Varying effects of hemodynamic forces on tissue factor RNA expression in human endothelial cells

The Joint Effect of a Combination of Components From the Fruit of Crataegus pinnatifida Bge. Var. major N.E. Br. and the Root of Salvia miltiorrhiza Bge. With Exercises on Swimming in Focal Cerebral Infraction in Rat

Background: In our previous study, we found that the combination of a traditional Chinese medicine (TCM) and swimming could prevent atherosclerosis through a synergistic interaction. However, whether the combined application of active components from the fruit of Crataegus pinnatifida Bge. Var. major N.E. Br. and the root of Salvia miltiorrhiza Bge. (CPSM) and swimming has been effective in the prevention and treatment of focal cerebral infraction remained unclear. This work aimed to conduct detailed investigation on the joint effects of CPSM extract with swimming on focal cerebral infraction in rats and its underlying mechanisms. Method: A photochemical method of the combination of Rose Bengal (RB) injection and cold-light source irradiation was performed to establish the rat focal cerebral thrombosis model. The pathological changes of the brain were observed by a DCP-7030 laser multifunction machine, and the protein levels of von Willebrand factor (vWF), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were detected by Western blotting. Blood samples were collected to assay tissue plasminogen activator (t-PA), plasminogen activator inhibitor type-1 (PAI-1), endothelin-1 (ET-1), 6-keto-prostaglandin F1α (6-keto-PGF1α), and thromboxane B2 (TXB2). Finally, the gene expression of t-PA, PAI-1, and ICAM-1 in human umbilical vein endothelial cells (HUVECs) stimulated by tumor necrosis factor-α (TNF-α) was assayed via real-time (RT) quantitative PCR (qPCR). Results: The joint effects of CPSM extract and swimming demonstrated significant interactions, which including increased blood perfusion, increased serum t-PA and 6-keto-PGF1α, decreased serum PAI-1 and TXB2, decreased protein levels of vWF, VCAM-1 and ICAM-1, and decreased ICAM-1 gene expression. Conclusion: This research demonstrated that the combined therapy of CP and SM extracts with swimming could prevent focal cerebral infraction through interactions on the regulation of vascular endothelial functions and inflammatory factors. It stresses the promising effects of the drugs and shear stress of blood flow in prevention and treatment of thrombosis. The mechanism may be related to regulating the protein expression of vWF, VCAM-1, and ICAM-1, and downregulating the gene expression of ICAM-1.

In vitro investigation of silica nanoparticle uptake into human endothelial cells under physiological cyclic stretch

BACKGROUND

In general the prediction of the toxicity and therapeutic efficacy of engineered nanoparticles in humans is initially determined using in vitro static cell culture assays. However, such test systems may not be sufficient for testing nanoparticles intended for intravenous application. Once injected, these nanoparticles are caught up in the blood stream in vivo and are therefore in continuous movement. Physical forces such as shear stress and cyclic stretch caused by the pulsatile blood flow are known to change the phenotype of endothelial cells which line the luminal side of the vasculature and thus may be able to affect cell-nanoparticle interactions.

METHODS

In this study we investigated the uptake of amorphous silica nanoparticles in primary endothelial cells (HUVEC) cultured under physiological cyclic stretch conditions (1 Hz, 5% stretch) and compared this to cells in a standard static cell culture system. The toxicity of varying concentrations was assessed using cell viability and cytotoxicity studies. Nanoparticles were also characterized for the induction of an inflammatory response. Changes to cell morphology was evaluated in cells by examining actin and PECAM staining patterns and the amounts of nanoparticles taken up under the different culture conditions by evaluation of intracellular fluorescence. The expression profile of 26 stress-related was determined by microarray analysis.

RESULTS

The results show that cytotoxicity to endothelial cells caused by silica nanoparticles is not significantly altered under stretch compared to static culture conditions. Nevertheless, cells cultured under stretch internalize fewer nanoparticles. The data indicate that the decrease of nanoparticle content in stretched cells was not due to the induction of cell stress, inflammation processes or an enhanced exocytosis but rather a result of decreased endocytosis.

CONCLUSIONS

In conclusion, this study shows that while the toxic impact of silica nanoparticles is not altered by stretch this dynamic model demonstrates altered cellular uptake of nanoparticles under physiologically relevant in vitro cell culture models. In particular for the development of nanoparticles for biomedical applications such improved in vitro cell culture models may play a pivotal role in the reduction of animal experiments and development costs.

Characterization of extracellular signal-regulated kinase 5 levels in human umbilical vein endothelial cells exposed to disturbed and uniform flow

Extracellular signal-regulated kinase 5 (ERK5) has been reported to regulate endothelial cell integrity and protect from vascular dysfunction under continuous laminar flow. However, the effect of flow on ERK5 levels has not been determined. Confluent human umbilical vein endothelial cells (HUVECs) were seeded on fibronectin coated glass slides and serum starved for 2 hours with 1% fetal bovine serum (FBS). HUVECs were then exposed to to and fro flow (TFF), pulsatile forward flow (PFF), or continuous laminar flow (CLF) in a parallel plate flow chamber for up to 2 hours. At the end of experiment, cell lysates were prepared and immunoblotted with antibodies to total ERK5. Both CLF and TFF exhibited a decrease in ERK5 after levels after 2-hour exposure. However, the level of ERK5 for PFF remained the same. Disturbed, but not uniform pulsatile, flow decreases ERK5 levels in HUVECs.

PECAM-1 phosphorylation and tissue factor expression in HUVECs exposed to uniform and disturbed pulsatile flow and chemical stimuli

INTRODUCTION

We analyzed the relationship between platelet endothelial cell adhesion molecule-1 (PECAM-1) activation and tissue factor (TF) RNA expression in human umbilical vein endothelial cells (HUVECs) exposed to mechanical and chemical stimulation.

METHODS

Fifty percent confluent and 100% confluent HUVEC cultures were exposed to pulsatile forward flow, as a model for uniform flow, or pulsatile to-and-fro flow, as a model for disturbed flow, using a parallel-plate flow chamber system for up to 4 hours in the presence or absence of 4 U/mL thrombin. Protein lysates were immunoprecipitated for PECAM-1 and then immunoblotted with anti-phospho-tyrosine antibody. TF RNA expression was determined using quantitative reverse transcription polymerase chain reaction.

RESULTS

HUVECs exposed to disturbed flow induced higher TF expression at 4 hours than HUVECs exposed to uniform flow in sparse cultures (16.8 ± 5.8 vs 5.1 ± 1.2; P < .05). HUVECs exposed to disturbed flow and thrombin induced higher TF RNA expression at 4 hours than cultures exposed to uniform flow and thrombin in both confluent (47.0 ± 6.0 vs 30.2 ± 4.9; P < .05) and sparse (72.3 ± 10.7 vs 49.8 ± 4.7; P < .05) cultures. In confluent HUVEC cultures, PECAM-1 is minimally phosphorylated by disturbed and uniform flow, while in sparse HUVEC cultures, PECAM-1 phosphorylation at 15 minutes is greater in both disturbed and uniform flow (2.0 ± 0.2 and 2.1 ± 0.4 respectively; P < .05). Thrombin treatment of static HUVECs exhibited greater PECAM-1 phosphorylation at 15 minutes in confluent compared with sparse cultures (3.0 ± 0.5 vs 2.3 ± 0.1; P < .05). PECAM-1 phosphorylation of HUVECs exposed to both flow and thrombin is significantly higher in sparse cultures compared with either flow or thrombin stimulation alone but was suppressed in confluent cultures.

CONCLUSIONS

The significantly higher TF RNA expression induced by disturbed flow and cell confluence indicates that suppression of PECAM-1 phosphorylation may be an important contributory mechanical signal pathway that promotes TF expression when HUVECs are exposed to disturbed flow.