Gliotoxin induces caspase-dependent neurite degeneration and calpain-mediated general cytotoxicity in differentiated human neuroblastoma SH-SY5Y cells

Development of an in vitro neuroblastoma 3D model and its application for sterigmatocystin-induced cytotoxicity testing

Given the increasing importance of establishing better risk assessments for mycotoxins, novel in vitro tools for the evaluation of their toxicity are mandatory. In this study, an in vitro 3D spheroid model from SH-SY5Y cells, a human neuroblastoma cell line, was developed, optimized and characterized to test the cytotoxic effects caused by the mycotoxin sterigmatocystin (STE). STE induced a concentration- and time-dependent cell viability decrease in spheroids. Spheroids displayed cell disaggregation after STE exposure, increasing in a dose-dependent manner and over time. STE also induced apoptosis as confirmed by immunofluorescence staining and Western blot. Following the decreased proliferation and increased apoptosis, STE cytostasis effects were observed by migration assays both in 2D and 3D cell culture. Increased ROS generation, as well as DNA damage were also observed. Taken together, these data highlight the cytotoxic properties of STE and suggest that cell culture models play a pivotal role in the toxicological risk assessment of mycotoxins. The evaluation of cytotoxicity in spheroids (3D) rather than monolayer cultures (2D) is expected to more accurately reflect in vivo-like cell behaviour.

The role of mycotoxins in neurodegenerative diseases: current state of the art and future perspectives of research

Mycotoxins are fungal metabolites that can cause various diseases in humans and animals. The adverse health effects of mycotoxins such as liver failure, immune deficiency, and cancer are well-described. However, growing evidence suggests an additional link between these fungal metabolites and neurodegenerative diseases. Despite the wealth of these initial reports, reliable conclusions are still constrained by limited access to human patients and availability of suitable cell or animal model systems. This review summarizes knowledge on mycotoxins associated with neurodegenerative diseases and the assumed underlying pathophysiological mechanisms. The limitations of the common in vivo and in vitro experiments to identify the role of mycotoxins in neurotoxicity and thereby in neurodegenerative diseases are elucidated and possible future perspectives to further evolve this research field are presented.

Role of quercetin on sterigmatocystin-induced oxidative stress-mediated toxicity

Oxidative stress appears to be a common trigger for many of the effects associated with the exposure to various mycotoxins, including sterigmatocystin (STE). However, studies to alleviate STE toxicity through the use of natural antioxidants are sparsely reported in literature. In the present study, the cytoprotective effect of quercetin (QUE) was tested in SH-SY5Y cells against STE-induced oxidative stress and cytotoxicity. The MTT assay revealed that STE decreased cell viability, whereas pre-treatment of cells with QUE restored it. The QUE was also found to counteract STE-induced ROS generation and decrease STE-induced up-regulation of the expression of the stress-inducible enzymes HO-1 and NOS-2. Pre-treatment with QUE also prevented STE-induced nuclear translocation of NF-κB, as measured by immunofluorescence. Finally, considering the key role played by NF-κB in the regulation of inflammation, the effect of STE on the pro-inflammatory cytokines TNF-α and IL-6 expression was evaluated. Our results showed the down-regulation of TNF-α and IL-6 following STE exposure, suggesting a negative immunomodulatory effect of STE. In QUE pre-treated samples, TNF-α and IL-6 were significantly further reduced, indicating the anti-inflammatory role of QUE. The results of the present study demonstrate for the first time that QUE exerts a cytoprotective role in STE-induced toxicity.

Sterigmatocystin-induced DNA damage triggers cell-cycle arrest via MAPK in human neuroblastoma cells

Sterigmatocystin (STE) is a common mycotoxin found in food and feed. Many studies showed that STE is genotoxic. However, up to now, the potential genotoxicity of STE on human neuronal system remains unknown. In this study, we explored the effect of STE on DNA damage and cell-cycle progression on human neuroblastoma SH-SY5Y cells exposed to various concentrations of STE (0.78, 1.56 and 3.12 µM) for 24 h. The results indicated that STE exposure induced DNA damage, as evidenced by DNA comet tails formation and increased γH2AX foci. Additionally, genotoxicity was confirmed by micronuclei (MN) analysis. Furthermore, we found that STE exposure led to cell-cycle arrest at the S and the G₂/M phase. Considering the important role played by MAPK and p53 signaling pathways in cell-cycle arrest, we explored their potential involvement in STE-induced cell-cycle arrest by using specific inhibitors. The inhibition of JNK and ERK resulted to attenuate S and G₂/M arrest, whereas the inhibition of p38 and p53 attenuated only STE-induced S phase arrest. In conclusion, the present study demonstrates that STE induced DNA damage and triggered MAPK and p53 pathways activation, resulting in cell-cycle arrest at the S and the G₂/M phase.

Time and space-resolved quantification of plasma membrane sialylation for measurements of cell function and neurotoxicity

While there are many methods to quantify the synthesis, localization, and pool sizes of proteins and DNA during physiological responses and toxicological stress, only few approaches allow following the fate of carbohydrates. One of them is metabolic glycoengineering (MGE), which makes use of chemically modified sugars (CMS) that enter the cellular biosynthesis pathways leading to glycoproteins and glycolipids. The CMS can subsequently be coupled (via bio-orthogonal chemical reactions) to tags that are quantifiable by microscopic imaging. We asked here, whether MGE can be used in a quantitative and time-resolved way to study neuronal glycoprotein synthesis and its impairment. We focused on the detection of sialic acid (Sia), by feeding human neurons the biosynthetic precursor N-acetyl-mannosamine, modified by an azide tag. Using this system, we identified non-toxic conditions that allowed live cell labeling with high spatial and temporal resolution, as well as the quantification of cell surface Sia. Using combinations of immunostaining, chromatography, and western blotting, we quantified the percentage of cellular label incorporation and effects on glycoproteins such as polysialylated neural cell adhesion molecule. A specific imaging algorithm was used to quantify Sia incorporation into neuronal projections, as potential measure of complex cell function in toxicological studies. When various toxicants were studied, we identified a subgroup (mitochondrial respiration inhibitors) that affected neurite glycan levels several hours before any other viability parameter was affected. The MGE-based neurotoxicity assay, thus allowed the identification of subtle impairments of neurochemical function with very high sensitivity.

Gliotoxin Aggravates Experimental Autoimmune Encephalomyelitis by Triggering Neuroinflammation

Gliotoxin (GTX) is the major and the most potent mycotoxin that is secreted by Aspergillus fumigatus, which is capable of injuring and killing microglial cells, astrocytes, and oligodendrocytes. During the last years, studies with patients and experimental models of multiple sclerosis (MS), which is an autoimmune disease of the central nervous system (CNS), suggested that fungal infections are among the possible initiators or aggravators of this pathology. The deleterious effect can occur through a direct interaction of the fungus with the CNS or by the toxin release from a non-neurological site. In the present work, we investigated the effect of GTX on experimental autoimmune encephalomyelitis (EAE) development. Female C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein and then intraperitoneally injected with three doses of GTX (1 mg/kg b.w., each) on days 4, 7, and 10. GTX aggravated clinical symptoms of the disease in a dose-dependent way and this outcome was concomitant with an increased neuroinflammation. CNS analyses revealed that GTX locally increased the relative expression of inflammatory genes and the cytokine production. Our results indicate that GTX administered in a non-neuronal site was able to increase neuroinflammation in EAE. Other mycotoxins could also be deleterious to many neurological diseases by similar mechanisms.

Binding of mycotoxins to proteins involved in neuronal plasticity: a combined in silico/wet investigation

We have applied a combined computational procedure based on inverse and direct docking in order to identify putative protein targets of a panel of mycotoxins and xenobiotic compounds that can contaminate food and that are known to have several detrimental effects on human health. This procedure allowed us to identify a panel of human proteins as possible targets for aflatoxins, gliotoxin, ochratoxin A and deoxynivalenol. Steady-state fluorescence and microscale thermophoresis experiments allowed us to confirm the binding of some of these mycotoxins to acetylcholinesterase and X-linked neuroligin 4, two proteins involved in synapse activity and, particularly for the second protein, neuronal plasticity and development. Considering the possible involvement of X-linked neuroligin 4 in the etiopathogenesis of autism spectrum syndrome, this finding opens up a new avenue to explore the hypothetical role of these xenobiotic compounds in the onset of this pathology.

Potential anti-HPV and related cancer agents from marine resources: an overview

Recently, the studies on the prevention and treatment of human papillomavirus (HPV) which is closely related to the cervical cancer and other genital diseases are attracting more and more attention all over the world. Marine-derived polysaccharides and other bioactive compounds have been shown to possess a variety of anti-HPV and related cancer activities. This paper will review the recent progress in research on the potential anti-HPV and related cancer agents from marine resources. In particular, it will provide an update on the anti-HPV actions of heparinoid polysaccharides and bioactive compounds present in marine organisms, as well as the therapeutic vaccines relating to marine organisms. In addition, the possible mechanisms of anti-HPV actions of marine bioactive compounds and their potential for therapeutic application will also be summarized in detail.

Fungal metabolites with anticancer activity

Covering: 1964 to 2013. Natural products from bacteria and plants have played a leading role in cancer drug discovery resulting in a large number of clinically useful agents. In contrast, the investigations of fungal metabolites and their derivatives have not led to a clinical cancer drug in spite of significant research efforts revealing a large number of fungi-derived natural products with promising anticancer activity. Many of these natural products have displayed notable in vitro growth-inhibitory properties in human cancer cell lines and select compounds have been demonstrated to provide therapeutic benefits in mouse models of human cancer. Many of these compounds are expected to enter human clinical trials in the near future. The present review discusses the reported sources, structures and biochemical studies aimed at the elucidation of the anticancer potential of these promising fungal metabolites.

Gliotoxin isolated from marine fungus Aspergillus sp. induces apoptosis of human cervical cancer and chondrosarcoma cells

Gliotoxin, a secondary metabolite produced by marine fungus Aspergillus sp., possesses various biological activities including anticancer activity. However, the mechanism underlying gliotoxin-induced cytotoxicity on human cervical cancer (Hela) and human chondrosarcoma (SW1353) cells remains unclear. In this study, we focused on the effect of gliotoxin induction on apoptosis, the activating expressions of caspase family enzymes in the cells. Apoptotic cell levels were measured through DAPI and Annexin V/Propidium Iodide (PI) double staining analysis. The apoptotic protein expression of Bcl-2 and caspase family was detected by Western blot in Hela and SW1353 cells. Our results showed that gliotoxin treatment inhibited cell proliferation and induced significant morphological changes. Gliotoxin induced apoptosis was further confirmed by DNA fragmentation, chromatin condensation and disrupted mitochondrial membrane potential. Gliotoxin-induced activation of caspase-3, caspase-8 and caspase-9, down-regulation of Bcl-2, up-regulation of Bax and cytochromec (cyt c) release showed evidence for the gliotoxin activity on apoptosis. These findings suggest that gliotoxin isolated from marine fungus Aspergillus sp. induced apoptosis in Hela and SW1353 cells via the mitochondrial pathway followed by downstream events leading to apoptotic mode of cell death.

High fidelity neuronal networks formed by plasma masking with a bilayer membrane: analysis of neurodegenerative and neuroprotective processes

Spatially defined neuronal networks have great potential to be used in a wide spectrum of neurobiology assays. We present an original technique for the precise and reproducible formation of neuronal networks. A PDMS membrane comprising through-holes aligned with interconnecting microchannels was used during oxygen plasma etching to dry mask a protein rejecting poly(ethylene glycol) (PEG) adlayer. Patterns were faithfully replicated to produce an oxidized interconnected array pattern which supported protein adsorption. Differentiated human SH-SY5Y neuron-like cells adhered to the array nodes with the micron-scale interconnecting tracks guiding neurite outgrowth to produce neuronal connections and establish a network. A 2.0 μm track width was optimal for high-level network formation and node compliance. These spatially standardized neuronal networks were used to analyse the dynamics of acrylamide-induced neurite degeneration and the protective effects of co-treatment with calpeptin or brain derived neurotrophic factor (BDNF).

Discrete responses of myenteric neurons to structural and functional damage by neurotoxins in vitro

Damage to the enteric nervous system is implicated in human disease and animal models of inflammatory bowel disease, diabetes, and Parkinson's disease, but the mechanism of death and the response of surviving neurons are poorly understood. We explored this in a coculture model of myenteric neurons, glia, and smooth muscle during exposure to the established or potential neurotoxins botulinum A, hydrogen peroxide, and acrylamide. Neuronal survival, axonal degeneration and regeneration, and neurotransmitter release were assessed during acute exposure (0-24 h) to neurotoxin and subsequent recovery (96-144 h). Unique and selective responses to each neurotoxin were found with acrylamide (0.5-2.0 mM) causing a 30% decrease in axon number without neuronal loss, whereas hydrogen peroxide (1-200 microM) caused a parallel loss in both axon and neuron number. Immunoblotting identified the loss of synaptic vesicle proteins that paralleled axon damage and was associated with marked suppression of depolarization-induced release of acetylcholine (ACh). The caspase inhibitor zVAD, but not DEVD, significantly prevented neuronal death, implying a largely caspase-3/7-independent mechanism of apoptotic death that was supported by staining for annexin V and cleaved caspase-3. In contrast, botulinum A (2 microg/ml) caused a 40% decrease in ACh release without effect on neuronal survival or axon structure. By 96 h after exposure to acrylamide or hydrogen peroxide, axon number was restored to or even surpassed the level of time-matched controls, regardless of partial neuronal loss, but ACh release remained markedly suppressed. Neural responses to toxic factors are initially unique but then converge upon robust axonal regeneration, whereas neurotransmitter release is both vulnerable to damage and slow to recover.

Comparison of an Automated Pattern Analysis Machine Vision Time-lapse System with Traditional Endpoint Measurements in the Analysis of Cell Growth and Cytotoxicity

Machine vision is an application of computer vision. It both collects visual information and interprets the images. Although the machine obviously does not ‘see’ in the same sense that humans do, it is possible to acquire visual information and to create programmes to identify relevant image features in an effective and consistent manner. Machine vision is widely applied in industrial automation, but here we describe how we have used it to monitor and interpret data from cell cultures. The machine vision system used (Cell-IQ) consisted of an inbuilt atmosphere-controlled incubator, where cell culture plates were placed during the test. Artificial intelligence (AI) software, which uses machine vision technology, took care of the follow-up analysis of cellular morphological changes. Basic endpoint and staining methods to evaluate the condition of the cells, were conducted in parallel to the machine vision analysis. The results showed that the automated system for pattern analysis of morphological changes yielded comparable results to those obtained by conventional methods. The inbuilt software analysis offers a promising way of evaluating cell growth and various cell phases. The continuous follow-up and label-free analysis, as well as the possibility of measuring multiple parameters simultaneously from the same cell population, were major advantages of this system, as compared to conventional endpoint measurement methodology.

Glucose promotes caspase-dependent delayed cell death after a transient episode of oxygen and glucose deprivation in SH-SY5Y cells

Brain ischemia causes neuronal cell death by several mechanisms involving necrotic and apoptotic processes. The contributions of each process depend on conditions such as the severity and duration of ischemia, and the availability of ATP. We examined whether glucose affected the development of apoptosis after transient ischemia, and whether this was sensitive to caspase inhibition. Retinoic acid-differentiated SH-SY5Y human neuroblastoma cells were subjected to oxygen and glucose deprivation for 15 h followed by various periods of reoxygenation in either the presence or absence of glucose. Oxygen and glucose deprivation induced cell death in the hours following reoxygenation, as detected by propidium iodide staining. At the end of the period of oxygen and glucose deprivation, both cytochrome c and apoptosis-inducing factor translocated from mitochondria to cytosol. Reoxygenation in the presence of glucose accelerated cell death, and enhanced caspase-3 activity and apoptosis. The glucose-dependent increase in apoptosis was prevented by treatment with the caspase inhibitor zVAD-fmk, but not with calpeptin, a calpain inhibitor. Nevertheless, both zVAD-fmk and calpeptin decreased cell death in the glucose-treated group. ATP levels dropped dramatically after oxygen and glucose deprivation, but recovered steadily thereafter, and were significantly higher at 6 h of reoxygenation in the glucose-treated group. This indicates that energy recovery may promote the glucose-dependent cell death. We conclude that glucose favours the development of caspase-dependent apoptosis during reoxygenation following oxygen and glucose deprivation.