Jundong Wang

Fluoride-induced thyroid dysfunction in rats: roles of dietary protein and calcium level:

To assess the roles of dietary protein (Pr) and calcium (Ca) level associated with excessive fluoride (F) intake and the impact of dietary Pr, Ca, and F on thyroid function, 144 30-day-old Wistar albino rats were randomly allotted to six groups of 24 (female:male = 1:1). The six groups were fed (1) a normal control (NC) diet (17.92% Pr, 0.85% Ca = NC group); (2) the NC diet and high F (338 mg NaF [=150 mg F ion]/L in their drinking water = NC+F group); (3) low Pr and low Ca diet (10.01% Pr, 0.24% Ca = LPrLCa group); (4) low Pr and low Ca diet plus high F = LPrLCa+F group; (5) high Pr and low Ca diet plus high F (25.52% Pr, 0.25% Ca = HPrLCa+F group); and (6) low Pr and high Ca diet plus high F (10.60% Pr, 1.93% Ca = LPrHCa+F group). The areas of thyroid follicles were determined by Image-Proplus 5.1, and triiodothyronine (T3), free T3 (FT3), thyroxine (T4), and free T4 (FT4) levels in serum were measured by radioimmunoassay. The histopathological study revealed obviously flatted follicular epithelia cells and hyperplastic nodules, consisting of thyroid parafollicular cells that appeared by excessive F ingestion, on the 120th day. Pr or Ca supplementation reverses the F-induced damage in malnutrition. The serum T3, FT3, T4, and FT4 levels in the NC+F group were significantly decreased and significantly increased in the LPrLCa+F group. Thus, excessive F administration induces thyroid dysfunction in rats; dietary Pr and Ca level play key roles in F-induced thyroid dysfunction.

Fluoride induces apoptosis and alters collagen I expression in rat osteoblasts.

In this study we investigated apoptosis and expression of the collagen I gene in newborn rat osteoblasts (OB) by the administration of varying concentrations of fluoride (F). Sodium fluoride (NaF) at concentrations of 0, 0.5, 5, 10, and 20mg/L was administered to cultured OB. The percentage of G(1)/G(0) (Gap 1/Gap 0), S (synthesis), G(2)/M (Gap 2/M, mitosis), and apoptosis rates in OB were analyzed with a Fluorescence-activated Cell Sorter (FACS) by propidium iodine (PI) staining after F treatment of 72 h. Effects of F treatment on COL1A1 and COL1A2 mRNA and collagen I protein levels were determined using quantitative real time RT-PCR (qRT-PCR) and immunofluorescence, respectively. This study demonstrates that there is a pronounced negative effect of long term NaF treatment on OB survival. These negative effects include an inhibition of the transformation from S phase into G(2)/M phase, increased apoptosis, and decreased COL1A1 mRNA, down-regulating the synthesis of COL I protein. The results suggest that COL I protein degradation in OB from F toxicity is due to a depletion of COL1A1 mRNA and not COL1A2.

Proteomic analysis of brain proteins of rats exposed to high fluoride and low iodine.

Epidemiological investigations reveal that high fluoride and low iodine have strong adverse effects on the intelligence quotient (IQ) of children. Studies also report that in some high fluoride areas, iodine deficiency also exists, especially in China. Here, with the proteomic techniques, we first report on the proteomic changes in brain proteins in offspring rats at postnatal day 20 exposed to high fluoride and/or low iodine. To investigate molecular mechanisms of central neural system injury induced by the above two elements, proteins were isolated and profiled by two-dimensional gel electrophoresis (2DE). By the analysis of Image-Master 2D Elite software, 71 protein spots in 2DE gels of treatment groups were gained and up- or down-regulated by two folds, and 5 proteins were regulated by five folds, with the comparison to the control group. The proteins changed by five folds were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The identified proteins are mainly related with cellular signaling, energy metabolism, and protein metabolism and provide a valuable clue to explore the mechanism underlining the neurotoxicity of high fluoride and low iodine. Moreover, these results could provide potential biomarkers for hazards caused by excessive fluoride and low iodine.

Changes in memory and synaptic plasticity induced in male rats after maternal exposure to bisphenol A.

Bisphenol A (BPA), a component of polycarbonate and epoxy resins, has been reported to adversely impact the central nervous system, especially with respect to learning and memory. However, the precise effect and specific mechanisms have not been fully elucidated. In the present study, pregnant Sprague-Dawley rats were orally administered with BPA at 0.05, 0.5, 5 or 50mg/kg·body weight (BW) per day from embryonic day 9 (E 9) to E 20. We examined the effects of maternal BPA exposure on memory and synaptic structure in the hippocampus of male offspring at postnatal day (PND) 21. Maternal BPA exposure significantly affected locomotor activity, exploratory habits, and emotional behavior in open field test, and increased reference and especially working memory errors in the radial arm maze during the postnatal developing stage. Maternal BPA exposure had an adverse effect on synaptic structure, including a widened synaptic cleft, a thinned postsynaptic density (PSD), unclear synaptic surface and disappeared synaptic vesicles. Furthermore, maternal BPA exposure decreased the mRNA and protein expressions of synaptophysin, PSD-95, spinophilin, GluR1 and NMDAR1 in the hippocampus of male offspring on PND 21. These results showed that fetal growth and development was more sensitive to BPA exposure. The decreased learning and memory induced by maternal exposure to BPA in this study may be involved in synaptic plasticity alteration.

Inflammatory responses induced by fluoride and arsenic at toxic concentration in rabbit aorta

Epidemiological and experimental studies have demonstrated the atherogenic effects of environmental toxicant arsenic and fluoride. Inflammatory mechanism plays an important role in the pathogenesis of atherosclerosis. The aim of the present study is to determine the effect of chronic exposure to arsenic and fluoride alone or combined on inflammatory response in rabbit aorta. We analyzed the expression of genes involved in leukocyte adhesion [P-selectin (P-sel) and vascular cell adhesion molecule-1(VCAM-1)], recruitment and transendothelial migration of leukocyte [interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1)] and those involved in pro-inflammatory cytokines [interleukin-6 (IL-6)]. We found that fluoride and arsenic alone or combined increased the expression of VCAM-1, P-sel, MCP-1, IL-8, and IL-6 at the RNA and protein levels. The gene expressions of inflammatory-related molecules were attenuated when co-exposure to the two toxicants compared with just one of them. We also examined the lipid profile of rabbits exposed to fluoride and (or) arsenic. The results showed that fluoride slightly increased the serum lipids but arsenic decreased serum triglyceride. We showed that inflammatory responses but not lipid metabolic disorder may play a crucial role in the mechanism of the cardiovascular toxicity of arsenic and fluoride.

Fluoride decreased the sperm ATP of mice through inhabiting mitochondrial respiration.

Fluoride-induced low sperm motility was observed in accumulated investigations. However, the effect of fluoride exposure on ATP generation which is essential to sperm motility remains to be elucidated. In this study, 120 healthy male mice were orally administrated with 0, 25, 50, and 100 mg L(-1) NaF for 90 d. Results showed that compared with controls, fluoride ingestion significantly reduced sperm count, survival, as well as mobility and total ATP level in sperm untreated with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or pyruvate, which was used to establish glycolysis or mitochondrial respiration model, respectively. Data further revealed that sperm mobility and ATP level under mitochondrial respiration condition were significantly suppressed, while no statistical difference occurred in the model of glycolysis, indicating ATP derived from mitochondria was affected. Moreover, mRNA expressions of mitochondrial cytochrome b (mt-Cytb) and cytochrome c oxidase subunit 2 (mt-COX2), two important molecules in mitochondrial electron transport chain (ETC), were down-regulated in all fluoride treatment groups. Mitochondria in sperm of mice exposed to 100 mg L(-1) NaF appeared to be irregular and vacuolated. These findings suggested that decreased sperm motility induced by fluoride may result from low ATP generation due to the disturbed ETC in sperm mitochondrial.

Effect of pubertal nano-TiO2 exposure on testosterone synthesis and spermatogenesis in mice

Titanium dioxide nanoparticles (nano-TiO2) are frequently used in cosmetics, paints, sunscreens and the like. Recent studies have demonstrated that nano-TiO2 might be deleterious for the male reproductive function. However, the effects of pubertal nano-TiO2 exposure on testosterone (T) synthesis and spermatogenesis remained to be elucidated. Here, we investigated the effect of pubertal nano-TiO2 exposure on the synthesis of T and spermatogenesis. Nano-TiO2 was orally administered daily to Kunming male mice from 28th postnatal day (PND 28) to PND 70. The percentage of spermatozoa abnormality in epididymides was markedly increased in mice exposed to nano-TiO2; decreased layers of spermatogenic cells and vacuoles in seminiferous tubules were also observed in the nano-TiO2 treated group. In addition, pubertal nano-TiO2 exposure significantly decreased the serum T levels in male mice. Moreover, mice exposures to nano-TiO2 significantly reduced the expression of 17β-hydroxysteroid dehydrogenase and P450 17α-hydroxysteroid dehydrogenase in the testis of mice, while the expression of cytochrome P450-19, a key enzyme for the translation of T to estradiol (E2), was increased. Taken together, these results indicated that nano-TiO2 could influence the levels of serum T through changes in both the synthesis and translation of T. Furthermore, the decreased serum T synthesis might contribute to the reduced spermatogenesis in mice exposed to nano-TiO2.

Decreased learning ability and low hippocampus glutamate in offspring rats exposed to fluoride and lead

Fluoride (F) and lead (Pb) are two common environmental pollutants which are linked to the lowered intelligence, especially for children. Glutamate, a major excitatory neurotransmitter in the central nervous system, plays an important role in the process of learning and memory. However, the impact of F and Pb alone or in combination on glutamate metabolism in brain is little known. The present study was conducted to assess the glutamate level and the activities of glutamate metabolism related enzymes including asparate aminotransferase (AST), alanine aminotransferase (ALT) and glutamic acid decarboxylase (GAD) in the hippocampus, as well as learning abilities of offspring rat pups at postnatal week 6, 8, 10 and 12 exposed to F and/or Pb. During lactation, the pups ingested F and/or Pb via the maternal milk, whose mothers were exposed to sodium fluoride (150 mg/L in drinking water) and/or lead acetate (300 mg/L in drinking water) from the day of delivery. After weaning at postnatal day 21, the pups were exposed to the same treatments as their mother. Results showed that the learning abilities and hippocampus glutamate levels were significantly decreased by F and Pb individually and the combined interaction of F and Pb. The activities of AST and ALT in treatment groups were significantly inhibited, while the activities of GAD were increased, especially in rats exposed to both F and Pb together. These findings suggested that alteration of hippocampus glutamate by F and/or Pb may in part reduce learning ability in rats.

Prevalence and dissemination of antibiotic resistance genes and coselection of heavy metals in Chinese dairy farms.

This study aims to explore prevalence and dissemination of antibiotic resistance genes (ARGs) in dairy farms. A variety of ARGs conferring resistance to most classes of antibiotics were detected in feces and soil samples obtained from dairy farms, using a high-throughput metagenomic sequencing approach. The ARGs observed in the feces and the soil samples were significantly correlated (p<0.01). The abundance of mobile genetics elements, such as transposase, was also examined to evaluate the potential risk of horizontal ARGs transfer. The positive correlation (p<0.001) between the total abundance of transposase genes and ARGs in the soil samples suggested strong dissemination capacity of ARGs in soil. In addition, the ARGs and metal resistance genes (MRGs) were significantly correlated with heavy metals in the feces (p<0.01), suggesting that the heavy metals promoted the emergence of metal resistance, and participated in the coselection processes for ARGs. The prevalence of ARGs with high levels of genetic mobile elements in the dairy farms suggests that cattle excrement is a major reservoir of ARGs with a high risk of dissemination, which increases the potential risk of environmental pollution and threatens public health.

Gestational nicotine exposure modifies myelin gene expression in the brains of adolescent rats with sex differences

Myelination defects in the central nervous system (CNS) are associated with various psychiatric disorders, including drug addiction. As these disorders are often observed in individuals prenatally exposed to cigarette smoking, we tested the hypothesis that such exposure impairs central myelination in adolescence, an important period of brain development and the peak age of onset of psychiatric disorders. Pregnant Sprague Dawley rats were treated with nicotine (3 mg kg−1 per day; gestational nicotine (GN)) or gestational saline via osmotic mini pumps from gestational days 4–18. Both male and female offsprings were killed on postnatal day 35 or 36, and three limbic brain regions, the prefrontal cortex (PFC), caudate putamen and nucleus accumbens, were removed for measurement of gene expression and determination of morphological changes using quantitative real-time PCR (qRT-PCR) array, western blotting and immunohistochemical staining. GN altered myelin gene expression at both the mRNA and protein levels, with striking sex differences. Aberrant expression of myelin-related transcription and trophic factors was seen in GN animals, which correlated highly with the alterations in the myelin gene expression. These correlations suggest that these factors contribute to GN-induced alterations in myelin gene expression and also indicate abnormal function of oligodendrocytes (OLGs), the myelin-producing cells in the CNS. It is unlikely that these changes are attributable solely to an alteration in the number of OLGs, as the cell number was changed only in the PFC of GN males. Together, our findings suggest that abnormal brain myelination underlies various psychiatric disorders and drug abuse associated with prenatal exposure to cigarette smoke.