Pathophysiology of Acute Pain in Patients With Sickle Cell Disease

Overview

Background: Sickle Cell Disease (SCD) is a blood disorder that occurs mainly in people of African descent. Researchers want to learn more about the painful attacks and complications associated with SCD. They want to look for a relationship between SCD and specific changes in the blood. They want to study the role of genetics, inflammation, and blood clotting factors in SCD. They will do this with blood samples collected during an acute painful attack and in between attacks. Objective: To learn more about the painful attacks and complications associated with SCD. Eligibility: People ages 18-80 with SCD or who are healthy Africans or African Americans without SCD Design: * Participants will be screened with medical history and physical exam. * Healthy participants will have one visit. * Participants with SCD will have their first visit when they are not having a pain attack. They will have their next visit during a pain attack. About 3-4 months after this attack, they will have a final visit. * Visits will include a physical exam, and blood and urine tests. * Participants may have their blood samples used for genetic testing for research.

Episodic pain is the most common acute morbidity and the leading cause of hospitalization in patients with sickle cell disease. It is caused by microvaso-occlusion induced by sickled red blood cells, an outcome of the polymerization of deoxygenated hemoglobin S (HbS). Factors that contribute to the acute sickle pain include the release of cell-free DNA (cfDNA) and heme that initiate a downstream of events involving inflammation and thrombosis, and ischemia-reperfusion injury. Cell-free DNA has been shown to be present in plasma of healthy subjects, but elevated in diseases and conditions that are characterized by increased cell death through necrosis or apoptosis. Indeed, we have previously shown that cfDNA in patients with sickle cell disease (SCD) increased dramatically during acute painful episodes. During acute sickle pain, marked elevation of plasma hemoglobin has also been observed due to the acute increase in sickled red blood cells and hemolysis. Both cfDNA and heme (break down product of hemoglobin), act as damage-associated molecular pattern (DAMP) molecules, initiating endothelial inflammation, stimulation of neutrophil extracellular trap (NET) formation, leukocyte recruitment, and microvascular thrombosis. Although there have been several studies of cytokines and chemokines in steady state and acute sickle cell disease, there has been no comprehensive study of how the inflammatory markers correlate with quantitative levels and profile of cfDNA. In this study, we would like to apply next generation sequencing (NGS) to analyze cfDNA from the plasma of patients with SCD in steadystate, and during painful crises to derive insights on the origin of tissue damage. In parallel with the free plasma DNA, we propose to measure markers of hemolysis and inflammation (cytokines, chemokines), and to investigate if interactions between these circulating molecules and blood cells (e.g. neutrophils) have the potential to modulate the progress and severity of the disease. In addition, we would also like to explore if there is a distinctive cell-free DNA and inflammatory signature in SCD in steady-state and during acute vaso-occlusive crises. Overall, this study provides an opportunity to evaluate new biomarkers of sickle cell pain crisis and to predict disease severity and prognosis. These measures may allow us to better understand the role of vaso-occlusion, hemolysis, and inflammation-related events and responses and serve as clinical endpoints in future studies of disease pathogenesis and/or therapeutic intervention for sickle cell disease.