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Anthocyanins are a group of naturally occurring phenolic compounds as colorants in several plants, flowers and fruits. These pigments have a great importance as quality indicators, as chemotaxonomic markers and antioxidants. The content of blackberry (Rubus species) juice was investigated by HPLC/ESI/MS using narrow bore HPLC columns. Using this method we demonstrated that cyanidin-3-O-glucoside represents about 80% of the total anthocyanin contents in blackberry extract. Here we investigated antioxidant activity of the blackberry juice and cyanidin-3-O-glucoside on the endothelial dysfunction in cells and in vascular rings exposed to peroxynitrite. In human umbilical vein endothelial cells (HUVEC) in vitro, peroxynitrite caused a significant suppression of mitochondrial respiration (38 +/- 2.1% of control cells), as measured by the mitochondrial-dependent conversion of the dye MTT to formazan. Peroxynitrite caused DNA strand breakage (63 +/- 1.9% single strand vs 3 +/- 0.9% single strand in control cells), as measured by the alkaline unwinding assay, and caused an activation of PARS, as measured by the incorporation of radiolabeled NAD(+) to nuclear proteins. Blackberry juice (different dilutions that contained 80 ppm;40 ppm;14.5 ppm of cyanidin-3-O-glucoside) and cyanidin-3-O-glucoside (as chloride) (0.085 microM; 0.028 microM; 0.0085 microM) reduced the peroxynitrite-induced suppression of mitochondrial respiration, DNA damage and PARS activation in HUVECs. Vascular rings exposed to peroxynitrite exhibited reduced endothelium-dependent relaxant responses in response to acetylcholine as well as a vascular contractility dysfunction in response to norepinephrine. The development of this peroxynitrite-induced vascular dysfunction was ameliorated by the blackberry juice (different dilutions that contained 80 ppm;40 ppm;14.5 ppm of cyanidin-3-O-glucoside) and cyanidin-3-O-glucoside (as chloride) (0.085 microM;0.028 microM;0.0085 microM). In conclusion our findings clearly demonstrate that blackberry juice containing cyanidin-3-O-glucoside is a scavenger of peroxynitrite and that exert a protective effect against endothelial dysfunction and vascular failure induced by peroxynitrite.

Helicobacter pylori (HP) related inflammation is mediated by tumour necrosis factor alpha (TNFalpha), which "in vitro" increases epithelial apoptosis in response to infection. In the early stages of HP gastritis, a raised epithelial apoptosis occurs; this phenomenon becomes less evident with progression towards intestinal metaplasia. Aim of our study was to analyze "in vivo" mucosal TNFalpha in relation to epithelial apoptosis in the progression of HP related histological damage. Antral biopsies from 20 HP positive patients were retrospectively studied: 10 with and 10 without intestinal metaplasia (IM and CG group respectively); samples of 10 dyspeptics with normal HP negative stomach (N) were used as control. The following parameters were evaluated by immunohistochemistry: 85 kDa caspase-cleaved fragment (p85) of human poly (ADP-ribose) polymerase (PARP) labelling index (LI) as marker of apoptosis and TNFalpha LI in stromal cells as marker of inflammatory response. Both epithelial apoptosis and mucosal TNFalpha expression were higher in chronic active gastritis compared to intestinal metaplasia and controls (PARP and TNFalpha LI: CG > IM > N; ANOVA & Student-Neumann-Keuls; p < 0.05 and p < 0.01, respectively). Pearson's coefficient showed a significant correlation between PARP and TNFalpha LI in IM and CG groups. Our data show that mucosal TNFalpha, similarly to what suggested "in vitro", may be related "in vivo" to epithelial apoptosis thus suggesting a possible mechanism for immune system involvement in the control of gastric epithelial turnover.

The present study compares some phenotypic and physiologic characteristics of microvascular and macrovascular endothelial cells from within one human organ. To this end microvascular endothelial cells from human full-term placenta (PLEC) were isolated using a new method and compared with macrovascular human umbilical vein endothelial cells (HUVEC) and an SV40-transformed placental venous endothelial cell line (HPEC-A2). PLEC were isolated by enzymatic perfusion of small placental vessels, purified on a density gradient and cultured subsequently. Histological sections of the enzyme-treated vessels showed a selective removal of the endothelial lining in the perfused placental cotyledons. The endothelial identity of the cells was confirmed by staining with the endothelial markers anti-von Willebrand factor, Ulex europaeus lectin and anti-QBEND10. The cells internalized acetylated low-density lipoprotein and did not show immunoreactivity with markers for macrophages, smooth muscle cells and fibroblasts. The spindle-shaped PLEC grew in swirling patterns similar to that described for venous placental endothelial cells. However, scanning electron microscopic examination clearly showed that PLEC remained elongated at the confluent state, in contrast to the more polygonal phenotype of HPEC-A2 and HUVEC that were studied in parallel. The amount of vasoactive substances (endothelin-1,2, thromboxane, angiotensin II, prostacyclin) released into the culture medium and the proliferative response to cytokines was more similar to human dermal microvessels (MIEC) derived from non-fetal tissue than to HUVEC. Potent mitogens such as vascular endothelial growth factors (VEGF121, VEGF165) and basic fibroblast growth factor (FGF-2) induced proliferation of all endothelial cell types. Placental growth factors PIGF-1 and PIGF-2 effectively stimulated cell proliferation on PLEC (142 +/- 7% and 173 +/- 10%) and MIEC (160 +/- 20% and 143 +/- 28%) in contrast to HUVEC (9 +/- 8% and 15 +/- 20%) and HPEC-A2 (15 +/- 7% and 24 +/- 6%) after 48 h incubation time under serum-free conditions. These data support evidence for (1) the microvascular identity of the isolated PLEC described in this study, and (2) the phenotypic and physiologic heterogeneity of micro- and macrovascular endothelial cells within one human organ.

The evidence for increased oxidative stress and DNA damage in amyotrophic lateral sclerosis (ALS) prompted studies to determine if the expression of poly(ADP-ribose) polymerase (PARP) is increased in ALS. Using Western analyses of postmortem tissue, we demonstrated that PARP-immunoreactivity (PARP-IR) was increased 3-fold in spinal cord tissues of sporadic ALS (sALS) patients compared with non-neurological disease controls. Despite the increased PARP-IR, PARP mRNA expression was not increased significantly. Immunohistochemical analyses revealed PARP-IR was increased in both white and gray matter of sALS spinal cord. While PARP-IR was predominantly seen in astrocytes, large motor neurons displayed reduced staining compared with controls. This result contrasts sharply to the staining of Alzheimer and MPTP-induced Parkinson diseased tissue, where poly(ADP-ribose) (PAR)-IR was seen mostly in neurons, with little astrocytic staining. PARP-IR was increased in the pellet fraction of sALS homogenates compared with control homogenates, representing potential PARP binding to chromatin or membranes and suggesting a possible mechanism of PARP stabilization. The present results demonstrate glial alterations in sALS spinal cord tissue and support the role of glial alterations in sALS pathogenesis. Additionally, these results demonstrate differences in sALS spinal motor neurons and astrocytes compared to brain neurons and astrocytes in Alzheimer disease and MPTP-induced Parkinson disease despite the presence of markers for oxidative stress in all 3 diseases.

Fanconi anemia (FA) is a hereditary disease of unknown pathogenic mechanisms, although mutations in seven different genes can be causative. Six of these genes have been cloned and sequenced. Only slight homology to the DNA of any other known gene has been found with the exception of FANCG which is identical to XRCC9. The function of these genes, including XRCC9, is presently unknown. Since pADP ribosyl transferase (pADPRT) plays a role in apoptosis, and apoptosis is affected in FA cells, we studied the correlation between pADPRT and FA cells. We reinvestigated the previously reported lack of pADPRT activity in fibroblasts from patients with Fanconi anemia. Here we describe the role of the lower redox potential of FA cells and demonstrate that this is an efficient strategy in the prevention of cell death due to the lack of energy under oxidative stress. This strategy is advantageous for the cells under the nonreplicative condition of confluency in which the risk of mutation is low and the prevention of apoptosis permits cell survival. pADPRT is not diminished to the same extent in all complementation groups of FA. It is prominent in FANCA, FANCG and FANCF cells, indicating that these genes control pADPRT diminution. Our experiments suggest that the pADPRT level is linked with the oxidoreduction reactions seen in FA.

In contrast to their inactive parent compound triptycene (code name TT0), new synthetic analogs (TT code number) mimic the antitumor effects of the anthracycline quinone antibiotic daunorubicin (DAU) in the nM range in vitro but have the additional advantage of also blocking nucleoside transport and retaining their efficacy in multidrug-resistant (MDR) tumor cells. Since TT bisquinones may induce DNA fragmentation at 24 h by an active mechanism that requires RNA and protein syntheses and protease activities, the most cytotoxic of them, TT24, was tested for its ability to induce poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, an early marker of apoptosis. PARP-1 cleavage starts at 2-3 h and is maximally induced at 6 h by 1.6 microM concentrations of TT24 and DAU in wild-type drug-sensitive HL-60-S cells. However, in MDR HL-60-RV cells, PARP-1 cleavage is still induced by 4 microM TT24 but not by 4-10 microM DAU. The magnitude of PARP-1 cleavage may increase with the number of quinoid rings in the triptych structure and, in contrast to TT0, all lead antitumor TT bisquinones share the ability to fully induce PARP-1 cleavage in HL-60-S cells. A 1 h pulse treatment is sufficient for TT24 and DAU to induce PARP-1 cleavage at 6 h. Since the abilities of TT24 and DAU to induce PARP-1 cleavage are inhibited by benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone but not by N-tosyl-L-phenylalanine chloromethyl ketone, caspase-mediated apoptosis may be involved in the mechanism by which these quinone antitumor drugs induce the proteolytic cleavage of PARP-1 at 6 h and the internucleosomal fragmentation of DNA at 24 h in the HL-60 tumor cell system.

Poly(ADP-ribose) polymerase (PARP) has strong affinity for DNA strand breaks and cycles on and off the DNA ends to allow DNA repair. A DNA-binding domain of PARP (PARP-DBD) acts as a dominant-negative mutant by binding to DNA strand breaks irreversibly and sensitizing mammalian cells to DNA-damaging agents. Therefore, expression of PARP-DBD in prostate carcinoma cells offers a strategy to achieve sensitization to genotoxic treatments. Toward this end, we developed recombinant plasmids expressing the PARP-DBD under the control of the 5'-flanking sequences of the human prostate-specific antigen (PSA) gene. Tissue specificity of PARP-DBD expression in human tumor cells was confirmed using the PSA-producing (LNCaP) and PSA-negative (PC-3) prostate cancer cells, as well as cells of nonprostate origin, Ewing's sarcoma (A4573 cells). LNCaP cells stably transfected with the PSA-regulated cDNA for PARP-DBD exhibit an androgen-dependent induction of PARP-DBD expression as determined by Western blotting, reverse transcription-PCR, and in situ immunofluorescence. Furthermore, we found that PARP-DBD sensitized LNCaP cells to DNA-damaging agents, such as ionizing radiation and etoposide. Androgen (R1881) -dependent stimulation of PARP-DBD expression resulted in a 2-fold growth inhibition in LNCaP cells as compared with controls, and an augmented apoptotic cell death in response to ionizing radiation or etoposide. Taken together, the plasmid vector developed in this study permits the expression of the human PARP-DBD in an androgen-inducible and PSA-dependent fashion, and sensitizes prostatic adenocarcinoma cells to DNA-damaging treatments. These results provide proof-of-principle for a novel therapeutic strategy for the treatment of prostate cancer.

poly(ADP-ribose) polymerase-2 (PARP-2) is a newly described member of the PARP family of nuclear enzymes. Previous studies have shown pharmacological inhibition of PARP activity to have a beneficial role in attenuating inflammation. We developed a chemically modified 2'-O-(2-methoxy)ethyl antisense oligonucleotide (ISIS 110251) inhibitor of PARP-2 and tested it for efficacy in the interleukin (IL)-10-deficient mouse. In tissue culture, ISIS 110251 reduced PARP-2 mRNA expression in a concentration- and sequence-specific manner. In 129 Sv/Ev mice, ISIS 110251 reduced PARP-2 mRNA in liver by 80%. This reduction was dependent upon treatment duration and was independent of the method of delivery. In interleukin-10-deficient mice with established colitis, treatment with ISIS 110251 normalized colonic epithelial barrier and transport function, reduced proinflammatory cytokine secretion and inducible nitric-oxide synthase activity, and attenuated inflammation. Our data demonstrate that selective inhibition of PARP-2 activity results in a marked improvement of colonic inflammatory disease in a mouse model of chronic colitis and a normalization of colonic function.

Citicoline has been demonstrated to be beneficial in several models of cerebral ischaemia. We tested the hypothesis that citicoline may provide apoptotic pathways following focal cerebral ischaemia. Focal cerebral ischaemia was produced by distal, permanent middle cerebral artery occlusion (MCAO) in Sprague-Dawley rats. The animals were randomised into four groups: (B+A) Citicoline 500 mg/kg IP 24 and 1 h before MCAO, and 23 h after MCAO; (A) citicoline 500 mg/kg IP, within 30 min after MCAO, and 23 h after MCAO; (C) vehicle IP; and (D) sham-operated. The animals were sacrificed at 12 h (n=8 per group) and 24 h (n=8 per group) after MCAO. Immunohistochemistry was performed on free-floating tissue sections with goat polyclonal antibodies to procaspase-1, -2, -3, -6 and -8, and in paraffin-embedded sections processed for cleaved caspase-3 (17 kDa) immunohistochemistry. Finally, some sections were stained with the method of in situ end-labelling of nuclear DNA fragmentation. For gel electrophoresis and Western blotting, antibodies to poly (ADP-ribose) polymerase (PARP) products of 89 kDa were used to reveal specific cleavage substrates of caspases. MCAO induced the expression of all procaspases and the expression of PARP products of 89 kDa, as well as cells with nuclear DNA fragmentation, at 12 and 24 h, in the infarcted core and penumbra. Citicoline reduced the expression of all procaspases at 12 and 24 h after MCAO, as well as the expression of cleaved caspase-3 in cells in the penumbra area. This was accompanied by a reduction in the number of cells bearing nuclear DNA fragments. The expression of caspase-cleaved products of PARP (PARP 89 kDa) was reduced in citicoline-treated ischaemic rats. These results show that citicoline inhibits the expression of proteins involved in apoptosis following MCAO.

Previously, we reported that EB1089 inhibited the growth of NCI-H929 myeloma cells via cell cycle arrest and apoptosis. In the present study, we investigated whether a combined EB1089 and TGF-beta1 synergistically inhibited the cell proliferation of myeloma cell lines. While TGF-beta1 alone could not inhibit the proliferation of any of the tested myeloma cells, synergistic effect between EB1089 (1 x 10(-8) M) and TGF-beta1 (1 ng/ml) was observed in NCI-H929 cells. TGF-beta1 intensified the decreased expression of CDK2, CDK4, CDK6 and cyclin D1 in EB1089-treated NCI-H929 cells. However, these effects did not intensify to decrease CDK2 activity of EB1089-treated NCI-H929 cells, resulting in no difference in the extent of G1 arrest between EB1089- and both agents-treated cells. Remarkably, both agents synergistically induce apoptosis of NCI-H929 cells, which was accompanied with up-regulation of Bax, degradation of PARP and Rb proteins, and loss of mitochondrial transmembrane potential (deltapsim). EB1089 caused the induction of SMAD4, a mediator of TGF-beta1 signaling. In addition, a combined EB1089 and TGF-beta1 increased p21 and JNK/SAPK activity whereas neither EB1089 nor TGF-beta1 affected p21 and JNK/SAPK activity. Taken together, these results suggest that treatment with both EB1089 and TGF-beta1 synergistically inhibits the proliferation of NCI-H929 cells through apoptosis.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme involved in a range of activities associated with DNA metabolism and plays a key role in maintaining the integrity of DNA and chromatin structure. As such, this enzyme is likely to provide a useful target when using a rational drug design approach to develop pharmaceutical reagents, including cancer therapeutics. However, there is still a great deal to learn about the mode of action of PARP-1 and therefore efforts are being directed at gaining a better understanding of the relationship between its structure and function. To this end we have developed a rapid and relatively simple approach to producing and purifying PARP-1. Unlike traditional PARP-1 purification protocols, the method described here requires only one chromatography step thus minimizing losses of the enzyme and also avoids the use of a competitive inhibitor-based affinity chromatography step, which is common to several other protocols in the literature. The product of the method described here is high-quality native PARP-1 with a high specific activity and K(m) and V(max) values similar to what is reported by other workers in the field. This protocol is particularly well suited to making PARP-1 in a quantity and of a quality suitable for structure-function studies., (Copyright 2001 Elsevier Science.)

Background: We have isolated a mycobacterial cell wall-DNA complex (MCC) possessing anti-cancer activity against bladder cancer cells. The anti-cancer activity of MCC appears to be due to two effects: a direct interaction with bladder cancer cells resulting in the induction of apoptosis and an indirect effect via the stimulation of monocytes and macrophages cytokine synthesis. In this study, the direct effect of MCC towards LNCaP cancer cells was evaluated., Methods: Inhibition of proliferation, cell cycle arrest and induction of apoptosis were evaluated in vitro using LNCaP cells treated with MCC. The synthesis of IL-12, GM-CSF, and TNF-alpha by LNCaP cells in response to MCC was also determined. Experiments were performed to gain insight into the mechanism of action of MCC towards LNCaP cells., Results: MCC caused a dose-dependent inhibition of the proliferation of LNCaP cells that was associated with cell cycle arrest at the G0/G1 phase. MCC-induced apoptosis of LNCaP cells was consistent with a mitochondrial pathway involving mitochondrial disruption, release of cytochrome c, and an increase in Bax protein levels leading to caspase-3 and -7 activation and cleavage of poly (ADP-ribose) polymerase and nuclear mitotic apparatus protein. Surprisingly, MCC also directly induced the synthesis of IL-12 and GM-CSF, but not TNF-alpha, by LNCaP cells., Conclusions: MCC possesses the ability to directly induce apoptosis of LNCaP cells and to trigger the synthesis of IL-12 and GM-CSF by these cells, suggesting a potential role of MCC for the treatment of prostate cancer., (Copyright 2001 Wiley-Liss, Inc.)

Poly(ADP-ribose) polymerase (PARP) can initiate an energy-consuming and inefficient repair cycle following cerebral ischemia/reperfusion by transferring ADP ribose units to nuclear proteins eventually leading to cellular dysfunction and neuronal death. 3-Aminobenzamide (3-AB) is a selective inhibitor of PARP that can significantly reduce brain damage after focal ischemia in rats and displays a low toxicity in vivo. The goals of this study were to determine if inhibiting PARP with 3-AB has a long-term neuroprotective effect and if functional outcome improves in rats following focal ischemia and treatment with 3-AB. Focal ischemia was induced by a 2-h occlusion of the middle cerebral artery (MCA), using an intraluminal filament. Motor functions were evaluated from 5 to 28 days after reperfusion in four groups of rats: stroke without treatment; stroke treated with 3-AB at doses of 15 mg/kg, stroke treated with 3-AB at doses of 55 mg/kg; and the non-ischemic control rats. Functional behaviors were tested by a series of motor function tasks (foot placing, parallel bar crossing, rope and ladder climbing), as well as a neurological examination. Infarct volume of stroke brain in the same rat was determined by Nissl staining 28 days after surgery. Comparison of the untreated stroke group (n=11) and the treated stroke groups indicates that impairment of motor function was significantly (P<0.001) reduced by administration of 3-AB at doses of 15 mg/kg (n=9) or 55 mg/kg (n=10). Neurological outcome was also improved significantly (P<0.001). Infarct volume was significantly (P<0.01) reduced in both treated groups. Long-term neuroprotection following ischemia/reperfusion injury to the brain can be obtained by administration of a PARP inhibitor. The motor tests employed in this study can be used as sensitive, objective and reproducible measurements of functional impairment in rats following an ischemic stroke.

The obligate intracellular protozoan parasite Toxoplasma gondii has been shown to protect different cell types from apoptosis induced by a variety of pro-apoptotic treatments. However, the precise cell biological mechanisms of this inhibition remained unknown. As shown in this study, apoptosis in human-derived HL-60 and U937 cells induced by treatment with actinomycin D or TNF-alpha in combination with cycloheximide, respectively, was indeed dose-dependently downregulated by prior infection with T. gondii, as determined by DNA fragmentation assays. Cleavage of caspase 3 and caspase 9 after treatment with pro-apoptotic stimuli was considerably diminished by T. gondii. Furthermore, release of mitochondrial cytochrome c during apoptosis in HL-60 cells was prevented by intracellular parasites and this was correlated with the absence of DNA strand breaks on the single cell level. Inhibition of cytochrome c release coincided with a twofold upregulation of Mcl-1 protein levels in HL-60 and U937 cells, while Bcl-2 expression did not increase after infection. Parasitic interference with the caspase cascade led to a reduced proteolytic cleavage of the nuclear target molecule protein kinase C delta. In parallel, poly(ADP-ribose) polymerase protein levels were prominently downregulated by T. gondii, irrespective of whether HL-60 and U937 cells had been treated with pro-apototic stimuli or left untreated. However, poly(ADP-ribose) polymerase mRNA levels remained unchanged after infection as determined by RT-PCR analyses. These observations suggest that T. gondii has evolved different mechanisms that may contribute to downregulation of host cell apoptosis, namely inhibition of cytochrome c release and subsequent caspase activation as well as downregulation of poly(ADP-ribose) polymerase protein levels.

Aspirin- and non-steroidal anti-inflammatory drug (NSAID)-induced apoptosis is one of the important mechanisms for their anti-tumour effect in gastric cancer. We aimed at determining the role of bcl-2 family proteins and caspases in the apoptotic process. Gastric cancer cell lines AGS (wild-type p53) and MKN-28 (mutant p53) were used. Cell proliferation was measured by MTT assay. Apoptosis was determined by acridine orange staining. Protein expressions were determined by western blotting. Aspirin and indomethacin inhibited cell proliferation and induced apoptosis in both cells. AGS cells were more sensitive compared with MKN-28 cells. The pro-apoptotic proteins bax and bak were overexpressed after treatment, while the protein level of bcl-2 remained unchanged. Apoptosis was accompanied by an increase in caspase-3 activity and cleavage of caspase-3 and poly(ADP-ribose) polymerase. Inhibition of caspase-3 rescued aspirin-induced apoptosis. Our results suggest that one of the major pathways which mediates the anti-tumour response of aspirin and indomethacin in gastric cancer cells is through up-regulation of bax and bak and activation of caspase-3. Bax and bak are important in the chemoprevention of gastric cancer.

To assess the significance of damaged nuclear DNA in autopsy brain tissue in Lewy body disease (LBD), we examined the patterns of expression of two DNA repair enzymes (PARP and DNA-PKCS), TUNEL and caspase-3 activation, in sections of midbrain and frontal cortex from nine patients with LBD who had not received L-DOPA, and from five neurologically normal controls. In LBD but not controls, many neurons and glia in the midbrain had translocated DNA-PKCS and PARP from the cytoplasm into the nucleus, particularly in the substantia nigra. LBD midbrains contained sparse TUNEL-positive neurons. Caspase-3 activity was largely restricted to microglia but was detected in an occasional nigral neuron. Nuclear DNA damage occurs in vivo in LBD but only rarely indicates neuronal apoptosis.

The presence of NAD-metabolizing enzymes (e.g., ADP-ribosyltransferase (ART)2) on the surface of immune cells suggests a potential immunomodulatory activity for ecto-NAD or its metabolites at sites of inflammation and cell lysis where extracellular levels of NAD may be high. In vitro, NAD inhibits mitogen-stimulated rat T cell proliferation. To investigate the mechanism of inhibition, the effects of NAD and its metabolites on T cell proliferation were studied using ART2a+ and ART2b+ rat T cells. NAD and ADP-ribose, but not nicotinamide, inhibited proliferation of mitogen-activated T cells independent of ART2 allele-specific expression. Inhibition by P2 purinergic receptor agonists was comparable to that induced by NAD and ADP-ribose; these compounds were more potent than P1 agonists. Analysis of the NAD-metabolizing activity of intact rat T cells demonstrated that ADP-ribose was the predominant metabolite, consistent with the presence of cell surface NAD glycohydrolase (NADase) activities. Treatment of T cells with phosphatidylinositol-specific phospholipase C removed much of the NADase activity, consistent with at least one NADase having a GPI anchor; ART2- T cell subsets contained NADase activity that was not releasable by phosphatidylinositol-specific phospholipase C treatment. Formation of AMP from NAD and ADP-ribose also occurred, a result of cell surface pyrophosphatase activity. Because AMP and its metabolite, adenosine, were less inhibitory to rat T cell proliferation than was NAD or ADP-ribose, pyrophosphatases may serve a regulatory role in modifying the inhibitory effect of ecto-NAD on T cell activation. These data suggest that T cells express multiple NAD and adenine nucleotide-metabolizing activities that together modulate immune function.

Lymphocytes express a number of NAD-metabolizing ectoenzymes, including mono(ADP-ribosyl)transferases (ART) and ADP ribosylcyclases. These enzymes may regulate lymphocyte functions following the release of NAD in injured or inflammatory tissues We report here that extracellular NAD induces apoptosis in BALB/c splenic T cells with an IC(50) of 3-5 microM. Annexin V staining of cells was observed already 10 min after treatment with NAD in the absence of any additional signal. Removal of GPI-anchored cell surface proteins by phosphatidylinositol-specific phospholipase C treatment rendered cells resistant to NAD-mediated apoptosis. RT-PCR analyses revealed that resting BALB/c T cells expressed the genes for GPI-anchored ART2.1 and ART2.2 but not ART1. ART2-specific antisera blocked radiolabeling of cell surface proteins with both [(32)P]NAD and NAD-mediated apoptosis. Further analyses revealed that natural knockout mice for Art2.a (C57BL/6) or Art2.b (NZW) were resistant to NAD-mediated apoptosis. Labeling with [(32)P]NAD revealed strong cell surface ART activity on T cells of C57BL/6 and little if any activity on cells of NZW mice. T cells of (C57BL/6 x NZW)F(1) animals showed strong cell surface ART activity and were very sensitive to NAD-induced apoptosis. As in BALB/c T cells, ART2-specific antisera blocked cell surface ART activity and apoptosis in (C57BL/6 x NZW)F(1) T cells. The fact that T cells of F(1) animals are sensitive to rapid NAD-induced apoptosis suggests that this effect requires the complementation of (at least) two genetic components. We propose that one of these is cell surface ART2.2 activity (defective in the NZW parent), the other a downstream effector of ADP-ribosylation (defective in the C57BL/6 parent).

Activation of telomerase is essential for in vitro cellular immortalization and tumorigenesis. In the present study, we investigated telomerase activation and its implications in plasma cell dyscrasias including monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM) and plasma cell leukaemia (PCL). All 5 patients with MGUS exhibited normal levels of telomerase activity in their plasma cells. Elevated telomerase activity was found in the samples from 21/27 patients with MM and 4/4 with PCL. In addition, 4 myeloma cell lines all expressed high levels of telomerase activity. The expression of telomerase reverse transcriptase (hTERT) and telomerase RNA template (hTER) was positively associated with the levels of telomerase activity in MM/PCL. Tankyrase expression was upregulated, concomitant with the induction of hTERT and activation of telomerase in MM/PCL. The present findings indicate that MGUS cells may not be immortalized and that activation of telomerase plays a role in the malignant transformation from MGUS to MM., (Copyright 2001 Cancer Research Campaign.)

Purpose: To assess the influence of trans-dominant inhibition of poly(ADP-ribosyl)ation on the rejoining kinetics of radiation-induced DNA double-strand breaks (DSB)., Materials and Methods: Stable transfectants of the SV40-transformed hamster cell line CO60 were used: COM3 cells contain a construct to overexpress the poly(ADP-ribose) polymerase (PARP-1) DNA-binding domain (DBD) when induced by dexamethasone, as well as a construct for the constitutive overexpression of the human glucocorticoid receptor (Hg0). COR3 are control cells containing only the Hg0 plasmid. DSB induction and rejoining in X-irradiated cells was assessed by DNA pulsed-field electrophoresis., Results: DSB induction was identical in both cell lines and independent of the presence of dexamethasone. DSB rejoining kinetics was independent of dexamethasone in COR3 cells and identical to COM3 cells without dexamethasone. However, in COM3 cells treated with dexamethasone to induce PARP-1 DBD overexpression, the fast component of the rejoining kinetic was largely reduced, and residual fragmentation increased concomitant with the increased damage fraction in slow rejoining., Conclusions: The results indicate that inhibition of cellular PARP-1 does not affect the rate-limiting step of either fast or slow DSB rejoining. Rather, it appears that absence of poly(ADP-ribosyl)ation due to dominant negative PARP-1 expression induces a shift from rapid to slow DSB rejoining and by this mechanism PARP inhibition may increase the risk of repair failures.

The incidence of non-Hodgkin's lymphoma has been increasing at a rate of 4% per year since 1950; more than 62,000 cases will be diagnosed in the United States in 2000. Diffuse large cell lymphoma (DLCL) is the prototype of curable non-Hodgkin's lymphoma. Empirically designed chemotherapy regimens did not increase the cure rate of 30-40% achieved by the original four-drug regimen introduced in the 1970s [cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)]. We studied the antitumor effects of the CHOP regimen alone or in combination with a unique protein kinase C activator, bryostatin 1, on a xenograft model for resistant DLCL in mice with severe combined immune deficiency (WSU-DLCL2-SCID). In this model, the efficacy of bryostatin 1 given at 75 microg/kg, i.p., alone for 1 or 2 days [B(1x) and B(2x)]was compared with the efficacy of CHOP alone, bryostatin 1 + CHOP (B+CHOP) given concurrently, bryostatin 1 for 1 day followed by CHOP on day 2 [B(1x)-CHOP], and bryostatin 1 for 2 days followed by CHOP on day 3 [B(2x)-CHOP]. CHOP doses were as follows: (a) cyclophosphamide, 40 mg/kg, i.v.; (b) doxorubicin, 3.3 mg/kg, i.v.; (c) vincristine, 0.5 mg/kg, i.v.; and (d) prednisone, 0.2 mg/kg, every day for 5 days, p.o. Tumor growth inhibition (T/C), tumor growth delay (T-C), and log10 kill for B(1x), B(2x), CHOP, B+CHOP, B(1x)-CHOP and B(2x)-CHOP were 49%, 39%, 25.8%, 15.1%, 14.6%, and 12%; 6, 7, 16, 25, 12, and 15 days; and 0.6, 0.5, 2.2, 3.6, 1.7, and 2.0, respectively. To begin elucidating the mechanism whereby bryostatin 1 potentiated the effects of CHOP in the mouse model; we studied the effect of bryostatin 1 on Bax, Bcl-2, and poly(ADP-ribose) polymerase proteins in vitro and in vivo. Bax protein increased in a time-dependent manner without any measurable change in Bcl-2 expression. However, significant cleavage of the preapoptotic marker poly(ADP-ribose) polymerase was not recorded, and the percentage of apoptotic cells detected by flow cytometry increased only slightly (approximately 8%) after 96 h of bryostatin 1 exposure. The in vitro and in vivo results emphasize the superiority of combining bryostatin 1 with the CHOP regimen against the WSU-DLCL2 model. One possible mechanism may be the modulatory effects of bryostatin 1 on the Bax:Bcl-2 family of apoptosis-regulatory proteins. The use of this combination should be further explored clinically in the treatment of lymphoma.

There is evidence that the excessive generation of reactive-oxygen radicals contributes to the brain injury associated with transient, cerebral ischemia. This study investigates the effects of tempol, a small, water-soluble molecule, that crosses biological membranes, on the brain injury caused by bilateral occlusion and reperfusion of both common carotid arteries in the gerbil (BCO). Treatment of gerbils with tempol (30 mg/kg i.p. at 30 min prior to reperfusion and at 1 and 6 h after the onset of reperfusion) reduced the formation of post-ischemic brain oedema. Tempol also attenuated the increase in the cerebral levels of malondialdehyde (MDA) and the hippocampal levels of myeloperoxidase (MPO) caused by cerebral ischemia and reperfusion. The immunohistochemical analysis of the hippocampal region of brains subjected to ischemia-reperfusion exhibited positive staining for nitrotyrosine (an indicator of the generation of peroxynitrite) and poly(ADP-ribose) synthetase (PARS) (an indicator of the activation of this nuclear enzyme secondary to single strand breaks in DNA). In gerbils subjected to BCO, which were treated with tempol, the degree of staining for nitrotyrosine and PARS was markedly reduced. Tempol increased survival and reduced the hyperactivity (secondary to the ischemia-induced neurodegeneration) caused by cerebral ischemia and reperfusion. The loss of neurons from the pyramidal layer of the CA1 region caused by ischemia and reperfusion was also attenuated by treatment of gerbils with tempol. This is the first evidence that the membrane-permeable, radical scavenger tempol reduces the cerebral injury caused by transient, cerebral ischemia in vivo.

The aim of the present study was to investigate the effects of tempol, a membrane-permeable radical scavenger, in rats subjected to splanchnic artery occlusion shock (SAO). Rats subjected to SAO developed a significant decrease in mean arterial blood pressure, a significant increase in tissue myeloperoxidase activity, and a marked injury to the distal ileum. SAO shock resulted in 100% mortality at 2 h after reperfusion. At 60 min after reperfusion, a marked increase in the immunoreactivity to nitrotyrosine and to poly (ADP-ribose) synthetase was observed in the necrotic ileum of rats with SAO. Staining of sections of the ileum obtained from SAO-shocked rats with anti-intercellular adhesion molecule (ICAM-1) and anti-P-selectin antibodies resulted in diffuse staining. Tempol (30 mg/kg bolus injection 5 min prior to reperfusion, followed by an infusion of 30 mg/kg/h intravenously) attenuated 1) the infiltration of the reperfused intestine with neutrophils, 2) the lipid peroxidation, 3) the production of peroxynitrite, 4) the degree of P-selectin and ICAM-1 staining in tissue sections from SAO-shocked rats, 5) histological signs of bowel injury, and 6) mortality at 2 h after reperfusion. Taken together, our results clearly demonstrate that the intracellular radical scavenger tempol reduces the intestinal injury of rats subjected SAO shock.

Background: The generation of reactive oxygen species (ROS) contributes to the pathogenesis of renal ischemia-reperfusion injury. The aim of this study was to investigate the effects of tempol in (1) an in vivo rat model of renal ischemia/reperfusion injury and on (2) cellular injury and death of rat renal proximal tubular (PT) cells exposed to oxidant stress in the form of hydrogen peroxide (H2O2)., Methods: Male Wistar rats underwent bilateral renal pedicle clamping for 45 minutes followed by reperfusion for six hours. Tempol (30 mg/kg/h), desferrioxamine (DEF; 40 mg/kg/h), or a combination of tempol (30 mg/kg/h) and DEF (40 mg/kg/h) were administered prior to and throughout reperfusion. Plasma concentrations of urea, creatinine, Na+, gamma-glutamyl transferase (gammaGT), aspartate aminotransferase (AST), and urinary Na+ and N-acetyl-beta-D-glucosaminidase (NAG) were measured for the assessment of renal function and reperfusion injury. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of nitrotyrosine and poly(ADP-ribose) synthetase (PARS). Primary cultures of rat PT cells were incubated with H2O2 (1 mmol/L for 4 h) either in the absence or presence of increasing concentrations of tempol (0.03 to 10 mmol/L), DEF (0.03 to 10 mmol/L), or a combination of tempol (3 mmol/L) or DEF (3 mmol/L). PT cell injury and death were determined by evaluating mitochondrial respiration and lactate dehydrogenase (LDH) release, respectively., Results: In vivo, tempol significantly reduced the increase in urea, creatinine, gammaGT, AST, NAG, and FENa produced by renal ischemia/reperfusion, suggesting an improvement in both renal function and injury. Tempol also significantly reduced kidney MPO activity and MDA levels, indicating a reduction in PMN infiltration and lipid peroxidation, respectively. Tempol reduced the histologic evidence of renal damage associated with ischemia/reperfusion and caused a substantial reduction in the staining for nitrotyrosine and PARS, suggesting reduced nitrosative and oxidative stress. In vitro, tempol significantly attenuated H2O2-mediated decrease in mitochondrial respiration and increase in LDH release from rat PT cells, indicating a reduction in cell injury and death. Both in vivo and in vitro, the beneficial actions of tempol were similar to those obtained using the Fe2+ chelator DEF. However, coadministration of DEF and tempol did not produce any additional beneficial actions against renal ischemia/reperfusion injury or against oxidative stress-mediated PT cell injury/death., Conclusion: Our results suggest that the membrane-permeable radical scavenger, tempol, reduces the renal dysfunction and injury associated with ischemia/reperfusion of the kidney.

The role of Pseudomonas aeruginosa exotoxin A (ETA) as a virulence factor in the lung infections of cystic fibrosis (CF) patients is not well understood. Transcript-accumulation studies of bacterial populations in sputum reveal high levels of transcription of toxA, which encodes ETA, in some patients with CF. However, in general, tissue damage in the lungs of patients with CF does not seem to be consistent with a high level of expression of active ETA. To address this discrepancy the authors analysed the production and activity of ETA produced by a number of P. aeruginosa CF isolates. One CF isolate, strain 4384, transcribed toxA at levels similar to the hypertoxigenic strain PA103 but produced an ETA with reduced ADP-ribosyltransferase (ADPRT) activity. Complementation in trans of strain 4384 with the wild-type toxA and a mixed toxin experiment suggested the absence of inhibitory accessory factors within this strain. The toxA gene from strain 4384 was cloned and sequenced, revealing only three mutations in the gene, all within the enzymic domain. The first mutation changed Ser-410 to Asn. The second mutation was located within an alpha-helix, altering Ala-476 to Glu. The third mutation, Ser-515 to Gly, was found at the protein surface. To date, Ser-410, Ala-476 and Ser-515 have not been reported to play a role in the ADPRT activity of ETA. However, it may be the combination of these mutations that reduces the enzymic activity of ETA produced by strain 4384. Expression of 4384 toxA and wild-type toxA in an isogenic strain revealed that 4384 ETA had 10-fold less ADPRT activity than wild-type ETA. ETA purified from strain 4384 also demonstrated 10-fold less ADPRT activity as compared to wild-type ETA. Cytotoxicity assays of purified ETA from strain 4384 indicated that the cytotoxicity of 4384 ETA is not reduced; it may be slightly more toxic than wild-type ETA. Analysis of five other CF isolates revealed a similar reduction in ADPRT activity to that seen in strain 4384. Sequence analysis of the enzymic domain of toxA from the five CF strains identified a number of mutations that could account for the reduction in ADPRT activity. These results suggest that some CF isolates produce an ETA with reduced enzymic activity and this may partially explain the pathogenesis of chronic lung infections of CF due to P. aeruginosa.

Poly(ADPR)polymerase (PARP) is a chromatin-associated enzyme with a presumptive role in DNA repair during replication and recovery from strand breaks caused by genotoxic agents. It catalyses the attachment and elongation of ADPribose polymers (pADPR) to a variety of acceptor proteins (including PARP itself, and histones) and is particularly active in the testis where its expression varies according to the stage of germ cell differentiation. PARP degradation is also one of the classic indicators of apoptosis. In this investigation we have examined the effects of heat stress on the adult rat testis with respect to the concentration and activity of PARP, the nature of the pADRP nuclear acceptor proteins, the length of ADPR polymers and the activity of the ADPR depolymerizing enzyme, poly(ADPR)glycohydrolase (PARG). Our results show a significant reduction in the concentration and activity of PARP 4 and 8 days after artificial cryptorchidism, but no significant changes were observed in PARG activity or in pADPR length. Unexpectedly, the apoptotic degradation of PARP was not detected following heat stress. These results confirm that PARP gene expression is developmentally regulated during spermatogenesis and indicate that it is suppressed coincidentally with the loss of meiotic spermatocytes during artificial cryptorchidism.

Poly (ADP-ribose) polymerase (PARP) is an abundant chromatin associated protein important in DNA repair, maintenance of chromosomal stability and programmed cell death. Here we report that an increase in caspase 3-activity and cleavage of PARP serves as an early execution phase signal in human neuroblastoma. Human neuroblastoma SK-N-SH cells were exposed to a protein kinase inhibitor, staurosporine, or a topoisomerase II inhibitor, etoposide, at various concentrations and time points. Cells exposed to staurosporine (0.1 microM) for 30 min showed an increase in caspase 3-activity and by 1 h an increase in PARP 116-kDa band and an 85-kDa cleavage product, which further increased in density with time after treatment. Quantitative analysis for condensed chromatin material using bisbenzimide, and DNA fragmentation enzyme immunoassays showed a significant increase in apoptosis 5 h after staurosporine treatment. This was further confirmed with a Klenow fragment of DNA polymerase I assay which primarily detects single-stranded DNA breaks. A significant decrease in mitochondrial metabolism occurred within 8-12 h after treatment. Studies using Trypan Blue exclusion, and lactic dehydrogenase (LDH) release revealed a significant increase in membrane permeability 8 h after staurosporine (0.1 microM) or etoposide (10 microM) treatments. Cleavage of lamin B1, a protein important in maintaining the nuclear envelope integrity was observed 12 h after staurosporine treatment. Our results show that activation of caspase 3 followed by PARP cleavage occur at much earlier time point than any other morphological or biochemical parameters of apoptosis or cytotoxicity.

Human T-cell leukemia virus type 1 (HTLV-1) encodes a transcriptional activator, Tax, whose activity is believed to contribute significantly to cellular transformation. Tax stimulates transcription from the proviral promoter as well as from promoters for a variety of cellular genes. The mechanism through which Tax communicates to the general transcription factors and RNA polymerase II has not been completely determined. We investigated whether Tax could function directly through the general transcription factors and RNA polymerase II or if other intermediary factors or coactivators were required. Our results show that a system consisting of purified recombinant TFIIA, TFIIB, TFIIE, TFIIF, CREB, and Tax, along with highly purified RNA polymerase II, affinity-purified epitope-tagged TFIID, and semipurified TFIIH, supports basal transcription of the HTLV-1 promoter but is not responsive to Tax. Two additional activities were required for Tax to stimulate transcription. We demonstrate that one of these activities is poly(ADP-ribose) polymerase (PARP), a molecule that has been previously identified to be the transcriptional coactivator PC1. PARP functions as a coactivator in our assays at molar concentrations approximately equal to those of the DNA and equal to or less than those of the transcription factors in the assay. We further demonstrate that PARP stimulates Tax-activated transcription in vivo, demonstrating that this biochemical approach has functionally identified a novel target for the retroviral transcriptional activator Tax.

UV-radiation is a major risk factor for non-melanoma skin cancer causing specific mutations in the p53 tumor suppressor gene and other genetic aberrations. We here propose that elevated temperature, as found in sunburn areas, may contribute to skin carcinogenesis as well. Continuous exposure of immortal human HaCaT skin keratinocytes (possessing UV-type p53 mutations) to 40 degrees C reproducibly resulted in tumorigenic conversion and tumorigenicity was stably maintained after recultivation of the tumors. Growth at 40 degrees C was correlated with the appearance of PARP, an enzyme activated by DNA strand breaks and the level corresponded to that seen after 5 Gy gamma-radiation. Concomitantly, comparative genomic hybridization (CGH) analyis demonstrated that chromosomal gains and losses were present in cells maintained at 40 degrees C while largely absent at 37 degrees C. Besides individual chromosomal aberrations, all tumor-derived cells showed gain of chromosomal material on 11q with the smallest common region being 11q13.2 to q14.1. Cyclin D1, a candidate gene of that region was overexpressed in all tumor-derived cells but cyclinD1/cdk4/cdk6 kinase activity was not increased. Thus, these data demonstrate that long-term thermal stress is a potential carcinogenic factor in this relevant skin cancer model, mediating its effect through induction of genetic instability which results in selection of tumorigenic cells characterized by gain of 11q.

Ewing's sarcoma (EWS) cells accumulate elevated steady-state levels of poly (ADP-ribose) polymerase (PARP) mRNA and protein. To understand the molecular mechanisms underlying PARP upregulation, we cloned and analysed the 5'-flanking region of the PARP gene from EWS cells. Nucleotide sequence analysis demonstrated no variations in the PARP promoter region in EWS cells. The PARP promoter encompasses multiple binding motifs for the ETS transcription factor. We have also observed that there is a coordinated up-regulation of the expression of both PARP and ETS1, relative to cells of other human tumor types expressing lower levels of PARP. Transient co-expression of ETS1 in EWS cells resulted in a strong enhancement of PARP-promoter activity. The participation of ETS in the regulation of PARP gene expression was further demonstrated in EWS cells stably transfected with Ets1 antisense cDNA constructs. Antisense-mediated down-regulation of endogenous ETS1 resulted in the inhibition of PARP expression in EWS cells, and sensitized these cells to ionizing radiation. These data provide support for ETS regulation of PARP expression levels, and implicate ETS transcription factors in the radiation response of EWS cells.

Earlier studies reported that Pseudomonas aeruginosa exoenzyme S (ExoS) possessed an absolute requirement for the eukaryotic protein factor activating exoenzyme S (FAS) for expressing ADP-ribosyltransferase activity. During the characterization of a serum-derived FAS-like activity, we observed the ability of a catalytic deletion peptide of ExoS (DeltaN222) to ADP-ribosylate target proteins in the absence of FAS. Characterization of the activation of DeltaN222 by FAS provided an opportunity to gain insight into the mechanism of ExoS activation by FAS. Under standard enzyme assay conditions, the initial rate of FAS-independent ADP-ribosyltransferase activity of DeltaN222 was not linear with time and rapidly approached zero. Dilution into high-ionic strength buffers stabilized DeltaN222 so it could express FAS-independent ADP-ribosyltransferase activity at a linear rate. This stabilization was a general salt effect, since dilution into a 1.0 M solution of either NaCH3COOH, NaCl, or KCl stabilized the ADP-ribosyltransferase activity of DeltaN222. Kinetic analysis in a high-ionic strength buffer showed that FAS enhanced the catalytic activity of DeltaN222 by increasing the affinity for NAD and stimulating the turnover rate. Velocity experiments indicated that the stabilization of DeltaN222 by high salt was not functionally identical to stabilization by FAS. Together, these data implicate a dual role for FAS in the allosteric activation of ExoS, involving both substrate binding and catalysis.

Poly(ADP-ribose) polymerase (PARP) and DNA-dependent protein kinase (DNA-PK) are important nuclear enzymes that cooperate to minimize genomic damage caused by DNA strand interruptions. DNA strand interruptions trigger the ADP-ribosylation activity and phosphorylation activity of PARP and DNA-PK respectively. In order to understand the relationship of PARP and DNA-PK with respect to DNA binding required for their activation, we analyzed the kinetics of the reactions and determined the apparent dissociation constants (Kd app) of the enzymes for DNA strand interruptions. PARP has a high binding affinity for blunt ends of DNA (Kd app=116 pM) and 3' single-base overhangs (Kd app=332 pM) in comparison to long overhangs (Kd app=2.6-5.0 nM). Nicks are good activators of PARP although the affinity of PARP for nicks (Kd app=467 pM) is 4-fold less than that for blunt ends. The Kd app of DNA-PK for 3' single-base overhangs, blunt ends and long overhangs is 704 pM, 1.3 nM and 1.4-2.2 nM respectively. These results demonstrate that (1) PARP, when compared to DNA-PK, has a greater preference for blunt ends and 3' single-base overhangs but a weaker preference for long overhangs, and (2) nicks are effective in attracting and activating PARP. The possible implications of the preferences of PARP and DNA-PK for DNA strand interruptions in vivo are discussed.

Purpose: The relationship between post-irradiation treatment with Trolox, an antioxidant that inhibits lipid peroxidation, and X-ray-induced apoptosis, with regard to signal transduction pathways, was examined in MOLT-4, a human leukaemia cell line., Materials and Methods: In MOLT-4 cells treated with Trolox after X-irradiation, viability, DNA fragmentation, expression of p53, BCL-2, BAX, active SAPK/JNK, active caspase-3 and the cleavage of PARP were measured by the trypan blue exclusion test, agarose gel electrophoresis and Western blotting., Results: Stained cells and ladder-like DNA cleavage were observed after X-irradiation. Cell death and DNA fragmentation were significantly inhibited by the post-irradiation treatment with Trolox. The expression of p53 and active SAPK/JNK was increased after X-irradiation, and fragments of PARP and the activated fragment of caspase-3 were produced. Post-irradiation treatment with Trolox attenuated the X-irradiation-induced expression, fragmentation or activation of these apoptosis-related biomolecules. The expression of BCL-2 and BAX, which would occur downstream from p53, was not changed by irradiation and Trolox treatment. Furthermore, cell death was associated with caspase-3 because the ladder-like DNA cleavage was completely inhibited by Ac-DEVD-CHO but not Ac-YVAD-CHO, TLCK and PMSF., Conclusion: Post-irradiation events such as membrane damage induce caspase-3-dependent apoptosis, which might be mediated by the activation of SAPK/JNK and be independent of p53.

Purpose: We have previously reported preferential repair of DNA interstrand crosslinks in the 4-hydroperoxycyclophosphamide-resistant human medulloblastoma cell line D-283 Med (4-HCR). We now report further studies that explored the potential mechanisms underlying this repair., Methods: Limiting dilution assays and Western, Southern, and Northern blots were used to compare specific differences between D-283 Med (4-HCR) and its parental line D-283 Med., Results: D-283 Med (4-HCR) was cross-resistant to melphalan and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), with O6-alkylguanine-DNA alkyltransferase (AGT) levels of 466+/-164 fmol/mg protein; AGT levels in the parental line, D-283 Med, were 76+/-96 fmol/mg. The increase in AGT activity was not a result of gene amplification. Depleting AGT with O6-benzylguanine partially restored sensitivity to BCNU. Both cell lines were deficient in the human mismatch protein MutLalpha. ERCC4 mRNA and poly(ADP-ribose) polymerase levels were similar in both cell lines, and ERCC1 mRNA levels were 2- to 2.5-fold lower in D-283 Med (4-HCR). Topoisomerase I levels were 2- to 2.5-fold higher in D-283 Med compared with D-283 Med (4-HCR)., Conclusion: These results, while illustrating the multiple differences between D-283 Med and D-283 Med (4-HCR), do not explain the enhanced DNA interstrand crosslink repair seen in D-283 Med (4-HCR).

We here report an alternatively spliced form of PARP lacking exon 5 of the Drosophila PARP gene encoding the auto-modification domain. The alternative form of PARP (PARP II) consists 804 amino acids with a molecular weight of 92.3 kDa. The deduced amino acid sequence of PARP II was completely matched to that of PARP I encoded by a full-length Drosophila PARP cDNA, except it lacks the region corresponding to the auto-modification domain. To examine the function of PARP II, stable transformants of Rat-1 cells in which PARP II was ectopically expressed by MMTV-LTR were isolated and characterized. After induction with dexamethasone, PARP II transformants showed slower growth and showed morphological changes with loss of spindled shape compared to cells transformed with the vector or PARP I. The PARP II-transformed cells incorporated propidium iodide after induction; however, Annexin V and TUNEL analysis indicated these changes were not due to apoptosis., (Copyright 1998 Academic Press.)

The human leukemia U937 cells differentiate into monocyte/macrophage-like cells when treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). We observed that during this process, both protein and mRNA levels for PARS markedly decreased in U937 cells. Through deletion analysis of the PARS regulatory gene, we found that the sequence within the first intron region was responsible for the TPA-dependent repression. Electrophoretic mobility shift assays (EMSAs) and Southwestern blot analysis indicate that this element bound specifically to a nuclear protein. TPA treatment abolished the binding of the protein in U937 cells but not in HeLa cells. DNase I footprinting data show that the cis regulatory element is located between residues 328 and 383. We further examined the function of this cis element (BS207) in a basal promoter regulatory reporter construct and found that this cis element (BS207) functions as an enhancer via the binding of an unknown trans-acting factor. TPA treatment diminished the binding activity of the factor in U937 cells, resulting in a decrease in the enhanced activity to the basal level. These results suggest that abolishment of the binding of a special nuclear protein to the first intron of the PARS gene is related to the TPA-responsive downregulation of PARS in U937 cells.

Two peroxisome proliferators, [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid (Wy-14,643) or di(2-ethylhexyl) phthalate (DEHP), were given orally to male F-344 rats for up to 78 or 97 weeks. At 1 week, the activity of poly(ADP-ribose) polymerase (pADPRP) was increased 2- and 1.8-fold in the liver of rats treated with Wy-14,643 and DEHP, respectively. The induction of the activity was maintained at 2.5- or 2-fold for up to 52 weeks. The immunoblot and Northern blot analyses revealed that the induction of pADPRP activity would be responsible for the increase in the amount of mRNA. In addition, in the liver tumor induced by Wy-14,643 and DEHP, the pADPRP mRNA level increased 3.6- or 3.7-fold. The magnitude of the increase in the mRNA level was higher than that in the non-tumor portion. These findings suggest that the induction of pADPRP may play an important role in the hepatocarcinogenesis induced by peroxisome proliferators.

ADP-ribosyltransferase (ADPRT) is a glycosylphosphatidylinositol-anchored cell surface enzyme on CTL. Expression of this enzyme correlates with suppression of CTL functions in the presence of its substrate beta-nicotinamide adenine dinucleotide (NAD). To investigate the immunoregulatory importance of ADPRT on normal lymphocytes in vivo, NAD was injected into mice and the effects on cell-mediated and humoral immunity were assessed. Induction of both delayed-type hypersensitivity and CTL, but not Ab responses, are shown to be suppressed by NAD. Consistent with this, mature T cells, but not B cells or macrophages, express ADPRT and are able to ADP-ribosylate cell surface proteins. ADP-ribosylated molecules were identified as LFA-1, CD8, CD27, CD43, CD44, and CD45. Concomitant to ADP-ribosylation of these molecules, T cell trafficking to secondary lymphoid organs is suppressed by NAD. To examine whether this is due to effects of NAD on cell activation, Ag-stimulated responses were assayed in vitro. NAD is shown to inhibit induction of cell proliferation, cytotoxicity, and cytokine secretion. It is suggested that ADPRT regulates T cells on the level of transmembrane signaling via ADP-ribosylation of cell surface molecules. This effect is reported to be indirect, as it involves transmission of signals through TCRs, which are not ADP-ribosylated.

We examined the timing of apoptosis and the expression of the DNA repair proteins poly(ADP-ribose) polymerase (PARP) and Ku80 in sections of frontal and temporal lobes from patients who had suffered severe brain ischaemia due to a cardiac arrent. In situ end-labelling (ISEL) was used to detect apoptotic cells, and immunohistochemistry to assess PARP and Ku80. ISEL of scattered neurons and glia was demonstrable predominantly during the first 24 h after ischaemia. PARP and Ku80 immunoreactivity increased markedly after cerebral ischaemia, PARP particularly in the regions of greatest susceptibility to hypoxic injury: the CA1 field of the hippocampus and the depths of neocortical sulci. The up-regulation of PARP is in keeping with experimental observations concerning the key role of this enzyme in mediating ischaemic cell death.

In order to investigate the radioresistance mechanism of human carcinoma cells, we measured intracellular manganese- (Mn-) and copper/zinc- (Cu/Zn-) superoxide dismutases (SODs), glutathione (GSH) and poly (ADP-ribose) polymerase (PARP) in radioresistant N10 and its parental KB cell lines. The Mn-SOD level was 1.3-fold less in N10 than in KB, but Mn-SOD was induced at 1.3 to 1.5-fold higher level in N10 than in KB by X-irradiation (4 Gy). Cu/Zn-SOD in N10 showed a higher level than that in KB both without and with irradiation. In addition, N10 had a 1.65-fold higher GSH level than did KB and became radiosensitive on treatment with buthionine sulfoximine, an inhibitor of GSH. Furthermore, PARP mRNA was highly expressed in N10 as compared to KB under unirradiated conditions. X-Irradiation reduced the PARP mRNA level in KB in a time-dependent manner, whereas the PARP mRNA level in N10 was still high at 6 h postirradiation. Assay for PARP activity demonstrated an approximately 3-fold higher activity in N10 than in KB under unirradiated conditions. X-Irradiation caused a rapid induction of PARP activity within 1 h in both cell lines, but treatment of cells with nicotinamide, a PARP inhibitor, markedly reduced the enzyme induction in N10, but not in KB, and potentiated the radiosensitivity in N10. These factors may all contribute to the radioresistance of the N10 cell line.

The tumor suppressor gene p53 is expressed in the contrasting cell fates apoptosis and proliferation. We examined whether the transactivation of the p53 target genes, waf1 and mdm2, is dependent on the cause of p53 induction in human peripheral blood mononuclear cells (PBMC). Both apoptosis triggered by the purine analog 2-chlorodeoxyadenosine (CdA) and growth stimulation by the mitogen phytohemagglutinin (PHA) induced a comparable level and time course of p53 mRNA expression. Both stimuli led also to an increase of p53 protein levels. The cytotoxic agent, but not the mitogen, led to transactivation of waf1 and mdm2 within 18 h. Transactivation was followed by apoptosis of 89% of the PBMC within 48 h. The c-myc oncogene and poly(ADP-ribose)polymerase (PARP), which also have a dual function in proliferation and apoptosis, showed an early induction by both CdA and PHA. These results add further evidence that growth stimulation and DNA damage-induced apoptosis share early gene activation pathways in normal cells. However, since p53 does selectively translate into transactivation of target genes depending on the cause of induction, this function of p53 seems to be regulated by additional factors, which are closely related to the ultimate fate of the cell.

Several proteins with NAD+:arginine ADP-ribosyltransferase (ART) activity are expressed in T cells and affect their function. Rat T cells that express the ART designated RT6 are determinants of the expression of autoimmune diabetes. In the mouse, a 35-kDa ecto-ART modulates the proliferation and functional activity of CTL. Here we report on mouse ARTs designated Rt6-1 and Rt6-2 in BALB/c and C57BL/6 mice. mRNAs for Rt6-1 and Rt6-2 were found in spleen, thymus, and intestinal tissue of both strains, but Rt6-1 mRNA in C57BL/6 mice was detected only at low levels. Rt6-1 and Rt6-2 cDNAs from both strains were cloned and sequenced. Predicted amino acid sequences of Rt6-2 were identical in both strains, but there was an in-frame stop codon in the sequence of Rt6-1 in C57BL/6 mice not present in BALB/c mice. Recombinant C57BL/6 Rt6-2 and BALB/c Rt6-1 proteins expressed in COS1 cells exhibited ART activity and were documented to be glycosylphosphatidylinositol-linked membrane proteins. COS-1 cells transfected with a C57BL/6 Rt6-1 cDNA construct expressed a truncated protein consistent in size with that predicted by the presence of the stop codon. This approximately 21-kDa protein appeared not to be glycosylphosphatidylinositol linked to the cell surface and lacked ART activity. C57BL/6 Rt6-1 therefore appears to be a naturally occurring ART knockout. The expression of Rt6-1 and Rt6-2 mRNAs in lymphoid tissues suggests that these ARTs may regulate immune system functions. Expression of Rt6-2 or another redundant ART may compensate for the lack of enzymatically active Rt6-1 in C57BL/6 mice.

Mature T cells are susceptible to activation-induced cell death in the periphery. Activation-induced cell death is thought to involve CD95/CD95 ligand interactions in vivo. Here we report that stimulated, CD45RO+ human T cell lines specific for myelin basic protein or tetanus toxoid from multiple sclerosis patients and healthy individuals resist apoptosis induced by soluble recombinant CD95 ligand in vitro. In contrast, the same CD95 ligand effectively kills Jurkat T lymphoma and human malignant glioma cells. The resistance of the T cell lines is not due to a lack of CD95 expression at the cell surface and is not overcome by coexposure to CD95 ligand and inhibitors of RNA or protein synthesis. The expression level of BCL-2 is lower in Jurkat than in Ag-specific T cells. After exposure to soluble CD95 ligand, Jurkat T cells, but not Ag-specific T cells, exhibit loss of BCL-2 and BCL-X expression whereas BAX expression is not affected. Surprisingly, Ag-specific T cells are rather sensitive to CD95 ligand expressed at the cell surface of N2A neuroblastoma cells. Accessory molecules expressed by the CD95 ligand-expressing effector cell are dispensable for apoptosis since the T cells are equally sensitive to agonistic APO-1 Ab. Further studies are required to determine whether resistance to soluble CD95 ligand-mediated apoptosis is a possible escape mechanism for T cells from peripheral deletion that may have relevance for autoimmune disorders.

The importance of a genetic polymorphism (A/B allele) of poly(ADP-ribose) polymerase (PARP) pseudogene on chromosome 13q34-qter, and PARP enzyme activities in the development of human breast cancer were evaluated in a cancer case-control study. A total of 309 Caucasian women (> or = 50 years old) were evaluated for the PARP genotype, 70 of whom had histologically confirmed breast cancer, 128 women with benign breast diseases as study controls, and 111 reference controls. Age was significantly associated with case-control status (p < 0.0001), but family history of breast cancer, age at menarche, age at first live birth and parity were not. The frequency of the PARP B allele was similar in breast cancer cases (0.14), study controls (0.13), and reference controls (0.15). In a subset of 14 breast cancer cases and 32 study controls, the mean PARP enzyme activities (induced by H2O2 or oligonucleotide) were observed to be lower in cancer cases; an age-adjusted odds ratio of 3.40 (95% confidence interval = 0.70-19.54) for the below-median oligonucleotide-induced PARP was suggestive of an association. In subjects with the AB or BB genotype, the mean H2O2-induced PARP enzyme activity was significantly higher (p = 0.02, adjusted for case-control status and age) compared with that in subjects with the AA genotype. These findings indicate that: (a) the genetic polymorphism of the PARP pseudogene on chromosome 13 is not associated with the development of breast cancer in our study population; (b) oligonucleotide-induced PARP activity may be useful for identifying postmenopausal women at increased risk for breast cancer; and (c) there is a possible functional link between the genotype of the PARP pseudogene and enzyme activation.

The effect of administration into rats of cycloheximide on the expression of genes, such as tissue transglutaminase, testosterone-repressed prostate message-2, Fas antigen, bcl-2, DNase I, and poly(ADP-ribose) polymerase, which were believed to be involved in the mechanism of apoptosis, was studied. While the effect of cycloheximide on the expression of genes other than Fas antigen was modest, only the expression of Fas antigen was elevated rapidly in most of the organs examined. A possible direct effect of cycloheximide on cells per se to induce Fas antigen mRNA expression was demonstrated by the tissue culture study using L929 fibroblast cells, although the magnitude of the induction detected in vitro was small compared with that in vivo. This induction of Fas antigen mRNA by cycloheximide is a first report on the modulation of Fas antigen mRNA expression in vivo.

Many cellular enzymes use NAD+ as coenzyme or substrate, depending on the nature of the enzymatic reaction. Under certain conditions the cellular NAD+ concentration may become rate-limiting for such enzymes. For instance, when eucaryotic cells are exposed to high concentrations of DNA-damaging agents, the resulting DNA strand breaks may stimulate the nuclear enzyme poly(ADP-ribose) polymerase (PARP) to such an extent that the cellular pool of NAD+, which is the substrate for this enzyme, is severely depleted, possibly leading to acute cell death. Here we show that NAD+ concentrations in CV-1 monkey and CO60 hamster cells can be raised 3- to 4-fold by electrotransfection of NAD+. This additional NAD+ is indeed available for PARP to synthesize higher-than-normal amounts of poly(ADP-ribose) after treatment with the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine. NAD+ loading of cells by electrotransfection may be useful also for the study of other cellular reactions in which NAD+ is involved.

A Clostridium difficile isolate was found to produce an actin-specific ADP-ribosyltransferase (CDT) homologous to the enzymatic components of Clostridium perfringens iota toxin and Clostridium spiroforme toxin (M. R. Popoff, E. J. Rubin, D. M. Gill, and P. Boquet, Infect. Immun. 56:2299-2306, 1988). The CDT locus from C. difficile CD196 was cloned and sequenced. It contained two genes (cdtA and cdtB) which display organizations and sequences similar to those of the iota toxin gene. The deduced enzymatic (CDTa) and binding (CDTb) components have 81 and 84% identity, respectively, with the corresponding components of iota toxin. CDTa and CDTb induced actin cytoskeleton alterations similar to those caused by other clostridial binary toxins. The lower level of production of binary toxin by CD196 than of iota toxin by C. perfringens was related to a lower transcript level, possibly due to a promoter region different from that of iota toxin genes. The cdtA and cdtB genes have been detected in 3 of 24 clinical isolates examined, and cdtB alone was found in 2 additional strains. One strain (in addition to CD196) was shown by Western blotting to produce CDTa and CDTb. These results indicate that some C. difficile strains synthesize a binary toxin that could be an additional virulence factor.