Telehealth on heart failure: results of the Recap project.

Telehealth has become a very important tool that allows the monitoring of heart failure patients in a home environment. However, little is known about the effect that such monitoring systems have on patients' compliance, evolution and self-care behaviour. In particular, the effect that the selected user interface has on these factors is unknown. This study aims to investigate this, and to determine some practicalities that must be considered when designing and implementing a telehealth programme for heart failure. To achieve this, daily measurements of blood pressure, pulse, SpO2 and weight were collected from 534 patients suffering from heart failure. In addition, they were asked to fill in the European heart failure self-care behaviour scale questionnaire and the EQ-5D quality of life questionnaire, before and after the monitoring period. Two telehealth systems were used, the Motiva platform provided by Philips and the standalone unit provided by Docobo, the Doc@Home system. Significant differences were found between both systems concerning the compliance and adherence of patients. Moreover, a general, positive effect of telehealth was identified due to the fact that patients showed an increased self-awareness when managing their condition. These findings are supported by behavioural changes and a better understanding of heart failure from the patients' perspective.

Homing endonuclease I-TevIII: dimerization as a means to a double-strand break.

Homing endonucleases are unusual enzymes, capable of recognizing lengthy DNA sequences and cleaving site-specifically within genomes. Many homing endonucleases are encoded within group I introns, and such enzymes promote the mobility reactions of these introns. Phage T4 has three group I introns, within the td, nrdB and nrdD genes. The td and nrdD introns are mobile, whereas the nrdB intron is not. Phage RB3 is a close relative of T4 and has a lengthier nrdB intron. Here, we describe I-TevIII, the H-N-H endonuclease encoded by the RB3 nrdB intron. In contrast to previous reports, we demonstrate that this intron is mobile, and that this mobility is dependent on I-TevIII, which generates 2-nt 3' extensions. The enzyme has a distinct catalytic domain, which contains the H-N-H motif, and DNA-binding domain, which contains two zinc fingers required for interaction with the DNA substrate. Most importantly, I-TevIII, unlike the H-N-H endonucleases described so far, makes a double-strand break on the DNA homing site by acting as a dimer. Through deletion analysis, the dimerization interface was mapped to the DNA-binding domain. The unusual propensity of I-TevIII to dimerize to achieve cleavage of both DNA strands underscores the versatility of the H-N-H enzyme family.

Platelet PECAM-1 inhibits thrombus formation in vivo.

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a cell surface glycoprotein receptor expressed on a range of blood cells, including platelets, and on vascular endothelial cells. PECAM-1 possesses adhesive and signaling properties, the latter being mediated by immunoreceptor tyrosine-based inhibitory motifs present on the cytoplasmic tail of the protein. Recent studies in vitro have demonstrated that PECAM-1 signaling inhibits the aggregation of platelets. In the present study we have used PECAM-1-deficient mice and radiation chimeras to investigate the function of this receptor in the regulation of thrombus formation. Using intravital microscopy and laser-induced injury to cremaster muscle arterioles, we show that thrombi formed in PECAM-1-deficient mice were larger, formed more rapidly than in control mice, and were more stable. Larger thrombi were also formed in control mice that received transplants of PECAM-1-deficient bone marrow, in comparison to mice that received control transplants. A ferric chloride model of thrombosis was used to investigate thrombus formation in carotid arteries. In PECAM-1-deficient mice the time to 75% vessel occlusion was significantly shorter than in control mice. These data provide evidence for the involvement of platelet PECAM-1 in the negative regulation of thrombus formation.

Endothelial cell PECAM-1 confers protection against endotoxic shock.

Platelet endothelial cell adhesion molecule-1 (PECAM-1; CD31) is a 130-kDa member of the Ig superfamily that is expressed on platelets and leukocytes and is highly enriched at endothelial cell-cell junctions. Previous studies showed that this vascular cell adhesion and signaling receptor functions to regulate platelet activation and thrombosis, to suppress apoptotic cell death, to mediate transendothelial migration of leukocytes, and to maintain the integrity of the vasculature. Because systemic exposure to the bacterial endotoxin LPS triggers an acute inflammatory response that involves many of these same processes, we compared the pathophysiological responses of wild-type versus PECAM-1-deficient mice to LPS challenge. We found that PECAM-1-deficient mice were significantly more sensitive to systemic LPS administration than their wild-type counterparts and that the lack of PECAM-1 expression at endothelial cell-cell junctions could account for the majority of the increased LPS-induced mortality observed. The diverse functional roles played by PECAM-1 in thrombosis, inflammation, apoptosis, and the immune response may make this molecule an attractive target for the development of novel therapeutics to manage and treat endotoxic shock.

Anti-GPVI-associated ITP: an acquired platelet disorder caused by autoantibody-mediated clearance of the GPVI/FcRgamma-chain complex from the human platelet surface.

Platelet glycoprotein (GP) VI is a 62-kDa membrane glycoprotein that exists on both human and murine platelets in a noncovalent complex with the Fc receptor (FcR) gamma chain. The GPVI/FcRgamma-chain complex serves as the major activating receptor for collagen, as evidenced by observations that platelets genetically deficient in GPVI or the FcRgamma chain are highly refractory to collagen-induced platelet activation. Recently, several different rat anti-murine GPVI monoclonal antibodies, termed JAQs 1, 2, and 3, were produced that had the unique property of "immunodepleting" GPVI from the murine platelet surface and rendering it unresponsive to collagen or GPVI-specific agonists like convulxin or collagen-related peptide (CRP). Herein, we describe a patient with a mild bleeding disorder and a moderately reduced platelet count whose platelets fail to become activated in response to collagen or CRP and inefficiently adhere to and form thrombi on immobilized collagen under conditions of arterial shear. Although the amount of GPVI platelet mRNA and the nucleotide sequence of the GPVI gene were found to be normal, both GPVI and the FcRgamma chain were nearly absent from the platelet surface and were markedly reduced in wholeplatelet detergent lysates. Patient plasma contained an autoantibody that bound specifically to GPVI-positive, normal platelets, and cleared soluble GPVI from the plasma, suggesting that the patient suffers from a rare form of idiopathic thrombocytopenic purpura caused by a GPVI-specific autoantibody that mediates clearance of the GPVI/FcRgamma-chain complex from the platelet surface. Since antibody-induced GPVI shedding now has been demonstrated in both humans and mice, these studies may provide a rationale for developing therapeutic reagents that induce temporary depletion of GPVI for the treatment of clinical thrombosis.

PECAM-1 negatively regulates GPIb/V/IX signaling in murine platelets.

Platelet adhesion at sites of vascular injury is mediated, in part, by interaction of the platelet plasma membrane glycoprotein (GP) Ib/V/IX complex with von Willebrand Factor (VWF) presented on collagen-exposed surfaces. Recent studies indicate that GPIb/V/IX may be functionally coupled with the Fc receptor gamma (FcR gamma)-chain, which, by virtue of its cytoplasmic immunoreceptor tyrosine-based activation motif, sends activation signals into the cell. Platelet endothelial cell adhesion molecule-1 (PECAM-1) is an inhibitory receptor that has previously been shown to negatively regulate platelet responses to collagen, which transduces activation signals via the GPVI/FcR gamma-chain complex. To determine whether PECAM-1 might similarly regulate signals emanating from GPIb/FcR gamma, we compared activation and aggregation responses to VWF of PECAM-1-positive and PECAM-1-deficient murine platelets. PECAM-1 and the FcR gamma-chain became rapidly tyrosine phosphorylated in platelets following botrocetin-induced VWF binding, but FcR gamma-chain tyrosine phosphorylation was delayed in PECAM-1-positive, versus PECAM-1-deficient, platelets. PECAM-1-deficient platelets were hyperaggregable to VWF, exhibited enhanced spreading and, under conditions of arterial flow, formed markedly larger thrombi on immobilized VWF than did wild-type platelets. Taken together, these data support the notion that engagement of the GPIb complex, in addition to sending activation signals, also initiates a negative feedback loop involving PECAM-1 that controls the rate and extent of platelet activation.