Interaction between AT1 and AT2 receptors during postinfarction left ventricular remodeling

Area of Science:

• Cardiovascular Biology
• Molecular Cardiology
• Medical Research

Background:

• The roles of angiotensin II receptors (AT1-R and AT2-R) in post-myocardial infarction (MI) cardiac remodeling are not fully understood.
• Understanding these roles is crucial for developing targeted therapies to improve heart function after MI.

Purpose of the Study:

• To investigate the distinct and combined contributions of AT1-R and AT2-R in cardiac remodeling following MI.
• To compare the effects of AT1-R blockade and AT2-R overexpression on post-MI cardiac remodeling.

Main Methods:

• Five groups of C57Bl/6 mice were studied after induced MI: wild type (untreated and losartan-treated), AT2-receptor transgenic (AT2-TG), AT2-TG with losartan, and AT2-TG/AT1a-receptor knockout (KO).
• Cardiac magnetic resonance imaging (CMR) assessed cardiac function and structure.
• Infarct size, myocyte hypertrophy, and collagen content were analyzed post-MI.

Main Results:

• Infarct size was similar across all groups.
• Wild-type mice showed significantly worse cardiac remodeling (higher volumes, lower ejection fraction) compared to other groups by day 28 post-MI.
• The AT2-TG/AT1a-KO group exhibited the best outcomes, with the highest ejection fraction and lowest cardiac volumes and mass, along with reduced fibrosis.
• Pharmacological AT1-R blockade was comparable to AT2-R overexpression in attenuating remodeling, while genetic AT1a-R knockout added to AT2-R overexpression benefits, partly via blood pressure reduction.

Conclusions:

• AT1-R and AT2-R are intricately involved in post-MI cardiac remodeling.
• Blocking AT1-R is as effective as AT2-R overexpression in mitigating adverse remodeling.
• Genetic deletion of AT1a-R enhances the benefits of AT2-R overexpression, suggesting a synergistic effect partly mediated by blood pressure modulation.