Genetic diminution of circulating prothrombin ameliorates multiorgan pathologies in sickle cell disease mice

Abstract

• Reduced prothrombin improves survival and ameliorates inflammation and end-organ damage without spontaneous bleeding in sickle cell mice.• An individual procoagulant, prothrombin, represents a novel therapeutic target that can improve sickle cell disease outcome.Sickle cell disease (SCD) results in vascular occlusions, chronic hemolytic anemia, and cumulative organ damage. A conspicuous feature of SCD is chronic inflammation and coagulation system activation. Thrombin (factor IIa [FIIa]) is both a central protease in hemostasis and a key modifier of inflammatory processes. To explore the hypothesis that reduced prothrombin (factor II [FII]) levels in SCD will limit vaso-occlusion, vasculopathy, and inflammation, we used 2 strategies to suppress FII in SCD mice. Weekly administration of FII antisense oligonucleotide "gapmer" to Berkeley SCD mice to selectively reduce circulating FII levels to ∼10% of normal for 15 weeks significantly diminished early mortality. More comprehensive, long-term comparative studies were done using mice with genetic diminution of circulating FII. Here, cohorts of FII lox/2 mice (constitutively carrying ∼10% normal FII) and FII WT mice were tracked in parallel for a year following the imposition of SCD via hematopoietic stem cell transplantation. This genetically imposed suppression of FII levels resulted in an impressive reduction in inflammation (reduction in leukocytosis, thrombocytosis, and circulating interleukin-6 levels), reduced endothelial cell dysfunction (reduced endothelial activation and circulating soluble vascular cell adhesion molecule), and a significant improvement in SCD-associated end-organ damage (nephropathy, pulmonary hypertension, pulmonary inflammation, liver function, inflammatory infiltration, and microinfarctions). Notably, all of these benefits were achieved with a relatively modest 1.25-fold increase in prothrombin times, and in the absence of hemorrhagic complications. Taken together, these data establish that prothrombin is a powerful modifier of SCD-induced end-organ damage, and present a novel therapeutic target to ameliorate SCD pathologies. (Blood. 2015;126(15):1844-1855

Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology

“…Over the ECG surveillance month, the mortality rate among the sickle mice was about 40%, consistent with the overall mortality in our Berk-SS mouse colony (56). All WT mice survived through adulthood.…”

Neutrophils, platelets, and inflammatory pathways at the nexus of sickle cell disease pathophysiology

“…97 More recently, it has been reported that genetic deletion of circulating prothrombin alleviates multiorgan pathologies in SCD mice. 98 In addition, thrombospondin-1 can stimulate microparticle release from RBCs. These microparticles trigger reactive oxygen species production by endothelial cells, promote leukocyte adhesion, and induce endothelial apoptosis in a phosphatidylserine-dependent manner, leading to acute vaso-occlusive events in SCD mice.…”

Calpain-1 regulates platelet function in a humanized mouse model of sickle cell disease

“…Activated platelets, in addition to sickle RBCs and leukocytes, ultimately contribute to VOC [7, 8]. Moreover, increased platelet and thrombotic activity in SCD correlates with clinical complications such as pulmonary arterial hypertension (PAH), deep vein thrombosis, and stroke [9–11]. Patients with SCD and mouse models show platelet activation [7, 12, 13], yet mechanisms underlying platelet dysfunction in SCD remain poorly understood.…”