Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids
Ontogenic changes in lung cholesterol metabolism, lipid content, and histology in mice with Niemann–Pick type C disease
Introduction
In Niemann–Pick type C (NPC) disease unesterified cholesterol (UC), gangliosides, and glycosphingolipids continually accumulate in the late endosomal/lysosomal (E/L) compartment of all cells in every organ. It is an autosomal recessive disorder primarily affecting children and is characterized by neurodegeneration, hepatic and pulmonary dysfunction, and premature death [1]. A lot of what we currently know about NPC1 and NPC2 function, and also the etiology and pathogenesis of NPC disease has come from the study of animal models with NPC1 or NPC2 deficiency, primarily in the mouse [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], and also from various in vitro systems as well as techniques such as X-ray crystallography [15], [16], [17]. Unequivocally, it is the sequestration of UC in the E/L compartment that is the fundamental cause of NPC disease [18]. This accumulation of UC is due to a loss of function mutation in genes encoding either NPC1 or NPC2, both of which are essential for facilitating cholesterol transport out of the late E/L compartment [17]. Disruption of this egress and the resultant buildup of UC, together with that of other types of lipids, leads to cell death and multi-organ damage. While neurodegeneration is a major cause of morbidity and mortality in NPC disease, there are cases where death occurs within about the first six months of life from either liver failure or severe pulmonary dysfunction [1].
Although there is currently no effective treatment for NPC disease, a variety of agents has been evaluated primarily in animal or in vitro models, with 2-hydroxypropyl-ß-cyclodextrin (2HPßCD) showing the best efficacy thus far [19], [20], [21], [22], [23], [24]. In a particularly definitive study it was demonstrated that continuous infusion of 2HPßCD into the ventricular system of Npc1−/− animals between 3 and 7 weeks of age normalized the biochemical abnormalities and completely prevented the expected neurodegeneration [25]. Earlier studies established that weekly subcutaneous administration of 2HPßCD to Npc1−/− mice, starting at 7 days of age, nearly normalized hepatic and whole animal cholesterol pools and prevented development of liver disease [26]. While there was also a slowing of cerebellar neurodegeneration and an increase in lifespan, systemic 2HPßCD treatment had little to no effect on the development of progressive pulmonary disease [26]. Subsequent studies further demonstrated lack of impact of systemically administered 2HPßCD on a number of parameters of lung function and pathology in the Npc1−/− mouse [27]. There is nothing intrinsically different about UC sequestration in the lungs in NPC1 or NPC2 deficiency because NPC2 replacement therapy in a mouse model of NPC2 disease resulted in a striking reduction in the cholesterol content of several organs including the lungs [28]. Rather, the inaction of 2HPßCD in the NPC lung may simply reflect lack of penetrance at a cellular level. Irrespective of whether this is the case, those studies revealed the paucity of published information about how NPC1 or NPC2 deficiency impacts lung cholesterol metabolism, particularly in early stage disease. In one of our initial studies in the Npcnih mouse model we found that even in 1-day old Npc1−/− pups the cholesterol concentration in most organs, including the lungs, was elevated [29]. More recently, a murine model of infantile NPC1 deficiency has been described but lungs were not included in the tissues examined [30].
The present studies represent the first systematic evaluation, in quantitative terms, of the ontogenic changes in lung mass, lipid composition, rates of cholesterol and fatty acid synthesis, and also histology in mice with NPC1 or NPC2 deficiency.
Section snippets
Animals and diets
Control (Npc1+/+ and Npc2+/+) and mutant (Npc1−/− and Npc2−/−) mice were generated from respective heterozygous breeding stock on a pure BALB/c background. The NPC1 mice (Npc1nih) originated from a colony at the National Institutes of Health (Dr. Peter Pentchev), while heterozygous Npc2 breeding stock was kindly provided by Dr. Peter Lobel. Depending on the age at which they were to be studied, the mice were genotyped anywhere from 6 to 19 days of age. Unless studied beforehand, all mice were
Results
Although several mouse models of Npc1 deficiency have been described [2], [11], [14], [30] all of our studies to date have used Npc1nih mice maintained on a low-cholesterol basal rodent chow diet. These mice exhibit a marked increase in whole body cholesterol synthesis and content [29], [36]. While all organs show elevated concentrations and rates of synthesis of cholesterol, these changes are particularly pronounced in the liver [36]. Consequently the Npc1−/− mice manifest an age-related
Discussion
Four main conclusions can be drawn from the current work. The first of these relates to changes in the mass of the lungs from early to late stage disease. An early publication describing lipid metabolism in the Npc1−/− mouse (then known as the NCTR-BALB/c mouse) noted a 2.3-fold higher relative lung weight in the mutants at about 70 days of age [3]. A comparable genotypic difference was seen in the relative lung weights in the 70 day old Npc1−/− mice in the present studies (Fig. 3A). It should be
Acknowledgements
We thank Mario Saucedo, Carolyn Crumpton, Taylor Wagner, Stephen Ostermann and Monti Schneiderman for their excellent technical assistance. This research was supported principally by US Public Health Service Grant R01HL009610 (SDT). Other support was provided by the Ara Parseghian Medical Research Foundation (CMR).
References (52)
- et al.
A lysosomal storage disorder in mice characterized by a dual deficiency of sphingomyelinase and glucocerebrosidase
Biochim. Biophys. Acta
(1980) - et al.
Fate of endogenously synthesized cholesterol in Niemann–Pick type C1 cells
J. Biol. Chem.
(2000) - et al.
Receptor-mediated and bulk-phase endocytosis cause macrophage and cholesterol accumulation in Niemann–Pick C disease
J. Lipid Res.
(2007) - et al.
Development of a Rab9 transgenic mouse and its ability to increase the lifespan of a murine model of Niemann–Pick type C disease
Am. J. Pathol.
(2009) - et al.
Quantitative role of LAL, NPC2, and NPC1 in lysosomal cholesterol processing defined by genetic and pharmacological manipulations
J. Lipid Res.
(2011) - et al.
Mechanism of cholesterol transfer from the Niemann–Pick type C2 protein to model membranes supports a role in lysosomal cholesterol transport
J. Biol. Chem.
(2006) - et al.
Structure of N-terminal domain of NPC1 reveals distinct subdomains for binding and transfer of cholesterol
Cell
(2009) - et al.
Defective cholesterol trafficking in Niemann–Pick C-deficient cells
FEBS Lett.
(2010) - et al.
Normalization of cholesterol homeostasis by 2-hydroxypropyl-β-cyclodextrin in neurons and glia from Niemann–Pick C1 (NPC1)-deficient mice
J. Biol. Chem.
(2012) - et al.
Cyclodextrin mediates rapid changes in lipid balance in Npc1−/− mice without carrying cholesterol through the bloodstream
J. Lipid Res.
(2012)
Pulmonary function and pathology in hydroxypropyl-beta-cyclodextin-treated and untreated Npc1−/− mice
Mol. Genet. Metab.
Npc1 deficiency in the C57BL/6J genetic background enhances Niemann–Pick disease type C spleen pathology
Biochem. Biophys. Res. Commun.
Marked reduction in bile acid synthesis in cholesterol 7 alpha-hydroxylase-deficient mice does not lead to diminished tissue cholesterol turnover or to hypercholesterolemia
J. Lipid Res.
Lysosomal unesterified cholesterol content correlates with liver cell death in murine Niemann–Pick type C disease
J. Lipid Res.
Determination of lipid phosphorus in the nanomolar range
Anal. Biochem.
Lipid homeostasis and lipoprotein secretion in Niemann–Pick C1-deficient hepatocytes
J. Biol. Chem.
Peroxisomal impairment in Niemann–Pick type C disease
J. Biol. Chem.
Deletion of Scap in alveolar type II cells influences lung lipid homeostasis and identifies a compensatory role for pulmonary lipofibroblasts
J. Biol. Chem.
Mitochondrial free cholesterol loading sensitizes to TNF- and Fas-mediated steatohepatitis
Cell Metab.
Pulmonary involvement in Niemann–Pick disease: case report and literature review
Respir. Med.
Fatal neonatal respiratory distress in Niemann–Pick C2 and prenatal diagnosis with mutations in gene HE1/NPC2
Arch. Pediatr.
Niemann–Pick disease type C
Orphanet J. Rare Dis.
Lysosome lipid storage disorder in NCTR-BALB/c mice. I. Description of the disease and genetics
Am. J. Pathol.
Type C Niemann–Pick disease in a boxer dog
Acta Neuropathol.
Genetic evidence for nonredundant functional cooperativity between NPC1 and NPC2 in lipid transport
Proc. Natl. Acad. Sci. U. S. A.
Characterization of liver disease and lipid metabolism in the Niemann–Pick C1 mouse
J. Cell. Biochem.
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