title: Caffeine and other xanthines as cytochemical blockers and removers of heterocyclic DNA intercalators from chromatin.
abstract: Caffeine (CAF) and other xanthines non-covalently bind with the cationic fluorescent dye acridine orange (AO) and with other heterocyclic mutagens and carcinogens that are known to intercalate into double-stranded DNA (dsDNA). Fluorescence microscopy and spectrofluorometry studies were employed to test the ability of caffeine and certain other methyl substituted xanthines, with different binding affinities for AO, to inhibit and to reverse the intercalation of AO and other heterocyclic agents from intercalation with the DNA of nuclear chromatin of air-dried cells. Results indicated that xanthines with binding affinity for AO greater than 150 m(-1) block the AO molecule in a concentration dependent manner and comply with mass action kinetics. Thus CAF and other xanthines can be used to either inhibit intercalation of AO into nuclear DNA or to remove AO once intercalated into nuclear DNA. The interactions between other planar heterocyclics, xanthines, and nuclear chromatin dsDNA were also found to be non-covalent. Studies are needed to determine the ability of CAF and other xanthines to block and/or remove polyaromatic hydrocarbon (PAH) intercalators from the DNA of living cells.
authors.affiliation: Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Lyles
authors.forename: Ivan L
authors.initials: IL
authors.lastname: Cameron
mesh_terms: D000165:Acridine Orange / Q000494:pharmacology; D000628:Aminophylline / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002467:Cell Nucleus / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002642:Chick Embryo; D002843:Chromatin / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism; D004247:DNA / Q000187:drug effects* / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000494:pharmacology; D007364:Intercalating Agents / Q000494:pharmacology*; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009153:Mutagens / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014527:Uric Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D019820:Xanthine / Q000494:pharmacology
chemical_list: D000697:Central Nervous System Stimulants; D002843:Chromatin; D005456:Fluorescent Dyes; D007364:Intercalating Agents; D009153:Mutagens; D010726:Phosphodiesterase Inhibitors; D019820:Xanthine; D014527:Uric Acid; D000628:Aminophylline; D002110:Caffeine; D004247:DNA; C077059:1,3,7,9-tetramethyluric acid; D000165:Acridine Orange