[Protection of radiosensitive human cells against the action of heavy metals by antimutagens and adapting factors: association with genetic and protein polymorphisms].

Cells of a diploid line obtained from embryos with the Down's syndrome, known to be unable to repair gamma-induced DNA damage, were treated with natural (garlic extract, retinol) and synthetic (crown compound) antimutagens and with adapting factors (heat shock, low CdCl2 concentrations, 10(-8) M). The protective effect was evaluated by registering DNA breaks and cell survival, and the protection coefficients were calculated. The most effective results were obtained with the use of the garlic extract and retinol. No protection of the DNA structure was observed when cells were treated with low concentrations of cadmium chloride and then with high concentrations, i. e., no adaptive response (AR) was formed under these conditions. The spectrum of proteins in treated and control cells as well as detoxication genes (GSTM1, GSTT1 , CYPIA1) were determined.

[Antimutagenes' protection action in human repair-defected cells].

The action of natural (garlick extract, retinol) and of synthetic (crown-compound) antimutagenes in lymphotytes with gamma-radiation-induced inhibition of DNA-damages repair in cases of Elers-Danlos, syndrom, progeria and gomocystinurea was studied. Antimutagen cells defence from mutagenes was shown at all cases except one: progeria cells treated by retinol. Thus the repair-deficient cells resistance against mutagenes could be increased by antimutagenes.

Cyclophane and acyclic cyclophane: novel channel blockers of N-methyl-D-aspartate receptor.

The effects of cyclophanes (CPCn, CPPy and TGDMAP) and acyclic cyclophane (ATGDMAP) on various glutamate receptors were studied with these receptors expressed in Xenopus oocytes using voltage-clamp recording. CPCn, CPPy, TGDMAP and ATGDMAP were found to inhibit macroscopic currents at heteromeric NMDA receptors (NR1/NR2), but not Ca(2+)-permeable AMPA receptors (GluR1), Ca(2+)-nonpermeable AMPA receptors (GluR1/GluR2) and metabotropic glutamate receptors (mGluR1alpha). The inhibition of NR1/NR2A receptors by these compounds was more potent than those of the other NMDA receptor subtypes. At a resting potential (-70 mV), the IC(50) values of CPCn, CPPy, TGDMAP and ATGDMAP for NR1/NR2A receptors were 0.5+/-0.1, 1.0+/-0.2, 8.0+/-0.8 and 4.9+/-0.5 microM, respectively. The inhibition by these compounds was voltage-dependent, that is, the degree of inhibition was in the order of negative holding potentials, -100 mV>-70 mV>-20 mV. Results of experiments using mutant NR1 and NR2 subunits identified residues that influence block by CPCn. The inhibition by CPCn was not altered significantly in the mutants at the critical asparagines in the M2 loop, NR1 N616, NR2B N615 and NR2B N616, these residues are known to form the narrowest region of the channel and the binding site of Mg(2+). However, mutations at NR1 N650, located in the vestibule of channel pore, and NR1 D669, located in the extracellular region, reduced the inhibition by CPCn, suggesting that these amino acid residues interact with CPCn. These results suggest that CPCn interacts directly with the mouth or vestibule of the ion channel, like a lid.

Antimutagenic characteristics of new diazacrown compounds with N-carboxyalkyl substitutes.

Two new benzodiaza-15-crown-5 compounds containing two N-hydroxycarbonylmethyl or N-hydroxycarbonylpropyl substitutes were synthesized. The first of these compounds exhibited more pronounced protective effects towards human cells according to criteria of primary DNA injury and cell survival after exposure to gamma-radiation and CdCl2; by antimutagenic activity this compound was comparable to garlic extract. The antimutagenic effect of these compounds was realized not through the antioxidant mechanism.

Charge dependence of cellular uptake and selective antitumor activity of porphyrazines.

Porphyrazines (pzs), or tetraazaporphyrins, can be viewed as porphyrinic macrocycles in which the porphyrin meso (CH) groups are replaced by nitrogen atoms; as such, it can be anticipated that pzs would show similar biocompatibility and biodistribution to those of porphyrins. However, distinctive chemical and physical features of the pzs differentiate them from either the porphyrins or phthalocyanines, in particular making them excellent candidates as optical imaging/therapeutic agents. The novelty of the pzs requires that we first determine how specific structures selectively alter biological function, leading to the development of "rules" that will be used to predict future biologically functional pzs. In the first of these studies, we present here a correlation of pz charge with biocompatibility for a suite of three pzs-neutral, negative, and positive. Confocal fluorescence microscopy and proliferation/viability measurements disclose that the three pzs differ in their toxicity, uptake, and localization in A549 human lung adenocarcinoma cells and WI-38 VA13 normal cells. Interestingly, the negatively charged pz exhibits selective dark toxicity in pulmonary adenocarcinoma cells.

AT2-selective angiotensin II analogues containing tyrosine-functionalized 5,5-bicyclic thiazabicycloalkane dipeptide mimetics.

This paper reports the synthesis of two angiotensin II analogues with tyrosine-functionalized 5,5-bicyclic thiazabicycloalkane dipeptide mimetics replacing the Tyr(4)-Ile(5) residues. The preparation of these analogues relies on the synthesis and incorporation of an alpha,alpha-disubstituted chimeric amino acid derivative and on-resin bicyclization to a cysteine residue. The synthesized analogues both displayed high angiotensin AT(2)/AT(1) receptor binding preferences and had AT(2) receptor affinities in the same low nanomolar range as angiotensin II itself. Conformational analysis, using experimental constraints derived from NMR studies, indicated that the Tyr(4) and His(6) residues in one of the angiotensin II analogues were in close proximity to each other.