Substrates modified by advanced glycation end-products cause dysfunction and death in retinal pericytes by reducing survival signals mediated by platelet-derived growth factor

AIMS/HYPOTHESIS

Premature death of retinal pericytes is a pathophysiological hallmark of diabetic retinopathy. Among the mechanisms proposed for pericyte death is exposure to AGE, which accumulate during diabetes. The current study used an in vitro model, whereby retinal pericytes were exposed to AGE-modified substrate and the mechanisms underlying pericyte death explored.

METHODS

Pericytes were isolated from bovine retinal capillaries and propagated on AGE-modified basement membrane (BM) extract or non-modified native BM. The extent of AGE modification was analysed. Proliferative responses of retinal pericytes propagated on AGE-modified BM were investigated using a 5-bromo-2-deoxy-uridine-based assay. The effect of extrinsically added platelet-derived growth factor (PDGF) isoforms on these proliferative responses was also analysed alongside mRNA expression of the PDGF receptors. Apoptotic death of retinal pericytes grown on AGE-modified BM was investigated using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling labelling, mitochondrial membrane depolarisation and by morphological assessment. We also measured both the ability of PDGF to reverse Akt dephosphorylation that was mediated by AGE-modified BM, and increased pericyte apoptosis.

RESULTS

Retinal pericytes exposed to AGE-modified BM showed reduced proliferative responses in comparison to controls (p<0.05-0.01), although this effect was reversed at low-AGE modifications. PDGF mRNA levels were differentially altered by exposure to low and high AGE levels, and AGE-modified BM caused significantly increased apoptosis in retinal pericytes. Pre-treatment of AGE-modified BM with PDGF-AA and -BB reversed the apoptosis (p<0.05-0.001) and restored Akt phosphorylation in retinal pericytes.

CONCLUSIONS/INTERPRETATION

Evidence suggests that substrate-derived AGE such as those that occur during diabetes could have a major influence on retinal pericyte survival. During diabetic retinopathy, AGE modification of vascular BM may reduce bioavailability of pro-survival factors for retinal pericytes.

Linkage analysis of chromosome 2q in osteoarthritis

BACKGROUND

In independent linkage studies chromosome 2q11-q24 and chromosome 2q23-35 have previously been implicated as regions potentially harbouring susceptibility loci for osteoarthritis (OA).

OBJECTIVE

To test chromosome 2q for linkage to idiopathic osteoarthritis.

METHODS

Using a cohort of 481 OA families that each contained at least one affected sibling pair with severe end-stage disease (ascertained by hip or knee joint replacement surgery), we conducted a linkage analysis of chromosome 2q using 16 polymorphic microsatellite markers at an average spacing of one marker every 8.5 cM.

RESULTS

Our results provide suggestive evidence for a locus at 2q31 with a maximum multipoint logarithm of the odds score (MLS) of 1.22 which increased to 2.19 in those families concordant for hip-only disease (n = 311). This suggestive linkage was greater in male-hip families (MLS = 1.57, n = 71) than in female-hip families (MLS = 0.71, n = 132).

CONCLUSIONS

Chromosome 2q is likely to contain at least one susceptibility locus for OA.

Linkage analysis of candidate genes as susceptibility loci for osteoarthritis-suggestive linkage of COL9A1 to female hip osteoarthritis

OBJECTIVE

To examine 11 candidate genes as susceptibility loci for osteoarthritis (OA).

METHODS

A total of 481 families have been ascertained in which at least two siblings have had joint replacement surgery of the hip, or knee, or hip and knee for idiopathic OA. Each candidate gene was targeted using one or more intragenic or closely linked microsatellite marker. The linkage data were analysed unstratified and following stratification by sex and by joint replaced (hip or knee).

RESULTS

The analyses revealed suggestive linkage of the type IX collagen gene COL9A1 (6q12-q13) to a subset of 132 families that contained affected females who were concordant for hip OA (female-hip) with a P-value of 0.00053 and logarithm of the odds (LOD) score of 2.33 [corrected P-value of 0. 0016, corrected LOD score of 1.85].

CONCLUSIONS

COL9A1 may therefore be a susceptibility locus for female hip OA. In addition, there was weak evidence of linkage to HLA/COL11A2 (6p21.3) in female hip OA with a corrected P-value of 0.016.

Osteoarthritis-susceptibility locus on chromosome 11q, detected by linkage

We present a two-stage genomewide scan for osteoarthritis-susceptibility loci, using 481 families that each contain at least one affected sibling pair. The first stage, with 272 microsatellite markers and 297 families, involved a sparse map covering 23 chromosomes at intervals of approximately 15 cM. Sixteen markers that showed evidence of linkage at nominal P</=.05 were then taken through to the second stage, with an additional 184 families. This second stage confirmed evidence of linkage for markers on chromosome 11q. Additional markers from this region were then typed to create a denser map. We obtained a maximum single-point LOD score, at D11S901, of 2.40 (P=.0004) and a maximum multipoint-LOD score of 3.15, between markers D11S1358 and D11S35. A subset of 196 of the 481 families, comprising affected female sibling pairs, generated a corrected LOD score of 2.54 (P=.0003) for marker D11S901, with evidence for linkage extending 12 cM proximal to this marker. When we stratified for affected male sibling pairs there was no evidence of linkage to chromosome 11. Our data suggest that a female-specific susceptibility gene for idiopathic osteoarthritis is located on chromosome 11q.

N-(o-tolyl)-2-bromo-4,5-dimethoxybenzamide

The molecular structure of the title compound, C16H16BrNO3, consists of 2-bromo-4,5-dimethoxy-benzene and o-methylphenyl rings linked by an amide group. The two methoxy groups are almost coplanar with the phenyl ring.

Erythro-1-(benzothiazol-2-yl)-1,2-dibromo-2-(2-chloro-5-nitrophenyl)ethane

The title compound, C15H9Br2CIN2O2S, was synthesized by electrophilic addition of bromine to 2-(2-chloro-5-nitrostyryl)benzothiazole. The molecule consists of benzothiazole and 2-chloro-5-nitrophenyl rings linked by a 1,2-dibromoethane moiety. The dihedral angle between the benzothiazole and phenyl rings is 8.2(9) degrees. The benzothiazole ring is planar with a mean deviation of 0.168(7)A. The Br1--C8 and Br2--C9 bond distances are 1.972(5) and 2.007(6)A, respectively.

Inhibition of human topoisomerase II by anti-neoplastic benzazolo[3,2-alpha]quinolinium chlorides

Previously we reported [20] that there is no correlation between the cytotoxic activity of four new structural analogs of the antitumor DNA intercalator 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQ-2) and their interaction with DNA. In the present study, we present evidence suggesting that the molecular basis for the anti-proliferative activity of these drugs is the inhibition of topoisomerase II. The NBQ-2 derivatives inhibited the relaxation of supercoiled DNA plasmid pRYG mediated by purified human topoisomerase II. Inhibition of the decatenation of kinetoplast DNA mediated by partially purified topoisomerase II extracted from the human histiocytic lymphoma U937 (a cell line previously shown to be sensitive to the drugs) was also caused by these drugs. The potency of the benzazolo[3,2-a]quinolinium drugs against topoisomerase II in vitro was the following: 7-(1-propenyl)-3-nitrobenzimidazolo[3,2-a]quinolinium chloride (NBQ-59) > 4-chlorobenzothiazolo[3,2-a]quinolinium chloride (NBQ-76) > 7-ethyl-3-nitrobenzimidazolo[3,2-a]quinolinium chloride (NBQ-48) > 7-benzyl-3-nitrobenzimidazolol[3,2-a]quinolinium chloride (NBQ-38). This rank of potency for topoisomerase II inhibition correlated very well with the cytotoxicity elicited by these drugs. Furthermore, significant levels of topoisomerase II/DNA cleavage complex induced by these drugs in vivo were detected when U937 cells were treated with NBQ-59 and NBQ-76 whereas NBQ-38 and NBQ-48 produced negligible amounts of the cleavage complex. Our results strongly suggest that topoisomerase II is the major cellular target of this family of compounds.

DNA binding-independent anti-proliferative action of benzazolo[3,2-alpha]quinolinium DNA intercalators

The proposed mechanism of action of the antineoplastic drug 3-nitrobenzothiazolo[3,2-alpha]quinolinium chloride (NBQ-2) involves its interaction with DNA by intercalation and inhibition of topoisomerase II activity by arresting the enzyme in a covalent cleavage complex. In an attempt to identify some structural determinants for activity and develop a molecular structure/cytotoxicity correlation, four new structural analogs of the antitumor NBQ-2 were prepared and their cytotoxic activity and DNA binding properties were investigated. The cytotoxic activity was evaluated against six different human tumor cell lines: U937, K-562, HL-60, HT-29, HeLa, and A431. The results showed that these new drugs elicit pronounced cytotoxic effects against U937, K-562, HL-60 and A431 while HeLa and HT-29 were less sensitive to the new drugs. This apparent selectivity was different to that of m-AMSA, a drug currently used for cancer treatment. Since the interaction of NBQ-2 to DNA by intercalation has been proposed as the initial step leading to its antineoplastic activity, DNA binding and changes in DNA contour length induced by the new NBQ-2 structural analogs were also investigated using calf thymus and human DNA. The drug, 7-(1-propenyl)-3-nitrobenzimidazolo[3,2-alpha]quinolinium chloride (NBQ-59) was the most cytotoxic agent of the analog series (IC50 = 16 microM for HL-60 cells), however, it demonstrated the weakest binding to DNA (Kint = 0.9 x 10[5] M-1 for calf thymus DNA). NBQ-59 was also found to be a poor intercalator into the DNA double helix. Therefore, our results suggest that DNA binding is not the primary mechanism of drug action for this family of compounds. In addition structural determinants important for cytotoxicity of the benzazolo quinolinium chlorides were suggested by our results. In particular, the nitro group in the 3 position does not seem to be necessary for bioactivity, while substitutions in the benzazolo moiety have striking effects on the biological activity of the drugs.

(E,Z)-2-(2-chloro-5-nitrostyryl)-1-(1-propenyl)benzimidazole

The title compound, C18H14ClN3O2, was synthesized by the condensation of 2-chloro-5-nitrobenzaldehyde with 2-methyl-1-propenylbenzimidazole, and the molecule comprises a 2-chloro-5-nitrobenzene and a 1-(Z)-propenylbenzimidazole. The two aromatic moieties are conjugated through the vinyl group. The dihedral angle between the two rings is 1.4(6) degrees. The propenyl group lies out of the benzimidazole plane with a dihedral angle of 112.9(9) degrees.

1-(1,3-Benzothiazol-2-yl)-2-(2-bromo-5-nitrophenyl)ethanone

The title compound, C15H9BrN2O3S, was isolated as an unexpected product from the reaction of the anion of sodium 2-(1,3-benzothiazolyl)ethanonitrile with alpha,2-dibromo-5-nitrotoluene. Its structure features a benzothiazole fragment and a bromo- and nitro-substituted phenyl ring linked by a methyl ketone group. The dihedral angle between the benzothiazole and phenyl rings is 103.7 (2) degrees. The benzothiazole fragment is planar, with a maximum deviation of 0.021 (2) A. The nitro group is slightly rotated out of the phenyl-ring plane, with a O(2)-N(2)-C(14)-C(15) torsion angle of 16.4(7) degrees.

Bis[(E)-2-(2,4-dichloro-5-nitrostyryl)-1,3-benzothiazole] hydrate

The title compound, bis[(E)-2-(2,4-dichloro-5-nitrostyryl)-1,3-benzothiazole] hydrate, 2C15H8Cl2N2O2S.-H2O, was obtained from the condensation of 2-methyl-benzothiazole with 2,4-dichloro-5-nitrobenzaldehyde. Single-crystal X-ray analysis showed that the asymmetric unit contains two crystallographically unique but structurally similar molecules. The dihedral angle between the benzothiazole fragment and the phenyl ring is 6.1 (4) degrees in molecule A and 19.5 (4) degrees in molecule B.

Some dream mechanisms in Finnegans Wake

This paper does not purport to offer a psychoanalytic reading of Finnegans Wake, but rather to demonstrate how, in recreating the mechanisms of the dream, Joyce's masterpiece offers to psychoanalysis a uniquely rich opportunity to explore the shadowy play of the dream in the permanence of a work of art. In particular, the manner in which Finnegans Wake tells its story through the distortions of dream narrative while bodying forth its protagonists in the substitutions of dream-identity are explored, with the help of certain Freudian and Lacanian concepts of unconscious structure.

Reductive activation of benzazolo[3,2-a]-quinolinium chlorides

Initial ferricytochrome c (Cyt(III)c) reduction rates occurring in aerobic or anaerobic solutions containing either 3-nitrobenzothiazolo[3,2-a]-(NBQCl), 1-ethyl-3-nitrobenzimidazolo[3,2-a]-(ENBIQCl), 7-ethylbenzimidazolo[3,2-a]quinolinium chloride (EHBIQCL), or nitrofurantoin (NFT) and xanthine/xanthine oxidase were measured. Maximum rates in nitrogen-saturated solutions follow the order NFT > NBQCL > ENBIQCL > EHBIQCL. These rates correlate linearly with the half-wave reduction potentials (E1/2) of these compounds. With the exception of EHBIQCl, smaller rates of Cyt(III)c reduction were obtained in air-saturated than in nitrogen-saturated solutions at the quinolinium salt concentrations used. Larger concentrations of superoxide dismutase (SOD) are needed for 50% inhibition of the Cyt(III)c reduction reaction for heterocyclic compounds with larger E1/2 values. Thus, measurement of the portion of the Cyt(III)c reduction rate under air that is inhibited by SOD does not account solely for the production of superoxide. These observations suggest that NBQCL, ENBIQCl, and less probably EHBIQCl may interfere with mitochondrial energy metabolism or induce DNA damage through reduced intermediates.

Absence of mutagenicity of the antitumor drug 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQ) in the germ cells of Drosophila melanogaster males

The antitumor drug, 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQ) was tested for genotoxicity with the sex-linked recessive lethal test by feeding Drosophila melanogaster males. Although toxic to adults, the drug tested negative at the concentrations studied.

Photochemistry of aqueous solutions of benzazolo[3,2-a]quinolinium salts. A spin-trapping study using 17O-enriched water and oxygen

The photolysis of buffered aqueous solutions containing the quinolinium salts, 3-nitro-7-ethyl-benzimidazolo[3,2-a]quinolinium perchlorate (NEBQClO4) and 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQCl), at 344 and 365 nm, respectively, was studied in the presence of the spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). Only a water-derived DMPO-OH.spin-adduct was obtained for both of these salts, at a DMPO concentration of 14 mM, as confirmed by H2 17O-enriched water experiments. A photosolvated intermediate is postulated as the OH donating species. Lower steady-state concentrations of the spin adduct were obtained in argon-saturated solutions, implying that oxygen gas is at least partially necessary in the water-derived DMPO-OH formation. Evidence for superoxide ion formation was obtained by the DMPO-17OH spin-adduct formation during the photolysis of NBQCl in an 17O-enriched oxygen atmosphere in the presence of 150 mM DMPO. An increase in the DMPO-OH steady-state concentration was observed if the photolysis of NBQCl was performed in the presence of superoxide dismutase (SOD). Our results suggest that this effect is due to the SOD inhibition of the destruction of DMPO-OH.by superoxide ion.

Structure of a styrylbenzothiazole platinum(II) complex: [NEt4][PtBr3(asb)]

Tetraethylammonium tribromo[2-(2- acetoxystyryl)benzothiazole]platinate(II), [(C2H5)4N]-[PtBr3(C17H13NO2S)], Mr = 860.4 monoclinic, P21/c, a = 11.230 (9), b = 19.333 (4), c = 13.685 (6) A, beta = 101.06 (4) degrees, V = 2916 (4) A3, Z = 4, D chi = 1.96 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 90.3 cm-1, F(000) = 1648, T = 296 K, final R = 0.047 for 3384 unique observed reflections. The [PtBr3(asb)]- unit has square-planar geometry about the Pt, with the asb coordinated to the Pt through the N of the thiazole ring and a Pt-N bond distance of 2.010 (8) A. The average Pt-Br distance is 2.426 (7) A. The ligand is non-planar with a dihedral angle of 22.4 (7) degrees between the benzothiazole and the acetoxybenzene rings. The dihedral angles between the platinum coordination plane and the benzothiazole and benzene rings are 85.7 (1) and 71.3 (3) degrees respectively.

Structure of cis-Pt(asb)2Cl2, a platinum(II) complex with a styrylbenzothiazole ligand

cis-Bis[2-(2-acetoxystyryl)benzothiazole]dichloroplatinum(II), [PtCl2(C17H13NO2S)2], Mr = 856.7, triclinic, P1, a = 12.145 (6), b = 12.859 (4), c = 11.021 (5) A, alpha = 105.88 (3), beta = 90.64 (4), gamma = 87.64 (4) degrees, V = 1654 (2) A3, Z = 2, D chi = 1.72 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 46.1 cm-1, F(000) = 840, T = 296 K, final R = 0.029 for 6121 unique observed reflections. The [PtCl2(asb)2] complex has square-planar geometry about the Pt, with the asb coordinated to the Pt through the N of the thiazole ring. The average Pt-N and Pt-Cl bond distances are 2.035 (1) and 2.287 (5) A. The ligand is non-planar with an average dihedral angle of 36 (3) degrees between the benzothiazole and the benzene rings. The dihedral angles between the platinum coordination plane and the benzothiazole and benzene rings are 78 (4) and 69 (7) degrees respectively. The acetoxybenzene rings in the two ligands have different orientations with respect to the olefin C atoms.

Charge transfer-oxy radical mechanism for anti-cancer agents

The proposal is advanced that anti-cancer drugs generally function by charge transfer resulting in formation of toxic oxy radicals which destroy the neoplasm. Electrochemical studies were performed with some of the main types of agents: iminium ions (adenine iminium from alkylating species, iminium metabolite of 6-mercaptopurine, nitidine, other polynuclear iminiums) and metal complexes (Pt(II)diaquodiammine-guanosine, copper salicylaldoximes). Reduction potentials ranged from -0.4 to -1.2 V. Literature data for quinones are presented and radiation is discussed. Based on the theoretical framework, a rationale is offered for the carcinogen-anti-cancer paradox and the role of antioxidants.