The effects of orchidectomy on toxicological responses to dietary ochratoxin A in Wistar rats

Renal Apoptosis in Male Rats Induced by Extensive Dietary Exposure to Ochratoxins

During the 70 years since the Balkan endemic nephropathy was recognised, failure to make a universal diagnostic cause continues for some critical researchers. Claims for cause by toxic molecules from microorganisms and/or plants are difficult to verify experimentally in retrospect, partly because no lifetime human experimentation is possible and partly since no experimental source is a convincing model. Apoptosis as a primary step in human nuclear decline has been a source of experiments for many years. Now, one has been used, which employs the detection of abnormal nuclear hydroxyls by using an Abcam histology protocol. Recent access to a few human tissues diagnosed for the Balkan nephropathy has enabled preliminary exploration to publish some positive human manifestations of apoptosis. Parallel use and positive findings have also now illustrated applications to experimental rats' kidneys after daily dietary exposure to ochratoxin A in lifetime experiments. Focus on renal cortical nephrons and their nuclei reveals a TUNEL-stained pattern with intensity linked to many months of the sub-clinical ochratoxin dietary exposure. The pattern survives long after exposure, but where experimental rats have internally developed cancer did not arise outside the kidney. Our experimental rat findings could not attribute the mechanism for the very different human urothelial tumours to traces of dietary ochratoxin A, but the present study encourages the exploration of more archived Balkan nephropathy renal cases to predict the focal urothelial origin of early tumours.

Membrane Receptor-Mediated Disruption of Cellular Homeostasis: Changes in Intracellular Signaling Pathways Increase the Toxicity of Ochratoxin A

Organisms maintain their cellular homeostatic balance by interacting with their environment through the use of their cell surface receptors. Membrane based receptors such as the transforming growth factor β receptor (TGFR), the prolactin receptor (PRLR), and hepatocyte growth factor receptor (HGFR), along with their associated signaling cascade, play significant roles in retaining cellular homeostasis. While these receptors and related signaling pathways are essential for health of cell and organism, their dysregulation can lead to imbalance in cell function with severe pathological conditions such as cell death or cancer. Ochratoxin A (OTA) can disrupt cellular homeostasis by altering expression levels of these receptors and/or receptor-associated intracellular downstream signaling modulators and/or pattern and levels of their phosphorylation/dephosphorylation. Recent studies have shown that the activity of the TGFR, the PRLR, and HGFR and their associated signaling cascades change upon OTA exposure. A critical evaluation of these findings suggests that while increased activity of the HGFR and TGFR signaling pathways leads to an increase in cell survival and fibrosis, decreased activity of the PRLR signaling pathway leads to tissue damage. This review explores the roles of these receptors in OTA-related pathologies and effects on cellular homeostasis.

Optimised Fermentation Production of Radiolabelled Ochratoxin A by Aspergillus ochraceus with Maximum 14C in the Pentaketide Moiety for Exploring Its Rat Renal Toxicology

In the context of the mysterious Balkan endemic nephropathy of the 1900s, and the discovery in the 1960s of the potent mycotoxin ochratoxin A, experimental research projects sought to explore any inter-relationship. Experimental lifetime administration of the toxin to male rats had revealed renal DNA adducts with the toxin, correlated with renal tumours, confirmation of which required molecular evidence. Consequently, production of 14C-ochratoxin A of a high specific radioactivity was required, practical biosynthetic detail of which had not previously been published. A fermentation study of Aspergillus ochraceous was carried out during 2002 for a European project, to select for the production of high-quality 14C-ochratoxin A, necessarily exploring for the maximum diversion of 14C-sodium acetate into the pentaketide portion of mycotoxin. Experimentation necessarily had to optimise the competitive context of fungal growth dynamics and addition of the biosynthetic precursor in the early days of shaken-flask fermentation before adding the radiolabelled precursor. From optimal fermentation, 50 mg of the 14C ochratoxin A was supplied within a European project for DNA adduct experimentation, but that proved negative as subsequently published. Experimental description of the radiolabelled ochratoxin A production was later made in a doctoral thesis, but is first publicised here. Further review of the literature reveals an explanation for the published failure to confirm rat DNA/ochratoxin A adduct formation, for which further experimentation is now recommended.

A one-generation reproductive toxicity study of the mycotoxin ochratoxin A in Fischer rats

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium molds. Grain-based foods account for most human dietary exposures to OTA. OTA is a teratogen, but its reproductive and developmental effects are poorly understood. A one-generation reproductive toxicity study was conducted with groups of 16 male and 16 female Fischer rats exposed to 0, 0.026, 0.064, 0.16, 0.4 or 1.0 mg OTA/kg in diet. Dams exposed to 1.0 mg OTA/kg diet had statistically significant F1 pup losses between implantation and postnatal day (PND 4). Delays in preputial separation (PPS) and vaginal opening (VO) were indicative of delayed puberty in F1 rats. Mild renal lesions in nursing pups indicated that exposure prior to weaning impacted the kidneys. The developing kidney was more susceptible to OTA than the adult kidney. Significant increases in multi-oocyte follicles (MOFs) and proportional changes in resting and growing follicles were observed in F1 female ovaries. Plasma testosterone was reduced in F0 males, and there were negative effects on sperm quality in F0 and F1 male rats. The results confirm that continuous dietary exposure to OTA causes post-implantation fetotoxicity in dams, and renal and reproductive toxicity in their male and female offspring.

Protective Effect of Astaxanthin on Ochratoxin A-Induced Kidney Injury to Mice by Regulating Oxidative Stress-Related NRF2/KEAP1 Pathway

The present study aimed to investigate the effects of astaxanthin (ASX) on ochratoxin A (OTA)-induced renal oxidative stress and its mechanism of action. Serum kidney markers, histomorphology, ultrastructural observation, and oxidative stress indicators were assessed. Meanwhile, quantitative real-time reverse transcription PCR and western blotting detection of NRF2 (encoding nuclear factor, erythroid 2 like) and members of the NRF2/KEAP1 signaling pathway (KEAP1 (encoding Kelch-like ECH-associated protein), NQO1 (encoding NAD(P)H quinone dehydrogenase), HO-1 (encoding heme oxygenase 1), γ-GCS (gamma-glutamylcysteine synthetase), and GSH-Px (glutathione peroxidase 1)) were performed. Compared with the control group, the OTA-treated group showed significantly increased levels of serum UA (uric acid) and BUN (blood urea nitrogen), tubular epithelial cells were swollen and degenerated, and the levels of antioxidant enzymes decreased significantly, and the expression of NRF2 (cytoplasm), NQO1, HO-1, γ-GCS, and GSH-Px decreased significantly. More importantly, after ASX pretreatment, compared with the OTA group, serum markers were decreased, epithelial cells appeared normal; the expression of antioxidant enzymes increased significantly, NQO1, HO-1, γ-GCS and GSH-Px levels increased significantly, and ASX promoted the transfer of NRF2 from the cytoplasm to the nucleus. These results highlight the protective ability of ASX in renal injury caused by OTA exposure, and provide theoretical support for ASX’s role in other mycotoxin-induced damage.

Role of mycotoxins in the pathobiology of autism: A first evidence

Objectives: Gene-environment interaction is an emerging hypothesis to expound not only the autism pathogenesis but also the increased incidence of neurodevelopmental disorders (such as autistic spectrum disorder, attention-deficit, hyperactivity disorder). Among xenobiotics, mycotoxins are worldwide contaminants of food that provoke toxicological effects, crucially resembling several symptoms associated with autism such as oxidative stress, intestinal permeability, and inflammation. Here, we focused on a group of mycotoxins to test their role in the manifestation of autism, try to explain their mechanism of action, and discuss possible preventive and therapeutic interventions. Methods: Autistic children (n = 52) and healthy children [n = 58 (31 siblings and 27 unrelated subjects)] were recruited and body fluids and clinical data collected. The diagnosis of autism was made according to DSM V criteria, then with GMDS 0-2, WPPSI, and ADOS. Ochratoxin A (OTA), gliotoxin, zearalenone, and sphingosine/sphinganine ratio were determined by LC analysis in sera and urines. Statistical analysis was performed by the Wilcoxon Rank Sum (Mann-Whitney) test and Spearman test. Results: By comparing the results of autistic patients with those of unrelated controls, a significant association was found for OTA levels in urines (P = 0.0002) and sera (P = 0.0017), and also comparing patients with siblings and unrelated controls together (P = 0.0081). Discussion: Our results are the first describing a possible role of OTA in the pathobiology of autism. Recalling the male prevalence of ASD (male/female = 4-5/1), it is noted that, in animal models, OTA exerts its neurotoxicity especially in males. Moreover, in vitro, OTA increases microRNA-132 that is dysregulated in autistic patients and involved in reciprocal regulation of the autism-related genes MeCP2 and PTEN. A personalized diet coupled with probiotic administration, especially OTA adsorbing Lactobacillus, could ameliorate autistic symptoms in OTA-positive patients.

Diabetogenic Effects of Ochratoxin A in Female Rats

In this study, the diabetogenic effects of long term Ochratoxin A (OTA) administration in rats were investigated, and its role in the etiology of diabetes mellitus (DM) was examined utilizing 42 female Wistar rats for these purposes. The rats were divided into three different study and control groups according to the duration of the OTA administration. The rats received 45 μg OTA daily in their feed for 6, 9 and 24 weeks, respectively. Three control groups were also used for the same time periods. Blood and pancreatic tissue samples were collected during the necropsy at the end of the 6, 9 and 24 weeks. The plasma values of insulin, glucagon and glucose were determined for the study and control groups. Pancreatic lesions were evaluated via histopathological examination and insulin and glucagon expression in these lesions was subsequently determined using immunohistochemical methods. Statistically significant decreases in insulin levels were observed, in contrast to increases in blood glucagon and glucose levels. Histopathological examinations revealed slight to moderate degeneration in Langerhans islet cells in all OTA-treated groups. Immunohistochemistry of pancreatic tissue revealed decreased insulin and increased glucagon expression. This study demonstrated that OTA may cause pancreatic damage in the Langerhans islet and predispose rats to DM.

Evaluation of renal in vitro models used in ochratoxin research

Ochratoxin A (OTA) induces renal carcinomas in rodents with a specific localisation in the S3 segment of proximal tubules and distinct early severe tissue alterations, which have been observed also in other species. Pronounced species- and sex-specific differences in toxicity occur and similar effects cannot be excluded in humans, however precise mechanism(s) remain elusive until today. In such cases, the use of in vitro models for mechanistic investigations can be very useful; in particular if a non-genotoxic mechanism of cancer formation is assumed which include cytotoxic effects. However, potential genotoxic mechanisms can also be investigated in vitro. A crucial issue of in vitro research is the choice of the appropriate cell model. Apparently, the cellular target of OTA is the renal proximal tubular cell; therefore cells from this tissue area are the most reasonable model. Furthermore, cells from affected species should be used and can be compared to cells of human origin. Another important parameter is whether to use primary cultures or to choose a cell line from the huge variety of cell lines available. In any case, important characteristics and quality controls need to be verified beforehand. Therefore, this review discusses the renal in vitro models that have been used for the investigation of renal ochratoxin toxicity. In particular, we discuss the choice of the models and the essential parameters making them suitable models for ochratoxin research together with exemplary results from this research. Furthermore, new promising models such as hTERT-immortalised cells and 3D-cultures are briefly discussed.

Development of sandwich dot-ELISA for specific detection of Ochratoxin A and its application on to contaminated cereal grains originating from India

In the present study, generation and characterization of a highly specific monoclonal antibody (mAb) against Ochratoxin A (OTA) was undertaken. The generated mAb was further used to develop a simple, fast, and sensitive sandwich dot-ELISA (s-dot ELISA) method for detection of OTA from contaminated food grain samples. The limit of detection (LOD) of the developed enzyme-linked immunosorbent assay (ELISA) method was determined as 5.0 ng/mL of OTA. Developed method was more specific toward OTA and no cross reactivity was observed with the other tested mycotoxins such as deoxynivalenol, fumonisin B1, or aflatoxin B1. To assess the utility and reliability of the developed method, several field samples of maize, wheat and rice (n = 195) collected from different geographical regions of southern Karnataka region of India were evaluated for the OTA occurrence. Seventy two out of 195 samples (19 maize, 38 wheat, and 15 rice) were found to be contaminated by OTA by s-dot ELISA. The assay results were further co-evaluated with conventional analytical high-performance liquid chromatography (HPLC) method. Results of the s-dot ELISA are in concordance with HPLC except for three samples that were negative for OTA presence by s-dot ELISA but found positive by HPLC. Although positive by HPLC, the amount of OTA in the three samples was found to be lesser than the accepted levels (>5 μg/kg) of OTA presence in cereals. Therefore, in conclusion, the developed s-dot ELISA is a better alternative for routine cereal based food and feed analysis in diagnostic labs to check the presence of OTA over existing conventional culture based, tedious analytical methods.