Angiotensin converting enzyme (ACE) expression in leukocytes of older adults

The renin angiotensin system (RAS) is composed of several enzymes and substrates on which angiotensin converting enzyme (ACE) 1 and renin act to produce angiotensin II. ACE1 and its substrates control blood pressure, affect cardiovascular and renal function, hematopoiesis, reproduction, and immunity. The increased expression of ACE1 has been observed in human monocytes during congestive heart failure and abdominal aortic aneurysm. Moreover, T lymphocytes from hypertensive patients presented increased expression of ACE1 gene after in vitro stimulation with Angiotensin-II (AngII) with the highest ACE1 expression observed in hypertensive patients with low-grade inflammation. Our group and others have shown that aging is associated with comorbidities, chronic inflammation and immunosenescence, but there is a lack of data about ACE1 expression on immune cells during the aging process. Therefore, our aim was to evaluate the levels of ACE1 expression in non-lymphoid as compared to lymphoid cells in association with the immunosenescence profile in adults older than 60 years. Cryopreserved peripheral blood mononuclear cells obtained from blood samples were used. Cells were stained with monoclonal antibodies and evaluated by flow cytometry. We found that ACE1 was expressed in 56.9% of non-lymphocytes and in more than 90% of lymphocytes (all phenotypes). All donors exhibited characteristics of immunosenescence, as evaluated by low frequencies of Naive CD4+ and CD8+ T cells, high frequencies of EMRA CD8+ T cells, and double-negative memory B cells. These findings in addition to the increased C-reactive protein levels are intriguing questions for the study of ACE1, inflammaging, immunosenescence and perspectives for drug development or repurposing.