Cyclic mechanical strain causes cAMP-response element binding protein activation by different pathways in cardiac...

Area of Science:

• Cardiovascular Biology
• Molecular Cell Biology
• Signal Transduction

Background:

• The transcription factor cAMP-response element binding protein (CREB) plays a crucial role in mediating mechanical strain-induced gene expression in the heart.
• Understanding the specific signaling pathways involved in CREB activation by mechanical stress is essential for comprehending cardiac adaptation and disease.

Purpose of the Study:

• To investigate the signaling pathways responsible for mechanical strain-induced activation of CREB in cultured adult rat ventricular fibroblasts.
• To elucidate the interplay between different signaling cascades, such as PKA, PKC, MEK, p38-MAPK, and PI3-kinase, in CREB phosphorylation.

Main Methods:

• Primary adult rat ventricular fibroblasts were subjected to cyclic mechanical strain (1 Hz, 5% elongation) for 15 minutes.
• CREB phosphorylation was quantified using immunocytochemistry and ELISA.
• Specific inhibitors and activators were used to probe the roles of PKA, PKC, MEK, p38-MAPK, and PI3-kinase pathways.

Main Results:

• Cyclic mechanical strain induced CREB phosphorylation in fibroblasts.
• Inhibition of PKA, PKC, MEK, p38-MAPK, or PI3-kinase partially reduced strain-induced CREB phosphorylation.
• PKC, MEK, p38-MAPK, and PI3-kinase pathways appeared to converge, while PKA acted additively.
• Strain-induced c-Fos expression was reduced by PKC inhibition but not PKA inhibition.

Conclusions:

• Mechanical strain activates CREB through a complex network of signaling pathways with synergistic effects.
• Multiple pathways, including PKA, PKC, MEK, p38-MAPK, and PI3-kinase, contribute to CREB phosphorylation.
• The level and duration of CREB stimulation dictate its influence on gene expression, providing a graduated control system for cardiac adaptation.