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

β-Cyclodextrin-threaded biocleavable polyrotaxanes ameliorate impaired autophagic flux in Niemann-Pick type C disease

Niemann-Pick type C (NPC) disease is characterized by the lysosomal accumulation of cholesterols and impaired autophagic flux due to the inhibited fusion of autophagosomes to lysosomes. We have recently developed β-cyclodextrin (β-CD)-threaded biocleavable polyrotaxanes (PRXs), which can release threaded β-CDs in response to intracellular environments as a therapeutic for NPC disease. The biocleavable PRXs exhibited effective cholesterol reduction ability and negligible toxic effect compared with hydroxypropyl-β-CD (HP-β-CD). In this study, we investigated the effect of biocleavable PRX and HP-β-CD on the impaired autophagy in NPC disease. The NPC patient-derived fibroblasts (NPC1 fibroblasts) showed an increase in the number of LC3-positive puncta compared with normal fibroblasts, even in the basal conditions; the HP-β-CD treatment markedly increased the number of LC3-positive puncta and the levels of p62 in NPC1 fibroblasts, indicating that autophagic flux was further perturbed. In sharp contrast, the biocleavable PRX reduced the number of LC3-positive puncta and the levels of p62 in NPC1 fibroblasts through an mTOR-independent mechanism. The mRFP-GFP-LC3 reporter gene expression experiments revealed that the biocleavable PRX facilitated the formation of autolysosomes to allow for autophagic protein degradation. Therefore, the β-CD-threaded biocleavable PRXs may be promising therapeutics for ameliorating not only cholesterol accumulation but also autophagy impairment in NPC disease.

Acid-labile polyrotaxane exerting endolysosomal pH-sensitive supramolecular dissociation for therapeutic applications

For achieving pH-sensitive dissociation and the subsequent release of threaded cyclic molecules from polyrotaxanes (PRXs) in weakly acidic environments, a novel acid-labile Pluronic/β-cyclodextrin-based PRX bearing ketal linkages was designed and its potential biomedical application was demonstrated.

Supramolecular flower micelle formation of polyrotaxane-containing triblock copolymers prepared from macro-chain transfer agents bearing molecular hooks

A precise synthesis of polyrotaxanes (PRX)-containing triblock copolymers was achieved using PRX macro-chain transfer agents with terminal hooks. Also, polymeric micelle formation of them in aqueous solution was investigated.

Threaded macromolecules as a versatile framework for biomaterials

In this feature article, the recent progress in biomaterial application of threaded macromolecules including polyrotaxanes such as drug delivery and gene delivery is described.