Aim: To study desipramine (Des)-induced apoptosis and regulation of caspase 3 gene expression and [Ca2+]i homeostasis in rat glioma C6 cells.
Methods: Apoptotic DNA breaks were quantified by propidium iodide (PI) incorporation using flow cytometry (FCM) and were detected by DNA agarose gel electrophoresis. Expression of apoptotic effector gene caspase 3 was assessed by reverse transcription polymerase chain reaction (RT-PCR). Single cell [Ca2+]i was measured using fluorescence indicator Fura-3/AM with confocal laser scanning microscopy.
Results: Des induced apoptotic DNA breaks in a concentration-dependent manner evidenced by hypodiploid peak on FCM histogram and the apoptotic cell percentage induced by Des 10, 20, and 40 micromol/L for 24 h was 5.2 %, 21.9 %, and 41.9 %, respectively. Apoptotic DNA breaks were further confirmed by a typical "DNA ladder" on agarose gel electrophoresis after exposure to Des 40 micromol/L for 24 h. Meanwhile, expression of caspase 3 gene was observed following Des 20 micromol/L treatment. Des 40 micromol/L resulted in an early sustained increase in [Ca2+]i over 28 min and the elevation magnitude was greatly decreased by removal of extracellular free [Ca2+]i with calcium-chelator egtazic acid, suggesting that Des elicited [Ca2+]i influx rather than intracellular calcium mobilization.
Conclusion: Up-regulation of caspase 3 gene expression and disturbance of homeostasis in calcium signaling system might play pivotal roles in Des-induced apoptotic DNA breaks of C6 cells.