Cadmium Activates Reactive Oxygen Species-dependent AKT/mTOR and Mitochondrial Apoptotic Pathways in Neuronal Cells / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To examine the role of Cd-induced reactive oxygen species (ROS) generation in the apoptosis of neuronal cells.</p><p><b>METHODS</b>Neuronal cells (primary rat cerebral cortical neurons and PC12 cells) were incubated with or without Cd post-pretreatment with rapamycin (Rap) or N-acetyl-L-cysteine (NAC). Cell viability was determined by MTT assay, apoptosis was examined using flow cytometry and fluorescence microscopy, and the activation of phosphoinositide 3'-kinase/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and mitochondrial apoptotic pathways were measured by western blotting or immunofluorescence assays.</p><p><b>RESULTS</b>Cd-induced activation of Akt/mTOR signaling, including Akt, mTOR, p70 S6 kinase (p70 S6K), and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Rap, an mTOR inhibitor and NAC, a ROS scavenger, blocked Cd-induced activation of Akt/mTOR signaling and apoptosis of neuronal cells. Furthermore, NAC blocked the decrease of B-cell lymphoma 2/Bcl-2 associated X protein (Bcl-2/Bax) ratio, release of cytochrome c, cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP), and nuclear translocation of apoptosis-inducing factor (AIF) and endonuclease G (Endo G).</p><p><b>CONCLUSION</b>Cd-induced ROS generation activates Akt/mTOR and mitochondrial pathways, leading to apoptosis of neuronal cells. Our findings suggest that mTOR inhibitors or antioxidants have potential for preventing Cd-induced neurodegenerative diseases.</p>

Regulation of matrix metalloproteinase-9 protein expression by 1alpha,25-(OH)2D3 during osteoclast differentiation

To investigate 1alpha,25-(OH)2D3 regulation of matrix metalloproteinase-9 (MMP-9) protein expression during osteoclast formation and differentiation, receptor activator of nuclear factor kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) were administered to induce the differentiation of RAW264.7 cells into osteoclasts. The cells were incubated with different concentrations of 1alpha,25-(OH)2D3 during culturing, and cell proliferation was measured using the methylthiazol tetrazolium method. Osteoclast formation was confirmed using tartrate-resistant acid phosphatase (TRAP) staining and assessing bone lacunar resorption. MMP-9 protein expression levels were measured with Western blotting. We showed that 1alpha,25-(OH)2D3 inhibited RAW264.7 cell proliferation induced by RANKL and M-CSF, increased the numbers of TRAP-positive osteoclasts and their nuclei, enhanced osteoclast bone resorption, and promoted MMP-9 protein expression in a concentration-dependent manner. These findings indicate that 1alpha,25-(OH)2D3 administered at a physiological relevant concentration promoted osteoclast formation and could regulate osteoclast bone metabolism by increasing MMP-9 protein expression during osteoclast differentiation.

Inhibitory effects of osteoprotegerin on osteoclast formation and function under serum-free conditions

The purpose of this study was to determine whether osteoprotegerin (OPG) could affect osteoclat differentiation and activation under serum-free conditions. Both duck embryo bone marrow cells and RAW264.7 cells were incubated with macrophage colony stimulatory factor (M-CSF) and receptor activator for nuclear factor kappaB ligand (RANKL) in serum-free medium to promote osteoclastogenesis. During cultivation, 0, 10, 20, 50, and 100 ng/mL OPG were added to various groups of cells. Osteoclast differentiation and activation were monitored via tartrate-resistant acid phosphatase (TRAP) staining, filamentous-actin rings analysis, and a bone resorption assay. Furthermore, the expression osteoclast-related genes, such as TRAP and receptor activator for nuclear factor kappaB (RANK), that was influenced by OPG in RAW264.7 cells was examined using real-time polymerase chain reaction. In summary, findings from the present study suggested that M-CSF with RANKL can promote osteoclast differentiation and activation, and enhance the expression of TRAP and RANK mRNA in osteoclasts. In contrast, OPG inhibited these activities under serum-free conditions.

Oxidative stress and apoptotic changes of rat cerebral cortical neurons exposed to cadmium in vitro / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the cytotoxic mechanism of cadmium (Cd) on cerebral cortical neurons.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>