Endothelin-1-evoked arachidonic acid release: a Ca(2+)-dependent pathway

Area of Science:

• Cardiovascular Biology
• Cellular Signaling
• Molecular Pharmacology

Background:

• Endothelins (ET) are potent vasoconstricting peptides.
• Endothelin-1 (ET-1) is known to stimulate arachidonic acid (AA) release in human pericardial smooth muscle cells (HPSMC).
• The ETA receptor is primarily involved in mediating the ET-1 response.

Purpose of the Study:

• To elucidate the signaling pathways involved in ET-1-stimulated AA release in HPSMC.
• To investigate the roles of phospholipase A2, calcium (Ca2+), and protein kinase C (PKC) in this process.

Main Methods:

• Utilized pharmacological inhibitors such as manoalide (phospholipase A2 inhibitor) and PKC inhibitors (staurosporine, chelerythrine chloride).
• Employed a Ca2+ ionophore (A-23187) and an intracellular Ca2+ chelator (MAPTAM).
• Assessed AA release in response to ET-1 stimulation under various conditions, including altered extracellular Ca2+ levels and in the presence of activators/inhibitors.

Main Results:

• ET-1-evoked AA release was significantly inhibited by manoalide, indicating the involvement of phospholipase A2.
• AA release closely correlated with intracellular Ca2+ concentration changes, and was reduced by Ca2+ removal or chelation.
• PKC inhibitors significantly reduced ET-1-evoked AA release, while a PKC activator potentiated the response.

Conclusions:

• ET-1 stimulates AA release in HPSMC predominantly through a phospholipase A2-dependent pathway.
• Both intracellular Ca2+ and protein kinase C play crucial modulatory roles in ET-1-induced AA release in HPSMC.