Oxyl radicals, redox-sensitive signalling cascades and antioxidants

Reactivation of p53 by a Cytoskeletal Sensor to Control the Balance Between DNA Damage and Tumor Dissemination

BACKGROUND

Abnormal cell migration and invasion underlie metastasis, and actomyosin contractility is a key regulator of tumor invasion. The links between cancer migratory behavior and DNA damage are poorly understood.

METHODS

Using 3D collagen systems to recapitulate melanoma extracellular matrix, we analyzed the relationship between the actomyosin cytoskeleton of migrating cells and DNA damage. We used multiple melanoma cell lines and microarray analysis to study changes in gene expression and in vivo intravital imaging (n = 7 mice per condition) to understand how DNA damage impacts invasive behavior. We used Protein Tissue Microarrays (n = 164 melanomas) and patient databases (n = 354 melanoma samples) to investigate the associations between markers of DNA damage and actomyosin cytoskeletal features. Data were analyzed with Student's and multiple t tests, Mann-Whitney's test, one-way analysis of variance, and Pearson correlation. All statistical tests were two-sided.

RESULTS

Melanoma cells with low levels of Rho-ROCK-driven actomyosin are subjected to oxidative stress-dependent DNA damage and ATM-mediated p53 protein stabilization. This results in a specific transcriptional signature enriched in DNA damage/oxidative stress responsive genes, including Tumor Protein p53 Inducible Protein 3 (TP53I3 or PIG3). PIG3, which functions in DNA damage repair, uses an unexpected catalytic mechanism to suppress Rho-ROCK activity and impair tumor invasion in vivo. This regulation was suppressed by antioxidants. Furthermore, PIG3 levels decreased while ROCK1/2 levels increased in human metastatic melanomas (ROCK1 vs PIG3; r = -0.2261, P < .0001; ROCK2 vs PIG3: r = -0.1381, P = .0093).

CONCLUSIONS

The results suggest using Rho-kinase inhibitors to reactivate the p53-PIG3 axis as a novel therapeutic strategy; we suggest that the use of antioxidants in melanoma should be very carefully evaluated.

Protocatechuic aldehyde inhibits TNF-α-induced fibronectin expression in human umbilical vein endothelial cells via a c-Jun N-terminal kinase dependent pathway

Fibronectin (FN) is one of the most important extracellular matrix proteins and plays an important role in the pathogenesis of atherosclerosis (AS). The aim of the present study was to evaluate the effect of a potent, water-soluble antioxidant, protocatechuic aldehyde (PA), which is derived from the Chinese herb Salvia miltiorrhiza, on the expression of FN in human umbilical vein endothelial cells (HUVECs) stimulated with tumor necrosis factor-α (TNF-α). The pharmacological effects of PA on the production of FN were investigated using ELISA and western blot analysis. In addition, ELISA and western blot analysis were used to examine the activation and suppression of the mitogen-activated protein kinase (MAPK) pathways and nuclear factor (NF)-κB in TNF-α-stimulated HUVECs, in order to explore the underlying pharmacological mechanism of PA. The inhibitory effect of PA on the total generation of reactive oxygen species (ROS) in TNF-α-stimulated HUVECs was assessed using 2',7'-dichlorofluorescein diacetate. Pretreatment of HUVECs with PA (0.15, 0.45 and 1.35 mM) for 18 h markedly attenuated the TNF-α-stimulated FN surface expression and secretion in a dose-dependent manner. Intracellular ROS generation and the expression of extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 MAPK (p38) were significantly induced by TNF-α (2 ng/ml) in HUVECs. TNF-α-induced ROS generation and JNK activation were inhibited by PA in a concentration-dependent manner. By contrast, ERK1/2 and p38 activation was not significantly affected by PA. Pretreatment of HUVECs with PA for 18 h markedly attenuated TNF-α-stimulated NF-κB activation. In conclusion, the present findings suggest that PA inhibits TNF-α-induced FN expression in HUVECs through a mechanism that involves ROS/JNK and NF-κB.

Effect of quercetin, genistein and kaempferol on glutathione and glutathione-redox cycle enzymes in 3T3-L1 preadipocytes

CONTEXT AND OBJECTIVE

Many studies have shown that cellular redox potential is largely determined by glutathione (GSH), which accounts for more than 90% of cellular nonprotein thiols. The aim of this study was to delineate the effect of three flavonoids - namely, quercetin, kaempferol and genistein - and exogenous GSH on oxidative damage by the Fenton's pathway through the GSH and GSH-redox cycle enzymes in 3T3-L1 cells.

MATERIALS AND METHODS

3T3-L1 preadipocytes were exposed to each flavonoid and GSH at concentrations of 0, 5, 10, 15, 20 and 25 µM and then GSH levels and activities of glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rx) and superoxide dismutase (SOD) were measured.

RESULTS

Exogenous GSH did not have significant effect on intracellular GSH although slight decrease was observed at 15-25 µM doses. However, each of the three flavonoids sustained intracellular GSH levels in the cells as compared to the respective controls. Quercetin had the most profound effect, followed by kaempferol and genistein in that order. GSH-Px, GSH-Rx and SOD activities increased for all the doses tested compared to their respective controls. Again, quercetin had the maximum increase in enzyme activities followed by kaempferol and genistein for the enzymes tested.

DISCUSSION AND CONCLUSION

These findings suggest that the flavonoids play an important role in diminishing oxidation-induced biochemical damages. The enhancement of these enzymes may increase the resistance of the organism against oxidative damage by the Fenton's pathway.

Cellular Mechanisms of Oxidative Stress and Action in Melanoma

Most melanomas occur on the skin, but a small percentage of these life-threatening cancers affect other parts of the body, such as the eye and mucous membranes, including the mouth. Given that most melanomas are caused by ultraviolet radiation (UV) exposure, close attention has been paid to the impact of oxidative stress on these tumors. The possibility that key epigenetic enzymes cannot act on a DNA altered by oxidative stress has opened new perspectives. Therefore, much attention has been paid to the alteration of DNA methylation by oxidative stress. We review the current evidence about (i) the role of oxidative stress in melanoma initiation and progression; (ii) the mechanisms by which ROS influence the DNA methylation pattern of transformed melanocytes; (iii) the transformative potential of oxidative stress-induced changes in global and/or local gene methylation and expression; (iv) the employment of this epimutation as a biomarker for melanoma diagnosis, prognosis, and drug resistance evaluation; (v) the impact of this new knowledge in clinical practice for melanoma treatment.

Oxidative stress and antioxidants in disease and cancer: a review

Reactive oxygen species (ROS), highly reactive molecules, are produced by living organisms as a result of normal cellular metabolism and environmental factors, and can damage nucleic acids and proteins, thereby altering their functions. The human body has several mechanisms to counteract oxidative stress by producing antioxidants. A shift in the balance between oxidants and antioxidants in favor of oxidants is termed as "oxidative stress". Paradoxically, there is a large body of research demonstrating the general effect of oxidative stress on signaling pathways, less is known about the initial and direct regulation of signaling molecules by ROS, or what we term the "oxidative interface." This review focuses on the molecular mechanisms through which ROS directly interact with critical signaling molecules to initiate signaling in a broad variety of cellular processes, such as proliferation and survival (MAP kinases and PI3 kinase), ROS homeostasis, and antioxidant gene regulation (Ref-1 and Nrf-2). This review also deals with classification as well as mechanisms of formation of free radicals, examining their beneficial and deleterious effects on cellular activities and focusing on the potential role of antioxidants in preventing and repairing damage caused by oxidative stress. A discussion of the role of phytochemical antioxidants in oxidative stress, disease and the epigenome is included.

Oxidative stress in neurodegenerative diseases

Reactive oxygen species are constantly produced in aerobic organisms as by-products of normal oxygen metabolism and include free radicals such as superoxide anion (O₂⁻) and hydroxyl radical (OH⁻), and non-radical hydrogen peroxide (H₂O₂). The mitochondrial respiratory chain and enzymatic reactions by various enzymes are endogenous sources of reactive oxygen species. Exogenous reactive oxygen species -inducing stressors include ionizing radiation, ultraviolet light, and divergent oxidizing chemicals. At low concentrations, reactive oxygen species serve as an important second messenger in cell signaling; however, at higher concentrations and long-term exposure, reactive oxygen species can damage cellular macromolecules such as DNA, proteins, and lipids, which leads to necrotic and apoptotic cell death. Oxidative stress is a condition of imbalance between reactive oxygen species formation and cellular antioxidant capacity due to enhanced ROS generation and/or dysfunction of the antioxidant system. Biochemical alterations in these macromolecular components can lead to various pathological conditions and human diseases, especially neurodegenerative diseases. Neurodegenerative diseases are morphologically featured by progressive cell loss in specific vulnerable neuronal cells, often associated with cytoskeletal protein aggregates forming inclusions in neurons and/or glial cells. Deposition of abnormal aggregated proteins and disruption of metal ions homeostasis are highly associated with oxidative stress. The main aim of this review is to present as much detailed information as possible that is available on various neurodegenerative disorders and their connection with oxidative stress. A variety of therapeutic strategies designed to address these pathological processes are also described. For the future therapeutic direction, one specific pathway that involves the transcription factor nuclear factor erythroid 2-related factor 2 is receiving considerable attention.

Peroxidase enzymes regulate collagen extracellular matrix biosynthesis

Myeloperoxidase and eosinophil peroxidase are heme-containing enzymes often physically associated with fibrotic tissue and cancer in various organs, without any direct involvement in promoting fibroblast recruitment and extracellular matrix (ECM) biosynthesis at these sites. We report herein novel findings that show peroxidase enzymes possess a well-conserved profibrogenic capacity to stimulate the migration of fibroblastic cells and promote their ability to secrete collagenous proteins to generate a functional ECM both in vitro and in vivo. Mechanistic studies conducted using cultured fibroblasts show that these cells are capable of rapidly binding and internalizing both myeloperoxidase and eosinophil peroxidase. Peroxidase enzymes stimulate collagen biosynthesis at a post-translational level in a prolyl 4-hydroxylase-dependent manner that does not require ascorbic acid. This response was blocked by the irreversible myeloperoxidase inhibitor 4-amino-benzoic acid hydrazide, indicating peroxidase catalytic activity is essential for collagen biosynthesis. These results suggest that peroxidase enzymes, such as myeloperoxidase and eosinophil peroxidase, may play a fundamental role in regulating the recruitment of fibroblast and the biosynthesis of collagen ECM at sites of normal tissue repair and fibrosis, with enormous implications for many disease states where infiltrating inflammatory cells deposit peroxidases.

N-terminal and C-terminal domains of calmodulin mediate FADD and TRADD interaction

FADD (Fas–associated death domain) and TRADD (Tumor Necrosis Factor Receptor 1-associated death domain) proteins are important regulators of cell fate in mammalian cells. They are both involved in death receptors mediated signaling pathways and have been linked to the Toll-like receptor family and innate immunity. Here we identify and characterize by database search analysis, mutagenesis and calmodulin (CaM) pull-down assays a calcium-dependent CaM binding site in the α-helices 1–2 of TRADD death domain. We also show that oxidation of CaM methionines drastically reduces CaM affinity for FADD and TRADD suggesting that oxidation might regulate CaM-FADD and CaM-TRADD interactions. Finally, using Met-to-Leu CaM mutants and binding assays we show that both the N- and C-terminal domains of CaM are important for binding.

Terminalia catappa L.: a medicinal plant from the Caribbean pharmacopeia with anti-Helicobacter pylori and antiulcer action in experimental rodent models

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia catappa L. (Combretaceae) is a medicinal plant listed as a pharmacopeia vegetable from Caribbean to treat gastritis. The objective of this study was to evaluate the gastroprotective and healing effect of the aqueous fraction (FrAq) obtained from the leaves of Terminalia catappa and to determine the antiulcer mechanism of action in experimental rodent models and its activity to Helicobacter pylori.

MATERIAL AND METHODS

In rodents, the FrAq was challenged by different necrotizing agents, such as absolute ethanol and ischemia-reperfusion injury. The antiulcer mechanism of action of FrAq was assessed and the healing effects of the fraction after seven and 14 days of treatment was evaluated by matrix metalloproteinase activity (MMP-2 and MMP-9). The toxicological effect of subacute treatment with FrAq during 14 days of treatment was also analyzed. The anti-Helicobacter pylori activity was determined by microdilution. The phytochemical study of the fraction was analyzed by experiments with FIA-ESI-IT-MS(n) (Direct Flow Analysis-ionization Electrospray Ion Trap Tandem Mass Spectrometry) and high performance liquid chromatography (HPLC) coupled to a photodiode array (PDA).

RESULTS

Oral treatment with FrAq (25mg/kg) significantly decreased the number of ulcerative lesions induced by ethanol and ischemia/reperfusion injury. The action of FrAq was mediated by the activation of defensive mucosa-protective factors, such as increases in mucus production, the nitric oxide (NO) pathway and endogenous prostaglandins. Oral treatment with FrAq for seven and 14 days significantly reduced the lesion area (80% and 37%, respectively) compared to the negative control group. Analyses of MMP-9 and MMP-2 activity from gastric mucosa confirmed the accelerated gastric healing effect of FrAq. This extract also presented considerable activity against Helicobacter pylori. The mass spectrum and MS/MS of the aqueous fraction indicates the existence of many different phenolic compounds, including punicalagin, punicalin, and gallagic acid, among others.

CONCLUSIONS

We concluded that FrAq from Terminalia catappa leaves has excellent preventive and curative effects on acute and chronic induced gastric ulcers and showed an important profile against Helicobacter pylori.

Free radicals: properties, sources, targets, and their implication in various diseases

Free radicals and other oxidants have gained importance in the field of biology due to their central role in various physiological conditions as well as their implication in a diverse range of diseases. The free radicals, both the reactive oxygen species (ROS) and reactive nitrogen species (RNS), are derived from both endogenous sources (mitochondria, peroxisomes, endoplasmic reticulum, phagocytic cells etc.) and exogenous sources (pollution, alcohol, tobacco smoke, heavy metals, transition metals, industrial solvents, pesticides, certain drugs like halothane, paracetamol, and radiation). Free radicals can adversely affect various important classes of biological molecules such as nucleic acids, lipids, and proteins, thereby altering the normal redox status leading to increased oxidative stress. The free radicals induced oxidative stress has been reported to be involved in several diseased conditions such as diabetes mellitus, neurodegenerative disorders (Parkinson's disease-PD, Alzheimer's disease-AD and Multiple sclerosis-MS), cardiovascular diseases (atherosclerosis and hypertension), respiratory diseases (asthma), cataract development, rheumatoid arthritis and in various cancers (colorectal, prostate, breast, lung, bladder cancers). This review deals with chemistry, formation and sources, and molecular targets of free radicals and it provides a brief overview on the pathogenesis of various diseased conditions caused by ROS/RNS.

Dietary ascorbic acid modulates the expression profile of stress protein genes in hepatopancreas of adult Pacific abalone Haliotis discus hannai Ino

This study was conducted to investigate the effects of dietary ascorbic acid (AA) on transcriptional expression patterns of antioxidant proteins, heat shock proteins (HSP) and nuclear factor kappa B (NF-κB) in the hepatopancreas of Pacific abalone Haliotis discus hannai Ino (initial average length: 84.36 ± 0.24 mm) using real-time quantitative PCR assays. L-ascorbyl-2-molyphosphate (LAMP) was added to the basal diet to formulate four experimental diets containing 0.0, 70.3, 829.8 and 4967.5 mg AA equivalent kg(-1) diets, respectively. Each diet was fed to triplicate groups of adult abalone in acrylic tanks (200 L) in a flow-through seawater system. Each tank was stocked with 15 abalone. Animals were fed once daily (17:00) to apparent satiation for 24 weeks. The results showed that the dietary AA (70.3 mg kg(-1)) could significantly up-regulate the expression levels of Cu/Zn superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), feritin (FT) and heat shock protein 26 (HSP26) in the hepatopancreas of abalone in this treatment compared to the controls. However, the expression levels of Mn-SOD, glutathione peroxidase (GPX), thioredoxin peroxidase (TPx), selenium-binding protein (SEBP), HSP70 and HSP90 were significantly down-regulated. Compared with those in the group with 70.3 mg kg(-1) dietary AA, the expression levels of CAT, GST and HSP26 were decreased in abalone fed with very high dietary AA (4967.5 mg kg(-1)). In addition, significant up-regulations of expression levels of Mn-SOD, GPX, TPx, SEBP, FT, HSP70, HSP90 and NF-κB were observed in abalone fed with apparently excessive dietary AA (829.8 and 4967.5 mg kg(-1)) as compared to those fed 70.3 mg kg(-1) dietary AA. These findings showed that dietary AA influenced the expression levels of antioxidant proteins, heat shock proteins and NF-κB in the hepatopancreas of abalone at transcriptional level. Levels of dietary AA that appeared adequate (70.3 mg kg(-1)) reduced the oxidative stress by influencing gene expression of antioxidant proteins, but excessive dietary AA (829.8 and 4967.5 mg kg(-1)) induced oxidative stress in Pacific abalone H. discus hannai.

New derivatives of 3,4-dihydroisoquinoline-3-carboxylic acid with free-radical scavenging, D-amino acid oxidase, acetylcholinesterase and butyrylcholinesterase inhibitory activity

A series of 3,4-dihydroisoquinoline-3-carboxylic acid derivatives were synthesised and tested for their free-radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^·), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS^·+), superoxide anion radical (O₂^·−) and nitric oxide radical (^·NO) assays. We also studied d-amino acid oxidase (DAAO), acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity. Almost each of newly synthesised compounds exhibited radical scavenging capabilities. Moreover, several compounds showed moderate inhibitory activities against DAAO, AChE and BuChE. Compounds with significant free-radical scavenging activity may be potential candidates for therapeutics used in oxidative-stress-related diseases.

Induction of glutathione synthesis in human hepatocytes by acute and chronic arsenic exposure: differential roles of mitogen-activated protein kinases

Glutathione (GSH) is a vital component of antioxidant defense which protects cells from toxic insults. Previously we found intracellular GSH was involved in cell resistance against arsenic-induced cytotoxicity. However, molecular mechanisms of GSH homeostasis during arsenic exposure are largely undefined. Here, we investigated roles of mitogen-activated protein kinases (MAPKs) in GSH synthesis pathway with two arsenic exposure strategies by using Chang human hepatocytes. In one strategy, acute arsenic exposure (20 μM, 24 h) was applied, as MAPK signaling is generally considered to be transient. In the other one, chronic arsenic exposure (500 nM, 20 weeks) was applied, which mimicked the general human exposure to arsenic. We found that acute arsenic exposure activated extracellular signal-regulated 1/2 kinases (ERK1/2) and c-Jun N-terminal kinase (JNK) in parallel with increased transcription and nuclear translocation of factor-erythroid 2-related factor 2 (NRF2) and enhanced expression of γ-glutamyl cysteine ligase catalytic subunit (GCLC), resulting in elevated intracellular GSH levels. Specific ERK inhibitor abolished arsenic-induced NRF2 nuclear translocation and GSH synthesis. During chronic arsenic exposure which induced a malignant cellular phenotype, continuous p38 activation and NRF2 nuclear translocation were observed with enhanced GSH synthesis. Specific p38 inhibitor attenuated arsenic-enhanced GSH synthesis without changing NRF2 nuclear translocation. Taken together, our results indicate MAPK pathways play an important role in cellular GSH homeostasis in response to arsenic. However, the specific activation of certain MAPK is different between acute and chronic arsenic exposure. Furthermore, it appears that during chronic arsenic exposure, GSH synthesis is regulated by p38 at least in part independent of NRF2.

Focus on molecular events in the anterior chamber leading to glaucoma

Primary open-angle glaucoma is a multifactorial disease that affects the retinal ganglion cells, but currently its therapy is to lower the eye pressure. This indicates a definite involvement of the trabecular meshwork, key region in the pathogenesis of glaucoma. This is the first target of glaucoma, and its functional complexity is a real challenge to search. Its functions are those to allow the outflow of aqueous humor and not the reflux. This article describes the morphological and functional changes that happen in anterior chamber. The "primus movens" is oxidative stress that affects trabecular meshwork, particularly its endothelial cells. In these develops a real mitochondriopaty. This leads to functional impotence, the trabecular meshwork altering both motility and cytoarchitecture. Its cells die by apoptosis, losing barrier functions and altering the aqueous humor outflow. All the morphological alterations occur that can be observed under a microscope. Intraocular pressure rises and the malfunctioning trabecular meshwork endotelial cells express proteins that completely alter the aqueous humor. This is a liquid whose functional proteomics complies with the conditions of the trabecular meshwork. Indeed, in glaucoma, it is possible detect the presence of proteins which testify to what occurs in the anterior chamber. There are six classes of proteins which confirm the vascular endothelium nature of the anterior chamber and are the result of the morphofunctional trabecular meshwork decay. It is possible that, all or in part, these proteins can be used as a signal to the posterior pole.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

NADPH oxidases as therapeutic targets in chronic myelogenous leukemia

PURPOSE

Cancer cells show higher levels of reactive oxygen species (ROS) than normal cells and increasing intracellular ROS levels are becoming a recognized strategy against tumor cells. Thus, diminishing ROS levels could be also detrimental to cancer cells. We surmise that avoiding ROS generation would be a better option than quenching ROS with antioxidants. Chronic myelogenous leukemia (CML) is triggered by the expression of BCR-ABL kinase, whose activity leads to increased ROS production, partly through NADPH oxidases. Here, we assessed NADPH oxidases as therapeutic targets in CML.

EXPERIMENTAL DESIGN

We have analyzed the effect of different NADPH oxidase inhibitors, either alone or in combination with BCR-ABL inhibitors, in CML cells and in two different animal models for CML.

RESULTS

NADPH oxidase inhibition dramatically impaired the proliferation and viability of BCR-ABL-expressing cells due to the attenuation of BCR-ABL signaling and a pronounced cell-cycle arrest. Moreover, the combination of NADPH oxidase inhibitors with BCR-ABL inhibitors was highly synergistic. Two different animal models underscore the effectiveness of NADPH oxidase inhibitors and their combination with BCR-ABL inhibitors for CML targeting in vivo.

CONCLUSION

Our results offer further therapeutic opportunities for CML, by targeting NADPH oxidases. In the future, it would be worthwhile conducting further experiments to ascertain the feasibility of translating such therapies to clinical practice.

Furan fatty acids efficiently rescue brain cells from cell death induced by oxidative stress

Treatment of rat brain C6 astroglioma cells with furan fatty acid F6 prior to exposure to hydrogen peroxide shows a strong protective effect of F6 against cell death resulting from oxidative stress. This protective effect is obtained only for F6 administered as a free fatty acid and with an intact furan ring. It is proposed that brain cells are rescued by F6 scavenging radicals elicited by lipid peroxidation within the cell membrane. Oxidative processes outside the cell membrane, such as protein carbonylation, are not affected by F6. Furan fatty acids such as those present in fish oils and marine organisms are likely beneficial for consumption in reducing the risk of diseases that have been implicated to arise from oxidative stress, such as Alzheimer's disease.

Lactoferrin directly scavenges hydroxyl radicals and undergoes oxidative self-degradation: a possible role in protection against oxidative DNA damage

In this study, we examined the protective effect of lactoferrin against DNA damage induced by various hydroxyl radical generation systems. Lactoferrin (LF) was examined with regard to its potential role as a scavenger against radical oxygen species using bovine milk LF. Native LF, iron-saturated LF (holo-LF), and apolactoferrin (apo-LF) effectively suppressed strand breaks in plasmid DNA due to hydroxyl radicals produced by the Fenton reaction. In addition, both native LF and holo-LF clearly protected calf thymus DNA from fragmentation due to ultraviolet irradiation in the presence of H2O2. We also demonstrated a protective effect of all three LF molecules against 8-hydroxydeoxyguanosine (8-OHdG) formation in calf thymus DNA following ultraviolet (UV) irradiation with H2O2. Our results clearly indicate that native LF has reactive oxygen species-scavenging ability, independent of its nature as a masking component for transient metals. We also demonstrated that the protective effect of LF against oxidative DNA damage is due to degradation of LF itself, which is more susceptible to degradation than other bovine milk proteins.

Dietary intake of natural antioxidants: vitamins and polyphenols

Oxidative stress is a condition in which oxidant metabolites exert their toxic effect because of an increased production or an altered cellular mechanism of protection; oxidative stress is rapidly gaining recognition as a key phenomenon in chronic diseases. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions by being oxidized themselves. Endogenous defence mechanisms are inadequate for the complete prevention of oxidative damage, and different sources of dietary antioxidants may be especially important. This article calls attention to the dietary antioxidants, such as vitamins A, C, and E and polyphenols. Compelling evidence has led to the conclusion that diet is a key environmental factor and a potential tool for the control of chronic diseases. More specifically, fruits and vegetables have been shown to exert a protective effect. The high content of minerals and natural antioxidant as vitamins A, C, and E and polyphenols in fruits and vegetables may be a main factor responsible for these effects.

α-Tocopherol administration blocks adaptive changes in cell NADH/NAD+ redox state and mitochondrial function leading to inhibition of gastric mucosa cell proliferation in rats

In experimentally induced chronic gastritis, a compensatory mucosal cell proliferation occurs with enhanced glucose oxidative metabolism linked to lipoperoxidative events. Therefore, this study was aimed at assessing the participation of cell NAD/NADH redox state and mitochondrial functions during gastric mucosa proliferation and the effects of in vivo α-tocopherol (vitamin E) administration. Glucose oxidation and oxygen consumption were tested in gastric mucosa samples obtained from rats with gastritis and from those also treated with α-tocopherol. Gastric mucosal mitochondria were isolated and structural and functional parameters were determined. Succinate oxidation, ADP phosphorylation, mitochondrial enzyme activities, and membrane lipid composition were measured. In addition, parameters indicative of cellular NAD/NADH redox state, proliferation, apoptosis, and nitric oxide (NO) metabolism were also determined. After ethanol withdrawal, the damaged gastric mucosa increased glucose and oxygen consumption, events associated with a more reduced cytoplasmic NAD/NADH ratio. Enhanced mitochondrial oxidative phosphorylation and increased mitochondrial enzyme activities occurred early, accompanied by recovery of lost mitochondrial protein and lipid composition in the gastric mucosa, events associated with increased NO production. When mitochondrial function and structural events were normalized, apoptosis was initiated as assessed by the mitochondrial Bax/Bcl2 ratio. Treatment with α-tocopherol inhibited cell proliferation and blocked enhanced glucose utilization, mitochondrial substrate oxidation, and changes in redox state, delaying the onset of these adaptive metabolic changes, whereas it inhibited cell proliferation. In conclusion, α-tocopherol could abolish damage-induced "stress" signaling by desynchronizing mitochondrial adaptive responses, including mitochondria biogenesis, and consequently NAD/NADH redox, which seems to regulate gastric mucosal cell proliferation.

Acute lung injury and pulmonary vascular permeability: use of transgenic models

Acute lung injury is a general term that describes injurious conditions that can range from mild interstitial edema to massive inflammatory tissue destruction. This review will cover theoretical considerations and quantitative and semi-quantitative methods for assessing edema formation and increased vascular permeability during lung injury. Pulmonary edema can be quantitated directly using gravimetric methods, or indirectly by descriptive microscopy, quantitative morphometric microscopy, altered lung mechanics, high-resolution computed tomography, magnetic resonance imaging, positron emission tomography, or x-ray films. Lung vascular permeability to fluid can be evaluated by measuring the filtration coefficient (Kf) and permeability to solutes evaluated from their blood to lung clearances. Albumin clearances can then be used to calculate specific permeability-surface area products (PS) and reflection coefficients (σ). These methods as applied to a wide variety of transgenic mice subjected to acute lung injury by hyperoxic exposure, sepsis, ischemia-reperfusion, acid aspiration, oleic acid infusion, repeated lung lavage, and bleomycin are reviewed. These commonly used animal models simulate features of the acute respiratory distress syndrome, and the preparation of genetically modified mice and their use for defining specific pathways in these disease models are outlined. Although the initiating events differ widely, many of the subsequent inflammatory processes causing lung injury and increased vascular permeability are surprisingly similar for many etiologies.

Role of p66shc in renal toxicity of oleic acid

BACKGROUND/AIMS

Adult and childhood obesity is an independent risk factor in development of chronic kidney disease (CKD) and its progression to end-stage kidney disease. Pathologic consequences of obesity include non-esterified fatty acid-induced oxidative stress and consequent injury. Since the serine36-phosphorylated p66shc is a newly recognized mediator of oxidative stress and kidney injury, we studied its role in oleic acid (OA)-induced production of reactive oxygen species (ROS), mitochondrial depolarization and injury in cultured renal proximal tubule cells.

METHODS

Renal proximal tubule cells were used and treated with OA: ROS production, mitochondrial depolarization as well as injury were determined. Transcriptional effects of OA on the p66shc gene were determined in a reporter luciferase assay. The role of p66shc in adverse effects of OA was determined using knockdown, p66shc serine36 phosphorylation and cytochrome c binding-deficient cells.

RESULTS

We found that OA increased ROS production via the mitochondria - and to a less extent via the NADPH oxidase - resulting in ROS-dependent mitochondrial depolarization and consequent injury. Interestingly, OA also stimulated the promoter of p66shc. Hence, knockdown of p66shc, impairment its Ser36 phosphorylation (mutation of Ser36 residue to alanine) or cytochrome c binding (W134F mutation) significantly attenuated OA-dependent lipotoxicity.

CONCLUSION

These results offer a novel mechanism by which obesity may lead to renal tubular injury and consequently development of CKD. Manipulation of this pathway may offer therapeutic means to ameliorate obesity-dependent renal lipotoxicity.

Mechanisms of nanoparticle-induced oxidative stress and toxicity

The rapidly emerging field of nanotechnology has offered innovative discoveries in the medical, industrial, and consumer sectors. The unique physicochemical and electrical properties of engineered nanoparticles (NP) make them highly desirable in a variety of applications. However, these novel properties of NP are fraught with concerns for environmental and occupational exposure. Changes in structural and physicochemical properties of NP can lead to changes in biological activities including ROS generation, one of the most frequently reported NP-associated toxicities. Oxidative stress induced by engineered NP is due to acellular factors such as particle surface, size, composition, and presence of metals, while cellular responses such as mitochondrial respiration, NP-cell interaction, and immune cell activation are responsible for ROS-mediated damage. NP-induced oxidative stress responses are torch bearers for further pathophysiological effects including genotoxicity, inflammation, and fibrosis as demonstrated by activation of associated cell signaling pathways. Since oxidative stress is a key determinant of NP-induced injury, it is necessary to characterize the ROS response resulting from NP. Through physicochemical characterization and understanding of the multiple signaling cascades activated by NP-induced ROS, a systemic toxicity screen with oxidative stress as a predictive model for NP-induced injury can be developed.

The effect of MAPK inhibitors and ROS modulators on cell growth and death of H₂O₂-treated HeLa cells

Reactive oxygen species (ROS) influence the signaling of mitogen‑activated protein kinases (MAPKs) involved in cell survival and death. In the present study, the toxicological effect of hydrogen peroxide (H2O2) on HeLa cervical cancer cells was evaluated following treatment with MAPK inhibitors [MAP kinase or ERK kinase (MEK), c‑Jun N‑terminal kinase (JNK) or p38], N‑acetyl cysteine (NAC) and propyl gallate (PG) (well‑known antioxidants), or L‑buthionine sulfoximine [BSO; an inhibitor of glutathione (GSH) synthesis]. Treatment with 100 µM H2O2 inhibited the growth of HeLa cells and induced cell death, which was accompanied by loss of the mitochondrial membrane potential (MMP; ΔΨm). H2O2 did not induce any specific phase arrests of the cell cycle. ROS levels increased, while GSH levels decreased in H2O2‑treated HeLa cells after 1 and 24 h of treatment. The MAPK inhibitors enhanced H2O2‑induced HeLa cell death, while only p38 inhibitor increased ROS levels. Both NAC and PG attenuated H2O2‑induced HeLa cell growth inhibition and death together with the suppression of ROS levels. BSO increased ROS levels in H2O2‑treated HeLa cells without increasing cell death. The levels of MMP (ΔΨm) loss and GSH depletion were not closely associated with the levels of apoptosis in HeLa cells treated with the MAPK inhibitors, NAC, PG or BSO, in the presence of H2O2. In conclusion, H2O2 induced HeLa cell growth inhibition and death. MAPK inhibitors generally enhanced H2O2‑induced HeLa cell death. In particular, p38 inhibitor increased ROS levels in H2O2‑treated HeLa cells, while NAC and PG attenuated H2O2‑induced HeLa cell death by suppressing ROS levels.

Effect of exposure to solid wastes in relation to employment duration on some important markers of health and disease in waste management workers of Ogun State in southwest Nigeria

Waste management workers (WMWs) around the world are at risk of work-related health disorders. The influence of employment duration on individuals occupationally exposed to solid waste was investigated in this study. The study comprised (n = 280) 180 WMWs and 100 controls. Employment duration was obtained from questionnaire survey and categorized into three groups: group I (0.5-2 years), group II (>2-4 years) and group III (>4-6 years). Blood sample (10 ml) was collected from the antecubital vein of subjects for analysis. WMWs exhibited significantly (p < 0.001) elevated inflammatory markers (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and ceruloplasmin (Cp)) relative to control. While Cp increased, ESR and CRP decreased with increasing WMWs' employment duration. Alteration in oxidant/antioxidant markers was characterized by significant (p < 0.001) decrease in ferric-reducing ability of plasma (FRAP) and catalase activity together with marked (p < 0.01) elevation of thiobarbituric acid reactive substances (TBARS) and uric acid (UA). TBARS, UA and FRAP increased while catalase decreased with WMWs' employment duration. In addition, WMWs exhibited significantly (p < 0.01) elevated immunoglobulin A (IgA) and IgG, which also increased and decreased, respectively, with job duration. The significantly (p < 0.01) decreased haemoglobin and haematocrit levels as well as the significantly (p < 0.001) elevated total leukocytes in WMWs increased with employment duration. Alanine aminotransferase increased and albumin decreased significantly (p < 0.05) in WMWs, and these changes also increased and decreased, respectively, with job duration. Data suggest that levels of alteration of important systemic markers of health/disease are related to WMWs' employment or exposure duration.

MAPK inhibitors augment gallic acid-induced A549 lung cancer cell death through the enhancement of glutathione depletion

Gallic acid (GA) is involved in various biological processes such as cell growth inhibition and apoptosis through changes in reactive oxygen species (ROS). In the present study, we investigated the effects of MAPK (MEK, JNK or p38) inhibitors on cell death in GA-induced A549 lung cancer cells in relation to ROS and glutathione (GSH). Treatment with 100 µM GA inhibited the growth of A549 cells and induced apoptosis and/or necrosis, which was accompanied by the loss of mitochondrial membrane potential (MMP; ∆Ψ(m)). GA increased ROS levels as well as GSH depletion in A549 cells at 24 h. MEK inhibitor seemed to enhance cell growth inhibition by GA. This inhibitor also increased cell death, MMP (∆Ψ(m)) loss and GSH depletion in GA-treated A549 cells. Both JNK and p38 inhibitors intensified growth inhibition, cell death, MMP (∆Ψ(m)) loss and GSH depletion by GA. However, none of the MAPK inhibitors significantly altered ROS levels in GA-treated A549 cells. In conclusion, MAPK inhibitors enhanced growth inhibition and death in GA-treated A549 cells, which were correlated with GSH depletion rather than ROS levels.

Tocopherol activity correlates with its location in a membrane: a new perspective on the antioxidant vitamin E

We show evidence of an antioxidant mechanism for vitamin E which correlates strongly with its physical location in a model lipid bilayer. These data address the overlooked problem of the physical distance between the vitamin's reducing hydrogen and lipid acyl chain radicals. Our combined data from neutron diffraction, NMR, and UV spectroscopy experiments all suggest that reduction of reactive oxygen species and lipid radicals occurs specifically at the membrane's hydrophobic-hydrophilic interface. The latter is possible when the acyl chain "snorkels" to the interface from the hydrocarbon matrix. Moreover, not all model lipids are equal in this regard, as indicated by the small differences in vitamin's location. The present result is a clear example of the importance of lipid diversity in controlling the dynamic structural properties of biological membranes. Importantly, our results suggest that measurements of aToc oxidation kinetics, and its products, should be revisited by taking into consideration the physical properties of the membrane in which the vitamin resides.

Comparative study of β-glucan induced respiratory burst measured by nitroblue tetrazolium assay and real-time luminol-enhanced chemiluminescence assay in common carp (Cyprinus carpio L.)

The respiratory burst is an important feature of the immune system. The increase in cellular oxygen uptake that marks the initiation of the respiratory burst is followed by the production of reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide which plays a role in the clearance of pathogens and tissue regeneration processes. Therefore, the respiratory burst and associated ROS constitute important indicators of fish health status. This paper compares two methods for quantitation of ROS produced during the respiratory burst in common carp: the widely used, single-point measurement based on the intracellular reduction of nitroblue tetrazolium (NBT) and a real-time luminol-enhanced assay based on the detection of native chemiluminescence. Both assays allowed for detection of dose-dependent changes in magnitude of the respiratory burst response induced by β-glucans in head kidney cells of carp. However, whereas the NBT assay was shown to detect the production of only superoxide anions, the real-time luminol-enhanced assay could detect the production of both superoxide anions and hydrogen peroxide. Only the chemiluminescence assay could reliably record the production of ROS on a real-time scale at frequent and continual time intervals for time course experiments, providing more detailed information on the respiratory burst response. The real-time chemiluminescence assay was used to measure respiratory burst activity in macrophage and neutrophilic granulocyte-enriched head kidney cell fractions and total head kidney cell suspensions and proved to be a fast, reliable, automated multiwell microplate assay to quantitate fish health status modulated by β-glucans.

Functional graphene oxide as a plasmid-based Stat3 siRNA carrier inhibits mouse malignant melanoma growth in vivo

Graphene oxide (GO) has attracted intensive interest in the biomedical field in recent years. We investigate whether the use of functional graphene oxide as an efficient delivery system for delivering specific molecular antitumor therapeutics in vivo could achieve a more excellent antitumor effect. Constitutive activation of signal transducer and activator of transcription 3 (Stat3) promotes survival in a wide spectrum of human cancers. In this paper, we study the in vivo behavior of graphene oxide chemically functionalized with polyethylenimine and polyethylene glycol (GO-PEI-PEG) as a plasmid-based Stat3-specific small interfering RNA (siRNA) carrier in mouse malignant melanoma. The in vivo results indicate significant regression in tumor growth and tumor weight after plasmid-based Stat3 siRNA delivered by GO-PEI-PEG treatment. Moreover, there was no significant side effect from GO-PEI-PEG treatment according to histological examination and blood chemistry analysis in mice. Thus, our work is the first success of using GO-PEI-PEG as a promising carrier for plasmid Stat3 siRNA delivery and down-regulation of Stat3 by a polymer-mediated vehicle and suggests the great promise of graphene in biomedical applications such as cancer treatment.

Thioredoxin-mediated redox regulation of resistance to endocrine therapy in breast cancer

Resistance to endocrine therapy in breast carcinogenesis due to the redox regulation of the signal transduction system by reactive oxygen species (ROS) is the subject of this review article. Both antiestrogens and aromatase inhibitors are thought to prevent cancer through modulating the estrogen receptor function, but other mechanisms cannot be ruled out as these compounds also block metabolism and redox cycling of estrogen and are free radical scavengers. Endocrine therapeutic agents, such as, tamoxifen and other antiestrogens, and the aromatase inhibitor, exemestane, are capable of producing ROS. Aggressive breast cancer cells have high oxidative stress and chronic treatment with exemestane, fulvestrant or tamoxifen may add additional ROS stress. Breast cancer cells receiving long-term antiestrogen treatment appear to adapt to this increased persistent level of ROS. This, in turn, may lead to the disruption of reversible redox signaling that involves redox-sensitive phosphatases, protein kinases, such as, ERK and AKT, and transcription factors, such as, AP-1, NRF-1 and NF-κB. Thioredoxin modulates the expression of estrogen responsive genes through modulating the production of H2O2 in breast cancer cells. Overexpressing thioredoxine reductase 2 and reducing oxidized thioredoxin restores tamoxifen sensitivity to previously resistant breast cancer cells. In summary, it appears that resistance to endocrine therapy may be mediated, in part, by ROS-mediated dysregulation of both estrogen-dependent and estrogen-independent redox-sensitive signaling pathways. Further studies are needed to define the mechanism of action of thioredoxin modifiers, and their effect on the redox regulation that contributes to restoring the antiestrogen-mediated signal transduction system and growth inhibitory action.

Effects of antioxidants and MAPK inhibitors on cell death and reactive oxygen species levels in H2O2-treated human pulmonary fibroblasts

H₂O₂-induced cytotoxicity in normal human pulmonary fibroblasts (HPFs) is of interest in toxicological research since HPFs are involved in lung inflammation, fibrosis and cancer. The present study investigated the cytotoxic effects of H₂O₂ on normal HPFs in relation to reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) using the well-known antioxidants N-acetyl cysteine (NAC) and propyl gallate (PG), as well as MAPK inhibitors. Treatment with 50 μM H₂O₂ inhibited the growth of the HPFs by ∼45% in 24 h. H₂O₂ induced cell death via apoptosis and triggered the loss of mitochondrial membrane potential (MMP; Δψ_m) in the HPFs. H₂O₂ also increased the ROS levels, including O₂^•−, in the HPFs and induced glutathione (GSH) depletion. NAC and PG attenuated the death of the HPFs and the loss of MMP (Δψ_m) through the use of H₂O₂. NAC decreased the ROS levels in the H₂O₂-treated HPFs and PG markedly prevented an increase in O₂^•− levels in these cells. However, PG alone induced cell death in the HPF control cells and increased the ROS levels in these cells. None of the MAPK (MEK, JNK and p38) inhibitors affected cell growth inhibition or cell death by H₂O₂. In addition, these inhibitors did not significantly affect the ROS levels and GSH depletion in the H₂O₂-treated HPFs. In conclusion, H₂O₂ induced growth inhibition and cell death in the HPFs via GSH depletion. NAC and PG attenuated H₂O₂-induced HPF cell death but each regulated the ROS levels in a different manner. Treatment with MAPK inhibitors did not affect cell death or the ROS levels in the H₂O₂-treated HPFs.

Exploring the mechanisms of alcohol-related damage in oral mucosa - is oxidative stress associated with the increase in cell proliferation in rat tongue epithelium?

CONTEXT

Alcohol consumption has been related to a cell proliferation increase in oral epithelium but its mechanism remains unclear.

OBJECTIVE

The aim of this study was to investigate whether oxidative stress parameters are implicated in the induction of cell proliferation in rat tongue epithelium after different times of chronic alcohol consumption.

MATERIALS AND METHODS

Cell proliferation was assessed in tongue epithelium using AgNOR (argyrophilic proteins related to active nucleolar organizer regions) quantification. Oxidative stress parameters [lipid peroxidation, protein carbonyls, superoxide dismutase activity and catalase (CAT) activity and immunocontent] and Nrf2 immunocontent were quantified in tongue homogenates.

RESULTS AND DISCUSSION

Mean AgNOR numbers (mAgNOR) per nucleus was 2.22 ± 0.30 in ventral tongue epithelium after 120 days of alcohol consumption (vs. 1.87 ± 0.18 for control animals and 1.91 ± 0.23 for animals treated with alcohol for 60 days) indicating cell proliferation increase (p < 0.05, ANOVA followed by Tukey post hoc). Interestingly, 60 days of alcohol consumption induced changes in oxidative stress parameters, but no alteration in cell proliferation. Vitamin E co-treatment was conduced in order to evaluate its possible protective effects. The 120 day Tween + vitamin E + alcohol treatment induced an increase in mAgNORs when compared to the Tween + vitamin E treated group (respectively 2.10 ± 0.30 vs. 1.77 ± 0.11, p < 0.05, ANOVA followed by Tukey post hoc), showing that vitamin E co-treatment had no protective effects. In addition, an inverse association was observed between CAT activity and AgNORs quantity (R = -0.32; p < 0.05, Person's correlation) as well as the possible involvement of Nrf2 in alcohol-related damage.

CONCLUSIONS

Our findings suggest that the increase in cell proliferation associated with alcohol-related damage has no direct relation with an imbalance in oxidative parameters. In contrast, our results indicate that hydrogen peroxide may be implicated in cellular signaling during proliferation in the oral mucosa.

Dimovski A. Natural antioxidants in cancer prevention

It is well known that oxidative stress is an inevitable event in aerobic life. When our cells use oxygen to create energy, a variety of reactive oxygen (ROS) and nitrogen species (RNS) are generated. These species could attack DNA directly and form mutagenic lesions afterwards. According to the oxidative stress hypothesis of aging, the oxidative damage to critical molecules accumulates over the life period and could ultimately impair the body’s function. Moreover, severe oxidative stress causes mutations of tumor suppressor genes, known as one of the initial events in carcinogenesis. Furthermore, it could also play a crucial role in the promotion of the multi-step carcinogenesis. On the other hand, the human body possesses a number of mechanisms that counteract oxidative stress by producing antioxidants in situ, or externally supplied them through foods and/or supplements. Indeed, a considerable amount of laboratory evidence from chemical, cell culture, and animal studies indicates that antioxidants may slow down or possibly prevent the cancer development. Yet, the information from recent cohort, case-control and/or ecological studies is less clear. Therefore, the objectives of this review are to compile a compendium of studies, and to identify effective and promising natural antioxidant interventions.

Metal interaction with redox regulation: an integrating concept in metal carcinogenesis?

The carcinogenicity of cadmium, arsenic, and chromium(VI) compounds has been recognized for some decades. However, the underlying molecular mechanisms seem to be complex and are not completely understood at present. Although, with the exception of chromium(VI), direct DNA damage seems to be of minor importance, interactions with DNA repair processes, tumor suppressor functions, and signal transduction pathways have been described in diverse biological systems. In addition to the induction of damage to cellular macromolecules by reactive oxygen species, the interference with cellular redox regulation by reaction with redox-sensitive protein domains or amino acids may provide one plausible mechanism involved in metal carcinogenicity. Consequences are the distortion of zinc-binding structures and the activation or inactivation of redox-regulated signal transduction pathways, provoking metal-induced genomic instability. Nevertheless, the relevance of the respective mechanisms depends on the actual metal or metal species under consideration and more research is needed to further strengthen this hypothesis.

Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases

The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.

The role of oxidative stress in Parkinson's disease

Oxidative stress plays an important role in the degeneration of dopaminergic neurons in Parkinson's disease (PD). Disruptions in the physiologic maintenance of the redox potential in neurons interfere with several biological processes, ultimately leading to cell death. Evidence has been developed for oxidative and nitrative damage to key cellular components in the PD substantia nigra. A number of sources and mechanisms for the generation of reactive oxygen species (ROS) are recognized including the metabolism of dopamine itself, mitochondrial dysfunction, iron, neuroinflammatory cells, calcium, and aging. PD causing gene products including DJ-1, PINK1, parkin, alpha-synuclein and LRRK2 also impact in complex ways mitochondrial function leading to exacerbation of ROS generation and susceptibility to oxidative stress. Additionally, cellular homeostatic processes including the ubiquitin-proteasome system and mitophagy are impacted by oxidative stress. It is apparent that the interplay between these various mechanisms contributes to neurodegeneration in PD as a feed forward scenario where primary insults lead to oxidative stress, which damages key cellular pathogenetic proteins that in turn cause more ROS production. Animal models of PD have yielded some insights into the molecular pathways of neuronal degeneration and highlighted previously unknown mechanisms by which oxidative stress contributes to PD. However, therapeutic attempts to target the general state of oxidative stress in clinical trials have failed to demonstrate an impact on disease progression. Recent knowledge gained about the specific mechanisms related to PD gene products that modulate ROS production and the response of neurons to stress may provide targeted new approaches towards neuroprotection.

New NSAID targets and derivatives for colorectal cancer chemoprevention

Clinical and preclinical studies provide strong evidence that nonsteroidal anti-inflammatory drugs (NSAIDs) can prevent numerous types of cancers, especially colorectal cancer. Unfortunately, the depletion of physiologically important prostaglandins due to cyclooxygenase (COX) inhibition results in potentially fatal toxicities that preclude the long-term use of NSAIDs for cancer chemoprevention. While studies have shown an involvement of COX-2 in colorectal tumorigenesis, other studies suggest that a COX-independent target may be at least partially responsible for the antineoplastic activity of NSAIDs. For example, certain NSAID derivatives have been identified that do not inhibit COX-2 but have demonstrated efficacy to suppress carcinogenesis with potential for reduced toxicity. A number of alternative targets have also been reported to account for the tumor cell growth inhibitory activity of NSAIDs, including the inhibition of cyclic guanosine monophosphate phosphodiesterases (cGMP PDEs), generation of reactive oxygen species (ROS), the suppression of the apoptosis inhibitor protein, survivin, and others. Here, we review several promising mechanisms that are being targeted to develop safer and more efficacious NSAID derivatives for colon cancer chemoprevention.