Genotoxic effects of occupational exposure to glass fibres - A human biomonitoring study

As part of a large human biomonitoring study, we conducted occupational monitoring in a glass fibre factory in Slovakia. Shopfloor workers (n = 80), with a matched group of administrators in the same factory (n = 36), were monitored for exposure to glass fibres and to polycyclic aromatic hydrocarbons (PAHs). The impact of occupational exposure on chromosomal aberrations, DNA damage and DNA repair, immunomodulatory markers, and the role of nutritional and lifestyle factors, as well as the effect of polymorphisms in metabolic and DNA repair genes on genetic stability, were investigated. The (enzyme-modified) comet assay was employed to measure DNA strand breaks (SBs) and apurinic sites, oxidised and alkylated bases. Antioxidant status was estimated by resistance to H₂O₂-induced DNA damage. Base excision repair capacity was measured with an in vitro assay (based on the comet assay). Exposure of workers to fibres was low, but still was associated with higher levels of SBs, and SBs plus oxidised bases, and higher sensitivity to H₂O₂. Multivariate analysis showed that exposure increased the risk of high levels of SBs by 20%. DNA damage was influenced by antioxidant enzymes catalase and glutathione S-transferase (measured in blood). DNA repair capacity was inversely correlated with DNA damage and positively with antioxidant status. An inverse correlation was found between DNA base oxidation and the percentage of eosinophils (involved in the inflammatory response) in peripheral blood of both exposed and reference groups. Genotypes of XRCC1 variants rs3213245 and rs25487 significantly decreased the risk of high levels of base oxidation, to 0.50 (p = 0.001) and 0.59 (p = 0.001), respectively. Increases in DNA damage owing to glass fibre exposure were significant but modest, and no increases were seen in chromosome aberrations or micronuclei. However, it is of concern that even low levels of exposure to these fibres can cause significant genetic damage.

A pooled analysis of molecular epidemiological studies on modulation of DNA repair by host factors

Levels of DNA damage represent the dynamics between damage formation and removal. Therefore, to better interpret human biomonitoring studies with DNA damage endpoints, an individual's ability to recognize and properly remove DNA damage should be characterized. Relatively few studies have included DNA repair as a biomarker and therefore, assembling and analyzing a pooled database of studies with data on base excision repair (BER) was one of the goals of hCOMET (EU-COST CA15132). A group of approximately 1911 individuals, was gathered from 8 laboratories which run population studies with the comet-based in vitro DNA repair assay. BER incision activity data were normalized and subsequently correlated with various host factors. BER was found to be significantly higher in women. Although it is generally accepted that age is inversely related to DNA repair, no overall effect of age was found, but sex differences were most pronounced in the oldest quartile (>61 years). No effect of smoking or occupational exposures was found. A body mass index (BMI) above 25 kg/m² was related to higher levels of BER. However, when BMI exceeded 35 kg/m², repair incision activity was significantly lower. Finally, higher BER incision activity was related to lower levels of DNA damage detected by the comet assay in combination with formamidopyrimidine DNA glycosylase (Fpg), which is in line with the fact that oxidatively damaged DNA is repaired by BER. These data indicate that BER plays a role in modulating the steady-state level of DNA damage that is detected in molecular epidemiological studies and should therefore be considered as a parallel endpoint in future studies.

DNA damage in circulating leukocytes measured with the comet assay may predict the risk of death

The comet assay or single cell gel electrophoresis, is the most common method used to measure strand breaks and a variety of other DNA lesions in human populations. To estimate the risk of overall mortality, mortality by cause, and cancer incidence associated to DNA damage, a cohort of 2,403 healthy individuals (25,978 person-years) screened in 16 laboratories using the comet assay between 1996 and 2016 was followed-up. Kaplan–Meier analysis indicated a worse overall survival in the medium and high tertile of DNA damage (p < 0.001). The effect of DNA damage on survival was modelled according to Cox proportional hazard regression model. The adjusted hazard ratio (HR) was 1.42 (1.06–1.90) for overall mortality, and 1.94 (1.04–3.59) for diseases of the circulatory system in subjects with the highest tertile of DNA damage. The findings of this study provide epidemiological evidence encouraging the implementation of the comet assay in preventive strategies for non-communicable diseases.

DNA repair gene polymorphisms and chromosomal aberrations in healthy, nonsmoking population

Nonspecific structural chromosomal aberrations (CAs) can be found at around 1% of circulating lymphocytes from healthy individuals but the frequency may be higher after exposure to carcinogenic chemicals or radiation. The frequency of CAs has been measured in occupational monitoring and an increased frequency of CAs has also been associated with cancer risk. Alterations in DNA damage repair and telomere maintenance are thought to contribute to the formation of CAs, which include chromosome type of aberrations and chromatid type of aberrations. In the present study, we used the result of our published genome-wide association studies to extract data on 153 DNA repair genes from 866 nonsmoking persons who had no known occupational exposure to genotoxic substances. Considering an arbitrary cut-off level of P< 5 × 10^-3, single nucleotide polymorphisms (SNPs) tagging 22 DNA repair genes were significantly associated with CAs and they remained significant at P < 0.05 when adjustment for multiple comparisons was done by the Binomial Sequential Goodness of Fit test. Nucleotide excision repair pathway genes showed most associations with 6 genes. Among the associated genes were several in which mutations manifest CA phenotype, including Fanconi anemia, WRN, BLM and genes that are important in maintaining genome stability, as well as PARP2 and mismatch repair genes. RPA2 and RPA3 may participate in telomere maintenance through the synthesis of the C strand of telomeres. Errors in NHEJ1 function may lead to translocations. The present results show associations with some genes with known CA phenotype and suggest other pathways with mechanistic rationale for the formation of CAs in healthy nonsmoking population.

The hCOMET project: International database comparison of results with the comet assay in human biomonitoring. Baseline frequency of DNA damage and effect of main confounders

The alkaline comet assay, or single cell gel electrophoresis, is one of the most popular methods for assessing DNA damage in human population. One of the open issues concerning this assay is the identification of those factors that can explain the large inter-individual and inter-laboratory variation. International collaborative initiatives such as the hCOMET project - a COST Action launched in 2016 - represent a valuable tool to meet this challenge. The aims of hCOMET were to establish reference values for the level of DNA damage in humans, to investigate the effect of host factors, lifestyle and exposure to genotoxic agents, and to compare different sources of assay variability. A database of 19,320 subjects was generated, pooling data from 105 studies run by 44 laboratories in 26 countries between 1999 and 2019. A mixed random effect log-linear model, in parallel with a classic meta-analysis, was applied to take into account the extensive heterogeneity of data, due to descriptor, specimen and protocol variability. As a result of this analysis interquartile intervals of DNA strand breaks (which includes alkali-labile sites) were reported for tail intensity, tail length, and tail moment (comet assay descriptors). A small variation by age was reported in some datasets, suggesting higher DNA damage in oldest age-classes, while no effect could be shown for sex or smoking habit, although the lack of data on heavy smokers has still to be considered. Finally, highly significant differences in DNA damage were found for most exposures investigated in specific studies. In conclusion, these data, which confirm that DNA damage measured by the comet assay is an excellent biomarker of exposure in several conditions, may contribute to improving the quality of study design and to the standardization of results of the comet assay in human populations.

DNA Repair Gene Polymorphisms and Chromosomal Aberrations in Exposed Populations

DNA damage and unrepaired or insufficiently repaired DNA double-strand breaks as well as telomere shortening contribute to the formation of structural chromosomal aberrations (CAs). Non-specific CAs have been used in the monitoring of individuals exposed to potential carcinogenic chemicals and radiation. The frequency of CAs in peripheral blood lymphocytes (PBLs) has been associated with cancer risk and the association has also been found in incident cancer patients. CAs include chromosome-type aberrations (CSAs) and chromatid-type aberrations (CTAs) and their sum CAtot. In the present study, we used data from our published genome-wide association studies (GWASs) and extracted the results for 153 DNA repair genes for 607 persons who had occupational exposure to diverse harmful substances/radiation and/or personal exposure to tobacco smoking. The analyses were conducted using linear and logistic regression models to study the association of DNA repair gene polymorphisms with CAs. Considering an arbitrary cutoff level of 5 × 10^-3, 14 loci passed the threshold, and included 7 repair pathways for CTA, 4 for CSA, and 3 for CAtot; 10 SNPs were eQTLs influencing the expression of the target repair gene. For the base excision repair pathway, the implicated genes PARP1 and PARP2 encode poly(ADP-ribosyl) transferases with multiple regulatory functions. PARP1 and PARP2 have an important role in maintaining genome stability through diverse mechanisms. Other candidate genes with known roles for CSAs included GTF2H (general transcription factor IIH subunits 4 and 5), Fanconi anemia pathway genes, and PMS2, a mismatch repair gene. The present results suggest pathways with mechanistic rationale for the formation of CAs and emphasize the need to further develop techniques for measuring individual sensitivity to genotoxic exposure.

Impact of genetic polymorphisms in kinetochore and spindle assembly genes on chromosomal aberration frequency in healthy humans

Genomic instability is a characteristic of a majority of human malignancies. Chromosomal instability is a common form of genomic instability that can be caused by defects in mitotic checkpoint genes. Chromosomal aberrations in peripheral blood are also indicative of genotoxic exposure and potential cancer risk. We evaluated associations between inherited genetic variants in 33 mitotic checkpoint genes and the frequency of chromosomal aberrations (CAs) in the presence and absence of environmental genotoxic exposure. Associations with both chromosome and chromatid type of aberrations were evaluated in two cohorts of healthy individuals, namely an exposed and a reference group consisting of 607 and 866 individuals, respectively. Binary logistic and linear regression analyses were performed for the association studies. Bonferroni-corrected significant p-value was 5 × 10^-4 for 99 tests based on the number of analyzed genes and phenotypes. In the reference group the most prominent associations were found with variants in CCNB1, a master regulator of mitosis, and in genes involved in kinetochore function, including CENPH and TEX14, whereas in the exposed group the main association was found with variants in TTK, also an important gene in kinetochore function. How the identified variants may affect the fidelity of mitotic checkpoint remains to be investigated, however, the present study suggests that genetic variation may partly explain interindividual variation in the formation of CAs.

Distinct pathways associated with chromosomal aberration frequency in a cohort exposed to genotoxic compounds compared to general population

Non-specific structural chromosomal aberrations (CAs) observed in peripheral blood lymphocytes of healthy individuals can be either chromosome-type aberrations (CSAs) or chromatid-type aberrations (CTAs) depending on the stage of cell division they are induced in and mechanism of formation. It is important to study the genetic basis of chromosomal instability as it is a marker of genotoxic exposure and a predictor of cancer risk. For that purpose, we conducted two genome-wide association studies (GWASs) on healthy individuals in the presence and absence of apparent genotoxic exposure from the Czech Republic and Slovakia. The pre-GWAS cytogenetic analysis reported the frequencies of CSA, CTA and total CA (CAtot). We performed both linear and binary logistic regression analysis with an arbitrary cut-off point of 2% for CAtot and 1% for CSA and CTA. Using the statistical threshold of 1.0 × 10-5, we identified five loci with in silico predicted functionality in the reference group and four loci in the exposed group, with no overlap between the associated regions. A meta-analysis on the two GWASs identified further four loci with moderate associations in each of the studies. From the reference group mainly loci within genes related to DNA damage response/repair were identified. Other loci identified from both the reference and exposed groups were found to be involved in the segregation of chromosomes and chromatin modification. Some of the discovered regions in each group were implicated in tumourigenesis and autism.

Titanium dioxide nanoparticles tested for genotoxicity with the comet and micronucleus assays in vitro, ex vivo and in vivo

The genotoxicity of TiO₂ nanoparticles (NPs) was assessed with the cytokinesis-block micronucleus (CBMN) assay in TK6 lymphoblastoid cells, lymphocytes from human volunteers, and bone marrow erythrocytes from rats exposed in vivo; and with the comet assay (detecting both strand breaks and oxidised purines) in human and rat peripheral blood mononuclear cells (PBMCs). NPs were dispersed using three different methods giving different size distribution and stability. On average, TiO₂ NPs caused no increase in micronuclei in TK6 cells, rat bone marrow erythrocytes or human lymphocytes (though lymphocytes from 3 out of 13 human subjects showed significant increases). PBMCs from rats treated in vivo with a single dose of NPs dispersed by a method with low agglomeration showed an increase in strand breaks after 1 day. TiO₂ NPs dispersed in a stable, non-agglomerated state induced DNA strand breaks at 75 μg/cm² after 4 h exposure of human PBMCs and at 15 μg/cm² and 75 μg/cm² after 24 h exposure, but no increase in DNA oxidation was seen. Overall, NPs in an agglomerated state did not cause DNA damage. However, at the individual level, significant increases in strand breaks were seen in PBMCs from most of the volunteers. Cells from one volunteer showed positive effects in all conditions and both tests, while cells from another volunteer appeared to be completely resitant to TiO₂ NPs. The implication is that some individuals may be more sensitive than others to effects of this nanomaterial. Differences seen in results obtained with the micronucleus and the comet assay may be due to the mechanisms underlying the genotoxic effects of TiO₂ NPs and the different endpoints represented by the two assays.

Genetic variation associated with chromosomal aberration frequency: A genome-wide association study

Chromosomal aberrations (CAs) in human peripheral blood lymphocytes (PBL) measured with the conventional cytogenetic assay have been used for human biomonitoring of genotoxic exposure for decades. CA frequency in peripheral blood is a marker of cancer susceptibility. Previous studies have shown associations between genetic variants in metabolic pathway, DNA repair and major mitotic checkpoint genes and CAs. We conducted a genome-wide association study on 576 individuals from the Czech Republic and Slovakia followed by a replication in two different sample sets of 482 (replication 1) and 1288 (replication 2) samples. To have a broad look at the genetic susceptibility associated with CA frequency, the sample sets composed of individuals either differentially exposed to smoking, occupational/environmental hazards, or they were untreated cancer patients. Phenotypes were divided into chromosome- and chromatid-type aberrations (CSAs and CTAs, respectively) and total chromosomal aberrations (CAtot). The arbitrary cutoff point between individuals with high and low CA frequency was 2% for CAtot and 1% for CSA and CTA. The data were analyzed using age, sex, occupation/cancer and smoking history as covariates. Altogether 11 loci reached the P-value of 10^-5 in the GWAS. Replication 1 supported the association of rs1383997 (8q13.3) and rs2824215 (21q21.1) in CAtot and rs983889 (5p15.1) in CTA analysis. These loci were found to be associated with genes involved in mitosis, response to environmental and chemical factors and genes involved in syndromes linked to chromosomal abnormalities. Identification of new genetic variants for the frequency of CAs offers prediction tools for cancer risk in future. Environ. Mol. Mutagen. 60:17-28, 2019. © 2018 Wiley Periodicals, Inc.

Respiratory toxicity of Fe3O4 nanoparticles: experimental study

INTRODUCTION

In the medical field, nanoparticles (NP) Fe3O4 are currently considered to be a relatively inert carrier for therapeutic and diagnostic pharmaceuticals, and they are also presumed for intravenous (i.v.) administration. Because they have nano dimensions, they probably can penetrate through various membranes and pass from the bloodstream to other organs in the body (Borm P, Muller-Schulte D. Nanoparticles in medicine, 2007, Chapter 21, pp. 387-413, Particle Toxicology, ed. Donaldson K, Borm P, Taylor & Francis Group, USA, 434 p., ISBN 0-8493-5092-1). Therefore, in our experiment, we have examined the impact of a NP Fe3O4 instilled i.v. (to a tail vein of an animal) on the select parameters of bronchoalveolar lavage (BAL). The aim of our study was to determine whether the NP investigated by us, pass through the vascular system to the respiratory tract, and if so, how they affect the selected inflammatory and cytotoxic parameters of BAL.

MATERIALS AND METHODS

Wistar rats were intravenously given a suspension of Fe3O4 and after time intervals of 1, 7, 14 and 28 days, the animals were sacrificed, BAL was performed and selected inflammatory and cytotoxic BAL parameters were examined.

CONCLUSION

Based on the results obtained by us, Fe3O4 NP exposure, compared to the control, induced inflammatory response, the cytotoxic damage and respiratory toxicity. The results further show that Fe3O4 NP, 28 days after i.v. instillation, were eliminated from the respiratory tract by defense mechanisms.

Suitability of human and mammalian cells of different origin for the assessment of genotoxicity of metal and polymeric engineered nanoparticles

Nanogenotoxicity is a crucial endpoint in safety testing of nanomaterials as it addresses potential mutagenicity, which has implications for risks of both genetic disease and carcinogenesis. Within the NanoTEST project, we investigated the genotoxic potential of well-characterised nanoparticles (NPs): titanium dioxide (TiO2) NPs of nominal size 20 nm, iron oxide (8 nm) both uncoated (U-Fe3O4) and oleic acid coated (OC-Fe3O4), rhodamine-labelled amorphous silica 25 (Fl-25 SiO2) and 50 nm (Fl-50 SiO) and polylactic glycolic acid polyethylene oxide polymeric NPs - as well as Endorem® as a negative control for detection of strand breaks and oxidised DNA lesions with the alkaline comet assay. Using primary cells and cell lines derived from blood (human lymphocytes and lymphoblastoid TK6 cells), vascular/central nervous system (human endothelial human cerebral endothelial cells), liver (rat hepatocytes and Kupffer cells), kidney (monkey Cos-1 and human HEK293 cells), lung (human bronchial 16HBE14o cells) and placenta (human BeWo b30), we were interested in which in vitro cell model is sufficient to detect positive (genotoxic) and negative (non-genotoxic) responses. All in vitro studies were harmonized, i.e. NPs from the same batch, and identical dispersion protocols (for TiO2 NPs, two dispersions were used), exposure time, concentration range, culture conditions and time-courses were used. The results from the statistical evaluation show that OC-Fe3O4 and TiO2 NPs are genotoxic in the experimental conditions used. When all NPs were included in the analysis, no differences were seen among cell lines - demonstrating the usefulness of the assay in all cells to identify genotoxic and non-genotoxic NPs. The TK6 cells, human lymphocytes, BeWo b30 and kidney cells seem to be the most reliable for detecting a dose-response.

Towards an alternative testing strategy for nanomaterials used in nanomedicine: lessons from NanoTEST

In spite of recent advances in describing the health outcomes of exposure to nanoparticles (NPs), it still remains unclear how exactly NPs interact with their cellular targets. Size, surface, mass, geometry, and composition may all play a beneficial role as well as causing toxicity. Concerns of scientists, politicians and the public about potential health hazards associated with NPs need to be answered. With the variety of exposure routes available, there is potential for NPs to reach every organ in the body but we know little about the impact this might have. The main objective of the FP7 NanoTEST project ( www.nanotest-fp7.eu ) was a better understanding of mechanisms of interactions of NPs employed in nanomedicine with cells, tissues and organs and to address critical issues relating to toxicity testing especially with respect to alternatives to tests on animals. Here we describe an approach towards alternative testing strategies for hazard and risk assessment of nanomaterials, highlighting the adaptation of standard methods demanded by the special physicochemical features of nanomaterials and bioavailability studies. The work has assessed a broad range of toxicity tests, cell models and NP types and concentrations taking into account the inherent impact of NP properties and the effects of changes in experimental conditions using well-characterized NPs. The results of the studies have been used to generate recommendations for a suitable and robust testing strategy which can be applied to new medical NPs as they are developed.

Immunotoxicity and genotoxicity testing of PLGA-PEO nanoparticles in human blood cell model

A human blood cell model for immunotoxicity and genotoxicity testing was used to measure the response to polylactic-co-glycolic acid (PLGA-PEO) nanoparticle (NP) (0.12, 3, 15 and 75 μg/cm(2) exposure in fresh peripheral whole blood cultures/isolated peripheral blood mononuclear cell cultures from human volunteers (n = 9-13). PLGA-PEO NPs were not toxic up to dose 3 μg/cm(2); dose of 75 μg/cm(2) displays significant decrease in [(3)H]-thymidine incorporation into DNA of proliferating cells after 4 h (70% of control) and 48 h (84%) exposure to NPs. In non-cytotoxic concentrations, in vitro assessment of the immunotoxic effects displayed moderate but significant suppression of proliferative activity of T-lymphocytes and T-dependent B-cell response in cultures stimulated with PWM > CON A, and no changes in PHA cultures. Decrease in proliferative function was the most significant in T-cells stimulated with CD3 antigen (up to 84%). Cytotoxicity of natural killer cells was suppressed moderately (92%) but significantly in middle-dosed cultures (4 h exposure). On the other hand, in low PLGA-PEO NPs dosed cultures, significant stimulation of phagocytic activity of granulocytes (119%) > monocytes (117%) and respiratory burst of phagocytes (122%) was recorded. Genotoxicity assessment revealed no increase in the number of micronucleated binucleated cells and no induction of SBs or oxidised DNA bases in PLGA-PEO-treated cells. To conclude on immuno- and genotoxicity of PLGA-PEO NPs, more experiments with various particle size, charge and composition need to be done.

Associations between environmental factors and incidence of cutaneous melanoma. Review

BACKGROUND

Cutaneous melanoma is one of the most serious skin cancers. It is caused by neural crest-derived melanocytes - pigmented cells normally present in the epidermis and, sometimes, in the dermis.

METHODS

We performed a review of current knowledge on the risk factors of cutaneous melanoma. Relevant studies were identified using the PubMed, Science Direct, Medline, Scopus, Scholar Google and ISI Web of Knowledge databases.

RESULTS

Melanoma incurs a considerable public health burden owing to the worldwide dramatic rise in incidence since the mid-1960s. Ultraviolet radiation exposure is the predominant environmental risk factor. The role of geographical (latitude) and individual factors such as skin type, life style, vitamin D levels and antioxidant protection, sunburn, and exposure to other environmental factors possibly contributing to melanoma risk (such as cosmetics including sunscreen, photosensitising drugs, and exogenous hormones) are reviewed in this article. Recently, both rare high risk susceptibility genes and common polymorphic genes contributing to melanoma risk have been identified.

CONCLUSIONS

Cutaneous melanoma is a complex cancer with heterogeneous aetiology that continues to increase in incidence. Introduction of new biomarkers may help to elucidate the mechanism of pathogenesis and individual susceptibility to the disease, and make both prevention and treatment more effective.

The relationship between cell surface markers, cytokines, ageing, and cigarette smoking

The purpose of this study was to investigate the modulation of selected cell surface markers and proinflammatory cytokines production in relation to ageing, and cigarette smoking. The analysis of cell surface receptors was performed by the flow cytometry and cytokines levels were evaluated by the sandwich enzyme immunoassays. We found a decreased expression of CD69, CD28, CD11b, CD95 markers in old population compared to young people (p<0.05; p<0.001). The memory CD45RO lymphocytes were markedly expanded in older population in comparison to young donors (12.93+/-5.92 %, p<0.001) and the selectin CD62L was significantly increased on granulocytes in aged people (p<0.05). Our findings demonstrated an augmented level of CD3 and CD28 on lymphocytes in smokers (p<0.05; p<0.005). The significant depression of CD16+56 molecule was recorded in smokers (10.86+/-0.80%) when compared to non-smokers (14.44+/-0.46; p<0.05). Our results showed a significantly diminished levels of interleukin (IL)-1beta (1.93+/-0.48 pg/ml), and increased levels of IL-6 and tumor necrosis factor (TNF)-alpha in elderly population compared to young people (p<0.05; p<0.001). The present data support previous suggestions that senescence and cigarette smoking may contribute to changes in the immune system activity, resulting in altered cell surface marker expression and cytokine levels (Tab. 1, Fig. 3, Ref. 81). Full Text (Free, PDF) www.bmj.sk.

Occupational exposure to mineral fibres. Biomarkers of oxidative damage and antioxidant defence and associations with DNA damage and repair

In order to study the effect of mineral wool exposure on oxidative DNA damage and lipid peroxidation, an epidemiological study was conducted in a mineral wool factory in Slovakia. Altogether 141 subjects were investigated (21-58 years old), 43 controls (20 men and 23 women: 27 non-smokers, 16 smokers) and 98 exposed (75 men and 23 women: 61 non-smokers, 37 smokers). We found higher malondialdehyde (MDA) levels in the group of all exposed workers (P = 0.025) and in exposed non-smokers (P = 0.003) and a significantly suppressed activity of ceruloplasmin oxidase (P = 0.02, P < 0.02, respectively) and catalase (CAT) (P = 0.04, P = 0.01, respectively) in these groups. The activity of glutathione S-transferase (GST) was affected by exposure to mineral wool; levels were significantly lower in all exposed subjects (P = 0.04), in the exposed non-smokers (P = 0.03) and in exposed men (P < 0.01). Concentrations of vitamin C in plasma and the ferric-reducing activity of plasma (FRAP) were not affected by the mineral wool exposure. There was a significant negative correlation between the activity of glutathione peroxidase (GPX) and MDA in the whole group (P < 0.01) and in the exposed group and between CAT activity and MDA in all subjects (P < 0.01). GST activity correlated inversely with oxidized pyrimidines in lymphocyte DNA, in almost all subgroups. We found significant negative correlations between DNA repair and GPX in all subjects (P = 0.03) as well as in control men (P < 0.03) and between DNA repair and CAT in all control subjects (P < 0.02) and in control men (P < 0.01). Interestingly, we found a positive correlation between DNA repair and MDA in all subjects (P < 0.01) and in all exposed subjects (P < 0.03). The presented results indicate that mineral wool exposure induces an increase in oxidative damage to biomolecules especially in the group of male non-smokers. However, optimal levels of antioxidants could have a protective effect. Biomarkers such as MDA, antioxidant enzymes and antioxidant vitamins measured in blood may be useful biomarkers of oxidative stress and antioxidant protection. We do not recommend FRAP as a marker of antioxidant status as interference from other constituents can provide false or confusing results. Our study supports the idea that there might also be other mechanisms by which antioxidant enzymes (especially GST) protect cells against oxidative DNA damage.

Multinucleate cells (MNC) as sensitive semiquantitative biomarkers of the toxic effect after experimental fibrous dust and cigarette smoke inhalation by rats

Changes in the counts of binucleate (BNC) and multinucleate cells (MNC) in cell mixtures from lung tissue and bronchoalveolar lavage fluid (BALF) as well as in proportions of four types of BALF cells: Alveolar macrophages (AM), lymphocytes, polymorphonuclears (PMN), BNC and in total BALF protein were followed in a study comparing the toxicity of wollastonite with that of amosite asbestos in Fischer 344 rats. Both of the fibrous dusts were inhaled every second day at 30 or 60 mg/m3 air combined with daily exposure to cigarette smoke at 30 mg of total particulate matter (TPM)/m3 air for 1 h. The exposures lasted 175 days. Both, proportions of BNC as well as of MNC in lung cell mixtures rose significantly after exposure to cigarette smoke only. After inhalation of wollastonite the BNC proportions in all except the lower dust exposure group compared to controls showed a significant rise with the maximal factor value of 2.1 in the higher dust plus smoke exposure group. Wollastonite caused only marginal changes in MNC and other inflammation parameters. After inhalation of amosite at comparing to controls the proportion of BNC rose 8 times in the 30 mg/m3 and 11 times in the 60 mg/m3 exposure group, respectively. The effect of smoking was additive. The proportions of MNC were 39 times higher in the 30 mg/m3 and 41 times higher in the 60 mg/m3 amosite exposure group than in controls. In the higher exposure group the effect of smoking was synergic in that the MNC proportion rose about 58 times over control values from 0.05% up to about 3.0% (99% confidence interval--CI = 2.7-3.3%). The other followed inflammation parameters showed the presence of inflammation in the lung. It could be concluded that wollastonite at the same inhalation exposure concentration caused in rats less toxic effects than amosite, and, that the number of MNC, as well as BNC in lung cell mixtures and in BALF may serve as an important semiquantitative biomarker of inflammation.

The pyridoindole antioxidant stobadine attenuates albuminuria, enzymuria, kidney lipid peroxidation and matrix collagen cross-linking in streptozotocin-induced diabetic rats

The aim of the present study was to investigate the effect of dietary supplementation with the pyridoindole antioxidant stobadine on kidney status and function in streptozotocin-induced diabetic rats. Diabetic male Wistar rats were fed a standard diet for 32 weeks or a diet supplemented with stobadine (0.05% w/w). The diabetic state was characterized by significantly elevated plasma levels of glucose, HbA1c and urea, severe reduction of total body weight and relatively enlarged kidneys. Elevated levels of conjugated dienes were recorded in the diabetic kidney confirming the presence of oxidative stress in diabetic animals. All diabetic rats showed marked proteinuria and albuminuria along with elevated excretion of the enzyme N-acetyl-beta-D-glucosaminidase. Long-term treatment of diabetic animals with stobadine significantly reduced total proteinuria, albuminuria and enzymuria, yet left the overall physical and glycemic status unaffected. It reduced oxidative damage of kidney tissue as shown by decreased conjugated diene level, and decreased matrix collagen cross-linking, as indicated by decreased breaking time values of rat tail tendons. These beneficial effects of stobadine, supported also by histological findings, may be brought about by virtue of the combination of its antioxidant potential with other effects, e.g., the postulated cholesterol-lowering ability or its ability to alter vascular reactivity and reduce the vascular tone.

Ventricular arrhythmias following coronary artery occlusion in rats: is the diabetic heart less or more sensitive to ischaemia?

Rhythm disorders are common complications in diabetic patients, due to their enhanced sensitivity to ischaemia. However, experimental studies are inconsistent, and both higher and lower vulnerability to injury has been reported. Our objectives were to compare susceptibility to ventricular arrhythmias in rats with prolonged duration of diabetes induced by streptozotocin (45 mg/kg, i.v.), utilising two different models. Following 8 weeks, either anaesthetised open-chest rats in vivo or isolated Langendorff-perfused hearts were subjected to 30 min regional zero-flow ischaemia induced by occlusion of LAD coronary artery. In addition, cardiac glycogenolysis and lactate production were measured. In open-chest rats, 90 % of the controls exhibited ventricular tachycardia (VT) which represented 55.4 % of total arrhythmias, whereby only 19.9 % of arrhythmias occurred as VT in 44 % of the diabetic rats (P < 0.05 vs controls). Duration of VT and ventricular fibrillation (VF) was reduced from 35.5 +/- 11.1 and 224.8 +/- 153.9 s in the controls to 4.8 +/- 2.5 and 2.2 +/- 0.2 s in the diabetics, respectively (P < 0.05). Accordingly, severity of arrhythmias (arrhythmia score, AS) was also lower in the diabetics (2.0 +/- 0.38 vs 3.3 +/- 0.3 in the controls; P < 0.05). In the isolated hearts, high incidence of VF was decreased in the diabetic hearts, and although VT occurred in almost all of the diabetic hearts, the duration of VT and VF was substantially shorter (61.5 +/- 14.5 and 5.5 +/- 0.5 s vs 221.5 +/- 37 and 398.5 +/- 55 s in the controls, respectively; P < 0.05). AS was reduced to 2.9 +/- 0.12 from 4.1 +/- 0.3 in the controls (P < 0.05). Postischaemic accumulation of lactate was lower in the diabetic than in the non-diabetic myocardium (20.4 +/- 1.9 vs 29.5 +/- 2.9 micromol/l/g w.wt.; P < 0.05). These results suggest that rat hearts with chronic diabetes, despite some differences in the arrhythmia profiles between the in vivo model and isolated heart preparation, are less sensitive to ischaemic injury and exhibit lower susceptibility to ventricular arrhythmias and reduced accumulation ofglycolytic metabolites.

Acute diabetes modulates response to ischemia in isolated rat heart

Diabetic hearts are suggested to exhibit either increased or lower sensitivity to ischemia. Detrimental effects of prolonged ischemia can be attenuated by preconditioning, however, relatively little is known about its effects in the diseased myocardium. This study was designed to test the susceptibility to ischemia-induced arrhythmias and the effect of preconditioning in the diabetic heart. Rats were made diabetic with streptozotocin (45 mg/kg, i.v.). After 1 week, isolated Langendorff-perfused hearts were subjected to 30 min occlusion of LAD coronary artery without or with preceding preconditioning induced by one cycle of 5 min ischemia and 10 min reperfusion. Glycogen and lactate contents were estimated in the preconditioned and non-preconditioned hearts before and after ischemia. Diabetic hearts were more resistant to ischemia-induced arrhythmias: incidence of ventricular tachycardia (VT) decreased to 42% and only transient ventricular fibrillation (VF) occurred in 17% of the hearts as compared to the non-diabetic controls (VT 100% and VF 70% including sustained VF 36%; p < 0.05). Preconditioning effectively suppressed the incidence and severity of arrhythmias (VT 33%, VF 0%) in the normal hearts. However, this intervention did not confer any additional protection in the diabetic hearts. Despite higher glycogen content in the diabetic myocardium and greater glycogenolysis during ischemia, production of lactate in these hearts was significantly lower than in the controls. Preconditioning caused a substantial decrease in the accumulation of lactate in the normal hearts, whereby in the diabetic hearts, this intervention did not cause any further reduction in the level of lactate. In conclusion, diabetic rat hearts exhibit lower susceptibility to ischemic injury and show no additional response to preconditioning. Reduced production of glycolytic metabolites during ischemia can account for the enhanced resistance of diabetic hearts to ischemia as well as for the lack of further protection by preconditioning.

Effect of dietary supplementation with the pyridoindole antioxidant stobadine on antioxidant state and ultrastructure of diabetic rat myocardium

Consistent with the postulated role of oxidative stress in the etiology of late diabetic complications, pharmacological interventions based on biological antioxidants have been suggested. The aim of the present study was to investigate the effect of dietary supplementation with the pyridoindole antioxidant stobadine on the myocardial antioxidant status and ultrastructure of streptozotocin-diabetic rats. Diabetic male Wistar rats were fed for 32 weeks a standard diet or a diet supplemented with stobadine (0.05% w/w). Control rats received a standard diet or stobadine-supplemented diet (0.16% w/w). Plasma levels of glucose, cholesterol and triglycerides were increased significantly by diabetes. Activities of superoxide dismutase and catalase were markedly elevated in the diabetic myocardium. Myocardial levels of conjugated dienes increased after eight months of diabetes, in spite of significantly increased myocardial alpha-tocopherol and coenzyme Q9 content. The long-term treatment of diabetic animals with stobadine (i) reduced plasma cholesterol and triglyceride levels yet left the severe hyperglycemia unaffected, (ii) reduced oxidative damage of myocardial tissue as measured by conjugated dienes, (iii) reversed myocardial levels of alpha-tocopherol and coenzyme Q9 to near control values, (iv) reduced elevated activity of superoxide dismutase in the diabetic myocardium, and (v) attenuated angiopathic and atherogenic processes in the myocardium as assessed by electron microscopy examination. These results are in accordance with the postulated prooxidant role of chronic hyperglycemia and provide further evidence that development of pathological changes in diabetic myocardium is amenable to pharmacological intervention by biological antioxidants.