DNA damage and repair efficiency in lymphocytes from schizophrenic patients

doi:10.1016/j.canlet.2003.09.022

Cancer Letters

Volume 204, Issue 1, 10 February 2004, Pages 33-40

https://doi.org/10.1016/j.canlet.2003.09.022 Get rights and content

Abstract

In the present study we examined schizophrenic patients' lymphocytes sensitivity to the effects of external factors, such as hydrogen peroxide and γ-irradiation and also their repair efficiency with the comet assay. Our results did no show any difference in basal levels of DNA damage between schizophrenic and normal populations. The slightly increased sensitivity of the schizophrenic population to the externally induced DNA damage compared to controls was not statistically significant. Also the small reduction in the DNA repair efficiency in schizophrenics in comparison to normal population was found to be not statistically significant. Finally, patients with heritable predisposition to schizophrenia did not show any difference in their response from the other schizophrenics.

Introduction

Schizophrenia is a relatively common debilitating, chronic, psychotic disorder. Its lifetime prevalence is approximately 0.85% in the general population. Its etiology is unknown, but appears to have a strong genetic component, as shown by family, twin and adoption studies [1], [2]. However, other factors must be involved since identical twins, who share 100% of their genes, have only about 50% proband-wise concordance (although estimates differ)—rather than the 100% which would be expected if it were a fully penetrant genetic lesion [3].

It has been reported in the literature that persons diagnosed with schizophrenia have a lower incidence of cancer [4]. On the other hand it is well known that persons diagnosed with schizophrenia have a high rate of smoking which should increase their incidence of cancer.

Defects in DNA repair systems have been reported in a number of neurodegenerative diseases including Friedrich's ataxia, Alzheimer's disease and ataxia telangiectasia [5]. As postulated by Robbins [6], efficient DNA repair is necessary to prevent premature neuronal death. For genetically inherited disorders, this ‘neuronal DNA integrity theory’ posits an inherited inability to repair DNA lesions following exposure to DNA-damaging agents, which leads to neuronal degeneration. Such a mechanism could explain the puzzling genetics of schizophrenia, where both inherited and environmental factors appear to be operative [7].

To investigate the possible role of DNA repair in schizophrenia we used the comet assay technique. In particular we investigated the levels of basal DNA damage on peripheral blood lymphocytes of a schizophrenic population (including a heritable predisposed one) and a corresponding control. The effects of additional external factors [hydrogen peroxide (H₂O₂) and γ-irradiation], and the efficiency of the DNA repair systems was also examined.

Section snippets

Chemicals and media

Plastics were from Corning (NY, USA). RPMI 1640 medium with phenol red, fetal calf serum, phytohemagglutinin (PHA) and trypan blue were obtained from Biochrom KG (Berlin, Germany). Lymphoprep was supplied by Nycomed (Oslo, Norway). l-Glutamine, penicillin and streptomycin were from ICN Flow (Irvine, UK). Low and normal melting point agarose were supplied by Gibco BRL (UK). Phosphate-buffered saline tablets (PBS), dextrose, H₂O₂ and 4′,6-diamidine-2-phenylindole dihydrochloride (DAPI) were

Results

After 5 min treatment of lymphocytes with doses of 0, 50, 100 and 150 μM H₂O₂ the mean extent of basal and H₂O₂ induced DNA damage was measured. These values are presented in Fig. 1. There is a small difference in the extent of DNA damage between schizophrenics and control group although not statistically significant (P>0.05). The basal DNA damage was found to be similar in both schizophrenics and controls (P>0.05). Patients with heritable predisposition showed no difference in their response

Discussion

Elaborate repair mechanisms evolved to maintain integrity of DNA, and their defects result in a variety of disorders [16], [17].

Zasukhina [18] has reported repair defects studying reactivation of viral host cells and increased sister-chromatid exchanges in lymphocytes from 26 patients suffering from schizophrenia of different types following treatment with 4-nitroquinolone and γ-radiation. Topinka et al. [19] in a short abstract reported decreased DNA-repair capacity in the lymphocytes of

Acknowledgements

We thank Dr G. Sideridis of the University of Massachusetts, Boston, USA, for helping us in the power analysis.

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Evaluation of DNA repair efficiency in autistic children by molecular cytogenetic analysis and transcriptome profiling
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Isolated lymphocytes were cultured at 37 °C for 2 h then cooled on ice. The selected cultures were then irradiated with γ-rays (60Co radiotherapy producer, Gammacell 220; Nordion International Inc., Canada) at a dose of 4 Gy/min [25]. Cell viability was greater than 95 % as evaluated by trypan blue exclusion assay.
Data regarding DNA repair perturbations in autism, which might increase the risk of malignancy, are scarce. To evaluate whether DNA repair may be disrupted in autistic children, we assessed the incidence of endogenous basal DNA strand breaks as well as the efficiency of repairing DNA damage caused by γ-ray in lymphocytes isolated from autistic and healthy children. The incidence of DNA damage and the kinetics of DNA repair were determined by comet assay, while the incidence of residual DNA damage was evaluated by structural chromosomal aberration analysis. Transcriptome profiling of 84 genes associated with DNA damage and repair-signaling pathways was performed by RT² Profiler PCR Array. The array data were confirmed by RT-PCR and western blot studies. Our data indicate that the incidence of basal oxidative DNA strand breaks in autistic children was greater than that in nonautistic controls. Lymphocytes from autistic children displayed higher susceptibility to damage by γ-irradiation and slower repair rate than those from nonautistic children. Although the total unstable chromosomal aberrations were unaffected, lymphocytes from autistic children were more susceptible to chromosomal damage caused by γ-ray than those from nonautistic children. Transcriptomic analysis revealed that several genes associated with repair were downregulated in lymphocytes from autistic individuals and in those exposed to γ-irradiation. This may explain the increased oxidative DNA damage and reduced repair rate in lymphocytes from autistic individuals. These features may be related to the possible correlation between autism and the elevated risk of cancer and may explain the role of the disruption of the DNA repair process in the pathogenesis of autism.
An evaluation of the differences in DNA damage in lymphocytes and repair efficiencies in patients with schizophrenia and schizoaffective disorder
2018, Schizophrenia Research
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In our study, the use of quetiapine, olanzapine, risperidone, amisulpride, paliperidone, or clozapine did not increase DNA damage; in fact, DNA damage was significantly low in patients using clozapine and paliperidone, which was consistent with the literature. In the present study, the effects of drugs on DNA damage were also checked by the in vitro assay method, and consistent with the literature (Andreazza et al., 2007; Psimadas et al., 2004), our findings showed that these drugs did not induce any DNA damage to the lymphocytes. The antioxidant and neuroprotective features of mood stabilizers have been demonstrated in animal and cell-based studies.
Schizophrenia and schizoaffective disorder are chronic and debilitating psychiatric disorders. The present study was designed to determine DNA damage in patients with schizophrenia and schizoaffective disorder to assess the roles of oxidative metabolism and DNA repair mechanisms in this process, to assess the contribution of drugs, and thus to demonstrate the differences between schizophrenia and schizoaffective disorder. Thirty schizophrenia and 30 schizoaffective disorder patients, each having at least five years of disease history, aged between 18 and 60 years with no physical or neurological diseases, and 30 healthy volunteers participated in the study. Psychometric scales were applied, and 5 ml of blood was taken from all participants. The DNA damage was measured in lymphocytes by the comet assay method; the total oxidative parameters by ELISA; OGG1 and NEIL1 gene expressions by real-time PCR; and the role of drugs by in vitro assays. The most important finding in this study was that patients with schizophrenia had significantly greater DNA damage than schizoaffective disorder patients and the controls. This study also provides evidence of high oxidative stress statuses and inadequate DNA repair capacities in patients with schizophrenia. Moreover, psychotropic drugs did not induce any DNA damage to the lymphocytes according to in vitro analyses. The use of clozapine and adequate repair processes of the patients were the decisive factors in the prevention of DNA damage. The results of this study provide a reexamination of schizoaffective disorder within the schizophrenia spectrum and indicate that schizoaffective disorder may be considered a different diagnostic category.
CometQ: An automated tool for the detection and quantification of DNA damage using comet assay image analysis
2016, Computer Methods and Programs in Biomedicine
DNA damage analysis plays an important role in determining the approaches for treatment and prevention of various diseases like cancer, schizophrenia and other heritable diseases. Comet assay is a sensitive and versatile method for DNA damage analysis. The main objective of this work is to implement a fully automated tool for the detection and quantification of DNA damage by analysing comet assay images.
The comet assay image analysis consists of four stages: (1) classifier (2) comet segmentation (3) comet partitioning and (4) comet quantification. Main features of the proposed software are the design and development of four comet segmentation methods, and the automatic routing of the input comet assay image to the most suitable one among these methods depending on the type of the image (silver stained or fluorescent stained) as well as the level of DNA damage (heavily damaged or lightly/moderately damaged). A classifier stage, based on support vector machine (SVM) is designed and implemented at the front end, to categorise the input image into one of the above four groups to ensure proper routing. Comet segmentation is followed by comet partitioning which is implemented using a novel technique coined as modified fuzzy clustering. Comet parameters are calculated in the comet quantification stage and are saved in an excel file.
Our dataset consists of 600 silver stained images obtained from 40 Schizophrenia patients with different levels of severity, admitted to a tertiary hospital in South India and 56 fluorescent stained images obtained from different internet sources. The performance of “CometQ”, the proposed standalone application for automated analysis of comet assay images, is evaluated by a clinical expert and is also compared with that of a most recent and related software—OpenComet. CometQ gave 90.26% positive predictive value (PPV) and 93.34% sensitivity which are much higher than those of OpenComet, especially in the case of silver stained images. The results are validated using confusion matrix and Jaccard index (JI). Comet assay images obtained after DNA damage repair by incubation in the nutrient medium were also analysed, and CometQ showed a significant change in all the comet parameters in most of the cases.
Results show that CometQ is an accurate and efficient tool with good sensitivity and PPV for DNA damage analysis using comet assay images.
Assessment of DNA damage and repair efficiency in drug naïve schizophrenia using comet assay
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Only one previous study has evaluated DNA repair efficiency in schizophrenia using a similar methodology and invitro stimulating agent like ours. Their sample size was smaller and the results did not show any significant differences between patients and healthy controls (Psimadas et al., 2004). The findings of the present research must be viewed in the backdrop of its limitations.
The etiology of schizophrenia continues to be confounding and elusive. Some knowledge gaps exist in the neurodegenerative theory of schizophrenia. Oxidative DNA damage and repair deficits are relevant to the mechanisms of neurodegeneration but have not been studied in drug naïve schizophrenia. The present study used the comet assay technique to study the extent of DNA damage in circulating peripheral lymphocytes of patients with drug naïve schizophrenia (n = 40) along with an age and gender matched control group (n = 40). We also assessed the DNA repair efficiency in cases following incubation in a nutrient medium. All the assayed comet parameters demonstrated significantly greater baseline DNA damage in cases in comparison to the controls except for head diameter (p < 0.001 for all significant results, p = 0.32 for head diameter). Gender, age and duration of illness (p = 0.21, 0.69 and 0.12 respectively for tail length) did not influence any of the parameters significantly. Significant decrease was noted in the comet tail length and percentage of DNA in comet tail (p < 0.001 for both) in cases following incubation suggesting that the DNA repair machinery was preserved. No difference in DNA repair efficiency was noted between the genders (p = 0.23 for tail length). Our findings confirm the presence of significant baseline DNA damage in schizophrenia even prior to the initiation of anti-psychotic treatment. Additionally, intact genomic repair efficiency was noted in this group as a whole. These results provide some evidence for oxidative DNA damage as molecular link underpinning neurodegeneration in drug naïve schizophrenia.
Oxidative stress in bipolar and schizophrenia patients
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Oxidative stress has an important place in studies investigating the pathophysiology of psychiatric diseases. In spite of this fact, longitudinal studies are required to clarify the subject. Therefore, in this study, we examined lipid peroxidation, protein oxidation, total oxidized guanine species, superoxide dismutase (SOD) and total glutathione (GSH) levels in blood collected from adult bipolar patients (n=18) during manic and euthymic episodes, schizophrenic patients (n=18) during acute psychotic attack and remission phases and the control group (n=18). There was a significant increase in the level of lipid peroxidation in the bipolar disorder manic episode group (BD-ME) compared to control group. The level of protein oxidation was significantly higher in the schizophrenia acute psychotic attack group (SZ-APA) compared to the control group. The level of total oxidized guanine species was statistically higher in all psychiatric groups compared to the control group. There was no significant difference among the groups with regard to SOD and GSH. Consequently, we believe that lipid peroxidation may be effective in the pathogenesis of bipolar patients; that protein oxidation may be of importance in the pathogenesis of schizophrenia and that total oxidized guanine species may be crucial in the pathogeneses of both psychiatric disorders.
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DNA damage and repair efficiency in lymphocytes from schizophrenic patients

Abstract

Introduction

Section snippets

Chemicals and media

Results

Discussion

Acknowledgements

Schizophr. Res.

Prog. Brain Res.

Mutat. Res.

Int. J. Hyg. Environ. Health

Mutat. Res.

Mutat. Res.

Mutat. Res.

Schizophr. Res.

A Darwinian approach to the origins of psychosis

Br. J. Psychiatry

Mental illness and the sciences of brain and behavior

Nat. Med.

Are we overestimating the genetic contribution to schizophrenia?

Schizophr. Bull.

Hypersensitivity to DNA damaging agents in primary degeneration of excitable tissue