Medicinal Chemistry - Volume 2, Issue 5, 2006

A series of 8 europium (III) tris-β-diketonates with common formula Eu(L)3Int, where L is acetyl acetone, thenoyltrifluoroacetone, benzoylacetone, dibenzoylmethane and Int is 1,10-phenanthroline or 2,2'-bipyridine, together with an analog without intercalating moiety (Eu(III)(acetyl acetone)3(H2O)2) were tested for cytotoxic activity in a panel of human tumor cell lines, using the MTT-dye reduction assay. The panel consisted of the leukemias HL-60, BV-173, SKW- 3, K-562, LAMA-84 and the urinary bladder carcinoma 5637. The tested europium complexes with appended intercalator moieties exhibited profound cytotoxic effects with IC50 values lower or comparable to those of the referent drug cis-DDP, whereby the 1,10-phenanthroline bearing compounds were invariably more active than the corresponding 2,2'-bipyridine analogs. The established low cytotoxic potential of Eu(III)(acetyl acetone)3(H2O)2 as compared to its highly potent analogs with either 1,10-phenanthroline or 2,2'-bipyridine ligand demonstrated that the abundance of intercalating motif is a mandatory structural prerequisite for optimal activity within this series of cytotoxic agents. Selected compound caused DNA-fragmentation when applied in cytotoxic concentration, which suggests that the induction of programmed cell death (apoptosis) at least partly mediates the cytotoxic effects of tested compounds. Taken together our data give us reason to conclude that the presented Eu(III) complexes represent a unique class of cytotoxic metal coordination compounds and necessitate further detailed evaluation in order to define the structure activity relationships as well as the predominant mode of action. To the best knowledge of the authors this is among the first reports of potent cytotoxic Eu(III) compounds..

Meloxicam was launched as a major new NSAID for the treatment of arthritis following extensive published research confirming its selectivity for COX-2. Several studies proposed possible explanations for its effectiveness and superior safety profile. The proposed theories included chemical structural relationships between meloxicam and other effective NSAIDs with low gastrointestinal toxic effects. However, other oxicams have similar chemical groups, but despite this, are not considered COX-2 selective drugs and exhibit less gastric tolerance. Hence, the aim of this work was to investigate the interactions between oxicams and biomembrane models as it could influence their resorption from the upper gastrointestinal tract and may affect their local gastromucosal tolerability. The partition of oxicams within membranes was determined by calculating their partition coefficients between liposomes and water. Moreover, their location within the bilayer was determined by fluorescence quenching. Finally, zeta-potential measurements were made to complete the information about the binding behaviour of the oxicams and steady-state anisotropy measurements were made to determine their induced perturbation in membrane structure. These studies proved that, in spite of structural similarities, oxicams present different interactions with membranes making possible a virtual division of the class in two groups. Tenoxicam and piroxicam known as COX-1 inhibitors demonstrated higher partition capacity in liposomes/water systems together with a smaller ability to change the membrane fluidity and surface potential. In contrast lornoxicam and meloxicam, which demonstrated activity against COX-2, have revealed smaller partition capacity in liposomes/water systems together with a higher ability to change the membrane fluidity and surface potential.

Pancreatic cancer is one of the tumors with the highest mortality, poorly responding to available chemotherapeutic agents. The objective of this study was to study the anticancer effects of all-trans retinoid acid, a functional form of vitamin A, on pancreatic cancer cells. Human pancreatic cancer MiaPaCa-2 cells were treated with 1, 5, 10, 20, 30, 40 and 50 μM ATRA for 1, 2, 3, 4, 5 or 6 d, respectively. Cell growth was determined by MTT viability assay. The cell cycle distribution and the alkaline phosphatase (ALP) activity were analyzed by flow cytometry and chemical analyzer, respectively. The results show that ATRA significantly inhibited the growth of MiaPaCa-2 cells at 40 and 50μM. ATRA arrested pancreatic cancer cells at G0/G1 phase. The sub-G1 peak and DNA fragmentation were observed. There were time and dose dependent increases in alkaline phosphatase activity (ALP), an indicator of cell differentiation, upon treatment with ATRA when compared to controls. In conclusion, ATRA has an inhibitory effect on the cell growth of MiaPaCa-2, and its tumor suppressive effect is by means of cell cycle arrest and apoptosis induction.

The cerium (III) and neodymium (III) complexes with 3,3 -benzylidenebis[4-hydroxycoumarin] were synthesized and characterized by different analytical and spectral methods. The synthesis of these complexes is taken into consideration with cytotoxic screening and study of their antioxidant effect. Their cytotoxicity toward cancerous cell cultures correlated with the weakness of the coordinative bond between the cation and organic ligand and with the capability to scavenge superoxide radicals as well. On the basis of the data reported by us earlier and our new results, it was proposed that cerium (III) complex with 3,3 -benzylidenebis[4-hydroxycoumarin] might induce intracellular acidification along with control over the extracellular oxidative stress.

Cannabinoids have been suggested as potential neuroprotective compounds in Alzheimer's disease (AD). Despite intense investigation, the detailed intracellular mechanism(s) involved in cannabinoids survival effect remains to be elucidated. The present study shows that CP55,940 (a CB1 and CB2 agonist) and JWH-015 (a CB2 agonist) protect and rescue peripheral blood lymphocytes (PBL) from (10μM) Aβ [25-35] and (50μM) H2O2-induced apoptosis by two alternative mechanisms: (1) receptor-independent pathway, as demonstrated by no-dihydrorhodamine oxidation into fluorescent rhodamine 123 (R-123) as a result of cannabinoid inhibition of Aβ -generated H2O2; (2) receptor-dependent pathway through NF-κ B activation and p53 down regulation involving phosphoinositide 3-kinase (PI-3K), as demonstrated by using either (25μM) LY294002 (a PI-3K inhibitor),(50nM) pifithrin-α(PFT, a specific p53 inhibitor) or by using immunocytochemistry detection of NF-κ B and p53 transcription factors activation. Importantly, cannabinoid agonists and PFT were able to protect and rescue lymphocytes pre-exposed to toxicants-, even when the three compounds were added up-to 12 h post-Aβ [25-35]/(H2O2) exposure. These results suggest that CP55,940/( JWH-015) protection/rescue of PBL from noxious stimuli is determined by p53 inactivation. These findings may contribute to a better understanding of the role played by cannabinoids as neuroprotective agents to target and interrupt molecular signaling that induce damage in AD disorder.

This study presents the first QSAR model for Galectin-3 glycomimetic inhibitors based on docked structures to the carbohydrate recognition domain (CRD). Quantitative numerical methods such as PLS (Partial Least Squares) and ANN (Artificial Neural Networks) have been used and compared on QSAR models to establish correlations between molecular properties and binding affinity values (Kd). Training and validation of QSAR predictive models was performed on a master dataset consisting of 136 compounds. The molecular structures and binding affinities (Kd) (136 compounds) were obtained from the literature. To address the issue of dimensionality reduction, molecular descriptors were selected with PLS contingency approach, ANN, PCA (Principal Component Analysis) and GA (Genetic Algorithms) for the best predictive Galectin-3 binding affinity (Kd). Final sets comprising 56, 31 and 35 descriptors were obtained with PLS, PCA and ANN, respectively. The objective of this prototype QSAR model is to serve as a first guideline for the design of novel and potent Gal-3 selective inhibitors with emphasis on modification at both C-3' and at O-3 positions [1].

HIV-1 RT is one of the most important antiviral targets in the treatment of acquired immunodeficiency syndrome (AIDS). Several crystallographic structures are available for this enzyme, mostly with bound inhibitors. Despite their importance for structure based drug design towards new anti-HIV retrovirals, the X-ray structures of the unliganded enzyme could only be obtained incomplete, with a low resolution and until recently even the conformation of the p66 thumb was controversial. In this work we have aligned different X-ray RT structures, and built up a computational model of RT using homology modeling, which was afterwards refined and validated through MD simulations with explicit solvent. The model enzyme was structurally stable through the whole MD simulation, showing a RMSD of 2Å from the starting geometry. The Ramanchandram plot has improved along the simulation. Both intra-domain and interdomain movements were observed. The thumb kept its closed conformation through the whole simulation. A contact map, hydration sites study and a detailed analysis of the solvation of the nucleotide binding site are also presented.

Gene therapy is a promising therapeutic modality for the treatment of cystic fibrosis (CF). Despite a better understanding of the molecular organization of the cystic fibrosis transmembrane conductance regulator (CFTR) gene and mutations resulting in pathophysiological and phenotypic alterations, several forms of treatments including gene therapy have failed to yield clinical success. Major limitations for the delivery of drugs and gene therapy vectors from reaching target cells in CF patients lie in physical and immunological barriers of airway epithelium. Over the last decade, non-viral and viral gene therapy approaches have been tested in preclinical studies and human clinical trials of CF. Outcomes of these studies have helped to identify hurdles that need to be overcome before such approaches can be routinely applied to patients. In addition to the physiological and immunological barriers of airway epithelium, vector transduction is also impaired by the absence or low-abundance of cellular receptors and co-receptors for viral binding and internalization. Thus, the initial enthusiasm for gene replacement therapy for CF following cloning of the CFTR gene dampened, as more limitations were recognized. Research directed towards improving the efficiency of gene transfer technology in CF, is focused on testing of compounds to enhance vector permeability and trafficking, identification and development of vectors which can transduce through alternate pathways, identification of airway epithelium-specific targeting ligands, and the identification of stem cells for combining cell therapy and gene therapy by ex vivo methods. Details provided in this article will give a comprehensive analysis of the prospects and limitations in CF gene therapy using viral and nonviral vectors.

The present study extends our previous work regarding new antifolates for Mycobacterium avium (MAC) dihydrofolate reductase (DHFR). The objectives of this study were to synthesize and test new derivatives in the general class of 2,4-diamino-5-methyl-5-deazapteridines in an effort to improve solubility and selectivity for the MAC DHFR, while maintaining lack of selectivity for the human DHFR. New 6-[2', 5'-dialkoxyphenyl) methyl]-substituted DMDP analogs were synthesized as previously described. Three clinical isolates of MAC (NJ211, NJ3404, and NJ168) and M. tuberculosis H37Ra (MTB) were used to evaluate the new derivatives. A previously described colorimetric (alamarBlue®) microdilution broth assay was used to determine minimal inhibitory concentrations (MIC). Purified recombinant human (rDHFR), MAC rDHFR, and MTB rDHFR were used in a validated enzyme assay to obtain IC50 values and to determine selectivity ratios (SR) for the derivatives. For the MAC strains, the MICs ranged from 0.25 to > 16μg/mL. The most active derivative against MAC was SRI-20920 which had MICs of 0.25, 0.25, and 8μg/mL for the three strains, respectively. The most selective derivative was SRI-20730 with IC50s of 29 and 67,781 nM for MAC rDHFR and hDHFR, respectively, and a SR of 2,337. MICs for MTB ranged from 4 to >64μg/mL and the SR, in general, ranged from 0.32 to 2.5. These results further substantiate the utility of this group of DMDP derivatives for selective activity against MAC.

The synthesis and evaluation as hypoxic selective cytotoxins of new derivatives of 2-amino or 2- hydroxyphenazine 5,10-dioxide are described. The compounds were developed as structural analogs of other bioreductive compounds and its in vitro cytotoxicities on V79 cells under hypoxic and aerobic conditions were determined. To gain insight into its mechanism of action electrochemical behavior, interaction with DNA experiments and QSAR studies were performed.

Matrix Metalloproteinases (MMPs) are a class of zinc-dependent enzymes that degrade extracellular matrix components, particularly collagen. MMPs have been implicated in a diverse list of pathological processes, including cancer and cardiovascular disease. Recent efforts to bring MMP inhibitors to clinical trials, however, have proved disappointing. These failures are attributed, in part, to the non-selective nature of current inhibitors. The possibility also exists, however, that inhibition of a particular MMP type will lead to feedback accumulation of parallel MMP members. MMP-7, also known as matrilysin, has a broad list of substrates, including denatured collagen and other MMPs involved in the collagenolytic pathway, namely MMP-1, MMP-2, and MMP-9. Whether the additional collagenases, MMP-8 and MMP-13, are also activated by MMP-7 has not been explored. We show here that recombinant active MMP-7 was able to process MMP-8 to its active form in vitro, but did not activate MMP-13. In the left ventricles of mice lacking the MMP-7 gene, MMP-8 levels increased while MMP-13 levels decreased in vivo. The switch in MMP profile was not accompanied by a change in left ventricular dimensions or wall thickness. Together, these data suggest that MMP-8 is an in vivo substrate of MMP-7, and that the accumulation of pro-MMP-8 in the absence of MMP-7 downregulates pro-MMP-13 levels in order to maintain baseline collagenolytic function. The interplay between MMP-8 and MMP-13 suggest that these MMPs may play reciprocal roles. The design of selective MMP inhibitors, therefore, must take into consideration changes in parallel MMP types as a potential compensatory mechanism.

Calcium channel blockers are widely used in therapy for hypertension and angina pectoris, and among these blockers some 1,4-dihydropyridines (e.g. amlodipine, nitrendipine and nifedipine) have had widespread clinical use. In this work we investigated the vascular effects of four bis-1,4-dihydropyridines (bis-DHPs: 01-04), structurally related to nifedipine, in which a second 1,4-dihydropyridinic moiety was incorporated in the corresponding arylic moiety in para and meta position. Of these four bis-DHPs, the meta regioisomers (bis-DHP-03 and bis-DHP-04; 0.01-3.16 mg kg-1) and nifedipine induced a greater decrease on diastolic and systolic blood pressure than the para isomers (bis-DHP-01 and bis- DHP-02), as shown in two experimental models: normotensive and spontaneously hypertensive rats. Complementarily, bis-DHPs action was examined in intact and endothelium-denuded rat aorta, depolarized by KCl [80 mM] in one group and stimulated by noradrenaline (1x10-7 M) in another and the corresponding IC50 values were obtained (1.5x10-6-2.4x10- 7M). Later, the relaxing action of bis-DHP-03,04 and nifedipine on the contraction evoked by Ca2+ in K+-depolarized rat aorta was analyzed and the corresponding EC50 values for the meta isomers and nifedipine were obtained. The results showed a concentration dependent vasodilating activity in both KCl precontracted and noradrenaline stimulated aorta rings. The apparent order of potency with and without endothelium in both experimental models was nifedipine>bis-DHP- 04>bis-DHP-03. The cumulative concentration-effect curves for Ca2+ in the presence of the bis-DHPs tested show the same potency order. Unlike nifedipine, the tested compounds are not photosensitive, which makes them more attractive in therapy for hypertension related diseases.

Highly selective Cav2.2 voltage-gated calcium channel (VGCC) inhibitors have emerged as a new class of therapeutics for the treatment of chronic and neuropathic pain. Cone snail venoms provided the first drug in class with FDA approval granted in 2005 to Prialt (ω-conotoxin MVIIA, Elan) for the treatment of neuropathic pain. Since this pioneering work, major efforts underway to develop alternative small molecule inhibitors of Cav2.2 calcium channel have met with varied success. This review focuses on the properties of the Cav2.2 calcium channel in different pain states, the action of ω-conotoxins GVIA, MVIIA and CVID, describing their structure-activity relationships and potential as leads for the design of improved Cav2.2 calcium channel therapeutics, and finally the development of small molecules for the treatment of chronic pain.