Endocytosis of beta-cyclodextrins is responsible for cholesterol reduction in Niemann-Pick type C mutant cells

Abstract

Niemann-Pick type C disease (NPC) is a lysosomal storage disorder causing accumulation of unesterified cholesterol in lysosomal storage organelles. Recent studies have shown that hydroxypropyl-β-cyclodextrin injections in npc1 −/− mice are partially effective in treating this disease. Using cultured fibroblasts, we have investigated the cellular mechanisms responsible for reduction of cholesterol accumulation. We show that decreased levels of cholesterol accumulation are maintained for several days after removal of cyclodextrin from the culture medium. This suggests that endocytosed cyclodextrin can reduce the cholesterol storage by acting from inside endocytic organelles rather than by removing cholesterol from the plasma membrane. To test this further, we incubated both NPC1 and NPC2 mutant cells with cholesterol-loaded cyclodextrin for 1 h, followed by chase in serum-containing medium. Although the cholesterol content of the treated cells increased after the 1-h incubation, the cholesterol levels in the storage organelles were later reduced significantly. We covalently coupled cyclodextrin to fluorescent dextran polymers. These cyclodextrin-dextran conjugates were delivered to cholesterol-enriched lysosomal storage organelles and were effective at reducing the cholesterol accumulation. We demonstrate that methyl-β-cyclodextrin is more potent than hydroxypropyl-β-cyclodextrin in reducing both cholesterol and bis(monoacylglycerol) phosphate accumulation in NPC mutant fibroblasts. Brief treatment of cells with cyclodextrins causes an increase in cholesterol esterification by acyl CoA:cholesterol acyl transferase, indicating increased cholesterol delivery to the endoplasmic reticulum. These findings suggest that cyclodextrin-mediated enhanced cholesterol transport from the endocytic system can reduce cholesterol accumulation in cells with defects in either NPC1 or NPC2.acyl CoA:cholesterol acyl transferase | cholesterol accumulation | lysosomal storage organelles | bis(monoacylgycerol)phosphate, pinocytosis

Efficacy of 2-Hydroxypropyl-β-cyclodextrin in Niemann–Pick Disease Type C Model Mice and Its Pharmacokinetic Analysis in a Patient with the Disease

“…However, a small portion of HPBCD appears to be incorporated into the intracellular compartment to act as a cholesterol carrier instead of NPC1. 20) Therefore, dose adjustment appears to be required according to renal function to achieve a therapeutic concentration and to avoid toxicity during HPBCD therapy in NPC patients.…”

Hearing Loss and Otopathology Following Systemic and Intracerebroventricular Delivery of 2-Hydroxypropyl-Beta-Cyclodextrin

“…Since it is known that the cochlea exhibits decreased sensitivity to oxidative stress from base to apex (Ohinata et al 2003;Schacht et al 2012;Usami et al 1996) and the basal to apical pattern of OHC loss seen in our study parallels that of aminoglycosides and cisplatin, it is possible that HPβCD mediates its effects through ROS. There is evidence to suggest that β-cyclodextrin derivatives are capable of altering mitochondrial bioenergetics (Ziolkowski et al 2010), and this could be through direct action on intracellular organelles (Rosenbaum et al 2010). It is unclear whether HPβCD accumulates in OHCs, but it remains possible that HPβCD ototoxicity is mediated through a direct interaction with intracellular signaling and ROS production.…”

Glycosylation inhibition reduces cholesterol accumulation in NPC1 protein-deficient cells

“…LDL added to NPC1 mutant cells fails to increase ACAT-mediated cholesterol ester synthesis; cyclodextrin can overcome this block and permit cholesterol export to the ER (25,26). To show directly that lysosomal cholesterol export is improved in NPC1-deficient ldl-D cells containing a less elaborate glycocalyx, we tested the ability of these cells to transfer LDL-derived cholesterol to the ER, as monitored by its availability for esterification by ERlocalized ACAT.…”