Effects of a novel platelet nitric oxide donor (LA816), aspirin, clopidogrel, and combined therapy in inhibiting flow- and lesion-dependent thrombosis in the porcine ex vivo model

Platelet P2Y12 Receptor Inhibition and Perioperative Patient Management

P2Y12 receptor inhibitor use increases bleeding risk in surgical patients by inhibiting platelet aggregation. Preoperative monitoring, platelet transfusion, and targeted reversal strategies with novel therapies may help to optimize patient management.

Comparative Evaluation of Two Paclitaxel-Coated Stents in an Experimental Setting

INTRODUCTION

Unlike paclitaxel-coated balloons, pre-clinical data comparing different paclitaxel-coated stents (PCSs) are weak. The study objective was to compare the features of the 2 main PCSs: Eluvia® (Boston Scientific, Marlborough, MA) versus ZilverPTX® (Cook Medical, Bloomington, IN).

METHOD

Analysis was carried out on 12 pigs divided into 2 groups: Eluvia® (n=6) and ZilverPTX® (n=6). The pigs received the PCS corresponding to their group in each external iliac artery and were paired one by one, to examine 6 different post-implantation timepoints: after 30 minutes, 6 hours, 24 hours, 3 days, 7 days, and 14 days. The paclitaxel concentration measurements and the histological analysis were carried out under blind testing on the plasma, arterial, lymph node, and muscle samples. A linear regression model and Wilcoxon Mann-Whitney test were used to study the variables.

RESULTS

The plasma paclitaxel rate decrease over 24 hours after PCS implantation was significantly different between the two groups, expressed by the correlation coefficient 0.19 (0.14-0.23; p<0.001) with an undetectable concentration at the 10th hour for Eluvia® versus 3 days for ZilverPTX®. Significantly higher paclitaxel concentrations with ZilverPTX® PCS were observed in muscle samples at each timepoint: extensor digitorum brevis 3.2 (1.17-5.23; p=0.005), biceps femoris 4.27 (2.27-6.26; p<0.001), semi-tendinosus 3.79 (1.85-5.73; p=0.001), tibialis anterior 3.0 (1.37-4.64; p=0.001), and in the femoral nodes 2.27±1.74 ng/g versus 0.14±0.13 ng/g (p<0.001). Histological analysis revealed a trend for more marked intimal inflammation in the arteries stented with ZilverPTX® (p=0.063), especially after the 7th and 14th days.

CONCLUSION

Such a difference in the concentration of paclitaxel in the plasma, muscles, and lymph nodes between the two stents was higher than expected based on differences in device design. The clinical consequences of these results remain to be elucidated, particularly regarding the concerning presence of paclitaxel in muscles and adjacent lymph nodes.

CLINICAL IMPACT

This experimental study compares 2 paclitaxel-coated stents. It demonstrates that differences in stent designs and drug features (coatings and concentrations) translate into differences in terms of concentrations of paclitaxel in the plasma, muscles, and lymph nodes. Our results favor the Eluvia® stent over the ZilverPTX® stent, although more studies are required to confirm this conclusion.

Efficacy and safety of next-generation tick transcriptome-derived direct thrombin inhibitors

Despite their limitations, unfractionated heparin (UFH) and bivalirudin remain standard-of-care parenteral anticoagulants for percutaneous coronary intervention (PCI). We discovered novel direct thrombin inhibitors (DTIs) from tick salivary transcriptomes and optimised their pharmacologic activity. The most potent, ultravariegin, inhibits thrombin with a K_i of 4.0 pM, 445-fold better than bivalirudin. Unexpectedly, despite their greater antithrombotic effect, variegin/ultravariegin demonstrated less bleeding, achieving a 3-to-7-fold wider therapeutic index in rodent thrombosis and bleeding models. When used in combination with aspirin and ticagrelor in a porcine model, variegin/ultravariegin reduced stent thrombosis compared with antiplatelet therapy alone but achieved a 5-to-7-fold lower bleeding time than UFH/bivalirudin. Moreover, two antibodies screened from a naïve human antibody library effectively reversed the anticoagulant activity of ultravariegin, demonstrating proof-of-principle for antidote reversal. Variegin and ultravariegin are promising translational candidates for next-generation DTIs that may reduce peri-PCI bleeding in the presence of antiplatelet therapy.

Ticagrelor With or Without Aspirin After PCI: The TWILIGHT Platelet Substudy

BACKGROUND

An evolving strategy in the setting of percutaneous coronary intervention (PCI) involves withdrawal of acetylsalicylic acid (ASA), or aspirin, while maintaining P2Y₁₂ inhibition. However, the pharmacodynamic effects of this approach on blood thrombogenicity and platelet reactivity remain unknown.

OBJECTIVES

This study sought to compare the antithrombotic potency of ticagrelor alone versus ticagrelor plus ASA among high-risk patients undergoing PCI with drug-eluting stents.

METHODS

This was a mechanistic substudy within the TWILIGHT (Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention) trial, which randomized patients undergoing PCI to ticagrelor plus placebo versus ticagrelor plus ASA following 3 months of dual antiplatelet therapy. Substudy participants were enrolled after randomization, at which time ex vivo assays to quantify thrombus size under dynamic flow conditions and platelet reactivity were performed. Pharmacodynamic assessments were repeated 1 to 6 months thereafter. The primary endpoint was thrombus size at the post-randomization visit with platelet reactivity following stimuli to arachidonic acid, collagen, adenosine diphosphate, and thrombin as secondary endpoints. Results were analyzed using analysis of covariance.

RESULTS

A total of 51 patients were enrolled, among whom 42 underwent perfusion assays at baseline and follow-up with a median time between studies of 1.5 months. The adjusted mean difference in post-randomization thrombus area was similar between groups: -218.2 μm² (95% confidence interval [CI]: -575.9 to 139.9 μm²; p = 0.22). Markers sensitive to cyclo-oxygenase-1 blockade, including platelet reactivity in response to arachidonic acid (mean difference: 10.9 U; 95% CI: 1.9 to 19.9 U) and collagen (mean difference: 9.8 U; 95% CI: 0.8 to 18.8 U) stimuli were higher among patients receiving placebo, whereas levels of platelet reactivity were similar with adenosine diphosphate and thrombin.

CONCLUSIONS

Among high-risk patients receiving drug-eluting stents, the antithrombotic potency of ticagrelor monotherapy is similar to that of ticagrelor plus ASA with respect to ex vivo blood thrombogenicity, whereas markers sensitive to cyclo-oxygenase-1 blockade are increased in the absence of ASA. (Platelet Substudy of the TWILIGHT Trial; NCT04001374).

What is the potential use of platelet-rich-plasma (PRP) in cancer treatment? A mini review

Platelet-rich-plasma (PRP) is an autologous human platelet concentrate extracted from plasma. PRP has been investigated in order to be used in many fields, with emphasis on the musculoskeletal field applied to sports injuries, as well as on other medical fields such as cardiac surgery, gynecology, pediatric surgery, urology, ophthalmology and plastic surgery. Cancer treatment is another important field where PRP should be investigated; thus, it is important validating PRP preparation protocols to be used in clinical research. Many protocols should be revised since, overall, most studies do not provide necessary information to allow them to be multiplied or replicated. The current review focuses on several topics about cancer, mainly on innovative studies about PRP use as a feasible therapeutic alternative to treat bladder cancer - a field where it could play a key role. Relevant aspects such as platelets' contribution to immune regulation and the supportive role they play in innate and adaptive immune functions are also addressed. Another important topic reviewed in the current study refers to inflammatory process regulation associated with cancer and thrombosis sites, which indicated that tumor-induced platelet activation could be used as an important therapeutic target in the future. New aspects concerning nitric oxide's ability to restrain platelet adhesion and aggregation in order to slow metastasis progress in cancer patients provide an important advantage in cancer treatment. Finally, the current review has pointed out perspectives and the main concerns about, and possibilities of, PRP use in cancer treatment.

Guanosine exerts antiplatelet and antithrombotic properties through an adenosine-related cAMP-PKA signaling

BACKGROUND

Guanosine is a natural product and an endogenous nucleoside that has shown to increase during myocardial ischemia. Platelets are critically involved in ischemic coronary events. It remains unknown, however, whether guanosine may affect platelet activation and function. We sought to investigate the potential antiplatelet and antithrombotic properties of guanosine and decipher the mechanisms behind.

METHODS

We firstly assessed the effects of guanosine on platelet activation/aggregation upon stimulation with several platelet agonists including adenosine diphosphate (ADP), collagen, arachidonic acid (AA), and TRAP-6. Guanosine antithrombotic potential was also evaluated both in vitro (Badimon perfusion chamber) and in vivo (murine model). In addition we assessed any potential effect on bleeding. At a mechanistic level we determined the release of thromboxane B2, intraplatelet cAMP levels, the binding affinity on platelet membrane, and the activation/phosphorylation of protein kinase A (PKA), phospholipase C (PLC) and PKC.

RESULTS

Guanosine markedly inhibited platelet activation/aggregation-challenged by ADP and, although to a lesser extent, also reduced platelet aggregation challenged by collagen, AA and TRAP-6. Guanosine significantly reduced thrombus formation both in vitro and in vivo without significantly affects bleeding. Guanosine antiplatelet effects were associated with the activation of the cAMP/PKA signaling pathway, and a reduction in thromboxane B2 levels and PLC and PKC phosphorylation. The platelet aggregation and binding affinity assays revealed that guanosine effects on platelets were mediated by adenosine.

CONCLUSION

Guanosine effectively reduces ADP-induced platelet aggregation and limits thrombotic risk. These antithrombotic properties are associated with the activation of the cAMP/PKA signaling pathway.

Synthesis, antiplatelet and antithrombotic activities of resveratrol derivatives with NO-donor properties

Resveratrol (RVT) is a stilbene with a protective effect on the cardiovascular system; however, drawbacks including low bioavailability and fast metabolism limit its efficacy. In this work we described new resveratrol derivatives with nitric oxide (NO) release properties, ability to inhibit platelet aggregation and in vivo antithrombotic effect. Compounds (4a-f) were able to release NO in vitro, at levels ranging from 24.1% to 27.4%. All compounds (2a-f and 4a-f) have exhibited platelet aggregation inhibition using as agonists ADP, collagen and arachidonic acid. The most active compound (4f) showed reduced bleeding time compared to acetylsalicylic acid (ASA) and protected up to 80% against in vivo thromboembolic events. These findings suggest that hybrid resveratrol-furoxan (4f) is a novel lead compound able to prevent platelet aggregation and thromboembolic events.

A comprehensive study on different modelling approaches to predict platelet deposition rates in a perfusion chamber

Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30 minutes) at shear rates of 212 s⁻¹, 1390 s⁻¹ and 1690 s⁻¹. Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables.

Characterization of platelet aggregation responses in microminipigs: Comparison with miniature pigs and the influence of dual antiplatelet administration of aspirin plus prasugrel

We aimed to characterize platelet aggregation responses and the impact of dual antiplatelet therapy in microminipigs. In this in vitro study, both adenosine-5'-diphosphate (ADP, 5-50μM) and collagen (2-20μg/ml) induced concentration-related platelet aggregation in the microminipigs; 20μM ADP and 5 and 12.5μg/ml collagen were selected for further ex vivo studies. Aspirin plus prasugrel were administered orally for 7days (n=4/each group). Ex vivo platelet aggregation was analyzed on Day 1 (1 and 4h after administration), Day 4 (4h), and Day 7 (4h) under three different prasugrel dosing regimens: LD0/MD1 (1mg/kg/day), LD0/MD3 (3mg/kg/day), and LD10/MD1 (10mg/kg loading dose and 1mg/kg/day maintenance dose). Aspirin (10mg/kg/day) was administered to all groups. In the presence of aspirin, prasugrel at 3 and 10mg/kg significantly inhibited ADP-induced platelet aggregation on Day 1. On Days 4 and 7, significant inhibition of platelet aggregation (IPA) was also observed in each group. With 5μg/ml collagen-induced platelet aggregation, all three groups showed significant IPA at 4h on Day 1 or later. In 12.5μg/ml collagen-induced platelet aggregation, all groups showed significant effects on Days 4 and 7; however, the 30%-35% IPA was considerably lower than that (50%-60%) found with 5μg/ml collagen. In Clawn miniature pigs, similar inhibitory patterns were observed for both ADP- and collagen-induced ex vivo platelet aggregation. In conclusion, these results indicated that microminipigs as well as miniature pigs may represent useful experimental animals for thrombosis research.

The antithrombotic effects of statins

Hypercholesterolemia is considered the primary risk factor for cardiovascular disease. An estimated 200 million prescriptions are issued per year for statins to treat hypercholesterolemia. Importantly, statins have additional beneficial effects independent of their effects on lipids. Recent studies have shown that statins reduce thrombosis via multiple pathways, including inhibiting platelet activation and reducing the pathologic expression of the procoagulant protein tissue factor. Many of the antithrombotic effects of statins are attributed to inhibiting prenylation of RhoA and effects on other intracellular signaling molecules such as NF-κB and KLF2. These antithrombotic activities of statins likely contribute to the ability of statins to reduce the incidence of cardiovascular death.

Changes in thrombus composition and profilin-1 release in acute myocardial infarction

AIM

Thrombus formation is a dynamic process regulated by flow, blood cells, and plasma proteins. The present study was performed to investigate the characteristics of human coronary thrombus in ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Patients admitted with ST-elevation myocardial infarction, in which thrombectomy was performed, were included (n = 86). Intracoronary thrombi and blood from the culprit coronary site and the systemic circulation were obtained during percutaneous coronary intervention (PCI). Thrombi were categorized by onset-of-pain-to-PCI elapsed time in thrombus of <3 (T3) and more than 6 h of evolution (T6). Clinical, morphological, and proteomic variables were investigated. While T3 were mainly composed by platelets and fibrin(ogen), T6 were characterized by a reduced platelet content, increased leucocytes infiltration (including monocytes, neutrophils, T-cells, and B-cells), and appearance of undifferentiated progenitor cells. Significant differences between T3 and T6 were found in the cell cytoskeleton-associated proteome (beta-actin and tropomyosin 3 and 4). By discovery proteomics, we have identified profilin-1 (Pfn-1) in the coronary thrombi and detected higher levels in T3 than in T6. While plasma Pfn-1 levels were low in T3 patients, levels significantly increased in both coronary and peripheral circulation in T6 patients indicating release. In vitro platelet aggregation studies showed that platelets secrete Pfn-1 upon complete activation.

CONCLUSION

Coronary thrombi show rapid dynamic changes both in structure and cell composition as a function of elapsed onset-of-pain-to-PCI time. Aged ischaemic thrombi were more likely to have reduced Pfn-1 content releasing Pfn-1 to the circulation. Onset-of-pain-to-PCI elapsed time in STEMI patients and hence age of occlusive thrombus can be profiled by Pfn-1 levels found in the peripheral circulation.

Monomerization of C-reactive protein requires glycoprotein IIb-IIIa activation: pentraxins and platelet deposition

BACKGROUND

Pentraxins are inflammatory mediators linked to cardiovascular disease; however, their role in thrombosis remains to be fully elucidated.

AIMS

We investigated the role of pentraxins in thrombus formation on different vascular substrates under flow conditions.

METHODS

Native C-reactive protein (nCRP) and serum amyloid P (SAP) effects on thrombosis were evaluated under flow conditions on substrates placed in flat perfusion chambers. nCRP and dissociated monomeric CRP (mCRP) distributions were visualized by use of confocal microscopy. The effects of nCRP on vascular substrates were tested in the Badimon chamber.

RESULTS

mCRP, but not nCRP, induced a significant activation in platelet deposition, whereas SAP induced an activation only on fibrinogen-coated substrates. The effects of CRP on platelet deposition were significantly reduced by statin treatment. mCRP resulting from recirculation of blood containing nCRP over a thrombogenic vessel wall induced increased platelet deposition. Blocking glycoprotein IIb-IIIa prevented the effects of CRP dissociation and significantly reduced platelet deposition. Annexin V treatment did not block monomerization of CRP on activated platelets.

CONCLUSIONS

Under flow conditions, platelet deposited on all tested biological substrates support nCRP dissociation into mCRP. The effect is dependent on the thrombogenic potency of the substrate to trigger initial platelet deposition. Exposure of glycoprotein IIb-IIIa in the platelet surface supports nCRP dissociation. CRP monomerization was not dependent on the aminophospholipid exposed on the surface of activated platelets. The dissociated mCRP is trapped in the growing platelet aggregate and stimulates further platelet deposition. SAP increases platelet deposition only on fibrin monolayers. Therefore, pentraxins induce a platelet activation effect linking inflammation and thrombosis.

Blockade of the purinergic P2Y12 receptor greatly increases the platelet inhibitory actions of nitric oxide

Circulating platelets are constantly exposed to nitric oxide (NO) released from the vascular endothelium. This NO acts to reduce platelet reactivity, and in so doing blunts platelet aggregation and thrombus formation. For successful hemostasis, platelet activation and aggregation must occur at sites of vascular injury despite the constant presence of NO. As platelets aggregate, they release secondary mediators that drive further aggregation. Particularly significant among these secondary mediators is ADP, which, acting through platelet P2Y12 receptors, strongly amplifies aggregation. Platelet P2Y12 receptors are the targets of very widely used antithrombotic drugs such as clopidogrel, prasugrel, and ticagrelor. Here we show that blockade of platelet P2Y12 receptors dramatically enhances the antiplatelet potency of NO, causing a 1,000- to 100,000-fold increase in inhibitory activity against platelet aggregation and release reactions in response to activation of receptors for either thrombin or collagen. This powerful synergism is explained by blockade of a P2Y12 receptor-dependent, NO/cGMP-insensitive phosphatidylinositol 3-kinase pathway of platelet activation. These studies demonstrate that activation of the platelet ADP receptor, P2Y12, severely blunts the inhibitory effects of NO. The powerful antithrombotic effects of P2Y12 receptor blockers may, in part, be mediated by profound potentiation of the effects of endogenous NO.

Extracorporeal assays of thrombosis

Platelet deposition, adhesion/aggregation, to the damaged vessel wall or atherosclerotic plaque components has shown to play a major role in hemostasis, thrombosis, and the development of atherosclerosis. Platelet-vessel wall interaction and thrombus formation is driven by blood flow rheology/hemodynamics (changes in local flow conditions), the nature of the flowing blood, and the characteristics of the triggering substrate (lesion type). An extracorporeal perfusion system (the Badimon chamber) was developed to investigate the dynamics of platelet deposition and thrombus formation on: (a) different surfaces (biological and synthetic); (b) under controlled blood flow conditions with varying degrees of stenosis mimicking various vascular conditions (patent and stenotic arteries); and (c) with varying perfusing blood treatments. In the following chapter, we thoroughly describe this experimental approach that has helped to improve the understanding of the pathophysiology of the acute coronary syndromes (Badimon et al., Arteriosclerosis 6:312-320, 1986; Badimon et al., J Lab Clin Med 110:706-718, 1987; Badimon et al., Blood 73:961-967, 1989; Mailhac et al., Circulation 90:988-996, 1994) and is a useful tool for the study and screening of new antithrombotic and platelet-inhibitory compounds (Badimon et al., Thromb Haemost 71:511-516, 1994; Vilahur et al., Circulation 110:1686-1693; Vilahur et al., Thromb Haemost 92:191-200, 2004; Vilahur et al., Cardiovasc Res 61:806-816; Vilahur et al., Thromb Haemost 98:662-669, 2007; Vilahur et al., Thromb Haemost 97:650-657, 2007; Zafar et al., J Thromb Haemost 5:1195-1200, 2007; Lev et al., J Am Coll Cardiol 43:966-971) and for the evaluation of the thrombogenicity associated to synthetic/prosthetic surfaces (Badimon et al., J Biomater Appl 5:27-48, 1990; Badimon et al., ASAIO Trans 33:621-625, 1987) and/or plasma components (cholesterol, glucose levels, etc.) (Badimon et al., Arterioscler Thromb 11:395-402, 1991; Osende et al., J Am Coll Cardiol 38:1307-1312; 2001).

In the presence of strong P2Y12 receptor blockade, aspirin provides little additional inhibition of platelet aggregation

BACKGROUND

Aspirin and antagonists of platelet ADP P2Y(12) receptors are often coprescribed for protection against thrombotic events. However, blockade of platelet P2Y(12) receptors can inhibit thromboxane A(2) (TXA(2))-dependent pathways of platelet activation independently of aspirin.

OBJECTIVES

To assess in vitro whether aspirin adds additional antiaggregatory effects to strong P2Y(12) receptor blockade.

METHODS

With the use of platelet-rich plasma from healthy volunteers, determinations were made in 96-well plates of platelet aggregation, TXA(2) production and ADP/ATP release caused by ADP, arachidonic acid, collagen, epinephrine, TRAP-6 amide and U46619 (six concentrations of each) in the presence of prasugrel active metabolite (PAM; 0.1-10 μmol L(-1)), aspirin (30 μmol L(-1)), PAM + aspirin or vehicle. results: PAM concentration-dependently inhibited aggregation; for example, aggregation in response to all concentrations of ADP and U46619 was inhibited by ≥ 95% by PAM at > 3 μmol L(-1) . In further tests of PAM (3 μmol L(-1)), aspirin (30 μmol L(-1)) and PAM + aspirin, aspirin generally failed to produce more inhibition than PAM or additional inhibition to that caused by PAM. The antiaggregatory effects of PAM were associated with reductions in the platelet release of both TXA(2) and ATP + ADP. Similar effects were found when either citrate or lepirudin were used as anticoagulants, and when traditional light transmission aggregometry was conducted at low stirring speeds.

CONCLUSIONS

P2Y(12) receptors are critical to the generation of irreversible aggregation through the TXA(2) -dependent pathway. As a result, strong P2Y(12) receptor blockade alone causes inhibition of platelet aggregation that is little enhanced by aspirin. The clinical relevance of these observations remains to be determined.

Atherosclerosis and thrombosis: insights from large animal models

Atherosclerosis and its thrombotic complications are responsible for remarkably high numbers of deaths. The combination of in vitro, ex vivo, and in vivo experimental approaches has largely contributed to a better understanding of the mechanisms underlying the atherothrombotic process. Indeed, different animal models have been implemented in atherosclerosis and thrombosis research in order to provide new insights into the mechanisms that have already been outlined in isolated cells and protein studies. Yet, although no model completely mimics the human pathology, large animal models have demonstrated better suitability for translation to humans. Indeed, direct translation from mice to humans should be taken with caution because of the well-reported species-related differences. This paper provides an overview of the available atherothrombotic-like animal models, with a particular focus on large animal models of thrombosis and atherosclerosis, and examines their applicability for translational research purposes as well as highlights species-related differences with humans.

Protective effect of new nitrosothiols on the early inflammatory response to kidney ischemia/reperfusion and transplantation in rats

Renal ischemia/reperfusion (I/R) is characterized by severe inflammatory damage. We assessed the effect of administrating recently developed nitrosothiol compounds acting as nitric oxide (NO) donors on the production of cytokines and other markers of acute inflammatory reaction in an experimental model of warm (I/R), and in a model of cold ischemia and transplant in rats. Warm ischemia was achieved by ligation of left renal pedicle for 60 min, followed by contralateral nephrectomy. NO-donors LA-803, LA-807, LA-810 were administered i.v. (1.8 micromol/kg) during 30 min before reperfusion. Cold ischemia was achieved by preservating the kidney for 24 h in Euro Collins and grafting it in consanguineous Fisher 344/Ico rats. LA-803 was administered in the preservation fluid and in the recipient rat. Reperfusion time was 4 h in warm ischemia and 3 h in cold ischemia + transplantation. Administration of LA-803, LA-807 and, in a lower proportion, LA-810 prevented from the enhanced production of tumor necrosis factor (TNF), interferon-gamma (IFN-gamma), and interleukin-1beta (IL-1beta), the decrease in interleukin-6 (IL-6) and interleukin-10 (IL-10), the increase in tissue level of superoxide anion (SOA) and superoxide dismutase (SOD), and the increase in neutrophil infiltration induced by warm I/R. Treatment with LA-803 in animals with renal transplantation after cold ischemia was also associated with reduced plasma levels of TNF, IFN-gamma, and IL-1beta, increased plasma levels of IL-6 and IL-10, reduced renal levels of SOA and SOD, and reduced neutrophil infiltration. These data demonstrate that systemic administration of new NO-donors with nitrosothiol structure diminished inflammatory responses in a kidney subjected to warm I/R or cold ischemia and transplantation.

Effects of nitric oxide donor and nitric oxide synthase inhibitor on the resistance, exchange and capacitance functions of the canine intestinal vasculature

In the present study, we determined the vascular functions using a canine model of isolated intestinal segment perfused with constant flow. The effects of an NO donor, S-nitroso-N-acetylpenicillamine (SNAP) and an NO synthase inhibitor, N(omega)-nitro-l-arginine methyl ester (l-NAME) on the vascular factors (resistance, exchange and capacitance) were evaluated. In condition of venous pressure at 0 mmHg, we determined and calculated arterial pressure (Pa) and capillary pressure (Pc). Vascular factors including total, pre- and post-capillary resistance (R(T), Ra and Rv), vascular compliance (VC) and capillary filtration coefficient (K(fc)) were obtained. SNAP at doses 10(-6) to 10(-4) mol/l produced vasodilatory effects. It dose-dependently reduced the Pa, Pc, R(T) and Ra, as well as the Ra/Rv ratio. The Rv was slightly decreased. This agent increased the vascular capacity, VC and K(fc). NO inhibition with l-NAME (10(-6) to 10(-4) mol/l) produced the opposite effects. The vasoconstrictory effects of l-NAME increased Pa, Pc, R(T) and Ra as well as the Ra/Rv ratio. It slightly raised the Rv. l-NAME reduced the vascular capacity, VC and K(fc). The effects of l-NAME were also dose-dependent. This study has provided a detailed data of the vasodilatory and vasoconstrictory effects NO donation and inhibition on vascular factors in the intestinal vasculature.

Antithrombotic effect of a new nitric oxide donor (LA419) on experimental thrombogenesis

BACKGROUND

The ability of nitrous compounds to donate nitric oxide (NO), an agent with vasodilating and inhibitory effects on platelet function, has been considered a useful pharmacologic strategy for cardiovascular complications. The purpose of this study was to investigate the effects of a new NO donor, LA419, on platelet interaction in an ex vivo model with human blood circulating through collagen-rich surfaces.

MATERIALS AND METHODS

Platelet adhesive and cohesive function were analyzed by morphometric procedures after perfusion techniques. Treated blood was exposed to thrombogenic surfaces and platelet interactions were morphometrically evaluated.

RESULTS

All the concentrations studied of LA419 (10 microM, 20 microM and 100 microM) reduced overall platelet interaction with a collagen surface (27.19 +/- 4.72; 25.52 +/- 3.52; and 23.44 +/- 3.01, P < 0.05, respectively, vs. 32.31 +/- 1.61% in the control). The antithrombotic effect was confirmed by results in cross-sectional studies performed in arterial vessels exposed to circulating blood. Values of thrombus and covered surface at 20 microM LA419 were, respectively, 13.67 +/- 4.97% and 19.01 +/- 5.89%; respect to controls 34.80 +/- 5.29% and 37.93 +/- 5.34% (P < 0.05). Moreover, LA419 reduced significantly thrombus area (88.45 +/- 21.97 microm(2); P < 0.05) with respect to controls (168.45 +/- 21.97 microm(2)) and thrombus height, from an average of 10.27 +/- 1.05 microm in nontreated blood to 7.16 +/- 0.6 microm in treated samples (P < 0.05).

CONCLUSION

From the present data we can conclude that LA419 possesses a strong antiplatelet action, as demonstrated by its ability to significantly inhibit the interaction of platelet with highly thrombogenic collagen surfaces.