Telomerase activity and telomerase reverse transcriptase expression induced by selenium in rat hepatocytes / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the effects of sodium selenite on telomerase activity, apoptosis and expression of TERT, c-myc and p53 in rat hepatocytes.</p><p><b>METHODS</b>Selenium at doses of 2.5, 5.0, and 10 micromol/kg was given to SD rats by gavage. In rat hepatocytes, telomerase activity was measured by the telomeric repeat amplification protocol (TRAP), apoptosis was detected by flow cytometry, and expressions of telomerase reverse transcriptase (TERT), c-myc and p53 were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). c-Myc and P53 proteins were detected by immunochemistry.</p><p><b>RESULTS</b>Selenium at doses of 2.5, 5.0, and 10 micromol/kg significantly increased hepatocellular telomerase activity and induced apoptosis in a dose-dependent manner. Although selenium at doses of 2.5, 5.0, and 10 micromol/kg displayed no obvious enhancing effect on the TERT mRNA expression in rat hepatocytes (P > 0.05), it significantly increased the c-myc mRNA and p53 mRNA expression at the dose of 10 micromol/kg (P < 0.05). Selenium at doses of 5.0 and 10 micromol/kg obviously increased the content of P53 protein in rat hepatocytes, but only at the dose of 10 micromol/kg, it significantly promoted the value of c-Myc protein in them.</p><p><b>CONCLUSION</b>Selenium can slightly increase telomerase activity and TERT expression, and significantly induce apoptosis and over-expression of c-myc and p53 at relatively high doses. The beneficial effects of selenium on senescence and aging may be mediated by telomerase activation and expression of TERT, c-myc, and p53 in rat hepatocytes.</p>

Inhibitory effects of selenium on telomerase activity and hTERT expression in cadmium-transformed 16HBE cells / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the effects of sodium selenite on telomerase activity and expression of hTERT mRNA in cadmium-transformed 16HBE cells.</p><p><b>METHODS</b>Telomerase activity and expression of genes were measured after cultured cadmium-transformed 16HBE cells were exposed to sodium selenite at different doses (0.625, 1.25, 2.50, 5.00 micromol/L) for 24 hours.</p><p><b>RESULTS</b>Selenium decreased telomerase activity in cadmium-transformed 16HBE cells. There existed an obvious dose-effect relationship between the selenium concentration and these changes. The expression of hTERT and c-myc mRNA also decreased but the expression of mad1 mRNA increased after exposure to selenium for 24 hours. No difference was found in expression of hTRF1 and hTRF2 mRNA after incubated with sodium selenite for 24 hours, compared with control group.</p><p><b>CONCLUSION</b>Selenium inhibits telomerase activity by decreasing hTERT and c-myc mRNA expression and increasing mad1 mRNA expression in cadmium-transformed 16HBE cells and selenium concentration is significantly correlated with these changes.</p>

Effects of selenium on expression of TERT, c-Myc and p53 induced by cadmium in rat liver / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of sodium selenite on expression of telomerase reverse transcriptase mRNA, c-Myc and p53 induced by cadmium chloride in rat liver.</p><p><b>METHODS</b>Male SD rats were divided randomly into 6 groups, each group had 5 animals. The groups comprised the control group, Se group (5 micromol/kg sodium selenite), 5 micromol/kg cadmium chloride group, 10 micromol/kg cadmium chloride group, Se (5 micromol/kg sodium selenite) + 5 micromol/kg cadmium chloride group, Se (5 micromol/kg sodium selenite) + 10 micromol/kg cadmium chloride group. After 48 hours of the first injection, the expression of TERT mRNA was measured with RT-PCR and c-Myc, and p53 proteins were measured by immunohistochemistry method.</p><p><b>RESULTS</b>Compared with control group, the expression of TERT was increased in 5 micromol/kg Cd group and 10 micromol/kg Cd group, c-Myc protein was increased in 10 micromol/kg Cd group, and the expression of p53 protein was increased in 5 micromol/kg group and 10 micromol/kg Cd group. TERT expression in Se + 10 micromol/kg Cd group was lower than that of 10 micromol/kg Cd group significantly. c-Myc protein was decreased in Se + 10 micromol/kg Cd group compared with 10 micromol/kg Cd group. p53 protein of Se + 5 micromol/kg Cd group and Se + 10 micromol/kg Cd group were decreased significantly compared with 5 micromol/kg Cd group and 10 micromol/kg Cd group respectively.</p><p><b>CONCLUSION</b>The cadmium at the doses of between 5 and 10 micromol/kg can activate TERT and up-regulate c-Myc and p53 proteins. The selenium at the dose of 5 micromol/kg has the antagonistic effect on expression of TERT, c-Myc and p53 induced by cadmium in rat liver.</p>