Sister-chromatid exchange (SCE) and cell proliferation in lymphocytes from infected and non-infected children with severe protein calorie malnutrition (PCM)

Moderate malnutrition in rats induces somatic gene mutations

The relationship between malnutrition and genetic damage has been widely studied in human and animal models, leading to the observation that interactions between genotoxic exposure and micronutrient status appear to affect genomic stability. A new assay has been developed that uses the phosphatidylinositol glycan class A gene (Pig-a) as a reporter for measuring in vivo gene mutation. The Pig-a assay can be employed to evaluate mutant frequencies (MFs) in peripheral blood reticulocytes (RETs) and erythrocytes (RBCs) using flow cytometry. In the present study, we assessed the effects of malnutrition on mutagenic susceptibility by exposing undernourished (UN) and well-nourished (WN) rats to N-ethyl-N-nitrosourea (ENU) and measuring Pig-a MFs. Two week-old UN and WN male Han-Wistar rats were treated daily with 0, 20, or 40mg/kg ENU for 3 consecutive days. Blood was collected from the tail vein one day before ENU treatment (Day-1) and after ENU administration on Days 7, 14, 21, 28, 35, 42, 49, 56 and 63. Pig-a MFs were measured in RETs and RBCs as the RET(CD59-) and RBC(CD59-) frequencies. In the vehicle control groups, the frequencies of mutant RETs and RBCs were significantly higher in UN rats compared with WN rats at all sampling times. The ENU treatments increased RET and RBC MFs starting at Day 7. Although ENU-induced Pig-a MFs were consistently lower in UN rats than in WN rats, these differences were not significant. To understand these responses, further studies should use other mutagens and nucleated surrogate cells and examine the types of mutations induced in UN and WN rats.

Malnutrition and infection influence the peripheral blood reticulocyte micronuclei frequency in children

Malnutrition is a serious public health problem that affects approximately one third of all children. Developing countries have the highest incidence of malnourished children, and approximately 60% of deaths that occur in children under five are directly related to malnutrition and associated diseases. The relationship between malnutrition and genetic damage has been widely studied in humans and animal models. The micronucleus (MN) assay is useful in detecting chromosome damage induced by several factors. The aim of this study was to evaluate the effects of infection and malnutrition on the frequency of MN in erythrocytes from the peripheral blood of well-nourished, uninfected (WN) and well-nourished, infected (WNI) children, and moderately malnourished (UNM) and severely malnourished (UNS) children, both with infection, using a flow cytometric analysis technique. The percentage of reticulocytes (RETs) was significantly higher (1.5-fold) in WNI children than well-nourished controls. In addition, the UNS group had a 2.2-fold increase in the percentage of RETs compared to the WNI group. The frequency of micronucleated reticulocytes (MN-RETs) was 2.5 times greater, in WNI group compared to the WN group. These frequencies were significantly higher (1.7- and 2.1-fold) in UNM and UNS, respectively, compared to the WNI group. The results suggest that infection and malnutrition induce DNA damage in children.

Effects of calorie restriction on chromosomal stability in rhesus monkeys (Macaca mulatta)

The basic tenet of several theories on aging is increasing genomic instability resulting from interactions with the environment. Chromosomal aberrations have been used as classic examples of increasing genomic instability since they demonstrate an increase in numerical and structural abnormalities with age in many species including humans. This accumulating damage may augment many aging processes and initiate age-related diseases, such as neoplasias. Calorie restriction (CR) is one of the most robust interventions for reducing the frequency of age-related diseases and for extending life span in many short-lived organisms. However, the mechanisms for the anti-aging effects of CR are not yet well understood. A study of rhesus monkeys was begun in 1987 to determine if CR is also effective in reducing the frequency of age-related diseases and retarding aging in a long-lived mammal. Male monkeys were begun on the diet in 1987, and females were added in 1992 to examine a possible difference in response to CR by sex. The CR monkeys have been maintained for over 10 years on a low-fat nutritional diet that provides a 30% calorie reduction compared to a control (CON) group. Because of the greater similarity of nonhuman primates to humans in life span and environmental responses to diet compared with those of rodents, the rhesus monkey provides an excellent model for the effects of CR in humans. This study examined the effects of CR on chromosomal instability with aging. Significant age effects were found in both CR and CON groups for the number of cells with aneuploidy: old animals had a higher loss and a higher gain than young animals. However, there was no effect of age on chromosomal breakage or structural aberrations in either diet group. Diet had only one significant effect: the CR group had a higher frequency of chromatid gaps than did the CON group. CR, implemented in adult rhesus monkeys, does not have a major effect on the reduction of numerical or structural aberrations related to aging.

Spontaneous and mitomycin C-induced micronuclei in peripheral blood reticulocytes from severely malnourished rats

Severe malnutrition caused by deficiencies in protein, calorie, and micronutrient intake is widely distributed throughout the world and is a particular problem in developing countries. Animal models have been useful for studying the effects of malnutrition under different experimental conditions. In this study, we have evaluated the effect of malnutrition on the frequency of spontaneous and mitomycin C (MMC)-induced micronuclei in the peripheral blood of rats measured using a flow cytometric analysis technique. Neonatal rats were experimentally malnourished during lactation and assayed at weaning (21 days of age). The malnourished rats weighed 49.2% less than well-nourished controls and had lower concentrations of serum protein, triglycerides, and cholesterol. In rats not treated with MMC, the frequency of micronucleated reticulocytes (MN-RETs) was 1.6 times greater in malnourished rats than in well-nourished rats (0.48% +/- 0.16% vs. 0.31% +/- 0.09%). The mean MN-RET frequency measured 32 hr after treatment with single i.p. doses of 0.5, 0.75, or 1.0 mg/kg of MMC was 0.60 +/- 0.10 vs. 0.84 +/- 0.14, 1.21 +/- 0.52 vs. 2.36 +/- 0.47, and 2.50 +/- 0.06 vs. 4.64 +/- 1.14 for well-nourished vs. malnourished rats, respectively. Statistical comparisons indicate significant differences between the two groups of rats at all doses tested. Malnourishment and MMC treatment had no significant effects on the frequencies of RETs or micronucleated normochromatic erythrocytes. The data indicate that protein-calorie malnutrition during lactation is associated with increased frequencies of MN-RETs, which are indicative of chromosome damage. These findings suggest that malnutrition could result in greater susceptibility to environmental damage.

Micronucleus frequency and proliferation in human lymphocytes after exposure to herbicide 2,4-dichlorophenoxyacetic acid in vitro and in vivo

Widespread use of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its association with non-Hodgkin's lymphoma (NHL) and other cancers has raised public concern. Here, micronucleus (MN) formation has been used as a biomarker of genotoxicity, and replicative and mitotic indices (MIs) as biomarkers of cell cycle kinetics in human lymphocytes. Cells were cultured either as whole blood or isolated lymphocytes and treated with pure or commercial forms of 2,4-D at doses between 0.001 and 1 mM for 48 h. Exposure to 2,4-D produced a minimal increase in MN in whole blood and even smaller one in isolated lymphocyte cultures. This induction took place only at levels approaching cytotoxicity and was accompanied by a significant inhibition of replicative index (RI). At a low (0.005 mM) dose of commercial 2,4-D, a small, marginally significant increase in RI (12-15%) was found in two independent sets of experiments (P=0.052). Additionally, we found that lymphocyte RI was more affected by commercial 2,4-D containing 9.4% of the chemically pure 2,4-D, than with an equal concentration of the latter suggesting that other ingredients present in the commercial pesticide may be responsible or may enhance the effect of 2,4-D. Mitotic index, however, did not show any significant change with either commercial or pure 2,4-D. The lymphocytes of 12 male applicators exposed solely to 2,4-D during a 3-month period had a significantly higher RI than the same group prior to exposure and than a control group (P<0.01), in accordance with the in vitro finding of increased RI at low doses.

Hydrogen peroxide-induced DNA damage and DNA repair in lymphocytes from malnourished children

The aim of this study was to assess DNA repair capacity in lymphocytes of children with protein calorie malnutrition using the single-cell gel electrophoresis (comet) assay. Repair capacity was assessed by estimating the relative decrease of DNA migration length 5, 15, 30, and 60 min after hydrogen peroxide treatment, in three groups of children: well-nourished (WN), well-nourished infected (WN-I), and malnourished infected (MN-I). In addition, the DNA migration length was evaluated in all groups before and after peroxide treatment. Comparison of mean migration lengths observed in WN and WN-I children showed significant differences at all times tested; between WN-I and MN-I differences were also observed, except after hydrogen peroxide exposure. This implies that lymphocytes of WN-I and MN-I children were equally sensitive to hydrogen peroxide. Nevertheless, the MN-I group clearly shows the greatest overall percentage of damaged cells at all times tested. In relation to repair capacity, at 5 min it was approximately 30% in both groups of well-nourished children, but only 20% in MN-I; 15 min after exposure, repair capacity increased to 51% in well-nourished children but only to 31% in MN-I; and at 60 min this capacity increased to 82% in well-nourished but only to 55% in MN-I. These data indicate that lymphocytes of malnourished children show a decreased capacity to repair hydrogen peroxide-induced DNA damage compared to that of well-nourished controls. This reflects that only malnutrition is associated with decreased DNA repair capacity. Additionally, the data confirm that severe infection and malnutrition are two factors clearly associated with increased DNA damage.

CD45RA and CD45RO isoforms in infected malnourished and infected well-nourished children

The aim of this study was to determine if the distribution in vivo of CD4(+)CD45RA(+)/CD45RO(-) (naive), CD4(+)CD45RA(+)/CD45RO(+) (Ddull) and CD4(+)CD45RO(+) (memory) lymphocytes differs in malnourished infected and well-nourished infected children. The expression of CD45RA (naive) and CD45RO (memory) antigens on CD4(+) lymphocytes was analysed by flow cytometry in a prospectively followed cohort of 15 malnourished infected, 12 well-nourished infected and 10 well-nourished uninfected children. Malnourished infected children showed higher fractions of Ddull cells (11.4 +/- 0.7%) and lower fractions of memory cells (20.3 +/- 1.7%) than the well-nourished infected group (8.8 +/- 0.8 and 28.1 +/- 1.8%, respectively). Well-nourished infected children showed increased percentages of memory cells, an expected response to infection. Impairment of the transition switch to the CD45 isoforms in malnourished children may explain these findings, and may be one of the mechanisms involved in immunodeficiency in these children.

Assessment of DNA damage in spleen, bone marrow, and peripheral blood from malnourished rats by single cell gel electrophoresis assay

Severe malnutrition is widely distributed throughout the world and exhibits a high prevalence in developing countries. Experimental malnutrition models have been useful to study the effects of malnutrition at early ages. The purpose of this study was to determine if severe malnutrition induced during lactation in rats increases DNA damage in spleen, peripheral blood, and bone marrow cells, as well as in isolated lymphocytes or lymphoid cells from the same tissues. These cells were obtained from malnourished rats at weaning (21 days of age). DNA damage was estimated by using the alkaline single cell electrophoresis assay. The results obtained in this study indicate that malnutrition is associated with a significant increase in DNA damage in all cell types that were studied in malnourished rats. The analysis of the length of DNA migration and dispersion coefficient showed that some cell types were more susceptible to DNA damage related with malnutrition. The damage observed could be due to the deficiency of several essential nutrients required for protein synthesis that are associated with DNA integrity, impaired DNA repair mechanisms, and/or to the unavailability of molecules necessary to protect the cells against DNA oxidative damage. This damage may produce negative effects for the further development of the organism, since bone marrow is the main site of hematopoiesis and spleen is an important lymphopoietic organ. Also, the increased level of DNA damage in peripheral blood lymphocytes and leukocytes could be related to negative effects such as a deficient immune response.

Vitamin D and genomic stability

1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] has been shown to act on novel target tissues not related to calcium homeostasis. There have been reports characterizing 1,25(OH)(2)D(3) receptors and activities in diverse tissues such as brain, pancreas, pituitary, skin, muscle, placenta, immune cells and parathyroid. The receptor hormone complex becomes localized in the nucleus, and undergoes phosphorylation by reacting with a kinase. This form of the receptor then interacts with the Vitamin D responsive element of target gene and modifies the transcription of those genes to develop the action. The modulation of gene transcription results in either the induction or repression of specific messenger RNAs (m-RNAs), ultimately resulting in changes in protein expression needed to produce biological responses. Genes for carbonic anhydrase that are expressed at high levels in osteoclast are known to be involved in bone resorption and Id genes role in osteoblast-osteoclast differentiation reflects the genomic effect of Vitamin D on bones. Genomic action of Vitamin D also explains the biosynthesis of oncogenes, polyamines, lymphokines and calcium binding proteins. However, there is a possibility that some of the actions of 1,25(OH)(2)D(3) may be mediated by non-genomic mechanisms and may not require the binding to Vitamin D receptor (VDR). Vitamin D offers a protection from genotoxic effects of Vitamin D deficiency by increasing the insulin receptor gene expression and BSP (bone sialoprotein), bone-remodeling by decreasing the osteopontin (OPN) m-RNAs, maintaining the normal epidermal structure and enamel matrix. Gonadal insufficiency in Vitamin D deficiency was corrected by vitamin mediated direct regulation of the expression of aramotase gene. The supportive role of Vitamin D in placental function is also evident by its influence on human placental lactogen (hpl) gene transcription accompanied by increase hpl m-RNA levels. Further role of Vitamin D is envisaged in identifying cyclin C as an important target for Vitamin D in cell-cycle regulation. Vitamin D at physiological concentration has been found to protect cell proteins and membranes against oxidative stress by inhibiting the peroxidative attack on membrane lipids. Vitamin D, at a concentration range of 2x10(-8)-5x10(-8)M, induces apoptosis in most cancer cells, stabilizes chromosomal structure and prevents DNA double-strand breaks induced either by endogenous or exogenous factors. Vitamin D is also effective in stimulating DNA synthesis in adult alveolar II cells and provides a novel mechanism of modulation of epithelial cell proliferation in the context of lung development and repair against injury. The regulation of various proto-oncogenes (c-myc, c-fos, c-jun), differentiation inducing properties, antiproliferative effects on keratinocytes and inhibitory effects in several human malignancy ranks Vitamin D as a novel hormone that may have physiological and clinical implication in the carcinogenic process.

Sister chromatid exchange in patients with joint prostheses

The evaluation of sister chromatid exchanges (SCE) is used to establish the cytogenic damage in subjects exposed to toxic substances. The test is considered to be 1 of the most sensitive and accurate indicators of damage and responds to toxic chemicals at low doses. We evaluated the incidence of SCE in peripheral lymphocytes of patients with articular prostheses. Subjects with prostheses made of titanium-aluminium-vanadium alloys presented a significantly higher SCE number than the control population (6.3+/-2.3 vs 4.4+/-1.3; P = .0128), whereas subjects with prostheses made of chrome-cobalt alloy or mixed prostheses presented a higher SCE value than the controls but not significantly different. The presence of high-frequency cells was alarming only in 5 patients, 4 of whom had titanium alloy prostheses, whereas none belonged to the control group. The number of SCE was not affected by the presence of bone-cement used in prosthesis fixation or by the implant duration. The indication of possible cytogenic damage in patients with titanium alloy prostheses that emerged from this study should be considered carefully, even though the sample population was small.

Molecular epidemiology in cancer research

The use of molecular biomarkers in epidemiological investigations brings clear advantages of economy, speed and precision. Epidemiology--the study of the factors that control the patterns of incidence of disease--normally requires large numbers of subjects and/or long periods of time, because what is measured (the occurrence of disease) is a rare event. Biomarkers are measurable biological parameters that reflect, in some way, an individual's risk of disease-because they indicate exposure to a causative (or protective) agent, or because they represent an early stage in development of the disease, or because they allow an assessment of individual susceptibility. Biomarkers must be usable on one of the few materials available for biomonitoring of humans, i.e. blood, urine, exfoliated epithelial cells and, with some difficulty, biopsies. The approach of molecular epidemiology has a great potential is several areas of cancer research: investigating the aetiology of the disease; monitoring cancer risk in people exposed to occupational or environmental carcinogens; studying factors that protect from cancer; and assessing intrinsic factors that might predispose to cancer. The biomarkers most commonly employed in cancer epidemiology include: measurements of DNA damage--DNA breaks, altered bases, bulky adducts--in lymphocytes; the surrogate marker of chemical modifications to blood proteins, caused by agents that also damage DNA; the presence of metabolites of DNA-damaging agents (or the products of DNA damage themselves) in urine; chromosome alterations, including translocations, micronuclei and sister chromatid exchange, resulting from DNA damage; mutations in marker genes; DNA repair; and the differential expression of a variety of enzymes, involved in both activation and detoxification of carcinogens, that help to determine individual susceptibility. The molecular approach has been enthusiastically employed in several studies of occupational/environmental exposure to carcinogens. While the estimation of biological markers of exposure has certainly shown the expected effects in terms of DNA damage and adducts, the detection of the biological effects of exposure (e.g. at the level of chromosome alterations) has not been so clear-cut. This is true also when smokers are examined as a group compared with non-smokers. Several markers (especially of chromosome damage and mutation) show a strong correlation with age-indicating either an increasing susceptibility to damage with age, or an accumulation of long-lived changes. DNA repair--a crucial player in the removal of damage before it can cause mutation--may vary between individuals, and may be modulated by intrinsic or extrinsic factors, but limited data are available because of the lack of a reliable assay. Information on other enzymes determining individual susceptibility does exist, and some significant effects of phenotypic or genotypic polymorphisms have emerged, although the interactions between various enzymes make the situation very complex. The important question of whether oxidative DNA damage in normal cells is decreased by dietary antioxidants (vitamin C, carotenoids etc., from fruit and vegetables) has been tackled in antioxidant supplementation experiments. The use of poorly validated assays for base oxidation has not helped us to reach a definitive answer; it seems that, in any case, the level of oxidative damage has been greatly exaggerated. DNA-damaging agents lead to characteristic kinds of base changes (transitions, transversions, deletions). The investigation of the spectrum of mutations in cancer-related genes studied in tumour tissue should lead to a better understanding of the agents ultimately responsible for inducing the tumour. Similarly, studying mutations in a neutral marker gene (not involved in tumorigenesis) can tell us about the origins of the 'background' level of mutations. So far, interpretation of the growing databases is largely speculative. (ABSTRACT

Assessment of the role of diet in cancer prevention

Population studies have demonstrated a clear relationship between the incidence of various cancers and consumption of different classes of foods, indicating that diet can have a protective effect. Diets, however, contain many hundreds of nutrient and non-nutrient compounds. Moving beyond the generalities provided by population studies requires short-term studies in which diets can be adjusted to test the effects of specific ingredients or compounds. The cost of this approach is the loss of direct outcome measures. Biomarkers related to early events in the cancer process which can show significant change within the duration of a trial, have to substitute. The choice of marker and the ability to validate its use are crucial both to the refining of dietary advice and to the search for the active principles of diet.

Analysis of mitomycin C-induced micronuclei in lymphocytes from malnourished infected children

The purpose of this study was to determine if peripheral blood lymphocytes from malnourished children with gastrointestinal or respiratory bacterial infection show increased frequencies of Mitomycin C (MMC)-induced micronuclei as compared to well-nourished, infected children. The results indicate that cells from malnourished, infected children had greater chromosome damage. This may indicate that such children would be more susceptible to environmental damage and malignant transformation. Micronucleus frequencies were analyzed in binucleate cells produced by the cytokinesis block method; the overall micronucleus frequency was significantly higher in binucleate cells from malnourished, infected children. The mean micronucleus frequency in MMC-free cultures was 4.3/1000 in malnourished infected children and 1.0/1000 in well-nourished infected children. In MMC-exposed cultures the mean induced micronucleus frequency was 32.6 +/- 6.1 vs. 12.9 +/- 2.3; 68.6 +/- 12.1 vs. 21.0 +/- 5.1, and 88.1 +/- 16.2 vs. 41.7 +/- 5.0 for malnourished and well-nourished children at 20, 40, and 60 ng/ml MMC, respectively. The number of binucleated cells with more than one micronucleus was also higher in malnourished, infected children at all doses tested, including cells with two micronuclei in MMC-free cultures from malnourished, infected children. This increase was not found in peripheral blood lymphocytes from well-nourished infected children.

Cell cycle phase duration in bone marrow cells from malnourished rats during suckling

The generation time and duration of the different phases of the cell cycle were estimated in cultured bone marrow cells from malnourished and well-nourished rats during the lactation period by the percentage labeled mitosis (PLM) technique after a short pulse treatment with tritiated thymidine. The PLM were obtained in sequential analysis after every 3 h from removing labeled thymidine to 27 h of incubation. Results have shown a longer cell cycle time in cells from malnourished rats. The G1 + 1/2M phases are sensitive to experimental severe protein malnutrition (PCM), while S and G2 + 1/2 M phases did not show any differences in duration between malnourished and well-nourished rats.

Assessment of DNA damage in leukocytes from infected and malnourished children by single cell gel electrophoresis/comet assay

The alkaline single cell gel (SCG) assay is a sensitive electrophoretic technique for detecting the presence of DNA single strand breaks and alkali-labile damage in individual cells. This technique was used to assess and compare the level of DNA damage in peripheral blood leukocytes/lymphocytes from well-nourished children with infection, well-nourished children with infection and under drug treatment, and from malnourished infected children with and without previous drug treatment. The present study shows that severe infection is associated with a significant increase in DNA damage. The average migration length was five times greater in severely infected well-nourished children compared to that found in healthy, well-nourished children. The results obtained in this study indicate that malnutrition is another factor associated with an increase in DNA migration. The average tail length for malnourished, severely infected children was twice as great as that obtained for cells from well-nourished, severely infected children. We also detected a variable increase in DNA migration associated with treatment for severe infection. Nevertheless, the excessive heterogeneity, the concurrent number of drugs used and the limited size of the treated population precludes an accurate assessment of which drugs were involved in the increase in DNA damage. Further studies will be necessary involving a large number of patients to address the relation between levels of DNA damage and specific kinds of infection, various drug treatments, and the type and severity of malnutrition. The increased level of DNA damage in severely infected and malnourished children could be related to negative effects such as a deficient immune response resulting in an increased susceptibility to malignant transformation.

Effect of renutrition on the proliferation kinetics of PHA stimulated lymphocytes from malnourished children

The fraction of lymphocytes that responded to phytohemagglutinin (PHA) stimulation and initiated cellular proliferation (stimulation index or SI) was determined in groups of healthy and severely malnourished children. SI was determined again in the latter group after a period of nutritional recovery. The proportion of interphasic cells showing PHA response was assessed adding bromodeoxyuridine to the culture, so proliferative nuclei appear big and stain light blue, with dispersed granular chromatin and apparent nucleoli, while non-proliferative nuclei look small, stain red, and have compact and homogeneous chromatin. In mitotic nuclei, differential staining of sister chromatids made it possible to distinguish cells that had gone through one, two and three or more proliferation cycles. Based on the data obtained from interphase nuclei and mitosis, the SI was estimated at 48 and 72 h of culture. SI were higher in lymphocytes from healthy children than in those from children with severe malnutrition, even after the period of nutritional recovery. However, the SI was significantly higher in lymphocytes from malnourished children after nutritional recovery. Although in these children more cells are stimulated, there seems to be still damage that causes a cycling delay.