Session: 113. Hemoglobinopathies, Excluding Thalassemia: Basic and Translational: Poster I
Hematology Disease Topics & Pathways:
Research, Sickle Cell Disease, Translational Research, Hemoglobinopathies, Diseases
Objective: To investigate the role of PAR-1 in a mouse model of heme-induced ACS using two PAR-1 inhibitors: vorapaxar or parmodulin-2 (PM2).
Methods: Townes wild type (AA) and sickle (SS) mice (3-4 months) were used in three experiments. 1) AA females (n=4), SS males (n=6) and SS females (n=11) received 140 µmol/kg heme via retro-orbital injection. 2) SS females received vehicle (n=6) or Vorapaxar (105 µmolar/kg BW, oral gavage) (n=7) daily for 5 days, then treated with heme (140 µmol/kg). 3) SS females received vehicle (n=5) or PM2 (10 mg/kg, intraperitoneal, n=5) 30 minutes prior to heme (140µmol/kg). In all experiments, mice were monitored for signs of ALI (endpoint criteria: severe discomfort with disability) and lungs were collected for histopathology at endpoint or 120 mins after heme infusion.
Results: Heme infusion caused 11/11 of SS females to reach endpoint (median survival = 18 min, p=0.0006 vs AA and SS males), whereas only 2/6 of SS males and 0/4 AA mice reached endpoint. Correlation analysis for RBCs and endpoint time showed that SS females with RBC counts less than 7 x 1012/L were vulnerable to heme-induced ACS; yet even males with significant anemia did not reach endpoint. The lung histology showed alveolar thickening, edema and hemorrhage in heme-treated SS females. Hence, only female SS mice were used for the remaining studies. Interestingly, vorapaxar did not protect SS mice from heme-induced ACS (5/7 mice, median survival 17 min) compared to vehicle treatment (4/6 mice, median survival 16 min). In contrast, PM2 treatment significantly protected the SS mice from heme induced ACS with 0/5 reaching endpoint, compared to 4/5 of vehicle -treated SS mice reaching endpoint (p=0.013), and prevented lung damage observed by histology.
Conclusions: We found that female mice are more susceptible to heme-induced ACS than males. Vorapaxar, an irreversible antagonist of PAR-1 which blocks all PAR-1 signaling pathways, did not protect SS mice against heme-induced ACS. In contrast, PM2 completely alleviated heme-induced lung injury and death in SS mice. This could be attributed to the fact that PM2 allosterically blocks thrombin/PAR-1 signaling while preserving cytoprotective signaling similar to that mediated by APC. Targeting PAR-1 by preserving (or inducing) beneficial signaling might be effective in preventing the development of ACS.
Disclosures: Pawlinski: CSL Behring: Consultancy, Research Funding.
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