Mitochondrial function in human neuroblastoma cells is up-regulated and protected by NQO1, a plasma membrane redox enzyme

NQO1 polymorphism and susceptibility to ischemic stroke in a Chinese population

BACKGROUND

Ischemic stroke (IS) is a major cause of death and disability worldwide. Genetic factors are important risk factors for the development of IS. The quinone oxidoreductase 1 gene (NQO1) has antioxidant, anti-inflammatory, and cytoprotective properties. Thus, in this study, we investigated the relationship between NQO1 gene polymorphism and the risk of IS.

METHODS

Peripheral blood was collected from 143 patients with IS and 124 the control groups in Yunnan, China, and NQO1 rs2917673, rs689455, and rs1800566 were genotyped. Logistic regression was used to analyze the relationship between the three NQO1 loci and IS susceptibility. The difference in the expression levels of NQO1 between the control groups and IS groups was verified using public databases and enzyme-linked immunosorbent assay.

RESULTS

The rs2917673 locus increased the risk of IS by 2.375 times in TT genotype carriers under the co-dominance model compared with CC carriers and was statistically associated with the risk of IS (OR = 2.375, 95% CI = 1.017-5.546, P = 0.046). In the recessive model, TT genotype carriers increased IS risk by 2.407 times compared with CC/CT carriers and were statistically associated with the risk of IS (OR = 2.407, 95% CI = 1.073-5.396, P = 0.033).

CONCLUSIONS

NQO1 rs2917673 polymorphism is significantly associated with IS. Mutant TT carriers are risk factors for IS.

NAD(P)H-quinone oxidoreductase 1 induces complicated effects on mitochondrial dysfunction and ferroptosis in an expression level-dependent manner

NAD(P)H-quinone oxidoreductase 1 (NQO1) is an essential redox enzyme responsible for redox balance and energy metabolism. Despite of its importance, the brain contains high capacity of polyunsaturated fatty acids and maintains low levels of NQO1 expression. In this study, we examined how levels of NQO1 expression affects cell survival in response to toxic insults causing mitochondrial dysfunction and ferroptosis, and whether NQO1 has a potential as a biomarker in different stressed conditions. Following treatment with rotenone, overexpressed NQO1 in SH-SY5Y cells improved cell survival by reducing mitochondrial reductive stress via increased NAD+ supply without mitochondrial biogenesis. However, NQO1 overexpression boosted lipid peroxidation following treatment with RSL3 and erastin. A lipid droplet staining assay showed increased lipid droplets in cells overexpressing NQO1. In contrast, NQO1 knockdown protected cells against ferroptosis by increasing GPX4, xCT, and the GSH/GSSG system. Also, NQO1 knockdown showed lower iron contents and lipid droplets than non-transfectants and cells overexpressing NQO1, even though it could not attenuate cell death when exposed to rotenone. In summary, our study suggests that different NQO1 levels may have advantages and disadvantages depending on the surrounding environments. Thus, regulating NQO1 expression could be a potential supplementary tool when treating neuronal diseases.

A New Quinone-Based Inhibitor of Mitochondrial Complex I in D-Conformation, Producing Invasion Reduction and Sensitization to Venetoclax in Breast Cancer Cells

Mitochondrial Complex I plays a crucial role in the proliferation, chemoresistance, and metastasis of breast cancer (BC) cells. This highlights it as an attractive target for anti-cancer drugs. Using submitochondrial particles, we identified FRV-1, an ortho-carbonyl quinone, which inhibits NADH:duroquinone activity in D-active conformation and reduces the 3ADP state respiration dependent on Complex I, causing mitochondrial depolarization, ATP drop, increased superoxide levels, and metabolic remodeling towards glycolysis in BC cells. Introducing methyl groups at FRV-1 structure produced analogs that acted as electron acceptors at the Complex I level or increased the inhibitory effect of FCCP-stimulated oxygen consumption rate, which correlated with their redox potential, but increased toxicity on RMF-621 human breast fibroblasts was observed. FRV-1 was inactive in the naphthoquinone oxidoreductase 1 (NOQ1)-positive BC cell line, MCF7, but the sensitivity was recovered by dicoumarol, a NOQ1 inhibitor, suggesting that FRV-1 is a NOQ1 substrate. Importantly, FRV-1 selectively inhibited the proliferation, migration, and invasion of NQO1 negative BC cell, MDA-MB-231, in an OXPHOS- and ROS-dependent manner and sensitized it to the BH3 mimetic drug venetoclax. Overall, FRV-1 is a novel Complex I inhibitor in D-active conformation, blocking possibly the re-activation to A-state, producing selective anti-cancer effects in NQO1-negative BC cell lines.

NRF2: A crucial regulator for mitochondrial metabolic shift and prostate cancer progression

Metabolic alterations are a common survival mechanism for prostate cancer progression and therapy resistance. Oxidative stress in the cellular and tumor microenvironment dictates metabolic switching in the cancer cells to adopt, prosper and escape therapeutic stress. Therefore, regulation of oxidative stress in tumor cells and in the tumor-microenvironment may enhance the action of conventional anticancer therapies. NRF2 is the master regulator for oxidative stress management. However, the overall oxidative stress varies with PCa clinical stage, metabolic state and therapy used for the cancer. In agreement, the blanket use of NRF2 inducers or inhibitors along with anticancer therapies cause adverse effects in some preclinical cancer models. In this review, we have summarized the levels of oxidative stress, metabolic preferences and NRF2 activity in the different stages of prostate cancer. We also propose condition specific ways to use NRF2 inducers or inhibitors along with conventional prostate cancer therapies. The significance of this review is not only to provide a detailed understanding of the mechanism of action of NRF2 to regulate oxidative stress-mediated metabolic switching by prostate cancer cells to escape the radiation, chemo, or hormonal therapies, and to grow aggressively, but also to provide a potential therapeutic method to control aggressive prostate cancer growth by stage specific proper use of NRF2 regulators.

β-Lapachone, an NQO1 activator, alleviates diabetic cardiomyopathy by regulating antioxidant ability and mitochondrial function

BACKGROUND

Diabetic cardiomyopathy (DC) is one of the major lethal complications in patients with diabetes mellitus (DM); however, no specific strategy for preventing or treating DC has been identified.

PURPOSE

This study aimed to investigate the effects of β-lapachone (Lap), a natural compound that increases antioxidant activity in various tissues, on DC and explore the underlying mechanisms.

STUDY DESIGN AND METHODS

As an in vivo model, C57BL/6 mice were fed with the high-fat diet (HF) for 10 weeks to induce type 2 DM. Mice were fed Lap with the HF or after 5 weeks of HF treatment to investigate the protective effects of Lap against DC.

RESULTS

In the two in vivo models, Lap decreased heart weight, increased heart function, reduced oxidative stress, and elevated mitochondrial content under the HF. In the in vitro model, palmitic acid (PA) was used to mimic the effects of an HF on the differentiated-cardiomyoblast cell line H9c2. The results demonstrated that Lap reduced PA-induced ROS production by increasing the expression of antioxidant regulators and enzymes, inhibiting inflammation, increasing mitochondrial activity, and thus reducing cell damage. Via the use of specific inhibitors and siRNA, the protective effects of Lap were determined to be mediated mainly by NQO1, Sirt1 and mitochondrial activity.

CONCLUSION

Heart damage in DM is usually caused by excessive oxidative stress. This study showed that Lap can protect the heart from DC by upregulating antioxidant ability and mitochondrial activity in cardiomyocytes. Lap has the potential to serve as a novel therapeutic agent for both the prevention and treatment of DC.

A New Insight into an Alternative Therapeutic Approach to Restore Redox Homeostasis and Functional Mitochondria in Neurodegenerative Diseases

Neurodegenerative diseases are accompanied by oxidative stress and mitochondrial dysfunction, leading to a progressive loss of neuronal cells, formation of protein aggregates, and a decrease in cognitive or motor functions. Mitochondrial dysfunction occurs at the early stage of neurodegenerative diseases. Protein aggregates containing oxidatively damaged biomolecules and other misfolded proteins and neuroinflammation have been identified in animal models and patients with neurodegenerative diseases. A variety of neurodegenerative diseases commonly exhibits decreased activity of antioxidant enzymes, lower amounts of antioxidants, and altered cellular signalling. Although several molecules have been approved clinically, there is no known cure for neurodegenerative diseases, though some drugs are focused on improving mitochondrial function. Mitochondrial dysfunction is caused by oxidative damage and impaired cellular signalling, including that of peroxisome proliferator-activated receptor gamma coactivator 1α. Mitochondrial function can also be modulated by mitochondrial biogenesis and the mitochondrial fusion/fission cycle. Mitochondrial biogenesis is regulated mainly by sirtuin 1, NAD⁺, AMP-activated protein kinase, mammalian target of rapamycin, and peroxisome proliferator-activated receptor γ. Altered mitochondrial dynamics, such as increased fission proteins and decreased fusion products, are shown in neurodegenerative diseases. Due to the restrictions of a target-based approach, a phenotype-based approach has been performed to find novel proteins or pathways. Alternatively, plasma membrane redox enzymes improve mitochondrial function without the further production of reactive oxygen species. In addition, inducers of antioxidant response elements can be useful to induce a series of detoxifying enzymes. Thus, redox homeostasis and metabolic regulation can be important therapeutic targets for delaying the progression of neurodegenerative diseases.

The upregulation of Nur77 decreases ketamine-induced hippocampal neurons toxicity in rats

Ketamine is clinically used as a narcotic. However, ketamine has certain deficits and produces toxicity to neurons. As a member of the NR4A receptor subfamily, Nur77 decreases neurodegenerative disorders. The study aims to investigate the effects of upregulated Nur77 on ketamine-induced rat hippocampal neurons damage and the active mechanism. Neurons were obtained from rat hippocampal and identified by immunofluorescence assays. The treatment groups contained ketamine group, Nur77 group, ketamine + Nur77 group and ketamine + L-cam group. Neurons apoptosis and reactive oxygen species (ROS) were determined by a related kit using flow cytometry. Enzyme NAD(P)H quinone oxidoreductase 1 (NQO1), enzyme heme oxygenase 1 (HO1), Nur77, the expression of Bax, Bcl-2 and cleaved-caspase-3 and inflammatory cytokines were measured using western blot assays and reverse transcription-quantitative PCR (RT-qPCR) assays. Ketamine-induced neurons apoptosis; however, Nur77 decreased ketamine-induced neurons apoptosis. A low level of ROS was observed in two combination groups. Neurons treated by ketamine only had the lowest levels of Nur77, NQO1 and HO1, compared with other treatment groups. The levels of Bax and cleaved-caspase-3 in two combination groups were lower than those in the ketamine group. Furthermore, the ketamine group had higher levels of tumor necrosis factor alpha, IL-1β and IL-6 but the lowest level of IL-4. Upregulated Nur77 reduced the ketamine-induced toxicity in neurons. The mechanism of Nur77 involved antioxidation, apoptosis signaling pathway and inflammation signaling pathway. Our study provides a novel therapy that could attenuate ketamine-induced toxicity.

Cooperation between CYB5R3 and NOX4 via coenzyme Q mitigates endothelial inflammation

NADPH oxidase 4 (NOX4) regulates endothelial inflammation by producing hydrogen peroxide (H₂O₂) and to a lesser extent O₂^•-. The ratio of NOX4-derived H₂O₂ and O₂^•- can be altered by coenzyme Q (CoQ) mimics. Therefore, we hypothesize that cytochrome b5 reductase 3 (CYB5R3), a CoQ reductase abundant in vascular endothelial cells, regulates inflammatory activation. To examine endothelial CYB5R3 in vivo, we created tamoxifen-inducible endothelium-specific Cyb5r3 knockout mice (R3 KO). Radiotelemetry measurements of systolic blood pressure showed systemic hypotension in lipopolysaccharides (LPS) challenged mice, which was exacerbated in R3 KO mice. Meanwhile, LPS treatment caused greater endothelial dysfunction in R3 KO mice, evaluated by acetylcholine-induced vasodilation in the isolated aorta, accompanied by elevated mRNA expression of vascular adhesion molecule 1 (Vcam-1). Similarly, in cultured human aortic endothelial cells (HAEC), LPS and tumor necrosis factor α (TNF-α) induced VCAM-1 protein expression was enhanced by Cyb5r3 siRNA, which was ablated by silencing the Nox4 gene simultaneously. Moreover, super-resolution confocal microscopy indicated mitochondrial co-localization of CYB5R3 and NOX4 in HAECs. APEX2-based electron microscopy and proximity biotinylation also demonstrated CYB5R3's localization on the mitochondrial outer membrane and its interaction with NOX4, which was further confirmed by the proximity ligation assay. Notably, Cyb5r3 knockdown HAECs showed less total H₂O₂ but more mitochondrial O₂^•-. Using inactive or non-membrane bound active CYB5R3, we found that CYB5R3 activity and membrane translocation are needed for optimal generation of H₂O₂ by NOX4. Lastly, cells lacking the CoQ synthesizing enzyme COQ6 showed decreased NOX4-derived H₂O₂, indicating a requirement for endogenous CoQ in NOX4 activity. In conclusion, CYB5R3 mitigates endothelial inflammatory activation by assisting in NOX4-dependent H₂O₂ generation via CoQ.

Idebenone Ameliorates Rotenone-Induced Parkinson's Disease in Rats Through Decreasing Lipid Peroxidation

Oxidative stress is considered one of the mechanisms responsible for neurodegenerative diseases, especially for Parkinson's disease. Since oxidative stress causes pathological changes in neuronal structures antioxidant compounds gained significant attention the last decades. Although several antioxidant compounds showed neuroprotective actions in Parkinson's disease models, only a few of them demonstrated protective effects against loss of striatal dopaminergic neurons. Idebenone is an analog of the well-known antioxidant compound coenzyme Q10 (CoQ10). Clinical safety of idebenone is well described, and due to its high antioxidant capacity currently used to treat Freidrich's ataxia and Alzheimer's disease. Like Parkinson's disease, these diseases are characterized by oxidative stress and impaired mitochondrial balance in neurons. However, knowledge about the effects of idebenone on Parkinson's disease is limited. Therefore, in this study we aimed to investigate and delineate the possible effects of idebenone in rotenone-induced Parkinson's disease models. Idebenone (200 mg/kg, p.o.) inhibited the decrease of striatal expression of NAD(P)H dehydrogenase[quinone]-1, which is an essential element for mitochondrial respiration. Idebenone decreased the striatal levels of the lipid peroxidation products and increased the expression of glutathione peroxidase-4 (GPx-4), which is primarily known for lipid peroxidation and ferroptosis. Furthermore, idebenone mitigated motor impairment and increased tyrosine hydroxylase-positive neuron survival. Together our results thus indicate that that idebenone has protective effects against a rotenone insult with pleiotropic actions on the cellular oxidative enzymes and lipid peroxidation.

Docosahexanoic acid signals through the Nrf2-Nqo1 pathway to maintain redox balance and promote neurite outgrowth

Evidence suggests that n-3 polyunsaturated fatty acids may act as activators of the Nrf2 antioxidant pathway. The antioxidant response, in turn, promotes neuronal differentiation and neurite outgrowth. Nrf2 has recently been suggested to be a cell intrinsic mediator of docosohexanoic acid (DHA) signaling. In the current study, we assessed whether DHA-mediated axodendritic development was dependent on activation of the Nrf2 pathway and whether Nrf2 protected from agrochemical-induced neuritic retraction. Expression profiling of the DHA-enriched Fat-1 mouse brain relative to wild type showed a significant enrichment of genes associated with neuronal development and neuronal projection and genes associated with the Nrf2-transcriptional pathway. Moreover, we found that primary cortical neurons treated with DHA showed a dose-dependent increase in Nrf2 transcriptional activity and Nrf2-target gene expression. DHA-mediated activation of Nrf2 promoted neurite outgrowth and inhibited oxidative stress-induced neuritic retraction evoked by exposure to agrochemicals. Finally, we provide evidence that this effect is largely dependent on induction of the Nrf2-target gene NAD(P)H: (quinone acceptor) oxidoreductase 1 (NQO1), and that silencing of either Nrf2 or Nqo1 blocks the effects of DHA on the axodendritic compartment. Collectively, these data support a role for the Nrf2-NQO1 pathway in DHA-mediated axodendritic development and protection from agrochemical exposure.

Increasing Nrf2 Activity as a Treatment Approach in Neuropsychiatry

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor encoded by NFE2L2. Under oxidative stress, Nrf2 does not undergo its normal cytoplasmic degradation but instead travels to the nucleus, where it binds to a DNA promoter and initiates transcription of anti-oxidative genes. Nrf2 upregulation is associated with increased cellular levels of glutathione disulfide, glutathione peroxidase, glutathione transferases, thioredoxin and thioredoxin reductase. Given its key role in governing the cellular antioxidant response, upregulation of Nrf2 has been suggested as a common therapeutic target in neuropsychiatric illnesses such as major depressive disorder, bipolar disorder and schizophrenia, which are associated with chronic oxidative and nitrosative stress, characterised by elevated levels of reactive oxygen species, nitric oxide and peroxynitrite. These processes lead to extensive lipid peroxidation, protein oxidation and carbonylation, and oxidative damage to nuclear and mitochondrial DNA. Intake of N-acetylcysteine, coenzyme Q₁₀ and melatonin is accompanied by increased Nrf2 activity. N-acetylcysteine intake is associated with improved cerebral mitochondrial function, decreased central oxidative and nitrosative stress, reduced neuroinflammation, alleviation of endoplasmic reticular stress and suppression of the unfolded protein response. Coenzyme Q₁₀, which acts as a superoxide scavenger in neuroglial mitochondria, instigates mitohormesis, ameliorates lipid peroxidation in the inner mitochondrial membrane, activates uncoupling proteins, promotes mitochondrial biogenesis and has positive effects on the plasma membrane redox system. Melatonin, which scavenges mitochondrial free radicals, inhibits mitochondrial nitric oxide synthase, restores mitochondrial calcium homeostasis, deacetylates and activates mitochondrial SIRT3, ameliorates increased permeability of the blood-brain barrier and intestine and counters neuroinflammation and glutamate excitotoxicity.

Antimycin A shows selective antiproliferation to oral cancer cells by oxidative stress-mediated apoptosis and DNA damage

The antibiotic antimycin A (AMA) is commonly used as an inhibitor for the electron transport chain but its application in anticancer studies is rare. Recently, the repurposing use of AMA in antiproliferation of several cancer cell types has been reported. However, it is rarely investigated in oral cancer cells. The purpose of this study is to investigate the selective antiproliferation ability of AMA treatment on oral cancer cells. Cell viability, flow cytometry, and western blotting were applied to explore its possible anticancer mechanism in terms of both concentration- and exposure time-effects. AMA shows the higher antiproliferation to two oral cancer CAL 27 and Ca9-22 cell lines than normal oral HGF-1 cell lines. Moreover, AMA induces the production of higher reactive oxygen species (ROS) levels and pan-caspase activation in oral cancer CAL 27 and Ca9-22 cells than in normal oral HGF-1 cells, providing the possible mechanism for its selective antiproliferation effect of AMA. In addition to ROS, AMA induces mitochondrial superoxide (MitoSOX) generation and depletes mitochondrial membrane potential (MitoMP). This further supports the AMA-induced oxidative stress changes in oral cancer CAL 27 and Ca9-22 cells. AMA also shows high expressions of annexin V in CAL 27 and Ca9-22 cells and cleaved forms of poly (ADP-ribose) polymerase (PARP), caspase 9, and caspase 3 in CAL 27 cells, supporting the apoptosis-inducing ability of AMA. Furthermore, AMA induces DNA damage (γH2AX and 8-oxo-2'-deoxyguanosine [8-oxodG]) in CAL 27 and Ca9-22 cells. Notably, the AMA-induced selective antiproliferation, oxidative stress, and DNA damage were partly prevented from N-acetylcysteine (NAC) pretreatments. Taken together, AMA selectively kills oral cancer cells in an oxidative stress-dependent mechanism involving apoptosis and DNA damage.

Insights into the New Cancer Therapy through Redox Homeostasis and Metabolic Shifts

Modest levels of reactive oxygen species (ROS) are necessary for intracellular signaling, cell division, and enzyme activation. These ROS are later eliminated by the body’s antioxidant defense system. High amounts of ROS cause carcinogenesis by altering the signaling pathways associated with metabolism, proliferation, metastasis, and cell survival. Cancer cells exhibit enhanced ATP production and high ROS levels, which allow them to maintain elevated proliferation through metabolic reprograming. In order to prevent further ROS generation, cancer cells rely on more glycolysis to produce ATP and on the pentose phosphate pathway to provide NADPH. Pro-oxidant therapy can induce more ROS generation beyond the physiologic thresholds in cancer cells. Alternatively, antioxidant therapy can protect normal cells by activating cell survival signaling cascades, such as the nuclear factor erythroid 2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway, in response to radio- and chemotherapeutic drugs. Nrf2 is a key regulator that protects cells from oxidative stress. Under normal conditions, Nrf2 is tightly bound to Keap1 and is ubiquitinated and degraded by the proteasome. However, under oxidative stress, or when treated with Nrf2 activators, Nrf2 is liberated from the Nrf2-Keap1 complex, translocated into the nucleus, and bound to the antioxidant response element in association with other factors. This cascade results in the expression of detoxifying enzymes, including NADH-quinone oxidoreductase 1 (NQO1) and heme oxygenase 1. NQO1 and cytochrome b5 reductase can neutralize ROS in the plasma membrane and induce a high NAD⁺/NADH ratio, which then activates SIRT1 and mitochondrial bioenergetics. NQO1 can also stabilize the tumor suppressor p53. Given their roles in cancer pathogenesis, redox homeostasis and the metabolic shift from glycolysis to oxidative phosphorylation (through activation of Nrf2 and NQO1) seem to be good targets for cancer therapy. Therefore, Nrf2 modulation and NQO1 stimulation could be important therapeutic targets for cancer prevention and treatment.

Fast Noninvasive Measurement of Brown Adipose Tissue in Living Mice by Near-Infrared Fluorescence and Photoacoustic Imaging

Aberrant brown adipose tissue (BAT) metabolism is linked to obesity as well as other metabolic disorders. However, the paucity of imaging tools limits the study of in vivo BAT metabolism in animal models. The current work evaluated a heptamethine dye (CyHF-8) in living mice as a dual-modality BAT-avid molecular probe for two imaging approaches, including near-infrared fluorescence imaging (NIRF) and photoacoustic imaging (PAI). CyHF-8 exhibited favorable spectral properties in the near-infrared window (786/787/805 nm) and accumulated in the subcellular mitochondria of brown adipocytes. After intravenous injection of CyHF-8, NIRF and PAI were both capable of noninvasively detecting interscapular BAT at early time points in living mice. Quantitative analysis of NIRF and PAI images showed that CyHF-8 signals respond to dynamic BAT changes in mice stimulated by norepinephrine (NE) and in diabetic mice induced by streptozotocin (STZ). In summary, dual-modality NIRF/PAI probe CyHF-8 can be used for both NIRF and PAI to noninvasively assess BAT metabolism in living animals.

Loss of NQO1 generates genotoxic estrogen-DNA adducts in Fuchs Endothelial Corneal Dystrophy

Fuchs Endothelial Corneal Dystrophy (FECD) is an age-related genetically complex disease characterized by increased oxidative DNA damage and progressive degeneration of corneal endothelial cells (HCEnCs). FECD has a greater incidence and advanced phenotype in women, suggesting a possible role of hormones in the sex-driven differences seen in the disease pathogenesis. In this study, catechol estrogen (4-OHE2), the byproduct of estrogen metabolism, induced genotoxic estrogen-DNA adducts formation, macromolecular DNA damage, and apoptotic cell death in HCEnCs; these findings were potentiated by menadione (MN)-mediated reactive oxygen species (ROS). Expression of NQO1, a key enzyme that neutralizes reactive estrogen metabolites, was downregulated in FECD, indicating HCEnC susceptibility to reactive estrogen metabolism in FECD. NQO1 deficiency in vitro exacerbated the estrogen-DNA adduct formation and loss of cell viability, which was rescued by the supplementation of N-acetylcysteine, a ROS scavenger. Notably, overexpression of NQO1 in HCEnCs treated with MN and 4-OHE2 quenched the ROS formation, thereby reducing the DNA damage and endothelial cell loss. This study signifies a pivotal role for NQO1 in mitigating the macromolecular oxidative DNA damage arising from the interplay between intracellular ROS and impaired endogenous estrogen metabolism in post-mitotic ocular tissue cells. A dysfunctional Nrf2-NQO1 axis in FECD renders HCEnCs susceptible to catechol estrogens and estrogen-DNA adducts formation. This novel study highlights the potential role of NQO1-mediated estrogen metabolite genotoxicity in explaining the higher incidence of FECD in females.

Mitohormesis in Mice via Sustained Basal Activation of Mitochondrial and Antioxidant Signaling

Transient mitochondrial stress can promote beneficial physiological responses and longevity, termed "mitohormesis." To interrogate mitohormetic pathways in mammals, we generated mice in which mitochondrial superoxide dismutase 2 (SOD2) can be knocked down in an inducible and reversible manner (iSOD2-KD mice). Depleting SOD2 only during embryonic development did not cause post-natal lethality, allowing us to probe adaptive responses to mitochondrial oxidant stress in adult mice. Liver from adapted mice had increased mitochondrial biogenesis and antioxidant gene expression and fewer reactive oxygen species. Gene expression analysis implicated non-canonical activation of the Nrf2 antioxidant and PPARγ/PGC-1α mitochondrial signaling pathways in this response. Transient SOD2 knockdown in embryonic fibroblasts from iSOD2-KD mice also resulted in adaptive mitochondrial changes, enhanced antioxidant capacity, and resistance to a subsequent oxidant challenge. We propose that mitohormesis in response to mitochondrial oxidative stress in mice involves sustained activation of mitochondrial and antioxidant signaling pathways to establish a heightened basal antioxidant state.

Isothiocyanate from Moringa oleifera seeds mitigates hydrogen peroxide-induced cytotoxicity and preserved morphological features of human neuronal cells

Reactive oxygen species are well known for induction of oxidative stress conditions through oxidation of vital biomarkers leading to cellular death via apoptosis and other process, thereby causing devastative effects on the host organs. This effect is believed to be linked with pathological alterations seen in several neurodegenerative disease conditions. Many phytochemical compounds proved to have robust antioxidant activities that deterred cells against cytotoxic stress environment, thus protect apoptotic cell death. In view of that we studied the potential of glucomoringin-isothiocyanate (GMG-ITC) or moringin to mitigate the process that lead to neurodegeneration in various ways. Neuroprotective effect of GMG-ITC was performed on retinoic acid (RA) induced differentiated neuroblastoma cells (SHSY5Y) via cell viability assay, flow cytometry analysis and fluorescence microscopy by means of acridine orange and propidium iodide double staining, to evaluate the anti-apoptotic activity and morphology conservation ability of the compound. Additionally, neurite surface integrity and ultrastructural analysis were carried out by means of scanning and transmission electron microscopy to assess the orientation of surface and internal features of the treated neuronal cells. GMG-ITC pre-treated neuron cells showed significant resistance to H₂O₂-induced apoptotic cell death, revealing high level of protection by the compound. Increase of intracellular oxidative stress induced by H₂O₂ was mitigated by GMG-ITC. Thus, pre-treatment with the compound conferred significant protection to cytoskeleton and cytoplasmic inclusion coupled with conservation of surface morphological features and general integrity of neuronal cells. Therefore, the collective findings in the presence study indicated the potentials of GMG-ITC to protect the integrity of neuron cells against induced oxidative-stress related cytotoxic processes, the hallmark of neurodegenerative diseases.

Dihydroartemisinin inhibits the viability of cervical cancer cells by upregulating caveolin 1 and mitochondrial carrier homolog 2: Involvement of p53 activation and NAD(P)H:quinone oxidoreductase 1 downregulation

Dihydroartemisinin (DHA) has been shown to inhibit the viability of various cancer cells. Previous studies have revealed that the mechanisms involved in the inhibitory effects of DHA are based on theactivation of p53 and the mitochondrial-related cell death pathway. However, the exact association between upstream signaling and the activation of cell death pathway remains unclear. In this study, we found that DHA treatment induced the upregulation of caveolin 1 (Cav1) and mitochondrial carrier homolog 2 (MTCH2) in HeLa cells, and this was associated with the DHA-induced inhibition of cell viability and DHA-induced apoptosis. Additionally, the overexpression of Cav1 and MTCH2 in HeLa cells enhanced the inhibitory effects of DHA on cell viability. Moreover, we also found that the upregulation of Cav1 contributed to the DHA-mediated p53 activation and the downregulation of the redox enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), which have been reported to contribute to the activation of the cell death pathway. Of note, we also found that DHA induced the nuclear translocation and accumulation of both Cav1 and p53, indicating a novel potential mechanism, namely the regulation of p53 activation by Cav1. On the whole, our study identified Cav1 and MTCH2 as the molecular targets of DHA and revealed a new link between the upstream Cav1/MTCH2 upregulation and the downstream activation of the cell death pathway involved in the DHA-mediated inhibition of cell viability.

Sulphoraphane Improves Neuronal Mitochondrial Function in Brain Tissue in Acute Carbon Monoxide Poisoning Rats

Carbon monoxide (CO) poisoning is one of the leading causes of toxicity-related mortality and morbidity worldwide, primarily manifested by acute and delayed central nervous system (CNS) injuries and other organ damages. However, its definite pathogenesis is poorly understood. The aim of this study was to explore the pathogenesis of the ultrastructural and functional impairment of mitochondria and the protection of sulphoraphane (SFP) at different dosages on hippocampus neurons in rats after exposure to CO. We found that CO poisoning could induce advanced cognitive dysfunction, while the mitochondrial ultrastructure of neurons in rats of the CO poisoning group was seriously damaged and mitochondrial membrane potential (ΔΨm) was accordingly reduced by transmission electron microscopy (TEM) and JC-1 fluorescent probe assay. CO poisoning could also increase the expressions of both nuclear factor erythroid 2-related factor 2 (Nrf-2) and thioredoxin-1 (Trx-1) proteins and their mRNA in brain tissue with immunohistochemistry and quantitative PCR (qPCR) techniques. Early administration of either middle-dose or high-dose SFP could efficiently improve mitochondrial structure and function and enhance the antioxidative stress ability, thus exerting a positive effect against brain damage induced by acute CO poisoning.

Novel high throughput pooled shRNA screening identifies NQO1 as a potential drug target for host directed therapy for tuberculosis

Chemical regulation of macrophage function is one key strategy for developing host-directed adjuvant therapies for tuberculosis (TB). A critical step to develop these therapies is the identification and characterization of specific macrophage molecules and pathways with a high potential to serve as drug targets. Using a barcoded lentivirus-based pooled short-hairpin RNA (shRNA) library combined with next generation sequencing, we identified 205 silenced host genes highly enriched in mycobacteria-resistant macrophages. Twenty-one of these "hits" belonged to the oxidoreductase functional category.

NAD(P)H

quinone oxidoreductase 1 (NQO1) was the top oxidoreductase "hit". NQO1 expression was increased after mycobacterial infection, and NQO1 knockdown increased macrophage differentiation, NF-κB activation, and the secretion of pro-inflammatory cytokines TNF-α and IL-1β in response to infection. This suggests that mycobacteria hijacks NQO1 to down-regulate pro-inflammatory and anti-bacterial functions. The competitive inhibitor of NQO1 dicoumarol synergized with rifampin to promote intracellular killing of mycobacteria. Thus, NQO1 is a new host target in mycobacterial infection that could potentially be exploited to increase antibiotic efficacy in vivo. Our findings also suggest that pooled shRNA libraries could be valuable tools for genome-wide screening in the search for novel druggable host targets for adjunctive TB therapies.

Calorie restriction as an intervention in ageing

Ageing causes loss of function in tissues and organs, is accompanied by a chronic inflammatory process and affects life- and healthspan. Calorie restriction (CR) is a non-genetic intervention that prevents age-associated diseases and extends longevity in most of the animal models studied so far. CR produces a pleiotropic effect and improves multiple metabolic pathways, generating benefits to the whole organism. Among the effects of CR, modulation of mitochondrial activity and a decrease in oxidative damage are two of the hallmarks. Oxidative damage is reduced by the induction of endogenous antioxidant systems and modulation of the peroxidability index in cell membranes. Mitochondrial activity changes are regulated by inhibition of IGF-1 and Target of Rapamycin (TOR)-dependent activities and activation of AMP-dependent kinase (AMPK) and the sirtuin family of proteins. The activity of PGC-1α and FoxO is regulated by these systems and is involved in mitochondria biogenesis, oxidative metabolism activity and mitochondrial turnover. The use of mimetics and the regulation of common factors have demonstrated that these molecular pathways are essential to explain the effect of CR in the organism. Finally, the anti-inflammatory effect of CR is an interesting emerging factor to be taken into consideration. In the present revision we focus on the general effect of CR and other mimetics in longevity, focusing especially on the cardiovascular system and skeletal muscle.

Cytochrome b5 reductase, a plasma membrane redox enzyme, protects neuronal cells against metabolic and oxidative stress through maintaining redox state and bioenergetics

The plasma membrane redox system (PMRS) containing NADH-dependent reductases is known to be involved in the maintenance of redox state and bioenergetics. Neuronal cells are very vulnerable to oxidative stress and altered energy metabolism linked to mitochondrial dysfunction. However, the role of the PMRS in these pathways is far from clear. In this study, in order to investigate how cytochrome b5 reductase (b5R), one of the PM redox enzymes, regulates cellular response under stressed conditions, human neuroblastoma cells transfected with b5R were used for viability and mitochondrial functional assays. Cells transfected with b5R exhibited significantly higher levels of the NAD(+)/NADH ratio, consistent with increased levels of b5R activity. Overexpression of b5R made cells more resistant to H2O2 (oxidative stress), 2-deoxyglucose (metabolic stress), rotenone and antimycin A (energetic stress), and lactacystin (proteotoxic stress), but did not protect cells against H2O2 and serum withdrawal. Overexpression of b5R induced higher mitochondrial functions such as ATP production rate, oxygen consumption rate, and activities of complexes I and II, without formation of further reactive oxygen species, consistent with lower levels of oxidative/nitrative damage and resistance to apoptotic cell death. In conclusion, higher NAD(+)/NADH ratio and consequent more efficient mitochondrial functions are induced by the PMRS, enabling them to maintain redox state and energy metabolism under conditions of some energetic stresses. This suggests that b5R can be a target for therapeutic intervention for aging and neurodegenerative diseases.

Differentiation of human neuroblastoma cells toward the osteogenic lineage by mTOR inhibitor

Current hypothesis suggest that tumors can originate from adult cells after a process of 'reprogramming' driven by genetic and epigenetic alterations. These cancer cells, called cancer stem cells (CSCs), are responsible for the tumor growth and metastases. To date, the research effort has been directed to the identification, isolation and manipulation of this cell population. Independently of whether tumors were triggered by a reprogramming of gene expression or seeded by stem cells, their energetic metabolism is altered compared with a normal cell, resulting in a high aerobic glycolytic 'Warburg' phenotype and dysregulation of mitochondrial activity. This metabolic alteration is intricately linked to cancer progression.The aim of this work has been to demonstrate the possibility of differentiating a neoplastic cell toward different germ layer lineages, by evaluating the morphological, metabolic and functional changes occurring in this process. The cellular differentiation reported in this study brings to different conclusions from those present in the current literature. We demonstrate that 'in vitro' neuroblastoma cancer cells (chosen as experimental model) are able to differentiate directly into osteoblastic (by rapamycin, an mTOR inhibitor) and hepatic lineage without an intermediate 'stem' cell step. This process seems owing to a synergy among few master molecules, metabolic changes and scaffold presence acting in a concerted way to control the cell fate.

Effects of N-butylphthalide on the activation of Keap1/Nrf-2 signal pathway in rats after carbon monoxide poisoning

Carbon monoxide (CO) is the leading cause of death by poisoning all over the world and may result in neuropathologic changes and cognitive and neurologic sequelae, yet little is known regarding its outcomes. The present study aimed to evaluate the neuroprotective effects of N-butylphthalide (NBP) against brain damage after acute CO poisoning. The animal model of CO poisoning was established by exposed to 1000 ppm CO in air for 40 min and then to 3000 ppm for another 20 min. RT-PCR was used to assess the expressions of apoptosis-associated genes Bcl-2 mRNA and Bax mRNA. Mitochondrial membrane potential (MMP) was detected by fluorescent probe JC-1. Immunohistochemistry stain and Western blot assay were used to evaluate the expression levels of Kelch-like ECH-associated protein 1 (Keapl), nuclear factor erythroid 2-related factor 2 (Nrf-2) and

NAD(P)H

quinone oxidoreductase 1(NQO-1). CO poisoning could increase the levels of Bcl-2 mRNA and Bax mRNA expressions, and obviously decrease the MMP of cells. NBP treatment could maintain the high MMP, significantly up-regulate Bcl-2 mRNA and down-regulate Bax mRNA expression, and the ratio of Bcl-2 mRNA/Bax mRNA expressions was higher than that in the CO poisoning group (P<0.05). CO poisoning could start oxidative stress response. The expressions of Keap1, Nrf-2 and NQO-1 proteins significantly increased at 1, 3 and 7 day after NBP administration as compared with the CO poisoning group (P<0.01). These findings suggest that N-butylphthalide may protect mitochondrial function, balance the expressions of anti-apoptosis genes and pro-apoptosis genes, be in part associated with activation of Keap1-Nrf-2/antioxidant response element (ARE) signaling pathway, and play a neuroprotective role in brain damage after acute CO poisoning.

Novel antioxidants protect mitochondria from the effects of oligomeric amyloid beta and contribute to the maintenance of epigenome function

Alzheimer's disease is associated with metabolic deficits and reduced mitochondrial function, with the latter due to the effects of oligomeric amyloid beta peptide (AβO) on the respiratory chain. Recent evidence has demonstrated reduction of epigenetic markers, such as DNA methylation, in Alzheimer's disease. Here we demonstrate a link between metabolic and epigenetic deficits via reduction of mitochondrial function which alters the expression of mediators of epigenetic modifications. AβO-induced loss of mitochondrial function in differentiated neuronal cells was reversed using two novel antioxidants (1 and 2); both have been shown to mitigate the effects of reactive oxygen species (ROS), and compound 1 also restores adenosine triphosphate (ATP) levels. While both compounds were effective in reducing ROS, restoration of ATP levels was associated with a more robust response to AβO treatment. Our in vitro system recapitulates key aspects of data from Alzheimer's brain samples, the expression of epigenetic genes in which are also shown to be normalized by the novel analogues.

Idebenone and neuroprotection: antioxidant, pro-oxidant, or electron carrier?

Ubiquinone, commonly called coenzyme Q10 (CoQ), is a lipophilic electron carrier and endogenous antioxidant found in all cellular membranes. In the mitochondrial inner membrane it transfers electrons to complex III of the electron transport chain. The short chain CoQ analogue idebenone is in clinical trials for a number of diseases that exhibit a mitochondrial etiology. Nevertheless, evidence that idebenone ameliorates neurological symptoms in human disease is inconsistent. Although championed as an antioxidant, idebenone can also act as a pro-oxidant by forming an unstable semiquinone at complex I. The antioxidant function of idebenone is critically dependent on two-electron reduction to idebenol without the creation of unstable intermediates. Recently, cytoplasmic

NAD(P)H

quinone oxidoreductase 1 (NQO1) was identified as a major enzyme catalyzing idebenone reduction. While reduction allows idebenone to act as an antioxidant, evidence also suggests that NQO1 enables idebenone to shuttle reducing equivalents from cytoplasmic NAD(P)H to mitochondrial complex III, bypassing any upstream damage to the electron transport chain. In this mini-review we discuss how idebenone can influence mitochondrial function within the context of cytoprotection. Importantly, in the brain NQO1 is expressed primarily by glia rather than neurons. As NQO1 is an inducible enzyme regulated by oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway, optimizing NQO1 expression in appropriate cell types within a specific disease context may be key to delivering on idebenone's therapeutic potential.