Changes in sphingomyelinases, ceramide, Bax, Bcl2, and caspase-3 during and after experimental status epilepticus

Abstract

Status epilepticus (SE) induces a number of events leading to programmed cell death (PCD). The aim of our work is to study the time sequence of activation of different factors in experimental SE (intraperitoneal kainic acid (KA) model). We studied ceramide, a known mediator of apoptosis in multiple models, sphingomyelinases (SMases), enzymes that break down sphingomyelin and increase ceramide thus leading to apoptosis in many models, Bcl(2), Bax, and caspase-3. SE induced a sustained ceramide increase starting 2h after kainic acid injection followed by an increase in Bax protein at 6 and 12h, and the appearance of caspase-3-activated fragment (caspase-3a) immunostaining and TUNEL positivity at 12h. Status epilepticus also induced an increase in acidic and neutral sphingomyelinases that preceded (acidic sphingomyelinase) and parallelled (acidic and neutral sphingomyelinase) the increases in ceramide. These data suggest that, in this model, Bax is activated early in the process and that its increase is sustained till 12h after kainic acid injection which is the time of first appearance of caspase-3 activation and TUNEL positivity, and that SMases contribute to increases in ceramide levels during and after status epilepticus.