Shigehito Wada

Ultrasound-induced apoptosis in the presence of Sonazoid and associated alterations in gene expression levels: a possible therapeutic application.

Ultrasound (US) has been shown to induce apoptosis and cell lysis in cancer cells. In this study, we report on the potential of using Sonazoid, a new echo-contrast agent, that is chemically more stable and US-resistant in combination with US in cancer therapy. The biological effects and their mechanisms in the presence or absence of ultrasonic exposure in vitro were investigated. In addition, the impact of the agent on the expression levels of genes responsive to US was studied using global-scale microarrays and computational gene expression analysis tools. Our results show that the combination led to enhanced cell killing in the presence of 1 MHz acoustic field. The apoptosis induction was shown to be mediated by the mitochondrial pathway. The occurrence of US-induced DNA damage was also observed. Despite these findings, the agent at concentrations similar to those clinically used can be considered as well tolerated. Furthermore, Sonazoid enhanced expression of genes that related to apoptosis and are responsive to US, although it alone had almost no effect. These results indicate the potential of Sonazoid for US contrast enhancement as well as the possibility of its use in US-aided therapies.

Genes and genetic networks responsive to mild hyperthermia in human lymphoma U937 cells

In this study, to better understand the molecular mechanism underlying cellular responses to mild hyperthermia, we investigated gene expression patterns and genetic networks in human myelomonocytic lymphoma U937 cells using high-density oligonucleotide microarrays and computational gene expression analysis tools. The cells were incubated at 41°C for 30 min (mild hyperthermia treatment) and then at 37°C for 0–6 h. Although the mild hyperthermia treatment of the cells did not induce apoptosis, significant increases in the protein expression levels of heat shock proteins (HSPs), namely, Hsp27, Hsp40 and Hsp70, were observed following the activation of heat shock factor-1. Of the 22,283 probe sets analyzed, 423 probe sets were up-regulated and 515 probe sets were down-regulated by >1.5-fold in the cells 3 h post-treatment. Computational gene network analysis demonstrated that the significant genetic network A that contained many HSPs such as DNAJB1, HSPA1A, and HSPA1B was associated with cellular function and maintenance, post-transcriptional modification, or protein folding. Moreover, the significant genetic network B whose core contained v-myc myelocytomatosis viral oncogene homolog (MYC) was associated with cell morphology, cell cycle, and cellular development. The expression levels of nine selected genes were comparable to those determined by microarray analysis with real-time quantitative PCR assay. The present results indicate that mild hyperthermia affects the expression of a large number of genes and provides additional novel insights into the molecular basis of mild hyperthermia in cells.

Genetic networks responsive to low-intensity pulsed ultrasound in human lymphoma U937 cells.

To clarify the detailed molecular mechanism underlying cellular responses to nonthermal low-intensity pulsed ultrasound (LIPUS), gene expression patterns and genetic networks in human lymphoma U937 cells were examined using global-scale microarrays and computational gene expression analysis tools. Six hours after LIPUS treatment (0.3W/cm(2) for 1min), apoptosis (14+/-3.8%, mean+/-SD) without no cell lysis was observed. Of 22,283 probe sets analyzed, LIPUS down-regulated 193 genes and up-regulated 201 genes by >1.5-fold. For down-regulated genes, the significant genetic network D was associated with cellular growth and proliferation, gene expression, or cellular development. For up-regulated genes, the significant genetic network U was associated with cellular movement, cell morphology, and cell death. The present results indicate that LIPUS affects the expression of many genes and will provide novel insight into the biomolecular mechanisms of LIPUS in therapeutic application for cancer therapy.

Enhancement of radiation-induced apoptosis by 6-formylpterin.

Radiation-induced apoptosis and its possible enhancement in the presence of 6-formylpterin (6-FP), a metabolite of folic acid, were examined in human myelomonocytic lymphoma U937 cells. When cells were treated with 6-FP at a nontoxic concentration of 300 μM, and then exposed to X-rays at a dose of 10 Gy, significant enhancement of radiation-induced apoptosis as determined by nuclear morphological change, phosphatidylserine (PS) externalization and DNA fragmentation were observed. Flow cytometry for the detection of intracellular hydrogen peroxide (H2O2) revealed that 6-FP increased the formation of intracellular H2O2, which further increased when the cells were irradiated. Decrease of mitochondria trans-membrane potential (MMP), release of cytochrome c from mitochondria, and activation of caspase-3 were enhanced after the combined treatment. Remarkable activation of protein kinase C δ (PKC δ) and its translocation from cytosol to mitochondria were detected in combined treatment. Increase of intracellular Ca2+ concentrations ([Ca2+]i) was also observed, however, neither calpain I nor calpain II could inhibit the apoptosis. In addition, c-Jun NH2-terminal kinase ( JNK) activation was not enhanced in the combined treatment. A protein involved in a caspase-independent apoptosis pathway, apoptosis inducing factor (AIF), remained unchanged even 3 h after treatment. These results indicate that intracellular H2O2 generated by 6-FP enhances radiation-induced apoptosis via the mitochondria-mediated caspase-dependent pathway, with the active involvement of PKC δ.

Identification of biological functions and gene networks regulated by heat stress in U937 human lymphoma cells

Although cancer cells exposed to temperatures >42.5°C undergo cell death as the temperature rises, exposure of up to 42.5°C induces slight or no cytotoxicity. The temperature of 42.5°C is, therefore, well known to be the inflection point of hyperthermia. To better understand the molecular mechanisms underlying cellular responses to heat stress at temperatures higher and lower than the inflection point, we carried out global scale microarray and computational gene expression analyses. Human leukemia U937 cells were incubated at 42°C or 44°C for 15 min and cultured at 37°C for 0-6 h. Apoptosis accompanied by the activation of caspase-3 and DNA fragmentation was only observed in cells treated with heat stress at 44°C, but not at 42°C. Although a large number of genes were differentially expressed by a factor of 2.0 or greater, we found substantial differences with respect to the biological functions and gene networks of the genes differentially expressed at the two temperatures examined. Interestingly, we identified temperature-specific gene networks that were considered to be mainly associated with cell death or cellular compromise and cellular function and maintenance at 44°C or 42°C, respectively, by using the Ingenuity pathway analysis tools. These findings provide the molecular basis for a further understanding of the mechanisms of the biological changes that are responsive to heat stress in human lymphoma cells.

Monohydroxylated polycyclic aromatic hydrocarbons inhibit both osteoclastic and osteoblastic activities in teleost scales

AIMS We previously demonstrated that monohydroxylated polycyclic aromatic hydrocarbons (OHPAHs) bound to a human estrogen receptor (ER) by a yeast two-hybrid assay, but polycyclic aromatic hydrocarbons did not have a binding activity. Therefore, the direct effect of 3-hydroxybenz[a]anthracene (3-OHBaA) and 4-hydroxybenz[a]anthracene (4-OHBaA) on osteoclasts and osteoblasts in teleosts was examined. As a negative control, 1-hydroxypyrene (1-OHPy), which has no binding activity to human ER, was used. MAIN METHODS The effect of OHPAHs on osteoclasts and osteoblasts was examined by an assay system using teleost scale as each marker: tartrate-resistant acid phosphatase for osteoclasts and alkaline phosphatase for osteoblasts. Changes in cathepsin K (an osteoclastic marker) and insulin-like growth factor-I (IGF-I) (an osteoblastic marker) mRNA expressions in 4-OHBaA-treated goldfish scales were examined by using a reverse transcription-polymerase chain reaction. KEY FINDINGS In both goldfish (a freshwater teleost) and wrasse (a marine teleost), the osteoclastic activity in the scales was significantly suppressed by 3-OHBaA and 4-OHBaA, although 1-OHPy did not affect the osteoclastic activity. In reference to osteoblasts, the osteoblastic activity decreased with both 3-OHBaA and 4-OHBaA and did not change with the 1-OHPy treatment. However, 17beta-estradiol (E(2)) significantly increased both the osteoclastic and osteoblastic activities in the scales of both goldfish and wrasse. The mRNA expressions of both cathepsin K and IGF-I decreased in the 4-OHBaA-treated scales but increased in the E(2)-treated scales. SIGNIFICANCE The current data are the first to demonstrate that 3-OHBaA and 4-OHBaA inhibited both osteoclasts and osteoblasts and disrupted the bone metabolism in teleosts.

A hydrogen peroxide-generating agent, 6-formylpterin, enhances heat-induced apoptosis

The enhancement of heat-induced apoptosis by 6-formylpterin, an intra-cellular generator of hydrogen peroxide (H2O2), was examined in human myelomonocytic lymphoma U937 cells. The cells were treated with either 6-formylpterin alone at a nontoxic concentration of 300 µM (37°C), heat shock (44°C per 20 min) alone or a combination of the two, then incubated at 37°C for 6 h. Assessments of apoptosis, mitochondrial membrane potential and caspase-3 activation were performed by flow cytometry. Moreover, caspase-8 activation and changes in the intra-cellular Ca2+ concentration ([Ca2+]i) were examined. Bax, Bcl-2, Bcl-XL, Bid, cytochrome c and PKCδ were detected by Western blotting. The induction of heat-induced apoptosis evaluated by morphological observation and DNA fragmentation were promoted by the addition of 6-formylpterin. Mitochondrial membrane potential was decreased and the activation of caspase-3 and -8 was enhanced in the cells treated with the combination. A decreased-expression of Bid was noted, although no significant changes in Bax, Bcl-2 and Bcl-XL expression were observed after the combined treatment. Furthermore, both the release of cytochrome c from mitochondria to cytosol and the translocation of PKCδ from cytosol to mitochondria, which were induced by heat shock, were enhanced by the addition of 6-formylpterin. The number of cells with a higher [Ca2+]i was also increased by the addition of 6-formylpterin. These findings suggest that the increase in [Ca2+]i, the activation of the mitochondria–caspase dependent pathway and the translocation of PKCδ to mitochondria play principal roles in the enhancement of heat-induced apoptosis by 6-FP.

Gene networks related to the cell death elicited by hyperthermia in human oral squamous cell carcinoma HSC-3 cells

Local hyperthermia (HT) for various types of malignant tumors has shown promising antitumor effects. To confirm the detailed molecular mechanism underlying cell death induced by HT, gene expression patterns and gene networks in human oral squamous cell carcinoma (OSCC) cells were examined using a combination of DNA microarray and bioinformatics tools. OSCC HSC-3 cells were treated with HT at 44˚C for 90 min or mild hyperthermia (MHT) at 42˚C for 90 min, followed by culturing at 37˚C for 0-24 h. Treatment of cells with HT prevented cell proliferation (62%) and induced cell death (17%), whereas these alterations were not observed in cells treated with MHT. Microarray analysis revealed substantial differences with respect to gene expression patterns and biological function for the two different hyperthermic treatments. Moreover, we identified the temperature-specific gene networks D and H that were obtained from significantly up-regulated genes in the HT and MHT conditions, respectively, using Ingenuity pathway analysis tools. Gene network D, which contains 14 genes such as ATF3, DUSP1 and JUN, was associated with relevant biological functions including cell death and cellular movement. Gene network H, which contains 13 genes such as BAG3, DNAJB1 and HSPA1B, was associated with cellular function and maintenance and cellular assembly and organization. These findings provide a basis for understanding the detailed molecular mechanisms of cell death elicited by HT in human OSCC cells.

Gene networks involved in apoptosis induced by hyperthermia in human lymphoma U937 cells.

To define the molecular mechanisms that mediate hyperthermia‐induced apoptosis, we performed microarray and computational gene expression analyses. U937 cells, a human myelomonocytic lymphoma cell line, were treated with hyperthermia at 42 °C for 90 min and cultured at 37 °C. Apoptotic cells (∼15%) were seen 6 h after hyperthermic treatment, and elevated expression of heat shock proteins (HSPs) including Hsp27, Hsp40, and Hsp70 was detected, following the activation of heat shock factor‐1. Of the 54,675 probe sets analyzed, 1334 were upregulated and 4214 were downregulated by >2.0‐fold in the cells treated with hyperthermia. A non‐hierarchical gene clustering algorithm, K‐means clustering, demonstrated 10 gene clusters. The gene network U1 or U2 that was obtained from up‐regulated genes in cluster I or IX contained HSPA1B, DNAJB1, HSPH1, and TXN or PML, LYN, and DUSP1, and were mainly associated with cellular compromise, and cellular function and maintenance or death, and cancer, respectively. In the decreased gene cluster II, the gene network D1 including CCNE1 and CEBPE was associated with the cell cycle and cellular growth and proliferation. These findings will provide a basis for understanding the detailed molecular mechanisms of apoptosis induced by hyperthermia at 42 °C in cells.

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), α-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°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.