Frequency Of Sister Chromatid Exchanges Research Articles

Telomere alterations and genomic instability in long-term cultures of normal human fibroblasts irradiated with X rays and protons

Telomeres are the end of linear chromosomes, responsible for chromosome stability and cell viability. It is well known that radiations are able to induce chromosome instability but it has not yet been investigated whether telomere structure is affected by the radiation exposure and if radiations with different quality act in a different way on telomeres. The effect of radiations with different quality on telomere structure and chromosome instability was analysed in human primary fibroblasts exposed to X rays or low-energy protons (28.5 keV μm(-1)). Telomere length was evaluated at different harvesting times from 24 h up to 360 h (15 days), whereas chromosome instability was evaluated in terms of sister chromatid exchanges (SCEs) (48 h from irradiation) and chromosome painting (360 h from irradiation). Results indicated a delayed telomere lengthening 360 h after X-ray treatment, whereas protons were able to induce such a lengthening shortly from irradiation as well as at longer harvesting times. Data obtained from chromosome instability analysis indicated an increase of SCE frequency only after proton irradiation, but, on the contrary, at the longer harvesting time chromosome painting analysis displayed a higher frequency of aberrations after X-ray treatment, suggesting a role of selective process against highly damaged cells.

KIAA1018/FAN1 nuclease protects cells against genomic instability induced by interstrand cross-linking agents

Fanconi anemia (FA) is a rare genetic disease characterized by congenital defects, bone marrow failure, chromosomal instability, and cancer susceptibility. One hallmark of cells from FA patients is hypersensitivity to interstrand cross-linking agents, such as the chemotherapeutics cisplatin and mitomycin C (MMC). We have recently characterized a FANCD2/FANCI-associated nuclease, KIAA1018/FAN1, the depletion of which sensitizes human cells to these agents. However, as the down-regulation of FAN1 in human cells was mediated by siRNA and thus only transient, we were unable to study the long-term effects of FAN1 loss on chromosomal stability. We now describe the generation of chicken DT40 B cells, in which the FAN1 locus was disrupted by gene targeting. FAN1-null cells are highly sensitive to cisplatin and MMC, but not to ionizing or UV radiation, methyl methanesulfonate, or camptothecin. The cells do not display elevated sister chromatid exchange frequencies, either sporadic or MMC-induced. Interestingly, MMC treatment causes chromosomal instability that is quantitatively, but not qualitatively, comparable to that seen in FA cells. This finding, coupled with evidence showing that DT40 cells deficient in both FAN1 and FANCC, or FAN1 and FANCJ, exhibited increased sensitivity to cisplatin compared with cells lacking only FAN1, suggests that, despite its association with FANCD2/FANCI, FAN1 in DT40 cells participates in the processing of damage induced by interstrand cross-linking-generating agents also independently of the classical FA pathway.

Cytogenetic study of the effect of Schistosoma mansoni infection on human peripheral blood lymphocytes and the role of β-carotene and vitamin E in modulating this effect

This study has been made to determine the potential genotoxicity of Schistosoma mansoni on lymphocytes of infected patients using different mutagenic end points. The protective role of antioxidants pro vitamin β-carotene and vitamin E in minimizing these genotoxic effect was also studied. The study focused on the effect of schistosomiasis on the induction of sister chromatid exchange (SCEs) and other chromosomal aberrations. This work was conducted on 24 Schistosoma mansoni infected patients and 10 healthy adults as a control group. Lymphocytes from peripheral blood of patients and control group were used for culture and subsequent cytogenetic studies. The results indicated that schistosomiasis was genotoxic in all examined tests. It induced a significant increase in the percentage of structural chromosomal aberrations and the frequency of SCEs. It also inhibited cell division and caused cell cycle delay. Lymphocyte cultures of S. mansoni patients treated with 10 μg/ml β-carotene or 20mg/ml vitamin E showed a significant decrease in the percentage of structural chromosomal aberrations and the frequency of SCEs. Schistosomiasis has a genotoxic effect on peripheral blood lymphocytes. The use of the antioxidants β-carotene and vitamin E can be considered a promising approach not only toward inhibiting the genetic damage of schistosomiasis but also as prophylactic agents against infection with S mansoni. Furthermore, higher doses of antioxidant drugs, β-carotene and vitamin E, should be tried as an adjuvants to conventional therapy in a trial to improve treatment of schistosomiasis.

Induction of SCEs and DNA fragmentation in bovine peripheral lymphocytes by in vitro exposure to tolylfluanid-based fungicide

The potential for genotoxic and cytotoxic effects of tolylfluanid-based fungicide (50% active agent) was evaluated using sister chromatid exchange (SCE) and proliferation indices (PI) in cultured bovine peripheral lymphocytes. For the detection of possible genetic damage, DNA fragmentation assay was also applied. Bovine lymphocytes cultured for 72 h were treated with the fungicide at the final concentrations of 1.75, 3.5, 8.75, and 17.5 μg/mL for the last 24 and 48 h of culture without S9 metabolic activation, and during the last 2 h of culture with S9 metabolic activation. In the SCE assays no evidence for genotoxic activity of the fungicide was found in treatments of 24 h without and 2 h with S9. After the 24 h exposure to tolylfluanid, a weak decrease in the PI was observed. With the prolonged exposure time (48 h), dose dependence in the increase of SCE frequencies was observed. Moreover, after 48 h exposure slight fragmentation of DNA at the concentrations of 3.5 and 8.75 μg/mL was demonstrated. SCE quantification is the most widely used approach for the assessment of genotoxic/cytogenetic effects of chemical compounds. Positive results in the assay at 48 h exposure indicated a potential of the fungicide to increase frequency of chromosomal damage (replication injuries) that is the confirmation of early effect of exposure.

Atypically low spontaneous sister chromatid exchange formation in uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular cancer of adults and is characterized by several well-established chromosomal changes. More recently, a specific mutation of guanine nucleotide binding protein Gq alpha subunit (GNAQ) has also been identified in a proportion of UM. Although some of these alterations have been suggested to be early changes, the genetic alterations responsible for the development of UM have yet to be clearly determined. Cancers are characterized by increased genetic instability, and analysis of established cancer cell lines and blood from cancer patients has universally been associated with an increased level of sister chromatid exchange (SCE). We have observed that the spontaneous frequency of SCE in primary cultures of UM and UM-derived cell lines is decreased below normal baseline levels, a phenomenon unique to UM when compared with multiple other cancers. This finding was specific to the tumor and not found in lymphocytes from the patients. Although we cannot exclude the possibility that low SCE (LSCE) is peculiar to the uveal melanocytes lineage, as it was consistently observed in all UM studied, regardless of other genetic defects, we propose that this phenomenon contributes to the molecular pathogenesis of UM.

Deletion of the nuclear isoform of poly(ADP-ribose) glycohydrolase (PARG) reveals its function in DNA repair, genomic stability and tumorigenesis

Poly(ADP-ribose) metabolism, mediated mainly by poly(ADP-ribose) polymerase (PARP) 1 and poly(ADP-ribose) glycohydrolase (PARG), regulates various cellular processes in response to genotoxic stress. PARP1 has been shown to be important in multiple cellular processes, including DNA repair, chromosomal stability, chromatin function, apoptosis and transcriptional regulation. However, whether PARP1's polymer synthesizing activity or polymer homeostasis is responsible for these functions remains largely unknown. Given a concerted action of multiple PARPs and unique PARG in the homeostasis of poly(ADP-ribosyl)ation, PARG is hypothesized to function in these processes. The lethal phenotype of the PARG null mutation in mouse embryos, however, hampers further investigation on biological function of PARG. Here, we show that mouse embryonic fibroblasts carrying a hypomorphic mutation of PARG, i.e. lacking the nuclear 110 kD isoform (PARG(110)(-/-)), have defects in the repair of DNA damage caused by various genotoxic agents. PARG(110)(-/-) cells exhibit genomic instability, characterized by a high frequency of sister chromatid exchange, micronuclei formation and chromosomal aberrations. Moreover, mutant cells contain supernumerary centrosomes, another hallmark of genomic instability, which correlates with an accumulation of S-phase cells after replication poison. Intriguingly, PARG(110)(-/-) cells accumulate more Rad51 foci in response to hydroxyurea, indicative of a defective repair of replication fork damage. Finally, PARG(110)(-/-) mice are susceptible to diethylnitrosamine-induced hepatocellular carcinoma. These data demonstrate that the homeostasis of poly(ADP-ribosyl)ation is important for an efficient DNA repair of damaged replication forks and for stabilizing the genome, thereby preventing carcinogenesis.

Sister Chromatid Exchange Frequency in Early Embryos and Offspring Derived from IVF or ICSI in Mice

To demonstrate chromosomal injuries associated with in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), sister chromatid exchange (SCE), an indicator of DNA damage, was investigated and the cytogenetic influence of embryonic manipulation on chromosomes of early embryos and offspring was investigated. SCE analysis was performed in early embryos and offspring obtained by IVF, ICSI, or in vivo fertilization (control). To label chromosomes of early embryos, the embryos were cultured in BrdU-supplemented medium for 2 cell cycles. For offspring, BrdU solution was repeatedly injected intraperitoneally. Chromosome samples prepared from the embryos and the bone marrow cells of offspring were stained by the Fluorescence plus Giemsa (FPG) method. In the IVF and ICSI groups, the rates of early development, implantation and offspring were lower than those in the control group. The SCE frequency of early embryos was significantly higher in the IVF and ICSI groups than in the control group (P < 0.05). In contrast, the SCE frequency of offspring in the IVF and ICSI groups was not significantly different from that in the control group. These findings suggest that embryos having serious DNA damage due to embryonic manipulation may be eliminated in a relatively early developmental step and may not reach term.

Sister chromatid exchange (SCE) and high-frequency cells (HFC) in peripheral blood lymphocytes of healthy Tunisian smokers

Cigarette smoking is a major public health problem in Tunisia as it concerns up to 30–35% of the adult population, raising important national issues on tobacco-related disease. The aim of this study was to establish whether cigarette smoking increases sister chromatid exchange (SCE) in peripheral blood lymphocytes of smokers (n=14) compared with non-smokers (n=15) in Sfax, Tunisia. The smokers were subdivided in two subgroups according to the duration of the smoking habit: heavy smokers (>10 years) and light smokers (≤10 years). After signing a consent form, volunteers provided a blood sample (5ml) to establish cell cultures during 72h. For SCE analysis, 30 second-division metaphases were examined from each subject. We determined the frequency of SCE, the percentage of high-frequency cells (HFC) and that of the high-frequency cell individual (HFI). The results show a significantly higher SCE frequency in smokers (8.65±1.43) than in non-smokers (7.16±1.3; p<0.01). A significant difference in SCE frequency was also shown when comparing the two subgroups of smokers (p<0.05). Interestingly, no significant difference was found when comparing the light smokers with non-smokers (7.82±1 vs 7.16±1.3, respectively, p>0.05). The percentages of HFC and HFI were significantly higher in smokers (11.2±7.8% and 78.6%, respectively) than in non-smokers (4±2.2% and 20%, respectively, p<0.01). Our study indicates that the genotoxic effects in lymphocytes from healthy Tunisian smokers are most likely caused by cigarette-smoke constituents. This effect was mainly observed in smokers who had been smoking during more than 10 years. These results provide scientific evidence to urge the prevention of tobacco consumption.

Susceptibility to the cytogenetic effects of dichloromethane is related to the glutathione S-transferase theta phenotype

The carcinogenicity of dichloromethane (DCM) has been demonstrated by mutagenicity studies using bacteria and yeasts and using animal bioassays. Epidemiological studies indicate that exposure to DCM increases the incidences of liver and pancreas cancers. In the present study, we determine whether DCM generates DNA damage in human peripheral blood mononuclear cells (PBMCs) and whether that process depends on glutathione S-transferase theta (GSTT)-1 activity. GSTT1 is one of the enzymes that biotransforms DCM. To this end, PBMC cultures from healthy men were treated with DCM (15–500 ppm) for 72 h. Cell cultures were harvested and processed according to classical cytogenetic techniques. The frequency of sister chromatid exchanges (SCEs), the mitotic index (MI), the cell proliferation kinetic (CPK) value, and the level of GSTT1 activity were determined. DCM exposure decreased the MI in a dose-dependent manner in all individuals tested (20). The CPK value decreased from 125 ppm DCM, and the SCEs frequency increased from 60 ppm DCM. A significantly different response was observed when the group of individuals with low GSTT1 enzymatic activity (4 individuals), the group with medium GSTT1 activity (10 individuals), and the group of individuals with high GSTT1 enzymatic activity (6 individuals) were compared (0.077 ± 0.0124, 0.325 ± 0.0269, and 7.365 ± 1.3474 nmol HCOH/min/mg protein, respectively). These differences were reflected in the amount of change for all of the evaluated cytogenetic parameters ( p < 0.05, ANOVA) and indicated a clear susceptibility to DCM genotoxic effects related to GSTT1 activity because the cytogenetic effects were directly related to the GSTT1-specific activity. DCM was highly cytotoxic in PBMCs, even at doses within the safety range. Due to this toxicity, a review of the maximal limits for occupational exposure to DCM is advised.

Increased frequency of sister chromatid exchanges and decrease in cell viability and proliferation kinetics in human peripheral blood lymphocytes after in vitro exposure to whole bee venom

The present study was aimed to investigate the impact of bee venom on frequency of sister chromatid exchanges (SCE) and viability in human peripheral blood lymphocytes in vitro. In addition, the proportion of lymphocytes that undergo one, two or three cell divisions as well as proliferative rate index (PRI) have been determined. Aqueous solution of whole bee venom was added to whole blood samples in concentrations ranging from 0.1 μg/mL to 20 μg/mL in different lengths of time. Results showed that whole bee venom inhibited cell viability, resulting in a 22.86 ± 1.14% and 51.21 ± 0.58% reduction of viable cells at 1 hour and 6 hours, respectively. The mean SCE per cell in all the exposed samples was significantly higher than in the corresponding controls. In addition, the percentage of high frequency cells (HFC) for each sample was estimated using the pooled distribution of all SCE measurements. This parameter was also significantly higher compared to the control. Inhibition of proliferation was statistically significant for both exposure times and concentrations and was time and dose dependent. These data indicate that whole bee venom inhibited cell proliferation, resulting in a 36.87 ± 5.89% and 38.43 ± 1.96% reduction of proliferation at 1 hour and 6 hours, respectively. In conclusion, this report demonstrated that whole bee venom is capable of inducing DNA alterations by virtue of increasing sister chromatid exchanges in addition to the cell viability decrease and inhibition of proliferation kinetics in human peripheral blood lymphocytes in vitro.

The efficiacy of bismuth subnitrate against genotoxicity and oxidative stress induced by aluminum sulphate

Aluminum (Al) is commonly used in industrial processes and drugs and is thought to induce erythrocytes damage via activation of oxidative stress. Recently, bismuth (Bi)-containing drugs are used in the treatment of various diseases. However, uncertain effects of Bi in blood tissue may participate in the therapeutic efficacy of Bi compounds as related to metals. Hence, this study aimed to determine the roles on human blood cells of the various concentrations of aluminum sulphate (Al(2)(SO(4))(3)) and bismuth subnitrate (BSN), separate and together. With this aim, oxidative status was assessed on erythrocytes by measuring following oxidative stress markers: reduced glutathione (GSH), superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G-6-PDH) and catalase (CAT). Two chemicals were tested for their ability to induce cytogenetic change in human lymphocytes using assays for chromosome aberrations (CAs) and sister chromatid exchanges (SCEs). Our results showed that high dose of Al(2)(SO(4))(3) (20 µg/mL) caused oxidative stress and increased CA and SCE frequencies. Whereas, BSN doses did not change CA and SCE rates. Moreover, it led to changes of antioxidant capacity at different concentrations. After concomitant treatment with Al(2)(SO(4))(3) and BSN, the effects of BSN doses were different on enzyme activities and decreased the genotoxic damage. However, the high dose of BSN and Al(2)(SO(4))(3) was shown to enhance the frequencies of CAs and SCEs in a synergistic manner. In conclusion, BSN could be effective in the protection against the blood toxicity of Al(2)(SO(4))(3).

Genotoxic and cytotoxic in vitro evaluation of ivermectin and its formulation ivomec® on Aedes albopictus larvae (CCL-126™) cells

Genotoxic effects of ivermectin (IVM) and its commercial formulation ivomec® (IVM 1.0%) were studied on Aedes albopictus larvae (CCL-126™) cells by sister chromatid exchange (SCE) and single cell gel electrophoresis (SCGE) while cytotoxicity was determined by cell-cycle progression (CCP), proliferative rate index (PRI), mitotic index (MI), 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and neutral red (NR) endpoints within a 1–250 µg mL−1 concentration range. While IVM and ivomec® did not markedly affect SCE frequencies, these agents induced DNA-strand breaks enhancing both slightly damaged and damaged cells at 25–50 and 5–50 µg mL−1 IVM and ivomec®, respectively. Both compounds exerted a delay in CCP and reduction of PRI at 10 µg mL−1. Cytotoxicity was observed at concentrations higher than 25 µg mL−1. A marked reduction of about 98% and 94% of MI compared to controls was noted with 25 µg mL−1 of IVM and ivomec®, respectively. NR and MTT assays revealed that both compounds induced a cell growth inhibition within the 1–250 µg mL−1 concentration range. Data indicated that IVM and ivomec® exert both genotoxicity and cytotoxicity in insect cells in vitro, at least in A. albopictus larvae CCL-126™ cells.

Assessment of genotoxicity of waterpipe and cigarette smoking in lymphocytes using the sister‐chromatid exchange assay: A comparative study

Tobacco smoking is a major world health problem. Recently, waterpipe smoking has become more popular in many countries. Although the genotoxicity associated with cigarette smoking has been extensively investigated, studies evaluating such toxicity in waterpipe users are still lacking. In this study, we examined the genotoxicity of waterpipe smoking in lymphocytes compared with the genotoxicity of cigarette smoking. Genotoxicity was evaluated using the sister chromatid exchanges (SCEs) assay. Fifty waterpipe smokers and 18 healthy nonsmokers participated in this study. Additionally, 18 heavy cigarette smokers (CS) were recruited for comparison. The results show that waterpipe smoking and cigarette smoking significantly increase the frequencies of SCEs (P < 0.01) compared with those of nonsmokers, indicating the genotoxic effect of tobacco smoking. In addition, frequencies of SCEs were significantly higher among waterpipe smokers compared with CS (P < 0.01), indicating that waterpipe smoking is more genotoxic than cigarette smoking. Moreover, the frequency of SCEs increased with the extent of waterpipe use. In conclusion, waterpipe smoking is genotoxic to lymphocytes and the magnitude of its genotoxicity is higher than that induced by regular cigarette smoking.

Hyper telomere recombination accelerates replicative senescence and may promote premature aging

Werner syndrome and Bloom syndrome result from defects in the RecQ helicases Werner (WRN) and Bloom (BLM), respectively, and display premature aging phenotypes. Similarly, XFE progeroid syndrome results from defects in the ERCC1-XPF DNA repair endonuclease. To gain insight into the origin of cellular senescence and human aging, we analyzed the dependence of sister chromatid exchange (SCE) frequencies on location [i.e., genomic (G-SCE) vs. telomeric (T-SCE) DNA] in primary human fibroblasts deficient in WRN, BLM, or ERCC1-XPF. Consistent with our other studies, we found evidence of elevated T-SCE in telomerase-negative but not telomerase-positive backgrounds. In telomerase-negative WRN-deficient cells, T-SCE-but not G-SCE-frequencies were significantly increased compared with controls. In contrast, SCE frequencies were significantly elevated in BLM-deficient cells irrespective of genome location. In ERCC1-XPF-deficient cells, neither T- nor G-SCE frequencies differed from controls. A theoretical model was developed that allowed an in silico investigation into the cellular consequences of increased T-SCE frequency. The model predicts that in cells with increased T-SCE, the onset of replicative senescence is dramatically accelerated even though the average rate of telomere loss has not changed. Premature cellular senescence may act as a powerful tumor-suppressor mechanism in telomerase-deficient cells with mutations that cause T-SCE levels to rise. Furthermore, T-SCE-driven premature cellular senescence may be a factor contributing to accelerated aging in Werner and Bloom syndromes, but not XFE progeroid syndrome.

Genotoxicity of barley stripe mosaic virus in infected host plants

Abstract A comparative study of the effect of barley stripe mosaic virus (BSMV) and gamma irradiation on mitotic divisions in barley (Hordeum vulgare L.) roots was performed by evaluating the mitotic index (MI), micronucleus (MN) frequency and sister chromatid exchanges (SCE). Results indicate that, similarly to gamma irradiation at doses of 100, 150 and 250 Gy, BSMV reduces the mitotic activity, increases the micronucleus frequency and the rate of SCE and promotes the formation of C-metaphases. In root meristematic cells of the three barley cultivars studied (Galactic, Sonor and Unirea), the mitotic index of infected plants was found to be 52.5, 54.48 and 64.17%, respectively, lower than the uninfected control. An increase in frequency of sister chromatid exchanges was observed in all the experimental variants. In treatments involving viral infection alone or in combination with gamma irradiation chromosomes with three and more chromatid exchanges were observed, while their percentage in the control or in treatments with gamma irradiation alone was reduced. The results of the study indicate that in plants derived from irradiated seeds, BSMV produces an effect that is correlated nonlinearly with the radiation dose applied. Cytological analysis of mitotic divisions in barley roots revealed the genotoxicity of BSMV infection.

The R438W polymorphism of human DNA polymerase lambda triggers cellular sensitivity to camptothecin by compromising the homologous recombination repair pathway

The human DNA polymerase lambda (Polλ) is a DNA repair polymerase, which is believed not only to play a role in base excision repair but also to contribute to DNA double-strand break repair by non-homologous end joining. We described here that cellular expression of the recently described natural polymorphic variant of Polλ, Polλ(R438W), affects the homologous recombination (HR) pathway and sister chromatid exchange (SCE) events. We show that the HR defect provoked by this polymorphism enhances cellular sensitivity to the anticancer agent camptothecin (CPT), most of whose DNA damage is repaired by HR. All these effects were dependent on the DNA polymerase activity of Polλ(R438W) as the expression of a catalytically inactive Polλ(R438W) did not affect either the HR and SCE frequencies or the cellular sensitivity to CPT. These results suggest that sensitivity to CPT could result from cancer-related mutation in specialized DNA repair polymerases.

Genomic instability in patients with Barrett's esophagus

Our study aimed to determine, by counting sister chromatid exchange (SCE) and micronucleus (MN) frequencies, whether genetic impairment and DNA damage have an effect on the pathogenesis of Barrett's esophagus (BE). This study was conducted between June 2007 and November 2008 in the Erzurum Training and Research Hospital. We analyzed SCE and MN frequencies in 30 patients with BE, and in 30 control cases. SCE was significantly increased in BE patients compared with controls (6.89 ± 1.04 vs. 5.01± 0.88, P < 0.001). Similarly, MN was significantly increased in BE patients compared with controls (3.48 ± 1.08 vs. 1.83 ± 0.64, P < 0.001). Our data indicate that the increased SCE and MN rates in lymphocytes of patients with BE may reflect genomic instability or deficiency of DNA repair capacity.

The effects of some boron compounds against heavy metal toxicity in human blood

Heavy metals can accumulate in the environment and cause serious damages to ecosystems and human health. Boron is considered to be essential micronutrient with its well established biological functions and the antioxidant effects of boric acid (BA) are controversial. However, the potential of important boron compounds in cellular activities remains unexplored. Therefore, we aimed to assess the efficacies of some boron compounds (BA, borax, colemanite and ulexite) on the genotoxicity induced by heavy metals (arsenic trioxide, colloidal bismuth subcitrate, cadmium chloride, mercury chloride and lead chloride) in human blood cultures. For this aim, sister chromatid exchange (SCE) and micronuclei (MN) assays were performed to establish DNA damages in lymphocytes. Besides, oxidative stress was monitored by estimating the changes of main antioxidant enzyme activities and the levels of total glutathione (TGSH) in erythrocytes. The present study showed that heavy metal treatments increased the frequencies of SCE and MN and the plasma malondialdehyde (MDA) level; decreased the antioxidant enzyme activities and the level of TGSH compared to controls. Whereas, the tested boron compounds (5–20 ppm) significantly reduced the genotoxic effects induced by low doses of heavy metals. Our results revealed that the protective roles of boron compounds occurred with the effectiveness on their anti-oxidant capacity. In conclusion, these compounds could be useful in the development of functional food and raw materials of medicine.

In vitro effect of the antimalarial drug proguanil hydrochloride on viability and DNA damage in human peripheral blood lymphocytes

This study aimed to evaluate the effect of proguanil, a chemical substance used for treatment and prevention of malaria on viability and DNA integrity in human lymphocytes in vitro. Two different concentrations of proguanil obtained from the plasma concentrations were used: 130 ng/ml used for prophylactic treatment and 520 ng/ml used in treatment of malaria. Testing was done with and without metabolic activation. Viability of lymphocytes decreased in time and dose dependent manner. Comet assay parameters showed similar effects, indicating that some damage to DNA molecule can occur. Frequency of sister chromatid exchanges did not show significant deviation from the control samples. As for the proliferation kinetics no significant changes were noticed. Since majority of DNA damaging effect is induced after metabolic activation it is to be concluded that activity of proguanil is dependent upon the active metabolite cycloguanil and that monitoring should be conducted especially among frequent travellers.

Protective effects of selenium against sister chromatid exchange induced by AFG 1 in human lymphocytes in vitro

Aflatoxins have been shown to be hepatotoxic, carcinogenic, mutagenic and teratogenic to different species of animals. Besides, at low concentrations, Selenium (Se(4+)) is antimutagenic and anticarcinogenic while it is toxic, mutagenic and carcinogenic at high concentrations. In this study, we aimed to evaluate the effect of Se(4+) against aflatoxin GAFG(1) (AFG(1)) on blood cultures in relation to induction of sister chromatid exchange (SCE). The results showed that at 0.4 and 0.8 parts per million (ppm) concentration of AFG(1), the frequency of SCE increased in cultured human lymphocytes. When different concentration of Se(4+) (0.08 and 8 ppm) were added to AFG(1), the frequencies of SCE decreased. Howewer, when 800 ppm concentration of Se(4+) together with 0.08 ppm AFG(1) were added to cell division inhibited in the cultures. Results suggested that Se(4+) could effectively inhibit AFG(1)-induced SCE. Besides, the protective role of Se(4+) against AFG(1)-induced SCE is probably related to its doses.