Nitric Oxide Donors: Chemical Activities and Biological Applications

Recent developments in the synthesis and utilization of chiral sulfoxides.

Autophagy is originally named as a process of protein recycling. It begins with sequestering cytoplasmic organelles in a membrane vacuole called autophagosome. Autophagosomes then fuse with lysosomes, where the materials inside are degraded and recycled. To date, however, little is known about the role of autophagy in cancer therapy. In this study, we present that temozolomide (TMZ), a new alkylating agent, inhibited the viability of malignant glioma cells in a dose-dependent manner and induced G2/M arrest. At a clinically achievable dose (100 microM), TMZ induced autophagy, but not apoptosis in malignant glioma cells. After the treatment with TMZ, microtubule-associated protein light-chain 3 (LC3), a mammalian homologue of Apg8p/Aut7p essential for amino-acid starvation-induced autophagy in yeast, was recruited on autophagosome membranes. When autophagy was prevented at an early stage by 3-methyladenine, a phosphatidylinositol 3-phosphate kinase inhibitor, not only the characteristic pattern of LC3 localization, but also the antitumor effect of TMZ was suppressed. On the other hand, bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, that prevents autophagy at a late stage by inhibiting fusion between autophagosomes and lysosomes, sensitized tumor cells to TMZ by inducing apoptosis through activation of caspase-3 with mitochondrial and lysosomal membrane permeabilization, while LC3 localization pattern stayed the same. These results indicate that TMZ induces autophagy in malignant glioma cells. Application of an autophagy inhibitor that works after the association of LC3 with autophagosome membrane, such as bafilomycin A1, is expected to enhance the cytotoxicity of TMZ for malignant gliomas.

/pdf/role-of-autophagy-in-temozolomide-induced-cytotoxicity-for-2pey4bbe5w.pdf

Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells

We explore the question of what are the best ligands for macromolecular targets. A survey of experimental data on a large number of the strongest-binding ligands indicates that the free energy of binding increases with the number of nonhydrogen atoms with an initial slope of ≈−1.5 kcal/mol (1 cal = 4.18 J) per atom. For ligands that contain more than 15 nonhydrogen atoms, the free energy of binding increases very little with relative molecular mass. This nonlinearity is largely ascribed to nonthermodynamic factors. An analysis of the dominant interactions suggests that van der Waals interactions and hydrophobic effects provide a reasonable basis for understanding binding affinities across the entire set of ligands. Interesting outliers that bind unusually strongly on a per atom basis include metal ions, covalently attached ligands, and a few well known complexes such as biotin–avidin.

/pdf/the-maximal-affinity-of-ligands-m4wpmlub01.pdf

The maximal affinity of ligands

Temozolomide: a review of its discovery, chemical properties, pre-clinical development and clinical trials

Meso-ionic heterocycles (1976–1980)

Interaction of 5-diazoimidazole-4-carboxamide and alkyl and aryl isocyanates in the dark affords 8-carbamoyl-3-substituted-imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-on es. In cold methanol or ethanol, the 3-(2-chloroethyl) derivative 7a decomposes to afford 2-azahypoxanthine (14) and methyl and ethyl N-(2-chloroethyl)carbamates, respectively. Compound 7a has curative activity against L-1210 and P388 leukemia and may act as a prodrug modification of the acyclic triazene 5-[3-(2-chloroethyl)triazen-1-yl]imidazole-4-carboxamide (MCTIC), since it ring opens to form the triazene in aqueous sodium carbonate.

Antitumor imidazotetrazines. 1. Synthesis and chemistry of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one , a novel broad-spectrum antitumor agent.

The systematic variation of the potent antitumor agent mitozolomide (1) is extended to cover alteration of substituents at positions 6 and 8 and to change the imidazo[5,1-d]-1,2,3,5-tetrazinone (1) skeleton to the isomeric pyrazolo-[5,1-d]-1,2,3,5-tetrazinone (17) skeleton. The series of eight 6-alkyl and 6-aralkyl derivatives of 1 showed optimal antitumor activity when the group was small or linear, but activity diminished as size and branching of this substituent increased. This may reflect altered transport characteristics, or failure of the enlarged derivatives to fit a binding site, or possibly a reduced tendency for the derivatives having bulky groups at position 6 to hydrolytically generate the putatively active triazenes (21). Testing of 14 derivatives of 1 differently substituted at position 8 revealed a complex structure-activity relationship, with good antitumor activity obtained for carbamoyl and sulfamoyl groups bearing small substituents. The 8-methylsulfonyl compound had noteworthy activity, but the 8-cyano, 8-nitro, and 8-phenyl derivatives were devoid of useful antitumor activity in these tests. From the limited number of pyrazolotetrazinones (17) reported here, it is suggested that the same conclusions as regards activity also hold true for this ring system.

Antitumor imidazotetrazines. 14. Synthesis and antitumor activity of 6- and 8-substituted imidazo[5,1-d]-1,2,3,5-tetrazinones and 8-substituted pyrazolo[5,1-d]-1,2,3,5-tetrazinones

The preparation and plasma lipid altering characteristics of a series of 4H-3,1-benzoxazin-4-ones are described. Hypocholesterolemic, hypotriglyceridemic, and high-density-lipoprotein elevating properties are found for derivatives bearing a 4-(1,1-dimethylethyl)phenyl group at the 2-position, and this activity is displayed in both hypercholesterolemic and in normolipidemic rats when the ring system is substituted at position 6 with hydrogen, methyl, chloro, or iodo groups, and is optimal when the 6-position is substituted by a bromine atom. Evidence is presented suggesting that a metabolite or degradation product is responsible for the changes in lipoprotein concentration observed with active molecules of this type. Synthesis of anticipated degradation products of the active molecules gave products displaying the expected in vivo activity, but no improvement in the narrow therapeutic margin of the best compound, 6-bromo-2-[4-(1,1-dimethylethyl)phenyl]-4H-3,1-benzoxazin-4-one, was obtained.

Hypolipidemic 2-[4-(1,1-dimethylethyl)phenyl]-4H-3,1-benzoxazin-4-ones. Structure-activity relationships of a novel series of high-density lipoprotein elevators.

A potent, bioavailable ACAT inhibitor may have beneficial effects in the treatment of atherosclerosis by (i) reducing the absorption of dietary cholesterol, (ii) reducing the secretion of very low density lipoproteins into plasma from the liver, and (iii) preventing the transformation of arterial macrophages into foam cells We have found that a mevalonate derivative 2, which contains a 4,5-diphenyl-1H-imidazol-2-yl moiety, inhibits rat hepatic microsomal ACAT in vitro and produces a significant hypocholesterolemic effect in the cholesterol-fed rat Structure-activity relationships for analogues of 2 demonstrate that the 4,5-diphenyl-1H-imidazole moiety is a pharmacophore for inhibition of rat microsomal ACAT

Christopher G. Newton

Papers

Meso-ionic heterocycles (1976–1980)

Antitumor imidazotetrazines. 1. Synthesis and chemistry of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one , a novel broad-spectrum antitumor agent.

Antitumor imidazotetrazines. 14. Synthesis and antitumor activity of 6- and 8-substituted imidazo[5,1-d]-1,2,3,5-tetrazinones and 8-substituted pyrazolo[5,1-d]-1,2,3,5-tetrazinones

Hypolipidemic 2-[4-(1,1-dimethylethyl)phenyl]-4H-3,1-benzoxazin-4-ones. Structure-activity relationships of a novel series of high-density lipoprotein elevators.

Acyl-CoA:cholesterol O-acyl transferase (ACAT) inhibitors. 1. 2-(Alkylthio)-4,5-diphenyl-1H-imidazoles as potent inhibitors of ACAT.