The development of a novel endovascular grasper for challenging inferior vena cava filter retrieval.

OBJECTIVE: Although inferior vena cava (IVC) filters are commonly retrieved using a snare, lateral tilt and fibrosis around struts can complicate the procedure and sometimes require the use of off-label devices. We describe the development of a novel articulating endovascular grasper designed to remove permanent and retrievable IVC filters in any configuration. METHODS: For in vitro testing, the IVC filters were anchored to the inner wall of a flexible tube in a centered or tilted configuration. A high-contrast backlit camera view simulated the two-dimensional fluoroscopy projection during retrieval. The time from the retrieval device introduction into the camera field to complete filter retrieval was measured in seconds. The control experiment involved temporary IVC filter retrieval with a snare. There were four comparative groups: (1) retrievable filter in centered configuration; (2) retrievable filter in tilted configuration; (3) permanent filter in centered configuration; and (4) permanent filter in tilted configuration. Every experiment was repeated five times, with median retrieval time compared with the control group. For in vivo testing in a porcine model, six tilted infrarenal IVC filters were retrieved with grasper via right jugular approach. Comparison analysis between animal and patient procedures was performed for the following variables: total procedure time, the retrieval time, and fluoroscopy time. RESULTS: The in vitro experiments showed comparable retrieval times between the experimental groups 1, 2, and 4 and the control. However, grasper removal of a centered permanent filter (group 3) required significantly less time than in the control (29 vs 79 seconds; P = .009). In the animal model, all IVC filters were retrieved using the grasper with no adverse events. The total procedure time (21.2 vs 43.5 minutes; P = .01) and the fluoroscopy time (4.3 vs 10 minutes; P = .044) were significantly shorter in the animal model compared with the patient group. Moreover, in the patient group, 16.7% of retrievals required advanced endovascular techniques, and one IVC filter could not be retrieved (success rate = 91.7%), whereas all the IVC filters were successfully retrieved in the animal model without the use of additional tools. CONCLUSIONS: The novel endovascular grasper is effective in retrieving different types of IVC filters in different configurations and compared favorably with the snare in the in vitro model. In vivo experiments demonstrated more effective retrieval when compared with matched patient retrievals.

A modified bonded model approach for molecular dynamics simulations of New Delhi Metallo-ß-lactamase.

Modelling metalloproteins using the classical force fields is challenging. Several methods have been devised to model metalloproteins in force fields. Of these methods, the bonded model, combined with Restrained Electrostatic Potential (RESP) charge fitting, proved its superiority. The latter method was facilitated by the development of the python-based Metal Centre Parameter Builder (MCPB.py) AmberTool. However, the standard bonded model method offered by the MCPB.py tool may not be appropriate for validating and refining the binding modes predicted by docking when crystal structures are lacking. That is because the representation of coordination interactions between any bound ligand and metal ions by covalent bonds can hinder the flexibility of the ligand. Therefore, a new modification to the standard bonded model approach is proposed here. Molecular dynamics (MD) simulations based on the new modified bonded model (MBM) approach avoid the bias caused by coordination bonds and, unlike hybrid QM/MM MD, allow for sufficient sampling of the binding mode given the currently available computational power. The MBM MD approach reproduced the studied crystal structure conformations of New Delhi Metallo-ß-lactamase 1 (NDM-1). Furthermore, the MBM approach described the binding interactions of intact ß-lactams with NDM-1 reasonably, and predicted a non-productive binding mode for the poor NDM-1 substrate aztreonam whilst predicting productive binding modes for known good substrates. This study presents a useful MD method for metallo-ß-lactamases and provides better understanding of ß-lactam substrates recognition by NDM-1. The proposed MBM approach might also be useful in the investigation of other metal-containing protein targets.

Design, stability and efficacy of a new targeting peptide for nanoparticulate drug delivery to SH-SY5Y neuroblastoma cells.

In recent years, rabies virus-derived peptide (RDP) has shown promise as a specific neural cell targeting ligand, however stability of the peptide in human serum was unknown. Herein, we report the molecular modelling and design of an optimised peptide sequence based on interactions of RDP with the α7 subunit of the nicotinic acetylcholine receptor (nAChR). The new sequence, named DAS, designed around a 5-mer sequence which demonstrated optimal nAChR binding in silico, showed greatly improved stability for up to 8 hours in human serum in comparison to RDP, which degraded within 2 hours at 37 °C. In vitro analysis using SH-SY5Y neuroblastoma cells showed that DAS-conjugated nanoparticles containing the cytotoxic drug doxorubicin (DAS-Dox-NP) displayed significantly enhanced cytotoxicity compared with untargeted doxorubicin-loaded nanoparticles (Dox-NP). DAS-Dox-NP had no significant effect on non-neural cell types, confirming its neural-specific targeting properties. In this manuscript, we report the design and testing of an optimised peptide ligand, conjugated to a nanoparticulate delivery vehicle and specifically targeted to neural cells. Future impact of an innovative targeting peptide ligand combining the ability to selectively identify the target and facilitate cellular internalisation could enable the successful treatment of many neural cell disorders.

Development of Potent and Selective Tissue Transglutaminase Inhibitors: Their Effect on TG2 Function and Application in Pathological Conditions.

Potent-selective peptidomimetic inhibitors of tissue transglutaminase (TG2) were developed through a combination of protein-ligand docking and molecular dynamic techniques. Derivatives of these inhibitors were made with the aim of specific TG2 targeting to the intra- and extracellular space. A cell-permeable fluorescently labeled derivative enabled detection of in situ cellular TG2 activity in human umbilical cord endothelial cells and TG2-transduced NIH3T3 cells, which could be enhanced by treatment of cells with ionomycin. Reaction of TG2 with this fluorescent inhibitor in NIH3T3 cells resulted in loss of binding of TG2 to cell surface syndecan-4 and inhibition of translocation of the enzyme into the extracellular matrix, with a parallel reduction in fibronectin deposition. In human umbilical cord endothelial cells, this same fluorescent inhibitor also demonstrated a reduction in fibronectin deposition, cell motility, and cord formation in Matrigel. Use of the same inhibitor in a mouse model of hypertensive nephrosclerosis showed over a 40% reduction in collagen deposition.

Structure-activity relationships of the N-terminus of calcitonin gene-related peptide: key roles of alanine-5 and threonine-6 in receptor activation.

BACKGROUND AND PURPOSE: The N-terminus of calcitonin gene-related peptide (CGRP) is important for receptor activation, especially the disulphide-bonded ring (residues 1-7). However, the roles of individual amino acids within this region have not been examined and so the molecular determinants of agonism are unknown. This study has examined the role of residues 1, 3-6 and 8-9, excluding Cys-2 and Cys-7. EXPERIMENTAL APPROACH: CGRP derivatives were substituted with either cysteine or alanine; further residues were introduced at position 6. Their affinity was measured by radioligand binding and their efficacy by measuring cAMP production in SK-N-MC cells and ß-arrestin 2 translocation in CHO-K1 cells at the CGRP receptor. KEY RESULTS: Substitution of Ala-5 by cysteine reduced affinity 270-fold and reduced efficacy for production of cAMP in SK-N-MCs. Potency at ß-arrestin translocation was reduced by ninefold. Substitution of Thr-6 by cysteine destroyed all measurable efficacy of both cAMP and ß-arrestin responses; substitution with either alanine or serine impaired potency. Substitutions at positions 1, 4, 8 and 9 resulted in approximately 10-fold reductions in potency at both responses. Similar observations were made at a second CGRP-activated receptor, the AMY(1(a)) receptor. CONCLUSIONS AND IMPLICATIONS: Ala-5 and Thr-6 are key determinants of agonist activity for CGRP. Ala-5 is also very important for receptor binding. Residues outside of the 1-7 ring also contribute to agonist activity.

Imidazolium-based warheads strongly influence activity of water-soluble peptidic transglutaminase inhibitors.

New peptidic water-soluble inhibitors are reported. In addition to the carboxylate moiety, a new polar warhead was explored. Depending on the size of its substituents, the newly appended imidazolium scaffold designed to enhance the hydrophilic character of the inhibitors could induce a good inhibition for tissue transglutaminase (TG2) and blood coagulation factor XIIIa (FXIIIa). Correlated with the narrow tunnel that hosts the target catalytic cysteine residue, the various modulations suggest a bent conformation of the ligands as the binding pattern mode. Analogues in the dialkylsulfonium series were also tested and showed specificity for TG2 over FXIIIa.

Structure-activity relationships for α-calcitonin gene-related peptide.

UNLABELLED: Calcitonin gene-related peptide (CGRP) is a member of the calcitonin (CT) family of peptides. It is a widely distributed neuropeptide implicated in conditions such as neurogenic inflammation. With other members of the CT family, it shares an N-terminal disulphide-bonded ring which is essential for biological activity, an area of potential α-helix, and a C-terminal amide. CGRP binds to the calcitonin receptor-like receptor (CLR) in complex with receptor activity-modifying protein 1 (RAMP1), a member of the family B (or secretin-like) GPCRs. It can also activate other CLR or calcitonin-receptor/RAMP complexes. This 37 amino acid peptide comprises the N-terminal ring that is required for receptor activation (residues 1-7); an α-helix (residues 8-18), a region incorporating a ß-bend (residues 19-26) and the C-terminal portion (residues 27-37), that is characterized by bends between residues 28-30 and 33-34. A few residues have been identified that seem to make major contributions to receptor binding and activation, with a larger number contributing either to minor interactions (which collectively may be significant), or to maintaining the conformation of the bound peptide. It is not clear if CGRP follows the pattern of other family B GPCRs in binding largely as an α-helix. LINKED ARTICLES: This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.

Indwelling catheters and medical implants with FXIIIa inhibitors: A novel approach to the treatment of catheter and medical device-related infections.

Central venous catheters (CVCs) are being utilized with increasing frequency in intensive care and general medical wards. In spite of the extensive experience gained in their application, CVCs are related to the long-term risks of catheter sheath formation, infection, and thrombosis (of the catheter or vessel itself) during catheterization. Such CVC-related-complications are associated with increased morbidity, mortality, duration of hospitalization, and medical care cost [1]. The present study incorporates a novel group of Factor XIIIa (FXIIIa, plasma transglutaminase) inhibitors into a lubricious silicone elastomer in order to generate an optimized drug delivery system whereby a secondary sustained drug release profile occurs following an initial burst release for catheters and other medical devices. We propose that the incorporation of FXIIIa inhibitors into catheters, stents, and other medical implant devices would reduce the incidence of catheter sheath formation, thrombotic occlusion, and associated staphylococcal infection. This technique could be used as a local delivery system for extended release with an immediate onset of action for other poorly aqueous soluble compounds.

Functional characterization of two human receptor activity-modifying protein 3 variants.

Adrenomedullin (AM) and amylin are involved in angiogenesis/lymphangiogenesis and glucose homeostasis/food intake, respectively. They activate receptor activity-modifying protein (RAMP)/G protein-coupled receptor (GPCR) complexes. RAMP3 with the calcitonin receptor-like receptor (CLR) forms the AM(2) receptor, whereas when paired with the calcitonin receptor AMY(3) receptors are formed. RAMP3 interacts with other GPCRs although the consequences of these interactions are poorly understood. Therefore, variations in the RAMP3 sequence, such as single nucleotide polymorphisms or mutations could be relevant to human health. Variants of RAMP3 have been identified. In particular, analysis of AK222469 (Homo sapiens mRNA for receptor (calcitonin) activity-modifying protein 3 precursor variant) revealed several nucleotide differences, three of which encoded amino acid changes (Cys40Trp, Phe100Ser, Leu147Pro). Trp56Arg RAMP3 is a polymorphic variant of human RAMP3 at a conserved amino acid position. To determine their function we used wild-type (WT) human RAMP3 as a template for introducing amino acid mutations. Mutant or WT RAMP3 function was determined in Cos-7 cells with CLR or the calcitonin receptor (CT((a))). Cys40Trp/Phe100Ser/Leu147Pro RAMP3 was functionally compromised, with reduced AM and amylin potency at the respective AM(2) and AMY(3(a)) receptor complexes. Cys40Trp and Phe100Ser mutations contributed to this phenotype, unlike Leu147Pro. Reduced cell-surface expression of mutant receptor complexes probably explains the functional data. In contrast, Trp56Arg RAMP3 was WT in phenotype. This study provides insight into the role of these residues in RAMP3. The existence of AK222469 in the human population has implications for the function of RAMP3/GPCR complexes, particularly AM and amylin receptors.

Structure-function analysis of RAMP1-RAMP3 chimeras.

The role of receptor activity modifying protein 1 (RAMP1) in forming receptors with the calcitonin receptor-like receptor (CLR) and the calcitonin receptor (CTR) was examined by producing chimeras between RAMP1 and RAMP3. RAMPs have three extracellular helices. Exchange of helix 1 of the RAMPs or residues 62-69 in helix 2 greatly reduced CLR trafficking (a marker for CLR association). Modeling suggests that these exchanges alter the CLR recognition site on RAMP1, which is more exposed than on RAMP3. Exchange of residues 86-89 of RAMP1 had no effect on the trafficking of CLR but reduced the potency of human (h) alphaCGRP and adrenomedullin. However, these alterations to RAMP1 had no effect on the potency of hbetaCGRP. These residues of RAMP1 lie at the junction of helix 3 and its connecting loop with helix 2. Modeling suggests that the loop is more exposed in RAMP1 than RAMP3; it may play an important role in peptide binding, either directly or indirectly. Exchange of residues 90-94 of RAMP1 caused a modest reduction in CLR expression and a 15-fold decrease in CGRP potency. It is unlikely that the decrease in expression is enough to explain the reduction in potency, and so these may have dual roles in recognizing CLR and CGRP. For CTR, only 6 out of 26 chimeras covering the extracellular part of RAMP1 did not reduce agonist potency. Thus the association of CTR with RAMP1 seems more sensitive to changes in RAMP1 structure induced by the chimeras than is CLR.