We hypothesized that transgenic mice overexpressing the p22phox subunit of the NADPH oxidase selectively in smooth muscle (Tgp22smc) would exhibit an exacerbated response to transluminal carotid injury compared to wild-type mice. To examine the role of reactive oxygen species (ROS) as a mediator of vascular injury, the injury response was quantified by measuring wall thickness (WT) and cross-sectional wall area (CSWA) of the injured and noninjured arteries in both Tgp22smc and wild-type animals at days 3, 7, and 14 after injury. Akt, p38 MAPK, and Src activation were evaluated at the same time points using Western blotting. WT and CSWA following injury were significantly greater in Tgp22smc mice at both 7 and 14 days after injury while noninjured contralateral carotids were similar between groups. Apocynin treatment attenuated the injury response in both groups and rendered the response similar between Tgp22smc mice and wild-type mice. Following injury, carotid arteries from Tgp22smc mice demonstrated elevated activation of Akt at day 3, while p38 MAPK and Src activation was elevated at day 7 compared to wild-type mice. Both increased activation and temporal regulation of these signaling pathways may contribute to enhanced vascular growth in response to injury in this transgenic model of elevated vascular ROS.

Platelet derived growth factor (PDGF) is a pro‐migratory factor released in response to vascular injury. Vascular smooth muscle cells (VSMCs) mediate this response and contribute significantly to neointimal formation, thus delineating the molecular mechanisms of VSMC migration is critical to understanding the vascular repair process. Signaling cascades activated by PDGF ultimately converge upon the actin cytoskeleton which is a key regulator of migration. Recent studies report that cofilin, which upon activation depolymerizes actin and it's phosphatase Slingshot (SSH) are essential to PDGF‐induced VSMC migration. In addition to SSH, cofilin activity is also regulated by LIM‐kinase, which attenuates its activity. Thus, in these studies we examined the role of LIMK in PDGF‐induced VSMC migration. Immunoblotting with phosphospecific antibodies confirmed that LIMK activity was increased in a time dependent manner in response to PDGF. Transfection of VSMCs cells with LIMK siRNA attenuated PDGF induced migration by 70% vs. control VSMCs. The knockdown of LIMK expression by siRNA also decreased basal phosphorylation of cofilin and potentiated the cofilin response to PDGF‐induced activation. As PDGF‐induced LIMK regulation appears to mediate VSMC migration, these studies show the importance of further examining the SSH/LIMK balance in mediating cytoskeletal events associated with cofilin activity.