Elastase-2, a Tissue Alternative Pathway for Angiotensin II Generation, Plays a Role in Circulatory Sympathovagal Balance in Mice

Elastase-2, a Tissue Alternative Pathway for Angiotensin II Generation, Plays a Role in Circulatory Sympathovagal Balance in Mice Christiane Becari 1, 2, 3† , Marina T. Durand1, 4† , Alessander O. Guimaraes5, 6 , Renata M. Lataro1 , Cibele M. Prado7 , Mauro de Oliveira1 , Sarai C. O. Candido1 , Paloma Pais1 , Mauricio S. Ribeiro8 , Michael Bader 5, 9, 10 , Joao B. Pesquero6 , Maria C. O. Salgado2 and Helio C. Salgado1 * 1Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil, 2 Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil, 3 Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA, 4 Department of Medicine, University of Ribeirão Preto, Ribeirão Preto, Brazil, 5Max Delbruck Center for Molecular Medicine, Berlin, Germany, 6 Department of Biophysics, Federal University of São Paulo, São Paulo, Brazil, 7 Department of Pathology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil, 8Department of Surgery and Anatomy, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil, 9 Berlin Institute of Health, Charité—University Medicine Berlin, Berlin, Germany, 10 German Center for Cardiovascular Research, Partner Site Berlin, Berlin, Germany In vitro and ex vivo experiments indicate that elastase-2 (ELA-2), a chymotrypsin-serine protease elastase family member 2A, is an alternative pathway for angiotensin II (Ang II) generation. However, the role played by ELA-2 in vivo is unclear. We examined ELA-2 knockout (ELA-2KO) mice compared to wild-type (WT) mice and determined whether ELA-2 played a role in hemodynamics [arterial pressure (AP) and heart rate (HR)], cardiocirculatory sympathovagal balance and baroreflex sensitivity. The variability of systolic arterial pressure (SAP) and pulse interval (PI) for evaluating autonomic modulation was examined for time and frequency domains (spectral analysis), whereas a symbolic analysis was also used to evaluate PI variability. In addition, baroreflex sensitivity was examined using the sequence method. Cardiac function was evaluated echocardiographically under anesthesia. The AP was normal whereas the HR was reduced in ELA-2KO mice (425 ± 17 vs. 512 ± 13 bpm from WT). SAP variability and baroreflex sensitivity were similar in both strains. The LF power from the PI spectrum (33.6 ± 5 vs. 51.8 ± 4.8 nu from WT) and the LF/HF ratio (0.60 ± 0.1 vs. 1.45 ± 0.3 from WT) were reduced, whereas the HF power was increased (66.4 ± 5 vs. 48.2 ± 4.8 nu from WT) in ELA-2KO mice, indicating a shift toward parasympathetic modulation of HR. Echocardiographic examination showed normal fractional shortening and an ejection fraction in ELA-2KO mice; however, the cardiac output, stroke volume, and ventricular size were reduced. These findings provide the first evidence that ELA-2 acts on the sympathovagal balance of the heart, as expressed by the reduced sympathetic modulation of HR in ELA-2KO mice.