Browsing by Author "Castro, Juan Francisco"
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- ItemDisruption in connexin-based communication is associated with intracellular Ca²⁺ signal alterations in astrocytes from Niemann-Pick type C mice(2013) Sáez Pedraza, Pablo José; Orellana Roca, Juan Andrés; Vega-Riveros, Natalia; Figueroa, Vania A.; Hernández Trejo, Diego Eduardo; Castro, Juan Francisco; Klein Posternack, Andrés David; Jean X. Jiang; Zanlungo Matsuhiro, Silvana; Sáez Carreño, Juan CarlosReduced astrocytic gap junctional communication and enhanced hemichannel activity were recently shown to increase astroglial and neuronal vulnerability to neuroinflammation. Moreover, increasing evidence suggests that neuroinflammation plays a pivotal role in the development of Niemann-Pick type C (NPC) disease, an autosomal lethal neurodegenerative disorder that is mainly caused by mutations in the NPC1 gene. Therefore, we investigated whether the lack of NPC1 expression in murine astrocytes affects the functional state of gap junction channels and hemichannels. Cultured cortical astrocytes of NPC1 knock-out mice (Npc1⁻/⁻) showed reduced intercellular communication via gap junctions and increased hemichannel activity. Similarly, astrocytes of newborn Npc1⁻/⁻ hippocampal slices presented high hemichannel activity, which was completely abrogated by connexin 43 hemichannel blockers and was resistant to inhibitors of pannexin 1 hemichannels. Npc1⁻/⁻ astrocytes also showed more intracellular Ca²⁺ signal oscillations mediated by functional connexin 43 hemichannels and P2Y₁ receptors. Therefore, Npc1⁻/⁻ astrocytes present features of connexin based channels compatible with those of reactive astrocytes and hemichannels might be a novel therapeutic target to reduce neuroinflammation in NPC disease.
- ItemLysosomal vitamin E accumulation in Niemann-Pick type C disease(2011) Yévenes, Luz Fernanda; Klein Posternack, Andrés David; Castro, Juan Francisco; Marín Marín, Tamara Alejandra; Leal Reyes, Nancy Valeria; Leighton Puga, Federico; Álvarez, Alejandra R.; Zanlungo Matsuhiro, SilvanaNiemann-Pick C disease (NPC) is a neuro-visceral lysosomal storage disorder mainly caused by genetic defects in the NPC1 gene. As a result of loss of NPC1 function large quantities of free cholesterol and other lipids accumulate within late endosomes and lysosomes. In NPC livers and brains, the buildup of lipids correlates with oxidative damage; however the molecular mechanisms that trigger it remain unknown. Here we study potential alterations in vitamin E (α-tocopherol, α-TOH), the most potent endogenous antioxidant, in liver tissue and neurons from NPC1 mice. We found increased levels of α-TOH in NPC cells. We observed accumulation and entrapment of α-TOH in NPC neurons, mainly in the late endocytic pathway. Accordingly, α-TOH levels were increased in cerebellum of NPC1 mice. Also, we found decreased mRNA levels of the α-TOH transporter, α-Tocopherol Transfer Protein (α-TTP), in the cerebellum of NPC1 mice. Finally, by subcellular fractionation studies we detected a significant increase in the hepatic α-TOH content in purified lysosomes from NPC1 mice. In conclusion, these results suggest that NPC cells cannot transport vitamin E correctly leading to α-TOH buildup in the endosomal/lysosomal system. This may result in a decreased bioavailability and impaired antioxidant function of vitamin E in NPC, contributing to the disease pathogenesis.
- ItemNpc1 deficiency in the C57BL/6J genetic background enhances Niemann–Pick disease type C spleen pathology(2011) Parra Cares, Julio Alejandro; Klein, Andres D.; Castro, Juan Francisco; Morales France, María Gabriela; Mosqueira Montero, Matías José; Valencia Araya, Ilse; Cortés Mora, Víctor Antonio; Rigotti Rivera, Attilio; Zanlungo Matsuhiro, SilvanaNiemann–Pick type C (NPC) disease is an autosomal recessive neurovisceral lipid storage disorder. The affected genes are NPC1 and NPC2. Mutations in either gene lead to intracellular cholesterol accumulation. There are three forms of the disease, which are categorized based on the onset and severity of the disease: the infantile form, in which the liver and spleen are severely affected, the juvenile form, in which the liver and brain are affected, and the adult form, which affects the brain. In mice, a spontaneous mutation in the Npc1 gene originated in the BALB/c inbred strain mimics the juvenile form of the disease. To study the influence of genetic background on the expression of NPC disease in mice, we transferred the Npc1 mutation from the BALB/c to C57BL/6J inbred background. We found that C57BL/6J-Npc1−/− mice present with a much more aggressive form of the disease, including a shorter lifespan than BALB/c-Npc1−/− mice. Surprisingly, there was no difference in the amount of cholesterol in the brains of Npc1−/− mice of either mouse strain. However, Npc1−/− mice with the C57BL/6J genetic background showed striking spleen damage with a marked buildup of cholesterol and phospholipids at an early age, which correlated with large foamy cell clusters. In addition, C57BL/6J Npc1−/− mice presented red cell abnormalities and abundant ghost erythrocytes that correlated with a lower hemoglobin concentration. We also found abnormalities in white cells, such as cytoplasmic granulation and neutrophil hypersegmentation that included lymphopenia and atypias. In conclusion, Npc1 deficiency in the C57BL6/J background is associated with spleen, erythrocyte, and immune system abnormalities that lead to a reduced lifespan.
- ItemVitamin E Dietary Supplementation Improves Neurological Symptoms and Decreases c-Abl/p73 Activation in Niemann-Pick C Mice(2014) Marín, Tamara; Contreras Soto, Pablo Andrés; Castro, Juan Francisco; Chamorro Veloso, David Daniel; Balboa Castillo, Elisa Ivana; Bosch Morató, Mónica; Muñoz, Francisco J.; Álvarez Rojas, Alejandra; Zanlungo Matsuhiro, Silvana