditional Chinese medicine of "syndrome-based treatment during pregnancy", the present study induced the mice blood stasis model by immersing mice in ice water. Pregnant C57 BL/6 wild type(WT) mice and pregnant Nrf2 knock out(KO) mice were randomly divided into control groups and Rhizoma Curcumae exposure groups. The mice were exposed to Rhizoma Curcumae during day 5 to day 18 after pregnancy. The neurodevelopment was examined to evaluate the differences of developmental neurotoxicity between normal and blood-stasis pregnant mice exposed to Rhizoma Curcumae. caspase-3 and caspase-9 activity in brain of the offspring were measured by colorimetric assays. Bcl-2 mRNA and protein expression in brain of the offspring were examined by Real-time RT-PCR and Western blot, respectively. According to the findings, C57 BL/6 mice exposed to Rhizoma Curcumae(10.0 g·kg~(-1)) had a longer positive occurring time of the surface righting reflex test of offspring and higher caspase-3 and caspase-9 activities in brain of offspring, compared with the normal control group, but with no significant change in those of blood-stasis pregnant mice offspring. However, mice exposed to Rhizoma Curcumae(10.0 g·kg~(-1)) showed no change in Bcl-2 gene expression and p38 MAPK phosphorylation in brain of the offspring. Nrf2 gene knockout using CRISPR/Cas9 resulted in a longer positive occurring time of the surface righting reflex test of offspring and higher caspase-3 and caspase-9 activities in brain of offspring. In conclusion, developmental neurotoxicity of the blood-stasis pregnant mice exposed to Rhizoma Curcumae was weaker than that of the normal pregnant mice. Nrf2 activation involved in the phenomenon of Rhizoma Curcumae of "syndrome-based treatment during pregnancy", but the upstream signal pathway mechanism value shall be further investigated.