Melamine causes apoptosis of rat kidney epithelial cell line (NRK-52e cells) via excessive intracellular ROS (reactive oxygen species) and the activation of p38 MAPK pathway

Current Insights into the Neurotoxicity of Melamine: A Comprehensive Review

Melamine, a heterocyclic nitrogen-rich triazine chemical compound, is widely used in various household products, including furniture, dinnerware, and kitchen appliances. The unauthorized addition of the mixture to various foodstuffs to misrepresent protein content resulted in catastrophic, frequently life-threatening health consequences for kids as well as canines and has garnered international attention. Numerous primary studies and evaluations have been focused on melamine toxicity's implications on kidney function. Despite the profusion of literature on melamine's nephrotoxicity, evidence regarding its toxicity to other organs remains scarce. A number of recent studies suggest melamine can disrupt central nervous system (CNS) function and bring about cognitive impairments, contradicting the commonly held belief that melamine's detrimental effects are limited to the urinary system. The accumulation of melamine in the body is linked to various adverse effects, including depression, impaired synaptic transmission, oxidative stress, and neurodegenerative diseases. Several mechanisms may lead to such complications. However, numerous safeguards against melamine accumulation have been identified. This review could shed light on the potential neurological effects and mechanisms underlying melamine toxicity. Afterward, we will dive into the body's possible protective mechanisms against melamine-induced toxicity.

Biological and chemical contamination of illegal, uncontrolled refuse storage areas in Poland

This study focused on assessing the microbiological and chemical contamination of air, soil and leachate in uncontrolled refuse storage areas in central Poland. The research included an analysis of the number of microorganisms (culture method), endotoxin concentration (gas chromatography-mass spectrometry), heavy metals level (atomic absorption spectrometry), elemental characteristics (elemental analyser), cytotoxicity assessment against A-549 (human lung) and Caco-2 (human colon adenocarcinoma) cell lines (PrestoBlue™ test) and toxic compound identification (ultra-high-performance liquid chromatography-quadrupole time-of-flight ultrahigh-resolution mass spectrometry). Microbial contamination differed depending on the dump and the group of tested microorganisms. The number of bacteria was: 4.3 × 10² - 1.8 × 10³ CFU m^-3 (air); 1.1 × 10³ - 1.2 × 10⁶ CFU mL^-1 (leachate); 1.0 × 10⁶ - 3.9 × 10⁶ CFU g^-1 (soil). Respectively, for air and soil the number of fungi was: 2.2 × 10² - 4.6 × 10² CFU m^-3; 1.8 × 10² - 3.9 × 10³ CFU g^-1. Metal levels (Fe, Mn, Pb, Zn, Al, Hg, Cd, Cu, Cr) were higher than in the control sample; however, the average concentrations did not exceed the permissible standards. The cytotoxicity of soil and leachate samples depended on the dump, sample and cell line tested. The leachates were more cytotoxic than soil extracts. Compounds belonging to pesticides, surfactants and biocides, chemicals and/or polymer degradation products, medicinal drugs and insect repellents were found. The detection of potential pathogens in the air, soil and leachate, the presence of toxic compounds and the confirmation of the cytotoxic effect of leachate and soil on human cell lines justify the need for further research on the risks posed by illegal dumps. These studies should aim at developing a unified assessment method and a method to minimise the risk of contaminants spreading in the environment, including harmful biological agents.

Elevated levels of biomarkers of oxidative stress and renal injury linked to nitrogenous flame retardants exposure in e-waste dismantling site: A case study in China

Nitrogenous flame retardants (NFRs) have aroused worldwide public concern as their nephrotoxic effect. However, knowledge regarding the pathogenesis mechanism of their exposure to induce kidney injury remains largely unknown. In this study, eight NFRs, four oxidative stress biomarkers (OSBs), and one kidney injury biomarker, namely neutrophil gelatinase-associated lipocalin (NGAL), were measured in urine specimens collected from residents living around e-waste disassembly and reference areas, representing two exposure scenarios. Significant higher concentrations of Σ₈NFR (median: 70.6 vs. 33.8 μg/g Cre) and five biomarkers (124 vs. 97.4 μg/g Cre) were found in urines of populations living in e-waste site compared to those in the reference site (p < 0.05). Primary NFRs exhibited significant positive associations with OSBs and NGAL regardless of the population examined, implying that chronic NFRs exposure could induce oxidative stress and kidney damage. By using structure equation model, we found that oxidative stress, particularly DNA and RNA oxidation mediated 16.1% of the total effect of NFRs on NGAL in e-waste related people, but not on the general population. Overall, this study suggests long-term chronic exposure to NFRs can induce oxidative stress and renal injury in humans but the pathogenesis mode may be scenario-specific.

Associations of exposure to melamine, cyanuric acid, phthalates with markers of early kidney impairment, and their interactions in US adults: analyses of NHANES 2003-2004 data

Melamine (MEL), cyanuric acid (CYA), and phthalates have kidney toxicity, respectively. Still, no study has explored whether there is an interaction of co-exposure to MEL, CYA, and phthalates on early kidney impairment, including cystatin C (CYST), beta 2-microglobulin (β2-MG), albumin creatinine ratio (ACR), and estimated glomerular filtration rate (eGFR). Urine samples were collected from 333 adults in the National Health and Nutrition Examination Survey (NHANES) 2003-2004, and urinary MEL, CYA, and ten metabolites of phthalates were quantified. The multiple markers of early kidney impairment were also measured, including serum CYST, β2-MG, urinary ACR, and eGFR. Their associations were explored by multiple linear and multivariate logistic regression models. Meanwhile, the interactions of co-exposure to MEL, CYA, and phthalates on early kidney impairment were analyzed by Wilcoxon rank-sum test combined with the LSD test. In the multiple linear regression model, urinary concentrations of monobenzyl phthalate (MBzP), mono(3-carboxypropyl) phthalate (MCPP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), and mono(2-ethylhexyl) phthalate (MEHP) were positively associated with urinary ACR, serum β2-MG, and CYST, respectively. Urinary concentrations of MBzP and MCPP were negatively associated with eGFR. In the multivariate logistic regression model, increased urinary CYA concentration was the risk factor of CYST abnormality with an odds ratio (OR) (95% confidence interval, 95% CI) of 2.38 (1.01, 5.60) (P = 0.047) and increased urinary MBzP concentration was the risk factor of ACR abnormality with an OR of 2.59 (1.41, 4.75) (P = 0.002). The co-exposure to MEL, CYA, and four phthalate metabolites (MEHP, MBzP, MCPP, and MECPP) presented significantly interactive effects on the markers of early kidney impairment, respectively. There were the independent and interactive effects of exposure to MEL, CYA, and specific phthalate metabolites on early kidney impairment. Due to co-exposure to multiple environmental chemicals in our daily life, more attention should be paid to the health damage raised by the synergistic effects of environmental chemicals.

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.

Hydroxyproline alleviates 4-hydroxy-2-nonenal-induced DNA damage and apoptosis in porcine intestinal epithelial cells

Oxidative stress has been confirmed in relation to intestinal mucosa damage and multiple bowel diseases. Hydroxyproline (Hyp) is an imino acid abundant in sow's milk. Compelling evidence has been gathered showing the potential antioxidative properties of Hyp. However, the role and mechanism of Hyp in porcine intestinal epithelial cells in response to oxidative stress remains unknown. In this study, small intestinal epithelial cell lines of piglets (IPEC-1) were used to evaluate the protective effects of Hyp on 4-hydroxy-2-nonenal (4-HNE)-induced oxidative DNA damage and apoptosis. IPEC-1 pretreated with 0.5 to 5 mmol/L Hyp were exposed to 4-HNE (40 μmol/L) in the presence or absence of Hyp. Thereafter, the cells were subjected to apoptosis detection by Hoechst staining, flow cytometry, and Western blot or DNA damage analysis by comet assay, immunofluorescence, and reverse-transcription quantitative PCR (RT-qPCR). Cell apoptosis and the upregulation of cleaved-caspase-3 induced by 4-HNE (40 μmol/L) were inhibited by 5 mmol/L of Hyp. In addition, 5 mmol/L Hyp attenuated 4-HNE-induced reactive oxygen species (ROS) accumulation, glutathione (GSH) deprivation and DNA damage. The elevation in transcription of GADD45a (growth arrest and DNA-damage-inducible protein 45 alpha) and GADD45b (growth arrest and DNA-damage-inducible protein 45 beta), as well as the phosphorylation of H2AX (H2A histone family, member X), p38 MAPK (mitogen-activated protein kinase), and JNK (c-Jun N-terminal kinase) in cells treated with 4-HNE were alleviated by 5 mmol/L Hyp. Furthermore, Hyp supplementation increased the protein abundance of Krüppel like factor 4 (KLF4) in cells exposed to 4-HNE. Suppression of KLF4 expression by kenpaulone impeded the resistance of Hyp-treated cells to DNA damage and apoptosis induced by 4-HNE. Collectively, our results indicated that Hyp serves to protect against 4-HNE-induced apoptosis and DNA damage in IPEC-1 cells, which is partially pertinent with the enhanced expression of KLF4. Our data provides an updated explanation for the nutritional values of Hyp-containing animal products.

Melamine induced changes in histopathology of the main organs and transcriptional levels of MAPK signaling genes in kidneys of female mice

Melamine is an important chemical raw material used in industries, which has potential health risks to animals and humans. Current research mainly focuses on the toxic effects of high-dose melamine ingestion. However, there are few reports on whether melamine at the current limited standard dose has adverse effects on various tissues and organs, and whether there are sensitive target genes for risk evaluation. For this, 24 female Kunming mice were fed 0, 1.8-, 3.6-, and 7.2- mg/kg/d melamine via drinking water for consecutive 28 days, respectively. The morphological changes of the ovarian, hepatic, and renal tissues were firstly observed. The results demonstrated that the histopathology of ovary, liver, and especially in kidney had been altered by melamine intake in female. And then, the transcriptional levels of MAPK signaling genes including p38, ERK1, ERK2, JNK1, and JNK2 in kidneys were investigated by real-time PCR. The data showed that ERK1 and p38 mRNAs expressions were up-regulated significantly by melamine, suggesting that ERK1 and p38 transcriptional levels in the kidney might to be considered as candidate targets for lower-dose melamine toxicity. This study not only provides potential targets for the diagnosis and prevention of melamine damage, but also helps to assess the health risks of the current minimum allowable levels of melamine in food and environment.

The Anti-Inflammatory, Anti-Apoptotic and Antioxidant Effects of a Pomegranate-Peel Extract against Acrylamide-Induced Hepatotoxicity in Rats

The Acrylamide is a toxic compound generated under oxidative stress arising from intracellular ROS production and induced toxicity. It is frequently used in industry and generated through the heating of tobacco and foods high in carbohydrates. The exact mechanism of its toxicity is still unclear. In this study, an extract of the peels of pomegranate (Punica granatum L.), a nutritious and visually appealing fruit with a diverse bioactive profile, was examined for its potential anti-apoptotic, antioxidant, and anti-inflammatory effects. A total of 40 adult male Wistar rats were allocated into four groups of 10 rats each: Group 1 was a negative-control group (CNT) and received normal saline; Group 2 was a positive-control acrylamide group and received acrylamide orally at a dose of 20 mg/kg/bw; in Group 3, the rats were supplemented with pomegranate-peel extract (P.P; 150 mg/kg/bw) orally on a daily basis for 3 weeks, administered simultaneously with the acrylamide treatment described for Group 2; Group 4 was a protective group, and the animals received the pomegranate-peel extract and acrylamide as stated for Groups 2 and 3, with the pomegranate-peel extract (P.P. extract) administered 1 week earlier than the acrylamide. The results indicate that acrylamide exposure increased the serum levels of AST, ALT, creatinine, interleukin-1 beta, and interleukin-6 in an extraordinary manner. In addition, it increased the lipid peroxidation marker malondialdehyde (MDA) and simultaneously weakened antioxidant biomarker activities (SOD, GSH, and catalase) and reduced the levels of interleukin-10. The pomegranate-peel extract was shown to reduce the inflammatory blood markers of interleukin-1 beta and IL-6. Glutathione peroxidase, superoxide dismutase, catalase, and interleukin-10 were all significantly elevated in comparison to the acrylamide-treatment group as a result of the significant reduction in MDA levels induced by the P.P extract. In addition, the pomegranate-peel extract normalized the cyclooxygenase-2 (COX2), transforming growth factor-beta 1 (TGF-β1), and caspase-3 levels, with a significant upregulation of the mRNA expression of heme oxygenase-1 (HO-1), nuclear factor erythroid 2 (Nrf2), and Bcl-2. Therefore, these data reveal that pomegranate peel has anti-inflammatory, antiapoptotic, free-radical-scavenging, and powerful antioxidant activity that protects against acrylamide toxicity.

Genetic Polymorphisms of MnSOD Modify the Impacts of Environmental Melamine on Oxidative Stress and Early Kidney Injury in Calcium Urolithiasis Patients

Environmental melamine exposure increases the risks of oxidative stress and early kidney injury. Manganese superoxide dismutase (MnSOD), glutathione peroxidase, and catalase can protect the kidneys against oxidative stress and maintain normal function. We evaluated whether their single-nucleotide polymorphisms (SNPs) could modify melamine’s effects. A total of 302 patients diagnosed with calcium urolithiasis were enrolled. All patients provided one-spot overnight urine samples to measure their melamine levels, urinary biomarkers of oxidative stress and renal tubular injury. Median values were used to dichotomize levels into high and low. Subjects carrying the T allele of rs4880 and high melamine levels had 3.60 times greater risk of high malondialdehyde levels than those carrying the C allele of rs4880 and low melamine levels after adjustment. Subjects carrying the G allele of rs5746136 and high melamine levels had 1.73 times greater risk of high N-Acetyl-β-d-glucosaminidase levels than those carrying the A allele of rs5746136 and low melamine levels. In conclusion, the SNPs of MnSOD, rs4880 and rs5746136, influence the risk of oxidative stress and renal tubular injury, respectively, in calcium urolithiasis patients. In the context of high urinary melamine levels, their effects on oxidative stress and renal tubular injury were further increased.

Longitudinal changes in oxidative stress and early renal injury in children exposed to DEHP and melamine in the 2011 Taiwan food scandal

In 2011, phthalates, mainly di-(2-ethylhexyl) phthalate (DEHP), were found to have been added to a variety of foods in Taiwan, increasing the risk of microalbuminuria in children. Exposure to melamine perhaps modifies that risk. This prospective cohort study investigates whether renal injury resulting from exposure to DEHP-tainted foods from the 2011 Taiwan Food Scandal is reversed over time. The temporal and interactive effects of past daily DEHP intake, current daily DEHP intake, and urinary melamine levels on oxidative stress and renal injury were also examined. Two hundred possibly DEHP-affected children (aged < 18 years) were enrolled in the first survey wave (August 2012-January 2013), with 170 and 159 children in the second (July 2014-February 2015) and third waves (May 2016-October 2016), respectively. The first wave comprised questionnaires that were used to collect information about possible past daily DEHP intake from DEHP-tainted foods. One-spot first morning urine samples were collected to measure melamine levels, phthalate metabolites, and markers indicating oxidative stress (malondialdehyde and 8-oxo-2'-deoxyguanosine), and renal injury (albumin/creatinine ratio (ACR) and N-acetyl-beta-D-glucosaminidase) in all three waves. Generalized estimating equation (GEE) modeling revealed that both past daily DEHP intake and time might affect urinary ACR. However, most interactions were negative and significant correlation was observed only during the second wave (P for interaction = 0.014) in the group with the highest past daily DEHP intake (>50 μg/kg/day). Urinary melamine levels were found to correlate significantly with both urinary ACR and oxidative stress markers. The highest impact associated with exposure to DEHP-tainted foods in increasing urinary ACR of children was observed during the first wave, and the effect may partially diminish over time. These results suggest that continuous monitoring of renal health and other long-term health consequences is required in individuals who were affected by the scandal in 2011.

Protective prospects of eco-friendly synthesized selenium nanoparticles using Moringa oleifera or Moringa oleifera leaf extract against melamine induced nephrotoxicity in male rats

Nanotechnology is used in a wide range of applications, including medical therapies that precisely target disease prevention and treatment. The current study aimed firstly, to synthesize selenium nanoparticles (SeNPs) in an eco-friendly manner using Moringa oleifera leaf extract (MOLE). Secondly, to compare the protective effects of green-synthesized MOLE-SeNPs conjugate and MOLE ethanolic extract as remedies for melamine (MEL) induced nephrotoxicity in male rats. One hundred and five male Sprague Dawley rats were divided into seven groups (n = 15), including 1st control, 2nd MOLE (800 mg/kg BW), 3rd SeNPs (0.5 mg/kg BW), 4th MOLE-SeNPs (200 μg/kg BW), 5th MEL (700 mg/kg BW), 6th MEL+MOLE, and 7th MEL+MOLE SeNPs. All groups were orally gavaged day after day for 28 days. SeNPs and the colloidal SeNPs were characterized by TEM, SEM, and DLS particle size. SeNPs showed an absorption peak at a wavelength of 530 nm, spherical shape, and an average size between 3.2 and 20 nm. Colloidal SeNPs absorption spectra were recorded between 400 and 700 nm with an average size of 3.3-17 nm. MEL-induced nephropathic alterations represented by a significant increase in serum creatinine, urea, blood urea nitrogen (BUN), renal TNFα, oxidative stress-related indices, and altered the relative mRNA expression of apoptosis-related genes Bax, Caspase-3, Bcl2, Fas, and FasL. MEL-induced array of nephrotoxic morphological changes, and up-regulated immune-expression of proliferating cell nuclear antigen (PCNA) and proliferation-associated nuclear antigen Ki-67. Administration of MOLE or MOLE-SeNPs significantly reversed MEL-induced renal function impairments, oxidative stress, histological alterations, modulation in the relative mRNA expression of apoptosis-related genes, and the immune-expression of renal PCNA and Ki-67. Conclusively, the green-synthesized MOLE-SeNPs and MOLE display nephron-protective properties against MEL-induced murine nephropathy. This study is the first to report these effects which were more pronounced in the MOLE group than the green biosynthesized MOLE-SeNPs conjugate group.

Protective effects of curcumin on chemical and drug-induced cardiotoxicity: a review

Cardiotoxicity is a major adverse effect that can be induced by both therapeutic agents and industrial chemicals. The pathogenesis of such cardiac damage is multifactorial, often injuring the cardiac tissue by generating free radicals, oxidative stress, and/or inflammation. Curcumin (CUR) is a bright yellow chemical produced by Curcuma longa plants. It is the principal curcuminoid of turmeric (Curcuma longa), a member of the ginger family, Zingiberaceae. Administration of CUR has been reported to ameliorate the chemical and drug-induced cardiac injury in several studies. CUR has been suggested to act as an effective candidate against oxidative stress and inflammation in heart tissue via regulation of Nrf2 and suppression of p38 MAPK/NF-κB and NLRP3 inflammasomes. The anti-apoptotic properties of CUR have also been reported to modulate the AMPK, Akt, JNK, and ERK signaling pathways. This review explores the potential protective effects of CUR regarding the detrimental effects often observed in cardiac tissue following exposure to several chemicals including drugs.

Alpha lipoic acid attenuates iron induced oxidative acute kidney injury in rats

Iron has been implicated in oxidative tissue injury owing to its ability to generate reactive oxygen species (ROS). We investigated the reno-protective effects of alpha lipoic acid (ALA) by investigating its effects on the kidney isoform of NADPH oxidase (Nox4) and the specific signaling pathways, p38 MAPK and PI3K/Akt, which participate in apoptosis and survival, respectively. We established four groups of seven rats: control, 100 mg/kg ALA, 80 mg/kg iron sucrose (IS) and IS + ALA. IS and ALA were injected intravenously and rats were sacrificied after 6 h. The mRNA expression of the subunits of NADPH oxidase, Nox4 and p22phox; tumor necrosis factor-alpha (TNF-α); and kidney injury molecule-1 (KIM-1) were measured using quantitative real time polymerase chain reaction (qRT-PCR). Active caspase-3 protein expression was evaluated by immunostaining. Also, p38 MAPK and PI3K/Akt signaling pathways were analyzed using western blot. ALA suppressed the mRNA expression of Nox4, p22phox, TNF-α and KIM-1. Active caspase-3 protein expression induced by IS was decreased by ALA. ALA also suppressed p38 MAPK and activated the PI3K/Akt signaling pathway following IS administration. We found that ALA may be an effective strategy for preventing oxidative acute kidney injury caused by IS.

Prevention of melamine-induced hepatorenal impairment by an ethanolic extract of Moringa oleifera: Changes in KIM-1, TIMP-1, oxidative stress, apoptosis, and inflammation-related genes

BACKGROUND/AIMS

Melamine (ML) is a common food adulterant and contaminant. Moringa oleifera is a well-known medicinal plant with many beneficial biological properties. This study investigated the possible prophylactic and therapeutic activity of an ethanolic extract of M. oleifera (MEE) against ML-induced hepatorenal damage.

METHOD

Fifty male Sprague Dawley rats were orally administered distilled water, MEE (800 mg/kg bw), ML (700 mg/kg bw), MEE/ML (prophylactically) or MEE+ML (therapeutically). Hepatic aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphate (ALP) in serum were measured. Serum total bilirubin, direct bilirubin, indirect bilirubin, protein, albumin, and globulin contents were also assayed, and urea and creatinine levels were determined. Moreover, antioxidant enzyme activity of glutathione peroxidase (GPx) and catalase (CAT) in serum levels were quantified. Complementary histological and histochemical evaluation of renal and hepatic tissues was conducted, and expression of oxidative stress (GPx and CAT) and apoptosis-related genes, p53 and Bcl-2, in hepatic tissue were assessed. In parallel, transcriptional expression of inflammation and renal injury-related genes, including kidney injury molecule 1 (KIM-1), metallopeptidase inhibitor 1 (TIMP1), and tumor necrosis factor alpha (TNF-α) in the kidney tissue were determined.

RESULTS

ML caused significant increases in serum levels of ALT, AST, ALP, total bilirubin, direct bilirubin, indirect bilirubin, urea, and creatinine. Further, ML treated rats showed significant reductions in serum levels of protein, albumin, globulin, GPx, and CAT. Distinct histopathological damage and disturbances in glycogen and DNA content in hepatic and renal tissues of ML treated rats were observed. KIM-1, TIMP-1, and TNF-α gene expression was significantly upregulated in kidney tissue. Also, GPx, CAT, and Bcl-2 genes were significantly downregulated, and p53 was significantly upregulated in liver tissue after ML treatment. MEE significantly counteracted the ML-induced hepatorenal damage primarily for co-exposed rats.

CONCLUSION

MEE could be an effective therapeutic supplement for treatment of ML-induced hepato-renal damage, probably via modulating oxidative stress, apoptosis, and inflammation.

Renal function and the exposure to melamine and phthalates in Shanghai adults

[Background] Melamine and phthalates have been reported to damage renal function in children. This association is scarce in general adults. [Method] A cross-sectional subsample population of 611 adults participating in the 2012 Shanghai Food Consumption Survey (SHFCS) was analyzed for urinary biomarkers of melamine, metabolites of phthalates, and renal function parameters. The correlations between renal function parameters and chemical exposure (either independently or interactively) were explored by linear regression models. To simplify the analysis, phthalate metabolites were dimensionally reduced using principal component analysis (PCA) method. [Result] Urinary melamine was positively associated with renal function parameters of both albumin-to-creatinine ratio (ACR) and β2-microglobulin (B2M) in multivariate linear regression models (P < 0.05). A PCA pattern characterized by high-molecular-weight phthalates (HMWP) was positively associated with all three parameters of renal function (ACR, B2M, and N-acetyl-β-d-glucosaminidase (NAG)). The co-exposure to melamine and HMWP presented an additive effect on increasing these parameters (ACR, B2M, and NAG). [Conclusion] Impaired renal function in Shanghai adults was associated with exposure to both melamine and HMWP.

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.

Melamine promotes calcium crystal formation in three-dimensional microfluidic device

Melamine, which induces proximal tubular (PT) cell damage has a greater nephrotoxic effect when combined with cyanuric and uric acids; however, it is unknown whether such effect can stimulate calcium phosphate (CaP)/calcium oxalate (CaOx) stone formation. Here, we show that melamine acts as an inducer of CaP, CaOx and CaP + CaOx (mixed) crystal formations in a time and concentration-dependent manner by stabilizing those crystals and further co-aggregating with melamine. To explore the physiological relevance of such melamine-augmented calcium crystal formation, we used 2-dimensional (2D) and 3D microfluidic (MF) device, embedded with PT cells, which also resembled the effect of melamine-stimulated CaP, CaOx and mixed crystal formation. Significantly, addition of preformed CaP and/or CaOx crystal in the presence of melamine, further potentiated those crystal formations in 3D MFs, which helped the growth and aggregation of mixed crystals. Our data show that the mechanism of such predisposition of stone formation could be largely due to co-crystallization between melamine and CaP/CaOx and pronounced effect on induction of stone-forming pathway activation in 3D MF. Taken together, melamine-induced CaP and/or CaOx crystal formation ex-vivo will help us in understanding the larger role of melamine as an environmental toxicant in producing the pathology in similar cellular microenvironments.

Blueberry Malvidin-3-galactoside Suppresses Hepatocellular Carcinoma by Regulating Apoptosis, Proliferation, and Metastasis Pathways In Vivo and In Vitro

Anthocyanin, a natural antioxidant, is reported to have cytotoxicity against cancer cells; however, the mechanism remains unclear. The aim of the present study was to investigate the mechanism by which malvidin-3-galactoside (M3G), the prominent anthocyanin in blueberry, suppresses the development of hepatocellular carcinoma. In vitro, M3G suppressed the proliferation, polarization, migration, and invasion activities of HepG2 cells by regulating the protein expression of cyclin D1, cyclin B, cyclin E, caspase-3, cleaved caspase-3, Bax, p-JNK, and p-p38, activating phosphatase and tensin homologue deleted on chromosome 10 (PTEN), accompanied by a decrease in the p-AKT level, and lowering the protein expression levels of MMP-2 and MMP-9. In vivo, M3G promoted the apoptosis of liver tumor cells, as determined by immunohistochemistry (cleaved caspase-3, Ki-67, PTEN, and p-AKT), a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and hematoxylin-eosin staining. Overall, these results suggest that M3G, as an adjuvant ingredient or nutritional supplement, may be beneficial for liver cancer prevention and the modulatory mechanism seems to be associated with inhibition of proliferation, apoptosis, migration, and invasion-related pathways.

Paricalcitol attenuates indoxyl sulfate-induced apoptosis through the inhibition of MAPK, Akt, and NF-kB activation in HK-2 cells

BACKGROUND/AIMS

Indoxyl sulfate (IS) is a uremic toxin and an important causative factor in the progression of chronic kidney disease. Recently, paricalcitol (19-nor-1,25-dihydroxyvitamin D2) was shown to exhibit protective effects in kidney injury. Here, we investigated the effects of paricalcitol treatment on IS-induced renal tubular injury.

METHODS

The fluorescent dye 2',7'-dichlorofluorescein diacetate was used to measure intracellular reactive oxygen species (ROS) following IS administration in human renal proximal tubular epithelial (HK-2) cells. The effects of IS on cell viability were determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays and levels of apoptosis-related proteins (Bcl-2-associated protein X [Bax] and B-cell lymphoma 2 [Bcl-2]), nuclear factor-κB (NF- κB) p65, and phosphorylation of mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) were determined by semiquantitative immunoblotting. The promoter activity of NF-κB was measured by luciferase assays and apoptosis was determined by f low cytometry of cells stained with f luorescein isothiocyanate-conjugated Annexin V protein.

RESULTS

IS treatment increased ROS production, decreased cell viability and induced apoptosis in HK-2 cells. IS treatment increased the expression of apoptosis-related protein Bax, decreased Bcl-2 expression, and activated phosphorylation of MAPK, NF-κB p65, and Akt. In contrast, paricalcitol treatment decreased Bax expression, increased Bcl-2 expression, and inhibited phosphorylation of MAPK, NF-κB p65, and Akt in HK-2 cells. NF-κB promoter activity was increased following IS, administration and was counteracted by pretreatment with paricalcitol. Additionally, flow cytometry analysis revealed that IS-induced apoptosis was attenuated by paricalcitol treatment, which resulted in decreased numbers of fluorescein isothiocyanate-conjugated Annexin V positive cells.

CONCLUSION

Treatment with paricalcitol inhibited IS-induced apoptosis by regulating MAPK, NF-κB, and Akt signaling pathway in HK-2 cells.

GLP-1 treatment protects endothelial cells from oxidative stress-induced autophagy and endothelial dysfunction

Endothelial dysfunction and excessively stimulated autophagy, often caused by oxidant injury or inflammation, will lead to atherosclerosis development and progression in diabetes. The aim of this study is to investigate the protective effect of glucagon-like peptide-1 (GLP-1) treatment on preventing oxidative stress-induced endothelial dysfunction and excessively stimulated autophagy. Treatment of endothelial cells with GLP-1 significantly attenuated oxidative stress-induced endothelial dysfunction and autophagy, which was associated with the reduction of intracellular reactive oxygen species (ROS) levels. These protective effects of GLP-1 were likely mediated by reducing phosphorylation of ERK1/2. We further demonstrated that GLP-1 treatment could reverse downregulation of epigenetic factor histone deacetylase 6 (HDAC6), a downstream molecular of the EKR1/2, induced by oxidant injury. In conclusion, our results suggest that GLP-1 produces a protective effect on endothelial cells from oxidant injury by preventing endothelial dysfunction and autophagy, which may be dependent on restoring HDAC6 through a GLP-1R-ERK1/2-dependent manner.

Urinary melamine excretion and increased markers of renal tubular injury in patients with calcium urolithiasis: A cross-sectional study

Environmental low-dose melamine exposure has been associated with urolithiasis risk in adults, but it is unclear if this exposure can cause early renal damage. This cross-sectional study investigated the association of this exposure and early renal damage in patients with calcium urolithiasis. We recruited patients diagnosed with upper urinary tract calcium urolithiasis from three hospitals in southwestern Taiwan between November 2010 and January 2015. All patients completed a structured questionnaire and provided one-spot urine samples for the measurement of melamine level and markers of early renal injury, including N-acetyl b-d-glucosaminidase (NAG), β2-microglobulin (β2-MG), and microalbumin. We used urinary melamine levels as an indicator of environmental melamine exposure. A total of 309 patients (mean age of 54.7 ± 12.8 years) were studied. Median urinary melamine level (μg/mmol Cr) was 1.26 (interquartile range 0.48-3.29). A significant and positive correlation was found between urinary melamine concentration and urinary NAG levels (Spearman correlation coefficient, r = 0.157, p = 0.006, n = 309). With urinary melamine levels categorized into quartiles, multivariate regression results showed the same relationship, particularly in those with first stone episode. In this group, patients with the highest quartile of urinary melamine concentration had a 3.95-fold risk (95% confidence interval = 1.43-10.94) of high NAG levels (dichotomized by median), compared to the lowest quartile after adjustment. No association was found between urinary melamine concentration and urinary microalbumin levels. In conclusion, urinary melamine is significantly associated with urinary marker of early renal tubular injury, NAG, in urolithiasis patients, especially ones with first stone episode.

Melamine induces Ca2+-sensing receptor activation and elicits apoptosis in proximal tubular cells

Melamine causes renal tubular cell injury through inflammation, fibrosis, and apoptosis. Although melamine affects the rise in intracellular Ca²⁺ concentration ([Ca²⁺]_i)_, reactive oxygen species (ROS) production, and proapoptotic pathway activation, the mechanism of upstream Ca²⁺ signaling is unknown. Because melamine has some structural similarities with l-amino acids, which endogenously activate Ca²⁺-sensing receptors (CSR), we examined the effect of melamine on CSR-induced Ca²⁺ signaling and apoptotic cell death. We show here that melamine activates CSR, causing a sustained Ca²⁺ entry in the renal epithelial cell line, LLC-PK1. Moreover, such CSR stimulation resulted in a rise in [Ca²⁺]_i, leading to enhanced ROS production. Furthermore, melamine-induced elevated [Ca²⁺]_i and ROS production caused a dose-dependent increase in apoptotic (by DAPI staining, DNA laddering, and annexin V assay) and necrotic (propidium iodide staining) cell death. Upon examining the downstream mechanism, we found that transforming growth factor β1 (TGF-β1), which increases extracellular matrix genes and proapoptotic signaling, was also upregulated at lower doses of melamine, which could be due to an early event inducing apoptosis. Additionally, cells exposed to melamine displayed a rise in pERK activation and lactate dehydrogenase release resulting in cytotoxicity. These results offer a novel insight into the molecular mechanisms by which melamine exerts its effect on CSR, causing a sustained elevation of [Ca²⁺]_i, leading to ROS generation, fibronectin production, proapoptotic pathway activation, and renal cell damage. Together, these results thus suggest that melamine-induced apoptosis and/or necrosis may subsequently result in acute kidney injury and promote kidney stone formation.

Melamine and/or formaldehyde exposures affect steroidogenesis via alteration of StAR protein and testosterone synthetic enzyme expression in male mice

The reproductive effects of melamine and formaldehyde, either alone or in combination, on mature male Swiss mice were investigated. The animals were orally administered melamine (50mg/kg/day), formaldehyde (25mg/kg/day), a mixture of melamine and formaldehyde, or a vehicle control for 65 consecutive days. As a result, the deterioration of sperm characteristics and inhibition of testicular enzyme activity were observed in the melamine- and formaldehyde-exposed groups. In addition, testosterone and luteinizing hormone levels were significantly reduced in the melamine but not in the formaldehyde-exposed group, which correlated with down-regulation of transcription levels of steroidogenic-related genes. Histopathologically, both compounds caused lesions in the testes. However, the co-exposure reduced the induced alterations in spermatogenesis, steroidogenesis, and testicular architecture that were obviously observed in the melamine-exposed group. Consequently, we demonstrated that melamine exhibited more pronounced reproductive impact in comparison with formaldehyde. In addition, formaldehyde was able to substantially temper the melamine -induced reproductive toxic effect.

Ovarian Toxicity in Female Rats after Oral Administration of Melamine or Melamine and Cyanuric Acid

Although the toxicity of melamine to the kidneys and testes is well known, few studies have investigated the effects of melamine on female reproductive organs. Therefore, this study explores the effects of oral administration melamine or melamine and cyanuric acid for 28 days on the ovaries of female rats. Rats that were exposed to the mixture exhibited reduced ovarian and uterine weights, a shorter estrous cycle, and reduced serum estrogen and progesterone levels compared to rats that were exposed to melamine and control rats. Furthermore, morphological analysis revealed pathological changes in the ovaries of rats exposed to melamine or the mixture, such as more atretic follicles and necrosis of oocytes and granulosa cells. TUNEL staining revealed that the exposed groups had a higher proportion of TUNEL-positive granulosa cells than the control group, and the mRNA expressions of SOD1, GPX1, GPX2, P450scc, 17β-HSD I, and 17β-HSD II were reduced in the exposure groups compared with the control group. These results indicated that exposure to melamine alone or to the melamine-cyanuric acid mixture could damage the ovaries in rats.

Lonicera caerulea berry extract suppresses lipopolysaccharide-induced inflammation via Toll-like receptor and oxidative stress-associated mitogen-activated protein kinase signaling

The protective effects of Lonicera caerulea berry extract (LCBE) against hepatic inflammation and the underlying mechanisms were investigated in a rat model of lipopolysaccharide (LPS)-induced chronic liver inflammation.

Ghrelin protects against depleted uranium-induced apoptosis of MC3T3-E1 cells through oxidative stress-mediated p38-mitogen-activated protein kinase pathway

Depleted uranium (DU) mainly accumulates in the bone over the long term. Osteoblast cells are responsible for the formation of bone, and they are sensitive to DU damage. However, studies investigating methods of reducing DU damage in osteoblasts are rarely reported. Ghrelin is a stomach hormone that stimulates growth hormones released from the hypothalamic-pituitary axis, and it is believed to play an important physiological role in bone metabolism. This study evaluates the impact of ghrelin on DU-induced apoptosis of the osteoblast MC3T3-E1 and investigates its underlying mechanisms. The results show that ghrelin relieved the intracellular oxidative stress induced by DU, eliminated reactive oxygen species (ROS) and reduced lipid peroxidation by increasing intracellular GSH levels; in addition, ghrelin effectively suppressed apoptosis, enhanced mitochondrial membrane potential, and inhibited cytochrome c release and caspase-3 activation after DU exposure. Moreover, ghrelin significantly reduced the expression of DU-induced phosphorylated p38-mitogen-activated protein kinase (MAPK). A specific inhibitor (SB203580) or specific siRNA of p38-MAPK could significantly suppress DU-induced apoptosis and related signals, whereas ROS production was not affected. In addition, ghrelin receptor inhibition could reduce the anti-apoptosis effect of ghrelin on DU and reverse the effect of ghrelin on intracellular ROS and p38-MAPK after DU exposure. These results suggest that ghrelin can suppress DU-induced apoptosis of MC3T3-E1 cells, reduce DU-induced oxidative stress by interacting with its receptor, and inhibit downstream p38-MAPK activation, thereby suppressing the mitochondrial-dependent apoptosis pathway.

Pharmacokinetic and nephroprotective benefits of using Schisandra chinensis extracts in a cyclosporine A-based immune-suppressive regime

Cyclosporine A (CsA) is a powerful immunosuppressive drug. However, nephrotoxicity resulting from its long-term usage has hampered its prolonged therapeutic usage. Schisandra chinensis extracts (SCE) have previously been used in traditional Chinese medicine and more recently coadministered with Western medicine for the treatment of CsA-induced side effects in the People’s Republic of China. This study aimed to investigate the possible effects of SCE on the pharmacokinetics of CsA in rats and elucidate the potential mechanisms by which it hinders the development of CsA-induced nephrotoxicity. A liquid chromatography/tandem mass spectrometry method was developed and validated for determining the effect of SCE on the pharmacokinetics of CsA. Male Sprague Dawley rats, which were administered with CsA (25 mg/kg/d) alone or in combination with SCE (54 mg/kg/d and 108 mg/kg/d) for 28 days, were used to evaluate the nephroprotective effects of SCE. Our study showed that SCE increased the mean blood concentration of CsA. Furthermore, we found that the concomitant administration of SCE alongside CsA prevented the disruption of catalase activity and reduction in creatinine, urea, renal malondialdehyde, and glutathione peroxidase levels that would have otherwise occurred in the absence of SCE administration. SCE treatment markedly suppressed the expression of 4-hydroxynonenal, Bcl-2-associated X protein, cleaved caspase 3, and autophagy-related protein LC3 A/B. On the other hand, the expression of heme oxygenase-1, nuclear factor erythroid 2-related factor 2 (Nrf2), and P-glycoprotein was enhanced by the very same addition of SCE. SCE was also able to increase the systemic exposure of CsA in rats. The renoprotective effects of SCE were thought to be mediated by its antiapoptotic and antioxidant abilities, which caused the attenuation of CsA-induced autophagic cell death. All in all, these findings suggest the prospective use of SCE as an effective adjunct in a CsA-based immunosuppressive regimen.

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.

Glycated albumin triggers fibrosis and apoptosis via an NADPH oxidase/Nox4-MAPK pathway-dependent mechanism in renal proximal tubular cells

Glycated albumin (GA), an Amadori product used as a marker of hyperglycemia and the early-stage glycation products compared to AGEs, might further promote kidney lesions in diabetic nephropathy (DN). However, the mechanisms how GA cause proximal tubular cells damage remain poorly understood. In this study, we investigated the effects of GA on fibrosis and apoptosis of renal proximal tubular cells (NRK-52E) in vitro experiments. Our results showed that GA promoted α-SMA, fibronectin (FN) and TGF-β expressions in NRK-52E cells. GA also increased cell apoptosis and stimulated the expressions of pro-caspase 3/cleaved-caspase 3. GA overloading enhanced the phosphorylation of MAPK pathway. GA-induced α-SMA, FN, TGF-β and caspase 3 expressions were completely suppressed by the NADPH oxidase inhibitor apocynin (Apo), the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) and the latent antioxidant Astragaloside IV (AS-IV). Real-time PCR showed that GA increased Nox1, Nox2 and Nox4 mRNA expressions, especially the Nox4 expression. Furthermore, Nox4 siRNA blocked GA-induced tubular damages and the MAPK pathway activation. These results demonstrate that GA increases the permissiveness of proximal tubular cells to fibrosis and apoptosis in vitro by triggering a pathway that involves NADPH oxidase/Nox4-MAPK signaling pathway. This event may represent a key cellular effect in increasing the susceptibility of tubular cells to fibrosis and apoptosis when the tubules cope with a high GA load. This effect is instrumental to renal damage and disease progression in patients with DN.

Autophagy Alleviates Melamine-Induced Cell Death in PC12 Cells Via Decreasing ROS Level

Since melamine was illegally added to raw milk for increasing the apparent protein content, such a scandal has not been quite blown out. Previous studies showed that melamine induced apoptosis and oxidative damage in both in vivo and in vitro experiments. It is well known that autophagy is closely related to oxidative stress. In the present study, we examined whether autophagy played an important role in protecting PC12 cells, which were damaged by melamine. Immunofluorescence assay showed that melamine enhanced the number of punctuate dot, indicating the increase of autophagosomes. Western blot assay presented that melamine significantly elevated the expression level of autophagy markers including LC3-II/LC3-I ratio, beclin-1, and Atg 7. Rapamycin further enhanced the effect, whereas 3-methyadenine (3-MA) inhibited it. MTT assay exhibited that rapamycin significantly enhanced the cell viability (P < 0.01), while 3-MA considerably reduced it in melamine-treated PC12 cells (P < 0.01). Furthermore, flow cytometry assay showed that rapamycin considerably reduced the reactive oxygen species (ROS) level of the cells (P < 0.01), but 3-MA increased the generation of ROS (P < 0.01). Additionally, the superoxide dismutase (SOD) activity was notably increased by rapamycin in melamine-treated PC12 cells (P < 0.01), while the activity of which was prominently decreased by 3-MA (P < 0.01). Malondialdehyde (MDA) assay showed that rapamycin remarkably decreased the MDA level of the cells (P < 0.05), while 3-MA increased it (P < 0.01). Consequently, this study demonstrated that autophagy protected PC12 cells from melamine-induced cell death via inhibiting the excessive generation of ROS. Regulating autophagy may become a new targeted therapy to relieve the damage induced by melamine.

Effect of melamine toxicity on Tetrahymena thermophila proliferation and metallothionein expression

Melamine is a raw material in the chemical industry. Because of its high nitrogen content, melamine has been utilized by unscrupulous businessmen as a food additive to enhance the indices of protein content in food and feed testing. Tetrahymena has long been used as an excellent model organism in toxicological studies. The purpose of the present study was to determine the effect of melamine on Tetrahymena. In the present study, the effects of melamine on the proliferation and mating rate of Tetrahymena were examined by microscopic counting of the cell numbers. The comet assay and DAPI nuclear staining were performed to analyze the changes in the Tetrahymena genome. Flow cytometric analysis was conducted to detect apoptosis. Furthermore, RT-PCR was performed to determine the changes in the expression of the metallothionein gene in Tetrahymena that underwent stress treatment with varying concentrations of melamine. The results indicated that melamine affected the proliferation and sexual reproduction of Tetrahymena. High melamine concentrations damaged the Tetrahymena genome to a certain extent and induced apoptosis in the organism. Expression of the metallothionein gene was upregulated in Tetrahymena exposed to melamine stress to ameliorate melamine-induced damage. These results indicated that melamine displayed significant toxicity to Tetrahymena cells.

Effect of melamine on [Ca(2+)]i and viability in PC3 human prostate cancer cells

Melamine is thought to be an endocrine disrupter that affects physiology in cells. This study examined the effect of melamine on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells. Melamine evoked [Ca(2+)]i rises concentration-dependently. Melamine-evoked Ca(2+) entry was inhibited by nifedipine, econazole, SKF96365, GF109203X and phorbol 12-myristate 13 acetate. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin inhibited melamine-evoked [Ca(2+)]i rise. Conversely, treatment with melamine abolished thapsigargin-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 did not alter melamine-evoked [Ca(2+)]i rise. Melamine at 500-800μM decreased cell viability, which was not reversed by pretreatment with the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, our data suggest that in PC3 cells, melamine induced [Ca(2+)]i rises by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum, and Ca(2+) entry via protein kinase C-regulated store-operated Ca(2+) entry. Melamine also caused Ca(2+)-independent cell death.

The selective NADPH oxidase inhibitor apocynin has potential prophylactic effects on melamine-related nephrolithiasis in vitro and in vivo

The objective of this study is to examine the effects of apocynin on melamine-cyanuric acid mixture (MCM)-induced nephrolithiasis in vitro and in vivo. For the in vitro experiments, changes in oxidative stress (OS) markers and the expression of osteopontin (OPN) and phospho-p38 (p-p38) were measured to assess the effects of apocynin treatment after MCM-induced crystallization in HK-2 cells, a human renal epithelial-derived cell line. For in vivo studies, the potential effects of apocynin in preventing and treating nephrolithiasis were analyzed with a MCM-induced nephrolithiasis rat model, and urea and creatinine levels were measured. Urinary 8-IP (a product of lipid peroxidation) and malondialdehyde levels and superoxide dismutase activity were assessed in the kidneys as markers of renal OS. The kidneys were removed, weighed, and subjected to histopathological examination. The urolithiasis-associated proteins p-p38 and OPN were evaluated by immunohistochemistry and Western blotting. Apocynin treatment prevented the MCM-induced changes in OS and in OPN and p-p38 expression in HK-2 cells. For in vivo experiments, the expression of OS markers, renal OPN, and p-p38 increased after MCM administration, and these increases were diminished by apocynin. In addition, apocynin prevented MCM-induced renal crystallization. Moreover, prophylactic apocynin treatment reduced MCM-induced nephrotoxicity. After therapeutic apocynin treatment in nephrolithic rats, OS decreased, but the other indicators did not improve significantly. Prophylactic apocynin administration reduced renal melamine-related-crystal deposition, potentially by modulating OS and thereby decreasing p-p38 and OPN expression.

Reversible effects of vitamins C and E combination on oxidative stress-induced apoptosis in melamine-treated PC12 cells

Due to its high nitrogen content, melamine was deliberately added to raw milk for increasing the apparent protein content. Previous studies showed that melamine-induced apoptosis and oxidative damage on PC12 cells and rats' hippocampus. Several evidences suggested that vitamin antioxidant reduced oxidative stress and improved organic function. Whether treatments with antioxidant vitamins C or E, otherwise combination of them can attenuate oxidative stress after melamine administration remains to be elucidated. In this study, the reversible effects of vitamin antioxidants was investigated on melamine-induced neurotoxicity in cultured PC12 cells, an in vitro model of neuronal cells. When comparing vitamin C and E, the combination of both statistically increased PC12 cells viability. The results further showed that vitamin complex has effectively reduced the formation of reaction oxygen species, decreased the level of malondialdehyde, and elevated the activities of antioxidative enzymes. Hoechst 33342 staining and flow cytometric analysis of apoptosis showed that vitamin combination treatment effectively prevented PC12 cells from this melamine-induced apoptosis. It revealed the apoptotic nuclear features of the melamine-induced cell death. Additionally, a combination treatment of vitamins effectively inhibited apoptosis via blocking the increased activation of caspase-3. In summary, the vitamin E and C combination treatment could rescue PC12 cells from the injury induced by melamine through the downregulation of oxidative stress and prevention of melamine-induced apoptosis.

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.

Astragaloside IV suppresses collagen production of activated hepatic stellate cells via oxidative stress-mediated p38 MAPK pathway

Oxidative stress is involved in hepatic fibrogenesis. Activation of hepatic stellate cells (HSCs), the key effectors in hepatic fibrogenesis, is characterized by overproduction of extracellular matrix. Astragaloside IV, the active component of Radix Astragali, has antioxidant properties and antifibrotic potential in renal fibrosis. Little is known about the role of astragaloside IV in liver and its involvement in hepatic fibrosis. This study aims at evaluating the antifibrotic potential of astragaloside IV and characterizing involved signal transduction pathways in culture-activated HSCs. Our results show that astragaloside IV attenuates oxidative stress in culture-activated HSCs, as demonstrated by scavenging reactive oxygen species and reducing lipid peroxidation, and elevates the level of cellular glutathione by stimulating Nrf2gene expression. Depletion of cellular glutathione by buthionine sulfoximine or abrogation of p38 MAPK by SB-203580 evidently eliminates the inhibitory effects of astragaloside IV on genes relevant to HSC activation. These results demonstrate that astragaloside IV inhibits HSC activation by inhibiting generation of oxidative stress and associated p38 MAPK activation and provide novel insights into the mechanisms of astragaloside IV as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

Melamine activates NFκB/COX-2/PGE2 pathway and increases NADPH oxidase-dependent ROS production in macrophages and human embryonic kidney cells

Melamine is a wildly used compound in manufactures of plastics and resins. A variety of toxic effects from melamine, including nephrolithiasis, chronic kidney inflammation, and bladder carcinoma, have been mentioned. Oxidative stress is considered to be an important pathogenic mechanism of kidney disease which may develop from an increasing free radical production through inflammation. The aim of this study is to investigate melamine-induced oxidative stress and inflammation in macrophage-like cell line RAW 264.7 and human embryonic kidney cell line HEK293. Results indicated melamine activated nuclear factor (NF)-κB through increasing IκB-α degradation and NF-κB p65/p50 DNA-binding activity. In addition, melamine significantly increased COX-2 expression and prostaglandin E2 (PGE2) production. Moreover, melamine activated NADPH oxidase (NOX), including NOX1, NOX2 and NOX4, accompanied with an increase in reactive oxygen species (ROS) production. Furthermore, melamine-induced ROS production could be attenuated by apocynin, a NOX inhibitor. In conclusion, our findings suggest melamine increased inflammation and oxidative stress via activation of NF-κB/COX-2 and NOX/ROS pathway, and first revealed the critical role of NOX in melamine-induced ROS production, suggesting the potential of NOX inhibitor against melamine toxicity.

Antioxidant responses and renal crystal formation in rainbow trout treated with melamine administered individually or in combination with cyanuric acid

In 2007 and 2008, renal stone formation and kidney damage in human infants were linked to consumption of melamine (MEL)-contaminated infant formula, as well as renal failure and death in pets due to pet food containing both MEL and cyanuric acid (CYA). The aim of this study was to examine the effects of MEL and CYA administered individually or in combination on concentrations of certain metabolites and enzyme activities that serve as markers for oxidative stress in kidney and liver of rainbow trout. In addition, the levels of muscle MEL and renal crystal formation were determined. Trout were fed MEL and/or CYA for 8 wk at 250, 500, or 1000 mg of each compound/kg in feed. Fish muscle residues of MEL exhibited a dose-response relationship. Coexposure of trout to MEL and CYA at the highest dose led to lower MEL residue concentrations in muscle compared to exposure to MEL alone. Renal MEL-CYA complexes were found in kidneys of fish treated with combined MEL and CYA. A dose response was evident with respect to both (1) number of trout displaying renal crystals and (2) number of crystals per fish. Changes in concentration of antioxidant parameters, such as glutathione, superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase, were recorded in both tissues of MEL- and CYA-dosed trout. Lipid peroxidation was more pronounced in kidney than liver. Therefore, feed contaminated with both MEL and CYA could be problematic for fish, as MEL administered to trout, individually or in combination with CYA, may facilitate the onset of oxidative damage in trout.

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.