Novel iron complexes bearing N6-substituted adenosine derivatives: synthesis, magnetic, 57Fe Mössbauer, DFT, and in vitro cytotoxicity studies

Iron complexes (1-7) involving N6-benzyladenosine derivatives of the predominant composition [Fe(L(n))Cl(3)].H(2)O {where L(1)=N6-(2-fluorobenzyl)adenosine (1), L(2)=N6-(4-fluorobenzyl)adenosine (2), L(3)=N6-(2-trifluoromethylbenzyl)adenosine (3), L(4)=N6-(3-trifluoromethylbenzyl)adenosine (4), L(5)=N6-(4-trifluoromethylbenzyl)adenosine (5), L(6)=N6-(4-trifluoromethoxybenzyl)adenosine (6), and L(7)=N6-(4-chlorobenzyl)adenosine (7)} have been synthesized. The compounds have been characterized by elemental analysis, variable-temperature and in-field 57Fe M?ssbauer, ES+ MS, FTIR, 1H and 13C NMR spectroscopies, magnetochemical and conductivity measurements, thermal (TGA/DSC/DTA) analyses, and DFT calculations. It has been found that the organic molecule is coordinated to iron via N7 atom of the appropriate adenosine derivative and the products are represented by mixtures of complexes with various iron oxidation (Fe(III)/Fe(II)) and spin states (S=5/2, 4/2, 3/2, 2/2) and geometries (tetrahedral or trigonal bipyramidal). It is caused by the fact that partial redox processes proceed during the reactions due to the presence of a ribose moiety, which is oxidized to the corresponding 5'-ribotic acid, and simultaneously, a portion of Fe(III) cations is reduced to Fe(II) ones. Moreover, a significant effect of crystal water molecules on stereochemistry, and hence, on magnetic and spectral properties of the prepared complexes has been found. The compounds have been tested for their in vitro cytotoxicity against the following human cancer cell lines: malignant melanoma (G-361), osteogenic sarcoma (HOS), chronic myelogenous leukemia (K-562), and breast adenocarcinoma (MCF-7). The most important results have been obtained for complex 2 with IC(50) values 8-16 microM against HOS, K-562, and MCF-7 cell lines, and for complex 6 with IC(50) value 4 microM against MCF-7 cell line.     

Synthesis and structure-activity relationship studies of theophylline analogs on population responses in the rat hippocampus in vitro

We synthesized several theophylline analogs and tested the hypothesis that these compounds may be nootropic or cognitive enhancers by examining their effects on evoked population spikes recorded extracellularly in the CA1 region of the rat hippocampus. Whereas the length of the carbon chain on N7 had no effect, different size of the terminal lactam ring strongly influenced neuroactivity. Our results suggest that hexahydroazepin-2-one analogs have potential for further development as cognitive enhancers.     

Synthesis, cytostatic and anti-HCV activity of 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides

An efficient and facile synthesis of a large series of diverse 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides (55 examples of both ribo- and 2'-deoxyribonucleosides), aimed at identifying novel homologues of natural nucleosides, was developed. The key transformation involved nucleophilic substitutions of Tol-protected 6-(mesyloxymethyl)purine nucleosides by primary or secondary amines, alcoholates or thiolates. While the 2'-deoxyribonucleosides were inactive, the ribonucleosides exerted considerable cytostatic effects and some anti-HCV activity with low selectivity.     

Oxidised derivatives of silybin and their antiradical and antioxidant activity

Carboxylic acids derived from silybin (1) and 2,3-dehydrosilybin (2) with improved water solubility were prepared by selective oxidation of parent compounds and a new inexpensive method for preparation of 2,3-dehydrosilybin from silybin was developed and optimised. The antioxidative properties of the above-mentioned compounds and of side product 3a from oxidation of compound 1 were determined by cyclic voltammetry, free radical scavenging (DPPH, superoxide) assays, and by inhibition of in vitro generated liver microsomal lipid peroxidation. Dehydrogenation at C((2))-C((3)) in flavonolignans (silybin vs 2,3-dehydrosilybin; silybinic acid vs 2,3-dehydrosilybinic acid) strongly improved antioxidative properties (analogously as in flavonoids taxifolin vs quercetin). Thus, in antioxidative properties, dehydrosilybin was superior to silybin by one order, but its water solubility is too low for application in aqueous milieu. On the other hand, 2,3-dehydrosilybinic acid is a fairly soluble derivative with antilipoperoxidation and antiradical activities better than that of silybin.     

Dipeptidyl peptidase IV activity and/or structure homologues (DASH) and their substrates in cancer

Post-translational modification of proteins is an important regulatory event. Numerous biologically active peptides that play an essential role in cancerogenesis contain an evolutionary conserved proline residue as a proteolytic-processing regulatory element. Proline-specific proteases could therefore be viewed as important "check-points". Limited proteolysis of such peptides may lead to quantitative but, importantly, due to the change of receptor preference, also qualitative changes of their signaling potential.Dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5, identical with CD26) was for many years believed to be a unique cell membrane protease cleaving X-Pro dipeptides from the N-terminal end of peptides and proteins. Subsequently, a number of other molecules were discovered, exhibiting various degree of structural homology and DPP-IV-like enzyme activity, capable of cleaving similar set of substrates. These comprise for example, seprase, fibroblast activation protein alpha, DPP6, DPP8, DPP9, attractin, N-acetylated-alpha-linked-acidic dipeptidases I, II and L, quiescent cell proline dipeptidase, thymus-specific serine protease and DPP IV-beta. It is tempting to speculate their potential participation on DPP-IV biological function(s). Disrupted expression and enzymatic activity of "DPP-IV activity and/or structure homologues" (DASH) might corrupt the message carried by their substrates, promoting abnormal cell behavior. Consequently, modulation of particular enzyme activity using e.g. DASH inhibitors, specific antibodies or DASH expression modification may be an attractive therapeutic concept in cancer treatment. This review summarizes recent information on the interactions between DASH members and their substrates with respect to their possible role in cancer biology.     

Recognition of hyaluronan released in sterile injury involves a unique receptor complex dependent on Toll-like receptor 4, CD44, and MD-2

Inflammation under sterile conditions is not well understood despite its importance in trauma and autoimmune disease. To investigate this process we established mouse models of sterile injury and explored the role of hyaluronan in mediating inflammation following injury. The response of cultured monocytes to hyaluronan was different than the response to lipopolysaccharide (LPS) despite both being dependent on Toll-like receptor 4 (TLR4). Cultured cells exposed to hyaluronan showed a pattern of gene induction that mimics the response seen in mouse skin after sterile injury with an increase in molecules such as transforming growth factor-beta2 and matrix metalloproteinase-13. These factors were not induced by LPS despite the mutual dependence of both hyaluronan and LPS on TLR4. Explanation for the unique response to hyaluronan was provided by observations that a lack of TLR4 or CD44 in mice diminished the response to sterile injury, and together with MD-2, was required for responsiveness to hyaluronan in vitro. Thus, a unique complex of TLR4, MD-2, and CD44 recognizes hyaluronan. Immunoprecipitation experiments confirmed the physical association of TLR4 and CD44. Taken together, our results define a previously unknown mechanism for initiation of sterile inflammation that involves recognition of released hyaluronan fragments as an endogenous signal of tissue injury.     

Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis

To examine the role of endothelial heparan sulfate during angiogenesis, we generated mice bearing an endothelial-targeted deletion in the biosynthetic enzyme N-acetylglucosamine N-deacetylase/N-sulfotransferase 1 (Ndst1). Physiological angiogenesis during cutaneous wound repair was unaffected, as was growth and reproductive capacity of the mice. In contrast, pathological angiogenesis in experimental tumors was altered, resulting in smaller tumors and reduced microvascular density and branching. To simulate the angiogenic environment of the tumor, endothelial cells were isolated and propagated in vitro with proangiogenic growth factors. Binding of FGF-2 and VEGF(164) to cells and to purified heparan sulfate was dramatically reduced. Mutant endothelial cells also exhibited altered sprouting responses to FGF-2 and VEGF(164), reduced Erk phosphorylation, and an increase in apoptosis in branching assays. Corresponding changes in growth factor binding to tumor endothelium and apoptosis were also observed in vivo. These findings demonstrate a cell-autonomous effect of heparan sulfate on endothelial cell growth in the context of tumor angiogenesis.