RESEARCH ARTICLE Hyperactive Glial Cells Contribute to Axonal Pathologies in the Spinal Cord of Npc1 Mutant Mice Xin Yan, 1 Fan Yang, 1 Jan Lukas, 1 Martin Witt, 2 Andreas Wree, 2 Arndt Rolfs, 1 and Jiankai Luo 1 Niemann-Pick disease type C1 (NPC1) is a neurodegenerative disease with various progressive pathological features, for example, neuronal loss, dysmyelination, abnormal axon swelling, and gliosis, in the brain. Pathological activation of p38- mitogen-activated protein kinase (MAPK) results in hyperphosphorylation of tau protein, which contributes to the develop- ment of neurodegenerative diseases. In this study, axonal varicosities or spheroids and presynaptic aggregates in the spinal cord of the Npc1 mutant mice were found from postnatal day (P) 35 onwards, as indicated by the increased hyperphosphory- lated neurofilament and synaptophysin immunoreactivity as well as the findings from electron microscopy. However, activities of astrocytes and microglia in the Npc1 mutant spinal cord were progressively increased earlier from P10 onwards, accompa- nied by increased expression of interleukin-1b and apolipoprotein E, as well as up-regulated p38-MAPK activity and enhanced phosphorylated tau protein, but not cyclin-dependent kinase 5/p35 complex and glycogen synthase kinase-3b. Taken together, our data suggest that the axonal pathologies in the Npc1 mutant spinal cord are strongly correlated with the increase of activated glial cells, which produce IL-1b and ApoE, resulting in the activation of p38-MAPK signaling pathway and enhanced phosphorylated tau protein. GLIA 2014;62:1024–1040 Key words: Npc1, neurodegeneration, astrocytes, microglia, IL-1b, ApoE, p38-MAPK Introduction N iemann-Pick disease type C (NPC) is an autosomal recessive neurodegenerative disease characterized by an intracellular abnormal cholesterol metabolism (Morris et al., 1999). Generally, NPC is caused by a mutation of the Niemann-Pick disease type C1 (Npc1) or Npc2 proteins, which are involved in the intracellular transport of cholesterol (Bauer et al., 2002; Carstea et al., 1997; Naureckiene et al., 2000; Walkley and Suzuki, 2004). Npc1 mutations are responsible for 95% NPC patients, and Npc2 mutations for 5%. The Npc1 mutant (Npc1 2/2 ) mouse with a sponta- neous mutation in the Npc1 gene is an excellent murine model to recapitulate the main features of NPC1 in patients (Loftus et al., 1997). The Npc1 2/2 mouse exhibits progres- sive pathologies in the central nervous system (CNS), includ- ing intracellular accumulation of lipids, dysmyelination, abnormal axon swelling, gliosis, and widespread neuronal degeneration (Bi et al., 2005; Bu et al., 2002; Liao et al., 2007; Pressey et al., 2012; Yu and Lieberman, 2013). Although the mechanism of NPC1 is still not clear, alter- ation of important proteins and signaling pathways has been supposed to be a reason for neurodegeneration in this disease. For example, enhanced phosphorylated tau protein, mediated by increasing cyclin-dependent kinase 5 (CDK5) and/or mitogen-activated protein kinase (MAPK) signaling, forms aggregates in neurons, contributing to neurodegeneration in NPC1 (Bu et al., 2002; Sawamura et al., 2001). Disruption of nuclear factor (NF)-jB, mediated by depressed glycogen View this article online at wileyonlinelibrary.com. DOI: 10.1002/glia.22659 Published online March 18, 2014 in Wiley Online Library (wileyonlinelibrary.com). Received Nov 28, 2013, Accepted for publication Mar 4, 2014. Address correspondence to Dr. Jiankai Luo, Albrecht-Kossel-Institute for Neuroregeneration, Rostock University Medical Center, University of Rostock, Gehlsheimer Strasse 20, D-18147 Rostock, Germany. E-mail: jiankai.luo@uni-rostock.de From the 1 Albrecht-Kossel-Institute for Neuroregeneration, Rostock University Medical Center, University of Rostock, Rostock, Germany; 2 Institute of Anatomy, Rostock University Medical Center, University of Rostock, Rostock, Germany. Additional Supporting Information may be found in the online version of this article. 1024 V C 2014 Wiley Periodicals, Inc.