Mode of action assessment for propylene dichloride as a human carcinogen.

As part of a systematic review of the non-cancer and cancer hazards of propylene dichloride (PDC), with a focus on potential carcinogenicity in workers following inhalation exposures, we determined that a mode of action (MOA)-centric framing of cancer effects was warranted. In our MOA analysis, we systematically reviewed the available mechanistic evidence for PDC-induced carcinogenesis, and we mapped biologically plausible MOA pathways and key events (KEs), as guided by the International Programme on Chemical Safety (IPCS)-MOA framework. For the identified pathways and KEs, biological concordance, essentiality of KEs, concordance of empirical observations among KEs, consistency, and analogy were evaluated. The results of this analysis indicate that multiple biologically plausible pathways may contribute to the cancer MOA for PDC, but that the relevant pathways vary by exposure route and level, tissue type, and species; further, more than one pathway may occur concurrently at high exposure levels. While several important data gaps exist, evidence from in vitro mechanistic studies, in vivo experimental animal studies, and ex vivo human tumor tissue analyses indicates that the predominant MOA pathway likely involves saturation of cytochrome p450 2E1 (CYP2E1)-glutathione (GSH) detoxification (molecular initiating event; MIE), accumulation of CYP2E1-oxidative metabolites, cytotoxicity, chronic tissue damage and inflammation, and ultimately tumor formation. Tumors may occur through several subsets of inflammatory KEs, including inflammation-induced aberrant expression of activation-induced cytidine deaminase (AID), which causes DNA strand breaks and mutations and can lead to tumors with a characteristic mutational signature found in occupational cholangiocarcinoma. Dose concordance analysis showed that low-dose mutagenicity (from any pathway) is not a driving MOA, and that prevention of target tissue damage and inflammation (associated with saturation of CYP2E1-GSH detoxification) is expected to also prevent the cascade of processes responsible for tumor formation.

1,2-Dichloropropane induces γ-H2AX expression in human cholangiocytes only in the presence of macrophages.

Recent epidemiological studies reported cases of cholangiocarcinoma in workers exposed to 1,2-dichloropropane (1,2-DCP) in an offset proof printing factory in Japan. The present study investigated the effects of 1,2-DCP on the expression of histone family member X (H2AX) phosphorylated on Ser 139 (γ-H2AX), a marker of DNA double strand break, in human immortalized cholangiocytes MMNK-1 cells. Mono-cultures of MMNK-1 cells and co-cultures of MMNK-1 cells with THP-1 macrophages were exposed to 1,2-DCP at concentrations of 100 and 500 µM for 24 h. Expression of γ-H2AX was visualized by immunofluorescence staining. Exposure to 1,2-DCP had no effect on the expression of γ-H2AX in mono-cultured MMNK-1 cells, but significantly increased the number of nuclear foci stained by γ-H2AX in MMNK-1 cells co-cultured with THP-1 macrophages. Exposure to 1,2-DCP also significantly increased the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in co-cultured MMNK-1 cells. The results suggest that macrophages play a critical role by producing cytokines in 1,2-DCP-induced DNA double strand break in MMNK-1 cells.

Hazard characterization of carcinogenicity, mutagenicity, and reproductive toxicity for short chain primary nitroalkanes.

Nitroalkanes are organic aliphatic hydrocarbon compounds with a nitro moiety that are commonly used as solvents or intermediates to synthesize a variety of organic compounds due to their inherent reactivity. In June 2020, a harmonized classification and labeling (CLH) proposal was submitted to the European Chemicals Agency (ECHA) for the following harmonized carcinogenicity, mutagenicity, and reproductive toxicity ("CMR") classifications for nitromethane (NM), nitroethane (NE), and 1-nitropropane (1-NP): NM Carc. 1B and Repr. 1B; NE Repr. 1B; and 1-NP Repr. 2. In this assessment, a weight of evidence (WoE) evaluation of studies on animal carcinogenicity and reproductive and developmental toxicity, genotoxicity, and mode of action for these three nitroalkanes was performed to critically assess the relevance of the proposed CMR classifications. Overall, the WoE indicates that NM, NE, and 1-NP are not carcinogenic, genotoxic, nor selective reproductive or developmental toxicants. Based on our analysis, classifying NM, NE, and 1-NP as Category 2 reproductive toxicants is most appropriate. Furthermore, not classifying NE and 1-NP with respect to their carcinogenicity is appropriate based on the available studies for this endpoint coupled with negative results in genotoxicity studies, metabolism data, and in silico predictions. We determined that the classification for NM of Carc. 1B is not appropriate, based on the fact that rat mammary and harderian tumors are likely not relevant to humans and lung and liver tumors reported in mice were equivocal in their dose-response and statistical significance.

Providing first evidence of the behaviour and potential environmental impacts of an accidental underwater release of propane.

Aquaculture activities in southern Chile demand floating devices to produce electricity powered by diesel generators. It has been recently proposed to replace this fuel with propane. However, little is known about the behaviour and possible environmental impacts of an accidental release of propane underwater. In this study we evaluated the impact of water temperature and salinity on the saturation and further release of propane under controlled laboratory experiments. Results showed that under extreme environmentally relevant scenarios (high and low temperature and salinity), propane saturated the water more quickly. However, while it is important to consider that saturation times can be similar (∼2 h), the magnitudes of propane dissolved can be different. Experiments showed that cold waters (5 °C) propane is dissolved twice than warm waters (20 °C). Residence time was more affected by water temperature and almost independent of water salinity. Propane may take at least 2 days to be released from waters (around 90% of the initial amount dissolved under laboratory conditions). Additionally, we evaluated the impact on dissolved oxygen displacement and the embryotoxicity of the dissolved fraction by using Zebrafish Embryo Toxicity Assay. Results showed that dissolved oxygen was quickly removed. However, the levels of dissolved oxygen were promptly recovered in the studied systems. We also observed that propane can generate genotoxic effects (3-10% mortality), but after 2 days the system can be almost free of propane and the effects may become much lower. Comparatively with the literature, propane showed to be less toxic than diesel and it is a viable and less environmentally hazardous replacement for diesel.

[Changes of serum markers in acute liver injury induced by oral 1, 2-dichloropropane in BALB/cA-nu mice].

Objective: To investigate the characteristics of inflammatory response in BALB/cA-nu mice induced by oral 1, 2-dichloropropane (1, 2-DCP) , and to provides theoretical reference for further study of subchronic, chronic toxicity and carcinogenic mechanism. Methods: From October 2018, Clean grade healthy BALB/cA-nu mice were randomly divided into 5 groups with 10 mice in each group. And 860, 1150, 1500, 1950, 2535 mg/kg 1, 2-DCP were given by gavage respectively. Meanwhile, blank group and solvent control group (corn oil) were set up. Blood samples were collected from eyeballs and liver and bile tissues were collected for histopathological examination within 24 hours after exposure. The expression of alanine aminotransferase (ALT) , total bilirubin (TBLI) , C-reactive protein (CRP) , interleukin-6 (IL-6) , tumor necrosis factor-α (TNF-α) and tumor necrosis factor-ß (TNF-ß) were detected by enzyme-linked immunosorbent assay. Results: With the increase of the dose of 1, 2-DCP, the number of microbubbles in liver cells and the infiltration of inflammatory cells increased gradually. No pathological changes were found in the gallbladder. Compared with the blank group and solvent control group, the content of serum ALT in each exposure group was increased, the serum levels of IL-6 and TNF-ß in 860, 1150, 1950 and 2350 mg/kg exposure groups were increased, the serum TNF-α and TBLI levels in 1 950, 2535 mg/kg groups were significantly higher (P<0.05) . The levels of ALT, TBLI and TNF-ß in serum of female mice were significantly different (P<0.05) . There were significant differences in ALT, TBLI, CRP, IL-6, TNF-α, TNF-ß in serum of male mice (P<0.05) . Conclusion: Oral 1, 2-DCP may cause acute liver injury in BALB/cA-nu mice and increase the expression of serum inflammatory factors. Moreover, the types of inflammatory factors activated in male mice are more than those in female mice.

The mutational signature profile of known and suspected human carcinogens in mice.

Epidemiological studies have identified many environmental agents that appear to significantly increase cancer risk in human populations. By analyzing tumor genomes from mice chronically exposed to 1 of 20 known or suspected human carcinogens, we reveal that most agents do not generate distinct mutational signatures or increase mutation burden, with most mutations, including driver mutations, resulting from tissue-specific endogenous processes. We identify signatures resulting from exposure to cobalt and vinylidene chloride and link distinct human signatures (SBS19 and SBS42) with 1,2,3-trichloropropane, a haloalkane and pollutant of drinking water, and find these and other signatures in human tumor genomes. We define the cross-species genomic landscape of tumors induced by an important compendium of agents with relevance to human health.

Proteomic analysis of liver proteins of mice exposed to 1,2-dichloropropane.

1,2-Dichloropropane (1,2-DCP) is recognized as the causative agent for cholangiocarcinoma among offset color proof-printing workers in Japan. The aim of the present study was to characterize the molecular mechanisms of 1,2-DCP-induced hepatotoxic effects by proteomic analysis. We analyzed quantitatively the differential expression of proteins in the mouse liver and investigated the role of P450 in mediating the effects of 1,2-DCP. Male C57BL/6JJcl mice were exposed to 0, 50, 250, or 1250 ppm 1,2-DCP and treated with either 1-aminobenzotriazole (1-ABT), a nonselective P450 inhibitor, or saline, for 8 h/day for 4 weeks. Two-dimensional difference in gel electrophoresis (2D-DIGE) combined with matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF/MS) was used to detect and identify proteins affected by the treatment. PANTHER overrepresentation test on the identified proteins was conducted. 2D-DIGE detected 61 spots with significantly different intensity between 0 and 250 ppm 1,2-DCP groups. Among them, 25 spots were identified by MALDI-TOF/TOF/MS. Linear regression analysis showed significant trend with 1,2-DCP level in 17 proteins in mice co-treated with 1-ABT. 1-ABT mitigated the differential expression of these proteins. The gene ontology enrichment analysis showed overrepresentation of proteins functionally related to nickel cation binding, carboxylic ester hydrolase activity, and catalytic activity. The results demonstrated that exposure to 1,2-DCP altered the expression of proteins related with catalytic and carboxylic ester hydrolase activities, and that such effect was mediated by P450 enzymatic activity.

Derivation of cancer no significant risk levels and screening safety assessment for 2-nitropropane in spray products.

Two proposition 65 no-significant-risk level (NSRL)-type values were derived for 2-nitropropane (2-NP), in the absence of a Californian published NSRL. In addition, a safety assessment was performed based on estimated typical consumer inhalation and dermal exposure to 2-NP during indoor application of paint from a spray can containing the solvent 1-nitropropane. For the NSRL derivation, benchmark dose (BMD) modeling was performed using hepatocellular carcinoma incidence data from 2-NP single exposure inhalation studies in Sprague-Dawley rats. Several BMD models provided an acceptable fit for the male rat hepatocellular carcinoma incidence data (gamma, log-probit, log-logistic and multistage); therefore, the mean of the BMD lower limits from each model were used as the point of departure to derive the inhalation cancer potency. The oral human cancer potency was derived from the inhalation human cancer potency based on the ratio of the uptake factors for inhalation vs. oral routes. The derived inhalation and oral NSRLs are 67 µg/day and 32 µg/day, respectively. For the inhalation and dermal exposure assessment, three key factors were analyzed: the 2-NP residual concentration in the spray paint product, the mass of spray paint used and the frequency of use. Based on the screening exposure assessment, potential consumer inhalation and dermal exposure to 2-NP from indoor application of paint from a spray can does not exceed our proposed NSRLs, and a warning label is therefore not required for spray can products containing the solvent 1-nitropropane where 2-NP is a minor contaminant.

Exposure to 1,2-Dichloropropane Upregulates the Expression of Activation-Induced Cytidine Deaminase (AID) in Human Cholangiocytes Co-Cultured With Macrophages.

1,2-dichloropropane (1,2-DCP) was reclassified recently by IARC as a Group 1 carcinogen based on epidemiological studies on an outbreak of cholangiocarcinoma in offset-printing workers exposed to 1,2-DCP in Japan. However, the underlying mechanism of 1,2-DCP-induced cholangiocarcinoma remains obscure. A previous whole-genome mutation analysis of cholangiocarcinoma of 4 cases exposed to 1,2-DCP suggested the involvement of activation-induced cytidine deaminase (AID), based on specific signatures of mutation patterns. The objective of the present study is to determine whether exposure to 1,2-DCP induces expression of AID in human cholangiocytes. Human MMNK-1 cholangiocytes, differentiated THP-1 macrophages, and co-cultures of MMNK-1/THP-1 cells were exposed to 1,2-DCP at different concentrations and time intervals. The mRNA expression levels of AID and related genes were quantified by real-time PCR. Protein expression was measured by immunostaining. Alkaline Comet assay was performed to examine DNA damage. The results showed that 1,2-DCP alone did not change AID expression in MMNK-1 cholangiocytes. 1,2-DCP significantly increased pro-inflammatory cytokine TNF-α expression in THP-1 macrophages. TNF-α treatment upregulated expression of AID, NF-κB, and IκB in MMNK-1 cholangiocytes. SN50, a NF-κB inhibitor, significantly downregulated TNF-α-induced AID expression, suggesting the involvement of NF-κB pathway in TNF-α-induced AID expression. Exposure to 1,2-DCP significantly increased AID expression in MMNK-1 cholangiocytes co-cultured with THP-1 macrophages. Comet assay showed that 1,2-DCP-induced DNA damage in MMNK-1 cholangiocytes, as indicated by increased tail DNA% and tail moment, was enhanced when co-cultured with macrophages. The results suggest that inflammatory response of macrophages and consequent aberrant AID expression or DNA damage in the cholangiocytes underlie the mechanism of 1,2-DCP-induced cholangiocarcinoma in humans.

Acute inhalation co-exposure to 1,2-dichloropropane and dichloromethane cause liver damage by inhibiting mitochondrial respiration and defense ability in mice.

1,2-Dichloropropane (1,2-DCP) is used as an industrial solvent, insecticide fumigant and household dry cleaning product. Carcinogenicity caused by long-term exposure to 1,2-DCP is well established. However, the possible liver damage and related toxic mechanisms associated with acute inhalation exposure to 1,2-DCP are rarely reported. In this study, we investigated the effects of individual and combined exposure to 1,2-DCP and dichloromethane (DCM) on mice liver. The results showed that 1,2-DCP significantly caused liver necrosis, possibly due to 1,2-DCP-induced inhibition of the mitochondrial respiratory chain complex I-IV activities, resulting in mitochondrial dysfunction and extreme ATP consumption. Moreover, 1,2-DCP also decreased mitochondrial defense ability by inhibiting the mitochondrial glutathione S-transferase 1 (MGST1) activity, further aggravating liver damage. Additionally, we found that DCM co-exposure potentially enhanced 1,2-DCP toxicity. Our findings suggest that inhibition of mitochondrial function and MGST1 activity play critical roles in modulating 1,2-DCP-induced liver damage. Furthermore, our results contribute to study the new mechanism of mitochondria-dominated signaling pathways underlying liver injury induced by 1,2-DCP and DCM.

Effect of endocrine disruptors on the ratio of X and Y chromosome-bearing live spermatozoa.

Although equal numbers of X and Y spermatozoa are produced during spermatogenesis, the sex chromosome ratio in ejaculated spermatozoa can be altered by exposure to endocrine-disrupting chemicals (EDCs), which can be reflected by altered sex ratios at birth. Here, we hypothesized EDCs affect sperm functions and viability of X and Y chromosome-bearing human spermatozoa. After exposure to genistein (Gen), bisphenol A (BPA), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dibromochloropropane (DBCP), and diazinon (Diaz), we evaluated motility, viability, capacitation, and differential viability of X and Y spermatozoa. All EDCs tested altered sperm viability, motility, and capacitation. Interestingly, the Y/X ratio of live spermatozoa was significantly lower in sperm treated with TCDD, DBCP, and Diaz than control spermatozoa. Our results suggest that some of EDCs have larger effects on the viability of Y spermatozoa than X spermatozoa, implicating that a reduction in Y sperm viability may result in a female-biased sex ratio of offspring at birth.

Hazardous gases (CO, NOx, CH4 and C3H8) released from CO2 fertilizer unit lead to oxidative damage and degrades photosynthesis in strawberry plants.

CO2 boilers/direct heating systems used in greenhouses often lead to incomplete combustion, which results in the formation of hazardous gases, such as carbon monoxide (CO), nitroxide (NOX) and other hydrocarbons. In this study, strawberry plants that were grown on rockwool cubes were transferred to airtight bottles and treated with CO, NOX, CH4 and C3H8 gases for 1-48 hours. Oxidative damage due to hazardous gases was observed, as indicated by H2O2 and [Formula: see text] determination. Photosynthetic pigments were reduced, and stomatal guard cells were damaged and remained closed compared to the control. The activity of other photosynthetic parameters was negatively related to hazardous gases. Reduction in the expression of multiprotein complexes was highly observed under hazardous gas treatments. This study highlighted that hazardous gases (CO, NOX, CH4 and C3H8) emitted due to incomplete combustion of CO2 fertilization units/or direct heating systems resulted in the formation of ROS in shoots and limited photosynthetic metabolism. We predicted that major steps must be incorporated to improve the efficiency of CO2 boiler/heating systems to decrease the emission of these hazardous gases and other hydrocarbons and to reduce the observed risks that are key to the reduction of crops.

Acute toxic encephalopathy induced by occupational exposure to 1,2-dichloropropane.

1,2-Dichloropropane (1,2-DCP) is used widely in Korea as a substitute for trichloroethylene or methylene chloride. Some companies mistakenly consider that 1,2-DCP is an eco-friendly detergent because its use is not regulated, but 1,2-DCP is known to inhibit the central nervous system in animals; a few cases of accidental exposure have been reported in humans. We present a case of acute encephalopathy caused by exposure to 1,2-DCP. A 41 yr-old male presented with dizziness, headache, and diplopia after exposure to the detergent without protective equipment. Brain magnetic resonance imaging suggested metabolic encephalopathy, but the patient had no thiamine deficiency and no other metabolic disorder. As the symptoms had commenced after exposure to a large amount of solvent while skimming rust from the surface, and as the symptoms were more severe during the work week, improved on weekends, and disappeared after solvent exposure ceased, the toxic encephalopathy was likely induced by inhalation of the detergent.

Exposure of Mice to 1,2-Dichloropropane Induces CYP450-Dependent Proliferation and Apoptosis of Cholangiocytes.

1,2-Dichloropropane (1,2-DCP) has been used as a paint remover in the industry. The International Agency for Research on Cancer reclassified this compound recently to group 1 (carcinogenic to humans) based on epidemiological studies of cholangiocarcinoma among offset-color proof-printing workers exposed to 1,2-DCP in Japan. Two-year rodent carcinogenicity bioassays demonstrated that 1,2-DCP induced tumors in liver and lung, but not in bile duct. The present study was designed to assess the toxic effects of 1,2-DCP on proliferation and apoptosis in mice bile duct and the role of cytochrome P450 (CYP450) in any such effect. Male C57BL/6JJcl mice were cotreated or untreated with 1-aminobenzotriazole (1-ABT), a CYP450 inhibitor, and exposed to inhalation of 1,2-DCP at 0, 50, or 250 ppm alone, or at 0, 50, 250, or 1250 ppm 8 h/day for 4 weeks. Exposure to 1,2-DCP increased proliferation and apoptosis of cholangiocytes and induced severe hepatic damage, but had no effect on the lungs. Cotreatment with 1-ABT abrogated the effects of 1,2-DCP on proliferation and apoptosis of cholangiocytes. The results revealed that 1,2-DCP induces proliferation and apoptosis of cholangiocytes and that this effect is mediated through CYP450.

Effects of free radical initiators on polyethylene glycol dimethacrylate hydrogel properties and biocompatibility.

Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene glycol) (PEG) hydrogels for tissue engineering application development. Due to the limited penetration of ultraviolet light through tissue, Irgacure 2959 polymerized hydrogels are not suitable for use in tissues where material injection is desirable, such as the spinal cord. To address this, several free radical initiators (thermal initiator VA044, ammonium persulfate (APS)/TEMED reduction-oxidation reaction, and Fenton chemistry) are evaluated for their effects on the material and mechanical properties of PEG hydrogels compared with Irgacure 2959. To emulate the effects of endogenous thiols on in vivo polymerization, the effects of chain transfer agent (CTA) dithiothreitol on gelation rates, material properties, Young's and shear modulus, are examined. Mouse embryonic stem cells and human induced pluripotent stem cell derived neural stem cells were used to investigate the cytocompatibility of each polymerization. VA044 and Fenton chemistry polymerization of PEG hydrogels both had gelation rates and mechanical properties that were highly susceptible to changes in CTA concentration and showed poor cytocompatibility. APS/TEMED polymerized hydrogels maintained consistent gelation rates and mechanical properties at high CTA concentration and had a similar cytocompatibility as Irgacure 2959 when cells were encapsulated within the PEG hydrogels. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3059-3068, 2017.

Spontaneous Production of Glutathione-Conjugated Forms of 1,2-Dichloropropane: Comparative Study on Metabolic Activation Processes of Dihaloalkanes Associated with Occupational Cholangiocarcinoma.

Recently, epidemiological studies revealed a positive relationship between an outbreak of occupational cholangiocarcinoma and exposure to organic solvents containing 1,2-dichloropropane (1,2-DCP). In 1,2-DCP-administered animal models, we previously found biliary excretion of potentially oncogenic metabolites consisting of glutathione- (GSH-) conjugated forms of 1,2-DCP (GS-DCPs); however, the GS-DCP production pathway remains unknown. To enhance the understanding of 1,2-DCP-related risks to human health, we examined the reactivity of GSH with 1,2-DCP in vitro and compared it to that with dichloromethane (DCM), the other putative substance responsible for occupational cholangiocarcinoma. Our results showed that 1,2-DCP was spontaneously conjugated with GSH, whereas this spontaneous reaction was hardly detected between DCM and GSH. Further analysis revealed that glutathione S-transferase theta 1 (GSTT1) exhibited less effect on the 1,2-DCP reaction as compared with that observed for DCM. Although GSTT1-mediated bioactivation of dihaloalkanes could be a plausible explanation for the production of reactive metabolites related to carcinogenesis based on previous studies, this catalytic pathway might not mainly contribute to 1,2-DCP-related occupational cholangiocarcinoma. Considering the higher catalytic activity of GSTT1 on DCM as compared with that on 1,2-DCP, our findings suggested differences in the activation processes associated with 1,2-DCP and DCM metabolism.

1,2-Dichloropropane generates phosphorylated histone H2AX via cytochrome P450 2E1-mediated metabolism.

1,2-Dichloropropane (1,2-DCP), a synthetic chlorinated solvent, was recently classified as carcinogenic. Genotoxic events are known as a crucial step in the initiation of cancer. However, studies on the genotoxicity of 1,2-DCP are very limited, particularly studies investigating the mechanism behind DNA damage by 1,2-DCP. In this study, we examined the genotoxicity of 1,2-DCP using phosphorylated histone H2AX (γ-H2AX), a sensitive DNA damage marker. 1,2-DCP showed dose- (1-10mM: 4h) and time-dependent (1-24h: 5mM) γ-H2AX generation in cultured human hepatocytes (WRL-68) and cholangiocytes (MMNK-1). Additionally, γ-H2AX generation was observed in the livers of mice inhalationally exposed to 1,2-DCP at concentrations of 100, 200, and 400 ppm. During an in vitro mechanistic investigation, we found that γ-H2AX generation by 1,2-DCP was clearly attenuated in the presence of disulfiram and 4-methylpyrazole, a specific cytochrome P450 2E1 (CYP2E1) inhibitor. Furthermore, we showed that 1,2-DCP increased the levels of intracellular reactive oxygen species (ROS), with the increase significantly inhibited by CYP2E1 inhibitors. These results suggested that ROS produced via the cytochrome P450 2E1 metabolic process of 1,2-DCP was a major causal factor for γ-H2AX generation by treatment with 1,2-DCP.

Lack of in vivo mutagenicity of 1,2-dichloropropane and dichloromethane in the livers of gpt delta rats administered singly or in combination.

1,2-Dichloropropane (1,2-DCP) and dichloromethane (DCM) are possible causative agents associated with the development of cholangiocarcinoma in employees working in printing plant in Osaka, Japan. However, few reports have demonstrated an association between these agents and cholangiocarcinoma in rodent carcinogenicity studies. Moreover, the combined effects of these compounds have not been fully elucidated. In the present study, we evaluated the in vivo mutagenicity of 1,2-DCP and DCM, alone or combined, in the livers of gpt delta rats. Six-week-old male F344 gpt delta rats were treated with 1,2-DCP, DCM or 1,2-DCP + DCM by oral administration for 4 weeks at the dose (200 mg kg-1 body weight 1,2-DCP and 500 mg kg-1 body weight DCM) used in the carcinogenesis study performed by the National Toxicology Program. In vivo mutagenicity was analyzed by gpt mutation/Spi- assays in the livers of rats. In addition, gene and protein expression of CYP2E1 and GSTT1, the major enzymes responsible for the genotoxic effects of 1,2-DCP and DCM, were analyzed by quantitative polymerase chain reaction and western blotting. Gpt and Spi- mutation frequencies were not increased by 1,2-DCP and/or DCM in any group. Additionally, there were no significant changes in the gene and protein expression of CYP2E1 and GSTT1 in any group. These results indicated that 1,2-DCP, DCM and 1,2-DCP + DCM had no significant impact on mutagenicity in the livers of gpt delta rats under our experimental conditions. Copyright © 2016 John Wiley & Sons, Ltd.

RIFM fragrance ingredient safety assessment, 1-(1,2,3,4-tetrahydro-4,4-dimethyl-1-naphthyl)propan-1-one, CAS Registry Number 74499-60-8.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental and reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, as well as environmental safety. Data from the target material and the suitable read across analog 6-acetyl-1,1,2,4,4,7-hexamethyltetraline (CAS # 21145-77-7) show that this material is not genotoxic. Data from the suitable read across analog 6-acetyl-1,1,2,4,4,7-hexamethyltetraline (CAS # 21145-77-7) provided a MOE > 100 for the repeat dose and developmental toxicity endpoints. The reproductive and local respiratory toxicity endpoints were completed using the TTC (Threshold of Toxicological Concern) for a Cramer Class II material (0.009 mg/kg/day and 0.47 mg/day, respectively). Data on the target material showed that this material is below the non-reactive DST for skin sensitization and did not have the potential for phototoxicity or photoallergenicity. The environmental endpoint was completed as described in the RIFM Framework.

In vitro toxicity of reuterin, a potential food biopreservative.

Reuterin has a high potential as a food preservative due to both its chemical characteristics and its antimicrobial activity against food-borne pathogens and spoilage bacteria. However, there is a lack of information about its toxicity and its capacity to interfere with the metabolism of drugs by inhibiting cytochrome P450 (CYP) activity. The results of this study indicated that reuterin exhibited a moderate cytotoxicity in the human hepatoma cell line HepG2 according to assays measuring three different endpoints in the same set of cells. Reuterin was much less toxic than acrolein and only four times more toxic than diacetyl, a generally recognized as safe flavoring compound. In vitro experiments utilizing human liver microsomes showed that reuterin presents low possibility of displaying in vivo drug interactions by inhibition of CYP3A4, CYP2D6, and CYP2C9. Therefore, reuterin can be considered a promising food biopreservative, although additional toxicology research is needed before permission for use can be granted.