B-type natriuretic peptide enhances mild hypoxia-induced apoptotic cell death in cardiomyocytes

Area of Science:

• Cardiology
• Molecular Biology
• Cellular Physiology

Background:

• Left ventricle remodeling post-myocardial infarction involves cardiomyocyte apoptosis due to stimuli like chronic hypoxia.
• B-Type natriuretic peptide is a known prognostic marker in cardiovascular pathology, but its role in cardiomyocyte apoptosis is unclear.

Purpose of the Study:

• To investigate the effect of B-Type natriuretic peptide on hypoxia-induced cardiomyocyte apoptosis.
• To elucidate the molecular mechanisms underlying B-Type natriuretic peptide's action on apoptotic cardiomyocytes.

Main Methods:

• Assessment of cardiomyocyte apoptosis markers (phosphatidylserine evagination, fragmented nuclei).
• Measurement of mitochondrial membrane potential (delta psi(m)), intracellular ATP levels, and caspase-3 activity.
• Investigation of the role of cyclic guanosine monophosphate (cGMP) and its signaling pathways using 8-Bromo-cGMP and Rp-8-br-cGMP.
• Analysis of Bcl-2 mRNA expression.

Main Results:

• B-Type natriuretic peptide enhanced mild hypoxia-induced cardiomyocyte apoptosis.
• It aggravated mitochondrial dysfunction (delta psi(m) dissipation, ATP depletion) and increased caspase-3 activity.
• cGMP mimicked B-Type natriuretic peptide's effects, and cGMP-dependent protein kinase inhibition blocked them, indicating a role for cGMP.
• B-Type natriuretic peptide down-regulated Bcl-2 mRNA expression under hypoxia.

Conclusions:

• B-Type natriuretic peptide exacerbates cardiomyocyte apoptosis induced by hypoxia, at least in this model.
• The peptide acts via the mitochondrial death pathway and intracellular cGMP signaling.
• These findings highlight a potential detrimental role of B-Type natriuretic peptide in myocardial infarction under hypoxic conditions.