Characterizing the small molecule Pyr-4MDM for modulation of the LTA4H enzyme as a potential anti-inflammatory drug

Abstract

Leukotriene A4 hydrolase (LTA4H) is an enzyme that affects neutrophil infiltration in emphysematous chronic obstructive pulmonary disease (COPD). There are two different enzymatic pathways for LTA4H: the pro-inflammatory epoxy hydrolase (EH) pathway, where the LTA4H converts LTA4 to LTB4; and the anti-inflammatory aminopeptidase (AP) pathway, where the LTA4H cleaves proline-glycine-proline to proline and gly-pro. Many studies that focus on EH inhibitors of LTA4H have been conducted to inhibit pro-inflammatory effects but did not show clinical benefit. Our strategy is to activate the LTA4H AP pathway to promote anti-inflammatory effects. Our hypothesis for this study was that a novel compound, Pyr-4MDM, synthesized in our labs will activate the LTA4H AP activity. We used Ala-pNA as a reporter group for AP activity. To determine whether Pyr-4MDM was either an activator or an inhibitor of LTA4H AP activity, we treated recombinant LTA4H with escalating concentrations of Pyr-4MDM and measured the rate of Ala-pNA cleavage, which was monitored at 405 nm. We also characterized 4MDM or bestatin as positive controls for LTA4H activation or inhibition, measuring the corresponding AC50 and IC50 values, respectively. We then analyzed the activity of our Pyr-4MDM to determine whether it was an activator or inhibitor of LTA4H. Preliminary research shows that Pyr-4MDM is an activator of LTA4H’s AP and is able to cleave Ala-pNA successfully, supporting our hypothesis. Next steps will be to test this compound in a mouse model for COPD to see if the compound is efficacious.