Resistance of Ehrlich tumor cells to apoptosis can be due to accumulation of heat shock proteins

Niosomes loading N-acetyl-L-cysteine for cancer treatment in vivo study

Scientists are seeking to find an effective treatment for tumors that has no side effects. N-Acetyl-l-cysteine (NAC) is a thiol compound extracted from garlic. Current study explores the potential of NAC-loaded niosomes (NAC-NIO) for tumor treatment in mice. NAC-loaded niosomes' efficiency, morphology, UV absorption, size distribution, zeta potential, release, and FTIR analysis were evaluated. For vivo study, 25 male BALB/c mice were divided to five groups: gp1 negative control (receive saline), gp2 positive control (tumor group), gp3 treated with NAC, gp4 treated with NAC-NIO at the same time of tumor injection, and gp5 treated with NAC-NIO after tumor growth (day 14). The impact of NAC-NIO on the tumor treatment was evaluated by measuring tumor size progress, comet assay, oxidative stress parameters (GSH, nitric oxide, MDA), western blot analysis, and histopathological investigation of tissues. NAC-NIO showed 72 ± 3% encapsulation efficiency and zeta potential - 5.95 mV with spherical shape. It was found that oral administration of NAC-NIO in a dose of 50 mg/kg provided significant protection against tumor cells. Our formulation decreases DNA injury significantly (P < 0.05). It was noticed that NAC-NIO can increase oxidative stress levels in tumor tissue. On the other hand, the caspase 3 and caspase 9 gene expression were upregulated significantly (P < 0.001) in mice administrated NAC-NIO compared with all other groups. Histological studies confirmed the protective effect of NAC-NIO against tumor especially for treatment during tumor growth protocol. The results suggested that oral delivery of NAC-NIO formulation improved antioxidant effect.

2-Aminoethyl Dihydrogen Phosphate (2-AEH2P) Associated with Cell Metabolism-Modulating Drugs Presents a Synergistic and Pro-Apoptotic Effect in an In Vitro Model of the Ascitic Ehrlich Tumor

The progression and maintenance of cancer characteristics are associated with cellular components linked to the tumor and non-cellular components with pro-tumoral properties. Pharmacological association with antagonists of the cellular components of the tumor, such as anti- and pro-apoptotic drugs, represents a novel adjuvant strategy. In this study, the antiproliferative, pro-apoptotic, and pharmacological effects of the combination of monophosphoester 2-AEH2P with Simvastatin, Coenzyme Q10, the chemotherapeutic drug paclitaxel, and colony-stimulating factor (GM-CSF) were evaluated. Tests were conducted to determine cytotoxic activity using the MTT method, cell cycle phases, and fragmented DNA by flow cytometry, mitochondrial membrane potential, expression of cell markers Bcl2, TNF-α/DR-4, Cytochrome c, caspase 3, and P53, and analysis of drug combination profiles using Synergy Finder 2.0 Software. The results showed a synergistic effect among the combinations, compared to individual treatments with the monophosphoester and other drugs. In addition, there was modulation of marker expression, indicating a pro-apoptotic and immunomodulatory effect of 2-AEH2P. Pharmacological analysis revealed that tumor cells treated with GM-CSF + 2-AEH2P exhibited a synergistic effect, while groups of tumor cells treated with paclitaxel, Coenzyme Q10, and Simvastatin showed additive effects. Furthermore, treatment with the paclitaxel + 2-AEH2P combination (12 h) resulted in a significant reduction in mitochondrial membrane potential. Pharmacological combinations for normal cells did not exhibit deleterious effects compared to mammary carcinomatosis tumor (EAT) cells.

HspBP1 is a dual function regulatory protein that controls both DNA repair and apoptosis in breast cancer cells

The Hsp70-binding protein 1 (HspBP1) belongs to a family of co-chaperones that regulate Hsp70 activity and whose biological significance is not well understood. In the present study, we show that when HspBP1 is either knocked down or overexpressed in BRCA1-proficient breast cancer cells, there were profound changes in tumorigenesis, including anchorage-independent cell growth in vitro and in tumor formation in xenograft models. However, HspBP1 did not affect tumorigenic properties in BRCA1-deficient breast cancer cells. The mechanisms underlying HspBP1-induced tumor suppression were found to include interactions with BRCA1 and promotion of BRCA1-mediated homologous recombination DNA repair, suggesting that HspBP1 contributes to the suppression of breast cancer by regulating BRCA1 function and thereby maintaining genomic stability. Interestingly, independent of BRCA1 status, HspBP1 facilitates cell survival in response to ionizing radiation (IR) by interfering with the association of Hsp70 and apoptotic protease-activating factor-1. These findings suggest that decreased HspBP1 expression, a common occurrence in high-grade and metastatic breast cancers, leads to genomic instability and enables resistance to IR treatment.

What are the immune responses during the growth of Ehrlich's tumor in ascitic and solid form?

Traditionally, Ehrlich's tumor is used in experimental oncology to investigate the therapeutic capacity of different synthetic chemotherapeutic agents or to evaluate the antitumoral activity of different substances of natural origin. However, the understanding of immune mechanisms during Ehrlich carcinogenesis is still limited. In this review, we seek to describe the immune response during Ehrlich's tumor growth, and natural response without the influence of pharmacological administration, immunotherapies or concomitant challenges. The study followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). A systematic review was carried out that included experimental trials with mice challenged with Ehrlich's tumor. The research was carried out in three databases including MEDLINE/PubMed, Scopus, Latin American and Caribbean Literature in Health Sciences (LILACS). The searches resulted in 913 papers being found, of which 55 articles were considered eligible, and of these 55, 29 were selected for analysis. Findings indicate that there is an increase in the expression of M2 and T Helper (TH2) macrophages and of the cytokines IL-17, IL-1B, IL-6 and PGE in the ascitic form of Ehrlich. These phenotypic expressions are also found in ascitic neoplasms in humans. Ehrlich's solid tumor was characterized by increased expression of CD4, CD8, neutrophils and TNF-a, Foxp3 + and Qa-2 +, and these characteristics are analogous to human breasts cancers. It is our understanding that further studies are needed to assess the immune mechanisms in Ehrlich's tumor, since these findings can be used to improve cancer treatments that are analogous to Ehrlich's tumor.

Integrating Loco-Regional Hyperthermia Into the Current Oncology Practice: SWOT and TOWS Analyses

Moderate hyperthermia at temperatures between 40 and 44°C is a multifaceted therapeutic modality. It is a potent radiosensitizer, interacts favorably with a host of chemotherapeutic agents, and, in combination with radiotherapy, enforces immunomodulation akin to “in situ tumor vaccination.” By sensitizing hypoxic tumor cells and inhibiting repair of radiotherapy-induced DNA damage, the properties of hyperthermia delivered together with photons might provide a tumor-selective therapeutic advantage analogous to high linear energy transfer (LET) neutrons, but with less normal tissue toxicity. Furthermore, the high LET attributes of hyperthermia thermoradiobiologically are likely to enhance low LET protons; thus, proton thermoradiotherapy would mimic ¹²C ion therapy. Hyperthermia with radiotherapy and/or chemotherapy substantially improves therapeutic outcomes without enhancing normal tissue morbidities, yielding level I evidence reported in several randomized clinical trials, systematic reviews, and meta-analyses for various tumor sites. Technological advancements in hyperthermia delivery, advancements in hyperthermia treatment planning, online invasive and non-invasive MR-guided thermometry, and adherence to quality assurance guidelines have ensured safe and effective delivery of hyperthermia to the target region. Novel biological modeling permits integration of hyperthermia and radiotherapy treatment plans. Further, hyperthermia along with immune checkpoint inhibitors and DNA damage repair inhibitors could further augment the therapeutic efficacy resulting in synthetic lethality. Additionally, hyperthermia induced by magnetic nanoparticles coupled to selective payloads, namely, tumor-specific radiotheranostics (for both tumor imaging and radionuclide therapy), chemotherapeutic drugs, immunotherapeutic agents, and gene silencing, could provide a comprehensive tumor-specific theranostic modality akin to “magic (nano)bullets.” To get a realistic overview of the strength (S), weakness (W), opportunities (O), and threats (T) of hyperthermia, a SWOT analysis has been undertaken. Additionally, a TOWS analysis categorizes future strategies to facilitate further integration of hyperthermia with the current treatment modalities. These could gainfully accomplish a safe, versatile, and cost-effective enhancement of the existing therapeutic armamentarium to improve outcomes in clinical oncology.

Assessment of Anticancer Drug Effects on Pancreatic Cancer Cells under Glucose-Depleted Conditions Using Intracellular and Extracellular Amino Acid Metabolomics

Previously, we developed a method to evaluate states of cells treated with anticancer drugs via the comprehensive analysis of amino acids, termed amino acid metabolomics. In the present study, we evaluated the effects of the anticancer drugs, gemcitabine hydrochloride and pyrvinium pamoate, on the proliferation of a pancreatic cancer cell line (PANC-1) under hypoglycemic conditions using amino acid metabolomics. Intracellular and extracellular amino acid profiles of PANC-1 were determined by hydrophilic interaction chromatography-tandem mass spectrometry with simple pretreatment. Changes to the drugs' anticancer effects resulting from glucose starvation conditions were presented in score plots obtained from principal component analyses. In particular, the analysis of intracellular amino acids was found to be the superior approach because the results allowed a clearer assessment of the cell state. Further, orthogonal partial least squares discriminant analysis was performed to search for amino acid candidates that discriminate with anticancer drug-treated PANC-1 cells. We identified several amino acids that might be able to distinguish the drug-treated group from the control group. These results might provide a better understanding of the mechanisms underlying cell responses such as drug resistance or austerity. The present study is the first to evaluate the efficacy of anticancer drugs under glucose starvation based on the analysis of the variation of extracellular and intracellular amino acid profiles in vitro.

Targeting HSP70 and GRP78 in canine osteosarcoma cells in combination with doxorubicin chemotherapy

Heat shock proteins (HSPs) are molecular chaperones subdivided into several families based on their molecular weight. Due to their cytoprotective roles, these proteins may help protect cancer cells against chemotherapy-induced cell death. Investigation into the biologic activity of HSPs in a variety of cancers including primary bone tumors, such as osteosarcoma (OSA), is of great interest. Both human and canine OSA tumor samples have aberrant production of HSP70. This study assessed the response of canine OSA cells to inhibition of HSP70 and GRP78 by the ATP-mimetic VER-155008 and whether this treatment strategy could sensitize cells to doxorubicin chemotherapy. Single-agent VER-155008 treatment decreased cellular viability and clonogenic survival and increased apoptosis in canine OSA cell lines. However, combination schedules with doxorubicin after pretreatment with VER-155008 did not improve inhibition of cellular viability, apoptosis, or clonogenic survival. Treatment with VER-155008 prior to chemotherapy resulted in an upregulation of target proteins HSP70 and GRP78 in addition to the co-chaperone proteins Herp, C/EBP homologous transcription protein (CHOP), and BAG-1. The increased GRP78 was more cytoplasmic in location compared to untreated cells. Single-agent treatment also revealed a dose-dependent reduction in activated and total Akt. Based on these results, targeting GRP78 and HSP70 may have biologic activity in canine osteosarcoma. Further studies are required to determine if and how this strategy may impact the response of osteosarcoma cells to chemotherapy.

Hsp70 in cancer: back to the future

Mechanistic studies from cell culture and animal models have revealed critical roles for the heat shock protein Hsp70 in cancer initiation and progression. Surprisingly, many effects of Hsp70 on cancer have not been related to its chaperone activity, but rather to its role(s) in regulating cell signaling. A major factor that directs Hsp70 signaling activity appears to be the co-chaperone Bag3. Here, we review these recent breakthroughs, and how these discoveries drive drug development efforts.

The Chemical Biology of Molecular Chaperones--Implications for Modulation of Proteostasis

Protein homeostasis (proteostasis) is inextricably tied to cellular health and organismal lifespan. Aging, exposure to physiological and environmental stress, and expression of mutant and metastable proteins can cause an imbalance in the protein-folding landscape, which results in the formation of non-native protein aggregates that challenge the capacity of the proteostasis network (PN), increasing the risk for diseases associated with misfolding, aggregation, and aberrant regulation of cell stress responses. Molecular chaperones have central roles in each of the arms of the PN (protein synthesis, folding, disaggregation, and degradation), leading to the proposal that modulation of chaperone function could have therapeutic benefits for the large and growing family of diseases of protein conformation including neurodegeneration, metabolic diseases, and cancer. In this review, we will discuss the current strategies used to tune the PN through targeting molecular chaperones and assess the potential of the chemical biology of proteostasis.

Hyperthermia Induces Apoptosis of 786-O Cells through Suppressing Ku80 Expression

Hyperthermia as an anticancer method has been paid increasing attention in recent years. Several studies have shown that hyperthermia can kill tumor cells by inducing apoptosis. However, the underlying molecular mechanisms of hyperthermia-induced apoptosis are largely unknown. To investigate the effects and molecular mechanism of hyperthermia on the apoptosis in renal carcinoma 786-O cells, we firstly examined apoptosis and Ku expression in 786-O cell line treated with heat exposure (42°C for 0-4 h). The results showed that hyperthermia induced apoptosis of 786-O cells, and suppressed significantly Ku80 expression, but not Ku70 expression. Next, we knock-down Ku80 in 786-O cells, generating stable cell line 786-O-shKu80, and detected apoptosis, cell survival and cell cycle distribution. Our data showed higher apoptotic rate and lower surviving fraction in the stable cell line 786-O-shKu80 compared with those in control cells, exposed to the same heat stress (42°C for 0-4 h). Moreover, the results also showed suppression of Ku80 led to G2/M phase arrest in the stable cell line 786-O-shKu80 following heat treatment. Together, these findings indicate that Ku80 may play an important role in hyperthermia-induced apoptosis and heat-sensitivity of renal carcinoma cells through influencing the cell cycle distribution.

The discovery of Hsp70 domain with cell-penetrating activity

Chaperone Hsp70 can cross the plasma membrane of living cells using mechanisms that so far have not received much research attention. Searching the part of the molecule that is responsible for transport ability of Hsp70, we found a cationic sequence composed of 20 amino acid residues on its surface, KST peptide, which was used in further experiments. We showed that KST peptide enters living cells of various origins with the same efficiency as the full-length chaperone. KST peptide is capable of carrying cargo with a molecular weight 30 times greater than its own into cells. When we compared the membrane-crossing activity of KST peptide in complex with Avidin (KST-Av complex) with that of similarly linked canonical TAT peptide, we found that TAT peptide penetrated SK-N-SH human neuroblastoma cells at a similar rate and efficiency as the KST peptide. Furthermore, KST peptide can carry protein complexes consisting of a specific antibody coupled to the peptide through the Avidin bridge. An antibody to Hsp70 delivered to SK-N-SH cells with high expression level of Hsp70 reduced the protective power of the chaperone and sensitized the cells to the pro-apoptotic effect of staurosporine. We studied the mechanisms of penetration of KST-Av and full-length Hsp70 inside human neuroblastoma SK-N-SH and human erythroleukemia K-562 cells and found that both used an active intracellular transport mechanism that included vesicular structures and negatively charged lipid membrane domains. Competition analysis of intracellular transport showed that the chaperone reduced intracellular penetration of KST peptide and conversely KST peptide prevented Hsp70 transport in a dose-dependent manner.

Hyperthermia, radiation and chemotherapy: the role of heat in multidisciplinary cancer care

The compelling biologic basis for combining hyperthermia with modern cancer therapies including radiation and chemotherapy was first appreciated nearly half a century ago. Hyperthermia complements radiation as conditions contributing to radio-resistance generally enhance sensitivity to heat and sensitizing effects occur through increased perfusion/tumor oxygenation and alteration of cellular death pathways. Chemosensitization with hyperthermia is dependent on the particular mechanism of effect for each agent with synergistic effects noted for several commonly used agents. Clinically, randomized trials have demonstrated benefit including survival with the addition of hyperthermia to radiation or chemotherapy in treatment of a wide range of malignancies. Improvements in treatment delivery techniques, streamlined logistics, and greater understanding of the relationship of thermal dosimetry to treatment outcomes continue to facilitate wider clinical implementation. Evolving applications include thermal enhancement of immunotherapy, targeted drug delivery and application of principals of thermal biology towards integration of thermal ablation into multimodality oncologic care.

Antitumor activity of cucumarioside A2-2

BACKGROUND

The cytotoxic activity of sea cucumber glycosides against different types of cells and cell lines, including human tumor cell lines, has been studied for many years. However, the molecular mechanism(s) of the antitumor action of triterpene glycosides on cancer cells remain unclear. This article reports a continuation of investigations of triterpene glycoside cucumarioside A2-2 isolated from the Far-Eastern sea cucumber Cucumaria japonica. It describes a study of glycoside anticancer activity in vivo and glycoside interaction with mouse Ehrlich carcinoma cells in vitro.

METHODS

The cytotoxicity of cucumarioside A2-2 and its effect on apoptosis, the cell cycle, DNA biosynthesis and p53 activity, and glycoside anticancer action against Ehrlich carcinoma cells were studied.

RESULTS

Cucumarioside A2-2 influences tumor cell viability at micromolar concentrations. The EC50 for glycoside estimated by nonspecific esterase assay and MTT assay was 2.1 and 2.7 μM, respectively. Cucumarioside A2-2 at a subcytotoxic range of concentrations exhibits a cytostatic effect by blocking cell proliferation and DNA biosynthesis in the S phase. It may induce apoptosis in tumor cells in a caspase-dependent way, bypassing the activation of the p53-dependent segment.

CONCLUSION

The anticancer and proapoptotic properties of cucumarioside A2-2 may be due to direct interaction of the glycoside with tumor cells. The in vivo anticancer effect of cucumarioside A2-2 may be associated with the ability of the drug to arrest the cell cycle in the synthetic phase and induce programmed tumor cell death.

Autophagy, protein aggregation and hyperthermia: a mini-review

PURPOSE

We aim to explore the role of macroautophagy in cellular responses to hyperthermia. Protein damage incurred during hyperthermia can either lead to cell death or may be repaired by polypeptide quality control pathways including: (1) the deterrence of protein unfolding by molecular chaperones and (2) proteolysis of the denatured proteins within the proteasome. A third pathway of protein quality control is triggered by formation of protein aggregates in the heat shocked cell. This is the macroautophagy pathway in which protein aggregates are transported to specialised organelles called autolysosomes capable of degrading the aggregates. The consequences for cell viability of triggering this pathway are complex and may involve cell death, although under many circumstances, including exposure of cells to hyperthermia, autophagy leads to enhanced cell survival. We have discussed mechanisms by which cells detect protein aggregates and recruit them into the macroautophagy pathway as well as the potential role of inhibiting this process in hyperthermia.

CONCLUSIONS

Directed macroautophagy, with its key role in protein quality control, seems an attractive target for a therapy such as hyperthermia that functions principally through denaturing the proteome. However, much work is needed to decode the mechanisms of thermal stress-mediated macroautophagy and their role in survival/death of cancer cells before recommendations can be made on targeting this pathway in combination with hyperthermia.

Systemic analysis of heat shock response induced by heat shock and a proteasome inhibitor MG132

The molecular basis of heat shock response (HSR), a cellular defense mechanism against various stresses, is not well understood. In this, the first comprehensive analysis of gene expression changes in response to heat shock and MG132 (a proteasome inhibitor), both of which are known to induce heat shock proteins (Hsps), we compared the responses of normal mouse fibrosarcoma cell line, RIF- 1, and its thermotolerant variant cell line, TR-RIF-1 (TR), to the two stresses. The cellular responses we examined included Hsp expressions, cell viability, total protein synthesis patterns, and accumulation of poly-ubiquitinated proteins. We also compared the mRNA expression profiles and kinetics, in the two cell lines exposed to the two stresses, using microarray analysis. In contrast to RIF-1 cells, TR cells resist heat shock caused changes in cell viability and whole-cell protein synthesis. The patterns of total cellular protein synthesis and accumulation of poly-ubiquitinated proteins in the two cell lines were distinct, depending on the stress and the cell line. Microarray analysis revealed that the gene expression pattern of TR cells was faster and more transient than that of RIF-1 cells, in response to heat shock, while both RIF-1 and TR cells showed similar kinetics of mRNA expression in response to MG132. We also found that 2,208 genes were up-regulated more than 2 fold and could sort them into three groups: 1) genes regulated by both heat shock and MG132, (e.g. chaperones); 2) those regulated only by heat shock (e.g. DNA binding proteins including histones); and 3) those regulated only by MG132 (e.g. innate immunity and defense related molecules). This study shows that heat shock and MG132 share some aspects of HSR signaling pathway, at the same time, inducing distinct stress response signaling pathways, triggered by distinct abnormal proteins.

[The therapeutic contribution of proteomic approaches in cancers]

Up to now, there are no protein tumor markers with a specificity and sensitivity sufficient to have a utility in prognosis and early diagnosis of cancer. Recent advances in proteomics approaches have led to the identification of novel tumor markers of cancer that may have a utility in screening strategies and treatment. The purpose of the current review is to describe the major advances in cancer proteomics, especially those related to the study of serum biomarkers, immune-related responses (autoantibodies) and alterations in cellular proteins.

2-GHz band CW and W-CDMA modulated radiofrequency fields have no significant effect on cell proliferation and gene expression profile in human cells

We investigated the mechanisms by which radiofrequency (RF) fields exert their activity, and the changes in both cell proliferation and the gene expression profile in the human cell lines, A172 (glioblastoma), H4 (neuroglioma), and IMR-90 (fibroblasts from normal fetal lung) following exposure to 2.1425 GHz continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) RF fields at three field levels. During the incubation phase, cells were exposed at the specific absorption rates (SARs) of 80, 250, or 800 mW/kg with both CW and W-CDMA RF fields for up to 96 h. Heat shock treatment was used as the positive control. No significant differences in cell growth or viability were observed between any test group exposed to W-CDMA or CW radiation and the sham-exposed negative controls. Using the Affymetrix Human Genome Array, only a very small (< 1%) number of available genes (ca. 16,000 to 19,000) exhibited altered expression in each experiment. The results confirm that low-level exposure to 2.1425 GHz CW and W-CDMA RF fields for up to 96 h did not act as an acute cytotoxicant in either cell proliferation or the gene expression profile. These results suggest that RF exposure up to the limit of whole-body average SAR levels as specified in the ICNIRP guidelines is unlikely to elicit a general stress response in the tested cell lines under these conditions.

Investigation of heat stress response in the camel fibroblast cell line dubca

We have used a camel cell line model (Dubca) to investigate the effect of heat stress on cell survival. The mechanism(s) of such survival response are very important not only for normal physiological function, but also, in pathological conditions, such as cancer. Those cells that have escaped the normal response to heat are an important model in helping us better understand the intricate signaling change(s) that might have occurred in changing a cell's phenotype from normal to cancerous. Our findings in this study indicate that unlike comparative fibroblast cells (L929), Dubca cells are quite resistant and survive the 42 degrees C heat stress in a time-dependent manner; indeed, the cells even show growth on par with those cells that are kept at the control temperature of 37 degrees C. Expression levels of Akt, an important prosurvival kinase, are uniform, and irrespective of the experimental or control temperature, show basal control levels. In other words, there is no loss of Akt protein level following heat stress at 42 degrees C. Similarly, no significant change in HSP70 expression level is observed. In contrast, the stress transcription factor c-Jun, and the stress activated kinase (Jnk) were induced during this heat-shock condition. This is in line with the fact that suppression of stress kinase Jnk renders cells thermoresistant. On the other hand, acquired tolerance to severe heat shock is associated with downregulation of Jnk.

Heat shock induced apoptosis in normal and tumor human umbilical vein cells (HUVECs)

Human endothelial cell injury may play an important role tumor damage hyperthermia in vivo. In this study, human umbilical vein cells were heat shocked in vitro at different temperatures (41-55 degrees C). Cells were observed 0, 12, 24, 36, 48, 60 and 72 hours after heat shock. By incrementally increasing the heat load from 41-55 degrees C, we observed a gradually increase in apoptosis with a significant change from apoptotic to necrotic death at temperature beyond 45 degrees C. Further, an in vitro human breast tumor endothelial cell model was established to compare the heat shock response between normal and tumor endothelial cells.

Spontaneous apoptosis and expression of cell surface heat-shock proteins in cultured EL-4 lymphoma cells

The expression of heat-shock proteins (HSPs) is enhanced in stressed cells and can protect cells from stress-induced injury. However, existing data about the relationship between apoptosis and HSP expression is contradictory. In this paper, a mouse lymphoma cell death model system is used to detect simultaneously both the process of apoptosis and the level of HSP expression. The model was established after discovering that spontaneous apoptosis and spontaneous cell surface HSP expression occurs in EL-4 mouse lymphoma cells during normal optimal culture conditions. The data show that apoptotic EL-4 cells had higher levels of hsp25, hsp60, hsp70 and hsp90 exposed on the plasma membrane surface than viable cells. The level of surface HSPs was found to increase through several stages of early and late apoptotic death as measured by flow cytometry, with the highest levels observed during the loss of cell membrane phospholipid asymmetry. Heat shock and actinomycin D significantly increased the proportion of apoptotic cells in culture. However, hyperthermia only stimulated a weak and temporary increase in surface HSP expression, whereas actinomycin D strongly elevated the level of surface and intracellular HSPs, particularly in live cells. These results show an associative relationship between apoptosis and HSP expression. The relationship between the progression of cell death and HSP expression suggests a role for membrane HSP expression in programmed cell death.

The magnitude and time-dependence of the apoptotic response of normal and malignant cells subjected to ionizing radiation versus hyperthermia

PURPOSE

The purpose of the study was to examine the optimal time of exposure and dose of heat and ionizing radiation that results in the killing of human cancer cells in vitro via apoptosis vs. necrosis.

MATERIALS AND METHODS

Human mammary carcinoma, colorectal carcinoma and normal bovine capillary endothelial (BCE) cell lines were subjected to 20 Gy ionizing radiation and 6, 12, 24, and 72 h later assessed for apoptosis using detection of apoptotic bodies and caspase assays. Necrosis was detected by loss of cells from the surface and lactate dehydrogenase (LDH) release. The colorectal carcinoma cells were subjected to hyperthermia using temperatures ranging from 39 - 44 degrees C for 5, 15 or 45 min. exposures and at varying times post-treatment, apoptosis and necrosis were measured.

RESULTS

In response to ionizing radiation, none of the cells underwent necrosis and some cell types apoptosed 24 and 72 h posttreatment. The colorectal cancer cells exhibited a steady increase of apoptosis at 6, 12, and 24 h. When these cells were exposed to 40 degrees C for 5 min, caspases increased within 6 h and a significant fraction (50%) of cells apoptosed. If the time of exposure to 40 degrees C was increased to 15 or 45 min, 80% and 100% of the dying cells apoptosed, respectively. A temperature of 39 degrees C did not cause cell death even after 45 min exposures. If heat was elevated to 42 or 44 degrees C, increased necrosis was observed with a corresponding decrease in apoptosis.

CONCLUSIONS

These studies reveal time and temperature dependent in vitro cell responses to ionizing radiation and water-bath hyperthermia.

Prostasome-derived proteins capable of eliciting an immune response in prostate cancer patients

Prostate cancer consistently remains a difficult clinical enigma. Therefore, the development of novel strategies for diagnosis and treatment (e.g. immunotherapy) of prostate cancer is essential. We tried to identify the prostasome-derived proteins that were immunogenic in prostate cancer patients. Prostate cancer patients' sera (n = 44) with high enzyme-linked immunosorbent assay (ELISA) titers against prostasomes were selected for immunoblotting against purified seminal prostasomes. The SDS-PAGE and immunoblotting experiments were performed with Bio-Rad systems. Twenty-five of the recognized proteins were isolated and analyzed by means of mass spectrometry. Out of 44 patients' sera, 31 (70%) demonstrated in immunoblotting experiments reactivity against several prostasomal protein bands in the molecular weight range of 10-200 kDa. Some of the bands (55, 70 and 170 kDa) were more frequently recognized by the patients' sera. Concomitantly run control sera generated only very weak or no bands at all. The most frequently occurring prostasomal proteins were identified as heat shock proteins (HSP 70, 71) and clusterin. This study identified the most important molecular targets of autoantibodies against prostasomes generated in connection with the development of prostate cancer in man. These immunogenic prostasomal proteins could be appropriate target molecules for specific immunotherapy of prostate cancer patients.

Docetaxel and hyperthermia: factors that modify thermal enhancement

BACKGROUND

Hyperthermia enhances the cytotoxicity of some chemotherapeutic agents and recent studies suggest that docetaxel may show improved response at elevated temperatures. Factors that may modify the thermal enhancement of docetaxel were studied to optimize its clinical use with hyperthermia.

METHODS

The tumor studied was an early-generation isotransplant of a spontaneous C3Hf/Sed mouse fibrosarcoma, Fsa-II. All studies were approved by the Animal Care and Use Committee. Docetaxel was given as a single intraperitoneal injection. Hyperthermia was achieved by immersing the tumor-bearing foot into a constant temperature water bath. Four factors were studied: duration of hyperthermia, sequencing of hyperthermia with docetaxel, intensity of hyperthermia, and tumor size. To study duration of hyperthermia tumors were treated at 41.5 degrees C for 30 or 90 min immediately after intraperitoneal administration of docetaxel. For sequencing of hyperthermia and docetaxel, animals received hyperthermia treatment of tumors for 30 min at 41.5 degrees C immediately after drug administration, hyperthermia both immediately and 3 hr after docetaxel administration and hyperthermia given only at 3 hr after administration of docetaxel. Intensity of hyperthermia was studied using heat treatment of tumors for 30 min at 41.5 or 43.5 degrees C immediately following docetaxel administration. Effect of tumor size was studied by delaying experiments until three times the tumor volume (113 mm(3)) was observed. Treatment of tumors lasted for 30 min at 41.5 degrees C immediately following drug administration. Tumor response was studied using the mean tumor growth time.

RESULTS

Hyperthermia in the absence of docetaxel had a small but significant effect on tumor growth time at 43.5 degrees C but not at 41.5 degrees C. Hyperthermia at 41.5 degrees C for 90 min immediately after docetaxel administration significantly increased mean tumor growth time (P = 0.0435) when compared to tumors treated with docetaxel at room temperature. Treatment for 30 min had no effect. Application of hyperthermia immediately and immediately plus 3 hr following docetaxel was effective in delaying tumor growth. Treatment at 3 hr only had no effect. No significant difference in mean tumor growth time was observed with docetaxel and one half hour of hyperthermia at 41.5 or 43.5 degrees C. For larger tumors, hyperthermia alone caused a significant delay in tumor growth time. Docetaxel at 41.5 degrees C for 30 min did not significantly increase mean tumor growth time compared to large tumors treated with docetaxel at room temperature.

CONCLUSIONS

Docetaxel shows a moderate increase in anti-tumor activity with hyperthermia. At 41.5 degrees C the thermal enhancement of docetaxel is time dependent if hyperthermia is applied immediately following drug administration. With large tumors docetaxel alone or docetaxel plus hyperthemia showed the greatest delays in tumor growth time in the experiments.

TNFalpha mediates susceptibility to heat-induced apoptosis by protein phosphatase-mediated inhibition of the HSF1/hsp70 stress response

TNFalpha uniquely combines proinflammatory features with a proapoptotic potential. Activation of HSF1 followed by induction of hsp70 is part of a stress response, which protects cells from apoptosis. Herein, the effects of TNFalpha on the hsp70 stress response were investigated. TNFalpha caused transient downregulation of HSF1 activation and hsp70 synthesis, leading to increased sensitivity to heat-induced apoptosis. Blockade of TNF-R1, but not TNF-R2, as well as inhibition of protein phosphatases PP1/PP2a and PP2b completely blocked this effect. In contrast, blockade of MAPK/SAPK-, NF-kappaB (NF-kappaB)-, and PKC- pathways as well as the caspase cascade did not prevent downregulation of HSF1/hsp70. These data demonstrate that TNFalpha transiently inhibits the hsp70 stress response via TNF-R1 and activation of protein phosphatases. The price of inhibition of an essential cellular stress response is increased sensitivity to apoptotic cell death.

Kigamicin D, a novel anticancer agent based on a new anti-austerity strategy targeting cancer cells' tolerance to nutrient starvation

Both tolerance to nutrient starvation and angiogenesis are essential for cancer progression because of the insufficient supply of nutrients to tumor tissue. Since chronic nutrient starvation seldom occurs in normal tissue, cancer's tolerance to nutrient starvation should provide a novel target for cancer therapy. In this study, we propose an anti-austerity strategy to exploit the ability of agents to eliminate cancer cells' tolerance to nutrient starvation. We established a simple screening method for agents that inhibit cancer cell viability preferentially during nutrient starvation, using PANC-1 cell line cultured in nutrient-rich and nutrient-deprived media. After screening over 2000 culture media of actinomycetes, we identified a new compound, kigamicin D (C(48)H(59)NO(19)), which shows preferential cytotoxicity to cancer cells under nutrient-deprived conditions, but hardly any cytotoxicity under nutrient-rich conditions. Both subcutaneous and oral administration of kigamicin D strongly suppressed the tumor growth of several tested pancreatic cancer cell lines in nude mice. Moreover, kigamicin D was observed to block the activation of Akt induced by nutrient starvation. Therefore, our results suggest that kigamicin D be a candidate for implementing our novel concept, anti-austerity, which may serve as a new strategy for cancer therapy.

Modulation of macrophage apoptosis by antimycobacterial therapy: physiological role of apoptosis in the control of Mycobacterium tuberculosis

Apoptosis is a form of cell death that avoids inflammatory responses. We had previously reported that Mycobacterium tuberculosis (Mtb) and Purified Protein Derivative (PPD) induce apoptosis in murine macrophages. The production of TNFalpha and IL-10 in response to Mtb infection modulates apoptosis by controlling nitric oxide production and caspase activation. Furthermore, Mtb triggers calcium influx responsible for mitochondrial alterations, an early pathway of apoptosis, independently of TNFalpha and IL-10. In tuberculosis patients apoptotic macrophages are found in granulomas and bronchoalveolar lavages, suggesting that apoptosis may participate in the control of Mtb. To further explore the role of macrophage apoptosis in tuberculosis, we studied the capacity of standard antimycobacterial drugs to modulate different events associated with the induction of apoptosis. The B10R murine macrophage line was infected or not with Mtb (5:1 bacteria to macrophage ratio) or exposed to PPD (10 microg/ml), in the presence or absence of varying concentrations (1-20 microg/ml) of anti mycobacterial drugs (isoniazid, rifampin, thiacetazone, streptomycin, and ethambutol). Inhibition of the intracellular growth of M. tuberculosis by all drugs studied/correlated with inhibition of permeability transition (PT) alterations; TNFalpha, IL-10, and nitric oxide production, and caspase-1 activation. However, these drugs did not affect PPD-induced apoptosis or its associated events, suggesting that the ability of antimycobacterial drugs to block macrophage apoptosis could be explained by their effects on the metabolic activities of Mtb. All drugs, except isoniazid, at higher concentrations, induced PT alterations in noninfected macrophages in a way that appears to be dependent of calcium, since a calcium chelator prevented it. The results presented herein suggest that the pharmacological manipulation of pathways associated with macrophage apoptosis may affect the intracellular growth of Mtb.

Cholesteryl glucoside-induced protection against gastric ulcer

The cytoprotective effect of heat shock proteins (HSPs) promises new therapeutic modalities for medical treatment. We examined the anti-ulcer effect of cholesteryl glucoside (1-O-cholesteryl-beta-D-glucopyranoside, CG) on cold-restraint stress-induced gastric ulcer in rats, in terms of its correlative ability to activate heat shock factor (HSF) and to induce HSP70. Rapid induction of CG occurred in animal tissues, especially in stomach, after exposure to stress, indicating that this glycolipid might act as an anti-stress, lipid mediator involved in the very early stages of stress-induced signal transduction. Orally administered CG apparently showed anti-ulcer activity in rats via HSF activation and HSP70 induction. When compared with geranylgeranylacetone (GGA), the well known as an effective, synthetic anti-ulcer agent, CG proved to have the same level of strength on ulcer inhibition. GGA caused CG and HSP70 induction in gastric mucosa, indicating that GGA induced HSP70 via CG production. CG thus might be useful for medical treatment of stress-induced diseases, and as an anti-stress supplement for daily diet.

Steryl glucoside is a lipid mediator in stress-responsive signal transduction

We previously reported that steryl glucoside (SG) is rapidly induced in cells from molds to humans by exposure to environmental stress (Murakami-Murofushi et al. (1997) J. Biol. Chem., 272, 486-489, Kunimoto et al. (2000) Cell Stress & Chaperones, 5, 3-7), and in mold cells SG production is followed by activation of a certain protein kinase and induction of heat shock proteins (HSP) (Maruya et al. (1997) Cell Struct. Funct., 21, 533-538). To determine the biological significance of SG in stress responsive signal transduction, we added SG to the culture of human fibroblasts and examined its effect on HSP induction. We demonstrated a rapid activation of heat shock transcription factor 1 (HSF1) to bind to heat shock element (HSE) and induction of heat shock protein 70 (HSP70) in fibroblast cells by exposure to exogenously added human major SG, cholesteryl glucoside (CG). In addition, enzyme activity to form CG from cholesterol and UDP-glucose was detected in the homogenate of fibroblast cells. These results strongly suggest that CG acts as a mediator in the early stage of stress responsive signal transduction.

Involvement of protein tyrosine phosphorylation and reduction of cellular sulfhydryl groups in cell death induced by 1' -acetoxychavicol acetate in Ehrlich ascites tumor cells

Elucidation of the mechanisms underlying potential anticancer drugs continues and unraveling these mechanisms would not only provide a conceptual framework for drug design but also promote use of natural products for chemotherapy. To further evaluate the efficacy of the anticancer activity of 1'-acetoxychavicol acetate (ACA), this study investigates the underlying mechanisms by which ACA induces death of Ehrlich ascites tumor cells. ACA treatment induced loss of cell viability, and Western blotting analysis revealed that the compound stimulated tyrosine phosphorylation of several proteins with 27 and 70 kDa proteins being regulated in both dose- and time-dependent manner prior to loss of viability. Protein tyrosine kinase inhibitor herbimycin A moderately protected cells from ACA-induced toxicity. In addition, cellular glutathione and protein sulfydryl groups were also significantly reduced both dose- and time-dependently during evidence of cell death. Replenishing thiol levels by antioxidant, N-acetylcysteine (NAC), an excellent supplier of glutathione and precursor of glutathione, substantially recovered the viability loss, but the recovery being time-dependent, as late addition of NAC (at least 30 min after ACA addition to cultures) was, however, ineffective. Addition of NAC to ACA treated cultures also abolished tyrosine phosphorylation of the 27 kDa protein. These results, at least partly, identify cellular sulfhydryl groups and protein tyrosine phosphorylation as targets of ACA cytotoxicity in tumor cells.

Heat shock and ceramide have different apoptotic pathways in radiation induced fibrosarcoma (RIF) cells

Heat shock induces various cellular responses including inhibition of protein synthesis, production of heat shock proteins (HSPs) and induction of thermotolerance. The molecular mechanisms of the processes have not been well understood. It has been proposed that ceramide formation during heat shock mediates heat shock induced apoptosis. We examined whether C2-ceramide mimicked the cellular response to heat shock in RIF-1 cells and their thermotolerant derivative TR-RIF-1 cells. Discernible effects between heat shock and C2-ceramide treatments were observed in cellular changes such as total protein synthesis, HSP synthesis, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) activity and PARP cleavage. Heat shock immediately inhibited cellular protein synthesis, which was recovered by synthesizing HSPs first and then whole proteins later. Heat shock also activated SAPK/JNK and increased PARP cleavage in dose-dependent manner. Thermotolerant TR-RIF-1 cells responded to heat shock more insensitively than RIF-1 cells. On the other hand, C2-ceramide treatment did not accompany any changes induced by heat shock. No discernible differences between RIF-1 and TR-RIF-1 cells were observed by C2-ceramide treatment. We tried to figure out how C2-ceramide interacts with cellular membrane and found that exogenous C2-ceramide was incorporated into the outer monolayer and flipped into the inner monolayer of human erythrocytes in ATP-dependent manner. However, the rate of C2-ceramide incorporation was similar in control and thermotolerant cells. In summary, thermotolerant cells are resistant to heat shock induced apoptotic signaling but not resistant, rather sensitive to membrane disturbing C2-ceramide mediated apoptosis. These results suggest that heat shock and ceramide have different signal transduction pathways.

Spontaneous nitric oxide in hepatocyte monolayers and inhibition of compound-induced apoptosis

Primary cultures of hepatocytes are a widely used in vitro model for biochemical research. Following isolation, hepatocytes produce large amounts of nitric oxide (NO), which is known to have both pro- and anti-apoptotic effects in hepatocytes in vivo and in vitro. Previous work has not determined the effect of these increased levels of NO on the response of hepatocytes to apoptotic stimuli. Here we report that levels of nitrites are elevated in hepatocyte monolayers from 24 h onwards. Addition of the inducible nitric oxide synthase (iNOS) inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME), to the medium inhibited this increase in nitrites. These results indicate that the increase in nitrite is most likely due to the formation of NO. Elevated nitrite levels had no effect either on basal levels of apoptosis or on ATP and GSH. Apoptosis was induced by transforming growth factor beta-1 (TGFbeta-1) or glycochenodeoxycholate (GCDC). Both compounds caused moderate hepatocyte apoptosis; however, addition of L-NAME prior to exposure significantly increased the level of apoptosis observed with the two compounds. Both TGFbeta-1 and GCDC had no effect on hepatocyte ATP or GSH levels; however, as a consequence of secondary necrosis, TGFbeta-1 exposure significantly increased levels of lactate dehydrogenase (LDH) leakage. These findings indicate that the increased levels of NO associated with the culture of hepatocytes have an inhibitory effect on compound-induced apoptosis in the cells.

Growth inhibitory effect of green tea extract in Ehrlich ascites tumor cells involves cytochrome c release and caspase activation

We reported previously that the mechanism by which Green tea extract (GTE) elicited growth-inhibitory effects in Ehrlich ascites tumor cells involved a decrease in ornithine decarboxylase (ODC) activity and in cell viability. Decrease in ODC activity has been associated with apoptotic cell death and we therefore studied changes in cytochrome c release and caspase activation, which characterize apoptosis. GTE caused a dose- and time-dependent increase in caspase-3-like protease activation, preceded by a release of cytochrome c from the mitochondria. Inhibiting the activation of caspase-3 with acetyl-Asp-Glu-Val-Asp-alpha-aldehyde (caspase inhibitor) caused a reversal in the effect on cell viability.

Induced hsp70 is in small, cytoplasmic complexes in a cell culture model of renal ischemia: a comparative study with heat shock

A number of clinical conditions are known to result in the induction of heat shock proteins, but detailed studies on stress response have focused mostly on heat shock as a model. We have analyzed the induction and intracellular distribution of heat shock proteins in a reversible adenosine triphosphate (ATP) depletion model of renal ischemia. Two Hsp70 homologues, Hsp70 in the cytoplasm and BiP in the endoplasmic reticulum (ER) lumen, were found significantly induced during the recovery phase of ATP depletion. Other members of the heat shock protein family, such as Hsp90, constitutive Hsc70, and a related protein Hop60, were not induced. The induction of stress proteins on ATP depletion differed from that after heat shock in the kinds of proteins elaborated, their induction kinetics, and their intracellular distributions. Biochemical fractionation and indirect immunofluorescence experiments indicated that Hsp70 was predominantly cytoplasmic in the recovery phase of ischemia-like stress. Velocity sedimentation on sucrose gradients showed that induced Hsp70 sedimented as small, soluble complexes, ranging in size from 4S20,w to 8S20,w. The results suggest a role for induced Hsp70 that may be different from one of protecting aggregated proteins as under heat shock and emphasize the need for their characterization in other clinical conditions that result in stress response.

Induced hsp70 is in small, cytoplasmic complexes in a cell culture model of renal ischemia: a comparative study with heat shock

A number of clinical conditions are known to result in the induction of heat shock proteins, but detailed studies on stress response have focused mostly on heat shock as a model. We have analyzed the induction and intracellular distribution of heat shock proteins in a reversible adenosine triphosphate (ATP) depletion model of renal ischemia. Two Hsp70 homologues, Hsp70 in the cytoplasm and BiP in the endoplasmic reticulum (ER) lumen, were found significantly induced during the recovery phase of ATP depletion. Other members of the heat shock protein family, such as Hsp90, constitutive Hsc70, and a related protein Hop60, were not induced. The induction of stress proteins on ATP depletion differed from that after heat shock in the kinds of proteins elaborated, their induction kinetics, and their intracellular distributions. Biochemical fractionation and indirect immunofluorescence experiments indicated that Hsp70 was predominantly cytoplasmic in the recovery phase of ischemia-like stress. Velocity sedimentation on sucrose gradients showed that induced Hsp70 sedimented as small, soluble complexes, ranging in size from 4S20,w to 8S20,w. The results suggest a role for induced Hsp70 that may be different from one of protecting aggregated proteins as under heat shock and emphasize the need for their characterization in other clinical conditions that result in stress response.

Hsp72-mediated suppression of c-Jun N-terminal kinase is implicated in development of tolerance to caspase-independent cell death

Pretreatment with mild heat shock is known to protect cells from severe stress (acquired thermotolerance). Here we addressed the mechanism of this phenomenon by using primary human fibroblasts. Severe heat shock (45 degrees C, 75 min) of the fibroblasts caused cell death displaying morphological characteristics of apoptosis; however, it was caspase independent. This cell death process was accompanied by strong activation of Akt, extracellular signal-regulated kinase 1 (ERK1) and ERK2, p38, and c-Jun N-terminal (JNK) kinases. Suppression of Akt or ERK1 and -2 kinases increased cell thermosensitivity. In contrast, suppression of stress kinase JNK rendered cells thermoresistant. Development of thermotolerance was not associated with Akt or ERK1 and -2 regulation, and inhibition of these kinases did not reduce acquired thermotolerance. On the other hand, acquired tolerance to severe heat shock was associated with downregulation of JNK. Using an antisense-RNA approach, we found that accumulation of the heat shock protein Hsp72 is necessary for JNK downregulation and is critical for thermotolerance. The capability of naive cells to withstand moderate heat treatment also appears to be dependent on the accumulation of Hsp72 induced by this stress. Indeed, exposure to 45 degrees C for 45 min caused only transient JNK activation and was nonlethal, while prevention of Hsp72 accumulation prolonged JNK activation and led to massive cell death. We also found that JNK activation by UV irradiation, interleukin-1, or tumor necrosis factor was suppressed in thermotolerant cells and that Hsp72 accumulation was responsible for this effect. Hsp72-mediated suppression of JNK is therefore critical for acquired thermotolerance and may play a role in tolerance to other stresses.

Heat induced expression of CD95 and its correlation with the activation of apoptosis upon heat shock in rat histiocytic tumor cells

The heat shock response is a universal phenomenon and is among the most highly conserved cellular responses. However, BC-8, a rat histiocytoma, fails to mount a heat shock response unlike all other eukaryotic cells. In the absence of induction of heat shock proteins, apoptotic cell death is activated in BC-8 tumor cells upon heat shock. We demonstrate here that stable transformants of BC-8 tumor cells transfected with hsp70 cDNA constitutively express hsp70 protein and are transiently protected from heat induced apoptosis for 6-8 h. In addition heat stress induces CD95 gene expression in these tumor cells. There is a delay in CD95 expression in hsp70 transfected cells suggesting a correlation between the cell surface expression of CD95 and the time of induction of apoptosis in this tumor cell line. Also expression of CD95 antigen appears to inhibit the interaction between heat shock factors and heat shock elements in these cells resulting in the lack of heat shock response.

A natural extracellular factor that induces Hsp72, inhibits apoptosis, and restores stress resistance in aged human cells

Experiments with cultured cells showed that most cellular stress resistance components are specialized for certain types of damage. For example, superoxide dismutase protects from oxidative damage; DNA repair enzymes guard against mutagens and other DNA-damaging agents. On the other hand, the major inducible heat shock protein Hsp72 protects cells from a large variety of stresses and thus represents a generalized repair/stress resistance component. Hsp72 not only refolds damaged proteins but also interferes with programmed cell death signaling pathways, thus providing cells with time to repair the damage, hence its universality as a stress protector. In the present study we demonstrate the occurrence in murine and human ascites fluids (AF) of a natural nontoxic extracellular factor (ascites Hsp72-inducing factor, AHIF) capable of activating Hsp72 expression in different types of cells via a pathway distinct from the heat shock response pathway. AHIF is unique in that it is the first physiological factor capable of inducing synthesis of Hsp72 not only in young cells but, remarkably, also in aged human cells that largely have lost the ability to express Hsp72 in response to stresses, a manifestation at the cellular level of a progressive impairment in the ability to adapt to environmental changes which characterizes aging. Pretreatment of aged human cells with AF triggers Hsp72 expression at levels seen in young stressed cells and protects cells from a variety of otherwise lethal stressful treatments such as heat shock, TNF, UV irradiation, etoposide, and menadione. Activation of Hsp72 expression is essential for antiapoptotic action of AHIF because specific inhibition of Hsp72 expression by antisense RNA abolishes the cytoprotective effect of AF. In view of an important link between stress resistance and longevity in different organisms, the abilities of AHIF make it a unique candidate for the role of a systemic regulator of the aging process. While a cell-autonomous stress response diminishes with aging, aged cells retain the ability to respond to an extracellular factor which induces the expression of Hsp72. This finding opens up exciting possibilities for using AF factor to restore stress resistance to old cells and organisms and the possibility of interfering with the aging process. The ability to induce stress resistance in young cells and to restore it in aged cells could serve as a basis for developing effective antiapoptotic therapies.

The function of HSP72 in suppression of c-Jun N-terminal kinase activation can be dissociated from its role in prevention of protein damage

Activation of the c-Jun N-terminal kinase (JNK) by a variety of stimuli is critical for regulation of many cellular processes including apoptosis. The major inducible heat shock protein Hsp72 has previously been demonstrated to inhibit activation of JNK in cells exposed to heat shock and other protein-damaging agents, thus suppressing apoptosis. Hsp72 can protect proteins from stress-induced damage. To test if this protective function of Hsp72 is involved in JNK suppression, we investigated whether Hsp72 can avert activation of JNK by stimuli that do not cause protein damage. We show that Hsp72 suppresses activation of JNK induced by non-protein-damaging stimuli, interleukin-1 and UV irradiation, as well as by constitutively active components of the JNK signaling cascade Cdc42 and MEKK1. Furthermore, Hsp72 strongly reduced activation of JNK by phosphatase inhibitors. We also demonstrate that an Hsp72 mutant that lacks the ATPase domain is still capable of JNK suppression, thus indicating that the protein refolding activity of Hsp72 is not critical for inhibition of JNK activation. Taken together these data suggest that Hsp72 plays a regulatory role in JNK signaling and that the function of Hsp72 in protein protection or refolding is not involved in JNK regulation.

Activation of Fas inhibits heat-induced activation of HSF1 and up-regulation of hsp70

Activation of heat shock factor (HSF) 1-DNA binding and inducible heat shock protein (hsp) 70 (also called hsp72) expression enables cells to resist various forms of stress and survive. Fas, a membrane-bound protein, is a central proapoptotic factor; its activation leads to a cascade of events, resulting in programmed cell death. These two mechanisms with contradictory functions, promoting either cell survival or death, were examined for their potential to inhibit each other's activation. Induction of FAS-mediated signaling was followed by a rapid decrease in HSF1-DNA binding and inducible hsp70 expression. Inhibition of HSF1-DNA binding was demonstrated to be based on absent hyperphosphorylation of HSF1 during FAS signaling. These effects of FAS activation on the HSF1/hsp70 stress response were blocked by ICE (caspase 1) inhibitors, suggesting an ICE-mediated process. Furthermore, inhibition of HSF1/hsp70 was accompanied by an increase in apoptosis rates from 20% to 50% in response to heat stress. When analyzing the effects of HSF1/hsp70 activation on Fas-mediated apoptosis, protection from apoptosis was seen in cells with induced hsp70 protein levels, but not in cells that were just induced for HSF1-DNA binding. Thus, we conclude that inhibition of HSF1/hsp70 stress response during Fas-mediated apoptosis and vice versa may facilitate a cell to pass a previously chosen pathway, stress resistance or apoptosis, without the influence of inhibitory signals.

Altered expression of constitutive type and inducible type heat shock proteins in response of D-galactosamine-sensitized mice to lipopolysaccharide as an experimental endotoxic shock model

The expression of heat shock proteins (HSPs) as stress-induced proteins was studied in mice injected with D-galactosamine (D-GalN) and lipopolysaccharide (LPS) as an experimental endotoxic shock model. The expression of constitutive type heat shock protein 70 (HSC70) was significantly reduced in livers of mice injected with D-galactosamine and lipopolysaccharide, while its expression was unaffected in livers of mice injected with D-galactosamine or lipopolysaccharide alone. The expression of other constitutive type heat shock proteins, namely HSP60, HSP32 and HSP25 was also reduced in mice injected with D-galactosamine and lipopolysaccharide. On the other hand, inducible type HSP70 was detected in livers from mice injected with D-galactosamine and lipopolysaccharide, but not in livers from mice injected with D-galactosamine or lipopolysaccharide alone. Simultaneous injection of anti-tumor necrosis factor (TNF)-alpha antibody prevented the liver from reduced expression of constitutive type HSC70, and lead to marked expression of inducible type HSP70 in the liver. Reduced expression of constitutive type HSC70 was also found when D-galactosamine and recombinant TNF-alpha was injected. Therefore, TNF-alpha was suggested to play a critical role on altered expression of constitutive HSC70 and inducible type HSP70 in response of D-galactosamine-sensitized mice to lipopolysaccharide.

Proteasome inhibitors activate stress kinases and induce Hsp72. Diverse effects on apoptosis

Inhibition of the major cytosolic protease, proteasome, has been reported to induce programmed cell death in several cell lines, while with other lines, similar inhibition blocked apoptosis triggered by a variety of harmful treatments. To elucidate the mechanism of pro- and antiapoptotic action of proteasome inhibitors, their effects on U937 lymphoid and 293 kidney human tumor cells were tested. Treatment with peptidyl aldehyde MG132 and other proteasome inhibitors led to a steady increase in activity of c-Jun N-terminal kinase, JNK1, which is known to initiate the apoptotic program in response to certain stresses. Dose dependence of MG132-induced JNK activation was parallel with that of apoptosis. Furthermore, inhibition of the JNK signaling pathway strongly suppressed MG132-induced apoptosis. These data indicate that JNK is critical for the cell death caused by proteasome inhibitors. An antiapoptotic action of proteasome inhibitors could be revealed by a short incubation of cells with MG132 followed by its withdrawal. Under these conditions, the major heat shock protein Hsp72 accumulated in cells and caused suppression of JNK activation in response to certain stresses. Accordingly, pretreatment with MG132 reduced JNK-dependent apoptosis caused by heat shock or ethanol, but it was unable to block JNK-independent apoptosis induced by TNFalpha. Therefore, proteasome inhibitors activate JNK, which initiates an apoptotic program, and simultaneously they induce Hsp72, which suppresses JNK-dependent apoptosis. A balance between these two effects might define the fate of cells exposed to the inhibitors.

Thermotolerance inhibits various stress-induced apoptosis in NIH3T3 cells

When NIH3T3 cells were exposed to mild heat and recovered at 37 degrees C for various time intervals, they were thermotolerant and resistant to subsequent stresses including heat, oxidative stresses, and antitumor drug methotrexate which are apoptotic inducers. The induction kinetics of apoptosis by stresses were determined by DNA fragmentation and protein synthesis using [35S]methionine pulse labeling. We investigated the hypothesis that thermotolerant cells were resistant to apoptotic cell death compared to control cells when both cells were exposed to various stresses inducing apoptosis. The cellular changes in thermotolerant cells were examined to determine which components are involved in this resistance. At first, the degree of resistance correlates with the extent of heat shock protein synthesis which were varied depending on the heating times at 45 degrees C and recovery times at 37 degrees C after heat shock. Secondly, membrane permeability change was observed in thermotolerant cells. When cells prelabeled with [3H]thymidine were exposed to various amounts of heat and recovered at 37 degrees C for 1/2 to 24 h, the permeability of cytosolic [3H]thymidine in thermotolerant cells was 4 fold higher than that in control cells. Thirdly, the protein synthesis rates in thermotolerant and control cells were measured after exposing the cells to the same extent of stress. It turned out that thermotolerant cells were less damaged to same amount of stress than control cells, although the recovery rates are very similar to each other. These results demonstrate that an increase of heat shock proteins and membrane changes in thermotolerant cells may protect the cells from the stresses and increase the resistance to apoptotic cell death, even though the exact mechanism should be further studied.

Hsp70 prevents activation of stress kinases. A novel pathway of cellular thermotolerance

Harmful conditions including heat shock, oxidative stress, UV, and so forth cause programmed cell death, whose triggering requires activation of the Jun N-terminal kinase, JNK. High levels of Hsp72, a heat-inducible member of Hsp70 family, protect cells against a variety of stresses by a mechanism that is unclear at present. Here we report that elevated levels of Hsp72 inhibit a signal transduction pathway leading to programmed cell death by preventing stress-induced activation of JNK. Stress-induced activation of another stress-kinase, p38 (HOG1), is also blocked when the level of Hsp72 is increased. Similarly, addition of a purified recombinant Hsp72 to a crude cell lysate reduced p38 kinase activation, while depletion of the whole family of Hsp70 proteins with a monoclonal antibody enhanced such activation. In addition, we have found that accumulation of abnormal proteins in cells upon incubation with amino acid analogs causes activation of JNK and p38 kinases, which can be prevented by overproduction of Hsp72. Taken together, these data suggest that, in regulation of JNK and p38 kinases, Hsp70 serves as a "sensor" of the build-up of abnormal proteins after heat shock and other stresses. The inhibitory effect of an increased level of Hsp70 on JNK appears to be a major contributor to acquired thermotolerance in mammalian cells.

Cell Signaling and Heat Shock Protein Expression

Exposure of cells and organs to heat shock is associated with numerous changes in various cellular metabolic parameters and overexpression of proteins collectively known as heat shock proteins (HSP). In this communication we review the cell-signaling events that are altered in response to heat shock as they relate to the subsequent induction of HSP 70 kd (HSP-70) expression. We also review the mechanisms by which HSP-70 is involved in conferring cytoprotective effects. The possibility of altering HSP expression through manipulations of the cell-signal process has clinical importance. Copyright 1996 S. Karger AG, Basel