Assessment of the developmental toxicity, metabolism, and placental transfer of N,N-dimethylformamide administered to pregnant rats

The potential health risks of N,N-dimethylformamide: An updated review

N,N-dimethylformamide (DMF) is a universally used industrial material with exponential growth in production and consumption worldwide. The frequently reported occupational DMF poisoning cases in some countries and the gradually recognized unavoidable health risks to the general population highlight that DMF should still be a matter of concern. Previous studies have demonstrated that the liver is the primary target organ of DMF exposure and multiple mechanisms have been revealed. However, most of these studies investigate the detrimental effects of acute and subacute DMF exposure, while the effects of chronic DMF exposure are rarely studied. Furthermore, the key mechanism for the acute hepatotoxicity of DMF remains to be elucidated. Future research may focus on the identification of efficient preventive measures against the toxicity of DMF to occupational workers, the investigation of the detrimental effects of DMF at environmentally relevant doses, and the studies on the elimination and recycling of DMF in industrial wastes. Herein, we present an updated review of the metabolism of DMF, the biomarker of DMF exposure, underlying molecular mechanisms of DMF-induced hepatotoxicity, and the toxicity of DMF to both occupational workers and general populations and discuss the possible directions in future studies.

Human Biomonitoring Initiative (HBM4EU): Human Biomonitoring Guidance Values Derived for Dimethylformamide

Within the European Joint Program on Human Biomonitoring HBM4EU, human biomonitoring guidance values (HBM-GVs) for the general population (HBM-GV_GenPop) or for occupationally exposed adults (HBM-GV_Worker) are derived for prioritized substances including dimethylformamide (DMF). The methodology to derive these values that was agreed upon within the HBM4EU project was applied. A large database on DMF exposure from studies conducted at workplaces provided dose–response relationships between biomarker concentrations and health effects. The hepatotoxicity of DMF has been identified as having the most sensitive effect, with increased liver enzyme concentrations serving as biomarkers of the effect. Out of the available biomarkers of DMF exposure studied in this paper, the following were selected to derive HBM-GV_Worker: total N-methylformamide (tNMF) (sum of N-hydroxymethyl-N-methylformamide and NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in urine. The proposed HBM-GV_Worker is 10 mg·L⁻¹ or 10 mg·g⁻¹ creatinine for both biomarkers. Due to their different half-lives, tNMF (representative of the exposure of the day) and AMCC (representative of the preceding days’ exposure) are complementary for the biological monitoring of workers exposed to DMF. The levels of confidence for these HBM-GV_Worker are set to “high” for tNMF and “medium-low” for AMCC. Therefore, further investigations are required for the consolidation of the health-based HBM-GV for AMCC in urine.

Fast Heck-Cassar-Sonogashira (HCS) Reactions in Green Solvents

The replacement of toxic solvents with greener alternatives in Heck–Cassar–Sonogashira (HCS) cross-couplings was investigated. The fine-tuning of the HCS protocol allowed to achieve complete conversions and high speed under mild conditions. N-Hydroxyethylpyrrolidone (HEP) gave the best results. Moreover, the methodology was successfully applied to the synthesis of an intermediate of the anticancer drug Erlotinib, demonstrating the versatility of the new green protocol.

Effects of N,N-dimethylformamide on behaviour and regeneration of planarian Dugesia japonica

In this study, the toxicity, behavioural and regeneration effects of dimethylformamide (DMF) on planarian Dugesia japonica were investigated. One control and six different concentrations of DMF (10 ppm, 100 ppm, 500 ppm, 1000 ppm, 5000 ppm and 10,000 ppm) were used in triplicate. The results showed that the mortality was directly proportional to the DMF concentration and planarian locomotor velocity (pLMV) was significantly reduced by increasing the exposure time and DMF concentration. pLMV of D. japonica was significantly reduced at a lower concentration of 10 ppm after 7 days of continuous exposure to DMF. The recovery of the motility of planarians pretreated with DMF was found to be time- and dose dependent, all planarians had complete recovery in their motility after 48 h. The appearance of auricles in regenerating animals was easily affected by DMF exposure in comparison with the appearance of eyespot. The present results suggest that the intact adult mobility in the aquatic planarian D. japonica is a more sensitive biomarker than mortality, and the appearance of auricles in regenerating animals is a more sensitive biomarker than eyespot.

The use of biomarkers of exposure of N,N-dimethylformamide in health risk assessment and occupational hygiene in the polyacrylic fibre industry

BACKGROUND

N,N-dimethylformamide (DMF) was recently prioritised for field studies by the National Toxicology Program based on the potency of its reproductive toxic effects.

AIMS

To measure accurately exposure to DMF in occupational settings.

METHODS

In 35 healthy workers employed in the polyacrylic fibre industry, N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in urine, and N-methylcarbamoylated haemoglobin (NMHb) in blood were measured. Workplace documentation and questionnaire information were used to categorise workers in groups exposed to low, medium, and high concentrations of DMF.

RESULTS

All three biomarkers can be used to identify occupational exposure to DMF. However, only the analysis of NMHb could accurately distinguish between workers exposed to different concentrations of DMF. The median concentrations were determined to be 55.1, 122.8, and 152.6 nmol/g globin in workers exposed to low, medium, and high concentrations of DMF, respectively. It was possible by the use of NMHb to identify all working tasks with increased exposure to DMF. While fibre crimpers were found to be least exposed to DMF, persons washing, dyeing, or towing the fibres were found to be highly exposed to DMF. In addition, NMHb measurements were capable of uncovering working tasks, which previously were not associated with increased exposure to DMF; for example, the person preparing the fibre forming solution.

CONCLUSIONS

Measurement of NMHb in blood is recommended rather than measurement of NMF and AMCC in urine to accurately assess exposure to DMF in health risk assessment. However, NMF and AMCC are useful biomarkers for occupational hygiene intervention. Further investigations regarding toxicity of DMF should focus on highly exposed persons in the polyacrylic fibre industry. Additional measurements in occupational settings other than the polyacrylic fibre industry are also recommended, since the population at risk and the production volume of DMF are high.

Maternal Exposure to Bisphenol A during Late Pregnancy Resulted in an Increase of Calbindin-D9k mRNA and Protein in Maternal and Postnatal Rat Uteri

It has been reported that Calbindin-D9k (CaBP-9k) is rapidly and strongly induced by environmental estrogenic compounds, possibly through estrogen receptors (ERalpha) in the uterus of mammals. CaBP-9k can be evaluated as an early gene marker for assaying estrogenic effects of putative environmental chemicals in the rat uterus. This study was undertaken to investigate CaBP-9k mRNA and protein expression in the postnatal rat uterus following maternal exposure to 17beta-estradiol (E2) and bisphenol A (BPA) during the neonatal period. Treatment with a high dose of BPA (600 mg/kg body weight (BW) per day) resulted in a 3-fold increase in CaBP-9k mRNA expression for 3 days, while a single dose of E2 (40 microg/kg BW per day) induced 2-fold increase of this gene in the maternal uterus. In an agreement with maternal CaBP-9k mRNA, postnatal CaBP-9k mRNA in the uterus increased 4-fold when treated with BPA (600 mg/kg BW per day). In addition, treatment with increasing concentrations of BPA resulted in significant increases in CaBP-9k protein in the maternal rat uterus. It is of interest that increasing doses of BPA induced a significant ERalpha mRNA increase in the postnatal uterus. Furthermore, immunohistochemistry revealed that treatment with BPA induced CaBP-9k protein in the maternal uterus. We demonstrated that maternal exposure to BPA during late pregnancy induced CaBP-9k mRNA and protein in maternal and postnatal rat uteri. These results suggest that rapid absorption and distribution of environmental estrogenic compounds occurs in maternal and neonatal rat uteri and these chemicals can easily pass though the placenta during pregnancy to affect postnatal reproductive functions.

A study of vehicles for dosing rodent whole embryo culture with non aqueous soluble compounds

In rodent whole embryo culture (WEC), finding vehicles for non-aqueous-soluble compounds has been problematic due to developmental toxicity associated with many solvents. The purpose of this study was to identify alternative vehicles for insoluble compounds. In WEC, we evaluated carrier solutions containing bovine serum albumin (BSA) and glycerol as well as the solvents, formamide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and ethanol, for relative teratogenicity and delivery of the insoluble teratogen, all-trans retinoic acid (RA). At a concentration of <or=0.04%, formamide and DMF exhibited no significant toxicity to cultured rat embryos and were effective at delivering RA to the embryo. The BSA and glycerol carrier solutions were not teratogenic, although both inhibited robust formation of yolk sac vasculature. Both solutions delivered RA to the cultured rat embryos at higher doses. In summary, all four solvents/solutions may have utility as vehicles dependent upon the chemical properties of the compound to be solubilized.

Maternal-fetal transfer of endocrine disruptors in the induction of Calbindin-D9k mRNA and protein during pregnancy in rat model

Estrogenic compounds may influence the growth, differentiation and function in many target tissues, especially in the female reproductive tract during pregnancy. The present study was designed to investigate whether CaBP-9k expression in the maternal tissues and fetal uterus is altered following maternal treatment with diethylstilbestrol (DES), 17beta-estradiol (E2), 4-tert-octylphenol (OP), nonylphenol (NP) and bisphenol A (BPA) during late pregnancy. The expression level of CaBP-9k mRNA in maternal uterus significantly increased when treated with a high dose (600 mg/kg BW per day) of OP and NP. Interestingly, the expression level of CaBP-9k mRNA in extra-embryonic membrane decreased in a dose-dependent manner, suggesting that the expression level of CaBP-9k mRNA in the fetal membrane may be differentially regulated when compared to the expression of CaBP-9k in maternal uterus. In parallel with CaBP-9k mRNA level, a high dose (600 mg/kg) of OP and BPA resulted in an increase of CaBP-9k protein in maternal uterus and low dose of OP and NP increased the expression level of CaBP-9k protein in the placenta. High doses of BPA (400 and 600 mg/kg) resulted in an increase of CaBP-9k protein in maternal uterus and placenta, indicating that these estrogenic compounds may affect both maternal uterus and placenta in the induction of CaBP-9k mRNA and/or protein. In parallel with the expression level of CaBP-9k, mRNA decreased in extra-embryonic membrane, treatment with OP (400 and 600 mg/kg) resulted in a significant decrease of CaBP-9k protein in this tissue, suggesting that both CaBP-9k mRNA and protein may be conversely regulated by OP in extra-embryonic membrane when compared to other tissues. Treatment with OP, NP, and BPA induced a significant increase of CaBP-9k mRNA in fetal uterus, indicating that maternally injected estrogenic compounds may transfer directly from placenta to fetus in the induction of fetal uterus CaBP-9k gene. Taken together, we demonstrated for the first time that maternally injected estrogenic compounds resulted in an increase of CaBP-9k mRNA and/or protein in the maternal tissues (uterus and placenta) and fetal uterus during late pregnancy, suggesting that placenta may not be a reliable barrier against these estrogenic compounds for fetal health.

High-performance liquid chromatographic determination of n-methylformamide, a biological index for occupational exposure to dimethylformamide

This report describes an analytical method for the biological monitoring of workers exposed to N,N-dimethylformamide (DMF), a solvent widely used in the chemical industry. The human main metabolites of DMF are N-hydroxymethyl-N-methylformamide (HMMF) and the minor metabolites N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine. The metabolite selected by the American Conference of Governmental Hygienists for occupational biomonitoring purposes, is NMF measured by gas chromatographic analysis, as during it HMMF may be converted to the minor metabolite NMF. HMMF and NFM can be measured independently using HPLC analysis. The procedure proposed here involves the thermal transformation of the primary metabolite HMMF into the minor metabolite NMF, which is then determined by HPLC. This method makes it possible to determine, using HPLC, both metabolites of DMF by measuring only one peak, thus offering two major advantages: (i) it increases the sensitivity of the test and (ii) it deploys only one reference standard.