PS1521 THE SOLUBLE GUANYLATE CYCLASE STIMULATOR OLINCIGUAT ATTENUATES LEUKOCYTE/ENDOTHELIAL CELL INTERACTIONS IN BERKELEY SCD MICE
Authors: H. Li, S.-K. Lee, B. Tchernychev, R.M. Graul, J. Masferrer, P. Frenette
Journal: HemaSphere (2019)

Background: Patients with hemolytic anemias such as sickle cell disease (SCD) have reduced nitric oxide (NO) bioavailability (1). NO insufficiency results in suppression of NO-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) signaling pathway and has been implicated in vasoconstriction, intravascular inflammation, and formation of heterocellular vaso-occlusive aggregates in the venous microcirculation of SCD patients. In mouse models of SCD, cGMP amplifying agents, including NO donors and inhibitors of phosphodiesterase 9 (PDE9), reduce heterotypic adhesive interactions mediated by sickled red blood cells, leukocytes, platelets and activated endothelial cells (2, 3). Co-treatment of PDE9 inhibitors with hydroxyurea (HU) augments anti-inflammatory and anti-adhesive effects in these models (2, 3). Aims: In response to NO binding, soluble guanylate cyclase (sGC) catalyzes synthesis of cGMP from GTP. Therefore, we evaluated the effect of the sGC stimulator olinciguat on leukocyte-endothelial cell interactions in a mouse model of vaso-occlusive crisis (VOC). Methods: The effect of olinciguat in the absence or presence of HU on leukocyte-endothelial cell interactions was studied in chimeric C57BL/6 mice engrafted with the bone marrow from Berkeley SCD mice. Vaso-occlusive crisis in sickle cell mice was induced by intraperitoneal injection of mouse TNFα (0.5 μg/mouse). Olinciguat (10 mg/kg) and HU (100 mg/kg) were administered by oral gavage, 30 minutes before treatment with TNFα. Leukocyte-endothelial cell interactions in postcapillary venules of mouse cremaster muscle were analyzed by intravital microscopy 90 minutes after TNFα challenge. A flow rate and centerline blood shear rate in each venule was measured using optical Doppler velocimeter. Results: Animals pretreated with TNFα had significantly higher adhesion efficiency of leukocytes to the vascular wall compared to non-treated, naïve animals (mean ± SEM; 3.5 ± 0.8 and 0.7 ± 0.1 cells/100 μm2/rolling flux, respectively; p < 0.001). Adhesion efficiency of leukocytes was lower in mice pretreated with either olinciguat (10 mg/kg) or HU (100 mg/kg) than in vehicle-treated mice (0.9 ± 0.1, 1.6 ± 0.4 and 3.5 ± 0.8 cells/100 μm2/rolling flux, respectively; p < 0.001). Adhesion efficiency of leukocytes to activated endothelium was lowest in mice treated with both olinciguat and HU (0.5 ± 0.1 cells/100 μm2/rolling flux). Blood flow in TNFα-challenged mice that were pretreated with olinciguat, HU, or their combination was greater than vehicle-treated controls (287 ± 22, 277 ± 29, 261 ± 14, and 178 ± 15 pL/s respectively, p≤0.01). Relative to vehicle-treated mice, blood shear rates were only enhanced in HU and combination treated animals (497 ± 43 s−1, 808 ± 82, and 722 ± 30 respectively, p≤0.01). Finally, only mice treated with both olinciguat and HU survived longer (hours) than mice in the vehicle group (3.4 ± 0.3 vs 2.8 ± 0.3, p = 0.05). Summary/Conclusion: In summary, the data indicate that in a TNFα-induced model of VOC, pretreatment with the sGC stimulator olinciguat improved blood flow and attenuated leukocyte endothelial cell interactions in the venous microcirculation of sickle cell mice.