Jian Chun Bian

Oxidative Stress and Apoptotic Changes of Rat Cerebral Cortical Neurons Exposed to Cadmium in Vitro

OBJECTIVE To investigate the cytotoxic mechanism of cadmium (Cd) on cerebral cortical neurons. METHODS The primary cultures of rat cerebral cortical neurons were treated with different concentrations of cadmium acetate (0, 5, 10, and 20 micromol/L), and then the cell viability, apoptosis, ultrastructure, intracellular [Ca2+], and reactive oxygen species (ROS) levels, mitochondrial membrane potential (delta psi), activities of catalase (CAT) and superoxide dismutase (SOD) were measured. RESULTS A progressive loss in cell viability and an increased number of apoptotic cells were observed. In addition, Cd-induced apoptotic morphological changes in cerebral cortical neurons were also demonstrated by Hoechst 33258 staining. Meanwhile, ultrastructural changes were distortion of mitochondrial cristae and an unusual arrangement. Simultaneously, elevation of intracellular [Ca2+]i and ROS levels, depletion of Delta Psi were revealed in a dose-dependent manner during the exposure. Moreover, CAT and SOD activities in the living cells increased significantly. CONCLUSION Exposure of cortical neurons to different doses of Cd led to cellular death, mediated by an apoptotic mechanism, and the apoptotic death induced by oxidative stress may be a potential reason. And the disorder of intracellular homeostasis caused by oxidative stress and mitochondrial dysfunction may be a trigger for apoptosis in cortical neurons.

Zearalenone impairs the male reproductive system functions via inducing structural and functional alterations of sertoli cells.

The aim of this study was to investigate the effects of ZEA on the cytoskeletal structure, and factors specifically expressed by Sertoli cells. Primary Sertoli cells from rats aged 18-21 days were exposed to increasing ZEA concentrations (0, 5, 10, 20 μg mL(-1)) for 24 h. The results of immunofluorescence showed disruption of α-tubulin filaments and F-actin bundles, and damage to the nucleus of Sertoli cells on exposure to ZEA. In the control group, the protein level expression of androgen-binding protein (ABP), transferrin, vimentin, N-cadherin, and follicle-stimulating hormone receptor (FSHR) were decreased significantly (p<0.05, p<0.01). The mRNA levels of ABP, transferrin, vimentin, N-cadherin, and FSHR varied significantly in the experimental group (p<0.05). The results of enzyme-linked immunosorbent assay indicated a significant decrease in the levels of inhibin-β and transferrin in the cultural supernatants (p<0.05). Additionally, the ultrastructural analysis indicated the absence of mitochondria and Golgi apparatus, and presence of vacuoles in the cytoplasm. These findings showed that ZEA treatment can damage the cytoskeletal structure and affect specific secretory functions of Sertoli cells, which may be an underlying cause of ZEA-induced reproductive toxicity.

Effect of Cadmium on Rat Leydig Cell Testosterone Production and DNA Integrity in vitro

Cadmium(Cd)is an elemental heavy metal with widely recognized toxicity.Its long-term use in industrial processes and daily activities has caused alarming levels of Cd contamination in the natural environment.According to the estimates by the Agency of Toxic Substances and Disease Registry in the US,25 000 to 30 000 metric tons of Cd is annually released to the environment[1].Results of previous studies have demonstrated that several organs are targets of Cd,but the most important of these targeted organs may be the testes.Cadmium can cause the apoptosis of testis cells and modify the

Cadmium-induced autophagy is mediated by oxidative signaling in PC-12 cells and is associated with cytoprotection

Oxidative stress induced by cadmium (Cd) is a common phenomenon that has been observed in numerous studies. However, the underlying mechanism remains unknown. Recently, exposure of PC-12 cells to Cd has been shown to activate autophagy, which acts as a temporary survival pathway under stressful conditions by delaying the occurrence of apoptosis. The present study investigated the impact of oxidative stress on Cd‑induced autophagy in PC-12 cells. The results demonstrated that Cd‑induced autophagy (following treatment with Cd for 4 h), increased the levels of intracellular reactive oxygen species (ROS), decreased the mitochondrial membrane potential and resulted in apoptosis. A treatment with chloroquine (CQ; an autophagic inhibitor) sensitized the PC‑12 cells to Cd, due to the increased production of ROS, which was associated with the incapacity to reduce mitochondrial and cell death. N-acetyl-L-cysteine, an antioxidant agent, decreased Cd-induced autophagy and reduced intracellular ROS levels, but enhanced CQ‑induced apoptotic cell death. These findings indicate that moderate levels of ROS are essential in the regulation of Cd-induced autophagy, which subsequently enhances cell survival. Thus, the results of the present study provide an insight for future investigation of Cd-induced neurotoxicity.

Cadmium-induced autophagy promotes survival of rat cerebral cortical neurons by activating class III phosphoinositide 3-kinase/beclin-1/B-cell lymphoma 2 signaling pathways.

Autophagy is an evolutionarily conserved response that can be activated in response to heavy metal. Thus, the present study investigated the effect of autophagy on neurotoxic damage caused by cadmium (Cd) in rat cerebral cortical neurons. The results indicated that the viability of cortical neurons treated with Cd was markedly decreased in a dose-and time-dependent manner. The present study provided evidence that cortical neurons treated with Cd underwent autophagy: The conversion of microtubule-associated protein 1A/1B-light chain 3 (LC3) to LC3-II, an increase in the punctate distribution of endogenous LC3-II and the presence of autophagosomes were identified. Combined treatment with Cd and chloroquine, an autophagy inhibitor, reduced the amount of autophagocytosis and cell activity, whereas rapamycin, an autophagy inducer, reduced Cd-mediated cytotoxicity. Furthermore, it was found that beclin-1 and class III phosphoinositide 3 kinase (PI3K) levels were increased, while levels of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) were decreased after Cd treatment. LY294002, a specific inhibitor of PI3K, prevented the decline in Bcl-2 production and the increase in levels of beclin-1, class III PI3K and autophagy following Cd treatment. In conclusion, the results of the present study suggested that Cd can induce cytoprotective autophagy by activating the class III PI3K/beclin-1/Bcl-2 signaling pathway, and that the autophagy pathway can serve as a sensitive biomarker for nervous system injury after exposure to Cd.

Regulation of oncogenes and gap junction intercellular communication during the proliferative response of zearalenone in TM3 cells

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin produced by Fusarium species. The exposure risk to humans and animals is the consumption of contaminated food and animal feeds. The aim of this study was to investigate ZEA-induced effects and its tumorigenic mechanism in TM3 cells (mouse Leydig cells). Cell proliferation, apoptosis, and gap junction intercellular communication (GJIC) were assessed in this study. Results showed that low concentrations of ZEA could significantly promote the growth of TM3 cells. The percentage of cell distribution was decreased significantly in G1/G0 phase and was increased significantly in S phase with 10 and 20 μg/L of ZEA for 72 h (p < 0.05, p < 0.01). The expressions of cyclin D1 and Cdk4 were significantly increased in the exposure groups compared with the control group (p < 0.05, p < 0.01). Compared with the control group, the apoptosis was significantly decreased in 10 and 20 μg/L groups (p < 0.01), and the ratio of Bax/Bcl-2 protein level was significantly decreased in a dose-dependent manner. The protein levels of proto-oncogene c-Myc, c-Jun, and c-Fos were significantly elevated and the protein levels of anti-oncogene p53 and phosphatase and tensin homolog (PTEN) were decreased obviously compared with the control group (p < 0.05, p < 0.01). ZEA affected the expressions of connexins and inhibited the activity of GJIC. These results demonstrated that ZEA can disturb the dynamic balance between proliferation and apoptosis and causes abnormal regulation of oncogenes, GJIC, and connexins in TM3 cells, which may easily induce the translation of normal cells into tumor cells.