Heat shock induction of heme oxygenase mRNA in human Hep 3B hepatoma cells

Heat shock treatment of human Hep 3B hepatoma cells led to the induction of mRNA for microsomal heme oxygenase. The maximum induction of heme oxygenase mRNA (5----7-fold) was observed with treatment of cells at 43.5 degrees C, for 60 min. The heat-mediated induction of heme oxygenase mRNA was blocked by simultaneous treatment of cells with actinomycin D or cycloheximide. In contrast to Hep 3B cells, cells of another human hepatoma line, Hep G2, showed little induction of heme oxygenase mRNA by heat treatment. These findings suggest that heat shock treatment induces heme oxygenase mRNA in certain human hepatoma cells, but not in others.     

Simulated diving after heat stress potentiates the induction of heat shock protein 70 and elevates glutathione in human endothelial cells

Heat stress prior to diving has been shown to confer protection against endothelial damage due to decompression sickness. Several lines of evidence indicate a relation between such protection and the heat shock protein (HSP)70 and HSP90 and the major cellular red-ox determinant, glutathione (GSH). The present study has used human endothelial cells as a model system to investigate how heat stress and simulated diving affect these central cellular defense molecules. The results demonstrated for the first time that a simulated dive at 2.6 MPa (26 bar) had a potentiating effect on the heat-induced expression of HSP70, increasing the HSP70 concentration on average 54 times above control level. In contrast, a simulated dive had no significant potentiating effect on the HSP90 level, which might be due to the higher baseline level of HSP90. Both 2 and 24-h dive had similar effects on the HSP70 and HSP90, suggesting that the observed effects were independent of duration of the dive. The rapid HSP response following a 2-h dive with a decompression time of 5 min might suggest that the effects were due to compression or pressure per se rather than decompression and may involve posttranslational processing of HSP. The exposure order seemed to be critical for the HSP70 response supporting the suggestion that the potentiating effect of dive was not due to de novo synthesis of HSP70. Neither heat shock nor a simulated dive had any significant effect on the intracellular GSH level while a heat shock and a subsequent dive increased the total GSH level approximately 62%. Neither of these conditions seemed to have any effect on the GSH red-ox status.     

Tumor-derived heat shock protein 70 peptide complexes are cross-presented by human dendritic cells

Our study demonstrates that tumor-derived heat shock protein (HSP)70 chaperones a tyrosinase peptide and mediates its transfer to human immature dendritic cells (DCs) by receptor-dependent uptake. Human tumor-derived HSP70 peptide complexes (HSP70-PC) thus have the immunogenic potential to instruct DCs to cross-present endogenously expressed, nonmutated, and tumor antigenic peptides that are shared among tumors of the melanocytic lineage for T cell recognition. T cell stimulation by HSP70-instructed DCs is dependent on the Ag bound to HSP70 in that only DCs incubated with HSP70-PC purified from tyrosinase-positive (HSP70-PC/tyr(+)) but not from tyrosinase-negative (HSP70-PC/tyr(-)) melanoma cells resulted in the specific activation of the HLA-A*0201-restricted tyrosinase peptide-specific cytotoxic T cell clone. HSP70-PC-mediated T cell stimulation is very efficient, delivering the tyrosinase peptide at concentrations as low as 30 ng/ml of HSP70-PC for T cell recognition. Receptor-dependent binding of HSP70-PC and active cell metabolism are prerequisites for MHC class I-restricted cross-presentation and T cell stimulation. T cell stimulation does not require external DC maturation signals (e.g., exogenously added TNF-alpha), suggesting that signaling DC maturation is an intrinsic property of the HSP70-PC itself and related to receptor-mediated binding. The cross-presentation of a shared human tumor Ag together with the exquisite efficacy are important new aspects for HSP70-based immunotherapy in clinical anti-cancer vaccination strategies, and suggest a potential extension of HSP70-based vaccination protocols from a patient-individual treatment modality to its use in an allogeneic setting.     

Changes in the heat shock 70 kDa protein level in human neutrophils induced by heat shock

Changes in the content of constitutive and inducible proteins of the family of heat shock 70 kDa proteins (HSP70) caused by heat shock in human neutrophils, white blood cells with an atypically short lifespan, which provide a nonspecific defense of the organism against bacterial pathogens, have been studied. An analysis of the intracellular content of the constitutive and inducible HSP70 proteins by flow cytometry revealed a biphasic dynamics of changes in the protein level, which was characterized by an increase in the protein level immediately after heat shock followed by a decrease within 15–30 min after the termination of heat treatment. Because the inhibitor of protein synthesis cycloheximide did not change the dynamics profile, it was assumed that the increase in the HSP70 level is related not to the de novo synthesis of these proteins but to conformational changes of HSP70 molecules and an increased accessibility of some epitopes for antibody binding. Using a panel of antibodies specific to the N-terminal ATP-binding or the C-terminal substrate-binding domains of the protein, it was shown by cell immunofluorescence and flow cytometry that the heat shock-associated increase in the intracellular HSP70 level results from an increased efficiency of the binding of antibodies recognizing the substrate-binding domain. It was also demonstrated that the decrease in the intracellular HSP70 level after the heat shock, may be partially due to a release into the extracellular space of both the constitutive and inducible HSP70 proteins, which is regulated with the involvement of ABC-transporters.     

Clonogenicity of human leukemic cells protected from cell-lethal agents by heat shock protein 70

Pretreatment of human leukemia THP-1 cells with heat shock protein Hsp70 (Hsp70) protected them from the cell-lethal effects of the topoisomerase II inhibitor, lucanthone and from ionizing radiation. Cell viability was scored in clonogenic assays of single cells grown in liquid medium containing 0.5% methyl cellulose. Colonies were observed and rapidly scored after staining with the tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide. The frequency of abasic sites in the deoxyribonucleic acid (DNA) of THP-1 cells was reduced when these cells were treated with Hsp70. Hsp70 is presumed to have protected the cells by promoting repair of cell DNA, in agreement with previous studies that showed that Hsp70 enhanced base excision repair by purified enzymes. The shoulders of radiation dose-response curves were enhanced by pretreatment of cells with Hsp70 and, importantly, were reduced when cells were transfected with ribonucleic acid designed to silence Hsp70. Hsp70 influenced repair of sublethal damage after radiation.     

Heat shock protein 90 and heat shock protein 70 are components of dengue virus receptor complex in human cells

Dengue virus requires the presence of an unidentified cellular receptor on the surface of the host cell. By using a recently published affinity chromatography approach, an 84-kDa molecule, identified as heat shock protein 90 (HSP90) by matrix-assisted laser desorption ionization-time of flight mass spectrometry, was isolated from neuroblastoma and U937 cells. Based on the ability of HSP90 (84 kDa) to interact with HSP70 (74 kDa) on the surface of monocytes during lipopolysaccharide (LPS) signaling and evidence that LPS inhibits dengue virus infection, the presence of HSP70 was demonstrated in affinity chromatography eluates and by pull-down experiments. Infection inhibition assays support the conclusion that HSP90 and HSP70 participate in dengue virus entry as a receptor complex in human cell lines as well as in monocytes/macrophages. Additionally, our results indicate that both HSPs are associated with membrane microdomains (lipid rafts) in response to dengue virus infection. Moreover, methyl-beta-cyclodextrin, a raft-disrupting drug, inhibits dengue virus infection, supporting the idea that cholesterol-rich membrane fractions are important in dengue virus entry.     

Localization of heat shock protein 70 in rat mast cells

Heat shock proteins (Hsp) are intracellular chaperons, as well as extracellular molecules with immunomodulatory and signaling functions engaged in adaptation to stress on the cellular and organism levels. The presence of Hsp in secretory granules of mast cells (MCs) may be correlated with mast cells’ active participation in adaptation to stress. Using immunoelectron microscopy, we showed that Hsp70 was localized in secretory granules of rat pericardial and peritoneal mast cells. Localization of Hsp70 in rat peritoneal mast cells isolated by Percoll density gradient centrifugation was confirmed by immunoblotting. The possible involvement of mast cells in production of extracellular Hsp70, as well as Hsp70 functions inside the mast cells, is discussed.     

Natural resistance of human beta cells toward nitric oxide is mediated by heat shock protein 70

Human beta cells exhibit increased resistance against nitric oxide (NO) radicals as compared with rodent islet cells. Here we tested whether endogenous heat shock protein 70 (hsp70) accounts for the resistance of human cells. Stable transfection of the human beta cell line CM with an antisense hsp70 mRNA-expressing plasmid (ashsp70) caused selective suppression (>95%) of spontaneously expressed hsp70 but not of hsc70 or GRP75 protein. ashsp70 transfection abolished the resistance of CM cells to the NO donors (Z)-1- (2-(2-aminoethyl)-N-(2-ammonioethyl)amino)diazen-1-ium -1,2-diolate and sodium nitroprusside and increased the proportions of necrotic cells 3-5-fold (p < 0.05) and of apoptotic cells about 2-fold (p < 0.01). Re-induction of hsp70 expression by heat shock re-established resistance to NO toxicity. hsp70 did not exert its protective effect at the level of membrane lipid integrity because radical induced lipid peroxidation appeared independent of hsp70 expression. However, after NO exposure only hsp70-deficient cells showed significantly decreased mitochondrial activity, by 40-80% (p < 0.01). These results suggest a key role of hsp70 in the natural resistance of human beta cells against NO induced injury, by preserving mitochondrial function. These findings provide important implications for the development of beta cell protective strategies in type 1 diabetes and islet transplantation.     

Exogenous heat shock protein HSP70 reduces response of human neuroblastoma cells to lipopolysaccharide

The effect of exogenous heat shock protein HSP70 and lipopolysaccharide (LPS) on the production of reactive oxygen species (ROS), TNFα secretion, and mRNA expression by human neuroblastoma SK-N-SH cells. It was shown that exogenous HSP70 protects neuroblastoma cells from the action of LPS. The protection mechanism of HSP70 includes a reduction in the production of ROS and TNFα and a decrease in the expression of TLR4 and IL-1β mRNA in SK-N-SH cells induced by LPS.     

Toxoplasma gondii-derived heat shock protein 70 stimulates the maturation of human monocyte-derived dendritic cells

We investigated the role of Toxoplasma gondii-derived heat shock protein 70 (TgHSP70) as a dendritic cell (DC) maturation-inducing molecule. TgHSP70 induced the maturation of human monocyte-derived dendritic cells as determined by increased levels of surface markers, namely, CD40, CD80, CD86, and HLA-DR. Moreover, TgHSP70 also reduced phagocytic activity and increased the allostimulatory capacity of DCs, suggesting the functional maturation of DCs by TgHSP70. Maturation of DCs by TgHSP70 also elicited a significant increase in IL-12 production in a polymyxin B-insensitive manner. TgHSP70 also stimulated extracellular signal-regulated kinase and p38 kinase pathways in DCs, and TgHSP70-induced IL-12 production was inhibited by SB203580 but not by PD98059, thus indicating the role of p38 kinase in the maturation of DCs by TgHSP70. This study demonstrates the role of TgHSP70 in the functional maturation of DCs and suggests TgHSP70 as a useful molecule for the development of a vaccine against T. gondii.     

Activation of stress response by ionomycin in rat hepatoma cells

All living systems respond to a variety of stress conditions by inducing the synthesis of stress or heat shock proteins (HSPs), which transiently protect cells. HSP synthesis was preceded by an increase in intracellular free calcium concentration [(Ca(2+))i]. In this study, we show that Ca(2+) ionophore, ionomycin, induced an immediate increase in intracellular free Ca(2+) and examined how this increase affects heat shock response in rat hepatoma cell line H4II-E-C3. Results indicate that incubating H4II-E-C3 cells with 0.3 microM ionomycin at 37 degrees C for 15 min results in the induction of HSP 70 in both Ca(2+)-containing and Ca(2+)-free medium. Associated with this increase in free Ca(2+) is an in vivo change in membrane organization and activation of signaling molecules like ERKS and SAPKs/JNK. In Ca(2+) containing medium HSP 70 induction mediated by HSF-HSE interaction was faster upon ionomycin treatment as compared to heat shock. Our results show that ionomycin, at sub lethal concentration, increases intracellular free Ca(2+) concentration, activates SAPK/JNK and HSF-HSE interaction, and induces HSP 70 synthesis.     

Molecular identification and expression of heat shock cognate 70 (hsc70) and heat shock protein 70 (hsp70) genes in the Pacific oyster Crassostrea gigas

The 70-kDa heat shock protein (Hsp) family is composed of both environmentally inducible (Hsp) and constitutively expressed (Hsc) family members. We sequenced 2 genes encoding an Hsp70 and an Hsc70 in the Pacific oyster Crassostrea gigas. The Cghsc70 gene contained introns, whereas the Cghsp70 gene did not. Moreover, the corresponding amino acid sequences of the 2 genes presented all the characteristic motifs of the Hsp70 family. We also investigated the expression of Hsp70 in tissues of oysters experimentally exposed to metal. A recombinant Hsc72 was used as an antigen to produce a polyclonal antibody to quantify soluble Hsp70 by enzyme-linked immunosorbent assay in protein samples extracted from oysters. Our results showed that metals (copper and cadmium) induced a decrease in cytosolic Hsp70 level in gills and digestive gland of oysters experimentally exposed to metal. These data suggest that metals may inhibit stress protein synthesis.     

Specific stimulation of human apurinic/apyrimidinic endonuclease by heat shock protein 70

We previously demonstrated the stimulation of human apurinic/apyrimidinic endonuclease 1 (HAP1) by heat shock protein 70 (HSP70). In this work, we further defined the functional interaction between these proteins. Digestion of HSP70 by trypsin released 48 and 43 kDa amino terminal fragments that retained the ability to stimulate HAP1. In agreement with this result, an HSP70 N-terminal deletion mutant protein containing amino acids 1-385 was comparable to the full-length protein in its ability to enhance HAP1 activity. HSP70 mutants containing carboxy terminal amino acids 386-640 stimulated HAP1 only slightly, as did unrelated proteins. These results implicate the amino terminal portion of HSP70 in stimulating the activity of HAP1.     

Regulation of heat shock protein 70 synthesis by heat shock in the preimplantation murine embryo

Induced thermotolerance in murine embryos occurs at the 8-cell stage when embryos are maintained in vitro but not until the blastocyst stage if development proceeds in vivo. Present results indicate that ability of embryos to undergo induced thermotolerance is not limited by heat shock protein 70 (HSP70) synthesis. Exposure of 8-cell embryos to 40 degrees C enhanced synthesis of 2 constitutive HSP70 proteins (HSC70 and HSC72) and induced another protein, HSP68; exposure of 43 degrees C was required to induce similar responses in expanded blastocysts. Unlike induced thermotolerance, increased synthesis of HSP70 molecules did not depend on whether embryos were cultured or developed in vivo. Thus, other biochemical mechanisms in addition to HSP70 confer thermotolerance in the preimplantation-stage murine embryo. The observation that the temperature threshold for induction of HSP70 synthesis increased from the 8-cell to the blastocyst stage is indicative of these other biochemical processes.