Protective effect of ascorbic acid against renal injury induced by 3-chloropropane-1,2-diol-dipalmitate in rats

3-monochloropropane-1,2-diol esters (3-MCPDE) are a group of contaminants which are mainly formed during heat processing of edible oil and fat-based foods. The kidney is the primary target organ for the toxic effects of 3-MCPDE. 3-MCPD-di-palmitate exists in a variety of oils and fats, and is the most common and relatively high proportion of 3-MCPDE. In this study, we investigated the protective effect of ascorbic acid on 3-MCPD-di-palmitate-induced renal injury in rats. Thirty 8-week-old male Sprague-Dawley rats were randomly divided into 5 groups, namely control, 3-MCPD-di-palmitate (240 mg/kg·bw), 3-MCPD-di-palmitate (240 mg/kg·bw) + ascorbic acid (100 mg/kg·bw), 3-MCPD-di-palmitate (240 mg/kg·bw) + ascorbic acid (200 mg/kg·bw) and 3-MCPD-di-palmitate (240 mg/kg·bw) + ascorbic acid (500 mg/kg·bw). These treatments were administered via gavage for a duration of 4 weeks. The effects of ascorbic acid on 3-MCPDE-induced kidney injury in rats were investigated by evaluating the kidney index, renal function (BUN, CRE), renal histopathology, oxidative stress markers (ROS, GSH, MDA, and T-AOC), DNA oxidation marker (8-OHdG), and activities of Caspase 3 and 9. The results showed that the exposure to 3-MCPDE significantly increased the kidney index, BUN and CRE levels, ROS and MDA levels, 8-OHdG levels, and activities of Caspase 3 and 9, while decreasing GSH and T-AOC. The combined treatment with 3-MCPDE and ascorbic acid can effectively restore the aforementioned parameters. The present study concluded that ascorbic acid effectively attenuates the renal apoptosis and oxidative homeostasis induced by 3-MCPDE uptake thereby intervening in renal injury.

Boric Acid and Borax Protect Human Lymphocytes from Oxidative Stress and Genotoxicity Induced by 3-Monochloropropane-1,2-diol

3-chloro-1,2-propanediol (3-MCPD) is a member of the group of pollutants known as chloropropanols and is considered a genotoxic carcinogen. Due to the occurrence of 3-MCPD, which cannot be avoided in multiplexed food processes, it is necessary to explore novel agents to reduce or prevent the toxicity of 3-MCPD. Many recent studies on boron compounds reveal their superior biological roles such as antioxidant, anticancer, and antigenotoxic properties. In the current investigation, we have evaluated in vitro cytotoxic, oxidative, and genotoxic damage potential of 3-MCPD on human whole blood cultures and the alleviating effect of boric acid (BA) and borax (BX) for 72 h. In our in vitro experiments, we have treated blood cells with BA and BX (2.5, 5, and 10 mg/L) and 3-MCPD (at IC50 of 11.12 mg/l) for 72 h to determine the cytotoxic damage potential by using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and lactate dehydrogenase (LDH) release assays. Oxidative damage was assessed using total antioxidant capacity (TAC) and malondialdehyde (MDA) levels. Genotoxicity evaluations were performed using chromosome aberrations (CAs) and 8-hydroxy deoxyguanosine (8-OHdG) assays. The result of our experiments showed that the 3-MCPD compound induced cytotoxicity, oxidative stress, and genotoxicity in a clear concentration-dependent manner. BA and BX reduced cytotoxicity, oxidative stress, and genotoxicity induced by 3-MCPD. In conclusion, BA and BX are safe and non-genotoxic under the in vitro conditions and can alleviate cytotoxic, oxidative, and genetic damage induced by 3-MCPD in the human blood cells. Our findings suggest that dietary boron supplements may offer a novel strategy for mitigating hematotoxicity induced by xenobiotics, including 3-MCPD.

Nephrotoxicity evaluation of 3-monochloropropane-1,2-diol exposure in Sprague-Dawley rats using data-independent acquisition-based quantitative proteomics analysis

3-Monochloropropane-1,2-diol (3-MCPD), as a heat-induced food process contaminant, possesses strongly toxic effect on kidney. The present study focuses on characterizing the proteome and clarifying the underlying molecular regulatory mechanisms in a model of kidney injury in rats treated with 3-MCPD. Data-independent acquisition (DIA)-mass spectrometry (MS) based proteomics was used to identify dysregulated proteins in kidney tissues of Sprague-Dawley (SD) rats treated with 30 mg/kg/day 3-MCPD by gavage for 28 days. It was found that a total of 975 proteins were deregulated after 3-MCPD treatment. Bioinformatic analyses revealed that several enzymes related to the metabolisms of amino acid, lipid and carbohydrate in endogenous metabolism were altered in response to 3-MCPD treatment. Moreover, some proteins involved in these pathways were also changed, mainly including oxidative stress, oxidative phosphorylation, apoptosis and autophagy. Our study unravels the vital roles of loss of mitochondrial homeostasis and function and cell death pathways in the development of renal damage induced by 3-MCPD, which provides further valuable insights into the initiation and resolution of 3-MCPD nephrotoxicity. The proposed DIA-MS workflow not only provides a choice for proteomic analysis in toxicological research, but also provides a more comprehensive understanding of the molecular mechanisms of nephrotoxicity induced by toxins.

LKB1/AMPKα signaling pathway and mitochondrial fission/fusion dynamics regulate apoptosis induced by 3-chlorpropane-1,2-diol in HEK293 cells

Mitochondrial dynamics and bioenergetics are considered play pivotal roles in the maintenance of mitochondrial function and cell viability. During the widely distributed food contaminant 3-chlorpropane-1,2-diol (3-MCPD) induced nephrotoxicity, mitochondrial morphology and function were impaired, but the specific mechanism responsible for the process has not been fully elucidated. In the present study, using an in vitro human embryonic kidney 293 (HEK293) cell culture model, the role of LKB1/AMPK pathway and mitochondrial fission and fusion dynamics in 3-MCPD-induced cell apoptosis was investigated by using the AMPK inhibitor dorsomorphin and mitochondrial division inhibitor 1 (Mdivi-1), respectively. The results revealed that 3-MCPD significantly decreased the ATP levels, activated the energy-sensing regulator AMPKα and its upstream protein kinase LKB1, disrupted mitochondrial dynamics equilibrium characterized by promoting division and inhibiting fusion, thus inducing cell apoptosis. Notably, suppression of AMPK by dorsomorphin mitigated 3-MCPD-induced cytotoxicity through improvement of the function and dynamics of mitochondria and alleviated apoptosis via the mitochondria-dependent pathway. Moreover, inhibition of mitochondrial fission by Mdivi-1 protected against apoptosis induced by 3-MCPD. Taken together, these results suggest that 3-MCPD triggers apoptosis through activation of LKB1/AMPKα signaling pathway and regulation of mitochondrial fission and fusion dynamics in HEK293 cells.

3-MCPD and glycidol coexposure induces systemic toxicity and synergistic nephrotoxicity via NLRP3 inflammasome activation, necroptosis, and autophagic cell death

3-Monochloropropane-1,2-diol (3-MCPD), 2,3-epoxy-1-propanol (glycidol), and their esters are well-known food contaminants mainly formed by the heat processing of certain refined oils and coexist in various kinds of foodstuffs. However, the combined health effect and the underlying mechanism of 3-MCPD and glycidol coexposure are not well-understood. In this study, we investigated the systemic toxicity effects and the nephrotoxicity mechanisms of 3-MCPD and glycidol coexposure with in vitro and in vivo models, and next-generation sequencing (NGS) analysis. It was found that 3-MCPD and glycidol coexposure for 28 days synergistically induced toxicity in the kidney, lung, testis, and heart in C57BL/6 mice. Kidney was the most sensitive organ to coexposure, and the coexposure had a synergistic effect on inflammation and cytotoxicity through activation of the NLRP3 inflammasome, and the induction of necroptosis, and autophagic cell death in NRK-52E cells. Moreover, the NGS results revealed the genes changes associated with nephrotoxicity, inflammation and with the broad toxicity effects induced by 3-MCPD or glycidol alone or in combination, which were consistent with the results of in vitro and in vivo models. In summary, we report for the first time of the comprehensive toxicity effects and the mechanisms caused by 3-MCPD and glycidol coexposure.

Inhibition of ER stress attenuates kidney injury and apoptosis induced by 3-MCPD via regulating mitochondrial fission/fusion and Ca2+ homeostasis

3-Chloro-1, 2-propanediol (3-MCPD) is a food-borne toxic substance well-known for more than 40 years that is mainly associated with nephrotoxicity. A better understanding of 3-MCPD nephrotoxicity is required to devise efficacious strategies to counteract its toxicity. In the present work, the role of endoplasmic reticulum (ER) stress along with its underlying regulatory mechanism in 3-MCPD-mediated renal cytotoxicity was investigated in vivo and in vitro. Our data indicated that 3-MCPD-stimulated ER stress response evidenced by sustained activation of PERK-ATF4-p-CHOP and IRE1 branches in Sprague Dawley (SD) rats and human embryonic kidney (HEK293) cells. Moreover, ER stress-associated specific apoptotic initiator, caspase 12, was over-expressed. Blocking ER stress with its antagonist, 4-phenylbutyric acid (4-PBA), improved the morphology and function of kidney effectively. 4-PBA also increased cell viability, relieved mitochondrial vacuolation, and inhibited cell apoptosis through regulating caspase-dependent intrinsic apoptosis pathways. Furthermore, the enhanced expressions of two mitochondrial fission proteins, DRP1/p-DRP1 and FIS1, and the relocation of DRP1 on mitochondria subjected to 3-MPCD were reversed by 4-PBA, while the expression of the fusion protein, MFN2, was restored. Moreover, cellular Ca²⁺ overload, the over-expression of CaMKK2, and the loss of mitochondria-associated membranes (MAM) were also relieved after 4-PBA co-treatment. Collectively, our data emphasized that ER stress plays critical role in 3-MCPD-mediated mitochondrial dysfunction and subsequent apoptosis as well as blockage of ER stress ameliorated kidney injury through improving mitochondrial fission/fusion and Ca²⁺ homeostasis. These findings provide a novel insight into the regulatory role of ER stress in 3-MCPD-associated nephropathy and a potential therapeutic strategy. Graphical Headlights 1. 4-PBA inhibits ER stress mainly through regulating PERK-ATF4-CHOP and IRE1-XBP1s branches. 2. Inhibition of ER stress by 4-PBA mitigates ER associated and mitochondrial apoptosis 3. Inhibition of ER stress by 4-PBA helps maintaining calcium homeostasis and mitochondrial dynamic.

Absorption and metabolism of 3-MCPD in hepatic and renal cell lines

3-Monochloropropane-1,2-diol (3-MCPD) fatty acid esters are process contaminants mainly formed during the refinement of vegetable oils. Gastrointestinal hydrolysis yields free 3-MCPD, which is resorbed into the body. In long-term rat studies, 3-MCPD caused renal and testicular neoplasms. 3-MCPD metabolism via β-chlorolactic acid has been postulated to underlie the toxic effects of 3-MCPD. Various efforts are ongoing to characterize the toxicological mode of action of 3-MCPD using in vitro systems. Published results suggest a very low sensitivity of cell cultures in vitro, as compared to 3-MCPD levels causing toxic effects in vivo. The insensitivity of in vitro systems raises the question to which extent 3-MCPD is absorbed and metabolized in vitro. We therefore analyzed cytotoxicity, absorption and metabolism of 3-MCPD and its metabolite β-chlorolactic acid in renal and hepatic cells. Cytotoxicity tests using up to 100 mM 3-MCPD confirmed the low sensitivity of human and rat cell lines towards 3-MCPD toxicity. Furthermore, absorption and metabolism of 3-MCPD examined via GC-MS and LC-MS/MS were only observed to a minor degree, and 3-MCPD was also not converted by a metabolizing system (S9 fraction). In conclusion, our data indicate that current in vitro models are not well suited for studying 3-MCPD metabolism and toxicity.

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.

4-Octyl itaconate protects against renal fibrosis via inhibiting TGF-β/Smad pathway, autophagy and reducing generation of reactive oxygen species

Renal fibrosis is an inevitable course of all kinds of progressive chronic kidney disease (CKD). Itaconic acid is an endogenous metabolite that has shown anti-inflammatory and antioxidant effects. 4-octyl itaconate (OI), a derivative of itaconic acid with higher fat solubility, can penetrate the cell membranes and be metabolized into itaconic acid in vitro. However, whether OI has an anti-renal fibrotic effect is still unclear. The current study purposed to investigate the anti-fibrotic effect in renal and the underlying mechanisms of OI. The unilateral ureteral occlusion (UUO) model and adenine-induced fibrosis model in Sprague-Dawley (SD) rats and Transforming growth factor-β1 (TGF-β1) induced HK-2 cells were applied to investigate the renoprotective effects of OI. This study reports for the first time that OI ameliorated renal fibrosis by suppressing the activation of TGF-β/Smad and nuclear factor kappa B (NF-κB) pathways, reducing generation of reactive oxygen species and inhibiting autophagy. These results clearly suggest that OI has great clinical potential for managing renal fibrosis.