DNA Damage in T and B Lymphocytes, Bone Marrow, Spleens, and Livers of Rats Exposed to Benzene

Benzene induces spleen injury through the B cell receptor signaling pathway

Benzene is a toxic environmental pollutant that disrupts the immune system in humans. Benzene exposure reduces the abundance of immune cells in multiple immune organs; however, the biological mechanisms underlying benzene-induced immunotoxicity has not been elucidated. In this study, benzene was used to develop mouse model for immune dysfunction. A significant decrease in IgG, IL-2 and IL-6 levels, an increase in oxidative stress and spleen injury were observed after benzene exposure in a dose-dependent manner. Quantitative proteomics revealed that benzene-induced immune dysfunction was associated with deregulation of the B cell receptor (BCR) signaling pathway. Benzene exposure suppressed the expression of CD22, BCL10 and NF-κb p65. Also, a significant decrease in proliferation and an increase in apoptosis of splenic lymphocytes were found after benzene exposure. Moreover, we found that benzene exposure increased mitochondrial reactive oxygen species (mito-ROS) and decreased adenosine triphosphate (ATP). Overall, we revealed the damaging effects of benzene on spleen-related immune function and the underlying biological mechanism, involving the disruption of BCR signaling pathway, NF-κB deactivation, and mitochondrial dysfunction.

Quantitative measurement of oxidative damage in erythrocytes as indicator in benzene intoxications

The metabolism of aromatic hydrocarbons by the organism forms products that cause cell death depending on the type of exposure. Benzene exposure has been linked to oxidative stress, hepatic damage, aplastic anemia, and hematopoietic cancer as lymphoid and myeloid leukemia. However, there are not fast methods to evaluate chronic benzene exposure in human blood. The objective of this work was the evaluation of the correlation between oxidative damage with benzene exposure and the level of cellular plasma membrane stability (CPMS) in erythrocytes to use it as a future indicator to determine the grade of benzene intoxications. CPMS in vitro assays were used to evaluate damage for benzene, toluene, and xylene. Erythrocytes CPMS assays in vitro shows a progressive reduction with benzene, toluene, and xylene suggesting that aromatic hydrocarbons complexity favors CPMS damage. Eight groups of Wistar rats (n = 5) were used to study the level of damage on CPMS by acute and chronic benzene administration. Enzymatic, metabolic, histological, and oxidative damage tests were performed. Acute administration (100 μL/100 g/single dose) showed a decrease of 66.7% in CPMS, while 63.6% for chronic administration (5 μL/100 g/every 2 days/3 months) showing a correlation with liver damage principally (transaminases activity increase, glycogen level decrease, and high oxidative damage). Tissue damage was observed in bone marrow, kidney, spleen, and lungs. Benzene produces damage on CPMS depending on the exposure time and dose. The CPMS technique could be used as an important aromatic hydrocarbons intoxication indicator.

Inhalation exposure to chloramine T induces DNA damage and inflammation in lung of Sprague-Dawley rats

Chloramine T has been widely used as a disinfectant in many areas such as kitchens, laboratories and hospitals. It has been also used as a biocide in air fresheners and deodorants which are consumer products; however, little is known about its toxic effects by inhalation route. This study was performed to identify the subacute inhalation toxicity of chloramine T under whole-body inhalation exposure conditions. Male and female groups of rats were exposed to chloramine T at concentrations of 0.2, 0.9 and 4.0 mg/m³ for 6 hr/day, 5 days/week during 4 weeks. After 28-day repeated inhalation of chloramine T, there were dose-dependently significant DNA damage in the rat tissues evaluated and inflammation was histopathologically noted around the terminal airways of the lung in both genders. As a result of the expression of three types of antioxidant enzymes (SOD-2, GPx-1, PRX-1) in rat's lung after exposure, there was no significant change of all antioxidant enzymes in the male and female rats. The results showed that no observed adverse effect level (NOAEL) was 0.2 mg/m³ in male rats and 0.9 mg/m³ in female rats under the present experimental condition.

Subacute inhalation toxicity assessment of fly ash from industrial waste incinerators

Fly ash from industrial waste incinerators has been a significant concern because of their constituent toxic heavy metals and organic compounds. The objective of this study was to identify the subacute inhalation toxicity of fly ash from industrial waste incinerators, using whole body inhalation exposure chambers. Male and female groups of Sprague-Dawley rats were exposed to fly ash by inhalation of concentrations of 0, 50, 100, 200 mg/m(3), for 6 h/day, 5 days/week for 4 weeks. There was no significant difference in body weight, and relative organ weight to body weight, between the exposure groups and the control group. Hematological examinations revealed a significant increase of monocyte counts in fly ash exposed rats and brown pigment laden macrophage was found in the lungs of rats exposed to high concentration of fly ash. A decrease of blood glucose levels and an increase in glutamate oxaloacetate transaminase activity were observed in fly ash treated rats. There was also a significant increase of lactate dehydrogenase levels in rat blood exposed fly ash. A significant dose-dependent increase of DNA damage was found in lymphocytes, spleen, bronchoalveolar lavage, liver, lung, and thymus of rats exposed to fly ash. In addition, the level of lipid peroxidation was increased in the plasma of rats exposed to a high concentration of fly ash. These results suggest that inhalation of fly ash from industrial waste incinerators can induce histopathologic, hematological, and serum biochemical changes and oxidative damage.

ATSDR evaluation of health effects of benzene and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Benzene. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of benzene. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.

Cluster of Hodgkin’s lymphoma in residents near a non-operational petroleum refinery

This report examines the prevalence rate of Hodgkin’s disease in an American mid-west town located directly south of a non-operational oil refinery. The refinery has a history of benzene-containing gasoline leaks dating back to the early 1900s. Exposure data were assessed through the Toxic Release Inventory (TRI) data as published by the Environmental Protection Agency (EPA) and supplemented by exposure simulations using variations of residential exposure times and odour levels and the benzene content of the gasoline. Prevalence rates depended on the size of the population in question. The population size varied greatly between sources, with the more conservative and consistent estimates being reported by the local government and United States Census Bureau and the highest population figure being reported by the Agency for Toxic Substances Disease Registry. The prevalence of Hodgkin’s disease for the residents within 1 mile from the refinery was found to be elevated for every population figure, ranging from 72.11 cases per 100,000 using the ATSDR’s population to 182.34 per 100,000, whereas the prevalence for Hodgkin’s disease in all the United States is only 22 cases of Hodgkin’s disease per 100,000 people. The prevalence value reported in this report should be given greater weight than what would have been calculated using data from the ATSDR. Because of its significantly increased value compared with the rest of the United States, it provides evidence of benzene’s role as a causative agent in the etiology of Hodgkin’s disease.

Oxidative damages in the DNA, lipids, and proteins of rats exposed to isofluranes and alcohols

DNA damage, lipid peroxidation and protein oxidation were evaluated in rats exposed to a 1% isoflurane atmosphere with or without alcohol administration (administrated by gastric intubation at 4 g/kg body weight as a 50% solution). Single cell gel electrophoresis assays were performed in order to evaluate DNA damage occurring in the lymphocytes, spleen, bone marrow, brain, livers and lung of rats exposed to 1% isoflurane for 30 or 60 min with/without ethanol. Levels of malondialdehydes (MDA), a metabolite of lipid peroxidation, were determined in plasma and tissues. Carbonyl contents were also analyzed to determine levels of protein oxidation in plasma and tissues. Levels of DNA damage in lymphocytes, bone marrow, and the organ tissues of rats exposed to isoflurane were found to increase time dependently, and alcohol increased DNA damage. Lipid peroxidation and protein oxidation results showed patterns that differed from those of DNA damage. Levels of MDA in plasma, bone marrow, spleen, and the livers of rats exposed to isoflurane with/without ethanol were found to be time dependently increased, but this was not observed in the brain or lung. However, protein oxidation levels were significantly increased in the plasma, brains, and lungs of rats exposed to isoflurane, and exposure to isoflurane and alcohol, significantly increased these levels in plasma and brain. The present study demonstrates that isoflurane exposure results in significant DNA damage in rat lymphocytes, bone marrow, spleen, brain, livers, and lung. Moreover, alcohol was found to be as a strong inducer of DNA damage, lipid peroxidation and protein oxidation. However, no evidence in association between DNA damage, lipid peroxidation and protein oxidation was found. Regarding the effects of isoflurane and alcohol on oxidative damages, single strand DNA damages may be a useful biomarkers and blood cells and plasma appear to be more sensitive targets to oxidative damage than other tissues.