The impact of HLA class I and EBV latency-II antigen-specific CD8(+) T cells on the pathogenesis of EBV(+) Hodgkin lymphoma.

In 40% of cases of classical Hodgkin lymphoma (cHL), Epstein-Barr virus (EBV) latency-II antigens [EBV nuclear antigen 1 (EBNA1)/latent membrane protein (LMP)1/LMP2A] are present (EBV(+) cHL) in the malignant cells and antigen presentation is intact. Previous studies have shown consistently that HLA-A*02 is protective in EBV(+) cHL, yet its role in disease pathogenesis is unknown. To explore the basis for this observation, gene expression was assessed in 33 cHL nodes. Interestingly, CD8 and LMP2A expression were correlated strongly and, for a given LMP2A level, CD8 was elevated markedly in HLA-A*02(-) versus HLA-A*02(+) EBV(+) cHL patients, suggesting that LMP2A-specific CD8(+) T cell anti-tumoral immunity may be relatively ineffective in HLA-A*02(-) EBV(+) cHL. To ascertain the impact of HLA class I on EBV latency antigen-specific immunodominance, we used a stepwise functional T cell approach. In newly diagnosed EBV(+) cHL, the magnitude of ex-vivo LMP1/2A-specific CD8(+) T cell responses was elevated in HLA-A*02(+) patients. Furthermore, in a controlled in-vitro assay, LMP2A-specific CD8(+) T cells from healthy HLA-A*02 heterozygotes expanded to a greater extent with HLA-A*02-restricted compared to non-HLA-A*02-restricted cell lines. In an extensive analysis of HLA class I-restricted immunity, immunodominant EBNA3A/3B/3C-specific CD8(+) T cell responses were stimulated by numerous HLA class I molecules, whereas the subdominant LMP1/2A-specific responses were confined largely to HLA-A*02. Our results demonstrate that HLA-A*02 mediates a modest, but none the less stronger, EBV-specific CD8(+) T cell response than non-HLA-A*02 alleles, an effect confined to EBV latency-II antigens. Thus, the protective effect of HLA-A*02 against EBV(+) cHL is not a surrogate association, but reflects the impact of HLA class I on EBV latency-II antigen-specific CD8(+) T cell hierarchies.

A comprehensive analysis of the cellular and EBV-specific microRNAome in primary CNS PTLD identifies different patterns among EBV-associated tumors.

Primary central nervous system (pCNS) posttransplant lymphoproliferative disorder (PTLD) is a complication of solid organ transplantation characterized by poor outcome. In contrast to systemic PTLD, Epstein-Barr virus (EBV)-association of pCNS PTLD is almost universal, yet viral and cellular data are limited. To identify differences in the pattern of EBV-association of pCNS and systemic PTLD, we analyzed the expression of latent and lytic EBV transcripts and the viral and cellular microRNAome in nine pCNS (eight EBV-associated) and in 16 systemic PTLD samples (eight EBV-associated). Notably although 15/16 EBV-associated samples exhibited a viral type III latency pattern, lytic transcripts were also strongly expressed. Members of the ebv-miR-BHRF1 and ebv-miR-BART clusters were expressed in virtually all EBV-associated PTLD samples. There were 28 cellular microRNAs differentially expressed between systemic and pCNS PTLD. pCNS PTLD expressed lower hsa-miR-199a-5p/3p and hsa-miR-143/145 (implicated in nuclear factor kappa beta and c-myc signaling) as compared to systemic PTLD. Unsupervised nonhierarchical clustering of the viral and cellular microRNAome distinguished non-EBV-associated from EBV-associated samples and identified a separate group of EBV-associated pCNS PTLD that displayed reduced levels of B cell lymphoma associated oncomiRs such as hsa-miR-155, -21, -221 and the hsa-miR-17-92 cluster. EBV has a major impact on viral and cellular microRNA expression in EBV-associated pCNS PTLD.

The presence of KIR2DS5 confers protection against adult immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an autoimmune disorder of unknown aetiology, characterised by an isolated low platelet count in the absence of other identifiable causes. Genes influencing activation of the immune system have been identified as influencing predisposition. Killer cell immunoglobulin-like receptors (KIR) control T-cell and natural killer (NK) cell function via inhibitory and activating signalling pathways. The inhibitory KIR2DL3, KIR3DL2 and KIR3DL1 are up-regulated in the T-cells of patients with ITP in remission relative to those with active disease, and an association of KIR2DS2 and KIR2DL2 with ITP has also been reported. No comprehensive KIR analysis in ITP has been reported. We performed genotyping of all currently known KIR genes using sequence specific primer polymerase chain reaction (SSP-PCR) on a cohort of 83 adult patients with ITP (chronic/persistent or relapsed primary ITP identified by defined criteria) and 106 age matched healthy white volunteers. Non-white patients were not included in the analysis. There was an over-representation of KIR2DS3 (known to be in linkage disequilibrium with KIR2DS2 and 2DL2) and under-representation of KIR2DS5 (also protective against other immune mediated disorders) in adult ITP [odds ratio (OR) = 0.16, confidence interval (CI) 0.08-0.32, P < 0.001]. By multivariable binary logistic regression to adjust for age, sex and the effects of other KIR genes, the presence of KIR2DS2/2DL2 with KIR2DS5 abrogated the risk of KIR2DS2/2DL2 and the protective benefit of KIR2DS5. Further studies are required to establish the mechanistic basis for these observations and their potential impact on ITP therapy.

Homozygous FCGR3A-158V alleles predispose to late onset neutropenia after CHOP-R for diffuse large B-cell lymphoma.

BACKGROUND: Recent reports suggest genetic polymorphisms influence susceptibility to rituximab-induced late-onset neutropenia (LON), which in turn may be a predictor of good outcome in B-cell lymphoma. AIMS: We report the largest study to date assessing FCGR3A-V158F polymorphisms in diffuse large B-cell lymphoma (DLBCL) treated with cyclophosphamide/hydroxydaunorubicin/Oncovin (vincristine)/prednisone/rituximab (CHOP-R). The influence of C1qA-A276G polymorphisms in DLBCL, and the impact of both polymorphisms on susceptibility to LON and outcome were also examined. METHODS: 115 DLBCL patients treated with CHOP-R were compared with 105 healthy White people controls with regards to FCGR3A-V158F and C1qA-A276G polymorphisms. LON incidence and event-free and overall survival (EFS and OS) were analysed for linkage to either polymorphism. RESULTS: The FCGR3A-V158F but not the C1qA-A276G polymorphism influenced the risk of developing LON. 50% of FCGR3A-158V/V patients experienced LON. In contrast, only 7% V/F and 2% F/F experienced LON. The FCGR3A-158V/V genotype was associated with LON compared with V/F (P = 0.028) and F/F genotypes (P = 0.005). Although no patients with either LON or FCGR3A-158V homozygosity relapsed compared with 33% FCGR3A-158F/F and 21% non-LON, this did not translate into improved EFS or OS. CONCLUSIONS: Polymorphic analysis may be a predictive tool to identify those at high risk of LON. Prospective studies are required to establish definitively if LON or FCGR3A-158V/V genotype influences outcome.

Region-specific effects of N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide on nicotine-induced increase in extracellular dopamine in vivo.

BACKGROUND AND PURPOSE: Systemic administration of N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB), an antagonist of nicotinic acetylcholine receptors (nAChRs) attenuated the nicotine-induced increase in dopamine levels in nucleus accumbens (NAcc). EXPERIMENTAL APPROACH: Using in vivo microdialysis, we investigated the effects of local perfusion of the novel nAChR antagonist bPiDDB into the NAcc or ventral tegmental area (VTA) on increased extracellular dopamine in NAcc, induced by systemic nicotine. We also examined the concentration-dependent effects of bPiDDB on the acetylcholine (ACh)-evoked response of specific recombinant neuronal nAChR subtypes expressed in Xenopus oocytes, using electrophysiological methods. KEY RESULTS: Nicotine (0.4 mg kg(-1), s.c.) increased extracellular dopamine in NAcc, which was attenuated by intra-VTA perfusion of mecamylamine (100 microM). Intra-VTA perfusion of bPiDDB (1 and 10 microM) reduced nicotine-induced increases in extracellular dopamine in NAcc. In contrast, intra-NAcc perfusion of bPiDDB (1 or 10 microM) failed to alter the nicotine-induced increase in dopamine in NAcc. Intra-VTA perfusion of bPiDDB alone did not alter basal dopamine levels, compared to control, nor the increased dopamine in NAcc following amphetamine (0.5 mg kg(-1), s.c.). Using Xenopus oocytes, bPiDDB (0.01-100 microM) inhibited the response to ACh on specific combinations of rat neuronal nAChR subunits, with highest potency at alpha3beta4beta3 and lowest potency at alpha6/3beta2beta3. CONCLUSIONS AND IMPLICATIONS: bPiDDB-Sensitive nAChRs involved in regulating nicotine-induced dopamine release are located in the VTA, rather than in the NAcc. As bPiDDB has properties different from the prototypical nAChR antagonist mecamylamine, further development may lead to novel nAChR antagonists for the treatment of tobacco dependence.

Effects of nornicotine enantiomers on intravenous S(-)-nicotine self-administration and cardiovascular function in rats.

RATIONALE: Previous neurochemical evidence indicates that R(+)-nornicotine is more potent than S(-)-nornicotine in evoking dopamine release in rat nucleus accumbens slices. OBJECTIVE: The current study tested the hypothesis that R(+)-nornicotine is also more potent than S(-)-nornicotine in selectively decreasing intravenous S(-)-nicotine self-administration in rats. RESULTS: After acute pretreatment (1-10 mg/kg for each enantiomer), R(+)-nornicotine was more potent than S(-)-nornicotine in decreasing S(-)-nicotine self-administration; in contrast, within the same dose range, the nornicotine enantiomers were equipotent in decreasing sucrose-maintained responding. This enantioselectivity does not likely reflect a difference in bioavailability, since similar levels of nornicotine were recovered from the brain 60 min after injection (5.6 mg/kg for each enantiomer). With repeated pretreatment, tolerance did not develop to the rate-decreasing effect of either nornicotine enantiomer (3 or 5.6 mg/kg) with respect to the decrease in S(-)-nicotine self-administration, although the enantioselectivity dissipated across repeated pretreatments. While both enantiomers acutely produced a similar increase in blood pressure and heart rate, tolerance developed to the blood pressure effects of R(+)-nornicotine, but not to the effects of S(-)-nornicotine, across repeated treatments. CONCLUSION: Both R(+)- and S(-)-nornicotine may have potential utility as a novel tobacco use cessation agent.

Effect of a novel nicotinic receptor antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide, on nicotine self-administration and hyperactivity in rats.

RATIONALE AND OBJECTIVE: Recent work has shown that the novel compound N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB) may selectively block nicotinic acetylcholine receptors involved in regulating dopamine release. The current experiments examined the acute effect of bPiDDB on nicotine self-administration, sucrose-maintained responding, and nicotine-induced changes in acute and sensitized locomotor activity. METHODS: Rats were first trained to respond for either nicotine (i.v.) or sucrose pellets using a standard two-lever operant conditioning procedure using a fixed ratio 5 schedule of reinforcement and were then pretreated with bPiDDB (0, 0.3, 1, or 3 mg kg(-1)) 15 min prior to the session. In separate experiments, rats were assessed for nicotine-induced changes in locomotor activity following pretreatment with bPiDDB (1 or 3 mg kg(-1)) or mecamylamine (1 mg kg(-1)); pretreatments were assessed with both acute and repeated nicotine (0.4 mg kg(-1)) treatment. RESULTS: Results showed that bPiDDB dose-dependently decreased nicotine self-administration, but not sucrose-maintained responding. In the locomotor experiments, bPiDDB attenuated the hyperactivity produced by acute and repeated nicotine; however, this effect was not robust compared to mecamylamine. In contrast to mecamylamine, bPiDDB did not block the initial hypoactivity produced by acute nicotine. CONCLUSION: Since bPiDDB decreased nicotine self-administration specifically, this novel nicotinic receptor antagonist may constitute a lead for the development of a clinically useful treatment for tobacco dependence.

NF-κB-dependent and -independent epigenetic modulation using the novel anti-cancer agent DMAPT.

The transcription factor nuclear factor-kappaB (NF-κB) is constitutively active in several cancers and is a target of therapeutic development. We recently developed dimethylaminoparthenolide (DMAPT), a clinical grade water-soluble analog of parthenolide, as a potent inhibitor of NF-κB and demonstrated in vitro and in vivo anti-tumor activities in multiple cancers. In this study, we show DMAPT is an epigenetic modulator functioning in an NF-κB-dependent and -independent manner. DMAPT-mediated NF-κB inhibition resulted in elevated histone H3K36 trimethylation (H3K36me3), which could be recapitulated through genetic ablation of the p65 subunit of NF-κB or inhibitor-of-kappaB alpha super-repressor overexpression. DMAPT treatment and p65 ablation increased the levels of H3K36 trimethylases NSD1 (KMT3B) and SETD2 (KMT3A), suggesting that NF-κB directly represses their expression and that lower H3K36me3 is an epigenetic marker of constitutive NF-κB activity. Overexpression of a constitutively active p65 subunit of NF-κB reduced NSD1 and H3K36me3 levels. NSD1 is essential for DMAPT-induced expression of pro-apoptotic BIM, indicating a functional link between epigenetic modification and gene expression. Interestingly, we observed enhanced H4K20 trimethylation and induction of H4K20 trimethylase KMT5C in DMAPT-treated cells independent of NF-κB inhibition. These results add KMT5C to the list NF-κB-independent epigenetic targets of parthenolide, which include previously described histone deacetylase 1 (HDAC-1) and DNA methyltransferase 1. As NSD1 and SETD2 are known tumor suppressors and loss of H4K20 trimethylation is an early event in cancer progression, which contributes to genomic instability, we propose DMAPT as a potent pharmacologic agent that can reverse NF-κB-dependent and -independent cancer-specific epigenetic abnormalities.

Nanodelivery of Parthenolide Using Functionalized Nanographene Enhances its Anticancer Activity.

Advances in anticancer chemotherapy have been hindered by the lack of biocompatibility of new prospective drugs. One significant challenge concerns water insolubility, which compromises the bioavailability of the drugs leading to increased dosage and higher systemic toxicity. To overcome these problems, nanodelivery has been established as a promising approach for increasing the efficacy and lowering the required dosage of chemotherapeutics. The naturally derived compound, parthenolide (PTL), is known for its anti-inflammatory and anticancer activity, but its poor water solubility limits its clinical value. In the present study, we have used carboxyl-functionalized nanographene (fGn) delivery to overcome the extreme hydrophobicity of this drug. A water-soluble PTL analog, dimethylamino parthenolide (DMAPT), was also examined for comparison with the anticancer efficacy of our PTL-fGn complex. Delivery by fGn was found to increase the anticancer/apoptotic effects of PTL (but not DMAPT) when delivered to the human pancreatic cancer cell line, Panc-1. The IC50 value for PTL decreased from 39 µM to 9.5 µM when delivered as a mixture with fGn. The IC50 of DMAPT did not decrease when delivered as DMAPT-fGn and was significantly higher than that for PTL-fGn. There were significant increases in ROS formation and in mitochondrial membrane disruption in Panc-1 cells after PTL-fGn treatment as compared to PTL treatment, alone. Increases in toxicity were also seen with apoptosis detection assays using flow cytometry, ethidium bromide/acridine orange/DAPI staining, and TUNEL. Thus, fGn delivery was successfully used to overcome the poor water solubility of PTL, providing a strategy for improving the effectiveness of this anticancer agent.

Response of plasma arginine vasopressin to nicotine in normal man.

The response of plasma arginine vasopressin (AVP) to nicotine administered by chewing gum (Nicorette, 2 mg) was examined in nine healthy volunteers. Heart rate, mean arterial pressure, serum osmolality, plasma AVP level, and plasma nicotine level were measured at baseline (control) and at 30, 45, and 60 minutes after initial administration of the gum. There were small increases in heart rate (72 +/- 6.3 to 82 +/- 5.1 beats/min, p less than 0.05) and mean arterial pressure (88 +/- 8.2 to 93 +/- 10 mm Hg, p = NS), while the plasma nicotine level increased to a maximum of 16 +/- 2.0 ng/ml (p less than 0.001). No changes were seen in either osmolality (283 +/- 3.4 mOsm/kg) or AVP level (4.3 +/- 2.0 pg/ml) in eight of the nine subjects who remained asymptomatic. In one subject whose hemodynamic and plasma nicotine responses were similar to the others but who became nauseated, the plasma AVP level increased from 4.2 to 26 pg/ml. These data suggest that nicotine at the plasma concentrations achieved in this study is not associated with stimulation of plasma AVP secretion in normal man. Other factors in association with nicotine use, in this case nausea, may be required for AVP stimulation to occur.

Lobeline inhibits nicotine-evoked [(3)H]dopamine overflow from rat striatal slices and nicotine-evoked (86)Rb(+) efflux from thalamic synaptosomes.

The present study evaluated the interaction of lobeline with neuronal nicotinic acetylcholine receptors using two in vitro assays, [(3)H] overflow from [(3)H]dopamine ([(3)H]DA)-preloaded rat striatal slices and (86)Rb(+) efflux from rat thalamic synaptosomes. To assess agonist interactions, the effect of lobeline was determined and compared to S(-)-nicotine. To assess antagonist interactions, the ability of lobeline to inhibit the effect of S(-)-nicotine was determined. Both S(-)-nicotine (0.1-1 microM) and lobeline (>1.0 microM) evoked [(3)H] overflow from superfused [(3)H]DA-preloaded striatal slices. However, lobeline-evoked [(3)H] overflow is mecamylamine-insensitive, indicating that this response is not mediated by nicotinic receptors. Moreover, at concentrations (<1.0 microM) which did not evoke [(3)H] overflow, lobeline inhibited S(-)-nicotine (0.1-10 microM)-evoked [(3)H] overflow, shifting the S(-)-nicotine concentration-response curve to the right. S(-)-Nicotine (30 nM-300 microM) increased (EC(50) value=0.2 microM) (86)Rb(+) efflux from thalamic synaptosomes. In contrast, lobeline (1 nM-10 microM) did not evoke (86)Rb(+) efflux, and the lack of intrinsic activity indicates that lobeline is not an agonist at this nicotinic receptor subtype. Lobeline completely inhibited (IC(50) value=0.7 microM) (86)Rb(+) efflux evoked by 1 microM S(-)-nicotine, a concentration which maximally stimulated (86)Rb(+) efflux. Thus, the results of these in vitro experiments demonstrate that lobeline inhibits the effects of S(-)-nicotine, and suggest that lobeline acts as a nicotinic receptor antagonist.

Synthesis of spiro[tetralin-2,2'-pyrrolidine] and spiro[indan-2,2'-pyrrolidine] derivatives as potential analgesics.

Spiro[tetralin-2,2'-pyrrolidine] (13) and spiro[6-methoxytetralin-2,2'-pyrrolidine] (17) were prepared by initial Michael condensation of 2-nitrotetralin and 6-methoxy-2-nitrotetralin, respectively, with methyl acrylate to give 7 and 8, both of which could be reductively cyclized to 10 and 11, followed by LiAlH4 reduction. Spiro[indan-2,2'-pyrrolidine] (15) was prepared in an analogous manner form 2-nitroindan, and spiro[6-hydroxytetralin-2,2'-pyrrolidine] (19) was prepared by O-demethylation of 17. Compound 13 and its N-methyl derivative, 14, both showed good analgesic activity. Compounds 13-16 all possessed weak antidepressant properties, but neither 19 nor its N-methyl derivative 20 had any significant CNS activity.

Synthesis and analgesic properties of some conformationally restricted analogues of profadol.

N-Methylspiro[5-hydroxytetralin-1,3'-pyrrolidine] (2j) and N-methylspiro[7-hydroxytetralin-1,3'-pyrrolidine] (2n), conformationally restricted analogues of profadol, were synthesized via initial reaction of the appropriately substituted 1-tetralone with ethyl cyanoacetate to give the ethyl 1-tetralylidenecyanoacetate derivative (3), which was then reacted with KCN to give the corresponding 1-cyano-1-(cyanomethyl)tetralin (4). Treatment of 4 with either HBr in dry ether-dichloromethane or acetic acid-sulfuric acid afforded the spiro[tetralin-1,3'-pyrrolidine-2',5'-dione] derivative (5), which was then reduced with LiAlH4-THF and N-methylated with HCHO-HCO2H to give the appropriately substituted spiro[tetralin-1,3'-pyrrolidine] (2). Both 2j and 2n and the isomeric 6-hydroxy derivative 21 all showed no significant analgesic activity in hot-plate and writhing tests. However, spiro[tetralin-1,3'-pyrrolidine] (2a) and its N-methyl derivative (2b) both possessed codeine-level analgesic activity.

Multisubstrate adducts as potential inhibitors of S-adenosylmethionine dependent methylases: inhibition of indole N-methyltransferase by (5'-deoxyadenosyl)[3-(3-indolyl)prop-1-yl]methylsulfonium and (5'-deoxyadenosyl)[4-(3-indolyl)but-1-yl]methylsulfonium salts.

Multisubstrate adducts of the indole N-methyltransferase reaction have been designed in which a structural moiety representing the nucleophilic methyl acceptor is attached through the sulfur atom to the 5-(methylthio)adenosine and/or methionine moieties of the methyl donor, S-adenosyl-L-methionine. Indole derivatives attached through a 4-(3-indolyl)butyl sulfide or a 3-(3-indolyl)propyl sulfide linkage to 5'-thioadenosine or homocysteine have been synthesized, together with their corresponding methylsulfonium salts. These compounds have been assayed for their ability to inhibit rabbit lung indole N-methyltransferase. The adenosylsulfonium salts (5'-deoxyadenosyl)[4-(3-indolyl)but-1-yl]methylsulfonium perchlorate and (5'-deoxyadenosyl)[3-(3-indolyl)prop-1-yl]-methylsulfonium perchlorate were found to be inhibitors of this enzyme with Ki's of 12 and 44 microM, respectively. Neither of these compounds was effective in inhibiting the methylation of 3,4-dihydroxybenzoic acid, catalyzed by purified porcine catechol O-methyltransferase.

Synthesis and analgesic properties of two leucine-enkephalin analogues containing a conformationally restrained N-terminal tyrosine residue.

Two analogues of Leu-enkephalin, in which the terminal tyrosine-1 residue has been replaced by a conformationally restrained tyrosine analogue, have been synthesized by classical solution methods, and their opiate agonist potencies on electrically stimulated guinea pig ileum and mouse vas deferens preparations were determined in comparison with Leu-enkephalin. The restriction in the degree of freedom of the tyrosine moiety in [(2-amino-6-hydroxy-2-tetralinyl)carbonyl]glycylglycylphenylalanylleucine methyl ester (3e) leads to a 7 to 8 times higher agonist activity at the mu-receptor subtype in guinea pig ileum when compared to Leu-enkephalin, and an almost 30-fold decrease in potency, vs. Leu-enkephalin, on mouse vas deferens preparation. [(2-Amino-5-hydroxy-2-indanyl)carbonyl]-glycylglycylphenylalanylleucine methyl ester (2e) was inactive in the above tests. These results demonstrate the differential effect of restricting conformational flexibility on receptor recognition. Neither analogue had any analgesic properties when evaluated by the hot-plate test in mice after sc and icv administration.

Synthesis and dopaminergic properties of some exo- and endo-2-aminobenzonorbornenes designed as rigid analogue of dopamine.

Stereospecific syntheses of exo-2-amino-5,6-dihydroxybenzonorbornene (11f), exo-2-amino-6,7-dihydroxybenzonorbornene (11h), exo-2-amino-7,8-dihydroxybenzonorbornene (11g), and endo-2-amino-6,7-dihydroxybenzonorbornene (14d), rigid analogues of dopamine, are described. Compounds 11 h and 14d, their N-methyl (11i and 11j) and N,N-dimethyl (14i and 14j) derivatives, and compounds 11f and 11g were inactive as dopamine agonists when evaluated for dopaminergic activity by their ability to induce stereotyped behavior in mice after subcutaneous injection and by their ability to cause hyperactivity in rats after bilateral injection into the nucleus accumbens. However, compounds 11f, 11g, 11h, and the N-methyl derivatives 11i and 14d were all effective in displacing [3H]-2-amino-6,7-dihydroxytetralin ([3H]ADTN) and [3h[-N-n-propylnorapomorphine ([3H]NPA) from rat striatal membranes.

Measurement of adenosine concentration in aqueous and vitreous.

PURPOSE: The release of adenosine by the ischemic retina may be an initial signal in the development of ischemic macular edema and neovascularization. The levels of adenosine have never been quantified in ocular fluids. In this study, a technique was developed for in vivo measurement of the concentration of adenosine in aqueous and vitreous. METHODS: Aqueous and vitreous samples were obtained from bovine eyes after death and from live porcine eyes with the subject under general anesthesia. Samples from live eyes were immediately incubated in the sampling syringe with pentoxifylline, erythro-9-(2-hydroxy-3-nonyl) adenine, and dipyridamole to prevent synthesis or degradation of adenosine during the collection procedure, filtered, and flash-frozen in liquid nitrogen. All samples were then filtered and purified on phenylboronate agarose columns and incubated with chloroacetaldehyde to convert the adenosine present in the sample to the fluorescent derivative 1,N6-ethenoadenosine. The 1,N6-ethenoadenosine was separated by high-pressure liquid chromatography and then measured by fluorometry. RESULTS: Levels of adenosine as low as 0.5 pmole could be detected with this procedure, compared with 20 pmoles by UV detection. By using this technique to measure adenosine levels in the eyes of normal weanling domestic pigs, it was determined that the adenosine concentration in the aqueous was 321.3 +/- 164.9 nM and in the vitreous was 210.8 +/- 41.5 nM. CONCLUSIONS: The conversion of adenine-containing compounds to fluorescent 1,N6-etheno derivatives offers analytical advantages of selectivity and sensitivity for the quantitative determination of these compounds, with the fluorometric detection providing substantially greater sensitivity than direct detection by UV absorption. The levels obtained in vivo from anesthetized but otherwise healthy pigs presumably reflected basal aqueous and vitreous adenosine levels under the described conditions. This method should be useful in investigating more directly the role of adenosine in models of retinal or ocular ischemia in vivo and in measuring adenosine levels in vitreous or aqueous samples from human patients.

Intravitreal sustained release corticosteroid-5-fluoruracil conjugate in the treatment of experimental proliferative vitreoretinopathy.

PURPOSE: Proliferative vitreoretinopathy (PVR) remains the most common cause of failed retinal detachment (RD) surgery. The authors compared the effectiveness of two intraocular sustained-release codrugs in suppressing PVR in a rabbit model a surgically implantable pellet releasing 5-fluorouracil (FU) and dexamethasone (DX) for 1 week and an injectable intravitreal sustained-release suspension releasing 5-FU and triamcinolone acetonide for 1 month. METHODS: Sustained-release devices and suspensions were prepared to deliver equimolar quantities of corticosteroid and 5-FU. In group 1, devices were implanted surgically into the vitreous of the right eye of 10 New Zealand White rabbits. Ten control rabbits received surgical implantation of the suture only. In group 2, drug suspension was injected into the vitreous of the right eye of 10 New Zealand White rabbits. Ten control rabbits received injection of the vehicle only. One day later, each rabbit was injected intravitreally with 250,000 homologous rabbit dermal fibroblasts. Severity of PVR was graded clinically by two masked observers on days 3, 7, 10, 14, 21, and 28. RESULTS: In group 1, clinical severity of PVR was less in the experimental group than in the control group at all time points, this was only statistically significant on day 10 (P = 0.04). Six eyes developed moderate to severe tractional RD or bullous RD in the control group by day 10 compared with none in the experimental group (P = 0.01). In group 2, the median clinical grading of eyes in the experimental group was significantly less than that in the control group at all time points through day 21 (P < or = 0.01). CONCLUSIONS: Both the intravitreal sustained-release dexamethasone-5-FU device and the triamcinolone-5-FU suspension effectively inhibit the progression of PVR in a rabbit model. Simultaneous delivery of 5-FU and corticosteroid may target different components of the wound-healing process in this disease.

Pharmacological similarities between native brain and heterologously expressed alpha4beta2 nicotinic receptors.

1 We studied the pharmacological properties of native rat brain and heterologously expressed rat alpha4beta2 nicotinic receptors immunoprecipitated onto a fixed substrate with the anti-alpha4 antibody mAb 299. 2 Immunodepletion with the anti-beta2 antibody mAb 270 showed that 89% of the mAb-299-precipitated rat brain receptors contained beta2. 3 The association and dissociation rate constants for 30 pM +/-[3H]-epibatidine binding to alpha4beta2 receptors expressed in oocytes were 0.02+/-0.01 and 0.03+/-0.01 min-1 (+/-standard error, degrees of freedom=7 - 8) at 20 - 23 degrees C. 4 The Hill coefficients for +/-[3H]epibatidine binding to the native brain, alpha4beta2 receptors expressed in oocytes, and alpha4beta2 receptors expressed in CV-1 cells (using recombinant adenovirus) were 0.69 - 0.70 suggesting a heterogeneous receptor population. Fits of the +/-[3H]-epibatidine concentration-binding data to a two-site model gave KD s of 8 - 30 and 560 - 1,200 pM. The high-affinity sites comprised 73 - 74% of the native brain and oocyte alpha4beta2 receptor population, 85% of the CV-1 alpha4beta2 receptor population. 5 The expression of rat alpha4beta2 receptors in CV-1 cells using vaccinia viral infection-transfection resulted in a more homogeneous receptor population (Hill coefficient of 1. 0+/-0.2). Fits of the +/-[3H]-epibatidine binding data to a single-site model gave a KD of 40+/-3 pM. 6 DHbetaE (IC50=260-470 nM) and the novel nicotine analogue NDNI (IC50=7-10 microM) inhibited 30 pM+/-[3H]-epibatidine binding to the native brain and heterologously expressed alpha4beta2 receptors equally well. 7 The results show that alpha4beta2-containing nicotinic receptors in the rat brain and heterologously expressed rat alpha4beta2 receptors have similar affinities for +/-[3H]-epibatidine, DHbetaE, and NDNI.

L-Canavanine modulates cellular growth, chemosensitivity and P-glycoprotein substrate accumulation in cultured human tumor cell lines.

L-Canavanine (L-CAV) is a naturally occurring L-arginine analog that induces the formation of non-functional proteins in a variety of organisms. Previous studies have shown that L-CAV is cytotoxic for several human tumor cell lines. In this study, we have evaluated the cytotoxicity of L-CAV for both parental and multi-drug resistant (MDR) human tumor cells. We have also determined the effect of L-CAV exposure on cellular expression and activity of the MDR P-glycoprotein (P-gp) membrane efflux pump, and the effect of L-CAV on cellular accumulation of P-gp substrates. The effect of pre-treatment with non-cytotoxic doses of L-CAV on cellular sensitivity to ten standard antineoplastic agents was also evaluated, in order to assess the chemosensitization potential of L-CAV. 3-(4,5-Dimethylthiazol-)2,5-diphenyl tetrazolium bromide (MTT) cytotoxicity assays revealed that the MDR variants of human uterine sarcoma and leukemic cells were equally sensitive to L-CAV as compared with their respective parental controls. Although the presence of free L-CAV in the uptake media did not influence cellular accumulation of P-gp substrates, cells cultured for 72 h in 250 microM L-CAV accumulated from 16 to 23% less P-gp substrate than untreated controls. Although L-CAV-cultured sarcoma cells accumulated 17% less doxorubicin (DOX) than untreated controls, they were three times more sensitive to its cytotoxic effects. L-CAV-treated cells were also significantly more sensitive to cisplatin, 5-fluorouracil, mitoxantrone and bleomycin than were untreated controls. Indirect immunofluorescence revealed that 72-h exposure to as much as 1000 microM L-CAV did not alter cellular expression of P-gp. These studies suggest that L-CAV may be equally cytotoxic for both parental and MDR tumor cells, and that L-CAV neither induces the expression of, nor is a substrate for, P-gp. The observation that L-CAV pre-treatment reduces cellular accumulation of DOX, yet sensitizes tumor cells to DOX and other DNA-targeting antineoplastic drugs, suggests a role for L-CAV as a chemosensitizer for the chemotherapy of cancer.