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Introduction: Niemann-Pick type C2 disease (NP-C2) is a fatal neurovisceral disorder caused by defects in the lysosomal cholesterol transporter protein NPC2. Consequently, cholesterol and other lipids accumulate within the lysosomes, causing a heterogeneous spectrum of clinical manifestations. Murine models are essential for increasing the understanding of the complex pathology of NP-C2. This study, therefore, aims to describe the neurovisceral pathology in the NPC2-deficient mouse model to evaluate its correlation to human NP-C2., Methods: Npc2-/- mice holding the LST105 mutation were used in the present study (Npc2 Gt(LST105)BygNya ). Body and organ weight and histopathological evaluations were carried out in six and 12-week-old Npc2-/- mice, with a special emphasis on neuropathology. The Purkinje cell (PC) marker calbindin, the astrocytic marker GFAP, and the microglia marker IBA1 were included to assess PC degeneration and neuroinflammation, respectively. In addition, the pathology of the liver, lungs, and spleen was assessed using hematoxylin and eosin staining., Results: Six weeks old pre-symptomatic Npc2-/- mice showed splenomegaly and obvious neuropathological changes, especially in the cerebellum, where initial PC loss and neuroinflammation were evident. The Npc2-/- mice developed neurological symptoms at eight weeks of age, severely progressing until the end-stage of the disease at 12 weeks. At the end-stage of the disease, Npc2-/- mice were characterized by growth retardation, tremor, cerebellar ataxia, splenomegaly, foam cell accumulation in the lungs, liver, and spleen, brain atrophy, pronounced PC degeneration, and severe neuroinflammation., Conclusion: The Npc2 Gt(LST105)BygNya mouse model resembles the pathology seen in NP-C2 patients and denotes a valuable model for increasing the understanding of the complex disease manifestation and is relevant for testing the efficacies of new treatment strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Chronic inflammation in the substantia nigra (SN) accompanies conditions with progressive neurodegeneration. This inflammatory process contributes to gradual iron deposition that may catalyze formation of free-radical mediated damage, hence exacerbating the neurodegeneration. This study examined proteins related to iron-storage (ferritin) and iron-export (ferroportin) (aka metal transporter protein 1, MTP1) in a model of neurodegeneration. Ibotenic acid injected stereotactically into the striatum leads to loss of GABAergic neurons projecting to SN pars reticulata (SNpr), which subsequently leads to excitotoxicity in the SNpr as neurons here become vulnerable to their additional glutamatergic projections from the subthalamic nucleus. This imbalance between glutamate and GABA eventually led to progressive shrinkage of the SNpr and neuronal loss. Neuronal cell death was accompanied by chronic inflammation as revealed by the presence of cells expressing ED1 and CD11b in the SNpr and the adjacent white matter mainly denoted by the crus cerebri. The SNpr also exhibited changes in iron metabolism seen as a marked accumulation of inflammatory cells containing ferric iron and ferritin with morphology corresponding to macrophages and microglia. Ferritin was detected in neurons of the lesioned SNpr in contrast to the non-injected side. Compared to non-injected rats, surviving neurons of the SNpr expressed ferroportin at unchanged level. Analyses of dissected SNpr using RT-qPCR showed a rise in ferritin-H and -L transcripts with increasing age but no change was observed in the lesioned side compared to the non-lesioned side, indicating that the increased expression of ferritin in the lesioned side occurred at the post-transcriptional level. Hepcidin transcripts were higher in the lesioned side in contrast to ferroportin mRNA that remained unaltered. The continuous entry of iron-containing inflammatory cells into the degenerating SNpr and their subsequent demise is probably responsible for iron donation in neurodegeneration. This is accompanied by only a slight increase in neuronal ferritin and not ferroportin, which suggests that the iron-containing debris of dying inflammatory cells and degenerating neurons gets scavenged by invading macrophages and activated microglia to prevent an increase in neuronal iron., (Copyright © 2015 Elsevier Inc. All rights reserved.)

We examined differently aged postnatal (P) rats for the distribution and uptake of iron in the eye with the main emphasis on iron uptake in the retina. The concentration of iron in the eye was 48 μg/g in rats aged one postnatal day (P1). Then concentration fell to approximately 12 μg/g at P30 and rose to 35 μg/g at P70. Perls' stain which labels both ferrous and ferric iron was found to exhibit a weak labeling in the retina at P1 contrasted by a robust labeling of macrophages found in the choroid of the retina. In older aged rats, the labeling of cells of the retina was much more intense and confined to cells widespread in the layers of the retina. In both P16 and adult rats injected intravenously with [(59)Fe-(125)I]transferrin, the uptake of (59)Fe, estimated as the volume of distribution, was significantly higher than that of [(125)I]transferrin, and uptake of both compounds was higher than that of simultaneously injected [(131)I]albumin. In the P16 rat, the uptake of (59)Fe expressed as the volume of distribution, V(D), rose linearly reaching approximately 2500 nl at 60 min. In the adult rat, the uptake of (59)Fe was of the same magnitude. Comparing P1 and P16 rats, the uptake of (59)Fe, [(125)I]transferrin and [(131)I]albumin was higher at P1 in both eyeball and retina. Emulsion autoradiography of retinas from P16 and adult rats injected with [(55)Fe]transferrin into the vitreous body showed uptake mainly in photoreceptor cells and retinal ganglion cells. Adult rats injected into the vitreous body with [(59)Fe]transferrin showed anterograde axonal transport from the retina into the optic nerve, optic tract, and superior colliculus. Immunoprecipitates of homogenates of the optic nerve revealed that (59)Fe was precipitable with an antibody raised against ferritin, indicative of detachment of iron from transferrin within the axons of the retinal ganglion cells. The data demonstrate an age-dependent but continuous iron uptake by the retina, and are indicative of anterograde axonal transport of transferrin by retinal ganglion cells., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Metallothionein I+II (MT-I+II) are acute-phase proteins which are upregulated during pathological conditions in the brain. To elucidate the neuropathological importance of MT-I+II, we have examined MT-I+II-deficient mice following ip injection with 6-aminonicotinamide (6-AN). 6-AN is antimetabolic and toxic for bone marrow cells and grey matter astrocytes. In MT+/+ mice, injection with 6-AN resulted in breakdown of the blood-brain barrier (BBB) and absence of GFAP-positive astrocytes in specific grey matter areas of the brain stem. Reactive astrocytosis encircled the damaged grey matter areas, which were heavily infiltrated by microglia/macrophages. The recruitment of hematogenous macrophages was accompanied by leakage of the BBB. The immunoreactivity (ir) of granulocyte-macrophage-colony-stimulating factor (GM-CSF) and the receptor for GM-CSF (GM-CSFrec) was significantly upregulated in astrocytes and microglia/macrophages, respectively. MT-I+IIir was also clearly increased in astrocytes surrounding the damaged areas, while that of the CNS-specific MT isoform, MT-III, was mildly increased in both astrocytes and microglia/macrophages. In MT-/- mice injected with 6-AN, the BBB remained almost intact. The damage to specific grey matter areas was similar to that observed in MT+/+ mice, but reactive astrocytosis, microglia/macrophages infiltration, and GM-CSFir and GM-CSFrecir were clearly reduced in MT-/- mice. In contrast, MT-IIIir was dramatically increased in MT-/- mice. Total zinc decreased and histochemically detectable zinc increased in the brain stem after 6-AN similarly in MT+/+ and MT-/- mice. Bone marrow myeloid monocytes and macrophages were increased as a reaction to 6-AN only in MT+/+ mice. The results demonstrate that the capability of MT-/- mice to mount a normal inflammatory response in the brain is severely attenuated, at least in part because of 6-AN-induced bone marrow affectation, involving MT-I+II for the first time as major factors during CNS tissue damage., (Copyright 1999 Academic Press.)