RASSF1A suppresses the activated K-Ras-induced oxidative DNA damage

The mutant K-Ras elevates intracellular reactive oxygen species (ROS) levels and leads to oxidative DNA damage, resulting in malignant cell transformation. Ras association domain family 1 isoform A (RASSF1A) is known to play a role as a Ras effector. However, the suppressive effect of RASSF1A on K-RasV12-induced ROS increase and DNA damage has not been identified. Here, we show that RASSF1A blocks K-RasV12-triggered ROS production. RASSF1A expression also inhibits oxidative DNA damage and chromosomal damage. From the results obtained in this study, we suggest that RASSF1A regulates the cellular ROS levels enhanced by the Ras signaling pathway, and that it may function as a tumor suppressor by suppressing DNA damage caused by activated Ras.     

Gender-dependent differences of mitochondrial function and oxidative stress in rat skeletal muscle at rest and after exercise training

Objective: This study investigated gender-dependent differences of mitochondrial function and sensitivity to in vitro ROS exposure in rat skeletal muscle at rest and after exercise training.

Methods: Wistar rats underwent running training for 6 weeks. In vitro measurements of hydroxyl radical production, oxygen consumption (under basal and maximal respiration conditions) and ATP production were made on permeabilized fibers. Mitochondrial function was examined after exposure and non-exposure to an in vitro generator system of reactive oxygen species (ROS). Antioxidant enzyme activities and malondialdehyde (MDA) content were also determined.

Results: Compared with sedentary males, females showed a greater resistance of mitochondrial function (oxygen consumption and ATP production) to ROS exposure, and lower MDA content and antioxidant enzyme activities. The training protocol had more beneficial effects in males than females with regard to ROS production and oxidative stress. In contrast to male rats, the susceptibility of mitochondrial function to ROS exposure in trained females was unchanged.

Discussion: Exercise training improves mitochondrial function oxidative capacities in both male and female rats, but is more pronounced in males as a result of different mechanisms. The resistance of mitochondrial function to in vitro oxidative stress exposure and the antioxidant responses are gender- and training-dependent, and may be related to the protective effects of estrogen.     

Aspiration cytology of 147 adnexal cysts with histologic correlation.

OBJECTIVE: To assess the usefulness of cytology in the diagnosis of 147 histologically established adnexal cysts. STUDY DESIGN: Retrospective, macro-microscopic study based on fluid aspirated from 132 ovarian and 15 extraovarian cysts and projected as a cytohistologic correlation. RESULTS: Typical macroscopic features were identified in 76% of endometriotic cysts, in 53% of mucinous neoplasms and in 67% of dermoid cysts. Cytology helped to identify 67% of nonneoplastic and 56% of neoplastic cysts. The lowest diagnostic sensitivities were observed in functional cysts and benign serous neoplasms (50%), while the highest were shown by endometriotic cysts (76%) and malignant epithelial neoplasms (71%). Inadequate samples were obtained from all types of cysts, even malignant ones (two mucinous cystadenocarcinomas). Diagnostic cytology was useless in extraovarian cysts (33% sensitivity). An adult granulosa cell tumor was erroneously diagnosed as a follicular cyst by cytologic examination. CONCLUSION: Examination of the cyst fluids obtained by aspiration demonstrated low sensitivity, with 43% of inadequate samples obtained from all types of cysts. Malignant cystic neoplasms may be overlooked in inadequate samples. Our study also revealed that specificity in this type of analysis is high in inadequate samples, provided that the technique is carried out correctly.     

In vivo antioxidant role of astaxanthin under oxidative stress in the green alga Haematococcus pluvialis

Intracellular production of active oxygen in the green alga Haematococcus pluvialis was studied by measuring the capacity for in vivo conversion of 2′,7′-dichlorohydrofluorescein diacetate to the fluorescent dye dichlorofluorescein in different algal cell types (i.e., vegetative, immature cyst and mature cyst cells). The increase in formation of dichlorofluorescein by methyl viologen (superoxide anion radical generator) was linear for 2 h in immature cyst cells (low astaxanthin) in a methyl viologen-concentration-dependent manner, while no production was detected in mature (high astaxanthin) cysts. Compared to cyst cells, formation of dichlorofluorescein in vegetative cells (no astaxanthin) was markedly increased by methyl viologen. The formation of dichlorofluorescein in cyst cells was decreased with higher astaxanthin content under excessive oxidative stress. All of the active oxygen species tested (singlet oxygen, superoxide anion radical, hydrogen peroxide and peroxy radical) at 10⁻³ M increased the intracellular dichlorofluorescein formation in immature cysts, but did not increase the dichlorofluorescein content of mature cysts. Therefore, astaxanthin in cyst cells appeared to function as an antioxidant agent against oxidative stress. Received: 26 January 2000 / Received revision: 5 April 2000 / Accepted: 1 May 2000     

Hepatitis C virus core or NS3/4A protein expression preconditions hepatocytes against oxidative stress and endoplasmic reticulum stress

Objectives: The occurrence of oxidative stress and endoplasmic reticulum (ER) stress in hepatitis C virus (HCV) infection has been demonstrated and play an important role in liver injury. During viral infection, hepatocytes must handle not only the replication of the virus, but also inflammatory signals generating oxidative stress and damage. Although several mechanisms exist to overcome cellular stress, little attention has been given to the adaptive response of hepatocytes during exposure to multiple noxious triggers.

Methods: In the present study, Huh-7 cells and hepatocytes expressing HCV Core or NS3/4A proteins, both inducers of oxidative and ER stress, were additionally challenged with the superoxide anion generator menadione to mimic external oxidative stress. The production of reactive oxygen species (ROS) as well as the response to oxidative stress and ER stress were investigated.

Results: We demonstrate that hepatocytes diminish oxidative stress through a reduction in ROS production, ER-stress markers (HSPA5 [GRP78], sXBP1) and apoptosis (caspase-3 activity) despite external oxidative stress. Interestingly, the level of the autophagy substrate protein p62 was downregulated together with HCV Core degradation, suggesting that hepatocytes can overcome excess oxidative stress through autophagic degradation of one of the stressors, thereby increasing cell survival.

Duscussion: In conclusion, hepatocytes exposed to direct and indirect oxidative stress inducers are able to cope with cellular stress associated with viral hepatitis and thus promote cell survival.     

Peripheral biomarkers of oxidative stress and their limited potential in evaluation of clinical features of Huntington's patients

Abstract

Context: Peripheral oxidative biomarkers could be useful for monitoring clinical features of Huntington's disease (HD).

Materials and methods: Cu/Zn-superoxide dismutase (Cu/Zn-SOD), neuron-specific enolase (NSE) and 8-hydroxy-2′-deoxyguanosine (8-oxoGua) serum levels were analysed in 18 HD patients and 10 controls. Clinical measures were recorded from each HD patients.

Results: Cu/Zn-SOD, NSE and 8-oxoGua values were higher in HD patients than in controls. Cu/Zn-SOD and NSE correlated positively. No correlation was observed between the biomarkers analysed and the clinical measures assessed.

Discussion and conclusion: Serum oxidative biomarkers could express the neuronal oxidative processes going on in HD patients but are inadequate to evaluate clinical features of the disease.     

The toxic dinoflagellate Cochlodinium polykrikoides (Dinophyceae) produces resting cysts

While harmful algal blooms (HABs) caused by the toxic dinoflagellate Cochlodinium polykrikoides have been known to science for more than a century, the past two decades have witnessed an extraordinary expansion of these events across Asia, North America, and even Europe. Although the production of resting cysts and subsequent transport via ships’ ballast water or/and the transfer of shellfish stocks could facilitate this expansion, confirmative evidence for cyst production by C. polykrikoides is not available. Here, we provide visual confirmation of the production of resting cysts by C. polykrikoides in laboratory cultures isolated from North America. Evidence includes sexually mating cell pairs, planozygotes with two longitudinal flagella, formation of both pellicular (temporary) cysts and resting cysts, and a time series of the cyst germination process. Resting cyst germination occurred up to 1 month after cyst formation and 2–40% of resting cysts were successfully germinated in cultures maintained at 18–21 °C. Pellicular cysts with hyaline membranes were generally larger than resting cysts, displayed discernable cingulum and/or sulcus, and reverted to vegetative cells within 24 h to ∼1 week of formation. A putative armored stage of C. polykrikoides was not observed during any life cycle stage in this study. This definitive evidence of resting cyst production by C. polykrikoides provides a mechanism to account for the recurrence of annual blooms in given locales as well as the global expansion of C. polykrikoides blooms during the past two decades.     

Oxidative stress in myelin sheath: The other face of the extramitochondrial oxidative phosphorylation ability

Abstract

Oxidative phosphorylation (OXPHOS) is not only the main source of ATP for the cell, but also a major source of reactive oxygen species (ROS), which lead to oxidative stress. At present, mitochondria are considered the organelles responsible for the OXPHOS, but in the last years we have demonstrated that it can also occur outside the mitochondrion. Myelin sheath is able to conduct an aerobic metabolism, producing ATP that we have hypothesized is transferred to the axon, to support its energetic demand.

In this work, spectrophotometric, cytofluorimetric, and luminometric analyses were employed to investigate the oxidative stress production in isolated myelin, as far as its respiratory activity is concerned. We have evaluated the levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), markers of lipid peroxidation, as well as of hydrogen peroxide (H₂O₂), marker of ROS production. To assess the presence of endogenous antioxidant systems, superoxide dismutase, catalase, and glutathione peroxidase activities were assayed. The effect of certain uncoupling or antioxidant molecules on oxidative stress in myelin was also investigated.

We report that isolated myelin produces high levels of MDA, 4-HNE, and H₂O₂, likely through the pathway composed by Complex I–III–IV, but it also contains active superoxide dismutase, catalase, and glutathione peroxidase, as antioxidant defense. Uncoupling compounds or Complex I inhibitors increase oxidative stress, while antioxidant compounds limit ROS generation.

Data may shed new light on the role of myelin sheath in physiology and pathology. In particular, it can be presumed that the axonal degeneration associated with myelin loss in demyelinating diseases is related to oxidative stress caused by impaired OXPHOS.     

Mechanisms involved in the development of diabetic retinopathy induced by oxidative stress

Background: Diabetic retinopathy (DR) is one of the main complications in patients with diabetes and has been the leading cause of visual loss since 1990. Oxidative stress is a biological process resulting from excessive production of reactive oxygen species (ROS). This process contributes to the development of many diseases and disease complications. ROS interact with various cellular components to induce cell injury. Fortunately, there is an antioxidan t system that protects organisms against ROS. Indeed, when ROS exceed antioxidant capacity, the resulting cell injury can cause diverse physiological and pathological changes that could lead to a disease like DR.

Objective: This paper reviews the possible mechanisms of common and novel biomarkers involved in the development of DR and explores how these biomarkers could be used to monitor the damage induced by oxidative stress in DR, which is a significant complication in people with diabetes.

Conclusion: The poor control of glucemy in pacients with DB has been shown contribute to the development of complications in eyes as DR.     

Application of a YHB1-GFP reporter to detect nitrosative stress in yeast

Abstract

Yeast flavohemoglobin (Yhb1p) plays a pivotal role in NO^? detoxification and has also been implicated in oxidative/reductive stress responses. In this study, we have used a YHB1-GFP reporter expressing a full-length chromosome-tagged Yhb1-GFP fusion protein to monitor changes in flavohemoglobin levels after cell treatment with oxidants, antioxidants and nitric oxide donors. Only nitric oxide donors were found to induce a dose-dependent increase in Yhb1-GFP expression while hydrogen peroxide, menadione and diamide caused a moderate diminution of YHB1-GFP fluorescence. Additionally, the levels of endogenous and hydroperoxide-induced ROS production in the Δyhb1 mutant were comparable to those in the isogenic wild-type strain. Although peroxides increased NO^? generation while nitrite and nitric oxide donors augmented ROS levels in yeast cells, their effects were generally not more pronounced in Δyhb1 than in wild-type cells. Taken together, these data suggest that yeast flavohemoglobin does not contribute to cross-protection against oxidative and nitrosative stress.     

Intracellular free radical production by peripheral blood T lymphocytes from patients with systemic sclerosis: role of NADPH oxidase and ERK1/2

IntroductionAbnormal oxidative stress has been described in systemic sclerosis (SSc) and previous works from our laboratory demonstrated an increased generation of reactive oxygen species (ROS) by SSc fibroblasts and monocytes. This study investigated the ability of SSc T lymphocytes to produce ROS, the molecular pathway involved, and the biological effects of ROS on SSc phenotype.MethodsPeripheral blood T lymphocytes were isolated from serum of healthy controls or SSc patients by negative selection with magnetic beads and activated either with PMA or with magnetic beads coated with anti-CD3 and anti-CD28 antibodies. Intracellular ROS generation was measured using a DCFH-DA assay in a plate reader fluorimeter or by FACS analysis. CD69 expression and cytokine production were analyzed by FACS analysis. Protein expression was studied using immunoblotting techniques and mRNA levels were quantified by real-time PCR. Cell proliferation was carried out using a BrdU incorporation assay.ResultsPeripheral blood T lymphocytes from SSc patients showed an increased ROS production compared to T cells from healthy subjects. Since NADPH oxidase complex is involved in oxidative stress in SSc and we found high levels of gp91phox in SSc T cells, SSc T cells were incubated with chemical inhibititors or specific siRNAs against gp91phox. Inhibition of NADPH oxidase partially reverted CD69 activation and proliferation rate increase, and significantly influenced cytokine production and ERK1/2 activation.ConclusionsSSc T lymphocityes are characterized by high levels of ROS, generated by NADPH oxidase via ERK1/2 phosphorylation, that are essential for cell activation, proliferation, and cytokine production. These data confirm lymphocytes as key cellular players in the pathogenesis of systemic sclerosis and suggest a crucial link between ROS and T cell activation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0591-8) contains supplementary material, which is available to authorized users.     

OXR1 signaling pathway as a possible mechanism of elastase-induced oxidative damage in pulmonary cells: the protective role of ellagic acid

Background and objective

Oxidative stress is a process that occurs through free radicals on the cell membranes which causes damage to the cell and intracellular organelles, especially mitochondria membranes. H2O2 induced oxidative stress in human cells is of interest in toxicological research since oxidative stress plays a main role in the etiology of several pathological conditions. Neutrophil Elastase (Serine proteinase) is involved in the pathology process of emphysema as a respiratory disease through lung inflammation, and destruction of alveolar walls. The present study investigated the direct oxidative stress effects of Elastase in comparison with H2O2 on human lung epithelial cells (A549 cells) concerning the generation of reactive oxygen species (ROS) and modulation of oxidation resistance 1 (OXR1) and its downstream pathway using the well-known antioxidant Ellagic acid as an activator of antioxidant genes.

Materials and methods

The human pulmonary epithelial cells (A549) were divided into the nine groups including Negative control, Positive control (H2O2), Elastase (15, 30, and 60 mU/mL), Ellagic acid (10 μmol/L), and Elastase?+?Ellagic acid. Cytotoxicity, ROS generation, oxidative stress profile, level of reactive metabolites, and gene expression of OXR1 and its downstream genes were measured in all groups.

Results

The obtained data demonstrated that Elastase exposure caused oxidative stress damage in a dose-depended manner which was associated with decreases in antioxidant defense system genes. Conversely, treatment with Ellagic acid as a potent antioxidant showed improved antioxidant enzyme activity and content which was in line with the upregulation of OXR1 signaling pathway genes.

Conclusions

The present findings can highlight the novel mechanism underlying the oxidative stress induced by Neutrophil Elastase through OXR1 and related genes. Moreover, the benefit of Ellagic acid on cytoprotection, resulting from its antioxidant properties was documented.

     

Effect of ubiquinol supplementation on biochemical and oxidative stress indexes after intense exercise in young athletes

Objectives: Physical exercise significantly impacts the biochemistry of the organism. Ubiquinone is a key component of the mitochondrial respiratory chain and ubiquinol, its reduced and active form, is an emerging molecule in sport nutrition. The aim of this study was to evaluate the effect of ubiquinol supplementation on biochemical and oxidative stress indexes after an intense bout of exercise.

Methods: 21 male young athletes (26?+?5 years of age) were randomized in two groups according to a double blind cross-over study, either supplemented with ubiquinol (200?mg/day) or placebo for 1 month. Blood was withdrawn before and after a single bout of intense exercise (40 min run at 85% maxHR). Physical performance, hematochemical parameters, ubiquinone/ubiquinol plasma content, intracellular reactive oxygen species (ROS) level, mitochondrial membrane depolarization, paraoxonase activity and oxidative DNA damage were analyzed.

Results: A single bout of intense exercise produced a significant increase in most hematochemical indexes, in particular CK and Mb while, on the contrary, normalized coenzyme Q₁₀ plasma content decreased significantly in all subjects. Ubiquinol supplementation prevented exercise-induced CoQ deprivation and decrease in paraoxonase activity. Moreover at a cellular level, in peripheral blood mononuclear cells, ubiquinol supplementation was associated with a significant decrease in cytosolic ROS while mitochondrial membrane potential and oxidative DNA damage remained unchanged.

Discussion: Data highlights a very rapid dynamic of CoQ depletion following intense exercise underlying an increased demand by the organism. Ubiquinol supplementation minimized exercise-induced depletion and enhanced plasma and cellular antioxidant levels but it was not able to improve physical performance indexes or markers of muscular damage.     

Parameters of oxidative stress in saliva from patients with aggressive and chronic periodontitis

Objectives: Free radicals play an important role in the onset and progression of many diseases. The aim of this study was to investigate the contribution of oxidative stress in the pathology of aggressive (AgP) and chronic (CP) periodontitis and its relation with the clinical periodontal status.

Methods: Eighty subjects were divided into two groups: 20 patients with AgP and 20 patients with CP with their 20 corresponding matched controls, based on clinical attachment loss (CAL), probing pocket depth (PPD), and bleeding on probing (BOP). Saliva reactive oxygen species (ROS), lipid peroxidation, and non-enzymatic antioxidant defences were measured by luminol-dependent chemiluminescence assay, as thiobarbituric acid-reactive substances (TBARs) and total radical-trapping antioxidant potential (TRAP), respectively. Pearson's correlation and multivariate analysis were used to determine the relationship between ROS and TBARs and the clinical parameters.

Results: ROS and TBARs were increased in AgP while TRAP was decreased, comparing with CP. In AgP, a strong and positive correlation was observed between ROS and TBARs and they were closely associated with CAL and PPD.

Discussion: In AgP, but not in CP, oxidative stress is a high contributor to periodontal pathology and it is closely associated with the clinical periodontal status.     

Effects of selenite and selenate on the antioxidant systems in Senecio scandens L

Abstract

Selenate and selenite are the most prevalent bioavailable selenium (Se) forms and most easily taken up by plants. Some studies indicate that they are differently absorbed and accumulated in plants and that selenium is toxic if accumulated at high concentrations. Toxicity is due to substitution of sulphur by selenium in cysteine and methionine aminoacids with alteration of the tertiary structure and catalytic activity of proteins and with inhibition of enzymes involved in chlorophyll biosynthesis. Moreover, the interaction between Se and thiol groups induces loss of efficiency of plant defence systems and increases the reactive oxygen species (ROS) production thus enhancing the oxidative stress. To further elucidate the role of Se in higher plants, in this study the antioxidative response to the phytotoxicity of selenite and selenate in Senecio scandens L. was evaluated. The data indicate that while selenite induces oxidative stress enhancing ROS production, lipid peroxidation and the oxidised forms of ascorbate and glutathione, selenate does not significantly affect the analysed pathways. This article outlines that the synergistic action of different antioxidant components is necessary to overcome the phytotoxicity of selenium in Senecio.     

Vitamin complex (ascorbic acid,alpha-tocopherol and beta-carotene) induces micronucleus formation in PBMNC unrelated to ROS production

Abstract

Objectives

To evaluate the correlation between reactive oxygen species (ROS) production and micronucleus formation induced by a vitamin complex in peripheral blood mononuclear cells from healthy people aged between 40 and 85 years old.

Methods

Peripheral blood mononuclear cells (PBMNCs) were purified utilizing ficoll-hypaque gradient. ROS production by PBMNCs was quantified by luminol-dependent chemiluminescence in the presence or in the absence of the vitamin complex. DNA damage in PBMNC by the vitamin complex was detected by the micronucleus technique. Statistical analyses were made with the Student's ‘t’ test and the Pearson correlation. P < 0.05 was considered significant.

Results

The vitamin complex induced MN formation in PBMNC but did not augment ROS production. There was no correlation between ROS production and MN formation either in the presence or in the absence of the vitamin complex.

Discussion

There was no increase in the ROS production in the presence of the vitamin complex. The vitamin complex induced an augmentation in the MN formation. There was no correlation between ROS production and the induction of MN formation. Since no association could be detected between ROS production and MN formation, additional studies are required in order to investigate the possible mechanism of vitamin-induced MN formation.     

Synergic prooxidant,apoptotic and TRPV1 channel activator effects of alpha-lipoic acid and cisplatin in MCF-7 breast cancer cells

Background: Resistance to cisplatin (Cisp) in the treatment of breast cancer is a major obstacle. Alpha-lipoic acid (ALA) has both antioxidant and oxidant properties. ALA has been used on stimulation mechanisms of apoptosis and oxidative stress in the treatment of cancer with a combination of chemotherapeutic agents, although its role on molecular mechanisms in the cancer cells has not been clarified yet. The aim of this study was to evaluate if a combination therapy of ALA with Cisp can alter the effect of this chemotherapy drug in the MCF-7 breast cancer cells.

Materials: The MCF-7 cells were divided into four treatment groups as control, Cisp (0.025?mM), ALA (0.05?mM), and Cisp?+?ALA.

Results: Apoptosis, mitochondrial membrane depolarization, reactive oxygen species (ROS) production, lipid peroxidation, PARP1, caspase 3 and 9 expression levels are increased through activating TRPV1 in the cells by the Cisp and ALA treatments, although cell viability, reduced glutathione and glutathione peroxidase (GPx) values were decreased by the treatments. The Cisp and ALA-induced increase of intracellular free Ca²⁺ concentration was decreased with the TRPV1 blocker, capsazepine.

Conclusions: Apoptosis and oxidant effects of Cisp were increased by activation of TRPV1 channels, but its action on the values was further increased by the ALA treatment. Combination therapy of ALA and Cisp could be used as an effective strategy in the treatment of breast cancer.     

Oxidative stress and susceptibility to mitochondrial permeability transition precedes the onset of diabetes in autoimmune non-obese diabetic mice

Abstract

Beta cell destruction in type 1 diabetes (TID) is associated with cellular oxidative stress and mitochondrial pathway of cell death. The aim of this study was to determine whether oxidative stress and mitochondrial dysfunction are present in T1D model (non-obese diabetic mouse, NOD) and if they are related to the stages of disease development. NOD mice were studied at three stages: non-diabetic, pre-diabetic, and diabetic and compared with age-matched Balb/c mice. Mitochondria respiration rates measured at phosphorylating and resting states in liver and soleus biopsies and in isolated liver mitochondria were similar in NOD and Balb/c mice at the three disease stages. However, NOD liver mitochondria were more susceptible to calcium-induced mitochondrial permeability transition as determined by cyclosporine-A-sensitive swelling and by decreased calcium retention capacity in all three stages of diabetes development. Mitochondria H₂O₂ production rate was higher in non-diabetic, but unaltered in pre-diabetic and diabetic NOD mice. The global cell reactive oxygen species (ROS), but not specific mitochondria ROS production, was significantly increased in NOD lymphomononuclear and stem cells in all disease stages. In addition, marked elevated rates of 2′,7′-dichlorodihydrofluorescein (H₂DCF) oxidation were observed in pancreatic islets from non-diabetic NOD mice. Using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) and lipidomic approach, we identified oxidized lipid markers in NOD liver mitochondria for each disease stage, most of them being derivatives of diacylglycerols and phospholipids. These results suggest that the cellular oxidative stress precedes the establishment of diabetes and may be the cause of mitochondrial dysfunction that is involved in beta cell death.     

Oxidative insults disrupt OPA1-mediated mitochondrial dynamics in cultured mammalian cells

Objective: To explore the impact of oxidative insults on mitochondrial dynamics. In mammalian cells, oxidative insults activate stress response pathways including inflammation, cytokine secretion, and apoptosis. Intriguingly, mitochondria are emerging as a sensitive network that may function as an early indicator of subsequent cellular stress responses. Mitochondria form a dynamic network, balancing fusion, mediated by optic atrophy-1 (OPA1), and fission events, mediated by dynamin-related protein-1 (DRP1), to maintain homeostasis.

Methods: Here, we examine the impact of oxidative insults on mitochondrial dynamics in 143B osteosarcoma and H9c2 cardiomyoblast cell lines via confocal microscopy, flow cytometry, and protein-based analyses.

Results: When challenged with hydrogen peroxide (H₂O₂), a ROS donor, both cell lines display fragmentation of the mitochondrial network and loss of fusion-active OPA1 isoforms, indicating that OPA1-mediated mitochondrial fusion is disrupted by oxidative damage in mammalian cells. Consistent with this, cells lacking OMA1, a key protease responsible for cleavage of OPA1, are protected against OPA1 cleavage and mitochondrial fragmentation in response to H₂O₂ challenge.

Discussion: Taken together, these findings indicate that oxidative insults damage OPA1-mediated mitochondrial dynamics in mammalian cells via activation of OMA1, consistent with an emerging role for mitochondrial dynamics as an early indicator of cellular stress signaling.     

Oxidative stress in otosclerosis

Objectives: Otosclerosis is a disease involving abnormal bone turnover in the human otic capsule that results in hearing loss. Several hypotheses have been suggested for the etiopathogenesis of otosclerosis; however, its etiology remains unclear.

Methods: This study evaluated the correlation between otosclerosis and levels of paraoxonase-1 (PON1), arylesterase, total antioxidant status, total oxidant status (TOS), oxidative stress index (OSI), total sulfhydryl (-SH) groups, lipid hydroperoxide, and ceruloplasmin in the serum of otosclerosis patients and healthy subjects with respect to oxidative stress.

Results: In our study, TOS and OSI levels were higher in the otosclerosis patients than in the controls. The PON1 levels showed that oxidative stress was severe, and as a result, antioxidants were consumed and depleted.

Discussion: When an imbalance between oxygen free radical production and antioxidative defense mechanisms occurs, reactive oxygen species levels may increase, which in turn may damage cells and tissues through the peroxidation of phospholipid membrane structures. The body initially responds with increased antioxidant production, but if the oxidative stress is severe, decreased antioxidant levels may result. This study reports expression levels of oxidative stress species in otosclerosis patients.