The toxic effects of melamine on spleen lymphocytes with or without cyanuric acid in mice

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.

Modulation of immune functions, inflammatory response, and cytokine production following long-term oral exposure to three food additives; thiabendazole, monosodium glutamate, and brilliant blue in rats

The food additives thiabendazole (TBZ), monosodium glutamate (MSG), and brilliant blue (BB) are commonly used in many daily-consumed food products worldwide. They are widely used in major agricultural and industrial applications. Yet, many of its toxicological aspects are still unclear, especially immune modulation. This research was therefore intended to investigate the effects of male Wistar rats' daily oral exposure for 90 days to TBZ (10 mg/kg b.wt), MSG (20 mg/kg b.wt), or BB (1.2 mg/kg b.wt) on the blood cells, immunity, and inflammatory indicators. The three tested food additives showed varying degrees of hematological alterations. Initially, megaloblastic anemia and thrombocytopenia were evident with the three tested food additives. At the same time, TBZ showed no significant changes in the leukogram element except eosinopenia. MSG induced leukopenia, lymphocytopenia, neutrophilia, and eosinophilia. BB evoked neutrophilia and lymphopenia. The immunoglobins M (IgM) and IgG were significantly reduced with the three tested food additives. In contrast, lysozyme and nitric oxide levels were elevated. A reduced considerably lymphocyte proliferation was detected with TBZ and MSG exposure without affecting the phagocytic activity. Various pathologic disturbances in splenic tissues have been detected. An obvious increase in CD4⁺ but a lessening in CD8⁺ immunolabeling was evident in TBZ and MSG groups. The cytokines, including interferon-gamma, tumor necrosis factor-alpha, and interleukin 1β, 6, 10, and 13, were significantly upregulated in the spleen of rats exposed to TBZ, MSG, and BB. These results concluded that TBZ, MSG, and BB negatively affect hematological parameters, innate and humoral immune functions together with inflammatory responses. TBZ achieved the maximal negative impacts followed by MSG and finally with BB. Given the prevalence of these food additives, TBZ and MSG should be limited to a minimal volume use, or natural food additives should be used instead.

The pathologic lesions of liver caused by melamine alone or in combination with cyanuric acid in mice

The toxicity of melamine (MA) and its analogue cyanuric acid (CA) in multiple organs has been widely investigated. The purpose of this study was to characterize the pathological lesions of the liver caused by melamine alone or in combination with CA. Mice were oral administered 0, 25, 50, or 100 mg/kg/day MA and CA mixture (MC), or 25, 50, and 100 mg/kg/day MA alone for 7 days. We found MC caused increase of liver weight index and elevations of the serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatinine (Cr). Histopathologically, both MA and MC caused scattered necrosis and inflammation cell infiltration in liver. Notably, at 100 mg/kg/day MC, melamine-related crystals were observed in hepatic sinusoid. The liver at high-dose MA and MC groups were further examined by TEM. There were marked degeneration of the mitochondria, and crystal deposition in the Disse space or cytoplasm of hepatic cells and Kupffer cells. TUNEL staining revealed that MA and MC caused apoptosis of hepatocytes and Kupffer cells. Western blotting showed the expression of Bcl-2 decreased, and Bax and caspase-3 increase in liver. The analysis of oxidative stress showed that the expression and activities of two key antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) decreased, and the concentration of malondialdehyde (MDA) elevated in MA- and MC-treated mice. These results from this study demonstrated that both MA and MC caused pathological damage to the liver in mice, especially when ingested in high concentration.

Untargeted and Targeted Metabolomics Profiling of Muscle Reveals Enhanced Meat Quality in Artificial Pasture Grazing Tan Lambs via Rescheduling the Rumen Bacterial Community

Tan is a local fat-tail sheep that is famous for its great eating quality but with little attention to its meat metabolome. The aim of this study was to investigate Tan-lamb meat metabolome as well as the key rumen bacteria related to the beneficial compound deposition in the muscle using untargeted and targeted metabolomics under different feeding regimes: indoor feeding (F), artificial pasture grazing with indoor feeding (GF), and pure artificial pasture grazing (G). The untargeted metabolome was detected by ultraperformance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. Ruminal bacterial communities were detected by 16S rRNA sequencing. Using untargeted metabolomics, the main three altered metabolic pathways in the lamb, including amino acid, lipid, and nucleotide metabolisms, were found in the G group compared to the GF and F groups. Increased N-acetyl-l-aspartic acid, N-acetylaspartylglutamate, acetylcarnitine, and l-carnitine, but decreased carnosine and creatinine, were the main newly found G group-associated metabolites, which might contribute to the improved lamb meat functional quality. Compared to the F group, the G group feeding increased the contents of sweet amino acids (e.g., glycine, alanine, serine, and threonine) and umami amino acids (e.g., glutamic acid and aspartic acid) in the muscle, and G and GF groups increased the level of meat polyunsaturated fatty acid (PUFA), especially the concentration of n3 PUFA, and reduced n6/n3 in the muscle by targeted metabolomics. The abundance of ruminal Moryella was decreased, and Schwartzia and Anaeroplasma were increased in the G group, which were both strongly correlated with the n3 PUFA and other functional compounds in the muscle of lambs. In conclusion, artificial pasture grazing modified the meat amino acid and fatty acid composition as well as the related biological pathways through rescheduling the rumen bacterial community, which would be a better selection for production of healthier lamb meat products.

The long-term oral exposure to titanium dioxide impaired immune functions and triggered cytotoxic and genotoxic impacts in rats

BACKGROUND

Titanium dioxide "TiO₂, E171″ is a widely used food additive that exists in various everyday food products all over the world together with vast applications in cosmetics and industry. However, many toxicological aspects particularly following oral exposure still unclear.

METHODS

Hence, this study was planned to examine the effect of oral exposure of male Wistar rats to two doses of TiO₂ (20 or 40 mg/kg b.wt.) through oral gavage once daily for 90 consecutive days on the blood components, immunity, cytotoxic, and genotoxic indicators.

RESULTS

A dose-dependent leukopenia, eosinophilia, neutrophilia, and thrombocytopenia were noted. Also, the immunoglobins G (IgG) and IgM were significantly elevated in TiO₂ treated rats. The phagocytic activities, lysozyme, nitric oxide, and immunoglobulin levels were significantly depleted following TiO₂ exposure. A significantly reduced lymphocyte proliferation but elevated LDH activity was prominent in TiO₂ treated rats. Different pathological perturbations were observed in both splenic tissue and bone marrow. A marked increase in CD4⁺ and CD8⁺ immunolabeling was evident. A significant increase in the comet variables was recorded in response to the exposure of rats to the increasing level of TiO₂ at both levels.

CONCLUSION

Overall, these results indicated that TiO₂ could induce hematotoxicity, genotoxic, and immunotoxic alterations with exposure for long durations.

Does melamine exposure during infancy cause rhabdomyolysis?

We investigated the possible toxic effects of melamine on muscle tissue in rats using biochemical, hematological and histopathological methods. We used three groups of female albino Wistar rats. The first group was given 0.1 ml saline. The second and third groups were given 50 and 75 mg/kg melamine dissolved in 0.1 ml saline, respectively, daily for 21 days. On day 45, all rats were sacrificed, and whole blood and plasma were analyzed for hematologic and biochemical characteristics. Muscle samples were stained with hematoxylin and eosin for histopathological investigation. Other sections were immunostained for matrix metalloproteinase-9 (MMP-9) and type IV collagen. We found a significant increase in the lymphocytosis-compliant leukocyte number in the 75 mg/kg melamine group compared to the other groups. We also found significant decreases in the hemoglobin levels and hematocrit values in the 75 mg/kg compared to the other groups. We found that the 75 mg/kg melamine group exhibited a significant increase in plasma aspartate aminotransferase (AST) activity compared to the other groups. Changes in plasma creatine kinase and lactate dehydrogenase activity were not statistically significant. Plasma AST activity and mean corpuscular hemoglobin levels were correlated with the lymphocyte:neutrophil ratio. We found mononuclear cell infiltration at the periphery of muscle bundles and in the connective tissue bundles in the melamine treated group. We found MMP-9 expression in muscle cell membranes and type IV collagen expression in degenerative connective tissue fibers. Whole blood, plasma and muscle tissue analysis indicated that the 75 mg/kg melamine group exhibited rhabdomyolysis that was associated with lymphocytosis and anemia. The underlying mechanisms by which melamine causes rhabdomyolytic effects remain unclear.

Palliative effects of Moringa olifera ethanolic extract on hemato-immunologic impacts of melamine in rats

Melamine (MEL) is a widespread food contaminant and adulterant. Moringa olifera is a widely known medicinal plant with various pharmacological properties. Herein, this study aimed to investigate, for the first time, the probable protective or therapeutic role of M. olifera ethanolic extract (MOE) against MEL induced hemato-immune toxic hazards. Fifty Sprague Dawely male rats were orally treated with distilled water, MOE (800 mg/kg bw), MEL (700 mg/kg bw), MOE/MEl or MOE + MEl. Erythrogram and leukogram profiling were evaluated to assess hematological status. Innate immune functions were evaluated via measuring lysozyme levels, nitric oxide concentration, and bactericidal activity of phagocytes. Serum immunoglobulin levels were estimated as indicators of humoral immunity. Histologic and immunohistochemical evaluations of splenic tissues were also performed. The results indicated that MEL caused a significant decline in RBC, Hb, PCV, total WBC, neutrophil, lymphocyte, phagocytes bactericidal activity, lysozyme activity, nitric oxide, total IgM and IgG levels. Also, MEL induced various pathologic lesions in the spleen with strong expression of CD4 and CD8 positive cells. MOE significantly counteracted the former anaemic, leucopenic, innate and humoral depressant effects of MEL particularly at co-exposure. In conclusion, these findings revealed that MOE could be candidate therapy against MEL hemato-immunotoxic impacts.

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.

The effects of melamine with or without cyanuric acid on immune function in ovalbumin-sensitized mice

Melamine is commonly used in the chemical industry, and it has been found to exist on food processing equipment and utensils. Previous investigations suggested that melamine alone or its combination with cyanuric acid appears to be toxic to immune system in animals. The objective of this study is to investigate the potential effects of melamine with or without cyanuric acid on immune function in ovalbumin- sensitized mice. Our data indicated that melamine-related administration caused a significant decreasing in the content of IL-4 in mice in comparison to negative control group. Significant increasing in the content of histamine (HIS) was recorded in almost all treated groups. The co-administration of melamine and cyanuric acid with high dose (each at 16mgkg^-12d^-1) led to a significantly lower contents of IL-10, IL-16 and monocyte chemoattractant protein-1 (MCP-1) in mouse serum in comparison to negative control group. Moreover, our data indicated that the number of Th1 and Th2 cells, and the ratio of Th1/Th2 spleen lymphocytes were significantly changed after treatment. Also, our results demonstrated that the profiles of both CD40 and CD40L were significantly altered in spleen lymphocytes after treatment.

Melamine negatively affects oocyte architecture, oocyte development and fertility in mice

STUDY QUESTION

Does melamine have a toxic effect on oocyte development and fertility in vivo?

SUMMARY ANSWER

Melamine had toxic effects on oocyte quality and fertility due to its effects on the oocyte cytoskeleton, apoptosis and autophagy induction, and epigenetic modifications in an in vivo mouse model.

WHAT IS KNOWN ALREADY

Melamine is a chemical compound that is widely used during the manufacture of amino resins and plastics. In 2008, melamine was reported to adulterate milk and infant formulas in China, which sparked food safety concerns worldwide. Ingesting melamine may result in reproductive damage, and bladder or kidney stones, which can lead to bladder cancer.

STUDY DESIGN, SIZE, DURATION

Mice were randomly assigned to three groups and fed a diet that included melamine (0, 10 and 50 mg/kg/day) for 8 weeks. The in vivo effect of melamine on female reproduction was examined.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used immunofluorescent staining, western blotting and qRT-PCR to examine the effect of melamine on oocyte quality.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results showed the following effects of this melamine-containing diet. (i) Ovary weights were reduced in melamine fed mice. Oocyte developmental competence was also reduced, as shown by reduced polar body extrusion rates. (ii) Melamine feeding resulted in abnormal oocyte cytoskeletons, as shown by increased rates of aberrant spindles and reduced actin microfilament expression. (iii) Melamine exposed oocytes had higher rates of abnormal mitochondrial distributions and early stage apoptosis/autophagy, which were shown by increased microtubule-associated protein 1 light chain 3 (LC3) protein expression level and caspase 9, autophagy-related protein 14 (atg14), and lc3 mRNA levels. (iv) Fluorescence intensity analysis showed that DNA methylation levels were reduced in the oocytes of melamine fed mice. Histone methylation levels were also altered, as Di-methyl-Histone H3 (Lys4) (H3K4me2) level was increased and Tri-methyl-Histone H3 (Lys9) (H3K9me3), Di-methyl-Histone H3 (Lys9) (H3K9me2), and Tri-methyl-Histone H3 (Lys27) (H3K27me3) levels were reduced in oocytes from melamine fed mice. (v) The litter sizes of melamine fed mice were significantly reduced when compared with those of controls.

LIMITATIONS, REASONS FOR CAUTION

Although we examined the possible effects of melamine on oocyte quality and fertility, we did not determine the effect of melamine on offspring development.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that melamine plays a major role in oocyte quality and fertility. This information could contribute to a better understanding of melamine toxicity in female reproduction.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the National Basic Research Program of China (2014CB138503) and the Natural Science Foundation of Jiangsu Province (BK20140030). The authors have no conflict of interest to disclose.