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Maintenance of the endothelial cell (EC) layer of the vessel wall is essential for proper functioning of the vessel and prevention of vascular disorders. Replacement of damaged ECs could occur through division of surrounding ECs. Furthermore, EC progenitor cells (EPCs), derived from the bone marrow and circulating in the bloodstream, can differentiate into ECs. Therefore, these cells might also play a role in maintenance of the endothelial layer in the vascular system. The proliferative potential of both cell types is limited by shortening of telomeric DNA. Accelerated telomere shortening might lead to senescent vascular wall cells and eventually to the inability of the endothelium to maintain a continuous monolayer. The aim of this study was to describe the dynamics of EC damage and repair and telomere shortening by a mathematical model. In the model, ECs were integrated in a two-dimensional structure resembling the endothelium in a large artery. Telomere shortening was described as a stochastic process with oxidative damage as the main cause of attrition. Simulating the model illustrated that increased cellular turnover or elevated levels of oxidative stress could lead to critical telomere shortening and senescence at an age of 65 yr. The model predicted that under those conditions the EC layer could display defects, which could initiate severe vascular wall damage in reality. Furthermore, simulations showed that 5% progenitor cell homing/yr can significantly delay the EC layer defects. This stresses the potential importance of EPC number and function to the maintenance of vascular wall integrity during the human life span. atherosclerosis; computer simulation; endothelial cells; progenitor cells

Nitric oxide donor induces temporal and dose-dependent reduction of gene expression in human endothelial cells. Am J Physiol Heart Circ Physiol 287: H1977-H1986, 2004. First published July 8, 2004; doi:10.1152/ ajpheart.00323.2004.--The present study tested the hypothesis that acute increases in nitric oxide (NO) exert substantial influences on gene transcription in endothelial cells (ECs) via guanylyl cyclase (GC). Human umbilical veins ECs (HUVECs) were exposed to 0.1, 1, and 10 mM of sodium nitroprusside (SNP) for 4 h and to 1 mM SNP or 250 [micro]M of (Z)-1[N-(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-l-ium-1,2-diolate (DETA-NONOate) for 2, 4, 8, and 24 h. Also, cells were exposed to DETA-NONOate in the presence and absence of the GC inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1one (ODQ; 10 [micro]M) for 4 h. RNA was isolated, reverse transcribed, Cy3 and Cy5 labeled, and analyzed using cDNA microarrays. Increasing doses of SNP predominantly depressed gene expression in HUVECs. Gene function was related to growth, adhesion, and cell structure. DETA-NONOate evoked a wave of expression changes (maximum at 4 h), with a remarkable downregulation of the transcription factors MSX1, RELB, and Egr-1. Both SNP- and DETANONOate-induced gene expression had faded after 24 h, despite continued elevation of cGMP in the medium. Coadministration of ODQ decreased many, but not all, of the transcriptional responses to DETA-NONOate. NO pronouncedly depressed EC gene expression, in particular of transcription factors. The observation that many, but not all, transcriptional changes induced by NO could be inhibited by inhibition of GC indicates the presence of GC-independent NO actions on gene expression. Thus EC gene expression responds to NO; however, the transcriptional response fades during prolonged exposure. This could allow the EC to respond to increased shear, without vigorous changes in gene expression. microarray; nitrate tolerance; guanylate cyclase; Egr-1; V-Rel avian reticuloendotheliosis viral oncogene homolog B

Abstract Background Nanoparticle (NP) toxicity testing comes with many challenges. Characterization of the test substance is of crucial importance and in the case of NPs, agglomeration/aggregation state in physiological media needs to be considered. In this study, we have addressed the effect of agglomerated versus single particle suspensions of nano- and submicron sized gold on the inflammatory response in the lung. Rats were exposed to a single dose of 1.6 mg/kg body weight (bw) of spherical gold particles with geometric diameters of 50 nm or 250 nm diluted either by ultrapure water or by adding phosphate buffered saline (PBS). A single dose of 1.6 mg/kg bw DQ12 quartz was used as a positive control for pulmonary inflammation. Extensive characterization of the particle suspensions has been performed by determining the zetapotential, pH, gold concentration and particle size distribution. Primary particle size and particle purity has been verified using transmission electron microscopy (TEM) techniques. Pulmonary inflammation (total cell number, differential cell count and pro-inflammatory cytokines), cell damage (total protein and albumin) and cytotoxicity (alkaline phosphatase and lactate dehydrogenase) were determined in bronchoalveolar lavage fluid (BALF) and acute systemic effects in blood (total cell number, differential cell counts, fibrinogen and C-reactive protein) 3 and 24 hours post exposure. Uptake of gold particles in alveolar macrophages has been determined by TEM. Results Particles diluted in ultrapure water are well dispersed, while agglomerates are formed when diluting in PBS. The particle size of the 50 nm particles was confirmed, while the 250 nm particles appear to be 200 nm using tracking analysis and 210 nm using TEM. No major differences in pulmonary and systemic toxicity markers were observed after instillation of agglomerated versus single gold particles of different sizes. Both agglomerated as well as single nanoparticles were taken up by macrophages. Conclusion Primary particle size, gold concentration and particle purity are important features to check, since these characteristics may deviate from the manufacturer's description. Suspensions of well dispersed 50 nm and 250 nm particles as well as their agglomerates produced very mild pulmonary inflammation at the same mass based dose. We conclude that single 50 nm gold particles do not pose a greater acute hazard than their agglomerates or slightly larger gold particles when using pulmonary inflammation as a marker for toxicity.

Maintenance of the endothelial cell (EC) layer of the vessel wall is essential for proper functioning of the vessel and prevention of vascular disorders. Replacement of damaged ECs could occur through division of surrounding ECs. Furthermore, EC progenitor cells (EPCs), derived from the bone marrow and circulating in the bloodstream, can differentiate into ECs. Therefore, these cells might also play a role in maintenance of the endothelial layer in the vascular system. The proliferative potential of both cell types is limited by shortening of telomeric DNA. Accelerated telomere shortening might lead to senescent vascular wall cells and eventually to the inability of the endothelium to maintain a continuous monolayer. The aim of this study was to describe the dynamics of EC damage and repair and telomere shortening by a mathematical model. In the model, ECs were integrated in a twodimensional structure resembling the endothelium in a large artery. Telomere shortening was described as a stochastic process with oxidative damage as the main cause of attrition. Simulating the model illustrated that increased cellular turnover or elevated levels of oxidative stress could lead to critical telomere shortening and senescence at an age of 65 yr. The model predicted that under those conditions the EC layer could display defects, which could initiate severe vascular wall damage in reality. Furthermore, simulations showed that 5% progenitor cell homing/yr can significantly delay the EC layer defects. This stresses the potential importance of EPC number and function to the maintenance of vascular wall integrity during the human life span. [ABSTRACT FROM AUTHOR]