Browsing by Author "Cea, Luis A."

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Active acetylcholine receptors prevent the atrophy of skeletal muscles and favor reinnervation
    (2020) Cisterna, Bruno A.; Vargas, Anibal A.; Puebla, Carlos; Fernandez, Paola; Escamilla, Rosalba; Lagos, Carlos F.; Matus, Maria F.; Vilos, Cristian; Cea, Luis A.; Barnafi, Esteban; Gaete, Hugo; Escobar, Daniel F.; Cardozo, Christopher P.; Saez, Juan C.
    Denervation of skeletal muscles induces severe muscle atrophy, which is preceded by cellular alterations such as increased plasma membrane permeability, reduced resting membrane potential and accelerated protein catabolism. The factors that induce these changes remain unknown. Conversely, functional recovery following denervation depends on successful reinnervation. Here, we show that activation of nicotinic acetylcholine receptors (nAChRs) by quantal release of acetylcholine (ACh) from motoneurons is sufficient to prevent changes induced by denervation. Using in vitro assays, ACh and non-hydrolysable ACh analogs repressed the expression of connexin43 and connexin45 hemichannels, which promote muscle atrophy. In co-culture studies, connexin43/45 hemichannel knockout or knockdown increased innervation of muscle fibers by dorsal root ganglion neurons. Our results show that ACh released by motoneurons exerts a hitherto unknown function independent of myofiber contraction. nAChRs and connexin hemichannels are potential molecular targets for therapeutic intervention in a variety of pathological conditions with reduced synaptic neuromuscular transmission.
  • Thumbnail Image
    Item
    De novo expression of connexin hemichannels in denervated fast skeletal muscles leads to atrophy
    (2013) Cea, Luis A.; Cisterna Irrazabal, Bruno Alejandro; Puebla Aracena, Carlos Alberto; Frank, Marina; Figueroa, Xavier; Cardozo, Christopher; Willecke, Klaus; Latorre, Ramón; Sáez, Juan Carlos
  • No Thumbnail Available
    Item
    Extracellular gentamicin reduces the activity of con nexin hemichannels and interferes with purinergic Ca2+ signaling in HeLa cells
    (2014) Figueroa, Vania A.; Retamal, Mauricio A.; Cea, Luis A.; Salas, Jose D.; Vargas, Anibal A.; Verdugo, Christian A.; Jara, Oscar; Martinez, Agustin D.; Saez, Juan C.
    Gap junction channels (GJCs) and hemichannels (HCs) are composed of protein subunits termed connexins (Cxs) and are permeable to ions and small molecules. In most organs, GJCs communicate the cytoplasm of adjacent cells, while HCs communicate the intra and extracellular compartments. In this way, both channel types coordinate physiological responses of cell communities. Cx mutations explain several genetic diseases, including about 50% of autosomal recessive non-syndromic hearing loss. However, the possible involvement of Cxs in the etiology of acquired hearing loss remains virtually unknown. Factors that induce post-lingual hearing loss are diverse, exposure to gentamicin an aminoglycoside antibiotic, being the most common. Gentamicin has been proposed to block GJCs, but its effect on HCs remains unknown. In this work, the effect of gentamicin on the functional state of HCs was studied and its effect on GJCs was reevaluated in HeLa cells stably transfected with Cxs. We focused on Cx26 because it is the main Cx expressed in the cochlea of mammals where it participates in purinergic signaling pathways. We found that gentamicin applied extracellularly reduces the activity of HCs, while dye transfer across GJCs was not affected. HCs were also blocked by streptomycin, another aminoglycoside antibiotic. Gentamicin also reduced the adenosine triphosphate release and the HC-dependent oscillations of cytosolic free-Ca2+ signal. Moreover, gentamicin drastically reduced the Cx26 HC-mediated membrane currents in Xenopus laevis oocytes. Therefore, the extracellular gentamicin-induced inhibition of Cx HCs may adversely affect autocrine and paracrine signaling, including the purinergic one, which might partially explain its ototoxic effects.
  • Thumbnail Image
    Item
    Pannexin channels mediate the acquisition of myogenic commitment in C2C12 reserve cells promoted by P2 receptor activation
    (2015) Riquelme, Manuel; Cea, Luis A.; Vega, José L.; Puebla Aracena, Carlos Alberto; Vargas Ríos, Aníbal Antonio; Shoji Sánchez, Kenji Fabricio; Subiabre Morales, Mario Enrique; Sáez, Juan Carlos
  • Thumbnail Image
    Item
    Sepsis-Induced Channelopathy in Skeletal Muscles is Associated with Expression of Non-Selective Channels
    (2018) Balboa Castillo, Elisa Ivana; Saavedra Leiva, Fujiko; Cea, Luis A.; Vargas, Aníbal, A.; Ramírez, Valeria; Escamilla, Rosalba; Sáez, Juan Carlos; Regueira Heskia, Tomás
  • No Thumbnail Available
    Item
    Skeletal Muscle Atrophy Induced by Diabetes Is Mediated by Non-Selective Channels and Prevented by Boldine
    (2023) Cea, Luis A.; Vasquez, Walter; Hernandez-Salinas, Romina; Vielma, Alejandra Z.; Castillo-Ruiz, Mario; Velarde, Victoria; Salgado, Magdiel; Saez, Juan C.
    Individuals with diabetes mellitus present a skeletal muscle myopathy characterized by atrophy. However, the mechanism underlying this muscular alteration remains elusive, which makes it difficult to design a rational treatment that could avoid the negative consequences in muscles due to diabetes. In the present work, the atrophy of skeletal myofibers from streptozotocin-induced diabetic rats was prevented with boldine, suggesting that non-selective channels inhibited by this alkaloid are involved in this process, as has previously shown for other muscular pathologies. Accordingly, we found a relevant increase in sarcolemma permeability of skeletal myofibers of diabetic animals in vivo and in vitro due to de novo expression of functional connexin hemichannels (Cx HCs) containing connexins (Cxs) 39, 43, and 45. These cells also expressed P2X(7) receptors, and their inhibition in vitro drastically reduced sarcolemma permeability, suggesting their participation in the activation of Cx HCs. Notably, sarcolemma permeability of skeletal myofibers was prevented by boldine treatment that blocks Cx43 and Cx45 HCs, and now we demonstrated that it also blocks P2X(7) receptors. In addition, the skeletal muscle alterations described above were not observed in diabetic mice with myofibers deficient in Cx43/Cx45 expression. Moreover, murine myofibers cultured for 24 h in high glucose presented a drastic increase in sarcolemma permeability and levels of NLRP3, a molecular member of the inflammasome, a response that was also prevented by boldine, suggesting that, in addition to the systemic inflammatory response found in diabetes, high glucose can promote the expression of functional Cx HCs and activation of the inflammasome in skeletal myofibers. Therefore, Cx43 and Cx45 HCs play a critical role in myofiber degeneration, and boldine could be considered a potential therapeutic agent to treat muscular complications due to diabetes.
  • No Thumbnail Available
    Item
    Vitamin E Blocks Connexin Hemichannels and Prevents Deleterious Effects of Glucocorticoid Treatment on Skeletal Muscles
    (2020) Balboa, Elisa; Saavedra, Fujiko; Cea, Luis A.; Ramirez, Valeria; Escamilla, Rosalba; Vargas, Anibal A.; Regueira, Tomas; Saez, Juan C.
    Glucocorticoids are frequently used as anti-inflammatory and immunosuppressive agents. However, high doses and/or prolonged use induce undesired secondary effects such as muscular atrophy. Recently, de novo expression of connexin43 and connexin45 hemichannels (Cx43 HCs and Cx45 HCs, respectively) has been proposed to play a critical role in the mechanism underlying myofiber atrophy induced by dexamethasone (Dex: a synthetic glucocorticoid), but their involvement in specific muscle changes promoted by Dex remains poorly understood. Moreover, treatments that could prevent the undesired effects of glucocorticoids on skeletal muscles remain unknown. In the present work, a 7-day Dex treatment in adult mice was found to induce weight loss and skeletal muscle changes including expression of functional Cx43/Cx45 HCs, elevated atrogin immunoreactivity, atrophy, oxidative stress and mitochondrial dysfunction. All these undesired effects were absent in muscles of mice simultaneously treated with Dex and vitamin E (VitE). Moreover, VitE was found to rapidly inhibit the activity of Cx HCs in freshly isolated myofibers of Dex treated mice. Exposure to alkaline pH induced free radical generation only in HeLa cells expressing Cx43 or Cx45 where Ca2+ was present in the extracellular milieu, response that was prevented by VitE. Besides, VitE and two other anti-oxidant compounds, Tempol and Resveratrol, were found to inhibit Cx43 HCs in HeLa cells transfectants. Thus, we propose that in addition to their intrinsic anti-oxidant potency, some antioxidants could be used to reduce expression and/or opening of Cx HCs and consequently reduce the undesired effect of glucocorticoids on skeletal muscles.