Acute cytogenetic effect of benzene on rat bone marrow cells in vivo and the effect of inducers or inhibitors of drug-metabolizing enzymes

Identification of the Mechanism of Feiduqing on Viral Pneumonia Based on Network Pharmacology Analysis

Feiduqing (FDQ) is a traditional Chinese medicine formula used for many years in the treatment of viral pneumonia (VP). However, the effective components of FDQ and the mechanism by which it affects VP remain unclear. The purpose of this study is to determine the multitarget mechanism of the effect of FDQ on VP through determination and in vivo pharmacodynamics combined with network pharmacology. Firstly, the compound–target–pathway network was constructed by using TCMSP, UniProt, GeneCards, STRING, and DAVID databases through Cytoscape 3.7.0. Secondly, the content of the effective components of the original prescription of FDQ was determined. Finally, the pharmacological activity of FDQ in vivo was verified by an animal model, and the active ingredient composition (AIC), selected by network pharmacology was used for antipyretic, antiinflammatory, antitussive, and expectorant symptoms. Seven compounds of FDQ and 22 potential target genes in the treatment of VP with FDQ were identified by network pharmacology analysis. Kyoto Encyclopedia of genes and genomes enrichment analysis results indicated that the mechanism of FDQ in the treatment of VP was mainly related to pathways in cancer, hepatitis b, tumor necrosis factor (TNF) signaling pathway, Chagas disease, tuberculosis, influenza A, human T-cell leukemia virus, type 1 infection, toxoplasmosis and toll-like receptor signaling pathways, osteoclast differentiation, nonalcoholic fatty liver disease, and leishmaniasis. The results of pharmacodynamic experiments showed that FDQ and AIC possessed antipyretic, cough relieving, and reducing sputum effects. Besides, FDQ and AIC could also significantly reduce the content of prostaglandin E2, TNF-α, cyclic adenosine monophosphate, interleukin-1β, and myeloperoxidase in vivo, while increasing the content of interleukin-10 in vivo. The active ingredients of FDQ prescriptions could be accurately screened by network pharmacological analysis, as they clarified the mechanism of FDQ in the treatment of VP. The research results provided potential ideas and methods for the screening and purification of active ingredients in traditional Chinese medicine prescriptions.

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.

Zizyphus jujuba and Origanum majorana extracts protect against hydroquinone-induced clastogenicity

Hydroquinone (HQ) is a myelotoxin that is found in many foods and formed through the metabolism of benzene. HQ is genotoxic in several in vitro and in vivo test systems, inducing micronuclei (MN), sister-chromatid exchange (SCE), and chromosomal aberrations. The aim of the current study was to explore the protective effect of Zizyphus jujuba and Origanum majorana extracts against HQ-induced genotoxicity in male mice. Five groups of mice included the control group, HQ-treated group, and the groups treated with the extracts alone or in combination with HQ. The results indicated that treatment with HQ resulted in significant clastogenetic effects and histological changes typical to those reported in the literature. Both extracts exhibited a protection against HQ-induced cytogenesis and histological changes. Moreover, Z. jujuba extract was effective than O. majorana extract. It could be concluded that both extracts are useful especially for people who are occupationally exposed to benzene or its metabolites.

Genotoxicity of benzene and its metabolites

The potential role of genotoxicity in human leukemias associated with benzene (BZ) exposures was investigated by a systematic review of over 1400 genotoxicity test results for BZ and its metabolites. Studies of rodents exposed to radiolabeled BZ found a low level of radiolabel in isolated DNA with no preferential binding in target tissues of neoplasia. Adducts were not identified by 32P-postlabeling (equivalent to a covalent binding index <0.002) under the dosage conditions producing neoplasia in the rodent bioassays, and this method would have detected adducts at 1/10,000th the levels reported in the DNA-binding studies. Adducts were detected by 32P-postlabeling in vitro and following high acute BZ doses in vivo, but levels were about 100-fold less than those found by DNA binding. These findings suggest that DNA-adduct formation may not be a significant mechanism for BZ-induced neoplasia in rodents. The evaluation of other genotoxicity test results revealed that BZ and its metabolites did not produce reverse mutations in Salmonella typhimurium but were clastogenic and aneugenic, producing micronuclei, chromosomal aberrations, sister chromatid exchanges and DNA strand breaks. Rodent and human data were compared, and BZ genotoxicity results in both were similar for the available tests. Also, the biotransformation of BZ was qualitatively similar in rodents, humans and non-human primates, further indicating that rodent and human genotoxicity data were compatible. The genotoxicity test results for BZ and its metabolites were the most similar to those of topoisomerase II inhibitors and provided less support for proposed mechanisms involving DNA reactivity, mitotic spindle poisoning or oxidative DNA damage as genotoxic mechanisms; all of which have been demonstrated experimentally for BZ or its metabolites. Studies of the chromosomal translocations found in BZ-exposed persons and secondary human leukemias produced by topoisomerase II inhibitors provide some additional support for this mechanism being potentially operative in BZ-induced leukemia.

Antigenotoxic effects of cimetidine against benzene induced micronuclei in mouse bone marrow erythrocytes

An in vivo micronucleus assay using Balb/C male mice was used to examine antigenotoxic effects of cimetidine (CM) on benzene (BZN) induced genotoxic effects. CM not only has therapeutic and immunomudolatory role, but it has also been shown to protect bone marrow stem cells from radiation induced clastogenic effects. Therefore, in the present study we attempt to investigate the protective effects and possible mechanisms involved in the effects of CM. An 8-week-old male Balb/C mice (22+/-4 g weight) were treated with different doses of BZN (400, 600 and 800 mg/kg body weight), i.p. and sampled at 24, 48 and 72 h after treatment by cervical dislocation. Various doses of CM (10, 15, 30 mg/kg) were used in association with BZN and 1-2 h prior to BZN treatment. Results show that BZN effectively induced micronuclei in polychromatic erythrocytes (PCEs). Application of CM led to a significant reduction of micronuclei in PCEs, i.e. 2-fold after 10 mg/kg and 3-fold after 30 mg/kg CM treatment. Results also indicate CM was more effective when used in combination with BZN. Therefore, results indicate that CM could reduce clastogenic effects of BZN. Although further investigations are needed to reveal the mechanistical background behind the effect, the most probable mechanism involved might be free radical scavenging. This mechanism might be associated with amplification of glutathione system and cytochrome P-450 inhibition.

A perspective on benzene leukemogenesis

Although benzene is best known as a compound that causes bone marrow depression leading to aplastic anemia in animals and humans, it also induces acute myelogenous leukemia in humans. The epidemiological evidence for leukemogenesis in humans is contrasted with the results of animal bioassays. This review focuses on several of the problems that face those investigators attempting to unravel the mechanism of benzene-induced leukemogenesis. Benzene metabolism is reviewed with the aim of suggesting metabolites that may play a role in the etiology of the disease. The data relating to the formation of DNA adducts and their potential significance are analyzed. The clastogenic activity of benzene is discussed both in terms of biomarkers of exposure and as a potential indication of leukemogenesis. In addition to chromosome aberrations, sister chromatid exchange, and micronucleus formation, the significance of chromosomal translocations is discussed. The mutagenic activity of benzene metabolites is reviewed and benzene is placed in perspective as a leukemogen with other carcinogens and the lack of leukemogenic activity by compounds of related structure is noted. Finally, a pathway from exposure to benzene to eventual leukemia is discussed in terms of biochemical mechanisms, the role of cytokines and related factors, latency, and expression of leukemia.

Long-Evans A and C rat strains susceptible to clastogenic effects of chemicals in the bone marrow cells

The clastogenic responses to direct- and indirect-acting carcinogens in bone marrow cells of LEA, LEC, Wistar and SD rats were compared. The frequency of chromosome aberrations (CA) induced by n-butyl-N-nitrosourea or methylmethanesulfonate (MMS), which does not need metabolic activation, was significantly higher in both LEA and LEC rats than in Wistar or SD rats. When bone marrow cells of each rat strain were exposed to MMS in vitro, they also showed the same tendency in CA frequency. Therefore, the high sensitivity of both LEA and LEC rats to the clastogenic effects of direct-acting carcinogens seems to result from the sensitivity of the bone marrow cells themselves. On the other hand, the CA frequency induced by 7,12-dimethylbenz[a]anthracene (DMBA) or aflatoxin B1 (AFB1), which requires metabolic activation, was lower in LEC rats than in the other 3 strains. The CA frequency induced by DMBA or AFB1 in LEC rats fed Cu-free diet since birth (Cu-free LEC rats) was higher than that in LEC rats given normal diet and lower than that in LEA rats, although the difference was statistically significant only between Cu-free LEC rats and LEC rats treated with DMBA. The copper concentrations in the livers of LEA, Cu-free LEC and LEC male rats aged 4 weeks were 5.0 +/- 0.4, 33 +/- 7.7 and 106 +/- 3.4 micrograms/g wet weight, respectively. These results suggest that the lower sensitivity of LEC rats to the clastogenic effects of indirect-acting carcinogens may be due to the effect of the large amount of copper accumulated in LEC rat liver.