Sickle cell anemia (SCA) is caused by a point mutation in the ²-hemoglobin gene, producing abnormal hemoglobin S (HbS). When deoxygenated, HbS polymerizes, causing the red blood cell to become sickle shaped and to rupture more easily. As a result, the disease is characterized by anemia, intravascular hemolysis and vaso-occlusive disease, which can result in painful vaso-occlusive episodes as well as a number of acute and chronic complications. Currently, the only therapeutic approach available for the treatment of the effects of SCA is hydroxyurea (HU), which modifies the disease process, improves hematological parameters and reduces hospitalization and mortality. Much of the pathophysiology of SCA is caused by chronic inflammatory processes, possibly resulting from the release of damage-associated molecular patterns (DAMPs) from red blood cells (RBC) and as a result of ischemia/reperfusion processes. DAMPs can be recognized by numerous classes of PRR (pattern recognition receptor), including the cytosolic sensors of the NOD-like receptor (NLR) family, which participate in the formation of the inflammasome platform. Once activated, the NLR or sensor protein recruits the inflammasome-adaptor protein, ASC, which in turn interacts with caspase-1, leading to its dimerization and subsequent activation. After activation of the inflammasome, the cell undergoes a programmed necrotic and inflammatory cell death process, called pyroptosis, mediated by the inflammatory caspases (caspase-1, caspase-4, and caspase-5). These caspases appear to also participate in the assembly and/or activation of the inflammasome; however, methodologies used to detect the activation of specific caspases have been shown to be poorly effective. Caspase BiFC is a real-time single cell imaging-based technique that measures the proximal step in caspase activation by detecting the induced proximity of caspase monomers upon recruitment to activation platforms. Given the difficulty in ascertaining and identifying the activities of specific caspases in cells and the necessity to define mechanisms by which IL-1² processing occurs (either by canonical inflammasome or non-canonical pathways), this project aims to investigate the ability of serum from SCA to induce specific caspase activity in the presence of inflammasome components. Furthermore, we aim to identify the role of neutrophils from SCA individuals in caspase activation.
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