Isofagomine In Vivo Effects in a Neuronopathic Gaucher Disease Mouse

Ying Sun,Kazuyuki Kitatani,Wujuan Zhang,Brian Quinn,Huimin Ran,Jacek Bielawski,Kenneth D R Setchell,Matt Zamzow,Yusuf A Hannun,Benjamin Liou,Gregory A Grabowski,Raphael Schiffmann

doi:10.1371/journal.pone.0019037

Abstract

The pharmacological chaperone, isofagomine (IFG), enhances acid β-glucosidase (GCase) function by altering folding, trafficking, and activity in wild-type and Gaucher disease fibroblasts. The in vivo effects of IFG on GCase activity, its substrate levels, and phenotype were evaluated using a neuronopathic Gaucher disease mouse model, 4L;C* (V394L/V394L + saposin C-/-) that has CNS accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) as well as progressive neurological deterioration. IFG administration to 4L;C* mice at 20 or 600 mg/kg/day resulted in life span extensions of 10 or 20 days, respectively, and increases in GCase activity and protein levels in the brain and visceral tissues. Cerebral cortical GC and GS levels showed no significant reductions with IFG treatment. Increases of GC or GS levels were detected in the visceral tissues of IFG treated (600 mg/kg/day) mice. The attenuations of brain proinflammatory responses in the treated mice were evidenced by reductions in astrogliosis and microglial cell activation, and decreased p38 phosphorylation and TNFα levels. Terminally, axonal degeneration was present in the brain and spinal cord from untreated and treated 4L;C* mice. These data demonstrate that IFG exerts in vivo effects by enhancing V394L GCase protein and activity levels, and in mediating suppression of proinflammation, which led to delayed onset of neurological disease and extension of the life span of 4L;C* mice. However, this was not correlated with a reduction in the accumulation of lipid substrates.

Highlights

Gaucher disease is caused by mutations in GBA1 that encodes acid b-glucosidase
At postnatal day 7 (P7), one cohort was maintained on 20 mg/kg/d IFG and a second cohort on 600 mg/kg/d (Fig. 1A)
The body weights (BW) of the mice were recorded from P7 to terminal stage

Summary

Introduction

Gaucher disease is caused by mutations in GBA1 that encodes acid b-glucosidase (glucocerebrosidase, GCase, EC3.2.1.45). Reductions in GC levels can be achieved by partial inhibition of GC synthase, an essential enzyme in the biosynthesis of complex glycosphingolipids [7], i.e. substrate reduction therapy (SRT). Eliglustat Tartrate {(1R,2R)-Octanoic acid [2(29,39-dihydro-benzo [1,4] dioxin-69-yl)-2-hydroxy-1-pyrrolidin-1methyl-ethyl]-amide-L-tartaric acid salt}, an analog of 1-phenyl-2decanoylamino-3-morpholino-1-propanol (PDMP), is a novel potent inhibitor (IC50,24 nM) of GC synthase. This compound significantly reduces GC accumulation in visceral tissues and cells in the Gaucher disease mouse model [9,10]. Phase 2 studies in humans show therapeutic effects that mimic those of higher dose enzyme therapy [11]. The compound does not reach significant levels in the brain since it is a pGP substrate. [9]

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Conclusion