Dysregulation of nuclear factor kappa B activity and osteopontin expression in oxidant-induced atherogenesis

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Title: Dysregulation of nuclear factor kappa B activity and osteopontin expression in oxidant-induced atherogenesis
Author: Williams, Edward Spencer
Abstract: NF - ?B activity is critical in the regulation of atherosclerotic vascular smooth muscle cell (vSMC ) phenotypes induced following oxidative injury by allylamine . The present studies were designed to detail dysregulation of NF - ?B activity in these altered phenotypes , and to assess the importance of NF - ?B in the regulation of osteopontin , a cytokine which modulates atherosclerosis . Increased degradation of I ?B ? was observed in allylamine -induced atherosclerotic vSMC phenotypes (henceforth referred to as allylamine cells ) . Enhanced phosphorylation of I - ? -kinases was observed by Western immunoblotting . NF - ?B DNA binding activity as assessed by electrophoretic mobility shift assay demonstrated changes in the kinetics and magnitude of induction of binding . Enhancement of NF - ?B binding activity was evident in allylamine cells compared to controls when seeded on plastic , fibronectin , and laminin , but not collagen I . Posttranscriptional alterations in Rel protein expression and nuclear localization partly account for changes in NF - ?B DNA binding activity . Promoter -specific NF - ?B binding profiles suggest altered dimer prevalence as a consequence of the changes in Rel protein expression . The expression of NF - ?B regulated genes osteopontin and MMP -2 was enhanced in allylamine -treated aortas , while cyclin D1 and MMP -9 were unchanged . As the importance of osteopontin in atherosclerosis has been described in several models , subsequent studies were designed to assess osteopontin promoter activity . Activity of the osteopontin promoter was significantly reduced in allylamine cells compared to controls as assessed using a luciferase reporter . Deletion analysis suggested the presence of inhibitory cis -acting elements in the regulatory region of the gene . Mutation of these elements , including VDRE , AP -1 , NF - ?B , and USF1 , indicated that NF - ?B and USF1 mediate suppression of osteopontin promoter activity in allylamine cells . Decreased serine phosphorylation of immunoprecipitated RelA /p65 was observed in allylamine cells , indicating decreased ability of this protein to transactive gene promoters . NF - ?B was found to play a role in suppression of osteopontin promoter activity by collagen I -mediated integrin signaling . These findings suggest that enhancements in NF - ?B activity suppress osteopontin promoter activity in oxidant -activated vSMC cultures . Dysregulation of NF - ?B activity occurs as a result of altered matrix and intracellular signaling upstream of the nucleus and possibly differential dimer assembly leading to cell -specific profiles of NF - ?B -dependent gene regulation .
URI: http : / /hdl .handle .net /1969 .1 /175
Date: 2004-09-30

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Dysregulation of nuclear factor kappa B activity and osteopontin expression in oxidant-induced atherogenesis. Available electronically from http : / /hdl .handle .net /1969 .1 /175 .

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