The hidden mechanism behind blood pressure medication may be a side effect
In short: For decades, we believed ACE inhibitors lowered blood pressure primarily by blocking angiotensin II. However, emerging research suggests that their most significant cardioprotective benefits might actually stem from a different pathway: the accumulation of bradykinin, a potent vasodilator that the drug inadvertently leaves active in the body.
Historically, the primary focus of angiotensin-converting enzyme (ACE) inhibitors has been the renin-angiotensin-aldosterone system (RAAS). By inhibiting ACE, these drugs reduce the production of angiotensin II, a powerful vasoconstrictor, to treat hypertension, heart failure, and renal diseases. However, ACE is not exclusive to this pathway; it also serves as a primary enzyme for the degradation of bradykinin.
Recent mechanistic concepts suggest that ACE inhibitors may be more effective at inhibiting bradykinin degradation than at blocking angiotensin II production. This is supported by evidence showing that the affinity of ACE for bradykinin is higher than its affinity for angiotensin I. Consequently, the accumulation of bradykinin in the endothelium may be a major target of the medication. This signaling promotes vasodilation, natriuresis, and reduced oxidative stress.
This shift in understanding suggests that the most cardioprotective benefits of ACE inhibitors—especially at high dosages—might be due to increased bradykinin signaling rather than decreased angiotensin II. While bradykinin is essential for these benefits, its accumulation can also lead to clinical side effects such as swelling, edema, and angioedema. These reactions occur because bradykinin influences vascular permeability and recruits inflammatory cells like neutrophils and lymphocytes.
Beyond the heart and kidneys, the RAAS is expressed in various tissues including the liver, spleen, and neurons. Because ACE inhibitors affect these local systems, they may also influence glucose and lipid metabolism, potentially reducing total cholesterol and LDL levels. Understanding the dual role of ACE in balancing these two peptide systems is key to modern pharmacology.
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Sources
- Summary by Intellect · source: Bradykinin Pharmacology and ACE inhibitors - Immunology - Pathology
- Also: Unraveling the Pivotal Role of Bradykinin in ACE Inhibitor Activity - PubMed
- Also: ACE inhibitors and their interaction with systems and molecules involved in metabolism
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