Free radicals and the regulation of mammalian cell proliferation

Reduction of Hydrogen Peroxide by Human Mitochondrial Amidoxime Reducing Component Enzymes

The mitochondrial amidoxime reducing component (mARC) is a human molybdoenzyme known to catalyze the reduction of various N-oxygenated substrates. The physiological function of mARC enzymes, however, remains unknown. In this study, we examine the reduction of hydrogen peroxide (H2O2) by the human mARC1 and mARC2 enzymes. Furthermore, we demonstrate an increased sensitivity toward H2O2 for HEK-293T cells with an MTARC1 knockout, which implies a role of mARC enzymes in the cellular response to oxidative stress. H2O2 is a reactive oxygen species (ROS) formed in all living cells involved in many physiological processes. Furthermore, H2O2 constitutes the first mARC substrate without a nitrogen-oxygen bond, implying that mARC enzymes may have a substrate spectrum going beyond the previously examined N-oxygenated compounds.

Positive effects of low-dose photodynamic therapy with aminolevulinic acid or its methyl ester in skin rejuvenation and wound healing: An update

In dermatology, photodynamic therapy (PDT) is widely used in skin tumors, infections, etc., because of the killing effect triggered by toxic reactive oxygen species (ROS). However, the ROS concentration is determined by various photosensitizer concentrations and formulations, as well as various irradiation parameters. Low-dose PDT leads to sufficiently low ROS level, which results in biological effects that are the exact opposite of the killing potency. Therefore, in recent years, low-dose PDT has been exploited in improving aging and wound. Low-dose ALA/MAL PDT might improve aging through promoting the proliferation of fibroblasts, blocking DNA damage, counteracting oxidative stress, inhibiting melanogenesis, and remodeling lymphatic vessels in aged skin. Promoting fibroblasts and epidermal stem cells proliferation and migration, promoting granulation tissue formation and angiogenesis and regulating the inflammatory process might be the mechanisms of low-dose ALA/MAL PDT in wound healing. Nevertheless, the positive effects of low-dose PDT have not been thoroughly investigated in dermatology, and high-quality studies are still needed to fill the relevant vacancy.

Dopamine toxicity contributes to melanocyte loss via melanocytorrhagy: an in vitro study

BACKGROUND

Catecholamines (epinephrine, norepinephrine, and dopamine) have been proposed as a possible cause of melanocyte loss. Dopamine has been observed to cause apoptosis in melanocytes via reactive oxygen species development, but the effect on melanocyte adhesion and proliferation still remains to be elucidated. Thus, we explored the dose- and time-dependent toxicity of catecholamines and the effect of dopamine on the proliferation and adhesion potential of melanocytes.

MATERIALS AND METHODS

Primary culture of melanocytes was investigated in vitro for toxic effects of epinephrine, norepinephrine, and dopamine on metabolic activity via MTT [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide) assay. Cells were observed microscopically for any phenotypic changes. Further cell proliferation, cell adhesion, and cell death pathway were explored under dopamine toxicity in dose- and time-dependent manner with RNase/PI method of cell cycle analysis, cell adhesion assay, and Annexin V-FITC/PI assay, respectively. Altered gene expressions were confirmed with a real-time polymerase chain reaction.

RESULTS

Metabolic activity of cells varied with time and different doses of epinephrine, norepinephrine, and dopamine. Dopamine was observed to be more toxic than epinephrine and norepinephrine. Melanocytes were observed to follow different cell death pathways at comparatively lower and higher concentrations of dopamine. Persistent exposure to dopamine resulted in decreased cell proliferation and adhesion potential with apoptotic changes. Gene expression changes also confirmed the weak adhesion and survival potential of cells under the toxic effects of dopamine.

CONCLUSION

Dopamine can alter melanocytes' adhesion and survival potential, leading to apoptotic cell death or melanocytorrhagic loss.

Impact of Oxidative Stress on Embryogenesis and Fetal Development

Multiple cellular processes are regulated by oxygen radicals or reactive oxygen species (ROS) where they play crucial roles as primary or secondary messengers, particularly during cell proliferation, differentiation, and apoptosis. Embryogenesis and organogenesis encompass all these processes; therefore, their role during these crucial life events cannot be ignored, more so when there is an imbalance in redox homeostasis. Perturbed redox homeostasis is responsible for damaging the biomolecules such as lipids, proteins, and nucleic acids resulting in leaky membrane, altered protein, enzyme function, and DNA damage which have adverse impact on the embryo and fetal development. In this article, we attempt to summarize the available data in literature for an in-depth understanding of redox regulation during development that may help in optimizing the pregnancy outcome both under natural and assisted conditions.

ROMO1 is required for mitochondrial metabolism during preimplantation embryo development in pigs

Background

Reactive oxygen species (ROS) modulator 1 (ROMO1) is a mitochondrial membrane protein that is essential for the regulation of mitochondrial ROS production and redox sensing. ROMO1 regulates ROS generation within cells and is involved in cellular processes, such as cell proliferation, senescence, and death. Our purpose is to investigates the impact of ROMO1 on the mitochondria during porcine embryogenesis.

Results

We found that high expression of ROMO1 was associated with porcine preimplantation embryo development, indicating that ROMO1 may contribute to the progression of embryogenesis. Knockdown of ROMO1 disrupted porcine embryo development and blastocyst quality, thereby inducing ROS production and decreasing mitochondrial membrane potential. Knockdown of ROMO1 induced mitochondrial dysfunction by disrupting the balance of OPA1 isoforms to release cytochrome c, reduce ATP, and induce apoptosis. Meanwhile, ROMO1 overexpression showed similar effects as ROMO1 KD on the embryos. Overexpression of ROMO1 rescued the ROMO1 KD-induced defects in embryo development, mitochondrial fragmentation, and apoptosis.

Conclusions

ROMO1 plays a critical role in embryo development by regulating mitochondrial morphology, function, and apoptosis in pigs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13008-021-00076-7.

Examination of the effect of curcumin in experimental liver damage created by diethylnitrosamine in swiss albino mice to superoxide dismutase and catalase activities and glutathione, malondialdehyde, advanced oxidation protein products levels

In this study, the effects of curcumin, glutathione (GSH), malondialdehyde (MDA) levels, advanced protein oxidation products (AOPP), superoxide dismutase (SOD) and catalase (CAT) activities in experimental liver damage with diethylnitrosamine (DEN) in Swiss albino mice were investigated. Subjects (n = 9) were divided into 5 as tumor control 1, tumor control 2, curcumin preservative and treatment, and healthy controlgroup. Curcumin oral gavage (in 150 mg/kg of ethylalcohol) was given to the protecting group for 19 days, 5 days before the administration of Diethylnitrosamine, and 24 hours after the administration of Diethylnitrosamine. 100 μl of ethylalcohol oral gavage was given to the healthy group for 19 days. While MDA levels decreased significantly in the curcumin preservative group (p<0.05) (p = 0.002), the decrease was not significant in the treatment groups (p>0.05), (p = 0.128). AOPP levels decreased significantly in the curcumin protective group (p<0.05) (p = 0.009) but the decrease in the treatment group was not found significant (p> 0.05), (p = 0.073). SOD activities increased significantly in both groups. It was found as (p<0.05), (p = 0.001) and (p<0.05), (p = 0.002), respectively. GSH levels decreased but these reductions were not found statistically significant. CAT activities increased significantly in both groups. It was determined as (p<0.05), (p = 0.001) for both groups. The significant CAT activities were found in both the curcumin protective group and the curcumin treatment group AOPP values decreased in curcumin protective group MDA levels decreased significantly in the curcumin protective group This article is protected by copyright. All rights reserved.

Plasma membrane anchored nanosensor for quantifying endogenous production of H2O2 in living cells

Hydrogen peroxide (H₂O₂) is one of the main second messengers involved in signaling pathways controlling cell metabolism. During tumorigenesis H₂O₂ is generated on the extracellular space by membrane-associated NADPH oxidases and superoxide dismutase to stimulate cell proliferation and preservation of the transformed state. Accordingly, a characteristic feature of malignant cells is overproduction of H₂O₂ in the extracellular milieu and the subsequent absorption in the cytosol. Since the most significant gradients of endogenous extracellular H₂O₂ can be observed only in a very shallow region of the fluid in contact with the plasma membrane, we show here the use of a newly designed nanosensor anchored to the outer cell surface and capable of quantifying H₂O₂ at nanometer distance from the membrane proteins responsible for its production. This biosensor is built upon gold nanoparticles functionalized with a H₂O₂-sensitive boronate compound that is probed using surface enhanced Raman spectroscopy (SERS). The highly localized information obtained on the cell surface by SERS analysis is combined with analytical methods of redox biology to estimate the associated levels of intracellular H₂O₂ responsible for cell signaling. The results obtained from A549 lung cancer cell line show localized spots on the cell surface at concentration up to 12 μM, associated to intracellular concentration up to 5.1 nM.

It takes two to tango: coupling of Hippo pathway and redox signaling in biological process

Hippo pathway is a chain of kinases consists of a series of protein kinases and transcription factors. Meanwhile, oxidative stress is a condition of elevated concentrations of reactive oxygen species (ROS) that cause molecular damage to vital structures and functions. Both of them are key regulators in cell proliferation, survival, and development. These processes are strictly regulated by highly coordinated mechanisms, including c-Jun n-terminal kinase (JNK) pathway, mTOR pathway and a number of extrinsic and intrinsic factors. Recently, emerging evidence suggests that Hippo pathway is involved in the responses to cellular stresses, including mechanic stress, DNA damage, and oxidative stress, to mediate biological process, such as apoptosis, pyroptosis, and metastasis. But the exact mechanism remains to be further explored. Therefore, the purpose of this review is to summarize recent findings and discuss how Hippo pathway, oxidative stress, and the crosstalk between them regulate some biological process which determines cell fate.

Boto R, Ferreira D, R. Fernandes J, Almeida P, F. V. Ferreira L, Silva AM, V. Reis L. Red and Near-Infrared Absorbing DicyanomethyleneSquaraine Cyanine Dyes: PhotophysicochemicalProperties and Anti-Tumor Photosensitizing Effects

Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singlet oxygen quantum yields, were a core of dyes that exhibited relevant in vitro photodynamic activity, as there was an evident increase in the toxicity of some of the tested dyes exclusive to radiation treatments.

Evolution of the Knowledge of Free Radicals and Other Oxidants

Free radicals are chemical species (atoms, molecules, or ions) containing one or more unpaired electrons in their external orbitals and generally display a remarkable reactivity. The evidence of their existence was obtained only at the beginning of the 20th century. Chemists gradually ascertained the involvement of free radicals in organic reactions and, in the middle of the 20th century, their production in biological systems. For several decades, free radicals were thought to cause exclusively damaging effects . This idea was mainly supported by the finding that oxygen free radicals readily react with all biological macromolecules inducing their oxidative modification and loss of function. Moreover, evidence was obtained that when, in the living organism, free radicals are not neutralized by systems of biochemical defences, many pathological conditions develop. However, after some time, it became clear that the living systems not only had adapted to the coexistence with free radicals but also developed methods to turn these toxic substances to their advantage by using them in critical physiological processes. Therefore, free radicals play a dual role in living systems: they are toxic by-products of aerobic metabolism, causing oxidative damage and tissue dysfunction, and serve as molecular signals activating beneficial stress responses. This discovery also changed the way we consider antioxidants. Their use is usually regarded as helpful to counteract the damaging effects of free radicals but sometimes is harmful as it can block adaptive responses induced by low levels of radicals.

Bioinorganics and Wound Healing

Wound dressings and the healing enhancement (increasing healing speed and quality) are two components of wound care that lead to a proper healing. Wound care today consists mostly of providing an optimal environment by removing waste and necrotic tissues from a wound, preventing infections, and keeping the wounds adequately moist. This is however often not enough to re-establish the healing process in chronic wounds; with the local disruption of vascularization, the local environment is lacking oxygen, nutrients, and has a modified ionic and molecular concentration which limits the healing process. This disruption may affect cellular ionic pumps, energy production, chemotaxis, etc., and will affect the healing process. Biomaterials for wound healing range from simple absorbents to sophisticated bioactive delivery vehicles. Often placing a material in or on a wound can change multiple parameters such as pH, ionic concentration, and osmolarity, and it can be challenging to pinpoint key mechanism of action. This article reviews the literature of several inorganic ions and molecules and their potential effects on the different wound healing phases and their use in new wound dressings.

Hydrogen peroxide-producing NADPH oxidases and the promotion of migratory phenotypes in cancer

The cellular microenvironment plays a critical role in cancer initiation and progression. Exposure to oxidative stress, specifically hydrogen peroxide (H₂O₂), has been linked to aberrant cellular signaling through which the development of cancer may be promoted. Three members of the NADPH oxidase family (NOX4, DUOX1 and DUOX2) explicitly generate this non-radical oxidant in a wide range of tissues, often in support of the inflammatory response. This review summarizes the contributions of each H₂O₂-producing NOX to the invasive behaviors of tumors and/or the epithelial-mesenchymal transition (EMT) in cancer that plays an essential role in metastasis. Tissue localization in tumorigenesis is also highlighted, with patient-derived TCGA microarray data profiled across 31 cancer cohorts to provide a comprehensive guide to the relevance of NOX4/DUOX1/DUOX2 in cancer studies.

The presence of osteocalcin, osteopontin and reactive oxygen species-positive cells in pulp tissue after dental bleaching

AIM

To analyse the influence of H₂ O₂ on pulp repair through osteocalcin and osteopontin immunolabelling and in cellular defence by using the antireactive oxygen species (ROS) antibody.

METHODOLOGY

The maxillary molars of 50 rats were treated with 35% H₂ O₂ (Ble groups) or placebo gel (control groups). At 0 h and 2, 7, 15 and 30 days (n = 10 hemimaxillae), the rats were killed and pulp tissue was evaluated using inflammation and immunolabelling scores (osteocalcin/osteopontin); ROS-positive cells were counted. Paired t-test and Wilcoxon signed-rank test were used (P < 0.05).

RESULTS

The Ble group had necrosis in the coronal pulp at 0 h and in the occlusal third of the coronal pulp at 2 days; at 7, 15 and 30 days, no inflammation was noted similar to the controls (P > 0.05). Osteocalcin was absent in the Ble at 0 h, moderate at 2 days and increased thereafter, differing from the controls at all two periods (P < 0.05). Osteopontin was higher principally at 7 and 15 days in Ble groups, but differing with control groups from 2 days after bleaching (P < 0.05). The Ble group had more ROS-positive cells in the pulp at 7 and 15 days (P < 0.05). Tertiary dentine was observed at 7 days, increasing thereafter (P < 0.05).

CONCLUSIONS

Post-bleaching pulp repair was associated with increased osteocalcin over time. Osteopontin also participated in this process, and anti-ROS was involved in cellular defence against H₂ O₂ .

Effects of Millimolar Steady-State Hydrogen Peroxide Exposure on Inflammatory and Redox Gene Expression in Immune Cells from Humans with Metabolic Syndrome

Reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) can exert opposed effects depending on the dosage: low levels can be involved in signalling and adaptive processes, while higher levels can exert deleterious effects in cells and tissues. Our aim was to emulate a chronic ex vivo oxidative stress situation through a 2 h exposure of immune cells to sustained H₂O₂ produced by glucose oxidase (GOX), at high or low production rate, in order to determine dissimilar responses of peripheral blood mononuclear cells (PBMCs) and neutrophils on ROS and cytokine production, and mitochondrial dynamics-related proteins, pro/anti-inflammatory and anti-oxidant gene expression. Immune cells were obtained from subjects with metabolic syndrome. H₂O₂ at low concentrations can trigger a transient anti-inflammatory adiponectin secretion and reduced gene expression of toll-like receptors (TLRs) in PBMCs but may act as a stimulator of proinflammatory genes (IL6, IL8) and mitochondrial dynamics-related proteins (Mtf2, NRF2, Tfam). H₂O₂ at a high concentration enhances the expression of pro-inflammatory genes (TLR2 and IL1β) and diminishes the expression of mitochondrial dynamics-related proteins (Mtf1, Tfam) and antioxidant enzymes (Cu/Zn SOD) in PBMCs. The GOX treatments produce dissimilar changes in immune cells: Neutrophils were more resistant to H₂O₂ effects and exhibited a more constant response in terms of gene expression than PBMCs. We observe emerging roles of H₂O₂ in mitochondrial dynamics and redox and inflammation processes in immune cells.

Modulation of Oxidative Status by Normoxia and Hypoxia on Cultures of Human Dermal Fibroblasts: How Does It Affect Cell Aging?

Reactive oxygen species (ROS) production in the skin is among the highest compared to other organs, and a clear correlation exists between ROS production and skin aging. Many attempts are underway to reduce oxidative stress in the skin by topical treatment or supplementation with antioxidants/cosmeceuticals, and cultures of human dermal fibroblasts (HDF) are widely used for these studies. Here, we examined the influence of oxygen tension on cell aging in HDF and how this impacted ROS production, the enzymatic and nonenzymatic antioxidant response system, and the efficacy of this defense system in limiting DNA damage and in modulating gene expression of proteins involved in the extracellular matrix, linked to skin aging. We investigated a selection of parameters that represent and reflect the behavior of cellular responses to aging and oxygen tension. Serial passaging of HDF under normoxia (21%) and hypoxia (5%) leads to cell aging as confirmed by β-galactosidase activity, p16 expression, and proliferation rate. However, in HDF under 21% O₂, markers of aging were significantly increased compared to those under 5% O₂ at matched cell passages despite having lower levels of intracellular ROS and higher levels of CoQ₁₀, total GSH, SOD1, SOD3, and mitochondrial superoxide anion. miRNA-181a, which is known to be upregulated in HDF senescence, was also analyzed, and indeed, its expression was significantly increased in old cells at 21% O₂ compared to those at 5% O₂. Upregulation of MMP1 and downregulation of COL1A1 along with increased DNA damage were also observed under 21% O₂ vs 5% O₂. The data highlight that chronic exposure to atmospheric 21% O₂ is able to trigger hormetic adaptive responses in HDF that however fail, in the long term, to prevent cellular aging. This information could be useful in further investigating molecular mechanisms involved in adaptation of skin fibroblasts to oxidative stress and may provide useful hints in addressing antiaging strategies.

Minocycline plus N-acteylcysteine induces remyelination, synergistically protects oligodendrocytes and modifies neuroinflammation in a rat model of mild traumatic brain injury

Mild traumatic brain injury afflicts over 2 million people annually and little can be done for the underlying injury. The Food and Drug Administration-approved drugs Minocycline plus N-acetylcysteine (MINO plus NAC) synergistically improved cognition and memory in a rat mild controlled cortical impact (mCCI) model of traumatic brain injury.³ The underlying cellular and molecular mechanisms of the drug combination are unknown. This study addressed the effect of the drug combination on white matter damage and neuroinflammation after mCCI. Brain tissue from mCCI rats given either sham-injury, saline, MINO alone, NAC alone, or MINO plus NAC was investigated via histology and qPCR at four time points (2, 4, 7, and 14 days post-injury) for markers of white matter damage and neuroinflammation. MINO plus NAC synergistically protected resident oligodendrocytes and decreased the number of oligodendrocyte precursor cells. Activation of microglia/macrophages (MP/MG) was synergistically increased in white matter two days post-injury after MINO plus NAC treatment. Patterns of M1 and M2 MP/MG were also altered after treatment. The modulation of neuroinflammation is a potential mechanism to promote remyelination and improve cognition and memory. These data also provide new and important insights into how drug treatments can induce repair after traumatic brain injury.

Remodeling of dermal collagen in photoaged skin using low-dose 5-aminolevulinic acid photodynamic therapy occurs via the transforming growth factor-β pathway

5-Aminolevulinic acid photodynamic therapy (ALA-PDT) is known to be effective in the treatment of photoaged skin. However, the molecular mechanisms still remain elusive. Protoporphyrin IX (PpIX) fluorescence is primarily located in the epidermis while ALA-PDT affects the dermal collagen, presumably by an indirect mechanism. This study aimed to investigate the molecular communication in low-dose ALA-PDT occurring between epidermal keratinocytes and dermal fibroblasts. Western blotting and enzyme-linked immunosorbent assays were performed to evaluate collagen expression and transforming growth factor-β (TGF-β) signaling in human keratinocytes and dermal fibroblasts. The impact on fibroblast proliferation was assessed by morphology and proliferating cell nuclear antigen immunofluorescence. Skin biopsies from mice were used to analyze the histological changes in dermal collagen and PpIX distribution. When fibroblasts were cocultured with keratinocytes treated with low-dose ALA-PDT, collagen synthesis and fibroblast proliferation were enhanced. Low-dose ALA-PDT stimulated TGF-β1 expression in keratinocytes. Fibroblasts cocultured with low-dose ALA-PDT-treated keratinocytes also showed activation of the TGF-β pathway. In vivo, PpIX fluorescence was densely distributed in photoaged mouse epidermis while collagen in the mouse dermis underwent remodeling. This study suggests that low-dose ALA-PDT can stimulate keratinocytes to release TGF-β1, activating the TGF-β pathway in dermal fibroblasts to remodel collagen in the dermis.

ROS and RNS signalling: adaptive redox switches through oxidative/nitrosative protein modifications

Over the last decade, a dual character of cell response to oxidative stress, eustress versus distress, has become increasingly recognized. A growing body of evidence indicates that under physiological conditions, low concentrations of reactive oxygen and nitrogen species (RONS) maintained by the activity of endogenous antioxidant system (AOS) allow reversible oxidative/nitrosative modifications of key redox-sensitive residues in regulatory proteins. The reversibility of redox modifications such as Cys S-sulphenylation/S-glutathionylation/S-nitrosylation/S-persulphidation and disulphide bond formation, or Tyr nitration, which occur through electrophilic attack of RONS to nucleophilic groups in amino acid residues provides redox switches in the activities of signalling proteins. Key requirement for the involvement of the redox modifications in RONS signalling including ROS-MAPK, ROS-PI3K/Akt, and RNS-TNF-α/NF-kB signalling is their specificity provided by a residue microenvironment and reaction kinetics. Glutathione, glutathione peroxidases, peroxiredoxins, thioredoxin, glutathione reductases, and glutaredoxins modulate RONS level and cell signalling, while some of the modulators (glutathione, glutathione peroxidases and peroxiredoxins) are themselves targets for redox modifications. Additionally, gene expression, activities of transcription factors, and epigenetic pathways are also under redox regulation. The present review focuses on RONS sources (NADPH-oxidases, mitochondrial electron-transportation chain (ETC), nitric oxide synthase (NOS), etc.), and their cross-talks, which influence reversible redox modifications of proteins as physiological phenomenon attained by living cells during the evolution to control cell signalling in the oxygen-enriched environment. We discussed recent advances in investigation of mechanisms of protein redox modifications and adaptive redox switches such as MAPK/PI3K/PTEN, Nrf2/Keap1, and NF-κB/IκB, powerful regulators of numerous physiological processes, also implicated in various diseases.

Nanosecond-Pulsed DBD Plasma-Generated Reactive Oxygen Species Trigger Immunogenic Cell Death in A549 Lung Carcinoma Cells through Intracellular Oxidative Stress

A novel application for non-thermal plasma is the induction of immunogenic cancer cell death for cancer immunotherapy. Cells undergoing immunogenic death emit danger signals which facilitate anti-tumor immune responses. Although pathways leading to immunogenic cell death are not fully understood; oxidative stress is considered to be part of the underlying mechanism. Here; we studied the interaction between dielectric barrier discharge plasma and cancer cells for oxidative stress-mediated immunogenic cell death. We assessed changes to the intracellular oxidative environment after plasma treatment and correlated it to emission of two danger signals: surface-exposed calreticulin and secreted adenosine triphosphate. Plasma-generated reactive oxygen and charged species were recognized as the major effectors of immunogenic cell death. Chemical attenuators of intracellular reactive oxygen species successfully abrogated oxidative stress following plasma treatment and modulated the emission of surface-exposed calreticulin. Secreted danger signals from cells undergoing immunogenic death enhanced the anti-tumor activity of macrophages. This study demonstrated that plasma triggers immunogenic cell death through oxidative stress pathways and highlights its potential development for cancer immunotherapy.

Alterations of hepatocyte function with free radical generators and reparation or prevention with coffee polyphenols

Liver diseases are linked in the majority of cases to oxidative stress that antioxidants could neutralize with reducing liver injury. Chlorogenic acid, a coffee polyphenol, possesses antioxidant prosperities. The aim of this study was to evaluate in vitro preventive and corrective effects of cholorogenic acid in hepatocyte toxicity induced by free radicals. Hepatocytes were isolated from adult male Wistar rats. To determine corrective effects and reparation, cells were first exposed to two free radical generators (hydrogen peroxide/iron sulfate for hydroxyl radical formation, and phenazine methosulfate/nicotinamide adenine dinucleotide for superoxide anion formation) for 12H and thereafter treated by chlorogenic acid (1 and 10 μM final concentration) for another 12H. To show preventive effects, cells were pretreated by chlorogenic acid and thereafter exposed to free radical generators. Hepatocyte proliferation, glucose uptake, ATP contents, membrane fluidity and integrity, and intracellular redox status were investigated after 24H culture. The results showed that chlorogenic acid reversed the decrease in cell proliferation, glucose uptake and ATP levels, the increased LDH release and the reduced membrane fluidity and restored the oxidant/antioxidant status under oxidative stress. When pre-treated with chlorogenic acid, hepatocytes became very resistant to oxidative conditions and cellular homeostasis was maintained. In conclusion, chlorogenic acid displayed not only corrective but also preventive effects in hepatocytes exposed to oxidative stress and could be beneficial in patients with or at risk of liver diseases.

The role of modulation of antioxidant enzyme systems in the treatment of neurodegenerative diseases

Oxidative stress is a much-appreciated phenomenon associated with the progression of neurodegenerative diseases (NDDs) due to imbalances in redox homeostasis. The poor correlations between the in vitro benefits and clinical trials of direct radical scavengers have prompted research into indirect antioxidant enzymes such as Nrf2. Activation of Nrf2 leads to the upregulation of a myriad of cytoprotective and antioxidant enzymes/proteins. Traditionally, early Nrf2-activators were studied as chemoprotective agents. There is a consequential lack of clinical trials testing Nrf2 activation in NDDs. However, there is abundant evidence of their utility in pre-clinical studies. Herein, we review the endogenous Nrf2 regulatory pathway and avenues for targeting this pathway. Furthermore, we provide updated information on pre-clinical studies for natural and synthetic Nrf2 activators. On the basis of our findings, we posit that successful therapeutics for NDDs rely on the design of potent synthetic Nrf2 activators with a careful combination of other neuroprotective activities.

Reactive Oxygen Species Derived from NOX3 and NOX5 Drive Differentiation of Human Oligodendrocytes

Reactive oxygen species (ROS) are signaling molecules that mediate stress response, apoptosis, DNA damage, gene expression and differentiation. We report here that differentiation of oligodendrocytes (OLs), the myelin forming cells in the CNS, is driven by ROS. To dissect the OL differentiation pathway, we used the cell line MO3-13, which display the molecular and cellular features of OL precursors. These cells exposed 1-4 days to low levels of H2O2 or to the protein kinase C (PKC) activator, phorbol-12-Myristate-13-Acetate (PMA) increased the expression of specific OL differentiation markers: the specific nuclear factor Olig-2, and Myelin Basic Protein (MBP), which was processed and accumulated selectively in membranes. The induction of differentiation genes was associated with the activation of ERK1-2 and phosphorylation of the nuclear cAMP responsive element binding protein 1 (CREB). PKC mediates ROS-induced differentiation because PKC depletion or bis-indolyl-maleimide (BIM), a PKC inhibitor, reversed the induction of differentiation markers by H2O2. H2O2 and PMA increased the expression of membrane-bound NADPH oxidases, NOX3 and NOX5. Selective depletion of these proteins inhibited differentiation induced by PMA. Furthermore, NOX5 silencing down regulated NOX3 mRNA levels, suggesting that ROS produced by NOX5 up-regulate NOX3 expression. These data unravel an elaborate network of ROS-generating enzymes (NOX5 to NOX3) activated by PKC and necessary for differentiation of OLs. Furthermore, NOX3 and NOX5, as inducers of OL differentiation, represent novel targets for therapies of demyelinating diseases, including multiple sclerosis, associated with impairment of OL differentiation.

Cytoprotective and Cytotoxic Effects of Rice Bran Extracts in Rat H9c2(2-1) Cardiomyocytes

This study was aimed at preliminarily assessing the cytoprotective and antioxidative effects of rice bran extracts (RBEs) from a Sarawak local rice variety (local name: "BJLN") and a commercial rice variety, "MR219," on oxidative stress in rat H9c2(2-1) cardiomyocytes. The cardiomyocytes were incubated with different concentrations of RBE and hydrogen peroxide (H2O2), respectively, to identify their respective IC50 values and safe dose ranges. Two nonlethal and close-to-IC50 doses of RBE were selected to evaluate their respective effects on H2O2 induced oxidative stress in cardiomyocytes. Both RBEs showed dose-dependent cytotoxicity effects on cardiomyocytes. H2O2 induction of cardiomyocytes pretreated with RBE further revealed the dose-dependent cytoprotective and antioxidative effects of RBE via an increase in IC50 values of H2O2. Preliminary analyses of induction effects of RBE and H2O2 on cellular antioxidant enzyme, catalase (CAT), also revealed their potential in regulating these activities and expression profile of related gene on oxidative stress in cardiomyocytes. Pretreated cardiomyocytes significantly upregulated the enzymatic activity and expression level of CAT under the exposure of H2O2 induced oxidative stress. This preliminary study has demonstrated the potential antioxidant effects of RBE in alleviating H2O2-mediated oxidative injuries via upregulation in enzymatic activities and expression levels of CAT.

Application of clotrimazole via a novel controlled release device provides potent retinal protection

Age-related macular degeneration is the leading cause of legal blindness among older individuals. Therefore, the development of new therapeutic agents and optimum drug delivery systems for its treatment are crucial. In this study, we investigate whether clotrimazole (CLT) is capable of protecting retinal cells against oxidative-induced injury and the possible inhibitory effect of a sustained CLT-release device against light-induced retinal damage in rats. In vitro results indicated pretreatment of immortalized retinal pigment epithelium cells (RPE-J cells) with 10-50 µM CLT before exposure to oxygen/glucose deprivation conditions for 48 h decreased the extent of cell death, attenuated the percentage of reactive oxygen species-positive cells, and decreased the levels of cleaved caspase-3. The device consists of a separately fabricated reservoir, a CLT formulation, and a controlled release cover, which are made of poly(ethyleneglycol) dimethacrylate (PEGDM) and tri(ethyleneglycol) dimethacrylate (TEGDM). The release rate of CLT was successfully tuned by changing the ratio of PEGDM/TEGDM in the cover. In vivo results showed that use of a CLT-loaded device lessened the reduction of electroretinographic amplitudes after light exposure. These findings indicate that the application of a polymeric CLT-loaded device may be a promising method for the treatment of some retinal disorders.

Spatial and temporal expression of zebrafish glutathione peroxidase 4 a and b genes during early embryo development

Antioxidant cellular mechanisms are essential for cell redox homeostasis during animal development and in adult life. Previous in situ hybridization analyses of antioxidant enzymes in zebrafish have indicated that they are ubiquitously expressed. However, spatial information about the protein distribution of these enzymes is not available. Zebrafish embryos are particularly suitable for this type of analysis due to their small size, transparency and fast development. The main objective of the present work was to analyze the spatial and temporal gene expression pattern of the two reported zebrafish glutathione peroxidase 4 (GPx4) genes during the first day of zebrafish embryo development. We found that the gpx4b gene shows maternal and zygotic gene expression in the embryo proper compared to gpx4a that showed zygotic gene expression in the periderm covering the yolk cell only. Following, we performed a GPx4 protein immunolocalization analysis during the first 24-h of development. The detection of this protein suggests that the antibody recognizes GPx4b in the embryo proper during the first 24 h of development and GPx4a at the periderm covering the yolk cell after 14-somite stage. Throughout early cleavages, GPx4 was located in blastomeres and was less abundant at the cleavage furrow. Later, from the 128-cell to 512-cell stages, GPx4 remained in the cytoplasm but gradually increased in the nuclei, beginning in marginal blastomeres and extending the nuclear localization to all blastomeres. During epiboly progression, GPx4b was found in blastoderm cells and was excluded from the yolk cell. After 24 h of development, GPx4b was present in the myotomes particularly in the slow muscle fibers, and was excluded from the myosepta. These results highlight the dynamics of the GPx4 localization pattern and suggest its potential participation in fundamental developmental processes.

Increased Oxidative Stress as a Selective Anticancer Therapy

Reactive oxygen species (ROS) are closely related to tumorgenesis. Under hypoxic environment, increased levels of ROS induce the expression of hypoxia inducible factors (HIFs) in cancer stem cells (CSCs), resulting in the promotion of the upregulation of CSC markers, and the reduction of intracellular ROS level, thus facilitating CSCs survival and proliferation. Although the ROS level is regulated by powerful antioxidant defense mechanisms in cancer cells, it is observed to remain higher than that in normal cells. Cancer cells may be more sensitive than normal cells to the accumulation of ROS; consequently, it is supposed that increased oxidative stress by exogenous ROS generation therapy has an effect on selectively killing cancer cells without affecting normal cells. This paper reviews the mechanisms of redox regulation in CSCs and the pivotal role of ROS in anticancer treatment.

Quantifying intracellular hydrogen peroxide perturbations in terms of concentration

Molecular level, mechanistic understanding of the roles of reactive oxygen species (ROS) in a variety of pathological conditions is hindered by the difficulties associated with determining the concentration of various ROS species. Here, we present an approach that converts fold-change in the signal from an intracellular sensor of hydrogen peroxide into changes in absolute concentration. The method uses extracellular additions of peroxide and an improved biochemical measurement of the gradient between extracellular and intracellular peroxide concentrations to calibrate the intracellular sensor. By measuring peroxiredoxin activity, we found that this gradient is 650-fold rather than the 7–10-fold that is widely cited. The resulting calibration is important for understanding the mass-action kinetics of complex networks of redox reactions, and it enables meaningful characterization and comparison of outputs from endogenous peroxide generating tools and therapeutics across studies.

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2-cys peroxiredoxin is the dominant scavenger of H₂O₂ in mammalian cells.

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H₂O₂ gradient across the plasma membrane is ~650-fold, 100 times higher than cited in literature.

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We developed an approach that converts fold-change in H₂O₂ sensor HyPer into change in actual concentration.

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The range of intracellular perturbations associated with the onset of apoptosis is less than 10 nM.

Hydrogen peroxide sensing, signaling and regulation of transcription factors

The regulatory mechanisms by which hydrogen peroxide (H₂O₂) modulates the activity of transcription factors in bacteria (OxyR and PerR), lower eukaryotes (Yap1, Maf1, Hsf1 and Msn2/4) and mammalian cells (AP-1, NRF2, CREB, HSF1, HIF-1, TP53, NF-κB, NOTCH, SP1 and SCREB-1) are reviewed. The complexity of regulatory networks increases throughout the phylogenetic tree, reaching a high level of complexity in mammalians. Multiple H₂O₂ sensors and pathways are triggered converging in the regulation of transcription factors at several levels: (1) synthesis of the transcription factor by upregulating transcription or increasing both mRNA stability and translation; (ii) stability of the transcription factor by decreasing its association with the ubiquitin E3 ligase complex or by inhibiting this complex; (iii) cytoplasm–nuclear traffic by exposing/masking nuclear localization signals, or by releasing the transcription factor from partners or from membrane anchors; and (iv) DNA binding and nuclear transactivation by modulating transcription factor affinity towards DNA, co-activators or repressors, and by targeting specific regions of chromatin to activate individual genes. We also discuss how H₂O₂ biological specificity results from diverse thiol protein sensors, with different reactivity of their sulfhydryl groups towards H₂O₂, being activated by different concentrations and times of exposure to H₂O₂. The specific regulation of local H₂O₂ concentrations is also crucial and results from H₂O₂ localized production and removal controlled by signals. Finally, we formulate equations to extract from typical experiments quantitative data concerning H₂O₂ reactivity with sensor molecules. Rate constants of 140 M⁻¹ s⁻¹ and ≥1.3 × 10³ M⁻¹ s⁻¹ were estimated, respectively, for the reaction of H₂O₂ with KEAP1 and with an unknown target that mediates NRF2 protein synthesis. In conclusion, the multitude of H₂O₂ targets and mechanisms provides an opportunity for highly specific effects on gene regulation that depend on the cell type and on signals received from the cellular microenvironment.

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Complexity of redox regulation increases along the phylogenetic tree.

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Complex regulatory networks allow for a high degree of H₂O₂ biological plasticity.

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H₂O₂ modulates gene expression at all steps from transcription to protein synthesis.

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Fast response (s) is mediated by sensors with high H₂O₂ reactivity.

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Low reactivity H₂O₂ sensors may mediate slow (h) or localized H₂O₂ responses.

Oxidative stress reduced by a green tea concentrate and Capsicum combination: synergistic effects

Reactive oxygen species that are produced by aerobic metabolism and signaling cascades have the potential to play important roles in maintaining homeostatic redox and cell proliferation. When the balance between the production and elimination of reactive oxygen species is perturbed toward production, the result is oxidative stress. High levels of oxidative stress are a general characteristic of cancer. The altered redox state within a tumor microenvironment confers a growth advantage through increased proliferation rates, evasion of apoptosis, and increased resistance to therapeutic compounds. We have tested a synergistic combination of green tea-Camellia sinensis-concentrate and powdered Capsicum powder (TeaFense™/Capsol-T™) as a dietary supplement to reduce oxidative stress as an approach to elimination of malignant cells. Here, we demonstrate that the green tea-powdered Capsicum mixture effectively reduces levels of oxidative stress in both cancer (HeLa) and noncancer (MCF-10A) cells as determined from measurements of levels of the oxidative stress indicator Nrf-2 by western blot analysis. Nrf-2 is a transcription factor that controls an antioxidant response element. Increased expression of Nrf-2 is linked to high levels of oxidative stress and vice versa. Based on levels of Nrf-2, the mixture of green tea concentrate plus powdered Capsicum reduced oxidative stress by more than 50% compared with 15% by the green tea concentrate alone.

Role of reactive oxygen species and NADPH-oxidase in the development of rat cerebellum

Experimental evidence suggests that reactive oxygen species (ROS) could participate in the regulation of some physiological conditions. In the nervous system, ROS have been suggested to act as signaling molecules involved in several developmental processes including cell differentiation, proliferation and programmed of cell death. Although ROS can be generated by several sources, it has been suggested that NADPH oxidase (NOX) could be critical in the production of ROS acting as a signal in some of these events. It has been reported that ROS production by NOX enzymes participate in neuronal maturation and differentiation during brain development. In the present study, we found that during rat cerebellar development there was a differential ROS generation at different ages and areas of the cerebellum. We also found a differential expression of NOX homologues during rat cerebellar development. When we treated developing rats with an antioxidant or with apocynin, an inhibitor of NOX, we found a marked decrease of the ROS levels in all the cerebellar layers at all the ages tested. Both treatments also induced a significant change in the cerebellar foliation as well as an alteration in motor behavior. These results suggest that both ROS and NOX have a critical role during cerebellar development.

Aiding and abetting roles of NOX oxidases in cellular transformation

NADPH oxidases of the NADPH oxidase (NOX) family are dedicated reactive oxygen species-generating enzymes that broadly and specifically regulate redox-sensitive signalling pathways that are involved in cancer development and progression. They act at specific cellular membranes and microdomains through the activation of oncogenes and the inactivation of tumour suppressor proteins. In this Review, we discuss primary targets and redox-linked signalling systems that are influenced by NOX-derived ROS, and the biological role of NOX oxidases in the aetiology of cancer.

Ovarian-protective effects of clotrimazole on ovarian ischemia/reperfusion injury in a rat ovarian-torsion model

BACKGROUND/AIMS

To evaluate the ovarian-protective effects of clotrimazole on ovarian ischemia/reperfusion injury in a rat ovarian-torsion model.

METHODS

32 Sprague-Dawley rats were randomly divided into four groups: (1) ischemia group (n = 8) in which only left adnexal torsion was performed for 2 h, but no treatment was given; (2) vehicle group (n = 8) in which left adnexal torsion was performed for 2 h and at the end of 2 h ischemia polyethylene glycol (3% PEG, 1 ml, i.p.) was administered and a 24-hour reperfusion was continued; (3) clotrimazole group (n = 8) in which left adnexal torsion was performed for 2 h and at the end of 2 h ischemia clotrimazole (30 mg/kg, i.p.) was administered and a 24-hour reperfusion was continued, and (4) control group (sham-operated, n = 6) in which no adnexal torsion and no treatment were given. The criteria for ovarian ischemia were follicular cell degeneration, vascular congestion, hemorrhage and infiltration by inflammatory cells. Each specimen was scored for each criterion (0, none; 1, mild; 2, moderate; 3, severe).

RESULTS

Clotrimazole significantly decreased plasma levels of serum malondialdehyde, ischemia-modified albumin, and total oxidant status.

CONCLUSION

This study showed the ovarian-protective effects of clotrimazole on ovarian ischemia/reperfusion injury.

Regulation of reactive oxygen species generation in cell signaling

Reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide (H(2)O(2)) are thought to be byproducts of aerobic respiration with damaging effects on DNA, protein, and lipid. A growing body of evidence indicates, however, that ROS are involved in the maintenance of redox homeostasis and various cellular signaling pathways. ROS are generated from diverse sources including mitochondrial respiratory chain, enzymatic activation of cytochrome p450, and NADPH oxidases further suggesting involvement in a complex array of cellular processes. This review summarizes the production and function of ROS. In particular, how cytosolic and membrane proteins regulate ROS generation for intracellular redox signaling will be detailed.

Hydrogen peroxide: a Jekyll and Hyde signalling molecule

Reactive oxygen species (ROS) are a group of molecules produced in the cell through metabolism of oxygen. Endogenous ROS such as hydrogen peroxide (H₂O₂) have long been recognised as destructive molecules. The well-established roles they have in the phagosome and genomic instability has led to the characterisation of these molecules as non-specific agents of destruction. Interestingly, there is a growing body of literature suggesting a less sinister role for this Jekyll and Hyde molecule. It is now evident that at lower physiological levels, H₂O₂ can act as a classical intracellular signalling molecule regulating kinase-driven pathways. The newly discovered biological functions attributed to ROS include proliferation, migration, anoikis, survival and autophagy. Furthermore, recent advances in detection and quantification of ROS-family members have revealed that the diverse functions of ROS can be determined by the subcellular source, location and duration of these molecules within the cell. In light of this confounding paradox, we will examine the factors and circumstances that determine whether H₂O₂ acts in a pro-survival or deleterious manner.

Do reactive oxygen species play a role in myeloid leukemias?

Reactive oxygen species (ROS) are a heterogeneous group of molecules that are generated by mature myeloid cells during innate immune responses, and are also implicated in normal intracellular signaling. Excessive production of ROS (and/or a deficiency in antioxidant pathways) can lead to oxidative stress, a state that has been observed in several hematopoietic malignancies including acute and chronic myeloid leukemias (AML and CML). Currently it is unclear what the cause of oxidative stress might be and whether oxidative stress contributes to the development, progression, or maintenance of these diseases. This article reviews the current evidence suggesting a role for ROS both in normal hematopoiesis and in myeloid leukemogenesis, and discusses the usefulness of therapeutically targeting oxidative stress in myeloid malignancy.

Romo1 is a negative-feedback regulator of Myc

Degradation of Myc protein is mediated by E3 ubiquitin ligases, including SCF(Fbw7) and SCF(Skp2), but much remains unknown about the mechanism of S-phase kinase-associated protein (Skp2)-mediated Myc degradation. In the present study, we show that upregulated Myc protein, which triggers the G1-S phase progression in response to growth-stimulatory signals, induces reactive oxygen species modulator 1 (Romo1) expression. Romo1 subsequently triggers Skp2-mediated ubiquitylation and degradation of Myc by a mechanism not previously reported in normal lung fibroblasts. We also show that reactive oxygen species (ROS) derived from steady-state Romo1 expression are necessary for cell cycle entry of quiescent cells. From this study, we suggest that the generation of ROS mediated by pre-existing Romo1 protein is required for Myc induction. Meanwhile, Romo1 expression induced by Myc during G1 phase stimulates Skp2-mediated Myc degradation in a negative-feedback mechanism.

Reactive oxygen species mediate shear stress-induced fluid-phase endocytosis in vascular endothelial cells

To elucidate the role of shear stress in fluid-phase endocytosis of vascular endothelial cells (EC), we used a rotating-disk shearing apparatus to investigate the effects of shear stress on the uptake of lucifer yellow (LY) by cultured bovine aortic endothelial cells (BAEC). Exposure of EC to shear stress (area-mean value of 10 dynes/cm2) caused an increase in LY uptake that was abrogated by the antioxidant, N-acetyl-L-cysteine (NAC), the NADPH oxidase inhibitor, acetovanillone, and two inhibitors of protein kinase C (PKC), calphostin C and GF109203X. These results suggest that fluid-phase endocytosis is regulated by both reactive oxygen species (ROS) and PKC. Shear stress increased both ROS production and PKC activity in EC, and the increase in ROS was unaffected by calphostin C or GF109203X, whereas the activation of PKC was reduced by NAC and acetovanillone. We conclude that shear stress-induced increase in fluid-phase endocytosis is mediated via ROS generation followed by PKC activation in EC.

Effects of clotrimazole on experimental spinal cord ischemia/reperfusion injury in rats

OBJECTIVE

The effect of clotrimazole was examined using a spinal cord ischemia/reperfusion model.

METHODS

Twenty albino Wistar rats weighing 234 +/- 12.3 g were used in this study. Rats were anesthetized intraperitoneally with 50 mg/kg ketamine HCl. All animals underwent laparotomy under aseptic conditions. Abdominal aortas of the animals in all but the sham group were exposed. After opening the retroperitoneum, the infrarenal abdominal aorta was clipped for 45 minutes to produce ischemia/reperfusion injury. Polyethylene glycol (PEG, 1 mL) was administrated to the vehicle group. PEG (1 mL) and clotrimazole (30 mg/kg) were administered intraperitoneally in the clotrimazole group. Total laminectomy of T8-T12 was performed on all rats under a microscope. Spinal cords were excised for a length of 2-cm rostrally and 1-cm caudally to the injury site and deep frozen at -76 degrees C for biochemical studies. The levels of malondialdehyde, glutathione-peroxidase, superoxide dismutase, and catalase were measured as an indicator of ischemia level. The most cranial part of the specimens was evaluated morphologically.

RESULTS

Treatment with clotrimazole significantly decreased malondialdehyde, glutathione-peroxidase, superoxide dismutase, and catalase levels in comparison with other groups (P = 0.008). Morphologic evaluation revealed that clotrimazole protected the axons and their myelin sheaths from ischemic damage.

CONCLUSION

This study showed the neuroprotective effects of clotrimazole on spinal cord ischemia/reperfusion injury.

Catalase ameliorates polychlorinated biphenyl-induced cytotoxicity in nonmalignant human breast epithelial cells

Polychlorinated biphenyls (PCBs) are environmental chemical contaminants believed to adversely affect cellular processes. We investigated the hypothesis that PCB-induced changes in the levels of cellular reactive oxygen species (ROS) induce DNA damage resulting in cytotoxicity. Exponentially growing cultures of human nonmalignant breast epithelial cells (MCF10A) were incubated with PCBs for 3 days and assayed for cell number, ROS levels, DNA damage, and cytotoxicity. Exposure to 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) or 2-(4-chlorophenyl)benzo-1,4-quinone (4-Cl-BQ), a metabolite of 4-chlorobiphenyl (PCB3), significantly decreased cell number and MTS reduction and increased the percentage of cells with sub-G1 DNA content. Results from electron paramagnetic resonance (EPR) spectroscopy showed a 4-fold increase in the steady-state levels of ROS, which was suppressed in cells pretreated with catalase. EPR measurements in cells treated with 4-Cl-BQ detected the presence of a semiquinone radical, suggesting that the increased levels of ROS could be due to the redox cycling of 4-Cl-BQ. A dose-dependent increase in micronuclei frequency was observed in PCB-treated cells, consistent with an increase in histone 2AX phosphorylation. Treatment of cells with catalase blunted the PCB-induced increase in micronuclei frequency and H2AX phosphorylation that was consistent with an increase in cell survival. Our results demonstrate a PCB-induced increase in cellular levels of ROS causing DNA damage, resulting in cell killing.

Effects of ginsenosides Re and Rg3 on intracellular redox state and cell proliferation in C6 glioma cells

Background

Cellular redox state is important to cell growth and death. The growth of tumor cells may be modulated by intracellular reduced glutathione/oxidized glutathione (GSH/GSSG). The present study aims to investigate the effects of ginsenosides Re and Rg3 on cellular redox state and cell proliferation in C6 glioma cells.

Methods

Cultured C6 glioma cells were exposed to various concentrations of either Rg3 or Re for 24 hours. Cell growth and death were measured by the BrdU incorporation assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay respectively. Cellular redox state was determined by free radical production using flow cytometry and GSH/GSSG using spectrofluorometry.

Results

At a sub-lethal concentration, Re suppressed cell proliferation with a significant decrease in BrdU incorporation. Re did not increase reactive oxygen species (ROS) production but increased GSH/GSSG via increased activity of gamma glutamylcystenyl synthase (γ-GCS). In contrast, Rg3 increased free radical production and reduced GSH/GSSG. The effects of Rg3 were probably due to increased activity of glutathione peroxidase (GPx).

Conclusion

Re and Rg3 alter cellular redox state of C6 glioma cells in opposite directions. Changes in cellular redox state induced by Re and Rg3 are correlated with the proliferation rates of C6 glioma cells.

Inflammation induced by photocoagulation laser is minimized by copper chelators

The effect of trientine hydrochloride (TRIEN), a copper-selective chelating agent, on retinal inflammation induced by photocoagulation laser treatment was studied. Nine Long-Evans rats were treated with TRIEN (0.5 mmol/kg per day, intraperitoneal injection) for 9 days. On day 8, each animal underwent unilateral photocoagulation laser treatment with an argon dye laser. On day 9, animals were killed and the eyes processed for immunohistochemistry and light microscopy. In the TRIEN-treated group, retinal thickness and number of macrophages (ED-1) were both significantly lower than in the saline-treated, control group exposed to laser photocoagulation. The results support the hypothesis that selective copper chelation prior to laser treatment may inhibit ocular inflammation. The results suggest that pretreatment with a selective copper-chelating compound can minimize retinal inflammation secondary to laser photocoagulation treatment, which may improve overall outcome of photocoagulation treatment for diabetic retinopathy.