Oxidative damage and cytogenetic analysis in leukocytes of Parkinson's disease patients

Carbon nanotubes induce oxidative DNA damage in RAW 264.7 cells

The induction of DNA and chromosome damage following in vitro exposure to carbon nanotubes (CNT) was assessed on the murine macrophage cell line RAW 264.7 by means of the micronucleus (MN) and the comet assays. Exposures to two CNT preparations (single-walled CNT (SWCNT > 90%) and multiwalled CNT (MWCNT > 90%) were performed in increasing mass concentrations (0.01-100 microg/ml). The frequency of micronuclei was significantly increased in cells treated with SWCNT (at doses above 0.1 microg/ml), whereas MWCNT had the same effect at higher concentrations (1 microg/ml) (P < 0.05). The results of the comet assay revealed that the effects of treatment with SWCNT were detectable at all concentrations tested (1-100 microg/ml); oxidized purines increased significantly, whereas pyrimidines showed a significant increase (P < 0.001) only at the highest concentration (100 microg/ml). In cells treated with MWCNT, an increase in DNA migration due to the oxidative damage to purines was observed at a concentration of 1 and 10 microg/ml, whereas pyrimidines showed a significant increase only at the highest mass concentration tested. However, both SWCNT and MWCNT induced a statistically significant cytotoxic effect at the highest concentrations tested (P < 0.001). These findings suggest that both the MN and comet assays can reliably detect small amount of damaged DNA at both chromosome and nuclear levels in RAW 264.7 cells. Moreover, the modified version of the comet assay allows the specific detection of the induction of oxidative damage to DNA, which may be the underlying mechanism involved in the CNT-associated genotoxicity.

Dietary reference values of individual micronutrients and nutriomes for genome damage prevention: current status and a road map to the future

Damage to the genome is recognized as a fundamental cause of developmental and degenerative diseases. Several micronutrients play an important role in protecting against DNA damage events generated through endogenous and exogenous factors by acting as cofactors or substrates for enzymes that detoxify genotoxins as well as enzymes involved in DNA repair, methylation, and synthesis. In addition, it is evident that either micronutrient deficiency or micronutrient excess can modify genome stability and that these effects may also depend on nutrient-nutrient and nutrient-gene interaction, which is affected by genotype. These observations have led to the emerging science of genome health nutrigenomics, which is based on the principle that DNA damage is a fundamental cause of disease that can be diagnosed and nutritionally prevented on an individual, genetic subgroup, or population basis. In this article, the following topics are discussed: 1) biomarkers used to study genome damage in humans and their validation, 2) evidence for the association of genome damage with developmental and degenerative disease, 3) current knowledge of micronutrients required for the maintenance of genome stability in humans, 4) the effect of nutrient-nutrient and nutrient-genotype interaction on DNA damage, and 5) strategies to determine dietary reference values of single micronutrients and micronutrient combinations (nutriomes) on the basis of DNA damage prevention. This article also identifies important knowledge gaps and future research directions required to shed light on these issues. The ultimate goal is to match the nutriome to the genome to optimize genome maintenance and to prevent pathologic amounts of DNA damage.

Alpha-synuclein nitration and autophagy response are induced in peripheral blood cells from patients with Parkinson disease

Several lines of evidence implicate a central role for alpha-synuclein (aSN) in the pathogenesis of Parkinson's disease (PD). Besides rare genetic mutations, post-translational mechanisms, such as oxidative stress-related nitration, may alter the protein properties in terms of propensity to aggregate or be degraded. Our group previously described increased reactive oxygen species (ROS) production within easily accessible peripheral blood mononuclear cells (PBMCs) in PD patients compared to healthy elderly subjects. In the present work, we demonstrated a significant induction of nitrotyrosine (NT)-modifications of aSN within PBMCs derived from individuals with idiopathic PD compared to controls, while aSN protein appeared similarly expressed in the two populations. The amount of NT-modified aSN within PBMCs was positively correlated with intracellular ROS concentration and inversely related to daily dosage of levodopa, making its measurement potentially relevant for disease-intervention studies. Neither aSN expression nor its NT-modifications showed any correlation to specific REP1 genotypes, polymorphic variants within aSN gene promoter whose association to PD susceptibility may occur through the modulation of aSN protein expression. Moreover, although NT-modified aSN has been linked to enhanced propensity to aggregate, we failed to detect an increased presence of insoluble aSN aggregates in PBMCs from PD subjects relative to controls, despite a lack of changes in the ubiquitin-proteasome expression or activity. Nonetheless, a significant activation of the autophagy response was identified within PBMCs from PD individuals, which could represent a protective mechanism against abnormal protein accumulation and may explain the lack of aSN aggregation. We discuss the relevance of these findings with respect to PD pathogenesis and biomarker development.

Calcium homeostasis is dysregulated in parkinsonian patients with L-DOPA-induced dyskinesias

Long-term treatment of Parkinson disease (PD) is frequently associated with l-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesias (LIDs). L-DOPA-induced dyskinesias are likely due to changes in the signal transduction pathways, at the striatal level, related to pulsatile stimulation of dopamine receptors. We investigated whether markers of this phenomenon can also be detected peripherally. We analyzed mRNA expression for D5 (D1-like) and D3 (D2-like) receptors and levels of second messengers, such as cAMP and free intracellular Ca2+ ([Ca2+]i), in peripheral blood lymphocytes of PD patients with (LID+) or without LIDs (LID-). Patients with PD showed depressed [Ca2+]i rise in response to mitogen-induced activation. The defect was more pronounced in LID+ (-33% with respect to healthy controls) than in LID- patients (-20%). Peripheral blood lymphocyte levels of cAMP were decreased in both LID+ (3.8 +/- 2.9 pmol/10 cells) and LID- patients (4.2 +/- 2.4 pmol/10(6) cells), with respect to controls (6 +/- 2.6 pmol/10(6) cells). No differences were found in dopamine receptor mRNA expression. Our results demonstrate that second messenger levels are altered in the peripheral blood lymphocytes of PD patients treated with dopaminergic agents and that patients with LIDs show further alterations in the regulation of [Ca2+]i homeostasis. This may represent a distinctive trait of patients prone to develop dyskinetic movements.

Oxidative stress in macrophages from spleen of Nile tilapia (Oreochromis niloticus) exposed to sublethal concentration of endosulfan

Endosulfan is a widely used insecticide with immunosuppressive or immunopotentiating effects which alters the immune response of fish. The effects of the acute exposure to endosulfan on a series of parameters of the innate immune response (IIR) of Nile tilapia (Oreochromis niloticus) were investigated-phagocytosis, production of oxygen reactive species, lipoperoxidation as well as spleen cell viability, relative spleen weight and splenocyte concentration-to fully document the effects of this pesticide on Nile tilapia. Juvenile Nile tilapia were exposed in vivo and for 96h to each one of nine concentrations of endosulfan in order to determine the pesticide's acute toxicity level and calculate the lethal concentration of endosulfan to these organisms (LC(50)=12,795ppb). Functional assays showed that endosulfan, at a level equivalent to (1)/(2)LC(50), altered some parameters of the spleen macrophages of Nile tilapia. Phagocytosis, production of oxygen reactive species, and lipoperoxidation increased significantly in exposed fish. Spleen cell viability and relative spleen weight were lower in exposed organisms compared to non-exposed ones, without reaching statistical significance. Splenocyte concentration was not altered in the present experimental conditions. Thus, in vivo exposure (7ppb) of juvenile organisms stimulated the phagocytic activity up to significant oxidative stress levels as indicated by the increased lipid peroxidation in plasma. It can be concluded that short exposure to low concentration of endosulfan stimulated macrophage activity but that there was no significant reduction in the structural parameters of the IIR.

In vitroradiosensitivity of peripheral blood lymphocytes in multiple sclerosis patients

PURPOSE

To assess the in vitro radiosensitivity of peripheral blood lymphocytes of secondary progressive multiple sclerosis (MS) patients in comparison to healthy individuals.

MATERIAL AND METHODS

Radiosensitivity of MS patients lymphocytes to in vitro irradiation of 2 Gy 60Co gamma-rays was studied in whole blood cultures and separated peripheral blood mononuclear cell (PBMC) cultures. Chromosomal radiosensitivity was investigated by means of the G0-micronucleus (MN) assay. The radio-induction of micronuclei was also studied in separated subsets of CD4+ (helper) and CD8+ (suppressor) T cells. Apoptosis was analysed in PBMC cultures using fluorescence microscopy techniques.

RESULTS

The spontaneous MN induction was significantly higher in MS patients compared to healthy controls for whole blood and PBMC cultures. After gamma-irradiation of whole blood cultures no difference in radiosensitivity was observed between patients and controls for MN induction. In irradiated PBMC cultures, the CD4+ lymphocytes of MS patients were less radiosensitive compared to healthy controls and this more resistant behaviour increased with increasing illness duration. Radiation induced apoptosis in G0 lymphocytes of MS patients was lower than in controls.

CONCLUSION

After gamma irradiation, a radioresistant behaviour in PBMC cultures of MS patients was revealed. This radioresistant behaviour was expressed by lower MN induction in CD4+ lymphocytes and by lower apoptosis induction in G0 PBMC cultures and may point to an adaptive response. The higher radiation response in whole blood cultures compared to PBMC cultures was significantly more pronounced in MS patients, suggesting special characteristics of the whole blood environment associated with this pathology.

Chromosomal Radiosensitivity in Secondary‐Progressive Multiple Sclerosis Patients

PURPOSE

To investigate chromosomal radiosensitivity of secondary progressive (SP) multiple sclerosis (MS) patients in comparison to a group of healthy individuals.

MATERIAL AND METHODS

Chromosomal radiosensitivity was assessed in vitro with the G2 assay and the G0-micronucleus (MN) assay. For the G2 assay phytohaemagglutinin (PHA) stimulated blood cultures were irradiated with a dose of 0.4 Gy 60Co gamma rays in the G2 phase of the cell cycle. For the MN assay unstimulated diluted blood samples were exposed to 3.5 Gy 60Co gamma rays delivered at a high dose-rate (HDR = 1 Gy/min) or low dose-rate (LDR = 4 mGy/min).

RESULTS

No significant differences in the number of chromatid breaks were observed between MS patients and healthy individuals. With the G0-MN assay a higher spontaneous MN yield was found in MS patients. At HDR irradiation no significant differences were shown, while at LDR irradiation, MS patients were found less sensitive than healthy controls. The dose-rate sparing index was higher for MS patients, pointing to a better repair capacity.

CONCLUSIONS

MS patients are not characterised by an enhanced in vitro chromosomal radiosensitivity. The radioresistant response, which was only observed with the MN assay after LDR irradiation, may point to an adaptive response induced by in vivo oxidative stress in SPMS patients.

Aging-associated alteration of subtelomeric methylation in Parkinson's disease

A telomere is a repetitive DNA structure capping the chromosomal ends. Telomeres stabilize the chromosome structure and prevent harmful end-to-end recombinations. The telomere length of somatic cells can be determined as the terminal restriction fragment length provided by a genomic Southern blotting analysis, and the telomere length becomes shorter at each mitotic cycle due to an "end-replication problem." Therefore, older somatic cells, which have undergone more mitotic cycles, bear shorter telomeres. This telomere shortening is accelerated by various disease conditions. Parkinson's disease (PD) also yields telomere fragility, thus accelerating the telomere shortening of the circulating leukocytes. This study found that peripheral leukocytes of Japanese PD patients bear fewer short telomeres with constant subtelomeric methylation status in comparison with the healthy controls with increasing short telomeres and also increasing hypomethylated subtelomeres in short telomeres with aging. The correlation between the telomeric attrition and the subtelomeric methylated state in PD is herein discussed.

A single-nucleotide polymorphism of the osteopontin gene may contribute to a susceptibility to Lewy body disease

In Lewy body disease, inflammation is discussed to be involved in the pathophysiological cascade. Osteopontin (OPN) is a multifunctional molecule, which is increased in inflammatory states. Here, we analyzed the allele frequency of two SNPs of the OPN gene, serum, and CSF OPN levels in Lewy body disease patients and controls. In accordance with our previous findings, we detected increased serum (P = 0.006) and CSF OPN levels (P = 0.0003) in the Lewy body disease cohort, compared to non-Lewy body disease subjects. The genotypic variation of SNP-66 was associated with the occurrence of Lewy body disease (odds ratio: 2.64, 95% CI 1.07-6.54, unadjusted P = 0.036). SNP+1239 was not related to Lewy body disease prevalence (odds ratio 1.61, 95% CI 0.66-3.91, P = 0.29). Genotype prevalence and OPN levels were not significantly related. These findings suggest that OPN is associated with the occurrence of Lewy body disease and SNP-66 may be a susceptibility factor.

Lymphocyte proteomics of Parkinson’s disease patients reveals cytoskeletal protein dysregulation and oxidative stress

Aims: There is increasing evidence of biochemical alterations in peripheral blood lymphocytes of Parkinson’s disease (PD) patients. In this work, we describe the changes in protein levels in peripheral lymphocytes of PD patients in order to identify potential peripheral biomarkers. Materials & methods: By means of 2D electrophoresis and mass spectrometry protein identification, we compared patients under L-3,4-dihydroxyphenylalanine (L-DOPA) treatment, patients under subthalamic nucleus deep-brain stimulation and healthy controls. Results: Statistical analysis of the results demonstrated that cofilin-1, tropomyosin, and a specific actin isoform vary significantly in patients, regardless of the therapy. Two different isoforms of γ-fibrinogen either correlate with the disease state or with the disease duration. Eventually, specific changes associated with the different therapies allowed to highlight oxidative stress conditions in lymphocytes in patients treated with higher doses of L-DOPA. Conclusions: As a whole, peripheral blood lymphocytes are sensitive reporters of PD over inter-individual variability, and allow the identification of specific alterations that could be further exploited for diagnostic purposes.

Comparative genome hybridization array analysis for sporadic Parkinson's disease

Parkinson disease (PD) is a common neurodegenerative disorder, characterized by the loss of midbrain dopamine neurons and Lewy body inclusions. We investigated array CGH to analyze gain or loss of genetic material from 30 patients with PD. We identified the frequent copy number variations in PD; gains in 1p21.1, 4p15.31, 5p15.33, 6q24.1, 7q35, 8q24.3, 10q26.3, 11p15.5-15.4, 12q21.2, 16p13.3, 18q12.3 and 22q13.31, and losses in 1p36.33, and 5q13.2. These findings enable a better description of genetic variations in PD, and could provide a foundation for understanding the critical regions of the genome that may be involved in the development of PD.

Biomarkers for evaluation of clinical efficacy of multipotential neuroprotective drugs for Alzheimer's and Parkinson's diseases

During the last century, the world population has shown a staggering increase in its proportion of elderly members and thus neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD), respectively, are becoming an increasing burden on society. Among the diverse, significant challenges facing clinicians, is the improvement of diagnostic measures to detect early and subtle symptoms, a phase in which prevention efforts might be expected to have their greatest impact and provide a measure of disease progression that can be evaluated during the course of drug treatment. At present, clinical diagnosis of AD and PD is based on a constellation of symptoms and manifestations, although the disease originated several years earlier. Given the multiple etiological nature of AD and PD, it is reasonable to assume that the initial causative pathobiological processes may differ between the affected individuals. Therefore, the availability of biological markers or biomarkers will help not only early disease diagnosis, but also delineate the pathological mechanisms more definitively and reliably than the traditional cognitive and neurological phenotypes. In the current article, we review the literature on biochemical, genetic, and neuroimaging biomarkers and discuss their predictive value as indicative for disease vulnerability to detect individuals at risk for PD and AD, and to determine the clinical efficacy of novel, disease-modifying (neuroprotective) strategies.

Dopamine transporter immunoreactivity in peripheral blood lymphocytes in multiple system atrophy

Previous studies showed the reduction of dopamine transporter immunoreactivity (DAT-IR) in peripheral blood lymphocytes (PBL) in Parkinson's disease. Here we report the reduction of DAT-IR in PBL in the extrapyramidal variant of multiple system atrophy. These results suggest the reduction of DAT-IR in PBL in a variety of neurodegenerative disorders, provided the presence of damage of the central dopaminergic systems. The reduction of DAT-IR in PBL in these disorders may represent a compensatory phenomenon aimed at reducing intracellular dopamine influx and, consequently, dopamine-mediated aggravation of oxidative stress in these cells.

Increased oxidative damage in peripheral blood correlates with severity of Parkinson's disease

Increased oxidative stress contributes to neuronal dysfunction in Parkinson's disease (PD). We investigated whether the pathological changes in PD brains may also be present in peripheral tissues. Leukocyte 8-hydroxydeoxyguanosine (8-OHdG), plasma malondialdehyde (MDA), erythrocyte glutathione peroxidase (GPx) and plasma vitamin E (Vit E) were measured for 211 PD patients and 135 healthy controls. Leukocyte 8-OHdG and plasma MDA were elevated, whereas erythrocyte GPx and plasma Vit E were reduced in PD patients when compared to the controls. After adjusting for environmental factors, logistic regression analysis showed that PD severity was independently correlated with 8-OHdG and MDA level, and inversely correlated with GPx activity and Vit E level. Leucocyte 8-OHdG level was continuously increased with advanced PD Hoehn-Yahr stages, while plasma MDA level peaked at early disease stages, among PD patients. These results suggest increased oxidative damage and decreased anti-oxidant capacity in peripheral blood, and a significant correlation between leucocyte 8-OHdG level and disease severity in PD.

Central and peripheral dopamine transporter reduction in Parkinson's disease

OBJECTIVE

Previous reports showed the reduction of dopamine transporter immunoreactivity in peripheral blood lymphocytes in Parkinson's disease. In this work, we sought to investigate the possible correlation between central and peripheral dopamine transporter immunoreactivity values in a group of 11 drug-naive patients with Parkinson's disease.

METHODS

Densitometric measurements of dopamine transporter immunoreactivity in peripheral blood lymphocytes was accomplished as described recently, using a monoclonal antidopamine transporter antibody. Dopamine transporter binding in the caudate and putamen nuclei was measured by means of (123)I-fluopane single-photon emission computed tomography in the same patients.

RESULTS

The results failed to show any significant correlation between dopamine transporter immunoreactivity in peripheral blood lymphocytes and the caudate or putamen dopamine transporter binding. Moreover, dopamine transporter immunoreactivity in peripheral blood lymphocytes was reduced also in the single patient with normal striatal dopamine transporter binding.

DISCUSSION

These results indicate the lack of correlation between central and peripheral dopamine transporter reduction in Parkinson's disease, using the methodologies applied herein. They therefore suggest that the two phenomena are unlikely to share a common pathogenetic mechanism.

A percentage analysis of the telomere length in Parkinson's disease patients

Telomeres are the repeated sequences at the chromosome ends which undergo shortening with cell division. The telomere shortening of the peripheral leukocytes is also facilitated by enhanced oxidative stress in various kinds of disease including ischemic heart disease, diabetes mellitus, apoplexy, and Alzheimer's disease. Telomere shortening in Parkinson's disease (PD) has not yet been reported. The pathogenesis for PD is also regarded to be associated with oxidative stress. We investigated 28 Japanese male PD patients ages 47-69. Although we could not find a statistical difference in the mean telomere length of peripheral leukocytes between the PD patients and the control participants, we found the mean telomere lengths to be shorter than 5 kb in only the PD patients and a significant PD-associated decrease in the telomeres with a length ranging from 23.1 to 9.4 kb in the patients in their 50s and 60s. These observations suggest that telomere shortening is accelerated in PD patients in comparison to the normal population.

Levodopa therapy reduces DNA damage in peripheral blood cells of patients with Parkinson's disease

Oxidative stress seems to play a major role in the pathogenesis of neurodegeneration. In Parkinson's disease (PD) patients, the dopaminergic neurons are subjected to oxidative stress resulting from reduced levels of antioxidant defenses such as glutathione and high amount of intracellular iron. Levodopa (LD) is widely used for the symptomatic treatment of PD, but its role in oxidative damage control is still unclear. The aim of this study was to analyze the presence of DNA damage in peripheral blood lymphocytes (PBL) of PD patients, during a washout and a controlled LD dosage and to evaluate the oxidative damage fluctuation after LD intake. The standard and the Fpg-modified version of Comet assay were applied in analyzing DNA damage in PBL from blood samples of nine PD patients and nine matched controls. Due to the limited number of patients we cannot reach definite conclusions even if our data confirm the accumulation of DNA lesions in PD patients; these lesions decrease after LD intake.

Proteasomal inhibition and apoptosis regulatory changes in human isolated lymphocytes: The synergistic role of dopamine

Abnormal deposition of protein aggregates and increased susceptibility to apoptotic cell death may result from defects in the activity of the ubiquitin-proteasome system (UPS); neurotoxicity related to UPS defects seems to require dopamine to be fully expressed. The aim of this study was to investigate the pro-apoptotic effects caused by proteasomal activity inhibition, as well as the synergistic effect of dopaminergic stimulation in human lymphocytes isolated from healthy volunteers. Cells were incubated 20 h at 37 degrees C, with: (1) lactacystin, (2) increasing concentrations of dopamine or (3) mixture of dopamine and lactacystin. Activities of proteasome 20S and pro-apoptotic caspases-3 and -9 and levels of anti-apoptotic Bcl-2 were measured with fluorimetric or immunochemical assays, while a "DNA diffusion" assay was used to determine the apoptosis. Incubation of lymphocytes with lactacystin, which caused reduction of proteasomal activity, was associated with activation of caspases. A clear, dose-dependent reduction of proteasomal activity was also seen in the presence of increasing doses of dopamine, which was accompanied by a slight dose-dependent increase of caspases activities and Bcl-2 levels. Both effects on proteasome and caspase activities were enhanced when cells were simultaneously exposed to lactacystin and elevated concentrations of dopamine. Apoptosis was detected in all treated samples, but not in controls, without significant differences among the treatment groups; however, the association of dopamine and lactacystin induced a clear reduction in the number of cells being analyzed, pointing to marked cytotoxicity. Our data confirm the potentiation of cytotoxicity related to proteasome inhibition, in the presence of dopaminergic stimulation.

Gazing into the future: Parkinson's disease gene therapeutics to modify natural history

PD gene therapy clinical trials have primarily focused on increasing the production of dopamine (DA) through supplemental amino acid decarboxylase (AADC) expression, neurotrophic support for surviving dopaminergic neurons (DAN) or altering brain circuitry to compensate for DA neuron loss. The future of PD gene therapy will depend upon resolving a number of important issues that are discussed in this special issue. Of particular importance is the identification of novel targets that are amenable to early intervention prior to the substantial loss of DAN. However, for the most part the etiopathogenesis of PD is unknown making early intervention a challenge and the development of early biomarker diagnostics imperative.

Vitamin E and neurodegenerative diseases

Vitamin E is essential for neurological function. This fact, together with a growing body of evidence indicating that neurodegenerative processes are associated with oxidative stress, lead to the convincing idea that several neurological disorders may be prevented and/or cured by the antioxidant properties of vitamin E. In this review, some aspects related to the role of vitamin E against Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and ataxia with vitamin E deficiency will be presented.

Oxidative stress and oxidative DNA damage is characteristic for mixed Alzheimer disease/vascular dementia

Oxidative DNA damage may contribute to neuronal cell loss and may be involved in pathogenesis of some neurodegenerative diseases. We assessed the broad spectrum of oxidative DNA damage biomarkers and antioxidants in mixed Alzheimer disease/vascular dementia (MD) and in control patients. The amount of the products of oxidative DNA damage repair (8-oxo-2'-deoxyguanosine and 8-oxoguanine) excreted into urine and cerebrospinal fluid (CSF) was measured by gas chromatography/mass spectrometry with HPLC pre-purification. The level of 8-oxo-2'-deoxyguanosine in leukocytes' DNA, antioxidant vitamins and uric acid concentrations in blood plasma were analyzed by the mean of HPLC technique. For the first time we demonstrated oxidative DNA damage on the level of whole organism and in CSF of MD patients. Urinary excretion of oxidative DNA damage repair products were higher in patients with MD than in the control group. The level 8-oxoguanine in cerebrospinal fluid of MD patients almost doubled the level found in the control group. Also the concentrations of ascorbic acid and retinol in plasma were reduced in MD patients. Oxidative stress/DNA damage is an important factor that may be involved in pathogenesis of mixed dementia. It is likely that treatment of these patients with antioxidants may slow down the progression of the disease.

DNA fragmentation and oxidative stress in the hippocampal formation: a bridge between 3,4-methylenedioxymethamphetamine (ecstasy) intake and long-lasting behavioral alterations

Intake of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) in humans leads to marked behavioral alterations. In a recent paper, we demonstrated that chronic MDMA intake produces a latent hippocampal hyperexcitability that parallels a reduced threshold for limbic seizures and a slowing of electroencephalographic activity. These phenomena suggest an alteration in hippocampal function. So far, only a few studies have focused on the hippocampal formation as a potential target for the effects induced by MDMA. In this study we sought to evaluate whether the intrinsic cells of the hippocampus might be modified chronically by ecstasy intake. In particular, we examined whether administration of MDMA, at doses producing hippocampal hyperexcitability also produces rearrangements of DNA strands measured by the comet assay. We found that MDMA, at very low doses, comparable with those self-administered by humans, produces acute oxidative stress and DNA single and double-strand breaks, which persist together with long-lasting metabolic changes in the hippocampal formation. These persisting effects are accompanied by behavioral sensitization, reduced seizure threshold and long-lasting slowing of electroencephalographic activity, and hyperexcitability of the hippocampus, without affecting the basal ganglia. The present data indicate that the intake of very low doses of MDMA, comparable to those consumed by humans, produces selective hippocampal alterations which may underlie cognitive impairment and seizure susceptibility.

DNA repair, mitochondria, and neurodegeneration

Accumulation of nuclear and mitochondrial DNA damage is thought to be particularly deleterious in post-mitotic cells, which cannot be replaced through cell division. Recent experimental evidence demonstrates the importance of DNA damage responses for neuronal survival. Here, we summarize current literature on DNA damage responses in the mammalian CNS in aging and neurodegeneration. Base excision repair (BER) is the main pathway for the removal of small DNA base modifications, such as alkylation, deamination and oxidation, which are generated as by-products of normal metabolism and accumulate with age in various experimental models. Using neuronal cell cultures, human brain tissue and animal models, we and others have shown an active BER pathway functioning in the brain, both in the mitochondrial and nuclear compartments. Mitochondrial DNA repair may play a more essential role in neuronal cells because these cells depend largely on intact mitochondrial function for energy metabolism. We have characterized several BER enzymes in mammalian mitochondria and have shown that BER activities change with age in mitochondria from different brain regions. Together, the results reviewed here advocate that mitochondrial DNA damage response plays an important role in aging and in the pathogenesis of neurodegenerative diseases.

The comet assay as a method of assessment of neurotoxicity: usefulness for drugs of abuse

Comet assay is a quick and versatile method for assessing DNA damage in individual cells. It allows the detection of single and double DNA strand breaks, as well as the presence of alkali labile sites. DNA breaks may represent the direct effect of some damaging agent, or they may be intermediates in cellular repair. DNA strand breaks may also come from the action of free radicals generated by oxidative stress processes. The present article summarizes some data from our and other groups underlining the suitability of the Comet assay in assessing neurotoxicity and its potential in evaluating drugs of abuse-related genotoxicity.

Neuroinflammation, Oxidative Stress and the Pathogenesis of Parkinson's Disease

Neuroinflammatory processes play a significant role in the pathogenesis of Parkinson's disease (PD). Epidemiologic, animal, human, and therapeutic studies all support the presence of an neuroinflammatory cascade in disease. This is highlighted by the neurotoxic potential of microglia . In steady state, microglia serve to protect the nervous system by acting as debris scavengers, killers of microbial pathogens, and regulators of innate and adaptive immune responses. In neurodegenerative diseases, activated microglia affect neuronal injury and death through production of glutamate, pro-inflammatory factors, reactive oxygen species, quinolinic acid amongst others and by mobilization of adaptive immune responses and cell chemotaxis leading to transendothelial migration of immunocytes across the blood-brain barrier and perpetuation of neural damage. As disease progresses, inflammatory secretions engage neighboring glial cells, including astrocytes and endothelial cells, resulting in a vicious cycle of autocrine and paracrine amplification of inflammation perpetuating tissue injury. Such pathogenic processes contribute to neurodegeneration in PD. Research from others and our own laboratories seek to harness such inflammatory processes with the singular goal of developing therapeutic interventions that positively affect the tempo and progression of human disease.

Neuroprotection by transgenic expression of glucose-6-phosphate dehydrogenase in dopaminergic nigrostriatal neurons of mice

Oxidative damage to dopaminergic nigrostriatal (DNS) neurons plays a central role in the pathogenesis of Parkinson's disease (PD). Glucose-6-phosphate dehydrogenase (G6PD) is a key cytoprotective enzyme that provides NADPH, the major source of the reducing equivalents of a cell. Mutations of this enzyme are the most common enzymopathies worldwide. We have studied in vivo the role of G6PD overexpressed specifically in the DNS pathway and show that the increase of G6PD activity in the soma and axon terminals of DNS neurons, separately from other neurons or glial cells, protects them from parkinsonism. Analysis of DNS neurons by histological, neurochemical, and functional methods showed that even a moderate increase of G6PD activity rendered transgenic mice more resistant than control littermates to the toxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The neuroprotective action of G6PD was also observed in aged animals despite that they had a greater susceptibility to MPTP. Therefore, overexpression of G6PD in dopaminergic neurons or pharmacological activation of the native enzyme should be considered as potential therapeutic strategies to PD.

Analysis of chromosome damage in circulating lymphocytes of radiological workers affected by thyroid nodules

The aim of our study was to assess whether or not thyroid nodularity in combination with occupational exposure to low levels of ionising radiation would be correlated with chromosome damage in peripheral lymphocytes. Conventional chromosome-aberration analysis was performed on a group of 92 hospital workers with or without thyroid nodules. On the basis of measurements of their exposure levels, the workers were classified into a low (mean total level=0.03 mSv), medium (mean total level=1.04 mSv) or high (mean total level=8.60 mSv) exposure category. Our results indicate that among workers with thyroid nodules, the high-exposed workers showed significantly higher levels of both total (2.35+/-0.34 per 100 cells) and chromosome-type aberrations (1.46+/-0.20 per 100 cells) than medium-exposed (0.98+/-0.42 and 0.68+/-0.25 per 100 cells, respectively) or low-exposed workers (1.11+/-0.29 and 0.58+/-0.17 per 100 cells, respectively). Workers without thyroid nodules had comparable frequencies of chromosome aberrations among the three exposure categories. To our knowledge, this is the first study revealing a slight, but significant increase of chromosome damage in peripheral lymphocytes from hospital workers who developed thyroid nodules under conditions of occupational exposure to radiation well below the threshold limit for the workplace. The existence of a possible association between chromosome aberrations and development of thyroid nodularity will be discussed.

Our recent experiences with sarin poisoning cases in Japan and pesticide users with references to some selected chemicals

Attention has been paid to neurobehavioral effects of occupational and environmental exposures to chemicals such as pesticides, heavy metals and organic solvents. The area of research that includes neurobehavioral methods and effects in occupational and environmental health has been called "Occupational and Environmental Neurology and Behavioral Medicine." The methods, by which early changes in neurological, cognitive and behavioral function can be assessed, include neurobehavioral test battery, neurophysiological methods, questionnaires and structured interview, biochemical markers and imaging techniques. The author presents his observations of neurobehavioral and neurophysiological effects in Tokyo subway sarin poisoning cases as well as in pesticide users (tobacco farmers) in Malaysia in relation to Green Tobacco Sickness (GTS). In sarin cases, a variety effects were observed 6-8 months after exposure, suggesting delayed neurological effects. Studies on pesticide users revealed that organophosphorus and dithiocarbamate affected peripheral nerve conduction and postural balance; subjective symptoms related to GTS were also observed, indicating the effects of nicotine absorbed from wet tobacco leaves. In addition, non-neurological effects of pesticides and other chemicals are presented, in relation to genetic polymorphism and oxidative stress.

Oxidative stress in peripheral blood mononuclear cells from patients with Parkinson's disease: negative correlation with levodopa dosage

Oxidative stress, resulting from the imbalance between reactive oxygen species (ROS) formation and antioxidant defenses, plays a major role in the pathogenesis of Parkinson's disease (PD). However, the contribution of levodopa (LD) therapy to oxidative damage is still debated. We investigated oxidative stress in peripheral blood mononuclear cells (PBMCs) from LD-treated PD patients and healthy subjects. Increased ROS production associated with unaltered glutathione reductase activity was detected in PBMC from PD patients. LD daily dosage appeared to be inversely correlated with ROS levels and positively associated with GR activity, suggesting a protective role for LD on PBMCs redox status. Our data support the view of systemic oxidative stress involvement in PD and give further rationale for using PBMCs as an easily accessible ex-vivo dopaminergic model for exploring the biological effects of LD therapy.

Cytogenetic biomarkers, urinary metabolites and metabolic gene polymorphisms in workers exposed to styrene

The present study comprised a biomonitoring study in 95 workers occupationally exposed to styrene and 98 unexposed controls, employing an integrated approach involving biomarkers of exposure, effect, and susceptibility. Airborne styrene was evaluated at workplace, and urinary styrene metabolites, mandelic acid (MA), phenylglyoxylic acid (PGA), vinylphenols (VPTs) and phenylhydroxyethylmercapturic acids (PHEMAs), were measured as biomarkers of internal dose. Cytogenetic alterations were evaluated by analysing the frequency of chromosomal aberrations (CAs) and micronucleated binucleated cells (MNBN) in peripheral blood lymphocytes. The micronucleus assay was coupled with centromeric fluorescence in situ hybridization to distinguish micronuclei (MN) arising from chromosomal breakage (C- MN) from those harboring whole chromosomes (C+ MN). The possible influence of genetic polymorphisms of xenobiotic-metabolizing enzymes involved in styrene biotransformation (EPHX1, GSTT1, GSTM1, GSTP1) and NAT2 on the cytogenetic endpoints was investigated. The exposed workers showed a significantly higher frequency of MNBN (13.8+/-0.5% versus 9.2+/-0.4%; P<0.001) compared to control subjects. The effect appeared to concern both C- and C+ MN. A positive correlation was seen between the frequency of C+ MN and urinary level of MA+PGA (P<0.05) and VPTs (P<0.001). Chromosome-type CAs positively correlated with airborne styrene level and VPTs (P<0.05), whereas chromatid-type CAs correlated with PHEMAs (P<0.05). Workers bearing GSTM1 null genotype showed lowered levels of PHEMAs (P<0.001). The GSTT1 null genotype was associated with increased MNBN frequencies in the exposed workers (P<0.05) and the fast activity EPHX genotype with a moderate decrease in both MNBN and CAs in the controls. Our results suggest that occupational exposure to styrene has genotoxic effects that are potentiated by the GSTT1 gene deletion. These observations may have relevance considering the risk of lymphatic and haematopoietic malignancies tentatively associated with styrene exposure.

Neuroprotection by rasagiline: a new therapeutic approach to Parkinson's disease?

Neuronal death in Parkinson's disease (PD) may originate from the reciprocal interactions of a restricted number of conditions, such as mitochondrial defects, oxidative stress and protein mishandling, which would favor a state of apoptotic cell death in the nigrostriatal pathway. The search for pharmacological treatments able to counteract the nigrostriatal degeneration, possibly by interfering with these phenomena, has recently raised considerable interest in rasagiline [R(+)-N-propargyl-1-aminoindan], a potent, selective, and irreversible inhibitor of monoamine oxidase B (MAO-B). Rasagiline, like selegiline, is a propargylamine, but is approximately 10 times more potent. Unlike selegiline, rasagiline is not metabolized to amphetamine and/or methamphetamine and is devoid of sympathomimetic activity. Numerous experimental studies, conducted both in vitro and in vivo, have shown that rasagiline possesses significant protective properties on neuronal populations. The pro-survival effects of the drug appear to be linked to its propargyl moiety, rather than to the inhibitory effect on MAO-B. Rasagiline's major metabolite, aminoindan--which possesses intrinsic neuroprotective activity--may also contribute to the beneficial effects of the parent compound. Rasagiline has been recently evaluated in early PD patients, with results that are consistent with slowing the progression of the disease. Therefore, the neuroprotective activity shown by the drug under experimental conditions may be reflected in the clinic, thus providing new perspectives for the treatment of PD.

Evaluation of cytogenetic and DNA damage induced by the antibacterial drug, trimethoprim

Trimethoprim, a widely used antimicrobial drug was tested for its effect on the level of nuclear DNA damage in cultured peripheral blood lymphocytes in terms of chromosome and DNA alterations. The extent of cytogenetic damage, expressed as chromosome breakage and chromosome loss, was evaluated employing the cytokinesis block micronucleus method (CBMN) in cultured peripheral blood lymphocytes coupled with fluorescence in situ hybridization (FISH) using a digoxigenin-labelled alphoid DNA probe specific for the centromere of all human chromosomes. The DNA breakage level was evaluated by the Comet assay. Cultures were set up by using blood samples from two healthy donors. A range of concentrations of the test agent (from 1 to 100 microg/ml) was used for the micronuclei (MN) frequency and cytogenetic origin of MN. For the Comet assay the range of doses used was from 0.5 to 150 microg/ml. From the results obtained it appears that this antifolic agent has a significant clastogenic potential, as detected by a dose-dependent increase of the incidence of C-MN and significantly greater than control levels at the highest concentrations tested (25,100 microg/ml). In addition, the results obtained in the Comet assay also show that trimethoprim induces a dose-dependent increase in the level of DNA breakage, this increase attaining statistical significance at the highest concentrations tested (25, 100, 150 microg/ml), which would confirm its genotoxicity.

The effect of smoking on DNA effects in the comet assay: a meta-analysis

The comet assay (alkaline single-cell gel electrophoresis, SCG or SCGE) is frequently used in biomonitoring to detect genotoxic effects in humans exposed at the workplace or in their environment. Because of its ready accessibility, blood is most frequently used in such studies. Many studies investigated cigarette smoking either as a genotoxic exposure itself or as a potential confounding factor in occupational studies. However, although smoking is considered to be a relevant exposure towards various genotoxins, conflicting results have been reported in the comet assay studies. The actual reasons for this discrepancy are not known. To further evaluate evidence for smoking-related DNA effects in the comet assay, we now used a meta-analysis approach based on a literature search. We identified 38 studies from 37 publications which were suited for a formal meta-analysis based on the standardized mean difference (SMD) between the study groups. The evaluation of these 38 studies indicated higher levels of DNA damage in smokers than in non-smokers [under a random effects model, SMD = 0.55, 95% confidence interval = (0.16-0.93)]. Subdividing these studies into studies investigating the effect of smoking as a genotoxic exposure (Type A studies, n = 12) and studies investigating smoking as a potential confounder in occupational studies (Type B, n = 26) indicated a significant difference only in Type A studies but not in Type B studies. Furthermore, studies using image analysis or image length measurements (n = 23) only indicated a tendency for a genotoxic effect of smoking, whereas studies using an arbitrary score (n = 15) found a significantly higher level of DNA damage in smokers.

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.

Challenging conventional wisdom: the etiologic role of dopamine oxidative stress in Parkinson's disease

Oxidative stress is well documented in Parkinson's disease (PD) and has been attributed to dopamine oxidative metabolism. However, evidence of oxidative stress is found in a variety of neurodegenerative disorders, suggesting that more general factors are responsible or that cytodestructive processes secondarily generate oxyradical products. Increasing evidence points away from dopamine metabolism as an important contributor to PD neurodegeneration. Predictions from the dopamine oxidative stress hypothesis of PD reveal multiple inconsistencies. Although the clinical and therapeutic importance of the nigrostriatal dopaminergic system is undeniable, PD neuropathology is much more widespread.

Oxidative DNA damage in peripheral leukocytes of mild cognitive impairment and AD patients

It is well established that oxidative stress plays a key role in the degenerative neuronal death and progression of Alzheimer's disease (AD), although it is not clear if it is the primary triggering event in the pathogenesis of this disorder. Mild cognitive impairment (MCI) is a clinical condition between normal aging and AD, characterized by a memory deficit without loss of general cognitive and functional abilities. We performed this study by a comet assay analysis to evaluate the level of primary and oxidative DNA damage in two groups of MCI and AD patients, compared to healthy controls. Data showed a significantly higher level of primary DNA damage in leukocytes of AD and also of MCI patients compared to control individuals (average: 2.09+/-0.79 and 2.47+/-1.01, respectively for AD and MCI, versus 1.04+/-0.31 in controls). Moreover, the amount of oxidised DNA bases (both purines and pyrimidines) was significatively higher in the two groups of patients (AD and MCI) compared to controls. Our results give a further indication that oxidative stress, at least at the DNA level, is an earlier event in the pathogenesis of AD.

Searching for the role and the most suitable biomarkers of oxidative stress in Alzheimer's disease and in other neurodegenerative diseases

The contribution of oxidative stress to neurodegeneration is not peculiar of a specific neurodegenerative disease, oxidative stress has been found implicated in a number of neurodegenerative disorders among which Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS). Even increasing are studies dealing with the search for peripheral biomarkers of oxidative stress in biological fluids or even in peripheral tissues themselves such as fibroblasts or blood cells. The application of the modified version of the comet assay for the detection of oxidised purines and pyrimidines in peripheral blood leukocytes results particularly useful if the study requires repeated blood drawn from the same individual, for instance if a clinical trial is performed with a preventive therapy. Likely damage occurs to every category of biological macromolecules and we consider, in the context of neurodegenerative diseases, particularly critical the proteic level. The identification of subjects at risk to develop AD or with pre-pathogenic conditions, the possibility to use "a battery of assays" for the detection of oxidative damage at peripheral level, together with recent advances in brain imaging, will allow to better address studies aimed not only to therapeutic purposes but also mainly to primary prevention.

Somatic DNA damage in interventional cardiologists: a case-control study

Interventional cardiologists who work in cardiac catheterization laboratories are exposed to low doses of ionizing radiation that could pose a health hazard. DNA damage is considered to be the main initiating event by which radiation damage to cells results in development of cancer and hereditary disease. The aim of the present study was to assess the effects of chronic low-dose X-ray radiation exposure on somatic DNA damage of interventional cardiologists working in high-volume cardiac catheterization laboratories. For this analysis, we used peripheral lymphocytes and the assay for micronuclei (MNs), which is considered to be a reliable biological dosimeter for radiation exposure. We obtained peripheral blood from 62 physicians (mean age+/-se = 40.6+/-1.5 years): 31 interventional cardiologists (group I, exposed) and 31 age- and sex-matched clinical cardiologists (group II, nonexposed). Interventional cardiologists showed higher MN values (group I=20.5+/-1.6 vs. group II=12.8+/-1.3, P=0.001), although some overlap was apparent in the individual subject analysis. A correlation between years of professional activity and MN frequency value was detectable for interventional cardiologists (r=0.428, P=0.02) but not for clinical cardiologists (r=0.253, P=0.17). The results indicated that, overall, interventional cardiologists working in a high-volume catheterization laboratory have higher levels of somatic DNA damage when compared with clinical cardiologists working outside the catheterization laboratory. The amount of this damage varies and is only weakly related to the duration of professional exposure, which suggests that a dominant modulation of the underlying genetic substrate by environmental factors has a role in determining the harm in individual physicians.

Risk of cancer after the diagnosis of Parkinson's disease: A historical cohort study

We investigated the risk of cancer after the diagnosis of Parkinson's disease (PD) through a historical cohort study. We used the medical records-linkage system of the Rochester Epidemiology Project to identify all incident cases of PD in Olmsted County, Minnesota from 1976 through 1995. Patients with PD were matched by age (+/- 1 year) and gender to referent subjects from the same population. For 196 patients and 185 referent subjects, we ascertained the incidence of cancer through medical records abstraction between the date of diagnosis (or index date) and death, loss to follow-up, or end of study. The risk of cancer was higher among patients than in referent subjects (relative risk [RR] = 1.64; 95% confidence interval [CI] = 1.15-2.35; P = 0.007). The RR did not change noticeably after adjustment for smoking. The increased risk was significant for nonmelanoma skin cancer (RR = 1.76; 95% CI = 1.07-2.89; P = 0.03), but not for other more severe types of cancer; therefore, we cannot exclude the occurrence of a surveillance bias. Among PD patients, there was no relation between the risk of cancer and the cumulative dose of levodopa received or the use of other PD medications.

Neurodegenerative conditions associated with ageing: a molecular interplay?

The ageing process precipitates dramatic alterations in the physiology of all organisms, including reduced cellular function, compromised resistance to stress and pathological agents, and increased likelihood of developing age-related diseases. Among the most characteristic pathologies associated with old age are numerous late-onset neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's diseases. In addition to stroke, which also inflicts loss of neuronal cells, these conditions account for ever-increasing debilitation among the elderly. Recent studies in model organisms such as the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster, which offer the prowess of sophisticated genetic approaches, have uncovered significant, novel aspects of the molecular mechanisms that underlie both neurodegeneration and the ageing process. These advances hold promise that the intimate link between the aged state and the manifestation of several neurodegenerative diseases will be deciphered. Here, we discuss the mechanisms by which ageing interfaces with, and influences, the progression of neurodegeneration.

Peripheral markers of apoptosis in Parkinson's disease: the effect of dopaminergic drugs

In this study, we measured the lymphocyte levels of proteins involved in apoptosis regulation, such as Bcl-2, the peripheral benzodiazepine receptor (PBR), caspase-3, and Cu/Zn superoxide dismutase (Cu/Zn SOD), in patients with Parkinson's disease (PD), either untreated or under therapy with dopaminergic agents (l-Dopa alone or l-dopa + dopamine agonists) and in healthy volunteers. All PD groups showed increased activity of caspase-3, compared to controls, particularly those under treatment only with l-Dopa. In this latter group, the increase in caspase-3 activity was also paralleled by an increase in the concentration of Cu/Zn SOD. In addition, patients taking l-Dopa + dopamine agonists showed marked decrease in Bcl-2 levels and increased PBR expression, which seems in keeping with the hypothesis that PBR may be functionally related to Bcl-2. In conclusion, we found clear modifications in the levels of proteins involved in the control of apoptosis in lymphocytes of PD patients. These changes were disease related but also modulated by the pharmacological treatment, which confirms the potential role of apoptosis in PD pathogenesis and the modulatory influence of dopaminergic agents.

Effects of homocysteine on apoptosis-related proteins and anti-oxidant systems in isolated human lymphocytes

Homocysteine (Hcy) is a nonprotein-forming sulphur amino acid that plays an important role in remethylation and trans-sulphuration processes. In recent years, it has been suggested that increased levels of plasma Hcy may play a role in the pathogenesis of various diseases, particularly at the cardiovascular level. The pathogenic mechanism of hyperhomocysteinemia, however, has not been clarified. Because oxygen radicals can be generated by the auto-oxidation of this amino acid, it has been suggested that Hcy may cause cellular damage through oxidative mechanisms, ultimately leading to apoptotic cell death. In this study, we sought to investigate the effects of Hcy on oxidative damage and antioxidant agent levels, as well as on apoptosis-related proteins and apoptosis occurrence in human cells. For this purpose, we measured levels of Bcl-2, caspase-3 and caspase-9 activity, Cu/Zn superoxide dismutase, reduced glutathione, lipid peroxidation [malondialdehyde and 4-hydroxy-2 (E)-nonenal concentrations], apoptotic single-stranded DNA and nuclear changes in human isolated lymphocytes exposed to increasing concentrations of Hcy. Incubation with Hcy did not induce significant changes in any of these biomarkers. Therefore, our results do not support the existence of a direct link between increased levels of Hcy and the occurrence of a pro-apoptotic state mediated by enhanced oxidative stress.

Evaluation of EMS-induced DNA damage in the single cell gel electrophoresis (Comet) assay and with flow cytometric analysis of micronuclei

Toxic agents in the environment pose serious threats to ecosystems and to the public health. The single cell gel electrophoresis (SCGE) or Comet assay quantitatively measures genomic damage as DNA strand breaks. The micronucleus (MCN) test is an established assay that measures chromosomal damage. Micronuclei are formed from chromosome fragments or from whole chromosomes that have not undergone mitosis properly. This test is usually conducted microscopically. However, micronuclei can also be analyzed using flow cytometry. Chinese hamster ovary (CHO) cells were exposed to ethylmethanesulfonate (EMS), for 4 h in a total volume of 25 microl. These cells were immediately analyzed for genomic DNA damage by SCGE. In concurrent parallel experiments, CHO cells were treated with EMS in 6-well plates for 4 h, the cells were washed and fresh medium was added. The cells were allowed to grow for 45 to 48 h to express micronuclei. The data demonstrated that both DNA strand breaks and micronuclei were induced in a significant and concentration-dependent manner. There was a significant and high correlation (r = 0.91; P < or = 0.001) between the acute induction of DNA strand breaks and the subsequent generation of micronuclei. These data indicate that using molecular and computer technologies, the genotoxic impact of toxic and environmental agents can be rapidly and comprehensively evaluated in mammalian cell systems.