Ambient pressure upregulates nitric oxide synthase in a phosphorylated-extracellular regulated kinase– and protein kinase C–dependent manner

PurposeUsing endothelial cell/smooth muscle cell (SMC) cocultures, we have demonstrated that pressurized endothelial cell coculture inhibits SMC proliferation and promotes apoptosis, and that this effect is transferable through pressurized endothelial medium. We now hypothesized that endothelial nitric oxide synthase (eNOS) plays a significant role in mediating these pressure-induced effects.MethodsConditioned media from endothelial cells and SMCs exposed to ambient and increased pressure were transferred to recipient SMCs. We counted cells after 5 days of incubation with these media and evaluated eNOS and inducible NOS (iNOS) levels by Western blot.ResultsConditioned media from pressurized endothelial cells significantly decreased recipient SMC counts. This effect was sustained when N-nitro-L-arginine-methyl ester (L-NAME) was added to recipient cells but abolished when L-NAME was added to donor cells. SMCs were then exposed to control and pressurized conditions in monoculture or in coculture with endothelial cells. Pressure and coculture caused similar increase in iNOS levels but had no additive effect in combination. Finally, endothelial cells were exposed to control and pressurized environments. Pressure caused a 24% ± 1.6% increase in eNOS protein (P = .04, n = 12). This effect was sustained when cells were treated with L-NAME (32% ± 1.6% increase, P = .02) but abolished when endothelial cells were treated with calphostin C or PD98059 to block protein kinase C (PKC) or extracellular regulated kinase (ERK). Pressure also increased endothelial phosphorylated ERK (p-ERK) by 1.8-fold to 2.6-fold compared with control conditions after exposure of 2, 4, and 6 hours (P = .02, n = 4). This increase was sustained after pretreatment with calphostin C.ConclusionPressure modulates endothelial cell effects on SMC growth by increasing eNOS in an ERK-dependent and PKC-dependent manner.Clinical RelevanceIntimal hyperplasia is the main cause for restenosis that complicates 10% to 30% of all such vascular procedures and 30% to 40% of endovascular procedures. This article provides some novel information about smooth muscle cell/endothelial cell interaction, one of the main regulators of vascular remodeling and intimal hyperplasia. The role of endothelial cell/smooth muscle cell interaction cannot be studied well in vivo because these interactions cannot be distinguished from other factors that coexist in vivo, such as flow dynamics, matrix proteins, inflammatory factors, and interactions with other cells in the vascular wall and in the bloodstream. In this work, we use pressure as a triggering stimulus to alter in vitro endothelial behavior and identify important changes in endothelial regulation of smooth muscle cell biology. The pathways involved in this process and discussed in this article could ultimately be used to manipulate endothelial cell/smooth muscle cell interaction in clinical disease

The role of type I collagen in aortic wall strength with a homotrimeric [α1(I)]3 collagen mouse model

AbstractPurpose: Elastin and collagen (types I and III) are the primary load-bearing elements in aortic tissue. Deficiencies and derangements in elastin and type III collagen have been associated with the development of aneurysmal disease. However, the role of type I collagen is less well defined. The purpose of this study was to define the role of type I collagen in maintaining biomechanical integrity in the thoracic aorta, with a mouse model that produces homotrimeric type I collagen [α1(I)]3, rather than the normally present heterotrimeric [α1(I)]2 α2(I) type I collagen isotype. Methods: Ascending and descending thoracic aortas from homozygous (oim/oim ), heterozygous (oim /+), and wildtype (+/+) mice were harvested. Circumferential and longitudinal load-extension curves were used as a means of determining maximum breaking strength (Fmax) and incremental elastic modulus (IEM). Histologic analyses and hydroxyproline assays were performed as a means of determining collagen organization and content. Results: Circumferentially, the ascending and descending aortas of oim /oim mice demonstrated significantly reduced Fmax, with an Fmax of only 60% and 23%, respectively, of wildtype mice aortas. Oim/oim descending aortas demonstrated significantly greater compliance (decreased IEM), and the ascending aortas also exhibited a trend toward increased compliance. Reduced breaking strength was also demonstrated with longitudinal extension of the descending aorta. Conclusion: The presence of homotrimeric type I collagen isotype (absence of α2(I) collagen) significantly weakens the aorta. This study demonstrates the integral role of type I collagen in the biomechanical and functional properties of the aorta and may help to elucidate the role of collagen in the development of aneurysmal aortic disease or dissection. (J Vasc Surg 2001;33:1263-70.

Percutaneous intervention for infrainguinal occlusive disease in women: equivalent outcomes despite increased severity of disease compared with men

Experience with open surgical bypass suggests similar overall outcomes in women compared with men, but significantly increased risk of wound complications. Percutaneous treatment of lower extremity occlusive disease is therefore an attractive alternative in women, although it is not clear whether there is a difference in outcomes between women and men treated with this technique. We sought to determine the results and predictors of failure in women treated by percutaneous intervention. Percutaneous infrainguinal revascularization was performed on 309 women between 2001 and 2006. Procedures, complications, demographics, comorbidities, and follow-up data were entered into a prospective database for review. Patency was assessed primarily by duplex ultrasonography. Outcomes were expressed by Kaplan-Meier curves and compared by log-rank analysis. A total of 447 percutaneous interventions performed in 309 women were analyzed and compared with 553 interventions in men. Mean age in women was 73.2 years; comorbidities included hypertension (HTN) (86%), diabetes melitus (DM) (58%), chronic renal insufficiency (CRI) (15%), hemodialysis (7%), hypercholesterolemia (52%), coronary artery disease (CAD) (42%), and tobacco use (47%). Indications in women included claudication (38.0%), rest pain (18.8%), and tissue loss (43.2%). Overall primary & secondary patency and limb-salvage rates for women were 38% +/- 4%, 66% +/- 3%, and 80% +/- 4% at 24 months. In this patient sample, women were significantly more likely than men to present with limb-threatening ischemia (61.6% vs 47.3%, P < 0.001) and have lesions of TASC C and D severity (71.4% vs 61.7%, P < .005). However, there were no significant differences in primary and secondary patency rates or limb-salvage rates between genders. Furthermore, while women with limb-threat, diabetes, and advanced TASC severity lesions were at increased risk of failure overall, there were no differences between women and men with these characteristics. Percutaneous infrainguinal revascularization is a very effective modality in women with lower extremity occlusive disease. Although women in this sample were more likely to present with limb-threat than men, patency and limb-salvage rates were equivalent between genders, even in high-risk subsets such as diabetics or those with lesions of increased TASC severity