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Background: Nitric oxide is produced by different nitric oxide synthases isoforms. NO activates two signaling pathways, one dependent on soluble guanylate cyclase and protein kinase G, and other where NO post-translationally modifies proteins through S-nitrosylation, which is the modification induced by NO in free-thiol cysteines in proteins to form S-nitrosothiols. High levels of NO have been detected in blood of breast cancer patients and increased NOS activity has been detected in invasive breast tumors compared to benign or normal breast tissue, suggesting a positive correlation between NO biosynthesis, degree of malignancy and metastasis. During metastasis, the endothelium plays a key role allowing the adhesion of tumor cells, which is the first step in the extravasation process leading to metastasis. This step shares similarities with leukocyte adhesion to the endothelium, and it is plausible that it may also share some regulatory elements. The vascular cell adhesion molecule-1 (VCAM-1) expressed on the endothelial cell surface promotes interactions between the endothelium and tumor cells, as well as leukocytes. Data show that breast tumor cells adhere to areas in the vasculature where NO production is increased, however, the mechanisms involved are unknown., Results: We report that the stimulation of endothelial cells with interleukin-8, and conditioned medium from breast tumor cells activates the S-nitrosylation pathway in the endothelium to induce leukocyte adhesion and tumor cell extravasation by a mechanism that involves an increased VCAM-1 cell surface expression in endothelial cells. We identified VCAM-1 as an S-nitrosylation target during this process. The inhibition of NO signaling and S-nitrosylation blocked the transmigration of tumor cells through endothelial monolayers. Using an in vivo model, the number of lung metastases was inhibited in the presence of the S-nitrosylation inhibitor N-acetylcysteine (NAC), which was correlated with lower levels of S-nitrosylated VCAM-1 in the metastases., Conclusions: S-Nitrosylation in the endothelium activates pathways that enhance VCAM-1 surface localization to promote binding of leukocytes and extravasation of tumor cells leading to metastasis. NAC is positioned as an important tool that might be tested as a co-therapy against breast cancer metastasis., (© 2023. Sociedad de Biologia de Chile.)

Purpose: Patients with clinically evident chronic venous insufficiency were evaluated to relate the degree of insufficiency and calf muscle pump dysfunction to venous ulceration., Methods: Sixty-nine limbs in 55 patients with chronic venous insufficiency by Society for Vascular Surgery/International Society for Cardiovascular Surgery Classification were compared in three groups: classes 1 and 2 with no history of ulceration (19 limbs); class 3 with healed ulceration (20 limbs); and class 3 with active ulcers (30 limbs). Air plethysmography measurements of outflow fraction, venous volume, venous filling time, venous filling index, ejection fraction, ejection volume, residual volume fraction, and residual volume were made. In 62 of the 69 limbs, color-flow duplex ultrasonography was used to determine the pattern of reflux., Results: The outflow fraction was normal in 84%, 75%, and 77% of nonulcerated, healed, and ulcerated limbs. The venous filling index was abnormal in most limbs (nonulcerated 95%, healed 90%, ulcerated 98%) but not significantly different among groups. Differences in calf muscle pump function were significant. Ulcerated limbs had significantly poorer ejection fractions (p = 0.0002) and greater residual volume fractions (p = 0.0006) than nonulcerated or healed limbs. By ultrasonography, deep and superficial vein incompetence was present in most limbs and was not statistically different among groups. Although venous insufficiency was not measurably different among groups, limbs with active venous ulcers had significantly poorer calf muscle pump function than those with healed ulcers or with no history of ulceration., Conclusion: Venous insufficiency is necessary but not sufficient to cause ulceration, and a deficiency of the calf muscle pump is significant to the severity of venous ulceration.

Color-flow and duplex ultrasonography were used to determine the optimal method for documenting venous valvular reflux. Popliteal veins were examined in 10 normal limbs and 11 limbs with clinical evidence of chronic venous insufficiency (CVI). Peak reflux velocity (spectral) and duration of reflux (spectral and color) were measured with the patient in supine and standing positions, with manual and pneumatic compression applied sequentially to thigh and calf. Manual and pneumatic compression produced equivalent reflux velocity and duration. In normal limbs peak reflux velocity was always less than 22 cm/sec, with a mean reverse flow duration of 0.3 sec +/- 0.03 (SEM). In limbs with CVI, reflux velocity varied widely among protocols. Reflux duration and velocity were greater in the supine position than in the standing position for both normal limbs and limbs with CVI (p < 0.04). Duration was significantly increased for thigh versus calf compression in normal limbs (p < 0.001) but decreased in limbs with CVI (p < 0.003). Methods that used thigh compression or supine position were less capable of discriminating normal limbs from limbs with CVI. Standing calf compression provided the greatest rates of sensitivity (91%), specificity (100%), and accuracy (95%). Compared with spectral Doppler scanning, color-flow ultrasonography produced a consistently shorter reflux duration (p < 0.001). In limbs with CVI with a mean spectral duration of 2.5 sec +/- 0.2 (SEM), mean color Doppler duration was 0.7 sec shorter. Our results demonstrate that popliteal vein incompetence is identified optimally by reflux duration after standing calf compression; adequate manual compression is sufficient to identify reflux; color-flow Doppler ultrasonography may underestimate reflux duration.

Increased vascular permeability is an early and sensitive indicator of ischemic muscle injury, occurring before significant histologic or radionuclide changes are evident. We investigated the effect of iloprost, a stable prostacyclin analog, on microvascular permeability in a rat striated muscle model. In six control and six experimental animals the cremaster muscle was dissected, placed in a closed-flow acrylic chamber, and suffused with a bicarbonate buffer solution. Dextran labeled with fluorescein was injected intravenously as a macromolecular tracer, and microvascular permeability was determined on the basis of clearance of the fluorescent tracer. Two hours of ischemia were followed by 2 hours of reperfusion. In the experimental group iloprost (0.5 microgram/kg/min) was given in a continuous intravenous infusion. Microvascular permeability increased significantly during reperfusion in both control and experimental animals (p less than 0.0001). Treatment with iloprost, however, significantly attenuated this response compared to the control group, 4.8 +/- 0.3 versus 7.3 +/- 0.5 microliters/gm/min, respectively (p less than 0.0001). Iloprost decreases the rise in vascular permeability after ischemia and reperfusion. Experimental clinical use of iloprost under controlled conditions in the treatment of patients with acute skeletal muscle ischemia appears justified.