Phosphodiesterase expression in the normal and failing heart

Area of Science:

• Cardiovascular Medicine
• Molecular Cardiology
• Pharmacology

Background:

• Heart failure with preserved ejection fraction (HFpEF) lacks effective therapies, despite hypotheses that increasing cyclic guanosine monophosphate (cGMP) could be beneficial.
• Previous clinical trials (RELAX, NEAT-HFpEF) targeting cGMP pathways did not demonstrate clinical benefit in heart failure patients.
• The expression of phosphodiesterases (PDEs), enzymes that degrade cGMP, in cardiac muscle remains incompletely understood, hindering targeted therapy development.

Purpose of the Study:

• To investigate the expression of specific phosphodiesterases (PDEs) in cardiac muscle from both normal and failing hearts in canines and humans.
• To determine which PDEs are viable therapeutic targets for heart failure by confirming their presence in cardiac tissue.

Main Methods:

• Immunoblotting techniques were employed to analyze cardiac tissue lysates.
• Samples were obtained from canines with normal and heart failure with preserved ejection fraction (HFpEF) conditions, and from humans with normal and heart failure with reduced ejection fraction (HFrEF) conditions.
• Expression levels of PDE1C, PDE2A, PDE3A, PDE5A, PDE7A, and PDE9A were specifically examined.

Main Results:

• Phosphodiesterase 1C (PDE1C) and Phosphodiesterase 3A (PDE3A) were detected in cardiac muscle tissue from both normal and failing hearts.
• No detectable expression of Phosphodiesterase 2A (PDE2A), Phosphodiesterase 5A (PDE5A), Phosphodiesterase 7A (PDE7A), and Phosphodiesterase 9A (PDE9A) was found in the analyzed cardiac tissue lysates.
• These findings indicate a limited range of PDE targets within cardiac muscle for heart failure therapies.

Conclusions:

• PDE1C and PDE3A are expressed in cardiac muscle and may represent potential therapeutic targets for heart failure.
• The lack of detectable expression for PDE2A, PDE5A, PDE7A, and PDE9A suggests that targeting these specific PDEs is unlikely to yield clinical benefit in heart failure.
• This study underscores the critical need for rigorous validation of therapeutic targets' expression in relevant tissues before initiating clinical trials for heart failure.