Browsing by Author "Oyarzún Isamitt, Juan Esteban"

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    Análisis y modulación de la vía de Catepsinas B y D en la fibrosis hepática en modelos in vitro e in vivo de la enfermedad de Niemann-Pick tipo C
    (2019) Oyarzún Isamitt, Juan Esteban; Zanlungo Matsuhiro, Silvana; Pontificia Universidad Católica de Chile. Escuela de Medicina
    La enfermedad de Niemann-Pick tipo C (NPC) es un desorden hereditario autosómico recesivo caracterizado por la acumulación de colesterol en los lisosomas. Esta enfermedad es causada por mutaciones en los genes que codifican para las proteínas NPC1 y NPC2, las cuales están implicadas en el eflujo del colesterol desde los lisosomas. La deficiencia de NPC1 ó NPC2 lleva a una acumulación primaria de colesterol libre lisosomal y posteriormente el consecuente daño celular. Si bien no se conoce del todo los mecanismos subyacentes por los cuales el colesterol libre generaría el daño hepático en la enfermedad de NPC, se han postulado diversas opciones, entre los que destaca el estrés oxidativo, la disfunción en la dinámica de endosomas y lisosomas, así como también la disfunción en la autofagia lisosomal. El sistema nervioso central (SNC) es el más afectado en los pacientes NPC, los cuales padecen una rápida neurodegeneración progresiva a edad temprana. Otro órgano muy afectado en los pacientes NPC es el hígado, ya que muchos pacientes padecen de enfermedad hepática incluso llegando a falla hepática fulminante. Sin embargo, las causas que conllevan al daño hepático en NPC han sido poco estudiadas y dilucidadas. En los hígados de pacientes NPC se ha reportado un aumento en el contenido de colesterol libre, fibrosis progresiva y apoptosis. Recientes reportes han postulado a las catepsinas B y D como potenciales candidatos en la vía que conecta la acumulación de colesterol libre con el daño hepático, particularmente con la fibrosis hepática. Considerando todos los antecedentes previos, se formuló la siguiente hipótesis: “Las vías de las catepsinas B y D contribuyen a la fibrosis hepática en la enfermedad de NiemannPick tipo C”. El objetivo general planteado fue: “Demostrar que las vías de las catepsinas B y D contribuyen a la fibrosis en modelos hepáticos in vitro e in vivo de la enfermedad de Niemann-Pick tipo C”. Los resultados de esta tesis muestran aumento en los niveles de catepsinas B y D, los que se correlacionaron con aumento en la fibrosis e inflamación en hígados de ratones NPC. Este aumento en la fibrosis también fue reproducido en los modelos hepáticos in vitro NPC. Interesantemente, la utilización de inhibidores de catepsinas B y D, CA-074 y pepstatina A, respectivamente, además de shRNA contra catepsina D, disminuyó el fenotipo pro-fibrótico en modelos celulares de hepatocitos y células estrelladas hepáticas NPC. Por otro lado, la sobreexpresión de catepsina B aumentó la fibrosis en los modelos in vitro. Los resultados obtenidos nos llevan a la conclusión que las catepsinas B y D participan en la fibrosis hepática en NPC y proponemos su inhibición como una aproximación terapéutica para tratar el daño hepático en esta enfermedad.
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    Connexin 43 hemichannels and pannexin-1 channels contribute to the alpha-synuclein-induced dysfunction and death of astrocytes
    (2019) Díaz Jara, Esteban Fernando; Labra Ramírez, Valeria Cristina; Alvear, Tanhia F.; Mellado, Luis A.; Inostroza, Carla A.; Oyarzún Isamitt, Juan Esteban; Salgado Cortés, Nicole Andrea; Quintanilla Gómez, Rodrigo Arthur; Orellana Roca, Juan Andrés
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    Connexin and Pannexin-Based Channels in Oligodendrocytes: Implications in Brain Health and Disease
    (2019) Vejar, Sebastián; Oyarzún Isamitt, Juan Esteban; Retamal, Mauricio A.; Ortiz, Fernando C.; Orellana Roca, Juan Andrés
    Oligodendrocytes are the myelin forming cells in the central nervous system (CNS). In addition to this main physiological function, these cells play key roles by providing energy substrates to neurons as well as information required to sustain proper synaptic transmission and plasticity at the CNS. The latter requires a fine coordinated intercellular communication with neurons and other glial cell types, including astrocytes. In mammals, tissue synchronization is mainly mediated by connexins and pannexins, two protein families that underpin the communication among neighboring cells through the formation of different plasma membrane channels. At one end, gap junction channels (GJCs; which are exclusively formed by connexins in vertebrates) connect the cytoplasm of contacting cells allowing electrical and metabolic coupling. At the other end, hemichannels and pannexons (which are formed by connexins and pannexins, respectively) communicate the intra-and extracellular compartments, serving as diffusion pathways of ions and small molecules. Here, we briefly review the current knowledge about the expression and function of hemichannels, pannexons and GJCs in oligodendrocytes, as well as the evidence regarding the possible role of these channels in metabolic and synaptic functions at the CNS. In particular, we focus on oligodendrocyte-astrocyte coupling during axon metabolic support and its implications in brain health and disease.
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    Gadolinium chloride rescues niemann-pick type C liver damage
    (2018) Klein, Andres D.; Oyarzún Isamitt, Juan Esteban; Cortez, Cristian; Zanlungo Matsuhiro, Silvana
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    Hepatoprotective species from the Chilean medicinal flora : Junellia spathulata (Verbenaceae)
    (2021) Bridi, Raquel; Lino von Poser, G.; Gómez, Miguel; Andía Kohnenkampf, Marcelo Edgardo; Oyarzún Isamitt, Juan Esteban; Núñez, P.; Vasquez Arias, A. J.; Espinosa Bustos, Christian Marcelo
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    Non-invasive near-infrared spectroscopy assessment of the spinal neurovascular response in a patient with transverse myelitis: a case report
    (2022) Oyarzún Isamitt, Juan Esteban; Caulier Cisterna, Raúl; González Appelgren, Juan Pablo; Gonzalez, Leticia; Trujillo, Oscar; Eblen-Zajjur, Antonio; Uribe Arancibia, Sergio A.
    Background: Transverse myelitis (TM) is characterized by acute development of motor, sensory and autonomic dysfunctions due to horizontally diffused inflammation in one or more segments of the spinal cord in the absence of a compressive lesion. The not well-known inflammation process induces demyelination resulting in neurological dysfunction. Case presentation: In this case report we used a functional Near-Infrared Spectroscopy (fNIRS) technique to evaluate changes in the peri-spinal vascular response induced by a peripheral median nerve electrical stimulation in a patient with chronic transverse myelitis (TM). fNIRS showed drastically reduced signal amplitude in the peri-spinal vascular response, compared to that obtained from a healthy control group throughout most of the C7-T1 and T10-L2 spinal cord segments. Conclusion: The potential use of this relatively non-invasive fNIRS technology support the potential clinical application of this method for functional test of the spinal cord through the assessment of the spinal neurovascular response.
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    Proteomic Analysis of Niemann-Pick Type C Hepatocytes Reveals Potential Therapeutic Targets for Liver Damage
    (2021) Balboa Castillo, Elisa Ivana; Marín Marín, Tamara Alejandra; Oyarzún Isamitt, Juan Esteban; Contreras, Pablo S.; Hardt, Robert; Van Den Bosch, Thea; Álvarez Rojas, Alejandra; Rebolledo Jaramillo, Boris; Klein, Andres D.; Winter, Dominic; Zanlungo Matsuhiro, Silvana
    Niemann-Pick type C disease (NPCD) is a lysosomal storage disorder caused by mutations in the NPC1 gene. The most affected tissues are the central nervous system and liver, and while significant efforts have been made to understand its neurological component, the pathophysiology of the liver damage remains unclear. In this study, hepatocytes derived from wild type and Npc1(-/-) mice were analyzed by mass spectrometry (MS)-based proteomics in conjunction with bioinformatic analysis. We identified 3832 proteins: 416 proteins had a p-value smaller than 0.05, of which 37% (n = 155) were considered differentially expressed proteins (DEPs), 149 of them were considered upregulated, and 6 were considered downregulated. We focused the analysis on pathways related to NPC pathogenic mechanisms, finding that the most significant changes in expression levels occur in proteins that function in the pathways of liver damage, lipid metabolism, and inflammation. Moreover, in the group of DEPs, 30% (n = 47) were identified as lysosomal proteins and 7% (n = 10) were identified as mitochondrial proteins. Importantly, we found that lysosomal DEPs, including CTSB/D/Z, LIPA, DPP7 and GLMP, and mitocondrial DEPs, AKR1B10, and VAT1 had been connected with liver fibrosis, damage, and steatosis in previous studies, validiting our dataset. Our study found potential therapeutic targets for the treatment of liver damage in NPCD.
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    The Opening of Connexin 43 Hemichannels Alters Hippocampal Astrocyte Function and Neuronal Survival in Prenatally LPS-Exposed Adult Offspring
    (2019) Chávez Chaname, Carolina Elizabeth; Oyarzún Isamitt, Juan Esteban; Avendaño, Beatriz C.; Mellado, Luis A.; Inostroza, Carla A.; Alvear Soto, Tanhia Francheska; Orellana Roca, Juan Andrés
    Clinical evidence has revealed that children born from mothers exposed to viral and bacterial pathogens during pregnancy are more likely to suffer various neurological disorders including schizophrenia, autism bipolar disorder, major depression, epilepsy, and cerebral palsy. Despite that most research has centered on the impact of prenatal inflammation in neurons and microglia, the potential modifications of astrocytes and neuron-astrocyte communication have received less scrutiny. Here, we evaluated whether prenatally LPS-exposed offspring display alterations in the opening of astrocyte hemichannels and pannexons in the hippocampus, together with changes in neuroinflammation, intracellular Ca2+ and nitric oxide (NO) signaling, gliotransmitter release, cell arborization, and neuronal survival. Ethidium uptake recordings revealed that prenatal LPS exposure enhances the opening of astrocyte Cx43 hemichannels and Panx1 channels in the hippocampus of adult offspring mice. This enhanced channel activity occurred by a mechanism involving a microglia-dependent production of IL-1 beta/TNF-alpha and the stimulation of p38 MAP kinase/iNOS/[Ca2+](i)-mediated signaling and purinergic/glutamatergic pathways. Noteworthy, the activity of Cx43 hemichannels affected the release of glutamate, [Ca2+](i) handling, and morphology of astrocytes, whereas also disturbed neuronal function, including the dendritic arbor and spine density, as well as survival. We speculate that excitotoxic levels of glutamate triggered by the activation of Cx43 hemichannels may contribute to hippocampal neurotoxicity and damage in prenatally LPS-exposed offspring. Therefore, the understanding of how astrocyte-neuron crosstalk is an auspicious avenue toward the development of broad treatments for several neurological disorders observed in children born to women who had a severe infection during gestation.