Transplacental transfer of melamine

Prenatal cyanuric acid exposure disrupts cognitive flexibility and mGluR1-mediated hippocampal long-term depression in male rats

Cyanuric acid is one of the most widely used classes of industrial chemicals and is now well known as food adulterant and contaminant in pet food and infant formula. Previously, it was reported that animals prenatally exposed to cyanuric acid showed neurotoxic effects that impaired memory consolidating and suppressed long-term potentiation (LTP) in the hippocampus. However, it is not clear if prenatal exposure to cyanuric acid induces deficits in reversal learning and long-term depression (LTD), which is required for the developmental reorganization of synaptic circuits and updating learned behaviors. Here, pregnant rats were i.p. injected with cyanuric acid (20 mg/kg) during the whole of gestation, and male offspring were selected to examine the levels of hippocampal mGluR1 and mGluR2/3 in young adulthood. The LTD at the Schaffer collateral-CA1 pathway was induced by low-frequency stimulation (LFS) and recorded. Reversal learning and hippocampus-dependent learning strategy were tested in Morris-water maze (MWM) and T-maze tasks, respectively. To further confirm the potential mechanism, selective agonists of mGluR1 and mGluR2/3 and antagonists of mGluR were intra-hippocampal infused before behavioral and neuronal recording. We found the levels of alkaline phosphatase were markedly increased in the maternal placenta and fetal brain following prenatal exposure. The expression of mGluR1 but not mGluR2/3 was significantly decreased and mGluR1-mediated LTD was selectively weakened. Prenatal cyanuric acid impaired reversal learning ability, without changing place learning strategy. The mGluR1 agonist could effectively enhance LFS-induced LTD and mitigate reversal learning deficits. Meanwhile, the reductions in the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPAR)-mediated spontaneous excitatory postsynaptic currents (sEPSCs) amplitude and frequency of cyanuric acid offspring were simultaneously alleviated by mGluR1 agonist infusions. Therefore, the results indicate the cognitive and synaptic impairments induced by prenatal cyanuric acid exposure are attributed to the disruption of the hippocampal mGluR1 signaling. Our findings provided the first evidence for the deteriorated effects of cyanuric acid on synaptic depression and advanced cognitive performance.

Prenatal cyanuric acid exposure depresses hippocampal synaptic plasticity and induces spatial learning and memory deficits

The infant and fetus may be exposed to cyanuric acid (CA) via several different routes into the diet or milk product as well as deliberate contamination. Previous findings indicated chronic CA treatment caused neurotransmission and synaptic impairment in the early developing hippocampus. This study was designed to characterize the effects of different doses (10 mg/kg, 20 mg/kg and 40 mg/kg) of CA exposure on the developing fetus. Pregnant rats were intraperitoneally exposed to CA during the entire period of gestation and male offspring were selected for water maze task, neural recording and N-methyl-d-aspartate (NMDA) receptor detection around the eighth postnatal week. We found that CA exposure impaired the learning and memory function in a dose-dependent manner. The paired-pulse ratio (PPR) and GluN2A-dependent long-term potentiation (LTP) at the Schaffer collateral-CA1 pathway were affected in CA-exposed rats. Remarkably, hippocampal levels of NMDA-GluN2A, but not NMDA-GluN2B, were significantly decreased. Meanwhile, the spine density of hippocampal CA1 neurons was not altered by the CA exposure. Our findings are consistent with the hypothesis that CA treatment during the prenatal period produces deficits in spatial cognition by disrupting hippocampal synaptic function.

FT-IR fingerprinting as an Analytical tool for determination of Melamine leaching from Melamine tablewares and their Biological implications

In recent years Melamine is upgraded as a type three carcinogen. It is a sorry fact that still; people are in the fantasy mode and abaft the melamine tableware as they are a good piece of decorative material which sets dining an opulent look. The present study focuses on the determination of melamine leaching from melamine tablewares. The food stimulants culled for this study are conventional Indian cuisines. FT-IR is used as an analytical tool to determine the leaching of melamine from melamine diners. The present study reveals melamine leaching when hot food articles are in contact with melamine wares. Microwave heating is unsuitable for melamine tablewares. This is the first report in India, on the leaching of melamine from melamine tablewares. Calf thymus (ct) DNA is added to the samples and the extent of DNA damage in vitro is analyzed by Comet assay (also called Single cell gel electrophoresis). The results from comet assay portray significant DNA damage with the treated samples. This is a vigilance study that helps the mundane man to avoid such decorative materials and to voluntarily move to our traditional dining culture.

Development of analytical method of melamine in placenta from pregnant women by isotope-dilution liquid chromatography/tandem mass spectrometry

RATIONALE

Melamine is ubiquitously present in our daily life. It has a known effect on the kidneys, but it may also adversely affect the reproduction system. We have developed an analytical method for measuring melamine levels in maternal placenta and correlated these levels with melamine concentrations in urine, a necessary step in finding out if melamine might cross the placenta and enter the circulation of the fetus.

METHODS

We used liquid-liquid extraction, clean up by solid-phase extraction (SPE), and isotope-dilution liquid chromatography/tandem mass spectrometry (LC/MS/MS) to measure melamine in placenta specimens. The results of this method were assessed for linearity, limits of quantitation (LOQs), and intra- and inter-assay precision as well as accuracy, matrix effect, and recovery rate.

RESULTS

Calibration curves indicated good linearity (r >0.995) over concentrations ranging from 5 to 500 ng/mL in placenta specimens, intra- and inter-assay precision from 0.89% to 27.07%, and accuracy from 92.4% to123.5%. Recovery ranged from 63.9 to 83.9%, and the LOQ was 5 ng/mL in placenta (0.2 g). Placental melamine levels ranged from 7.87 to19.64 ng/mL, all detectable (n = 8). Pregnant women with higher levels of urinary melamine had higher placenta melamine levels than those with non-detectable urinary melamine, though the results were not significantly different (p = 0.149, n = 4 in each group).

CONCLUSIONS

The results of this study suggest that pregnant women were exposed to low doses of melamine in their daily lives as measured in urine samples and placenta specimens. It is unclear whether placenta melamine concentrations can better represent long-term exposure than urine or whether melamine in the uterus can enter the fetus via this route.

Activities of metabolizing enzymes in human placenta

In addition to the transfer across the placenta, placenta displays hormonal and xenobiotic metabolism, as well as enzymatic defense against oxidative stress. We analyzed aromatase (CYP19A1), uridine 5'-diphospho-glucuronyltransferase (UGT), glutathione-S-transferase (GST) and catalase (CAT) activities in over 70 placentas from nonsmokers stored at -80 °C from former perfusion studies. A wide interindividual variation in all activities was found. Longterm storage at -80 °C did not affect the activities. Ethoxyresorufin-O-deethylase (EROD, CYP1A1) was not detected in any of the studied placentas perfused with chemicals. Several compounds in placental perfusion changed statistically significantly the enzyme activities in placental tissue. Melamine and nicotine increased CYP19A1, melamine increased UGT and GST, PhIP with ethanol decreased CYP19A1 and increased GST, and PhIP with buprenorphine decreased CAT. Antipyrine in 100 μg/ml also changed the studied enzyme activities, but not statistically significantly. Because antipyrine is a reference compound in placental perfusions, its potential effects must be taken into account in human placental perfusion. Enzyme activities deserve further studies as biomarkers of placental toxicity. Finally, enzyme activities deserve further studies as biomarkers of placental toxicity.

Extracellular vesicles generated by placental tissues ex vivo: A transport system for immune mediators and growth factors

PROBLEM

To study the mechanisms of placenta function and the role of extracellular vesicles (EVs) in pregnancy, it is necessary to develop an ex vivo system that retains placental cytoarchitecture and the primary metabolic aspects, in particular the release of EVs and soluble factors. Here, we developed such a system and investigated the pattern of secretion of cytokines, growth factors, and extracellular vesicles by placental villous and amnion tissues ex vivo.

METHODS OF STUDY

Placental villous and amnion explants were cultured for 2 weeks at the air/liquid interface and their morphology and the released cytokines and EVs were analyzed. Cytokines were analyzed with multiplexed bead assays, and individual EVs were analyzed with recently developed techniques that involved EV capture with magnetic nanoparticles coupled to anti-EV antibodies and flow cytometry.

RESULTS

Ex vivo tissues (i) remained viable and preserved their cytoarchitecture; (ii) maintained secretion of cytokines and growth factors; (iii) released EVs of syncytiotrophoblast and amnion epithelial cell origins that contain cytokines and growth factors.

CONCLUSION

A system of ex vivo placental villous and amnion tissues can be used as an adequate model to study placenta metabolic activity in normal and complicated pregnancies, in particular to characterize EVs by their surface markers and by encapsulated proteins. Establishment and benchmarking the placenta ex vivo system may provide new insight in the functional status of this organ in various placental disorders, particularly regarding the release of EVs and cytokines. Such EVs may have a prognostic value for pregnancy complications.

Melamine, beyond the kidney: A ubiquitous endocrine disruptor and neurotoxicant?

Melamine is commonly used in a variety of consumer products such as furniture, dining ware, and food utensils. The chemical infamously gained worldwide attention by its illegal addition to a variety of foodstuffs in order to falsify protein content, which led to serious, sometimes fatal, health impacts in children and pets. This resulted in a large amount of published primary studies and reviews of the impacts of melamine exposure on kidney function. However, a growing body of literature suggests that melamine may have impacts beyond renal dysfunction. We conducted a scoping review of this literature which yielded more than 40 studies with human, animal, and in vitro findings. Neurological impacts, reproductive function, and anthropometric outcomes were identified as possible candidates for systematic review based on evidence stream and replication of endpoints. The results of this analysis provide a basis for prioritizing future research on health impacts associated with melamine exposure.

Adverse reproductive effects of maternal low-dose melamine exposure during pregnancy in rats

Melamine is a heterocyclic, aromatic amine and nitrogen-enriched environmental toxicant, found in not only adulterated foodstuffs but also industrial household tableware and paints. Previous studies demonstrated adverse effects of high-dose melamine on human infants and pregnant animals, but effects of low-dose melamine on pregnancy have not been reported. In this study, reproductive effects of low-dose melamine were investigated in pregnant rats. Melamine in the range of 12.5-50 mg/kg was administered to pregnant rats at different gestational stages. Maternal weight gain was not significantly affected, and other maternal morbidity was not observed. Low-dose melamine exposure during pregnancy increased fetal size but reduced somite number in gastrulation (GD8.5-GD10.5) and organogenesis (GD10.5-GD16.5) periods, and increased incidence of stillbirth in whole gestational period (GD0.5 to delivery). Embryotoxicity of melamine was further confirmed by whole embryo culture in vitro that melamine retarded embryonic growth, impaired development of brain and heart, and induced open neural tube and atrioventricular defects with increased apoptosis. In conclusion, adverse reproductive effects of low-dose melamine during pregnancy were identified in the developing rat embryos and the perinatal effects of melamine were gestational and developmental stage dependent. Detailed hazard and risk assessment of melamine in reproduction system are warrant. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 131-138, 2017.

Cytotoxicity, organ distribution and morphological effects of melamine and cyanuric acid in rats

Melamine (Mel) is used widely as a basic organic chemical intermediate in several products. Within the last 10 years there have been two high-profile Mel exposures that caused toxicological concern, especially regarding food adulteration.

OBJECTIVE

This study aimed to determine the toxicity of Mel and one of its homologs, cyanuric acid (Cya), in vitro and in vivo.

MATERIALS AND METHODS

The IC₅₀ of Mel and Cya was determined by the MTT assay in NRK-52E and 293T cell lines. Organ-specific toxicity was assessed using the following dosing paradigm of Wistar rats: group 1: normal saline; group 2: Mel (180 mg/kg); group 3: Cya (150 mg/kg); and group 4: Mel (180 mg/kg) + Cya (150 mg/kg).

RESULTS

The NRK cell toxicity studies on Mel and Cya revealed IC₅₀ values of 1.89 mg/mL and 4.20 mg/mL, respectively. Similarly, Mel and Cya IC₅₀ values in 293T cells were 2.07 mg/mL and 3.71 mg/mL, respectively. Histopathologic studies revealed crystals in the renal medulla-cortex and loss of chief cells in the lining of the stomach in the group receiving Mel plus Cya. HPLC-MS analysis of organ homogenates showed that the concentration of Mel was greatest in the animals receiving a combination of both Mel and Cya.

DISCUSSION AND CONCLUSION

Mel is more toxic than its homolog Cya. The kidney is the most affected organ. Mel was present at high concentration not only in the kidneys, but also in the uterus and liver, informing the scope of future studies on the mechanism of Mel and Cya toxicity.

Reproductive toxicity in rats with crystal nephropathy following high doses of oral melamine or cyanuric acid

The industrial chemical melamine was used in 2007 and 2008 to raise the apparent protein content in pet feed and watered down milk, respectively. Because humans may be exposed to melamine via several different routes into the human diet as well as deliberate contamination, this study was designed to characterize the effect of high dose melamine or cyanuric acid oral exposure on the pregnant animal and developing fetus, including placental transfer. Clear rectangular crystals formed following a single triazine exposure which is a different morphology from the golden spherulites caused by combined exposure or the calculi formed when melamine combines with endogenous uric acid. Crystal nephropathy, regardless of cause, induces renal failure which in turn has reproductive sequelae. Specifically, melamine alone-treated dams had increased numbers of early and late fetal deaths compared to controls or cyanuric acid-treated dams. As melamine was found in the amniotic fluid, this study confirms transfer of melamine from mammalian mother to fetus and our study provides evidence that cyanuric acid also appears in the amniotic fluid if mothers are exposed to high doses.

Urinary melamine: proposed parameter of melamine adulteration of food

Melamine is widely being reported as a food adulterant. Although its toxicity is currently recognized, melamine adulterations of food items are ongoing for falsely inflating the protein content of the food. Melamine alone or in combination with cyanuric acid or uric acid causes nephrotoxicity, and melamine-induced nephrotoxicity is now a global concern. It has been proven that when consumed, melamine is metabolized at a slower rate and excreted unchanged in urine. There is every possibility that when individuals consume melamine-adulterated food items, the melamine may be excreted unchanged in the urine. Therefore, melamine estimation in urine may be a yardstick to check for melamine adulteration of food items. In the present review, recent literature on this subject is analyzed justifying.

The placenta in toxicology. Part IV: Battery of toxicological test systems based on human placenta

This review summarizes the potential and also some limitations of using human placentas, or placental cells and structures for toxicology testing. The placenta contains a wide spectrum of cell types and tissues, such as trophoblast cells, immune cells, fibroblasts, stem cells, endothelial cells, vessels, glands, membranes, and many others. It may be expected that in many cases the relevance of results obtained from human placenta will be higher than those from animal models due to species specificity of metabolism and placental structure. For practical and economical reasons, we propose to apply a battery of sequential experiments for analysis of potential toxicants. This should start with using cell lines, followed by testing placenta tissue explants and isolated placenta cells, and finally by application of single and dual side ex vivo placenta perfusion. With each of these steps, the relative workload increases while the number of feasible repeats decreases. Simultaneously, the predictive power enhances by increasing similarity with in vivo human conditions. Toxic effects may be detected by performing proliferation, vitality and cell death assays, analysis of protein and hormone expression, immunohistochemistry or testing functionality of signaling pathways, gene expression, transport mechanisms, and so on. When toxic effects appear at any step, the subsequent assays may be cancelled. Such a system may be useful to reduce costs and increase specificity in testing questionable toxicants. Nonetheless, it requires further standardization and end point definitions for better comparability of results from different toxicants and to estimate the respective in vivo translatability and predictive value.

Toxicity of melamine: the public health concern

Melamine contamination in food has resulted in sickness and deaths of human infants, pets, and farm animals in the past decade. The majority of the victims suffered from acute kidney injury, nephrolithiasis, and urolithiasis. Since then, animal studies have revealed the possible target organs of the melamine toxicity and the extent of the adverse effects of the contaminant. State-of-the-art analytical methods have been developed to achieve the "zero tolerance" aim for such economically motivated adulteration. These studies provide in-depth understanding of the melamine toxicity and promising analytical methods, which can help us safeguard our dairy food source.