Angiotensin II and tumor necrosis factor-alpha upregulate survivin and Kruppel-like factor 5 in smooth muscle cells: Potential relevance to vein graft hyperplasia.

BACKGROUND: Survivin (SVV) is a unique inhibitor of apoptosis protein (IAP) that regulates both apoptosis and mitosis. Recent work suggests that SVV plays a critical role in the vascular injury response, but the molecular pathways remain unclear.
METHODS: We examined the expression of SVV and the transcription factor, KLF5, in human venous smooth muscle cells (VSMC) by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot analysis after treatment with angiotensin II (Ang II) or tumor necrosis factor-alpha (TNF-alpha). An adenoviral construct expressing SVV or GFP was also employed to assess effects on KLF5 expression. A rabbit carotid interposition vein graft model was used to assess the relevance of KLF5 to bypass graft healing.
RESULTS: Stimulation of VSMC with Ang II and TNF-alpha led to a rapid upregulation of KLF5 expression, and a later increase in SVV, which was cell-cycle independent. Overexpression of SVV in VSMC led to an early and persistent induction of KLF5. KLF5 was upregulated in rabbit vein grafts early (1 day) after grafting.
CONCLUSIONS: We speculate that SVV is a central point of convergence of multiple signaling pathways in vascular injury, and that it regulates the local amplification of these pathways in the vessel wall.