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At least 19 recordsLinked to original sources

PubMed1978

Relationship between mutant amidases of Pseudomonas aeruginosa and hydroxyurea as an inhibitor.

Hydroxyurea inhibited growth of Pseudomonas aeruginosa strain AI 3 on media containing either acetanilide (N-phenyl acetamide) or acetamide as sole carbon sources. Mutants resistant to hydroxyurea inhibition of growth on acetanilide (OUCH strains) and acetamide (AmOUCH strains) displayed altered growth properties on various amide media compared with the parent strain AI3. AI3 amidase, which catalyses the initial step in the metabolism of acetanilide and acetamide, was inhibited by hydroxyurea in a time-dependent reaction that was slowly reversible at pH 7.2. Compared with AI3 amidase, amidases from the OUCH mutants were much less sensitive to inhibition by hydroxyurea and showed altered substrate specificities and pH/activity profiles; amidases from the AmOUCH mutants were more sensitive to hydroxyurea inhibition but showed increased activity towards acetamide. Association of resistance to hydroxyurea inhibition with a mutation in the amidase structural gene of strain OUCH 4 was confirmed by transduction.

Amidohydrolases↗

PubMed1976

The mutagenic activity of hydroxyurea in Chlamydomonas reinhardi.

Hydroxyurea, an inhibitor of ribonucleotide reductase, increases the frequency of streptomycin resistant mutants in liquid cultures of Chlamydomonas reinhardi after 45 h incubation. After more prolonged incubation in hydroxyurea medium the frequency of streptomycin resistant mutants declines. This may be due to the slower growth rate of streptomycin resistant mutants compared to wild type cells in hydroxyurea containing medium. Studies on solid medium show that both the rate of forward mutation to streptomycin resistance and reverse mutation to nicotinamide independence are increased several fold by growth on hydroxyurea.

Chlamydomonas↗

PubMed1979

Single-strand breaks in DNA during repair of UV-induced damage in normal human and xeroderma pigmentosum cells as determined by alkaline DNA unwinding and hydroxylapatite chromatography: effects of hydroxyurea, 5-fluorodeoxyuridine and 1-beta-D-arabinofuranosylcytosine on the kinetics of repair.

A simple and sensitive technique for detection of strand breaks in DNA has been further developed. The method has been used to follow UV-induced excision-repair in human fibroblasts. It has been possible to study the kinetics of enzymic reactions in intact cells, in which strand breaks in DNA are produced and sealed again. Hydroxyurea, 5-fluorodeoxyuridine and 1-beta-D-arabinofuranosylcytosine, potent inhibitors of DNA synthesis, drastically increased the number of breaks observed during the repair process. This was probably due to a decreased polymerase activity, which will cause the strand breaks formed by endonuclease to remain open longer. The initial rate of strand-break formation did not seem to be influenced by hydroxyurea or araC, and was about 4000 breaks per minute in a diploid genome, at a dose of 20 J/m2. After 5--30 min, depending on the dose of UV, the number of breaks reached a maximum and started to decrease again. Hydroxyurea decreased the rate of polymerization in the sites under repair. However, there was no concomitant reduction of repair-induced incorporation of [3H]thymidine and no reduction of the excision of pyrimidine dimers. It therefore seems that the action of the polymerase was not a rate-limiting event, but rather an earlier step. It is likely that the endonucleolytic activity determined the rate of repair. As a consequence, the endonuclease and polymerase cannot be bound in a permanent complex. Under certain assumptions, the time for repair of a site, i.e. the time from incision to final ligase sealing, can be estimated as between 3 and 10 min. Essentially no breaks were produced in Xeroderma pigmentosum cells belonging to complementation group A, and there was no enhancement by hydroxyurea. Cells from the variant type of Xeroderma pigmentosum behaved like normal cells in this respect.

Cell Line↗

PubMed1977

[Partial synchronization of tumor cells in vivo with hydroxyurea (author's transl)].

For the partial synchronization of tumor cells, Yoshida ascitic sarcoma bearing rats were treated with Hydroxyurea using two methods, one in the form of a single intraperitoneal injection (0.5 mg/g body weight) and the other by continuous intraascitic infusion over a period of 12h (1.428 mg/g body weight total dose). The synchronization obtained by continuous infusion of Hydroxyurea is superior to that by a one time injection with respect to cell accumulation in one phase of the cell cycle and in the duration of synchronous proliferation. The degree of cell loss caused by infusion depends on the concentration of Hydroxyurea. Concentrations of slightly more than the minimal inhibitory concentration of DNA synthesis cause the least damage to the tumor cells.

Animals↗

PubMed1979

Aeration sensitizes Streptococcus faecalis to hydroxyurea.

Hydroxyurea in up to 60 mM concentration did not inhibit growth or DNA synthesis in nonaerated cultures of Streptococcus faecalis ATCC 8043. In contrast, in cultures aerated by shaking already 1 mM hydroxyurea decreased the rate of net DNA synthesis and in higher concentrations of the drug the growth of the total cell mass also slowed down and the number of cells per chain increased from 1-2 to 10. The differential rate of DNA synthesis, but not the growth of the total cell mass, could be restored almost to the control level by adding thymidine to the medium. Thus there are at least two targets for hydroxyurea in the cells of S. faecalis grown in aerated cultures.

Air↗

PubMed1976

Repair replication in human cells. Simplified determination utilizing hydroxyurea.

A simplified and shortened procedure has been developed for the determination of repair replication of DNA in cultured mammalian cells. The procedure, using the bromodeoxyuridine density label and a radio-isotopic label has been applied to normal diploid human cells (WI38) and to their SV40 transformants (VA13). After incubation with the repair label the cells are lysed and digested for two hours at 50 degrees C with proteinase K. This digest can then be immediately subjected to alkaline cesium chloride density gradient centrifugation with no need for DNA extraction. Hydroxyurea is used to reduce the level of semi-conservative synthesis that a quantitative determination of repair replication can be accomplished by a single centrifugation. The method is not affected by variation in the effectiveness of the inhibitor although a small amount of semi-conservative synthesis normally occurs in the presence of the drug. The time course of repair replication in WI38 cells is unaffected by the drug. The apparent amount of repair synthesis in ultraviolet irradiated cells is increased 25 to 40% in the presence of hydroxyurea when thymidine is used as tracer. Under certain conditions in which the level of semiconservative synthesis is low (e.g., contact inhibited cells, high ultraviolet doses) the use of hydroxyurea is unnecessary.

Bromodeoxyuridine↗

PubMed2024

Towards genomic medicine: a tailored next-generation sequencing panel for hydroxyurea pharmacogenomics in Tanzania.

BACKGROUND: Pharmacogenomics of hydroxyurea is an important aspect in the management of sickle cell disease (SCD), especially in the era of genomic medicine. Genetic variations in loci associated with HbF induction and drug metabolism are prime targets for hydroxyurea (HU) pharmacogenomics, as these can significantly impact the therapeutic efficacy and safety of HU in SCD patients. METHODS: This study involved designing of a custom panel targeting BCL11A, ARG2, HBB, HBG1, WAC, HBG2, HAO2, MYB, SAR1A, KLF10, CYP2C9, CYP2E1 and NOS1 as potential HU pharmacogenomics targets. These genes were selected based on their known roles in HbF induction and HU metabolism. The panel was designed using the Illumina Design Studio (Illumina, San Diego, CA, USA) and achieved a total coverage of 96% of all genomic targets over a span of 51.6 kilobases (kb). This custom panel was then sequenced using the Illumina MiSeq platform to ensure high coverage and accuracy. RESULTS: We are reporting a successfully designed Illumina (MiSeq) HU pharmacogenomics custom panel encompassing 51.6 kilobases. The designed panel achieved greater than 1000x amplicon coverage which is sufficient for genomic analysis. CONCLUSIONS: This study provides a valuable tool for research in HU pharmacogenomics, especially in Africa where SCD is highly prevalent, and personalized medicine approaches are crucial for improving patient outcomes. The custom-designed Illumina (MiSeq) panel, with its extensive coverage and high sequencing depth, provides a robust platform for studying genetic variations associated with HU response. This panel can contribute to the development of tailored therapeutic strategies, ultimately enhancing the management of SCD through more effective and safer use of hydroxyurea.

Hydroxyurea↗

PubMed1978

Differential effect of hydroxyurea on the replication of plasmid and chromosomal DNA in Bacillus subtilis.

The replication in Bacillus subtilis of the staphylococcal R plasmids pE194, pBD15, pUB110, pSA0501, and pSA2100 has been studied in the presence of hydroxyurea. In all cases, an enrichment for covalently closed circular DNA compared with chromosomal DNA was observed. In this respect, hydroxyurea mimics the effect previously observed with pUB110, using strains carrying the conditional mutation dnaA13. This mutation has been reported to affect ribonucleotide reductase (G. W. Bazill and D. Karamata, Mol. Gen. Genet. 117:19-29, 1972). An explanation for these effects is offered, together with some supporting evidence.

Bacillus subtilis↗

PubMed1978

The influence of hydroxyurea and colchicine on growth and morphology of Trypanosoma cruzi.

Cultures of Trypanosoma cruzi have been exposed to the drugs hydroxyurea and colchicine. We found that hydroxyurea (200 microgram/ml) completely inhibited growth and differentiation of T. cruzi Y strain. Colchicine (200 microgram/ml) reduced the growth of T. cruzi 30% and stimulated cell differentiation from epimastigotes to trypomastigotes. Furthermore it caused anuclear cells with apparently intact kinetoplasts. The possible use of these anuclear forms in studies on kinetoplast DNA organization and expression is suggested.

Colchicine↗

PubMed2026

Plasma Proteome Signatures in Sickle Cell Anemia and the Effect of Hydroxyurea Treatment.

Sickle Cell Anaemia (SCA) is a monogenic blood disorder caused by a mutation in the β-globin gene, yet it presents with marked clinical variability. Although hydroxyurea (HU) is an established therapy, its precise mechanism of action remains incompletely understood. Plasma proteins represent valuable biomarkers for elucidating disease mechanisms and treatment responses. In this study, plasma proteome profiling of 31 healthy controls and 76 SCA patients identified 43 differentially abundant proteins (DAPs) that form a highly interconnected interaction network. Proteins with increased abundance in SCA were largely associated with immune and inflammatory responses, whereas those with reduced levels were linked to coagulation and proteolytic pathways. HU therapy was associated with elevated levels of haptoglobin (HP) and hemopexin (HPX), key mediators of free hemoglobin scavenging. We also identified several previously unreported plasma proteins altered in SCA, broadening the landscape of potential biomarkers and HU-responsive targets. Many DAPs significantly correlated with clinical indices, such as transfusion frequency, vaso-occlusive crises, white blood cell counts, and platelet counts, offering insights into disease mechanisms and potential utility in disease management. Notably, overlap with β-thalassemia-associated signatures suggests shared pathophysiological pathways between these hemoglobinopathies. Collectively, these findings provide a strong foundation for translational validation in larger, independent cohorts.

Humans↗

PubMed1978

Comparison of thymidine, fluorodeoxyuridine, hydroxyurea, and methotrexate blocking at the G1/S phase transition of the cell cycle, studied by replication patterns.

Cultures of human amniotic fluid cells and fibroblasts were temporarily blocked by the replication inhibitors thymidine (dT) surplus, fluorodeoxyuridine (FdU), hydroxyurea (HU), or methotrexate uridine (MU). The respective arresting point at G1-S transition and the homogeneity of the blocked cell population were determined by means of BrdU replication patterns. Most variation of patterns were found after HU. After MU, cells were arrested before the onset of replication, while with dT surplus of FdU an arresting point in early S seemed more likely.

Amniotic Fluid↗

PubMed1977

Compared effects of N-hydroxyurethan, urethan and hydroxyurea on DNA synthesis. In vivo and in vitro studies.

The effect of N-hydroxyurethan (HUR) on DNA synthesis has been tested both in vivo on various tissues and in vitro on concanavalin A (ConA)-stimulated rat thymocytes and compared with the action of urethan and hydroxyurea. HUR suppresses scheduled DNA synthesis, except that of non-stimulated spleen cells in vitro. The inhibition is efficient and rapid and takes place immediately if the drug is administered at the peak of the S-phase. UR inhibits DNA synthesis in vitro only at much higher doses and with different time course. It is effective or slightly effective if it is administered at the peak of the S-phase. A conversion of urethan into HUR the latter depressing DNA synthesis could partly explain the differences observed. No toxicity was found after treatment with drugs at the concentration employed. Finally, the relationships between drug doses and cell responses have been particularly observed in vivo.

Animals↗

PubMed1975

Inhibitory effect of hydroxyurea on [3-H]leucine incorporation in human peripheral lymphocytes.

Hydroxyurea (HU), generally considered to be a specific inhibiter of DNA synthesis, has an inhibitory effect on the incorporation of TCA-precipitable [3-H]leucine in peripheral lymphocytes. This action is not secondary to the inhibition of DNA synthesis since incorporation of [3-H]leucine is unaffected when DNA synthesis is inhibited by 5-fluorodeoxyuridine (FUdR); it does not appear to be directly related to inhibition of RNA synthesis; and it is not mediated at the level of translation since HU has no effect on protein synthesis in rabbit reticulocytes. The relevance of these findings to the use of HU as a DNA inhibitor is discussed.

Animals↗

PubMed1979

The effects of concanavalin A, cerulenin, hydroxyurea and tunicamycin on the incorporation of amino acids and glucosamine in Tetrahymena pyriformis.

1. Pulse labelling of conjugating Tetrahymena pyriformis with glycine and glucosamine gave results consistent with a requirement for de novo synthesis of a lipid-like component which is involved in the addition of sugar to cell glycoprotein. 2. Conjugation of complementary strains of Tetrahymena can be inhibited without gross morphologic and metabolic changes in the cells. The observed inhibition of conjugation is reversible. 3. Concanavalin A stopped conjugation and stimulated both glycine and glucosamine incorporation. 4. Tunicamycin inhibited conjugation but had little influence on total glucosamine incorporation. Amino acid incorporation was slightly enhanced. 5. Hydroxyurea blocked conjugation, inhibited the incorporation of glucosamine and seemed to induce a transient increase in glycine incorporation. 6. Cerulenin inhibited conjugation but had little effect on the incorporation of glycine and glucosamine into the cell.

Amino Acids↗

PubMed2026

Association of hydroxyurea use and sickle cell retinopathy: A systematic review and meta-analysis.

Hydroxyurea (HU) is prescribed to reduce systemic complications of sickle cell disease; however, its association with sickle cell retinopathy (SCR) remains unclear. This meta-analysis (PROSPERO: CRD420251079006) evaluates the pooled association between HU use and SCR. In the primary analysis, HU use was not associated with a statistically significant reduction in SCR (OR = 0.90, 95% CI [0.41, 1.97], p = 0.79; I² = 77%). In a prespecified leave-one-out analysis, exclusion of the outlier study did not produce a statistically significant association, although the estimate shifted toward a stronger protective effect with reduced heterogeneity (OR = 0.70, 95% CI [0.39, 1.27], p = 0.25; I² = 67%). In a subgroup analysis excluding high-risk-of-bias studies, HU use was also not associated with a statistically significant reduction in SCR (OR = 0.84, 95% CI [0.39, 1.82], p = 0.66; I² = 77%). In post hoc analyses, HU use was not associated with a statistically significant reduction in SCR in non-adult populations (OR = 1.14, 95% CI [0.43, 3.05], p = 0.79; I² = 81%) or genotype-restricted analyses (OR = 1.22, 95% CI [0.81, 1.84], p = 0.35; I² = 0%). In post hoc analyses restricting studies to retinopathy phenotype, however, HU was associated with statistically significant lower odds of non-proliferative SCR (OR = 0.73, 95% CI [0.54, 0.98], p = 0.04; I² = 0%) and proliferative SCR (OR = 0.24, 95% CI [0.09, 0.60], p = 0.002; I² = 12%). Very low-certainty evidence suggests mixed associations between HU and SCR. Prospective studies are needed to clarify its role in SCR prevention.

Humans↗

PubMed1975

Electron microscopic studies on assembly of herpes simplex virus upon removal of hydroxyurea block.

The release of hydroxyurea-treated, herpes simplex virus-infected cells from the drug-induced block resulted in the prompt assembly of infectious virus. Electron microscope observations at sequential intervals following removal of the drug revealed considerable synchrony of replication. This synchrony permitted stages in the complex process of core assembly to be examined in detail. The data suggest that after partial or complete assembly the nucleoprotein enters the differentiated capsid to become enfolded.

Cell Nucleus↗

PubMed2020

Distinct roles of BRCA2 in replication fork protection in response to hydroxyurea and DNA interstrand cross-links.

DNA interstrand cross-links (ICLs) are a form of DNA damage that requires the interplay of a number of repair proteins including those of the Fanconi anemia (FA) and the homologous recombination (HR) pathways. Pathogenic variants in the essential gene BRCA2/FANCD1, when monoallelic, predispose to breast and ovarian cancer, and when biallelic, result in a severe subtype of Fanconi anemia. BRCA2 function in the FA pathway is attributed to its role as a mediator of the RAD51 recombinase in HR repair of programmed DNA double-strand breaks (DSB). BRCA2 and RAD51 functions are also required to protect stalled replication forks from nucleolytic degradation during response to hydroxyurea (HU). While RAD51 has been shown to be necessary in the early steps of ICL repair to prevent aberrant nuclease resection, the role of BRCA2 in this process has not been described. Here, based on the analysis of BRCA2 DNA-binding domain (DBD) mutants (c.8488-1G>A and c.8524C>T) discovered in FA patients presenting with atypical FA-like phenotypes, we establish that BRCA2 is necessary for the protection of DNA at ICLs. Cells carrying BRCA2 DBD mutations are sensitive to ICL-inducing agents but resistant to HU treatment consistent with relatively high HR repair in these cells. BRCA2 function at an ICL protects against DNA2-WRN nuclease-helicase complex and not the MRE11 nuclease that is implicated in the resection of HU-induced stalled replication forks. Our results also indicate that unlike the processing at HU-induced stalled forks, the function of the SNF2 translocases (SMARCAL1, ZRANB3, or HLTF), implicated in fork reversal, are not an integral component of the ICL repair, pointing to a different mechanism of fork protection at different DNA lesions.

BRCA2 Protein↗

PubMed1979

Effects of hydroxyurea on Crithidia fasciculata.

Hydroxyurea (HU) inhibits increase in cell number in cultures of Crithidia fasciculata. Complete inhibition is produced by 8 mM and higher concentrations. If HU is not removed, population growth resumes in 45-50 h; if HU is removed, partially synchronous growth occurs through 2 cycles. During HU inhibition, the rate of DNA synthesis is reduced to 1% of that in exponentially growing cultures; protein and RNA syntheses continue at slightly reduced rates. Mean cell size and protein and RNA contents per cell increase; rate of oxygen consumption per mg cell protein remains constant. The behavior of a culture upon addition of HU and upon its removal agrees with predictions based on the hypothesis that the only direct effect of HU is to block DNA synthesis. The synchrony produced by HU is judged satisfactory for investigations of kinetoplast and nuclear replication but not for biochemical characterization of other aspects of the cell cycle.

Animals↗