Opioid Peptide gene expression in the myocardial cell

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Neuropharmacology

Background:

• Myocardial cells express kappa (κ) and delta (δ) opioid receptors.
• Opioid receptor stimulation influences intracellular calcium (Ca2+), pH, and contractility.
• Cardiac myocytes express proenkephalin and prodynorphin genes.

Purpose of the Study:

• Investigate the role of opioid receptors and genes in cardiac function.
• Examine dynorphin B synthesis and secretion in cardiomyopathic hearts.
• Elucidate signaling pathways involved in prodynorphin gene regulation.

Main Methods:

• Isolation of ventricular myocytes from Syrian cardiomyopathic hamsters (BIO 14.6 strain) and normal controls.
• Measurement of prodynorphin mRNA and dynorphin B expression.
• Analysis of nuclear protein kinase C (PKC) activation and intracellular Ca2+ levels.

Main Results:

• Prodynorphin mRNA and dynorphin B levels are significantly elevated in cardiomyopathic myocytes.
• Nuclear PKC activation and Ca2+ overload are key signaling mechanisms driving increased prodynorphin transcription.
• Secreted dynorphin B activates cell surface κ opioid receptors, creating an autocrine loop that enhances PKC activity and prodynorphin gene transcription.

Conclusions:

• Dynorphin B acts in an autocrine manner in cardiomyopathic hearts.
• This autocrine signaling loop contributes to altered myocardial Ca2+ homeostasis and potentially cardiac growth.
• Opioid gene expression may play a significant role in the pathophysiology of cardiac hypertrophy and dysfunction.