Jun Harada and Masahiko Sugimoto
Neuroscience Research Laboratories, Sankyo Co., Ltd., 1-2-58 Hiromachi,
Shinagawa-ku, Tokyo 140-8710, Japan
Abstract: Both p38 mitogen-activated protein kinase (p38) and c-Jun
N-terminal kinase (JNK) are known to play important roles in neuronal apoptosis.
However, the relationship between these kinases and caspases, another key
mediator of apoptosis, is unclear. In the present study, we investigated
the possible effects of SB203580 [(4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)
-5-(4-pyridyl)-imidazole], an inhibitor of p38, on caspase activation
and apoptosis of cultured rat cerebellar granule neurons. In granule neurons,
SB203580 prevented apoptosis that was induced by lowering the concentration
of KCI in the culture medium for 24 hr. SB203580 also prevented augmentation
of caspase-3-like protease activity at 8 hr after the low KCI treatment.
The IC50 values of SB203580 for both events were between 3 microM
and 10 microM. Expression and phosphorylation of c-Jun, potently induced
by low KCI treatment, were prevented by SB203580 at 10 microM. Z-Asp-CH2-DCB,
a caspase inhibitor with anti-apoptotic activity, did not inhibit the induction
and phosphorylation of c-Jun. Granule neurons displayed high levels of p38
and JNK activities. SB203580 inhibited not only p38 but also JNK activities
extracted from granule neurons. These results suggest that activation of
c-Jun by p38 and/or JNK mediates the activation of caspase in the low KCI-induced
apoptosis in cerebellar granule neurons.
Keywords: Apoptosis, p38, Jun N-terminal kinase, Caspase-3, Cerebellar
granule cell