Improving image quality of mid-trimester fetal sonography in obese women: role of ultrasound propagation velocity

OBJECTIVE

The quality of ultrasound images is impaired in obese patients. All ultrasound scanners are calibrated for an ultrasound propagation velocity of 1540 m/s, but the propagation in fatty tissue is slower (in the order of 1450 m/s). The main objective of this study was to evaluate the quality of images obtained with different ultrasound propagation velocity settings during the mid-trimester fetal ultrasound examination in obese patients.

METHODS

This was a cross-sectional study using image sets of four recommended scanning planes collected from 32 obese pregnant women during their mid-trimester fetal scan. Each image set comprised three images obtained successively at three different propagation velocity settings (1540 m/s, 1480 m/s and 1420 m/s). A panel of 114 experts assessed the quality of 100 image sets, grading them from A (most acceptable) to C (least acceptable). Scanning-plane-specific indicators of adiposity (fatty layer thickness, probe-to-organ distance) were analyzed for each scanning plane.

RESULTS

The experts had a mean of 18.1 ± 10.2 years of experience. The grade distribution (A, B, C) differed significantly (P < 0.0001) between the three propagation velocity settings tested; at the lower speed of 1480 m/s, images were most often graded A, while at the conventional speed of 1540 m/s, they were most often graded C. Regardless of the scanning plane, the thicker the fatty layer of the abdominal wall in a given plane, the lower the preferred speed (P < 0.0001).

CONCLUSION

The construction of images taking into account ultrasound propagation velocities lower than 1540 m/s can improve significantly the quality of images obtained during mid-trimester fetal ultrasonography in obese women. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

[Psychiatrists' decision making and monitoring of antipsychotic prescription for elderly schizophrenia patients]

OBJECTIVE

Advancing age entails specific treatment modalities for patients with schizophrenia. The choice of appropriate antipsychotic therapy (AP) and the monitoring of treatment is a major challenge. However, little is known about the real-world prescribing practices of psychiatrists for elderly schizophrenia patients. The aim of this study was to assess prescribing practices and treatment monitoring in elderly schizophrenia patients and whether socio-professional psychiatrists' characteristics are related to their practices.

METHODS

We contacted by mail 190 psychiatrists to take part in an observational survey of their AP prescribing practices for elderly (aged over 65) schizophrenia patients.

RESULTS

The response rate was 44.2%, and of the psychiatrists who replied 75% were treating elderly schizophrenia patients. A second-generation AP (SGAP) was prescribed as first-line of treatment by 87.7% of the psychiatrists. The most frequently used SGAPs were risperidone and olanzapine (respectively preferred by 54.4% and 19.3% of the psychiatrists taking part). At the beginning of treatment, 91.1% of the psychiatrists prescribed a lower dose than for middle-aged patients. Of the psychiatrists taking part, 64.9% prescribed monotherapy; and among these psychiatrists, 65% cited insufficient control of the disease as the reason for their choice, while 48.7% of those who elected not to prescribe combined AP did so in order to limit the side-effects. Of the psychiatrists taking part, 54.4% prescribed long-acting injectable AP (LAAP); better therapeutic compliance and alliance was the main argument in the choice of LAAP given by the psychiatrists taking part who prescribed the drug, whereas the absence of indications and problems of tolerance were arguments against for those who did not. "Personal experience" emerged as the governing factor in the choice of AP. The AP side-effect profile was the main criterion of choice of the AP agent for 3.5% of the psychiatrists taking part, and the most frequently chosen secondary criterion (29.8%). Monitoring of treatment was partly performed according to professional recommendations: pre-treatment and post-prescription assessments of waist circumference and ophthalmological monitoring were very infrequent (8.8 to 18.5%) as were pre-treatment and early post-prescription assessments of prolactinaemia (14.8 to 20.4%); long-term cardiac monitoring was infrequent (43.9%). The psychiatrists taking part whose first-line drug was SGAP were more familiar with professional recommendations than those who prescribed first generation antipsychotic (FGA) drugs (72% as against 14.3%, P=0.006). Of the psychiatrists taking part in the study, 64.9% reported they commonly use professional recommendations. Psychiatrists who declared they commonly use professional recommendations measured pulse rate and blood pressure significantly more often over the long-term than those who did not (74.3% as against 41.2%, P=0.0315). They also measured waist circumference over the long-term significantly more often than psychiatrists who did not commonly use professional recommendations (22.9% as against 0%, P=0.0420). Psychiatrists treating more than ten of these patients yearly measured significantly more often over the long-term pulse rate and blood pressure than those treating fewer patients (80% as against 50%, P=0.0399). Over the long-term monitoring, psychiatrists with a larger number of elderly schizophrenia patients in their care also performed more often fasting blood glucose test, lipid profile and referral for cardiac consultation with ECG (respectively, 95.5% as against 70.8%, P=0.0489; 90.9% as against 58.3%, P=0.0182; 81.8% as against 29.2%, P<0.0001).

CONCLUSIONS

The results of this survey need to be confirmed in a larger population sample. The antipsychotic prescribing practices were broadly in agreement with current recommendations except for the tolerance profile which was not the first element taken into account in the choice of the AP agent. Some clinical and paraclinical medical examinations were carried out infrequently, in particular cardiac monitoring over the long-term, which is essential in this elderly patient population. One important element to emerge from our results was that common use of professional recommendations is associated with better monitoring.

Qualité de vie des conjoints de patients âgés souffrant de dépression

Objectifs

Évaluer la qualité de vie liée à la santé (QVS) et la charge en soins des conjoints vivant en couple avec un patient de 65 ans et plus souffrant de dépression, en début de prise en charge, en comparaison à des témoins appariés.

Méthode

Patients de 65 ans et plus souffrant d’un épisode dépressif caractérisé suivant les critères du DSM-IV-TR et leurs conjoints étaient inclus dans l’étude. L’évaluation des patients comportait : une échelle de dépression gériatrique (GDS-15) et une échelle de QVS spécifique sujets âgés validée en français (LEIPAD) [1,2]. L’évaluation des conjoints des patients comportait : la GDS-15, une échelle d’évaluation du fardeau subjectif de l’aidant (Zarit) et l’échelle LEIPAD. Les scores à la LEIPAD des patients et de leurs conjoints étaient comparés à ceux de contrôles appariés sur l’âge et le sexe. Tous les participants avaient donné leur consentement éclairé.

Résultats

Dix-neuf patients (76,6 ± 8,1 ans ; score GDS-15 : 9,7 ± 2,9) et leurs conjoints (75,3 ± 8,2 ans ; score GDS-15 : 4,0 ± 2,8) ont été inclus. Pour les conjoints, le score total à la Zarit était de 31,9 ± 14,4. Comparés à des témoins appariés, la QVS des conjoints est dégradée pour la dimension « Fonctionnement sexuel ». Chez les conjoints, on retrouve des corrélations statistiquement significatives entre : les scores à la Zarit et les scores à la LEIPAD pour les dimensions « Prendre soin de soi », « Fonctionnement sexuel » et « Satisfaction de vie » ; les scores à la GDS-15 des patients et les scores à la LEIPAD des conjoints pour la dimension « Fonctionnement sexuel ».

Conclusion

La QVS des conjoints est dégradée pour la dimension « Fonctionnement sexuel ». Lorsque le fardeau des conjoints augmente, certaines dimensions de leur QVS se dégradent ; de même, lorsque la sévérité de la dépression des patients augmente.

[Health-related quality of life evaluation of elderly aged 65 years and over living at home]

BACKGROUND

To assess health-related quality of life in French adults aged 65 years and over, living at home, with a specific self-administered questionnaire, the LEIPAD, cross-culturally adapted in French.

METHODS

Elderly completed socio-demographic and medical questionnaires, a questionnaire about negative life events during the last 12 months and the LEIPAD.

RESULTS

Data of 195 subjects (mean age: 72.6 years, men: 56.5%) were analyzed. The response rates to the LEIPAD scales were superior to 90%. Elderly reported on the whole a good health-related quality of life. Age had a negative effect on quality on life, which deteriorates over years. Age was correlated to the scales "Physical function", "Self-care", "Cognitive functioning" and "Sexual functioning". Elderly hospitalized in the last year had worse quality of life with a significant difference for "Physical function" scale. The number of health problems was positively correlated to "Physical function" scale. Elderly declaring at least one health problem had worse quality of life for this scale. Problems in couple, materials and financial problems had also negative effects on health-related quality of life.

CONCLUSION

Our study highlights a good health-related quality of life for the majority of these adults aged 65 years and over, as well as the negative effect of age, health, couple, materials and financial problems on their quality of life.

Cross-cultural evaluation of the French version of the LEIPAD, a health-related quality of life instrument for use in the elderly living at home

PURPOSE

To cross-culturally adapt a French version of the LEIPAD, a self-administered questionnaire assessing the health-related quality of life (HRQoL) in adults aged 65 years and over living at home, and to evaluate its psychometric properties.

METHODS

After having translated LEIPAD in accordance with guidelines, we studied psychometric properties: reliability and construct validity-factor analysis, relationships between items and scales, internal consistency, concurrent validity with the Medical Outcome Study Short-Form 36 and known-groups validity.

RESULTS

The results obtained in a sample of 195 elderly from the general population showed very good acceptability, with response rates superior to 93 %. Exploratory factor analysis extracted eight factors providing a multidimensionality structure with five misclassifications of items in the seven theoretical scales. Good internal consistency (Cronbach's alpha ranging from 0.73 and 0.86) and strong test-retest reliability (ICCs higher than 0.80 for six scales and 0.70 for one) were demonstrated. Concurrent validity with the SF-36 showed small to strong expected correlations.

CONCLUSION

This first evaluation of the French version of LEIPAD's psychometric properties provides evidence in construct validity and reliability. It would allow HRQoL assessment in clinical and common practice, and investigators would be able to take part in national and international research projects.

Simultaneously monitoring DNA binding and helicase-catalyzed DNA unwinding by fluorescence polarization

A new method for helicase-catalyzed DNA unwinding is described. This assay takes advantage of the substantial change in fluorescence polarization (FP) upon helicase binding and DNA unwinding. The low anisotropy value, due to the fast tumbling of the free oligonucleotide in solution, increases abruptly upon binding of helicase to the fluorescein-labeled oligonucleotide. The high anisotropy of the helicase- DNA complex decreases as the fluorescein-labeled oligonucleotide is released from the complex through helicase-catalyzed DNA unwinding. This FP signal can be measured in real time by fluorescent spectroscopy. This assay can simultaneously monitor DNA binding and helicase-catalyzed DNA unwinding. It can also be used to determine the polarity in DNA unwinding mediated by helicase. This FP assay should facilitate the study of the mechanism by which helicase unwinds duplex DNA, and also aid in screening for helicase inhibitors, which are of growing interest as potential anticancer agents.

DNA binding induces dissociation of the multimeric form of HIV-1 integrase: a time-resolved fluorescence anisotropy study

Self-assembly of HIV-1 integrase (IN) in solution has been studied previously by time-resolved fluorescence, using tryptophan anisotropy decay. This approach provides information on the size of macromolecules via the determination of rotational correlation times (theta). We have shown that, at submicromolar concentration, IN is characterized by a long rotational correlation time (theta(20 degrees C) = 90-100 ns) corresponding to a high-order oligomeric form, likely a tetramer. In the present work, we investigated the self-assembly properties of the DNA-bound IN by using three independent fluorophores. Under enzymatic assay conditions (10(-7) M IN, 2 x 10(-8) M DNA), using either fluorescein-labeled or fluorescent guanosine analog-containing oligonucleotides that mimic a viral end long terminal repeat sequence, we found that the DNA-IN complex was characterized by shorter theta(20 degrees C) values of 15.5-19.5 and 23-27 ns, calculated from experiments performed at 25 degrees C and 37 degrees C, respectively. These results were confirmed by monitoring the Trp anisotropy decay as a function of the DNA substrate concentration: the theta of IN shifted from 90-100 ns to lower values (<30 ns) upon increasing the DNA concentration. Again, the normalized theta(20 degrees C) values were significantly higher when monitored at 37 degrees C as compared with 25 degrees C. These results indicate that upon binding the viral DNA end, the multimeric enzyme undergoes a dissociation, most likely into a homogeneous monomeric form at 25 degrees C and into a monomer-dimer equilibrium at 37 degrees C.

Tautomers of styrylquinoline derivatives containing a methoxy substituent: computation of their population in aqueous solution and their interaction with RSV integrase catalytic core

8-Hydroxy-2-[2-(3-hydroxy-4-methoxyphenyl)ethenyl]-7-quinoline carboxylic acid and 8-hydroxy-2-[2-(3-methoxy-4-hydroxyphenyl)ethenyl]-7-quinoline carboxylic acid inhibit the processing and strand transfer reactions catalyzed by HIV-1 integrase with an IC50 of 2 microM. Some of their spectral properties are briefly reported. Their fluorescence is so weak that it is of no use in an experimental determination of the binding to the protein and we resorted to computer simulation. Both styrylquinoline derivatives, in their monoanionic form, have several dozens of tautomers and each of these forms has four planar rotamers. In this work computer simulations have been performed to determine which tautomer is the most abundant in aqueous solution and which binds to the Rous sarcoma virus (RSV) integrase catalytic core. As the substituents on the quinoline moiety are the same as on salicylic acid, the energies of hydroxy benzoic acid tautomers were also computed both in vacuo and embedded in a continuous medium which had the dielectric constant of bulk water, using the recent CPCM technique. The CPCM method was then applied to the two integrase inhibitors to estimate the tautomer population in water. The binding site of the compounds on the RSV integrase catalytic core was determined through a docking protocol, consisting of coupling a grid search method with full energy minimization. The designed method is a way leading to identification of potent integrase inhibitors using in silico experiments.

Involvement of histone H4 gene transcription factor 1 in downregulation of vimentin gene expression during skeletal muscle differentiation

Upon in vitro myogenesis, the intermediate filament protein vimentin is replaced by desmin, the switch in gene expression occurring essentially at the transcriptional level. Trying to elucidate the molecular mechanisms of this genetic control, we show here that the vimentin promoter is specifically recognized and activated by a protein most probably identical to H4TF-1, and that this factor is present in proliferating myoblasts but disappears upon fusion of these cells into multinucleated myotubes. Our results suggest that H4TF-1 is a differentiation stage-specific factor involved in the downregulation of vimentin gene expression during myogenesis.

EWS fli-1 antisense nanocapsules inhibits ewing sarcoma-related tumor in mice

EWS Fli-1, a fusion gene resulting from a t(11;22) translocation is found in 90% of both Ewing's sarcoma and primitive neuroectodermal tumor (PNET). In the present study, we show that recently developed polyisobutylcyanoacrylate nanocapsules with an aqueous core were able to encapsulate efficiently high amounts of phosphorothioate oligonucleotides (ODN) directed against EWS Fli-1 chimeric RNA. Release of these ODN in serum medium was shown to be biphasic which was explained by the presence of two types of nanocapsules able to release ODN with different kinetics. In addition, nanocapsules were found to provide protection of these oligonucleotides from the degradation in serum. These ODN nanocapsules permitted to obtain inhibition of Ewing sarcoma-related tumor in mice after intratumoral injection of a cumulative dose as low as 14.4 nanomoles. This new type of non viral vector shows great potential for in vivo administration of oligonucleotides.

Determinants of Mg2+-dependent activities of recombinant human immunodeficiency virus type 1 integrase

The relationship between Mg(2+)-dependent activity and the self-assembly state of HIV-1 integrase was investigated using different protein preparations. The first preparations, IN(CHAPS) and IN(dial), were purified in the presence of detergent, but in the case of IN(dial), the detergent was removed during a final dialysis. The third preparation, IN(zn), was purified without any detergent. The three preparations displayed comparable Mn(2+)-dependent activities. In contrast, the Mg(2+)-dependent activity that reflects a more realistic view of the physiological activity strongly depended on the preparation. IN(CHAPS) was not capable of using Mg(2+) as a cofactor, whereas IN(zn) was highly active under the same conditions. In the accompanying paper [Deprez, E., et al. (2000) Biochemistry 39, 9275-9284], we used time-resolved fluorescence anisotropy to demonstrate that IN(CHAPS) was monomeric at the concentration of enzymatic assays. Here, we show that IN(zn) was homogeneously tetrameric under similar conditions. Moreover, IN(dial) that exhibited an intermediary Mg(2+)-dependent activity existed in a monomer-multimer equilibrium. The level of Mg(2+)- but not Mn(2+)-dependent activity of IN(dial) was altered by addition of detergent which plays a detrimental role in the maintenance of the oligomeric organization. Our results indicate that the ability of integrase to use Mg(2+) as a cofactor is related to its self-assembly state in solution, whereas Mn(2+)-dependent activity is not. Finally, the oligomeric IN(zn) was capable of binding efficiently to DNA regardless of the cationic cofactor, whereas the monomeric IN(CHAPS) strictly required Mn(2+). Thus, we propose that a specific conformation of integrase is a prerequisite for its binding to DNA in the presence of Mg(2+).

Oligomeric states of the HIV-1 integrase as measured by time-resolved fluorescence anisotropy

Self-assembly properties of HIV-1 integrase were investigated by time-resolved fluorescence anisotropy using tryptophanyl residues as a probe. From simulation analyses, we show that suitable photon counting leads to an accurate determination of long rotational correlation times in the range of 20-80 ns, permitting the distinction of the monomer, dimer, and tetramer from higher oligomeric forms of integrase. The accuracy of correlation times higher than 100 ns is too low to distinguish the octamer from other larger species. The oligomeric states of the widely used detergent-solubilized integrase were then studied in solution under varying parameters known to influence the activity. In the micromolar range, integrase exists as high-order multimers such as an octamer and/or aggregates and a well-defined tetramer, at 25 and 35 degrees C, respectively. However, integrase is monomeric at catalytically active concentrations (in the sub-micromolar range). Detergents (NP-40 and CHAPS) and divalent cation cofactors (Mg(2+) and Mn(2+)) have a clear dissociative effect on the high multimeric forms of integrase. In addition, we observed that Mg(2+) and Mn(2+) have different effects on both the oligomeric state and the conformation of the monomer. This could explain in part why these two metal cations are not equivalent in terms of catalytic activity in vitro. In contrast, addition of Zn(2+) stimulates dimerization. Interestingly, this role of Zn(2+) in the multimerization process was evident only in the presence of Mg(2+) which by itself does not induce oligomerization. Finally, it is highly suggested that the presence of detergent during the purification procedure plays a negative role in the proper self-assembly of integrase. Accordingly, the accompanying paper [Leh, H., et al. (2000) Biochemistry 39, 9285-9294] shows that a detergent-free integrase preparation has self-assembly and catalytic properties different from those of the detergent-solubilized enzyme.

Modeling of the inhibition of retroviral integrases by styrylquinoline derivatives

Styrylquinoline derivatives, known to be potent inhibitors of HIV-1 integrase, have been experimentally tested for their inhibitory effect on the disintegration reaction catalyzed by catalytic cores of HIV-1 and Rous sarcoma virus (RSV) integrases. A modified docking protocol, consisting of coupling a grid search method with full energy minimization, has been specially designed to study the interaction between the inhibitors and the integrases. The inhibitors consist of two moieties that have hydroxyl and/or carboxyl substituents: the first moiety is either benzene, phenol, catechol, resorcinol, or salicycilic acid; the hydroxyl substituents on the second (quinoline) moiety may be in the keto or in the enol forms. Several tautomeric forms of the drugs have been docked to the crystallographic structure of the RSV catalytic core. The computed binding energy of the keto forms correlates best with the measured inhibitory effect. The docking procedure shows that the inhibitors bind closely to the crystallographic catalytic Mg(2+) dication. Additional quantum chemistry computations show that there is no direct correlation between the binding energy of the drugs with the Mg(2+) dication and their in vitro inhibitory effect. The designed method is a leading way for identification of potent integrase inhibitors using in silico experiments.

Structure-activity relationships and binding mode of styrylquinolines as potent inhibitors of HIV-1 integrase and replication of HIV-1 in cell culture

Our prior studies showed that polyhydroxylated styrylquinolines are potent HIV-1 integrase (IN) inhibitors that block the replication of HIV-1 in cell culture at nontoxic concentrations. To explore the mechanism of action of these inhibitors, various novel styrylquinoline derivatives were synthesized and tested against HIV-1 IN and in cell-based assays. Regarding the in vitro experiments, the structural requirements for biological activity are a carboxyl group at C-7, a hydroxyl group at C-8 in the quinoline subunit, and an ancillary phenyl ring. However the in vitro inhibitory profile tolerates deep alterations of this ring, e.g. by the introduction of various substituents or its replacement by heteroatomic nuclei. Regarding the ex vivo assays, the structural requirements for activity are more stringent than for in vitro inhibition. Thus, in addition to an o-hydroxy acid group in the quinoline, the presence of one ortho pair of substituents at C-3' and C-4', particularly two hydroxyl groups, in the ancillary phenyl ring is imperatively required for inhibitory potency. Starting from literature data and the SARs developed in this work, a putative binding mode of styrylquinoline inhibitors to HIV-1 IN was derived.

Tautomers of styrylquinoline derivatives containing a methoxy substituent: computation of their population in aqueous solution and their interaction with RSV integrase catalytic core

8-Hydroxy-2-[2-(3-hydroxy-4-methoxyphenyl)ethenyl]-7-quinoline carboxylic acid and 8-hydroxy-2-[2-(3-methoxy-4-hydroxyphenyl)ethenyl]-7-quinoline carboxylic acid inhibit the processing and strand transfer reactions catalyzed by HIV-1 integrase with an IC50 of 2 microM. Some of their spectral properties are briefly reported. Their fluorescence is so weak that it is of no use in an experimental determination of the binding to the protein and we resorted to computer simulation. Both styrylquinoline derivatives, in their monoanionic form, have several dozens of tautomers and each of these forms has four planar rotamers. In this work computer simulations have been performed to determine which tautomer is the most abundant in aqueous solution and which binds to the Rous sarcoma virus (RSV) integrase catalytic core. As the substituents on the quinoline moiety are the same as on salicylic acid, the energies of hydroxy benzoic acid tautomers were also computed both in vacuo and embedded in a continuous medium which had the dielectric constant of bulk water, using the recent CPCM technique. The CPCM method was then applied to the two integrase inhibitors to estimate the tautomer population in water. The binding site of the compounds on the RSV integrase catalytic core was determined through a docking protocol, consisting of coupling a grid search method with full energy minimization. The designed method is a way leading to identification of potent integrase inhibitors using in silico experiments.

Branched oligonucleotide-intercalator conjugate forming a parallel stranded structure inhibits HIV-1 integrase

Integration of a DNA copy of the HIV-1 genome into chromosomal DNA of infected cells is a key step of viral replication. Integration is carried out by integrase, a viral protein which binds to both ends of viral DNA and catalyses reactions of the 3'-end processing and strand transfer. A 3'-3' branched oligonucleotide functionalised by the intercalator oxazolopyridocarbazole at each 5'-end was found to inhibit integration in vitro. We show that both a specific (G,A) sequence and the OPC intercalating agent contribute to the capability of the branched oligonucleotide to form a parallel stranded structure responsible for the inhibition.

Early steps of replication of moloney murine leukemia virus in resting lymphocytes

We explored the role of cell type in the early steps of replication of Moloney murine leukemia virus (Mo-MLV) by comparing viral entry and reverse transcription in physiologically quiescent peripheral blood B and T lymphocytes. Virus entry was identical in both cell types. In contrast to previous results, full-length viral DNA was synthesized in resting B lymphocytes, but in agreement with earlier reports, reverse transcription was abortive in resting T lymphocytes. The addition of exogenous nucleosides in the culture medium of resting T lymphocytes allowed reverse transcription to proceed in these cells, without inducing cell cycling. These data suggest that the difference in the ability of quiescent T and B lymphocytes to sustain reverse transcription of Mo-MLV can be explained by a difference in the dNTP pool sizes of these two populations of quiescent cells.

Optimization of alternate-strand triple helix formation at the 5"-TpA-3" and 5"-ApT-3" junctions

Alternate-strand triple helix formation was optimized at the two junction steps, the 5"-TpA-3" and 5"-ApT-3" junctions. Footprint experiments, gel retardation assays and thermal denaturation measures on a sequence appropriately designed with two adjacent alternate-strand polypurine tracts points out that the addition of an adenine residue and the removal of one nucleotide should facilitate the crossing strands at the 5"-TpA-3" junction and at the 5"-ApT-3" junction, respectively. These results provide a 'switch code' for the construction of alternate-strand triple helix forming oligonucleotides which open new possibilities for extending the range of applications of antigene strategy.

Inhibition of HIV-1 integration by mono- & bi-functionalized triple helix forming oligonucleotides

HIV-1 DNA integration is carried out by integrase, a viral protein which binds to specific sequences located on both extremities of the HIV-1 DNA LTR. Inhibition of integration was observed with submicromolar concentrations of mono- or bifunctionalized 11-mer oligonucleotide-intercalators, which were designed to form an alternate strand triple helix with the U5 LTR end containing two adjacent purine tracts on opposite strands 5'-GGAAAATCTCT-3'/3'-CCTTTTAGAGA-5'.

Phenotypic and functional evidence for the expression of CXCR4 receptor during megakaryocytopoiesis

The identification of stromal cell-derived factor (SDF)-1alpha as a chemoattractant for human progenitor cells suggests that this chemokine and its receptor might represent critical determinants for the homing, retention, and exit of precursor cells from hematopoietic organs. In this study, we investigated the expression profile of CXCR4 receptor and the biological activity of SDF-1alpha during megakaryocytopoiesis. CD34(+) cells from bone marrow and cord blood were purified and induced to differentiate toward the megakaryocyte lineage by a combination of stem-cell factor (SCF) and recombinant human pegylated megakaryocyte growth and development factor (PEG-rhuMGDF). After 6 days of culture, a time where mature and immature megakaryocytes were present, CD41(+) cells were immunopurified and CXCR4mRNA expression was studied. High transcript levels were detected by a RNase protection assay in cultured megakaryocytes derived from cord blood CD34(+) cells as well as in peripheral blood platelets. The transcript levels were about equivalent to that found in activated T cells. By flow cytometry, a large fraction (ranging from 30% to 100%) of CD41(+) cells showed high levels of CXCR4 antigen on their surface, its expression increasing in parallel with the CD41 antigen during megakaryocytic differentiation. CXCR4 protein was also detected on peripheral blood platelets. SDF-1alpha acts on megakaryocytes by inducing intracellular calcium mobilization and actin polymerization. In addition, in in vitro transmigration experiments, a significant proportion of megakaryocytes was observed to respond to this chemokine. This cell migration was inhibited by pertussis toxin, indicating coupling of this signal to heterotrimeric guanine nucleotide binding proteins. Although a close correlation between CD41a and CXCR4 expession was observed, cell surface markers as well as morphological criteria indicate a preferential attraction of immature megakaryocytes (low level of CD41a and CD42a), suggesting that SDF-1alpha is a potent attractant for immature megakaryocytic cells but is less active on fully mature megakaryocytes. This hypothesis was further supported by the observation that SDF-1alpha induced the migration of colony forming unit-megakaryocyte progenitors (CFU-MK) and the expression of activation-dependent P-selectin (CD62P) surface antigen on early megakaryocytes, although no effect was observed on mature megakaryocytes and platelets. These results indicate that CXCR4 is expressed by human megakaryocytes and platelets. Furthermore, based on the lower responses of mature megakaryocytes and platelets to SDF-1alpha as compared with early precursors, these data suggest a role for this chemokine in the maintenance and homing during early stages of megakaryocyte development. Moreover, because megakaryocytes are also reported to express CD4, it becomes important to reevaluate the role of direct infection of these cells by the human immunodeficiency virus (HIV)-1 in HIV-1-related thrombocytopenia.

Conformational aspects of HIV-1 integrase inhibition by a peptide derived from the enzyme central domain and by antibodies raised against this peptide

Monospecific antibodies were raised against a synthetic peptide K159 (SQGVVESMNKELKKIIGQVRDQAEHLKTA) reproducing the segment 147-175 of HIV-1 integrase (IN). Synthesis of substituted and truncated analogs of K159 led us to identify the functional epitope reacting with antibodies within the C-terminal portion 163-175 of K159. Conformational studies combining secondary structure predictions, CD and NMR spectroscopy together with ELISA assays, showed that the greater is the propensity of the epitope for helix formation the higher is the recognition by anti-K159. Both the antibodies and the antigenic peptide K159 exhibited inhibitory activities against IN. In contrast, neither P159, a Pro-containing analog of K159 that presents a kink around proline but with intact epitope conformation, nor the truncated analogs encompassing the epitope, were inhibitors of IN. While the activity of antibodies is restricted to recognition of the sole epitope portion, that of the antigenic K159 likely requires interactions of the peptide with the whole 147-175 segment in the protein [Sourgen F., Maroun, R.G., Frère, V., Bouziane, A., Auclair, C., Troalen, F. & Fermandjian, S. (1996) Eur. J. Biochem. 240, 765-773]. Actually, of all tested peptides only K159 was found to fulfill condition of minimal number of helical heptads to achieve the formation of a stable coiled-coil structure with the IN 147-175 segment. The binding of antibodies and of the antigenic peptide to this segment of IN hampers the binding of IN to its DNA substrates in filter-binding assays. This appears to be the main effect leading to inhibition of integration. Quantitative analysis of filter-binding assay curves indicates that two antibody molecules react with IN implying that the enzyme is dimeric within these experimental conditions. Together, present data provide an insight into the structure-function relationship for the 147-175 peptide domain of the enzyme. They also strongly suggest that the functional enzyme is dimeric. Results could help to assess models for binding of peptide fragments to IN and to develop stronger inhibitors. Moreover, K159 antibodies when expressed in vivo might exhibit useful inhibitory properties.

Antisense-mediated repression of DNA topoisomerase II expression leads to an impairment of HIV-1 replicative cycle

Previously, we have observed a strong restriction of the Moloney murine leukemia virus (MoMLV) replicative cycle in a cell line displaying resistance to topoisomerase II (topo II)-interactive drugs. Resistance towards these antitumoral inhibitors was associated with decreased expression and activity of topo II, suggesting that such a decrease may be responsible for MoMLV restriction. To more specifically assess the role of topo II during the retroviral cycle, we have used the antisense strategy to obtain a selective decrease of cellular topo II expression. The RNA antisense was isolated from a retroviral library expressing random fragments of human topo II (alpha form). This system allowed us to investigate the HIV-1 replicative cycle in two related human CEM cell lines expressing different levels of topo II. Expression of the enzyme is decreased four- to sixfold following formation of a sense-antisense RNA hybrid. Repression of the topo II enzyme results in an impairment of the HIV-1 replicative cycle. Using the polymerase chain reaction, we showed that the number of integration events was decreased in cells repressing the enzyme, although viral DNA synthesis and circularization were equivalent to those in the parent cells.

Styrylquinoline derivatives: a new class of potent HIV-1 integrase inhibitors that block HIV-1 replication in CEM cells

On the basis of the fact that several polynucleotidyl transferases, related to HIV integrase, contain in their active site two divalent metal cations, separated by ca. 4 A, new potential HIV integrase inhibitors were designed, in which a quinoline substructure is linked to an aryl nucleus possessing various hydroxy substitution patterns, by means of an ethylenic spacer. Although the most active compounds contain the catechol structure, this group is not essential for the activity, since compound 21 that lacks such a moiety is a potent drug, implicating the presence of a different pharmacophore. The most promising styrylquinolines thus synthesized inhibit HIV-1 integrase in vitro at micromolar or submicromolar concentrations and block HIV replication in CEM cells, with no significant cellular toxicity in a 5-day period assay. These inhibitors are active against integrase core domain-mediated disintegration, suggesting that fragment 50-212 is their actual target. These new styrylquinolines may provide lead compounds for the development of novel antiretroviral agents for AIDS therapeutics, based upon inhibition of HIV integrase. They might also be used in the elucidation of the mechanism of inhibition of this enzyme; e.g., they could serve as candidates for cocrystallization studies with HIV integrase.

Human immunodeficiency virus type 1 nucleocapsid protein specifically stimulates Mg2+-dependent DNA integration in vitro

The integrase (IN) protein of the human immunodeficiency virus mediates integration of the viral DNA into the cellular genome. In vitro, this reaction can be mimicked by using purified recombinant IN and model DNA substrates. IN mediates two reactions: an endonucleolytic cleavage at each 3' end of the proviral DNA (terminal cleavage) and the joining of the linear viral DNA to 5' phosphates in the target DNA (strand transfer). Previous investigators have shown that purified IN requires Mn2+ or Mg2+ to promote strand transfer in vitro, although Mg2+ is the likely metal cofactor in vivo. IN activity in the presence of Mg2+ in vitro requires high IN concentrations and low concentrations of salt. Here, we show that the viral nucleocapsid protein NCp7 allows efficient IN-mediated strand transfer in the presence of Mg2+ at low enzyme concentrations. This potentiating effect appears to be unique to NCp7, as other small DNA-binding proteins, while capable of stimulating integration in the presence of Mn2+, all failed to stimulate strand transfer in the presence of Mg2+.

Clastogenic activity in the plasma of scleroderma patients: a biomarker of oxidative stress

BACKGROUND

Scleroderma patients exhibit increased chromosomal instability due to circulating clastogenic plasma factors (CF). Formation and action mechanisms of CF are mediated by superoxide. In addition, previous work detected inosine triphosphate (ITP) in the plasma of 2 patients, and the enzyme adenosine deaminase (ADA) was found to be increased.

OBJECTIVE

To study correlations between CF, ITP and ADA levels, CF and disease activity, as well as other biomarkers of oxidative stress.

METHODS

Clastogenic activity was evaluated by means of cytogenetic methods in 48 patients and 55 healthy subjects. ITP was detected by mass spectrometry and electrospray ionisation. ADA was measured with a colorimetric assay and malondialdehyde using the Yagi method.

RESULTS

Clastogenic activity was significantly increased in patients' plasma compared to controls. In 10 patients CF, ITP and ADA were studied simultaneously. All three parameters were increased in the 7 patients of subgroups 2 (skin and esophagus involvement) and 3 (skin plus multiple organ involvement). ITP was not detected in 2 patients of subgroup 1 (skin involvement only) with low ADA and CF values.

CONCLUSION

ITP, the deamination product of ATP, is one of the clastogenic and superoxide generating components of CF. The formation of this deamination product of ATP is probably related to the increase in ADA. CF are biomarkers of oxidative stress and can be used for evaluation of antioxidant treatments in scleroderma.

DNA minor groove cleaving agents: synthesis, binding and strand cleaving properties of anthraquinone-oligopyrrolecarboxamide hybrids

Three 9,10-anthraquinone-oligopyrrolecarboxamide hybrids have been prepared as potential DNA minor groove cleaving agents. Each conjugate was designed to contain a bis- or tris-pyrrolecarboxamide moiety related to netropsin or distamycin covalently linked to a 2-substituted anthraquinone chromophore capable of triggering photocleavage of DNA. AQ(NC)-Dist, having three pyrrole rings, is related to distamycin. AQ(NC)-Net and AQ(CN)-Net are related to netropsin; they differ only by the orientation of the amide bond between the anthraquinone and the netropsin moiety. The binding properties of these compounds to various natural DNAs have been studied by footprinting and circular dichroism. The introduction of the chromophore does not abolish the capacity of the drugs to recognize AT-rich sequences in DNA selectively. There is apparently little correlation between this property and the ability to trigger photo-induced DNA cleavage. AQ(CN)-Net is almost totally inactive in the cleavage assays whereas it manifestly binds selectively to AT-rich tracts. With AQ(NC)-Net and AQ(NC)-Dist, complete conversion of form I to form II of circular DNA is obtained. Moreover, in most cases the cleavage of DNA proved to be non-specific.

A synthetic peptide from the human immunodeficiency virus type-1 integrase exhibits coiled-coil properties and interferes with the in vitro integration activity of the enzyme. Correlated biochemical and spectroscopic results

Integration of the human immunodeficiency virus (HIV-1) DNA into the host genome is catalysed by a virus-encoded protein integrase. Here, we report some of the structural and functional properties of two synthetic peptides: integrase-(147-175)-peptide reproducing the residues 147-175 (SQGVVESMNKELK159KIIGQVRDQAEHLKTAY) of the HIV-1 integrase, and [Pro159] integrase-(147-175)-peptide where the lysine 159 is substituted for a proline. Circular dichroism revealed that both peptides are mostly under unordered conformation in aqueous solution, contrasting with the alpha-helix exhibited by residues 147-175 in the protein crystal structure. In a weak alpha-helix-promoting environment, integrase-(147-175)-peptide self-associated into stable coiled-coil oligomers, while [Pro159] integrase-(147-175)-peptide did not. This property was further confirmed by cross-linking experiments. In our in vitro experiments, only integrase-(147-175)-peptide was able to reduce the integration activity of the enzyme. We propose that the inhibitory activity shown by integrase-(147-175)-peptide is dependent on its ability to bind to its counterpart in integrase through a peptide-protein coiled-coil structure disturbing the catalytic properties of the enzyme.

Binding of Net-Fla, a netropsin-flavin hybrid molecule, to DNA: molecular mechanics and dynamics studies in vacuo and in water solution

We have studied the binding of the hybrid netropsin-flavin (Net-Fla) molecule onto four sequences containing four A. T base pairs. Molecular mechanics minimizations in vacuo show numerous minimal conformations separated by one base pair. 400 ps molecular dynamics simulations in vacuo have been performed using the lowest minima as the starting conformations. During these simulations, the flavin moiety of the drug makes two hydrogen bonds with an amino group of a neighboring guanine. A 200 ps molecular dynamics simulation in explicit water solution suggests that the binding of Net-Fla upon the DNA substrate is enhanced by water bridges. A water molecule bridging the amidinium of Net-Fla to the N3 atom of an adenine seems to be stuck in the drug-DNA complex during the whole simulation. The fluctuations of the DNA helical parameters and of the torsion angles of the sugar-phosphate backbone are very similar in the simulations in vacuo and in water. The time auto-correlation functions for the DNA helical parameters decrease rapidly in the picosecond range in vacuo. The same functions computed from the water solution molecular dynamics simulations seem to have two modes: the rapid mode is similar to the behavior in vacuo, and is followed by a slower mode in the 10 ps range.

Alternate strand DNA triple helix-mediated inhibition of HIV-1 U5 long terminal repeat integration in vitro

Integration of the human immunodeficiency virus (HIV) DNA into the host genome is an obligatory process in the replicative life cycle of the virus. This event is mediated in vitro by integrase, a viral protein which binds to specific sequences located on both extremities of the DNA long terminal repeats (LTRs). These sites are highly conserved in all HIV genomes and thus provide potential targets for the selective inhibition of integration. The integrase-binding site located on the HIV-1 U5 LTR end contains two adjacent purine tracts on opposite strands, 5' . . . GGAAAATCTCT-3'/3'-CCTTTTAGAGA . . . 5', in parallel orientations. A single strand oligonucleotide 5'-GGTTTTTGTGT-3' was designed to associate with these tracts via its ability to form a continuous alternate strand DNA triplex. Under neutral pH and physiological temperature, the oligonucleotide, tagged with an intercalator chromophore oxazolopyridocarbazole, formed a stable triplex with the target DNA. The occurrence of this unusual triplex was demonstrated by both DNase I footprinting and electron microscopy. The triplex inhibits the two steps of the integrase-mediated reactions, namely, the endonucleolytic cleavage of the dinucleotide 5'-GT-3' from the 3' end of the integration substrate and the integration of the substrate into the heterologous target DNA. The midpoints for both inhibition reactions were observed at oligonucleotide concentrations of 50-100 nM. We believe that these results open new possibilities for the specific targeting of viral DNA LTR ends with the view of inhibiting integration under physiological conditions.

A molecular mechanics and dynamics study of alternate triple-helices involving the integrase-binding site of the HIV-1 virus and oligonucleotides having a 3'-3' internucleotide junction

Triple helix formation by oligonucleotides can be extended beyond polypurine tracts with the help of specially designed linkers. In this paper we focus our attention on the integrase-binding site of the HIV-1 virus located on the U5 LTR end which contains two adjacent purine tracts on opposite strands. Two alternate triple helices with a 3'-3' junction in the third strand are considered: 5'-GGTTTTp3'-3'pTGTGT-5' and 5'-GGAAAAp3'-3'pAGAGA-5' The structural plausibility of these triplexes is investigated using molecular mechanics and dynamics simulations, both in vacuo and in aqua. The non-isomorphism of the triplets in the GpT steps in the first sequence, gives rise to non canonical conformations in the torsion angles, hydration appears to be crucial for this triplex. Sugar puckers are predominantly South during in vacuo simulations while they turn East in aqua. In the simulation in aqua the triplexes are shrouded by an hydration shell, however, we have not been able to detect any permanent hydrogen bond bridge between DNA and water. The solvation of ions as well as their radial distribution, appear to be relatively well behaved despite the artifacts known to be generated by the simulation procedure. The experimental feasibility of these structures is discussed.

Enhanced topoisomerase II-induced DNA breaks and free radical production by a new anthracycline with potent antileukemic activity

In a previous study we reported that a new anthracycline derivative (moflomycin) exhibited a higher antileukemic activity compared to other anthracyclines, such as daunorubicin and doxorubicin. To explain the superior antileukemic effect of moflomycin and to disclose a possible structure-activity relationship, we investigated the three main mechanisms by which anthracyclines are though to exert their antitumor effect: DNA binding, free radical production and topoisomerase II inhibition. The DNA interaction was assessed both by DNA binding and DNA unwinding assays, free radical generation was studied by electron spin resonance, and topoisomerase II interaction by analysis of the stimulation of enzyme-induced DNA breaks. The results showed a higher free radical production and a greater stimulation of topoisomerase II-mediated DNA cleavage by moflomycin than doxorubicin, associated with a lower DNA affinity. The different biochemical characteristics of moflomycin, particularly its interaction with topoisomerase II, are related to the structural modifications performed on the chromophore. These properties, associated with a higher stability of the molecule induced by the presence of an iodine atom on the sugar moiety, are probably responsible for the higher antileukemic activity of this compound.

Sequence-directed single strand cleavage of DNA by a netropsin-flavin hybrid molecule

In an attempt to obtain sequence specific DNA-cleaving molecules, we have synthesized a series of hybrid minor groove binders composed of a photoactiveable isoalloxazine (flavin) chromophore linked through a polymethylenic chain to a bis-pyrrolecarboxamide moiety related to netropsin. Like netropsin, the hybrid derivatives preferentially bind to A+T-rich sequences. Activation of the flavin chromophore by visible light results in the appearance of single strand breaks in the vicinity of the DNA binding site. We have further investigated the cleavage affinity properties of one of these compounds referred to as netropsin-flavin (Net-Fla) and considered as representative of the series. Net-Fla cleaves only one strand at a specific locus downstream of 5'-AAAT-3', upstream of 5'-TAAA-3' and on either side of a 5'-AAAA-3' sequence. Net-Fla cleaves both strands downstream to 5'-AATT-3'. This makes the properties of Net-Fla similar to that of a restriction endonuclease and provides additional insight into establishing the rules for the readout of B-DNA helix by non-nucleotidic compounds. Using molecular modeling, we show that Net-Fla binds to an asymmetric site in one orientation. The values of the energetic minima lie in the same order as expected from the cleavage patterns, which suggests that the oriented cleavage is a consequence of a sequence-oriented binding of Net-Fla in the DNA minor groove.

Impairment of Moloney murine leukemia virus integration in a cell line underexpressing DNA topoisomerase II

The possible intervention of nuclear proteins as cofactors of integrase-catalyzed integration of retroviral DNA into the host cell genome is not fully understood. Among various nuclear proteins, DNA topoisomerase II appears to be a plausible candidate. This hypothesis is supported by a series of evidence, including the fact that integration is markedly affected by the topology of the target DNA and mainly occurs in transcribed regions in which topoisomerase II is preferentially located. In an attempt to confirm the validity of this hypothesis, we have comparatively investigated the early stages of a recombinant Moloney murine leukemia virus (psi neo) in two related Chinese hamster cell lines (DC3F and R/DC3F) expressing different levels of both isoforms of topoisomerase II. R/DC3F is derived from the parental cell line DC3F and displays a resistant phenotype towards the usual anticancer topoisomerase II inhibitors (actinomycin D, doxorubicin, and taxol). Results show that the early stages of the retroviral cycle are markedly impaired in cells underexpressing topoisomerase II (R/DC3F). This alteration mimics Fv-1 restriction and is characterized by about a 6-fold decrease in viral DNA synthesis and total inhibition of viral genome integration. The specific impairment of integration in R/DC3F cells compared to DC3F cells is assessed by the absence of G418-resistant colonies upon viral infection and a lack of the viral genome in cellular nuclear DNA as detected by the PCR procedure. These features are observed in relevant infecting conditions leading, in both cell lines, to the same amount of linear viral DNA and to the occurrence of two long terminal repeats containing circular DNA in the nuclear fractions.

Safety profile of didanosine among patients with advanced HIV disease who are intolerant to or deteriorate despite zidovudine therapy: results of the Canadian Open ddI Treatment Program

The aim of this study was to ascertain the safety profile of didanosine (Videx; ddI) within the Canadian Open Treatment Program. Symptomatic HIV+ subjects with AIDS or ARC or CD4 < 200/mm3 were eligible to receive didanosine if they were either (a) intolerant to zidovudine (Retrovir, ZDV) or (b) deteriorating despite ZDV therapy. The dose of didanosine (powder formulation) was based on body weight as follows: > or = 75 kg, 375 mg b.i.d.; 50-74 kg, 250 mg b.i.d.; 35-49 kg, 167 mg b.i.d. Participants were monitored with physical examinations and prespecified laboratory studies by their treating physicians on a monthly basis. Follow-up data were collected in a central database through five regional coordinators. A total of 168 physicians across Canada participated in the program, and 825 subjects who started didanosine after July 1, 1990, were included in the analysis. Of these, 97% were male, 88% homosexual, and 59% had a prior diagnosis of AIDS. Reasons for enrolling was ZDV intolerance in 39%, failure in 25%, both in 32%, and other in 4%. Data were prospectively collected until July 31, 1991. Total follow-up was 3,440 patient-months and median follow-up was 4.3 months. A total of 78 deaths were reported, 44 of which occurred within a month after the last dose of didanosine. Causes of death included AIDS-related unspecified causes (13 patients), MAC (11), wasting (7), AIDS-related CNS involvement other than OI's (7), Kaposi's sarcoma (7), Pneumocystis carinii pneumonia (6), sudden death, including suicides and accidents (6), lymphoma (5), toxoplasmosis (4), cryptococcosis (4), cytomegalovirus (3), unspecified causes (2), tuberculosis (1), PML (1), and disseminated histoplasmosis (1). Didanosine was discontinued in 140 (17%) subjects during the study period due to adverse events.(ABSTRACT TRUNCATED AT 250 WORDS)

Triplex-mediated inhibition of HIV DNA integration in vitro

Integration of human immunodeficiency virus (HIV) DNA into the genome of host cells is an obligatory step in the replicative cycle of the virus. The overall process is carried out in vitro by a single viral protein, the integrase, which binds to short sequences located at the ends of viral DNA long terminal repeats (LTRs). These end sequences are highly conserved in all HIV genomes and are therefore attractive targets for selective DNA binding compounds. The integrase-binding site located in U3 LTR contains a purine motif, 5'-GGAAGGG-3' which can be selectively targeted by oligonucleotide-intercalator conjugates. Under neutral pH and physiological temperature, these conjugates readily form a stable complex with the viral DNA which involves a short DNA triplex. Triple-helix formation prevents the catalytic functions of the integrase in vitro which results in a sequence-specific inhibition of the U3 integration process.

Inhibition of the in vitro integration of Moloney murine leukemia virus DNA by the DNA minor groove binder netropsin

In search of potential inhibitors of integration of retroviral DNA into host cells genome, we have investigated the effect of the external DNA binder netropsin on the in vitro insertion of long terminal repeat (LTR) ends of Moloney murine leukemia virus (M.MuLV) as catalysed by integrase purified from baculovirus strain expression vector. In agreement with the preferential binding of netropsin to A+T rich sequences, footprinting experiments have shown that this drug selectively binds to the 5'-TTTCAT LTR end sequence which is included in the DNA binding site of integrase. This feature results in the potent inhibition of both reactions involved in the insertion process, namely, nucleolytic cleavage and strand transfer. The relation between netropsin binding to A+T rich region of M.MuLV LTR end and inhibition of insertion is strongly suggested from the inability of the drug to inhibit the insertion of HIV U3 LTR end which displays a G+C rich sequence. Selective inhibition of integration of viral DNA appears to be feasible using drugs recognizing LTR end sequences.

Potentiation of 2',3'-dideoxycytidine (ddC) by hydroxyurea and thymidine on the Moloney murine leukemia virus (MoMLV) early replicative steps

Combinations of ddC with either the ribonucleotide reductase inhibitor hydroxyurea (HU) or with the natural nucleoside thymidine have been investigated on the cycle of a defective (psi neo) Moloney Leukemia Virus (MoMLV) using 3T3 fibroblasts as host cells. In this experimental model, ddC displayed very poor antiviral action which was obvious given an IC50 value close to 100 microM, i.e. an efficiency about thirty thousand fold lower than that of AZT. Both HU and thymidine alone resulted in significant inhibition of MoMLV replication with IC50 values of 40 microM and 100 microM respectively. The combination of ddC with 50 microM HU lowered the IC50 of ddC by a factor of 10. A similar but more pronounced effect was obtained by combining ddC and 100 microM thymidine, which decreases the IC50 value of ddC by a factor of 50. Combining 40 microM ddC and 100 microM thymidine resulted in the quite complete inhibition of viral replication. These results show that in cell types with strongly restricted ddC action, combination treatment with compounds known to ultimately decrease dCTP biosynthesis leads to the restoration of efficient antiviral activity.

Triple helix formation with short oligonucleotide-intercalator conjugates matching the HIV-1 U3 LTR end sequence

In an attempt to target short purine sequences in view of pharmacological application, we have synthesized three new TFO (triple-helix-forming oligonucleotide) conjugates in which an intercalating oxazolopyridocarbazole (OPC) chromophore is linked by a pentamethylene linker to a 7-mer oligonucleotide matching the polypurine/polypyrimidine sequence located in the HIV-1 U3 LTR end region. The TFO moiety of conjugates are 5'CCTTCCC, 5'GGGAAGG, and 5'GGGTTGG. Their ability to bind to double-stranded DNA targets was examined. This binding is demonstrated by a footprinting technique using DNase I as a cleaving agent. The complex involved intermolecular pyr-pur*pyr or pur-pur*pyr triple helix. Pyrimidine TFO-OPC binds in a pH-dependent manner, whereas the others do not. The formation of the complex has been investigated at neutral pH and increasing temperature. We observed that the protection due to the purine and mixed TFO-OPC was pH independent and remained identical up to 40 degrees C. To determine the position of the OPC chromophore, molecular modeling was undertaken on the purine-conjugate/target complex. It has been suggested that the complex involved the intercalation of the OPC at the triplex-duplex junction with a small unwinding at the next excluded site.

Exogenous nucleosides promote the completion of MoMLV DNA synthesis in G0-arrested Balb c/3T3 fibroblasts

We studied Moloney murine leukemia virus replication in newly infected Balb c/3T3 cells brought to the G0 phase by serum depletion. Using the polymerase chain reaction method, we showed that Moloney murine leukemia virus can be efficiently internalized in nonproliferating fibroblasts, although reverse transcription of the viral RNA in these cells remains incomplete. It seems likely that a lower availability of deoxyribonucleotides in G0-arrested cells is responsible for this premature termination of the reverse transcription step. Accordingly, the addition of high concentrations of nucleosides to the culture medium of nondividing cells simultaneously with infection enables them to complete the reverse transcription process, without re-initiating the cell cycle. Inhibition of reverse transcription by hydroxyurea confirms the dependence of this retroviral step on the intracellular nucleotide pool rather than on the precise arrest point of the host cell cycle. Furthermore, the pyrimidine nucleotide pool, and more particularly the cytidine pool, appears to play a central regulatory role in this step.

Selective binding to polynucleotides of the hybrid intercalating groove binder bis(pyrrolecarboxamide)-oxazolopyridocarbazole: a molecular modeling study

In order to further characterize the binding of the hybrid molecule NetOPC [bis(pyrrolecarboxamide)-oxazolopyridocarbazole conjugate] to double-stranded DNA, we have performed a molecular modeling study to investigate the binding modes of the complexes possibly formed between NetOPC and synthetic polynucleotides poly [(dA-dT)]2, poly [(dA).d(T)], and poly [d(G-C)]2 and interpreted the results in the light of the experimentally determined binding parameters. In agreement with experimental data, the modeling study suggests that whatever was the binding mode of the complex formed, the complexation energy is markedly lower (thus favorable) for AT-containing polynucleotides than for poly d[(G-C)]2. With both poly [d(A).d(T)] and poly [d(A-T)]2, the most energetically favored complex has netropsin and OPC moieties bound simultaneously in the minor groove of DNA. The second favored complex exhibits the bimodal binding, i.e., intercalation of OPC and minor groove binding of the netropsin moiety. For both types of complex, the energy of complex formation is slightly lower with poly [d(A).d(T)]. The binding site sizes of the modeled complexes are about seven and four base pairs to the full groove and bimodal binding, respectively.

Poly(pyrrolecarboxamides) linked to photoactivable chromophore isoalloxazine. Synthesis, selective binding, and DNA cleaving properties

In an attempt to obtain DNA sequence-specific cleaving molecules, we have synthesized two types of hybrid groove binders composed of an isoalloxazine (flavin) chromophore linked through a polymethylenic chain to either a bis- or a tris(pyrrolecarboxamide) moiety related to netropsin and distamycin, respectively. In both types of molecules, the polymethylenic chain is linked to the alloxazine ring either in the N10 position or in the N3 position. As netropsin and distamycin, the hybrid derivatives preferentially bind to A + T-rich sequences and recognize sequences such as 5'-ATTT. Upon visible light irradiation the flavin moiety undergoes a redox cycling process generating superoxide anion and hydroxyl radical. Generation of oxy radicals appears to be more efficient with the hybrids in which the polymethylenic chain is linked at the N10 position. The generation of oxy radicals results in the occurrence of single strand break in supercoiled DNA. Breaks preferentially occur in the vicinity of A + T-rich sequences. The advantage of flavin relative to other oxy radicals generating compounds such as ferrous-EDTA is that it does not require chemical reduction but can be reduced either by visible light or by cellular enzymes, both conditions being compatible with pharmacological constraints.

Inhibitory effect of the polyanionic drug suramin on the in vitro HIV DNA integration reaction

An obligatory step in retroviral growth is the integration of a DNA copy of the viral RNA into the genomic DNA of the host. Recombinant human immunodeficiency virus type I (HIV-1) integrase (IN) expressed in Escherichia coli efficiently catalyzes the overall in vitro integration reaction, namely the processing of the LTR ends and the strand transfer reaction. Using the 3' end of synthetic oligonucleotides which match the termini of the HIV-1 U5 LTR as substrate and supercoiled pSP65 DNA as target, we have investigated the effect of the polyanionic drug suramin on the catalytic activity of the IN protein. It was found that at stoichiometric suramin to protein ratios, suramin displays a strong inhibitory effect on both the processing and strand transfer reactions. This inhibitory effect is related to the decrease of IN protein binding efficiency to the LTR end DNA fragment.