The level and phosphorylation of Hsp70 in the rat liver cytosol after adrenalectomy and hyperthermia

Hepatic heat shock protein Hsp70 synthesis and in vitro phosphorylation were studied in the liver cytosol of intact, adrenalectomized and dexamethasone-administered adrenalectomized rats after 41 degrees C whole body hyperthermic stress. Hsp70 was detected by immunoblotting with N27F3-4 monoclonal antibody recognizing both constitutive and inducible forms of the protein. A comparison between basal and heat stress-induced levels of the protein in the liver cytosol of the three groups of animals suggested that glucocorticoid hormones stimulate the basal synthesis of Hsp70 and inhibit its induction by stress. In both unstressed and hyperthermia-exposed animals, hepatic Hsp70 was detected as a phosphoprotein. The extent of its in vitro phosphorylation was found to be significantly reduced by heat stress or adrenalectomy, but dexamethasone failed to restore it to the original level.     

Subcellular localization and chaperone activities of Borrelia burgdorferi Hsp60 and Hsp70.

Subcellular locations and chaperone functions of Hsp60 and Hsp70 with flagellin were investigated in Borrelia burgdorferi. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) analysis of fractionated cells showed Hsp60 to be present in the soluble fractions and the Triton X-100 detergent-soluble membrane fraction at growth temperatures ranging from 20 to 37 degrees C. The relative amount of Hsp60 associated with the membrane increased with growth temperature. Hsp70 was found in soluble fractions at growth temperatures between 28 and 37 degrees C, but at 20 degrees C it was also present in the Triton X-100-insoluble membrane fraction. Immunoelectron microscopy revealed that the majority of Hsp60 was localized in the cytoplasm but a detectable fraction (approximately 30%) was associated with the cell envelope. The chaperone functions of Hsp60 and Hsp70 were analyzed by immunoprecipitation of [35S]methionine-labeled cell lysates under nondenaturing conditions in the presence or absence of ATP. Hsp70 was found to bind flagellin at all temperatures tested between 33 and 41 degrees C. This association could be decreased with ATP when cells had been incubated at 41 degrees C during radioactive labeling but not at lower temperatures. Both flagellin and Hsp70 were found to associate with Hsp60, forming a complex of the three proteins. Hsp70 association with this complex could be decreased with ATP, but flagellin binding to Hsp60 was ATP independent at all temperatures studied. Both Hsp70 and flagellin were inaccessible to monoclonal antibodies against them when bound to Hsp60. These studies suggest that in B. burgdorferi, a major function of Hsp60 and Hsp70 is in the molecular processing of flagellin.     

Heat shock protein induction in the freshwater prawn Macrobrachium malcolmsonii: acclimation-influenced variations in the induction temperatures for Hsp70

The intracellular build-up of thermally damaged proteins following exposure to heat stress results in the synthesis of heat shock proteins (Hsps). In the present study, the upper thermal tolerance and expression of heat shock protein 70 (Hsp70) were examined in juveniles of the freshwater prawn Macrobrachium malcolmsonii that had been acclimated at two different temperatures, i.e. 20 degrees C (group A) and 30 degrees C (group B), in the laboratory for 30 days. Upper thermal tolerance was determined by a standard method. For heat-shock experiments, prawns in groups A and B were exposed to various elevated temperatures for 3 h each, followed by 1 h recovery at the acclimation temperature. Endogenous levels of Hsp70 were determined in the gill, heart, hepatopancreas and skeletal muscle tissues by Western blotting analysis of one dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The critical thermal maximum (CT max) for prawns in groups A and B was 37.7+/-0.27 degrees C and 41.41+/-0.16 degrees C, respectively. In general, Western blotting analysis for Hsp70 revealed one band at the 70 kDa region, containing both constitutive (Hsc70) and inducible (Hsp70) isoforms, in the gill and heart tissues; these were not detected in the hepatopancreas and skeletal muscle tissues. The onset temperature for Hsp70 induction in both gill and heart tissues was 30 degrees C for prawns in group A and 34 degrees C for those in group B. The optimum induction temperatures (at which Hsp70 induction was maximum) were found to be 34 degrees C and 32 degrees C, respectively, in the gill and heart tissues of group A prawns, and 38 degrees C and 36 degrees C, respectively, for group B prawns. These results suggest that the temperature at which acclimation occurs influences both upper thermal tolerance and Hsp70 induction in M. malcolmsonii.     

A comparison of Hsp70 expression and thermotolerance in adults and larvae of three Drosophila species

Heat shock proteins (Hsps) and other molecular chaperones perform diverse physiological roles. One is to facilitate, in part, organismal thermotolerance, of which the functional consequences depend on Hsp70 concentration and developmental stage in Drosophila melanogaster. To test whether an Hsp70-thermotolerance relationship is a general phenomenon within Drosophila, I assayed Hsp70 concentration at a range of temperatures in intact larvae and adults of three species, D. melanogaster, D. simulans, and D. mojavensis, and compared those results to the increase in survival to heat shock that occurs after an Hsp70 inducing pretreatment. Larvae of D. melanogaster and D. simulans responded similarly to heat; they expressed Hsp70 maximally at 36-37 degrees C, and their tolerance of 1 h heat shocks increased by 1.5-2 degrees C. By contrast, D. mojavensis, which tolerates higher temperatures than do D. melanogaster and D. simulans, expressed Hsp70 only at higher temperatures, although the 36 degrees C pretreatment still increased thermotolerance. Critically, the temperature that maximally induced Hsp70 was a poor inducer of thermotolerance in D. mojavensis and may have harmed larvae. Results for Drosophila adults, which tolerated heat poorly compared to larvae, likewise suggest that a close link between peak Hsp70 expression and maximal induction of thermotolerance is a feature of D. melanogaster, and not of the other species. Neither D. simulans nor D. mojavensis adults increased tolerance after exposure to the temperatures that maximally induced Hsp70.     

The effect of hyperthermia in vitro on vitality of rabbit preimplantation embryos

The aim of our study was to test the influence of short exposure (6 h) of preimplantation rabbit embryos to elevated temperatures (41.5 degrees C or 42.5 degrees C) in vitro on their developmental capacity. Fertilized eggs recovered from female oviducts at the pronuclear stage (19 hpc) were cultured at standard temperature (37.5 degrees C) until the morula stage (72 hpc). Afterwards, the embryos were divided into two groups, cultured for 6 h either at hyperthermic (41.5 degrees C or 42.5 degrees C) or standard temperature (control 37.5 degrees C), post-incubated overnight (16-20 h) at 37.5 degrees C and then evaluated for developmental stages, apoptosis (TUNEL), proliferation (cell number), actin cytoskeleton and presence of heat-shock proteins Hsp70. It was observed that hyperthermia at 41.5 degrees C did not alter progression of embryos to higher preimplantation stages (expanded and hatching/hatched blastocysts), rate of apoptosis, total cell number of blastocysts and structure of actin filament compared to 37.5 degrees C. Western-blotting revealed the presence of heat stress-induced 72 kDa fraction of Hsp70 proteins in granulosa cells (exposed to 41 degrees C) and embryos (exposed to 41.5 degrees C). Following the elevation of temperature to 42.5 degrees C embryo development was dramatically compromised. The embryos were arrested at the morula or early blastocyst stage, showed an increased rate of apoptosis and decreased total cell number compared to control. The structure of actin filaments in most of blastomeres was damaged and such blastomeres often contained apoptotic nuclei. In this group a presence of heat-stress-induced fraction of Hsp70 proteins had not been confirmed. This is the first report demonstrating a threshold of thermotolerance of rabbit preimplantation embryos to hyperthermic exposure in vitro. A detrimental effect of higher temperature on the embryo is probably associated with the loss of their ability to produce Hsp70 de novo, which leads to cytoskeleton alterations and enhanced apoptosis.     

Thermotolerance and HSP70 expression in the Mediterranean fruit fly Ceratitis capitata

The relationship between Hsp70 expression and thermotolerance has been well documented in Drosophila melanogaster. However, there is limited information on this relationship in other insect species. In this report we describe the Hsp70-thermotolerance relationship in one of the major fruit fly pests, Ceratitis capitata (medfly). Hsp70 expression and thermotolerance were assayed at a range of temperatures in several stages of medfly development. The most thermotolerant stage was found to be the late larval stage (100% survival at 41 °C) followed by adult flies and late embryos (100% survival at 39 °C). These three stages showed a positive relationship between Hsp70 expression and thermotolerance. Mid-larval and mid-embryonic stages were found less thermotolerant and the Hsp70-thermotolerance relationship was not evident. Early embryos did not express Hsp70 at any temperature and exhibited the lowest thermotolerance. The relationship between Hsp70 and inducible thermotolerance was also studied in late larvae. A pretreatment at 37-39 °C increased thermotolerance at higher temperatures by approximately 1 °C. In parallel, the pretreatment increased Hsp70 expression suggesting a close link between Hsp70 expression and inducible thermotolerance. The increased Hsp70 levels after pretreatment were found to be due to the increased levels of the hsp70 RNA.     

Tissue-specific variations in the induction of Hsp70 and Hsp64 by heat shock in insects

The patterns of heat-induced synthesis (37 degrees C to 45 degrees C) of heat shock proteins (Hsps) in different tissues of grasshoppers and cockroaches from natural populations and in laboratory-reared gram-pest (Heliothis armigera) were examined by 35S-methionine labeling and sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorography. Whereas 45 degrees C was lethal in most cases, optimal induction of Hsp synthesis was seen between 37 degrees C and 42 degrees C. The ongoing protein synthesis was not much affected at these temperatures, except in the tissues of adult H. armigera exposed to 42 degrees C. The profiles of the Hsps induced in the tissues of the insects, however, were different. From the relative abundance of the synthesis of 70-kDa (Hsp70) and 64-kDa (Hsp64) polypeptides, three categories of heat shock response were identified: (1) induction of abundant Hsp70 but little Hsp64 (malpighian tubules, male accessory glands, and ovaries of adult grasshoppers), (2) abundant Hsp64 but little Hsp70 (testes of adult grasshoppers, testes and malpighian tubules of adult cockroaches, and testes, malpighian tubules, and fat bodies of H. armigera larvae), and (3) induction of both Hsp70 and Hsp64 in more or less equal abundance (ovaries of adult cockroaches, salivary glands of H. armigera larvae, and malpighian tubules, male accessory glands, testes, and ovaries of adult H. armigera). Cockroaches collected from storerooms showed detectable synthesis of Hsp64 and/or Hsp70 only after heat shock, but those collected from drains showed detectable synthesis of both Hsp70 and Hsp64 in different tissues without heat stress. Western blotting showed that the 64-kDa polypeptide in these insects is a member of the Hsp60 family. Grasshopper testes, which synthesized negligible Hsp70 but abundant Hsp64 after heat shock, developed thermotolerance. Thus, heat shock response is modulated by developmental and environmental factors in different tissues of insects.     

Regulated expression of MCP-1 by osteoblastic cells in vitro and in vivo.

Inflammation is characterized by the recruitment of leukocytes from the vasculature. Recent studies have implicated chemokines as an important class of mediators that function principally to stimulate leukocyte recruitment, and in some cases, leukocyte activity. There are four defined chemokine subfamilies based on their primary structure, CXC, CC, C and CX3C. Members of the CC chemokine subfamily, such as monocyte chemoattractant protein 1 (MCP-1), are chemotactic for monocytes and other leukocyte subsets. The studies described below focus on the expression of MCP-1 in vitro and in vivo in an osseous environment. These studies indicate that MCP-1 is typically not expressed in normal bone or by normal osteoblasts in vitro. Upon stimulation by inflammatory mediators, MCP-1 is up-regulated. This expression is temporally and spatially associated with the recruitment of monocytes in both osseous inflammation and during developmentally regulated bone remodelling. Furthermore, exogenous MCP-1 applied to inflamed bone enhances the recruitment of monocytes. Because monocytes produce factors that influence osseous metabolism, including but not limited to prostglandins, platelet-derived growth factor, interleukin-1 or tumor necrosis factor, chemokines that initiate their recruitment are likely to be highly important.     

Rapid, transient, and dose-dependent expression of hsp70 messenger RNA in the rat brain after morphine treatment

Induction of Hsp70 in the brain has been reported after intake of drugs of abuse like amphetamine and lysergic acid diethylamide. In this investigation, gene expression of Hsp70 and other heat shock genes in the rat brain was studied in response to morphine. Twenty milligrams per kilogram morphine intraperitoneally resulted in a marked induction of Hsp70 messenger RNA (mRNA) expression in the frontal cortex with a maximum increase of 13.2-fold after 2 hours. A moderate increase of Hsp27 mRNA expression (6.7-fold) could be observed after 4 hours, whereas mRNA expression of Hsp90 and of the constitutive Hsc70 did not exceed a mean factor of 1.8-fold during the 24 hours interval. The increase in Hsp70 mRNA was dose dependent, showing a significant elevation after doses ranging from 10 to 50 mg/kg morphine. In situ hybridization revealed enhanced Hsp70 mRNA expression mainly in cortical areas, in the hippocampus, in the paraventricular and supraoptic nuclei of the hypothalamus, in the locus coeruleus, as well in the pineal body. The double in situ hybridization technique revealed increased Hsp70 mRNA expression mainly in VGLUT1-positive neurons and to a lesser extent in olig1-positive oligodendroglia. Immunohistochemistry revealed a marked increase of Hsp70 protein in neuronal cells and blood vessels after 12 hours. In contrast to animal experiments, morphine did not increase Hsp70 mRNA expression in vitro in micro-opioid receptor (MOR1)-expressing human embryonic kidney 293 cells, suggesting no direct MOR1-mediated cellular effect. To exclude a body temperature-related morphine effect on Hsp70 mRNA expression, the temperature was recorded. Five to 20 mg/kg resulted in hyperthermia (maximum 40.6 degrees), whereas a high dose (50 mg/kg) that produced the highest mRNA induction, showed a clear hypothermia (minimum 37.2 degrees C). These findings argue against the possibility that Hsp70 induction by morphine is caused by its effect on body temperature. It may be speculated that increased expression of Hsp70 after morphine application protects brain structures against potentially hazardous effects of opiates.     

Heat-shock protein 70 (Hsp70) expression in four limpets of the genus Lottia: interspecific variation in constitutive and inducible synthesis correlates with in situ exposure to heat stress

Limpets of the genus Lottia occupy a broad vertical distribution on wave-exposed rocky shores, a range that encompasses gradients in the frequency and severity of thermal and desiccation stress brought on by aerial emersion. Using western blot analysis of levels of heat-shock protein 70 (Hsp70), we examined the heat-shock responses of four Lottia congeners: Lottia scabra and L. austrodigitalis, which occur in the high-intertidal zone, and L. pelta and L. scutum, which are restricted to the low- and mid-intertidal zones. Our results suggest distinct strategies of Hsp70 expression in limpets occupying different heights and orientations in the rocky intertidal zone. In freshly field-collected animals and in specimens acclimated at ambient temperature ( approximately 14 degrees C) for 14 days, the two high-intertidal species had higher constitutive levels of Hsp70 than the low- and mid-intertidal species. During aerial exposure to high temperatures, the two low-shore species and L. austrodigitalis exhibited an onset of Hsp70 expression at 28 degrees C; no induction of Hsp70 occurred in L. scabra. Our findings suggest that high-intertidal congeners of Lottia employ a "preparative defense" strategy involving maintenance of high constitutive levels of Hsp70 in their cells as a mechanism for protection against periods of extreme and unpredictable heat stress.     

Acclimation of the photosynthetic machinery to high temperature in Chlamydomonas reinhardtii requires synthesis de novo of proteins encoded by the nuclear and chloroplast genomes

The mechanism responsible for the enhancement of the thermal stability of the oxygen-evolving machinery of photosystem II during acclimation of Chlamydomonas reinhardtii to high temperatures such as 35 degrees C remains unknown. When cells that had been grown at 20 degrees C were transferred to 35 degrees C, the thermal stability of the oxygen-evolving machinery increased and within 8 h it was equivalent to that in cells grown initially at 35 degrees C. Such enhancement of thermal stability was prevented by cycloheximide and by lincomycin, suggesting that the synthesis de novo of proteins encoded by both the nuclear and the chloroplast genome was required for this process. No increase in thermal stability was observed when cells that had been grown at 35 degrees C were exposed to heat shock at 41 degrees C, optimum conditions for the induction of the synthesis of homologs of three heat shock proteins (Hsps), namely, Hsp60, Hsp70, and Hsp22. Moreover, no synthesis of these homologs of Hsps was induced at 35 degrees C. Thus it appears likely that Hsps are not involved in the enhancement of the thermal stability of the oxygen-evolving machinery.     

The role of heat shock protein 70 in the thermoresistance of prostate cancer cell line spheroids

Heat shock protein 70 (Hsp70), a protein induced in cells exposed to sublethal heat shock, is present in all living cells and has been highly conserved during evolution. The aim of the current study was to determine the role of heat shock proteins in the resistance of prostate carcinoma cell line spheroids to hyperthermia. In vitro, the expression of Hsp70 by the DU 145 cell line, when cultured as monolayer or multicellular spheroids, was studied using Western blotting and enzyme-linked immunosorbent assay methods. The level of Hsp70 in spheroid cultures for up to 26 days at 37 degrees C remained similar to monolayer cultures. However, in samples treated with hyperthermia at 43 degrees C for 120 min, the spheroid cultures expressed a higher level of Hsp70 as compared to monolayer culture. Under similar conditions of heat treatment, the spheroids showed more heat resistance than monolayer cultures as judged by the number of colonies that they formed in suspension cultures. The results suggest that cells cultured in multicellular spheroids showed more heat resistance as compared to monolayer cultures by producing higher levels of Hsp70.     

Synthesis of 70K stress protein by human leukocytes: effect of exercise in the heat

To determine whether reinduction of 70,000-Da (70K) stress protein synthesis could be used as an assay for thermal history and/or cellular levels of 70K stress protein in hyperthermic humans, leukocytes were obtained before and after 2 h of exercise and then incubated at 37 or 41 degrees C. Five healthy males completed 2 h of treadmill exercise consisting of running at 4-6 km/h for 30-45 min followed by 75-90 min of walking up a 2-10% grade. This exercise bout was performed by two subjects in hot (46 degrees C, 15% relative humidity) and by five subjects in cooler (30 degrees C, 40% relative humidity) environmental conditions. Exercise resulting in rectal temperature (Tre) less than 40 degrees C did not alter the amount of 70K stress protein synthesized by leukocytes incubated at 41 degrees C. In contrast, exercise resulting in Tre greater than 40 degrees C reduced the amount of 70K stress protein synthesized by leukocytes incubated at 41 degrees C. A protein immunoblot, probed with an antibody specific for the inducible 72K stress protein, showed that the reduction of 35S-labeled 70K stress protein in these postexercise leukocyte samples occurred without marked elevations of this protein. In vitro incubation of human leukocytes at 40 degrees C for 15-120 min reduced, in a time-dependent manner, the amount of 70K stress protein synthesized during a subsequent 41 degrees C heat stress. This reduction of 70K stress protein synthesis in 41 degrees C-treated leukocytes was abolished when cycloheximide was present during the 40 degrees C preincubation.(ABSTRACT TRUNCATED AT 250 WORDS)