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Acrylonitrile (AN) is a known animal carcinogen and suspected human carcinogen. Recently, occupational exposure to AN has considerably increased. Previously, we demonstrated that streptozotocin-induced diabetes potentiates AN-induced acute toxicity in rats and that the induced cytochrome P450 2E1 (CYP2E1) is responsible for this effect. In the present study, we examined whether induction of CYP2E1 is also the underlying mechanism for the potentiation of AN-induced acute toxicity in type 2 diabetes in db/db mice. The effect of phenethyl isothiocyanate (PEITC) in reducing potentiation was also investigated. The mice were randomly divided into the normal control, diabetic control, AN, diabetes + AN, PEITC + AN, and diabetes + PEITC + AN groups. PEITC (40 mg/kg) was orally administered to rats for 3 days, and 1 h after the last PEITC gavage, 45 mg/kg AN was intraperitoneally injected. Time to death was observed. The CYP2E1 level and enzymatic activity, cytochrome c oxidase (CCO) activity, and reactive oxygen species (ROS) levels were measured. The survival rate was decreased in AN-treated db/db mice compared with that in AN-treated wild-type mice. The hepatic CYP2E1 level and enzymatic activity remained unaltered in db/db mice. Phenethyl isothiocyanate alleviated AN-induced acute toxicity in db/db mice as evident in the increased survival rate, restored CCO activity, and decreased ROS level in both the liver and brain. The study results suggested that CYP2E1 may not be responsible for the sensitivity to AN-induced acute toxicity in db/db mice and that PEITC reduced the potentiation of AN-induced acute toxicity in db/db mice.

Hydrogen sulfide (H 2 S) as the third gasotransmitter molecule serves various biological regulatory roles in health and disease. Acrylonitrile (AN) is a common occupational toxicant and environmental pollutant, causing brain and liver damage in mammals. The biotransformation of AN is dependent-upon reduced glutathione (GSH), cysteine and other sulfur-containing compounds. However, the effects of AN on the endogenous H 2 S biosynthesis pathway have yet to be determined. Herein, we demonstrated that a single exposure to AN (at 25, 50, or 75 mg/kg for 1, 6 or 24 h) decreased the endogenous H 2 S content and H 2 S-producing capacity in a dose-dependent manner, both in the cerebral cortex and liver of rats in vivo. In addition, the inhibitory effects of AN (1, 2.5, 5, 10 mM for 12 h) on the H 2 S content and/or the expression of H 2 S-producing enzymes were also found both in primary rat astrocytes and rat liver cell line (BRL cells). Impairment in the H 2 S biosynthesis pathway was also assessed in primary rat astrocytes treated with AN. It was found that inhibition of the cystathionine-β-synthase (CBS)/3-mercaptopyruvate sulfurtransferase (3-MPST)-H 2 S pathway with the CBS inhibitor or 3-MPST-targeted siRNA significantly increased the AN-induced (5 mM for 12 h) cytotoxicity in astrocytes. In turn, CBS activation or 3-MPST overexpression as well as exogenous NaHS supplementation significantly attenuated AN-induced cytotoxicity. Taken together, endogenous H 2 S biosynthesis pathway was disrupted in rats acutely exposed to AN, which contributes to acute AN neurotoxicity in primary rat astrocytes., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Diabetes mellitus is a significant global public health issue. The diabetic state not only precipitates chronic disease but also has the potential to change the toxicity of drugs and chemicals. Acrylonitrile (AN) is a potent neurotoxin widely used in industrial products. This study used a streptozotocin (STZ)-induced diabetic rat model to examine the role of cytochrome P450 2E1 (CYP2E1) in acute AN toxicity. The protective effect of phenethyl isothiocyanate (PEITC), a phytochemical inhibitor of CYP2E1, was also investigated. A higher incidence of convulsions and loss of the righting reflex, and decreased rates of survival, as well as elevated CYP2E1 activity, were observed in diabetic rats treated with AN when compared to those in non-diabetic rats, suggesting that diabetes confers susceptibility to the acute toxicity of AN. Pretreatment with PEITC (20-80 mg/kg) followed by AN injection alleviated the acute toxicity of AN in diabetic rats as evidenced by the decreased incidence of convulsions and loss of righting reflex, and increased rates of survival. PEITC pretreatment at 40 and 80 mg/kg decreased hepatic CYP2E1 activity in AN-exposed diabetic rats. PEITC pretreatment (20 mg/kg) increased the glutathione (GSH) content and glutathione S-transferase (GST) activity and further decreased ROS levels in AN-exposed diabetic rats. Collectively, STZ-induced diabetic rats were more sensitive to AN-induced acute toxicity mainly due to CYP2E1 induction, and PEITC pretreatment significantly alleviated the acute toxicity of AN in STZ-induced diabetic rats. PEITC might be considered as a potential effective chemo-preventive agent against AN-induced acute toxicity in individuals with an underlying diabetic condition.

Cytochrome P450 2E1 (CYP2E1) can be induced by diabetes mellitus, nonalcoholic liver disease, and obesity. This study assessed the protective effects of three sulfur compounds, namely phenethyl isothiocyanate (PEITC), dimethyl trisulfide (DMTS), and sodium thiosulfate (STS), on acrylonitrile (ACN)-induced acute toxicity in rats enriched with CYP2E1. PEITC and DMTS were administered intragastrically (i.g.), whereas STS was injected intraperitoneally (i.p.) at an identical dose of 0.5 mmol/kg for 3 days in acetone-pretreated rats before ACN (90 mg/kg) injection (i.p.). Acetone-treated rats that expressed high levels of CYP2E1 were more susceptible to ACN-induced acute toxicity. The sulfur compounds reduced the rate of convulsions and loss of the righting reflex in acute ACN-exposed CYP2E1-induced rats; PEITC and DMTS also increased the survival rates. PEITC inhibited hepatic CYP2E1 activity and protected hepatic and cerebral cytochrome c oxidase (CcOx) activities in acute ACN-exposed CYP2E1-enriched rats; DMTS protected hepatic CcOx activity. DMTS attenuated ACN-induced oxidative injury by reducing malondialdehyde (MDA) levels and increasing glutathione content in the brain. STS only reduced cerebral MDA levels, whereas PEITC did not exhibit any antioxidant effects. Collectively, PEITC provided superior protective effects against ACN-induced acute toxicity in rats with increased CYP2E1 activity, followed by DMTS; STS provided limited effects. PEITC and DMTS might be considered as promising chemopreventive agents against ACN-induced acute toxicity in vulnerable subpopulations with increased CYP2E1 activity.

Hydrogen sulfide (H 2 S), the third gasotransmitter, has been shown to act as a neuroprotective factor in numerous pathological processes; however, its underlying mechanism(s) of action remain unclear. It is widely accepted that activation of moderate autophagy and the Nrf2/ARE signaling pathway play important roles in the biological self-defense systems. In the present study, we investigated whether exogenous H 2 S protects against the cytotoxicity of acrylonitrile (AN), a neurotoxin, in primary rat astrocytes. We found that pretreatment for 1 h with sodium hydrosulfide (NaHS), a donor of H 2 S (200-800 µM), significantly attenuated the AN-induced decrease in cell viability, increase in lactate dehydrogenase release and morphological changes. Furthermore, NaHS significantly attenuated AN-induced oxidative stress by reducing reactive oxygen species (ROS) levels and increasing glutathione (GSH) concentration. Moreover, NaHS activated the autophagic flux, detectable as a change in autophagy-related proteins (Beclin-1, Atg5 and p62), the formation of acidic vesicular organelles and LC3B aggregation, confirmed by adenoviral expression of mRFP-GFP-LC3. Additionally, NaHS stimulated translocation of Nrf2 into the nucleus and increased expression of heme oxygenase-1 and γ-glutamylcysteine synthetase, downstream targets of Nrf2. Notably, the autophagy inhibitor 3-methyladenine and Beclin-1, or Nrf2-targeted siRNA, significantly attenuated the neuroprotective effects of NaHS against AN-induced neurotoxicity. In conclusion, we identified a crucial role of  autophagy and the Nrf2/ARE signaling pathway in H 2 S-mediated neuroprotection against AN-induced toxicity in primary rat astrocytes. Our findings provide novel insights into the mechanisms of H 2 S-mediated neuroprotection, and suggest that H 2 S-based donors may serve as potential new candidate drugs to treat AN-induced neurotoxicity.

Cytochrome P450 2E1 (CYP2E1) plays an essential role in the susceptibility to acute acrylonitrile (AN)-induced toxicity. Here, we investigated the toxicity and mechanism of AN in fasting mice and potential underlying mechanisms. Convulsions, loss of righting reflex, and death 4 h after AN treatment were observed and recorded for each group of mice. Relative to ad lib-fed mice, 48 h fasting significantly increased the acute toxicity of AN, as noted by a more rapid onset of convulsions and death. In addition, fasting significantly enhanced CYP2E1-mediated oxidative metabolism of AN, resulting in increased formation of CN- (one of the end-metabolites of AN). Moreover, fasting decreased hepatic GSH content, abrogating the detoxification of GSH. However, trans-1,2-dichloroethylene (DCE), a CYP2E1 inhibitor, altered the level of hepatic CYP2E1 activity in response to fasting, reduced the acute toxic symptoms of AN and the content of CN- in AN-treated mice. These data establish that fasting predisposes to AN toxicity, attributable to induced CYP2E1 and reduced hepatic GSH. [ABSTRACT FROM AUTHOR]

Background Hydrogen sulfide (H2S), as the third gasotransmitter participates in both cellular physiological and pathological processes, including chemical-induced injuries. We recently reported acute acrylonitrile (AN) treatment inhibited endogenous H2S biosynthesis pathway in rat and astrocyte models. However, there is still no evidence to address the correlation between endogenous H2S and sub-chronic AN exposure. Objectives This study aims to explore the modulatory effects of prolonged AN exposure on endogenous H2S levels and its biosynthetic enzymes in rat blood, brain and liver. Methods A total of 50 male Sprague-Dawley rats were randomly divided into 5 groups, including the control group and AN-treated groups at dosages of 6.25, 12.5, 25 or 50 mg/kg. Rats received one exposure/day, 5 days/week, for 4 consecutive weeks. The rat bodyweight and brain/liver organ coefficient were detected, along with liver cytochrome P450 2E1(CYP2E1) expression. In addition, the H2S contents in rat serum and plasma, and in cerebral cortex and liver tissues were measured by methylene blue method. The expression of H2S-generating enzymes, including cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MPST) was also measured with Western blot both in rat cerebral cortex and liver. Results Subchronic exposure to AN significantly inhibited bodyweight-gain and increased the liver CYP2E1 expression compared with the control. In addition, AN significantly increased H2S levels in rat plasma and serum, but not in liver. The endogenous H2S level in rat cerebral cortex was also significantly increased upon AN treatment, when expression of the major H2S-generating enzymes, CBS and 3-MPST were significantly enhanced. However, hepatic protein levels of CBS and CSE were significantly increased, whereas hepatic levels of 3-MPST were significantly decreased. Conclusion This study showed that sub-chronic AN exposure increased endogenous H2S contents in rat blood and brain tissues, but not liver, which may be resulted from the distinct expression profile of H2S-producing enzymes in response to AN. The blood H2S contents may be applied as a potential novel biomarker for surveillance of chronically AN-exposed populations. Highlights Subchronic intraperitoneal exposure to acrylonitrile increased H2S content in rat blood and cerebral cortex, but not in liver. Distinct tissue expression profiles of H2S-producing enzymes contribute to the acrylonitrile-induced differential effects on the H2S level. Blood H2S level may be a biomarker for subchronic exposure to acrylonitrile. [ABSTRACT FROM AUTHOR]

The present study was designed to examine the effects of the inhibition or induction of CYP2E1 activity on acute acrylonitrile (AN) toxicity in rats. Increased or decreased hepatic CYP2E1 activity was achieved by pretreatment with acetone or trans-1,2-dichloroethylene (DCE), respectively. AN (50 mg/kg) was administered by intraperitoneal injection. Onset of convulsions and death were observed in rats with increased CYP2E1 activity, whereas convulsions and death did not appear in rats within 1 h after treatment with AN alone. Convulsions occurred in all AN-treated animals with increased CYP2E1 activity at approximately 18 min. The levels of cyanide (CN−), a terminal metabolite of AN, were significantly increased in the brains and livers of the AN-treated rats with increased CYP2E1 activity, compared with the levels in rats treated with AN alone, DCE + AN or acetone + DCE + AN. The cytochrome c oxidase (CcOx) activities in the brains and livers of the rats treated with AN or AN + acetone were significantly lower than those in the normal control rats and the rats treated with DCE, whereas the CcOx activities in the brains and livers of rats with decreased CYP2E1 activity were significantly higher than those in AN-treated rats. Brain lipid peroxidation was enhanced, and the antioxidant capacity was significantly compromised in rats with decreased CYP2E1 activity compared with rats with normal or increased CYP2E1 activity. Therefore, inhibition of CYP2E1 and simultaneous antioxidant therapy should be considered as supplementary therapeutic interventions in acute AN intoxication cases with higher CYP2E1 activity, thus a longer window of opportunity would be got to offer further emergency medication. [ABSTRACT FROM AUTHOR]