Ghr
Unidad
de Cardiologia celular y
molecular, Laboratorio de Investigacion
1, Planta Baja, Area de Investigacion
y Docencia, Hospital Clinico
Universitario de Santiago de Compostela,
Travesia Choupana s/n,
15706 Santiago de Compostela, Spain.
The use of GH to treat heart failure has received considerable attention in
recent years. Although the mechanisms of its beneficial effects are unknown, it
has been implicated in the regulation of apoptosis in several cell types, and cardiomyocyte apoptosis is known to occur in heart failure.
We therefore decided to investigate whether GH protects cardiomyocytes
from apoptosis. Preliminary experiments confirmed the expression of the GH
receptor (GHR) gene in primary cultures of neonatal rat cardiomyocytes
(PC), the specific binding of GH by HL-1 cardiomyocytes, and the GH-induced activation of GHR and its
classical downstream effectors in the latter. That GH prevented the apoptosis
of PC cells deprived of serum for 48 h was shown by DNA electrophoresis and by
Hoechst staining assays in which GH reduced the percentage of cells undergoing
apoptosis. Similarly, the TUNEL-evaluated pro-apoptotic effect of cytosine arabinoside (AraC) on HL-1 cells
was almost totally prevented by pre-treatment with GH. Fluorescence-activated
cell sorter (FACS) analysis showed apoptosis in 9.7% of HL-1 cells growing in
normal medium, 21.1% of those treated with AraC and
13.9% of those treated with AraC+GH, and that GH
increased the percentage of AraC-treated cells in the
S/G(2)/M phase from 36.9% to 52.8%. GH did not modify IGF-I mRNA levels or
IGF-I secretion in HL-1 cells treated with AraC, and
the protection afforded by GH against AraC-induced
apoptosis in HL-1 cells was not affected by the presence of anti-IGF-I
antibodies, but was largely abolished by the calcineurin-inhibiting
combination cyclosporin+FK506. GH also reduced AraC-induced
phosphorylation of mitogen-activated
protein kinase p38 (MAPK p38) in HL-1 cells. In
summary, GH protects PC and HL-1 cells from apoptosis. This effect is not
mediated by IGF-I and may involve MAPK p38 as well as calcineurin.
PMID: 14765985 [PubMed - in process]