Diallyl disulfide prevents 1,3-dichloro-2-propanol-induced hepatotoxicity through mitogen-activated protein kinases signaling

We investigated whether diallyl disulfide (DADS) has protective effects against 1,3-dichloro-2-propanol (1,3-DCP)-induced hepatotoxicity and oxidative damage in rats and HepG2 cells. DADS was administered to rats once daily for 7 days at doses of 30 and 60 mg/kg/day. One hour after the final DADS treatment, the rats were administered 90 mg/kg 1,3-DCP to induce acute hepatotoxicity. DADS treatment significantly suppressed the increase in serum aminotransferase levels induced by 1,3-DCP administration, and reduced histopathological alterations in the liver. DADS treatment reduced 1-3-DCP-induced apoptotic changes in the liver, as revealed by terminal deoxynucleotidyl transferase dUTP nick end labeling staining and immunohistochemistry for caspase-3. DADS treatment competitively inhibited or reduced cytochrome p450 2E1 (CYP2E1) expression, which is involved in the metabolic activation of 1,3-DCP, and enhanced antioxidant properties. Furthermore, DADS treatment inhibited phosphorylation of mitogen-activated protein kinases (MAPKs) and apoptotic signaling. In in vitro experiments, MAPKs inhibitors reduced the expression of Bax/Bcl-2/Caspase 3 signaling, which effects were more significant in co-treated cells with DADS and MAPKs inhibitors. In conclusion, the protective effect of DADS against 1,3-DCP-induced hepatotoxicity may be related to blocking the metabolic activation of 1,3-DCP by suppressing CYP2E1 expression, inducing antioxidant enzyme activity, and reducing apoptotic activity by inhibiting phosphorylation of MAPKs.

1,3-dichloro-2-propanol induced hepatic lipid accumulation by inhibiting autophagy via AKT/mTOR/FOXO1 pathway in mice

Our study investigated the effects of food contaminant 1,3-dichloro-2-propanol (1,3-DCP) on hepatic lipid metabolism and its mechanism. We found that triglyceride (TG), total cholesterol (TC) and the number of lipid droplets (LDs) were increased in the liver of C57BL/6 mice given intragastric administration of 1,3-DCP for 30 days. Meanwhile, 1,3-DCP inhibited autophagosomes and lysosomes formation, reflected by decreased LC3-II, LAMP1, LAMP2, CTSD, CTSB expression, increased p62 expression and decreased LC3 fluorescence. Subsequently, we detected the changes of hepatic lipid accumulation caused by 1,3-DCP using an autophagy inducer or inhibitor. In vivo, Hepatic lipid accumulation caused by 1,3-DCP was mitigated by the autophagy inducer Rapa. On the contrary, the autophagy inhibitor (chloroquine or 3-methyladenine) further exacerbated hepatic lipid accumulation caused by 1,3-DCP. 1,3-DCP reduced the number of autophagosomes encapsulated LDs, assessed by colocalization of LD and LC3. These data demonstrated that 1,3-DCP induced lipid accumulation by inhibiting autophagy. We further investigated the mechanism of 1,3-DCP-inhibited autophagy and found 1,3-DCP increased the ratios of p-AKT/AKT, p-mTOR/mTOR, p-FOXO1/FOXO1, decreased FOXO1 nuclear localization in vivo. These proteins may be involved in the regulation of 1,3-DCP-mediated autophagy. We detected the changes in autophagy marker protein LC3-II and lipid accumulation using an AKT inhibitor ARQ-092 or a mTOR inhibitor rapamycin in HepG2 cells. Compared with 1,3-DCP group, lipid accumulation was decreased, LC3-II and FOXO1 nuclear localization were increased, p-FOXO1 levels were decreased in HepG2 cells pretreated with ARQ-092 or rapamycin. Taken together, these data revealed that the effects of 1,3-DCP on lipid accumulation by inhibiting autophagy were dependent on AKT/mTOR/FOXO1 signaling pathway. Our study not only supplied the mechanism of 1,3-DCP toxicity, but also provided experimental basis for effective intervention measures of 1,3-DCP toxicity.

In vivo mutagenicity and tumor-promoting activity of 1,3-dichloro-2-propanol in the liver and kidneys of gpt delta rats

1,3-Dichloro-2-propanol (1,3-DCP), a food contaminant, exerts carcinogenic effects in multiple organs, including the liver and kidneys, in rats. However, the underlying mechanisms of 1,3-DCP-induced carcinogenesis remain unclear. Here, the in vivo mutagenicity and tumor-promoting activity of 1,3-DCP in the liver and kidneys were evaluated using medium-term gpt delta rat models previously established in our laboratory (GPG and GNP models). Six-week-old male F344 gpt delta rats were treated with 0 or 50 mg/kg body weight/day 1,3-DCP by gavage for 4 weeks. After 2 weeks of cessation, partial hepatectomy or unilateral nephrectomy was performed to collect samples for in vivo mutation assays, followed by single administration of diethylnitrosamine (DEN) for tumor initiation. One week after DEN injection, 1,3-DCP treatment was resumed, and tumor-promoting activity was evaluated in the residual liver or kidneys by histopathological analysis of preneoplastic lesions. gpt mutant frequencies increased in excised liver and kidney tissues following 1,3-DCP treatment. 1,3-DCP did not affect the development of glutathione S-transferase placental form-positive foci in residual liver tissues, but enhanced atypical tubule hyperplasia in residual kidney tissues. Detailed histopathological analyses revealed glomerular injury and increased cell proliferation of renal tubular cells in residual kidney tissues of rats treated with 1,3-DCP. These results suggested possible involvement of genotoxic mechanisms in 1,3-DCP-induced carcinogenesis in the liver and kidneys. In addition, we found that 1,3-DCP exhibited limited tumor-promoting activity in the liver, but enhanced clonal expansion in renal carcinogenesis via proliferation of renal tubular cells following glomerular injury.

Extracts from Erythronium japonicum and Corylopsis coreana Uyeki reduce 1,3-dichloro-2-propanol-mediated oxidative stress in human hepatic cells

In this study, it was demonstrated that 1,3-dichloro-2-propanol (1,3-DCP) induced oxidative stress and cell death in HuH7, human hepatocytes. The protective effects of Erythronium japonicum (E. japonicum) and Corylopsis coreana Uyeki (C. coreana Uyeki) extracts against 1,3-DCP-treated cells were also investigated. First, the activities of superoxide dismutase (SOD) and catalase (CAT) were diminished by the treatment of 1,3-DCP. Moreover, 1,3-DCP stimulated the expression and catalytic activity of cytochrome P450 2E1 (CYP2E1), an enzyme that generates reactive oxygen species in the liver. In contrast, co-treatment of 1,3-DCP with the extracts significantly decreased ROS generation and inhibited CYP2E1 activity without affecting its expression. The co-administration of extracts also restored the activities of SOD and CAT reduced by 1,3-DCP and protected against 1,3-DCP-mediated cell death. In conclusion, these results suggest that 1,3-DCP induces oxidative stress through the elevated CYP2E1 level, which is inhibited by the extracts, protecting cells against the effects of 1,3-DCP.

Analysis of 3-MCPD and 1,3-DCP in Various Foodstuffs Using GC-MS

3-Monochloro-1,2-propanediol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) are not only produced in the manufacturing process of foodstuffs such as hydrolyzed vegetable proteins and soy sauce but are also formed by heat processing in the presence of fat and low water activity. 3-MCPD exists both in free and ester forms, and the ester form has been also detected in various foods. Free 3-MCPD and 1,3-DCP are classified as Group 2B by the International Agency for Research on Cancer. Although there is no data confirming the toxicity of either compound in humans, their toxicity was evidenced in animal experimentation or in vitro. Although few studies have been conducted, free 3-MCPD has been shown to have neurotoxicity, reproductive toxicity, and carcinogenicity. In contrast, 1,3-DCP only has mutagenic activity. The purpose of this study was to analyze 3-MCPD and 1,3-DCP in various foods using gas chromatography -mass spectrometry. 3-MCPD and 1,3-DCP were analyzed using phenyl boronic acid derivatization and the liquid-liquid extraction method, respectively. The analytical method for 3-MCPD and 1,3-DCP was validated in terms of linearity, limit of detection (LOD), limit of quantitation, accuracy and precision. Consequently, the LODs of 3-MCPD and 1,3-DCP in various matrices were identified to be in the ranges of 4.18~10.56 ng/g and 1.06~3.15 ng/g, respectively.

Time-course and molecular mechanism of hepatotoxicity induced by 1,3-dichloro-2-propanol in rats

This study investigated the time-course of 1,3-dichloro-2-propanol (1,3-DCP)-induced hepatotoxicity and the molecular mechanism of its oxidative stress and apoptotic changes in rats. Thirty-six male rats were randomly assigned to six groups of six rats each and were administered a single oral dose of 1,3-DCP (90 mg/kg) or its vehicle. 1,3-DCP caused acute hepatic damage, as evidenced by marked increases in serum aminotransferase, alkaline phosphatase, and histopathological alterations. These functional and histopathological changes in the liver peaked at 12h after administration and then decreased progressively. Oxidative stress indices were increased significantly at 6h, peaked at 12h, and then decreased progressively. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)- and caspase-3-positive cells increased after 6h, peaked at 12 and 24h, and then decreased. The protein levels of phosphorylated mitogen-activated protein kinases (MAPKs) including p-Erk1/2 and p-JNK showed a similar trend to the numbers of TUNEL- and caspase-3-positive cells. These results indicate that 1,3-DCP increases oxidative stress, nuclear translocation of Nrf2, and expression of Nrf2-targeted genes, followed by increased functional and histopathological alterations in the liver. The increase in hepatocellular apoptosis induced by 1,3-DCP may be related to oxidative stress-mediated MAPK activation.

Evaluation of Maternal Toxicity in Rats Exposed to 1,3-Dichloro-2-propanol during Pregnancy

The present study was carried out to investigate the potential adverse effects of 1,3-dichloro-2-propanol on pregnant dams after maternal exposure during the gestational days (GD) 6 through 19 in Sprague-Dawley rats. The tested chemical was administered orally to pregnant rats at dose levels of 0, 10, 30, or 90 mg/kg/day. During the test period, clinical signs, mortality, body weights, food consumption, serum biochemistry, gross findings, organ weights, and Caesarean section findings were examined. In the 90 mg/kg group, decreases in the body weight gain and food consumption, and increases in the weights of liver and adrenal glands were observed. Serum biochemical investigations revealed increases in aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol (CHO), triglyceride (TG), alkaline phosphatase (ALP), and bilirubin (BIL) and decreases in glucose (GLU), albumin (ALB) and total protein (TP). In the 30 mg/kg group, a decrease in the food consumption and an increase in the liver weight were observed. Serum biochemical investigation also showed increases in CHO and TG and a decrease in glucose. Since there were no signs of maternal toxicity in the 10 mg/kg group, it is considered to be the no-observed-adverse-effect level (NOAEL) of 1,3-dichloro-2-propanol. It is concluded that successive oral administration of 1,3-dichloro-2-propanol to pregnant rats for 14 days may cause significant toxicities in body weight and liver at a dose rate ≥ 30 mg/kg/day.