Page 112 - Haematologica March 2020

J.G. McArthur et al.
radioactive cGMP enzyme immunoassay (ENZO Life Sciences, France) with the acetylation protocol and protein levels were quantified by the BCA assay (Pierce, France). IMR-687 incubated for 6 h induced cGMP in a dose- dependent manner at a dose that was well tolerated (Figure 1A).
Almeida et al. reported that exposure to the PDE9i
BAY73-6691 and the sGC activator BAY 41-2271, increased HbF mRNA expression in K562 cells.38 To con- firm this finding with IMR-687, actively growing K562 cells were exposed to increasing concentrations of IMR- 687 or HU, and HbF expression was assessed by ELISA after 72 h. IMR-687 dose-dependently induced more HbF than either BAY73-6691 or BAY 41-2271 and was 4.6
ABC
DEF
GHI
JK
Figure 2. Treatment of phosphodiesterase 9A inhibitor (IMR-687) in sickle mice for 30 days results in fetal hemoglobin (HbF) induction, reduced hemolysis and reduced reticulocytosis. Townes-HbSS mice were dosed orally for 30 days with IMR-687 at 30 mg/kg or hydroxyurea (HU) at 25, 50 or 100 mg/kg. Treatment with IMR-687, or HU at the highest dose resulted in an increase in HbF (A) in Ter-119+ red blood cells (RBC), reduction in the percentage of RBC with a sickle shape observed on blood smear (B), and a reduction in hemolysis as indicated by reduced plasma free hemoglobin (C), plasma bilirubin levels (D), and lactate dehydroge- nase (LDH) levels (E), and indirectly with an increase in plasma nitrate levels (F) and reduction in lung arginase levels (G). Commensurate with these changes there was a reduction in evidence of reticulocytosis including reduced reticulocyte counts (H), increased mature RBC counts (I), increased hematocrit (J) and hemoglobin (K). Statistical significance was calculated for each agent and dose compared to a vehicle-treated control (n=7). *P<0.05; **P<0.01; ***P<0.001; ns: not significant (P>0.05). Data are presented as means±Standard Errors.
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Lung Arginase activity (U/L)