Genetic activity of the human carcinogen sulphur mustard towards Salmonella and the mouse bone marrow

Proteomic, Metabolomic, and Lipidomic Analyses of Lung Tissue Exposed to Mustard Gas

Sulfur mustard (HD) poses a serious threat due to its relatively simple production process. Exposure to HD in the short-term causes an inflammatory response, while long-term exposure results in DNA and RNA damage. Respiratory tract tissue models were exposed to relatively low concentrations of HD and collected at 3 and 24 h post exposure. Histology, cytokine ELISAs, and mass spectrometric-based analyses were performed. Histology and ELISA data confirmed previously seen lung damage and inflammatory markers from HD exposure. The multi-omic mass spectrometry data showed variation in proteins and metabolites associated with increased inflammation, as well as DNA and RNA damage. HD exposure causes DNA and RNA damage that results in variation of proteins and metabolites that are associated with transcription, translation and cellular energy.

DNA repair mechanisms in response to genotoxicity of warfare agent sulfur mustard

Sulfur mustard (SM) is an alkylating agent that causes severe damages to the skin, eyes, and the respiratory system. DNA alkylation is one of the most critical lesions that could lead to monoadducts and cross-links, as well as DNA strand breaks. In response to these adducts, cells initiate a series of reactions to recruit specific DNA repair pathways. The main DNA repair pathways in human cells, which could be involved in the DNA SM-induced DNA damages, are base excision repair (BER), nucleotide excision repair (NER), homologous recombination (HR) and non-homologous end joining (NHEJ). There is, thus, a need for a short review to clarify which damage caused by SM is repaired by which repair pathway. Increasing our knowledge about different DNA repair mechanisms following SM exposure would lay the first step for developing new therapeutic agents to treat people exposed to SM. In this review, we describe the major DNA repair pathways, according to the DNA adducts that can be caused by SM.

Combinations of genotoxic tests for the evaluation of group 1 IARC carcinogens

Many of the known human carcinogens are potent genotoxins that are efficiently detected as carcinogens in human populations but certain types of compounds such as immunosuppressants, sex hormones, etc. act via non-genotoxic mechanism. The absence of genotoxicity and the diversity of modes of action of non-genotoxic carcinogens make predicting their carcinogenic potential extremely challenging. There is evidence that combinations of different short-term tests provide a better and efficient prediction of human genotoxic and non-genotoxic carcinogens. The purpose of this study is to summarize the in vivo and in vitro comet assay (CMT) results of group 1 carcinogens selected from the International Agency for Research on Cancer and to discuss the utility of the comet assay along with other genotoxic assays such as Ames, in vivo micronucleus (MN), and in vivo chromosomal aberration (CA) test. Of the 62 agents for which valid genotoxic data were available, 38 of 61 (62.3%) were Ames test positive, 42 of 60 (70%) were in vivo MN test positive and 36 of 45 (80%) were positive for the in vivo CA test. Higher sensitivity was seen in in vivo CMT (90%) and in vitro CMT (86.9%) assay. Combination of two tests has greater sensitivity than individual tests: in vivo MN + in vivo CA (88.6%); in vivo MN + in vivo CMT (92.5%); and in vivo MN + in vitro CMT (95.6%). Combinations of in vivo or in vitro CMT with other tests provided better sensitivity. In vivo CMT in combination with in vivo CA provided the highest sensitivity (96.7%).

Sulfur mustard toxicity: history, chemistry, pharmacokinetics, and pharmacodynamics

Sulfur mustard (SM) and similar bifunctional agents have been used as chemical weapons for almost 100 years. Victims of high-dose exposure, both combatants and civilians, may die within hours or weeks, but low-dose exposure causes both acute injury to the eyes, skin, respiratory tract and other parts of the body, and chronic sequelae in these organs are often debilitating and have a serious impact on quality of life. Ever since they were first used in warfare in 1917, SM and other mustard agents have been the subjects of intensive research, and their chemistry, pharmacokinetics and mechanisms of toxic action are now fairly well understood. In the present article we review this knowledge and relate the molecular-biological basis of SM toxicity, as far as it has been elucidated, to the pathological effects on exposure victims.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Delayed haematological complications of mustard gas

Haematopoiesis could be affected by mustard gas. We randomly selected 318 chemical victims exposed to mustard gas and compared their cell blood counts and peripheral blood smears (PBS) with those of 377 healthy men, and also various haematological indices of 57 of these victims compared with previous data 5 years ago. The average number of red blood cells and haemoglobin of victims compared with the controls was not significantly different, but they were increased compared with data from 5 years ago. White blood cell counts, neutrophils and lymphocytes did not show any clinically meaningful difference compared with the control group but 20 cases with atypical lymphocytes in their PBS have been found. Change in lymphocyte shape may be related to committed stem cell involvement. Further studies on bone marrow cells and cell markers are needed to document this hypothesis. The mild increase in erythroid cells and haemoglobin concentration may be due to chronic obstructive pulmonary disorder and other respiratory diseases in these patients.

A sequential approach to testing with the rodent bone marrow micronucleus assay--obviation of the need for statistical analyses of data

The 'sequential' protocol we use for the conduct of mouse bone marrow micronucleus assays is described. The most important criterion for activity in the assay is the reproducibility of any induced effects. The frequencies of micronucleated polychromatic erythrocytes among 239 male CBA control mice are displayed and discussed. Our decision to avoid statistical analysis when assessing mouse bone marrow micronucleus data is explained.

Dose dependent effects on lymphoid organs following a single dermal application of sulphur mustard in mice

The effects of a single dermal application of sublethal doses [15.5, 7.75 and 3.88 mg kg-1] of bis(2-chloroethyl)sulphide [sulphur mustard, SM] on body weight, organ/body weight ratio, haematology, histology and cellularity of spleen and thymus were studied after 7 days, in Balb/c mice. A progressive fall in body weight was noticed from the fifth day onwards after SM treatment. A dose-dependent decrease in the relative weights of spleen, liver and peripheral lymph nodes, and an increase in adrenal weight were also seen. An increase in red blood cell count, packed cell volume and haemoglobin concentration following SM intoxication were also dose dependent. These changes, together with a significant reduction in the cellularity of the spleen and thymus and degenerative histological changes, show that a single sublethal dermal dose of SM can cause considerable dose dependent systemic effects in Balb/c mice.

Historical origins of current concepts of carcinogenesis

The first attempts to understand the causes of cancer were based on generalizations of what might now be termed a "holistic" nature, and hereditary influences were recognized at an early stage; these views survive principally through a supposed positive connection between psychological factors such as stress and diminished ability to combat the progressive development of tumors through some form of immunologically mediated rejection of potentially cancerous cells. While evidence for immunosurveillance is generally accepted, it is now widely regarded as almost wholly confined to instances where tumor viruses are involved as causative agents. The earliest theorists drew an analogy between the processes of carcinogenesis and of evolution; the cancer cells acquired the ability to outstrip their normal counterparts in their capacity for proliferation. This was even before evolution had been interpreted as involving a continuous succession of mutations. Evidence was already to hand before the end of the 18th century that exogenous agents, notably soot, a product of the "industrial revolution," could cause skin cancer. Somewhat over 100 years later, another industrial innovation, the manufacture of synthetic dyestuffs, implicated specific chemical compounds that could act systemically to cause bladder cancer. Meanwhile, the 19th century saw the establishment of the fundamentals of modern medical science; of particular relevance to cancer was the demonstration that it involved abnormalities in the process of cell division. The commencement of the 20th century was marked by a rediscovery of the concept of mutation; and it was proposed that cancer originated through uncontrolled division of somatically mutated cells. At around this time, two further important exogenous causative agents were discovered: X-rays and tumor viruses. In the late 1920s, x-radiation became the first established exogenous cause of mutagenesis. The discoverer of this phenomenon, H. J. Muller, suggested that while mutation in a single cell was the primary causative mechanism in carcinogenesis, its generally observed logarithmic increase in incidence with age reflected a "multihit" process, and that multiple successive mutations were required in the progeny of the original mutants. He also recognized that the rate of proliferation of potentially cancerous cells would markedly influence the probability of their subsequent mutation. These considerations are essentially the foundation of the generally accepted view of carcinogenesis that now seems unlikely to be superseded. However, this acceptance did not come about unopposed. The analogy between carcinogenesis and evolution was disliked by many biologists because it embodied the concept that cancer was an inevitable consequence of our evolutionary origins.(ABSTRACT TRUNCATED AT 400 WORDS)

Bone marrow micronucleus assay: a review of the mouse stocks used and their published mean spontaneous micronucleus frequencies

We have examined published negative control data from 581 papers on micronucleated bone marrow polychromatic erythrocytes (mnPCE) for differences in mean frequency and the frequency distribution profile among the mouse stocks used with the bone marrow micronucleus assay. For the 55 mouse stocks with published micronucleus assay data, the overall mean frequency is 1.95 mnPCE/1,000 PCE (1.95 mnPCE/1,000); for the 13 stocks most commonly used in the assay, it is 1.88 mnPCE/1,000. During the last 5 years, the mnPCE rate for these 13 major stocks has been 1.74 mnPCE/1,000. This current mean frequency is a substantial decrease from the mean of 3.07 mnPCE/1,000 observed for these 13 stocks for data published prior to 1981. Of the major stocks, the highest mean mnPCE negative control frequencies were observed for MS/Ae > BALB/c > C57Bl/6, and the lowest for CD-1 < Swiss Webster. We note that hybrid mouse stocks appear to have lower and less variable negative control frequencies than either of their parent strains and that the negative control frequency for some progeny stocks have diverged significantly from that of the parent stocks. Overall mean negative control frequencies appear to be correlated with breadth of the frequency distribution profile of published mean negative control values. Furthermore, a possible correlation between negative control frequency in the micronucleus assay and sensitivity to clastogens of different mouse strains may be indicated. The databases generated here allow us to define a range of norms for both the historical mean frequency and individual experimental mean frequencies for most stocks, but in particular, for the more commonly used mouse stocks. Our analysis, for the most part, bears out the recommendation of the first Gene-Tox Report on the micronucleus assay that the historical negative control frequency for a mouse stock should fall between 1 and 3 mnPCE/1,000. Eighty-six percent of the most commonly used mouse stocks have historical mean frequencies within this range. Though individual experimental mean values would not necessarily be expected to fall within the 1-3.00 mnPCE/1,000 range, 65.3% of the 2,327 published negative control values do, and 83.5% are < 3 mnPCE/1,000. The frequency with which an individual experimental mean value lies outside the 1.00 to 3.00 mnPCE/1,000 range differs among stocks and appears related to the mouse mean frequency. We suggest that the recommended range for historical mean frequency be extended slightly, to approximately 3.4 mnPCE/1,000, to accommodate some commonly used strains with overall mean negative control frequencies just above 3.00 mnPCE/1,000.(ABSTRACT TRUNCATED AT 400 WORDS)

Mutagenicity to Salmonella, Drosophila and the mouse bone marrow of the human antineoplastic agent fotemustine: prediction of carcinogenic potency

The antineoplastic agent fotemustine is shown to be a base-pair mutagen to Salmonella. Activity is more marked in the uvrB-proficient strain G46 than in the repair-deficient strain TA1535. This is consistent with its ability to cross-link DNA. Potent activity as a somatic and germ-cell mutagen to Drosophila was also observed. A potent clastogenic response was given by fotemustine in the mouse bone marrow following either oral gavage or intraperitoneal injection of a single dose of 5 mg/kg. In each of these respects it is shown to be indistinguishable from the structurally related antineoplastic agent and human carcinogen MeCCNU. It is concluded that fotemustine should be regarded as having clear potential to induce cancer in humans. Based on these data, including the preponderance of chromosome breakages over recessive lethal mutations in Drosophila, an estimated rodent carcinogenic potency (TD50) of between 15-150 mg/kg is suggested for fotemustine.

The genotoxicity of industrial wastes and effluents

A review of the literature published on the genotoxicity of industrial wastes and effluents using short-term genetic bioassays is presented in this document. The importance of this task arises from the ubiquity of genotoxic compounds in the environment and the need to identify the sources of contamination so that efforts aimed at control and minimization can be implemented. Of even greater significance is the immediate concern for the welfare of human health and the environment. Subheadings of this document include a description of the genetic bioassays that have been used to test industrial wastes, a compendium of methods commonly used to prepare crude waste samples for bioassay, and a review of the genetic toxicity of wastes and effluents. Wastes and effluents have been grouped according to industrial source. Major categories include chemical and allied products, pulp and paper manufacturing, defense and munitions, petroleum refining, primary metal industries, and miscellaneous industrial manufacturers. Within each industrial category, a synopsis of individual genetic toxicity studies is presented, followed by an interpretation of results on a comprehensive, industry-wide basis. In this evaluation, a discussion of the types and extent of genotoxic damage caused by a particular set of wastes is presented, and potential sources of genotoxic activity are identified. Concluding the document is a commentary, which discloses potential shortcomings in the way in which current legislation protects human heath and the environment from the release of genotoxic substances via industrial wastes and effluents. It also provides an assessment of the genotoxic burden that industrial wastes place on the environment.

Definitive relationships among chemical structure, carcinogenicity and mutagenicity for 301 chemicals tested by the U.S. NTP

An analysis is presented in which are evaluated correlations among chemical structure, mutagenicity to Salmonella, and carcinogenicity to rats and mice among 301 chemicals tested by the U.S. NTP. Overall, there was a high correlation between structural alerts to DNA reactivity and mutagenicity, but the correlation of either property with carcinogenicity was low. If rodent carcinogenicity is regarded as a singular property of chemicals, then neither structural alerts nor mutagenicity to Salmonella are effective in its prediction. Given this, the database was fragmented and new correlations sought between the derived sub-groups. First, the 301 chemicals were segregated into six broad chemical groupings. Second, the rodent cancer data were partially segregated by target tissue. Using the previously assigned structural alerts to DNA reactivity (electrophilicity), the chemicals were split into 154 alerting chemicals and 147 non-alerting chemicals. The alerting chemicals were split into three chemical groups; aromatic amino/nitro-types, alkylating agents and miscellaneous structurally-alerting groups. The non-alerting chemicals were subjectively split into three broad categories; non-alerting, non-alerting containing a non-reactive halogen group, and non-alerting chemical with minor concerns about a possible structural alert. The tumor data for all 301 chemicals are re-presented according to these six chemical groupings. The most significant findings to emerge from comparisons among these six groups of chemicals were as follows: (a) Most of the rodent carcinogens, including most of the 2-species and/or multiple site carcinogens, were among the structurally alerting chemicals. (b) Most of the structurally alerting chemicals were mutagenic; 84% of the carcinogens and 66% of the non-carcinogens. 100% of the 33 aromatic amino/nitro-type 2-species carcinogens were mutagenic. Thus, for structurally alerting chemicals, the Salmonella assay showed high sensitivity and low specificity (0.84 and 0.33, respectively). (c) Among the 147 non-alerting chemicals less than 5% were mutagenic, whether they were carcinogens or non-carcinogens (sensitivity 0.04).