Sodium selenite induces apoptosis in cultured cortical neurons with special concomitant changes in expression of the apoptosis-related genes

Sodium selenite was used to examine whether selenium compound is able to trigger apoptotic degeneration in cultured cortical neurons in vitro and to explore the detailed changes in expression of the related genes during the apoptotic processes using molecular biological and flow cytometric examinations. The results indicated that: (1) cortical neurons treated with sodium selenite with different dosages (0.0008, 0.004, 0.0200, 0.1000, and 0.5000 μM) and different exposure times (2, 4, 24, and 48 h) exhibited dose- and time-dependent apoptotic processes as revealed by typical DNA ladder formation detected by agarose gel electrophoresis; (2) the internucleosomal DNA fragmentation detected by flow cytometric examination showed a prominent peak of hypodiploid DNA contents as early as 4 h after exposure of 0.1 μM sodium selenite; (3) the DNA fragmentation induced by sodium selenite as revealed by the above two examinations could be blocked by aurintricarboxylic acid; (4) the transcriptions of mRNAs related to bcl-2, bax, c-fos, p53, and acetylcholinesterase (AChE) genes, as detected by RT-PCR assays, showed down-regulation for bcl-2 and up-regulation for bax, c-fos, p53, and AChE genes after exposure of sodium selenite. This study suggests that the sodium selenite is effective for inducing apoptosis in cultured cortical neurons and that relevant changes in expression of several apoptosis-related genes might further our understanding of the mechanism(s) that initiates and maintains the apoptotic processes.