Role of Orexin-B/Orexin 2 receptor in myocardial protection

Area of Science:

• Cardiovascular Physiology
• Endocrinology
• Molecular Cardiology

Background:

• Orexins/hypocretins (ORs) are known for regulating cardiovascular responses, but their direct cardiac effects are unclear.
• Cardiovascular diseases remain a leading cause of global mortality, necessitating novel therapeutic targets.
• Understanding orexin signaling within the heart is crucial for developing new treatments.

Purpose of the Study:

• To investigate the direct role of orexins in myocardial protection and heart function.
• To identify the specific orexin peptides and receptors involved in cardiac regulation.
• To explore the therapeutic potential of orexin signaling in heart failure.

Main Methods:

• Detection of orexin-A (OR-A) and orexin-B (OR-B) in rat cardiac tissue and cardiomyocytes.
• Assessment of the direct effects of OR-A and OR-B on heart rate and contractility in vitro.
• Analysis of signaling pathways, including myosin light chain (MLC), troponin-I (TnI), ERK1/2, and Akt phosphorylation.
• Correlation of orexin receptor-2 (OX2R) expression with clinical severity in heart failure patients.

Main Results:

• Orexin-A and orexin-B were identified within the heart and cardiomyocytes.
• Orexin-B, acting via orexin receptor-2 (OX2R), demonstrated direct cardioprotective effects in heart failure models.
• OR-B/OX2R signaling increased MLC and TnI phosphorylation, enhancing cardiac contractility.
• This effect was mediated by ERK1/2 and Akt phosphorylation in both rat and human heart samples.
• Reduced OX2R expression correlated with increased heart failure severity.

Conclusions:

• Orexins, particularly orexin-B, act directly on the heart via OX2R to modulate cardiac function.
• OR-B/OX2R signaling enhances myocardial contractility through specific phosphorylation pathways.
• OX2R represents a potential therapeutic target for preventing and treating cardiovascular diseases, including heart failure.