Ferritin in glioblastoma

Elevated levels of serum ferritin (SF) are observed in several types of cancer; however, little is known on the association between ferritin and glioma, the most frequent type of human primary brain tumour. Here we report that GBM patients show significantly increased pre-surgical SF levels (i.e. ferritinaemia) within the SF reference range and a marked ferritin immunoreactivity of resected tumour tissue. Our findings account for an indirect association between ferritin synthesis in glioma-tissue and altered SF levels, which limits the clinical value of SF as a tumour marker in glioma. Importantly, we show for the first time that GBM-derived glioma cells release ferritin in vitro, which exerts an apoptosis-stimulating activity. Albeit the pathophysiologic context of apoptosis induction by a tumour-derived ferritin remains to be defined, our findings account for a distinct growth-regulatory role of these ferritin species in tumour biology.

A Helicobacter pylori-associated insulin resistance in asymptomatic sedentary young men does not correlate with inflammatory markers and urine levels of 8-iso-PGF2-α or 1,4-dihydroxynonane mercapturic acid

A potential contribution of H. pylori contamination to low-grade inflammation, oxidative stress (OS) and insulin resistance as well as correlations between these parameters in asymptomatic sedentary males was analysed. We enrolled 30 apparently healthy asymptomatic young subjects (18 H. pylori negative and 12 positive) and measured whole blood glucose, glycated haemoglobin, insulin, C-peptide, cortisol, aldosterone, testosterone, thyroid stimulating hormone, C-reactive protein, interleukins 6 and 10, TNF-alpha and comet assay. As markers of OS, we used urine levels of iso-PGF₂-α and 1,4-dihydroxynonane mercapturic acid (DHN-MA). Twofold elevation of fasting insulin level and HOMA index in H. pylori-positive subjects (p < .05) was shown. Inflammatory parameters and monocyte DNA damage, urine levels of DHN-MA and iso-PGF2-α did not show significant differences between the groups. The early stage of H. pylori-triggered metabolic derangements in sedentary subjects include development of insulin resistance in H. pylori-positive subjects; however, there is no evidence of systemic inflammatory and OS-related changes.

New horizons in microbiological food safety: Photodynamic Decontamination based on a curcumin derivative

Outbreaks of foodborne diseases are regularly reported worldwide. In particular, uncooked plant food is considered risky in terms of microbiological safety. Food is also the most important transmission route for resistant microorganisms from animals to humans. Photodynamic Decontamination (PDc) of foodstuff was recently introduced as a novel approach for increasing microbiological food safety. We investigated the efficiency of PDc on plant food with different geometries (flat, spherical and complex) using a two-dimensional LED array as a light source (435 nm, 33.8 J cm-2) and the cationic curcumin derivative SACUR-3 as a photosensitiser. A photoantibacterial effect (>3 log10 CFU reduction) was achieved on all flat substrates (slices of cucumber, tomato and lettuce) with 10 μM, 50 μM or 100 μM SACUR-3. The maximal photokilling with a relative inactivation of 5.6 log10 was measured on lettuce using 50 μM of the photoactive compound. Phototreatment of non-germinated fenugreek seeds and mung beans was successful if the spherical objects were rotated while under illumination (antibacterial effect at 100 μM SACUR-3). The decontamination of mung bean germlings with a more complex geometry using the PDc approach was ineffective with the two-dimensional light source. In conclusion, PDc based on the cationic curcumin derivative SACUR-3 is very effective at improving the microbiological safety of plant food with a flat or spherical geometry. More complex objects will require the development of novel illumination devices.

Helicobacter pylori in sedentary men is linked to higher heart rate, sympathetic activity, and insulin resistance but not inflammation or oxidative stress

AIM

To compare anthropometric parameters, body composition, hormonal and inflammatory profiles, oxidative stress indices, and heart rate variability (HRV) in Heliobacter pylori (H.pylori) positive and negative healthy sedentary participants.

METHODS

Among 30 recruited apparently healthy male participants (age between 20 and 40) enrolled in this cross-sectional study, 18 were H.pylori negative and 12 were positive (stool antigen test). Participants underwent routine physical examination and body composition determination. The following biochemical parameters were determined in blood: fasting whole blood glucose, glycated hemoglobin, insulin, C-peptide, cortisol, aldosterone, testosterone, thyroid stimulating hormone, C-reactive protein, interleukins 6 and 10, tumor necrosis factor-α, and the urinary level of 1,4-dihydroxynonane mercapturic acid. For HRV evaluation, electrocardiogram in supine position and in orthostatic test was performed.

RESULTS

H.pylori contamination was not significantly associated with any changes in anthropometric parameters, body composition, blood pressure, fasting glucose, or glycated hemoglobin levels. No significant difference was found for inflammatory markers as well as 1,4-dihydroxynonane mercapturic acid. H.pylori-positive participants, however, had significantly higher heart rate (P=0.009), sympathetic/parasympathetic balance in orthostatic test (P=0.029), fasting insulin level (P=0.037), and HOMA-index (P=0.047).

CONCLUSIONS

H.pylori contamination is linked to a significantly higher heart rate, sympathetic activation, and increased insulin resistance, while inflammatory and oxidative stress markers remain unaffected in healthy sedentary male subjects.

The correlations of glycated hemoglobin and carbohydrate metabolism parameters with heart rate variability in apparently healthy sedentary young male subjects

INTRODUCTION

Sedentary lifestyle is a major risk factor for diabetes, cardiovascular and many other age-related diseases. Heart rate variability (HRV) reflects the function of regulatory systems of internal organs and may sensitively indicate early metabolic disturbances. We hypothesize that quantitative and qualitative changes of HRV in young subjects may reflect early metabolic derangements responsible for further development of clinically significant disease.

AIM

The aim of our study was to determine whether the parameters of carbohydrate metabolism (fasting blood glucose, HBA1c and surrogate insulin sensitivity/resistance indices) correlate with anthropometric data and HRV.

METHODS

The study group consisted of 30 healthy sedentary male subjects aged 20-40, nonsmokers, mainly office and research employees, medical staff and students. Athletes, actively training more than one hour per week, severely obese and men of physical work were excluded from the study. HRV parameters were derived from short term ECG records (five minutes intervals) in supine position and during orthostatic test. Anthropometric data included height, weight, body mass index (BMI), age and body composition (estimation by bioelectric impedance method). The fasting blood glucose, insulin and C-peptide, homeostatic model assessment (HOMA-IR) index and glycated hemoglobin (HbA1c) were evaluated. Linear correlation coefficient (r) was calculated using Statistica 10.0 software.

RESULTS AND DISCUSSION

HOMA-IR index correlated positively with body weight, visceral fat and BMI (p=0.047, 0.027 and 0.017 respectively). In supine position pNN50 positively correlated with glucose/insulin ratio (p=0.011) and heart rate with HOMA-IR (p=0.006). In orthostatic test negative correlations of HBA1c with standard deviation, total and low frequency power were determined (p=0.034, 0.400 and 0.403 respectively), which indicates a gradual worsening of functional capacity of cardiovascular system with low-grade increase (under the conventional threshold) of HBA1c.

CONCLUSIONS

In apparently healthy sedentary subjects HRV reduction correlates with the age advancement, subclinical deteriorations of carbohydrate metabolism and excessive fat accumulation.

N-nitrosodiethylamine genotoxicity evaluation: a cytochrome P450 induction study in rat hepatocytes

In rats, N-nitrosodiethylamine (NDEA) induces tumors mainly in the liver. This could be because various enzymes are responsible for the metabolic activation of NDEA, besides the hepatic NDEA metabolizing enzyme, CYP2E1. We examined NDEA genotoxicity and cytotoxicity in primary cultures of female rat hepatocytes; we also looked at how it affected CYP mRNA expression. Single incubation with 0.9% NaCl resulted in a mean of 0.2% apoptotic cells, which doubled with 105 μg NDEA/mL. The frequency of necrosis with NDEA treatment was also doubled. Besides the cytotoxic effects, there was also a 4-fold decrease in mitotic index and a 3-fold decrease in the percentage of cells with micronuclei. A significant increase in micronucleus cells when hepatocytes were incubated with 2.1 μg NDEA/mL suggests that DNA repair was inactive. The chromosomal aberration evaluation revealed a discrete dose-response curve. Treatment with NDEA induced increases in CYP mRNA: CYP2B2 (1.8 times) and CYP2E1 (1.6 times) with non-cytotoxic NDEA concentrations (0.21-21 μg/mL). CYP2B1 mRNA levels decreased at 0.21 μg NDEA/mL (2.5-fold), while CYP4A3 mRNA decreased 1.3-fold. NDEA treatment at 2.1 μg/ mL induced a 1.9-fold increase in CYP3A1 mRNA. Understanding the cumulative effects in target cells during precarcinogenesis is crucial to understanding the mode of action of potential carcinogens and in order to develop comprehensive chemical toxicity profiles.

Solid-phase extraction and GC-MS analysis of potentially genotoxic cleavage products of β-carotene in primary cell cultures

A validated method for the simultaneous determination of prominent volatile cleavage products (CPs) of β-carotene in cell culture media has been developed. Target CPs comprised β-ionone (β-IO), cyclocitral (CC), dihydroactinidiolide (DHA), and 1,1,6-trimethyltetraline (TMT). CPs were extracted by solid-phase extraction applying a phenyl adsorbent, eluted with 10% (v/v) tetrahydrofuran in n-hexane, and identified and quantified by gas chromatography-mass spectrometry with electron impact ionization. Method validation addressed linearity confirmation over two application ranges and homoscedasticity testing. Recoveries from culture media were between 71.7% and 95.7% at 1.0 μg/ml. Precision of recoveries determined in intra-day (N = 5) and inter-day (N = 15) assays were <2.0% and <4.8%, respectively. Limit of detection and limit of quantification of the analysis method were <18.0 and <53.0 ng/ml for β-IO, CC, and TMT, whereas 156 and 474 ng/ml were determined for DHA, respectively. Although extractions of blank matrix proved the absence of interfering peaks, statistical comparison between slopes determined for instrumental and total method linearity revealed significant differences. The method was successfully applied in selecting an appropriate solvent for the fortification of culture media with volatile CPs, including the determination of their availability over the incubation period. For the first time, quantification of volatile CPs in treatment solutions and culture media for primary cells becomes accessible by this validated method.

Figure

Changes in the endogenous BMP expression during redifferentiation of chondrocytes in 3D cultures

Engineering cartilage tissue is challenging, mainly because chondrocytes lose their differentiated phenotype when cultured in monolayer. The aim of this study was to analyse the influence of 3D-culture conditions on the redifferentiation of chondrocytes, devoting special attention to BMPs. Dedifferentiated chondrocytes were seeded onto two different scaffolds (Bio-Gide and HYAFF-11) and were then cultured for 38 days. Every week, samples were taken for gene expression analysis and immunohistochemistry. In both scaffolds an increasing differentiation was observed caused by an increase in Col2 and a reduction in Col1 expression. The various BMPs were regulated, albeit differently by the changing culture conditions. While GDF-5 and BMP-4 expression increased in the monolayer culture in comparison with native cartilage and decreased again in the 3D culture, the BMP-2 and BMP-6 expression decreased dramatically in the monolayer as well as in the 3D culture. BMP-7 was not detectable in any probe. Scaffold cultivation appears to stimulate the induction of redifferentiation, but is not sufficient to induce expression of BMP-2 -6 or -7. Since, in comparison to cartilage development, there is a lack of surrounding signal centres, external stimuli seem to be required to obtain complete redifferentiation. Our data indicate that a combination of BMP-2, -6 and -7 may be promising for this purpose.

Influence of 4-hydroxynonenal and spleen cells on primary hepatocyte culture and a novel liver-derived cell line resembling hepatocyte stem cells

Liver is a unique mammalian organ with a great capacity of regeneration related to its function. After surgical resection or injury, hepatic cells, especially hepatocytes, can proliferate rapidly to repair the damage and to regenerate the structure without affecting the function of the liver. Loss of catalase activity during regeneration indicates that oxidative stress is present in the liver not only in pathological conditions but also as a 'physiological' factor during regeneration. As we have shown in our previous work, liver stem cell-like cells treated with 4-hydroxynonenal (HNE), a cytotoxic and growth regulating lipid peroxidation product, recover in the presence of spleen cells. In the current study we characterized this novel cell line as liver-derived progenitor/oval-like cells, (LDP/OCs), i.e. functional liver stem-like cells. We showed that LDP/OC were OV6 positive, with abundant glycogen content in the cytoplasm and expressed alpha-fetoprotein, albumin, biliverdin reductase and gamma-glutamyl transferase. Also, we compared their growth in vitro with the growth of cultured primary hepatocytes stressed with HNE and co-cultured with autologous spleen cells. The influence of spleen cells on HNE-treated primary hepatocytes and on LDP/OCs showed that spleen cells support in a similar manner the recovery of both types of liver cells indicating their important role in regeneration. Hence, LDP/OC cells may provide a valuable tool to study cell interactions and the role on HNE in liver regeneration.

Influence of 4-hydroxynonenal and spleen cells on primary hepatocyte culture and a novel liver-derived cell line resembling hepatocyte stem cells

Liver is a unique mammalian organ with a great capacity of regeneration related to its function. After surgical resection or injury, hepatic cells, especially hepatocytes, can proliferate rapidly to repair the damage and to regenerate the structure without affecting the function of the liver. Loss of catalase activity during regeneration indicates that oxidative stress is present in the liver not only in pathological conditions but also as a 'physiological' factor during regeneration. As we have shown in our previous work, liver stem cell-like cells treated with 4-hydroxynonenal (HNE), a cytotoxic and growth regulating lipid peroxidation product, recover in the presence of spleen cells. In the current study we characterized this novel cell line as liver-derived progenitor/oval-like cells, (LDP/OCs), i.e. functional liver stem-like cells. We showed that LDP/OC were OV6 positive, with abundant glycogen content in the cytoplasm and expressed alpha-fetoprotein, albumin, biliverdin reductase and gamma-glutamyl transferase. Also, we compared their growth in vitro with the growth of cultured primary hepatocytes stressed with HNE and co-cultured with autologous spleen cells. The influence of spleen cells on HNE-treated primary hepatocytes and on LDP/OCs showed that spleen cells support in a similar manner the recovery of both types of liver cells indicating their important role in regeneration. Hence, LDP/OC cells may provide a valuable tool to study cell interactions and the role on HNE in liver regeneration.

Dedifferentiation of human articular chondrocytes is associated with alterations in expression patterns of GDF-5 and its receptors

Human articular chondrocytes are expanded in monolayer culture in order to obtain sufficient cells for matrix-associated cartilage transplantation. During this proliferation process, the cells change their shape as well as their expression profile. These changes resemble those that occur during embryogenesis, when the limb anlagen form the interzone that later develops the joint cleft. We analysed the expression profile of genes that are reportedly important for these changes during embryogenesis within the dedifferentiation process of adult articular chondrocytes. We found GDF-5, BMPR-Ib and connexin 43 up-regulated, as well as a down-regulation of BMPR-Ia and noggin. Connexin 32 could not be detected in either native cartilage or in dedifferentiated cells. The newly synthesized proteins were detected by immunofluorescence. There is evidence from our results that dedifferentiated chondrocytes resemble the cells from the interzone in developing synovial joints.

Alterations in CD44 isoforms and HAS expression in human articular chondrocytes during the de- and re-differentiation processes

The purpose of this study was to investigate the expression of different CD44 and hyaluronan synthase isoforms in cartilage, their alterations during the chondrocyte dedifferentiation process in monolayer culture and during the redifferentiation process on 3D scaffolds. Chondrocytes isolated from human articular cartilage were cultured as a monolayer for up to 36 days and were seeded on two different 3D scaffolds (HYAFF 11 and Bio-Gide). Expression levels of CD44s, CD44-lt, CD44-st, HAS1, HAS2, HAS3 and UDPGD were determined by real-time RT-PCR at different time points. At the protein level CD44 and CD90 were analyzed by flow cytometry. HAS2 was found to be the predominantly expressed hyaluronan synthase in chondrocytes and was not subjected to any regulation during the dedifferentiation process. CD44s, CD44-lt, CD44-st and UDPGD, however, were upregulated immediately after cell isolation. In addition, a high cell density was found to significantly increase CD44-st and CD44-lt expression. Redifferentiation on 3D scaffolds reversed the increase of the CD44 expression. Our data point out that CD44 expression does not correlate with matrix assembly in chondrocytes and that CD44 has a regulatory function in chondrocytes, not necessarily on differentiation, but probably on proliferation.

Effects of dietary intake of a fungal beta-D-glucan derivative on the level of DNA damage induced in primary rat hepatocytes by various carcinogens

Water-soluble derivative of chitin-glucan complex used in our study, carboxymethyl chitin-glucan (CM-CG), enables oral administration without harmful side-effects, which can occur upon parenteral administration of the insoluble fungal beta-D-glucans. The aim of this study was to determine in ex vivo experiments the effects of dietary CM-CG on the level of DNA lesions in primary rat hepatocytes induced by various indirectly acting carcinogens. Multiorgan carcinogen benzo[a]pyrene (BaP); two hepatocarcinogens, dimethyldibenzocarbazole (diMeDBC) and N-nitrosomorpholine (NMOR); as well as a complex mixture of organic compounds adsorbed on ambient air particles (TP-S) were used for this purpose. The amount of DNA lesions was assessed using the comet assay and the micronucleus test. In addition, the mitotic indexes and the frequencies of necrotic and apoptotic cells were evaluated as well. Our results showed that the diet enriched with CM-CG (200 mg/kg of body weight) during 21 days did not induce any negative effect on DNA nor did the mitotic indexes and the frequencies of necrotic and apoptotic cells differ statistically from the controls. On the other hand, the hepatocytes isolated from CM-CG fed animals were more resistant to the action of all genotoxins used in our study [BaP (5-20 microM), diMeDBC (0.2-2 microM), NMOR (3.4-10.2 mM), TP-S (5-20 microM)]. We can conclude that in addition to the known immunopotentiating activity of beta-D-glucans, they can efficiently inhibit the genotoxicity of carcinogens requiring metabolic activation in rat heptocytes.

Comparative evaluation of DNA damage by genotoxicants in primary rat cells applying the comet assay

Various compounds known to cause DNA damage (hydrogen peroxide, visible light-excited methylene blue, N-nitrosomorpholine and benzo[a]pyrene) were tested with different primary rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) to determine the range of induced DNA damage applying the comet assay. A dose-dependent increase of DNA breaks was observed after treatment with hydrogen peroxide in all cell types studied. The most prominent effect was observed in lymphocytes, whereas only a slight increase of DNA breaks was observed in hepatocytes. Visible light-excited methylene blue caused significant oxidative DNA damage, which did not significantly differ between the cell types used with the exception of hepatocytes, for which a lower level of DNA damage was observed. N-Nitrosomorpholine and benzo[a]pyrene induced a moderate but significant increase of DNA strand breaks in pneumocytes and hepatocytes while in lymphocytes no effect was observed. Our results clearly demonstrate that due to their differential function which is also expressed by the level of drug metabolizing and/or antioxidant enzymes, freshly isolated rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) respond differently to the exposure to genotoxic agents as detected by comet assay.

Astrocytes are more resistant than cerebral endothelial cells toward geno- and cytotoxicity mediated by short-term oxidative stress

Evidence is accumulating that capillary endothelial cells (cEC) and astrocytes play a pivotal role in neuroprotection, in particular with respect to counteract oxidative injury. Furthermore, differences among both cell types in response to oxidative stress have been shown and astrocytes seem to be more tolerant in terms of cytotoxicity, however, no reports exist on oxidative stress mediated genotoxicity in astrocytes. We investigated genotoxic and cytotoxic effects of oxidative stress in astrocytes and cECs induced by hypoxia/reoxygenation or by the redox cycling quinone DMNQ. Additionally, the dependence of these effects on glucose availabilty was also studied. On exposure to Hy/Re or 10 muM DMNQ for 24 hr, the frequency of micronucleated and apoptotic cells was significantly increasing, however, astrocytes proved to be more resistant to apoptosis induction, in particular on use of DMNQ. In astrocytes, the low background rates of necrotic cells were not affected and a significant necrosis induction was only detectable in cECs exposed to DMNQ for 24 hr. Short-term exposure to DMNQ (1 hr) had no effect in astrocytes but exerted significant geno- and cytotoxicity in cECs. Increasing the glucose concentration markedly reduced oxidative stress mediated geno- and cytotoxicity in astrocytes. Surprisingly, glucose deprivation (aglycemia) suppressed DMNQ induced micronucleus formation in astrocytes without affecting the frequency of apoptotic cells. Our results indicate that astrocytes are more resistant to oxidative stress than cECs, in particular regarding the potential to counteract genotoxicity as well as apoptosis induction mediated by a short term oxidative insult.

The Aral Sea disaster – human biomonitoring of Hg, As, HCB, DDE, and PCBs in children living in Aralsk and Akchi, Kazakhstan

Mercury and arsenic have been measured in urine samples and HCB, DDE and PCBs in blood samples of children from Aralsk and Akchi, Kazakhstan. Due to the special situation of Aralsk in the desert left by the drying out Aral Sea, environmental pollution with heavy metals and organic contaminants is believed to be higher than elsewhere in Kazakhstan. Aralsk was formerly located at the shore of the Aral Sea and is now far away from it. Akchi is a similar village and was included in this study as a Kazakh reference site. Urine concentrations of arsenic were higher in Akchi (9.4 microg/l) than in Aralsk (5.5 microg/l) and compared to children from Mannheim, Germany (4.25 microg/l; Median values). Regarding Hg, differences between children of Aralsk and Akchi were not significant and concentrations were lower than reference values from Germany. DDE contamination of children from Aralsk (2.48 microg/l) was significantly higher compared to Akchi (1.35 microg/l). DDE concentrations in blood samples from children in both cities were also significantly higher than the German reference value (0.7 microg/l). HCB and PCBs levels differed significantly between both Kazakh groups. However, concentrations of these compounds were lower than German reference values and there was no significant difference to samples from Mannheim children.

Protective effects of fungal (1$rarr;3)-$beta;--glucan derivatives against oxidative DNA lesions in V79 hamster lung cells

beta-Glucans belong to the class of substances known as biological response modifiers with a broad range of activity. We have investigated two types of glucans: (1-->3)-beta-D glucan from the baker's yeast Saccharomyces cerevisiae and beta-glucan-chitin complex from the mycelium of filamentous fungus Aspergillus niger. Since these fibrillar beta-glucans are insoluble in water, their water-soluble derivatives--carboxymethyl glucan (CM-G), sulfoethyl glucan (SE-G), and carboxymethyl chitin-glucan (CM-CG) were prepared and tested. The aim of the present work was to investigate the protective effect of the prepared glucan derivatives against oxidative DNA damage induced by H2O2 and visible light-excited Methylene Blue in V79 hamster lung cells. The level of DNA damage (DNA strand breaks) was measured using the single cell gel electrophoresis, so called comet assay. Our findings demonstrate that all three tested glucans reduce oxidative DNA damage. The ability to reduce genotoxic activity increased in the order: CM-G<SE-G<CM-CG. We suggest that the analyzed glucans exhibit protective effects against oxidative damage to DNA as a consequence of scavenging of both *OH radicals and singlet oxygen.

Translational regulator RpL10p/Grc5p interacts physically and functionally with Sed1p, a dynamic component of the yeast cell surface

Biogenesis of an active ribosome complement and a dynamic cell surface complement are two major determinants of cellular growth. In yeast, the 60S ribosomal subunit protein RpL10p/Grc5p functions during successive stages in ribosome biogenesis, specifically rRNA processing, nucle(ol)ar preribosomal subunit assembly, nucleo-cytoplasmic transport and cytoplasmic maturation of ribosomes. Here, we report that a two-hybrid screen identified yeast genes SED1, ACS2 and PLB3 as encoding proteins physically interacting with both ribosomal RpL10p/Grc5p and its human homologue hRpL10p/QMp. SED1 encodes a differentially expressed cell wall protein which is proposed to be first transiently secreted to the plasma membrane as a GPI (glycosylated derivative of phosphoinositol)-anchored form and to be then transferred to the glucan layer of the cell wall. Ectopic expression of SED1 rescues both the aberrant growth phenotype and the translation defect of grc5-1(ts) temperature-sensitive cells. Furthermore, we report that Sed1p associates with translating ribosomes suggesting a novel, cytoplasmic role for Sed1p. ACS2 encodes one of the two yeast acetyl-CoA synthases and represents a key enzyme in one of several metabolic routes to produce acetyl-CoA, which in turn is indispensable for lipid biosynthesis. PLB3 encodes a phospholipase, which is active in the breakdown of membrane lipids. Our results support the view that Grc5p/RpL10p links ribosome function to membrane turnover and cell surface biogenesis.

Effect of dietary intake of vitamin A or E on the level of DNA damage, chromosomal aberrations, and micronuclei induced in freshly isolated rat hepatocytes by different carcinogens

Hepatocytes freshly isolated from male Wistar rats fed a common diet or a vitamin A- or vitamin E-supplemented diet (each for 21, 28, or 41 days) were assayed for sensitivity to DNA breakage and cytogenetic changes induced by carcinogens. Different indirectly acting carcinogens were assayed. N-nitrosomorpholine (NMOR) was the only agent that induced DNA breaks, chromosomal aberrations, and micronuclei in all experiments. Benzo[a]pyrene (B[a]p) and dimethyldibenzo [c,g]carbazole (diMeDBC) induced only DNA breaks in all experiments. Occasionally, B[a]P induced chromosomal aberrations and micronuclei, and diMeDBC induced micronuclei, but not chromosomal aberrations. These results demonstrated that the tested carcinogens assayed at concentrations highly effective in a hypoxanthine phosphoribosyltransferase/V79 system significantly increased DNA damage, while cytogenetic changes were less frequent. In hepatocytes from rats fed vitamin A, a reduction in the severity of all three end points was observed after NMOR treatment. After B[a]P treatment, we found a reduction in DNA breaks and chromosomal aberrations; after treatment with diMeDBC, we observed a reduction in DNA breaks. Treatment with vitamin E was less effective: it reduced DNA strand breaks induced by B[a]P and partially reduced those induced by diMeDBC and NMOR and the level of micronuclei induced by NMOR and B[a]P. Both vitamins reduced the level of DNA strand breaks induced by the oxidative effect of a visible light-excited photosensitizer.

Genotoxic response of Austrian groundwater samples treated under standardized UV (254 nm)--disinfection conditions in a combination of three different bioassays

Ground water samples from different geographic areas in Austria, with different amounts of natural and anthropogenic organic compounds were treated with a standardized low pressure UV (254 nm)-irradiation laboratory flow-through system (UV fluence: 800 J/m2). The genotoxic activities of the water samples before and after the UV disinfection were investigated using a combination of three different bioassays which complement each other with regard to their sensitivity detecting different genotoxins. The test battery comprises the Salmonella/microsome assay (Ames test with TA98. TA 100 and TA 102, with and without S9 mix) and two micronucleus tests with the plant Tradescantia (clone #4430) and with primary rat hepatocytes. Overall, the tested Austrian groundwater samples used for human consumption caused only weak genotoxic activities compared to drinking water samples reported from other countries under similar experimental conditions. With the exception of one weak positive result in the Ames test (only in strain TA98 without S9 mix) with an induction factor of 1.9) all samples after UV disinfection were devoid of additional mutagenic and clastogenic activities compared to the samples before UV disinfection.

Chromosomal aberrations of blood lymphocytes induced in vitro by radon-222 daughter alpha-irradiation

Blood samples were irradiated in vitro with alpha-rays emitted from short-lived radon decay products dissolved in the culture medium at doses between 0.03 and 41.4 mGy. The data were collected from experiments conducted during the period 1984-1992 and comprise a total of about 64000 scored metaphases. For statistical reasons, only 60,022 metaphases were used for the subsequent analysis. The results for total chromosome aberrations and dicentrics indicate a linear dose dependence in the dose range above about 10 mGy, consistent with other experimental observations. At doses below about 10 mGy, aberration frequencies cannot be linearly extrapolated from higher doses, suggesting that there is no dependence on dose within a certain low-dose range. In addition, a statistically significant minimum has been observed at a dose of about 0.03 mGy, which is consistently lower than the related control values. The behavior of the aberration frequencies in the low-dose region seems to be influenced by the control values, which also depend on the environmental radiation burdens to the donors before blood sampling and thus were significantly affected by the Chernobyl fallout.

Adaptive response and dose-response plateaus for initiation in a state-vector model of carcinogenesis

PURPOSE

To investigate whether it is possible to explain dose-response plateaus for in-vitro X-ray irradiation of different cell lines with radioprotective mechanisms such as radiologically induced expression of scavengers and repair enzymes.

MATERIALS AND METHODS

A biomathematical model was developed based on a previous state-vector model. New features of the model are a mathematical description of enhanced repair and radical scavenging as a result of irradiation.

RESULTS

The model produces a plateau in the dose-response for in-vitro tranformations between 0.5 and 1 Gy and for chromosome aberrations and it predicts an inverse-fractionation effect within a selected range of doses.

CONCLUSIONS

Adaptive response mechanisms within a state-vector model provide a coherent explanation of the dose-response characteristics for in-vitro transformations and chromosomal aberrations. These results suggest the need for new experimental studies described in the paper.

Possible mutagens derived from lipids and lipid precursors

Free radicals can initiate the oxidative decomposition of cellular membranes by lipid peroxidation. In this process a great variety of reactive aldehydes are produced intracellularly. Some of them, such as 4-hydroxynonenal or malonaldehyde, are biologically very active and might be involved in free radical-mediated DNA damage. A short review of the effects of aldehydic lipid peroxidation products on isolated DNA, their genotoxic effect in prokaryotes and eukaryotes and their in vivo carcinogenicity is given. Additionally own experiments on cytotoxic and genotoxic effects of 4-hydroxynonenal, 2-nonenal and nonanal in primary cultures of rat hepatocytes are reported. 4-Hydroxynonenal was highly cytotoxic at 100 microM, at subcytotoxic concentrations of 0.1-10 microM 4-hydroxynonenal increased the frequency of micronuclei, chromosomal aberrations and sister-chromatid exchange. 2-Nonenal and nonanal were not cytotoxic at 100 microM, the maximum dose tested. At 100 microM 2-nonenal led to a slight increase in micronuclei; chromosomal aberrations were not significantly altered. Nonanal had no detectable genotoxic effects. The level of endogenous 4-hydroxynonenal in tissues is in the range of 0.1-3.0 microM and can increase to 10 microM in conditions of oxidative stress; such levels appear to be sufficiently high to produce DNA damages, whether such damages are transient or irreversible is not known.

An in vitro micronucleus assay for determining the radiosensitivity of hepatocytes

An in vitro micronucleus assay was developed for primary cultures of rat hepatocytes and utilized to determine the oxygen enhancement ratio (OER). Freshly isolated Fischer 344 female rat hepatocytes were irradiated in suspension either in air or in anoxia, cultured for 60 h to allow for the maximum expression of micronuclei, fixed with methanol-glacial acetic acid, stained with the fluorescent dye 4',6-diamidino-2-phenylindole (DAPI), and scored with a fluorescent microscope for the presence of micronuclei. The percentage of cells with micronuclei increased linearly with dose, and the slopes of the relationships were 0.044 +/- 0.001 Gy-1 and 0.015 +/- 0.001 Gy-1 in air and anoxia, respectively. The calculated OER of 2.9 +/- 0.5 is similar to that previously obtained for hepatocyte cell survival. Our data demonstrate that this in vitro hepatocyte micronucleus assay is a rapid and sensitive method to further investigate those factors which influence the radiosensitivity of hepatocytes.