Browsing by Author "Olesen, Margrethe A."

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    Neurodegeneration in Multiple Sclerosis: The Role of Nrf2-Dependent Pathways
    (2022) Maldonado, Paloma P.; Guevara, Coram; Olesen, Margrethe A.; Orellana Roca, Juan Andrés; Quintanilla, Rodrigo A.; Ortiz, Fernando C.
    Multiple sclerosis (MS) encompasses a chronic, irreversible, and predominantly immune-mediated disease of the central nervous system that leads to axonal degeneration, neuronal death, and several neurological symptoms. Although various immune therapies have reduced relapse rates and the severity of symptoms in relapsing-remitting MS, there is still no cure for this devastating disease. In this brief review, we discuss the role of mitochondria dysfunction in the progression of MS, focused on the possible role of Nrf2 signaling in orchestrating the impairment of critical cellular and molecular aspects such as reactive oxygen species (ROS) management, under neuroinflammation and neurodegeneration in MS. In this scenario, we propose a new potential downstream signaling of Nrf2 pathway, namely the opening of hemichannels and pannexons. These large-pore channels are known to modulate glial/neuronal function and ROS production as they are permeable to extracellular Ca2+ and release potentially harmful transmitters to the synaptic cleft. In this way, the Nrf2 dysfunction impairs not only the bioenergetics and metabolic properties of glial cells but also the proper antioxidant defense and energy supply that they provide to neurons.
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    Superoxide dismutase 2 deficiency is associated with enhanced central chemoreception in mice: Implications for breathing regulation
    (2024) Diaz-Jara, Esteban; Pereyra, Katherine; Vicencio, Sinay; Olesen, Margrethe A.; Schwarz, Karla G.; Toledo, Camilo; Diaz, Hugo S.; Quintanilla, Rodrigo A.; Del Rio, Rodrigo
    Aims: In mammals, central chemoreception plays a crucial role in the regulation of breathing function in both health and disease conditions. Recently, a correlation between high levels of superoxide anion (O2.-) in the Retrotrapezoid nucleus (RTN), a main brain chemoreceptor area, and enhanced central chemoreception has been found in rodents. Interestingly, deficiency in superoxide dismutase 2 (SOD2) expression, a pivotal antioxidant enzyme, has been linked to the development/progression of several diseases. Despite, the contribution of SOD2 on O2.-regulation on central chemoreceptor function is unknown. Accordingly, we sought to determine the impact of partial deletion of SOD2 expression on i) O2.-accumulation in the RTN, ii) central ventilatory chemoreflex function, and iii) disordered-breathing. Finally, we study cellular localization of SOD2 in the RTN of healthy mice.Methods: Central chemoreflex drive and breathing function were assessed in freely moving heterozygous SOD2 knockout mice (SOD2+/-mice) and age-matched control wild type (WT) mice by whole-body plethysmography. O2.-levels were determined in RTN brainstem sections and brain isolated mitochondria, while SOD2 protein expression and tissue localization were determined by immunoblot, RNAseq and immunofluorescent staining, respectively.Results: Our results showed that SOD2+/-mice displayed reductions in SOD2 levels and high O2.-formation and mitochondrial dysfunction within the RTN compared to WT. Additionally, SOD2+/-mice displayed a heightened ventilatory response to hypercapnia and exhibited overt signs of altered breathing patterns. Both, RNAseq analysis and immunofluorescence co-localization studies showed that SOD2 expression was confined to RTN astrocytes but not to RTN chemoreceptor neurons. Finally, we found that SOD2+/-mice displayed alterations in RTN astrocyte morphology compared to RTN astrocytes from WT mice.Innovation & conclusion: These findings provide first evidence of the role of SOD2 in the regulation of O2.-levels in the RTN and its potential contribution on the regulation of central chemoreflex function. Our results suggest that reductions in the expression of SOD2 in the brain may contribute to increase O2.-levels in the RTN being the outcome a chronic surge in central chemoreflex drive and the development/maintenance of altered breathing patterns. Overall, dysregulation of SOD2 and the resulting increase in O2.-levels in brainstem respiratory areas can disrupt normal respiratory control mechanisms and contribute to breathing dysfunction seen in certain disease conditions characterized by high oxidative stress.