Defective Cytochrome P450-Catalysed Drug Metabolism in Niemann-Pick Type C Disease.

Niemann-Pick type C (NPC) disease is a neurodegenerative lysosomal storage disease caused by mutations in either the NPC1 or NPC2 gene. NPC is characterised by storage of multiple lipids in the late endosomal/lysosomal compartment, resulting in cellular and organ system dysfunction. The underlying molecular mechanisms that lead to the range of clinical presentations in NPC are not fully understood. While evaluating potential small molecule therapies in Npc1-/- mice, we observed a consistent pattern of toxicity associated with drugs metabolised by the cytochrome P450 system, suggesting a potential drug metabolism defect in NPC1 disease. Investigation of the P450 system in the context of NPC1 dysfunction revealed significant changes in the gene expression of many P450 associated genes across the full lifespan of Npc1-/- mice, decreased activity of cytochrome P450 reductase, and a global decrease of multiple cytochrome P450 catalysed dealkylation reactions. In vivo drug metabolism studies using a prototypic P450 metabolised drug, midazolam, confirmed dysfunction in drug clearance in the Npc1-/- mouse. Expression of the Phase II enzyme uridinediphosphate-glucuronosyltransferase (UGT) was also significantly reduced in Npc1-/- mice. Interestingly, reduced activity within the P450 system was also observed in heterozygous Npc1+/- mice. The reduced activity of P450 enzymes may be the result of bile acid deficiency/imbalance in Npc1-/- mice, as bile acid treatment significantly rescued P450 enzyme activity in Npc1-/- mice and has the potential to be an adjunctive therapy for NPC disease patients. The dysfunction in the cytochrome P450 system were recapitulated in the NPC1 feline model. Additionally, we present the first evidence that there are alterations in the P450 system in NPC1 patients.

Improved neuroprotection using miglustat, curcumin and ibuprofen as a triple combination therapy in Niemann-Pick disease type C1 mice.

OBJECTIVES: Niemann-Pick disease type C (NPC) is a neurodegenerative lysosomal storage disorder characterised by the storage of multiple lipids, reduced lysosomal calcium levels, impaired late endosome:lysosome fusion and neuroinflammation. NPC is caused by mutations in either of the two genes, NPC1 or NPC2, which are believed to function in a common cellular pathway, the function of which remains unclear. The complexity of the pathogenic cascade in NPC disease provides a number of potential clinical intervention points. To date, drugs that target pivotal stages in the pathogenic cascade have been tested as monotherapies or in combination with a second agent, showing additive or synergistic benefit. In this study, we have investigated whether we can achieve greater therapeutic benefit in the Npc1(-/-) mouse by combining three therapies that each targets unique aspects of the pathogenic cascade. METHODS: We have treated Npc1(-/-) mice with miglustat that targets sphingolipid synthesis and storage, curcumin that compensates for the lysosomal calcium defect by elevating cytosolic calcium, and the non-steroidal anti-inflammatory drug ibuprofen to reduce central nervous system inflammation. RESULTS/INTERPRETATION: We have found that triple combination therapy has a greater neuroprotective benefit compared with single and dual therapies, increasing the time period that Npc1(-/-) mice maintained body weight and motor function and maximally delaying the onset of Purkinje cell loss. In addition, ibuprofen selectively reduced microglial activation, while curcumin had no anti-inflammatory effects, indicating differential mechanisms of action for these two therapies. When taken together, these results demonstrate that targeting multiple unique steps in the pathogenic cascade maximises the clinical benefit in a mouse model of NPC1 disease.