Heat shock induces apoptosis in mouse thymocytes and protects them from glucocorticoid-induced cell death (original) (raw)
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Pathology Research and Practice, 2000
The aim of our study was to investigate a possible expression of different HSPs in rat's thymuses after hydrocortisone administration. The thymuses of 41 young rats (25 to 45 days age old) were studied immunocytochemically: 12 rats were not injected, 8 received an injection of physiological serum, and 21 received HC (125 mg/kg). HSP27, 70 and 110 expression was investigated following the PAP method. HSPs27 were expressed neither in normal thymic lobules nor in the cortical thymic cells after HC injection. HSPs70 were objectivated only in I control animal, but were frankly expressed in cortical thymic cells I to 48 hours after HC injection and remained significantly expressed until the 7th day after HC injection. HSPs II 0 were present in only I control animal and appeared to be distinctly expressed 48 hours after HC injection. HSPs70 and 110 were never expressed in the regenerated thymuses 14 and 21 days after HC injection. This report objectivates for the first time 70 and 110 kDa "stress proteins" expression during the Ihymic apoptosis induced by glucocorticoids.
Critical parameters influencing hyperthermia-induced apoptosis in human lymphoid cell lines
Apoptosis, 1998
Brief mild hyperthermia is sufficient to induce apoptosis (programmed cell death) in many cell lines. Here we describe the effects of a number of factors modulating heat shock induced apoptosis outcomes. We report the effects of cell type, heat load, recovery times, cellular growth phase, and protein synthesis on the levels of apoptoses seen in heat stressed cell populations. We observe that a number of cell lines are competent to undergo heat stress induced apoptosis using both the comet assay and cellular and nuclear morphologies. Of the cell lines tested we saw a wide spectrum of sensitivities, ranging from resistant (less than 1% apoptotic after 12 h) to exquisitely sensitive (>95%). By incrementally increasing the heat load from 37-49 • C, we observed a gradual increase in apoptosis with a significant change from apoptotic to necrotic death at temperatures beyond 45 • C. The kinetics of the apoptotic response to heat shock were also examined. A time dependent increase in apoptotic cell death was seen after initial hyperthermic treatment with most cell types reaching a 'plateau' at 18 h. In addition to these parameters we report that growth phase has a strong influence on the number of apoptoses induced as a result of heat stress. Cultured cells, grown to a plateau, undergo apoptosis at a much higher level than similarly treated cells taken during an exponential phase of growth. Finally, we determined the necessity of protein synthesis for apoptotic competency.
Journal of Pathology, 1991
Mild hyperthermia is known to enhance apoptosis in a range of normal and neoplastic cell populations. Studies of tumours previously shown to respond to heating in this manner might be expected to provide insights not only into the mechanism of hyperthermic cell killing, but also into the apoptotic process in general. In the present study, cell death induced by 43°C heating for 30 min in two human Burkitt's lymphoma lines, BM 13674 and WWl, and in murine mastocytoma P-8 15 x 2.1 was found to be exclusively apoptotic in type, identification being based on light and electron microscopic appearances and on the presence of internucleosomal cleavage of DNA into fragments that are multiples of 18G-200 base pairs, which was demonstrated by agarose gel electrophoresis, The heat-induced apoptosis was prevented by the presence of zinc sulphate, an inhibitor of the endonuclease considered to be responsible for the DNA cleavage, but was not suppressed by the protein synthesis inhibitor cycloheximide. The findings question the validity of the widely held view that active protein synthesis is an invariable prerequisite for the execution of apoptosis. It is suggested that an inositol triphosphate-mediated increase in cytosolic Ca2+, resulting from limited membrane damage, might be the critical event responsible for activation of apoptosis by mild hyperthermia.
Heat-shock protein expression on the membrane of T cells undergoing apoptosis
Immunology, 1996
Heat-shock proteins (hsp) represent a highly conserved family of proteins, normally localized in the cytoplasm and nucleus, whose expression is induced in situations involving cell stress. This paper reports the unusual translocation of hsp to the cell membrane of T cells undergoing apoptosis. We observed that glucocorticosteroid-induced thymocyte death is associated to the surface expression of hsp 60 and hsp 70 in a discrete fraction of apoptotic cells. hsp surface
Heat Shock Proteins Increase Resistance to Apoptosis
Experimental Cell Research, 1996
Heat shock treatment of cells increases their survival and resistance to apoptosis. The kinetics of development of this resistance correlates with the kinetics of synthesis of heat shock proteins (hsps). U937 and Wehi-s cells were cultured for 1 h at 42 degrees C, conditions which induced the synthesis of heat shock proteins 27, 70, and 90. The cells were subsequently permitted to recover for a 2-h period, prior to exposure to the apoptosis inducing agents actinomycin-D (5 micrograms/ml), camptothecin (5 micrograms/ml), and etoposide (25 micrograms/ml). Apoptosis was determined by both DNA fragmentation and flow cytometric analysis. Heat-shocked cultures had a smaller number of apoptotic compared to control cultures when both were exposed to apoptosis inducing stimuli. Transfected Wehi-s cells constitutively overexpressing human hsp 70 or 27 were then examined for their resistance to apoptosis inducing by these drugs. Using the MTT assay, hsp 27 and 70 overexpressing cells exhibited an increased resistance to cell death when compared to the parental line. The parental line demonstrated features of apoptosis, that is, cell shrinkage and single- and double-strand DNA breaks. Taken together these results demonstrate that an increase in cellular levels of hsp 27 or 70, either by a mild heat shock treatment or by stable transfection, increases the resistance of U937 and Wehi-s cells to apoptotic cell death.
Induced thermotolerance to apoptosis in a human T lymphocyte cell line
Journal of Cellular Physiology, 1992
A brief exposure to elevated temperatures elicits, in all organisms, a transient state of increased heat resistance known as thermotolerance. The mechanism for this thermotolerant state is unknown primarily because it is not clear how mild hyperthermia leads to cell death. The realization that cell death can occur through an active process of self destruction, known as apoptosis, led us to consider whether thermotolerance provides protection against this mode of cell death. Apoptosis is a common and essential form of cell death that occurs under both physiological and pathological conditions. This mode of cell death requires the active participation of the dying cell and in this way differs mechanistically from the alternative mode of cell death, necrosis. Here we show that mild hyperthermia induces apoptosis in a human leukemic T cell line. This is evidenced by chromatin condensation, nuclear fragmentation and the cleavage of DNA into oligonucleosome size units. DNA fragmentation is a biochemical hallmark of apoptosis and requires the activation of an endogenous endonuclease. The extent of DNA fragmentation was proportional to the severity of heat stress for cells heated at 43°C from 30 to 90 minutes. A brief conditioning heat treatment induced a resistance to apoptosis. This was evident as a resistance to DNA fragmentation and a reduction in the number of apoptotic cells after a heat challenge. Resistance to DNA fragmentation developed during a recovery period at 37°C and was correlated with enhanced heat shock protein (hsp) synthesis. This heat-induced resistance to apoptosis suggests that thermotolerant cells have gained the capacity to prevent the onset of this pathway of self-destruction. An examination of this process in heated cells should provide new insights into the molecular basis of cellular thermotolerance. © 1992 Wiley-Liss, Inc.
Lack of heat shock response triggers programmed cell death in a rat histiocytic cell line
FEBS Letters, 1999
Stress response is a universal phenomenon. However, a rat histiocytic cell line, BC-8, showed no heat shock response and failed to synthesize heat shock protein 70 (hsp70) upon heat shock at 42³C for 30 min. BC-8 is a clone of AK-5, a rat macrophage tumor line that is adapted to grow in culture and has the same chromosome number and tumorigenic potential as AK-5. An increase in either the incubation temperature or time or both to BC-8 cells leads to loss of cell viability. In addition, heat shock conditions activated apoptotic cell death in these cells as observed by cell fragmentation, formation of nuclear comets, apoptotic bodies, DNA fragmentation and activation of ICE-like cysteine proteases. Results presented here demonstrate that BC-8 cells cannot mount a typical heat shock response unlike all other eukaryotic cells and that in the absence of induction of hsps upon stress, these cells undergo apoptosis at 42³C.
Antioxidant-mediated inhibition of the heat shock response leads to apoptosis
FEBS Letters, 1999
We examined the hypothesis that reactive oxygen species (ROS) contribute to the induction of heat shock proteins (hsps) during stress response. Exposure of HL-60 human myelocytic cells to 42 degrees C induced both hsp72 and hsp27. In the presence of the antioxidant molecules pyrrolidine dithiocarbamate or 1,10-phenanthroline induction of hsp72 and 27 was significantly decreased, while N-acetyl-L-cysteine caused a slight reduction. Prevention of hsp induction was associated with heat sensitization and increased caspase activity, indicating that the cells were undergoing apoptosis. These data suggest that ROS contribute to the induction of hsps and furthermore, that hsp induction and apoptosis are mutually exclusive events within the same cell.