Basic and Translational Research Program (BTRP) in Sickle Cell Disease

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DESCRIPTION (provided by applicant): The challenge of sickle cell disease (SCD) is how a point mutation, which changes a single amino acid in a single protein, causes a disease with protean manifestations. The Marian Anderson Comprehensive Sickle Cell Center (MAC) has in past studies used the first years of life, a physiologically crucial period, to evaluate the biologic biomarker footprint created as the infant grows. Our studies have recently demonstrated that HbF does not protect patients with HbSS against endothelial activation which occurs by 2 years of life. We note, however, that these biomarkers correlate with markers of hemolysis such as LDH. Phosphatidylserine-positive (PS+) erythrocytes demonstrate osmotic fragility, with correlates between this circulating cohort and endothelial activation. Clinical evidence in the child with HbSS confirms our results, since there is an alarming rate of silent CNS infarction in the young HbSS patient. PS+ red cells were also noted to correlate with abnormal intracranial TCDs (Styles et al), suggesting additionally a tie-in with large vessel disease. Such studies make us acutely aware that modulating hemolysis remains at the forefront of sickle cell patient care. Recent clinical trials have been disheartening including L-Arginine, a Gardos Inhibitor, Mg Pidolate is beset with side effects, and nitric oxide (NO) inhalation in vasocclusion is still under evaluation. Two of our projects (Inter-Center Trial and Translational) will evaluate novel approaches to hemolysis. In the first, we will use oral enhancers of NO (nitrite and BH4) to decrease NO-related endothelial dysfunction in SCD by providing a long term vasodilatory effect. The translational project will use n-3 fatty acid supplementation to reduce hemolysis by protecting the red cell membrane. This study is novel in light of exciting work by Serhan et al, who recently showed that Eicosapentaenoic and Docosahexaenoic acids are precursors of potent new classes of compounds, the Protectins and Resolvins that stop the clock on inflammation, and inhibit ischemia-reperfusion injury. An additional rationale for this work is that these fatty acids have been shown to be deficient in the membranes of the circulating cellular elements of blood in HbSS disease. We have forged a collaboration with Dr. Serhan who will assess levels of his novel mediators in our Translational Project. Our Basic Science Project capitalizes on the theme of hemolysis by deconstructing this challenge into its major components of heme and microparticles (given separately and in combination to Berk mice). We will specifically assess two new areas, i.e. procoagulant phenotype (based on our demonstration in vitro that heme causes endothelial TF expression), and an adhesive phenotype (our data demonstrates that heme upregulates an endothelial PS receptor). Modulation of hemolysis-induced phenotypes by upstream inhibitors is planned, and also the use of Protectins and Resolvins. The Patient Services Project is an innovative proposal to develop and evaluate a brief family-based intervention targeting QoL and school functioning in SCD. If successful, its results will be potentially transferable to sickle care organizations as part of standard patient services programs. Crucial to the MAC edifice is a robust clinical core of dedicated staff supporting the Center's growing patient population, which includes adults and children in Philadelphia and Louisville. Rounding out the Center is a patient services core translating our state of the art research and patient care into practice through education and community outreach in Pennsylvania and Kentucky.