Asunto(s)
Citoesqueleto/metabolismo , ADN Complementario , Expresión Génica , Células Jurkat/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Vuelo Espacial , División Celular , Regulación de la Expresión Génica , Genes Supresores de Tumor , Humanos , Proteínas de Filamentos Intermediarios/genética , Células Jurkat/ultraestructura , Cinética , Microtúbulos/ultraestructura , Plectina , Proteínas/genética , ARN Mensajero/análisis , Vibración , IngravidezRESUMEN
Heat shock protein levels are increased in cells as a result of exposure to stress. To determine whether heat shock protein regulation could be used to evaluate stress in cells during spaceflight, the response of Jurkat cells to spaceflight and simulated space shuttle launch vibration was investigated by evaluating hsp70 and hsp27 gene expression. Gene expression was assessed by reverse transcription-polymerase chain reaction using mRNA extracted from vibrated, nonvibrated, space-flown, and ground control cells. Results indicate that mechanical stresses of vibration and low gravity do not up-regulate the mRNA for hsp70, although the gene encoding hsp27 is up-regulated by spaceflight but not by vibration. In ground controls, the mRNA for hsp70 and hsp27 increased with time in culture. We conclude that hsp70 gene expression is a useful indicator of stress related to culture density but is not an indicator of the stresses of launch vibration or microgravity. Up-regulation of hsp27 gene expression in microgravity is a new finding.
Asunto(s)
Regulación de la Expresión Génica , Proteínas HSP70 de Choque Térmico/genética , Proteínas de Choque Térmico , Proteínas de Neoplasias/genética , Vuelo Espacial , Estrés Fisiológico , Vibración/efectos adversos , División Celular , Supervivencia Celular , Proteínas de Choque Térmico HSP27 , Humanos , Células Jurkat , Chaperonas Moleculares , ARN Mensajero , Albúmina Sérica Bovina , Linfocitos T/citología , Linfocitos T/metabolismo , Factores de TiempoRESUMEN
Human lymphocytes flown on the Space Shuttle respond poorly to mitogen stimulation and populations of the lymphoblastoid T cell line, Jurkat, manifest growth arrest, increase in apoptosis and time- and microgravity-dependent increases in the soluble form of the cell death factor, Fas/APO-1 (sFas). The potential role of apoptosis in population dynamics of space-flown lymphocytes has not been investigated previously. We flew Jurkat cells on Space Transportation System (STS)-80 and STS-95 to determine whether apoptosis and the apparent microgravity-related release of sFas are characteristic of lymphocytes in microgravity. The effects of spaceflight and ground-based tests simulating spaceflight experimental conditions, including high cell density and low serum concentration, were assessed. Immunofluorescence microscopy showed increased cell associated Fas in flown cells. Results of STS-80 and STS-95 confirmed increase in apoptosis during spaceflight and the release of sFas as a repeatable, time-dependent and microgravity-related response. Ground-based tests showed that holding cells at 1.5 million/ml in medium containing 2% serum before launch did not increase sFas. Reports of increased Fas in cells of the elderly and the increases in spaceflown cells suggest possible similarities between aging and spaceflight effects on lymphocytes.
Asunto(s)
Linfocitos/inmunología , Ingravidez/efectos adversos , Receptor fas/metabolismo , Envejecimiento/inmunología , Apoptosis , Recuento de Células , División Celular , Medios de Cultivo , Humanos , Células Jurkat , Linfocitos/citología , Vuelo EspacialRESUMEN
Alteration in cytoskeletal organization appears to underlie mechanisms of gravity sensitivity in space-flown cells. Human T lymphoblastoid cells (Jurkat) were flown on the Space Shuttle to test the hypothesis that growth responsiveness is associated with microtubule anomalies and mediated by apoptosis. Cell growth was stimulated in microgravity by increasing serum concentration. After 4 and 48 h, cells filtered from medium were fixed with formalin. Post-flight, confocal microscopy revealed diffuse, shortened microtubules extending from poorly defined microtubule organizing centers (MTOCs). In comparable ground controls, discrete microtubule filaments radiated from organized MTOCs and branched toward the cell membrane. At 4 h, 30% of flown, compared to 17% of ground, cells showed DNA condensation characteristic of apoptosis. Time-dependent increase of the apoptosis-associated Fas/ APO-1 protein in static flown, but not the in-flight 1 g centrifuged or ground controls, confirmed microgravity-associated apoptosis. By 48 h, ground cultures had increased by 40%. Flown populations did not increase, though some cells were cycling and actively metabolizing glucose. We conclude that cytoskeletal alteration, growth retardation, and metabolic changes in space-flown lymphocytes are concomitant with increased apoptosis and time-dependent elevation of Fas/APO-1 protein. We suggest that reduced growth response in lymphocytes during spaceflight is linked to apoptosis.