Synthesis, characterization, and evaluation of pluronic-based β-cyclodextrin polyrotaxanes for mobilization of accumulated cholesterol from Niemann-Pick type C fibroblasts

Synthesis of cyclodextrin-based polyrotaxanes and polycatenanes for supramolecular pharmaceutical sciences

Cyclodextrins (CDs) are essential in the pharmaceutical industry and have long been used as food and pharmaceutical additives. CD-based interlocked molecules, such as rotaxanes, polyrotaxanes, catenanes, and polycatenanes, have been synthesized and have attracted considerable attention in supramolecular chemistry. Among them, CD polyrotaxanes have been employed as slide-ring materials and biomaterials. CD polycatenanes are new materials; therefore, to date, no examples of applied research on CD polycatenanes have been reported. Consequently, we expect that applied research on CD polycatenanes will accelerate in the future. This review article summarizes the syntheses and structural analyses of CD polyrotaxanes and polycatenanes to facilitate their applications in the pharmaceutical industry. We believe that this review will promote further research on CD-based interlocked molecules.

Cyclodextrins and derivatives in drug delivery: New developments, relevant clinical trials, and advanced products

Cyclodextrins (CD) and derivatives are functional excipients that can improve the bioavailability of numerous drugs. Because of their drug solubility improving properties they are used in many pharmaceutical products. Furthermore, the stability of small molecular drugs can be improved by the incorporation in CDs and an unpleasant taste and smell can be masked. In addition to well-established CD derivatives including hydroxypropyl-β-CD, hydroxypropyl-γ-CD, methylated- β-CD and sulfobutylated- β-CD, there are promising new derivatives in development. In particular, CD-based polyrotaxanes exhibiting cellular uptake enhancing properties, CD-polymer conjugates providing sustained drug release, enhanced cellular uptake, and mucoadhesive properties, and thiolated CDs showing mucoadhesive, in situ gelling, as well as permeation and cellular uptake enhancing properties will likely result in innovative new drug delivery systems. Relevant clinical trials showed various new applications of CDs such as the formation of CD-based nanoparticles, stabilizing properties for protein drugs or the development of ready-to-use injection systems. Advanced products are making use of various benefical properties of CDs at the same time. Within this review we provide an overview on these recent developments and take an outlook on how this class of excipients will further shape the landscape of drug delivery.

Polymer-based drug delivery systems under investigation for enzyme replacement and other therapies of lysosomal storage disorders

Lysosomes play a central role in cellular homeostasis and alterations in this compartment associate with many diseases. The most studied example is that of lysosomal storage disorders (LSDs), a group of 60 + maladies due to genetic mutations affecting lysosomal components, mostly enzymes. This leads to aberrant intracellular storage of macromolecules, altering normal cell function and causing multiorgan syndromes, often fatal within the first years of life. Several treatment modalities are available for a dozen LSDs, mostly consisting of enzyme replacement therapy (ERT) strategies. Yet, poor biodistribution to main targets such as the central nervous system, musculoskeletal tissue, and others, as well as generation of blocking antibodies and adverse effects hinder effective LSD treatment. Drug delivery systems are being studied to surmount these obstacles, including polymeric constructs and nanoparticles that constitute the focus of this article. We provide an overview of the formulations being tested, the diseases they aim to treat, and the results observed from respective in vitro and in vivo studies. We also discuss the advantages and disadvantages of these strategies, the remaining gaps of knowledge regarding their performance, and important items to consider for their clinical translation. Overall, polymeric nanoconstructs hold considerable promise to advance treatment for LSDs.

Structure-function relationships of cholesterol mobilization from the endo-lysosome compartment of NPC1-deficient human cells by β-CD polyrotaxanes

Niemann-Pick Type C is a rare metabolic disorder characterized by the cellular accumulation of cholesterol within endosomal and lysosomal compartments. 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD) containing polyrotaxanes represent an attractive approach for treating this disease due to their ability to circulate in the blood stream for longer periods of time as a prodrug form of HP-β-CD. Once inside the cell, the macromolecular structure is thought to break down into the Pluronic precursor and the active cyclodextrin agent that promotes cholesterol mobilization from the aberrant accumulations within NPC-deficient cells. We now report that both cholesterol and decaarginine (R10) endcapped polyrotaxanes are able to remove cholesterol from NPC1 patient fibroblasts. R10 endcapped materials enter these cells and are localized within endosomes after 16 h. The cholesterol mobilization from endo-lysosomal compartments of NPC1 cells by the polyrotaxanes was directly related to their extent of endcapping and their threading efficiency. Incorporation of 4-sulfobutylether-β-cyclodextrin (SBE-β-CD) significantly improved cholesterol mobilization due to the improved solubility of the compounds. Additionally, in our efforts to scale-up the synthesis for preclinical studies, we prepared a library of polyrotaxanes using a solid phase synthesis method. These compounds also led to significant cholesterol mobilization from the cells, however, cytotoxicity studies showed that they were substantially more toxic than those prepared by the solvent-assisted method, thus limiting the therapeutic utility of agents prepared by this expedited method. Our findings demonstrate that complete endcapping of the polyrotaxanes and improved solubility are important design features for delivering high copy numbers of therapeutic β-CD to promote enhanced sterol clearance in human NPC1-deficient cells.

Hierarchically Releasing Bio-Responsive Nanoparticles for Complete Tumor Microenvironment Modulation via TGF-β Pathway Inhibition and TAF Reduction

The aggressive progression of breast cancer is impacted significantly by the tumor microenvironment (TME). The current chemotherapy normally causes cytotoxicity to tumor cells, while does not effectively modulate the TME. Thus, the chemotherapy effect of breast cancer is usually dissatisfactory. In this study, a kind of hierarchically releasing bio-responsive nanoparticles (R(D)/H(S) NPs), constructed by β-cyclodextrin-grafted heparin and pH-sensitive pseudorotaxane, were investigated to enhance the breast cancer chemotherapeutic efficacy through TME modulation. Doxorubicin (DOX) and transforming growth factor-β (TGF-β) receptor inhibitor (SB431542) loaded onto R(D)/H(S) NPs were released rapidly for the respective response to low pH in endosomes/lysosomes and heparanase (HPSE) in TME. Our results showed that R(D)/H(S) NPs effectively inhibited the formation of tumor-associated fibroblasts (TAFs) and reduced TGF-β and collagen I secretion. Besides, the immunosuppressive microenvironment was effectively reversed into immunogenic, characterized by increased CD8⁺ and CD4⁺ T cell infiltration, which distinctly inhibited breast cancer metastasis. Therefore, R(D)/H(S) NPs remodeled the TME by downregulating TAFs, TGF-β, and collagen I; activating the immune microenvironment; and then amplifying the chemotherapeutic efficacy of DOX.

Biodegradable Polyester of Poly (Ethylene glycol)-sebacic Acid as a Backbone for β -Cyclodextrin-polyrotaxane: A Promising Gene Silencing Vector

BACKGROUND

Polyrotaxane, a macromolecular interlocked assembly, consisting of cyclodextrin has excellent inclusion capabilities and functionalization capacity, which makes it a versatile material as a vector for gene delivery applications.

OBJECTIVE

A biodegradable linear aliphatic polyester axle composed of Polyethylene Glycol (PEG) and Sebacic Acid (SA) was used to fabricate the β-Cyclodextrin (β-CD) based polyrotaxane as a cationic polymeric vector and evaluated for its potential gene silencing efficiency.

METHODS

The water-soluble aliphatic polyester was synthesized by the solvent esterification process and characterized using viscometry, GPC, FT-IR and 1H NMR spectroscopy. The synthesized polyester was further evaluated for its biodegradability and cellular cytotoxicity. Hence, this water-soluble polyester was used for the step-wise synthesis of polyrotaxane, via threading and blocking reactions. Threading of β-CD over PEG-SA polyester axle was conducted in water, followed by end-capping of polypseudorotaxane using 2,4,6-trinitrobenzenesulfonic acid to yield polyester-based polyrotaxane. For gene delivery application, cationic polyrotaxane (PRTx⁺) was synthesized and evaluated for its gene loading and gene silencing efficiency.

RESULTS AND DISCUSSION

The resulting novel macromolecular assembly was found to be safe for use in biomedical applications. Further, characterization by GPC and ¹H NMR techniques revealed successful formation of PE-β-CD-PRTx with a threading efficiency of 16%. Additionally, the cellular cytotoxicity assay indicated biosafety of the synthesized polyrotaxane, exploring its potential for gene delivery and other biomedical applications. Further, the biological profile of PRTx⁺: siRNA complexes was evaluated by measuring their zeta potential and gene silencing efficiency, which were found to be comparable to Lipofectamine 3000, the commercial transfecting agent.

CONCLUSION

The combinatory effect of various factors such as biodegradability, favourable complexation ability, near zero zeta potentials, good cytotoxicity properties of poly (ethylene glycol)-sebacic acid based β-Cyclodextrin-polyrotaxane makes it a promising gene delivery vector for therapeutic applications.

Recent advances in the treatment of Niemann pick disease type C: A mini-review

Niemann Pick disease Type C (NPC) is a recessive rare disease caused by the mutation on NPC1 and/or NPC2 genes changing the processing of the Low-density proteins (LDL) resulting in an accumulation of lipids in the cells. Until today there is not a cure, the current treatment is based on palliative affairs to reduce the symptoms and prevent its appearance. Among all the treatments proposed the use of cyclodextrins (CDs), nanocarriers which can complex cholesterol, is one of the most useful alternatives. Indeed, for several years 2-hydroxypropyl-β-CD (HPβ-CD) is approved as orphan drug for FDA and EMA to the treatment. However, different CDs based materials are created each year to improve the cholesterol uptake. This review is focused on the novelty of CD based materials for NPC treatment.

PEGylated β-cyclodextrins: Click synthesis and in vitro biological insights

We present three easily rationalized star-shaped PEGylated β-cyclodextrin (βCD) derivatives synthesized via conjugation of different molecular weight PEG chains (5000, 2000, and 550 Da) to the βCD primary face by click chemistry (βCD-PEG₅₀₀₀, βCD-PEG₂₀₀₀, βCD-PEG₅₅₀ respectively). βCDPEG systems are envisioned to further carry bioactive molecules, therefore, their interactions with biological interfaces must be determined at an early stage of development. Hence, the effect of βCDPEGs chain length on cell viability was investigated. To this aim, three models were selected: Vero cells for their fibroblast-like features; HeLa cells that are commonly used for preliminary viability screening; and human peripheral monocytes which are macrophage precursors. Of the three pegylated derivatives, βCD-PEG₅₅₀ was the one that significantly affected HeLa cells and human monocytes viability. Despite the popularity of PEGylation approach, our results underscore the importance of careful and systematic PEGylated materials design for their future success in drug delivery systems.

Synthesis of the Anionic Hydroxypropyl-β-cyclodextrin:Poly(decamethylenephosphate) Polyrotaxane and Evaluation of its Cholesterol Efflux Potential in Niemann-Pick C1 Cells

Niemann-Pick type C disease (NPC) is a lysosomal storage disease that is characterized by a progressive accumulation of unesterified cholesterol in the lysosomes leading to organ damage from cell dysfunction. Hydroxypropyl-β-cyclodextrin (HP-β-CD) is an attractive drug candidate for treating NPC, as it diminishes cholesterol accumulation in NPC cells. Systemic HP-β-CD treatment, however, is limited by rapid renal clearance. We designed a new anionic HP-β-CD polyrotaxane to act as a slow release formulation based on a polyalkylene phosphate core to improve the pharmacokinetics. The polyalkylene phosphate comprises hydrophobic decamethylene spacers linked by biodegradable anionic phosphodiester bonds. HP-β-CD was threaded onto this polymer first and α-CD afterwards to prevent burst release of the threaded HP-β-CD. Our findings show that HP-β-CD was slowly released from the watersoluble polyrotaxane over a 30 days period. The polyrotaxane provided persistently diminished cholesterol levels in NPC1 cells by 20% relative to untreated cells. These results demonstrate the therapeutic potential of this novel HP-β-CD polyrotaxane for the mobilization of aberrantly stored cholesterol in NPC1 cells.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Linear Cyclodextrin Polymer Prodrugs as Novel Therapeutics for Niemann-Pick Type C1 Disorder

Niemann-Pick Type C1 disorder (NPC) is a rare lysosomal storage disease characterized by the accumulation of cholesterol in lysosomes. NPC has no FDA approved treatments yet, however 2-hydroxypropyl-β-cyclodextrin (HPβCD) has shown efficacy for treating the disease in both mouse and feline NPC models and is currently being investigated in late stage clinical trials. Despite promising results, therapeutic use of HPβCD is limited by the need for high doses, ototoxicity and intrathecal administration. These limitations can be attributed to its poor pharmacokinetic profile. In the attempt to overcome these limitations, we have designed a β-cyclodextrin (βCD) based polymer prodrugs (ORX-301) for an enhanced pharmacokinetic and biodistribution profile, which in turn can potentially provide an improved efficacy at lower doses. We demonstrated that subcutaneously injected ORX-301 extended the mean lifespan of NPC mice at a dosage 5-fold lower (800 mg/kg, body weight) the HPβCD dose proven efficacious (4000 mg/kg). We also show that ORX-301 penetrates the blood brain barrier and counteracts neurological impairment. These properties represent a substantial improvement and appear to overcome major limitations of presently available βCD-based therapy, demonstrating that this novel prodrug is a valuable alternative/complement for existing therapies.

Supramolecular Pharmaceutical Sciences: A Novel Concept Combining Pharmaceutical Sciences and Supramolecular Chemistry with a Focus on Cyclodextrin-Based Supermolecules

Supramolecular chemistry is an extremely useful and important domain for understanding pharmaceutical sciences because various physiological reactions and drug activities are based on supramolecular chemistry. However, it is not a major domain in the pharmaceutical field. In this review, we propose a new concept in pharmaceutical sciences termed "supramolecular pharmaceutical sciences," which combines pharmaceutical sciences and supramolecular chemistry. This concept could be useful for developing new ideas, methods, hypotheses, strategies, materials, and mechanisms in pharmaceutical sciences. Herein, we focus on cyclodextrin (CyD)-based supermolecules, because CyDs have been used not only as pharmaceutical excipients or active pharmaceutical ingredients but also as components of supermolecules.

Removal of trace thorium(IV) from aqueous solutions using a pseudo-polyrotaxane

The adsorption of thorium(IV) was studied using a pseudo-polyrotaxane, which was obtained by the reaction of poly(propyleneglycol) (PPG) and 6-OTs-β-CD. The adsorption of thorium(IV) was examined as a function of the contact time, pH of the solution, adsorbent dose, concentration of thorium(IV) and temperature using batch adsorption experiments. The experimental results suggested that the optimum conditions were found to be at pH 3.5, contact time 40 min, 10 mg adsorbent doses, 20 mg L−1 thorium(IV) concentration and 298 K. The maximum adsorption capacity was found to be 15.366 mg g−1. The thermodynamic parameters (ΔG 0<0, ΔH 0<0) were calculated, the result showed that the adsorption of thorium(IV) was exothermic and spontaneous process.

Pluronic based β-cyclodextrin polyrotaxanes for treatment of Niemann-Pick Type C disease

Niemann-Pick Type C disease (NPC) is a rare metabolic disorder characterized by disruption of normal cholesterol trafficking within the cells of the body. There are no FDA approved treatments available for NPC patients. Recently, the cycloheptaglucoside 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) has shown efficacy as a potential NPC therapeutic by extending lifetime in NPC mice, delaying neurodegeneration, and decreasing visceral and neurological cholesterol burden. Although promising, systemic HP-β-CD treatment is limited by a pharmacokinetic profile characterized by rapid loss through renal filtration. To address these shortcomings, we sought to design a family of HP-β-CD pro-drug delivery vehicles, known as polyrotaxanes (PR), capable of increasing the efficacy of a given injected dose by improving both pharmacokinetic profile and bioavailability of the HP-β-CD agent. PR can effectively diminish the cholesterol pool within the liver, spleen, and kidney at molar concentrations 10-to-100-fold lower than monomeric HP-β-CD. In addition to this proof-of-concept, use of PR scaffolds with differing physiochemical properties reveal structure-activity relationships in which PR characteristics, including hydrophobicity, threading efficiency and surface charge, were found to both decisively and subtly effect therapeutic efficacy. PR scaffolds exhibit absorption, pharmacokinetics, and biodistribution patterns that are significantly altered from monomeric HP-β-CD. In all, PR scaffolds hold great promise as potential treatments for visceral disease in NPC patients.

Potential Use of Cyclodextrins as Drug Carriers and Active Pharmaceutical Ingredients

Cyclodextrins (CyDs) are extensively used in various fields, and especially have been widely utilized as pharmaceutical excipients and drug carriers in the pharmaceutical field. Owing to the multi-functional and biocompatible characteristics, CyDs can improve the undesirable properties of drug molecules. This review outlines the current application of CyDs in pharmaceutical formulations, focusing on their use as CyD-based drug carriers for several kinds of drugs. Additionally, CyDs have great potential as active pharmaceutical ingredients against various diseases with few side effects.

Stoppering/unstoppering of a rotaxane formed between an N-hetorycle ligand containing surfactant: β-cyclodextrin pseudorotaxane and pentacyanoferrate(II) ions

The assembly of a surfactant-based rotaxane by adding the labile aquopentacyanoferrate(II) ion to the previously formed pseudorotaxane between the surfactant 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide and β-cyclodextrin was investigated by ¹H NMR and kinetic measurements. NMR spectroscopy has showed that the rotaxane can be formed through two different mechanisms. The rotaxane can be unstoppered by using the pyridine ligand substitution reaction by the high-field cyanide ligand. In this work a new method is developed for the preparation of several new surfactant-based rotaxanes by changing the hydrophilic and hydrophobic regions of the surfactants and the nature of the macrocycle.

Influence of Molecular Structure on the In Vivo Performance of Flexible Rod Polyrotaxanes

Polyrotaxanes, a family of rod-shaped nanomaterials comprised of noncovalent polymer/macrocycle assemblies, are being used in a growing number of materials and biomedical applications. Their physiochemical properties can vary widely as a function of composition, potentially leading to different in vivo performance outcomes. We sought to characterize the pharmacokinetic profiles, toxicities, and protein corona compositions of 2-hydroxypropyl-β-cyclodextrin polyrotaxanes as a function of variations in macrocycle threading efficiency, molecular weight, and triblock copolymer core structure. We show that polyrotaxane fate in vivo is governed by the structure and dynamics of their rodlike morphologies, such that highly threaded polyrotaxanes are long circulating and deposit in the liver, whereas lung deposition and rapid clearance is observed for species bearing lower 2-hydroxypropyl-β-cyclodextrin threading percentages. Architecture differences also promote recruitment of different serum protein classes and proportions; however, physiochemical differences have little or no influence on their toxicity. These findings provide important structural insights for guiding the development of polyrotaxanes as scaffolds for biomedical applications.

Efficient pDNA Delivery Using Cationic 2-Hydroxypropyl-β-Cyclodextrin Pluronic-Based Polyrotaxanes

A family of cationic Pluronic-based polyrotaxanes (PR(+)), threaded with 2-hydroxypropyl-β-cyclodextrin (HPCD), was synthesized for pDNA delivery into multiple cell lines. All PR(+) formed highly stable, positively charged pDNA complexes that were < 250 nm in diameter. The cellular uptake and pDNA transfection efficiencies of the PR(+):pDNA complexes was enhanced relative to the commercial transfection standards L2K and bPEI, while displaying similar or lower toxicity profiles. Charge density and threading efficiency of the PR(+) agent significantly influenced the colloidal stability and physical properties of the complexes, which impacted their intracellular transfection efficiencies. Taken together, our results suggest that HPCD: Pluronic PR(+) can be used as potent vectors for pDNA-based therapeutics.

Impact of Mixed β-Cyclodextrin Ratios on Pluronic Rotaxanation Efficiency and Product Solubility

Water-soluble polyrotaxanes have been prepared under heterogeneous conditions from mixtures of β-cyclodextrin (β-CD), 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), methyl-β-cyclodextrin, or 6-monoazido-β-cyclodextrin with 4-sulfobutyl ether-β-cyclodextrin (SBE-β-CD) and Pluronic L81 copolymer modified with cholesterol end caps. Threading reactions gave polyrotaxane products in modest chemical yield that were reflective of the β-CD feed ratios in the reaction. Polyrotaxanes containing mixtures of HP-β-CD and SBE-β-CD were screened and found to be biologically active in an in vitro model of Niemann-Pick Type C disease where they mobilize aberrantly stored cholesterol similarly to monomeric cyclodextrin controls.

Gd3+-1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-2-hydroxypropyl-β-cyclodextrin/Pluronic Polyrotaxane as a Long Circulating High Relaxivity MRI Contrast Agent

A multivalent magnetic resonance imaging agent based on a 2-hydroxypropyl-β-cyclodextrin (HPCD):Pluronic F127 polyrotaxane carrier has been synthesized, and its blood pool contrast properties have been characterized. This Gd3+-DO3A-HPCD/Pluronic polyrotaxane construct is shown to circulate for more than 30 min and provide >100-fold vascular enhancement relative to the monomeric Gd3+-DO3A-HPCD control that is rapidly cleared via the kidney. The high r1 relaxivity at 37 °C (23.83 mM(-1) s(-1) at 1.5 T; 34.08 mM(-1) s(-1) at 0.5 T), extended blood circulation, well-known pharmacology of the polyrotaxane precursors, and absence of acute toxicity make it a highly attractive blood pool contrast agent candidate.

Systemic administration of 2-hydroxypropyl-β-cyclodextrin to symptomatic Npc1-deficient mice slows cholesterol sequestration in the major organs and improves liver function

In Niemann-Pick type C (NPC) disease, loss-of-function mutations in either NPC1 or NPC2 result in progressive accumulation of unesterified cholesterol (UC) and glycosphingolipids in all organs, leading to neurodegeneration, pulmonary dysfunction and sometimes liver failure. There is no cure for this disorder. Studies using primarily NPC mouse models have shown that systemic administration of 2-hydroxypropyl-β-cyclodextrin (2HPβCD), starting in early neonatal life, diminishes UC accumulation in most organs, slows disease progression and extends lifespan. The key question now is whether delaying the start of 2HPβCD treatment until early adulthood, when the amount of entrapped UC throughout the body is markedly elevated, has any of the benefits found when treatment begins at 7 days of age. In the present study, Npc1(-/-) and Npc1(+/+) mice were given saline or 2HPβCD subcutaneously at 49, 56, 63 and 70 days of age, with measurements of organ weights, liver function tests and tissue cholesterol levels performed at 77 days. In Npc1(-/-) mice, treatment with 2HPβCD from 49 days reduced whole-liver cholesterol content at 77 days from 33.0 ± 1.0 to 9.1 ± 0.5 mg/organ. Comparable improvements were seen in other organs, such as the spleen, and in the animal as a whole. There was a transient increase in biliary cholesterol concentration in Npc1(-/-) mice after 2HPβCD. Plasma alanine aminotransferase and aspartate aminotransferase activities in 77-day-old 2HPβCD-treated Npc1(-/-) mice were reduced compared with saline-treated controls. The lifespan of Npc1(-/-) mice given 2HPβCD marginally exceeded that of the saline-treated controls (99 ± 1.1 vs 94 ± 1.4 days, respectively; P < 0.05). Thus, 2HPβCD is effective in mobilizing entrapped cholesterol in late-stage NPC disease leading to improved liver function.

Niemann-Pick C disease and mobilization of lysosomal cholesterol by cyclodextrin

Niemann-Pick type C (NPC) disease is a lysosomal storage disease in which endocytosed cholesterol becomes sequestered in late endosomes/lysosomes (LEs/Ls) because of mutations in either the NPC1 or NPC2 gene. Mutations in either of these genes can lead to impaired functions of the NPC1 or NPC2 proteins and progressive neurodegeneration as well as liver and lung disease. NPC1 is a polytopic protein of the LE/L limiting membrane, whereas NPC2 is a soluble protein in the LE/L lumen. These two proteins act in tandem and promote the export of cholesterol from LEs/Ls. Consequently, a defect in either NPC1 or NPC2 causes cholesterol accumulation in LEs/Ls. In this review, we summarize the molecular mechanisms leading to NPC disease, particularly in the CNS. Recent exciting data on the mechanism by which the cholesterol-sequestering agent cyclodextrin can bypass the functions of NPC1 and NPC2 in the LEs/Ls, and mobilize cholesterol from LEs/Ls, will be highlighted. Moreover, the possible use of cyclodextrin as a valuable therapeutic agent for treatment of NPC patients will be considered.

Lysosomal-specific cholesterol reduction by biocleavable polyrotaxanes for ameliorating Niemann-Pick type C disease

Niemann-Pick type C (NPC) disease is an autosomal recessive lysosomal trafficking disorder, in which the cholesterols are abnormally accumulated in lysosomes. Recently, the β-cyclodextrin (CD) derivatives are revealed to show therapeutic effect for NPC disease through the removal of accumulated cholesterols in lysosomes. Herein, to enhance the therapeutic effect and reduce the toxicity of β-CD derivatives, biocleavable Pluronic/β-CD-based polyrotaxanes (PRXs) bearing terminal disulfide linkages that can release threaded β-CDs in lysosomes were developed. The biocleavable PRXs show negligible interaction with the plasma membrane, leading to avoiding the toxicity of β-CDs derived from their hydrophobic cavity. Additionally, lysosomal release of threaded β-CDs from biocleavable PRXs by the intracellular cleavage of terminal disulfide linkages is found to achieve approximately 100-fold higher cholesterol removal ability from NPC disease-derived cells than β-CD derivatives. Consequently, the biocleavable PRXs is considered to be a noninvasive and effective therapeutics for NPC disease.

Synthesis of 2-hydroxypropyl-β-cyclodextrin/pluronic-based polyrotaxanes via heterogeneous reaction as potential Niemann-Pick type C therapeutics

Five polyrotaxanes were synthesized by threading 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) onto a variety of α,ω-ditriethylenediamino-N-carbamoyl-poly-(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic) triblock copolymers using a two-pot strategy under heterogeneous, nonaqueous conditions. The threaded HP-β-CD units were retained on the pseudopolyrotaxane precursors by end-capping the branched diamine termini with sodium 2,4,6-trinitrobenzene sulfonate. Inclusion of the Pluronic copolymers within the HP-β-CD cavities was more favorable in nonpolar solvents, such as diethyl ether and n-hexane, both of which gave better coverage ratios than polar solvents. (1)H NMR and MALDI-TOF were used to estimate the average molecular weights of the purified polyrotaxane products. A globular morphology of aggregated polyrotaxanes was observed by tapping-mode AFM imaging of dried samples. Treatment of Niemann-Pick C (NPC) type 2-deficient fibroblasts with the polyrotaxane derivatives produced substantial reductions in sterol accumulation, as seen by diminished filipin staining in these cells, suggesting that Pluronic-based polyrotaxanes may be promising vehicles for delivery of HP-β-CD to cells with abnormal cholesterol accumulation.