The role of intracellular Ca(2+) in apoptosis induced by hyperthermia and its enhancement by verapamil in U937 cells

Nanoparticle-mediated TRPV1 channel blockade amplifies cancer thermo-immunotherapy via heat shock factor 1 modulation

The survival of malignant tumors is highly dependent on their intrinsic self-defense pathways such as heat shock protein (HSP) during cancer therapy. However, precisely dismantling self-defenses to amplify antitumor potency remains unexplored. Herein, we demonstrate that nanoparticle-mediated transient receptor potential vanilloid member 1 (TRPV1) channel blockade potentiates thermo-immunotherapy via suppressing heat shock factor 1 (HSF1)-mediated dual self-defense pathways. TRPV1 blockade inhibits hyperthermia-induced calcium influx and subsequent nuclear translocation of HSF1, which selectively suppresses stressfully overexpressed HSP70 for enhancing thermotherapeutic efficacy against a variety of primary, metastatic and recurrent tumor models. Particularly, the suppression of HSF1 translocation further restrains the transforming growth factor β (TGFβ) pathway to degrade the tumor stroma, which improves the infiltration of antitumor therapeutics (e.g. anti-PD-L1 antibody) and immune cells into highly fibrotic and immunosuppressive pancreatic cancers. As a result, TRPV1 blockade retrieves thermo-immunotherapy with tumor-eradicable and immune memory effects. The nanoparticle-mediated TRPV1 blockade represents as an effective approach to dismantle self-defenses for potent cancer therapy.

Decrease in MAP3Ks expression enhances the cell death caused by hyperthermia

PURPOSE

Hyperthermia is a promising anticancer treatment modality. However, the molecular mechanism underlying the thermal sensitivity of tumor cells is largely unknown. The aim of this study was to clarify how biochemical changes triggered by heat stimulate antitumor activity.

METHODS AND MATERIALS

The expression levels of various MAPK members in HeLa cells with or without hyperthermia were evaluated by western blotting and RT-PCR. The intracellular Ca²⁺ concentration [Ca²⁺]_i was monitored by digital imaging using CaTM-2 AM. An in vitro cleavage assay was used to determine whether calcium-dependent protease calpain cleaves MAPK components. Cell proliferation and clonogenicity were assessed in the absence or presence of siRNAs targeting MAPK members.

RESULTS

Hyperthermia decreased the levels of MAP3K TAK1, RAF1 and MEKK2 but not of the downstream MAP2K and MAPK members. The hyperthermia-induced degradation of TAK1 and MEKK2 was rescued by either the proteasome inhibitor MG132 or the calpain inhibitor ALLN; however, RAF1 was not affected by the inhibitors. Heat induced down regulation of RAF1. Hyperthermia increased [Ca²⁺]_i and calpain I expression. The calcium ionophore A23187 decreased TAK1 and MEKK2 levels. An in vitro cleavage assay demonstrated that TAK1 and MEKK2 are calpain I substrates. Knockdown of TAK1, RAF1 and MEKK2 suppressed cell proliferation and clonogenicity.

CONCLUSIONS

Hyperthermia decreased the levels of MAP3K TAK1, RAF1 and MEKK2, without reduction of the downstream components in the MAP3K-MAP2K-MAPK cascade, by a calpain-dependent degradation pathway or transcriptional regulation. TAK1, RAF1 and/or MEKK2 play crucial roles in cell proliferation and clonogenicity and are potential molecular targets for hyperthermia.

Quantifying cell death induced by doxorubicin, hyperthermia or HIFU ablation with flow cytometry

Triggered release and targeted drug delivery of potent anti-cancer agents using hyperthermia-mediated focused-ultrasound (FUS) is gaining momentum in the clinical setting. In early phase studies, tissue biopsy samples may be harvested to assess drug delivery efficacy and demonstrate lack of instantaneous cell death due to FUS exposure. We present an optimised tissue cell recovery method and a cell viability assay, compatible with intra-cellular doxorubicin. Flow cytometry was used to determine levels of cell death with suspensions comprised of: (i) HT29 cell line exposed to hyperthermia (30 min at 47 °C) and/or doxorubicin, or ex-vivo bovine liver tissue exposed to (ii) hyperthermia (up to 2 h at 45 °C), or (iii) ablative high intensity FUS (HIFU). Flow cytometric analysis revealed maximal cell death in HT29 receiving both heat and doxorubicin insults and increases in both cell granularity (p < 0.01) and cell death (p < 0.01) in cells recovered from ex-vivo liver tissue exposed to hyperthermia and high pressures of HIFU (8.2 MPa peak-to-peak free-field at 1 MHz) relative to controls. Ex-vivo results were validated with microscopy using pan-cytokeratin stain. This rapid, sensitive and highly quantitative cell-viability method is applicable to the small masses of liver tissue typically recovered from a standard core biopsy (5–20 mg) and may be applied to tissues of other histological origins including immunostaining.

Combined treatment with modulated electro-hyperthermia and an autophagy inhibitor effectively inhibit ovarian and cervical cancer growth

PURPOSE

Modulated electro-hyperthermia (mEHT), known as oncothermia, is an anticancer therapy that induces radiofrequency thermal damage to the cancer tissues. This study aimed to evaluate the potential effectiveness of mEHT as a therapeutic tool in ovarian and cervical cancer.

MATERIALS AND METHODS

We used both tumor-bearing mice and ovarian and cervical OVCAR-3, SK-OV-3, HeLa and SNU-17 cancer cell lines to investigate the effects of mEHT in vivo and in vitro, respectively, and determine whether it was enhanced by cotreatment with an autophagy inhibitor.

RESULTS

We discovered that phosphorylation of p38, a stress-dependent kinase, was induced at the Thr180/Tyr182 residue in cancer cells exposed to mEHT. Apoptotic markers such as cleaved caspase-3 and poly-ADP ribose polymerase (PARP) were increased in OVCAR-3 and SNU-17 cells. Fluorescence-activated cell sorting (FACS) analysis showed a significant increase in the population of sub-G1 mEHT-exposed cells, which are dying and apoptotic cells. mEHT also reduced both weight and volume of xenograft tumors in mice transplanted with ovarian and cervical cancer cells and patient-derived cancer tissues. We determined that mEHT-induced cellular damage recovery was mediated by autophagy and, therefore, expectedly, cotreatment with mEHT and 3-methyladenine (3-MA), an autophagy inhibitor, more effectively inhibited cancer cell growth than individual treatment did.

CONCLUSIONS

mEHT treatment alone was sufficient to inhibit cancer growth, while a combined treatment with mEHT and an autophagy inhibitor amplified this inhibition effect.

Comparison of biological effects of modulated electro-hyperthermia and conventional heat treatment in human lymphoma U937 cells

Loco-regional hyperthermia treatment has long history in oncology. Modulated electro-hyperthermia (mEHT, trade name: oncothermia) is an emerging curative treatment method in this field due to its highly selective actions. The impedance-matched, capacitive-coupled modulated radiofrequency (RF) current is selectively focused in the malignant cell membrane of the cancer cells. Our objective is studying the cell-death process and comparing the cellular effects of conventional water-bath hyperthermia treatment to mEHT. The U937 human histiocytic lymphoma cell line was used for the experiments. In the case of conventional hyperthermia treatment, cells were immersed in a thermoregulated water bath, whereas in the case of mEHT, the cells were treated using a special RF generator (LabEHY, Oncotherm) and an applicator. The heating dynamics, the maximum temperature reached (42 °C) and the treatment duration (30 min) were exactly the same in both cases. Cell samples were analysed using different flow cytometric methods as well as microarray gene expression assay and western blot analysis was also used to reveal the molecular basis of the induced effects. Definite difference was observed in the biological response to different heat treatments. At 42 °C, only mEHT induced significant apoptotic cell death. The GeneChip analysis revealed a whole cluster of genes, which are highly up-regulated in case of only RF heating, but not in conventional heating. The Fas, c-Jun N-terminal kinases (JNK) and ERK signalling pathway was the dominant factor to induce apoptotic cell death in mEHT, whereas the cell-protective mechanisms dominated in case of conventional heating. This study has clearly shown that conventional hyperthermia and RF mEHT can result in different biological responses at the same temperature. The reason for the difference is the distinct, non-homogenous energy distribution on the cell membrane, which activates cell death-related signalling pathways in mEHT treatment but not in conventional heat treatment.

Hyperthermia: an effective strategy to induce apoptosis in cancer cells

Heat has been used as a medicinal and healing modality throughout human history. The combination of hyperthermia (HT) with radiation and anticancer agents has been used clinically and has shown positive results to a certain extent. However, the clinical results of HT treatment alone have been only partially satisfactory. Cell death following HT treatment is a function of both temperature and treatment duration. HT induces cancer cell death through apoptosis; the degree of apoptosis and the apoptotic pathway vary in different cancer cell types. HT-induced reactive oxygen species production are responsible for apoptosis in various cell types. However, the underlying mechanism of signal transduction and the genes related to this process still need to be elucidated. In this review, we summarize the molecular mechanism of apoptosis induced by HT, enhancement of heat-induced apoptosis, and the genetic network involved in HT-induced apoptosis.

Gene expression in enhanced apoptosis of human lymphoma U937 cells treated with the combination of different free radical generators and hyperthermia

The effects of various free radicals derived from 6-formylpterin (6-FP), alpha-phenyl-tert-butyl nitrone (PBN) and 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) combined with hyperthermia, on gene expression in similarly enhanced apoptosis of human lymphoma U937 cells were investigated using cDNA microarrays containing approximately 16,600 genes and computational gene expression analysis tools. When the cells were treated for 10 min at 44 degrees C (15% apoptosis level), 39 up-regulated and 3 down-regulated genes were identified. In the up-regulated genes, apoptosis- and unfolded protein response-associated genes were contained. The combined treatment with heat and either chemical enhanced apoptosis level (approximately 30%) and showed a chemical-specific gene expression pattern. Furthermore, the expression levels of selected genes were confirmed by a real-time quantitative PCR. The present results will provide a basis for further understanding the molecular mechanisms in enhancement of heat-induced apoptosis by different intracellular oxidative stress.

Molecular mechanism of apoptosis and gene expressions in human lymphoma U937 cells treated with anisomycin

Anisomycin is known as a potent apoptosis inducer by activating JNK/SAPK and inhibiting protein synthesis during translation. However, only few details are known about the mechanism of apoptosis induced by this compound. The present study was undertaken to further elucidate the molecular mechanism of apoptosis and the changes of gene expression elicited by anisomycin using DNA microarrays and computational gene-expression analysis tools in human lymphoma U937 cells. Anisomycin was found to induce apoptosis in time- and concentration-dependent manner as confirmed by phosphatidylserine externalization and DNA fragmentation analysis. Furthermore, anisomycin-treated cells also showed caspase-8 activation, mitochondrial membrane potential collapse, Bid activation, caspase-3 cleavage and cytochrome c release into the cytosol. In the gene-expression analysis, six gene clusters were detected. From clusters I and II, three significant genetic networks were identified. Interestingly, many bZIP family transcription factors were observed in the up-regulated genetic networks. Moreover, the expression of protein-synthesis-related genes, such as EIF4 family proteins and ribosomal proteins, were inhibited. This finding could explain the reason why anisomycin inhibits the protein synthesis at the translation steps. These results provide novel information for understanding the molecular mechanism of apoptosis induced by anisomycin.

Identification of genetic networks involved in the cell injury accompanying endoplasmic reticulum stress induced by bisphenol A in testicular Sertoli cells

To identify detailed mechanisms by which bisphenol A (BPA), an endocrine-disrupting chemical, induces cell injury in mouse testicular Sertoli TTE3 cells, we performed genome-wide microarray and computational gene network analyses. BPA (200muM) significantly decreased cell viability and simultaneously induced an increase in mRNA levels of HSPA5 and DDIT3, endoplasmic reticulum (ER) stress marker genes. Of the 22,690 probe sets analyzed, BPA down-regulated 661 probe sets and up-regulated 604 probe sets by >2.0-fold. Hierarchical cluster analysis demonstrated nine gene clusters. In decreased gene clusters, two significant genetic networks were associated with cell growth and proliferation and the cell cycle. In increased gene clusters, two significant genetic networks including many basic-region leucine zipper transcription factors were associated with cell death and DNA replication, recombination, and repair. The present results will provide additional novel insights into the detailed molecular mechanisms of cell injury accompanying ER stress induced by BPA in Sertoli cells.

Genetic networks responsive to sodium butyrate in colonic epithelial cells

We performed microarray and computational gene network analyses to identify the detailed mechanisms by which sodium butyrate (SB) induces cell growth arrest and the differentiation of mouse colonic epithelial MCE301 cells. Two thousand six hundred four differentially expressed probe sets were identified in the cells treated with 2mM SB and were classified into four groups. Of these, the gradually increased group and the gradually and remarkably decreased group contained the genetic networks for cellular development and cell cycles or canonical pathways for fatty acid biosynthesis and pyrimidine metabolism, respectively. The present results provide a basis for understanding the detailed molecular mechanisms of action of SB in colonic epithelial cells.

The novel phospholipase C activator, m-3M3FBS, induces monocytic leukemia cell apoptosis

We investigated the effect of the novel phospholipase C activator, m-3M3FBS, on the apoptosis of leukemic cells. m-3M3FBS inhibited the growth of the leukemic cell lines U937 and THP-1, but not primary monocytes. m-3M3FBS induced the apoptosis of U937 cells, which was accompanied by chromatin condensation and DNA fragmentation. Moreover, m-3M3FBS-induced apoptosis appeared to involve the down-regulation of anti-apoptotic Bcl-2, the up-regulation of pro-apoptotic Bax, the release of cytochrome c, and caspase activation. m-3M3FBS-induced apoptosis of U937 cells was also partly inhibited by BAPTA-AM and EGTA, indicating the involvement of intracellular calcium signaling on the apoptosis in U937 cells. The results of our study suggest that m-3M3FBS can be developed as a novel anti-leukemic agent.

Genes involved in nonpermissive temperature-induced cell differentiation in Sertoli TTE3 cells bearing temperature-sensitive simian virus 40 large T-antigen

Sertoli TTE3 cells, derived from transgenic mice bearing temperature-sensitive simian virus 40 large T (tsSV40LT)-antigen, proliferated continuously at a permissive temperature (33 degrees C) whereas inactivation of the large T-antigen by a nonpermissive temperature (39 degrees C) led to differentiation as judged by elevation of transferrin. To clarify the detailed mechanisms of differentiation, we investigated the time course of changes in gene expression using cDNA microarrays. Of the 865 genes analyzed, 14 genes showed increased levels of expression. Real-time quantitative PCR revealed that the mRNA levels of p21(waf1), milk fat globule membrane protein E8, heat-responsive protein 12, and selenoprotein P were markedly elevated. Moreover, the differentiated condition induced by the nonpermissive temperature significantly increased mRNA levels of these four genes in several cell lines from the transgenic mice bearing the oncogene. The present results regarding changes in gene expression will provide a basis for a further understanding of molecular mechanisms of differentiation in both Sertoli cells and cell lines transformed by tsSV40LT-antigen.

Analysis of gene expression in apoptosis of human lymphoma U937 cells induced by heat shock and the effects of α-phenyl N-tert-butylnitrone (PBN) and its derivatives

Hyperthermia, a modality of cancer therapy, has been known as a stress to induce apoptosis. However, the molecular mechanism of heat shock-induced apoptosis, especially on roles of intracellular oxidative stress, is not fully understood. First, when human lymphoma U937 cells were treated with heat shock (44 degrees C, 30 min), the fraction of apoptosis, revealed by phosphatidylserine externalization, increased gradually and peaked at 6 hr after the treatment. In contrast, intracellular superoxide formation increased early during the heat shock treatment and peaked at 30 min after the treatment. When the cells were treated with heat shock in the presence of alpha -phenyl-N-tert-butylnitrone (PBN) and its derivatives, which are potent antioxidants, the DNA fragmentation was inhibited in an order according to the agents' hydrophobicity. PBN showing the highest inhibitory effects suppressed not only intracellular superoxide formation but also various apoptosis indicators. cDNA microarray was employed to analyze gene expression associated with heat shock-induced apoptosis, and the time-course microarray analysis revealed 5 groups showing changes in their pattern of gene expression. Among these genes, c-jun mRNA expression showed more than 40 fold increase 2 hr after heat treatment. The expression level of c-jun mRNA verified by quantitative real-time PCR was about 20 fold increase, and c-jun expression was similarly suppressed by PBN and its derivatives. These results suggest that the change of c-jun expression is an excellent molecular marker for apoptosis mediated by intracellular oxidative stress induced by heat shock.

Both calcium and ROS as common signals mediate Na(2)SeO(3)-induced apoptosis in SW480 human colonic carcinoma cells

Recent studies have shown that reactive oxygen species (ROS) play a crucial role in Se-induced cell apoptosis. A number of studies have demonstrated that perturbed cellular calcium homeostasis has been implicated in apoptosis. The main objective of this study was to evaluate the role of Ca(2+) in Na(2)SeO(3)-induced apoptosis and the relationship between Ca(2+) and ROS in human colonic carcinoma cells SW480. When SW480 cells were exposed to 25-100 microM Na(2)SeO(3), both cell apoptosis and growth inhibition were observed by flow cytometric analysis and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Na(2)SeO(3) was able to induce increase of [Ca(2+)](i) and ROS production and disrupt mitochondrial membrane potential (Delta Psi m) in SW480 cells monitored by using a confocal laser scanning microscope. Ca(2+) channel inhibitor CoCl(2) and an intracellular Ca(2+) chelator o-phtalaldehyde, 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester (BAPTA) completely inhibited [Ca(2+)](i) increase, but catalase had no effect on Na(2)SeO(3)-induced increase of [Ca(2+)](i). BAPTA-AM, CoCl(2), and mitochondrial Ca(2+) uptake inhibitor ruthenium red blocked Delta Psi m dissipation. The increase of ROS was also suppressed by CoCl(2), BAPTA, ruthenium red, N-acetylcysteine and catalase, respectively. The mitochondrial uncoupler carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) completely inhibited Na(2)SeO(3)-induced ROS increase. This showed that ROS increase is due to mitochondrial Ca(2+) overload. The Na(2)SeO(3)-induced apoptosis of SW480 cells was also inhibited by CoCl(2), BAPTA, ruthenium red, N-acetylcysteine, and catalase, respectively. The results mentioned above imply that both calcium and Ca(2+)-dependent ROS as a signal molecule mediate apoptosis induced by Na(2)SeO(3) in SW480 cells.

Enhanced ultrasound-induced apoptosis and cell lysis by a hypotonic medium

PURPOSE

To test the hypothesis that non-lethal hypotonia will enhance ultrasound-induced cell killing in vitro and that the mechanism is mechanical in nature.

MATERIALS AND METHODS

Hypotonic RPMI medium (146 mOsm) was used to induce non-lethal osmotic swelling of human myelomonocytic leukaemia U937 cells. Hypotonia for 10 min was started just before exposure to 1 MHz ultrasound at 0.5 or 1.0 Wcm(-2) for 10 min, or 5 min before exposure to 2.0 Wcm(-2) for 1 min. Surviving intact cells were then determined by the trypan blue dye exclusion test immediately after treatment. After 6-h incubation of the treated cells, early apoptosis and secondary necrosis were measured using a flow cytometer. Intracellular free calcium ion imaging by Fura-2 fluorescence and cellular ion scanning using a secondary ion mass spectrometer were also performed.

RESULTS

Enhancement of ultrasound-induced cell lysis was observed at all intensities, and most prominently at 2.0 Wcm(-2), while apoptosis induction was significantly enhanced at intensities of 0.5 and 1.0 Wcm(-2), but not at 2.0 Wcm(-2). The enhanced cell lysis is attributed to the increased susceptibility of the cells to mechanical damage. This is consistent with previous reports describing the effects of mechanical stresses on cell membranes. Cellular ion scanning images also suggest that hypotonia has an effect on the membrane damage-and-repair mechanism of the cells.

CONCLUSIONS

The results support the hypothesis that non-lethal hypotonia can enhance ultrasound-induced cell killing. These findings also suggest the 'sonomechanical' nature of the effects on the cells.

Signal transduction of p53-independent apoptotic pathway induced by hexavalent chromium in U937 cells

It has been reported that the hexavalent chromium compound (Cr(VI)) can induce both p53-dependent and p53-independent apoptosis. While a considerable amount of information is available on the p53-dependent pathway, only little is known about the p53-independent pathway. To elucidate the p53-independent mechanism, the roles of the Ca(2+)-calpain- and mitochondria-caspase-dependent pathways in apoptosis induced by Cr(VI) were investigated. When human lymphoma U937 cells, p53 mutated cells, were treated with 20 microM Cr(VI) for 24 h, nuclear morphological changes and DNA fragmentation were observed. Production of hydroxyl radicals revealed by electron paramagnetic resonance (EPR)-spin trapping, and increase of intracellular calcium ion concentration monitored by digital imaging were also observed in Cr(VI)-treated cells. An intracellular Ca(2+) chelator, BAPTA-AM, and calpain inhibitors suppressed the Cr(VI)-induced DNA fragmentation. The number of cells showing low mitochondrial membrane potential (MMP), high level of superoxide anion radicals (O(2)(-)), and high activity of caspase-3, which are indicators of mitochondria-caspase-dependent pathway, increased significantly in Cr(VI)-treated cells. An antioxidant, N-acetyl-l-cysteine (NAC), decreased DNA fragmentation and inhibited the changes in MMP, O(2)(-) formation, and activation of caspase-3 induced by Cr(VI). No increase of the expressions of Fas and phosphorylated JNK was observed after Cr(VI) treatment. Cell cycle analysis revealed that the fraction of G2/M phase tended to increase after 24 h of treatment, suggesting that Cr(VI)-induced apoptosis is related to the G2 block. These results indicate that Ca(2+)-calpain- and mitochondria-caspase-dependent pathways play significant roles in the Cr(VI)-induced apoptosis via the G2 block, which are independent of JNK and Fas activation. The inhibition of apoptosis and all its signal transductions by NAC suggests that intracellular reactive oxygen species (ROS) are important for both pathways in Cr(VI)-induced apoptosis of U937 cell.

Role of intracellular calcium ions and reactive oxygen species in apoptosis induced by ultrasound

Recently, we have reported that ultrasound (US)-induced apoptosis is due to inertial cavitation and that extracellular reactive oxygen species (ROS) generated by inertial cavitation are not directly correlated with the apoptosis (Honda et al. 2002). The molecular mechanism of apoptosis induced by US is not yet sufficiently clear. Here, we examine the role of intracellular calcium ions and the intracellular ROS on apoptosis induced by US. Human myelomonocytic lymphoma U937 cells were exposed to continuous 1-MHz US at an intensity of 4.9 W/cm(2) (I(SPTA)) in the presence of air, and changes of intracellular calcium ion concentration ([Ca(2+)]i) in individual cells by digital imaging, various flow cytometric analyses of endpoints of apoptosis (early apoptosis, secondary necrosis, loss of mitochondria membrane potential, superoxide formation, caspase-3 activation) and DNA fragmentation were explored. Furthermore, the effects of an intracellular calcium ion chelator (BAPTA-AM), an antioxidant (N-acetyl-L-cysteine, NAC), a calcium channel blocker (verapamil), Ca(2+)-free buffer and Levovist were also investigated. These results indicate that: 1. the mitochondria-caspase pathway and the Ca(2+)-dependent pathway play cardinal roles in apoptosis induced by US because BAPTA-AM partially inhibited DNA fragmentation, loss of mitochondria membrane potential and caspase-3 activation; 2. intracellular ROS generated from mitochondria, rather than extracellular ROS (which were directly produced by inertial cavitation in the medium), are involved in the regulation of apoptosis induced by US because addition of NAC after sonication showed effective suppression of the apoptosis; and 3. increase of [Ca(2+)]i appears to be due to nonspecific influx from outside the cells because verapamil is not effective and no increase of [Ca(2+)]i due to sonication could be observed in the Ca(2+)-free buffer.

A free radical initiator, 2,2'-azobis (2-aminopropane) dihydrochloride enhances hyperthermia-induced apoptosis in human uterine cervical cancer cell lines

Hyperthermia-induced apoptosis and its enhancement in the presence of a temperature-dependent free radical initiator, 2,2'-azobis (2-aminopropane) dihydrochloride (AAPH) were examined in human uterine cervical cancer cell lines, CaSki and HeLa. When both cell lines were treated with hyperthermia at 44 degrees C for 60 min, minimal apoptosis was observed. When combined with nontoxic AAPH (50mM), significant enhancement of apoptosis was observed, where the initial rate of free radical formation was about twice as high than that at 37 degrees C. Augmentation of the growth delay, lipid peroxidation (LPO), activation of caspase-3 and increase in [Ca2+]i were also observed after the combined treatment. A water-soluble vitamin E, Trolox, blocked the increase in [Ca2+]i and an intracellular Ca2+ chelator, BAPTA-AM, prevented the DNA fragmentation induced by the combination. Cytochrome c release was also revealed by fluorescence microscopy. However, no significant change in mitochondrial membrane potential and expression of Bax and Bcl-2 was observed. A slight increase in Fas expression was observed only in CaSki cells after the combined treatment. These results indicate that hyperthermia and AAPH induce enhanced apoptosis and subsequent cell killing via two pathways; a pathway dependenton increase in LPO and [Ca2+]i, and a pathway associated with cytochrome c release and subsequent caspase activation without changes of mitochondrial membrane potential and Bax/Bcl-2 expression in these cell lines. Since it is known that cancer cells are generally resistant to physical and chemical stress-induced apoptosis, free radical generators like AAPH appear to be a useful thermosensitizer for hyperthermic cancer therapy.

cDNA microarray analysis reveals chop-10 plays a key role in Sertoli cell injury induced by bisphenol A

We examined the time course of changes in gene expression in detail using cDNA microarray analysis of mouse Sertoli TTE3 cells treated with bisphenol A (BPA). A subtoxic dose of BPA (200 microM) transiently increased intracellular Ca(2+) concentration and time-dependently induced an increase in mRNA level of 78-kDa glucose-regulated protein, indicating that BPA induces endoplasmic reticulum stress. Of the 865 genes analyzed, 31 genes showed increased levels of expression. TaqMan analysis confirmed that the mRNA levels of chop-10, fra-2, c-myc, and ornithine decarboxylase were increased, and showed that chop-10 is the most sensitive gene. The expression level of chop-10 protein and cell injury induced by BPA were significantly reduced in stable TTE3 cells overexpressing full-length chop-10 antisense RNA. We conclude that chop-10 plays a key role in Sertoli cell injury induced by BPA.

Enhancement of hyperthermia-induced apoptosis by local anesthetics on human histiocytic lymphoma U937 cells

The combined effects of hyperthermia at 44 degrees C and local anesthetics on apoptosis in human histiocytic lymphoma U937 cells were investigated. When the cells were exposed to hyperthermia for l0 min marginal DNA fragmentation and nuclear fragmentation were observed. In the presence of amide-type local anesthetics further enhancement was found depending on concentration. The order of the concentration required for maximum induction was the reverse order of the lipophilicity (prilocaine > lidocaine > bupivacaine). Western blotting revealed that in hyperthermia there was initial release of Ca(2+) from the intracellular store site as indicated by increased expression of the type 1 inositol-1,4,5-trisphosphate receptor. However, the combination with lidocaine did not induce any further enhancement. Lidocaine enhanced the decrease in ATP content and the increase in intracellular Ca(2+) concentration in individual cells induced by hyperthermia. In addition, superoxide formation, decrease in the mitochondrial membrane potential, and activation of intracellular caspase-3 were found in the cells treated with hyperthermia and lidocaine. All of these were suppressed in part in the presence of the intracellular Ca(2+) ion chelator BAPTA-AM (bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl). The present results indicate that local anesthetics at optimal concentrations enhance hyperthermia-induced apoptosis via Ca(2+)- and mitochondria-dependent pathways. Initial release of Ca(2+) from intracellular store sites caused by hyperthermia and followed by the subsequent increase in the intracellular Ca(2+) concentration and the additional activation of the mitochondrial caspase-dependent pathway (partly regulated by intracellular Ca(2+) concentration) plays a crucial role in the enhancement of apoptosis induced by the combination of hyperthermia and lidocaine.

Identification of genes responsive to sodium butyrate in colonic epithelial cells

We identified genes responsive to sodium butyrate (SB) in colonic epithelial cells using cDNA microarrays. Treatment with 2 mM SB of colonic epithelial cells (MCE301), which was derived from transgenic mice harboring a temperature-sensitive simian virus 40 large T-antigen, arrested cell growth and showed a differentiated phenotype accompanying an increase in alkaline phosphatase activity. Of the approximately 900 genes analyzed, SB down-regulated 25 genes and up-regulated 88 genes by a factor of 2.0 or greater. Northern blot or TaqMan and Western blot analyses confirmed that the mRNA and protein levels of cyclin D1 and the level of proliferating cell nuclear antigen decreased, whereas the levels of integrin beta1 and osteopontin increased. The present results regarding the changes in gene expression, arrived at using microarrays, will provide a basis for a further understanding of the molecular mechanisms of cell growth arrest and differentiation in response to SB in colonic epithelial cells.

Cell cycle induction in post-mitotic neurons proceeds in concert with the initial phase of programmed cell death in rat

Neuronal programmed cell death (PCD) is increasingly becoming recognized as a dynamic process that may be amenable to resolution. Critical to this resolution is the identification of the cellular pathways that modulate the initial stages of apoptotic death. In this regard, we examined whether the activation of a latent cell cycle was associated with the initial phase of PCD. We demonstrate that free radical nitric oxide induced PCD results in the rapid generation of membrane phosphatidylserine residue exposure. This early phase of PCD functions in parallel with an untoward attempt to enter the cell cycle in the same population of post-mitotic neurons. We therefore offer an attractive molecular target to prevent or reverse neuronal PCD by elucidating a novel mechanism through which the majority of neurons meet their demise by attempting to enter a latent cell cycle.