The Effects of Sickle Erythrocytes on Endothelial Permeability
Brown, Lola A.
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Sickle cell anemia is a hematological disorder that is caused by a single point mutation in the beta-globin chain of hemoglobin. It results in several complications related to the small and large vessels in patients with the disease. Large vessel complications include cerebral infarcts, which are observed in children under ten years old. The mechanism behind this complication is not completely understood. It is the goal of this project to begin to understand the role sickle erythrocytes may play in causing endothelial dysfunction as a precursor to sickle related complications. The hypothesis of this work is that exposure of large vessel endothelium to sickle erythrocytes causes an increase in endothelial permeability through loosening of adherens junctions. In the first goal of this work, bovine aortic endothelial cells (BAECs) are grown on coverslips and exposed to sickle erythrocytes for 5 minutes and either immediately fixed or incubated in 30 minutes and then fixed. Immunofluorescent studies labeling VE cadherin show changes in VE cadherin dynamics, suggesting sickle erythrocytes may be involved in this observation. Next, BAECs were grown on transwell inserts and exposed to sickle erythrocytes for 5 minutes. The erythrocytes are washed off and the BAEC are incubated with 10,000 MW dextran conjugated to lucifer yellow or FITC-BSA or to determine BAEC permeability. When dextran is used as the test molecule, endothelial permeability did not show a significant change from baseline. However, when BSA is used as the test molecule, increases in endothelial permeability are observed. Explanations into the differences between the transport mechanisms of the two molecules are discussed. These experiments show changes in VE cadherin localization due to sickle erythrocyte exposure. This may cause increases in endothelial permeability and an experimental model and preliminary studies are performed. This study provides potential mechanisms to explain the changes in VE cadherin localization and provide suggestions for further studies to test the effect of sickle erythrocytes on endothelial permeability. This work provides a strong foundation for continuing studies on the effects of sickle erythrocytes on endothelial dysfunction within the confines of sickle related complications.