The effect of exposure to carcinogenic metals on histone tail modifications and gene expression in human subjects

The precise mechanisms by which nickel and arsenic compounds exert their carcinogenic properties are not completely understood. In recent years, alterations of epigenetic mechanisms have been implicated in the carcinogenesis of compounds of these two metals. In vitro exposure to certain nickel or arsenic compounds induces changes in both DNA methylation patterns, as well as, in the levels of posttranslational modifications of histone tails. Changes in DNA methylation patterns have been reported in human subjects exposed to arsenic. Here we review our recent reports on the alterations in global levels of posttranslational histone modifications in peripheral blood mononuclear cells (PBMCs) of subjects with occupational exposure to nickel and subjects exposed to arsenic in their drinking water. Occupational exposure to nickel was associated with an increase in H3K4me3 and decrease in H3K9me2. A global increase in H3K9me2 and decrease in H3K9ac was found in subjects exposed to arsenic. Additionally, exposure to arsenic resulted in opposite changes in a number of histone modifications in males when compared with females in the arsenic population. The results of these two studies suggest that exposure to nickel or arsenic compounds, and possibly other carcinogenic metal compounds, can induce changes in global levels of posttranslational histone modifications in peripheral blood mononuclear cells.

DNA single strand breaks induced by low levels of occupational exposure to styrene: the gap between standards and reality

Styrene is a known mutagen and suspected carcinogen, used in the reinforced plastic industry. This study aims to identify the occurrence of DNA single strand breaks (SSBs) in workers exposed to styrene levels far below the recommended standards. We compared 26 exposed workers with 26 control subjects and found a significant increase in the incidence of DNA-SSBs in the exposed individuals. The levels of the biological indices of exposure (urinary mandelic and phenyl glyoxylic acids) were less than 25% of the recommended limits. Reduction of the threshold limit values/time-weighted-average (TLV-TWA) applied is strongly recommended.

Anaemia among young male workers in Alexandria, Egypt

In a cross-sectional survey, we investigated exposure to and the presence of factors associated with anaemia, such as socioeconomic conditions, dietary habits, intestinal parasitic infections and lead among 355 young male workers (7-19 years of age) employed in private workshops. Of the total study sample, 44.5% (158 participants) were found to be anaemic. The major risk factors for anaemia were multiple parasitic infection, high intensity of parasitic (Ascaris lumbricoides) infection and drinking tea soon after a meal. A significantly lower prevalence of anaemia was noted after Ramadan; it appeared to be the main factor associated with the presence or absence of anaemia and warrants further attention.

Neuroimmunotoxicology: humoral assessment of neurotoxicity and autoimmune mechanisms

The interactions between the nervous and immune systems have been recognized in the development of neurodegenerative disease. This can be exploited through detection of the immune response to autoantigens in assessing the neurotoxicity of environmental chemicals. To test this hypothesis, the following questions were addressed. a) Are autoantibodies to nervous system (NS) antigens detected in populations exposed to environmental or occupational chemicals? In sera of male workers exposed to lead or mercury, autoantibodies, primarily IgG, to neuronal cytoskeletal proteins, neurofilaments (NFs), and myelin basic protein (MBP) were prevalent. These findings were confirmed in mice and rats exposed to either metal. b) Do autoantibodies to NS antigens relate to indices of exposure? In humans exposed to either metal, and similarly in exposed rats, titers of IgG against NFs and MBP significantly correlated with blood lead or urinary mercury, the typical indices of exposure. c) Do autoantibodies correlate with sensorimotor deficits? In workers exposed to lead or mercury, a significant correlation was observed between IgG titers and subclinical deficits. Doses of metals used in rat exposures were subclinical, suggesting that autoantibodies may be predictive of neurotoxicity. d) Is the detection indicative of nervous system pathology? In rats exposed to metals, histopathology indicated central nervous system (CNS) and peripheral nervous system (PNS) damage. In addition there was evidence of astrogliosis, which is indicative of neuronal damage in the CNS, and the presence of IgG concentrated along the blood-brain barrier, as indicated by immunostaining for antibodies. e) Are immune responses to NS antigens pathogenic? Immunoglobulin fractions from rat and human sera interfered with neuromuscular function. These studies suggest that the detection of autoantibodies to NS-specific antigens may be used to monitor the development of neurotoxicity to environmental chemicals and that immune mechanisms may be involved in the progression of neurodegeneration.

Autoantibodies to neurofilaments (NF), glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) in workers exposed to lead

An expanded follow-up assessment of the autoantibody response to neuronal and astroglial autoantigens (NF68; NF160; NF200; MBP; GFAP) as early markers of neurotoxicity was performed in male workers exposed to lead (Pb) of a battery factory (n=50) and a matched reference group (R) of workers at a food packing plant (n=39). Mean age, years of exposure and blood lead (PbB ug/dl) (+/-SD) for lead and R, respectively, were: Age:39 +/- 6; 41 +/- 7; Yrs. Exposed: 14 +/- 6:0; PbB: 32 +/- 11: 16 +/- 5 percent with detectable titers to nervous system proteins in the Pb and R populations, respectively, were: Anti-NF68: 59; 17; Anti-NF160: 28; 15; Anti-NF200: 25; 0; Anti-GFAP: 90; 20; Anti-MBP: 16; 4. Autoantibodies to nervous system proteins predominated in workers occupationally exposed to Pb compared to R. Anti-NF68 and GFAP titers were the most frequently encountered. Anti-NF68 titers were significantly correlated with years of exposure (r = 0.538, p < 0.0001) and with PbB (r=0.325, p < 0.05). Furthermore, the number of detectable autoantibody types correlated with clinical scores of sensorimotor deficits (r = 0.459, p < 0.0001). This study suggests that autoantibodies provide a promising biomarker of neurotoxicity while providing information on subcellular targets. It also raises concerns of toxicant-induced autoimmune neuropathy.

Anaemia and intestinal parasitic infections among school age children in Behera Governorate, Egypt. Behera Survey Team

Anaemia is considered a serious public health problem in Egypt, although updated population-based data are lacking. Similarly, data on prevalence and intensity of infection with intestinal parasites, which are considered one possible cause of anaemia, are available only from small, unrepresentative sample surveys. The present research was implemented on an entire Governorate representative sample. The aim of the study was to assess the prevalence of anaemia and intestinal parasites in the area and to evaluate the role of each parasite in the epidemiology of anaemia among school age children. At the end of the survey, results of faecal analyses from direct smear and the Kato-Katz examination techniques were available from 1844 and 1783 children respectively, as well as haemoglobin levels measured by spectrophotometer from 1238 children aged 6-12 years. The prevalence of anaemia in the area was high (90 per cent), but very few serve forms were detected (< 2 per cent). Prevalence of intestinal parasites was high only for protozoa (Giardia intestinalis 24.7 per cent Entamoeba histolytica 17.5 per cent) and Schistosoma mansoni (20.7 per cent). From analysis of the results, Fasciola infection appeared to be highly endemic, even among children (3 per cent), and emerged as the factor most strongly correlated with low levels of haemoglobin (p < 0.0001). The effect of Fasciola on haemoglobin levels was related to the intensity of infection with this parasite. The role of S. mansoni as a risk factor for anaemia was supported by the present study. Among the protozoa, G. intestinalis was significantly correlated with low haemoglobin levels (p < 0.05). The present results substantiated similar findings from smaller studies. In future research, the relationship between Fasciola infection and anaemia needs to be studied with a well-controlled longitudinal design.

Different patterns of intestinal helminth infection among young workers in urban and rural areas of Alexandria Governorate, Egypt

The process of urbanisation taking place in most developing countries is creating favourable conditions for an increase in prevalence of infections, especially with intestinal parasites, in the marginal areas of the towns. The present study was implemented in 1996 to assess the varying prevalence and intensity of infection among young workers in urban and rural areas of the same Governorate (Alexandria, Egypt). The sample comprised 408 male subjects, 8 to 19 years of age, in various occupations: 308 from urban areas, 67 from an industrialised village close to the desert, and 33 from a rural village. A quantitative diagnosis of intestinal helminth infections was made using the Kato-Katz technique, with a double reading of each slide. The results showed a higher prevalence (> 50%) and intensity of infection (indirectly measured as number of eggs per gram of faeces) than in previous studies. Furthermore, a higher prevalence and intensity of infection with Ascaris lumbricoides and Trichuris trichiura was detected in urban districts, as compared to rural areas. This difference was statistically significant. High crowding index, latrine shared with other families and no piped water inside the household, were more common in urban areas as compared with rural settlements and also associated with a higher intensity of infection by soil-transmitted helminths. The trend toward urbanisation seems to have caused deterioration of living conditions and sanitation standards in some areas of Alexandria city, with the most vulnerable people experiencing an increase in intestinal parasitic infections.

Assessment of antisperm antibody in sera of mercury and lead exposed workers

Occupational exposure to lead or mercury was found to make protein better antigens. The production of autoantibodies to nervous system protein is one example of such effect. The present study aims to detect the possibility of induction of antisperm autoantibodies due to occupational exposure to lead or mercury. Male workers exposed to lead (n = 50) or to mercury (n = 39) were selected for this purpose and compared to a matched control group (n = 39). A negative control consisting of 17 females was also included. All subjects had two or more children. Blood samples were collected and the ELISA technique was applied to detect antisperm antibodies. Also, the levels of lead in blood and mercury in urine were determined as biological indices of exposure. Antisperm antibodies were detected in 90% of workers exposed to lead with the predominance of the IgG type and 84.6% of workers exposed to mercury with the predominance of the IgM type. Although the results did not correlate with the biological indices of exposure, it seems advisable to use the detection of sperm antibodies of sera of workers exposed to metals as a biological monitoring tool.

Biological monitoring of occupational exposure to contraceptive drugs

The present study was carried out for screening some biochemical changes due to occupational exposure to contraceptive drugs. It included 18 male workers and 22 female workers involved in the manufacture of contraceptive pills and 34 female workers manufacturing contraceptive ampoules. The levels of some sex hormones and gonadotropins were evaluated. Some parameters of blood picture, blood coagulation, liver and kidney functions, lipid profile and trace elements metabolism were assessed. Results were compared with those of a control group composed of 19 males and 27 females. Increased levels of estrogen among exposed workers was the main finding. It has been attributed to liver rather than pituitary dysfunction. A less atherogenic lipid profile has also been found. Referral to preventive measures has been recommended.

Chromosomal aberrations and micronuclei in reinforced plastics workers exposed to styrene

The aim of this study was to investigate the cytogenetic changes induced in humans exposed to styrene in a reinforced plastics plant. Blood and urine samples were collected from 18 styrene exposed workers and 18 age and sex matched control subjects from the administrative department of the same factory. Chromosome aberrations (CAs) and micronuclei (MN) (cytokinesis block method) were analyzed in blood lymphocytes. All of the subjects included in the study were male non-smokers. The duration of employment ranged from 10 to 22 years (14.3 +/- 4.4). In order to monitor exposure to styrene, urinary mandelic acid (MA) levels were measured using a standard colorimetric method. The level of thioethers in the urine was also determined colorimetrically. The mean level of mandelic acid was significantly higher in the exposed workers (328.44 +/- 266.21 mg/g creatinine) compared with that of the controls (50.09 +/- 16.84 mg/g creatinine) (p < 0.05). The level of urinary thioethers was found to be higher among the exposed workers. The number of cells with chromosomal aberrations was significantly higher in the workers (6.06 +/- 4.41) compared with the controls (3.44 +/- 2.28) (p < 0.05). There was no significant increase in the frequency of micronuclei in the exposed workers compared to controls. Our results support earlier findings on increased rates of chromosomal aberrations in reinforced plastics workers.

Study of some biochemical changes among workers occupationally exposed to phenol, alone or in combination with other organic solvents

The present study was aimed for the effects of exposure to multiple organic solvent vapors in comparison with single exposure to phenol. It included 20 workers exposed to phenol alone and 32 workers of combined exposure to phenol, benzene, toluene and methyl ethyl ketone. A control group of 30 subjects was also included. The levels of transaminases, total proteins, prothrombin time, bleeding time, clotting time, fasting blood sugar, serum creatinine and some trace elements (copper, zinc, iron, magnesium, manganese and calcium) were determined in blood together with a complete blood picture. Urine samples were analyzed for phenol, hippuric acid and methyl ethyl ketone. The effects of combined exposure did not differ from that of exposure to phenol alone concerning the majority of the tested parameters. Only the levels of platelets count, prothrombin time, eosinophils, copper and iron have been affected by combined exposure in a probably additive manner.

Effect of nickel sulfate alone and with ultraviolet light on micronuclei frequency in cultured human lymphocytes

Comutagenic or cocarcinogenic activities have been reported between nickel compounds and UV light. The presence of micronuclei in a binucleated lymphocyte is regarded as an alternative to classical cytogenic methods for monitoring chromosomal damage. The present study aimed to detect this comutagenicity as regards micronuclei induction. Human peripheral lymphocytes were treated with different concentrations of nickel sulfate and/or with UV light at 200 and 1000 ergs/mm2. Cells have been cultured and 100 binucleated cells were counted and the micronuclei frequency recorded. The observed values for all concentrations of nickel sulfate combined with UV were less than expected for an additive response of two agents computed as the combined increase over the values of the control for the metal and UV alone. Caution is advised when interpreting cytogenic values in multiple exposures.