Novel Targets and Precision Medicine for Prostate Cancer-Part 2: Tumor Profiling and Personalized Therapy in Patients With Castration-Resistant Prostate Cancer

Despite advances in the treatment of castration-resistant prostate cancer (CRPC), options remain limited and non-curative; thus, prostate cancer remains one of the deadliest cancers in men. The discovery of novel therapeutic targets is needed to improve outcomes for men with metastatic CRPC. Precision/personalized medicine creates new opportunities to discover these targets. With an increase in the use of next-generation sequencing and tumor profiling, potentially clinically relevant tumor mutations are being identified. Here, we review the current use of and future direction for genetic testing and tumor profiling in patients with metastatic CRPC.

Iduna protects the brain from glutamate excitotoxicity and stroke by interfering with poly(ADP-ribose) polymer-induced cell death

Glutamate acting on N-methyl-D-aspartate (NMDA) receptors induces neuronal injury following stroke, through activation of poly(ADP-ribose) polymerase-1 (PARP-1) and generation of the death molecule poly(ADP-ribose) (PAR) polymer. Here we identify Iduna, a previously undescribed NMDA receptor-induced survival protein that is neuroprotective against glutamate NMDA receptor-mediated excitotoxicity both in vitro and in vivo and against stroke through interfering with PAR polymer-induced cell death (parthanatos). Iduna's protective effects are independent and downstream of PARP-1 activity. Iduna is a PAR polymer-binding protein, and mutation at the PAR polymer binding site abolishes the PAR binding activity of Iduna and attenuates its protective actions. Iduna is protective in vivo against NMDA-induced excitotoxicity and middle cerebral artery occlusion-induced stroke in mice. To our knowledge, these results define Iduna as the first known endogenous inhibitor of parthanatos. Interfering with PAR polymer signaling could be a new therapeutic strategy for the treatment of neurologic disorders.

New advances in ovarian cancer

Epithelial ovarian cancer is the leading cause of death from gynecologic malignancy in the United States, with approximately 15,000 deaths per year. Platinum/taxane doublets have long been considered the standard treatment regimen for advanced-stage disease; however, recent studies have sought to improve on the outcome from this therapy. Intraperitoneal (IP) chemotherapy has been shown to yield superior progression-free survival (PFS) and overall survival (OS); however, logistical problems and toxicities have limited more widespread adoption. Recent studies have also suggested that a "dose-dense" schedule of paclitaxel in combination with carboplatin may result in improved outcomes, and the impact of biological therapies in the first-line setting is under active investigation. In the setting of recurrent disease, preliminary results suggest that novel doublet regimens such as carboplatin and pegylated liposomal doxorubicin may have similar activity to standard platinum/taxane doublets while carrying a reduced risk of allergic reactions. Additionally, targeted therapy remains an active area of investigation, with evidence of activity from agents such as PARP inhibitors, anti-angiogenics, and PI3 kinase inhibitors. Here, we review recent advances in our understanding of ovarian cancer and its treatment in both the newly diagnosed and recurrent settings.

Prolonged exposures of cerebellar granule neurons to S-nitroso-N-acetylpenicillamine (SNAP) induce neuronal damage independently of peroxynitrite

Nitric oxide (NO) induces cell proliferation or cell death, depending on the cell type involved, the isoform of nitric oxide synthase activated, and its cellular localisation. In neurons, the damaging effect of NO is usually attributed to the highly toxic peroxynitrite, formed by its reaction with superoxide. Peroxynitrite induces DNA damage and consequently the activation of poly (ADP-ribose) polymerase (PARP). This study set out to examine the contribution of peroxynitrite to the damage induced in cerebellar granule neurons (CGNs) by treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), for short (6 h) or prolonged (24 h) exposures. The Alamar blue assay was used to quantify CGN viability, which was also assessed by morphological examination. SNAP (10 microM-1 mM) induced a concentration- and time-dependent reduction of CGN viability, with associated damage to cell bodies and neurite processes evident following 100 microM SNAP treatments. Damage from 6 h exposures was prevented by the presence of haemoglobin (a NO scavenger), uric acid (a peroxynitrite scavenger), melatonin (a non-specific antioxidant), and by cyclosporin A (a permeability transition pore blocker). It was reduced by the PARP-1 inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), whilst superoxide dismutase (SOD) potentiated the effects. Following 24 h exposure to SNAP, damage was only partially blocked by haemoglobin, melatonin, cyclosporin A and DPQ, but was not affected by uric acid or SOD. The data suggest that short exposure to NO induces neuronal damage through peroxynitrite produced by its interaction with superoxide, whereas a longer exposure to NO can induce damage partly by a mechanism which is independent of peroxynitrite formation.

Renoprotective and antihypertensive effects of S-allylcysteine in 5/6 nephrectomized rats

Progressive renal damage and hypertension are associated with oxidative and nitrosative stress. On the other hand, S-allylcysteine (SAC), the most abundant organosulfur compound in aged garlic extract (AG), has antioxidant properties. The effects of SAC and AG on blood pressure, renal damage, and oxidative and nitrosative stress were studied in five-sixths nephrectomized rats treated with SAC (200 mg/kg ip) and AG (1.2 ml/kg ip) every other day for 30 days. Proteinuria and serum creatinine and blood urea nitrogen concentrations were measured on days 0, 5, 10, 15, and 30, and systolic blood pressure was recorded on days 0, 15, and 30. The degree of glomerulosclerosis and tubulointerstitial damage, the immunostaining for inducible nitric oxide synthase, 3-nitrotyrosine, poly(ADP-ribose), and the subunits of NADPH oxidase p22phox and gp91phox, and the activity of SOD were determined on day 30. SAC and AG reduced hypertension, renal damage, and the abundance of inducible nitric oxide synthase, 3-nitrotyrosine, poly(ADP-ribose), p22phox, and gp91phox and increased SOD activity. Our data suggest that the antihypertensive and renoprotective effects of SAC and AG are associated with their antioxidant properties and that they may be used to ameliorate hypertension and delay the progression of renal damage.

Poly(ADP-ribose) polymerase inhibition combined with irradiation: a dual treatment concept to prevent neointimal hyperplasia after endarterectomy

PURPOSE

In a rat model of endarterectomy we investigated the potential role of the peroxynitrite-poly(ADP-ribose) polymerase (PARP) pathway in neointima formation and the effects of irradiation, pharmacologic inhibition of PARP, or combined pharmacologic inhibition of PARP and irradiation on vascular remodeling.

METHODS AND MATERIALS

Carotid endarterectomy was performed by incision of the left carotid artery with removal of intima in Sprague-Dawley rats. Six groups were studied: sham-operated rats (n = 10), control endarterectomized rats (n = 10), or endarterectomized rats irradiated with 15 Gy (n = 10), or treated with PARP inhibitor, INO-1001 (5 mg/kg/day) (n = 10), or with combined treatment with INO-1001 and irradiation with 5 Gy (n = 10) or with 15 Gy (n = 10). After 21 days, neointima formation and vascular remodeling were assessed.

RESULTS

Neointima formation after endarterectomy was inhibited by postoperative irradiation with 15 Gy and was attenuated by PARP inhibition. However, in parallel to inhibition of neointimal hyperplasia, activation of the peroxynitrite-PARP pathway in the outer vessel wall layers was triggered by postoperative irradiation. Combined pharmacologic PARP inhibition and irradiation with 15 Gy significantly reduced both neointimal hyperplasia and activation of the peroxynitrite-PARP pathway in the outer vessel wall layers. Combination of PARP inhibition and irradiation with 5 Gy was less effective than both PARP inhibition or irradiation with 15 Gy alone.

CONCLUSIONS

We conclude, that combined PARP inhibition and irradiation with 15 Gy may be a new dual strategy for prevention of restenosis after surgical vessel reconstruction: combining the strong antiproliferative effect of irradiation and ameliorating irradiation-induced side effects caused by excessive PARP activation.

Blockade of PARP activity attenuates poly(ADP-ribosyl)ation but offers only partial neuroprotection against NMDA-induced cell death in the rat retina

Recent reports have linked neuronal cell death by necrosis to poly(ADP-ribose) polymerase-1 (PARP-1) hyperactivation. It is believed that under stress, the activity of this enzyme is up-regulated, resulting in extensive poly(ADP-ribosyl)ation of nuclear proteins, using NAD(+) as its substrate, which, in turn, leads to the depletion of NAD(+). In efforts to restore the level of NAD(+), depletion of ATP occurs, resulting in the shutdown of ATP-dependent ionic pumps. This results in cell swelling and eventual loss of membrane selectivity, hallmarks of necrosis. Reports from in vitro and in vivo studies in the brain have shown that NMDA receptor activation stimulates PARP activity and that blockade of the enzyme provides substantial neuroprotection. The present study was undertaken to determine whether PARP activity is regulated by NMDA in the rat retina, and whether blockade of PARP activity provides protection against toxic effects of NMDA. Rat retinas exposed to intravitreal injections containing NMDA, with or without the PARP inhibitor N-(6-oxo-5, 6-dihydrophenanthridin-2-yl)-(N,-dimethylamino) acetamide hydrochloride (PJ-34), were assessed for changes in PARP-1 activity as evidenced by poly(ADP-ribosyl)ation (PAR), loss of membrane integrity, morphological indicators of apoptosis and necrosis, and ganglion cell loss. Results showed that: NMDA increased PAR formation in a concentration-dependent manner and caused a decline in retinal ATP levels; PJ-34 blockade attenuated the NMDA-induced formation of PAR and decline in ATP; NMDA induced the loss of membrane selectivity to ethidium bromide (EtBr) in inner retinal neurons, but loss of membrane selectivity was not prevented by blocking PARP activity; cells stained with EtBr, or reacted for TUNEL-labeling, displayed features characteristic of both apoptosis and necrosis. In the presence of PJ-34, greater numbers of cells exhibited apoptotic features; PJ-34 provided partial neuroprotection against NMDA-induced ganglion cell loss. These findings suggest that although blockade of PARP activity fully attenuates NMDA-induced PAR formation and loss of retinal ATP content, and improves the survival of select populations of ganglion cells, this approach does not provide full neuroprotection. In contrast, blockade of PARP activity promotes apoptotic-like cell death in the majority of cells undergoing cell death. Furthermore, these studies show that the loss of membrane selectivity is not dependent upon PAR formation or the resulting decline of ATP, and suggests that an alternative pathway, other than PARP activation, exists to mediate this event.

Nitric oxide reverses endotoxin-induced inflammatory hyperalgesia via inhibition of prostacyclin production in mice

We examined whether nitric oxide (NO), derived from constitutive NO synthase (NOS) and/or inducible NOS (iNOS), could contribute to endotoxin-induced inflammatory hyperalgesia via interacting with nuclear factor-kappaB (NF-kappaB), inducible cyclooxygenase (COX-2) and/or polyADP-ribose synthase (PARS). Injection of endotoxin (10 mg kg(-1), i.p.) to mice elicited hyperalgesia, determined by hot plate test, which is prevented by NO precursor (L-arginine), cNOS/iNOS inhibitor (N(G)-nitro-L-arginine methyl ester; L-NAME), NF-kappaB inhibitor (N-acetylserotonin), COX inhibitor (indomethacin), COX-2 inhibitor (DFU) and PARS inhibitor (3-aminobenzamide). Endotoxin caused a decrease in serum nitrite levels prevented by N-acetylserotonin, L-arginine, indomethacin, DFU or 3-aminobenzamide. Endotoxin increased serum 6-keto-PGF(1alpha) levels diminished by L-arginine or aminoguanidine (iNOS inhibitor). L-Arginine, L-NAME, aminoguanidine, DFU or 3-aminobenzamide prevented endotoxin-induced decrease in heart, lungs, kidneys and brain nitrite and malonedialdehyde levels and myeloperoxidase activity. In conclusion, NO reverses endotoxin-induced inflammatory hyperalgesia via inhibition of prostacyclin production, and also contributes to the analgesic effect of NF-kappaB, COX or PARS inhibitors.

Benzamide and 4-amino 1,8 naphthalimide treatment inhibit telomerase activity by down-regulating the expression of telomerase associated protein and inhibiting the poly(ADP-ribosyl)ation of telomerase reverse transcriptase in cultured cells

To test the role of poly(ADP-ribose) polymerase on the telomerase activity, we determined the telomerase activity in leukemic cells K562 treated with benzamide and 4-amino 1,8 naphthalimide (NAP), the inhibitors of PARP. We observed that both the agents inhibited telomerase activity in a dose-dependent manner. The doses of benzamide and NAP that inhibited telomerase activity to 50% of untreated control cells were 10.7 +/- 0.6 mm and 200 +/- 7 microm, respectively. Benzamide treatment (10 mm) inhibited telomerase activity in a time-dependent manner. We also tested the ability of benzamide to inhibit the telomerase activity in Chinese hamster V79 cells and observed similar inhibition of the telomerase activity. Expression of telomerase reverse transcriptase (TERT) and telomerase RNA component, detected by RT-PCR, remained unaltered by treatment with benzamide or NAP. On the contrary, the expression of telomerase associated protein (TEP1/TP1), as detected by RT-PCR and western blot analysis, was reduced by both the agents. Further, in K562 cells, immunoprecipitation with the anti-TERT IgG and probed anti-poly (ADP-ribose) IgG revealed that TERT was poly(ADP-ribosyl)ated in the physiological condition of cell growth and such poly(ADP-ribosyl)ation was inhibited by benzamide treatment. Decrease in TEP1/TP1 expression and poly(ADP-ribosyl)ation of TERT were correlated with the inhibition of PARP activity by benzamide, indicating that PARP had a role in telomerase activity through poly(ADP-ribosyl)ation of TERT and down-regulation of TEP1/TP1.

Determination of apoptosis, uracil incorporation, DNA strand breaks, and sister chromatid exchanges under conditions of thymidylate deprivation in a model of BER deficiency

Thymidylate synthase (TS) is an important target of several chemotherapeutic agents. During TS inhibition, dTTP levels decrease with a subsequent increase in dUTP. Uracil incorporated into the genome is removed by base excision repair (BER). BER has been hypothesized to play a role in the response to thymidylate deprivation, despite a lack of direct evidence. We previously found that beta-pol null murine fibroblasts were approximately six-fold more resistant than wild-type cells to raltitrexed, a folate-based inhibitor specific for TS. In this study, a number of endpoints were determined to understand the influence of BER and beta-pol during raltitrexed treatment. Raltitrexed induced apoptosis in wild-type cells to a greater extent than in beta-pol null cells. A PARP inhibitor decreased the sensitivity to raltitrexed, although the extent was not different between wild-type and beta-pol null cells. No evidence was seen for extensive strand break formation that preceded apoptosis, although raltitrexed induced more sister chromatid exchanges in wild-type cells. Increased levels of uracil in DNA were detected following treatment in wild-type and beta-pol null cells. However, uracil levels were only approximately two-fold higher in DNA from treated cells compared to untreated. Uracil DNA glycosylase activity was slightly higher in beta-pol null cells, although not sufficiently different to explain the difference in sensitivity to raltitrexed. Taken together, the data suggest that the sensitivity of the wild-type cells to raltitrexed is not associated with activation of PARP-1 dependent BER, extensive uracil incorporation into DNA and persistent strand breaks, but rather with changes suggestive of DNA recombination.

Polyadenosine diphosphate-ribose polymerase inhibition modulates skeletal muscle injury following ischemia reperfusion

HYPOTHESIS

Polyadenosine diphosphate-ribose polymerase (PARP) has been implicated as a mediator of inflammation and tissue necrosis in murine models of human stroke and myocardial infarction. This study was designed to determine whether PARP modulates skeletal muscle injury and cytokine-growth factor levels during ischemia-reperfusion.

DESIGN

Prospective controlled animal study.

SETTING

Medical school-affiliated university hospital.

INTERVENTIONS

Mice were divided into 2 groups-treated (PJ) and untreated; all mice were subjected to unilateral hind limb tourniquet ischemia followed by 4 or 48 hours of reperfusion. In treated mice, PJ34, an ultrapotent-specific PARP inhibitor was given immediately before ischemia and prior to reperfusion. A group of PARP-1 knockout mice (PARP-/-) were also subjected to hind limb ischemia followed by 48 hours of reperfusion.

MAIN OUTCOME MEASURES

After ischemia-reperfusion, muscle was harvested for measurement of edema, viability, cytokine, and vascular endothelial growth factor content.

RESULTS

The PJ34-treated mice had increased skeletal muscle viability when compared with the untreated mice after 4 and 48 hours of reperfusion (P<.01). Viability between PARP-/- and PJ34-treated mice were similar at 48 hours of reperfusion (P>.05), and it exceeded that of untreated mice (P<.01). Tissue edema was unaltered by PARP inhibition. Tissue levels of cytokine were only different (P<.05) in PJ34-treated vs untreated mice at 48 hours of reperfusion. Vascular endothelial growth factor levels in PJ34-treated mice were markedly reduced when compared with untreated mice only after 4 hours of reperfusion (P<.01), and in PARP-/- mice (P<.01) at 48 hours of reperfusion.

CONCLUSIONS

Polyadenosine diphosphate-ribose polymerase modulates skeletal muscle viability, cytokine and vascular endothelial growth factor synthesis during reperfusion. Polyadenosine diphosphate-ribose polymerase inhibition may represent a novel method to modulate skeletal muscle ischemia-reperfusion injury.

Effect of poly(ADP-ribosyl)ation inhibitors on the genotoxic effects of the boron neutron capture reaction

The boron neutron capture (BNC) reaction results from the interaction of 10B with low-energy thermal neutrons and gives rise to highly damaging lithium and alpha-particles. In this work the genotoxicity caused by the BNC reaction in V79 Chinese hamster cells was evaluated in the presence of poly(ADP-ribosyl)ation inhibitors. Poly(ADP-ribose) polymerase-1 (PARP-1), the most important member of the PARP enzyme family, is considered to be a constitutive factor of the DNA damage surveillance network present in eukaryotic cells, acting through a DNA break sensor function. Inhibition of poly(ADP-ribosyl)ation was achieved with the classical compound 3-aminobenzamide (3-AB), and with two novel and very potent inhibitors, 5-aminoisoquinolinone (5-AIQ) and PJ-34. Dose-response increases in the frequencies of aberrant cells excluding gaps (%ACEG) and chromosomal aberrations excluding gaps per cell (CAEG/cell) were observed for increasing exposures to the BNC reaction. The presence of 3-AB did not increase the %ACEG or CAEG/cell, nor did it change the pattern of the induced chromosomal aberrations. Results with 5-AIQ and PJ-34 were in agreement with the results obtained with 3-AB. We further studied the combined effect of a PARP inhibitor and a DNA-dependent protein kinase (DNA-PK) inhibitors (3-AB and wortmannin, respectively) on the genotoxicity of the BNC reaction, by use of the cytokinesis-block micronucleus assay. DNA-PK is also activated by DNA breaks and binds DNA ends, playing a role of utmost importance in the repair of double-strand breaks. Our results show that the inhibition of poly(ADP-ribosyl)ation does not particularly modify the genotoxicity of the BNC reaction, and that PARP inhibition together with a concomitant inhibition of DNA-PK revealed barely the same sensitizing effect as DNA-PK inhibition per se.

Role of the activation of the nuclear enzyme poly(ADP-ribose) polymerase in the pathogenesis of periodontitis

We have investigated the role of the activation of nuclear poly(ADP-ribose) polymerase (PARP) enzyme, a mediator of downstream nitric oxide toxicity, using a combined approach of pharmacological inhibition and genetic disruption in a ligature-induced-periodontitis model in rats and mice. Immunohistochemical analysis revealed significantly increased poly(ADP-ribose) nuclear staining (indicative of PARP activation) in the subepithelial connective tissue of the ligated side compared with the non-ligated side. Ligation-induced periodontitis resulted in marked plasma extravasation in the gingivomucosal tissue and led to alveolar bone destruction compared with the non-ligated side, as measured by the Evans blue technique and by videomicroscopy, respectively. PARP inhibition with PJ34, as well as genetic PARP-1 deficiency, significantly reduced the extravasation and the alveolar bone resorption of the ligated side compared with controls. Thus, PARP activation contributes to the development of periodontal injury. Inhibition of PARP may represent a novel host response modulatory approach for the therapy of periodontitis.

Effects 3-aminobenzamide on ultrastructure of hippocampal CA1 layer after global ischemia in gerbils

Poly(ADP-ribose) polymerase (PARP EC 2.4.2.30) is a key enzyme in the DNA repair machinery, but its excessive stimulation during reperfusion after ischemia could play a critical role in cell death. Our previous study indicated that the PARP inhibitor 3-aminobenzamide (3-AB) significantly protected neuronal cells against death after a short ischemic insult. In this study we investigated the effect of 3-AB on the ischemia-evoked alterations in intracellular organelles. Gerbils were submitted to 3 min of transient forebrain ischemia followed by reinstitution of recirculation for 1-7 days. Electron microscopy showed only the signs of necrotic cell death after ischemia-reperfusion. The examination of specimens revealed a pronounced protective effect of 3-AB on the swelling of astrocytes and neurons 1 day after the ischemic insult. 3-AB also decreased the swelling of pericytes, but it had no effect on the accumulation of osmiophilic inclusions and fibril formation in astrocytes. 3-AB decreased the ischemia-induced swelling of mitochondria. The protective effects of 3-AB on cellular ultrastructure were also observed 7 days after reperfusion. These findings indicate that the inhibition of PARP may have a protective effect on cell swelling and on the state of intracellular organelles after a short-term ischemic episode.

Nicotinamide is a potent inhibitor of proinflammatory cytokines

The present study investigates the modulating effects of nicotinamide on the cytokine response to endotoxin. In an in vitro model of endotoxaemia, human whole blood was stimulated for two hours with endotoxin at 1 ng/ml, achieving high levels of the proinflammatory cytokines IL-1 beta, IL-6, IL-8 and TNF alpha. When coincubating whole blood, endotoxin and the vitamin B3 derivative nicotinamide, all four cytokines measured were inhibited in a dose dependent manner. Inhibition was observed already at a nicotinamide concentration of 2 mmol/l. At a concentration of 40 mmol/l, the IL-1 beta, IL-6 and TNF alpha responses were reduced by more than 95% and the IL-8 levels reduced by 85%. Endotoxin stimulation activates poly(ADP-ribose)polymerase (PARP), a nuclear DNA repair enzyme. It has been hypothesized that the anti-inflammatory properties of nicotinamide are due to PARP inhibition. In the present study, the endotoxin induced PARP activation was dose dependently decreased with 4-40 mmol/l nicotinamide or 4-100 micro mol/l 6(5H) phenanthridinone, a specific PARP inhibitor. 6(5H)phenanthridinone however, failed to inhibit the proinflammatory cytokines. Thus, the mechanism behind the cytokine inhibition in our model seems not to be due to PARP inhibition. In conclusion, the present study could not only confirm previous reports of a down-regulatory effect on TNFalpha, but demonstrates that nicotinamide is a potent modulator of several proinflammatory cytokines. These findings demonstrate that nicotinamide has a potent immunomodulatory effect in vitro, and may have great potential for treatment of human inflammatory disease.

Poly(ADP-ribose) degradation by post-nuclear extracts from human cells

The nuclear metabolism of poly(ADP-ribose) is mainly regulated by poly(ADP-ribose) polymerase-1 (PARP-1) and by poly(ADP-ribose) glycohydrolase (PARG). A PARP-like enzyme, V-PARP, and a PARG isoform are present in the extra-nuclear compartment of mammalian cells, even if poly(ADP-ribose) has never been detected therein. In this work, we demonstrate the ability of post-nuclear extracts from HeLa and HL60 cells to degrade synthetic 32P-polymers of ADP-ribose to ADP-ribose and, further, to AMP. This reaction implies the combined action of PARG and of an ADP-ribose-degrading activity, possibly corresponding to a phosphodiesterase and/or to an ADP-ribose pyrophosphatase. The inhibition of PARG or ADP-ribose-degrading enzymes allowed the demonstration that in vitro synthesized 32P-poly(ADP-ribose) is first digested to ADP-ribose monomers by a typical PARG reaction, and that ADP-ribose is further rapidly converted into AMP by an Mg(2+)-dependent activity. Collectively, our results demonstrate the ability of the human cell post-nuclear fraction to convert synthetic poly(ADP-ribose) into utilizable AMP units by the concerted action of PARG and ADP-ribose-degrading activities.

Halothane potentiation of hydrogen peroxide-induced inhibition of surfactant synthesis: the role of type II cell energy status

Small concentrations of inhaled anesthetics can affect Type II cell surfactant production and exacerbate oxidant-mediated lung injury. We hypothesized that inhaled anesthetics augment oxidant-induced Type II pneumocyte dysfunction related to their different effects on cellular adenosine triphosphate (ATP) status. Freshly isolated Type II cells were exposed to different concentrations of hydrogen peroxide (H2O2) in the presence or absence of an in vitro halothane exposure. Cells exposed to 100 microM H2O2 alone demonstrated a 23% decrease in ATP levels and a 32% decrease in phosphatidylcholine (PC) synthesis compared with controls. Halothane alone decreased PC synthesis by only 12% and reduced ATP levels by 20%. However, when exposed to both halothane and H2O2 together, ATP levels decreased by 40%, and PC synthesis rates decreased by 51%. Pretreatment of cells with nicotinamide, an inhibitor of poly adenosine diphosphate ribose polymerase, completely prevented the ATP loss and PC synthesis decline caused by H2O2 alone, but it had no effect on the halothane-augmented portion of the cell injury. These data suggest that the ability of halothane to enhance oxidative damage may be related to its own specific effects on cell energetics that may not be amenable to the same treatments used to mitigate other cellular mechanisms of oxidative stress.

IMPLICATIONS

A mediator of inflammation (hydrogen peroxide) and an inhaled anesthetic (halothane) interact to decrease cell energy and secretion of a substance (surfactant) required for healthy lung function from cells that line gas-exchange compartments. This interaction represents a possible mechanism by which inflammatory lung disease may become more severe intraoperatively.

Increase in de novo HBV DNA integrations in response to oxidative DNA damage or inhibition of poly(ADP-ribosyl)ation

Chronic infection with hepatitis B virus (HBV) is associated with an increased risk for the development of cirrhosis and hepatocellular carcinoma (HCC). Although clonal HBV DNA integrations are detected in nearly all HCCs the role of these integrations in hepatocarcinogenesis is poorly understood. We have used a cloning protocol that allows studying the frequency and the natural history of HBV DNA integrations in cell culture. Southern blot analysis of the genomic DNA of HepG2 2.2.15 subclones, which replicate HBV, enabled us to detect new HBV DNA integrations in approximately 10% of the HepG 2.2.15 subclones over 4 rounds of sequential subcloning, whereas no loss of any preexisting HBV DNA integrations was observed. Treatments of HepG2 cells with H(2)O(2), designed to increase DNA damage, increased the frequency of HBV integrations to approximately 50% of the subclones and treatments designed to inhibit DNA repair, by inhibiting Poly(ADP-ribosyl)ation, also increased the frequency of HBV integration to 50%. These findings suggest that DNA strand breaks induced by oxidative stress during persistent HBV infection in humans may increase HBV DNA integration events, whereas PARP-1 activity may function to limit the occurrence of de novo HBV DNA integrations.

Impairment of the neuronal dopamine transporter activity in MPP(+)-treated rat was not prevented by treatments with nitric oxide synthase or poly(ADP-ribose) polymerase inhibitors

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite MPP(+), damages of the nigrostriatal dopaminergic pathway, similar to those observed in Parkinson's disease. An intranigral injection of 10 microg MPP(+) in rat induced a decrease of about 30% of the neuronal dopamine transporter (DAT) activity 21 days after lesion. Based on the hypothesis that MPTP/MPP(+) neurotoxicity involves the nitric oxide (NO) production and/or an activation of poly(ADP-ribose) polymerase (PARP), we investigated the preventive effects of a treatment either with L-Name, a NO synthase (NOS) inhibitor or 3-aminobenzamide, a PARP inhibitor on the reduction of dopamine uptake induced by MPP(+). Rats received a daily injection i.p. of 50 mg/kg L-Name or 10 mg/kg 3-aminobenzamide 3 days before and during 21 days after the MPP(+) lesion. The results showed that inhibitors of NOS and PARP did not prevent the alteration of DAT activity induced by 10 microg MPP(+), indicating that NO and PARP were not involved in the biochemical cascade leading to the inhibition of rat DAT activity by MPP(+) in our experimental conditions.

3-Aminobenzamide, a poly (ADP-ribose) synthetase inhibitor, attenuates the acute inflammatory responses and brain injury in experimental Escherichia coli meningitis in the newborn piglet

The aim of the present study was to evaluate the anti-inflammatory and neuroprotective effects of a poly (ADP-ribose) synthetase inhibitor 3-aminobenzamide during the early phase of experimental bacterial meningitis in the newborn piglet. Meningitis was induced by intracisternal injection of 10(8) colony forming units of Escherichia coli in 100 microl of saline. 3-Aminobenzamide, given 30 mg kg(-1) as a bolus i.v. injection 30 min before induction of meningitis, significantly attenuated the meningitis-induced acute inflammatory responses such as increased cerebrospinal fluid (CSF) lactate concentration, CSF leukocytosis and increased CSF tumor necrosis factor-alpha level. However, meningitis-induced increase in intracranial pressure and decrease in CSF glucose level were not significantly improved. Increased cerebral cortical cell membrane lipid peroxidation products (conjugated dienes) and decreased brain ATP/phosphocreatine levels observed in the meningitis group were also significantly improved with 3-aminobenzamide treatment. However, the improvement of reduced Na+, K+-ATPase activity did not reach a statistical significance (p = 0.06). In summary, 3-aminobenzamide significantly attenuated the acute inflammatory responses and the ensuing brain injury during the early phase of neonatal bacterial meningitis. These findings suggest that poly (ADP-ribose) synthetase inhibitors such as 3-aminobenzamide might be a promising novel anti-inflammatory and neuroprotective adjuvant therapy in neonatal bacterial meningitis.

Calpain inhibitor I reduces the development of acute and chronic inflammation

There is limited evidence that inhibition of the activity of the protease calpain I reduces inflammation. Here we investigate the effects of calpain inhibitor I in animal models of acute and chronic inflammation (carrageenan-induced pleurisy and collagen-induced arthritis). We report here for the first time that calpain inhibitor I (given at 5, 10, or 20 mg/kg i.p. in the pleurisy model or at 5 mg/kg i.p every 48 hours in the arthritis model) exerts potent anti-inflammatory effects (eg, inhibition of pleural exudate formation, mononuclear cell infiltration, delayed the development of the clinical signs and histological injury) in vivo. Furthermore, calpain inhibitor I reduced (1) the staining for nitrotyrosine and poly (ADP-ribose) polymerase (immunohistochemistry) and (2) the expression of inducible nitric oxide synthase and cyclooxygenase-2 in the lungs of carrageenan-treated rats and in joints from collagen-treated rats. Thus, prevention of the activation of calpain I reduces the development of acute and chronic inflammation. Inhibition of calpain I activity may represent a novel therapeutic approach for the therapy of inflammation.

Modulation of apoptosis signaling in etoposide-treated lymphoma cells

Signals of etoposide (ETO) induced apoptosis were studied in a human (B) lymphoma cell line, HT58. Morphology and DNA fragmentation assays proved the appearance of apoptosis after a short ETO treatment (4 hours). Modulation of signal components of this apoptotic pathway resulted the following a) phorbol ester (PMA) or heat shock inhibited apoptosis, which was prevented by staurosporine b) 3-amino-benzamide, a potent poly(ADP-ribose)polymerase inhibitor, had no significant effect; c) cysteine reactive compounds, such as iodoacetamide and phenylarsine oxide, as well as protease inhibitor TPCK were very active inhibitors of apoptosis; d) protein synthesis inhibitor, cycloheximide, potentiated cell death; e) the ETO-induced p53 protein overexpression had neither enhancing nor protecting effect on the apoptotic process. In conclusion, in the majority of HT58 lymphoma cells the apoptotic machinery is "primed" (the components are already expressed) and ETO-induced apoptosis is regulated by STA sensitive phosphorylation and proteolysis by cystein proteases, but not affected by ADP-ribozylation or p53.

Combination effects of poly(ADP-ribose) polymerase inhibitors and DNA-damaging agents in ovarian tumor cell lines--with special reference to cisplatin

The effects of the poly(ADP-ribose) polymerase inhibitors 4-amino-1,8-naphthalimide (4-ANI), 6(5H)-phenanthridinone (PHD), 1,5-isoquinolinediol (IQD), 3-aminobenzamide (3-AB) or 4-hydroxyquinazoline (4-HYA) on the cytotoxicity of cisplatin were investigated. The human ovarian tumor cell lines SK-OV-3 and OAW 42 and the rat ovarian tumor cell line O-342 as well as its cisplatin (DDP)-resistant subline O-342/DDP were used. Cytotoxicity was determined with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. 1-Methyl-3-nitro-1-nitrosoguanidine (MNNG) plus its respective combinations with poly(ADP-ribose) polymerase inhibitors served as positive controls. In addition, the alkylating agents L-threitol-1,4-bismethanesulfonate (DHB) and 1,3-bis(2-chloroethyl)-1-nitrosourea (carmustine) as well as two other DNA-repair inhibitors caffeine and theophylline were included in the investigations. The cytotoxicity of cisplatin could not be increased by 4-ANI, PHD, IQD, 4-HYA or 3-AB in any cell line investigated, while it was increased by caffeine in lines O-342/DDP and SK-OV-3 as well as by theophylline in lines O-342/DDP, SK-OV-3 and OAW 42. The cytotoxicity of MNNG was increased by combination with 4-ANI, PHD, IQD, 4-HYA, 3-AB or theophylline for all lines except OAW42; in the latter line, only 4-ANI, PHD and IQD increased MNNG cytotoxicity. The cytotoxicity of DHB was increased by 4-ANI, PHD, 4-HYA, theophylline and caffeine in line O-342/DDP; by 4-HYA, theophylline and caffeine in line SK-OV-3; and by theophylline and caffeine in line OAW42. The cytotoxicity of carmustine was increased only by 3-AB in two lines (SK-OV-3 and OAW 42). Results are discussed with regard to different DNA-repair mechanisms.

Benzamide, an inhibitor of poly(ADP-ribose) polymerase, attenuates methamphetamine-induced dopamine neurotoxicity in the C57B1/6N mouse

Previous studies have indicated that the activation of poly(ADP-ribose) polymerase (PARP), an enzyme involved in DNA plasticity-related phenomena, is an early event occurring in glutamate-induced neurotoxicity in vitro, and that inhibitors of PARP, including benzamide, are protective against both glutamate- and methamphetamine (METH)-induced neurotoxicity in vitro. To evaluate a central neuroprotective potential of benzamide in vivo, the present study examined the effect of benzamide on the nigrostriatal dopamine toxicity (i.e., long-lasting striatal dopamine depletion) induced by METH in the C57B1/6N mouse. Intraperitoneal injection of METH at 2-h intervals (4 injections of 5 mg/kg, 4 injections of 10 mg/kg, or 2 injections of 20 mg/kg) dose-dependently reduced the levels of striatal dopamine in male C57B1/6N mice by up to 53% at 7 days post-treatment. Administration of benzamide (2 injections of 160 mg/kg spaced by a 4 interval) during the different METH treatment protocols partially and significantly attenuated the METH-induced dopamine depletions. Benzamide (160 mg/kg i.p.) by itself had no acute effect on striatal dopamine metabolism and did not reduce body temperature. The concentrations of benzamide measured in the striatum at different times following this same dose of drug were in a range (0.09-0.64 mM) reported in in vitro studies to be both neuroprotective and effective in inhibiting PARP activity. These results indicate a neuroprotective potential of benzamide in vivo and suggest a role of PARP in METH neurotoxicity.

Nerve growth factor effects on pyridine nucleotides after oxidant injury of rat pheochromocytoma cells

Neurotrophic factors regulate neuronal survival and neurite growth in development and following injury. Oxidative stress produced in neurons as a consequence of primary injury, or during reperfusion following ischemia, may contribute to cell death. Here, the effects of nerve growth factor (NGF) on the response to H2O2 injury were examined in the PC12 rat pheochromocytoma cell line. Specifically, the effect of NGF on cell viability after H2O2 injury was measured. Pretreatment with NGF enhanced survival after H2O2 treatment, as measured by Trypan blue dye exclusion, radiolabeled amino acid incorporation, tetrazolium salt reduction, or cytoplasmic enzyme release. One early event associated with H2O2 treatment was a rapid decrease in NAD+. Although initial decreases in NAD+ levels were similar in control and NGF-treated cells, the latter recovered more rapidly and extensively. The decline in total NAD observed after NGF treatment was almost equal in magnitude to the measured increase in NADP. Inhibition of poly(ADP-ribose) polymerase also enhanced viability following H2O2 injury. Treatment with both NGF and an inhibitor of this enzyme resulted in a greater reduction of H2O2 toxicity than was observed with either agent alone. These data suggest that NGF protection is multifactorial and that a significant component of the NGF effect is due to its regulatory role in the metabolism of pyridine nucleotides.

[An experimental study of the amides of aromatic carboxylic acids as radiosensitizing agents]

In experiments with mice a study was made of the radiosensitizing efficacy of 10 aromatic carbonic acid amides, benzene, naphthalene, pyridine and quinoline derivatives. It has been found, for this group of substances, that there is a direct correlation between the ability of the substance to reduce the splenic endocolonies production and the inhibitory activity with regard to poly(ADP-ribose) polymerase of thymocyte nuclei. Within the group of substances under study, new agents are found and described and new relationships are revealed between their chemical structure and biological activity.

[An experimental study of ADP-ribosylation inhibitors as anti-influenza agents]

Tri-substituted benzamide derivatives are described as a new class of antiviral drugs. Three compounds (3, N-acetylaminobenzamide, 3, N-butyrylaminobenzamide, and 3-methoxybenzamide) protected mice inoculated with influenza type A virus. 3, N-acetylaminobenzamide was found to be most active. It is suggested that the antiviral effect may be due to the specific inhibitory action of these compounds on NAD(+)-dependent ADP-ribosylation.

Cellular NAD+ and ATP levels in alkylation-induced cytotoxicity enhanced by an inhibitor of poly(ADP-ribose) synthesis

Alkylating agents cause a marked depletion of cellular NAD+ levels by activating nuclear ADP-ribosyl transferase (ADPRT), which utilizes NAD+ as a substrate in the synthesis of poly(ADP-ribose). As a consequence of NAD+ depletion, it is possible that cellular ATP pools could be depleted. Because of this, exogenously supplied NAD+ had been proposed as a way to counteract some of the effects of an alkylator. We found that exogenously supplied NAD+ significantly increased intracellular levels of NAD+ in MMS- and MNNG-treated V79 Chinese hamster cells. Cytotoxicity was not changed by the exogenously supplied NAD+, however. 3-Aminobenzamide (3-ABA), an ADPRT inhibitor, prevented the depletion of intracellular NAD+ by MMS or MNNG treatment and potentiated cytotoxicity. As was the case without 3-ABA, exogenously supplied NAD+ plus 3-ABA did not change the cytotoxicity, even though NAD+ levels were increased. Intracellular ATP levels were also measured and were found to be unaffected following MMS treatment, and only slightly depleted following MNNG treatment. Exogenously supplied NAD+ raised these levels above those for their respective controls. Because survival was unaffected by elevated levels of NAD+ and ATP, our results suggest that depletion of cellular NAD+ pools following MMS and MNNG treatment is not a critical factor in determining cytotoxicity for these V79 cells. The energy reserves of V79 cells, at doses of MMS or MNNG which kill 99% of the cells, are apparently adequate to maintain normal levels of ATP.

Elevation of polycyclic aromatic hydrocarbon-inducible aryl hydrocarbon hydroxylase activity in rat hepatocytes in primary culture by inhibitors of poly(ADP-ribose) polymerase

Induction of aryl hydrocarbon hydroxylase (AHH) activity was studied in primary cultures of rat hepatocytes. AHH activity was induced by treatment with benz[a]anthracene and combined treatment with cycloheximide for an initial short period during the induction enhanced benz[a]anthracene-inducible AHH activity. The enhancement was correlated to amounts of cytochrome P-450 RNA, indicating that cycloheximide treatment increased transcription of benz[a]anthracene-inducible cytochrome P-450 gene species. 3-Methoxybenzamide and 3-aminobenzamide, known to be physiologically specific inhibitors for poly(ADP-ribose) polymerase, but not the structurally related non-inhibitor, 3-aminobenzoic acid, also increased benz[a]anthracene-induced AHH activity. In addition, 3-methoxybenzamide was found to further increase the enhancing effects of cycloheximide on benz[a]anthracene induction of AHH. The effects of poly(ADP-ribose) polymerase inhibitors were not mediated by reduction of cyclic nucleotide phosphodiesterase activity. This was in clear contrast to the situation with the xanthine derivative, aminophylline, which also brought about a similar enhancement of AHH induction by benz[a]anthracene. The results suggest the participation of poly(ADP-ribose) in the regulation of expression of benz[a]anthracene-inducible cytochrome P-450 genes.

Adenosine, deoxyadenosine, and deoxyguanosine induce DNA cleavage in mouse thymocytes

When thymocytes were cultured with adenosine, deoxyadenosine, or deoxyguanosine at 1 mM for 24 h, DNA cleavage at internucleosomal sites with multiples of approximately 180 bp was induced, followed by lactate dehydrogenase release into the medium. In the presence of coformycin, an adenosine deaminase inhibitor, or formycin B, a purine nucleoside phosphorylase inhibitor, DNA cleavage was induced by these nucleosides at concentrations of less than 50 microM. Other purine and pyrimidine ribo- and deoxyribonucleosides did not induce DNA cleavage or LDH release. Because thymocyte nuclei contain a Ca2+,Mg2+-dependent endonuclease, which preferentially cuts DNA in its linker regions, DNA fragmentation induced by the three purine nucleosides was suggested to occur through increased activity of the endonuclease. The DNA cleavage induced by the nucleosides required protein phosphorylation and synthesis, inasmuch as it was inhibited by an inhibitor of protein kinases, H-7, and by an inhibitor of protein synthesis, cycloheximide. The inhibition of DNA cleavage was accompanied by a reduction in lactate dehydrogenase release, suggesting a causal relationship between DNA cleavage and cell death. The DNA cleavage and subsequent cell lysis might be related to the selective thymocyte deletion observed in patients with adenosine deaminase or purine nucleoside phosphorylase deficiency.

Enhanced ligation of repair sites under conditions of inhibition of poly(ADP-ribose) synthesis by 3-aminobenzamide

The rate of intracellular ligation of excision-repair patches has been measured under conditions of inhibition of poly(ADP-ribose) synthesis by 3-aminobenzamide. Excision-repair patches in DNA of cells damaged by methyl methanesulfonate were labeled with [3H]thymidine and blocked at an intermediate stage by aphidicolin, an inhibitor of DNA polymerase alpha. Removal of [3H]thymidine and aphidicolin permitted the intracellular ligation rate to be determined by rapid digestion of [3H]-labeled 3' termini with exonuclease III. Contrary to previous conclusions from more indirect experiments, inhibition of poly(ADP-ribose) synthesis by 3-aminobenzamide actually facilitates rapid ligation.

Influence of poly(ADP-ribose) synthesis inhibitors on the repair of sublethal and potentially lethal damage in gamma-irradiated mammalian cells

The influence of poly(ADP-ribose) synthesis inhibitors on mammalian cell radiosensitivity was investigated. Four different inhibitors were studied: 3-methoxybenzamide, 3-aminobenzamide, 6-aminonicotinamide and nicotinamide. When exponentially growing or plateau phase cells are incubated before irradiation with non-toxic concentrations of these compounds, their radiosensitivity is enhanced except in the case of nicotinamide. The poly(ADP-ribose) inhibitors do not modify the repair of sublethal damage, but totally suppress the repair of potentially lethal damage, as shown by the survival of CHO cells and of a human osteosarcoma cell line.

Inhibition of malignant transformation in vitro by inhibitors of poly(ADP-ribose) synthesis

Malignant transformation in vitro of hamster embryo cells and mouse C3H 10T 1/2 cells by x-rays, ultraviolet light, and chemical carcinogens was inhibited by benzamide and by 3-aminobenzamide at concentrations that are specific for inhibition of poly(ADP-ribose) formation. These compounds slow the ligation stage of repair of x-ray and alkylation damage but not of ultraviolet light damage. At high concentrations they also inhibited de novo synthesis of DNA purines and DNA methylation by S-adenosylmethionine. The suppression of transformation by the benzamides is in striking contrast to their reported effectiveness in enhancing sister chromatid exchange, mutagenesis, and killing in cells exposed to alkylating agents. Our results suggest that mechanisms regulating malignant transformation are different from those regulating DNA repair, sister chromatid exchange, and mutagenesis and may be associated with changes in gene regulation and expression caused by alterations in poly(ADP-ribosyl)ation.

Role of poly(adenosine diphosphate ribose) in deoxyribonucleic acid repair in human fibroblasts

We have investigated the role of poly(adenosine diphosphate ribose) in DNA repair in human fibroblasts by observing the effects of 3-aminobenzamide (3AB), a specific inhibitor of poly(ADP-ribose) synthesis, on various aspects of DNA repair. After treatment of human fibroblasts with dimethyl sulfate (DMS), 3AB retarded the joining of strand breaks; unscheduled DNA synthesis was unaffected after low doses of DMS but was stimulated after high doses. 3AB also enhanced the cytotoxicity of DMS. After gamma irradiation there was a slight inhibition by 3AB of the rejoining of single-strand breaks but no effect on the rejoining of double-strand breaks, unscheduled DNA synthesis, DNA replicative synthesis, or cytotoxicity. There were no effects of 3AB on the repair of UV damage. On the basis of the different kinetics of the various steps of excision repair processes after different treatments of fibroblasts, our results are interpreted as evidence that the synthesis of poly(ADP-ribose) is involved in the ligation step of excision repair.