Ochratoxin A causes mitochondrial dysfunction, apoptotic and autophagic cell death and also induces mitochondrial biogenesis in human gastric epithelium cells

Biodegradation of ochratoxin A by Brevundimonas diminuta HAU429: Characterized performance, toxicity evaluation and functional enzymes

Ochratoxin A (OTA) is a notorious mycotoxin commonly contaminating food products worldwide. In this study, an OTA-degrading strain Brevundimonas diminuta HAU429 was isolated by using hippuryl-L-phenylalanine as the sole carbon source. The biodegradation of OTA by strain HAU429 was a synergistic effect of intracellular and extracellular enzymes, which transformed OTA into ochratoxin α (OTα) through peptide bond cleavage. Cytotoxicity tests and cell metabolomics confirmed that the transformation of OTA into OTα resulted in the detoxification of its hepatotoxicity since OTA but not OTα disturbed redox homeostasis and induced oxidative damage to hepatocytes. Genome mining identified nine OTA hydrolase candidates in strain HAU429. They were heterologously expressed in Escherichia coli, and three novel amidohydrolase BT6, BT7 and BT9 were found to display OTA-hydrolyzing activity. BT6, BT7 and BT9 showed less than 45 % sequence identity with previously identified OTA-degrading amidohydrolases. BT6 and BT7 shared 60.9 % amino acid sequence identity, and exhibited much higher activity towards OTA than BT9. BT6 and BT7 could completely degrade 1 μg mL-1 of OTA within 1 h and 50 min, while BT9 hydrolyzed 100 % of OTA in the reaction mixture by 12 h. BT6 was the most thermostable retaining 38 % of activity after incubation at 70 °C for 10 min, while BT7 displayed the highest tolerance to ethanal remaining 76 % of activity in the presence of 6 % ethanol. This study could provide new insights towards microbial OTA degradation and promote the development of enzyme-catalyzed OTA detoxification during food processing.

Ochratoxin A induces hepatic and renal toxicity in mice through increased oxidative stress, mitochondrial damage, and multiple cell death mechanisms

Ochratoxin A (OTA) is a widespread food toxin produced by Aspergillus ochraceus and other molds. In this study, we developed and established acute OTA toxicity conditions in mice, which received daily oral doses of OTA between 0.5 up to 8 mg/kg body weight up to 7 days and were subjected to histological and biochemical analysis to characterize renal and hepatic damage. Oral administration of OTA for 7 days resulted in loss of body weight in a dose-dependent manner and increased the levels of serum biomarkers of hepatic and renal damage. The kidney was more sensitive to OTA-induced damage than the liver. In addition to necrosis, OTA induced hepatic and renal apoptosis in dose- and time-dependent manners. Especially, a high dose of OTA (8 mg/kg body weight) administered for 7 days led to necroptosis in both liver and kidney tissues. OTA dose-dependently increased the oxidative stress levels, including lipid peroxidation, in the liver and kidneys. OTA disrupted mitochondrial dynamics and structure in hepatic and renal cells, leading to the dysregulation of mitochondrial homeostasis. OTA increased transferrin receptor 1 and decreased glutathione peroxidase 4 levels in a dose- and time-dependent manner. These results suggest the induction of ferroptosis. Collectively, this study highlighted the characteristics of acute OTA-induced hepatic and renal toxicity in mice in terms of oxidative stress, mitochondrial damage, and multiple cell death mechanisms, including necroptosis and ferroptosis.

The Novel Role of the NLRP3 Inflammasome in Mycotoxin-Induced Toxicological Mechanisms

Mycotoxins are secondary metabolites produced by several fungi and moulds that exert toxicological effects on animals including immunotoxicity, genotoxicity, hepatotoxicity, teratogenicity, and neurotoxicity. However, the toxicological mechanisms of mycotoxins are complex and unclear. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric cytosolic protein complex composed of the NLRP3 sensor, ASC adapter protein, and caspase-1 effector. Activation of the NLRP3 inflammasome plays a crucial role in innate immune defence and homeostatic maintenance. Recent studies have revealed that NLRP3 inflammasome activation is linked to tissue damage and inflammation induced by mycotoxin exposure. Thus, this review summarises the latest advancements in research on the roles of NLRP3 inflammasome activation in the pathogenesis of mycotoxin exposure. The effects of exposure to multiple mycotoxins, including deoxynivalenol, aflatoxin B1, zearalenone, T-2 toxin, ochratoxin A, and fumonisim B1, on pyroptosis-related factors and inflammation-related factors in vitro and in vivo and the pharmacological inhibition of specific and nonspecific NLRP3 inhibitors are summarized and examined. This comprehensive review contributes to a better understanding of the role of the NLRP3 inflammasome in toxicity induced by mycotoxin exposure and provides novel insights for pharmacologically targeting NLRP3 as a novel anti-inflammatory agent against mycotoxin exposure.

Grape pomace as a novel functional ingredient: Mitigating ochratoxin A bioaccessibility and unraveling cytoprotective mechanisms in vitro

Mycotoxins, secondary metabolites produced by molds, pose significant health risk through contamination of globally consumed cereals. Ochratoxin A (OTA), a prevalent mycotoxin in cereals, is associated with various health hazards, including immunotoxicity. This study explores the bioaccessibility of OTA in bread and its impact on the gastrointestinal barrier. A focus is placed on grape pomace (GP), a by-product of the wine industry, as a potential mitigator of OTA toxicity. Results demonstrate that GP reduces OTA bioaccessibility in the human gastrointestinal system from 94% to 81% at intestinal level, showing promise in limiting the absorption of the harmful toxin. Additionally, GP exhibits cytoprotective effects, enhancing cell viability and mitigating OTA-induced toxicity in both Caco-2 and Jurkat T cells. In view of the above, to understand the mechanisms by which OTA exhibits its toxic effects, flow cytometry was chosen as the main technique for the analysis of cell cycle, reactive oxygen species levels and mitochondrial parameters. Cytofluorimetric evaluation indicates GP's potential in limiting OTA-induced damage at cellular level. The study suggests that GP could serve as functional ingredient to reduce mycotoxin bioaccessibility and toxicity in cereal-based foods, offering a novel and promising approach to enhance food safety and protect public health. The finding highlights the potential of utilizing grape pomace in food formulations to mitigate mycotoxin contamination, providing a valuable contribution to the ongoing efforts to ensure the safety of globally consumed cereal products.

AMPK and metabolic disorders: The opposite roles of dietary bioactive components and food contaminants

AMPK is a key player in a variety of metabolic and physiological processes, which might be considered one of the most promising targets for both prevention and treatment of metabolic syndrome and its associated diseases. Many dietary components and contaminants have been recently demonstrated to prevent or promote the development these diseases via AMPK-mediated pathways. AMPK can be activated by diverse phytochemical substances such as EGCG, chicoric acid, tomatidine, and others, all of which have been found to contribute to preventing or ameliorating chronic disorders. On the other hand, recent studies have found that metabolic disruptions induced by pesticides such as 1,3-Dichloro-2-propanol, imidacloprid, permethrin, are attributed to the inactivation of AMPK. This review may contribute to the development of functional foods for treatment of metabolic syndrome and associated diseases through modulating AMPK pathway.

Ochratoxin A-enhanced glycolysis induces inflammatory responses in human gastric epithelium cells through mTOR/HIF-1α signaling pathway

Ochratoxin A (OTA) is a mycotoxin commonly found in several food commodities worldwide with potential nephrotoxic, hepatotoxic and carcinogenic effects. We previously showed for the first time that OTA treatment enhanced glycolysis in human gastric epithelium (GES-1) cells in vitro. Here, we found that OTA exposure activated inflammatory responses, evidenced by increasing of NF-κB signaling pathway-related protein (p-p65 and p-IκBα) expressions and elevating of inflammatory cytokine (IL-1β and IL-6) mRNA expressions in GES-1 cells. To elucidate the role of glycolysis in inflammatory effects triggered by OTA, we pretreated GES-1 cells with glycolysis inhibitor (2-deoxy-D-glucose, 2-DG) before OTA exposure. The result showed that 2-DG reduced the protein expressions of p-p65 and p-IκBα and alleviated the mRNA expressions of inflammatory cytokines in OTA-treated GES-1 cells. Furthermore, OTA activated the mTOR/HIF-1α pathway by increasing the protein expressions of p-mTOR, p-eIF4E and HIF-1α, and inhibition of mTOR with rapamycin or silencing HIF-1α with siRNA significantly attenuated OTA-enhanced glycolysis by reducing glycolysis related genes and thereby decreasing inflammatory effects of GES-1 cells. These results demonstrate that OTA activates inflammatory responses in GES-1 cells and this is controlled by mTOR/HIF-1α pathway-mediated glycolysis enhancement. Our findings provide a novel mechanistic view into OTA-induced gastric cytotoxicity.

Farnesoid X Receptor Plays a Key Role in Ochratoxin A-Induced Nephrotoxicity by Targeting Ferroptosis In Vivo and In Vitro

The mycotoxin ochratoxin A (OTA) causes nephrotoxicity, hepatotoxicity, and immunotoxicity in animals and humans. The farnesoid X receptor (FXR) is a member of the NR family and is highly expressed in the kidney, which has an antilipid production function. Ferroptosis is an iron-dependent form of regulated cell death involved in several pathophysiological cell death and kidney injury. The present study aims to evaluate the role of FXR and ferroptosis in OTA-induced nephrotoxicity in mice and HK-2 cells. Results showed that OTA induced nephrotoxicity as demonstrated by inducing the histopathological lesions and neutrophil infiltration of the kidney, increasing serum BUN, CRE, and UA levels, increasing Ntn-1, Kim-1, and pro-inflammatory cytokine expression, and decreasing IL-10 expression and the cell viability of HK-2 cells. OTA treatment also induced FXR deficiency, ROS release, MDA level increase, GSH content decrease, and 4-HNE production in the kidney and HK-2 cells. OTA treatment induced ferroptosis as demonstrated by increasing labile iron pool and lipid peroxidation levels as well as Acsl4, TFR1, and HO-1 mRNA and protein levels, decreasing GPX4 and FTH mRNA and protein expressions, and inducing mitochondrial injury. The FXR activator (GW4064) rescued the accumulation of lipid peroxides, intracellular ROS, and Fe2+, inhibited ferroptosis, and alleviated OTA-induced nephrotoxicity. The ferroptosis inhibitor (Fer-1) prevented ferroptosis and attenuated nephrotoxicity. Collectively, this study elucidates that FXR played a critical role in OTA-induced nephrotoxicity via regulation of ferroptosis, which provides a novel strategy against OTA-induced nephrotoxicity.

New perspective on mechanism in muscle toxicity of ochratoxin A: Model of juvenile grass carp (Ctenopharyngodon idella)

Ochratoxin A (OTA) is a common fungal toxin that pollutes raw materials of aquatic feeds (such as corn, soybean meal, and wheat). This study explored the effects of OTA through diet on muscle toxicity in juvenile grass carp (Ctenopharyngodon idella). The following results were obtained for the muscle. (1) With an increase in dietary OTA, the residue of OTA in muscle increased, muscle fiber diameter and density decreased, and even muscle fiber breakage. (2) OTA caused oxidative stress by downregulating GPx1 (a, b) and Trx via inhibited the PGC1-α/Nrf2 signaling pathway. (3) OTA exacerbated endoplasmic reticulum stress in the muscle by causing endoplasmic reticulum expansion (results of transmission electron microscopy) and upregulating the expression of GRP78, eIF2α, ATF6, PERK, and CHOP. (4) OTA reduced muscle fiber diameter by inhibiting protein synthesis (AKT, TOR, and S6K1) and promoting the mRNA expression of protein degradation-related genes (MURF1, MAFBX, and FoxO3a), as well as by reducing AKT and promoting the immunofluorescence expression of FoxO3. (5) OTA inhibits collagen deposition by downregulating TGF-β1, TGF-βR1, Smad2, Smad3, Smad4, CTGF, TIMP, PHD, and LOX mRNA expressions as well as the CTGF immunofluorescence expression. Moreover, based on the GSH and collagen content contents, the upper safe dose for OTA-induced toxicity was 963.6 and 1129.6 μg/kg diet, respectively. Using the example of OTA, our research has provided new insights that raise concerns about the quality of aquatic products by exploring muscle toxicity caused by mycotoxins.

Lactobacillus paracasei subsp. paracasei X12 Strain Induces Apoptosis in HT-29 Cells through Activation of the Mitochondrial Pathway

L. paracasei subsp. paracasei X12 was obtained from traditional cheese produced in northwestern China. In this study, we showed that whole peptidoglycan (WPG), extracted from L. paracasei subsp. paracasei X12, inhibited proliferation and induced apoptosis in HT-29 cells in a dose-dependent manner. In addition, WPG-induced apoptosis was associated with the loss of mitochondrial membrane potential (Ψm), the release of cytochrome c (Cyto-C) from mitochondrialto cytosolic spaces, activation of Caspase 3, and accumulation of intracellular reactive oxygen species (ROS). Finally, semi-quantitative RT-PCR showed that these events were accompanied by upregulation of proapoptotic genes (Bax or Bad) and downregulation of antiapoptotic genes (Bcl-xl). Taken together, our results demonstrated that WPG induced apoptosis in HT-29 cells through activation of the mitochondrial pathway. WPG exerted only minor toxicity upon noncancerous cells and therefore might be used as a natural agent in the treatment of cancer in future.

AFG1-induced TNF-α-mediated inflammation enhances gastric epithelial cell injury via CYP2E1

Aflatoxin G₁ (AFG₁), a member of the aflatoxin family with cytotoxic and carcinogenic properties, is one of the most common mycotoxins occurring in various agricultural products, animal feed, and human foods and drinks worldwide. Epithelial cells in the gastrointestinal tract are the first line of defense against ingested mycotoxins. However, the toxicity of AFG₁ to gastric epithelial cells (GECs) remains unclear. In this study, we explored whether and how AFG₁-induced gastric inflammation regulates cytochrome P450 to contribute to DNA damage in GECs. Oral administration of AFG₁ induced gastric inflammation and DNA damage in mouse GECs associated with P450 2E1 (CYP2E1) upregulation. Treatment with the soluble TNF-α receptor sTNFR:Fc inhibited AFG₁-induced gastric inflammation, and reversed CYP2E1 upregulation and DNA damage in mouse GECs. TNF-α-mediated inflammation plays an important role in AFG₁-induced gastric cell damage. Using the human gastric cell line GES-1, AFG₁ upregulated CYP2E1 through NF-κB, causing oxidative DNA damage in vitro. The cells were also treated with TNF-α and AFG₁ to mimic AFG₁-induced TNF-α-mediated inflammation. TNF-α activated the NF-κB/CYP2E1 pathway to promote AFG₁ activation, which enhanced DNA cellular damage in vitro. In conclusion, AFG₁ ingestion induces TNF-α-mediated gastric inflammation, which upregulates CYP2E1 to promote AFG₁-induced DNA damage in GECs.

Low doses of fumonisin B1 exacerbate ochratoxin A-induced renal injury in mice and the protective roles of heat shock protein 70

Fumonisin B1 (FB1) and ochratoxin A (OTA) possess nephrotoxicity to animals and widely co-exist in food and feedstuffs. FB1 rarely, while OTA often, causes toxicosis in animals. Heat shock protein 70 (Hsp70) resists lung injury induced by pneumolysin, but whether Hsp70 could remission mycotoxins-induced renal injury is still unknown. The present study aims to explore the impacts of nontoxic doses of FB1 on OTA-induced nephrotoxicity and the protective roles of Hsp70. In the mycotoxins-challenge experiment, ICR mice were co-exposed to nontoxic doses of FB1 (0, 0.2, 0.5, 1.0 mg/kg bw, IP) and toxic dose of OTA (0.4 mg/kg bw, IP) for 16 d. The results showed that the levels of BUN, Cr, MDA in serum, the Cyto C in renal tubes or glomerulus, pro-apoptosis genes and p-JNK protein expression in kidney were significantly increased. Histopathological results revealed the glomerular swelling. The above all indexes were dose-dependent. In the protection experiment, the mice were pretreated with the eukaryotic plasmid of pEGFP-C3-Hsp70, these increasing parameters in the mycotoxins-challenge experiment were reversed. In vitro, after pK-15 cells were treated with 8 μM FB1 and 5 μM OTA for 48 h, the mitochondrial membrane potential was significantly reduced, mitochondrial ROS was remarkably increased, more Cyto C was leaked from mitochondria into cytoplasm, and pro-apoptosis genes were significantly up-regulated. After the Hsp70 level was up-regulated by pEGFP-C3-Hsp70 or ML346 in pK-15 cells, these above indexes were reversed. However, activation of JNK by anisomycin significantly suppressed the protective effects of Hsp70. Our results demonstrate that the nontoxic doses of FB1 exacerbate the toxic dose of OTA-induced renal injury, while Hsp70 alleviates renal injury by inhibiting the JNK/MAPK signaling pathway. Hsp70 up-regulation may be an efficient strategy for protecting against tissue damage and bio-function impairment induced by co-exposure to FB1 and OTA.

Ochratoxin A induces cytotoxicity through ROS-mediated endoplasmic reticulum stress pathway in human gastric epithelium cells

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium species that greatly threatens human health. We previously showed that OTA induced cycle arrest, apoptosis and autophagy in human gastric epithelium cells (GES-1). However, the mechanism underlying these effects is still unclear. Here, we showed that OTA exposure increased the expression of endoplasmic reticulum (ER) stress indicators (GRP78, PERK, ATF6, eIF2α, and CHOP), suggesting the activation of the unfolded protein response pathway. 4-phenylbutyric acid (4-PBA), an ER stress-specific inhibitor, attenuated OTA-induced loss of cell viability and apoptosis in GES-1 cells. It also attenuated the G2 phase arrest and autophagy induced by OTA, as evidenced by upregulated G2 phase-related proteins (Cdc2, Cdc25C, and cyclinB1) and downregulated autophagy markers (LC3B and Beclin-1). Moreover, OTA was found to increase ROS generation, and the inhibition of ROS formation by N-acetylcysteine (NAC), an ROS inhibitor, attenuated OTA-induced ER stress and subsequent apoptosis, cell cycle arrest, and autophagy. Collectively, these results suggest that the ROS-mediated ER stress pathway contributes to the OTA toxin-induced cytotoxicity in GES-1 cells. This study offers new insights into the molecular mechanisms underlying OTA toxicity in gastric cells.

BNIP3 mediates the different adaptive responses of fibroblast-like synovial cells to hypoxia in patients with osteoarthritis and rheumatoid arthritis

Background

Hypoxia is one of the important characteristics of synovial microenvironment in rheumatoid arthritis (RA), and plays an important role in synovial hyperplasia. In terms of cell survival, fibroblast-like synovial cells (FLSs) are relatively affected by hypoxia. In contrast, fibroblast-like synovial cells from patients with RA (RA-FLSs) are particularly resistant to hypoxia-induced cell death. The purpose of this study was to evaluate whether fibroblast-like synovial cells in patients with osteoarthritis (OA-FLSs) and RA-FLSs have the same adaptation to hypoxia.

Methods

CCK-8, flow cytometry and BrdU were used to detect the proliferation of OA-FLSs and RA-FLSs under different oxygen concentrations. Apoptosis was detected by AV/PI, TUNEL and Western blot, mitophagy was observed by electron microscope, laser confocal microscope and Western blot, the state of mitochondria was detected by ROS and mitochondrial membrane potential by flow cytometry, BNIP3 and HIF-1α were detected by Western blot and RT-qPCR. The silencing of BNIP3 was achieved by stealth RNA system technology.

Results

After hypoxia, the survival rate of OA-FLSs decreased, while the proliferation activity of RA-FLSs further increased. Hypoxia induced an increase in apoptosis and inhibition of mitophagy in OA-FLSs, but not in RA-FLSs. Hypoxia led to a more lasting adaptive response. RA-FLSs displayed a more significant increase in the expression of genes transcriptionally regulated by HIF-1α. Interestingly, they showed higher BNIP3 expression than OA-FLSs, and showed stronger mitophagy and proliferation activities. BNIP3 siRNA experiment confirmed the potential role of BNIP3 in the survival of RA-FLSs. Inhibition of BNIP3 resulted in the decrease of cell proliferation, mitophagy and the increase of apoptosis.

Conclusion

In summary, RA-FLSs maintained intracellular redox balance through mitophagy to promote cell survival under hypoxia. The mitophagy of OA-FLSs was too little to maintain the redox balance of mitochondria, resulting in apoptosis. The difference of mitophagy between OA-FLSs and RA-FLSs under hypoxia is mediated by the level of BNIP3 expression.

An integrated systems-level model of ochratoxin A toxicity in the zebrafish (Danio rerio) embryo based on NMR metabolic profiling

Ochratoxin A (OTA) is one of the most widespread mycotoxin contaminants of agricultural crops. Despite being associated with a range of adverse health effects, a comprehensive systems-level mechanistic understanding of the toxicity of OTA remains elusive. In the present study, metabolic profiling by high-resolution magic angle spinning (HRMAS) NMR, coupled to intact zebrafish embryos, was employed to identify metabolic pathways in relation to a systems-level model of OTA toxicity. Embryotoxicity was observed at sub-micromolar exposure concentrations of OTA. Localization of OTA, based on intrinsic fluorescence, as well as a co-localization of increased reactive oxygen species production, was observed in the liver kidney, brain and intestine of embryos. Moreover, HRMAS NMR showed significant alteration of metabolites related to targeting of the liver (i.e., hepatotoxicity), and pathways associated with detoxification and oxidative stress, and mitochondrial energy metabolism. Based on metabolic profiles, and complementary assays, an integrated model of OTA toxicity is, thus, proposed. Our model suggests that OTA hepatotoxicity compromises detoxification and antioxidant pathways, leading to mitochondrial membrane dysfunction manifested by crosstalk between pathways of energy metabolism. Interestingly, our data additionally aligns with a possible role of mitochondrial fusion as a "passive mechanism" to rescue mitochondrial integrity during OTA toxicity.

Zearalenone Induces Apoptosis and Autophagy in a Spermatogonia Cell Line

Zearalenone (ZEN), a widely known mycotoxin, is mainly produced by various Fusarium species, and it is a potent estrogenic metabolite that affects reproductive health in livestock and humans. In this study, the molecular mechanisms of toxicity and cell damage induced by ZEN in GC-1 spermatogonia (spg) cells were evaluated. Our results showed that cell viability decreased and apoptosis increased in a dose-dependent manner when GC-1 spg cells were exposed to ZEN. In addition, the key proteins involved in apoptosis, cleaved caspase-3 and -8, BAD, BAX, and phosphorylation of p53 and ERK1/2, were significantly increased in ZEN-exposed GC-1 spg cells for 24 h, and cytochrome c was released from mitochondria by ZEN. Interestingly, ZEN also triggered autophagy in GC-1 spg cells. The expression levels of the autophagy-related genes Atg5, Atg3, Beclin 1, LC3, Ulk1, Bnip 3, and p62 were significantly higher in ZEN-treated GC-1 spg cells, and the protein levels of both LC3A/B and Atg12 were remarkably increased in a dose-dependent manner in ZEN-exposed GC-1 spg cells compared to the control. In addition, immunostaining results showed that ZEN-treated groups showed a remarkable increase in LC 3A/B positive puncta as compared to the control in a dose-dependent manner based on confocal microscopy analysis in GC-1 spg cells. Our findings suggest that ZEN has toxic effects on tGC-1 spg cells and induces both apoptosis and autophagy.

H2S exposure induces cell death in the broiler thymus via the ROS-initiated JNK/MST1/FOXO1 pathway

Hydrogen sulfide (H₂S) is a common toxic gas in chicken houses that endangers the health of poultry. Harbin has a cold climate in winter, and the conflict between heat preservation and ventilation in poultry houses is obvious. In this study, we investigated the H₂S content in chicken houses during winter in Harbin and found that the H₂S concentration exceeded the national standard in individual chicken houses. Then, a model of H₂S exposure was established in an environmental simulation chamber. We also developed a NaHS exposure model of chicken peripheral blood lymphocytes in vitro. Proteomics analysis was used to reveal the toxicology of thymus injury in broilers, the FOXO signaling pathway was determined to be significantly enriched, ROS bursts and JNK/MST1/FOXO1 pathway activation induced by H₂S exposure were detected, and ROS played an important switch role in the JNK/MST1/FOXO1 pathway. In addition, H₂S exposure-induced thymus cell death involved immune dysregulation. Overall, the present study adds data for H₂S contents in chicken houses, provides new findings for the mechanism of H₂S poisoning and reveals a new regulatory pathway in immune injury.

Hepatotoxicity of food-borne mycotoxins: molecular mechanism, anti-hepatotoxic medicines and target prediction

Mycotoxins are metabolites produced by fungi. The widespread contamination of food and feed by mycotoxins is a global food safety problem and a serious threat to people's health. Most food-borne mycotoxins have strong hepatotoxicity. However, no effective methods have been found to prevent or treat Mycotoxin- Induced Liver Injury (MILI) in clinical and animal husbandry. In this paper, the molecular mechanisms and potential anti-MILI medicines of six food-borne MILI are reviewed, and their targets are predicted by network toxicology, which provides a theoretical basis for further study of the toxicity mechanism of MILI and the development of effective strategies to manage MILI-related health problems in the future and accelerate the development of food safety.

Fine particles in surgical smoke affect embryonic cardiomyocyte differentiation through oxidative stress and mitophagy

Surgical smoke is widespread in operating rooms, and fine particles are the main toxic components. However, the effect of fine particles in surgical smoke on embryonic development has not yet been studied. This study evaluated the effect of fine particles in surgical smoke on embryonic development and compared it with that of atmospheric fine particles. Afterwards, differentiated cardiomyocytes were purified, and the effect of exposure to fine particles in surgical smoke on cardiomyocyte differentiation was evaluated. Fine particles in surgical smoke exhibited weak embryotoxicity toward an embryonic stem cell test model, and their inhibitory effect on cardiomyocyte differentiation was slightly stronger than that of atmospheric fine particles. Fine particles in surgical smoke specifically inhibited the differentiation of the mesoderm lineage and promoted the differentiation of the ectoderm lineage. Furthermore, fine particles in surgical smoke reduced the beating rate of purified cardiomyocytes, promoted mitophagy, reduced ATP production and increased the reactive oxygen species (ROS) content. Antioxidants attenuated the inhibition of cardiomyocyte differentiation and the reduction in the cardiomyocyte beating rate caused by fine particles in surgical smoke and simultaneously restored mitophagy and other processes to the control levels. However, mitophagy inhibitors treatment blocked only the inhibition of cardiomyocyte differentiation caused by fine particles in surgical smoke; it had little effect on other changes caused by fine particles. Based on the results described above, we propose that fine particles in surgical smoke and atmospheric fine particles exhibit similar levels of toxicity toward embryonic development. Fine particles in surgical smoke potentially affect the beating of cardiomyocytes by damaging mitochondria and increasing oxidative stress.

Autophagy in Gastric Mucosa: The Dual Role and Potential Therapeutic Target

The incidence of stomach diseases is very high, which has a significant impact on human health. Damaged gastric mucosa is more vulnerable to injury, leading to bleeding and perforation, which eventually aggravates the primary disease. Therefore, the protection of gastric mucosa is crucial. However, existing drugs that protect gastric mucosa can cause nonnegligible side effects, such as hepatic inflammation, nephritis, hypoacidity, impotence, osteoporotic bone fracture, and hypergastrinemia. Autophagy, as a major intracellular lysosome-dependent degradation process, plays a key role in maintaining intracellular homeostasis and resisting environmental pressure, which may be a potential therapeutic target for protecting gastric mucosa. Recent studies have demonstrated that autophagy played a dual role when gastric mucosa exposed to biological and chemical factors. More indepth studies are needed on the protective effect of autophagy in gastric mucosa. In this review, we focus on the mechanisms and the dual role of various biological and chemical factors regulating autophagy, such as Helicobacter pylori, virus, and nonsteroidal anti-inflammatory drugs. And we summarize the pathophysiological properties and pharmacological strategies for the protection of gastric mucosa through autophagy.

The Impact of the Nephrotoxin Ochratoxin A on Human Renal Cells Studied by a Novel Co-Culture Model Is Influenced by the Presence of Fibroblasts

The kidney is threatened by a lot of potentially toxic substances. To study the influence of the nephrotoxin ochratoxin A (OTA) we established a cell co-culture model consisting of human renal proximal tubule cells and fibroblasts. We studied the effect of OTA on cell survival, the expression of genes and/or proteins related to cell death, extracellular matrix and energy homeostasis. OTA-induced necrosis was enhanced in both cell types in the presence of the respective other cell type, whereas OTA-induced apoptosis was independent therefrom. In fibroblasts, but not in tubule cells, a co-culture effect was visible concerning the expression of the cell-cycle-related protein p21. The expression of the epithelial-to-mesenchymal transition-indicating protein vimentin was independent from the culture-condition. The expression of the OTA-induced lncRNA WISP1-AS1 was enhanced in co-culture. OTA exposure led to alterations in the expression of genes related to energy metabolism with a glucose-mobilizing effect and a reduced expression of mitochondrial proteins. Together we demonstrate that the reaction of cells can be different in the presence of cells which naturally are close-by, thus enabling a cellular cross-talk. Therefore, to evaluate the toxicity of a substance, it would be an advantage to consider the use of co-cultures instead of mono-cultures.

Review of the Efficacy and Mechanisms of Traditional Chinese Medicines as a Therapeutic Option for Ionizing Radiation Induced Damage

Ionizing radiation damage refers to acute, delayed, or chronic tissue damage associated with ionizing radiation. Specific or effective therapeutic options for systemic injuries induced by ionizing radiation have not been developed. Studies have shown that Chinese herbal Medicine or Chinese Herbal Prescription exhibit preventive properties against radiation damage. These medicines inhibit tissue injuries and promote repair with very minimal side effects. This study reviews traditional Chinese herbal medicines and prescriptions with radiation protective effects as well as their mechanisms of action. The information obtained will guide the development of alternative radioprotectants.

Cdk5-Mediated Phosphorylation of Sirt1 Contributes to Podocyte Mitochondrial Dysfunction in Diabetic Nephropathy

Aims: Mitochondrial dysfunction contributes to podocyte injury, which is the leading cause of proteinuria in diabetic nephropathy (DN). In this study, we explored the role of cyclin-dependent kinase 5 (Cdk5) in mitochondrial dysfunction of podocytes under diabetic conditions. Results: Our results showed that the expression and activity of Cdk5 were significantly upregulated in vivo and in vitro under diabetic conditions, accompanied by the downregulation of synaptopodin and nephrin, as well as structural and functional mitochondrial dysfunction. Inhibition of Cdk5 with roscovitine or dominant-negative Cdk5 led to the attenuation of podocyte injury by upregulating synaptopodin and nephrin. The inhibition of Cdk5 also ameliorated mitochondrial dysfunction by decreasing reactive oxygen species levels and cytochrome c release, while increasing adenosine triphosphate production. Sirt1, an NAD⁺-dependent deacetylase, was decreased in podocytes with high glucose (HG) treatment; however, its phosphorylation level at S47 was significantly upregulated. We demonstrated that HG levels cause overactive Cdk5 to phosphorylate Sirt1 at S47. Suppression of Cdk5 reduced Sirt1 phosphorylation levels and mutation of S47 to nonphosphorable alanine (S47A), significantly attenuated podocyte injury and mitochondrial dysfunction in diabetic condition in vivo and in vitro. Innovation and Conclusion: Our study has demonstrated the role of Cdk5 in regulating mitochondrial function through Sirt1 phosphorylation and thus can potentially be a new therapeutic target for DN treatment. IRB number: 20190040. Antioxid. Redox Signal. 34, 171-190.

Tubeimoside I Inhibits Cell Proliferation and Induces a Partly Disrupted and Cytoprotective Autophagy Through Rapidly Hyperactivation of MEK1/2-ERK1/2 Cascade via Promoting PTP1B in Melanoma

Tubeimoside I (TBMS1), also referred to as tubeimoside A, is a natural compound extracted from the plant Tu Bei Mu (Bolbostemma paniculatum), which is a traditional Chinese herb used to treat multiple diseases for more than 1,000 years. Studies in recent years reported its anti-tumor activity in several cancers. However, whether it is effective in melanoma remains unknown. In the current study, we discovered that TBMS1 treatment inhibited melanoma cell proliferation in vitro and tumorigenecity in vivo. Besides, we also observed that TBMS1 treatment induced a partly disrupted autophagy, which still remained a protective role, disruption of which by chloroquine (CQ) or 3-methyladenine (3-MA) enhanced TBMS1-induced cell proliferation inhibition. CQ combined with TBMS1 even induced cellular apoptosis. BRAF(V600E) mutation and its continuously activated downstream MEK1/2-ERK1/2 cascade are found in 50% of melanomas and are important for malanomagenesis. However, hyperactivating MEK1/2-ERK1/2 cascade can also inhibit tumor growth. Intriguingly, we observed that TBMS1 rapidly hyperactivated MEK1/2-ERK1/2, inhibition of which by its inhibitor SL-327 rescued the anti-cancerous effects of TBMS1. Besides, the targets of TBMS1 were predicted by the ZINC Database based on its structure. It is revealed that protein-tyrosine phosphatase 1B (PTP1B) might be one of the targets of TBMS1. Inhibition of PTP1B by its selective inhibitor TCS401 or shRNA rescued the anti-cancerous effects of TBMS1 in melanoma cells. These results indicated that TBMS1 might activate PTP1B, which further hyperactivates MEK1/2-ERK1/2 cascade, thereby inhibiting cell proliferation in melanoma. Our results provided the potentiality of TBMS1 as a drug candidate for melanoma therapy and confirmed that rapidly hyperactivating an oncogenic signaling pathway may also be a promising strategy for cancer treatment.

Ochratoxin A induces reprogramming of glucose metabolism by switching energy metabolism from oxidative phosphorylation to glycolysis in human gastric epithelium GES-1 cells in vitro

Ochratoxin A (OTA) is a ubiquitous mycotoxin with potential nephrotoxic, hepatotoxic and immunotoxic effects. We previously demonstrated that OTA could cause mitochondrial function disturbance in GES-1 cells in vitro, which lead to the presumption that the glucose metabolism of GES-1 cells will be altered by OTA. Therefore in the present study, we explored the toxicity of OTA on glucose metabolism of GES-1 cells and the molecular mechanism. We found that OTA could induce aerobic glycolysis, evidenced shown by increase of glucose consumption, lactate production and cellular ATP concentration. We further detected expressions of GLUT1 and glycolytic enzymes including HK2, PFK1, PKM2 and LDHA as well as tricarboxylic acid (TCA) cycle-associated enzymes including IDH1, OGDH and CS. The results showed that expression of GLUT1 as well as the activities and expressions of HK2, PFK1 and LDHA were significantly increased while IDH1 and OGDH were reduced by OTA. As to PKM2, western blot showed that OTA could elevated the phospho-PKM2 Ser37 protein level and induce the nuclear accumulation of PKM2, which was further supported by immunofluorescence analyses, in addition, pyruvate kinase activity was reduced by OTA. In conclusion, these findings suggest that OTA exposure induces the metabolic shift from oxidative phosphorylation to aerobic glycolysis via regulating the activities and expressions of glycolysis and TCA-cycle associated molecules in GES-1 cells.

Role of Parkin-mediated mitophagy in glucocorticoid-induced cardiomyocyte maturation

Glucocorticoids can promote cardiomyocyte maturation. However, the mechanism underlying glucocorticoid-mediated cardiomyocyte maturation is still unclear. Mitophagy plays a key role in cardiomyocyte maturation. Based on current knowledge, our study evaluated the effects of the glucocorticoid dexamethasone (100 nM) on the maturation of mouse embryonic stem cell-derived cardiomyocytes and the role of mitophagy in this maturation. The results showed that dexamethasone can promote embryonic stem cell-derived cardiomyocyte maturation, inhibit cardiomyocyte proliferation, and promote myocardial fiber arrangement. However, dexamethasone did not affect mitochondrial morphology in cardiomyocytes. Glucocorticoid receptor inhibitors (RU486, 1 nM) can inhibit dexamethasone-mediated cardiomyocyte maturation. Additionally, dexamethasone can promote mitophagy in embryonic stem cell-derived cardiomyocytes and induce LC3 and lysosomal aggregation in mitochondria. The inhibition of mitophagy can inhibit the cardiomyocyte maturation effect of dexamethasone. Furthermore, our research found that dexamethasone may mediate the occurrence of mitophagy in cardiomyocytes through Parkin. The siRNA-mediated inhibition of Parkin expression can inhibit mitochondrial autophagy caused by dexamethasone, thus inhibiting cardiomyocyte maturation. Overall, our study found that dexamethasone can promote embryonic stem cell-derived cardiomyocyte maturation through Parkin-mediated mitophagy.

Regulation of taurine in OTA-induced apoptosis and autophagy

Ochratoxin A (OTA), one of the most deleterious mycotoxins, could cause a variety of toxicological effects especially nephrotoxicity in animals and humans. Taurine, a wide-distributed cytoprotective amino acid, plays an important role as a basic factor for maintaining cellular integrity homeostasis. However, the potential effect of taurine in OTA-induced nephrotoxicity remains unknown. In the present study, we demonstrated that OTA treatment at 4.0-8.0 μM increased apoptosis in PK-15 cells as shown by increased the ratio of apoptosis and protein expression of Bax and cleaved-caspase-3, decreased protein expression of Bcl-2. Meantime, OTA treatment triggered autophagy, as indicated by markedly increased the protein expression of LC3-II and fluorescence intensity of GFP-LC3 dots. Taurine supplementation decreased OTA-induced cytotoxicity and attenuated apoptosis as shown by the decreased Annexin V/PI staining and the decreased expression of apoptosis-related proteins including Bax and caspase-3. Meanwhile, taurine attenuated OTA-induced autophagy by decreased the protein expression of LC3-II and fluorescence intensity of GFP-LC3 dots to maintain cellular homeostasis. In conclusion, taurine treatment could alleviate OTA-induced apoptosis and inhibit the triggered autophagy in PK-15 cells. Our study provides supportive data for the potential roles of taurine in reducing OTA-induced renal toxicity.

Knockdown of TFAM in Tumor Cells Retarded Autophagic Flux through Regulating p53 Acetylation and PISD Expression

Mitochondrial transcription factor A (TFAM) is required for mitochondrial DNA replication and transcription, which are essential for mitochondrial biogenesis. Previous studies reported that depleting mitochondrial functions by genetic deletion of TFAM impaired autophagic activities. However, the underlying mechanisms remain largely unknown. In the current study, we identified that knockdown of TFAM repressed the synthesis of autophagy bio-marker LC3-II in tumor cells and decreased the expression of phosphatidyl-serine decarboxylase (PISD). Besides, downregulation of PISD with siRNA reduced the level of LC3-II, indicating that depletion of TFAM retarded autophagy via inhibiting PISD expression. Furthermore, it was found that the tumor repressor p53 could stimulate the transcription and expression of PISD by binding the PISD enhancer. Additionally, the protein stability and transcriptional activity of p53 in TFAM knockdown tumor cells was attenuated, and this was associated with decreased acetylation, especially the acetylation of lysine 382 of p53. Finally, we identified that TFAM knockdown increased the NAD⁺/NADH ratio in tumor cells. This led to the upregulation of Sirtuin1 (SIRT1), a NAD-dependent protein deacetylase, to deacetylate p53 and attenuated its transcriptional activation on PISD. In summary, our study discovered a new mechanism regarding disturbed autophagy in tumor cells with mitochondrial dysfunction due to the depletion of TFAM.

Mitoepigenetics and Its Emerging Roles in Cancer

In human beings, there is a ∼16,569 bp circular mitochondrial DNA (mtDNA) encoding 22 tRNAs, 12S and 16S rRNAs, 13 polypeptides that constitute the central core of ETC/OxPhos complexes, and some non-coding RNAs. Recently, mtDNA has been shown to have some covalent modifications such as methylation or hydroxylmethylation, which play pivotal epigenetic roles in mtDNA replication and transcription. Post-translational modifications of proteins in mitochondrial nucleoids such as mitochondrial transcription factor A (TFAM) also emerge as essential epigenetic modulations in mtDNA replication and transcription. Post-transcriptional modifications of mitochondrial RNAs (mtRNAs) including mt-rRNAs, mt-tRNAs and mt-mRNAs are important epigenetic modulations. Besides, mtDNA or nuclear DNA (n-DNA)-derived non-coding RNAs also play important roles in the regulation of translation and function of mitochondrial genes. These evidences introduce a novel concept of mitoepigenetics that refers to the study of modulations in the mitochondria that alter heritable phenotype in mitochondria itself without changing the mtDNA sequence. Since mitochondrial dysfunction contributes to carcinogenesis and tumor development, mitoepigenetics is also essential for cancer. Understanding the mode of actions of mitoepigenetics in cancers may shade light on the clinical diagnosis and prevention of these diseases. In this review, we summarize the present study about modifications in mtDNA, mtRNA and nucleoids and modulations of mtDNA/nDNA-derived non-coding RNAs that affect mtDNA translation/function, and overview recent studies of mitoepigenetic alterations in cancer.

T-2 Toxin-Induced Oxidative Stress Leads to Imbalance of Mitochondrial Fission and Fusion to Activate Cellular Apoptosis in the Human Liver 7702 Cell Line

T-2 toxin, as a highly toxic mycotoxin to humans and animals, induces oxidative stress and apoptosis in various cells and tissues. Apoptosis and mitochondrial fusion/fission are two tightly interconnected processes that are crucial for maintaining physiological homeostasis. However, the role of mitochondrial fusion/fission in apoptosis of T-2 toxin remains unknown. Hence, we aimed to explore the putative role of mitochondrial fusion/fission on T-2 toxin induced apoptosis in normal human liver (HL-7702) cells. T-2 toxin treatment (0, 0.1, 1.0, or 10 μg/L) for 24 h caused decreased cell viability and ATP concentration and increased production of (ROS), as seen by a loss of mitochondrial membrane potential (∆Ψm) and increase in mitochondrial fragmentation. Subsequently, the mitochondrial dynamic imbalance was activated, evidenced by a dose-dependent decrease and increase in the protein expression of mitochondrial fusion (OPA1, Mfn1, and Mfn2) and fission (Drp1 and Fis1), respectively. Furthermore, the T-2 toxin promoted the release of cytochrome c from mitochondria to cytoplasm and induced cell apoptosis triggered by upregulation of Bax and Bax/Bcl-2 ratios, and further activated the caspase pathways. Taken together, these results indicate that altered mitochondrial dynamics induced by oxidative stress with T-2 toxin exposure likely contribute to mitochondrial injury and HL-7702 cell apoptosis.