Converting enzyme inhibitors and the interaction between kinins and eicosanoids

Area of Science:

• Pharmacology
• Cardiovascular Physiology

Background:

• Angiotensin-converting enzyme (ACE) inhibitors possess a dual mechanism: inhibiting angiotensin II formation and kinin degradation.
• The blood pressure-lowering effect of ACE inhibitors may involve non-renin-dependent pathways beyond angiotensin II blockade.

Purpose of the Study:

• To investigate the role of kinin degradation inhibition and associated vasodilator mechanisms in the acute hypotensive effects of ACE inhibitors.
• To explore the contribution of bradykinin-mediated prostaglandin release to the action of ACE inhibitors.

Main Methods:

• Utilizing experimental and clinical hypertension models.
• Employing selective angiotensin II and bradykinin receptor antagonists.
• Investigating the effects of cyclooxygenase inhibitors (e.g., indomethacin) on ACE inhibitor action.
• Examining bradykinin-induced signaling pathways involving B2 receptors, G-proteins, and arachidonic acid release.

Main Results:

• ACE inhibitors amplify kinin-mediated effects on local vessel tone.
• The acute hypotensive action of ACE inhibitors is attenuated by cyclooxygenase inhibitors, indicating a role for prostaglandins.
• Bradykinin stimulates receptor-mediated release of arachidonic acid and subsequent eicosanoid generation.
• Bradykinin-induced vasodilation involves indirect mechanisms, including the release of eicosanoids and endothelium-derived relaxing factor (EDRF).

Conclusions:

• ACE inhibitors exert vasodilatory effects through mechanisms beyond angiotensin II inhibition, notably by potentiating bradykinin activity.
• Bradykinin-induced prostaglandin release significantly contributes to the acute blood pressure-lowering effects of ACE inhibitors.
• Understanding these complex kinin-mediated pathways is crucial for appreciating the full pharmacological profile of ACE inhibitors.