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  • Title: Overexpression of truncated IkappaBalpha induces TNF-alpha-dependent apoptosis in human vascular smooth muscle cells.
    Author: Obara H, Takayanagi A, Hirahashi J, Tanaka K, Wakabayashi G, Matsumoto K, Shimazu M, Shimizu N, Kitajima M.
    Journal: Arterioscler Thromb Vasc Biol; 2000 Oct; 20(10):2198-204. PubMed ID: 11031204.
    Abstract:
    Dysregulation of apoptosis is one of the likely underlying mechanisms of neointimal thickening, a disorder in which proinflammatory cytokines may influence the function of vascular smooth muscle cells (VSMCs) and contribute to atherogenesis. One of these cytokines, tumor necrosis factor-alpha (TNF-alpha), induces 2 possibly conflicting pathways, 1 leading to the activation of nuclear factor-kappaB (NF-kappaB) and the other leading to caspase-mediated apoptosis. We investigated whether specific inhibition of NF-kappaB affects TNF-alpha-dependent apoptosis in human VSMCs. To inhibit NF-kappaB activation specifically, we constructed a recombinant adenovirus vector expressing a truncated form of the inhibitor protein IkappaBalpha (AdexIkappaBDeltaN) that lacks the phosphorylation sites essential for activation of NF-kappaB. The IkappaBDeltaN was overexpressed by adenoviral infection and was resistant to stimulus-dependent degradation. Electromobility gel shift and luciferase assays demonstrated that overexpression of IkappaBDeltaN inhibited NF-kappaB activation induced by TNF-alpha or interleukin-1beta (IL-1beta). In cells overexpressing IkappaBDeltaN, TNF-alpha dramatically induced apoptosis, whereas IL-1beta had no effect. The induction was suppressed by treatment with a selective inhibitor of the caspase-3 family, Z-DEVD-fmk, and the overexpression of IkappaBDeltaN induced TNF-alpha-mediated caspase-3 and caspase-2 activity. These results indicate that overexpression of IkappaBDeltaN induces TNF-alpha-dependent apoptosis by efficient and specific suppression of NF-kappaB and upregulation of caspase-3 and caspase-2 activity in human VSMCs. Our findings suggest that adenovirus-mediated IkappaBDeltaN gene transfer may be useful in the treatment of disorders associated with inflammatory conditions, such as the response to vascular injury and atherosclerosis.
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