A HEAT-SHOCK-LIKE RESPONSE WITH CYTOSKELETAL DISRUPTION OCCURS FOLLOWING HYDROSTATIC-PRESSURE IN MG-63 OSTEOSARCOMA CELLS

Human osteosarcoma cells, MG-63, were exposed to a hydrostatic pressur e shock of 4.0 MPa for 20 min. Changes in subcellular distribution of the cytoskeletal elements and heat shock protein 70 (hsp70) were follo wed by indirect immunofluorescence and by avidin-biotin-peroxidase pro tocols. During recovery, total cellular RNA was determined and actin a nd aldolase mRNA content was followed using reverse transcription - po lymerase chain reaction techniques. Hydrostatic pressure caused cell r ounding (but not cell death), disruption of microtubules, collapse of intermediate filaments to a perinuclear location, collapse of actin st ress fibers into globular aggregates in the cytoplasm, and the formati on of several large elongated intranuclear actin inclusions. During re covery, the cells flattened, reorganized microtubules, and redistribut ed intermediate filaments prior to the reappearance of actin stress fi bers. At 20 and 60 min following the initiation of hydrostatic pressur e, there was increased anti-hsp70 staining at the nuclear membrane and concentration of hsp70 in four to six granules in the nucleus. At 120 min following the hydrostatic pressure, hsp70 showed intense staining in the cytoplasm and hsp70-containing granules in the nucleus disappe ared. Cellular RNA decreased during the first 120-min posthydrostatic pressure shock and then recovered to near prehydrostatic pressure trea tment levels by 240 min. Actin mRNA abundance, in relation to aldolase mRNA abundance, showed the same temporal pattern of initial decrease, followed by increase as did total RNA. Review of the literature indic ated that eukaryotic cells respond to heat shock and to hydrostatic pr essure by disruption of the cytoskeletal elements and by similar modif ications in genetic expression. In this study, the observed responses of MG-63 cells to a 4-MPa hydrostatic pressure shock was like the repo rted response of mammalian cells to a 43 degrees C heat shock.