Comparative hepatotoxicity and metabolism of N-methylformamide in rats and mice

Evaluation of the Antinociceptive Effect of Sesamin: Role of 5HT1A Serotonergic Receptors

Background/Objectives: Sesame (Sesamum indicum L.) is used in folk medicine to treat painful disorders. Sesamin is the main lignan found in this plant; however, its antinociceptive potential has scarcely been studied. The aim was to investigate the antinociceptive effect of sesamin on inflammatory and neuropathic pain models, as well as the possible mechanism of action through which sesamin mediates its own antinociceptive effect. Methods: Formalin and carrageenan animal models were used to assess inflammatory pain, whereas an L5/L6-spinal-nerve-ligated rat model was employed to evaluate neuropathic pain. Results: Oral sesamin significantly reduced carrageenan-induced hyperalgesia and inflammation, formalin-induced nociception, and L5/L6-spinal-nerve-ligation-induced allodynia. Sesamin was more effective than diclofenac in the inflammatory pain models, but it was less effective than pregabalin in the neuropathic pain model. The antinociceptive effect of sesamin, in the formalin test, was prevented by the intraperitoneal administration of methiothepin (5-HT1/5 antagonist), but not by naltrexone (an opioid antagonist) or L-NAME (an NOS inhibitor). In addition, WAY-100635 (5-HT1A antagonist), but not SB-224289 (5-HT1B antagonist), BRL-15542 (5-HT1D antagonist), and SB-699551 (5-HT5A antagonist), impeded sesamin-induced antinociception. Conclusions: This study's results support the use of sesamin to treat inflammatory pain disorders and suggest that 5-HT1A receptors influence the antinociceptive effect of this drug.

N-methylformamide induces multiple organ toxicity in Fischer 344 rats

N-Methylformamide (NMF) is a widely used chemical (CAS No.: 123-39-7) in several industries and its usage is continuously increasing. However, studies for NMF have been focused on hepatotoxicity from now. Its toxicity profile has not yet been established owing to limited toxicity data. Therefore, we evaluated systemic toxicity via NMF inhalation. We exposed 0, 30, 100, and 300 ppm NMF to Fischer 344 rats for 6 h/day, 5 days a week for 2 weeks. Clinical signs, body weights, food consumption, hematologic parameters, serum chemistry measurements, organ weights, necropsy, and histopathology were performed. Two females exposed to 300 ppm NMF died during exposure period. Decrease of food consumption and body weight in both sexes exposed to 300 ppm in females exposed to 100 ppm were noted during exposure period. Increased RBC and HGB were noted in females exposed to 300 ppm. A decrease in the levels of ALP and K and increase in the levels of TCHO and Na were observed in both sexes exposed to 300 and 100 ppm. Increased levels of ALT, AST, BUN and decreased levels of TP, ALB, Ca were observed in females exposed to 300 and 100 ppm. The relative liver weight was elevated in both sexes exposed to 300 and 100 ppm NMF. Hypertrophy in the liver and submandibular glands and nasal cavity injuries were noted in both sexes exposed to 300 and 100 ppm NMF. Tubular basophilia of the kidneys were noted in females exposed to 300 ppm NMF. We revealed that NMF affect several organs including the kidneys not only the liver and NMF-related toxicity is predominant in female rats. These results could contribute to the development of NMF toxicity profile and may help in developing strategies for the control of occupational environmental hazards related to NMF.

The influence of airborne N,N-dimethylformamide on liver toxicity measured in industry workers: A systematic review and meta-analysis

Background:

Modern industry is developing and so is the consumption of N, N-dimethylformamide (DMF) and the occupational population exposed to DMF. However, chronic occupational and experimental exposure to DMF has been especially linked to liver and gastrointestinal disturbances.

Aims:

This study aims to systematically review and evaluate with a meta-analysis the influence of DMF exposure on human liver toxicity.

Methods:

The PubMed/Medline, the ECHA restriction dossier and the Web of Science were searched. Midpoint DMF exposure levels were calculated, and the association between DMF exposure and liver toxicity was investigated. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

Results:

Of 92 screened articles, 19 articles were included in the review and of them, 10 articles were included in the meta-analysis. No association was observed when the midpoint DMF exposure was less than 20 mg/m3 (OR: 1.58, 95% CIs: 0.68–3.65). A positive association between DMF exposure and liver toxicity was observed when the midpoint DMF exposure was between 21 mg/m3 and 25 mg/m3 (OR: 3.26, 95% CIs: 1.38–7.73).

Conclusions:

Higher exposure DMF levels are associated with liver toxicity. However, these results tend to overestimate potential risks because the use of midpoint exposures includes and gives weight to populations at the upper end of the exposure distributions and because liver toxicity was defined as a statistical significant difference in liver enzyme levels compared to control groups, which is not identical to biologically relevant effects and adverse health effects.

Spectroscopic and molecular modeling studies on the interactions of N-Methylformamide with superoxide dismutase

N-Methylformamide, a polar solvent has a wide industrial applications and it is well-known for hepatotoxicity. The interaction between NMF with superoxide dismutase, an antioxidant defense enzyme has been studied for the first time using spectroscopic methods including Fourier transform infrared (FT-IR) spectroscopy, Circular dichroism (CD) spectroscopy and UV-visible spectroscopy under simulative physiological conditions and also by molecular modelling. Fourier Transform Infra Red analysis showed that the change in peak positions and shapes revealed that the secondary structure of SOD had been changed by the interaction with NMF. The data of CD spectra also confirmed that NMF decreased the degree of secondary structure of SOD, which directly resulted in destabilization of enzyme. We studied the inhibitory effect of NMF on enzyme kinetics by pyrogallol autoxidation revealed that protein-ligand complex caused structural unfolding which resulted in enzymatic inhibition. Thus the spectral behaviour of superoxide dismutase provides data concerning its conformational changes in the presence of NMF. Furthermore, molecular docking was applied to explore the binding mode between the protein-ligand complex. This suggested that Asn54 and Val302 residues of dimeric protein were predicted to interact with NMF. The present study provides direct evidence at a molecular level to show that exposure to NMF cause perturbation in its structure and function.

Oxidation of N,N-dimethylformamide and N,N-diethylformamide by human liver microsomes and human recombinant P450s

N-N, dimethyl- (DMF) and N-N, diethyl-formamide (DEF) are two hepatotoxic solvents, whose metabolism has not been investigated in humans. To identify the P450 isoforms involved in the microsomal oxidation of these solvents we used (a) 12 human liver samples; (b) human recombinant P450 isoforms (1A1, 1A2, 2B6, 2C10, 2E1, 3A4); (c) chemical and immunological inhibitions. When correlation analyses were performed using enzymatic markers in human liver microsomes, the p-nitrophenol hydroxylation rate significantly correlated (r=0.87) with the dealkylation rate of DMF but not with that of DEF. Among the tested recombinant P450s only 2E1 oxidised DMF, while DEF was oxidised by 2E1, 2C10 and 3A4. 4-Methylpyrazole and anti human 2E1 IgG strongly inhibited the DMF demethylation but only partially the DEF deethylation. These findings indicate that, in the DMF metabolism, the role of 2E1 is crucial and its expression may be an important factor in determining the susceptibility of human to this solvent.

Hepatotoxicity and P-4502E1-dependent metabolic oxidation of N,N-dimethylformamide in rats and mice

A comparative biochemical and histological study on the hepatotoxicity of a single dose of N,N-dimethylformamide (DMF) and N-methylformamide (NMF) in control and acetone-treated SD male rats and CD-1 male mice was performed. In control and acetone-pretreated rats, neither DMF nor NMF caused hepatic damage or elevation of plasma transaminases. In contrast, in acetonized but not in control mice, DMF administration yielded some evidence of liver necrosis and elevation of ALAT (alanine-amino transferase) activity. After a DMF dose of 1000 mg/kg, ALAT activity was found 1215 +/- 832 mU/ml and 47 +/- 18 mU/ml in acetonized and control mice, respectively. NMF treatment was hepatotoxic in control mice and lethal in acetonized mice. In control mice, an NMF dose of 600 mg/kg increased ALAT activity from a basal value of 35 +/- 5 to 2210 +/- 1898 mU/ml. When the oxidative metabolism of DMF was investigated, microsomes from both rats and mice preinduced by acetone increased the demethylation rate of DMF 7 to 10-fold compared to that (about 0.25 nmol/min per mg protein) of the corresponding control microsomes. The enzymatic affinities for DMF oxidation, however, were different: in mice the Km (0.05 mM) was one order of magnitude lower than that (0.56 mM) found in rats. The experiments performed with purified rat and mouse P-450 2E1 in a reconstituted system confirmed that the P-450 2E1 isoforms are very active catalysts towards DMF oxidation (the turnover was about 10 nmol/min per nmol P-450 for both enzymes) but with a strikingly different affinity. Whereas the Km for mouse P-450 2E1 was 0.08 +/- 0.03 mM, that for rat P-450 2E1 was 1.1 +/- 0.2 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological monitoring of workers exposed to N,N-dimethylformamide by determination of the urinary metabolites, N-methylformamide and N-acetyl-S-(N-methylcarbamoyl) cysteine

Biological monitoring of workers exposed to N,N-dimethylformamide (DMF) was carried out by determination of the urinary metabolites, N-methylformamide (MF, mainly from N-hydroxymethylformamide) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), which were derived from two different routes of metabolism of the solvent. The urinary levels of MF increased rapidly at the start of the work shift, and decreased almost to zero within 24 h after the beginning of the last exposure. The highest level was found between the end of the afternoon shift and bedtime. AMCC levels remained constant over the consecutive work days and increased after the cessation of exposure, with the peak concentration being observed at 16-40 h after the cessation of exposure. AMCC levels at the beginning of the next morning shift were closely correlated with personal exposure levels of DMF in air, although the correlation of MF and DMF in air was highest in the urine at the end of the shift. Hence urinary AMCC represents an index of the average exposure during several preceding work days and may indicate the internal dose. By contrast, MF represents an index of daily exposure.