Inactivation of rat liver cytochrome P450 (P450) by N,N-dimethylformamide and N,N-dimethylacetamide

Allyl methyl disulfide (AMDS) prevents N,N-dimethyl formamide-induced liver damage by suppressing oxidative stress and NLRP3 inflammasome activation

N,N-dimethylformamide (DMF), a widely consumed industrial solvent with persistent characteristics, can induce occupational liver damage and pose threats to the general population due to the enormous DMF-containing industrial efflux and emission from indoor facilities. This study was performed to explore the roles of allyl methyl disulfide (AMDS) in liver damage induced by DMF and the underlying mechanisms. AMDS was found to effectively suppress the elevation in the liver weight/body weight ratio and serum aminotransferase activities, and reduce the mortality of mice induced by DMF. In addition, AMDS abrogated DMF-elicited increases in malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) levels and decreases in glutathione (GSH) levels in mouse livers. The increase in macrophage number, mRNA expression of M1 macrophage biomarkers, and protein expression of key components in the NF-κB pathway and NLRP3 inflammasome induced by DMF exposure were all suppressed by AMDS in mouse livers. Furthermore, AMDS inhibited DMF-induced cell damage and NF-κB activation in cocultured AML12 hepatocytes and J774A.1 macrophages. However, AMDS per se did not significantly affect the protein level and activity of CYP2E1. Collectively, these results demonstrate that AMDS effectively ameliorates DMF-induced acute liver damage possibly by suppressing oxidative stress and inactivating the NF-κB pathway and NLRP3 inflammasome.

Integration of proteomics, lipidomics, and metabolomics reveals novel metabolic mechanisms underlying N, N-dimethylformamide induced hepatotoxicity

N, N-Dimethylformamide (DMF) is a universal organic solvent which widely used in various industries, and a considerable amount of DMF is detected in industrial effluents. Accumulating animal and epidemiological studies have identified liver injury as an early toxic effect of DMF exposure; however, the detailed mechanisms remain poorly understood. In this study, we systematically integrated the quantitative proteomics, lipidomics, and metabolomics data obtained from the primary human hepatocytes exposed to DMF, to depict the complicated biochemical reactions correlated to liver damage. Eventually, we identified 284 deregulated proteins (221 downregulated and 63 upregulated) and 149 deregulated lipids or metabolites (99 downregulated and 50 upregulated) induced by DMF exposure. Further, the integration of the protein-metabolite (lipid) interactions revealed that N-glycan biosynthesis (involved in the endoplasmic reticulum stress and the unfolded protein response), bile acid metabolism (involved in the lipid metabolism and the inflammatory process), and mitochondrial dysfunction and glutathione depletion (both contributed to reactive oxygen species) were the typical biochemical reactions disturbed by DMF exposure. In summary, our study identified the versatile protein, lipid, and metabolite molecules in multiple signaling and metabolic pathways involved in DMF induced liver injury, and provided new insights to elucidate the toxic mechanisms of DMF.

Dimethylacetamide-induced toxic hepatitis in spandex workers: clinical presentation and treatment outcomes

BACKGROUND

Dimethylacetamide (DMAc) exposure has been associated with toxic hepatitis, and no clinical treatment has been reported.

AIM

To investigate the clinical manifestations of DMAc-induced symptoms and how to rescue the functional loss due to occupational exposure.

DESIGN

Clinical observations of 60 spandex factory workers with the exposure to DMAc from January, 2017-19.

METHODS

Chinese drugs (reduced glutathione, polyene phosphatidylcholine, glycyrrhizin compound, Hugan tablets and ornithine aspartate) were used to evaluate the therapeutic improvements in DMAc-exposed patients.

RESULTS

Our data found that 58.3% patients had no distinct clinical symptoms, but 41.7% patients felt fatigue, and 21.7% patients suffered abdominal discomfort and appetite loss, and 8.3% patients had yellow skin and sclera. The ultrasonic and CT imaging revealed that some patients have fatty livers, intrahepatic calcifications, hepatomegaly, gallbladder wall edema and abdominal effusions. Biochemical analysis showed that the alanine aminotransferase (ALT) (P < 0.001), aspartate aminotransferase (AST) (P < 0.001), lactate dehydrogenase (LDH) (P < 0.001) and bilirubin (P < 0.01) statistically decreased after the drug treatment, but alkaline phosphatase (P >0.05) and glutamyl transpeptidase (P> 0.05) did not decrease. Twenty-nine out of the thirty-one patients' abnormal blood ammonia recovered. The risk factor of ALT on hospitalization time was significantly related (P < 0.01).

CONCLUSIONS

The drugs above are sufficient to rescue functional loss in DMAc-induced toxic hepatitis, in part via the regulations of ALT, AST, LDH, bilirubin and ammonia. Workers with the exposure to DMAc should receive specific drugs to maintain the health and prevent functional loss in the long term.

Enhancement of Flame Retardancy of Colorless and Transparent Semi-Alicyclic Polyimide Film from Hydrogenated-BPDA and 4,4'-oxydianiline via the Incorporation of Phosphazene Oligomer

Enhancement of flame retardancy of a colorless and transparent semi-alicyclic polyimide (PI) film was carried out by the incorporation of phosphazene (PPZ) flame retardant (FR). For this purpose, PI-1 matrix was first synthesized from hydrogenated 3,3′,4,4′-biphenyltetracarboxylic dianhydride (HBPDA) and 4,4′-oxydianiline (ODA). The soluble PI-1 resin was dissolved in N,N-dimethylacetamide (DMAc) to afford the PI-1 solution, which was then physically blended with PPZ FR with the loading amounts in the range of 0–25 wt.%. The PPZ FR exhibited good miscibility with the PI-1 matrix when its proportion was lower than 10 wt.% in the composite films. PI-3 composite film with the PPZ loading of 10 wt.% showed an optical transmittance of 75% at the wavelength of 450 nm with a thickness of 50 μm. More importantly, PI-3 exhibited a flame retardancy class of UL 94 VTM-0 and reduced total heat release (THR), heat release rate (HRR), smoke production rate (SPR), and rate of smoke release (RSR) values during combustion compared with the original PI-1 film. In addition, PI-3 film had a limiting oxygen index (LOI) of 30.9%, which is much higher than that of PI-1 matrix (LOI: 20.1%). Finally, incorporation of PPZ FR decreased the thermal stability of the PI films. The 10% weight loss temperature (T_10%) and the glass transition temperature (T_g) of the PI-3 film were 411.6 °C and 227.4 °C, respectively, which were lower than those of the PI-1 matrix (T_10%: 487.3 °C; T_g: 260.6 °C)

The essential role of CYP2E1 in metabolism and hepatotoxicity of N,N-dimethylformamide using a novel Cyp2e1 knockout mouse model and a population study

N,N-Dimethylformamide (DMF) is a widespread contaminant of leather factories and their surrounding environment. There is a lack of direct in vivo evidence supporting CYP2E1 as a primary enzyme responsible for DMF metabolism and hepatotoxicity. In this study, a novel Cyp2e1 knockout (KO) mouse model was generated and used to assess whether DMF metabolism and hepatotoxicity is CYP2E1 dependent using an acute toxicity protocol with a single dose of 1500 mg DMF/kg. An epidemiological study in 698 DMF-exposed workers and 188 non-DMF-exposed controls was conducted to investigate the associations between functional polymorphisms of CYP2E1 (rs6413432/rs2031920) and DMF metabolite (N-methylcarbmoylated-hemoglobin [NMHb]). We successfully established Cyp2e1 KO mice with evidence from DNA sequence analysis, which showed 1-bp insertion at 65 bp (C) site of Cyp2e1 Exon 1. In addition, western blot and in vivo pharmacokinetic study also showed a complete absence of CYP2E1 protein and a 92% and 88% reduction in CYP2E1 activity among males and females, respectively. DMF metabolism as evidenced by increased blood NMHb, and hepatotoxicity as evidenced by elevated liver/body weight ratio, activity of liver enzymes and massive liver necrosis were detected in wild-type (WT) mice but were completely abrogated in KO mice, strongly supporting a CYP2E1-dependent pattern of DMF metabolism and hepatotoxicity. Moreover, variant allele of CYP2E1-rs6413432 was also significantly associated with higher NMHb levels in DMF-exposed workers (P = 0.045). The increase of glucose-regulated protein 94 detected in WT mice but not in KO mice suggested CYP2E1-dependent endoplasmic reticulum stress may be a key mechanism underlying DMF-induced hepatotoxicity.

Study on the potential way of hepatic cytotoxicity of N,N-dimethylformamide

The intermediate metabolites and redox status imbalance were supported as the two major points for N,N-dimethylformamide (DMF)-induced hepatotoxicity. However, the potential mechanism has not yet been concerned. By applying two inhibitors, this study tried to seek the major role in DMF-induced toxicity on HL7702 cell. We observed that DMF induced cell apoptosis through mitochondrial-dependent and p53 pathway. Inhibition reactive oxygen species by catalase remarkably attenuated the mitochondrial transmembrane potential (MMP), apoptotic proteins, and apoptosis. On the contrary, it reduced the biodegradation rate of DMF by coincubation with CYP2E1 antagonist (DDC) partially reduced late apoptosis. However, the change in MMP, the ratio of Bax to Bcl-xl, and cleaved-caspase 9 was not attenuated by DDC. The pathway in DDC coincubation groups was related to the p53 rather than the mitochondrial pathway. Restoring the redox balance during biodegradation is much more effective than attenuating the metabolite rate of DMF. This study may provide a suitable prevention method to occupational workers.

Mechanism of free radical generation in platelets and primary hepatocytes: A novel electron spin resonance study

Oxygen free radicals have been implicated in the pathogenesis of toxic liver injury and are thought to be involved in cardiac dysfunction in the cirrhotic heart. Therefore, direct evidence for the electron spin resonance (ESR) detection of how D‑galactosamine (GalN), an established experimental hepatotoxic substance, induced free radicals formation in platelets and primary hepatocytes is presented in the present study. ESR results demonstrated that GalN induced hydroxyl radicals (OH•) in a resting human platelet suspension; however, radicals were not produced in a cell free Fenton reaction system. The GalN‑induced OH• formation was significantly inhibited by the cyclooxygenase (COX) inhibitor indomethasin, though it was not affected by the lipoxygenase (LOX) or cytochrome P450 inhibitors, AA861 and 1‑aminobenzotriazole (ABT), in platelets. In addition, the present study demonstrated that baicalein induced semiquinone free radicals in platelets, which were significantly reduced by the COX inhibitor without affecting the formed OH•. In the mouse primary hepatocytes, the formation of arachidonic acid (AA) induced carbon‑centered radicals that were concentration dependently enhanced by GalN. These radicals were inhibited by AA861, though not affected by indomethasin or ABT. In addition, GalN did not induce platelet aggregation prior to or following collagen pretreatment in human platelets. The results of the present study indicated that GalN and baicalein may induce OH• by COX and LOX in human platelets. GalN also potentiated AA induced carbon‑centered radicals in hepatocytes via cytochrome P450. The present study presented the role of free radicals in the pathophysiological association between platelets and hepatocytes.

Cu(ii)-Mediated keto C(sp3)–H bond α-acyloxylation of N,N-dialkylamides with aromatic carboxylic acids

The first example of Cu(ii)-mediated oxidative coupling of aromatic carboxylic acids with the C(sp³)–H bond adjacent to the keto group of N,N-dialkylamides has been developed.

The tubular MFC with carbon tube air-cathode for power generation and N,N-dimethylacetamide treatment

A continuous flow microbial fuel cell (MFC) was assembled with carbon tube air-cathode and carbon felt anode. The organic solvent N,N-dimethylacetamide (DMAC) was used as the only carbon source for power generation. After the adaptive phase, the cell potential was gradually increased from 0.15 to 0.45 V with 200 Ω of external resistor during 150 h of operation. The calculated power density of this MFC was 100 mW L(-1) when the cell potential was 0.45 V. The reversible redox peaks of carbon tube were obtained in cyclic voltammogram between -0.5 and -0.25 V under aerobic circumstance. The removal rate of DMAC was 15-50% after treatment with hydraulic retention time of 12 min. The results indicated that it is possible to realize the power extraction from DMAC wastewater in the form of electricity by the bioconversion process of MFC.

The Simplest Flowchart Stating the Mechanisms for Organic Xenobiotics-induced Toxicity: Can it Possibly be Accepted as a "Central Dogma" for Toxic Mechanisms?

Xenobiotics causing a variety of toxicity in biological systems could be classified as two types, inorganic and organic chemicals. It is estimated that the organic xenobiotics are responsible for approximately 80~90% of chemical-induced toxicity in human population. In the class for toxicology, we have encountered some difficulties in explaining the mechanisms of toxicity caused especially by organic chemicals. Here, a simple flowchart was introduced for explaining the mechanism of toxicity caused by organic xenobiotics, as the central dogma of molecular biology. This flowchart, referred to as a central dogma, was described based on a view of various aspects as follows: direct-acting chemicals vs. indirect-acting chemicals, cytochrome P450-dependent vs. cytochrome P450-independent biotransformation, reactive intermediates, reactivation, toxicokinetics vs. toxicodynamics, and reversibility vs. irreversibility. Thus, the primary objective of this flowchart is to help better understanding of the organic xenobiotics-induced toxic mechanisms, providing a major pathway for toxicity occurring in biological systems.

Influence of small doses of various drug vehicles on acetaminophen-induced liver injury

The biological effects of drug vehicles are often overlooked, often leading to artifacts in acetaminophen-induced liver injury assessment. Therefore, we decided to investigate the effect of dimethylsulfoxide, dimethylformamide, propylene glycol, ethanol, and Tween 20 on acetaminophen-induced liver injury. C57BL/6 male mice received a particular drug vehicle (0.6 or 0.2 mL/kg, i.p.) 30 min before acetaminophen administration (300 mg/kg, i.p.). Control mice received vehicle alone. Liver injury was assessed by measuring the concentration of alanine aminotransferase in plasma and observing histopathological changes. The level of reduced glutathione (GSH) was assessed by measuring total nonprotein hepatic sulfhydrils. Dimethylsulfoxide and dimethylformamide (at both doses) almost completely abolished acetaminophen toxicity. The higher dose of propylene glycol (0.6 mL/kg) was markedly protective, but the lower dose (0.2 mL/kg) was only slightly protective. These solvents also reduced acetaminophen-induced GSH depletion. Dimethylformamide was protective when given 2 h before or 1 h after acetaminophen administration, but was ineffective if given 2.5 h after acetaminophen. Ethanol at the higher dose (0.6 mL/kg) was partially protective, whereas ethanol at the lower dose (0.2 mL/kg) as well as Tween 20 at any dose had no influence. None of the vehicles (0.6 mL/kg) was hepatotoxic per se, and none of them was protective in a model of liver injury caused by d-galactosamine and lipopolysaccharide.

The effects of pharmaceutical excipients on drug disposition

Many new chemical entities are poorly soluble, requiring the use of co-solvents or excipients to produce suitable intravenous formulations for early pre-clinical development studies. There is some evidence in the literature that these formulation components can have significant physiological and physicochemical effects which may alter the distribution and elimination of co-administered drugs. Such effects have the potential to influence the results of pre-clinical pharmacokinetic studies, giving a false impression of a compound's intrinsic pharmacokinetics and frustrating attempts to predict the drug's ultimate clinical pharmacokinetics. This review describes the reported effects of commonly used co-solvents and excipients on drug pharmacokinetics and on physiological systems which are likely to influence drug disposition. Such information will be useful in study design and evaluating data from pharmacokinetic experiments, so that the potential influence of formulation components can be minimised.

Activity of human P450 2D6 in biphasic solvent systems

Several limitations have restricted the use of P450 enzymes in synthesis, including the narrow substrate specificity of some P450 isoforms, the need for a redox partner and an expensive cofactor, incompatibility with organic solvents, and poor stability. We previously demonstrated that the natural redox partner and cofactor of the promiscuous P450s 3A4 and 2D6 can be efficiently substituted with some cheap hydrogen peroxide donors or organic peroxides. We report here that P450 2D6 maintains as much as 76% of its activity when used in buffer/organic emulsions. Product formation in biphasic solvent systems is comparable whether the natural redox partner and cofactor are used, or a surrogate. As reported for other enzymes, a correlation is observed between the logP and the suitability of a solvent for enzymatic activity. Moreover, the utility of our system was established by demonstrating the transformation of a novel hydrophobic substrate, not modified by P450 2D6 in the absence of organic solvent.

Mitochondrial DNA alterations in blood of the humans exposed to N,N-dimethylformamide

N,N-Dimethylformamide (DMF) has been widely used in industries because of its extensive miscibility with water and solvents. Its health effects include hepatotoxicity and male reproductoxicity, possibly linked with mitochondrial DNA (mtDNA) alterations including mtDNA common deletion (DeltamtDNA(4977)) and mtDNA copy number. The relationship between DMF exposure and mtDNA alterations, however, has not been postulated yet. The purposes of this study were to investigate whether the DMF exposure is associated with DeltamtDNA(4977) and mtDNA copy number and to evaluate the DMF-derived mtDNA alterations are more associated with exposure to the airborne DMF concentrations or to the levels of two urinary DMF biomarkers of N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoryl) cysteine(AMCC). Thirteen DMF-exposed workers and 13 age and seniority-matched control workers in a synthetic leather factory were monitored on their airborne DMF, NMF and AMCC in the urine as well as DeltamtDNA(4977) and mtDNA copy number in blood cells. We found that the frequencies of relative DeltamtDNA(4977) in DMF-exposed group were significantly higher than those in the control group. Moreover, elevation in the proportion of DeltamtDNA(4977) of individuals with high urine AMCC (U-AMCC) and airborne DMF levels were significantly higher than those without. We conclude that long-term exposure to DMF is highly associated with the alterations of mtDNA in urine and blood cells. The DeltamtDNA(4977) was more significantly related to repeated exposure to DMF and mtDNA copy number was more closely related to short-term DMF exposure. We also confirmed that U-AMCC is more appropriate to serve as a toxicity biomarker for DMF exposure than U-NMF. Further study with a larger number of subjects is warranted.

Incidence of dimethylacetamide induced hepatic injury among new employees in a cohort of elastane fibre workers

OBJECTIVE

To investigate the incidence of N,N-dimethylacetamide (DMA) induced hepatic injury among new elastane fibre workers and to explore factors relating to DMA induced hepatic injury.

METHODS

Elastane fibre workers exposed to DMA were monitored for hepatic injury. Four hundred and forty new workers employed from 1 January 2002 to 31 July 2004 were included as study subjects. DMA exposure estimates were based on urinary N-methylacetamide (NMA) concentrations.

RESULTS

There were 28 cases of DMA induced hepatic injury. The overall incidence of DMA induced hepatic injury among new elastane fibre workers was 0.089/person-year. Incidence rates were 7-10 times higher in high exposure groups than in low exposure groups. Fewer DMA induced hepatic injuries occurred among workers employed for a longer period. Workers whose exposure duration was more than seven months showed no hepatic injury in either the high or low exposure groups. Exposure category and duration of employment were significant variables in the multiple logistic regression analysis.

CONCLUSIONS

Results suggest the existence of dose dependent DMA induced hepatic injury. The inverse relation between the incidence of DMA induced hepatic injury and duration of employment may reflect a type of healthy survivor effect or tolerance to DMA induced hepatic injury.

Acute and chronic effects of carrier solvents in aquatic organisms: a critical review

Recognising the scientific and regulatory need for testing relatively hydrophobic or 'difficult substances', the OECD currently recommends that selected organic solvents may be used in aquatic toxicity testing in order to help achieve more effective dispersion of the toxicant. The OECD recommends a maximum solvent concentration of 100 microl l(-1) (with specific gravity equivalents to 100 microl l(-1) in parentheses) for acetone (79 mg l(-1)), dimethylformamide (95 mg l(-1)), dimethylsulfoxide (1.10 mg l(-1)), ethanol (78.9 mg l(-1)), methanol (79.2 mg l(-1)) and triethylene glycol (1.12 mg l(-1)). While this recommendation is supported by historical data, we have recently observed evidence that some solvents may affect the reproduction of certain fish species, and also impact biomarkers of endocrine disruption. This review presents available data on the effects of solvents in aquatic organisms, supplemented by relevant information from mammalian studies (e.g. effects on liver enzyme induction potentially altering the metabolism of sex hormones). In conclusion, it is recommended that maximum effort should be given to avoiding the use of carrier solvents wherever possible, for example through the use of saturation columns or other physical methods (e.g. stirring or ultrasonification). Where solvent use is necessary, however, it is recommended that in reproduction studies with aquatic organisms, the maximum solvent concentration should not exceed 20 microl l(-1) of dilution water.