Search

Zearalenone (ZEA) is a mycotoxin commonly found in contaminated livestock feed and human food with levels in the range of ppb and low ppm. It was hypothesized that ZEA, an endocrine disruptor, could affect puberty and early pregnancy. To test this hypothesis, newly weaned (3 weeks old) C57BL/6J female mice were exposed to 0, 0.002, 4, 10, and 40 ppm ZEA and 0.05 ppm diethylstilbestrol (positive control) in phytoestrogen-free AIN-93G diet. Females exposed to 10 and 40 ppm ZEA diets showed earlier onset of vaginal opening. Those treated with 40 ppm ZEA diet also had earlier first copulation plug and irregular estrous cyclicity. At 8 weeks old, all females were mated with untreated stud males on AIN-93G diet during mating. Treatment resumed upon identification of a vaginal plug on gestation day 0.5 (D0.5). Embryo implantation was assessed on D4.5. Exposure to 40 ppm ZEA diet resulted in reduced percentage of plugged mice with implantation sites, distended uterine appearance, and retained expression of progesterone receptor in D4.5 uterine epithelium. To determine the exposure timing and mechanisms of disrupted embryo implantation, four groups of females were fed with 0 or 40 ppm ZEA diets during premating (weaning to mating) and postmating (D0.5-D4.5), respectively. Premating exposure to 40 ppm ZEA diet reduced fertilization rate, whereas postmating exposure to 40 ppm ZEA diet delayed embryo transport and preimplantation embryo development, which subsequently affected embryo implantation. These data demonstrate that postweaning exposure to dietary ZEA can promote premature onset of puberty and disrupt early pregnancy events.

Consumption of deoxynivalenol (DON), a trichothecene mycotoxin known to commonly contaminate grain-based foods, suppresses growth of experimental animals, thus raising concerns over its potential to adversely affect young children. Although this growth impairment is believed to result from anorexia, the initiating mechanisms for appetite suppression remain unknown. Here, we tested the hypothesis that DON induces the release of satiety hormones and that this response corresponds to the toxin's anorectic action. Acute ip exposure to DON had no effect on plasma glucagon-like peptide-1, leptin, amylin, pancreatic polypeptide, gastric inhibitory peptide, or ghrelin; however, the toxin was found to robustly elevate peptide YY (PYY) and cholecystokinin (CCK). Specifically, ip exposure to DON at 1 and 5mg/kg bw induced PYY by up to 2.5-fold and CCK by up to 4.1-fold. These responses peaked within 15-120 min and lasted up to 120 min (CCK) and 240 min (PPY), corresponding with depressed rates of food intake. Direct administration of exogenous PYY or CCK similarly caused reduced food intake. Food intake experiments using the NPY2 receptor antagonist BIIE0246 and the CCK1A receptor antagonist devazepide, individually, suggested that PYY mediated DON-induced anorexia but CCK did not. Orolingual exposure to DON induced plasma PYY and CCK elevation and anorexia comparable with that observed for ip exposure. Taken together, these findings suggest that PYY might be one critical mediator of DON-induced anorexia and, ultimately, growth suppression.

Ochratoxin A (OTA) is a mycotoxin often found in cereals as a contaminant, and it is known to cause severe nephrotoxicity in animals and humans. There have been several investigations studying the mode of action of this toxicant, suggesting inhibition of protein synthesis, formation of DNA adducts, and provocation of DNA single-strand breaks as a result of oxidative stress, but little is known about the transcriptional alterations underlying OTA-derived nephrotoxicity so far. We carried out DNA microarray analyses to assess OTA-specific expression profiles in vivo and in vitro. Cultures of primary rat proximal tubular cells and male Wistar rats were treated with a low dose (5 microM and 1 mg/kg, respectively) or a high dose (12.5 microM and 10 mg/kg, respectively) of OTA for 24 or 72 h. Microarray experiments were carried out after dual fluorescent labeling of sample cDNA, and data analysis was performed utilizing different statistical methods. Validity of selected microarray data was confirmed by quantitative real-time PCR. We were able to demonstrate that microarray data derived from our proximal tubule cell (PTC) culture model were highly comparable to the in vivo situation. Marked treatment-specific transcriptional changes were detected for genes involved in DNA damage response and apoptosis (upregulation of GADD 153, GADD 45, annexin V), response to oxidative stress (differential expression of hypoxia-inducible factor 1 and catalase), and inflammatory reactions (upregulation of alpha 2 macroglobulin, ceruloplasmin, and cathepsin S). We conclude that our results provide a molecular basis for interpretation of OTA-induced nephrotoxicity.

In order to evaluate the tumorigenic potential of kojic acid (KA), used as a food additive for preventing enzymatic browning of crustaceans and a cosmetic agent for the purpose of skin whitening, heterozygous p53-deficient CBA [p53(+/-)] mice, which are recognized as useful for detecting genotoxic carcinogens, and wild-type littermates [p53(+/+) mice] were fed diet containing 0, 1.5, and 3% KA for 26 weeks. KA induced diffuse hypertrophy and hyperplasia of thyroid follicular epithelial cells with decreased serum thyroxine levels in both p53 (+/-) and p53 (+/+) mice, but caused no thyroid tumors. In the liver, the incidence of altered hepatocellular foci was significantly increased at 1.5 and 3% in p 53(+/-) and 1.5% in p53 (+/+) mice, and that of hepatocellular adenomas was increased at 1.5 and 3% in p 53(+/-) and 3% in p53 (+/+) mice. p53 (+/-) mice thus appeared to be more susceptible in terms of the tumorigenic dose of KA with a greater prevalence of hepatic proliferative lesions. The results of the present study indicate tumorigenic potential of KA in the liver, but not thyroid follicular epithelial cells in CBA mice and a contribution of genotoxicity on hepatocellular tumor development cannot be ruled out.

These studies determined (1) the time course for sphingoid base elevation in the small intestines, liver, and kidney of mice following a single 25 mg/kg body weight (bw) oral dose (high dose) of fumonisin B(1) (FB(1)), (2) the minimum threshold dose of FB(1) that would prolong the elevated sphingoid base concentration in kidney following the single high dose, and (3) the importance of the balance between the rate of sphingoid base biosynthesis and degradation in the persistence of sphingoid base accumulation. Following the high dose of FB(1), there was an increase in sphinganine in intestinal cells and liver that peaked at 4 to 12 h and declined to near the control level by 48 h. In kidney, sphinganine peaked at 6-12 h but remained elevated until 72 h, approaching control levels at 96-120 h. Oral administration of 0.03 mg FB(1)/kg bw (low dose) for 5 days had no effect on the sphingoid bases in kidney. However, following an initial high dose, daily administration of the low dose prolonged the elevation in kidney sphinganine compared to mice receiving a single high dose. Thus, a single exposure to a high dose of FB(1) followed by daily exposure at low levels will prolong the elevation of sphinganine in kidney. In cultured renal cells FB(1) was rapidly eliminated, but elevated sphinganine was persistent. This persistence in renal cells was rapidly reversed in the presence of the serine palmitoyltransferase inhibitor (ISP-1), indicating that the persistence was due to differences in the rates of sphinganine biosynthesis and degradation. The in vivo persistence in kidney may be due to similar differences.

Secalonic acid D (SAD), a teratogenic mycotoxin, induces cleft palate (CP) in the offspring of exposed mice by inhibiting palatal shelf growth. Since reduced proliferation, increased apoptosis, and/or decreased extracellular matrix (ECM) synthesis of palatal mesenchymal cells (PMC) can all contribute to smaller shelf size, the hypothesis that teratogenically relevant concentrations (0 to 120 microg/ml) of SAD will have adverse effects on one or more of these cellular processes was tested, using primary murine PMC cultures. Exposure to SAD resulted in significant and dose-dependent decreases in mesenchymal cell number, uptake of (3)H-thymidine, and expression of proliferating cell nuclear antigen (PCNA). Trypan blue dye exclusion assay, however, revealed significant cell death only at higher doses, suggesting that the decrease in cell number at lower (more realistic) doses is likely a consequence of reduced cell proliferation and not cell death. Further, negative results in the DNA fragmentation analysis following SAD exposure suggested that cell death caused by higher levels of SAD was unrelated to apoptosis. Similarly, results of (3)H-glucosamine uptake assay indicated inhibitory effect of SAD on accumulation of hyaluronic acid (HA) or sulfated glycosaminoglycans (sGAG) only at the highest dose tested. Also, SAD affected neither extracellular nor cell-associated fibronectin expression at any dose tested. Taken together, these data suggest that the pathogenesis of CP by SAD is likely a result of a reduction in the size of the palatal shelf caused by SAD-induced inhibition of mesenchymal cell proliferation.

The effects of prenatal rubratoxin-B (RB) exposure on 8 behavioral parameters in JCL:ICR mice were assessed. Pregnant mice were injected intraperitoneally with 0.1 or 0.2 mg/kg/day of RB dissolved in propylene glycol water solution on days 7-9 (Group A) or 10-12 (Group B) of gestation. Controls received the vehicle similarly on days 7-12 of gestation. Before weaning, the offspring of both sexes were examined to test their the surface righting reflex (5 days of age), cliff avoidance response (6 days), negative geotaxis response (7 days), and swimming development (8, 10, and 12 days). After weaning, male animals were examined using the rotarod test (6 weeks of age), the open-field test (7 weeks), the shuttle-box-avoidance-learning test (9 weeks), and the water E-maze test (10 weeks). The preweanling offspring in the 0.2 mg/kg-B group showed significantly lower success rates and longer response times than controls in the cliff-avoidance response. In swimming development, the offspring in the 0.2 mg/kg B group had significantly lower scores than controls for swimming angle at 10 and 12 days of age. The avoidance learning of the mice in all RB-exposed A and B groups was significantly poorer than that of controls. These results indicate that prenatal exposure to RB produced a delay of early response development and impaired learning ability in the offspring of mice exposed to RB during middle pregnancy.

Fumonisin B(1) is the most toxic and commonly occurring form of a group of mycotoxins that alter sphingolipid biosynthesis and induce leukoencephalomalacia in horses and pulmonary edema in pigs. Purified fumonisin B(1) (1 mg/kg, iv, daily) increased serum sphinganine and sphingosine concentrations and decreased cardiovascular function in pigs within 5 days. We therefore examined whether the same dosage schedule of fumonisin B(1) produced a similar effect in calves. Ten milk-fed male Holstein calves were instrumented to obtain blood and cardiovascular measurements. Treated calves (n = 5) were administered purified fumonisin B(1) at 1 mg/kg, iv, daily for 7 days and controls (n = 5) were administered 10 ml 0.9% NaCl, iv, daily. Each calf was euthanized on day 7. In treated calves, serum sphinganine concentration increased from day 3 onward (day 7, 0.237 +/- 0.388 micromol/l; baseline, 0.010 +/- 0.007 micromol/l; mean +/- SD), whereas, serum sphingosine concentration was unchanged (day 7, 0.044 +/- 0.065 micromol/l; baseline, 0.021 +/- 0.025 micromol/l). Heart rate, cardiac output, stroke volume, mean arterial pressure, mean pulmonary artery pressure, pulmonary artery wedge pressure, central venous pressure, plasma volume, base-apex electrocardiogram, arterial Po(2), and systemic oxygen delivery were unchanged in treated and control calves. Fumonisin-treated calves developed metabolic acidosis (arterial blood pH, 7.27 +/- 0.11; base excess, -9.1 +/- 7.6 mEq/l), but all survived for 7 days. We conclude that calves are more resistant to fumonisin B(1) cardiovascular toxicity than pigs.

Fumonisins are a group of mycotoxins that alter sphingolipid biosynthesis and induce leukoencephalomalacia in horses and pulmonary edema in pigs. Experimental administration of fumonisin induces hepatotoxicity in all species, including cattle, as well as nephrotoxicity in rats, rabbits, and sheep. We investigated the hepatotoxicity and nephrotoxicity of fumonisin B(1) to calves. Ten milk-fed male Holstein calves aged 7 to 14 days were instrumented to obtain blood and urine. Treated calves (n = 5) were administered fumonisin B(1) at 1 mg/kg, iv, daily and controls (n = 5) 10 ml 0.9% NaCl, iv, daily until euthanized on day 7. Fumonisin B(1)-treated calves were lethargic and had decreased appetite from day 4 onward, serum biochemical evidence of severe liver and bile duct injury, and impaired hepatic function. Treated calves also had biochemical evidence of renal injury that functionally involved the proximal convoluted tubules. Sphinganine and sphingosine concentrations in liver, kidney, lung, heart, and skeletal muscle were increased in treated calves. Sphinganine, but not sphingosine, concentration was increased in brains of treated calves. In fumonisin B(1)-treated calves, hepatic lesions were characterized by disorganized hepatic cords, varying severity of hepatocyte apoptosis, hepatocyte proliferation, and proliferation of bile ductular cells. Renal lesions in treated calves consisted of vacuolar change, apoptosis, karyomegaly, and proliferation of proximal renal tubular cells, as well as dilation of proximal renal tubules, which contained cellular debris and protein. This is the first report of fumonisin B(1)-induced renal injury and organ sphingolipid alterations in cattle.