In this study we have determined the ability of IGF-1 to protect cardiac fi
broblasts against osmotic-induced apoptosis and investigated the potential
mechanism(s) underlying this protection. Treatment with IGF-1 (1-100 ng/ml)
promoted a dose dependent increase in cell survival against osmotic cell d
eath. Both Akt and ERK1/2 were rapidly phosphorylated by IGF-1 and blocked
by wortmannin and PD98059, inhibitors of their upstream activators respecti
vely. However, IGF-l-induced protection was mediated via a wortmannin-depen
dent but PD98059-independent pathway as determined by cell survival assay s
uggesting a role of PI3-K/Akt. Furthermore, IGF-1 appeared to reduce the ac
tivation of a number of early components in the apoptotic pathway in a wort
mannin dependent manner including the osmotic stress-induced perturbation i
n mitochondrial membrane potential, cleavage and activation of caspase-3 an
d DNA fragmentation. Thus, the results suggest that IGF-1 regulates osmotic
stress-induced apoptosis via the activation of the PI3-K/Akt pathway at a
point upstream of the mitochondria and caspase-3. (C) 2000 Academic Press.