RT Journal Article
SR Electronic
T1 Apoptosis in cerebellar granule cells is blocked by high KCl, forskolin, and IGF-1 through distinct mechanisms of action: the involvement of intracellular calcium and RNA synthesis
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 1172
OP 1179
DO 10.1523/JNEUROSCI.15-02-01172.1995
VO 15
IS 2
A1 C Galli
A1 O Meucci
A1 A Scorziello
A1 TM Werge
A1 P Calissano
A1 G Schettini
YR 1995
UL http://www.jneurosci.org/content/15/2/1172.abstract
AB Cerebellar granule cells deprived of depolarizing concentration of extracellular potassium, [K+]o, undergo apoptosis. We here report that this apoptotic process is associated with an immediate and permanent decrease in the levels of free intracellular calcium, [Ca2+]i. Although forskolin and IGF-1 are both able to prevent apoptosis, only forskolin is able to counteract the instantaneous decrease of [Ca2+]i. However, the early effect of forskolin on [Ca2+]i is lost after longer incubation in low [K+]o. The calcium antagonist nifedipine is able to inhibit the survival effect of high [K+]o, while not affecting forskolin and IGF-1 promoted survival, as assessed by viability and genomic DNA analysis. Accordingly, the L-type calcium channels agonist Bay K8644 significantly enhanced the survival of low KCl treated neurons. To temporally characterize the signal transduction events and the essential transcriptional step in cerebellar granule cells apoptosis, we determined the time course of the rescue capacity of high [K+]o, forskolin, IGF-1, and actinomycin D. Addition of high KCl, forskolin, or IGF-1 6 hr after the initial KCl deprivation saves 50% of cells. Remarkably, 50% of neurons loss the potential to be rescued by actinomycin D after only 1 hr in low [K+]o. Finally, we show that the survival promoting activities of high [K+]o, forskolin, and IGF-1 do not require RNA synthesis. We conclude that [Ca2+]i is involved in the survival promoting activity exerted by high [K+]o but not in those of forskolin and IGF-1, and that all three agents, although rescuing neurons from apoptosis through distinct mechanisms of action, do not necessitate RNA transcription.