Modification of nucleic acids with 1-nitropyrene in the rat: identification of the modified nucleic acid base.

A modified nucleic acid base was isolated from liver DNA of rats treated with 1-nitropyrene. The structure of the modified nucleic acid base was identified as 1-(guanin-8-yl)-aminopyrene by comparison with an authentic sample.

Effect of liver S9 from 3,4,5,3',4'-pentachlorobiphenyl-pretreated rats on the mutagenic activity of the various carcinogens toward Salmonella typhimurium TA 98.

Effects of liver 9000 X g supernatant fraction from 3,4,5,3',4'-pentachlorobiphenyl- and 2,4,5,2',4',5'-hexachlorobiphenyl-pretreated rats (PenCB-S9 and HexCB-S9, respectively) on the mutagenic activities of well-known carcinogens, benzo-[a]pyrene (BP), Glu-P-1 (2-amino-6-methyldipyrido [1,2-a:3',2'-d]imidazole), Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole), and aflatoxin B1 (AFB), toward Salmonella typhimurium TA 98 have been described. Although the mutagenic activities of all of these carcinogens were enhanced by these S9, PenCB-S9 especially highly activated BP, Glu-P-1, and Trp-P-1. The ability of PenCB-S9 to activate the carcinogens was much higher than that of liver 9000 X g supernatant fraction from 3-methylcholanthrene-pretreated rats (MC-S9).

Effects of synthetic analogues of teleocidin, indolactam-V, on the differentiation of murine pre-adipose cells.

The ability of 4 steric isomers of indolactam-V, the synthetic analogues of the tumor promoter teleocidin, to affect the adipose conversion of ST-13 murine pre-adipose cells was investigated. The isomers share the common skeleton with teleocidin A and B, but unlike teleocidins, none of them possess the terepenoid chain in the molecule. We found that only one of the isomers, (-)-indolactam-V, was biologically active and produced up to 70% inhibition of adipose conversion, while the other 3 isomers were without effect.

Two bases are eliminated from DNA by treatment with bleomycin or with hemin-intercalators.

A hemin-intercalator, H4G-His, which possesses 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1) as an intercalator moiety and histidine as an intramolecular ligand of the ferrous ion of the hemin ring, cleaves DNA very efficiently, and acts at guanine-pyrimidine sequences preferentially. Bleomycin (BLM) also cleaves DNA with the same base-sequence selectivity shown by H4G-His. The 5'-terminal of the DNA fragments cleaved by H4G-His or by BLM bears a phosphoryl group, while the 3'-terminal of the cleaved DNA fragments does not possess a 3'-phosphoryl group.

Structure-activity studies on synthetic analogues (indolactams) of the tumor promoter teleocidin.

Synthetic analogues (indolactams) related to the tumor promoter teleocidin were synthesized chemically. Of four indolactam-Vs lacking the monoterpenoid moiety of native teleocidin, (-)-indolactam-V bound to the 12-O-tetradecanoylphorbol-13-acetate receptor in cell membranes and induced both adhesion of HL-60 cells and ornithine decarboxylase activity in mouse skin, although its effects were weaker than those of teleocidin. (+)-Indolactam-V and two isomers of epi-indolactam-V showed no induction of ornithine decarboxylase.

Studies on olivoretins indicate a requirement for a free hydroxyl group for teleocidin B activity.

Three olivoretins, A, B and C (isolated from Streptoverticillium olivoreticuli), which are O-methylated teleocidin B isomers, were found to be biologically inactive. A fourth olivoretin, D, which has a free hydroxyl group and is identical to one of the four teleocidin B isomers, teleocidin B-4 (teleocidin B of Hirata) was biologically active. These findings indicate that the free primary hydroxyl group of teleocidin B isomers is necessary for activity.

Inhibition by hemin of dinitropyrene-induced mutagenesis in Chinese hamster V79 cells.

The inhibitory effects of hemin on the mutagenic activities of 1,3-, 1,6- and 1,8-dinitropyrenes (1,3-,1,6- and 1,8-DNPs) were investigated in Chinese hamster V79 cells. Mutant cells were selected on the basis of their resistance to ouabain. Hemin itself did not have any cytotoxic effect on Chinese hamster V79 cells, and did not induce mutations when added at a concentration of 10 micrograms/ml.

Functional analogs of bleomycin: sequence-specific DNA cleavage with porphyrin (Fe) intercalators.

Synthetic porphyrin (Fe) intercalators cleave DNA at guanine-cytosine and guanine-thymine sequences. The specificity for cleavage of base sequences of DNA is quite similar to that of bleomycin.

2-Aminodipyrido[1,2-a:3',2'-d]imidazole-porphyrin(Fe) derivatives as sequence specific DNA cleaving reagents.

Some porphyrin (Fe)-intercalators were synthesized. We chose 2-aminodipyrido[1, 2-a:3',2'-d]imidazoles (Glu-P's), which were muta-carcinogens isolated from a pyrolysate of L-glutamic acid, as intercalator moieties. These synthetic porphyrin (Fe)-intercalators cleave DNA at G-C and G-T sequences.

Sequence selective modification of DNA with muta-carcinogenic 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole.

2-Acetoxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole binds covalently to the 8 position of guanine residues in DNA. Treatment of the modified DNA with aqueous piperidine causes the liberation of the modified nucleic acid base, 2-(C8-guanyl)amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole, and cleavage of DNA at the sites of the modified guanylic acid residues. By use of 5'-end 32P-labelled DNA and sequence analysing gel electrophoresis, we discovered the base sequence specificity of DNA modification with 2-acetoxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole.

Nakahara memorial lecture. New classes of tumor promoters: teleocidin, aplysiatoxin, and palytoxin.

Teleocidin and aplysiatoxin, which are structurally different from 12-O-tetradecanoylphorbol-13-acetate (TPA), were found to be potent tumor promoters in two-step mouse skin carcinogenesis. The class of teleocidin includes dihydroteleocidin B, teleocidin, and lyngbyatoxin A. Teleocidin, which is a mixture of 93% teleocidin A and 7% teleocidin B, was isolated from Streptomyces mediocidicus as a strong skin irritant.

Clastogenic potential of heavy oil extracts and some aza-arenes in Chinese hamster cells in culture.

Chromosomal aberration tests in vitro, with a Chinese hamster fibroblast cell line, CHL, were carried out on B class heavy oil fractions, obtained by silica-gel column chromatography and a liquid-liquid extraction method. The original oil and basic nitrogen-containing fractions induced structural chromosomal aberrations in the CHL cells in the presence of rat-liver microsome fraction (S9 mix). 8 tricyclic or pentacyclic aza-arenes, which possibly exist in the positive fractions, were also examined for their clastogenic activities in the system with or without S9 mix.

Modification of nucleic acids with muta-carcinogenic heteroaromatic amines in vivo. Identification of modified bases in DNA extracted from rats injected with 3-amino-1-methyl-5H-pyrido[4,3-b]indole and 2-amino-6-methyldipyrido[1,2-a3:3',2'-d]imidazole.

Potent muta-carcinogens isolated from amino-acid pyrolysates, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-1-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1), were injected intraperitoneally into Male Wistar rats. DNA and rRNA modified with these muta-carcinogens were then extracted from the livers of the rats, and modified nucleic-acid bases were isolated and analysed by high-performance liquid chromatography (HPLC). These modified nucleic-acid bases were identified as 3-(C8-guanyl)amino-1-methyl-5H-pyrido[4,3-b]indole (Gua-Trp-P-2) and 2-(C8-guanyl)amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Gua-Glu-P-1) by comparison of their retention times on HPLC and UV spectra with those of authentic compounds.