Excessive Free Radical Generation Research Articles

Developing ROS Scavenging Agents for Pharmacological Purposes: Recent Advances in Design of Manganese-Based Complexes with Anti-Inflammatory and Anti- Nociceptive Activity

Reactive oxygen and nitrogen species, which are normal products of cell metabolism, may play a dual beneficial/deleterious role, depending on local concentration and mode of generation. As such, they have been identified as key pathogenic factors for many inflammatory and degenerative disorders, carcinogenesis, nociception and ageing. In this perspective, low molecular weight transition metal complexes with organic ligands have been and are still viewed as promising pharmaceutical agents with antioxidant/free radical scavenging properties, owing to their ability to interact and/or react with reactive oxygen or nitrogen species and counterbalance excessive endogenous free radical generation in biological systems. Among these compounds, manganese(II/III) complexes have resulted effective as ROS scavengers both in vitro and in vivo. In particular, Mn(III) complexes with porphyrins and salen derivatives as well as Mn(II) complexes with macrocyclic pentaamines and polyamine-polycarboxylic acids have been recently analyzed as ROS scavengers for therapeutic purposes. In this article, we summarize the chemical and biological properties of manganese complexes with low molecular weight synthetic ligands as scavengers of pro-oxidant species, with particular attention to the mechanisms operating at the metal center in the scavenging process. A proper design of the organic scaffolds may yield manganese complexes capable to catalyze different scavenging reactions, including superoxide and/or hydrogen peroxide dismutation and peroxynitrite decomposition. These manganese complexes can be viewed either as a novel class of drugs helpful to reduce oxidative tissue injury or as useful tools to get further light on the role played by ROS in biological systems.

Hydrocortisone attenuates cyclosporin A‐induced nephrotoxicity in rats

Cyclosporin A (CsA) is the prototype of immunosuppressant drugs that have revolutionized the management of all transplantation and autoimmune diseases. Side effects of CsA mainly affecting the kidney but also observed in liver and heart, limit the therapeutic use of this drug after organ transplantation. The renal toxicity of CsA is attributed to reduced renal blood flow which leads to hypoxia-reoxygenation injury accompanied by excessive generation of oxygen-derived free radicals. In several therapeutic protocols, CsA is used in association with corticosteroids to obtain better therapeutic results. Recently, our studies showed that hydrocortisone (HY) has a protective effect on CsA-induced cardiotoxicity. In fact our previous results demonstrated that in rat cardiomyocytes, CsA toxicity is due to a calcium overload, which in turn induce lipid peroxidation and determines oxidative stress-induced cell injury. Treatment with HY effectively inhibits CsA-induced toxicity, decreasing lipid peroxidation as well as calcium intracellular concentration. In this study we evaluated in vivo the effects of CsA, used alone or in association with HY, on some parameters of renal dysfunction (blood urea nitrogen; BUN, creatinine, and cholesterol), malondialdheyde (MDA) levels, antioxidant enzyme catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and apoptosis. CsA administration for 24 days resulted in a marked renal oxidative stress, which significantly deranged the renal functions. Treatment with CsA in association with HY significantly improved the renal dysfunction and renal oxidative status. This study clearly suggests the role of oxidative stress in the pathogenesis of CsA-induced nephrotoxicity.

Glycemic and oxidative status of patients with type 2 diabetes mellitus following oral administration of alpha-lipoic acid: a randomized double-blinded placebo-controlled study.

Despite well-controlled blood glucose levels, diabetic complications still inevitably take place via several mechanisms including excessive generation of free radicals in patients who suffer from diabetes mellitus (DM). A randomized double-blind placebo-controlled clinical trial to investigate the effectiveness of oral supplementation of DL-alpha-lipoic acid (ALA) on glycemic and oxidative status in DM patients was conducted. Thirty eight outpatients with type 2 DM were recruited and randomly assigned to either placebo or treatment in various doses of ALA (300, 600, 900, and 1200 mg/day) for 6 months. Following the treatment, all subjects were evaluated for glucose status and oxidative biomarkers. Results showed that fasting blood glucose, HbA1c trended to decrease in a dose-dependent manner. Increase of urinary PGF2α-Isoprostanes (F2α-IsoP) was noted in placebo but not ALA-treated groups, indicating possible suppressing action of ALA on lipid peroxidation in DM subjects. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) levels, however, were similar in both placebo and ALA groups as well as urinary microalbumin and serum creatinine. Safety evaluation was monitored and treatment was found to be well tolerated despite some minor side effects. Results from this study reflected the benefits of ALA in glucose status with slight efficiency on oxidative stress-related deterioration in DM patients.

Free radical scavenging properties of pyrimidine derivatives

Free radicals are well known for playing a dual role in our body- deleterious as well as beneficial. It includes a metabolic pathway for its generation. Oxidative stress in our body occurs due to excessive generation of free radicals and reduced level of antioxidants, but at low concentrations, these radicals help to perform normal physiological functions of the body. Scientific evidence suggests that antioxidants reduce the risk for chronic diseases including cancer and heart disease. This review shows current tendency in the pyrimidine synthesis and reveals the pyrimidine core to be a very potent moiety which can be a rich source for the synthesis of new compounds having desirable antioxidant activity.

Differences in Antioxidant/Protective Efficacy of Hydrated C60 Fullerene Nanostructures in Liver and Brain of Rats with Streptozotocin-Induced Diabetes

Background: Diabetes mellitus causes damage to many vital organs, including brain and liver, mostly due to excessive free radical generation and development of oxidative stress. Some water-soluble forms of C60 fullerene and their hydrated nanostructures are proposed for prevention as well as treatment of various pathological conditions caused by oxidative stress. Aim of the study: Assessment and comparison of antioxidant effects of hydrated C 60 fullerene (C 60 HyFn) in brain and liver of rats with experimental streptozotocin (STZ)-induced hyperglycemia and evaluation of possible neuroprotective capacity of C 60 HyFn acting as potent agent to suppress reactive astrocytosis. Materials and methods: To induce hyperglycemia, male Wistar rats received single intraperitoneal (i.p.) injection of STZ in a dose of 45 mg/kg body weight (b.w). Thirty five rats were divided into 5 groups (7 animals per group): Group I (control, saline-injected rats); Group II (STZ-diabetic rats); Group III (rats injected with C60HyFn in a dose of 0.3 mg/kg b.w–C 60 HyFn control); Group IV (rats received single i.p. injection of C 60 HyFn in the same dose one week prior to STZ injection – prophylactic regime); Group V (rats received single i.p. injection of C 60 HyFn in the same dose one week after development of stable hyperglycemia–therapeutic regime). The following parameters were assessed in the groups of control and experimental animals: blood glucose concentration, levels of end-products of lipid peroxidation (LPO) and carbonylated proteins as markers of protein oxidative modifications (POM) in liver and brain tissues. Levels of astrogliosis in various sections of rat brain were monitored as additional parameter of C 60 HyFn neuroprotection. Immunochemical and immunohystochemical determination of glial fibrillary acidic protein (GFAP) as sensitive marker of astrocyte response were applied to evaluate intensity of astrocyte reactivity. Results: STZ induced consistent hyperglycemia accompanied by extended oxidative damage of lipids and proteins in rats’ central nervous system (CNS) and liver. Beneficial effects of C 60 HyFn on oxidative status in liver of rats with hyperglycemia were observed in both regimes of administration. However, C 60 HyFn markedly reduced abnormally high levels of macromolecule oxidation in diabetic brain tissues only when used in therapeutic regime. In addition, diabetic rats were characterized by significant elevation of GFAP levels due to increase of astrocyte reactivity in brain cortex and hippocampus. C60HyFn treatment restored GFAP levels near to normal supposedly by lowering of astrogliosis caused by hyperglycemia. Though, C 60 HyFn, serving as high-performance antioxidant and alleviating harmful side-effects of diabetes such as oxidative stress, does not affect the blood glucose levels in diabetic rats and therefore not remove the prime cause of metabolic disturbance. Conclusion: Nanostructures of hydrated C60 fullerene have been shown to exert beneficial effects in brain and liver of rats with STZ-induced diabetes mainly through the diminution of oxidative stress and can be applied for prevention and treatment of diabetic complications such as liver injury and neuropathy.

The Role of Oxidative Stress in the Metabolic Syndrome

Loss of reduction-oxidation (redox) homeostasis and generation of excess free oxygen radicals play an important role in the pathogenesis of diabetes, hypertension, and consequent cardiovascular disease. Reactive oxygen species are integral in routine in physiologic mechanisms. However, loss of redox homeostasis contributes to proinflammatory and profibrotic pathways that promote impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. Redox control of metabolic function is a dynamic process with reversible pro- and anti-free radical processes. Labile iron is necessary for the catalysis of superoxide anion, hydrogen peroxide, and the generation of the damaging hydroxyl radical. Acute hypoxia and cellular damage in cardiovascular tissue liberate larger amounts of cytosolic and extracellular iron that is poorly liganded; thus, large increases in the generation of oxygen free radicals are possible, causing tissue damage. The understanding of iron and the imbalance of redox homeostasis within the vasculature is integral in hypertension and progression of metabolic dysregulation that contributes to insulin resistance, endothelial dysfunction, and cardiovascular and kidney disease.

The influence of reactive oxygen species on the central nervous system

Oxidative stress can be defined as a rise of oxidative potential or decrease of antioxidant status. Oxidative stress is caused by reactive oxygen species (ROS) which are produced by one-electron reduction of oxygen in the electron transport chain, as well as many other reactions. Effects of ROS can result in cellular membrane damage, structural and functional changes in enzymatic and non-enzymatic proteins, and damage to the DNA structure. Excessive generation of free radicals, decrease of enzymatic antioxidant activity, and/or reducing agents are considered as the main causes of oxidative stress. Since the brain contains a large amount of polyunsaturated fatty acids, consumes up to 20% of oxygen used by the whole body, and shows low antioxidant activity, it seems to be especially vulnerable to oxidative stress. Numerous data show the significant role of oxidative stress in pathogenesis of many neurodegenerative diseases.

S-Nitrosylation of Critical Protein Thiols Mediates Protein Misfolding and Mitochondrial Dysfunction in Neurodegenerative Diseases

Excessive nitrosative and oxidative stress is thought to trigger cellular signaling pathways leading to neurodegenerative conditions. Such redox dysregulation can result from many cellular events, including hyperactivation of the N-methyl-D-aspartate-type glutamate receptor, mitochondrial dysfunction, and cellular aging. Recently, we and our colleagues have shown that excessive generation of free radicals and related molecules, in particular nitric oxide species (NO), can trigger pathological production of misfolded proteins, abnormal mitochondrial dynamics (comprised of mitochondrial fission and fusion events), and apoptotic pathways in neuronal cells. Emerging evidence suggests that excessive NO production can contribute to these pathological processes, specifically by S-nitrosylation of specific target proteins. Here, we highlight examples of S-nitrosylated proteins that regulate misfolded protein accumulation and mitochondrial dynamics. For instance, in models of Parkinson's disease, these S-nitrosylation targets include parkin, a ubiquitin E3 ligase and neuroprotective molecule, and protein-disulfide isomerase, a chaperone enzyme for nascent protein folding. S-Nitrosylation of protein-disulfide isomerase may also be associated with mutant Cu/Zn superoxide dismutase toxicity in amyotrophic lateral sclerosis. Additionally, in models of Alzheimer's disease, excessive NO generation leads to the formation of S-nitrosylated dynamin-related protein 1 (forming SNO-Drp1), which contributes to abnormal mitochondrial fragmentation and resultant synaptic damage.

From Normal Cells to Malignancy: Distinct Role of Pro-inflammatory Factors and Cellular Redox Mechanisms

The genesis of many solid cancers is a complex, multistep process that includes cellular neoplastic transformation, resistance to apoptosis, loss of control of cell cycle, angiogenesis and acquisition of invasive properties. Among a number of factors, the simultaneous existence of chronic inflammatory mechanism and downregulation of antioxidant defense mechanism of cells are emerging major causes of neoplastic transformation and the progression of many solid cancers. The Longer the inflammation persists, higher the risk of developing many age related malignancies such as organs of colon, stomach and prostate etc. Concurrent occurrence of these processes that may affects DNA mutations in cells by excessive generation of free radicals, Reactive Oxygen Species (ROS) and other active intermediates that exceed the limit of the cells ability to neutralize it. Chronic inflammatory conditions may activate a variety of pro-tumorigenic activities, such as stimulation of proliferative pathway, chemotactic activity, increased invasive potential of cells and angiogenesis. However, many of the antioxidant or cellular redox molecules play a crucial role in maintaining cellular homeostasis and response to oxidative damage but down-regulation of some of the cellular molecules of this process may leads to malignant transformation. We provide an overview of the possible mechanism(s) of interaction of pro-inflammatory factors in down-regulating the antioxidant and cellular redox mechanism(s) making cells susceptible to carcinogenesis. The elucidation of specific effects and interactions of these factors may provide the opportunity for the identification of new target molecules at early stage of human malignancies.

Update on the use of melatonin in pediatrics

Melatonin, an endogenously produced indoleamine, is a highly effective antioxidant, free radical scavenger, and a primary circadian regulator. Melatonin has important antioxidant properties owing to direct and indirect effects. It directly scavenges reactive oxygen and reactive nitrogen species, prevents molecular oxidation, improves mitochondrial physiology, and restores glutathione homeostasis. Its indirect antioxidant effects stem from its ability to stimulate the activities of the enzymes involved in the glutathione cycling and production. Melatonin, by reducing free radical damage, may be an effective protective agent for the fetus as it is in adults. Several clinical studies on melatonin have shown that it reduces oxidative stress in human newborns with sepsis, hypoxic distress, or other conditions, where there is excessive free radical generation. A role of melatonin in infant development has also been suggested. Pineal dysfunction may be associated with deleterious outcomes in infants and may contribute to an increased prevalence of sudden infant death syndrome. Delayed melatonin production is evident in infants who had experienced an apparent life-threatening event. Melatonin has been used as a pharmacologic treatment for insomnias associated with shift work, jet lag, and delayed sleep onset in adults for decades. In children as well, melatonin has value as a sleep-promoting agent. Evidence suggests that melatonin has utility as an analgesic agent presumably related to its ability to release β-endorphin. The data support the notion that melatonin, or one of its analogs, might find use as an anesthetic agent in children.

Low Molecular Weight Compounds with Transition Metals as Free Radical Scavengers and Novel Therapeutic Agents

Molecules able to modulate the levels of endogenous free radicals, such as reactive oxygen species (ROS) and nitric oxide (NO), are of pivotal interest for pharmacological and pharmaceutical sciences because of their potential therapeutic relevance. In fact, ROS and NO, which are normal products of cell metabolism, may play a dual beneficial/deleterious role, depending on local concentration and mode of generation. As such, they have been identified as key pathogenic factors for many inflammatory, vascular dysfunctional and degenerative disorders, including atherosclerosis, hypertension, cardiovascular and neurodegenerative diseases, cancer, diabetes mellitus, and ageing. Therefore, the identification and characterization of novel antioxidant/free radical scavenger molecules may expand the current therapeutic implements for the treatment and prevention of the above diseases. In this perspective, low molecular weight complexes of transition metals with organic scaffolds are viewed and investigated as promising pharmaceutical agents. These complexes take advantage of the known principles of inorganic chemistry, i.e. the ability of transition metals, Fe(II), Co(II), Mn(II) and Ru(II), to bind to and react with NO and/or ROS, to counterbalance excessive endogenous free radical generation in biological systems. Among NO scavengers, representative examples are iron complexes with dithiocarbamates or ruthenium compounds with polyamine-polycarboxylate scaffolds; on the other hand, manganese-based molecules appear effective as ROS scavengers. Of note, Mn(II)-containing molecules, currently under study as ROS scavengers, have major functional similarities to Mn-superoxide dismutase (SOD), a Mn-containing enzyme acting as potent endogenous anti-oxidant. In this article, we briefly summarize the state-of-the-art concerning the chemical and biological properties of transition metal ion complexes with low molecular weight synthetic ligands as ROS/NO scavengers provided with therapeutic effectiveness in animal models of free radical-induced diseases. A proper design of the organic scaffolds may yield metal complexes which are stable in aqueous solution in a wide range of physical and chemical conditions, thus preventing release of the metal and the related toxicity. These metal-based compounds may be viewed as a novel class of drugs helpful to reduce vascular dysfunction and oxidative tissue injury due to derangements of the endogenous generation/catabolism of NO and ROS.

Pharmacologic effects on mitochondrial function

The vast majority of energy necessary for cellular function is produced in mitochondria. Free-radical production and apoptosis are other critical mitochondrial functions. The complex structure, electrochemical properties of the inner mitochondrial membrane (IMM), and genetic control from both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) are some of the unique features that explain why the mitochondria are vulnerable to environmental injury. Because of similarity to bacterial translational machinery, mtDNA translation is likewise vulnerable to inhibition by some antibiotics. The mechanism of mtDNA replication, which is required for normal mitochondrial maintenance and duplication, is inhibited by a relatively new class of drugs used to treat AIDS. The electrochemical gradient maintained by the IMM is vulnerable to many drugs that are weak organic acids at physiological pH, resulting in excessive free-radical generation and uncoupling of oxidative phosphorylation. Many of these drugs can cause clinical injury in otherwise healthy people, but there are also examples where particular gene mutations may predispose to increased drug toxicity. The spectrum of drug-induced mitochondrial dysfunction extends across many drug classes. It is hoped that preclinical pharmacogenetic and functional studies of mitochondrial toxicity, along with personalized genomic medicine, will improve both our understanding of mitochondrial drug toxicity and patient safety.

Mitochondrial medicine for neurodegenerative diseases

Mitochondrial dysfunction has been reported in a wide array of neurological disorders ranging from neuromuscular to neurodegenerative diseases. Recent studies on neurodegenerative diseases have revealed that mitochondrial pathology is generally found in inherited or sporadic neurodegenerative diseases and is believed to be involved in the pathophysiological process of these diseases. Commonly seen types of mitochondrial dysfunction in neurodegenerative diseases include excessive free radical generation, lowered ATP production, mitochondrial permeability transition, mitochondrial DNA lesions, perturbed mitochondrial dynamics and apoptosis. Mitochondrial medicine as an emerging therapeutic strategy targeted to mitochondrial dysfunction in neurodegenerative diseases has been proven to be of value, though this area of research is still at in its early stage. In this article, we report on recent progress in the development of several mitochondrial therapies including antioxidants, blockade of mitochondrial permeability transition, and mitochondrial gene therapy as evidence that mitochondrial medicine has promise in the treatment of neurodegenerative diseases.

New Horizons in Research on Diabetic Complications of the Eye: Special Emphasis on Diabetic Cataracts and Retinopathy

The incidence of diabetes is increasing at an alarming rate all over the world. As a consequence, the complications related to diabetes, including those affecting the eye (cataracts and retinopathy), nerve, and kidneys, are also becoming more prevalent. In the eye, diabetes affects both lens and retina resulting in devastating effects on vision. Although significant advances have been made towards understanding their pathophysiology using animal models of diabetes, progress in the area of development of pharmacological means for their prevention and treatment is still very minimal, if any. The pathogenetic mechanisms underlying both of these ocular complications of diabetes are considered multifactorial. The major factors considered to be involved in diabetic cataractogenesis are the hyperglycemia-induced excessive generation of free radicals and consequent oxidative stress as well as aberrations in tissue metabolism. Free radicals have also been implicated in the pathogenesis of diabetic retinopathy (DR). In addition, DR is considered to be associated with aberrations in several other cellular signaling pathways mediated via inflammatory intermediators, pigment epithelium-derived factor, various kinases, and Rho and Ras GTPases. Identification of pathways/molecules that can be targeted for modification by appropriate compounds is highly essential for the development of pharmacological therapy for these highly prevalent blinding diseases. In this special issue intended to present new research on diabetic cataracts and retinopathy, we have invited papers that address these issues. The first four articles in this issue are focused on cataract formation in diabetes. The first one provides an overview of the pathogenesis of diabetic cataracts, clinical studies investigating the association between diabetes and the development of cataract, and current treatment of cataracts in the diabetic population. The anticataractogenic potential of aldose reductase inhibitors and antioxidants has also been discussed. The article by Petrash et al. focuses on the role of aldo-ketoreductases in the eye. The expression profiles of the AKR1B1 and AKRB10 have been characterized in various human ocular tissues and their implications in the pathogenesis of diabetic cataract have been discussed. The next article examines the role of glyoxalase I in the inhibition of methylglyoxal advanced glycation end products-AGEs formation in lenses of transgenic mice overexpressing human glyoxalase I, and the fourth one reviews the pathophysiological characteristics of ocular complications in the Spontaneously Diabetic Torii rat such as the formation of cataracts which can become hypermature. It also suggests the suitability of this model for the study of DR. Subsequent articles in this issue focus on the pathogenesis of DR and examine possible targets for pharmacological intervention. The article by Daniel Ng reviews the genetic aspects of DR, and the next article identifies genes associated with DR among Mexican Americans from Starr County in Texas using genome-wide association study. The seventh paper examines the possibility of treatment with the angiotensin-converting enzyme inhibitor, trandolapril, for regression of DR, and the 8th paper discusses the role of toxic AGEs receptor in the pathogenesis of DR. This is followed by a review implicating Rho/ROCK (Rho Kinase) pathway in DR and suggests the possibility of this pathway being a target for therapeutic intervention. The article by Wu et al. investigates the role of extracellular signal-regulated kinase 5 (ERK5) mediated signaling in modulating glucose-induced expression of VEGF. The final paper in this issue compares NADPH oxidase versus mitochondria-derived reactive oxygen species in glucose-induced apoptosis of pericytes in early DR. This special issue will therefore provide the readers an insight into some of the latest research being pursued to elucidate the mechanisms underlying DR and cataracts. It also presents some interesting targets which could be manipulated pharmacologically for potential clinical use. Kavita R. Hegde Renu A. Kowluru Susanne Mohr Ram H. Nagaraj J. Mark Petrash

Detection and Identification of Free Radicals Generated by UV and Visible Light in Ex Vivo Human Skin

Citation: IFSCC Magazine, 11 (2008) (3) 207–215Contrary to the skin biological end points used for determination of the sun protection factor and UVA protection factor, generation of excess free radicals in skin – mainly reactive oxygen species – is potentially the source of much skin damage and so represents a more general biophysical answer to the effects of sun exposure of different wavelengths. By applying electron spin resonance spectroscopy to human skin biopsies, we determined in previous work a free radical action spectrum covering the ultraviolet and visible light range. Convolution of the action spectrum with sunlight spectral irradiance (280–700nm) showed the importance of visible light in free radical generation. This unexpected finding led us to perform further investigations. Firstly, an existing sun simulator was modified so that its output truly mimics the sun's full spectrum, including visible light. Human skin biopsies were irradiated either by this device or a conventional UV source, confirming our previous calculations: half of the free radicals are generated in the 400–700nm visible wavelength range. Secondly, the visible spectrum of the modified sun simulator was divided into narrow‐band lights using different pairs of short‐ and long‐pass filters. Human skin biopsies impregnated with specific spin traps were exposed to the different narrow‐band lights to identify different types of free radicals. Generation of dangerous radical species like •O2‐, •OH and •CH‐R was observed in different parts of the visible range, confirming the relevance of the free radical action spectrum and its ability to predict skin protection.Keywords: UV + VIS solar simulator, ex vivo human skin, free radicals, action spectrum, Electron Spin Resonance

Different adaptation patterns of antioxidant system in natives and sojourners at high altitude

Comparative studies on the adaptation pattern of antioxidant status among high altitude natives and acclimatized sojourners are very scanty. The aim of the present study was to compare the differences in antioxidant profile between two groups of active male volunteers, i.e. native highlanders (HAN, n=66) in their natural hypoxic environment with that of sojourners (SOJ, n=81) from sea level (SL) after 4 weeks of stay at an altitude of 4560m. Blood samples of SOJ were collected at SL and HA. Same was collected from HAN once at HA. HAN had significantly higher SOD activity and significantly lower catalase, GPX and GR activities than SOJ at HA. Ratio of GSH/GSSG was also significantly higher in HAN than SOJ at HA. In SOJ, antioxidant profile showed an upregulation after HA stay but it was not effective to reduce the levels of oxidative stress markers. Therefore, it can be stated that lifelong exposure to hypoxia has beneficial adaptive effects on antioxidant system in HAN. Similarly, acclimatization to HA also has beneficial preconditioning effects on antioxidant system in SOJ, but, may not be sufficient to ameliorate oxidative stress completely. Transient increase in metabolic rate due to hypoxia may be a causative factor for excess free radical generation among sojourners at HA.

Effects of Hyaluronic Acid on Mitochondrial Function and Mitochondria-driven Apoptosis following Oxidative Stress in Human Chondrocytes

Hyaluronic acid is widely used in the treatment of osteoarthritis and exerts significant chondroprotective effects. The exact mechanisms of its chondroprotective action are not yet fully elucidated. Human articular chondrocytes actively produce reactive oxygen and nitrogen species capable of causing cellular dysfunction and death. A growing body of evidence indicates that mitochondrial dysfunction and mitochondrial DNA damage play a causal role in disorders linked to excessive generation of oxygen free radicals. We hypothesized that the chondroprotective effects of hyaluronic acid on oxidatively stressed chondrocytes are due to preservation of mitochondrial function and amelioration of mitochondria-driven apoptosis. When primary human chondrocyte cultures were exposed to reactive oxygen or nitrogen species generators, mitochondrial DNA damage along with mitochondrial dysfunction and mitochondria-driven apoptosis accumulated as a consequence. In addition, cytokine-treated primary human chondrocytes showed increased levels of mitochondrial DNA damage. Pretreatment of chondrocytes with hyaluronic acid caused a decrease of mitochondrial DNA damage, enhanced mitochondrial DNA repair capacity and cell viability, preservation of ATP levels, and amelioration of apoptosis. The results of these studies demonstrate that enhanced chondrocyte survival and improved mitochondrial function under conditions of oxidative injury are probably important therapeutic mechanisms for the actions of hyaluronic acid in osteoarthritis.

Effects of PARP-inhibitor (HO3089) and SOD-mimetic (H2545) in bilateral common carotid artery occlusion induced retinal degeneration

Event Abstract Back to Event Effects of PARP-inhibitor (HO3089) and SOD-mimetic (H2545) in bilateral common carotid artery occlusion induced retinal degeneration Krisztina Szabadfi1*, Tamas Atlasz1, Dóra Reglődi2, Peter Kiss2, Laszlo Mester3, Robert Gabriel1, Balazs Sumegi3, Marius Opsahl2, Narve Braaten2, Aliz Szabo3, Ferenc Gallyas3 and Krisztina J. Kovacs3 1 Department of Experimental Zoology and Neurobiology, University of Pecs, Hungary 2 Department of Anatomy, Medical School, University of Pecs, Hungary 3 Department of Biochemistry and Medical Chemistry, University of Pecs, Hungary Poly (ADP-ribose) polymerase (PARP) activation plays a role in the pathogenesis of various cardiovascular, inflammatory and neurological diseases. Pharmacological inhibitors of PARP attenuate ischemic and inflammatory injury and reduce brain damage in various stroke models. Excessive generation of free radicals and decreased levels of the antioxidant enzymes such as superoxide dismutase (SOD) and catalase have been observed after brain ischemia/reperfusion injury. SOD has been shown to play a protective role in many pathological states: inflammatory diseases, ischemia/reperfusion, neurodegenerative disorders and cancer. In the present study, we investigated the neuroprotective potential of HO3089 (PARP-inhibitor) and H2545 (SOD-mimetic) in BCCAO-induced retinal degeneration. Two-month-old rats were subjected to BCCAO and their retinas were processed for histology after 3 weeks survival. We measured the number of the cells /100 µm in the ganglionic cell layer, and the thickness of outer nuclear-, outer plexiform-, inner nuclear-, and inner plexiform layers. Outer limiting membrane-inner limiting membrane distances were also examined. BCCAO resulted in severely reduced thickness of retinal layers three weeks after ligation. Neuroprotective effects of HO3089 were observed in ischemic retinal degeneration. Intraocular HO3089 treatment led to a nearly intact appearance of the retinal layers. In contrast, administration of a single dose of H2545 produced no significant neuroprotection in BCCAO-model. Our results may have clinical implications in reducing ischemic retinal degeneration in ophthalmic diseases. Support:OTKA:K72592;F67830;78480;T061766;Richter Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Pathophysiology and neurology - degenerative disorders Citation: Szabadfi K, Atlasz T, Reglődi D, Kiss P, Mester L, Gabriel R, Sumegi B, Opsahl M, Braaten N, Szabo A, Gallyas F and Kovacs KJ (2009). Effects of PARP-inhibitor (HO3089) and SOD-mimetic (H2545) in bilateral common carotid artery occlusion induced retinal degeneration. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.174 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Mar 2009; Published Online: 05 Mar 2009. * Correspondence: Krisztina Szabadfi, Department of Experimental Zoology and Neurobiology, University of Pecs, Pecs, Hungary, kriszta.szabadfi@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Krisztina Szabadfi Tamas Atlasz Dóra Reglődi Peter Kiss Laszlo Mester Robert Gabriel Balazs Sumegi Marius Opsahl Narve Braaten Aliz Szabo Ferenc Gallyas Krisztina J Kovacs Google Krisztina Szabadfi Tamas Atlasz Dóra Reglődi Peter Kiss Laszlo Mester Robert Gabriel Balazs Sumegi Marius Opsahl Narve Braaten Aliz Szabo Ferenc Gallyas Krisztina J Kovacs Google Scholar Krisztina Szabadfi Tamas Atlasz Dóra Reglődi Peter Kiss Laszlo Mester Robert Gabriel Balazs Sumegi Marius Opsahl Narve Braaten Aliz Szabo Ferenc Gallyas Krisztina J Kovacs PubMed Krisztina Szabadfi Tamas Atlasz Dóra Reglődi Peter Kiss Laszlo Mester Robert Gabriel Balazs Sumegi Marius Opsahl Narve Braaten Aliz Szabo Ferenc Gallyas Krisztina J Kovacs Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Diminished mitochondrial DNA integrity and repair capacity in OA chondrocytes

Osteoarthritis (OA) is characterized by the failure of chondrocytes to respond to injury and perform the cartilage remodeling process. Human articular chondrocytes actively produce reactive oxygen and nitrogen species (ROS and RNS) capable of causing cellular dysfunction and death. A growing body of evidence indicates that mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage play a causal role in disorders linked to excessive generation of oxygen free radicals. The aim of this study was to determine whether mtDNA damage was present in OA chondrocytes, and whether mtDNA repair capacity is compromised in OA chondrocytes following oxidative stress, leading to chondrocyte death. Human articular cartilage was isolated from knee joints of cadavers available through the Anatomical Gifts Program at the University of South Alabama (normal donors) or OA patients undergoing total knee replacement surgeries (OA patients). Total DNA was isolated from either chondrocytes released following collagenase digestion, or from first passage chondrocytes grown in culture and exposed to ROS or RNS. mtDNA integrity and repair capacity were analyzed by quantitative Southern blot analysis, using a mtDNA-specific radioactive probe. Cell viability was determined by the trypan blue exclusion method. mtDNA damage was found in chondrocytes from OA patients compared to normal donors. It was accompanied with reduced mtDNA repair capacity, cell viability, and increased apoptosis in OA chondrocytes following exposure to ROS and RNS. These results indicate that mtDNA damage and poor mtDNA repair capacity for removing damage caused by oxidative stress may contribute to the pathogenesis of OA.

Antioxidant and pro-oxidant properties of boldine on hippocampal slices exposed to oxygen–glucose deprivation in vitro

Boldine is one of the most potent natural antioxidants and displays some important pharmacological activities, such as cytoprotective and anti-inflammatory activities, which may arise from its free radical scavenging properties. Given that the pathogenesis of brain ischemia/reperfusion has been associated with an excessive generation of oxygen free radicals, the aim of this study was to evaluate the neuroproperties of boldine using hippocampal slices from Wistar rats exposed to oxygen and glucose deprivation (OGD), followed by reoxygenation, to mimic an ischemic condition. The OGD ischemic condition significantly impaired cellular viability, increased lactate dehydrogenase (LDH) leakage and increased free radical generation. In non-OGD slices, incubation with 100 μM boldine significantly increased LDH released into incubation media and decreased mitochondrial activity, suggesting an increase of tissue damage caused by boldine. However, slices incubated with 10 μM boldine during and after OGD exposure had significantly increased cellular viability with no effect on cell damage. Total reactive antioxidant potential (TRAP) levels measured for this alkaloid showed an antioxidant potential three times higher than Trolox, which acts as a peroxyl radical scavenger. Moreover, boldine prevented the increase in lipoperoxidation levels induced by ischemia, but higher concentrations potentiated this parameter. These results confirm the potent antioxidant properties of this alkaloid, and add evidence to support the need for further investigations in order to confirm the potential pro-oxidant effects of boldine at higher doses.