Toxicokinetics and metabolism of deoxynivalenol in animals and humans.

Deoxynivalenol (DON) is the most widespread mycotoxin in food and feedstuffs, posing a persistent health threat to humans and farm animals. The susceptibilities of DON vary significantly among animals, following the order of pigs, mice/rats and poultry from the most to least susceptible. However, no study comprehensively disentangles factors shaping species-specific sensitivity. In this review, the toxicokinetics and metabolism of DON are summarized in animals and humans. Generally, DON is fast-absorbed and widely distributed in multiple organs. DON is first enriched in the plasma, liver and kidney and subsequently accumulates in the intestine. There are also key variations among animals. Pigs and humans are highly sensitive to DON, and they have similar absorption rates (1 h < tmax < 4 h), high bioavailability (> 55%) and long clearance time (2 h < t1/2 < 4 h). Also, both species lack detoxification microorganisms and mainly depend on liver glucuronidation and urine excretion. Mice and rats have similar toxicokinetics (tmax < 0.5 h, t1/2 < 1 h). However, a higher proportion of DON is excreted by feces as DOM-1 in rats than in mice, suggesting an important role of gut microbiota in rats. Poultry is least sensitive to DON due to their fast absorption rate (tmax < 1 h), low oral bioavailability (5-30%), broadly available detoxification gut microorganisms and short clearance time (t1/2 < 1 h). Aquatic animals have significantly slower plasma clearance of DON than land animals. Overall, studies on toxicokinetics provide valuable information for risk assessment, prevention and control of DON contamination.

Deoxynivalenol induces caspase-3/GSDME-dependent pyroptosis and inflammation in mouse liver and HepaRG cells.

Deoxynivalenol (DON), a frequent food and feed contaminant, poses a severe threat to human and livestock health. Some studies have demonstrated that DON could induce liver damage and cell death. However, novel cell death styles and detailed mechanisms to explain DON-induced liver inflammatory injury are still lacking. Here, we found both chronic and subacute oral administration of DON (3 mg/kg for 4 weeks and 4 mg/kg for 8 days) induced mouse liver inflammatory injury and activated caspase-3, PARP and gasdermin E (GSDME), which were inhibited by caspase-3 inhibitor Z-DEVD and Ac-DEVD. In vitro, HepaRG cells showed typical pyroptotic characteristics after 32 and 64 µM DON exposure for 24 h, including balloon-like bubbling emerging, release of lactate dehydrogenase (LDH), secretion of IL-1ß and IL-6 and activation of caspase-3 and GSDME. Furthermore, knocking down GSDME and inhibiting caspases activity by Z-VAD and Z-DEVD dramatically blocked DON-induced pyroptotic characteristics, while over-expressed GSDME prompted that. These data demonstrate that caspase-3/GSDME pathway plays a key factor in DON-induced pyroptosis and inflammation in liver. Interestingly, knocking down GSDME could inhibit DON-induced pyroptosis but prompt DON-induced apoptosis, while opposite results were obtained when over-expressed GSDME, indicating the critical role of GSDME in DON-induced crosstalk between apoptosis and pyroptosis. Taken together, our data determine DON-induced caspase-3/GSDME-dependent pyroptosis in liver and its role in DON-induced liver inflammatory injury, which provide a novel mechanistic view into DON-induced hepatotoxicity and may offer a new target to reduce latent harm of DON to both humans and animals.

Inhibition of EZH2 and activation of ERRγ synergistically suppresses gastric cancer by inhibiting FOXM1 signaling pathway.

BACKGROUND: Gastric cancer (GC) is a leading cause of cancer-related mortality worldwide, because of the low efficacy of current therapeutic strategies. Estrogen-related receptor γ (ERRγ) was previously showed as a suppressor of GC. However, the mechanism and effective therapeutic method based on ERRγ is yet to be developed. METHODS: The expression levels of ERRγ, EZH2, and FOXM1 were detected by immunohistochemistry, qRT-PCR, and western blot. The regulatory mechanisms of ERRγ and FOXM1 were analyzed by ChIP, EMSA, and siRNA. The effects of EZH2 inhibitor (GSK126) or/and ERRγ agonist (DY131) on the tumorigenesis of gastric cancer cell lines were examined by cell proliferation, transwell migration, wound healing, and colony formation assays. Meanwhile, the inhibitory effects of GSK126 or/and DY131 on tumor growth were analyzed by xenograft tumor growth assay. RESULTS: The expression of ERRγ was suppressed in tumor tissues of GC patients and positively correlated with prognosis, as opposed to that of EZH2 and FOXM1. EZH2 transcriptionally suppressed ERRγ via H3K27me3, which subsequently activated the expression of master oncogene FOXM1. The combination of GSK126 and DY131 synergistically activated ERRγ expression, which subsequently inhibited the expression of FOXM1 and its regulated pathways. Synergistic combination of GSK126 and DY131 significantly inhibited the tumorigenesis of GC cell lines and suppressed the growth of GC xenograft. CONCLUSION: The FOXM1 signaling pathway underlying the ERRγ-mediated gastric cancer suppression was identified. Furthermore, combined treatment with EZH2 inhibitor and ERRγ agonist synergistically suppressed GC progression by inhibiting this signaling pathway, suggesting its high potential in treating GC patients.

Quantitative proteomics implicates YggT in streptomycin resistance in Salmonella enterica serovar Enteritidis.

OBJECTIVES: To identify proteins that may be associated with antibiotic resistance in the multidrug-resistant Salmonella enterica D14, by constructing proteomic profiles using mass spectrometry-based label-free quantitative proteomics (LFQP). RESULTS: D14 was cultured with four antibiotics (ampicillin, nalidixic acid, streptomycin, and tetracycline) separately. Subsequently, the findings from an equal combination of the four cultures were compared with the profile of sensitive S. enterica 104. 2255 proteins, including 149 differentially up-regulated proteins, were identified. Many of these up-regulated proteins were associated with flagellar assembly and chemotaxis, two-component system, amino acid metabolism, ß-lactam resistance, and transmembrane transport. A subset of 10 genes was evaluated via quantitative real-time PCR (qPCR), followed by the construction of cheR, fliS, fliA, arnA, and yggT deletion mutants. Only the yggT-deleted D14 mutant showed decrease in streptomycin resistance, whereas the other deletions had no effect. Furthermore, complementation of yggT and the overexpression of yggT in S. enterica ATCC 14028 increased the streptomycin resistance. Additionally, spot dilution assay results confirmed that Salmonella strains, harboring yggT, exhibited an advantage in the presence of streptomycin. CONCLUSIONS: The above proteomic and mutagenic analyses revealed that yggT is involved in streptomycin resistance in S. enterica.

T-2 Toxin Induces Oxidative Stress at Low Doses via Atf3ΔZip2a/2b-Mediated Ubiquitination and Degradation of Nrf2.

T-2 toxin is mainly produced by Fusarium species, which is an extremely toxic mycotoxin to humans and animals. It is well known that T-2 toxin induces oxidative stress, but the molecular mechanism is still unknown. In this study, we found that T-2 toxin significantly promoted reactive oxygen species (ROS) accumulation in MCF-7 cells at low doses which maintains cell viability at least 80%. Further analysis showed that T-2 toxin downregulated the expression of the master regulator of antioxidant defense gene, nuclear factor erythroid 2-related factor (Nrf2), and its targeted antioxidant genes. Overexpression of Nrf2 or its target gene heme oxygenase 1 (HO1) significantly blocked the ROS accumulation in MCF-7 cells under T-2 toxin treatment. Moreover, we found that T-2 toxin downregulated the antioxidant genes via inducing the expression of ATF3ΔZip2a/2b. Importantly, overexpression of ATF3ΔZip2a/2b promoted the ubiquitination and degradation of Nrf2. Altogether, our results demonstrated that T-2 toxin-induced ROS accumulation via ATF3ΔZip2a/2b mediated ubiquitination and degradation of Nrf2, which provided a new insight into the mechanism of T-2 toxin-induced oxidative stress.

Aflatoxin B1 Induces Neurotoxicity through Reactive Oxygen Species Generation, DNA Damage, Apoptosis, and S-Phase Cell Cycle Arrest.

Aflatoxin B1 (AFB1) is a mycotoxin widely distributed in a variety of food commodities and exhibits strong toxicity toward multiple tissues and organs. However, little is known about its neurotoxicity and the associated mechanism. In this study, we observed that brain integrity was markedly damaged in mice after intragastric administration of AFB1 (300 µg/kg/day for 30 days). The toxicity of AFB1 on neuronal cells and the underlying mechanisms were then investigated in the neuroblastoma cell line IMR-32. A cell viability assay showed that the IC50 values of AFB1 on IMR-32 cells were 6.18 µg/mL and 5.87 µg/mL after treatment for 24 h and 48 h, respectively. ROS levels in IMR-32 cells increased significantly in a time- and AFB1 concentration-dependent manner, which was associated with the upregulation of NOX2, and downregulation of OXR1, SOD1, and SOD2. Substantial DNA damage associated with the downregulation of PARP1, BRCA2, and RAD51 was also observed. Furthermore, AFB1 significantly induced S-phase arrest, which is associated with the upregulation of CDKN1A, CDKN2C, and CDKN2D. Finally, AFB1 induced apoptosis involving CASP3 and BAX. Taken together, AFB1 manifests a wide range of cytotoxicity on neuronal cells including ROS accumulation, DNA damage, S-phase arrest, and apoptosis-all of which are key factors for understanding the neurotoxicology of AFB1.

N-oxide reduction of quinoxaline-1,4-dioxides catalyzed by porcine aldehyde oxidase SsAOX1.

Quinoxaline-1,4-dioxides (QdNOs) are a class of quinoxaline derivatives that are widely used in humans or animals as drugs or feed additives. However, the metabolic mechanism, especially the involved enzymes, has not been reported in detail. In this study, the N-oxide reduction enzyme, porcine aldehyde oxidase SsAOX1 was identified and characterized. The SsAOX1 gene was cloned from pig liver through reverse-transcription polymerase chain reaction using degenerate primers, which encode a 147-kDa protein with typical aldehyde oxidase motifs, two [2Fe-2S] centers, a flavin adenine dinucleotide (FAD) binding domain, and a molybdenum cofactor domain. After heterologous expression in a prokaryote, purified SsAOX1 formed a functional homodimer under native conditions. Importantly, the SsAOX1 catalyzed the N-oxide reduction at the N1 position of three representative QdNOs (quinocetone, mequindox, and cyadox), which are commonly used as animal feed additives. SsAOX1 has the highest activity toward quinocetone, followed by mequindox and cyadox, with kcat/K(m) values of 1.94 ± 0.04, 1.27 ± 0.15, and 0.43 ± 0.09 minute(-1) µM(-1), respectively. However, SsAOX1 has the lowest substrate affinity for quinocetone, followed by the cyadox and mequindox, with K(m) values of 4.36 ± 0.56, 3.16 ± 0.48, and 2.96 ± 0.51 µM, respectively. In addition, using site-directed mutagenesis, we found that substitution of glycine 1019 with threonine endows SsAOX1 with N-oxide reductive activity at the N4 position. The goal of this study was to identify and characterize the N-oxide reduction enzyme for a class of veterinary drugs, QdNOs, which will aid in the elucidation of the metabolic pathways of QdNOs and will provide a theoretical basis for their administration and new veterinary drug design.

Haspin mediates H3.3S31 phosphorylation downstream of Aurora B in mouse embryonic stem cells.

Histone phosphorylation is instrumental in regulating diverse cellular processes across eukaryotes. Unraveling the kinases that target specific histone sites is key to deciphering the underlying mechanisms. Among the various sites on histone tails that can undergo phosphorylation, the kinase responsible for H3.3S31 phosphorylation remained elusive. Since both H3.3S31ph and H3T3ph occur specifically during mitosis, and Haspin is the known kinase for H3T3 phosphorylation, we investigated its potential role in H3.3S31 phosphorylation. We employed CRISPR/Cas9, RNA interference, and specific small molecule inhibitors to eliminate Haspin function in various cell types. Our data consistently revealed a link between Haspin and H3.3S31ph. Furthermore, in vitro kinase assays provided evidence supporting Haspin's contribution to H3.3S31ph. Loss- and gain-of-function experiments targeting Haspin and Aurora B further suggested a hierarchical relationship. Haspin acts as a downstream kinase of Aurora B, specifically orchestrating H3.3S31 phosphorylation in mESCs. This study unveils a novel role for Haspin as a kinase in regulating H3.3S31 phosphorylation during mitosis. This discovery holds promise for expanding our understanding of the functional significance of Haspin and H3.3S31ph in mammals.

Pyrroloquinoline quinone production defines the ability of Devosia species to degrade deoxynivalenol.

Deoxynivalenol (DON) is a prevalent mycotoxin that primarily contaminates cereal crops and animal feed, posing a significant risk to human and animal health. In recent years, an increasing number of Devosia strains have been identified as DON degradation bacteria, and significant efforts have been made to explore their potential applications in the food and animal feed industries. However, the characteristics and mechanisms of DON degradation in Devosia strains are still unclear. In this study, we identified a novel DON degrading bacterium, Devosia sp. D-G15 (D-G15), from soil samples. The major degradation products of DON in D-G15 were 3-keto-DON, 3-epi-DON and an unidentified product, compound C. The cell viability assay showed that the DON degradation product of D-G15 revealed significantly reduced toxicity to HEK293T cells compared to DON. Three enzymes for DON degradation were further identified, with G15-DDH converting DON to 3-keto-DON and G15-AKR1/G15-AKR6 reducing 3-keto-DON to 3-epi-DON. Interestingly, genome comparison of Devosia strains showed that the pyrroloquinoline quinone (PQQ) synthesis gene cluster is a unique feature of DON degradation strains. Subsequently, adding PQQ to the cultural media of Devosia strains without PQQ synthesis genes endowed them with DON degradation activity. Furthermore, a novel DON-degrading enzyme G13-DDH (<30% homology with known DON dehydrogenase) was identified from a Devosia strain that lacks PQQ synthesis ability. In summary, a novel DON degrading Devosia strain and its key enzymes were identified, and PQQ production was found as a distinct feature among Devosia strains with DON degradation activity, which is important for developing Devosia strain-based technology in DON detoxification.

Two mitochondrial DNA polymorphisms modulate cardiolipin binding and lead to synthetic lethality.

Genetic screens have been used extensively to probe interactions between nuclear genes and their impact on phenotypes. Probing interactions between mitochondrial genes and their phenotypic outcome, however, has not been possible due to a lack of tools to map the responsible polymorphisms. Here, using a toolkit we previously established in Drosophila, we isolate over 300 recombinant mitochondrial genomes and map a naturally occurring polymorphism at the cytochrome c oxidase III residue 109 (CoIII109) that fully rescues the lethality and other defects associated with a point mutation in cytochrome c oxidase I (CoIT300I). Through lipidomics profiling, biochemical assays and phenotypic analyses, we show that the CoIII109 polymorphism modulates cardiolipin binding to prevent complex IV instability caused by the CoIT300I mutation. This study demonstrates the feasibility of genetic interaction screens in animal mitochondrial DNA. It unwraps the complex intra-genomic interplays underlying disorders linked to mitochondrial DNA and how they influence disease expression.

Proteomic changes in chicken primary hepatocytes exposed to T-2 toxin are associated with oxidative stress and mitochondrial enhancement.

T-2 toxin is a mycotoxin that is toxic to plants, animals, and humans. However, its molecular mechanism remains unclear, especially in chickens. In this study, using 2D electrophoresis with MALDI-TOF/TOF-MS, 53 proteins were identified as up- or downregulated by T-2 toxin in chicken primary hepatocytes. Functional network analysis by ingenuity pathway analysis showed that the top network altered by T-2 toxin is associated with neurological disease, cancer, organismal injury, and abnormalities. Most of the identified proteins were associated with one of eight functional classes, including cell redox homeostasis, transcriptional or translational regulation, cell cycle or cell proliferation, stress response, lipid metabolism, transport, carbohydrate metabolism, and protein degradation. Subcellular location categorization showed that the identified proteins were predominantly located in the mitochondrion (34%) and interestingly, the expression of all the identified mitochondrial proteins was increased. Further cellular analysis showed that T-2 toxin was able to induce the ROS accumulation and could lead to an increase in mitochondrial mass and adenosine 5'-triphosphate content, which indicated that oxidative stress and mitochondrial enhancement occurred in T-2 toxin-treated cells. Overall, these results characterize the global proteomic response of chicken primary hepatocytes to T-2 toxin, which may lead to a better understanding of the molecular mechanisms underlying its toxicity.

REC drives recombination to repair double-strand breaks in animal mtDNA.

Mechanisms that safeguard mitochondrial DNA (mtDNA) limit the accumulation of mutations linked to mitochondrial and age-related diseases. Yet, pathways that repair double-strand breaks (DSBs) in animal mitochondria are poorly understood. By performing a candidate screen for mtDNA repair proteins, we identify that REC-an MCM helicase that drives meiotic recombination in the nucleus-also localizes to mitochondria in Drosophila. We show that REC repairs mtDNA DSBs by homologous recombination in somatic and germline tissues. Moreover, REC prevents age-associated mtDNA mutations. We further show that MCM8, the human ortholog of REC, also localizes to mitochondria and limits the accumulation of mtDNA mutations. This study provides mechanistic insight into animal mtDNA recombination and demonstrates its importance in safeguarding mtDNA during ageing and evolution.

Improvement of catalytic activity of sorbose dehydrogenase for deoxynivalenol degradation by rational design.

Deoxynivalenol (DON) is the most frequently contaminated mycotoxin in food and feed worldwide, causing significant economic losses and health risks. Physical and chemical detoxification methods are widely used, but they cannot efficiently and specifically remove DON. In the study, the combination of bioinformatics screening and experimental verification confirmed that sorbose dehydrogenase (SDH) can effectively convert DON to 3-keto-DON and a substance that removes four hydrogen atoms for DON. Through rational design, the Vmax of the mutants F103L and F103A were increased by 5 and 23 times, respectively. Furthermore, we identified catalytic sites W218 and D281. SDH and its mutants have broad application conditions, including temperature ranges of 10-45 °C and pH levels of 4-9. Additionally, the half-lives of F103A at 90 °C (processing temperature) and 30 °C (storage temperature) were 60.1 min and 100.5 d, respectively. These results suggest that F103A has significant potential in the detoxification application of DON.

Carbonyl reduction of mequindox by chicken and porcine cytosol and cloned carbonyl reductase 1.

Mequindox (MEQ) is a novel synthetic quinoxaline 1,4-dioxides derivative, which is widely used as a veterinary drug and animal feed additive. However, the metabolic mechanism of MEQ is rarely reported. The N-oxide reduction mechanism of MEQ was reported in our previous work. In this article, the toxicity and the reduction of the carbonyl of MEQ were studied. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assays demonstrated that the carbonyl-reduced MEQ, 2-isoethanol MEQ was much less toxic than MEQ. High-performance liquid chromatography analysis showed that the cytosol extracts of chicken and pig livers were able to reduce MEQ to 2-isoethanol MEQ and the reaction was NADPH-dependent. Further study via enzyme-inhibitory experiment revealed that carbonyl reductase 1 (CBR1) participated in this metabolism. The enzyme activity analysis showed that both chicken CBR1 (cCBR1) and porcine CBR1 (pCBR1) were capable of catalyzing the carbonyl reduction of MEQ and its N-oxide reductive metabolite, 1-deoxymequindox. By comparison of the kinetic constants, we observed that the activity of cCBR1 was higher than pCBR1 to MEQ and the standard substrate of CBR1, menadione. On the other hand, both CBR1s exhibited higher activity to 1-deoxymequindox than MEQ. Mutation analysis suggested that the difference of amino acid at position 141/142 may be one possible reason that caused the activity difference between cCBR1 and pCBR1. Thus far, CBR1 was first reported to participate in the carbonyl reduction of MEQ. Our results will be helpful to recognize the metabolic pathways of quinoxaline drugs deeply and to provide a theoretical basis for controlling the negative effects of these drugs.

Mequindox induced cellular DNA damage via generation of reactive oxygen species.

Mequindox, a quinoxaline-N-dioxide derivative that possesses antibacterial properties, has been widely used as a feed additive in the stockbreeding industry in China. While recent pharmacological studies have uncovered potential hazardous effects of mequindox, exactly how mequindox induces pathological changes and the cellular responses associated with its consumption remain largely unexplored. In this study, we investigated the cellular responses associated with mequindox treatment. We report here that mequindox inhibits cell proliferation by arresting cells at the G2/M phase of the cell cycle. Interestingly, this mequindox-associated deleterious effect on cell proliferation was observed in human, pig as well as chicken cells, suggesting that mequindox acts on evolutionarily conserved target(s). To further understand the mequindox-host interaction and the mechanism underlying mequindox-induced cell cycle arrest, we measured the cellular content of DNA damage, which is known to perturb cell proliferation and compromise cell survival. Accordingly, using γ-H2AX as a surrogate marker for DNA damage, we found that mequindox treatment induced cellular DNA damage, which paralleled the chemical-induced elevation of reactive oxygen species (ROS) levels. Importantly, expression of the antioxidant enzyme catalase partially alleviated these mequindox-associated effects. Taken together, our results suggest that mequindox cytotoxicity is attributable, in part, to its role as a potent inducer of DNA damage via ROS.

OsPFA-DSP1, a rice protein tyrosine phosphatase, negatively regulates drought stress responses in transgenic tobacco and rice plants.

Dephosphorylation plays a pivotal role in regulating plant growth, development and abiotic/biotic stress responses. Here, we characterized a plant and fungi atypical dual-specificity phosphatase (PFA-DSP) subfamily member, OsPFA-DSP1, from rice. OsPFA-DSP1 was determined to be a functional protein tyrosine phosphatase (PTP) in vitro using phosphatase activity assays. Quantitative real-time PCR and GENEVESTIGATOR analysis showed that OsPFA-DSP1 mRNA was induced by drought stress. Transfection of rice protoplasts showed that OsPFA-DSP1 accumulated in both the cytoplasm and nucleus. Ectopic overexpression of OsPFA-DSP1 in tobacco increased sensitivity to drought stress and insensitivity to ABA-induced stomatal closure and inhibition of stomatal opening. Furthermore, overexpression of OsPFA-DSP1 in rice also increased sensitivity to drought stress. These results indicated that OsPFA-DSP1 is a functional PTP and may act as a negative regulator in drought stress responses.

Indoor microbiome, air pollutants and asthma, rhinitis and eczema in preschool children - A repeated cross-sectional study.

BACKGROUND: Indoor microbiome exposure is associated with asthma, rhinitis and eczema. However, no studies report the interactions between environmental characteristics, indoor microbiome and health effects in a repeated cross-sectional framework. METHODS: 1,279 and 1,121 preschool children in an industrial city (Taiyuan) of China were assessed for asthma, rhinitis and eczema symptoms in 2012 and 2019 by self-administered questionnaires, respectively. Bacteria and fungi in classroom vacuum dust were characterized by culture-independent amplicon sequencing. Multi-level logistic/linear regression was performed in two cross-sectional and two combined models to assess the associations. RESULTS: The number of observed species in bacterial and fungal communities in classrooms increased significantly from 2012 to 2019, and the compositions of the microbial communities were drastically changed (p < 0.001). The temporal microbiome variation was significantly larger than the spatial variation within the city (p < 0.001). Annual average outdoor SO2 concentration decreased by 60.7%, whereas NO2 and PM10 concentrations increased by 63.3% and 40.0% from 2012 to 2019, which were both associated with indoor microbiome variation (PERMANOVA p < 0.001). The prevalence of asthma (2.0% to 3.3%, p = 0.06) and rhinitis (28.0% to 25.3%, p = 0.13) were not significantly changed, but the prevalence of eczema was increased (3.6% to 7.0%; p < 0.001). Aspergillus subversicolor, Collinsella and Cutibacterium were positively associated with asthma, rhinitis and eczema, respectively (p < 0.01). Prevotella, Lactobacillus iners and Dolosigranulum were protectively (negatively) associated with rhinitis (p < 0.01), consistent with previous studies in the human respiratory tract. NO2 and PM10 concentrations were negatively associated with rhinitis in a bivariate model, but a multivariate mediation analysis revealed that Prevotella fully mediated the health effects. CONCLUSIONS: This is the first study to report the interactions between environmental characteristics, indoor microbiome and health in a repeated cross-sectional framework. The mediating effects of indoor microorganisms suggest incorporating biological with chemical exposure for a comprehensive exposure assessment.

Cell fate determined by the activation balance between PKR and SPHK1.

Double-stranded RNA (dsRNA)-dependent protein kinase R (PKR) activation via autophosphorylation is the central cellular response to stress that promotes cell death or apoptosis. However, the key factors and mechanisms behind the simultaneous activation of pro-survival signaling pathways remain unknown. We have discovered a novel regulatory mechanism for the maintenance of cellular homeostasis that relies on the phosphorylation interplay between sphingosine kinase 1 (SPHK1) and PKR during exogenous stress. We identified SPHK1 as a previously unrecognized PKR substrate. Phosphorylated SPHK1, a central kinase, mediates the activation of PKR-induced pro-survival pathways by the S1P/S1PR1/MAPKs/IKKα signal axis, and antagonizes PKR-mediated endoplasmic reticulum (ER) stress signal transduction under stress conditions. Otherwise, phosphorylated SPHK1 also acts as the negative feedback factor, preferentially binding to the latent form of PKR at the C-terminal kinase motif, inhibiting the homodimerization of PKR, suppressing PKR autophosphorylation, and reducing the signaling strength for cell death and apoptosis. Our results suggest that the balance of the activation levels between PKR and SPHK1, a probable hallmark of homeostasis maintenance, determines cell fate during cellular stress response.

Low doses of deoxynivalenol inhibit the cell migration mediated by H3K27me3-targeted downregulation of TEM8 expression.

Deoxynivalenol (DON) is a mycotoxin produced by multipleFusariumspecies that often contaminates cereals and threatens human and animal health. A wide range of cytotoxic effects, such as the induction of DNA damage, an increase in mitochondrial permeability and the inhibition of macromolecule synthesis, have been reported. However, the effects of DON on cell migration-a fundamental process in living cells critical for normal development, immune responses, and disease processes-and the mechanism underlying these effects are still unclear. Here, we showed that DONsignificantly inhibited the migration of MRC-5, CCD-18Co, HCT116 and WM793 cells at 50 ng/ml, 50 ng/ml, 400 ng/ml and 250 ng/ml, respectively, which maintained cell viability at 90%. Further analysis showed that DON inhibited the expression of tumour endothelial marker 8 (TEM8), a key gene in cell migration. Furthermore, we showed that DON inhibited the expression of TEM8 through increasing the level of H3K27me3 in the TEM8 promoter. Finally, overexpression of TEM8 or treating by H3K27me3-specific inhibitor GSK126 attenuated the inhibitory effect of DON on cell migration. In summary, low doses of DON at approximately dietary exposure significantly inhibited cell migration by downregulating the expression of TEM8 in a manner mediated by H3K27me3, which may generate increasing concerns for the risk of DON exposure.

Lactobacillus rhamnosus GG supplementation modulates the gut microbiota to promote butyrate production, protecting against deoxynivalenol exposure in nude mice.

Deoxynivalenol (DON) is the most common mycotoxin in grains, and DON exposure causes gastrointestinal inflammation and systemic immunosuppression. The immunosuppression caused by DON has raised serious concerns about whether it is safe to use probiotics in immunocompromised hosts. Gut microbiota remodeling by Lactobacillus is a potential effective strategy to prevent DON exposure. The athymic nude mice were chose as the model of immunocompromised animals. We tested the effect of the probiotic Lactobacillus rhamnosus GG (LGG) or Lactobacillus acidophilus (LA) supplementation on host protection against DON exposure and the underlying mechanisms in nude mice. DON exposure induced endoplasmic reticulum (ER) stress and impaired intestinal barrier function and microbiota, which were relieved by LGG supplementation but not LA supplementation. LGG supplementation significantly enhanced the intestinal barrier function, increased the body weight and the survival rate in nude mice that exposed to DON for two weeks. Furthermore, LGG supplementation modulated the gut microbiota by increasing the abundance of Bacteroidetes and the levels of the butyrate-producing genes But and Buk to promote butyrate production. Butyrate inhibited the IRE1α/XBP1 signaling pathway to reduce DON-induced intestine injury. In conclusion, LGG supplementation modulated the gut microbiota to promote butyrate production, protecting against DON exposure in nude mice. Both LGG and butyrate show promise for use in protecting against DON exposure.