Decreased estradiol release from astrocytes contributes to the neurodegeneration in a mouse model of Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a deadly neurodegenerative disease often caused by mutation in a gene called NPC1, which results in the accumulation of unesterified cholesterol and glycosphingolipids in the endosomal-lysosomal system. Most studies on the mechanisms of neurodegeneration in NPC have focused on neurons. However, the possibility also exists that NPC1 affects neuronal functions indirectly by acting on other cells that are intimately interacting with neurons. In this study, using a heterotypic neuron-glia coculture system, we found that wild-type neurons cultured on a layer of NPC1-/- astrocytes showed decreased neurite growth compared with those cultured on wild-type astrocytes. RT-PCR and immunohistochemical assessments showed significantly lower expression of neurosteroid enzymes and StAR (steroidogenic acute regulatory protein) in NPC1-/- astrocyte cultures than in wild-type cultures. Furthermore, a reduced level of estradiol was measured from both astrocyte culture medium and whole brains from NPC1-/- mice. Administration of 17 beta-estradiol to neonatal NPC1-/- mice significantly delayed the onset of neurological symptoms, increased Purkinje cell survival, and extended the animals' life span. Our findings suggest that astrocyte dysfunction contributes to the neurodegeneration of NPC and estradiol treatment may be useful in ameliorating progression of the disease. (C) 2007 Wiley-Liss, Inc.