Thiol modulation of TNF alpha and IL-1 induced MnSOD gene expression and activation of NF-kappa B

In Vitro Assessment of Anti-Adipogenic and Anti-Inflammatory Properties of Black Cumin (Nigella sativa L.) Seeds Extract on 3T3-L1 Adipocytes and Raw264.7 Macrophages

Background and Objectives: This study evaluated the in vitro anti-adipogenic and anti-inflammatory properties of black cumin (Nigella sativa L.) seed extract (BCS extract) as a potential candidate for developing herbal formulations targeting metabolic disorders. Materials and Methods: We evaluated the BCS extract by assessing its 2,2-diphenyl-1-picrohydrazyl (DPPH) radical scavenging activity, levels of prostaglandin E2 (PGE2) and nitric oxide (NO), and mRNA expression levels of key pro-inflammatory mediators. We also quantified the phosphorylation of nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPK) signaling molecules. To assess anti-adipogenic effects, we used differentiated 3T3-L1 cells and BCS extract in doses from 10 to 100 μg/mL. We also determined mRNA levels of key adipogenic genes, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/BEPα), adipocyte protein 2 (aP2), lipoprotein lipase (LPL), fatty acid synthase (FAS), and sterol-regulated element-binding protein 1c (SREBP-1c) using real-time quantitative polymerase chain reaction (qPCR). Results: This study showed a concentration-dependent DPPH radical scavenging activity and no toxicity at concentrations up to 30 μg/mL in Raw264.7 cells. BCS extract showed an IC50 of 328.77 ± 20.52 μg/mL. Notably, pre-treatment with BCS extract (30 μg/mL) significantly enhanced cell viability in lipopolysaccharide (LPS)-treated Raw264.7 cells. BCS extract treatment effectively inhibited LPS-induced production of PGE2 and NO, as well as the expression of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), interleukin (IL)-1β and IL-6, possibly by limiting the phosphorylation of p38, p65, inhibitory κBα (I-κBα), and c-Jun N-terminal kinase (JNK). It also significantly attenuated lipid accumulation and key adipogenic genes in 3T3-L1 cells. Conclusions: This study highlights the in vitro anti-adipogenic and anti-inflammatory potential of BCS extract, underscoring its potential as a promising candidate for managing metabolic disorders.

Fragmentation of Small-Cell Lung Cancer Regulatory States in Heterotypic Microenvironments

Small-cell lung cancers derive from pulmonary neuroendocrine cells, which have stem-like properties to reprogram into other cell types upon lung injury. It is difficult to uncouple transcriptional plasticity of these transformed cells from genetic changes that evolve in primary tumors or secondary metastases. Profiling of single cells is also problematic if the required sample dissociation activates injury-like signaling and reprogramming. Here we defined cell-state heterogeneities in situ through laser capture microdissection-based 10-cell transcriptomics coupled with stochastic-profiling fluctuation analysis. In labeled cells from a small-cell lung cancer mouse model initiated by neuroendocrine deletion of Rb1-Trp53, variations in transcript abundance revealed cell-to-cell differences in regulatory state in vitro and in vivo. Fluctuating transcripts in spheroid culture were partly shared among Rb1-Trp53-null models, and heterogeneities increased considerably when cells were delivered intravenously to colonize the liver. Colonization of immunocompromised animals drove a fractional appearance of alveolar type II-like markers and poised cells for paracrine stimulation from immune cells and hepatocytes. Immunocompetency further exaggerated the fragmentation of tumor states in the liver, yielding mixed stromal signatures evident in bulk sequencing from autochthonous tumors and metastases. Dozens of transcript heterogeneities recurred irrespective of biological context; their mapped orthologs brought together observations of murine and human small-cell lung cancer. Candidate heterogeneities recurrent in the liver also stratified primary human tumors into discrete groups not readily explained by molecular subtype but with prognostic relevance. These data suggest that heterotypic interactions in the liver and lung are an accelerant for intratumor heterogeneity in small-cell lung cancer. SIGNIFICANCE: These findings demonstrate that the single-cell regulatory heterogeneity of small-cell lung cancer becomes increasingly elaborate in the liver, a common metastatic site for the disease.See related articles by Singh and colleagues, p. 1840 and Sutcliffe and colleagues, p. 1868.

Aerobic exercise training attenuates detrimental effects of cigarette smoke exposure on peripheral muscle through stimulation of the Nrf2 pathway and cytokines: a time-course study in mice

Cigarette smoke (CS) exposure reduces skeletal muscle function; however, the mechanisms involved have been poorly investigated. The current study evaluated the temporal effects of aerobic exercise training on oxidant and antioxidant systems as well as inflammatory markers in skeletal muscle of mice exposed to CS. Mice were randomly allocated to control, exercise, smoke, and smoke+exercise groups and 3 time points (4, 8, and 12 weeks; n = 12 per group). Exercise training and CS exposure were performed for 30 min/day, twice a day, 5 days/week for 4, 8, and 12 weeks. Aerobic exercise improved functional capacity and attenuated the increase in the cachexia index induced by CS exposure after 12 weeks. Concomitantly, exercise training downregulated tumor necrosis factor α concentration, glutathione oxidation, and messenger RNA (mRNA) expression of Keap1 (P < 0.01) and upregulated interleukin 10 concentration, total antioxidant capacity, and mRNA expression of Nrf2, Gsr, and Txn1 (P < 0.01) in muscle. Exercise increased mRNA expression of Hmox1 compared with the control after 12 weeks (P < 0.05). There were no significant differences between smoke groups for superoxide dismutase activity and Hmox1 mRNA expression. Exercise training improved the ability of skeletal muscle to adequately upregulate key antioxidant and anti-inflammatory defenses to detoxify electrophilic compounds induced by CS exposure, and these effects were more pronounced after 12 weeks. Novelty Exercise attenuates oxidative stress in skeletal muscle from animals exposed to CS via Nrf2 and glutathione pathways. Exercise is a helpful tool to control the inflammatory balance in skeletal muscle from animals exposed to CS. These beneficial effects were evident after 12 weeks.

BRAF Mutant Melanoma Adjusts to BRAF/MEK Inhibitors via Dependence on Increased Antioxidant SOD2 and Increased Reactive Oxygen Species Levels

B-Rapidly Accelerated Fibrosarcoma (BRAF) mutations are found in about 50% of melanoma patients. Treatment with Food and Drug Administration (FDA)-approved BRAF and MAP/ERK kinase (MEK) inhibitors has improved progression free and overall survival of patients with BRAF mutant melanoma. However, all responders develop resistance typically within 1 year of treatment with these inhibitors. Evidence indicates that reactive oxygen species (ROS) levels are elevated after BRAF pathway inhibition treatment. We aim to decipher the role of mitochondrial antioxidant proteins relative to ROS levels and BRAF pathway inhibitor resistance. We observed BRAF mutant melanoma cells treated with the combination of a MEK inhibitor (trametinib) and a BRAF inhibitor (dabrafenib), exhibited elevated ROS levels, both in in vitro and in vivo melanoma models. We next generated trametinib- and dabrafenib-resistant (TDR) cells and found increased ROS levels after acquisition of resistance. An immunofluorescence experiment showed an increase of DNA damage in TDR cell lines. Furthermore, we observed that TDR cells increased superoxide dismutase 2 (SOD2), an antioxidant, at both mRNA and protein levels, with the upregulation of the transcription factor Nuclear Factor (NF)-κB. Knockdown of SOD2 significantly reduced the growth of BRAF pathway inhibitor-resistant cells. In addition, the results indicate that TDR cells can be re-sensitized to BRAF pathway inhibitors by the ROS scavenger, N-Acetyl Cysteine (NAC). Overall, these data indicate that BRAF pathway inhibitor-resistant cells can compensate for elevated ROS via increased expression of the antioxidant SOD2.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

Hydrogen Indirectly Suppresses Increases in Hydrogen Peroxide in Cytoplasmic Hydroxyl Radical-Induced Cells and Suppresses Cellular Senescence

Bacteria inhabiting the human gut metabolize microbiota-accessible carbohydrates (MAC) contained in plant fibers and subsequently release metabolic products. Gut bacteria produce hydrogen (H₂), which scavenges the hydroxyl radical (•OH). Because H₂ diffuses within the cell, it is hypothesized that H₂ scavenges cytoplasmic •OH (cyto •OH) and suppresses cellular senescence. However, the mechanisms of cyto •OH-induced cellular senescence and the physiological role of gut bacteria-secreted H₂ have not been elucidated. Based on the pyocyanin-stimulated cyto •OH-induced cellular senescence model, the mechanism by which cyto •OH causes cellular senescence was investigated by adding a supersaturated concentration of H₂ into the cell culture medium. Cyto •OH-generated lipid peroxide caused glutathione (GSH) and heme shortage, increased hydrogen peroxide (H₂O₂), and induced cellular senescence via the phosphorylation of ataxia telangiectasia mutated kinase serine 1981 (p-ATM^ser1981)/p53 serine 15 (p-p53^ser15)/p21 and phosphorylation of heme-regulated inhibitor (p-HRI)/phospho-eukaryotic translation initiation factor 2 subunit alpha serine 51 (p-eIF2α)/activating transcription factor 4 (ATF4)/p16 pathways. Further, H₂ suppressed increased H₂O₂ by suppressing cyto •OH-mediated lipid peroxide formation and cellular senescence induction via two pathways. H₂ produced by gut bacteria diffuses throughout the body to scavenge cyto •OH in cells. Therefore, it is highly likely that gut bacteria-produced H₂ is involved in intracellular maintenance of the redox state, thereby suppressing cellular senescence and individual aging. Hence, H₂ produced by intestinal bacteria may be involved in the suppression of aging.

Clair DK, Kyprianou N. Profiles of Radioresistance Mechanisms in Prostate Cancer

Radiation therapy (RT) is commonly used for the treatment of localized prostate cancer (PCa). However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently causing metastasis and cancer recurrence. Understanding the molecular events that cause radioresistance in PCa will enable us to develop adjuvant treatments for enhancing the efficacy of RT. Radioresistant PCa depends on the elevated DNA repair system and the intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and scavenge anti-cancer regimens, whereas the elevated heat shock protein 90 (HSP90) and the epithelial-mesenchymal transition (EMT) enable radioresistant PCa cells to metastasize after exposure to radiation. The up-regulation of the DNA repairing system, ROS, HSP90, and EMT effectors has been studied extensively, but not targeted by adjuvant therapy of radioresistant PCa. Here, we emphasize the effects of ionizing radiation and the mechanisms driving the emergence of radioresistant PCa. We also address the markers of radioresistance, the gene signatures for the predictive response to radiotherapy, and novel therapeutic platforms for targeting radioresistant PCa. This review provides significant insights into enhancing the current knowledge and the understanding toward optimization of these markers for the treatment of radioresistant PCa.

Redox Regulation of the Superoxide Dismutases SOD3 and SOD2 in the Pulmonary Circulation

When evaluating the role of redox-regulating signaling in pulmonary vascular diseases, it is intriguing to consider the modulation of key antioxidant enzymes like superoxide dismutase (SOD) because SOD isoforms are regulated by redox reactions, and, in turn, modulate downstream redox sensitive processes. The emerging field of redox biology is built upon understanding the regulation and consequences of tightly controlled and specific reduction-oxidation reactions that are critical for diverse cellular processes including cell signaling. Of relevance, both the site of production of specific reactive oxygen and nitrogen species and the site of the antioxidant defenses are highly compartmentalized within the cell. For example, superoxide is generated during oxidative phosphorylation in the mitochondria as well as by a number of enzymatic sources within the cytosol and at the cell membrane. In the pulmonary circulation, these sources include the mitochondrial electron transport chain, NADPH oxidases (NOX1-4, Duox1,2), nitric oxide synthases, and xanthine oxidase; this important topic has been thoroughly reviewed recently [1]. In parallel with these different cellular sites of superoxide production, the three SOD isoforms are also specifically localized to the cytosol (SOD1), mitochondria (SOD2) or extracellular compartment (SOD3). This chapter focuses on the role of redox mechanisms regulating SOD2 and SOD3, with an emphasis on these processes in the setting of pulmonary hypertension.

Low-dose radiation may be a novel approach to enhance the effectiveness of cancer therapeutics

It has been generally accepted that both natural and man-made sources of ionizing radiation contribute to human exposure and consequently pose a possible risk to human health. However, accumulating evidence has shown that the biological effects of low-dose radiation (LDR) are different from those of high-dose radiation. LDR can stimulate proliferation of normal cells and activate their defense systems, while these biological effects are not observed in some cancer cell types. Although there is still no concordance on this matter, the fact that LDR has the potential to enhance the effects of cancer therapeutics and reduce the toxic side effects of anti-cancer therapy has garnered significant interest. Here, we provide an overview of the current knowledge regarding the experimental data detailing the different responses of normal and cancer tissues to LDR, the underlying mechanisms, and its significance in clinical application.

Protein kinase Cδ upregulation in microglia drives neuroinflammatory responses and dopaminergic neurodegeneration in experimental models of Parkinson's disease

Chronic microglial activation has been linked to the progressive degeneration of the nigrostriatal dopaminergic neurons evidenced in Parkinson's disease (PD) pathogenesis. The exact etiology of PD remains poorly understood. Although both oxidative stress and neuroinflammation are identified as co-contributors in PD pathogenesis, signaling mechanisms underlying neurodegenerative processes have yet to be defined. Indeed, we recently identified that protein kinase C delta (PKCδ) activation is critical for induction of dopaminergic neuronal loss in response to neurotoxic stressors. However, it remains to be defined whether PKCδ activation contributes to immune signaling events driving microglial neurotoxicity. In the present study, we systematically investigated whether PKCδ contributes to the heightened microglial activation response following exposure to major proinflammatory stressors, including α-synuclein, tumor necrosis factor α (TNFα), and lipopolysaccharide (LPS). We report that exposure to the aforementioned inflammatory stressors dramatically upregulated PKCδ with a concomitant increase in its kinase activity and nuclear translocation in both BV-2 microglial cells and primary microglia. Importantly, we also observed a marked upregulation of PKCδ in the microglia of the ventral midbrain region of PD patients when compared to age-matched controls, suggesting a role for microglial PKCδ in neurodegenerative processes. Further, shRNA-mediated knockdown and genetic ablation of PKCδ in primary microglia blunted the microglial proinflammatory response elicited by the inflammogens, including ROS generation, nitric oxide production, and proinflammatory cytokine and chemokine release. Importantly, we found that PKCδ activated NFκB, a key mediator of inflammatory signaling events, after challenge with inflammatory stressors, and that transactivation of NFκB led to translocation of the p65 subunit to the nucleus, IκBα degradation and phosphorylation of p65 at Ser536. Furthermore, both genetic ablation and siRNA-mediated knockdown of PKCδ attenuated NFκB activation, suggesting that PKCδ regulates NFκB activation subsequent to microglial exposure to inflammatory stimuli. To further investigate the pivotal role of PKCδ in microglial activation in vivo, we utilized pre-clinical models of PD. We found that PKCδ deficiency attenuated the proinflammatory response in the mouse substantia nigra, reduced locomotor deficits and recovered mice from sickness behavior in an LPS-induced neuroinflammation model of PD. Likewise, we found that PKCδ knockout mice treated with MPTP displayed a dampened microglial inflammatory response. Moreover, PKCδ knockout mice exhibited reduced susceptibility to the neurotoxin-induced dopaminergic neurodegeneration and associated motor impairments. Taken together, our studies propose a pivotal role for PKCδ in PD pathology, whereby sustained PKCδ activation drives sustained microglial inflammatory responses and concomitant dopaminergic neurotoxicity consequently leading to neurobehavioral deficits. We conclude that inhibiting PKCδ activation may represent a novel therapeutic strategy in PD treatment.

Effects of Yishen Pinggan Recipe on Renal Protection and NF-κB Signaling Pathway in Spontaneously Hypertensive Rats

Inflammation is an important etiological factor of hypertensive renal damage. The effects of Yishen Pinggan Recipe (YPR) on urine microalbumin, histology, and NF-κB/P65, IκB-α, IL-1β, IL-6, and TNF-α in renal tissues were evaluated in SHR to explore the mechanism of its renal protection in hypertensive renal damage. The SBP of 12-week-old SHR was 192.41 ± 3.93 mmHg and DBP was 142.38 ± 5.79 mmHg. Without treatment, the 24-week-old SHRs' SBP was 196.96 ± 3.77 mmHg and DBP was 146.08 ± 4.82 mmHg. After the 12-week-old SHR were administered YPR for 12 weeks, the rats' SBP was 161.45 ± 7.57 mmHg and DBP was 117.21 ± 5.17 mmHg; YPR could lower blood pressure in SHR. And renal function damage was observed in 24-week-old SHR without treatment, manifested as urine protein and morphological changes which could be inhibited by YPR. In addition, YPR could reduce the expression of inflammatory cytokines (IL-1β, IL-6, and TNF-α) in kidneys. It could also inhibit the nuclear translocation of NF-κB p65 and degradation of IκB-α in renal cells, indicating that the NF-κB signaling pathway was inhibited by YPR. Finally, the study suggests that YPR could significantly improve the renal function in SHR. The mechanism could be attributed to its inhibition of renal NF-κB signaling pathway and inflammation.

Thioredoxin Activates MKK4-NFκB Pathway in a Redox-dependent Manner to Control Manganese Superoxide Dismutase Gene Expression in Endothelial Cells

The mitogen-activated protein kinase kinase 4 (MKK4) is activated via phosphorylation of Ser-257 and Thr-261 by upstream MAP3Ks and activates JNK and p38 MAPKs in response to cellular stress. We show that thioredoxin (Trx), a cellular redox protein, activates MKK4 via Cys-246 and Cys-266 residues as mutation of these residues renders MKK4 insensitive to phosphorylation by MAP3Ks, TNFα, or Trx. MKK4 is activated in vitro by reduced Trx but not oxidized Trx in the absence of an upstream kinase, suggesting that autophosphorylation of this protein occurs due to reduction of Cys-246 and Cys-266 by Trx. Additionally, mutation of Cys-246 and Cys-266 resulted in loss of kinase activity suggesting that the redox state of Cys-246 and Cys-266 is a critical determinant of MKK4 activation. Trx induces manganese superoxide dismutase (MnSOD) gene transcription by activating MKK4 via redox control of Cys-246 and Cys-266, as mutation of these residues abrogates MKK4 activation and MnSOD expression. We further show that MKK4 activates NFκB for its binding to the MnSOD promoter, which leads to AP-1 dissociation followed by MnSOD transcription. Taken together, our studies show that the redox status of Cys-246 and Cys-266 in MKK4 controls its activities independent of MAP3K, demonstrating integration of the endothelial redox environment to MAPK signaling.

MnSOD in oxidative stress response-potential regulation via mitochondrial protein influx

SIGNIFICANCE

The mitochondrial antioxidant manganese superoxide dismutase (MnSOD) is encoded by genomic DNA and its dismutase function is fully activated in the mitochondria to detoxify free radical O2(•-) generated by mitochondrial respiration. Accumulating evidence shows an extensive communication between the mitochondria and cytoplasm under oxidative stress. Not only is the MnSOD gene upregulated by oxidative stress, but MnSOD activity can be enhanced via the mitochondrial protein influx (MPI).

RECENT ADVANCES

A cluster of MPI containing cytoplasmic/nuclear proteins, such as cyclins, cyclin-dependent kinases, and p53 interact with and alter MnSOD activity. These proteins modulate MnSOD superoxide scavenging activity via post-translational modifications in the mitochondria. In addition to well-established pathways in gene expression, recent findings suggest that MnSOD enzymatic activity can also be enhanced by phosphorylation of specific motifs in mitochondria. This review attempts to discuss the pre- and post-translational regulation of MnSOD, and how these modifications alter MnSOD activity, which induces a cell adaptive response to oxidative stress.

CRITICAL ISSUES

MnSOD is biologically significant to aerobic cells. Its role in protecting the cells against the deleterious effects of reactive oxygen species is evident. However, the exact network of MnSOD-associated cellular adaptive reaction to oxidative stress and its post-translational modifications, especially its enzymatic enhancement via phosphorylation, is not yet fully understood.

FUTURE DIRECTIONS

The broad discussion of the multiple aspects of MnSOD regulation, including gene expression, protein modifications, and enzymatic activity, will shed light onto the unknown mechanisms that govern the prosurvival networks involved in cellular and mitochondrial adaptive response to genotoxic environment.

Respiratory syncytial virus infection: mechanisms of redox control and novel therapeutic opportunities

Respiratory syncytial virus (RSV) is one of the most important causes of upper and lower respiratory tract infections in infants and young children, for which no effective treatment is currently available. Although the mechanisms of RSV-induced airway disease remain incompletely defined, the lung inflammatory response is thought to play a central pathogenetic role. In the past few years, we and others have provided increasing evidence of a role of reactive oxygen species (ROS) as important regulators of RSV-induced cellular signaling leading to the expression of key proinflammatory mediators, such as cytokines and chemokines. In addition, RSV-induced oxidative stress, which results from an imbalance between ROS production and airway antioxidant defenses, due to a widespread inhibition of antioxidant enzyme expression, is likely to play a fundamental role in the pathogenesis of RSV-associated lung inflammatory disease, as demonstrated by a significant increase in markers of oxidative injury, which correlate with the severity of clinical illness, in children with RSV infection. Modulation of ROS production and oxidative stress therefore represents a potential novel pharmacological approach to ameliorate RSV-induced lung inflammation and its long-term consequences.

Acquisition of resistance of pancreatic cancer cells to 2-methoxyestradiol is associated with the upregulation of manganese superoxide dismutase

Acquired resistance of cancer cells to anticancer drugs or ionizing radiation (IR) is one of the major obstacles in cancer treatment. Pancreatic cancer is an exceptional aggressive cancer, and acquired drug resistance in this cancer is common. Reactive oxygen species (ROS) play an essential role in cell apoptosis, which is a key mechanism by which radio- or chemotherapy induce cell killing. Mitochondria are the major source of ROS in cells. Thus, alterations in the expression of mitochondrial proteins, involved in ROS production or scavenging, may be closely linked to the resistance of cancer cells to radio- or chemotherapy. In the present study, we generated a stable cell line by exposing pancreatic cancer cells to increasing concentrations of ROS-inducing, anticancer compound 2-methoxyestradiol (2-ME) over a 3-month period. The resulting cell line showed strong resistance to 2-ME and contained an elevated level of ROS. We then used a comparative proteomics method to profile the differential expression of mitochondrial proteins between the parental and the resistant cells. One protein identified to be upregulated in the resistant cells was manganese superoxide dismutase (SOD2), a mitochondrial protein that converts superoxide radicals to hydrogen peroxides. Silencing of SOD2 resensitized the resistant cells to 2-ME, and overexpression of SOD2 led the parental cells to 2-ME resistance. In addition, the 2-ME-resistant cells also showed resistance to IR. Our results suggest that upregulation of SOD2 expression is an important mechanism by which pancreatic cancer cells acquire resistance to ROS-inducing, anticancer drugs, and potentially also to IR.

Intersection of FOXO- and RUNX1-mediated gene expression programs in single breast epithelial cells during morphogenesis and tumor progression

Gene expression networks are complicated by the assortment of regulatory factors that bind DNA and modulate transcription combinatorially. Single-cell measurements can reveal biological mechanisms hidden by population averages, but their value has not been fully explored in the context of mRNA regulation. Here, we adapted a single-cell expression profiling technique to examine the gene expression program downstream of Forkhead box O (FOXO) transcription factors during 3D breast epithelial acinar morphogenesis. By analyzing patterns of mRNA fluctuations among individual matrix-attached epithelial cells, we found that a subset of FOXO target genes was jointly regulated by the transcription factor Runt-related transcription factor 1 (RUNX1). Knockdown of RUNX1 causes hyperproliferation and abnormal morphogenesis, both of which require normal FOXO function. Down-regulating RUNX1 and FOXOs simultaneously causes widespread oxidative stress, which arrests proliferation and restores normal acinar morphology. In hormone-negative breast cancers lacking human epidermal growth factor receptor 2 (HER2) amplification, we find that RUNX1 down-regulation is strongly associated with up-regulation of FOXO1, which may be required to support growth of RUNX1-negative tumors. The coordinate function of these two tumor suppressors may provide a failsafe mechanism that inhibits cancer progression.

Lysosomal thiol reductase negatively regulates autophagy by altering glutathione synthesis and oxidation

Redox regulation is critical for a number of cellular functions and has been implicated in the etiology and progression of several diseases, such as cardiovascular diseases, neurodegenerative diseases, and cancer. It has been shown that, in the absence of gamma-interferon inducible lysosomal thiol reductase (GILT), cells are under increased oxidative stress with higher superoxide levels and decreased stability, expression, and function of mitochondrial manganese superoxide dismutase (SOD2). Here, we further elucidate the role of GILT in the homeostatic regulation of oxidative stress. We show that GILT-deficient fibroblasts exhibit reduced glutathione levels, shift in GSSG/GSH ratio toward the oxidized form, and accumulate dysfunctional mitochondria. Redox-sensitive pathways involving Erk1/2 activation and nuclear high mobility group box 1 (HMGB1) protein cytosolic translocation are both activated and associated with increased autophagy in GILT-/- fibroblasts. We hypothesize that these events are responsible for degrading the damaged mitochondria and mitochondrial SOD2 in the absence of GILT. This is the first time to our knowledge that a lysosomal enzyme has been implicated in global effects within the cell.

Reactive oxygen species: impact on skeletal muscle

It is well established that contracting muscles produce both reactive oxygen and nitrogen species. Although the sources of oxidant production during exercise continue to be debated, growing evidence suggests that mitochondria are not the dominant source. Regardless of the sources of oxidants in contracting muscles, intense and prolonged exercise can result in oxidative damage to both proteins and lipids in the contracting myocytes. Further, oxidants regulate numerous cell signaling pathways and modulate the expression of many genes. This oxidant-mediated change in gene expression involves changes at transcriptional, mRNA stability, and signal transduction levels. Furthermore, numerous products associated with oxidant-modulated genes have been identified and include antioxidant enzymes, stress proteins, and mitochondrial electron transport proteins. Interestingly, low and physiological levels of reactive oxygen species are required for normal force production in skeletal muscle, but high levels of reactive oxygen species result in contractile dysfunction and fatigue. Ongoing research continues to explore the redox-sensitive targets in muscle that are responsible for both redox regulation of muscle adaptation and oxidant-mediated muscle fatigue.

Low-dose γ-radiation-induced oxidative stress response in mouse brain and gut: regulation by NFκB-MnSOD cross-signaling

Radiation-induced amplification of reactive oxygen species (ROS) may be a sensing mechanism for activation of signaling cascades that influence cell fate. However, the regulated intrinsic mechanisms and targets of low-dose ionizing radiation (LDIR) are still unclear. Accordingly, we investigated the effects of LDIR on NFκB signal transduction and manganese superoxide dismutase (SOD2) activity in mice brain and gut. LDIR resulted in both dose-dependent and persistent NFκB activation in gut and brain. QPCR displayed a dose- and tissue-dependent differential modulation of 88 signaling molecules. With stringent criteria, a total of 15 (2cGy), 43 (10cGy) and 19 (50cGy) genes were found to be commonly upregulated between brain and gut. SOD2 immunostaining showed a LDIR-dose dependent increase. Consistent with the NFκB results, we observed a persistent increase in SOD2 activity after LDIR. Moreover, muting of LDIR-induced NFκB attenuated SOD2 transactivation and cellular localization. These results imply that exposure of healthy tissues to LDIR results in induced NFκB and SOD2 activity and transcriptional activation of NFκB-signal transduction/target molecules. More importantly, the results suggest that NFκB initiates a feedback response through transcriptional activation of SOD2 that may play a key role in the LDIR-induced oxidative stress response and may control the switch that directs cell fate.

Phosphorylation of p50 NF-kappaB at a single serine residue by DNA-dependent protein kinase is critical for VCAM-1 expression upon TNF treatment

The DNA binding activity of NF-κB is critical for VCAM-1 expression during inflammation. DNA-dependent protein kinase (DNA-PK) is thought to be involved in NF-κB activation. Here we show that DNA-PK is required for VCAM-1 expression in response to TNF. The phosphorylation and subsequent degradation of I-κBα as well as the serine 536 phosphorylation and nuclear translocation of p65 NF-κB were insufficient for VCAM-1 expression in response to TNF. The requirement for p50 NF-κB in TNF-induced VCAM-1 expression may be associated with its interaction with and phosphorylation by DNA-PK, which appears to be dominant over the requirement for p65 NF-κB activation. p50 NF-κB binding to its consensus sequence increased its susceptibility to phosphorylation by DNA-PK. Additionally, DNA-PK activity appeared to increase the association between p50/p50 and p50/p65 NF-κB dimers upon binding to DNA and after binding of p50 NF-κB to the VCAM-1 promoter. Analyses of the p50 NF-κB protein sequence revealed that both serine 20 and serine 227 at the amino terminus of the protein are putative sites for phosphorylation by DNA-PK. Mutation of serine 20 completely eliminated phosphorylation of p50 NF-κB by DNA-PK, suggesting that serine 20 is the only site in p50 NF-κB for phosphorylation by DNA-PK. Re-establishing wild-type p50 NF-κB, but not its serine 20/alanine mutant, in p50 NF-κB(-/-) fibroblasts reversed VCAM-1 expression after TNF treatment, demonstrating the importance of the serine 20 phosphorylation site in the induction of VCAM-1 expression. Together, these results elucidate a novel mechanism for the involvement of DNA-PK in the positive regulation of p50 NF-κB to drive VCAM-1 expression.

Redox control of asthma: molecular mechanisms and therapeutic opportunities

An imbalance in reducing and oxidizing (redox) systems favoring a more oxidative environment is present in asthma and linked to the pathophysiology of the defining symptoms and signs including airflow limitation, hyper-reactivity, and airway remodeling. High levels of hydrogen peroxide, nitric oxide ((*)NO), and 15-F(2t)-isoprostane in exhaled breath, and excessive oxidative protein products in lung epithelial lining fluid, peripheral blood, and urine provide abundant evidence for pathologic oxidizing processes in asthma. Parallel studies document loss of reducing potential by nonenzymatic and enzymatic antioxidants. The essential first line antioxidant enzymes superoxide dismutases (SOD) and catalase are reduced in asthma as compared to healthy individuals, with lowest levels in those patients with the most severe asthma. Loss of SOD and catalase activity is related to oxidative modifications of the enzymes, while other antioxidant gene polymorphisms are linked to susceptibility to develop asthma. Monitoring of exhaled (*)NO has entered clinical practice because it is useful to optimize asthma care, and a wide array of other biochemical oxidative and nitrative biomarkers are currently being evaluated for asthma monitoring and phenotyping. Novel therapeutic strategies that target correction of redox abnormalities show promise for the treatment of asthma.

Oxidative stress in the brain of nicotine-induced toxicity: protective role of Andrographis paniculata Nees and vitamin E

Mitochondria are the crossroads of several crucial cellular activities; they produce considerable quantities of superoxide radical and hydrogen peroxide, which can damage important macromolecules. Nicotine affects a variety of cellular processes, from induction of gene expression to modulation of enzymatic activities. The aim of this study was to elucidate the protective effects of andrographolide (ANDRO) aqueous extract (AE-Ap) of Andrographis paniculata, and vitamin E on nicotine-induced brain mitochondria. In this investigation, nicotine (1 mg.kg body mass-1.day-1) was treated, for the period of 7 days, simultaneously with 2 A. paniculata products, ANDRO and AE-Ap (250 mg.kg body mass-1.day-1); and vitamin E (50 mg.kg body mass-1.day-1) was supplemented in different group of male Wistar rats. The activities of mitochondrial electron transport chain (Mito-ETC) complexes (I, II, III), nitric oxide production, superoxide anion, catalase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase, and concentrations of reduced glutathione and oxidized glutathione were measured in discrete regions of brain (the cerebral hemisphere, cerebellum, diencephalons, and brain stem). The study revealed that nicotine inhibits the Mito-ETC complexes and produces nitric oxide, which suppressed the mitochondrial oxidative stress scavenger system in different brain regions. In these circumstances, lipid peroxidation and protein oxidation were noted in different discrete regions of brain mitochondria. ANDRO, AE-Ap, and vitamin E showed the protective potentiality against nicotine toxicity. The analysis of such alterations is important in determining the basis of normal dysfunction in the brain associated with nicotine toxicity, which could be ameliorated by A. paniculata and vitamin E, and may help to develop therapeutic means against nicotine-induced disorders.

Respiratory syncytial virus induces oxidative stress by modulating antioxidant enzymes

Oxidative stress plays an important role in the pathogenesis of lung inflammation. Respiratory syncytial virus (RSV) infection induces reactive oxygen species (ROS) production in vitro and oxidative injury in lungs in vivo; however, the mechanism of RSV-induced cellular oxidative stress has not been investigated. Therefore, we determined whether RSV infection of airway epithelial cells modified the expression and/or activities of antioxidant enzymes (AOE). A549 cells, a human alveolar type II-like epithelial cell line, and small airway epithelial (SAE) cells, normal human cells derived from terminal bronchioli, were infected with RSV and harvested at various time points to measure F(2)-8 isoprostanes by enzyme-linked immunosorbent assay and total and reduced glutathione (GSH and GSSG) by colorimetric assay. Superoxide dismutase (SOD) 1, 2, and 3, catalase, glutathione peroxidase (GPx), and glutathione S-transferase (GST) expression was determined by quantitative real-time PCR and Western blot, and their activity was measured by colorimetric assays. RSV infection induced a significant increase of lipid peroxidation products as well as a significant decrease in the GSH/GSSG ratio. There was a significant decrease in SOD 1, SOD 3, catalase, and GST expression with a concomitant increase of SOD 2 in RSV-infected cells, compared with uninfected cells. Total SOD activity was increased, but catalase, GPx, and GST activities were decreased, after RSV infection. Our findings suggest that RSV-induced cellular oxidative damage is the result of an imbalance between ROS production and antioxidant cellular defenses. Modulation of oxidative stress represents a potential novel pharmacologic approach to ameliorate RSV-induced acute lung inflammation.

Age-dependent dichotomous effect of superoxide dismutase Ala16Val polymorphism on oxidized LDL levels

We investigated the association between superoxide dismutase (SOD) Ala16Val polymorphism and the levels of oxidized LDL lipoprotein-C (ox-LDL-C) in two age-different Greek cohorts. Four hundred fifteen middle-aged (n=147 females: 43.2+/-13 years, n=268 males: 43.3+/-14 years) Caucasian Greek subjects consisted the middle aged cohort. One hundred seventy five elderly (n=88 females: 79.9+/-4 years; n=87 males: 80.6+/-4 years) were selected from the elderly cohort. Genotype data were obtained for all of them. Multiple linear regression analysis, stratified by gender and adjusted for age, smoking habits and body mass index as covariates, showed higher ox-LDL-C levels for the middle aged men with the Val/Val genotype, compared to the other allele (Ala/Ala and Ala/Val) carriers (65.9+/-25.7 vs. 55.7+/-20.5 mg/dl; standardized beta coefficient=0.192, P=0.012). On the contrary, elderly women with the Val/Val genotype occurred with lower ox-LDL-C levels compared to the Ala/Ala or Ala/Val genotype (74.2+/-22.1 vs. 86.5+/-26.6 mg/dl; standardized beta coefficient= -0.269, P=0.015). The same trend was also recorded in elderly men, however without reaching statistical significance (standardized beta coefficient= -0.187, P=0.077). Moreover, elderly men and women with the Ala/Ala or Ala/Val genotype presented higher triglycerides levels compared to Val/Val (women: 145.2+/-68.7 vs. 114.3+/- 34.3 mg/dl, P= 0.027; men: 147.8+/-72.4 vs. 103.7 +/-38.0 mg/dl, P=0.002). Additionally, middle aged men with the Val/Val genotype had higher HDL-C levels compared to the Ala allele carriers. The results suggest that SOD Ala16Val polymorphism is an age-dependent modulator of ox-LDL-C levels in middle-aged men and elderly women.

An unexpected functional link between lysosomal thiol reductase and mitochondrial manganese superoxide dismutase

Gamma interferon-inducible thiol reductase (GILT) is an enzyme involved in the initial steps of antigen processing and presentation. Recently we have shown that GILT is also expressed in mouse T cells, where it exerts an inhibitory role on T cell activation. In this study, we identified mitochondrial manganese superoxide dismutase (SOD2) as one of the key intermediaries affected by GILT expression in fibroblasts. Expression and activity of SOD2 is reduced in the absence of GILT because of reduced SOD2 protein stability. The forced increase in SOD2 expression in the absence of GILT restores fibroblast proliferation to wild-type levels. Thus, GILT appears to have a fundamental role in cellular proliferation mediated through its influence on SOD2 protein activity and expression.

Modulation of skeletal muscle antioxidant defense by exercise: Role of redox signaling

Contraction-induced production of reactive oxygen species has been shown to cause oxidative stress to skeletal muscle. As an adaptive response, muscle antioxidant defense systems are upregulated in response to exercise. Nuclear factor kappaB and mitogen-activated protein kinase are two major oxidative-stress-sensitive signal transduction pathways that have been shown to activate the gene expression of a number of enzymes and proteins that play important roles in maintenance of intracellular oxidant-antioxidant homeostasis. This mini-review will discuss the main mechanisms and gene targets for these signaling pathways during exercise and the biological significance of the adaptation.

NF-kappa B-mediated adaptive resistance to ionizing radiation

Ionizing radiation (IR) began to be a powerful medical modality soon after Wilhelm Röntgen's discovery of X-rays in 1895. Today, more than 50% of cancer patients receive radiotherapy at some time during the course of their disease. Recent technical developments have significantly increased the precision of dose delivery to the target tumor, making radiotherapy more efficient in cancer treatment. However, tumor cells have been shown to acquire a radioresistance that has been linked to increased recurrence and failure in many patients. The exact mechanisms by which tumor cells develop an adaptive resistance to therapeutic fractional irradiation are unknown, although low-dose IR has been well defined for radioadaptive protection of normal cells. This review will address the radioadaptive response, emphasizing recent studies of molecular-level reactions. A prosurvival signaling network initiated by the transcription factor NF-kappa B, DNA-damage sensor ATM, oncoprotein HER-2, cell cyclin elements (cyclin B1), and mitochondrial functions in radioadaptive resistance is discussed. Further elucidation of the key elements in this prosurvival network may generate novel targets for resensitizing the radioresistant tumor cells.

Mechanisms of protection against pulmonary hyperbaric O(2) toxicity by intermittent air breaks

Intermittent exposure to air is used as a protective strategy against hyperbaric O(2) (HBO(2)) toxicity. Little is known about optimal intermittent exposure schedules and the mechanism of protection. In this study, we examined the role of antioxidant enzymes, and inflammatory cytokines in the mechanism of HBO(2) tolerance by intermittent air breaks. One group of rats was exposed continuously to 282 kPa O(2) until death. Other groups were exposed to 30, 60, and 120 min intervals of HBO(2) with different numbers of intermittent 30 min air breaks (1-12 breaks). After the final break, animals were exposed to HBO(2) until death. In a separate experiment, animals were sacrificed before terminal exposure and lung tissues were collected for analysis of gene expression. Two intermittent schedules with 6 h cumulative O(2) time (30/30 and 60/30 min schedules) were compared with continuous exposure to HBO(2) for 6 h and with intermittent exposure of 8 h (120/30 min schedule) duration. Continuous exposure resulted in activation of inflammatory cytokine TNF-alpha and IL-1beta mRNA expression, an increase in lung protein nitration and activation of inducible NOS (iNOS) mRNA. Inflammatory response was not observed at intermittent exposures of the same cumulative O(2) time duration (30/30 and 60/30 min schedule). Expression of heme oxygenase-1 (HO-1) mRNA was significantly increased in all exposure groups while manganese superoxide dismutase (MnSOD) mRNA expression was increased only in continuous and 120/30 exposure groups. Results show that intermittent exposure to air protects against pulmonary HBO(2) toxicity by inhibiting inflammation. The mechanism of inhibition may involve the antiinflammatory and antioxidative effect of HO-1 but some other mechanisms may also be involved in protection by intermittent air breaks.

Manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by the free thiol form of amifostine and tumor necrosis factor alpha

RKO36 cells, a subclone of RKO colorectal carcinoma cells that have been stably transfected with the pCMV-EGFP2Xho vector, were grown to confluence and then exposed to either the radioprotector WR-1065, i.e. the active thiol form of amifostine, for 30 min at doses of 40 microM and 4 mM or the cytokine tumor necrosis factor alpha (TNFalpha, TNFA) for 30 min at a concentration of 10 ng/ml and then washed. Total protein was isolated as a function of time up to 32 h after these treatments. Both doses of WR-1065 as well as the concentration of TNFalpha used were effective in elevating intracellular levels of the antioxidant protein SOD2 (also known as MnSOD) at least 15-fold over background levels as determined by Western blot analysis, while measured SOD2 activity was elevated between 5.5- and 6.9-fold. SOD2 reached a maximal level 24 h and 20 h after WR-1065 and TNFalpha treatments, respectively. The antioxidant proteins catalase and glutathione peroxidase (GPX) were also monitored over the 32-h period. In contrast to the robust changes observed in intracellular levels of SOD2 as a function of time after exposure of cells to WR-1065, catalase levels were elevated only 2.6-fold over background as determined by Western blot analysis, while GPX activity was unaffected by WR-1065 exposure. GPX protein levels were extremely low in cells, and analysis of GPX activity using a spectrophotometric method based on the consumption of reduced NADPH also revealed no measurable change as a function of WR-1065 or TNFalpha exposure. RKO36 cells either were irradiated with X rays in the presence of either 40 microM or 4 mM WR-1065 or 10 ng/ml TNFalpha or were irradiated 24 or 20 h later, respectively, when SOD2 protein levels were most elevated. The concentrations and exposure conditions used for WR-1065 and TNFalpha were not cytotoxic and had no effect on plating efficiencies or cell survival compared to untreated controls. No protection or sensitization was observed for cells irradiated in the presence of 40 microM WR-1065 or TNFalpha. Survival was elevated 1.90-fold for cells irradiated in the presence of 4 mM WR-1065. When RKO36 cells were irradiated with 2 Gy 24 h after 40 microM or 4 mM WR-1065 and 20 h after TNFalpha treatments when SOD2 levels were the most increased, survival was elevated 1.42-, 1.48- and 1.36-fold, respectively. This increased survival represents a SOD2-mediated delayed radioprotective effect. SOD2 appears to be an important antioxidant gene whose inducible expression is an important element in adaptive cellular responses in general, and the delayed radioprotective effect in particular. It can be induced by a range of agents including cytoprotective nonprotein thiols such as WR-1065 and pleiotropic cytokines such as TNFalpha.

Microtubules are required for NF-kappaB nuclear translocation in neuroblastoma IMR-32 cells: modulation by zinc

The relevance of a functional cytoskeleton for Nuclear Factor-kappaB (NF-kappaB) nuclear translocation was investigated in neuronal cells, using conditions that led to a disruption of the cytoskeleton [inhibition of tubulin (vinblastine, colchicine), or actin (cytochalasin D) polymerization and zinc deficiency]. We present evidence that an impairment in tubulin polymerization can inhibit the formation of the complex tubulin-dynein-karyopherin alpha-p50 that is required for neuronal retrograde and nuclear NF-kappaB transport. Cells treated with vinblastine, colchicine or cytochalasin D, and zinc deficient cells, all showed a low nuclear NF-kappaB binding activity, and low nuclear concentrations of RelA and p50. The altered nuclear translocation was reflected by a decreased transactivation of NF-kappaB-driven genes. The immunocytochemical characterization of cellular RelA showed that cytoskeleton disruption can lead to an altered distribution of RelA resulting in the formation of peripheral accumuli. These results support the concept that cytoskeleton integrity is necessary for the transport and translocation of NF-kappaB required for synapse to nuclei communication. We suggest that during development, as well as in the adult brain, conditions such as zinc deficiency, that affect the normal structure and function of the cytoskeleton can affect neuronal proliferation, differentiation, and survival by altering NF-kappaB nuclear translocation and subsequent impairment of NF-kappaB-dependent gene regulation.

Overexpression of manganese superoxide dismutase by N-acetylcysteine in hyperoxic lung injury

BACKGROUND

Exposure of animals to hyperoxia causes lung injury, characterized by diffuse alveolar damage and exudation of plasma into the alveolar space. Reactive oxygen species (ROS) play an important role in the development of hyperoxic lung injury. Mitochondrial oxidative phosphorylation is one of the major sources of ROS. N-acetylcysteine (NAC) is a precursor of glutathione (GSH), which functions as an antioxidant by reducing hydrogen peroxide to water and alcohols. NAC has been shown to diminish lung injury in a large variety of animal models.

AIM

We elucidated the mechanism underlying the protective effects of NAC in hyperoxia-induced lung injury.

METHODS

Male BALB/c mice were exposed to 98% oxygen for 72 h. The mice inhaled NAC or saline twice a day from 72 h before oxygen exposure to the end of experiment.

RESULTS

Inhaled NAC increased the GSH level in lung homogenate. NAC also attenuated cellular infiltrations in both bronchoalveolar lavage fluid (BALF) and lung tissue. The total protein level in BALF and the level of 8-isoprostane, a marker of lipid peroxidation, in lung homogenate were decreased by inhalation of NAC. Inhaled NAC induced the overexpression of Mn superoxide dismutase (MnSOD) mRNA and protein, but did not alter the expressions of other antioxidant enzymes, including CuZnSOD, extracellular SOD, and glutathione peroxydase 1.

CONCLUSION

These findings suggest that the antioxidant properties of NAC in hyperoxic lung injury involve a decrease in mitochondrial ROS in association with the induction of MnSOD, in addition to its role as a precursor of GSH.

Thioredoxin and its role in premature newborn biology

Thioredoxin (Trx) is a redox-active protein that has been shown to regulate various cellular processes due to its thiol-disulfide exchange reaction. It has antioxidant properties and also induces the expression of critical antioxidant enzymes such as manganese superoxide dismutase. Trx along with thioredoxin reductase and peroxiredoxins forms a complete system similar to the glutathione system, but with different and divergent functions. This review is a mini-update on key advances in the role of Trx in signal transduction and premature newborn biology. In addition, this mini-update also reviews recently reported prooxidant properties of Trx that relate to anthracycline redox cycling.

Inhibition of TNFalpha in vivo prevents hyperoxia-mediated activation of caspase 3 in type II cells

Background

The mechanisms during the initial phase of oxygen toxicity leading to pulmonary tissue damage are incompletely known. Increase of tumour necrosis factor alpha (TNFalpha) represents one of the first pulmonary responses to hyperoxia. We hypothesised that, in the initial phase of hyperoxia, TNFalpha activates the caspase cascade in type II pneumocytes (TIIcells).

Methods

Lung sections or freshly isolated TIIcells of control and hyperoxic treated rats (48 hrs) were used for the determination of TNFalpha (ELISA), TNF-receptor 1 (Western blot) and activity of caspases 8, 3, and 9 (colorimetrically). NF-kappaB activation was determined by EMSA, by increase of the p65 subunit in the nuclear fraction, and by immunocytochemistry using a monoclonal anti-NF-kappaB-antibody which selectively stained the activated, nuclear form of NF-kappa B. Apoptotic markers in lung tissue sections (TUNEL) and in TIIcells (cell death detection ELISA, Bax, Bcl-2, mitochondrial membrane potential, and late and early apoptotic cells) were measured using commercially available kits.

Results

In vivo, hyperoxia activated NF-kappaB and increased the expression of TNFalpha, TNF-receptor 1 and the activity of caspase 8 and 3 in freshly isolated TIIcells. Intratracheal application of anti-TNFalpha antibodies prevented the increase of TNFRI and of caspase 3 activity. Under hyperoxia, there was neither a significant change of cytosolic cytochrome C or of caspase 9 activity, nor an increase in apoptosis of TIIcells. Hyperoxia-induced activation of caspase 3 gradually decreased over two days of normoxia without increasing apoptosis. Therefore, activation of caspase 3 is a temporary effect in sublethal hyperoxia and did not mark the "point of no return" in TIIcells.

Conclusion

In the initiation phase of pulmonary oxygen toxicity, an increase of TNFalpha and its receptor TNFR1 leads to the activation of caspase 8 and 3 in TIIcells. Together with the hyperoxic induced increase of Bax and the decrease of the mitochondrial membrane potential, activation of caspase 3 can be seen as sensitisation for apoptosis. Eliminating the TNFalpha effect in vivo by anti-TNFalpha antibodies prevents the pro-apoptotic sensitisation of TIIcells.

Delayed radioprotection by NFkappaB-mediated induction of Sod2 (MnSOD) in SA-NH tumor cells after exposure to clinically used thiol-containing drugs

The ability of thiol-containing reducing agents to activate transcription factors leading to changes in gene expression and enzyme activities provides an additional mechanism to potentially protect against radiation-induced cell killing. Manganese superoxide dismutase (Sod2) is one such gene whose expression levels have been shown to be elevated after exposure to the thiol compounds WR-1065 and N-acetyl-L-cysteine (NAC), resulting in an increase in radiation resistance. To further characterize this effect, SA-NH sarcoma cells, both wild-type and a clone stably transfected with a plasmid containing an IkappaBalpha gene mutated at serines 32 and 36, which prevents the inducible phosphorylation of these residues and the subsequent activation of NFkappaB (SA-NH+mIkappaBalpha1), were grown to confluence and then exposed to amifostine's free thiol WR-1065 at a concentration of 4 mM for 30 min. Effects of thiol exposure on NFKB activation in SA-NH+mIkappaBalpha1 cells were determined by a gel shift assay, and changes in Sod2 protein levels in these cells 24 h after exposure to 40 microM or 4 mM WR-1065 were measured by Western blot analysis and compared with wild-type cells exposed to the NFkappaB inhibitor BAY 11-7082. Changes in radiation response, measured immediately after thiol exposure or 24 h later, were determined using a colony-forming assay and were correlated with NFKB activation and Sod2 protein levels. The effects of captopril, mesna and NAC, each at a dose of 4 mM, on radiation response were also determined and contrasted with those of WR-1065. Only WR-1065 and captopril protected SA-NH cells when present during irradiation, i.e. 1.57 and 1.31 times increase in survival at 2 Gy, respectively. All four thiols were protective if irradiation with 2 Gy occurred 24 h later; i.e. increases in survival of 1.40, 1.22, 1.35, and 1.25 times were found for WR-1065, captopril, mesna and NAC, respectively. This delayed radioprotective effect correlated with elevated Sod2 protein levels in wild-type SA-NH tumor cells but was not observed in SA-NH+mIkappaBalpha1 cells, indicating that interference with thiol-induced NFKB activation abrogates this delayed radioprotective effect. Because the delayed radioprotective effect is readily demonstrable at a radiation dose of 2 Gy 24 h after exposure to clinically approved thiol-containing drugs such as amifostine, captopril, mesna and NAC, it suggests a new potential concern regarding the issue of tumor protection and the use of these agents in cancer therapy.

The regulation and role of extracellular glutathione peroxidase

Reactive oxygen species and reactive nitrogen species are mediators of lung tissue damage. To minimize the effect of oxidative stress, the lung is well equipped with an integrated antioxidant system. In some circumstances, antioxidants increase in response to oxidants and reduce tissue injury. The lung is somewhat unique in that it has an extracellular surface, which is often directly exposed to oxidative stresses. In this context, the extracellular antioxidant system, comprised primarily of glutathione and glutathione peroxidase, is especially important in protecting against oxidant injury. Induction of extracellular glutathione peroxidase occurs in airway inflammation and undoubtedly plays an important defense against oxidative injury to the airway surface.

A biphasic role of nuclear transcription factor (NF)-κB in the islet β-cell apoptosis induced by interleukin (IL)-1β

IL-1beta is an important mediator in the pathogenesis of type 1 diabetes both in vivo and in vitro and it has been shown to induce islet beta-cell apoptosis. Most of the IL-1beta effects seem to be mediated by NF-kappaB transcription factor activation, but its role in the induction of islet beta-cell apoptosis has not yet been clarified. Taking advantage of the protease inhibitor TPCK (N-tosyl-L-phenylalanine chloromethyl ketone), which specifically inhibits the nuclear transcription factor NF-kappaB activation, we studied the role of NF-kappaB in the rIL-1beta treated rat pancreatic islets. Our results show that TPCK blocked rIL-1beta-mediated early increase of MnSOD activity and beta-cell defence/repair protein expression, suggesting a protective role for NF-kappaB at the beginning of IL-1beta treatment; but, in a second phase, NF-kappaB induces a sustained decrease of specific beta-cell proteins like insulin, GLUT-2 and PDX-1 with a concomitant increase of aspecific proteins and iNOS transcription. The appearance of iNOS expression correlates with increased levels of nitrite + nitrate levels and appearance of mitochondrial damage detected either at morphological and biochemical level. After 36 h of IL-1beta treatment islet beta-cells begin to undergo apoptosis. Since IL-1beta induction of apoptosis is completely prevented by TCPK treatment, this finding underscores the central role of NF-kappaB in this process. Thus, our results clearly indicate that NF-kappaB regulates MnSOD genes expression and MnSOD activity, which protects islet beta-cells by IL-1beta damage. Furthermore, when the IL-1beta stress impairs islet beta-cell function, NF-kappaB activation regulates the entrance of islet beta-cell into the cell death program.

Involvement of Rel/NF-kappa B transcription factors in senescence

Senescence is now established as a genetically controlled phenomenon that alters different cell functions, including proliferation, apoptosis, resistance to stress, and energetic metabolism. Underlying changes in gene expression are governed by some transcription factors, whose expression or activity must change with senescence as well. Transcription factors of the Rel/NF-kappa B family are good candidates to participate in the establishment of senescence. Arguments range from correlation between cell functions controlled by these factors and cell functions altered during senescence, to phenotypes resulting from in vitro manipulations of Rel/NF-kappa B activity.

Identification of nucleophosmin as an NF-kappaB co-activator for the induction of the human SOD2 gene

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme essential for the survival of life. We have reported that NF-kappaB is essential but not sufficient for the synergistic induction of MnSOD by phorbol 12-myristate 13-acetate and cytokines. To further identify transcription factors and co-activators that participate in the induction of MnSOD, we used NF-kappaB affinity chromatography to isolate potential NF-kappaB interacting proteins. Proteins eluted from the NF-kappaB affinity column were subjected to proteomic analysis and verified by Western analysis. Nucleophosmin (NPM), a nucleolar phosphoprotein, is the most abundant single protein identified. Co-immunoprecipitation studies suggest a physical interaction between NPM and NF-kappaB proteins. To verify the role of NPM on MnSOD gene transcription, cells were transfected with constructs expressing NPM in sense or antisense orientation as well as interference RNA. The results indicate that an increase NPM expression leads to increased MnSOD gene transcription in a dose-dependent manner. Consistent with this, expression of small interfering RNA for NPM leads to inhibition of MnSOD gene transcription but does not have any effect on the expression of interleukin-8, suggesting that the effect of NPM is selective. These results identify NPM as a partner of the NF-kappaB transcription complex in the induction of MnSOD by phorbol 12-myristate 13-acetate and cytokines.

Construction of a subtractive library from hexavalent chromium treated winter flounder (Pseudopleuronectes americanus) reveals alterations in non-selenium glutathione peroxidases

Chromium is released during several industrial processes and has accumulated in some estuarine areas. Its effects on mammals have been widely studied, but relatively little information is available on its effects on fish. Gene expression changes are useful biomarkers that can provide information about toxicant exposure and effects, as well as the health of an organism and its ability to adapt to its surroundings. Therefore, we investigated the effects of Cr(VI) on gene expression in the sediment dwelling fish, winter flounder (Pseudopleuronectes americanus). Winter flounder ranging from 300 to 360 g were injected i.p. with Cr(VI) as chromium oxide at 25 microg/kg chromium in 0.15N KCl. Twenty-four hours following injections, winter flounder were euthanized with MS-222 and the livers were excised. Half of the livers were used to make cytosol and the other half were used to isolate mRNA for subtractive hybridization. Subtractive clones obtained were spotted onto nylon filters, which revealed several genes with potentially altered expression due to Cr(VI), including an alpha class GST, 1-Cys peroxiredoxin (a non-selenium glutathione peroxidase), a P-450 2X subfamily member, two elongation factors (EF-1 gamma and EF-2), and complement component C3. Semi-quantitative RT-PCR was performed and confirmed that Cr(VI) down-regulated complement component C3, an EST, and two potential glutathione peroxidases, GSTA3 and 1-Cys peroxiredoxin. In addition, cytosolic GSH peroxidase activity was reduced, and silver stained SDS-PAGE gels from glutathione-affinity purified cytosol demonstrated that a 27.1 kDa GSH-binding protein was down-regulated greater than 50%. Taken together, Cr(VI) significantly altered the expression of several genes including two potential glutathione peroxidases in winter flounder.

Redox events in interleukin-1 signaling

There is increasing evidence that reactive oxygen species (ROS) are mediators in growth factor and cytokine signaling pathways. Mechanisms by which ROS can interfere with signaling cascades may include regulation of protein activities by the modification of essential cysteines. Modification can be performed chemically or enzyme-catalyzed. Enzymes catalyzing a reversible thiol modification within proteins are to be able to react with both, ROS and protein thiols. If hydroperoxides are involved, promising candidates are peroxiredoxins and glutathione peroxidases (GPx), especially the phospholipid hydroperoxide GPx. Interleukin-1, one of the key players in inflammatory response, stimulates the production of ROS itself, but its signaling cascade can also be influenced by ROS and by thiol modifying agents. Targets are located in early, intermediate, and late events in the signaling cascade. We here summarize what is known about the effects of thiol modifying agents, selenium and glutathione peroxidases, on the assembly of the IL-1 receptor signaling complex as an early event, on the activation of NF-kappa B as an intermediate event, and on the expression of cell adhesion molecules as a late event in IL-1 signaling.

Superoxide dismutases in malignant cells and human tumors

Reactive oxygen metabolites have multifactorial effects on the regulation of cell growth and the capacity of malignant cells to invade. Overexpression of the superoxide dismutases (SODs) in vitro increases cell differentiation, decreases cell growth and proliferation, and can reverse a malignant phenotype to a nonmalignant one. The situation in vivo is more complex due to multiple interactions of tumor cells with their environment. Numerous in vivo studies show that the superoxide dismutases can be highly expressed in aggressive human solid tumors. Furthermore, high SOD has occasionally been associated with a poor prognosis and with resistance to cytotoxic drugs and radiation. Most of the apparent conflicts between the above in vitro and in vivo observations can be reconciled by considering the net redox status of tumor cells in different environments. Administering high concentrations of SOD to cells in vitro is usually associated with a non- or less malignant phenotype, whereas secondary induction of SOD in tumors in vivo can be associated with an aggressive malignant transformation probably due to the altered (oxidative) redox state in the malignant cells. This concept suggests that for many types of tumors antioxidants could be used to diminish the invasive capability of malignant cells.

Mitochondrial formation of reactive oxygen species

The reduction of oxygen to water proceeds via one electron at a time. In the mitochondrial respiratory chain, Complex IV (cytochrome oxidase) retains all partially reduced intermediates until full reduction is achieved. Other redox centres in the electron transport chain, however, may leak electrons to oxygen, partially reducing this molecule to superoxide anion (O2-*). Even though O2-* is not a strong oxidant, it is a precursor of most other reactive oxygen species, and it also becomes involved in the propagation of oxidative chain reactions. Despite the presence of various antioxidant defences, the mitochondrion appears to be the main intracellular source of these oxidants. This review describes the main mitochondrial sources of reactive species and the antioxidant defences that evolved to prevent oxidative damage in all the mitochondrial compartments. We also discuss various physiological and pathological scenarios resulting from an increased steady state concentration of mitochondrial oxidants.

Glutathione mediates LPS-stimulated COX-2 expression via early transient p42/44 MAPK activation

This study examines whether endotoxin (LPS)-stimulated COX-2 is modulated by an interaction between mitogen activated protein kinases (MAPK) and intracellular glutathione. Bovine pulmonary artery endothelial cells (BPAEC) were pretreated for 30 min with the following prior to addition of 0.1 microg/ml endotoxin in 2% FBS in medium 199: 5 mM N-acetylcysteine (NAC) or 5 mM glutathione ethyl ester (GSE) (modulators of intracellular glutathione); 10 microM SB203580 or 25 microM PD98059 (inhibitors of p38 and p42/44 MAPKs, respectively). End-points included assessment of COX-1 and COX-2 gene expression by reverse transcription polymerase chain reaction (RT-PCR); COX-1, COX-2, p38, and p42/44 protein by Western analysis; and measurement of PGE2 and 6-keto-PGF1alpha releases by GC/MS. Both GSE and NAC resulted in significant exacerbation of the LPS-stimulated increase in COX-2 gene and protein expression and prostaglandin release, and suppressed the LPS-induced decrease in COX-1. LPS caused a biphasic activation of p42/44 MAPKs, an early increase peaking at 30 min and a second sustained phase, lasting up to 24 h; LPS also caused an early and sustained increase p38 MAPK activity. Pretreatment of cells with either GSE or NAC increased the early LPS-stimulated activation of p42/44 but had little effect on the sustained phase. Inhibition of either p38 or p42/44 MAPKs suppressed LPS-stimulated COX-2 gene and protein expression, and prostaglandin release (P<0.05) but had little effect on COX-1. We conclude that intracellular glutathione modulates LPS-stimulated COX-2 gene expression and prostaglandin synthesis in BPAEC via early activation of p42/44 MAPKs.

Superoxide dismutases in the lung and human lung diseases

The lungs are directly exposed to higher oxygen concentrations than most other tissues. Increased oxidative stress is a significant part of the pathogenesis of obstructive lung diseases such as asthma and chronic obstructive pulmonary disease, parenchymal lung diseases (e.g., idiopathic pulmonary fibrosis and lung granulomatous diseases), and lung malignancies. Lung tissue is protected against these oxidants by a variety of antioxidant mechanisms among which the superoxide dismutases (SODs) are the only ones converting superoxide radicals to hydrogen peroxide. There are three SODs: cytosolic copper-zinc, mitochondrial manganese, and extracellular SODs. These enzymes have specific distributions and functions. Their importance in protecting lung tissue has been confirmed in transgenic and knockout animal studies. Relatively few studies have been conducted on these enzymes in the normal human lung or in human lung diseases. Most human studies suggest that there is induction of manganese SOD and, possibly, extracellular SOD during inflammatory, but not fibrotic, phases of parenchymal lung diseases and that both copper-zinc SOD and manganese SOD may be downregulated in asthmatic airways. Many previous antioxidant therapies have been disappointing, but newly characterized SOD mimetics are being shown to protect against oxidant-related lung disorders in animal models.

Science review: Redox and oxygen-sensitive transcription factors in the regulation of oxidant-mediated lung injury: role for nuclear factor-kappaB

The primary role of pulmonary airways is to conduct air to the alveolar epithelium, where gas exchange can efficiently occur. Injuries to airways resulting from inhalation of airborne pollutants and parenteral exposure to ingested pollutants that cause oxidative stress have the potential to interfere with this process. A progressive rise of oxidative stress due to altered reduction-oxidation (redox) homeostasis appears to be one of the hallmarks of the processes that regulate gene transcription in lung physiology and pathophysiology. Reactive metabolites serve as signaling messengers for the evolution and perpetuation of the inflammatory process that is often associated with cell death and degeneration. Redox-sensitive transcription factors are often associated with the development and progression of many human disease states and inflammatory-related injury, particularly of the lung. The present review elaborates on the role of the redox-sensitive and oxygen-sensitive transcription factor NF-kappaB in mediating lung injury. Changes in the pattern of gene expression through regulatory transcription factors are crucial components of the machinery that determines cellular responses to oxidative and redox perturbations. Additionally, the discussion of the possible therapeutic approaches of antioxidants, thiol-related compounds and phosphodiesterase inhibitors as anti-inflammatory agents will thereby help understand the oxidant/redox-mediated lung injury mechanisms.

Heat-shock protein 25 (Hspb1) regulates manganese superoxide dismutase through activation of Nfkb (NF-kappaB)

We previously demonstrated that overexpression of HSP25 (now known as Hspb1) conferred increased resistance to ionizing radiation (Radiat Res. 154, 421-428, 2000). In the present study, L929 cells overexpressing Hspb1 were shown to have increased expression of the manganese superoxide dismutase gene (now known as SOD2) and its enzyme activity. To elucidate Hspb1-induced pathways leading to activation of these antioxidant enzymes, the production of the tumor necrosis factor alpha (Tnf) and interleukin 1 beta (Il1b) genes was examined. Increased expression of Tnf and Il1b resulting from Hspb1 overexpression was detected by RT-PCR. Increased activation of Nfkb (degradation of Ikb, a member of the Nfkb family) was also found in Hspb1-overexpressing cells. When treated with Tnf, Nfkb activation and SOD2 gene expression were increased more by Hspb1 overexpression. Moreover, transfection with the Hspb1 antisense gene abrogated all of the Hspb1-mediated phenomena. To further elucidate the exact relationship between induction of SOD2 and Nfkb activation, a dominant negative I-kBalpha (now known as Nfkb1a) construct was transfected into Hspb1-overexpressing cells. The dominant negative Nfkb1a inhibited Hspb1-mediated SOD2 gene expression. In addition, Hspb1-mediated radioresistance was blocked by dominant negative Nfkb1a transfection. When the SOD2 gene was transfected into L929 cells, a somewhat increased radioresistance was detected by a clonogenic survival assay compared to control cells. Hspb1 produced Tnf and Il1b and facilitated SOD2 gene expression through Nfkb activation, possibly resulting in Hspb1-mediated radioresistance.

Propapoptotic effects of NF-kappaB in LNCaP prostate cancer cells lead to serine protease activation

LNCaP prostate cancer cells are resistant to induction of apoptosis by gamma-irradiation and partially sensitive to TNF-alpha or FAS antibody, irradiation sensitizes cells to apoptosis induced by FAS antibody or TNF-alpha. LNCaP cell clones stably expressing IkappaBalpha super repressor were resistant to apoptosis induced by death ligands in the presence or absence of irradiation. IkappaBalpha super repressor expression also increased clonogenic survival after exposure to TNF-alpha+irradiation, but had no effect on survival after irradiation alone. IkappaBalpha super repressor expression blocked the increase of whole cell and cell surface FAS expression induced by TNF-alpha, but did not effect induction of FAS expression and cell surface FAS expression that resulted from irradiation. In cells expressing IkappaBalpha super repressor there was diminished activation of caspases-8 and -7 and diminished production of proscaspases-8 and -7, usually required for death induction in LNCaP cells. Peptide inhibitors of caspase activation complemented the IkappaBalpha super repressor inhibition of apoptosis, but peptide inhibitors of serine proteases had no effect on LNCaP cells expressing IkappaBalpha super repressor. Moreover, cleavage of a serine protease substrate was induced by treatment of LNCaP cells with TNF-alpha and irradiation. The data suggest that in LNCaP cells NF-kappaB mediates a proapoptotic pathway that leads to activation of proapoptotic serine proteases.

Regulation of enzymatic lipid peroxidation: the interplay of peroxidizing and peroxide reducing enzymes

For a long time lipid peroxidation has only been considered a deleterious process leading to disruption of biomembranes and thus, to cellular dysfunction. However, when restricted to a certain cellular compartment and tightly regulated, lipid peroxidation may have beneficial effects. Early on during evolution of living organisms special lipid peroxidizing enzymes, called lipoxygenases, appeared and they have been conserved during phylogenesis of plants and animals. In fact, a diverse family of lipoxygenase isoforms has evolved starting from a putative ancient precursor. As with other enzymes, lipoxygenases are regulated on various levels of gene expression and there are endogenous antagonists controlling their cellular activity. Among the currently known mammalian lipoxygenase isoforms only 12/15-lipoxygenases are capable of directly oxygenating ester lipids even when they are bound to membranes and lipoproteins. Thus, these enzymes represent the pro-oxidative part in the cellular metabolism of complex hydroperoxy ester lipids. Its metabolic counterplayer, representing the antioxidative part, appears to be the phospholipid hydroperoxide glutathione peroxidase. This enzyme is unique among glutathione peroxidases because of its capability of reducing ester lipid hydroperoxides. Thus, 12/15-lipoxygenase and phospholipid hydroperoxide glutathione peroxidase constitute a pair of antagonizing enzymes in the metabolism of hydroperoxy ester lipids, and a balanced regulation of the two proteins appears to be of major cell physiological importance. This review is aimed at summarizing the recent developments in the enzymology and molecular biology of 12/15-lipoxygenase and phospholipid hydroperoxide glutathione peroxidase, with emphasis on cytokine-dependent regulation and their regulatory interplay.

Delayed cytoprotection after enhancement of Sod2 (MnSOD) gene expression in SA-NH mouse sarcoma cells exposed to WR-1065, the active metabolite of amifostine

SA-NH mouse sarcoma cells were grown to confluence and then exposed to either 40 microM or 4 mM of WR-1065, i.e. the active thiol form of amifostine, for 30 min and then washed. Total RNA and protein were isolated at various times up to 24 h after exposure. Both concentrations of WR-1065 were equally effective in affecting Sod2 (also known as MnSOD) gene expression and protein levels. Northern blot analysis using a mouse cDNA probe revealed three Sod2 transcripts of 1, 4 and 6 kb. Expression of both the 4- and 6-kb transcripts increased by 20 and 60%, respectively, and remained elevated over a period of 4 to 20 h. Sod2 protein levels, as determined by Western blot analysis, increased 15-fold over background control levels over the same interval. Sod2 protein was evaluated using activity gels and was found to be active. SA-NH cells were irradiated with X rays either in the presence of 40 microM or 4 mM WR-1065 or 24 h later after its removal, when Sod2 protein levels were most elevated. No protection was observed for cells irradiated in the presence of 40 microM WR-1065. In contrast, survival after a dose of 2 Gy was elevated 1.27-, 1.14- and 1.20-fold in SA-NH cells irradiated in the presence of 4 mM WR-1065 or 24 h after exposure of the cells to 40 microM and 4 mM WR-1065, respectively. The increased survival levels observed 24 h after exposure to WR-1065 represents a delayed radioprotective effect of WR-1065 and corresponds to the time at which Sod2 protein levels are most elevated. These data demonstrate a novel mechanism for radioprotection by WR-1065 and suggest a new potential concern regarding the issue of tumor protection.

Induction of MnSOD gene by arachidonic acid is mediated by reactive oxygen species and p38 MAPK signaling pathway in human HepG2 hepatoma cells

Metabolism of arachidonic acid (AA) is known to induce in different cell types an oxidative stress via the production of reactive oxygen species. As these latter may be scavenged by antioxidant enzymes as manganese and copper/zinc-dependent superoxide dismutase (MnSOD and Cu/ZnSOD, respectively), we investigated the effects of AA on their expression in human HepG2 hepatoma cells. RT-PCR and Western blot data revealed that AA induced an increase in the MnSOD, but not Cu/ZnSOD, expression at the mRNA and protein levels, respectively. This induction was also marked by an increase in MnSOD activity. The AA-induced MnSOD expression required de novo transcription as demonstrated by cotreatment of HepG2 cells with AA and actinomycin D. The fact that MnSOD expression was not induced when HepG2 cells were cultured with 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolizable analog of AA, or with different inhibitors of the AA metabolism pathways suggested that the metabolism of AA was required. Further investigations into the mechanisms by which AA induced MnSOD expression showed that superoxide anions released from AA metabolism act as second messengers via a signal-controlling pathway involving protein kinase C and p38 mitogen activated protein kinase (MAPK). These results define a novel role of p38 MAPK dependent-pathway in the regulation of MnSOD gene.