In vitro toxicological assessment of free 3-MCPD and select 3-MCPD esters on human proximal tubule HK-2 cells

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.

3-Monochloropropane-1,2-diol esters induce HepG2 cells necroptosis via CTSB/TFAM/ROS pathway

3-monochloropropane-1,2-diol esters (3-MCPDE) are toxic substances that form in food thermal processing and have a diverse range of toxicities. In this study, we found that 3-MCPDE triggered necroptosis by RIPK1/RIPK3/MLKL pathway in HepG2 cells. Previous studies have shown that ROS is an important activator of RIPK1 and RIPK3. The data showed that 3-MCPDE induced excessive ROS production through mitochondrial damage. After treatment with ROS inhibitor N-acetylcysteine (NAC), 3-MCPDE-induced necroptosis was relieved. Further, we explored how 3-MCPDE destroys mitochondria. The data suggested that 3-MCPDE induced mitochondrial dysfunction through the CTSB/TFAM pathway. Overall, the results indicated that 3-MCPDE induced necroptosis through CTSB/TFAM/ROS pathway in HepG2 cells. Our study provided a new mechanism for 3-MCPDE hepatotoxicity.

Ginsenoside Rb1 alleviates 3-MCPD-induced renal cell pyroptosis by activating mitophagy

Ginsenoside Rb1 (Gs-Rb1) is among the most significant effective pharmacological components in ginseng. 3-monochloropropane-1,2-diol (3-MCPD), a chloropropanol-like contaminant, is produced in the production of refined oils and thermal processing of food. Pyroptosis is a type of programmed cell death triggered by inflammasomes. Excessive pyroptosis causes kidney injury and inflammation. Previous studies have revealed that 3-MCPD induced pyroptosis in mice and NRK-52E cells. In the present study, we find that Gs-Rb1 attenuates 3-MCPD-induced renal cell pyroptosis by assaying GSDMD-N, caspase-1, IL-18, and IL-1β in mice and NRK-52E cells. In further mechanistic studies, we show that Gs-Rb1 removes damaged mitochondria via mitophagy and reduces intracellular reactive oxygen species (ROS) generation, therefore alleviating 3-MCPD-induced NOD-like receptor family pyrin domain containing 3 (NLRP3) activation and pyroptosis. The above results are further validated by the addition of autophagy inhibitor Chloroquine (CQ) and mitophagy inhibitor Cyclosporin A (CsA). Afterward, we explore how Gs-Rb1 activated mitophagy in vitro. We determine that Gs-Rb1 enhances the protein expression and nuclear translocation of Transcription factor EB (TFEB). However, silencing of the TFEB gene by small interfering RNA technology reverses the role of Gs-Rb1 in activating mitophagy. Therefore, we conclude that 3-MCPD damages mitochondria and leads to ROS accumulation, which causes NLRP3 activation and pyroptosis in ICR mice and NRK-52E cells, while Gs-Rb1 mitigates this phenomenon via the TFEB-mitophagy pathway. Our findings may provide new insights for understanding the molecular mechanisms by which Gs-Rb1 mitigates renal injury.

Lipidomics Analysis Explores the Mechanism of Renal Injury in Rat Induced by 3-MCPD

3-monochloropropane-1,2-diol (3-MCPD) is a food-process toxic substance, and its main target organ is the kidney. The present study examined and characterized the nephrotoxicity and the lipidomic mechanisms in a model of kidney injury in Sprague Dawley (SD) rats treated with high (45 mg/kg) and low (30 mg/kg) doses of 3-MCPD. The results showed that the ingestion of 3-MCPD led to a dose-dependent increase in serum creatinine and urea nitrogen levels and histological renal impairment. The oxidative stress indicators (MDA, GSH, T-AOC) in the rat kidney altered in a dose-dependent manner in 3-MCPD groups. The lipidomics analysis revealed that 3-MCPD caused kidney injury by interfering with glycerophospholipid metabolism and sphingolipid metabolism. In addition, 38 lipids were screened as potential biomarkers. This study not only revealed the mechanism of 3-MCPD renal toxicity from the perspective of lipidomics but also provided a new approach to the study of 3-MCPD nephrotoxicity.

Bibliometric Analysis of Research Trends on 3-Monochloropropane-1,2-Diol Esters in Foods

3-Monochloropropane-1,2-diol esters (3-MCPDE) are common food contaminants mainly formed in the edible oil refining process. Due to their potential hazards, 3-MCPDE has become a widespread food safety concern. In this study, CiteSpace and VOSviewer were used to conduct a bibliometric analysis on the 3-MCPDE research papers collected in the Web of Science Core Collection from 1998 to 2022. The results showed that the number of research publications on 3-MCPDE has increased rapidly since 2010. Analysis of the hotspots in 3-MCPDE studies showed that more attention has been paid to the exposure assessment, formation mechanism, detection methods, mitigation methods and toxicity, and toxicology of 3-MCPDE. Finally, the future trends of research on 3-MCPDE were analyzed and proposed. The mitigation methods and toxicology studies of 3-MCPDE are still the research hotspots in the future. In addition, nutritional intervention for 3-MCPDE toxicity will be an emerging trend.

Analysis of MCPD and Glycidyl Fatty Acid Esters in Refined Plant Oils by Supercritical Fluid Chromatography– High-Resolution Mass Spectrometry

2- and 3-chloropropane-1,2-diol (2- and 3-MCPD) and their fatty acid esters (2- and 3-MCPDEs) together with glycidyl fatty acids esters (GEs) belong to a group of process-induced contaminants. They are formed in high temperature environments and most commonly occur in refined vegetable oils. Since 2021, maximum limits for GEs and 3-MCPDEs have been enforceable in the EU, and the requirement for adequate analytical methods is constantly increasing. The aim of this study was to develop an efficient method to enable a rapid determination of nine 3-MCPDEs and seven GEs in vegetable oils within a single run employing supercritical fluid chromatography coupled to high-resolution tandem mass spectrometry (SFC–HRMS/MS). Contrary to a routine gas chromatography mass spectrometry method aimed at determination of the total MCPD pool, the sample throughput when using SFC–HRMS/MS was greatly increased, as the “dilute-and shoot” approach did not require any hydrolysis and derivatization. Additionally, the pattern of natural MCPDEs was characterized. The performance characteristics of this new method met the criteria required by Commision Regulation 2019/2093 for all target analytes.

Synthesis, Characterization and Biological Evaluation of Novel Benzamidine Derivatives: Newer Antibiotics for Periodontitis Treatment

Periodontal disease (PD) is complex polymicrobial disease which destroys tooth-supporting tissue. Although various synthetic inhibitors of periodontitis-triggering pathogens have been recognized, their undesirable side effects limit their application. Hence, the present study intended to perform the synthesis, characterization, antimicrobial evaluation, and cytotoxicity analysis of novel benzamidine analogues (NBA). This study involved the synthesis of novel imino bases of benzamidine (4a–c), by reacting different aromatic aldehydes with 2-(4-carbamimidoylphenoxy) acetohydrazide (3), which was synthesized by the hydrazination of ethyl 2-(4-carbamimidoylphenoxy) acetate (2), the derivative of 4-hydroxybenzene carboximidamide (1). This was followed by characterization using FTIR, ¹H, ¹³C NMR and mass spectrometry. All synthesized compounds were further tested for antimicrobial potential against PD-triggering pathogens by the micro broth dilution method. The cytotoxicity analysis of the NBA against HEK 293 cells was conducted using an MTT assay. The present study resulted in a successful synthesis of NBA and elucidated their structures. The synthesized NBA exhibited significant antimicrobial activity values between 31.25 and 125 µg/mL against tested pathogens. All NBA exhibited weak cytotoxicity against HEK 293 cells at 7.81 µg, equally to chlorhexidine at 0.2%. The significant antimicrobial activity of NBA against PD-triggering pathogens supports their potential application in periodontitis treatment.

Mst2 Overexpression Inhibits Thyroid Carcinoma Growth and Metastasis by Disrupting Mitochondrial Fitness and Endoplasmic Reticulum Homeostasis

Although the incidence of thyroid carcinoma has increased over the past several decades, it has an excellent prognosis and overall 5-year survival, with a stable mortality rate, except in cases with advanced stages or rare malignant tumor types. Biomarkers have emerged as effective targets of molecular therapy against thyroid carcinoma due to their rapid and convenient detection; however, there has been little clinical application. Macrophage stimulating 2 (Mst2) is a proapoptotic protein with implications in carcinogenesis and metastasis. We found that Mst2 overexpression-induced endoplasmic reticulum (ER) stress in MDA-T32 thyroid carcinoma cells, accompanied by elevated caspase-12 activity, increased apoptotic rate, and reduced cell viability. In addition, Mst2 overexpression contributed to mitochondrial damage, as evidenced by increased mitochondrial oxidative stress and activated the mitochondrial apoptotic pathway. Inhibition of the JNK pathway abolished these effects. These results show Mst2 to be a novel tumor suppressor that induces mitochondrial dysfunction and ER stress via the JNK pathway. Thus, Mst2 could potentially serve as a biomarker for developing targeted therapy against thyroid carcinoma.

Abnormal Mitochondria-Endoplasmic Reticulum Communication Promotes Myocardial Infarction

Myocardial infarction is characterized by cardiomyocyte death, and can be exacerbated by mitochondrial damage and endoplasmic reticulum injury. In the present study, we investigated whether communication between mitochondria and the endoplasmic reticulum contributes to cardiomyocyte death after myocardial infarction. Our data demonstrated that hypoxia treatment (mimicking myocardial infarction) promoted cardiomyocyte death by inducing the c-Jun N-terminal kinase (JNK) pathway. The activation of JNK under hypoxic conditions was dependent on overproduction of mitochondrial reactive oxygen species (mtROS) in cardiomyocytes, and mitochondrial division was identified as the upstream inducer of mtROS overproduction. Silencing mitochondrial division activators, such as B cell receptor associated protein 31 (BAP31) and mitochondrial fission 1 (Fis1), repressed mitochondrial division, thereby inhibiting mtROS overproduction and preventing JNK-induced cardiomyocyte death under hypoxic conditions. These data revealed that a novel death-inducing mechanism involving the BAP31/Fis1/mtROS/JNK axis promotes hypoxia-induced cardiomyocyte damage. Considering that BAP31 is localized within the endoplasmic reticulum and Fis1 is localized in mitochondria, abnormal mitochondria-endoplasmic reticulum communication may be a useful therapeutic target after myocardial infarction.

Perovskite Nanomaterial-Engineered Multiplex-Mode Fluorescence Sensing of Edible Oil Quality

Water-soluble fluorescence nanomaterials are widely applied for water-phase food safety monitoring. However, there is still a challenge for the development of oil-soluble fluorescence nanomaterials for oil-phase food safety detection. Particularly, the edible oil quality has a huge impact on human health, in which excessive acid number (AN), 3-chloro-1,2-propanediol (3-MCPD), and moisture content (MC) are critical monitoring factors. Herein, orange-emitting oil-soluble CsPbBr_1.5I_1.5 quantum dots (QDs) were prepared and applied for AN and 3-MCPD detection depending on fluorescence quenching and wavelength shifts. A "turn-off" fluorescence sensor and "wavelength-shift" fluorescence colorimetric sensor were fabricated for AN and 3-MCPD detection. Water-sensitive mesoporous silica-coated CsPbBr_1.5I_1.5 QDs were employed for the establishment of ratiometric fluorescence sensors for MC monitoring by introducing water-stable green-emitting CsPbBr₃ nanosheets (NSs) as reference probes. Perovskite nanomaterial-engineered multiplex-mode fluorescence sensors were proposed for the detection of AN, 3-MCPD, and MC in edible oil, with the limits of detection (LODs) of 0.71 mg KOH/g, 39.8 μg/mL 3-MCPD, and 0.45% MC, respectively. This work not only expands the application of perovskite nanomaterials in the bioanalysis field but also provides new materials and novel approaches for the multiplex-mode oil-phase food safety monitoring.

Mitofusin-2 Enhances Mitochondrial Contact With the Endoplasmic Reticulum and Promotes Diabetic Cardiomyopathy

Diabetic cardiomyopathy has been associated with mitochondrial damage. Mitochondria–endoplasmic reticulum (ER) contact is an important determinant of mitochondrial function and ER homeostasis. We therefore investigated whether hyperglycemia can damage the mitochondria by increasing their contact with the ER in cardiomyocytes. We found that hyperglycemia induced mitochondria–ER contact in cardiomyocytes, as evidenced by the increased MMM1, MDM34, and BAP31 expressions. Interestingly, the silencing of Mfn2 reduced the cooperation between the mitochondria and the ER in cardiomyocytes. Mfn2 silencing improved cardiomyocyte viability and function under hyperglycemic conditions. Additionally, the silencing of Mfn2 markedly attenuated the release of calcium from the ER to the mitochondria, thereby preserving mitochondrial metabolism in cardiomyocytes under hyperglycemic conditions. Mfn2 silencing reduced mitochondrial reactive oxygen species production, which reduced mitochondria-dependent apoptosis in hyperglycemia-treated cardiomyocytes. Finally, Mfn2 silencing attenuated ER stress in cardiomyocytes subjected to high-glucose stress. These results demonstrate that Mfn2 promotes mitochondria–ER contact in hyperglycemia-treated cardiomyocytes. The silencing of Mfn2 sustained mitochondrial function, suppressed mitochondrial calcium overload, prevented mitochondrial apoptosis, and reduced ER stress, thereby enhancing cardiomyocyte survival under hyperglycemic conditions.

Evaluation of transporter expression in HK-2 cells after exposure to free and ester-bound 3-MCPD

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3-Monochloropropane-1,2-diol (3-MCPD) and its fatty acid esters have the potential to induce nephrotoxicity.

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We used an in vitro cellular model of human proximal tubule cells to test the effects of 3-MCPD compound exposures on transporter gene expression.

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3-MCPD-related nephrotoxicity could be associated with indirect modes of action relating to aquaporin homeostasis.

3-Monochloropropane-1,2-diol (3-MCPD) is a food processing contaminant in some infant formula products and other foods in the United States. Although rodent studies have demonstrated that 3-MCPD and its palmitic esters have the potential to induce nephrotoxicity, our recent human cell culture studies using the human renal proximal tubule cell line HK-2 have not strongly supported this finding. Considering this disparity, we sought to examine whether changes in transporter gene expression on proximal tubule cells could be modulated by these compounds and allow us to glean mechanistic information on a possible indirect path to proximal tubule injury in vivo. If fundamental processes like water and solute transport could be disrupted by 3-MCPD compounds, then a new avenue of toxicity could be further explored in both infant and adult models. In our current study, we used HK-2 cells as an in vitro cellular model of human proximal tubule cells to investigate the effects of low (10 μM) and high (100 μM) 3-MCPD compound exposures to these cells for 24 hours (h) on the expression of 20 transporter genes that are known to be relevant to proximal tubules. Although we detected consistent upregulation of AQP1 expression at the RNA transcript level following HK-2 treatment with both low and high doses of several ester-bound 3-MCPD compounds, these increases were not associated with statistically significant elevations in their protein expression levels. Moreover, we observed a lack of modulation of other members of the AQP protein family that are known to be expressed by human proximal tubule cells. Overall, our study suggests the possibility that 3-MCPD-related nephrotoxicity could be associated with indirect modes of action relating to aquaporin homeostasis, but additional studies with other human-derived models would be pertinent to further explore these findings and to better understand transporter expression differences under different stages of proximal tubule development.

Current Progresses on Monochloropropane Diol Esters in 2018-2019 and Their Future Research Trends

The fatty acid esters of monochloropropane diol (MCPD) are a group of food source contaminants formed during thermal processing. These components were recognized as potential food source toxicants in the past few decades, and growing evidence has proven their toxic effects, especially to kidneys and testes. Therefore, increasing research articles reported their results about MCPD esters in recent years. In this perspective, a total of 35 research articles/reviews about MCPD esters, including the studies concerning the analytical methods, occurrences, toxicity, formation mechanism, and mitigation strategies of MCPD esters in 2018-2019 have been summarized and discussed. Updating the latest research results about MCPD esters could improve our understandings about these components, especially on the toxic effects and the mitigation approaches in both academia and industry.

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.

Long-term in vitro effects of exposing the human HK-2 proximal tubule cell line to 3-monochloropropane-1,2-diol

3-Monochloropropane-1,2-diol (3-MCPD) is a food processing contaminant in the U.S. food supply, detected in infant formula. In vivo rodent model studies have identified a variety of possible adverse outcomes from 3-MCPD exposure including renal effects like increased kidney weights, tubular hyperplasia, kidney tubular necrosis, and chronic progressive nephropathy. Given the lack of available in vivo toxicological assessments of 3-MCPD in humans and the limited availability of in vitro human cell studies, the health effects of 3-MCPD remain unclear. We used in vitro human proximal tubule cells represented by the HK-2 cell line to compare short- and long-term consequences to continuous exposure to this compound. After periodic lengths of exposure (0-100 mM) ranging from 1 to 16 days, we evaluated cell viability, mitochondrial integrity, oxidative stress, and a specific biomarker of proximal tubule injury, Kidney Injury Molecule-1 (KIM-1). Overall, we found that free 3-MCPD was generally more toxic at high concentrations or extended durations of exposure, but that its overall ability to induce cell injury was limited in this in vitro system. Further experiments will be needed to conduct a comprehensive safety assessment in infants who may be exposed to 3-MCPD through consumption of infant formula, as human renal physiology changes significantly during development.

A method to dissolve 3-MCPD mono- and di-esters in aqueous cell culture media

Fatty acid esters of 3-monochloropropane-1,2-diol (3-MCPD) are chemical contaminants found in a wide range of edible oils that are thermally processed during industrial manufacturing of infant formula and other lipid-containing foods in the United States. Rodent studies have unequivocally demonstrated a plethora of in vivo toxicological effects including reproductive, neurological and renal dysfunction. To determine if similar effects are observed in human organ systems, in vitro studies using human cell lines are conducted to assess concordance of the data collected. One limitation to performing such in vitro research is the extremely high hydrophobicity of 3-MCPD esters; dissolving them into aqueous cell culture media is a tremendous challenge. To address this obstacle, we developed a simple protocol to circumvent the immiscibility of 3-MCPD esters and their corresponding free fatty acids into aqueous cell culture media in order to assess the effect of these esters on epithelial cells of kidney origin in vitro.