Ventilación líquida. Metaanálisis y revisión sistemática de la literatura

Introducción: En 1990 con base en las propiedades de los pfc (perfluorocarbonos) se realizó el primer ensayo clínico de ventilación líquida en humanos, en seis recién nacidos prematuros con insuficiencia respiratoria grave observándose mejoría significativa en la oxigenación y en la distensibilidad pulmonar. ¿Qué son los pfc? Producidas en la Segunda Guerra Mundial, son sustancias químicas cuyas propiedades dependen de la unión de los átomos de Fluor-Carbono. Su utilidad para la ventilación mecánica depende de su capacidad de disolver 20 veces más O2 y 3 veces más CO2, que el plasma, evaporándose más rápidamente que el agua a temperatura corporal. Los pfc han sido aprobados para aplicaciones biomédicas como transportadores de oxigeno aplicados intravenosos en situaciones de desastres o en individuos que rechazan ser transfundidos, sin embargo, el interés se ha despertado para su uso en la ventilación mecánica y en el síndrome de insuficiencia respiratoria aguda (sira). Por ello, el objetivo de este metaanálisis y revisión sistemática es la valoración de su uso, en especial de la década de los 90 hasta 2020. Analizando lo que dice la literatura y cómo ha funcionado en pacientes con Covid-19 y sira que ameritaron internamiento en unidades de cuidados intensivos. Material y métodos: Se buscaron revisiones sistemáticas, metaanálisis y ensayos clínicos de las revistas The New England Journal of Medicine, The Lancet , Science, Journal of Apply Physiology, Crit Care Med, Chest, Lung, Journal of Pediatrics, American Journal of Respiratory and Critical Care Medicine, Medicina Intensiva, Revista de la Facultad de Medicina de la UNAM, utilizando las bases de datos de Pubmed, medline, y www.mdconsult.com. Se buscó que los artículos estuvieran enfocados en los resultados del uso de la Ventilación Líquida, tanto en recién nacidos, prematuros, en lactantes y en adultos. El estudio se llevó a cabo de agosto de 2021 a febrero de 2022 y se realizó en el Departamento de Neumología de la Facultad de Medicina de la Universidad Autónoma del Estado de México. Resultados y Discusión: Para el año 2000 existían 1104 publicaciones sobre ventilación líquida, y 564 de ellas eran ensayos clínicos en humanos (medline), que demostraban que la Ventilación Líquida Parcial resulta más ventajosa en neonatos. En adultos sólo ha habido pocos resultados buenos con la Ventilación Líquida Total que mantiene recirculando los pfc dentro de un sistema cerrado. En las revisiones de la Fundación Cochrane se ha demostrado en dos revisiones sistemáticas y en dos metaanálisis que no hay pruebas de efectos beneficiosos de la ventilación líquida parcial en adultos con lesión pulmonar aguda. Sin embargo, surge la pregunta del uso de los pfc asociados al surfactante artificial y de mayor número de estudios con grandes grupos comparativos. La pandemia ocasionada por el Covid-19 ha generalizado el uso de la ventilación mecánica en las unidades de cuidados intensivos. Conclusiones: La ventilación líquida con pfc es una realidad y constituye una nueva alternativa terapéutica para el manejo de los enfermos con síndrome de insuficiencia respiratoria aguda. Su uso con la ventilación líquida parcial no ha demostrado la utilidad esperada en adultos, que seguramente requerirán de la ventilación líquida total. En los neonatos con la ventilación líquida parcial existe ya suficiente evidencia para tenerla como una alternativa en los prematuros y el uso combinado con la administración de surfactante no se debe pasar por alto en los Hospitales de Perinatología a nivel mundial

Large Isoforms of UNC-89 (Obscurin) Are Required for Muscle Cell Architecture and Optimal Calcium Release in Caenorhabditis elegans

Calcium, a ubiquitous intracellular signaling molecule, controls a diverse array of cellular processes. Consequently, cells have developed strategies to modulate the shape of calcium signals in space and time. The force generating machinery in muscle is regulated by the influx and efflux of calcium ions into the muscle cytoplasm. In order for efficient and effective muscle contraction to occur, calcium needs to be rapidly, accurately and reliably regulated. The mechanisms underlying this highly regulated process are not fully understood. Here, we show that the Caenorhabditis elegans homolog of the giant muscle protein obscurin, UNC-89, is required for normal muscle cell architecture. The large immunoglobulin domain-rich isoforms of UNC-89 are critical for sarcomere and sarcoplasmic reticulum organization. Furthermore, we have found evidence that this structural organization is crucial for excitation-contraction coupling in the body wall muscle, through the coordination of calcium signaling. Thus, our data implicates UNC-89 in maintaining muscle cell architecture and that this precise organization is essential for optimal calcium mobilization and efficient and effective muscle contraction

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

Two components of integrin containing attachment complexes, UNC-97/PINCH and UNC-112/MIG-2/Kindlin-2, were recently identified as negative regulators of muscle protein degradation and as having decreased mRNA levels in response to spaceflight. Integrin complexes transmit force between the inside and outside of muscle cells and signal changes in muscle size in response to force and, perhaps, disuse. We therefore investigated the effects of acute decreases in expression of the genes encoding these multi-protein complexes. We find that in fully developed adult Caenorhabditis elegans muscle, RNAi against genes encoding core, and peripheral, members of these complexes induces protein degradation, myofibrillar and mitochondrial dystrophies, and a movement defect. Genetic disruption of Z-line– or M-line–specific complex members is sufficient to induce these defects. We confirmed that defects occur in temperature-sensitive mutants for two of the genes: unc-52, which encodes the extra-cellular ligand Perlecan, and unc-112, which encodes the intracellular component Kindlin-2. These results demonstrate that integrin containing attachment complexes, as a whole, are required for proper maintenance of adult muscle. These defects, and collapse of arrayed attachment complexes into ball like structures, are blocked when DIM-1 levels are reduced. Degradation is also blocked by RNAi or drugs targeting calpains, implying that disruption of integrin containing complexes results in calpain activation. In wild-type animals, either during development or in adults, RNAi against calpain genes results in integrin muscle attachment disruptions and consequent sub-cellular defects. These results demonstrate that calpains are required for proper assembly and maintenance of integrin attachment complexes. Taken together our data provide in vivo evidence that a calpain-based molecular repair mechanism exists for dealing with attachment complex disruption in adult muscle. Since C. elegans lacks satellite cells, this mechanism is intrinsic to the muscles and raises the question if such a mechanism also exists in higher metazoans

The Atypical Calpains: Evolutionary Analyses and Roles in Caenorhabditis elegans Cellular Degeneration

The calpains are physiologically important Ca2+-activated regulatory proteases, which are divided into typical or atypical sub-families based on constituent domains. Both sub-families are present in mammals, but our understanding of calpain function is based primarily on typical sub-family members. Here, we take advantage of the model organism Caenorhabditis elegans, which expresses only atypical calpains, to extend our knowledge of the phylogenetic evolution and function of calpains. We provide evidence that a typical human calpain protein with a penta EF hand, detected using custom profile hidden Markov models, is conserved in ancient metazoans and a divergent clade. These analyses also provide evidence for the lineage-specific loss of typical calpain genes in C. elegans and Ciona, and they reveal that many calpain-like genes lack an intact catalytic triad. Given the association between the dysregulation of typical calpains and human degenerative pathologies, we explored the phenotypes, expression profiles, and consequences of inappropriate reduction or activation of C. elegans atypical calpains. These studies show that the atypical calpain gene, clp-1, contributes to muscle degeneration and reveal that clp-1 activity is sensitive to genetic manipulation of [Ca2+]i. We show that CLP-1 localizes to sarcomeric sub-structures, but is excluded from dense bodies (Z-disks). We find that the muscle degeneration observed in a C. elegans model of dystrophin-based muscular dystrophy can be suppressed by clp-1 inactivation and that nemadipine-A inhibition of the EGL-19 calcium channel reveals that Ca2+ dysfunction underlies the C. elegans MyoD model of myopathy. Taken together, our analyses highlight the roles of calcium dysregulation and CLP-1 in muscle myopathies and suggest that the atypical calpains could retain conserved roles in myofilament turnover

Molecular, genetic and physiological characterisation of dystrobrevin-like (dyb-1) mutants of Caenorhabditis elegans

Dystrobrevins are protein components of the dystrophin complex, whose disruption leads to Duchenne muscular dystrophy and related diseases. The Caenorhabditis elegans dystrobrevin gene (dyb-1) encodes a protein 38 % identical with its mammalian counterparts. The C. elegans dystrobrevin is expressed in muscles and neurons. We characterised C. elegans dyb-1 mutants and showed that: (1) their behavioural phenotype resembles that of dystrophin (dys-1) mutants; (2) the phenotype of dyb-1 dys-1 double mutants is not different from the single ones; (3) dyb-1 mutants are more sensitive than wild-type animals to reductions of acetylcholinesterase levels and have an increased response to acetylcholine; (4) dyb-1 mutations alone do not lead to muscle degeneration, but synergistically produce a progressive myopathy when combined with a mild MyoD/hlh-1 mutation. All together, these findings further substantiate the role of dystrobrevins in cholinergic transmission and as functional partners of dystrophin.<br/

The SLO-1 BK channel of Caenorhabditis elegans is critical for muscle function and is involved in dystrophin-dependent muscle dystrophy

The Caenorhabditis elegans SLO-1 channel belongs to the family of calcium-activated large conductance BK potassium channels. SLO-1 has been shown to be involved in neurotransmitter release and ethanol response. Here, we report that SLO-1 also has a critical role in muscles. Inactivation of the slo-1 gene in muscles leads to phenotypes similar to those caused by mutations of the dystrophin homologue dys-1. Notably, slo-1 mutations result in a progressive muscle degeneration when put into a sensitized genetic background. slo-1 localization was observed by gfp reporter gene in both the M-line and the dense bodies (Z line) of the C.elegans body-wall muscles. Using the inside-out configuration of the patch clamp technique on body-wall muscle cells of acutely dissected wild-type worms, we characterized a Ca2+-activated K+ channel that was identified unambiguously as SLO-1. Since neither the abundance nor the conductance of SLO-1 was changed significantly in dys-1 mutants compared to wild-type animals, it is likely that the inactivation of dys-1 causes a misregulation of SLO-1. All in all, these results indicate that SLO-1 function in C.elegans muscles is related to the dystrophin homologue DYS-

ZYX-1, the unique zyxin protein of \textitCaenorhabditis elegans, is involved in dystrophin-dependent muscle degeneration

In vertebrates, zyxin is a LIM-domain protein belonging to a family composed of seven members. We show that the nematode Caenorhabditis elegans has a unique zyxin-like protein, ZYX-1, which is the orthologue of the vertebrate zyxin subfamily composed of zyxin, migfilin, TRIP6, and LPP. The ZYX-1 protein is expressed in the striated body-wall muscles and localizes at dense bodies/Z-discs and M-lines, as well as in the nucleus. In yeast two-hybrid assays ZYX-1 interacts with several known dense body and M-line proteins, including DEB-1 (vinculin) and ATN-1 (α-actinin). ZYX-1 is mainly localized in the middle region of the dense body/Z-disk, overlapping the apical and basal regions containing, respectively, ATN-1 and DEB-1. The localization and dynamics of ZYX-1 at dense bodies depend on the presence of ATN-1. Fluorescence recovery after photobleaching experiments revealed a high mobility of the ZYX-1 protein within muscle cells, in particular at dense bodies and M-lines, indicating a peripheral and dynamic association of ZYX-1 at these muscle adhesion structures. A portion of the ZYX-1 protein shuttles from the cytoplasm into the nucleus, suggesting a role for ZYX-1 in signal transduction. We provide evidence that the zyx-1 gene encodes two different isoforms, ZYX-1a and ZYX-1b, which exhibit different roles in dystrophin-dependent muscle degeneration occurring in a C. elegans model of Duchenne muscular dystrophy