Oxygen Consumption Rate Analysis of Mitochondrial Dysfunction Caused by Bacillus cereus Cereulide in Caco-2 and HepG2 Cells

Radiation-induced changes in energy metabolism result in mitochondrial dysfunction in salivary glands

Salivary glands are indirectly damaged during radiotherapy for head and neck cancer, resulting in acute and chronic hyposalivation. Current treatments for radiation-induced hyposalivation do not permanently restore function to the gland; therefore, more mechanistic understanding of the damage response is needed to identify therapeutic targets for lasting restoration. Energy metabolism reprogramming has been observed in cancer and wound healing models to provide necessary fuel for cell proliferation; however, there is limited understanding of alterations in energy metabolism reprogramming in tissues that fail to heal. We measured extracellular acidification and oxygen consumption rates, assessed mitochondrial DNA copy number, and tested fuel dependency of irradiated primary salivary acinar cells. Radiation treatment leads to increases in glycolytic flux, oxidative phosphorylation, and ATP production rate at acute and intermediate time points. In contrast, at chronic radiation time points there is a significant decrease in glycolytic flux, oxidative phosphorylation, and ATP production rate. Irradiated salivary glands exhibit significant decreases in spare respiratory capacity and increases in mitochondrial DNA copy number at days 5 and 30 post-treatment, suggesting a mitochondrial dysfunction phenotype. These results elucidate kinetic changes in energy metabolism reprogramming of irradiated salivary glands that may underscore the chronic loss of function phenotype.

Evaluation of Glycolysis and Mitochondrial Function in Endothelial Cells Using the Seahorse Analyzer

Endothelial bioenergetics have emerged as a key regulator of endothelial barrier function. Glycolytic parameters have been linked to barrier enhancement, and interruption with mitochondrial complexes was shown to disrupt endothelial barrier. Therefore, a new technology that has been introduced to assess bioenergetics and metabolism has also made it possible to determine roles of specific energy production pathways in endothelial health. The Seahorse extracellular flux analysis by Agilent technologies is a state of the art tool that has been more frequently used to evaluate bioenergetics of endothelial cells. This chapter includes details about different assays that can be used to study endothelial cells using the Seahorse analyzer and how interpretation of the results can provide novel insight about endothelial metabolism.

Mixture design of α-pinene, α-terpineol, and 1,8-cineole: A multiobjective response followed by chemometric approaches to optimize the antibacterial effect against various bacteria and antioxidant activity

α-Pinene, α-terpineol, and 1,8-cineole are compounds naturally present in essential oils, although their amounts vary from oil to oil. Although several studies have reported their antibacterial and antioxidant effects, there are few reports on the synergistic or antagonistic effects of their combinations. The objective of this study was to investigate the combined antibacterial effect of these three compounds. To our knowledge, this is the first report on the prediction of their optimal combination using the mixture design approach. The experimental antibacterial activity of the α-pinene, α-terpineol, and 1,8-cineole mixtures depended on the proportion of each compound in the mixture and the target strain, with minimum inhibitory concentrations (MIC) ranging from 0.31 to 1.85 mg/mL. Using the increased simplex-centroid mixture design, the mixture containing 0.33% of each molecule proved to be the most effective against Bacillus cereus and had the lowest MIC values. In addition, α-pinene, α-terpineol, and 1,8-cineole showed significant antioxidant activity against 2,2-picryl-1-hydrazyl radical (DPPH), with IC50 values of 24.53 ± 0.05, 65.63 ± 0.71, and 63.58 ± 0.01 μg/mL, respectively. Statistical planning and the development of utility profiles of the substance mixtures can predict the optimal composition that will exhibit the highest antibacterial activity against B. cereus as well as antioxidant properties. Furthermore, the synergistic effect of the mixtures can contribute significantly to their successful use as natural preservatives in various applications.

Radiation-Induced Changes in Energy Metabolism Result in Mitochondrial Dysfunction in Salivary Glands

Salivary glands are indirectly damaged during radiotherapy for head and neck cancer, resulting in acute and chronic hyposalivation. Current treatments for radiation-induced hyposalivation do not permanently restore function to the gland; therefore, more mechanistic understanding of the damage response is needed to identify therapeutic targets for lasting restoration. Energy metabolism reprogramming has been observed in cancer and wound healing models to provide necessary fuel for cell proliferation; however, there is limited understanding of alterations in energy metabolism reprogramming in tissues that fail to heal. We measured extracellular acidification and oxygen consumption rates, assessed mitochondrial DNA copy number, and tested fuel dependency of irradiated primary salivary acinar cells. Radiation treatment leads to increases in glycolytic flux, oxidative phosphorylation, and ATP production rate at acute and intermediate time points. In contrast, at chronic radiation time points there is a significant decrease in glycolytic flux, oxidative phosphorylation, and ATP production rate. Irradiated salivary glands exhibit significant decreases in spare respiratory capacity and increases in mitochondrial DNA copy number at days 5 and 30 post-treatment, suggesting a mitochondrial dysfunction phenotype. These results elucidate kinetic changes in energy metabolism reprogramming of irradiated salivary glands that may underscore the chronic loss of function phenotype.

The toxicological spectrum of the Bacillus cereus toxin cereulide points towards niche-specific specialisation

Most microbes share their environmental niches with very different forms of life thereby engaging in specialised relationships to enable their persistence. The bacterium Bacillus cereus occurs ubiquitously in the environment with certain strain backgrounds causing foodborne and opportunistic infections in humans. The emetic lineage of B. cereus is capable of producing the toxin cereulide, which evokes emetic illnesses. Although food products favouring the accumulation of cereulide are known, the ecological role of cereulide and the environmental niche of emetic B. cereus remain elusive. To better understand the ecology of cereulide-producing B. cereus, we systematically assayed the toxicological spectrum of cereulide on a variety of organisms belonging to different kingdoms. As cereulide is a potassium ionophore, we further tested the effect of environmental potassium levels on the action of cereulide. We found that adverse effects of cereulide exposure are species-specific, which can be exacerbated with increased environmental potassium. Additionally, we demonstrate that cereulide is produced within an insect cadaver indicating its potential ecological function for a saprophytic lifestyle. Collectively, distinct cereulide susceptibilities of other organisms may reflect its role in enabling competitive niche specialization of emetic B. cereus.

Bacillus cereus Sensu Lato Accelerate Cellular Bioenergetic Metabolism of Human Colorectal Adenocarcinoma Caco-2 Cell Line

How foodborne enterotoxigenic Bacillus cereus rewires energy metabolism during intestinal tract infection is still not understood. In this study, we used the Seahorse XFe technology to simultaneously analyze oxygen consumption and acidification rates to estimate bioenergetic changes in the intestinal Caco-2 cell line after exposure to the B. cereus sensu lato (s.l.) enterotoxin-producing pathotypes, American Type Culture Collection (ATCC) 14579 (836), NVH0391-98 (828), and NVH0075/95 (825). Infection of Caco-2 led to a more energetic phenotype due to increased flux through oxidative phosphorylation and glycolysis. Strain 836 caused the most pronounced effects toward the specific energy phenotype, followed by strains 828 and 825. However, the metabolic potential of Caco-2 cells was most strongly induced by the 828 strain. Furthermore, infected cells manifested an increased adenosine triphosphate (ATP) production rate. Strain 828 caused the highest glycolytic and mitochondrial ATP production rates, followed by the 836 and 825 B. cereus s.l. strains. The glycolytic stress assay showed that strains 828 and 826 slightly increased compensatory glycolysis, providing a better understanding of the pathogenicity of this versatile pathogen. The results of this study underline that extracellular flux measurement can be used to accurately estimate bioenergetic perturbations of Caco-2 cells as a consequence of infection. Our findings enhance our understanding of how intestinal cells adjust their metabolism during infection with B. cereus s.l.

New insights into the combined toxicity of aflatoxin B1 and fumonisin B1 in HepG2 cells using Seahorse respirometry analysis and RNA transcriptome sequencing

Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are widely (co-)detected in food and known for their hepatotoxicity in humans. Still, their combined toxicity needs to be investigated, especially the impact on mitochondria. In our previous work, we examined the effect of short-term exposure to different doses of AFB1, FB1, and their binary mixture (MIX) on the bioenergetic status of HepG2 cells, a well-recognized in vitro model system for studying liver cell function. In the current work, we further investigated the (combined) effect of AFB1 and FB1 on the mitochondrial and glycolytic activity of HepG2 cells using Seahorse respirometry analysis and RNA transcriptome sequencing. The results showed that the co-exposure, especially at high doses, is more toxic due to a more inhibition of all parameters of mitochondrial respiration. However, FB1 contributes more to the MIX effects than AFB1. RNA transcriptome sequencing showed that the p53 signaling pathway, a major orchestrator of mitochondrial apoptosis, was differentially expressed. Moreover, the co-exposure significantly downregulated the genes encoding for Complexes I, II, III, and IV, representing the onset of the suppressed mitochondrial respiration in HepG2 cells.

An Experimental Approach to Address the Functional Relationship between Antioxidant Enzymes and Mitochondrial Respiratory Complexes

Mitochondrial dysfunction and cytosolic oxidative stress are pathological biomarkers interlinked in several chronic diseases and cellular toxicity promoted by high-energy radiation or xenobiotics. Thus, assessing the activities of the mitochondrial redox chain complexes and the cytosolic antioxidant enzymes in the same cell culture system is a valuable approach to addressing the challenge of chronic diseases or unveiling the molecular mechanisms underlying the toxicity of physical and chemical stress agents. The present article gathers the experimental procedures to obtain, from isolated cells, a mitochondria-free cytosolic fraction and a mitochondria-rich fraction. Furthermore, we describe the methodologies to evaluate the activity of the main antioxidant enzymes in the mitochondria-free cytosolic fraction (superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase), and the activity of the individual mitochondrial complexes I, II and IV, as well as the conjugated activity of complexes I-III and complexes II-III in the mitochondria-rich fraction. The protocol to test the citrate synthase activity was also considered and used to normalize complexes. The procedures were optimized within an experimental setup to allow that each condition to be tested only requires sampling of one T-25 flask of cells 2D cultured, as the typical results presented and discussed here.

Cereulide and Emetic Bacillus cereus: Characterizations, Impacts and Public Precautions

Cereulide, which can be produced by Bacillus cereus, is strongly associated with emetic-type food poisoning outbreaks. It is an extremely stable emetic toxin, which is unlikely to be inactivated by food processing. Considering the high toxicity of cereulide, its related hazards raise public concerns. A better understanding of the impact of B. cereus and cereulide is urgently needed to prevent contamination and toxin production, thereby protecting public health. Over the last decade, a wide range of research has been conducted regarding B. cereus and cereulide. Despite this, summarized information highlighting precautions at the public level involving the food industry, consumers and regulators is lacking. Therefore, the aim of the current review is to summarize the available data describing the characterizations and impacts of emetic B. cereus and cereulide; based on this information, precautions at the public level are proposed.

Optical 4D oxygen mapping of microperfused tissue models with tunable in vivo-like 3D oxygen microenvironments

Sufficient and controllable oxygen supply is essential for in vitro 3D cell and tissue culture at high cell densities, which calls for volumetric in situ oxygen analysis methods to quantitatively assess the oxygen distribution. This paper presents a general approach for accurate and precise non-contact 3D mapping of oxygen tension in high cell-density cultures via embedded commercially available oxygen microsensor beads read out by confocal phosphorescence lifetime microscopy (PLIM). Optimal acquisition conditions and data analysis procedures are established and implemented in a publicly available software package. The versatility of the established method is first demonstrated in model-assisted fluidic design of microperfused 3D printed hydrogel culture chips with the aim of full culture oxygenation, and subsequently for monitoring and maintenance of physiologically relevant spatial and temporal oxygen gradients in the 3D printed chips controlled by static or dynamic flow conditions during 3D culture.

Bioenergetic Status of the Intestinal and Hepatic Cells after Short Term Exposure to Fumonisin B1 and Aflatoxin B1

Fumonisin B1 (FB1) and aflatoxin B1 (AFB1) are frequent contaminants of staple foods such as maize. Oral exposure to these toxins poses health hazards by disrupting cellular signaling. However, little is known regarding the multifaced mitochondrial dysfunction-linked toxicity of FB1 and AFB1. Here, we show that after exposure to FB1 and AFB1, mitochondrial respiration significantly decreased by measuring the oxygen consumption rate (OCR), mitochondrial membrane potential (MMP) and reactive oxygen species (ROS). The current work shows that the integrity of mitochondria (MMP and ROS), that is the central component of cell apoptosis, is disrupted by FB1 and AFB1 in undifferentiated Caco-2 and HepG2 cells as in vitro models for human intestine and liver, respectively. It hypothesizes that FB1 and AFB1 could disrupt the mitochondrial electron transport chain (ETC) to induce mitochondrial dysfunction and break the balance of transferring H⁺ between the mitochondrial inner membrane and mitochondrial matrix, however, the proton leak is not increasing and, as a result, ATP synthesis is blocked. At the sub-toxic exposure of 1.0 µg/mL for 24 h, i.e., a viability of 95% in Caco-2 and HepG2 cells, the mitochondrial respiration was, however, stimulated. This suggests that the treated cells could reserve energy for mitochondrial respiration with the exposure of FB1 and AFB1, which could be a survival advantage.

Under-Oil Autonomously Regulated Oxygen Microenvironments: A Goldilocks Principle-Based Approach for Microscale Cell Culture

Oxygen levels in vivo are autonomously regulated by a supply-demand balance, which can be altered in disease states. However, the oxygen levels of in vitro cell culture systems, particularly microscale cell culture, are typically dominated by either supply or demand. Further, the oxygen microenvironment in these systems is rarely monitored or reported. Here, a method to establish and dynamically monitor autonomously regulated oxygen microenvironments (AROM) using an oil overlay in an open microscale cell culture system is presented. Using this method, the oxygen microenvironment is dynamically regulated via the supply-demand balance of the system. Numerical simulation and experimental validation of oxygen transport within multi-liquid-phase, microscale culture systems involving a variety of cell types, including mammalian, fungal, and bacterial cells are presented. Finally, AROM is applied to establish a coculture between cells with disparate oxygen demands-primary intestinal epithelial cells (oxygen consuming) and Bacteroides uniformis (an anaerobic species prevalent in the human gut).

Morphine-induced modulation of Nrf2-antioxidant response element signaling pathway in primary human brain microvascular endothelial cells

Morphine is one of the most potent opioid analgesic used for pain treatment. Morphine action in the central nervous system requires crossing the blood-brain barrier. Due to the controversial relationship between morphine and oxidative stress, the potential pro- or antioxidant effects of morphine in the blood-brain barrier is important to be understood, as oxidative stress could cause its disruption and predispose to neurodegenerative diseases. However, investigation is scarce in human brain endothelial cells. Therefore, the present study evaluated the impact of morphine exposure at three different concentrations (1, 10 and 100 µM) for 24 h and 48 h on primary human brain microvascular endothelial cells. A quantitative data-independent acquisition mass spectrometry strategy was used to analyze proteome modulations. Almost 3000 proteins were quantified of which 217 were reported to be significantly regulated in at least one condition versus untreated control. Pathway enrichment analysis unveiled dysregulation of the Nrf2 pathway involved in oxidative stress response. Seahorse assay underlined mitochondria dysfunctions, which were supported by significant expression modulations of relevant mitochondrial proteins. In conclusion, our study revealed the dysregulation of the Nrf2 pathway and mitochondria dysfunctions after morphine exposure, highlighting a potential redox imbalance in human brain endothelial cells.

Cereulide and Deoxynivalenol Increase LC3 Protein Levels in HepG2 Liver Cells

Food contaminants of bacterial or fungal origin frequently contaminate staple foods to various extents. Among others, the bacterial toxin cereulide (CER) and the mycotoxin deoxynivalenol (DON) co-occur in a mixed diet and are absorbed by the human body. Both toxins exert dis-tinctive mitotoxic potential. As damaged mitochondria are removed via autophagy, mitochondrial and lysosomal toxicity were assessed by applying low doses of single and combined toxins (CER 0.1-50 ng/mL; DON 0.01-5 µg/mL) to HepG2 liver cells. In addition to cytotoxicity assays, RT-qPCR was performed to investigate genes involved in lysosomal biogenesis and autophagy. CER and DON caused significant cytotoxicity on HepG2 cells after 5 and 24 h over a broad concentration range. CER, alone and in combination with DON, increased the transcription of the autophagy related genes coding for the microtubule associated protein 1A/1B light chain 3 (LC3) and sequestome 1 (SQSTM1) as well as LC3 protein expression which was determined using immunocytochemistry. DON increased LC3 protein expression without induction of gene transcription, hence it seems plausible that CER and DON act on different pathways. The results support the hypothesis that CER induces autophagy via the LC3 pathway and damaged mitochondria are therefore eliminated.

Methylglyoxal induces ambience for cancer promotion in HepG2 cells via Warburg effect and promotes glycation

Methylglyoxal (MGO) is a toxic, highly reactive metabolite derived mainly from glucose and amino acids degradation. MGO is also one of the prime precursors for advanced glycation end products formation. The present research was performed to check whether MGO has any role in the promotion of cancer in HepG2 cells. For this, cells were incubated with MGO (50 µM) for 24 h and subjected to various analyses. Aminoguanidine (200 µM) was positive control. The various biochemical and protein expression studies, relevant to the MGO detoxification system, oxidative stress, and glycolysis were performed. MGO caused the reduction of expression of GLO 1 (27%) and GLO 2 (11%) causing weakening of the innate detoxification system. This is followed by an increase of RAGE (95%), AGEs or methylglyoxal adducts. We also observed hypoxia via estimation of oxygen consumption rate and surplus reactive oxygen species (ROS) (24%). To investigate the off-target effect of MGO we checked its effect on glucose transport, and its associated proteins. Glucose uptake was found to increase (15%) significantly with overexpression of GLUT 1 (35%). We also found a significant increase of glycolytic enzymes such as hexokinase II, phosphofructokinase 1, and lactate dehydrogenase along with lactate production. Observation of surplus ROS and enhanced glycolysis led us to check the expression of HIF 1α which is their downstream signaling pathway. Interestingly HIF 1α was found to increase significantly (35%). It is known that enhanced glycolysis and oxidative stress are catalysts for the overexpression of HIF 1α which in turn creates an ambience for the promotion of cancer. Aminoguanidine was able to prevent the adverse effect of MGO partially. This is the first study to show the potential of MGO for the promotion of cancer in the non-tumorigenic HepG2 cells via the Warburg effect and glycation.

Acute Liver Failure after Ingestion of Fried Rice Balls: A Case Series of Bacillus cereus Food Poisonings

Bacillus cereus foodborne intoxications and toxicoinfections are on a rise. Usually, symptoms are self-limiting but occasionally hospitalization is necessary. Severe intoxications with the emetic Bacillus cereus toxin cereulide, which is notably resistant heat and acid during cooking, can cause acute liver failure and encephalopathy. We here present a case series of food poisonings in five immunocompetent adults after ingestion of fried rice balls, which were massively contaminated with Bacillus cereus. The patients developed a broad clinical spectrum, ranging from emesis and diarrhoea to life-threatening acute liver failure and acute tubular necrosis of the kidney in the index patient. In the left-over rice ball, we detected 8 × 10⁶Bacillus cereus colony-forming units/g foodstuff, and cereulide in a concentration of 37 μg/g foodstuff, which is one of the highest cereulide toxin contaminations reported so far from foodborne outbreaks. This report emphasizes the potential biological hazard of contaminated rice meals that are not freshly prepared. It exemplifies the necessity of a multidisciplinary approach in cases of Bacillus cereus associated food poisonings to rapidly establish the diagnosis, to closely monitor critically ill patients, and to provide supportive measures for acute liver failure and—whenever necessary—urgent liver transplantation.

Chronic cereulide exposure causes intestinal inflammation and gut microbiota dysbiosis in mice

Known as a cause of food poisoning, Bacillus cereus (B. cereus) is widespread in nature. Cereulide, the heat-stable and acid-resistant emetic toxin which is produced by some B. cereus strains, is often associated with foodborne outbreaks, and causes acute emetic toxicity at high dosage exposure. However, the toxicological effect and underlying mechanism caused by chronic low-dose cereulide exposure require to be further addressed. In the study, based on mouse model, cereulide exposure (50 μg/kg body weight) for 28 days induced intestinal inflammation, gut microbiota dysbiosis and food intake reduction. According to the cell models, low dose cereulide exposure disrupted the intestinal barrier function and caused intestinal inflammation, which were resulted from endoplasmic reticulum (ER) stress IRE1/XBP1/CHOP pathway activation to induce cell apoptosis and inflammatory cytokines production. For gut microbiota, cereulide decreased the abundances of Lactobacillus and Oscillospira. Furthermore, cereulide disordered the metabolisms of gut microbiota, which exhibited the inhibitions of butyrate and tryptophan. Interestingly, cereulide exposure also inhibited the tryptophan hydroxylase to produce the serotonin in the gut and brain, which might lead to depression-like food intake reduction. Butyrate supplementation (100 mg/kg body weight) significantly reduced intestinal inflammation and serotonin biosynthesis suppression caused by cereulide in mice. In conclusion, chronic cereulide exposure induced ER stress to cause intestinal inflammation, gut microbiota dysbiosis and serotonin biosynthesis suppression. IRE1 could be the therapeutic target and butyrate supplementation is the potential prevention strategy.

Cereulide Exposure Caused Cytopathogenic Damages of Liver and Kidney in Mice

Cereulide is one of the main food-borne toxins for vomiting synthesized by Bacillus cereus, and it widely contaminates meat, eggs, milk, and starchy foods. However, the toxicological effects and mechanisms of the long-time exposure of cereulide in vivo remain unknown. In this study, oral administration of 50 and 200 μg/kg body weight cereulide in the mice for 28 days caused oxidative stress in liver and kidney tissues and induce abnormal expression of inflammatory factors. In pathogenesis, cereulide exposure activated endoplasmic reticulum stress (ER stress) via the pathways of inositol-requiring enzyme 1α (IRE1α)/Xbox binding protein (XBP1) and PRKR-like ER kinase (PERK)/eukaryotic translation initiation factor 2α (eIF2α), and consequently led to the apoptosis and tissue damages in mouse liver and kidney. In vitro, we confirmed that the accumulation of reactive oxygen species (ROS) caused by cereulide is the main factor leading to ER stress in HepaRG and HEK293T cells. Supplementation of sodium butyrate (NaB) inhibited the activations of IRE1α/XBP1 and PERK/eIF2α pathways caused by cereulide exposure in mice, and reduced the cell apoptosis in liver and kidney. In conclusion, this study provides a new insight in understanding the toxicological mechanism and prevention of cereulide exposure.

Suppressed mitochondrial respiration via NOX5-mediated redox imbalance contributes to the antitumor activity of anlotinib in oral squamous cell carcinoma

Anlotinib, a novel multitarget tyrosine kinase inhibitor, has shown promising results in the management of various carcinomas. This study aimed to investigate the antitumor activity of anlotinib in oral squamous cell carcinoma (OSCC) and the underlying molecular mechanism. A retrospective clinical study revealed that anlotinib improved the median progression-free survival (mPFS) and median overall survival (mOS) of patients with recurrent and metastatic (R/M) OSCC, respectively. Functional studies revealed that anlotinib markedly inhibited in vitro proliferation of OSCC cells and impeded in vivo tumor growth of OSCC patient-derived xenograft models. Mechanistically, RNA-sequencing identified that oxidative stress, oxidative phosphorylation and AKT/mTOR signaling were involved in anlotinib-treated OSCC cells. Anlotinib upregulated NADPH oxidase 5 (NOX5) expression, elevated reactive oxygen species (ROS) production, impaired mitochondrial respiration, and promoted apoptosis. Moreover, anlotinb also inhibited phospho-Akt (p-AKT) expression and elevated p-eIF2α expression in OSCC cells. NOX5 knockdown attenuated these inhibitory effects and cytotoxicity in anlotinib-treated OSCC cells. Collectively, we demonstrated that anlotinib monotherapy demonstrated favorable anticancer activity and manageable toxicities in patients with R/M OSCC. The antitumor activity of anlotinib in OSCC may be mainly involved in the suppression of mitochondrial respiration via NOX5-mediated redox imbalance and the AKT/eIF2α pathway.

A novel standalone microfluidic device for local control of oxygen tension for intestinal-bacteria interactions

The intestinal environment is unique because it supports the intestinal epithelial cells under a normal oxygen environment and the microbiota under an anoxic environment. Due to importance of understanding the interactions between the epithelium and the microbiota, there is a strong need for developing representative and simple experimental models. Current approaches do not capture the partitioned oxygen environment, require external anaerobic chambers, or are complex. Another major limitation is that with the solutions that can mimic this oxygen environment, the oxygenation level of the epithelial cells is not known, raising the question whether the cells are hypoxic or not. We report standalone microfluidic devices that form a partitioned oxygen environment without the use of an external anaerobic chamber or oxygen scavengers to coculture intestinal epithelial and bacterial cells. By changing the thickness of the device cover, the oxygen tension in the chamber was modulated. We verified the oxygen levels using several tests: microscale oxygen sensitive sensors which were integrated within the devices, immunostaining of Caco-2 cells to determine hypoxia levels, and genetically encoded bacteria to visualize the growth. Collectively, these methods monitored oxygen concentrations in the devices more comprehensively than previous reports and allowed for control of oxygen tension to match the requirements of both intestinal cells and anaerobic bacteria. Our experimental model is supported by the mathematical model that considered diffusion of oxygen into the top chamber. This allowed us to experimentally determine the oxygen consumption rate of the intestinal epithelial cells under perfusion.

Bacillus cereus food intoxication and toxicoinfection

Bacillus cereus is one of the leading etiological agents of toxin-induced foodborne diseases. Its omnipresence in different environments, spore formation, and its ability to adapt to varying conditions and produce harmful toxins make this pathogen a health hazard that should not be underestimated. Food poisoning by B. cereus can manifest itself as an emetic or diarrheal syndrome. The former is caused by the release of the potent peptide toxin cereulide, whereas the latter is the result of proteinaceous enterotoxins (e.g., hemolysin BL, nonhemolytic enterotoxin, and cytotoxin K). The final harmful effect is not only toxin and strain dependent, but is also affected by the stress responses, accessory virulence factors, and phenotypic properties under extrinsic, intrinsic, and explicit food conditions and host-related environment. Infamous portrait of B. cereus as a foodborne pathogen, as well as a causative agent of nongastrointestinal infections and even nosocomial complications, has inspired vast volumes of multidisciplinary research in food and clinical domains. As a result, extensive original data became available asking for a new, both broad and deep, multifaceted look into the current state-of-the art regarding the role of B. cereus in food safety. In this review, we first provide an overview of the latest knowledge on B. cereus toxins and accessory virulence factors. Second, we describe the novel taxonomy and some of the most pertinent phenotypic characteristics of B. cereus related to food safety. We link these aspects to toxin production, overall pathogenesis, and interactions with its human host. Then we reflect on the prevalence of different toxinotypes in foods opening the scene for epidemiological aspects of B. cereus foodborne diseases and methods available to prevent food poisoning including overview of the different available methods to detect B. cereus and its toxins.

Aclonifen causes developmental abnormalities in zebrafish embryos through mitochondrial dysfunction and oxidative stress

The herbicide aclonifen is commonly used in agriculture. Aclonifen is toxic to experimental animals, causing developmental abnormalities, decreased energy production for survival, and impaired organogenesis. However, no studies have reported the functional defects and toxicity caused by aclonifen in embryonic development. We hypothesized that the mechanism underlying the toxicity of several herbicides in various organisms involves mitochondrial dysfunction, which subsequently promotes genotoxicity, cytotoxicity, and acute organotoxicity. In the present study, we demonstrated that mitochondrial dysfunction during development results in decreased body length, delayed yolk sac absorption, malformed spinal cord, disrupted brain and eye formation, and the activation of apoptosis in zebrafish embryos. Aclonifen induced oxidative stress by elevating the level of reactive oxygen species, causing mitochondrial damage. Likewise, impaired embryonic vascularization can promote cardiovascular disorders. In this study, we characterized the toxicity of aclonifen in a non-target organism. These findings increase our understanding of the toxicological effects of herbicides in unexpected environments.

Assessing Mixture Effects of Cereulide and Deoxynivalenol on Intestinal Barrier Integrity and Uptake in Differentiated Human Caco-2 Cells

The human intestine is regularly exposed to ingested food contaminants, such as fungal and bacterial toxins, which have been described to co-occur in a mixed diet. Thus, it is of utmost importance to understand possible interactions between contaminants of different origin. Hence, we investigated the single and combined effects of one of the most abundant mycotoxins, deoxynivalenol (DON; 0.1 to 10 µg/mL), and the bacterial toxin cereulide (CER; 1 to 100 ng/mL) on differentiated human Caco-2 (C2BBe1) cells cultured in a transwell system. We tested the capacity of the two toxins to alter the intestinal integrity and further investigated the uptake of both compounds and the formation of selected DON metabolites. CER alone (10 and 100 ng/mL) and in combination with DON (10 ng/mL CER with 1 µg/mL DON) was found to alter the barrier function by increasing the transepithelial electrical resistance and the expression of the tight junction protein claudin-4. For the first time, DON-3-sulfate was identified as a metabolite of human intestinal cells in vitro. Moreover, co-incubation of CER and DON led to an altered ratio between DON and DON-3-sulfate. Hence, we conclude that co-exposure to CER and DON may alter the intestinal barrier function and biotransformation of intestinal cells.

The Food Poisoning Toxins of Bacillus cereus

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.

CPNE1 Enhances Colorectal Cancer Cell Growth, Glycolysis, and Drug Resistance Through Regulating the AKT-GLUT1/HK2 Pathway

Introduction

Colorectal cancer (CRC) is a major cause of cancer-related mortality worldwide. Copines-1 (CPNE1) has been shown to be overexpressed in various cancers; however, the role of CPNE1 in CRC remains unknown. Therefore, it is of great importance to elucidate the role of CPNE1 in CRC and its underlying mechanism of action.

Methods

CPNE1 expression in CRC tissues was measured by quantitative real-time PCR and immunohistochemical (IHC) staining. CPNE1 was knocked down (KD) or overexpressed using small inferring RNAs or lentiviral transduction in CRC cells. The proliferation, apoptosis, glycolysis, and mitochondrial respiration of CRC cells were assessed by cell counting kit-8, flow cytometry, and Xfe24 extracellular flux analyzer assays, respectively. The role of CPNE1 in tumor growth and chemoresistance was further confirmed in xenograft and patient-derived tumor xenograft models, respectively.

Results

CPNE1 mRNA and protein were upregulated in CRC tissues. CPNE1 promoted proliferation, inhibited apoptosis, increased mitochondrial respiration, enhanced aerobic glycolysis by activating AKT signaling, upregulated glucose transporter 1 (GLUT1) and hexokinase 2 (HK2), and downregulated the production of cleaved Caspase-3 (c-Caspase 3). CPNE1 also contributed to chemoresistance in CRC cells. CPNE1 KD inhibited tumor growth and increased the sensitivity of tumors to oxaliplatin in vivo.

Conclusion

CPNE1 promotes CRC progression by activating the AKT-GLUT1/HK2 cascade and enhances chemoresistance.

Candida Administration Worsens Uremia-Induced Gut Leakage in Bilateral Nephrectomy Mice, an Impact of Gut Fungi and Organismal Molecules in Uremia

The impact of gut fungi and (1→3)-β-d-glucan (BG), a major fungal cell wall component, on uremia was explored by Candida albicans oral administration in bilateral nephrectomy (BiNx) mice because of the prominence of C. albicans in the human intestine but not in mice. As such, BiNx with Candida administration (BiNx-Candida) enhanced intestinal injury (colon cytokines and apoptosis), gut leakage (fluorescein isothiocyanate [FITC]-dextran assay, endotoxemia, serum BG, and bacteremia), systemic inflammation, and liver injury at 48 h postsurgery compared with non-Candida BiNx mice. Interestingly, uremia-induced enterocyte apoptosis was severe enough for gut translocation of viable bacteria, as indicated by culture positivity for bacteria in blood, mesenteric lymph nodes (MLNs), and other organs, which was more severe in BiNx-Candida than in non-Candida BiNx mice. Candida induced alterations in the gut microbiota of BiNx mice as indicated by (i) the higher fungal burdens in the feces of BiNx-Candida mice than in sham-Candida mice by culture methods and (ii) increased Bacteroides with decreased Firmicutes and reduced bacterial diversity in the feces of BiNx-Candida mice compared with non-Candida BiNx mice by fecal microbiome analysis. In addition, lipopolysaccharide plus BG (LPS+BG), compared with each molecule alone, induced high supernatant cytokine levels, which were enhanced by uremic mouse serum in both hepatocytes (HepG2 cells) and macrophages (RAW264.7 cells). Moreover, LPS+BG, but not each molecule alone, reduced the glycolysis capacity and mitochondrial function in HepG2 cells as determined by extracellular flux analysis. Additionally, a probiotic, Lactobacillus rhamnosus L34 (L34), attenuated disease severity only in BiNx-Candida mice but not in non-Candida BiNx mice, as indicated by liver injury and serum cytokines through the attenuation of gut leakage, the fecal abundance of fungi, and fecal bacterial diversity but not fecal Gram-negative bacteria. In conclusion, Candida enhanced BiNx severity through the worsening of gut leakage and microbiota alterations that resulted in bacteremia, endotoxemia, and glucanemia.IMPORTANCE The impact of fungi in the intestine on acute uremia was demonstrated by the oral administration of Candida albicans in mice with the removal of both kidneys. Because fungi in the mouse intestine are less abundant than in humans, a Candida-administered mouse model has more resemblance to patient conditions. Accordingly, acute uremia, without Candida, induced intestinal mucosal injury, which resulted in the translocation of endotoxin, a major molecule of gut bacteria, from the intestine into blood circulation. In acute uremia with Candida, intestinal injury was more severe due to fungi and the alteration in intestinal bacteria (increased Bacteroides with decreased Firmicutes), leading to the gut translocation of both endotoxin from gut bacteria and (1→3)-β-d-glucan from Candida, which synergistically enhanced systemic inflammation in acute uremia. Both pathogen-associated molecules were delivered to the liver and induced hepatocyte inflammatory responses with a reduced energy production capacity, resulting in acute uremia-induced liver injury. In addition, Lactobacillus rhamnosus attenuated intestinal injury through reduced gut Candida and improved intestinal bacterial conditions.

DhHP-6 ameliorates hepatic oxidative stress and insulin resistance in type 2 diabetes mellitus through the PI3K/AKT and AMPK pathway

Insulin resistance is one major features of type 2 diabetes mellitus (T2DM). Deuterohemin-βAla-His-Thr-Val-Glu-Lys (DhHP-6), a novel microperoxidase mimetic designed and synthesized based on microperoxidase 11 (MP-11), can scavenge reactive oxygen species (ROS) in vivo. In our previous studies, we showed that oral DhHP-6 could reduce blood glucose and improve insulin resistance. To investigate the mechanisms of how DhHP-6 ameliorates oxidative stress and insulin resistance, we established T2DM mouse models and glucosamine-induced HepG2 cell insulin resistance models. The results suggested that DhHP-6 decreased blood glucose, increased antioxidant enzyme activity, and inhibited glycogen synthesis in T2DM mice. In addition, DhHP-6 improved insulin resistance by activating phosphatidylinositol 3-kinase (PI3K)/AKT, and AMP-activated protein kinase (AMPK) pathway in T2DM mice. Furthermore, DhHP-6 also activated PI3K/AKT and AMPK pathway in glucosamine-induced HepG2 cells. However, LY294002 did not completely inhibit AKT phosphorylation, and partially inhibited AMPK phosphorylation, whilst compound C only partially reduced AMPK phosphorylation, and also partially inhibited AKT phosphorylation, suggesting that AKT and AMPK interact to improve insulin resistance. Thus, these data suggest that DhHP-6 attenuates insulin resistance via the PI3K/AKT and AMPK pathway.

Candida Administration Worsens Cecal Ligation and Puncture-Induced Sepsis in Obese Mice Through Gut Dysbiosis Enhanced Systemic Inflammation, Impact of Pathogen-Associated Molecules From Gut Translocation and Saturated Fatty Acid

Obesity induces gut leakage and elevates serum lipopolysaccharide (LPS), a major cell wall component of Gram-negative bacteria, through gut translocation. Because Candida albicans is prominent in human gut but not in mouse, C. albicans, a source of (1→3)-β-D-glucan (BG) in gut contents, was administered in high-fat diet (HFD)–induced obese mice at 1 week before sepsis induction by cecal ligation and puncture (CLP). As such, sepsis in Candida-administered obese mice was more severe than obese mice without Candida as determined by mortality, organ injury (liver and kidney), serum cytokines, gut leakage, endotoxemia, serum BG, and fecal Gram-negative bacteria (microbiome analysis). Mice subjected to CLP and fed a HFD, but not treated with Candida demonstrated a similar mortality to non-obese mice with more severe gut leakage and higher serum cytokines. In vitro experiments demonstrated that LPS plus BG (LPS + BG) induced higher supernatant cytokines from hepatocytes (HepG2) and macrophages (RAW264.7), compared with the activation by each molecule alone, and were amplified by palmitic acid, a representative saturated fatty acid. The energy production capacity of HepG2 cells was also decreased by LPS + BG compared with LPS alone as evaluated by extracellular flux analysis. However, Lactobacillus rhamnosus L34 (L34) improved sepsis, regardless of Candida administration, through the attenuation of gut leakage and gut dysbiosis. In conclusion, an impact of gut Candida was demonstrated by Candida pretreatment in obese mice that worsened sepsis through (1) gut dysbiosis–induced gut leakage and (2) amplified systemic inflammation due to LPS, BG, and saturated fatty acid.

A systematic review of mitochondrial abnormalities in myalgic encephalomyelitis/chronic fatigue syndrome/systemic exertion intolerance disease

Background

Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or Systemic Exertion Intolerance Disease (SEID) present with a constellation of symptoms including debilitating fatigue that is unrelieved by rest. The pathomechanisms underlying this illness are not fully understood and the search for a biomarker continues, mitochondrial aberrations have been suggested as a possible candidate. The aim of this systematic review is to collate and appraise current literature on mitochondrial changes in ME/CFS/SEID patients compared to healthy controls.

Methods

Embase, PubMed, Scopus and Medline (EBSCO host) were systematically searched for articles assessing mitochondrial changes in ME/CFS/SEID patients compared to healthy controls published between January 1995 and February 2020. The list of articles was further refined using specific inclusion and exclusion criteria. Quality and bias were measured using the Joanna Briggs Institute Critical Appraisal Checklist for Case Control Studies.

Results

Nineteen studies were included in this review. The included studies investigated mitochondrial structural and functional differences in ME/CFS/SEID patients compared with healthy controls. Outcomes addressed by the papers include changes in mitochondrial structure, deoxyribonucleic acid/ribonucleic acid, respiratory function, metabolites, and coenzymes.

Conclusion

Based on the included articles in the review it is difficult to establish the role of mitochondria in the pathomechanisms of ME/CFS/SEID due to inconsistencies across the studies. Future well-designed studies using the same ME/CFS/SEID diagnostic criteria and analysis methods are required to determine possible mitochondrial involvement in the pathomechanisms of ME/CFS/SEID.

Delta-9-tetrahydrocannabinol disrupts mitochondrial function and attenuates syncytialization in human placental BeWo cells

The psychoactive component in cannabis, delta-9-tetrahydrocannabinol, can restrict fetal growth and development. Delta-9-tetrahydrocannabinol has been shown to negatively impact cellular proliferation and target organelles like the mitochondria resulting in reduced cellular respiration. In the placenta, mitochondrial dysfunction leading to oxidative stress prevents proper placental development and function. A key element of placental development is the proliferation and fusion of cytotrophoblasts to form the syncytium that comprises the materno-fetal interface. The impact of delta-9-tetrahydrocannabinol on this process is not well understood. To elucidate the nature of the mitochondrial dysfunction and its consequences on trophoblast fusion, we treated undifferentiated and differentiated BeWo human trophoblast cells, with 20 µM delta-9-tetrahydrocannabinol for 48 hr. At this concentration, delta-9-tetrahydrocannabinol on BeWo cells reduced the expression of markers involved in syncytialization and mitochondrial dynamics, but had no effect on cell viability. Delta-9-tetrahydrocannabinol significantly attenuated the process of syncytialization and induced oxidative stress responses in BeWo cells. Importantly, delta-9-tetrahydrocannabinol also caused a reduction in the secretion of human chorionic gonadotropin and the production of human placental lactogen and insulin growth factor 2, three hormones known to be important in facilitating fetal growth. Furthermore, we also demonstrate that delta-9-tetrahydrocannabinol attenuated mitochondrial respiration, depleted adenosine triphosphate, and reduced mitochondrial membrane potential. These changes were also associated with an increase in cellular reactive oxygen species, and the expression of stress responsive chaperones, HSP60 and HSP70. These findings have important implications for understanding the role of delta-9-tetrahydrocannabinol-induced mitochondrial injury and the role this might play in compromising human pregnancies.

6-Amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol Derivatives as Efficacious Mitochondrial Uncouplers in STAM Mouse Model of Nonalcoholic Steatohepatitis

Small molecule mitochondrial uncouplers have recently garnered great interest for their potential in treating nonalcoholic steatohepatitis (NASH). In this study, we report the structure-activity relationship profiling of a 6-amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol core, which utilizes the hydroxy moiety as the proton transporter across the mitochondrial inner membrane. We demonstrate that a wide array of substituents is tolerated with this novel scaffold that increased cellular metabolic rates in vitro using changes in oxygen consumption rate as a readout. In particular, compound SHS4121705 (12i) displayed an EC50 of 4.3 μM in L6 myoblast cells and excellent oral bioavailability and liver exposure in mice. In the STAM mouse model of NASH, administration of 12i at 25 mg kg-1 day-1 lowered liver triglyceride levels and improved liver markers such as alanine aminotransferase, NAFLD activity score, and fibrosis. Importantly, no changes in body temperature or food intake were observed. As potential treatment of NASH, mitochondrial uncouplers show promise for future development.

Advanced Methods for Detection of Bacillus cereus and Its Pathogenic Factors

Bacillus cereus is an opportunistic foodborne pathogen causing food intoxication and infectious diseases. Different toxins and pathogenic factors are responsible for diarrheal syndrome, like nonhemolytic enterotoxin Nhe, hemolytic enterotoxin Hbl, enterotoxin FM and cytotoxin K, while emetic syndrome is caused by the depsipeptide cereulide toxin. The traditional method of B. cereus detection is based on the bacterial culturing onto selective agars and cells enumeration. In addition, molecular and chemical methods are proposed for toxin gene profiling, toxin quantification and strain screening for defined virulence factors. Finally, some advanced biosensors such as phage-based, cell-based, immunosensors and DNA biosensors have been elaborated to enable affordable, sensitive, user-friendly and rapid detection of specific B. cereus strains. This review intends to both illustrate the state of the B. cereus diagnostic field and to highlight additional research that is still at the development level.

Combinatory effects of cereulide and deoxynivalenol on in vitro cell viability and inflammation of human Caco-2 cells

Deoxynivalenol (DON), one of the most abundant mycotoxins in cereal products, was recently detected with other mycotoxins and the emetic bacterial toxin cereulide (CER) in maize porridge. Within a cereal-based diet, co-exposure to these toxins is likely, hence raising the question of combinatory toxicological effects. While the toxicological evaluation of DON has quite progressed, consequences of chronic, low-dose CER exposure are still insufficiently explored. Information about the combinatory toxicological effects of these toxins is lacking. In the present study, we investigated how CER (0.1-100 ng/mL) and DON (0.01-10 µg/mL) alone and in a constant ratio of 1:100 (CER:DON) affect the cytotoxicity and immune response of differentiated human intestinal Caco-2 cells. While DON alone reduced cell viability only in the highest concentration (10 µg/mL), CER caused severe cytotoxicity upon prolonged incubation (starting from 10 ng/mL after 24 h and 48 h, 2.5 ng/mL and higher after 72 h). After 72 h, synergistic effects were observed at 2.5 ng/mL CER and 0.25 µg/mL DON. Different endpoints of inflammation were investigated in interleukin-1β-stimulated Caco-2 cells. Notably, DON-induced interleukin-8 transcription and secretion were diminished by the presence of 10 and 25 ng/mL CER after short-term (5 h) incubation, indicating immunosuppressive properties. We hypothesise that habitual consumption of cereal-based foods co-contaminated with CER and DON may cause synergistic cytotoxic effects and an altered immune response in the human intestine. Therefore, further research concerning effects of co-occurring bacterial toxins and mycotoxins on the impairment of intestinal barrier integrity, intestinal inflammation and the promotion of malnutrition is needed.

Parkin-mediated mitophagy and autophagy flux disruption in cellular models of MERRF syndrome

Mitochondrial diseases are considered rare genetic disorders characterized by defects in oxidative phosphorylation (OXPHOS). They can be provoked by mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). MERRF (Myoclonic Epilepsy with Ragged-Red Fibers) syndrome is one of the most frequent mitochondrial diseases, principally caused by the m.8344A>G mutation in mtDNA, which affects the translation of all mtDNA-encoded proteins and therefore impairs mitochondrial function. In the present work, we evaluated autophagy and mitophagy flux in transmitochondrial cybrids and fibroblasts derived from a MERRF patient, reporting that Parkin-mediated mitophagy is increased in MERRF cell cultures. Our results suggest that supplementation with coenzyme Q₁₀ (CoQ), a component of the electron transport chain (ETC) and lipid antioxidant, prevents Parkin translocation to the mitochondria. In addition, CoQ acts as an enhancer of autophagy and mitophagy flux, which partially improves cell pathophysiology. The significance of Parkin-mediated mitophagy in cell survival was evaluated by silencing the expression of Parkin in MERRF cybrids. Our results show that mitophagy acts as a cell survival mechanism in mutant cells. To confirm these results in one of the main affected cell types in MERRF syndrome, mutant induced neurons (iNs) were generated by direct reprogramming of patients-derived skin fibroblasts. The treatment of MERRF iNs with Guttaquinon CoQ₁₀ (GuttaQ), a water-soluble derivative of CoQ, revealed a significant improvement in cell bioenergetics. These results indicate that iNs, along with fibroblasts and cybrids, can be utilized as reliable cellular models to shed light on disease pathomechanisms as well as for drug screening.

Predominant Mycotoxins, Pathogenesis, Control Measures, and Detection Methods in Fermented Pastes

Fermented pastes are some of the most popular traditional products in China. Many studies reported a strong possibility that fermented pastes promote exposure to mycotoxins, including aflatoxins, ochratoxins, and cereulide, which were proven to be carcinogenic and neurotoxic to humans. The primary mechanism of pathogenicity is by inhibiting protein synthesis and inducing oxidative stress using cytochrome P450 (CYP) enzymes. The level of mycotoxin production is dependent on the pre-harvest or post-harvest stage. It is possible to implement methods to control mycotoxins by using appropriate antagonistic microorganisms, such as Aspergillus niger, Lactobacillus plantarum, and Saccharomyces cerevisiae isolated from ordinary foods. Also, drying products as soon as possible to avoid condensation or moisture absorption in order to reduce the water activity to lower than 0.82 during storage is also effective. Furthermore, organic acid treatment during the soaking process reduces toxins by more than 90%. Some novel detection technologies based on magnetic adsorption, aptamer probes, and molecular-based methods were applied to rapidly and accurately detect mycotoxins in fermented pastes.

An in vitro intestinal platform with a self-sustaining oxygen gradient to study the human gut/microbiome interface

An oxygen gradient formed along the length of colonic crypts supports stem-cell proliferation at the normoxic crypt base while supporting obligate anaerobe growth in the anoxic colonic lumen. Primary human colonic epithelial cells derived from human gastrointestinal stem cells were cultured within a device possessing materials of tailored oxygen permeability to produce an oxygen-depleted luminal (0.8% ± 0.1% O2) and oxygen-rich basal (11.1% ± 0.5% O2) compartment. This oxygen difference created a stable oxygen gradient across the colonic epithelial cells which remained viable and properly polarized. Facultative and obligate anaerobes Lactobacillus rhamnosus, Bifidobacterium adolescentis, and Clostridium difficile grew readily within the luminal compartment. When formed along the length of an in vitro crypt, the oxygen gradient facilitated cell compartmentalization within the crypt by enhancing confinement of the proliferative cells to the crypt base. This platform provides a simple system to create a physiological oxygen gradient across an intestinal mimic while simultaneously supporting anaerobe co-culture.

Simulated biological fluid exposure changes nanoceria's surface properties but not its biological response

Nanoscale cerium dioxide (nanoceria) has industrial applications, capitalizing on its catalytic, abrasive, and energy storage properties. It auto-catalytically cycles between Ce³⁺ and Ce⁴⁺, giving it pro-and anti-oxidative properties. The latter mediates beneficial effects in models of diseases that have oxidative stress/inflammation components. Engineered nanoparticles become coated after body fluid exposure, creating a corona, which can greatly influence their fate and effects. Very little has been reported about nanoceria surface changes and biological effects after pulmonary or gastrointestinal fluid exposure. The study objective was to address the hypothesis that simulated biological fluid (SBF) exposure changes nanoceria's surface properties and biological activity. This was investigated by measuring the physicochemical properties of nanoceria with a citric acid coating (size; morphology; crystal structure; surface elemental composition, charge, and functional groups; and weight) before and after exposure to simulated lung, gastric, and intestinal fluids. SBF-exposed nanoceria biological effect was assessed as A549 or Caco-2 cell resazurin metabolism and mitochondrial oxygen consumption rate. SBF exposure resulted in loss or overcoating of nanoceria's surface citrate, greater nanoceria agglomeration, deposition of some SBF components on nanoceria's surface, and small changes in its zeta potential. The engineered nanoceria and SBF-exposed nanoceria produced no statistically significant changes in cell viability or cellular oxygen consumption rates.

Why be serious about emetic Bacillus cereus: Cereulide production and industrial challenges

Cereulide, a potent toxin produced by Bacillus cereus, is a small, highly heat- and acid-resistant depsipeptide toxin, which confronts food industry with several challenges. Due to the ubiquitous presence of B. cereus in the environment, this opportunistic pathogen can enter food production and processing at almost any stage. Although the bacteria itself might be removed during food processing, the cereulide toxin will most likely not be destroyed or inactivated by these processes. Because of the high toxicity of cereulide and the high incidence rates often observed in connection with foodborne outbreaks, the understanding of the mechanisms of toxin production as well as accurate data on contamination sources and factors promoting toxin formation are urgently needed to prevent contamination and toxin production in food production processes. Over the last decade, considerable progress had been made on the understanding of cereulide toxin biosynthesis in emetic B. cereus, but an overview of current knowledge on this toxin with regards to food industry perspective is lacking. Thus, we aim in this work to summarize data available on extrinsic parameters acting on cereulide toxin synthesis in emetic B. cereus and to discuss the food industry specific challenges related to this toxin. Furthermore, we emphasize how identification of the cardinals in food production processes can lead to novel effective strategies for prevention of toxin formation in the food processing chain and could contribute to the improvement of existing HACCP studies.

First Insights Into Within Host Translocation of the Bacillus cereus Toxin Cereulide Using a Porcine Model

Bacillus cereus is a gram-positive pathogen mainly known to evoke two types of foodborne poisonings. The diarrheal syndrome is caused by enterotoxins produced during growth in the intestine. In contrast, the emetic type is caused by the dodecadepsipeptide cereulide pre-formed in food. Usually, both diseases are self-limiting but occasionally more severe forms, including fatal ones, are reported. Since the mechanisms of cereulide toxin uptake and translocation within the body as well as the mechanism of its toxic action are still unknown, we used a porcine model to investigate the uptake, routes of excretion and distribution of cereulide within the host. Pigs were orally challenged with cereulide using single doses of 10-150 μg cereulide kg^-1 body weight to study acute effects or using daily doses of 10 μg cereulide kg^-1 body weight administered for 7 days to investigate effects of longtime, chronic exposure. Our study showed that part of cereulide ingested with food is rapidly excreted with feces while part of the cereulide toxin is absorbed, passes through membranes and is distributed within the body. Results from the chronic trial indicate bioaccumulation of cereulide in certain tissues and organs, such as kidney, liver, muscles and fat tissues. Beside its detection in various tissues and organs, our study also demonstrated that cereulide is able to cross the blood-brain-barrier, which may partially explain the cerebral effects reported from human intoxication cases. The neurobehavioral symptoms, such as seizures and lethargy, observed in our porcine model resemble those reported from human food borne intoxications. The rapid onset of these symptoms indicates direct effects of cereulide on the central nervous system (CNS), which warrant further research. The porcine model presented here might be useful to study the specific neurobiological effect in detail. Furthermore, our study revealed that typical diagnostic specimens used in human medicine, such as blood samples and urine, are not suitable for diagnostics of food borne cereulide intoxications. Instead, screening of fecal samples by SIDA-LC-MS may represent a simple and non-invasive method for detection of cereulide intoxications in clinical settings as well as in foodborne outbreak situations.