Mammalian biology adapts to physical activity but the molecular mechanisms sensing the activity remain enigmatic. Recent studies have revealed how Piezo1 protein senses mechanical force to enable vascular development. Here, we address Piezo1 in adult endothelium, the major control site in physical activity. Mice without endothelial Piezo1 lack obvious phenotype but close inspection reveals a specific effect on endothelium-dependent relaxation in mesenteric resistance artery. Strikingly, the Piezo1 is required for elevated blood pressure during whole body physical activity but not blood pressure during inactivity. Piezo1 is responsible for flow-sensitive non-inactivating non-selective cationic channels which depolarize the membrane potential. As fluid flow increases, depolarization increases to activate voltage-gated Ca2+ channels in the adjacent vascular smooth muscle cells, causing vasoconstriction. Physical performance is compromised in mice which lack endothelial Piezo1 and there is weight loss after sustained activity. The data suggest that Piezo1 channels sense physical activity to advantageously reset vascular control.

Interactions between advanced glycation end products (AGEs) and the receptor for AGE (RAGE) are implicated in the vascular complications in diabetes. We have identified eight novel polymorphisms, of which the ؊1420 (GGT)n, ؊1393 G/T, ؊1390 G/T, and ؊1202 G/A were in the overlapping PBX2 3 untranslated region (UTR), and the ؊429 T/C (66.5% TT, 33.5% TC/CC), ؊407 to -345 deletion (99% I, 1% I/D, 0% D), ؊374 T/A (66.4% TT, 33.6% TA/AA), and ؉20 T/A were in the RAGE promoter. To evaluate the effects on transcriptional activity, we measured chloramphenicol acetyl transferase (CAT) reporter gene expression, driven by variants of the -738 to ؉49 RAGE gene fragment containing the four polymorphisms identified close to the transcriptional start site. The -429 C, ؊374 A, and 63-bp deletion alleles resulted in a mean increase of CAT expression of twofold (P < 0.0001), threefold (P < 0.001), and fourfold (P < 0.05), respectively, with the -374 T and A alleles yielding highly differential binding of nuclear protein extract from both monocyte-and hepatocyte-derived cell lines. The prevalence of the functional polymorphisms were investigated in subjects with type 2 diabetes (106 with and 109 without retinopathy), with the -429 C allele showing an increase in the retinopathy group (P < 0.05). These data suggest that the polymorphisms involved in differences in RAGE gene regulation may influence the pathogenesis of diabetic vascular complications. Diabetes 50:1505-1511, 2001

Rationale Abdominal aortic aneurysm (AAA) is a complex disease with both genetic and environmental risk factors. Together, 6 previously identified risk loci only explain a small proportion of the heritability of AAA. Objective To identify additional AAA risk loci using data from all available genome-wide association studies (GWAS). Methods and Results Through a meta-analysis of 6 GWAS datasets and a validation study totalling 10,204 cases and 107,766 controls we identified 4 new AAA risk loci: 1q32.3 (SMYD2), 13q12.11 (LINC00540), 20q13.12 (near PCIF1/MMP9/ZNF335), and 21q22.2 (ERG). In various database searches we observed no new associations between the lead AAA SNPs and coronary artery disease, blood pressure, lipids or diabetes. Network analyses identified ERG, IL6R and LDLR as modifiers of MMP9, with a direct interaction between ERG and MMP9. Conclusions The 4 new risk loci for AAA appear to be specific for AAA compared with other cardiovascular diseases and related traits suggesting that traditional cardiovascular risk factor management may only have limited value in preventing the progression of aneurysmal disease.

To cite this article: Komanasin N, Catto AJ, Futers TS, van Hylckama Vlieg A, Rosendaal FR, Arië ns RAS. A novel polymorphism in the factor XIII B-subunit (His95Arg): relationship to subunit dissociation and venous thrombosis. J Thromb Haemost 2005; 3: 2487-96.Summary. Background: Factor (F)XIII B-subunit, which plays a carrier role for zymogen FXIIIA, is highly polymorphic, but the molecular basis for these polymorphisms and their relationship to disease remains unknown. Objectives: To screen the FXIIIB gene coding region for common variation and analyze possible functional effects. Methods and Results: We examined the FXIIIB gene by PCR-SSCP and identified three common single nucleotide polymorphisms: A8259G, C29470T and A30899G. A8259G results in substitution of His95Arg in the second Sushi domain. An FXIII tetramer ELISA was developed to analyze B-subunit dissociation from A-subunit (leading to access to the catalytic site of FXIII). Increased subunit dissociation, 0.51 vs. 0.45 (fraction of total tetramer), was found in plasma from subjects possessing the Arg-allele. However, when the variants were purified to homogeneity and binding was analyzed by steady-state kinetics, no difference was observed. The relationship between His95Arg and venous thrombosis was investigated in 214 patients and 291 controls from Leeds. His/ Arg + Arg/Arg genotypes were more frequent in patients than controls (22.4% vs. 15.1%). His95Arg was also investigated in the Leiden Thrombophilia Study, in which a similar difference was observed for 471 patients vs. 472 controls (18.5% vs. 14.0%), for a pooled odds ratio (OR) of 1.5 (CI95 1.1-2.0). Conclusions: We have identified three FXIIIB polymorphisms, one of which codes for substitution of His95Arg. The Arg95 variant associates with a moderately increased risk for venous thrombosis, and with increased dissociation of the FXIII subunits in plasma, although in vitro steady-state binding between purified subunits was not affected.

Summary Endogenous PIEZO1 channels of native endothelium lack the hallmark inactivation often seen when these channels are overexpressed in cell lines. Because prior work showed that the force of shear stress activates sphingomyelinase in endothelium, we considered if sphingomyelinase is relevant to endogenous PIEZO1. Patch clamping was used to quantify PIEZO1-mediated signals in freshly isolated murine endothelium exposed to the mechanical forces caused by shear stress and membrane stretch. Neutral sphingomyelinase inhibitors and genetic disruption of sphingomyelin phosphodiesterase 3 (SMPD3) cause PIEZO1 to switch to profoundly inactivating behavior. Ceramide (a key product of SMPD3) rescues non-inactivating channel behavior. Its co-product, phosphoryl choline, has no effect. In contrast to ceramide, sphingomyelin (the SMPD3 substrate) does not affect inactivation but alters channel force sensitivity. The data suggest that sphingomyelinase activity, ceramide, and sphingomyelin are determinants of native PIEZO gating that enable sustained activity.

Summary. Tissue factor pathway inhibitor (TFPI) inhibits tissue factor-induced coagulation. The major part of TFPI is releasable by heparin. We recently found eight patients with thrombosis and low levels of heparin-releasable TFPI in whom we investigated the TFPI gene for mutations. A transition of G to A coding for Valine264Methionine in the heparin-binding domain was found. The Val264Met polymorphism had an allele frequency of 3% in 96 healthy individuals. A silent polymorphism was identified in TFPI exon IV (T!C), which does not alter Tyrosine 56. Apart from Val264Met, which was detected in one out of the eight patients, no other mutations in the TFPI gene were found in patients with low heparin-releasable TFPI. Analysis of Val264Met in 317 patients with deep vein thrombosis (DVT) and 292 controls showed no association between Val264-Met and DVT. However, a study of total TFPI antigen levels in 122 DVT patients and 126 controls demonstrated an association between TFPI levels and venous thrombosis (P 0´0001). These results provide evidence for a relationship between venous thrombosis and total TFPI level as a possible risk factor, whereas they do not support a link between DVT and mutations in the nine exons of the TFPI gene.

We recently demonstrated that reducing IGF-1 receptor (IGF-1R) numbers in the endothelium enhances nitric oxide (NO) bioavailability and endothelial cell insulin sensitivity. In the present report, we aimed to examine the effect of increasing IGF-1R on endothelial cell function and repair. To examine the effect of increasing IGF-1R in the endothelium, we generated mice overexpressing human IGF-1R in the endothelium (human IGF-1R endothelium-overexpressing mice [hIGFREO]) under direction of the Tie2 promoter enhancer. hIGFREO aorta had reduced basal NO bioavailability (percent constriction to NG-monomethyl-l-arginine [mean (SEM) wild type 106% (30%); hIGFREO 48% (10%)]; P < 0.05). Endothelial cells from hIGFREO had reduced insulin-stimulated endothelial NO synthase activation (mean [SEM] wild type 170% [25%], hIGFREO 58% [3%]; P = 0.04) and insulin-stimulated NO release (mean [SEM] wild type 4,500 AU [1,000], hIGFREO 1,500 AU [700]; P < 0.05). hIGFREO mice had enhanced endothelium regeneration after denuding arterial injury (mean [SEM] percent recovered area, wild type 57% [2%], hIGFREO 47% [5%]; P < 0.05) and enhanced endothelial cell migration in vitro. The IGF-1R, although reducing NO bioavailability, enhances in situ endothelium regeneration. Manipulating IGF-1R in the endothelium may be a useful strategy to treat disorders of vascular growth and repair.

Mechanical force is a determinant of Notch signalling but the mechanism of force detection and its coupling to Notch are unclear. We propose a role for Piezo1 channels, which are mechanically-activated non-selective cation channels. In cultured microvascular endothelial cells, Piezo1 channel activation by either shear stress or a chemical agonist Yoda1 activated a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), a Ca2+-regulated transmembrane sheddase that mediates S2 Notch1 cleavage. Consistent with this observation, we found Piezo1-dependent increase in the abundance of Notch1 intracellular domain (NICD) that depended on ADAM10 and the downstream S3 cleavage enzyme, γ-secretase. Conditional endothelial-specific disruption of Piezo1 in adult mice suppressed the expression of multiple Notch1 target genes in hepatic vasculature, suggesting constitutive functional importance in vivo. The data suggest that Piezo1 is a mechanism conferring force sensitivity on ADAM10 and Notch1 with downstream consequences for sustained activation of Notch1 target genes and potentially other processes.