Thymidine esters as substrate analogue inhibitors of angiogenic enzyme thymidine phosphorylase in vitro

Integrating metabolomics and network pharmacology to assess the effects of quercetin on lung inflammatory injury induced by human respiratory syncytial virus

Quercetin (QR) has significant anti-respiratory syncytial virus (RSV) effects. However, its therapeutic mechanism has not been thoroughly explored. In this study, a lung inflammatory injury model caused by RSV was established in mice. Untargeted lung tissue metabolomics was used to identify differential metabolites and metabolic pathways. Network pharmacology was used to predict potential therapeutic targets of QR and analyze biological functions and pathways modulated by QR. By overlapping the results of the metabolomics and the network pharmacology analyses, the common targets of QR that were likely to be involved in the amelioration of RSV-induced lung inflammatory injury by QR were identified. Metabolomics analysis identified 52 differential metabolites and 244 corresponding targets, while network pharmacology analysis identified 126 potential targets of QR. By intersecting these 244 targets with the 126 targets, hypoxanthine-guanine phosphoribosyltransferase (HPRT1), thymidine phosphorylase (TYMP), lactoperoxidase (LPO), myeloperoxidase (MPO), and cytochrome P450 19A1 (CYP19A1) were identified as the common targets. The key targets, HPRT1, TYMP, LPO, and MPO, were components of purine metabolic pathways. The present study demonstrated that QR effectively ameliorated RSV-induced lung inflammatory injury in the established mouse model. Combining metabolomics and network pharmacology showed that the anti-RSV effect of QR was closely associated with purine metabolism pathways.

Thymidine phosphorylase and prostrate cancer cell proliferation inhibitory activities of synthetic 4-hydroxybenzohydrazides: In vitro, kinetic, and in silico studies

Over-expression of thymidine phosphorylase (TP) plays a key role in many pathological complications, including angiogenesis which leads to cancer cells proliferation. Thus in search of new anticancer agents, a series of 4-hydroxybenzohydrazides (1-29) was synthesized, and evaluated for in vitro thymidine phosphorylase inhibitory activity. Twenty compounds 1-3, 6-14, 16, 19, 22-24, and 27-29 showed potent to weak TP inhibitory activities with IC50 values in the range of 6.8 to 229.5 μM, in comparison to the standards i.e. tipiracil (IC50 = 0.014 ± 0.002 μM) and 7-deazaxanthine (IC50 = 41.0 ± 1.63 μM). Kinetic studies on selected inhibitors 3, 9, 14, 22, 27, and 29 revealed uncompetitive and non-competitive modes of inhibition. Molecular docking studies of these inhibitors indicated that they were able to interact with the amino acid residues present in allosteric site of TP, including Asp391, Arg388, and Leu389. Antiproliferative (cytotoxic) activities of active compounds were also evaluated against mouse fibroblast (3T3) and prostate cancer (PC3) cell lines. Compounds 1, 2, 19, and 22-24 exhibited anti-proliferative activities against PC3 cells with IC50 values between 6.5 to 10.5 μM, while they were largely non-cytotoxic to 3T3 (mouse fibroblast) cells proliferation. Present study thus identifies a new class of dual inhibitors of TP and cancer cell proliferation, which deserves to be further investigated for anti-cancer drug development.

Natural compounds as angiogenic enzyme thymidine phosphorylase inhibitors: In vitro biochemical inhibition, mechanistic, and in silico modeling studies

Natural flora is the richest source of novel therapeutic agents due to their immense chemical diversity and novel biological properties. In this regard, eighteen natural products belonging to different chemical classes were evaluated for their thymidine phosphorylase (TP) inhibitory activity. TP shares identity with an angiogenic protein platelet derived endothelial cell growth factor (PD-ECGF). It assists tumor angiogenesis and is a key player in cancer progression, thus an ideal target to develop anti-angiogenic drugs. Eleven compounds 1–2, 5–10, 11, 15, and 18 showed a good to weak TP inhibitory activity (IC₅₀ values between 44.0 to 420.3 μM), as compared to standards i.e. tipiracil (IC₅₀ = 0.014 ± 0.002 μM) and 7-deazaxanthine (IC₅₀ = 41.0 ± 1.63 μM). Kinetic studies were also performed on active compounds, in order to deduce the mechanism of ligand binding to enzyme. To get further insight into receptor protein (enzyme) and ligand interaction at atomic level, in- sillico studies were also performed. Active compounds were finally evaluated for cytotoxicity test against mouse fibroblast (3T3) cell line. Compound 18 (Masoprocol) showed a significant TP inhibitory activity (IC₅₀ = 44.0 ± 0.5 μM). Kinetic studies showed that it inhibits the enzyme in a competitive manner (Ki = 25.6 ± 0.008 μM), while it adopts a binding pose different than the substrate thymidine. It is further found to be non-toxic in MTT cytotoxicity assay. This is the first report on TP inhibitory activity of several natural compounds, some of which may serve as leads for further research towards drug the development.

Nuclear genes involved in mitochondrial diseases caused by instability of mitochondrial DNA

Mitochondrial diseases are defined by a respiratory chain dysfunction and in most of the cases manifest as multisystem disorders with predominant expression in muscles and nerves and may be caused by mutations in mitochondrial (mtDNA) or nuclear (nDNA) genomes. Most of the proteins involved in respiratory chain function are nuclear encoded, although 13 subunits of respiratory chain complexes (together with 2 rRNAs and 22 tRNAs necessary for their translation) encoded by mtDNA are essential for cell function. nDNA encodes not only respiratory chain subunits but also all the proteins responsible for mtDNA maintenance, especially those involved in replication, as well as other proteins necessary for the transcription and copy number control of this multicopy genome. Mutations in these genes can cause secondary instability of the mitochondrial genome in the form of depletion (decreased number of mtDNA molecules in the cell), vast multiple deletions or accumulation of point mutations which in turn leads to mitochondrial diseases inherited in a Mendelian fashion. The list of genes involved in mitochondrial DNA maintenance is long, and still incomplete.