MLN-4760

In vitro, conversion from angiotensin II to angiotensin-(1–7) by mouse ACE2 is blocked by MLN-4760 (10 μM). MLN-4760 inhibits both human and mouse ACE2 activity.^[3] In huMNCs, MLN-4760-B (an isomer of MLN-4760) detects 63% ACE2 with 28-fold selectivity over ACE. In huCD34+ cells, MLN-4760-B detects 38% of ACE2 activity with 63-fold selectivity. In mu-heart and muMNCs, MLN-4760-B is 100- and 228-fold selective for ACE2, respectively. In muLin- cells, MLN-4760-B detects 25% ACE2 activity with a pIC50 of 6.3. The racemic mixture and MLN-4760-A shows lower efficacy and poor selectivity for ACE2 in MNCs and mu-heart.^[4]

In the case of cell lysates, 10 μg of total protein is assayed for activity in a buffer with the following composition: 50mM MES (4-morpholineethanesulphonic acid), 300mM NaCl, 10μM ZnCl2 and 0.01% Triton X-100, pH 6.5. Reaction is initiated by the addition of 5×10^-5 M substrate. Where applicable, recombinant enzymes are used at a concentration of 0.01 μg per reaction. The fluorescence measurements are performed in the black microtiter plates in a total volume of 100 μl. The plates are read using a fluorescence plate reader SpectraMax M5 at an excitation wavelength 320 nm and emission wavelength 405 nm Fluorescence resulting from the substrate hydrolysis increased with time, and achieved maximum by 1 h with recombinant enzyme however with cell/tissue lysates the maximum fluorescence is observed by 4 h of incubation. Therefore fluorescence recorded at 1 and 4 h of reaction time is taken for calculation of percent enzyme inhibition, when using recombinant enzymes and cell/tissue lysates, respectively. ACE2 activity is defined as the ACE2 inhibitor-sensitive fluorescence and ACE activity is defined as the ACE inhibitor, captopril-sensitive fluorescence, and are expressed as percent inhibition. Unless specified, MLN4760 is used in concentration ranging from 0.01 nM to 300 μM.

MLN-4760 blocks ACE2 activity, thus significantly reverses the elevation of carotid Ang-(1-7) level and the decline of carotid Ang II level induced by NaHS in mice. The anti-atherosclerotic property of NaHS is also significantly abolished by treatment with MLN-4760.^[2]