Enhanced therapeutic effect of cytidine-5'-diphosphate choline when associated with GM1 containing small liposomes as demonstrated in a rat ischemia model

Highly Stable, Ultrasmall Polymer-Grafted Nanobins (usPGNs) with Stimuli-Responsive Capability

Highly stable and stimuli/pH-responsive ultrasmall polymer-grafted nanobins (usPGNs) have been developed by grafting a small amount (10 mol %) of short (4.3 kDa) cholesterol-terminated poly(acrylic acid) (Chol-PAA) into an ultrasmall unilamellar vesicle (uSUV). The usPGNs are stable against fusion and aggregation over several weeks, exhibiting over 10-fold enhanced cargo retention in biologically relevant media at pH 7.4 in comparison with the parent uSUV template. Coarse-grained molecular dynamics (CGMD) simulations confirm that the presence of the cholesterol moiety can greatly stabilize the lipid bilayer. They also show extended PAA chain conformations that can be interpreted as causing repulsion between colloidal particles, thus stabilizing them against fusion. Notably, CGMD predicted a clustering of the Chol-PAA chains on the lipid bilayer under acidic conditions due to intra- and interchain hydrogen bonding, leading to the destabilization of local membrane areas. This explains the experimental observation that usPGNs can be triggered to release a significant amount of cargo upon acidification to pH 5. These developments put the lipid-bilayer-embedded Chol-PAA in stark contrast with traditional poly(acrylic acid) systems where the molar mass (Mn) of the polymer chains must exceed 16.5 kDa to achieve stimuli-responsive changes in conformation. They also distinguish the small usPGNs from the much-larger polymer-caged nanobin platform where the Chol-PAA chains must be covalently cross-linked to engender stimuli-responsive behaviors.

Citicoline in severe traumatic brain injury: indications for improved outcome : A retrospective matched pair analysis from 14 Austrian trauma centers

Goal-oriented management of traumatic brain injury (TBI) can save the lives and/or improve the long-term outcome of millions of affected patients worldwide. Additionally, enhancing quality of life will save enormous socio-economic costs; however, promising TBI treatment strategies with neuroprotective agents, such as citicoline (CDP-choline), lacked evidence or produced contradictory results in clinical trials. During a prehospital TBI project to optimize early TBI care within 14 Austrian trauma centers, data on 778 TBI patients were prospectively collected. As preceding evaluations suggested a beneficial outcome in TBI patients treated at the Wiener Neustadt Hospital (WNH), we aimed to investigate the potential role of citicoline administration, solely applied in WNH, in those patients. In a retrospective subgroup analysis we compared 67 patients from WNH with citicoline administration and 67 matched patients from other Austrian centers without citicoline use. Patients with Glasgow Coma Scale score <13 on site and/or Abbreviated Injury Scale of the region "head" >2 were included. Our analysis revealed significantly reduced rates of intensive care unit (ICU) mortality (5% vs. 24%, p < 0.01), in-hospital mortality (9% vs. 24%, p = 0.035) and 6‑month mortality (13% vs. 28%, p = 0.031), as well as of unfavorable outcome (34% vs. 57%, p = 0.015) and observed vs. expected ratio for mortality (0.42 vs. 0.84) in the WNH (citicoline receivers) group. Despite the limitations of a retrospective subgroup analysis our findings suggest a possible correlation between early and consequent citicoline administration and beneficial outcomes. Therefore, we aim to set up an initiative for a prospective, multicenter randomized controlled trial with citicoline in sTBI (severe TBI) patients.

Interaction between PEG lipid and DSPE/DSPC phospholipids: An insight of PEGylation degree and kinetics of de-PEGylation

The degree to which liposomes are PEGylated is the feature, which most influences the length of the presence of stealth liposomes in the bloodstream. In order to thoroughly investigate the maximum amount of DSPE-PEG₂₀₀₀ that can be used to stabilize stealth liposomes, these were synthesized at different concentrations of DSPE-PEG₂₀₀₀ and their physicochemical properties were investigated by using differential scanning calorimetry (DSC). The kinetics of PEGylation and de-PEGylation were performed by incubating non-stealth liposomes in a DSPE-PEG₂₀₀₀ suspension at different incubation times, and then analyzing the data using DSC and dynamic light scattering (DLS) techniques. The results demonstrated that DSPE-PEG₂₀₀₀ was self-assembled in the phospholipid bilayers, thus forming stealth liposomes. The different amounts of DSPE-PEG₂₀₀₀ in the bilayer triggered a de-PEGylation phenomenon, resulting in mixed nanoaggregates, which derived from the detergent-like properties of the PEGylated phospholipids.

Getting into the brain: liposome-based strategies for effective drug delivery across the blood-brain barrier

This review summarizes articles that have been reported in literature on liposome-based strategies for effective drug delivery across the blood–brain barrier. Due to their unique physicochemical characteristics, liposomes have been widely investigated for their application in drug delivery and in vivo bioimaging for the treatment and/or diagnosis of neurological diseases, such as Alzheimer’s, Parkinson’s, stroke, and glioma. Several strategies have been used to deliver drug and/or imaging agents to the brain. Covalent ligation of such macromolecules as peptides, antibodies, and RNA aptamers is an effective method for receptor-targeting liposomes, which allows their blood–brain barrier penetration and/or the delivery of their therapeutic molecule specifically to the disease site. Additionally, methods have been employed for the development of liposomes that can respond to external stimuli. It can be concluded that the development of liposomes for brain delivery is still in its infancy, although these systems have the potential to revolutionize the ways in which medicine is administered.

Development of HIV reservoir targeted long acting nanoformulated antiretroviral therapies

Human immunodeficiency virus (HIV) infection commonly results in a myriad of comorbid conditions secondary to immune deficiency. Infection also affects broad organ system function. Although current antiretroviral therapy (ART) reduces disease morbidity and mortality through effective control of peripheral viral load, restricted infection in HIV reservoirs including gut, lymphoid and central nervous system tissues, is not eliminated. What underlies these events is, in part, poor ART penetrance into each organ across tissue barriers, viral mutation and the longevity of infected cells. We posit that one means to improve these disease outcomes is through nanotechnology. To this end, this review discusses a broad range of cutting-edge nanomedicines and nanomedicine platforms that are or can be used to improve ART delivery. Discussion points include how polymer-drug conjugates, dendrimers, micelles, liposomes, solid lipid nanoparticles and polymeric nanoparticles can be harnessed to best yield cell-based delivery systems. When completely developed, such nanomedicine platforms have the potential to clear reservoirs of viral infection.

Cytidine 5'-diphosphocholine (CDP-choline) adversely effects on pilocarpine seizure-induced hippocampal neuronal death

Citicoline (CDP-choline; cytidine 5'-diphosphocholine) is an important intermediate in the biosynthesis of cell membrane phospholipids. Citicoline serves as a choline donor in the biosynthetic pathways of acetylcholine and neuronal membrane phospholipids, mainly phosphatidylcholine. The ability of citicoline to reverse neuronal injury has been tested in animal models of cerebral ischemia and clinical trials have been performed in stroke patients. However, no studies have examined the effect of citicoline on seizure-induced neuronal death. To clarify the potential therapeutic effects of citicoline on seizure-induced neuronal death, we used an animal model of pilocarpine-induced epilepsy. Temporal lobe epilepsy (TLE) was induced by intraperitoneal injection of pilocarpine (25mg/kg) in adult male rats. Citicoline (100 or 300 mg/kg) was injected into the intraperitoneal space two hours after seizure onset and a second injection was performed 24h after the seizure. Citicoline was injected once per day for one week after pilocarpine- or kainate-induced seizure. Neuronal injury and microglial activation were evaluated at 1 week post-seizure. Surprisingly, rather than offering protection, citicoline treatment actually enhanced seizure-induced neuronal death and microglial activation in the hippocampus compared to vehicle treated controls. Citicoline administration after seizure-induction increased immunoglobulin leakage via BBB disruption in the hippocampus compared with the vehicle-only group. To clarify if this adverse effect of citicoline is generalizable across alternative seizure models, we induced seizure by kainate injection (10mg/kg, i.p.) and then injected citicoline as in pilocarpine-induced seizure. We found that citicoline did not modulate kainate seizure-induced neuronal death, BBB disruption or microglial activation. These results suggest that citicoline may not have neuroprotective effects after seizure and that clinical application of citicoline after seizure needs careful consideration.

Anticancer activity of liposomal bergamot essential oil (BEO) on human neuroblastoma cells

Citrus extracts, particularly bergamot essential oil (BEO) and its fractions, have been found to exhibit anticancer efficacy. However, the poor water solubility, low stability and limited bioavailability have prevented the use of BEO in cancer therapy. To overcome such drawbacks, we formulated BEO liposomes that improved the water solubility of the phytocomponents and increased their anticancer activity in vitro against human SH-SY5Y neuroblastoma cells. The results warrant further investigation of BEO liposomes for in vivo applications.

Investigations of the antibacterial properties of ciprofloxacin@SiO2

The antibacterial activity of ciprofloxacin-encapsulated silica nanoshells synthesized from gold@silica core-shell nanoparticles has been investigated. The minimum inhibitory concentration of the material was found using the agar dilution method, and it showed better antibacterial activity compared to free ciprofloxacin in the case of Escherichia coli DH5, whereas the same activity was found for Lactococcus lactis MG 1363. Hydrophobicity measurements carried out in an octanol-water mixture suggested that ciprofloxacin@SiO2 is distributed almost equally in the aqueous and nonaqueous phases. The kinetics of the uptake of ciprofloxacin@SiO2 was compared with that of free ciprofloxacin. Fluorescence imaging studies carried out using fluorescein isothiocyanate@SiO2 showed that the nanoshells enter the bacterial cell. The uptake of silica shells has been probed by transmission electron microscopy also.

Radioprotective effect of transferrin targeted citicoline liposomes

The high level of expression of transferrin receptors (Tf-R) on the surface of endothelial cells of the blood-brain-barrier (BBB) had been widely utilized to deliver drugs to the brain. The primary aim of this study was to use transferrin receptor mediated endocytosis as a pathway for the rational development of holo-transferrin coupled liposomes for drug targeting to the brain. Citicoline is a neuroprotective agent used clinically to treat for instance Parkinson disease, stroke, Alzheimer's disease and brain ischemia. Citicoline does not readily cross the BBB because of its strong polar nature. Hence, citicoline was used as a model drug. (Citicoline liposomes have been prepared using dipalmitoylphosphatidylcholine (DPPC) or distearoylphosphatidylcholine (DSPC) by dry lipid film hydration-extrusion method). The effect of the use of liposomes composed of DPPC or DSPC on their citicoline encapsulation efficiency and their stability in vitro were studied. Transferrin was coupled to liposomes by a technique which involves the prevention of scavenging diferric iron atoms of transferrin. The coupling efficiency of transferrin to the liposomes was studied. In vitro evaluation of transferrin-coupled liposomes was performed for their radioprotective effect in radiation treated cell cultures. In this study, OVCAR-3 cells were used as a model cell type over-expressing the Tf-R and human umbilical vein endothelial cells (HUVEC) as BBB endothelial cell model. The average diameter of DPPC and DSPC liposomes were 138 +/- 6.3 and 79.0 +/- 3.2 nm, respectively. The citicoline encapsulation capacity of DPPC and DSPC liposomes was 81.8 +/- 12.8 and 54.9 +/- 0.04 microg/micromol of phospholipid, respectively. Liposomes prepared from DSPC showed relatively better stability than DPPC liposomes at 37 degrees C and in the presence of serum. Hence, DSPC liposomes were used for transferrin coupling and an average of 46-55 molecules of transferrin were present per liposome. Free citicoline has shown radioprotective effect at higher doses tested. Interestingly, encapsulation of citicoline in pegylated liposomes significantly improved the radioprotective effect by 4-fold compared to free citicoline in OVCAR-3 but not in HUVEC. Further, citicoline encapsulation in transferrin-coupled liposomes has significantly improved the radioprotective effect by approximately 8-fold in OVCAR-3 and 2-fold in HUVEC cells with respect to the free drug. This is likely due to the entry of citicoline into cells via transferrin receptor mediated endocytosis. In conclusion, our results suggest that low concentrations of citicoline encapsulated in transferrin-coupled liposomes could offer therapeutic benefit in treating stroke compared to free citicoline.

Tolerability and improved protective action of idebenone-loaded pegylated liposomes on ethanol-induced injury in primary cortical astrocytes

The potential therapeutic advantages of the encapsulation of idebenone within pegylated liposomes were investigated in vitro on primary cortical astrocytes of rats. In particular, both the concentration-dependent effects and the therapeutic effectiveness toward excitotoxic injury, elicited by chronic treatment with ethanol (100 microM) for 12 days, were evaluated. The following parameters were taken into consideration to assay free or liposomally entrapped idebenone: lactic dehydrogenase release, respiratory capacity measured by tetrazolium salt conversion, glutamine synthetase, and the levels of constitutive and inducible 70-kDa heat shock proteins. To evaluate the effects on astrocytes, three different drug concentrations were used (0.5 microM, 5 microM, and 50 microM). At the highest concentration used (50 microM), a toxic effect of the free and liposomally entrapped drug was observed. Toxic effects seem to be due to a cellular membrane perturbation, as demonstrated by (45)Ca(2+) permeation. The therapeutic effect of free or liposomally entrapped idebenone on ethanol-induced injury of primary cortical astrocytes was evaluated as a function of the drug concentration. The drug liposome formulation was much more effective than the free drug in counteracting the ethanol-induced damage in astrocytes, i.e., 10-times-lower doses of liposomally entrapped idebenone are able to provide a greater protective action than the free drug. The improved action of idebenone-loaded liposomes is probably due to the greater drug bioavailability at the cellular level.

Citicoline mechanisms and clinical efficacy in cerebral ischemia

Citicoline, an intermediate in the biosynthesis of phosphatidylcholine (PtdCho), has shown beneficial effects in various CNS injury models and neurodegenerative diseases. PtdCho hydrolysis by phospholipase A(2) (PLA(2)) after cerebral ischemia and reperfusion yields arachidonic acid (ArAc) and lyso-PtdCho. ArAc oxidative metabolism results in formation of reactive oxygen species and lipid peroxides. Lyso-PtdCho could inhibit activity of cytidine triphosphate-phosphocholine cytidylyltransferase (the rate-limiting enzyme in PtdCho biosynthesis), resulting in impaired PtdCho synthesis. Citicoline significantly increased glutathione levels and attenuated release of ArAc and the loss of PtdCho, cardiolipin, and sphingomyelin following transient cerebral ischemia. These effects could be explained by an effect of citicoline on PLA(2). Based on these observations, a mechanism has been hypothesized. This Mini-Review summarizes recent experimental data on the effects of citicoline in cerebral ischemia and evaluates several factors that might have hindered efficacy of citicoline in stroke clinical trials in the United States. Clinical stroke trials of citicoline in Europe and Japan have demonstrated beneficial effects. U.S. trials shown only marginal effects, which might be due to the 24 hr time window, the dose and route of administration, and the stringency of the primary outcome parameters. Recent evaluation of U.S. clinical data suggests that reduction of infarct growth may be a more sensitive measure of the citicoline effect than improvement on the NIH Stroke Scale (NIHSS) by > or =7 points. The citicoline neuroprotective mechanism has not been clearly identified, and its potential in stroke treatment might still be fully recognized in the United States. The clinical efficacy of citicoline should be examined further in light of the recent phase III stroke clinical trials and experimental data for cerebral ischemia.

The cholinergic approach for the treatment of vascular dementia: evidence from pre-clinical and clinical studies

The involvement of an impaired cholinergic neurotransmission in the pathophysiology of cognitive impairment occurring in vascular dementia (VaD), as well as the possibility of treating it by stimulating cholinergic neurotransmission was reviewed. Pre-clinical data suggest that similarly as documented in dementia disorders of neurodegenerative origin, a cholinergic deficit is involved in the pathophysiology of cognitive impairment of vascular origin. In the past, clinical trials have evaluated cholinergic precursors such as lecithin, citicoline and choline alphoscerate. More recent investigations have assessed acetylcholinesterase (AChE) and cholinesterase (ChE) inhibitors such as donepezil, rivastigmine and galantamine. In general, treatment with citicoline, choline alphoscerate, as well as with AChE and ChE inhibitors induced favourable effects on cognitive function in dementia disorders of vascular origin. These positive results should be regarded with caution due to the small number of patients included in controlled clinical trials using cholinergic precursors and to the limited number and sample size of trials with AChE and ChE inhibitors. Among compounds investigated, choline alphoscerate was well tolerated, improved cognitive function in VaD patients to a better extent than citicoline and to similar or better extent than other more recently developed drugs. This particular profile would justify reconsideration of the compound in larger controlled clinical trials for the treatment of cognitive dysfunction associated with dementia disorders of vascular origin.

Ofloxacin-loaded liposomes: in vitro activity and drug accumulation in bacteria

Different ofloxacin-loaded unilamellar vesicles were prepared by the extrusion technique, and their antimicrobial activities were determined in comparison to those of the free drug by means of MIC determinations with both American Type Culture Collection standards and wild-type bacterial strains (six strains of Enterococcus faecalis, seven strains of Escherichia coli, six strains of Staphylococcus aureus, and six strains of Pseudomonas aeruginosa). The accumulation of ofloxacin and liposome-ofloxacin was measured by determining the amount of the drug inside the bacteria as a function of time. Encapsulated fluoroquinolone yielded MICs which were at least twofold lower than those obtained with the free drug. In particular, liposomes made up of dimyristoylphosphatidylcholine-cholesterol-dipalmitoylphosphatidylser ine and dimyristoylphosphatidylcholine-cholesterol-dihexadecylphosphate (4:3:4 molar ratio) provided the best improvement in antimicrobial activity against the various bacterial strains investigated. The liposome formulation produced higher intracellular fluoroquinolone concentrations than those achieved simultaneously with the free drug in both E. coli and P. aeruginosa.

Evaluating the efficacy of citicoline in embolic ischemic stroke in rats: neuroprotective effects when used alone or in combination with urokinase

The combination of thrombolysis with neuroprotection, because of different mechanisms, would be expected to show better results when used after onset of focal ischemia. In this study we report our experience with the neuronal protective effects of citicoline alone and in combination with urokinase in a model of focal ischemia. Both medications were injected 2 h after onset of a focal occlusion of the middle cerebral artery (MCA) in rats. Focal ischemia was produced with embolization of a clot into the origin of the MCA. This produces a large infarction involving the cortex and the basal ganglia. Animals were observed for neuronal deficts at 2 and 24 h after surgery and were sacrificed 72 h after onset of ischemia. Saline-treated animals showed a large infarction involving the cerebral cortex and basal ganglion in most animals (volume 33.1 +/- 9.7%). Animals treated with citicoline alone were divided in two groups. The first group of animals were treated with a single injection (300 mg/kg, ip) of the medication 2 h after the arterial occlusion. The second group was treated with the active medication intermittently (3 x 300 mg/kg, ip) over a 72-h period. There was a significant decrease in the neuronal damage in the cortex in the animals treated with citicoline (single dose, 20.9 +/- 9.7%, P = 0.01; intermittent injection, 18.9 +/- 11.4%, P < 0.008). The last experiment evaluated the usefulness of the combination of citicoline with intraarterial urokinase. The combination showed significantly more protection than with urokinase or citicoline alone (volume 13.6 +/- 9.1%, P < 0.001). We conclude from our experiments that citicoline may offer significant neuronal protection that may be further enhanced with the addition of a thrombolytic agent.

Reduction of maturation phenomenon in cerebral ischemia with CDP-choline-loaded liposomes

PURPOSE

Cerebral ischemia represents a serious therapeutic challenge. We investigated the therapeutic efficacy of CDP-choline-loaded liposomes against cerebral ischemia. The determination of post-ischemic brain recovery by EEG analysis was carried out to evaluate the effect of CDP-choline-loaded liposomes with respect to the free drug on the maturation of ischemic injury.

METHODS

Long-circulating unilamellar liposomes were prepared by a freeze and thaw procedure followed by an extrusion through polycarbonate membranes. Wistar rats were ischemized by bilateral clamping of the common carotid arteries. Free or liposomally entrapped drug was administered (20 mg/kg) just after ischemia and thereafter once a day for six days. Post-ischemic survival, neuronal membrane peroxidation and brain recovery (EEG analysis) were evaluated.

RESULTS

The post-ischemic reperfused rats treated with CDP-choline-loaded liposomes showed a higher survival rate than animals treated with the free drug. The delayed cerebral neurodegenerative injury due to an ischemic event, referred to as maturation phenomenon, was substantially reduced with the administration of the liposomal formulation. The liposomal carrier showed a marked protection against lipoperoxidative damage.

CONCLUSIONS

Liposomes ensured a rapid recovery of the damaged membranous structure of the neuronal cells, allowing a significant improvement of brain functionality. The reduction of the maturation phenomenon may probably be of particular importance in humans, where a fundamental problem is the quality of life after an ischemic event.

Characterization and in-vivo ocular absorption of liposome-encapsulated acyclovir

The potential of liposomes as an in-vivo ophthalmic drug delivery system for acyclovir was investigated. The drug-membrane interaction was evaluated by means of differential scanning calorimetry analysis. These experiments showed that acyclovir is able to interact with both positively and negatively charged membranes via electrostatic or hydrogen bonds. No interaction was observed with neutral membranes made up of dipalmitoylphosphatidylcholine. Different liposome preparation procedures were carried out to encapsulate acyclovir. The drug encapsulation mainly depends on the amount of water which the liposome system is able to entrap. In the case of multilamellar vesicles, charged systems showed the highest encapsulation efficiency. No particular difference in the encapsulation efficiency was observed for oligolamellar vesicles prepared with the reverse-phase evaporation technique. Oligolamellar liposomes showed the highest acyclovir encapsulation parameters and had release profiles similar to those of multilamellar liposomes. In-vivo experiments using male New Zealand albino rabbits were carried out to evaluate the aqueous humour concentration of acyclovir bioavailability. The most suitable ophthalmic drug delivery system was oligolamellar systems made up of dipalmitoylphosphatidylcholine-cholesterol-dimethyldioctadecyl glycerole bromide (7:4:1 molar ratio), which presented the highest encapsulation capacity and were able to deliver greater amounts of the drug into the aqueous humour than a saline acyclovir solution or a physical liposome/drug blend.

Liposomal delivery of a 30-mer antisense oligodeoxynucleotide to inhibit proopiomelanocortin expression

An oligodeoxynucleic sequence of 30 bases (30-mer ODN), complementary to a region of beta-endorphin mRNA, was synthesized to have an antisense effect with regard to the expression of this oligopeptide. Following the solid-phase synthesis of the oligodeoxynucleotide, the 30-mer ODN was encapsulated within liposomes to provide a higher resistance against DNases and an improved entrance into cells. The most suitable liposome formulation as a 30-mer ODN carrier consisted of small unilamellar vesicles (50 nm) with an encapsulation capacity of 4.76 microL/micromol. The liposomal formulations containing dipalmitoyl-DL-alpha-phosphatidyl-L-serine presented fusogenic properties, which are of great importance for the delivery of antisense compounds. The antisense activity of 30-mer ODN-loaded liposomes was evaluated by the determination of beta-endorphin levels in AtT-20 cells. The free 30-mer ODN did not provide any lowering of the beta-endorphin production, whereas the liposomally entrapped compound elicited a concentration-dependent inhibition. The inhibition was determined by a sequence-specific binding of the 30-mer ODN with the target mRNA.

Survival rate improvement in a rat ischemia model by long circulating liposomes containing cytidine-5I-diphosphate choline

Unilamellar liposomes made up of DPPC-DPPS-Chol (7:4:7 molar ratio) and ganglioside GM1 8% mol were used to deliver cytidine-5I-diphosphate choline (CDP-choline) to the brain. The liposomal suspension consisted of unilamellar vesicles with a mean size of 50 nm and a very narrow size distribution. The therapeutic effectiveness of CDP-choline-loaded liposomes was investigated by an in vivo model of cerebral ischemia on Wistar rats (320-350 g). The animals were made ischemic to different extents (5, 15 and 30 min) by bilateral clamping of the common carotid arteries. The effect of free and liposomally encapsulated CDP-choline on the survival rate of post-ischemic reperfused rats was evaluated. The liposome formulation was much more active against ischemic injury than the free CDP-choline, ensuring a noticeable improvement of the survival rate with regards to the free drug ranging from 45% to 100% as a function of the duration of the ischemic event.