Chronic occupational N, N-dimethylformamide poisoning induced death: a case report

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.

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.

Pathological characteristics of liver injury induced by N,N-dimethylformamide: From humans to animal models

N,N-Dimethylformamide (DMF) is widely used in chemical industries because of its excellent solvent properties. Poisoning accidents caused by DMF have been frequently reported, particularly hepatotoxicity; however, the hepatic pathological changes have rarely been described. This study aimed to summarise the pathological characteristics of the hepatotoxicity associated with DMF in clinical cases and to verify in animal models. Liver pathologies of two patients with liver failure due to DMF were retrospectively analysed. Thirty-six rats were categorised into the DMF group (intraperitoneally injected with 4 g/kg DMF once a week), carbon tetrachloride (CCl₄) group (intraperitoneally injected with 0.5 g/kg CCl₄ twice a week) and control group (intraperitoneally injected with normal saline once a week). The general condition and changes in hepatic pathology at 48 h and 8 weeks were observed. Liver tissues of patients exhibited multiple unevenly distributed inflammatory and fibrotic lesions. The DMF-induced liver injury animal model was successfully established. Inflammation and fibrosis were heterogeneously observed throughout the liver in the DMF group, contrast to entirely homogeneous lesions in the CCl₄ group. Specific hepatic pathological findings (heterogeneous lesions) caused by DMF detected for the first time in humans and animal model, may be significant in the clinical diagnosis of DMF poisoning.

N, N-dimethylformamide exposure induced liver abnormal mitophagy by targeting miR-92a-1-5p-BNIP3L pathway in vivo and vitro

N, N-dimethylformamide (DMF) is a widely existing harmful environmental pollutant from industrial emission which can threat human health for both occupational and general populations. Epidemiological and experimental studies have indicated liver as the primary target organ of DMF. However, the molecular mechanism under DMF-induced hepatoxicity remains unclear. In the present study, we identified that DMF could induce abnormal autophagy flux in cells. We also showed that DMF-induced mitochondrial dysfunction and lethal mitophagy which further leads to autophagic cell death. Next, miRNA microarray analysis identified miR-92a-1-5p as the most down-regulated miRNA upon DMF exposure. Mechanistically, miR-92a-1-5p regulated mitochondrial function and mitophagy by targeting mitochondrial protein BNIP3L. Exogenous miR-92a-1-5p significantly attenuated DMF-induced mitochondrial dysfunction and mitophagy in vitro and in vivo. Our study highlights the mechanistic link between miRNAs and mitophagy under environmental stress, which provided a new clue for the mitochondrial epigenetics mechanism on environmental toxicant-induced hepatoxicity.

N,N-dimethylformamide-induced acute liver damage is driven by the activation of NLRP3 inflammasome in liver macrophages of mice

N,N-dimethylformamide (DMF) is a non-negligible volatile hazardous material in indoor and outdoor environments. Although the hepatotoxicity of DMF has been well recognized, the underlying mechanisms remain unclear and prophylactic medicine is still lacking. Herein, we established a DMF-induced acute liver injury mouse model and investigated the underlying mechanisms focusing on oxidative stress and the nucleotide-binding domain and leucine-rich repeat receptor (NLR) family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome. DMF was found to induce oxidative stress, evidenced by the elevation of hepatic malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) adducts levels, and the decline of reduced glutathione (GSH) levels. However, neither N-acetyl cysteine (NAC) nor sulforaphane (SF) ameliorated the hepatoxicity induced by DMF in mice. Interestingly, DMF exposure led to focal necrosis of hepatocytes and NLRP3 inflammasome activation before the onset of obvious liver damage. In addition, DMF exposure induced infiltration and proinflammatory/M1 polarization of macrophages in mice livers. Furthermore, the inactivation of hepatic macrophages by GdCl₃ significantly suppressed DMF-induced elevation of serum aminotransferase activities, neutrophile infiltration, and activation of NLRP3 inflammasome in mice liver. Collectively, these results suggest that DMF-induced acute hepatotoxicity may be attributed to the activation of NLRP3 inflammasome in liver macrophages, but not oxidative stress.

A Case of Autoimmune Hepatitis after Occupational Exposure to N,N-Dimethylformamide

N,N-dimethylformamide (DMF), a widely used solvent in the chemical industry, is known to induce toxic hepatitis. However, there have been no reported cases of DMF-associated autoimmune hepatitis. A 31-year-old healthy man working at a glove factory since July 2015 had intermittently put his bare hands into a diluted DMF solution for his first 15 days at work. After 2 months, he felt nausea, fatigue, and hand cramping, and a jaundice followed. His laboratory findings showed positive autoantibodies and elevated immunoglobulin G (IgG), and his liver biopsy pathology was typical of autoimmune hepatitis (AIH). Prednisolone and azathioprine therapy began, and he recovered rapidly without adverse events. Though his liver chemistry was normalized, the IgG level remained persistently upper normal range. His 2nd liver biopsy performed in April 2019 showed mild portal activity, and he was well under a low dose immunosuppressive therapy up to April 2020. This case warns of the hazard of occupational exposure to DMF, and clinicians should be aware of DMF-related AIH for timely initiation of immunosuppressive therapy.

The effects of dimethylformamide exposure on liver and kidney function in the elderly population: A cross-sectional study

Dimethylformamide (DMF) is widely used as a solvent in the production of synthetic leather. Previous studies have focused on workers exposed to DMF in leather factories; however, little attention has been paid to the general population. This study was conducted to examine the effects of DMF exposure on elderly residents living near synthetic leather factories. A total of 962 subjects over 60 years of age in proximity to these factories (monitoring points) were enrolled as the exposure group, and 1924 permanent residents living distant from the factories were enrolled as the control group. The exposure group was divided into 3 groups according to their distance from the monitoring points. Physical examination, routine blood tests, and liver and renal function data were collected, and the DMF concentration in the air was analyzed by gas chromatography-mass spectroscopy. The prevalence of abnormal heart rhythm, electrocardiogram and B-mode ultrasound results in the exposure group was significantly greater than in the control group. Aspartate transaminase (AST), alanine transaminase (ALT), and blood urea nitrogen (BUN) levels in the exposure group also were higher than those in the control group (P < .01). There was an effect of distance from leather factories on liver and kidney dysfunction in the 3 exposure groups. Compared with the exposure group at >3 km distance from the source, the prevalence of increased AST, ALT, and BUN in the exposure group at <1 km was significantly greater (P < .001). It was concluded that DMF exposure was related to an increased risk of a cardiac injury and liver and kidney dysfunction.

Retinoid X receptor α (RXRα)-mediated erythroid-2-related factor-2 (NRF2) inactivation contributes to N,N-dimethylformamide (DMF)-induced oxidative stress in HL-7702 and HuH6 cells

N,N-dimethylformamide (DMF) is a colorless industrial solvent that is frequently used for chemical reactions. Epidemiologic studies and clinical case reports have consistently indicated that the main toxic effect after exposure to DMF is hepatotoxicity. Previous studies have suggested that oxidative stress is the pivotal molecular event of DMF-mediated hepatotoxicity; however, its underlying mechanism remains unclear. In this study, we found that DMF (0-150 mM) exposure induced an increase in reactive oxygen species (ROS) levels and inhibited the transcriptional activity of nuclear factor erythroid-2-related factor-2 (NRF2) in a dose-dependent manner. Subsequently, our research revealed that the elevated ROS levels and the decline in NRF2-mediated anti-oxidative response in HL-7702 and HuH6 cells might be due to the DMF-induced accumulation of retinoid X receptor α (RXRα) protein. Further investigation demonstrated that phosphorylation of the RXRα protein, which is mediated by the activation of extracellular signal-regulated kinase (ERK), leads to the inhibition of RXRα protein degradation and in turn the accumulation of RXRα after DMF exposure. These findings provide information that improves our understanding of the role of RXRα in DMF-induced hepatotoxicity.

N,N-dimethylformamide-induced acute hepatic failure: A case report and literature review

N,N-dimethylformamide (DMF) is a major solvent predominantly used in the chemical industry. The main toxic effects following exposure to DMF are gastric irritation, skin eruption and hepatotoxicity. However, hepatic failure induced by DMF is rare. In this report, we present a case of acute hepatic failure following exposure to a toxic dose of DMF via respiratory tract inhalation and skin absorption with detailed abdominal computed tomography scan, sequential laboratory data and polymorphisms. The patient recovered satisfactorily following artificial liver support therapy and pharmacological agents to protect the liver in addition to plasma, blood platelet and albumin transfusions. In view of the high mortality rate and rare occurrence rate of acute hepatic failure, the clinical characteristics, polymorphisms and therapeutic strategy of DMF poisoning are discussed.