Effects Of Pyrimidines Research Articles

Diverse Pharmacological Potential of Various Substituted Pyrimidine Derivatives

Abstract: In many significant bioactive heterocyclic compounds, the six-membered ring pyrimidines play a major role as bioactive components. There is a lot of room for innovation in the fields of medicinal chemistry and the chemical industries because of the numerous pyrimidine synthesis methods and their varied reactions. The pharmacological effects of pyrimidine derivatives include anticonvulsant, antibacterial, antifungal, antiviral, antitubercular, anticancer, antimicrobial, antihypertensive, antiulcer, anti-inflammatory, antimalarial, antioxidant, analgesic, sedative, anti-depressive, antipyretic properties, etc. The synthetic adaptability of pyrimidine has made it possible to create a wide range of structurally different analogs, including analogs from substitution on the pyrimidine ring at various places, which has aided the design of a wide variety of therapeutic targets. This review's goal is to examine the pharmacological effects of numerous pyrimidine derivatives. This review provides an overview of pyrimidine compounds for biological activities and examines the novel pharmacological molecules containing pyrimidine rings in the future.

Role of Cell-Penetrating Peptides in Intracellular Delivery of Peptide Nucleic Acids Targeting Hepadnaviral Replication.

Peptide nucleic acids (PNAs) are potentially attractive antisense agents against hepatitis B virus (HBV), although poor cellular uptake limits their therapeutic application. In the duck HBV (DHBV) model, we evaluated different cell-penetrating peptides (CPPs) for delivery to hepatocytes of a PNA-targeting hepadnaviral encapsidation signal (ε). This anti-ε PNA exhibited sequence-specific inhibition of DHBV RT in a cell-free system. Investigation of the best in vivo route of delivery of PNA conjugated to (D-Arg)8 (P1) showed that intraperitoneal injection to ducklings was ineffective, whereas intravenously (i.v.) injected fluorescein-P1-PNA reached the hepatocytes. Treatment of virus carriers with i.v.-administered P1-PNA resulted in a decrease in viral DNA compared to untreated controls. Surprisingly, a similar inhibition of viral replication was observed in vivo as well as in vitro in primary hepatocyte cultures for a control 2 nt mismatched PNA conjugated to P1. By contrast, the same PNA coupled to (D-Lys)4 (P2) inhibited DHBV replication in a sequence-specific manner. Interestingly, only P1, but not P2, displayed anti-DHBV activity in the absence of PNA cargo. Hence, we provide new evidence that CPP-PNA conjugates inhibit DHBV replication following low-dose administration. Importantly, our results demonstrate the key role of CPPs used as vehicles in antiviral specificity of CPP-PNA conjugates.

The Effect of Pyrimidine Bases on the Hole-Transfer Coupling in DNA†

Electron hole migration along the π-stack of DNA is mediated by the electronic coupling between the purines (guanine, adenine) of adjacent Watson-Crick pairs (WCPs). We have investigated the effect of the complementary pyrimidines (cytosine, thymine) on this coupling using the two-state model of electron transfer where, at the Hartree-Fock level, the hole-transfer coupling can be described by the energy splitting of the HOMO and HOMO-1 molecular orbitals of WCP dimers. Using the constrained space orbital variation method, we considered the effects of exchange, polarization, and electrostatic interactions (including hydrogen bonds of a WCP) of pyrimidines on the purine-purine electronic couplings. We also performed a detailed analysis of HOMO and HOMO-1 of the duplexes. We conclude that the effect of pyrimidines on the electronic coupling of neighboring purines cannot be described via perturbation theory nor simply reduced to an electrostatic polarization of the purines. However, the combination of exchange (frozen core) and electrostatic effects reproduces the coupling matrix elements between adjacent WCPs rather well. Analysis of the spatial overlap between orbital fragments of HOMO and HOMO-1 suggests that hydrogen bonds between complementary bases play a crucial role in the electronic coupling of neighboring WCPs.

Gertrude Belle Elion (1918-1999).

G ertrude Elion, a pioneer in drug development and one of only 11 women scientists to win the Nobel Prize, earned her master's degree in chemistry from New York University in 1941. She found work teaching nurses and testing food products—finding employment as a research scientist was difficult for women in those days. Her opportunity came with the arrival of the Second World War and the diminished supply of male scientists. She was hired by the Burroughs Wellcome Company to work as a research assistant in the laboratory of George Hitchings. And so began a collaboration that would last for Elion's entire career. Elion and Hitchings started to investigate the mechanisms of purine and pyrimidine metabolism and the incorporation of these building blocks into nucleic acid. By exploring the effects of incorporating purine and pyrimidine structural analogs into DNA—a revolutionary approach—they discovered a long list of extremely important drugs: thioguanine and 6-mercaptopurine for treating acute leukemia, pyrimethamine for malaria and toxoplasmosis, and the antibacterial trimethoprim. Next came azathioprine, an immunosuppressive drug that improved the success of renal transplantation and the treatment of autoimmune disease. They developed the first truly effective antiviral compound: acyclovir for the treatment of herpesvirus infection. Further studies of the antiviral effects of pyrimidine and purine analogs led to the discovery of AZT, the first drug for HIV. These discoveries were triumphs of rational drug design based on the exploration of metabolic pathways. In recognition of their work, Elion and Hitchings (together with James Black) were awarded the 1988 Nobel Prize for Physiology or Medicine. Worldwide recognition of Trudy Elion's role as a pioneer in rational drug design and as an articulate spokeswoman for science continued to grow even after her formal retirement from Burroughs Wellcome in 1983. To the end of her life she maintained a demanding travel schedule, which she pursued not for personal reward but for the opportunities her travels provided to promote the cause of science and to encourage those just beginning a career in research. It was at the end of her magnificent career with Burroughs Wellcome that Trudy's association with Duke University in Durham, North Carolina, began. Trudy enthusiastically accepted an offer to join the faculty at Duke in a part-time appointment to work with and mentor medical and graduate students. From 1983 until the end of her life, Trudy served as a mentor for many medical and graduate students in the neuro-oncology and pediatric bone marrow transplant programs. Despite her hectic travel schedule, Trudy spent a great deal of time with her students and was an inspiration to them all. During her years at Duke, she published more than 25 papers with her students and taught them invaluable lessons about how to do science and, just as important, why to do science. Trudy regularly attended the American Association for Cancer Research annual meetings where the students presented their work, and she made a point of being at their presentations whenever possible. Most of her students are now pursuing successful careers in academic medicine. All of them remember the experience of working with a Nobel laureate who was brilliant and insightful, as expected, but who was also stimulating, supportive, and inspirational. Trudy's material rewards for this effort were meager—a small stipend and a modest office—but she never asked for more. Ironically, she was looking forward to moving into a much larger and nicer office—with two windows—but died the evening before the move. We know that Trudy enjoyed her career with our students, and we know that her mentorship was a career highlight for them. But perhaps the greatest beneficiaries of her time at Duke were the faculty and staff, especially those of us who worked most closely with her, who were able to know and learn from a most gracious person and a brilliant and determined scientist.

Structure-activity relationship of a pyrimidine receptor in the rat isolated superior cervical ganglion.

1. The effects of pyrimidines and purines on the d.c. potential of the rat isolated superior cervical ganglion (SCG) have been examined by a grease-gap technique to determine the structure-activity requirements of the receptor activated by pyrimidines, i.e. a pyrimidinoceptor. 2. 5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranosyl (ZTP), the pyrimidines, cytidine 5'-triphosphate (CTP), uridine 5'-triphosphate (UTP) and thymidine 5'-triphosphate (TTP) and the purines, adenosine 5'-triphosphate (ATP; in the presence of an A1-purinoceptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (1 microM)), adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), guanosine 5'-triphosphate (GTP), inosine 5'-triphosphate (1TP) depolarized ganglia in a concentration-dependent manner. The relative order of ZTP and purine 5'-triphosphates in depolarizing ganglia was ZTP > or = ATP gamma S > > ATP > or = ITP = GTP, and for the pyrimidine 5'-triphosphates UTP > TTP > or = CTP. Depolarizations evoked by ATP gamma S were followed by concentration-dependent hyperpolarizations at 100 and 1000 microM. 3. At concentrations of between 0.1 microM and 1 mM, uridine 5'-diphosphate (UDP), uridine 5'-diphosphoglucose (UDPG) and uridine 5'-diphosphoglucuronic acid (UDPGA) evoked significant and concentration-dependent depolarizations, whereas uridine 5'-monophosphate (UMP), uridine and uracil were inactive or produced small (< 45 microV) depolarizations. The relative order of potency of uridine analogues in depolarizing ganglia was UDP > or = UTP > UDPG > UDPGA > > uracil > or = UMP = pseudouridine > or = uridine. At 3 and 10 mM, uridine produced concentration-dependent hyperpolarizations. Nikkomycin Z, a nucleoside resembling UTP (viz. the triphosphate chain at the 5'-position on the ribose moiety being replaced by a peptide), was inactive between 1 microM and 1 mM. Generally, a concentration of 10 mM was required before thymidine, 6-azathymine, 6-azauracil or 6-azauridine depolarized ganglia. 4. Suramin (300 microM), a P2-purinoceptor antagonist, significantly depressed depolarizations evoked by alpha, beta-methylene-ATP (alpha, beta-MeATP; 100 microM), ATP gamma S (100 microM), CTP (1 mM), GTP (1 mM), ZTP (30 microM) and ATP (300 microM) in the presence of DPCPX (1 microM). Suramin reversed a small depolarization evoked by UMP (1 mM) into a small hyperpolarization. In contrast depolarizations evoked by UDP, UTP, UDPG (all at 100 microM) and TTP (300 microM) were unaltered or enhanced by suramin. 5. It is concluded that the rat SCG contains distinct nucleotide receptors including a P2-purinoceptor (activated by alpha, beta-MeATP, ATP, GTP, ITP and ZTP) and a pyrimidinoceptor (activated by UTP, UDP, UDPG, UDPGA and TTP). The pyrimidinoceptor on rat SCG neurones had specific structure activity requirements with the di- and triphosphates of uridine being the most effective depolarizing agonists examined.

Effects of pyrimidines on the guinea‐pig coronary vasculature

1. The effects of the pyrimidines, uridine 5'-triphosphate (UTP), thymidine 5'-triphosphate (TTP) and cytidine 5'-triphosphate (CTP), were examined in the guinea-pig coronary bed, by use of a Langendorff technique. Comparisons were made with the actions of the purines adenosine 5'-triphosphate (ATP), inosine 5'-triphosphate (ITP) and guanosine 5'-triphosphate (GTP). The effect of, the nitric oxide synthase inhibitor, L-NG-nitroarginine methyl ester (L-NAME) and, the prostaglandin synthesis inhibitor, indomethacin on the vasodilator response to these purines and pyrimidines was examined. The effects of these inhibitors were assessed on their ability to inhibit both the amplitude and the area of the vasodilator response. 2. The relative order of potency of the purines and pyrimidines studied was ATP > UTP > ITP >> GTP, TTP, CTP. 3. The maximum amplitude and area of the vasodilator response to the pyrimidines, UTP (5 x 10(-10)-5 x 10(-7) mol), TTP (5 x 10(-8)-5 x 10(-7) mol) and CTP (5 x 10(-7) mol), and purines, ITP (5 x 10(-9)-5 x 10(-7) mol) and GTP (5 x 10(-8)-5 x 10(-7) mol), were significantly reduced by L-NAME (3 x 10(-5) and 10(-4) M). 4. The inhibition of the response to ATP (5 x 10-8 mol), UTP (5 x 10-8 mol), ITP (5 x 10-8 mol), TTP(5 x 10-7 mol), CTP (5 x 10- mol) and GTP (5 x 10- mol) by L-NAME (3 x 10-5 M) was significantly reversed by L-arginine (1.5 x 10-3 M).5. L-NAME (3 x 10-5 and 10-4 M) only inhibited the amplitude of the vasodilator response to a low dose of ATP (5 x 10-mol), although the area of vasodilator response to ATP(5 x 10-11-5 x 10-7 mol) was significantly reduced by L-NAME (3 x 10-5 and 10-4 M).6. The maximum amplitude of the vasodilator response to ATP (5 x 10-10-5 x 10-7 mol) was significantly reduced by indomethacin (10-6 M), although the area of the vasodilator response to ATP was only significantly reduced at one intermediate dose (5 x 10-9 mol). Indomethacin (10-6 M) did not affect the maximum amplitude or area of the vasodilator responses to UTP (5 x 10-11-5 x 10-7 mol),ITP (5 x 10-10-5 x 10-7 mol), CTP (5 x 10-7 mol), TTP (5 x 10-8-5 x 10-7 mol) and GTP(5 x 10-8-5 x 10-7 mol).7. It is concluded that in the guinea-pig coronary vasculature, the vasodilatation evoked by the pyrimidines, UTP, TTP and CTP, was mediated in large part via nitric oxide, as were the vasodilatations evoked by the purines ITP and GTP. The vasodilatations evoked by ATP, however, appear to involve prostanoids in addition to the release of nitric oxide.

Characterization of the arginine repressor from Salmonella typhimurium and its interactions with the carAB operator

Primer extension experiments showed that the argR gene, encoding the arginine repressor in Salmonella typhimurium, is transcribed from a single promoter that is negatively regulated by arginine. A repressor overproducing strain was constructed and the repressor was purified to homogeneity. Gel filtration, sedimentation and cross-linking studies established that the native repressor is a hexamer of identical 17,000 M r subunits. Gel retardation experiments indicate that the apparent dissociation constant for repressor/ carAB operator is 6 × 10 −12 m. These experiments showed that arginine is essential for binding of the repressor to the DNA and that pyrimidine nucleotides have no significant effect on this binding. These results indicate that the effect of pyrimidines on expression of the arginine sensitive “downstream” carAB promoter is not directly mediated by the arginine repressor. These experiments also suggest that a single hexamer binds to the carAB operator, which carries two previously defined “ARG box” sequences that characterize operators for arg genes. Gel retardation experiments with DNA fragments carrying the individual ARG boxes showed that both boxes are required for effective binding of the hexameric repressor to the operator, indicating that the ARG boxes comprise a single binding site for the repressor. Analysis of the potential secondary structure of the arginine repressor does not reveal any of the recognizable structural motifs common to a number of DNA-binding proteins. A combination of DNase I, premethylation interference, depurination and hydroxyl radical footprinting techniques were employed to characterize the interactions of the repressor with the carAB operator, with the results suggesting that the repressor predominantly interacts with A · T residues in this region. Comparative DNA sequence analysis of the known arginine operators of enteric bacteria further indicates that the specificity of interaction may be based more on the precise distance between two defined A · T-rich regions rather than on the specific nucleotide sequence.

Pyrimidine regulation of tandem promoters for carAB in Salmonella typhimurium.

The carAB operon of Salmonella typhimurium encodes the two subunits of the enzyme carbamoylphosphate synthetase. Transcription of the operon is initiated at tandem promoters that are subject to control by pyrimidines and arginine. Pyrimidine regulation was examined by quantitative primer extension experiments under conditions in which densitometric measurements of the transcripts were linear with the amount of RNA. RNA was obtained from mutant strains that permit manipulations of pyrimidine nucleotide pools. The data showed that a uridine nucleotide repressed the upstream promoter (Pl), whereas arginine repressed the downstream promoter (P2). Exogenous cytidine, which increased the intracellular CTP pool in certain mutant strains, did not affect either promoter. However, CTP limitation resulted in derepression of the pyrimidine-specific promoter as well as the downstream arginine-specific promoter. The effect of pyrimidines on P2 was confirmed in a carA::lacZ transcriptional fusion in which the activity of the pyrimidine-specific promoter was abolished. Primer extension experiments with an argR::Tn10 derivative showed that repression of Pl by uridine nucleotides did not require a functional arginine repressor and that repression of P2 by arginine did not interfere with elongation of transcripts initiated at the upstream Pl promoter.

DUP 785 (NSC 368390): Schedule-dependency of growth-inhibitory and antipyrimidine effects

DUP 785 (NSC 368390; Brequinar sodium) is a new inhibitor of pyrimidine de novo biosynthesis with antitumor activity against several experimental tumors. DUP 785 inhibits the mitochondrial enzyme dihydroorotate dehydrogenase, blocking the conversion of dihydroorotate to orotate. We examined the influence of exposure time to DUP 785 on its growth-inhibitory effects in L1210 murine leukemia and WiDR human adenocarcinoma cells and the effects of pyrimidine (deoxy) nucleosides on reversal of growth-inhibition. The results were correlated with changes in intracellular pyrimidine nucleotide pools and cell cycle distribution. In L1210 cells, a continuous exposure to 25 μM DUP 785 up to 96 hr caused complete growth inhibition. A 2 hr exposure of cells to the drug did not affect growth. In WiDR cells, exposure to the drug for 1–24 hr, followed by cultivation in drug-free medium resulted in recovery of growth. However, cells exposed to the drug for 48 hr or longer were not able to resume growth when recultured in drug-free medium. Reversal studies were performed to know whether selective depletion of one of the pyrimidine (deoxy) nucleotides might be related to the growth-inhibitory effects of DUP 785. Neither thymidine, deoxycytidine alone, deoxycytidine plus tetrahydrouridine; nor cytidine plus tetrahydrouridine added after 24 hr were able to reverse cell growth inhibition induced by 25 μM DUP 785. However, uridine and cytidine alone reversed growth inhibition. UTP and CTP pools in L1210 cells decreased to about 30–40% of control levels after 4 hr of drug exposure, while dTTP and dCTP pools decreased to about 30% of control levels. There were no significant changes in purine nucleotide pools. In WiDR cells, UTP and CTP pools decreased rapidly after drug exposure and were substantially depleted after 24 hr. Reculture of cells in drug-free medium resulted in a significant recovery of UTP and CTP levels only for cells exposed to DUP 785 for 1–24 hr. For cells exposed to the drug for 48 and 72 hr recovery of nucleotide pools was minimal. In L1210 cells, a 12-hr exposure to the drug caused an accumulation of cells in the early S-phase. In WiDR cells, there was a clear accumulation of cells in the S-phase of the cell cycle after 24 hr drug exposure. After culture in drug-free medium cells continued to traverse through the cell cycle. Our results demonstrate that prolonged exposure of cells to DUP 785 was necessary for a long-lasting depletion of pyrimidine nucleotides and a substantial suppression of RNA and DNA synthesis. Selective repletion of one of the (deoxy) ribonucleotides did not restore cell growth. Only repletion of all nucleotides by uridine and/or cytidine restored cell growth. The failure of short-term drug exposure to cause effects may be explained by the rapid recovery of pyrimidine nucleotide pools in drug-free medium, presumably allowing cells to continue RNA and DNA synthesis and to reverse the S-phase block in the cell cycle.

Ribavirin antagonizes inhibitory effects of pyrimidine 2',3'-dideoxynucleosides but enhances inhibitory effects of purine 2',3'-dideoxynucleosides on replication of human immunodeficiency virus in vitro.

The combined antiviral effects of various 2',3'-dideoxynucleosides and ribavirin on the replication of human immunodeficiency virus type 1 in MT-4 cells have been examined. Ribavirin antagonized the antiviral activity of the pyrimidine 2',3'-dideoxynucleosides (3'-azido-2',3'-dideoxythymidine, 2',3'-dideoxythymidin-2'-ene, 2',3'-dideoxycytidine, and 2',3'-dideoxycytidin-2'-ene), but enhanced the antiviral activity of the purine 2',3'-dideoxynucleosides (2',3'-dideoxyadenosine and 2',3'-dideoxyguanosine). Combinations of the 2',3'-dideoxynucleosides with each other were also examined. These combinations resulted in an additive to subsynergistic effect.

Effect of pyrimidines, purines and their nucleosides on antitumor activity of 5-fluorouracil against L-1210 leukemia.

The chemotherapeutic action of 5-fluorouracil (5-FU) monotherapy on L-1210 leukemia in mice was compared with combinations of pyrimidines (uracil, uridine, deoxyuridine, cytosine, cytidine, deoxycytidine, thymine and thymidine) or purines (adenine, adenosine, deoxyadenosine, guanine, guanosine, deoxyguanosine and inosine) with 5-FU. The antitumor activity of 5-FU was enhanced by coadministration of uracil, thymine or guanosine, but the toxicity of the first two compounds was also enhanced. Only when 5-FU was administered with guanosine, was not only the antitumor activity but also the therapeutic ratio potentiated without increasing its toxicity. A time interval between the administration of 5-FU and guanosine diminished the survival effect. Therefore, the 5-FU-guanosine combination produced its optimal chemotherapeutic effect by simultaneous injection. The potentiation of antitumor effect of 5-FU by guanosine was prevented completely by cytidine or uridine, and partially by deoxyuridine, adenosine or deoxyadenosine.

Effects of pyrimidine enriched medium on the female sterile mutants,Rudimentary andSonless inDrosophila

The effect of pyrimidine-enriched medium on the expression of the sex-linked female sterile mutationsrudimentary (r) andsonless (snl) ofDrosophila melanogaster was investigated. Although pyrimidine supplementation did significantly improve the fertility ofr females, as others have previously reported, it had no effect onsnl females. The total ribonucleic acid (RNA) content of eggs produced byr, snl, and control females was also measured. Eggs produced from homozygousr females mated tor males contained less total RNA than did eggs from other matings. These results support the hypothesis that certain sex-linked female sterile mutations cause the production of eggs deficient in some respect. In the case ofr, the deficiency seems to by pyrimidines. The biochemical deficiency associated withsnl requires further investigation.

The effect of pyrimidines on the incorporation of purines into riboflavin and RNA by Eremothecium ashbyii

1. 1. The distribution of radioactivity from [2- 14C]adenine between riboflavin and RNA produced by Eremothecium ashbyii changed upon the addition of uracil to the medium. Less riboflavin was produced and a larger share of the adenine activity appeared in the RNA. 2. 2. The radioactivity from [2- 14C]uracil and from [2- 14C]guanine increased in the RNA when unlabeled adenine and cytosine, respectively, were added. 3. 3. Analysis of the bases recovered from the hydrolysis of RNA showed that the transfer of radioactivity from adenine to guanine was less in the presence of uracil. Similarly, the transfer of radioactivity from labeled guanine to adenine was diminished when cytosine was provided. 4. 4. The increased uptake of labeled precursors into RNA appears to be related to the specific base pairing, but the mechanism by which it occurs remains obscure.

The Effects of Pyrimidines on the Growth of Lactobacillus casei

The Effects of Pyrimidines on the Growth of <i>Lactobacillus casei</i>