Ionizing radiation stimulates unidentified tyrosine-specific protein kinases in human B-lymphocyte precursors, triggering apoptosis and clonogenic cell death

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

The role of isoflavones in augmenting the effects of radiotherapy

Cancer is one of the major health problems and the second cause of death worldwide behind heart disease. The traditional soy diet containing isoflavones, consumed by the Asian population in China and Japan has been identified as a protective factor from hormone-related cancers. Over the years the research focus has shifted from emphasizing the preventive effect of isoflavones from cancer initiation and promotion to their efficacy against established tumors along with chemo- and radiopotentiating effects. Studies performed in mouse models and results of clinical trials emphasize that genistein or a mixture of isoflavones, containing in traditional soy diet, could be utilized to both potentiate the response of cancer cells to radiotherapy and reduce radiation-induced toxicity in normal tissues. Currently ongoing clinical research explores a potential of another significant isoflavone, idronoxil, also known as phenoxodiol, as radiation enhancing agent. In the light of the recent clinical findings, this article reviews the accumulated evidence which support the clinically desirable interactions of soy isoflavones with radiation therapy resulting in improved tumor treatment. This review discusses important aspects of the development of isoflavones as anticancer agents, and mechanisms potentially relevant to their activity in combination with radiation therapy of cancer. It gives a critical overview of studies characterizing isoflavone targets such as topoisomerases, ENOX2/PMET, tyrosine kinases and ER receptor signaling, and cellular effects on the cell cycle, DNA damage, cell death, and immune responses.

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

Exposure to ionizing radiation, mechanical trauma, toxic chemicals or infections, or combinations thereof (i.e., combined injury) can induce organic injury to brain tissues, the structural disarrangement of interactive networks of neurovascular and glial cells, as well as on arrays of the paracrine and systemic destruction. This leads to subsequent decline in cognitive capacity and decompensation of mental health. There is an ongoing need for improvement in mitigating and treating radiation- or combined injury-induced brain injury. Cranial irradiation per se can cause a multifactorial encephalopathy that occurs in a radiation dose- and time-dependent manner due to differences in radiosensitivity among the various constituents of brain parenchyma and vasculature. Of particular concern are the radiosensitivity and inflammation susceptibility of: 1. the neurogenic and oligodendrogenic niches in the subependymal and hippocampal domains; and 2. the microvascular endothelium. Thus, cranial or total-body irradiation can cause a plethora of biochemical and cellular disorders in brain tissues, including: 1. decline in neurogenesis and oligodendrogenesis; 2. impairment of the blood-brain barrier; and 3. ablation of vascular capillary. These changes, along with cerebrovascular inflammation, underlie different stages of encephalopathy, from the early protracted stage to the late delayed stage. It is evident that ionizing radiation combined with other traumatic insults such as penetrating wound, burn, blast, systemic infection and chemotherapy, among others, can exacerbate the radiation sequelae (and vice versa) with increasing severity of neurogenic and microvascular patterns of radiation brain damage.

Low-dose ionizing radiation effects on differentiation of HL-60 cells

The biological effects of low-dose radiation have attracted attention, but data are currently insufficient to fully understand the beneficial role of the phenomenon. In the present study, we have investigated the effects of low doses of gamma-irradiation alone and in combination with all-trans-retinoic acid (RA) on proliferation, apoptosis and differentiation of the human promyelocytic leukemia HL-60 cells. Changes in cell behavior and protein expression were determined with the use of light and fluorescent microscopy, immunocytochemical and Western blot analysis. Low-dose irradiation with 1–100 cGy caused a dose-dependent inhibition of HL-60 cell proliferation, and induced apoptosis and differentiation to granulocytes with an increase in the number of CD15-positive cells. Pre-irradiation with 1–100 cGy for 24 h before treatment with RA promoted apoptosis but did not impair RA-induced differentiation. Both processes were associated with a decrease in the expression of the proliferating cell nuclear antigen (PCNA), BCL-2, c-MYC, and changes in both cytosolic and nuclear levels of protein tyrosine-phosphorylation as well as protein kinase C alpha or beta isoforms. These results demonstrate the beneficial role of low-dose irradiation in modulating leukemia cell proliferation, differentiation and apoptosis.

Post-surgical irradiation causes cellular immune suppression in patients with breast cancer

According to several studies, even the locoregional irradiation of patients with carcinoma can cause a severe and rather alarming cellular immune defect. We thus designed a prospective research in order to study the effect of post-operative irradiation on cellular immunity in patients suffering from breast cancer. In 35 patients with breast cancer who required post-operative irradiation, four blood samples were taken at indicated point times. Nineteen out of 35 patients received post-surgical chemotherapy before irradiation. The total lymphocytes as well as CD4 and CD8 subpopulations were measured by using flow cytometry analysis. The mean T-lymphocyte (Tol) count dropped from 1487.77 to 1227.91 (P = 0.0013) and the CD4+ count from 674.17 to 580.91 (P = 0.0189). The mean value of CD8+ dropped from 421.31 to 314.00 (P = 0.0003). Moreover, a statistically significant difference regarding the pattern of temporal change was observed between a group of patients that received irradiation only and a group that received radiation therapy (RT) with chemotherapy (P-values 0.0015, 0.01 and 0.092 for Tol, CD4+ and CD8+ respectively). The group of patients that received RT only presented a more rapid decrease of Tol concerning the decrease observed in the group that underwent chemotherapy and RT.

The decrease of PAMAM dendrimer-induced cytotoxicity by PEGylation via attenuation of oxidative stress

Due to their unique structure, poly(amidoamine) (PAMAM) dendrimers have been widely used in medical applications. However, PAMAM dendrimers bearing amino terminals show certain cytotoxicity. In order to improve their biocompatibility, we modified Generation-5 PAMAM dendrimers by conjugating them with poly(ethylene glycol) (PEG) of two different molecular weights and different number of chains. The IC(50) values of PEGylated dendrimers were 12-105 fold higher than those of PAMAM dendrimers. To investigate the influence of PEGylation on PAMAM-induced cytotoxicity, the intracellular responses, reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), and apoptosis were examined. The results indicated that conjugation with PEG could effectively reduce the PAMAM-induced cell apoptosis by attenuating the ROS production and inhibiting PAMAM-induced MMP collapse. Meanwhile, dendrimers conjugated with less PEG of lower molecular weight did not significantly change the endocytic properties. Dendrimers conjugated with more PEG of higher molecular weight were much less cytotoxic. This study provided a novel insight into the effects of PEGylation on the decrease of cytotoxicity at the molecular level.

Involvement of CD45 in DNA fragmentation in apoptosis induced by mitochondrial perturbing agents

CD45 is a type I transmembrane molecule with phosphatase activity which comprises up to 10% of the cell surface area in nucleated haematopoietic cells. We have previously demonstrated the absence of nuclear apoptosis in CD45-negative T cells after chemical-induced apoptosis. The aim of this study was to characterize the role of CD45 in nuclear apoptosis. In contrast to wild type CD45-positive T cells, the CD45-deficient T cell lines are resistant to the induction of DNA fragmentation and chromatin condensation following tributyltin (TBT) or H2O2 exposure, but not to cycloheximide-induced apoptosis. CD45 transfection in deficient cell lines led to the restoration of chromatin condensation and DNA fragmentation following TBT exposure. In both CD45-positive and negative T cell lines, TBT exposure mediates intracellular calcium mobilization, caspase-3 activation and DFF45 cleavage. Moreover, DNA fragmentation was also induced by TBT in cells deficient in expression of p56lck, ZAP-70 and SHP-1. Subcellular partitioning showed a decrease in nuclear localisation of caspase-3 and DFF40. Together, these results demonstrate for the first time, that CD45 expression plays a key role in internucleosomal DNA fragmentation and chromatin condensation processes during apoptosis. CD45 activity or its substrates' activity, appears to be located downstream of caspase-3 activation and plays a role in retention of DFF40 in the nucleus.

Protein phosphorylation in irradiated human melanoma cells

In the present study, we examined the response of confluent, primary human fibroblasts and cells of a melanoma (YUSAC2) cell line to ionizing radiation mediated through post-translational protein phosphorylation. Since the purpose of our study was to identify novel radiation-induced phosphoproteins in the DNA damage stress response of melanoma cells, we were primarily interested in changes in protein phosphoserine expression at early times after irradiation. Our rationale was that by examining the overall protein phosphorylation profile (the phosphoproteome) in irradiated cells, we might discover novel radiation-induced phosphoproteins that distinguish fibroblasts from melanoma cells. Cell proteins were separated by gel electrophoresis and phosphoproteins were identified by Western blot analysis using nonspecific anti-phosphoamino acid antibodies. This approach was not pursued previously since adequate antibodies for examining global protein phosphoserine expression were unavailable. While some radiation-induced phosphoprotein changes in high-abundance proteins were identified, in general the sensitivity of this approach was not sufficient to detect changes in low-abundance, regulatory proteins. Characterization of these phosphoproteins will require greater enrichment of low-abundance proteins.

Cell killing, nuclear damage and apoptosis in Chinese hamster V79 cells after irradiation with heavy-ion beams of (16)O, (12)C and (7)Li

Chinese hamster V79 cells were exposed to high LET (linear energy transfer) (16)O-beam (625keV/mum) radiation in the dose range of 0-9.83Gy. Cell survival, micronuclei (MN), chromosomal aberrations (CA) and induction of apoptosis were studied as a follow up of our earlier study on high LET radiations ((7)Li-beam of 60keV/mum and (12)C-beam of 295keV/mum) as well as (60)Co gamma-rays. Dose dependent decline in surviving fraction was noticed along with the increase of MN frequency, CA frequency as well as percentage of apoptosis as detected by nuclear fragmentation assay. The relative intensity of DNA ladder, which is a useful marker for the determination of the extent of apoptosis induction, was also increased in a dose dependent manner. Additionally, expression of tyrosine kinase lck-1 gene, which plays an important role in response to ionizing radiation induced apoptosis, was increased with the increase of radiation doses and also with incubation time. The present study showed that all the high LET radiations were generally more effective in cell killing and inflicting other cytogenetic damages than that of low LET gamma-rays. The dose response curves revealed that (7)Li-beam was most effective in cell killing as well as inducing other nuclear damages followed by (12)C, (16)O and (60)Co gamma-rays, in that order. The result of this study may have some application in biological dosimetry for assessment of genotoxicity in heavy ion exposed subjects and in determining suitable doses for radiotherapy in cancer patients where various species of heavy ions are now being generally used.

Effect of genistein on mouse blastocyst development in vitro

AIM

To examine the cytotoxic effects of genistein, an isoflavone compound, on early postimplantation embryonic development in vitro.

METHODS

Mouse blastocysts were incubated in medium with or without genistein (25 or 50 micromol/L) or daidzein (50 micromol/L) for 24 h. Cell proliferation and growth was investigated by dual differential staining, apoptosis was analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and apoptotic or necrotic cells were visualized by Annexin-V and propidium iodide (PI) staining. Implantation and postimplantation development of embryos were measured by in vitro development analysis.

RESULTS

TUNEL staining and Annexin-V/PI staining showed that genistein dose-dependently increased apoptosis in mouse blastocysts, while daidzein, another soy isoflavone, had no such effect. The pretreatment of the blastocysts with genistein caused fewer cells than the control group and this effect was primary in the inner cell mass. The genistein-pretreated blastocysts showed normal levels of implantation on culture dishes in vitro, but significantly fewer genistein-pretreated embryos reached the later stages of embryonic development versus the controls, with many of the former embryos dying at relatively early stages of development. In addition, genistein treatment decreased the development of morulas into blastocysts, and dietary genistein was found to induce cell apoptosis and decrease cell proliferation in an animal assay model of embryogenesis.

CONCLUSIONS

Our results collectively indicate that genistein treatment of mouse blastocysts induces apoptosis, decreases cell numbers, retards early postimplantation blastocyst development, and increases early-stage blastocyst death in vitro, while dietary genistein appears to negatively affect mouse embryonic development in vivo by inducing cell apoptosis and inhibiting cell proliferation. These novel findings provide important new insights into the effect of genistein on mouse blastocysts.

Vinorelbine-based salvage chemotherapy for therapy-refractory aggressive leukaemias

This study examined the ability of the semi-synthetic vinca alkaloid, Vinorelbine/Navelbine, to cause apoptotic death in freshly obtained primary leukaemia cells from 53 patients with haematological malignancies, including 22 patients with acute lymphoblastic leukaemia (ALL), 24 patients with chronic lymphocytic leukaemia (CLL), three patients with chronic myeloid leukaemia in blast crisis (CML-BC) and four patients with acute myeloid leukaemia (AML). Vinorelbine caused apoptosis in primary leukaemia cells from 42 (79%) of these leukaemia patients. Objective responses, including complete remission (CR) and CR with incomplete haematological recovery, were achieved in 12 of 17 (71%) patients with aggressive and therapy-refractory leukaemias, including five of nine patients with relapsed ALL, three of three patients with CML-BC and four of five patients with rapidly progressive CLL, who were treated with a vinorelbine-based salvage chemotherapy regimen. Drug sensitivity profiling of multidrug-resistant primary cancer cells using apoptosis assays revealed a significant association between Vinorelbine sensitivity in vitro and the likelihood of an objective clinical response to Vinorelbine-based chemotherapy. Vinorelbine-sensitivity testing of primary leukaemia cells might help tailor Vinorelbine-based salvage regimens to those patients who are most likely to respond.

Apoptosis is induced in leishmanial cells by a novel protein kinase inhibitor withaferin A and is facilitated by apoptotic topoisomerase I-DNA complex

Protein kinase C (PKC) is an important constituent of the signaling pathways involved in apoptosis. We report here that like staurosporine, withaferin A is a potent inhibitor of PKC. In Leishmania donovani, the inhibition of PKC by withaferin A causes depolarization of DeltaPsim and generates ROS inside cells. Loss of DeltaPsim leads to the release of cytochrome c into the cytosol and subsequently activates caspase-like proteases and oligonucleosomal DNA cleavage. Moreover, in treated cells, oxidative DNA lesions facilitate the stabilization of topoisomerase I-mediated cleavable complexes, which also contribute to DNA fragmentation. However, withaferin A and staurosporine cannot induce cleavable complex formation in vitro with recombinant topoisomerase I nor with nuclear extracts from control cells. Taken together, our results indicate that inhibition of PKC by withaferin A is a central event for the induction of apoptosis and that the stabilization of topoisomerase I-DNA complex is necessary to amplify apoptotic process.

Redox regulation of CD21 shedding involves signaling via PKC and indicates the formation of a juxtamembrane stalk

Soluble CD21 (sCD21), released from the plasma membrane by proteolytic cleavage (shedding) of its extracellular domain (ectodomain) blocks B cell/follicular dendritic cell interaction and activates monocytes. We show here that both serine- and metalloproteases are involved in CD21 shedding. Using the oxidant pervanadate to mimic B cell receptor activation and thiol antioxidants such as N-acetylcysteine (NAC) and glutathione (GSH) we show that CD21 shedding is a redox-regulated process inducible by oxidation presumably through activation of a tyrosine kinase-mediated signal pathway involving protein kinase C (PKC), and by reducing agents that either directly activate the metalloprotease and/or modify intramolecular disulfide bridges within CD21 and thereby facilitate access to the cleavage site. Lack of short consensus repeat 16 (SCR16) abolishes CD21 shedding, and opening of the disulfide bridge between cys-2 (Cys941) and cys-4 (Cys968) of SCR16 is a prerequisite for CD21 shedding. Replacing these cysteines with selenocysteines (thereby changing the redox potential from -180 to -381 mV) results in a loss of inducible CD21 shedding, and removing this bridge by exchanging these cysteines with methionines increases CD21 shedding.

Mitochondrial membrane potential and reactive oxygen species content of endothelial and smooth muscle cells cultured on poly(epsilon-caprolactone) films

A transitory but significant stimulation of mitochondrial activity, increase of reactive oxygen species (ROS) and oxidative stress were previously observed in L929 fibroblasts cultured on poly(epsilon-caprolactone) (PCL) films. ROS, mainly formed in mitochondria, play a physiological role but an excessive production can promote endothelial dysfunction, cause oxidative injury to vascular cells, oxidize lipoproteins and accelerate atherothrombogenesis. On the other hand, mitochondria have a crucial position in programmed cell death control and are responsible for ATP synthesis through the coupling of oxidative phosphorylation to respiration. This coupling requires the existence of a mitochondrial membrane potential (Deltapsi(m)). The aim of the present study was to evaluate by flow cytometry the ROS content and Deltapsi(m) of both endothelial (EC) and smooth muscle cells (SMC) cultured on PCL films as a potential substrate for vascular graft development. Cell size, internal complexity and cell cycle were also analyzed to detect the possible appearance of the subG(1) cell fraction, characteristic of apoptotic cells. The effect of treating PCL films with NaOH before culture was also studied. PCL decreases the ROS content of EC during the culture but produces an increase of these levels in SMC after 7 days. PCL also induces variations of Deltapsi(m) which show a significant parallelism with the changes observed in ROS levels proving the importance and sensitivity of these measurements as indicators of the mitochondrial function. The treatment of PCL with NaOH decreases these effects demonstrating the benefits of increasing the surface hydrophilicity before cell culture which improves cell adhesion and proliferation and reduces oxidative stress. Since no important changes have been detected in subG(1) fraction of EC and SMC cultured on either PCL or PCL-NaOH, the changes of Deltapsi(m) observed in the present study cannot be related to apoptosis. These results confirm the potential utility of PCL as a suitable scaffold in Vascular Tissue Engineering.

Genistein stimulates hematopoiesis and increases survival in irradiated mice

Radiation protection from death and stimulating hematopoietic recovery by oral administrations of genistein, 160 mg/kg b.w., once daily for seven consecutive days before whole-body gamma-rays irradiation, were confirmed by tests with adult male BALB/c mice. Moreover, the protective action of genistein was compared to that of diethylstilbestrol (DES). Based on the studies of survival, behavior of hematograms, endogenous hematopoietic spleen colony formation (endoCFUs), and numbers of nucleated cell, granulocyte-macrophage colony forming units (CFU-GM) in bone marrow following irradiation, it was demonstrated that genistein was an effective radioprotector. The survival of irradiated mice protected by genistein was significantly increased and statistically higher than that of mice pre-treated with DES. Stimulated recovery of leukocytes, erythrocytes, lymphocytes and thrombocytes were observed in mice pre-treated with genistein or DES, however, the effects of genistein on promoting recovery of bone marrow nucleated cells, leukocytes and lymphocytes were significantly higher than those of DES. Enhanced endoCFUs, numbers of bone marrow nucleated cells and CFU-GM were also found in mice pre-treated with genistein as well as DES. Meanwhile, endoCFU numbers in mice pre-treated with genistein was 3.47-fold higher than that in the irradiated control group, although no significant difference was found between genistein administration and DES administration. It could be deduced that the radioprotective action against death is induced by a possible process of enhanced regeneration of the hematopoietic stem cells due to not only strengthened radioresistance and increased numbers of remained hematopoietic cells, but also enhanced post-irradiation repair or promoted proliferation of the hematopoietic stem cells. These effects of genistein may have some therapeutic implications for radiation-induced injuries.

Tyrphostins reduce chemotherapy-induced intestinal injury in mice: assessment by a biochemical assay

Intestinal injury that results from chemotherapy belongs to the major factors of dose-limitation in tumour therapy. The tyrphostins AG1714 and AG1801 reduce cisplatin and 5-FU-induced small intestinal mucosal damage, using a quantitative biochemical assay. The assay is based on the determination of the enzymatic activity of gamma-glutamyl transpeptidase, a marker of the brush border epithelium of the small intestine.

Radiobiology of radioimmunotherapy: targeting CD20 B-cell antigen in non-Hodgkin's lymphoma

The radiobiology of radioimmunotherapy is an important determinant of both the toxicity and the efficacy associated with the treatment of B-cell non-Hodgkin's lymphoma with radiolabeled anti-CD20 monoclonal antibodies. The properties of the target, CD20, and the mechanisms of action of both the monoclonal antibodies and the associated exponentially decreasing low-dose-rate radiotherapy are described. The radiation dose and dose-rate effects are discussed and related to both the tumor responses and normal organ toxicity. Finally, the use of either unlabeled or radiolabeled anti-CD20 monoclonal antibodies as a component of combined modality therapy (including the sequential or concurrent use of sensitizers) and future directions of the field are discussed.

Differential activation of kinases in ex vivo and in vivo irradiated mice lymphocytes

Various kinases, such as tyrosine, protein kinase C (PKC) and MAP kinase, play important role in the cellular response to radiation, but little is known about the specific response in the whole animal. Most studies, except a few, are based on single cells. There is a paucity of data where signaling following whole body irradiation is concerned. In this study a comparison has been made between the activities of these kinases following ex vivo and in vivo irradiation. Tyrosine kinase activity showed no difference in the lymphocytes irradiated ex vivo or in vivo. A significant differential dose-dependent response could be observed in PKC activity. PKC was seen to be activated at the higher dose, i.e., 1 Gy in, in vivo irradiated lymphocytes, whereas in ex vivo irradiated lymphocytes, PKC was seen to be activated at the lower dose, i.e., 0.1 Gy. MAP kinase activity was seen to decrease with an increasing dose in ex vivo irradiated lymphocytes. In vivo MAP kinase activity was seen to increase as the dose increased, with maximum activation at 3 Gy. These kinases are being used to manipulate the tumor response to radiotherapy. Thus it is essential to study the behavior of the above kinases in the whole animal because the difference in response of a single cell to the whole animal may be different.

Radiobiology of radioimmunotherapy with 90Y ibritumomab tiuxetan (zevalin)

Radioimmunotherapy represents a significant advance over unlabeled immunotherapy for the treatment of patients with B-cell non-Hodgkin's lymphoma. The efficacy of radioimmunotherapeutic agents depends in large part on the basic biological effects associated with their components, monoclonal antibodies and radionuclides, separately and in combination. The radiobiological effects associated with yttrium 90-labeled ibritumomab tiuxetan (Zevalin; Biogen Idec Inc, Cambridge, MA) include the induction of apoptosis and cell-cycle redistribution (eg, arrest of cells in the G(2)/M phase of the cell cycle). Because of dose-rate effects, tumor cells may, in some cases, be more susceptible to the low-dose-rate radiation used in radioimmunotherapy than to the high-dose-rate radiation used in external beam radiotherapy. The efficacy of radioimmunotherapy may potentially be optimized through a variety of approaches, including the use of agents that increase the expression of certain tumor antigens (thus facilitating improved biodistribution of radiolabeled monoclonal antibodies) or that sensitize tumor cells to radiation.

Hypermethylation of the spleen tyrosine kinase promoter in T-lineage acute lymphoblastic leukemia

Sequence analysis of the noncoding first exon (exon 1) of the Syk gene demonstrated the presence of a previously cloned CpG island (GenBank #Z 65706). Transient transfection analysis in Daudi cells demonstrated promoter activity (18-fold increase over parental luciferase plasmid) for a 348 bp BstXI-BsrBI fragment containing this island. This region exhibits a high GC content (approximately 75%), contains several SP1 binding sites and a potential initiator sequence, but lacks a strong TATA consensus. Bisulfite sequencing and methylation-specific PCR (MSP) of this region demonstrated that the Syk promoter CpG island was largely unmethylated in B-lineage leukemia cell lines, control peripheral blood cells, human thymocytes and CD3(+) T lymphocytes. However, dense methylation was seen in four T-lineage leukemia cell lines, Jurkat, H9, Molt 3 and HUT 78. MSP screening of leukemia cells from six T-lineage acute lymphoblastic leukemia (ALL) patients demonstrated methylation of the Syk promoter CpG island in one T-lineage ALL patient. Promoter methylation was correlated with reduced to absent expression of Syk mRNA and SYK protein in the T-lineage leukemia cell lines. Treatment of the leukemia lines Ha and Molt 3, with the methylation inhibitor, 5-aza-2'-deoxycytidine (5-aza-CdR) resulted in increased Syk mRNA expression. The presence of a methylated promoter sequence in these T-lineage leukemia cell lines and in one T-lineage patient suggests a potential role for SYK as a tumor suppressor in T-ALL.

Genistein treatment protects mice from ionizing radiation injury

The radioprotective and behavioral effects of an acute administration of the isoflavone genistein (4',5,7-trihydroxyflavone) were investigated in adult CD2F1 male mice. Mice were administered a single subcutaneous (s.c.) dose of genistein either 24 h or 1 h before a lethal dose of gamma radiation (9.5-Gy of cobalt-60 at 0.6 Gy min(-1)). Mice received saline, PEG-400 vehicle or genistein at 3.125, 6.25, 12.5, 25, 50, 100, 200, or 400 mg kg(-1) body weight. For mice treated 24 h before irradiation there was a significant increase in 30-day survival for animals receiving genistein doses of 25 to 400 mg kg(-1) (p<0.001). In contrast, the 30-day survival rates of mice treated with genistein 1 h before irradiation were not significantly different from those of the vehicle control group. Additionally, the acute toxicity of genistein was evaluated in non-irradiated male mice administered a single s.c. injection of saline, vehicle, or genistein at 100, 200 or 400 mg kg(-1). At these genistein doses there were no adverse effects, compared with controls, on locomotor activity, grip strength, motor coordination, body weight, testes weight, or histopathology. These results demonstrate that a single s.c. administration of the flavonoid genistein at non-toxic doses provides protection against acute radiation injury.

IFN-gamma and TNF-alpha production in gamma-irradiated blood units by mononuclear cells and GVHD prevention

Gamma-radiation of blood products is considered the mainstay of transfusion-associated graft-versus-host disease prevention. Previous studies have detected lymphocyte inhibition rate in blood components just one time after irradiation but there is evidence of cellular variability with production of cytokines at different storage time which could be related with irradiation activity and cellular damage repair. IFN-gamma, a Th1 cytokine, and TNF-alpha, a pro-inflammatory one, had a central role in the stimulation of cellular and inflammatory reactions. In this study whole blood was collected from five volunteer healthy donors and each donor bag was divided into two satellite bags: one of them was exposed to 137Cs-irradiation with a 2500 cGy dose. Samples for cytokine production, detected by ELISA methods, and proliferative response, evaluated by incorporation of H3 thymidine, were taken at the following storage time: 0, 24, 48, 72 and 96 h. The time-response curve of irradiated mononuclear cells from blood bags (BBMC) in mitogenic activation showed a time-related inhibition of cell proliferation with an enhanced response only after 24 h of storage and about 84% inhibition at 96 h. A similar pattern is follow by IFN-gamma production after OKT3 stimulation. TNF-alpha levels both in lipopolysaccharide stimulated or unstimulated cells were always high. This data suggest that BBMC cells maintain the ability to produce cytokines after gamma-radiation. On the ground of this study seems to be necessary to evaluate hypothetical risk associated with the administration of cytokine via irradiated blood components.

Hydrogen peroxide as second messenger in lymphocyte activation

Oxidants such as H2O2 are connected to lymphocyte activation, but the molecular mechanisms behind this phenomenon are less clear. Here, I review data suggesting that by inhibiting protein tyrosine phosphatases, H2O2 plays an important role as a secondary messenger in the initiation and amplification of signaling at the antigen receptor. These findings explain why exposure of lymphocytes to H2O2 can mimic the effect of antigen. In addition, more recent data show that antigen receptors themselves are H2O2-generating enzymes and that the oxidative burst in macrophages seems to play a role not only in pathogen killing but also in the activation of these as well as neighboring cells. Thus, by controlling the activity of the negative regulatory phosphatases inside the cell, H2O2 can set and influence critical thresholds for lymphocyte activation.

4-Nitrobenzylidene malononitrile reduces apoptosis-mediated liver injury in mice

BACKGROUND

Apoptosis plays a role in experimental and clinically related liver damage. Inhibitors of tyrosine kinases were shown to modulate apoptosis induced by different agents in various cell types.

AIMS

Investigation of the effect of 4-nitrobenzylidene malononitrile (belonging to the tyrphostins family which are selective inhibitors of protein tyrosine kinases) on apoptosis-mediated acute liver injury.

METHODS

Two murine experimental models exhibiting apoptosis-mediated liver injury were used: (1) mice treated with tumor necrosis factor-alpha and D-galactosamine; and (2) mice treated with anti-Fas antibody. Liver injury was assessed by serum levels of transaminases and by microscopic analysis. Apoptosis was assessed by labeling of apoptotic cells in the liver by the TUNEL assay and by determination of caspase-3 activity.

RESULTS

Pretreatment of mice with 4-nitrobenzylidene malononitrile reduced tumor necrosis factor-alpha/D-galactosamine-induced hepatotoxicity. TUNEL positive cells in sections from livers treated with vehicle (control), 4-nitrobenzylidene malononitrile, tumor necrosis factor-/d-galactosamine and tumor necrosis factor-alpha/D-galactosamine and 4-nitrobenzylidene malononitrile, were >0.2, >0.2, 49+/-2.3 and 4+/-0.2 per mm(2), respectively. 4-Nitrobenzylidene malononitrile also reduced hepatotoxicity induced by anti-Fas antibody. Caspase-3 activation induced by either tumor necrosis factor-alpha/D-glactosamine or by anti-Fas treatment, was reduced by pretreatment with N-nitrobenzylidene malononitrile.

CONCLUSIONS

The findings may provide a base for development of a new therapeutic modality to reduce apoptosis-mediated liver damage.

Protein tyrosine kinase inhibitors modulate radiosensitivity and radiation-induced apoptosis in K562 cells

We studied the modulating effect of protein tyrosine kinase inhibitors on the response of cells of the human chronic myelogenous leukemia cell line K562 to radiation. The radiosensitivity of the cells was increased by treatment with herbimycin A and decreased by treatment with genistein. This modulating effect of protein tyrosine kinase inhibitors on radiation sensitivity was associated with the alteration of the mode of radiation-induced cell death. After X irradiation, the cells arrested in the G(2) phase of the cell cycle, but these TP53(-/-) cells were unable to sustain cell cycle arrest. This G(2)-phase checkpoint deficit caused cell death. The morphological pattern of cell death was characterized by swelling of the cytoplasmic compartments, cytosolic vacuolation, disruption of the plasma membrane, less evident nuclear condensation, and faint DNA fragmentation, all of which were consistent with oncosis or cytoplasmic apoptosis. The nonreceptor protein tyrosine kinase inhibitor herbimycin A accelerated the induction of typical apoptosis by X irradiation, which was demonstrated by morphological assessments using nuclear staining and electron microscopy as well as oligonucleosomal fragmentation and caspase 3 activity. Herbimycin A is known to be a selective antagonist of the BCR/ABL kinase of Philadelphia chromosome-positive K562 cells; this kinase blocks the induction of apoptosis after X irradiation. Our results showed that the inhibition of protein tyrosine kinase by herbimycin A enhanced radiation-induced apoptosis in K562 cells. This effect was associated with the activation of caspase 3 and rapid abrogation of the G(2)-phase checkpoint with progression out of G(2) into G(1) phase. In contrast, the receptor-type protein tyrosine kinase inhibitor genistein protected K562 cells from all types of radiation-induced cell death through the inhibition of caspase 3 activity and prolonged maintenance of G(2)-phase arrest. Further investigations using this model may give valuable information about the mechanisms of radiation-induced apoptosis and about the radiosensitivity and radioresistance of chronic myelogenous leukemia cells having the Philadelphia chromosome.

cAMP-induced apoptosis in granulosa cells is associated with up-regulation of P53 and bax and down-regulation of clusterin

Evidence indicates that cAMP induces apoptosis in granulosa cells of rat and human ovary. The mechanism by which cAMP induces apoptosis is not known. This study was carried out to evaluate changes in expression of cell death promoters, P53 and bax, and cell death repressor, bcl-2, in cAMP-treated granulosa cells. Treatment of granulosa cells with forskolin (FSK), or 8-bromo-cAMP induced apoptosis as evidenced by internucleosomal DNA fragmentation and chromatin condensation as revealed by gel electrophoresis and fluorescent DAPI staining, respectively. The apoptotic effect of cAMP was accompanied by an increase in the expression of P53 and bax proteins as evaluated by Western blot and immunocytochemistry. No change in bcl-2 protein level was observed in cAMP-treated granulosa cells as compared to control. These data suggest that cAMP may activate apoptosis in granulosa cells by shifting the ratio of the death promoter to death repressor genes via alteration of P53 and bax expression. cAMP was also shown to inhibit gene expression of clusterin, an apoptosis-associated protein, suggesting a role for this protein in cAMP-induced apoptosis in granulosa cells. The data of the present study provide a basis for future studies to elucidate the molecular mechanism of follicular atresia and regulation of apoptotic cell death in ovarian follicles.

Effect of protein kinase C inhibitor (PKCI) on radiation sensitivity and c-fos transcription

PURPOSE

The human genetic disorder ataxia-telangiectasia (AT) is a multisystem disease characterized by extreme radiosensitivity. Although ionizing radiation was known to induce c-fos transcription and cellular protein kinase C (PKC) induces the expression of this immediate response gene, little is known about how mutated AT (ATM) or PKC-mediated signal transduction pathway modulates the c-fos gene transcription and gene expression. Here we have studied the effect of PKC inhibitor (PKCI) on radiation sensitivity and c-fos transcription in normal and AT cells, and also studied whether PKCI effect on c-fos occurs in Ras-dependent pathway.

METHODS AND MATERIALS

Normal (LM217) and AT (AT5BIVA) cells were transfected with PKCI expression plasmid and integration and overexpression of PKCI was evaluated by polymerase chain reaction and northern blotting, respectively. Cells were irradiated at a dose of 5 Gy/min with 137Cs irradiator and harvested 48 h after irradiation and investigated apoptosis with TUNEL method. The c-fos transcription activity was studied by performing compute assisted tomography (CAT) assay of reporter gene after transfection of c-fos CAT plasmid into LM and AT cells. Overexpression of Ras protein in transfected cells was shown by western blotting.

RESULTS

Our results demonstrated for the first time a role of PKCI on the radiation sensitivity and c-fos transcription in LM and AT cells. PKCI increased radiation induced apoptosis in LM cells (5% to 20%) but reduced apoptosis slightly in AT cells. The basal c-fos transcription activity is 70 times lower in AT cells than in LM cells. This c-fos transcription activity was repressed by overexpression of PKCI in LM cells but not in AT cells. After induction of c-fos by Ras protein, overexpression of PKCI repressed c-fos transcription in LM cells but not in AT cells.

CONCLUSIONS

Overexpression of PKCI increased radiation sensitivity and repressed c-fos transcription in LM cells but not in AT cells, and this is related with Ras. These results suggest that the effect of PKCI on c-fos transcription activity is related with Ras dependent signal transduction pathways and these mechanisms are different between normal fibroblasts, LM and ATM mutated, AT cells. The data obtained by this study provided evidence for novel transcriptional difference between LM and AT cells and this may be a reason for increased radiation sensitivity of AT cells.

Rapid patterning in 2-D cultures of Dictyostelium cells and its relationship to zonal differentiation

Rapid patterning has been observed in confined 2-D cultures of Dictyostelium discoideum Ax-2 cells as an outer dark zone and a inner light zone. The width of outer zone was usually approximately100 microm, irrespective of the size of cell masses under atmospheric conditions. The width of the outer zone, however, changed depending on external O2 concentrations and reached up to 250 microm at 100% O2. A clear regional difference in tetramethyl rhodamine methyl ester (TMRM) staining was noticed between the outer zone and the inner zone: the inner zone was more strongly stained with TMRM than the outer zone, which faced the air. Using inhibitors of oxidative phosphorylation (dinitrophenol (DNP) or NaN3) and a specific inhibitor of CN-resistant respiration (benzohydroxamic acid (BHAM)), it has been demonstrated that the outer zone is basically formed by the O2 threshold for oxidative phosphorylation, while the inner cells mainly perform cyanide-resistant respiration. When cells around the early mound stage (just before prestalk and prespore differentiation) were cultured as 2-D cell masses, ecmA-expressing cells (pstA cells), ecmB-expressing cells (pstB cells) and D19-expressing cells (prespore; psp cells), arose in a position-dependent manner in the outer zone. In the inner zone, cell motility seemed to be markedly impaired and neither prestalk nor prespore differentiation occurred. In addition, once-differentiated prespore cells were found to dedifferentiate rapidly in the inner zone. The reason for dedifferentiation as well as for failure of cells to differentiate in the inner zone is discussed with reference to O2 radicals.

Stimulation of Bruton's tyrosine kinase (BTK) and inositol 1,4,5-trisphosphate production in leukemia and lymphoma cells exposed to low energy electromagnetic fields

We examined the effects of low energy electromagnetic field (EMF) exposure on the BTK kinase activity in B18-2 ([Btk-, rBTK(wt)] DT40) chicken lymphoma B cells and NALM-6 leukemic pre-B cells. Exposure of B 18-2 cells to EMF resulted in activation of BTK within 1 to 15 minutes in 8 of 8 independent experiments with stimulation indexes ranging from 1.2 to 13.3. While in some experiments the BTK stimulation was transient, in others the BTK activity continued to be significantly elevated for up to 4 hours. Similarly, exposure of NALM-6 cells to EMF resulted in activation of BTK within 30 minutes in 7 of 7 experiments with stimulation indexes ranging from 1.2 to 7.4. Stimulation of BTK activity in EMF exposed cells was associated with enhanced phosphoinositide turnover and increased inositol-1,4,5-trisphosphate (IP3) production in 7 of 13 experiments with DT40 cells and 7 of 13 experiments with NALM-6 cells. The likelihood and magnitude of an IP3 response after EMF exposure were similar to those after BCR ligation on DT40 cells and CD19 ligation on NALM-6 cells. These results confirm and extend our previous studies regarding EMF-induced biochemical signaling events in B-lineage lymphoid cells.

Regulation of FOS by different compartmental stresses induced by low levels of ionizing radiation

We irradiated different cellular compartments and measured changes in expression of the FOS gene at the mRNA and protein levels. [(3)H]Thymidine and tritiated water were used to irradiate the nucleus and the whole cell, respectively. (125)I-Concanavalin A binding was used to irradiate the cell membrane differentially. Changes in FOS mRNA and protein levels were measured using semi-quantitative RT-PCR and SDS-PAGE Western blotting, respectively. Irradiation of the nucleus or the whole cell at a dose rate of 0.075 Gy/h caused no change in the level of FOS mRNA expression, but modestly (1.5-fold) induced FOS protein after 0.5 h. Irradiation of the nucleus at a dose rate of 0.43 Gy/h induced FOS mRNA by 1.5-fold after 0.5 h, but there was no significant effect after whole-cell irradiation. FOS protein was transiently induced 2.5-fold above control levels 0.5 h after a 0. 43-Gy/h exposure of the nucleus or the whole cell. Irradiation of the cell membrane at a dose rate of 1.8 Gy/h for up to 2 h caused no change in the levels of expression of FOS mRNA or protein, but a dose rate of 6.8 Gy/h transiently increased the level of FOS mRNA 3-fold after 0.5 h. These data demonstrate the complexity of the cellular response to radiation-induced damage at low doses. The lack of quantitative agreement between the transcript and protein levels for FOS suggests a role for post-transcriptional regulation.

Selective phosphotyrosine phosphatase inhibition and increased ceramide formation is associated with B-cell death by apoptosis

Bis(maltolato)oxovanadium(IV) (BMOV), a protein phosphotyrosine phosphatase inhibitor, selectively induced apoptosis (as quantitated by TUNEL staining) in a B-cell line (Ramos) but not in a T-cell line (Jurkat). The pattern of BMOV-induced protein tyrosine phosphorylation was different in B-cells versus T-cells. Further, BMOV induced a 2-fold increase in ceramide levels in B-cells but not in T-cells and this resembled the ceramide increase following activation of the B-cell antigen receptor. A 2-fold increase in the ratio of ceramide to sphingomyelin in B-cells treated with BMOV suggested that sphingomyelinase activation was the result of the sustained tyrosine phosphorylation of specific proteins and activated the cell death pathway.

Inhibition of UV irradiation-induced oxidative stress and apoptotic biochemical changes in human epidermal carcinoma A431 cells by genistein

Ultraviolet (UV) light is a strong apoptotic trigger that can induce a caspase-dependent biochemical change in cells. We previously showed that UV irradiation can elicit caspase-3 activation and the subsequent cleavage and activation of p21-activated kinase 2 (PAK2) in human epidermal carcinoma A431 cells. We report that genistein, an isoflavone compound with known inhibitory activities to protein tyrosine kinases (PTKs) and topoisomerase-II (topo-II), can prevent UV irradiation-induced apoptotic biochemical changes (DNA fragmentation, caspase-3 activation, and cleavage/activation of PAK2) in A431 cells. Surprisingly, two typical PTK inhibitors (tyrphostin A47 and herbimycin A) and three known topo-II inhibitors (etoposide, daunorubicin, and novomycin) had no effect on UV irradiation-induced apoptotic biochemical changes, suggesting that the inhibitory effect of genistein is not dependent on its property as a PTK/topo-II inhibitor. In contrast, azide, a reactive oxygen species (ROS) scavenger, could effectively block the UV irradiation-induced apoptotic cell responses. Flow cytometric analysis using the cell-permeable dye 2',7'-dichlorofluorescin diacetate as an indicator of the generation of ROS showed that UV irradiation caused increase of the intracellular oxidative stress and that this increase could be abolished by azide, suggesting that oxidative stress plays an important role in mediating the apoptotic effect of UV irradiation. Importantly, the UV irradiation-induced oxidative stress in cells could be significantly attenuated by genistein, suggesting that impairment of ROS formation during UV irradiation is responsible for the antiapoptotic effect of genistein. Collectively, our results demonstrate the involvement of oxidative stress in the UV irradiation-induced caspase activation and the subsequent apoptotic biochemical changes and show that genistein is a potent inhibitor for this process.

Ionizing radiation alters Fas antigen ligand at the cell surface and on exfoliated plasma membrane-derived vesicles: implications for apoptosis and intercellular signaling

Resident proteins that reside on the plasma membrane are continually exfoliated from the cell surface. Exfoliation is a selective, energy-dependent process that mediates intercellular communication. Ionizing radiation modulates the expression of many plasma membrane-bound growth regulators, including the "death" ligand, TNFSF6 (formerly known as FasL, CD95L). Here we report that ionizing radiation induces dose-dependent up-regulation of TNFSF6 on plasma membranes purified from SW620 cells, a TNFSF6-expressing colon cancer cell line. Serum-free medium conditioned by exposed and control cells was collected and exfoliated vesicles were obtained by ultracentrifugation. Western blot analysis of vesicles from unexposed cells and from cells treated with 10 Gy showed increased amounts of TNFSF6 compared to that on vesicles from unexposed cells. Cells treated with 4 Gy released vesicles having a low level of TNFSF6 on their surface relative to that on vesicles exfoliated from unexposed cells. When assayed for bioactivity, vesicles from unexposed cells induced the greatest level of apoptosis in TNFRSF6 (formerly known as FAS) receptor-bearing Jurkat cells (cell surviving fraction of 43.7 +/- 6.1; P < 0.05), followed by vesicles collected from cells treated with 4 Gy (79.6 +/- 2.6%; P < 0.05). Despite having a high level of TNFSF6 by Western analysis, vesicles collected from cells exposed to 10 Gy display minimal biological activity (77.9 +/- 3.2%; P < 0.05), suggesting that modification of the vesicle-associated ligand has occurred. Our results indicate that ionizing radiation increases the level of TNFSF6 exfoliated on extracellular vesicles. The data may provide a mechanism for abscopal and bystander effects after irradiation.

Ionizing radiation stimulates existing signal transduction pathways involving the activation of epidermal growth factor receptor and ERBB-3, and changes of intracellular calcium in A431 human squamous carcinoma cells

Previous studies demonstrated that ionizing radiation activates the epidermal growth factor receptor (EGFR), as measured by Tyr autophosphorylation, and induces transient increases in cytosolic free [Ca2+], [Ca2+]f. The mechanistic linkage between these events has been investigated in A431 squamous carcinoma cells with the EGFR Tyr kinase inhibitor, AG1478. EGFR autophosphorylation induced by radiation at doses of 0.5-5 Gy or EGF concentrations of 1-10 ng/ml is inhibited by >75% at 100 nM AG1478. Activation of EGFR enhances IP3 production as a result of phospholipase C (PLC) activation. At the doses used, radiation stimulates Tyr phosphorylation of both, PLCgamma and erbB-3, and also mediates the association between erbB-3 and PLCgamma not previously described. The increased erbB-3 Tyr phosphorylation is to a significant extent due to transactivation by EGFR as >70% of radiation- and EGF-induced erbB-3 Tyr phosphorylation is inhibited by AG 1478. The radiation-induced changes in [Ca2+]f are dependent upon EGFR, erbB-3 and PLCgamma activation since radiation stimulated IP3 formation and Ca2+ oscillations are inhibited by AG1478, the PLCgamma inhibitor U73122 or neutralizing antibody against an extracellular epitope of erbB-3. These results demonstrate that radiation induces qualitatively and quantitatively similar responses to EGF in stimulation of the plasma membrane-associated receptor Tyr kinases and immediate downstream effectors, such as PLCgamma and Ca2+.

Cytochrome c-mediated apoptosis in cells lacking mitochondrial DNA. Signaling pathway involving release and caspase 3 activation is conserved

Mitochondria serve as a pivotal component of the apoptotic cell death machinery. However, cells that lack mitochondrial DNA (rho(0) cells) retain apparently normal apoptotic signaling. In the present study, we examined mitochondrial mechanisms of apoptosis in rho(0) osteosarcoma cells treated with staurosporine. Immunohistochemistry revealed that rho(0) cells maintained a normal cytochrome c distribution in mitochondria even though these cells were deficient in respiration. Upon staurosporine treatment, cytochrome c was released concomitantly with activation of caspase 3 and loss of mitochondrial membrane potential (Deltapsi(m)). After mitochondrial loss of cytochrome c, rho(0) cells underwent little change in glutathione (GSH) redox potential whereas a dramatic oxidation in GSH/glutathione disulfide (GSSG) pool occurred in parental rho(+) cells. These results show that mitochondrial signaling of apoptosis via cytochrome c release was preserved in cells lacking mtDNA. However, intracellular oxidation that normally accompanies apoptosis was lost, indicating that the mitochondrial respiratory chain provides the major source of redox signaling in apoptosis.

Genistein is neuroprotective in murine models of familial amyotrophic lateral sclerosis and stroke

Amyotrophic lateral sclerosis (ALS), whether sporadic or familial (FALS), is a progressive, fatal neurodegenerative disorder involving the motor neurons of the cortex, brain stem, and spinal cord. In some studies, the male/female ratio of ALS patients was as high as 2 to 1. In FALS mice, disease onset and mortality were earlier among males than among females. This sexual dimorphism was due to estrogen, as treatment with genistein, a phytoestrogen, eliminated the observed sexual dimorphism in FALS mice. Genistein treatment also protected against oxygen singlet-induced cerebral damage in vivo. However, sexual dimorphism was not observed in this model of stroke; and genistein was equally effective in males and females. These data suggest that genistein has both estrogen-dependent and estrogen-independent neuroprotective activities and it should be investigated as a prophylactic agent against pathologic conditions such as ALS and stroke.

The complexity of radiation stress responses: analysis by informatics and functional genomics approaches

Molecular responses to genotoxic stress are complex and are mediated by a variety of regulatory pathways. One key element in cellular response is the stress gene transcription factor p53, which can regulate nearly 100 genes that have already been identified. Although p53 plays a central role in the cellular response to DNA-damaging agents such as ionizing radiation (IR), other pathways can also have important roles. One example is the transcriptional responses associated with IR-induced apoptosis, where induction of some genes is limited to p53 wild-type (wt) cells that also have the ability to undergo rapid apoptosis after irradiation. In contrast, other genes are triggered after IR in lines undergoing rapid apoptosis regardless of p53 status. From this and other examples, it is apparent that the pattern of stress gene expression is cell type specific in both primary and transformed lines. The premise will be developed that such differences in stress gene responsiveness can be employed as molecular markers using a combination of informatics and functional genomics approaches. An example is given using the panel of lines of the NCI anticancer drug screen where both the p53 status and sensitivity to a large collection of cytotoxic agents have been determined. The utility of cDNA microarray hybridization to measure IR-stress gene responses has recently been demonstrated and a large number of additional IR-stress genes have been identified. The responses of some of these genes to IR and other DNA-damaging agents varied widely in cell lines from different tissues of origin and different genetic backgrounds, highlighting the importance of cellular context to genotoxic stress responses; this also highlights the need for informatics approaches to discover and prioritize hypotheses regarding the importance of particular cellular factors. The aim of this review is to demonstrate the utility of combining an informatics approach with functional genomics in the study of stress responses.

Reactive oxygen species activate focal adhesion kinase, paxillin and p130cas tyrosine phosphorylation in endothelial cells

Reactive oxygen species (ROS), particularly hydroxyl radical (HO*), increase neutrophil adherence to hypoxanthine-xanthine oxidase (HX-XO)-treated human umbilical vein endothelial cells (HUVEC) in culture. This adherence is inhibited by the tyrosine kinase inhibitors genistein (30 microM) and herbimycin A (0.9 microM), suggesting the involvement of tyrosine kinase. Phosphorylation of several HUVEC proteins in the range of 120-130 and 70 kDa was found to depend on the XO concentration and stimulation time. This phosphorylation was inhibited by the antioxidants dimethylthiourea (DMTU, 0.75 to 7.5 mM) and pentoxifylline (Ptx, 0.1 mM), and by the iron chelators desferrioxamine (DF, 1 mM) and hydroxybenzyl ethylene diamine (HBED, 0.5 mM), suggesting the involvement of HO*. Three tyrosine-phosphorylated proteins, focal adhesion kinase (p125FAK), paxillin (PAX) and p130cas were isolated and characterized by immunoprecipitation and western blotting. Antioxidants and iron chelators reduced their phosphorylation. HUVEC treated with ROS for 15 min showed actin stress fiber formation. Cytochalasin D (5 microM) inhibited tyrosine phosphorylation and PMN-HUVEC adherence, showing the importance of cytoskeleton integrity in these two functions. In conclusion, HO*, which is involved in increased PMN-HUVEC adhesion, also increases tyrosine phosphorylation on three major cytoskeleton proteins which seem to play a role in this adhesion.

Protein phosphorylation associated with epipodophyllotoxin-induced apoptosis of lymphoid cells: role of a serine/threonine protein kinase

We have previously shown that apoptosis induced in thymocytes by dexamethasone or teniposide (VM-26) could be inhibited by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7) and sangivamycin, both relatively specific inhibitors for protein kinase C, but not by N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA1004), a more specific inhibitor for cAMP-dependent protein kinases. Apoptosis in this model system was not blocked by EGTA and no increase in cytosolic Ca2+ was observed during apoptosis induced by either dexamethasone or VM-26, suggesting that this kinase was Ca2+-independent. In the present study, we demonstrate that addition of 10 microM sangivamycin to thymocyte cultures up to 2 h after addition of either inducer resulted in virtually complete inhibition of apoptosis. Addition of 10 microM sangivamycin at 3 or 4 h after addition of inducer resulted in partial inhibition of apoptosis. Computerized image analysis of two-dimensional PAGE analyses of whole-cell lysates demonstrated that treatment of mouse thymocytes with VM-26 resulted in a limited number of de novo phosphorylation events within 1 h of treatment. The most prominent phosphorylation events associated with VM-26-induced apoptosis were that two intracellular protein species (Protein 1: m.w. = 22.9 kDa, pI, 5.11; and Protein 2: m.w. = 22.9 kDa, pI, 4.98). Similar phosphorylation events were seen in cells treated with dexamethasone. Finally, Western blot analysis suggests that de novo protein phosphorylation induced by VM-26 is on serine/threonine residues. These results provide further evidence that the mechanism of VM-26-induced apoptosis of murine thymocytes involves the action of one or more serine/threonine kinases.

Induction of apoptosis and tyrosine phosphorylation of cellular proteins in T cells and non-T cells by stimulation with concanavalin A

A high concentration (30 microg/ml or more) of Con A caused the death of not only thymocytes but also splenic cells of BALB/c mice, whereas a moderate concentration (3 microg/ml) of Con A induced proliferation of these cells. A high concentration of Con A also induced the death of splenic cells of athymic BALB/c-nu/nu mice and the bone marrow cells of BALB/c mice which mainly consist of non-T cells. However, any concentration (1-30 microg/ml) of Con A failed to induce the proliferation of these cells. Specific binding of tetrameric Con A to mannose-containing receptors was required for the induction of cell death. DNA fragmentation was observed by both laser flow cytometry and electrophoresis in Con A-stimulated T cells and non-T cells. This indicated that the mechanism of induction of apoptosis with Con A is not necessarily TCR-dependent. Con A induced tyrosine phosphorylation of a number of proteins in various types of cells. Interestingly, phosphorylation of the 40 kDa protein developed only in the thymocytes and spleen cells that contain T cells, whereas phosphorylation of the 80 and 120 kDa proteins appeared in both T cells and non-T cells. These results suggested that the Con A-induced apoptosis of T cells and non-T cells involves different but possibly mutually related protein tyrosine phosphorylation-linked signals.

Molecular mechanisms of programmed cell death

Programmed cell death and apoptosis have now been recognised as biological phenomena which are of fundamental importance to the integrity of organisms. What may have evolved as an altruistic defence against pathogen invasion in simple organisms is now a major regulatory mechanism in the development and maintenance of multi-cellular organisms. The classically defined morphological characteristics of apoptosis are now accompanied by a plethora of information regarding common biochemical and genetic mediators of programmed cell death. It is apparent that life and death decisions are taken by individual cells based on their interpretation of physiological signals, or their own self-assessment of internal damage. The knowledge that cell death is a genetically regulated process has highlighted an inherent potential for manipulation and offered new avenues for research into several diseases, and also productivity improvements in the biotechnology industry. This relatively "new frontier" in cell science has undoubtedly widened our perspectives and may provide novel strategies to expedite both medical and biotechnological research.

Cellular immune defect caused by postsurgical radiation therapy in patients with head and neck cancer

The effects of locoregional postoperative radiation therapy (60 Gy on average) on cellular immunity were investigated in 11 patients with squamocellular carcinomas of the oral cavity, pharynx, or larynx. During radiation treatment, the total lymphocyte counts, CD8+ T-lymphocyte count, and especially CD4+ T-lymphocyte count decreased significantly. The mean CD4+ T-lymphocyte counts dropped from an average of 739/microl to 183/microl (p <0.001), and the CD4+/CD8+ quotient also decreased significantly. Not only the lymphocyte counts but also the in vitro lymphocyte stimulation responses to several mitogens decreased, with reductions averaging 10% to 50% of normal responses by the end of radiation therapy. Within 3 to 4 weeks after radiation therapy, the CD4+ T-lymphocyte counts and the in vitro lymphocyte stimulation responses showed a tendency toward normalization. This study shows that postoperative locoregional radiation therapy in patients with head and neck cancer induces a severe generalized impairment of cellular immunity.

Bruton's tyrosine kinase (BTK) as a dual-function regulator of apoptosis

Multiple counterregulatory mechanisms have been identified in B-cell precursors that operate to regulate cell survival and growth, thereby ensuring the orderly development and differentiation of B-cells. Inappropriate apoptosis may underlie the pathogenesis of immunodeficiencies, as well as pathogenesis and drug/radiation resistance of human leukemias and lymphomas, which makes control of apoptosis an important potential target for therapeutic interventions. Therefore, identification of the molecular regulators of apoptosis is an area of intense investigation. Bruton's tyrosine kinase (BTK) is the first tyrosine kinase to be identified as a dual-function regulator of apoptosis, which promotes radiation-induced apoptosis but inhibits Fas-activated apoptosis in B-cells. BTK functions in a pro-apoptotic manner when B-cells are exposed to reactive oxygen intermediates, at least in part, by down-regulating the anti-apoptotic activity of STAT-3 transcription factor. In contrast, BTK associates with the death receptor Fas and impairs its interaction with Fas-associated protein with death domain (FADD), which is essential for the recruitment and activation of FLICE by Fas during the apoptotic signal, thereby preventing the assembly of a pro-apoptotic death inducing signaling complex (DISC) after Fas-ligation. The identification of BTK as a dual-function regulator of apoptosis will significantly increase our understanding of both the biological processes involved in programmed cell death and the diseases associated with dysregulation of apoptosis. New agents with BTK-modulatory activity may have clinical potential in the treatment of B-cell malignancies (in particular acute lymphoblastic leukemia, the most common form of childhood cancer), as well as B-cell immunodeficiencies.