Effects of pluronic F-68 (poloxamer 188) on platelet aggregation in human whole blood

Vepoloxamer Enhances Fibrinolysis of tPA (Tissue-Type Plasminogen Activator) on Acute Ischemic Stroke

Background and Purpose- Thrombolytic treatment of acute ischemic stroke with tPA (tissue-type plasminogen activator) is hampered by its narrow therapeutic window and potential hemorrhagic complication. Vepoloxamer is a nonionic surfactant that exerts potent hemorheologic and antithrombotic properties in various thrombotic diseases. The current study investigated the effect of vepoloxamer on tPA treatment in a rat model of embolic stroke. Methods- Male Wistar rats subjected to embolic middle cerebral artery occlusion were treated with the combination of vepoloxamer and tPA, vepoloxamer alone, tPA alone, or saline initiated 4 hours after middle cerebral artery occlusion. Results- Monotherapy with tPA did not reduce infarct volume, and adversely potentiated microvascular thrombosis and vascular leakage compared with the saline treatment. Vepoloxamer monotherapy reduced infarct volume by 25% and improved brain perfusion. However, the combination treatment with vepoloxamer and tPA significantly reduced infarct volume by 32% and improved neurological function, without increasing the incidence of gross hemorrhage. Compared with vepoloxamer alone, the combination treatment with vepoloxamer and tPA robustly reduced secondary thrombosis and tPA-augmented microvascular leakage and further improved brain perfusion, which was associated with substantial reductions of serum active PAI-1 (plasminogen activator inhibitor-1) level and tPA-upregulated PAI-1 in the ischemic brain. Mechanistically, exosomes derived from platelets of ischemic rats treated with tPA-augmented cerebral endothelial barrier permeability and elevated protein levels of PAI-1 and TF (tissue factor) in the endothelial cells, whereas exosomes derived from platelets of rats subjected to the combination treatment with vepoloxamer and tPA diminished endothelial permeability augmented by tPA and fibrin and reduced PAI-1 and TF levels in the endothelial cells. Conclusions- The combination treatment with vepoloxamer and tPA exerts potent thrombolytic effects in rats subjected to acute ischemic stroke. Vepoloxamer reduces tPA-aggravated prothrombotic effect of platelet-derived exosomes on cerebral endothelial cells, which may contribute to the therapeutic effect of the combination treatment.

Nanoencapsulation Enhances Anticoagulant Activity of Adenosine and Dipeptide IleTrp

It is well-known that drugs administered into an organism intravenously or through the gastrointestinal tract are degraded by enzymes of the body, reducing their therapeutic effect. One of the ways to decrease this undesirable process is through the inclusion of drugs in nanomaterials. Earlier strong anticoagulant activity was demonstrated for dipeptide IleTrp (IW) and adenosine (Ado). In this work, the effect of inclusion in nanomaterials on the biological activity of IW and Ado was studied. For this purpose, Ado and IW were incorporated into thermosensitive nanogel composed of pluronic P123-grafted heparin. The prepared nanocarrier was characterized by transmission electron microscopy, dynamic light scattering, and ζ-potential. Biological activity was determined by measuring the bleeding time from mouse tail in vivo and the time of clot formation in vitro. It was found that encapsulation of Ado and IW into nanomaterial significantly increased their effects, resulting in an increase in the bleeding time from mouse tail and clot formation time. Thus, inclusion of low molecular weight anticoagulants Ado and IW into nanomaterials may be considered a way to increase their biological activity.

Strategic approach to developing a self-microemulsifying drug delivery system to enhance antiplatelet activity and bioavailability of ticagrelor

Background

Ticagrelor (TCG) is used to inhibit platelet aggregation in patients with acute coronary syndrome, but its poor solubility and low bioavailability limit its in vivo efficacy. The purpose of this study was to manufacture an optimized TCG-loaded self-microemulsifying drug delivery system (SMEDDS) to enhance the oral bioavailability and antiplatelet activity of TCG.

Materials and methods

Solubility and emulsification tests were conducted to determine the most suitable oils, surfactants, and cosurfactants. Scheffé's mixture design was applied to optimize the percentage of each component applied in the SMEDDS formulation to achieve optimal physical characteristics, ie, high solubility of TCG in SMEDDS, small droplet size, low precipitation, and high transmittance.

Results

The optimized TCG-loaded SMEDDS (TCG-SM) formulation composed of 10.0% Capmul MCM (oil), 53.8% Cremophor EL (surfactant), and 36.2% Transcutol P (cosurfactant) significantly improving the dissolution of TCG in various media compared with TCG in Brilinta^® (commercial product). TCG-SM exhibited higher cellular uptake and permeability in Caco-2 cells than raw TCG suspension. In pharmacokinetic studies in rats, TCG-SM exhibited higher oral bioavailability with 5.7 and 6.4 times higher area under the concentration-time curve and maximum plasma concentration, respectively, than a raw TCG suspension. Antiplatelet activity studies exhibited that the TCG-SM formulation showed significantly improved inhibition of platelet aggregation compared with raw TCG at the same dose of TCG. And, a 10 mg/kg dose of raw TCG suspension and a 5 mg/kg dose of TCG-SM had a similar area under the inhibitory curve (907.0%±408.8% and 907.8%±200.5%⋅hours, respectively) for antiplatelet activity.

Conclusion

These results suggest that the developed TCG-SM could be successfully used as an efficient method to achieve the enhanced antiplatelet activity and bioavailability of TCG.

The Protective Effect of Poloxamer-188 on Platelet Functions

BACKGROUND

Poloxamer-188 (MST-188) is effective in the repair/recovery of damaged cell membranes. MST-188 is a promising agent for protecting blood cell viability. The aim of the study is to test the hypothesis that MST-188 can extend the duration of platelet function.

MATERIALS AND METHODS

Blood samples were collected from 20 healthy volunteers. MST-188 (10 or 2 mg/mL) containing platelet-rich plasma (PRP) was prepared with 2 procedures. First, PRP prepared from MST-188 added whole blood (WB); second, MST-188 was added to PRP. These were referred to MST-188-WB preparation (WBP) and MST-188-PRP preparation (PRPP), respectively. For control, saline was used in the same manner. Agonist-induced aggregation (AIA) studies were performed at 30, 180, and 300 minutes using Platelet Aggregation Profiler (PAP-8) aggregometer (Bio/Data Corporation, Horsham, Pennsylvania) and Adenosine diphosphate (ADP), arachidonic acid, collagen, and epinephrine as agonists at final concentration of 20 µM, 500 µg/mL, 0.19 mg/mL, and 100 µM, respectively.

RESULTS

There was a protective effect of MST-188 on ADP and collagen AIA. At 300 minutes, ADP AIA was found to be 50.2% higher than saline control in 2-mg WBP, 43% at 10-mg PRPP, and 10.4% at 2-mg PRPP. Protective effect of on collagen AIA was 65.9% in 2-mg WBP, 42.74% at 10-mg PRPP, and 11.42% at 2-mg PRPP. In comparison between 30 and 300 minutes, MST-188 showed significant protection in terms of ADP and collagen receptors and for both types of preparations (WBP and PRPP).

CONCLUSION

The protective effects of MST-188 on ADP- and collagen-induced platelet aggregation may contribute to the preservation of platelet functionality upon storage in blood banks.

Effects of poloxamer 188 on human PMN cells

BACKGROUND

Poloxamer 188 (P188), a nonionic block copolymer chemical surfactant known to have cytoprotective, rheologic, anti-inflammatory, and anti-thrombotic activity, has shown promise in the management of selected trauma patients. We studied human PMN oxidative burst and adhesion molecule expression when exposed to P188.

METHODS

After RBC lysis of whole blood samples, white blood cell components were primed with phosphotidylcholine, primed and activated with fMLP, primed and activated with PMA, or left unstimulated. Each group was treated with vehicle or P188 (0.005-15 mg/ml concentrations). Flow cytometry quantified: (1) PMN superoxide anion production and (2) PMN marker expression of CD11b and L-selectin.

RESULTS

Among non-PMA activated PMNs, P188 increased superoxide anion production. PMA-activated PMNs decreased superoxide anion production, proportional to P188 dose. Among fMLP-activated PMNs, the highest P188 dose increased the expression of CD11b. Among PMA-activated PMNs, decreased CD11b expression was seen for the mid-range doses.

CONCLUSIONS

PMNs altered their oxidative burst and marker expression after exposure to P188. When used at lower doses, P188 may increase the oxidative burst response and, when used at very high doses, increase CD11b expression. However, if PMNs are in a maximally activated state, a higher dose of P188 may decrease the oxidative burst response and decrease CD11b expression.

Safety Assessment of Poloxamers 101, 105, 108, 122, 123, 124, 181, 182, 183, 184, 185, 188, 212, 215, 217, 231, 234, 235, 237, 238, 282, 284, 288, 331, 333, 334, 335, 338, 401, 402, 403, and 407, Poloxamer 105 Benzoate, and Poloxamer 182 Dibenzoate as Used in Cosmetics

Poloxamers are polyoxyethlyene, polyoxypropylene block polymers. The impurities of commercial grade Poloxamer 188, as an example, include low-molecular-weight substances (aldehydes and both formic and acetic acids), as well as 1,4-dioxane and residual ethylene oxide and propylene oxide. Most Poloxamers function in cosmetics as surfactants, emulsifying agents, cleansing agents, and/or solubilizing agents, and are used in 141 cosmetic products at concentrations from 0.005% to 20%. Poloxamers injected intravenously in animals are rapidly excreted in the urine, with some accumulation in lung, liver, brain, and kidney tissue. In humans, the plasma concentration of Poloxamer 188 (given intravenously) reached a maximum at 1 h, then reached a steady state. Poloxamers generally were ineffective in wound healing, but were effective in reducing postsurgical adhesions in several test systems. Poloxamers can cause hypercholesterolemia and hypertriglyceridemia in animals, but overall, they are relatively nontoxic to animals, with LD50 values reported from 5 to 34.6 g/kg. Short-term intravenous doses up to 4 g/kg of Poloxamer 108 produced no change in body weights, but did result in diffuse hepatocellular vacuolization, renal tubular dilation in kidneys, and dose-dependent vacuolization of epithelial cells in the proximal convoluted tubules. A short-term inhalation toxicity study of Poloxamer 101 at 97 mg/m3 identified slight alveolitis after 2 weeks of exposure, which subsided in the 2-week postexposure observation period. A short-term dermal tox-icity study of Poloxamer 184 in rabbits at doses up to 1000 mg/kg produced slight erythema and slight intradermal inflammatory response on histological examination, but no dose-dependent body weight, hematology, blood chemistry, ororgan weight changes. A6-month feeding study in rats and dogs of Poloxamer 188 at exposures up to 5% in the diet produced no adverse effects. Likewise, Poloxamer 331 (tested up to 0.5 g/kg day-1), Poloxamer 235 (tested up to 1.0 g/kg day-1), and Poloxamer 338 (at 0.2 or 1.0 g/kg day-1) produced no adverse effects in dogs. Poloxamer 338 (at 5.0 g/kg day-1) produced slight transient diarrhea in dogs. Poloxamer 188 at levels up to 7.5% in diet given to rats in a 2-year feeding study produced diarrhea at 5% and 7.5% levels, a small decrease in growth at the 7.5% level, but no change in survival. Doses up to 0.5 mg/kg day-1 for 2 years using rats produced yellow discoloration of the serum, high serum alkaline phosphatase activity, and elevated serum glutamicpyruvic transaminase and glutamic-oxalacetic transaminase activities. Poloxamers are minimal ocular irritants, but are not dermal irritants or sensitizers in animals. Data on reproductive and developmental toxicity of Poloxamers were not found. An Ames test did not identify any mutagenic activity of Poloxamer 407, with or without metabolic activation. Several studies have suggested anti-carcinogenic effects of Poloxamers. Poloxamers appear to increase the sensitivity to anticancer drugs of multidrug-resistant cancer cells. In clinical testing, Poloxamer 188 increased the hydration of feces when used in combination with a bulk laxative treatment. Compared to controls, one study of angioplasty patients receiving Poloxamer 188 found a reduced myocardial infarct size and a reduced incidence of reinfarction, with no evidence of toxicity, but two other studies found no effect. Poloxamer 188 given to patients suffering from sickle cell disease had decreased pain and decreased hospitilization, compared to controls. Clinical tests of dermal irritation and sensitization were uniformly negative. The Cosmetic Ingredient Review (CIR) Expert Panel stressed that the cosmetic industry should continue to use the necessary purification procedures to keep the levels below established limits for ethylene oxide, propylene oxide, and 1,4-dioxane. The Panel did note the absence of reproductive and developmental toxicity data, but, based on molecular weight and solubility, there should be little skin penetration and any penetration of the skin should be slow. Also, the available data demonstrate that Poloxamers that are introduced into the body via routes other than dermal exposure have a rapid clearance from the body, suggesting that there would be no risk of reproductive and/or developmental toxicity. Overall, the available data do not suggest any concern about carcinogenesis. Although there are gaps in knowledge about product use, the overall information available on the types of products in which these ingredients are used, and at what concentration, indicates a pattern of use. Based on these safety test data and the information that the manufacturing process can be controlled to limit unwanted impurities, the Panel concluded that these Poloxamers are safe as used.

Second-generation perfluorocarbon emulsion blood substitutes

A novel series of perfluorocarbon (PFC) emulsions, based on perfluorodecalin (C10F18) and stabilised with up to 2.5% (w/v) of lecithin have been produced for evaluation as injectable, temporary respiratory gas-carrying blood substitutes. Some formulations contained 1.0% (w/v) of perfluorodimorpholinopropane (C11F22N2O2) to retard droplet growth through molecular diffusion (Ostwald Ripening). Other emulsions contained novel, amphiphilic fluorinated surfactants, such as, for example, the monocarbamate, C8F17C2H4NHC(O)(CH2CH2O)2Me (designated compound P6), at 0.1% (w/v) to enhance stability. Emulsions were prepared by homogenisation, were steam sterilisable and were stable for > 300 days (25 degrees C). Injection of rats (7.5 ml kg-1 b.w.) with emulsions produced significant (P < 0.05), transient increases in liver and spleen weights. One emulsion inhibited phorbol 12-myristate 13-acetate (PMA)-stimulated, Luminol-enhanced, chemiluminescence of human polymorphonuclear leucocytes (PMNL) in vitro, suggesting possible applications in ischaemic tissues for suppressing PMNL-mediated inflammation. The P6 fluoro-surfactant inhibited spontaneous platelet aggregation in hirudin-anticoagulated human blood in vitro, suggesting possible applications as an anti-thrombotic agent.

Pluronic F-68 inhibits agonist-induced platelet aggregation in human whole blood in vitro

The effects have been studied of Pluronic F-68 at 0.04% (w/v) on platelet aggregation in hirudin (50 micrograms ml-1)-anticoagulated, human whole blood in vitro in response to the following aggregation agonists: (i) phorbol 12-myristate 13-acetate (PMA; 0.05, 0.1 or 0.15 microgram ml-1), (ii) collagen (0.125, 0.25 or 0.5 microgram ml-1), or (iii) ristocetin (0.3, 0.6 or 1.2 micrograms ml-1). Pluronic F-68 significantly (P < 0.05) inhibited platelet aggregation that followed the addition of all agonists at their lowest concentration tested. Pluronic F-68 had markedly less pronounced inhibitory effects on the platelet aggregation that occurred in response to 0.15 microgram ml-1 PMA, where the mean % aggregation after 8 min was 67% of control (P < 0.05). Pluronic F-68 did not alter platelet aggregation in blood treated with 0.25 or 0.5 microgram ml-1 of collagen.

Effects of the co-polymer surfactant, Pluronic F-68, on platelet aggregation in human whole blood

The effects have been studied of Pluronic F-68 on platelet aggregation in human whole blood. The median spontaneous platelet aggregation in normal blood (n = 15) was 18.4% [interquartile range (IQ) = 10.5-24.2%]. Commercial grade Pluronic F-68 significantly (P < 0.05) reduced platelet aggregation at 7.3 microM (median = 8.4%, IQ = 3.9-13.4; n = 12) and almost eliminated aggregation at concentrations of > 58 microM (median = 2.0%, IQ = 0.0-3.5). Similar results were obtained with a silica gelpurified Pluronic F-68 fraction (n = 3). Pluronic F-68 also accelerated the rate of platelet dis-aggregation in blood treated with 0.3, 1.0 or 3.0 mM adenosine di-phosphate. These results suggest that the therapeutic effects of Pluronic F-68 in ischaemic injury may be due, in part, to inhibition of platelet aggregation in the microcirculation. The beneficial effects of tissue perfusion with oxygen-carrying perfluorochemical emulsions, containing Pluronic F-68, may also involve direct effects of the surfactant on platelets.

Novel fluorinated surfactants for perfluorochemical emulsification: biocompatibility assessments of glycosidic and polyol derivatives

A novel series of fluoro-surfactants, derived from glycosides (monosaccharides) or polyols (ureas or carbamates), have been produced for use in respiratory gas-carrying perfluorochemical emulsions. Compounds were synthesised via simple, but highly selective, routes using highly fluorinated isocyanates with amino alcohols, polyethoxylated alcohols and partially protected sugars at anomeric carbon; yields were 88-95%. Resultant compounds were perfluoroalkylated with hydroxylic "head" groups. The biocompatibility of surfactants with human blood in vitro was assessed using a conventional haemolysis test. Compounds showing insignificant haemolysis at up to 10 g l-1 were further evaluated (i) for their effects on neutrophil chemiluminescence, and (ii) in a human platelet aggregation assay. Some fluoro-surfactants inhibited spontaneous platelet aggregation, in blood anti-coagulated with hirudin, at concentrations of 0.01% (w/v), suggesting possible applications as antithrombotic agents.