Gulati, Rajiv

Background— Bone marrow–derived cells have been shown to contribute to endothelial replacement after vascular injury. In vitro culture of peripheral blood mononuclear cells produces cells with phenotypic characteristics of endothelium. To test the hypothesis that delivery of autologous culture-modified mononuclear cells (CMMCs) to injured arteries could attenuate the vascular response to injury, a rabbit model was studied. Methods and Results— Rabbit peripheral blood mononuclear cells were cultured in endothelial growth media for 7 to 12 days, yielding highly proliferative cells with distinct endothelial phenotype (expressing CD31 and endothelial nitric oxide synthase and capable of acetylated LDL uptake). A rabbit model of balloon carotid injury was used to evaluate the effect of day 7 CMMC delivery on vascular responses. Animals underwent balloon injury and immediate delivery of autologous CMMCs or buffered saline by 20 minutes of local dwelling. Fluorescence-labeled CMMCs were detected in all vessel layers 4 weeks after delivery. Colonies of cells that localized to the lumen and stained for endothelial markers were also identified. Local CMMC administration at the time of balloon injury accelerated reendothelialization at 4 weeks compared with saline ( P <0.05). Moreover, CMMC delivery markedly improved endothelium-dependent vasoreactivity at 4 weeks compared with saline ( P <0.005). Finally, CMMC treatment reduced neointimal formation by 55% at 4 weeks ( P <0.05). Conclusions— These data demonstrate that delivery of CMMCs to balloon-injured arteries is associated with accelerated reendothelialization, enhanced endothelium-dependent vasoreactivity, and reduced neointimal formation. Thus, delivery of autologous CMMCs represents a novel vasculoprotective approach to attenuate the response to acute vascular injury.

ABSTRACT The ubiquitin‐proteasome system (UPS) is involved in the removal of damaged proteins and the activation of transcription factors, such as nuclear‐factor‐κB. Recent reports, however, questioned the functional activity of the UPS under conditions of increased oxidative stress, such as experimental hypercholesterolemia, which was the objective of our study. Pigs were placed on a normal chow diet (N) or on a hypercholesterolemic diet without (HC) or with vitamin C and E supplementation (HC+VIT) for 12 weeks. Compared with N, plasma concentration of total cholesterol increased in both HC and HC+VIT [76 ± 21 vs. 400 ± 148 ( P <0.05) and 329 ± 102 ( P <0.05) mg/dL], whereas increase in lipid peroxidation, as assessed by LDL‐malondialdehyde plasma concentration, was found in HC but not in HC+VIT [6.6 ± 0.7 vs. 8.5 ± 0.3 ( P <0.05) and 6.8 ± 0.7 nmol/mg protein]. In comparison with N, the level of ubiquitin conjugates in the coronary artery, as assessed by immunoblotting, increased by 42% in HC but not in HC+VIT and was localized predominantly to media vascular smooth muscle cells by immunostaining. There was no difference in proteasome proteolytic activity among the study groups. These results demonstrate that the UPS is functionally active in early atherogenesis despite increase in oxidative stress with important repercussions in the pathophysiology and therapy of cardiovascular diseases.

Background— Caveolin-1 is a regulator of signaling events originating from plasma membrane microdomains termed caveolae. This study was performed to determine the regulatory role of caveolin-1 on the proliferative events induced by platelet-derived growth factor (PDGF) in vascular smooth muscle cells (VSMCs). Methods and Results— Treatment of VSMCs with PDGF for 24 hours resulted in a loss of caveolin-1 protein expression and plasma membrane–associated caveolae, despite a 3-fold increase in caveolin-1 mRNA. Pretreatment of VSMCs with chloroquine, an inhibitor of lysosomal function, inhibited the PDGF-induced loss of caveolin-1. These studies demonstrated that caveolin-1 was a target of PDGF signaling events. Adenoviral overexpression of caveolin-1 was associated with a switch in PDGF-induced signaling events from a proliferative response to an apoptotic response. This overexpression inhibited PDGF-induced expression of cyclin D1 in the presence of unaffected mitogen-activated protein kinase activation. Conclusions— Taken together, these studies suggest that caveolin-1 is an inhibitor of PDGF proliferative responses and might be capable of transforming PDGF-induced proliferative signals into death signals.