Yachen Li

Subchronic Exposure to Arsenic Inhibits Spermatogenesisand Downregulates the Expression of Ddx3y in Testisand Epididymis of Mice

Arsenic (As) is a ubiquitous environmental contaminant. Excess As exposure is considered one of the top health threats worldwide. As-induced Male reproductive toxicity is causing wide concern. The goal of this study is to determine whether subchronic As exposure inhibits Ddx3y expression, an Y-linked gene important in spermatogenesis and sperm maturation, and whether the inhibited expression of Ddx3y is closely associated with As-induced male reproductive toxicity Adult mice were given drinking water alone or water containing 1, 2, and 4mg/l arsenic trioxide (As(2)O(3)) for 60 days. After the treatment, the weights of testis and epididymis were analyzed. The sperm quality, spermatogenesis, and histological alteration of the testis and epididymis were observed by microscope. Furthermore, the expressions of Ddx3y gene and its protein in the testis and epididymis were examined by real-time reverse transcription PCR, Western blotting, and immunohistochemistry. Compared with untreated mice, the weights of testis and epididymis were reduced, sperm motility and the number of stage VII cells in the seminiferous epithelium section were decreased, sperm malformation ratio was increased, and histopathological alterations were observed in As-treated mice. The gene and protein expression of Ddx3y in testis and epididymis were significantly downregulated in As-exposed mice. Subchronic As exposure has detrimental effects on spermatogenesis and sperm development. It also downregulates Ddx3y expressions in testis and epididymis. Our results indicated that Ddx3y may be an important target gene of As and the downregulated expression of Ddx3y may be closely related to male reproductive toxicity induced by As.

Protective Effect of Taurine on the Decreased Biogenic Amine Neurotransmitter Levels in the Brain of Mice Exposed to Arsenic

Arsenic (As) exposure has a toxic effect on the central nervous system, especially on learning and memory. Norepinephrine (NE), dopamine (DA), and serotonin (5-HT) play an important role in learning and memory function of the brain. In the present study, the protective effect of taurine on the disturbed biogenic amine neurotransmitter levels in the mouse brain induced by arsenic was examined. Sixty SPF mice were divided into three groups. The As exposure group was administered with 4 ppm As(2)O(3) through drinking water for 60 days. The protective group was treated with both 4 ppm As(2)O(3) and 150 mg/kg taurine. The control group was given drinking water alone. The levels of NE, DA, and 5-HT were determined by HPLC in the cerebrum and cerebellum of mice. Ultrastructure of synapses in brain tissue of mice was observed in these groups by transmission electron microscopy. The mRNA expressions of dopamine beta hydroxylase (DBH), tyrosine hydroxylase (TH), and tryptophan hydroxylase (TPH) as NE, DA, and 5-HT synzymes were also analyzed by real-time RT-PCR. The results showed that the concentrations of NE, DA, and 5-HT; the number of synaptic vesicles; and the expressions of TH, TPH, and DBH genes in the brains of mice exposed to As alone were significantly decreased. However, administration of taurine significantly alleviated the toxic effect on biochemicals detected in the experiment, compared with that in the brain of mice exposed to As alone. These results indicated that taurine was effective in counteracting the decreased biogenic amine neurotransmitter level and the mRNA expressions of their synzymes induced by arsenic.

Chlorpyrifos Induces MLL Translocations Through Caspase 3-Dependent Genomic Instability and Topoisomerase II Inhibition in Human Fetal Liver Hematopoietic Stem Cells

Household pesticide exposure during pregnancy has been associated with a more than 2-fold increased risk in infant leukemia, and chlorpyrifos (CPF) is among the most frequently applied insecticides. During early fetal development, liver is a hematopoietic organ with majority of cells being CD34(+) hematopoietic stem cells (CD34(+)HSC). The in utero injury to CD34(+)HSC has been known to underlie the pathogenesis of several blood disorders, often involving rearrangements of the mixed-lineage leukemia (MLL) gene on 11q23. In this study, we evaluated the leukemogenic potential of CPF in human fetal liver-derived CD34(+)HSC. Specifically, exposure to 10 μM CPF led to decrease in viability, inhibition in proliferation and induction of DNA double-strand breaks (DSBs) and occurrence of MLL(+) rearrangements. In particular, we observed CPF-mediated cell cycle disturbance as shown by G0/G1 arrest, in contrast to etoposide (VP-16), an anticancer drug used as a positive control and known to induce G2/M arrest. Further study on mechanisms underlying DNA DSBs and MLL(+) rearrangements revealed that CPF might act as topoisomerase II poison, a mechanism of action similar to VP-16. On the other hand, CPF was also shown to induce early apoptosis through active caspase-3 activation, a pathway known to underlie DNA DSBs and MLL(+) translocations. Our data indicate that in utero injury of CD34(+)HSC by CPF may contribute to the increased risk of infant leukemia. Future work will elucidate the mechanism and the type of CPF-induced MLL(+) translocations in HSC.

Subchronic exposure to lead acetate inhibits spermatogenesis and downregulates the expression of Ddx3y in testis of mice

Male mice were given drinking water alone or containing 0.5, 1.0 and 1.5g/L Pb acetate for 60 days. After the treatment, the concentrations of Pb were determined in the serum and testis of mice by ICP-MS. The gene transcription of Usp9y, Ddx3y and Uty and their protein levels in the testis were examined by real-time PCR, Western blotting and immunohistochemistry. The sperm quality, spermatogenesis, and histological alteration of the testis and epididymis were observed by microscope. The probability of impregnating female mice by lead-exposed male was evaluated. It was shown that the concentrations of Pb in serum and testis of mice significantly increased in the groups exposed to Pb in a dose-dependent manner. The male fertility significantly decreased in the groups exposed to 1.0 and 1.5g/L Pb acetate. Moreover, exposure to Pb also inhibited spermatogenesis and sperm development, and significantly downregulated expressions of Ddx3y gene expression in testis of mice, but Usp9y and Uty expressions unaffected.

Evaluation of PFOS-mediated neurotoxicity in rat primary neurons and astrocytes cultured separately or in co-culture.

Perfluorooctane sulfonate (PFOS) is a potential neurotoxicant reported by epidemiological investigations and experimental studies, while the underlying mechanisms are still unclear. Astrocytes not only support for the construction of neurons, but also conduct neuronal functions through glutamate-glutamine cycle in astrocyte-neuron crosstalk. In the present study, the effect of PFOS exposure on rat primary hippocampal neurons or cortex astrocytes was evaluated. Then the role of the astrocytes in PFOS-induced toxic effect on neurons was explored with astrocyte-neuron co-culture system. Exposure of rat primary hippocampal neurons to PFOS has led to oxidation-antioxidation imbalance, increased apoptosis and abnormal autophagy. The adverse effect of PFOS on rat primary cortex astrocytes manifested in the form of altered extracellular glutamate and glutamine concentrations, decreased glutamine synthase activity, as well as decreased gene expression of glutamine synthase, glutamate transporters and glutamine transporters in the glutamate-glutamine cycle. Especially, the alleviation of PFOS-inhibited neurite outgrowth in neurons could be observed in astrocyte-neuron co-culture system, though the ability of astrocytes in fostering neurite outgrowth was affected by PFOS. These results indicated that both astrocytes and neurons might be the targets of PFOS-induced neurotoxicity, and astrocytes could protect against PFOS-inhibited neurite outgrowth in primary cultured neurons. Our research might render some information in explaining the mechanisms of PFOS-induced neurotoxicity.

Taurine Ameliorates Arsenic-Induced Apoptosis in the Hippocampus of Mice Through Intrinsic Pathway

Our group previously reported that arsenic (As) exposure induced apoptosis in hippocampus neurons. The aim of the present study was to clarify the protective capacity of taurine (Tau) on As-induced neuronal apoptosis and the related mechanism in mouse hippocampus. Mice were divided into: control group, Tau control group, As exposure group and Tau protective group, randomly. The apoptotic rate of mouse hippocampus was determined by TUNEL staining. The levels of Bcl-2 and Bax gene and protein were analyzed by real time RT-PCR and WB, respectively. Furthermore, cytochrome c (Cyt C) release, and the activity of caspase-8 and caspase-3 were also determined. The results showed that Tau treatment induced the decrease of TUNEL-positive cells, prohibited the disturbance of Bcl-2 and Bax expression, and inhibited Cyt C release and caspase-8 and caspase-3 activation significantly. The results indicated that Tau supplement markedly ameliorates As-induced apoptosis by mitochondria-related pathway in mouse hippocampus.

Protective Effect of Taurine on Triorthocresyl Phosphate (TOCP)-Induced Cytotoxicity in C6 Glioma Cells

Triorthocresyl phosphate (TOCP) an organophosphorus ester can cause neurotoxicity via oxidative stress pathway. Taurine is an antioxidant. The objective of this study was to investigate the protective effect of taurine on TOCP-induced cytotoxicity in C6 glioma cell. The C6 glioma cells were pretreated with 0, 1, 3, and 9 mM of taurine for 30 min prior to 1 mM TOCP treatment. After 48 h, cell survival was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release. The content of glutathione (GSH) and the activity of glutathione peroxidase (GPx) were also analyzed by kits. Our results showed that survival of the glioma cells decreased in the group treated with TOCP alone and increased significantly in the groups pretreated with taurine in a concentration-dependent manner. TOCP induced decrease in the activity of GPx and the content of GSH. However, taurine prevented these decreases. Our results suggested that taurine has protective effect on TOCP-induced toxicity to glioma cells via elevating antioxidant capacity.

Protection of Taurine Against PFOS-Induced Neurotoxicity in PC12 Cells

As a new member of persistent organic pollutants, the potent neurotoxicity of perfluorooctane sulfonates (PFOS) found in epidemiological studies and laboratory research has drawn increasing attention around the world. Previous studies showed that apoptosis driven by oxidative stress and autophagy were both observed in PFOS-induced toxicity. Taurine has been demonstrated to exert potent protections against oxidative stress as an efficient antioxidant. Whether taurine could protect against the PFOS neurotoxicity is not known. In the present study, PC12 cells were treated with several concentrations of PFOS (31.25, 250 μM) for 24 h. 3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was applied to assess the cell viability. DCFH-DA detector was used to explore the production of ROS. Caspase 3 activity was used to reflect the possible apoptosis pathway. The lyso-tracker red dying was invited to evaluate the autophagy. Our data showed that taurine could significantly reverse the decreased viability and the increased ROS production in PC12 cells treated with PFOS. Moreover, the increased autophagy and apoptosis elicited by PFOS in PC12 cells could also be attenuated by taurine. Collectively, our results indicate that taurine may be an effective antioxidant in fighting against PFOS cytotoxicity and therefore could potentially serve as a preventative and therapeutic agent for environmental pollution-related toxicities.

Protective Effect of Taurine on Down-Regulated Expression of Thyroid Hormone Receptor Genes in Brains of Mice Exposed to Arsenic

This study aimed at evaluating protective effect of taurine on the down-regulated expressions of thyroid hormone receptor (TR) genes in brains of mice exposed to arsenic (As). The SPF mice were randomly divided into As exposure group, protective group, and control group. The As exposure group was administered with 4 ppm As(2)O(3) through drinking water for 60 days. The protective group was treated with both 4 ppm As(2)O(3) and 150 mg/kg taurine. The control group was given with drinking water alone. The gene expressions of TR in the mouse brains of the three groups were analyzed by real-time PCR. Their protein expressions were examined by Western blot and immunohistochemistry. Our results showed that the gene expression of TRβ, a very important regulator of Camk4 transcription, was down-regulated in cerebral and cerebellar tissues of mice exposed to As. The expression of TRβ1 protein in the cerebral or cerebellar tissue significantly decreased in the group exposed to As compared to the control group. However, the expressions of TRβ gene and TRβ1 protein were significantly rescued in the group coadministered with taurine as antioxidant. These results indicated that taurine may have the protective effect on the down-regulated expressions of TR in brains of mice exposed to As.

Taurine Attenuates As 2 O 3 -Induced Autophagy in Cerebrum of Mouse Through Nrf2 Pathway

We previously reported that the impairment of cerebrum may relate with neurotoxicity induced by arsenic (As) exposure. In the present study, we investigated whether autophagy of the cerebrum neurons were responsible for As-induced neurotoxicity and the protective role of taurine (Tau). Forty mice were randomly divided into control group, Tau control group, As exposure group and Tau protection group. The results showed that LC3 II expression was elevated and P62 expression was lower after As exposure, whereas the effects were obviously attenuated by Tau treatment. More important, As induced increase of MDA level and decrease of Nrf2 expression were significantly inversed in protective group. In sum, autophagy inhibition might play a strong role in the neuroprotection of Tau in As-induced toxicity via Nrf2 pathway.