Vascular remodeling and the local delivery of cytochalasin B after coronary angioplasty in humans

Cytoskeleton-disrupting agent cytochalasin B reduces oxidative stress caused by high glucose in the human arterial smooth muscle

The role of cytoskeleton dynamics in the oxidative stress toward human vasculature has been unclear. The current study examined whether the cytoskeleton-disrupting agent cytochalasin B reduces oxidative stress caused by high glucose in the human arterial smooth muscle. All experiments in the human omental arteries without endothelium or the cultured human coronary artery smooth muscle cells were performed in d-glucose (5.5 mmol/L). The exposure toward d-glucose (20 mmol/L) for 60 min reduced the relaxation or hyperpolarization to an ATP sensitive K⁺ channel (KATP) opener levcromakalim (10^-8 to 3 × 10^-6 mol/L and 3 × 10^-6 mol/L, respectively). Cytochalasin B and a superoxide inhibitor Tiron, restored them similarly. Cytochalasin B reduced the NADPH oxidase activity, leading to a decrease in superoxide levels of the arteries treated with high d-glucose. Also, cytochalasin B impaired the F-actin constitution and the membrane translocation of an NADPH oxidase subunit p47phox in artery smooth muscle cells treated with high d-glucose. A clinical concentration of cytochalasin B prevented human vascular smooth muscle malfunction via the oxidative stress caused by high glucose. Regulation of the cytoskeleton may be essential to keep the normal vascular function in patients with hyperglycemia.

Patent foramen ovale and left atrial appendage: new devices and methods for closure

Transcatheter closure of atrial septal defects (ASDs) has become a routine procedure in many countries of the world. It spares many patients cardiac surgery and has proven efficacy in long-term studies. Device improvements have resulted in a continuous reduction of complications and of residual shunt frequency. ASD closure devices are also used for transcatheter closure of patent foramen ovale (PFO) for prevention of paradoxical embolism. In the past few years, there has been increasing interest in developing devices specifically designed for PFO closure. Although transcatheter closure of ASDs is well established, interventional closure of the left atrial appendage is in its development stage. Closure of the left atrial appendage is designed to reduce the risk of stroke in patients with atrial fibrillation in whom anticoagulation with Warfarin-type drugs is contraindicated. This article describes the latest developments in catheter closure of PFO and the left atrial appendage.

New strategies to prevent restenosis

The Holy Grail of cardiovascular pharmacology has been the search for an effective therapy targeting restenosis after angioplasty and/or intra-arterial stenting. The failure of promising therapeutics in clinical trials underscores the complexity and redundancy of the signaling cascades regulating mitogenesis and fibrogenesis. Novel therapeutic modalities have potential to target dysfunctional signaling elements directly in vascular smooth muscle cells. Significant progress in the treatment against restenosis will require the exploitation and cross-fertilization of developments in the fields of pharmacology, bioengineering, genetics, and molecular biology. Collaboration among researchers in these fields will be essential.

Biodegradable nanoparticles for drug and gene delivery to cells and tissue

Biodegradable nanoparticles formulated from poly (D,L-lactide-co-glycolide) (PLGA) have been extensively investigated for sustained and targeted/localized delivery of different agents including plasmid DNA, proteins and peptides and low molecular weight compounds. Research about the mechanism of intracellular uptake of nanoparticles, their trafficking and sorting into different intracellular compartments, and the mechanism of enhanced therapeutic efficacy of nanoparticle-encapsulated agent at cellular level is more recent and is the primary focus of the review. Recent studies in our laboratory demonstrated rapid escape of PLGA nanoparticles from the endo-lysosomal compartment into cytosol following their uptake. Based on the above mechanism, various potential applications of nanoparticles for delivery of therapeutic agents to the cells and tissue are discussed.

Transforming growth factor-beta: a promising target for anti-stenosis therapy

Transforming growth factor-beta (TGF-beta) is the general name for a family of cytokines which have widespread effects on many aspects of growth and development. The TGF-beta isoforms are produced by most cell types and exert a wide range of effects in a context-dependent autocrine, paracrine or endocrine fashion via interactions with distinct receptors on the cell surface. TGF-beta is involved in the wound healing process and, thus plays a significant role in the formation of a restenotic lesion after percutaneous transluminal coronary angioplasty (PTCA) or stenting. Perhaps because of its wide-ranging effects, TGF-beta is usually released from cells in a latent form, and its activation and signaling are complex. Manipulation of the TGF-beta1, TGF-beta2, and TGF-beta3 isoforms by inhibiting their expression, activation, or signaling reduces scarring and fibrosis in animal models. However, to date, few have reached clinical trial. This review summarizes current knowledge on the activation and signaling of TGF-beta, and focuses on the anti-TGF-beta strategies which may lead to clinical applications in the prevention of restenosis following PTCA or stenting.

Effects of local cytochalasin D delivery on smooth muscle cell migration and on collar-induced intimal hyperplasia in the rabbit carotid artery

1. Smooth muscle cell (SMC) migration has been implicated in neointima formation after angioplasty. Therefore, we investigated whether cytochalasin D, a fungal metabolite that inhibits actin filament formation, suppressed SMC migration and collar-induced intimal hyperplasia in the rabbit carotid artery. 2. To establish effective concentrations, contractions of carotid artery rings to phenylephrine were determined after incubation with cytochalasin D (10(-8) - 10(-6) M) for 30 min or 3 days. In vitro cell migration was studied using carotid artery explants and a modified Boyden chamber with SMCs isolated from the rabbit aorta. The in vivo effect was tested after infusion of 10(-8) - 10(-4) M cytochalasin D into collars placed around the left carotid artery; collars placed around the right artery served as controls. 3. Contractions to phenylephrine decreased after 30 min or 3 days exposure to 10(-7) and 10(-6) M cytochalasin D; the effect was partly reversible. These concentrations also inhibited cellular outgrowth and SMC migration in the in vitro assays. 4. Immunohistochemistry showed that local delivery of 10(-5) or 10(-4) M cytochalasin D for 2 weeks suppressed collar-induced alpha-SMC actin expression in the intima by 68% and 84% respectively. However, the cross-sectional area of the intima was not reduced due to an influx of T-lymphocytes and macrophages. 5. It is concluded that cytochalasin D suppressed SMC contractility and migration in vitro. Although perivascular infusion of cytochalasin D inhibited collar-induced SMC migration from media to intima in vivo as well, the intimal hyperplasia was not reduced due to concomitant development of an inflammatory response.

Formulation and delivery mode affect disposition and activity of tyrphostin-loaded nanoparticles in the rat carotid model

Poor drug residence in the arterial wall hinders clinical implementation of local drug delivery strategies for the treatment of restenosis. A rat carotid model of vascular injury and intraluminal delivery of tyrphostin-containing polylactic acid (PLA) nanoparticles (NPs) were used to determine the relationship between residence properties and biological activity of different formulations and administration modes. The effects of delivery modes (denudation and delivery time) and formulation variables (adsorbed vs encapsulated drug, and NP size) on arterial drug/NP retention were examined. Antirestenotic effects of large (160 nm) and small (90 nm) tyrphostin-containing NPs, surface-absorbed tyrphostin, and systemic treatment were compared. Fluorescent NPs were used to study the spatial distribution of the carrier in the arterial wall. The decrease in arterial tyrphostin level over time fitted a biexponential model. Delivery time and pressure, endothelium integrity, particle size, and drug-polymer association affected local pharmacokinetics and the antirestenotic results after 14 days. The PLA-based tyrphostin NP formulation ensured a prolonged drug residence at the angioplasty site after single intraluminal application. Several readily adjustable formulation and procedural factors considerably modified arterial ingress of the drug-loaded NPs and governed their subsequent redistribution, tissue binding, elimination, and ensuing antirestenotic effect.

Current approaches to therapy for vascular injury

Vascular injury is a ubiquitous phenomenon which can be both occult (such as with hyperlipidemia) and overt (such as with angioplasty). While the exact pathophysiology differs between acute and chronic atherosclerosis, both lesions can be mechanistically explained by the vasculature's exaggerated response to injury. Pharmacological attempts to treat atherosclerotic cardiovascular disease can be categorised by their role in modifying this inflammatory response. This manuscript reviews current therapy for cardiovascular injury at two levels: the chronic smouldering atheromatous lesion and intimal hyperplasia associated with acute vascular intervention. In addition, future therapeutic strategies, based within this inflammatory paradigm, are discussed.