Visit our Expo - Redox and Inflammation signaling 2012

Session III : Protein kinase cascades as therapeutic targets Poster III, 26
Different signaling pathways mediates the strain-induced CREB activation in cardiac
fibroblasts
Britta E. Husse, Gerrit Isenberg
Julius Bernstein Institute of Physiology, Martin Luther University Halle-Wittenberg, D-
06097 Halle/S., Germany. E-mail: britta.husse@medizin.uni-halle.de
The transcription factor CREB (cAMP response element binding protein) mediates the
mechanical strain-induced gene expression in the heart. We investigated which signaling
pathways are involved in the CREB activation by strain using cultured ventricular fibroblasts
from adult rat hearts. The analysis of phospho-CREB by immunocytochemistry showed a
nearly complete CREB activation (93.2±6.1%) by cyclical mechanical strain (1 Hz, 5%
elongation, 15 min) which did not distinguish from the whole number of CREB-positive
fibroblasts (87.8±9.6%). The strain-induced CREB activation was partially reduced by PKA
inhibition (19.9±11.2%), by PKC inhibition (31.2±11.2%) but not by CaMK II inhibition. The
inhibition of several members of the MAPK cascade revealed a reduction of strain-induced
CREB phosphorylation by 24.4±5.8% (Src-inhibition), by 27.7±5.8% (Raf1-inhibition) and
by 23.8±8.6% (MEK-inhibition). The PI3-K inhibition reduced strain-caused phospho-CREB
by 19.3±5.4%. The inhibition of p38, the stress-sensitive pathway, decreased the straininduced
CREB phosphorylation by 21.5±12.8%. The time-dependent CREB activation by
cAMP stimulation with 10µM forskolin was transient with a peak after 5 min; from
18.5±6.3% to 42.9±15.9% phospho-CREB positive cells. The PKC-induced CREB activation
by 500 nM PMA was sustained beginning after 10 min; from 12.1±5.0% to 54.3±10.4%
phospho-CREB positive cells. Our results suggest that the complete strain-induced CREB
phosphorylation includes several signaling pathways. We discuss this wide-ranging
possibilities of CREB activation as safety for CREB-mediated gene expression in the heart.
- 212 -