Overexpression of mutated IκBα inhibits vascular smooth muscle cell proliferation and intimal hyperplasia formation

AbstractPurposeVascular injury and inflammation are associated with elaboration of a number of cytokines that signal through multiple pathways to act as smooth muscle cell (SMC) mitogens. Activation of the nuclear factor–kappa B (NF-κB) transcription factor is essential for SMC proliferation in vitro and is activated by vascular injury in vivo. Activation of NF-κB is controlled by several upstream regulators, including the inhibitors of kappa B (IκB). These proteins bind to and keep NF-κB inactivated. The purpose of this study was to determine whether adenoviral gene transfer of a mutated IκBα super-repressor (AdIκBαSR) could inhibit development of intimal hyperplasia in vivo and to investigate how over-expression of this construct influences in vitro SMC proliferation and cell cycle regulatory proteins.MethodsA rat carotid injury model was used to study prevention of intimal hyperplasia. Arteries were assayed 14 days after injury and infection with AdIκBαSR or adenoviral β-galactosidase (AdLacZ). Untreated SMC or SMC infected with AdLacZ or AdIκBαSR were stimulated with 10% fetal bovine serum, interleukin-1β, or tumor necrosis factor-α. Electrophoretic mobility shift assays were used to assay for NF-κB activation. Protein levels of IκBα and cyclin-dependent kinase inhibitors p21Cip1/Waf1 and p27Kip1 were determined with Western blot analysis. Proliferation was measured with 3H-thymidine incorporation assays.ResultsAdIκBαSR inhibited the development of intimal hyperplasia by 49% (P < .05). Infection with AdIκBαSR significantly suppressed in vitro SMC proliferation when stimulated with serum, interleukin 1, or tumor necrosis factor α, and did not result in cell death. Inhibition of proliferation was associated with increased p21Cip1/Waf1 and p27Kip1 protein levels.ConclusionsGene transfer of IκBα super-repressor inhibited development of intimal hyperplasia in vivo and SMC proliferation in vitro. The antiproliferative activity may be related to cell cycle arrest through upregulation of the cyclin-dependent kinase inhibitors p21 and p27. Overexpression of IκBα may be a future therapeutic option in treatment of vascular diseases