UBC Theses and Dissertations
Development and application of proteomic tools to quantify the redox status change in blood cells Li, Ru
Cardiovascular diseases (CVDs) remain the number one killer around the world, representing a huge unmet need in innovative therapies. Platelet activation and their interaction with monocytes are critical in the development of CVDs, particularly atherosclerosis. Activated platelets release the contents of their granules, commonly called “platelet releasate”, and recruit monocytes to damaged endothelium. However, the molecular mechanisms of the redox regulation in monocytes in response to platelet releasate are not fully understood. To extend our knowledge in this area, the modified biotin switch assays were developed and applied to an atherosclerotic model in sequential experiments, i.e. the quantification of reversible cysteine oxidations and sulfenic acid modification. We found that monocytes treated with platelet releasate activated NADPH oxidase (NOX) to produce reactive oxygen species (ROS) and resulted in cysteine oxidations. The proteome of reversible cysteine oxidations was analyzed in the atherosclerotic model using the modified biotin switch assay, and several biological processes were identified including glycolysis, cytoskeleton arrangement, and redox regulation. To better understand redox regulation in monocytes, the proteome of the sulfenic acid modification, a subtype of reversible cysteine oxidations, was obtained in the same model. Bioinformatics analysis of the proteome of sulfenic acid modification highlighted the biological process of monocyte transendothelial migration, which included integrin β₂. Flow cytometry confirmed the activation of LFA-1 (αLβ₂), a subfamily of integrin β₂ complex, on human primary monocytes following platelet releasate treatment, which was mediated by the NOX-derived ROS. Furthermore, dyslipidemia is closely associated with hyperactivity of platelets in atherosclerosis and the generation of biologically active oxidized phospholipids including oxidized phosphatidylcholine (oxPC). Through our studies, we found a previous unknown inhibitory effect of oxPC species on platelet activation via soluble guanylyl cyclase (sGC)– cyclic guanosine monophosphate (cGMP) pathway. In summary, the versatile modified biotin switch assay provides an approach for the quantification of reversible cysteine oxidation in biological systems. The application of this assay has extended our understanding of redox regulation in platelet-monocyte interaction and platelet function in atherosclerosis. The better understanding of redox regulation in atherosclerosis has the potential to advance the design of more targeted antioxidant therapies for CVDs.
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