A20 attenuates vascular smooth muscle cell proliferation and migration through blocking PI3k/Akt singling in vitro and in vivo.

A20 was originally characterized as a TNF-inducible gene in human umbilical vein endothelial cells. It is also induced in many other cell types by a wide range of stimuli. Expression of A20 has been shown to protect from TNF-induced apoptosis and also functions via a negative-feedback loop to block NF-kappaB activation induced by TNF and other stimuli. However, there are no reports on whether A20 can inhibit vascular smooth muscle cell proliferation in vivo. Here, we examined the effects of A20 on neointimal formation after balloon injury and TNF-alpha-induced vascular smooth muscle cells (VSMCs) proliferation and migration, as well as related molecular mechanisms in vitro and in vivo. We introduced adenovirus expressing A20 or GFP into rat carotid arterial segments after balloon injury. The effects of A20 were evaluated 14 days after gene delivery with morphometry and immunohistochemical staining for proliferating and apoptotic cells. Ad-A20 infection resulted in a significantly lower intima to media ratio and a greater lumen area compared with Ad-GFP infected group. Proliferation index was significantly reduced 14 days in Ad-A20 infection group. However, apoptotic index and caspase-3 activity were not significantly different between any groups at 14 days. In vitro experiments were performed to show that A20 markedly inhibited TNF-alpha-induced proliferation and migration in VSMCs. Further studies showed that A20 expression blocked artery injury- and TNF-alpha-activated PI3K/Akt/GSK3beta/CREB pathway in vivo and in vitro. In conclusion, A20 attenuates neointimal formation after arterial injury as well as cell proliferation and migration in response to TNF-alpha in VSMCs through blocking PI3K/Akt/GSKbeta-dependent activation of CREB.