A novel free radical scavenger, nicaraven, inhibits human platelet aggregation in vitro

The Effect of Antioxidant Added to Preservation Solution on the Protection of Kidneys before Transplantation

Ischemia–reperfusion injury is a key clinical problem of transplantology. Current achievements in optimizing organ rinse solutions and storage techniques have significantly influenced the degree of graft damage and its survival after transplantation. In recent years, intensive research has been carried out to maintain the viability of tissues and organs outside the integral environment of the body. Innovative solutions for improving the biochemical functions of the stored organ have been developed. The article discusses directions for modifying preservation solutions with antioxidants. Clinical and experimental studies aimed at optimizing these fluids, as well as perfusion and organ preservation techniques, are presented.

Nicaraven inhibits TNFα-induced endothelial activation and inflammation through suppression of NF-κB signaling pathway

Inflammation-induced activation and dysfunction of endothelial cells play an important role in the pathology of multiple vascular diseases. Nicaraven, a potent hydroxyl radical scavenger, has recently been found to have anti-inflammatory roles; however, the mechanism of its action is not fully understood. Here we investigated the effects of Nicaraven on tumor necrosis factor α (TNFα) - induced inflammatory response in human umbilical vein endothelial cells and we explore the underlying mechanisms related to the nuclear factor-κB (NF-κB) signaling pathway. Our results showed that Nicaraven significantly reduced the reactive oxygen species production after TNFα stimulation. Nicaraven suppressed TNFα-induced mRNA expression of multiple adhesion molecules and pro-inflammatory cytokines, including vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), E-selectin, MCP-1, TNFα, interleukin-1β (IL-1β), IL-6, and IL-8. In addition, Nicaraven inhibited monocyte adhesion and reduced the protein levels of VCAM-1 and ICAM-1. Mechanistically, Nicaraven prevented TNFα-induced activation of NF-κB signaling pathway by suppressing the phosphorylation of NF-κB p65, IκBα, and IκB kinase (IKK)α/β, stabilizing IκBα, and inhibiting the translocation of p65 from cytosol to nucleus. Finally, we showed that Nicaraven improved the functions of endothelial cells, seen as the upregulation of endothelial nitric oxide synthase and increased nitric oxide levels. Our findings indicated that Nicaraven effectively inhibits TNFα-induced endothelial activation and inflammatory response at least partly through inhibiting NF-κB signaling pathway.

Antiplatelet and antithrombotic effect of Phyllostachys pubescens leaves and Mume Fructus combination

Background

Agents currently used for the treatment and prevention of thrombosis have a number of side effects. We conducted this study to develop antithrombotic agents from herbs that are used in food.

Methods

The 80% (v/v) ethanol extracts of Phyllostachys pubescens leaf (PL) and Mume Fructus (MF) and their combinations—2:1 (PM21), 1:1 (PM11), and 1:2 (PM12)—were evaluated on rat platelet aggregation induced by adenosine diphosphate (ADP) in vitro and on arteriovenous shunt thrombosis after 3 days of oral treatment in rats in vivo.

Results

At 100 μg/mL, PM21 and PM11 inhibited in vitro ADP-induced aggregation by 44.0 ± 4.3% and 30.0 ± 3.2%, respectively, whereas PL, MF, and PM12 weakly or scarcely inhibited ADP-induced aggregation by 3.9 ± 3.2%, 13.0 ± 2.7%, and 5.2 ± 1.3%, respectively. The IC₅₀ values of PM21 on ADP-, collagen-, and thrombin-induced platelet aggregations were 135.6 ± 7.4 μg/mL, 142.7 ± 5.8 μg/mL, and 186.5 ± 9.7 μg/mL, respectively. In an in vivo rat arteriovenous-shunt thrombosis model, thrombus weight was significantly decreased after the oral administration of 400 mg/kg PL (27.8 ± 3.0%, p < 0.01) or MF (35.2 ± 2.1%, p < 0.01), and with a good accord to the in vitro results, the combination of PL and MF in the ratio of 2:1, PM21 (60.9 ± 1.2%, p < 0.001), showed a superior antithrombotic effect to those of individual extracts. At dosages of 200 mg/kg, 100 mg/kg, and 50 mg/kg, PM21 dose-dependently decreased thrombosis weight (ED₅₀, 314 mg/kg).

Conclusion

These results suggest that combination preparations of PL and MF, especially their 2:1 combination, can increase antiplatelet and antithromboticeffects more than PL and MF alone, offering evidence for a potential novel combination antithrombotic therapy.

Role of reactive nitrogen species in blood platelet functions

Blood platelets, in analogy to other circulating blood cells, can generate reactive oxygen/nitrogen species (ROS/RNS) that may behave as second messengers and may regulate platelet functions. Accumulating evidence suggest a role of ROS/RNS in platelet activation. On the other hand, an increased production of ROS/RNS causes oxidative stress, and thus, may contribute to the development of different diseases, including vascular complications, inflammatory and psychiatric illnesses. Oxidative stress in platelets leads to chemical changes in a wide range of their components, and platelet proteins may be initial targets of ROS/RNS action. It has been demonstrated that reaction of proteins with ROS/RNS results in the oxidation and nitration of some amino acid residues, formation of aggregates or fragmentation of proteins. In oxidized proteins new carbonyl groups and protein hydroperoxides are also formed. In platelets, low molecular weight thiols such as glutathione (GSH), cysteine and cysteinylglycine and protein thiols may be also target for ROS/RNS action. This review describes the chemical structure and biological activities of reactive nitrogen species, mainly nitric oxide ((*)NO) and peroxynitrite (ONOO(-)) and their effects on blood platelet functions, and the mechanisms involved in their action on platelets.

Effect of Armagnac fractions on human platelet aggregation in vitro and on rat arteriovenous shunt thrombosis in vivo probably not related only to polyphenols

Previous studies showed that alcohol-free extracts of Armagnac, an oak cask aged spirit rich in polyphenols, inhibit human platelet function in vitro and in vivo, in an experimental rat arteriovenous shunt thrombosis model and in human healthy volunteers. To identify active compounds, we fractionated a freeze-dried extract of a 10-year-old Armagnac using successively chloroform, diethyl ether and ethyl acetate. The 4 resulting fractions were tested on in vitro human platelet aggregation induced by ADP and in vivo on arteriovenous shunt thrombosis after 10 days oral treatment in rats. Active components were found mainly in fractions 1 and 3: at the highest concentration (2.4 10(-2) g/l), in vitro ADP-induced aggregation was inhibited by 62.7+/-2.1% and 51.2+/-3.8% for F1 and F3, respectively, vs 18.9+/-2.4% and 13.9+/-0.4% for fractions 2 and 4 and 33.6+/-1.5% for the crude extract. There was a significant decrease in thrombus weight with the crude extract and all fractions tested after 10 days treatment with 2.5 mg/kg/day orally, greatest with fraction 1. Characterisation of phenol content showed that fraction 1, the most biologically active, was essentially devoid of ellagic acid and ellagitannins, the polyphenols initially thought responsible for the effect, whereas fraction 2 which was mostly inactive, was the richest in polyphenols.

CONCLUSION

The antiplatelet and antithrombotic activity of Armagnac seems mostly unrelated to polyphenols.

Aqueous extracts of Ocimum basilicum L. (sweet basil) decrease platelet aggregation induced by ADP and thrombin in vitro and rats arterio--venous shunt thrombosis in vivo

OBJECTIVE

To study the effects of aqueous extract of Ocimum basilicum L (OBL) on platelet aggregation and experimental thrombus.

METHODS

Platelet aggregation induced by ADP (5 muM) and thrombin (4 UI), and thrombus weight in an arteriovenous thrombosis (AVT) model were tested after 2 weeks treatment with 15, 75 and 375 mg/kg OBL orally in rats, compared to 8.8 mg/kg/day aspirin. AVT was also tested 2 h after 75 mg/kg OBL orally, after 3 and 7 days treatment, and one, three and seven days after the end of a two-week treatment. Analysis was done by ANOVA followed by protected t-tests (Tukey).

RESULTS

OBL (15, 75, 375 mg/Kg) dose-dependently inhibits platelet aggregation by ADP and thrombin, with 75 mg/kg/day having approximately the same effect as 8.8 mg/kg/day aspirin. ADP induced aggregation reached 45%, 28% and 18% for OBL, respectively, 15, 75, 375 mg/kg compared to 71% for control and 27% for aspirin (all p<0.01 except aspirin vs. OBL 75 mg/kg/day p=0.7). Thrombin-induced aggregation reached 33%, 22%, 21% for OBL, respectively, 15, 75, 375 mg/kg compared to 67% for control and 48% for aspirin (all p<0.01 except OBL 75 vs. OBL 375 mg/kg/day, p=1.0). Compared to a control thrombus weight of 48.1 mg (SD 4.9), thrombus weight was 29.4 (3.3), 19.0 (1.9) and 12.3 (1.7) after treatment for 2 weeks with 15, 75 and 375 mg/kg OBL, respectively, and 27.4 (5.3) after 8.8 mg/kg aspirin (all p<0.001 except aspirin vs. OBL 75 mg/kg/day p=1.0). Maximum effect of OBL was reached after one week's treatment. The effect subsided between 3 and 7 days.

CONCLUSION

OBL possesses an inhibitory effect on platelet aggregation induced by ADP and thrombin, that is dose-dependent and results in an anti-thrombotic effect in vivo which develops progressively over 7 days and disappears over 3-7 days. The active ingredient now needs to be characterized.

Effects of armagnac extracts on human platelet function in vitro and on rat arteriovenous shunt thrombosis in vivo

INTRODUCTION

The "French paradox", a low cardiovascular mortality compared to the prevalent risk factors, has been attributed to the regular use of red wine, and to the polyphenols it contains. These have among other effects an antioxidant and antithrombotic effect. The French paradox is maximal in southwest France, a region which is the region of production of armagnac, an oak cask aged spirit also rich in polyphenols.

METHOD

We tested the effects of a freeze-dried extract of 12-year-old armagnac (EA88) on in vitro human platelet adhesion, and on aggregation induced by collagen or ADP, in the presence or absence of hypoxanthine-xanthine oxidase (HX/XO), at concentrations ranging from 5 x 10(-9) to 5 x 10(-3) g/l, after 15-60 min incubation. We also tested the effects of 2-week oral treatment with 1, 5 and 25 mg/kg EA88 in a rat arteriovenous shunt thrombosis model.

RESULTS

EA88 inhibited ADP-induced but not collagen-induced human platelet aggregation in vitro in a concentration- and incubation time-dependent manner, which was greater in the presence of HX/XO. In vivo, giving rats a daily oral dose of EA88 for 2 weeks inhibited thrombus formation in a dose-dependent manner, for doses consistent with the habitual human use of armagnac.

CONCLUSION

Armagnac extract EA88 had an antiplatelet and antithrombotic effect that if confirmed in man could contribute to explain the intensity of the French paradox in southwest France.

A novel hydroxyl radical scavenger, nicaraven, protects the liver from warm ischemia and reperfusion injury

BACKGROUND

Reactive oxygen species have been considered to be involved in liver injury at the procurement, preservation, and transplantation from donors without beating hearts. A novel hydroxyl radical scavenger, nicaraven with hydrophilic and lipophilic properties, infiltrates both intracellular and extracellular spaces where it effectively scavenges reactive oxygen species. Protection by nicaraven against ischemia and reperfusion damage of the brain, heart, and kidneys has been shown. The effect of this agent on the liver remains unclear.

METHODS

Two-hour total hepatic vascular exclusion was used. Eighteen beagle dogs were randomly assigned to 2 groups: 12 animals were not treated (group I) and 6 were treated with nicaraven (group II). Nicaraven was administered intravenously (2mg/kg/min) for 60 minutes before ischemia and for 3 hours, starting 30 minutes before reperfusion.

RESULTS

Two-week survival rates were 25% in group I and 100% in group II (P <.01). Nicaraven inhibited lipid peroxidation in the liver, improved hepatic and systemic hemodynamics and energy metabolism, and suppressed liver enzyme release, endothelin-1 elevation in hepatic venous blood, histologic damage, and neutrophil infiltration into the liver.

CONCLUSIONS

Nicaraven exerted hepatic protection against warm ischemia and reperfusion injury. This may indicate nicaraven as a potential candidate to attenuate liver injury from warm ischemia and preservation in transplantation from donors without beating hearts.

Nicaraven for the treatment of cerebral vasospasm in subarachnoid haemorrhage

Cerebral vasospasm is a complication of subarachnoid haemorrhage and can cause cerebral ischaemia. Antivasospastic agents are used to relieve vasospasm after subarachnoid haemorrhage. A large number of agents with varying modes of action currently being investigated are reviewed. Pharmacology and clinical trials of nicaraven are discussed. The drug has been found to have both antivasospastic as well as neuroprotective effects. Clinically, the most documented efficacy of nicaraven is in the management of vasospasm associated with subarachnoid haemorrhage based on its free radical scavenging effect. Other potential areas for application are cerebral oedema associated with intracerebral haemorrhage and for neuroprotection in cerebral infarction. Nicaraven is in pre-registration by Chugai Pharma Ltd. in Japan for the treatment of vasospasm following subarachnoid haemorrhage. The regulatory atmosphere in Japan regarding the approval of neuroprotectives is reviewed and nicaraven is likely to be approved by the year 2001 when the patent on it expires.