Oxidative Damage In Neuronal Cells Research Articles

Mechanisms of ozone-induced neurotoxicity in the development and progression of dementia: a brief review

Dementia encompasses a spectrum of neurodegenerative disorders significantly impacting global health, with environmental factors increasingly recognized as crucial in their etiology. Among these, ozone, has been identified as a potential exacerbator of neurodegenerative processes, particularly in Alzheimer’s disease (AD). Ozone exposure induces the production of reactive oxygen species (ROS), which penetrate the BBB, leading to oxidative damage in neuronal cells. This oxidative stress is closely linked with mitochondrial dysfunction and lipid peroxidation, processes that are foundational to the pathology observed in dementia, such as neuronal death and protein aggregation. Furthermore, ozone triggers chronic neuroinflammation, exacerbating these neurodegenerative processes and perpetuating a cycle of CNS damage. Recent studies highlight the role of peripheral biomarkers like High Mobility Group Box 1 (HMGB1) and Triggering Receptor Expressed on Myeloid cells 2 (TREM2) in mediating ozone’s effects. Disruption of these and other identified proteins by ozone exposure impairs microglial function and response to amyloid plaques, suggesting a novel pathway through which ozone may influence AD pathology via immune dysregulation. This review discusses the concept of a bidirectional lung-brain axis, illustrating that systemic responses to air pollutants like ozone may reflect and contribute to neurodegenerative processes in the CNS. By delineating these mechanisms, we emphasize the critical need for integrating environmental health management into strategies for the prevention and treatment of dementia.

High‐salt diet enhances Helicobacter pylori infection and increases the prevalence of Alzheimer’s disease

AbstractBackgroundThe American Heart Association recommends that adults consume less than 2,300 milligrams of salt (sodium chloride) daily; anything surpassing this limit is classified as a “high‐salt diet (HSD)” [1]. Research has shown that excessive salt intake stimulates the gastric mucosa, favoring Helicobacter pylori (Hp) colonization [2]. In this review, the relationship between HSD and the susceptibility to Hp infection will be discussed. It is proposed that increased salt consumption will cause neurodegeneration, i.e. Alzheimer’s disease (AD) by way of increased expression of Hp strains in the gastric mucosa.MethodsA complex and specific literature search was conducted across various scientific, international databases for English, peer‐reviewed articles and reviews published in the last decade using the following terms: Helicobacter pylori, amyloid‐β, high‐salt diet, and Alzheimer’s disease. Case reports were excluded. The main objectives were predominantly focused on animal‐based studies.ResultsExperimental data shows HSD enhances Hp growth in mice. The subsequent microglial activation containing H. pylori‐specific IgG, IL‐8 and TNF‐α in the cerebrospinal fluid, induces oxidative damage in neuronal cells. In addition, urease in Hp increases cytosolic [Ca2+] apoptosis and autophagy of neurons. Hp filtrate induces tau hyperphosphorylation at AD‐tau phosphorylation sites such as Thr231 and Ser404. Hp ‐infected mice show a significantly larger GFAP‐positive astrocyte area than non‐infected mice. Immunostaining reveals microglia and astrocytes to be found adjacent to amyloid‐β plaques in Hp‐infected AD model mice. Injection of Hp filtrate impairs the maturation of dendritic spines, increasing Aβ42 production in the hippocampus and cortex, and enhancing expression of PS‐2, resulting in delayed spatial learning and impaired memory in rats.ConclusionThis review provides comprehensive evidence of potential synergistic effects of HSD and Hp on the brain resulting in neurodegeneration and AD progression. Understanding the pathologic consequences of salt consumption on this infection may be key in the prevention of dementia and AD. Thus, further research is required for substantiation of causality, the role of antibiotics and to examine other novel therapeutics.

Protective Effects of Jujubosides on 6-OHDA-Induced Neurotoxicity in SH-SY5Y and SK-N-SH Cells.

6-hydroxydopamine (6-OHDA) is used to induce oxidative damage in neuronal cells, which can serve as an experimental model of Parkinson’s disease (PD). Jujuboside A and B confer free radical scavenging effects but have never been examined for their neuroprotective effects, especially in PD; therefore, in this study, we aimed to investigate the feasibility of jujubosides as protectors of neurons against 6-OHDA and the underlying mechanisms. 6-OHDA-induced neurotoxicity in the human neuronal cell lines SH-SY5Y and SK-N-SH, was used to evaluate the protective effects of jujubosides. These findings indicated that jujuboside A and B were both capable of rescuing the 6-OHDA-induced loss of cell viability, activation of apoptosis, elevation of reactive oxygen species, and downregulation of the expression levels of superoxide dismutase, catalase, and glutathione peroxidase. In addition, jujuboside A and B can reverse a 6-OHDA-elevated Bax/Bcl-2 ratio, downregulate phosphorylated PI3K and AKT, and activate caspase-3, -7, and -9. These findings showed that jujubosides were capable of protecting both SH-SY5Y and SK-N-SH neuronal cells from 6-OHDA-induced toxicity via the rebalancing of the redox system, together with the resetting of the PI3K/AKT apoptotic signaling cascade. In conclusion, jujuboside may be a potential drug for PD prevention.

Lycopene protects neuroblastoma cells against oxidative damage via depression of ER stress.

Lycopene is a pigment derived from tomatoes and other red fruits, and has potent antioxidant and antitumor effects. However, its potential role in alleviating oxidative damage in neuronal cells is not well defined. In this study, we investigated the effects of lycopene on H2 O2 -induced damage in neuroblastoma cells, as well as the underlying mechanisms. Exposure to H2 O2 markedly decreased the viability of SH-SY5Y cells and increased LDH release, both of which were reversed by lycopene pretreatment. Lycopene also ameliorated H2 O2 -induced damage and reduced the expression of apoptotic markers, such as Bcl-2, Bax, and cleaved caspase 3. In addition, the H2 O2 -induced oxidative markers, including MDA, 8-OHdG, and protein carbonyls, were also downregulated by lycopene. Exogenous H2 O2 activated the GRP78/PERK/eIF2α signaling pathway, which was inhibited by pretreatment with lycopene. Finally, lycopene significantly ameliorated ER stress-induced activation and nuclear translocation of CHOP. Overexpression of CHOP markedly reversed the antiapoptotic effects of lycopene, indicating that it is essential for the latter's protective effects. Taken together, lycopene protects neuroblastoma cells from oxidative stress and ER stress-induced damage by inhibiting the PERK-CHOP signaling pathway, which is a potential therapeutic target in neurodegenerative diseases. PRACTICAL APPLICATION: Lycopene demonstrated antioxidative damage properties in protecting the neural system in vitro. The present study provides a novel preventive strategy against neurodegenerative diseases. Increased consumption of lycopene-based products and lycopene-rich fruits and vegetables may result in a lower risk for neurodegenerative diseases.

Neuroprotective Effects of Ocimum basilicum Extract against Hydrogen Peroxide-Induced Oxidative Stress in SK-N-SH Neuroblastoma Cells

Neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease are characterized by the progressive loss of neurons. One of the contributing factors for these diseases is oxidative stress, characterized by the imbalance of free radicals production and antioxidant defense mechanisms. In the present study, the neuroprotective effects of Ocimum basilicum var. thyrsiflora against hydrogen peroxide (H2O2)-induced oxidative stress in SK-N-SH neuroblastoma cells were evaluated. The exposure of SK-N-SH cells to 50 μM H2O2 for 24 h induced cytotoxicity and apoptosis as measured by cell viability and flow cytometry, respectively. Pretreatment with ethyl acetate (ObEA) fraction at 3.1-25 μg/mL showed the highest protection against H2O2-induced cell death compared to other fractions and crude extract by increasing cell viability and reducing apoptosis. The evaluation of antioxidant capacity via 1, 1-diphenyl-2-picrylahydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays showed ObEA possessed the highest antioxidative properties. The intracellular reactive oxygen species (ROS) production of H2O2 in untreated cells increased by 2.39-fold compared to the control and was significantly attenuated by the 2 h pre-treatment of O. basilicum (p<0.05). The reduction in intracellular superoxide dismutase (SOD) induced by H2O2 was also abrogated by the pretreatment of O. basilicum. These findings suggested that O. basilicum is potentially neuroprotective against oxidative damage in neuronal cells by scavenging free radicals, restoring SOD activities and eventually prevent cell death.

Neurovascular Unit Protection From Cerebral Ischemia-Reperfusion Injury by Radical-Containing Nanoparticles in Mice.

Reperfusion therapy by mechanical thrombectomy is used to treat acute ischemic stroke. However, reactive oxygen species generation after reperfusion therapy causes cerebral ischemia-reperfusion injury, which aggravates cerebral infarction. There is limited evidence for clinical efficacy in stroke for antioxidants. Here, we developed a novel core-shell type nanoparticle containing 4-amino-4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (nitroxide radical-containing nanoparticles [RNPs]) and investigated its ability to scavenge reactive oxygen species and confer neuroprotection. C57BL/6J mice underwent transient middle cerebral artery occlusion and then received RNPs (9 mg/kg) through the common carotid artery. Infarction size, neurological scale, and blood-brain barrier damage were visualized by Evans blue extravasation 24 hours after reperfusion. RNP distribution was detected by rhodamine labeling. Blood-brain barrier damage, neuronal apoptosis, and oxidative neuronal cell damage were evaluated in ischemic brains. Multiple free radical-scavenging capacities were analyzed by an electron paramagnetic resonance-based method. RNPs were detected in endothelial cells and around neuronal cells in the ischemic lesion. Infarction size, neurological scale, and Evans blue extravasation were significantly lower after RNP treatment. RNP treatment preserved the endothelium and endothelial tight junctions in the ischemic brain; neuronal apoptosis, O2- production, and gene oxidation were significantly suppressed. Reactive oxygen species scavenging capacities against OH, ROO, and O2- improved by RNP treatment. An intra-arterial RNP injection after cerebral ischemia-reperfusion injury reduced blood-brain barrier damage and infarction volume by improving multiple reactive oxygen species scavenging capacities. Therefore, RNPs can provide neurovascular unit protection.

The anti-ageing hormone klotho induces Nrf2-mediated antioxidant defences in human aortic smooth muscle cells.

Vascular ageing in conditions such as atherosclerosis, diabetes and chronic kidney disease, is associated with the activation of the renin angiotensin system (RAS) and diminished expression of antioxidant defences mediated by the transcription factor nuclear factor erythroid 2‐related factor 2 (Nrf2). The anti‐ageing hormone klotho promotes longevity and protects against cardiovascular and renal diseases. Klotho has been shown to activate Nrf2 and attenuate oxidative damage in neuronal cells, however, the mechanisms by which it protects against vascular smooth muscle cell VSMC dysfunction elicited by Angiotensin II (AngII) remain to be elucidated. AngII contributes to vascular ageing and atherogenesis by enhancing VSMC oxidative stress, senescence and apoptosis. This study demonstrates that soluble klotho (1 nM, 24 hrs) significantly induces expression of Nrf2 and the antioxidant enzymes haeme oxygenase (HO‐1) and peroxiredoxin‐1 (Prx‐1) and enhances glutathione levels in human aortic smooth muscle cells (HASMC). Silencing of Nrf2 attenuated the induction of HO‐1 and Prx‐1 expression by soluble klotho. Furthermore, soluble klotho protected against AngII‐mediated HASMC apoptosis and senescence via activation of Nrf2. Thus, our findings highlight a novel Nrf2‐mediated mechanism underlying the protective actions of soluble klotho in HAMSC. Targeting klotho may thus represent a therapeutic strategy against VSMC dysfunction and cardiovascular ageing.

The Neuro-Protective Effect of the Methanolic Extract of Perilla frutescens var. japonica and Rosmarinic Acid against H2O2-Induced Oxidative Stress in C6 Glial Cells

Neurodegenerative diseases are often associated with oxidative damage in neuronal cells. This study was conducted to investigate the neuro-protective effect of methanolic (MeOH) extract of Perilla frutescens var. japonica and its one of the major compounds, rosmarinic acid, under oxidative stress induced by hydrogen peroxide (H2O2) in C6 glial cells. Exposure of C6 glial cells to H2O2 enhanced oxidative damage as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and thiobarbituric acid-reactive substance assays. The MeOH extract and rosmarinic acid prevented oxidative stress by increasing cell viability and inhibiting cellular lipid peroxidation. In addition, the MeOH extract and rosmarinic acid reduced H2O2-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the transcriptional level. Moreover, iNOS and COX-2 protein expression was down-regulated in H2O2-indcued C6 glial cells treated with the MeOH extract and rosmarinic acid. These findings suggest that P. frutescens var. japonica and rosmarinic acid could prevent the progression of neurodegenerative diseases through attenuation of neuronal oxidative stress.

치콘 추출물의 항산화 활성

본 연구는 치콘 추출물의 항산화 효능을 확인하고자 물과 에탄올로 추출하였다. 치콘에 포함된 총 폴리페놀 함량을 측정한 결과, 에탄올 추출물(37.3±5.2 ㎎/GAE/g extract)과 열수 추출물(36.3±1.0 ㎎/GAE/g extract)이 유사한 총 폴리페놀 함량을 포함하고 있었으며, 총 플라보노이드 함량은 물 추출물이 47.0±3.8 ㎎ CE/g extract 그리고 에탄올 추출물이 53.9±5.1 ㎎ CE/g extract를 나타내었다. ABTS를 이용한 라디칼 소거활성, FRAP를 이용한 환원력을 통한 항산화 활성을 측정한 결과에서도 치콘 추출물이 항산화 효과를 나타내었다. 한편, 세포 독성을 살펴보기 위하여 신경세포를 이용하여 MTT assay를 수행한 결과, 세포의 생존율은 1.0 ㎎/㎖의 농도 이상에서는 생존에 영향을 미치지 않았고 신경세포 보호효능 실험에서는 2.5 mM의 H<SUB>2</SUB>O<SUB>2</SUB>로 유발시킨 산화적 손상에 대해 농도 의존적인 신경세포 보호 효과가 있었으며, 항산화 효소 활성을 SOD와 CAT로 분석한 결과 SOD는 0.5 mg/mL 농도에서 95% 이상의 활성과 CAT는 손상그룹에 비해 2배 이상의 활성을 각각 확인하였다. 또한 치콘 추출물이 세포사와 관련이 있는 단백질인 Bax와 Bcl-2의 발현을 조절하는 것을 확인하였다. 이와 같은 결과는 치콘 추출물이 산화적 손상의 억제를 통해 세포를 보호하는 효과가 있는 것으로 사료된다.

Protein kinase D1 (PKD1) activation mediates a compensatory protective response during early stages of oxidative stress-induced neuronal degeneration

BackgroundOxidative stress is a key pathophysiological mechanism contributing to degenerative processes in many neurodegenerative diseases and therefore, unraveling molecular mechanisms underlying various stages of oxidative neuronal damage is critical to better understanding the diseases and developing new treatment modalities. We previously showed that protein kinase C delta (PKCδ) proteolytic activation during the late stages of oxidative stress is a key proapoptotic signaling mechanism that contributes to oxidative damage in Parkinson's disease (PD) models. The time course studies revealed that PKCδ activation precedes apoptotic cell death and that cells resisted early insults of oxidative damage, suggesting that some intrinsic compensatory response protects neurons from early oxidative insult. Therefore, the purpose of the present study was to characterize protective signaling pathways in dopaminergic neurons during early stages of oxidative stress.ResultsHerein, we identify that protein kinase D1 (PKD1) functions as a key anti-apoptotic kinase to protect neuronal cells against early stages of oxidative stress. Exposure of dopaminergic neuronal cells to H2O2 or 6-OHDA induced PKD1 activation loop (PKD1S744/748) phosphorylation long before induction of neuronal cell death. Blockade of PKCδ cleavage, PKCδ knockdown or overexpression of a cleavage-resistant PKCδ mutant effectively attenuated PKD1 activation, indicating that PKCδ proteolytic activation regulates PKD1 phosphorylation. Furthermore, the PKCδ catalytic fragment, but not the regulatory fragment, increased PKD1 activation, confirming PKCδ activity modulates PKD1 activation. We also identified that phosphorylation of S916 at the C-terminal is a preceding event required for PKD1 activation loop phosphorylation. Importantly, negative modulation of PKD1 by the RNAi knockdown or overexpression of PKD1S916A phospho-defective mutants augmented oxidative stress-induced apoptosis, while positive modulation of PKD1 by the overexpression of full length PKD1 or constitutively active PKD1 plasmids attenuated oxidative stress-induced apoptosis, suggesting an anti-apoptotic role for PKD1 during oxidative neuronal injury.ConclusionCollectively, our results demonstrate that PKCδ-dependent activation of PKD1 represents a novel intrinsic protective response in counteracting early stage oxidative damage in neuronal cells. Our results suggest that positive modulation of the PKD1-mediated compensatory protective mechanism against oxidative damage in dopaminergic neurons may provide novel neuroprotective strategies for treatment of PD.

Nanoparticulated Quercetin in Combating Age Related Cerebral Oxidative Injury

Reactive oxygen species e.g. O(2)(*-), H(2)O(2) and *OH generated by the induction of oxidative stress exert a potential threat on the activity of endogenous antioxidant enzymes and substantially influence the aging process and age-dependant neuropathology. Chemical antioxidant is almost ineffective in protecting neuronal cells from oxidative damage as Blood Brain Barrier exists in between blood and brain interstitial fluid that restricts undegradable influx from the circulation into cerebral region. Quercetin (QC), a flavonoidal antioxidant is known as a potent antioxidant for its polyphenolic configuration. Formulation of QC in polylactide nanocapsule has been done and the efficacy of this vesicular flavonoid has been tested against cerebral ischemia induced oxidative damage in young and old rat brains. Antioxidant potential of QC loaded in nanocapsule (QC 7.2 mmol/kg b.wt., size 50 nm) was investigated by an in vivo model of cerebral ischemia and reperfusion on Sprague Dawley young (2 months, b.wt. 160-180 g) and aged (20 months, b.wt. 415-440 g) rats. Diene level, the index of lipid peroxidation and GSSG/GSH ratio were found to be higher in normal aged, compared to normal young rat brain. Endogenous antioxidants activities were lower in aged rat brain compared to young. Further reduction of these antioxidants were observed in aged rat brain by the induction of cerebral ischemia - reperfusion. Nanocapsule encapsulated QC treatment resulted a significant protection to endogenous antioxidant enzymes against ischemia induced oxidative damage in neuronal cells of young and old rats.

Molecular implications of the human glutathione transferase A-4 gene ( hGSTA4) polymorphisms in neurodegenerative diseases

Several lines of evidence, including an increased level of lipid peroxidation and the depletion of antioxidant molecules like as glutathione (GSH), indicate that oxidative stress plays an important role in the pathogenesis of several neurodegenerative disorders, such as Parkinson's disease (PD) and Alzheimer's disease (AD). We previously observed a significant increased level of DNA oxidative damage in peripheral blood cells of PD patients, with respect to controls, moreover, the activity of glutathione transferases (GSTs) measured in circulating plasma was higher in controls than in PD patients, suggesting a lower enzymatic protection in PD individuals. Among human GSTs, glutathione transferase A4-4 displays a high catalitic activity towards 4-hydroxy-2-nonenal (HNE), a marker of lipid peroxidation whose levels have been found significantly increased in the substantia nigra of Parkinson's disease patients, in respect to controls. We performed this study to determine the presence of allelic variants of functional interest in the coding region of the hGSTA4 gene on 60 PD patients and 60 healthy controls. By the combined effort of polymerase chain reaction/single-strand conformation polymorphisms (PCR/SSCP) techniques, we observed a single nucleotide polymorphism (SNP) G351A leading to the silent mutation Gln117Gln. No significant difference was observed in the distribution of this polymorphism between PD individuals and controls, moreover, we did not observe any other polymorphism in the hGSTA4 gene in our population. Further studies are required to test the role played by both factors regulating the level of the expression of the hGSTA4 gene and any possible post-translational modification of the protein, in the protection against oxidative damage in neuronal cells.

Protective effects of fangchinoline and tetrandrine on hydrogen peroxide-induced oxidative neuronal cell damage in cultured rat cerebellar granule cells.

The present study was performed to examine the neuroprotective effects of fangchinoline (FAN) and tetrandrine (TET), bis-benzylisoquinoline alkaloids, which exhibit the characteristics of Ca 2+ channel blockers, on H2O2 -induced neurotoxicity using cultured rat cerebellar granule neurons. H2O2 produced a concentration-dependent reduction of cell viability, which was blocked by (5 R,10 S)-(+)-5-methyl-10,11-dihydro-5 H-dibenzo[ a,d]cyclohepten-5,10-imine (MK-801), an N-methyl- D-aspartate (NMDA) receptor antagonist, verapamil, an L-type Ca 2+ channel blocker, and NG-nitro- L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Pretreatment with FAN and TET over a concentration range of 0.1 to 10 microM significantly decreased the H2O2 -induced neuronal cell death as assessed by a trypan blue exclusion test, a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay and the number of apoptotic nuclei. In addition, FAN and TET inhibited the H2O2 -induced elevation of glutamate release into the medium, elevation of the cytosolic free Ca 2+ concentration ([Ca 2+] c ), and generation of reactive oxygen species (ROS). These results suggest that FAN and TET may mitigate the harmful effects of H2O2 -induced neuronal cell death by interfering with the increase of [Ca 2+] c, and then by inhibiting glutamate release and generation of ROS. Abbreviations. AP5:D(-)-2-amino-5-phosphonopentanoic acid DMSO:dimethyl sulfoxide FAN:fangchinoline H 2 DCF-DA:2',7'-dichlorodihydrofluorescin diacetate MK-801:(5 R,10 S)-(+)-5-methyl-10,11-dihydro-5 H-dibenzo[ a,d]cyclohepten-5,20-imine MTT:3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide L-NAME: NG-Nitro- L-arginine methyl ester NMDA: N-methyl- D-aspartate TET:tetrandrine

Scavenging of reactive oxygen species and prevention of oxidative neuronal cell damage by a novel gallotannin, Pistafolia A

Pistafolia A is a novel gallotannin isolated from the leaf extract of Pistacia weinmannifolia. In the present investigation, the ability of Pistafolia A to scavenge reactive oxygen species including hydroxyl radicals and superoxide anion was measured by ESR spin trapping technique. The inhibition effect on iron-induced lipid peroxidaiton in liposomes was studied. The protective effects of Pistafolia A against oxidative neuronal cell damage and apoptosis induced by peroxynitrite were also assessed. The results showed that Pistafolia A could scavenge both hydroxyl radicals and superoxide anion dose-dependently and inhibit lipid peroxidation effectively. In cerebellar granule cells pretreated with Pistafolia A, peroxynitrite-induced oxidative neuronal damage and apoptosis were prevented markedly. The antioxidant capacity of Pistafolia A was much more potent then that of the water-soluble analog of vitamin E, Trolox. The results suggested that Pistafolia A might be used as an effective natural antioxidant for the prevention and cure of neuronal diseases associated with the production of peroxynitrite and related reactive oxygen species.

Attenuation of oxidative DNA damage with a novel antioxidant EPC-K1 in rat brain neuronal cells after transient middle cerebral artery occlusion

EPC-K1, L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl-hydrogen phosphate] potassium salt, is a novel antioxidant. In this study, we investigated a reduction of oxidative neuronal cell damage with EPC-K1 by immunohistochemical analysis for 8-hydroxy-2′-deoxyguanosine (8-OHdG) in rat brain with 60 min transient middle cerebral artery occlusion, in association with terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) and staining for total and active caspase-3. Treatment with EPC-K1 (20mg kg-1 i.v.) significantly reduced infarct size (p < 0.05) at 24 h of reperfusion. There were no positive cells for 8-OHdG and TUNEL in sham-operated brain, but numerous cells became positive for 8-OHdG, TUNEL and caspase-3 in the brains with ischemia. The number was markedly reduced in the EPC-K1 treated group. These reductions were particularly evident in the border zone of the infarct area, but the degree of reduction was less in caspase-3 staining than in 8-OHdG and TUNEL stainings. These results indicate EPC-K1 attenuates oxidative neuronal cell damage and prevents neuronal cell death. [Neurol Res 2001; 23: 676-680]

Synergistic induction of DNA strand breakage caused by nitric oxide together with catecholamine: implications for neurodegenerative disease.

Oxidative damage in neuronal cells and DNA has been implicated in the pathogenesis of various neurodegenerative diseases. We have demonstrated that DNA strand breakage is induced synergistically when plasmid DNA is incubated in the presence of both an NO-releasing compound (diethylamine NONOate, spermine NONOate, sodium nitroprusside) and a catecholamine (e.g., L-DOPA, dopamine, etc.). Either an NO-releasing compound or a catecholamine alone induced much fewer strand breaks. Tyrosine and tyramine as well as O-methylated derivatives of DOPA and dopamines did not exert this synergistic effect in the presence of NO. The DNA strand breakage induced by NO plus dopamine was inhibited by carboxy-PTIO (a trapping agent of NO and possibly other radicals), superoxide dismutase, and antioxidants such as N-acetylcysteine and ascorbate but not by HO. scavengers such as dimethyl sulfoxide, ethanol, and D-mannitol. These results suggest that the free HO. is not involved; rather a new oxidant(s) formed by the reaction between NO and catecholamine could be responsible for causing the DNA strand breakage. We propose that one of the responsible compounds is peroxynitrite (ONOO-), which is a strong oxidant and nitrating agent formed by the reaction between NO and O2.-. NO has been shown to oxidize catecholamines to form quinone derivatives, which lead to the generation of O2.- by the quinone/hydroquinone redox system. O2.- then reacts rapidly with NO to form peroxynitrite. However, it is also possible that other compounds such as NOx generated from catecholamines and NO may cause DNA damage. Our results implicate a synergistic interaction of catecholamines formed in dopaminergic neurons and NO formed by microglia or astrocytes or the two compounds produced within the same neuronal cells to produce a potent oxidant(s) which could cause damage in cells and DNA, thus playing an important role in the pathogenesis of various neurodegenerative diseases.