High frequency of sister chromatid exchanges in lymphocytes of the patients with Behçet's disease

Assessment of genotoxicity associated with Behcet's disease using sister-chromatid exchange assay: vitamin E versus mitomycin C

Behcet's disease (BD) is a multisystemic chronic inflammatory disorder that presents throughout the world with high frequency in Turkey and Middle East. BD has been shown to be associated with genotoxicity as patients with the disease have demonstrated high rates of sister chromatid exchange (SCE) and oxidative DNA damage. In this study, we examined the effect of vitamin E, which is known for its strong antioxidant activity, on the rate of SCE in cultured lymphocytes obtained from BD patients. In addition, the susceptibility of patient lymphocytes to the mutagenic agent mitomycin C (MMC) was also investigated. The results showed significant elevation in the rate of SCE in lymphocytes obtained from patients compared to those from healthy subjects (P < 0.01). Treatment with vitamin E normalized the elevated rate of SCE to a comparable level observed in the control group (P < 0.01). Finally, treatment of cultures with MMC significantly increased the rate of SCE in the lymphocytes of both patients and controls (P < 0.001). The magnitude of change in the rate of SCE induced by MMC was equivalent in both groups. This result suggests similar sensitivity of BD lymphocytes and control ones to MMC. In conclusion, genotoxicity associated with BD can be overcome by treatment with vitamin E. Lymphocytes of BD have normal sensitivity to the mutagenic agent MMC.

Comparison of the frequency of sister chromatid exchange in pan chewers and oral submucous fibrosis patients

Sister chromatid exchange (SCE) test is a sensitive, biomarker of genotoxic substances. The frequency of SCE in lymphocytes of ten pan chewing patients, oral submucous fibrosis (OSF) patients and age matched healthy controls were investigated. The frequency of mean SCE/cell was found to be 10.428 ± 0.755 in OSF patients, 8.752 ± 0.383 in case of pan chewers as compared to 5.912 ± 0.310 in controls. These values show a significant increase in frequency of SCE/cell in OSF patients and pan chewers when compared with that of healthy controls. There is a positive correlation co-efficient of SCE/cell with frequency, quantity, duration, intensity and period of exposure of pan-parag to oral mucosa in pan chewers and OSF patients indicating genotoxic effect of pan. Thus SCE could be used as a biomarker in chewers also to assess the level of genomic damage and to advocate efficient control measures.

Sister chromatid exchange analysis in patients with psoriasis

Psoriasis is a common, chronic inflammatory skin disease with unknown aetiology. An increased reactive oxygen species (ROS) and insufficient antioxidant activity have been determined in psoriatic lesions. The analysis of sister chromatid exchange (SCE) is a cytogenetic technique used to show DNA damage caused by an exchange of DNA fragments between sister chromatids. The study aimed to determine the rates of SCE in psoriatic patients (17 female and 19 male) and healthy controls (15 female and 15 male) as well as superoxide dismutase (SOD), glutathione peroxidase (GP) and catalase (CAT) activity in both groups. We found significantly higher SCE rates in the patients (P < 0.00001). In addition, statistically significant decreased levels of erythrocyte SOD and CAT activities were noted in the patients(P < 0.001 and P < 0.05 respectively). Furthermore, a statistically significant increased erythrocyte GP activity was found in the psoriasis group (P < 0.05). Our results indicate that chromosomal instability may play an important part in the aetiology of psoriasis. In addition, the results support the hypothesis of an imbalance in the oxidant-antioxidant system in psoriasis.

Chromosome and sister chromatid exchange studies in Behcet's patients

Behcet's disease is a chronic multisystemic disease of unknown pathogenesis characterized by four major symptoms: oral aphthous ulcers, skin lesions, ocular symptoms and genital ulcerations. The disease is spread throughout the world, but it is most frequent in Turkey, Japan, Korea and China. Although HLA-Bw51 has been found to predominate in Behcet's cases, the genetic etiology has not yet been clarified. In this study, we investigated the chromosomal abnormalities and sister chromatid exchange rates in patients with Behcet's diseases. Thirty-eight patients with Behcet's disease (diagnosed for the first time) and 30 healthy subjects (as controls) were included in this study. Although numerical and structural chromosomal abnormalities were not detected in our patients, we found an increased rate of sister chromatid exchange in patients over the control groups (P < 0.01). On the basis of these results, we discuss the genetic etiology of Behcet's disease.

The alteration of sister chromatid exchange frequencies in Behçet's disease with and without HLA-B51

BACKGROUND

The analysis of sister chromatid exchange (SCE) is a cytogenetic technique used to show DNA damage as a result of an exchange of DNA fragments between sister chromatids. It is known that there is an increased SCE frequency in Behçet's disease (BD).

OBJECTIVE

To investigate whether human leucocyte antigen (HLA)-B51-positive patients with Behçet's disease exhibit higher SCE frequencies than those without HLA-B51.

METHODS

Lymphocytes from 75 patients (38 women, 37 men) and from 50 controls (28 women, 22 men) were cultured in darkness for 72 h in the presence of bromodeoxyuridine. Metaphase chromosomes were stained with a fluorescence plus Giemsa technique after a standard harvest procedure. For HLA-B51 typing, DNA was extracted from ethylenediaminetetraacetic acid blood samples and HLA-B5 allele genotyping was performed by the polymerase chain reaction (PCR)-sequence specific primer method.

RESULTS

Thirty-nine of 75 patients with BD (52%) and 15 of 50 controls (30%) were found HLA-B51-positive. The SCE frequencies in HLA-B51-positive patients were higher than in HLA-B51-negative ones (P < 0.001), whereas no difference was detected in the control group.

CONCLUSION

This study revealed that there was a significant association between elevated SCE frequencies and existence of HLA-B51 patients with BD.

Micronucleus frequency in the oral mucosa and lymphocytes of patients with Behcet's disease

Behçet's disease (BD) is a chronic, multisystemic, inflammatory disorder characterized mainly by recurrent oral and genital aphthous ulcerations and uveitis. Our study aimed to determine the genetic damage in patients with BD. The micronucleus (MN) frequency was counted in peripheral lymphocytes and exfoliated cells of the patients with BD. MN analysis was performed in peripheral lymphocytes of 30 patients with BD and in 20 healthy controls by the cytokinesis-block method, and on uncultured cells of the oral cavity in 10 patients and 9 healthy controls. We found significantly higher MN rates in lymphocytes of the patients than the control subjects (P = 0.000). There were no significant differences between the patients with or without treatment (P = 0.860). The MN frequency in exfoliated cells of the patients was higher than in those of healthy controls (P = 0.013), and there was no significant difference between the exfoliated cells of the treated and untreated patients (P = 0.201). Our results indicate that genetic damage may play a secondary but important part in the aetiology of BD and that treatment with colchicine does not induce MN.

Investigation of DNA damage in lymphocytes exposed to benzathine penicillin G

BACKGROUND

Benzathine penicillin G (BPG) is a widely used antibiotic for treatment or prophylaxis of certain infectious diseases. Previous in vivo studies using sister chromatid exchange (SCE) frequency and comet assay, had showed that long-term administration of benzathine penicillin G may cause some degree of DNA damage in children with rheumatic fever.

METHODS

Because DNA damage has also been reported in various connective tissue disorders, to rule out the possible effects of underlying disease on DNA integrity, 3-day-cultured lymphocytes obtained from nine healthy individuals were exposed to BPG at different concentrations (0.002, 0.02 and 0.1 micro g/mL), and sister chromatid exchange frequencies were studied. The mean SCE frequency per metaphase was calculated from 20 selected cells for each individual.

RESULTS

The incidence of SCE frequency did not differ when all groups were compared. Comparing between each concentration group, exposure to BPG did not cause a dose-dependent increase in SCE frequency (Student's t-test, P > 0.05).

CONCLUSION

Insignificant changes (P > 0.05) in SCE, within the 3-day exposure to BPG, may suggest that DNA damage did not occur. Short-term exposure to BPG does not have toxic effects on DNA. In contrast, this preliminary study should be supported by other genotoxicity assays, expanding the exposure time to longer periods, in order to exclude rapid DNA repair mechanisms. and a possible role of underlying disease on DNA integrity should not be ignored.

Evaluation of DNA damage using the comet assay in children on long-term benzathine penicillin for secondary prophylaxis of rheumatic fever

BACKGROUND

Benzathine penicillin is the most widely used antibiotic in the prophylaxis of children with rheumatic fever. The aim of the present study was to evaluate the DNA damage in children receiving one dose of 1.2 million units benzathine penicillin every 4 weeks over a long period to prevent recurrences of rheumatic fever.

METHODS

Thirty-five children with confirmed rheumatic fever under benzathine penicillin prophylaxis were enrolled in the study and 35 healthy children with similar ages and socioeconomic backgrounds served as controls. To detect any DNA damage, the comet assay was performed on circulating lymphocytes from the study subjects.

RESULTS

Damaged (limited and extensive migration) cells in children on prophylactic therapy were higher than those in controls (P<0.001).

CONCLUSIONS

It has been suggested that differences in the comet scores were induced by the administration of benzathine penicillin over a long period of time and further investigations are needed to confirm this toxic effect.

Sister-chromatid exchange analysis on long-term benzathine penicillin for secondary prophylaxis of rheumatic fever

A single intra-muscular injection of 1.2 millions units of benzathine penicillin every 4 weeks is the most widely used method for the antibiotic prophylaxis of rheumatic fever. The aim of this study is to evaluate the effect of long-term benzathine penicillin on DNA in patients with rheumatic fever. Thirty children with confirmed rheumatic fever who were on the benzathine penicillin prophylaxis were enrolled in the study, and 30 similar normal children served as a control group. To detect any DNA damage, SCE analysis were performed in circulating lymphocytes of the subjects. A statistically significant increased frequency of SCE was observed in children on the benzathine penicillin prophylaxis (no = 30, mean SCEs/cell +/- SD 7.54 +/- 1.81) as compared to a control group (no = 30, mean SCEs/cell +/- SD 5.82 +/- 1.40). It has been suggested that the difference in the SCE frequencies was induced by the administration of the benzathine penicillin for a long time, and further investigations are needed to confirm this toxic effect.