Ethylene oxide as a biological reactive intermediate of endogenous origin

Phytochemical analysis and protective effects of Vaccinium macrocarpon (cranberry) in rats (Rattus norvegicus) following ethylene oxide-induced oxidative insult

The Vaccinium genus comprises more than 126 genera of perennial flowering plants that are commonly adapted to poor and acidic soils or epiphytic environments. Their molecular and genomic characterization is a result of the recent advent in next-generation sequencing technology. In the current research, extracts were prepared in different media, such as petroleum ether, methanol and ethanol. An extract of Vaccinium macrocarpon (cranberry) was used at a dose of 200–400 mg/kg by weight (B.wt). Levels of oxidative stress markers, i.e., superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), advanced oxidation protein products (AOPPs) and malondialdehyde (MDA), were measured. A histopathological study of six vital organs in rats was also conducted. The results indicated that the antioxidant levels were lower in the group given only ethylene oxide (EtO) but higher in the groups receiving cranberry extract as a treatment. Major improvements were also observed in stress markers such as advanced oxidation protein products (AOPPs) and MDA following cranberry treatment. Histopathological changes induced by EtO were observed in the heart, kidney, liver, lung, stomach and testis and were reversed following cranberry treatment. The major toxic effects of EtO were oxidative stress and organ degeneration, as observed from various stress markers and histopathological changes. Our study showed that this extract contains strong antioxidant properties, which may contribute to the amelioration of the observed toxic effects.

A speculative discussion of four animal carcinogens endogenously produced in humans and a formula for cancer development

The major factors (macro) which cause human cancer have been elucidated and include tobacco use, diet, infection, reproductive and sexual behavior and, to a lesser extent, alcohol consumption and occupational factors. Several reports have been published about endogenous chemicals made in humans which produce DNA adducts; however, few have linked them to possible carcinogenic activity. This paper discussed four chemicals made in humans (formaldehyde, acetaldehyde, isoprene and ethylene oxide), pathways of their formation, their animal carcinogenicity and questions about these and other endogenous chemicals’ possible role in human cancer. In addition, the author posits a simplified formula for development of cancer and a formula for causing mutations by various agents.

Analysis of hemoglobin adducts from acrylamide, glycidamide, and ethylene oxide in paired mother/cord blood samples from Denmark

The knowledge about fetal exposure to acrylamide/glycidamide from the maternal exposure through food is limited. Acrylamide, glycidamide, and ethylene oxide are electrophiles and form adducts with hemoglobin (Hb), which could be used for in vivo dose measurement. In this study, a method for analysis of Hb adducts by liquid chromatography-mass spectrometry, the adduct FIRE procedure, was applied to measurements of adducts from these compounds in maternal blood samples (n = 87) and umbilical cord blood samples (n = 219). The adduct levels from the three compounds, acrylamide, glycidamide, and ethylene oxide, were increased in tobacco smokers. Highly significant correlations were found between cord and maternal blood with regard to measured adduct levels of the three compounds. The mean cord/maternal hemoglobin adduct level ratios were 0.48 (range 0.27-0.86) for acrylamide, 0.38 (range 0.20-0.73) for glycidamide, and 0.43 (range 0.17-1.34) for ethylene oxide. In vitro studies with acrylamide and glycidamide showed a lower (0.38-0.48) rate of adduct formation with Hb in cord blood than with Hb in maternal blood, which is compatible with the structural differences in fetal and adult Hb. Together, these results indicate a similar life span of fetal and maternal erythrocytes. The results showed that the in vivo dose in fetal and maternal blood is about the same and that the placenta gives negligible protection of the fetus to exposure from the investigated compounds. A trend of higher levels of the measured adducts in cord blood with gestational age was observed, which may reflect the gestational age-related change of the cord blood Hb composition toward a higher content of adult Hb. The results suggest that the Hb adduct levels measured in cord blood reflect the exposure to the fetus during the third trimester. The evaluation of the new analytical method showed that it is suitable for monitoring of background exposures of the investigated electrophilic compounds in large population studies.

Acrylamide in food: the discovery and its implications: a historical perspective

The unexpected finding that humans are regularly exposed to relatively high doses of acrylamide (AA) through normal consumption of cooked food was a result of systematic research and relevant developments in methodology over decades, as well as a chain of certain coincidences. The present paper describes the scientific approach, investigations and events leading to the discovery of the formation of AA during cooking of foods. In addition, related issues concerning assessment, communication and management of cancer risks and associated ethical questions raised by the finding of the presence of AA in foods will be discussed.

Residues of genotoxic alkyl mesylates in mesylate salt drug substances: Real or imaginary problems?

Mesylate esters of short-chain (n = 1-3) alcohols are reactive, direct-acting, genotoxic and possibly carcinogenic alkylating agents. Their chemical and biological properties appear to correlate well with Swain-Scott s constants; for example, high S(N)1 character (low s value) is associated with enhanced carcinogenic potential, but also a rapid hydrolysis rate. Concerns over the possible formation of such esters during the preparation of mesylate salt drug substances, by addition of methane sulfonic acid (MSA) to the free base dissolved in an alcoholic solvent, have led regulatory agencies to require applicants to demonstrate that the synthetic method employed does not lead to the presence of detectable levels of alkyl mesylates. Mechanistic considerations, relating mainly to the extremely low nucleophilicity of the mesylate anion, and experimental data, both indicate that alkyl mesylates should not be formed (except from MSA impurities) during mesylate salt synthesis. Mechanistic arguments also predict that residues of alkyl halides (possibly formed in the preparation of amine hydrochlorides or hydrobromides) could represent a similar or greater potential hazard than alkyl mesylates. The perceived risk of alkyl mesylate formation seems to rely on mistaken assumptions and so the concerns appear unjustified. Further reassurance could be achieved however by applying a variety of strategies during synthesis, including pH control, and use of high-purity MSA or of a non-hydroxylic reaction solvent.

Proceedings of a workshop on DNA adducts: biological significance and applications to risk assessment Washington, DC, April 13-14, 2004

In April 2004, the Health and Environmental Sciences Institute, a branch of the International Life Sciences Institute, with support from the National Institute of Environmental Health Sciences, organized a workshop to discuss the biological significance of DNA adducts. Workshop speakers and attendees included leading international experts from government, academia, and industry in the field of adduct detection and interpretation. The workshop initially examined the relationship between measured adduct levels in the context of exposure and dose. This was followed by a discussion on the complex response of cells to deal with genotoxic insult in complex, interconnected, and interdependent repair pathways. One of the major objectives of the workshop was to address the recurring question about the mechanistic and toxicological relevance of low-concentration measured adducts and the presentations in the session entitled "Can low levels of DNA adducts predict adverse outcomes?" served as catalysts for further discussions on this subject during the course of the workshop. Speakers representing the regulatory community and industry reviewed the value, current practices, and limitations of utilizing DNA adduct data in risk assessment and addressed a number of practical questions pertaining to these issues. While no consensus statement emerged on the biological significance of low levels of DNA adducts, the workshop concluded by identifying the need for more experimental data to address this important question. One of the recommendations stemming from this workshop was the need to develop an interim "decision-logic" or framework to guide the integration of DNA adduct data in the risk assessment process. HESI has recently formed a subcommittee consisting of experts in the field and other key stakeholders to address this recommendation as well as to identify specific research projects that could help advance the understanding of the biological significance of low levels of DNA adducts.

Effects of ethylene oxide and ethylene inhalation on DNA adducts, apurinic/apyrimidinic sites and expression of base excision DNA repair genes in rat brain, spleen, and liver

Ethylene oxide (EO) is an important industrial chemical that is classified as a known human carcinogen (IARC, Group 1). It is also a metabolite of ethylene (ET), a compound that is ubiquitous in the environment and is the most used petrochemical. ET has not produced evidence of cancer in laboratory animals and is "not classifiable as to its carcinogenicity to humans" (IARC, Group 3). The mechanism of carcinogenicity of EO is not well characterized, but is thought to involve the formation of DNA adducts. EO is mutagenic in a variety of in vitro and in vivo systems, whereas ET is not. Apurinic/apyrimidinic sites (AP) that result from chemical or glycosylase-mediated depurination of EO-induced DNA adducts could be an additional mechanism leading to mutations and chromosomal aberrations. This study tested the hypothesis that EO exposure results in the accumulation of AP sites and induces changes in expression of genes for base excision DNA repair (BER). Male Fisher 344 rats were exposed to EO (100 ppm) or ET (40 or 3000 ppm) by inhalation for 1, 3 or 20 days (6h/day, 5 days a week). Animals were sacrificed 2h after exposure for 1, 3 or 20 days as well as 6, 24 and 72 h after a single-day exposure. Experiments were performed with tissues from brain and spleen, target sites for EO-induced carcinogenesis, and liver, a non-target organ. Exposure to EO resulted in time-dependent increases in N7-(2-hydroxyethyl)guanine (7-HEG) in brain, spleen, and liver and N7-(2-hydroxyethyl)valine (7-HEVal) in globin. Ethylene exposure also induced 7-HEG and 7-HEVal, but the numbers of adducts were much lower. No increase in the number of aldehydic DNA lesions, an indicator of AP sites, was detected in any of the tissues between controls and EO-, or ET-exposed animals, regardless of the duration or strength of exposure. EO exposure led to a 3-7-fold decrease in expression of 3-methyladenine-DNA glycosylase (Mpg) in brain and spleen in rats exposed to EO for 1 day. Expression of 8-oxoguanine DNA glycosylase, Mpg, AP endonuclease (Ape), polymerase beta (Pol beta) and alkylguanine methyltransferase were increased by 20-100% in livers of rats exposed to EO for 20 days. The only effects of ET on BER gene expression were observed in brain, where Ape and Pol beta expression were increased by less than 20% after 20 days of exposure to 3000 ppm. These data suggest that DNA damage induced by exposure to EO is repaired without accumulation of AP sites and is associated with biologically insignificant changes in BER gene expression in target organs. We conclude that accumulation of AP sites is not a likely primary mechanism for mutagenicity and carcinogenicity of EO.