Liposomal Formulations of Tacrolimus and Rapamycin Increase Graft Survival and Fiber Outgrowth of Dopaminergic Grafts

Drug delivery strategies for local immunomodulation in transplantation: Bridging the translational gap

Drug delivery strategies for local immunomodulation hold tremendous promise compared to current clinical gold-standard systemic immunosuppression as they could improve the benefit to risk ratio of life-saving or life-enhancing transplants. Such strategies have facilitated prolonged graft survival in animal models at lower drug doses while minimizing off-target effects. Despite the promising outcomes in preclinical animal studies, progression of these strategies to clinical trials has faced challenges. A comprehensive understanding of the translational barriers is a critical first step towards clinical validation of effective immunomodulatory drug delivery protocols proven for safety and tolerability in pre-clinical animal models. This review overviews the current state-of-the-art in local immunomodulatory strategies for transplantation and outlines the key challenges hindering their clinical translation.

Nano biomaterials based strategies for enhanced brain targeting in the treatment of neurodegenerative diseases: an up-to-date perspective

Neurons and their connecting axons gradually degenerate in neurodegenerative diseases (NDs), leading to dysfunctionality of the neuronal cells and eventually their death. Drug delivery for the treatment of effected nervous system is notoriously complicated because of the presence of natural barriers, i.e., the blood-brain barrier and the blood cerebrospinal fluid barrier. Palliative care is currently the standard care for many diseases. Therefore, treatment programs that target the disease's origin rather than its symptoms are recommended. Nanotechnology-based drug delivery platforms offer an innovative way to circumvent these obstacles and deliver medications directly to the central nervous system, thereby enabling treatment of several common neurological problems, i.e., Alzheimer's, Parkinson's, Huntington's, and amyotrophic lateral sclerosis. Interestingly, the combination of nanomedicine and gene therapy enables targeting of selective mutant genes responsible for the progression of NDs, which may provide a much-needed boost in the struggle against these diseases. Herein, we discussed various central nervous system delivery obstacles, followed by a detailed insight into the recently developed techniques to restore neurological function via the differentiation of neural stem cells. Moreover, a comprehensive background on the role of nanomedicine in controlling neurogenesis via differentiation of neural stem cells is explained. Additionally, numerous phytoconstituents with their neuroprotective properties and molecular targets in the identification and management of NDs are also deliberated. Furthermore, a detailed insight of the ongoing clinical trials and currently marketed products for the treatment of NDs is provided in this manuscript.

Nanotechnology in Kidney and Islet Transplantation: An Ongoing, Promising Field

Organ transplantation has evolved rapidly in recent years as a reliable option for patients with end-stage organ failure. However, organ shortage, surgical risks, acute and chronic rejection reactions and long-term immunosuppressive drug applications and their inevitable side effects remain extremely challenging problems. The application of nanotechnology in medicine has proven highly successful and has unique advantages for diagnosing and treating diseases compared to conventional methods. The combination of nanotechnology and transplantation brings a new direction of thinking to transplantation medicine. In this article, we provide an overview of the application and progress of nanotechnology in kidney and islet transplantation, including nanotechnology for renal pre-transplantation preservation, artificial biological islets, organ imaging and drug delivery.

Implantable Immunosuppressant Delivery to Prevent Rejection in Transplantation

An innovative immunosuppressant with a minimally invasive delivery system has emerged in the biomedical field. The application of biodegradable and biocompatible polymer forms, such as hydrogels, scaffolds, microspheres, and nanoparticles, in transplant recipients to control the release of immunosuppressants can minimize the risk of developing unfavorable conditions. In this review, we summarized several studies that have used implantable immunosuppressant delivery to release therapeutic agents to prolong allograft survival. We also compared their applications, efficacy, efficiency, and safety/side effects with conventional therapeutic-agent administration. Finally, challenges and the future prospective were discussed. Collectively, this review will help relevant readers understand the different approaches to prevent transplant rejection in a new era of therapeutic agent delivery.

Intra-Organ Delivery of Nanotherapeutics for Organ Transplantation

Targeted delivery of therapeutics through the use of nanoparticles (NPs) has emerged as a promising method that increases their efficacy and reduces their side effects. NPs can be tailored to localize to selective tissues through conjugation to ligands that bind cell-specific receptors. Although the vast majority of nanodelivery platforms have focused on cancer therapy, efforts have begun to introduce nanotherapeutics to the fields of immunology as well as transplantation. In this review, we provide an overview from a clinician's perspective of current nanotherapeutic strategies to treat solid organ transplants with NPs during the time interval between organ harvest from the donor and placement into the recipient, an innovative technology that can provide major benefits to transplant patients. The use of ex vivo normothermic machine perfusion (NMP), which is associated with preserving the function of the organ following transplantation, also provides an ideal opportunity for a localized, sustained, and controlled delivery of nanotherapeutics to the organ during this critical time period. Here, we summarize previous endeavors to improve transplantation outcomes by treating the organ with NPs prior to placement in the recipient. Investigations in this burgeoning field of research are promising, but more extensive studies are needed to overcome the physiological challenges to achieving effective nanotherapeutic delivery to transplanted organs discussed in this review.

Recent Advances in Liposomal-Based Anti-Inflammatory Therapy

Liposomes can be seen as ideal carriers for anti-inflammatory drugs as their ability to (passively) target sites of inflammation and release their content to inflammatory target cells enables them to increase local efficacy with only limited systemic exposure and adverse effects. Nonetheless, few liposomal formulations seem to reach the clinic. The current review provides an overview of the more recent innovations in liposomal treatment of rheumatoid arthritis, psoriasis, vascular inflammation, and transplantation. Cutting edge developments include the liposomal delivery of gene and RNA therapeutics and the use of hybrid systems where several liposomal bilayer features, or several drugs, are combined in a single formulation. The majority of the articles reviewed here focus on preclinical animal studies where proof-of-principle of an improved efficacy-safety ratio is observed when using liposomal formulations. A few clinical studies are included as well, which brings us to a discussion about the challenges of clinical translation of liposomal nanomedicines in the field of inflammatory diseases.

Biomaterials for topical and transdermal drug delivery in reconstructive transplantation

Lifelong systemic immunosuppression remains the biggest challenge in vascularized composite allotransplantation (VCA) due to the adverse effects it causes. Since VCA is a life-enhancing procedure as compared with solid organ transplant which is life-saving; one needs to weigh the benefits and risks carefully. Thus, there is a huge unmet clinical need to design biomaterial-based vehicles that can deliver drugs more efficiently, topically and locally to eliminate adverse effects of systemic immune suppression. This review discusses several biomaterial-based systems that have been carefully designed, conceived and attempted to make VCA a more patient compliant approach. Variety of promising preclinical studies has shown the feasibility of the approaches, and clinical trials are required to bridge the gap. Several challenges for the future and new approaches have been discussed.

The Emerging Role of Nanotechnology in Cell and Organ Transplantation

Transplantation is often the only choice many patients have when suffering from end-stage organ failure. Although the quality of life improves after transplantation, challenges, such as organ shortages, necessary immunosuppression with associated complications, and chronic graft rejection, limit its wide clinical application. Nanotechnology has emerged in the past 2 decades as a field with the potential to satisfy clinical needs in the area of targeted and sustained drug delivery, noninvasive imaging, and tissue engineering. In this article, we provide an overview of popular nanotechnologies and a summary of the current and potential uses of nanotechnology in cell and organ transplantation.

Drug Delivery Systems for Imaging and Therapy of Parkinson's Disease

BACKGROUND

Although a variety of therapeutic approaches are available for the treatment of Parkinson's disease, challenges limit effective therapy. Among these challenges are delivery of drugs through the blood brain barier to the target brain tissue and the side effects observed during long term administration of antiparkinsonian drugs. The use of drug delivery systems such as liposomes, niosomes, micelles, nanoparticles, nanocapsules, gold nanoparticles, microspheres, microcapsules, nanobubbles, microbubbles and dendrimers is being investigated for diagnosis and therapy.

METHODS

This review focuses on formulation, development and advantages of nanosized drug delivery systems which can penetrate the central nervous system for the therapy and/or diagnosis of PD, and highlights future nanotechnological approaches.

RESULTS

It is esential to deliver a sufficient amount of either therapeutic or radiocontrast agents to the brain in order to provide the best possible efficacy or imaging without undesired degradation of the agent. Current treatments focus on motor symptoms, but these treatments generally do not deal with modifying the course of Parkinson's disease. Beyond pharmacological therapy, the identification of abnormal proteins such as α -synuclein, parkin or leucine-rich repeat serine/threonine protein kinase 2 could represent promising alternative targets for molecular imaging and therapy of Parkinson's disease.

CONCLUSION

Nanotechnology and nanosized drug delivery systems are being investigated intensely and could have potential effect for Parkinson's disease. The improvement of drug delivery systems could dramatically enhance the effectiveness of Parkinson's Disease therapy and reduce its side effects.

Sirolimus-loaded polymeric micelles with honokiol for oral delivery

Objectives

The aims of the present study were to design polymeric micelles loading sirolimus with honokiol to increase drug solubility and to gain an insight into the effect of honokiol on oral transport of P-glycoprotein substrate (P-gp).

Methods

Particle size distribution, encapsulation efficiency, drug-loading content and in-vitro release of sirolimus-loaded micelles with honokiol were determined. Transport of sirolimus-loaded micelles across Caco-2 cell monolayers and jejunum segment of rats were investigated. In-vitro cytotoxicity experiments and the cellular uptake study were carried out via sulforhodamine B assay and flow cytometry, respectively.

Key findings

A coadministration of honokiol with sirolimus in micelles did not significantly modify the particle size, polydispersity index and release of drugs demonstrating successful loading within the micelles. The apparent transport coefficients (Papp) and effective permeability (Peff) of sirolimus were increased with more amount of honokiol loaded in micelles. Cellular uptake study demonstrated that rhodamine123 uptake rate was enhanced by honokiol-loaded micelles, indicating substantial P-gp inhibition action by honokiol and mPEG-PLA-based micelles.

Conclusion

Oral transport of sirolimus was significantly improved by coadministration with honokiol, an inhibitor of the P-gp, in polymeric micelles formulation.

Enhanced supersaturation and oral absorption of sirolimus using an amorphous solid dispersion based on Eudragit® e

The present study aimed to investigate the effect of Eudragit^® E/HCl (E-SD) on the degradation of sirolimus in simulated gastric fluid (pH 1.2) and to develop a new oral formulation of sirolimus using E-SD solid dispersions to enhance oral bioavailability. Sirolimus-loaded solid dispersions were fabricated by a spray drying process. A kinetic solubility test demonstrated that the sirolimus/E-SD/TPGS (1/8/1) solid dispersion had a maximum solubility of 196.7 μg/mL within 0.5 h that gradually decreased to 173.4 μg/mL after 12 h. According to the dissolution study, the most suitable formulation was the sirolimus/E-SD/TPGS (1/8/1) solid dispersion in simulated gastric fluid (pH 1.2), owing to enhanced stability and degree of supersaturation of E-SD and TPGS. Furthermore, pharmacokinetic studies in rats indicated that compared to the physical mixture and sirolimus/HPMC/TPGS (1/8/1) solid dispersion, the sirolimus/E-SD/TPGS (1/8/1) solid dispersion significantly improved oral absorption of sirolimus. E-SD significantly inhibited the degradation of sirolimus in a dose-dependent manner. E-SD also significantly inhibited the precipitation of sirolimus compared to hydroxypropylmethyl cellulose (HPMC). Therefore, the results from the present study suggest that the sirolimus-loaded E-SD/TPGS solid dispersion has great potential in clinical applications.

Characterization and pharmacokinetic analysis of crystalline versus amorphous rapamycin dry powder via pulmonary administration in rats

The pharmacokinetics of inhaled rapamycin (RAPA) is compared for amorphous versus crystalline dry powder formulations. The amorphous formulation of RAPA and lactose (RapaLac) was prepared by thin film freezing (TFF) using lactose as the stabilizing agent in the weight ratio 1:1. The crystalline formulation was prepared by wet ball milling RAPA and lactose and posteriorly blending the mixture with coarse lactose (micronized RAPA/micronized lactose/coarse lactose=0.5:0.5:19). While both powders presented good aerosolization performance for lung delivery, TFF formulation exhibited better in vitro aerodynamic properties than the crystalline physical mixture. Single-dose 24h pharmacokinetic studies were conducted in Sprague-Dawley rats following inhalation of the aerosol mist in a nose-only inhalation exposure system. Lung deposition was higher for the crystalline group than for the TFF group. Despite higher pulmonary levels of drug that were found for the crystalline group, the systemic circulation (AUC₀₋₂₄) was higher for the amorphous group (8.6 ngh/mL) than for crystalline group (2.4 ngh/mL) based on a five-compartmental analysis. Lung level profiles suggest that TTF powder stays in the lung for the same period of time as the crystalline powder but it presented higher in vivo systemic bioavailability due to its enhanced solubility, faster dissolution rate and increased FPF at a more distal part of the lungs.

Optimized formulation of solid self-microemulsifying sirolimus delivery systems

BACKGROUND

The aim of this study was to develop an optimized solid self-microemulsifying drug delivery system (SMEDDS) formulation for sirolimus to enhance its solubility, stability, and bioavailability.

METHODS

Excipients used for enhancing the solubility and stability of sirolimus were screened. A phase-separation test, visual observation for emulsifying efficiency, and droplet size analysis were performed. Ternary phase diagrams were constructed to optimize the liquid SMEDDS formulation. The selected liquid SMEDDS formulations were prepared into solid form. The dissolution profiles and pharmacokinetic profiles in rats were analyzed.

RESULTS

In the results of the oil and cosolvent screening studies, Capryol™ Propylene glycol monocapry late (PGMC) and glycofurol exhibited the highest solubility of all oils and cosolvents, respectively. In the surfactant screening test, D-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) was determined to be the most effective stabilizer of sirolimus in pH 1.2 simulated gastric fluids. The optimal formulation determined by the construction of ternary phase diagrams was the T32 (Capryol™ PGMC:glycofurol:vitamin E TPGS = 30:30:40 weight ratio) formulation with a mean droplet size of 108.2 ± 11.4 nm. The solid SMEDDS formulations were prepared with Sucroester 15 and mannitol. The droplet size of the reconstituted solid SMEDDS showed no significant difference compared with the liquid SMEDDS. In the dissolution study, the release amounts of sirolimus from the SMEDDS formulation were significantly higher than the raw sirolimus powder. In addition, the solid SMEDDS formulation was in a more stable state than liquid SMEDDS in pH 1.2 simulated gastric fluids. The results of the pharmacokinetic study indicate that the SMEDDS formulation shows significantly greater bioavailability than the raw sirolimus powder or commercial product (Rapamune® oral solution).

CONCLUSION

The results of this study suggest the potential use of a solid SMEDDS formulation for the delivery of poorly water-soluble drugs, such as sirolimus, through oral administration.

Survival of neural progenitors allografted into the CNS of immunocompetent recipients is highly dependent on transplantation site

Allografts continue to be used in clinical neurotransplantation studies; hence, it is crucial to understand the mechanisms that govern allograft tolerance. We investigated the impact of transplantation site within the brain on graft survival. Mouse [Friend leukemia virus, strain B (FVB)] glial precursors, transfected with luciferase, were injected (3 × 10(5)) into the forceps minor (FM) or striatum (STR). Immunodeficient rag2(-/-) and immunocompetent BALB/c mice were used as recipients. Magnetic resonance imaging (MRI) confirmed that cells were precisely deposited at the selected coordinates. The graft viability was assessed noninvasively with bioluminescent imaging (BLI) for a period of 16 days. Regardless of implantation site, all grafts (n = 10) deposited in immunodeficient animals revealed excellent survival. In contrast, immunocompetent animals only accepted grafts at the STR site (n = 10), whereas all the FM grafts were rejected (n = 10). To investigate the factors that led to rejection of FM grafts, with acceptance of STR grafts, another group of animals (n = 19) was sacrificed during the prerejection period, on day 5. Near-infrared fluorescence imaging with IRDye 800CW-polyethylene glycol probe displayed similar blood-brain barrier disruption at both graft locations. The morphological distribution of FM grafts was cylindrical, parallel to the needle track, whereas cells transplanted into the STR accumulated along the border between the STR and the corpus callosum. There was significantly less infiltration by both innate and adaptive immune cells in the STR grafts, especially along the calloso-striatal border. With allograft survival being dependent on the transplantation site, the anatomical coordinates of the graft target should always be taken into account as it may determine the success or failure of therapy.

Cografting of carotid body cells improves the long-term survival, fiber outgrowth and functional effects of grafted dopaminergic neurons

AIMS

A major limiting factor for cell therapy in Parkinson's disease is that the survival of grafted dopaminergic neurons is very poor, which may be improved by administration of GDNF, for which the carotid body is a good source.

MATERIALS & METHODS

Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic neuroblasts with or without cell aggregates from the rat carotid body. At 1, 2 and 3 months after grafting, the rats were tested in the cylinder and the rotometer and killed 4 months after grafting.

RESULTS

We observed that the survival of dopaminergic neurons and graft-derived dopaminergic innervation were higher in rats that received mixed grafts. Both grafted groups showed complete recovery in the amphetamine-induced rotation test. However, rats with cografts performed significantly better in the cylinder test.

CONCLUSION

Cografting of carotid body cells may constitute a useful strategy for cell therapy in Parkinson's disease.

The immunological challenges of cell transplantation for the treatment of Parkinson's disease

Dopaminergic cell transplantation is an experimental therapy for Parkinson's disease (PD). It has many potential theoretical advantages over current treatment strategies such as providing continuous local dopaminergic replenishment, eliminating motor fluctuations and medication-induced dyskinesias, slowing down disease progression or even reversing disease pathology in the host. Recent studies also show that dopaminergic cell transplants provide long-term neuromodulation in the basal ganglia that simulates the combined effects of oral dopaminergic therapy and surgical therapies like deep brain stimulation, the contemporary therapeutic approach to advanced PD. However, dopaminergic cell transplantation in PD as not been optimized and current experimental techniques have many drawbacks. In published experiments to date of attempted dopaminergic grafting in PD, the major challenges are unacceptable graft-induced dyskinesias or failure of such grafts to exceed the benefits afforded by sham surgery. A deleterious host immune response to the transplant has been implicated as a major putative cause for these adverse outcomes. This article focuses on recent advances in understanding the immunology of the transplantation in PD and possible methods to overcome adverse events such that we could translate cell replacement strategies into viable clinical treatments in the future.

Enhanced bioavailability of sirolimus via preparation of solid dispersion nanoparticles using a supercritical antisolvent process

Background

The aim of this study was to improve the physicochemical properties and bioavailability of poorly water-soluble sirolimus via preparation of a solid dispersion of nanoparticles using a supercritical antisolvent (SAS) process.

Methods

First, excipients for enhancing the stability and solubility of sirolimus were screened. Second, using the SAS process, solid dispersions of sirolimus-polyvinylpyrrolidone (PVP) K30 nanoparticles were prepared with or without surfactants such as sodium lauryl sulfate (SLS), tocopheryl propylene glycol succinate, Sucroester 15, Gelucire 50/13, and Myrj 52. A mean particle size of approximately 250 nm was obtained for PVP K30-sirolimus nanoparticles. Solid state characterization, kinetic solubility, powder dissolution, stability, and pharmacokinetics were analyzed in rats.

Results

X-ray diffraction, differential scanning calorimetry, and high-pressure liquid chromatography indicated that sirolimus existed in an anhydrous amorphous form within a solid dispersion of nanoparticles and that no degradation occurred after SAS processing. The improved supersaturation and dissolution of sirolimus as a solid dispersion of nanoparticles appeared to be well correlated with enhanced bioavailability of oral sirolimus in rats. With oral administration of a solid dispersion of PVP K30-SLS-sirolimus nanoparticles, the peak concentration and AUC_0→12h of sirolimus were increased by approximately 18.3-fold and 15.2-fold, respectively.

Conclusion

The results of this study suggest that preparation of PVP K30-sirolimus-surfactant nanoparticles using the SAS process may be a promising approach for improving the bioavailability of sirolimus.

Cationic Gd-DTPA liposomes for highly efficient labeling of mesenchymal stem cells and cell tracking with MRI

In the current study cell labeling was performed with water-soluble gadolinium (Gd)-DTPA containing liposomes, to allow for cell tracking by MRI. Liposomes were used to assure a highly concentrated intracellular build up of Gd, aiming to overcome the relatively low MRI sensitivity of Gd (compared to T2 contrast agents). Liposomes were positively charged (cationic) to facilitate uptake by binding to anionic charges in the cell membrane of bone marrow-derived mesenchymal stem cells (MSCs). We determined the cellular Gd load by variations in labeling time (1, 4, and 24 h) and liposome concentration (125, 250, 500, 1000 μM lipid), closely monitoring effects on cell viability, proliferation rate, and differentiation ability. Labeling was both time and dose dependent. Labeling for 4 h was most efficient regarding the combination of processing time and final cellular Gd uptake. Labeling for 4 h with low-dose concentration (125 μM lipid, corresponding to 52 ± 3 μM Gd) yielded an intracellular load of 30 ± 2.5 pg Gd cell(-1), without any effects on cell viability, proliferation, and cell differentiation. Gd liposomes, colabeled with fluorescent dyes, exhibited a prolonged cellular retention, with an endosomal distribution pattern. In vitro assay over 20 days demonstrated a drop in the average Gd load per cell, as a result of mitosis. However, there was no significant change in the sum of the Gd load in all daughter cells at endpoint (20 days), indicating an excellent cellular retention of Gd. MSCs labeled with Gd liposomes were imaged with MRI at both 1.5T and 3.0T, resulting in excellent visualization both in vitro and in vivo. Prolonged in vivo imaging of 500,000 Gd-labeled cells was possible for at least 2 weeks (3.0T). In conclusion, Gd-loaded cationic liposomes (125 μM lipid) are an excellent candidate to label cells, without detrimental effects on cell viability, proliferation, and differentiation, and can be visualized by MRI.

Development and characterization of liposomal formulations for rapamycin delivery and investigation of their antiproliferative effect on MCF7 cells

Rapamycin (Sirolimus) is a macrolide lactone with antifungal, immunosuppressant, and antiproliferative actions. The mechanism of rapamycin action involves the inhibition of mTOR and subsequent cytostasis. Rapamycin also prevents angiogenesis in tumors and can prevent cancer cells' resistance to other chemotherapeutic agents. However, very poor water solubility, bioavailability, only slight solubility in acceptable parenteral excipients, chemical instability, and major sequestration (95%) of free rapamycin into the erythrocytes have prevented its development as an anticancer drug. To address these problems, it was attempted to develop liposomal rapamycin delivery systems in this study. Conventional and pegylated liposomes were prepared with various lipid and cholesterol ratios. They were then characterized; these liposomes contained 0.68-0.90 mg of rapamycin per milliliter of liposome suspension. Having suitable particle size, these liposomes successfully retained the entrapped drug. Both types of liposomes were found to be effective; however, conventional liposomes showed better antiproliferative activity against MCF-7 cells than pegylated liposomes. But, pegylated liposome showed better stability than conventional liposomes. In conclusion, the enhanced permeability and retention effects of tumors should provide the opportunity for pegylated liposomal rapamycin to be applied as an intravenous drug-delivery system for targeted delivery to cancer cells, avoiding the major sequestration of free rapamycin into the erythrocytes.

Gene and cell delivery to the degenerated striatum: status of preclinical efforts in primate models

Significant progress has been achieved in developing restorative neurosurgical strategies for movement disorders on the basis of preclinical gene and cell therapy experiments in primates. Because of the unique similarities between human and primate anatomy and physiology, experiments in primate models are the critical step in translating these innovative neurosurgical treatment concepts into successful human applications. To clarify progress toward this goal, we have examined recent preclinical data regarding the delivery of gene and cell therapy to the lesioned primate striatum. Improved behavioral outcomes after in vivo gene transduction, achieved by brain delivery of adeno-associated vectors, have resulted in the initiation of ongoing clinical trials. Cell transplantation experiments are transitioning from the grafting of fetal tissue, which has met with mixed clinical success, to the grafting of expanded neural stem cells, for which preliminary results in primates are encouraging. Careful attention to the surgical delivery parameters for these agents in primate studies, along with the ability to realistically model imaging and behavioral outcomes in these animals, is essential for optimizing the restoration of function for patients. The authors review data obtained from primate models that form the basis for ongoing clinical trials to consider how new preclinical models should be developed to answer questions that arise from experimental clinical data.

Nanomedicines in renal transplant rejection--focus on sirolimus

Nanomedicine, known as the application of nanotechnology in medicine, has been applied to overcome the problems of poor bioavailability, in vitro and in vivo stability, and targeted delivery in the preparation of pharmaceutical products. Sirolimus, a water-insoluble immunosuppressant, has been formulated into an oral solid dosage form by using NanoCrystal^® technology to increase the water solubility and thereby the bioavailability. The efficacy, safety, and pharmacokinetic properties are not significantly different between liquid and solid formulations except that less fluctuation of sirolimus blood concentration was observed in solid dosage form. The tablet formulation offers the advantages of better palatability and more convenience for long-term use. Sirolimus tablets are not only a successful example of nanomedicine, but also a more cost-effective treatment in renal transplantation than cyclosporine and tacrolimus.

Intracerebral co-transplantation of liposomal tacrolimus improves xenograft survival and reduces graft rejection in the hemiparkinsonian rat

Immunosuppression remains a key issue in neural transplantation. Systemic administration of cyclosporin-A is currently widely used but has many severe adverse side effects. Newer immunosuppressive agents, such as tacrolimus (TAC) and rapamycin (RAPA), have been investigated for their neuroprotective properties on dopaminergic neurons. These drugs have been formulated into liposomal preparations [liposomal tacrolimus (LTAC) and liposomal rapamycin (LRAPA)] which retain these neuroprotective properties. Due to the slower release of the drugs from the liposomes, we hypothesized that co-transplantation of either LTAC or LRAPA within a xenogeneic cell suspension would increase cell survival and decrease graft rejection in the hemiparkinsonian rat, and that a combination of the two drugs may have a synergistic effect. 6-hydroxydopamine-lesioned rats were divided to four groups which received intra-striatal transplants of the following: 1) a cell suspension containing 400,000 fetal mouse ventral mesencephalic cells; 2) the cell suspension containing 0.63 microM LRAPA; 3) the cell suspension containing a dose of 2.0 microM LTAC; 4) the cell suspension containing 2.0 microM LTAC and 0.63 microM LRAPA. Functional recovery was assessed by amphetamine-induced rotational behavior. Animals were killed at 4 days or 6 weeks post-transplantation, and immunohistochemistry was performed to look at the expression of tyrosine hydroxylase and major histocompatibility complex classes I and II. Only the group receiving LTAC had a decrease in rotational behavior. This observation correlated well with significantly more surviving tyrosine hydroxylase immunoreactive cells compared with the other groups and significantly lower levels of immunorejection as assessed by major histocompatibility complex class I and II staining. This study has shown the feasibility of using local immunosuppression in xenotransplantation. These findings may be useful in optimizing immunosuppression in experimental neural transplantation in the laboratory and its translation into the clinical setting.

Pharmacological targeting of catalyzed protein folding: the example of peptide bond cis/trans isomerases

Peptide bond isomerases are involved in important physiological processes that can be targeted in order to treat neurodegenerative disease, cancer, diseases of the immune system, allergies, and many others. The folding helper enzyme class of Peptidyl-Prolyl-cis/trans Isomerases (PPIases) contains the three enzyme families of cyclophilins (Cyps), FK506 binding proteins (FKBPs), and parvulins (Pars). Although they are structurally unrelated, all PPIases catalyze the cis/trans isomerization of the peptide bond preceding the proline in a polypeptide chain. This process not only plays an important role in de novo protein folding, but also in isomerization of native proteins. The native state isomerization plays a role in physiological processes by influencing receptor ligand recognition or isomer-specific enzyme reaction or by regulating protein function by catalyzing the switch between native isomers differing in their activity, e.g., ion channel regulation. Therefore elucidating PPIase involvement in physiological processes and development of specific inhibitors will be a suitable attempt to design therapies for fatal and deadly diseases.

Failure of FK506 (tacrolimus) to alleviate apomorphine-induced circling in rat Parkinson model in spite of some cytoprotective effects in SH-SY5Y dopaminergic cells

The mechanism of action of the neurotoxin 6-hydroxydopamine (6-OHDA) is thought to involve the generation of free radicals and subsequent apoptotic processes. We have demonstrated in vitro that the neuroimmunophilin, FK506 (10-100 nM), dose dependently and significantly restored the ROS production to the control level, increased the Bcl-2 protein level, partly inhibited the cytochrome C release from mitochondria and reduced the caspase-3 activation in SH-SY5Y cells. On the other hand, there was no significant restoration of the ATP level by FK506 and the toxin activated proteins, p53 and Bax, were not normalized by FK506. In support of these latter results, daily administration of FK506 for 7 days to rats (0.5, 1 and 3 mg/kg i.p.) did not significantly prevent the apomorphine-induced contralateral circling, measured 2 weeks after unilateral nigral lesioning. Moreover, FK506 pretreatment did not significantly lower the toxin elevated lipid peroxidation levels, indicating that oxidative stress was present even after the FK506 treatment in the lesioned striatum. Taken together, our results with FK506 are inconsistent. We confirm the antioxidant nature of FK506, that is, it blocks ROS production in SH-SY5Y cells. However, there were no significant protective effects in any apoptotic analyses in SH-SY5Y cells and in animal studies, a 7-day FK506 pre-treatment was not able to reverse the toxic effect of 6-OHDA in a rat model of Parkinson's disease.