Although
IGF-II activating the
IGF-II receptor signaling pathway has been found to stimulate cardiomyocyte
hypertrophy, the role of
IGF-II in cardiac cell apoptosis remains unclear. This study aimed to identify the roles of
IGF-II and/or
IGF-II receptors (
IGF-II/IIR) in cardiomyoblast apoptosis and in hypertensive rat hearts with abdominal aorta
ligation. Cultured rat heart-derived H9c2 cardiomyoblasts and excised hearts from Sprague-Dawley rats with 0- to 20-day complete abdominal aorta
ligation, a model of ANG II elevation and
hypertension, were used.
IGF-II/IIR expression,
caspase activity, DNA fragmentation, and apoptotic cells were measured by RT-PCR, Western blot,
agarose gel electrophoresis, and TUNEL assay following various combinations of ANG II,
IGF-II/IIR antibody, CsA (
calcineurin inhibitor), SP-600125 (JNK inhibitor),
SB-203580 (p38 inhibitor),
U-0126 (
MEK inhibitor), or
Staurosporine (PKC inhibitor) in H9c2 cells. ANG II-induced DNA fragmentation and TUNEL-positive cells were blocked by
IGF-II/IIR
antibodies and antisense
IGF-II, but not by
IGF-II sense.
IGF-II-induced apoptosis was blocked by IGF-IIR antibody and CsA. The increased gene expressions of
IGF-II and -IIR induced by ANG II were reversed by
U-0126 and
Sp600125, respectively.
Caspase 8 activities induced by ANG II were attenuated by
U-0126, SP-600125, and CsA. DNA fragmentation induced by ANG II was totally blocked by SP-600125, and CsA and was attenuated by
U-0126. In rats with 0- to 20-day complete abdominal aorta
ligation, the increases in
IGF-II/IIR levels in the left ventricle were accompanied by
hypertension as well as increases in
caspase 9 activities and TUNEL-positive cardiac myocytes. ANG II-induced apoptosis was reversed by
IGF-II/IIR blockade and coexisted with increased transactivation of
IGF-II and -IIR, which are mediated by ERK and JNK pathways, respectively, both of which further contributed to cardiomyoblast apoptosis via
calcineurin signaling. The increased cardiac
IGF-II, IGF-IIR,
caspase 9, and cellular apoptosis were also found in hypertensive rats with abdominal aorta
ligation.