3-Chloro-1, 2-propanediol inhibits autophagic flux by impairment of lysosomal function in HepG2 cells

1,3-Dichloro-2-propanol induced ferroptosis through Nrf2/ARE signaling pathway in hepatocytes

1,3-Dichloro-2-propanol (1,3-DCP) is a representative chloropropane environmental contaminant with multiple toxicities. Ferroptosis is a novel iron-dependent form of regulated cell death that is closely associated with the accumulation of lipid peroxides, Fe²⁺ and reactive oxygen species (ROS). In this study, we found that 1,3-DCP could induce mouse liver injury via ferroptosis. Administrating of C57BL/6J mice with 12.5, 25, and 50 mg/kg 1,3-DCP for 4 weeks via oral gavage, the data showed that 1,3-DCP exposure led to the pathological changes in mouse livers, remarkably induced accumulation of malondialdehyde (MDA) and Iron, reduction of glutathione (GSH), and changed in the expression of ferroptosis marker proteins glutathione peroxidase 4 (GPX4) and acyl-CoA synthetase-4 (ACSL4). Then, we also proved the results with HepG2 cells in vitro. The data showed that treatment 1,3-DCP significantly triggered the ferroptosis in vitro. Furthermore, we found that the ferroptosis-related signal pathways were significantly activated in mice livers and HepG2 cells in response to 1,3-DCP exposure. The data showed that 1,3-DCP induced ferroptosis by inhibiting nuclear factor erythroid 2-related factor 2 (Nrf2) translocation into nuclear and thereby suppressing the expression of its downstream target proteins including GPX4, ferritin heavy chain (FTH), ferroportin (FPN), cystine/glutamate transporter xCT (SLC7A11), and heme oxygenase 1 (HO-1). Taken together, our findings confirmed that 1,3-DCP induced ferroptosis via the Nrf2/ARE signaling pathway in hepatocytes. Our works provide new toxicity mechanisms of 1,3-DCP with ferroptosis on hepatocytes injury.

SIRT1/mTOR pathway-mediated autophagy dysregulation promotes Pb-induced hepatic lipid accumulation in HepG2 cells

Lead (Pb) is a common and toxic metal pollutant in the ecological environment and has drawn significant attention due to its presence in various channels, including the use of lead-based paint, mineral extraction and smelting, exhaust gas from gasoline combustion. Autophagy is an essential catabolic pathway and blocked autophagy may result in abnormal lipid metabolism in liver. A body of evidence demonstrates that Pb exposure causes abnormal lipid droplet (LDs) accumulation in the liver, but the mechanism remains unknown. Here, we investigated whether Pb induced lipid accumulation by regulating autophagy in HepG2 cells. In this study, we found that Pb (50 μM) blocked the autophagy flux mainly by transcription factor EB (TFEB)-mediated impairment of lysosome formation and activity. Then we demonstrated that the dense lipid accumulation was observed upon Pb exposure, and induction of autophagy by the autophagy activator rapamycin (Rap) alleviated Pb-induced lipid accumulation, while suppression of autophagy by chloroquine (CQ) exacerbated Pb-induced lipid accumulation, suggested that Pb-induced autophagy blockage might be responsible for lipid accumulation. Moreover, we demonstrated that the SIRT1/mTOR pathway participated in Pb-induced autophagy dysregulation, leading to Pb-induced hepatic lipid accumulation. In summary, these results revealed a new insight into the relationship between Pb-caused autophagy dysregulation and lipid accumulation for the first time and highlight autophagy as a novel therapeutic target against Pb-induced hepatic lipid accumulation which supplying the theoretical basis and potential strategies for the intervention and treatment of Pb-related disease.

Ginsenoside Rb1 alleviates liver injury induced by 3-chloro-1,2-propanediol by stimulating autophagic flux

In recent years, foodborne pollutants have become a hot issue in the field of food safety. 3-chloro-1,2-propanediol (3-MCPD) is a widely existing food contaminant. In our previous study, it was confirmed that 3-MCPD can block autophagic flux by inhibiting lysosomal function, thus causing liver injury. Ginseng is a traditional Chinese herbal medicine that contains a variety of bioactive ingredients, among which ginsenoside Rb1 (Gs-Rb1) is the most abundant. In this study, we aim to use Gs-Rb1 to improve 3-MCPD-induced autophagic flux blockage to alleviate liver injury. First, a nontoxic dose of Gs-Rb1 was identified by screening with the MTT method in which Gs-Rb1was added to HepG2 cells and co-treated with 3-MCPD. We found that Gs-Rb1 effectively enhanced the cell activity inhibited by 3-MCPD. Meanwhile, apoptosis data showed that Gs-Rb1 significantly alleviated the apoptosis of HepG2 cells induced by 3-MCPD. Subsequently, we found that Gs-Rb1 could alleviate autophagic flux blockage caused by 3-MCPD in a dose-dependent manner by detecting autophagy-related protein levels and transfecting mRFP-GFP-LC3 adenovirus. On this basis, we used Western blotting and qPCR to explore whether miR-128 was involved in the alleviation effect of Gs-Rb1 on autophagic flux blockade induced by 3-MCPD. The results showed that Gs-Rb1 inhibited the expression of miR-128 and promoted the nuclear expression and target gene transcription of TFEB. Finally, the findings were confirmed by using a hsa-miR-128 inhibitor and mimic. We found that hsa-miR-128 inhibitor alleviated the autophagic flux blockage and apoptosis caused by 3-MCPD and Gs-Rb1 also had a certain alleviation effect on the autophagic flux blockage and apoptosis caused by hsa-miR-128 mimic. This study elaborated the mechanism by which Gs-Rb1 alleviates hepatotoxicity induced by foodborne 3-MCPD by stimulating autophagic flux via miR-128-targeted TFEB, which provides a reliable theoretical basis and target for the use of natural substances to reduce the harm of food processing pollutants on the human body. PRACTICAL APPLICATION: We found that natural ginsenoside Rb1 can alleviate liver injury induced by 3-MCPD(a toxic substance found in foods such as refined vegetable oil, soy sauce, and baby milk powder), which is conducive to the development and utilization of ginseng and has practical significance for the prevention of foodborne liver injury.

Drp1-mediated mitochondrial fission induced autophagy attenuates cell apoptosis caused by 3-chlorpropane-1,2-diol in HEK293 cells

3-chlorpropane-1,2-diol (3-MCPD) is a heat-induced food process contaminant that threatens human health. As the primary target organ, the morphological and functional impairment of kidney and the related mechanism such as apoptosis and mitochondrial dysfunction were observed. However, the precise molecular mechanism remains largely unclear. This study aimed to explore the important role of mitochondrial fission and autophagy in the 3-MCPD-caused apoptosis of human embryonic kidney 293 (HEK293) cells. The results showed that blockage of dynamin-related protein-1 (Drp1) by mitochondrial division inhibitor 1 (Mdivi-1, 15 μM) apparently restored 3-MCPD-induced mitochondrial dysfunction, accompanied by prevented the collapse of mitochondrial membrane potential and ATP depletion, and suppressed the occurrence of autophagy. Induction of autophagy occurred following 2.5-10 mM 3-MCPD treatment for 24 h via AMPK mediated mTOR signaling pathway. Meanwhile, enhancement of autophagy by pretreatment with rapamycin (1 nM) alleviated the loss of cell viability and apoptosis induced by 3-MCPD whereas suppression of autophagy by 3-methyladenine (1 mM) further accelerated apoptosis, which was modulated through the mitochondria-dependent apoptotic pathway. Taking together, this study provides novel insights into the 3-MCPD-induced apoptosis in HEK293 cells and reveals that autophagy has potential as an effective intervention strategy for the treatment of 3-MCPD-induced nephrotoxicity.