L-arginine polymers inhibit the development of vein graft neointimal hyperplasia

Graft preservation confers myocardial protection during coronary artery bypass grafting

Background

During on-pump coronary artery bypass grafting (ONCAB), graft flushing for distal anastomoses testing also perfuses the downstream myocardium. This single-center retrospective study evaluated the impact of specific preservation solutions on myocardial protection during ONCAB.

Materials and methods

Between July 2019 and March 2020 either DuraGraft (DG) or 0.9% Saline/Biseko (SB) was applied to 272 ONCAB. Overall, 166 patients were propensity-matched into two groups. Cardiac enzymes [high-sensitive Troponin I (hs-TnI) and creatine kinase (CK)] were evaluated 7 days post-surgery.

Results

Post-surgery, hs-TnI values were significantly lower from 3 to 6 h (h) up to 4 days in the DG group: 3–6 h: 4,034 ng/L [IQR 1,853–8,654] vs. 5,532 ng/L [IQR 3,633—8,862], p = 0.05; 12–24 h: 2,420 ng/L [IQR 1,408–5,782] vs. 4,166 [IQR 2,052–8,624], p < 0.01; 2 days: 1,095 ng/L [IQR 479–2,311] vs. 1,564 ng/L [IQR 659–5,057], p = 0.02 and at 4 days: 488 ng/L [IQR 232–1,061] vs. 745 ng/L [IQR 319–1,820], p = 0.03. The maximum value: 4,151 ng/L [IQR 2,056–8,621] vs. 6,349 ng/L [IQR 4,061–12,664], p < 0.01 and the median area under the curve (AUC): 6,146 ng/L/24 h [IQR 3,121–13,248] vs. 10,735 ng/L/24 h [IQR 4,859–21,484], p = 0.02 were lower in the DG group. CK values were not significantly different between groups: maximum value 690 [IQR 417–947] vs. 631 [464–979], p = 0.61 and AUC 1,986 [1,226–2,899] vs. 2,081 [1,311–3,063], p = 0.37.

Conclusion

Repeated graft flushing with DG resulted in lower Troponin values post-surgery suggesting enhanced myocardial protection compared to SB. Additional studies are warranted to further assess the myocardial protection properties of DG.

Electrospun orally disintegrating film formulation of telmisartan

Telmisartan (TEL) is an antihypertensive BCS class II drug with low solubility at physiological pH. However, the solubility of TEL increases with the presence of an alkalizer. Electrospinning is one of the most recent techniques for the solubility enhancement studies. In this study, an electrospun orally disintegrating film (ODF) formulation of TEL was developed with L-arginine and polyvinylpyrrolidone K90 (PVP), and its characterization studies were performed. Preformulation studies were performed to investigate possible incompatibilities in the components of formulation with differential scanning calorimetry (DSC) and Fourier transform infrared spectrometer (FT-IR) analyses. ODFs were characterized in terms of drug content and uniformity, mechanical properties, fiber shape and diameter and in vitro dissolution profile. Smooth nanofibers without any beads were obtained. The dissolution rate of the TEL significantly increased. The chosen formulation had acceptable mechanical properties with much faster dissolution compared to the commercially available product. Developed ODF and marketed product were compared with a dissolution study in phosphate-buffered solution (pH 7.4). ODF and marketed product both reached 100% release in the 45th minute, and ODF results showed that ODF had much faster release than marketed product. In this study, TEL ODF formulation was successfully produced and characterized.

The effect of storage solutions on endothelial function and saphenous vein graft patency

Vein graft failure is a complex mechanism that can be triggered immediately after surgical harvesting. Storage solutions have a major role in preventing endothelial cell damage during harvesting. While normal saline is still widely used, buffered solutions seem to better preserve endothelial integrity and function. This review aims to summarize the current literature surrounding vein graft storage solutions.

Role of metabolic environment on nitric oxide mediated inhibition of neointimal hyperplasia in type 1 and type 2 diabetes

Nitric oxide (NO) is well known to inhibit neointimal hyperplasia following arterial injury. Previously, we reported that NO was more effective at inhibiting neointimal hyperplasia in a type 2 diabetic environment than control. We also found that NO was ineffective in an uncontrolled type 1 diabetic environment; however, insulin restored the efficacy of NO. Thus, the goal of this study was to more closely evaluate the effect of insulin and glucose on the efficacy of NO at inhibiting neointimal hyperplasia in both type 1 and type 2 diabetic environments using different doses of insulin as well as pioglitazone. Type 1 diabetes was induced in male lean Zucker (LZ) rats with streptozotocin (60 mg/kg IP). Groups included control, moderate glucose control, and tight glucose control. Zucker diabetic fatty (ZDF) rats fed Purina 5008 chow were used as a type 2 diabetic model. Groups included no therapy, insulin therapy, or pioglitazone therapy. After 4 weeks of maintaining group assignments, the carotid artery injury model was performed. Treatment groups included: control, injury and injury plus NO. 2 weeks following arterial injury, in the type 1 diabetic rats, NO most effectively reduced the neointimal area in the moderate and tightly controlled groups (81% and 88% vs. 33%, respectively, p=0.01). In type 2 diabetic rats, the metabolic environment had no impact on the efficacy of NO (81-82% reduction for all groups). Thus, in this study, we show NO is effective at inhibiting neointimal hyperplasia in both type 1 and type 2 diabetic environments. A greater understanding of how the metabolic environment may impact the efficacy of NO may lead to the development of more effective NO-based therapies for patients with diabetes.

Vascular grafts

Autogenous vein is the conduit of choice in the surgical creation of bypasses of small-to-medium-caliber vessels in patients with peripheral occlusive arterial disease and will remain so for the near future. The success rate of bypasses using conduits of diameters greater than 6 mm has been excellent, whereas the majority of bypasses using smaller conduits fail within 5 years. In addition, due to a steep increase in rates of diabetes and decreasing cardiovascular mortality rates, increasing challenges are presented by this population. These facts have motivated much of the research in the cardiovascular arena over the past four decades, with improved techniques and new materials. Strategies to improve outcomes include the use of alternative materials including autologous, nonautologous and prosthetic grafts, utilizing different methods for their harvesting and preservation; tissue engineering, using either polymer- or biological-based scaffolds for cell seeding; endovascular methodologies; and gene therapy. This report presents an overview of the several options currently available in the management of patients with peripheral arterial occlusive disease, as well as the ongoing research directed towards the creation of an artificial engineered vessel, discussing experimental work in which endothelial cells have been seeded on different scaffolds and finally the potential application of gene therapy in the field of vascular reconstruction.

Nitric oxide and nitrite-based therapeutic opportunities in intimal hyperplasia

Vascular intimal hyperplasia (IH) limits the long term efficacy of current surgical and percutaneous therapies for atherosclerotic disease. There are extensive changes in gene expression and cell signaling in response to vascular therapies, including changes in nitric oxide (NO) signaling. NO is well recognized for its vasoregulatory properties and has been investigated as a therapeutic treatment for its vasoprotective abilities. The circulating molecules nitrite (NO(2)(-)) and nitrate (NO(3)(-)), once thought to be stable products of NO metabolism, are now recognized as important circulating reservoirs of NO and represent a complementary source of NO in contrast to the classic L-arginine-NO-synthase pathway. Here we review the background of IH, its relationship with the NO and nitrite/nitrate pathways, and current and future therapeutic opportunities for these molecules.

The role of estrogen receptor α and β in regulating vascular smooth muscle cell proliferation is based on sex

BACKGROUND

We previously demonstrated that vascular smooth muscle cells (VSMC) proliferation and development of neointimal hyperplasia as well as the ability of nitric oxide (NO) to inhibit these processes is dependent on sex and hormone status. The aim of this study was to evaluate the role of estrogen receptor (ER) in mediating proliferation in male and female VSMC.

MATERIALS AND METHODS

Proliferation was assessed in primary rat aortic male and female VSMC using (3)H-thymidine incorporation in the presence or absence of ER alpha (α) inhibitor methyl-piperidino-pyrazole, the ER beta (β) inhibitor (R,R)-5,11-Diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol, the combined ERαβ inhibitor ICI 182,780, and/or the NO donor DETA/NO. Proliferation was also assessed in primary aortic mouse VSMC harvested from wildtype (WT), ERα knockout (ERα KO), and ERβ knockout (ERβ KO) mice in the presence or absence of DETA/NO and the ERα, ERβ, and ERαβ inhibitors. Protein levels were assessed using Western blot analysis.

RESULTS

Protein expression of ERα and ERβ was present and equal in male and female VSMC, and did not change after exposure to NO. Inhibition of either ERα or ERβ had no effect on VSMC proliferation in the presence or absence of NO in either sex. However, inhibition of ERαβ in rat VSMC mitigated NO-mediated inhibition in female but not male VSMC (P < 0.05). Evaluation of proliferation in the knockout mice revealed distinct patterns. Male ERαKO and ERβKO VSMC proliferated faster than male WT VSMC (P < 0.05). Female ERβKO proliferated faster than female WT VSMC (P < 0.05), but female ERαKO VSMC proliferated slower than female WT VSMC (P < 0.05). Last, we evaluated the effect of combined inhibition of ERα and ERβ in these knockout strains. Combined ERαβ inhibition abrogated NO-mediated inhibition of VSMC proliferation in female WT and knockout VSMC (P < 0.05), but not in male VSMC.

CONCLUSIONS

These data clearly demonstrate a role for the ER in mediating VSMC proliferation in both sexes. However, these data suggest that the antiproliferative effects of NO may be regulated by the ER in females but not males.

Insulin enhances the effect of nitric oxide at inhibiting neointimal hyperplasia in a rat model of type 1 diabetes

Diabetes confers greater restenosis from neointimal hyperplasia following vascular interventions. While localized administration of nitric oxide (NO) is known to inhibit neointimal hyperplasia, the effect of NO in type 1 diabetes is unknown. Thus the aim of this study was to determine the efficacy of NO following arterial injury, with and without exogenous insulin administration. Vascular smooth muscle cells (VSMC) from lean Zucker (LZ) rats were exposed to the NO donor, DETA/NO, following treatment with different glucose and/or insulin concentrations. DETA/NO inhibited VSMC proliferation in a concentration-dependent manner to a greater extent in VSMC exposed to normal-glucose vs. high-glucose environments, and even more effectively in normal-glucose/high-insulin and high-glucose/high-insulin environments. G(0)/G(1) cell cycle arrest and cell death were not responsible for the enhanced efficacy of NO in these environments. Next, type 1 diabetes was induced in LZ rats with streptozotocin. The rat carotid artery injury model was performed. Type 1 diabetic rats experienced no significant reduction in neointimal hyperplasia following arterial injury and treatment with the NO donor PROLI/NO. However, daily administration of insulin to type 1 diabetic rats restored the efficacy of NO at inhibiting neointimal hyperplasia (60% reduction, P < 0.05). In conclusion, these data demonstrate that NO is ineffective at inhibiting neointimal hyperplasia in an uncontrolled rat model of type 1 diabetes; however, insulin administration restores the efficacy of NO at inhibiting neointimal hyperplasia. Thus insulin may play a role in regulating the downstream beneficial effects of NO in the vasculature.

Identification and characterization of a novel cell-penetrating peptide

Cell-penetrating peptides (CPPs) are short amino acid sequences that promote their own translocation across cell plasma membrane. When linked with cargo such as polypeptides, nucleic acid, or liposomes, CPPs can facilitate the transport of these entities across the cell membrane. Therefore, CPPs are receiving increased interest in drug delivery and gene therapy. The majority of CPPs identified so far are polycationic peptides which interact with heparin sulfate chains of plasma membrane for internalization. Here, we report the identification and characterization of a conformationally constrained 13 amino acid peptide (CVQWSLLRGYQPC, designated as S41) which is clearly distinct from classical polycationic peptides. Immunofluorescence assay was employed to test the cellular uptake of S41 in mouse neuroblastoma cell line Neuro2A (N2A) and rat cerebellar granule neurons (CGNs). Internalization of S41 was further examined in N2A cells by means of mutational analysis, flow cytometry and confocal microscopy. Our results demonstrate that S41 can enter cells through lipid rafts dependent endocytosis.

Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions

Nitric oxide (NO(.)) is a reactive nitrogen radical produced by the NO synthase (NOS) enzymes; it affects a plethora of downstream physiological and pathological processes. The past two decades have seen an explosion in the understanding of the role of NO(.) biology, highlighting various protective and damaging modes of action. Much of the controversy surrounding the role of NO(.) relates to the differing concentrations generated by the three isoforms of NOS. Both calcium-dependent isoforms of the enzyme (endothelial and neuronal NOS) generate low-nanomolar/picomolar concentrations of NO(.). By contrast, the calcium-independent isoform (inducible NOS (iNOS)) generates high concentrations of NO(.), 2-3 orders of magnitude greater. This review summarizes the current literature in relation to iNOS gene therapy for the therapeutic benefit of various pathological conditions, including various states of vascular disease, wound healing, erectile dysfunction, renal dysfunction and oncology. The available data provide convincing evidence that manipulation of endogenous NO(.) using iNOS gene therapy can provide the basis for future clinical trials.

The cell-penetrating peptide octa-arginine is a potent inhibitor of proteasome activities

Oligo-arginines are cell-penetrating peptides and find use as carriers for transportation of various membrane-impermeable biopharmaceuticals into target cells. We have found that oligo-arginines of a length of 4-10 amino acids, but especially (Arg)(8), are able to inhibit the major intracellular proteolytic system, the proteasome, with mixed-type inhibition characteristics. The IC(50) values of (Arg)(8) for the proteasomal chymotrypsin-like and caspase-like activities are approximately 100 and 200 nM, respectively. The inhibition of the trypsin-like activity never exceeds 50% even at micromolar concentrations. (Arg)(8) also inhibits 20S proteasome/PA28 complexes as well as 26S proteasomes, although with a decreased efficiency. Due to its cell membrane-penetrating capability, incubation of HeLa cells in the presence of (Arg)(8) resulted in an impaired activity of proteasomes going along with an accumulation of high-molecular mass ubiquitin-conjugated proteins, the preferred substrates of 26S proteasomes. The in vivo susceptibility of the three proteasome activities resembles that found in vitro with chymotrypsin-like>caspase-like>trypsin-like activities. Since inhibition of the proteasome system might affect fundamental basic cellular processes but on the other side might also prevent the degradation of a proteinacous cargo, we suggest that this proteasome inhibitory activity should be taken into account when oligo-arginines are being considered for use as vectors for the intracellular delivery of pharmaceuticals.

Biofunctionalization of biomaterials for accelerated in situ endothelialization: a review

The higher patency rates of cardiovascular implants, including vascular bypass grafts, stents, and heart valves are related to their ability to inhibit thrombosis, intimal hyperplasia, and calcification. In native tissue, the endothelium plays a major role in inhibiting these processes. Various bioengineering research strategies thereby aspire to induce endothelialization of graft surfaces either prior to implantation or by accelerating in situ graft endothelialization. This article reviews potential bioresponsive molecular components that can be incorporated into (and/or released from) biomaterial surfaces to obtain accelerated in situ endothelialization of vascular grafts. These molecules could promote in situ endothelialization by the mobilization of endothelial progenitor cells (EPC) from the bone marrow, encouraging cell-specific adhesion (endothelial cells (EC) and/or EPC) to the graft and, once attached, by controlling the proliferation and differentiation of these cells. EC and EPC interactions with the extracellular matrix continue to be a principal source of inspiration for material biofunctionalization, and therefore, the latest developments in understanding these interactions will be discussed.

Nitric oxide: what a vascular surgeon needs to know

Atherosclerosis in the form of peripheral arterial disease results in significant morbidity and mortality. Surgical treatment options for peripheral arterial disease include angioplasty with and without stenting, endarterectomy, and bypass grafting. Unfortunately, all of these procedures injure the vascular endothelium, which impairs its ability to produce nitric oxide (NO) and ultimately leads to neointimal hyperplasia and restenosis. To improve on current patency rates after vascular procedures, investigators are engaged in research to improve the bioavailability of NO at the site of vascular injury in an attempt to reduce the risk of thrombosis and restenosis after successful revascularization. This article reviews some of the previous research that has aimed to improve NO bioavailability after vascular procedures whether through systemic or local delivery, as well as to describe some of the NO-releasing products that are currently undergoing study for use in clinical practice.

Nitric oxide and nanotechnology: a novel approach to inhibit neointimal hyperplasia

OBJECTIVE

Nitric oxide (NO) has been shown to inhibit neointimal hyperplasia after arterial interventions in several animal models. To date, however, NO-based therapies have not been used in the clinical arena. Our objective was to combine nanofiber delivery vehicles with NO chemistry to create a novel, more potent NO-releasing therapy that can be used clinically. Thus, the aim of this study was to evaluate the perivascular application of spontaneously self-assembling NO-releasing nanofiber gels. Our hypothesis was that this application would prevent neointimal hyperplasia.

METHODS

Gels consisted of a peptide amphiphile, heparin, and a diazeniumdiolate NO donor (1-[N-(3-Aminopropyl)-N-(3-ammoniopropyl)]diazen-1-ium-1,2-diolate [DPTA/NO] or disodium 1-[(2-Carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate [PROLI/NO]). Nitric oxide release from the gels was evaluated by the Griess reaction, and scanning electron microscopy confirmed nanofiber formation. Vascular smooth muscle cell (VSMC) proliferation and cell death were assessed in vitro by (3)H-thymidine incorporation and Personal Cell Analysis (PCA) system (Guava Technologies, Hayward, Calif). For the in vivo work, gels were modified by reducing the free-water content. Neointimal hyperplasia after periadventitial gel application was evaluated using the rat carotid artery injury model at 14 days (n = 6 per group). Inflammation and proliferation were examined in vivo with immunofluorescent staining against CD45, ED1, and Ki67 at 3 days (n = 2 per group), and graded by blinded observers. Endothelialization was assessed by Evans blue injection at 7 days (n = 3 per group).

RESULTS

Both DPTA/NO and PROLI/NO, combined with the peptide amphiphile and heparin, formed nanofiber gels and released NO for 4 days. In vitro, DPTA/NO inhibited VSMC proliferation and induced cell death to a greater extent than PROLI/NO. However, the DPTA/NO nanofiber gel only reduced neointimal hyperplasia by 45% (intima/media [I/M] area ratio, 0.45 +/- 0.07), whereas the PROLI/NO nanofiber gel reduced neointimal hyperplasia by 77% (I/M area ratio, 0.19 +/- 0.03, P < .05) vs control (injury alone I/M area ratio, 0.83 +/- 0.07; P < .05). Both DPTA/NO and PROLI/NO nanofiber gels significantly inhibited proliferation in vivo (1.06 +/- 0.30 and 0.19 +/- 0.11 vs injury alone, 2.02 +/- 0.20, P < .05), yet had minimal effect on apoptosis. Only the PROLI/NO nanofiber gel inhibited inflammation (monocytes and leukocytes). Both NO-releasing nanofiber gels stimulated re-endothelialization.

CONCLUSIONS

Perivascular application of NO-releasing self-assembling nanofiber gels is an effective and simple therapy to prevent neointimal hyperplasia after arterial injury. Our study demonstrates that the PROLI/NO nanofiber gel most effectively prevented neointimal hyperplasia and resulted in less inflammation than the DPTA/NO nanofiber gel. This therapy has great clinical potential to prevent neointimal hyperplasia after open vascular interventions in patients.

Beneficial effect of a short-acting NO donor for the prevention of neointimal hyperplasia

Nitric oxide (NO)-based therapies effectively inhibit neointimal hyperplasia in animal models of arterial injury and bypass grafting, but are not available clinically. We created a simple, effective, locally applied NO-eluting therapy to prevent restenosis after vascular procedures. We investigated the efficacy of perivascular delivery of two distinctly different diazeniumdiolate NO donors, 1-[2-(carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate (PROLI/NO) (short half-life) and diazeniumdiolated poly(acrylonitrile) (PAN/NO) (long half-life), in powder or gel form (30% poloxamer 407), at inhibiting neointimal hyperplasia using the rat carotid artery injury model. Two weeks postinjury, all of the NO-eluting therapies successfully reduced neointimal hyperplasia. However, most dramatically, PROLI/NO powder reduced intimal area by 91.2% (p<0.05) versus injury alone. PROLI/NO powder was noted to reduce the medial area (40.2% vs injury alone, p<0.05), whereas other groups showed no such effect. Three days postinjury, each NO treatment group significantly reduced cellular proliferation. However, inflammatory markers revealed a distinct pattern: PAN/NO groups displayed increased leukocyte infiltration (p<0.05), whereas PROLI/NO groups displayed less macrophage infiltration (p<0.05). In conclusion, perivascular delivery of diazeniumdiolate NO donors in powder or gel form effectively inhibits neointimal hyperplasia. Application of short-acting PROLI/NO powder most effectively inhibited neointimal hyperplasia and inflammation and may represent a simple, clinically applicable NO-eluting therapy to prevent neointimal hyperplasia and restenosis after open vascular interventions.

The role of nitric oxide in the pathophysiology of intimal hyperplasia

Since its discovery, nitric oxide (NO) has emerged as a biologically important molecule and was even named Molecule of the Year by Science magazine in 1992. Specific to our interests, NO has been implicated in the regulation of vascular pathology. This review begins with a summary of the molecular biology of NO, from its discovery to the mechanisms of endogenous production. Next, we turn our attention to describing the arterial injury response of neointimal hyperplasia, and we review the role of NO in the pathophysiology of neointimal hyperplasia. Finally, we review the literature regarding NO-based therapies. This includes the development of inhalational-based NO therapies, systemically administered L-arginine and NO donors, NO synthase gene therapy, locally applied NO donors, and NO-releasing prosthetic materials. By reviewing the current literature, we emphasize the tremendous clinical potential that NO-based therapies can have on the development of neointimal hyperplasia.

Effect of vein graft harvesting on endothelial nitric oxide synthase and nitric oxide production

BACKGROUND

Although the saphenous vein is the most commonly used conduit for coronary artery bypass surgery occlusion rates are high, with more than 50% grafts failing within 10 years. Nitric oxide, a potent vasodilator, also inhibits platelet aggregation, thrombus formation and vascular smooth muscle cell proliferation, is implicated in various vascular pathologies, including graft failure.

METHODS

Saphenous veins were obtained from patients undergoing bypass surgery harvested by conventional methods and with minimal handling, using a "no-touch" technique. Tissue distribution and protein expression of endothelial nitric oxide synthase was compared using immunohistochemistry and Western blot analysis. Nitric oxide generation was assessed using the citrulline assay.

RESULTS

There was injury to conventional compared with no-touch vein segments, in particular to the lumenal endothelium and tunica adventitia. This injury was accompanied by an absence of endothelial nitric oxide synthase immunostaining at regions of endothelial denudation and damaged adventitial layer of conventional veins and a significant reduction (p < 0.05) in endothelial nitric oxide synthase protein expression. Furthermore, nitric oxide release from conventional tissue extracts was significantly (p < 0.05) lower than no-touch vein segments.

CONCLUSIONS

Our results show that there is a reduction in endothelial nitric oxide synthase and nitric oxide release in saphenous veins harvested by conventional surgical methods compared with those prepared atraumatically. These observations may influence graft performance.

Modulating role of estradiol on arginase II expression in hyperlipidemic rabbits as an atheroprotective mechanism

We evaluated the effects of a 0.5% cholesterol-enriched diet (HCD) on nitric-oxide synthase (NOS) and arginase expression and the modulating role of 17beta-estradiol (E(2)) on this phenomenon. Thirty oopherectomized rabbits were divided into three groups and treated for 15 weeks. Group I received normal chow; group II, HCD; and group III, HCD plus E(2) pellets. Animals in group II showed an increase in plasma lipids, and they demonstrated atheromatous lesions as well as expression of arginase I and II accompanied by a significant number of BrdU-positive cells in endothelial cells and intimal muscle cells, suggestive of an increase in cellular proliferation. There was significant expression of inducible NOS and increased staining of nitrotyrosine-positive areas. These were not observed in group I animals. In both groups, E(2) levels were low. In group III animals, E(2) supplementation led to a decrease in atheromatous lesions and BrdU-positive cells and reduced expression of both inducible NOS and arginase I and II accompanied by a decrease in nitrotyrosine staining. E(2) levels were increased. Our results suggest that E(2) was responsible for these effects, despite the animals being hyperlipidemic, similar to those in group II. Because arginase is responsible for cell proliferation by converting l-arginine to polyamines, our results indicate that expression of arginase may play an important role in cellular proliferation in atherosclerosis, and inhibition of arginase expression by E(2) may be another potential mechanism in attenuating atherogenesis.

Pharmacologic inhibition of vein graft neointimal hyperplasia

Although arterial conduits are widely used and have improved the long-term results of coronary artery bypass grafting, vein grafts remain important additional conduits in coronary surgery. Newer studies show a saphenous vein graft patency of 60% or more at 10 years postoperatively. The pathology of vein graft disease consists of thrombosis, neointimal hyperplasia, and vein graft atherosclerosis, which limit graft longevity. Therapeutic strategies to prevent vein graft disease include external stenting, pharmacotherapy, and gene therapy. The potential benefits of a pharmacologic approach are as follows: (1) Drugs with a broad clinical experience can be used; (2) side effects of systemic application can be minimized by local therapy; and (3) no vascular injury, such as pressurizing the vein for a viral transfection approach, is necessary. The different sites for pharmacotherapy in vein graft disease are reviewed in this article.

Medium-sized peptides as built in carriers for biologically active compounds

A growing number of oligopeptides of natural and/or synthetic origin have been described and considered as targeting structures for delivery bioactive compounds into various cell types. This review will outline the discovery of peptide sequences and the corresponding mid-sized oligopeptides with membrane translocating properties and also summarize de novo designed structures possessing similar features. Conjugates and chimera constructs derived from these sequences with covalently attached bioactive peptide, epitope, oligonucleotide, PNA, drug, reporter molecule will be reviewed. A brief note will refer to the present understanding on the uptake mechanism at the end of each section.

iNOS Gene Transfer for Graft Disease

Vascular bypass surgery involves the use of a vascular conduit to circumvent a site of vascular compromise. Vascular graft failure continues to plague both the patients receiving and the surgeons performing these interventions. Demand for the development of a therapy to reduce intimal hyperplasia--the most common cause of bypass graft failure--is significant and has been the goal of many biotechnology groups. The development of gene therapy as a feasible clinical intervention has allowed for novel methods of inhibiting intimal hyperplasia to be conceived. This review describes the evolution of gene transfer of the inducible nitric oxide synthase (iNOS) gene, one of the most successful preclinical interventions to date for vascular disease.

Arginine containing peptides as delivery vectors

Recently several membrane translocalizational signals (MTS) have been identified and applied to various applications. These peptide signals, ranging between nine and 30 amino acid residues in length, have the capability of crossing plasma membrane, in addition to delivering other biological molecules into cells. To date, small molecules, peptides, proteins, oligonucleotides, plasmids and even nanometer-sized particles have been delivered. These MTS sequences vary from hydrophobic to purely hydrophilic, and, surprisingly, all of them are able to penetrate cellular membrane in an energy-independent pathway. Potentially, MTS could be used as delivery vectors for a number of therapeutic agents. In this review, we specifically focus on arginine-containing MTS, and their properties, characteristics, in vitro and in vivo applications are discussed in detail.

Effects of the cationic protein poly-L-arginine on airway epithelial cells in vitro

BACKGROUND

Allergic asthma is associated with an increased number of eosinophils in the airway wall. Eosinophils secrete cationic proteins, particularly major basic protein (MBP).

AIM

To investigate the effect of synthetic cationic polypeptides such as poly-L-arginine, which can mimic the effect of MBP, on airway epithelial cells.

METHODS

Cultured airway epithelial cells were exposed to poly-L-arginine, and effects were determined by light and electron microscopy.

RESULTS

Poly-L-arginine induced apoptosis and necrosis. Transmission electron microscopy showed mitochondrial damage and changes in the nucleus. The tight junctions were damaged, as evidenced by penetration of lanthanum. Scanning electron microscopy showed a damaged cell membrane with many pores. Microanalysis showed a significant decrease in the cellular content of magnesium, phosphorus, sodium, potassium and chlorine, and an increase in calcium. Plakoglobin immunoreactivity in the cell membrane was decreased, indicating a decrease in the number of desmosomes

CONCLUSIONS

The results point to poly-L-arginine induced membrane damage, resulting in increased permeability, loss of cell-cell contacts and generalized cell damage.