No abstract

Oxidative stress has been implicated in pathophysiology of different human stress- and age-associated disorders, including osteoporosis for which antioxidants could be considered as therapeutic remedies as was suggested recently. The 1,4-dihydropyridine (DHP) derivatives are known for their pleiotropic activity, with some also acting as antioxidants. To find compounds with potential antioxidative activity, a group of 27 structurally diverse DHPs, as well as one pyridine compound, were studied. A group of 11 DHPs with 10-fold higher antioxidative potential than of uric acid, were further tested in cell model of human osteoblast-like cells. Short-term combined effects of DHPs and 50 µM H2O2 (1-h each), revealed better antioxidative potential of DHPs if administered before a stressor. Indirect 24-h effect of DHPs was evaluated in cells further exposed to mild oxidative stress conditions induced either by H2O2 or tert-butyl hydroperoxide (both 50 µM). Cell growth (viability and proliferation), generation of ROS and intracellular glutathione concentration were evaluated. The promotion of cell growth was highly dependent on the concentrations of DHPs used, type of stressor applied and treatment set-up. Thiocarbatone III-1, E2-134-1 III-4, Carbatone II-1, AV-153 IV-1, and Diethone I could be considered as therapeutic agents for osteoporosis although further research is needed to elucidate their bioactivity mechanisms, in particular in respect to signaling pathways involving 4-hydroxynoneal and related second messengers of free radicals.

The effects of eleven 1,4-dihydropyridine derivatives (DHPs) used alone or together with prooxidant anticancer drug doxorubicin were examined on two cancer (HOS, HeLa) and two nonmalignant cell lines (HMEC, L929). Their effects on the cell growth (3H-thymidine incorporation) were compared with their antiradical activities (DPPH assay), using well-known DHP antioxidant diludine as a reference. Thus, tested DHPs belong to three groups: (1) antioxidant diludine; (2) derivatives with pyridinium moieties at position 4 of the 1,4-DHP ring; (3) DHPs containing cationic methylene onium (pyridinium, trialkylammonium) moieties at positions 2 and 6 of the 1,4-DHP ring. Diludine and DHPs of group 3 exerted antiradical activities, unlike compounds of group 2. However, novel DHPs had cell type and concentration dependent effects on 3H-thymidine incorporation, while diludine did not. Hence, IB-32 (group 2) suppressed the growth of HOS and HeLa, enhancing growth of L929 cells, while K-2-11 (group 3) enhanced growth of every cell line tested, even in the presence of doxorubicin. Therefore, growth regulating and antiradical activity principles of novel DHPs should be further studied to find if DHPs of group 2 could selectively suppress cancer growth and if those of group 3 promote wound healing.

Aim. To the determine DNA interaction modes for a series of 1,4-dihydropyridines with different biological activities synthesized in the Latvian Institute of Organic Synthesis. Methods. Affinity of the compounds to DNA was detected by UV/VIS spectrometry and re-proofed by means of spectrofluorimetry, EBr extrusion assay, cyclic voltammetry and DNA melting. Radical scavenging was tested by electron paramagnetic resonance spectroscopy, peroxynitrite binding was monitored spectrophotometrically, protection of DNA against hydroxyl radical was determined by gel electrophoresis. Results. In a series of water-soluble monocyclic derivatives of 1,4-dihydropyridine with carboxylate groups in position-4 the different affinity to DNA was determined mainly by substituents in positions 3 and 5. 1,4-DHP with ethoxycarbonyl groups in positions 3 and 5 (AV-153) manifested high affinity to DNA. Strong effects were observed in the spectra of tricyclic fused derivatives (PP-150-Na and PP-544-NH 4). Unlike AV-153, J-4-96 did not extrude EtBr from the complex with DNA, this indicates binding to minor groove. Ability of PP-544-NH 4 to intercalate DNA molecule was proved electrochemically and by DNA melting. No correlation between affinity of a 1,4-DHP to DNA and capabilities of the compound to bind peroxynitrite, to scavenge hydroxyl radical or to protect DNA against the above radical were observed. Conclusions. DNA-binding activities of 1,4-DHP are evidently determined by groups in positions 3 and 5. Tricyclic fused 1,4-DHP derivatives are also good DNA binders. Ability to interact with DNA does not correlate with other effects produced by the compounds. K e y w o r d s: 1,4-dihydropyridines, DNA binding, peroxynitrite binding, hydroxyl radical scavenging, DNA protection.

A set of six new 4-pyridinio-1,4-dihydropyridine (1,4-DHP) compounds has been synthesized. The calcium channel modulating activity of these compounds was evaluated in an aorta vascular smooth muscle cell line (A7R5), in an isolated rat aortic ring model, and in human neuroblastoma cell lines (SH-SY5Y). The antagonistic effect of these 1,4-DHP was tested by modulating the impact of carbachol-dependent mobilization of intracellular Ca 2+ in SH-SY5Y cells. The intracellular free Ca 2+ concentration was measured in confluent monolayers of SH-SY5Y cells and A7R5 cells with the Ca 2+ -sensitive fluorescent indicator Fluo-4 NW. Only four compounds showed calcium channel blocking activity in SH-SY5Y and A7R5 cells as well as in the aortic ring model. Among them, compound 3 was the most active calcium channel antagonist, which had 3 times higher activity on carbachol-activated SH-SY5Y cells than amlodipine. Two of the compounds were inactive. Compound 4 had 9 times higher calcium agonist activity than the classic DHP calcium agonist Bay K8644. The intracellular mechanism for the action of compound 4 using inhibitor analysis was elucidated. Nicotinic as well as muscarinic receptors were not involved. Sarcoplasmic reticulum (ER) Ca 2+ (SERCA) stores were not affected. Ryanodine receptors (RyRs), another class of intracellular Ca 2+ releasing channels, participated in the agonist response evoked by compound 4. The electrooxidation data suggest that the studied compounds could serve as antioxidants in OS.