A novel compound,
TDN-345, not bearing
catechol moiety, induced
NGF synthesis/secretion in C6-10A
glioma cells. Both intracellular and extracellular
nerve growth factor (
NGF)
protein levels increased within 3 h and reached a maximum around 12 h after the addition of
TDN-345. The induction of
NGF synthesis/secretion by
TDN-345 occurred in a concentration-dependent manner, beginning with about 0.1 microM and reaching a maximum
at 10 microM. The ED50 was 0.88 microM. The induction was accompanied by an increase in
NGF mRNA but not
beta-actin mRNA. In a time-course study, the
NGF mRNA level was found to reach a maximum 2-3 h after the addition of
TDN-345 and then to return to control levels. The induction occurred dose-dependently. The catecholaminergic compound
epinephrine, which induces
NGF synthesis/secretion, increased the intracellular
cyclic AMP content by more than 1000-times
at 10 microM. In contrast,
TDN-345 did not cause such a prominent increase in cAMP even at 100 microM. These results indicate that
TDN-345 induces
NGF synthesis/secretion by increasing
NGF mRNA expression, and the action of
TDN-345 clearly differs from that of
epinephrine, as it does not seem to involve cAMP as a second messenger. The results of the present study suggest the existence of a signal transduction pathway for
NGF synthesis/secretion which is not mediated by cAMP.