Prostaglandin E2 Reduces Cardiac Contractility via EP3 Receptor

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Prostanoid Signaling

Background:

• Prostaglandin E2 (PGE2) exerts diverse cellular effects through EP3 and EP4 receptors, influencing cyclic adenosine monophosphate (cAMP) levels.
• Previous studies indicated that cardiomyocyte-specific EP4 knockout mice exhibit dilated cardiomyopathy and reduced ejection fraction.

Purpose of the Study:

• To investigate the distinct roles of PGE2 EP3 and EP4 receptors in regulating cardiac contractility.
• To elucidate the signaling mechanisms, including phospholamban phosphorylation, underlying these effects.

Main Methods:

• Utilized isolated mouse hearts (Langendorff preparation) and adult mouse cardiomyocytes to assess contractility.
• Employed Western blotting to analyze protein expression (phosphorylated phospholamban, SERCA2a).
• Conducted in vivo studies using pressure-volume loops to evaluate cardiac function.

Main Results:

• PGE2 and the EP1/EP3 agonist sulprostone decreased cardiac contractility (+dp/dt, left ventricular developed pressure), an effect reversed by an EP3 antagonist.
• An EP4 agonist demonstrated opposing effects, increasing contractility.
• PGE2 and sulprostone reduced phospholamban phosphorylation, while the EP4 agonist increased it; SERCA2a expression remained unchanged.

Conclusions:

• Cardiac contractility is modulated oppositely by EP3 (decreased) and EP4 (increased) receptors.
• These effects are potentially mediated by alterations in phospholamban phosphorylation.
• Findings have implications for understanding the detrimental effects of inflammation on cardiac function.