Role of 5-Lipoxygenase in Interleukin-4-Induced Oxidative Stress and Inflammation in Vascular Endothelium
Kim, Paul Hyunchul
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Cardiovascular disease (CVD) including atherosclerosis is the leading cause of illness and death in the United States. The American Heart Association indicated that an estimated 81,100,000 American adults have one or more types of CVD and the estimated direct and indirect cost of CVD for 2010 is $503.2 billion, which is $27.9 billion more than last year. Although the exact cause of this disease remains unsolved, previous studies have demonstrated that pro-oxidative and pro-inflammatory pathways in vascular endothelium play a critical role in early pathological events of atherosclerosis. However, the detailed molecular signaling mechanisms underlying this process are not yet completely understood. Recently, the role of interleukin-4 (IL-4) in atherogenesis became controversial and gained attention. IL-4 is a pleiotropic immunomodulatory cytokine secreted by T-helper 2 (Th2) lymphocytes, eosinophils, and mast cells. It was traditionally believed to be an anti-inflammatory cytokine. Increasing evidence, however, has suggested that IL-4 contributes to the initiation and progression of atherosclerosis by oxidative stress-mediated up-regulation of pro-inflammatory mediators such as vascular cell adhesion moledule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1), and interleukin-6 (IL-6) in vascular endothelium. 5-Lipoxygenase (5-LOX) is one of the key sources that generate reactive oxygen species (ROS) via metabolic pathways of arachidonic acid. Although 5-LOX has been implicated in the development of atherosclerosis, it remains unclear whether 5-LOX-mediated ROS generation is associated with IL-4-induced MCP-1 expression in vascular endothelium. The present study was focused on the oxidative mechanisms by which IL-4 induces vascular inflammation as well as how 5-LOX is involved in this process. The results showed that IL-4 significantly up-regulates mRNA and protein expression of MCP-1 in vascular endothelium. In addition, DHE and DCF fluorescence staining demonstrated that IL-4 increases ROS production in human vascular endothelial cells. We have also provided the first novel evidence that 5-LOX, one of the enzymes associated with arachidonic acid metabolism, is responsible for the IL-4-induced ROS generation and MCP-1 expression in human vascular endothelial cells.
- Masters Theses