Prolyl endopeptidase inhibition ameliorates cardiovascular changes in a smoking mouse model

Rational Cigarette smoke exposure (CSE) is known to be a major risk factor for developing several diseases, such as chronic obstructive pulmonary disease (COPD) and eventually right sided heart failure. The extracellular matrix derived tripeptide proline-glycine-proline (PGP) has been shown to have neutrophil activating and chemotactic properties. Prolyl endopeptidase (PE), a serine protease present in neutrophils, is the terminal enzyme in the PGP-generation pathway. We hypothesized that inhibition of PE by the inhibitor benzyloxycarbonyl-prolyl-prolinal (ZPP) would reduce PGP formation, and thus the neutrophilic inflammation in a whole body smoke exposure murine model. Methods Female 8-10 week old Balb/c mice were exposed to cigarette smoke or air one hour a day, five days a week during 6 weeks. Fifteen minutes prior to each whole body smoke exposure the mice received either ZPP or vehicle (0.1% DMSO in saline) via intratracheal instillation (n= 8-10 mice per group). At week six, an echocardiogram was performed to measure heart function. Sixteen hours after the last smoke exposure the mice were sacrificed to collect bronchoalveolar lavage fluid (BALF), blood, heart and lungs. Results The echocardiogram showed that the pulmonary artery (PA) pressure was significantly increased due to smoke exposure in the 0.1% DMSO treated groups, whereas the ZPP treated mice showed baseline values. This correlated with post mortem analysis of the hearts demonstrating right ventricular hypertrophy (RVH). ZPP significantly inhibited the development of RVH due to CSE (figure 1). The total leukocytes in the BALF were significantly increased due to CSE in the 0.1% DMSO treated groups (5∗105), whereas ZPP reduced the total leukocytes by 68%. Neutrophils and macrophages were reduced by 70% and 52% respectively (p