Stress-induced Fas ligand expression in T cells is mediated through a MEK kinase 1-regulated response element in the Fas ligand promoter

T lymphocytes undergo apoptosis in response to a variety of stimuli, including exposure to UV radiation and gamma-irradiation. While the mechanism by which stress stimuli induce apoptosis is not well understood, we have previously shown that the induction of Fas ligand (FasL) gene expression by environmental stress stimuli is dependent on c-Jun N-terminal kinase (JNK) activation. Using inducible dominant-active (DA) JNK kinase kinase (MEKK1) expression in Jurkat cells, we map a specific MEKK1-regulated response element to positions -338 to -316 of the Fas ligand (FasL) promoter. Mutation of that response element abrogated MEKK1-mediated FasL promoter activation and interfered in stress-induced activation of that promoter. Using electrophoretic mobility shift assays, we demonstrate that activator protein 1 (AP-1) binding proteins, namely, activating transcription factor 2 (ATF2) and c-Jun, bind to the MEKK1 response element. Transient transfection of interfering c-Jun and ATF2 mutants, which lack the consensus JNK phosphorylation sites, abrogated the transcriptional activation of the FasL promoter, demonstrating the involvement of these transcription factors in the regulation of the FasL promoter. Taken together, our data indicate that MEKK1 and transcription factors regulated by the JNK pathway play a role in committing lymphocytes to undergo apoptosis by inducing FasL expression via a novel response element in the promoter of that gene.

The effects of intense submicrosecond electrical pulses on cells

A simple electrical model for living cells predicts an increasing probability for electric field interactions with intracellular substructures of both prokaryotic and eukaryotic cells when the electric pulse duration is reduced into the sub-microsecond range. The validity of this hypothesis was verified experimentally by applying electrical pulses (durations 100 micros-60 ns, electric field intensities 3-150 kV/cm) to Jurkat cells suspended in physiologic buffer containing propidium iodide. Effects on Jurkat cells were assessed by means of temporally resolved fluorescence and light microscopy. For the longest applied pulses, immediate uptake of propidium iodide occurred consistent with electroporation as the cause of increased surface membrane permeability. For nanosecond pulses, more delayed propidium iodide uptake occurred with significantly later uptake of propidium iodide occurring after 60 ns pulses compared to 300 ns pulses. Cellular swelling occurred rapidly following 300 ns pulses, but was minimal following 60 ns pulses. These data indicate that submicrosecond pulses achieve temporally distinct effects on living cells compared to microsecond pulses. The longer pulses result in rapid permeability changes in the surface membrane that are relatively homogeneous across the cell population, consistent with electroporation, while shorter pulses cause surface membrane permeability changes that are temporally delayed and heterogeneous in their magnitude.

Sensitization of resistant lymphoma cells to irradiation-induced apoptosis by the death ligand TRAIL

A combination of antitumor approaches acting on different death pathways seems ideal for increasing therapeutic responses, especially when defined resistance mechanisms interfere with individual cellular processes. Apoptosis pathways triggered by ionizing radiation (XRT) and the death ligand TRAIL were analysed in Jurkat lymphoma cells. Both induced the activation of caspase-8, caspase-3, BID and mitochondrial potential loss. TRAIL induced apoptosis required caspase-8, whereas it was not essential for radiation induced apoptosis. The inhibition of mitochondrial damage by Bcl-2 abrogated XRT induced apoptosis and caspase activation, but only marginally attenuated TRAIL induced cell death. The combined treatment with TRAIL and XRT exerted additive apoptotic effects in control cells, whereas highly synergistic effects occurred in cells overexpressing Bcl-2. In addition, a strong effect of TRAIL on radiation induced clonogenic cell death was found. In conclusion, TRAIL seems to be of high potential value for a combination with ionizing radiation in tumor therapy.

Macrophages from patients with SLE and rheumatoid arthritis have defective adhesion in vitro, while only SLE macrophages have impaired uptake of apoptotic cells

BACKGROUND

It has been suggested that defective handling of apoptotic cells by macrophages plays a key role in the development of systemic lupus erythematosus (SLE). The relative contribution of intrinsic defects and serum factors remains controversial.

OBJECTIVE

To compare monocytes from SLE patients, patients with rheumatoid arthritis, and healthy controls for their ability to differentiate in vitro into macrophages and to bind/engulf apoptotic cells.

METHODS

Peripheral blood derived monocytes from healthy donors or from patients with SLE or rheumatoid arthritis were allowed to differentiate into macrophages. The in vitro uptake of apoptotic cells by macrophages was evaluated by a flow cytometry assay that allowed discrimination between binding and internalisation.

RESULTS

Monocytes from SLE and rheumatoid patients showed a striking defect in adherence to plastic compared with healthy donors. Absence or heat inactivation of serum resulted in a reduction in the binding and engulfment of apoptotic cells by macrophages. Macrophages from rheumatoid and SLE patients had similar percentages of apoptotic cells bound to their surface compared with normal controls. However, macrophages from SLE patients showed a significant defect in the internalisation of apoptotic cells compared with those from healthy controls, even in the presence of normal human serum.

CONCLUSIONS

Monocytes from patients with SLE and rheumatoid arthritis have a similar defect in their capacity to adhere to plastic. However, only macrophages from SLE patients showed an impaired ability to engulf apoptotic cells, which indicates that an intrinsic cellular defect may be responsible for this phenomenon.

Levitation and movement of human tumor cells using a printed circuit board device based on software-controlled dielectrophoresis

In this study we describe an original, efficient, and innovative printed circuit board (PCB) device able to generate dielectrophoresis-based, software-controlled cages that can be moved to any place inside a microchamber. Depending on their dielectrophoretic properties, eukaryotic cells can be "entrapped" in cages and moved under software control. The main conclusion gathered from the experimental data reported is that the PCB device based on dielectrophoresis permits levitation and movement of different tumor cells at different dielectrophoresis conditions. The results presented herein are therefore the basis for experiments aimed at forced interactions or separation of eukaryotic cells using "lab-on-a-chip." In fact, because many cages can be controlled at the same time, and two or more cages can be forced to share the same or a different location, it is possible, in principle, either to bring in contact cells of a differing histotype or to separate them.

The effect of strong static magnetic field on lymphocytes

We investigated whether static electromagnetic fields (EMFs) at a flux density of 4.75 T, generated by an NMR apparatus (NMRF), could promote movements of Ca2+, cell proliferation, and the eventual production of proinflammatory cytokines in human peripheral blood mononuclear cells (PBMC) as well as in Jurkat cells, after exposure to the field for 1 h. The same study was also performed after activation of cells with 5 mg/ml phytohaemagglutinin (PHA). Our results clearly demonstrate that static NMRF exposure has neither proliferative, nor activating, nor proinflammatory effects on both normal and PHA activated PBMC. Moreover, the concentration of interleukin-1beta, interleukin-2, interleukin-6, interferon, and tumour necrosis factor alpha (TNFalpha) remained unvaried in exposed cells. Exposure of Jurkat cells statistically decreased the proliferation and the proliferation indexes, which 24 and 48 h after exposure were 0.7 +/- 0.29 and 0.87 +/- 0.12, respectively. Moreover, in Jurkat cells the [Ca2+]i was higher than in PBMC and was reduced significantly to about one half after exposure. This is consistent with the decrease of proliferation and with the low levels of IL-2 measured. On the whole, our data suggest that NMRF exposure failed to affect the physiologic behaviour of normal lymphomonocytes. Instead in Jurkat cells, by changing the properties of cell membranes, NMRF can influence Ca2+ transport processes, and hence Ca2+ homeostasis with improvement of proliferation.

The 72-kDa component of signal recognition particle is cleaved during apoptosis

Proteins cleaved by apoptotic caspases are commonly recognized by autoantibodies found in the serum of patients with rheumatic disease. We report that the 72-kDa signal recognition particle (SRP) protein, a rare target of autoantibodies found in the serum of patients with dermatomyositis and systemic lupus erythematosus, is rapidly cleaved in Jurkat T cells treated with apoptotic (i.e. Fas ligation, treatment with gamma or ultraviolet radiation, or co-culture with anisomycin or staurosporine) but not proliferative (CD3 cross-linking) stimuli. Cleavage of SRP 72 produces a 66-kDa amino-terminal fragment and a 6-kDa carboxyl-terminal fragment that is selectively phosphorylated on serine residues. Cleavage of SRP 72 is prevented by chemical and peptide caspase inhibitors, and by overexpression of bcl-2, an inhibitor of apoptotic cell death. Analysis of the carboxyl terminus of SRP 72 has identified a putative cleavage site (SELD/A) for group III caspases, and carboxyl-terminal serine residues that are highly conserved in phylogeny. Both serine phosphorylation and caspase cleavage of SRP 72 are observed in cells derived from human, dog, rat, and mouse. Canine SRP 72 is cleaved in vitro by recombinant caspase 3 but retains the ability to mediate transport of a signal peptide-containing protein into the endoplasmic reticulum lumen. The 72-kDa component of the SRP joins a growing list of autoantigens that undergo post-translational modifications during programmed cell death.

Water-Soluble Polymer Conjugates of ZnPP for Photodynamic Tumor Therapy

Zn-protoporphyrin (ZnPP) is a promising candidate for cancer therapy. It is known to inhibit heme-oxygenase-1 (HO-1), resulting in suppressed biliverdin/bilirubin production accompanying lowered antioxidative capacity. As a consequence, a significant suppression of tumor growth in vivo was reported. Recent findings also showed that ZnPP efficiently generated reactive singlet oxygen under illumination of visible light. In the present report, we describe the photosensitizing capabilities of water-soluble polymer conjugates of ZnPP as novel compounds for photodynamic therapy against solid tumors. The polymer conjugation made ZnPP water-soluble, thus possible for injection for its aqueous solution. The cellular uptake and photobiological activity of ZnPP derivatives have been tested using a human T-cell leukemia cell line in vitro and demonstrated most potent phototoxic effects of SMA-ZnPP followed by PEG-ZnPP under aerobic conditions.

MEK/ERK pathway protects ionizing radiation-induced loss of mitochondrial membrane potential and cell death in lymphocytic leukemia cells

MEK/ERK-mediated signals have recently been found to inhibit Fas-mediated cell death through inhibition of caspase-8 activity. It remains unknown whether MEK/ERK-mediated signals affect ionizing radiation (IR)-induced cell death. Here we demonstrate that MEK/ERK-mediated signals selectively inhibit IR-induced loss of mitochondrial membrane potential (DeltaPsi(m)) and subsequent cell death. In Jurkat cells, TPA strongly activated ERK and inhibited the IR-induced caspase-8/Bid cleavage and the loss of DeltaPsi(m). The inhibitory effect of TPA was mostly abrogated by pretreatment of a specific MEK inhibitor PD98059, indicating that the effect depends upon MEK/ERK-mediated signals. Moreover, BAF-B03 transfectants expressing IL-2 receptor (IL-2R) beta(c) chain lacking the acidic region, which is responsible for MEK/ERK-mediated signals, revealed higher sensitivity to IR than the transfectants expressing wild-type IL-2R. Interestingly, the signals could neither protect the DeltaPsi(m) loss nor cell death in UV-irradiated cells. These data imply that the anti-apoptotic effect of MEK/ERK-mediated signals appears to selectively inhibit the IR-induced cell death through protection of the DeltaPsi(m) loss. Our data enlighten an anti-apoptotic function of MEK/ERK pathway against IR-induced apoptosis, thereby implying its contribution to radioresistance.

Apoptosis- and necrosis-inducing potential of cladribine, cytarabine, cisplatin, and 5-fluorouracil in vitro: a quantitative pharmacodynamic model

PURPOSE

The purpose of this study was to characterize the concentration-dependent induction of apoptosis by anticancer drugs in vitro.

METHODS

The apoptosis- and necrosis-inducing potential of the anticancer drugs cladribine (CDA), cytarabine (ARA-C), cisplatin (CDDP), and 5-fluorouracil (5FU) were studied in vitro in the human leukemia cell lines HSB2 and Jurkat using a flow-cytometry assay that permits the simultaneous quantification of vital, apoptotic, and necrotic cells by double-staining with fluorescein isothiocyanate (FITC)-labeled Annexin-V and propidium iodide. The results were fit to different multicompartmental models and the sensitivity of the cell lines to apoptosis and necrosis was estimated.

RESULTS

A time- and dose-dependent decrease in vital cells as well as an increase in apoptotic and necrotic cells was observed in HSB2 cells upon continuous incubation with 10(-5)-10(-7) MCDA, 10(-5)-10(-8) MARA-C, 5 x10(-5)-5 x 10(-6) M CDDP, and 10(-4)-10(-5) M 5FU, whereas no effect was observed relative to controls upon incubation with 10(-8)-10(-9) M CDA, 10(-9) M ARA-C, 10(-7)-10(-8) M CDDP, or 10(-6)-10(-9) M 5FU. In Jurkat cells, apoptosis- and necrosis-inducing effects were observed at 10(-4)-5 x 10(-6) M CDA, 10(-5)-10(-7) M ARA-C, 5 x 10(-5)-5 x 10(-6) M CDDP, and 10(-4)-10(-5) M 5FU. In all experiments, apoptotic cells reached a peak after 6-48 h of drug exposure. These data were best fit by a model in which vital cells became irreversibly apoptotic by a direct pathway and necrotic by an irreversible indirect pathway following the apoptotic state (mean R = 0.9876; range 0.9510-0.9993; mean modified Akaike's information criterion 3.88; range 1.86-5.82) and the rate constants of either pathway (Kva and Kan, respectively) were assessed. The sensitivity of both cell lines to apoptosis and necrosis (expressed as EC50 and Emax values) induced by the anticancer drugs could be calculated from the sigmoidal concentration-effect curves. Furthermore, it was shown that drug treatment (10(-6) M CDA or 10(-6) M ARA-C) potentiated the apoptosis-inducing effects of irradiation (6 Gy) but not its necrosis-inducing potential.

CONCLUSION

This study demonstrates that CDA, ARA-C, CDDP, and 5FU possess concentration-dependent apoptosis-inducing potential in the cell lines studied. The cytotoxic mechanism and cell-killing potential of these drugs is different, which is reflected by different EC50 and Emax values. Furthermore, a method for pharmacodynamic modeling is introduced that permits a quantitative approach for the assessment of the sensitivity of tumor cells to anticancer drugs and combined treatments.

JNK/SAPK activity is not sufficient for anticancer therapy-induced apoptosis involving CD95-L, TRAIL and TNF-alpha

We report here that stress stimuli such as gamma-irradiation or the anticancer drug doxorubicin activate expression of the death-inducing ligands (DILs) CD95-L, TNF-alpha and TRAIL. Apoptosis induced by gamma-irradiation or doxorubicin engages a FADD- and caspase-dependent apoptosis pathway which is inhibited by dominant negative FADD or the caspase inhibitor zVAD. zVAD did not prevent activity of JNK/SAPKs in response to doxorubicin suggesting that JNK/SAPK activity is independent of death receptor triggering during cellular stress-induced apoptosis. In addition, JNK/SAPKs remained activated by doxorubicin in resistant cell lines in which cleavage of caspases and apoptosis was not observed. These data uncouple JNK/SAPK activation and apoptosis signaling and indicate that cellular stress-induced apoptosis involves signaling via DILs which is paralleled by activation of JNK/SAPKs. Activation of these kinases may contribute e.g., to the expression of molecules involved in apoptosis but is not sufficient for induction of the apoptosis program following cellular stress.

Intracellular calcium signaling by Jurkat T-lymphocytes exposed to a 60 Hz magnetic field

To explore possible biochemical mechanisms whereby electromagnetic fields of around 0.1 mT might affect immune cells or developing cancer cells, we studied intracellular calcium signaling in the model system Jurkat E6-1 human T-leukemia cells during and following exposure to a 60 Hz magnetic field. Cells were labeled with the intracellular calcium-sensitive fluorescent dye Fluo-3, stimulated with a monoclonal antibody against the cell surface structure CD3 (associated with ligand-stimulated T-cell activation), and analyzed on a FACScan flow-cytometer for increases in intensity of emissions in the range of 515-545 nm. Cells were exposed during or before calcium signal-stimulation to 0.15 mTrms 60 Hz magnetic field. The total DC magnetic field of 78.2 microT was aligned 17.5 degrees off the vertical axis. Experiments used both cells cultured at optimal conditions at 37 degrees C and cells grown under suboptimal conditions of 24 degrees C, lowered external calcium, or lowered anti-CD3 concentration. These experiments demonstrate that intracellular signaling in Jurkat E6-1 was not affected by a 60 Hz magnetic field when culture and calcium signal-stimulation were optimal or suboptimal. These results do not exclude field-induced calcium-related effects further down the calcium signaling pathway, such as on calmodulin or other calcium-sensitive enzymes.

Influence of hypoxia on TRAIL-induced apoptosis in tumor cells

PURPOSE

Tumor hypoxia reduces the efficacy of radiotherapy, many types of chemotherapy, and tumor necrosis factor-alpha (TNF-alpha). TRAIL (TNF-alpha-related apoptosis-inducing ligand) is a ligand for death receptors of the TNF superfamily shown to be selectively toxic for tumor cells and thereby a promising antineoplastic tool. The impact of hypoxia on TRAIL-induced apoptosis was examined in this study.

METHODS AND MATERIALS

Apoptosis induction and growth rates of various tumor cell lines under hypoxia were evaluated in vitro. Biologically effective induction of hypoxia was verified by determination of hypoxia-inducible factor-1 (HIF-1) activation. The efficacy of TRAIL- and radiation-induced apoptosis under different oxygen conditions was quantified in vitro. The impact of Bcl-2 on TRAIL-induced apoptosis under hypoxia or normoxia was evaluated by comparing cells expressing Bcl-2 with a vector control.

RESULTS

Moderate hypoxia caused no growth retardation or apoptosis, but led to activation of HIF-1 as a prerequisite of hypoxic gene induction. Cellular responses to TRAIL differed considerably among the cell lines tested. Hypoxia reduced radiation-induced, but not TRAIL-induced, apoptosis in the tested cell lines. Hypoxia did not induce Bcl-2 expression. Bcl-2 had a minor impact on the efficacy of TRAIL-induced apoptosis.

CONCLUSION

Taken together, the data indicate that TRAIL is clearly effective under conditions of proven hypoxia.

The tyrosine kinase Lck is involved in regulation of mitochondrial apoptosis pathways

The induction of apoptosis requires the activation of a highly coordinated signaling network ultimately leading to the activation of caspases. In previous experiments we and others have shown that the tyrosine kinase Lck is required for adequate apoptosis induction in response to ionizing radiation, ceramide incubation and overexpression of the HIV-TAT protein. However, the position of Lck within given apoptotic signaling cascades remains unclear. We therefore aimed to define the role of Lck during radiation-induced apoptosis. Apoptosis induction in response to ionizing radiation, CD95 or TRAIL receptor stimulation was determined in Jurkat T-cells, the Lck-deficient Jurkat clone JCaM1.6- and Lck-retransfected JCaM1.6/Lck. No apoptosis, release of cytochrome c, breakdown of the mitochondrial potential were detectable during the first 48 h after irradiation of JCaM1.6 cells. In parallel, no activation of caspase-9, -8 and -3 was detectable. Since mitochondrial apoptosis pathways act within a feedback mechanism during death-receptor-mediated apoptosis, the influence of the Lck defect on CD95/Fas/Apo-1-L or TRAIL-induced apoptosis was also tested. Both stimuli induced apoptosis in Lck-deficient cells. However, the kinetics of apoptosis induction determined by caspase-8, -9 and -3 activation as well as deltapsi(m) breakdown was slowed. We conclude that the Lck deficiency influences early steps during radiation-induced mitochondrial alterations.

Pantothenic acid protects jurkat cells against ultraviolet light-induced apoptosis

Human leukemic T lymphocytes (Jurkat cells) were induced to undergo apoptosis by brief irradiation with ultraviolet C light (254 nm). This was accompanied by accumulation of lipid peroxidation products in the form of conjugated dienes, a decrease of total glutathione content, and a shift of its redox state towards the oxidized form. Preincubation of the cells with 1 mM pantothenate resulted in a significant elevation of total glutathione content of the cells, reaching its maximum level, 160% of the control, after 3 h. Similar increase was observed after preincubation with 5 mM N-acetylcysteine, a known precursor of glutathione. Both pantothenic acid and N-acetylcysteine alleviated the ultraviolet-induced decrease of glutathione content, diminished lipid peroxidation, and partly protected the cells against apoptosis produced by ultraviolet irradiation.

Inhibition of JNK signaling diminishes early but not late cellular stress-induced apoptosis

The human leukemic T-cell line Jurkat was used to define the role of the cellular stress pathway with its key player kinase JNK in cancer therapy-induced apoptosis. JNK activity was inhibited by stable transfection with a dominant negative mutant of the upstream kinase JNKK/MKK4 or with the novel, potent and selective JNK1, -2 and -3 inhibitor SP600125. Inhibition of JNK activity delayed the onset of apoptosis induced by cisplatin, doxorubicin, gamma-irradiation and CD95-L but did not prevent apoptosis per se. Early events during apoptosis such as induction of CD95-L, activation of caspase-8 and exposure of phosphatidylserine on the cell surface were strongly inhibited. Also, at early time points of apoptosis, loss of the mitochondrial membrane potential and release of cytochrome c were markedly impaired. However, late signaling events during apoptosis such as cleavage of PARP and DNA fragmentation apoptosis were only marginally affected. These findings are in accordance with the activity of initiator and effector caspases. Whereas activity of the initiator caspase-8 was strongly inhibited early and late after induction, an inhibition of caspase-3 activity was only observed early after induction of apoptosis. We therefore suggest that cellular stress signaling contributes to the initiation of apoptosis, whereas it might be dispensable for the progression of apoptosis. Dysfunction of this pathway under pathological conditions might contribute to therapy resistance of cancer cells.

Degradation of nonylphenol polyethoxylates by ultraviolet B irradiation and effects of their products on mammalian cultured cells

Nonylphenol polyethoxylates (NPEOs) are widely used as non-ionic surfactants and their biodegradation products such as 4-n-nonylphenol are stable and have been demonstrated to be cytotoxic. In the aquatic environment, these compounds are usually exposed to sunlight, and while the correlation between the biodegradation of NPEOs and changes in cytotoxicity has been reported, the relationship between the photodegradation of NPEOs and cytotoxicity has not. In this study, we investigated the degradation of NPEO by ultraviolet (UV) irradiation, especially UVB irradiation, and the effects on mammalian cell lines. NPEO with a smaller number of ethylene oxide (EO) units showed greater cytotoxicity. Although NPEO (10) completely inhibited the proliferation of the cells, NPEO (70) showed no toxicity. UVB irradiation significantly induced a shortening of the side chain, which was due to the production of ROS. The EO side chain of NPEO (10), was gradually degradated, but that of NPEO (70) was degradated near the benzene ring. Furthermore, the degradation of the benzene ring was more effective in NPEO (70) than NPEO (10). The toxicity of NPEO (10) in cultured cells decreased following UVB irradiation, whereas that of NPEO (70) was induced after UVB irradiation at 500 J/cm2 and disappeared at 1000 J/cm2. This might be due to the production of NPEO with a short side chain and 4-n-nonylphenol by the degradation of EO and due to the degradation of the benzene ring at higher doses of UVB irradiation. This study shows the significance of UV exposure to the degradation of alkylphenol polyethoxylates in the environment.

Caspase 7-induced cleavage of kinectin in apoptotic cells

Kinectin has been characterized as the first known receptor for the molecular motor kinesin, which is critically involved in microtubule-based vesicle transport and membrane trafficking. Here we identify kinectin as a target for caspase-mediated proteolysis during apoptosis. Treatment of cells with diverse apoptotic stimuli including TNF, anti-Fas, anticancer drugs, gamma-radiation or ceramide leads to rapid proteolytic cleavage of the 160-kDa form of kinectin to a 120-kDa fragment. Evidence is provided that kinectin cleavage is mediated by caspase 7.

Photonic approach to the selective inactivation of viruses with a near-infrared subpicosecond fiber laser

We report a photonic approach for selective inactivation of viruses with a near-infrared subpicosecond laser. We demonstrate that this method can selectively inactivate viral particles ranging from nonpathogenic viruses such as the M13 bacteriophage and the tobacco mosaic virus to pathogenic viruses such as the human papillomavirus and the human immunodeficiency virus (HIV). At the same time, sensitive materials such as human Jurkat T cells, human red blood cells, and mouse dendritic cells remain unharmed. The laser technology targets the global mechanical properties of the viral protein shell, making it relatively insensitive to the local genetic mutation in the target viruses. As a result, the approach can inactivate both the wild and mutated strains of viruses. This intriguing advantage is particularly important in the treatment of diseases involving rapidly mutating viral species such as HIV. Our photonic approach could be used for the disinfection of viral pathogens in blood products and for the treatment of blood-borne viral diseases in the clinic.

MDP: A Deinococcus Mn2+-Decapeptide Complex Protects Mice from Ionizing Radiation

The radioprotective capacity of a rationally-designed Mn²⁺-decapeptide complex (MDP), based on Mn antioxidants in the bacterium Deinococcus radiodurans, was investigated in a mouse model of radiation injury. MDP was previously reported to be extraordinarily radioprotective of proteins in the setting of vaccine development. The peptide-component (DEHGTAVMLK) of MDP applied here was selected from a group of synthetic peptides screened in vitro for their ability to protect cultured human cells and purified enzymes from extreme damage caused by ionizing radiation (IR). We show that the peptides accumulated in Jurkat T-cells and protected them from 100 Gy. MDP preserved the activity of T4 DNA ligase exposed to 60,000 Gy. In vivo, MDP was nontoxic and protected B6D2F1/J (female) mice from acute radiation syndrome. All irradiated mice treated with MDP survived exposure to 9.5 Gy (LD_70/30) in comparison to the untreated mice, which displayed 63% lethality after 30 days. Our results show that MDP provides early protection of white blood cells, and attenuates IR-induced damage to bone marrow and hematopoietic stem cells via G-CSF and GM-CSF modulation. Moreover, MDP mediated the immunomodulation of several cytokine concentrations in serum including G-CSF, GM-CSF, IL-3 and IL-10 during early recovery. Our results present the necessary prelude for future efforts towards clinical application of MDP as a promising IR countermeasure. Further investigation of MDP as a pre-exposure prophylactic and post-exposure therapeutic in radiotherapy and radiation emergencies is warranted.

NF-kappaB activation plays an antiapoptotic role in human leukemic K562 cells exposed to ionizing radiation

Exposure of cells to ionizing radiation (IR) determines cellular lesions, such as DNA and membrane damage, which involve a coordinate network of signal transduction pathways responsible for resistance to or delay of apoptosis, depending on cell type and administered dose. Since, after IR exposure, the apoptotic profile appeared different in the two chosen cell lines K562 and Jurkat along with caspase-3 activation, we paid attention to the influence exerted by Protein kinase C delta on transcription factor NF-kappaB activation. Interestingly, K562 resist to IR carrying out a survival strategy which includes PKC delta/NF-kappaB pathway activation, probably mediated by novel IKKs and a role for PI-3-kinase in activating PKC delta at Thr 505 by PDK-1 phosphorylation is suggested. In addition, since caspase-3 is not activated in these cells upon ionizing radiation exposure, it could be supposed that NF-kappaB antagonizes apoptosis induction interfering with pathways which lead to caspase activation, may be by inducing expression of IAP, caspases 3, 7, 9, inhibitor. Thus NF-kappaB activation explains the resistance displayed by K562 to IR and drug potential interference directed to this protein could overcome apoptosis resistance in clinical settings.

Light-induced mutagenicity in Salmonella TA102 and genotoxicity/cytotoxicity in human T-cells by 3,3'-dichlorobenzidine: a chemical used in the manufacture of dyes and pigments and in tattoo inks

DCB, 3,3'-dichlorobenzidine, is used primarily as an intermediate in the manufacture of diarylide yellow or azo red pigments for printing ink, textile, paint, and plastics. It is also used in tattoo inks. In this article, we investigate light-induced toxicity of DCB in both bacteria and human Jurkat T-cells. DCB itself is not toxic or mutagenic to Salmonella typhimurium TA102, but is photomutagenic at concentrations as low as 2 microM and phototoxic at concentrations >100 microM when bacteria are exposed to DCB and light at the same time (1.2 J/cm2 of UVA and 2.1 J/cm2 of visible light). Furthermore, DCB is both photocytotoxic and photogenotoxic to human Jurkat T-cells. Under a light irradiation dose of 2.3 J/cm2 of UVA and 4.2 J/cm2 of visible light, it causes the Jurkat T-cells to become nonviable in a DCB dose-dependent manner and the nonviable cells reaches 60% at DCB concentrations higher than 50 microM. At the same time, DNA fragmentation is observed for cells exposed to both DCB and light, determined by single cell gel electrophoresis (alkaline comet assay). As much as 5% (average) DNA fragmentation was observed when exposed to 200 microM DCB and light irradiation. This suggests that DCB can penetrate the cell membrane and enter the cell. Upon light activation, DCB in the cells can cause various cellular damages, leading to nonviable Jurkat T-cells. It appears, the nonviable cells are not caused solely by fragmentation of cellular DNA, but by other damages such as to proteins and cell membranes, or DNA alkylation. Therefore, persons exposed to DCB through environmental contamination or through tattoo piercing using DCB-containing inks must not only concern about its toxicity without exposing to light, but also its phototoxicity.

Antiapoptotic effect of dipyrone on HL-60, Jurkat and Raji cell lines submitted to UV irradiation, arachidonic acid and cycloheximide treatments

The effect of dipyrone (metamizol) on cell viability was evaluated in human leukocyte cell lines upon different apoptotic treatments: arachidonic acid (AA), cycloheximide (CHX), tumor necrosis factor (TNF) and ultraviolet (UV) irradiation. Dipyrone had a dual effect: at high concentrations (beyond 300 microM), it was cytotoxic, leading to apoptosis, whereas at lower concentrations (37.5-300 microM), it was cytoprotective, delaying the loss of membrane integrity triggered by arachidonic acid (100-200 microM) and UV irradiation and the cytotoxicity of cycloheximide (25-50 microM). No effect of dipyrone was found on TNF-induced cytotoxicity (250 ng/ml). The cytoprotective effect of dipyrone is associated with a decrease in DNA fragmentation, as assessed by electrophoresis of genomic DNA and by flow cytometry; a reduction in the percentage of condensed nuclei, as evaluated by DNA staining with Hoescht 33342 and a decrease in poly(ADP)-ribose polymerase (PARP) cleavage, as assessed by Western blotting. The cytoprotective effect of dipyrone on leukocyte apoptosis occurs at concentrations usually found for the main active metabolite of the drug and may have implications on the therapeutic and side effects caused by this agent.

ELF magnetic fields initiate protein tyrosine phosphorylation of the T cell receptor complex

The human T cell line Jurkat registers a sinusoidal extremely low frequency (ELF), 0.10 mT magnetic fields (MFs) at the level of the plasma membrane. In this study, the protein tyrosine phosphorylation (PY) of two membrane-associated proteins in Jurkat cells were examined following a short-term MFs exposure, the zeta chains and the Src kinases p56lck. These proteins are interesting to study since the earliest biochemical event upon T cell receptor (TcR) activation is PY of the zeta chains. These signalling chains in the TcR complex was assessed using Western blotting and the activation of the p56lck kinase was analysed by in vitro kinase assay. The MFs exposure of Jurkat for 5 min activated p56lck and resulted in PY of zeta. These findings are in line with earlier reports on how MFs exposure affects signal transduction in Jurkat.

Autoreactive IgG to intracellular proteins in sera of MS patients

IgG binding to multiple protein constituents in lysates of Jurkat cells was detected by Western blot in sera of patients with multiple sclerosis (MS) and systemic lupus erythematosus (SLE). The distribution patterns of bands with sera tested against protein lysates from normal Jurkat cells or from Jurkat cells exposed to apoptosis or oxidative stress inducing conditions were similar in most patients, but with inter-individual differences. The number of bands with sera of both patient populations far exceeded those (0 or 2 bands) detected with sera of healthy controls. Proteinase K, RNase and DNase pre-treatment of cell lysates suggested a protein nature for all of the antigens and a ribonucleoprotein (RNP) nature for some of the antigens recognized by serum IgG of MS and SLE patients. Only two MS patients had positive anti-nuclear antibody (ANA) titers, while all of them had positive Western blots. In addition to similarities, dissimilarities were also recognized between the humoral immune responses in MS and SLE. No IgG molecules were detected against phosphorylated proteins in the sera of MS patients, while multiple phosphoproteins were recognized by IgG molecules of SLE patients in immunoprecipitation experiments. These data suggest that in addition to ANA, the sera of MS patients contain autoantibodies directed against multiple intracellular proteins. The protein recognition patterns of immunoglobulins in MS share similarities, but also have distinct features when compared to those in SLE. The biological significance of these autoantibodies in MS remains to be understood.