Local Renin-Angiotensin II Systems, Angiotensin-Converting Enzyme and its Homologue ACE2: Their Potential Role in the Pathogenesis of Chronic Obstructive Pulmonary Diseases, Pulmonary Hypertension and Acute Respiratory Distress Syndrome

Renin-angiotensin II-aldosterone axis has long been known as a regulator of blood pressure and fluid homeostasis. Yet, local renin-angiotensin II systems have been discovered and novel actions of angiotensin II (AngII) have emerged among which its ability to act as a immunomodulator and profibrotic molecule. The enzyme responsible for its synthesis, Angiotensin-converting-enzyme (ACE), is present in high concentrations in lung tissue. In the present paper, we review data from studies of the past decade that implicate AngII and functional polymorphisms of the ACE gene that increase ACE activity with increased susceptibility for asthma and chronic obstructive pulmonary disease (COPD) and for pulmonary hypertension. Moreover, drugs that inhibit the synthesis of AngII (ACE inhibitors) or that antagonize its actions on its receptors (Angiotensin II receptor blockers -ARBs) have been shown to provide beneficial effects. Another recent discovery reviewed is the presence of a homologue of ACE, ACE2, which cleaves a single amino acid from AngII and forms a heptapeptide with vasodilatory actions, Ang 1-7. The balance between ACE and ACE2 is crucial for controlling AngII levels. ACE and ACE2 also appear to modify the severity of Acute Respiratory Distress Syndrome (ARDS), with ACE2 playing a protective role. Finally, mention is made to the recent discovery of ACE2 as a receptor for the SARS Corona Virus.