Mutation des p53 Gen ist die häufigste genetische Veränderung in allen humanen Tumoren. Weit verbreitete p53 misssense-Mutationen heben die Tumor suppressive Funktion auf und führen zu gain-of-function Eigenschaften, die Tumorproliferation, Chemoresistenz, Angiogenese, Migration, Invasion und Metastasen fördern. In dieser Arbeit haben ich für drei solche Hotspot-Mutationen, p53R245Q, p53R246S und p53R270H, eine höhere Sensitivität gegenüber Behandlung mit Piperlongumine in p53-defizienten MEFs und Eµ-myc Lymphomzellen im Vergleich zur Kontrolle und den anderen drei Hotspot-Mutationen, p53R172H, p53G242S und p53R279Q, gefunden. Nachfolgend, haben ich entdeckt, dass Piperlongumine-induzierter Zelltod durch ROS Akkumulation über die Aktivierung von p38 und JNK, vermittelt wurde. Das Antioxidans N-acetyl-L-cysteine (NAC) oder p38/JNK Inhibitoren konnten vollständig oder teilweise Piperlongumine-induzierten Zelltod unterdrücken. Nach Behandlung mit Piperlongumine, haben die p53R245Q, p53R246S und p53R270H-Mutanten die Aktivierung von p21 inhibiert und so die Aktivierung und Funktion von NRF2, durch Piperlongumine induziert, blockiert, dass zu dem massiven Zelltod in Zellen mit diesen Mutationen beiträgt. Auf ähnliche Weise, verursachte der klinisch verwendete Inhibitor von Crm1, KPT-330, schweren Zelltod in p53-/- MEFs mit den p53R245Q, p53R246S und p53R270H-Mutationen. Folglich könnte Crm1 als potenzielles Target für Lymphome mit p53R245Q, p53R246S und p53R270H-Mutationen berücksichtigt werden. Zusammenfassend bekräftigen die Daten in dieser Arbeit das Phänomen, dass oxidativer Stress oder Crm1 Inhibitoren effektiv Zellen mit p53R245Q, p53R246S und p53R270H-Mutationen eliminieren können, mit niedriger Toxizität für Kontrollzellen. Demzufolge, könnten oxidativer Stress Signalwege oder Crm1 als potenzielle Angriffsziele für Lymphome mit p53R245Q, p53R246S und p53R270H-Mutationen dienen. / Mutation of the p53 gene is the most common genetic alteration among all human cancers. Prevalent p53 missense mutations abrogate its tumor suppressive function and lead to gain-of-function properties that promote cancer cell proliferation, chemoresistance, angiogenesis, migration, invasion, and metastasis. This doctoral thesis aims to identify the metabolic vulnerabilities of six p53 hotspot mutants in lymphomas. In this work, three hotspot mutants, p53R245Q, p53R246S and p53R270H, were more sensitive to piperlongumine treatment in p53-deficient MEFs and Eμ-myc lymphoma cells than the empty control and the other three hotspot mutants, p53R172H, p53G242S and p53R279Q. Thereafter, I found piperlongumine-induced cell death was mediated by ROS accumulation via the activation of p38 and JNK. Antioxidant N-acetyl-L-cysteine (NAC) or p38/JNK inhibitors could completely or partially suppress piperlongumine-induced cell death. Upon piperlongumine treatment, p53R245Q, p53R246S and p53R270H-mutant inhibited piperlongumine-induced activation of p21 and consequently attenuated the activation and function of NRF2 induced by piperlongumine, contributing to the massive cell death in cells harboring these mutants. Similarly, KPT-330, a clinical inhibitor of Crm1, also caused severe cell death in p53-/- MEFs harboring p53R245Q, p53R246S and p53R270H-mutant. This implied that Crm1 could be also considered as a potential target for lymphomas harboring p53R245Q, p53R246S and p53R270H-mutant. Taken together, data presented in this work underscore the phenomenon that exogenous oxidative stress or Crm1 inhibitor is effective in eliminating cells harboring p53R245Q, p53R246S and p53R270H-mutant with low toxicity to cells harboring the empty control, suggesting oxidative stress pathways or Crm1 as potential targets in lymphomas with p53R245Q, p53R246S and p53R270H-mutant.

This literature review posits that the transcription factor Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is an attractive candidate therapeutic target in the setting of acute myocardial infarction (AMI). This transcription factor binds to antioxidant response elements (ARE) in the promoter region of a battery of genes that collectively encode an array of antioxidant, phase II drug metabolism, metabolically stabilizing, and overall cytoprotective enzymes, facilitating their transcription at basal levels and increasing transcription in response to various cellular stressors. Following a brief background tutorial on normal cardiac myocyte cellular physiology, key events that occur early in ischemia and reperfusion are outlined and integrated. These include ionic and metabolic dysregulation, electron transport chain uncoupling, mitochondrial depolarization, and the generation of reactive oxygen species (ROS). Abrupt changes in response to ischemia prime opening of the mitochondrial permeability transition pore (MPTP) and cardiac myocytes to generate a burst of ROS upon reperfusion–two key events that contribute to the umbrella term ischemia-reperfusion injury (IRI). How ROS damage cells is then outlined, and through a ROS-centric viewpoint, a case will be made as to how exogenous upregulation of Nrf2 could protect and/or salvage at-risk tissue immediately subjected to infarction and neighboring tissue in the peri-infarct zone (PIZ). The history of how Nrf2 came to be known as the "master regulator of oxidative stress" is reviewed, as well as the discovery of the canonical mechanism of Nrf2 regulation via Kelch-like ECH-associated protein 1 (Keap1) and other alternative mechanisms of endogenous Nrf2 regulation. Finally, compiling interdisciplinary evidence from research publications around the world, the benefits of therapeutically targeting Nrf2 are considered given the timescale and context of acute MI. Drug delivery methods, potential challenges, and limitations are then considered. Cardiac tissue is a dynamic substrate that exhibits changes for up to 90 days after AMI and patient outcomes are directly related to the extent of tissue lost following infarction/reperfusion. Targeting Nrf2 addresses an unmet need, as current clinical therapies focus on precluding occlusions and prompt reperfusion of infarcted tissue, but do not explicitly target at-risk tissue following infarcts and/or present-day reperfusion methodologies.

Background: Strategies to maintain BBB integrity in diseases with a hypoxia/reoxygenation (H/R) component involve preventing glutathione (GSH) loss from endothelial cells. GSH efflux transporters include multidrug resistance proteins (Mrps). Therefore, characterization of Mrp regulation at the BBB during H/R is required to advance these transporters as therapeutic targets. Our goal was to investigate, in vivo, regulation of Abcc1, Abcc2, and Abcc4 mRNA expression (i.e., genes encoding Mrp isoforms that transport GSH) by nuclear factor E2-related factor (Nrf2) using a well-established H/R model. Methods: Female Sprague-Dawley rats (200-250 g) were subjected to normoxia (Nx, 21% O-2, 60 min), hypoxia (Hx, 6% O-2, 60 min) or H/R (6% O-2, 60 min followed by 21% O-2, 10 min, 30 min, or 1 h) or were treated with the Nrf2 activator sulforaphane (25 mg/kg, i.p.) for 3 h. Abcc mRNA expression in brain microvessels was determined using quantitative real-time PCR. Nrf2 signaling activation was examined using an electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) respectively. Data were expressed as mean +/- SD and analyzed via ANOVA followed by the post hoc Bonferroni t test. Results: We observed increased microvascular expression of Abcc1, Abcc2, and Abcc4 mRNA following H/R treatment with reoxygenation times of 10 min, 30 min, and 1 h and in animals treated with sulforaphane. Using a biotinylated Nrf2 probe, we observed an upward band shift in brain microvessels isolated from H/R animals or animals administered sulforaphane. ChIP studies showed increased Nrf2 binding to antioxidant response elements on Abcc1, Abcc2, and Abcc4 promoters following H/R or sulforaphane treatment, suggesting a role for Nrf2 signaling in Abcc gene regulation. Conclusions: Our data show increased Abcc1, Abcc2, and Abcc4 mRNA expression at the BBB in response to H/R stress and that Abcc gene expression is regulated by Nrf2 signaling. Since these Mrp isoforms transport GSH, these results may point to endogenous transporters that can be targeted for BBB protection during H/R stress. Experiments are ongoing to examine functional implications of Nrf2-mediated increases in Abcc transcript expression. Such studies will determine utility of targeting Mrp isoforms for BBB protection in diseases with an H/R component.

Activation of the stress-responsive transcription factor NRF2 is the major line of defense to combat oxidative or electrophilic insults. Under basal conditions, NRF2 is continuously ubiquitylated by the KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex and is targeted to the proteasome for degradation ( the canonical mechanism). However, the path from the CUL3 complex to ultimate proteasomal degradation was previously unknown. p97 is a ubiquitin-targeted ATP-dependent segregase that extracts ubiquitylated client proteins from membranes, protein complexes, or chromatin and has an essential role in autophagy and the ubiquitin proteasome system ( UPS). In this study, we show that p97 negatively regulates NRF2 through the canonical pathway by extracting ubiquitylated NRF2 from the KEAP1-CUL3 E3 complex, with the aid of the heterodimeric cofactor UFD1/NPL4 and the UBA-UBX containing protein UBXN7, for efficient proteasomal degradation. Given the role of NRF2 in chemoresistance and the surging interest in p97 inhibitors to treat cancers, our results indicate that dual p97/NRF2 inhibitors may offer a more potent and long-term avenue of p97-targeted treatment.

CONTEXTE: Bien que la dysfunction mitochondriale et le stress oxydant jouent des rôles prépondérants dans plusieurs conditions pathologiques, ils n’ont pas été étudiés de façon extensive au niveau du tube digestif qui est constamment exposé aux oxydants (provenant de l’alimentation) et à divers agents pathogènes. L’ingestion simultanée de sels ferreux et d’acide ascorbique peut causer le dommage des macromolécules par oxydation. Le ‘’Nuclear factor erythroid 2 related factor’’ (Nrf2) est un important facteur de transcription sensible au potentiel redox et qui protège contre le stress oxydant en induisant des gènes anti-oxydants et de detoxification par sa liaison à l’élément de réponse antioxydante (ARE). Les fonctions anti-oxydantes et anti-inflammatoires de Nrf2 ont été décrites dans une variété de types cellulaires et de tissus. Cependant son rôle est très peu connu au niveau du tube digestif. OBJECTIFS: Les objectifs sont d’évaluer comment la peroxydation lipidique médiée par le fer/ascorbate (FE/ASC) affecte les fonctions mitochondriales dans les cellules Caco-2/15, et de déterminer l’ampleur de l’implication de Nrf2. MÉTHODES: Le stress oxydant a été induit dans les cellules Caco2/15 en les traitant avec 0.2mm/2mm de FE/ASC. L’augmentation de l’expression de Nrf2 a été obtenue suite au prétraitement des cellules Caco2/15 avec 50 μM d’Olitpraz (OPZ), un puissant activateur. L’invalidation du gène de Nrf2 a été réalisée dans les cellules par transfection avec un vecteur lentiviral contenant un shRNA contre Nrf2. RÉSULTATS: Nos résultats montrent que le traitement des cellules Caco-2/15 avec du FE/ASC (0.2 mm/2 mm) augmente les niveaux du malondialdehyde (MDA), réduit la production d’ATP, entraîne une surcharge mitochondriale de calcium, active l’expression protéique du cytochrome C et de l’AIF (apoptotic inducing factor), réduit l’activité des complexes I, II, 2 III et IV de la chaîne respiratoire mitochondriale, augmente les niveaux de 8-OHdG, un marqueur des dommages à l’ADN mitochondrial, diminue la DNA glycosylase, et altère les expressions génique et protéique des facteurs de transcription mitochondriaux (mtTFA, mtTFB1, mtTFB2). De plus, nos observations montrent que l’induction et l’activation de Nrf2 dans les cellules Caco-2/15 résultent en: une augmentation des enzymes anti-oxydantes endogènes (catalase, glutathion peroxydase, et superoxyde dismutase), une réduction du facteur nucléaire NFκβ et de TNF-α, une augmentation de la production d’ ATP et de l’activité des complexes respiratoires (I, II, III, IV) et de PGC-1α, et une régulation des niveaux de la prohibitine mitochondriale, du Bcl-2 anti-apoptotique et de l’occludine. CONCLUSION: Dans l’ensemble, nos résultats montrent que l’exposition aigüe des cellules Caco-2/15 à la peroxydation par le FE/ASC entraîne des effets pathologiques sur les fonctions mitochondriales et l’intégrité de l’ADN, qui sont abolis par l’induction de Nrf2. Il en ressort que Nrf2 joue un rôle majeur dans la protection de l’épithélium intestinal contre le stress oxydant. / Background: Although mitochondrial dysfunction and oxidative stress are key mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods and pathogens. Key among these is the simultaneous ingestion of iron salts and ascorbic acid, which can cause oxidative damage to macromolecules. The protein ‘’Nuclear factorerythroid 2- related factor’’ (Nrf2) is an important redox-sensitive transcription factor, which protects against oxidative stress by inducing antioxidant and detoxifying genes through binding with antioxidant response element (ARE). Many of Nrf2 antioxidant protective and anti-inflammatory functions have been established in various cells and tissues. However, limited information is available on its role in the gastrointestinal tract. Objectives: The objectives are to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation affects mitochondrion functioning in Caco-2/15 cells, and to mechanistically determine the role of Nrf2. Methods: Caco2/15 cells were treated with 0.2mm/2mm of FE/ASC to induce oxidative stress. To increase Nrf2 expression, cultured Caco2/15 cells were pre-treated with 50 μM Olitpraz (OPZ). To down regulate the Nrf2 function, Nrf2 gene was knocked down by transfecting Caco-2/15 cells with a pGFP-RS lentiviral vector containing shRNA against Nrf2. 4 RESULTS: Our results show that the treatment of Caco-2/15 cells with FE/ASC (0.2 mm/2 mm): increased the levels of malondialdehyde (MDA), a marker of oxidative stress; reduced ATP production; raised mitochondrial calcium content; regulated the protein expression of cytochrome C and apoptotic inducing factor (AIF); decreased mitochondrial respiratory chain complexes I, II, III and IV activity; prevented mtDNA damage as illustrated by the raised levels of 8-OHdG; lowered DNA Glycosylase, and altered the gene expression and protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2). Furthermore, our observations indicate that the induction and activation of Nrf2 in Caco2/15 cells resulted in an augmentated endogenous antioxidants enzymes (catalase, glutathione peroxidase, and superoxide dismutase), a reduction of nuclear factor-kappaB (NFκβ) and Tumor Necrosis Factor- Alpha (TNF-α), an increase in the ATP production, mitochondrial respiratory complexes (I, II, III, VI), PGC1α , and a regulation of the mitochondrial Prohibitin, anti-apoptotic Bcl-2 protein, and Occludin level. CONCLUSION: Findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation produces pathological effects on mitochondrial functions and DNA integrity, which were diminished by Nrf2 induction. It appears that Nrf2 plays a critical cytoprotective role in intestinal epithelial cells against oxidative stress.

京都大学 / 0048 / 新制・課程博士 / 博士(薬学) / 甲第22401号 / 薬博第839号 / 新制||薬||241(附属図書館) / 京都大学大学院薬学研究科薬学専攻 / (主査)教授 金子 周司, 教授 土居 雅夫, 教授 竹島 浩 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

Cancer, which is characterised by aggressiveness and increased capacity for metastatic spread still requires basic researchers and clinicians to direct enormous efforts toward the development of novel therapeutic targets. Potential novel targets can be identified and exploited in combination with currently existing therapeutic approaches to improve their efficacy and overcome treatment resistance of tumour cells, protecting the patient from recurrence. To achieve this, different strategies and techniques can be proposed to identify the most promising candidate molecules for further exploitation as therapeutic targets. Human epidermal growth factor receptors (HERs) and NF-E2-related factor 2 (NRF2) are regulators of cellular proliferation and determinants of cancer initiation and progression. NRF2 and HERs confer cancers with resistance to several therapeutic agents. Nevertheless, there is limited understanding of the regulation of HER expression and activation, and the link between NRF2 and HER signalling pathways. This research has demonstrated that pharmacological activation of NRF2 by tert-butyl hydroquinone (tBHQ) upregulates the expression of HER family receptors, HER1 and HER4, elevates phospho protein kinase B (pAKT) levels, and enhances the proliferation of ovarian cancer cells. Pharmacological inhibition using retinoic acid (RA) and bexarotene and genetic inhibition using small interfering RNA (siRNA), did the opposite. Further, tBHQ caused transcriptional induction of HER1 and HER4 with different levels of expression, while siRNA-mediated knockdown of NRF2 prevented this and further caused transcriptional repression. A panel of potent NRF2 inhibitors were screened with the hope of finding the most potent for further investigation. Bexarotene was found to be the most potent and was used either alone, or in combination with lapatinib or erlotinib. The use of these drugs in combination with bexarotene resulted in the repression of HER1, HER2, HER3 and HER4 expression, inhibition of NRF2, elevation of ROS, depletion of glutathione and enhanced cytotoxicity in PEO1, OVCAR3, SKOV3 and MCF7-AREc32 cell lines. This explained the crosstalk mechanism between HER receptor family and NRF2 and the role of NRF2 in drug resistance and as a relevant anti-cancer target which opens up novel avenues of targeting HER receptor kinase family and NRF2 pathways for improving cancer therapy.

Mastitis, the inflammation of the mammary gland by bacterial infection, is one of the costliest diseases to the dairy industry primarily due to a loss in milk production. The aim of this study was to investigate the mechanisms underlying reduced milk production during mastitis. We hypothesized that bacterial endotoxin induces cell apoptosis, oxidative stress and increases hypoxia while inhibiting milk gene expression in the mammary gland. To test this hypothesis, mice were bred to pregnancy, and 3 days post-partum the left and right sides of the 4th pair of mammary glands were alternately injected with either the endotoxin liposaccharide (LPS, E. coli 055:B5, 100 ul of 0.2 mg/ml) or sterile PBS through the teat meatus. At 10.5 and 22.5 h post-injection, pimonidazole HCl, a hypoxyprobe, was injected intraperitoneally. At 12 or 24 h after the LPS injection, the fourth glands were individually collected (n=8 pairs) and analyzed for hypoxia, gene expression and oxidative stress. LPS treatment induced mammary gland inflammation as shown by increases in inflammatory cytokine expression (P < 0.001) and neutrophil recruitment at 12 and 24 h. LPS promoted cell apoptosis in a transient manner; an abundance of cleaved caspase 3 was evident only at 12 h after LPS challenge (P = 0.02). Increased H2O2 content was seen at 12 h (P < 0.001) but decreased dramatically after 24 h of LPS treatment (P < 0.001). Total antioxidative capacity tended to decrease at both 12 and 24 h (P = 0.067 and 0.061, respectively). In agreement with these findings, LPS activated Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidative signaling in the mammary gland, demonstrated by increased expression of its target gene Nqo1 at 12 h (P = 0.05) and xCT at 24 h (P = 0.076). Hypoxyprobe staining, indicative of hypoxia, was greater in the alveoli of PBS-treated glands than LPS-treated glands at both 12 and 24 h. This suggests oxygen tension rises in response to LPS treatment. Conversely, milk expression genes, β-casein gene (CSN2) and α-lactalbumin (LALBA), were inhibited by LPS treatment across time. Expression of α-S1 casein (CSN1S1) mRNA increased with LPS treatment at 24 h, but protein expression was reduced at this same time point (P < 0.05). In summary, intramammary LPS challenge incurs inflammation, augments cell apoptosis, induces oxidative stress and activation of the Nrf2 antioxidation pathway, increases oxygen tension, and inhibits milk protein expression in the mammary gland. This study provides functional insight into mechanisms of reduced milk production during mastitis and provides possible approaches to combat reduction in milk production, such as enhancing the Nrf2-antioxidative signaling pathway and reducing inhibition of milk protein expression.

CONTEXTE: Bien que la dysfunction mitochondriale et le stress oxydant jouent des rôles prépondérants dans plusieurs conditions pathologiques, ils n’ont pas été étudiés de façon extensive au niveau du tube digestif qui est constamment exposé aux oxydants (provenant de l’alimentation) et à divers agents pathogènes. L’ingestion simultanée de sels ferreux et d’acide ascorbique peut causer le dommage des macromolécules par oxydation. Le ‘’Nuclear factor erythroid 2 related factor’’ (Nrf2) est un important facteur de transcription sensible au potentiel redox et qui protège contre le stress oxydant en induisant des gènes anti-oxydants et de detoxification par sa liaison à l’élément de réponse antioxydante (ARE). Les fonctions anti-oxydantes et anti-inflammatoires de Nrf2 ont été décrites dans une variété de types cellulaires et de tissus. Cependant son rôle est très peu connu au niveau du tube digestif. OBJECTIFS: Les objectifs sont d’évaluer comment la peroxydation lipidique médiée par le fer/ascorbate (FE/ASC) affecte les fonctions mitochondriales dans les cellules Caco-2/15, et de déterminer l’ampleur de l’implication de Nrf2. MÉTHODES: Le stress oxydant a été induit dans les cellules Caco2/15 en les traitant avec 0.2mm/2mm de FE/ASC. L’augmentation de l’expression de Nrf2 a été obtenue suite au prétraitement des cellules Caco2/15 avec 50 μM d’Olitpraz (OPZ), un puissant activateur. L’invalidation du gène de Nrf2 a été réalisée dans les cellules par transfection avec un vecteur lentiviral contenant un shRNA contre Nrf2. RÉSULTATS: Nos résultats montrent que le traitement des cellules Caco-2/15 avec du FE/ASC (0.2 mm/2 mm) augmente les niveaux du malondialdehyde (MDA), réduit la production d’ATP, entraîne une surcharge mitochondriale de calcium, active l’expression protéique du cytochrome C et de l’AIF (apoptotic inducing factor), réduit l’activité des complexes I, II, 2 III et IV de la chaîne respiratoire mitochondriale, augmente les niveaux de 8-OHdG, un marqueur des dommages à l’ADN mitochondrial, diminue la DNA glycosylase, et altère les expressions génique et protéique des facteurs de transcription mitochondriaux (mtTFA, mtTFB1, mtTFB2). De plus, nos observations montrent que l’induction et l’activation de Nrf2 dans les cellules Caco-2/15 résultent en: une augmentation des enzymes anti-oxydantes endogènes (catalase, glutathion peroxydase, et superoxyde dismutase), une réduction du facteur nucléaire NFκβ et de TNF-α, une augmentation de la production d’ ATP et de l’activité des complexes respiratoires (I, II, III, IV) et de PGC-1α, et une régulation des niveaux de la prohibitine mitochondriale, du Bcl-2 anti-apoptotique et de l’occludine. CONCLUSION: Dans l’ensemble, nos résultats montrent que l’exposition aigüe des cellules Caco-2/15 à la peroxydation par le FE/ASC entraîne des effets pathologiques sur les fonctions mitochondriales et l’intégrité de l’ADN, qui sont abolis par l’induction de Nrf2. Il en ressort que Nrf2 joue un rôle majeur dans la protection de l’épithélium intestinal contre le stress oxydant. / Background: Although mitochondrial dysfunction and oxidative stress are key mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods and pathogens. Key among these is the simultaneous ingestion of iron salts and ascorbic acid, which can cause oxidative damage to macromolecules. The protein ‘’Nuclear factorerythroid 2- related factor’’ (Nrf2) is an important redox-sensitive transcription factor, which protects against oxidative stress by inducing antioxidant and detoxifying genes through binding with antioxidant response element (ARE). Many of Nrf2 antioxidant protective and anti-inflammatory functions have been established in various cells and tissues. However, limited information is available on its role in the gastrointestinal tract. Objectives: The objectives are to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation affects mitochondrion functioning in Caco-2/15 cells, and to mechanistically determine the role of Nrf2. Methods: Caco2/15 cells were treated with 0.2mm/2mm of FE/ASC to induce oxidative stress. To increase Nrf2 expression, cultured Caco2/15 cells were pre-treated with 50 μM Olitpraz (OPZ). To down regulate the Nrf2 function, Nrf2 gene was knocked down by transfecting Caco-2/15 cells with a pGFP-RS lentiviral vector containing shRNA against Nrf2. 4 RESULTS: Our results show that the treatment of Caco-2/15 cells with FE/ASC (0.2 mm/2 mm): increased the levels of malondialdehyde (MDA), a marker of oxidative stress; reduced ATP production; raised mitochondrial calcium content; regulated the protein expression of cytochrome C and apoptotic inducing factor (AIF); decreased mitochondrial respiratory chain complexes I, II, III and IV activity; prevented mtDNA damage as illustrated by the raised levels of 8-OHdG; lowered DNA Glycosylase, and altered the gene expression and protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2). Furthermore, our observations indicate that the induction and activation of Nrf2 in Caco2/15 cells resulted in an augmentated endogenous antioxidants enzymes (catalase, glutathione peroxidase, and superoxide dismutase), a reduction of nuclear factor-kappaB (NFκβ) and Tumor Necrosis Factor- Alpha (TNF-α), an increase in the ATP production, mitochondrial respiratory complexes (I, II, III, VI), PGC1α , and a regulation of the mitochondrial Prohibitin, anti-apoptotic Bcl-2 protein, and Occludin level. CONCLUSION: Findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation produces pathological effects on mitochondrial functions and DNA integrity, which were diminished by Nrf2 induction. It appears that Nrf2 plays a critical cytoprotective role in intestinal epithelial cells against oxidative stress.

Τα ευεργετικά αποτελέσματα των αναστολέων της αναγωγάσης του HMG-CoA (3-υδροξυ-3-μεθυλ-γλουταρυλ-συνένζυμο Α) έχουν αποδοθεί όχι μόνο στη μείωση των επιπέδων χοληστερόλης αλλά και στις πλειοτροπικές τους δράσεις και ιδιαίτερα στις αντιοξειδωτικές τους δράσεις. Ο Nrf2 (NF-E2-related factor 2) είναι ένας μεταγραφικός παράγοντας που ενορχηστρώνει τη μεταγραφική απάντηση των κυττάρων στο οξειδωτικό στρες και σε ηλεκτροφιλικά ξενοβιοτικά με την έκφραση αντιοξειδωτικών-κυτταροπροστατευτικών γονιδίων. Στην παρούσα μελέτη, χρησιμοποιήθηκαν επίμυες Wistar, πρωτογενείς καλλιέργειες ηπατοκυττάρων, ST-2 κύτταρα και πρωτογενείς εμβρυϊκοί ινοβλάστες από μυς C57BL6J αγρίου τύπου (WT) ή με απαλοιφή του Nrf2 (KO-Nrf2) για τη μελέτη του ρόλου του Nrf2 στη διαμεσολάβηση των αντιοξειδωτικών δράσεων των στατινών. Η σιμβαστατίνη ενεργοποίησε τον Nrf2, δηλαδή οδήγησε στη μετακίνησή του στον πυρήνα στο ήπαρ επίμυων και σε πρωτογενή καλλιέργεια ηπατοκυττάρων. Η ανωτέρω δράση ήταν εξαρτώμενη από το μεβαλονικό και ανεξάρτητη από τη χοληστερόλη. Σε πυρηνικά πρωτεϊνικά εκχυλίσματα από ήπαρ επίμυων που έλαβαν σιμβαστατίνη, η μεταγραφική ενεργότητα του Nrf2 αυξήθηκε σημαντικά και το mRNA δύο γνωστών στόχων του Nrf2, ΗΟ-1 (Heme Oxygenase 1) και GPX-2 (Glutathione Peroxidase 2) αυξήθηκε. Σε ST-2 κύτταρα μόνιμα διαμολυσμένα με πλασμίδιο που φέρει αλληλουχία DNA στην οποία προσκολλάται ο Nrf2 (ARE-Antioxidant Response Element) (ARE-ST2 κύτταρα), η σιμβαστατίνη αύξησε τη μεταγραφική ενεργότητα του Nrf2 με τρόπο εξαρτώμενο από το μεβαλονικό και ανεξάρτητο από τη χοληστερόλη. Επίσης, χρησιμοποιώντας πρωτογενείς καλλιέργειες εμβρυϊκών ινοβλαστών από μυς WT και ΚΟ-Nrf2 και μετρώντας τα επίπεδα των αντιδραστικών ειδών οξυγόνου (ROS) μετά από επώαση με οξειδάση της γλυκόζης έπειτα από επίδραση ή μη με σιμβαστατίνη, διαπιστώθηκε ότι η σιμβαστατίνη μειώνει τα επίπεδα των παραχθέντων ROS στους WT ινοβλάστες και όχι σε μεγάλο βαθμό στους KO-Nrf2 ινοβλάστες Τέλος, με τη χρήση αναστολέων του μονοπατιού της PI3K/Akt σε ARE-ST2 κύτταρα στα οποία είχαμε επιδράσει με σιμβαστατίνη, διαπιστώθηκε ότι αίρεται σε μεγάλο βαθμό η ενεργοποίηση του Nrf2 από τη σιμβαστατίνη. Στην παρούσα μελέτη παρουσιάζεται για πρώτη φορά α) η ενεργοποίηση του Keap1/Nrf2 σηματοδοτικού μονοπατιού σε in vivo και in vitro μοντέλα από τη σιμβαστατίνη με τρόπο εξαρτώμενο από το μεβαλονικό και ανεξάρτητο από τη χοληστερόλη και β) ότι η σιμβαστατίνη μειώνει τα παραγόμενα αντιδραστικά είδη οξυγόνου (ROS) μέσω της ενεργοποίησης του Nrf2 διαμέσου του μοριακού μονοπατιού της PI3K/Akt. H ενεργοποίηση αυτή του Nrf2 από τη σιμβαστατίνη εκτός του ότι προσφέρει αποτελεσματική προστασία του κυττάρου από τις δυσμενείς επιπτώσεις του οξειδωτικού στρες, εξηγεί και μέρος των πλειοτροπικών δράσεων των στατινών. / The beneficial effects of HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase inhibitors (statins) have been attributed not only to their cholesterol lowering effect but also to their pleiotropic actions and especially to their anti-oxidant activity. Nrf2 (NF-E2-related factor 2) is a transcription factor that orchestrates the transcriptional response of cells to oxidative stressors and electrophilic xenobiotics. In the present study, Wistar rats, primary hepatocytes, ST-2 cells and primary mouse embryonic fibroblasts from wild type or Nrf2 knock out C57BL6J mice were used to explore the potential role of Nrf2 in mediating the antioxidant effects of statins. Simvastatin triggered nuclear translocation of Nrf2 in rat liver and in primary rat hepatocytes in a mevalonate-dependent and cholesterol-independent way. In liver nuclear extracts from simvastatin-treated rats, the DNA-binding activity of Nrf2 was significantly increased and the mRNA of two known targets of Nrf2, HO-1 (Heme Oxygenase 1) and GPX-2 (Glutathione Peroxidase 2) was induced. In ST-2 cells (ARE-ST2) stably transfected with constructs bearing Nrf2-binding site (antioxidant responsive element), simvastatin enhanced Nrf2-mediated transcriptional activity in a mevalonate-dependent and cholesterol-independent fashion. Moreover, in WT and KO-Nrf2 primary mouse embryonic fibroblasts, after incubation with simvastatin, the addition of glucose-oxidase resulted in much greater levels of ROS (Reactive Oxygen Species) in simvastatin treated KO-Nrf2 fibroblasts compared to their WT counterparts, which means that simvastatin eliminates ROS in a Nrf2 dependent way. Finally, the use of PI3K/Akt pathway inhibitors in simvastatin treated ARE-ST2 cells leads to the attenuation of the simvastatin-induced enhanced Nrf2 transcriptional activity. In the present study, it is shown for the first time that a) simvastatin activates the Keap1/Nrf2 signaling pathway in in vivo and in vitro models in a mevalonate- dependent, cholesterol-independent fashion and b) that simvastatin lowers reactive oxygen species level by Nrf2 activation via PI3K/Akt pathway. The activation of Nrf2 by simvastatin besides providing effective protection of the cell from the deleterious effects of oxidative stress, it explains in part the pleiotropic actions of statins.