Increased local angiotensin II formation in aneurysmal aorta

Area of Science:

• Cardiovascular Science
• Enzymology
• Vascular Biology

Background:

• Aortic aneurysms are characterized by abnormal dilation of the aorta.
• The renin-angiotensin system plays a role in cardiovascular homeostasis.
• Angiotensin II is a key effector peptide in the renin-angiotensin system.

Purpose of the Study:

• To investigate the levels and cellular localization of angiotensin II-forming enzymes, specifically angiotensin converting enzyme (ACE) and chymase, in human aneurysmal and normal aortas.
• To determine if increased activity of these enzymes is associated with aortic aneurysm development.

Main Methods:

• Aneurysmal aortic specimens (n=14) and normal aortic specimens (n=16) were collected.
• ACE and chymase activities were measured in tissue homogenates.
• Immunohistochemistry was performed to identify the cellular distribution of ACE and chymase.

Main Results:

• ACE activity was significantly higher in aneurysmal aortas (0.82 mU/mg protein) compared to normal aortas (0.14 mU/mg protein).
• Chymase activity was markedly elevated in aneurysmal aortas (17.9 mU/mg protein) versus normal aortas (1.02 mU/mg protein).
• ACE-positive cells (macrophages) and chymase-positive cells (mast cells) were increased in the intima, media, and adventitia of aneurysmal aortas compared to normal aortas.

Conclusions:

• Both ACE and chymase, key enzymes in angiotensin II formation, are significantly increased in human aortic aneurysms.
• The enhanced presence and activity of these enzymes in specific aortic wall layers suggest a role in the pathogenesis of aortic aneurysms.
• Elevated local angiotensin II production may be a contributing factor to the development and progression of aortic aneurysms.