Cholesterol deficiency in a mouse model of Smith-Lemli-Opitz syndrome reveals increased mast cell responsiveness

Mutation of the 3β-hydroxysterol Δ7-reductase gene (Dhcr7−/−) results in Smith-Lemli-Opitz syndrome (SLOS). Patients, and genetically altered mice, are unable to produce cholesterol and accumulate 7-dehydrocholesterol (DHC) in serum and tissue. This causes multiple growth and developmental abnormalities as well as immune system anomalies including allergy. Because cholesterol is a key component of liquid-ordered membranes (lipid rafts) and these domains have been implicated in regulating mast cell activation, we examined whether mast cell responsiveness is altered in this model. Mast cells derived from Dhcr7−/− mice (DHCR KO) showed constitutive cytokine production and hyper-degranulation after stimulation of the high affinity IgE receptor (FcɛRI). DHCR KO mast cells, but not wild-type mast cells, accumulated DHC in lipid rafts. DHC partially disrupted lipid raft stability and displaced Lyn kinase protein and activity from lipid rafts. This led to down-regulation of some Lyn-dependent signaling events but increased Fyn kinase activity and Akt phosphorylation. The Lyn-dependent phosphorylation of Csk-binding protein, which negatively regulates Fyn activity, was decreased. This phenotype reproduces some of the characteristics of Lyn-null mast cells, which also demonstrate hyper-degranulation. These findings provide the first evidence of lipid raft dysfunction in SLOS and may explain the observed association of allergy with SLOS

1H NMR-Linked Metabolomics Analysis of Liver from a Mouse Model of NP-C1 Disease

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A human iPSC-derived inducible neuronal model of Niemann-Pick disease, type C1

BACKGROUND: Niemann-Pick disease, type C (NPC) is a childhood-onset, lethal, neurodegenerative disorder caused by autosomal recessive mutations in the genes NPC1 or NPC2 and characterized by impaired cholesterol homeostasis, a lipid essential for cellular function. Cellular cholesterol levels are tightly regulated, and mutations in either NPC1 or NPC2 lead to deficient transport and accumulation of unesterified cholesterol in the late endosome/lysosome compartment, and progressive neurodegeneration in affected individuals. Previous cell-based studies to understand the NPC cellular pathophysiology and screen for therapeutic agents have mainly used patient fibroblasts. However, these do not allow modeling the neurodegenerative aspect of NPC disease, highlighting the need for an in vitro system that permits understanding the cellular mechanisms underlying neuronal loss and identifying appropriate therapies. This study reports the development of a novel human iPSC-derived, inducible neuronal model of Niemann-Pick disease, type C1 (NPC1). RESULTS: We generated a null i3Neuron (inducible × integrated × isogenic) (NPC1 CONCLUSION: Our data demonstrate the utility of this new cell line in high-throughput drug/chemical screens to identify potential therapeutic agents. The NPC

Brain type carnosinase in dementia: a pilot study

Research articl

Human and mouse neuroinflammation markers in Niemann‐Pick disease, type C1

Niemann‐Pick disease, type C1 (NPC1) is an autosomal recessive lipid storage disorder in which a pathological cascade, including neuroinflammation occurs. While data demonstrating neuroinflammation is prevalent in mouse models, data from NPC1 patients is lacking. The current study focuses on identifying potential markers of neuroinflammation in NPC1 from both the Npc1 mouse model and NPC1 patients. We identified in the mouse model significant changes in expression of genes associated with inflammation and compared these results to the pattern of expression in human cortex and cerebellar tissue. From gene expression array analysis, complement 3 (C3) was increased in mouse and human post‐mortem NPC1 brain tissues. We also characterized protein levels of inflammatory markers in cerebrospinal fluid (CSF) from NPC1 patients and controls. We found increased levels of interleukin 3, chemokine (C‐X‐C motif) ligand 5, interleukin 16 and chemokine ligand 3 (CCL3), and decreased levels of interleukin 4, 10, 13 and 12p40 in CSF from NPC1 patients. CSF markers were evaluated with respect to phenotypic severity. Miglustat treatment in NPC1 patients slightly decreased IL‐3, IL‐10 and IL‐13 CSF levels; however, further studies are needed to establish a strong effect of miglustat on inflammation markers. The identification of inflammatory markers with altered levels in the cerebrospinal fluid of NPC1 patients may provide a means to follow secondary events in NPC1 disease during therapeutic trials.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147148/1/jimd0083.pd

Relative acidic compartment volume as a lysosomal storage disorder–associated biomarker

Lysosomal storage disorders (LSDs) occur at a frequency of 1 in every 5,000 live births and are a common cause of pediatric neurodegenerative disease. The relatively small number of patients with LSDs and lack of validated biomarkers are substantial challenges for clinical trial design. Here, we evaluated the use of a commercially available fluorescent probe, Lysotracker, that can be used to measure the relative acidic compartment volume of circulating B cells as a potentially universal biomarker for LSDs. We validated this metric in a mouse model of the LSD Niemann-Pick type C1 disease (NPC1) and in a prospective 5-year international study of NPC patients. Pediatric NPC subjects had elevated acidic compartment volume that correlated with age-adjusted clinical severity and was reduced in response to therapy with miglustat, a European Medicines Agency–approved drug that has been shown to reduce NPC1-associated neuropathology. Measurement of relative acidic compartment volume was also useful for monitoring therapeutic responses of an NPC2 patient after bone marrow transplantation. Furthermore, this metric identified a potential adverse event in NPC1 patients receiving i.v. cyclodextrin therapy. Our data indicate that relative acidic compartment volume may be a useful biomarker to aid diagnosis, clinical monitoring, and evaluation of therapeutic responses in patients with lysosomal disorders

Dysregulation of cholesterol homeostasis

Cholesterol plays a critical role in the health and normal function of every mammalian cell. Cholesterol has multiple cellular functions including maintenance of cell membrane stability and fluidity, steroid hormone and bile acid synthesis, and membrane receptor signaling. As with any critical metabolite, cholesterol is highly regulated. I will detail my research focusing on the two prevalent disorders of cholesterol homeostasis. The first is a disorder of cholesterol biosynthesis, Smith-Lemli-Opitz syndrome (SLOS), and the second a disorder of cholesterol trafficking, Niemann-Pick disease, type C1 (NPC). I have identified a unique cellular phenotypic overlap between these two previously unrelated disorders. Specifically, increasing concentrations of the precursor sterol present in SLOS, 7-dehydrocholesterol, leads to the induction of an NPC-like cellular phenotype. Aspects of the NPC cellular phenotype that can be induced in SLOS fibroblasts include lysosomal storage of unesterified cholesterol, sphingosine, and glycosphingolipids. Also, similar to what is observed in NPC, dysregulation of acidic calcium stores is present in SLOS. Further research indicates that this cellular phenotype extends into both the mouse models of SLOS and the patients. The dysregulation of cholesterol trafficking in SLOS cells likely decreases cellular cholesterol bioavailabilty and thus potentially limits the therapeutic efficacy of dietary cholesterol supplementation in SLOS patients. I also show that treatment of SLOS cells with miglustat, an established therapy for NPC, ameliorates the NPC-like cellular phenotype and thus may have therapeutic benefit in SLOS. The incidence of both SLOS and NPC has been the subject of debate. Thus, using data generated from massively parallel sequencing of the human exome, I demonstrate that the previously predicted incidence of SLOS of 1:40,000 births is likely correct, but call into question the predicted NPC rate of 1:120,000 . In fact, NPC maybe closer to a rate of 1:40,000. The role of oxysterols in the teratogenicity of SLOS and the underlying secondary storage of lipids in the phenotypic presentation of SLOS has been investigated.</p